DFT Studies on the Isomerization of Butene Double Bond Catalyzed by 1-Butyl-3-methyl-imidazolium in Ionic Liquid

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.

LOCATION OF DOUBLE BOND POSITION OF INSECT SEX PHEROMONE BY GC/MS ANALYSIS WITH CHEMICAL IONIZATION

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.

IDENTIFICATION OF DOUBLE BOND POSITION IN HEXADECENYL ACETATES BY MASS SPECTROMETRY

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.

A novel formula for location of double bond in alkenyl acetates and alcohols based on mass spectral data of dimethyl disulfide derivatives

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.

Copper/Palladium-Cocatalyzed Aerobic Synthesis of Bisaryl Ketones from Olefins via C-C Double Bonds Cleavage

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.

Mass spectrometric identification of double bond positional isomers of hexadecenyl acetate without chemical derivatization

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.

Theoretical study on non-sequential double ionization of carbon disulfide with different bond lengths in linearly polarizedlaser fields

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.

Introducing an Extended Covalent Bond between Oxygen Atoms with an OXO-Shape in Ions and Molecules: Compatibility with the Even-Odd and the Isoelectronicity Rules

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°.

Highly Efficient Oxidative Cleavage of Carbon-Carbon Double Bond over meso-Tetraphenyl Cobalt Porphyrin Catalyst in the Presence of Molecular Oxygen

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.

Chemo- and regioselective hydroboration of Δ^(14,15) in certain cephalostatin analogue

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.

Complex Featuring Two Double Dative Bonds Between Carbon(0)and Uranium

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.

THEORETICAL ANALYSIS OF HYDROGENATION MECHANISM CATALYZED BY Pd-Fe_2O_3/D_(3520)

The mechanism of catalytic hydrogenation of styrene is analyzed by catalysis theory and frontier molecular orbital theory.

Metal composition of layered double hydroxides(LDHs) regulating ClO_4^- adsorption to calcined LDHs via the memory effect and hydrogen bonding

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.

Reactive poly(divinyl benzene-co-maleic anhydride) nanoparticles:Preparation and characterization

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.

Genome mining of fungal globin-like enzymes for catalyzing the synthesis of linear terpenes

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.

Cascade reaction involving intramolecular oxygen-migration:Efficient synthesis of 3-allylidene-indolin-2-one compounds under metal-free conditions

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.

Putting aniline radical cations in a bottle

Salts containing aniline radical cations have been isolated and characterized by electron paramagnetic resonance(EPR)spectroscopy, UV-Vis absorption spectroscopy and single crystal X-ray diffraction. The EPR spectra and theoretical calculations indicate the unpaired electron is delocalized on phenyl rings and nitrogen atoms. Both radical cations feature a quinoidal geometry with a partially double C–N bond, but are distinct in that the C–N bond is coplanar to the phenyl plane in one cation while deviates from the plane in the other due to steric crowding. The work provides the first unequivocal examples of stable aniline radical cations.

Comprehensive Characterization of Phospholipid Isomers in Human Platelets

Lipids play an important role in platelet integrity and function.However,most of lipid molecular compositions in platelets still remain unknown,especially for phospholipids.In this work,we characterized detailed structures of different classes of phospholipids in human platelets.Using a flow microreactor,the acetone Paternò-Büchi reaction was introduced for online derivatization of carbon-carbon double bond(C=C)of lipids right after separation by liquid chromatography(LC).Tandem mass spectrometry(MS/MS)methods were developed for multi-level structural identification of phospholipids,including head group,chain composition,and C=C locations in the fatty acyl/alkyl chains.After optimization of the workflow,a total of 110 molecular species of phospholipids were identified in the human platelet samples,including many C=C location isomers.At lipid class level,phosphatidylserine was found more abundant in the platelet samples than that of the plasma samples;at isomer level,the relative ratio of C18:1(Δ9)vs C18:1(Δ11)also increased in platelet samples comparing with that of the plasma samples.The detailed structural information of phospholipids and their C=C isomers ratios would be useful for investigation of potential functions of human platelets potentially associated with phospholipid isomers.

Theoretical Investigation for Unexpected Transition Metal-π Interaction Enhanced Fluorescence in Cu-π-diborene

Unexpected transition metal(TM)-π interaction enhanced fluorescence in Cu-π-diborene complexes is a novel phenomenon compared with other metal enhanced fluorescence. In order to discover the mechanism, theoretical investigation was carried out for Cu-π-diborene as well as diborene. Simulation results show the main decay method in diborene and Cu-π-diborene are internal conversion(IC) and fluorescence(FL), respectively. TM-π interaction leads to larger HOMO-LUMO gap of Cu-π-diborene than that of the free diborene, which results in lower IC rates and makes them smaller than the FL rates. At the same time, ISC rates are always smaller than IC and FL rates, which cause enhanced fluorescence of Cu-π-diborene. More interestingly, even though Cu-π-diborene shows enhanced fluorescence, intersystem crossing(ISC) in Cu-π-diborene is enhanced from diborene. The theoretical analysis shows the competition among IC, FL and ISC is the key factor for TM-π interactions enhanced fluorescence, which also shows that cation-π complexes have potential to be used as luminescent probes.

Characteristics of mass spectra of dichlorocarbene derivatives of isomeric dodecen-1-ols

The m/z of characteristic ion of the mass spectra of the dichlorocarbene of dodecen-1-ols was used as a parameter to locate the position of double bond in these isomers by a new formula.