Investigation on the Unexplored Photochemistry of 5,5-Dimethyl-1-pyrroline 1-Oxide (DMPO).

A comparative study of 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) and its 2-methyl-substituted analogue (2-Me-DMPO) has revealed their contrasting reaction pathways of oxaziridine and lactam (pyrrolidone) formation. The initial photoexcitation populates the second excited singlet states (S) in both the systems with S-S transition moment value of 3 D (oscillator strength 0.4); this subsequently undergoes (S/S) conical intersection through a structure having a CNO-kink and situated around 35-40 kcal/mol below the vertically excited geometry of the first excited singlet state (S).