Chemistry · Haloalkanes And Haloarenes · NEET
'Ambi' means both, 'dent' means tooth. So an ambident nucleophile is a nucleophile that has TWO different atoms that both carry a lone pair and can attack the carbon. Only one atom attacks at a time, but which atom attacks decides the product. NCERT lists two main ambident nucleophiles for this chapter: the cyanide ion (C≡N, can attack through C or N) and the nitrite ion (O-N=O, can attack through N or O). This matters for NEET because the same alkyl halide can give two totally different products depending on the reagent.
It is about ionic vs covalent bonding. KCN is mostly ionic, so it gives a FREE cyanide ion (CN⁻) in solution. This free ion attacks through carbon because the C-C bond formed is stronger and more stable than a C-N bond. So you get R-C≡N (alkyl cyanide / nitrile). AgCN is mostly covalent, so the cyanide is NOT free — the carbon is already tied up with silver. Only the nitrogen lone pair is free to attack. So nitrogen bonds to the carbon and you get R-N≡C (isonitrile / isocyanide). This is the exact NCERT reason and a favourite NEET question.
Look at which atom of the cyanide group is joined to the alkyl carbon. In R-C≡N (nitrile / alkyl cyanide) the CARBON is attached to R. In R-N≡C (isonitrile / isocyanide / carbylamine) the NITROGEN is attached to R. The 'iso' one is the nitrogen-attached one from AgCN, and it smells foul. Trick: iso-NitrileNitrogen attached; both start with N.
The nitrite ion, ⁻O-N=O, is also ambident: it can attack through nitrogen or through oxygen. When it attacks through NITROGEN you get a nitroalkane (R-NO2, the nitro group). When it attacks through OXYGEN you get an alkyl nitrite (R-O-N=O, an ester of nitrous acid). In practice, ionic sodium nitrite (NaNO2, also written KNO2) mainly gives the nitroalkane R-NO2 (nitrogen attack), while silver nitrite (AgNO2) mainly gives the alkyl nitrite R-ONO (oxygen attack). This is the same ionic-vs-covalent silver logic as the cyanide case.
Yes — chemically they are the same type of compound. Isocyanides (R-NC) are also called isonitrites/isocyanides/carbylamines. You can make R-NC two ways: (1) alkyl halide + AgCN, or (2) a primary amine + CHCl3 + ethanolic KOH (the carbylamine reaction). Both give the same foul-smelling isocyanide. NEET 2026 tested exactly this — two different routes reaching the SAME isocyanide product.
Both carbon and nitrogen in CN⁻ have a lone pair, so both CAN attack. But when the free ion is available (from ionic KCN), attack through carbon wins because it forms a C-C bond, which is stronger and more stable than a C-N bond. So the product is the nitrile R-C≡N. Nitrogen only wins when carbon is blocked (as in covalent AgCN).
Which of the following reactions of alkyl halides produces an isocyanide (isonitrile) as the major product? (P) R-X + HCN → (Q) R-X + AgCN → (R) R-X + KCN → (S) R-X + NaCN → (H2O/C2H5OH) Choose the most appropriate answer.
The following two reactions give the same foul-smelling product Z. Reaction 1: C2H5Cl + X → Z Reaction 2: C2H5CONH2 →(Br2, NaOH) Y →(CHCl3 / ethanolic KOH, Δ) Z X and Z, respectively, are:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
AgCN gives the isocyanide (R-NC) as the major product because it is covalent and nitrogen attacks. KCN gives the normal alkyl cyanide (R-CN) because it is ionic and carbon attacks.
Cyanide ion (⁻C≡N, can bond through C or N) and nitrite ion (⁻O-N=O, can bond through N or O). NCERT names both.
Ionic NaNO2 (or KNO2) mainly gives the nitroalkane R-NO2 (nitrogen attack). Covalent AgNO2 mainly gives the alkyl nitrite R-O-N=O (oxygen attack).
Because the C-C bond it forms is more stable than a C-N bond. So the free CN⁻ from ionic KCN/NaCN prefers carbon attack, giving the nitrile R-CN.
Yes, all three names mean R-N≡C. It is foul-smelling and can be made from an alkyl halide + AgCN or from a primary amine via the carbylamine reaction.
