Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5418945 | Journal of Molecular Structure: THEOCHEM | 2007 | 12 Pages |
Abstract
The keto-enol tautomerism of cyanuric acid, both in the gas phase and in water and methanol, has been studied at the B3LYP/aug-cc-pvDZ level of theory in this paper. The harmonic frequencies of all the structures are calculated. The results show that the transition states of the tautomerism are four-membered ring conformations in gas phase, whereas six-membered ring conformations in water and methanol. In the first proton transfer, the activation energy ÎE# is 69.9 and 62.0Â kJ/mol for water and methanol, respectively, which is much lower than that in gas phase (189.7Â kJ/mol). Water and methanol molecules produce an important catalytic effect in the tautomerism, especially for methanol system. The AIM and NBO analyses show that there exists an H-bonding complex between the cyanuric acid and the water (methanol). By viewpoints of the reaction enthalpy and reaction rate, keto-enol tautomerism in water and methanol systems is easier than that in gas phase. The keto-enol tautomerisms are endothermic both in gas phase and in water and methanol, so the enol forms are less stable than the keto ones.
Related Topics
Physical Sciences and Engineering
Chemistry
Physical and Theoretical Chemistry
Authors
Xiaoqin Liang, Xuemei Pu, Hongwei Zhou, Ning-Bew Wong, Anmin Tian,