Methylamine

Methylamine is an organic compound with a formula of CH3NH2. This colorless gas is a derivative of ammonia, but with one hydrogen atom being replaced by a methyl group. It is the simplest primary amine. It is sold as a solution in methanol, ethanol, tetrahydrofuran, or water, or as the anhydrous gas in pressurized metal containers. Industrially, methylamine is transported in its anhydrous form in pressurized railcars and tank trailers. It has a strong odor similar to fish. Methylamine is used as a building block for the synthesis of many other commercially available compounds.

Methylamine
Ball and stick model of methylamine
Spacefill model of methylamine
Names
Preferred IUPAC name
Methanamine[1]
Other names
  • Aminomethane
  • Monomethylamine
Identifiers
CAS Number
3D model (JSmol)
3DMet
Abbreviations MMA
Beilstein Reference
 741851
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.746
EC Number
  • 200-820-0
Gmelin Reference
 145
KEGG
MeSH methylamine
PubChem CID
RTECS number
  • PF6300000
UN number 1061
Properties
Chemical formula
 CH5N
Molar mass 31.058 g·mol−1
Appearance Colorless gas
Odor Fishy, ammoniacal
Density 656.2 kg m−3 (at 25 °C)
Melting point −93.10 °C; −135.58 °F; 180.05 K
Boiling point −6.6 to −6.0 °C; 20.0 to 21.1 °F; 266.5 to 267.1 K
Solubility in water
 1080 g.L−1 (at 20 °C)
log P −0.472
Vapor pressure 186.10 kPa (at 20 °C)
Henry's law
constant (kH)
 1.4 mmol Pa−1 kg−1
Basicity (pKb) 3.36
Magnetic susceptibility (χ)
 -27.0·10−6 cm3/mol
Viscosity 230 μPa s (at 0 °C)
Dipole moment
 1.31 D
Thermochemistry
Std enthalpy of
formation (ΔfH⦵298)
 −23.5 kJ mol−1
Hazards
Safety data sheet emdchemicals.com
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H220, H315, H318, H332, H335
GHS precautionary statements
 P210, P261, P280, P305+351+338, P410+403
NFPA 704 (fire diamond)
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
4
3
0
Flash point −10 °C; 14 °F; 263 K (liquid, gas is extremely flammable)[2]
Autoignition
temperature
 430 °C (806 °F; 703 K)
Explosive limits 4.9–20.7%
Lethal dose or concentration (LD, LC):
100 mg kg−1 (oral, rat)
1860 ppm (mouse, 2 hr)[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 10 ppm (12 mg/m3)[2]
REL (Recommended)
 TWA 10 ppm (12 mg/m3)[2]
IDLH (Immediate danger)
 100 ppm[2]
Related compounds
Related alkanamines
 ethylamine, dimethylamine, trimethylamine
Related compounds
 ammonia
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Industrial production

Methylamine is prepared commercially by the reaction of ammonia with methanol in the presence of an aluminosilicate catalyst. Dimethylamine and trimethylamine are co-produced; the reaction kinetics and reactant ratios determine the ratio of the three products. The product most favored by the reaction kinetics is trimethylamine.[3]

CH3OH + NH3 → CH3NH2 + H2O

In this way, an estimated 115,000 tons were produced in 2005.[4]

Laboratory methods

Methylamine was first prepared in 1849 by Charles-Adolphe Wurtz via the hydrolysis of methyl isocyanate and related compounds.[4][5] An example of this process includes the use of the Hofmann rearrangement, to yield methylamine from acetamide and bromine gas.[6][7]

In the laboratory, methylamine hydrochloride is readily prepared by various other methods. One method entails treating formaldehyde with ammonium chloride.[8]

NH4Cl + H2CO → [CH2=NH2]Cl + H2O
[CH2=NH2]Cl + H2CO + H2O → [CH3NH3]Cl + HCO2H

The colorless hydrochloride salt can be converted to an amine by the addition of a strong base, such as sodium hydroxide (NaOH):

[CH3NH3]Cl + NaOH → CH3NH2 + NaCl + H2O

Another method entails reducing nitromethane with zinc and hydrochloric acid.[9]

Another method of methylamine production is spontaneous decarboxylation of glycine with a strong base in water.

Reactivity and applications

Methylamine is a good nucleophile as it is an unhindered amine.[10] As an amine it is considered a weak base. Its use in organic chemistry is pervasive. Some reactions involving simple reagents include: with phosgene to methyl isocyanate, with carbon disulfide and sodium hydroxide to the sodium methyldithiocarbamate, with chloroform and base to methyl isocyanide and with ethylene oxide to methylethanolamines. Liquid methylamine has solvent properties analogous to those of liquid ammonia.[11]

Representative commercially significant chemicals produced from methylamine include the pharmaceuticals ephedrine and theophylline, the pesticides carbofuran, carbaryl, and metham sodium, and the solvents N-methylformamide and N-methylpyrrolidone. The preparation of some surfactants and photographic developers require methylamine as a building block.[4]

Biological chemistry

Methylamine arises as a result of putrefaction and is a substrate for methanogenesis.[12]

Additionally, methylamine is produced during PADI4-dependent arginine demethylation.[13]

Safety

The LD50 (mouse, s.c.) is 2.5 g/kg.[14]

The Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) have set occupational exposure limits at 10 ppm or 12 mg/m3 over an eight-hour time-weighted average.[15]

Regulation

In the United States, methylamine is controlled as a List 1 precursor chemical by the Drug Enforcement Administration[16] due to its use in the illicit production of methamphetamine.[17]

In the TV series Breaking Bad, Walter White manufactures methamphetamine through the reductive amination of phenylacetone with methylamine. The methylamine was stolen from a warehouse in the season one episode "A No-Rough-Stuff-Type Deal" and from a moving train in the season five episode "Dead Freight."

See also
  • Methylammonium halide

References
  1. Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 670. doi:10.1039/9781849733069-00648. ISBN 978-0-85404-182-4.
  2. NIOSH Pocket Guide to Chemical Hazards. "#0398". National Institute for Occupational Safety and Health (NIOSH).
  3. Corbin D.R.; Schwarz S.; Sonnichsen G.C. (1997). "Methylamines synthesis: A review". Catalysis Today. 37 (24): 71–102. doi:10.1016/S0920-5861(97)00003-5.
  4. Karsten Eller, Erhard Henkes, Roland Rossbacher, Hartmut Höke "Amines, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a02_001
  5. Charles-Adolphe Wurtz (1849) "Sur une série d'alcalis organiques homologues avec l'ammoniaque" (On a series of homologous organic alkalis containing ammonia), Comptes rendus … , 28 : 223-226. Note: Wurtz's empirical formula for methylamine is incorrect because chemists in that era used an incorrect atomic mass for carbon (6 instead of 12).
  6. Mann, F. G.; Saunders, B. C. (1960). Practical Organic Chemistry, 4th Ed. London: Longman. p. 128. ISBN 9780582444072.
  7. Cohen, Julius (1900). Practical Organic Chemistry 2nd Ed. London: Macmillan and Co., Limited. p. 72.
  8. Marvel, C. S.; Jenkins, R. L. (1941). "Methylamine Hydrochloride". Organic Syntheses.CS1 maint: multiple names: authors list (link); Collective Volume, 1, p. 347
  9. Gatterman, Ludwig & Wieland, Heinrich (1937). Laboratory Methods of Organic Chemistry. Edinburgh, UK: R & R Clark, Limited. pp. 157–158.
  10. Peter Scott (ed.). Linker Strategies in Solid-Phase Organic Synthesis. p. 80. ...an unhindered amine such as methylamine
  11. Debacker, Marc G.; Mkadmi, El Bachir; Sauvage, François X.; Lelieur, Jean-Pierre; Wagner, Michael J.; Concepcion, Rosario; Kim, Jineun; McMills, Lauren E. H.; Dye, James L. (1996). "The Lithium−Sodium−Methylamine System: Does a Low-Melting Sodide Become a Liquid Metal?". Journal of the American Chemical Society. 118 (8): 1997. doi:10.1021/ja952634p.
  12. Thauer, R. K. (1998). "Biochemistry of methanogenesis: A tribute to Marjory Stephenson:1998 Marjory Stephenson Prize Lecture". Microbiology. 144 (9): 2377–406. doi:10.1099/00221287-144-9-2377. PMID 9782487.
  13. Ng, SS; Yue, WW; Oppermann, U; Klose, RJ (February 2009). "Dynamic protein methylation in chromatin biology". Cellular and Molecular Life Sciences. 66 (3): 407–22. doi:10.1007/s00018-008-8303-z. PMC 2794343. PMID 18923809.
  14. The Merck Index, 10th Ed. (1983), p.864, Rahway: Merck & Co.
  15. CDC - NIOSH Pocket Guide to Chemical Hazards
  16. Title 21 Code of Federal Regulations
  17. Frank, R. S (1983). "The Clandestine Drug Laboratory Situation in the United States". Journal of Forensic Sciences. 28: 12235J. doi:10.1520/JFS12235J.
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