Aldehydes, addition derivatives sodium bisulphite reaction

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. 

Reactions.—The general properties and reactions of the aromatic aldehydes and ketones are like those of their aliphatic relatives. The aldehydes are easily oxidized to acids and reduce ammoniacal silver nitrate solution. Both aldehydes and ketones are easily reduced to alcohols. The aldehydes form addition products with sodium bisulphite and with hydrogen cyanide. With ammonia, however, they do not form addition products but react with the elimination of wafer and the formation of a condensation product which is a derivative of two molecules of ammonia. 

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See also in sourсe #XX -- [ ]

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