Tests for Complete Sulphonation

Tests for Complete Sulphonation.—The sulphonation is tested by the solubility of the product in water or dilute alkali. Complete solubility is seldom obtained owing to the formation of a sulphone by condensation. 

The sulphones are insoluble in water, but may be distinguished, say, from unchanged naphthalene by extracting and taking the melting point. The following factors influence the formation of sulphones concentration of acid (HjSC or S03), temperature of sulphonation, duration of sulphonation. Conditions have to be chosen so that the quantity of sulphone is reduced to a minimum. 

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