57E - Organic Chemistry (Mcmurry)

Question

A chemist in need of 2,2-dimethylpentanoic acid decided to synthesize some by reaction of 2-chloro-2-methyl pentane with NaCN, followed by hydrolysis of the product. After the reaction sequence was carried out, however, none of the desired products could be found. What do you suppose went wrong?

Step-by-Step Solution

Answer

The reason for not obtaining the expected product can be explained.

Step 1: Explanation for nitrile hydrolysis method

The preparation of carboxylic acids from alkyl halides using the nitrile hydrolysis method. The involvement of SN² displacement of halide using nitrile and thus there is the only usage of primary and secondary alkyl halides.

Step 2: Explanation for possible conversion of alkyl halides to nitriles

There is a possibility for the conversion of the alkyl halide to nitrile with primary and secondary halides due to the SN²-type reaction. The tertiary alkyl halide is 2-Chloro-2-methyl pentane will yield the nitrile which is treated with NACN. Thus, 2,2-dimethylpentanoic acid will not be prepared using the reaction with NACN and 2-Chloro-2-methyl pentane and product hydrolysis.