期刊
JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
卷 730, 期 1-3, 页码 199-205出版社
ELSEVIER
DOI: 10.1016/j.theochem.2005.06.023
关键词
DFT; 2-mercaptoimidazole; tautomerism; water-assisted proton transfer
A systematic investigation of the proton transfer in the tautomerization of 2-mercaptoimidazole was undertaken. Calculations in aqueous solution were performed using the combined supramolecular/continuum and the direct continuum models, respectively. Complexes containing one and two water molecules around the hydrophilic site of 2-mercaptoimidazole were used for the combined supramolecular/continuum calculation. DFT results predict that the barrier height for non-water-assisted intramolecular proton transfer is very high (175.8 kJ/mol). Hydrogen bonding between 2-mercaptoimidazole and the water molecule(s) will dramatically lower the barrier by the concerted multiple proton transfer mechanism. The proton transfer process through a eight-member ring formed by 2-mercaptoimidazole and two water molecules is found to be more efficient one and the calculated barrier height is reduced to ca. 72 kJ/mol. (c) 2005 Elsevier B.V. All rights reserved.
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