Complete: C₆H₅N₂^+Cl^- reacts with: (a) CuCN (b) HBF₄ (c) H₃PO₂ + H₂O — JEE Chemistry

(a) Sandmeyer reaction with CuCN:

$$C_6H_5N_2^+Cl^- + CuCN \rightarrow C_6H_5CN (benzonitrile) + N_2$$

(b) Balz–Schiemann reaction:

$$C_6H_5N_2^+Cl^- + HBF_4 \rightarrow C_6H_5N_2^+BF_4^- \xrightarrow{\Delta} C_6H_5F (fluorobenzene) + N_2 + BF_3$$

(c) Deamination (replacement by H):

$$C_6H_5N_2^+Cl^- + H_3PO_2 + H_2O \rightarrow C_6H_6 (benzene) + N_2 + HCl + H_3PO_3$$