Elektrische Leitfähigkeiten geschmolzener Salzmischungen aus Strontiumchlorid und Alkalimetallchloriden

Electrical Conductivity of Molten Strontium Chloride-Alkali Chloride Salt Mixtures The temperature and concentration dependence of the specific electrical conductivity is measured for binary fused mixtures SrCl₂–MeCl (Me = Li, Na, K, Rb, Cs). Minima of the conductivity are found at the concentration x · 0.5 in the systems SrCl₂–(KCl, RbCl, CsCl).     

Atomic Dopants Involved in the Structural Evolution of Thermally Graphitized Graphene

Thermally doped nitrogen atoms on the sp²‐carbon network of reduced graphene oxide (rGO) enhance its electrical conductivity. Atomic structural information of thermally annealed graphene oxide (GO) provides an understanding on how the heteroatomic doping could affect electronic property of rGO. Herein, the spectroscopic and microscopic variations during thermal graphitization from 573 to 1 373 K are reported in two different rGO sheets, prepared by thermal annealing of GO (rGO_therm) and post‐thermal annealing of chemically nitrogen‐doped rGO (post‐therm‐rGO). The spectroscopic transitions of rGO in thermal annealing ultimately showed new oxygen‐functional groups, such as cyclic edge ethers and new graphitized nitrogen atoms at 1 373 K. During the graphitization process, the microscopic evolution resolved by scanning tunneling microscopy (STM) produced more wrinkled surface morphology with graphitized nanocrystalline domains due to atomic doping of nitrogen on a post‐therm‐rGO sheet. As a result, the post‐therm‐rGO‐containing nitrogen showed a less defected sp²‐carbon network, resulting in enhanced conductivity, whereas the rGO_therm sheet containing no nitrogen had large topological defects on the basal plane of the sp²‐carbon network. Thus, our investigation of the structural evolution of original wrinkles on a GO sheet incorporated into the graphitized N‐doped rGO helps to explain how the atomic doping can enhance the electrical conductivity.     

The mechanism of O(3P) atom reaction with ethylene and other simple olefins

Reactions of oxygen atoms with ethylene, propene, and 2-butene were studied at room temperature under discharge flow conditions by resonance fluorescence spectroscopy of O and H atoms at pressures of 0.08 to 12 torr. The measured total rate constants of these reactions are K = (7.8 ± 0.6)·10^?13cm³s^?1,K = (4.3 ± 0.4) ± 10^?12 cm³ s^?1, K = (1.4 ± 0.4) · 10^?11 cm³ s^?1. The branching ratios of H atom elimination channels were measured for reactions of O atoms with ethylene and propene. No H-atom elimination was found for the reaction of O-atoms with 2-butene. A redistribution of reaction O + C₂ channels with pressure was found. A mechanism of the O + C₂ reaction was proposed and the possibility of its application to other olefins is discussed. On the basis of mechanism the pressure dependence of the total rate constant for reaction O + C₂ was predicted and experimentally confirmed in the pressure range 0.08–1.46 torr.     

Peculiar kinetics of the complex formation in the iron(III)–sulfate system

The results of comprehensive equilibrium and kinetic studies of the iron(III)–sulfate system in aqueous solutions at I = 1.0 M (NaClO₄), in the concentration ranges of T = 0.15–0.3 mM, and at pH 0.7–2.5 are presented. The iron(III)–containing species detected are FeOH²⁺ (=FeH_?1), (FeOH) (=Fe₂H_?2), FeSO, and Fe(SO₄) with formation constants of log β = ?2.84, log β = ?2.88, log β = 2.32, and log β = 3.83. The formation rate constants of the stepwise formation of the sulfate complexes are k_1a = 4.4 × 10³ M^?1 s^?1 for the ${\rm Fe}^{3+} + {\rm SO}_4^{2-}\,\stackrel{k_{1a}}{\rightleftharpoons}\, {\rm FeSO}_4^+The results of comprehensive equilibrium and kinetic studies of the iron(III)–sulfate system in aqueous solutions at I = 1.0 M (NaClO₄), in the concentration ranges of T = 0.15–0.3 mM, and at pH 0.7–2.5 are presented. The iron(III)–containing species detected are FeOH²⁺ (=FeH_?1), (FeOH) (=Fe₂H_?2), FeSO, and Fe(SO₄) with formation constants of log β = ?2.84, log β = ?2.88, log β = 2.32, and log β = 3.83. The formation rate constants of the stepwise formation of the sulfate complexes are k_1a = 4.4 × 10³ M^?1 s^?1 for the ${\rm Fe}^{3+} + {\rm SO}_4^{2-}\,\stackrel{k_{1a}}{\rightleftharpoons}\, {\rm FeSO}_4^+$ step and k₂ = 1.1 × 10³ M^?1 s^?1 for the ${\rm FeSO}_4^+ + {\rm SO}_4^{2-} \stackrel{k_2}{\rightleftharpoons}\, {\rm Fe}({\rm SO}_4)_2^-$ step. The mono‐sulfate complex is also formed in the ${\rm Fe}({\rm OH})^{2+} + {\rm SO}_4^{2-} \stackrel{k_{1b}}{\longrightarrow} {\rm FeSO}_4^+$ reaction with the k_1b = 2.7 × 10⁵ M^?1 s^?1 rate constant. The most surprising result is, however, that the 2 FeSO? Fe³⁺ + Fe(SO₄) equilibrium is established well before the system as a whole reaches its equilibrium state, and the main path of the formation of Fe(SO₄) is the above fast (on the stopped flow scale) equilibrium process. The use and advantages of our recently elaborated programs for the evaluation of equilibrium and kinetic experiments are briefly outlined. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 114–124, 2008     

Solubility and hydrolysis of HCFC‐22 (CHF2Cl): Upward revision of rate constants for aqueous reactions of CHF2Cl with OH− at elevated temperature

Henry's law constants of CHF₂Cl in water at temperature T in K, K_H(T) in M atm^?1, were determined to be ln(K_H(T))=?(11.1±1.5)+((2290±500)/T) at 313–363 K by means of a phase ratio variation headspace method. The temperature‐dependent rate constants for aqueous reactions of CHF₂Cl with OH^?, k(T) in M^?1 s^?1, were also determined to be 3.7×10¹³exp(?(11, 200/T)) at 313–353 K, by considering the gas–water equilibrium, the aqueous reaction at room temperature, and liquid‐phase diffusion control. The liquid‐phase diffusion control was approximated with a one‐dimensional diffusion first‐order irreversible chemical reaction model. The k(T) value we determined is 10 times (at 353 K) or 3 times (at 313 K) as large as the value reported (R. C. Downing, Fluorocarbon Refrigerants Handbook, Prentice Hall: Englewood Cliffs, NJ, 1988). This upward revision of k(T) indicates that the removal efficiency of CHF₂Cl directly through the hydrolysis (CHF₂Cl + OH^?) is higher than previously expected at temperatures, such as 353 K, relevant to wet flue gas cleaning systems for ozone‐destruction substance‐destruction facilities. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 639–647, 2011     

2–Butoxyethanol and benzyl alcohol reactions with the nitrate radical: Rate coefficients and gas‐phase products

The bimolecular rate coefficients k and k were measured using the relative rate technique at (297 ± 3) K and 1 atmosphere total pressure. Values of (2.7 ± 0.7) and (4.0 ± 1.0) × 10^?15 cm³ molecule^?1 s^?1 were observed for k and k, respectively. In addition, the products of 2‐butoxyethanol + NO₃^? and benzyl alcohol + NO₃^? gas‐phase reactions were investigated. Derivatizing agents O‐(2,3,4,5,6‐pentafluorobenzyl)hydroxylamine and N, O‐bis (trimethylsilyl)trifluoroacetamide and gas chromatography mass spectrometry (GC/MS) were used to identify the reaction products. For 2‐butoxyethanol + NO₃^? reaction: hydroxyacetaldehyde, 3‐hydroxypropanal, 4‐hydroxybutanal, butoxyacetaldehyde, and 4‐(2‐oxoethoxy)butan‐2‐yl nitrate were the derivatized products observed. For the benzyl alcohol + NO₃^? reaction: benzaldehyde ((C₆H₅)C(?O)H) was the only derivatized product observed. Negative chemical ionization was used to identify the following nitrate products: [(2‐butoxyethoxy)(oxido)amino]oxidanide and benzyl nitrate, for 2‐butoxyethanol + NO₃^? and benzyl alcohol + NO₃^?, respectively. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with a plausible 2‐butoxyethanol or benzyl alcohol + NO₃^? reaction mechanisms based on previously published volatile organic compound + NO₃^? gas‐phase mechanisms. © 2012 Wiley Periodicals, Inc.

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

© 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 778–788, 2012     

The 13C and D kinetic isotope effects in the reaction of CH4 with Cl

The kinetic isotope effects in the reaction of methane (CH₄) with Cl atoms are studied in a relative rate experiment at 298 ± 2 K and 1013 ± 10 mbar. The reaction rates of ¹³CH₄, ¹²CH₃D, ¹²CH₂D₂, ¹²CHD₃, and ¹²CD₄ with Cl radicals are measured relative to ¹²CH₄ in a smog chamber using long path FTIR detection. The experimental data are analyzed with a nonlinear least squares spectral fitting method using measured high‐resolution spectra as well as cross sections from the HITRAN database. The relative reaction rates of ¹²CH₄, ¹³CH₄, ¹²CH₃D, ¹²CH₂D₂, ¹²CHD₃, and ¹²CD₄ with Cl are determined as k/k = 1.06 ± 0.01, k/k = 1.47 ± 0.03, k/k = 2.45 ± 0.05, k/k = 4.7 ± 0.1, k/k = 14.7 ± 0.3. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 110–118, 2005     

The effect of water content on the ultimate properties of rubbery nanocomposite gels

An investigation was conducted into the effects of water content (R) on the ultimate tensile properties of nanocomposite hydrogels (NC gels) based on poly(N‐isopropylacrylamide)/clay networks. Rubbery NC gels with low clay contents (<NC10) exhibited unique changes in their stress–strain curves, depending on the R. At high R, where PNIPA chains are fully hydrated, NC gels retained their rubbery tensile properties, whereas they changed to exhibit plastic‐like deformations with decreasing R. Consequently, for a series of NC gels with different R, a failure envelope was obtained by connecting the rupture points in the stress–strain curves. Here, the counterclockwise movement was observed as either the R decreased or the strain rate increased. This seemed to be analogous to that of a conventional elastomer (e.g., SBR), although the mechanisms are different in the two cases. From the R and C_clay dependences of the ultimate properties, three critical values of R were defined, where R showed a maximum strain at break, a steep increase in initial modulus, and onset of brittle fracture. Compared with NC gels, OR gels (chemically crosslinked hydrogels) showed similar but very small changes in their stress–strain curves on altering R, whereas LR (viscous PNIPA solution) showed a monotonic decrease (increase) in ε_b (E_i) with decreasing R. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2328–2340, 2009     

The kinetics of the reaction F + H2 → HF + H. A critical review of literature data

Published experimental studies concerning the determination of rate constants for the reaction F + H₂ → HF + H are reviewed critically and conclusions are presented as to the most accurate results available. Based on these results, the recommended Arrhenius expression for the temperature range 190–376 K is k = (1.1 ± 0.1) × 10⁻¹⁰ exp |-(450 ± 50)/T| cm³ molecule⁻¹ s⁻¹, and the recommended value for the rate constant at 298 K is k = (2.43 ± 0.15) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The recommended Arrhenius expression for the reaction F + D₂ → DF + D, for the same temperature range, based on the recommended expression for k and accurate results for the kinetic isotope effect k/k is k = (1.06 ± 0.12) × 10^×10 exp |-(635 ± 55)/T|cm³ molecule⁻¹ s⁻¹, and the recommended value for 298 K is k = (1.25 ± 0.10) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 67–71, 1997.     

Kinetics of the reaction of poly(α-methylstyryl sodium,potassium, and cesium) with t-butyl chloride in tetrahydrofuran

The kinetics of the reaction of “living” poly(α-methylstyrl sodium, potassium, and cesium) with t-butyl chloride have been studied spectrophotometrically in tetrahydrofuran (THF) in the temperature range 283–303 K. The reactions, when the free ions present in solution are suppressed by tetraphenylboron salt, are first order with respect to both living ends and halide concentrations. Additions of tetraphenylboron salts produce a slight retardation effect on the rate of reaction in the case of sodium, indicating only a small contribution of free ions to the overall rate; in the case of potassium, there is no apparent effect. Analysis of the data indicates that the free ion is approximately 30 times more reactive than the sodium ion pair. The Arrhenius plots for contact ion-pair termination are linear and the activation energies and preexponential factors determined are E = 38.6 kJ mole^?1, log A = 4.44 liter mole^?1 sec^?1 and E = 46.0 kJ mole^?1, log A = 5.10 liter mole^?1 sec^?1. The reaction mechanism is interpreted in terms of elimination plus some side reaction to produce two unexpected reaction products—isobutane and a 315–320-nm absorbing grouping in the polymer.     

Barriers to internal rotation in neopentylbenzenes substituted on the benzyl group. A 13C NMR band shape study

Two series of neopentylbenzenes with one or two substituents on the benzyl group have been synthesized. In one series the substituents were H, F, Cl, Br, I, OCH₃, OCOCH₃, OSi(CH₃)₃ CH₃ and CH₂CH₃, and in the other OH and R [R ? H, CH₃, CH₂CH₃, (CH₂)₃CH₃, CH(CH₃)₂ and C(CH₃)₃]. Barriers to internal C? C and C? C rotation have been estimated by ¹³C NMR band shape methods. Estimated barriers were found to increase as the size of the substituent increases. The results are discussed in terms of possible initial and transition states, based on summations of results from molecular mechanics (MM) calculations, using the Allinger MMP1 program. Barriers estimated experimentally are compared with results from other systems found in the literature.     

Thermisches Verhalten und Kristallstruktur von YAl3Cl12

Thermal Behaviour and Crystal Structure of YAl₃Cl₁₂ We determined the thermodynamic data of YAl₃Cl₁₂ ΔH = ?739.9 ± 3 kcal/mol and S = 136.1 ± 4 cal/K · mol by total pressure measurements and ΔH = ?739.1 ± 1.6 kcal/mol by solution calorimetry. Using DTA-investigations we established the phase diagram in the system AlCl₃–YCl₃. The crystal structure was refined on the basis of single crystal data (P3₁ 12; Z = 3; a = 1 046.8(2); c = 1 562.3(3) pm).     

Zur Struktur der LiMIIMIIIF6-Verbindungen. Neue Verbindungen mit MIII=In und Ti

On the Structure of LiM^IIM^IIIF₆ Compounds. New Compounds with M^III=IN and Ti LiMn^IIInF₆ compounds with M^II = Mg, Mn, Co, Ni, Zn, Cd and Ca crystallize in the Na₂SiF₆ structure. The Ti(III) compound LiMgTiF₆ has trirutile structure, LiMnTiF₆ has Na₂SiF₆ and trirutile structure (H.-T. modification), LiCaTiF₆ and LiCdTiF₆ have Li₂ZrF₆ superstructure. With M^II = Co, Ni and Zn solid solutions trirutile — MF₂(rutile) could be only prepared. The lattice constants of all compounds are reported. For LiMnVF₆ and LiFeGaF₆ too dimorphism Na₂SiF₆ trirutile was observed. In the system LiNiCrF₆ (trirutile) — LiMnCrF₆ (Na₂SiF₆ structure) phase limits of both structures are determined in dependence on the ratio of ionic radii r/r. Magnetic data of the In compounds with M^II = Co and Ni and of the Ti(III) compounds with M^II = Mg, Zn, Mn, just as of α- and β-LiMnVF₆ are also given. The three structures only exist if r reaches from 0.6 to 1.2 Å and r from 0.5 to 0.8 Å. The stability-fields are determined by the ratio of ionic radii r/r_Li, r/r_Li and r/r: trirutile 0.9–1.2, Na₂SiF₆ type 1.2–～1.4 and Li₂ZrF₆ superstructure >1.4. The dependence of rate of ionic radii is explained by the different sharing of MF₆ octahedra.     

Verdampfung von Kupfer(II)chlorid und Struktur des Dampfes untersucht mit UV./VIS.- und Raman-Spektroskopie

The vapour pressure of CuCl₂ and the dimerization of CuCl₂(g) have been investigated by optical spectroscopy in the range 420–650°C, p = 0.5-5 atm. The enthalpy of dimerization of CuCl₂(g) was determined by visible and by Raman spectroscopy and good agreement was found (?154 kJmol^?1 and ?143 kJmol^?1). CuCl₂(g) shows two totally symmetric Raman modes (373 and 127 cm^?1) indicating that, at least at elevated temperatures, CuCl₂(g) is not a linear molecule. The optical spectra of Cu₂Cl₄(g) and CuLCl₅(g) (L ? Ga, In) are very similar supporting a CuCl₃-chromophor in both cases. The formerly proposed structure of CuL₂Cl₈(g) (L ? Al, Ga) contains bridging and terminal chlorides, structural elements also present in Cu₂Cl₄(g). In agreement with the proposed structure v is identical in Cu₂Cl₄(g) and CuL₂Cl₈(g), while V is at lower energies (20–30 cm^?1) in CuL₂Cl₈(g) than in Cu₂Cl₄(g).     

Generalized statistical gelation theory

Gel points in random polymerizations of the general type Σ_iRA + Σ_jRB in which A-groups react with A- and B-groups, and B-groups react only with A-groups are considered. (The symbols Σ_i and Σ_i signify that the A- and B-bearing reactants RA and RB can be mixtures of monomers of different functionalities, denoted generally as f_ai and f_bj.) The usual case of A-groups reacting only with B-groups is a special case of the present theory. The effects of chemical kinetics, the competitive reaction of A- and B-groups, are separated from the generalized statistical condition for gelation. The former are used to define reaction curves and the latter, gelation curves. Both types of curve are represented as p_a as a function of p_b. For a given polymerization, gelation occurs when the reaction curve and the gelation curve intersect. When A-groups react only with B-groups, the gel points are those for the usual type of Σ_iRA + Σ_jRB polymerization, and, in the limit of A-groups only reacting with A-groups, the gel points are those for Σ_iRA self polymerizations.     

Rate constants for the gas‐phase reactions of nitrate radicals with geraniol,citronellol, and dihydromyrcenol

Terpenes and terpene alcohols are prevalent compounds found in a wide variety of consumer products including soaps, flavorings, perfumes, and air fresheners used in the indoor environment. Knowing the reaction rate of these chemicals with the nitrate radical is an important factor in determining their fate indoors. In this study, the bimolecular rate constants of k (16.6 ± 4.2) × 10^?12, k (12.1 ± 3) × 10^?12, and k (2.3 ± 0.6) × 10^?14 cm³ molecule^?1 s^?1 were measured using the relative rate technique for the reaction of the nitrate radical (NO₃?) with 2,6‐dimethyl‐2,6‐octadien‐8‐ol (geraniol), 3,7‐dimethyl‐6‐octen‐1‐ol (citronellol), and 2,6‐dimethyl‐7‐octen‐2‐ol (dihydromyrcenol) at (297 ± 3) K and 1 atmosphere total pressure. Using the geraniol, citronellol, or dihydromyrcenol + NO₃? rate constants reported here, pseudo‐first‐order rate lifetimes (k′) of 1.5, 1.1, and 0.002 h^?1 were determined, respectively. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 669–675, 2010     

Recommendations for measuring second-order rate constants and kinetic solvent isotope effects on acid-catalyzed reactions

Kinetic solvent isotope effects (KSIE) were measured for the hydrolyses of acetals of benzaldehydes in aqueous solutions covering the pH (pD) range of 1–6. For p-methoxybenzaldehyde diethyl acetal, k/k = 1.8–3.1, depending on the procedure used to calculate the KSIE and on the pH (pD) range used as the basis for k(k). It is shown that this variation is an experimental artifact, and is a characteristic of KSIE measurements in general. It is recommended that k be calculated from a least-squares fit of data to the equation k_obs = k[L⁺], and that the KSIE be reported as k/k. The limitation remains, however, that the KSIE measured for a variety of substances over quite different pH (pD) ranges may not be comparable to more than ?20%. The source of these observations is discussed in terms of small changes in the activity coefficient ratios (a specific salt effect), including the solvent isotope effect on the activity coefficient ratio [eq. (3)].     

Gas‐phase reaction of Cl with dimethyl sulfide: Temperature and oxygen partial pressure dependence of the rate coefficient

The kinetics of the reaction of Cl atoms with dimethyl sulfide has been investigated using a relative rate technique. Experiments were performed with oxygen partial pressures of 0, 200, and 500 mbar at a total pressure of 1000 mbar (N₂ + O₂) over the temperature range 283–308 K in a 1080 L reactor using long path in situ Fourier transform infrared absorption spectroscopy to monitor the reactants. The 254 nm photolysis of trichloroacetyl chloride was used as the Cl atom source. Three reference hydrocarbons, cyclohexane, n‐butane, and propene were employed. Good agreement was found between the rate coefficients determined using the different reference compounds. The rate coefficients were found to decrease with increasing temperature at constant O₂ pressure and increase moderately with increasing O₂ partial pressure at constant temperature. The temperature dependences of the Cl atom reaction with dimethyl sulfide for the three O₂ partial pressure investigated can be expressed by the simple Arrhenius expressions: k = (4.22 ± 1.78) × 10^?13 exp((1968 ± 379)/T), k = (5.42 ± 1.85) × 10^?13 exp((1946 ± 381)/T), and k = (6.90 ± 2.04) × 10^?13 exp((1912 ± 381)/T). The errors are a combination of the 2σ statistical errors from the kinetic data analysis plus an estimated systematic error that includes the error in the reference hydrocarbon. The mechanistic implications of the results are discussed. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 66–73, 2005     

Upper- and lower-bound Hylleraas–CI calculations for the nonrelativistic Po states of the 4He isotope

Extensive Hylleraas–CI calculations for the lowest P^o states of ⁴He were performed. The dependence of the variational energy values E_κ on the mass parameter κ given by κ=m/m is discussed. Furthermore, lower bounds to E_κ were calculated using variance minimization. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66 : 25–30, 1998     

Chemical actinometry at 147.0 nm

Hexafluoroacetone (HFA) and O₂ were photolyzed at 147.0 nm to investigate their use in chemical actinometry. The products, CO for the former and O₃ in the latter case, were monitored. For accurate comparison, both of these substances were irradiated by a single light source with two identical reaction cells at 180° to each other. The light intensities I were measured under the same integrated as well as instantaneous photon flux based on ? and ?_CO (quantum yield) as 2 and 1, respectively. Optimum conditions for maximum product yield were 5.0 torr HFA pressure and an O₂ flow rate of 200 ml/min at 1 atm pressure for a 20-minute photolysis period. For light intensity variations between 1.09 × 10¹⁴ and 2.10 × 10¹⁵ photons absorbed/sec, the ratio I/I_HFA was found to be unity. Calibration with the commonly used N₂O actinometer for a ? value of 1.41 showed that I/I_HFA and I/I are unity. Both HFA and O₂ are suitable chemical actinometers at 147.0 nm with ?_CO and ? of 1 and 2, respectively. The light intensity determination in the first case involves the measurement of only one product which is noncondensible at 77°K, whereas wet analysis for O₃, the only product, in the second actinometer is necessary. Both of these determinations are quite simple and are preferable over product analysis in N₂O actiometry, wherein N₂ separation from other noncondensibles at 77°K is required.