Preferences of Substitution and Elimination Mechanisms

nonbulky base

strong base: E2

weak base: E1

weak base and nucleophile: Sn1

strong base and nucleophile: Sn2

bulky base

strong base: E2

common strong bases, strong nucleophiles

OH^-, OR, MeO, EtO

common strong bases, weak nucleophiles

t-BuO, DBU, DBN

common weak bases, weak nucleophiles

ROH, ROOH, H₂O

common weak bases, strong nucleophiles

Cl ^- , Br ^-, I ^-, RS ^-, HS ^-, RHS ^-, CN ^-, RNH₂ ^-, H₂S

common bulky bases

common nonbulky bases

polar aprotic solvents

DMSO or DMF

doen’t hydrogen bond; look at high energy based on smaller atomic size

Sn2, E2

polar protic solvents

hydrogen-bonds; contains F, O, or N bonded directly to an H

Sn1, E1