Computational Chemistry and Molecular Modeling
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
An ab initio 3-21G study of the direct addition of HF to C2HnF(4-n), with n = 0 to 4, has been performed to investigate the effect of the substituent on the reaction. Geometry optimization of all charge-transfer complexes and transition states has been done. Standard analysis of activation energies of addition reactions, vibrational and thermodynamical analysis, as well as Morokuma energy decomposition, BSSE correction, PMO analysis, and Pauling bond orders were used to explain the results. A subset of the reactions, including that of C2H4 as reference one and the two most favorable cases, was also studied at the MP2/6-31G(d,p)//HF/6-31G(d,p) level. The barriers so obtained are in agreement with the indirectly found from experimental data. It was found that the effect of the substituent is not monotonic for the additions. Decomposition of the interaction energy is shown to be adequate to explain this nonmonotonic behavior. The implications for laser chemistry of the addition of hydrogen halides to fluorosubstituted olefins is briefly discussed.
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