Which of the 2 geometric isomers of `Me_(3)C CH=CHCMe_(3)` has higher heat of combustion and why?

Explanation

cis - isomer is less stable because of very large steric hindrance between two bulky t - butyl groups lying on the same side of the double bond. On the other hand, trans - isomer is more stable because the bulky t - butyl groups are on the opposite sides of the double bond. Thus cis - isomer has higher heat of hydrogenation.