Read the following passage and answer questions.
Nucleophiles attack at that part of the substrate molecule which is electron deficient. The reaction in which a nucleophile replaces already existing nucleophile in a molecule is called nucleophilic substitution reaction. Haloalkanes are substrates in these reactions. In this type of reaction, a nucleophile reacts with haloalkane (the substrate) having a partial positive charge on the carbon atom bonded to halogen. A substitution reaction takes place and halogen atom, called leaving group departs as halide ion. Since the substitution reaction is initiated by a nucleophile, it is called nucleophilic substitution reaction.
When AgCN reacts with R-X, what is the major product ?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Isonitrile
The cyanide group is an ambident nucleophile (–C≡N:). AgCN is mainly covalent: the carbon of the cyanide group is bonded to silver, so it is not free to attack. The nitrogen lone pair attacks the carbon of the haloalkane instead, and the main product is an alkyl isocyanide (isonitrile):
\( \displaystyle \ce{R-X + AgCN -> R-N#C + AgX} \)
Why the other options are incorrect
Option (1) Alcohol — Incorrect. It is formed with \( \ce{OH-} \) (aqueous KOH).
Option (2) Ether — Incorrect. It is formed with an alkoxide ion.
Option (4) Nitrile — Incorrect. It is the main product with KCN, which is ionic and attacks through carbon.
NCERT (2026-27 edition):
Reactions of Haloalkanes – Table 6.4: Nucleophilic Substitution of Alkyl Halides (R–X)
| Reagent | Substitution product R–Nu | Class of main product |
|---|---|---|
| NaOH (KOH) | ROH | Alcohol |
| H2O | ROH | Alcohol |
| NaOR′ | ROR′ | Ether |
| NaI | R—I | Alkyl iodide |
| NH3 | RNH2 | Primary amine |
| R′NH2 | RNHR′ | Sec. amine |
| R′R″NH | RNR′R″ | Tert. amine |
| KCN | RCN | Nitrile (cyanide) |
| AgCN | RNC | Isonitrile (isocyanide) |
| KNO2 | R—O—N=O | Alkyl nitrite |
| AgNO2 | R—NO2 | Nitroalkane |
| R′COOAg | R′COOR | Ester |
| LiAlH4 | RH | Hydrocarbon |
| R′– M+ | RR′ | Alkane |