Sodium bisulphite, addition product preparation

The experimental procedure to be followed depends upon the products of hydrolysis. If the alcohol and aldehyde are both soluble in water, the reaction product is divided into two parts. One portion is used for the characterisation of the aldehyde by the preparation of a suitable derivative e.g., the 2 4-dinitrophenylhydrazone, semicarbazone or di-medone compound—see Sections 111,70 and 111,74). The other portion is employed for the preparation of a 3 5-dinitrobenzoate, etc. (see Section 111,27) it is advisable first to concentrate the alcohol by dis tillation or to attempt to salt out the alcohol by the addition of solid potassium carbonate. If one of the hydrolysis products is insoluble in the reaction mixture, it is separated and characterised. If both the aldehyde and the alcohol are insoluble, they are removed from the aqueous layer separation is generally most simply effected with sodium bisulphite solution (compare Section Ill,74),but fractional distillation may sometimes be employed. 

This double spot formation is not observed on silica gel or alumina layers. The sensitivity to oxidation of the adrenaline derivatives is, however, increased by the metal or heavy metal impurities present in such layers. Adrenaline and noradrenaline have therefore been chromatographed on buffered silica gel layers (Sorensen buffer, pH 6.8), prepared with addition of sodium bisulphite and using 10% ethanol as solvent [163]. The sympathomimetics and the secondary products formed by oxidation tend moreover to form complex salts this manifests itself in elongated spots. Silica gel layers which had been prepared with O.IM EDTA have been used with the solvent acetone-formic acid-water (70 + 10 + 20) for the separation of adrenaline, noradrenaline and various substances of similar structure [110] silica gel HR (Krm 88) ought to be especially advisable for this purpose. On the other hand, Halmekoski [74] has made use of this very ability of the adrenaline-type of sympathomimetic to form complexes, in order to accomplish fractionation on buffered layers containing molybdate, tungstate or borax components... 

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