Theoretical Study of the Enthalpies of Formation and the Mechanism of Radical Scavenging Effect for Carotenoids

• Main Authors: Fu-Xing Liao, 廖福興
• Other Authors: Ching-Han Hu
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/82945863216953980887

碩士 === 國立彰化師範大學 === 化學系 === 99 === Abstract In this work, firstly, we developed a computational method, namely correlation corrected atomization (CCAZ), for the purpose of accurately determining enthalpies of formation (ΔHf at 298 K) for carotenoid species. The CCAZ approach is based on the concept similar to bond and group equivalent (BGE), in which possible errors in a computational theory (DFT in this case) are corrected by adding 1,2-, 1,3-, and 1,4- functional interaction terms. CCAZ along with two DFT functions (B3LYP and MPWB1K) were parameterized against reference data obtained using G3 theory. The CCAZ predicted ΔHf within the training set is fairly accurate, and high accuracy is expected when applied to the carotenoids. In contrast, DFT computed ΔHf using the atomization and isodesmic schemes resulted in poor predictions. The equivalent methods, atomic equivalent (AEQ) and group equivalent (GEQ) provide improved predictions, however the accuracies are lower than that of CCAZ. Secondly, we applied quantum chemical methods to investigate the chain-termination function of cartenoids (CARs). Hydrogen atom transfer and peroxide addition mechanisms were studied using model peroxide and linoleic acid . For most investigated carotenoids, addition reactions are kinetically favored. In addition, 3,3’-dihydroxyisorenieratene (DHIR) by way of hydrogen abstraction is kinetically and thermodynamically more favorable than peroxide addition.