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ORGANIC CHEMISTRY (INTRODUCTION AND REACTIONS)A2 TOPIC 23
QUESTIONSHEETS A2 LevelCHEMISTRY
17 marks
23 marks
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11 marks
E/Z (CIS/TRANS) ISOMERISM
OPTICAL ISOMERISM
TEST QUESTION ON ISOMERISM
STRUCTURE OF BENZENE
STRUCTURES OF CYCLOALKENES
BOND TYPE AND REACTIVITY
REACTION CONDITIONS AND PRODUCT
NITRATION OF ARENES
HALOGENATION OF ARENES
ALKYLATION AND ACYLATION OF ARENES
PHENOL
ALDEHYDES AND KETONES
USE OF 2,4-DINITROPHENYLHYDRAZINE
THE TRIIODOMETHANE REACTION
GRIGNARD REAGENTS
CARBOXYLIC ACIDS I
CARBOXYLIC ACIDS II
ACYL CHLORIDES
ESTERS
NITRILES
AMIDES
AMINES
DIAZOTISATION
AMINO ACIDS
PROTEINS
TEST QUESTION I
TEST QUESTION II
Questionsheet 1
Questionsheet 2
Questionsheet 3
Questionsheet 4
Questionsheet 5
Questionsheet 6
Questionsheet 7
Questionsheet 8
Questionsheet 9
Questionsheet 10
Questionsheet 11
Questionsheet 12
Questionsheet 13
Questionsheet 14
Questionsheet 15
Questionsheet 16
Questionsheet 17
Questionsheet 18
Questionsheet 19
Questionsheet 20
Questionsheet 21
Questionsheet 22
Questionsheet 23
Questionsheet 24
Questionsheet 25
Questionsheet 26
Questionsheet 27
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17
E/Z (CIS/TRANS ISOMERISM)TOPIC 23 Questionsheet 1
a) Explain why there are two stereoisomers of pent-2-ene. Sketch their structures and name them.
Explanation ......................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
Structures and names
[4]b) Suggest why 1,2-dichlorocyclopentane can exhibit the same type of isomerism. Sketch the two structures.
Suggestion .................................................................................................................................................... [1]
Structures
[2]
c) Inspect each of the following compounds and state whether or not it can exhibit geometrical isomerism. In thelight of your answers, state what structural feature (apart from C=C) is necessary for the existence of E/Zisomers.
CH2=CHCH
2CH
3......................................................................................................................................... [1]
(CH3)
2C=CH
2............................................................................................................................................... [1]
CHCl=CHCl .................................................................................................................................................. [1]
CHCl=CHCH3
.............................................................................................................................................. [1]
CHCl=CClCH3
............................................................................................................................................. [1]
CH3CH=CClCH
2CH
3.................................................................................................................................... [1]
Structural feature .............................................................................................................................................
....................................................................................................................................................................... [1]
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OPTICAL ISOMERISM
a) (i) Draw the structures of the two stereoisomers of butan-2-ol and state how they can be distinguished inthe laboratory.
Structures
[2]
Means of distinguishing between them..................................................................................................
...................................................................................................................................................................
............................................................................................................................................................... [3]
(ii) Why is it that, although butan-2-ol can exhibit this type of isomerism, its oxidation product, butanone,does not?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
b) A chemist, who synthesised 2-hydroxypropanoic acid (lactic acid) by reacting ethanal with hydrogencyanide and then boiling the product with concentrated hydrochloric acid, reported that the 2-hydroxypropanoic acid was “an equal mixture of enantiomers”.
(i) What are enantiomers?
....................................................................................................................................................................... [1]
(ii) How did the chemist know that an equal mixture had been formed?
....................................................................................................................................................................... [1]
(iii) What name is given to such a mixture?
....................................................................................................................................................................... [1]
(iv) Explain why such a mixture is formed.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
TOPIC 23 Questionsheet 2
(Continued...)
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OPTICAL ISOMERISMTOPIC 23 Questionsheet 2 Continued
23
c) On the structures shown below, mark any chiral centre using *. There may be none or one or more centresper molecule.
H C HC C C C
H
H
HH
H H
O
H
C
H
HH
CH3
CH3
CH2
CH C
O
O H
NH2
C
H
C N H
OH
H H
CH3
HO
HO
[6]
d) L-dopa, the drug used to treat Parkinson’s disease, is a single optical isomer. Explain why pharmaceuticalcompanies choose to use medicines containing only the single isomer.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
CH2C
CH3
CH3CH
2
CH2
C CH3
H
NH2
H C C
CH2OH
N
CH2Cl
CH3CH3
C O CH2
CH2
CH CH3
O CH3
CHCl
CH2
C O
CH2
CH2
CH2
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TEST QUESTION ON ISOMERISM
16
TOPIC 23 Questionsheet 3
a) “In the context of isomerism, compounds of molecular formula C4H
10O are particularly interesting, because
they can exhibit skeletal isomerism, positional isomerism, functional group isomerism and stereoisomerism.”
(i) Illustrate this statement by writing the structural formulae of suitable pairs of compounds to show eachkind of isomerism.
Skeletal isomerism
............................................................................................................................................................... [2]
Positional isomerism
............................................................................................................................................................... [2]
Functional group isomerism
............................................................................................................................................................... [2]
Stereoisomerism
[2]
(ii) Explain why it is that compounds of molecular formula C4H
10O can exhibit one kind of stereoisomerism
but not another.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
b) Butanone and phenylhydrazine react together as shown by the following equation to give butanonephenylhydrazone, a compound which exhibits stereoisomerism.
(i) What kind of stereoisomerism is shown by butanone phenylhydrazone?
....................................................................................................................................................................... [1]
(ii) Draw the structural formulae of the two stereoisomers.
[2]
(iii) State one physical property which could help you to distinguish between the stereoisomers.
....................................................................................................................................................................... [1]
C = O + H2N – NHC
6H
5 → C = N – NHC
6H
5 + H
2O
C2H
5
CH3
C2H
5
CH3
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A2 Level TOPIC 23 Questionsheet 4
13
STRUCTURE OF BENZENE
a) Cyclohexene, C6H
10, reacts with hydrogen to form cyclohexane, C
6H
12. The enthalpy of hydrogenation
is –120 kJ mol-1.
(i) Suggest the conditions that would be used for this reaction.
....................................................................................................................................................................... [1]
(ii) Give the structure of the hypothetical species cyclohexa-1,3,5-triene.
[1]
(iii) Calculate the value you would expect for the enthalpy of hydrogenation of this species.
...........................................................................................................................................................................
....................................................................................................................................................................... [1]
(iv) Benzene, C6H
6, has essentially the same formula as cyclohexa-1,3,5-triene, but its enthalpy of
hydrogenation is only –208 kJ mol-1. Comment upon the difference between this value and thatobtained in a) (iii).
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
b) The structure of benzene is said to consist of a 6-membered carbon ring, with a system of delocalisedelectrons. Although unsaturated, it exhibits different reactions from those of the alkenes.
(i) Explain the meaning of the terms delocalised and unsaturated.
Delocalised ...............................................................................................................................................
............................................................................................................................................................... [2]
Unsaturated ......................................................................................................................................... [1]
(ii) What structure would you expect benzene to have if it showed reactions similar to the alkenes?
[1]
(iii) Give three pieces of evidence that benzene does not have such a structure.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
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STRUCTURES OF CYCLOALKENESTOPIC 23 Questionsheet 5
I II IIIa) Name the alkenes I, II and III.
Alkene I ......................................................................................................................................................... [1]
Alkene II ....................................................................................................................................................... [1]
Alkene III ...................................................................................................................................................... [1]
b) Complete the following equations for the complete hydrogenation of alkenes I and II.
+ .......... H2
→ ∆Hê r = -119.6 kJ mol-1 [1]
+ .......... H2
→ ∆Hê r = -231.7 kJ mol-1 [1]
c) Use the molar enthalpies of hydrogenation shown in b) to draw what conclusions you can about the bondingbetween the carbon atoms in alkene II.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
d) How would you expect the lengths of the carbon-carbon bonds in alkene II to compare with one another? Inyour answer, refer to the bonds by the letters a, b, c, d, e and f as shown below.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
e) Estimate, with reasons, the molar enthalpy of hydrogenation of alkene III.
Estimate ......................................................................................................................................................... [1]
Reasons .............................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
a
b
cd
e
f
...............
...............
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BOND TYPE AND REACTIVITYTOPIC 23 Questionsheet 6
a) Alkenes are readily attacked by electrophiles, but alkanes resist attack by both electrophiles and nucleophiles.(i) Give two reasons for the high reactivity of alkenes towards electrophiles.
1 .................................................................................................................................................................
2 ............................................................................................................................................................. [2]
(ii) Give two reasons for the low reactivity of alkanes.
1 .................................................................................................................................................................
2 ............................................................................................................................................................. [2]
b) The negative inductive effect (-I effect) is said to be responsible for the nucleophilic substitution reactions ofhaloalkanes.(i) What is the immediate consequence of the ‘negative inductive effect’, and what is responsible for it?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(ii) List the haloalkanes RBr, RCl and RI in increasing order of reactivity in nucleophilic substitution reactions.
....................................................................................................................................................................... [1]
(iii) Explain your answer to b)(ii).
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
c) Despite the strength of the C=O bond (average bond enthalpy = 743 kJ mol-1), aldehydes and ketones reactreadily with numerous reagents, e.g. HCN.(i) What type of reagent attacks aldehydes and ketones?
....................................................................................................................................................................... [1]
(ii) Give two reasons why species such as CN- are strongly attracted to the carbonyl carbon atom of analdehyde or ketone.
1 .........................................................................................................................................................................
2 ..................................................................................................................................................................... [2]
(iii)When HCN reacts with an aldehyde or ketone, why does an addition reaction occur rather than substitution?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(iv) Species, such as CN-, which react with aldehydes and ketones, do not generally attack alkenes. Why is this?
....................................................................................................................................................................... [1]
(v) It can be argued that HCN should react with alkenes in the same way as HBr, yet this does not happen.Explain this.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]17
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REACTION CONDITIONS AND PRODUCTTOPIC 23 Questionsheet 7
16
a) In the presence of ultraviolet light, methylbenzene reacts with chlorine to give (chloromethyl)benzene:
The mechanism resembles that for the chlorination of methane.(i) Name this mechanism.
....................................................................................................................................................................... [1]
(ii) What type of fission does the chlorine molecule undergo?
....................................................................................................................................................................... [1]
(iii) Write likely equations for the three mechanistic stages.Stage 1
[1]Stage 2
[2]Stage 3
[1]
b) In the absence of ultraviolet light, methylbenzene reacts with chlorine to give an entirely different product.(i) Write an equation for this reaction.
[1]
(ii) Name a suitable catalyst for the reaction.
....................................................................................................................................................................... [1]
(iii) What type of mechanism is involved?
....................................................................................................................................................................... [1]
(iv) What type of fission does the chlorine molecule undergo?
....................................................................................................................................................................... [1]
c) By referring to the chemistry of a haloalkane of your own choice, give another example of the way in whichthe product of a reaction can be completely altered by changing the conditions. In your answer you shouldmention reaction conditions, identity of products, and types of mechanism.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [6]
CH3
+ Cl2 → + HCl
CH2Cl
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NITRATION OF ARENES
14
a) Give the reagents, conditions and equation for the mononitration of benzene.
Reagents ........................................................................................................................................................ [2]
Conditions ..................................................................................................................................................... [1]
Equation
[1]
b) (i) In what way must the conditions be modified when carrying out the mononitration of methylbenzene(toluene)?
....................................................................................................................................................................... [1]
(ii) Suggest two ways in which the conditions could be changed so as to bring about dinitration or polynitrationof arenes.
1 .................................................................................................................................................................
2 ............................................................................................................................................................. [2]
(iii) Write down the formula of the end-product of the trinitration of methylbenzene and state the use of thiscompound.
Formula
[1]
Use......................................................................................................................................................... [1]
c) Nitroarenes can be converted to primary aromatic amines.
(i) Write an equation for the conversion of nitrobenzene to phenylamine.
....................................................................................................................................................................... [1]
(ii) What type of reaction is this?
....................................................................................................................................................................... [1]
(iii) What reagent (or reagents) would be used for this conversion in the laboratory?
....................................................................................................................................................................... [2]
(iv) Of what commercial importance is this type of reaction?
....................................................................................................................................................................... [1]
TOPIC 23 Questionsheet 8
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11
HALOGENATION OF ARENES
a) Cyclohexene and benzene are both cyclic hydrocarbons with a six-membered carbon ring, yet they behavevery differently in their reactions with halogens.
(i) State the conditions and write an equation for the reaction between bromine and cyclohexene.
Conditions ............................................................................................................................................. [2]
Equation
[1]
(ii) What type of reaction is this?
....................................................................................................................................................................... [1]
b) (i) State the conditions and write an equation for the reaction between bromine and benzene.
Conditions ............................................................................................................................................. [2]
Equation
[1]
(ii) What type of reaction is this?
....................................................................................................................................................................... [1]
c) How do you account for the relative resistance to bromination of benzene compared with cyclohexene?
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
TOPIC 23 Questionsheet 9
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13
ALKYLATION AND ACYLATION OF ARENES
a) (i) Benzene can be converted into methylbenzene by a so-called Friedel-Crafts reaction. Name a suitablereagent for the conversion, state the reaction conditions, and write an equation.
Reagent .................................................................................................................................................. [1]
Conditions ............................................................................................................................................. [2]
Equation
[1]
(ii) What is the major disadvantage of this method of preparing methylbenzene?
....................................................................................................................................................................... [1]
(iii) How could methylbenzene be converted into benzenecarboxylic acid? State the type of reaction andsuggest a suitable reagent.
Type of reagent ...................................................................................................................................... [1]
Reagent .................................................................................................................................................. [1]
b) (i) How does benzene react with ethanoyl chloride? State the reaction conditions, write an equation andname the product.
Conditions ............................................................................................................................................. [2]
Equation
[1]
Name of product .................................................................................................................................... [1]
(ii) How could the product of b)(i) be converted into 1-phenylethanol? State the type of reaction and suggesta suitable reagent.
Type of reaction ..................................................................................................................................... [1]
Reagent .................................................................................................................................................. [1]
TOPIC 23 Questionsheet 10
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18
PHENOL
a)
Compounds I-IV are all aromatic hydroxy-compounds, yet not all of them are phenols. Identify the phenolsand give the basis of your identification.
Identity of phenols ......................................................................................................................................... [1]
Basis of identification ........................................................................................................................................
....................................................................................................................................................................... [1]
b) (i) To demonstrate its acidic character, phenol (which has a low solubility in water) can be dissolved inaqueous sodium hydroxide to give a colourless solution, A. On adding dilute hydrochloric acid, thissolution becomes cloudy at first and then separates to give a colourless oil, B, as a lower layer. IdentifyA and B, and write equations for the reactions involved.
Identity of A .......................................................................................................................................... [1]
Identity of B ......................................................................................................................................... [1]
Equations
[2]
(ii) Give two reasons which together explain the fact that phenols are acidic, although alcohols have almostno acidic properties.
Reason 1 ....................................................................................................................................................
............................................................................................................................................................... [3]
Reason 2 ....................................................................................................................................................
............................................................................................................................................................... [3]
c) (i) State what is observed when bromine water is added to an aqueous solution of phenol.
....................................................................................................................................................................... [1]
(ii) Write an equation for the reaction.
[1]
(iii) How do you account for the relative ease of bromination of phenol compared with benzene?
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
d) State one use of phenols in everyday life.
....................................................................................................................................................................... [1]
OH CH2OHCH
3
OH
OH
OHI II III IV
TOPIC 23 Questionsheet 11
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10
ALDEHYDES AND KETONES
a) A CH3CH
2CHO B (CH
3)
2CHCHO C CH
3CH
2COCH
3
From the above list, select all the compounds which satisfy the following requirements. Write down theirletters and name them.
(i) Could be reduced to a secondary alcohol.
....................................................................................................................................................................... [1]
(ii) Could be oxidised to a carboxylic acid.
....................................................................................................................................................................... [2]
TOPIC 23 Questionsheet 12
b) Aldehydes can be distinguished from ketones by their reaction with Tollens’ reagent (ammoniacal silver nitrateor diammine silver(1))(i) Describe what you would see with an aldehyde
....................................................................................................................................................................... [1]
(ii) What would propanal become when treated with Tollens’ reagent
....................................................................................................................................................................... [1]
(iii) Name a reagent that could be used in place of Tollens’ reagent for this test and state the observation withthe aldehyde.
Reagent .....................................................................................................................................................
Observation ..............................................................................................................................................
............................................................................................................................................................... [2]
c) Aldehydes and ketones can be reduced to alcohols by a reducing agent.(i) Name a reducing agent
....................................................................................................................................................................... [1]
(ii) State the conditions under which this reagent is used...
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
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20
USE OF 2,4-DINITROPHENYLHYDRAZINE
A compound contains C 69.8% H 11.6% O 18.6%Its mass spectrum shows that its relative molecular mass is 86. On treatment with 2,4-dinitrophenylhydrazine,an orange-yellow crystalline precipitate is produced.
a) Determine the molecular formula of the compound.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
b) Give the structural formulae of all the relevant isomers and classify each one as an aldehyde or a ketone.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [7]
c) Write an equation to show how any one of these compounds will react with 2,4-dinitrophenylhydrazine.
[2]
d) Give one chemical method of distinguishing the aldehydes from the ketones. State the reagent you woulduse, the conditions of the test, and what would expect to observe with aldehydes and with ketones.
Test ................................................................................................................................................................. [1]
Conditions ..................................................................................................................................................... [1]
Observation with aldehydes .......................................................................................................................... [1]
Observation with ketones ........................................................................................................................... [1]
e) The precipitate obtained when an aldehyde or ketone is reacted with 2,4-dinitrophenylhydrazine can be used toidentify the original compound if its melting point is determined.(i) How can this melting point be used to identify the original carbonyl compound?
....................................................................................................................................................................... [1](ii) What must be done to the precipitate before the melting point is determined and why?
....................................................................................................................................................................... [3]
TOPIC 23 Questionsheet 13
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14
THE TRIIODOMETHANE REACTION
a) Ethanal reacts with a solution of iodine in KI(aq), followed by a limited amount of NaOH(aq), to givetriiodomethane.
(i) What is observed?
....................................................................................................................................................................... [1]
(ii) Write balanced chemical equations for the two reactions which occur.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(iii) If excess NaOH(aq) is used, no precipitate is formed. Suggest what causes this difference
....................................................................................................................................................................... [1]
(iv) Explain why a mixture of KI(aq) and NaClO(aq) could be used instead of iodine solution.
...........................................................................................................................................................................
...................................................................................................................................................................... [2]
b) The group CH3CO is essential for the production of triiodomethane. Bearing this in mind, suggest why
(i) compounds with the CH3CH(OH) group undergo this reaction
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
(ii) compounds with the CH3COO- group do not undergo this reaction
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
c) Study the following compounds, and write down the reference letters of all those which will producetriiodomethane on treatment with iodine and sodium hydroxide.
A C6H
5COCH
3F CH
3CH(OH)CH
3
B C6H
5COOCH
3G CH
3CH(OH)C
2H
5
C C6H
5COC
2H
5H (CH
3)
3COH
D CH3CH
2CHO I C
2H
5CH(OH)C
2H
5
E CH3COC
2H
5J CH
3CH
2CH
2CH
2OH
....................................................................................................................................................................... [4]
TOPIC 23 Questionsheet 14
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16
GRIGNARD REAGENTS
a) Describe the preparation of methylmagnesium iodide and write an equation for its formation.
Preparation ........................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
Equation ........................................................................................................................................................ [4]
b) Starting from methylmagnesium iodide, how would you prepare (i) ethanol, and (ii) ethanoic acid?In each case name the required reagent, show the structure of the intermediate, and state any necessaryconditions for the second stage.
(i) Ethanol
Reagent .................................................................................................................................................. [1]
Intermediate
[1]
Conditions for second stage .................................................................................................................. [1]
(ii) Ethanoic acid
Reagent .................................................................................................................................................. [1]
Intermediate
[1]
Conditions for second stage .................................................................................................................. [1]
c) Methylmagnesium iodide was allowed to react with each of two isomeric compounds A and B of molecularformula C
3H
6O. The final products were isomeric compounds C and D, of molecular formula C
4H
10O. The
mass spectrum of C showed peaks at m/z values of 29 and 30, but that of D did not. Identify A, B, C and D,and suggest the species responsible for the peaks mentioned in the mass spectrum of C.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [6]
TOPIC 23 Questionsheet 15
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15
CARBOXYLIC ACIDS I
a) Ethanoic acid reacts with (i) aqueous potassium hydroxide, and (ii) solid magnesium oxide?Name the product and type of reaction in each case, and give a balanced equation.
(i) aqueous potassium hydroxide
Product ................................................................................................................................................. [1]
Type of reaction ................................................................................................................................... [1]
Equation ............................................................................................................................................... [1]
(ii) solid magnesium oxide
Product ................................................................................................................................................. [1]
Type of reaction ................................................................................................................................... [1]
Equation ............................................................................................................................................... [1]
b) Give a reagent that can be used, at room temperature, to show that an unknown organic compound is acarboxylic acid rather than an alcohol. State your expected observation, and write an equation to show thisreagent reacting with a carboxylic acid, RCOOH.
Reagent ......................................................................................................................................................... [1]
Observation .................................................................................................................................................. [1]
Equation ....................................................................................................................................................... [1]
c) Butyl ethanoate (‘pear drops’) is a useful solvent for cellulose lacquers, but occurs naturally only in traces.How can it be made synthetically? Name the reagents you would use, state the reaction conditions, write anequation and describe the type of reaction occurring.
Reagents ........................................................................................................................................................ [3]
Conditions ..................................................................................................................................................... [1]
Equation ........................................................................................................................................................ [1]
Type of reaction .................................................................................................................................................
....................................................................................................................................................................... [1]
TOPIC 23 Questionsheet 16
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20
CARBOXYLIC ACIDS IIa) How do you explain the following facts?
(i) Carboxylic acids have lower pKa values than alcohols, showing that they are more strongly acidic.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
(ii) Trichloroethanoic acid is a relatively strong carboxylic acid.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
b) Starting with propanoic acid, how could you obtain (i) propanoyl chloride and then (ii) propanamide? Givea reagent and write an equation for each reaction.
(i) Reagent .................................................................................................................................................. [1]
Equation ................................................................................................................................................ [1]
(ii) Reagent .................................................................................................................................................. [1]
Equation ................................................................................................................................................ [1]
c) Benzene-1,4-dicarboxylic acid has the normal reactions of a carboxylic acid. Describe how would you expectit to react with each of the following reagents and give the formula of the organic product.
(i) Aqueous sodium carbonate
Description ................................................................................................................................................
............................................................................................................................................................... [2]
Formula of product ............................................................................................................................... [1]
(ii) Methanol
Description ................................................................................................................................................
............................................................................................................................................................... [2]
Formula of product .............................................................................................................................. [1]
d) Benzene-1,2-dicarboxylic acid is an isomer of benzene-1,4-dicarboxylic acid. Which of the two isomerswould you expect to have the higher melting point? Give your reasons.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
TOPIC 23 Questionsheet 17
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16
ACYL CHLORIDES
a) The ester, ethyl propanoate, can be prepared by the reaction between ethanol and propanoic acid. This method,however, is not entirely satisfactory. Name an acyl chloride which could be used instead of propanoic acid,and state two advantages and two disadvantages of doing so.
Name .............................................................................................................................................................. [1]
Two advantages .................................................................................................................................................
....................................................................................................................................................................... [2]
Two disadvantages ............................................................................................................................................
....................................................................................................................................................................... [2]
b) Acyl chlorides can also be used to prepare other derivatives of carboxylic acids, such as amides.
(i) What acyl chloride and what reagent would be needed to prepare benzenecarboxamide (benzamide)?
Acyl chloride ......................................................................................................................................... [1]
Reagent .................................................................................................................................................. [1]
(ii) What type of reaction is this?
....................................................................................................................................................................... [1]
(iii) What problem might be encountered when carrying out such preparations in the laboratory? Explain thechemical origin of the problem, and state what precaution could be taken to minimise it.
Problem ................................................................................................................................................. [1]
Origin .................................................................................................................................................... [1]
Precaution ............................................................................................................................................. [1]
c) Certain acyl chlorides are useful reagents for the positive identification of amines.
(i) Describe how ethanoyl chloride can be used to confirm the identity of an amine, believed (from itsboiling point) to be ethylamine.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
(ii) Write an equation for the reaction occurring in c)(i) and name the product.
Equation ................................................................................................................................................ [1]
Name ..................................................................................................................................................... [1]
TOPIC 23 Questionsheet 18
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17
ESTERS
a) Give the structural formulae and names of three isomeric esters of molecular formula C4H
8O
2.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [6]
b) Study the following scheme and answer the questions below.
Conversion 1
O
CH2 – O – C – CH
2CH
2CH
3
CH2 – O – C – CH
2CH
2CH
3
O
Compound 1 Compound II Compound III
(i) Complete Conversion 1 by writing down the structural formulae of Compound II (molecular formulaC
2H
6O
2) and Compound III (C
4H
8O
2)
[2]
(ii) What types of compound are I, II and III?
Compound I ........................................................................................................................................... [1]
Compound II .......................................................................................................................................... [1]
Compound III ........................................................................................................................................ [1]
(iii) What type of reaction is represented by Conversion 1?
....................................................................................................................................................................... [1]
(iv) Why is Conversion 1 carried out using aqueous sodium hydroxide rather than aqueous mineral acid?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
c) Give three commercial applications of esters.
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
Boil under reflux with NaOH(aq)
Then acidify with dil. HCl(aq).............................. + ..............................
TOPIC 23 Questionsheet 19
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15
NITRILES
4.0 g of an aliphatic nitrile, G, was boiled under reflux with excess sodium hydroxide solution until reaction wascomplete. The reaction mixture was then acidified with excess dilute sulfuric acid to displace the organic acid, H.After distillation, a total of 4.5 g of H were recovered. 1.0 g of H was then diluted to 250 cm3 with water; 25.0cm3 of this solution required 16.65 cm3 of 0.1 M sodium hydroxide solution for complete neutralisation.
a) Calculate the relative molecular mass of H.
...........................................................................................................................................................................
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
b) Identify H, and hence identify G.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
c) Write the equation for:
(i) the reaction of G with aqueous sodium hydroxide.
....................................................................................................................................................................... [1]
(ii) the subsequent reaction with dilute sulfuric acid.
....................................................................................................................................................................... [1]
d) Calculate the percentage yield of H.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
e) How could the nitrile G be reduced? Suggest a suitable reducing agent, together with any conditions, andwrite an equation.
Reducing agent .............................................................................................................................................. [1]
Conditions ..................................................................................................................................................... [1]
Equation ........................................................................................................................................................ [1]
TOPIC 23 Questionsheet 20
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14
AMIDES
a) It is possible to convert an amide into two primary amines. Scheme A shows how ethanamide can be convertedto ethylamine. How can it be converted to methylamine?
Scheme A
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
b) Nitriles have been described as the ‘anhydrides of amides’.(i) Give the name and formula of the nitrile which can be regarded as the anhydride of ethanamide.
....................................................................................................................................................................... [2]
(ii) How can ethanamide be converted into the nitrile you have named in b)(i)?
....................................................................................................................................................................... [2]
(iii) What type of reaction is this?
....................................................................................................................................................................... [1]
c) Amides, like esters, can be hydrolysed in either acidic or alkaline solution. These reactions can be used in thelaboratory to detect the presence of an amide, as illustrated for ethanamide by Scheme B.
Scheme B Solution A
Solution B + Gas C
Solution A smells of vinegar, and gas C, which has a characteristic smell, turns moist red litmus paper blue.Identify the smelly compound in Solution A, the compound in Solution B, and also gas C.
Smelly compound in Solution A ..................................................................................................................... [1]
Compound in Solution B ............................................................................................................................... [1]
Gas C ............................................................................................................................................................. [1]
d) All amides contain the following group of atoms : – C – N – This group forms a link in various long chainmolecules.(i) What name is given to this link?
....................................................................................................................................................................... [1]
(ii) Name a synthetic polymer containing this link.
....................................................................................................................................................................... [1]
(iii) What type of natural polymer contains this link?
....................................................................................................................................................................... [1]
Li[AlH4]
Ethylamine
Methylamine
CH3CONH
2
Ethanamide
CH3CH
2NH
2
CH3NH
2
Boil with H2SO4
(aq)
CH3CONH
2 Boil with NaOH(aq)
O H
in dry ether
TOPIC 23 Questionsheet 21
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20
AMINES
a) (i) Write an ionic equation to show why an aqueous solution of methylamine is alkaline.
....................................................................................................................................................................... [1]
(ii) Use your equation to explain why, on adding NaOH(aq), the fishy, ammoniacal smell of methylamineis intensified.
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
b) Although phenylamine is almost insoluble in water, it dissolves readily in dilute hydrochloric acid to give acolourless solution of compound A. On neutralising this solution with aqueous sodium hydroxide, a colourless,oily liquid, B is formed. Name compounds A and B, and write equations for the two reactions.
Name of A .................................................................................................................................................... [1]
Name of B .................................................................................................................................................... [1]
Equation 1 .................................................................................................................................................... [1]
Equation 2 .................................................................................................................................................... [1]
c) State whether (i) ethylamine, and (ii) phenylamine is a weaker or stronger base than ammonia, and givereasons for your answers in both cases.
(i) EthylamineStrength compared with ammonia ......................................................................................................... [1]
Reasons .....................................................................................................................................................
...................................................................................................................................................................
............................................................................................................................................................... [3]
(ii) PhenylamineStrength compared with ammonia ......................................................................................................... [1]
Reasons .....................................................................................................................................................
...................................................................................................................................................................
............................................................................................................................................................... [3]
d) The acylation of amines is useful in their identification. The product is purified by recrystallisation, afterwhich its melting point is determined and compared with published values in a data book.
(i) What is meant by the term ‘acylation’?
....................................................................................................................................................................... [2]
(ii) Name a suitable acylating agent.
....................................................................................................................................................................... [1]
(iii) What type of compound is the product?
....................................................................................................................................................................... [1]
(iv) Write an equation to show phenylamine reacting with the reagent you have chosen in d)(ii).
....................................................................................................................................................................... [1]
TOPIC 23 Questionsheet 22
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17
DIAZOTISATION
a) (i) What is the meaning of the term ‘diazotisation’?
....................................................................................................................................................................... [1]
(ii) Name the compounds you would use in the laboratory for the diazotisation of phenylamine. Also namethe product, and write the equation for the reaction.
Compound needed for diazotisation ..................................................................................................... [2]
Name of product .................................................................................................................................... [1]
Equation ................................................................................................................................................ [1]
(iii) Give the optimum temperature (or temperature range) for the diazotisation of phenylamine, and state theproblems that would be encountered if the temperature were too high or too low.
Optimum temperature ........................................................................................................................... [1]
Problem if the temperature were too high .................................................................................................
............................................................................................................................................................... [2]
Problem if the temperature were too low .............................................................................................. [1]
b) (i) How does the product from a)(ii) react with 2-naphthol (β-naphthol)?Give the conditions, state what you would observe as a result of this reaction, and write an equation.
Conditions ............................................................................................................................................. [2]
Observation ........................................................................................................................................... [1]
Equation
[2]
(ii) What name is given to the type of reaction in b)(i)?
....................................................................................................................................................................... [1]
c) How would the type of reaction in b) help you to distinguish between the following compounds?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
NH2
CH3
CH2NH
2
A B
TOPIC 23 Questionsheet 23
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13
AMINO ACIDS
a) Naturally occurring amino acids are described as α-amino acids. Write down the general formula of anα-amino acid.
....................................................................................................................................................................... [1]
b) Glycine, H2NCH
2COOH, and glycollic acid, HOCH
2COOH, have very similar relative molecular masses, yet the
melting point of glycine (232 °C) is much higher than that of glycollic acid (79 °C). How can you explain this?
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [4]
c) (i) Experiments on electrophoresis, i.e. the movement of charged particles in an electric field, show that, inaqueous solution at low pH, amino acid particles migrate to the negative electrode, while at high pHthey move to the positive electrode. Write ionic equations to show the formation of particles responsiblefor electrophoresis at low and high pH values.
Equation (low pH) ................................................................................................................................. [1]
Equation (high pH) ............................................................................................................................... [1]
(ii) At an intermediate pH, there is no electrophoretic movement. Why?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
d) (i) CH3 CH
2OH
H2N – CH – COOH H
2N – CH – COOH
Alanine Serine
The two amino acids alanine and serine, shown above, can combine together by an enzyme catalysedreaction to form one of two dipeptides; compounds which are essentially amides. Write equations toshow the formation of two different dipeptides from alanine and serine.
[2]
(ii) Although the two dipeptides in d)(i) are amino acids, they are not α-amino acids. Explain this statement.
...........................................................................................................................................................................
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
TOPIC 23 Questionsheet 24
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13
PROTEINS
a) Proteins and polypeptides are natural polymers derived from α-amino acid molecules.
(i) Give the name and formula of the link between the amino acid molecules.
Name .............................................................................................................................................................. [1]
Formula ......................................................................................................................................................... [1]
(ii) What type of polymerisation is involved?
....................................................................................................................................................................... [1]
(iii) Explain why it is that the same combination of amino acids can give rise to different proteins orpolypeptides.
....................................................................................................................................................................... [1]
(iv) Give one difference between a protein and a polypeptide.
....................................................................................................................................................................... [1]
b) State two ways in which the structure of a protein depends on hydrogen bonding.
1 .........................................................................................................................................................................
2 ..................................................................................................................................................................... [2]
c) (i) To identify its constituent amino acids, a protein must first be broken down into those amino acids. Howcan this be achieved in the laboratory?
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
(ii) Suggest a method by which the individual amino acids could then be separated and identified.
....................................................................................................................................................................... [1]
d) Insulin, used in the treatment of diabetes, is a peptide which is taken by injection through the skin. Whycannot medicines, of which the active ingredient is a peptide, be taken by mouth?
...........................................................................................................................................................................
....................................................................................................................................................................... [2]
TOPIC 23 Questionsheet 25
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TEST QUESTION 1CARBONYL COMPOUNDS
TOPIC 23 Questionsheet 26
Below is the skeletal formula of testosterone.
a) What is its molecular formula?
....................................................................................................................................................................... [1]
b) State what you would expect to see when it is treated with the following reagents:(i) Brady’s reagent (2,4-dinitrophenylhydrazine)
....................................................................................................................................................................... [1](ii) Heating under reflux with acidified potassium dichromate(VI)
....................................................................................................................................................................... [1](iii) Aqueous bromine
....................................................................................................................................................................... [1]
c) Draw the skeletal formula of the compound that you would expect to be formed when testosterone is treatedwith either aqueous sodium borohydride or lithium aluminium hydride in dry ether.
[2]
d) Draw the skeletal formula of the compound that you would expect to be formed when testosterone is heatedunder reflux with acidified potassium dichromate(VI)
[2]
(Continued...)
CH3
OH
CH3
O
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TEST QUESTION 1CARBONYL COMPOUNDS
TOPIC 23 Questionsheet 26 Continued
12
e) Z-hex-3-enal (cis-hex-3-enal), whose skeletal formula is shown below, is the smell of newly cut grass.
Draw the skeletal formula of the product you would expect to be produced when it is heated under reflux withacidified potassium dichromate(VI).
[2]f) The skeletal formulae of three other compounds are labelled A- C below.
(i) Which of the above compounds is a stereoisomer of Z-hex-3-enal?
....................................................................................................................................................................... [1]
(ii) Which of the above compounds is a structural isomer of Z-hex-3-enal?
....................................................................................................................................................................... [1]
O
O O OA B C
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TEST QUESTION 1IPHENOLS
TOPIC 23 Questionsheet 27
Quinizarin is currently used as a marker in low taxed fuel, which can only be used forpurposes such as agricultural tractors. Customs and Excise can test fuels by adding aqueoussodium hydroxide. If a purple colour appears in the sodium hydroxide solution, the quinizarinwas in the fuel and therefore only a low tax was paid.
a) Other than phenol, what functional group is present in quinizarin?
....................................................................................................................................................................... [1]
b) What is the molecular formula of quinizarin?
....................................................................................................................................................................... [1]
c) What is the empirical formula of quinizarin?
....................................................................................................................................................................... [1]
d) (i) Draw the structural formula of the product of the reaction of quinizarin with excess sodium hydroxide.
[2](ii) Why does this compound dissolve in water, whilst quinizarin dissolves in the hydrocarbon fuel?
...........................................................................................................................................................................
....................................................................................................................................................................... [3]
e) Draw the structural formula that you would expect when the compoundis treated with excess bromine dissolved in an inert solvent.
[2]
11
H O CH CH2
OH
OH
O
O
Quinizarin
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