|Jmol-3D images||Image 1|
|Molar mass||31.06 g mol−1|
|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||1.08 kg L−1 (at 20 °C)|
|Vapor pressure||186.10 kPa (at 20 °C)|
|kH||1.4 mmol Pa−1 kg−1|
|Viscosity||230 μPa s (at 0 °C)|
|Dipole moment||1.31 D|
|Std enthalpy of
|−23.5 kJ mol−1|
|GHS signal word||DANGER|
|GHS hazard statements||H220, H315, H318, H332, H335|
|GHS precautionary statements||P210, P261, P280, P305+351+338, P410+403|
|EU classification||F+ Xn|
|R-phrases||R12, R20, R37/38, R41|
|S-phrases||(S2), S16, S26, S39|
|Flash point||<−30 °C|
|LD50||100 mg kg−1 (oral, rat)|
|Related alkanamines||ethylamine, dimethylamine, trimethylamine|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Methylamine is the organic compound with a formula of CH3NH2. This colorless gas is a derivative of ammonia, but with one H atom 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 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. Over 1 million tonnes are produced annually.
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. The product most favoured by the reaction kinetics is trimethylamine.
- CH3OH + NH3 → CH3NH2 + H2O
In this way, more than 400 tons are produced annually.
Methylamine was first prepared in 1849 by Wurtz by the hydrolysis of methyl isocyanate and related compounds. An example of this process includes the use of Hofmann rearrangement to yield methylamine from acetamide and bromine gas.
- NH4Cl + H2CO → [CH2=NH2]Cl + H2O
- [CH2=NH2]Cl + H2CO + H2O → [CH3NH3]Cl + HCOOH
The colorless hydrochloride salt can be converted to the amine by the addition of strong base, like NaOH:
- [CH3NH3]Cl + NaOH → CH3NH2 + NaCl + H2O
Reactivity and applications
Methylamine is a good nucleophile as it is highly basic and unhindered, although, 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 for liquid ammonia.
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.
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.
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