The table below shows the normal boiling points of benzene and benzene derivatives. (e) Why is the boiling point of phenol the highest of all?

Key Concepts

Hydrogen Bonding

Hydrogen bonding is a strong type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like oxygen or nitrogen. In phenol, the hydroxyl (-OH) group can form hydrogen bonds with other phenol molecules, leading to increased intermolecular attractions. This results in a higher boiling point compared to compounds that do not exhibit hydrogen bonding.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion between molecules. They include hydrogen bonds, dipole-dipole interactions, and London dispersion forces. The strength and type of these forces significantly influence the physical properties of substances, such as boiling points. Phenol's ability to engage in strong hydrogen bonding elevates its boiling point relative to other benzene derivatives.

Molecular Structure and Polarity

The molecular structure and polarity of a compound play crucial roles in determining its boiling point. Phenol has a polar -OH group, which contributes to its overall polarity. This polarity enhances the strength of intermolecular forces, particularly hydrogen bonding, making phenol's boiling point higher than that of non-polar or less polar benzene derivatives.