Theodore S. Dibble
Professor and Associate Chair for Graduate and Undergraduate Programs
421 Jahn Lab
1 Forestry Dr.
Syracuse, New York 13210
Ph.D., 1992, University of Michigan. Postdoctoral, Wayne State University (1992-1994), Purdue University (1994-1995), California Institute of Technology (1995-1996)
Theodore Dibble is interested in the chemistry of compounds important for energy and the environment. His research focuses mostly on atmospheric chemistry, the combustion of biofuels, and chemistry initiated by electron beams. The tools of the Dibble group range from standard analytical instrumentation to lasers and computational chemistry.
Atmospheric Mercury Chemistry
Mercury is a neurotoxin. It is transferred from the atmosphere to ecosystems upon oxidation from Hg(0) to Hg(II). Oxidation is initiated by Br:
Br• + Hg → BrHg•
Models of mercury oxidation had then assumed:
BrHg• + •Y → BrHgY (Y= •OH or Br•)
This type of reaction has a large rate constant because there is no barrier to bond formation. In 2012, we proposed that many other radicals, •Y, would be much more important than •OH or Br• because they are much more abundant. The most important Y should be HOO• and •NO2, but other radicals (halogen oxides) also contribute. The problem was that none of the BrHgY compounds we proposed had every been previously studied! Our quantum chemistry calculations proved the BrHgY products to be stable (see images below), but we need much more information if we are to understand this chemistry.
Even today, none of these reactions has been studied experimentally, even in the laboratory. So there is a great deal of new work to be done to arrive at a basic understanding of this chemistry!
Atmospheric Organic Chemistry
The main focus is alkoxy radicals, whose chemistry influences production of ozone and aerosols. We recently investigated deuterium isotope effects in the reaction below:
for two reasons: (1) it tests our understanding of the kinetics and dynamics of alkoxy + O2 reactions, generally; and (2) because the HD produced from CHD=O is monitored to investigate the global hydrogen cycle. We want to extend our studies of alkoxy radicals to species with functional groups, for which direct experimental data is lacking.
We maintain an interest in isoprene chemistry, both because of its importance and complexity, and because of curioisity aboout the role of intramolecular hydrogen bonds to their radical centers, which can promote unusual chemistry.
Electron Beam Chemistry
As part of an old project we constructed a model of hundreds of reactions to investigate the mechanism of degradation of organic compounds by electron beams. The organic compounds of interest are ordinary pollutants. We are asking basic questions about effectiveness and reaction mechanism, which will be answered by determining destruction rate and product yields, kinetic modeling, and determination of radical concentrations in plasmas by cavity ringdown spectroscopy. We are extending the model to look at processing CO2 into commodity chemicals.
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- First kinetic study of the atmospherically important reactions BrHg• + NO2 and BrHg• + HOO, Y. Jiao and T. S. Dibble, Phys. Chem. Chem. Phys. 2017, 19, 1826-1838.
- Thermodynamics limits the reactivity of BrHg• radical with volatile organic compounds, T. S. Dibble and A. C. Schwid, Chem. Phys. Lett. 2016, 659, 289-294.
- Quantum Chemical Study of Autoignition of Methyl Butanoate, Y. Jiao, F. Zhang, and T. S. Dibble, J. Phys. Chem. A, 2015, 119, 7282–7292.
- Quantum Chemistry Guide to PTRMS Studies of as-yet Undetected Products of the Bromine-Atom Initiated Oxidation of Gaseous Elemental Mercury, T. S. Dibble, M. J. Zelie, and Y. Jiao, J. Phys. Chem. A, 2014,118, 7847–7854.
- Rate Constants and Kinetic Isotope Effects for Methoxy Radical Reacting with NO2 and O2, J. Chai, H. Hu, T. S. Dibble, G. S. Tyndall, and J. J. Orlando. J. Phys. Chem. A, 2014, 118, 3552–3563.