The correct order of boiling points of 2, 2-dimethylpropane, 2 methylbutane and n pentane is

Options

A. n-pentane gt 2, 2-dimethylpropane gt 2-methylbutane
B. n-pentane gt 2-methylbutane gt 2, 2-dimethylpropane
C. 2, 2-dimethylpropane gt 2-methylbutane gt n-pentane
D. 2-methylbutane gt n-pentane gt 2, 2-dimethylpropane

Answer

B

Explanation

Branching of the chain makes the molecule more compact and thereby decreases the surface area. The intermolecular forces which depend upon the surface area, become small in magnitude on account of branching. Consequently, the boiling points of branched chain alkanes are less than the straight chain isomers.