With the increase in the size of a halogen atom, the magnitude of van der Waal forces increases and consequently boiling point increases.
The boiling point of haloalkene
There is a large electronegativity difference between halogens and carbon resulting in highly polarized molecules. The higher molecular mass and greater polarity as compared to the parent hydrocarbon results in stronger intermolecular forces of attraction (dipole-dipole and van der Waals) in the halogen derivatives.
- The boiling point depends upon the intermolecular forces of attraction and hence the boiling points of chlorides, bromides and iodides are considerably higher than those of the hydrocarbons of comparable molecular mass.
- As we go down in the homologs series of haloalkanes, the forces of attraction become stronger due to the increase in molecular size and its mass, hence the boiling point increases down the homologs series. But the boiling point decreases with branching.