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Participants/Project Abstracts

Summer 2006 Bioanalytical Science REU Participants

Don Pham, Florida Atlantic University

2-QUINUCLIDONE: EXPERIMENTALLY DETERMINED HIGH PROTON AFFINITY AND GAS PHASE SYNTHESIS OF A TWISTED AMIDE

 

Don K. Pham * , Michael Krout † , Brian Stoltz † , and Ryan R. Julian ‡
Department of Chemistry, University of California–Riverside ‡ , UCR 92521 , California Institute of Technology † , Pasadena , CA , 91125 and Florida Atlantic University–Wilkes Honors College * , Jupiter , FL , 33458

Knowledge of the amide bonds which define peptide linkages is essential to understanding protein backbone chemistry. Typically amides are planar and display low basicity and reactivity; however, when an amide is twisted the properties of the bond change because electron delocalization is inhibited. This makes 2-quinuclidone, an inherently twisted bicyclic bridgehead lactam, an excellent candidate to better understand the reactivity of non-planar amides. We have calculated the proton affinity of this molecule to be 230.1 kcal/mol from B3LYP/6-31++G** single-point energy calculations of B3LYP/6-31+G* optimized structures. This proton affinity agrees with our experimentally determined value of 230.5 kcal/mol obtained via the kinetic method. We have also developed a new synthetic route for 2-quinuclidone. Collisional excitation of 4-piperidylacetic acid yields 2-quinuclidone in the gas phase by the elimination of water . The structure was confirmed by comparing the collision induced dissociation spectra of 2-quinuclidone generated in the gas phase to the spectra of a bona fide sample. Both revealed a single characteristic loss of forty-four Daltons .

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