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1.
The thermodynamics of adsorption of mono-, di-, and tricyclic aromatic compounds by MIL-53(Al) metal-organic framework from their solutions in MeCN, MeOH and n-C6H14–PriOH was studied for the first time. It was found that the adsorption of the test substances from solutions in MeCN and MeOH is characterized by positive values of enthalpy and entropy changes, and the adsorption from n-C6H14–PriOH medium is characterized by negative enthalpy and entropy changes. Upon adsorption by MIL-53(Al) framework from polar media, aromatic compounds were proposed to transfer from the liquid phase with a higher degree of association into the solvent medium with a lower degree of association, molecules of which are disordered due to the strong interaction with the hydrophobic walls of the framework pores. It was concluded that the driving force of adsorption by MIL-53(Al) from MeCN and MeOH is increase in entropy of the system, while the factor of adsorption from n-C6H14–PriOH medium is decrease in enthalpy of the adsorption system. The compensation effect in liquid-phase adsorption of aromatic compounds by MIL-53(Al) framework was discovered. The effect of the liquid phase nature on selectivity of adsorption from solutions onto investigated metal-organic framework was demonstrated. 相似文献
2.
Carbamic acid formation from amine and carbon dioxide in a variety of solvents was investigated by measuring NMR (1H, 13C, HMBC) and IR spectra in situ. Bubbling of CO2 through solutions of naphthylalkylamines 1-3 in DMSO, DMF or pyridine (protophilic, highly dipolar, aprotic solvent) resulted in complete conversion of the amines to the corresponding carbamic acids 4-6. In dioxane (protophilic, dipolar, aprotic solvent), the carbamic acid and a small amount of the ammonium carbamate were formed. By contrast, in MeCN (protophobic, dipolar, aprotic solvent), in benzene or CHCl3 (apolar, aprotic solvent), or in 2-PrOH or MeOH (dipolar, amphiprotic solvent), ammonium carbamates 7-9 rather than 4-6 were formed, although the ammonium bicarbonates/carbonates were competitively formed in MeOH. The ammonium carbamates precipitated in many cases and hence they could be separated. The selective generation of the undissociated carbamic acids in preference to the ammonium carbamates in protophilic, dipolar, aprotic solvents (DMSO, DMF, pyridine, and dioxane) is rationalized by considering the acid-base equilibria between the amines 1-3 and the carbamic acids 4-6 in nonaqueous media. The obtained selectivity is likely due to the larger pKa values for 4-6 than the amines 1-3 in these solvents. Interestingly, the fluorescence intensities for 1-3 were dramatically enhanced (4-50 times) in DMSO or DMF upon introduction of CO2, while they were not altered very much in dioxane, MeCN, benzene, CHCl3, 2-PrOH, and MeOH, except small to medium increases (1.3-3 times) for 1 in dioxane, MeCN, 2-PrOH and MeOH. As a whole, the solvent effects observed in these fluorescence studies are consistent with those observed in the above NMR and IR studies. Finally, methoxycarbonylation of amine 3 into the methyl carbamate was successfully accomplished by using (trimethylsilyl)diazomethane in the presence of CO2. 相似文献
3.
The dependence of absorption and fluorescence spectra, quantum yields, and lifetimes of fluorescence on the solvent composition
in the MeOH-C5H12 and MeOH-MeCN mixtures was studied for 2,2,4,6-tetramethyl-1,2-dihydroquinoline (TMDHQ). The variations in the parameters of deconvolution of the absorption and fluorescence spectra by the Gaussian functions
in the MeOH-C5H12 mixtures of various compositions indicate the specificity of methanol clustering in saturated hydrocarbons and hydrogen bonding
between TMDHQ and the methanol clusters of different compositions. At low MeOH concentrations (∼0.2 vol %), TMDHQ molecules
are practically completely bound with the MeOH molecules by hydrogen bonds. In the MeOH-MeCN mixtures, the changes in the
absorption and fluorescence spectra are observed at a substantially higher MeOH concentration (≥10 vol %) and monotonically
change at the further increase in the MeOH concentration that is caused by the peculiarities of MeOH clustering in acetonitrile
and the distribution of the TMDHQ molecules between the solvent components. At 50–95 vol % of MeOH in the mixture with MeCN,
the fluorescence decay kinetics is described by the biexponential curve with the lifetime of the major component (τ1) decreasing from 7.5 to 1.1 ns in pure MeCN and MeOH, respectively, and the lifetime of the minor component τ2 ≈ 4 ns corresponding to the fluorescence lifetime in the solution containing 50 vol % MeOH. This indicates the existence
of the free TMDHQ molecules, which are not bound with MeOH molecules or their clusters. 相似文献
4.
The stability constants of acetylcholinium, carbamoylcholinium, and cholinium diiodochlorides and diiodobromides in chloroform solutions were determined and the kinetics of disproportionation of these systems in 1 : 9 CHCl3—MeOH (MeCN) mixtures were studied by UV spectroscopy. A possible mechanism of mutual transformations of the polyhalides is proposed and an interrelation between the nature of the iodine-coordinating solvent and the extent of reversibility of the process is established. The electronic structures and relative stabilities of acetylcholinium iodohalides and charge-transfer complexes S·XI2
– and S·I2 (S = MeOH, MeCN, CHCl3; X = Cl, Br, I) were studied by ab initio RHF and MP2(full) methods in the HW+(3d) and 6-31G++(d,p) basis sets. It was found that all the solvents studied favor the decomposition of the iodohalide anions to liberate molecular iodine; however, disproportionation of I2 is possible only for the S·I2 complexes with a high extent of charge transfer. 相似文献
5.
Karl J. Box Gergely Völgyi Rebeca Ruiz John E. Comer Krisztina Takács‐Novák Elisabeth Bosch Clara Ràfols Martí Rosés 《Helvetica chimica acta》2007,90(8):1538-1553
A mixture of cosolvents is described that significantly improves the solubility of most pharmaceutical compounds. The mixture consists of equal volumes of MeOH, 1,4‐dioxane, and MeCN, thereby containing polar and nonpolar solvents, and is referred to as MDM (from MeOH, dioxane, and MeCN). MDM is mixed with H2O until the required composition is reached. The utility of this system is that it enables analytical measurements to be performed on a wide range of compounds where measurements would be impaired in aqueous solution. We present the physicochemical characteristics of MDM/H2O mixtures (density, dielectric constant, psKw) and the principles of pKa measurement in this solvent/H2O mixture. We also present pKa values in H2O of several drug compounds determined from values measured in MDM/H2O mixtures. 相似文献
6.
V. G. Badelin I. N. Mezhevoi 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(7):1121-1124
The integral heats of solution Δsol H m of L-cysteine and L-asparagine in mixtures of water with 1,4-dioxane and acetone were measured by solution calorimetry at organic solvent concentrations of up to 0.30 mole fractions. The standard enthalpies of solution (Δsol H o) and transfer (Δtr H o) of amino acids from water to mixed solvents were calculated. The calculated enthalpy coefficients of pair interactions of L-cysteine and L-asparagine with cosolvent molecules were positive. The results were interpreted from the point of view of the predominance of interactions of various types in solutions and the influence of the nature of cosolvents and amino acid side substituents on the thermochemical characteristics of solution. 相似文献
7.
V. G. Badelin V. I. Smirnov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(7):1163-1168
The integral enthalpies of solution of L-methionine in water-methanol, water-ethanol, water-n-propanol, and water-iso-propanol mixtures were measured calorimetrically at alcohol concentrations x
2 = 0–0.4 mole fractions. The standard enthalpies of solution (Δsol
H
o) and transfer of L-methionine (Δtr
H
o) from water to a binary solvent were calculated. The influence of the structure and properties of L-methionine and the composition
of aqueous-organic mixtures on its enthalpy characteristics was considered. The enthalpic pair interaction coefficients (h
xy
) between L-methionine and alcohol molecules were calculated; they were positive and increased in the series methanol (MeOH),
ethanol (EtOH), n-propanol (n-PrOH), iso-propanol (i-PrOH). The enthalpy characteristics of solution and transfer of L-methionine were compared with those of glycine, L-threonine,
L-alanine, and L-valine in similar binary solvents. 相似文献
8.
V. G. Badelin V. I. Smirnov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(1):40-43
The enthalpies of L-tryptophane solution in water-methanol, water-ethanol, water-1-propanol, and water-2-propanol mixtures at alcohol concentrations of x 2 = 0–0.4 mole fractions were measured by calorimetry. The standard enthalpies of L-tryptophane solution (Δsol H °) and transfer (Δtr H °) from water to the binary solvent were calculated. The influence of the composition of the water-alcohol mixture and the structure and properties of L-tryptophane on the enthalpy characteristics of the latter was considered. The enthalpy coefficients of pair interactions (h xy ) of L-tryptophane with alcohol molecules were calculated. The coefficients were positive and increased in the series: methanol (MeOH), ethanol (EtOH), 1-propanol (1-PrOH), and 2-propanol (2-PrOH). The solution and transfer enthalpies of L-tryptophane were compared with those of aliphatic amino acids (glycine, L-threonine, DL-alanine, L-valine, and L-phenylalanine) in similar binary solvents. 相似文献
9.
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
10.
V. P. Korolev O. A. Antonova N. L. Smirnova A. V. Kustov 《Journal of Thermal Analysis and Calorimetry》2009,96(3):903-910
The heats of solution of tetrabutylammonium bromide have been measured in mixtures of formamide (FA) with methanol (MeOH)
and ethylene glycol (EG) at 313.15 K by calorimetric method. The standard enthalpies of solution in binary mixtures have been
extrapolated to infinite dilution by Redlich–Rosenfeld–Meyer type equation using the literary data at 298.15 K and the present
paper data at 313.15 K. The Debye–Hückel limiting law slope A
H required for calculation of the ∆sol
H
0 value has been obtained with application the new additive scheme of determination of the physic-chemical characteristics
of binaries. The scheme is tested on the example of Bu4NBr solutions in FA–MeOH mixture at 298.15 K. Its application yields the ∆sol
H
0 value very closed on the ones determined with the real (non-additive) characteristics of binaries. The standard enthalpies
of solution extrapolated by Redlich–Rosenfeld–Meyer type equation are in a good agreement with the ones computed in terms
of the Debye–Hückel theory in the second approximation. The heat capacities characteristics of Bu4NBr have been calculated in H2O–FA, MeOH–FA and EG–FA mixtures using the literary and present data. The sequence of solvents H2O > FA > EG > MeOH located on their ability to solvophobic solvation found by us earlier for enthalpic characteristics is
confirmed by the ∆C
p
0 values. The comparison of thermochemical characteristics of Bu4NBr solutions in aqueous and non-aqueous mixtures containing FA has been carried out. The own structure of water remains in
the region of small additions of formamide to co-solvents. It considerably differs the H2O–FA mixture from the investigated non-aqueous systems. 相似文献
11.
The spin-lattice relaxation time (T
1) of7Li+ was measured in solutions of LiCl and LiClO4 in protic (MeOH, EtOH,n-PrOH,i-PrOH,n-BuOH, sec-BuOH, formamide, N-methylformamide) and aprotic (MeCN, acetone, methyl ethyl ketone, propylene carbonate, dimethyl sulfoxide, dimethylformamide, hexamethylphosphotriamide) solvents and in mixtures of H2O-formamide, H2O–N-methylformamide, H2O–N,N-dimethylformamide, H2O-DMSO, H2O-hexamethylphosphotriamide, and formamide-N,N-dimethylformamide at 25°C. The values of (1/T
1)0 obtained by extrapolation are discussed in terms of current theories of the magnetic relaxation of ionic nuclei. Linear correlations were found between (1/T
1)0 and Gutmann's donor numbers and Kosower's Z-values. These correlations indicate that relaxation of7Li+ is dominated by donor-acceptor interaction of the cation with solvent molecules. Concentration dependences of 1/T
1 for LiCl and LiClO4 differ from one another in a given solvent, a fact which is accounted for by a specific cation-anion short-range potential. The quantity 1/T
1 of7Li+ atC=1 mole per 55.5 moles of mixed solvent as a function of solvent composition show characteristic features, which are discussed in terms of the relaxation mechanism proposed. 相似文献
12.
The dependence of the quantum yield and the decay rate constant for the carbocation generated in the photolysis of 6-ethoxy-1,2,2,4-tetramethyl-1,2-dihydroquinoline
(6-EtO-DHQ) in methanol on the solvent composition was studied in the mixtures of methanol with isopropanol, acetonitrile,
and pentane by pulse photolysis. The addition of these solvents decreases the yield of the carbocation and differently affects
the kinetic parameters of its decay. The carbocation decay in the mixtures MeOH-i-PrOH and MeOH-C5H12 is described by the pseudo-first order equation (k
1), with the dependence of k
1 having a maximum at 50 vol % of MeOH in the MeOH-i-PrOH mixtures, and k
1 increasing with a decrease in the MeOH concentration in the MeOH-C5H12 mixtures. In the MeOH-MeCN mixtures, the value of k
1 decreases with a decrease in the MeOH concentration, and, at the concentration of MeOH lower than 50 vol %, the contribution
of the second-order reaction (k
2) is observed. The activation energies and preexponential factors were determined in the MeOH-C5H12 mixtures of different compositions, and it was shown that E
act practically did not depend on the solvent composition and were close to E
act for other carbocations obtained in MeOH. The increase in k
1 with a decrease in the MeOH concentration is caused by an increase in the preexponential factor. The results were discussed
on the basis of the reaction mechanism involving the competing reactions of the carbocation combination with two nucleophilic
particles, the MeOH molecule and the MeO− anion. The composition of the mixture and the nature of the inert solvent affect strongly the course of these reactions.
Published in Russian in Kinetika i Kataliz, 2009, Vol. 50, No. 3, pp. 411–416.
The article was translated by the authors. 相似文献
13.
Torquato Mussini Maurizio Cicognini Paolo Longhi Sandra Rondinini Arthur K. Covington 《Analytica chimica acta》1984
Standard pH(S) values for 0.05 mol kg?1 potassium hydrogenphthalate (KHpH) reference buffer solutions in 10, 30 and 50% (w/w) 1,4-dioxane/water solvent mixtures within the temperature range 288.15–318.15 K are determined from e.m.f. measurements of the cell without transference Pt|H2|KHPh + KCl|AgCl|Ag|Pt. The consistency of the results is analysed by a recently described method of multilinear regression of the quantity p(aHγCl) as a function of both solution composition and temperature. The standard pH(S) determined can be reproduced to within ±0.01 by the equation pH(S) - 4.004 + 3.309w + 0.408z + 1.037w3 - 14.95zw2 + 27.1zw3, where w is the weight fraction of dioxane in the solvent mixture,z = (T –θ)/θ, and θ - 298.15 K. Values of the first ionization constant of phthalic acid (H2Ph; benzene-1,2-dicarboxylic acid) in the above solvent mixtures are also determined from e.m.f. measurements of the cell without transference Pt|H2|H2Ph + KHPh + KCl|AgCl|Ag|Pt. 相似文献
14.
M. Woldan 《Thermochimica Acta》1985,94(2):358
The enthalpies of solution of NaCl, KCl, KBr, KNO3 and CsI have been measured in mixtures of acetamide with water at 298.15 K in the miscibility range. The standard enthalpies of solutions (ΔH0) of the investigated electrolytes have been evaluated The corresponding enthalpies of solvation (ΔHs0) and enthalples of transfer (ΔHt0) from water to water-acetamide mixtures have been calculated The dependence of the standard enthalpies of solution and enthalpies of transfer of the investigated electrolytes on the solvent composition is discussed 相似文献
15.
使用双沸点仪测定了丙酮、乙酸乙酯、对二氧六环、乙腈或三乙胺与甲醇或1,2→二氯乙烷以及二者混合物等十一组二元体系在99.3 kPa下的汽液平衡数据(T,x,p), 计算了有关体系的过量吉布斯自由能。结果表明, 六种非质子溶剂与甲醇组成的二元系GE>0; 乙腈或三乙胺与1,2-二氯乙烷组成的二元系GE>0, 而丙酮、乙酸乙酯或对二氧六环与1,2-二氯乙烷的二元混合物GE<0。从同种分子间或不同种分子间的缔合作用对上述结果进行了讨论。本文还在固定极性非质子溶剂(第三组分)物质的量浓度的条件下, 测定了非质子溶剂+1,2-二氯乙烷+甲醇三元混合物的汽液平衡数据, 考察了非质子溶剂的加入对甲醇+1,2-二氯乙烷二元系GE的影响。 相似文献
16.
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
17.
Summary The kinetics of aquation of cis-[Co(en)2(H2O)Br]2+ and cis-[Cr(en)2(H2O)Br]2+ (en = ethylenediamine) were investigated in aqueous mixtures of MeOH, EtOH, i-PrOH and t-BuOH. The values of transfer functions corresponding to the transfer of reactants and activated complex from water to the solvent mixtures were evaluated from kinetic measurements and from solubilities of the complex salt. Analysis of the solvent effect confirmed a common Id mechanism for the aquation of the CoIII and CrIII complexes. 相似文献
18.
Protonation pattern strongly affects the properties of molecular systems. To determine protonation equilibria, proton solvation free energy, which is a central quantity in solution chemistry, needs to be known. In this study, proton affinities (PAs), electrostatic energies of solvation, and pKA values were computed in protic and aprotic solvents. The proton solvation energy in acetonitrile (MeCN), methanol (MeOH), water, and dimethyl sulfoxide (DMSO) was determined from computed and measured pKA values for a specially selected set of organic compounds. pKA values were computed with high accuracy using a combination of quantum chemical and electrostatic approaches. Quantum chemical density functional theory computations were performed evaluating PA in the gas‐phase. The electrostatic contributions of solvation were computed solving the Poisson equation. The computations yield proton solvation free energies with high accuracy, which are in MeCN, MeOH, water, and DMSO ?255.1, ?265.9, ?266.3, and ?266.4 kcal/mol, respectively, where the value for water is close to the consensus value of ?265.9 kcal/mol. The pKA values of MeCN, MeOH, and DMSO in water correlates well with the corresponding proton solvation energies in these liquids, indicating that the solvated proton was attached to a single solvent molecule. © 2016 Wiley Periodicals, Inc. 相似文献
19.
Trejo Rodríguez, A. and Patterson, D., 1984. Prediction of activity coefficients and Henry's constants at infinite dilution for mixtures of n-alkanes. Fluid Phase Equilibria, 17: 265–279.The corresponding-states principle (CSP) for chain molecules has been used to predict activity coefficients γi∞ at infinite dilution and Henry's constants Hi,j for mixtures of n-alkanes. The mixtures for which predictions of γi∞ are made include n-C4 through n-C10 as the solute in several pure higher n-alkanes, at several temperatures from 30 to 90°C. Predictions of Hi,j are made for mixtures where the solute is C2 through n-C8 and the solvent any n-alkane from n-C4 through n-C22, also at several temperatures, from –15 to 177°C. The predicted values are compared with experimental data from the literature, and in all cases the agreement is remarkably good. The temperature dependence of Hi,j for some mixtures is used to derive heats of solution ΔHs, and comparison is again carried out with available experimental values. 相似文献
20.
The integral enthalpies of solution Δsol H m of L-cysteine and L-asparagine in mixtures of water with ethanol, n-propanol, and isopropanol at a mole fraction of alcohol of up to 0.32 were determined by calorimetry of solution. The standard enthalpies of solution (Δsol H 0) of L-serine and of its transfer (Δtr H 0) from water to a mixed solvent were calculated. The dependences of Δsol H 0 and Δtr H 0 on the composition of water-alcohol mixtures pass through a maximum. The calculated enthalpy coefficients of pair interaction of amino acids with alcohol molecules are positive and increase in the order ethanol, n-propanol, isopropanol. The data obtained were interpreted from the viewpoint of various types of interaction in solution and effect of the amino acid residue on the thermochemical characteristics of solution. 相似文献