Analysis of individual sites reveals that type C exhibits the lowest energy for Me2Al + cleavage, while type E is most favorable for Me -abstraction. The high reactivity of type C sites towards Me2Al + cleavage can be rationalized structurally: the initial Me2Al + group is bound to both a 4-C oxygen and a bridging methyl group, and its removal restores two characteristic features of bulk MAO: 3-C oxygen atoms and tetrahedral aluminum centers with terminal methyl groups. Me2Al + cleavage from type C sites typically generates a terminal OAlMe3 -moiety, which can form chelating interactions with adjacent AlMe2 groups when sterically feasible. This same OAlMe3 -end group can also form via Me -abstraction from type E sites (3-C OAlMe2 groups). While type E sites are energetically most favorable for Me -abstraction, they are relatively uncommon as they tend to convert to less reactive type B sites.