Q13P - Organic Chemistry (Mcmurry)

Question

How would you prepare the following carbonyl compounds from a nitrile?

(a)

 

(b)

Step-by-Step Solution

Answer

(a)

The given carbonyl compound (3-pentanone) is prepared from propanenitrile as

shown below:

(b)

The target carbonyl compound (p-nitroacetophenone) is prepared from 4-

nitrobenzonitrile as shown below:

Step 1: Preparation of 3-pentanone from the respective nitrile.

The target compound, 3-pentanone is a symmetrical ketone that would be prepared by the Grignard reaction of ethylmagnesium bromide with propanenitrile through an intermediate imine anion. The addition of aqueous acid to the imine salt to produce the final product as shown below:

Step 2: Preparation of p-nitroacetophenone from 4-nitrobenzonitrile.

The desired carbonyl compound, p-nitroacetophenone would be prepared from 4-nitrobenzonitrile as a starting material. The starting material is treated with Grignard reagent, methylmagnesium bromide to generate an intermediate imine anion (unstable). The acidic hydrolysis of this imine anion gives p-nitroacetophenone as shown below: