The present paper employed density function theory to investigate two reaction pathways for isomerization of enol ester proposed by Yang(path a) and the present authors(path a), respectively. The base catalytic effect...The present paper employed density function theory to investigate two reaction pathways for isomerization of enol ester proposed by Yang(path a) and the present authors(path a), respectively. The base catalytic effects of solvent triethylamine on these two reactions were also evaluated. It is demonstrated that path B is more preferable than path a due to low barrier height for the rate-determining step.展开更多
Earlier it was shown by different authors that there are cavities (vacancies, holes) in any liquid. The cavities should play a prominent role in dissolution processes. Nevertheless this fact was ignored in previous mo...Earlier it was shown by different authors that there are cavities (vacancies, holes) in any liquid. The cavities should play a prominent role in dissolution processes. Nevertheless this fact was ignored in previous model of dissolution. The sizes of the cavities in different solvents containing benzene molecules were determined using solvent induced spectral shift method. The measurements of S1←S0 benzene transition spectral shifts permit to conclude that 1) macroscopic excess volumes play an almost negligible role in processes of benzene dissolution in very different solvents and 2) the minimal size of the cavity in water able to accommodate benzene molecule coincides with the solute size. Generalization of this conclusion to other nonpolar aromatics leads to evaluation contraction of the solutes under aqueous solvent influence permits to predict the solubility values of other aromatics in water and to evaluate effect of enhancement hydrate cell around these molecules on solubility.展开更多
13C-NMR relaxation times of polystyrene (PS) in its 8 solvent, cyclohexane, are measured at different temperatures. A two-step model for the dissolution is proposed. Swelling of the polymer below the 8 temperature is ...13C-NMR relaxation times of polystyrene (PS) in its 8 solvent, cyclohexane, are measured at different temperatures. A two-step model for the dissolution is proposed. Swelling of the polymer below the 8 temperature is eventually the dispersion of the side group phenyl rings only. While above the 6 temperature, complete dissolution is the dispersion of the main chain at a molecular level. The results of T1(C) are confirmed by 1H-NMR imaging. NMR and its imaging are powerful tools to study the dynamic behavior of dissolution process of polymers in their 6 solvents.展开更多
Magnetic resonane imaging (MRI) has already been widely used in medical diagnosis,but its potential application to material science has not been fully acknowledged yet. AsMRI is highly sensitive to protons, and organi...Magnetic resonane imaging (MRI) has already been widely used in medical diagnosis,but its potential application to material science has not been fully acknowledged yet. AsMRI is highly sensitive to protons, and organic materials contain abundant protons, thereis ample scope of its application. It is gradually becoming a powerful tool for studyingmaterials because it is rich in content and noninvasive to samples under investigation.展开更多
Faults existing in the current theories of non- equilibrium solvation have been clarified in this report. Based on a novel expression of solvation free energy for nonequilibrium, generalized formulations of solvent re...Faults existing in the current theories of non- equilibrium solvation have been clarified in this report. Based on a novel expression of solvation free energy for nonequilibrium, generalized formulations of solvent reor- ganization energy for electron transfer and of solvation shift for spectrum have been established. Furthermore, a new form of solvent reorganization energy for electron transfer in two-sphere case, which greatly differs from the one by Mar- cus, has been deduced. A single-sphere model for solvation shift of spectrum has been put forward both by deducing the generalized formulations and by showing the correct forms of self-energy of reaction field. It has been concluded that the current theories overestimate the solvent reorganization energy and the solvation shift by a factor of about 2. By apply- ing the models established, the discrepancies between the theory and experiments before have been perfectly explained.展开更多
文摘The present paper employed density function theory to investigate two reaction pathways for isomerization of enol ester proposed by Yang(path a) and the present authors(path a), respectively. The base catalytic effects of solvent triethylamine on these two reactions were also evaluated. It is demonstrated that path B is more preferable than path a due to low barrier height for the rate-determining step.
文摘Earlier it was shown by different authors that there are cavities (vacancies, holes) in any liquid. The cavities should play a prominent role in dissolution processes. Nevertheless this fact was ignored in previous model of dissolution. The sizes of the cavities in different solvents containing benzene molecules were determined using solvent induced spectral shift method. The measurements of S1←S0 benzene transition spectral shifts permit to conclude that 1) macroscopic excess volumes play an almost negligible role in processes of benzene dissolution in very different solvents and 2) the minimal size of the cavity in water able to accommodate benzene molecule coincides with the solute size. Generalization of this conclusion to other nonpolar aromatics leads to evaluation contraction of the solutes under aqueous solvent influence permits to predict the solubility values of other aromatics in water and to evaluate effect of enhancement hydrate cell around these molecules on solubility.
基金Project Supported by the National Key Projects for Fundamental Research"Macromolecular condensed state",the State Science and Technology Commission of China.
文摘13C-NMR relaxation times of polystyrene (PS) in its 8 solvent, cyclohexane, are measured at different temperatures. A two-step model for the dissolution is proposed. Swelling of the polymer below the 8 temperature is eventually the dispersion of the side group phenyl rings only. While above the 6 temperature, complete dissolution is the dispersion of the main chain at a molecular level. The results of T1(C) are confirmed by 1H-NMR imaging. NMR and its imaging are powerful tools to study the dynamic behavior of dissolution process of polymers in their 6 solvents.
基金Project supported by the Chinese Academy of Sciences and the State Science and Technology Commission of China.
文摘Magnetic resonane imaging (MRI) has already been widely used in medical diagnosis,but its potential application to material science has not been fully acknowledged yet. AsMRI is highly sensitive to protons, and organic materials contain abundant protons, thereis ample scope of its application. It is gradually becoming a powerful tool for studyingmaterials because it is rich in content and noninvasive to samples under investigation.
基金supported by the National Natural Science Foundation of Chinathe Trans-Century Training Program Foundation for the Talents by the Ministry of Education of China
文摘Faults existing in the current theories of non- equilibrium solvation have been clarified in this report. Based on a novel expression of solvation free energy for nonequilibrium, generalized formulations of solvent reor- ganization energy for electron transfer and of solvation shift for spectrum have been established. Furthermore, a new form of solvent reorganization energy for electron transfer in two-sphere case, which greatly differs from the one by Mar- cus, has been deduced. A single-sphere model for solvation shift of spectrum has been put forward both by deducing the generalized formulations and by showing the correct forms of self-energy of reaction field. It has been concluded that the current theories overestimate the solvent reorganization energy and the solvation shift by a factor of about 2. By apply- ing the models established, the discrepancies between the theory and experiments before have been perfectly explained.
