The Malonic ester synthesis uses diethyl malonate to form what type of product after alkylation and decarboxylation?

• A. Substituted acetic acids (R-CH2-COOH)
• B. Primary alcohols
• C. Aldehydes
• D. Ketones

Answer: (A)

Malonic ester synthesis builds a carbon chain by first making an enolate from an active methylene compound, then alkylating it, and finally hydrolyzing and decarboxylating to reveal a carboxylic acid with an extra methylene unit. With diethyl malonate, removing a proton gives a nucleophilic carbanion that attacks an alkyl halide to install the desired carbon framework. After hydrolysis of the esters to a dicarboxylic acid and heating to drive off CO2, one carboxyl group is lost, leaving the remaining fragment as R-CH2-CO2H. So the product is a substituted acetic acid, where the alkyl group from the alkyl halide becomes attached as a methylene next to the carboxyl group. This sequence does not produce primary alcohols, aldehydes, or ketones, because the process culminates in a carboxylic acid after decarboxylation rather than forming those other carbonyl-containing species.