Quinones of bicyclo[3.1.0]hexa-1,3,5-triene were examined computationally. The six compounds considered were the five possible classical and one non-classical quinone: bicyclo[3.1.0] hexa-1(6),4-diene-2, 3-dione (and its monocyclic isomer with a long trans-annular bond), bicyclo[3.1.0] hexa-1(5),3-diene-2,6- dione, bicyclo[3.1.0]hexa-1,4-diene-3,6-dione (and its monocyclic isomer with a long trans-annular bond), and bicyclo[3.1.0] hexa-1(5),4-diene-2,4-dione-3,6-diyl, a non-classical (non-Kekule) zwitterion. The two long trans-annular bond structures are akin to that found for m-benzyne. Geometries were calculated (BLYP/6-31G*, CASSCF(2,2)/6-31G*, MP2/6-31G*) and electronic structural inferences were made from the geometries. Also calculated were relative energies and heats of formation (CBS-QB3), singlet and triplet energies (BLYP/6-31G*), and ionization energies and electron affinities (HF/6-311+G**//BLYP/6-31G*). The NICS(1) calculations were performed as a probe of the aromaticity of the diverse quinones. (C) 2012 Elsevier Ltd. All rights reserved.