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Trimethylamine
Chemical compound responsible for rotten fish odor From Wikipedia, the free encyclopedia
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Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a trimethylated derivative of ammonia. TMA is widely used in industry.[5][6] At higher concentrations it has an ammonia-like odor, and can cause necrosis of mucous membranes on contact.[7] At lower concentrations, it has a "fishy" odor, the odor associated with rotting fish.
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Physical and chemical properties
TMA is a colorless, hygroscopic, and flammable tertiary amine. It is a gas at room temperature but is usually sold as a 40% solution in water. It is also sold in pressurized gas cylinders.
TMA protonates to give the trimethylammonium cation. Trimethylamine is a good nucleophile, and this reactivity underpins most of its applications. Trimethylamine is a Lewis base that forms adducts with a variety of Lewis acids.[8]
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Production
Industry and laboratory
Trimethylamine is prepared by the reaction of ammonia and methanol employing a catalyst:[5]
- 3 CH3OH + NH3 → (CH3)3N + 3 H2O
This reaction coproduces the other methylamines, dimethylamine (CH3)2NH and methylamine CH3NH2.
Trimethylammonium chloride has been prepared by a reaction of ammonium chloride and paraformaldehyde:[9]
- 9 (CH2=O)n + 2n NH4Cl → 2n (CH3)3N•HCl + 3n H2O + 3n CO2
Biosynthesis
Trimethylamine is produced by several routes in nature. Well studied are the degradation of choline and carnitine.[10]
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Applications
Trimethylamine is used in the synthesis of choline, tetramethylammonium hydroxide, plant growth regulators, herbicides, strongly basic anion exchange resins, dye leveling agents and a number of basic dyes.[5][6] Gas sensors to test for fish freshness detect trimethylamine.
Toxicity
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In humans, ingestion of certain plant and animal (e.g., red meat, egg yolk) food containing lecithin, choline, and L-carnitine provides certain gut microbiota with the substrate to synthesize TMA, which is then absorbed into the bloodstream.[11][12] High levels of trimethylamine in the body are associated with the development of trimethylaminuria, or fish odor syndrome, caused by a genetic defect in the enzyme which degrades TMA; or by taking large doses of supplements containing choline or L-carnitine.[11][12] TMA is metabolized by the liver to trimethylamine N-oxide (TMAO); TMAO is being investigated as a possible proatherogenic substance which may accelerate atherosclerosis in those eating foods with a high content of TMA precursors.[12] TMA also causes the odor of some human infections, bad breath, and bacterial vaginosis.
Trimethylamine is a full agonist of human TAAR5,[13][14][15] a trace amine-associated receptor that is expressed in the olfactory epithelium and functions as an olfactory receptor for tertiary amines.[15][16] One or more additional odorant receptors appear to be involved in trimethylamine olfaction in humans as well.[16]
Acute and chronic toxic effects of TMA were suggested in medical literature as early as the 19th century. TMA causes eye and skin irritation, and it is suggested to be a uremic toxin.[17] In patients, trimethylamine caused stomach ache, vomiting, diarrhoea, lacrimation, greying of the skin and agitation.[18] Apart from that, reproductive/developmental toxicity has been reported.[7] Some experimental studies suggested that TMA may be involved in etiology of cardiovascular diseases.[19][20]
Guidelines with exposure limit for workers are available e.g. the Recommendation from the Scientific Committee on Occupational Exposure Limits by the European Union Commission.[21]
Trimethylaminuria
Trimethylaminuria is an autosomal recessive genetic disorder involving a defect in the function or expression of flavin-containing monooxygenase 3 (FMO3) which results in poor trimethylamine metabolism. Individuals with trimethylaminuria develop a characteristic fish odor—the smell of trimethylamine—in their sweat, urine, and breath after the consumption of choline-rich foods. A condition similar to trimethylaminuria has also been observed in a certain breed of Rhode Island Red chicken that produces eggs with a fishy smell, especially after eating food containing a high proportion of rapeseed.[22][23]
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In the history of psychoanalysis
The first dream of his own which Sigmund Freud tried to analyse in detail, when he was developing his theories about the interpretation of dreams, involved a patient of Freud's who had to have an injection of trimethylamine, and the chemical formula of the substance, written in bold letters on the bottle, jumping out at Freud.[24]
See also
- Ammonia, NH3
- Ammonium, NH4+
- Methylamine, (CH3)NH2
- Triethylamine (TEA)
References
External links
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