Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C

The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO₃, KBr, KI, KNO₃, CaCl₂, SrCl₂, BaCl₂, Li₂SO₄, K₂SO₄, Mn(NO₃)₃)] as a function of concentration at 25°C. The solubilities, mol (kg-H₂O)^–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg^–1)

P,N-Bidentate Phosphorus Derivatives of (S)-Prolinol

Phosphorylation of (S)-prolinol with P(NEt₂)₃was used to synthesize aminophosphite (2R,5S)- , which was reacted with the corresponding amino alcohols to afford (2S,5R)- (Va) and (2S,5R)- (Vb). Reaction of Vawith [Rh(CO)₂Cl]₂(P/Rh = 1) yields the mononuclear chelate [Rh(CO)(P^N)Cl] (VIIa), while the analogous reaction with Vbresults in a mixture of products with cis- and trans-orientation of the coordinated phosphorus and nitrogen atoms. Spectral characteristics of the products of coordination of ligands Vaand Vbwere compared with those for the binuclear reference complex [Rh(CO)(L)Cl]₂(VIII), where L is P-monodentate ligand (2S,5R)- (VI). The ligands and complexes were studied by IR, NMR, ³¹P and ¹³C spectroscopy, mass spectrometry, and elemental analysis methods. X-ray diffraction analysis of crystals VIIIwas performed.     

Thermodynamics of Solutions of Trimethyl Aluminum and Trimethyl Gallium with Tetramethyl Tin

The enthalpies and entropies of evaporation of Al(CH₃)₃–Sn(CH₃)₄and Ga(CH₃)₃–Sn(CH₃)₄solutions were determined. It was established that solvates are formed in these systems and that the dissociation energies of specific interactions in them change in the following order: (10.3) > > > (4.08 kJ mol^–1), (6.52) > (5.14) > > (4.08 kJ mol^–1).     

Polymerization of methyl methacrylate by charge-transfer mechanism with aliphatic primary amines and carbon tetrachloride

Polymerization of methyl methacrylate (MMA) with aliphatic primary amines and carbon tetrachloride has been investigated in th dimethylsulfoxide medium by employing a dilatometric technique at 60°C. The rate of polymerization (R_p) has been evaluated under the conditions, [CCl₄]/[amine] < 1 and > 1. The kinetic data indicate possible participation of the charge transfer complexes formed between the amine + CCl₄ and the amine + MMA in the polymerization of MMA. In the absence of CCl₄ or amine, no polymerization of MMA was observed under the present experimental conditions. The polymerization of MMA was inhibited by hydroquinone, indicating a free radical initiation. The energy of activation varied from 32 to 58 kJ mol^?1.     

Kinetics and mechanism of the oxidation of hydrogen peroxide by the octacyanotungstate(V) ion in alkaline aqueous media

Summary The oxidation of H₂O₂ by [W(CN)₈]^3– has been studied in aqueous media between pH 7.87 and 12.10 using both conventional and stopped-flow spectrophotometry. The reaction proceeds without generation of free radicals. The experimental overall rate law, , strongly suggests two types of mechanisms. The first pathway, characterized by the pH-dependent rate constant k _s, given by , involves the formation of [W(CN)₈· H₂O₂]^3–, [W(CN)₈· H₂O₂·W(CN)₈]^6– and [W(CN)₈· HO]^3– intermediates in rapid pre-equilibria steps, and is followed by a one-electron transfer step involving [W(CN)₈·HO]^3– (k _a) and its conjugate base [W(CN)₈·O]^4– (k _b). At 25 °C, I = 0.20 m (NaCl), the rate constant with H _a =40±6kJmol^–1 and S _a =–151±22JK^–1mol^–1; the rate constant with H _b =36±1kJmol^–1 and S _b =–136±2JK^–1mol^–1 at 25 °C, I = 0.20 m (NaCl); the acid dissociation constant of [W(CN)₈·HO]^3–, K ₅ =(5.9±1.7)×10^–10 m, with and is the first acid dissociation constant of H₂O₂. The second pathway, with rate constant, k _f, involves the formation of [W(CN)₈· HO₂]^4– and is followed by a formal two-electron redox process with [W(CN)₈]^3–. The pH-dependent rate constant, k _f, is given by . The rate constant k ₇ =23±6m ^–1 s ^–1 with and at 25°C, I = 0.20 m (NaCl).     

Iodine Hydrolysis Equilibrium

The equilibrium constant for the hydrolytic disproportionation of I₂

Dissociation Constants for Citric Acid in NaCl and KCl Solutions and their Mixtures at 25 °C

The constants for the dissociation of citric acid (H₃C) have been determined from potentiometric titrations in aqueous NaCl and KCl solutions and their mixtures as a function of ionic strength (0.05–4.5 mol-dm^–3) at 25 °C. The stoichiometric dissociation constants (K_i^*)

Interaction of Nitromethane with Modified Paramagnetic Defects on a Thermochemically Activated Silica Surface

It was found that the interaction of the modified paramagnetic defects SiO(CH₂) _n H₂ (n = 0.1) with nitromethane on a thermochemically activated silica surface at 300 K results in the formation of the following nitroxyl radicals: SiO(CH₂) _n CH₂ON( )CH₃ and SiO(CH₂) _n CH₂N( )CH₃. It was suggested that these radicals are the products of two different reactions of the modified paramagnetic defects: the first results from a reaction with free nitromethane; the second, from a reaction with nitromethane bound as complexes with diamagnetic surface defects.     

Molecular Structure and Conformation of p-Bis(trimethylsilyl)benzene: A Study by Gas-Phase Electron Diffraction and Theoretical Calculations

The molecular structure and conformation of p-bis(trimethylsilyl)benzene have been investigated by gas-phase electron diffraction, ab initio MO calculations at the HF/6-31G*, MP2(f.c.)/6-31G*, and B3LYP/6-31G* levels, and MM3 molecular mechanics calculations. The calculations indicate the syn- and anti-coplanar conformations, with two bonds in the plane of the benzene ring, to be energy minima. The perpendicular conformations, with two bonds in a plane orthogonal to the ring plane, are transition states. The two coplanar conformers have nearly the same energy with a low interconversion barrier, 0.3–0.5 kJ mol^–1. The calculated lengths of the and bonds differ by only a few thousandths of an angstrom, in agreement with electron diffraction results from molecules containing either or bonds. The geometrical distortion of the benzene ring in p-bis(trimethylsilyl)-benzene may be described by superimposing independent distortions from each of the two SiMe₃ groups. The electron diffraction intensities from a previous study (Rozsondai, B.; Zelei, B.; Hargittai, I. J. Mol. Struct. 1982, 95, 187) have been reanalyzed, imposing constraints from the theoretical calculations, and using a model based on a 1:1 mixture of the two coplanar conformers. The effective torsion angles of the SiMe₃ groups may indicate nearly free rotation. Important geometrical parameters from the present electron diffraction analysis are , and . While the mean bond lengths are virtually the same from the previous and present analyses, the new ipso angle is in better agreement with the MO calculations [HF, 116.9° MP2(f.c.), 117.1° B3LYP, 116.9°].     

PbCu3(OH)(NO3)(SeO3)3·1/2H2O und Pb2Cu3O2(NO3)2(SeO3)2: Synthese und Kristallstrukturuntersuchung

Crystals of PbCu₃(OH)(NO₃)(SeO₃)₃·1/2H₂O [a=7.761(3)Å,b=9.478(4)Å,c=9.514(4)Å, =66.94(2)°, =69.83(2)°, =81.83(2)°, space group P ,Z=2] and Pb₂Cu₃O₂(NO₃)₂(SeO₃)₂ [a=5.884(2)Å,b=12.186(3)Å,c=19.371(4)Å, space group Cmc2₁,Z=4] were synthesized under hydrothermal conditions. Their crystal structures were refined with three-dimensional X-ray data toR _w=0.033 resp. 0.055. In PbCu₃(OH)(NO₃)(SeO₃)₃·1/2H₂O the Cu atoms are [4+1] and [4+2] coordinated and via SeO₃ groups a three-dimensional atomic arrangement is built up. In Pb₂Cu₃O₂(NO₃)₂(SeO₃)₂ there are sheets, which are connected only via Pb-O bonds ranging from 2.98 Å to 3.16 Å.

     

Kinetic study of RuIII‐catalyzed polymerization of methylmethacrylate initiated with n‐butylamine in the presence of carbon tetrachloride by a charge‐transfer mechanism

Ruthenium trichloride (RuCl₃ or Ru^III) catalyzed polymerization of methylmethacrylate (MMA) initiated with n‐butylamine (BA) in the presence of carbon tetrachloride (CCl₄) by a charge‐transfer mechanism has been investigated in a dimethylsulfoxide (DMSO) medium by employing a dilatometric technique at 60°C. The rate of polymerization (R_p) has been obtained under the conditions [CCl₄]/[BA] ? 1 and [CCl₄]/[BA] ? 1. The kinetic data indicate the possible participation of the charge‐transfer complex formed between the amine–Ru^III complex and CCl₄ in the polymerization of MMA. In the absence of either CCl₄ or BA, no polymerization of MMA is observed under the present experimental conditions. The rate of polymerization is inhibited by hydroquinone, suggesting a free‐radical initiation. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 70–77, 2011     

Solubility of Rhodochrosite (MnCO3) in NaCl Solutions

The solubility of rhodochrosite (MnCO₃) at 25°C under constant carbon dioxide partial pressure p(CO₂) was determined in NaCl solutions as a function of ionic strength I. The dissolution of MnCO₃(s) for the reaction

Reactivity of the Ge–H,Sn–H,P–H,and Se–H Bonds in Radical Abstraction Reactions

The experimental data for the liquid- and gas-phase reactions of atoms and radicals with organoelement compounds R _{n – 1}E–H

Synthesis of thiols,disulfides, and sulfonic acids containing trichloromethyl,dichloro vinyl,and carboxy groups

Summary Starting from...-tetrachloroalkanes, trichloroalkenes of structure CCl₂=CH(CH₂)_nCl, and-chloro carboxylic acids, we obtained ithio, mercapto, and sulfo compounds and some of their derivatives of structure; [CCl₃(CH₂)₄]₂S₂; [CCl₂=CH(CH₂)₃]₂S₂; [ROOC(CH₂)₄]₂S₂ (in which ); CCl₃(CH₂)₄SCl; CCl₃(CH₂)_nSH (in which n=4,6,8); CCl₂=CH(CH₂)₃SH; ROOC(CH₂)₄SH (in which R=H, C₂H₅); CCl₃(CH₂)_nSO₃Na (in which n=4,6,8); C₂H₅OOC(CH₂)₄SO₃Na.     

Kinetics and mechanism of oxidation of hydroxylamine by tetrachloroaurate(III) ion

The oxidation of H₂NOH is first-order both in [NH₃OH⁺] and [AuCl₄ ^–]. The rate is increased by the increase in [Cl^–] and decreased with increase in [H⁺]. The stoichiometry ratio, [NH₃OH⁺]/[AuCl₄ ^–], is 1. The mechanism consists of the following reactions.

Molecular Structure of tert-Butylazide: A Gas-Phase Electron Diffraction and Quantum Chemical Study

The molecular structure of tert-butylazide has been determined by gas-phase electron diffraction and quantum chemical calculations. The HF/6-31G* and B3LYP/6-31G** calculations yielded near C _s symmetry for the tert-butyl group, anti conformation of the (C)N—N bond with respect to one of the bonds, and an essentially free rotation around the bond with a 0.34 kcal/mol energy difference between syn and anti conformations of the CNNN moiety, the anti being the more stable form. The electron diffraction analysis was carried out by modeling a mixture of conformational isomers, generated by rotating the terminal nitrogen of the azide group, using a computed rotational potential. The data are consistent with C _s symmetry for the tert-butyl group. The bond, however, was found to be rotated out of the anti position, with respect to one of the bonds, by 12.5(12)°. The electron diffraction analysis yielded the following bond lengths (r _g), bond angles, and torsional angles: , .     

Characterization of Potassium Chloride as an Equitransferent “Intersolvental” Salt Bridge

The electromotive forces (emf) E _A and E _C of the following concentration cells with transference: respectively, together with the emfs E _MAX of the corresponding double cell without transference: have been measured at KCl molalities m (m ₁ fixed and m ₂ varied, with m ₂>m ₁) approximately up to the KCl solubility limit in 12 solvent mixtures for the three aqueous–organic solvent systems (ethylene glycol+water), (acetonitrile + water), and (1,4-dioxane + water) up to 0.8 mass fraction of organic component. For all the cases explored, the E _A vs. E _MAX relation is linear over the whole KCl molality range. The ionic transference numbers t of KCl determined therefrom show a curvilinear dependence on the mass fraction of the organic component of the relevant solvent mixture and are found to fall in the range 0.52–0.48, viz., within ±4% of exact equitransference (t ₊ = t _– = 0.5). In particular, KCl becomes exactly equitransferent (i.e., an ideal salt bridge) in aqueous mixtures with the following mass fractions of organic component: 0.4 ethylene glycol and 0.09 acetonitrile, as well as 0.12 methanol, and 0.08 and 0.34 ethanol from our recent work. Even if use of KCl as a salt bridge would be somewhat restricted by its limited solubility in high mass fractions of dioxane and acetonitrile and pending extension of investigation to other mixed-solvent systems, the above figures characterize KCl as a fairly good intersolvental salt bridge in electrochemistry, electroanalysis, and corrosion science.     

Kinetics of PdII‐catalyzed polymerization of methyl methacrylate by triethanolamine in the presence of CCl4

Polymerization of methyl methacrylate (MMA) with triethanolamine (TEA) and carbon tetrachloride has been investigated in the presence of PdCl₂ and in a dimethylsulfoxide (DMSO) medium by employing a dilatometric technique at 60°C. The rate of polymerization has been obtained under the conditions [CCl₄]/[TEA] ≤ 1. The kinetic date indicate the possible participation of the charge‐transfer complex formed between the {amine–Pd^II} complex and CCl₄ in the polymerization of MMA. In the absence of either CCl₄ or amine, no polymerization of MMA was observed under the present experimental conditions. The rate of polymerization was inhibited by hydroquinone, suggesting a free‐radical initiation. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 171–177, 2000     

The thermal decomposition of zirconium oxyhydroxide

The thermal decomposition of zirconium oxyhydroxides prepared by the mixture of aqueous zirconium oxychloride solutions and aqueous solutions of sodium hydroxide or ammonium hydroxide under various conditions has been examined by thermogravimetry, differential thermal analysis, X-ray diffraction study and infrared spectrophotometry. As a result, it is seen that the thermal decomposition of zirconium oxyhydroxide, in which the composition is ZrO_2-x(OH)_2xyH₂O where x2 and 1y<2, proceeds according to the following process:

The Second Dissociation Constant of Carbonic Acid in Ethanol–Water Mixtures from 5 to 45°C

The determination of the second dissociation constant of carbonic acid K ₂ in 5, 15, and 25 mass% ethanol—water mixed solvents has been made using cell of the type: