Question

Among the following, select the alkane that is expected to have lowest boiling point?

• A. Hexane
• B. 2 -methylpentane
• C. 3 -methylpentane
• D. 2,2 -dimethyl propane

Answer 1

Answer: (D)

As number of C atoms increases in alkanes, the van der waal's forces also increase. However, branching results in decrease in boiling point due to decreased surface area which results in weaker van der waal forces, Thus; order of boiling point of given alkanes is

Hexane $>$ 2-Methyl pentane> $3$ - methyl pentane $>2$; 2 - dimethyl butane.