Question

Which of the following alcohols will dehydrate most rapidly when treated with conc. $H_{2}S{O}_4$?

• A. $C{H}_{3}CH\left(OH\right)C(C{H}_3{)}_3$
• B. $C{H}_{3}C\left(C{H}_3\right)\left(OH\right)CH(C{H}_3{)}_2$
• C. $\left(C{H}_3{)}_{2}CHCH\right(OH)C{H}_3$
• D. $C{H}_{3}C{H}_{2}C{H}_{2}C{H}_{2}OH$

Answer 1

Answer: (B)

$C{H}_{3}C\left(C{H}_3\right)\left(OH\right)CH(C{H}_3{)}_2$

The speed of dehydration will be proportional to the stability of carbo-cation formed after the protonated $-OH$ group leaves.

Thus for option (B), the carbo-cation would be (in the figure).

This is the most stable carbo-cation since it is on a $3°$ carbon. The reaction will proceed big E1 mechanism.

Therefore, option B is correct.