scholarly journals Solvation enthalpies of the proton in polar and non-polar solvents: Theoretical study

2013 ◽  
Vol 6 (1) ◽  
pp. 60-63 ◽  
Author(s):  
Lenka Rottmannová ◽  
Peter Škorňa ◽  
Ján Rimarčík ◽  
Vladimír Lukeš ◽  
Erik Klein
Keyword(s):  
Integral Equation ◽  
Proton Transfer ◽  
Continuum Model ◽  
Theoretical Study ◽  
Solvent Molecule ◽  
Solution Phase ◽  
Basis Sets ◽  
Polar Solvents ◽  
Polarized Continuum Model ◽  
Acceptor Atom

Abstract In spite of the importance of proton transfer in solution-phase processes, there is still no systematic theoretical study of proton solvation enthalpies. We have investigated the solvation enthalpies of the proton in seven solvents of various polarities (benzene, chloroform, acetone, methanol, ethanol, DMSO, water) using the Integral Equation Formalism Polarized Continuum Model (IEF-PCM). All computations were performed at the B3LYP and BHLYP levels of theory with aug-cc-pVDZ, aug-cc-pVTZ and aug-cc-pVQZ basis sets. Our calculations have shown that the B3LYP and BHLYP functionals provide similar solvation enthalpies. Finally, differences in the solvation enthalpy of the proton values stemming from the various basis sets do not exceed 6 kJ mol-1, with exception of DMSO and chloroform. Distance between H+ and the acceptor atom of the solvent molecule is the shortest in the case of water. It has been also found that the B3LYP distances are slightly longer.

scholarly journals Solvation enthalpies of the electron in polar and non-polar solvents: Theoretical study

2014 ◽  
Vol 7 (1) ◽  
pp. 31-33 ◽  
Author(s):  
Peter Škorňa ◽  
Ján Rimarčík ◽  
Erik Klein
Keyword(s):  
Integral Equation ◽  
Electron Transfer ◽  
Continuum Model ◽  
Theoretical Study ◽  
Solution Phase ◽  
Basis Sets ◽  
Polar Solvents ◽  
Electron Solvation ◽  
Polarized Continuum Model ◽  
Benzene Toluene

Abstract Although the electron transfer is a part of many important processes in biosystems that occur in the solution-phase, there is still no systematic theoretical study of the electron solvation enthalpies. The solvation enthalpies of the electron in different solvents of various polarities: benzene, toluene, acetone, methanol, ethanol, DMSO and water, are investigated. All calculations were performed by B3LYP, BHLYP and PBE approaches with aug-cc-pVDZ, aug-cc-pVTZ and aug-cc-pVQZ basis sets, using the Integral Equation Formalism Polarized Continuum Model (IEF-PCM). The calculations show that the B3LYP and PBE functionals provide similar results. With the exception of benzene, toluene and DMSO, the differences in values for all solvents are lower than 6 kJ mol-1. The BHLYP solvation enthalpies are higher by 20-25 kJ mol-1 than the B3LYP ones.

scholarly journals Improving Solvation Energy Predictions Using The SMD Solvation Method and Semiempirical Electronic Structure Methods

2018 ◽  
Author(s):  
Jimmy C. Kromann ◽  
Casper Steinmann ◽  
Jan Halborg Jensen
Keyword(s):  
Continuum Model ◽  
Solvation Energy ◽  
Solvation Model ◽  
Polar Solvents ◽  
Data Set ◽  
Solvation Energies ◽  
Polarized Continuum Model ◽  
Electronic Structure Methods ◽  
Aqueous Solvation ◽  
Model C

The PM6 implementation in the GAMESS program is extended to elements requiring d-integrals and interfaced with the conducter-like polarized continuum model (C-PCM) of solvation, in- cluding gradients. The accuracy of aqueous solvation energies computed using AM1, PM3, PM6, and DFTB and the SMD continuum solvation model is tested using the MNSOL data set. The errors in SMD solvation energies predicted using NDDO-based methods is considerably larger than when using DFT and HF, with RMSE values of 3.4-5.9 (neutrals) and 6-15 kcal/mol (ions) compared to 2.4 and ca 5 kcal/mol for HF/6-31G(d). For the NDDO-based methods the errors are especially large for cations and considerably higher than the corresponding COSMO results, which suggests that the NDDO/SMD results can be improved by re-parameterizing the SMD parameters focusing on ions. We found the best results are obtained by changing only the radii for hydrogen, carbon, oxygen, nitrogen, and sulfur and this leads to RMSE values for PM3 (neutrals: 2.8/ions: ca 5 kcal/mol), PM6 (4.7/ca 5 kcal/mol), and DFTB (3.9/ca 5 kcal/mol) that are more comparable to HF/6-31G(d) (2.4/ca 5 kcal/mol). Though the radii are optimized to reproduce aqueous solvation energies, they also lead more accurate predictions for other polar solvents such as DMSO, acetonitrile, and methanol, while the improvements for non-polar solvents are negligible.

scholarly journals Improving Solvation Energy Predictions Using The SMD Solvation Method and Semiempirical Electronic Structure Methods

2018 ◽  
Author(s):  
Jimmy C. Kromann ◽  
Casper Steinmann ◽  
Jan Halborg Jensen
Keyword(s):  
Continuum Model ◽  
Solvation Energy ◽  
Solvation Model ◽  
Polar Solvents ◽  
Data Set ◽  
Solvation Energies ◽  
Polarized Continuum Model ◽  
Electronic Structure Methods ◽  
Aqueous Solvation ◽  
Model C

The PM6 implementation in the GAMESS program is extended to elements requiring d-integrals and interfaced with the conducter-like polarized continuum model (C-PCM) of solvation, in- cluding gradients. The accuracy of aqueous solvation energies computed using AM1, PM3, PM6, and DFTB and the SMD continuum solvation model is tested using the MNSOL data set. The errors in SMD solvation energies predicted using NDDO-based methods is considerably larger than when using DFT and HF, with RMSE values of 3.4-5.9 (neutrals) and 6-15 kcal/mol (ions) compared to 2.4 and ca 5 kcal/mol for HF/6-31G(d). For the NDDO-based methods the errors are especially large for cations and considerably higher than the corresponding COSMO results, which suggests that the NDDO/SMD results can be improved by re-parameterizing the SMD parameters focusing on ions. We found the best results are obtained by changing only the radii for hydrogen, carbon, oxygen, nitrogen, and sulfur and this leads to RMSE values for PM3 (neutrals: 2.8/ions: ca 5 kcal/mol), PM6 (4.7/ca 5 kcal/mol), and DFTB (3.9/ca 5 kcal/mol) that are more comparable to HF/6-31G(d) (2.4/ca 5 kcal/mol). Though the radii are optimized to reproduce aqueous solvation energies, they also lead more accurate predictions for other polar solvents such as DMSO, acetonitrile, and methanol, while the improvements for non-polar solvents are negligible.

scholarly journals PROTON TRANSFER IN PHOSPHORUS-CONTAINING ACID–N,N-DIMETHYLFORMAMIDE SYSTEM WITH GLANCE OF ENVIRONMENT

2018 ◽  
Vol 59 (6) ◽  
pp. 37
Author(s):  
Lyubov P. Safonova ◽  
Irina V. Fedorova ◽  
Michael A. Krestyaninov
Keyword(s):  
Proton Transfer ◽  
Solvent Effect ◽  
Gas Phase ◽  
Energy Barrier ◽  
Continuum Model ◽  
Energy Surface ◽  
Molecular Complexes ◽  
Transfer Processes ◽  
Polarized Continuum Model ◽  
Phosphorus Containing

Proton transfer processes in the molecular and ion-molecular complexes of phosphorus acids (phosphoric H3PO4, phosphorous H3PO3, methylphosphonic СН3Н2РО3) with N,N-dimethylformamide (DMF) was studied. The potential energy surface (PES) for proton transfer was studied using the B3LYP/6-31++G(d,p) level of theory, and the solvent effect (here DMF) on the PES was included using the conductor polarized continuum model (CPCM). For all cases, the energy profile for proton transfer represents a double well curve, if intermolecular O…Odistance for the hydrogen bond considered has a fixed length equal to 2.7 Å. The solvent effect favors a proton transfer in the molecular complexes, but no shift of the equilibrium towards ionic pairs is observed. As a result, the energy values associated with proton transfer are significantly reduced in comparison with those found for the gas phase. The proton transfer in the complexes of H3PO4 with DMF is more favored than this process for the cases with H3PO3 and СН3Н2РО3. The probability of proton transfer in the Н3РО4–DMF and (Н3РО4)2–DMF is nearly identical. On the contrary, the barrier height for transfer in Н3РО4–(DMF)n for n=1÷3 increases with increasing number of DMF molecules. The energy barrier for proton transfer in the DMFH+–DMF and H3PO4–H2PO4– is lower than the ones for the molecular complexes.

Theoretical Study of Solvent Effect on π-EDA Complexation I. SCF and DFT Calculations Within Polarized Continuum Model on TCNE-Benzene Complex

2003 ◽  
Vol 68 (12) ◽  
pp. 2355-2376 ◽  
Author(s):  
Ondrej Kyseľ ◽  
György Juhász ◽  
Pavel Mach
Keyword(s):  
Complex Formation ◽  
Gibbs Energy ◽  
Solvent Effect ◽  
Gas Phase ◽  
Continuum Model ◽  
Solvent Polarity ◽  
Polar Solvents ◽  
Complexation Constant ◽  
Polarized Continuum Model ◽  
Eda Complex

SCF, MP2, DFT(B3LYP) and the polarizable continuum model (PCM) were used to study geometry, charge distribution and energetics of the π-EDA complex formation between tetracyanoethene (TCNE) and benzene both in gas phase and in various polar solvents (cyclohexane, dichloromethane and water). MP2/6-31G*, MP2/6-31+G*, MP2/6-31G*(0.25) calculations have shown that geometry of the complex is planparallel with interplane distance of 3.05 × 10-10 m on the MP2/6-31G* level and the complexation energy is equal to -6.8 to -8.95 kcal/mol, while dominant contributions to the complexation energy come from intermolecular correlation and energy. The PCM continuum model of polar solvents describes well both the Gibbs energy of solvation of individual solutes and the difference between the complex and its constituents and also agrees with the experimental finding that the polar solvent effect decreases the complexation constant of the π-EDA complex formation by a factor of 2-4 when chloroform is replaced by more polar dichloromethane, and by a factor of 9, when tetrachlormethane is replaced by dichloromethane. It seems that the solvation Gibbs energy of the π-EDA complex formation always prefers stability of solvated constituents to that of the solvated complex. The electrostatic polarization Gibbs energy of solvation is responsible for the tendency of complexation constants to decrease with increasing solvent polarity; however, non-electrostatic terms contribute as well. While the enthalpy of complexation between benzene and TCNE in gas phase is about -10.0 kcal/mol due to the negative complexation entropy ∆(∆S) = -22.56 cal/mol K, the ∆G of complexation is -3.8 kcal/mol. The solvation part of the complexation Gibbs energy in dichloromethane is +5.14 kcal/mol (PCM-SCF/6-31G* calculation) so that complexation constant K = 0.1 dm3/mol in this solvent was found.

Ionic dimerisation of trifluoropropenenitrile and its addition reactions with methyl trifluoropropenoate

1980 ◽  
Vol 45 (2) ◽  
pp. 406-414 ◽  
Author(s):  
Jiří Svoboda ◽  
Oldřich Paleta ◽  
Václav Dědek
Keyword(s):  
Reaction Mechanism ◽  
Proton Transfer ◽  
Substituent Effect ◽  
Solvent Molecule ◽  
Addition Product ◽  
Potassium Fluoride ◽  
Relative Reactivity ◽  
Addition Reactions ◽  
Tertiary Amines ◽  
Optimum Conditions

Dimerisation of trifluoropropenenitrile (I) in the presence of potassium fluoride and tertiary amines afforded a mixture of stereoisomeric perfluoro-4-methyl-pentenedinitriles (II), higher-boiling compounds, and 2,3,3,3-tetrafluoropropanenitrile (III) which arises by proton transfer from the solvent molecule. Under optimum conditions, product II was obtained in about 50% yield. Reaction of the nitrile I with methyl trifluoropropenoate (IV) gave, besides the dimers II and V, the product of addition of the nitrile I to the propenoate, IV, i.e. methyl 4-cyanoperfluoro-2-pentenoate (VI), and the addition product of the propenoate IV to the nitrile I, i.e. methyl 4-cyanoperfluoro-2-methyl-3-butenoate (VII). The relative reactivity if I and IV is discussed. The ratio of stereoisomers in II, V, VI and VII indicates that the magnitude of the steric substituent effect, operating in the reaction mechanism, decreases in the order -CFCF3.(COOCH3) > -CFCF3(CN) > -COOCH3 > -CN.

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