“N-Methylethanolamine”的意思、由来-开放百科全书

N-Methylethanolamine is an alkanolamine with the formula CH₃NHCH₂CH₂OH. It is flammable, corrosive, colorless, viscous liquid.^[2] It is an intermediate in the biosynthesis of choline.

With both an amine and a hydroxyl functional groups, it is a useful intermediate in the chemical synthesis of various products including polymers and pharmaceuticals. It is also used as a solvent, for example in the natural gas-processing industry together with its analogs ethanolamine and dimethylethanolamine.

Production

N-Methylethanolamine is produced industrially by reacting ethylene oxide with excess methylamine in aqueous solution. This reaction yields a mixture of the 1:1 addition product NMEA (1) and - by a further addition of another ethylene oxide - the 1:2 addition product methyl diethanolamine (MDEA) (2):

In order to obtain high yields of the desired target product, the reactants are continuously fed to a flow reactor and reacted with a more than two-fold excess of methylamine.^[3] In the downstream process steps, the excess methylamine and the water is removed and NMEA (bp. 160 °C) and MDEA (bp. 243 °C) are isolated from the product mixture by fractional distillation. The poly(methyl-ethanolamine) formed by further addition of ethylene oxide to methylethanolamine remains in the distillation bottoms.

Properties

Use

Like other alkylalkanolamines, N-methylethanolamine is used in water- and solvent-based paints and coatings as a solubilizer for other components, such as pigments and as a stabilizer.

In cathodic dip-coating, N-methylaminoethanol serves as cation neutralizer for the partial neutralization of the epoxy resin. It also serves as a chain extender in the reaction of high molecular weight polyepoxides with polyols.

Being a base, N-methylaminoethanol forms neutral salts with fatty acids, which are used as surfactants (soaps) with good emulsifying properties and find applications in textile and personal care cleansing products. When bleaching cotton-polyester blends, NMEA is used as a brightener.^[5]

By methylation of N-methylaminoethanol, dimethylaminoethanol and choline [(2-hydroxyethyl)-trimethyl-ammonium chloride] can be prepared.

In the reaction of N-methylaminoethanol with fatty acids, long-chain N-methyl-N-(2-hydroxyethyl)amides are formed upon elimination of water. These are used as neutral surfactants. Such amides also act as flow improvers and pour point depressants in heavy oils and middle distillates.^[6]

By catalytic oxidation of N-methylaminoethanol, the non-proteinogenic amino acid sarcosine is obtained.^[7]

In analogy to aziridine, N-methylaziridine can be obtained by a Wenker synthesis from N-methylaminoethanol. This is done either via the sulfuric acid ester or after replacement of the hydroxy group by a chlorine atom (for example by thionyl chloride or chlorosulfonic acid^[9]) to N-methyl-2-chloroethylamine and then by using a strong base (cleavage of HCl) in an intramolecular nucleophilic substitution:

See also

References

1. ^Merck Index, 12th Edition, 6096.
2. ^Matthias Frauenkron, Johann-Peter Melder, Günther Ruider, Roland Rossbacher, Hartmut Höke "Ethanolamines and Propanolamines" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a10_001}}
3. ^Miura Trading & Finvest Pvt. Ltd.: Methyl Ethanolamines Technology {{webarchive|url=https://web.archive.org/web/20160306055734/http://www.miura.co.in/files/Methyl%20Ethanolamines.pdf |date=2016-03-06 }} (PDF; 152 kB).
4. ^Product Safety Assessment, DOW^TM N-Methylethanolamine, The Dow Chemical Company, Version vom 24. März 2010.
5. ^The Dow Chemical Company: Alkyl Alkanolamines, March 2003.
6. ^{{Cite patent |number = 30,238 |country = US |invent1= E.H. Specht, J.H. O’Mara |date = 25 March 1980 |link = http://www.freepatentsonline.com/RE30238.pdf}}
7. ^US-Patent US 8,227,638, Process for preparing creatine, creatine monohydrate and guanidinoacetic acid, Inventor: F. Thalhammer, T. Gastner, Anmelder: Alzchem Trostberg GmbH, 24. July 2012.
8. ^A. Kleemann u. J. Engel, Pharmazeutische Wirkstoffe: Synthese, Patente, Anwendungen, 2. überarb. u. erw. Aufl., Georg Thieme Verlag, Stuttgart, New York, 1982, {{ISBN|3-13-558402-X}}.
9. ^J.H. Drese, [https://smartech.gatech.edu/bitstream/handle/1853/42829/drese_jeffrey_h_201012_phd.pdf The design, synthesis, and characterization of aminosilica adsorbants for CO₂ capture from dilute sources] (PDF; 5,3 MB), Ph.D. Thesis, Georgia Institute of Technology, Dezember 2010, S. 175.