Question

hexane, 2,3 - dimethylbutane, and 2 - methylpentane are constitutional isomers. which answer lists the isomers in order of decreasing boiling point? 2 - methylpentane > hexane > 2,3 - dimethylbutane; hexane > 2 - methylpentane > 2,3 - dimethylbutane; 2 - methylpentane > 2,3 - dimethylbutane > hexane; hexane > 2,3 - dimethylbutane > 2 - methylpentane; 2,3 - dimethylbutane > 2 - methylpentane > hexane

Explanation:

For isomers of alkanes, the more branched - the structure, the lower the boiling point. Hexane is a straight - chain alkane, 2 - methylpentane is a branched alkane with one methyl group, and 2,3 - dimethylbutane is a more highly branched alkane. As branching increases, the surface area of the molecule decreases, leading to weaker London dispersion forces and a lower boiling point.

Answer:

hexane > 2 - methylpentane > 2,3 - dimethylbutane