His work on the oxyacids and oxyanions of the halogens was important. Their molecular structure, however, is much more complicated than that of inorganic oxyacids. Antimony forms antimony(III) oxide and antimonite but not oxyacids. Sulfonic acids, which are organic oxyacids, are a class of strong acids. These anhydrides react quickly with water and form those oxyacids again. Sulfonic acids, such as p-toluenesulfonic acid (tosylic acid) are a class of strong organic oxyacids. Other important oxyacids of phosphorus are phosphoric acid (HPO) and hypophosphorous acid (HPO). Most of the commonly encountered acids are oxyacids. Many organic acids, like carboxylic acids and phenols, are oxyacids.