91Ó°ÊÓ

A liquid boils when its vapor pressure becomes equal to the pressure of the vapor above the liquid surface.

The temperature at which these two pressures become equal is called the boiling point. During vaporization, the temperature of the compound remains constant due to latent heat.

It is determined by heating the compound at a constant rate till the temperature of the liquid remains constant for some time.

Atmospheric pressure, molecular weight, impurities, and structure of the compound determine the boiling point of the compound.

An attractive force between molecules increases the boiling point. Polar molecules have a higher boiling point than non-polar molecules due to dipole-dipole attractive forces.

Hydrogen bonding also increases the boiling point of molecules as more heat is required to break the attractive forces.

The given compounds are toluene, 4-methyl tetrahydropyran, and aniline.

Toluene is a non polar molecule. Therefore, it will have the lowest boiling point.

4-methyl tetrahydropyran has dipole-dipole attractive forces and aniline has hydrogen bonding. The force of attraction due to hydrogen bonding is greater than dipole-dipole interaction. Therefore, aniline has a higher boiling point.

Therefore, the order of boiling point is given by:

Increasing order of boiling point