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Higher (National 6) Unit 2b: Natures Chemistry Esters, Fats and oils/Proteins

Esters

1. Give the systematic name for the following esters:

a) b) c)

2.

a) Name and draw the full and shortened structural formula for the ester formed when ethanol and propanoic acid combine.

b) What name is given to this type of reaction?

c) Using structural formula, write the equation for the formation of the ester propyl ethanoate.

d) Which word can be used to describe both the ester in (a) and (c)?

3. A pupil made the ester propyl propanoate in a test tube and the reaction mixture was poured into a beaker containing sodium hydrogen carbonate solution.

a) Draw the structural formula of propyl propanoate.

b) Name the acid and carboxylic acid used to make this ester.

c) What two things would the pupil observe when the ester is poured into the sodium hydrogen carbonate solution?

d) The pupil heated the mixture in a water bath. Why was the reaction not heated directly using a Bunsen burner?

e) Name the chemical added to the reaction mixture and explain why it was added?

4. The ester pentyl ethanoate can be hydrolysed using sodium hydroxide.

a) What is meant by HYDROLYSIS of and ester?

b) Draw the structural formula to show the products of this hydrolysis reaction and name the products.

c) Other than the addition of the sodium hydroxide, what else should be done to ensure the ester can by hydrolysed.

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Fats and oils

5.A B C D

a) Which of the molecules shown above are:

(i) Trihydric (ii) dihydric

b) Give both the systematic name and industrial name for the molecule in box A.

c) Which molecule shown above can form polyesters? (Revision of national 5)

6.

A C24H49COOH B C3H7OH C C2H5COOHD C7H13COOC4H9 E C14H21COOH F HOOC(CH2)4COOH

a) Which are unsaturated fatty acids?

b) Which contains the greatest degree of unsaturation?

c) Why is C not a fatty acid?

d) Which is an ester?

e) i) Which can form a polyester?ii) Draw the structural formula of an alcohol molecule it could combine with to form polyester.

7. What is formed when a molecule of fat is hydrolysed?

8.

(i) Draw the structure of the products when the fat shown opposite is hydrolysed with hydrochloric acid.

(ii) Soap is formed if sodium hydroxide is used. Draw the structure of the soap formed.

(iii) Give the chemical/industrial name for soap production.

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Proteins

9.

a) Draw the full structural formula of an amino acid with the molecular formula C3H7NO2.

b) The following molecules contains both amine and carboxyl functional groups. Identify both groups in the molecules shown.

(i) (ii) (iii)

c) The diagram below shows a sequence of amino acids that have been joined together forming a polyamide.

(i) How many different amino acids are present in the structure shown above.

(ii) Label the amide links with the letter P and explain why the letter P is appropriate.

(iii) Name the type of chemical reaction that occurs when amino acids combine.

10. Use the amino acids below to draw the protein structure which could be produced by linking amino acids to produce the sequence -A-C-B -.

A B C

11. Examine the graphs shown opposite:

a) Which graph is likely to represent an enzyme reaction?

b) Enzymes are proteins. Is the enzyme given fibrous or globular?

c) Underline which of the following could affect the hydrolysis of a protein?

i) mass of protein ii) mass of enzyme iii) pH of solution.

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12. Below are diagrams of two proteins:

A B

a) A is fibrous. Give an example of a fibrous protein and state a property of this type of protein.

b) Describe how the shape of B allows it to catalyse reactions.

c) Describe two ways to denature B.

d) What happens to B when it is denatured?

13. Use the grid to answer the questions that follow:

AC2H5NH2

BC13H27COOH

C D

E F G HC11H19COOH

a) Which compounds are alcohols?

b) Which compound is an ester?

c) Which pair of compounds can react to form a polyester?

d) Which compound forms a protein on polymerisation?

e) Which compound is an unsaturated fatty acid?

f) Which compound has a pH > 7?

e) Which compound has the amide link?

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Exam style questions (20014 – 2011)

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27. An ester can be prepared from a mixture of ethanol and methanoic acid.

(i) Name another substance that should be added to the mixture.

(ii) Why should the reaction mixture be heated using a water bath and not a Bunsen burner?

(iii) Draw a structural formula for the ester that would be produced in this reaction.

28. Proteins are made from monomers called amino acids. Human hair is composed of long strands of a protein called keratin.

(a) What type of protein is keratin?

(b) Part of the structure of a keratin molecule is shown.

Circle a peptide link in the above structure.

(c) Hair products contain a large variety of different chemicals. Chemicals called hydantoins are used as preservatives in shampoos to kill any bacteria.

A typical hydantoin is shown.

Name the functional group circled.

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28. Continued…

(d) Some hair conditioners contain the fatty acid behenic acid, CH3(CH2)19CH2COOH.

Behenic acid is produced by hydrolysing the edible oil, ben oil.

(i) Name the compound, other than fatty acids, which is produced by hydrolysing ben oil.

(ii) When conditioner containing behenic acid is applied to hair, the behenic acid molecules make intermolecular hydrogen bonds to the keratin protein molecules.

On the diagram below use a dotted line to show one hydrogen bond that could be made between a behenic acid molecule and the keratin.

29. A calorie-free replacement for fat can be made by reacting fatty acids with the hydroxyl groups on a molecule of sucrose. A structural formula for sucrose is shown.

How many fatty acid molecules can react with one molecule of sucrose?

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30. Dental anaesthetics are substances used to reduce discomfort during treatment.

(a) Procaine is a dental anaesthetic.

(i) Name the functional group circled above.(ii) Procaine causes numbness when applied to the gums. This effect wears off as the procaine is hydrolysed.

One of the products of the hydrolysis of procaine is shown below.

Draw a structural formula for the other compound produced when procaine is hydrolysed.

(b) The table below shows the duration of numbness for some anaesthetics.

Estimate the duration of numbness, in minutes, for anaesthetic X.

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31. Aspirin, a common painkiller, can be made by the reaction of salicylic acid with ethanoic anhydride.

Name the type of reaction that takes place in the formation of aspirin from salicylic acid and ethanoic anhydride.

32. Aspartame is an artificial sweetener which has the structure shown below.

(a) Name the functional group circled.

(b) In the stomach, aspartame is hydrolysed by acid to produce methanol and two amino acids, phenylalanine and aspartic acid.

Two of the products of the hydrolysis of aspartame are shown below.

Draw a structural formula for aspartic acid.

(c) The body cannot make all the amino acids it requires and is dependent on protein in the diet for the supply of certain amino acids.

What term is used to describe the amino acids the body cannot make?

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33. A fatty acid is a long chain carboxylic acid.

Examples of fatty acids are shown in the table below.

(a) Describe a chemical test, with the expected result, that could be used to distinguish between stearic and oleic acids.

(b) What is the systematic name for linolenic acid?

(c) Stearic acid can be reacted with sodium hydroxide solution to make a soap.

The structure of the soap is shown.

One part of the soap molecule is soluble in fat and the other part is soluble in water.

Circle the part of the soap molecule which is soluble in water.

34. Paracetamol is a widely used painkiller.

(a) Write the molecular formula for paracetamol.

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34. Continued…

(b) One antidote for paracetamol overdose is methionine.

To what family of organic compounds does methionine belong?

35. When vegetable oils are hydrolysed, mixtures of fatty acids are obtained. The fatty acids can be classified by their degree of unsaturation.

The table below shows the composition of each of the mixtures of fatty acids obtained when palm oil and olive oil were hydrolysed.

(a) Why does palm oil have a higher melting point than olive oil?

(b) One of the fatty acids produced by the hydrolysis of palm oil is linoleic acid, C17H31COOH.

To which class (saturated, monounsaturated or polyunsaturated) does this fatty acid belong?

(c) When a mixture of palm oil and olive oil is hydrolysed using a solution of sodium hydroxide, a mixture of the sodium salts of the fatty acids is obtained.

State a use for these fatty acid salts.

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Unit 2: Natures Chemistry Esters, Fats & oils and Proteins Ink exercise

1. Fats are naturally occurring esters. Many liquid fats (oils) will rapidly decolourise bromine water. When treated with hydrogen in the presence of a nickel catalyst these oils undergo a change in melting point, such that, many of them become solids. It is found that they no longer decolourise bromine water.

(a) What is the main function of fats in a balanced diet? (1)

(b) Which polyhydric alcohol is common to all fats? (1)

(c) What can you deduce from the oils from the fact they all decolourise bromine water? (1)

(d) Explain how this property accounts for their low melting point. (1)

(e) The fat below was boiled with a potassium hydroxide solution to form 3 molecules of water and the carboxylate salt K+ C17H35COO-.

Name the other product formed in the reaction. (1)

2. Protein molecules are polymers resulting in condensation reactions involving amino acids. Proteins are classified as fibrous or globular.

(a) Explain the meaning of the words in bold print. (1)

(b) What function do:i) fibrousii) globular proteins have in the body? (2)

(c) Enzymes are proteins. Describe two ways in which enzymes can be denatured. (1)

(d) Proteins can be hydrolysed by refluxing with hydrochloric acid for two hours. Name the method used to separate and identify specific amino acids formed.

(1)

Please turn over for question 3..

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3. The following diagrams represent three different amino acids.

(a) Draw the molecule formed when the three amino acids above combine. (1)

(b) In your diagram circle i) the peptide links.ii) place an A at the amino group iii) place a C at the carboxyly group. (3)

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