Sodium propynide reacts with 2-bromo-2-methylpropane The major product obtained is

Options

A. propyne and 2-methylpropene
B. propyne and 2-methylpropane
C. 4,4-dimethylpent-2-yne
D. no reaction takes place

Answer

A

Explanation

The alkynide ion acts as a nucleophile and displaces a halide ion from the primary alkyl halide through an `S_N2` reaction: The unshared `e^(-)`. pair of the alkynide ion attacks the back side of the c atom that bears the halogen atom and forms a bond to it. The halogen atom depars as a halide ion. this synthesis fails when `2^@` or `3^@` halides are used because the alkynide ion acts as a base rather than as a nucleophile and the major reaction is an E2 elimination.The products of the elimination are an alkene and the alkyne from which the sodium alkynide originally formed: