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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 6
BKCSDE 32(6)
June 20, 2011 

 
Title
Comprehensive Studies on the Free Energies of Solvation and Conformers of Glycine: A Theoretical Study
Author
Chang Kon Kim, Byung-Ho Park, Hai Whang Lee, Chan Kyung Kim *
Keywords
Conformers of glycine, Free energies of solvation, Cavity models in CPCM, Neutral and Zwitterionic conformers
Abstract
The stable conformers of glycine and the inter-conversions between them were studied theoretically at various levels of theory, B3LYP, MP2, CCSD and CCSD(T), in the gas phase and in aqueous solution. In aqueous solution, the structures examined by use of the conductor-like polarizable continuum model (CPCM) with various cavity models, UA0, UAHF, UAKS, UFF, BONDI and PAULING, and by use of a discrete/continuum solvation model with eight water clusters. The Gibbs free energy differences between the neutral (NE) and zwitterionic conformers (ZW), ΔGZ-N [= GZW – GNE], in aqueous solution were well reproduced by using the BONDI and PAULING cavity models. However the ΔGZ-N values were underestimated in other cavity models, although the ZW conformers existed as stable species in aqueous solution. In the studies of a discrete/ continuum solvation model with eight water clusters, gas phase results are still insufficient to reproduce the experimental findings. However the ΔGZ-N values calculated by use of CPCM method in aqueous solution agreed well with the experimental ones.
Page
1985 - 1992
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