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0212U004387,
0107U003006
,
Investigation of cycloalkanes substrate selectivity in reactions with electrophiles and of C-H bond breaking mechanisms
Rudakov Elisey Sergeevych,
09-02-2012
The L.M.Litvinenko Institute of Physical-Organic Chemistry and Coal Chemistry
The object of research: reactions of cycloalkanes с-С6Н12, с-С6D12, с-С5Н10 with cations of adamantyl Ad+, hydroxyl ОН+, vanadium dioxide (V) VO2+, with oxidizers HOONO and HMnO4, with the systems Pt(II) - Pt(IV) and Ru(IV) - oxidant, the reactions of saturated hydrocarbons (RH) with radicals OH as well as arenes (ArH) and RH with Ad+. The goal of the investigation: the study of substrate selectivity of these reactions, kinetic isotope effect (KIE), с-С6Н12 / с-С6D12, (5 / 6) effects, с-С5Н10 / с-С6Н12, and the difference in activation energies Е6 - Е5 and ЕD - ЕH. The methods of the investigation: the original kinetics methods, GLCH, pH- metering. The novel approach to understanding of mechanisms C-H bonds activation based on investigation of a temperature dependences of (5 / 6) effects and KIE was proposed. The detected early separation of electrophiles in sulfuric acid towards two groups respect to designation of parameter Е6 - Е5: Е6 - Е5 > 0 and Е6 - Е5 < 0 was confirmed for the reactions with Ad+, ОН+ and VO2+. The first (named H-elerctrophiles, divided hydride ion from RH) include Hg2+ and carbocations including Ad+; the second (C-elerctrophiles, breaked C-H bond by electophilic substitution manner) are cations Pd2+, and reagents ОН+ and VO2+ studied in reporting period. The novel phenomenon was found: for reactions RH with ОН and with HOONO in water (in contrast to gas-phase reactions and other known reactions with oxidizers) KIE increase with temperature (ЕD - ЕH) < 0, that was interpreted by a model of the cage effect. The same anomaly, (ЕD - ЕH) < 0, is found for reactions with Pt(II) chloride in water. For reactions RH with HMnO4 - H2O and Ru(IV) - HCl - HNO3 (or HVO3) - H2O solutions is found: ED - EH > 0 and E6 - E5 > 0. It was shown, that in solution of 1- adamantanol active species in reaction with RH ([H2SO4] > 85 %) and with ArH ([H2SO4] > 59 %) is Ad+; the main contribution in reaction with ArH inserts adamantilation in p- and m-positions of benzyl rings. These results shed new light on the mechanisms of activation of alkanes in solution and are useful for in-depth study of kinetics and reactivity theory. The development of this research provides the investigations of compensation relations for (5 / 6) effects and KIE.
Волкова Лариса Костянтинівна
Зімцева Галина Петрівна
Лобачов Володимир Леонідович
Мінько Лариса Олександрівна
Матвієнко Ярослав Вікторович
Попов Віталій Георгієвич
Третьяков Володимир Петрович
2020-04-02
Updated: 2025-12-09
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