Relative stability of keto-enol tautomers in 5,6-substituted uracils: Ab initio, DFT and PCM study

Lukmanov, T. I.; Ivanov, S. P.; Khamitov, E. M.; Хурсан, С. Л.

doi:10.1016/j.comptc.2013.09.005

Cited by 31 publications

(31 citation statements)

References 35 publications

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“…According to experimental data obtained by UV‐spectroscopy, uracil exists as dioxo tautomer A in the condensed phase . The stability orders of substituted uracils calculated by ab initio (MP2 and RI‐MP2) as well as DFT methods (B3LYP, M05‐2X) in different media also indicate the predomination of form A over the remaining tautomers. In an aqueous solution, the tautomers are distributed in the following order of stability:

boldA > > boldD > boldB > boldЕ > boldС .

…”

Section: Introductionmentioning

confidence: 95%

“…). The nomenclature used to distinguish the different tautomers is described in . Tautomer F is energetically so unfavorable that it is not considered in most theoretical works .…”

Section: Introductionmentioning

confidence: 99%

“…The mechanisms of deprotonation are very contentious because there are several areas in the uracil molecule that are able to lose a proton. The most probable is the formation of anions AN1 and AN3 (Fig. ).…”

Section: Introductionmentioning

confidence: 99%

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5-Fluorouracil solutions: NMR study of acid-base equilibrium in water and DMSO

Abdrakhimova

Ovchinnikov

Лобов

et al. 2014

J. Phys. Org. Chem.

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A comprehensive analysis of solutions of 5‐fluorouracil (5FU) in water and an organic medium (dimethylsulfoxide, DMSO) was carried out using quantum chemical methods and nuclear magnetic resonance (NMR) spectroscopy. The details of anionic form generation in the solution of 5FU with an equimolar amount of potassium hydroxide were studied by 13С, 1Н, 15N and 19F NMR. Interpretation of NMR spectral data was carried out using quantum chemical calculations at the TPSSTPSS/6‐311+G(d,p) level of theory. Specific solvation of 5FU and 1THF‐5FU was modeled in approximation using the five‐water cluster model and solvate complex including two DMSO molecules. It was established that in an alkaline medium in DMSO 5FU occurred mainly as a type of an anion with a deprotonation on N(1) position of a pyrimidine ring whereas in water alkaline solution—as a mixture of two anions with a deprotonation on N(1) and N(3) positions with a predominant content of the latter form. For the quantitative definition of the deprotonation forms of 5FU the technique based on the data of theoretical and experimental NMR 13C spectroscopy, tested on a model compound 1‐(tetrahydrofuranyl‐2)‐5‐fluoro‐pyrimidinedione‐2,4 (tegafur, THF‐5FU), was offered. The N(3) anion was found from spectral data to be more thermodynamically stable than the N(1) anion by 2.40 kJ mol−1 (calculated value 2.24 kJ mol−1) in an alkaline–water solution. Both alkaline–water and alkaline–DMSO solutions of THF‐5FU (THF‐5FU/KOH = 1/1) were characterized by the ratio of the equilibrium concentrations of the anion and diketo‐tautomer as 9:1 and 4.3:1, respectively. Copyright © 2014 John Wiley & Sons, Ltd.

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boldA > > boldD > boldB > boldЕ > boldС .

…”

Section: Introductionmentioning

confidence: 95%

“…). The nomenclature used to distinguish the different tautomers is described in . Tautomer F is energetically so unfavorable that it is not considered in most theoretical works .…”

Section: Introductionmentioning

confidence: 99%

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5-Fluorouracil solutions: NMR study of acid-base equilibrium in water and DMSO

Abdrakhimova

Ovchinnikov

Лобов

et al. 2014

J. Phys. Org. Chem.

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“…11 On the one hand, these dis crepancies can be due to the fact that the G 298 values used to calculate the concentrations of tautomers in solutions (see Table 2) were computed ignoring specific solvation, which can introduce considerable errors. 16,26, 27 On the other hand, the results of calculations based on spectro scopic data 11 can also include errors owing to the use of the chemical shift of the C(5) atom in the triazole ring of free aminotriazole bases as the "model" value of the signal of tautomer A, while the effect of protonation of the pyri dine ring on the chemical shift of the C(5) atom in tauto mers A was ignored.…”

Section: Resultsmentioning

confidence: 99%

The structure of protonated 3-pyridyl-substituted 5-amino-1H-1,2,4-triazoles: an experimental and theoretical study

et al. 2014

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The molecular and crystal structures and tautomerism of protonated isomeric 3 pyridyl substituted 5 amino 1H 1,2,4 triazoles were studied within the framework of density function al theory and by X ray analysis. According to B3LYP/6 311++G(2d,2p) calculations of six possible tautomeric forms A-F, tautomers A with the N protonated pyridine moiety are pre dominant in the gas phase. 5 Amino 4H 1 onium compounds (tautomers D) of higher polarity are next in stability; their relative energies decrease as follows: 3 pyridin 4 yl , 3 pyridin 3 yl , and 3 pyridin 2 yl 5 amino 4H 1,2,4 triazol 1 onium cation. A comparison of experimental 13 C NMR spectra of tautomers A and D with their NMR spectra calculated by the GIAO method showed that both tautomeric forms can coexist in comparable amounts in DMSO solutions. Tautomers A and D were detected by X ray analysis in crystals of 5 amino 3 (pyrid in 2 yl) 1H 1,2,4 triazolium salts.

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“…Previous the quantum chemical calculations had shown that the diketo form of HMU ( I ) is energetically the most favorable both in the gas phase and in case of hydration . It is stabilized by the intramolecular hydrogen bond.…”

Section: Resultsmentioning

confidence: 99%

Specific Intermolecular Interactions in the Supramolecular Structure of 5‐Hydroxy‐6‐Methyluracil: A DFT Study of the Hydrogen‐bonded Dimers

Shayakhmetova

Khamitov

Мустафин

et al. 2016

J Chinese Chemical Soc

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Studying the self‐assembly of uracil derivatives has great importance for biochemistry and nanotechnology. For example, modification of the sorbent surfaces by 5‐hydroxy‐6‐methyluracil (HMU) enhances their adsorption activity. It is assumed that these changes are caused by the self‐assembly of the network‐like supramolecular associates of the uracil derivative on the sorbent surface. In the present work, the relative stabilities of 15 hydrogen‐bonded dimers HMU have been studied by the TPSSh/TZVP density functional theory method and the strengths of the noncovalent interactions analyzed in terms of the reduced density gradient and natural bond orbital approaches. It was found that the symmetric dimer stabilized by two intermolecular hydrogen bonds N1–H∙∙∙O–C2 (dimer 1‐1) is the most stable. This suggests that the self‐assembly of HMU should occur through the intermediate formation of the dimer 1‐1. The results may be useful for understanding the processes of self‐assembly of the uracil derivatives and the rationalized design of the uracil‐based supramolecular structures with specific properties.

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Relative stability of keto-enol tautomers in 5,6-substituted uracils: Ab initio, DFT and PCM study

Cited by 31 publications

References 35 publications

5-Fluorouracil solutions: NMR study of acid-base equilibrium in water and DMSO

5-Fluorouracil solutions: NMR study of acid-base equilibrium in water and DMSO

The structure of protonated 3-pyridyl-substituted 5-amino-1H-1,2,4-triazoles: an experimental and theoretical study

Specific Intermolecular Interactions in the Supramolecular Structure of 5‐Hydroxy‐6‐Methyluracil: A DFT Study of the Hydrogen‐bonded Dimers

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