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1986 Volume 2 Issue 3
1986, 2(03): 193-194
doi: 10.3866/PKU.WHXB19860301
Abstract:
Signal averaging technique was used to detect the weak photoelectric responses. at the interface of unpretreated 1Cr18Ni9Ti stainless steel electrode/solution over the visible range of radiation. Photoresponse of open-circuit electrode potential curve and potential dependence of the peak-peak photovoltages were obtained quantitatively for the first time. Similarity between the photoresponses of stainless steel and those of thicker Fe_2O_3 film suggests the existence of very thin n-type semiconductor film on the surface of stainless steel and the applicability of semiconductor physics to such thin film within proper limits. This technique may be developed into and improved in-situ method to characterize the structures and passive films at various metal/solution interfaces.
Signal averaging technique was used to detect the weak photoelectric responses. at the interface of unpretreated 1Cr18Ni9Ti stainless steel electrode/solution over the visible range of radiation. Photoresponse of open-circuit electrode potential curve and potential dependence of the peak-peak photovoltages were obtained quantitatively for the first time. Similarity between the photoresponses of stainless steel and those of thicker Fe_2O_3 film suggests the existence of very thin n-type semiconductor film on the surface of stainless steel and the applicability of semiconductor physics to such thin film within proper limits. This technique may be developed into and improved in-situ method to characterize the structures and passive films at various metal/solution interfaces.
1986, 2(03): 195-198
doi: 10.3866/PKU.WHXB19860302
Abstract:
Crystal structure of MBILF-BTRY complex was successfully solved by molecular replacement method and its 3-dimensional molecular model was thereby derived.
Mung bean trypsin inhibitor belongs to Bowman-Birk inhibitor group, which is by far the most complicated among the ten fundamental groups of serine protease inhibitor. Neither the 3-dimensional structure of Bowman-Birk inhibitor group nor the stereoscopic conformation of its complex with protease has ever been reported. The crystallographic data of MBILF-BTRY complex are found to be a=....
Crystal structure of MBILF-BTRY complex was successfully solved by molecular replacement method and its 3-dimensional molecular model was thereby derived.
Mung bean trypsin inhibitor belongs to Bowman-Birk inhibitor group, which is by far the most complicated among the ten fundamental groups of serine protease inhibitor. Neither the 3-dimensional structure of Bowman-Birk inhibitor group nor the stereoscopic conformation of its complex with protease has ever been reported. The crystallographic data of MBILF-BTRY complex are found to be a=....
1986, 2(03): 199-206
doi: 10.3866/PKU.WHXB19860303
Abstract:
The kinetics and mechanism of the thermolysis for five model compounds were studied in tetralin under N_2 pressure about 50-60 atm. The results show that:
(1) Diphenyl methane and diphenyl ether are stable under 435 ℃ for 2 hours reaction, which implies that the cracking of C—C and C—O bounds in coal liquefaction is not similiar to one of these compounds.
(2) The reaction of thermolysis of dibenzyl and phenyl benzyl ether are first Order and can he explained by free radical mechanism. Experimental rate constants are well consistent with the results of thermochemical kinetics calculation.
(3) The thermolysis of dibenzyl ether is well explained by te intramolecular hydrogen transfer model. Benzyl aldehyde produced by reaction is further deoxygenated. This is probably a very important deoxygenation process in coal liquefaction.
The kinetics and mechanism of the thermolysis for five model compounds were studied in tetralin under N_2 pressure about 50-60 atm. The results show that:
(1) Diphenyl methane and diphenyl ether are stable under 435 ℃ for 2 hours reaction, which implies that the cracking of C—C and C—O bounds in coal liquefaction is not similiar to one of these compounds.
(2) The reaction of thermolysis of dibenzyl and phenyl benzyl ether are first Order and can he explained by free radical mechanism. Experimental rate constants are well consistent with the results of thermochemical kinetics calculation.
(3) The thermolysis of dibenzyl ether is well explained by te intramolecular hydrogen transfer model. Benzyl aldehyde produced by reaction is further deoxygenated. This is probably a very important deoxygenation process in coal liquefaction.
1986, 2(03): 207-213
doi: 10.3866/PKU.WHXB19860304
Abstract:
By means of FT-IR and subtraction techniques the absorption spectra of Poly A film have been studied systematically in the 4000 to 800 cm~1 region at (25±1) ℃ as a function of relative humidity (from 0％ to 100％) at static equilibrium. According to the peak position and intensity changes of infrared bands it proves that the hydration of Poly A has happened mainly on the-NH_2 group of pbase, -PO_2 group and ribose ring; and the possible hydrating sequence is as shown in Fig.9. In comparision with the previous investigators~[2] many new informations are obtained. First, the —NH_2 band (～1712 cm~(-1)) shows strongest variation in intensity at RH≤30% (Fig.4) and obvious frequency shift at RH≥75% (Fig.6). So it is one of the strongest hydrating sites. Then, the P=0 band (～1240 cm~(-1)) does not only behave as a 20 cm~(-1) frequency shift pointed out by Falk but splits into two peaks and coexists at high relative humidity (see Fig.3 and Fig.5). Besides, the spectra of water molecule also varies obviously and splits into multiple peaks during hydration (Fig.7). This indicates that the molecules bonding to Poly A have different structure status.
By means of FT-IR and subtraction techniques the absorption spectra of Poly A film have been studied systematically in the 4000 to 800 cm~1 region at (25±1) ℃ as a function of relative humidity (from 0％ to 100％) at static equilibrium. According to the peak position and intensity changes of infrared bands it proves that the hydration of Poly A has happened mainly on the-NH_2 group of pbase, -PO_2 group and ribose ring; and the possible hydrating sequence is as shown in Fig.9. In comparision with the previous investigators~[2] many new informations are obtained. First, the —NH_2 band (～1712 cm~(-1)) shows strongest variation in intensity at RH≤30% (Fig.4) and obvious frequency shift at RH≥75% (Fig.6). So it is one of the strongest hydrating sites. Then, the P=0 band (～1240 cm~(-1)) does not only behave as a 20 cm~(-1) frequency shift pointed out by Falk but splits into two peaks and coexists at high relative humidity (see Fig.3 and Fig.5). Besides, the spectra of water molecule also varies obviously and splits into multiple peaks during hydration (Fig.7). This indicates that the molecules bonding to Poly A have different structure status.
1986, 2(03): 214-223
doi: 10.3866/PKU.WHXB19860305
Abstract:
In the presence of electron donor, molybdovanadophosphoricacid (H_(3+n)PMo_(12-n) V_nO_(40)) are proved to possess catalytic activities in oxygen activation and benzene hydroxylation. O_2 absorption kinetics and hydroxylation activity are different for the two reducing agents used in this paper—ascorbic acid and sodium sulfite. Based on the results obtained from potentiometric titration, cyclic voltammogram measurement, electrolytic reduction hydroxylation and UV, ESR spectrum, plausible mechanisms of O_2 activation for both reducing systems could be drawn. Being reduced by ascorbic acid, the anion of heteropoly acid might directly coordinate to O_2 by transfering 3 electrons to it. The control step may be the coordination of O_2 to reduced anion. But in sodium sultite medium, the electron donor might directly take part in the process of O_2 activation forming a precursor complex with the anion. The reducing coordination of electron donor with anion could be regarded as the control step in this system.
In the presence of electron donor, molybdovanadophosphoricacid (H_(3+n)PMo_(12-n) V_nO_(40)) are proved to possess catalytic activities in oxygen activation and benzene hydroxylation. O_2 absorption kinetics and hydroxylation activity are different for the two reducing agents used in this paper—ascorbic acid and sodium sulfite. Based on the results obtained from potentiometric titration, cyclic voltammogram measurement, electrolytic reduction hydroxylation and UV, ESR spectrum, plausible mechanisms of O_2 activation for both reducing systems could be drawn. Being reduced by ascorbic acid, the anion of heteropoly acid might directly coordinate to O_2 by transfering 3 electrons to it. The control step may be the coordination of O_2 to reduced anion. But in sodium sultite medium, the electron donor might directly take part in the process of O_2 activation forming a precursor complex with the anion. The reducing coordination of electron donor with anion could be regarded as the control step in this system.
1986, 2(03): 224-228
doi: 10.3866/PKU.WHXB19860306
Abstract:
The crystallite sizes and degrees of lattice distortion of annealed PET fibers have been determined with the variance-range functions of 105 diffraction profile with the assumption that the crystallites in the materials are paracrystalline. The corrections of the diffraction profile data were simple and reliable because there was not any overlapping with other reflexions in tie range of 2θ=35°—51°.
It has been shown that: (1) the use of the variance-range function for the determination of crystallite size results in a “number-average” size; (2) annealing produces larger crystallite sizes and smaller degrees of lattice distortion; (3) the correlation between the crystallite sizes and distortion factors is in od agreement with Hosemann′s a~* law~[11].
The crystallite sizes and degrees of lattice distortion of annealed PET fibers have been determined with the variance-range functions of 105 diffraction profile with the assumption that the crystallites in the materials are paracrystalline. The corrections of the diffraction profile data were simple and reliable because there was not any overlapping with other reflexions in tie range of 2θ=35°—51°.
It has been shown that: (1) the use of the variance-range function for the determination of crystallite size results in a “number-average” size; (2) annealing produces larger crystallite sizes and smaller degrees of lattice distortion; (3) the correlation between the crystallite sizes and distortion factors is in od agreement with Hosemann′s a~* law~[11].
1986, 2(03): 229-233
doi: 10.3866/PKU.WHXB19860307
Abstract:
By using a precision automatic adiabatic calorimeter the heat capacity of hydrazine nitrate in the temperature range of 220-370 K have been measured. The heat of fusion, melting point and entropy of fusion for the sample have been obtained from the results of heat capcity measurements. The precision of heat capacity measurements for hydrazine nitrate is ±0.2％, as shown by the root-mean-square (r. m. s.) of the percentage deviation, and the relative error for heat of fusion measurement is 0.1％. In order to varify the reliability for all of these measurements we have determined the heat capacity, heat of fusion as well as the melting point of pure ice with the same apparatu and the results were found to be in agreement with the data in literature. Then, the heat of fusion and melting point of hydrazine nitrate have been measured with the SETARAM high temperature calorimeter. The results obtained by the two apparatuses coincided with each other. Besides, the purity derived from the heat capacity measurements of the sample is in agreement with the results from chemical analysis. The facts show that the data from calorimetric measurements for hydrazine nitrate are reliable.
By using a precision automatic adiabatic calorimeter the heat capacity of hydrazine nitrate in the temperature range of 220-370 K have been measured. The heat of fusion, melting point and entropy of fusion for the sample have been obtained from the results of heat capcity measurements. The precision of heat capacity measurements for hydrazine nitrate is ±0.2％, as shown by the root-mean-square (r. m. s.) of the percentage deviation, and the relative error for heat of fusion measurement is 0.1％. In order to varify the reliability for all of these measurements we have determined the heat capacity, heat of fusion as well as the melting point of pure ice with the same apparatu and the results were found to be in agreement with the data in literature. Then, the heat of fusion and melting point of hydrazine nitrate have been measured with the SETARAM high temperature calorimeter. The results obtained by the two apparatuses coincided with each other. Besides, the purity derived from the heat capacity measurements of the sample is in agreement with the results from chemical analysis. The facts show that the data from calorimetric measurements for hydrazine nitrate are reliable.
1986, 2(03): 234-242
doi: 10.3866/PKU.WHXB19860308
Abstract:
Crystal Raman (40—3100 cm~(-1)), infrared (70—3100 cm~(-1)) spectra and depolarization ratios of some Raman bands of dibenzyl disulphide have been measured. In view of the specific oriention of dibenzyl disulphide molecules in crystal cell, the crystal can be considered approximately as a single molecule in crystal Raman experiment.
Normal coordinate analysis of the molecule has been carried out based on force field of benzene proposed by Pulay and that of sulphides given by Shimanouchi. Four force constants of S—S, S—C, SSC and SCC are proposed and refined by observed frequencies.
All vibration bands, from 180 to 3100 cm~(-1), of dibenzyl diulphide are assigned by comprehensive information of frequencies, in tensities of crystal Raman and infrared bands, depolarization ratios, normal coordinate calculation and empirical assignments of similar compounds.
Crystal Raman (40—3100 cm~(-1)), infrared (70—3100 cm~(-1)) spectra and depolarization ratios of some Raman bands of dibenzyl disulphide have been measured. In view of the specific oriention of dibenzyl disulphide molecules in crystal cell, the crystal can be considered approximately as a single molecule in crystal Raman experiment.
Normal coordinate analysis of the molecule has been carried out based on force field of benzene proposed by Pulay and that of sulphides given by Shimanouchi. Four force constants of S—S, S—C, SSC and SCC are proposed and refined by observed frequencies.
All vibration bands, from 180 to 3100 cm~(-1), of dibenzyl diulphide are assigned by comprehensive information of frequencies, in tensities of crystal Raman and infrared bands, depolarization ratios, normal coordinate calculation and empirical assignments of similar compounds.
1986, 2(03): 243-248
doi: 10.3866/PKU.WHXB19860309
Abstract:
The diffusion coefficient D of hydrogen in TiNi alloys was determination with electrochemical method at 20±0.3℃. The value of D was (6.45±0.78)×10~(-7) cm~2·s~(-1). (fig.1,2). The activity energy of hydrogen diffusion in TiNi alloy was. 16.59 kJ·mol~(-1) (fig.3). The data of X-ray protolelctron spectroscopy (XPS), auger electron spectroscopy (AES), scan electron microscop (SEM) and energy dispersive analysis of X-ray (EDAX) showed that after charged-discharged hydrogen several cycls by electrochemical method, a layer of titanium oxide which contains no nickel was coated on surface of TiNi alloy electrode, beneath this oxide layer there was a Nickel-rich alloy layer, in which the ratio of titanium to nickel is 1:1.28. Thus we concluded that there is a layer of Nickel metal beneath the oxide coating surface. This results coincide with the conclusion of van waldkirch~[15].
The diffusion coefficient D of hydrogen in TiNi alloys was determination with electrochemical method at 20±0.3℃. The value of D was (6.45±0.78)×10~(-7) cm~2·s~(-1). (fig.1,2). The activity energy of hydrogen diffusion in TiNi alloy was. 16.59 kJ·mol~(-1) (fig.3). The data of X-ray protolelctron spectroscopy (XPS), auger electron spectroscopy (AES), scan electron microscop (SEM) and energy dispersive analysis of X-ray (EDAX) showed that after charged-discharged hydrogen several cycls by electrochemical method, a layer of titanium oxide which contains no nickel was coated on surface of TiNi alloy electrode, beneath this oxide layer there was a Nickel-rich alloy layer, in which the ratio of titanium to nickel is 1:1.28. Thus we concluded that there is a layer of Nickel metal beneath the oxide coating surface. This results coincide with the conclusion of van waldkirch~[15].
1986, 2(03): 249-253
doi: 10.3866/PKU.WHXB19860310
Abstract:
The equilibrium geometry and hyperfine coupling constants of cation CH_2CO~+ have been calculated by the UHF method, within the ab initio MO LCAO SCF approximation. The minimal basis set STO-3G was used. The ground state of this cation is ~2B_1 and it is a π-radical. Compared with its neutral parent molecule, the cation has a markedly long C=C bond (0.14138 nm) and a slightly short C=O bond (0.11738 nm), which have been explained by raeans of the analysis of their electronic structures.
Based on the theory of Amos and Snyder, annihilation of the quartet contamination in the UHF wavefunction results in an approximate pure doublet wavefunction. The isotropic hyperfine coupling constants a_H of cation CH_2CO~+ were evaluated from both the spin densities without and with quartet annihilation, which are 49.9G and 16.3G, respectively. The latter one is close to the experimental value (≈20G).
The equilibrium geometry and hyperfine coupling constants of cation CH_2CO~+ have been calculated by the UHF method, within the ab initio MO LCAO SCF approximation. The minimal basis set STO-3G was used. The ground state of this cation is ~2B_1 and it is a π-radical. Compared with its neutral parent molecule, the cation has a markedly long C=C bond (0.14138 nm) and a slightly short C=O bond (0.11738 nm), which have been explained by raeans of the analysis of their electronic structures.
Based on the theory of Amos and Snyder, annihilation of the quartet contamination in the UHF wavefunction results in an approximate pure doublet wavefunction. The isotropic hyperfine coupling constants a_H of cation CH_2CO~+ were evaluated from both the spin densities without and with quartet annihilation, which are 49.9G and 16.3G, respectively. The latter one is close to the experimental value (≈20G).
1986, 2(03): 254-262
doi: 10.3866/PKU.WHXB19860311
Abstract:
The complexes, Sm(TTA)_4·HP and Dy(TTA)_4·HP, have been prepared, and their UV-VIS-NIR absorption spectra measured. The matrix element expressions with I=1/2 to 15/2 of the configurations f~5 and f~9 in a D_4~* symmetry field were derived with Double Sphere Coordination Point Charge Field Model. And the influence of change in symmetry of complex unit R_EO_8 on the DSCPCF splitting of their levels was discussed. Based on theoretical ealcalation, the intra-f transition peaks in the absorption bands were assigned.
The complexes, Sm(TTA)_4·HP and Dy(TTA)_4·HP, have been prepared, and their UV-VIS-NIR absorption spectra measured. The matrix element expressions with I=1/2 to 15/2 of the configurations f~5 and f~9 in a D_4~* symmetry field were derived with Double Sphere Coordination Point Charge Field Model. And the influence of change in symmetry of complex unit R_EO_8 on the DSCPCF splitting of their levels was discussed. Based on theoretical ealcalation, the intra-f transition peaks in the absorption bands were assigned.
1986, 2(03): 263-270
doi: 10.3866/PKU.WHXB19860312
Abstract:
We use ab initio STO-3G method and Foster-Boys localization procedure to perform calculations on about 20 organic molecules containing H, C, N, O elements. As a result, we obtain all useful parameters, i. e. the energies of LMO and their interactions. According to LMO model and applying these parameters, we have calculated the ionization energies of alcohol series which are in quite od agreement with experimental values obtained from photoelectron spectra.
We use ab initio STO-3G method and Foster-Boys localization procedure to perform calculations on about 20 organic molecules containing H, C, N, O elements. As a result, we obtain all useful parameters, i. e. the energies of LMO and their interactions. According to LMO model and applying these parameters, we have calculated the ionization energies of alcohol series which are in quite od agreement with experimental values obtained from photoelectron spectra.
1986, 2(03): 271-277
doi: 10.3866/PKU.WHXB19860313
Abstract:
A formula with second-order perturbation correction is obtained for the calculation NMR coupling constants by means of the unit operator consisting of non-ortho nal LMO and adjoint basis sets The electron densities at the carbon and hydrogen nucleus and the NMR coupling constants ~1J_(CH) for the CH_4, C_2H_4 and C_2H_2 were evalnated respectively. It has been shown that ~1J_(CH) is principally determined by bonding and anti-bonding LMO of the C-H bond and approximately proportional to the product of electron density at the carbon and hydrogen nucleus.
A formula with second-order perturbation correction is obtained for the calculation NMR coupling constants by means of the unit operator consisting of non-ortho nal LMO and adjoint basis sets The electron densities at the carbon and hydrogen nucleus and the NMR coupling constants ~1J_(CH) for the CH_4, C_2H_4 and C_2H_2 were evalnated respectively. It has been shown that ~1J_(CH) is principally determined by bonding and anti-bonding LMO of the C-H bond and approximately proportional to the product of electron density at the carbon and hydrogen nucleus.
1986, 2(03): 278-283
doi: 10.3866/PKU.WHXB19860314
Abstract:
The crystal and molecular structure of titanium ether complex has been determined by X-ray diffraction. TiCl_4 and Et_2O can form 1:2 complex, TiCl_4·2Et_2O, which is in cis-configuration. The crystal belongs to monoclinic space group C_(2h)~5P21/n with unit cell parameters: a=0.8877(4) nm, b=1.3115(8) nm, c=1.3437(8) nm, β=98.27(5)°, Z=4. The structure was refined to R_1=0.108、R_2=0.127 for 1002 reflections.
It has been showed that the titanium ether complex which has been used to modify the catalyst (3TICl_3·AlCl_3) is TiCl_4·2Et_2O. The powder pattern and infrared spectra of the complex have also been t. Some bases for characterizing the catalyst have provided.
The crystal and molecular structure of titanium ether complex has been determined by X-ray diffraction. TiCl_4 and Et_2O can form 1:2 complex, TiCl_4·2Et_2O, which is in cis-configuration. The crystal belongs to monoclinic space group C_(2h)~5P21/n with unit cell parameters: a=0.8877(4) nm, b=1.3115(8) nm, c=1.3437(8) nm, β=98.27(5)°, Z=4. The structure was refined to R_1=0.108、R_2=0.127 for 1002 reflections.
It has been showed that the titanium ether complex which has been used to modify the catalyst (3TICl_3·AlCl_3) is TiCl_4·2Et_2O. The powder pattern and infrared spectra of the complex have also been t. Some bases for characterizing the catalyst have provided.
1986, 2(03): 284-287
doi: 10.3866/PKU.WHXB19860315
Abstract:
The unimolecular reaction of CF_2HCl on W filament has been studied. This reaction shows zero order at rather high pressure. The temperature threshold is about 440 ℃. The apparent activation energy of this reaction is 119.7 kJ mol~(-1) which is about a half of the activation energy for homogeneous unimolecular reaction of CF_2HCl, 233.5 kJ mol~(-1).
The unimolecular reaction of CF_2HCl on W filament has been studied. This reaction shows zero order at rather high pressure. The temperature threshold is about 440 ℃. The apparent activation energy of this reaction is 119.7 kJ mol~(-1) which is about a half of the activation energy for homogeneous unimolecular reaction of CF_2HCl, 233.5 kJ mol~(-1).
