1. The Low Energy Unimolecular Reaction Rate Constants for the Gas Phase Ni + Mediated Dissociation of the C-C  -bond in Acetone. NiAc + → NiCO + + C 2 H 6 Vanessa Castleberry and Darrin Bellert, PhD Baylor University

2. Our Instrument

3. A Parent Mass Spectrum

4. Tuning the Hemispherical Energy Analyzer

5. Scheme

6. Kinetic Studies

7. How we make our measurements

8. How We Interpret the Data

9. C – C  -bond activation occurs In Acetone photolysis of 2 C-C  - bond * Acetone dissociation catalyzed by Ni + in our studies * Woodbridge, et. al., JPC, 1988, 92(19)

10. Rate Constants for Different Energies Internal energy (cm -1 ) k(E)(  s -1 ) 18800 0.113 ± 0.005 18000 0.087 ± 0.003 16400 0.059 ± 0.002 16100 0.058 ± 0.003 156000.055 ± 0.003

11. Which Step is Rate Limiting??

12. 2 Probable Candidates

13. But, these results can’t reveal which step is rate limiting Comparison studies using the isotope effect: d 6 - Acetone

14. Kinetic Isotope Effect

15. Apparent Rate Limiting Step?

16. Acknowledgements Bellert group: – Ivanna Laboren – Otsmar Villarroel – Jason Dee – Sarah Frey (enthusiastic undergraduate) Baylor University Department of Chemistry and Biochemistry

17. Questions?