Strainless reference states for poly- and perfluorocycloalkanes: the ultradiagonal strain energy approach

It is well-established that the strain energy of cycloalkanes is affected b y fluorination. While the strain energies of cyclopropane and cyclobutane a re very nearly equal, perfluorination markedly increases the strain energy of the fortner and correspondingly decreases the latter. The numerical valu e for the strain energy of a given molecule is model-dependent. We discuss the strain energies of fluorinated cycloalkanes in terms of the "ultradiago nal" approach, a method earlier found useful for the understanding of fluor inated cyclopropanes and other species containing three-membered rings. (C) 2001 Elsevier Science B.V. All rights reserved.