Consider the following statements about the reactions of haloalkanes with cyanides and nitrites.
(A) Groups like cyanides and nitrites possess two nucleophilic centres and are called ambident nucleophiles.
(B) KCN is predominantly ionic, and haloalkanes react with it to form alkyl cyanides as the main product.
(C) AgCN is mainly ionic in nature, and haloalkanes react with it to form isocyanides as the main product.
(D) The linkage of the nitrite ion through its oxygen atom leads to nitroalkanes.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A) and (B) only
An ambident nucleophile can attack through either of two atoms. The cyanide ion can link through C or N, and the nitrite ion through O or N; the atom that links decides which product is formed.
(A) Groups like cyanides and nitrites possess two nucleophilic centres and are called ambident nucleophiles. — True. This is the meaning of an ambident nucleophile.
(B) KCN is predominantly ionic, and haloalkanes react with it to form alkyl cyanides as the main product. — True. KCN gives free CN− ions. Attack takes place mainly through carbon, because a C–C bond is more stable than a C–N bond:
\( \displaystyle \ce{R-X + KCN -> R-CN + KX} \)
(C) AgCN is mainly ionic in nature, and haloalkanes react with it to form isocyanides as the main product. — False. Isocyanides are indeed the main product, but AgCN is mainly covalent. Carbon is held by silver, so the nitrogen is free to donate its electron pair, giving R–NC.
(D) The linkage of the nitrite ion through its oxygen atom leads to nitroalkanes. — False. Linkage through oxygen gives alkyl nitrites (R–O–N=O); nitroalkanes (R–NO2) are formed when the nitrite links through nitrogen.
NCERT (2026-27 edition):
6.7.1 Reactions of Haloalkanes – “Groups like cyanides and nitrites possess two nucleophilic centres and are called ambident nucleophiles.”
Example 6.5 – “KCN is predominantly ionic and provides cyanide ions in solution. Although both carbon and nitrogen atoms are in a position to donate electron pairs, the attack takes place mainly through carbon atom and not through nitrogen atom since C—C bond is more stable than C—N bond. However, AgCN is mainly covalent in nature and nitrogen is free to donate electron pair forming isocyanide as the main product.”
6.7.1 Reactions of Haloalkanes – “…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.”