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The very low‐pressure pyrolysis of phenyl methyl sulfide and benzyl methyl sulfide. The enthalpy of formation of the methylthio and phenylthio radicals
Author(s) -
Colussi A. J.,
Benson S. W.
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.550090212
Subject(s) - chemistry , radical , sulfide , enthalpy , medicinal chemistry , kinetics , bond dissociation energy , standard enthalpy of formation , pyrolysis , standard enthalpy change of formation , dissociation (chemistry) , activation energy , fission , photochemistry , organic chemistry , physics , quantum mechanics , neutron
The kinetics and mechanisms of the unimolecular decompositions of phenyl methyl sulfide (PhSCH 3 ) and benzyl methyl sulfide (PhCH 2 SCH 3 ) have been studied at very low pressures (VLPP). Both reactions essentially proceed by simple carbon‐sulfur bond fission into the stabilized phenylthio (PhS·) and benzyl (PhCH 2 ·) radicals, respectively. The bond dissociation energies BDE(PhS‐CH 3 ) = 67.5 ± 2.0 kcal/mol and BDE(PhCH 2 ‐SCH 3 ) = 59.4 ± 2 kcal/mol, and the enthalpies of formation of the phenylthio and methylthio radicals Δ H ° ,298K (PhS·, g) = 56.8 ± 2.0 kcal/mol and Δ H ° f , 298K (CH 3 S·, g) = 34.2 ± 2.0 kcal/mol have been derived from the kinetic data, and the results are compared with earlier work on the same systems. The present values reveal that the stabilization energy of the phenylthio radical (9.6 kcal/mol) is considerably smaller than that observed for the related benzyl (13.2 kcal/mol) and phenoxy (17.5 kcal/mol) radicals.