Direct evidence of singlet molecular oxygen [O2 (1Δg)] production in the reaction of acetonitrile with hydrogen peroxide in alkaline solutions

In this work, we report direct evidence of the formation of singlet molecular oxygen [O-2 ((1)Delta(g))] in the reaction of hydrogen peroxide (H2O2) with acetonitrile in alkaline solutions. The formation Of O-2 ((1)Delta(g)) was characterized by: (i) the dimol light emission in the red spectral region (>610 nm) using a red-sensitive photomultiplier tube (PMT); (ii) the monomol light emission in the near-infrared region (1270 nm) with a newly available tube coupled to a monochromator; and (iii) the quenching effect of sodium azide. Direct spectral characterization of the near-infrared emission that attributes the emission to the transition Of O-2 ((1)Delta(g)) to the triplet ground state (O-2 ((3)Sigma(g)(-))) was done to unequivocally demonstrate the presence Of O-2 ((1)Delta(g)). For comparison, O-2 ((1)Delta(g)) derived from the thermolysis of the endoperoxide of 1,4-dimethylnaphthalene or from the H2O2/hypochlorite system were also monitored. The product of the reaction (acetamide) was also detected by mass spectrometry (MS). This evidence clearly demonstrates that the reaction of H2O2 with acetonitrile in alkaline solutions generates O-2 ((1)Delta(g)), continuing the mechanism proposed by McKeown and Waters. (C) 2003 Elsevier Science B.V. All rights reserved.