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Quantum energy flow and the kinetics of water shuttling between hydrogen bonding sites on trans-formanilide

Agbo, JK and Leitner, DM and Myshakin, EM and Jordan, KD (2007) Quantum energy flow and the kinetics of water shuttling between hydrogen bonding sites on trans-formanilide. Journal of Chemical Physics, 127 (6). ISSN 0021-9606

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Abstract

A potential energy surface for trans-formanilide (TFA)- H2 O is calculated and applied to study energy flow in the complex as well as the kinetics of water shuttling between hydrogen bonding sites on TFA. In addition to the previously identified H2 O-TFA (CO) and H2 O-TFA (NH) minima, with the water monomer bound to the CO and NH groups, respectively, the new surface reveals a second local minimum with the water bound to the CO group, and which lies energetically 310 cm-1 above the previously identified H2 O-TFA (CO) global minimum. On this surface, the energy barrier for water shuttling from H2 O-TFA (CO) global minimum to H2 O-TFA (N-H) is 984 cm-1, consistent with the experimental bounds of 796 and 988 cm-1 [J. R. Clarkson Science 307, 1443 (2005)]. The ergodicity threshold of TFA is calculated to be 1450 cm-1; for the TFA- H2 O complex, the coupling to the water molecule is found to lower the ergodicity threshold to below the isomerization barrier. Energy transfer between the activated complex and the vibrational modes of TFA is calculated to be sufficiently rapid that the Rice-Ramsperger-Kassel-Marcus (RRKM) theory does not overestimate the rate of water shuttling. The possibility that the rate constant for water shuttling is higher than the RRKM theory estimate is discussed in light of the relatively high energy of the ergodicity threshold calculated for TFA. © 2007 American Institute of Physics.


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Details

Item Type: Article
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Agbo, JK
Leitner, DM
Myshakin, EM
Jordan, KDjordan@pitt.eduJORDAN
Centers: Other Centers, Institutes, or Units > Center for Molecular and Materials Simulations
Date: 20 August 2007
Date Type: Publication
Journal or Publication Title: Journal of Chemical Physics
Volume: 127
Number: 6
DOI or Unique Handle: 10.1063/1.2754689
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 0021-9606
MeSH Headings: Chemistry, Physical--methods; Electrons; Energy Transfer; Formamides--chemistry; Hydrogen Bonding; Kinetics; Models, Chemical; Models, Theoretical; Molecular Conformation; Molecular Structure; Peptides--chemistry; Quantum Theory; Thermodynamics; Water--chemistry
PubMed ID: 17705604
Date Deposited: 29 Oct 2012 21:28
Last Modified: 02 Feb 2019 15:56
URI: http://d-scholarship.pitt.edu/id/eprint/16082

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