Walter S. Trahanovsky
Pyrolysis of Organic Compounds.
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Research Interests
Most of our research is concerned with the pyrolysis of organic compounds. Two major goals of this research are: (1) to understand in detail the fundamental thermal reactions of organic compounds and (2) to develop pyrolytic reactions that have utility in the synthesis of complex organic molecules. Part of our work is directed toward understanding the fundamental thermal reactions of coal, coal-derived liquids, and biomass.
Our effort is concentrated on the isolation, preparation, and characterization of the products of the primary thermal reactions of simple organic compounds, some of which model structural features found in complex materials such as coal. The products of primary thermal reactions are often very reactive molecules, i.e., species which have no overall electronic charge, but do have an exceptionally reactive bond or group of bonds. Our research has been directed toward the study of these reactive molecules and we are interested in their chemistry as well as their preparation and spectroscopic properties. Our experimental approach involves extensive use of low-pressure gas-phase pyrolysis, a technique called "Flash Vacuum Pyrolysis (FVP)". This technique is useful for the study of primary thermal reactions because it reduces the chances of bimolecular reactions and allows even fairly reactive products of unimolecular reactions to be isolated and studied.
Many reactive molecules known to be important in pyrolytic reactions can be prepared in solution by non-pyrolytic reactions. For example, the parent benzenoid o-quinodimethane (1), called o-xylylene, can be prepared by the Ito-Nakatsuka-Saegusa (INS) reaction.
Although 1 is exceptionally reactive and dimerizes within seconds, we found that the INS reaction is so rapid that 1 can be prepared by this reaction and detected by UV-visible spectroscopy before it dimerizes. Taking advantage of this discovery, we have used stopped-flow techniques to study the kinetics of the dimerization of 1 and other very reactive o-quinodimethanes.
Using the same chemistry, we have developed a flow 1H NMR technique, in collaboration with Professor Gerstein, which allows us to obtain the 1H NMR spectra of very reactive o-quinodimethanes. This technique allows us to mix the two solutions a short distance above the NMR detector coils and to obtain the spectrum of the mixed solution within a few tenths of a second after mixing. Under our conditions the
initial half-life of dimerization of 1 is a few tenths of a second and indeed we have obtained a 1H NMR spectrum of 1 in the presence of its dimers. o-Quinodimethane 1 is one of the most reactive molecules that has been detected by NMR in solution to date. We have also observed the NMR spectrum of benzocyclobutadiene, a highly reactive simple derivative of the smallest 4nπ-electron ring system, cyclobutadiene.
