Unimolecular decomposition kinetics at resolved internal energies.


The kinetic behavior of microcanonical unimolecular decomposition reactions involving clusters formed by the electrostatic interaction between transition metal cations and simple organic molecules has been measured at multiple internal energies. The presence of the metal lowers the energy necessary for the reactions to take place. Thus, these reactions serve as a useful model for catalysis. These measurements were made in a custom built molecular beam apparatus, in which the experimental environment is free of the many complicating effects which are inherent to condensed phase measurements. The reacting clusters are formed in a supersonic expansion and bound by the charge-dipole interaction between the organic and the transition metal cation. Rearrangement reactions are initiated by absorption of a visible photon from a dye laser. The most widely used formalism for unimolecular kinetic calculations is Rice- Ramsperger-Kassel-Marcus (RRKM) theory, which states that the rate constant for a unimolecular reaction is dependent on the way in which the internal energy is distributed to the various modes of motion of the molecule. The rate constant is then proportional to the ratio of the sum of states of the transition state to the density of states of the reactant. This theory is utilized by our group to determine the reaction activation energies. This dissertation will focus on the unimolecular decomposition of Ni+propanal and Ni+acetic acid. The two reactions involve competition between C-C bond activation and either C-H or C-O bond activation.



Chemical kinetics.