Hydrogen Bonds, Conformations, Reactivity, and Solvation

University Of California-San Diego, La Jolla CA

Investigators

Abstract

Since this is a performance based proposal, the proposed research of the Perrin Laboratory perforce covers a wide range of topics, including symmetry of hydrogen bonds (H-bonds), conformational analysis, anomeric effects, steric hindrance to ionic solvation, isotope effects (IEs) on acidity, NMR coupling constants, and the chemical reactivity of para-benzynes and malonic anhydrides. Techniques include multinuclear NMR, NMR titration, calorimetry, and computation. A frequent theme of these projects is solvation, which (1) affects H-bonds by breaking the symmetry of the local environment, (2) becomes less effective for sterically hindered ionic groups, (3) affects IEs by H-bonding to lone pairs, and (4) reduces the reactivity of nucleophiles toward para-benzynes. Examples of specific projects include the study of anomeric effects on stabilizations of anions that arise from properly positioned electron pairs in certain small organic molecules, NMR titration studies on deuterium IEs on acidity and their conformational dependence, and calculations of the conformational dependence of NMR coupling constants in ethers, amines, thioethers and their derivatives. The broader impact of these studies for advancing discovery remains quite long-range, since the studies are not aimed at practical application but at developing a thorough understanding of some fundamental chemistry, to guide further research in physical organic chemistry. The broader educational impact of these studies is far-reaching. Students learn to ask and answer questions, to solve problems, and to think critically. In recent years many of them have been inspired to enter academia. In addition, Prof. Perrin was elected chair of the 2006 Gordon Conference on Isotopes, where he made special efforts to encourage participation by graduate students and postdoctoral researchers, and provided financial support to them.