Computational study of keto–enol equilibria of tropolone in gas and aqueous solution phase

Paine, Stuart W.; Salam, A.

doi:10.1016/j.chemphys.2006.09.027

Cited by 15 publications

(10 citation statements)

References 29 publications

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“…For instance in gas phase, relative ratios of numbers of molecules of (8) relative to (10) and (11) (reciprocal of equilibrium constant) are 7.71 × 10 13 :1 and 1.30 × 10 16 :1, respectively, while in solution, relative proportions of species (9) to molecules (10) and (11) are 4.04 × 10 15 :1 and 8.63 × 10 16 :1, respectively. The trends observed follow that found previously for hydroxycyclopropenone,13 tropolone,14 and C 3 H 2 S 2 38. As expected from the small differences in relative Gibbs free energy between species (9) and (8), and between (11) and (10), the corresponding equilibrium constants are not too far from unity.…”

Section: Resultssupporting

confidence: 87%

“…Similar behavior is evident when examining the four dithio‐substituted tropolone species, with HF predicting compound (9) to be the least stable, with (10) being more stable than (11), and (8) lying lowest in energy. For each of the other methods, energies increase in the order (8), (9), (10), and (11), and match the order obtained previously for the keto‐enol tautomers of hydroxycyclopropenone13 and tropolone 14. Consistent results are again found for each of the methods that incorporate electron correlation effects.…”

Section: Resultssupporting

confidence: 85%

“…This has been rationalized on the basis of aromaticity featuring in the delocalized enolate ring structure, and is often simply understood using Hückel theory2 and the concept of resonance stabilization. These species have been studied extensively, both experimentally3–9 and theoretically,10–14 and not only in the context of tautomerism, but also to elucidate their properties and characteristics—both chemical and physical. These include the three‐membered ring system hydroxycyclopropenone,13, 15–17 a photochemical precursor to hydroxyacetylene, the six carbon ring compound phenol,11, 12 and tropolone,7–9, 14, 18–27 a seven‐membered cyclic conjugated ketone.…”

Section: Introductionmentioning

confidence: 99%

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Computational study of tautomerism and aromaticity in mono‐ and dithio‐substituted tropolone

Paine

Salam

2012

Int J of Quantum Chemistry

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Keto-enol tautomerism in mono-and dithio-substituted analogs of tropolone was investigated using electronic structure computations. Seven structural isomers of C 7 H 6 OS and four of C 7 H 6 S 2 were optimized fully in gas phase at HF and B3LYP theoretical levels in combination with the 6-311þþg** basis set, as well as with the CBS-QB3 and G3 methods. To examine the effects of an aqueous solvent on tautomeric equilibrium constants, each species was optimized in water using the selfconsistent reaction field polarizable continuum model at HF/6-311þþg** and B3LYP/6-311þþg** model chemistries. In both phases it was found that the enol forms were significantly more stable with respect to electronic energy and Gibbs free energy compared to the keto isomers, and outnumbered the keto species by several orders of magnitude. This was understood on the basis of elementary Hü ckel theory and the 4n þ 2 rule, and supported by nucleus independent chemical shifts computations of NMR chemical shifts in these seven membered cyclic systems.

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Section: Resultssupporting

confidence: 87%

Section: Resultssupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Computational study of tautomerism and aromaticity in mono‐ and dithio‐substituted tropolone

Paine

Salam

2012

Int J of Quantum Chemistry

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“…One of the ways of getting the most stable tautomer is to calculate the tautomeric equilibrium constant, K T , which is readily calculated from the Gibb's free energy via K T = e −Δ G /RT , where Δ G is the change in Gibb's free energy between products and reactants at temperature T and R is ideal gas constant 85. The Δ G value at B3LYP/6‐31G(d) level is predicted to be 0.349 kJ/mol between enol‐imine and keto‐amine tautomers of I .…”

Section: Resultsmentioning

confidence: 99%

Density functional computational studies on 2‐[(2,4‐Dimethylphenyl)iminomethyl]‐3,5‐dimethoxyphenol

Tanak

2011

Int J of Quantum Chemistry

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Density functional calculations of the structure, molecular electrostatic potential, and thermodynamic functions have been performed at B3LYP/6-31G(d) level of theory for the title compound of 2-[(2,4-dimethylphenyl)iminomethyl]-3,5dimethoxyphenol (I). To investigate the tautomeric stability, optimization calculations at B3LYP/6-31G(d) level were performed for the enol and keto forms of I. Calculated results reveal that the enol form of I is more stable than its keto form. The predicted nonlinear optical properties of I are much greater than ones of urea. The changes of thermodynamic properties for the formation of the title compound with the temperature ranging from 200 to 500 K have been obtained using the statistical thermodynamic method. At 298.15 K, the change of Gibbs free energy for the formation reaction of I is 32.973 kJ/mol. The title compound can not be spontaneously produced from the isolated monomers at room temperature. The tautomeric equilibrium constant is computed as 0.868 at 298.15 K for enol-imine$keto-amine tautomerization of I. In addition, natural bond orbital analysis of I was performed using the B3LYP/6-31G(d) method. V C 2011 Wiley Periodicals, Inc.

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“…One of the ways to get the most stable tautomer is to calculate the tautomeric equilibrium constant, K eq , which is readily calculated from the Gibb's free energy via K eq = e -DG/RT , where DG is the change in Gibb's free energy between products and reactants at temperature T, and R is the ideal gas constant [82]. The DG value at the B3LYP/6-311?…”

Section: Transition State and Kineticmentioning

confidence: 99%

Synthesis, spectroscopic investigations and computational study of monomeric and dimeric structures of 2-methyl-4-quinolinol

et al. 2015

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The present study aimed to determine an efficient and solvent-free method to synthesize 2-methyl-4-quinolinol (2MQ, also known as 4-hydroxy-2-methylquinoline) and includes spectroscopic investigations and computational studies. Molecular geometry and vibrational wavenumbers of 2MQ were investigated using the density functional (DFT/B3LYP) method with 6-311??G(d,p) and 6-311??G(2d,p) basis sets. According to calculations, the keto form of 2MQ is more stable than the annual form, and the dimeric conformation is predicted to be more stable than the monomeric conformations. A detailed analysis of the nature of the hydrogen bonding, using topological parameters such as electronic charge density, Laplacian, kinetic and potential energy density evaluated at the bond critical point, is also presented. The 1 H nuclear magnetic resonance chemical shifts of the molecule were calculated by the GIAO method. The molecule orbital contributions were studied by using total (TDOS) and partial (PDOS) density of states. The UV-visible spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were investigated by the time-dependent DFT (TD-DFT) approach. The linear polarizability (a) and the first-order hyperpolarizability (b) values of the investigated molecule were computed using DFT quantum mechanical calculations. The results show that the 2MQ molecule may have a nonlinear optical comportment with non-zero values. The stability and charge delocalization of the molecule was studied by natural bond orbital analysis.Electronic supplementary material The online version of this article (

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Computational study of keto–enol equilibria of tropolone in gas and aqueous solution phase

Cited by 15 publications

References 29 publications

Computational study of tautomerism and aromaticity in mono‐ and dithio‐substituted tropolone

Computational study of tautomerism and aromaticity in mono‐ and dithio‐substituted tropolone

Density functional computational studies on 2‐[(2,4‐Dimethylphenyl)iminomethyl]‐3,5‐dimethoxyphenol

Synthesis, spectroscopic investigations and computational study of monomeric and dimeric structures of 2-methyl-4-quinolinol

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