Alkenes and Alcohols

WMP/Jun10/CHEM2

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Section B

Answer all questions in the spaces provided.

8 Glucose, produced during photosynthesis in green plants, is a renewable source fromwhich ethanol can be made. Ethanol is a liquid fuel used as a substitute for petrol.The processes involved can be summarised as follows.

Process 1 Photosynthesis in green plants6CO2 + 6H2O C6H12O6 + 6O2

Process 2 Fermentation of glucose to form ethanol

Process 3 Complete combustion of ethanolCH3CH2OH + 3O2 2CO2 + 3H2O

8 (a) State three essential conditions for the fermentation of aqueous glucose in Process 2.

Write an equation for the reaction that takes place during this fermentation.

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8 (b) It has been claimed that there is no net carbon (greenhouse gas) emission to theatmosphere when ethanol made by Process 2 is used as a fuel.

State the term that is used to describe fuels of this type.

Use the equations for Processes 1, 2 and 3 to show why it can be claimed that there isno net emission of carbon-containing greenhouse gases.

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WMP/Jun10/CHEM2

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8 (c) Use the information from the equation for Process 3 on page 16 and the mean bondenthalpies from the table below to calculate a value for the enthalpy change for thisprocess.

Give one reason why the value calculated from mean bond enthalpies is different fromthe value given in a data book.

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C–H C–C C–O O–H C=O O=O

Mean bondenthalpy / kJ mol–1 +412 +348 +360 +463 +743 +496

WMP/Jun10/CHEM2

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8 (d) A student carried out a simple laboratory experiment to measure the enthalpy changefor Process 3. The student showed that the temperature of 200 g of water increasedby 8.0 °C when 0.46 g of pure ethanol was burned in air and the heat produced wasused to warm the water.

Use these results to calculate the value, in kJ mol–1, obtained by the student for thisenthalpy change. (The specific heat capacity of water is 4.18 J K–1 g–1)

Give one reason, other than heat loss, why the value obtained from the student’sresults is less exothermic than a data book value.

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WMP/Jan10/CHEM2(16)

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9 There are four isomeric alcohols with the molecular formula C4H10O

9 (a) Two of these are butan-l-ol (CH3CH2CH2CH2OH) and butan-2-ol.The other two isomers are alcohol X and alcohol Y.

Draw the displayed formula for butan-2-ol.

Alcohol X does not react with acidified potassium dichromate(VI) solution.Give the structure of alcohol X.

Name the fourth isomer, alcohol Y.

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SECTION B

Answer all questions in the spaces provided.

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9 (b) The infrared spectrum of one of these isomeric alcohols is given below.

Identify one feature of the infrared spectrum which supports the fact that this is analcohol. You may find it helpful to refer to Table 1 on the Data Sheet.

Explain how infrared spectroscopy can be used to identify this isomeric alcohol.

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4000 3000 2000Wavenumber / cm–1

1500 1000 500

Transmittance / %

100

50

0

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9 (c) British scientists have used bacteria to ferment glucose and produce the biofuelbutan-l-ol.

Write an equation for the fermentation of glucose (C6H12O6) to form butan-l-ol, carbondioxide and water only.

State one condition necessary to ensure the complete combustion of a fuel in air.

Write an equation for the complete combustion of butan-l-ol and state why it can bedescribed as a biofuel.

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9 (d) Butan-l-ol reacts with acidified potassium dichromate(VI) solution to produce twoorganic compounds.

State the class of alcohols to which butan-l-ol belongs.

Draw the displayed formula for both of the organic products.

State the type of reaction that occurs and the change in colour of the potassiumdichromate(VI) solution.

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WMP/Jun12/CHEM2

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7 (b) The equation for the first reaction in the conversion of hex-3-ene into hexan-3-ol isshown below.

CH3CH2CH CHCH2CH3 + H2SO4 CH3CH2CH2CH(OSO2OH)CH2CH3

Outline a mechanism for this reaction.

(4 marks)

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WMP/Jun12/CHEM2

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Section B

Answer all questions in the spaces provided.

8 The reaction of butane-1,4-diol with butanedioic acid produces the polymer PBS usedin biodegradable packaging and disposable cutlery.

Butanedioic acid is produced by two different processes.

Process 1

l Aqueous sodium hydroxide reacts with 1,4-dibromobutane to make butane-1,4-diol. l Butane-1,4-diol is oxidised to butanedioic acid.

Process 2

l Glucose reacts with carbon dioxide in the presence of microorganisms to producebutanedioic acid directly.

l The carbon dioxide used in this process is obtained from a local factory thatproduces bioethanol.

8 (a) Deduce one safety reason and one environmental reason why Process 2 is preferredto Process 1.

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WMP/Jun12/CHEM2

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8 (c) In the production of bioethanol, glucose (C6H12O6) is converted into a dilute aqueoussolution of ethanol and carbon dioxide.

Give the name of this process and state three essential conditions necessary toproduce a good yield of ethanol.

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8 (d) State the class of alcohols to which the diol butane-1,4-diol belongs.

Identify a suitable reagent or combination of reagents for the conversion ofbutane-1,4-diol into butanedioic acid (HOOCCH2CH2COOH).

Write an equation for this oxidation reaction using [O] to represent the oxidising agent.

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WMP/Jan12/CHEM2

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Section B

Answer all questions in the spaces provided.

9 Three different ways of producing ethanol are shown below.

Reaction 1 Reaction 2C6H12O6 CH3CH2OH CH3CH2Brglucose ethanol bromoethane

Reaction 3

H2C CH2ethene

9 (a) Reaction 1 produces a 15% aqueous solution of ethanol.It is claimed that the ethanol produced in this way is a carbon-neutral biofuel.

Write an equation for Reaction 1 and name the process.

Write an equation for the complete combustion of ethanol.

Explain why the ethanol produced by this process may not be a carbon-neutral biofuel.

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WMP/Jan12/CHEM2

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9 (b) Give a reagent and conditions for Reaction 2.

Reaction 2CH3CH2Br CH3CH2OH

Name and outline a mechanism for Reaction 2.

Suggest one reason, other than safety, why this method is not used in industry tomake ethanol.

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9 (c) Reaction 3 is used in industry.

Reaction 3H2C CH2 CH3CH2OH

Identify a suitable catalyst for Reaction 3.

Identify the type of reaction.

Give two conditions, in addition to the presence of a catalyst, necessary for Reaction 3to produce a high yield of ethanol.

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WMP/Jan13/CHEM2

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5 Glucose is an organic molecule. Glucose can exist in different forms in aqueoussolution.

5 (a) In aqueous solution, some glucose molecules have the following structure.

5 (a) (i) Deduce the empirical formula of glucose.

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5 (a) (ii) Consider the infrared spectrum of solid glucose.

State why it is possible to suggest that in the solid state very few molecules have thestructure shown.You may find it helpful to refer to Table 1 on the Data Sheet.

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C

H OH

OH

C

H

CH

OHH

OH

C

H

C O

H

OH

C

HH

30004000 2000

Wavenumber / cm–1

1500 1000 500

Transmittance / %

100

50

0

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5 (b) In the absence of oxygen, an aqueous solution of glucose can be fermented to produceethanol for use in alcoholic drinks.

Write an equation for this fermentation reaction.Give two other essential conditions for the production of ethanol in this fermentation.

Equation

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Condition 1 ..............................................................................................................................

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5 (c) Any ethanol present in the breath of a drinker can be detected by using a breathalyser.The ethanol is converted into ethanoic acid. The breathalyser has negative and positiveelectrodes. A current is measured and displayed in terms of alcohol content.

The overall redox equation is as follows

CH3CH2OH(I) + O2(g) CH3COOH(I) + H2O(I)

5 (c) (i) Draw the displayed formula for ethanoic acid.

(1 mark)

5 (c) (ii) Deduce a half-equation for the reduction of atmospheric oxygen to water in acidicsolution at one electrode of the breathalyser.

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5 (c) (iii) Deduce a half-equation for the oxidation of ethanol in water to ethanoic acid at the otherelectrode of the breathalyser.

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5 (c) (iv) The earliest breathalysers used laboratory chemicals to oxidise the ethanol to ethanoic acid. Detection was by a colour change.

Identify a reagent or combination of reagents that you would use in the laboratory tooxidise ethanol to ethanoic acid.State the colour change that you would expect to see.

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Colour change ....................................................................................................................(2 marks)

5 (d) The fermentation of glucose from crops is the main method for the production ofethanol. The product is called bioethanol. The European Union has declared thatbioethanol is carbon-neutral.

5 (d) (i) State the meaning of the term carbon-neutral.

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5 (d) (ii) Other than carbon-neutrality, state the main advantage of the use of glucose fromcrops as the raw material for the production of ethanol.

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5 (d) (iii) Give one disadvantage of the use of crops for the production of ethanol.

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WMP/Jun14/CHEM2

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9 Ethanol is an important fuel.

9 (a) A dilute aqueous solution of ethanol can be produced by the fermentation of an aqueous solution of glucose.

It is claimed that the ethanol obtained from this solution is a carbon-neutral biofuel.

Write an equation for this fermentation reaction.

Give two other essential conditions for this reaction to produce a good yield of ethanol.

Name a process used to produce a much more concentrated solution of ethanol from

a dilute aqueous solution.

State the meaning of the term carbon-neutral in the context of this biofuel.[5 marks]

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2 The following pairs of compounds can be distinguished by simple test-tube reactions.

For each pair of compounds, give a reagent (or combination of reagents) that, whenadded separately to each compound, could be used to distinguish between them.State what is observed in each case.

2 (a) Butan-2-ol and 2-methylpropan-2-ol[3 marks]

Reagent ..............................................................................................................................

Observation with butan-2-ol

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Observation with 2-methylpropan-2-ol

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2 (b) Propane and propene[3 marks]

Reagent ...............................................................................................................................

Observation with propane

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Observation with propene

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(04)WMP/Jun15/CHEM2

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6 (b) Draw a displayed formula for the organic product that is formed when propanal isoxidised by warm Tollens’ reagent.

[1 mark]

6 (c) Prop-2-en-1-ol is an isomer of propanal and can be polymerised to form a polymerrepresented by the following structure.

6 (c) (i) Draw the structure of prop-2-en-1-ol.[1 mark]

6 (c) (ii) Deduce the type of polymerisation that results in the formation of this polymer fromprop-2-en-1-ol.

[1 mark]

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(14)WMP/Jun15/CHEM2

H

C C

H

H

CH2OH

n)(

16

7 (a) Propanone can be formed when glucose comes into contact with bacteria in theabsence of air.

7 (a) (i) Balance the following equation for this reaction of glucose to form propanone, carbondioxide and water.

[1 mark]

..........C6H12O6 ..........CH3COCH3 + ..........CO2 + ..........H2O

7 (a) (ii) Deduce the role of the bacteria in this reaction.[1 mark]

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7 (b) Propanone is also formed by the oxidation of propan-2-ol.

7 (b) (i) Write an equation for this reaction using [O] to represent the oxidising agent.[1 mark]

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7 (b) (ii) State the class of alcohols to which propan-2-ol belongs.[1 mark]

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9 Alcohols can be prepared from alkenes in various ways.

9 (a) On a laboratory scale, a mixture of propan-1-ol and propan-2-ol can be prepared frompropene in two steps.

In step 1, propene reacts with cold, concentrated sulfuric acid to form intermediatecompounds.

In step 2, the intermediate compounds react with water to form the mixture of alcohols.

Name and outline the mechanism for the reaction between propene and concentratedsulfuric acid to form the intermediate compound which gives propan-2-ol in step 2.

Explain why propan-2-ol is the major product of this preparation.[7 marks]

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9 (b) On an industrial scale ethanol can be produced from ethene by direct hydration or fromglucose by fermentation.

State the conditions for the direct hydration reaction.

State two advantages and two disadvantages of the fermentation method compared withthe direct hydration method.

[6 marks]

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