sulfonate - hydrocarbon in which a hydrogen atom has been replaced with the highly polar (S020X) group, where X is a metallic ion or alkyl radical. Petroleum sulfonates are refinery by-products of the sulfuric acid treatment of white oils. Sulfonates have important applications as emulsifiers and chemical intermediates in petrochemical manufacture. Synthetic sulfonates can be manufactured from special feed stocks rather than from white oil base stocks. See polar compound.