| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 88 === The first section of this work is the solvolysis of aroyl bromides. The reaction mechanism was investigated based on the parameter of solvent ionizing power (YBnBr). Results suggest that the mechanism is dependent on both the substituent and solvent. We conclude that compund I-B-4 exhibits a limiting SN1 mechanism and the solvolysis of compound I-B-5 involves a nuclephilic solvent participation. The extent of solvent participation increases as the electron-donating ability of the substituent decreases.
In the second part of this work, we performed both the ab initio and the semi-empirical calculations to study the solvolysis of compound II-C-1. The molecular structure and energy were optimized by the ab initio HF self-consistent-field method using the package of Gaussian 98, where a basis set of 6-31G* or 6-31+G** was adopted. The structure at a local minimum was further verified by the vibrational frequency analysis. Calculations were also performed using the SPARTAN semi-empirical/AM1 method, and compared with those from the high level ab initio calculations. Results suggest that the replacement of ethanol by TFE reduces the solvation stabilization on the cation, but enhances the stabilization on the anion in the transition state. The overall solvation effect is TFE > ethanol. Our theoretical calculations thus provide a reasonable explanation for the larger solvolysis rate of II-C-1 in TFE vs. ethanol.
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