Hypothetical carbon -migration

FIGURE 18.5 Hypothetical orbital movement for a thermal [1,5] sigmatropic migration of carbon. To move from one — lobe to the other — lobe, the migrating carbon use only its own — lobe, retaining its configuration. 

L8.6 Hypothetical orbital movement for a thermal [1,3] sigmatropic migration of carbon. The migrating carbon moves from a — to a + lobe, requiring it to switch its own bonding lobe from — to -f, inverting its configuration. 

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