Explain the followinng in one or two sentences (i) Displacement of cyanide and amide ion is never observed in nucleophilic substitution reaction. (ii) RCl is hydrolysed to ROH slowly but the reaction is rapid if a catalytic amount of KI is added to the reaction mixture.

Explain the followinng in one or two sentences (i) Displacement of cya

1.	Explain the followinng in one or two sentences (i) Displacement of cyanide and amide ion is never observed in nucleophilic substitution reaction. (ii) RCl is hydrolysed to ROH slowly but the reaction is rapid if a catalytic amount of KI is added to the reaction mixture.
Answer» Solution :(i) HCN `(pK_(a)10) and NH_(3)(pK_(a)11.25)` are very weak acids. Therefore, their conjugate bases, i.e., `CN^(-)` ion and `NH_(2)^(-)` are very strong bases. Since strong bases are bad leaving groups, their DISPLACEMENT in nucleophilic substitution reactions is never observed. (ii) Iodide ion is a powerful nucleophile and hence reacts rapidly with RCl to form RI. Further because `I^(-)` ion is a better leaving group than `Cl^(-)` ion, therefore, RI is more rapidly hydrolysed than RCl to form ROH, . The `I^(-)` ion thus regenerated recycles in the above reaction thereby explaining its catalytic effect.