methylamine

Methylamine
IUPAC name	aminomethane
Other names	monomethylamine MMA
Identifiers
CAS number	74-89-5 Y
RTECS number	PF6300000
SMILES	CN
Properties
Molecular formula	CH5N
Molar mass	31.06 g mol−1
Appearance	Colorless Gas
Density	d40.699 (−10.8 °C) / 0.902 g/cm³, 40w/w% in water
Melting point	−94 °C (179.15 K)
Boiling point	−6 °C (267.2 K)
Solubility in water	108 g/100 mL (20 °C)
Acidity (pKa)	10.64 (value for protonated amine, pKaH)
Basicity (pKb)	3.36
Viscosity	0.23 cP at 0 °C
Structure
Molecular shape	tetrahedral
Dipole moment	1.31 D (gas)
Hazards
MSDS	From EMD Chemicals [1]
R-phrases	11-36/37 (40% solution in water)
NFPA 704	4 3 0
Flash point	8 °C
Related compounds
Related amines	Ammonia dimethylamine trimethylamine
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Methylamine is the organic compound with a formula of CH₃NH₂. This colourless gas is a derivative of ammonia, wherein one H atom is replaced by a methyl group. It is the simplest primary amine. It is sold as a solution in methanol, ethanol, THF, and water, or as the anhydrous gas in pressurized metal containers. Industrially methylamine is sold in its anhydrous form in pressurized railcars and tank trailers. It has a strong odour similar to fish. Methylamine is used as a building block for the synthesis of many other commercially available compounds. Hundreds of millions of kilograms are produced annually.

Production

Methylamine is prepared commercially by the reaction of ammonia with methanol in the presence of a silicoaluminate catalyst. Dimethylamine and trimethylamine are coproduced; the reaction kinetics and reactant ratios determine the ratio of the three products.^[1]

CH₃OH + NH₃ → CH₃NH₂ + H₂O

In this way, more than 400M kg are produced annually.

In the laboratory, methylamine hydrochloride is readily prepared by the reaction of hydrochloric acid with hexamine or by treating formaldehyde with ammonium chloride.^[2]

NH₄Cl + H₂CO → CH₂=NH·HCl + H₂O

CH₂=NH·HCl + H₂CO + H₂O → CH₃NH₂·HCl + HCOOH

The colourless hydrochloride salt can be converted to the amine by the addition of strong base, like NaOH:

CH₃NH₂·HCl + NaOH → CH₃NH₂ + NaCl + H₂O

Methylamine was first prepared by Wurtz by the hydrolysis of methylisocyanate and related compounds.^[3]

Reactivity and applications

Methylamine is a good nucleophile as it is highly basic and unhindered. 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.

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.^[3]

Liquid methylamine can be used as a solvent analogous to liquid ammonia. It shares some of the properties of liquid ammonia, but is better for dissolving organic substances, in the same way that methanol is better than water.^[4]

Can also be used for scavenging H2S from hydrocarbon in refining applications. This substance typically has a strong fish odor.

Biological chemistry

Methylamine arises naturally as the result of putrefaction and is a substrate for methanogenesis.^[5] It serves as a buffering agent in the lumen of the chloroplast in plants, effectively siphoning off protons that are heading for ATP synthase.^{[citation needed]}

Safety

The LC50 (mouse) is 2400 mg/m³. Methylamine is also controlled as a List 1 substance by the United States Drug Enforcement Agency (DEA); the DEA lists methylamine as a precursor (to methamphetamine).

References

1. ^ 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. 
2. ^ Marvel, C. S.; Jenkins, R. L. (1941), "Methylamine Hydrochloride", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0347 ; Coll. Vol. 1: 347 
3. ^ ^{a b} Karsten Eller, Erhard Henkes, Roland Rossbacher, Hartmut Höke "Amines, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.
4. ^ H. D. Gibbs (1906). "Liquid methylamine as a solvent, and a study of its chemical reactivity". J. Am. Chem. Soc. 28: 1395–1422. doi:10.1021/ja01976a009. 
5. ^ Thauer, R. K., "Biochemistry of Methanogenesis: a Tribute to Marjory Stephenson", Microbiology, 1998, 144, 2377-2406.