Haloalkanes
- General formula: R-X (R = alkyl group, X = halogen)
- Preparation:
- From alcohols using HX or PCl5, PCl3, SOCl2
- From alkyl halides by SN1 or SN2 reactions
- Properties:
- Polar molecules due to electronegativity difference
- Undergo nucleophilic substitution reactions (SN1, SN2)
- Undergo elimination reactions (E1, E2)
- Can be used as solvents and refrigerants
- Examples: Chloroform, iodoform
Haloarenes
- General formula: Ar-X (Ar = aryl group, X = halogen)
- Preparation:
- From benzene derivatives using halogenation (Cl2/FeCl3, Br2/FeBr3)
- From diazonium salts using Sandmeyer reaction
- Properties:
- Less reactive towards nucleophilic substitution than haloalkanes due to resonance stabilization
- Undergo electrophilic aromatic substitution reactions
- Can be used as pesticides and dyes
- Examples: Chlorobenzene, bromobenzene
Comparison
| Feature | Haloalkanes | Haloarenes |
|---|---|---|
| Reactivity towards nucleophilic substitution | Higher | Lower |
| Reactivity towards electrophilic aromatic substitution | Lower | Higher |
| Preparation methods | From alcohols, alkyl halides | From benzene derivatives, diazonium salts |
Additional Notes
- Haloalkanes and haloarenes can be used as starting materials for various organic compounds.
- The reactivity of haloalkanes and haloarenes depends on the nature of the halogen and the alkyl or aryl group.
- Haloalkanes can be classified as primary, secondary, or tertiary based on the carbon atom attached to the halogen.
