Accurate Theoretical Thermochemistry for Fluoroethyl Radicals

An accurate coupled-cluster (CC) based model chemistry was applied to calculate reliable thermochemical quantities for hydrofluorocarbon derivatives including radicals 1-fluoroethyl (CH3–CHF), 1,1-difluoroethyl (CH3–CF2), 2-fluoroethyl (CH2F–CH2), 1,2-difluoroethyl (CH2F–CHF), 2,2-difluoroethyl (CHF2–CH2), 2,2,2-trifluoroethyl (CF3–CH2), 1,2,2,2-tetrafluoroethyl (CF3–CHF), and pentafluoroethyl (CF3–CF2). The model chemistry used contains iterative triple and perturbative quadruple excitations in CC theory, as well as scalar relativistic and diagonal Born–Oppenheimer corrections. To obtain heat of formation values with better than chemical accuracy perturbative quadruple excitations and scalar relativistic corrections were inevitable. Their contributions to the heats of formation steadily increase with the number of fluorine atoms in the radical reaching 10 kJ/mol for CF3–CF2. When discrepancies were found between the experimental and our values it was always possible to resolve the issue by recalculating ...