| Abstract
| - The surprisingly high stability of the dioxiraneCF2O2 (2), its unusual geometry, itsinfrared spectrum,and NMR chemical shifts are determined and analyzed on the basis ofextended ab initio calculations includingseven different methods and nine different basis sets. At thehighest level of theory, the CCSD(T) approach hasbeen used together with a cc-VTZ2P+f basis set, which leads to anaccurate description of geometry and vibrationalfrequencies. Stabilizing CF,CF bond interactions add 19.5kcal/mol and CF,CO bond interactions 12 kcal/mol tothe stability of the dioxirane ring. The latter effect reducesring strain from 32.8 (dioxirane) to 20.5 kcal/mol(2)where 17 kcal/mol are due to CO bond strengthening and 4.6 kcal/mol toOO bond weakening. Changes in CO andOO bond strength are caused by a transfer of negative charge from theCF2 group to the antisymmetric Walsh MOof the ring. The calculatedΔHf°(298) value of 2 is−102 ± 1.5 kcal/mol, which indicates that 2 isthermodynamicallyrather stable. Calculated 13C (133 ppm) and17O NMR chemical shifts (403 ppm) are unusually positivefor anorganic cyclic peroxide, but should facilitate the identification of2 in the presence of its isomers F2COOandFC(O)OF, which possessΔHf°(298) values of −60 and −104kcal/mol, respectively.
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