sulfonic acids

https://doi.org/10.1351/goldbook.S06118
HS(=O)2OH, sulfonic acid, and its S-hydrocarbyl derivatives.
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1369 (https://doi.org/10.1351/pac199567081307)