Cheat sheet · Class 12 · CBSE · Science Chemistry
Haloalkanes and Haloarenes cheat sheet
The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.
CBSE Class 12 · Chemistry
Cheat sheet
Chapter 6Haloalkanes and Haloarenes
SN1: carbocation, racemisation, 3° fastest. SN2: one step, inversion, 1° fastest.
1. Preparation
- Alcohols + HX, PCl₅, SOCl₂ (best: gases escape).
- Alkenes + HX (Markovnikov).
- Finkelstein (NaI/acetone), Swarts (AgF).
- Sandmeyer: diazonium salt + CuX → haloarene.
2. SN1 vs SN2
| Feature | SN1 | SN2 |
|---|---|---|
| Steps | two (carbocation) | one (concerted) |
| Order | first | second |
| Reactivity | 3° > 2° > 1° | 1° > 2° > 3° |
| Stereo | racemisation | inversion (Walden) |
3. Reactions
- Elimination with alc. KOH: Saytzeff (more substituted alkene).
- Wurtz (R–R), Wurtz–Fittig, Fittig.
- Grignard: RX + Mg in dry ether → RMgX.
4. Haloarenes
- Less reactive to nucleophiles (resonance, sp² C).
- –NO₂ at o/p increases reactivity.
- Electrophilic substitution at o/p positions.
5. Key Points
- Chirality: non-superimposable mirror images.
- Freons damage ozone.
- DDT: persistent pesticide.
- Iodoform is an antiseptic.
Remember: Preparation | SN1 vs SN2 | haloarene reactivity
Haloalkanes and Haloarenes: questions and notes
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