Why Benzene Resists Hydrogenation

Benzene resists catalytic hydrogenation much more than an alkene does. When stilbene is reduced, the alkene bond is hydrogenated while the benzene ring stays unchanged. Alkene hydrogenation is exothermic and happens easily under mild conditions.

Benzene behaves differently because its ring is res...

Recall that catalytic hydrogenation of an alkene double bond occurs under normal reaction conditions. Under similar conditions, however, a benzene double bond will not be reduced.

This is illustrated in the hydrogenation of stilbene, where under normal conditions, only the olefinic bond is selectively reduced, leaving the benzene rings un...