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1992 Volume 8 Issue 5
1992, 8(05): 577-579
doi: 10.3866/PKU.WHXB19920501
Abstract:
Single chain amphiphiles containing Schiff base chromophore can organize into bilayer membrane as vesicles in aqueous solution. The fluorescence excitation and emission intensities of Schiff base group are markdly influenced by the phase states of the bilayer membrane. At T<30 ℃, fluorescence intensities decrease slightly, but dras-tically between 30—40 ℃ and between 45—55 ℃, just corresponding to the phase tran-sition temperatures 37 ℃ and 46 ℃ respectively, given by DSC. So the tight arrange-ment in molecules greatly enhances the lumination efficiency. According to the aggregate states, the fluorescence emission intensity follows the series as: I(gel state)>I(liquid state)>I(molecular dispersion state).
Single chain amphiphiles containing Schiff base chromophore can organize into bilayer membrane as vesicles in aqueous solution. The fluorescence excitation and emission intensities of Schiff base group are markdly influenced by the phase states of the bilayer membrane. At T<30 ℃, fluorescence intensities decrease slightly, but dras-tically between 30—40 ℃ and between 45—55 ℃, just corresponding to the phase tran-sition temperatures 37 ℃ and 46 ℃ respectively, given by DSC. So the tight arrange-ment in molecules greatly enhances the lumination efficiency. According to the aggregate states, the fluorescence emission intensity follows the series as: I(gel state)>I(liquid state)>I(molecular dispersion state).
1992, 8(05): 580-582
doi: 10.3866/PKU.WHXB19920502
Abstract:
The electroreduction of C_(60) was investigated by microelectrode voltammetry and in-situ optically transparent thin layer electrode technique(OTTLE). From the mea-surements of steady-state polarization curves and the absorbance dependence of C_(60) on reduction potentials, it is found that the electroreduction of C_(60) occurs in a succes-sive three step one-electron reduction. The diffusion coefficient and standard equilib-rium potential were evaluated to be 5.3×10~(-6)cm~2·s~(-1) and -0.40±0.02 V(vs. Ag/AgCl) respectively.
The electroreduction of C_(60) was investigated by microelectrode voltammetry and in-situ optically transparent thin layer electrode technique(OTTLE). From the mea-surements of steady-state polarization curves and the absorbance dependence of C_(60) on reduction potentials, it is found that the electroreduction of C_(60) occurs in a succes-sive three step one-electron reduction. The diffusion coefficient and standard equilib-rium potential were evaluated to be 5.3×10~(-6)cm~2·s~(-1) and -0.40±0.02 V(vs. Ag/AgCl) respectively.
1992, 8(05): 583-585
doi: 10.3866/PKU.WHXB19920503
Abstract:
1992, 8(05): 586-594
doi: 10.3866/PKU.WHXB19920504
Abstract:
Hydrogen absorption kinetics of LaNi_5-H system in α and α+β phases has been investigated. Taking the reversibility of hydrogen absorption and desorption into account, an analytical solution has been obtained for the α phase. In a temperature range of 20—50 ℃, the rate constant of hydrogen absorption, k_a, was found to be 0.08—0.41 s~(-1) and that of hydrogen desorption, k_a, 4.8—25 MPa·s~(-1) respectively. The apparent activation energy of hydrogen absorption was 35 kJ(mol H_2)~(-1). Hydrogen absorption in α+β phase was slower than that of the α-phase. The initial rate of hydrogen absorption is in first order with the hydrogen pressure used. The reaction is controlled by the dissociation of hydrogen on the alloy surface. With increasing of the reaction depth, the controlling step will shift to the reaction occuring on the α-β interface. The rate constants are weakly dependent on the temperature. The hydrogen absorption rates on the initial and final stage of the pressure plateau in α-β phase are obviously different.
Hydrogen absorption kinetics of LaNi_5-H system in α and α+β phases has been investigated. Taking the reversibility of hydrogen absorption and desorption into account, an analytical solution has been obtained for the α phase. In a temperature range of 20—50 ℃, the rate constant of hydrogen absorption, k_a, was found to be 0.08—0.41 s~(-1) and that of hydrogen desorption, k_a, 4.8—25 MPa·s~(-1) respectively. The apparent activation energy of hydrogen absorption was 35 kJ(mol H_2)~(-1). Hydrogen absorption in α+β phase was slower than that of the α-phase. The initial rate of hydrogen absorption is in first order with the hydrogen pressure used. The reaction is controlled by the dissociation of hydrogen on the alloy surface. With increasing of the reaction depth, the controlling step will shift to the reaction occuring on the α-β interface. The rate constants are weakly dependent on the temperature. The hydrogen absorption rates on the initial and final stage of the pressure plateau in α-β phase are obviously different.
1992, 8(05): 595-601
doi: 10.3866/PKU.WHXB19920505
Abstract:
The N_2 adsorption and desorption isotherms of Y zeolites modified by hydrothermal treatment (HUSY), H_4EDTA dealumination (HEY) and (NH_4)_2SiF_6 isomorphous substitution (HSY) were measured and compared with that of the original NaY and HY zeolites. The size and the shape of the hysteresis loops on the isotherms are different, which shows that the secondary pore systems of these zeolites vary with the modification procedures. The sequence of the secondary pore volumes of the samples is as follows
HY (2.6)<HSY(5.7)<HSY(9.8)HUSY(2.9)<HEY(4.9)
The pore distributions of the samples deduced from the theoretical treatment of the N_2 desorption isotherms according to non interconnected cylindrical pore model (BJH model) show that the maximum of secondary porosity of all the modified zeolite Y samples is due to pores of ~2.0 nm radius. However, for HUSY and HEY there are pores with radii >2.0 nm and <2.0 nm as well.
Reactant with various molecular sizes such as propanol, cumene and 1,3,5-tritert-butylbenzene were used as probes to study the catalytic behavior of the modified zeolite samples. The catalytic activities of the probe molecules on the zeolite were correlated with the data of the acidity and the secondary pore volume. It is clear that for larger molecules as cumene and 1,3,5-tri-tert-butylbenzene the presence of secondary mesopores in the zeolite structure promotes the cracking reactions considerably.
The N_2 adsorption and desorption isotherms of Y zeolites modified by hydrothermal treatment (HUSY), H_4EDTA dealumination (HEY) and (NH_4)_2SiF_6 isomorphous substitution (HSY) were measured and compared with that of the original NaY and HY zeolites. The size and the shape of the hysteresis loops on the isotherms are different, which shows that the secondary pore systems of these zeolites vary with the modification procedures. The sequence of the secondary pore volumes of the samples is as follows
HY (2.6)<HSY(5.7)<HSY(9.8)HUSY(2.9)<HEY(4.9)
The pore distributions of the samples deduced from the theoretical treatment of the N_2 desorption isotherms according to non interconnected cylindrical pore model (BJH model) show that the maximum of secondary porosity of all the modified zeolite Y samples is due to pores of ~2.0 nm radius. However, for HUSY and HEY there are pores with radii >2.0 nm and <2.0 nm as well.
Reactant with various molecular sizes such as propanol, cumene and 1,3,5-tritert-butylbenzene were used as probes to study the catalytic behavior of the modified zeolite samples. The catalytic activities of the probe molecules on the zeolite were correlated with the data of the acidity and the secondary pore volume. It is clear that for larger molecules as cumene and 1,3,5-tri-tert-butylbenzene the presence of secondary mesopores in the zeolite structure promotes the cracking reactions considerably.
1992, 8(05): 602-608
doi: 10.3866/PKU.WHXB19920506
Abstract:
In this work, after the synthesis of a series of substituted diphenyl pyrazoline compounds, their solvatochromic behavior has been studied. The Bilot-Kawaski equation was used for calculating the difference of dipole moment of these compounds in their ground state and excited state respectively. Results indicated that the dipole moment can be changed dramatically when an electron-withdrawing group was attached with C-3 atom in the molecule. It demonstrated that the introduction of an electron-withdrawing group to the molecule may promote the intramolecular charge transfer process significantly. The E_T(30) value was used as an index for evaluating the polarity of solvents. It reveals that a series of photophysical properties of these compounds such as the fluorescence quantum yield, the fluorescence lifetime, the Stokes' shift and especially the radiation and radiationless decay rate constants may be correlated with E_T(30) value in linearity.
In this work, after the synthesis of a series of substituted diphenyl pyrazoline compounds, their solvatochromic behavior has been studied. The Bilot-Kawaski equation was used for calculating the difference of dipole moment of these compounds in their ground state and excited state respectively. Results indicated that the dipole moment can be changed dramatically when an electron-withdrawing group was attached with C-3 atom in the molecule. It demonstrated that the introduction of an electron-withdrawing group to the molecule may promote the intramolecular charge transfer process significantly. The E_T(30) value was used as an index for evaluating the polarity of solvents. It reveals that a series of photophysical properties of these compounds such as the fluorescence quantum yield, the fluorescence lifetime, the Stokes' shift and especially the radiation and radiationless decay rate constants may be correlated with E_T(30) value in linearity.
1992, 8(05): 609-612
doi: 10.3866/PKU.WHXB19920507
Abstract:
The surface structure and other related properties of copper electrodes in 0.25 mol·L~(-1) Na_2S_2O_8+1.25 mol·L~(-1) NaOH solution were studied by using electrolumine-scence method. The experimental results showed that the electroluminescence method can be employed as a tool for probing the structure of copper-electroplating layer.
The surface structure and other related properties of copper electrodes in 0.25 mol·L~(-1) Na_2S_2O_8+1.25 mol·L~(-1) NaOH solution were studied by using electrolumine-scence method. The experimental results showed that the electroluminescence method can be employed as a tool for probing the structure of copper-electroplating layer.
1992, 8(05): 613-618
doi: 10.3866/PKU.WHXB19920508
Abstract:
The properties of pore structure of high-silica Y zeolites prepared by combined hydrothermal-chemical treatments have been characterized by measuring N_2 adsorption-desorption isotherms at 77.4 K. The surface area and micropore volume for the sam-ples have been calculated by means of t-method and MP method. It has been found that two zeolites Y samples dealuminated by different chemical agents have apparent differences in their pore structures. But, when these two samples are further submitted to hydrothermal treatments combined chemical treatments, an evolution with similar tendencies in pore structure has been observed, namely, their total surface area, the surface area of micropores and micropore volume have reduced after hydrothermal treatments and increased after chemical treatments. On the contrary, the surface area of the secondary pore systems has been increased after hydrothermal treatments and reduced after chemical treatments. This evolution of pore structure may be related to the formation and elimination of non-framework aluminium species.
The properties of pore structure of high-silica Y zeolites prepared by combined hydrothermal-chemical treatments have been characterized by measuring N_2 adsorption-desorption isotherms at 77.4 K. The surface area and micropore volume for the sam-ples have been calculated by means of t-method and MP method. It has been found that two zeolites Y samples dealuminated by different chemical agents have apparent differences in their pore structures. But, when these two samples are further submitted to hydrothermal treatments combined chemical treatments, an evolution with similar tendencies in pore structure has been observed, namely, their total surface area, the surface area of micropores and micropore volume have reduced after hydrothermal treatments and increased after chemical treatments. On the contrary, the surface area of the secondary pore systems has been increased after hydrothermal treatments and reduced after chemical treatments. This evolution of pore structure may be related to the formation and elimination of non-framework aluminium species.
1992, 8(05): 619-624
doi: 10.3866/PKU.WHXB19920509
Abstract:
Metallothionein (MT) is a protein of molecular weight about 6000 Dalton obtained from liver of rat, rabbit and silver carp in our laboratory. Mammal's MT consists of 61 amino acid residues including 20 cysteine residues which has high affinity to metal and it appears to coordinate metals in two distinct configurations. Ions of at least eighteen different metals were associated with the protein. Most metals exhibited saturation binding at 7 mol eq forming M_7-MT. These included Bi(Ⅲ), Cd(Ⅱ), Co(Ⅱ), Hg(Ⅱ), In(III), Ni(II), Pb(II), Sb(III), and Zn(II). Other metals including Os(III), Pd(II), Pt(IV), Re(V), Rh(III) and Tl(III) give a positive indication of binding but their stoichiometries remained unclear. Ag(I) and Cu(I) bound in clusters as M_(12)-MT.
In this paper, rabbit liver MT which combined with 5 Cd(II) and 2 Zn(II) ion per protein was obtained by gel filtration and ion exchange after homogenization, centrifugation and deposition with ethanol from rabbits received cadmium chloride by subcutaneously injection. In 0.01 mol·L~(-1) perchloric acid medium, the metal ions released from MT and apo-MT were obtained by gel filtration on a Sephadex G-25 column, the titration with sodium hydroxide and cadmium nitrate solution were carried out by combined pH electrode and cadmium ion selective electrode under nitrogen at 298 K.
According to the sequences of amino acid from rabbit liver MT-2, the binding sites were divide into six types. By using a simplified complexing model, six types of protonation group and two types of metal complexing region (α- and β- domain) were obtained. The results were listed as follows.
...
Metallothionein (MT) is a protein of molecular weight about 6000 Dalton obtained from liver of rat, rabbit and silver carp in our laboratory. Mammal's MT consists of 61 amino acid residues including 20 cysteine residues which has high affinity to metal and it appears to coordinate metals in two distinct configurations. Ions of at least eighteen different metals were associated with the protein. Most metals exhibited saturation binding at 7 mol eq forming M_7-MT. These included Bi(Ⅲ), Cd(Ⅱ), Co(Ⅱ), Hg(Ⅱ), In(III), Ni(II), Pb(II), Sb(III), and Zn(II). Other metals including Os(III), Pd(II), Pt(IV), Re(V), Rh(III) and Tl(III) give a positive indication of binding but their stoichiometries remained unclear. Ag(I) and Cu(I) bound in clusters as M_(12)-MT.
In this paper, rabbit liver MT which combined with 5 Cd(II) and 2 Zn(II) ion per protein was obtained by gel filtration and ion exchange after homogenization, centrifugation and deposition with ethanol from rabbits received cadmium chloride by subcutaneously injection. In 0.01 mol·L~(-1) perchloric acid medium, the metal ions released from MT and apo-MT were obtained by gel filtration on a Sephadex G-25 column, the titration with sodium hydroxide and cadmium nitrate solution were carried out by combined pH electrode and cadmium ion selective electrode under nitrogen at 298 K.
According to the sequences of amino acid from rabbit liver MT-2, the binding sites were divide into six types. By using a simplified complexing model, six types of protonation group and two types of metal complexing region (α- and β- domain) were obtained. The results were listed as follows.
...
1992, 8(05): 625-629
doi: 10.3866/PKU.WHXB19920510
Abstract:
The present paper developes a simple method for calculating the rovibrationally excited states of diatomic molecules. In principle, the results can retain the same accuracy as conventional numerical integration. As an example, the energy levels and wave functions of H_2 for the first 162 rovibrational states are given by this method.
The present paper developes a simple method for calculating the rovibrationally excited states of diatomic molecules. In principle, the results can retain the same accuracy as conventional numerical integration. As an example, the energy levels and wave functions of H_2 for the first 162 rovibrational states are given by this method.
1992, 8(05): 630-635
doi: 10.3866/PKU.WHXB19920511
Abstract:
The correlation of the composition, structure, IR, TPR and catalytic activity for CO and CH_3OH oxidation on LaMn_(1-x)Ni_xO_3 (0.0≤x≤1.0) has been studied. The single crystalline phase was perovskite in the range of 0.0≤x≤1.0; samples for 0.0≤x≤0.4 and x=1.0 were rhombohedral, and cubic with 0.5≤x≤0.8, and the samples with x=0.4 and 0.8 were close to the transitional region of rhombohedral to cubic or cubic to rhombohedral. IR and TPR studies proved that there was interaction between Mn and Ni in the B site of ABO_3. The catalytic activity of the oxides was related to the symmetry of the crystal, the higher the symmetry, the lower the activity.
The correlation of the composition, structure, IR, TPR and catalytic activity for CO and CH_3OH oxidation on LaMn_(1-x)Ni_xO_3 (0.0≤x≤1.0) has been studied. The single crystalline phase was perovskite in the range of 0.0≤x≤1.0; samples for 0.0≤x≤0.4 and x=1.0 were rhombohedral, and cubic with 0.5≤x≤0.8, and the samples with x=0.4 and 0.8 were close to the transitional region of rhombohedral to cubic or cubic to rhombohedral. IR and TPR studies proved that there was interaction between Mn and Ni in the B site of ABO_3. The catalytic activity of the oxides was related to the symmetry of the crystal, the higher the symmetry, the lower the activity.
1992, 8(05): 636-641
doi: 10.3866/PKU.WHXB19920512
Abstract:
Isobaric vapor-liquid equilibrium data have been measured at 99.3 kPa for the binary mixtures of acetone(AON), ethyl acetate(EA), p-dioxane (p-DXN), acetonitrile(AN) or triethylamine (TEA) with methanol or 1,2-dichloroethane (DCE) and of DCE with methanol by using a double ebulliometer. Van Laar equation and Wilson equation were used to correlate VLE data and Barker's method to estimate the vapor composi-tion from (T,x,p) data. Excess Gibbs free energies for the reported binary mixtures were also calculated from the two equations. The values of G~E for the methanol negative. The results are briefly discussed based on the hydrogen bonding between like and unlike molecules and some physical properties of aprotic solvents. Additionally, vapor-liquid equilibrium data for the ternary mixtures, aprotic solvent+MeOH+DCE, were also measured under the given concentration of aprotic solvent.
Isobaric vapor-liquid equilibrium data have been measured at 99.3 kPa for the binary mixtures of acetone(AON), ethyl acetate(EA), p-dioxane (p-DXN), acetonitrile(AN) or triethylamine (TEA) with methanol or 1,2-dichloroethane (DCE) and of DCE with methanol by using a double ebulliometer. Van Laar equation and Wilson equation were used to correlate VLE data and Barker's method to estimate the vapor composi-tion from (T,x,p) data. Excess Gibbs free energies for the reported binary mixtures were also calculated from the two equations. The values of G~E for the methanol negative. The results are briefly discussed based on the hydrogen bonding between like and unlike molecules and some physical properties of aprotic solvents. Additionally, vapor-liquid equilibrium data for the ternary mixtures, aprotic solvent+MeOH+DCE, were also measured under the given concentration of aprotic solvent.
1992, 8(05): 642-646
doi: 10.3866/PKU.WHXB19920513
Abstract:
The crystal structure of erbium (Ⅲ) complex of benzene acetic acid is reported. The complex crystallizes in the monoclinic space group P_2_1/a with a=0.9008(3) nm, b=1.4242(5) nm, c=1.8437(7) nm; β=98.80(3)°, V=2.337(1) nm~3, Z=4. The mechanism of thermal decomposition of complex has been studied by TG-DTG-DTA. The activation energy for dehydration reaction has been calculated by Freeman-Carroll method. The enthalpy change for dehydration and phase change process has been determined.
The crystal structure of erbium (Ⅲ) complex of benzene acetic acid is reported. The complex crystallizes in the monoclinic space group P_2_1/a with a=0.9008(3) nm, b=1.4242(5) nm, c=1.8437(7) nm; β=98.80(3)°, V=2.337(1) nm~3, Z=4. The mechanism of thermal decomposition of complex has been studied by TG-DTG-DTA. The activation energy for dehydration reaction has been calculated by Freeman-Carroll method. The enthalpy change for dehydration and phase change process has been determined.
1992, 8(05): 647-653
doi: 10.3866/PKU.WHXB19920514
Abstract:
~(13)C NMR spectral studies have been performed on the structure of the adducts of lanthanide ions and L-lysine using aqueous lanthanide shift reagents. The lanthanide-induced shifts are separated into contact and dipolar components by a new method of separation with a self-consistent manner. The geometry of L-lysine is described by the geometric factors derived from dipolar shifts, optimized by computer search, and checked by Euler transformation.
~(13)C NMR spectral studies have been performed on the structure of the adducts of lanthanide ions and L-lysine using aqueous lanthanide shift reagents. The lanthanide-induced shifts are separated into contact and dipolar components by a new method of separation with a self-consistent manner. The geometry of L-lysine is described by the geometric factors derived from dipolar shifts, optimized by computer search, and checked by Euler transformation.
1992, 8(05): 654-658
doi: 10.3866/PKU.WHXB19920515
Abstract:
The tautomeric mechanism of acetaldehyde into vinyl alcohol and ketene into ethynol have been investigated theoretically by ab initio MO method and AM_1 MO method respectively. The geometry of various critical points in reaction pathways had been optimized on the corresponding potential energy surfaces. The reaction heat and the rate constant of the two reactions were also calculated. The results show that the stability of vinyl alcohol is higher than ethynol while the reaction rate of acetalde-hyde into vinyl alcohol is lower than that of ketene into ethynol.
The tautomeric mechanism of acetaldehyde into vinyl alcohol and ketene into ethynol have been investigated theoretically by ab initio MO method and AM_1 MO method respectively. The geometry of various critical points in reaction pathways had been optimized on the corresponding potential energy surfaces. The reaction heat and the rate constant of the two reactions were also calculated. The results show that the stability of vinyl alcohol is higher than ethynol while the reaction rate of acetalde-hyde into vinyl alcohol is lower than that of ketene into ethynol.
1992, 8(05): 659-663
doi: 10.3866/PKU.WHXB19920516
Abstract:
Solvent effect on the conformations of α,ω-bis(4-nitrophenoxy)-alkanes with different chain lengths(N_n) was studied by UV spectra. In poor solvents such as EG-H_2O and THF-H_2O, with the increase of water content, the K-bands of N_4, N_5, N_6 and N_(10) in the UV absorption spectra shifted to longer wavelengths as compared with 4-nitrophenoxyethane(N_0). It is suggested that in poor solvents the two aromatic groups are close in parallel to each other, forming ground state complexes. The K-band of N_4 showed a blue shift from that of N_0 when the water content was around 5% this may probably be attributable to a conformation with the nitro group of one benzene ring siting on the plane of the other benzene ring.
Solvent effect on the conformations of α,ω-bis(4-nitrophenoxy)-alkanes with different chain lengths(N_n) was studied by UV spectra. In poor solvents such as EG-H_2O and THF-H_2O, with the increase of water content, the K-bands of N_4, N_5, N_6 and N_(10) in the UV absorption spectra shifted to longer wavelengths as compared with 4-nitrophenoxyethane(N_0). It is suggested that in poor solvents the two aromatic groups are close in parallel to each other, forming ground state complexes. The K-band of N_4 showed a blue shift from that of N_0 when the water content was around 5% this may probably be attributable to a conformation with the nitro group of one benzene ring siting on the plane of the other benzene ring.
1992, 8(05): 664-667
doi: 10.3866/PKU.WHXB19920517
Abstract:
The interlayer spacing of lamellar liquid crystal decreased with increase of the weight ratio of decanol/SDS at constant solvent content in the system of SDS/decanol/glycerol, but increased in system of SDS/decanol/formamide. At a constant weight ratio of decanol/SDS, tbe interlayer spacing decreased when formamide was used as solvent instead of glycerol. These results are related to the effects of hydrogen bond formed between solvent and SDS, decanol and the similarities of glycerol and decanol for the penetration of the solvent in to the lamellar liquid crystal.
The interlayer spacing of lamellar liquid crystal decreased with increase of the weight ratio of decanol/SDS at constant solvent content in the system of SDS/decanol/glycerol, but increased in system of SDS/decanol/formamide. At a constant weight ratio of decanol/SDS, tbe interlayer spacing decreased when formamide was used as solvent instead of glycerol. These results are related to the effects of hydrogen bond formed between solvent and SDS, decanol and the similarities of glycerol and decanol for the penetration of the solvent in to the lamellar liquid crystal.
1992, 8(05): 668-672
doi: 10.3866/PKU.WHXB19920518
Abstract:
In this paper the electrode kinetics of cathodic reduction of dichloro-bis(triphenyl-phosphine) palladium complex and zinc chloride in DMF was studied. Using electro-chemical techniques we found that the reduction of Pd(PPh_3)_2Cl_2 is irreversible and is charge transfer controlled. The J~0(exchange current) and α(transfer coefficient) were 5.67×10~(-8) A and 0.15 respectively. We also confirmed that the reduction of ZnCl_2 in DMF is diffusion-charge transfer controlled.
In this paper the electrode kinetics of cathodic reduction of dichloro-bis(triphenyl-phosphine) palladium complex and zinc chloride in DMF was studied. Using electro-chemical techniques we found that the reduction of Pd(PPh_3)_2Cl_2 is irreversible and is charge transfer controlled. The J~0(exchange current) and α(transfer coefficient) were 5.67×10~(-8) A and 0.15 respectively. We also confirmed that the reduction of ZnCl_2 in DMF is diffusion-charge transfer controlled.
1992, 8(05): 673-676
doi: 10.3866/PKU.WHXB19920519
Abstract:
In the light of the interactions between particles, this paper is a calculation of the standard solvation enthalpies for ions Li~+, Na~+, K~+, Rb~+, Cs~+, Ag~+, Cl~-, Br~- and I~- in solvents as H_2O, MeOH, FA, DMF, DMSO, MeCN, PC and SL. The contributions from the cavity formation process, electrostatic attraction, electrostatic repulsion and those from nonelectrostatic interactions are considered. The accordance between the calculated values and those from literature is od except Li~+.
In the light of the interactions between particles, this paper is a calculation of the standard solvation enthalpies for ions Li~+, Na~+, K~+, Rb~+, Cs~+, Ag~+, Cl~-, Br~- and I~- in solvents as H_2O, MeOH, FA, DMF, DMSO, MeCN, PC and SL. The contributions from the cavity formation process, electrostatic attraction, electrostatic repulsion and those from nonelectrostatic interactions are considered. The accordance between the calculated values and those from literature is od except Li~+.
1992, 8(05): 677-680
doi: 10.3866/PKU.WHXB19920520
Abstract:
In this paper, we reported the Raman Scattering characteristics of a new Organo-metallic complex crystal-Triallylthiourea Cadmium Bromide [Cd(C_4H_8N_2S)_3Br_2, ATCB for short]. Different vibrational modes for different geometric configurations were obtained. Vibrations under different symmetry have been assigned and the relationship between the structure and Raman scattering has been discussed.
In this paper, we reported the Raman Scattering characteristics of a new Organo-metallic complex crystal-Triallylthiourea Cadmium Bromide [Cd(C_4H_8N_2S)_3Br_2, ATCB for short]. Different vibrational modes for different geometric configurations were obtained. Vibrations under different symmetry have been assigned and the relationship between the structure and Raman scattering has been discussed.
1992, 8(05): 681-684
doi: 10.3866/PKU.WHXB19920521
Abstract:
The DL-α-tocopherol neutral radical (α-T) produced by the hydrogen abstraction of DL-α-tocopheral (α-TH) with di-tert-butylperoxide (DBPO), 2,2'-azo-(2,4-di-methyl-valeronitrile) (ADVN), γ-Al_2O_3 or SiO_2/Al_2O_3 has been studied by EPR spec-troscopy. From these experimental results, the mechanism of α-T radical generation is discussde.
The DL-α-tocopherol neutral radical (α-T) produced by the hydrogen abstraction of DL-α-tocopheral (α-TH) with di-tert-butylperoxide (DBPO), 2,2'-azo-(2,4-di-methyl-valeronitrile) (ADVN), γ-Al_2O_3 or SiO_2/Al_2O_3 has been studied by EPR spec-troscopy. From these experimental results, the mechanism of α-T radical generation is discussde.
1992, 8(05): 685-689
doi: 10.3866/PKU.WHXB19920522
Abstract:
XRD and SPM techniques were used to identify the products and reaction rates for CuCl oxidization. The results showed tbe reaction between CuCl, O_2 and H_2O is rapid at ambient conditions. The bronze powder-corrosion with Cu(Ⅱ) formed through the corrosion with Cu(Ⅰ) such as (CuCl), as soon as the Cu_2(OH)_3Cl once formed, Cu(Ⅱ) ion occured in the mean while; the fresh corrosion products dispersed in solution as colloidal dispersions, and CuCl transformed into Cu_2(OH)_3Cl through Cu_2O.
The experimental phenomena were discussed. The reaction order, reaction rate, and apparent activation energy of these reaction were calculated.
XRD and SPM techniques were used to identify the products and reaction rates for CuCl oxidization. The results showed tbe reaction between CuCl, O_2 and H_2O is rapid at ambient conditions. The bronze powder-corrosion with Cu(Ⅱ) formed through the corrosion with Cu(Ⅰ) such as (CuCl), as soon as the Cu_2(OH)_3Cl once formed, Cu(Ⅱ) ion occured in the mean while; the fresh corrosion products dispersed in solution as colloidal dispersions, and CuCl transformed into Cu_2(OH)_3Cl through Cu_2O.
The experimental phenomena were discussed. The reaction order, reaction rate, and apparent activation energy of these reaction were calculated.
1992, 8(05): 690-693
doi: 10.3866/PKU.WHXB19920523
Abstract:
When C_7H_(16) was solubilized, both the molecular number ratio of CTMAB and C_5H_(11)OH in the interfacial layer of O/W microemulsion droplets in system CTMAB-C_5H_(11)OH-H_2O and the weight ratio of CTMAB/C_5H_(11)OH at the maximum water content solubilized in the W/O microemulsion are conserved, but the interlayer spacing of lamellar liquid crystal was extended.
When C_7H_(16) was solubilized, both the molecular number ratio of CTMAB and C_5H_(11)OH in the interfacial layer of O/W microemulsion droplets in system CTMAB-C_5H_(11)OH-H_2O and the weight ratio of CTMAB/C_5H_(11)OH at the maximum water content solubilized in the W/O microemulsion are conserved, but the interlayer spacing of lamellar liquid crystal was extended.
1992, 8(05): 694-696
doi: 10.3866/PKU.WHXB19920524
Abstract:
Surface tension and density of NaCl-NaF-RE_2O_3 melts have been measured by means of maximum buble pressure and Archimedes methods. The results are expressed by two mathematic models. Mass fraction of RE_2O_3 in the melts from 0.0 to 0.6% and that of NaF/NaCl, 50—90%. This investigation shows that there might be complexes in the melts. The information obtained can be used as a reference in the preparation of Al-RE alloys.
Surface tension and density of NaCl-NaF-RE_2O_3 melts have been measured by means of maximum buble pressure and Archimedes methods. The results are expressed by two mathematic models. Mass fraction of RE_2O_3 in the melts from 0.0 to 0.6% and that of NaF/NaCl, 50—90%. This investigation shows that there might be complexes in the melts. The information obtained can be used as a reference in the preparation of Al-RE alloys.
1992, 8(05): 697-701
doi: 10.3866/PKU.WHXB19920525
Abstract:
The quenchings of pyrene fluorescence were studied with tetradecylbenzyldime- thylammonium chloride (Zeph) and benzyltrimethylammonium bromide (TMBA) through their Stern-Volmer plots. Transient and steady state fluorescence experiments indicated that the quenching was dynamic and the quenching rate constant (k_q) of Zeph was much larger than that of TMBA with a ratio of 23.2. Theoretical calculations based on conductance measurement and the full-anti configuration of quencher molecule showed that the k_q of TMBA was larger than that of Zeph with a ratio of 2.29 and 1.85, respectively, which were opposite to the experimental results. Coilin of the long alkyl chain in Zeph molecule and the hydrophobic interaction between pyrene and the coiled microenvironment were considered as the causes for the contradiction between experimental results and theoretical calculations.
The quenchings of pyrene fluorescence were studied with tetradecylbenzyldime- thylammonium chloride (Zeph) and benzyltrimethylammonium bromide (TMBA) through their Stern-Volmer plots. Transient and steady state fluorescence experiments indicated that the quenching was dynamic and the quenching rate constant (k_q) of Zeph was much larger than that of TMBA with a ratio of 23.2. Theoretical calculations based on conductance measurement and the full-anti configuration of quencher molecule showed that the k_q of TMBA was larger than that of Zeph with a ratio of 2.29 and 1.85, respectively, which were opposite to the experimental results. Coilin of the long alkyl chain in Zeph molecule and the hydrophobic interaction between pyrene and the coiled microenvironment were considered as the causes for the contradiction between experimental results and theoretical calculations.
1992, 8(05): 702-706
doi: 10.3866/PKU.WHXB19920526
Abstract:
A sample was produced by heating the mixture of boric acid, strontium carbonate added europium oxide at 800—1000 ℃ in reductive atmosphere for 4 hours. According to the pattern of X-ray diffraction of the sample, Its phase and mechanism of emission under the ultraviolet excitation of sample are discussed. It was shown that the emission was relative with the content of Sr_(1-x)Eu_xB_4O_7 as well as the impurity of the sample.
A sample was produced by heating the mixture of boric acid, strontium carbonate added europium oxide at 800—1000 ℃ in reductive atmosphere for 4 hours. According to the pattern of X-ray diffraction of the sample, Its phase and mechanism of emission under the ultraviolet excitation of sample are discussed. It was shown that the emission was relative with the content of Sr_(1-x)Eu_xB_4O_7 as well as the impurity of the sample.
1992, 8(05): 707-711
doi: 10.3866/PKU.WHXB19920527
Abstract:
The electroxidation mechanism of methanol at ld electrode with different supporting electrolytes in anhydrous methanol was investigated using In situ FTIR spec-troscopy. It has been proved that the electroxidation pathway and products are different for different supporting electrolytes. When NaOH was used as supporting electrolyte, the electroxidation products are HCOOCH_3 and HCOO~- ion; moreover, the relative quantities of HCOOCH_3 and HCOO~- produced are affected by tbe concentration of NaOH. When NaClO_4 and TBABF_4 are used as supporting electrolyte, HCOOCH_3 and CH_3OCH_2OCH_3 will be the only products.
The electroxidation mechanism of methanol at ld electrode with different supporting electrolytes in anhydrous methanol was investigated using In situ FTIR spec-troscopy. It has been proved that the electroxidation pathway and products are different for different supporting electrolytes. When NaOH was used as supporting electrolyte, the electroxidation products are HCOOCH_3 and HCOO~- ion; moreover, the relative quantities of HCOOCH_3 and HCOO~- produced are affected by tbe concentration of NaOH. When NaClO_4 and TBABF_4 are used as supporting electrolyte, HCOOCH_3 and CH_3OCH_2OCH_3 will be the only products.
1992, 8(05): 712-720
doi: 10.3866/PKU.WHXB19920528
Abstract:
