title: The Diels-Alder reaction of ethene and 1,3-butadiene: an extended multireference ab initio investigation.
abstract: The concerted and stepwise mechanisms of the Diels-Alder reaction between 1,3-butadiene and ethene have been investigated using highly correlated multireference methods (MRAQCC) and extended basis sets. Full MRAQCC geometry optimizations have been performed in all cases. The best estimate for the energy barrier of the Diels-Alder reaction is 22 kcalmol(-1). Anti- and gauche-out minima for the biradical structures and corresponding fragmentation saddle points have been determined. The biradical anti fragmentation saddle point is located 6.5 kcalmol(-1) above the concerted saddle point. The gauche-in structure does not correspond to a local minimum, but leads on geometry optimization directly to cyclohexene.
authors.affiliation: Institute for Theoretical Chemistry and Structural Biology University of Vienna Währingerstrasse 17, 1090 Vienna (Austria). hans.lischka@univie.ac.at
authors.forename: Hans
authors.initials: H
authors.lastname: Lischka
authors.forename: Elizete
authors.initials: E
authors.lastname: Ventura
authors.forename: Michal
authors.initials: M
authors.lastname: Dallos
mesh_terms: D002070:Butadienes / Q000737:chemistry*; D003198:Computer Simulation; D005030:Ethylenes / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure
chemical_list: D002070:Butadienes; D005030:Ethylenes; C036216:ethylene; C031763:1,3-butadiene