Question

The relative rate of acid catalyzed dehydration of following alcohols would be:

• A. I > III > IV > II
• B. III > I > IV > II
• C. III > IV > II > I
• D. III > IV > I > II

Answer 1

The correct option is B III > I > IV > II

Rate of acid catalyzed dehydration is directly proportional to the stability of carbocation.
The carbocations generated from the given compounds are:




(iii) will be dehydrated at the fastest rate as the carbocation is $3^{\circ }$ and stabilised by the phenyl group.
(ii) will be dehydrated at the slowest rate as the carbocation is $2^{\circ }$.
Between (i) and (iv), (i) has a faster rate because after an H shift, the resulting carbocation is more stable.