Rotation Of Water Molecules Research Articles

Dielectric Properties of Montmorillonites Saturated by Bivalent Cations

AbstractThis study deals with the analysis of dielectric measurements made on montmorillonites saturated by bivalent cations. These measurements are performed between — 150°C and +30°C at frequencies ranging from 300 to 10,000 Hz. Their interpretation is based on a numerical analysis allowing determination of the dielectric losses due to free charge carriers conductivity phenomena and losses due to relaxation phenomena. The free charge carriers conductivity is due to the movement of protons. It depends very much on the nature of compensating cations and on the water content and seems to be closely related to the characteristics of the swelling.Two types of relaxation phenomenon are described: a Debye relaxation due to electric dipole rotations and a Maxwell-Wagner relaxation due to heterogeneity effects. The analysis of the first phenomenon leads to the examination of the values of the relaxation time. It appears that the rotations of water molecules are difficult with bivalent cations. This essentially is shown by the high activation energy of the phenomenon. The discussion of these parameters shows that the state of adsorbed water molecules are certainly different as compared to the state of water molecules in ice or in liquid water. The characteristics of the second relaxation phenomenon are closely dependent on the free carriers charge conductivity.

Dispersion of proton spin-lattice relaxation in tissues

The dispersion of the proton spin-lattice relaxation time was measured for selected mouse tissue in the laboratory ( T 1) and rotating ( T 1 ϱ ) frames at 25°C. These measurements covered the 17–45 MHz and 10 3–10 5 kHz (from H 1 = 0.25–25 G) ranges, respectively. If it is assumed that molecular and atomic motions with discrete correlation times are responsible for the observed relaxation, two correlation times and a region of mostly free water are required to characterize the results. The correlation times for the exchange of protons and for the rotation of water molecules at 25°C were found to be approximately 7 × 10 −6 and 2 × 10 −8 sec, respectively. The fast processes relaxing the free water have the correlation time less than ∼10 −10 sec.

Proton exchange and molecular orientation of water in hydrated collagen fibers. An NMR study of H2O and D2O

An experimental study of proton and deuteron magnetic resonance of the hydration of collagen as a function of water content, temperature, and the addition of salts has been made. From the temperature dependency of linewidths, correlation times for molecular rotation of water molecules and proton exchange times have been determined. For a water content of 45 g H2O per 100 g collagen the rotational correlation time is 3× 10−8sec at 25 °C, with an activation energy of 4.8 kcal/mole, and the proton exchange time is 1.3 × 10−4sec with an activation energy of 10 kcal/mole. Ammonium ions increase the proton exchange rate. The proton exchange most probably occurs between proton donating and proton accepting groups on the macromolecule, intermediated by hydrogen-bonded water molecules. It is shown that the exchange theory of Gutowsky, McCall, and Slichter is applicable to dipole coupling in anisotropic systems. From an analysis of the anisotropy of H2O and D2O rotation in terms of Saupe's parameters, is is concluded that a model with two specific water binding sites is consistent with experimental results.

Work function, electronegativity, and electrochemical behaviour of metals: III. Electrolytic hydrogen evolution in acid solutions

Summary The dependence of the exchange current for the electrolytic evolution of hydrogen on metals ( i 0,H ) on the work function () is analyzed on the basic of a new list offor polycrystalline surfaces. It is shown that log i 0,H is linearly related toirrespective of the detailed nature of the mechanism involved in the rate determining step (rds). i 0,H on sp metals depends on the sign of the surface charge. Results confirm previous suggestions that the main difference in double layer structure between sp and transition metals arises as a result of hindered rotation of water molecules on the latter. If the strength of the M−H bond is taken into consideration, then metals divide into two groups: (a) sp metals, with slow discharge at usual overvoltages, and probably slow hydrogen removal close to equilibrium, and (b) transition metals, with slow hydrogen removal as the rate determining step. Mn is anomalous and cannot be assigned to either class in correlations. Dependence of M−H bond strength onis also shown and discussed.

Structure and properties of ethylene—methacrylic acid copolymers and their sodium salts: Dielectric and proton magnetic relaxation studies

AbstractDielectric and proton magnetic relaxation data have been obtained for an ethylene‐methacrylic acid copolymer (containing about 4 mole% methacrylic acid units) and its 53% ionised sodium salt. The degrees of crystallinity and percentage ionisation of the samples investigated were estimated by infra‐red methods.The dielectric results were obtained principally in the frequency range 100 Hz to 10 kHz and at temperatures ranging from 80° to – 120°. A few results are also reported at frequencies down to 0·1 Hz and up to 100 MHz. For the acid copolymer, two dielectric loss regions are observed and these are correlated with the reported mechanical β′‐ and γa‐processes respectively. The partly ionised copolymer exhibits three dielectric relaxation regions which correlate with the mechanical α‐, β‐ and γa‐relaxations respectively. In addition, a dielectric peak appears at about —40° in the presence of absorbed water, a result similar to that found in the polyamides.The proton magnetic relaxation results were obtained by pulse methods which yielded the spin‐lattice relaxation times T1 (at 30 MHz) and T1p (at kilohertz frequencies) as a function of temperature from −180° to 100°. Two components were generally observed for T1p. For the acid copolymer the β′‐ and γ‐processes have been observed from these results, as well as a lower‐temperature (δ) process which has not been detected by the mechanical or dielectric methods. For the sodium salt the γ‐ and δ‐processes are also found, in addition to a high‐temperature process in the region of the merged α‐ and β‐processes.The present data are consistent with previous assignments for the β′‐, α‐, β‐ and γ‐processes. The ‘water’ relaxation appears to involve some rotation of water molecules, or of ionic segments to which water molecules are attached, in the proposed ionic domains. The δ‐process is ascribed to the rotations of methyl groups present in the methacrylic acid units.

Influence of ions on the rotation of water molecules in aqueous solutions as a function of temperature

Influence of ions on the rotation of water molecules in aqueous solutions as a function of temperature

Far-Infrared Absorption Spectra of Aqueous Solutions of Strong Electrolytes

The infrared absorption of solutions of LiCl, KF, KCl, KBr, KI, NaCl, NaBr, NaI, NaNO3, NaClO3, DCl, and NaOD in NaClO4 has been studied in the spectral region 75 to 650 D2O; the absorption of HCl and NaOH solutions in H2O in the region 75 to 1000 cm−1 has also been investigated. Even for the highest concentrations, the solution spectra have a striking resemblance to the spectrum of the solvent. A broad, intense band attributable to the hindered rotation of water molecules and a much less intense band attributable to the hindered translation of water molecules appear in the spectrum of each solution. The frequencies, widths, and shapes of these bands are compared in some detail with the corresponding bands in the spectrum of pure water. Small but significant differences between the spectra of the solutions and the spectrum of water are noted.

Primary processes in the photolysis of the iodide ion in aqueous solution

By product identification and competition studies with selected solutes it has been shown that the reducing species generated in the ultraviolet photolysis of aqueous iodide ion is the solvated electron. Thus it does not react much more rapidly with O 2 than with N 2 O, it reacts with 1:2-dichloroethane to form chloride (Cl - ) and not H 2 and reacts readily with I 3 - ion at a rate which increases with ionic strength so that the slope of the Bronsted plot is approximately unity. In solutions with μ = 0.23 at solute concentrations where e aq - reacts in less than 3 x 10 -10 s there is insufficient time for the ion atmosphere to form and the rate constant diminishes accordingly. The primary quantum yield is greater at 2288 Å than at 2537 Å and at each wavelength it increases markedly with temperature. Evidence is presented that the electron moves rapidly to a distance (of at least 10 Å) from the site of its formation and that this process, which occurs when the excited iodide ion dissociates and is not deactivated, involves the rotation of water molecules.

Protonic Conduction in the Water I Region

Abstract : The activation energies, Ea, of electrical conduction for aqueous HCl solutions of various concentrations have been determined from precision cnductivity measurements over the temperature range -1 to -10 C. In contrast to normal ionic conduction in aqueous solution which exhibits a pronounced maximum in Ea near the temperature of maximum density, Ea for protonic conduction remains fairly constant. Protonic conduction is composed of two components: normal ionic conduction whose ratedetermining step is hole-formation in the solvent water and which presumably can occur in both the free and clustered water and Grotthuss conduction whose rate-determining step is the rotation of water molecules and which is confined to the 'free,' rotatable water monomers between the clusters. Ordinarily the latter process dominates, but below about 2 C the influence of the former becomes appreciable. There also appears to be a tendency of Ea for HCl, as in the case of salts, to decrease with increasing HCl concentration. (Author)

ROLE OF THE GROTTHUSS MECHANISM FOR PROTONIC AND ELECTRONIC TRANSPORT IN THE TRANSMISSION OF IMPULSES ALONG MUSCLE FIBRES.

THE rate-determining step in the Grotthuss mechanism for protonic conduction in aqueous solution at ordinary pressures is the rotation of water molecules to assume the particular H-bonded mutual orientation necessary for the actual proton flip1. Our present work on the activation energy of protonic conduction in 0.10 M aqueous solution of hydrochloric acid in the 0°–10° C region has failed to disclose a maximum in this parameter at the temperature of maximum density in contrast to sea water2 and 0.10 M potassium chloride solutions3.

Effect of Pressure on the Activation Energy of Electrical Conduction in Aqueous Solution

The specific conductances of aqueous KCl, KOH, and HCl solutions have been measured as functions of hydrostatic pressure and temperature over the ranges 5° to 45°C and 1 to 6900 bars. The activation energy for the conductance of KCl solutions varies in roughly the same way with pressure as does the viscosity of the medium. The activation energy for the conductance of HCl solutions does not vary with pressure in the same way as do KCl solutions and the viscosity because the principal contribution to the conductance arises from a Grotthuss-type protonic transfer rather than from simple translational ionic movement. At lower pressures the rotation of water molecules appears to be the rate-controlling step, but above about 1380 bars the proton jump becomes rate determining.

Proton magnetic resonance in borax

Proton magnetic resonance spectra of borax have been recorded from −196° C to +46°C. The change in second moment of 11 G 2 between −40°C and room temperature is not due to free rotation of water molecules. It is possibly caused by their large amplitude hindered oscillations. The energy of activation for this motion and a change in second moment of 1·6 ± 0·3 G 2 at +36°C is discussed in relation to proton conductivity of borax.

SOME OBSERVATIONS ON THE THEORY OF DIELECTRIC RELAXATION IN ASSOCIATED LIQUIDS

The theory of absolute reaction rates is examined for the case of relaxation in associated polar liquids where the activation process is probably an excitation of a librational motion to one of complete rotation over a rotational potential energy barrier. The rotational barriers in water are calculated using the point-charge model of the water quadrupole and the effect of thermal bond bending is examined. The experimental heats of activation for dielectric relaxation in water and deuterium oxide are discussed and their temperature dependence examined; the heat capacity change for rotational activation is derived. Isotopic effects in the heats of activation, the relaxation times, and frequency factors are discussed. A qualitative explanation is sought for the homogeneity of relaxation times in water; rotation of water molecules in the fields of the hydroxonium and hydroxide ions present in water may account for the narrow distribution of relaxation times observed experimentally. This mechanism is shown to be consistent with other theoretically derived quantities and with the mechanism of proton mobility in water. A different mechanism is indicated in ice, where the proton concentration is lower, but in ice containing extra protons, the mechanism probably reverts to that existing in water.

Rotation of Water Molecules in Carbon Disulfide Solution

Rotation of Water Molecules in Carbon Disulfide Solution