| Abstract
| - The strain energies (SE) of the five smallest perfluorocycloalkanes (c-CnF2n; n = 3, 4, 5, 6, and 7) werecalculated by means of several homodesmotic processes using B3LYP/6-31++G(d,p) optimized molecularenergies. These values were compared with the energy difference between the linear and cyclic CF2 groupscalculated by means of the quantum theory of atoms in molecules (QTAIM) applied on charge densitiesobtained at the same computational level. The differences between the values computed with both methodsvary from 255 (n = 3) to 629 (n = 7) kJ mol-1. These differences arise because QTAIM-computed SEcontain the energy involved in opening the ring to give rise to nearly transferable central CF2 fragments oflinear perfluoroalkanes, whereas homodesmotic energies contain energy terms corresponding to transformationof nontransferable linear CF2 fragments and a ring-opening energy, which depending on the process, transformsCF2 cyclic compounds into nearly transferable or nontransferable linear CF2 groups.
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