Step 1: Identify the substrate (methyl, 1°, 2°, 3°, allyl, benzyl, vinyl, aryl) Step 2: Identify the reagent (strong Nu/base vs weak Nu/base, bulky vs small) Step 3: Identify the solvent (polar protic vs polar aprotic)

Decision:

• Methyl or 1° + strong Nu + aprotic → SN2
• Methyl or 1° + strong bulky base → E2
• 2° + strong Nu (small) + aprotic → SN2 (major) with some E2
• 2° + strong base (bulky) → E2 (major)
• 2° + weak Nu + protic + heat → SN1/E1 mixture
• 3° + ANY strong base → E2 only
• 3° + weak Nu + protic → SN1 (major) + E1
• Vinyl/Aryl → No SN1/SN2 under normal conditions