Hinsberg reagent is benzenesulfonyl chloride, whose formula is:$\mathrm{C_6H_5SO_2Cl}$It is used in the Hinsberg test to distinguish between:Primary aminesSecondary aminesTertiary aminesThe other options represent different compounds:(A) $\mathrm{C_6H_5COCl}$ $\rightarrow$ Benzoyl chloride(C) $\mathrm{C_6H_5CONHCH_3}$$\rightarrow$ An amide(D) $\mathrm{C_6H_6CH_2NH_2}$ $\rightarrow$ BenzylamineTherefore, the correct formula of Hinsberg’s reagent is $\mathrm{C_6H_5SO_2Cl}$ .