Chemistry 9701 · AS & A Level · Organic synthesis

Organic synthesis — practice question

A student carries out reactions on separate samples of butanal and butanone. The results with reagents L, M and N are shown below ($\checkmark$ indicates that a reaction occurs).
(a(i))[3]

Suggest a possible identity for each of the reagents L, M and N.

(a(ii))[1]

Give the structure of the organic product obtained when M reacts with butanal.

(a(iii))[1]

What is seen when N reacts with butanone?

(a(iv))[1]

What type of reaction occurs when N reacts with butanone?

(b(i))[3]

The organolithium compound methyl lithium, $\text{CH}_3\text{Li}$, can supply $\text{CH}_3^-$ ions: $\text{CH}_3\text{Li} \rightleftharpoons \text{CH}_3^- + \text{Li}^+$. The $\text{CH}_3^-$ ion can act as a nucleophile. Suggest a mechanism for the reaction of butanal with $\text{CH}_3^-$ ions. Include every necessary curly arrow, lone pair and relevant dipole.

(b(ii))[1]

A chemist plans to make the following organic compound G from butanal. Draw the structure of the organolithium reagent that could be used to prepare G from butanal.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: appropriate reagents identified (for example 2,4-DNPH, LiAlH$_4$, Fehling’s)

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