Q.Complete the following reactions :
a. C6H5N2(+)Cl(-) + C2H5OH → ?
b. C6H5NH2 + Br2(aq) → ?

Step 1. (a) Diazonium salt + ethanol (section 13.7.1, Table 13.5, mild reduction row). Ethanol acts here as a mild reducing agent for the diazonium salt, itself being oxidised to acetaldehyde in the process: Ar-N2(+)Cl(-) + CH3-CH2-OH gives Ar-H + N2 + CH3-CHO + HCl. Applied to benzenediazonium chloride specifically: C6H5-N2(+)Cl(-) + C2H5OH gives C6H5-H (plain benzene) + N2 + CH3-CHO (acetaldehyde) + HCl. …

Applying section 13.7.1's Table 13.5 mild-reduction-by-ethanol row to part (a), and section 13.9's own wo …

• For part (a), confusing ethanol's mild-reduction role (Ar-N2+ to Ar-H, with ethanol itself oxidised to acetaldehyde) with the SEPARATE phenol-formation reaction that plain WATER gives with a diazonium salt (Ar-N2+ + H2O gives Ar-OH); these use different nucleophiles/reductants and give genuinely different products. …