Haloalkanes and Haloarenes: Concepts for JEE and CBSE Exams

• Nomenclature of haloalkanes and haloarenes:

• Haloalkanes are compounds in which one or more hydrogen atoms of an alkane are replaced by a halogen atom (fluorine, chlorine, bromine, or iodine).
• Haloarenes are compounds in which one or more hydrogen atoms of an arene (benzene or its derivatives) are replaced by a halogen atom.

• Classification of haloalkanes (primary, secondary, tertiary):

• Primary (1°): Only one carbon atom bonded to the halogen.
• Secondary (2°): Two carbon atoms bonded to the halogen.
• Tertiary (3°): Three carbon atoms bonded to the halogen.

• Preparation of haloalkanes:

• From alcohols: Reaction with hydrogen halides (HX).
• From alkenes: Electrophilic addition of hydrogen halides (HX).
• From alkanes: Free radical halogenation.

• Preparation of haloarenes:

• From benzene: Electrophilic aromatic substitution.
• From substituted benzenes: Further electrophilic aromatic substitution.

• Reactions of haloalkanes:

• Nucleophilic substitution
• Unimolecular (SN1) mechanism
• Bimolecular (SN2) mechanism
• Elimination (E1, E2)
• Addition

• Reactions of haloarenes:

• Electrophilic aromatic substitution:

• Nitration

• Halogenation

• Alkylation

• Sulfonation

• Nucleophilic substitution reactions:

• SN1: Involves two steps (formation of carbocation intermediate).
• SN2: Substitution occurs in a single step.

• Elimination reactions:

• E1: Proceeds via carbocation and is more favourable.
• E2: Elimination in a single step.

• Applications of haloalkanes and haloarenes:

• Solvents
• Pharmaceuticals
• Pesticides
• Plastics
• Refrigerants
• Fire extinguishers