Pyrazole

1,2- diazole

Colorless solid with pyridinartigem odor

Fixed

66-68 ° C

186-188 ° C

Soluble in ethanol, water and ether

Attention

105.4 kJ / mol

Template: Infobox chemical / molecular formula search available

Pyrazole is a five membered heterocycle of three carbon and two adjacent nitrogen atoms. It is the parent compound of the pyrazoles. 1H- pyrazole is a structural isomer of the imidazole and this is similar in the chemical properties. Its fully saturated analogue is the pyrazolidine. 1H- pyrazole is a heteroaromatic, 3H - and 4H- isomers are not aromatic.

Occurrence

Various derivatives of pyrazole have some importance in medicine, in agriculture as well as dyes. Of course pyrazole occurs as a component of the amino acid citrulline in the seeds of watermelon ( Citrullus vulgaris).

Representation

The method for the synthesis of pyrazole compounds most commonly used is the cyclization of 1,3-diketones with hydrazine derivatives. Contributions to the research in this area acquired in the 19th century, the Nobel laureate chemist Eduard Buchner and the Ludwig Knorr. In addition, there are alternative versions of the synthesis.

Properties

Pyrazole is a weak base ( pKb: 11.5 ), which smells like pyridine. At room temperature it forms colorless crystals which melt at 70 ° C. To acids, oxidizing and reducing agents pyrazole is quite stable.