Dimethylamine

Structural formula
General
Surname	Dimethylamine
other names	N -Methylmethanamine ( IUPAC ) Methyl methanamine N , N -dimethylamine DMA
Molecular formula	C 2 H 7 N
Brief description	colorless gas with a fish-like or ammonia-like odor
External identifiers / databases
CAS number 124-40-3 EC number 204-697-4 ECHA InfoCard 100.004.272 PubChem 674 ChemSpider 654 Wikidata Q408022
properties
Molar mass	45.08 g mol −1
Physical state	gaseous
density	0.67 g cm −3 ( at the boiling point of 7 ° C )
Melting point	−92.2 ° C
boiling point	7 ° C
Vapor pressure	1703 h Pa (20 ° C) 4596 hPa (52 ° C)
pK s value	10.71
solubility	soluble in water soluble in ethanol , diethyl ether and chloroform
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 220-280-315-318-332-335-412 P: 210-261-273-280-305 + 351 + 338-410 + 403
MAK	DFG : 2 ppm or 3.7 mg m −3 Switzerland: 2 ml m −3 or 4 mg m −3
Toxicological data	698 mg kg −1 ( LD 50 ,  rat ,  oral )
Thermodynamic properties
ΔH f 0	−18.8 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Dimethylamine (according to IUPAC nomenclature: N -methylmethanamine , also known as DMA for short ) is an organic-chemical compound from the group of secondary aliphatic amines . It comes on the market as a 40% aqueous solution , 33% solution in ethanol and as a liquefied gas under pressure .

Extraction and presentation

For the large-scale synthesis of dimethylamine, 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. In the first step, methanol reacts with ammonia to form methylamine . This then reacts with another equivalent of methanol to form dimethylamine.

In addition to water , methylamine and trimethylamine are also formed as by-products , which have to be separated off by multi-stage pressure and extractive distillation. The methylamine which has been separated off can be reacted separately with methanol in a further reactor to form dimethylamine. The weight ratio of mono-, di- and trimethylamine in this reaction is about 20:20:60.

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

properties

Physical Properties

Dimethylamine has a relative gas density of 1.60 (density ratio to dry air at the same temperature and pressure ) and a gas density of 2.013 kg · m ⁻³ under standard conditions (0 ° C, 1013 mbar). The density of the liquid phase at the boiling point is 0.6703 g · cm ⁻³ , the gas density at a temperature of 15 ° C and a pressure of 1 bar is 1.9426 kg · m ⁻³ . In addition, dimethylamine has a vapor pressure of 1703 hPa at 20 ° C and 4596 hPa at 52 ° C. At −92.2 ° C, the triple point is equal to the melting temperature . The critical temperature is 164.6 ° C, the critical pressure 53.1 bar and the critical density 0.256 g · cm ⁻³ .

Chemical properties

Dimethylamine is an extremely flammable gas from the group of secondary amines . It forms explosive mixtures with air. It dissolves well in water with hydrolysis , whereby the aqueous solutions have a strongly alkaline reaction ( pK _b 3.29). Dimethylamine is heavier than air. It is usually in liquefied form in pressurized gas cylinders and is also commercially available as a 40% aqueous solution and a 33% solution in ethanol . By reacting with alkylating agents , alkylene oxides , carbonyl compounds , organic acids , etc., dimethylamine can be converted into numerous subsequent compounds . Reaction with nitrosating agents (e.g. nitrites , nitrous acid , nitrous gases ) can lead to the formation of carcinogenic nitrosamines .

use

In the laboratory, dimethylamine is used to introduce a dimethylamino group into other organic compounds . In the chemical and processing industry it is also used as a stabilizer for latices , solvents , depilatories in leather production and as a gas absorbent. It is also used in the production of vulcanization accelerators , fungicides , herbicides , flotation chemicals , antioxidants , rocket fuels , quaternary ammonium salts , detergents and cleaning agents and pharmaceuticals . The large-scale processing into dimethylformamide (DMF) and N, N-dimethylglycine is also important .

safety instructions

Dimethylamine is an extremely flammable gas which forms explosive mixtures with air . At high concentrations there is also a risk of suffocation . Dimethylamine is mainly absorbed through the respiratory tract and skin . This leads to acute irritative to caustic effects on mucous membranes , eyes , respiratory tract and the skin. A weak central nervous mode of action was also found. Chronic disorders in the central nervous system and general malaise occur in the affected person. For Reproductive toxicity no sufficient information is known. Dimethylamine alone was not found to be mutagenic or carcinogenic , only the highly toxic secondary compounds such as nitrosamines show an increased carcinogenic and gene-changing potential. Dimethylamine has a lower explosion limit of about 2.80% by volume at 52 g / cm ³ and an upper explosion limit of about 14.4% by volume at 270 g / cm ³ . The ignition temperature is approx. 400 ° C. The substance therefore falls into temperature class T2 and explosion group IIA. The limit gap width was determined to be 1.15 mm. With a flash point of −55 ° C, dimethylamine is extremely flammable.

Individual evidence

1. ↑ ^{a b c d e f g h i j k l m n} Entry on dimethylamine in the GESTIS substance database of the IFA , accessed on March 6, 2019(JavaScript required) .
2. ↑ Hans Peter Latscha, Uli Kazmaier, Helmut Alfons Klein: Organic Chemistry: Chemistry Basics II . Springer DE, 2008, ISBN 978-3-540-77106-7 , p. 180 ( limited preview in Google Book Search).
3. ↑ ^{a b} entry on dimethylamine. In: Römpp Online . Georg Thieme Verlag, accessed on March 6, 2019.
4. ↑ Entry on Dimethylamine in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on March 6, 2019. Manufacturers or distributors can expand the harmonized classification and labeling .
5. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values , accessed on August 25, 2019.
6. ↑ 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. 5-23.
7. ^ ^{A b} Marco Bosch, Roderich Röttger, Jan Eberhardt, Thomas Krug, Theodor Weber, Karl-Heinz Ross, Manfred Julius: Shaped bodies containing an aluminosilicate and aluminum oxide and a process for the continuous production of methylamines. In: Google Patents. BASF SE, November 14, 2012, accessed on May 2, 2019 . 
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 .