Question

a. What carboxylic acid is formed when the malonic ester synthesis is carried out with one equivalent of malonic ester, one equivalent of 1,5-dibromopentane, and two equivalents of base?

b. What carboxylic acid is formed when the malonic ester synthesis is carried out with two equivalents of malonic ester, one equivalent of 1,5-dibromopentane, and two equivalents of base?

Short answer

Reactions such as alkylation of carbon and decarboxylation of 3-oxocarbxylic acid are used to make carboxylic acids of a particular chain length. This method is termed malonic ester synthesis.

The starting material used to prepare carboxylic acid is a diester of malonic acid.

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Step-by-step solution

Malonic ester synthesis

Reactions such as alkylation of carbon and decarboxylation of 3-oxocarbxylic acid are used to make carboxylic acids of a particular chain length. This method is termed malonic ester synthesis.

The starting material used to prepare carboxylic acid is a diester of malonic acid.

Identifying the carboxylic acid formed during the malonic ester synthesis

a. In this reaction, diethyl malonate reacts with ethanolate and 1,5-dibromopentane to form diethyl 2-(5-bromopentyl)malonate. This further reacts with ethanolate to form diethyl cyclohexane-1,1-dicarboxylate.

This further reacts with HCl, water, and heat to form cyclohexane carboxylic acid. Hence, the carboxylic acid formed in this reaction is cyclohexane carboxylic acid. The other products formed are carbon dioxide and ethanol.

The reaction is given below.

Reaction (a)

b.In this reaction, diethyl malonate reacts with ethanolate and 1,5-dibromopentane to form diethyl 2-(5-bromopentyl)malonate. This further reacts with ethanolate and malonic ester to form tetraethyl heptane-1,1,7,7-tetracarboxylate.

This reacts with HCl, water, and heat to form nonanedioic acid. The other products formed are carbon dioxide and ethanol. The reaction is given below.

Reaction (b)