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1985 Volume 1 Issue 2
1985, 1(02): 109-110
doi: 10.3866/PKU.WHXB19850201
Abstract:
~(23)Na~+ chemical shift of NaClO_4 in mixed solvents of water-aceton,water-ace- tonitrile, and water-ethanol and of NaBPh_4 in methanol-DMF,methanol-ben- zene, and methanol-dioxane were measured.By means of iso-solvation point the solvating abilities were compared as water>aceton≥acetonitrile≥ethanol and DMF>methanol. The preferential solvation free energies of Na~+ for the pairs of solvents, methanol-DMFand water-aceton,were evaluated as -2.7 kJ mol~(-1) for DMF to methanol and 4.6 kJ mol~(-1) for aceton to water.
~(23)Na~+ chemical shift in methanol-benzene is independent of the content of benzene. It verifies the simple solvation modle for ion in methanol-inert solvent mixture. However the chemical shift of ~(23)Na~+ in methanol-dioxane mixture varies with the composition of solvent. The inewidth of Na-23 resonance peak increases dramtically with the increasing of dioxane. It seems that the dioxane molecules disturb the primary solvation shell of Na~+ in methanol and result a unsymmetrical immediate surrounding for Na~+ cation.
~(23)Na~+ chemical shift of NaClO_4 in mixed solvents of water-aceton,water-ace- tonitrile, and water-ethanol and of NaBPh_4 in methanol-DMF,methanol-ben- zene, and methanol-dioxane were measured.By means of iso-solvation point the solvating abilities were compared as water>aceton≥acetonitrile≥ethanol and DMF>methanol. The preferential solvation free energies of Na~+ for the pairs of solvents, methanol-DMFand water-aceton,were evaluated as -2.7 kJ mol~(-1) for DMF to methanol and 4.6 kJ mol~(-1) for aceton to water.
~(23)Na~+ chemical shift in methanol-benzene is independent of the content of benzene. It verifies the simple solvation modle for ion in methanol-inert solvent mixture. However the chemical shift of ~(23)Na~+ in methanol-dioxane mixture varies with the composition of solvent. The inewidth of Na-23 resonance peak increases dramtically with the increasing of dioxane. It seems that the dioxane molecules disturb the primary solvation shell of Na~+ in methanol and result a unsymmetrical immediate surrounding for Na~+ cation.
1985, 1(02): 111-122
doi: 10.3866/PKU.WHXB19850202
Abstract:
The thermodynamics of the solution of binary mixture of surfactants has been studied.Considering the effect of counterion on the interactions between the surf- ace active ions in the micelle and at the interface,the general equations for calcu- lating the molecular interaction parameters in the micelle (β_m) and at the interface (β_σ) have been obtained:
β_m=ln[(cmc_1)/(cmc_1~0x_(1m))(c″_1/c′_1)~(K_1)]/x_(2m)~2=ln[(cmc_2)/(cmc_2~0x_(2m)(c″_2)/(c′_2)~(K_2)]/x_(1m)~2 β_σ=ln[((c_1(π))/(c_1~0(π)x_(1σ)))(c″_1/c′_1)~(K_1)]/x_2σ~2=ln[((c_2(π))/(c_2~0(π)x_(2σ)))(c″_2/c′_1)~(K_2)]/x_(1σ)~2
For the nonionic surfactants mixtures or the ionic ones in the presence of excess of inorganic electrolytes, as a limited case, the general equations reduce to
β_m=ln[(cmc_1)/(cmc_1~0x_(1m)]/x_2m~2=ln[(cmc_2)/(cmc_2~0x_(2m)]/x_(1m)~2
β_σ=ln[(c_1(π))/(c_1~0(π)x_(1σ)]/x_2σ~2=ln[(c_2(π))/(c_2~0(π)x_(2σ)]/x_(1σ)~2
...
The thermodynamics of the solution of binary mixture of surfactants has been studied.Considering the effect of counterion on the interactions between the surf- ace active ions in the micelle and at the interface,the general equations for calcu- lating the molecular interaction parameters in the micelle (β_m) and at the interface (β_σ) have been obtained:
β_m=ln[(cmc_1)/(cmc_1~0x_(1m))(c″_1/c′_1)~(K_1)]/x_(2m)~2=ln[(cmc_2)/(cmc_2~0x_(2m)(c″_2)/(c′_2)~(K_2)]/x_(1m)~2 β_σ=ln[((c_1(π))/(c_1~0(π)x_(1σ)))(c″_1/c′_1)~(K_1)]/x_2σ~2=ln[((c_2(π))/(c_2~0(π)x_(2σ)))(c″_2/c′_1)~(K_2)]/x_(1σ)~2
For the nonionic surfactants mixtures or the ionic ones in the presence of excess of inorganic electrolytes, as a limited case, the general equations reduce to
β_m=ln[(cmc_1)/(cmc_1~0x_(1m)]/x_2m~2=ln[(cmc_2)/(cmc_2~0x_(2m)]/x_(1m)~2
β_σ=ln[(c_1(π))/(c_1~0(π)x_(1σ)]/x_2σ~2=ln[(c_2(π))/(c_2~0(π)x_(2σ)]/x_(1σ)~2
...
1985, 1(02): 123-129
doi: 10.3866/PKU.WHXB19850203
Abstract:
The exchange reaction between a hydrogen atom and a hydogen molecule provi- des the simplest ease where for neutral species the concerted kinetic processes of bond breaking and bond formation can be studied experimentally and theoreti- cally. The collision dynamics of the H+H_2 system have been studied by quasi-and semielassical as well as by approximate and accurate quantum methods using semi- empirical and fitted ab initio H_3 surfaces. But both approximate approaches and close-coupling technique of the electroniclly adiabatic theory yield results of the rate constant of the exchange reaction H+H_2(v=1) which are over an order of magnitude lower than the measured total rate constant. The evident disagreement between theory and experiment for this reaction, which should be the best-under-stood of all chemical processes, surely provides a continuing theoretically and experimental challenge.
A closed-coupling differential equation of the collinear A+BC→AB+C system involving electronically excited effect has been obtained by us early, with which wa have calculated the reaction probabilities of colinear reaction H+H_2 (v=0, 1)→H_2(v′=0, 1)+H on the PK semiemperical H_3 potential energy surface.
...
The exchange reaction between a hydrogen atom and a hydogen molecule provi- des the simplest ease where for neutral species the concerted kinetic processes of bond breaking and bond formation can be studied experimentally and theoreti- cally. The collision dynamics of the H+H_2 system have been studied by quasi-and semielassical as well as by approximate and accurate quantum methods using semi- empirical and fitted ab initio H_3 surfaces. But both approximate approaches and close-coupling technique of the electroniclly adiabatic theory yield results of the rate constant of the exchange reaction H+H_2(v=1) which are over an order of magnitude lower than the measured total rate constant. The evident disagreement between theory and experiment for this reaction, which should be the best-under-stood of all chemical processes, surely provides a continuing theoretically and experimental challenge.
A closed-coupling differential equation of the collinear A+BC→AB+C system involving electronically excited effect has been obtained by us early, with which wa have calculated the reaction probabilities of colinear reaction H+H_2 (v=0, 1)→H_2(v′=0, 1)+H on the PK semiemperical H_3 potential energy surface.
...
1985, 1(02): 130-140
doi: 10.3866/PKU.WHXB19850204
Abstract:
The molar heats of solution of gaseousn-Butane, n-Butene-1 and Butadiene-1,3 in 4 pure dipolar aprotic solvents (dimethylformamide, dimethy sulfoxide, propylene carbonate and N-methy-2-pyrrolidone) and in a protic solvent(methanol) have been calorimetrically determined at 298.15 K and 1 atm(Table 3).
The calorimetric measurements were made by expansive calorimeter, the sensi- tivity was 0.01 cal. The solute molarities were all below 0.04. The measurements of solute content were made by gas chromatography.
The theoriti...
The molar heats of solution of gaseousn-Butane, n-Butene-1 and Butadiene-1,3 in 4 pure dipolar aprotic solvents (dimethylformamide, dimethy sulfoxide, propylene carbonate and N-methy-2-pyrrolidone) and in a protic solvent(methanol) have been calorimetrically determined at 298.15 K and 1 atm(Table 3).
The calorimetric measurements were made by expansive calorimeter, the sensi- tivity was 0.01 cal. The solute molarities were all below 0.04. The measurements of solute content were made by gas chromatography.
The theoriti...
1985, 1(02): 141-153
doi: 10.3866/PKU.WHXB19850205
Abstract:
Measurements of the autocorrelation function of scattered light intensity from aqueous tetradecylpyridinium bromide (TPB) solutions werec arried out to investigate the growth of TPB micelles in high salt (NaBr) concentration media. The mean hydrodynamic radius (R_h) of TPB micelles has been deduced as a function of temperature (15-85 ℃), NaBr concentration (0.5-2.0 M), and detergent concentration(2-21 gdm-3). In general, the size of the micelles increases with increasing salt or detergent concentration and decreasing temperature. A plot of measured R_h vs. relative scattered intensity, compared to theoretical curves corresponding to different model shapes, indicates that the enlarged TPB micelles have a shape of prolate spherocylinders. Based on these R_h measurements, values of the thermodynamic parameter K verning the sphere-to-rod transition are determined. Numerical values of enthalpy and entropy change for this transition on per monomer basis, deduced from the linear plot of lnK vs. 1/T in 0.5 and 1.0 M NaBr, are rather consistent with those of CPB micelles, indicating that these energy parameters are independent of the chain length. In respect to temperature-dependent micellar growth an anomalous behavior that a finite size of about 26.0 nm is asymtemperature has been observed under conditions of higher NaBr concentration (2.0 M). In this case the thermodynamic model of the sphere-to-rod transition is invlid and the possible causes are discussed.
1985, 1(02): 154-161
doi: 10.3866/PKU.WHXB19850206
Abstract:
So far, almost all systems which show chemical oscillation were discovered by chance.In this paper, we discuss the possibility of designing chemical oscillation by introducing a suitable slow feedback step to a system which shows multiple steady states. A criterion of existence of oscillation solution from kinetic equations for model system is given, and a method to identify the region of oscillation solu- tion in parameter space is proposed. With this method, the mechanism of oscilla- tion phenomena in the oxidation of carbon monoxide on Pt catalyst is analysed.
Experimentally, many chemical reacting systems show multiple steady states. A typical situation is shown in Fig.1, where x represents the value of state variable, λ the value of control parameter. The kinetics of the above system can be described by
dx/dt=f(x, λ) (1)
...
So far, almost all systems which show chemical oscillation were discovered by chance.In this paper, we discuss the possibility of designing chemical oscillation by introducing a suitable slow feedback step to a system which shows multiple steady states. A criterion of existence of oscillation solution from kinetic equations for model system is given, and a method to identify the region of oscillation solu- tion in parameter space is proposed. With this method, the mechanism of oscilla- tion phenomena in the oxidation of carbon monoxide on Pt catalyst is analysed.
Experimentally, many chemical reacting systems show multiple steady states. A typical situation is shown in Fig.1, where x represents the value of state variable, λ the value of control parameter. The kinetics of the above system can be described by
dx/dt=f(x, λ) (1)
...
1985, 1(02): 162-168
doi: 10.3866/PKU.WHXB19850207
Abstract:
PtL_Ⅲ absorption spectra of an electrically conductive polymer——H_2PtCl_6· 6H_2O-doped polyacetylene and the model compound K_2PtCl_6 were measured with a laboratory EXAFS system, which utilizes a high power rotating-anode X-ray gene- rator (Rigaku model RU-1000) as an X-ray source.The Fourier transforms of k~3-weighted EXAFS oscillations of sample and thc model compound are shown in Fig.3. The prominent peak in the Fourier transform for H_2PtCl_6·6H_2O-doped polyaeetylene can be attributed to the Cl atoms surrounding Pt atom. The curvefitting analysis for the first shell shows two types of neighboring Cl atoms with Pt-Cl distances of 0.2329 nm and 0.2277 nm, respectively.
According to the results from use of the theoretical and empircal methods, it is concluded that the dopant anion in polyacetylene film is PtCl_6~(2-). The result provides a direct structural information that supports the proposition: the following reaction accompanied by electron transfer from (CH)_x chains to platinum salt:
2H_2PtCl_6+2e~-→PtCl_6~(2-)+PtCl_2+4HCl
PtL_Ⅲ absorption spectra of an electrically conductive polymer——H_2PtCl_6· 6H_2O-doped polyacetylene and the model compound K_2PtCl_6 were measured with a laboratory EXAFS system, which utilizes a high power rotating-anode X-ray gene- rator (Rigaku model RU-1000) as an X-ray source.The Fourier transforms of k~3-weighted EXAFS oscillations of sample and thc model compound are shown in Fig.3. The prominent peak in the Fourier transform for H_2PtCl_6·6H_2O-doped polyaeetylene can be attributed to the Cl atoms surrounding Pt atom. The curvefitting analysis for the first shell shows two types of neighboring Cl atoms with Pt-Cl distances of 0.2329 nm and 0.2277 nm, respectively.
According to the results from use of the theoretical and empircal methods, it is concluded that the dopant anion in polyacetylene film is PtCl_6~(2-). The result provides a direct structural information that supports the proposition: the following reaction accompanied by electron transfer from (CH)_x chains to platinum salt:
2H_2PtCl_6+2e~-→PtCl_6~(2-)+PtCl_2+4HCl
1985, 1(02): 169-176
doi: 10.3866/PKU.WHXB19850208
Abstract:
This paper reports our measurements of the solubility of KCI in the mixtures of methanol-benzene, -toluene, -cyclohexane, -carbontetraehloride at 278.16, 288.15, 298.15, 308.15 K. These data can be expressed by
log(S_o/S_m)=kx_Ne (1)
and
log(S_o/S_m)=k_φφ_(Ne) (2)
where S_o and S_m are the solubilities of salts in pure methanol and mixed solvent, respectively, x_(Ne) and φ_(Ne) are the mole fraction and volume fraction of nonelec- trolytes in the mixed solvent,respectively, k_φ is called the second medium cons- tant. ...
This paper reports our measurements of the solubility of KCI in the mixtures of methanol-benzene, -toluene, -cyclohexane, -carbontetraehloride at 278.16, 288.15, 298.15, 308.15 K. These data can be expressed by
log(S_o/S_m)=kx_Ne (1)
and
log(S_o/S_m)=k_φφ_(Ne) (2)
where S_o and S_m are the solubilities of salts in pure methanol and mixed solvent, respectively, x_(Ne) and φ_(Ne) are the mole fraction and volume fraction of nonelec- trolytes in the mixed solvent,respectively, k_φ is called the second medium cons- tant. ...
1985, 1(02): 177-185
doi: 10.3866/PKU.WHXB19850209
Abstract:
Syngas conversion to ethanol by supported catalysts is an important progress in C_1 chemistry. It has been reported by our laboratory that Rh sites and niobia sites coexisted on Rh-Nb_2O_5/SiO_2 catalysts as detected by means of reaction chemi- stry involving the catalytic aromatization and polymerization of acetylene on such catalysts. This paper reports a further study consisting of the following three parts: (1)The probable existence of Nb-H bonds on hydrogen-reduced Rh-Nb_2O_5/ SiO_2 was deduced from the catalytic activity toward polymerization of acetylene to polyacetylene and the loss of catalytic activity toward cyclotrimerization of acetylene of such catalysts. (2) The FTIR spectra of the above mentioned catalysts were studied. The peak at 1740 cm~(-1) (vw) may be assigned to v_(Ph-H), that at 1560 cm~(-1) (m, broad) to v_(Nh-H), while that at 1269 cm~(-1) (s) most probably to a bridging species, Rh—H—Nb. (3) The existence of Ph~0, Rh~Ⅰ, Nb~Ⅴ, Nb~Ⅳ and two types of carboneceous deposits on syngas treated Rh-Nb_2O5/SiO_2 catalysts was detected by XPS; A model of active center, A (cf. Fig.3) (abbr. B), formed by partial reduction of niobia through hydrogen spillover and “wetting” or partial coating of the surfaces of rhodium particles (Rh_x~0Rh_y~I) by the partially reduced niobia, has been proposed. By analogy with known organometallic chemistry, the major reaction pathway might involve migratory insertion of chemisorbed species C to form E, hydrogenation to F cis-coupling with CO to form coordinated ketene, and further hydrogenation to ethanol or aldehyde with simultaneous regeneration of the active site by hydrogenation and elimination of H_2O; while methane CH_4 was produced by hydrogenation of the coordinated carbene CH_2 in a secondary reaction pathway. The true nature of SMPI in the present system has also been discussed.
Syngas conversion to ethanol by supported catalysts is an important progress in C_1 chemistry. It has been reported by our laboratory that Rh sites and niobia sites coexisted on Rh-Nb_2O_5/SiO_2 catalysts as detected by means of reaction chemi- stry involving the catalytic aromatization and polymerization of acetylene on such catalysts. This paper reports a further study consisting of the following three parts: (1)The probable existence of Nb-H bonds on hydrogen-reduced Rh-Nb_2O_5/ SiO_2 was deduced from the catalytic activity toward polymerization of acetylene to polyacetylene and the loss of catalytic activity toward cyclotrimerization of acetylene of such catalysts. (2) The FTIR spectra of the above mentioned catalysts were studied. The peak at 1740 cm~(-1) (vw) may be assigned to v_(Ph-H), that at 1560 cm~(-1) (m, broad) to v_(Nh-H), while that at 1269 cm~(-1) (s) most probably to a bridging species, Rh—H—Nb. (3) The existence of Ph~0, Rh~Ⅰ, Nb~Ⅴ, Nb~Ⅳ and two types of carboneceous deposits on syngas treated Rh-Nb_2O5/SiO_2 catalysts was detected by XPS; A model of active center, A (cf. Fig.3) (abbr. B), formed by partial reduction of niobia through hydrogen spillover and “wetting” or partial coating of the surfaces of rhodium particles (Rh_x~0Rh_y~I) by the partially reduced niobia, has been proposed. By analogy with known organometallic chemistry, the major reaction pathway might involve migratory insertion of chemisorbed species C to form E, hydrogenation to F cis-coupling with CO to form coordinated ketene, and further hydrogenation to ethanol or aldehyde with simultaneous regeneration of the active site by hydrogenation and elimination of H_2O; while methane CH_4 was produced by hydrogenation of the coordinated carbene CH_2 in a secondary reaction pathway. The true nature of SMPI in the present system has also been discussed.
1985, 1(02): 186-192
doi: 10.3866/PKU.WHXB19850210
Abstract:
The selectivity of intermolecular force is caused by the special interaction between two adaptable groups on the molecules. π bond and conjugated π bonds such as benzene ring are negative charged groups,which may attract stongly positively charged H groups such as 3H in β-C_6H_6Cl_6, and repulse other ne- gatively charged groups such as-C=O(Q).
Our experiments show that the reduced retention time tr of benzene on non- polar β-C_6H_6Cl_6 is much greater than that on polar fixed phases such as CH_3— —NO_2 in gas chromatography and that the het of solvation of β-C_6H_6Cl_6 in benzene is also much greater than that of the polar α-C_6H_6Cl_6 and γ-C_6H_6Cl_6. This can′t be explained by the usual Van de Waals′ force. It results from the selective intermoleccular force.
...
The selectivity of intermolecular force is caused by the special interaction between two adaptable groups on the molecules. π bond and conjugated π bonds such as benzene ring are negative charged groups,which may attract stongly positively charged H groups such as 3H in β-C_6H_6Cl_6, and repulse other ne- gatively charged groups such as-C=O(Q).
Our experiments show that the reduced retention time tr of benzene on non- polar β-C_6H_6Cl_6 is much greater than that on polar fixed phases such as CH_3— —NO_2 in gas chromatography and that the het of solvation of β-C_6H_6Cl_6 in benzene is also much greater than that of the polar α-C_6H_6Cl_6 and γ-C_6H_6Cl_6. This can′t be explained by the usual Van de Waals′ force. It results from the selective intermoleccular force.
...
1985, 1(02): 193-195
doi: 10.3866/PKU.WHXB19850211
Abstract:
The suitably doped polyacetylene film can be used for the conversion of sun- light energy into electrical or chemical energy. A new electrochemical technique was introduced for obtaining polyacetylene film by cathodic initiation of the poly- merization process. The advantage of this technique is that the polymerization process can be controlled by the wave form of electrode current and the composi- tion of the solution. Polyacetylene films of different properties and thickness can be conveniently prepared in this way.
The catalyst was dissolved in certain organic solvent and introduced into the electrolytic cell. The solution was then cooled down to low temperature and saturated with acetylene gas before cathodic polymerization. Several transition metals and other electric conducting materials have been used as electrodes. On passing suitable current, red color appeared at the cathode/solution interface and the polyacetylene film formed gradually.
...
The suitably doped polyacetylene film can be used for the conversion of sun- light energy into electrical or chemical energy. A new electrochemical technique was introduced for obtaining polyacetylene film by cathodic initiation of the poly- merization process. The advantage of this technique is that the polymerization process can be controlled by the wave form of electrode current and the composi- tion of the solution. Polyacetylene films of different properties and thickness can be conveniently prepared in this way.
The catalyst was dissolved in certain organic solvent and introduced into the electrolytic cell. The solution was then cooled down to low temperature and saturated with acetylene gas before cathodic polymerization. Several transition metals and other electric conducting materials have been used as electrodes. On passing suitable current, red color appeared at the cathode/solution interface and the polyacetylene film formed gradually.
...
1985, 1(02): 196-199
doi: 10.3866/PKU.WHXB19850212
Abstract:
In this paper we gave an improvement of the LEPS method for the reaction potential energy surface, in which the coulomb energy Q and exchange energy J include the overlap integral S with the parameter v:
J=S~vD_e{[1-e~(-β(r-r_0))]~2-1}
Q=(1-S~v)D_e{[1-e~(-β(r-r_o)]-1}
By this modified LEPS method we have calculated five reaction potential energy surfaces, of which the transition state parameters have been shown in the table:
Reaction Energy barrier Internuclear separation E≠/kcal mol~(-1) H_2+H=H+H_2 9.746 R≠H...
In this paper we gave an improvement of the LEPS method for the reaction potential energy surface, in which the coulomb energy Q and exchange energy J include the overlap integral S with the parameter v:
J=S~vD_e{[1-e~(-β(r-r_0))]~2-1}
Q=(1-S~v)D_e{[1-e~(-β(r-r_o)]-1}
By this modified LEPS method we have calculated five reaction potential energy surfaces, of which the transition state parameters have been shown in the table:
Reaction Energy barrier Internuclear separation E≠/kcal mol~(-1) H_2+H=H+H_2 9.746 R≠H...
1985, 1(02): 200-204
doi: 10.3866/PKU.WHXB19850213
Abstract:
The surface morphology,crystallite size distribution, and the surface and depth analyses for the coneentratons of impurity elements and cobalt oxide ions of several samples of Co_3O_4 catalyst for ammonia oxidation, which were obtained under various conditions for preparation, calination,usage,and regeneration, were observed by means of a transmission electron microscopy(TEM), a scanning electron microscopy(SEM),and an ion microprobe mass analyzer (IMMA). The observed results are discussed in relating with the experimental activity of the catalyt. It is concluded that the possible causes of the decline in the activity of the catalyst are that the impurity elements transport from the bulk phase and enrich onto the surface and the cobalt oxide ions on the surface decrease when the catalyst has been used at the high temperature for a long time.
The surface morphology,crystallite size distribution, and the surface and depth analyses for the coneentratons of impurity elements and cobalt oxide ions of several samples of Co_3O_4 catalyst for ammonia oxidation, which were obtained under various conditions for preparation, calination,usage,and regeneration, were observed by means of a transmission electron microscopy(TEM), a scanning electron microscopy(SEM),and an ion microprobe mass analyzer (IMMA). The observed results are discussed in relating with the experimental activity of the catalyt. It is concluded that the possible causes of the decline in the activity of the catalyst are that the impurity elements transport from the bulk phase and enrich onto the surface and the cobalt oxide ions on the surface decrease when the catalyst has been used at the high temperature for a long time.
