The division of thermodynamic solvation free energies of electrolytes into ionic constituents is conventionally accomplished by using the single-ion solvation free energy of one reference ion, conventionally the proton, to set the single-ion scales. Thus the determination of the free energy of solvation of the ...
PubMed Central
The COSMO cluster-continuum (CCC) solvation model is introduced for the calculation of standard Gibbs solvation energies of protons. The solvation sphere of the proton is divided into an inner proton-solvent cluster with covalent interactions and an outer ...
PubMed
... DIELECTRICS, SEMICONDUCTORS, ELECTRICAL CONDUCTIVITY, DEOXYRIBONUCLEIC ... TRANSFER, SOLVATION, PUMPS, HEMOGLOBIN ...
DTIC Science & Technology
The solvation of the lithium and sodium ions in dimethyl sulfoxide solution was theoretically investigated using ab initio calculations coupled with the hybrid cluster-continuum model, a quasichemical theory of solvation. We have investigated clusters of ions with up to five dimethyl sulfoxide (DMSO) molecules, and the bulk solvent was described by a ...
Energy Citations Database
The absolute hydration free energy of the proton, DGhyd298(H+), is one of the fundamental quantities for the thermodynamics of aqueous systems. Its exact value remains unknown despite extensive experimental and computational efforts. We report a first-principles determination of DGhyd298(H+) by using the latest developments in electronic structure theory ...
In solution, half-cell potentials are measured relative to other half-cells resulting in a ladder of thermodynamic values that is anchored to the standard hydrogen electrode (SHE), which is assigned an arbitrary value of exactly 0 V. A new method for measuring the absolute SHE potential is introduced in which reduction energies of ...
The relative acidities of water and methanol have been a nagging issue. In gas phase, methanol is more acidic than water by 36.0 kJ/mol; however, in aqueous solution, the acidities of methanol and water are almost identical. The acidity of an acid in solution is determined by both the intrinsic gas-phase ionization Gibbs energy and the solvent effects. With the availability of the accurate and ...
ERIC Educational Resources Information Center
This report from the Pennsylvania State University contains seven sections: (1) radiative rate effects in solvatlvatochromic probes; (2) intramolecular charge transfer reactions; (3) Solvation dynamics in low temperature alcohols; (4) Ionic solvation dynamics; (5) solvation and proton-transfer dynamics in ...
We developed a general theoretical framework to study the problem of proton solvation and transport in Nafion{reg_sign} and related materials.
This book presents information on the following topics: the Bronsted relation and the activation energy of electrode reactions; the chemical potential of an electron, absolute potential drop, and solvation energy in electrochemical kinetics; kinetic equations for discharge; the discharge of hydronium ions at a mercury cathode; the evolution of hydrogen at ...
... like radical formation, solvation of protons, and extensive ... both ion iormation and proton transfer. ... Mass resolved excitation spectra are presented for ...
Proton solvation and transport is a central element in innumerable fundamental chemical processes, from seemingly simple acid-base reactions to the exceedingly complicated proton transport channels integral to cellular respiration. The uniqueness of the hydrated proton, relative to other simple monovalent cations, ...
NASA Astrophysics Data System (ADS)
The hydrated electron is one of the most fundamental nucleophiles in aqueous solution, yet it is a transient species in liquid water, making it challenging to study. The solvation thermodynamics of the electron are important for determining the band structure and properties of water and aqueous solutions. However, a wide range of values for the electron ...
Solution-phase, half-cell potentials are measured relative to other half-cell potentials, resulting in a thermochemical ladder that is anchored to the standard hydrogen electrode (SHE), which is assigned an arbitrary value of 0 V. A new method for measuring the absolute SHE potential is demonstrated in which gaseous nanodrops containing divalent alkaline-earth or ...
... for the higher solvated protons which suggested differences in stability: no more than two molecules of dimethyl ether, acetaldehyde, or acetone will ...
... and Ethanol. Determination of Solvation Numbers and Exchange Rates. Descriptive Note : Semi-annual technical rept.,. ...
The experimental determination of the ionic work function is briefly described. Data for the proton, alkali metal ions, and halide ions in water, originally published by Randles (Randles, J. E. B. Trans Faraday Soc. 1956, 52, 1573) are recalculated on the basis of up-to-date thermodynamic tables. These calculations are extended to data for the same ions in four nonaqueous ...
... of a Prompt Gamma Ray Detector for Intense Bursts of Protons. ... for determining the intensity and duration of kiloampere pulsed proton beams is ...
Quasidegeneracy of Zwitterionic and Canonical Tautomers of Arginine Solvated by an Excess Electron it for arginine. New experimental efforts have concentrated on complexes of amino acids with neutral or ionic nonionic structure.13 In this contribution we focus on arginine, which has the largest proton affinity
E-print Network
A method for the study of preferential solvation in the outer coordination spheres from paramagnetic broadening of solvent proton n.m.r. signals was proposed by Frankel, Stengle, and Langford. It is now extended to determinations of the relative concentra...
National Technical Information Service (NTIS)
Many articles and papers were published; a few are still in preparation or will be published. The solvation dynamics studies will be extended to ionic solutions. Computer simulations were also performed. A new line of research was begun on excited-state proton-transfer reactions catalyzed by alcohol solvents. (DLC)
DOE Information Bridge
Ion channels and transporters are membrane proteins that selectively conduct ions either passively (channels) or actively using a chemical gradient of one ion (transporters). The H+/Cl- transporter, first discovered in bacteria, has now been shown to also occur in animals and plants. This talk will discuss computational approaches aimed at understanding the ion transit pathways through the ...
Values of the hydration constants K(f)(H(+)nw) of the proton in acetonitrile (AN) calculated previously from spectrophotometric measurements of the activity of the solvated proton, a(Hs+) in dilute perchloric acid solutions in the presence of water, using...
The protonation in acetonitrile (AN) of the bases (B) water, alcohols and diethyl ether has been studied by determining spectrophotometrically with Hammett indicators and dibromothymolbenzein their interaction with the solvated proton. Water forms the spe...
Proton solvation properties and transport mechanisms have been studied in hydrated Nafion using the self-consistent multistate empirical valence bond (SCI-MS-EVB) method that includes the effects excess proton charge defect delocalization and Grotthuss proton hopping. It was found that sulfonate groups influence ...
A new least-squares method based on cluster ion data and well-known bulk constraints has been used to determine the single-ion bulk solvation enthalpies of a set of monovalent ions. A value of -1153(6) kJ/mol has been determined for the standard solvation enthalpy of the proton. A value of 683(9) kJ/mol at 298 K has also been ...
The pulsed ion cyclotron resonance method for precise determinations of proton transfer equilibrium constants has been applied to 46 carbon, nitrogen, oxygen, phosphorus, sulfur, arsenic, and selenium bases, with duplicating overlapping sequences, to obtain the relative proton affinities of water and ammonia. Where comparison is possible, the results are ...
Figure 1) depend on water to solvate the protons generated by the ionization ofthe sulfonic acid groups. When the polymers are subjected to temperatures ...
NASA Website
The enthalpies of transfer of formamide, N-methylformamide and N,N-dimethylformamide from methanol to methanol + dimethylsulfoxide solvent systems have been measured. These data are analyzed in terms of a recently developed model of solvation in mixed solvents. The results of the data analyses indicate that preferential solvation of the different ...
Reactions of the hydroxide ion OH(-)(H2O)0,1,2,3, solvated with O-3 water molecules, have been studied in the gas phase using flow-tube and ion beam techniques. The reactions studied included proton transfer, nucleophilic displacement and isotope exchange...
... 1, 2 ..., n-3) hydrated proton cluster ions ... products (eg, benzyl radical, solvated protons, etc.) are ... two-color mass resolved excitation spectra of toluene ...
Page 1. I Jo H U Lf 00 I N ' " J> !939 " 3, FINAL REPORT CON CONTRACT N00014-85-K-0572 'I PROTONIC AND ELECTRONIC ...
Ionic reactions are reported for ammonia and the three methylamines. The major product ions are the protonated molecule ions and the higher solvates of these ions. Proton transfer, charge transfer, and hydride transfer reactions were observed in the tri-m...
(pyranine), indicator (fluorescein), and the bicarbonate ion that is made by the solvation), a pyranine molecule (FOH), which ejects a proton when excited by a photon; 2), fluorescein (Flu), a p of fluorescein is the carboxylate moiety of the fluorescein molecule, a site that differs from the chromophore
Ion cyclotron resonance techniques are used to measure relative heterolytic bond dissociation energies D(R/sup +/ - Br/sup -/) in the gas phase for a series of alkali cations, alkyl carbenium ions, acyl cations, and cyclic halonium ions. D(R/sup +/ - Br/sup -/) for adamantyl cation is found to be less than for tert-butyl cation. A proton affinity for norbornene of D(B - H/sup ...
A complete theoretical model chemistry algorithm (TMCA) for the prediction of thermodynamic properties of geochemically relevant gaseous and aqueous complexes, based on molecular quantum mechanics, is presented and discussed. Cr species are selected as a case study due to the high nuclear mass and the complex electronic structure of this transition metal. The various derived magnitudes are ...
Solvated interaction energy (SIE) is an end-point physics-based scoring function for predicting binding affinities from force-field nonbonded interaction terms, continuum solvation, and configurational entropy linear compensation. We tested the SIE function in the Community Structure-Activity Resource (CSAR) scoring challenge consisting of high-resolution ...
Nanoconfined liquids are of interest because of both their fundamental properties and their potential utility in an array of applications. The structure and dynamics of the liquid can be dramatically impacted by the geometrical constraints and the interactions with the interface. Understanding the molecular-level origins of these changes and how they are determined by the characteristics of the ...
The energetics of the ethylene ion-molecule reactions was investigated in more detail than previously possible in two body collision experiments by photoionization of the neutral van der Waals ethylene dimer. The stability of the (C/sub 2/H/sub 4/)/sup +/C/sub 2/H/sub 4/ ion-molecule collision complex has been determined to be 18.2 +- 0.5 kcal. The highest potential barriers along the reaction ...
The conventional resonance model describes carbonyls, imines, and thiocarbonyls, as well as their protonated analogues, by a superposition of two valence bond structures. Ab initio Breathing-Orbital Valence Bond computations on formaldehyde, formimine, and thioformaldehyde as well as their protonated forms are performed to directly quantify the weights of ...
A fast and accurate method to compute the total solvation free energies of proteins as a function of pH is presented. The method makes use of a combination of approaches, some of which have already appeared in the literature; (i) the Poisson equation is solved with an optimized fast adaptive multigrid boundary element (FAMBE) method; (ii) the electrostatic free energies of the ...
This paper investigates the relation between non-specific solvation and monofunctional aromatic compounds containing adehyde and nitro group also compounds capable of specific interaction with aromatic phenols. Enthalpies of solution of the compounds were determined on an isoperibolic calorimeter. The good agreement between the enthalpy of hydrogen-bond formation in the phenol ...
This book examines the physical chemistry of electrolytes in solution and in the molten state. Topics considered include ionic solvation (solvents, thermodynamic and transport properties, spectroscopic and diffraction methods, theoretical aspects of solvation), ionic interactions and activity behavior of electrolyte solutions (the Debye-Hueckel evaluation ...
The application of homogeneous-bias fields to a proton precessional magnetometer allows the measurement of the vector field by measuring the absolute scalar field F, declination variations DELTA D, and inclination variations DELTA I. The absolute scalar field can be measured to an accuracy of plus or minus 1 gamma and ...
This work presents a theoretical mechanistic study of the protonation of pyridine in water clusters, at the B3LYP/cc-pVDZ theory level. Clusters from one to five water molecules were used. Starting from previously determined structures, the reaction paths for the protonation process were identified. For complexes of pyridine with water clusters of up to ...
Recent calorimetric measurements of the solvation enthalpies of some dipeptide analogs confirm our earlier prediction that the principle of group additivity is not valid for the interaction of the peptide group with water. We examine the consequences for understanding the properties of peptide solvation. A major consequence is that the current value of the ...
ABS>By means of the pulse radiolysis technique, a short-lived transient species was observed in irradiated de-aerated ethanol and methanol, exhibiting an optical absorption throughout the visible and near infrared. This transient is suggested to be the solvated electron on the basis of the nature of the spectrum, the reactivity with hydrogen ion and with various ...
The excess proton in aqueous media plays a pivotal role in many fundamental chemical (e.g., acid-base chemistry) and biological (e.g., bioenergetics and enzyme catalysis) processes. Understanding the hydrated proton is, therefore, crucial for chemistry, biology, and materials sciences. Although well studied for over 200 years, excess ...
The objectives of this research endeavor are to determine the solvation numbers and rates of ligand exchange for selected aluminum, gallium, and indium salts in methanol and ethanol utilizing a Varian EM-390 Nuclear Magnetic Resonance Spectrometer.
This report examines point defects in ice: molecular defects (vacancies and interstitials), protonic point defects (ions and Bjerrum defects) and electronic point defects (solvated electrons and radicals). Experimental results and theoretical models of th...
Gaseous ionic reactions have been observed for a series of oxygenated compounds in the source of a mass spectrometer at pressures up to a few tenths of a torr. The major produce ions were the solvated protons. Major differences in relative abundances were...
Nuclear magnetic resonance chemical shifts of hydronium and hydroxyl ions with respect to water were calculated. The shifts for both ions were downfield and of the order of 10 ppm. The effects of solvation shifts were investigated. (M.C.G.)
We propose a method for calculating the Gibbs energies of hydrogen bonding of solutes with associated solvents via the thermodynamic analysis of experimental values of solvation Gibbs energies. The method is applied to solutions of different proton acceptors in methanol. It is shown that the contribution of hydrogen bonding processes to the ...
The solvate state (stoichiometry, constants of formation, stereochemical parameters of solvates) of the transyttrium lanthanide ions (Tb{sup 3+}, Dy{sup 3+}, Ho{sup 3+}, Er{sup 3+}, Tm{sup 3+}, Yb{sup 3+}) in water-hexamethylphosphoramide media is studied using the proton magnetic relaxation and paramagnetic birefringence methods in ...
For the first time, the dynamic protonation equilibrium between an amino acid side chain analogue and bulk water as well as the diffusion properties of the excess proton were successfully reproduced through unbiased computer simulations. During a 50 ns Q-HOP MD simulation, two different regimes of proton transfer were observed. ...
Proton transfer in a phenol-amine complex dissolved in polar molecule nanoclusters is investigated. The proton transfer rates and mechanisms, as well as the solvation of the complex in the cluster, are studied using both adiabatic and nonadiabatic dynamics. The phenol-amine complex exists in ionic and covalent forms and as the size of ...
In this paper, the absolute calibration of photostimulable image plates (IPs) used as proton detectors is presented. The calibration is performed in a wide range of proton energies (0.5-20 MeV) by exposing simultaneously the IP and calibrated detectors (radiochromic films and solid state detector CR39) to a source of broadband ...
Picosecond time-resolved emission spectroscopy has been used to measure the rate of charge transfer and solvation of 9,9'-bianthryl in several solvents and solvent mixtures. In nonpolar and aprotic polar solvents no rise times were detected, indicating that all charge transfer and solvation occur within the 10-ps experimental resolution. In linear ...
Gradual solvation of protons by water is observed in liquids by mixing strong mineral acids with various amounts of water in acetonitrile solutions, a process which promotes rapid dissociation of the acids in these solutions. The stoichiometry of the reaction XH(+) + n(H(2)O) = X + (H(2)O)(n)H(+) was studied for strong mineral acids (negatively charged X, ...
Quantum chemical solvation models usually rely on the equilibrium solvation condition and is thus not immediately applicable to the study of nonequilibrium solvation dynamics, particularly those associated with chemical reactions. Here we address this problem by considering an effective Hamiltonian for solution-phase reactions based on ...
Positional distributions, absolute intensities, energy spectra, and angular distributions of energetic electrons and protons in the Jovian magnetosphere are discussed. (GRA)
Diphenyldiazomethane radical anion (Ph{sub 2}CN{sub 2}{sup {sm bullet}{minus}}) has been generated by radiolytic reduction of diphenyldiazomethane (Ph{sub 2}CN{sub 2}) in both protic and aprotic solvents. The absolute kinetics of formation and reactivity of Ph{sub 2}CN{sub 2}{sup {sm bullet}{minus}} were obtained by monitoring its transient absorption following nanosecond ...
The fluorescence quantum yields of solutions of 4-dimethylaminochalcone (DMC) in a series of individual solvents of different chemical nature have been measured using a technique based on studying the kinetics of fluorescence decay. A new quantitative regularity, namely, the dependence of the fluorescence quantum yield on the absolute solvation shift in ...
... Antarctica, are conducted with a GSM-19W high sensitivity proton magnetometer sensor, using the Overhauser effect to detect the absolute magnetic field. ...
Double resonance was used to determine the value and absolute sign of the geminal coupling between carbon-13 and a proton. Acetaldehyde was used as an example. (Author)
and is terminated by addition of Norit A,. 3 but not the protons released. The Norit is. The release of tritium shows an absolute requirement for tetra- ...
Understanding the hydrated proton is a critically important problem that continues to engage the research efforts of chemists, physicists, and biologists because of its involvement in a wide array of phenomena. Only recently have several unique properties of the hydrated proton been unraveled through computer simulations. One such process is the detailed ...
Three different intensity monitors were tested in the external proton beam at LAMPF, and together cover the entire range of beam currents available. A 800 kg Faraday cup was installed and used to measure the absolute intensity to better than 1 percent for...
New insight into a variety of phenomena of interest in liquids have been derived from recent studies in our laboratory. In particular, new findings have contributed to identifying the structure of protonated complexes among species of varying proton affinities, and quantifying the variations in spectroscopic properties of chromophores as influenced by ...
Matrix proton ENDOR signals have been measured for stabilized excess electrons produced by x irradiation at 4 K in ethylene glycol/water and in 2-methyletrahydrofuran glasses. The matrix proton ENDOR linewidths are smaller when irradiation is carried out ...
The reaction free energies and associated pK(a) values for proton transfer from positively charged tryptophan (HTrp(+)) to the two pure ionic liquids (ILs) BMIM-PF6 and BMIM-BF4 are derived from molecular simulations. IL solvation effects are examined with molecular dynamics simulations together with an empirical force field in which the average charge ...
Based on an analysis of literature data, it is concluded that protonation of organic molecules B in B-AH fluid binary systems is accompanied by the formation of (B�H�B)+ and (A�H�A)- ions with strong hydrogen bond in which the proton is delocalized between molecules B or ions A-. Conditions for forming neutral structures (A-H+�B) with strong ...
Proton transfer in protic ionic liquids is poorly understood. Some acid/base proton transfer reactions do not proceed to the extent that is expected from Delta pK(a)(aq) data from aqueous solutions, yet some do. In this work we have investigated protic ionic liquids obtained by proton transfer from a common acid, acetic acid, to a ...
) S2 #12;Correction factors for the intensity reduction of NOEs from various ribose protons to the 2OH are then averaged for each type of ribose proton. The correction factors for the effect of passive couplings of ribose proton, because the absolute NOE intensity for each type of protons is ...
Details on the mechanism of HF catalyzed isobutylene-isobutane alkylation were investigated. On the basis of available experimental data and high-level quantum chemical calculations, a detailed reaction mechanism is proposed taking into account solvation effects of the medium. On the basis of our computational results, we explain why the density of the liquid media and ...
We have performed a series of first-principles electronic structure calculations to determine the most stable structures of F-(H2O)n clusters (n = 4, 8, 12, and 16) and to determine the hydration free energy of fluoride anion (F-). The calculated results show that a new, tetrahedrally coordinated fluoride anion hydration structure F-(H2O)4 cluster is lower in Gibbs free energy than the previously ...
Building on the SVPE (surface and volume polarization for electrostatics) model for electrostatic contributions to the free energy of solvation with explicit consideration of both surface and volume polarization effects, on the SMx approach to including first-solvation-shell contributions, and on the linear relationship between the electric field and ...
A new analysis for two pulse and three pulse electron spin echo modulation data is presented which is independent of the echo decay function. The experimental ratios of maxima to minima of the echo modulation curve are compared with simulated ones to obtain the number of interacting nuclei, their distances, and their isotropic coupling by a least squares fit. From the best simulation, the ...
In this work density functional calculations and continuum solvation methods are applied to various biomolecular systems spanning a wide range of sizes. Gas phase calculations at the B3LYP/6-311++G(3df,2p)//B3LYP/6-31++G(d,p) level of theory are used in conjunction with extensive experimental data collected by collaborators to derive a comprehensive infrared spectral ...
... 4. TITLE AND SUBTITLE "SOLVATION OF COBALT SALTS BY ... "SOLVATION OF COBALT SALTS BY OLIGOMERIC POLYETHERS" by ...
Proton transfer in biological systems is thought to often proceed through hydrogen-bonded chains of water molecules. The ion channel, gramicidin A (gA), houses within its helical structure just such a chain. Using the density functional theory based ab initio molecular dynamics Car-Parrinello method, the structure and dynamics of proton diffusion through a ...
The hydration free energies relative to that of the proton are calculated for a representative set of monatomic ions Z+/-. These include cationic forms of the alkali earth elements Li, Na, and K, and anionic forms of the halogens F, Cl, and Br. In the current model the relative ion hydration free energy is defined as ...
The characterization of two polymorphs of the title compound (F2692; 1) by differential scanning calorimetry (DSC), microanalysis, proton nuclear magnetic resonance spectroscopy, thermogravimetry, thermomicroscopy, infrared spectroscopy, and X-ray diffractometry is described. Both polymorphs are crystalline, with form II being more stable at temperatures less than 160 degrees ...
Proton resonance spectra of EDTA, MEDTA, and HEDTA complexes of diamagnetic ions including alkali, alkaline earth, and rare earth metals are described. Quartet splittings of the methylenic protons of the acetate groups, indicative of long-lived metal--nitrogen bonds, are found for each ligand in the complexes of the cations of higher charge density. The ...
Mixed clusters of protonated benzene and water are created via arc discharge in a molecular beam cluster source. Infrared spectroscopy (1000 Cm-1 to 4500 Cm-1) of these mixed clusters H+(H_2O)_x(Bz)_y (x=1-4, y=1-4) tagged with argon is employed to investigate the structures of these clusters, particularly with regards to the location of the proton. ...
Gas-phase basicities of four polyfunctional N1,N1-dimethyl-N2-azinylformamidines (1-4) are obtained from proton-transfer equilibrium constant determinations, using Fourier transform ion-cyclotron resonance mass spectrometry. Comparison with model amidines and azines (GB revised according to the recent compilation of Hunter and Lias) indicates the aza group as the favored site ...
Consequences of proton-transfer reactions in guanidine in the solid state, solution and gas phase are discussed. Y-delocalization, resonance and symmetry strongly influence the basicity of guanidine in the gas phase. These effects are however insufficient to explain the basicity of guanidine which in aqueous solution is stronger than that of trisubstituted alkylamines and ...
Variational transition state theory (VTST) is used to calculate rate constants for a model proton transfer reaction in a polar solvent. We start from an explicit description of the reacting solute in a solvent, and we model the effects of solvation on the reaction dynamics by a generalized Langevin equation (GLE) for the solute. In this description, the ...
The solvatochromic properties of the free base and the protonated 5, 10, 15, 20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) were studied in pure water, methanol, ethanol (protic solvents), dimethylsulfoxide, DMSO, (non-protic solvent), and their corresponding aqueous-organic binary mixed solvents. The correlation of the empirical solvent polarity scale (E(T)) values of TPPS ...
