Reactions of mono- and bimolecular hydrogen transfer in alkyl radicals: analysis using the parabolic model and density functional calculations |
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Authors: | Shestakov,A. F.,Denisova,T. G.,Denisov,E. T.,Emel" yanova,N. S. |
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Affiliation: | (1) Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow Region, Russian Federation |
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Abstract: | Experimental data on monomolecular hydrogen transfer in the reactions of the type RC·H(CH2)nCH2R1 RCH2(CH2)nC·HR1 (n = 2—4, R and R1 are alkyl substituents) were analyzed using the parabolic model (PM). The parameters characterizing this class of reactions were calculated. Isomerization of alkyl radicals via cyclic transition states (TS) is characterized by the following energy barriers to thermoneutral reaction Ee0: 53.5, 65.4, and 63.2 kJ mol–1 for the six-, five-, and seven-membered TS, respectively. The Ee0 energy and the strain energy change in parallel in the series of cycloparaffins CnH2n. Density functional calculations of intramolecular hydrogen transfer in the n-butyl and n-pentyl radicals and of the bimolecular hydrogen abstraction from the ethane molecule by the ethyl radical were performed. The activation energies of the intra- and intermolecular hydrogen transfer were compared. The parameters of the PM were compared with the interatomic distances in the reaction center of the TS calculated by the density functional method. |
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Keywords: | alkyl radical intramolecular shift of H atom bimolecular abstraction activation energy nonempirical quantum-chemical calculations density functional theory parabolic model of bimolecular reaction |
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