Peculiar structure of the potential energy surfaces of typical electrocyclic reactions in the areas of the symmetry-forbidden reaction paths

摘要: Abstract The mechanisms of the electrocyclic ring opening reactions cyсlobutene to trans-l,3-butadiene and 1,3-cyclohexadiene 1,3,5-hexatriene were computationally studied with use B3LYP/6-311++G(d,p), MP2/6-311G++(3df,2p), CCSD/6-311++G(df,p), CCSD/6-311G(df,p) CCSD(T)/6-311++G(df,p)//CCSD methods. Special attention was paid study potential energy surfaces (PESs) both systems in domains pertaining disrotatory movement vicinal methylene groups. No symmetry-forbidden reaction channel found within PES cyclobutene–1,3-butadiene system. Instead that, rotation two groups results elimination a molecule dihydrogen giving rise formation low-stable π-complex H2·cyсlobutadiene. Similar type H2·benzene also located on 1,3-cyclohexadiene–1,3,5-hexatriene along coordinate. topologies PESs analyzed basis patterns gradient lines are characterized by an existence them valley-ridge inflection (VRI) points corresponding bifurcation paths leading π-complexes formed upon from cyclobutene 1,3-cyclohexadiene.