Description of Chemical Reactions by the Method of the Full Optimized Reaction Space. The Ring-Opening of Unsubstituted and Substituted Cyclopropylidene to Allene

摘要

The ring-opening reaction of singlet cyclopropylidene to singlet D/sub 2d/ allene is studied by means of ab-initio FORS-MCSCF calculations. The energy surface is determined for many intermediate geometries defined by the C-C-C opening angle and the two CH sub 2 rotation angles. For each choice of these three variables, the remaining twelve internal coordinates are relaxed by energy minimization. The results obtained differ markedly from those of earlier, less sophisticated calculations. Since experimental evidence, based exclusively on the substituted species, suggests that the reaction is stereospecific, a potential simulating the steric effects of substituents is added to the originally calculated surface. The results are analyzed and it is shown that all experimental observations can be adequately explained solely by means of nonbonded interactions between substituent groups. 92 refs., 27 figs., 20 tabs. (ERA citation 10:044804)