Secondary amines on reaction with Hinsberg's reagent (benzene sulphonyl chloride) forms N,N-dialkyl benzene sulphonamide. The product formed is not acidic as no H-atom is attached to N thus it is insoluble in alkali. The reaction of 2∘ amine given in option (1) takes place as follows: 

On the other hand, 1∘ amines react with Hinsberg's reagent to yield N-alkyl benzene sulphonamide which is soluble in alkali and 3∘ amines do not react with C6H5SO2Cl. The remaining options contain 1∘ and 3∘ amines.
Thus, option (1) is correct.



