Beschreibung:
<jats:title>Abstract</jats:title><jats:p>DFT calculations on the photoisomerization of hydrazones of 1,2,4-oxadiazole derivatives to 1,2,5-triazoles have been performed showing that the reaction occurred through the first excited singlet state. The <jats:italic>Z</jats:italic> isomer gave the reaction through a hydrogen atom transfer of the hydrazonic nitrogen atom to the nitrogen atom in four position on the oxadiazole ring. In this case, the isomerization was a concerted reaction. The <jats:italic>E</jats:italic> isomer could undergo the same reaction. However, it could not be a concerted reaction but required the presence of a ring opening intermediate.</jats:p>