摘要:

AbstractThe reactions of CF3O radicals with (1) NO and (2) NO2were studied using two different experimental techniques. A laser photolysis/LIF detection method was applied for measuring the rate constants as a function of temperature (T= 222–302 K) and total pressure (ptot= 7–107 mbar). Whereas the reaction with (1) NO was found to be independent of temperature and pressure withk1= (4.5±1.2)×10−11cm3s−1, the reaction with (2) NO2was found to be dependent on both of these variables. The temperature dependence ofk2in the high pressure limit can be given by the expressionk2,∝(T) = (8±5)×10−13exp ((863±194) K/T) cm3s−1. The product distributions of the two reactions were determined in separate experiments using steady‐state photolysis combined with FTIR spectroscopy. For reaction (1) only CF2O was found as a reaction product with a yield of 0.93±0.10, independent of temperature. For reaction (2) several products (CF3ONO2, CF2O, FNO2) were identified, the overall yield, however, is dominated (≥90%) by the recombination product CF3ONO2. A theoretical analysis of the detailed mechanisms of both reactions was made by performing ab initio energy and geometry predictions in combination with RRKM calculations. Both reactions were found to proceed via an initial addition mechanism involving the CF3ONOx(x= 1, 2) intermediate and a four‐center transition state. A direct abstraction of an F atom by

ISSN:0005-9021    

DOI:10.1002/bbpc.199700001

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractFar infrared laser magnetic resonance (FIR‐LMR) spectra of CF3, CHF2, and CH2F radicals were observed in the 300–800 μm wavelength region in the reactions of F atoms with a series of different hydrocarbon and partially fluorinated hydrocarbon molecules. To identify the carriers of the observed resonance patterns and to exclude or identify contamination of the spectra by additional resonances from other paramagnetic species, numerous chemical tests were developed and performed. With optimized sources and the chemical tests in hand, many spectra could be unambiguously attributed to CF3, CHF2, and CH2F, respectively. The present study reports the first gas phase detection of CHF2radicals in their ground electronic s

ISSN:0005-9021    

DOI:10.1002/bbpc.199700002

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractThe rate constants of the reactions of CHCl (X̃1A′) with C2H2(k4), C2H4(k5) and C3H6(k6) were measured as a function of temperature. Experiments were carried out under quasistationary conditions at around 18.5 mbar total pressure. It is shown that excimer laser photolysis of CF2= CHCl at λPH= 193 nm is a suitable source for CHCl (X̃1A′) generation. The following rate constants were obtained from logarithm plots:k4= (4.2±0.1)·1012(T/295K)−(0.79±0.06)cm3mol−1s−1k5= (3.2±0.2)·1012(T/295 K)−(1.52±0.12)cm3mol−1s−1k6= (8.3±1.4)·1012(T/295 K)−(1.39±0.05)cm3mol−1s−1The reactivity of CHCl (X̃1A′) is

ISSN:0005-9021    

DOI:10.1002/bbpc.199700003

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractThe kinetics of the bimolecular reactions OH+C2H2+M ⟺ C2H2OH+M (1) and OH+C2H4+M ⟺ C2H4OH+M (2) have been investigated over an extended pressure (1–130 bar) and temperature (300–800 K) range. The OH radicals have been generated by laser flash photolysis of suited precursors and their decays have been measured by saturated laser‐induced fluorescence (SLIF) under pseudo‐first‐order conditions. The pressure dependences have been analyzed by constructing falloff curves at fixed temperatures leading to reliable extrapolations towards the high pressure limiting rate constantsk∞. In the given temperature range these rate constants are represented ask1,∞= 3.8×10−11exp (–910 K/T) cm3molecule−1s−1and ask2,∞= 1.0×10−11cm3molecule−1s−1. At temperatures above 700 K biexponential decay curves have been obtained. The chemical equilibria of reactions (1) and (2) could be determined. By a third law analysis the equilibrium constants have been evaluated with reaction enthalpies for the addition complex C2H2OH of δIHo1(O K) = ‐(146 ± 10) kJ/mol and for C2H4OH of δIHo2(O K) = ‐(123 ± 6) kJ/mol, respectively. The two equilibrium constants are given byK1,eq= (5.4±2.2)×10−2(T/K)−1.7±0.2exp ((17560±1200) K/T) bar−1andK2,eq= 2.1 × 10−

ISSN:0005-9021    

DOI:10.1002/bbpc.199700004

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractPicosecond time‐resolved fluorescence spectroscopy has been used to examine the dynamic solvent effect on the excited intramolecular charge‐transfer (ICT)‐state formation in 4‐(9‐anthrylmethyl)‐N,N‐dimethylaniline (AMDMA) in linear alcohol solvents as a function of pressure. The non‐exponential population decay of the local excited (LE)‐state emission is analyzed by fitting to a double exponential function. As solvent viscosity increases, the rate of the ICT‐state formation of AMDMA becomes noticeably faster than the solvent relaxation time, which is gauged by the longitudinal relaxation time of the solvent (τL). The pressure effect on the ICT reaction of AMDMA in the excited state can be accounted for in terms of the pressure‐tuning effect of the solvent viscosity.In addition, the time‐dependent Stokes shift (TDSS) of the ICT emission is me

ISSN:0005-9021    

DOI:10.1002/bbpc.199700005

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractThe kinetics of the oxidation of Fe(bpy)2+3by S2O2−8have been studied in water and different water‐cosolvent mixtures. The cosolvents used were methanol t‐butyl alcohol, ethane 1,2‐diol and glycerol. The results are explained assuming an additional component of the reorganization free energy of the solvent in the mixtures, caused by dynamics of the changes in the composition of the (at least) innermost solvation shells of the reactants produced by the electron transfer. A quantitative estimation of this component is at

ISSN:0005-9021    

DOI:10.1002/bbpc.199700006

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractHigh pressure‐high temperature procedure and equipment is described to determine the specific volume of ammonia as a function of pressure and temperature. An autoclave consisting of a nickel‐based superalloy and a suitable pressure‐sensitive separator between ammonia and the pressure‐transmitting fluid is used. Ten volume isotherms between 298 and 723 K and at pressures from 10 to 950 MPa have been determined. Previous literature data extend to 950 MPa but only up to 473 or to 723 K at pressures below 500 MPa. Polynomials with up to eleven terms are used to represent each experimental volume isotherm with a maximum average deviation of 0.16%. A table with smoothed density values is presented for the whole range of conditions. A comparison with data calculated earlier by Haar and Gallagher (1978) up to 500 MPa showed deviations between 0.06 and 1.1% with an average of 0.4%. The present isothermal volume data are reasonably well described by Tait equations. Parameters ar

ISSN:0005-9021    

DOI:10.1002/bbpc.199700007

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractVapour pressures of di‐n‐propylether with ethanol and with 1‐butanol were measured at eight temperatures between 278.15 and 323.15 K by a static method. Reduction of the vapour pressures to obtain activity coefficients and excess molar Gibbs free energies was carried out by Barker's method. Mixtures containing ethanol show azeotropy with a minimum boiling temperature.GE,HE, andVE, at 298.15 K, of mixtures of di‐n‐propylether + methanol, + ethanol, + 1‐propanol, + 2‐propanol, and + 1‐butanol are compared with predictions of the ERAS model observing that the model reproduces acceptably the experim

ISSN:0005-9021    

DOI:10.1002/bbpc.199700008

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractWhile linear and curved phase transition lines inP(T) orH(T) diagrams can be described by adding linear and quadratic terms in a joint expansion of the Landau coefficientsa, bin terms ofP–PtandT–Ttwhere (Pt,Tt) is a critical point, a new class of phase diagram is obtained by allowing for bilinear,ϵ(P–Pt)(T–Tt), and higher product terms. In this contribution we relate these new expansion terms to some hitherto unexplained experimentalP–TandH–Tph

ISSN:0005-9021    

DOI:10.1002/bbpc.199700009

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY

摘要:

AbstractExcitation of acoustic waves in electrolytes by means of a.c. electric fields has been used to examine the structural and dynamical properties of the solutions. The acoustical signal efficiency depends on the electrolyte concentration and on the frequency of the exciting electric field. Experimental results, obtained in the aqueous solutions of LiCl, NaCl and KCl, are discussed. The influence of the electroacoustic‐cell design on the obtained results is studied as wel

ISSN:0005-9021    

DOI:10.1002/bbpc.199700010

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1997

数据来源: WILEY