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.

Photorelaxation of imidazole and adenine via electron-driven proton transfer along H2O wires

2016 ◽  
Vol 195 ◽  
pp. 237-251 ◽  
Author(s):  
Rafał Szabla ◽  
Robert W. Góra ◽  
Mikołaj Janicki ◽  
Jiří Šponer
Keyword(s):  
Molecular Dynamics ◽  
Excited State ◽  
Potential Energy ◽  
Proton Transfer ◽  
Potential Energy Surface ◽  
Molecular Dynamics Simulations ◽  
Gas Phase ◽  
Energy Surface ◽  
Water Molecules ◽  
Dynamics Simulations

Photochemically created πσ* states were classified among the most prominent factors determining the ultrafast radiationless deactivation and photostability of many biomolecular building blocks. In the past two decades, the gas phase photochemistry of πσ* excitations was extensively investigated and was attributed to N–H and O–H bond fission processes. However, complete understanding of the complex photorelaxation pathways of πσ* states in the aqueous environment was very challenging, owing to the direct participation of solvent molecules in the excited-state deactivation. Here, we present non-adiabatic molecular dynamics simulations and potential energy surface calculations of the photoexcited imidazole–(H2O)5 cluster using the algebraic diagrammatic construction method to the second-order [ADC(2)]. We show that electron driven proton transfer (EDPT) along a wire of at least two water molecules may lead to the formation of a πσ*/S0 state crossing, similarly to what we suggested for 2-aminooxazole. We expand on our previous findings by direct comparison of the imidazole–(H2O)5 cluster to non-adiabatic molecular dynamics simulations of imidazole in the gas phase, which reveal that the presence of water molecules extends the overall excited-state lifetime of the chromophore. To embed the results in a biological context, we provide calculations of potential energy surface cuts for the analogous photorelaxation mechanism present in adenine, which contains an imidazole ring in its structure.

Bicyclo[2.1.1]hex-1-yl Cation: an Ab Initio Study of the C6H9+ Potential-Energy Surface

1993 ◽  
Vol 46 (8) ◽  
pp. 1301 ◽  
Author(s):  
CH Schiesser
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Gas Phase ◽  
Energy Barrier ◽  
Energy Surface ◽  
Molecular Orbital Theory ◽  
Extensive Investigation ◽  
Ab Initio Study ◽  
Orbital Theory

An extensive investigation of the C6H9+ potential-energy surface by ab initio molecular orbital theory is reported. Calculations at the RHF/6-31G* level of theory predict that the bicyclo[2.1.1]hex-1-yl cation (2b) rearranges to the 3-methylenecyclopentyl cation (7b) with an energy barrier of only 0.3 kJ mol-1. Inclusion of electron correlation in the calculation casts doubt on the gas-phase existence of (2b) which is predicted to rearrange without barrier at the MP2/6-31G* level of theory.

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 DFT study on the mechanism of simultaneous trifluoromethylation and oximation of aryl-substituted ethylene.

2021 ◽  
Author(s):  
Sen Wang ◽  
Ao He ◽  
Xuan Meng ◽  
Xiao wei Lan ◽  
Xianfu Wei ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Proton Transfer ◽  
Organic Solvent ◽  
Solvent Effect ◽  
Aromatic Ring ◽  
Organic Solvents ◽  
Energy Barrier ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

The effects of different substituents located at the para position of the aromatic ring and β carbon atom of the styrene on the reaction were investigated. The results showed that the reaction steps with higher energy barriers changed a little with the substituents of the reactants, which indicates that the reaction has a good adaptability to reactants containing different substituents. It was found the proton transfer in the final tautomerism step of nitroso intermediate to oxime is the rate limiting step under anhydrous conditions. Although the solvent effect did not influence the the rate limiting step significantly, the water mediated proton transfer significantly decreased the energy barrier of final tautomerism step. Compared with the direct proton transfer in vacuum, the energy barrier of the final tautomerism step decreased from 57.80kcal/mol in vacuum to 12.98kcal/mol with the water mediated proton transfer in water, which declined by 77.5%. When water participates in rate-limiting steps in organic solvents, the energy barrier also decreases significantly, which indicates that a small amount of water in the organic solvent is conducive to the reaction. This study is of great significance for the application of bifunctionalized reaction in the synthesis of organic fluoride compounds with different substituents.

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