Transition-state shape selectivity plays a crucial role in catalytic systems where reactants and products exhibit comparable molecular dimensions,as it restricts the accessible configuration space of reaction intermed...Transition-state shape selectivity plays a crucial role in catalytic systems where reactants and products exhibit comparable molecular dimensions,as it restricts the accessible configuration space of reaction intermediates.Herein,we designed a Cu@MFI catalyst by encapsulating Cu active sites within the well-defined micropores of MFI zeolite through a pore confinement strategy.This architecture preserves the zeolite framework integrity while maintaining unhindered internal mass transport,thereby enabling precise spatial control over transition-state configurations.Employing furfural hydrogenation as a probe reaction,the metal-zeolite synergy in Cu@MFI endowed the catalyst with exceptional activity(100%furfural conversion)and quantitative selectivity(100%furfuryl alcohol)at 70℃,sustained across a broad temperature window.Mechanistic studies reveal that the transition-state shape selectivity effectively prevented H2O interaction with the furan ring,offering valuable insights for other reaction systems seeking to exploit shape selectivity for specific transformations.展开更多
Ab initio Hartree-Fock theory at the aug-cc-pvtz level is used to investigate the equilibrium structures and isomerization of HSOF system. All of the transition states have been calculated and confirmed by the intri...Ab initio Hartree-Fock theory at the aug-cc-pvtz level is used to investigate the equilibrium structures and isomerization of HSOF system. All of the transition states have been calculated and confirmed by the intrinsic reaction coordinate (IRC). Four equilibrium structures, HSOF, HOSF, SO(H)F and OS(H)F, are predicted in this paper. Though OSF2 has been observed experimentally, the present calculated results suggest that the linear form isomer, HOSF, is more stable than OS(H)F by 35.2 kJ/mol. The linear form HSOF and the branched SO(H)F isomer are more unstable and the computed relative energies are 318.3 and 510.0 kJ/mol, respectively with respect to HOSF isomer corrected with zero point vibrational energy.展开更多
MP2 and DFT/B3LYP calculations with Aug-cc-pvTz and Aug-cc-pvQz basis set levels are used to investigate the equilibrium structures and isomerization of H2SO isomers. All of the transition states have been...MP2 and DFT/B3LYP calculations with Aug-cc-pvTz and Aug-cc-pvQz basis set levels are used to investigate the equilibrium structures and isomerization of H2SO isomers. All of the transition states have been calculated and confirmed by the intrinsic reaction coordinate (IRC). The calculated results show that H2SO isomers have three equilibrium structures and the linear structure is the most stable while the branched H2OS is the most unstable (the relative energies are 0.0, 82.1 and 155.3 kJ/mol for HSOH, H2SO and H2OS, respectively with the zero point vibrational energy correction at B3LYP/Aug-cc-pvQz level). It is difficult for the linear HSOH to convert to the branched H2SO and H2OS isomers due to the high activation energies (higher than ca. 200 and 160 kJ/mol, respectively). The predicted thermodynamic results also suggest that the linear structure is the most stable and may be the only species that can be found experimentally. The kinetic results demonstrate that the isomerization is a unimolecular one, and the reaction rate is slow.展开更多
The mechanism and dynamical properties for the reaction of NCS and OH radicals have been investigated theoretically. The minimum energy paths (MEP) of the reaction were calculated using the density functional theory (...The mechanism and dynamical properties for the reaction of NCS and OH radicals have been investigated theoretically. The minimum energy paths (MEP) of the reaction were calculated using the density functional theory (DFT) at the B3LYP/6-311+G** level, and the energies along the MEP were further refined at the QCISD(T)/6-311+G** level. As a result, the reaction mechanism of the title reaction involves three channels, producing HCS+NO and HNC+SO products, respectively. Path I and path II are competitive, with some advantages for path I in kinet-ics. As for path III, it looks difficult to react for its high energy barrier. Moreover, the rate constant have been cal-culated over the temperature range of 8002500 K using canonical variational transition-state theory (CVT). It was found that the rate constants for both path I and path II are negatively dependent on temperature, which is similar with the experimental results for reactions of NCS with NO and NO2, and the variational effect for the rate constant calculation plays an important role in whole temperature range.展开更多
Theoretical investigations have been carried out on the mechanism and kinetics for the reaction of CF 3 CHO + Cl using duallevel direct dynamics method. The potential energy surface information was obtained at the MCQ...Theoretical investigations have been carried out on the mechanism and kinetics for the reaction of CF 3 CHO + Cl using duallevel direct dynamics method. The potential energy surface information was obtained at the MCQCISD/3//MP2/cc-pVDZ level and the kinetic calculations were done using variational transition state theory with interpolated single-point energy (VTST-ISPE) approach. The calculated results show that the reaction proceeds primarily via the H-abstraction channel, while the Cl-addition channel is unfavorable due to the higher barriers. The improved canonical variational transition-state theory (ICVT) with the small-curvature tunneling correction (SCT) was used to calculate the rate constants. The theoretical rate constants at room temperature are in general agreement with the experimental values. A three-parameter rate constant expression was fitted over a wide temperature range of 200-2000 K.展开更多
The folding dynamics of small single-domain proteins is a current focus ofsimulations and experiments. Many of these proteins are ‘two-state folders’, i.e. pro-teins that fold rather directly from the denatured stat...The folding dynamics of small single-domain proteins is a current focus ofsimulations and experiments. Many of these proteins are ‘two-state folders’, i.e. pro-teins that fold rather directly from the denatured state to the native state, without pop-ulating metastable intermediate states. A central question is how to characterize theinstable, partially folded conformations of two-state proteins, in particular the rate-limiting transition-state conformations between the denatured and the native state.These partially folded conformations are short-lived and cannot be observed directlyin experiments. However, experimental data from detailed mutational analyses of thefolding dynamics provide indirect access to transition states. The interpretation ofthese data, in particular the reconstruction of transition-state conformations, requiressimulation and modeling. The traditional interpretation of the mutational data aimsto reconstruct the degree of structure formation of individual residues in the transitionstate, while a novel interpretation aims at degrees of structure formation of cooperativesubstructures such as α-helices and β-hairpins. By splitting up mutation-induced freeenergies into secondary and tertiary structural components, the novel interpretationresolves some of the inconsistencies of the traditional interpretation.展开更多
文摘Transition-state shape selectivity plays a crucial role in catalytic systems where reactants and products exhibit comparable molecular dimensions,as it restricts the accessible configuration space of reaction intermediates.Herein,we designed a Cu@MFI catalyst by encapsulating Cu active sites within the well-defined micropores of MFI zeolite through a pore confinement strategy.This architecture preserves the zeolite framework integrity while maintaining unhindered internal mass transport,thereby enabling precise spatial control over transition-state configurations.Employing furfural hydrogenation as a probe reaction,the metal-zeolite synergy in Cu@MFI endowed the catalyst with exceptional activity(100%furfural conversion)and quantitative selectivity(100%furfuryl alcohol)at 70℃,sustained across a broad temperature window.Mechanistic studies reveal that the transition-state shape selectivity effectively prevented H2O interaction with the furan ring,offering valuable insights for other reaction systems seeking to exploit shape selectivity for specific transformations.
基金The project was supported by the Fujian Provincial Department of Education (JA03020)and the Provincial Administration of Science and Technology of Fujian (2001J018)
文摘Ab initio Hartree-Fock theory at the aug-cc-pvtz level is used to investigate the equilibrium structures and isomerization of HSOF system. All of the transition states have been calculated and confirmed by the intrinsic reaction coordinate (IRC). Four equilibrium structures, HSOF, HOSF, SO(H)F and OS(H)F, are predicted in this paper. Though OSF2 has been observed experimentally, the present calculated results suggest that the linear form isomer, HOSF, is more stable than OS(H)F by 35.2 kJ/mol. The linear form HSOF and the branched SO(H)F isomer are more unstable and the computed relative energies are 318.3 and 510.0 kJ/mol, respectively with respect to HOSF isomer corrected with zero point vibrational energy.
基金The project was supported by Fujian Provincial Department of Education (JA03020) and the Provincial Administration of Science and Technology of Fujian (2002J018)
文摘MP2 and DFT/B3LYP calculations with Aug-cc-pvTz and Aug-cc-pvQz basis set levels are used to investigate the equilibrium structures and isomerization of H2SO isomers. All of the transition states have been calculated and confirmed by the intrinsic reaction coordinate (IRC). The calculated results show that H2SO isomers have three equilibrium structures and the linear structure is the most stable while the branched H2OS is the most unstable (the relative energies are 0.0, 82.1 and 155.3 kJ/mol for HSOH, H2SO and H2OS, respectively with the zero point vibrational energy correction at B3LYP/Aug-cc-pvQz level). It is difficult for the linear HSOH to convert to the branched H2SO and H2OS isomers due to the high activation energies (higher than ca. 200 and 160 kJ/mol, respectively). The predicted thermodynamic results also suggest that the linear structure is the most stable and may be the only species that can be found experimentally. The kinetic results demonstrate that the isomerization is a unimolecular one, and the reaction rate is slow.
基金Project supported by the Natural Science Foundation of Jilin Province (No. 20010344) the Foundation of Education Bureau of Hainan Province (No. hjkj200312) and the Science Foundation for Excellent Youth of Northeast Normal University (No. 111382).
文摘The mechanism and dynamical properties for the reaction of NCS and OH radicals have been investigated theoretically. The minimum energy paths (MEP) of the reaction were calculated using the density functional theory (DFT) at the B3LYP/6-311+G** level, and the energies along the MEP were further refined at the QCISD(T)/6-311+G** level. As a result, the reaction mechanism of the title reaction involves three channels, producing HCS+NO and HNC+SO products, respectively. Path I and path II are competitive, with some advantages for path I in kinet-ics. As for path III, it looks difficult to react for its high energy barrier. Moreover, the rate constant have been cal-culated over the temperature range of 8002500 K using canonical variational transition-state theory (CVT). It was found that the rate constants for both path I and path II are negatively dependent on temperature, which is similar with the experimental results for reactions of NCS with NO and NO2, and the variational effect for the rate constant calculation plays an important role in whole temperature range.
基金supported by the National Natural Science Foundation of China (20973077, 20303007)the Program for New Century Excellent Talents in University (NCET)
文摘Theoretical investigations have been carried out on the mechanism and kinetics for the reaction of CF 3 CHO + Cl using duallevel direct dynamics method. The potential energy surface information was obtained at the MCQCISD/3//MP2/cc-pVDZ level and the kinetic calculations were done using variational transition state theory with interpolated single-point energy (VTST-ISPE) approach. The calculated results show that the reaction proceeds primarily via the H-abstraction channel, while the Cl-addition channel is unfavorable due to the higher barriers. The improved canonical variational transition-state theory (ICVT) with the small-curvature tunneling correction (SCT) was used to calculate the rate constants. The theoretical rate constants at room temperature are in general agreement with the experimental values. A three-parameter rate constant expression was fitted over a wide temperature range of 200-2000 K.
文摘The folding dynamics of small single-domain proteins is a current focus ofsimulations and experiments. Many of these proteins are ‘two-state folders’, i.e. pro-teins that fold rather directly from the denatured state to the native state, without pop-ulating metastable intermediate states. A central question is how to characterize theinstable, partially folded conformations of two-state proteins, in particular the rate-limiting transition-state conformations between the denatured and the native state.These partially folded conformations are short-lived and cannot be observed directlyin experiments. However, experimental data from detailed mutational analyses of thefolding dynamics provide indirect access to transition states. The interpretation ofthese data, in particular the reconstruction of transition-state conformations, requiressimulation and modeling. The traditional interpretation of the mutational data aimsto reconstruct the degree of structure formation of individual residues in the transitionstate, while a novel interpretation aims at degrees of structure formation of cooperativesubstructures such as α-helices and β-hairpins. By splitting up mutation-induced freeenergies into secondary and tertiary structural components, the novel interpretationresolves some of the inconsistencies of the traditional interpretation.
