Showing papers on "Ethylene published in 2008"
TL;DR: In an effort to identify catalysts based on less expensive and more available metals, density functional calculations were performed that identified relations in heats of adsorption of hydrocarbon molecules and fragments on metal surfaces that verified the facility of known catalysts.
Abstract: The removal of trace acetylene from ethylene is performed industrially by palladium hydrogenation catalysts (often modified with silver) that avoid the hydrogenation of ethylene to ethane. In an effort to identify catalysts based on less expensive and more available metals, density functional calculations were performed that identified relations in heats of adsorption of hydrocarbon molecules and fragments on metal surfaces. This analysis not only verified the facility of known catalysts but identified nickel-zinc alloys as alternatives. Experimental studies demonstrated that these alloys dispersed on an oxide support were selective for acetylene hydrogenation at low pressures.
928 citations
TL;DR: The gaseous plant hormone ethylene plays important roles in plant growth and development and is affected by the rapid degradation of ethylene receptors upon ethylene binding and by dependence on a novel protein REVERSION-TO-ETHYLENE SENSITIVITY1 (RTE1)/GREEN-RIPE (GR).
258 citations
TL;DR: In this paper, the catalytic activity of the SBA-15 supported polyaminoamide (PAMAMAM) dendrimer was studied with ethylene hydrogenation at 273 and 293 K in 10 torr of ethylene and 100 torr H2 after reduction.
Abstract: Monodisperse rhodium (Rh) and platinum (Pt) nanoparticles as small as ∼1 nm were synthesized within a fourth generation polyaminoamide (PAMAM) dendrimer, a hyperbranched polymer, in aqueous solution and immobilized by depositing onto a high-surface-area SBA-15 mesoporous support. X-ray photoelectron spectroscopy indicated that the as-synthesized Rh and Pt nanoparticles were mostly oxidized. Catalytic activity of the SBA-15 supported Rh and Pt nanoparticles was studied with ethylene hydrogenation at 273 and 293 K in 10 torr of ethylene and 100 torr of H2 after reduction (76 torr of H2 mixed with 690 torr of He) at different temperatures. Catalysts were active without removing the dendrimer capping but reached their highest activity after hydrogen reduction at a moderate temperature (423 K). When treated at a higher temperature (473, 573, and 673 K) in hydrogen, catalytic activity decreased. By using the same treatment that led to maximum ethylene hydrogenation activity, catalytic activity was also evaluate...
254 citations
TL;DR: Data pertaining to ethylene biology specifically as related to fruit maturation is summarized and including recent insights into genetic control of the ripening process prior to and controlling ethylene are summarized.
183 citations
TL;DR: It is concluded that ethylene signaling in rice may be more intricate than in Arabidopsis and may have specific signaling outputs in semiaquatic plants such as rice as was shown for Yang cycle regulation.
165 citations
TL;DR: In this paper, the authors compared the performance and stability of four catalysts in the dehydration of ethanol to ethylene using X-ray powder diffraction (XRD), Infrared Spectroscopy (FT-IR), H2 temperature-programmed reduction (H2-TPR) technique and NH3 temperatureprogrammed desorption (NH3-TPD) technique.
156 citations
TL;DR: Copper-containing mesoporous silica HMS catalysts were prepared by an impregnation method as mentioned in this paper, and the surface structures of these catalysts are characterized by N 2 -physisorption, X-ray diffraction, transmission electron microscopy, H 2 temperature-programmed reduction, Fourier transform infrared spectroscopy, N 2 O titration and Xray photoelectron spectroscope.
Abstract: Copper-containing mesoporous silica HMS catalysts were prepared by an impregnation method. The surface structures of these catalysts were characterized by N 2 -physisorption, X-ray diffraction, transmission electron microscopy, H 2 temperature-programmed reduction, Fourier transform infrared spectroscopy, N 2 O titration and X-ray photoelectron spectroscopy. The results show that the copper-containing HMS catalysts exhibit superior catalytic performance in the selective hydrogenation of dimethyl oxalate to ethylene glycol compared to the commercial silica-supported ones obtained by the same method. The dimethyl oxalate conversion can reach 100% and the ethylene glycol selectivity can reach 92% at 473 K with 2.5 MPa H 2 pressure and 0.2 h −1 liquid hour space velocity of dimethyl oxalate over the 5 wt.% Cu-HMS catalyst. The enhanced catalytic performance of copper-HMS catalysts may be attributed to the homogeneous dispersion and uniformity of the active copper species and to the larger copper surface areas attained on the HMS supports with large pore diameters and surface areas.
133 citations
TL;DR: In this article, a Ni(II)Al(III) catalyst was synthesized from a lamellar double hydroxides (LDH) precursor and tested in ethanol steam reforming.
123 citations
TL;DR: Bis(phenoxy-imine) Ti complexes bearing a phenyl group ortho to the phenoxy-O can mediate the copolymerization of ethylene and 5-hexene-1-yl-acetate though they are group 4 transition metal catalysts.
Abstract: Bis(phenoxy−imine) Ti complexes bearing a phenyl group ortho to the phenoxy-O can mediate the copolymerization of ethylene and 5-hexene-1-yl-acetate though they are group 4 transition metal catalysts.
116 citations
TL;DR: It is observed that ethylene application at véraison led to a berry diameter increase, mainly because of sap intake and cell wall modifications, enabling cell elongation, which brings more clues about the ethylene involvement in the development and ripening of grape berries.
Abstract: Grape is considered as a non-climacteric fruit, the maturation of which is independent of ethylene. However, previous work had shown that ethylene is capable of affecting the physiological processes during maturation of grape berries. Experiments were designed to screen the gene pool affected by ethylene at the ripening inception in Cabernet Sauvignon berries. The results showed that only 73 of 14 562 genes of microarray slides were significantly modulated by a 24-h ethylene treatment (4 microl l(-1)), performed 8 weeks after flowering. The study then focused on accumulation of several mRNAs affected by ethylene in relation to the berry size. Indeed, we observed that ethylene application at veraison led to a berry diameter increase. This increase is mainly because of sap intake and cell wall modifications, enabling cell elongation. This was related to changes in the expression pattern of many genes, classified in two groups: (1) 'water exchange' genes: various aquaporins (AQUA) and (2) 'cell wall structure' genes: polygalacturonases, xyloglucan endotransglucosylases (XTH), pectin methyl esterases, cellulose synthases and expansins. The expression patterns were followed either along berry development or in three berry tissues (peel, pulp and seeds). Ethylene stimulates the accumulation of most gene transcripts in 1 h, and in several parts of the berry, this stimulation may last for 24 h in some cases. One XTH and one AQUA seem to be good candidates to explain the ethylene-induced berry expansion. This work brings more clues about the ethylene involvement in the development and ripening of grape berries.
110 citations
TL;DR: The ethylene-induced down-regulation of AdETR1 suggests that it may have a role in sensing ethylene and transmitting this response to other members of the receptor family, thus activating the signal transduction pathway.
Abstract: Gene families associated with the ethylene signal transduction pathway in ripening kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward) were isolated from a kiwifruit expressed sequence tag (EST) database, including five ethylene receptor genes, two CTR1-like genes, and an EIN3-like gene AdEIL1. All were differentially expressed among various kiwifruit vine tissues, and none was fruit specific. During fruit development, levels of transcripts of AdERS1a, AdETR3, and the two CTR1-like genes decreased, whereas those of AdERS1b and AdETR2 peaked at 97 d after full bloom. In ripening kiwifruit, there was a diverse response of the ethylene receptor family to internal and external ethylene. AdERS1a, AdETR2, and AdETR3 expression increased at the climacteric stage and transcripts were induced by external ethylene treatment, while AdERS1b showed no response to ethylene. AdETR1 was negatively regulated by internal and external ethylene in ripening fruit. The two CTR1-like genes also had different expression patterns, with AdCTR1 increasing at the climacteric stage and AdCTR2 undergoing little change. 1-Methylcyclopropene treatment prevented the ethylene response of all components, but transient down-regulation was only found with AdETR2 and AdCTR1. Similar gene and ethylene responses were found in both fruit flesh and core tissues. The ethylene-induced down-regulation of AdETR1 suggests that it may have a role in sensing ethylene and transmitting this response to other members of the receptor family, thus activating the signal transduction pathway.
TL;DR: Cycloaddition-desulfonylation strategy has been applied as a key step in the enantioselective synthesis of a biologically active C-azanucleoside.
Abstract: Enantioenriched 3-pyrrolines have been synthesized by highly enantioselective Fesulphos-Cu-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with trans-1,2-bisphenylsulfonyl ethylene, followed by reductive sulfonyl elimination. High levels of reactivity, exoselectivity, and enantioselectivity have been accomplished for a variety of substituted azomethine ylides. This cycloaddition−desulfonylation strategy has been applied as a key step in the enantioselective synthesis of a biologically active C-azanucleoside.
TL;DR: In this article, monodispersed Pd nanoparticles of 5 and 10 nm were obtained via reduction of Pd(acac)2 dissolved in ionic liquid (IL), supported on carbon nanofibers anchored to sintered metal fibers (SMF).
Abstract: Monodispersed Pd nanoparticles of 5 and 10 nm were obtained via reduction of Pd(acac)2 dissolved in ionic liquid (IL), [bmim][PF6], or [bmimOH][TF2N], supported on carbon nanofibers (CNF) anchored to sintered metal fibers (SMF). Using [bmimOH][TF2N], the monodispersed Pd nanoparticles were synthesized by simple heating in the absence of an additional reducing agent. The supported ionic liquid phase Pd nanoparticles on the structured CNF/SMF composites were tested for the selective hydrogenation of acetylene to ethylene and showed excellent long-term stability. The IL cation-anion network surrounding the nanoparticles suppressed the formation of active-site ensembles, known to catalyze the oligomerization of acetylene, responsible for the catalyst deactivation. The reaction rate was controlled by the internal diffusion of the reactants through the IL phase. The solubility of acetylene and ethylene in [bmim][PF6] was analyzed by NMR spectroscopy, which showed an order of magnitude difference. The lower solubility of ethylene compared to acetylene in the IL results in a high selectivity to ethylene, up to 85% at 150 °C. The catalytic system also demonstrated high efficiency and long-term stability without any deactivation in ethylene-rich feed (2 vol % of acetylene, 40 vol % of ethylene, 10 vol % of H2 in Ar), and therefore, the system shows promise for industrial application.
TL;DR: It is proposed that the mode of action of cyanide in sunflower seed dormancy alleviation does not involve ethylene production and that ERF1 is a common component of the ethylene and cyanide signalling pathways.
Abstract: Freshly harvested sunflower (Helianthus annuus L.) seeds are considered to be dormant because they fail to germinate at relatively low temperatures (10 °C). This dormancy results mainly from an embryo dormancy and disappears during dry storage. Although endogenous ethylene is known to be involved in sunflower seed alleviation of dormancy, little attention had been paid to the possible role of cyanide, which is produced by the conversion of 1-aminocyclopropane 1-carboxylic acid to ethylene, in this process. The aims of this work were to investigate whether exogenous cyanide could improve the germination of dormant sunflower seeds and to elucidate its putative mechanisms of action. Naked dormant seeds became able to germinate at 10 °C when they were incubated in the presence of 1 mM gaseous cyanide. Other respiratory inhibitors showed that this effect did not result from an activation of the pentose phosphate pathway or the cyanide-insensitive pathway. Cyanide stimulated germination of dormant seeds in the presence of inhibitors of ethylene biosynthesis, but its improving effect required functional ethylene receptors. It did not significantly affect ethylene production and the expression of genes involved in ethylene biosynthesis or in the first steps of ethylene signalling pathway. However, the expression of the transcription factor Ethylene Response Factor 1 (ERF1) was markedly stimulated in the presence of gaseous cyanide. It is proposed that the mode of action of cyanide in sunflower seed dormancy alleviation does not involve ethylene production and that ERF1 is a common component of the ethylene and cyanide signalling pathways.
TL;DR: In this paper, an autocatalytic burst of fruit ethylene production and accelerated fruit softening were associated with increased expression of genes related to ethylene biosynthesis (MdACS and MdACO), whereas reduced expression of an ethylene signal transduction gene (mdCTR1), and increased expression related to cell wall degradation (mddEG) in the fruit cortex occurred during fruit ripening.
Abstract: Expression of genes for ethylene biosynthesis, ethylene perception, and cell wall degradation in the fruit cortex and abscission zone was examined during fruit abscission and ripening in ‘Delicious’ apples (Malus × domestica). An autocatalytic burst of fruit ethylene production and accelerated fruit softening were associated with increased expression of genes related to ethylene biosynthesis (MdACS and MdACO), whereas reduced expression of ethylene receptor genes (MdETR and MdERS), increased expression of an ethylene signal transduction gene (MdCTR1), and increased expression of genes related to cell wall degradation (MdPG and MdEG) in the fruit cortex occurred during fruit ripening. Aminoethoxyvinylglycine (AVG) or 1−methylcyclopropene (1-MCP) inhibited fruit ethylene production, suppressed expression of MdACS1, MdACO1, MdERS1, and MdPG1 in the fruit cortex, and delayed fruit softening, whereas naphthaleneacetic acid (NAA) increased fruit ethylene production, increased expression of MdACS1, MdACO1, MdERS1 and MdPG1 in the fruit cortex, and accelerated fruit softening. Fruit abscission and expression of MdACS5A, MdACS5B, MdACO1, MdPG2, and MdEG1 in the fruit abscission zone were reduced by AVG and 1-MCP. NAA also reduced fruit abscission while reducing expression of MdPG2 and MdEG1 only in the fruit abscission zone. The levels of MdETR1, MdETR2, MdERS1, and MdERS2 transcripts in the fruit abscission zone decreased during fruit abscission and fruit ripening regardless of treatment. The combination of NAA and AVG was more effective in inhibiting expression of MdPG2 and MdEG1 in the fruit abscission zone and reducing fruit abscission than was either NAA or AVG used alone.
TL;DR: In this article, the behavior of catalysts was evaluated in relation to their texture and nickel cations/acid sites ratio, and the results showed that NiMCM-36 catalysts, with large accessibility in the mesoporous structure and mild acidity, showed an excellent activity (46 g of oligomers/g catalyst h) and selectivity (100% olefins with even number of carbon atoms) in ethylene oligomerization.
Abstract: Nickel ion-exchanged MCM-36 and MCM-22 zeolites were prepared, characterized, and tested in the ethylene oligomerization reaction performed in slurry semi-batch mode (T = 70–150 °C, p = 4 MPa). The behavior of catalysts was evaluated in relation to their texture and nickel cations/acid sites ratio. NiMCM-36 catalysts, with large accessibility in the mesoporous structure and mild acidity, showed an excellent activity (46 g of oligomers/gcatalyst h) and selectivity (100% olefins with even number of carbon atoms) in ethylene oligomerization, while lower catalytic activity and selectivity were observed over NiMCM-22 possessing microporous structure and high acid sites concentration.
TL;DR: The new binuclear phenoxyiminato zirconium complex {1,7-(O)2C10H4-2,7-[CH=N(2,6-iPr2C6H3)]2}Zr2Cl6(THF)2 (FI2- Zr2) polymerizes ethylene with greater activity (approximately 8x) than the mononuclear analogue.
Abstract: The new binuclear phenoxyiminato zirconium complex {1,7-(O)2C10H4-2,7-[CHN(2,6-iPr2C6H3)]2}Zr2Cl6(THF)2 (FI2-Zr2) polymerizes ethylene with greater activity (∼8×) than the mononuclear analogue. Also, this catalyst produces high molecular weight ethylene + 1-hexene copolymers, while the mononuclear analogue yields only traces of copolymer under identical conditions. This ability to produce copolymers suggests cooperativity between the two Zr centers which promotes 1-hexene co-enchainment.
TL;DR: The results indicate that ethylene biosynthesis in gynoecia is regulated developmentally, rather than autocatalytically, and ethylene may regulate flower opening mainly through the Rh-ETR3 gene in gynaecia.
Abstract: Ethylene production, as well as the expression of ethylene biosynthetic (Rh-ACS1-4 and Rh-ACO1) and receptor (Rh-ETR1-5) genes, was determined in five different floral tissues (sepals, petals, stamens, gynoecia, and receptacles) of cut rose (Rosa hybrida cv. Samantha upon treatment with ethylene or the ethylene inhibitor 1-methylcyclopropene (1-MCP). Ethylene-enhanced ethylene production occurred only in gynoecia, petals, and receptacles, with gynoecia showing the greatest enhancement in the early stage of ethylene treatment. However, 1-MCP did not suppress ethylene production in these three tissues. In sepals, ethylene production was highly decreased by ethylene treatment, and increased dramatically by 1-MCP. Ethylene production in stamens remained unchanged after ethylene or 1-MCP treatment. Induction of certain ethylene biosynthetic genes by ethylene in different floral tissues was positively correlated with the ethylene production, and this induction was also not suppressed by 1-MCP. The expression of Rh-ACS2 and Rh-ACS3 was quickly induced by ethylene in gynoecia, but neither Rh-ACS1 nor Rh-ACS4 was induced by ethylene in any of the five tissues. In addition, Rh-ACO1 was induced by ethylene in all floral tissues except sepals. The induced expression of ethylene receptor genes by ethylene was much faster in gynoecia than in petals, and the expression of Rh-ETR3 was strongly suppressed by 1-MCP in all floral tissues. These results indicate that ethylene biosynthesis in gynoecia is regulated developmentally, rather than autocatalytically. The response of rose flowers to ethylene occurs initially in gynoecia, and ethylene may regulate flower opening mainly through the Rh-ETR3 gene in gynoecia.
TL;DR: In this paper, a two-step tandem strategy combining Pd−diimine catalyzed ethylene living polymerization and atom transfer radical polymerization (ATRP) for the synthesis of functionalized polyethylene (PE) diblock copolymers containing an ethylene block and a functional monomer block, such as styrene and n-butyl acrylate.
Abstract: We report a new two-step tandem strategy combining two versatile “living” polymerization techniques, Pd−diimine catalyzed ethylene “living” polymerization and atom transfer radical polymerization (ATRP), for the synthesis of functionalized polyethylene (PE) diblock copolymers containing an ethylene block and a functional monomer block, such as styrene and n-butyl acrylate. The key to the success of this tandem strategy is the development of a novel functionalized Pd−diimine catalyst, [(ArNC(Me)−(Me)CNAr)Pd(CH2)3C(O)O(CH2)2OC(O)C(CH3)2Br]+SbF6- (Ar = 2,6-(iPr)2C6H3) (3), which uniquely contains a 2-bromoisobutyryl substituting group on its chelate structure. This catalyst was synthesized by convenient equimolar reaction of the acetonitrile Pd−diimine adduct, [(ArNC(Me)−(Me)CNAr)Pd(CH3)(N⋮CMe)]+SbF6- (Ar = 2,6-(iPr)2C6H3) (1), with a functional acrylate monomer, 2-(2-bromoisobutyryloxy) ethyl acrylate (BIEA). The remarkable feature of 3 lies in its unprecedented ability to catalyze ethylene “living” polymer...
TL;DR: expression data associated with the petiole indicated the occurrence of a double defensive strategy mediated by the activation of a biochemical programme including scavenging ROS, defence and PR genes, and a physical response mostly based on lignin biosynthesis and deposition.
Abstract: The main objective of this work was to identify and classify genes involved in the process of leaf abscission in Clementina de Nules (Citrus clementina Hort. Ex Tan.). A 7 K unigene citrus cDNA microarray containing 12 K spots was used to characterize the transcriptome of the ethylene-induced abscission process in laminar abscission zone-enriched tissues and the petiole of debladed leaf explants. In these conditions, ethylene induced 100% leaf explant abscission in 72 h while, in air-treated samples, the abscission period started later and took 240 h. Gene expression monitored during the first 36 h of ethylene treatment showed that out of the 12 672 cDNA microarray probes, ethylene differentially induced 725 probes distributed as follows: 216 (29.8%) probes in the laminar abscission zone and 509 (70.2%) in the petiole. Functional MIPS classification and manual annotation of differentially expressed genes highlighted key processes regulating the activation and progress of the cell separation that brings about abscission. These included cell-wall modification, lipid transport, protein biosynthesis and degradation, and differential activation of signal transduction and transcription control pathways. Expression data associated with the petiole indicated the occurrence of a double defensive strategy mediated by the activation of a biochemical programme including scavenging ROS, defence and PR genes, and a physical response mostly based on lignin biosynthesis and deposition. This work identifies new genes probably involved in the onset and development of the leaf abscission process and suggests a different but co-ordinated and complementary role for the laminar abscission zone and the petiole during the process of abscission.
TL;DR: In planta, salinity stress induced the expression of genes that respond to ethylene and reactive oxygen species, and also induced H(2)O( 2) production at the AZ, which preceded leaf abscission, indicating that H(1)O (2) has roles in leafAbscission associated with ethylene both in vitro and in planta.
Abstract: Although auxin and ethylene play pivotal roles in leaf abscission, the subsequent signaling molecules are poorly understood This is mainly because it is difficult to effectively treat the intact abscission zone (AZ) with pharmacological reagents We developed an in vitro experimental system that reproduces stress-induced leaf abscission in planta In this system, 1-mm-thick petiole strips, encompassing the AZ, were separated within 4 days of abscission at the AZ through cell wall degradation in an auxin depletion- and ethylene-dependent manner The system allowed us to show that hydrogen peroxide (H(2)O(2)) is involved in abscission signaling Microscopic analyses revealed continuous H(2)O(2) production by AZ cells H(2)O(2) scavengers and diphenylene iodonium, an inhibitor of NADPH oxidase, suppressed in vitro abscission and cellulase expression Conversely, the application of H(2)O(2) promoted in vitro abscission and expression of cellulase Ethephon-induced abscission was suppressed by inhibitors of H(2)O(2) production, whereas the expression of ethylene-responsive genes was unaffected by both H(2)O(2) and an H(2)O(2) inhibitor These results indicated that H(2)O(2) acts downstream from ethylene in in vitro abscission signaling In planta, salinity stress induced the expression of genes that respond to ethylene and reactive oxygen species, and also induced H(2)O(2) production at the AZ, which preceded leaf abscission These results indicate that H(2)O(2) has roles in leaf abscission associated with ethylene both in vitro and in planta
TL;DR: M(C2H4) (M=Cu, Au) mediate carbene-transfer reactions from ethyl diazoacetate to saturated and unsaturated hydrocarbons.
Abstract: A rare gold(I) ethylene complex and the closely related copper(I) ethylene adduct have been isolated using [N{(C3F7)C(2,6-Cl2C6H3)N}2]− as the supporting ligand [N{(C3F7)C(2,6-Cl2C6H3)N}2]Au(C2H4) (1) is an air-stable solid It features a U-shaped triazapentadienyl ligand backbone and a three-coordinate, trigonal-planar gold center The copper(I) adduct [N{(C3F7)C(2,6-Cl2C6H3)N}2]Cu(C2H4) (2) also has a similar structure The 13C NMR signal corresponding to the ethylene carbons of 1 appears at about 64 ppm upfield from the free ethylene, while the ethylene carbons of 2 show a relatively smaller (39 ppm) upfield shift [N{(C3F7)C(2,6-Cl2C6H3)N}2]M(C2H4) (M = Cu, Au) mediate carbene-transfer reactions from ethyl diazoacetate to saturated and unsaturated hydrocarbons
TL;DR: Data are presented which indicate that fruit-specific suppression of the ethylene receptor LeETR4 causes early ripening, whereas fruit size, yield and flavour-related chemical composition are largely unchanged.
Abstract: Tomato is an economically important crop and a significant dietary source of important phytochemicals, such as carotenoids and flavonoids. Although it has been known for many years that the plant hormone ethylene is essential for the ripening of climacteric fruits, its role in fruit growth and maturation is much less well understood. In this study, data are presented which indicate that fruit-specific suppression of the ethylene receptor LeETR4 causes early ripening, whereas fruit size, yield and flavour-related chemical composition are largely unchanged. Early fruit ripening is a highly desirable and valuable trait, and the approach demonstrated here should be applicable to any fruit species requiring ethylene to ripen. These results demonstrate that ethylene receptors probably act as biological clocks regulating the onset of tomato fruit ripening.
TL;DR: The results of sorption kinetics, in situ IR spectroscopy, single crystal X-ray crystallography, and in situ powder XRD studies show that small unsaturated hydrocarbons penetrate into the solid bulk of 1 through the pi-complexation with Ag(+).
Abstract: Ag2[Cr3O(OOCC2H5)6(H2O)3]2[α-SiW12O40] [1] is a nonporous flexible ionic crystal composed of 2D-layers of polyoxometalates ([α-SiW12O40]4−) and macrocations ([Cr3O(OOCC2H5)6(H2O)3]+) stacking along the b-axis. The silver ions are located in the vicinity of the oxygen atoms of the polyoxometalates. The sorption amounts of small unsaturated hydrocarbons such as ethylene, propylene, n-butene, acetylene, and methyl acetylene into 1 are comparable to or larger than 1.0 mol mol−1 and large hystereses are observed, while those of paraffins and larger unsaturated hydrocarbons are smaller than the adsorption on the external surface (<0.2 mol mol−1). Fine crystals of 1 exhibit ethylene/ethane and propylene/propane sorption ratios over 100 at 298 K and 100 kPa, and the values are larger by 1 order of magnitude among those reported. The results of sorption kinetics, in situ IR spectroscopy, single crystal X-ray crystallography, and in situ powder XRD studies show that small unsaturated hydrocarbons penetrate into the...
TL;DR: The observation of the H( 3)(+) production with the kinetic energy range of 3.5-5.0 eV from doubly ionized ethylene, allene, 1,3-butadiene, and cyclohexane showed the existence of the ultrafast hydrogen migration processes that enables three hydrogen atoms to come together to form H(3)(+) within a hydrocarbon molecule.
Abstract: The ejection processes of hydrogen molecular ion H3+ from 12 kinds of hydrocarbon molecular species, methanol, ethanol, 1-propanol, 2-propanol, acetone, acetaldehyde, methane, ethane, ethylene, allene, 1,3-butadiene, and cyclohexane, induced by intense laser fields (∼1014W∕cm2) have been investigated by time-of-flight mass spectroscopy. The observation of the H3+ production with the kinetic energy range of 3.5–5.0eV from doubly ionized ethylene, allene, 1,3-butadiene, and cyclohexane, which have no methyl groups, showed the existence of the ultrafast hydrogen migration processes that enables three hydrogen atoms to come together to form H3+ within a hydrocarbon molecule.
TL;DR: In this article, the surface reaction of ethanol on ZnO nanowires was studied by temperature-programmed desorption (TPDP) and the results showed that ethanol, ethylene, and hydrogen molecules are desorbed as the main desorbing products.
Abstract: The surface reaction of ethanol on ZnO nanowires was studied by temperature-programmed desorption (TPD). Desorption products of ethanol from ZnO nanowires were examined as function of temperature and exposure. During heating of the sample up to 900 K, ethanol, ethylene, and hydrogen molecules are desorbed as the main desorption products. Molecular desorption of ethanol was observed at 145 K from physisorbed layers. A higher desorption energy was observed for chemisorbed ethanol desorbing at 250−275 K. As decomposition products of ethanol on the ZnO nanowire surface, ethylene and hydrogen desorbed at 517 and 523 K, respectively. A reaction model is suggested for the surface decomposition of ethanol on ZnO nanowires.
TL;DR: It is concluded that ascorbate is not essential for initial O2 binding and activation but is required for rapid FeIVO formation under catalytic turnover, which acts as the reactive intermediate in substrate oxidation.
Abstract: Ethylene is a plant hormone important in many aspects of plant growth and development such as germination, fruit ripening, and senescence. 1-Aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACCO), an O2-activating ascorbate-dependent nonheme iron enzyme, catalyzes the last step in ethylene biosynthesis. The O2 activation process by ACCO was investigated using steady-state kinetics, solvent isotope effects (SIEs), and competitive oxygen kinetic isotope effects (18O KIEs) to provide insights into the nature of the activated oxygen species formed at the active-site iron center and its dependence on ascorbic acid. The observed large 18O KIE of 1.0215 ± 0.0005 strongly supports a rate-determining step formation of an FeIVO species, which acts as the reactive intermediate in substrate oxidation. The large SIE on kcat/Km(O2) of 5.0 ± 0.9 suggests that formation of this FeIVO species is linked to a rate-limiting proton or hydrogen atom transfer step. Based on the observed decrease in SIE and 18O KIE values for ACCO at limiting ascorbate concentrations, ascorbate is proposed to bind in a random manner, depending on its concentration. We conclude that ascorbate is not essential for initial O2 binding and activation but is required for rapid FeIVO formation under catalytic turnover. Similar studies can be performed for other nonheme iron enzymes, with the 18O KIEs providing a kinetic probe into the chemical nature of Fe/O2 intermediates formed in the first irreversible step of the O2 activation.
TL;DR: Current insights in the role of ethylene on growth processes and the influence of these different factors are discussed.
TL;DR: In this article, the authors describe their experiences in innovating new models of iron and cobalt complexes as catalysts for ethylene oligomerization and polymerization, and present several alternative models with similar coordination sphere.