Release Time:2019-03-09  Hits:

Indexed by: Journal Article

Date of Publication: 2014-08-01

Journal: JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY

Included Journals: Scopus、SCIE

Volume: 13

Issue: 5

ISSN: 0219-6336

Key Words: Antioxidant; diarylamine; DFT; bond dissociation enthalpy; one-electron oxidation potential; reaction rate constant

Abstract: Diarylamines (Ar2NH) are generally used as antioxidants to inhibit or retard the auto-oxidation degradation of lubricating oil by trapping ROO center dot radicals. In the present study, 20 kinds of 4,4'-disubstituted diphenylamine compounds were investigated through density functional theory (DFT) calculations. The results indicate that the N-H bond dissociation enthalpy (BDE) linearly correlates its one-electron oxidation potential, the difference in Mulliken atomic charge on the two atoms of N-H bond, the reaction rate constant of hydrogen transfer from Ar2NH to peroxy radical, and the chemical hardness of the resulted Ar2N center dot radical, respectively. The substitution of alkyl groups (electron-donating groups) decreases the N-H BDE, one-electron oxidation potential and the reaction rate constant, while that of significant electron-withdrawing groups such as -NO2 and -COOCH3 increases these three parameters. The electron-donating groups such as alkyls could improve the antioxidation performance of 4,4'-disubstitued diphenylamines whereas electron-withdrawing groups have the contrary effect. In addition, the frontier molecular orbital of Ar2NH has been also analyzed.