Chemistry 9701 · AS & A Level · Analytical techniques
Analytical techniques — practice question
Esterases are enzymes that hydrolyse esters.
$\text{RCOOR}' + \text{H}_2\text{O} \rightarrow \text{RCOOH} + \text{HOR}'$
Enzymes can be highly selective about the substrate structures they act on. For instance, an esterase obtained from the mould Aspergillus niger hydrolyses phenyl ethanoate, $\text{CH}_3\text{CO}_2\text{C}_6\text{H}_5$, but not its isomer methyl benzoate, $\text{C}_6\text{H}_5\text{CO}_2\text{CH}_3$.
(a)[3]
Outline how enzymes catalyse reactions, and explain why they are specific. Use diagrams where appropriate in your answer.
(b(i))[2]
The carbon-13 NMR spectra of isomers A and B show the peaks below. Use the Data Booklet to match the correct peaks to the labelled carbon atoms in the structures shown. Write each value beside the relevant carbon atom and therefore determine the identity of each isomer.
(b(ii))[3]
These two isomers are not easy to tell apart chemically. Describe a procedure for converting them into suitable products in step 1 that can then be tested in step 2. You should state the reagents and conditions for each step, and any observations you would make.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Substrate has a shape complementary to the enzyme active site” …