Question

In the replacement reaction

The reaction will be most favourable if M happens to be

(a) Na

(b) K

(c) Rb

(d) Li

Answer 1

Correct option (c) Rb

Explanation :

Tertiary halide shows S_N1 mechanism i.e., ionic mechanism. In the given reaction negative ion will attack on carbocation. Thus greater the tendency of ionisation (greater ionic character in M - F bond) more favourable will be reaction. The most ionic bond is Rb - F in the given examples thus most favourable reaction will be with Rb-F.