Basicity of C-substituted pyrazoles in the gas phase: an experimental (ICR) and theoretical study was written by Abboud, J. L. M.;Cabildo, P.;Canada, T.;Catalan, J.;Claramunt, R. M.;De Paz, J. L. G.;Elguero, J.;Homan, H.;Notario, R.. And the article was included in Journal of Organic Chemistry in 1992.Application of 54210-32-1 This article mentions the following:
The exptl. gas-phase proton affinities (PAs) of 32 N-H and N-Me pyrazoles have been determined by means of Fourier Transform Ion Cyclotron Resonance Spectroscopy (FTICR). Previously reported PAs for 12 C-methyl-substituted pyrazoles, in total provide a set of 57 data (counting each tautomer sep.). The remarkably large spread of PAs, ca. 55 kcal.mol-1, makes this set most suitable for structural analyses. In a few cases, ab initio 6-31G//6-31G protonation energies were calculated and found to be linearly related to the exptl. PAs to a very high degree of precision. A simple additive model of substituent effects on PAs (including substitutions at positions 3, 4, and 5) was found to hold, even for very crowded derivatives such as 1,4-dimethyl-3,5-di-tert-butylpyrazoles . The only significant interaction appears between Ph groups at positions 3 and 5. The statistically averaged substituent effects on PAs were successfully analyzed in terms of polarizability and field and resonance contributions, according to the Taft-Topsom model. Both positions 3 and 5 behave in a way similar to that of position 2 in the pyridines. From this interesting result it follows that, with the exception of 3-aminopyrazole, the tautomerism of pyrazoles is not very dependent of the nature of the 3(5)-substituent. In the experiment, the researchers used many compounds, for example, 1-Methyl-3-nitro-1H-pyrazole (cas: 54210-32-1Application of 54210-32-1).
1-Methyl-3-nitro-1H-pyrazole (cas: 54210-32-1) belongs to pyrazole derivatives. As is the case with imidazoles, the pyrazole ring offers many opportunities to create new multiring systems that incorporate this heterocycle. Pyrazoles can be selectively lithiated at different carbons and subsequently react with electrophiles depending on the substitution patterns.Application of 54210-32-1
Referemce:
Pyrazole – Wikipedia,
Pyrazoles – an overview | ScienceDirect Topics