Haloalkanes & Haloarenes
(Study Notes – AP EAMCET Chemistry)
1. Introduction
| Term | Example | Common Use |
|---|---|---|
| Haloalkane (alkyl halide) | 1‑bromobutane, 2‑chloropropane | Solvents, reagents, intermediates |
| Haloarene (halogenated benzene) | Chlorobenzene, bromobenzene | Dyes, pharmaceuticals, solvents |
- Halogens: F, Cl, Br, I.
- General formula: R–X, where R = alkyl or aryl group, X = halogen.
2. Haloalkanes
2.1 Definition & Nomenclature
- Alkyl halides: R–X where R is an alkyl radical.
- Sub‑classes:
- Primary (R–CH₂–X)
- Secondary (R–CH–X–R)
- Tertiary (R–C⁺(X)(R)₂)
IUPAC naming: Replace the end carbon of the longest chain with the halogen suffix (e.g., 2‑bromopropane).
2.2 Physical Properties
| Property | Trends | Notes |
|---|---|---|
| Boiling point | ↑ with chain length & branching, ↓ from F→Cl→Br→I | Larger halogens increase van der Waals forces |
| Density | ↑ with heavier halogen | Chlorofluorocarbons (CFCs) were common refrigerants |
| Solubility | Poor in water, good in organic solvents | Non‑polar nature |
2.3 Preparation (Radical Halogenation)
- Initiation – UV light or heat → formation of radicals
- Propagation – R–H + X₂ → R• +