Methylamine

Structural formula
General
Surname	Methylamine
other names	Methanamine ( IUPAC ) Aminomethane Monomethylamine Mercurialine R-630 MMA
Molecular formula	CH 5 N
Brief description	colorless gas with an ammonia-like odor
External identifiers / databases
CAS number 74-89-5 EC number 200-820-0 ECHA InfoCard 100,000,746 PubChem 6329 ChemSpider 6089 DrugBank DB01828 Wikidata Q409304
properties
Molar mass	31.06 g mol −1
Physical state	gaseous
density	1.43 kg m −3 (0 ° C, 1013 hPa) 0.69 kg l −1 (at the boiling point)
Melting point	−93.5 ° C
boiling point	−6.3 ° C
Vapor pressure	3.0 bar (20 ° C) 4.2 bar (30 ° C) 7.8 bar (50 ° C)
solubility	very easily soluble in water (1080 g l −1 at 20 ° C) Easily soluble in ethanol
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 220-280-332-315-318-335 P: 210-261-280-305 + 351 + 338-377-410 + 403
MAK	DFG : 5 ml m −3 or 6.4 mg m −3 Switzerland: 10 ml m −3 or 12 mg m −3
Toxicological data	100 mg kg −1 ( LD 50 ,  rat ,  oral )
Thermodynamic properties
ΔH f 0	−22.5 kJ mol −1
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Methylamine (according to IUPAC nomenclature: methanamine , often also referred to as aminomethane ) is an organic-chemical compound from the group of primary aliphatic amines . It is available as a 40% aqueous solution and as a liquefied gas under pressure .

history

The German chemist Heinrich Debus synthesized methylamine in 1863 by catalytic hydrogenation of hydrogen cyanide on platinum .

Occurrence

Methylamine comes in Bingel herbs (Mercurialis), the essential oil of the leaves of water mint , in some algae and in bone oil and wood distillates ago. It is a biogenic amine and has been found in small amounts in the urine of humans and animals . It is also assumed that it was part of the primordial atmosphere . Therefore, traces of methylamine can also be found in space .

Extraction and presentation

For the large-scale synthesis of methylamine, methanol is reacted with ammonia at temperatures of 350-450 ° C. and pressures of 15-25 bar in the presence of aluminum oxide ( silicate or phosphate ) in tubular reactors.

Besides water , dimethylamine and trimethylamine are also formed as by-products , which have to be separated off by multi-stage pressure and extractive distillation. The weight ratio of mono-, di- and trimethylamine in this reaction is on average about 20:20:60.

The global production capacity for methylamines in 1996 was approximately 830,000 tons per year .

In the laboratory, methylamine can be obtained in smaller quantities by reacting formaldehyde with ammonium chloride, whereby methylammonium chloride is obtained first . The colorless salt can then by a strong base, such as. B. Sodium hydroxide , into which methylamine are converted:

properties

Physical Properties

Methylamine has a relative gas density of 1.1 (density ratio to dry air at the same temperature and pressure ) and a gas density under standard conditions (0 ° C and 1013 mbar) of 1.4301 kg · m ⁻³ . The density of the liquid phase at the boiling point is 0.6942 kg · l ⁻¹ , the gas density at 15 ° C is given as 1.3283 kg · m ⁻³ . Monomethylamine also has a vapor pressure of 3.00 bar at 20 ° C, 4.20 bar at 30 ° C and 7.8 bar at 50 ° C. According to Antoine, the vapor pressure function results accordingly:

${\displaystyle \log _{10}(p)=4,51990-{\frac {1034,977}{T-37.574}}~~~\mathrm {(p~in~bar,~T~in~K)} }$

in the temperature range from 190 K to 267 K. The critical temperature is 156.9 ° C, the critical pressure 74.1 bar and the critical density 0.216 g · cm ⁻³ .

Chemical properties

Methylamine is an extremely flammable gas from the group of primary amines . The aqueous solutions react strongly alkaline . At 20 ° C, 1080 g · l ^{−1 dissolve} in water. An aqueous solution of methylamine at 20 ° C and a concentration of 100 g · l ⁻¹ has a pH value of 14. It reacts with acids to form crystallizing , water-soluble salts . The methylamine-air mixtures are explosive.

use

Methylamine is an important intermediate in the chemical and processing industries . It is used for the synthesis of pharmaceuticals (e.g. deoxyn , theophylline ) and pesticides (e.g. carbaryl , metham sodium , carbofuran ). A large part is also processed into N-methyl-2-pyrrolidone (NMP) , an important organic solvent . It is also the starting material for guanidines , amides , imines , amino alcohols , diamines , modified amino acids and α-aminophosphonates. It is also used for the synthesis of metal complexes and for the modification of polymers . In addition, methylamine is also converted to N , N '-dimethylurea , which in turn is used for the synthesis of caffeine , drugs or herbicides . In organic synthesis, monomethylamine is also used to introduce a methylamino group into other molecules.

safety instructions

Gaseous monomethylamine is mainly absorbed through the respiratory tract . Skin resorption can also occur on contact with aqueous solutions . Ingestion or inhalation can cause severe irritation of the mucous membranes , especially in the respiratory tract and eyes . These can quickly lead to chemical burns . Supercooled, liquid MMA can also cause the skin to freeze and burn . Long-term exposure also showed a disturbance of the general condition. In addition, methylamine forms explosive mixtures with air. At high concentration there is a risk of suffocation . The substance is also classified as hazardous to the aquatic environment. Methylamine has a lower explosion limit of 4.99% by volume at 60 g · cm ⁻³ and an upper explosion limit of 20.7% by volume at 270 g · cm ⁻³ . The ignition temperature is 430 ° C. The substance therefore falls into temperature class T2 and explosion class IIA. With a flash point of −30 ° C, methylamine is extremely flammable. The flash point of a 40% aqueous solution is −18 ° C

Individual evidence

1. ↑ ^{a b c d e f g h i j k l m n o p q} Entry on methylamine in the GESTIS substance database of the IFA , accessed on February 2, 2019(JavaScript required) .
2. ↑ ^{a b c d} Entry on methylamine. In: Römpp Online . Georg Thieme Verlag, accessed on February 2, 2019.
3. ↑ Entry on methylamines in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 2, 2019. Manufacturers or distributors can expand the harmonized classification and labeling .
4. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 74-89-5 or methylamine ), accessed on September 14, 2019.
5. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-20.
6. ↑ Heinrich Debus: About the representation of methylamine from hydrogen cyanide and hydrogen . In: Liebig's annals of chemistry . tape 128 , 1863, pp. 200 ( hathitrust.org [accessed March 20, 2019]).
7. ↑ ^{a b} Patent EP1931466B1 : Shaped bodies containing an aluminosilicate and aluminum oxide and a process for the continuous production of methylamines. Published on November 14, 2012 , applicant: BASF SE, inventor: Marco Bosch, Roderich Röttger, Jan Eberhardt, Thomas Krug, Theodor Weber, Karl-Heinz Ross, Manfred Julius. ‌
8. ↑ ^{a b} Hans-Jürgen Arpe: Industrial organic chemistry - important preliminary and intermediate products . 6th edition. WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 2007, ISBN 978-3-527-31540-6 , p. 55 .
9. ↑ C. S. Marvel, R. L. Jenkins: Methylamine Hydrochloride In: Organic Syntheses . 3, 1923, p. 67, doi : 10.15227 / orgsyn.003.0067 ; Coll. Vol. 1, 1941, p. 347 ( PDF ).
10. ↑ J. G. Aston, C. W. Stiller, G. H. Messerly: Heat capacities and entropies of organic compounds. III. Methylamine from 12K to the boiling point. Heat of vaporization and vapor pressure. The entropy from molecular data . In: Journal of the American Chemical Society . tape 59 , no. 9 , 1937, pp. 1743–1751 , doi : 10.1021 / ja01288a054 (English).