Conversion and Origin of Normal and Abnormal Temperature Dependences of Kinetic Isotope Effect in Hydride Transfer Reactions
العنوان: | Conversion and Origin of Normal and Abnormal Temperature Dependences of Kinetic Isotope Effect in Hydride Transfer Reactions |
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المؤلفون: | Su-Hui Han, Xiu-Tao Li, Lian-Rui Mei, Xiao-Qing Zhu |
المصدر: | The Journal of Organic Chemistry. 77:4774-4783 |
بيانات النشر: | American Chemical Society (ACS), 2012. |
سنة النشر: | 2012 |
مصطلحات موضوعية: | chemistry.chemical_compound, chemistry, Hydride, Organic Chemistry, Kinetic isotope effect, Substituent, Molecule, Reaction intermediate, Acetonitrile, Photochemistry, Chemical reaction, Ion |
الوصف: | The effects of substituents on the temperature dependences of kinetic isotope effect (KIE) for the reactions of the hydride transfer from the substituted 5-methyl-6-phenyl-5,6-dihydrophenanthridine (G-PDH) to thioxanthylium (TX(+)) in acetonitrile were examined, and the results show that the temperature dependences of KIE for the hydride transfer reactions can be converted by adjusting the nature of the substituents in the molecule of the hydride donor. In general, electron-withdrawing groups can make the KIE to have normal temperature dependence, but electron-donating groups can make the KIE to have abnormal temperature dependence. Thermodynamic analysis on the possible pathways of the hydride transfer from G-PDH to TX(+) in acetonitrile suggests that the transfers of the hydride anion in the reactions are all carried out by the concerted one-step mechanism whether the substituent is an electron-withdrawing group or an electron-donating group. But the examination of Hammett-type free energy analysis on the hydride transfer reactions supports that the concerted one-step hydride transfer is not due to an elementary chemical reaction. The experimental values of KIE at different temperatures for the hydride transfer reactions were modeled by using a kinetic equation formed according to a multistage mechanism of the hydride transfer including a returnable charge-transfer complex as the reaction intermediate; the real mechanism of the hydride transfer and the root that why the temperature dependences of KIE can be converted as the nature of the substituents are changed were discovered. |
تدمد: | 1520-6904 0022-3263 |
URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4863e1122f174246288eac9e861907a7 https://doi.org/10.1021/jo3005952 |
رقم الأكسشن: | edsair.doi.dedup.....4863e1122f174246288eac9e861907a7 |
قاعدة البيانات: | OpenAIRE |
تدمد: | 15206904 00223263 |
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