Classification of Haloalkanes (alkyl halides) Chemistry Tutorial
- Haloalkanes are organic molecules that contain a halogen atom (Group 17 atom) as the functional group.
Name of Halogen fluorine chlorine bromine iodine Symbol F Cl Br I
- Haloalkanes are molecules in which a halogen atom (X) has substituted for one of the hydrogen atoms in the parent alkane molecule.
- The carbon atom that is bonded to the halogen atom is referred to as the head carbon.
- Haloalkanes are also known as halogenoalkanes or alkyl halides.(1)
- Haloalkanes can be classified as methyl, primary, secondary or tertiary, depending on the location of the halogen atom (X):
Classification General Structure General Formula methyl H
H− C −X |
CH3X primary (1°) H
R− C −X |
R-CH2X secondary (2°) X
R− C −R' |
R-CHX-R' tertiary (3°) X
R− C −R' |
The head carbon is highlighted.
R, R' and R" are alkyl chains (chains of CH2 terminating in a CH3)
- The location of the halogen atom in a haloalkane determines the reactivity of the molecule.(2)
- In general, reactions of haloalkanes with OH- or RO- are dependent on the location of the halogen atom (3):
⚛ Substitution reactions are favoured by halomethanes and primary haloalkanes.
⚛ Elimination reactions are favoured by tertiary haloalkanes.
⚛ Substitution and elimination reactions are equally favoured by secondary haloalkanes.