Sulphonic acids, reactions aliphatic, preparation

The former are true aromatic sulphonic acids prepared by direct sulphonation, and reacting like benzene sulphonic acid. The latter are aliphatic sulphonic acids both in methods of preparation and reaction. 

Sulphonic Acids to Hydroxyl Compounds.—(4) Reactions with alkalies by fusion. In the aliphatic series the most important synthetic reaction for the formation of hydroxyl derivatives is the treatment of the alkyl halides with silver hydroxide, which reaction we have said does not occur in the benzene series when the substitution is in the ring and not in the side chain. The most important method for preparing ring-hydroxyl compounds is by the fusion of a sulphonic acid or its salt with alkalies, potassium or sodium hydroxide, a reaction which does not occur with the aliphatic sulphonic acids. 

When an aromatic compound is treated with sulphuric acid, a portion of the benzene-hydrogen is replaced by a sulphonic acid group, the reaction taking place in accordance with the equation below. The aliphatic compounds do not react in a similar manner. Under the preparation of benzene sulphonic acid, the details of the reaction will be discussed. 

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