Ring strain energies are recognized through representative ring substructures. These substructures are usually represented by the heavy atom (meaning no hydrogen) skeletal structure of the ring. For multiple ring structures, the largest matching ring is chosen. Currently there are 65 single ringed cyclic corrections corresponding to the cyclic structures in Benson's tables (Benson, 1976): Hydrocarbons (Table A.1), Oxygen-containing rings (Table A.2), nitrogen-containing rings (Table A.3) and organosulfur ring compounds (Table A.5). Data have been up dated and supplemented from Domalski and Hearing (1992) and Cohen (1993). Once again, the exact energetic contribution of a particular ring is a design decision as to which is the prominent or average configuration.
Benson SW. Thermochemical kinetics: methods for the estimation of thermochemical data and rate parameters, 2nd ed. 2nd ed. John Wiley & Sons; 1976.
Cohen N. Thermochemistry of alkyl free radicals. The Journal of Physical Chemistry 1992;96:9052-9058.
Domalski ES, Hearing ED. Estimation of the thermodynamic properties of c-h-n-o-s-halogen compounds at 298.15 k. J. Phys. Chem. Ref. Data 1993;22:805.