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Rate and mechanism of thermal decomposition of 4‐methyl‐l‐pentyne in a single‐pulse shock tube
Author(s) -
Tsang Wing
Publication year - 1970
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550020104
Subject(s) - chemistry , thermal decomposition , shock tube , pyrolysis , decomposition , pulse (music) , activation energy , tube (container) , shock (circulatory) , shock wave , photochemistry , thermodynamics , organic chemistry , composite material , materials science , medicine , physics , detector , electrical engineering , engineering
Dilute mixtures of 4‐methyl‐l‐pentyne have been pyrolyzed in a single‐pulse shock tube. The decomposition process involves bond breaking:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm HC} \equiv {\rm C} - {\rm CH}_2 ({\rm i - C}_{\rm 3} {\rm H}_{\rm 7} )\stackrel{k_B}{\longrightarrow}{\rm HC} \equiv {\rm C} - {\rm CH}_2 \cdot ({\rm propynyl}) + {\rm i - C}_{\rm 3} {\rm H}_{\rm 7} \cdot $$\end{document}as well as a molecular reaction:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm HC}\equiv {\rm C} - {\rm CH}_{\rm 2} ({\rm \rm i - C}_{\rm 3} {\rm H}_{\rm 7} )\stackrel{k_M}{\rightarrow}{\rm C}_{\rm 3} {\rm H}_4 ({\rm allene}) + {\rm C}_3 {\rm H}_6 . $$\end{document}The rate parameters are:\documentclass{article}\pagestyle{empty}\begin{document}$$k_{\bf B} = 10^{15.56} \exp {\rm (} - 34,940/T){\rm (sec}^{ - {\rm 1}}) $$ $$\begin{array}{*{20}c} k_{\rm M} = 10^{13.1} \exp {\rm (} - {\rm 29,670/}T){\rm (sec}^{ - {\rm 1}})&{\rm 1100}^ \circ {\rm K, 1}{\rm .5} - 5{\rm atm}\end{array}$$\end{document}The heat of formation of propynyl radical is thus Δ H f300 = 338 kJ mol −1 (80.7 kcal mol −1 )˙ This leads to a propynyl resonance energy of 40 kJ mol −1 (9.6 kcal mol −1 ).