Bisulfite compound, use for purification

Benzyl alcohol, 23, 14 BeNZYLAMINE, a-METHYL-, 23, 68 Benzyl carbamate, 23, 14 Benzyl chloride, 21, 99 Benzyl chloroeormate, 23, 13 Benzyl cyanide, 23, 71 Bisulfite compound, use for purification of an aldehyde, 23, 78 use for purification of a ketone, 23, 79 Blood, defibrinated, 21, 53 Booster pump, use of, for hydrogenation, 23, 69... 

A mixture of 1.38 grams of the above compound and 15 cc of dioxane was treated with 1.9 cc of a 0.5 N aqueous solution of perchloric acid and 600 mg of N-bromoacetamide, adding the latter in the dark, in three portions, in the course of half an hour and under continuous stirring. It was then stirred for a further 1% hours in the dark, then the excess of reagent was decomposed by the addition of aqueous sodium bisulfite solution and ice water was added the product was extracted with methylene chloride, washed with water, dried over anhydrous sodium sulfate and the solvent was evaporated under reduced pressure, thus giving a yellow oil consisting of the 16,21-diacetate of 6a-fluoro-9a-bromo-16o-hydroxy-hydrocortisone which was used for the next step without further purification. 

Bisulfite addition products are formed from aldehydes, methyl ketones, cyclic ketones (generally seven-membered and smaller rings), a-keto esters, and isocyanates, upon treatment with sodium bisulfite. Most other ketones do not undergo the reaction, probably for steric reasons. The reaction is reversible (by treatment of the addition product with either acid or base ) and is useful for the purification of the starting compounds, since the addition products are soluble in water and many of the impurities are not. ... 

The products are useful for two reasons. They are usually crystalline and so can be used to purify liquid aldehydes by recrystallization. This is of value only because this reaction, like several you have met in this chapter, is reversible. The bisulfite compounds are made by mixing the aldehyde or ketone with saturated aqueous sodium bisulfite in an ice bath, shaking, and crystallizing. After purification the bisulfite addition compound can be hydrolysed back to the aldehyde in dilute aqueous acid or base. 

Improvements to the techniques of synthesis of 8-alkyI-/V5-deazapterins have been reported for reactions between 2-amino-6-alkylaminopyrimidin-4(3//)ones and either 1,3-dicarbonyl compounds or 1,2-unsaturated carbonyl compounds which require the use of sodium bisulfite and the control of pH followed by chromatographic purification. The pKa data and protonation sites of the compounds which were prepared were recorded [94JHC1385]. 

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