Sensitized photooxygenation of mononitrophenols in micellar media

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Abstract
The singlet molecular oxygen‐mediated photooxidation of simple nitrophenols was studied in micellar (CTAB) alkaline solutions. A different behaviour for the values of the overall rate constant (Kt ) and the reactive rate constant (Kt ) in the interaction nitrophenol‐singlet molecular oxygen was observed as a function of surfactant concentration. The former decreases as [CTAB] increases, from values of 1–3 × 109 M–1 s–1 in the absence of surfactant to values at least one order of magnitude lower at [CTAB] ∼0.1 M. Parallel, kt remains practically unaffected, in values of the order of 106 — 107 M–l s–1, depending on the particular nitrophenol, within the same [CTAB] range. The quantum yield of nitrophenols photooxidation reaches a maximum at [CTAB] ∼0.1 M. The results are discussed in terms of a combination of causes, the polarity of the nitrophenolic microenvironment being the driving effect. The implication of the results on environmental decontamination are also analyzed.