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Density functional theory of chemical reactivity indices in some ion—molecule reaction systems
Author(s) -
Tachibana Akitomo,
Kawauchi Susumu,
Nakamura Koichi,
Inaba Hideyuki
Publication year - 1996
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1996)57:4<673::aid-qua14>3.0.co;2-1
Subject(s) - chemistry , reactivity (psychology) , reaction rate constant , electron transfer , excited state , reaction coordinate , density functional theory , ab initio , hydrogen atom abstraction , dipole , computational chemistry , reaction rate , molecule , ion , proton , chemical reaction , proton coupled electron transfer , hydrogen , atomic physics , kinetics , organic chemistry , catalysis , medicine , physics , alternative medicine , pathology , quantum mechanics
Three isoelectronic reactions, proton transfer ( PT ), hydrogen abstraction ( HA ), and electron transfer ( ET ), of NH + 3 with NH, 3 H 2 O, and HF have been studied using ab initio molecular orbital calculations. For the reaction of NH + 3 + H 2 O, the energy of the transition state (TS) is higher than that of the reactants. This is consistent with the experimental observation that the rate constant is less than the average dipole orientation (ADO) rate constant. It seems reasonable that the reaction rate for the reaction NH + 3 + H 2 O would hardly depend on the v 2 mode of NH + 3 at least for low‐lying excited states (E int ≤ 0.714 eV) of the v 2 mode, because the v 2 mode contributes mainly to the normal mode orthogonal to the reaction coordinate at the TS . This is consistent with experimental observation. A similar prediction can be made for the NH + 3 + HF reaction. The electron‐transfer processes for the HA reactions have been examined in terms of the intrinsic reaction coordinate ( IRC ). The order of reactivity with NH + 3 is NH 3 > H 2 O > HF. It is found that the degree of the electron transfer and the reactivity are correlated with the absolute hardness (η) of NH 3 , H 2 O, and HF. This is in accord with the softness as the chemical reactivity index in the density functional theory. © 1996 John Wiley & Sons, Inc.