Maharashtra State Board · Class 12 · Chemistry · Chapter 10

Halogen Derivatives — Formula Sheet

Board Formulas

11 formulas

1.SN2 Rate Law★
$Rate = k [R-X] [Nu^{-}]$
Second-order overall (bimolecular). Rate depends on both substrate and nucleophile concentrations.
2.SN1 Rate Law★
$Rate = k [R-X]$
First-order in substrate only. Rate-determining step is carbocation formation.
3.Reactivity Order (SN1)
$3° > 2° > 1° > methyl$
Reverse of SN2. Tertiary carbocations most stable.
4.Reactivity Order (SN2)★
$methyl > 1° > 2° > 3°$
Steric hindrance blocks back-side attack for bulky substrates.
5.Halide Leaving Group Order
$R - I > R - B r > R - C l > R - F$
Weaker C–X bond ⇒ better leaving group. Iodide leaves easiest.
6.Elimination E1 vs E2
$E 2 : concerted, anti-periplanar; E 1 : stepwise via carbocation$
E2 gives Zaitsev alkene (more substituted). E1 also usually Zaitsev but may rearrange.
7.Wurtz Reaction★
$2 R - X + 2 Na dry ether R - R + 2 NaX$
Two alkyl halides coupled by sodium. Used to make symmetric alkanes.
8.Finkelstein Reaction
$R - C l + NaI acetone R - I + NaCl$
Alkyl chloride/bromide → alkyl iodide via SN2 with NaI in acetone.
9.Swarts Reaction
$R - C l + AgF ⟶ R - F + AgCl$
Alkyl fluoride prep from alkyl chloride using AgF, Hg₂F₂, or SbF₃.
10.Grignard Reagent Formation★
$R - X + Mg dry ether R - MgX$
Alkyl magnesium halide; C in R–MgX has partial negative charge; strong nucleophile.
11.Rate — Haloalkane vs Haloarene
$k_{alkyl halide} ≫ k_{aryl halide}$
Aryl halides are ~10⁵ times less reactive under normal SN conditions.