Phenylhydrazine: preparation and application The above information is edited by the Chemicalbook of Dai Xiongfeng. In 1902, Fischer, because of the synthesis of purine and carbohydrate, was awarded for the Nobel Prize in Chemistry. He also had opened up the study of proteins and had demonstrated that amino acids forms polypeptide via peptide bond and successfully synthesized polypeptides. He has also demonstrated that the caffeine, theophylline, uric acid all belongs to purine derivatives and also had successfully synthesized purine. This is a powerful means for studying carbohydrate structures and synthesis of a variety of sugars and enables the theoretic clarification of the structure of glucose and summarizing of the general stereoisomerism phenomenon of saccharides and further using of Fischer projection for describing it. He used phenylhydrazine to react with carbohydrate and generate hydrazone and osazone and form a crystalline compound which is easy for purification. Phenylhydrazine (Hydrazinobenzene) is the chemical compound characterized by Hermann Emil Fischer in 1895. We can use the hydrazone generated through phenylhydrazine or 2, 4-dinitrophenylhydrazine to identify aldehydes and ketones, It can trigger Fischer indole synthesis upon reaction with aldehydes and ketones (first found by the Emil Hermann Fischer in 1883, the reaction is using phenylhydrazine and aldehyde, ketone for heating and rearrangement under acid-catalysis for the elimination of one molecule of ammonia to give 2-or 3-substituted indole.) to give indole ring-class compound. It can react with benzaldehyde to generate phenylhydrazine. It is also an important reagent for identification of carbonyl group and can be used for identifying aldehydes, ketones and carbohydrates. Phenylhydrazine can be applied to making dyes, drugs, and being used as developer. Acid precipitation can generate phenylhydrazine hydrochloride with neutralization generating phenylhydrazine. Common method of its preparation is through the reaction between aniline and sodium nitrite under the action of hydrochloric acid for generation of diazonium salt which is then reduced by sulfite/sodium reduction for obtaining it. It is miscible with ethanol, ethyl ether, chloroform and benzene. It is slightly soluble in water and alkali solution and can be dissolved in dilute acid. Phenylhydrazine is one of the hydrazine derivatives and is often abbreviated as PhNHNH2. It can be easily subject to oxidization in the air and exhibit dark brown or dark red.
At room temperature, it is a pale yellow crystalline or oily liquid while at low temperature it appears as monoclinic prismatic crystals. It was first successfully synthesized by the German organic chemist Hermann-Emil-Fischer in 1875 and is the first synthesized hydrazine derivatives. Phenylhydrazine is also known as the hydrazinobenzene.
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