Pyrolysis of Propyne/2‐Methylbut‐1‐ene‐3‐yne mixtures between 350 and 450°C

2‐Methylbut‐1‐ene‐3‐yne and Propyne mixtures were pyrolyzed at 350–450°C in the absence and presence of O 2 and NO. The major product of the reaction is a polymer, but m ‐xylene and p ‐xylene are also produced and were studied as the species of interest. The C 8 H 10 formation rate is first‐order in C 3 H 4 and C 5 H 6 . The rate coefficient is best fitted by\documentclass{article}\pagestyle{empty}\begin{document}$$\log [k({\rm C}_{\rm 8} {\rm H}_{{\rm 10}}),M^{ - 1} s^{ - 1}] = (11.2 \pm 1.0) - (166 \pm 13)/2.3RT$$\end{document}though it is not inconsistent with\documentclass{article}\pagestyle{empty}\begin{document}$$\log [k({\rm C}_{\rm 8} {\rm H}_{{\rm 10}}),M^{ - 1} s^{ - 1}] = (8.17) - (125.9)/2.3RT$$\end{document}where R is the ideal gas constant in kJ/mol‐K. Experiments in the presence of NO show that m ‐xylene and p ‐xylene formation occur by two processes: a concerted molecular mechanism (≃ 41%) and a singlet diradical mechanism (≃ 59%).