Title: quaternary ammonium compounds
Long Title: IUPAC Gold Book - quaternary ammonium compounds
DOI: 10.1351/goldbook.Q05003
Status: current

Definition
Derivatives of ammonium compounds, $\ce{(NH4^{+})Y^{−}}$, in which all four of the hydrogens bonded to nitrogen have been replaced with hydrocarbyl groups.

Note
Compounds having a carbon-nitrogen double bond (i.e. $\ce{R2C=N^{+}R2Y^{−}}$) are more accurately called iminium compounds.

Example
$\ce{[(CH3)4N]^{+}OH^{−}}$, tetramethylammonium hydroxide.

Related Terms
- ammonium compounds: https://goldbook.iupac.org//terms/view/A00290
- hydrocarbyl: https://goldbook.iupac.org//terms/view/H02891
- iminium compounds: https://goldbook.iupac.org//terms/view/I02958
- onium compounds: https://goldbook.iupac.org//terms/view/O04291

Source
- PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1361 (https://doi.org/10.1351/pac199567081307)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/Q05003/html
- json: https://goldbook.iupac.org/terms/view/Q05003/json
- xml: https://goldbook.iupac.org/terms/view/Q05003/xml

Citation: Citation: 'quaternary ammonium 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.Q05003
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Accessed: 2026-05-06T10:29:23+00:00