title: The reaction of cyclopentyne with ethene: concerted vs stepwise mechanism?
abstract: The cycloaddition of cyclopentyne with ethene was examined using (U)B3LYP and CASSCF methods to discern the reaction mechanism. (U)B3LYP/6-31G* and (U)B3LYP/6-311+G* slightly favor the concerted pathway, whereas CASSCF(4,4)/6-31G* and CASCF(6,6)/6-31G* favor the diradical pathway. MRMP2 using the CASSCF(4,4) wave function also favors the diradical mechanism. In the context of a diradical pathway, the experimentally observed complete retention of stereochemistry for this reaction is understood in terms of stereochemical control resulting from dynamic effects.
authors.affiliation: Department of Chemistry, Trinity University, 1 Trinity Place, San Antonio, Texas 78212, USA. sbachrach@trinity.edu
authors.forename: Steven M
authors.initials: SM
authors.lastname: Bachrach
authors.forename: John C
authors.initials: JC
authors.lastname: Gilbert