Chapter 9, Problem 9.6P

Interpretation Introduction

Interpretation:

The complete mechanism for the ${\text{S}}_{\text{N}}\text{2}$ reaction when $\text{hex-1-yne}$ is treated with NaH followed by the treatment with bromoethane is to be drawn.

Concept introduction:

Terminal alkynes are weak acids as the terminal carbon is $\text{sp}$ hybridized. Terminal alkynes can be deprotonated by strong bases like ${\text{H}}^{\text{-}}$ or ${\text{H}}_{\text{2}}{\text{N}}^{\text{-}}$ to generate a strongly nucleophilic, negatively charged carbanion.

Being a strong nucleophile, the carbanion can replace a halogen from a primary alkyl halide in an ${\text{S}}_{\text{N}}\text{2}$ reaction. Terminal alkynes are therefore useful in carbon-carbon bond formation reactions.