Haloalkanes and Haloarenes
Haloalkanes
These are organic compounds containing one or more carbon-halogen bonds (C-X, where X is a halogen: F, Cl, Br, or I).
They are also known as alkyl halides.
They are also known as aryl halides.
Example: CH₃-CH₂-Cl (ethyl chloride)
Secondary (2°): The carbon atom attached to the halogen is directly bonded to two other carbon atoms.
Example: CH₃-CHCl-CH₃ (2-chloropropane)
Tertiary (3°): The carbon atom attached to the halogen is directly bonded to three other carbon atoms.
Example: (CH₃)₃C-Cl (tert-butyl chloride)
Boiling point and density increase with the size of the halogen atom and the chain length of the alkyl group.
Haloalkanes are generally insoluble in water but soluble in organic solvents.
Chemical properties:
Nucleophilic substitution reactions: Haloalkanes undergo nucleophilic substitution reactions, where the halogen atom is replaced by a nucleophile.
Elimination reactions: Under certain conditions, haloalkanes can undergo elimination reactions to form alkenes.
Reactions with metals: Haloalkanes can react with metals to form organometallic compounds.
They are also known as alkyl halides.
Haloarenes
These are aromatic compounds containing one or more carbon-halogen bonds attached to the aromatic ring.They are also known as aryl halides.
Classification
Primary (1°): The carbon atom attached to the halogen is directly bonded to one other carbon atom.Example: CH₃-CH₂-Cl (ethyl chloride)
Secondary (2°): The carbon atom attached to the halogen is directly bonded to two other carbon atoms.
Example: CH₃-CHCl-CH₃ (2-chloropropane)
Tertiary (3°): The carbon atom attached to the halogen is directly bonded to three other carbon atoms.
Example: (CH₃)₃C-Cl (tert-butyl chloride)
Properties
Physical properties:Boiling point and density increase with the size of the halogen atom and the chain length of the alkyl group.
Haloalkanes are generally insoluble in water but soluble in organic solvents.
Chemical properties:
Nucleophilic substitution reactions: Haloalkanes undergo nucleophilic substitution reactions, where the halogen atom is replaced by a nucleophile.
Elimination reactions: Under certain conditions, haloalkanes can undergo elimination reactions to form alkenes.
Reactions with metals: Haloalkanes can react with metals to form organometallic compounds.
Uses
Haloalkanes and haloarenes have various applications, including:- Solvents
- Pesticides
- Pharmaceuticals
- Refrigerants (formerly, before the discovery of their ozone-depleting properties)
Note: The use of many haloalkanes, especially those containing chlorofluorocarbons (CFCs), has been restricted due to their harmful effects on the environment.
