Sodium bisulphite adducts

The metallic derivatives of organic compounds that are most likely to be encountered in the course of practice analyses are salts of carboxylic acids, sulphonic acids, phenols and enols, alkyl hydrogen sulphates metallic derivatives of amides, imides and sidpho-namides sodium bisulphite adducts of carbonyl compounds. 

Aldehydes and Ketones. The best derivative from which an aldehyde can be recovered readily is its bisulphite addition compound, the main disadvantage being the lack of a sharp melting point. The aldehyde (sometimes in ethanol) is shaken with a cold saturated solution of sodium bisulphite until no more solid adduct separates. The adduct is filtered off, washed with a little water, then alcohol. A better reagent is freshly prepared saturated aqueous sodium bisulphite solution to which 75% ethanol is added to near-saturation. (Water may have to be added dropwise to render this solution clear.) With this reagent the aldehyde need not be dissolved separately in alcohol and the adduct is finally washed with alcohol. The aldehyde is recovered by dissolving the adduct in the least volume of water and adding an equivalent quantity of sodium carbonate (not sodium hydroxide) or concentrated hydrochloric acid to react with the bisulphite, followed by steam distillation or solvent extraction. 

The invention also provides a process for the preparation of a bisulphite adduct of the general formula II, which comprises treating the appropriate compound of the general formula I, prepared as above, with an alkali metal bisulphite such as sodium bisulphite. 

A mixture of homoveratric acid (32 g), anhydrous sodium acetate (30.6 g) and acetic anhydride (52 mL) was refluxed for 4 hours, cooled and poured into 300 mL of ice-cold water. The resulting reddish bottom layer was separated and retained. The aqueous layer was extracted with two 50 mL. quantities of toluene and the combination of the reddish liquid and the toluene extracts was washed successively with four 100 mL. quantities of IN sodium hydroxide solution followed by two 50 mL. quantities of water. It was filtered through a plug of glass wool and distilled to remove the toluene and water. There was thus obtained about 25 g of crude phenylacetone. This was dissolved in 50 mL. IMS and added, with stirring, to 90 mL. of freshly prepared 40 % w/v sodium bisulphite solution. The mixture was stirred for 30 minutes and allowed to stand for 2 hours in a cold water bath. It was again stirred for 30 minutes, washed with 100 mL. of toluene and stirred for a further 15 minutes. It was then filtered and washed with 50 mL. of toluene and air dried. There was thus obtained 30 g of the bisulphite adduct of... 

Addition products are likewise formed by the reaction of adrenochrome with sodium bisulphite (71CI1021). The main adduct has been characterized by NMR and shown to bear a sulphonate group at the 9-position (144). No evidence for the enol tautomer was obtained. The preferential reactivity of adrenochrome through the 9-position is also reflected in the structure of the dimer 141 obtained under anaerobic conditions (88T6441). 

Direct reaction of the bisulphite adduct, 3-phenoxy-a-hydroxybenzylsulfonate, with sodium cyanide also gives the desired cyanohydrine [632]. 

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