Acetoxime, hydrolysis

Hydrolysis of Acetoxime. Place about i g. of the recrystallised oxime in a small distilling-flask (50 ml.), add 10 ml. of dilute HjSO, and heat gently until about half the solution has distilled over. Test [a] the aqueous distillate for acetone by the iodoform reaction (p.346), b) the residual solution in the distilling-flask for hydroxylamine by... 

Hydrolysis of oximes catalyzed by transition-metal complexes has not been studied prior to a report by Kostic et al. They have reported kinetics of hydrolysis of acetoxime to acetone catalyzed by two palladium(II) complexes, identified active species in the hydrolysis reaction, proposed a reaction mechanism, and fully characterized a bis(acetoxime) complex that is relatively stable toward hydrolysis.458... 

The acetoxime may be distilled by direct heating rather than by injection of steam when the prescribed quantities are taken, however, it will be found that the liquor becomes saturated with sodium sulfate at a point just before the expulsion of the oxime is complete, so that addition of water during the distillation is necessary. More rapid distillation can be obtained by the use of a current of steam, especially if a condensing receiver (Vol. II, pp. 80-82) be employed. The oxime can also, if desired, be isolated for hydrolysis by separation of the oily layer and extraction with benzene the resulting crude hydroxyl-amine hydrochloride is, however apt to be dark in color and to contain inorganic salts. 

Fig. 10. Rates of imidazole-catalyzed ester hydrolysis as a function of the rate of alkaline hydrolysis nucleophilic reactions of acetates, general base catalysis of acetates, a general base catalysis of methyl and ethyl esters, o (ionic strength 1-0 25°). Trifluoroethyl acetate measured with N-methylimidazole. From Kirsch and Jencks (1964a). Reproduced with permission of the American Chemical Society. (> = NOAc = acetoxime acetate).

Acetone may also be estimated by the method that is used for the determination of aldehydes and ketones by means of hydroxylamine hydrochloride this forms oximes, liberating the acid, which can be titrated direct. It is a very rapid process, Pemberton, Card and Craven finding that the titration can be completed in aqueous solution within a minute or two. In their opinion not more than three-quarters of the hydroxylamine salt should be decomposed, and under these conditions a constant factor must also be used for a given indicator depending on the hydrolysis of acetoxime at the end-point acidity. The factor for methyl orange-xylene cyanol (pH 3-7) was found to be 0-983 and for 4-5 indicator, 0-988. Haughton prefers the factor 0-974 for methyl orange-xylene cyanol. 

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