Benzil-a-dioxime

C14H12N2O2 ( , )- D iphenylgly oxime (a-Benzil dioxime) Extraction-photometric Fe, Ni 3... 

Di-dimethyl glyoxime may be used for separating small quantities of nickel from cobalt.1 Excess of the glyoxime is added to a boiling ammoniacal solution of the cobalt salt, when the scarlet nickel cc-dimethyl glyoxime is precipitated.2 ct-diphenyl glyoxime (a-benzil dioxime) may be used in a similar manner with corresponding results. 

A mixture of a-benzil dioxime and polyphosphoric acid heated 12 min. at 120° 3,5-diphenyl-1,2,4-oxadiazole. Y 99%. 

A quick perusal of Table 3 shows inverted stability for a and /3 isomers of phenyl-glyoxime and p-tolylglyoxime. Given uncertainties as to stereochemistry it is plausible that the structural assignments of Z and E, syn and anti, even a and /3 were reversed. This is understandable. However, it is inexplicable that the tolyl species have enthalpies of formation at least 150 kJ moH more positive than the phenyl compounds. This is an altogether implausible result. The solid phase reaction 35 is calculated to be ca 75 kJmol exothermic if we use the averaged value for the various stereoisomers of phenylglyoxime and benzil dioxime. This, too, is implausible. 

Other reducing conditions have also been widely used. Thus zinc and sodium hydroxide has been utilized for the conversion of 1-hydroxyimino-l-phenylacetone to 2,5-dimethyl-3,6-diphenylpyrazine (191) dithionite for the conversion of a-benzoyl a-hydroxyiminoacetanilide to 2,5-diphenyl-3,6-bis(7V-phenylcarbamoyl)-pyrazine (192) sodium amalgam for benzil monoxime to tetraphenylpyrazine (193) aluminum amalgam for hydroxyiminoacetoacetic ester to 2,5-bisethoxy-carbonyl-3,6-dimethylpyrazine (194) and sodium and alcohol for benzil dioxime to tetraphenylpyrazine (195). 

H. Goldschmidt discovered a second dioxime of benzil, but little notice was taken of this until the discovery of the Beckmann rearrangement (1886, see p. 833). Beckmann discovered a second isomer, isobenzaldoxime, of ben-zaldoxime, and the two modifications were supposed to be ... 

Ligand abbreviations rngH = methylglyoxime, a-fdH2 = furil dioxime, bdHg = benzil dioxime. 

Dioximes of a-diketones such as benzil on oxidation with IBTA are converted into 1,2,5-oxadiazole-A-oxides (furoxans) in high yields (75S445) (Eq. 35). Benzo- (Scheme 46) and pyrido-oxadiazoles (Eq. 36) are formed when o-nitroaniline and 3-amino-2-nitropyridine are subjected to similar oxidation. 

Diphenyl-furazan wird sowohl aus dem a- als auch aus dem (6-Dioxim von Benzil beim Erhitzen auf 200 210° ( 100%)68 bzw. mit Kupfersullat erhalten73. 

Hydrogenation of a-hydroxyimino ketones and esters, and also of 1,2-dioximes, may lead to the formation of pyrazines. Tetraphenylpyrazine became the predominant product in the hydrogenation of benzil monoxime and dioxime over nickel catalyst in ether or alcohol at around 100°C. Thepyrazine was formed even in the hydrogenation... 

Benzil acts like a ketone in that it forms oximes with hydroxylamine-The oximes are of exceptional interest, since our knowledge of the stereochemistry of nitrogen proceeds from them. Benzil forms two monoximes and three dioximes. The constitution of these compounds will be discussed later, under the preparation of benzophenone-oxime ... 

The a-diketone precursors used to prepare the dithiolene complexes discussed above can be used for the preparation of other potential ligands such as dioximes. Such ligands are directly obtained by the reaction of the corresponding benzil species with hydroxylamine chloride. Dioximato complexes with cf metals crystallize in columnar stacks with the formation of a chain of metals orthogonal to the molecular planes, and as such are potentially interesting candidates for the design of discotic systems with low-dimensional semiconducting properties. Ohta et al. reported a... 

Care must be taken that ferric and cobalt salts are not both present (see page 328). Instead of dimethylglyoxime, it is possible to use cyclohexane-1,2-dionedioxime (Nioxime),2 furil-a-dioxime and benzil-a-dioxime as reagents for Ni. 

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