The Low Energy Unimolecular Reaction Rate Constants for the Gas Phase Ni + Mediated Dissociation of...
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The Low Energy Unimolecular Reaction Rate Constants for the Gas Phase Ni+ Mediated Dissociation of
the C-C s-bond in Acetone.
NiAc+ → NiCO+ + C2H6
Vanessa Castleberry and Darrin Bellert, PhD Baylor University
Our Instrument
A Parent Mass Spectrum
Tuning the Hemispherical Energy Analyzer
Scheme
Kinetic Studies
How we make our measurements
0 10 20 30 40 50 60Time (ms)
0kt
tA A e
How We Interpret the Data
C – C s-bond activation occursIn Acetone photolysis of 2 C-C s-bond* Acetone dissociation catalyzed by Ni+ in
our studies
152 000cm 116 000cm
* Woodbridge, et. al., JPC, 1988, 92(19)
Rate Constants for Different Energies
Internal energy (cm-1) k(E)(ms-1)
18800 0.113 ± 0.005
18000 0.087 ± 0.003
16400 0.059 ± 0.002
16100 0.058 ± 0.003
15600 0.055 ± 0.003
Which Step is Rate Limiting??
2 Probable Candidates
But, these results can’t reveal which step is rate limiting
Comparison studies using the isotope effect: d6 - Acetone
Kinetic Isotope Effect
Apparent Rate Limiting Step?
Acknowledgements
• Bellert group:– Ivanna Laboren– Otsmar Villarroel– Jason Dee– Sarah Frey (enthusiastic undergraduate)
• Baylor University Department of Chemistry and Biochemistry
Questions?