Pyrazole
Pyrazole and its derivatives have displayed broad spectrum of pharmacological and biological activities such as antimicrobial, antitumor, antiviral, antidepressant, anticonvulsant, antihyperglycemic, and enzymes inhibitory activities.
Pyrazole is an organic compound with the formula C3H3N2H. It is a heterocycle characterized by a 5-membered ring of three carbonatoms and two adjacent nitrogen atoms. Pyrazole is a weak base, with pKb 11.5 (pKa oPf the conjugated acid 2.49 at 25 °C). Pyrazoles are also a class of compounds that have the ring C3N2 with adjacent nitrogen atoms. Notable drugs containing a pyrazole ring are celecoxib (Celebrex) and the anabolic steroid stanozolol.
Figure: 5-member ring Pyrazole
Pyrazole any of a class of organic compounds of the heterocyclic series characterized by a ring structure composed of three carbon atoms and two nitrogen atoms in adjacent positions. The simplest member of the pyrazole family is pyrazole itself, a compound with molecular formula C3H4N2.
The pyrazole compounds are not known to occur in nature; they are usually prepared by the reaction of hydrazines with 1,3 diketones. Many synthetic pyrazole compounds are of importance as dyes and medicinals. Among them are: antipyrine, used as an analgesic and febrifuge; tartrazine, most commonly used as a yellow dye for food; phenylbutazone (Butazolidin), an anti-inflammatory drug used in treatment of arthritis; and a series of dyes used as sensitizing agents in colour photography
Poreties of Pyrazol:
Pyrazole is a colorless crystal compound with weak pyridine smell, which is soluble in water, ethanol and ether. In inpolar solvents pyrazole forms dimers and trimmers through formation intermolecular hydrogen bonds.
Pyrazole is amphoteric compound. Pyrazole type nitrogen atom imidazole has weak acidic properties and by pyridine type nitrogen atom imidazole- basic properties
Hence, pyrazole can react acid and bases
Pyrazole refers both to the class of simple aromatic ring organic compound. They are composed of three carbon atoms and two nitrogen atoms in adjacent positions and to the unsubstituted parent compound. They are classified as alkaloids, although they are rare in nature.
Chemical formula: C3H4N2 , Melting point: 66 to 70 °C (151 to 158 °F; 339 to 343 K), Boiling point: 186 to 188 °C (367 to 370 °F; 459 to 461 K), Basicity (pkb): 11.5, Molecular mass: 68.08 g•mol−1
Preparation of pyrazole compounds for attachment to chelating resins:
Several new pyrazole ligands have been prepared for use in the separation of metal ion from aqueous solution. These hydroxy-substituted pyrazole compounds were covalently bonded to a macroreticular styrene-divinylbenzene (1%) copolymer. The structure of the functionalized resins was confirmed by IR spectrophotometry and elemental analysis. The complexation behavior of these pyrazole resins was investigated towards Pb(II), Hg(II), Cd(II), Ca(II), Cs(I), K(I), Li(I) and Na(I) ions in aqueous solution by a batch equilibration technique. Polymers can be regenerated by washing with a solution of hydrochloric acid (6 N).
Pyrazoles are synthesized by the reaction of α,β-unsaturated aldehydes with hydrazine and subsequent dehydrogenation:[3]
Substituted pyrazoles are prepared by condensation of 1, 3-diketones with hydrazine. For example, acetyl acetone and hydrazine gives 3,5 -dimethylpyrazole
CH3C (O)CH2C(O)CH3 + N2H4 → (CH3)2C3HN2H + 2 H2O