Semicarb azide

Acetaldehyde can be isolated and identified by the characteristic melting points of the crystalline compounds formed with hydrazines, semicarbazides, etc these derivatives of aldehydes can be separated by paper and column chromatography (104,113). Acetaldehyde has been separated quantitatively from other carbonyl compounds on an ion-exchange resin in the bisulfite form the aldehyde is then eluted from the column with a solution of sodium chloride (114). In larger quantities, acetaldehyde may be isolated by passing the vapor into ether, then saturating with dry ammonia acetaldehyde—ammonia crystallizes from the solution. Reactions with bisulfite, hydrazines, oximes, semicarb azides, and 5,5-dimethyl-1,3-cyclohexanedione [126-81 -8] (dimedone) have also been used to isolate acetaldehyde from various solutions. 

Busch and Frey [45] noted earlier that 2,4- and 1,4-substituted semicarb-azides are always formed when using arylhydrazines, the product depending on the reaction solvent used. The 1,4-substituted compounds are obtained in absolute ether, benzene, and neutral solvents. In alcoholic solution containing acetic or formic acid the 2,4-isomer is obtained in 25 % yield along with the 1,4-substituted isomer. 

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