Chemistry 9701 · AS & A Level · States of matter

States of matter — practice question

Capsaicin occurs in chilli peppers. In the reactions in this question, treat the $\text{CH}_3\text{O}$ group as unreactive.
(a)[1]

Name every functional group present in capsaicin apart from the $\text{CH}_3\text{O}$ group.

(b)[3]

Complete the equation for capsaicin reacting with excess $\text{Br}_2(aq)$ in the dark. Draw the structure of the organic product in the labelled box.

(c)[2]

Capsaicin is heated with excess hydrogen gas in the presence of platinum metal. The six-membered ring reacts in the same way as benzene under these conditions. Draw the structure of the organic product formed.

(d(i))[1]

When capsaicin is treated with reagent J under suitable conditions one of the products is methylpropanoic acid, CH$_3$CH(CH$_3$)COOH. Identify reagent J and any necessary conditions.

(d(ii))[3]

The proton ($^1$H) NMR spectrum of CH$_3$CH(CH$_3$)COOH in CDCl$_3$ contains three distinct peaks. Use Table 8.1 to complete Table 8.2 and state: the usual proton ($^1$H) chemical shift values ($\delta$) for the protons; the splitting pattern (singlet, doublet, triplet, quartet or multiplet) shown by each peak; the reason for the splitting patterns of the CH$_3$ protons and the CH proton.

(e(i))[2]

Capsaicin is heated with excess hot aqueous NaOH. Draw the structures of the two organic products H and K.

(e(ii))[1]

Name the two types of reaction occurring in (e)(i).

(f)[1]

Draw the structure of the organic product L formed when capsaicin is treated with LiAlH$_4$ in dry ether.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: Phenol, amide and alkene groups are identified

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