Dimethylamine

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 270,000 tons were produced in 2005.[5]

Dimethylamine
Skeletal formula of dimethylamine
Ball and stick model of dimethylamine
Names
Preferred IUPAC name
N-Methylmethanamine
Other names
(Dimethyl)amine
Identifiers
3D model (JSmol)
3DMet
605257
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.004.272
EC Number
  • 204-697-4
849
KEGG
MeSH dimethylamine
RTECS number
  • IP8750000
UNII
UN number 1032
  • InChI=1S/C2H7N/c1-3-2/h3H,1-2H3 checkY
    Key: ROSDSFDQCJNGOL-UHFFFAOYSA-N checkY
  • CNC
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:
GHS02: Flammable GHS05: Corrosive GHS07: Exclamation mark
Danger
H220, H302, H315, H318, H332, H335
P210, P261, P280, P305+P351+P338
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
2
4
0
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)[3]
4700 ppm (rat, 4 hr)
4540 ppm (rat, 6 hr)
7650 ppm (mouse, 2 hr)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 10 ppm (18 mg/m3)[4]
REL (Recommended)
 TWA 10 ppm (18 mg/m3)[4]
IDLH (Immediate danger)
 500 ppm[4]
Related compounds
Related amines
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure and synthesis

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

Natural occurrence

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]

Uses

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. 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.[9]

(CH3)2NH + NH2Cl → (CH3)2NNH2 ⋅ HCl

It is an attractant for boll weevils.[10]

Reactions

It is basic, in both the Lewis 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 is also a Lewis base.[11][12]

It reacts with many carbonyl compounds. Aldehydes give aminals. For example reaction of dimethylamine and formaldehyde gives bis(dimethylamino)methane:[13]

2 (CH3)2NH + CH2O → [(CH3)2N]2CH2 + H2O

It converts esters to dimethylamides.

Dimethylamine undergoes nitrosation to give dimethylnitrosamine, a carcinogen.

Safety

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.).[14]

See also

References
  1. "Dimethylamine". NIST Chemistry WebBook. USA: National Institute of Standards and Technology. Retrieved 15 February 2022.
  2. "Dimethylamine 38931 - ≥99.0%". Aldrich. Sigma-Aldrich Co. Retrieved 15 February 2022.
  3. "Dimethylamine". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. NIOSH Pocket Guide to Chemical Hazards. "#0219". National Institute for Occupational Safety and Health (NIOSH).
  5. Van Gysel, August B.; Musin, Willy (2000). "Methylamines". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_535.
  6. Corbin D.R.; Schwarz S.; Sonnichsen G.C. (1997). "Methylamines synthesis: A review". Catalysis Today. 37 (2): 71–102. doi:10.1016/S0920-5861(97)00003-5.
  7. Neurath, G. B.; et al. (1977). "Primary and secondary amines in the human environment". Food and Cosmetics Toxicology. 15 (4): 275–282. doi:10.1016/s0015-6264(77)80197-1. PMID 590888.
  8. Ashford's Dictionary of Industrial Chemicals, 3rd edition, 2011, pages 3284-3286
  9. Schirmann, Jean-Pierre; Bourdauducq, Paul (2001). "Hydrazine". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_177.
  10. The Merck Index, 10th Ed. (1983), p.470, Rahway: Merck & Co.
  11. Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 ISBN 978-0-470-74957-9
  12. Cramer, R. E.; Bopp, T. T. (1977). "Graphical display of the enthalpies of adduct formation for Lewis acids and bases". Journal of Chemical Education. 54: 612–613. doi:10.1021/ed054p612. The plots shown in this paper used older parameters. Improved E&C parameters are listed in ECW model.
  13. Gaudry, Michel; Jasor, Yves; Khac, Trung Bui (1979). "Regioselective Mannich Condensation with Dimethyl(Methylene)ammonium Trifluoroacetate: 1-(Dimethylamino)-4-methyl-3-pentanone". Org. Synth. 59: 153. doi:10.15227/orgsyn.059.0153.
  14. Chemical Information Profile for Dimethylamine Borane, National Toxicology Program, NIEHS, NIH (2008), p.4: http://ntp.niehs.nih.gov/ntp/htdocs/Chem_Background/ExSumPdf/DimethylamineBorane508.pdf
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