Phenylhydrazine

Phenylhydrazine is an organic compound with the chemical formula C6H5NHNH2. It is a derivative of benzene, where one hydrogen atom is replaced by a hydrazinyl group. It is a colorless to pale yellow oily liquid, though it can darken upon exposure to air and light. Phenylhydrazine is a weak base and is soluble in ethanol, ether, and chloroform.

This compound was first synthesized by Emil Fischer in 1875. It is primarily used in organic chemistry as a reagent for various synthetic transformations. A notable application is the Fischer indole synthesis, a method for producing indole derivatives, which are important in pharmaceuticals and dyes. Phenylhydrazine is also used for the detection and characterization of aldehydes and ketones, forming crystalline phenylhydrazones that can be identified by their melting points.

Phenylhydrazine is known for its toxicity and should be handled with care. It is a skin irritant and can be absorbed through the skin. Ingestion or inhalation can lead to serious health effects, including methemoglobinemia, a condition where the blood's ability to carry oxygen is reduced. Due to its hazardous nature, its use is often restricted to laboratory settings with appropriate safety precautions.