Direct evidence of singlet molecular oxygen [O 2[formula omitted]] production in the reaction of acetonitrile with hydrogen peroxide in alkaline solutions

Abstract

In this work, we report direct evidence of the formation of singlet molecular oxygen [O 2 ( 1 Δ g ) ] in the reaction of hydrogen peroxide (H 2O 2) with acetonitrile in alkaline solutions. The formation of O 2 ( 1 Δ 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 Δ g ) to the triplet ground state (O 2 ( 3 Σ g −) ) was done to unequivocally demonstrate the presence of O 2 ( 1 Δ g ) . For comparison, O 2 ( 1 Δ g ) derived from the thermolysis of the endoperoxide of 1,4-dimethylnaphthalene or from the H 2O 2/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 H 2O 2 with acetonitrile in alkaline solutions generates O 2 ( 1 Δ g ) , confirming the mechanism proposed by McKeown and Waters.