CnH2nX where X is the halogen. This is often shortned to R-X.
Halogens are more electronegative than carbon so:
As we go down the group, the bonds get less polar.
Solubility - the C-X bond is not polar enough to make the haloalkane soluble
- main intermolecular forces are dipole-dipole and van der Waal forces
- haloalkanes mix with hydrocarbons to make dry-cleaninng fluids
Boiling Point - increases with chain length and down the halogen group
This is because the larger th emolecules, the greater the number of electrons, therefore larger van der Waals. Haloalkanes have higher boiling points than alkanes because they have higher Mr and they are more polar.
Reactivity of C-X bond:
halogens are more electronegative than the carbon so the carbon is electron deficient. This means that it can be attacked by reagents that are electron-rich called nucleophiles.
Nucleophiles donate a pair of electrons.
The bonds get weaker as we go down the group. This is because the halogens have are bigger so have more shells and therefore there is greater shielding between the halogen nucleus and the covalent bond.