Question

Arrange the following in the increasing order of their boiling point and give a reason for your ordering.

Butan-2-ol, Butan-1-ol, 2-methyl propane-2-ol

Answer 1

Boiling points increase regularly as the molecular mass increases due to a corresponding increase in their Van der Waal's force of attraction. Among isomeric alcohols, 2° alcohols have lower boiling points than 1° alcohol due to a corresponding decrease in the extent of H-bonding because of steric hindrance. Thus the boiling point of Butan-2-ol is lower than that of Butan-1-ol. Overall increasing order of boiling points is, 2-methyl propane-2-ol < Butan-2-ol < Butan-1-ol.