Substitution vs. Elimination

Cl-

nucleophile only

Br-

nucleophile only

I-

nucleophile only

HS-

nucleophile only

RS-

nucleophile only

H2S

nucleophile only

RSH

nucleophile only

C≡N-

nucleophile only

N3-

nucleophile only

RC=OO-

nucleophile only

H-

base only

HO-

strong nucleophile/base

MeO-

strong nucleophile/base

EtO-

strong nucleophile/base

tBuO-

strong nucleophile/base

RC≡C-

strong nucleophile/base

H2O

weak nucleophile/base

MeOH

weak nucleophile/base

EtOH

weak nucleophile/base

Nucleophile only

SN

Base only

E2

Strong nucleophile/base

SN2 or E2

Look at substrate type and temp

SN2 or E2

Weak nucleophile/base

SN1 or E1

Look at temp only

SN1 or E1

CH3 + strong nucleophile/base

SN2

1° + strong nucleophile/base

SN2 or E2 (w/ tBuO)

2° + strong nucleophile/base

E2

3° + strong nucleophile/base

E2

1° + weak nucleophile/base

SN2

2° + weak nucleophile/base

SN1 (@ low temp) or E1 (@ high temp)

3° + weak nucleophile/base

SN1 (@ low temp) or E1 (@ high temp)