Chapter 8: Q.62 (page 330)

Explain why the reaction of 2-bromopropane with ${NaOCOCH}_{3}$ gives ${(CH}_{3})_{2} {CHOCOCH}_{3}$ exclusively as product, but the reaction of 2-bromopropane with ${NaOCH}_{2} {CH}_{3}$ gives a mixture of ${(CH}_{3})_{2} {CHOCH}_{2} {CH}_{3}$ (20%) and ${CH}_{3} {CH=CH}_{2}$ (80%).

Short Answer

Expert verified

The reason is acetate ion is a powerful nucleophile than a base and only promotes substitution product. But ethoxides act both as a strong base and a strong nucleophile.

Step by step solution

Function of ethoxide

Ethoxide is a strong base as well as a strong nucleophile. Hence they give both an elimination and a substitution product.

Function of acetate anion

Acetate anion acts only as a good nucleophile. Hence, they exclusively give a substitution product.

Keeping into account all the key points, the products with their mode of reaction are shown below:-

Representation of the substituted and eliminated products

The difference in the concentration is observed here because acetate ion is a powerful nucleophile than a base and only promotes substitution product. In contrast, ethoxides act both as a strong base and a strong nucleophile. Hence, they promote both substitution and elimination products.