| Summary: | 碩士 === 中正理工學院 === 應用化學研究所 === 85 === MP2/6-31G**// MP2/6-31G** and HF/6-31G**// HF/6-31G** methods selected from Gaussian 94 package have been carried out for the theoretical study of the methanoic acids, ethanoic acids, propanoic acids and benzoic acids. We found two kinds of local minima and two kinds of transition states for each of the carboxalic acid. One kind of local minima has intra-functional type hydrogen bond (L1) and another one (L2) has not. One kind of transition states (T1) is the peak of the potential barrier of internal rotation between L1 and L2 which is calculated by QST3 type geometrical optimization. Another kind of transition states (T2) is intra-functional proton transfer type which is optimized by symmetry regulated type geometrical optimization. All the molecular energy are evaluated and corrected by zero point energy (ZPE). Between tb6 local minima and their related transition states, we got the potential barriers. And between the local minima (L1 and L2), we got the energy differences. The intra-functional type hydrogen bond have been compared and evaluated. We also use our s-p separated INDO method on the most stable structures (L1) of these carboxalic acids. By this semieiipirical method, we got the "localized hydrogen bond energy" and "localized hydrogen bond order" of the intra-functional type hydrogen bond directly. From all kinds of results, we realize that the intra-functional type hydrogen bond is significantly important in the organic carboxylic acid series.
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