ENERGETICS OF THE GAS PHASE MONOHYDRATES OF TRANS-FORMANILIDE: A MICROSCOPIC APPROACH TO THE HYDRATION SITES OF THE PEPTIDE BOND
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Publisher:Ohio State University
The energy of binding a water molecule to two H-bonded sites of trans-N-phenyl formamide (formanilide), an amide molecule that mimics the planar-NH-CO-peptide bond, has been measured in the gas-phase and calculated by an ab initio study. For the first time, the D0 dissociation energies of two 1:1 complexes, simultaneously observed in a supersonic expansion, is measured experimentally. They are found to be very similar. At the CO site, the water molecule acts as a proton donor and the H-bond has a energy of $5.40 +/- 0.28$ kcal/mol. At the NH site, the water acts as an acceptor and the binding energy is $5.65 +/- 0.30$ kcal/mol. Comparison of IR shifts with binding energies shows that they do not always correlate when the donor groups are different.
Author Institution: Laboratoire Francis Perrin, URA CEA-CNRS 2453, Centre d'Etudes de Saclay; Physical and Theoretical Chemistry Laboratory, University of Oxford
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