A related example is shown in Fig. where the desmotropic reaction is the [1,5]-sigmatropic rearrangement of 3a to 3b via 4a. Here, only the coloured bonds are permuted with all other atom connectivities remaining unchanged (recall that, under this formalism, the bond order is not recognized). In contrast to the prior example, here all three species (3a, 3b, and 4a) correspond to precise locations on their PES (Fig. ).