Substitution and Elimination of Haloalkanes

Substrate            Nucleophile (Base)                    Primary Mechanism(s)                   Products

Methyl - X           Any Base                                     S_N2 Only                                   S_N2 Only

1° R - X               Weak Base                                   S_N2 Highly Favored                 S_N2 Mostly, E2 Trace

1° R - X               Strong Unhindered Base             S_N2, E2                                     S_N2 Major, E2 Minor

1° R - X               Strong Hindered Base                 S_N2, E2                                     E2 Major, S_N2 Minor

2° R - X               Weak Base                                S_N2, E2                                     S_N2 Major, E2 Trace

2° R - X               Strong Unhindered Base             S_N2, E2                                     S_N2 and E2 (Depends)

2° R - X               Strong Hindered Base                 E2 Highly Favored                   E2 Mostly, S_N2 Trace

3° R - X               Weak Base (Solvolysis)               S_N1 Favored, E1                       S_N1 Major, E1 Minor

3° R - X               Strong Unhindered Base             E2 Highly Favored                   E1, E2 Mostly, S_N1 Trace

3° R - X               Strong Hindered Base                 E2 Highly Favored                   E1, E2 Mostly, S_N1 Trace