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Chemically activated 3‐methyl‐l‐butene and 2‐methyl‐l‐butene from photolysis of diazomethane–isobutene–neopentane–oxygen mixtures
Author(s) -
Taylor G. W.,
Simons J. W.
Publication year - 1971
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.550030507
Subject(s) - chemistry , neopentane , arrhenius equation , reaction rate constant , diazomethane , decomposition , butene , rrkm theory , photodissociation , photochemistry , propene , kinetics , analytical chemistry (journal) , medicinal chemistry , organic chemistry , activation energy , ethylene , catalysis , physics , quantum mechanics , molecule
An experimental study of the decomposition kinetics of chemically activated 2‐methyl‐l‐butene and 3‐methyl‐l‐butene produced from photolysis of diazomethane‐isobutene‐neopentane‐oxygen mixtures is reported. The experimental rate constants for 3‐methyl‐l‐butene decomposition were 1.74 ± 0.44 × 10 8 sec −1 and 1.01 ± 0.25 × 10 8 sec −1 at 3660 and 4358 Å, respectively. 2‐Methyl‐l‐butene experimental decomposition rate constants were found to be 5.94 ± 0.59 × 10 7 sec −1 at 3660 Å and 3.42 ± 0.34 × 10 7 sec −1 at 4358 Å. Activated complex structures giving Arrhenius A ‐factors calculated from absolute rate theory of 10 16.6 ± 0.5 sec −1 for 3‐methyl‐l‐butene and 10 16.2 ± 0.4 sec −1 for 2‐methyl‐l‐butene, both calculated at 1000°K, were required to fit RRKM theory calculated rate constants to the experimental rate constants at reasonable E 0 and E * values. Corrected calculations (adjusted E 0 values) on previous results for 2‐pentene decomposition gave an Arrhenius A ‐factor of 10 16.45 ± 0.35 sec −1 at 1000°K. The predicted A ‐factors for these three alkene decompositions giving resonance‐stabilized methylully radicals are in good internal agreement. The fact that these A ‐factors are only slightly less than those for related alkane decompositions indicates that methylallylic resonance in the decomposition products leads to only a small amount of tightening in the corresponding activated complexes. This tightening is a significantly smaller factor than the large reduction in the critical energy due to resonance stabilization.