Acetamide

Structural formula
Crystal system	trigonal
Space group	R 3 c (No. 161)
Lattice parameters	a  = 1144  pm ; c  = 1350 pm with 18 formula units per unit cell
General
Surname	Acetamide
other names	Acetic acid amide Ethanamide Ethanoic acid amide
Molecular formula	C 2 H 5 NO
Brief description	colorless, odorless, hygroscopic crystals that smell like a mouse when contaminated
External identifiers / databases
CAS number 60-35-5 EC number 200-473-5 ECHA InfoCard 100,000,430 PubChem 178 ChemSpider 173 DrugBank DB02736 Wikidata Q421721
properties
Molar mass	59.07 g mol −1
Physical state	firmly
density	1.16 g cm −3
Melting point	81 ° C 65 ° C (metastable crystal form)
boiling point	222 ° C (decomposition)
Vapor pressure	1.3 Pa (20 ° C)
solubility	very light in water (2200 g l −1 at 20 ° C) good in ethanol, trichloromethane and glycerol, bad in diethyl ether
Dipole moment	3.68 (3) D (1.2 · 10 −29  C  ·  m )
Refractive index	1.4278
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary Caution H and P phrases H: 351 P: 308 + 313
MAK	not fixed
Toxicological data	7000 mg kg −1 ( LD 50 ,  rat ,  oral )
Thermodynamic properties
ΔH f 0	−317.0 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Acetamide is the amide of acetic acid . Acetamide is used as a solvent.

Extraction and presentation

Acetamide is made by heating ammonium acetate with dehydration :

${\displaystyle \mathrm {CH_{3}COONH_{4}\longrightarrow CH_{3}{-}CO{-}NH_{2}+H_{2}O} }$

It can also be produced by reacting acetyl chloride and ammonia : Acetic anhydride or alkyl acetates also react in a similar way with ammonia.

${\displaystyle \mathrm {H_{3}C{-}CO{-}Cl+NH_{3}\longrightarrow CH_{3}{-}CO{-}NH_{2}+HCl} }$

The direct reaction of ketene with ammonia also gives acetamide.

${\displaystyle \mathrm {H_{2}C{=}C{=}O+NH_{3}\longrightarrow CH_{3}{-}CO{-}NH_{2}} }$

Acetonitrile can be hydrolyzed to acetamide in the presence of acidic or basic catalysts .

${\displaystyle \mathrm {CH_{3}{-}C{\equiv }N+H_{2}O\rightarrow CH_{3}{-}CO{-}NH_{2}} }$

properties

Acetamide forms colorless, hygroscopic, hexagonal crystals that melt at 81 ° C. The heat of fusion is 15.6 kJ mol ⁻¹ . There is also a second metastable polymorphic crystal form that melts at 69 ° C with a heat of fusion of about 12.7 kJ mol ⁻¹ . The stable form crystallizes in a trigonal crystal lattice and is obtained by crystallization from solutions in organic solvents such as ethyl acetate . The metastable form crystallizing in an orthorhombic lattice results from crystallization from the melt. According to Antoine, the vapor pressure function results from log ₁₀ (P) = A− (B / (T + C)) (P in bar, T in K) with A = 5.3711, B = 2413.323 and C = −45.444 in the temperature range from 338 to 495 K. The mean heat of vaporization in this temperature range is 60.9 kJ · mol ⁻¹ . Liquid acetamide can enter into acid-base reactions. Here an autoprotolysis equilibrium can be formulated. At 94 ° C the pK _a value is 10.49.

${\displaystyle \mathrm {2\,CH_{3}{-}CO{-}NH_{2}\rightleftharpoons CH_{3}{-}CO{-}NH_{3}^{+}+CH_{3}{-}CO{-}NH^{-}} }$

Above 220 ° C it decomposes into the main products acetic acid, ammonia and acetonitrile, whereby water and nitrous gases can occur as by-products.

${\displaystyle \mathrm {2\,CH_{3}{-}CO{-}NH_{2}\rightarrow CH_{3}{-}COOH+CH_{3}{-}C{\equiv }N+NH_{3}} }$

use

It is mainly used as a solvent , as many substances dissolve well in it ( when molten). It is also used in the manufacture of methylamine . It is also used as a plasticizer additive in the leather, cloth and paper industries and as a vulcanization accelerator for synthetic rubber . The stable 1: 1 complex with hydrogen bromide is used for the bromination of acid-sensitive substances.

Biological importance

The crystals are flammable. When burned, toxic fumes ( nitrogen oxides ) are formed. The substance reacts with acids and strong oxidizing agents .

The substance is absorbed by inhalation and irritates the skin and eyes. Acetamide exposure can be recognized by redness and pain. Birth defects occurred in animal experiments. Acetamide is suspected to be carcinogenic in humans.

Acetamide as a mineral

Colorless to yellowish acetamide crystals on matrix from Shamokin , Northumberland County, Pennsylvania

Acetamide was found in 1974 as a natural product of formation in the coal mine near Tscherwonohrad in the Ukraine. It was therefore recognized by the International Mineralogical Association (IMA) as an independent mineral (internal register no. IMA1974-039 ). According to the systematics of minerals according to Strunz (9th edition) , these are listed as salts of organic acids in the mineral class of "organic compounds" under system no. "10.AA.20". However, the classification as a salt of organic acids does not correspond to the chemical composition, since acetamide is an uncharged molecule. The systematics of minerals according to Dana , which is also common in English-speaking countries , lists the mineral under system no. “50.04.07.01” (subdivision: salts of organic acids with various formulas ).

Acetamide crystallizes in the trigonal crystal system with the crystal chemical composition CH ₃ CONH ₂ , has a Mohs hardness of 1 to 1.5 and develops predominantly colorless, prismatic crystals up to about five millimeters in length and surfaces with a glass to fat gloss , but also stalactites and granular mineral Aggregates .

However, it also occurs in a metastable form with an orthorhombic crystal structure with the space group Pccn (space group no. 56) .

Acetamide forms at a temperature between 50 ° C and 150 ° C in ammonia-rich areas of burning coal heaps ( coal fire ). Due to its volatility and solubility, the mineral is not persistent and therefore can only be found in dry weather.

So far only the Tscherwonohrad type locality is known as a location for acetamide.

literature

• BI Srebrodol'skii: Acetamide - a new mineral. In: Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva. (1975): 104 (3), pp. 326-328; In: American Mineralogist. (1976): 61, p. 338.
• M. Windholz, S. Budavari, RF Blumetti, ES Otterbein (Eds.): The Merck Index. 10th edition. Merck & Co., Rahway (NJ, USA) 1983.
• BI Srebrodol'skii: Phases of mineral formation on spoil heaps of coal mines. Doklady Acad. Nauk SSSR: 290 (1986): 1730174.
• Frederic Senti, David Harker: "The Crystal Structure of Rhombohedral Acetamide", in: J. Am. Chem. Soc. , 1940 , 62  (8), pp. 2008-2019; doi : 10.1021 / ja01865a029 .
• WA Denne, RWH Small: "A Refinement of the Structure of Rhombohedral Acetamide", in: Acta Crystallographica , 1971 , B27 , pp. 1094-1098; doi : 10.1107 / S0567740871003583 .

Individual evidence

1. ↑ ^{a b c d} Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 717 .
2. ↑ ^{a b c d e f g h i j} Entry on acetamide in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
3. ↑ Günther Höhne, W. Hemminger, H.-J. Flammersheim: Differential Scanning Calorimetry . Springer Science & Business Media, 2003, ISBN 978-3-540-00467-7 , pp. 224 ( limited preview in Google Book search).
4. ↑ ^{a b c d e f g} Entry on acetamide. In: Römpp Online . Georg Thieme Verlag, accessed on November 12, 2014.
5. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Dipole Moments, pp. 9-52.
6. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-4.
7. ↑ Entry on Acetamide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
8. ↑ 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. 5-22.
9. ^ ^{A b} C. Le Berre, P. Serp, P. Kalck, GP Torrence: Acetic Acid , in: Ullmanns Enzyklopädie der Technischen Chemie , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2013; doi : 10.1002 / 14356007.a01_045.pub3 .
10. ^ S. Hauptmann , J. Graefe, H. Remane : Textbook of Organic Chemistry, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig 1980, p. 382.
11. ↑ ^{a b} Emons, HH ; Naumann, R .; Jahn, K .; Flammersheim, HJ: Thermal properties of acetamide in the temperature range from 298 K to 400 K in Thermochim. Acta 104 (1986) 127-137, doi : 10.1016 / 0040-6031 (86) 85191-7 .
12. ↑ ^{a b c d} Kerridge, DH: The chemistry of molten acetamide and acetamide complexes in Chem. Soc. Rev. 17 (1988) 181-227, doi : 10.1039 / CS9881700181 .
13. ^ ^{A b} Stull, DR: Vapor Pressure of Pure Substances. Organic and Inorganic Compounds in Ind. Eng. Chem. 39 (1947) 517-540, doi : 10.1021 / ie50448a022
14. ^ Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, p. 144.
15. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed October 15, 2019 . 
16. ^ WC Hamilton: The crystal structure of orthorhombic acetamide. In: Acta Crystallographica. 18, p. 866, doi : 10.1107 / S0365110X65002128 .
17. ↑ acetamide. (PDF; 66 kB) In: Handbook of Mineralogy.
18. ↑ Mindat - Acetamide (English).