12P - Organic Chemistry (Mcmurry)

Question

How could you use a malonic ester synthesis to prepare the following compound?

 

Step-by-Step Solution

Answer

Step 1: Explanation of malonic ester synthesis

 In malonic ester synthesis, the alkyl halide converts into carboxylic acid having two more carbons.

 

The steps of malonic ester synthesis are 

 

1. Formation of an enolate ion.
2. S_N² attack of the enolate ion on alkyl halide.
3. Hydrolysis and decarboxylation.

 

Step 2: Mechanism of the reaction

The compound represent by the model is 

Hence, the reaction is:

Step 3: Explanation

The given compound is a carboxylic acid hence it can be prepared by malonic ester synthesis.

The ethoxide ion abstracts a proton from the methylene group from the ester and forms an enolate ion.

The enolate ion attacks the   and removes the bromide ion.

Then, another proton abstraction happens by the base.

The new enolate ion attacks the methyl bromide and removes the bromide ion.

Lastly, after hydrolysis and decarboxylation, you get the desired product.

 

Step 4: Conclusion

The given compound can be prepared by malonic ester synthesis like