Q1. Define haloalkanes and haloarenes. Give one example for each.
Haloalkanes are compounds in which halogen is attached to an aliphatic carbon atom, usually sp³ carbon. Example: CH₃CH₂Br.
Haloarenes are compounds in which halogen is attached directly to an aromatic ring carbon. Example: chlorobenzene (C₆H₅Cl).
Q2. Classify halogen compounds based on the number of halogen atoms present.
Based on number of halogen atoms, compounds are classified as monohalo compounds, dihalo compounds, and polyhalo compounds.
Monohalo contains one halogen, dihalo contains two halogens, and polyhalo contains more than two halogens.
Q3. Distinguish between geminal and vicinal dihalides with one example each.
Geminal dihalides have both halogen atoms attached to the same carbon atom. Example: CH₃CHCl₂.
Vicinal dihalides have halogen atoms attached to adjacent carbon atoms. Example: CH₂Cl-CH₂Cl.
Q4. Explain the classification of halo compounds based on the hybridisation of the carbon attached to halogen.
If halogen is attached to sp³ hybridised carbon, the compound is an alkyl halide or haloalkane.
If halogen is attached to sp² hybridised carbon, it may be a vinyl halide or aryl halide.
Q5. Write short notes on primary, secondary, and tertiary alkyl halides.
Primary alkyl halide: carbon attached to halogen is bonded to one other carbon, e.g. CH₃CH₂Br.
Secondary alkyl halide: carbon attached to halogen is bonded to two other carbons, e.g. CH₃CHBrCH₃.
Tertiary alkyl halide: carbon attached to halogen is bonded to three other carbons, e.g. (CH₃)₃CBr.
Q6. Differentiate between vinyl halide and allylic halide with suitable examples.
In vinyl halide, the halogen is attached directly to a double bonded carbon atom. Example: CH₂=CHCl.
In allylic halide, the halogen is attached to the carbon next to a double bond. Example: CH₂=CH-CH₂Br.
Q7. Distinguish between aryl halide and benzylic halide with one example each.
Aryl halide has halogen attached directly to benzene ring carbon. Example: C₆H₅Cl.
Benzylic halide has halogen attached to the carbon adjacent to benzene ring. Example: C₆H₅CH₂Br.
Q8. Why should classification be done from the carbon carrying the halogen atom? Explain.
Classification depends on the nature of the carbon directly bonded to halogen. Its hybridisation and the number of carbon groups attached to it determine whether the compound is primary, secondary, tertiary, vinyl, allylic, aryl, or benzylic.
Q9. Classify the following: CH₃CH₂Br, CH₃CHBrCH₃, (CH₃)₃CBr.
CH₃CH₂Br is a primary alkyl halide.
CH₃CHBrCH₃ is a secondary alkyl halide.
(CH₃)₃CBr is a tertiary alkyl halide.
Q10. Write a compact summary note on the different methods of classifying haloalkanes and haloarenes.
Halo compounds are classified by number of halogens as mono, di, and polyhalo compounds. Dihalides are geminal or vicinal. They are also classified based on the hybridisation of carbon attached to halogen: sp³ gives alkyl halides; sp² gives vinyl or aryl halides. Alkyl halides are further classified as primary, secondary, tertiary. Special types include allylic and benzylic halides.