• (n.) A substance employed as a hypnotic, produced by the union of mercaptan and acetone.
Sul'pho·nal noun (Medicine) A substance employed as a hypnotic, produced by the union of mercaptan and acetone. 
Sulphonal (Dimethylmethane diethylsulphone) is a hypnotic manufactured by the interaction of acetone and ethyl mercaptan in the presence of zinc chloride and the oxidation of the resulting product with potassium permanganate.