acid anhydrides derived by loss of water between two oxoacid functions RkE(=O)l(OH)m
≠ 0) (carboxylic, sulfonic, etc.) in the same molecule so as to close a ring. Oxo oxygen replacement analogues are included, e.g.
See: acid anhydrides, thioanhydrides
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1329 (https://doi.org/10.1351/pac199567081307)