Question

Consider the heterogeneous catalytic hydrogenation of cis$-3,4$-dimethyl-$3$-hexene. What is stereo-chemical outcome of the reaction?

• A. Diastereomers
• B. A single enantiomer
• C. Racemate
• D. Meso form

Answer 1

Answer: (D)

Meso form

In a hydrogenation reaction, two hydrogen atoms are added across the double bond of an alkene, resulting in a saturated alkane. Hydrogenation of a double bond is a thermodynamically favorable reaction because it forms a more stable (lower energy) product. The two hydrogen must add to the same face of the double bond, displaying syn addition. Since, the resulting compound has the plane of symmetry along half plane, it is meso form as the hydrogenation takes place in syn addition.