sulfoxides

https://doi.org/10.1351/goldbook.S06124
Compounds having the structure R2S=O (R ≠ H), e.g. Ph2S=O diphenyl sulfoxide.
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1370 (https://doi.org/10.1351/pac199567081307)