Chapter 22.1, Problem 7SSC

Interpretation Introduction

Interpretation:

The boiling points of propane and 1-chloropropane needs to be compared.

Concept introduction:

The boiling point of an organic compound depends on the structure of the compound and its molecular mass. Intermolecular forces in organic compounds also play an important role in determining the boiling point.

Explanation of Solution

The three important factors on which the boiling point of an organic compound depends are as follows:

1. Intermolecular forces such as hydrogen bonding, ionic, dipole-dipole and Van der Waals forces.
2. If number of carbon atoms in an organic compound increases, boiling point also increases.
3. If in an organic compound branching increases, boiling point will decrease.

Now, the structure of propane and 1-chloropropane is as follows:

From the above structure, it can be seen that both the compounds have same number of C atoms that is 3. Also, both the compounds have straight chain structure that is there is no branching.

The boiling point depends on the intermolecular forces. In 1-chloropropane there are van der Waals dispersion and dipole-dipole forces due to the presence of electronegative Cl group. There are only Van der Waals dispersion forces in propane. Less energy will be required to break the weak Van der Waals dispersion forces in propane. Thus, boiling point of 1-chloropropane will be higher than propane.