Journal of Physical Chemistry, Vol.100, No.27, 11319-11324, 1996
Absolute Rate Constants for the Addition of Atomic-Hydrogen to Monosubstituted and Trisubstituted Olefins
A mechanism is established for the formation of the products resulting from the solution phase regioselective addition of atomic hydrogen to 1-methylcyclohexene. From this data and new data for the reactions of 1-octene, the absolute rates and activation parameters for the addition of hydrogen atom to an olefin can be extracted. A method was established to determine the absolute rate of addition of a hydrogen atom to a terminal olefin in the solution phase. The addition rate constants, k(a)(25 degrees C), to 1-octene [k(a) = (4.2 +/- 3.6) x 10(9) M(-1) s(-1)] and 1-methylcyclohexene [k(a) = (4.6 +/- 0.8) x 10(6) M(-1) s(-1), -78 degrees C] are found to be in reasonable agreement with the published values for the vapor phase rate of addition to ethylene. The large rate constants are supported by the observation that the activation parameters (E(a) = 5.3 +/- 2.9 kcal/mol and log A = 14 +/- 3.5 M(-1) s(-1) for 1-octene) are consistent with the values expected for this fast reaction.