Phenylenes conjugated-circuit model

Although the conjugated-circuit model [33] suggested that the linear [N]phenylenes are more stable than their angular isomers, the application of ah initio methods proved the opposite [126]. Schulman and Disch s examination of the problem by modem DFT methods placed the stabilization of 15 vs. 9b at 2.4 kcal mol [53]. Branched [4]phenylene 21b is the most stable of the five... 

In chemistiy, priority is to be given to experimental facts, not to calculations. Clar has offered experimental facts to support his model of the aromatic jr-sextet, but as we know, theoretical chemists have for the most part ignored his works. Recall the opening remark by R. G. Parr in this section. That is what has happened to Clar s aromatic jr-sextet. Now, with the synthesis of helical [/j]phenylenes by Vollhardt and co-workers, we may expect additional quantum chemical computations from theoretical circles. These are welcome. However, to fully appreciate the conjugated circuits model and the work of Clar, and to accept his model of the aromatic jr-sextet, apparently requires some imagination, or at least a... 

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