Mechanistic Organic Chemistry of Relevance to the Interstellar Medium

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Professor Robert J. McMahon, of the Department of Chemistry at the University of Wisconsin - Madison, is supported by the Organic and Macromolecular Chemistry Program for his studies directed toward the elucidation of the identity, structure, properties, and reactivity of organic molecules that occur in interstellar space. A combination of experimental and computational investigations are focused on organic species that are either known to or are likely to exist in the interstellar medium. These organic species will be generated in the laboratory, and their molecular structure investigated by infrared, ultraviolet/visible, electron spin resonance, and microwave spectrometry. In order to address the question of the existence of cyclic, aromatic species in interstellar space, as well as the mechanisms for their formation from acyclic molecules whose existence has been demonstrated, the fundamental chemical mechanisms by which open-chain organic molecules undergo ring closure will be investigated. Additional studies will attempt to detect aromatic species and their precursors in the interstellar medium through a combination of laboratory rotational spectroscopy and subsequent radio-astronomical searches. The origin of the so-called "diffuse interstellar bands" has been described as one of the fundamental problems in modern astronomy and molecular spectroscopy. At the present time, it is not known with certainty whether cyclic species displaying the unusual stabilization known as aromaticity exist in interstellar space and, if so, how these species can be formed from the acyclic molecules that are known to exist there. With the support of the Organic and Macromolecular Chemistry Program, Professor Robert J. McMahon, of the Department of Chemistry at the University of Wisconsin - Madison, is carrying out a combination of experimental and calculational studies designed to address these questions. By preparing acyclic precursors to aromatic species and examining their structure and reactivity, Professor McMahon explores the fundamental reaction chemistry which could occur in interstellar space. By probing these species with a variety of spectroscopic techniques, he both elucidates their structures and provides spectroscopic "signatures" which may be sought in the interstellar medium, providing evidence for the existence (or absence) of these species.