Physical Properties of Halides
- Alkyl halides are colourless when pure. However, bromides and iodides develop colour when exposed to light. Many volatile halogen compounds have sweet smell.
- The alkyl halides have higher molecular mass as compared to alkanes.
- Halogen compounds have higher boiling points than the corresponding hydrocarbon. This is because the greater polarity as well as higher molecular mass as compared to the parent hydrocarbon causes the intermolecular forces of attraction (dipole-dipole and van der Waals) to be stronger in the halogen derivatives.
- For monohalogen compounds, the boiling point increases with increasing molecular mass of the halogen group with a fixed hydrocarbon group,
- All halogen derivatives of hydrocarbon are insoluble in water as they are incapable of forming hydrogen bonds with water, but alkyl halides are soluble in non-polar solvents,
R‒F < R‒Cl < R‒Br < R‒I
- The density increases with increasing number and the atomic mass of the halogen.
- Halogen compounds are less inflammable than the hydrocarbons. The inflammability decreases with increasing halogen content.