The Phase‐dependent Photochemical Reaction Dynamics of Halooxides and Nitrosyl Halides^¶

Abstract

Recent progress in understanding the phasedependent reactivity of halooxides and nitrosyl halides is outlined. Halooxide reactivity is represented by the photochemistry of chlorine dioxide (OCIO) and dichlorine monoxide (ClOCl). The gas phase photochemical dynamics of OClO are contrasted with the dynamics in condensed environments. The role of excited-state symmetry in defining the reaction dynamics and the observation of photoisomerization resulting in the production of ClOO are discussed. The current understanding of the excited-state reaction dynamics of ClOCl and evidence for photoisomerization of this species resulting in the production of ClClO are outlined. Finally, the photochemical reaction dynamics of the nitrosyl halide ClNO are presented. The main difference between the gas and condensed phase reaction dynamics of this species is that whereas photodissociation to form Cl and NO dominates the gas phase reaction dynamics, photoisomerization resulting in ClON production occurs to an appreciable extent in condensed environments. The observation of photoisomerization for OClO, ClOCl and ClNO suggests that this process is a general feature of the condensed phase reaction dynamics for smaller halooxides and nitrosyl halides. Finally, future areas for study in both halooxide and nitrosyl halide photoreactivity are outlined.

Ab Initio Study Predicts That Enigmatic Isonitrosyl Fluoride Should Be Stable at Low Temperatures yet Unnoticeable Due to Its Photoreactivity

“…Our calculations show that these transitions lead to the 4 1 A′ state in Br-NO and Cl-NO, with a dipole moment of ∼8 D that is greater than that of the ground state (∼2 D). On the basis of having a large value for the dipole moment, we conclude that generation of Br–ON and Cl–ON was intermediated by the formation of the charge-transfer electronic state, as suggested in refs − .…”

“…Nitrosyls X-NO (where X is a monatomic or diatomic substituent) have been extensively studied for several decades − due to their unusual structure, − importance in atmospheric chemistry, − and possible practical applications . No less interesting are their isonitrosyl counterparts X–ON, ,− in which X forms a bond with the oxygen atom.…”