Mechanisms of pyrolysis for a specifically labeled deuterated urethane

The pyrolysis products of a model urethane prepared from trimethylolpropane (TMP) propoxylated with 3, 3, 3‐d3‐propylene oxide and PAPI have been extensively studied by gas chromatography in conjunction with electron‐impact, chemical‐ionization, and field‐ionization mass spectrometry. The isotope distributions for some of the lower‐molecular‐weight species (determined by electron‐impact and/or field‐ionization mass spectrometry) showed a greater amount of H/D mixing than was expected from previously postulated concerted mechanisms. The deuterium distributions of the higher‐molecular‐weight TMP species were, in general, consistent with previously described mechanisms. The results from this study support the proposal that pyrolytic degradation of urethanes occurs mainly by a systematic sequence of concerted reactions. However, the deuterium distributions in some compounds indicate that free‐radical reactions are important in the formation of some pyrolyzates.