Title: acyl species
Long Title: IUPAC Gold Book - acyl species
DOI: 10.1351/goldbook.A00129
Status: current

Definition
Acyl intermediates include acyl anions, acyl radicals and acyl cations (synonym acylium ions) which are formally derived from oxoacids $\ce{R_{k}E(=O)_{l}(OH)_{m}}$ ($l \neq 0$) by removal of a hydroxyl cation $\ce{HO^{+}}$, a hydroxyl radical $\ce{HO^{.}}$ or a hydroxyl anion $\ce{HO^{-}}$, respectively, and replacement analogues of such intermediates. Acyl anions, radicals and cations can formally be represented by canonical forms having a negative charge, an unpaired electron or a positive charge on the acid-generating element of the oxoacid.Acyl anions, e.g. Acyl radicals, e.g. Acyl cations, e.g. 

Related Terms
- acyl groups: https://goldbook.iupac.org//terms/view/A00123
- anion: https://goldbook.iupac.org//terms/view/A00358
- cation: https://goldbook.iupac.org//terms/view/C00907
- intermediates: https://goldbook.iupac.org//terms/view/I03096
- oxoacids: https://goldbook.iupac.org//terms/view/O04374

Sources
- PAC, 1993, 65, 1357. 'Revised nomenclature for radicals, ions, radical ions and related species (IUPAC Recommendations 1993)' on page 1357 (https://doi.org/10.1351/pac199365061357)
- PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1312 (https://doi.org/10.1351/pac199567081307)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/A00129/html
- json: https://goldbook.iupac.org/terms/view/A00129/json
- xml: https://goldbook.iupac.org/terms/view/A00129/xml

Citation: Citation: 'acyl species' 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.A00129
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Accessed: 2026-05-06T17:22:33+00:00