Time-Resolved Infrared Study on the Photochemistry of O -Fluoroformyl- and O -Chlorooxalyl-9-fluorenone Oxime: The Reactivity of the Fluoroformyl Radical in Acetonitrile Solution

This note describes the photochemistry of O-chlorooxalyl- and O-fluoroformyl-9-fluorenone oxime. The solution photochemistry of both precursors was investigated by time-resolved step/scan FTIR spectroscopy. Experiments on O-chlorooxalyl-9-fluorenone oxime only allowed for detection of CO2 and bleaching of the precursor, indicating predominant N-O cleavage. The chlorocarbonyl radical, ClCO*, was not detected. In contrast, TRIR investigations on fluoroformyl oxime 2 gave evidence for formation of the fluoroformyl radical FCO* (3), which rapidly adds to the solvent acetonitrile, yielding a fluoroformyl-functionalized iminyl radical 4. Its reaction with triplet molecular oxygen, on the other hand, is impeded by an activation enthalpy that has been calculated as deltaH# = 3.2 kcal/mol.