A betaine in chemistry is any neutral chemical compound with a positively charged cationic functional group such as an ammonium ion or phosphonium ion (generally: onium ions) and with a negatively charged functional group such as a carboxyl group. Historically the term was reserved for trimethylglycine only. Phosphonium betaines are intermediates in the Wittig reaction. For other uses, see Chemistry (disambiguation). ... A chemical compound is a chemical substance of two or more different chemically bonded chemical elements, with a fixed ratio determining the composition. ... A cation is an ion with positive charge. ... In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... A ball-and-stick model of the ammonium cation Fumes from hydrochloric acid and ammonia forming a white cloud of ammonium chloride Ammonium is also an old name for the Siwa Oasis in western Egypt. ... In chemistry, the phosphonium cation is a positively charged polyatomic ion with the chemical formula PH4+, resulting from protonation of phosphine. ... Onium compounds are cations derived by the protonation of mononuclear parent hydrides of elements of Groups V, VI and VII, and similar ions derived by the substitution of hydrogen atoms in the former by other groups, such as organic radicals, or halogens, including not only ions such as tetramethylammonium, but... A carboxyl or carboxylic group is a functional group consisting of a carbon atom and an oxygen atom doubly bonded to each other. ... Betaine Trimethylglycine (also known as Betaine) is more specifically N,N,N-trimethylglycine and is an organic compound with a structure similar to choline. ... The Wittig reaction is a chemical reaction of an aldehyde or ketone with a phosphonium ylide to give an alkene and triphenylphosphine oxide. ...

In biological systems, many betaines serve as organic osmolytes, substances synthesised or taken up from the environment by cells for protection against osmotic stress, drought, high salinity or high temperature. Intracellular accumulation of betaines, non-perturbing to enzyme function, protein structure and membrane integrity, permits water retention in cells, thus protecting from the effects of dehydration. It is also a methyl donor of increasing significance.

Glycine betaine

Main article: trimethylglycine

Betaine (N,N,N-trimethylglycine) was named after its discovery in sugar beets (Beta vulgaris) in the 19th century. It is a small N-trimethylated amino acid, existing in zwitterionic form at neutral pH. This substance is often called ‘‘glycine betaine’’ to distinguish it from other betaines that are widely distributed in microorganisms, plants and animals. Betaine Trimethylglycine (also known as Betaine) is more specifically N,N,N-trimethylglycine and is an organic compound with a structure similar to choline. ... A zwitterion (from German Zwitter — hybrid, hermaphrodite) is a compound with acidic and basic groups in the same molecule. ...

External links

• IUPAC Gold Book definition