ETUDE EXPERIMENTALE ET THEORIQUE DE LA PHOTOLYSE DE DERIVES DU CYCLE PYRAZOLONE

Article abstract of DOI:10.1016/S0040-4020(01)97985-2

When irradiated in protic solvents such as water and primary alcohols, pyrazolinone derivatives undergo photocleavage between the two nitrogen atoms.Substituting the C-4 atom with an electronegative group stabilizes the open chain which is obtained but a thermal transposition takes place from the linear intermediate when C-4 carries a hydrogen atom or a methyl group.The STO/3G ab initio scheme was used to study the photocleavage and the influence of the C-4 substituent, giving evidence of a mechanism which involves triplet excited states of the ?, ?* type.