The isomerization by ring opening and closing of singlet cyclopropyl nitrene has been studied using RHF method with STO-3G and 6-31G basis sets. The transition state has been obtained. The disrotation-conrotation mechanism has been proposed and discussed with Woodward-Hoffmann rules. Barrier height for the ring opening is 45.64kJ/mol. Triplet cyclopropyl nitrene is calculated which has lower energy than single one by 213.94 kJ/mol (6-31G level). The relative structure data have been given.

Key words: REACTION MECHANISM, CYCLOPROPANE P, RING CLOSURE REACTION, RING CLEAVAGE REACTION, WOODWARD-HOFFMANN RULE, SINGLET, TRIPLET, IMIDOGEN, ISOMERIZATION