Q.Identify compounds A, B and C in the following sequences of reactions:

Step 1. i) C6H5NO2 + Fe/HCl reduces to A = aniline. A + HNO2 at 273 K diazotises to B = benzenediazonium chloride. B + C6H5OH (phenol, an electron-rich coupling partner) is the coupling reaction (retention of the diazo group), giving C = p-hydroxyazobenzene, an orange azo dye, coupling occurring at phenol's para position.

Step 2. ii) C6H5N2+Cl- + CuCN is the Sandmeyer reaction, replacing -N2+ with -CN to give A = cyanobenzene (benzonitrile). A + H2O/H+ is complete acid hydrolysis of the nitrile, giving B = benzoic acid. B + NH3 forms the ammonium salt directly, giving C = ammonium benzoate (the same intermediate the unit's own P2O5-dehydration route to benzonitrile would start from, closing a loop back toward the nitrile if driven further). …

Trace each named reagent to its named reaction in turn (Fe/HCl reduction, HNO2 diazotisation, phenol coupling; CuCN Sandmeyer, acid hydrolysis, NH3 salt formation; NaCN substitution, PARTIAL hydroly …

• In sequence (iii), taking A + H3O+ all the way to the carboxylic acid (COMPLETE hydrolysis) instead of stopping at the amide -- the question specifies 'partial hydrolysis', which the unit's own two-stage hydrolysis rule (H2O2/OH- to the amide; 2H2O/H+ to the ac …