Characteristics of key intermediates generated in uncatalyzed bis(2,4-dinitrophenyl) oxalate (DNPO) chemiluminescence reactions

Abstract

The characteristics of two distinct perylene chemiluminescence (CL) decay curves generated by the reaction between bis(2,4-dinitrophenyl) oxalate (DNPO) and H₂O₂ in the absence of base catalysts were investigated. When the intensity of peroxyoxalate chemiluminescence (PO-CL) vs. time was measured under relatively low H₂O₂ and high DNPO concentrations in ethyl acetate, a slowly decaying curve appeared. However, upon increasing the H₂O₂ concentration under the same DNPO-CL reaction conditions, two distinct emission maxima were observed: a fast decaying CL curve and a slowly decaying CL curve. The fast decaying CL curve appeared alone when the H₂O₂ concentration greatly exceeded the DNPO concentration in ethyl acetate. To learn more about the properties of both CL decay curves, we further investigated the effects of adding H₂O or phenols having different nucleophilicity [2,4-dinitrophenol (DNP), 2,4-dichlorophenol (DCP), pentachlorophenol (PCP), and 2,4,6-trichlorophenol (TCP)] and the stability of DNPO used in the CL reaction. The slowly decaying curve was predominant with the addition of H₂O and relatively strong nucleophile. Based on the observed results, we propose that the likely high-energy intermediates generated in DNPO-CL reactions without added base catalysts are hydroperoxyoxalate ester and a six-membered cyclic peroxide.