Benzene diazonium chloride is a compound that contains a diazonium group (-N2+Cl-) attached to a benzene ring. When it reacts with hypophosphorus acid (H3PO2), it undergoes a reaction called the Sandmeyer reaction, which results in the substitution of the diazonium group with a hydrogen atom.

Explanation:

The reaction between benzene diazonium chloride and hypophosphorus acid proceeds as follows:

Step 1: Formation of diazonium salt
Benzene diazonium chloride reacts with hypophosphorus acid to form the diazonium salt. The hypophosphorus acid donates a hydride ion (H-) to the diazonium group, resulting in the formation of nitrogen gas (N2) and the formation of the diazonium salt.

C6H5N2+Cl- + H3PO2 → C6H5N2+ + Cl- + H3PO3

Step 2: Hydrolysis of diazonium salt
The diazonium salt formed in step 1 undergoes hydrolysis in the presence of water. This hydrolysis reaction results in the formation of phenol.

C6H5N2+ + H2O → C6H5OH + N2

Therefore, the overall reaction can be represented as:

C6H5N2+Cl- + H3PO2 + H2O → C6H5OH + N2 + H3PO3 + Cl-

The final product of this reaction is phenol (C6H5OH). Therefore, option A (Benzene) is the correct answer.

The Sandmeyer reaction is a useful method for the preparation of phenols from diazonium salts. It is a substitution reaction that involves the replacement of the diazonium group (-N2+) with a hydrogen atom. This reaction is widely used in the synthesis of various aromatic compounds, including phenols, anilines, and halogenated aromatic compounds. It is an important reaction in organic chemistry and has been extensively studied and utilized for the synthesis of diverse compounds.