The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,...The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCl) was formed in situ in conjunction with titanium tetrachloride (TiCl(4)). The Lewis acidity of TiCl(4) was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)(4)) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.展开更多
This article is based on the experimental data on reaction of FCC naphtha in the presence of acid catalysts. The data published in the literature were reprocessed and compared with experimental data and the relationsh...This article is based on the experimental data on reaction of FCC naphtha in the presence of acid catalysts. The data published in the literature were reprocessed and compared with experimental data and the relationship of hydrogen and methane contained in the dry gas with the conversion rate was identified.The similarity between the route for cracking of olefin enriched FCC gasoline and the route for reaction of individual hydrocarbons was deduced, while the route for formation of ethylene in dry gas was also proposed to identify the relationship between the reaction path for formation of ethylene and the conversion rate.展开更多
In order to investigate the impact of U-ore on organic matter maturation and isotopic fractionation,we designed hydrous pyrolysis experiments on Type-II kerogen samples,supposing that the water and water–mineral inte...In order to investigate the impact of U-ore on organic matter maturation and isotopic fractionation,we designed hydrous pyrolysis experiments on Type-II kerogen samples,supposing that the water and water–mineral interaction play a role.U-ore was set as the variable for comparison.Meanwhile,anhydrous pyrolysis under the same conditions was carried out as the control experiments.The determination of liquid products indicates that the presence of water and minerals obviously enhanced the yields of C（15＋） and the amounts of hydrocarbon and nonhydrocarbon gases.Such results may be attributed to waterorganic matter reaction in the high-temperature system,which can provide additional hydrogen and oxygen for the generation of gas and liquid products from organic matter.It is found that δD values of hydrocarbon gases generated in both hydrous pyrolysis experiments are much lower than those in anhydrous pyrolysis.What is more,δD values are lower in the hydrous pyrolysis with uranium ore.Therefore,we can infer that water-derived hydrogen played a significant role during the kerogen thermal evolution and the hydrocarbon generation in our experiments.Isotopic exchange was facilitated by the reversible equilibration between reaction intermediaries with hydrogen under hydrothermal conditions with uranium ore.Carbon isotopic fractionations of hydrocarbon gases were somehow affected by the presence of water and the uranium ore.The increased level of i-C4/n-C4ratios for gas products in hydrous pyrolysis implied the carbocation mechanism for water-kerogen reactions.展开更多
Proanthocyanidins(PAs)are natural flavan-3-ol polymers that contribute protection to plants under biotic and abiotic stress,benefits to human health,and bitterness and astringency to food products.They are also potent...Proanthocyanidins(PAs)are natural flavan-3-ol polymers that contribute protection to plants under biotic and abiotic stress,benefits to human health,and bitterness and astringency to food products.They are also potential targets for carbon sequestration for climate mitigation.In recent years,from model species to commercial crops,research has moved closer to elucidating the flux control and channeling,subunit biosynthesis and polymerization,transport mechanisms,and regulatory networks involved in plant PA metabolism.This review extends the conventional understanding with recent findings that provide new insights to address lingering questions and focus strategies for manipulating PA traits in plants.展开更多
What is the most favorite and original chemistry developed in your researchgroup?I hope it's always the next one.How do you get into this specific field?Could you please share some experiences with ourreaders?Natu...What is the most favorite and original chemistry developed in your researchgroup?I hope it's always the next one.How do you get into this specific field?Could you please share some experiences with ourreaders?Nature provides many astonishing catalytic machineries for building up molecular complexity and harnessing energy in the most efficient ways.Nature's recipe for catalysis serves as a starting point to develop new catalyst for synthetic and energy chemistry.展开更多
Carbocations such as tropylium and trityl cation, can be stable enough to be isolated and used without inert conditions. They can act as Lewis acids to lower the LUMO of electrophile, thus promoting reactions with nuc...Carbocations such as tropylium and trityl cation, can be stable enough to be isolated and used without inert conditions. They can act as Lewis acids to lower the LUMO of electrophile, thus promoting reactions with nucleophiles. Additionally, the interaction between carbocations and alcohols can form Bronsted acids with enhanced acidity. Furthermore, electrophoto activation of TAC^(+)(trisaminocyclopropenium ion)delivers the excited radical dication TAC·^(2+*), which is a strong oxidant and capable of oxidizing a range of challenging substrates. Moreover,^(n)Pr-DMQA^(+) is disclosed as a versatile photoredox catalyst as its excited state can be quenched through both oxidation and reduction. This review summarizes recent advance in carbocation-catalyzed reactions. These developed methods provide an environmentally friendly pathway for the synthesis of valuable compounds and will inspire chemists to discover more interesting transformations promoted by carbocations.展开更多
This work investigates the effect of reaction conditions on the copolymerization of isobutylene (IB) with alloocimene (Allo) in methyl chloride (MeCl) using AlCh and ethylaluminum dichloride (EtAlCh) as coinitiators a...This work investigates the effect of reaction conditions on the copolymerization of isobutylene (IB) with alloocimene (Allo) in methyl chloride (MeCl) using AlCh and ethylaluminum dichloride (EtAlCh) as coinitiators and adventitious moisture as the initiator. Both AlCh and EtAlCb produced high molecular weight (Mn > 1.0 x 10^5 g/mol) thermoplastic elastomers (TPEs) with good mechanical properties in short reaction time (< 10 min). These unique TPEs have unsaturations in the end blocks, leading to easy functionalization and/or crosslinking.展开更多
The low-activity cationic monomer tert-butyl-dimethyl-(4-methyl-pent-4-enyloxy)-silane was synthesized by Grignard reaction and hydroxyl-protection reaction. Living polyisobutylene chains were initially synthesized by...The low-activity cationic monomer tert-butyl-dimethyl-(4-methyl-pent-4-enyloxy)-silane was synthesized by Grignard reaction and hydroxyl-protection reaction. Living polyisobutylene chains were initially synthesized by controlled cationic polymerization and then capped with tert-butyl-dimethyl-(4-methyl-pent-4-enyloxy)-silane. The hydrolysis of these polyisobutylenes end capped with tert-butyl-dimethyl-(4-methyl-pent-4-enyloxy)-silane gave rise to hydroxytelechelic polyisobutylene. NMR analysis confirmed that the hydrolysis was complete. Results also showed that a low polymerization temperature favored the participation of tert-butyl-dimethyl-(4- methyl-pent-4?enyloxy)-silane in the end-capping reaction. Moreover, polyisobutylene-based polyurethane exhibited greater acid resistance than commercial polyurethane.展开更多
The hydrous thermo-simulation experiments on oil shale sample from Liushuhe basin have been performed using autoclave.The mechanism and kinetics of oil shale pyrolysis were investigated.The formation mechanism of pyro...The hydrous thermo-simulation experiments on oil shale sample from Liushuhe basin have been performed using autoclave.The mechanism and kinetics of oil shale pyrolysis were investigated.The formation mechanism of pyrolysates including retorting gas,oil and bitumen,were evaluated in the presence of saturated and unsaturated water,respectively.The results show that the physicochemical properties of water have greatly changed in high temperature and pressure.At the same time,water has three kinds of effect on the oil shale pyrolysis,including the protection of free radical,catalytic action and swelling.The pyrolysis temperature was carried out about 70C earlier,and the generated processing of hydrocarbon would be easier under the aqueous.The consecutive first order reaction model involving bitumen as an intermediate product was used in the data analysis in order to determine the pyrolysis kinetic parameters.It was found that the apparent activation energy of kerogen pyrolysis was lower than bitumen pyrolysis.展开更多
The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mech-anism triggered strategy is developed by using AI(OTf)_(3) as a hidden Br0nsted a...The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mech-anism triggered strategy is developed by using AI(OTf)_(3) as a hidden Br0nsted acid catalyst,which provides facile access to value-added acyclic tri-and tetra-substituted alkenes in good yields with high stereoselectivity under mild conditions.展开更多
Terpenoids comprise the largest family of natural products and include various structurally different genus which play important roles in living organisms. Biosynthetically, diterpenoids are derived from （E,E,E）-ger...Terpenoids comprise the largest family of natural products and include various structurally different genus which play important roles in living organisms. Biosynthetically, diterpenoids are derived from （E,E,E）-geranylgeranyl diphosphate （GGPP）. From GGPP, diterpene cyclase catalyzes a sequence of carbocation- mediated cyclizations, rearrangements, and further oxidations, leading to a class of structurally unique ent-kaurenes, such as cafestol, gibberellin A3 and oridonin. According to the biosynthesis pathway of ent-kaurene, we designed a chiral acetal-enabled and SnCln-promoted biomimetic polyene cationic cyclization. With a following Birch reduc- tiort/alkylation cascade, a core skeleton of representative ent-kaurenes diterpenoids was completed.展开更多
The orbital deletion procedure is introduced, which is suited to quantitatively investigating the electronic delocalization effect in carbocations and boranes. While the routineab initio molecular orbital methods can ...The orbital deletion procedure is introduced, which is suited to quantitatively investigating the electronic delocalization effect in carbocations and boranes. While the routineab initio molecular orbital methods can generate wavefunctions for real systems where all electrons are delocalized, the present orbital deletion procedure can generate wavefunctions for hypothetical reference molecules where electronic delocalization effect is deactivated. The latter wave-function normally corresponds to the most stable resonance structure in terms of the resonance theory. By comparing and analyzing the delocalized and the localized wavefunctions, one can obtain a quantitative and instinct picture to show how electronic delocalization inside a molecule affects the molecular structure, energy as well as other physical properties. Two examples are detailedly discussed. The first is related to the hyperconjugation of alkyl groups in carbocations and a comparison of the order of stability of carbocations is made. The second concerns the Lewis acidity of boron trihalides where the conjugation effect among the doubly-occupied π atomic orbitals on the halide atoms and the vacant π atomic rbital on the boron atom plays a dominant role in determining the relative acceptor properties. The results demonstrate that the orbital deletion procedure can be used to very successfully interpret some traditional chemical intuitions and concepts in a quantitative way.展开更多
Octanes in alkylation products obtained from industrial alkylation were studied by batch experiments.More than eight octane isomers were identified and quantified by gas chromatography-mass spectrometry.Based on a cla...Octanes in alkylation products obtained from industrial alkylation were studied by batch experiments.More than eight octane isomers were identified and quantified by gas chromatography-mass spectrometry.Based on a classic carbenium ion mechanism,the carbocation transition states in concentrated sulfuric acid catalyzed alkylation were investigated using quantum-chemical simulations and predicted the concentration and octane isomerization products including trimethylpentane and dimethylhexane as well as the formation of heavier compounds that resulted from the oligomerization of octane and butene.The agreement between model calculations and experimental data was quite satisfactory.Calculation results indicated that composition and content of trimethylpentanes in the alkylation products were 2,2,4-trimethylpentane>2,3,3-trimethylpentane>2,3,4-trimethylpentane>2,2,3-trimethylpentane whether the 2-butene or i-butene acts as olefin.Heavier compounds in the alkylate were primarily formed by the oligomerization of dimethylhexane with 1-butene.Hopefully,the carbocation transition state models developed in this work will be useful for understanding the product distributions of octane in alkylation products.展开更多
Since the discovery of the triphenylmethyl(trityl)cation 120 years ago,a variety of aromatic cations having various colors and luminescence properties have been rigorously studied.Many,differently substituted trityl c...Since the discovery of the triphenylmethyl(trityl)cation 120 years ago,a variety of aromatic cations having various colors and luminescence properties have been rigorously studied.Many,differently substituted trityl cations have been synthesized,and their optical properties have been elucidated.However,the optical properties of the parent,non-substituted and highly reactive trityl cation,which was observed to be very weakly luminescent,have not been subjected to detailed investigation.In the effort described herein,we explored the optical nature of non-substituted trityl hexafluorophosphate(PF_(6))in the crystalline state.Trityl PF_(6) was found to exist as two crystal polymorphs including a yellow(Y)and an orange(O)form.Moreover,we observed that these crystalline forms display crystalline-state emission with different colors.The results of X-ray crystallographic analysis showed that the two polymorphs have totally different molecular packing arrangements.Furthermore,an investigation of their optical properties revealed that the O-crystal undergoes a distinct color change to yellow upon cooling as a consequence of a change in the nature of the charge transfer interaction between the cation and PF6 anion,and that both the Y-and O-crystal exhibit phosphorescence.展开更多
Fungal bifunctional terpene synthases(BFTSs)catalyze the formation of numerous di-/sester-/tri-terpenes skeletons.However,the mechanism in controlling the cyclization pattern of terpene scaffolds is rarely deciphered ...Fungal bifunctional terpene synthases(BFTSs)catalyze the formation of numerous di-/sester-/tri-terpenes skeletons.However,the mechanism in controlling the cyclization pattern of terpene scaffolds is rarely deciphered for further application of tuning the catalytic promiscuity of terpene synthases for expanding the chemical space.In this study,we expanded the catalytic promiscuity of Fusarium oxysporum fusoxypene synthase(FoFS)by a single mutation at L89,leading to the production of three new sesterterpenes.Further computational analysis revealed that the reconstitution of the hydrogen-bond(H-bond)network of second-shell residues around the active site of FoFS influences the orientation of the aromatic residue W69 within the first-shell catalytic pocket.Thus,the dynamic orientation of W69 alters the carbocation transport,leading to the production of diverse ring system skeletons.These findings enhance our knowledge on understanding the molecular mechanisms,which could be applied on protein engineering terpene synthases on regulating the terpene skeletons.展开更多
基金supported by the Beijing Municipal Project for Developing Advanced Human Resources for Higher Education(Elastomers and Biomaterials).
文摘The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) (50/50 V/V) solvent mixture at -80 degrees C. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCl) was formed in situ in conjunction with titanium tetrachloride (TiCl(4)). The Lewis acidity of TiCl(4) was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)(4)) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.
文摘This article is based on the experimental data on reaction of FCC naphtha in the presence of acid catalysts. The data published in the literature were reprocessed and compared with experimental data and the relationship of hydrogen and methane contained in the dry gas with the conversion rate was identified.The similarity between the route for cracking of olefin enriched FCC gasoline and the route for reaction of individual hydrocarbons was deduced, while the route for formation of ethylene in dry gas was also proposed to identify the relationship between the reaction path for formation of ethylene and the conversion rate.
文摘In order to investigate the impact of U-ore on organic matter maturation and isotopic fractionation,we designed hydrous pyrolysis experiments on Type-II kerogen samples,supposing that the water and water–mineral interaction play a role.U-ore was set as the variable for comparison.Meanwhile,anhydrous pyrolysis under the same conditions was carried out as the control experiments.The determination of liquid products indicates that the presence of water and minerals obviously enhanced the yields of C（15＋） and the amounts of hydrocarbon and nonhydrocarbon gases.Such results may be attributed to waterorganic matter reaction in the high-temperature system,which can provide additional hydrogen and oxygen for the generation of gas and liquid products from organic matter.It is found that δD values of hydrocarbon gases generated in both hydrous pyrolysis experiments are much lower than those in anhydrous pyrolysis.What is more,δD values are lower in the hydrous pyrolysis with uranium ore.Therefore,we can infer that water-derived hydrogen played a significant role during the kerogen thermal evolution and the hydrocarbon generation in our experiments.Isotopic exchange was facilitated by the reversible equilibration between reaction intermediaries with hydrogen under hydrothermal conditions with uranium ore.Carbon isotopic fractionations of hydrocarbon gases were somehow affected by the presence of water and the uranium ore.The increased level of i-C4/n-C4ratios for gas products in hydrous pyrolysis implied the carbocation mechanism for water-kerogen reactions.
基金supported by the Program of Introducing Talents of Discipline to Universities(111 Project,B13007)the National Natural Science Foundation of China(32030010)the China Postdoctoral Science Foundation(2020M680404 to K.Y.).
文摘Proanthocyanidins(PAs)are natural flavan-3-ol polymers that contribute protection to plants under biotic and abiotic stress,benefits to human health,and bitterness and astringency to food products.They are also potential targets for carbon sequestration for climate mitigation.In recent years,from model species to commercial crops,research has moved closer to elucidating the flux control and channeling,subunit biosynthesis and polymerization,transport mechanisms,and regulatory networks involved in plant PA metabolism.This review extends the conventional understanding with recent findings that provide new insights to address lingering questions and focus strategies for manipulating PA traits in plants.
基金references,for their significant contributions to this project and the Natural Science Foundation of China(21861132003,91956000 and 22031006)Tsinghua University Initiative Scientific Research Program for financial support.
文摘What is the most favorite and original chemistry developed in your researchgroup?I hope it's always the next one.How do you get into this specific field?Could you please share some experiences with ourreaders?Nature provides many astonishing catalytic machineries for building up molecular complexity and harnessing energy in the most efficient ways.Nature's recipe for catalysis serves as a starting point to develop new catalyst for synthetic and energy chemistry.
基金Financial support from National Natural Science Foundation of China (No. 21871053)the Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang (No. 2019R01005)the Open Research Fund of School of Chemistry and Chemical Engineering, Henan Normal University (No. 2020ZD04) is gratefully acknowledged。
文摘Carbocations such as tropylium and trityl cation, can be stable enough to be isolated and used without inert conditions. They can act as Lewis acids to lower the LUMO of electrophile, thus promoting reactions with nucleophiles. Additionally, the interaction between carbocations and alcohols can form Bronsted acids with enhanced acidity. Furthermore, electrophoto activation of TAC^(+)(trisaminocyclopropenium ion)delivers the excited radical dication TAC·^(2+*), which is a strong oxidant and capable of oxidizing a range of challenging substrates. Moreover,^(n)Pr-DMQA^(+) is disclosed as a versatile photoredox catalyst as its excited state can be quenched through both oxidation and reduction. This review summarizes recent advance in carbocation-catalyzed reactions. These developed methods provide an environmentally friendly pathway for the synthesis of valuable compounds and will inspire chemists to discover more interesting transformations promoted by carbocations.
基金financially supported by the National Science Foundation (No. IIP-1434014) (Accelerating Innovation Research)Support by the Breast Cancer Innovation Foundation was also acknowledged
文摘This work investigates the effect of reaction conditions on the copolymerization of isobutylene (IB) with alloocimene (Allo) in methyl chloride (MeCl) using AlCh and ethylaluminum dichloride (EtAlCh) as coinitiators and adventitious moisture as the initiator. Both AlCh and EtAlCb produced high molecular weight (Mn > 1.0 x 10^5 g/mol) thermoplastic elastomers (TPEs) with good mechanical properties in short reaction time (< 10 min). These unique TPEs have unsaturations in the end blocks, leading to easy functionalization and/or crosslinking.
基金financially supported by the National Natural Science Foundation of China (No. 51573020)Beijing Natural Science Foundation (No. 2172022)+2 种基金Scientific Research Project of Beijing Educational Committee (No. KM201810017008)Project of Petrochina (No. kywx-18-002)URT program (No. 2018J00074)
文摘The low-activity cationic monomer tert-butyl-dimethyl-(4-methyl-pent-4-enyloxy)-silane was synthesized by Grignard reaction and hydroxyl-protection reaction. Living polyisobutylene chains were initially synthesized by controlled cationic polymerization and then capped with tert-butyl-dimethyl-(4-methyl-pent-4-enyloxy)-silane. The hydrolysis of these polyisobutylenes end capped with tert-butyl-dimethyl-(4-methyl-pent-4-enyloxy)-silane gave rise to hydroxytelechelic polyisobutylene. NMR analysis confirmed that the hydrolysis was complete. Results also showed that a low polymerization temperature favored the participation of tert-butyl-dimethyl-(4- methyl-pent-4?enyloxy)-silane in the end-capping reaction. Moreover, polyisobutylene-based polyurethane exhibited greater acid resistance than commercial polyurethane.
基金We thank the following foundation for the financial support:the National Basic Research Program of China(973 programs,No.2014CB744302)Taishan Scholar Constructive Engineering Foun-dation of Shandong province,China(No.ts20120518).
文摘The hydrous thermo-simulation experiments on oil shale sample from Liushuhe basin have been performed using autoclave.The mechanism and kinetics of oil shale pyrolysis were investigated.The formation mechanism of pyrolysates including retorting gas,oil and bitumen,were evaluated in the presence of saturated and unsaturated water,respectively.The results show that the physicochemical properties of water have greatly changed in high temperature and pressure.At the same time,water has three kinds of effect on the oil shale pyrolysis,including the protection of free radical,catalytic action and swelling.The pyrolysis temperature was carried out about 70C earlier,and the generated processing of hydrocarbon would be easier under the aqueous.The consecutive first order reaction model involving bitumen as an intermediate product was used in the data analysis in order to determine the pyrolysis kinetic parameters.It was found that the apparent activation energy of kerogen pyrolysis was lower than bitumen pyrolysis.
基金We gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.21901074)"Zijiang Scholar Program"of East China Normal University。
文摘The first transition metal-free highly stereoselective positional isomerization of various α-alkyl styrenes through a carbocation mech-anism triggered strategy is developed by using AI(OTf)_(3) as a hidden Br0nsted acid catalyst,which provides facile access to value-added acyclic tri-and tetra-substituted alkenes in good yields with high stereoselectivity under mild conditions.
文摘Terpenoids comprise the largest family of natural products and include various structurally different genus which play important roles in living organisms. Biosynthetically, diterpenoids are derived from （E,E,E）-geranylgeranyl diphosphate （GGPP）. From GGPP, diterpene cyclase catalyzes a sequence of carbocation- mediated cyclizations, rearrangements, and further oxidations, leading to a class of structurally unique ent-kaurenes, such as cafestol, gibberellin A3 and oridonin. According to the biosynthesis pathway of ent-kaurene, we designed a chiral acetal-enabled and SnCln-promoted biomimetic polyene cationic cyclization. With a following Birch reduc- tiort/alkylation cascade, a core skeleton of representative ent-kaurenes diterpenoids was completed.
基金Project supported by the National Natural Science Foundation of China (Grant No. 29892166)the Provincial Natural Science Foundation of Fujian (Grant No. B9810003)the State Key Laboratory for Physical Chemistry on Solid Surface at Xiamen Universit
文摘The orbital deletion procedure is introduced, which is suited to quantitatively investigating the electronic delocalization effect in carbocations and boranes. While the routineab initio molecular orbital methods can generate wavefunctions for real systems where all electrons are delocalized, the present orbital deletion procedure can generate wavefunctions for hypothetical reference molecules where electronic delocalization effect is deactivated. The latter wave-function normally corresponds to the most stable resonance structure in terms of the resonance theory. By comparing and analyzing the delocalized and the localized wavefunctions, one can obtain a quantitative and instinct picture to show how electronic delocalization inside a molecule affects the molecular structure, energy as well as other physical properties. Two examples are detailedly discussed. The first is related to the hyperconjugation of alkyl groups in carbocations and a comparison of the order of stability of carbocations is made. The second concerns the Lewis acidity of boron trihalides where the conjugation effect among the doubly-occupied π atomic orbitals on the halide atoms and the vacant π atomic rbital on the boron atom plays a dominant role in determining the relative acceptor properties. The results demonstrate that the orbital deletion procedure can be used to very successfully interpret some traditional chemical intuitions and concepts in a quantitative way.
基金International(regional)cooperation and exchange program(Grant No.21961160740)the open foundation of State Key Laboratory of Chemical Engineering(Grant No.SKL-ChE-19B02)the North University of China Graduate Science and Technology Project(Grant Nos.20191621,20191626).
文摘Octanes in alkylation products obtained from industrial alkylation were studied by batch experiments.More than eight octane isomers were identified and quantified by gas chromatography-mass spectrometry.Based on a classic carbenium ion mechanism,the carbocation transition states in concentrated sulfuric acid catalyzed alkylation were investigated using quantum-chemical simulations and predicted the concentration and octane isomerization products including trimethylpentane and dimethylhexane as well as the formation of heavier compounds that resulted from the oligomerization of octane and butene.The agreement between model calculations and experimental data was quite satisfactory.Calculation results indicated that composition and content of trimethylpentanes in the alkylation products were 2,2,4-trimethylpentane>2,3,3-trimethylpentane>2,3,4-trimethylpentane>2,2,3-trimethylpentane whether the 2-butene or i-butene acts as olefin.Heavier compounds in the alkylate were primarily formed by the oligomerization of dimethylhexane with 1-butene.Hopefully,the carbocation transition state models developed in this work will be useful for understanding the product distributions of octane in alkylation products.
基金JSPSKAKENHI Grant-in-Aid for Scientific Research(C),Grant/Award Number:JP20K05475(Tomohiko Nishiuchi)Scientific Research(B),Grant/Award Number:JP21H01887(Kenji Kamada)。
文摘Since the discovery of the triphenylmethyl(trityl)cation 120 years ago,a variety of aromatic cations having various colors and luminescence properties have been rigorously studied.Many,differently substituted trityl cations have been synthesized,and their optical properties have been elucidated.However,the optical properties of the parent,non-substituted and highly reactive trityl cation,which was observed to be very weakly luminescent,have not been subjected to detailed investigation.In the effort described herein,we explored the optical nature of non-substituted trityl hexafluorophosphate(PF_(6))in the crystalline state.Trityl PF_(6) was found to exist as two crystal polymorphs including a yellow(Y)and an orange(O)form.Moreover,we observed that these crystalline forms display crystalline-state emission with different colors.The results of X-ray crystallographic analysis showed that the two polymorphs have totally different molecular packing arrangements.Furthermore,an investigation of their optical properties revealed that the O-crystal undergoes a distinct color change to yellow upon cooling as a consequence of a change in the nature of the charge transfer interaction between the cation and PF6 anion,and that both the Y-and O-crystal exhibit phosphorescence.
基金We gratefully acknowledge the financial support from the National Key Research and Development Program of China(2019YFA0906201,2020YFA090032,2022YFC2105400)the National Natural Science Foundation of China(22307037,21907031,81903529,21977029,31720103901,21877124)the Open Project Funding of the State Key Laboratory of Bioreactor Engineering,the 111 Project(B18022).
文摘Fungal bifunctional terpene synthases(BFTSs)catalyze the formation of numerous di-/sester-/tri-terpenes skeletons.However,the mechanism in controlling the cyclization pattern of terpene scaffolds is rarely deciphered for further application of tuning the catalytic promiscuity of terpene synthases for expanding the chemical space.In this study,we expanded the catalytic promiscuity of Fusarium oxysporum fusoxypene synthase(FoFS)by a single mutation at L89,leading to the production of three new sesterterpenes.Further computational analysis revealed that the reconstitution of the hydrogen-bond(H-bond)network of second-shell residues around the active site of FoFS influences the orientation of the aromatic residue W69 within the first-shell catalytic pocket.Thus,the dynamic orientation of W69 alters the carbocation transport,leading to the production of diverse ring system skeletons.These findings enhance our knowledge on understanding the molecular mechanisms,which could be applied on protein engineering terpene synthases on regulating the terpene skeletons.
