Chapter 23, Problem 68A

Interpretation Introduction

Interpretation : To determine the reason for the higher boiling point of alcohols and also the reason for the decrease in the gap in boiling point.

Concept Introduction: As the molecular size increases, intermolecular forces of attraction also increase which in turn increases the boiling point. In this case, electronegativity also plays a role in the increase in the boiling point.

Answer to Problem 68A

The oxygen present is more electronegative therefore, alcohols have higher boiling points than that chloroalkanes.

When the chain length increase, the Vander Waals force decreases, and hence boiling point decrease. Therefore, the gap between the boiling points will decrease.

Explanation of Solution

Alcohols will have more boiling points as compared to that Chloroalkanes because the alcohol will have Vander Waal forces between the oxygen and hydrogen and also intermolecular hydrogen bonding. The intermolecular hydrogen bonding will dominate the dispersion forces therefore, it is difficult to break the intermolecular hydrogen bond between the hydrogen and the oxygen in the alcohol and it required more energy. Hence the boiling point of alcohols will be more than the Chloroalkanes.

When the branching of the alcohol and the alkyl group increase, the Vander Waals forces of attraction will increase. This in turn will result in an increase in the boiling point due to which the gap between the boiling points of alcohols and Chloroalkanes will increase.

Conclusion

The increase and decrease of the boiling point will depend on the increasing length of the alkyl groups because these factors will affect the Vander Waal forces of attraction and also the intermolecular bonding that is present in the molecule resulting in the increase and decrease of the boiling point.