The major product Z obtained in the following reaction scheme is:

When a diazonium salt is treated with copper (I) chloride (${\mathrm{Cu}}_2{\mathrm{Cl}}_2$Cu2Cl2) or copper (I) bromide (${\mathrm{Cu}}_2{\mathrm{Br}}_2$), the corresponding haloarene is formed. This reaction is known as Sandmeyer reaction. It is used for introducing a chloro or bromo group in the benzene ring.