Q19E - Organic Chemistry (Mcmurry)

Question

The following carboxylic acid can't be prepared from an alkyl halide by either the nitrile hydrolysis route or the Grignard carboxylation route.Explain.

Step-by-Step Solution

Answer

There is no possibility in nitrile hydrolysis route due to the tertiary alkyl halide as reactant. The route of Grignard carboxylation is not used due to the acidic hydroxyl group interfere the reaction and thus the expected acid will not formed.

Step 1: Representation of acid by the model

The acid model can be represented as,

The alkyl halide to be used as starting material can be drawn as,

Step 2: Prevention of reaction of Grignard reagent

The step 1 of nitrile hydrolysis route can be S_N² displacement using cyanide ion. 

The alkyl halide does not using through the displacement of S_N². This method will not be useful. The alkyl halide has acidic hydroxyl group with interference of the reaction with the formation of Grignard reagent. This is also not used. 

The Grignard reagent reaction with CO₂ can be prevented.