Question

The given compunds are individually heated in presence of concentrated $H_{2}S{O}_4$.
Choose the correct statement

• A. Rate of dehydration is higher for compound $I$ as compared to $II$
• B. Rate of dehydration is lower for compound $I$ as compared to $II$
• C. Rate of dehydration is equal for compound $I$ as compared to $II$
• D. None of them will react on heating in presence of concentrated $H_{2}S{O}_4$

Answer 1

The correct option is A Rate of dehydration is higher for compound $I$ as compared to $II$

Lone pair of oxygen attacks $H^{+}$ coming from $H_{2}S{O}_4$ and removal of water molecule (dehydration) occurs.
The rate of dehydration depends on the stability of carbocation so formed after the removal of water molecule.


In case I, the carbocation so formed is stabilized by conjugation whereas in case II , the carbocation so formed is vinylic which is very unstable because of positive charge on $s{p}^2$ hybridised carbon.
Order of carbocation stability
$I>II$
Rate of dehydration:
$I>II$
Hence (a) is correct.