Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/14764
Title: On the determination of accurate rate coefficients for hydrogen abstraction reactions of phenolic compounds by free radicals
Authors: CAROLINE MANONMANI
Keywords: transition state, kinetics, antioxidants, free radicals, gaussian
Issue Date: 26-Jul-2005
Source: CAROLINE MANONMANI (2005-07-26). On the determination of accurate rate coefficients for hydrogen abstraction reactions of phenolic compounds by free radicals. ScholarBank@NUS Repository.
Abstract: The transition state for hydrogen atom transfer from phenol to the biologically harmful hydroxyl radical was determined using the B3LYP density functional theory method. The transition state structure obtained revealed that the transferring hydrogen atom is rotated out of the phenol ring plane in contrast to the reactant phenol where it is in the aromatic ring plane. Analysis of reaction profile showed, in accordance with experiment, that the reaction is barrierless. The rate coefficient for the reaction was determined using the simple collision theory, capture theory and transition state theory under the harmonic and free rotor approximations. The value of rate coefficient obtained was closest to experiment when the free rotor approximation was used. Reaction profiles for hydrogen atom transfer from monosubstituted phenols to the methylperoxyl radical were also determined using the B3LYP density functional theory method. Results obtained indicate that the nature of the substituent group affects the angle through which the transferring hydrogen atom is rotated out of the phenol ring plane. Values for rate coefficients in these cases were comparable to that determined from the semi-empirical Intersecting Parabolas Model of reaction rate. These results indicate that the B3LYP functional is suitable in determining accurate rate coefficients for this class of reactions.
URI: http://scholarbank.nus.edu.sg/handle/10635/14764
Appears in Collections:Master's Theses (Open)

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