3.3.2. Systematic numbering for (C₃₆-C_s)[5,6]fullerene

In this fullerene the plane of symmetry corresponds to the plane of the paper in Fig. 27 and bisects only two six-membered rings which are preferred according to Fu-3.3.2.1 indicated as A and B in Fig. 27a. Ring A contains the highest-ranking atom at the first point of difference (namely, four 6,6,5 atoms in a row), whereas ring B contains two pairs of 6,6,5 atoms intercalated by single 6,5,5 atoms. According to Fu-3.3.2.1, ring A is preferred for beginning the numbering. There are six pathways to be considered: clockwise and anticlockwise from a, from b, and from c (Fig. 27b). Of these, only the two starting from c lead to contiguous numberings, shown in Figs. 27c and 27d, respectively. Since both start from an atom 0.5 bond removed from the plane of symmetry and terminate at an atom lying on the plane of symmetry, they cannot be distinguished on the basis of Fu-3.3.3. However, application of <Fu-3.3.4 shows that the numbering reported in Fig. 27d must be preferred because it features a 6,6,5 atom at position 2 instead of the 6,5,5 atom of the numbering of Fig. 27c.

Fig. 27. Systematic numbering of (C₃₆-C_s)[5,6]fullerene

5. P.W. Fowler and D.E. Manolopoulos, An Atlas of Fullerenes, Clarendon Press, Oxford, 1995