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Radical equilibrium studies; the thermodynamic parameters of n ‐propyl
Author(s) -
Marshall Roger M.,
Rahman Lutfor
Publication year - 1977
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.550090503
Subject(s) - chemistry , radical , thermodynamics , atmospheric temperature range , decomposition , heat capacity , thermal decomposition , thermodynamic equilibrium , olefin fiber , equilibrium constant , computational chemistry , organic chemistry , polymer , physics
A novel method for the investigation of the thermodynamic properties of free radicals is described. It involves the establishment of an equilibrium of the form\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm R}_1 {\rightleftharpoons} {\rm R + olefin} $$\end{document}where R 1 and R 2 are free radicals, and the measurement of the recombination products of R 1 and R 2 . The method is applied to the case where R 1 is n ‐propyl, R 2 is methyl, and the olefin is ethene, using the thermal decomposition of azomethane (a source of methyl) in the presence of ethene in the temperature range of 581–649°K. Using the best available thermodynamic parameters for methyl, it is concluded that those for n ‐propyl are in need of adjustment. We recommend the values ΔH f °(300°K) = 22.6 ± 1 kcal/mol and S 300 ° = 67.4 ± 3 cal/mol · K together with either the heat capacity data of O'Neal and Benson or the essentially identical data derivable from the results of Purnell and Quinn.