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The reaction of singlet oxygen with ethylene has been studied at the ab initio level with both HF/3-21G and HF/6-31G basis sets, fully optimizing the geometries of the critical points. The transition state leading to the intermediate peroxirane from the initial reactants is found,Iocated at 81.71 kJ/mol above the dissociation limit. The vibrational analysis is done with two basis sets. From the results it can be seen that the frequencies have not been made an improvement obviously with augmented 6-31G compared to 3-21G basis; it follows that main reason for too high HF/3-21G frequency could mainly be the vibrational anharmonicity. The eigenvector corresponding to the single imaginary vibrational frequency is dominated by the larger O-O distance. The finding of the transition state confirms that the peroxirane minimum can be reachable passing through a peroxirane-like saddle point. In addition , the mechanisms of the reaction forming oxirane are discussed as well.
The reaction of singlet oxygen with ethylene has been studied at the ab initio level with both HF / 3-21G and HF / 6-31G basis sets, fully optimizing the geometries of the critical points. The transition state leading to the intermediate peroxirane from the The result of the reaction is is found, Iocated at 81.71 kJ / mol above the dissociation limit. The results of it can be seen that the frequencies have not been made an improvement obviously with augmented 6-31G compared to The eigenvector corresponding to the single imaginary vibrational frequency is dominated by the larger OO distance. The finding of the transition state confirms that the peroxirane minimum can be reachable passing through a peroxirane-like saddle point. In addition, the mechanisms of the reaction forming oxirane are discussed as well.