⚗️ Reaction Mechanisms
SN2 = Strong nucleophile, Primary substrate, Backside attack, Inversion
SN2 Characteristics
SN2 requires: strong nucleophile (OH⁻, CN⁻, I⁻), primary (or methyl) substrate, polar aprotic solvent. One step — backside attack causes Walden inversion. Rate = k[substrate][nucleophile].
⚗️ Reaction Mechanisms
SN1 = Stable carbocation, Tertiary, Racemization, Polar protic
SN1 Characteristics
SN1 requires: stable carbocation intermediate, tertiary (or secondary) substrate, polar protic solvent (water, alcohol). Two steps. Racemization occurs. Rate = k[substrate] only.
⚗️ Reaction Mechanisms
E2 = Strong base + heat, anti-periplanar, Zaitsev product
E2 Elimination
E2: strong bulky base, heat, one concerted step. Requires anti-periplanar geometry (H and LG 180° apart). Follows Zaitsev's rule — most substituted alkene is major product.
⚗️ Reaction Mechanisms
'When in doubt: primary=SN2, tertiary=SN1 or E1, strong base=E2'
SN1/SN2/E1/E2 Decision
Strong nucleophile + primary = SN2. Strong base + heat = E2. Tertiary + weak nucleophile/base = SN1/E1. Polar protic solvent favors SN1/E1. Polar aprotic favors SN2.
⚗️ Reaction Mechanisms
Arrow pushing: electrons flow from nucleophile to electrophile
Curved Arrow Notation
Curved arrows show electron movement — always from electron-rich to electron-poor. Tail at electron source (lone pair or bond). Head at destination. Never draw arrows backwards.