m-benzyne and bicyclo[3.1.0]hexatriene - which isomer is more stable? - a quantum chemical investigation

Density functional theory (DFT) predicts that bicyclo[3.1.0]hexatriene (2) is more stable than its isomer m-benzyne (1). Hess [Eur. J. Org. Chem. (200 1) 2185] has argued that experimental findings suggesting 1 can equally or even better be associated with 2. However, high level ab initio calculation s (CCSD(T), CASPT2) show that 2 does not exist and that the previously meas ured infrared spectrum is correctly assigned to 1. Bond stretch isomers are possible for p-benzynes but not for m-benzynes. The electrophilic characte r of m-benzynes: is in line with 1 but not with 2. (C) 2001 Elsevier Scienc e B.V. All rights reserved.