Question

why does butan-2-ol has lesser boiling point than butan-1-ol?

Answer 1

butan-2-ol {CH3-CH(OH)-CH2CH3)is a branched chain alcohol and butan-1-ol {CH3CH2CH2CH2(OH)} is a straight chain alcohol. As a branching increases the steric crowding increases due to which strength of hydrogen bonding in alcohol decreases. Again more stronger is the hydrogen bonding in alcohol, extra energy is required to break that bond and hence boiling point increases. Since butan-2-ol is a branched alcohol, the strength of hydrogen bonding is less and hence has less boiling point than that in straight chain butan-1-ol where the strength of H bonding is greater.

Answer 2

Branching leads to lesser b. p of butan2ol as is decreases surface area and thus Decreases van der walls forces, as compared to butan1ol