β-Cyclodextrin(β-CD)-containing acrylic monomers were synthesized by using dicyclohexylcarbodiimide(DCC)as catalyst.Synthesis and characterization of using different reaction conditions,and the different mole cular ...β-Cyclodextrin(β-CD)-containing acrylic monomers were synthesized by using dicyclohexylcarbodiimide(DCC)as catalyst.Synthesis and characterization of using different reaction conditions,and the different mole cular structure with different substitution degree of β-CD-containing acrylic monomers were synthesized.Two kinds of β-CD-containing acrylic monomers,β-CD-3-A and β-CD-6-A carrying the same vinyl,were prepared reying on their reactivity of different hydroxyl groups in β-CD.Nuclear magnetic resonance(13C NMR)data indicated that,for β-CD-3-A,acylation occurs at C-2 and C-3 position of β-CD,and for β-CD-6-A,the acylation occurs at its C-2 and C-6 position,respectively.Moreover,the mono-[6-(2-acryloylaminoethyl)amino]-6-β-CD was obtained using acrylic acid as a raw material under the DCC catalyst.Its structure was confirmed by elemental analysis,1H NMR and IR.展开更多
To obtain detailed information on the potential energy, the evolution of species, the initial reaction paths, and thermal decomposition products, we conducted simulations on pyrolysis process of CL20/BTF co-crystal us...To obtain detailed information on the potential energy, the evolution of species, the initial reaction paths, and thermal decomposition products, we conducted simulations on pyrolysis process of CL20/BTF co-crystal using the ReaxFF/lg reaction force field, with temperature set at 2000 K to 3000 K. With the analysis of evolution curves of potential energy based on exponential function, we obtain the overall characteristic time. Via a description of the total package reaction with classical Arrhenius law, we obtain the activation energy of CL20/BTF co-crystal： Ea=60.8 kcal/mol. Based on the initial path of CL20/BTF co-crystal thermal decomposition we studied, we conclude that N-NO2 bond of CL20 molecules breaks first, working as a dominant role in the initial stage of thermal decomposition under the condition of different temperatures, and that all CL20 molecules completely decompose before BTF molecular regardless of different temperatures. We also find that the main products of CL20/BTF co-crystal are NO2, NO, NO3, HNO, O2, N2, H2O, CO2, N2O, and HONO, etc., on which the temperature forms certain influence.展开更多
Water oxidation is one of the most important reactions in natural and artificial energy conversion schemes.In nature,solar energy is converted to chemical energy via water oxidation at the oxygen-evolving center of ph...Water oxidation is one of the most important reactions in natural and artificial energy conversion schemes.In nature,solar energy is converted to chemical energy via water oxidation at the oxygen-evolving center of photosystem II to generate dioxygen,protons,and electrons.In artificial energy schemes,water oxidation is one of the half reactions of water splitting,which is an appealing strategy for energy conversion via photocatalytic,electrocatalytic,or photoelectrocatalytic processes.Because it is thermodynamically unfavorable and kinetically slow,water oxidation is the bottleneck for achieving large-scale water splitting.Thus,developing highly efficient water oxidation catalysts has attracted the interests of researchers in the past decades.The formation of O-O bonds is typically the rate-determining step of the water oxidation catalytic cycle.Therefore,better understanding this key step is critical for the rational design of more efficient catalysts.This review focuses on elucidating the evolution of metal-oxygen species during transition metal-catalyzed water oxidation,and more importantly,on discussing the feasible O-O bond formation mechanisms during the oxygen evolution reaction over synthetic molecular catalysts.展开更多
Density functional theory calculations were carried out to study the thermal cracking for chrysene molecule to estimate the bond energies for breaking C 10b-C 11, C 11-H 11 and C4a-C 12a bonds as well as the activatio...Density functional theory calculations were carried out to study the thermal cracking for chrysene molecule to estimate the bond energies for breaking C 10b-C 11, C 11-H 11 and C4a-C 12a bonds as well as the activation energies. It was found that for C 10b-C 11 C11-HI 1 and C4a-C12a reactions, it is often possible to identify one pathway for bond breakage through the singlet or triplet states. Thus, the C 11-H11 and C11-C10b bonds ruptured in triplet state whilst the C12a-C4a in singlet state. Also, it was fond that the activation energy value for C4a-C12a bond breakage is lower than required for C10b-C11 and C11-H11 bonds that enquired the C4a-C12a bond ＂bridge bond＂ is a weaker and ruptured firstly in thermal cracking process. It seems that the characteristic planarity for polyaromatic hydrocarbons is an important factor to acquire the molecule structure the required stability along the reaction paths as well as the full octet rule and Clar＇s n-sextet structure, especially when chrysene molecular lose the property of planarity. The atomic charges supported the observation that the breaking bonds C10b-C11, CI1-H11 and C4a-C12a in triplet or singlet states. The configurations in transition state and the conformation for the end products reaction were explained and discussed.展开更多
A reaction coupling system of transesterification and methoxycarbonylation with methyl phenyl carbonate （MPC） as intermediate was established to efficiently prepare 1,6-hexamethylene diurethane （HDU） from 1,6- bex...A reaction coupling system of transesterification and methoxycarbonylation with methyl phenyl carbonate （MPC） as intermediate was established to efficiently prepare 1,6-hexamethylene diurethane （HDU） from 1,6- bexametbylene diamine （HDA）. The feasibility of the system was explored using the thermodynamics analysis, the reaction mechanism and the experiment results. The optimal reaction was carried out to get higher HDU yield. The thermodynamic analysis showed that the metboxycarbonylation of HDA with MPC, the Gibbs free energy of which was negative, was a spontaneous process. Furthermore, the equilibrium constant of the methoxycarbonylation of HDA with MPC was much greater than that of the transesterification of dimethyl carbonate （DMC） with phenol, so the reaction coupling could be realized under mild conditions. The reaction mechanism analysis indicated that phenoxy anion was the key spedes for reaction coupling. Higher MPC concentration was detected when sodium phenoxide was used as transesterification reactant with DMC, since the phenoxy anion of sodium phenoxide could be dissociated more easily. Sodium pbenoxide was more suitable to prepare HHDU through reaction coupling. A yield of HDU as high as 98.3% could be reached under the optimal conditions of mPhONa/mDMC = 0.027 and nDMC/nHDa = 8/1 at 90 ℃ in 2 h.展开更多
Intramolecular ortho-C-H activation and C-N/C-O cyclizations of phenyl amidines and amides have recently been achieved under Cu catalysis. These reactions provide important examples of Cu-catalyzed functionalization o...Intramolecular ortho-C-H activation and C-N/C-O cyclizations of phenyl amidines and amides have recently been achieved under Cu catalysis. These reactions provide important examples of Cu-catalyzed functionalization of inert C-H bonds, but their mechanisms remain poorly understood. In the present study the several possible mechanisms including electrophilic aro- matic substitution, concerted metalation-deprotonation （CMD）, Friedel-Crafts mechanism, radical mechanism, and proton- coupled electron transfer have been theoretically examined. Cu（II）-assisted CMD mechanism is found to be the most feasible for both C-O and C-N cyclizations. This mechanism includes three steps, i.e. CMD with Cu（II）, oxidation of the Cu（II） inter- mediate, and reductive elimination from Cu（III）. Our calculations show that Cu（II） mediates the C-H activation through an six-membered ring CMD transition state similar to that proposed for many Pd-catalyzed C-H activation reactions. It is also in- teresting to find that the rate-limiting steps are different for C-N and C-O cyclizations： for the former it is concerted metalation-deprotonation with Cu（II）, whereas for the latter it is reductive elimination from Cu（III）. The above conclusions are consistent with the experimental kinetic isotope effects （1.0 and 2.1 for C-O and C-N cyclizations, respectively）, substituent effects, and the reactions under O2-free conditions.展开更多
文摘β-Cyclodextrin(β-CD)-containing acrylic monomers were synthesized by using dicyclohexylcarbodiimide(DCC)as catalyst.Synthesis and characterization of using different reaction conditions,and the different mole cular structure with different substitution degree of β-CD-containing acrylic monomers were synthesized.Two kinds of β-CD-containing acrylic monomers,β-CD-3-A and β-CD-6-A carrying the same vinyl,were prepared reying on their reactivity of different hydroxyl groups in β-CD.Nuclear magnetic resonance(13C NMR)data indicated that,for β-CD-3-A,acylation occurs at C-2 and C-3 position of β-CD,and for β-CD-6-A,the acylation occurs at its C-2 and C-6 position,respectively.Moreover,the mono-[6-(2-acryloylaminoethyl)amino]-6-β-CD was obtained using acrylic acid as a raw material under the DCC catalyst.Its structure was confirmed by elemental analysis,1H NMR and IR.
文摘To obtain detailed information on the potential energy, the evolution of species, the initial reaction paths, and thermal decomposition products, we conducted simulations on pyrolysis process of CL20/BTF co-crystal using the ReaxFF/lg reaction force field, with temperature set at 2000 K to 3000 K. With the analysis of evolution curves of potential energy based on exponential function, we obtain the overall characteristic time. Via a description of the total package reaction with classical Arrhenius law, we obtain the activation energy of CL20/BTF co-crystal： Ea=60.8 kcal/mol. Based on the initial path of CL20/BTF co-crystal thermal decomposition we studied, we conclude that N-NO2 bond of CL20 molecules breaks first, working as a dominant role in the initial stage of thermal decomposition under the condition of different temperatures, and that all CL20 molecules completely decompose before BTF molecular regardless of different temperatures. We also find that the main products of CL20/BTF co-crystal are NO2, NO, NO3, HNO, O2, N2, H2O, CO2, N2O, and HONO, etc., on which the temperature forms certain influence.
文摘Water oxidation is one of the most important reactions in natural and artificial energy conversion schemes.In nature,solar energy is converted to chemical energy via water oxidation at the oxygen-evolving center of photosystem II to generate dioxygen,protons,and electrons.In artificial energy schemes,water oxidation is one of the half reactions of water splitting,which is an appealing strategy for energy conversion via photocatalytic,electrocatalytic,or photoelectrocatalytic processes.Because it is thermodynamically unfavorable and kinetically slow,water oxidation is the bottleneck for achieving large-scale water splitting.Thus,developing highly efficient water oxidation catalysts has attracted the interests of researchers in the past decades.The formation of O-O bonds is typically the rate-determining step of the water oxidation catalytic cycle.Therefore,better understanding this key step is critical for the rational design of more efficient catalysts.This review focuses on elucidating the evolution of metal-oxygen species during transition metal-catalyzed water oxidation,and more importantly,on discussing the feasible O-O bond formation mechanisms during the oxygen evolution reaction over synthetic molecular catalysts.
文摘Density functional theory calculations were carried out to study the thermal cracking for chrysene molecule to estimate the bond energies for breaking C 10b-C 11, C 11-H 11 and C4a-C 12a bonds as well as the activation energies. It was found that for C 10b-C 11 C11-HI 1 and C4a-C12a reactions, it is often possible to identify one pathway for bond breakage through the singlet or triplet states. Thus, the C 11-H11 and C11-C10b bonds ruptured in triplet state whilst the C12a-C4a in singlet state. Also, it was fond that the activation energy value for C4a-C12a bond breakage is lower than required for C10b-C11 and C11-H11 bonds that enquired the C4a-C12a bond ＂bridge bond＂ is a weaker and ruptured firstly in thermal cracking process. It seems that the characteristic planarity for polyaromatic hydrocarbons is an important factor to acquire the molecule structure the required stability along the reaction paths as well as the full octet rule and Clar＇s n-sextet structure, especially when chrysene molecular lose the property of planarity. The atomic charges supported the observation that the breaking bonds C10b-C11, CI1-H11 and C4a-C12a in triplet or singlet states. The configurations in transition state and the conformation for the end products reaction were explained and discussed.
基金Supported by the National Natural Science Foundation of China(21276126,21306089)the Jiangsu Province Higher Education Natural Science Foundation(09KJA530004,13KJB530006)
文摘A reaction coupling system of transesterification and methoxycarbonylation with methyl phenyl carbonate （MPC） as intermediate was established to efficiently prepare 1,6-hexamethylene diurethane （HDU） from 1,6- bexametbylene diamine （HDA）. The feasibility of the system was explored using the thermodynamics analysis, the reaction mechanism and the experiment results. The optimal reaction was carried out to get higher HDU yield. The thermodynamic analysis showed that the metboxycarbonylation of HDA with MPC, the Gibbs free energy of which was negative, was a spontaneous process. Furthermore, the equilibrium constant of the methoxycarbonylation of HDA with MPC was much greater than that of the transesterification of dimethyl carbonate （DMC） with phenol, so the reaction coupling could be realized under mild conditions. The reaction mechanism analysis indicated that phenoxy anion was the key spedes for reaction coupling. Higher MPC concentration was detected when sodium phenoxide was used as transesterification reactant with DMC, since the phenoxy anion of sodium phenoxide could be dissociated more easily. Sodium pbenoxide was more suitable to prepare HHDU through reaction coupling. A yield of HDU as high as 98.3% could be reached under the optimal conditions of mPhONa/mDMC = 0.027 and nDMC/nHDa = 8/1 at 90 ℃ in 2 h.
基金the financial support from the National Basic Research Program of China (973 program, 2012CB215306)the National Natural Science Foundation of China (NSFC, 20832004, 20972148)CAS(KJCX2-EW-J02)
文摘Intramolecular ortho-C-H activation and C-N/C-O cyclizations of phenyl amidines and amides have recently been achieved under Cu catalysis. These reactions provide important examples of Cu-catalyzed functionalization of inert C-H bonds, but their mechanisms remain poorly understood. In the present study the several possible mechanisms including electrophilic aro- matic substitution, concerted metalation-deprotonation （CMD）, Friedel-Crafts mechanism, radical mechanism, and proton- coupled electron transfer have been theoretically examined. Cu（II）-assisted CMD mechanism is found to be the most feasible for both C-O and C-N cyclizations. This mechanism includes three steps, i.e. CMD with Cu（II）, oxidation of the Cu（II） inter- mediate, and reductive elimination from Cu（III）. Our calculations show that Cu（II） mediates the C-H activation through an six-membered ring CMD transition state similar to that proposed for many Pd-catalyzed C-H activation reactions. It is also in- teresting to find that the rate-limiting steps are different for C-N and C-O cyclizations： for the former it is concerted metalation-deprotonation with Cu（II）, whereas for the latter it is reductive elimination from Cu（III）. The above conclusions are consistent with the experimental kinetic isotope effects （1.0 and 2.1 for C-O and C-N cyclizations, respectively）, substituent effects, and the reactions under O2-free conditions.
