Pyrazole

Structural formula
General
Surname	Pyrazole
other names	1 H -pyrazole 1,2-diazole
Molecular formula	C 3 H 4 N 2
Brief description	colorless solid with a pyridine- like odor
External identifiers / databases
CAS number 288-13-1 EC number 206-017-1 ECHA InfoCard 100.005.471 PubChem 1048 ChemSpider 1019 DrugBank DB02757 Wikidata Q408908
properties
Molar mass	68.08 g mol −1
Physical state	firmly
Melting point	66-68 ° C
boiling point	186-188 ° C
solubility	soluble in ethanol, water and ether
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 302-311-315-318-373-412 P: 260-280-301 + 312 + 330-302 + 352 + 312-305 + 351 + 338
Thermodynamic properties
ΔH f 0	105.4 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

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

presentation

The most commonly used method for the synthesis of pyrazole compounds is the cyclization of 1,3- diketones with hydrazine derivatives . In the 19th century, the Nobel Prize winner Eduard Buchner and the chemist Ludwig Knorr earned merit in research in this field . There are also alternative synthesis variants.

properties

Pyrazole is a weak base (pK _b : 11.5) that smells like a pyridine . At room temperature it forms colorless crystals that melt at 70 ° C. Against acids , oxidation - and reducing agent pyrazole is relatively resistant.

use

Various derivatives of pyrazole are of certain importance in medicine , agriculture and as dyes .

literature

• A. Schmidt, A. Dreger: Recent Advances in the Chemistry of Pyrazoles. Properties, Biological Activities, and Syntheses , in: Current Organic Chemistry 15 (2011), 1423–1463, doi : 10.2174 / 138527211795378263 (review article on properties, biological activities and syntheses of pyrazoles)

Individual evidence

1. ↑ ^{a b c} data sheet pyrazole (PDF) from Merck , accessed on April 22, 2011.
2. ↑ Entry on 1H-pyrazole. In: Römpp Online . Georg Thieme Verlag, accessed on May 30, 2014.
3. ↑ ^{a b} Entry on pyrazole in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-23.
5. ↑ Entry on pyrazole in the ChemIDplus database of the United States National Library of Medicine (NLM) .