Question

Which compound in each of the following pairs will react faster in S_N2 reaction with OH ion? 

1. CH₃Br or CH₃I 

2. (CH₃)₃ CCl or CH₃Cl

Answer 1

1. Since I^- ion a better leaving group than Br^- ion, therefore CH₃I will react faster than CH₃Br in S_N2 reaction with OH^- ion. 

2. On steric grounds 1° alkyl halides are more reactive than tert alkyl halide in S_N2 reactions. Therefore, CH₃Cl will react at a faster rate than (CH₃)₃ CCl in a S_N2 reaction with OH^- ion.