The chemical lifetime of a given reagent is much more interesting than simply one reaction whose rate can be reduced to a number.† If a given reaction is initiated by a radical, chances are good that one of the products of that reaction will also be a radical.† What happens to that product?† The eventual fate of almost all organic species released into the atmosphere is to be oxidized to form carbon dioxide... but along the way, many intermediate species are formed.† Some of these species are toxic, some are caustic, some absorb solar radiation, and some exist as intermediates for some time.† We initiate reactions in our flow reactor and study the decay of reactants and the appearance of products.† From this, we can extract a reaction mechanism with the goal of tracing the path of our target molecule from release until eventual oxidation to CO2.† Along the way, we learn a lot more about the ways in which molecules interact and rearrange in a variety of atmospherically relevant conditions.

Current systems under investigation:

OH + Acrolein

OH + Methacrolein

Secondary Organic Aerosols

As part of a long-term collaboration with Jim Andersonís Group at Harvard University, we study the rates of important reactions in the atmosphere.† We expect most reactions to obey the Arrhenius Equation, which tells us that the rate constant of a given reaction increases with temperature as more of the population has sufficient energy to clear the activation barrier. By studying the rates of these reactions as a function of temperature, we learn about the activation barrier.† This, in turn, teaches us about the fundamental ways in which molecules react.† What governs the barrier heights of reactions important in the atmosphere? And what are the consequences of the more complicated potential energy surfaces which often occur in radical-molecule collisions?

Current systems under investigation:

OH + Cycloalkanes

Gas Phase Kinetics

Current Research Topics

Dr. Timothy Dransfield

Department of Chemistry

The Dransfield Group

Laboratory: S-1-36

Reaction Product Studies

In order to make any sense of our experimental results, we need a theoretical understanding of the interplay of forces at the molecular level.† Each experiment is accompanied by an in-depth theoretical study to map out the potential energy surface on which the reaction takes place, identifying likely transition states and intermediates and helping us to explain the pressure and temperature dependent effects observed in the experiments.† Of course, the truly interesting results occur when theory and experiment clash, and it becomes our job to decide which of the two is correct. In addition, our pure theory work isnít limited to the study of reactions which weíre performing in the lab.† Interesting and unusual reactions of any kind are fair game for a theoretical treatment.

Current systems under investigation:

OH + Acetic Acid

OH + Acrolein

OH + Methacrolein

The Chichibabin Reaction

Electronic Structure Calculations