Showing papers on "Double bond published in 2005"

Characterization of high-molecular-weight sulfur-containing aromatics in vacuum residues using Fourier transform ion cyclotron resonance mass spectrometry.

Abstract: Millions of tons of vacuum residues are produced in refineries every year and could be a potentially valuable resource for generating electricity and has possible application as heating and marine fuel. In this work, the polycyclic aromatic sulfur compounds (PASHs) from the aromatic fraction of vacuum residue before and after partial hydrodesulfurization (HDS) were derivatized by methylation to the methylsulfonium salts. Fourier transform ion cyclotron resonance mass spectrometry provided high-resolution data on these high-molecular-weight sulfur compounds. Compounds containing one and two S atoms were found to dominate, with masses up to ca. 900 Da. Classification according to hydrogen deficiency and the number of heteroatoms showed extensive series of homologues for double bond equivalents from 5 to 20. The sulfur-containing aromatics were separated using a palladium(II) complex as a liquid chromatographic phase into two compound groups: one containing compounds with an unconjugated thiophene ring and another with a condensed thiophene ring. This, combined with the mass spectrometry (MS) data, allows for the identification of several parent structures. Partial HDS removed primarily compounds with one S atom, whereas those with two S atoms were largely unaffected.

Trimetallic nitride endohedral metallofullerenes: reactivity dictated by the encapsulated metal cluster.

Abstract: The first derivatives of Y3N@C80 have been synthesized and fully characterized. 1,3-Dipolar cycloaddition of N-ethylazomethine ylide yielded mainly the pyrrolidine monoadduct of the icosahedral (Ih) symmetry cage exclusively at a [6,6] double bond. The same regioselectivity on a [6,6] double bond was observed when the endohedral compound was cyclopropanated with diethyl bromomalonate. These results are in pronounced contrast to those observed for icosahedral symmetry Sc3N@C80, for which all reported derivatives add completely regioselectively to [5,6] double bonds. 1H NMR, 13C NMR, and HMQC spectroscopy revealed that the addition pattern on Y3N@C80 resulted in a pyrrolidinofullerene derivative with unsymmetric pyrrolidine carbons and symmetric geminal protons. The cyclopropanated monoadduct exhibited symmetric ethyl groups on the malonate, consistent with regioselective addition at a [6,6] double bond. Attempts to perform the same cyclopropanation reaction on (Ih) Sc3N@C80 failed to yield any identifiable...

Enhanced photocatalytic formation of hydroxyl radicals on fluorinated TiO2

Abstract: Direct experimental evidence of the higher concentration of hydroxyl radicals generated on fluorinated titanium dioxide (F–TiO2) under irradiation was obtained by spin-trapping EPR measurements. The faster photoinduced bleaching of the azo dye Acid Red 1 (AR1) observed in the presence of F–TiO2 was explained by the high affinity of the azo double bond towards ˙OH radicals. Moreover, the pronounced decrease of the AR1 bleaching rate by addition of 2-propanol, as hydroxyl radicals scavenger, on F–TiO2 and not on naked TiO2 demonstrated that on fluorinated titania AR1 is mainly degraded via ˙OH radical attack.

The nature of the chemical bond revisited: an energy-partitioning analysis of nonpolar bonds.

Abstract: The nature of the chemical bond in nonpolar molecules has been investigated by energy-partitioning analysis (EPA) of the ADF program using DFT calculations. The EPA divides the bonding interactions into three major components, that is, the repulsive Pauli term, quasiclassical electrostatic interactions, and orbital interactions. The electrostatic and orbital terms are used to define the nature of the chemical bond. It is shown that nonpolar bonds between main-group elements of the first and higher octal rows of the periodic system, which are prototypical covalent bonds, have large attractive contributions from classical electrostatic interactions, which may even be stronger than the attractive orbital interactions. Fragments of molecules with totally symmetrical electron-density distributions, like the nitrogen atoms in N(2), may strongly attract each other through classical electrostatic forces, which constitute 30.0 % of the total attractive interactions. The electrostatic attraction can be enhanced by anisotropic charge distribution of the valence electrons of the atoms that have local areas of (negative) charge concentration. It is shown that the use of atomic partial charges in the analysis of the nature of the interatomic interactions may be misleading because they do not reveal the topography of the electronic charge distribution. Besides dinitrogen, four groups of molecules have been studied. The attractive binding interactions in H(n)E-EH(n) (E=Li to F; n=0-3) have between 20.7 (E=F) and 58.4 % (E=Be) electrostatic character. The substitution of hydrogen by fluorine does not lead to significant changes in the nature of the binding interactions in F(n)E-EF(n) (E=Be to O). The electrostatic contributions to the attractive interactions in F(n)E-EF(n) are between 29.8 (E=O) and 55.3 % (E=Be). The fluorine substituents have a significant effect on the Pauli repulsion in the nitrogen and oxygen compounds. This explains why F(2)N-NF(2) has a much weaker bond than H(2)N-NH(2), whereas the interaction energy in FO-OF is much stronger than in HO-OH. The orbital interactions make larger contributions to the double bonds in HB=BH, H(2)C=CH(2), and HN=NH (between 59.9 % in B(2)H(2) and 65.4 % in N(2)H(2)) than to the corresponding single bonds in H(n)E-EH(n). The orbital term Delta E(orb) (72.4 %) makes an even greater contribution to the HC triple bond CH triple bond. The contribution of Delta E(orb) to the H(n)E=EH(n) bond increases and the relative contribution of the pi bonding decreases as E becomes more electronegative. The pi-bonding interactions in HC triple bond CH amount to 44.4 % of the total orbital interactions. The interaction energy in H(3)E-EH(3) (E=C to Pb) decreases monotonically as the element E becomes heavier. The electrostatic contributions to the E-E bond increases from E=C (41.4 %) to E=Sn (55.1 %) but then decreases when E=Pb (51.7 %). A true understanding of the strength and trends of the chemical bonds can only be achieved when the Pauli repulsion is considered. In an absolute sense the repulsive Delta E(Pauli) term is in most cases the largest term in the EPA.

Synthesis, crystal structure, and properties of MnNCN, the first carbodiimide of a magnetic transition metal.

Abstract: Synthesis, single-crystal structure determination, and magnetic properties are reported for manganese carbodiimide, MnNCN. The presumably unstable but inert phase adopts the trigonal system (R3m) with a = 3.3583(4) A, c = 14.347(2) A, V = 140.13(3) A3, and Z = 3. Divalent manganese is octahedrally coordinated by nitrogen atoms at 2.26 A, and the NCN2- unit adopts the linear [NCN]2- carbodiimide shape with two CN double bonds of 1.23 A. MnNCN contains high-spin Mn(II) with five unpaired electrons and behaves like an antiferromagnet with an ordering temperature below 30 K.

Correlation between Raman wavenumbers and P?O bond lengths in crystalline inorganic phosphates

Abstract: A linear empirical correlation was established between Raman stretching wavenumbers of phosphorus–oxygen bonds and their bond lengths in inorganic crystalline phosphates. Although established on samples of inorganic crystalline phosphates, the correlation can be applied to glassy and amorphous phosphate materials (GAMs). Their unpolarized vibrational spectra are often similar because they are determined largely by short-range order. The correlation was used to predict PO bond length in the α-form of Li3PO4, which is stable over only a small range of temperatures below the melting-point. It can also be used to estimate the length of PO single bonds, terminal PO and OPO chain bonds and terminal double bonds in many technologically important amorphous materials containing phosphate groups. This correlation is expected to offer invaluable insight into the structures of phosphate species for which diffraction or other spectroscopic techniques provide incomplete structural information. That would enhance the value of Raman spectroscopy as a complementary technique in structural studies of phosphates. Copyright © 2004 John Wiley & Sons, Ltd.

A facile synthesis and properties of multicarbazole molecules containing multiple vinylene bridges.

Abstract: Multibranched π-conjugated materials and hyperbranched polymers have received considerable interest in both academic research and industrial applications because of their unusual molecular structures and properties. In this communication, we provide an efficient approach to synthesize two novel π-conjugated multibranch compounds, which have good solubility and are nanosize (about 5 nm). The double bonds of the multibranch compounds are synthesized using solvent-free Wittig−Horner−Emmons reactions. The reaction conditions are simple and mild. Their optical properties are discussed too.

Pd(II)-Bipyridine Catalyzed Conjugate Addition of Arylboronic Acid to α,β-Unsaturated Carbonyl Compounds

Abstract: A Pd(II)-catalyzed conjugate addition of arylboronic acid to α,β-unsaturated ketones, aldehydes, esters, etc. in the presence of 2,2‘-bipyridine was developed. A mechanism involving transmetalation, insertion of the carbon−carbon double bond into the C−Pd bond, and protonolysis of the resulting C−Pd bond is proposed. The reaction conditions are mild and the yield is high. The presence of 2,2‘-bipyridine is crucial for the reaction to inhibit β-hydride elimination.

Two-photon photosensitized production of singlet oxygen: sensitizers with phenylene-ethynylene-based chromophores.

Abstract: Singlet molecular oxygen (a1Δg) has been produced and optically monitored in time-resolved experiments upon nonlinear two-photon excitation of photosensitizers that contain triple bonds as an integral part of the chromophore. Both experiments and ab initio computations indicate that the photophysical properties of alkyne-containing sensitizers are similar to those in the alkene-containing analogues. Most importantly, however, in comparison to the analogue that contains double bonds, the sensitizer containing alkyne moieties is more stable against singlet-oxygen-mediated photooxygenation reactions. This increased stability can be advantageous, particularly with respect to two-photon singlet oxygen imaging experiments in which data are collected over comparatively long time periods.

ζ-Carotene cis isomers as products and substrates in the plant poly- cis carotenoid biosynthetic pathway to lycopene

Abstract: The plant carotenoid biosynthetic pathway to cyclic carotenes proceeds via carotene precursors in cis configuration. Involvement of individual isomers was elucidated by genetic complementation of desaturations and in vitro reactions of the corresponding enzyme. Determination of substrate and product specificity of phytoene and ζ-carotene desaturase revealed that 15-cis-phytoene is converted to 9,15,9′-tricis-ζ-carotene with 15,9′-dicis-phytofluene as intermediate by the first desaturase. Prior to a subsequent conversion by ζ-carotene desaturase, the 15-cis double bond of 9,15,9′-tricis-ζ-carotene has to be (photo)isomerized to all-trans. Then, the resulting 9,9′-dicis-ζ-carotene is utilized by ζ-carotene desaturase via 7,9,9′-tricis-neurosporene to 7,9,7′,9′-tetracis-lycopene. Other ζ-carotene isomers that are assumed to be spontaneous isomerization products were not converted, except for the asymmetric 9-cis-ζ-carotene. This isomer is desaturated only to 7,9-dicis-neurosporene resembling a dead-end of the pathway. Prolycopene, the product of the desaturation reactions, is finally isomerized by a specific isomerase to all-trans-lycopene, which is a prerequisite for cyclization to β-carotene. The 5-cis-lycopene and the 9-cis-and 13-cis-β-carotene isomers detected in leaves are thought to originate independently from cis precursors by non-enzymatic isomerization of their all-trans forms.

Structure-activity relationships for reactivity of carbonyl-containing compounds with glutathione

Abstract: For toxicological-based structure-activity relationships to advance, will require a better understanding of molecular reactivity. A rapid and inexpensive spectrophotometric assay for determining the reactive to glutathione (GSH) was developed and used to determine GSH reactivity (reactGSH) data for 21 aliphatic derivatives of esters, ketones and aldehydes. From these data, a series of structure-activity relationships were evaluated. The structure feature associated with reactGSH was an acetylenic or olefinic moiety conjugated to a carbonyl group (i.e. polarized alpha,beta-unsaturation). This structure conveys the capacity to undergo a covalent interaction with the thiol group of cysteine (i.e. Michael- addition). Quantitatively reactGSH of the alpha,beta-unsaturated carbonyl compounds is reliant upon the specific molecular structure with several tendencies observed. Specifically, it was noted that for alpha,beta-unsaturated carbonyl compounds: (1) the acetylenic-substituted derivatives were more reactive than the corresponding olefinic-substituted ones; (2) terminal vinyl-substituted derivatives was more reactive than the internal vinylene-substituted ones; (3) methyl substitution on the vinyl carbon atoms diminishes reactivity and methyl-substitution on the carbon atom farthest from the carbonyl group causes a larger reduction; (4) derivatives with carbon-carbon double bond on the end of the molecule (i.e. vinyl ketone) were more reactive than one with the carbon-oxygen bond at the end of the molecule (i.e. aldehyde) and (5) the ester with an additional unsaturated vinyl groups were more reactive than the derivative having an unsaturated ethyl group.

The Dichotomy of Dimetallocenes: Coaxial versus Perpendicular Dimetal Units in Sandwich Compounds

Abstract: Theoretical studies of the dimetallocene (η5-C5H5)2Zn2 lead to optimized D5h or D5d structures in which the Zn−Zn bond is coaxial with the C5 axes of the two Cp rings, with a Zn−Zn distance of 2.33 A, corresponding to a Zn−Zn single bond. (η5-C5H5)2Ni2 (singlet state) and (η5-C5H5)2Cu2 (triplet) have similar structures with a Ni⋮Ni triple bond (2.06 A) and a CuCu double bond (2.22 A). However, DFT computations on (C5H5)2Ni2 and (C5H5)2Cu2 (both singlet states) lead to a totally different type of optimized structure (Ci symmetry) lying at significantly lower energies, with the metal−metal bonds perpendicular to the C5 axes of the Cp rings.

The First Fulleropyrrolidine Derivative of Sc3N@C80: Pronounced Chemical Shift Differences of the Geminal Protons on the Pyrrolidine Ring

Abstract: The first pyrrolidine adduct on Sc3N@C80 was synthesized and fully characterized. Addition of the N-ethylazomethine ylide occurs regioselectively on a [5,6] double bond on the surface of the icosahedral symmetry Sc3N@C80, exactly in the same position as that described previously for a Diels−Alder adduct of the same compound.11a,b This addition pattern results in symmetric pyrrolidine carbons and unsymmetric geminal hydrogens on the pyrrolidine ring, as confirmed by 1H and 13C NMR spectroscopy, especially by HMQC. The shielding environment experienced by these geminal hydrogens differs by 1.26 ppm, indicative of pronounced ring current effects on the surface of this endohedral fullerene. This represents the first fully characterized pyrrolidine adduct on an endohedral metallofullerene.

Synthesis and characterization of novel biodegradable unsaturated poly(ester amide)s

Abstract: A series of novel biodegradable unsaturated poly(ester amide)s (UPEAs) were synthesized through the solution polycondensation of two unsaturated monomers, di-p-nitrophenyl fumarate and L-phenylalanine 2-butene-1,4-diol diester p-toluene sulfonate, and four other saturated monomers in different combinations. The UPEAs were obtained in fairly good yields with N,N-dimethylacetamide (DMA) as the solvent. The number-average and weight-average molecular weights of the UPEAs, measured by gel permeation chromatography, ranged from 10 to 30 kg/mol, they had a rather narrow molecular weight distribution of 1.40. The chemical structures of the novel biodegradable UPEAs were confirmed by both IR and NMR spectra. The UPEAs had higher glass-transition temperatures than saturated PEAs of similar structures, and their glass-transition temperatures were affected more by the C=C double bond located in the diamide part than by those in the diester part. The solubility of the polymers was poor in water but better in DMA and dimethyl sulfoxide. With the availability of these inherent C=C double bonds in the UPEA backbones, these UPEAs have the functionality of C=C bonds, such as photochemical reactivity or the ability to react with or be modified by other bioactive or other environmentally sensitive compounds, and this can easily extend their applications to biomedical and pharmaceutical areas.

Supramolecular interactions induced fluorescence in crystal: Anomalous emission of 2,5-diphenyl-1,4-distyrylbenzene with all cis double bonds

Abstract: 2,5-Diphenyl-1,4-distyrylbenzene with all cis double bonds shows strong fluorescence in crystal, which is due to the chemical processes, c.a. isomerization and photocyclization being limited by the lattice packing.

Binuclear Cyclopentadienylcobalt Carbonyls: Comparison with Binuclear Iron Carbonyls

Abstract: The binuclear cyclopentadienylcobalt carbonyls Cp2Co2(CO)n (n = 3, 2, 1; Cp = η5-C5H5) are studied by density functional theory using the B3LYP and BP86 functionals. The experimentally known monobridged isomer Cp2Co2(CO)2(μ-CO) and the tribridged isomer Cp2Co2(μ-CO)3 of Cp2Co2(CO)3 with formal Co−Co single bonds are found to be similar in energy, with the precise relative energies of the two isomers depending on the functional chosen. For Cp2Co2(CO)2, the experimentally known coaxial isomer Cp2Co2(μ-CO)2 with two bridging CO groups and a formal CoCo double bond (2.360 A by B3LYP or 2.346 A by BP86) is found to lie 38.2 (B3LYP) or 34.9 kcal/mol (BP86) below a perpendicular isomer ⊥-Cp2Co2(CO)2. Similarly, for Cp2Co2(CO), the coaxial isomer Cp2Co2(μ-CO) with one bridging CO group and a formal Co⋮Co triple bond (2.021 A by B3LYP or 2.050 A by BP86) is found to lie 9.36 (B3LYP) or 9.62 kcal/mol (BP86) below the corresponding perpendicular isomer ⊥-Cp2Co2(CO). This coaxial isomer Cp2Co2(μ-CO) is a possible int...

On the influence of the position of the double bond on the low-temperature chemistry of hexenes

Abstract: The chemistry of oxidation and autoignition of 1-, 2-, and 3-hexene has been studied after rapid compression between 630 and 850 K for stoichiometric mixtures with “air.” The phenomenology of autoignition has been recognized, and intermediate products formed before autoignition have been identified and analyzed. They mainly comprise of hexadienes, O-heterocycles, and aldehydes. There are many common products, because some of the intermediate alkenyl or alkenylperoxy radicals are delocalized. Saturated O -heterocycles are specific products formed by addition of HO 2 to the double bond. Unsaturated O-heterocycles are products typical of the long alkenyl chain. Saturated and unsaturated lower aldehydes are the products of OH addition to the double bond of hexenes and hexadienes. The relative abundance of the intermediates enables a better insight into the competition between the reactivity of the double bond and the reactivity of the alkenyl chain. According to the position of the double bond, the behavior of 3-hexene is dominated by the properties of the double bond whereas the behavior of 1-hexene is dominated by the properties of the alkenyl chain. The reactivity of the alkenyl chain is related to the type and number of C–H bonds, the ability of stabilized radicals to react, and the cyclic strain of the transition state of isomerization reactions. Therefore, 1-hexene reacts much more with the typical features of alkanes like a two-stage ignition with a cool flame and a negative temperature coefficient. 3-Hexene does not have typical features and 2-hexene has an intermediate behavior.

Pyrrolobenzodiazepines as key intermediates in the synthesis of dimeric cytotoxic pyrrolobenzodiazepines

Abstract: Compounds and a method of synthesis of compounds of formula (Ia) or (Ib): and salts, solvates, and chemically protected forms thereof, wherein the dotted lines indicate the optional presence of a double bond between C1 and C2 or C2 and C3; R2 and R3 are independently selected from -H, =O, =CH2, -CN, -R, OR, halo, =CH-R, O-SO2-R, CO2R and COR; R10 is a carbamate-based nitrogen protecting group; and R11 is an oxygen protecting group.

Quantum Chemical Calculation Studies on 4-Phenyl-1-(Propan-2-Ylidene)Thiosemicarbazide

Abstract: Ab initio calculations of the structure, atomic charges, natural bond orbital, and thermodynamic functions have been performed at HF/6-311G∗∗ and B3LYP/6-311G∗∗ levels of theory for the title compound of 4-phenyl-1-(propan-2-ylidene)thiosemicarbazide. The calculated results show that the sulfur atom and all of the nitrogen atoms have bigger negative charges and they are the potential sites to react with the metallic ions, which make the title compound become a multidentate ligand. The coordination ability of the sulfur atom and the nitrogen atom of C=N double bond will increase with the increase of the polarity of the solvent. Electronic absorption spectra have been calculated by time-dependent density functional theory (TD-DFT) method. The calculation of the second-order optical nonlinearity also has been carried out, and the molecular hyperpolarizability is 3.068×10−30 esu.

Antireflection film material, substrate having antireflection film and pattern forming method

Abstract: PROBLEM TO BE SOLVED: To provide an antireflection film material having an excellent antireflection effect on exposure at short wavelengths, having a high etching selection ratio and showing little changes in the film thickness even in long-term storage. SOLUTION: The antireflection film material to be used for lithography comprises: an antireflection silicone resin containing at least an organic group having a carbon-oxygen single bond and/or a carbon-oxygen double bond, a light-absorbing group and silicon atoms having Si-OH and/or Si-OR at an end; an organic solvent containing at least one kind or more of ether bond, carbonyl bond and ester bond in the molecule and having one or more hydroxyl groups; and an acid generating agent. Further, the organic solvent containing at least one kind or more of ether bond, carbonyl bond and ester bond in the molecule and having one or more hydroxyl groups is included by 60 mass% or more of the whole organic solvent. COPYRIGHT: (C)2007,JPO&INPIT

Molecular Structure of Glucopyranosylamide Lipid and Nanotube Morphology

Abstract: A series of glucopyranosylamide lipids, N-(X-octadecenoyl)-β-d-glucopyranosylamine [X = 13-cis (1), 11-cis (2), 9-cis (3), 6-cis (4), and 9-cis,12-cis (5)] and their saturated homologue N-octadecanoyl-β-d-glucopyranosylamine (6), which differ in the position of a cis double bond in the C18 hydrocarbon chains, have been synthesized. The effect of the cis double bond position on the chiral self-assembly of each glycolipid has been examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV, and circular dichroism (CD). The 11-cis derivative 2 was observed to self-assemble in water to form a uniform hollow cylinder structure with about 200-nm outer diameters in >98% yields. The obtained nanotubes from 2 showed the narrowest distribution of outer diameters and also gave a negative CD band around 234−236 nm, showing the largest CD intensity among the glycolipids investigated. Thus, we found that the position of a cis double bond significantly influences the homogeneity of ...

Synthesis and characterization of a coordinated oxoborane: Lewis acid stabilization of a boron-oxygen double bond

Abstract: The first example of a stable oxoborane monomer (LBO) stabilized by complexation to AlCl3 has been prepared by the reaction of LAlCl2 with BCl3 followed by treatment with H2O in CH2Cl2 (L = [HC(CMe)2(NC6F5)2]). DFT calculations reveal that considerable boron−oxygen double bond character is retained in this complex.

Structure, spectroscopy, and spectral tuning of the gas-phase retinal chromophore : The β-ionone handle and alkyl group effect

Abstract: The low-lying singlet states (i.e. S0, S1, and S2) of the chromophore of rhodopsin, the protonated Schiff base of 11-cis-retinal (PSB11), and of its all-trans photoproduct have been studied in isolated conditions by using ab initio multiconfigurational second-order perturbation theory. The computed spectroscopic features include the vertical excitation, the band origin, and the fluorescence maximum of both isomers. On the basis of the S0-->S1 vertical excitation, the gas-phase absorption maximum of PSB11 is predicted to be 545 nm (2.28 eV). Thus, the predicted absorption maximum appears to be closer to that of the rhodopsin pigment (2.48 eV) and considerably red-shifted with respect to that measured in solution (2.82 eV in methanol). In addition, the absorption maxima associated with the blue, green, and red cone visual pigments are tentatively rationalized in terms of the spectral changes computed for PSB11 structures featuring differently twisted beta-ionone rings. More specifically, a blue-shifted absorption maximum is explained in terms of a large twisting of the beta-ionone ring (with respect to the main conjugated chain) in the visual S-cone (blue) pigment chromophore. In contrast, the chromophore of the visual L-cone (red) pigment is expected to have a nearly coplanar beta-ionone ring yielding a six double bond fully conjugated framework. Finally, the M-cone (green) chromophore is expected to feature a twisting angle between 10 and 60 degrees. The spectroscopic effects of the alkyl substituents on the PSB11 spectroscopic properties have also been investigated. It is found that they have a not negligible stabilizing effect on the S1-S0 energy gap (and, thus, cause a red shift of the absorption maximum) only when the double bond of the beta-ionone ring conjugates significantly with the rest of the conjugated chain.

Pressure-induced polymerization in solid ethylene.

Abstract: Ethylene is the simplest organic molecule containing a double bond and is the starting monomeric unit in the synthesis of polyethylene, one of the most largely produced polymers. Here we report a high pressure infrared study of ethylene at room temperature. A polymerization reaction is observed when the crystalline phase I is compressed above 3.0 GPa. The reaction kinetics was investigated at two different pressures, 3.6 and 5.4 GPa. The recovered product was identified in both cases as polyethylene, but while a conformationally disordered and branched low-density polymer is obtained at the highest pressure, a high-density crystalline polymer is obtained at 3.6 GPa. A reaction mechanism was proposed on the basis of the kinetic data and the structural information.