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Số người truy cập: 107,079,114

 Substituent effects on the antioxidant capacity of monosubstituted diphenylamines: A DFT Study
Tác giả hoặc Nhóm tác giả: Pham Thi Thu Thao, Nguyen Minh Thong, Quan V. Vo, Mai Van Bay, Duong Tuan Quang, Pham Cam Nam
Nơi đăng: Vietnam Journal of Chemistry (accepted); Số: xxx;Từ->đến trang: xxx-xxx;Năm: 2020
Lĩnh vực: Chưa xác định; Loại: Bài báo khoa học; Thể loại: Trong nước
TÓM TẮT
There are undesirable effects leading to considerable changes in the properties of polymers and plastics since exposing to oxygen undergo oxidative degradation. Therefore, investigation of the bond dissociation enthalpies (BDEs) of N H bond for a series of monosubstituted diphenylamines is great interest. In this study, DFT-based method B3P86/6-311G was employed to perform this task. In comparison with the available experimental data, this method could reproduce the BDE(N H)s values more accuracy. Effects of substituents and substitution positions on the BDE(N H)s were also examined. While the general rule of the substituent effect is not revealed for ortho substitution and slightly change for meta substitution, a clear effect trend is found when substituent at the para position. For the latter, there is a good correlation of BDE(N -H)s with the Hammett's substituent constants. Depending on the nature of substituents, electron withdrawing groups increase the BDE(N -H)s but electron donating ones reduce the BDE(N -H)s. The hydrogen atom transfer processes from N -H bond of these diphenylamines to the peroxyl radical (CH 3OO ) were also analyzed via potential energy surfaces and kinetic calculations
ABSTRACT
There are undesirable effects leading to considerable changes in the properties of polymers and plastics since exposing to oxygen undergo oxidative degradation. Therefore, investigation of the bond dissociation enthalpies (BDEs) of N H bond for a series of monosubstituted diphenylamines is great interest. In this study, DFT-based method B3P86/6-311G was employed to perform this task. In comparison with the available experimental data, this method could reproduce the BDE(N H)s values more accuracy. Effects of substituents and substitution positions on the BDE(N H)s were also examined. While the general rule of the substituent effect is not revealed for ortho substitution and slightly change for meta substitution, a clear effect trend is found when substituent at the para position. For the latter, there is a good correlation of BDE(N -H)s with the Hammett's substituent constants. Depending on the nature of substituents, electron withdrawing groups increase the BDE(N -H)s but electron donating ones reduce the BDE(N -H)s. The hydrogen atom transfer processes from N -H bond of these diphenylamines to the peroxyl radical (CH 3OO ) were also analyzed via potential energy surfaces and kinetic calculations
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