| Summary: | 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.
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