A kinetic distinction between the operation of S N 1 and S N 2 modes can be made by observing the effect on the overall reaction rate by adding a competing nucleophile. The total nucleophilic concentration is thus increased, so this will result in an increased reaction rate in S N 2 route. By contrast for S N 1 mode, the [Nu: Θ ] will not appear in the rate equation, the addition of competing nucleophile will fails significant effect on the observed reaction rate, though it will naturally influcence the composition of the products.

(i) In which of the following reactions the overall reaction rate may increase by addition of NaN 3 .

(i) CH 3 Cl + NaOH ⎯→

(ii) (CH 3 ) 3 CCl + H 2 O ⎯→

(iii) ⎯→

(iv) (CH 3 ) 2 CH–OH + NaBr + H 2 SO 4 ⎯→