Question

In acid catalyzed dehydration of alcohol which of the following alkene is formed.
The reaction may involve rearrangement.

A)

B)

C)

D)

Answer 1

We must remember that the dehydration of alcohols is a way to synthesize alkenes is by dehydration of alcohols, a process during which alcohols undergo $E_1{\text{ }}or{\text{ }}E_2$ mechanisms to lose water and form a covalent bond. The dehydration reaction of alcohols to get alkene proceeds by heating the alcohols within the presence of a robust acid, like sulfuric or ortho phosphoric acid, at high temperatures.

Complete step by step answer: As we know that the ${H^ + }$ attach to OH group due to the presence of lone pair of electron and form $OH{2^ + }$ which may be a good leaving group so removal of water takes place and carbocation is made and then methyl shift takes place because tertiary carbocation is more stable than secondary carbocation and eventually removal of ${H^ + }$ ion happen and formation of most stable alkene takes place stability of alkene is defined by the amount of alpha hydrogen present; more the amount of alpha hydrogen more are going to be the stability so the merchandise formed have $11{\text{ }}\alpha$ hydrogen and hence most stable.
Therefore, Option (A) is correct.

Note: Now we discuss about the nature of carbocation as,
Carbocation:
An ion in which the carbon carries a positive charge is called carbocation and they are formed by the heterolytic cleavage.
Stability of the carbocation:
The stability of the allylic carbocation depends on the inductive effect of the alkyl group attached to the carbocation. The stability of the carbocation increases with an increase in the number of alkyl groups.
The stability order of carbocation is given below,
${{\text{3}}^{\text{o}}}{\text{ > }}{{\text{2}}^{\text{o}}}{\text{ > }}{{\text{1}}^{\text{o}}}$.