Trimethylamine N-oxide, also known by several other names and acronyms, is the organic compound with the formula (CH₃)₃NO. This colourless solid is usually encountered as the dihydrate. It is an oxidation product of trimethylamine and a common metabolite in animals. It is an osmolyte found in saltwater fish, sharks and rays, molluscs, and crustaceans. Along with free amino acids, it reduce the 3% saltiness of seawater to about 1% of dissolved solids inside cells. TMAO decomposes to trimethylamine (TMA), which is the main odorant that is characteristic of degrading seafood.

Synthesis

Treatment of aqueous trimethylamine with hydrogen peroxide affords the dihydrate (Me = CH₃):^[1]

H₂O₂ + Me₃N ? H₂O + Me₃NO

trimethylamine-N-oxide is biosynthesized from from trimethylamine, which is derived from choline.^[2]

Trimethylaminuria

Trimethylaminuria is a defect in the production of the enzyme flavin containing monooxygenase 3 (FMO3),^[3][4], causing incomplete breakdown of trimethylamine from choline-containing food into trimethylamine oxide. Trimethylamine then builds up and is released in the person's sweat, urine, and breath, giving off a strong fishy odor.

Laboratory applications

Trimethylamine oxide is used in protein folding experiments to counteract the unfolding effects of urea. ^[5]

In organometallic chemistry, Me₃NO is employed as a decarbonylation agent according to the following stoichiometry:

M(CO)_n + Me₃NO + L ? M(CO)_n-1L + Me₃N + CO₂

This reaction is used to decomplex organic ligands from metals, e.g. from (diene)Fe(CO)₃.^[1]

It is used in certain oxidation reactions, e.g. the conversion of alkyl iodides to the aldehyde.^[6]

References

1. ↑ ^{a b} A. J. Pearson "Trimethylamine N-Oxide" in Encyclopedia of Reagents for Organic Synthesis John Wiley & Sons, 2001: New York.
2. ↑ Baker, J.R.; Chaykin, S. ?The biosynthesis of trimethylamine-N-oxide? J. Biol. Chem. 1962, volume 237, pp. 1309-13.
3. ↑
4. ↑
5. ↑
6. ↑ Volker Franzen? Octanal? Organic Syntheses, Coll. Vol. 5, p.872 (1973). CV5P0872