AB-INITIO IGLO GIAO-MP2 STUDIES OF FLUOROCARBOCATIONS - EXPERIMENTAL AND THEORETICAL INVESTIGATION OF THE CLEAVAGE REACTION OF TRIFLUOROACETIC-ACID IN SUPERACIDS/

The structures of a number of fluorocarbocations were calculated at th e correlated MP2/6-31G level. C-13 and F-19 NMR chemical shifts of fl uorocarbocations were calculated for the first time using IGLO and GIA O-MPB methods. The data showed good correlation of calculated F-19 and C-13 NMR chemical shifts with the experimental chemical shifts of flu orocarbocations. The correlation for GIAO-MP2-calculated F-19 NMR chem ical shifts with the experimental data is excellent. Using theoretical calculations as guidance, the protolytic cleavage of trifluoroacetic acid (CF3COOH) in superacids forming CF4 was also investigated experim entally and by ab initio calculations. This reaction is suggested to i nvolve the gitonic CF3C(OH)(OH2)(2+) dication as an intermediate.