The correct pair(s) of the ambident nucleophiles is(are)
(A) AgCN/KCN
(B) RCOOAg/RCOOK
(C) AgNO₂/KNO₂
(D) AgI/KI

Solution

Chemistry ma’am · 3 steps

Look at the anion, not the metal: ambident means two different atoms that can each donate the lone pair.

1. What ambident means. An ambident nucleophile has two different donor atoms. Depending on which one attacks, you get two different products. The Ag or K salt only decides which atom ends up attacking.

   Anion	Donor atoms	Products with R-X	Ambident?
   CN⁻	C and N	KCN gives R-CN, AgCN gives R-NC	Yes
   RCOO⁻	two O atoms, equivalent by resonance	only the ester RCOOR'	No
   NO₂⁻	N and O	KNO₂ gives R-O-N=O, AgNO₂ gives R-NO₂	Yes
   I⁻	only I	only R-I	No

2. Why carboxylate fails. In RCOO⁻ the negative charge is shared equally between two oxygen atoms. Whichever oxygen attacks, the bond formed is the same C–O bond, so there is only one product.
3. So. Only cyanide and nitrite have two different donor atoms, so pairs (A) and (C) are ambident. The answer is (c).

The idea to keep. Call a nucleophile ambident only if two different atoms can attack and give two different products. Two identical resonance-equivalent atoms, like the O atoms of RCOO⁻, do not count.

Answer from the NTA final answer key. Solution by PrepWiser.