Methylamine

Skeletal formula of methylamine with all explicit hydrogens added

Names Pronunciation /ˌmɛθələˈmiːn/
(METH-ə-lə-MEEN), /ˌmɛθəˈlæmən/
(METH-ə-LA-mən), /məˈθɪləˌmiːn/
(mə-THIL-ə-meen)^[2] Preferred IUPAC name Other names Identifiers Abbreviations MMA 741851 ChEBI ChEMBL ChemSpider DrugBank ECHA InfoCard 100.000.746 Edit this at Wikidata EC Number 145 KEGG MeSH methylamine RTECS number UNII UN number 1061 Properties CH₃NH₂ Molar mass 31.058 g·mol⁻¹ Appearance Colorless gas Odor Fishy, ammoniacal Density 0.6562 g/cm³ (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 1008 g/L (at 20 °C) log P −0.472 Vapor pressure 186.10 kPa (at 20 °C) 1.4 mmol/(Pa·kg) Acidity (pK_a) 10.66 Conjugate acid [CH₃NH₃]⁺ (Methylammonium) -27.0·10⁻⁶ cm³/mol Viscosity 230 μPa·s (at 0 °C) 1.31 D Thermochemistry −23.5 kJ/mol Hazards GHS labelling: GHS02: Flammable GHS05: Corrosive GHS07: Exclamation mark Danger H220, H315, H318, H332, H335 P210, P261, P280, P305+P351+P338, P410+P403 NFPA 704 (fire diamond) Flash point −10 °C; 14 °F; 263 K (liquid, gas is extremely flammable)^[3] 430 °C (806 °F; 703 K) Explosive limits 4.9–20.7% Lethal dose or concentration (LD, LC): 100 mg/kg (oral, rat) 1860 ppm (mouse, 2 hr)^[3] NIOSH (US health exposure limits): TWA 10 ppm (12 mg/m³)^[3] TWA 10 ppm (12 mg/m³)^[3] 100 ppm^[3] Safety data sheet (SDS) emdchemicals.com Related compounds ethylamine, dimethylamine, trimethylamine ammonia

Methylamine, also known as methanamine, 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.

Methylamine 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 rotten fish. Methylamine is used as a building block for the synthesis of numerous other commercially available compounds.

Methylamine has been produced industrially since the 1920s (originally by Commercial Solvents Corporation for dehairing of animal skins).^[4] This was made possible by Kazimierz Smoleński  [pl] and his wife Eugenia who discovered amination of alcohols, including methanol, on alumina or kaolin catalyst after WWI, filed two patent applications in 1919^[5] and published an article in 1921.^{[4] [6]}

It is now 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.^[4]

CH₃OH + NH₃ → CH₃NH₂ + H₂O

In this way, an estimated 115,000 tons were produced in 2005.^[7]

Methylamine was first prepared in 1849 by Charles-Adolphe Wurtz via the hydrolysis of methyl isocyanate and related compounds.^{[7] [8]} An example of this process includes the use of the Hofmann rearrangement, to yield methylamine from acetamide and bromine.^{[9] [10]}

In the laboratory, methylamine hydrochloride is readily prepared by various other methods. One method entails treating formaldehyde with ammonium chloride.^[11]

[NH₄]Cl + CH₂O → [CH₂=NH₂]Cl + H₂O

[CH₂=NH₂]Cl + CH₂O + H₂O → [CH₃NH₃]Cl + HCOOH

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.^[12]

Another method of methylamine production is spontaneous decarboxylation of glycine with a strong base in water.^[13]

Methylamine is a good nucleophile as it is an unhindered amine.^[14] 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.^[15]

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.^[7]

Methylamine arises as a result of putrefaction and is a substrate for methanogenesis.^[16]

Additionally, methylamine is produced during PADI4-dependent arginine demethylation.^[17]

The LD₅₀ (mouse, s.c.) is 2.5 g/kg.^[18]

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.^[19]

In the United States, methylamine is controlled as a List 1 precursor chemical by the Drug Enforcement Administration ^[20] due to its use in the illicit production of methamphetamine.^[21]

Fictional characters Walter White and Jesse Pinkman use aqueous methylamine as part of a process to synthesize methamphetamine in the AMC series Breaking Bad .^{[22] [23]}

• Methylammonium halide