Huckel electron counting rule

Figure 7 shows where various planar carbon rings lie on the curve of Fig. 6. Notice that the results encompass Huckel s 4n + 2 rule ) quite nicely. The electron counts predicted by this rule to give stable structures lie in regions where the m ring is stabilized with respect to the molecule which contains no such loops. Thus we find stability for C He but not stability for C4HI2 but not C4H4 itself, etc. The moments method has...

Hiickel s MO work [4] in this area of course stands preeminent. But it has been much elaborated first, as regards the possibility of a Mobius cycle (with one P>0) whence [39,41] the electron-count conditions for stability and reactivity are interchanged, as indicated in Table 1 following second, as regards the interpretation of Huckel rule as a basis for the Woodward-Hoffmann rules (at least for electrocyclic reactions) and third, as regards the rules applicability [39] to cycles even when embedded in more extensive n-networks. 

As an aromatic molecule, a ir-electron count of the porphyrin macrocycle reveals 22 ir-electrons, which conforms nicely with Huckel s [4 =2] rule for aromaticity (n = 5). However, only 18 -ir-electrons are considered to lie in... 

A-4. For each of the following, determine how many tt electrons are counted toward satisfying Huckel s rule. Assuming the molecule can adopt a planar conformation, is it aromatic ... 

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