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 H2, 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‐H2 elimination of (Formula Presented.) where θ = 2.303RT in kcal/mol. There is some surface reaction of butadiene at these temperatures to yield H2 + 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‐H2 elimination from saturated organic compounds will have activation energies too high to observe.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry