Orthogonene: A computational study of a strongly twisted alkene

Abstract

The strongly twisted (calculated dihedral angle 84°) alkene orthogonene (tetracyclo[8,2,2,02,7,03,10]tetradecene-2(3)) was studied at the DFT (B3LYP/6-31G*) and ab initio (HF/6-31G* and MP2(fc)/6-31G*) levels with a view to exploring the question of how realistic a synthetic objective it is, particularly in view of the fact that an attempt was made to synthesize it. Orthogonene is a relative minimum on the potential energy surface at the B3LYP/6-31G* and MP2(fc)/6-31G* levels, but is predicted to have a very low barrier (1.2 kJ mol–1 from the B3LYP calculations) to rearrangement by a 1,2-carbon shift to a carbene, which in turn isomerizes to a cyclopropane and (or) an alkene (the carbene is perhaps not a stationary point on the potential energy surface). Thus, very likely orthogonene could be observed only at temperatures approaching absolute zero, if at all.Key words: orthogonene, tetracyclo[8,2,2,02,7,03,10]tetradecene-2(3), twisted double bond, orthogonal double bond, carbene-strained alkene isomerization, ab initio, DFT.