Autoxidation chemiluminescence mechanism

The data in Table I reveal a trend towards higher Ea values with increasing extent of singlet oxygenation or time of autoxidation. A possible interpretation of this observation may be sought in a consideration of the autoxidation-chemiluminescence mechanism (1-17). Since the rate... 

The weak chemiluminescence of Grignard compounds in air has been known since 1906. A radical chain mechanism similar to that of hydrocarbon autoxidation appears to provide the excitation energy of the emitting product. Until recently the relations between constitution and chemiluminescence in Grignard compounds were rather obscure j>-chloro-phenylmagnesium chloride was found to be the most efficient compound. 

When oxygen is removed from a reaction solution of tetrakis-(dimethylamino)ethylene (TMAE), the chemiluminescence decays slowly enough to permit rate studies. The decay rate constant is pseudo-first-order and depends upon TMAE and 1-octanol concentrations. The kinetics of decay fit the mechanism proposed earlier for the steady-state reaction. The elementary rate constant for the dimerization of TMAE with TMAE2+ is obtained. This dimerization catalyzes the decomposition of the autoxidation intermediate. 

The autoxidation of acridan esters has been of great value in the elucidation of the mechanism of luciferin oxidation, and is discussed as a model system for bioluminescence (Chap. (XII)). The following series of compounds which react in a related way summarises the main features which lead to moderately high light emission from the autoxidation of carbonyl compounds. The alkoxycarbamoyl furanones [37], whose chemiluminescent reactions are depicted in the scheme below, show the following useful features. 

In many polymers luminescence above the glass transition temperature due to increased molecular motion increases sample light emission. However, some polymers behave exactly the opposite with decreased light intensity in samples exposed to temperatures above the glass transition. The rate determining step is the termination reaction of free radicals. For Nylon 6/6, increases in sample temperature increase chemiluminescence due to quenching of the excited carbonyl C=0. A model of the mechanism of chemiluminescence applied to Nylon 6,6 is reported in the Appendix. Based on this model, oxygen is never consumed in an autoxidation reaction. 

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