[Maximum number: 2]

Oleocanthal, Q, is a natural compound found in olive oil. It has antioxidant and anti-inflammatory properties and is thought to have a protective effect against Alzheimer's disease.

(a)

Q shows optical and cis-trans isomerism.

On the structure of Q above, circle the functional group that shows cis-trans isomerism and indicate with an asterisk (*) the chiral carbon atom.

[ 1 ]

(b)

When a sample of Q synthesised in a laboratory was compared to a natural sample from olive oil, it was found that the therapeutic activity of the synthetic sample was lower.

Suggest a reason for this.

[ 1 ]

(a)

Compound H has the structural formula $\mathrm{CH}_{2}=\mathrm{CHCH}\left(\mathrm{NH}_{2}\right) \mathrm{COOH}$ .

[ 2 ]

(i)

Compound H exhibits stereoisomerism.

Draw three-dimensional structures for the two stereoisomers of H.
Name this type of stereoisomerism.

type of stereoisomerism

[ 2 ]

(a)

Perindopril is a drug used to treat heart disease.
perindopril

Fig. 6.1

[ 3 ]

(i)

State the number of chiral carbon atoms present in one molecule of perindopril.

[ 1 ]

(ii)

Suggest one benefit and one disadvantage of producing a drug such as perindopril as a single pure optical isomer.
benefit
disadvantage

[ 2 ]

(a)

Describe what is meant by a racemic mixture.

[ 1 ]

[Maximum number: 2]

Asparagine and valine are two naturally occurring amino acids.

asparagine

valine

(a)

Each valine molecule has one chiral carbon atom.

Draw three-dimensional diagrams to show the two optical isomers of valine. The $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}$ group can be represented as R .

[ 2 ]

(a)

Cortisone, $\mathrm{C}_{21} \mathrm{H}_{28} \mathrm{O}_{5}$ , is a naturally occurring chemical that contains chiral carbon atoms.
cortisone

Fig. 7.1

[ 1 ]

(i)

Cortisone is an optically active molecule.

Explain what is meant by optically active.

[ 1 ]

(a)

Many drug molecules are chiral, but are often produced as a mixture of optical isomers.

[ 2 ]

(i)

Suggest why a larger mass of the mixture is required than of a single optical isomer.

(ii)

Suggest a problem that might arise as a result of taking a mixture of optical isomers.

[ 2 ]

[Maximum number: 1]

2-Chloropropanoic acid, $\mathrm{CH}_{3} \mathrm{CHC} 1 \mathrm{COOH}$ , is used in many chemical syntheses.

(a)

When $\mathrm{CH}_{3} \mathrm{CHClCOOH}$ reacts with aqueous $\mathrm{NH}_{3}$ , alanine forms.

Fig. 5.1

Alanine is an amino acid. Its isoelectric point is 6.1.

[ 1 ]

(i)

Alanine exists as a pair of optical isomers. The structure of one optical isomer is shown in Fig. 5.2.

Draw the three-dimensional structure of the other optical isomer of alanine.

Fig. 5.2

[ 1 ]

(a)

Oseltamivir is a chiral drug. This drug is usually taken as a single optical isomer rather than as a mixture of isomers.

Suggest one benefit of taking a drug in this way.

[ 1 ]

(a)

Oseltamivir is a chiral drug. This drug is usually taken as a single optical isomer rather than as a mixture of isomers.

Suggest one benefit of taking a drug in this way.

[ 1 ]