Dimethylamine
Names Preferred IUPAC name Other names Identifiers 605257 ChEBI ChEMBL ChemSpider ECHA InfoCard 100.004.272 EC Number 849 KEGG MeSH dimethylamine RTECS number UNII UN number 1032 Properties[1][2] (CH3)2NH Molar mass 45.085 g·mol−1 Appearance Colorless gas Odor Fishy, ammoniacal Density 649.6 kg m−3 (at 25 °C) Melting point −93.00 °C; −135.40 °F; 180.15 K Boiling point 7 to 9 °C; 44 to 48 °F; 280 to 282 K 1.540 kg L−1 log P −0.362 Vapor pressure 170.3 kPa (at 20 °C) 310 μmol Pa−1 kg−1 Basicity (pKb) 3.29 Thermochemistry −21 to −17 kJ mol−1 Hazards GHS labelling: Danger H220, H302, H315, H318, H332, H335 P210, P261, P280, P305+P351+P338 NFPA 704 (fire diamond) Flash point −6 °C (21 °F; 267 K) (liquid) 401 °C (754 °F; 674 K) Explosive limits 2.8-14.4% Lethal dose or concentration (LD, LC): 698 mg/kg (rat, oral)316 mg/kg (mouse, oral)240 mg/kg (rabbit, oral)240 mg/kg (guinea pig, oral)[4] 4700 ppm (rat, 4 hr)4540 ppm (rat, 6 hr)7650 ppm (mouse, 2 hr)[4] NIOSH (US health exposure limits): TWA 10 ppm (18 mg/m3)[3] TWA 10 ppm (18 mg/m3)[3] 500 ppm[3] Related compounds
Dimethylamine is an organic compound with the formula (CH3)2NH. This secondary amine is a colorless, flammable gas with an ammonia-like odor. Dimethylamine is commonly encountered commercially as a solution in water at concentrations up to around 40%. An estimated 271,000 tons were produced in 2005.[5]
The molecule consists of a nitrogen atom with two methyl substituents and one hydrogen. Dimethylamine is a weak base and the pKa of the ammonium CH3-NH+2-CH3 is 10.73, a value above methylamine (10.64) and trimethylamine (9.79).
Dimethylamine reacts with acids to form salts, such as dimethylamine hydrochloride, an odorless white solid with a melting point of 171.5 °C. Dimethylamine is produced by catalytic reaction of methanol and ammonia at elevated temperatures and high pressure:[6]
2 CH3OH + NH3 → (CH3)2NH + 2 H2O
Dimethylamine is found quite widely distributed in animals and plants, and is present in many foods at the level of a few mg/kg.[7]
Dimethylamine is a precursor to several industrially significant compounds.[5][8] It reacts with carbon disulfide to give dimethyl dithiocarbamate, a precursor to zinc bis(dimethyldithiocarbamate) and other chemicals used in the sulfur vulcanization of rubber. Dimethylaminoethoxyethanol is manufactured by reacting dimethylamine and ethylene oxide.[9] Other methods are also available producing streams rich in the substance which then need to be further purified.[10] The solvents dimethylformamide and dimethylacetamide are derived from dimethylamine. It is raw material for the production of many agrichemicals and pharmaceuticals, such as dimefox and diphenhydramine, respectively. The chemical weapon tabun is derived from dimethylamine. The surfactant lauryl dimethylamine oxide is found in soaps and cleaning compounds. Unsymmetrical dimethylhydrazine, a rocket fuel, is prepared from dimethylamine.[11]
(CH3)2NH + NH2Cl → (CH3)2NNH2 ⋅ HCl
It is an attractant for boll weevils.[12]
It is basic, in both the Lewis[13][14] and Brønsted senses. It easily forms dimethylammonium salts upon treatment with acids. Deprotonation of dimethylamine can be effected with organolithium compounds. The resulting LiNMe2, which adopts a cluster-like structure, serves as a source of Me2N−. This lithium amide has been used to prepare volatile metal complexes such as tetrakis(dimethylamido)titanium and pentakis(dimethylamido)tantalum.
It reacts with many carbonyl compounds. Aldehydes give aminals. For example reaction of dimethylamine and formaldehyde gives bis(dimethylamino)methane:[15]
2 (CH3)2NH + CH2O → [(CH3)2N]2CH2 + H2O
It converts esters to dimethylamides.
Dimethylamine is not very toxic with the following LD50 values: 736 mg/kg (mouse, i.p.); 316 mg/kg (mouse, p.o.); 698 mg/kg (rat, p.o.); 3900 mg/kg (rat, dermal); 240 mg/kg (guinea pig or rabbit, p.o.).[16]
Although not acutely toxic, dimethylamine undergoes nitrosation to give dimethylnitrosamine, a carcinogen.
- Methylamine
- Trimethylamine
- International Chemical Safety Card 0260 (gas)
- International Chemical Safety Card 1485 (aqueous solution)
- NIOSH Pocket Guide to Chemical Hazards. “#0219”. National Institute for Occupational Safety and Health (NIOSH).
- Properties from Air Liquide
- MSDS at airliquide.com