Phenylhydrazine is a widely used reagent in conjunction with sugars, aldehydes, and ketones. In addition, to its use in the synthesis of dyes; pharmaceuticals, such as antipyrin; cryogenin, and pyramidone; and other organic chemicals. The hydrochloride salt is used in the treatment of polycythemia vera.

Application

 Phenyl-hydrazine is used to prepare indoles by the Fischer indole synthesis, which are intermediates in the synthesis of various dyes and pharmaceuticals. Phenylhydrazine is used to form phenylhydrazones of natural mixtures of simple sugars in order to render the differing sugars easily separable from each other.