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The very low-pressure dehydrogenation of cis-2-butene. The activation energy for 1,4-H2 elimination

✍ Scribed by Ze'ev B. Alfassi; David M. Golden; Sidney W. Benson

Publisher
John Wiley and Sons
Year
1973
Tongue
English
Weight
524 KB
Volume
5
Category
Article
ISSN
0538-8066

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✦ Synopsis

Abstract

Pyrolysis of cis‐butene‐2 under conditions of very low pressure (VLPP) has been studied in the range of 1100–1300°K. The principal products are butadiene and H~2~, obtained in a unimolecular reaction. A competing reaction to form butene‐l accounts for from 10% to 40% of the overall decomposition over the range. Using a «tight» model for the transition state and RRKM theory yields a high‐pressure, unimolecular rate constant for the 1,4‐H~2~ elimination of
where θ = 2.303__RT__ in kcal/mol. There is some surface reaction of butadiene at these temperatures to yield H~2~ + nonvolatile residue. Butene‐l proceeds to decompose irreversibly to allyl + methyl radicals which have been observed directly. Comparison with related reactions leads to the conclusion that orbital symmetry‐forbidden, 1,2‐H~2~ elimination from saturated organic compounds will have activation energies too high to observe.

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