Biacetyl monoxime

D. Dimethylglyoxime.—The crude biacetyl monoxime, remaining after distilling to 90° and containing about 5 moles of biacetyl monoxime, is added to the sodium hydroxylamine monosulfonate solution (which has been filtered to remove any sediment) and which is contained in a 15-I. flask. It is heated to 70° and allowed to remain warm (with occasional stirring) for several hours (Note 9). The dimethylglyoxime separates in crystals which can be filtered from the solution as soon as it has become cold (Note 10). The crystals are washed with cold water until free of sulfate. The yield of compound melting at 238-240° is 540-575 g-... 

The mixture is warmed to hasten the hydrolysis of disulfonate to monosulfonate, and also to increase the solubility of the biacetyl monoxime in the monosulfonate solution. 

Biacetyl monoxime has been prepared by the action of amyl nitrite on methyl ethyl ketone using sodium hydroxide1 or hydrochloric acid 2 as a condensing agent, and by melting nitroso-levulinic acid.3... 

Dimethylglyoxime has been prepared by the action of hydrochloric acid upon biacetyl monoxime 4 by the action of hydroxyl-amine on biacetyl 5 by the action of hydroxylamine on biacetyl... 

If pure biacetyl monoxime is desired, the crude product is neutralized with about 35 cc. of concentrated aqueous ammonia and diluted with half its volume of water. It is then distilled to remove alcohol, etc., until the distillate is no longer inflammable. 

The receiver is changed and the contents are now rapidly distilled, using superheated steam. Almost all of the biacetyl monoxime comes over in the first 5 1. of distillate. One to 1.5 kg. of salt is dissolved in the distillate, which is then cooled to o°. The solid biacetyl monoxime crystallizes out and may be filtered off. The yield is 480-520 g. The product can be further purified, if desired, by recrystallizing from water (Note 5). 

The methyl ethyl ketone should not be allowed to stand any length of time between the addition of the hydrochloric acid and the treatment with ethyl nitrite, inasmuch as the acid causes a condensation of the ketone with itself, thereby lowering the yield of biacetyl monoxime. 

About 70-80 per cent of the biacetyl monoxime is recovered on crystallization. Practically all of the monoxime left in the mother liquor can be recovered by steam distillation. The recrystallized and dried compound melts at 76.5°. Purification by distillation is not recommended. 

The biacetyl monoxime turns brown rapidly after preparation and it must not be allowed to stand before adding it to the hydroxylamine monosulfonate in the preparation of dimethylglyoxime if this final product is to be obtained in a colorless condition. 

Compounds having active methylene groups react with nitrous acid to form oximino derivatives. The attack on the a-methylene group of ketones is illustrated by the action of ethyl nitrite on methyl ethyl ketone, and by the action of methyl nitrite on propiophenone, to form biacetyl monoxime (60%) and isonitrosopropiophenone (68%), respectively. Methyl and ethyl nitrites are passed in gaseous form into the ketones in the presence of hydrochloric acid. In other preparations, n-butyl, amyl, or octyl nitrite in liquid form is employed. ... 

At-Methylenebenzylamine (11.9g, 0.09 mol) is added dropwise to a solution of biacetyl monoxime (10.1 g, 0.12 mol) in glacial acetic acid, and the solution is allowed to stand (12 h). After saturation with dry HCl and pouring into diethyl ether the semi-solid which separates is wa.shed with ether, taken up in methanol, and reprecipitated as a fine, white solid (12.7g, 53%) by addition of ether. The hydrochloride is made basic with ammonia (d. 0.88) and extracted with chloroform. The organic extracts are dried (MgS04), the solvent is removed, and the solid product recrystallized from acetone, to... 

Methyl ethyl ketone is converted to biacetyl monoxime in ethereal solution, and the latter is treated with sodium hydrox-ylamine disulfonate. Slotta and Jacobi, Z. anal. Chem. 83, I (1931)-... 

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