Which of the following has the lowest boiling point ?

In option A, 2-methyl butane has less branched chain. | 3 2 3 | 3 H CH C CH CH CH In option B, 2-methyl propane has branched chain with four carbons. 3 | 3 3 CH CH CH CH In option C, 2,2-dimethyl propane has more branched chain. 3 | 3 3 | 3 CH CH C CH CH In option D, n- pentane has linear chain with five of carbons. 3 2 2 2 3 CH –CH –CH –CH –CH 2- methylpropane has branched chain with lesser number of carbons than others which leads to less intermolecular forces of attraction. Therefore, it has lowest boiling point.