Delanson R. Crist
Emeritus Research Professor  

Department of Chemistry 
Georgetown University
37th and O Streets NW
Washington, DC 20057-1227

B.S. cum laude, 1962 Swarthmore College
Ph.D. 1967 Massachusetts Institute of Technology.
NSF Teaching Fellow, NIH Fellow; NSF Postdoctoral Fellow 1967-68, University of Illinois.

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General Chemistry I & II, Organic Chemistry I & II, Organic Chemistry Lab I & II, Reactive Intermediates, Organic Mechanisms

The physiological activity of nitrogen mustards results from formation of aziridinium ions, which are highly strained three-membered rings containing quaternary nitrogen (-NR 2 + -). Our electrochemical and theoretical studies of aziridinium salts led to insights into the reactive species involved. Other three-membered ring heterocycles are of similar interest due to their unusual bonding and reactivity, which includes synthetic and pharmaceutical applications. While generally known that such rings exhibit unsaturated character, we quantified and explained the effect of the ring heterogroup on this property for aziridinium salts, aziridines (-NR-) , oxiranes (-O-), and oxaziridines (-N-O-). An oxaziridine containing a C-alkoxy group was found to ring-open to a C-alkoxy nitrone (RO)CPh=N(O)R. Compared to the more widely known aldonitrones RCH=N(O)R and ketonitrones RCR=N(O)R, this C-alkoxy nitrone represents a “high oxidation state” nitrone. Such nitrones differ from usual nitrones in the same way that aldehydes and ketones differ from acids and acid derivatives. We developed a general synthesis of these nitrones and compared their structural, electrochemical, and spin-trapping ability properties to aldonitrones. In the course of these projects, we became interested the problem of the site of complexation of metal ions with multi functional donors such as aromatic ketones (aromatic, C=O pi, and C=O n sites) and oxaziridines (N or O), as well as the structural variations of metal complexes of nitrones. Since metal ions are often present in spin trapping by nitrones in biological systems, our work on the effect of metal complexing on the spin trapping ability of nitrones may find applications in biochemistry. In all of these projects, the “key to the new chem” has been to follow unexpected findings at each step along the way.