Methano annulenes valence tautomerism

Figure 15 presents a schematic view of how the atomic subspaces Cl, C6 and Cl 1 of 1,6-methanojl Ojannulene (35) change upon an approach of Cl to C6. Bond paths (solid lines between atoms), bond critical points (dots) and the traces of the zero-flux surfaces S (A, B) (perpendicular to bond paths) that separate the atomic subspaces are shown in Figure 15a. Clearly, the subspace C11 extends less and less into the region between C1 and C6 until the surfaces of C1 and C6 coincide and a bond path between C1 and C6 is formed. At the same time, the Laplace concentration between Cl and C6 gradually increases and coverges to the one found for a three-membered ring. As shown in Figure 15b, this change corresponds to the valence tautomerism of the l,6-methano[10]annulene to bisnorcaradiene27,54.

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