Benzil dioximes

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. 

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. 

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). 

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

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

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