Dimethylglyoxime

Structural formula
General
Surname	Dimethylglyoxime
other names	Diacetyl dioxime Biacetyl dioxime DMG DAD 2,3-butanedione dioxime Tschugaeff reagent
Molecular formula	C 4 H 8 N 2 O 2
Brief description	colorless, odorless powder
External identifiers / databases
CAS number 95-45-4 EC number 202-420-1 ECHA InfoCard 100.002.201 PubChem 5323784 Wikidata Q424895
properties
Molar mass	116.12 g mol −1
Physical state	firmly
Melting point	245–246 ° C (decomposition) 240–241 ° C (decomposition)
solubility	slightly soluble in water (0.6 g l −1 at 20 ° C)
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 228 P: 210-370 + 378
Toxicological data	250 mg kg −1 ( LD 50 ,  rat ,  oral )
Thermodynamic properties
ΔH f 0	−199.7 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Dimethylglyoxime , also diacetyldioxime , is a dioxime and is used as a detection reagent ( Tschugajew reagent) for various heavy metal ions .

history

The complexing agent was first described in 1905 by Lev Alexandrovich Tschugajew .

Extraction and presentation

Dimethylglyoxime is obtained in a multi-stage reaction. Butanone (methyl ethyl ketone) is converted into diacetyl monoxime by nitrosation with ethyl nitrite . Without prior isolation, this reacts with sodium hydroxylamine-O-sulfonate to form dimethylglyoxime.

Course of the synthesis of dimethyldioxime, starting from butanone and ethyl nitrite.

properties

Dimethylglyoxime is a complexing agent that forms colored chelate complexes with heavy metal ions such as Ni ²⁺ , Fe ²⁺ , Co ²⁺ , Cu ²⁺ , Pt ²⁺ , Pd ²⁺ and Re ⁷⁺ . As a qualitative proof, the complexes can be precipitated under the appropriate conditions ( pH and temperature). Complexes of Co, Fe, Ni, Pd and Re are suitable for quantitative, photometric determination .

The complexes have the following colors:

• Nickel (II) complex: raspberry red
• Copper (II) complex: brown-red
• Iron (II) complex: red
• Cobalt (II) complex: purple
• Palladium (II) complex: yellow-yellowish
• Platinum (II) complex: brown and blue
• Lead (II) complex: white
• Bismuth (III) complex: intense yellow

The heat of decomposition determined by DSC is −230 kJ · mol ⁻¹ or −1980 kJ · kg ⁻¹ .

Nickel complex

Precipitation of the nickel-dimethylglyoxime complex from a nickel (II) sulfate solution

In particular, the pink-red to raspberry-red, very poorly soluble bis (diacetylglyoximato) nickel (II) (nickel-dimethylglyoxime complex; [Ni (dmg) ₂ ]) in ammoniacal solution serves as a qualitative nickel (II) test (see also nickel test ) and is used for quantitative determination, both via photometric and gravimetric methods, for nickel salts. The chelate compound has a square planar structure.

The color can still be detected at 0.015 µg nickel / ml. (Limit concentration of 1: 4 · 10 ⁵ )

In the solid state, the complexes form stacks of molecules with a Ni – Ni distance of 325 pm.

Reagent

• 1% alcoholic solution of dimethyldioxime

Individual evidence

1. ↑ ^{a b c} Entry on biacetyldioxime. In: Römpp Online . Georg Thieme Verlag, accessed on June 12, 2014.
2. ↑ ^{a b c d} Entry on butanedione dioxime in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
3. ↑ Entry on dimethylglyoxime in the ChemIDplus database of the United States National Library of Medicine (NLM) .
4. ↑ 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. 5-26.
5. ↑ Lev Tschugaeff: About a new, sensitive reagent on nickel. In: Reports of the German Chemical Society. 1905, Vol. 38, No. 3, pp. 2520-2522, doi: 10.1002 / cber.19050380317 .
6. ^ KH Slotta, KR Jacobi: Production of organic reagents in the analytical laboratory. III. Diacetyl dioxime . In: Journal for Analytical Chemistry . tape 83 , no. 1-2 , January 1931, pp. 1–5 , doi : 10.1007 / bf01361818 ( PDF ).
7. ↑ Gerhard Jander: Jander⋅Blasius textbook of analytical and preparative inorganic chemistry , Hirzel, Stuttgart, 1985, pages 259, 359, 361st
8. ↑ ^{a b c} G. Jander, H. Wendt: Textbook of analytical and preparative inorganic chemistry . 2nd Edition. S. Hirzel Verlag, Leipzig 1954, p. 108 f., 191 .
9. ↑ Grewer, T .; Klais, O .: Exothermic decomposition - investigations of the characteristic material properties , VDI-Verlag, series "Humanisierung des Arbeitsleben", Volume 84, Düsseldorf 1988, ISBN 3-18-400855-X , p. 9.
10. ^ Wittko Francke and Wolfgang Walter: Textbook of organic chemistry . S. Hirzel Verlag Stuttgart; 24. revised 2004 edition, ISBN 3-7776-1221-9 ; P. 342.
11. ^ ^{A b} Wolfgang Werner: Qualitative inorganic analysis: for pharmacists and natural scientists Deutscher Apotheker Verlag; 4. completely rework. u. exp. Edition 2006; ISBN 3-8047-2264-4 ; P. 95.
12. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1715.