Which of following reagents will furnish ambident nucleophile?
(A) \( AgCN \)
(B) \( KCN \)
(C) \( AgNO_2 \)
(D) \( KNO_2 \)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B), (C) and (D)
An ambident nucleophile has two different atoms through which it can attack. The cyanide ion can attack through carbon or through nitrogen, since both atoms carry a lone pair, and the nitrite ion through oxygen or through nitrogen. Each of the four reagents furnishes one of these ions; which atom attacks depends on the reagent.
(A) \( \ce{AgCN} \) — Correct. Silver cyanide is mainly covalent (Ag–C bond), so the free lone pair on nitrogen attacks and an isocyanide is formed:
\( \displaystyle \ce{R-X + AgCN -> R-NC + AgX} \)
(B) \( \ce{KCN} \) — Correct. Potassium cyanide is ionic and gives free \( \ce{CN-} \) ions, which attack through carbon (the C–C bond is more stable), giving an alkyl cyanide:
\( \displaystyle \ce{R-X + KCN -> R-CN + KX} \)
(C) \( \ce{AgNO2} \) — Correct. With silver nitrite the nitrite group attacks through nitrogen, giving a nitroalkane:
\( \displaystyle \ce{R-X + AgNO2 -> R-NO2 + AgX} \)
(D) \( \ce{KNO2} \) — Correct. Potassium nitrite gives free \( \ce{O-N=O^-} \) ions, which attack through oxygen, giving an alkyl nitrite:
\( \displaystyle \ce{R-X + KNO2 -> R-O-N=O + KX} \)
NCERT (2026-27 edition):
Nucleophilic Substitution Reactions – “… Groups like cyanides and nitrites possess two nucleophilic centres and are called ambident nucleophiles. Actually cyanide group is a hybrid of two contributing structures and therefore can act as a nucleophile in two different ways [−C≡N ↔ :C=N−], i.e., linking through carbon atom resulting in alkyl cyanides and through nitrogen atom leading to isocyanides. Similarly nitrite ion also represents an ambident nucleophile with two different points of linkage [–O–N=O]. The linkage through oxygen results in alkyl nitrites while through nitrogen atom, it leads to nitroalkanes.”