Dimethylglyoxime

Dimethylglyoxime
IUPAC name 2,3-Butanedione Dioxime
Other names Dimethylglyoxime, Diacetyl dioxime, Chugaev's Reagent 2,3-diisonitrosobutane
Identifiers
CAS number	95-45-4 Y
ChemSpider	10606175 Y
UNII	2971MFT1KY Y
RTECS number	EK2975000
Jmol-3D images	Image 1
SMILES C\C(=N\O)\C(\C)=N\O
InChI InChI=1S/C4H8N2O2/c1-3(5-7)4(2)6-8/h7-8H,1-2H3/b5-3-,6-4+ Y Key: JGUQDUKBUKFFRO-CIIODKQPSA-N Y InChI=1/C4H8N2O2/c1-3(5-7)4(2)6-8/h7-8H,1-2H3/b5-3-,6-4+ Key: JGUQDUKBUKFFRO-CIIODKQPBA
Properties
Molecular formula	C4H8N2O2
Molar mass	116.12 g mol−1
Appearance	White/Off White Powder
Density	1.37 g/cm3
Melting point	240-241 °C, 513-514 K, 464-466 °F
Boiling point	decomp.
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	0 2 0
Related compounds
Related compounds	Hydroxylamine salicylaldoxime
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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 diacetyl (also known as 2,3-butanedione). 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

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

Ni(dmgH)₂

Structure of Ni(dmgH)₂

A sample of Ni(dmgH)₂

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

The nitrogen atoms in dmgH₂ and its complexes are sp² hybridized.^[3] Because of the planarity of the resulting ligand, the macrocycle [dmgH]₂^2- 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.

References

1. ^ Semon, W. L.; Damerell, V. R. (1943), "Dimethylglyoxime", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2p0204 ; 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.