Theoretical Study on Pyrolysis of 2-Phenoxycarboxylic Acids in the Gas Phase:an ONIOM Approach

초록

Several ONIOM methods!! ONIOM(HF/6-31G*:PM3). ONIOM(B3LYP/6-31G*:PM3), and ONIOM(MP2/6-31G*:HF/6-31G*) were applied to investigate the thermal decompositon nechanisms of four 2-phenoxycarboxyisobutyric acid) in gas phase. All the Transition states and intermediates of the reaction paths were optimized. The reaction pathway of four reactants yielding the phenol, CO, and the corresponding carbonyl compound was characterized on the potential energy surface and found to be a stepwise process: The first step corresponds to the elimination of phenol and the formation of a-lactone intermediate through a five-membered ring transition state:the second step is the cycloreversion process of three compounds to produce the carboxylix acid and phenol was also examined theoretically and shown to proceed through a concerted mechanism with a four-membered cyclic transition structure. Comparison wity experiment indicateds that the theoretical cativation parameters were accurately predicted at ONIOM(MP2/6-31G*:HF/3-21G) level of theory for first reaction channel.