Kinetics of the precipitation of palladium dimethylglyoximate from homogeneous solution.
The kinetics of formation of palladium dimethylglyoximate in the post-nucleation and pre-nucleation stages, and the effect of palladium on the reaction of biacetyl and hydroxylamine, have been studied.
Co-precipitation of metal dimethylglyoximates generated from biacetyl monoxime or biacetyl and hydroxylamine.
A study has been made of some aspects of the co-precipitation of gold and platinum(II) and (IV) with palladium(II) precipitated from homogeneous solution initially containing biacetyl and hydroxylamine in 0.3M hydrochloric acid. The co-precipitation of nickel(II) with palladium(II) and vice versa from near neutral solutions initially containing biacetyl and hydroxylamine was also explored; the solid is enriched in the minor constituent in both cases. As with biacetyl monoxime-hydroxylamine systems, both nickel(II) and palladium(II) promote formation of dimethylglyoxime from such solutions between pH 7 and 8. Factors leading to this unusual behaviour in co-precipitation are discussed and a qualitative explanation tentatively advanced. The co-precipitation of nickel and palladium(II) is different when biacetyl monoxime solutions are used; the former comes out of solution faster than the latter irrespective of their concentration ratio. This disparity in the reaction rates can be used to separate nickel directly from palladium(II) by precipitation or extraction of the dimethylglyoximate into chloroform.
SPECTROSCOPIC STUDIES OF KETO–ENOL EQUILIBRIA: PART 1. SOLVENT EFFECTS
Solvent effects on the keto–enol equilibria of ethyl acetoacetate, acetylacetone, ethyl cyclopentanone-2-carboxylate, and methyl 4-methylcyclopentane-1-,2-dione-3,4,5-tricarboxylate have been studied by ultraviolet spectroscopy. The extent of enolization is mainly determined by the stabilization of the keto form by local association with polar or proton-donating solvent molecules, just as in the case of n → π* transitions and infrared stretching frequencies. Solvent effects on infrared spectra reveal useful information regarding the characteristic frequencies of the tautomers.