The Diels-Alder reaction of ethene and 1,3-butadiene: an extended multireference ab initio investigation.
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.
Lischka
Hans
H
Institute for Theoretical Chemistry and Structural Biology University of Vienna Währingerstrasse 17, 1090 Vienna (Austria). hans.lischka@univie.ac.at
Ventura
Elizete
E
Dallos
Michal
M
D002070:Butadienes / Q000737:chemistry*; D003198:Computer Simulation; D005030:Ethylenes / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure
D002070:Butadienes; D005030:Ethylenes; C036216:ethylene; C031763:1,3-butadiene