Isomers of hexane, based on their branching, can be divided into three distinct classes asshown below:
The correct order their boiling point is:
Given classes contain isomeric hydrocarbons with different extents of branching. For the same molar mass, in general, the greater the branching, the lesser will be the surface area. With reduction in surface area, the scope for charge separation also goes down and thus, the boiling point will decrease with increased branching.
Hence, III > II > I