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 $KNO_2$ reacts with R-X, what is the major product?

Alkyl nitrite

The correct answer is Option (4) → Alkyl nitrite

When potassium nitrite (KNO₂) reacts with an alkyl halide (R–X), the reaction typically gives a mixture of two products:

• Nitroalkane (R–NO₂)

• Alkyl nitrite (R–O–NO)

However, the major product depends on the metal:

• With KNO₂, the major product is alkyl nitrite (R–O–NO)

• With AgNO₂, the major product is nitroalkane (R–NO₂)

This difference arises due to the nucleophilicity of the nitrite ion (NO₂⁻), which is ambident (can attack via N or O):

• K⁺NO₂⁻ → O-attack (→ R–O–NO) → Alkyl nitrite (major)

• Ag⁺NO₂⁻ → N-attack (→ R–NO₂) → Nitroalkane (major)

 So in this case (with KNO₂), the major product is: Alkyl nitrite