H2O D2O Research Articles

Ultrafast intermolecular energy transfer in heavy water

We report on a study of the vibrational energy relaxation and resonant vibrational (Förster) energy transfer of the OD vibrations of D2O and mixtures of D2O and H2O using femtosecond mid-infrared spectroscopy. We observe the lifetime of the OD vibrations of bulk D2O to be 400 +/- 30 fs. The rate of the Förster energy transfer is measured via the dynamics of the anisotropy of the OD vibrational excitation. For a solution of 0.5% D2O in H2O, resonant energy transfer is negligible, and the anisotropy shows a single exponential decay with a time constant of 2.6 +/- 0.1 ps, representing the time scale of the molecular reorientation. With increasing concentration, the anisotropy decay becomes faster and non-exponential, showing the increased contribution of resonant energy transfer between the OD vibrations. We determine the Förster radius of the OD vibration of HDO in H2O to be r0 = 2.3 +/- 0.2 A.

Excitation of the uranyl ion in U(IV) oxidation with xenon difluoride in frozen aqueous sulfuric acid solutions: III. Effect of solvent deuteration

The effect of the solvent deuteration on the reaction of U(IV) with XeF2 in solutions of H2SO4 in H2O and D2SO4 in D2O, occurring in the course of heating these solutions after their quick cooling (10–15 K s−1) to 77 K, was examined. The effect is manifested in essentially different temperature dependences of the chemiluminescence accompanying the oxidation of U(IV) with XeF2. The results obtained are interpreted within the framework of the concept that the low-temperature reaction of U(IV) with XeF2 is catalyzed by the juvenile surface of crystal hydrates of sulfuric and deuterosulfuric acids, formed in the course of low-temperature phase transitions. The isotope effect is due to different kinetics of the phase transitions in solutions of H2SO4 in H2O and D2SO4 in D2O. In the course of crystallization of supercooled H2SO4 solutions, depending on the mode of temperature variation, either one or two eutectics appreciably differing in the physical properties are formed. In the course of crystallization of supercooled solutions of D2SO4 in D2O, one stable eutectic is formed in each sample, and its characteristics depend on the thermal history of the sample. The eutectics melt in the course of heating of the frozen solution at temperatures differing by only 3–4 K.

Crystal field splitting of rovibrational transitions of water monomers isolated in solid parahydrogen

We report polarized infrared absorption spectra of water isotopologues isolated in solid parahydrogen (pH2) which reveal the crystal field induced splittings of the 1 01<--0 00 R(0) lines in the nu1 HDO, nu3 D2O, nu3 HDO, and nu3 H2O fundamental bands. For annealed pH2 solids, these spectra also reveal a strong alignment of the hexagonal-close-packed crystallites' c axes with the deposition substrate surface normal. This alignment effect explains our failure to detect the parallel-polarized components of these R(0) lines in spectra of pH2 solids produced on a transparent deposition substrate [M. E. Fajardo et al., J. Mol. Struct. 695, 111 (2004)]. This lesson applies more generally to comparison of solid pH2 spectra obtained in different laboratories. The spectra are consistent with water monomers existing in solid pH2 as very slightly hindered rotors. The individual components of the R(0) absorption lines show a Lorentzian lineshape, with vibrational depopulation the most important source of line broadening.

Anomalous scattering of keV neutrons fromH2O and D2O : I. Single scattering events

Scattering of neutrons in the 24–150 keV incident energy range fromH2O relativeto that of D2O and H2O–D2O mixtures was reported recently by Moreh et al. This work is related to neutron Comptonscattering experiments regarding the ‘anomalous’ scattering from protons, observed earlierat ISIS by Chatzidimitriou-Dreismann et al in the 5–100 eV range. Here we provide thecomplete data reduction scheme of time-of-flight integrated intensities measured atkeV energy transfers, within the impulse approximation of standard theory and for singlescattering events. Current investigations of multiple scattering events and the associatedpreliminary results are mentioned. Direct application of the theoretical results tothe new keV scattering data reveals an anomalous ratio of scattering intensity ofH2O relativeto that of D2O of about 20%, thus being in good agreement with the earlier results of the originalexperiment at ISIS.

Solvent effect and proton inventory in the hydrolysis of p‐methylphenyl trichloroacetate

AbstractHydrolysis of p‐methylphenyl trichloroacetate in water–acetonitrile mixtures was studied as a function of water concentration in the range 5.5–55.5 M. The proton inventory technique, in H2O–D2O mixtures, shows, for a value of D atom fraction in the solvent n = 0.5, deviations from the expected value (for a reaction with one proton being transferred) of 7.5 and 12.3%, for experiments in the presence of 16.6 and 33.3 M L2O (L = H or D), respectively. Theoretical treatment of the data obtained at [L2O] = 16.6 M using the Gross–Butler equation are consistent with a cyclic transition‐state structure with three protons involved. Conversely, similar experiments in the presence of [L2O] = 33.3 M show that multiple water molecules are involved in the transition state of the reaction. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Chloraminometric and bromaminometric oxidation of sulfanilic acid in alkaline medium: A comparative kinetic and mechanistic study

AbstractThe kinetics of oxidation of sulfanilic acid (SAA) by chloramine‐B (CAB) and bromamine‐B (BAB) has been investigated in alkaline medium at 35 ± 0.1°C. The oxidation reaction follows identical kinetics in the case of both the oxidants with first‐order dependence on each [oxidant]o and [SAA]o and an inverse first‐order dependence on [OH−]. The variation of ionic strength, dielectric constant of the medium, addition of the reaction product (benzenesulfonamide), and halide ions showed no significant influence on the reaction rate. Proton inventory studies made in H2O–D2O mixtures for CAB and BAB have been utilized to calculate the isotopic fractionation factor. The reaction has been studied at different temperatures, and activation parameters for the composite reaction have been computed from the Arrhenius plots. N‐Hydroxylaminobenzene‐4‐sulfonic acid was identified as the oxidation product of SAA from IR and GC‐MS analysis. A mechanism consistent with the kinetic results is proposed in which PhSO2NHX (X = Cl or Br) interact with the substrate in the rate‐limiting step. A suitable rate law is derived. The rate of oxidation of sulfanilic acid is about fourfold faster in BAB compared to CAB. The oxidation of SAA brought about by CAT and BAT was also investigated under identical experimental conditions, and the overall rate of oxidation of SAA increases in the order: BAB &gt; BAT &gt; CAB &gt; CAT. This may be attributed to the difference in electrophilicities of Cl+ and Br+ ions and also the van der Waal's radii of chlorine and bromine. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 48–56, 2006

Ultrafast memory loss and energy redistribution in the hydrogen bond network of liquid H2O

Many of the unusual properties of liquid water are attributed to its unique structure, comprised of a random and fluctuating three-dimensional network of hydrogen bonds that link the highly polar water molecules. One of the most direct probes of the dynamics of this network is the infrared spectrum of the OH stretching vibration, which reflects the distribution of hydrogen-bonded structures and the intermolecular forces controlling the structural dynamics of the liquid. Indeed, water dynamics has been studied in detail, most recently using multi-dimensional nonlinear infrared spectroscopy for acquiring structural and dynamical information on femtosecond timescales. But owing to technical difficulties, only OH stretching vibrations in D2O or OD vibrations in H2O could be monitored. Here we show that using a specially designed, ultrathin sample cell allows us to observe OH stretching vibrations in H2O. Under these fully resonant conditions, we observe hydrogen bond network dynamics more than one order of magnitude faster than seen in earlier studies that include an extremely fast sweep in the OH frequencies on a 50-fs timescale and an equally fast disappearance of the initial inhomogeneous distribution of sites. Our results highlight the efficiency of energy redistribution within the hydrogen-bonded network, and that liquid water essentially loses the memory of persistent correlations in its structure within 50 fs.

Eu(CO3)33? and the limiting carbonate complexes of other M3+ f-elements in aqueous solutions: a solubility and TRLFS study

Within the framework of environmental studies regarding radioactive waste management, the speciation of M3+ f-elements in concentrated carbonate solutions was investigated. Solubility measurements of NaEu(CO3)2·5H2O(s) were performed at 23 ± 1 °C under fixed [Na+], by using NaClO4. In 3 mol l−1 Na+ aqueous solutions, the limiting complex Eu(CO3)33− was identified in the range 0.01 < [CO32−] < 2 mol l−1; experimental solubilities were modelled with the equilibrium: NaEu(CO3)2·5H2O(s) + CO32− ⇌ Na+ + Eu(CO3)33− + 5H2O, and the logarithm of the corresponding equilibrium constant was found to be logKs,3 = −4.2 ± 0.2. To interpret the measurements at different [Na+], the activity coefficients of the species were calculated with the SIT formula. Time-resolved laser-induced fluorescence spectroscopy was used to verify the presence of a single complex of Eu(III) in aqueous solutions. From fluorescence lifetime measurements in 1 mol l−1 Na2CO3 solutions in H2O–D2O mixtures, it was determined that about two water molecules remained in the first coordination sphere of Eu(CO3)33−. From a critical review of literature data and sensitivity analysis, it was concluded that solubility results should be more reliable than solvent extraction and spectroscopic results in determining the stoichiometry of limiting carbonate complexes. Tricarbonate complexes of most M3+ f-elements appeared to be the limiting stable species in Na+ aqueous solutions, except for Ce(III), for which a tetracarbonate complex was indeed observed. Interestingly, supporting electrolytes based on K+ can favour tetracarbonate complexes at high ionic strength. Available values of thermodynamic constants related to various ionic media are compared on the basis of the SIT formula.

The polymerization of actin: Thermodynamics near the polymerization line

Studies of the dependence of actin polymerization on thermodynamic parameters are important for understanding processes in living systems, where actin polymerization and depolymerization are crucial to cell structure and movement. We report measurements of the extent of polymerization, Φ, of rabbit muscle actin as a function of temperature [T=(0–35) °C], initial G-actin concentration [[G0]=(1–3) mg/ml], and initiating salt concentration [[KCl]=(5–15) mmol/l with bound Ca2+], in H2O and D2O buffers and in the presence of adenosine triphosphate (ATP). A preliminary account of the data and analysis for H2O buffers has appeared previously [P. S. Niranjan, J. G. Forbes, S. C. Greer, J. Dudowicz, K. F. Freed, and J. F. Douglas, J. Chem. Phys. 114, 10573 (2001)]. We describe the details of the studies for H2O buffers, together with new data and analysis for D2O buffers. The measurements show a maximum in Φ(T) for H2O buffers and D2O buffers. For H2O buffers, Tp decreases as either [G0] or [KCl] increases. For D2O buffers, Tp decreases as [KCl] increases, but Tp is not monotonic in [G0]. The measurements are interpreted in terms of a Flory–Huggins-type lattice model that includes the essential steps: monomer activation, dimerization of activated species, and propagation of trimers to higher order polymers. The competition between monomer activation and chain propagation leads to the observed nonmonotonic variation of Φ(T). The actin polymerization in D2O buffer differs considerably from that in the H2O buffer and underscores the significant deuterium effect on hydrophobic interactions and hydrogen bonding in the polymerization process.

Small angle neutron scattering from D2O–H2O nanodroplets and binary nucleation rates in a supersonic nozzle

Small angle neutron scattering (SANS) experiments were used to characterize binary nanodroplets composed of D2O and H2O. The droplets were formed by expanding dilute mixtures of condensible vapor in a N2 carrier gas through a supersonic nozzle, while maintaining the onset of condensation at a fixed position in the nozzle. It is remarkable, given the small coherent scattering length density of light water, that even the pure H2O aerosol gave a scattering signal above background. The scattering spectra were analyzed assuming a log-normal distribution of droplets. On average, the geometric radius of the nanodroplets rg was rg=13 (±1) nm, the polydispersity ln σr was ln σr=0.19 (±0.07), and the number density N was N=(2±0.2)⋅1011 cm−3. The aerosol volume fractions derived from the SANS measurements are consistent with those derived from the pressure trace experiments, suggesting that the composition of the droplets was close to that of the initial condensible mixture. A quantitative analysis of the scattering spectra as a function of the isotopic composition gave further evidence that the binary droplets exhibit ideal mixing behavior. Because both the stagnation temperature T0 and the location of onset were fixed, the temperature corresponding to the maximum nucleation rate was constant at TJ max=229 (±1) K. Thus, the experiments let us estimate the isothermal peak nucleation rates as a function of the isotopic composition. The nucleation rates were found to be essentially constant with Jmax equal to (3.6±0.5)⋅1016 cm−3 s−1 at a mean supersaturation of 44 (±3).

Optically Stimulated Luminescence Study on γ-Irradiated Ice Frozen from H2O and D2O

Optically stimulated luminescence (OSL) and thermoluminescence (TL) for γ-irradiated ice samples have been investigated as future dating techniques for icy bodies in the solar system. The OSL around 400 nm lasted more than 600 s for γ-irradiated H2O ice and D2O ice under 623-nm-light stimulation at 90 K; the latter was used to study the migration of hydrogen atoms. A defect containing trapped electrons is the most suitable explanation of the OSL emissions. The intensity of the TL peak at 120 K increased linearly with γ-dosage increasing up to 15 kGy for both D2O ice and H2O ice. Intensities of both OSL and TL for D2O ice were larger than those for H2O ice. The TL peak related to H2O was observed but its thermal characteristics did not agree with those of OH and HO2 radicals measured by ESR. The OSL method should be employed in future surveys in the solar system.

A NOVEL MECHANISM FOR THE OXIDATION OF ERYTHRO-SERIES PENTOSES AND HEXOSES BY N-ARYLBROMOSULPHONAMIDES IN ALKALINE MEDIUM

Kinetic studies of the oxidation of d-mannose, d-glucose, d-fructose, l-arabinose and d-ribose by bromamine-T (sodium N-bromo-p-toluenesulphonamide or BAT) and bromamine-B (sodium N-bromobenzenesulphonamide or BAB) in alkaline medium were investigated at 30°C. The rate of the reaction was first order both with respect to the oxidant and the sugar and second order with respect to [HO−]. The addition of the reaction product, p-toluenesulphonamide (PTS) or benzenesulphonamide (BSA), and the variation of ionic strength of the medium have no effect on the rate. The rate decreases with decrease in dielectric constant of the medium and values of dAB, the size of activated complex, were calculated. Proton inventory studies were made in H2O–D2O mixtures. The activation parameters of the reaction were computed from Arrhenius plots. HPLC and GLC-MS analysis of the products indicated that the sugars were oxidized to a mixture of aldonic acids consisting of arabinonic, ribonic, erythronic and glyceric acids. A general mechanism consistent with the observed results has been proposed.

Isotope effects in liquid water by infrared spectroscopy

The light and heavy liquid water (H2O–D2O) mixtures in the 0–1 molar fraction were studied in the mid-infrared by Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy. Five principal factors were retrieved by factor analysis (FA). When D2O is mixed with H2O, the HDO formed because of the hopping nature of the proton (H or D) results in three types of molecules in equilibrium. Because of the nearest-neighbor interactions, the three molecules give rise to nine species. Some of the species evolve concomitantly with other species giving the five principal factors observed. We present the spectra of these factors with their abundances. The calculated probability of the species present at different molar fractions which when the concomitant species are combined gives the observed abundances. To appreciate clearly the difference between the principal spectra, a Gaussian simulation of the bands was made. Because of the numerous components that make up the stretch bands, they are not very sensitive to changes in composition of the solutions; nevertheless, they do indicate the presence of new entities other than the pure species. The deformation bands, more sensitive to such changes than the stretch bands, clearly indicate the presence of the three types of molecules as well as of intermediate species. These bands are sensitive to the two hydrogen bonds on the oxygen atom that a reference molecule makes with its nearest-neighbors, but not to the hydrogen bonds that the nearest-neighbors make with the next nearest neighbors.

Thermodynamic properties of mixtures of H2O and D2O in the critical region

An accurate equation of state is presented for the thermodynamic properties of mixtures of H2O and D2O in the critical region. The equation incorporates a crossover from fluctuation-induced singular behavior near the locus of vapor–liquid critical points to regular behavior outside the critical region. It is a generalization of a crossover equation-of-state previously developed for pure H2O and pure D2O extended to the mixtures on the basis of the principle of isomorphism of critical behavior. The equation represents the thermodynamic properties of mixtures of H2O and D2O in the same range of temperatures and densities as for the pure components. A comparison is made with available experimental data for the pressure, for the isochoric heat capacity, for the enthalpy of mixing, and for the isotope fraction ratio of mixtures of H2O and D2O. An analysis is presented of the near-critical behavior of various thermodynamic properties, such as the isobaric heat capacity, the partial molar volumes, Henry’s constant, and the vapor–liquid distribution ratio (K factor).

KINETIC AND MECHANISTIC INVESTIGATION OF OXIDATION OF URONIC ACIDS BY SODIUM N-BROMOARYLSULFONAMIDES IN ALKALINE MEDIUM

The kinetics of oxidation of uronic acids (UAs), d-glucuronic acid and d-galacturonic acid, by sodium N-bromo-p-toluenesulfonamide or bromamine-T (BAT) and sodium N-bromobenzenesulfonamide or bromamine-B (BAB) in alkaline medium at 30°C have been investigated and the rate law, rate=k [OX] [UA] [HO−] where [OX]˭[BAT] or [BAB] was observed. The product p-toluenesulfonamide (PTS) or benzenesulfonamide (BSA) and ionic strength have no influence on the rate. The rate decreased when the dielectric constant (ϵ) of the medium was decreased. The rate increased in D2O medium. Proton inventory studies were made in D2O–H2O mixtures. Effect of temperature was studied and from the Arrhenius plots, activation parameters were computed. A mechanism involving the formation of enediol anion, which reacts with positive bromine of the bromamine in the rate-limiting step is suggested.

Variations in coupled water, viscoelastic properties, and film thickness of a Mefp-1 protein film during adsorption and cross-linking: a quartz crystal microbalance with dissipation monitoring, ellipsometry, and surface plasmon resonance study.

We have measured the time-resolved adsorption kinetics of the mussel adhesive protein (Mefp-1) on a nonpolar, methyl-terminated (thiolated) gold surface, using three independent techniques: quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance, and ellipsometry. The QCM-D and ellipsometry data shows that, after adsorption to saturation of Mefp-1, cross-linking of the protein layer using NaIO4 transforms it from an extended (approximately 20 nm), water-rich, and hydrogel-like state to a much thinner (approximately 5 nm), compact, and less water-rich state. Furthermore, we show how quantitative data about the thickness, shear elastic modulus, and shear viscosity of the protein film can be obtained with the QCM-D technique, even beyond the Sauerbrey regime, if frequency (f) and energy dissipation (D) measurements measured at multiple harmonics are combined with theoretical simulations using a Voight-based viscoelastic model. The modeling result was confirmed by substituting H2O for D2O. As expected, the D2O substitution does not influence the actual adsorption behavior, but resulted in expected differences in the estimated effective density and shear viscosity. These results provide new insight and understanding about the adsorption kinetics and crosslinking behavior of Mefp-1. They also demonstrate how the above three techniques complement each other for biomolecule adsorption studies.

Real time observation of the hydrothermal crystallization of barium titanate using in situ neutron powder diffraction.

The hydrothermal crystallization of barium titanate, BaTiO3, has been studied in situ by time-resolved powder neutron diffraction methods using the recently developed Oxford/ISIS hydrothermal cell. This technique has allowed the formation of the ferroelectric ceramic to be followed in a noninvasive manner in real time and under genuine reaction conditions. In a first set of experiments, Ba(OD)2-8D2O was reacted with two different titanium sources, either crystalline TiO2 (anatase) or amorphous TiO2-H2O in D2O, at 100-140 degrees C and the reaction studied using the POLARIS time-of-flight neutron powder diffractometer, at the ISIS Facility. In a second series of experiments, the reaction between barium chloride and crystalline TiO2 (anatase) in NaOD/D2O was studied at temperatures between 100 and 200 degrees C and at different deuterioxide concentrations using the constant-wavelength D20 neutron powder diffractometer at the Institut Laue Langevin. Quantitative growth and decay curves were determined from analysis of the integrated intensities of Bragg reflections of starting materials and product phases. In both sets of experiments the rapid dissolution of the barium source was observed, followed by dissolution of the titanium source before the onset of crystallization of barium titanate. Using a nucleation-growth model we are able to simulate the growth curve of barium titanate at three temperatures. Our results indicate the predominance of a homogeneous dissolution-precipitation mechanism for the hydrothermal formation of barium titanate, rather than other possible mechanisms that have been discussed in the literature. Analysis of the line widths of the Bragg reflections in the neutron diffraction data indicates that the particle size of the BaTiO3 product phase prepared from the amorphous TiO2-H2O is smaller than that prepared from crystalline TiO2 (anatase).

Kinetics and mechanism of oxidation of neutral ? -amino acids by sodium N-chloro-p-toluenesulfonamide in acid medium

Kinetics of oxidation of α -amino acids, glycine, valine, alanine, and phenylalanine, by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) has been investigated in HClO4 medium at 30°C. The rate shows first-order dependence on both CAT and amino acid concentrations and an inverse first-order on [H+]. The variation of ionic strength and the addition of p-toluenesulfonamide and Cl− ion had no effect on the reaction rate. Decrease of dielectric constant of the medium by increasing the MeOH content decreased the rate. Rate studies in D2O medium showed the inverse solvent-isotope effect of kD2O/kH2O=0.50. Proton-inventory studies were carried out using H2O–D2O mixtures. The activation parameters have been computed. The proposed mechanism and the derived rate law are consistent with the observed kinetic data. An isokinetic relationship is observed with β=323 K, indicating enthalpy as a controlling factor. The rate of oxidation increases in the following order: Gly < Val < Phe < Ala. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 49–55, 2002

Electrolytic water splitting: Indications for the existence of protonic quantum interferences

Electrolysis of acidic H2O–D2O mixtures has been performed using the well established mercury drop electrode. The experiment was done in order to study, for the first time in a chemical reaction, possible quantum behaviour of hydrogen species which is evident from neutron and Raman light scattering studies. Rate constants and the Tafel slope of the examined reaction show striking deviations from the expected conventional behaviour for the nominal D and H concentrations. Limitations of the applicability of simple reversible thermodynamics and equilibrium statistical mechanics to the electrochemical process under consideration are revealed.

Solid–solid palladium-catalysed water reduction with zinc: mechanisms of hydrogen generation and direct hydrogen transfer reactions

Facile generation of hydrogen gas from water takes place under moderate conditions in the presence of zinc powder and catalytic palladium on carbon; 82% conversion of zinc is obtained. An unusually large kinetic isotope effect is observed using D2O (kH/kD=14), which may reflect the cleavage of both O–H bonds in the rate-determining step. Experiments using D2O–H2O mixtures evidence that water molecules adsorbed on the catalyst surface undergo H–D exchange reactions (with molecules from the solvent bulk) that are approximately 100 times faster than the hydrogen generation reaction. The primary factors in this system appear to be palladium–hydrogen and zinc–oxygen interactions. Conversely, in the presence of an organic hydrogen acceptor, such as benzaldehyde, a different course is realised, consisting of direct hydrogen transfer from ‘‘zinc-activated ’’ water to the substrate, without the participation of Pd–H intermediates. Quantitative hydrogenation of benzaldehyde to benzyl alcohol, and of aromatic nitro compounds to the corresponding amines, is obtained. Another application of the above system is the specific deutero-dehalogenation of aromatic halides. Possible mechanisms and the implications of a chemical reaction involving two macroscopic solid particles are discussed.