Complex fluorescence decay of quinine bisulphate in aqueous sulphuric acid solution

Fluorescence of quinine bisulphate is shown to be two-component. In 1.0 N H₂SO₄ solution the major component has a decay time ≈20 ns, but there is a minor component with decay time ≈2 ns with a different fluorescence spectrum. It is recommended that the compound not be used as a standard for decay-time measurements.     

Isotope effects in aqueous systems. X. Boiling point elevations for NaCl solutions in H2O and D2O

Solvent isotope effects on the osmotic coefficients of NaCl solutions in H₂O or D₂O have been determined by an ebulliometric technique at 100°C.     

Trapped hydrogen atoms in irradiated frozen solutions. Isotope effects

Isotope effects in the yields of H- and D-atoms in acid, neutral and alkaline matrices have been studied by EPR methods. In acid matrices the isotope effect is the same in UV- and X-irradiated matrices, but in neutral and alkaline matrices the effect is larger in UV-irradiated matrices. Furthermore, when the H- and D-atoms are formed by photobleaching of trapped electrons the isotope effect is strongly dependent on the wavelength of the bleaching light, increasing with increasing wavelenghts. The isotope effect in sulphuric acid matrices is dependent on the concentration of the acid. The observation are briefly discussed.     

Electroinitiated polymerization of acrylonitrile in aqueous sulphuric acid

The electroinitiated polymerization of acrylonitrile in aqueous sulphuric acid has been investigated. The polymerization, which occurs at the anode through the formation of radicals from HSO₄^?, is heterogeneous in nature and shows the occurrence of occlusion phenomena. A remarkable after-effect, connected with the occlusion of free radicals, was observed. Chain transfer to monomer, solvent and polymer have sufficiently low values to allow the formation of a polymer with high molecular weight.     

Isotope effects and H/D scrambling in the fragmentation of labelled propenes

The fragmentation reaction [C₃(H,D)₆]⁺· → [C₃(H,D)₅]⁺ + (H, D) has been examined in the metastable decomposition region for two pairs of labelled propenes: CH₃CD?CH₂,CD₃CH?CD₂ and CD₃CH?CH₂, CH₃CD?CD₂. The results indicate that complete hydrogen scrambling occurs in the propene molecular ion prior to fragmentation. The isotope effect kH/kD is in the range 2·1 to 3·3.     

Isotope effects in aqueous systems. VI. partial molal free energies in NaCl−H2O−D2O by freezing-point measurements. The heat of fusion of D2O

The freezing-point depressions of solutions of NaCl in normal and heavy water have been measured between 0.01 and 2m. Extrapolation of the isotope effect data to infinite dilution yields a new value for the heat of fusion of D₂O at its melting point (?1507±3 cal-mole^?1). The freezing-point data were employed to obtain osmotic coefficients at the feezing points of the solutions, which were corrected to rounded temperatures up to 40°C using the enthalpy data reported by Craft and Van Hook (previous paper). The data for H₂O solution are in quantitative agreement with well-established results. Those for the D₂O solvent establish the NaCl?D₂O system as an isopiestic reference. In contrast to the statements of earlier authors, examination of the isotope-effect data reveals a \(\surd \overline m\) dependence within experimental error.     

On the decay of the ozonide radical in aqueous alkaline solutions

In flash photolysis of an oxygenated aqueous potassium persulphate solution at pH 12.5 the decay of the ozonide radical has been found to follow $\text{3}\text{2}$ order kinetics which has been explained by reactions O^?₃ + O^? ? 2 O^?₂ and O^?₃ + HO₂ → 2 O₂ + OH^?     

Photogeneration of distant radical pairs in aqueous pyruvic acid glasses

The lambda > 300 nm photolysis of h4- or d4-pyruvic acid aqueous glasses at 77 K yields identical electron magnetic resonance (EMR) spectra arising from distant (r greater or similar 0.5 nm) triplet radical pairs. Spectra comprise: (1) well-resolved quartets, X, at g approximately ge, that closely match the powder spectra of spin pairs interacting across r approximately 1.0 nm with D approximately 3.0 mT, E approximately 0 mT zero field splittings (ZFS), and (2) broad signals, Y, centered at g approximately 2.07 that display marked g-anisotropy and g-strain, exclude D greater or similar 20.0 mT values (i.e., r less or similar 0.5 spin nm separations), and track the temperature dependence of related g approximately 4 features. These results imply that the n-pi excitation of pyruvic acid, PA, induces long-range electron transfer from the promoted carbonyl chromophore into neighboring carbonyl acceptors, rather than homolysis into contact radical pairs or concerted decarboxylation into a carbene. Since PA is associated into hydrogen-bonded dimers prior to vitrification, X signals arise from radical pairs ensuing intradimer electron transfer to a locked acceptor, while Y signals involve carbonyl groups attached to randomly arranged, disjoint monomers. The ultrafast decarboxylation of primary radical ion pairs, 3[PA+* PA-*], accounts for the release of CO2 under cryogenic conditions, the lack of thermal hysteresis displayed by magnetic signals between 10 and 160 K, and averted charge retrotransfer. All EMR signals disappear irreversibly above the onset of ice diffusivity at approximately 190 K.     

Reactive scattering of H and D atoms. II. isotope effect on the angular distribution of H,D + NO2

The chemical reactions of hydrogen and deuterium atoms with nitrogendioxide (NO₂) have been studied with crossed molecular beams. Angular and velocity distributions have been measured. The angular distribution peaks at small angles and shows a pronounced isotope effect; only 2̃4% of the available energy goes into translation. Al-though four very deep potential wells (2.1 eV) exist in the potential hypersurface no statistical complex is formed. The reaction can probably be described as intermediate between direct and complex scattering.     

Reaction of H and D atoms with deuterated propylenes

Effects of deuterium substitution in propylene on the relative rates of H(D) atom abstraction from and addition to the olefin, and on the orientation of H(D) atom addition, have been studied in the gas phase at room temperature. Effects of isotopic substitution of the olefinic hydrogen atoms on abstraction could not be observed, but abstraction is reduced five- to tenfold by deuteration of the methyl group. Deuteration of either olefinic position enhances the rate of addition to the substituted carbon atom. Disproportionation-combination ratios for deuterium-substituted propyl radicals are not greatly different from those for unsubstituted radicals, the largest effect being for C₃D₇ radicals, for which the overall k_d/k_c is reduced 10–15%.     

固体聚合物电解质水电解进行h/d同位素分离

固体聚合物电解质;水电解;电催化剂;氢同位素;分离     

Isotope effects in liquid water by infrared spectroscopy. II. Factor analysis of the temperature effect on H2O and D2O

Some 500 infrared (IR) spectra of light and heavy waters were obtained between 29 and 93 degrees C in order to identify the species present in liquid water. Factor analysis of these gives two species for each type of water with their IR spectra and abundance curves. Using an orthogonalization procedure, we obtained the temperature factor limits of -22 and +118 degrees C (+/-5 degrees C) that we coined cold and hot factors, respectively. Within experimental error, these limits are the same for light and heavy waters. The spectra of the orthogonalized factors presented show a decrease of the OH (OD) stretch band integrated intensities of almost 36% from the cold to the hot factors. No "free" OH (OD) group is present or formed in the temperature ramp. This indicates that all water molecules in the bulk are made of an oxygen atom surrounded with four hydrogen atoms, two covalently bonded, and two hydrogen bonded. This is consistent with the previous study of mixtures of H(2)O and D(2)O [part I: J.-J. Max and C. Chapados, J. Chem. Phys. 116, 4626 (2002)]. To maintain the ordinary liquid within the limits of 0 and 100 degrees C at atmospheric pressure, a fraction of the cold and hot factors are necessary. With the spectra of the cold and hot factors and the abundance curves, one can generate the spectrum at any temperature between -22 and +118 degrees C of light and heavy liquid waters.     

Osmium(VIII) oxidation of arsenic(III) in aqueous sulphuric acid

The oxidation of As^III by Os^VIII or Os^VI in aqueous H₂SO₄ follows the rate law:

The chromatographic retention of H and D atoms on quartz

The chromatographic retention of H and D atoms has been observed in a quartz tube using argon as a carrier gas for D and six different gases for H. The results give equilibrium constants for the reversible adsorption of H and D on quartz as well as the rates of desorption. Self-consistent conclusions can be drawn from the data. The adsorption energy appears to be ca. 50 kJ mol^?1 indicating weak chemisorption. The observations are consistent with vibration frequencies on the surface of around 700–900 cm^?1 for D. and around 1000–1300 cm^?1 for H. It appears that only a fraction of the surface atoms (ca. 10^?2) act as adsorption sites.     

Isotope effects in aqueous systems. V. Partial molal enthalpies of solution of NaCl−H2O−D2O and related systems (5 to 75°C)1

Solvent isotope effects on differential heats of solution of NaCl in HOH and DOD have been measured between 0.01 and 4m and from 5 to 40°C. These data are supplemented by integral heats of solution measured at 0.465m and from 5 to 75°C, and with heats of dilution over the same temperature range. The integral heat measurements include studies on otheralkali halides (KCl, NaI, NaBr), and the dilution measurements include some data for KCl. In the NaCl studies, particular attention was paid to the low-concentration region. Values of the partial molal enthalpiesL ₁ adL ₂ are derived for solution in both isotopic waters, and new values for the isotope effect on the standard enthalpy of solution ΔL ₂ ^s = (ΔH ₂ ⁰ ) _d←w as a function of temperature are reported. Comparisons are made with previous work where possible. In contrast to statements made by earlier authors, examination of the low-concentration data reveals a \(\surd \overline m\) dependence within experimental error.     

Kinetic studies of 2-methoxyethanol and 2-ethoxyethanol by pentavalent vanadium in aqueous sulphuric acid medium

Summary The kinetics of oxidation of 2-methoxyethanol and 2ethoxyethanol by vanadium (V) in aqueous sulphuric acid medium has been studied. The order of reaction with respect to the oxidant and substrate has been found to.be unity. The energy of activation has also been calculated graphically. A probable mechanism has been proposed.     

Isotope effects in the relaxation of6Li and7Li nuclei in paramagnetic aqueous solutions

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, p. 2429, October, 1988.