Analysis of the molecular bands of D2H and H2D at 5600 Å

Spectral simulation was used to analyze the molecular rovibrational bands of D₂H and H₂D at 5600 Å. These bands were previously measured by the ion beam neutralization method. They were assigned to the electronic 3p²B₁ ? 2s²A₁ and vibrational (ν - ν″) = (0, 0, 0,-0, 0, 0) transitions. Least squares fits to the experimental line-positions were made to determine the asymmetric rotator constants A, B and C for the 2s²A₁ and 3p²B₁ ν = 0 states of D₂H and H₂D, hitherto unknown. Lorentz line-profiles were assumed for the D₂H and H₂D rotational lines, whose widths are mainly governed by the lifetimes of the lower states. The bands at 5600 Å were simulated and the 2s²A₁ state lifetimes were estimated to be σ ≥ 0.5 ± 0.2 ps for D₂H and σ ≥ 0.4 ± 0.2 ps for H₂D. Vibrational constants of D₃ and D₂H in the 2s²A₁ states are determined from the positions of the 0-0 and 0-1 vibrational bands given in respective experimental spectra previously measured. For the first time the vibrational constants ω₁ and ω₂ of the 2s²A₁ state of H₂D were estimated from the positions of the 0-0 and 0-1 band maxima. These vibrational constants are compared with the corresponding vibrational constants of their ions.     

The effect of Er(III) on the thermal behavior of azo (–N=N–) and azomethinic (–CH=N–) chromophores

This paper reports the investigation of the thermal stability of a series of new complexes with azo and azomethinic chromophores of the type [Er(HL)₂(H₂O)₂](HO); ((B) H₂L: o,o’-dihydroxy-azobenzene (A); (D) H₂L: N-(2-hydroxy-1-naphthalidene)aminophenol (C); (F) H₂L: N-(2-hydroxy-1-naphthalidene)anthranilic acid (E)). The complexes thermal behaviour steps were investigated and comparatively presented with those of corresponding ligand. The thermal transformations are complex processes according to TG and DTG curves including phenol elimination, oxidative condensation and thermolysis processes. The final product of complexes decomposition is Er₂O₃.     

The H2 elimination reactions of Ã2B3g C2H4+ and C2D4+

Kinetic energy releases from the unimolecular H₂ (D₂) elimination reactions of energy-selected òB_3gC₂H₄⁺(C₂D₄⁺) have been obtained by a photoelectron-photoion coincidence technique. The energy releases suggest a 1,1 elimination and are compatible with the presence of a small reverse activation energy barrier of the order of 0.02 eV. Such a barrier was indicated by a detailed ab initio study of this dissociation and the present results are discussed in the light of this theoretical treatment.     

Tautomerism of aza cycles: I. Structure of 3(5)-butylsulfanyl-5(3)-methyl(phenyl)-1H-1,2,4-triazole tautomers in crystal. Preference of the 3-RA-5-RD-1H-tautomer of 3(5)-mono-and 3,5-disubstituted 1,2,4-triazoles

The X-ray diffraction study of potentially tautomeric 3(5)-butylsulfanyl-5(3)-methyl-1H-1,2,4-triazole and its 5(3)-phenyl-substituted analog showed that these compounds in crystal have the structure of 3-butylsulfanyl-5-methyl(phenyl)-1H-tautomers. Analysis of our experimental and published data indicated that 3(5)-monosubstituted 1,2,4-triazoles and 3,5-disubstituted derivatives having nonequivalent substituents in crystal as exist as a tautomer in which the electron-acceptor substituent (R_A) occupies the 3 position, while the electron-donor substituent (R_D) resides in the 5 position, i.e., as 3-R_A-5-R_D-1H-1,2,4-triazoles. Symmetric 3,5-disubstituted 1,2,4-triazoles could give rise to tautomeric equilibrium between the 1H-and 2H-structures even in crystal.     

Luminescence in near-thermal charge exchange. II. He+ + H2O and He+ + D2O

An ICR spectrometer fitted with synchronous photon counting equipment is used to study the emission produced by near-thermal (? 0.1 eV) collisions between He⁺ and H₂O (D₂). Within the investigated wavelength region, 185 to 500 nm, the only significant emission features are the A³Π (υ' ? 3) → X³Σ^? bands in OH⁺ and OD⁺, and the A²Σ⁺ → X²Π(0.0) band in OH and, possibly, in OD. The corresponding excitation rate constants represent only ? 2% of the total He⁺/H₂O (D₂O) charge transfer. The resonant electron-jump model for thermal-energy charge exchange is discussed in the light of recent information on the He⁺/H₂O reaction and on the excited states of H₂O⁺ and their excitation by electron and photon impact on H₂O (D₂O).     

Tetrakis(chloromethyl)phosphonium chloride monohydrate

Tetrakis­(chloro­methyl)­phospho­nium chloride monohydrate, C₄H₈Cl₄P⁺·Cl^?·H₂O or P(CH₂Cl)₄⁺·Cl^?·H₂O, is the first crystal structure determination of a tetrakis­(halogeno­methyl)­phospho­nium compound to date. The only comparable structures known so far are of phospho­nium ions containing just one halogeno­methyl group. The solvent water mol­ecule interacts with the Cl^? anion via hydrogen bonds, with O?Cl distances of 3.230 (2) and 3.309 (2) Å. The structure also contains several C—H?Cl^? and C—H?O contacts, though with longer D?A distances [D?A 3.286 (3)–3.662 (2) Å] or bent D—H?A angles. For these reasons, the C—H?Cl^? and C—H?O interactions should not be considered as strong hydrogen bonds.     

20‐Hydroxy­imino‐5α‐pregna‐9(11),16‐dien‐3β‐yl acetate and 17‐oxo‐5α‐androst‐9(11)‐en‐3β‐yl acetate

In the title compounds, C₂₃H₃₃NO₃ and C₂₁H₃₀O₃, respectively, the ester linkage in ring A is equatorial. In these steroids, the six‐membered rings A and B have chair conformations, but ring C can be better described as a half‐chair. The five‐membered ring D adopts a 14α‐envelop conformation. The A/B, B/C and C/D ring junctions are trans.     

A system-independent correlation between the enthalpy and the entropy of dilution for polymer solutions

The second osmotic virial coefficient (A₂) and its entropic and enthalpic parts (A_2,s and A_2,H) have been determined, by means of light-scattering measurements, for solutions of polystyrene, polymethylmethacrylate and cellulose nitrate of different molecular weights in 19 solvents. A distinct qualitative correlation exists between A₂ and A_2,H and between A_2,s and A_2,H. The elimination of the “geometric” parameters of the polymer, by dividing these coefficients by suitably chosen reduction parameters, shows that the reduced coefficients obtained A₂⁰ and A_2,s⁰ are predominantly functions of the reduced enthalpy coefficient A_2,H⁰.     

Diffusion coefficients of ions through ion excange membrane in Donnan dialysis using ions of different valence

Donnan dialysis with an ion exchange membrane was investigated for ions of different valence. The effective diffusion coefficients (D_e) of various kinds of ions in the membrane were obtained by fitting of the equation derived from the Nernst–Planck equation to three or more sets of experimental data for Donnan dialysis. It became apparent that the value of D_e/D_s of monovalent ions (e.g., K⁺ or Na⁺ ions) at z_A=1 and z_B=2 (feed ions are monovalent ones and driving ions are bivalent ones) remained constant at ca. 1/210 and that of bivalent ions (e.g., Ca²⁺, Cu²⁺, or Mg²⁺ ions) remained constant at ca. 1/526 where D_s denotes the diffusion coefficient of ions at infinite dilution in water calculated from the Nernst–Einstein equation, and z_A and z_B represent the valences of the feed and driving ions, respectively. D_e/D_s of monovalent ions (e.g., H⁺, K⁺, or Na⁺ ions) at z_A=2 and z_B=1 (feed ions are bivalent ones and driving ions are monovalent ones) was constant at ca. 1/23.3 and that of bivalent ions remained constant at ca. 1/58.4. It was proved that D_e/D using D_e at z_A=1 and z_B=2 was constant at 1/3.0 and that at z_A=2 and z_B=1 remained constant at 3.0 where D represents the diffusion coefficient of ions in the membrane at z_A=z_B (the valences of both feed and driving ions are equal). Therefore, it was found that a large flux of ions could be obtained using the monovalent driving ions in Donnan dialysis. On the other hand, the small flux can be obtained using bi- or higher-valent driving ions.     

Metal ions in biological systems, vol. 2, metal ligand complexes : ed. by H. Sigel, Dekker, New York, 1973, xiv + 294 pages, $25.25

The kinetic isotope effect for β-hydride elimination from alkyliridium(I) complexes has bee found to be k_H/k_D = 2.28 ± 0.20.     

A KINETIC ISOTOPE EFFECT IN THE PHOTOREACTIVATION OF U.V.-INACTIVATED TOBACCO MOSAIC VIRUS RNA*

Abstract— Inactivation of tobacco mosaic virus RNA (TMV-RNA) by u.v. radiation is slower in D₂O than in H₂O, and TMV-RNA which has been inactivated in D₂O is photoreactivated faster (on Pinto bean) than TMV-RNA which has been inactivated in H₂O. The maximum amount of photoreactivation is unaffected by the solvent, H₂O or D₂O, present during irradiation. These deuterium isotope effects for inactivation and photoreactivation suggest that pyrimidine hydrates are photoreactivable lesions on Pinto bean.     

A study of the phenyl radical by vacuum ultraviolet photoelectron spectroscopy

Part of a photoelectron band assigned to the phenyl radical, produced from the F + C₆H₆ reaction, has been recorded. The adiabatic ionization energy was measured as 8.32±0.04 eV. Two vibrational components separated by 2790±100 cm⁻¹ were observed in the C₆H₅ band corresponding to excitation of a CH stretching mode in the ion. For C₆D₅ this separation decreases to 2370±110 cm⁻¹. Ab initio CI calculations on the low-lying C₆H⁺₅ states, ³B₁ and ¹A₁, show that state of C₆H⁺₅ is ¹A₁ and the first adiabatic ionization energy is estimated as 8.0±0.1 eV. Evidence is presented to show that the observed photoelectron band should be assigned to the ionization of C₆H⁺₅ (a ³B₁) ← C₆H₅(X²A₁). In the F + C₆D₆ reaction, a photoelectron band assigned to C₆D₆F is observed at 7.80±0.02 eV which is seen only very weakly in the F + C₆H₆ reaction.     

Analysis of deuterium effects on the rate of multiphonon relaxation in hydrated cesium chloromanganate crystals (CsMnCl3-2H2O, -2D2O)

The assumption that OH (OD) stretch vibrations in CsMnCl₃-2H₂O and -2D₂O govern the rate of the ⁴T₁ → ⁶A₁ multiphonon transitions in Mn²⁺ is shown to account quantitatively for the observed 16-fold increase in the ⁴T₁ lifetime upon replacing H₂O by D₂O. The argument is generalized to include other coordination compounds.     

The anti‐inflammatory triterpenoid methyl 2‐cyano‐3,12‐dioxooleana‐1,9(11)‐dien‐28‐oate methanol solvate hydrate

The title compound, C₃₂H₄₃NO₄·CH₄O·H₂O, has a nearly planar cyano‐enone A ring in an otherwise normal oleanane triterpenoid. Rings A, B and C are non‐chairs, but rings D and E adopt essentially cyclo­hexane chair conformations. The structure clearly establishes the C‐D‐E ring stereochemistry as trans‐syn‐cis, as predicted from a nuclear Overhauser effect (NOE) NMR measurement.     

The effect of plasticization on the transport of gases in and through glassy polymers

The effects of plasticization on the transport of gases and vapors in and through glassy polymers are examined from the viewpoint of the “dual-mode” sorption model with partial immobilization. The analysis assumes the existence of two penetrant populations with different mobilities in the Henry's law and Langmuir domains of the glassy polymers. These mobilities are characterized by their mutual diffusion coefficients D_D and D_H. The plasticization of the polymer by penetrant gases is reflected in the concentration dependence of D_D and D_H. Expressions for the effective (apparent) diffusion and permeability coefficients are derived assuming that D_D and D_H are exponential functions of the penetrant concentration in the polymers. The results of this study are compared with a similar analysis which assumed the existence of a single mobile penetrant population. The present analysis provides information on the effects of plasticization on the penetrant transport in the Henry's law and Langmuir domains separately. The effects of antiplasticization or clustering of penetrant molecules on the effective diffusion and permeability coefficients are also examined.     

3β‐Acetoxy‐5α,6β‐di­hydroxybisnorcholanic acid 2216 lactone

In the title compound, C₂₄H₃₆O₆, the ester linkage in ring A is equatorial. The six‐membered rings A, B and C have chair conformations. The five‐membered ring D adopts a 13β,14α‐half‐chair conformation and the E ring adopts an envelope conformation. The A/B, B/C and C/D ring junctions are trans, whereas the D/E junction is cis.     

Anomalous kinetic hydrogen isotope effect in the oxidation of formate by bromine: Tunneling via an intermediate

Rates of oxidation of XCOO^? (X = H, D) by Br₂ in acid aqueous media were measured between 274 and 332 K. The derived Arrhenius parameters for both reactions where θ = 4.575T × 10^?3 kcal/mol, with (k_H/k_D)_298K = 2.85, reveal a primary isotope effect, but the difference (E_D - E_H) = 3.29 kcal/mol and the ratio A_D/A_H = 91 fall beyond the limits imposed by semiclassical transition-state theory, suggesting tunneling or a multiple-stage mechanism. However, it can be shown that either tunneling in a single step or a three-step, internal return mechanism can be ruled out as alternative models, since both require unreasonable kinetic parameters to fit the data. The simplest scheme accounting for the present observations involves tunneling in the decomposition of a charge transfer complex in equilibrium with the reactants.     

An investigation of nonequilibrium kinetic isotope effects in chemically activated vinyl radicals

New experimental data have been obtained for H + C₂H₂, D + C₂H₂, H + C₂D₂, and D + C₂D₂ at room temperature. Two previously described apparatus were used in order to measure the pressure dependence of the reactions. The absolute rate constants are compared to results from other laboratories. The present results and those of Payne and Stief are used to obtain the high-pressure limiting rate constant at room temperature. When the activation energy from the work of Payne and Stief is considered, it is shown that the A factor for H + C₂H₂ is too low by a factor of ～20. If a transmission coefficient is introduced which is constant for all isotopic variations, the pressure dependence can be explained in terms of the randomly energized radicals. RRKM theory is then invoked to explain the observed statistical nonequilibrium kinetic isotope effects.     

The adsorption of H<Subscript>2</Subscript>O and D<Subscript>2</Subscript>O on porous polystyrene adsorbents

The adsorption of H₂O and D₂O on porous polymers, Chromosorb-102 (styrene-divinylbenzene copolymer) and MN-200 (supercross-linked polystyrene), was studied by gas chromatography. Test adsorbates used to study the properties of the surface of these polymers were n-alkanes (C₆-C₉), C₆H₆, and the polar compounds CHCl₃, CH₃NO₂, CH₃CN, (CH₃)₂CO, C₂H₅COOCH₃, and (C₂H₅)₂O. The experimental data on the retention of the sorbates were used to determine the contributions of dispersion and specific intermolecular interactions to the total energy of adsorption for the systems studied. The electron donor K _D and electron acceptor K _A characteristics of the surfaces of Chromosorb-102 and MN-200 were determined. The K _D and K _A values obtained allow these polymers to be classified as weakly specific adsorbents with the predominance of electron acceptor properties. The adsorption isotherms of H₂O and D₂O were measured at 55, 67, and 80°C. The dependences of the isosteric heats of adsorption Q _st on adsorption values were determined. The conclusion was drawn that H₂O interacted with the surface of the polymers by the adsorption mechanism, whereas absorption likely made a noticeable contribution to the retention of D₂O.     

Marron-weare variational computation of energy differences for motions of C2H6, B2H6, CH3CH inf2 sup+ , and CH3BH2

The passage of D_3dC₂H₆ and B2H6 toward a D₂ h bridged structure, and the motion of a methyl proton maintaining C symmetry in C₂H _inf5 ^sup+ and CH₃BH₂ are described by integral Hellmann-Feynman computations in a Frost floating spherical Gaussian basis. Marron and Weare's variational corrections to the integral Hellmann-Feynman formula forAE between statesA andB are evaluated with variational functions of the form η(ψ_A/S_AB-ψ_B)) used to refine the stateB. An analogous function ξ(ψ_B/S_AB-ψ_A) refines state A. Both η and ξ are chosen variationally to minimize Marron and Weare's functional. No obvious advantage of the variational method became apparent in this simple application.