Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (09): 2035-2042.doi: 10.3866/PKU.WHXB20110903


Proton-Transfer Isomerization Reactions of 2-(2-Hydroxybenzylidenamino)pyrimidine-4,6-diol

ZHOU Zi-Yan1, LIU Min3, SU Zhong-Min2, XIE Yu-Zhong3, DING Shen-De1, WANG Hua-Jing1   

  1. 1. College of Chemical Engineering, Shandong University of Technology, Zibo 255049, Shandong Province, P. R. China;
    2. Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, P. R. China;
    3. Department of Chemistry, College of Science, Yanbian University, Yanji 133002, Jilin Province, P. R. China
  • Received:2011-02-28 Revised:2011-05-26 Published:2011-08-26
  • Contact: ZHOU ZI-Yan
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20703008) and Natural Science Foundation of Shandong Province, China (ZR2009BL024).

Abstract: To determine the tautomerism mechanism between the enol form and the keto form of 2- (2-hydroxybenzylidenamino)pyrimidine-4,6-diol (M1) the potential energy surface of the isomerization was studied using density functional theory (DFT) calculations at the B3LYP/6-311+G(d, p) level. We found that there were at least 8 isomers and 10 transition states in the possible reaction pathways. All the possible processes of the reaction were studied. The results showed that the energy of 6-hydroxy-2-(2- hydroxybenzylideneamino) pyrimidine-4(3H)-one (M6) was lower than those of the other isomers in the form of a monomer, a hydrate, and a dimer. Therefore, it was the most stable isomer. In these possible reaction pathways the activation free energy required for intramolecular prototropy was 143.8 kJ·mol-1 and for the proton transfer process that was catalyzed by water was 38.9 kJ·mol-1. The activation free energy in the double-proton transfer of the dimer was 0.6 kJ·mol-1, which was the lowest value. The latter pathway was feasible at room temperature. This implies that hydrogen bonding plays an important role in depressing the activation energy of the reaction.

Key words: 2-(2-Hydroxybenzylidenamino)pyrimidine)-4,6-diol, Density functional theory, Tautomerism, Proton transfer