Copyright (c) 2026 Sanjeev Kumar Mishra, Jyoti Tyagi
This work is licensed under a Creative Commons Attribution 4.0 International License.
Effect of Substituents at α- and β-Carbon Atoms on β-Elimination Reactions of N-Alkyl Pyrazoles: A Theoretical Approach
Corresponding Author(s) : Jyoti Tyagi
Asian Journal of Chemistry,
Vol. 38 No. 6 (2026): Vol. 38 Issue No 6, 2026
Abstract
The present study investigates the effect of substituents at the α- and β-carbon atoms on the β-elimination reactions of N-alkyl pyrazoles using density functional theory (DFT). Five elimination pathways involving different substituent combinations, namely hydrogen, methyl and ethyl groups, were examined in detail to evaluate their influence on reaction energetics and transition-state characteristics. N-Ethyl pyrazole, N-sec-butyl pyrazole, N-tert-butyl pyrazole and N-tert-pentyl pyrazole were selected as model reactants, which upon β-elimination yielded the corresponding alkene along with pyrazole as the common product. The variations in ΔH values are observed among the five reactions. Substitution with all methyl group has significant effect on activation energy and energy of reaction. Interestingly, this study reveals that methyl and ethyl group have negative inductive effect on α- and β-carbon atoms. The results obtained in this work align well with the previous reported experimental kinetic study and demonstrates improved accuracy as compared to semi-empirical study. Moreover, this study sheds light on the mechanistic aspects of β-elimination reactions of N-alkyl pyrazoles and enhances academic knowledge on the effect of methyl and ethyl group in organic molecules.
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- R.I.L. Meador, N.A. Mate and J.D. Chisholm, Organics, 3, 111 (2022); https://doi.org/10.3390/org3020009
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References
R.I.L. Meador, N.A. Mate and J.D. Chisholm, Organics, 3, 111 (2022); https://doi.org/10.3390/org3020009
J.V. Faria, P.F. Vegi, A.G.C. Miguita, M.S. dos Santos, N. Boechat and A.M.R. Bernardino, Bioorg. Med. Chem., 25, 5891 (2017); https://doi.org/10.1016/j.bmc.2017.09.035
M.-C. Ríos and J. Portilla, Chemistry, 4, 940 (2022); https://doi.org/10.3390/chemistry4030065
Y. Li, F.A. Lakhvich, T.S. Khlebnicova, Y. Fu and F. Ye, J. Agric. Food Chem., 73, 24528 (2025); https://doi.org/10.1021/acs.jafc.5c08390
M. El Boutaybi, A. Taleb, R. Touzani and Z. Bahari, Mater. Today Proc., 31, S96 (2020); https://doi.org/10.1016/j.matpr.2020.06.249
Y.Q. Gu, W.Y. Shen, Y. Zhou, S.F. Chen, Y. Mi, B.F. Long, D.J. Young and F.L. Hu, Spectrochim. Acta A Mol. Biomol. Spectrosc., 209, 141 (2019); https://doi.org/10.1016/j.saa.2018.10.030
A. Tigreros and J. Portilla, RSC Adv., 10, 19693 (2020); https://doi.org/10.1039/D0RA02394A
S. Zhang, Z. Gao, D. Lan, Q. Jia, N. Liu, J. Zhang and K. Kou, Molecules, 25, 3475 (2020); https://doi.org/10.3390/molecules25153475
G.I. Yranzo and E.L. Moyano, Curr. Org. Chem., 8, 1071 (2004); https://doi.org/10.2174/1385272043370113
J.D. Perez and L.M. Phagouape, Int. J. Chem. Kinet., 19, 571 (1987); https://doi.org/10.1002/kin.550190608
J.D. Perez, L.M. Phagouapé and G.E. Davico, J. Phys. Org. Chem., 2, 225 (1989); https://doi.org/10.1002/poc.610020305
A.D. Becke, Phys. Rev. A, 38, 3098 (1988); https://doi.org/10.1103/PhysRevA.38.3098
A.D. Becke, J. Chem. Phys., 98, 5648 (1993); https://doi.org/10.1063/1.464913
C. Lee, W. Yang and R.G. Parr, Phys. Rev. B Condens. Matter, 37, 785 (1988); https://doi.org/10.1103/PhysRevB.37.785
R.F.W. Bader, Acc. Chem. Res., 18, 9 (1985); https://doi.org/10.1021/ar00109a003
M.P. Andersson and P. Uvdal, J. Phys. Chem. A, 109, 2937 (2005); https://doi.org/10.1021/jp045733a
R.G. Parr and W. Yang, Density Functional theory of Atoms and Molecules, Oxford University Press: New York, Oxford, pp. IX+333 (1989).
J.K. Labanoeski and J.W. Andzelin, Density Functional Methods in Chemistry, Springer Verlag: New York (1991).
S.H. Vosko, L. Wilk and M. Nusair, Can. J. Phys., 58, 1200 (1980); https://doi.org/10.1139/p80-159
M.C. Elliott, C.E. Hughes, P.J. Knowles and B.D. Ward, Org. Biomol. Chem., 23, 352 (2025); https://doi.org/10.1039/D4OB01572J
