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CASSCF, MP2, and CASMP2 studies on addition reaction of singlet molecular oxygen to ethylene molecule
Author(s) -
Yoshioka Yasunori,
Tsunesada Tsunaki,
Yamaguchi Kizashi,
Saito Isao
Publication year - 1997
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(1997)65:5<787::aid-qua44>3.0.co;2-v
Subject(s) - dioxetane , chemistry , singlet state , electronic correlation , transition state , ab initio , molecule , moiety , computational chemistry , triplet state , molecular orbital , ethylene , ab initio quantum chemistry methods , photochemistry , atomic physics , excited state , stereochemistry , physics , chemiluminescence , biochemistry , organic chemistry , catalysis
The reaction mechanism and relative stabilities of the intermediates and transition states in the reaction of 1 O 2 plus ethylene molecule using ab initio molecular orbital (MO) theories at several levels of theory with the correction of the nondynamic and dynamic electron correlation effects were systematically investigated. Full geometry optimizations of the corresponding biradical (BR) intermediates, perepoxide (PE) and 1,2‐dioxetane (DO) were performed by complete‐active‐space CASSCF{2,2}/6‐31G* method with nondynamic electron correlation effect and Møller‐Plesset MP2/6‐31G* method with dynamic electron correlation effect. For the 1,4‐biradical intermediates, new gauche‐type 1 BR state was found at both CASSCF and MP2 levels, corresponding to the transition state of the rotation motion of the O 2 moiety. It was found from the intrinsic‐reaction‐coordinate (IRC) study that another gauche‐type 1 BR transition state connects smoothly to the reactant system 1 O 2 +H 2 C(DOUBLE BOND)CH 2 and the gauche minimum 1 BR state, showing that the reaction through the 1,4‐biradical intermediates initially proceeds through the gauche transition state to form the gauche minimum 1 BR state, following that the free rotation of O 2 moiety occurs due to the energy barrier less than 4.0 kcal/mol. The stability of the perepoxide is surprisingly sensitive to the levels of the theory and the basis sets employed. The coupled‐cluster methods, CCSD and CCSD(T), gave the reasonable stabilities of 1,4‐biradical intermediates, perepoxide, and dioxetane as a reaction product. From the results of the CCSD and CCSD(T) methods, the reaction of 1 O 2 +H 2 C(DOUBLE BOND)CH 2 proceeds by a two‐step mechanism through the 1,4‐biradical intermediates rather than through the perepoxide. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65 : 787–801, 1997