Increase in Strain Energy during Conversion of [4.4.4.5]Fenestrane to [4.4.4.4]Fenestrane: a Method for Estimating the Heats of Formation of Hydrocarbons and Their Derivatives from Ab Initio Energies

Re-Examination of Some Carbocations. Structures, Energies, and Charge Distributions

Chemists have had a long-standing interest in reactive intermediates such as carbenes, carbon radicals, carbanions, and carbocations. Carbocations are an interesting part of this group because of their tendency to undergo rearrangement, sometimes forming bridged ions, as well as their ability in many cases of spreading out the positive charge over several atoms. We have re-examined some of these cases using high-level compound procedures, W1BD and G4, as well as by considering the charge distributions making use of the Hirshfeld method that has been shown to uniquely correlate with several types of experimental data.

A Procedure for Computing Hydrocarbon Strain Energies Using Computational Group Equivalents, with Application to 66 Molecules †

A method is presented for the direct computation of hydrocarbon strain energies using computational group equivalents. Parameters are provided at several high levels of electronic structure theory: W1BD, G-4, CBS-APNO, CBS-QB3, and M062X/6-31+G(2df,p). As an illustration of the procedure, strain energies are computed for 66 hydrocarbons, most of them highly strained.