Question

Most acidic alcohol is:
A. ${(C{H_3})_3}OH$
B. $C{H_3}C{H_2}OH$
C. $C{H_3}OH$
D. $C{H_3}CHOHC{H_3}$

Answer 1

The acidic nature of the alcohol is related with the stability of carbocation formed by the alcohols. With decrease in the stability of carbocation the acidic nature of the alcohols increases.

Complete step by step answer:
The carbocations are the positive charge species with one electron less than the tetravalency. This makes carbocation a lewis acid as it can take more electrons.
The stability of the carbocation is determined by the amount of energy required by the compound to form carbocation. The tertiary alcohol dissociates easily to form the tertiary carbocation than the secondary alcohol and primary alcohol. Therefore, the stability order of the carbocation is shown below.
$3^\circ > 2^\circ > 1^\circ > Methyl\;carbocation$
The tertiary carbocation is more stable than secondary carbocation and secondary carbocation is more stable than primary carbocation. Methyl carbocation is least stable.
${(C{H_3})_3}OH$ is a tertiary alcohol as the central carbon is bonded with three other carbon atoms. Therefore, it will form a tertiary carbocation.
$C{H_3}C{H_2}OH$is a primary alcohol as the central carbon is bonded with one other carbon atom. Therefore, it will form a primary carbocation.
$C{H_3}OH$ forms methyl carbocation.
$C{H_3}CHOHC{H_3}$ is a secondary alcohol as the central carbon atom is bonded with two other carbon atoms. Therefore, it will form secondary carbocation.
The acidic nature of the alcohol increases with the decrease in the stability of carbocation. As methyl carbocation is least stable. Thus, $C{H_3}OH$ will be most acidic in nature.
So, the correct answer is “Option C”.

Note:
The stability of the carbocation also depends on the increasing number of adjacent carbon atoms and adjacent pi-bond which helps the p-orbital of the carbocation to take part in the conjugated pi- system.