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A flash photolysis–resonance fluorescence kinetics study of the reactions of ground‐state sulfur atoms. V. Rate parameters for the reaction of S( 3 P )with cis ‐2‐butene and tetramethylethylene
Author(s) -
Davis D. D.,
Klemm R. B.
Publication year - 1973
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.550050511
Subject(s) - chemistry , arrhenius equation , activation energy , flash photolysis , reaction rate constant , atmospheric temperature range , ground state , kinetics , resonance fluorescence , negative temperature , kinetic energy , transition state theory , reaction rate , sulfur , thermodynamics , fluorescence , atomic physics , organic chemistry , catalysis , physics , quantum mechanics
Rate parameters for the reaction of ground‐state atomic sulfur, S( 3 P ), with the olefins cis ‐2‐butene and tetramethylethylene have been determined over a temperature range of ∽280°K. A major finding of this study was that the rate constants for both reactions showed negative temperature dependencies. When k is expressed in the form of an Arrhenius equation, this necessarily leads to negative activation energies: k 1 = (4.68 ± 0.70) × 10 −12 exp (+0.23 ± 0.09 kcal/mole)/RT (219°‐500°K) k 2 = (4.68 ± 1.70) × 10 −12 exp (+1.29 ± 0.23 kcal/mole)/RT (252°‐500°K) Units are cm 3 molec −1 s −1 . When a threshold energy of 0.0 kcal/mole is assumed for reaction (2), the temperature dependence of the preexponential term has a value of T −2 . Making the usual simplifying assumptions, neither collision theory nor transition state theory leads to a preexponential factor with a strong enough negative temperature dependence. A comparison of these results with those derived from studies of the reactions of atomic oxygen, O( 3 P ), with the same olefins shows that in both studies simple bimolecular processes were being examined. Also discussed are the possible experimental and theoretical ramifications of these new results.