Molecules, properties cyclic symmetry

To sum up this second part of our contribution, we propose to describe the behaviour of the cyclic delocalized molecules in all the magnetic properties of the matter (i.e. N.M.R., diamagnetism, Faraday effect) by the concept of potential strobilism. This depends directly upon the electronic and geometrical characteristics of the ground state electron (o+ir) distribution, symmetry point group, etc. 

In a sense, the thermal decomposition of benzene-dimer can be regarded as the converse of the dimerization of CBD, in which two molecules of an antiaromatic cyclic polyene combine rapidly to the thermodynamically more stable dimer. The thermolysis of o, o -benzene-dimer exemplifies the relatively facile fragmentation of a strained polycyclic dimer to two molecules of its thermodynamically much more stable aromatic monomer. In the former case, the stereoselectivity of the dimerization was shown to be consistent with the greater ease of the two diplacements from D2/1 that are required to induce orbital correspondence between the reactant and the syn rather than the anti isomer. The question arises whether here too the symmetry properties of one of the stereoisomers may not be such as to facilitate concerted rupture of the two bonds that are broken in the process. 

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