Kinetics and mechanistic detail of Ni⁺ assisted organic decomposition reaction at low internal energies.

Abstract

The unimolecular decomposition kinetics of jet-cooled cluster ions have been monitored over ranges of internal energies. The clusters are formed by the combination of Ni cation with and organic ketone, aldehyde or ether molecules. The internal energy delivered to the clusters is provided through laser photon absorption. The quantum of photon energy approximates the total energy content of the reacting species as the clusters are jet cooled prior to photon absorption. The interaction of the organic substrate with the transition metal cation lowers the kinetic barriers to the activation of σ-bond. Thus the cation activates organic bonds and mediates the formation of products. The unimolecular decomposition products in these studies are a stable neutral with the corresponding ion. This dissertation will focus on the unimolecular decomposition kinetics of Ni⁺- Butanone. First order rate constants are acquired for the precursor ion dissociation into three product channels. The temporal growth of each fragment ion is selectively monitored and yields similar valued rate constants. The common-valued rate constants, comparisons to earlier studies, and the results of DFT calculations reveal the dissociation dynamics. This unimolecular decomposition reaction is proposed to proceed along two parallel reaction coordinates that originate with the rate-limiting Ni⁺ oxidative addition into either the OC-CH₃ or OC-C₂H₅ σ-bond in the butanone molecule. Rate constant values for the activation of both bonds are determined.