pyrazolen.
/ˈpʌɪrəzəʊl/, /ˈpɪrəzəʊl/, U.S. /ˈpaɪrəˌzoʊl/, /ˈpɪrəˌzoʊl/ Chemistry.
A weakly basic, crystalline, heterocyclic compound whose molecule is an unsaturated five-membered ring containing adjacent nitrogen atoms; any substituted derivative of this compound.Formula: CH=CH—CH=N—NH.
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pyrazole1887
1887 Jrnl. Chem. Soc. 52 ii. 665 To examine whether the formation of pyrazoline-derivatives from phenylhydrazine and acids of the acrylic series is analogous to the formation of pyrazole-derivatives from unsaturated ketones.
1926 H. G. Rule tr. J. Schmidt Text-bk. Org. Chem. iii. iii. 566 Pyrazole differs strongly from pyrrole in its remarkable stability and more definitely basic character.
1968 Kirk-Othmer Encycl. Chem. Technol. (ed. 2) XVI. 763 Neither pyrazoles nor pyrazolines have found extensive uses, but pyrazolones have been widely utilized.
2000 J. A. Joule & K. Mills Heterocyclic Chem. (ed. 4) xxii. 432 The higher basicity of pyrazole reflects the symmetry of the cation with its two equivalent contributing resonance structures.
Compounds
pyrazole blue n. rare a blue indigoid dye whose molecule consists of two substituted pyrazolone rings linked by a carbon–carbon double bond.Formula: C20H16N4O2.
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1894 H. F. Morley & M. M. P. Muir Watts' Dict. Chem. (rev. ed.) IV. 349/2 Pyrazole blue, C20H16N4O2.
1943 Thorpe's Dict. Appl. Chem. (ed. 4) VI. 456/2 Another dye of indigoid type, Pyrazole Blue..was discovered by Knorr..who showed its similarity to indigo.
1970 Tetrahedron 26 3449 Excess base in DMSO will cleave pyrazole-blue to yield the radical anion of 1-phenyl-3-methyl-2-pyrazoline-4,5-dione.
This entry has been updated (OED Third Edition, December 2007; most recently modified version published online March 2022).
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