Trimethylamine (TMA) is an organic compound with the formula N(CH₃)₃. It 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 is a nitrogenous base and can be readily protonated to give the trimethylammonium cation. Trimethylammonium chloride is a hygroscopic colorless solid prepared from hydrochloric acid. Trimethylamine is a good nucleophile, and this reaction is the basis of most of its applications. TMA is widely used in industry: it is used in the synthesis of choline, tetramethylammonium hydroxide, plant growth regulators or herbicides, strongly basic anion exchange resins, dye leveling agents, and a number of basic dyes. At higher concentrations it has an ammonia-like odor, and can cause necrosis of mucous membranes on contact. At lower concentrations, it has a "fishy" odor, the odor associated with rotting fish.

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. 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. 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. TMA also causes the odor of some human infections, bad breath, and bacterial vaginosis.

Trimethylamine is a full agonist of human TAAR5, a trace amine-associated receptor that is expressed in the olfactory epithelium and functions as an olfactory receptor for tertiary amines. One or more additional odorant receptors appear to be involved in trimethylamine olfaction in humans as well.

Production

Trimethylamine is prepared by the reaction of ammonia and methanol employing a catalyst:

3 CH₃OH + NH₃ → (CH₃)₃N + 3 H₂O

This reaction coproduces the other methylamines, dimethylamine (CH₃)₂NH and methylamine CH₃NH₂.

Trimethylamine has also been prepared by a reaction of ammonium chloride and paraformaldehyde:

9 (CH₂=O)_n + 2n NH₄Cl → 2n (CH₃)₃N•HCl + 3n H₂O + 3n CO₂↑

Toxicity

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. In patients, trimethylamine caused stomach ache, vomiting, diarrhoea, lacrimation, greying of the skin and agitation. Apart from that, reproductive/developmental toxicity has been reported.

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.

Some experimental studies suggested that TMA may be involved in etiology of cardiovascular diseases.

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. Gas sensors to test for fish freshness detect trimethylamine.

Reactions

Trimethylamine is a Lewis base that forms adducts with a variety of Lewis acids.

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.

External links

Molecule of the Month: Trimethylamine
NIST Webbook data
CDC - NIOSH Pocket Guide to Chemical Hazards

Wikimedia Commons has media related to Trimethylamine.

Human trace amine-associated receptor ligands

TAAR1

Agonists

Endogenous^†	Classical monoamine neurotransmitters Dopamine Histamine Norepinephrine Serotonin Trace amines 3-Iodothyronamine 3-Methoxytyramine N-Methylphenethylamine N-Methyltyramine m-Octopamine p-Octopamine Phenethylamine Phenylethanolamine Synephrine Tryptamine m-Tyramine p-Tyramine
Synthetic^‡	Amphetamine DOB DOET 4-Hydroxyamphetamine Isoprenaline MDA (tenamfetamine) MDMA (midomafetamine) 2-Methylphenethylamine 3-Methylphenethylamine 4-Methylphenethylamine β-Methylphenethylamine Methamphetamine 3-MMA Norfenfluramine Phentermine o-PIT Propylhexedrine Ralmitaront (RG-7906, RO-6889450) RO5166017 N,N-Dimethylphenethylamine Ulotaront (SEP-363856)

Neutral antagonists

Inverse agonists

EPPTB (RO5212773)

TAAR2

Agonists^‡
Neutral antagonists

TAAR5

Agonists^‡	N,N-Dimethylethylamine Trimethylamine
Neutral antagonists
Inverse agonists^‡	3-Iodothyronamine

^† References for all endogenous human TAAR1 ligands are provided at List of trace amines

^‡ References for synthetic TAAR1 agonists can be found at TAAR1 or in the associated compound articles. For TAAR2 and TAAR5 agonists and inverse agonists, see TAAR for references.

See also: Receptor/signaling modulators