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  • 1
    Electronic Resource
    Electronic Resource
    Pressure and solvent isotope effects on the mobility of monovalent cations in water (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3662-3670 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Limiting molar conductivities of alkali metal chlorides (LiCl to CsCl) and tetraalkylammonium bromides (Me4NBr to Bu4NBr) in H2O and D2O were determined at 25 °C as a function of pressure up to 196.1 MPa. The limiting molar conductivities of the ions were obtained with the aid of transference numbers of KCl under high pressure, and transformed into the residual friction coefficients Δζobs to see what kinds of factors are important in the mechanism of ion migration. The pressure and solvent isotope effects on Δζobs of the Li+ ion agree qualitatively with the predictions of the Hubbard–Onsager (HO) dielectric friction theory, which indicates that dielectric friction plays an important role for smaller ions. However, the Cs+ ion shows opposite pressure and solvent isotope effects. For the R4N+ ions, Δζobs increases with an increase in the ionic radius and the pressure, opposite to the predictions of the HO theory. The increase in Δζobs for large R4N+ ions with increasing pressure suggests that the structure of the hydrophobic hydration shell is not weakened by pressure as much as that of bulk water. To make sure of this, the rotational correlation times of water molecules in pure D2O (τc°) and coordinated to the Bu4N+ ions (τc+) were estimated from 2H NMR spin-lattice relaxation times (T1) of D2O molecules at high pressure. The pressure dependence of τ+c/τ°c was in qualitative agreement with that of Δζobs(Bu4N+). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472236
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  • 2
    Electronic Resource
    Electronic Resource
    Improved treatment of inertia and non-Markovian effects on short-time dynamics of diffusion-controlled reaction based on generalized diffusion equation (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 10113-10122 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Starting from a generalized diffusion equation and the Collins–Kimball boundary condition, we investigated the inertia and the non-Markovian effects on the time-dependent rate constant of a diffusion-controlled reaction at short times. In the short-time limit, we obtained the rate constant analytically, and found that the rate constant was independent of the friction coefficient, and was always smaller than the result of the classical Smoluchowski–Collins–Kimball (SCK) theory in which both of the inertia and the non-Markovian effects were neglected. At finite times, we obtained the rate constant numerically, and found that the decay of the rate constant was slower than that of the SCK result. When the non-Markovian effect became larger, the decay became much slower. Our results were consistent with a relevant theory based on a generalized Fokker–Planck equation. The results were compared with computer simulations, and a good agreement was obtained for the case of the maximum reactivity. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474045
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  • 3
    Electronic Resource
    Electronic Resource
    Pressure and temperature effects on 2H spin-lattice relaxation times and 1H chemical shifts in tert-butyl alcohol- and urea-D2O solutions (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1360-1367 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The pressure and temperature effects of hydrophobic hydration were studied by NMR spectroscopy. The 1H chemical shifts (δ) were measured at 7.7, 29.9, and 48.4 °C under high pressure up to 294 MPa for HDO contained as impurity in neat D2O, 1 mol kg−1 tert-butyl alcohol (TBA)-D2O, and 1 mol kg−1 urea-D2O solutions, for the methyl group of TBA in the TBA-D2O solution, and for the amino group of urea in the urea-D2O solution. The 2H spin-lattice relaxation times (T1) were measured under the same conditions as the chemical shift measurements for D2O in neat D2O, TBA-D2O and urea-D2O solutions with organic contents up to 8 mol%. The following features are observed for the pressure effect on δ (HDO) and 2H-T1 in TBA-D2O solutions: (1) The δ (HDO) exhibits a downfield shift relative to that in neat D2O, and the difference of δ (HDO) between TBA solution and neat D2O becomes larger with increasing pressure at lower temperature. (2) The decrement of the rotational correlation time of water in the hydration shell of TBA (τcs) relative to the value at atmospheric pressure is smaller than that in the bulk (τc0). (3) The pressure coefficients of T1 are positive in dilute solutions but are negative in more than 4 to 5 mol% solutions. These results suggest that the hydrophobic hydration shell of TBA is different than the open structure of water present in bulk, and resists pressure more strongly than the open structure of water in the bulk. In solutions of 4 to 5 mol%, the hydration shell collapses. On the other hand, the τcs in the hydration shell of urea is slightly larger than that in bulk water at lower pressure, but is obviously larger at higher pressure. In view of the rotational motion of water molecules, urea seems to strengthen the water structure slightly rather than weaken it, although δ (HDO) approaches that in the bulk with pressure. It is difficult to classify urea into a structure maker or a breaker. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475509
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of potential of mean force on short-time dynamics of a diffusion-controlled reaction in a hard-sphere fluid (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6594-6602 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We calculated the time-dependent rate constant of a diffusion-controlled reaction between hard-spheres in a hard-sphere fluid at short times starting from the Fokker–Planck–Kramers equation combined with the approximation of half-range Maxwellian velocity distributions. For the potential function, we employed the potential of mean force (PMF) obtained from the equilibrium radial distribution function. The rate constant at short times was much larger than that neglecting the PMF effect, though the steady state rate constant did not sensitively depend on the PMF effect. This indicates that the effect of the initial distribution of the reactants is important in determining the rate constant at short times. The results were compared with a computer simulation. The dependences of the survival probability of a target on the time, the transmission coefficient, and the reactant concentration were examined, and satisfactory agreements between the calculation and the simulation were obtained at a relatively low density. At a high density, the non-Markovian effect should be taken into account to explain the simulation result. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474902
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure and isotope effects on the proton jump of the hydroxide ion at 25°C (1993)
    Springer
    Journal of solution chemistry 22 (1993), S. 1135-1149 
    Details
    ISSN: 1572-8927
    Keywords: Potassium deuteroxide ; potassium hydroxide ; excess conductance ; isotope effect ; pre-rotation of water molecules ; bending of hydrogen bonds with pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The limiting molar conductances Λ0 of potassium deuteroxide KOD in D2O and potassium hydroxide KOH in H2O were determined at 25°C as a function of pressure to disclose the difference in the proton-jump mechanism between an OH− (OD−) and a H3O+ (D3O+) ion. The excess conductance of the OD− ion in D2O λ E O (OD -), as estimated by the equation $$\lambda _E^O (OD^ - ) = \Lambda ^O (KOD/D_2 O) - \Lambda ^O (KCl/D_2 O)$$ increases a little with pressure as well as the excess conductance of the OH− ion in H2O $$\lambda _E^O (OH^ - ) = \Lambda ^O (KOH/H_2 O) - \Lambda ^O (KCl/H_2 O)$$ However, their rates of increase with pressure are much smaller than those of the excess deuteron and proton conductances, λ E O (D +) and λ E O (H +). With respect to the isotope effect on the excess conductance, λ E O (OH -)/λ E O (D +) decreases with presure as in the case of λ E O (H +)/λ E O (D +), but the value of λ E O (OH -)/λ E O (OD -) itself is much larger than that of λ E O (H +)/λ E O (D +) at each pressure. These results are ascribed to the difference in the pre-rotation of water molecules, which is brought about by the difference in the intial orientation of the rotating water molecule adjacent to the OH− (OD−) or the H3O+ (D3O+) ion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651695
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of temperature, pressure and isotope effects on the proton jump between the hydroxide and oxonium ion (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 973-987 
    Details
    ISSN: 1572-8927
    Keywords: Potassium deuteroxide and hydroxide ; excess conductance ; pre-rotation ; proton-jump mechanism ; repulsive force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The limiting molar conductances Λ° of potassium deuteroxide KOD in D2O and potassium hydroxide KOH in H2O were determined at 5 and 45°C as a function of pressure to clarify the difference in the temperature, pressure and isotope effects on the proton jump between an OD− (OH−) and a D3O+ (H3O+) ion. The excess conductances of the OD− ion in D2O and the OH− ion in H2O, λ E 0 (OD-) and λ E 0 (OH-), increase with increasing temperature and pressure as in the case of the excess deuteron and proton conductances, λ E 0 (D+) and λ E 0 (H+). However, the temperature effect on the excess conductance is larger for the OD−(OH−) ion than for the D3O+ (H3O+) ion but the pressure effect is much smaller for the OD− (OH−) ion than for the D3O+ (H3O+) ion. These findings are correlated with larger activation energies and less negative activation volumes found for the OD− (OH−) ion than for the D3O+ (H3O+) ion. Concerning the isotope effect, the value of λ E 0 (OH-)/λ E 0 (OD-) deviates considerably from $$\surd 2$$ at each temperature and pressure in contrast with that of λ E 0 (H+)/λ E 0 (D+), although both of them decrease with increasing temperature and pressure. These results are discussed mainly in terms of the difference in repulsive force between the OD− (OH−) or the D3O+ (H3O+) ion and the adjacent water molecule, the difference in strength of hydrogen bonds in D2O and H2O, and their variations with temperature, pressure, and isotope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00974098
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  • 7
    Electronic Resource
    Electronic Resource
    Pressure and temperature effects on the excess deuteron and proton conductance (1992)
    Springer
    Journal of solution chemistry 21 (1992), S. 971-985 
    Details
    ISSN: 1572-8927
    Keywords: Deuterium chloride ; heavy water ; proton jump ; excess conductance ; pressure and temperature effect ; isotope effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The limiting molar conductances Λ° of deuterium chloride DCl in D2O were determined as a function of pressure and temperature in order to examine the proton-jump mechanism in detail. The excess deuteron conductances λ°E(D +), as estimated by the equation [λ°E(D +) = Λ°(DCl/D 2 O) − Λ°(KCl/D 2 O)], increases with an increase in the pressure and temperature as well as the excess proton conductance [λ°E(H +) = Λ°(HCl/H 2 O) − Λ°(KCl/H 2 O)]. The isotope effect on the excess conductances, however, depends on the pressure and temperature contrary to the model proposed by Conway et al.: λ°E(H +)/λ°E(D +) decreases with increasing pressure and temperature. The magnitude of the decrease with pressure becomes more prominent at lower temperature. These results are discussed in terms of the pre-rotation of adjacent water molecules, the bending of hydrogen bonds with pressure, and the difference in strength of hydrogen bonds between D2O and H2O.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00650873
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  • 8
    Electronic Resource
    Electronic Resource
    Tetraethanolammonium counterions in surfactant and classical colloidal systems (1992)
    Springer
    Journal of solution chemistry 21 (1992), S. 445-457 
    Details
    ISSN: 1572-8927
    Keywords: Tetraethanolammonium dodecylsulfate ; colloidal systems ; mica surfaces ; critical micelle concentrations ; aggregation numbers ; hydrophobic ions ; hydrophilic ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Interaction forces between mica surfaces as a function of added tetraethanolammonium bromide, (EtOH)4NBr, were determined using surface forces measurements. Critical micelle concentrations and aggregation numbers were determined for tetraethanolammonium dodecylsulfate, (EtOH)4NDS, using surface tension and fluorescence probe-quencher measurements. The properties of the large hydrophilic counterion (EtOH)4N+ are compared to those of its hydrophobic analogue Pr4N+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00649698
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  • 9
    Electronic Resource
    Electronic Resource
    Pressure effect on proton jumps in dioxane-water mixtures at 25°C (1995)
    Springer
    Journal of solution chemistry 24 (1995), S. 343-355 
    Details
    ISSN: 1572-8927
    Keywords: Proton jump ; hydrogen-bonded networks ; excess proton conductance ; 1,4-dioxane-water mixtures ; pressure effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The limiting molar conductances Λo of hydrochloric acid and potassium chloride in 2.5, 5, 10, and 15 mol% 1,4-dioxane-water mixtures were determined at 25°C as a function of pressure up to 196.1 MPa from the conductances measured in the dilute concentration range. The value of Λo(HCl) was two to three times larger than that of Λo(KCl) in each solvent mixture as well as in pure water. The excess proton conductance, as estimated by the equation [λ E o =Λo(HCl)−Λo(KCl)], increased with pressure in each solvent mixture, although the value of λ E o itself decreased rapidly with an increase in the dioxane content. The rate of increase in λ E o with pressure was not so large in dioxane-water mixtures as in pure water, and became smaller with an increase in the dioxane content in contrast to the cases of ethanol-water and t-butyl alcohol (TBA)-water mixtures. These results are discussed in terms of the difference between a dioxane and an ethanol or a TBA molecule in ability to stabilize the hydrogen-bonded networks of water in the water-rich region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01150873
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of pressure on the conductivities of HCl and KCl in water at 0°C (1979)
    Springer
    Journal of solution chemistry 8 (1979), S. 881-886 
    Details
    ISSN: 1572-8927
    Keywords: HCl ; KCl ; conductivity ; aqueous solution ; high pressure ; proton jump ; molecular reorientation ; water structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electrical conductivities of hydrochloric acid and potassium chloride in water have been measured in the concentration range of 3×10 −4 –10 −3 moles-dm −3 at 0°C up to 3500 bar. The limiting molar conductance (Λ0) for HCl increases with increasing pressure, while Λ0(KCl) has a maximum around 1700 bar. The excess conductance of hydrogen ion [λ 0 E =Λ0(HCl)−Λ0(KCl)] increases with increasing pressure. Its pressure dependence indicates that the reorientation of water molecules, which is the rate-determining step in the proton jump, becomes faster at higher pressure. This anomaly is attributed to the distortion with pressure of the hydrogen bonds in water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644884
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