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1988 Volume 4 Issue 2
1988, 4(02): 113-116
doi: 10.3866/PKU.WHXB19880201
Abstract:
We have carried out investigations of the surfaces of the Y-Ba-Cu-O superconductor with XPS. Our experiments deal with the chemical valence states of the elements at the surfaces as well as the changes of the surface species and the peak splitings with heating, etching and irradiation.
We have carried out investigations of the surfaces of the Y-Ba-Cu-O superconductor with XPS. Our experiments deal with the chemical valence states of the elements at the surfaces as well as the changes of the surface species and the peak splitings with heating, etching and irradiation.
1988, 4(02): 117-122
doi: 10.3866/PKU.WHXB19880202
Abstract:
This paper deals with 1-N-methyl-cinnoline TCNQ complex(1-N-M_(ci) TCNQ_2) and 2-N-methyl-cinnoline TCNQ complex(2-N-M_(ci) TCNQ_2).The molecular packing analyses of both complex crystals were performanced by using. OPEC program. The potential energies of 1-N-M_(ci) TCNQ_2 and 2-N-M_(ci) TCNQ_2 are -70.194 kcal mol~(-1) and -66.945 kcal mol~(-1), respectively. The result shows that the less anisotropy in dimensions of planar dondor molecules is, the less effect on the arrangement of TCNQ and the more favourable for TCNQ molecules to arrange in one-dimensional column there is.
This paper deals with 1-N-methyl-cinnoline TCNQ complex(1-N-M_(ci) TCNQ_2) and 2-N-methyl-cinnoline TCNQ complex(2-N-M_(ci) TCNQ_2).The molecular packing analyses of both complex crystals were performanced by using. OPEC program. The potential energies of 1-N-M_(ci) TCNQ_2 and 2-N-M_(ci) TCNQ_2 are -70.194 kcal mol~(-1) and -66.945 kcal mol~(-1), respectively. The result shows that the less anisotropy in dimensions of planar dondor molecules is, the less effect on the arrangement of TCNQ and the more favourable for TCNQ molecules to arrange in one-dimensional column there is.
1988, 4(02): 123-128
doi: 10.3866/PKU.WHXB19880203
Abstract:
The interaction of poly (methyl methacrylate) and its copolymer of methyl methacrylic acid with Rh6G in mixed solvent of ethyl acetate and ethyl alcohol with various proportions was studied. It was found that there did not exist any specific interaction between poly(methyl methacrylate) and Rh6G in all mixed solvent used. The case of copolymer was quite different. By addition of Rh6G the specific viscosity of copolymer in solvent of low alcohol content was enhanced and the polyelectrolyte effect of copolymer in solvent of high alcohol content was suppressed. The fluorescence intensity of Rh6G was decreased in presence of copolymer, especially in solvent of high alcohol content. All these experimental facts demonstrated there was interaction between copolymer and Rh6G. It was supposed the interaction was fulfilled through hydrogen bonding between Rh6G molecule and —COOH in low polar solvent and through electrostatic attraction mainly between the quaternary ammonium ion of Rh6G and —COO~- in high polar solvent.
The interaction of poly (methyl methacrylate) and its copolymer of methyl methacrylic acid with Rh6G in mixed solvent of ethyl acetate and ethyl alcohol with various proportions was studied. It was found that there did not exist any specific interaction between poly(methyl methacrylate) and Rh6G in all mixed solvent used. The case of copolymer was quite different. By addition of Rh6G the specific viscosity of copolymer in solvent of low alcohol content was enhanced and the polyelectrolyte effect of copolymer in solvent of high alcohol content was suppressed. The fluorescence intensity of Rh6G was decreased in presence of copolymer, especially in solvent of high alcohol content. All these experimental facts demonstrated there was interaction between copolymer and Rh6G. It was supposed the interaction was fulfilled through hydrogen bonding between Rh6G molecule and —COOH in low polar solvent and through electrostatic attraction mainly between the quaternary ammonium ion of Rh6G and —COO~- in high polar solvent.
1988, 4(02): 129-135
doi: 10.3866/PKU.WHXB19880204
Abstract:
The interactions between nonionic surfactant octylmethylsulfoxide (OMS) and ionic surfactants sodium decylsulfate(SDeS), sodium perfluorooctanoate(SPFO), and decyltrimethylammonium bromide (DeTAB) in aqueous solutions have been investi gated. The following results are obtained:
1) The critical micelll concentration (cmc)-mole fraction(α) curves of all mixtures discussed are lower than the ideal ones.
2) The surface adsorptions at cmc(Γ_(cmc,T)) of OMS-SDeS, OMS-SPFO mixtures have maximum values. But those of OMS-DeTAB mixtures have not.
3) The surface tension at cmc (γ_(cmc)) of OMS-SPFO solution can reach a value below 16 mNm~(-1) which is lower than those of single OMS and SPFO. However, γ_(cmc) of the other two kinds of mixtures are lower than that of single SDeS or DeTAB, but higher than that of single OMS.
4) All of the molecular interaction parameters of surfactants in micelles (β~m) and in surface layers (β~s) are negtive. Their variations are also discussed.
5) Interactions of OMS-SDeS, and OMS-SPFO are much stronger than that of OMS-DeTAB. It is explained with protonation of some of the oxygen atoms of OMS molecules in aqueous solutions.
The interactions between nonionic surfactant octylmethylsulfoxide (OMS) and ionic surfactants sodium decylsulfate(SDeS), sodium perfluorooctanoate(SPFO), and decyltrimethylammonium bromide (DeTAB) in aqueous solutions have been investi gated. The following results are obtained:
1) The critical micelll concentration (cmc)-mole fraction(α) curves of all mixtures discussed are lower than the ideal ones.
2) The surface adsorptions at cmc(Γ_(cmc,T)) of OMS-SDeS, OMS-SPFO mixtures have maximum values. But those of OMS-DeTAB mixtures have not.
3) The surface tension at cmc (γ_(cmc)) of OMS-SPFO solution can reach a value below 16 mNm~(-1) which is lower than those of single OMS and SPFO. However, γ_(cmc) of the other two kinds of mixtures are lower than that of single SDeS or DeTAB, but higher than that of single OMS.
4) All of the molecular interaction parameters of surfactants in micelles (β~m) and in surface layers (β~s) are negtive. Their variations are also discussed.
5) Interactions of OMS-SDeS, and OMS-SPFO are much stronger than that of OMS-DeTAB. It is explained with protonation of some of the oxygen atoms of OMS molecules in aqueous solutions.
1988, 4(02): 136-140
doi: 10.3866/PKU.WHXB19880205
Abstract:
The measurements of positron annihilation lifetime spectrum for chlorophyll in cyclohexane (77 K) and in alcohol (296 K) were carried out under illumination at different light intensity. A photomagnetic positronium annihilation model was proposed to explain the experimental facts. The changes of annihilation parameters I_2 and Λ_2 for frozen chlorophyll cyclohexan solution at 77 K with relative light intensity suggest that the photomagnetic quenching effect of positronium can serve to trace the concentration changes of photo-excited triplet states in photosensitive material.
The measurements of positron annihilation lifetime spectrum for chlorophyll in cyclohexane (77 K) and in alcohol (296 K) were carried out under illumination at different light intensity. A photomagnetic positronium annihilation model was proposed to explain the experimental facts. The changes of annihilation parameters I_2 and Λ_2 for frozen chlorophyll cyclohexan solution at 77 K with relative light intensity suggest that the photomagnetic quenching effect of positronium can serve to trace the concentration changes of photo-excited triplet states in photosensitive material.
1988, 4(02): 141-145
doi: 10.3866/PKU.WHXB19880206
Abstract:
In the water-insoluble polyelectrolyte complex of 2,10-Br and sodium polyacrylate the ratio of[COO~-]/[(?)] was found to be 6/4(equivalent ratio),which maintained constant even the total original concentration of polymers ranged from 1×10~(-4) to 1×10~(-2) mol L~(-1). In the KBr solution of high ionic strength the insoluble complex was dissolved due to the "shielding effect" of counterions. In water complexation could take place instantly and completely producing a stable complex. However the formatiom of complex developed with time in aqueous salt solution. The biological activity of the ionenes has been tested preliminarily. 2,6-Br, 2,10-Br and 6,10-Br could inhibit the growth of E.coli, of which 6,10-Br is most effective.
In the water-insoluble polyelectrolyte complex of 2,10-Br and sodium polyacrylate the ratio of[COO~-]/[(?)] was found to be 6/4(equivalent ratio),which maintained constant even the total original concentration of polymers ranged from 1×10~(-4) to 1×10~(-2) mol L~(-1). In the KBr solution of high ionic strength the insoluble complex was dissolved due to the "shielding effect" of counterions. In water complexation could take place instantly and completely producing a stable complex. However the formatiom of complex developed with time in aqueous salt solution. The biological activity of the ionenes has been tested preliminarily. 2,6-Br, 2,10-Br and 6,10-Br could inhibit the growth of E.coli, of which 6,10-Br is most effective.
1988, 4(02): 146-151
doi: 10.3866/PKU.WHXB19880207
Abstract:
A MINDO/3 MO method has been applied to study the tautomeric reaction of the N_1-H-4-NH_2-2-oxo-cytosine and 4-NH-2-oxo-cytosine. The geometries of the molecules involved in the tautomeric reaction are optimized by energy gradient method using MINDO/3 program. The results show that the amino-tautomer is more stable than imino-tautomer by △E=33.85 kJ mol~(-1).
The geometry of the transition state is optimized by Powell's method. The reaction path of the tautomeric reaction is presented, based on Fukui's IRC theory. The physical nature of the reaction is revealed by analysing the intramolecular charge transfer as the tautomeric reaction is occurring. The activation arrier of the forward reaction is 168.87 kJ mol~(-1), while it is 135.02 kJ mol~(-1) for the backward reaction.
A MINDO/3 MO method has been applied to study the tautomeric reaction of the N_1-H-4-NH_2-2-oxo-cytosine and 4-NH-2-oxo-cytosine. The geometries of the molecules involved in the tautomeric reaction are optimized by energy gradient method using MINDO/3 program. The results show that the amino-tautomer is more stable than imino-tautomer by △E=33.85 kJ mol~(-1).
The geometry of the transition state is optimized by Powell's method. The reaction path of the tautomeric reaction is presented, based on Fukui's IRC theory. The physical nature of the reaction is revealed by analysing the intramolecular charge transfer as the tautomeric reaction is occurring. The activation arrier of the forward reaction is 168.87 kJ mol~(-1), while it is 135.02 kJ mol~(-1) for the backward reaction.
1988, 4(02): 152-158
doi: 10.3866/PKU.WHXB19880208
Abstract:
The kinetics and mechanisms of the substitution reactions of (μ,μ-SCH_2S)Fe_2 (CO)_6 with PPh_3, PMe_2Ph, PEt_3, P(n-Bu)_3 and (μ-PhCH_2S)(μ-RS)Fe_2(CO)_6(R=Me, Et) with PPh_3 in various solvents have been studied by means of UV-spectra and ~1H NMR. The results support the mechanism of Ia (associative interchange) for the substitution reactions of first step and Id (dissociative interchange) for the reactions of second step. The electronic effects of the ligands, steric effects of the ligands and the parent complexes and the solvent effecs on the reaction rates have been discussed. It shows that the reaction rate is presumably determined by the volume of the incoming ligands. the nucleophilic solvents such as DMF can promote the reaction rate by means of base catalysis.
The kinetics and mechanisms of the substitution reactions of (μ,μ-SCH_2S)Fe_2 (CO)_6 with PPh_3, PMe_2Ph, PEt_3, P(n-Bu)_3 and (μ-PhCH_2S)(μ-RS)Fe_2(CO)_6(R=Me, Et) with PPh_3 in various solvents have been studied by means of UV-spectra and ~1H NMR. The results support the mechanism of Ia (associative interchange) for the substitution reactions of first step and Id (dissociative interchange) for the reactions of second step. The electronic effects of the ligands, steric effects of the ligands and the parent complexes and the solvent effecs on the reaction rates have been discussed. It shows that the reaction rate is presumably determined by the volume of the incoming ligands. the nucleophilic solvents such as DMF can promote the reaction rate by means of base catalysis.
1988, 4(02): 159-166
doi: 10.3866/PKU.WHXB19880209
Abstract:
The decarbonylation and the structural transformation of co_2(CO)_6(PBu_3)_2 supported on ZrO_2, Al_2O_3, TiO_2 and SiO_2 have been studied by IR spectroscopy, UV diffuse reflectance spectroscopy, X-ray photoelectron spectroscope and temperature-programmed decomposition technique. It is seen that when the complex is supported on various oxides, the frequency bands of the terminal carbonyls shift to low wave numbers respectively. The order of v(CO) is: complex/TiO_2=complex/SiO_2, complex/Al_2O_3, complex/ZrO_2. The position of the UV-DRS peaks for supported complexes, which are related to the nature of Co-Co bond and Co-CO (ligand) charge tranfer, are essentially the same as that for unsupported complex. It is found that when these supported complexes are heated in vacuum, intensity of the terminal carbonyl of those supported on ZrO_2 and Al_2O_3 diminishes somewhat with the increasing of temperature, and at the same time intensity of the bridged carbonyl increases. As the temperature is raised to 300′C and 200′C, the carbonyl bands disappear respectively. However, the C-H frequency bands persist in the IR spectra, showing that the phosphine ligands still exist on the surface. When CO is admitted to these decarbonylated samples, the frequency bands of adsorbed CO are observed. it is noticed that as the samples exposed to air, the bands disappear at once. The carbonyl bands of complexes supported on TiO_2 and SiO_2 disappear completely at 150′C and no bands of bridged carbonyl appear, on these decarbonylated samples CO can not be adsorbed.
The decarbonylation processes of these supported complexes in vacuum and air were investigated According the experimental results, the structrual transformation of surface complexes on various oxides are proposed respectively. In addition, the surface reaction of supported complexes in H_2 and He atmosphere during TPDE was also investigated.
*Project supported by the Science Fund of the Chinese Academy of Sciences.
The decarbonylation and the structural transformation of co_2(CO)_6(PBu_3)_2 supported on ZrO_2, Al_2O_3, TiO_2 and SiO_2 have been studied by IR spectroscopy, UV diffuse reflectance spectroscopy, X-ray photoelectron spectroscope and temperature-programmed decomposition technique. It is seen that when the complex is supported on various oxides, the frequency bands of the terminal carbonyls shift to low wave numbers respectively. The order of v(CO) is: complex/TiO_2=complex/SiO_2, complex/Al_2O_3, complex/ZrO_2. The position of the UV-DRS peaks for supported complexes, which are related to the nature of Co-Co bond and Co-CO (ligand) charge tranfer, are essentially the same as that for unsupported complex. It is found that when these supported complexes are heated in vacuum, intensity of the terminal carbonyl of those supported on ZrO_2 and Al_2O_3 diminishes somewhat with the increasing of temperature, and at the same time intensity of the bridged carbonyl increases. As the temperature is raised to 300′C and 200′C, the carbonyl bands disappear respectively. However, the C-H frequency bands persist in the IR spectra, showing that the phosphine ligands still exist on the surface. When CO is admitted to these decarbonylated samples, the frequency bands of adsorbed CO are observed. it is noticed that as the samples exposed to air, the bands disappear at once. The carbonyl bands of complexes supported on TiO_2 and SiO_2 disappear completely at 150′C and no bands of bridged carbonyl appear, on these decarbonylated samples CO can not be adsorbed.
The decarbonylation processes of these supported complexes in vacuum and air were investigated According the experimental results, the structrual transformation of surface complexes on various oxides are proposed respectively. In addition, the surface reaction of supported complexes in H_2 and He atmosphere during TPDE was also investigated.
*Project supported by the Science Fund of the Chinese Academy of Sciences.
1988, 4(02): 167-171
doi: 10.3866/PKU.WHXB19880210
Abstract:
A convenient technique of fabricating powder microelectrode was developed and the behaviors of reversible electrode reactions on such powder microelectrode were studied. Experimental results can be interpreted by assuming that powder microelectrode is equivalent to microdisc electrode and micro-thin layer electrode connected in parallel.
A convenient technique of fabricating powder microelectrode was developed and the behaviors of reversible electrode reactions on such powder microelectrode were studied. Experimental results can be interpreted by assuming that powder microelectrode is equivalent to microdisc electrode and micro-thin layer electrode connected in parallel.
1988, 4(02): 172-176
doi: 10.3866/PKU.WHXB19880211
Abstract:
The reduction of LaCoO_3 has been studied by XPS. It is shown that the degree of reduction of cobalt is characterized by the peak intensity of shake-up satellite of Co 2p_(1/2) level. The reduction of Co~(3+) to Co~(2+) in LaCoO_3 is appeared at 400 ℃. When LaCoO_3 is reduced by H_2 at 600 ℃, the cobalt is converted into metallic form, meanwhile the structure of La_2O_3 is identified by X-ray diffraction. After reduction of LaCoO_3 the separation energy between La 3d_(5/2) level and its shake-up satellite peak is 3.1 eV and the intensity ratio of shake-up satellite to its parent peak for La 3d_(5/2) level is 0.76. These values are approximately sam e as those of La(OH)_3, but they are different from those of La_2O_3. Therefore, La(OH)_3 is formed on surface after reduction of LaCoO_3.
The reduction of LaCoO_3 has been studied by XPS. It is shown that the degree of reduction of cobalt is characterized by the peak intensity of shake-up satellite of Co 2p_(1/2) level. The reduction of Co~(3+) to Co~(2+) in LaCoO_3 is appeared at 400 ℃. When LaCoO_3 is reduced by H_2 at 600 ℃, the cobalt is converted into metallic form, meanwhile the structure of La_2O_3 is identified by X-ray diffraction. After reduction of LaCoO_3 the separation energy between La 3d_(5/2) level and its shake-up satellite peak is 3.1 eV and the intensity ratio of shake-up satellite to its parent peak for La 3d_(5/2) level is 0.76. These values are approximately sam e as those of La(OH)_3, but they are different from those of La_2O_3. Therefore, La(OH)_3 is formed on surface after reduction of LaCoO_3.
1988, 4(02): 177-181
doi: 10.3866/PKU.WHXB19880212
Abstract:
Solubilities of KCl and NaCl in binary mixed solvents of CH_3OH-DMF and CH_3OH-DMSO with mole fraction of components from 0 to 1 were measured at 288, 303, 313 K for KCl and 278, 288, 298, 303 and 313 K for NaCl. A plot of solubility of KCl and NaCl vs composition of solvent shows a maximum. The coefficient of solubility with temperature for KCl is positive and for NaCl is negative. The transfer free energy and entropy of KCl and NaCl from pure methanol to mixed solvents were evaluated from the measurements, thus the structure property of solution, the effect of salt on it, the ionic solvation and the tendentiousness of solution were discussed preliminarily.
Solubilities of KCl and NaCl in binary mixed solvents of CH_3OH-DMF and CH_3OH-DMSO with mole fraction of components from 0 to 1 were measured at 288, 303, 313 K for KCl and 278, 288, 298, 303 and 313 K for NaCl. A plot of solubility of KCl and NaCl vs composition of solvent shows a maximum. The coefficient of solubility with temperature for KCl is positive and for NaCl is negative. The transfer free energy and entropy of KCl and NaCl from pure methanol to mixed solvents were evaluated from the measurements, thus the structure property of solution, the effect of salt on it, the ionic solvation and the tendentiousness of solution were discussed preliminarily.
1988, 4(02): 182-186
doi: 10.3866/PKU.WHXB19880213
Abstract:
Multiphoton ionization and fragmentation of acetone at 308nm laser radiation are studied by using diffuse molecular beam and multiphoton ionization mass spectroscopy. It is found that no parent ions of acetone are produced, but only the frag ment ions at m/e=15 and 43, corresponding to two neutral fragments of CH_3 and CH_3CO generated by photodissociation of acetone, respectively. The inten sities of these ions are proportional to the 3.6th and 3.0th power of the laserintensity, respectively. We argue that these fragment ions are from the ionization of the neutral radicals CH_3 and CH_3CO.
Multiphoton ionization and fragmentation of acetone at 308nm laser radiation are studied by using diffuse molecular beam and multiphoton ionization mass spectroscopy. It is found that no parent ions of acetone are produced, but only the frag ment ions at m/e=15 and 43, corresponding to two neutral fragments of CH_3 and CH_3CO generated by photodissociation of acetone, respectively. The inten sities of these ions are proportional to the 3.6th and 3.0th power of the laserintensity, respectively. We argue that these fragment ions are from the ionization of the neutral radicals CH_3 and CH_3CO.
1988, 4(02): 187-193
doi: 10.3866/PKU.WHXB19880214
Abstract:
Freon-114 (CClF_2CClF_2) with a pressure of 10 Torr is irradiated by means of a pulsed CO_2 laser at 10.6μm and 9.6μm, each of which corresponds to a specific C—F stretching band of gauche isomer. At both wavelengths, the reaction products are always CF_2Cl_2 and C_2F_4, which result from two different decomposition channels i.e. C—C bond breaking and C—Cl bond breaking. There is thermal effect in the laser induced decomposition of Freon-114, which may be approximately described by an Arrhenius formula. The activation energy E_a of laser induced decomposition for the two different channels canbe estimated from the experimental results. The values of E_a are approximately equal to that obtained from thermal decomposition. At the same time, the channel competition processes of unimolecular laser induced decomposition of Freon-114 can be interpreted by the RRKM theory of unimolecular reaction and the calculated results are in agreement with the experimental results.
Freon-114 (CClF_2CClF_2) with a pressure of 10 Torr is irradiated by means of a pulsed CO_2 laser at 10.6μm and 9.6μm, each of which corresponds to a specific C—F stretching band of gauche isomer. At both wavelengths, the reaction products are always CF_2Cl_2 and C_2F_4, which result from two different decomposition channels i.e. C—C bond breaking and C—Cl bond breaking. There is thermal effect in the laser induced decomposition of Freon-114, which may be approximately described by an Arrhenius formula. The activation energy E_a of laser induced decomposition for the two different channels canbe estimated from the experimental results. The values of E_a are approximately equal to that obtained from thermal decomposition. At the same time, the channel competition processes of unimolecular laser induced decomposition of Freon-114 can be interpreted by the RRKM theory of unimolecular reaction and the calculated results are in agreement with the experimental results.
1988, 4(02): 194-199
doi: 10.3866/PKU.WHXB19880215
Abstract:
It has been proved in our experiments that (1) Dihydrocoumarin can be formed from the reaction between coumarin and tetralin; (2) Dihydrocoumarin is rather stable, but it is able to react producting other products on certain conditions. The results of analyses of the intermediates and products of reactions using chromatograph-mass spectrum, nuclear magnetic resonance and infra-red spectrograph are given. A proof that most of the steps for the reaction of Dihydrocoumarin are consecutive has been given from kinetic experiments and analytical results of the products. A mechanism for the reaction has been suggested which can reasonably explain all the experimental results.
It has been proved in our experiments that (1) Dihydrocoumarin can be formed from the reaction between coumarin and tetralin; (2) Dihydrocoumarin is rather stable, but it is able to react producting other products on certain conditions. The results of analyses of the intermediates and products of reactions using chromatograph-mass spectrum, nuclear magnetic resonance and infra-red spectrograph are given. A proof that most of the steps for the reaction of Dihydrocoumarin are consecutive has been given from kinetic experiments and analytical results of the products. A mechanism for the reaction has been suggested which can reasonably explain all the experimental results.
1988, 4(02): 200-204
doi: 10.3866/PKU.WHXB19880216
Abstract:
The title compoud and its related derivatives show a certain degree of thermal lability and were reported as effective carbon-carbon type initiators for the polymerzation of styrene and other monomers.The crystal and molecular structrues of two isimers of the title compoud has been determined.
1, meso-(I), C_(22)H_(18)N_4O_8 space group, p1, a=0.7860(3), b=0.8350(2), c=0.9303(3) nm, a=89.29(2), β=65.49(2), γ=83.27(2), Z=1, V=0.5512 nm, μ(MoKα)=1.02 cm~(-1), D_c=1.405 mg m~(-3), final R=0.064 for 1729 observed reflections.
2, racemic-(I), C_(22)H_(18)O_8·C_6H_6, space group C2/C, a=1.8395(5), b=1.102(2), c=1.3865(4) nm, β=92.16(2)°, Z=4, V=2.809(1) nm, μ(MoKα)=0.89 cm~(-1), D_c=1.458 mg m~(-3), final R=0.084 for 2202 observed reflections.
There are numerous intramolecular non-bonded atomic eontacts shorter than the expected van der Waals distances. The strong steric interactions of these atomic pairs lead to enormous strain within the molecule and thus to anomalous bond lengths and angles as well as thermal instability The stretching of the centra C—C bonds, 0.1601(4) nm for meso-(I), 0.1587(6) nm for racemic-(I), is particularly remarkable. It was shown the “steric acceleration” plays an important role during the cleavage of the central C—C bonds.
The title compoud and its related derivatives show a certain degree of thermal lability and were reported as effective carbon-carbon type initiators for the polymerzation of styrene and other monomers.The crystal and molecular structrues of two isimers of the title compoud has been determined.
1, meso-(I), C_(22)H_(18)N_4O_8 space group, p1, a=0.7860(3), b=0.8350(2), c=0.9303(3) nm, a=89.29(2), β=65.49(2), γ=83.27(2), Z=1, V=0.5512 nm, μ(MoKα)=1.02 cm~(-1), D_c=1.405 mg m~(-3), final R=0.064 for 1729 observed reflections.
2, racemic-(I), C_(22)H_(18)O_8·C_6H_6, space group C2/C, a=1.8395(5), b=1.102(2), c=1.3865(4) nm, β=92.16(2)°, Z=4, V=2.809(1) nm, μ(MoKα)=0.89 cm~(-1), D_c=1.458 mg m~(-3), final R=0.084 for 2202 observed reflections.
There are numerous intramolecular non-bonded atomic eontacts shorter than the expected van der Waals distances. The strong steric interactions of these atomic pairs lead to enormous strain within the molecule and thus to anomalous bond lengths and angles as well as thermal instability The stretching of the centra C—C bonds, 0.1601(4) nm for meso-(I), 0.1587(6) nm for racemic-(I), is particularly remarkable. It was shown the “steric acceleration” plays an important role during the cleavage of the central C—C bonds.
1988, 4(02): 205-211
doi: 10.3866/PKU.WHXB19880217
Abstract:
The rate constants of eleven hydrocarbons and fluorocarbons with CN (V″=0, 1) at 300 K have been measured by using Laser Induced Fluorescence(LIF) method For the saturated hydrocarbons, the rate constants are changed from (5.6±0.3)×10~(-13) for CH_4 to (2.3±0.2)×10~(-10)cm~3 molecu~(-1).s~(-1) for C_7H_(16). The rate constants of the reaction of CN with alkenes and alkynes are close to the gas kinetic rate in spite of the structure of the molecules.The rate constants and mechanism of CN with the saturated hydrocarbons, H_2 and CH_3OH can be explained satisfactorily by the long distance attractive potential. The reaction of CN with alkenes and alkynes can only proceed through the addition into π bond. The influence of vibrational energy on the reaction rate was not found in the reactions of CN radical with hydrocarbon compounds.
The rate constants of eleven hydrocarbons and fluorocarbons with CN (V″=0, 1) at 300 K have been measured by using Laser Induced Fluorescence(LIF) method For the saturated hydrocarbons, the rate constants are changed from (5.6±0.3)×10~(-13) for CH_4 to (2.3±0.2)×10~(-10)cm~3 molecu~(-1).s~(-1) for C_7H_(16). The rate constants of the reaction of CN with alkenes and alkynes are close to the gas kinetic rate in spite of the structure of the molecules.The rate constants and mechanism of CN with the saturated hydrocarbons, H_2 and CH_3OH can be explained satisfactorily by the long distance attractive potential. The reaction of CN with alkenes and alkynes can only proceed through the addition into π bond. The influence of vibrational energy on the reaction rate was not found in the reactions of CN radical with hydrocarbon compounds.
1988, 4(02): 212-215
doi: 10.3866/PKU.WHXB19880218
Abstract:
The coordination reaction of lanthanum nitrate with 18-crown-6, dicyclohexyl-18-crown-6 and 2,3-benzo-11-methyl-18-crown-6 in acetonitrile was studied. The reaction enthalpies and stability constants were obtained by home-made titration calorimeter and computer program. We demonstrated that the reaction is exothermic on condition that the lanthanum nitrate was dehydrated ri rously. Supplementary experiments showed that the reaction heat is dependent obviously on water content in lanthanum nitrate. Because lanthanum (III) ion has strong hydrophilic ability and large hydration heat, large energy consumption is necessary when crown replaces the coordinated water. Therefore, if the lathanum nitrate has not been dehydrated ri rously, the reaction heat measured may be small negative or positive value.
The coordination reaction of lanthanum nitrate with 18-crown-6, dicyclohexyl-18-crown-6 and 2,3-benzo-11-methyl-18-crown-6 in acetonitrile was studied. The reaction enthalpies and stability constants were obtained by home-made titration calorimeter and computer program. We demonstrated that the reaction is exothermic on condition that the lanthanum nitrate was dehydrated ri rously. Supplementary experiments showed that the reaction heat is dependent obviously on water content in lanthanum nitrate. Because lanthanum (III) ion has strong hydrophilic ability and large hydration heat, large energy consumption is necessary when crown replaces the coordinated water. Therefore, if the lathanum nitrate has not been dehydrated ri rously, the reaction heat measured may be small negative or positive value.
1988, 4(02): 216-220
doi: 10.3866/PKU.WHXB19880219
Abstract:
The solubilities of the ternary system,Yb(NO_3)_3·3H_2O-B15C5·C_2H_5OH, at 18 ℃ have been investigated by the modified semimicro method for study of phase equilibrium. The results indicated that there are two solubility curves for this ternary system: the long one corresponds to the solid phase of the complex (Yb(NO_3)_3·B15C5·3H_2O·2.5C_2H_5OH), and the short one to the solid phase of B15C5. The curve of refractive indexes for saturated solutions consists of two branches, which correspond with two branches with solubility curve. We have not found other complex species having different ratio, Yb/crown.
The behavior of water for this system in equilibrium has been examined. The results are: the mole ratio, H_2O/Yb(NO_3)_3, no matter whether it is in liquid phase or solid phase, is alwaysl 3:1.
The complex has been isolated from organic solvent, C_2H_5OH. The composition of this complex has been determined by chemical analysis and it is Yb(NO_3)_3·B15C5·3H_2O·0.65C_2H_5OH. The properties of this complex have been investigated by chemical analysis, infrafed spectra, DTG and TG.
The solubilities of the ternary system,Yb(NO_3)_3·3H_2O-B15C5·C_2H_5OH, at 18 ℃ have been investigated by the modified semimicro method for study of phase equilibrium. The results indicated that there are two solubility curves for this ternary system: the long one corresponds to the solid phase of the complex (Yb(NO_3)_3·B15C5·3H_2O·2.5C_2H_5OH), and the short one to the solid phase of B15C5. The curve of refractive indexes for saturated solutions consists of two branches, which correspond with two branches with solubility curve. We have not found other complex species having different ratio, Yb/crown.
The behavior of water for this system in equilibrium has been examined. The results are: the mole ratio, H_2O/Yb(NO_3)_3, no matter whether it is in liquid phase or solid phase, is alwaysl 3:1.
The complex has been isolated from organic solvent, C_2H_5OH. The composition of this complex has been determined by chemical analysis and it is Yb(NO_3)_3·B15C5·3H_2O·0.65C_2H_5OH. The properties of this complex have been investigated by chemical analysis, infrafed spectra, DTG and TG.
1988, 4(02): 221-224
doi: 10.3866/PKU.WHXB19880220
Abstract:
Conductivity measurements of FeCl_3 doped cis rare-earth polyacetylenes have been performed under room temperature as well as at low temperature. Conductivities for the doped polyacetylene samples with various dopant concentrations decrease with decreasing temperature. The transportion process obeys qualitatively with the variable range hopping equation. Phase transition was also observed for a few doped samples.
Conductivity measurements of FeCl_3 doped cis rare-earth polyacetylenes have been performed under room temperature as well as at low temperature. Conductivities for the doped polyacetylene samples with various dopant concentrations decrease with decreasing temperature. The transportion process obeys qualitatively with the variable range hopping equation. Phase transition was also observed for a few doped samples.
