Theodore S. Dibble
Professor and Associate Chair
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 organic compounds important for energy and the environment. His research focuses mostly on atmospheric chemistry and the combustion of biofuels. The tools of the Dibble group range from standard analytical instrumentation to lasers and computational 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. Click thumbnail of molecule above to view animation.
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!
We are beginning to investigate the degradation of organic compounds by non-thermal plasmas, particularly electron beams. The organic compounds of interest are ordinary pollutants or chemical warfare agents (we use safer analogues in our laboratory). 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.
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- Quality Structures, Vibrational Frequencies, and Thermochemistry of BrHg• + NO2, HO2, ClO, BrO, and IO. Y. Jiao and T. S. Dibble, J. Phys. Chem. A, in press.
- 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.
- Quantum Chemistry, Reaction Kinetics and Tunneling Effects in the Reaction of Methoxy Radicals with O2. H. Hu and T. S. Dibble, J. Phys. Chem. A, 2013, 117, 14230-14242.
- Thermodynamics of reactions of ClHg and BrHg radicals with atmospherically abundant free radicals. T. S. Dibble, M. J. Zelie, and H. Mao. Atmos. Chem. Phys., 2012, 12, 10271-10279.
- Impact of tunneling on hydrogen-migration of the n-propylperoxy radical. F. Zhang and Theodore S. Dibble, Phys. Chem. Chem. Phys., 2011, 13, 17969-77.
- Understanding OH Yields in Electron Beam Irradiation of Humid N2. K. L. Schmitt and T. S. Dibble, Plasma Chem. Plasma Proc., 2011, 31, 41-50.