Molecular enthalpies: 2. ground-state thermodynamic and computed enthalpies of bicyclo[2.2.2]octa-2,5,7-triene and its hydrogenation products

This article is a continuation of our investigation of enthalpies of formation and strain-compensated enthalpies of hydrogenation of medium-sized hydrocarbons. We have carried out calculations of H _f by MM2, MM3, and by the MNDO, AM1, and PM3 semi-empirical molecular orbital methods. Results are given for the bicyclo2.2]octa-2,5,7-triene series (2.2.2]barrelenes) Two of these compounds are potentially homoantiaromatic. Comparisons with ab initio calculations are made. A novel method of estimating strain relaxation during the stepwise hydrogenation of 2.2.2]barrelene is given.