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1.
Viscosity B-coefficients for cesium chloride and lithium sulfate in methanol + water mixtures at 25 and 35 °C are reported. A general
treatment of the quasi-thermodynamics of viscous flow of electrolyte solutions is described. ΔG
3
Θ
(1→1′), the contribution made to the Gibbs energy of activation of the solution by the influence of the solute on the solvent,
is a function of solute–solvent interactions only; but, ΔH
3
Θ
(1→1′) and ΔS
3
Θ
(1→1′) also reflect the solvent–solvent interactions. In aqueous solution all alkali-metal ions except Li+ are sterically unsaturated, having solvent co-ordination numbers n<n
max , the maximum allowed sterically. Such complexes exchange molecules with the solvent more readily than saturated ones and
have energy–reaction co-ordinate diagrams in forms that explain the negative B or ΔG
3
Θ
(1→1′) values found in aqueous solution. Saturated complexes are the norm in non-aqueous solvents, and the ΔG
3
Θ
(1→1′) values are determined mainly by the secondary solvation. Behavior in mixed solvents reflects the transition from aqueous
to non-aqueous behavior across the range of solvent composition. 相似文献
2.
Yue Zhu Min Pu De-Cai Fang Yong-Qiang Ji Jing He David G. Evans 《Structural chemistry》2010,21(4):817-825
Abstract
The cis–trans isomerization pathways of 3,3′-azobenzene disulphonate in the S0 and T1 states are studied by DFT method at the B3LYP/6-31G(d,p) level. In the S0 state, the cis–trans isomerization concerns the complex pathway that is characterized by the inversion of one NNC angle combined with rotation around the NC bond, and the three sequential transition states are also found on the potential energy profile. Therefore, the cis–trans isomerization of 3,3′-azobenzene disulphonate can be understood in terms of a pathway involving successive rotation, inversion, and rotation processes. The energy barrier of the S0 state is 22.79 kcal mol−1. In the T1 state, the isomerization mainly concerns the rotational pathway around the NN double bond, and the two isomers are connected through only one transition state. The isomerization of the T1 state is related to a lower energy barrier, 5.02 kcal mol−1, but requires a change in spin-multiplicity. 相似文献3.
A series of ceria-incorporated zirconia (Ce1−xZrxO2,x = 0 to 1) solid solutions were prepared by employing the solution combustion synthesis route. The products were characterized
by XRD and UV-Vis-NIR diffuse reflectance spectroscopy. The materials are crystalline in nature and the lattice parameters
of the solid solution series follow Vegard’s law. Diffuse reflectance spectra of the solid solutions in the UV region show
two intense bands at 250 and 297 nm which are assigned respectively to Ce3+ ← O2−and Ce4+ ← O2− charge transfer transitions. The two vibrational bands in 6960 cm−1 and 5168 cm−1 in the NIR region indicate the presence of surface hydroxyl groups on these materials. 相似文献
4.
Ben Cherifa A. Rogez J. Jemal M. Mathieu J. C. 《Journal of Thermal Analysis and Calorimetry》2001,63(3):689-697
Using an isoperibol calorimeter for rapid reactions and a Calsol type microcalorimeter for slow processes, are applied to
determine the enthalpies of solution of two synthetic phosphate products in nitric acid. Namely, β tricalcium phosphate Ca3(PO4)2 and the calcium hydroxyapatite Ca10 (PO4)6 (OH)2 are measured by varying pH value of the solvent. Some dissolution mechanisms are proposed for various pH values. They are
ensured by complementary reactions of solution of Ca(NO3)2, Ca(H2 PO4)2 and H3 PO4 in the same solvents. An extrapolation of solution enthalpies to pH=7 leads to the enthalpy of solution of these products
in the pure water. These values are Δsol
H °=–138.3 kJ mol–1 for Ca3 (PO4)2 and –393.6 kJ mol–1 for Ca10 (PO4)6 (OH)2 .
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
W. Earle Waghorne 《Monatshefte für Chemie / Chemical Monthly》2003,134(5):655-667
Summary. The solubilities of the silver halides in three non-aqueous solvents: methanol, acetonitrile, and dimethylsulfoxide, and
in their aqueous mixtures, are reviewed. Values for the solubility product, K
SO
, the enthalpies of solution, Δ
sol
H
o
, and the equilibrium products for AgX
(i−1)−
i
silver halide complexes, β
i
, are listed and, where possible, compared. The solvent systems provide examples for three types of mixed aqueous solvent
system: aqueous alcohol mixtures and aqueous mixtures with dipolar aprotic solvents that are weakly or strongly basic. The
experimental data are discussed in terms of the solvation of the silver and halide ions in the mixed solvents.
E-mail: Earle.Waghorne@ucd.ie
Received September 30, 2002; accepted October 29, 2002
Published online April 7, 2003
RID="a"
ID="a" Dedicated to Prof. Heinz Gamsj?ger on the occasion of his seventieth birthday 相似文献
6.
The protonation constants of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin, H2tpps4−, were determined in water–ethanol and water–methanol mixed solvents, using a combination of spectrophotometric and potentiometric
methods at 20 °C and 0.1 mol⋅dm−3 sodium perchlorate as supporting electrolyte. Two protonation constants, K
1 and K
2, were characterized and were analyzed in various media in terms of the Kamlet, Abboud and Taft (KAT) parameters. Single-parameter
correlations of the protonation constant K
1 versus α (hydrogen-bond donor acidity) and π
* (dipolarity/polarizability) are poor in all solutions, but dual-parameter (α and π
*) correlation represents a significant improvement with regard to the single- and multi-parameter models. However, the single-parameter
correlation of log 10
K
2 in terms of β (hydrogen-bond acceptor basicity) shows a better result than dual- and multi-parameter correlations. Linear correlation is
observed when the experimental log 10
K
1 and log 10
K
2 values are plotted versus the calculated ones when the KAT parameters are considered. To evaluate the protonation constants
of H2tpps4−, the Yasuda-Shedlovsky extrapolation is used to obtain the log 10
K
1 and log 10
K
2 values at zero percent organic solvent. Finally, the results are discussed in terms of the effect of the solvent on protonation. 相似文献
7.
Excess molar volumes, V
m
E, and partial molar volumes, ↕
2, have been determined for dilute aqueous solutions of 1-butanol, 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol,
1,2,4-butanetriol and 1,2,3,4-butanetetrol (erythritol) at 298.15 K, as a function of composition from density measurements.
The limiting partial molar volumes, ↕
2∞, of alcohols in aqueous solution are evaluated through extrapolation. Interactions of the different solutes with water are
discussed in terms of the relationship among polar and non-polar groups on water structure and the effect of the position
of hydroxyl groups in the molecule. 相似文献
8.
H. Müller R. Franke S. Vogtner R. Jaquet W. Kutzelnigg 《Theoretical chemistry accounts》1998,100(1-4):85-102
Calculations at various coupled-cluster (CC) levels with and without the inclusion of linear r
i
j
-dependent terms are performed for the HF molecule in its ground state with a systematic variation of basis sets. The main
emphasis is on spectroscopic properties such as the equilibrium distance r
e and the harmonic vibration frequency ωe. Especially with the R12 methods (including linear r
i
j
-dependent terms), convergence to the basis set limit is reached. However, the results (at the basis set limit) are rather
sensitive to the level of the treatment of electron correlation. The best results are found for the CCSDT1-R12 and CCSD[T]-R12
methods (CCSD[T] was previously called CCSD+T(CCSD)), while CCSD(T) overestimates ωe by ≈6 cm−1. The good agreement of conventional CCSD(T) with experiment for basis sets far from saturation (e.g. truncated at g-functions) is probably the result of a compensation of errors. The contribution of core-correlation is non-negligible and
must be included (effect on ωe≈5 cm−1). Relativistic effects are also important (23 cm−1), while adiabatic effects are much smaller (<1cm−1) and non-adiabatic effects on ωe can be simulated in replacing nuclear by atomic masses; for rotation nuclear masses appear to be the better choice, at least
for hydrides. From a potential curve based on calculations with the CCSDT1-R12 method with relativistic corrections, the IR
spectrum is computed quantum-mechanically. Both the band heads and the rotational structures of the observed spectra are reproduced
with a relative error of ≈10−4 for the three isotopomers HF, DF, and TF.
Received: 3 July 1998 / Accepted: 4 August 1998 / Published online: 28 October 1998 相似文献
9.
T. M. Usacheva N. V. Lifanova V. I. Zhuravlev V. K. Matveev 《Journal of Structural Chemistry》2009,50(5):930-942
The dielectric spectra of polypropyleneglycols H-(C3H6O)
N
p
-OH (PPGs), where N
p
= 1, 2, 3, 7, 12, 17, 20, 34, 69, were analyzed in terms of the Dissado Hill (DH) cluster model above the vitrification temperatures.
In PPGs, the structural clusters are associates formed by intra- and intermolecular hydrogen bonds. The activation processes
of cleavage and formation of intermolecular hydrogen bonds in clusters, when the total number of intermolecular hydrogen bonds
changes, are characterized by the parameter n
DH. The fluctuation processes of simultaneous exchange of molecules between adjacent clusters correspond to redistributions
of intermolecular hydrogen bonds between clusters, when only the position but not the total number of intermolecular hydrogen
bonds changes, and are characterized by the parameter m
DH. The relaxation time τDH at 303 K and 423 K and the parameters n
DH and m
DH of the dielectric spectra were calculated. The activation energies of relaxation in the range 210–323 K were determined.
The mean statistic squares of the dipole moments of clusters 〈μc2〉 and di-PG, PPG-425 (N
p
= 7), and PPG-2025 (N
p
= 34) molecules 〈μm2〉 at 303 K and 423 K were calculated. The number of the units of the oxypropylene chains involved in relaxation was determined.
The dependence of the parameters of the DH model, relaxation energies, 〈μc2〉 and 〈μm2〉 on N
p
were studied. 相似文献
10.
W. Zielenkiewicz I. V. Terekhova A. Marcinowicz M. Koźbial J. Poznanski 《Journal of Thermal Analysis and Calorimetry》2008,93(2):365-372
Interactions of native and modified α- and β-cyclodextrins with nicotinic acid, pyridoxine and pyridoxal were studied by isothermal
titration calorimetry, solution calorimetry, and 1H NMR spectroscopy at 298.15 K and pH 6.8. Weak 1:1 complex formation was found only between α-cyclodextrin and nicotinic
acid. The stability constant and corresponding thermodynamic parameters of complex formation (Δc
G, Δc
H and Δc
S) were calculated using the calorimetric data. The 1H NMR data indicate the shallow insertion of the carboxylic group of the nicotinic acid molecule into α-CD cavity. For all
other compounds the weak interactions, not accompanied by complex formation, were characterized by the enthalpic virial coefficients
calculated on the basis of McMillan-Mayer approach. The obtained thermodynamic parameters were analyzed in the terms of influence
of the solutes’ structure on the selectivity of intermolecular host-guest interactions. 相似文献
11.
E. A. Skrypnikova S. A. Kaluzhina E. V. Orlova 《Russian Journal of Electrochemistry》2011,47(11):1231-1235
The effect of glycine, α-alanine, and asparagine acid on the kinetics of anode processes occurring for copper in alkali electrolytes
is studied. The experiments are performed in a background solution of 1 × 10−2 M NaOH (pH 12). The concentrations of glycine and α-alanine are varied in the range of 1 × 10−6-1 × 10−1 M, and the concentration of asparagine acid is varied in the range of 1 × 10−5-1 × 10−3 M. All amino acids used in this work have been found to stimulate anode oxidation of passivated copper, initiating local
activation (LA) of the metal. Depending on the nature of amino acids, this effect occurs in various concentration ranges:
for glycine and α-alanine, it takes place at c= 5 × 10−3-2 × 10−2 M, while for asparagine acid, at c = 1 × 10−5−1 × 10−3 M. In addition to this general regularity, several individual peculiarities have been revealed: in the systems containing
a monobasic amino acid additive, local activation occurs at E = 0.10–0.20 V, while in the presence of a dibasic amino acid, the local activation is observed at two potentials, E
LA1 = 0.20–0.30 V and = E
LA2 = 0.80–0.90 V, separated by the repassivation region. 相似文献
12.
W. Earle Waghorne 《Monatshefte für Chemie / Chemical Monthly》2003,29(2):655-667
The solubilities of the silver halides in three non-aqueous solvents: methanol, acetonitrile, and dimethylsulfoxide, and
in their aqueous mixtures, are reviewed. Values for the solubility product, K
SO
, the enthalpies of solution, Δ
sol
H
o
, and the equilibrium products for AgX
(i−1)−
i
silver halide complexes, β
i
, are listed and, where possible, compared. The solvent systems provide examples for three types of mixed aqueous solvent
system: aqueous alcohol mixtures and aqueous mixtures with dipolar aprotic solvents that are weakly or strongly basic. The
experimental data are discussed in terms of the solvation of the silver and halide ions in the mixed solvents. 相似文献
13.
Solubility measurements as a function of temperature have been shown to be a powerful tool for the determination of thermodynamic properties of sparingly-soluble transition metal carbonates. In contrast to calorimetric methods, such as solution calorimetry or drop calorimetry, the evaluation of solubility data avoids many systematic errors, yielding the enthalpy of solution at 298.15 K with an estimated uncertainty of ±3 kJ · mol−1. A comprehensive set of thermodynamic data for otavite (CdCO3), smithsonite (ZnCO3), hydrozincite (Zn5(OH)6(CO3)2), malachite (Cu2(OH)2CO3), azurite (Cu3(OH)2(CO3)2), and siderite (FeCO3) was derived. Literature values for the standard enthalpy of formation of malachite and azurite were disproved by these solubility experiments, and revised values are recommended. In the case of siderite, data for the standard enthalpy of formation given by various data bases deviate from each other by more than 10 kJ · mol−1 which can be attributed to a discrepancy in the auxiliary data for the Fe2+ ion. A critical evaluation of solubility data from various literature sources results in an optimized value for the standard enthalpy of formation for siderite. The Davies approximation, the specific ion-interaction theory, and the Pitzer concept are used for the extrapolation of the solubility constants to zero ionic strength in order to obtain standard thermodynamic properties valid at infinite dilution, T = 298.15 K, and p = 105 Pa. The application of these electrolyte models to both homogeneous and heterogeneous (solid-solute) equilibria in aqueous solution is reviewed. 相似文献
14.
The CEPA-PNO method is used for calculating the energy difference ΔE
ST between the3∑− and the1Δ states of diatomic molecules in electronic π2 configurations. An analysis of the contribution of electron correlation to ΔE
ST is performed in terms of physically understandable effects such as direct correlation, dynamic spin polarization, semiinternal
and internal excitations. It is shown that these effects are of completely different importance for the molecules treated
in this study: For C2 the direct correlation between the two singly occupied π-orbitals is the dominant correlation contribution to ΔE
ST; for O2, S2, SO the internal excitation π
u
2
→ π
g
2
is predominant, whereas for NH and PH there is a close competition between the direct correlation and the spin polarization
of the underlying σ-orbitals. The basis set dependence of these effects is investigated, in particular for NH. Our final results
reproduce experimental values of ΔE
ST within 0.05–0.10 eV. 相似文献
15.
Y. S. Murillo L. Giraldo J. C. Moreno-Piraján 《Journal of Thermal Analysis and Calorimetry》2011,104(2):555-559
A way to calculate the enthalpic contributions of each component of the mixture of activated carbon and water to the immersion
enthalpy using the concepts of the solution enthalpies is presented. By determining the immersion enthalpies of a microporous
activated carbon in water, with values that are between –18.97 and −27.21 Jg−1, from these and the mass ratio of activated carbon and water, differential enthalpies for the activated carbon,
ΔHDIFacH_{{\rm DIF}_{\rm ac}} and water, ΔHDIFwH_{{\rm DIF}_{\rm w}} are calculated, and values between –15.95 and –26.81 Jg−1 and between –19.14 and –42.45 Jg−1, respectively are obtained. For low ratios of the mixture, the components’ contributions to the immersion enthalpy of activated
carbon and water differ by 3.20 Jg−1. 相似文献
16.
The complex formation of native and substituted β-cyclodextrins with m-aminobenzoic acid in water was characterized by calorimetry, 1H NMR and UV spectroscopic studies. These studies showed that β-, hydroxypropyl-β- and methyl-β-cyclodextrins form 1:1 inclusion complexes with m-aminobenzoic acid. The thermodynamic properties of complex formation (K,Δc
G
o,Δc
H
o,Δc
S
o) were calculated. It was found that the processes of complexation are mainly favorable entropically. Introduction of hydroxypropyl-
and methyl-substituents into the β-CD molecule results in negligible enhancement of stability of the complexes formed. The structure of these substituents has
no influence on the stability constant values. The insertion of the carboxylic group of m-aminobenzoic acid into the cyclodextrin cavity was confirmed by 1H NMR data. 相似文献
17.
X. Y. Feng X. P. Geng J. J. Peng H. Y. Hou Q. Bai 《Journal of Thermal Analysis and Calorimetry》2010,102(2):799-807
The displacement adsorption enthalpies (ΔH) of denatured α-Amylase (by 1.8 mol L−1 GuHCl) adsorbed onto a moderately hydrophobic surface (PEG-600, the end-group of polyethylene glycol) from solutions (x mol L−1 (NH4)2SO4, 0.05 mol L−1 KH2PO4, pH 7.0) at 298 K are determined by microcalorimeter. Further, entropies (ΔS), Gibbs free energies (ΔG) and the fractions of ΔH, ΔS, and ΔG for net adsorption of protein and net desorption of water are calculated in combination with adsorption isotherms of α-Amylase
based on the stoichiometric displacement theory for adsorption (SDT-A) and its thermodynamics. It is found that the displacement
adsorptions of denatured α-Amylase onto PEG-600 surface are exothermic and enthalpy driven processes, and the processes of
protein adsorption are accompanied with the hydration by which hydrogen bond form between the adsorbed protein molecules favor
formation of β-sheet and β-turn structures. The Fourier transformation infrared spectroscopy (FTIR) analysis shows that the
contents of ordered secondary structures of adsorbed α-Amylase increase with surface coverages and salt concentrations increment. 相似文献
18.
R. Yu. Bek 《Russian Journal of Electrochemistry》2000,36(4):403-407
It is shown that the kinetics of electrochemical processes in a copper-thiocarbamide solution is of mixed character. The effective
cathodic and anodic transfer coefficients Β = 0.25 and α = 0.4, reactions orders with respect to the ligand 0.7 and 1.5, and
the exchange current densityi
0 ≅10-4 A/cm2 are determined. Using the literature data on the thiocarbamide adsorption on copper, the results are interpreted as evidence
for the involvement of one thiocarbamide molecule from the bulk solution, along with the adsorbed ligands, in an elementary
act of copper dissolution. 相似文献
19.
Alexander Konkin Frank Wendler Frank Meister Hans-Klaus Roth Albert Aganov Oliver Ambacher 《Cellulose (London, England)》2007,14(5):457-468
Degradation processes of N-methylmorpholine-N-oxide monohydrate (NMMO), cellulose and cellulose/NMMO solutions were studied by high performance liquid chromatography (HPLC)
and electron spin resonance (ESR) spectroscopy. Kinetics of radical accumulation processes under UV (λ = 248 nm) excimer laser
flash photolysis was investigated by ESR at 77 K. Beside radical products of cellulose generated and stabilized at low temperature,
radicals in NMMO and cellulose/NMMO solutions were studied for the first time in those systems and attributed to nitroxide
type radicals ∼CH2–NO•–CH2∼ and/or ∼CH2–NO•–CH3∼ at the first and methyl •CH3 and formyl •CHO radicals at the second step of the photo-induced reaction. Kinetic study of radicals revealed that formation and recombination
rates of radical reaction depend on cellulose concentration in cellulose/NMMO solutions and additional ingredients, e.g.,
Fe(II) and propyl gallate. HPLC measurements showed that the concentrations of ring degradation products, e.g., aminoethanol
and acetaldehyde, are determined by the composition of the cellulose/NMMO solution. Results based on HPLC are mainly maintained
by ESR that supports the assumption concerning a radical initiated ring-opening of NMMO. 相似文献
20.
A. V. Odinokov M. V. Bazilevskii N. Kh. Petrov A. K. Chibisov M. V. Alfimov 《High Energy Chemistry》2010,44(5):376-382
A model describing the effect of counterion X− (X = Cl, I) on the deactivation kinetics of the S
1 state of thiacarbocyanine Cy+X− is presented. According to the model, the ion pair Cy+X− in a binary solution is characterized by a distribution function f(r) over interatomic distances r, which depends on the composition of the mixture. The assumption of kinetically independent local states of the ion pair,
which decay with the rate constants k
i(r)(i = 1–4 is the index of the decay channel), is made. The statistic analysis of the experimental data in terms of the model
permitted us to find the functions f(r) and to estimate the parameters of the constants k
i(r). 相似文献