Sulphonic /(?)/

Sul·phon·ic

Sulphonic

a.
  1. Pertaining to, or derived from, a sulphone; -- used specifically to designate any one of a series of acids (regarded as acid ethereal salts of sulphurous acid) obtained by the oxidation of the mercaptans, or by treating sulphuric acid with certain aromatic bases (as benzene); as, phenyl sulphonic acid, C6H5.SO2.OH, a stable colorless crystalline substance. (Chem.)

Phrases & Compounds
Sulphonic group
the hypothetical radical, SO2.OH, the characteristic residue of sulphonic acids.