A research investigation into the synthesis of 1,4-diazabicyclo[2.2.2] octane from ethylendiamine over zeolite ZSM-5 was carried out. A number of side products such as alkylpyrazines, alkylpiperazines and alkyl-1, 4-diazabicyclo [2.2.2.] octanes were identified in the reaction mixture. A chemical mechanism based on elimination, condensation, cracking and proton transfer reactions was proposed for the formation of these compounds.