Energetics of the Gas Phase Hydrates of trans-Formanilide : A Microscopic Approach to the Hydration Sites of the Peptide bond

M. Mons (1) , I. Dimicoli (1) , B. Tardivel (1) , F. Piuzzi (1) , E.G. Robertson (2) , J.P. Simons (2)

1 LFP - URA 2453 - Laboratoire Francis PERRIN
2 Physical and Theoretical Chemistry Laboratory [Oxford]

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 energy 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.

Domaines: Chimie théorique et/ou physique

M. Mons, I. Dimicoli, B. Tardivel, F. Piuzzi, E.G. Robertson, et al.. Energetics of the Gas Phase Hydrates of trans-Formanilide : A Microscopic Approach to the Hydration Sites of the Peptide bond. Journal of Physical Chemistry A, 2001, 105 (6), pp.969-973. ⟨10.1021/jp003152p⟩. ⟨hal-00144742⟩