Definition of zwitterionic compounds/zwitterions

1. 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). See betaines, dipolar compounds, ylides. E.g. H3N+CH2C(=O) O ammonioacetate (glycine), (CH3)3N+-O- trimethylamine ox