A novel palladium/copper-catalyzed aerobic synthesis of bisaryl ketones from 1,2-diarylalkenes via C-C double bonds cleavage has been described.This reaction constitutes a new transformation from 1,2-diarylalkenes int...A novel palladium/copper-catalyzed aerobic synthesis of bisaryl ketones from 1,2-diarylalkenes via C-C double bonds cleavage has been described.This reaction constitutes a new transformation from 1,2-diarylalkenes into bisaryl ketones,providing a unifying,simple and environmentally friendly complement to the available methods.展开更多
A series of calcined carbonate layered double hydroxides （CLDHs） with various metal compositions and different M^2＋/M^3＋ ratios were prepared as adsorbents for perchlorate. Adsorption isotherms fit Langmuir model ...A series of calcined carbonate layered double hydroxides （CLDHs） with various metal compositions and different M^2＋/M^3＋ ratios were prepared as adsorbents for perchlorate. Adsorption isotherms fit Langmuir model well, and the adsorption amount followed the order of MgA1-CLDHs 1〉 MgFeCLDHs 〉〉 ZnA1-CLDHs. The isotherms of MgA1-CLDHs and MgFe-CLDHs displayed a two-step shape at low and high concentration ranges and increased with an increase in the M^2＋/M^3＋ ratio from 2 to 4. The two-step isotherm was not observed for ZnA1-CLDHs, and the adsorption was minimally affected by the M^2＋/M^3＋ ratio. The LDHs, CLDHs and the reconstructed samples were characterized by X-ray diffraction, SEM, FT-IR and Raman spectra to delineate the analysis of perchlorate adsorption mechanisms. The perchlorate adsorption of MgA1-CLDHs and MgFe-CLDHs was dominated by the structural memory effect and the hydrogen bonds between the free hydroxyl groups on the reconstructed-LDHs and the oxygen atoms of the perchlorates. For ZnAI-CLDHs, the perchlorate adsorption was controlled by the structural memory effect only, as the hydroxyl groups on the hydroxide layers preferred to form strong hydrogen bonds with carbonate over perchlorate, which locked the intercalated perchlorate into a more confined nano-interlayer. Several distinct binding mechanisms of perchlorate by CLDHs with unique M^2＋ ions were proposed.展开更多
The geometries of reactant, product and transition state of the title reaction have been optimized by using density functional theory (DFT) at the B3LYP/6-31G(d,p) and B3LYP/6- 311++G(d,p) levels. The variations of th...The geometries of reactant, product and transition state of the title reaction have been optimized by using density functional theory (DFT) at the B3LYP/6-31G(d,p) and B3LYP/6- 311++G(d,p) levels. The variations of the bond parameters in the course of reaction were analyzed. The zero point energy corrections were performed by vibrational analysis. The equilibrium states and the transition state were verified according to the number of virtue frequency of geometry. The intrinsic reaction coordinates (IRC) were calculated from the transition state. The calculated results show that the double bond rearrangement of butene catalyzed by 1-butyl-3-methyl-imidazolium cation is a one-step reaction. The forward energy barrier of isomerization from 1-butene to 2- butene is about 193 kJ·mol-1 and the reverse energy barrier about 209 kJ·mol-1 at the B3LYP/6- 31G(d,p) level, which means that the reaction is easy to proceed at or above room temperature.展开更多
Ozonolysis products of four lepidopteral pheromone were identified by methane CI-MS.The spectra obtained were notably simpler than those of EI-MS,the peak of molecular ion was normally close to the base peak,and the c...Ozonolysis products of four lepidopteral pheromone were identified by methane CI-MS.The spectra obtained were notably simpler than those of EI-MS,the peak of molecular ion was normally close to the base peak,and the characteristic fragment ions were high in m/z,thereby the interpretation was facilitated.展开更多
A method for locating double bond in hexadecenyl acetates has been developed by analyzing the mass spectral patterns on a fuzzy classification. The procedure was tested with the spectra of Δ~2- to Δ^(15)-isomers and...A method for locating double bond in hexadecenyl acetates has been developed by analyzing the mass spectral patterns on a fuzzy classification. The procedure was tested with the spectra of Δ~2- to Δ^(15)-isomers and the original double-bond position in these acetates was located unambiguously.展开更多
By using a two-dimensional Monte-Carlo classical ensemble method, we investigate the double ionization（DI） process of the CS_2 molecule with different bond lengths in an 800-nm intense laser field. The double ioniza...By using a two-dimensional Monte-Carlo classical ensemble method, we investigate the double ionization（DI） process of the CS_2 molecule with different bond lengths in an 800-nm intense laser field. The double ionization probability presents a ＂knee＂ structure with equilibrium internuclear distance R = 2.9245 a.u.（a.u. is short for atomic unit）. As the bond length of CS increases, the DI probability is enhanced and the ＂knee＂ structure becomes less obvious. In addition,the momentum distribution of double ionized electrons is also investigated, which shows the momentum mostly distributed in the first and third quadrants with equilibrium internuclear distance R = 2.9245 a.u. As the bond length of CS increases,the electron momentum becomes evenly distributed in the four quadrants. Furthermore, the energy distributions and the corresponding trajectories of the double-ionized electrons versus time are also demonstrated, which show that the bond length of CS in the CS_2 molecule plays a key role in the DI process.展开更多
As more and more studies have shown that lipid molecules play an important role in the whole biology,in-depth analysis of lipid structure has become particularly important in lipidomics.Mass spectrometry(MS),as the pr...As more and more studies have shown that lipid molecules play an important role in the whole biology,in-depth analysis of lipid structure has become particularly important in lipidomics.Mass spectrometry(MS),as the preferred tool for lipid analysis,has greatly promoted the development of this field.However,the existing MS methods still face many difficulties in the in-depth or even comprehensive analysis of lipid structure.In this review,we discuss recent advances in MS methods based on double bond-specific chemistries for the resolving of C=C location and geometry isomers of lipids.This progress has greatly advanced the lipidomics analysis to a deeper structural level and facilitated the development of structural lipid biology.展开更多
Light-driven artificial molecular machines[1,2]are a class of functional small molecules powered by photochemical reactions,broadly divided into molecular motors and molecular photoswitches.Molecular motors[3,4],owing...Light-driven artificial molecular machines[1,2]are a class of functional small molecules powered by photochemical reactions,broadly divided into molecular motors and molecular photoswitches.Molecular motors[3,4],owing to their intrinsic point chirality and dynamic axial chirality,undergo unidirectional rotation about a carbon–carbon double bond when irradiated with light.In nature,biological molecular motors and pumps are ubiquitous:driving vision,intracellular transport,energy conversion,signal transduction,muscle contraction,and locomotion.展开更多
Fluorinated fused azobenzene boron(FBAz)is a novel electron-deficient building block for polymer electron acceptors in all-polymer solar cells(all-PSC).The B←N bridging units impart a fixed configuration and low-lyin...Fluorinated fused azobenzene boron(FBAz)is a novel electron-deficient building block for polymer electron acceptors in all-polymer solar cells(all-PSC).The B←N bridging units impart a fixed configuration and low-lying LUMO/HOMO energy.Three polymer acceptor materials(P2f,P3f and P5f)with different fluorine substitution positions by copolymerizing FBAz with indacenodithiophene(IDT),are synthesized and investigated to study the influence of fluorinated forms on the all-polymer solar cell performance.The FBAz units are synthesized in just three steps,facilitating the straightforward production of polymer acceptors P2f,P3f,and P5f.These acceptors exhibit strong light absorption in the visible to near-infrared range of 500-1000nm and possess suitable LUMO/HOMO energy levels of-3.99/-5.66 eV which are very complementary to that(E_(LUMO/HOMO)=-3.59/-5.20 eV)of the widely-used polymer donor poly[(ethylhexylthiophenyl)-benzodithiophene-(ethylhexyl)-thienothiophene](PTB7-Th).All-polymer solar cells(all-PSCs)with PTB7-Th as electron donor and P3f as electron acceptor exhibits highest power conversion efficiencies(PCE)2.70%.When PC_(61)BM is added as the third component,the device efficiency can reach 5.36%.These preliminary results indicate that FBAz is a promising strong electron acceptor for the development of n-type polymer semiconductors,especially in organic photovoltaics(OPVs).To the best of our knowledge,this is the first example demonstrating the unique photovoltaic properties of the N=N double bond as an acceptor material.展开更多
An efficient synthesis of 3-(diarylallylidene)oxindoles from 3-(1 H-indol-3-yl)-1,1-diarylpropan-1-ol under metal-free conditions is described.NBS serves as a critical medium leading to a facile oxygenmigration in the...An efficient synthesis of 3-(diarylallylidene)oxindoles from 3-(1 H-indol-3-yl)-1,1-diarylpropan-1-ol under metal-free conditions is described.NBS serves as a critical medium leading to a facile oxygenmigration in the transformation.The protocol has advantages of high efficiency,simple opreation,mild reaction conditions,good atom-economy,wide substrate scope and good yields of products.A detailed mechanism is proposed after careful investigation.展开更多
Building on the recent success of the even-odd rule, the present paper explores its implications by studying the very specific case of OXO compounds. These compounds are usually represented with double bonds linking t...Building on the recent success of the even-odd rule, the present paper explores its implications by studying the very specific case of OXO compounds. These compounds are usually represented with double bonds linking two oxygen atoms to a central atom—as in carbon dioxyde—yet can sometimes be drawn in a triangular structure, such as in calcium dioxyde. Measurement data moreover indicate that most OXO compounds have an angle around 120° between oxygen atoms, although that seems incompatible with triangular representations. The aim here is to unify these commonly admitted representations by linking oxygen atoms through a single bond that is longer than usual covalent bonds: an “elongated bond”. This elongated bond has the interesting effect of suppressing the need for double bonds between oxygen and the central atom. The elongated bond concept is applied to about a hundred of molecules and ions and methodically compared to classical representations. It is shown that this new representation, associated to the even-odd rule, is compatible with all studied compounds and can be used in place of their classical drawings. Its usage greatly simplifies complex concepts like resonance and separated charges in gases. Elongated bonds are also shown to be practicable with the isoelectronic rule as well as isomers, and throughout chemical reactions. This study of an especially long and wide angle bond confirms the versatility of the even-odd rule: it is not limited to compounds with short covalent bonds and can include OO covalent bond lengths of more than 200 pm and with OXO angles above 90°.展开更多
Polymeric nanoparticles（NPs）have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare function...Polymeric nanoparticles（NPs）have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare functional polymeric NPs,especially for particle diameters smaller than 50 nm.In this work,we demonstrate a one-pot method to fabricate reactive poly（divinyl benzene-co-maleic anhydride）NPs（PDVBMAH NPs）through a self-stable precipitation polymerization process.The size and morphology of these PDVBMAH NPs were characterized in detail by scanning electronic microscopy,and their chemical structure was determined by IR.The results showed that these NPs were highly cross-linked and their diameter was about 30 nm with narrow distribution.Additionally,the DVB and MAH endow the NPs with reactive surface anhydride and pendant vinyl groups,and these particles could be further functionalized through reaction of these groups.A plausible pathway was proposed for the formation of PDVBMAH NPs.展开更多
Genome mining for the search and discovery of two new globin-like enzymes,TriB from Fusarium poae and TutaA from Schizophyllum commne,are involved in the synthesis of two linear terpenes tricinonoic acid(1)and 2-buten...Genome mining for the search and discovery of two new globin-like enzymes,TriB from Fusarium poae and TutaA from Schizophyllum commne,are involved in the synthesis of two linear terpenes tricinonoic acid(1)and 2-butenedioic acid(3).Both in vivo heterologous biosynthesis and in vitro biochemical assays showed that these two enzymes catalyzed the C-C double bond cleavage of a cyclic sesquiterpene precursor(-)-germacrene D(7)and a linear diterpene backbone schizostain(2),respectively.Our work presents an unusual formation mechanism of linear terpenes from fungi and expands the functional skills of globin-like enzymes in the synthesis of terpene compounds.展开更多
The symmetrical diketone Ⅱ, which can be synthesized in gram scale using a well established method, was used as a starting material to prepare the 11α-methoxy ketomethylene Ⅵ. This is in continuation of our study a...The symmetrical diketone Ⅱ, which can be synthesized in gram scale using a well established method, was used as a starting material to prepare the 11α-methoxy ketomethylene Ⅵ. This is in continuation of our study aiming at the synthesis of multihydroxylated cephalostatin analogues, as for example cephalostatin 1Ⅰ, a potent anti-tumor natural product. Compound Ⅵ underwent chemo- and regioselective hydroboration reaction at only one of △14.15 double bonds furnishing compound Ⅸ as a major product in a fair yield.展开更多
The uranyl with two U=O double bonds is a wellknown and predominant form of uranium in the environment,but the carbon-based analog with two U=C double bonds has rarely been synthesized.Here,we describe the formation o...The uranyl with two U=O double bonds is a wellknown and predominant form of uranium in the environment,but the carbon-based analog with two U=C double bonds has rarely been synthesized.Here,we describe the formation of an unprecedented uranium complex[(PyPh_(2)P)_(2)C]_(2)UCl_(2)]^(2+)·2(BPh_(4)^(−))from the reaction of UCl4 with carbodiphosphorane in the presence of NaBPh4.The nature of the U-C bonds was revealed by density functional theory calculations,which show that the 5f and 6d orbital electrons of uranium are remarkably involved in the U=C double bonds.The inspection of the bonding characteristics with an energy decomposition analysis suggests that the uranium-ligand bond may be alternatively described with double dative bonds[C⇉U⇇C]or strong electron-sharing π bonds and weak σ bonds.展开更多
Highly efficient and selective carbon-carbon double bond aerobic cleavage of olefins catalyzed by metallopor- phyrins was investigated, and carbonyl compounds and epoxide were produced as the main products. CoTPP （co...Highly efficient and selective carbon-carbon double bond aerobic cleavage of olefins catalyzed by metallopor- phyrins was investigated, and carbonyl compounds and epoxide were produced as the main products. CoTPP （co- balt meso-tetraphenyl porphyrin） showed excellent activity for the oxidative cleavage of carbon-carbon double bond by using styrene as model compound, in which the TOF （turnover frequency） and selectivity toward benzaldehyde was obtained with 2×10^4h-1 and 86%,respectively.展开更多
A new formula was presented for locating double bond position in dodecenols, tetradcenols hexadecenols and their acetates, based on mass spectral data of dimethyl disulfide derivatives. In this procedure, molecular io...A new formula was presented for locating double bond position in dodecenols, tetradcenols hexadecenols and their acetates, based on mass spectral data of dimethyl disulfide derivatives. In this procedure, molecular ion and base peak ion were utilized as characteristic parameters to identify the positional isomers. The method was tested with mass spectra of 25 dimethyl disulfide derivatives of mono-unsaturated acetates and alcohols, and the original double-bond position in each isomer was located unambiguously.展开更多
A method for the identification of the double bond positional isomers of hexadecenyl acetate has been established by analysing similarity of the mass spectra patterns on a fuzzy classification, in which the intensity ...A method for the identification of the double bond positional isomers of hexadecenyl acetate has been established by analysing similarity of the mass spectra patterns on a fuzzy classification, in which the intensity ratios of six diagnostic pairs of the predominant ions were selected as standard parameters for the characterization of the double bond position. The procedure was tested with △2 to △15-isomers of chemically unmodified hexadecenyl acetate, and the original double bond position in the acetates was located unambiguously.展开更多
Brassinosteroids(BRs)are essential plant steroids that regulate various growth and developmental processes(Nolan et al.,2020).Brassinosteroid biosynthesis involves multiple cytochrome P450 enzymes and a single nonCYP4...Brassinosteroids(BRs)are essential plant steroids that regulate various growth and developmental processes(Nolan et al.,2020).Brassinosteroid biosynthesis involves multiple cytochrome P450 enzymes and a single nonCYP450 enzyme DET2(Zebosi et al.,2024),which was named after its dark“de-etiolated”mutant phenotype(Chory et al.,1991).DET2,an Arabidopsis homolog of the mammalian steroid 5α-reductases(SRD5As),catalyzes the reduction of theΔ^(4,5)double bond of 3-oxo-Δ^(4,5)sterols(Li et al.,1996;Fujioka et al.,1997)(Figure S1).展开更多
基金We are grateful for the financial support from the State Ethnic Affairs Commission(No.12YNZ05)Opening Fund of Key Laboratory of Ethnic Medicine Resource Chemistry(No.MZY 1117).
文摘A novel palladium/copper-catalyzed aerobic synthesis of bisaryl ketones from 1,2-diarylalkenes via C-C double bonds cleavage has been described.This reaction constitutes a new transformation from 1,2-diarylalkenes into bisaryl ketones,providing a unifying,simple and environmentally friendly complement to the available methods.
基金supported by the National Natural Science Foundation of China(No.41071210)the Zhejiang Provincial Natural Science Foundation of China(No.R5100105)the Doctoral Fund of Ministry of Education China(No.J20130039)
文摘A series of calcined carbonate layered double hydroxides （CLDHs） with various metal compositions and different M^2＋/M^3＋ ratios were prepared as adsorbents for perchlorate. Adsorption isotherms fit Langmuir model well, and the adsorption amount followed the order of MgA1-CLDHs 1〉 MgFeCLDHs 〉〉 ZnA1-CLDHs. The isotherms of MgA1-CLDHs and MgFe-CLDHs displayed a two-step shape at low and high concentration ranges and increased with an increase in the M^2＋/M^3＋ ratio from 2 to 4. The two-step isotherm was not observed for ZnA1-CLDHs, and the adsorption was minimally affected by the M^2＋/M^3＋ ratio. The LDHs, CLDHs and the reconstructed samples were characterized by X-ray diffraction, SEM, FT-IR and Raman spectra to delineate the analysis of perchlorate adsorption mechanisms. The perchlorate adsorption of MgA1-CLDHs and MgFe-CLDHs was dominated by the structural memory effect and the hydrogen bonds between the free hydroxyl groups on the reconstructed-LDHs and the oxygen atoms of the perchlorates. For ZnAI-CLDHs, the perchlorate adsorption was controlled by the structural memory effect only, as the hydroxyl groups on the hydroxide layers preferred to form strong hydrogen bonds with carbonate over perchlorate, which locked the intercalated perchlorate into a more confined nano-interlayer. Several distinct binding mechanisms of perchlorate by CLDHs with unique M^2＋ ions were proposed.
基金This work was supported by the National Natural Science Key Foundation of China (20490209) and Young Teacher Foundation of Beijing Chemical Technology University (QN0308)
文摘The geometries of reactant, product and transition state of the title reaction have been optimized by using density functional theory (DFT) at the B3LYP/6-31G(d,p) and B3LYP/6- 311++G(d,p) levels. The variations of the bond parameters in the course of reaction were analyzed. The zero point energy corrections were performed by vibrational analysis. The equilibrium states and the transition state were verified according to the number of virtue frequency of geometry. The intrinsic reaction coordinates (IRC) were calculated from the transition state. The calculated results show that the double bond rearrangement of butene catalyzed by 1-butyl-3-methyl-imidazolium cation is a one-step reaction. The forward energy barrier of isomerization from 1-butene to 2- butene is about 193 kJ·mol-1 and the reverse energy barrier about 209 kJ·mol-1 at the B3LYP/6- 31G(d,p) level, which means that the reaction is easy to proceed at or above room temperature.
文摘Ozonolysis products of four lepidopteral pheromone were identified by methane CI-MS.The spectra obtained were notably simpler than those of EI-MS,the peak of molecular ion was normally close to the base peak,and the characteristic fragment ions were high in m/z,thereby the interpretation was facilitated.
文摘A method for locating double bond in hexadecenyl acetates has been developed by analyzing the mass spectral patterns on a fuzzy classification. The procedure was tested with the spectra of Δ~2- to Δ^(15)-isomers and the original double-bond position in these acetates was located unambiguously.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574117 and11604131)
文摘By using a two-dimensional Monte-Carlo classical ensemble method, we investigate the double ionization（DI） process of the CS_2 molecule with different bond lengths in an 800-nm intense laser field. The double ionization probability presents a ＂knee＂ structure with equilibrium internuclear distance R = 2.9245 a.u.（a.u. is short for atomic unit）. As the bond length of CS increases, the DI probability is enhanced and the ＂knee＂ structure becomes less obvious. In addition,the momentum distribution of double ionized electrons is also investigated, which shows the momentum mostly distributed in the first and third quadrants with equilibrium internuclear distance R = 2.9245 a.u. As the bond length of CS increases,the electron momentum becomes evenly distributed in the four quadrants. Furthermore, the energy distributions and the corresponding trajectories of the double-ionized electrons versus time are also demonstrated, which show that the bond length of CS in the CS_2 molecule plays a key role in the DI process.
基金financially supported by the National Natural Science Foundation of China(No.22074111)National Key Research and Development Program of China(No.2021YFC2700700)the Opening fund of Hubei Key Laboratory of Bioinorganic Chemistry&Materia Medica(No.BCMM202303)。
文摘As more and more studies have shown that lipid molecules play an important role in the whole biology,in-depth analysis of lipid structure has become particularly important in lipidomics.Mass spectrometry(MS),as the preferred tool for lipid analysis,has greatly promoted the development of this field.However,the existing MS methods still face many difficulties in the in-depth or even comprehensive analysis of lipid structure.In this review,we discuss recent advances in MS methods based on double bond-specific chemistries for the resolving of C=C location and geometry isomers of lipids.This progress has greatly advanced the lipidomics analysis to a deeper structural level and facilitated the development of structural lipid biology.
文摘Light-driven artificial molecular machines[1,2]are a class of functional small molecules powered by photochemical reactions,broadly divided into molecular motors and molecular photoswitches.Molecular motors[3,4],owing to their intrinsic point chirality and dynamic axial chirality,undergo unidirectional rotation about a carbon–carbon double bond when irradiated with light.In nature,biological molecular motors and pumps are ubiquitous:driving vision,intracellular transport,energy conversion,signal transduction,muscle contraction,and locomotion.
基金supported by the National Natural Science Foundation of China(No.22375123)the Shuguang Program of Shanghai Education Development Foundation,the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(No.2022SXTD012)。
文摘Fluorinated fused azobenzene boron(FBAz)is a novel electron-deficient building block for polymer electron acceptors in all-polymer solar cells(all-PSC).The B←N bridging units impart a fixed configuration and low-lying LUMO/HOMO energy.Three polymer acceptor materials(P2f,P3f and P5f)with different fluorine substitution positions by copolymerizing FBAz with indacenodithiophene(IDT),are synthesized and investigated to study the influence of fluorinated forms on the all-polymer solar cell performance.The FBAz units are synthesized in just three steps,facilitating the straightforward production of polymer acceptors P2f,P3f,and P5f.These acceptors exhibit strong light absorption in the visible to near-infrared range of 500-1000nm and possess suitable LUMO/HOMO energy levels of-3.99/-5.66 eV which are very complementary to that(E_(LUMO/HOMO)=-3.59/-5.20 eV)of the widely-used polymer donor poly[(ethylhexylthiophenyl)-benzodithiophene-(ethylhexyl)-thienothiophene](PTB7-Th).All-polymer solar cells(all-PSCs)with PTB7-Th as electron donor and P3f as electron acceptor exhibits highest power conversion efficiencies(PCE)2.70%.When PC_(61)BM is added as the third component,the device efficiency can reach 5.36%.These preliminary results indicate that FBAz is a promising strong electron acceptor for the development of n-type polymer semiconductors,especially in organic photovoltaics(OPVs).To the best of our knowledge,this is the first example demonstrating the unique photovoltaic properties of the N=N double bond as an acceptor material.
基金the National Natural Science Foundation of China(Nos.21772138 and 21672157)PAPD,the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX19_1899)+1 种基金the Project of Scientific and Technologic Infrastructute of Suzhou(No.SZS201708)State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials for financial support。
文摘An efficient synthesis of 3-(diarylallylidene)oxindoles from 3-(1 H-indol-3-yl)-1,1-diarylpropan-1-ol under metal-free conditions is described.NBS serves as a critical medium leading to a facile oxygenmigration in the transformation.The protocol has advantages of high efficiency,simple opreation,mild reaction conditions,good atom-economy,wide substrate scope and good yields of products.A detailed mechanism is proposed after careful investigation.
文摘Building on the recent success of the even-odd rule, the present paper explores its implications by studying the very specific case of OXO compounds. These compounds are usually represented with double bonds linking two oxygen atoms to a central atom—as in carbon dioxyde—yet can sometimes be drawn in a triangular structure, such as in calcium dioxyde. Measurement data moreover indicate that most OXO compounds have an angle around 120° between oxygen atoms, although that seems incompatible with triangular representations. The aim here is to unify these commonly admitted representations by linking oxygen atoms through a single bond that is longer than usual covalent bonds: an “elongated bond”. This elongated bond has the interesting effect of suppressing the need for double bonds between oxygen and the central atom. The elongated bond concept is applied to about a hundred of molecules and ions and methodically compared to classical representations. It is shown that this new representation, associated to the even-odd rule, is compatible with all studied compounds and can be used in place of their classical drawings. Its usage greatly simplifies complex concepts like resonance and separated charges in gases. Elongated bonds are also shown to be practicable with the isoelectronic rule as well as isomers, and throughout chemical reactions. This study of an especially long and wide angle bond confirms the versatility of the even-odd rule: it is not limited to compounds with short covalent bonds and can include OO covalent bond lengths of more than 200 pm and with OXO angles above 90°.
文摘Polymeric nanoparticles（NPs）have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare functional polymeric NPs,especially for particle diameters smaller than 50 nm.In this work,we demonstrate a one-pot method to fabricate reactive poly（divinyl benzene-co-maleic anhydride）NPs（PDVBMAH NPs）through a self-stable precipitation polymerization process.The size and morphology of these PDVBMAH NPs were characterized in detail by scanning electronic microscopy,and their chemical structure was determined by IR.The results showed that these NPs were highly cross-linked and their diameter was about 30 nm with narrow distribution.Additionally,the DVB and MAH endow the NPs with reactive surface anhydride and pendant vinyl groups,and these particles could be further functionalized through reaction of these groups.A plausible pathway was proposed for the formation of PDVBMAH NPs.
基金supported by the National Natural Science Foundation of China(No.31870022)Chongqing Science Funds for Distinguished Young Scientists(No.cstc2020jcyjjqX0005)。
文摘Genome mining for the search and discovery of two new globin-like enzymes,TriB from Fusarium poae and TutaA from Schizophyllum commne,are involved in the synthesis of two linear terpenes tricinonoic acid(1)and 2-butenedioic acid(3).Both in vivo heterologous biosynthesis and in vitro biochemical assays showed that these two enzymes catalyzed the C-C double bond cleavage of a cyclic sesquiterpene precursor(-)-germacrene D(7)and a linear diterpene backbone schizostain(2),respectively.Our work presents an unusual formation mechanism of linear terpenes from fungi and expands the functional skills of globin-like enzymes in the synthesis of terpene compounds.
文摘The symmetrical diketone Ⅱ, which can be synthesized in gram scale using a well established method, was used as a starting material to prepare the 11α-methoxy ketomethylene Ⅵ. This is in continuation of our study aiming at the synthesis of multihydroxylated cephalostatin analogues, as for example cephalostatin 1Ⅰ, a potent anti-tumor natural product. Compound Ⅵ underwent chemo- and regioselective hydroboration reaction at only one of △14.15 double bonds furnishing compound Ⅸ as a major product in a fair yield.
基金supported by the National Natural Science Foundation of China(grant nos.21772088,91961116,and 21973044)the Introduction Program of High-level Entrepreneurial and Innovative Talents in Jiangsu Province(individual and group programs)financial support from Nanjing Tech University(grant nos.39837123 and 39837132).
文摘The uranyl with two U=O double bonds is a wellknown and predominant form of uranium in the environment,but the carbon-based analog with two U=C double bonds has rarely been synthesized.Here,we describe the formation of an unprecedented uranium complex[(PyPh_(2)P)_(2)C]_(2)UCl_(2)]^(2+)·2(BPh_(4)^(−))from the reaction of UCl4 with carbodiphosphorane in the presence of NaBPh4.The nature of the U-C bonds was revealed by density functional theory calculations,which show that the 5f and 6d orbital electrons of uranium are remarkably involved in the U=C double bonds.The inspection of the bonding characteristics with an energy decomposition analysis suggests that the uranium-ligand bond may be alternatively described with double dative bonds[C⇉U⇇C]or strong electron-sharing π bonds and weak σ bonds.
文摘Highly efficient and selective carbon-carbon double bond aerobic cleavage of olefins catalyzed by metallopor- phyrins was investigated, and carbonyl compounds and epoxide were produced as the main products. CoTPP （co- balt meso-tetraphenyl porphyrin） showed excellent activity for the oxidative cleavage of carbon-carbon double bond by using styrene as model compound, in which the TOF （turnover frequency） and selectivity toward benzaldehyde was obtained with 2×10^4h-1 and 86%,respectively.
基金Project(29575190)supported by the National Natural Science Foundation of China and the Foundation of Bioorganic Molecular Engineering Laboratory(State Education Commission of China).
文摘A new formula was presented for locating double bond position in dodecenols, tetradcenols hexadecenols and their acetates, based on mass spectral data of dimethyl disulfide derivatives. In this procedure, molecular ion and base peak ion were utilized as characteristic parameters to identify the positional isomers. The method was tested with mass spectra of 25 dimethyl disulfide derivatives of mono-unsaturated acetates and alcohols, and the original double-bond position in each isomer was located unambiguously.
文摘A method for the identification of the double bond positional isomers of hexadecenyl acetate has been established by analysing similarity of the mass spectra patterns on a fuzzy classification, in which the intensity ratios of six diagnostic pairs of the predominant ions were selected as standard parameters for the characterization of the double bond position. The procedure was tested with △2 to △15-isomers of chemically unmodified hexadecenyl acetate, and the original double bond position in the acetates was located unambiguously.
基金partly supported by grants from the National Natural Science Foundation(NSFC31970187 to L.L.and NSFC31870253 to J.L.)funds from the South China Agricultural University+1 种基金Hong Kong Baptist Universitythe Hong Kong Jockey Club Charities Trust。
文摘Brassinosteroids(BRs)are essential plant steroids that regulate various growth and developmental processes(Nolan et al.,2020).Brassinosteroid biosynthesis involves multiple cytochrome P450 enzymes and a single nonCYP450 enzyme DET2(Zebosi et al.,2024),which was named after its dark“de-etiolated”mutant phenotype(Chory et al.,1991).DET2,an Arabidopsis homolog of the mammalian steroid 5α-reductases(SRD5As),catalyzes the reduction of theΔ^(4,5)double bond of 3-oxo-Δ^(4,5)sterols(Li et al.,1996;Fujioka et al.,1997)(Figure S1).
