Ab initio quantum-chemical calculations of protolytic cracking of ethane on Bronsted acid sites of high silica zeolites demonstrated the concerted mechanism of this reaction. The reaction coordinate represents the stretching of the O-H bond in combination with heterolytic splitting of the C-C ethane bond. This results in formation of methane and adsorption of the methyl group on the surface basic oxygen of the active site. The geometry of such activated complex is different from that of adsorbed carbonium ions which also represent highly excited surface complexes.