Reaction Rate Constants and Mechanistic Detail of the Ni⁺+ Butanone Reaction

Abstract

The unimolecular decomposition kinetics of the jet-cooled Ni(+)-butanone cluster ion has been monitored over a range of internal energies (16000-18800 cm⁻¹). 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 in a custom instrument and yields similar valued rate constants at a common ion internal energy. The decomposition reaction is proposed to proceed along two parallel reaction coordinates. Each dissociative pathway is rate-limited by the initial Ni(+) oxidative addition into either the C-CH₃ or C-C₂H₅ σ-bond in the butanone molecule. Ratios of integrated product ion intensities as well as the measured rate constants are used to determine values for each σ-bond activation rate constant. The lowest energy measurement presented in this study occurs when the binary complex ion possesses an internal energy of 16000 cm⁻¹. Under this condition, the Ni(+) assisted decomposition of the butanone molecule is rate limited by k(act)(C-C₂H₅) = (0.92 ± 0.08) × 10⁵ s⁻¹ and k(act)(C-CH₃) = (0.37 ± 0.03) × 10⁵ s⁻¹. The relative magnitudes of the two rate constants reflect the greater probability for reaction to occur along the C-C₂H₅ σ-bond insertion pathway, consistent with thermodynamic arguments. DFT calculations at the B3LYP/6-311++G(d,p) level of theory suggest the most likely geometries and relative energies of the reactants, intermediates, and products.

Co+-Assisted Decomposition of h6-Acetone and d6-Acetone: Acquisition of Reaction Rate Constants and Dynamics of the Dissociative Mechanism

“…Source conditions are optimized to form the coldest ionic clusters possible with stable concentrations. This is done by minimizing the distribution of precursor ion velocities in the beam and has been described previously …”

“…This is done by minimizing the distribution of precursor ion velocities in the beam and has been described previously. 32 The supersonic expansion is skimmed twice as the beam approaches a Wiley−McLaren 33 type orthogonal accelerator (OA). Pulsed laser radiation from a Nd 3+ :YAG pumped dye laser counterpropagates to, but is colinear with, the molecular beam.…”

Three Reaction Channels with Signature Proton Transfers in the Ni(I)-Catalyzed Decomposition of Ethyl Acetate

“…These rate constants provide mechanistic and dynamic details of the reaction. 58,59 Our goal is to provide accurate data on the catalytic behavior of bare metals with simple substrates such that an intimate knowledge of the actual catalytic capabilities of transition metals can be determined. This inherent catalytic power, once explored for a range of metals and substrates, should provide us with highly detailed information that can be exploited toward a rational design of new catalysts via fine tuning of the aforementioned environmental add-ons (ligands, counterions, solvent, etc.).…”

“…Analysis of these data sets yields the rate constant for the rate-determining step of each reaction at the activating photon energy. These rate constants provide mechanistic and dynamic details of the reaction. , …”

Submerged Barriers in the Ni+ Assisted Decomposition of Propionaldehyde

“…The technique pioneered in our research group makes direct kinetic measurements of ion/molecule reactions within the energy regime of TCA and KERD. − However, there are several key differences from these traditional approaches: here (i) the reactants are formed into a binary cluster within a jet-cooled expansion, (ii) the precursor is energized through absorption of a single laser photon and this initiates a rearrangement reaction, and (iii) reaction kinetics are directly monitored at well resolved precursor internal energies. Thus, this single photon initiated dissociative rearrangement reaction (SPIDRR) technique samples fragment production in real time with the subsequent analysis yielding the microcanonical rate constant k ( E ) for the dissociative reaction.…”