Enthalpies of formation of olefinic ethers by G3(MP2)//B3LYP calculations

摘要

The gas-phase enthalpies of formation at 298.15 K of a number of acyclic and cyclic olefinic ethers (mainly alpha,beta-unsaturated ethers), together with those of a few cyclic mono- and dienes, have been estimated by G3(MP2)//B3LYP calculations. In most cases, the computational and experimental data (if available) are in good mutual agreement. Whenever significant deviations between the experimental and computational data were found, the experimental enthalpies of formation arise from a single data source, and it appears that small experimental errors are embedded therein. A marked error was found in the experimental enthalpy of formation of 2-chloroethyl ethyl ether, used in this work as a reagent for estimation of the enthalpy of formation of 2-chloroethyl vinyl ether by an isodesmic reaction. Moreover, significant errors were also found in the literature values for the computational (B3LYP/6-311G**) enthalpies of formation of several Me-substituted derivatives of methyl vinyl ether. The present computational method, besides providing acceptable enthalpies of formation for unsaturated ethers, was also found to give accurate Delta H-f(m)o(g) values for cyclic mono- and dienes. Thus, the G3(MP2)//B3LYP computational method proved to be a valuable tool for investigating the energetics of olefinic ethers and hydrocarbons. Copyright (c) 2008 John Wiley & Sons, Ltd.