Dimethylglyoxime

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Dimethylglyoxime
Dimethylglyoxime
Dimethylglyoxime3D.jpg
Identifiers
CAS number 95-45-4 YesY
ChemSpider 10606175 YesY
UNII 2971MFT1KY YesY
RTECS number EK2975000
Jmol-3D images Image 1
Properties
Molecular formula C4H8N2O2
Molar mass 116.12 g mol−1
Appearance White/Off White Powder
Density 1.37 g/cm3
Melting point 240 to 241 °C (464 to 466 °F; 513 to 514 K)
Boiling point decomposes
Solubility in water low
Structure
Dipole moment 0
Hazards
MSDS External MSDS
R-phrases R20/22
S-phrases R22, R36/37
Main hazards Toxic, Skin/Eye Irritant
NFPA 704
Flammability (red): no hazard code Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity (yellow): no hazard code Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related compounds Hydroxylamine
salicylaldoxime
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Dimethylglyoxime is a chemical compound described by the formula CH3C(NOH)C(NOH)CH3. This colourless solid is the dioxime derivative of the diketone butane-2,3-dione (also known as diacetyl). DmgH2 is used in the analysis of palladium or nickel. Its coordination complexes are of theoretical interest as models for enzymes and as catalysts. Many related ligands can be prepared from other diketones, e.g. benzil.

Preparation[edit]

Dimethylglyoxime can be prepared from butanone first by reaction with ethyl nitrite followed by sodium hydroxylamine monosulfonate:[1]

Preparation of dimethylglyoxime.png

Ni(dmgH)2[edit]

Dimethylglyoxime is used as a chelating agent in the gravimetric analysis of nickel:

Ni-Dimethylglyoxime-complex.svg     
A sample of Ni(dmgH)2

The use of DMG as a reagent to detect nickel was discovered by L. A. Chugaev in 1905.[2] For qualitative analysis, dmgH2 is often used as a solution in ethanol. It is the conjugate base, not dmgH2 itself, that forms the complexes. Furthermore, a pair of dmgH- ligands are joined through hydrogen bonds to give a macrocyclic ligand. The most famous complex is the bright red Ni(dmgH)2, formed by treatment of Ni(II) sources with dmgH2. This planar complex is very poorly soluble and so precipitates from solution. This method is used for the gravimetric determination of nickel, e.g. in ores.

Cobaloximes[edit]

The nitrogen atoms in dmgH2 and its complexes are sp2 hybridized.[3] Because of the planarity of the resulting ligand, the macrocycle [dmgH]22- resembles some biologically important macrocyclic ligands, as found for example in vitamin B12 and myoglobin. A well known family of model complexes, the cobaloximes, have the formula CoR(dmgH)2L, where R is an alkyl group and L is typically pyridine. In such complexes, L and R occupy “axial” positions on the cobalt, perpendicular to the plane of the (dmgH)2. One of the examples of cobaloxime is chloro(pyridine)cobaloxime.

Structure of chloro(pyridine)cobaloxime
Sample of chloro(pyridine)cobaloxime

References[edit]

  1. ^ Semon, W. L.; Damerell, V. R. (1943), "Dimethylglyoxime", Org. Synth. ; Coll. Vol. 2: 204 
  2. ^ Lev Tschugaeff (1905). "Über ein neues, empfindliches Reagens auf Nickel". Berichte der deutschen chemischen Gesellschaft 38 (3): 2520–2522. doi:10.1002/cber.19050380317. 
  3. ^ Girolami, G.. S.; Rauchfuss, T.B.; Angelici, R. J. (1999). Synthesis and Technique in Inorganic Chemistry: A Laboratory Manual (3rd ed.). pp. 213–215.