Chapter 12.5, Problem 9P

Interpretation Introduction

Interpretation: Among the given pair of alkynes, the one which has a smaller heat of hydrogenation is to be identified.

Concept introduction: The addition of ${\text{H}}_{\text{2}}$ is known as hydrogenation reaction. This is a syn addition. Alkyne is reduced to alkane. In this reaction, two weak pi bond of alkyne and sigma bond between ${\text{H}}_{\text{2}}$ is broken and four $\text{C}-\text{H}$ bonds are formed.