Chapter 8, Problem 34P

Interpretation Introduction

Interpretation:

Two alkenes that undergo hydrogenation to yield a mixture of $\text{cis-}$ and $\text{trans-1,4-dimthylcyclohexane}$ are to be identified. Also, a third alkene that gives only $\text{cis}-1,4-\mathrm{d}\text{imthylcyclohexane}$ upon hydrogenation is to be identified.

Concept Introduction:

Alkenes, upon catalytic hydrogenation, are converted to the corresponding alkanes.

During hydrogenation, one hydrogen atom gets attached to each of the double bonded carbon atoms.

Catalytic hydrogenation is a stereospecific syn addition; both hydrogens add to the same face of the double bond.

The major product is the one in which the alkene is less hindered and better able to contact the catalyst surface.

In catalytic hydrogenation, the stereo selectivity depends on the direction from which hydrogen atoms are transferred from the catalyst to the double bond.