Density functional theory calculations have been carried out in order to study the formation and deprotonation of surface methyl oxonium ions, -OCH3, at aluminosilicate Bronsted acid sites. We have shown that acid-catalyzed deprotonation of methyl groups during the methanol to gasoline (MTG) conversion can occur to produce surface-stabilized carbenes with a calculated activation barrier of 215-232 kJ mol(-1). The calculated barriers are in reasonable agreement with recent experimental findings indicating that methyl group deprotonation may be the rate-determining step during methanol conversion. Participation of gas phase carbenes in the MTG process is shown to be unlikely. Other mechanistic details are discussed.