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Dimethylglyoxime



Dimethylglyoxime
General
Systematic name 2,3-Butanedione Dioxime
Other names Dimethylglyoxime,
Diacetyl dioxime,
Chugaev's Reagent
2,3-diisonitrosobutane
Molecular formula C4H8N2O2
Molar mass 116.1194 g/mol
Appearance White/Off White Powder
CAS number [95-45-4]
Properties
Density and phase 1.37 g/cm3
Solubility in water low
Other solvents ethanol, acetone
Melting point 240 - 241 °C (513.15 K)
Boiling point decomp.
Structure
trans, symmetric
Dipole moment 0
Hazards
MSDS External MSDS
Main hazards Toxic, Skin/Eye Irritant
NFPA 704
0
2
0
 
R/S statement R: 20/22
S: 22-36/37
RTECS number EK2975000
Supplementary data page
Structure and
properties
n, É√r, etc.
Thermodynamic
data
É¢Hsub 96.8kJ/mol
Spectral data UV, IR, NMR, MS
Related compounds
Related compounds Hydroxylamine, salicylaldoxime
Except where noted otherwise, data are given for
materials in their standard state (at 25°C, 100 kPa)
Infobox disclaimer and references

Dimethylglyoxime is a chemical compound described by the formula CH3C(NOH)C(NOH)CH3. It 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.

Additional recommended knowledge

Contents

Preparation

Dimethylglyoxime can be prepared from methyl ethyl ketone first by reaction with ethylnitrite followed by conversion of the biacetyl monoxime using sodium hydroxylamine monosulfonate:[1]

CH3C(O)CH2CH3 + CH3CH2ONO → CH3C(O)C(NOH)CH3 + CH3CH2OH
CH3C(O)C(NOH)CH3 + HONHSO3Na → CH3C(NOH)C(NOH)CH3 + NaHSO4

Ni(dmgH)2

 As an analytical reagent, 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 is used for the gravimetric determination of nickel, e.g. in ores.

Cobaloximes

The nitrogen atoms in dmgH2 and its complexes are sp2 hybridized.[2] 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 this complex, 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.; Coll. Vol. 2: 204. 
  2. ^ Girolami, G.. S.; Rauchfuss, T.B.; Angelici, R. J. (1999). Synthesis and Technique in Inorganic Chemistry: A Laboratory Manual, 3rd Ed, pp. 213-215. 
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Dimethylglyoxime". A list of authors is available in Wikipedia.
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