Question

Which of the following has the highest boiling point ?

• A. 1-chloropentane
• B. 1-chloro-2-methylbutane
• C. 2-chloro-3-methylbutane
• D. All have equal boiling point

Answer 1

The correct option is A 1-chloropentane

For the same molar mass, as branching increases, the overall surface area decreases. This leads to a reduction in the intermolecular forces (London dispersion forces), thereby decreasing boiling point.
1-chloro-2-methylbutane and 2-chloro-3-methylbutane are branched. So, its surface area is lower than that of 1-chloropentane. Thus, they have lower boiling point than 1-chloropentane.
Therefore, 1-chloropentane has the highest boiling point.