Question

The correct increasing order of heat of hydrogenation for the following compounds is:

• A. $III<II<I$
• B. $I<II<III$
• C. $II<III<I$
• D. $III<I<II$

Answer 1

The correct option is A $III<II<I$

Calculating the number of $\alpha -\text{hydrogens}$ in each :


More the number of alpha hydrogens, more are the number of hyperconjugative structures, higher the stability of alkene and lesser is the heat of hydrogenation value.
Stability order :
$I<II<III$
Heat of hydrogenation value order:
$III<II<I$