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pK a Constant Determination of Two Triazole Pesticides: Tebuconazole and Penconazole

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Abstract

We determined the acidity constants of tebuconazole and penconazole, two fungicides from the group of 1,2,4-triazoles. Potentiometric titrations were performed in a 20 % (v/v) acetonitrile/water mixture at 25 °C and at a fixed ionic strength (KNO3, 0.1 mol·dm−3). The pK a values (representing thermodynamic constants) were determined to be 5.0 ± 0.1 and 5.2 ± 0.1 for tebuconazole and penconazole, respectively. These values could be used in pure water solutions to consider the protonated or deprotonated forms when studying the field behavior of these fungicides. Molecular modeling calculations allowed identifying the N4 atom as the protonation site.

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Notes

  1. We have also tested the new PM7 method in MOPAC 2012. This method, which is still under development, gave enthalpy values within 5.3 % of the PM6 values. The relative stabilities of the protonated forms were unchanged.

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Acknowledgments

M. Komárek is grateful for the support obtained from the internal grant of the Faculty of Environmental Sciences, Czech University of Life Sciences (42900/1312/3166). Research at GRESE, University of Limoges, is supported by the ‘Conseil Régional du Limousin’.

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Author notes

  1. Eva Čadková

    Present address: Czech Geological Survey, Geologická 6, 152 00, Prague 5, Czech Republic

Authors and Affiliations

  1. Department of Agro-Environmental Chemistry and Plant Nutrition, Czech University of Life Sciences Prague, Kamýcká129, 165 21, Prague 6, Czech Republic

    Eva Čadková

  2. Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21, Prague 6, Czech Republic

    Michael Komárek

  3. Service de Pharmacologie-Toxicologie, Hôpital Dupuytren, 2 Avenue Martin Luther King, 87042, Limoges, France

    Jean Debord

  4. Groupement de Recherche Eau, Sol, Environnement (GRESE), Université de Limoges, 123 Avenue Albert Thomas, 87060, Limoges, France

    Loïc Della Puppa, François Bordas & Jean-Claude Bollinger

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  1. Eva Čadková
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  2. Michael Komárek
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  3. Jean Debord
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  4. Loïc Della Puppa
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  6. Jean-Claude Bollinger
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Correspondence to Jean-Claude Bollinger.

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Čadková, E., Komárek, M., Debord, J. et al. pK a Constant Determination of Two Triazole Pesticides: Tebuconazole and Penconazole. J Solution Chem 42, 1075–1082 (2013). https://doi.org/10.1007/s10953-013-0012-z

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  • DOI: https://doi.org/10.1007/s10953-013-0012-z

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