Zeolite Shape-Selectivity in the gem-Methylation of Aromatic Hydrocarbons

The kind of olefins obtained from methanol in zeolites is strongly dependent on specific combinations of the intermediate organic hydrocarbon-pool species and zeolite topology (see picture). If the cage is too large, neutral species are favored over reactive cations. If the cage is too small, transition-state-shape selectivity poses severe limitations on the reactivity of bulkier species.