Question

What alkyl bromide should be used in the acetoacetic ester synthesis of each of the following methyl ketones?

a. 2-pentanone b. 2-octanone c. 4-phenyl-2-butanone

Short answer

1. Ethyl bromide
2. Pentyl bromide
3. Benzyl bromide

Step-by-step solution

Step-by-Step SolutionStep 1: Acetoacetic ester

Another name for an acetoacetic ester is ethyl acetoacetate. Acetoacetic ester synthesis is a chemical reaction in which ethyl acetoacetate is alkylated at thecarbon to both carbonyl groups and then converted to a ketone.

The synthesis reaction is close to the synthesis of a malonic ester synthesis reaction.

Synthesis of acetoacetic ester

a) 2-pentanone

In the first step, acetoacetic is allowed to react with the LDA. As LDA is a non-nucleophilic base and removes acidic hydrogen of ${\text{-CH}}_2$. In the next step, ethyl bromide is allowed to react with the intermediate and ${}^{\text{-}}\text{CooEt}$remove as a by-product to give 2-pentanone as a product.

b) 2-octanone

In the first step, acetoacetic is allowed to react with the LDA. As LDA is a non-nucleophilic base and removes acidic hydrogen of ${\text{-CH}}_2$. In the next step, pentyl bromide is allowed to react with the intermediate and ${}^{\text{-}}\text{COOEt}$remove as a by-product to give 2-octanone as a product.

c) 4-phenyl-2-butanone

In the first step, acetoacetic is allowed to react with the LDA. As LDA is a non-nucleophilic base and removes acidic hydrogen of ${\text{-CH}}_2$. In the next step, benzyl bromide is allowed to react with the intermediate and ${}^{\text{-}}\text{CooEt}$is removed as a by-product to give 4-phenyl-2-butanone as a product.