(a) Sandmeyer Reaction: This reaction involves the conversion of a benzene diazonium salt into an aryl halide using a cuprous salt (like $$Cu_2Cl_2$$) as the reagent.
$$C_6H_5N_2^+Cl^- \xrightarrow{Cu_2Cl_2} C_6H_5Cl + N_2$$
(b) Gatterman Reaction: This is a modified version of the Sandmeyer reaction. Instead of a cuprous salt, it uses finely divided copper powder ($Cu$) in the presence of a halogen acid (like $$HCl$$) to convert the diazonium salt into an aryl halide.
$$C_6H_5N_2^+Cl^- \xrightarrow{Cu, HCl} C_6H_5Cl + N_2$$(c) Wurtz Reaction: This coupling reaction involves treating two moles of an alkyl halide (aliphatic) with sodium metal in the presence of dry ether to form a higher alkane.
$$2CH_3CH_2Cl + 2Na \xrightarrow{\text{Ether}} C_2H_5-C_2H_5 + 2NaCl$$
(d) Fittig Reaction: This is the aromatic equivalent of the Wurtz reaction. It involves treating two moles of an aryl halide (aromatic) with sodium metal in dry ether to couple the rings together, forming a diaryl compound (biphenyl).
$$2C_6H_5Cl + 2Na \xrightarrow{\text{Ether}} C_6H_5-C_6H_5 + 2NaCl$$
(a)→(ii), (b)→(iv), (c)→(i), (d)→(iii)
The correct match is the above. The correct option is option D.