What is the difference between malonic ester synthesis and acetoacetic ester synthesis?

Answer 1

The Malonic Ester Synthesis begins with the dimethyl ester of a malonic acid (a beta-carboxy ester). This reaction is used to make substituted CARBOXYLIC ACIDS.

1. You start with malonic ester (a beta-carboxy ester) and alkylate it with an alkyl halide. This step is what attaches the alkyl group from the alkyl halide to the malonic ester at the position beta to both carbonyls.

2. You then add water and strong base to hydrolyze the ester groups at the ends into carboxylic acid groups, giving you malonic acid (a beta-diacid). It looks like the product from the first step, only there are carboxylic acids in place of the esters at both ends.

3. Upon gentle heating, a CO2 leaves giving the enol. The enol tautomerizes, meaning it introconverts into its isomer, the carboxylic acid. The carboxylic acid contains that R group that we attached during step 1.

The Acetoacetic Ester Synthesis has a different starting material, but follows the same Akylation-Hydrolysis-Decarboxylation steps! It is used to make asymmetrical, substituted KETONES.

1. You start with acetoacetate (a beta-keto ester) and alkylate it with an alkyl halide. This step is what attaches the alkyl group from the alkyl halide to acetoacetate at the position beta to both carbonyls.

2. You then add water and strong base to hydrolyze the ester group into a carboxylic acid, giving you a beta-keto acid. It looks like the product from the first step, only there's a carboxylic acid in place of the ester at the end.

3. Upon gentle heating, a CO2 leaves giving the enol. The enol tautomerizes, meaning it introconverts into its isomer, the ketone. The ketone is unsymmetrical due to that R group that we attached during step 1.