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

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 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.

[1]  D. Golden,et al.  Very low pressure pyrolysis of 1,3-cyclohexadiene. Orbital symmetry nonallowed reaction , 1973 .

[2]  David M. Golden,et al.  Very Low-Pressure Pyrolysis (VLPP); A Versatile Kinetic Tool , 1973 .

[3]  G. Emanuel.  Table of the Kassel integral , 1972 .

[4]  D. Golden,et al.  Very low‐pressure pyrolysis. IV. The decomposition of i‐propyl iodide and n‐propyl iodide , 1971 .

[5]  A. B. Trenwith.  Dissociation of 1-butene, 3-methyl-1-butene, and of 3,3-dimethyl-1-butene and the resonance energy of the allyl, methyl allyl and dimethyl allyl radicals , 1970 .

[6]  W. Shaub,et al.  Shock Tube cis-trans Isomerization Studies , 1969 .

[7]  D. Golden,et al.  Additivity rules for the estimation of thermochemical properties , 1969 .

[8]  D. Golden,et al.  Thermal unimolecular isomerization of bicyclo [2.1.0]pent-2-ene , 1969 .

[9]  T. N. Sarachman.  Microwave Spectrum of cis‐2‐Butene , 1968 .

[10]  S. Benson,et al.  A Method for Estimating the Arrhenius A Factors for Four- and Six-Center Unimolecular Reactions , 1967 .

[11]  S. Benson,et al.  Very low-pressure pyrolysis. I. Kinetic studies of homogeneous reactions at the molecular level , 1967 .

[12]  S. Benson,et al.  Kinetics and mechanism of the pyrolysis of 1,4-cyclohexadiene , 1967 .

[13]  B. Rabinovitch,et al.  Thermal Unimolecular Geometric and Structural Isomerization of 1,2-Dideuterio-3-methylcyclopropane , 1964 .

[14]  E. Resler,et al.  Studies with a Single‐Pulse Shock Tube. I. The Cis—Trans Isomerization of Butene‐2 , 1963 .

[15]  R. Marcus,et al.  Dissociation and Isomerization of Vibrationally Excited Species. II. Unimolecular Reaction Rate Theory and Its Application , 1962 .

[16]  W. D. Walters,et al.  The Vapor Phase Decomposition of 2,5-Dihydrofuran1 , 1961 .

[17]  R. Cundall,et al.  Thermal isomerization of butene-2. Part 1 , 1961 .

[18]  B. Rabinovitch,et al.  The Thermal Unimolecular cis-trans Isomerization of cis-Butene-21 , 1959 .

[19]  W. F. Anderson,et al.  Rate of Thermal Isomerization of cis-Butene-2 , 1958 .

[20]  R. Marcus.  Unimolecular dissociations and free radical recombination reactions , 1952 .

[21]  W. D. Walters,et al.  The Thermal Decomposition of Cyclopentene1 , 1948 .

[22]  K. Pitzer,et al.  Normal coordinate analysis of the vibrational frequencies of ethylene, propylene, cis-2-butene, trans-2-butene, and isobutene , 1947 .