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The Diels–Alder Reaction of Ethene and 1,3‐Butadiene: An Extended Multireference ab initio Investigation
Author(s) -
Lischka Hans,
Ventura Elizete,
Dallos Michal
Publication year - 2004
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400104
Subject(s) - saddle point , ab initio , computational chemistry , diels–alder reaction , chemistry , fragmentation (computing) , cyclohexene , maxima and minima , ab initio quantum chemistry methods , transition state , molecule , geometry , organic chemistry , catalysis , mathematics , computer science , operating system , mathematical analysis
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 kcal mol −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 kcal mol −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.