The insertion of elemental selenium into the Csp(2)-Zr bond of alkenylchloro-zirconocenes affords (E)-vinylseleno zirconocenes, which were trapped by alkyl halides giving (E)-vinylic selenides in moderate to good yields.
Transition-metal-catalyzed C–H bond activation represents one of the most attractive research areas in organic synthesis.In contrast to the great developments made in directed C–H bond functionalization of arenes,th...Transition-metal-catalyzed C–H bond activation represents one of the most attractive research areas in organic synthesis.In contrast to the great developments made in directed C–H bond functionalization of arenes,the directing group-assisted activation of non-aromatic vinylic C–H bonds still remains challenging.During the recent years,significant progress has been made in this fascinating field with various functionalized alkenes,heterocycles and carbocycles being obtained.This article will focus on the recent achievements in the field of directing-group-assisted vinylic C–H bond functionalization.展开更多
This letter describes a method for the stereoselective synthesis of polymer supported vinylic selenides and their applications to synthesis of ( E ) and ( Z ) 1,2 disubstituted ethenes on solid phase by the ...This letter describes a method for the stereoselective synthesis of polymer supported vinylic selenides and their applications to synthesis of ( E ) and ( Z ) 1,2 disubstituted ethenes on solid phase by the coupling reaction with Grignard reagents under the catalysis of NiCl 2(PPh 3) 2.展开更多
Chain-growth radical polymerization of vinyl monomers is essential for producing a wide range of materials with properties tailored to specific applications.However,the inherent resistance of the polymer's C―C ba...Chain-growth radical polymerization of vinyl monomers is essential for producing a wide range of materials with properties tailored to specific applications.However,the inherent resistance of the polymer's C―C backbone to degradation raises significant concerns regarding long-term environmental persistence,which also limits their potential in biomedical applications.To address these challenges,researchers have developed strategies to either degrade preexisting vinyl polymers or incorporate cleavable units into the backbone to modify them with enhanced degradability.This review explores the various approaches aimed at achieving backbone degradability in chain-growth radical polymerization of vinyl monomers,while also highlighting future research directions for the development of application-driven degradable vinyl polymers.展开更多
Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in...Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in specialized fields.In this study,phytic acid(PA)was introduced as a halogen-free flame retardant and biochar(BC)was introduced as a reinforcement to achieve both flame resistance and mechanical robustness.We thoroughly investigated the effects of BC particle sizes(100-3000 mesh)and addition amounts(0 wt%-10 wt%),as well as PA addition amounts(0 wt%-15 wt%),on the properties of PVA composite films.Notably,the PA10/1000BC5 composite containing 10 wt%PA and 5 wt%1000 mesh BC exhibited optimal properties.The limiting oxygen index increased to 39.2%,and the UL-94 test achieved a V-0 rating.Additionally,the PA10/1000BC5 composite film demonstrated significantly enhanced water resistance,with a swelling ratio reaching 800%without dissolving,unlike that of the control PVA.The water contact angle was 70°,indicating that hydrophilic properties remained essentially unaffected.Most importantly,the tensile modulus and elongation at break were 213 MPa and 281.7%,respectively,nearly double those of the PVA/PA composite film.This study presents an efficient and straightforward method for preparing PVA composite films that are flame-retardant,tough,and waterresistant,expanding their potential applications in various fields.展开更多
Different reactive flame retardants have been extensively developed for vinyl ester resins(VERs),but very few of them can yield a flame-retardant resin that meets defined standards(e.g.UL-94 V-0 rating).In this work,p...Different reactive flame retardants have been extensively developed for vinyl ester resins(VERs),but very few of them can yield a flame-retardant resin that meets defined standards(e.g.UL-94 V-0 rating).In this work,phosphorous-containing 1-vinylimidazole salts(called VIDHP and VIDPP)were synthesized through the facile neutralization of the acid and 1-vinylimidazole.VIDHP and VIDPP were then applied as flame-retardant crosslinking agents of VERs,by which phosphorus-containing groups could be incorporated into the resin chain via ionic bonds.VIDHP/VER and VIDPP/VER showed a high curing activity and can be well cured in moderate temperatures.With 20 wt.%additions of VIDHP and VIDPP,VIDHP20/VER,and VIDPP20/VER presented a limiting oxygen index value of 29.7%and 28.4%,respectively,with the latter achieving a UL 94 V0 rating.In the cone calorimetric test,compared to the unmodified VERs,VIDPP20/VER exhibited large reductions in the peak heat release rate,total heat release rate,and total smoke release rate while VIDHP20/VER demonstrated comparatively inferior performance in terms of the heat release.VIDHP20/VER and VIDPP20/VER showed good thermal stability and presented a little lower glass transition temperature than the control sample.VIDPP with a low phosphorus oxidation state(+1)demonstrated high flame-retardant activities in the gaseous phase,whereas VIDHP with a high phosphorus oxidation state(+5)primarily exhibited efficacy in the condensed phase.展开更多
The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable che...The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable chemical production.In this study,we present NaVO_(3)as a surface-confined coupling center for·CH_(2)Cl radicals,demonstrating its superior performance in the selective coupling of methyl chloride to synthesize vinyl chloride.By incorporating NaVO_(3)onto the surface of CeO_(2),the catalyst enables effective capture of·CH_(2)Cl radicals during the CH_(3)Cl oxidative pyrolysis and their subsequent conversion into C_(2)H_(3)Cl.We experimentally validate the capability of highly dispersed Na-VO_(3)to controllably couple·CH_(2)Cl radicals through in-situ synchrotron-based vacuum ultraviolet photoionization mass spectrometry.The results demonstrate that the dispersion of NaVO_(3)on the catalyst surface has a considerable impact on the reaction efficiency of·CH_(2)Cl radicals and the overall MCTV performance.This discovery holds substantial implications for the controlled C_(1)radical transformation and provides a guidance for the design of catalysts for sustainable production of C_(2)H_(3)Cl.展开更多
The deformation mechanism of glycerol plasticized poly(vinyl alcohol)(PVA)with different hydrolyses(88%,92%,98%)at elevated temperatures(60-100℃)was elucidated by in situ synchrotron radiation X-ray scattering.The vi...The deformation mechanism of glycerol plasticized poly(vinyl alcohol)(PVA)with different hydrolyses(88%,92%,98%)at elevated temperatures(60-100℃)was elucidated by in situ synchrotron radiation X-ray scattering.The vinyl acetate(VAc)in PVA acts as a non-crystalline chain defect,which significantly influences the plastic deformation and stretching-induced crystallization behavior of PVA.The key microstructural parameters of PVA during deformation,such as crystallinity(χ_(c)),lateral crystallite size(L),and long period(l),in combination with the stress-strain curves,were obtained.The experimental results show that the deformation process of the plasticized PVA film present a three-stage evolution:(i)a plastic deformation zone.The plastic deformation of the crystallite occurs as evidenced by the apparent decrease in crystallinity and lamellar reorientation induced by stretching;(ii)the stress softening zone.The decreasing trend of crystallinity becomes slow,and the long period becomes smaller,which indicates that PVA crystallization is induced by stretching;and(iii)the strain-hardening zone.There is a synergistic effect between the crystallite destruction and formation.Further research reveals that a high temperature and low degree of alcoholysis favor the stretching-induced crystallization of PVA,while the system with a high degree of alcoholysis shows significant characteristics of preferred crystal growth.展开更多
The Pfitzinger reaction has long served as a notable synthesis pathway for quinoline-4-carboxylic acids.Although recognized for its synthetic potential since its discovery>138 years ago,a truly catalytic variant ha...The Pfitzinger reaction has long served as a notable synthesis pathway for quinoline-4-carboxylic acids.Although recognized for its synthetic potential since its discovery>138 years ago,a truly catalytic variant has remained elusive until now.Herein,we present a novel 2-tert-butyl-1,1,3,3-tetramethylguanidine(BTMG)-catalyzed Pfitzinger reaction that employs N-[(α-trifluoromethyl)vinyl]isatins with amines and alcohols,providing direct routes to 2-CF_(3)-quinoline-4-carboxamides and carboxylic esters.This method is not only green and environmentally benign but also accommodates the introduction of other functional groups like CF_(2)H and CO_(2)Me at the C2 position of quinoline skeleton.The utility of this methodology was demonstrated by the broad substrate scope,the late-stage modification of commercial drugs,and the diverse derivatization of quinoline framework.More importantly,this work not only opens up a new avenue for the activation of amide C-N bonds in catalytic reaction development,but also unlocks the huge potential of some 2-trifluoromethyl quinolines with strong inhibitory activity against PTP1B or optoelectronic application in organic light-emitting diodes.展开更多
Meeting the demands of complex and advanced applications requires the development of high-performance hybrid materials with unique properties.However,the integration of polymeric frameworks with MgO/WO_(3) composite l...Meeting the demands of complex and advanced applications requires the development of high-performance hybrid materials with unique properties.However,the integration of polymeric frameworks with MgO/WO_(3) composite layers faces challenges due to the lack of understanding of the formation mechanism and the challenge of determining the impact of self-assembled architecture on anticorrosive properties.In this study,we aimed to enhance the corrosion resistance of the MgO layer produced by plasma electrolysis(PE)of AZ31 Mg alloy by incorporating WO_(3) with partially phosphorated poly(vinyl alcohol)(PPVA).Two types of porous MgO layers were produced using the PE process with an alkaline-phosphate electrolyte,one with and one without WO_(3) nanoparticles,which were subsequently immersed in an aqueous solution of PPVA.Incorporating PPVA into the WO_(3)-MgO layer resulted in hybrids being deposited in a fragmented manner,creating a“laminar reef-like structure”that sealed most of the structural defects in the layer.The PPVA-sealed WO_(3)-based coating exhibited superior corrosion resistance compared to the other samples.Computational analyses were employed to explore the mechanism underlying the formation of PPVA/WO_(3) hybrids on the MgO layer.These findings suggest that PPVA-WO_(3)-MgO hybrid coatings can potentially improve corrosion resistance in various fields.展开更多
The chain dynamics heterogeneity of the poly(vinyl butyral)(PVB) plasticized by triethylene glycol bis(2-ethylhexa noate)(TEG-EH) was investigated by various solid-state NMR techniques.The plasticized PVB shows two do...The chain dynamics heterogeneity of the poly(vinyl butyral)(PVB) plasticized by triethylene glycol bis(2-ethylhexa noate)(TEG-EH) was investigated by various solid-state NMR techniques.The plasticized PVB shows two domains in distinct molecular dynamics differences,namely,rigid and soft domains,where the latter is the plasticizer-rich domain.The time domain low field NMR was first used to investigate the dynamics heterogeneity of the plasticized PVB,and the results show the decreasing activated energy of components in the soft domain of plasticized PVB(E_a=20.2 kJ/mol) as compared with that of the pristine one(E_a=24.3 kJ/mol).Detailed dynamics heterogeneity was obtained by high-field NMR with site-specific features.The quadrupole-echo ~2H-NMR was adopted to elucidate the dynamics heterogeneity of the vinyl alcohol(VA) units,where only the hydroxyl group of VA is deuterated.The ~1H-^(13)C WISE NMR spectra show that there is not much difference in the mobility of the VB unit in PVB with and without plasticizer,whereas the glass transition temperature differed by approximately 53℃.This is further supported by Torchia's T_1 relaxation measurements.The origin of such an unusual phenomenon is attributed to the critical role of the remaining VA(~22%) in the soft domain,where the VA units locally aggregate through hydrogen bonding.Also,the existence of a mobility gradient in the VB unit has been demonstrated.Moreover,the mobility difference for VB with different stereo-geometry(meso or racemic conformation) is observed for the first time.This indicates the importance of modulating the ratio of meso over racemic VB for controlling the macroscopic perfo rmance of PVB.展开更多
The purpose of this study was to identify and compare the degradation efficiencies of free and entrapped bacterial consortia(Staphylococcus capitis CP053957.1 and Achromobacter marplatensis MT078618.1)to different pol...The purpose of this study was to identify and compare the degradation efficiencies of free and entrapped bacterial consortia(Staphylococcus capitis CP053957.1 and Achromobacter marplatensis MT078618.1)to different polymers such as Sodium Alginate(SA),Sodium Alginate/Poly(Vinyl Alcohol)(SA/PVA),and Bushnell Haas Agar(BHA).In addition to SA and SA/PVA,which are cost-effective,non-toxic and have different functional groups,BHA,which is frequently encountered in laboratory-scale studies but has not been used as an entrapment material until now.Based on these,the polymers with different surface morphologies and chemical compositions were analyzed by SEM and FT-IR.While the petroleum removal efficiency was higher with the entrapped bacterial consortia than with the free one,BHA-entrapped bacterial consortium enhanced the petroleum removal more than SA and SA/PVA.Accordingly,the degradation rate of bacterial consortia entrapped with BHA was 2.039 day^(-1),SA/PVA was 1.560,SA was 0.993,the half-life period of BHA-entrapped bacterial consortia is quite low(t_(1/2)=0.339)compared with SA(t_(1/2)=0.444)and SA/PVA(t_(1/2)=0.697).The effects of the four main factors such as:amount of BHA(0.5,1,1.5,2,2.5,3 g),disc size(4,5,6,7,8 mm),inoculum concentration(1,2.5,5,7.5,10 mL),and incubation period on petroleum removal were also investigated.The maximum petroleum removal(94.5%)was obtained at≥2.5 mL of bacterial consortium entrapped in 2 g BHA with a 7 mm disc size at 168 h and the results were also confirmed by statistical analysis.Although a decrease was observed during the reuse of bacterial consortium entrapped in BHA,the petroleum removal was still above 50%at 10th cycle.Based on GC-MS analysis,the removal capacity of BHA-entrapped consortium was over 90%for short-chain n-alkanes and 80%for medium-chain n-alkanes.Overall,the obtained data are expected to provide a potential guideline in cleaning up the large-scale oil pollution in the future.Since there has been no similar study investigating petroleum removal with the bacterial consortia entrapped with BHA,this novel entrapment material can potentially be used in the treatment of petroleum pollution in advanced remediation studies.展开更多
Cesium carbonate was used as a base to achieve the desulfurization reaction of alkenyl sulfonium salts and phosphine oxides at room temperature,forming C(sp2)—P bonds.This method features simple operation,mild reacti...Cesium carbonate was used as a base to achieve the desulfurization reaction of alkenyl sulfonium salts and phosphine oxides at room temperature,forming C(sp2)—P bonds.This method features simple operation,mild reaction conditions,and good functional group compatibility,offering a straightforward and efficient preparation route for terminal vinyl phosphine oxides.展开更多
Vinylcarbenes are abundant and attractive feedstock molecules for organic synthesis.Many methods for their cycloaddition reaction require precious catalysts,while recent years have seen a vast in-crease in the number ...Vinylcarbenes are abundant and attractive feedstock molecules for organic synthesis.Many methods for their cycloaddition reaction require precious catalysts,while recent years have seen a vast in-crease in the number of complex transformations using inexpensive catalysts,as well as the direct utiliza-tion of vinyl N-sulfonylhydrazones as carbene precursors.This Review discusses cycloaddition reactions involving metal vinylcarbenes derived from vinyl diazoacetates and vinyl N-sulfonylhydrazones.The main content of this review is divided into three sections based on the number of carbon atoms of the metal vi-nylcarbene involved in the reaction:(1)as one-carbon synthon in[2+1]cycloaddition reactions,(2)as a two-carbon synthon to enable[2+n]cycloaddition reactions(n=3,4)employing the vinyl positions,(3)as a three-carbon synthon in[3+n]cycloaddition reactions(n=1-5).A particular emphasis is giv-en to scope and limitations,mechanistic studies,and potential applications in the synthesis of biologically and medically important cyclic scaffolds.展开更多
Based on commercially available polyvinyl alcohol (PVA) stabilised polyvinyl acetate (PVAc), emulsion adhesives are neither heat nor moisture-resistant and show weak strength at high relative humidity and high tempera...Based on commercially available polyvinyl alcohol (PVA) stabilised polyvinyl acetate (PVAc), emulsion adhesives are neither heat nor moisture-resistant and show weak strength at high relative humidity and high temperatures. Pre- or post-crosslinking is another method used to manufacture a conventional vinyl-based homopolymers or copolymers system with improved water resistance. Vinyl neodecanoate (VeoVa), N-methylolacrylamide (NMA), Methacrylamide, methacrylic acid (MAA), and other self-crosslinking comonomers are typically inserted to produce highly water-resistant vinyl based homopolymers or copolymers. Additionally, organic crosslinkers like glyoxal, glutaraldehyde, citric acid, tartaric acid, and the like, as well as inorganic crosslinkers like acidic metal salts like aluminium chloride, aluminium nitrate, boric acid, and the like, can be used to prepare the highly water-resistant vinyl based homopolymers or copolymers. It is also possible to combine the self-crosslinking comonomers with the organic crosslinkers. Recently, a different hybrid chemistry has been developed that improves lap shear strength, has outstanding water resistance, good durability, and doesn’t require any additional crosslinker agents. Two distinct polymers were combined to develop hybrid polymers. They usually involve mixing an organic polymer with a polymer. There are many capping agents that are used for polyurethanes to produce acrylics that are capped with polyurethane and used as an oligomer in PVAc wood glue. Here, in this paper, we reviewed the different hybrid chemistry based on polyurethane chemistry for wood bonding applications.展开更多
Nitrogen‐doped ordered mesoporous carbon （N‐OMC） catalysts were directly synthesized using SBA‐15 as a hard template and sucrose as a carbon source. Urea, which was used as the nitrogen source, was carbonized wit...Nitrogen‐doped ordered mesoporous carbon （N‐OMC） catalysts were directly synthesized using SBA‐15 as a hard template and sucrose as a carbon source. Urea, which was used as the nitrogen source, was carbonized with sucrose. A 3.6 wt% nitrogen doping of the carbon framework was achieved, with more than 70%of the nitrogen incorporated as quaternary nitrogen species. Only 0.2 wt% nitrogen doping, with only 32.7% quaternary nitrogen incorporation was obtained in an N‐OMC catalyst （N‐OMC‐T） prepared using a two‐step post‐synthesis method. The acetylene hy‐drochlorination activities of N‐OMC catalysts prepared via the one‐step method were higher than that of the N‐OMC‐T catalyst because of the higher nitrogen loadings.展开更多
A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts c...A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.展开更多
文摘The insertion of elemental selenium into the Csp(2)-Zr bond of alkenylchloro-zirconocenes affords (E)-vinylseleno zirconocenes, which were trapped by alkyl halides giving (E)-vinylic selenides in moderate to good yields.
基金supported by the National Basic Research Program of China(2015CB856600)the National Natural Science Foundation of China(21332002,21272010)
文摘Transition-metal-catalyzed C–H bond activation represents one of the most attractive research areas in organic synthesis.In contrast to the great developments made in directed C–H bond functionalization of arenes,the directing group-assisted activation of non-aromatic vinylic C–H bonds still remains challenging.During the recent years,significant progress has been made in this fascinating field with various functionalized alkenes,heterocycles and carbocycles being obtained.This article will focus on the recent achievements in the field of directing-group-assisted vinylic C–H bond functionalization.
基金theNationalNaturalScienceFoundationofChina (No .2 993 2 0 2 0 )
文摘This letter describes a method for the stereoselective synthesis of polymer supported vinylic selenides and their applications to synthesis of ( E ) and ( Z ) 1,2 disubstituted ethenes on solid phase by the coupling reaction with Grignard reagents under the catalysis of NiCl 2(PPh 3) 2.
基金funding from the National Natural Science Foundation of China(No.22401037)funding from JST CREST(No.JPMJCR23L1)。
文摘Chain-growth radical polymerization of vinyl monomers is essential for producing a wide range of materials with properties tailored to specific applications.However,the inherent resistance of the polymer's C―C backbone to degradation raises significant concerns regarding long-term environmental persistence,which also limits their potential in biomedical applications.To address these challenges,researchers have developed strategies to either degrade preexisting vinyl polymers or incorporate cleavable units into the backbone to modify them with enhanced degradability.This review explores the various approaches aimed at achieving backbone degradability in chain-growth radical polymerization of vinyl monomers,while also highlighting future research directions for the development of application-driven degradable vinyl polymers.
基金supported by the Zhejiang Provincial"Vanguard"and"Leading Goose"R&D Program(No.2025C02203)the Zhejiang Provincial Natural Science Foundation of China(No.LTGS24C130001)the Fund for Key Scientific Research in the Public Interest of Ningbo(No.2024S009)。
文摘Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in specialized fields.In this study,phytic acid(PA)was introduced as a halogen-free flame retardant and biochar(BC)was introduced as a reinforcement to achieve both flame resistance and mechanical robustness.We thoroughly investigated the effects of BC particle sizes(100-3000 mesh)and addition amounts(0 wt%-10 wt%),as well as PA addition amounts(0 wt%-15 wt%),on the properties of PVA composite films.Notably,the PA10/1000BC5 composite containing 10 wt%PA and 5 wt%1000 mesh BC exhibited optimal properties.The limiting oxygen index increased to 39.2%,and the UL-94 test achieved a V-0 rating.Additionally,the PA10/1000BC5 composite film demonstrated significantly enhanced water resistance,with a swelling ratio reaching 800%without dissolving,unlike that of the control PVA.The water contact angle was 70°,indicating that hydrophilic properties remained essentially unaffected.Most importantly,the tensile modulus and elongation at break were 213 MPa and 281.7%,respectively,nearly double those of the PVA/PA composite film.This study presents an efficient and straightforward method for preparing PVA composite films that are flame-retardant,tough,and waterresistant,expanding their potential applications in various fields.
基金supported by the National Natural Science Foundation of China(Grant Nos.51991351 and51903132)the Young Elite Scientist Sponsorship Program by CAST(No.2022QNRC001).
文摘Different reactive flame retardants have been extensively developed for vinyl ester resins(VERs),but very few of them can yield a flame-retardant resin that meets defined standards(e.g.UL-94 V-0 rating).In this work,phosphorous-containing 1-vinylimidazole salts(called VIDHP and VIDPP)were synthesized through the facile neutralization of the acid and 1-vinylimidazole.VIDHP and VIDPP were then applied as flame-retardant crosslinking agents of VERs,by which phosphorus-containing groups could be incorporated into the resin chain via ionic bonds.VIDHP/VER and VIDPP/VER showed a high curing activity and can be well cured in moderate temperatures.With 20 wt.%additions of VIDHP and VIDPP,VIDHP20/VER,and VIDPP20/VER presented a limiting oxygen index value of 29.7%and 28.4%,respectively,with the latter achieving a UL 94 V0 rating.In the cone calorimetric test,compared to the unmodified VERs,VIDPP20/VER exhibited large reductions in the peak heat release rate,total heat release rate,and total smoke release rate while VIDHP20/VER demonstrated comparatively inferior performance in terms of the heat release.VIDHP20/VER and VIDPP20/VER showed good thermal stability and presented a little lower glass transition temperature than the control sample.VIDPP with a low phosphorus oxidation state(+1)demonstrated high flame-retardant activities in the gaseous phase,whereas VIDHP with a high phosphorus oxidation state(+5)primarily exhibited efficacy in the condensed phase.
文摘The production of C_(2)H_(3)Cl from CH_(3)Cl(MCTV)represents a promising non-petroleum route for synthesizing C_(2)alkenes from C_(1)molecules.Exploration of new MCTV catalysts is crucial for advancing sustainable chemical production.In this study,we present NaVO_(3)as a surface-confined coupling center for·CH_(2)Cl radicals,demonstrating its superior performance in the selective coupling of methyl chloride to synthesize vinyl chloride.By incorporating NaVO_(3)onto the surface of CeO_(2),the catalyst enables effective capture of·CH_(2)Cl radicals during the CH_(3)Cl oxidative pyrolysis and their subsequent conversion into C_(2)H_(3)Cl.We experimentally validate the capability of highly dispersed Na-VO_(3)to controllably couple·CH_(2)Cl radicals through in-situ synchrotron-based vacuum ultraviolet photoionization mass spectrometry.The results demonstrate that the dispersion of NaVO_(3)on the catalyst surface has a considerable impact on the reaction efficiency of·CH_(2)Cl radicals and the overall MCTV performance.This discovery holds substantial implications for the controlled C_(1)radical transformation and provides a guidance for the design of catalysts for sustainable production of C_(2)H_(3)Cl.
基金supported by the National Natural Science Foundation of China(No.52422302)Anhui Provincial Natural Science Foundation(Nos.2308085UM02,2408055UM001,and 2308085UM04)the Major Science and Technology Project“Unveiling and Commanding”of Hefei City,Anhui Province(No.2022-SZD-005).
文摘The deformation mechanism of glycerol plasticized poly(vinyl alcohol)(PVA)with different hydrolyses(88%,92%,98%)at elevated temperatures(60-100℃)was elucidated by in situ synchrotron radiation X-ray scattering.The vinyl acetate(VAc)in PVA acts as a non-crystalline chain defect,which significantly influences the plastic deformation and stretching-induced crystallization behavior of PVA.The key microstructural parameters of PVA during deformation,such as crystallinity(χ_(c)),lateral crystallite size(L),and long period(l),in combination with the stress-strain curves,were obtained.The experimental results show that the deformation process of the plasticized PVA film present a three-stage evolution:(i)a plastic deformation zone.The plastic deformation of the crystallite occurs as evidenced by the apparent decrease in crystallinity and lamellar reorientation induced by stretching;(ii)the stress softening zone.The decreasing trend of crystallinity becomes slow,and the long period becomes smaller,which indicates that PVA crystallization is induced by stretching;and(iii)the strain-hardening zone.There is a synergistic effect between the crystallite destruction and formation.Further research reveals that a high temperature and low degree of alcoholysis favor the stretching-induced crystallization of PVA,while the system with a high degree of alcoholysis shows significant characteristics of preferred crystal growth.
基金National Natural Science Foundation of China(Nos.22171056,22122402,21801050)Outstanding Youth Project of Guangdong Natural Science Foundation(Nos.2024B1515020036,2021B1515020048)+3 种基金Guangdong Natural Science Foundation(Nos.2023A1515011313,2021A1515010510,2024A1515030037)Tertiary Education Scientific Research Project of Guangzhou Municipal Education Bureau(No.202235305)the Open Fund from Key Laboratory of Organofluorine ChemistryShanghai Engineering Research Center of Molecular Therapeutics and New Drug Development are gratefully acknowledged for financial support.
文摘The Pfitzinger reaction has long served as a notable synthesis pathway for quinoline-4-carboxylic acids.Although recognized for its synthetic potential since its discovery>138 years ago,a truly catalytic variant has remained elusive until now.Herein,we present a novel 2-tert-butyl-1,1,3,3-tetramethylguanidine(BTMG)-catalyzed Pfitzinger reaction that employs N-[(α-trifluoromethyl)vinyl]isatins with amines and alcohols,providing direct routes to 2-CF_(3)-quinoline-4-carboxamides and carboxylic esters.This method is not only green and environmentally benign but also accommodates the introduction of other functional groups like CF_(2)H and CO_(2)Me at the C2 position of quinoline skeleton.The utility of this methodology was demonstrated by the broad substrate scope,the late-stage modification of commercial drugs,and the diverse derivatization of quinoline framework.More importantly,this work not only opens up a new avenue for the activation of amide C-N bonds in catalytic reaction development,but also unlocks the huge potential of some 2-trifluoromethyl quinolines with strong inhibitory activity against PTP1B or optoelectronic application in organic light-emitting diodes.
基金supported by the National Research Foundation of Korea(NRF)funded by the Korean government(MSIT)(no.2022R1A2C1006743)。
文摘Meeting the demands of complex and advanced applications requires the development of high-performance hybrid materials with unique properties.However,the integration of polymeric frameworks with MgO/WO_(3) composite layers faces challenges due to the lack of understanding of the formation mechanism and the challenge of determining the impact of self-assembled architecture on anticorrosive properties.In this study,we aimed to enhance the corrosion resistance of the MgO layer produced by plasma electrolysis(PE)of AZ31 Mg alloy by incorporating WO_(3) with partially phosphorated poly(vinyl alcohol)(PPVA).Two types of porous MgO layers were produced using the PE process with an alkaline-phosphate electrolyte,one with and one without WO_(3) nanoparticles,which were subsequently immersed in an aqueous solution of PPVA.Incorporating PPVA into the WO_(3)-MgO layer resulted in hybrids being deposited in a fragmented manner,creating a“laminar reef-like structure”that sealed most of the structural defects in the layer.The PPVA-sealed WO_(3)-based coating exhibited superior corrosion resistance compared to the other samples.Computational analyses were employed to explore the mechanism underlying the formation of PPVA/WO_(3) hybrids on the MgO layer.These findings suggest that PPVA-WO_(3)-MgO hybrid coatings can potentially improve corrosion resistance in various fields.
基金financially supported by the National Natural Science Foundation of China (No.U20A20256)。
文摘The chain dynamics heterogeneity of the poly(vinyl butyral)(PVB) plasticized by triethylene glycol bis(2-ethylhexa noate)(TEG-EH) was investigated by various solid-state NMR techniques.The plasticized PVB shows two domains in distinct molecular dynamics differences,namely,rigid and soft domains,where the latter is the plasticizer-rich domain.The time domain low field NMR was first used to investigate the dynamics heterogeneity of the plasticized PVB,and the results show the decreasing activated energy of components in the soft domain of plasticized PVB(E_a=20.2 kJ/mol) as compared with that of the pristine one(E_a=24.3 kJ/mol).Detailed dynamics heterogeneity was obtained by high-field NMR with site-specific features.The quadrupole-echo ~2H-NMR was adopted to elucidate the dynamics heterogeneity of the vinyl alcohol(VA) units,where only the hydroxyl group of VA is deuterated.The ~1H-^(13)C WISE NMR spectra show that there is not much difference in the mobility of the VB unit in PVB with and without plasticizer,whereas the glass transition temperature differed by approximately 53℃.This is further supported by Torchia's T_1 relaxation measurements.The origin of such an unusual phenomenon is attributed to the critical role of the remaining VA(~22%) in the soft domain,where the VA units locally aggregate through hydrogen bonding.Also,the existence of a mobility gradient in the VB unit has been demonstrated.Moreover,the mobility difference for VB with different stereo-geometry(meso or racemic conformation) is observed for the first time.This indicates the importance of modulating the ratio of meso over racemic VB for controlling the macroscopic perfo rmance of PVB.
文摘The purpose of this study was to identify and compare the degradation efficiencies of free and entrapped bacterial consortia(Staphylococcus capitis CP053957.1 and Achromobacter marplatensis MT078618.1)to different polymers such as Sodium Alginate(SA),Sodium Alginate/Poly(Vinyl Alcohol)(SA/PVA),and Bushnell Haas Agar(BHA).In addition to SA and SA/PVA,which are cost-effective,non-toxic and have different functional groups,BHA,which is frequently encountered in laboratory-scale studies but has not been used as an entrapment material until now.Based on these,the polymers with different surface morphologies and chemical compositions were analyzed by SEM and FT-IR.While the petroleum removal efficiency was higher with the entrapped bacterial consortia than with the free one,BHA-entrapped bacterial consortium enhanced the petroleum removal more than SA and SA/PVA.Accordingly,the degradation rate of bacterial consortia entrapped with BHA was 2.039 day^(-1),SA/PVA was 1.560,SA was 0.993,the half-life period of BHA-entrapped bacterial consortia is quite low(t_(1/2)=0.339)compared with SA(t_(1/2)=0.444)and SA/PVA(t_(1/2)=0.697).The effects of the four main factors such as:amount of BHA(0.5,1,1.5,2,2.5,3 g),disc size(4,5,6,7,8 mm),inoculum concentration(1,2.5,5,7.5,10 mL),and incubation period on petroleum removal were also investigated.The maximum petroleum removal(94.5%)was obtained at≥2.5 mL of bacterial consortium entrapped in 2 g BHA with a 7 mm disc size at 168 h and the results were also confirmed by statistical analysis.Although a decrease was observed during the reuse of bacterial consortium entrapped in BHA,the petroleum removal was still above 50%at 10th cycle.Based on GC-MS analysis,the removal capacity of BHA-entrapped consortium was over 90%for short-chain n-alkanes and 80%for medium-chain n-alkanes.Overall,the obtained data are expected to provide a potential guideline in cleaning up the large-scale oil pollution in the future.Since there has been no similar study investigating petroleum removal with the bacterial consortia entrapped with BHA,this novel entrapment material can potentially be used in the treatment of petroleum pollution in advanced remediation studies.
文摘Cesium carbonate was used as a base to achieve the desulfurization reaction of alkenyl sulfonium salts and phosphine oxides at room temperature,forming C(sp2)—P bonds.This method features simple operation,mild reaction conditions,and good functional group compatibility,offering a straightforward and efficient preparation route for terminal vinyl phosphine oxides.
基金supported by the Research and Development Fund Project of Jilin Engineering Normal University(2024hx58kj)Science&Technology and Biotechnology Department,Govt.of West Bengal,India(1856(Sanc.)/ST/P/S&T/15G-6/2019).
文摘Vinylcarbenes are abundant and attractive feedstock molecules for organic synthesis.Many methods for their cycloaddition reaction require precious catalysts,while recent years have seen a vast in-crease in the number of complex transformations using inexpensive catalysts,as well as the direct utiliza-tion of vinyl N-sulfonylhydrazones as carbene precursors.This Review discusses cycloaddition reactions involving metal vinylcarbenes derived from vinyl diazoacetates and vinyl N-sulfonylhydrazones.The main content of this review is divided into three sections based on the number of carbon atoms of the metal vi-nylcarbene involved in the reaction:(1)as one-carbon synthon in[2+1]cycloaddition reactions,(2)as a two-carbon synthon to enable[2+n]cycloaddition reactions(n=3,4)employing the vinyl positions,(3)as a three-carbon synthon in[3+n]cycloaddition reactions(n=1-5).A particular emphasis is giv-en to scope and limitations,mechanistic studies,and potential applications in the synthesis of biologically and medically important cyclic scaffolds.
文摘Based on commercially available polyvinyl alcohol (PVA) stabilised polyvinyl acetate (PVAc), emulsion adhesives are neither heat nor moisture-resistant and show weak strength at high relative humidity and high temperatures. Pre- or post-crosslinking is another method used to manufacture a conventional vinyl-based homopolymers or copolymers system with improved water resistance. Vinyl neodecanoate (VeoVa), N-methylolacrylamide (NMA), Methacrylamide, methacrylic acid (MAA), and other self-crosslinking comonomers are typically inserted to produce highly water-resistant vinyl based homopolymers or copolymers. Additionally, organic crosslinkers like glyoxal, glutaraldehyde, citric acid, tartaric acid, and the like, as well as inorganic crosslinkers like acidic metal salts like aluminium chloride, aluminium nitrate, boric acid, and the like, can be used to prepare the highly water-resistant vinyl based homopolymers or copolymers. It is also possible to combine the self-crosslinking comonomers with the organic crosslinkers. Recently, a different hybrid chemistry has been developed that improves lap shear strength, has outstanding water resistance, good durability, and doesn’t require any additional crosslinker agents. Two distinct polymers were combined to develop hybrid polymers. They usually involve mixing an organic polymer with a polymer. There are many capping agents that are used for polyurethanes to produce acrylics that are capped with polyurethane and used as an oligomer in PVAc wood glue. Here, in this paper, we reviewed the different hybrid chemistry based on polyurethane chemistry for wood bonding applications.
基金supported by the National Natural Science Foundation of China (20803064)the Natural Science Foundation of Zhejiang Province (Y4090348)~~
文摘Nitrogen‐doped ordered mesoporous carbon （N‐OMC） catalysts were directly synthesized using SBA‐15 as a hard template and sucrose as a carbon source. Urea, which was used as the nitrogen source, was carbonized with sucrose. A 3.6 wt% nitrogen doping of the carbon framework was achieved, with more than 70%of the nitrogen incorporated as quaternary nitrogen species. Only 0.2 wt% nitrogen doping, with only 32.7% quaternary nitrogen incorporation was obtained in an N‐OMC catalyst （N‐OMC‐T） prepared using a two‐step post‐synthesis method. The acetylene hy‐drochlorination activities of N‐OMC catalysts prepared via the one‐step method were higher than that of the N‐OMC‐T catalyst because of the higher nitrogen loadings.
基金ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China （No.20873125）,
文摘A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.
