Theoretical investigation of solvent effect on the keto-enol tautomerization of pentane-2,4-dione and a comparison between experimental data and theoretical calculations

2020 ◽  
Author(s):  
Sepideh Mehrani ◽  
Sayyed Faramarz Tayyari ◽  
Mohamad Momen-Heravi ◽  
Ali Morsali
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Equilibrium Constants ◽  
Solvent Polarity ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Mechanical Methods ◽  
Intramolecular Hydrogen

The equilibrium constants of stable keto and enol forms of pentane-2,4-dione (known as acetylacetone) are estimated, using the second-order Møller−Plesset (MP2), density functional theory (B3LYP and M06-2X), composite methods (G4, G3, G3B3, CBS-QB3, and G3MP2B3), and double-hybrid density functional theory (B2PLYP), long-range corrected (LC) hybrid functional (ωB97X-D). These methods are integrated with the PCM, CPCM, and SMD models to elucidate the effect of solvent on thermodynamic parameters. The reported measured enol contents in the solutions and gas phase are utilized to benchmark the predictions of different quantum mechanical methods for the keto-enol equilibrium in acetylacetone, AA. In this study, we calculated the enol content in sixteen acetylacetone solutions as well as in the gas phase. Among the applied methods, the MP2 level underestimates while the B3LYP level overestimates the enol content of acetylacetone in the gas phase and solutions. The G3B3 and G3MP2B3 levels give reasonable agreement with the measured data. The best results obtained by calculations at the B2PLYP/6-31+G(2d,p) and CBS-QB3 levels, with mean absolute errors (MAE) relative to experiments of 2.30 and 5.45 and root mean square deviation (RMSD) errors in the 0.78 and 1.66 respectively. According to our calculations, one enol and two keto forms (Ket1 and Ket2) coexist in polar solutions. The effect of the solvent was more pronounced on the structure and stability of Ket2 tautomer than others. The strength of the intramolecular hydrogen bond in the enol form of AA is almost independent of the solvent polarity.

scholarly journals Density Functional Theory Calculation of Molecular Descriptors for Simple Coumarins in Gas and Different Solvents

2020 ◽  
Vol 32 (10) ◽  
pp. 2545-2552
Author(s):  
Poodari Sumalatha ◽  
Mannam Subbarao
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Energy Gap ◽  
Theoretical Calculations ◽  
Density Functional Theory Calculation ◽  
Log P ◽  
Full Geometry Optimization ◽  
Functional Theory ◽  
Functional Density Theory

The primary aim of this study is to show the importance of molecular structure analysis of pharmaceutical active coumarins compounds using quantum chemistry methods based on density functional theory. To explore the theoretical calculations for global descriptors, the standard Gaussian 09W program was used for coumarins compounds. The full geometry optimization was carried out by the B3LYP/6-311G level of theory. The octanol-water and air-water partition coefficients were also estimated using functional density theory. The order of the HOMO-LUMO energy gap for studied coumarins in the gas phase is umbelliferone (UBA) < (herniarin) HNR ~ (crenulatin) CNT < (scopoletin) SCT < (scoparone) SCO < (isoscopoletin) IST < (4-methylesculetin) MST < (umbelliferone-2- carboxylic acid) UCA < (isofraxidin) IFD < (fraxetin) FXT < (aesculetine) ACT < (dapnetine) DPT. Therefore, UBA molecule in gas phase is less stable. Compared to the measured index of electrophilicity (DE). The MST molecule is stronger, more reactive, nucleophile electrophile at the gas phase and in solvents. In all solvent phases, CNT and UCA molecules have lower values, which mean they are strong nucleophiles. From the log P values of ACT and MST coumarins are in between 1.35-1.8, so ACT and MST coumarins use oral and intestinal absorptions.

THERMOCHEMICAL PROPERTIES OF THE THIOCARBONYLTHIO COMPOUNDS FROM CONVENTIONAL DENSITY FUNCTIONAL THEORY CALCULATIONS

2010 ◽  
Vol 09 (supp01) ◽  
pp. 201-217
Author(s):  
ZHI-HUI ZHANG ◽  
TAO GAO ◽  
XIAO-FENG TIAN ◽  
NA HE
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Theoretical Data ◽  
Density Functional Theory Calculations ◽  
Good Method ◽  
Free Energies ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Reversible Addition

Density functional theory (DFT) calculations employed at two levels, B3LYP/6-31G+(d) and B3P86/6-31G+(d), are reported for the geometry, enthalpy, and free energy of reaction of a number of dithiobenzoate reversible addition fragmentation transfer (RAFT) reagents ( S=C(Ph)S–R , S=C(Z)S–CH2Ph ). Based on these theoretical data, the effectiveness of these RAFT reagents is analyzed. The conclusions, especially obtained at B3LYP/6-31G+(d) level, are in good agreement with the experimental results. Our calculations suggest that the dithiobenzoate ( S=C(Z)S–CH2Ph ), where Z is OC6H5 or N(alkyl)2 , is a poor RAFT reagent. Contrarily, the compound S=C(Ph)S–R , where R is C(Me)2Ph or C(Me)2CN , is a highly efficient RAFT reagent. Our results reveal the utility of the theoretical calculations of physical magnitudes for the rationalization of judging the effectiveness of RAFT reagents and demonstrated that DFT is a good method to calculate these data. In addition, our results on the enthalpies and Gibbs free energies of formation for the R radicals are calculated with the same method. These data are important for the design of logical and economical chemical process. Finally, the B3LYP hybrid functional is employed to predict the values of thermodynamic magnitudes for several new ithiobenzoates. Those results need to be verified by future experimental measurements or theoretical calculations.

scholarly journals Strong intramolecular hydrogen bonding in protonated β-methylaminoalanine: A vibrational spectroscopic and computational study

2018 ◽  
Vol 25 (1) ◽  
pp. 133-141 ◽  
Author(s):  
Bryan D Linford ◽  
Andrea Le Donne ◽  
Debora Scuderi ◽  
Enrico Bodo ◽  
Travis D Fridgen
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Gas Phase ◽  
Secondary Amine ◽  
Density Functional ◽  
Experimental Spectrum ◽  
Intramolecular Hydrogen Bonding ◽  
Energy Structure ◽  
Functional Theory ◽  
Intramolecular Hydrogen

The gas-phase structure of protonated β-methylaminoalanine was investigated using infrared multiple photon dissociation spectroscopy in the C–H, N–H, O–H stretching region (2700–3800 cm−1) and the fingerprint region (1000–1900 cm−1). Calculations using density functional theory methods show that the lowest energy structures prefer protonation of the secondary amine. Formation of hydrogen bonds between the primary and secondary amine, and the secondary amine and carboxylic oxygen further stabilize the lowest energy structure. The infrared spectrum of the lowest energy structure originating with harmonic density functional theory has features that generally match the positions of the experimental spectra; however, the overall agreement with the experimental spectrum is poor. Molecular dynamics calculations were used to generate a gas-phase infrared spectrum. With these calculations a reasonable match with the experimental spectrum, especially in the high-energy region, was obtained. The results of the molecular dynamics simulation support the density functional theory calculations, with protonation of the secondary amine and the formation of a hydrogen bond between the protonated secondary amine and the primary amine. This work shows the importance of accounting for anharmonic effects in systems with very strong intramolecular hydrogen bonding.

Theoretical and Experimental Evaluation of the Effect of Fluorinated Substituent on the Topological Landscape and Thermodynamic Stability of Zeolitic Imidazolate Framework Polymorphs

2018 ◽  
Author(s):  
Mihails Arhangelskis ◽  
Athanassis Katsenis ◽  
Novendra Novendra ◽  
Zamirbek Akimbekov ◽  
Dayaker Gandrath ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Mechanochemical Synthesis ◽  
Thermodynamic Stability ◽  
Experimental Evaluation ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Zeolitic Imidazolate Framework ◽  
Functional Theory ◽  
Calorimetric Measurements ◽  
And Calorimetry

By combining mechanochemical synthesis and calorimetry with theoretical calculations, we demonstrate that dispersion-corrected periodic density functional theory (DFT) can accurately survey the topological landscape and predict relative energies of polymorphs for a previously inaccessible fluorine-substituted zeolitic imidazolate framework (ZIF). Experimental screening confirmed two out of three theoretically anticipated polymorphs, and the calorimetric measurements provided an excellent match to theoretically calculated energetic difference between them.<br>

Exploring chemistry features of favipiravir in octanol/water solutions

2021 ◽  
pp. 1-12
Author(s):  
Halimeh Rajabzadeh ◽  
Ayla Sharafat ◽  
Maryam Abbasi ◽  
Maryam Eslami Gharaati ◽  
Iraj Alipourfard
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Partition Coefficients ◽  
Density Functional ◽  
Water Solution ◽  
Peptide Group ◽  
Functional Theory ◽  
Water Solutions ◽  
Group Rotations ◽  
Heterocyclic Structure

Favipiravir (Fav) has become a well-known drug for medication of patients by appearance of COVID-19. Heterocyclic structure and connected peptide group could make changes for Fav yielding different features from those required features. Therefore, it is indeed a challenging task to prepare a Fav compound with specific features of desired function. In this work, existence of eight Fav structures by tautomeric formations and peptide group rotations were obtained using density functional theory (DFT) optimization calculations. Gas phase, octanol solution, and water solution were employed to show impact of solution on features of Fav besides obtaining partition coefficients (LogP) for Fav compounds. Significant impacts of solutions were seen on features of Fav with the obtained LogP order: Fav-7 >  Fav-8 >  Fav-4 >  Fav-3 >  Fav-2 >  Fav-5 >  Fav-1 >  Fav-6. As a consequence, internal changes yielded significant impacts on features of Fav affirming its carful medication of COVID-19 patients.

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