Ab initio molecular orbital theory has been employed to investigate the structures, energies, and conformations of trans-and cis-methyldiazene, trans-azomethane, diazetine, pyrazolone, 1,2,4,5-tetraazacyciohexa-1,4-diene, and trans, trans-1,2,4,5-tetraaza-1,4-pentadiene. A force field has been developed, on the basis of available experimental and theoretical (ab initio) data, to permit molecular mechanics calculations on azoalkanes. Structures, heats of formation, strain energies, and conformations of more than 50 molecules studied by the developed force field are presented. Extensive comparison is made with previous results for analogous alkenes and some striking features are revealed. © 1979, American Chemical Society. All rights reserved.