Question

Dehydration of alcohols by conc. $H_{2}S{O}_4$ takes place according to following steps.

The slowest and fastest steps in the above reaction are:

• A. Step 1 is slowest, while 3 is fastest
• B. Step 2 is slowest, while 3 is fastest
• C. Step 3 is slowest, while 4 is fastest
• D. All steps proceed at equal rate

Answer 1

The correct option is B Step 2 is slowest, while 3 is fastest

Formation of carbocation is the slowest step because the formation of a carbocation is not energetically favored, so this step in the reaction is the slowest step and determines the overall rate of the reaction.
Rearrangement of carbocation is the fastest step here.