Kinetic Analysis of the Photoinitiated Autocatalytic Chain Decomposition of Phenyl Azide. A Molecular Explosion in Solution

Article abstract of DOI:10.1021/ja00292a048

Quantum yields of disappearance of pheny azide <Φ(-PhN3)> were determined for oxygen-purged, oxygen-saturated, and air-saturated solutions in acetonitrile ranging in concentration () from 1.40E-5 to 7.93E-1 M.A kinetic analysis of a simplified four-step reaction mechanism, based upon the reaction of phenylnitrene and phenyl azide to form two phenylnitrenes, affords a mathematical expression that relates experimentally determined Φ(-PhN3) values to experimentally measured , I₀ (intensity of the excitation light), and V₀ (volume of solution irradiated) values.One general expression accurately fits 56 experimental determinations of Φ(-PhN3), correctly relating it to and I₀, whereby Φ(-PhN3) increases with increasing ² and decreases with increasing I₀.The Φ(-PhN3) data along with the kinetic analysis provide definitive evidence of the first molecular explosion in solution as a result of the photoinitiated autocatalytic (branching) chain decomposition reaction of phenyl azide.