An organic chemistry student is investigating the relationship between molecular structure and physical properties of heptane isomers. Which of the following structural isomers of C7H16\text{C}_7\text{H}_{16}C7H16 has the lowest boiling point?
CH3(CH2)5CH3\text{CH}_3(\text{CH}_2)_5\text{CH}_3CH3(CH2)5CH3
(CH3)3CCH2CH2CH3(\text{CH}_3)_3\text{CCH}_2\text{CH}_2\text{CH}_3(CH3)3CCH2CH2CH3
(CH3)2CH(CH2)3CH3(\text{CH}_3)_2\text{CH}(\text{CH}_2)_3\text{CH}_3(CH3)2CH(CH2)3CH3
(CH3)2CHCH(CH3)CH2CH3(\text{CH}_3)_2\text{CHCH}(\text{CH}_3)\text{CH}_2\text{CH}_3(CH3)2CHCH(CH3)CH2CH3
