Title: oxo compounds
Long Title: IUPAC Gold Book - oxo compounds
DOI: 10.1351/goldbook.O04377
Status: current

Definition
Compounds containing an oxygen atom, $\ce{=O}$, doubly bonded to carbon or another element. The term thus embraces aldehydes, carboxylic acids, ketones, sulfonic acids, amides and esters. Oxo used as an adjective (and thus separated by a space) modifying another class of compound, as in oxo carboxylic acids, indicates the presence of an oxo substituent at any position. To indicate a double-bonded oxygen that is part of a ketonic structure, the term keto is sometimes used as a prefix, but such use has been abandoned by IUPAC for naming specific compounds. A traditional use of keto is for indicating oxidation of $\ce{CHOH}$ to $\ce{C=O}$ in a parent compound that contains $\ce{OH}$ groups, such as carbohydrates, e.g. 3-ketoglucose.

Related Terms
- aldehydes: https://goldbook.iupac.org//terms/view/A00208
- amides: https://goldbook.iupac.org//terms/view/A00266
- carbohydrates: https://goldbook.iupac.org//terms/view/C00820
- carboxylic acids: https://goldbook.iupac.org//terms/view/C00852
- esters: https://goldbook.iupac.org//terms/view/E02219
- keto: https://goldbook.iupac.org//terms/view/K03382
- ketoaldonic acids: https://goldbook.iupac.org//terms/view/K03383
- ketoaldoses: https://goldbook.iupac.org//terms/view/K03384
- ketones: https://goldbook.iupac.org//terms/view/K03386
- oxidation: https://goldbook.iupac.org//terms/view/O04362
- oxo carboxylic acids: https://goldbook.iupac.org//terms/view/O04376
- sulfonic acids: https://goldbook.iupac.org//terms/view/S06118

Source
- PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1355 (https://doi.org/10.1351/pac199567081307)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/O04377/html
- json: https://goldbook.iupac.org/terms/view/O04377/json
- xml: https://goldbook.iupac.org/terms/view/O04377/xml

Citation: Citation: 'oxo compounds' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.O04377
License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.
Collection: If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .
Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-06-21T05:21:38+00:00