Betaine
A betaine () is any neutral chemical compound with a positively charged cationic functional group that bears no hydrogen atom, such as a quaternary ammonium or phosphonium cation (generally: onium ions), and with a negatively charged functional group, such as a carboxylate group that may not be adjacent to the cationic site. They are thus zwitterions, but cannot isomerize because there is no labile hydrogen atom attached to the nitrogen atom.