Theodore S. Dibble
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.
The main focus is alkoxy radicals, whose chemistry influences production of ozone and aerosols. We are extending our studies to alkoxy radicals with functional groups, for which direct experimental data is lacking. We are also investigating deuterium isotope effects in the reaction:
because it tests our understanding of the kinetics and dynamics of alkoxy + O2 reactions, generally, and because the HD produced from CHD=O is monitored to investigate the global hydrogen cycle.
We maintain an interest in isoprene chemistry, and have begun investigating the atmospheric chemistry of gas-phase elemental mercury. Another recent focus has been alkoxy and peroxy radicals containing intramolecular hydrogen bonds to their radical centers, whose hydrogen bonds can promote unusual chemistry. Click thumbnail of molecule above to view animation.
Combustion of Biofuels
We are investigating how molecular structure affects the ignition of biodiesel fuel and the production of Hazardous Air Pollutants. Biodiesel fuel is composed of methyl esters of long chain fatty acids. The key reaction in ignition involves the isomerization of peroxy radicals, ROO•, as illustrated below. This reaction can lead to ignition of diesel fuel, while competing reactions do not. The reaction coordinate diagram below shows that the activation barriers for isomerization does not depend in a simple way on reaction thermochemistry. This figure also suggests that the presence of C=C double bonds and ester groups in biodiesel fuel can enormously influence the kinetics of diesel ignition. The Arrhenius plot shows the enormous effect of structure on reaction rate constants. Competition between reactions determines the extent of formation of aldehydes and other pollutants.
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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- 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, in press.
- 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.
- Temperature-Dependent Branching Ratios of Deuterated Methoxy Radicals (CH2DO•) Reacting With O2. H. Hu, T. S. Dibble, G. S. Tyndall, and J. J. Orlando. J. Phys. Chem. A, 2012, 116, 6295-6302.
- 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.