已传文件：photo/1773121782.png
The core of the N-substituted hydrazone synthesis is the nucleophilic addition-decomposition reaction between phenylhydrazine (or its hydrochloride) and aldehyde. The free phenylhydrazine can directly react with an equal molar amount of aldehyde at room temperature, and stirring for 1-2 hours is sufficient. The phenylhydrazine hydrochloride needs to be neutralized with an equal molar amount of base to release the free phenylhydrazine, otherwise the hydrochloric acid will inhibit the reaction.
For solvent selection, aromatic aldehydes are preferably dissolved in room temperature dichloromethane. Weakly polar solvents can reduce side reactions and facilitate product precipitation; for insoluble aldehydes or fatty aldehydes, 60°C methanol is selected, and heating accelerates the reaction, but the time must be strictly controlled to prevent aldehyde polymerization.
During post-treatment, the amine hydrochloride precipitate is filtered first, and the crude product is purified by recrystallization / column chromatography to avoid loss of the product during water washing. The entire process is protected from light to prevent oxidation and decomposition of phenylhydrazine and hydrazone compounds.
