The leaving group is that functional group which is ejected with `overline e^, s` of the `sigma` -bond in a reaction. Better the leaving group, faster is the reaction. The relative leaving ability of the leaving group `X` in `(R - X)` is increased by :
(i) The polarisability of `(R - X)` bond.
(ii) The stability of `X^(Ө)`.
(iii) The degree of stabilisation through solvation of `X`.
(iv) The strength of `(R - X)` bond.
The leaving group tendency is also called fugacity.
Which statement is correct ?

Options

A. `EtO^(Ө)` is a strong base and therefore a good leaving group.
B. The amine group in `ArNH_2` is converted into a good leaving group be reacting `ArNH_2` with `NaNO_2 + HCl` at `0^@ C`.
C. The `(OH)` group is converted into a good leaving group by reacting alcohols with `TsCl` (p-toluene sulphonyl chloride)
D. The amine group in `RNH_2` is converted into leaving group by reacting `RNH_2` with `NaNO_2 + HCl` at `0^@ C`.

Answer

C

Explanation

(a) `EtO^(Ө)` is a strong base and so a poor leaving group.
(b) `ArNH_2 + NaNO_2 + HCl overset (at 0^@ C)rarr Ar - overset (oplus)N -= N - Cl`
The benzene diazonium ion `(Ar overset (oplus) N H_2)` is stabilised by resonance. So it is a poor leaving group. But in `R overset (oplus) N_2`. it is not stabilised, so it is a good leaving group because it is conjugate base (weak base) of a strong acid `(TsOH)`

(d) `RNH_2 + NaNO_2 + HCl rarr ROH + N_2 + NaCl`.