Which statement is NOT correct for p-toluenesulphonyl chloride?

We need to identify the statement that is NOT correct about p-toluenesulphonyl chloride (Hinsberg's reagent).

p-Toluenesulphonyl chloride ($$CH_3C_6H_4SO_2Cl$$) is known as Hinsberg's reagent. It is used to distinguish between primary, secondary, and tertiary amines based on their different reactions with this reagent.

Option A: "It is Hinsberg's reagent" — This is correct. p-Toluenesulphonyl chloride is indeed Hinsberg's reagent.

Option B: "It is used to distinguish primary and secondary amines" — This is correct. Primary amines form N-alkyl sulphonamides that are soluble in alkali (due to the acidic N-H), while secondary amines form N,N-dialkyl sulphonamides that are insoluble in alkali (no N-H for salt formation).

Option C: "On treatment with secondary amine, it leads to a product that is soluble in alkali" — This is NOT correct. When a secondary amine reacts with Hinsberg's reagent, the product is $$CH_3C_6H_4SO_2NR_2$$, which has no acidic hydrogen on nitrogen. Therefore, it is insoluble in alkali. Only the product from primary amines ($$CH_3C_6H_4SO_2NHR$$) is soluble in alkali because the N-H hydrogen is acidic enough to form a sodium salt.

Option D: "It does not react with tertiary amine" — This is correct. Tertiary amines have no N-H bond, so they cannot undergo the sulphonamide reaction with Hinsberg's reagent.

Therefore, the correct answer is Option C.