Fig. 6. (A) Six low-barrier C–O bond cleavage patterns (type I to VI) identified from the reaction database; (B) the charge density difference contour plot for three low-barrier C–O bond cleavage TSs that appeared in glycerol hydrogenolysis, i.e., TS of retro-Michael addition (type III), TS1 (type IV) and TS3 (type VI). Also see Fig. 5 for TS1 and TS3. The charge density difference is obtained by subtracting the total electron density of the surface and the reacting molecule from that of the TS. The isosurface density is at 0.003|e|/bohr.3 Blue: density increase; yellow: density decrease.
