Haloalkanes react with potassium nitrite (KNO2) to form alkyl nitrites while silver nitrite (AgNO2) forms nitroalkanes as the chief product. Explain.
Answer : Nitrite ion is an ambident nucleophile because it has two sites — oxygen and nitrogen — through which attack can take place.
Potassium nitrite (KNO2) is predominantly ionic and one of the oxygen atoms has a negative charge (O=N−O−K+). Nucleophilic attack through this negatively charged oxygen atom mainly gives alkyl nitrite.
Silver nitrite (AgNO2), on the other hand, is predominantly covalent and both oxygen and nitrogen atoms have lone pair of electrons. Since nitrogen is less electronegative than oxygen, the lone pair of electrons on nitrogen are more easily available for bond formation. In short, nucleophilic attack takes place through nitrogen; hence, nitroalkanes are obtained as chief products.