Term: zwitterionic compounds/zwitterions
https://doi.org/10.1351/goldbook.Z06752

Definition:
Neutral compounds having formal unit electrical charges of opposite sign. Some chemists restrict the term to compounds with the charges on non-adjacent atoms. Sometimes referred to as inner salts, dipolar ions (a misnomer). E.g. H3N+CH2C(=O)O− ammonioacetate (glycine), (CH3)3N+–O− trimethylamine oxide.

Related Terms:
1) betaines (http://doi.org/10.1351/goldbook.B00637).
2) dipolar compounds (http://doi.org/10.1351/goldbook.D01753).
3) ylides (http://doi.org/10.1351/goldbook.Y06728).

Source: PAC, 1994, 66, 1077. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)' on page 1176 (https://doi.org/10.1351/pac199466051077)

Citation: 'zwitterionic compounds/zwitterions' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.Z06752

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