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1

Reaction Rate and Isomer-Specific Product Branching Ratios of C2H + C4H8: 1-Butene, cis-2-Butene, trans-2-Butene, and Isobutene at 79 K.  

PubMed

The reactions of C2H radicals with C4H8 isomers 1-butene, cis-2-butene, trans-2-butene, and isobutene are studied by laser photolysis-vacuum ultraviolet mass spectrometry in a Laval nozzle expansion at 79 K. Bimolecular-reaction rate constants are obtained by measuring the formation rate of the reaction product species as a function of the reactant density under pseudo-first-order conditions. The rate constants are (1.9 ± 0.5) × 10(-10), (1.7 ± 0.5) × 10(-10), (2.1 ± 0.7) × 10(-10), and (1.8 ± 0.9) × 10(-10) cm(3) s(-1) for the reaction of C2H with 1-butene, cis-2-butene, trans-2-butene, and isobutene, respectively. Bimolecular rate constants for 1-butene and isobutene compare well to values measured previously at 103 K using C2H chemiluminescence. Photoionization spectra of the reaction products are measured and fitted to ionization spectra of the contributing isomers. In conjunction with absolute-ionization cross sections, these fits provide isomer-resolved product branching fractions. The reaction between C2H and 1-butene yields (65 ± 10)% C4H4 in the form of vinylacetylene and (35 ± 10)% C5H6 in the form of 4-penten-1-yne. The cis-2-butene and trans-2-butene reactions yield solely 3-penten-1-yne, and no discrimination is made between cis- and trans-3-penten-1-yne. Last, the isobutene reaction yields (26 ± 15)% 3-penten-1-yne, (35 ± 15)% 2-methyl-1-buten-3-yne, and (39 ± 15)% 4-methyl-3-penten-1-yne. The branching fractions reported for the C2H and butene reactions indicate that these reactions preferentially proceed via CH3 or C2H3 elimination rather than H-atom elimination. Within the experimental uncertainties, no evidence is found for the formation of cyclic species. PMID:23701666

Bouwman, Jordy; Fournier, Martin; Sims, Ian R; Leone, Stephen R; Wilson, Kevin R

2013-06-11

2

Vacuum ultraviolet-infrared photo-induced Rydberg ionization spectroscopy: C-H stretching frequencies for trans-2-butene and trichloroethene cations  

NASA Astrophysics Data System (ADS)

We have demonstrated the two-color vacuum ultraviolet (VUV)-infrared (IR) photoinduced Rydberg ionization (PIRI) experiment. Trichloroethene (ClCH=CCl2) and trans-2-butene (trans-CH3CH=CHCH3) were prepared in Rydberg states in the range of effective principal quantum number n*~7-93 by VUV excitation prior to IR-induced autoionization. The observed VUV-IR-PIRI spectra are found to be independent of n*, suggesting that the electron Rydberg orbital is conserved, i.e., the Rydberg electron is behaving as a spectator during the excitation process. The observed IR active C-H stretching vibrational frequencies ?12+=3072+/-5 cm-1 for ClCH=CCl2+ and ?23+=2908+/-3 cm-1, ?25+=2990+/-10 cm-1 and ?30+=3022+/-10 cm-1 for trans-CH3CH=CHCH3+ are compared with predictions based on ab initio quantum-chemical procedures and density functional calculations.

Woo, H. K.; Wang, P.; Lau, K.-C.; Xing, X.; Ng, C. Y.

2004-01-01

3

Oxidative dehydrogenation of 1-butene over manganese oxide octahedral molecular sieves  

SciTech Connect

Steady state kinetic studies of the oxidative dehydrogenation of 1-butene to 1,3-butadiene have been carried out on manganese oxide octahedral molecular sieve (OMS) and octahedral layered (OL) materials. Process parameters such as temperature, feed composition of 1-butene and oxygen, and feed flow rates were varied to study their effect on the activity and selectivity toward the oxidative dehydrogenation process. In addition to process parameters, modifications in the catalyst such as the ion-exchange of tunnel cations and framework substitution of manganese cations were also implemented in order to observe their effects on catalytic activity and the selectivity of 1,3-butadiene production. The ion-exchanged OMS and OL materials showed rapid deactivation with time when subjected to reaction mixtures of 1% 1-butene/0.7% oxygen/Ar and 1% 1-butene/1.1% oxygen/Ar at reaction temperatures greater than 400 C. Their selectivity toward 1,3-butadiene were typically from 15--20% (yield of 4--6%). The other products were cis and trans 2-butene and carbon dioxide and water (40--60% selectivity). Much of the oxidation was therefore nonselective. XRD data have shown that there is a phase change of the original precursor to a mixture of Mn{sub 3}O{sub 4}/MnO or plain MnO, in some cases after exposing the catalyst to reaction conditions for about 1--2 h. Framework substitution of some of the manganese with copper (OMS and OL), however, has led to higher yields and selectivities toward 1,3-butadiene. [Cu] OL-1 showed a yield of 11.8% and a maximum selectivity of 26% toward 1,3-butadiene. [Cu] OMS-1 shows a dramatically high selectivity of 36% and a yield of 11% toward 1,3-butadiene. The effect of framework substitution seems to also impede the phase change to Mn{sub 3}O{sub 4} (Hausmannite). The TPR spectra also show an increase in the lattice oxygen peak by about 40 C, in comparison with ion-exchanged OMS. This is sufficient indication that framework substitution of manganese by copper, partially, has enhanced the stability of the catalyst and improved its capacity for selective oxidation.

Krishnan, V.V.; Suib, S.L. [Univ. of Connecticut, Storrs, CT (United States)

1999-06-10

4

Adsorption of 2-methylpropene and 1,3-butadiene on activated carbon  

SciTech Connect

Four adsorption isotherms at 278, 288, 293, and 303 K of 2-methylpropene and 1, 3-butadiene on activated carbon are given. The results at pressures up to 0.8P/P[sub s] are measured using an automated apparatus and correlated by the vacancy solution model of Cochran and Danner. This work aims at determining the influence of a double bond and a branched structure on the adsorption capacity. For their industrial separation by an adsorption process, it is important to have equilibrium data on the same adsorbent and at different temperatures.

Olivier, M.G.; Berlier, K.; Bougard, J. (Faculte Polytechnique de Mons (Belgium). Service de Thermodynamique)

1994-10-01

5

Adsorption of oxygen and 1-butene on magnesium ferrite  

SciTech Connect

The kinetics of the adsorption of oxygen and 1-butene on magnesium ferrite was studied. Conductometry and thermal desorption methods were used to investigate the adsorption of oxygen on magnesium ferrite. Two forms of adsorbed oxygen were found. The formation of these forms affects the kinetics of the adsorption of 1-butene.

Samuilova, O.K.; Kozlova, M.M.; Yagodovskii, V.D.

1986-08-01

6

A pulsed electron beam, variable temperature, high pressure mass spectrometric re-evaluation of the proton affinity difference between 2-methylpropene and ammonia  

Microsoft Academic Search

A new constructed pulsed electron beam high pressure mass spectrometer which incorporates a reverse geometry, BE, sector mass spectrometer has been used to examine proton transfer equilibria as a function of temperature for a series of bases intermediate in proton affinity between 2-methylpropene and ammonia. The data obtained support the recent conclusion of Meot-Ner and Sieck (J. Am. Chem. Soc.,

J. E. Szulejko; T. B. McMahon

1991-01-01

7

Isolation of 3-methyl-1-butene from a hydrocarbon stream  

SciTech Connect

A process is described for recovering 3-methyl-1-butene from a hydrocarbon stream containing 3-methyl-1-butene and compounds which form azeotropes with 3-methyl-1-butene comprising extractive distillation of the hydrocarbon stream with a solvent mixture comprising dimethylformamide and sulfolane solvent mixture present in an amount ranging from about 0.1 to about 20 times the weight of the hydrocarbon stream. The dimethylformamide in the dimethylformamide/Sulfolane solvent mixture is present in an amount ranging from about 30 weight percent to about 70 weight percent based on the weight of the mixture. This separates insolubles containing the 3-methyl-l-butene as the overhead product stream from the bottoms product containing soluble compounds, the compounds that form azeotropes with 3-methyl-l-butene and the solvent mixture and thereafter recovering the 3-methyl-1-butene from the insolubles.

Drake, C.A.

1986-12-16

8

Skeletal isomerization of 1-butene over mesoporous materials  

Microsoft Academic Search

On the skeletal isomerization of 1-butene, mesoporous materials with mesopores too large to expect any shape selectivity have\\u000a been used in order to investigate the effects of the concentration of acid sites on the conversion of 1-butene and the selectivity\\u000a for isobutene. The concentrations of acid sites can be varied through the control of the Si\\/Al ratio. The conversion of

Gon Seo; Na-Hyeon Kim; Young-Hee Lee; Jong-Ho Kim

1999-01-01

9

Skeletal isomerization of 1?butene on synthetic clinoptilolite zeolite  

Microsoft Academic Search

A pure, highly crystalline clinoptilolite (CLI) zeolite with a Si\\/Al ratio of 5.8 has been synthesized using a small amount\\u000a (1%) of seed crystals and tested as a catalyst for the skeletal isomerization of 1?butene at 623–723 K at atmospheric pressure.\\u000a The catalytic results are compared to those obtained from a ferrierite (FER) zeolite with a Si\\/Al ratio of 7.6.

Gon Seo; Byung Joon Ahn; Suk Bong Hong; Young Sun Uh

1998-01-01

10

Toxicology and Carcinogenesis Studies of 3-Chloro-2-Methylpropene (Technical Grade Containing 5% Dimethylvinyl Chloride) (CAS No. 563-47-3) in F344/N Rats and B6C3F1 Mice (Gavage Studies).  

National Technical Information Service (NTIS)

Toxicology and carcinogenesis studies of technical-grade 3-chloro-2-methylpropene (containing 5% dimethylvinyl chloride), a widely used insecticide and chemical intermediate, were performed on F344/N rats and B6C3F1 mice. In the 13-week studies, 50%-100% ...

1986-01-01

11

Crossed-beam slice imaging of cl reaction dynamics with butene isomers.  

PubMed

We present a crossed-beam imaging study of the reaction of chlorine atoms with several butene isomers. A high-intensity pulsed ablation Cl source is used with DC slice imaging and single-photon ionization detection at 157 nm to record the velocity-flux contour maps for these reactions. The target unsaturated hydrocarbons are 1-butene, trans-2-butene, cis-2-butene, and isobutene (2-methylpropene). Data are obtained at collision energies of ?13.0 kcal·mol(-1). Distinct differences in the scattering distributions and in particular the coupling of angular and translational energy release provide insight into the dynamics of this little-studied class of reactions. We find that these distributions reflect the energetics for competition between addition/elimination and direct abstraction in line with ab initio thermochemical data. A possible role for Cl atom roaming mediating the addition/elimination pathway is suggested. PMID:23721246

Joalland, Baptiste; Van Camp, Richard; Shi, Yuanyuan; Patel, Nitin; Suits, Arthur G

2013-06-13

12

Skeletal isomerisation of 1-butene on tungsten oxide catalysts  

SciTech Connect

Several {gamma}-Al{sub 2}O{sub 3}-supported tungsten oxide catalysts have been studied in the skeletal isomerisation of 1-butene. It appears that the presence of small tungsten oxide particles induces skeletal isomerisation. Large particles can be activated by prereduction treatment with hydrogen. It was shown that the selectivity and stability of the catalysts depend strongly on the tungstate loading. A sudden increase in selectivity is observed when dimeric WO{sup 2-}{sub 4} species are formed. A low density of active sites presents deactivation, which is caused by carbonization of the catalyst due to oligomerisation of isobutene. The main by-products, C{sub 3} and C{sub 5} hydrocarbons, arise from the dimerisation and cracking of isobutene. 33 refs., 10 figs., 1 tab.

Gielgens, L.H.; Kampen, M.G.H. van; Broek, M.M. [Leiden Univ. (Netherlands)] [and others

1995-07-01

13

Oligomerization of 2-methylpropene and transformation of 2,4,4-trimethyl-2-pentene over supported and unsupported perfluorinated resinsulfonic acid catalysts  

SciTech Connect

Oligomerization of 2-methylpropene was studied with two types of supported (on alumina and on silicon carbide) as well neat perfluorinated resinsulfonic acid catalysts. The heterogeneous reactions were carried out over the solid acid catalysts in a continuous flow reactor at temperatures between 85 and 170 C under atmospheric pressure. Under the studied conditions (85 to 105 C, 1 atm pressure, WHSV:1-3 g/g {center dot} h) all catalysts studied are suitable for oligomerization of 2-methyl-propene. Product distributions show regular temperature dependence: upon increasing temperature the molecular weight of oligomers decreases, with no difference in the selectivity of the catalysts. Transformation of 2,4,4-trimethyl-2-pentene in the liquid phase at room temperature shows surprising selectivity using either the hydrated or dehydrated forms of the resinsulfonic acids. In the case of the hydrated forms of the acids, only double bond isomerization takes place. With dehydrated acids oligomerization as well as isomerization occurs. Above 50 C the selectivity is lost.

Bucsi, I.; Olah, G.A. (Univ. of Southern California, University Park, Los Angeles (United States))

1992-09-01

14

21 CFR 177.1570 - Poly-1-butene resins and butene/ethylene copolymers.  

Code of Federal Regulations, 2013 CFR

...2) of this section. (1) Specifications â(i) Infrared identification. Poly-1-butene resins and butene...ethylene copolymers can be identified by their characteristic infrared spectra. (ii) Viscosity....

2013-04-01

15

Analysis of torsional spectra of molecules with two internal C3v rotors. XXIII. Microwave, infrared, and Raman spectra, barriers to internal rotation, and vibrational assignment of 3,3,3-trifluoro-2-methylpropene  

Microsoft Academic Search

The microwave spectrum of 3,3,3-trifluoro-2-methylpropene, H2C=C(CH3)CF3 has been recorded from 18.5 to 39.0 GHz. Only a-type transitions were observed and R-branch assignments have been made for the ground vibrational state as well as for three vibrational excited states of the CF3 torsion and one excited state of the CH3 torsion. The rotational constants for the ground vibrational state were found

G. A. Guirgis; J. R. Durig; Y. S. Li

1985-01-01

16

Interaction of 1-butene and n-butane with a sulfate-promoted iron oxide  

SciTech Connect

Interactions of sulfate-promoted iron oxide So{sub 4}{sup 2-} -Fe{sub 2}O{sub 3} with 1-butene and n-butane were investigated by means of infrared spectroscopy and temperature-programmed desorption/reaction coupled with mass spectrometry. By reacting with the sulfate ion, 1-butene adsorbed on SO{sub 4}{sup 2-}-Fe{sub 2}O{sub 3} promoted sulfate decomposition. In contrast, adsorbed n-butane desorbed readily upon heating above 320 K. Implications of these findings in catalysis by this material are discussed.

Lee, J.S.; Yeom, M.H.; Park, D.S. (Pohang Institute of Science and Technology and Research Institute of Industrial Science and Technology (Korea))

1990-12-01

17

Radial Distribution Function (RDF) Analysis of the Semi-crystalline Isotactic Poly(1-butene)  

NASA Astrophysics Data System (ADS)

Isotactic poly(1-butene) is known to have a metastable tetragonal structure upon crystallization from the melt, which transforms to a stable trigonal form over time at room temperature. Using X-ray diffraction we carried out a radial distribution function (RDF) analysis of the stable trigonal structure in a semicrystalline sample of poly(1-butene). We find a prominent characteristic repeat distance of ~ 4 ÅHowever, unlike in the melt, the long range periodicity relating to helix-helix correlations was not distinctively seen in the crystalline material. The local intramolecular structure (bond length, bond angle, and torsion angles) is also examined.

Kim, Man-Ho; Habenschuss, Anton

2001-03-01

18

Preparation and reactions of 2-chloro-3,4-epoxy-1-butene: a convenient route to (Z)-3-chloroallylic alcohols.  

PubMed

Epoxide 2 was prepared from 3,4-dichloro-1-butene (1) by epoxidation with m-CPBA and subsequent dehydrohalogenation of the intermediate dichloroepoxide with molten KOH, affording 2 in 64% overall yield (2 steps). Catalytic CuBr/SMe(2)-mediated S(N)2' addition of sp(2)- or sp(3)-hybridized Grignard reagents to 2-chloro-3,4-epoxy-1-butene (2) afforded (Z)-3-chloroallylic alcohols such as 3 in good yields and with high regio- and stereoselectivity. PMID:12027702

Taber, Douglass F; Mitten, Jeffrey V

2002-05-31

19

Alkylation to form trimethylpentanes from isobutane and 1-butene catalyzed by solid superacids of sulfated metal oxides  

Microsoft Academic Search

The gas-phase alkylation of 1-butene with isobutane was carried out over 0.2g of superacids of sulfated metal oxides, SO4\\/Fe2O3, SO4\\/Al2O3, SO4\\/TiO2, SO4\\/SnO2, and SO4\\/ZrO2, at 0°C with a 10:1 ratio of isobutane to 1-butene in a closed recirculation reactor. The products were pentanes (C5), hexanes (C6), heptanes (C7), and octanes (C8). The highest acid strength of the catalysts was linearly

Kunihiko Satoh; Hiromi Matsuhashi; Kazushi Arata

1999-01-01

20

Electron momentum spectroscopy of 1-butene: a theoretical analysis using molecular dynamics and molecular quantum similarity.  

PubMed

The results of experimental studies of the valence electronic structure of 1-butene by means of electron momentum spectroscopy (EMS) have been reinterpreted on the basis of molecular dynamical simulations in conjunction with the classical MM3 force field. The computed atomic trajectories demonstrate the importance of thermally induced nuclear dynamics in the electronic neutral ground state, in the form of significant deviations from stationary points on the potential energy surface and considerable variations of the C-C-C-C dihedral angle. These motions are found to have a considerable influence on the computed spectral bands and outer-valence electron momentum distributions. Euclidean distances between spherically averaged electron momentum densities confirm that thermally induced nuclear motions need to be fully taken into account for a consistent interpretation of the results of EMS experiments on conformationally flexible molecules. PMID:23902590

Shojaei, S H Reza; Vandenbussche, Jelle; Deleuze, Michael S; Bultinck, Patrick

2013-08-22

21

The Photocycloaddition of Acetone to 1-Methoxy-1-Butene. A Comparison of Singlet and Triplet Mechanisms and Singlet and Triplet Biradical Intermediates.  

National Technical Information Service (NTIS)

The photocycloaddition of acetone to trans-1-methoxy-1-butene and cis-1-methoxy-1-butene has been studied in detail. Four isomeric oxetanes are formed in good yield. Sensitized cis-trans isomerization of the butene also occurs. Kinetic analysis and quantu...

N. J. Turro P. A. Wriede

1969-01-01

22

Role of Hydroperoxide and Peroxy Radicals in the Mechanism of the Liquid-Phase Oxidation of 1-Butene.  

National Technical Information Service (NTIS)

The example of the liquid-phase oxidation of 1-butene the problem of clarifying the kinetic role of hydroperoxide and peroxy radicals in the mechanism of the formation of olefins oxides and other products of the reaction has been established. (Author)

B. I. Chernyak B. I. Koshovskii R. V. Kucher

1970-01-01

23

Phase relationships and thermodynamic interactions of isotactic poly(1-butene) and organic solvent systems.  

PubMed

Isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, was synthesised by using a metallocene catalyst. The molecular weight was determined by GPC. The chemical structure of iPBu-1 was verified by using high-temperature (13)C NMR spectroscopy and the thermal properties by differential scanning calorimetry (DSC). The (solid+liquid) equilibria, SLE, of iPBu-1 with different hydrocarbons (n-hexadecane, 1-heptene, 1-heptyne, cyclopentane, cyclohexane, cycloheptane, cyclooctane, benzene and propylbenzene) were studied by a dynamic method. By performing these experiments over a large concentration range, the temperature-mole fraction phase diagrams of the polymer-solvent systems could be constructed. From these diagrams it was found that iPBu-1 had the highest solubility in small-ring cycloalkanes and the lowest in n-hexadecane, 1-heptyne and benzene in the mole fraction range measured. The excess Gibbs energy models were used to describe the nonideal behaviour of the liquid phase and to estimate the solubility of iPBu-1 in the whole mole fraction range. Activity coefficients at infinite dilution of polymer and solvent were determined from the solubility measurements and were predicted by using the UNIFAC FV model and molecular Monte Carlo simulations. PMID:15558808

Doma?ska, Urszula; Koz?owska, Marta Karolina

2005-01-01

24

Palladium salts of heteropolyacids as catalysts in the Wacker oxidation of 1-butene  

SciTech Connect

Palladium salts of heteropolyacids (PdHPAs) of the Keggin series H{sub 3+n}PV{sub n}Mo{sub 12-n}O{sub 40} supported on silica, have been used successfully as catalysts in the gas-phase Wacker oxidation of 1-butene. In such catalysts the palladium reaction centre and the redox component are combined in one complex. At 343 K and atmospheric pressure a high initial butanone yield of more than 0.2 g g{sup -1}{sub cat}h{sup -1}, in combination with a very high butanone selectivity of more than 98%, can be obtained. In the steady state, the activity of the catalyst is more than a factor of 10 lower than the initial activity, due to slow reoxidation of reduced palladium-heteropolyanion complexes. The rate of reoxidation depends on the composition of the HPA, the palladium loading, and the reaction conditions. The reaction order of 0.5 in the O{sub 2} partial pressure indicates the dissociation of dioxygen to be rate determining. The degree of hydration of the HPA appears to be important for the activity and stability of the catalysts. Spent catalysts can be regenerated by an oxidation treatment in air at temperatures around 525 K. Regeneration becomes more difficult with high palladium loading of the catalyst. 8 refs., 8 figs.

Stobbe-Kreemers, A.W.; van der Lans, G.; Makkee, M. [Delft Univ. of Technology (Netherlands)] [and others

1995-07-01

25

Thermal behaviour and morphology of homogeneous ethylene–propylene and ethylene–1-butene copolymers with high comonomer contents  

Microsoft Academic Search

The thermal behaviour and morphology of series of homogeneous ethylene–propylene and ethylene–1-butene copolymers, which cover wide ranges in comonomer content, are studied by differential scanning calorimetry (DSC), time-resolved small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The thermal behaviour and the morphology of the copolymers change in a continuous way as the comonomer content is

S. Vanden Eynde; V. Mathot; M. H. J. Koch; H. Reynaers

2000-01-01

26

Mass spectrum of the 1-butene-3-yne-2-yl radical (i-C4H3; X2A')  

NASA Astrophysics Data System (ADS)

The crossed molecular beams method has been applied to produce the 1-butene-3-yne-2-yl radical, i-C4H3(X2A') under single collision conditions via the reaction of dicarbon molecules with ethylene. We recorded time-of-flight spectra of the radical at the center-of-mass angle (28.0°) of the parent ion (m/z = 51; C4H3+) and of the fragments at m/z = 50 (C4H2+), m/z = 49 (C4H+), m/z = 48 (C4+), m/z = 39 (C3H3+), m/z = 38 (C3H2+), m/z = 37 (C3H+), and m/z = 36 (C3+). This yielded relative intensity ratios of I(m/z = 51):I(m/z = 50):I(m/z = 49):I(m/z = 48):I(m/z = 39):I(m/z = 38):I(m/z = 37):I(m/z = 36) = 0.47 +/- 0.01:0.94 +/- 0.01:1.0:0.07 +/- 0.02:0.31 +/- 0.01:0.23 +/- 0.02:0.24 +/- 0.01:0.12 +/- 0.01 at 70 eV electron impact energy. Upper limits at mass-to-charge ratios between 27 and m/z = 24 and m/z = 14-12 were derived to be 0.02 +/- 0.01. Note that the intensity of the 13C isotopic peak of the 1-butene-3-yne-2-yl radical at m/z = 52 (13C12C3H3+) is about 0.04 +/- 0.01 relative to m/z = 51. Employing linear scaling methods, the absolute electron impact ionization cross section of the 1-butene-3-yne-2-yl radical was computed to be 7.8 +/- 1.6 × 10-16 cm2. These data can be employed to monitor the 1-butene-3-yne-2-yl radical in oxygen-poor combustion flames and in the framework of prospective explorations of planetary atmospheres (Jupiter, Saturn, Uranus, Neptune, Pluto) and of their moons (Titan, Triton, Oberon) in situ via matrix interval arithmetic assisted mass spectrometry.

Guo, Ying; Gu, Xibin; Kaiser, Ralf I.

2006-03-01

27

Determination of thermodynamic properties of isotactic poly(1-butene) at infinite dilution using density and inverse gas chromatography  

Microsoft Academic Search

The partial molar volumes, V1M, and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V1, have been calculated from the measured density of {iPBu-1+solvent (n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons (n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of

Marta Karolina Koz?owska; Urszula Doma?ska; Ma?gorzata Lempert; Marek Rogalski

2005-01-01

28

Photoassisted adsorption of allylamine and 1-butene on H:Si(111) studied by surface vibrational spectroscopies.  

PubMed

Ultraviolet photoassisted adsorption of terminally double-bonded molecules, allylamine (CH2=CH-CH2-NH2) and 1-butene (CH2=CH-CH2-CH3), on hydrogen-terminated silicon (111) surface was attempted to obtain adsorbates covalently terminating the surface Si atoms. The adsorption process was monitored by high-resolution electron energy loss spectroscopy, multiple internal infrared reflection-absorption spectroscopy, and Auger electron spectroscopy. Allylamine adsorbates emerged upon delivery of allylamine gas under ultraviolet irradiation. The N-H bonds in allylamine were evidenced to survive over the photoadsorption process by vibrational analysis and by the reaction with ketene. CH3- groups were detected at low coverage, indicating anchoring of the organic moieties by the secondary (sec-) type carbon atoms, which were taken over by the primary (n-) type with increasing coverage. C-D bonds were detected after deposition on deuterium-terminated Si(111) upon incorporation of Si-terminating H into the hydrocarbon part of adsorbates. In the case of 1-butene, not only the C=C end but also the CH3- end of a molecule might attach on Si, resulting in emergence of adsorbates composed of CH2 groups. The newly obtained adsorbates are prospective as a material applied for nanolithography, fine electrochemistry, and nano-biotechnology. PMID:16570980

Yamada, Taro; Noto, Madomi; Shirasaka, Kaoru; Kato, Hiroyuki S; Kawai, Maki

2006-04-01

29

A molecular approach to heterogeneous catalysis. Part 2. 1-Butene isomerization catalyzed by silica-anchored osmium carbonyls  

SciTech Connect

The title reaction has been investigated at 115{degree}C using HOs{sub 3}(CO){sub 10}(OSi chemical bond) as catalyst or catalyst precursor. By FTIR and XP spectroscopy and by TPDE, evidence exists for the in situ formation of molecular oxidized osmium moieties, covalently anchored to the surface, which are the active catalytic species. The intermediate formation of an olefin adduct during the in situ decomposition of the cluster precursors is supported by chemical extraction of the surface species and further FTIR and {sup 1}H NMR characterization. The reversible poisoning effect of CO and the beneficial influence of H{sub 2} on the catalytic activity and selectivity are also reported and discussed. The catalytic behavior of preformed oxidized osmium surface species has been found to be markedly dependent on the preparation method. The highest activity was obtained when they are formed in situ in the presence of 1-butene. Silica-supported metallic osmium catalysts displayed different activity and selectivity, thus confirming the molecular nature of the catalytic process.

Dossi, C. (Northwestern Univ., Evanston, IL (USA)); Fusi, A.; Grilli, E.; Psaro, R.; Ugo, R. (CNR, Milano (Italy)); Zanoni, R. (Universita La Sapienza, Rome (Italy))

1990-05-01

30

Electrical conductivity and equation of state of liquid nitrogen, oxygen, benzene, and 1-butene shocked to 60 GPa  

SciTech Connect

Measurements are reported for the electrical conductivity of liquid nitrogen (N/sub 2/), oxygen (O/sub 2/) and benzene (C/sub 6/H/sub 6/), and Hugoniot equation of state of liquid 1-butene (C/sub 4/H/sub 8/) under shock compressed conditions. The conductivity data span 7 x 10/sup -4/ to 7 x 10/sup 1/ ..cap omega../sup -1/cm/sup -1/ over a dynamic pressure range 18.1 to 61.5 GPa and are discussed in terms of amorphous semiconduction models which include such transport phenomena as hopping, percolation, pseudogaps, and metallization. Excellent agreement is found between the equation-of-state measurements, which span a dynamic pressure range 12.3 to 53.8 GPa, and Ree's calculated values which assume a 2-phase mixture consisting of molecular hydrogen and carbon in a dense diamond-like phase. There is a 2-1/2 fold increase in the thermal pressure contribution over a less dense, stoichiometrically equivalent liquid. 90 refs., 48 figs., 8 tabs.

Hamilton, D.C.

1986-10-08

31

Comparison of two-body and three-body decomposition of ethanedial, propanal, propenal, n-butane, 1-butene, and 1,3-butadiene.  

PubMed

We investigated two-body (binary) and three-body (triple) dissociations of ethanedial, propanal, propenal, n-butane, 1-butene, and 1,3-butadiene on the ground potential-energy surfaces using quantum-chemical and Rice-Ramsperger-Kassel-Marcus calculations; most attention is paid on the triple dissociation mechanisms. The triple dissociation includes elimination of a hydrogen molecule from a combination of two separate terminal hydrogen atoms; meanwhile, the rest part simultaneously decomposes to two stable fragments, e.g., C(2)H(4), C(2)H(2), or CO. Transition structures corresponding to the concerted triple dissociation were identified using the B3LYP/6-311G(d,p) level of theory and total energies were computed using the method CCSD(T)/6-311+G(3df, 2p). The forward barrier height of triple dissociation has a trend of ethanedial < propanal < propenal < n-butane < 1-butene < 1,3-butadiene, pertaining to the reaction enthalpy. Ratios of translational energies of three separate fragments could be estimated from the transition structure of triple dissociation. The synchronous concerted dissociation of propanal, propenal, and 1-butene leading to three different types of molecular fragments by breaking nonequivalent chemical bonds is rare. The triple dissociation of propanal, n-butane, 1-butene, and 1,3-butadiene were investigated for the first time. To outline a whole picture of dissociation mechanisms, some significant two-body dissociation channels were investigated for the calculations of product branching ratios. The triple dissociation plays an important role in the three carbonyl compounds, but plays a minor or negligible role in the three hydrocarbons. PMID:22260580

Chin, Chih-Hao; Lee, Shih-Huang

2012-01-14

32

The Assignment of the Vibrational Spectra of the C4 Hydrocarbons Butyne1, Butene1 and Vinyl Acetylene, to the Normal Modes of Vibration of These Molecules  

Microsoft Academic Search

An attempt has been made to assign all the normal modes of vibration of the C4 hydrocarbons butyne?1, butene?1, and vinyl acetylene, in terms of frequencies observed in the infra-red and Raman spectra. It has been found to be possible to do this in a satisfactory manner which takes into account the structural similarities of these and other hydrocarbon molecules.

N. Sheppard

1949-01-01

33

Propane\\/Propylene Separation by Simulated Moving Bed II. Measurement and Prediction of Binary Adsorption Equilibria of Propane, Propylene, Isobutane, and 1Butene on 13X Zeolite  

Microsoft Academic Search

The design of a simulated moving bed (SMB) process relies on valid thermodynamic predictions of multicomponent adsorption built up from accurate binary adsorption equilibrium data. Experimental adsorption equilibria of binary mixtures constituted by propane, propylene, isobutane and 1-butene on 13X zeolite were determined using breakthrough experiments at 373 K and 150 kPa. In addition, these binary adsorption experiments allow to confirm

Nabil Lamia; Miguel A. Granato; Pedro SÁ Gomes; Carlos A. Grande; Luc Wolff; Philibert Leflaive; Damien Leinekugel-le-Cocq; Alírio E. Rodrigues

2009-01-01

34

Chirality Effect on Flory-Huggins Interaction Parameters in Polylactide-b-Poly(ethylene-co-1-butene)-b-Polylactide Triblock Copolymers  

NASA Astrophysics Data System (ADS)

In this work, a set of well-defined polylactide-b-poly(ethylene-co-1-butene)-b-polylactide (PLA-PEB-PLA) triblock copolymers were synthesized by controlled ring-opening polymerization of corresponding lactide monomers (L-lactide and racemic mixture of D- and L-lactides) using Sn(Oct)2 as the catalyst. The volume fractions of PLA in the triblock copolymers were adjusted by tuning its molecular weight. The mesophase morphology and phase transitions in these triblock copolymers were studied by temperature-dependent small-angle X-ray scattering (SAXS). The Flory-Huggins interaction parameter ? between EB and lactide as a function of temperature were estimated from the order-disorder transition temperature (TODT) using the mean-field critical (?N)c values. The effects of PLA chirality on both Flory-Huggins interaction parameter and segmental lengths were investigated.

Cao, Weiqiang; Zhu, Lei; Rong, Lixia; Hsiao, Benjamin S.

2009-03-01

35

Modeling chemical growth processes in Titan's atmosphere 2. Theoretical study of reactions between C 2H and ethene, propene, 1-butene, 2-butene, isobutene, trimethylethene, and tetramethylethene  

NASA Astrophysics Data System (ADS)

Barrierless reactions between unsaturated hydrocarbons and the ethynyl radical (C 2H) can contribute to the growth of organic particulates in the haze-forming regions of Titan's atmosphere as well as in the gas giants and in the interstellar medium. We employed a combination of quantum chemistry and statistical rate theories to characterize reactions between ground state C 2H and seven alkenes of the general structure RRCdbnd CRR containing up to six carbons. The alkenes included ethene (C 2H 4); propene (C 3H 6); 1-butene, 2-butene, and isobutene (C 4H 8); trimethylethene (C 5H 10); and tetramethylethene (C 6H 12). Density functional theory calculations at the B3LYP/6-31 + G ?? level were used to characterize the adducts, isomers, products, and the intervening transition states for the addition-elimination reactions of all seven species. A multiple-well treatment was then employed to determine the outcome distributions for the range of temperatures and pressures relevant to Titan's atmosphere, the interstellar medium, and the outer atmospheres of the gas giants. Finally, trajectory calculations using an ROMP2 potential energy surface were used to calculate kinetic rates for the ethene + C 2H reaction, where the agreement between the computed and measured values is very good. At low pressure and temperature, vinyl acetylene is a dominant product of several of the reactions, and all of the reactions yield at least one dominant product with both a double and a triple C sbnd C bond.

Woon, David E.; Park, Jin-Young

2009-08-01

36

The C1s core shake-up spectra of alkene molecules: An experimental and theoretical study  

Microsoft Academic Search

The C1s core photoelectron spectra of a series of alkene molecules, ethene, propene, 1-butene, cis and trans 2-butene, 2-methyl-propene, and 1-pentene are discussed. The experimental spectra are assigned using intermediate neglect of differential overlap-configuration interaction (INDO-CI) calculations and comparative discussions. It is shown that hyperconjugation is a useful concept in the assignment of the transitions. INDO-CI is shown to give

B. Sjögren; S. Svensson; A. Naves de Brito; N. Correia; M. P. Keane; C. Enkvist; S. Lunell

1992-01-01

37

Hydrodesulfurization of thiophene over synthetic cobalt-containing smectite-like mesoporous materials  

Microsoft Academic Search

Mesoporous smectite-like materials containing cobalt, SM(Co), were synthesized by a hydrothermal method under different conditions. The materials were used as catalysts for hydrodesulfurization (HDS) of thiophene. The SM(Co) sample is a new type of active HDS catalyst. The activity depends on the synthetic conditions used, but the product distribution does not change so much, giving trans-2-butene, cis-2-butene, and 1-butene with

Kuriko Aoki; Yui Minato; Kazuo Torii; Masayuki Shirai; Masahiko Arai

2001-01-01

38

In situ FT-IR study on the reaction path of skeletal isomerization of n-butene over different zeolites  

Microsoft Academic Search

Adsorption and reaction of 1-butene, cis- and trans-2-butene and isobutene on H-ZSM-5 and H-FER were studied by FT-IR spectroscopy between 30–450°C. n-Butenes were monomolecularly adsorbed via ?-bonding on H-FER at 30°C. At elevated temperatures butadiene was monitored on H-FER, which was then transformed into dialkyldiphenyl. On H-ZSM-5 all butene isomers were adsorbed via ?-bonds, followed by dimerization. From these results

P. Ivanov; H. Papp

2001-01-01

39

Migration of butene isomers onto the acidic OH groups in small micropores of ferrierite  

Microsoft Academic Search

Kinetics on the adsorption of n-butene onto the acidic OH groups existing in the small pores of ferrierite (FER) were studied between 233 and 253K by IR spectroscopy. The activation energies for the adsorption of 1-butene and cis-2-butene were estimated as 23.3 and 28.4kJmol?1, while that of trans-2-butene was not obtained due to its rapid adsorption. The activation energy for

Junko N Kondo; Eisuke Yoda; Fumitaka Wakabayashi; Kazunari Domen

2000-01-01

40

Reconstruction of Calorimetric Curves from X-ray Diffraction Data during the Melting-Recrystallization Process of Polymers: Simultaneous Calorimetry\\/X-ray Diffraction Measurements of Isotactic Poly(1-butene) in Form III  

Microsoft Academic Search

To understand complex phase behaviors of crystalline or semi-crystalline polymers, it is indispensable to clarify the correlation between the thermal and structural change events. Simultaneous calorimetry\\/X-ray diffraction measurement is one of the powerful methods to clarify such correlation. Isotactic poly(1-butene) (PB-1) exhibits complex phase transformation among the various crystal forms (Forms I, II, III, etc.). Here, we studied the transformation

Hiroshi Takahashi; Kenichiro Shimada; Yuzo Yamamoto; Hiroki Uehara

2012-01-01

41

Reconstruction of Calorimetric Curves from X-ray Diffraction Data during the Melting-Recrystallization Process of Polymers: Simultaneous Calorimetry\\/X-ray Diffraction Measurements of Isotactic Poly(1-butene) in Form III  

Microsoft Academic Search

To understand complex phase behaviors of crystalline or semi-crystalline polymers, it is indispensable to clarify the correlation between the thermal and structural change events. Simultaneous calorimetry\\/X-ray diffraction measurement is one of the powerful methods to clarify such correlation. Isotactic poly(1-butene) (PB-1) exhibits complex phase transformation among the various crystal forms (Forms I, II, III, etc.). Here, we studied the transformation

Hiroshi Takahashi; Kenichiro Shimada; Yuzo Yamamoto; Hiroki Uehara

2011-01-01

42

MoO sub 3 catalysts promoted by MnMoO sub 4. II. Effect of O sub 2 concentration and temperature in selective oxidation of 1-butene to maleic anhydride  

SciTech Connect

In a previous paper, the authors have reported the results of a study where they focused their attention on catalytic activity and selectivity of pure MoO{sub 3} and attempted to modify its catalytic behavior by bringing its surfaces into close contact with MnMoO{sub 4}. While their characterization experiments revealed the two-phase nature of the MnMoO{sub 4}/MoO{sub 3} catalyst, the activity studies showed a pronounced promoter effect in selective oxidation of both 1-butene and 1,3-butadiene to maleic anhydride, suggesting a possible synergy between the two phases. This note presents the results of their selective oxidation studies where the effect of temperature and oxygen partial pressure on catalytic behavior of the pure phases (MoO{sub 3} and MnMoO{sub 4}) as well as the two phase catalyst (MnMoO{sub 4}/MoO{sub 3}) has been investigated in conversion of 1-butene to maleic anhydride. All catalysts were characterized in detail using BET surface area measurement, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray analysis, laser Raman spectroscopy and Raman microprobe techniques.

Gill, R.C.; Ozkan, U.S. (Ohio State Univ., Columbus (USA))

1990-04-01

43

Reactions of OH with butene isomers: measurements of the overall rates and a theoretical study.  

PubMed

Reactions of hydroxyl (OH) radicals with 1-butene (k(1)), trans-2-butene (k(2)), and cis-2-butene (k(3)) were studied behind reflected shock waves over the temperature range 880-1341 K and at pressures near 2.2 atm. OH radicals were produced by shock-heating tert-butyl hydroperoxide, (CH(3))(3)-CO-OH, and monitored by narrow-line width ring dye laser absorption of the well-characterized R(1)(5) line of the OH A-X (0, 0) band near 306.7 nm. OH time histories were modeled using a comprehensive C(5) oxidation mechanism, and rate constants for the reaction of OH with butene isomers were extracted by matching modeled and measured OH concentration time histories. We present the first high-temperature measurement of OH + cis-2-butene and extend the temperature range of the only previous high-temperature study for both 1-butene and trans-2-butene. With the potential energy surface calculated using CCSD(T)/6-311++G(d,p)//QCISD/6-31G(d), the rate constants and branching fractions for the H-abstraction channels of the reaction of OH with 1-butene were calculated in the temperature range 300-1500 K. Corrections for variational and tunneling effects as well as hindered-rotation treatments were included. The calculations are in good agreement with current and previous experimental data and with a recent theoretical study. PMID:21388160

Vasu, Subith S; Huynh, Lam K; Davidson, David F; Hanson, Ronald K; Golden, David M

2011-03-09

44

In situ FT-IR study on the reaction path of skeletal isomerization of n-butene over different zeolites  

NASA Astrophysics Data System (ADS)

Adsorption and reaction of 1-butene, cis- and trans-2-butene and isobutene on H-ZSM-5 and H-FER were studied by FT-IR spectroscopy between 30-450°C. n-Butenes were monomolecularly adsorbed via ?-bonding on H-FER at 30°C. At elevated temperatures butadiene was monitored on H-FER, which was then transformed into dialkyldiphenyl. On H-ZSM-5 all butene isomers were adsorbed via ?-bonds, followed by dimerization. From these results and from catalytic measurements a monomolecular pathway is proposed on H-FER and a bimolecular one on H-ZSM-5.

Ivanov, P.; Papp, H.

2001-07-01

45

Theoretical studies on the butene double bond isomerization catalyzed by 5-H of 1-ethyl-3-methyl-imidazolium fluoride  

Microsoft Academic Search

The isomerization of 1-butene to trans-2-butene catalyzed by 5-H proton of 1-ethyl-3-methyl-imidazolium fluoride (EMImF) has been studied with density functional theory of quantum chemistry. The equilibrium states geometries and transition state geometry are optimized at the levels of B3LYP\\/6-31G(d,p) and B3LYP\\/6-311++G(d,p), respectively. The apparent activation barrier of isomerization is about 208 kJ\\/mol theoretically. It indicates that the 5-H proton on the

Min Pu; Biao-Hua Chen; De-Cai Fang

2006-01-01

46

Thermal chemistry of C4 hydrocarbons on Pt(111): Mechanism for double-bond isomerization.  

PubMed

The thermal chemistry of a number of C4 hydrocarbons (1,3-butadiene, 1-bromo-3-butene, 1-bromo-2-butene, trans-2-butene, cis-2-butene, 1-butene, 2-iodobutane, 1-iodobutane, and butane) was investigated on clean and hydrogen- and deuterium-predosed Pt(111) single-crystal surfaces by temperature-programmed desorption and reflection-absorption infrared spectroscopy. A combination of rapid beta-hydride eliminations from alkyls to olefins and the reverse insertions of those olefins into metal-hydrogen bonds explains the hydrogenation, dehydrogenation, and H-D exchange products that desorb from the surface. A preference for hydrogenation at the end carbons and dehydrogenation from the inner carbons also explains the extent of the isotope exchange and the preferential isomerization of 1-butene to 2-butene observed on this Pt(111) surface. The reactions of more dehydrogenated C4 species is also discussed. PMID:16851283

Lee, Ilkeun; Zaera, Francisco

2005-02-24

47

Epoxidation of lower olefins with hydrogen peroxide and titanium silicalite  

SciTech Connect

The epoxidation of lower olefins, catalyzed by titanium silicalite (TS-1) under mild conditions, is reported. The reaction may be performed at near room temperature, in dilute alcoholic or aqueous solutions of hydrogen peroxide. In methanol C[sub 4]-C[sub 8] linear olefins, allyl chloride, and allyl alcohol show fast reaction rates and high selectivities (72-97% on H[sub 2]O[sub 2]). The solvolysis of the oxirane ring and the oxidation of the solvent are the main side reactions. Yields and kinetics are decreased by increasing the chain length or the cross-section of the olefin (n-C[sub n] > n-C[sub n+1], 1-hexene [much gt] cyclohexene), by electron-withdrawing substituents (1-butene > allyl chloride > allyl alcohol), and by solvents in the order methanol > ethanol > t-butanol. The rate of reaction also depends on the position and steric configuration of the double bond and on the branching, as a result of inductive and shape selectivity effects: trans 2-butene < iso-butene < 1-butene < cis 2-butene, 2-methyl-1-butene < 1-pentene, and 3-methyl-1-butene < 2-methyl-1-butene < 2-methyl-2-butene. The epoxidation occurs with retention of configuration. Basic compounds at low concentration do not slow the kinetics, but do improve significantly the yields, up to 97% in the epoxidation of 1-butene. At higher concentrations, TS-1 activity is decreased and eventually inhibited by bases. No effect on kinetics is exerted by tetrapropylammonium hydroxide. Catalytic activity is improved by acids. A heterolytic peracid-like mechanism is envisaged in the oxygen-transfer step. A five-membered cyclic structure, formed by a titanium hydroperoxo moiety Ti-OOH, and a protic molecule ROH at Ti sites, is proposed as the active species. 41 refs., 5 figs., 4 tabs.

Clerici, M.G.; Ingallina, P. (Eniricerche SpA, Milano (Italy))

1993-03-01

48

Electron collisions with isomers of C4H8 and C4H10  

NASA Astrophysics Data System (ADS)

We report integral, differential and momentum transfer cross sections for elastic scattering of low-energy electrons by several isomers of the C4H8 molecules, such as isobutene, trans-2-butene, cis-2-butene, skew-1-butene and syn-1-butene, and by two isomers of C4H10, the isobutane and the butane molecules. To calculate the cross sections, we use the Schwinger multichannel method with pseudopotentials (Bettega et al 1993 Phys. Rev. A 47 1111) applied at the static exchange level of approximation for incident energies from 10 to 50 eV. Although the C4H8 isomers have different geometric structures, our results show that the integral cross sections for each of these isomers present a broad shape resonance around 10 eV; our results also show that for all C4H8 molecular targets, integral cross sections are very similar in shape and magnitude. Similarities are also found in the momentum transfer and in the differential cross sections of these isomers. The same pattern is found in the cross sections of the C4H10 isomers. Through comparison of the integral and momentum transfer cross sections of 1,3-butadiene (C4H6), trans-2-butene (C4H8) and butane (C4H10), all belonging to the C2h group and having similar structures, we discuss the role of the hydrogen atoms in the scattering process by these molecules. Further we show that the integral elastic cross sections of all simple hydrocarbons present strong similarities after a scaling. We present a simple geometric model for this scaling that works quite well for a whole family of CnHm molecules (with combinations of n = 1, 2, 3, 4 and m = 2, 4, 6, 8, 10).

Lopes, A. R.; Bettega, M. H. F.; Lima, M. A. P.; Ferreira, L. G.

2004-03-01

49

Mesophases in polyethylene, polypropylene, and poly(1-butene)  

SciTech Connect

This paper contains new views about the amorphous and partially ordered phases of the three polymers listed in the title. The discussion is based on information on structure, thermodynamic stability, and large-amplitude molecular motion. Polyethylene is the basic backbone of all alkene polymers, and the other two are the first members of the vinyl polymers which have stereospecifically placed alkyl side chains. Their multiphase structures consist of metastable crystals, mesophases, and surrounding rigid and mobile amorphous fractions. All these phases have sizes ranging from micrometer dimensions down to nanometers. Besides the phase structures, information about the molecular coupling between the phases must be considered. Depending on temperature, the polymer phases can vary from solid (rigid) to liquid (mobile). New knowledge is also gained by cross-comparison of the title polymers. The experimental information was gained from (a) various forms of slow, fast, and temperature-modulated thermal analysis to identify equilibrium and non-equilibrium states, (b) measurement of structure and morphology at various length scales, and (c) tracing of the large-amplitude molecular motion, the kinetics of order/disorder changes, and the liquid/solid transitions (glass transitions). It is shown that much more needs to be known about the various phases and their coupling to characterize a given polymer and to fine-tune its properties for a given application.

Androsch, Rene J [ORNL; Di Lorenzo, Maria [ORNL; Schick, Christoph [Rostock University, Rostock, Germany; Wunderlich, Bernhard {nmn} [ORNL

2010-01-01

50

Absorption spectra of contact-charge-transfer bans and photochemical reactions of simple alkenes in the cryogenic oxygen matrix  

SciTech Connect

The UV-vis absorption spectra and photochemistry of alkene-oxygen pairs in solid oxygen at 10 K have been studied. The contact-charge-transfer (CCT) bands well separated from the intrinsic absorption bands of isolated alkenes were recorded with the maxima at 218, 243, 234, 235, 263, and 287 nm for propene, 2-methylpropene (MP), cis-2-butene (CB), trans-2-butene (TB), 2-methyl-2-butene (MB), and 2,3-dimethyl-2-butene (DMB), respectively. The vertical transition energy correlated linearly with the ionization potential of the alkenes. Photochemical reaction products in the excitation within the CCT bands were studied by using FTIR. The reaction in the ion pair state can be classified into the following four pathways: (i) photooxygenation to given an oxygen adduct, which is observed only for DMB; (ii) cis-trans isomerization, which is the major reaction path for CB and TB, suggesting the crossing to the alkene triplet state; (iii) double-bond scission to give two corresponding carbonyl compounds, which is observed for all alkenes studied with energy threshold higher than the photooxygenation and cis-trans isomerization; (iv) formation of CO/sub 2/, CO, and O/sub 3/ which occurs at still shorter wavelength than the double-bond scission. In the case of ethene and propene, HO/sub 2/ was also produced. Relevance of the present results to those in the CCT photochemistry in the oxygen-saturated organic liquid and on the semiconductor surfaces has been discussed.

Hashimoto, S.; Akimoto, H.

1987-03-12

51

Equilibrium and Fixed Bed Adsorption of 1?Butene, Propylene and Propane Over 13X Zeolite Pellets  

Microsoft Academic Search

Propylene?propane separation is one of the most difficult and demanding energetic operation currently practiced using cryogenic distillation. Extensive studies on various alternatives showed that cyclic adsorption processes, and particularly pressure swing adsorption (PSA), might be an option to replace the traditional distillation. In spite of the promising results of the PSA process, much attention is currently being paid to the

Nabil Lamia; Luc Wolff; Philibert Leflaive; Pedro Sá Gomes; Carlos A. Grande; Alírio E. Rodrigues

2008-01-01

52

Mechanistic studies of a protonolytic organomercurial cleaving enzyme: bacterial organomercurial lyase  

SciTech Connect

Studies with stereochemically defined substrates cis-2-butenyl-2-mercuric chloride (1) and endo-norbornyl-2-mercuric bromide (2) reveal that a high degree of configurational retention occurs during the bond cleavage, while studies with exo-3-acetoxynortricyclyl-5-mercuric bromide (3) and cis-exo-2-acetoxy-bicyclo(2.2.1)hept-5-enyl-3-mercuric bromide (4) show that the protonolysis proceeds without accompanying skeletal rearrangement. Kinetic data for the enzymatic reactions of cis-2-butenyl-2-mercuric chloride (1) and trans-1-propenyl-1-mercuric chloride (6) indicate that these substrates show enhanced reaction rates of ca. 10-200-fold over alkylvinylmercurials and unsubstituted vinylmercurials, suggesting that the olefinic methyl substituent may stabilize an intermediate bearing some positive charge. Enzymatic reaction of 2-butenyl-1-mercuric bromide (5) yields a 72/23/5 mixture of 1-butene/trans-2-butene/cis-2-butene, indicative of intervening SE2' cleavage. The observation of significant solvent deuterium isotope effects at pH 7.4 of Vmax (H/sub 2/O)/Vmax(D/sub 2/O) = 2.1 for cis-2-butenyl-2-mercuric chloride (1) turnover and Vmax(H/sub 2/O)/Vmax(D/sub 2/O) = 4.9 for ethylmercuric chloride turnover provides additional support for a kinetically important proton delivery. Finally, the stoichiometric formation of butene and Hg(II) from 1 and methane and Hg(II) from methylmercuric chloride eliminates the possibility of an SN1 solvolytic mechanism. As the first well-characterized enzymatic reaction of an organometallic substrate and the first example of an enzyme-mediated SE2 reaction the organomercurial lyase catalyzed carbon-mercury bond cleavage provides an arena for investigating novel enzyme structure-function relationships.

Begley, T.P.; Walts, A.E.; Walsh, C.T.

1986-11-04

53

The oligomerization of 1-butene using NaY zeolite ion-exchanged with different nickel precursor salts  

Microsoft Academic Search

A number of catalysts were prepared by ion exchanging NaY extrudates with different nickel precursor salts. These nickel exchanged NaY catalysts (NiNaY) were used to oligomerize butenes in the liquid phase using a batch reactor. The acidity of catalysts, determined by temperature programmed desorption, was found to be dependent on the type of nickel precursor salt. The catalyst derived from

B. Nkosi; F. T. T. Ng; G. L. Rempel

1997-01-01

54

Effect of water on silica-supported phosphotungstic acid catalysts for 1-butene double bond shift and alkane skeletal isomerization  

Microsoft Academic Search

The thermal stability, acidity, catalytic activity and regenerability of silica-supported phosphotungstic acid were evaluated in reference to the bulk solid acid. Samples were prepared with 5, 10, and 25wt.% heteropolyacid (HPA) on fumed silica to examine the effect of loading on the properties of supported acid catalysts. X-ray absorption spectroscopy indicated that the supported heteropolyacids did not completely decompose when

Billy B Bardin; Robert J Davis

2000-01-01

55

On the use of 1-butene double-bond isomerization as a probe reaction on cesium-loaded zeolite X  

Microsoft Academic Search

Oxides of cesium and potassium were synthesized in the supercages of zeolite X by impregnation and decomposition of acetate precursors. The alkali-loaded zeolites were characterized by N2 adsorption, CO2 adsorption microcalorimetry and stepwise TPD of CO2. For a loading of about two alkali metal atoms per zeolite supercage, the majority of CO2 adsorption sites at 373K were characterized by a

Junhui Li; Robert J Davis

2003-01-01

56

Shock tube studies on the decomposition of 2-butanol.  

PubMed

The thermal decomposition of 2-butanol have been studied at temperatures of 1045-1221 K and pressures of 1.5-6 bar using the single pulse shock tube technique. Dilute concentrations of 2-butanol have been decomposed in the presence of large quantities of a radical inhibitor. The mechanism for decomposition involves direct elimination of water producing cis- and trans-2-butene, and 1-butene, and C-C bond fission producing ethylene. Acetaldehyde, propionaldehyde, and propene were also observed in much smaller yields from C-C bond fission. The respective unimolecular rate expressions are as follows: k(C(3)H(6)(OH)CH(3) ? cis-CH(3)CH?CHCH(3) + H(2)O) = 10(13.1 ± 0.3) exp(-33414 ± 755 K/T) s(-1); k(C(3)H(6)(OH)CH(3) ? trans-CH(3)CH?CHCH(3) + H(2)O) = 10(13.5 ± 0.3) exp(-33820 ± 755 K/T) s(-1); k(C(3)H(6)(OH)CH(3) ? CH(3)CH(2)CH?CH(2) + H(2)O) = 10(13.6 ± 0.3) exp(-33002 ± 755 K/T) s(-1); k(C(3)H(6)(OH)CH(3) ? C(2)H(5)(•) + (•)CH(OH)CH(3)) = 10(15.9 ± 0.3) exp(-39252 ± 755 K/T) s(-1). These rate expressions are compared with analogous reactions for primary and tertiary butanols. They form a basis for the prediction of those for related systems. Comparison with estimated values used in the simulation of butanol combustion is indicative of the uncertainties in the rate constants that are used in such models. The activation energy of 326 kJ/mol leads to a bond dissociation energy of the CH(OH)CH(3) radical (H-CH(OH)CH(3)) of 400 kJ/mol, in excellent agreement with earlier calculated results from theory and disagreement with the experimental results from iodination studies in the expected range. PMID:22946999

Rosado-Reyes, Claudette M; Tsang, Wing

2012-09-20

57

Evaluation of non-methane hydrocarbon (NMHC) emissions based on an ambient air measurement in Tokyo area, Japan  

NASA Astrophysics Data System (ADS)

Non-methane hydrocarbons (NMHCs) are known to have an important role on air quality due to their high reactivity. NMHC analysis has been performed on 148 ambient air samples collected at five different sites in the Kanto area (Tokyo metropolitan area and surrounding six prefectures) of Japan in summer and winter of 2008, and fifty NMHCs have been determined and quantified. A field measurement campaign has been conducted at one of the busiest intersections in Tokyo metropolitan area in winter of 2008. NMHC emissions are evaluated through comparison of distributions of individual NMHCs emitted from motor vehicles, which are estimated from the measurements, with those determined from the current emissions inventory. The comparison revealed that the measured distributions of acetylene, ethylene and toluene showed a good agreement with those estimated from the emissions inventory (the values estimated from the measurements are a factor of 1.5, 0.56 and 2.3 larger than the emissions inventory in median, respectively), however, propane and isobutane are found to be significantly underestimated in the emissions inventory (the measured values were a factor of 18 and 5.1 larger than the emissions inventory, respectively). The significant underestimate of propane can be explained by that the current emissions inventory does not consider emissions from liquefied propane gas (LPG) fueled vehicles. However, for isobutane, reasons for the underestimate are still unclear. Another field measurement has been conducted in summer of 2008, where the air samples have been collected at three different sites on the ground and by a helicopter as well. Remarkable high concentrations of 1-butene and cis- and trans-2-butenes have been sporadically observed in the samples collected at Urayasu in the coastal area of Tokyo bay. Calculated propylene equivalent (PE) concentrations of butenes revealed that those have a significantly important role in ozone formation when the air plume is affected by emissions from their emission sources. The PE concentrations of butenes varied from 0.1 to 39 ppbC, and accounted for 1.5-75% of total PE concentrations at Urayasu. Most of the continuous air quality monitoring stations does not record concentrations of individual hydrocarbons, therefore, the importance of reactive and low concentration hydrocarbon such as butenes might be overlooked in the current emissions inventory and/or air quality model. In this paper, the reliability of NMHC emissions is evaluated based on the field measurements. Their possible impacts on air quality in the Kanto area are discussed as well, based on the calculated propylene equivalent concentrations.

Matsunaga, Sou N.; Chatani, Satoru; Morikawa, Tazuko; Nakatsuka, Seiji; Suthawaree, Jeeranut; Tajima, Yosuke; Kato, Shungo; Kajii, Yoshizumi; Minoura, Hiroaki

2010-12-01

58

Laboratory Analysis Of Water, Hydrocarbon And Ammonia Ice Mixtures Exposed To High-energy Electron Irradiation  

NASA Astrophysics Data System (ADS)

Irradiation of low temperature ices in the laboratory provides insight into processes that may be occurring on icy bodies in the solar system. Here we report on results from high-energy (10keV) electron irradiation of thin ice films at 1e-8 torr and 70-120K. Mixtures include water with CO2, C3H8, C3H6, C4H10 (butane and isobutane), C4H8,(1-butene and cis/trans-2-butene), and NH3. During irradiation of H2O + alkane films at 80K, CO2 and CH4 production is observed and both species are retained in the ice, possibly trapped in clathrates. The -CH3 infrared bands initially present are seen to decrease with increasing dose. Bands associated with -CH2- persist, indicating polymerization of the initial short-chain hydrocarbons. In alkenes a similar evolution toward polymerization is observed, however the first step appears to be the destruction of the C=C bond. Upon warming of the film, mass spectra data compliment the mid-infrared data and indicate the production of H2CO, however glycolic acid is not explicitly seen in the mass spectra. When warmed to 300K, residues remained for all irradiated films except that of the H2O + CO2 mixtures. Residues were analyzed with Matrix Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI). Results show the production of large aliphatic, very refractory, hydrocarbons (with m/z up to 2500). Mid-infrared spectra of the residues indicate carbonyls and alcohols, likely due to polymerized aldehydes and carboxylic acids. Films of H2O + C3H8 + NH3 at 70K show the production of OCN- (cyanate ion), formamide, along with other possible amides and hydrocarbons. HPLC results indicate the production of racemic alanine. Finally, results of abiotic experiments are compared to results from the irradiation of bacterial spores in ice. The application to Europa and Enceladus is discussed.

Hand, Kevin P.; Carlson, R. W.; Tsapin, A. I.

2006-09-01

59

1,1-bis(3,5-dimethyl-1-pyrazolyl)- and 1Amino1-(3,5-dimethyl-1-pyrazolyl)-4,4-dichloro-1-buten-3-ones  

Microsoft Academic Search

Reaction of 1,1,4,4-tetrachloro-3-buten-2-one with 3,5-dimethylpyrazole gave 1,1-dichloro- 4,4-bis-(3,5-dimethyl-1-pyrazolyl)-3-buten-2-one. Treatment of the latter with amines resulted in replacement of one pyrazole ring by the amine residue with formation of the corresponding 4-amino-1,1-dichloro-4-(3,5- dimethyl-1-pyrazolyl)-3-buten-2-ones.

V. I. Potkin; S. K. Petkevich; R. V. Kaberdin; P. V. Kurman

2004-01-01

60

EXTENDED ALKYLATE PRODUCTION ACTIVITY DURING FIXED-BED SUPERCRITICAL 1-BUTENE/ISOBUTANE ALKYLATION ON SOLID ACID CATALYSTS USING CARBON DIOXIDE AS DILUENT. (R824729)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

61

Effect of photochemically produced oxidants on growth of avena coleoptile sections  

Microsoft Academic Search

Avena coleoptile sections incubated in solutions through which photochemically produced oxidant mixtures, ozone or peroxyacetyl nitrate (PAN) are passed, display subsequent repressed growth in fresh solutions to which auxin has been supplied. Treatment by oxidant recording as 1.4 ppm derived from an irradiated mixture of trans-2-butene and NOâ results in about 50% inhibition of elongation. About 1.5 ppm PAN also

L. Ordin; B. Propst

1961-01-01

62

A Comparison Between Conventional and Ultrasound-Mediated Heterogeneous Catalysis: Hydrogenation of 3-buten-1-ol Aqueous Solutions  

SciTech Connect

A power flow scheme applicable to probe-type ultrasound reactors is presented, that has been deduced from both experimental measurements employing an unjacketed vessel and theoretical predictions. Under typical conditions for water, 77% of the electrical power is converted into mechanical motion of the probe, that in turn is dissipated to both acoustic power (~12%) and cavitational heating (~88%). Approximately 92% of the mechanical power of the probe was converted into heat, with the remaining power presumably converted into audible acoustic and/or mechanical motion. Heterogeneous catalysis experiments have been performed at 298 K in an isothermal (i.e., jacketed) reaction vessel comparing chemistry in conventional (e.g., thermal) versus ultrasound-assisted systems. Both product state distribution and reaction rate measurements have been performed for the hydrogenation (using hydrogen gas) of aqueous 3-buten-1-ol solutions employing Pd-black powder. Products from the heterogeneous catalysis include isomerization to cis and trans 2-buten-1-ol, as well as hydrogenation to 1-butanol. Based on the observed differences in cis- to trans- 2-buten-1-ol ratios in conventional experiments, employing untreated and pre-reduced catalysts, it has been determined that a kinetic effect controls the observed product state distribution. In addition, differences in the ratio between cis- plus trans- 2-buten-1-ol to 1-butanol, comparing ultrasound-assisted to conventional catalysis, reveal a ~5-fold enhancement in isomerization relative to the more energetically favored hydrogenation due to application of ultrasound. Finally, the product formation rates for 1-butanol, as well as isomerization plus hydrogenation, revealed that conventional and ultrasound experiments showed both a non-linear dependence with applied ultrasound power and no differences between untreated and pre-reduced catalysts. The observed reaction rate enhancements were 1:36:183 for the conventional, 90 W ultrasound, and 190 W ultrasound experiments, respectively.

Disselkamp, Robert S.; Judd, Kayte M.; Hart, Todd R.; Peden, Charles HF; Posakony, Gerald J.; Bond, Leonard J.

2004-01-25

63

Transport Properties of Gaseous Hydrocarbons  

Microsoft Academic Search

Measurements have been made, at temperatures between 35 and 100 degrees C, of the viscosities and thermal conductivities of gaseous methane, ethane, ethylene, propane, propylene, cyclo-propane, n-butane, cis-2-butene, trans-2-butene, 1:3-butadiene, iso-butane, n-pentane, iso-pentane, neo-pentane, cyclo-pentane, n-hexane, neo-hexane, cyclo-hexane, benzene, n-heptane, 2:4-dimethyl-pentane, n-octane, 2:3:4-trimethyl-pentane and of carbon tetrafluoride. Viscosities were measured by observing the damping of a pendulum swinging in the

J. D. Lambert; K. J. Cotton; M. W. Pailthorpe; A. M. Robinson; J. Scrivins; W. R. F. Vale; R. M. Young

1955-01-01

64

Environmental Decision Memo for Food Contact Notification ...  

Center for Food Safety and Applied Nutrition (CFSAN)

... 869 – propylene/1-butene/ethylene copolymer (PBER) with high 1-butene content (28%wt max.) for use as elastomers in food-contact applications. ... More results from www.fda.gov/food/ingredientspackaginglabeling/environmentaldecisions

65

Bactericidal effects of photochemical smog constituents produced by a flow reactor. III. Communication: determination of mutagenic effects of photochemical smog on E. coli K 12 343/113.  

PubMed

The multipurpose strain E. coli K12 343/113 allows the simultaneous detection of different DNA alterations such as base-pair changes, frameshifts and deletions. The investigations show the detection of mutagenic potency in the mixture which is called photochemical smog, produced by a flow reactor. Responsible for these effects were ozone and hydrocarbon-radicals, but not NOx, hydrocarbons (propene, isobutene, trans-2-butene) and peroxiacetylnitrate (PAN). In the given conditions these mutagenic substances are involved in DNA alterations like base-pair changes and deletions due to the amounts of colonies in the gal+-, MTR-, and arg+-system. No frameshifts could be detected in the nad+-system. PMID:3901606

Nover, H; Botzenhart, K

1985-06-01

66

Double methyl substitution in simple alkenes leads to low-barrier reactions towards molecular fluorine  

NASA Astrophysics Data System (ADS)

The reactions of F 2 with isomers of butene were investigated with crossed-beam reactive scattering and ab initio computations. Only one product channel F + C 4H 8F was observed in the experiments; the HF + C 4H 7F channel was searched but not found. The reaction path of F 2 + C 4H 8 ? F + C 4H 8F was studied theoretically. Very low barriers of less than 1 kcal/mol were found for the F 2 reactions with cis-2-butene, trans-2-butene, and isobutene, which all contain two methyl substitution groups. This theoretical prediction, yet to be confirmed experimentally, suggests that double methyl substituted C dbnd C double bonds can react with F 2 almost without a barrier.

Li, Zhi-Qiang; Tsai, Chen-Hsun; Chen, Andrew F.; Lu, Yu-Ju; Lin, Jim J.

2011-06-01

67

Fermentative production of isobutene  

Microsoft Academic Search

Isobutene (2-methylpropene) is one of those chemicals for which bio-based production might replace the petrochemical production in the future. Currently, more than 10 million metric tons of isobutene are produced on a yearly basis. Even though bio-based production might also be achieved through chemocatalytic or thermochemical methods, this review focuses on fermentative routes from sugars. Although biological isobutene formation is

B. N. M. Van Leeuwen; A. M. Van der Wulp; I. Duijnstee; A. J. A. Van Maris; A. J. J. Straathof

2012-01-01

68

Reinvestigation of the reaction of tert-butyllithium with uranium tetrachloride: formation of catalytically active uranium(III) hydride complexes  

Microsoft Academic Search

The reaction of UClâ with t-CâHâLi in alkane solvents has been reinvestigated in detail by quantitative collection and identification of gaseous products and by spectral, analytical, and chemical characterization of the solid uranium products. Treatment of UClâ with 4 equiv of t-CâHâLi generates 1.5 to 1.8 equiv of 2-methylpropane and 2-methylpropene in a 2.5-3 to 1 ratio and a solid

William J. Evans; Donald J. Wink; David R. Stanley

1982-01-01

69

Equilibrium constants for methyl tert-butyl ether and ethyl tert-butyl ether liquid-phase syntheses using C[sub 4] olefinic cut  

Microsoft Academic Search

Equilibrium constants for the liquid-phase syntheses of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) were determined experimentally in the temperature range 313--353 K and at 1.6 MPa, using as source of 2-methylpropene (isobutylene) a C[sub 4] olefinic cut proceeding from a steam cracking unit. To reach etherification equilibrium, the macroporous sulfonic acid resin K-2631 (Bayer) was used as

J. F. Izquierdo; F. Cunill; M. Vila; M. Iborra; J. Tejero

1994-01-01

70

Selective hydrogenation of an acetylenic bond conjugated with an ethylenic bond over a zinc catalyst  

Microsoft Academic Search

1.Taking isoprene and piperylene as examples, we showed that hydrogen does not add to conjugated double bonds over a zinc catalyst at 60–140° under normal pressure.2.1-Buten-3-yne and 2-methyl-1-buten-3-yne are hydrogenated selectively over a zinc catalyst with formation of butadiene and isoprene, respectively.

L. Kh. Freidlin; V. I. Gorshkov; T. K. Lavrovskaya

1959-01-01

71

Two-color photoionization-photoelectron spectroscopy using tunable vacuum ultraviolet and infrared laser sources  

NASA Astrophysics Data System (ADS)

A photoion-photoelectron apparatus has been constructed for photoion and photoelectron spectroscopic studies allowing for high-resolution photoion and photoelectron spectroscopic studies of polyatomic molecules trans -2-butene (trans-CH3CH=CHCH3), cis-2-butene, (cis-CH3CH=CHCH3), trans-1-bromopropene (trans-CH3CH=CHBr), cis-1-brompropene (cis-CH3CH=CHBr) and trichloroethene, (ClCH=CCl2) using tunable vacuum ultraviolet (VUV) and infrared (IR) lasers. Coherent VUV laser radiation is generated via nonlinear four-wave frequency mixing techniques, while IR laser light is generated via an optical parametric oscillator/amplifier based on difference-frequency mixing. The high-resolution photoelectron techniques employed are pulsed field ionization-photoelectron (PFI-PE) spectroscopy and photo-induced Rydberg ionization (PIRI) spectroscopy. The single-photon VUV-PFI-PE spectra of trans -2-butene, cis-2-butene, trans-1-bromopropene, and cis-1-bromopropene have been measured, yielding highly precise ionization energies and vibrational frequencies of the corresponding cations. The VUV-IR-PIRI detection scheme is used to probe the high-frequency vibrational modes associated with the symmetric and asymmetric C--H stretching motions in trans-CH3CH=CHCH3 + and ClCH=CCl2+, which cannot be observed in VUV-PFI-PE spectroscopic studies because of the limitation of negligible Franck-Condon factors. We show that by exciting the neutral molecule to a vibrational state prior to VUV photoionization, state-selected and state-to-state photoionization cross sections can be obtained. As a demonstration experiment, we have obtained the frequency for the nu12 (C--H stretching) mode of ClCH=CCl2 by IR-VUV-PFI-PE-depletion and IR-VUV-photoion measurements. By fixing the IR laser at the nu12 frequency followed by VUV-PIE measurements, we have determined the relative state-to-state photoionization cross sections for the processes, ClCH=CCl2+(nu 12+ = 1) ClCH=CCl2(nu12 = 1), ClCH=CCl2+ ? ClCH=CCl2, and ClCH=CCl 2+ ? ClCH=CCl2(nu12 = 1), where ClCH=CCl2 and ClCH=CCl2+ are in their vibrational states.

Woo, Hin-Koon

72

Theoretical determination of molecular structure and conformation. IV. Electronic effects influencing the stability of methyl substituted primary ozonidesa),b)  

NASA Astrophysics Data System (ADS)

The conformational surfaces of three methyl substituted primary ozonides (PO), namely, 4-methyl-1,2,3-trioxolane (propene PO), cis-4,5-dimethyl-1,2,3-trioxolane (cis-2-butene PO) and the corresponding trans PO (trans-2-butene PO), are studied with restricted Hartree-Fock (RHF) theory employing a split valence [3s2p/2s] and an augmented split valence [3s2p1d/2s] basis set. An analysis of the computed RHF energies reveals that only with polarization functions in the basis set is a reliable theoretical description of the three PO's guaranteed. In the case of propene PO and trans-2-butene PO, reasonable results are obtained by means of a rigid pseudorotor model based on the theoretically determined structures of various 1,2,3-trioxolane conformations. However, a flexible pseudorotor model is necessary in the case of cis-2-butene PO in order to achieve a realistic account of substituent-substituent interactions. The conformational surfaces of all three PO's closely resemble that of the parent PO, 1,2,3,-trioxolane. Thus, the preferential interconversional process of a methyl substituted PO is pseudorotation hindered by barriers between 2.3 and 3.5 kcal/mole. In marked contrast to previous semiempirical results, the oxygen envelope (E) conformations are calculated to be the most stable puckered PO forms. This finding is most important with regard to the stereochemical aspects of the ozonolysis mechanism. The methyl groups either stabilize or destabilize the puckered PO ring depending on the position of the substituent. With the aid of the pseudorotation phase angle and a well-defined substituent orientation angle, reliable predictions with regard to the electronic effect of a methyl group can be made. It is shown that only an equatorially placed methyl group leads to a favorable orbital mixing between the ?-type MO's of the ring and the substituent and a resultant lowering of the two highest occupied MO's of the PO. The puckered ring is stabilized by back-donation of electron charge to the substituent which is not possible if this is axially positioned.

Cremer, Dieter

1979-02-01

73

Catalytic activity of some transition metal complexes with lactam ligands  

SciTech Connect

Coordination compounds are widely used in the national economy and in chemical technology as catalysts. The authors studied complexes (I-V) as catalysts of isomerization of 1,4-dichloro-2-butene into 3,4-dichloro-1-butene.

Shestakova, S.I.; Kaplan, G.I.; Sinyukova, S.V. [Research Institute of Chemical Means for Plant Protection, Moscow (Russian Federation)] [and others

1994-08-10

74

Abscission: The Role of Ethylene, Ethylene Analogues, Carbon Dioxide, and Oxygen.  

National Technical Information Service (NTIS)

Ethylene was the most effective abscission accelerant examined, with decreasing activity shown by propene, carbon monoxide, acetylene, vinyl fluoride, 1-butene, and 1,3-butadiene. Carbon dioxide inhibited abscission, but its effect was overcome by ethylen...

F. B. Abeles H. E. Gahagan

1968-01-01

75

MOF-supported selective ethylene dimerization single-site catalysts through one-pot postsynthetic modification.  

PubMed

The one-pot postfunctionalization allows anchoring a molecular nickel complex into a mesoporous metal-organic framework (Ni@(Fe)MIL-101). It is generating a very active and reusable catalyst for the liquid-phase ethylene dimerization to selectively form 1-butene. Higher selectivity for 1-butene is found using the Ni@(Fe)MIL-101 catalyst than reported for molecular nickel diimino complexes. PMID:23470137

Canivet, Jerome; Aguado, Sonia; Schuurman, Yves; Farrusseng, David

2013-03-11

76

Stabilities of C 3–C 5 alkoxide species inside H-FER zeolite: a hybrid QM\\/MM study  

Microsoft Academic Search

Adsorption (?-complex formation) and chemisorption (alkoxide formation) of ethene, propene, 1-butene, and 1-pentene, as well as of isobutene and 2-methyl-1-butene, in zeolite H-FER are examined by a hybrid quantum mechanics\\/molecular mechanics (QM\\/MM) method that takes van der Waals (dispersion) interactions into account. The predicted heats of adsorption (36, 51, 45, 64, 41, 47 kJ\\/mol, respectively) fall into energy ranges inferred

Ville Nieminen; Marek Sierka; Dmitry Yu. Murzin; Joachim Sauer

2005-01-01

77

Structure sensitivity of double bond isomerization of butene over MgO surfaces: A periodic DFT study  

Microsoft Academic Search

Using periodic density functional theory calculations, the double bond isomerization of 1-butene to 2-butene over MgO surfaces with and without structure defects is investigated. The basicity of these surfaces was characterized by the adsorption of H2O and CO2. The isomerization process involves two steps: (i) the abstract of H atom from 1-butene to form chemisorbed 2-butenide with allyl group and

Chuan-Ming Wang; Yang-Dong Wang; Jing Dong; Su Liu; Zai-Ku Xie

2011-01-01

78

Sulfonated polymeric dispersant compositions for subterranean well drilling, completion, and cementing  

SciTech Connect

A fluid is described, comprising: a mixture of a drilling fluid and a cement slurry; and a dispersant copolymer comprising a first monomer and a second monomer, wherein said first monomer comprises maleic anhydride and wherein said second monomer is selected from the group consisting of sulfonated ethene, sulfonated propene, sulfonated 1-butene, sulfonated 2-butene, sulfonated 1-pentene, sulfonated 2-penetene, sulfonated 2-methyl-1-butene, sulfonated 2-methyl-2-butene, sulfonated 3-methyl-1-butene, sulfonated cyclopentene, sulfonated cyclohexene, sulfonated 1-hexene, sulfonated 2-hexene, sulfonated 3-hexene, sulfonated 2-methyl-1-pentene, sulfonated 2-methyl-2-pentene, sulfonated 2-methyl-3-pentene, sulfonated 3-methyl-1-pentene, sulfonated 3-methyl-2-pentene, sulfonated 4-methyl-1-pentene, sulfonated 3,-dimethyl-1-butene, sulfonated 2,3-dimethyl-1-butene, sulfonated 2,3-dimethyl-2-butene, sulfonated 2-ethyl-1-butene, sulfonated 1,3-butadiene, sulfonated 1,3-pentadiene, sulfonated 1,4-pentadiene, sulfonated 2-methyl-1,3-butadiene, sulfonated 2,3,-dimethyl-1,3-butadiene, sulfonated 2-ethyl-butadiene, sulfonated 2-methyl-1,3-pentadiene, sulfonated 3-methyl-1,3-pentadiene, sulfonated 4-methyl-1,3-pentadiene, sulfonated 2-methyl-1,4-pentadiene, sulfonated 3-methyl-1,4-pentadiene, sulfonated 4-methyl-1,4-pentadiene, sulfonated 1,3-hexadiene, sulfonated 2,4-hexadiene, and sulfonated 1,3,5-hexatriene.

Bloys, J.B.; Morgan, R.F.

1993-06-22

79

Vibronic excitation of oxygen-atom transfer from NO sub 2 to ethylene by long-wavelength visible light in a cryogenic matrix  

SciTech Connect

Chemical reaction has been observed upon irradiation of ethylene{center dot}NO{sub 2} pairs in solid Ar with continuous-wave dye laser light at visible wavelengths as long as 574 nm, well below the 398-nm dissociation limit of isolated NO{sub 2}. Reaction products were acetaldehyde, ethylene oxide, NO, and ethyl nitrite radical, as established by FT infrared spectroscopy. Kinetic analysis of product absorbance growth showed that acetaldehyde is the prevalent final oxidation product of direct, single-photon photolysis of ethylene{center dot}{sub 2} pairs, while ethylene oxide is exclusively produced by yellow and shorter wavelength induced photodissociation of trapped ethyl nitrite radical. Experiments with trans- and cis-CHD{double bond}CHD yielded nitrite radical CHD-CHD-ONO under retention of stereochemistry but with scrambling in the epoxide product. On the basis of these results and those of their earlier work on NO{sub 2} photooxidation of cis- and trans-2-butene, a reaction path is proposed that involves O-atom transfer from NO{sub 2} to the C{double bond}C bond to give a short-lived singlet oxirane biradical. The photolysis wavelength dependence of the reaction quantum efficiency indicates that NO{sub 2} reactant vibrational excitation plays an essential role and opens a reaction path that is unique to visible light induced alkene + NO{sub 2} chemistry in a matrix.

Nakata, Munetaka; Frei, Heinz (Lawrence Berkeley Lab., CA (USA)); Shibuya, Kazuhiko (Tokyo Institute of Technology (Japan))

1990-10-18

80

The use of design-of-experiments methodology to optimize polymer capsule fabrication. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports  

SciTech Connect

Future inertial-fusion experiments on Omega will utilize {approximately} 1 mm-diameter cryogenic targets that have a {approximately} 100-{micro}m-thick, uniformly-frozen fuel layer on their interior. It is desired that they have a stress-free wall thickness < 1 {micro}m and an rms surface roughness < 20 nm. A design-of-experiments (DOE) approach was used to characterize a glow-discharge-polymerization coater built at LLE to fabricate smooth, stress-free capsules with submicron wall thicknesses. The DOE approach was selected because several parameters can be changed simultaneously in a manner which allows the minimum number of runs to be performed to obtain statistically-relevant data. Planar, silicon substrates were coated with {approximately} 3--5 {micro}m of polymer and profilometry was used to determine the coating rate, the film stress, and the surface roughness. The coating rate was found to depend on the trans-2-butene/hydrogen ratio, the total gas-flow rate, the total chamber pressure, and the RF power. In addition, a two-parameter interaction between the total pressure and the RF power also affects the coating rate. The film stress depends on the total chamber pressure and the total mass-flow rate. The surface roughness is independent of the parameters studied. Preliminary results indicate that capsules can be produced rapidly without affecting the smoothness of their outside surface and without residual stress in their walls.

Lai, L. [Pittsford Mendon High School, NY (United States)

1999-03-01

81

Pulmonary function in normal and elastase-treated hamsters exposed to a complex mixture of olefin-ozone-sulfur dioxide reaction products  

SciTech Connect

An elastase-induced emphysema model was utilized to determine if hamsters with preexisting lung disease were more susceptible to lung damage from air-pollutant exposure. Male golden hamsters, divided into two treatment groups, were given a single intratracheal injection of either 6 units of porcine pancreatic elastase (EMP) or buffer (CNT). After a 4-week recovery period, equal numbers of each group were exposed 23 hr/day x 28 day to filtered air (AIR) or to the complex by-products from a dark-phase-reaction mixture of trans-2-butene, ozone, and sulfur dioxide (MIX). Lung-function measurements on the elastase-treated groups showed changes consistent with mild emphysema. There were no significant differences in lung volumes or lung compliance between the AIR- and MIX-exposed animals. However, the nitrogen washout slope decreased and the diffusing capacity for carbon monoxide increased in both the CNT and EMP hamsters exposed to the MIX. The change in diffusing capacity was greater in normal hamsters than in hamsters with emphysema, and it is hypothesized that animals with impaired lung function had a decreased ability to respond to a pulmonary insult from the mix.

Raub, J.A.; Miller, F.J.; Graham, J.A.; Gardner, D.E.; O'Neil, J.J.

1983-01-01

82

Production of OH radicals from the reactions of C 4-C 6 internal alkenes and styrenes with ozone in the gas phase  

NASA Astrophysics Data System (ADS)

OH formation from the ozonolysis reactions of seven internal alkenes with 4-6 carbons, styrene, trans- ?-methyl styrene, and ?-methyl styrene was studied using complementary techniques. A small-ratio relative-rate technique in which small quantities of OH tracers are added to monitor OH formation yields provided the following results: trans-2-butene, 0.64±0.12; cis-2-butene, 0.33±0.05; trans-2-pentene, 0.46±0.08; cis-2-pentene, 0.29±0.06; trans-3-hexene, 0.53±0.08; cis-3-hexene, 0.36±0.07; and 2-methyl-2-butene, 0.98±0.24. For styrene, trans- ?-methyl styrene, and ?-methyl styrene, OH yields of 0.07±0.04, 0.22±0.09, and 0.23±0.12 were measured, respectively. A second method, which monitors product formation from the OH reaction with 2-butanol was used to derive OH formation yields from 2,3-dimethyl-2-butene, 2-methyl-2-butene and cis-2-pentene, and provided yields of 0.91±0.14, 0.80±0.12, and 0.27±0.07, respectively. The results are briefly discussed in terms of the relationship between structures of these alkenes and OH formation.

Orzechowska, Grazyna E.; Paulson, Suzanne E.

83

The effect of process parameters on the surface finish of plasma polymers  

SciTech Connect

The surface finish of plasma polymers deposited in an inductively coupled discharge were measured as a function of gas flow rates. Surface finish was measured both optically and by AFM. The process parameters of the plasma polymerization were found to effect the surface finish. The gases used were trans-2- butene and hydrogen for hydrocarbon polymers. For bromocarbon polymers we added ethylbromide. The smoothest hydrocarbon polymer coatings had an RMS surface finish better than 1 nm. Bumps 200 nm high spaced approximately 1 {mu}m apart grew on the surface of bromocarbon coatings when they were exposed to air. The composition of the bumps was found to be NH{sub 4}Br by XRD and XPS analysis. We believe that nitrogen (from a small leak or desorption) dissociates in the discharge and reacts with hydrogen to form ammonia. The ammonia then reacts with HBr, a dissociation product of ethylbromide, to form NH{sub 4}Br which is dispersed throughout the deposited layer. Humidity facilitates the transport of the NH{sub 4}Br to the surface where it crystallizes. Bump growth was prevented by either dry storage or overcoating with 3 {mu}m of hydrocarbon plasma polymer. Alternatively, the bumps could be washed from the surface with water.

Letts, S.A.; Cook, R.C.; Welch, P.; McEachern, R.; Fearon, E.

1992-12-09

84

Evaluation of Fluidized Beds for Mass Production of IFE Targets  

SciTech Connect

Of the building blocks of an inertial fusion energy (IFE) plant, target fabrication remains a significant credibility issue. For this reason, an extensive parametric study has been conducted on mass production of glow discharge polymer (GDP) shells in a vertical fluidized bed. Trans-2-butene was used as a reactant gas with hydrogen as a diluting and etching agent. Coating rates in the range of 1 to 2 {mu}m/h were demonstrated on batches of 30 shells where National Ignition Facility-quality surfaces were obtained for 3- to 5-{mu}m-thick coatings. Thick coatings up to 325 {mu}m were also demonstrated that are visually transparent, without void and stress fracture. A phenomenological understanding of the GDP growth mechanisms to guide future experiments was further established. Specifically, gas-phase precipitation and high-impact collisions were identified as the main surface-roughening mechanisms. The former produces dense cauliflower-like surface patterns that can be eliminated by adjusting the gas flow rates and the flow ratio. The latter produces isolated domelike surface defects that can be reduced by introducing concerted motion between the shells. By converting from a vertical to a horizontal configuration, fully transparent coatings were obtained on 350 shells. Collisions in a fluidized bed have been identified as the limiting factor in meeting IFE specifications, and a related-rotary kiln technique is recommended for scale-up.

Huang, H.; Vermillion, B.A.; Brown, L.C.; Besenbruch, G.E.; Goodin, D.T.; Stemke, R.W.; Stephens, R.B. [General Atomics (United States)

2005-01-15

85

Synthesis of the E and Z isomers of the antiestrogen tamoxifen and its metabolite, hydroxytamoxifen, in tritium-labeled form  

SciTech Connect

Both isomers of the potent antiestrogen tamoxifen (1,2-diphenyl-1-(4-(2-(dimethylamino)ethoxy)phenyl)-1-butene: E isomer = ICI-47699; Z isomer = ICI-46474, Nolvadex) and its metabolite, hydroxytamoxifen (1-(4-(2-(dimethylamino)ethoxy)phenyl)-1-(4-hydroxyphenyl)-2-phenyl-1-butene), have been synthesized in a high specific activity, tritium-labeled form by catalytic tritium-halogen exchange performed on brominated precursors. The synthesis of another precursor to labeled tamoxifen which would enable the incorporation of three tritium atoms into the molecule by tritium-halogen exchange is reported.

Robertson, D.W.; Katzenellenbogen, J.A.

1982-06-04

86

Nonchelated d0 zirconium-alkoxide-alkene complexes.  

PubMed

The reaction of Cp'2Zr(O(t)Bu)Me (Cp' = C5H4Me) and [Ph3C][B(C6F5)4] yields the base-free complex [Cp'2Zr(O(t)Bu)][B(C6F5)4] (6), which exists as Cp'2Zr(O(t)Bu)(ClR)+ halocarbon adducts in CD2Cl2 or C6D5Cl solution. Addition of alkenes to 6 in CD2Cl2 solution at low temperature gives equilibrium mixtures of Cp'2Zr(O(t)Bu)(alkene)+ (12a-l), 6, and free alkene. The NMR data for 12a-l are consistent with unsymmetrical alkene bonding and polarization of the alkene C=C bond with positive charge buildup at C(int) and negative charge buildup at C(term). These features arise due to the lack of d-pi* back-bonding. Equilibrium constants for alkene coordination to 6 in CD2Cl2 at -89 degrees C, K(eq) = [12][6](-1)[alkene](-1), vary in the order: vinylferrocene (4800 M(-1)) > ethylene (7.0) approximately alpha-olefins > cis-2-butene (2.2) > trans-2-butene (<0.1). Alkene coordination is inhibited by sterically bulky substituents on the alkene but is greatly enhanced by electron-donating groups and the beta-Si effect. Compounds 12a-l undergo two dynamic processes: reversible alkene decomplexation via associative substitution of a CD2Cl2 molecule, and rapid rotation of the alkene around the metal-(alkene centroid) axis. PMID:16787081

Stoebenau, Edward J; Jordan, Richard F

2006-06-28

87

The role of transition metal promoters on sulfated zirconia catalysts for low-temperature butane isomerization  

SciTech Connect

The low temperature isomerization of butane to isobutane was catalyzed by sulfated zirconia promoted with transition metals like Fe, Mn, and Pt. At 323 K, the Fe,Mn-promoted sample exhibited the usual induction period to a highly active state, followed by rapid deactivation. At the same conditions, a Pt-promoted catalyst also showed an induction period but was followed by a period of unusually stable activity, even in the absence of dihydrogen. The mechanism of the isomerization reaction, evaluated by using {sup 13}C-labeled butane over Fe,Mn-promoted at 323 K and unpromoted sulfated zirconia at 473 K, was found to be intermolecular. Because the formation of a C{sub 8} intermediate in a bimolecular pathway most likely involves the reaction of olefins, the effect of adding trans-2-butene to the butane feed was investigated. The increase in isomerization activity that accompanied butene addition was consistent with a mechanism in which butene is protonated by acid sites of the catalyst to initiate a chain reaction that eventually produces isobutane. Since the calculated chain length (moles isobutane formed/moles butene added) was similar for all of the materials studied, the acidities of the catalysts appear to be unaffected by the presence of transition metals. Therefore, the role of transition metal promoters in sulfated zirconia is to increase the surface concentration of intermediate butenes that subsequently react to form isobutane. Due to the very different stabilities of the promoted catalysts at low temperatures, the authors speculate that the Fe,Mn-promoted sample forms butene non-catalytically whereas the Pt-promoted sample forms butene catalytically. 46 refs., 8 figs., 4 tabs.

Tabora, J.E.; Davis, R.J. [Univ. of Virginia, Charlottesville, VA (United States)

1996-08-01

88

Roughness Optimization at High Modes for GDP CHx Microshells  

SciTech Connect

For the ''Megajoule'' Laser (LMJ) facility of the CEA, amorphous hydrogenated carbon (a-C:H) is the nominal ablator to be used for inertial confinement fusion (ICF) experiments. These capsules contain the fusible deuterium-tritium mixture to achieve ignition. Coatings are prepared by glow discharge polymerization (GDP) with trans-2-butene and hydrogen. The films properties have been investigated. Laser fusion targets must have optimized characteristics: a diameter of about 2.4 mm for LMJ targets, a thickness up to 175 {mu}m, a sphericity and a thickness concentricity better than 99% and an outer and an inner roughness lower than 20 nm at high modes. The surface finish of these laser fusion targets must be extremely smooth to minimize hydrodynamic instabilities.Movchan and Demchishin, and later Thornton introduced a structure zone model (SZM) based on both evaporated and sputtered metals. They investigated the influence of base temperature and the sputtering gas pressure on structure and properties of thick polycrystalline coatings of nickel, titanium, tungsten, aluminum oxide. An original cross-sectional analysis by atomic force microscopy (AFM) allows amorphous materials characterization and permits to make an analogy between the amorphous GDP material and the existing model (SZM). The purpose of this work is to understand the relationship between the deposition parameters, the growing structures and the surface roughness.The coating structure as a function of deposition parameters was first studied on plane silicon substrates and then optimized on PAMS shells. By adjusting the coating parameters, the structures are modified, and in some case, the high modes roughness decreases dramatically.

Theobald, M.; Dumay, B.; Chicanne, C.; Barnouin, J.; Legaie, O.; Baclet, P. [CEA, Commissariat a l'Energie Atomique (France)

2004-03-15

89

Source profiles of volatile organic compounds (VOCs) measured in China: Part I  

NASA Astrophysics Data System (ADS)

The profiles of major volatile organic compound (VOC) sources in China, including vehicle exhaust, gasoline vapor, paint, asphalt, industrial and residential coal burning, biomass burning, and the petrochemical industry, were experimentally determined. Source samples were taken using a dilution chamber for mobile and stationary sources, biomass burning in an actual Chinese farmer's house, and ambient air in a petrochemical industrial area. The concentrations of 92 VOC species were quantified using canister sampling and a gas chromatography-flame ionization detection/mass spectrometry system, and VOC source profiles were developed for source apportionment of VOCs in the Pearl River Delta region. Based on the measurement of source profiles, possible tracers for various emission sources were identified; e.g., 2-methylpentane and 1,3-butadiene could be used as tracers for vehicle exhaust; the characteristic compounds of architectural coating were aromatics such as toluene and m, p-xylene; the light hydrocarbons, namely n-butane, trans-2-butene, and n-pentane, dominated the composition of gasoline vapor; and n-nonane, n-decane, and n-undecane were found to be typical of diesel vapor and asphalt application processes. As different emission sources are characterized by overlapping VOC species, the ratio of possible VOC tracers could be used to assess the contribution of various sources. The ratios between n-butane and isobutane, 1,3-butadiene and isoprene, and the ratios of aromatics (e.g., toluene to benzene and ethylbenzene to m, p-xylene) in the measured sources were compared.

Liu, Ying; Shao, Min; Fu, Linlin; Lu, Sihua; Zeng, Limin; Tang, Dagang

90

Improved synthesis of (9 Z)-9,13-tetradecadien-11-ynal, the sex pheromone of the avocado seed moth, Stenoma catenifer  

Microsoft Academic Search

The terminal dienyne of (9Z)-9,13-tetradecadien-11-ynal, the sex pheromone of the avocado seed moth, Stenoma catenifer, was constructed by coupling a vinyl iodide precursor with commercially available 1-buten-3-yne with Pd catalysis, resulting in a short and efficient synthesis of the pheromone.

Yunfan Zou; Jocelyn G. Millar

2010-01-01

91

Organic chemistry in the oceans of Titan  

Microsoft Academic Search

On Titan, most of the organics present in the atmosphere must condense in the lower stratosphere and be solid near the surface, except methane, ethane, propane, propene and 1-butene which must be liquid and could form oceans containing large fractions of dissolved N2. Chemical evolution on Titan must have followed a way very different from the terrestrial one, involving physical

F. Raulin

1987-01-01

92

TAME (tertiary-amyl-methyl ether) gasoline additive production process development.  

National Technical Information Service (NTIS)

PETROFLEX and COPESUL jointly developed a TAME production process. Tertiary- amyl-methyl ether (TAME) is obtained by the methoxylation of isoamylenes (2- methyl-1-butene and 2-methyl-2-butene) in a C(sub s) cut over a sulfonic acid resin. Process was deve...

H. Lovisi R. Piccoli

1992-01-01

93

In vitro antifungal activity of new series of homoallylamines and related compounds with inhibitory properties of the synthesis of fungal cell wall polymers  

Microsoft Academic Search

The synthesis, in vitro antifungal evaluation and SAR studies of 101 compounds of the 4-aryl-, 4-alkyl-, 4-pyridyl or -quinolinyl-4-N-arylamino-1-butenes series and related compounds, are reported here. Active structures showed to inhibit (1,3)-?-d-glucan and mainly chitin synthases, enzymes that catalyze the synthesis of the major fungal cell wall polymers.

Leonor Y Vargas M; Mar??a V Castelli; Vladimir V Kouznetsov; Juan M Urbina G; Silvia N López; Maximiliano Sortino; Ricardo D Enriz; Juan C Ribas; Susana Zacchino

2003-01-01

94

Determination of Tamoxifen and its Major Metabolites in Exposed Fish  

EPA Science Inventory

Tamoxifen (TAM), (Z)-1-(p-dimethylaminoethoxyphenyl)-1, 2-diphenyl-1-butene, is a nonsteroidal agent that has been used in breast cancer treatment for decades. Its major metabolites are 4-hydroxytamoxifen (4-OHT), N-desmethyltamoxifen (DMT), and endoxifen. While TAM and metabolit...

95

n-Butane isomerization on sulfated zirconia: the effect of nonspecific olefin addition  

Microsoft Academic Search

Butene has been suggested to be an intermediate in the proposed bimolecular mechanism for n-butane isomerization over sulfated zirconia (SZ). The addition of butene has been shown to significantly increase the rate of this reaction. The question can be asked as to whether other olefins would affect this reaction as well. In this study, the effects of propylene, 1-butene and

Nattaporn Lohitharn; James G. Goodwin; Edgar Lotero

2005-01-01

96

Studies of vanadium-phosphorus-oxygen selective oxidation catalysts by sup 31 P and sup 51 V NMR spin-echo and volume susceptibility measurements  

SciTech Connect

The purpose of this work is to characterize the vanadium-phosphorous oxide (V-P-O) catalysts for the selective oxidation of n-butane and 1-butene to maleic anhydride. The utility of solid state nuclear magnetic resonance as an analytical tool in this investigation lies in its sensitivity to the electronic environment surrounding the phosphorous and vanadium nuclei, and proximity of paramagnetic species. Spin-echo mapping NMR of {sup 31}p and {sup 51}v and volume magnetic susceptibility measurements were used as local microscopic probes of the presence of V{sup 5+}, V{sup 4+}, V{sup 3+} species in the model compounds: {beta}-VOPO{sub 4}, {beta}-VOPO{sub 4} treated with n-butane/1-butene, (VO){sub 2}P{sub 2}O{sub 7} treated with n-butane/1-butene; and industrial catalysts with P/V (phosphorus to vanadium) ratio of 0.9, 1.0 and 1.1, before and after treatment with n-butane and 1-butene. The NMR spectra provide a picture of how the oxidation states of vanadium are distributed in these catalysts. 73 refs., 32 figs., 8 tabs.

Li, Juan.

1991-10-01

97

The Origin of Regioselectivity in 2-butanol Dehydration on Solid Acid Catalysts  

SciTech Connect

The origin in the variations of trans-/cis-2-butene product selectivity ratios in 2-butanol dehydration over solid acid catalysts were investigated using a combined experimental-theory approach. Reactivity measurements over ?-Al2O3, AlOx/SBA-15, and H-form zeolites with widely varying Si/Al ratios and pore structures showed over two orders of magnitude change in the trans-/cis-2-butene product ratio. Activation energy barriers calculated for the concerted C-O and ?-C-H bond breakings of adsorbed butoxy intermediates by dispersion-corrected DFT calculations correctly predicted the trans-/cis-2-butene product ratio observed on ?-Al2O3. The very low trans-2-butene selectivity on ?-Al2O3 can now be understood by the formation of a late transition state with high energy barrier caused by the strong van der Waals interaction between the ?-H atoms and the flat catalyst surface. Decreasing the dispersive attractive force between the adsorbed butoxide and the surface (e.g., by moving it further away from the support surface in AlOx/SBA-15) leads to almost equimolar formation of the trans- and cis-2-butene isomers. Trans-/cis-2-butene selectivity ratios much higher than that dictated by thermodynamic equilibrium can be achieved by introducing additional geometric constraints around the active catalytic site (e.g., varying the 3D environment around the active center in zeolites). We propose a model to explain the widely varying trans-/cis-2-butene selectivity in 2-butanol dehydration over solid acid catalysts that is consistent with the experimental results in this study. A key outcome of the study is the realization that van der Waals interactions between the reactant and the active catalyst surface must be included in the theoretic models in order to be able to accurately predict product selectivities. This information, in turn, significantly advances our ability to develop catalyst materials with designed active centers in order to achieve desired regioselectivities.

Kwak, Ja Hun; Rousseau, Roger J.; Mei, Donghai; Peden, Charles HF; Szanyi, Janos

2011-10-17

98

The effect of cavitating ultrasound on the aqueous phase hydrogenation of cis-2-buten-1-ol and cis-2-penten-1-ol on Pd-black  

SciTech Connect

We have studied the effect of cavitating ultrasound on the heterogeneous aqueous hydrogenation of cis-2-buten-1-ol (C4 olefin) and cis-2-penten-1-ol (C5 olefin) on Pd-black to form the trans-olefins (trans-2-buten-1-ol and trans-2-penten-1-ol) and saturated alcohols (1-butanol and 1-pentanol, respectively). Silent (and magnetically stirred) experiments served as control experiments. As described in an earlier publication by our group, we have added an inert dopant, 1-propanol, in the reaction mixture to ensure the rapid onset of cavitation in the ultrasound-assisted reactions that can lead to altered selectivity compared to silent reaction systems [R.S. Disselkamp, Ya-Huei Chin, C.H.F. Peden, J. Catal. 227 (2004) 552]. The motivation for this study is to examine whether cavitating ultrasound can reduce the [trans-olefin/saturated alcohol] molar ratio during the course of the reaction. This could have practical application in that it may offer an alternative processing methodology of synthesizing healthier edible seed oils by reducing trans-fat content.We have observed that cavitating ultrasound results in a [(trans-olefin/saturated alcohol)ultrasound/(trans-olefin/saturated alcohol)silent] ratio quantity less than 0.5 at the reaction mid-point for both the C4 and C5 olefin systems. This indicates that ultrasound reduces trans-olefin production compared to the silent control experiment. Furthermore, there is an added 30% reduction for the C5 versus C4 olefin compounds again at reaction mid-point. We attribute differences in the ratio quantity as a moment of inertia effect. In principle, the C4 versus C5 olefins has a {approx}52% increase in moment of inertia about C2 C3 double bond slowing isomerization. Since seed oils are C18 multiple cis-olefins and have a moment of inertia even greater than our C5 olefin here, our study suggests that even a greater reduction in trans-olefin content may occur for partial hydrogenation of C18 seed oils.

Disselkamp, Robert S.; Denslow, Kayte M.; Hart, Todd R.; White, James F.; Peden, Charles HF.

2005-07-15

99

The Effect of Cavitating Ultrasound on the Aqueous Phase Hydrogenation of Cis-2-buten-1-ol and Cis-2-penten-1-ol on Pd-black  

SciTech Connect

We have studied the effect of cavitating ultrasound on the heterogeneous aqueous hydrogenation of cis-2-buten-1-ol (C4 olefin) and cis-2-penten-1-ol (C5 olefin) on Pd-black to form the trans-olefins (trans-2-buten-1-ol and trans-2-penten-1-ol) and saturated alcohols (1-butanol and 1-pentanol, respectively). Silent (and magnetically stirred) experiments served as control experiments. As described in an earlier publication by our group, we have added an inert dopant, 1-propanol, in the reaction mixture to ensure the rapid onset of cavitation in the ultrasound-assisted reactions that can lead to altered selectivity compared to silent reaction systems [Disselkamp et al., J. Catal., 227 (2004) 552]. The motivation for this study is to examine whether cavitating ultrasound can reduce the [trans-olefin/saturated alcohol] molar ratio during the course of the reaction. This could have practical application in that it may offer an alternative processing methodology of synthesizing healthier edible seed oils by reducing trans-fat content. We have observed that cavitating ultrasound results in a [(trans-olefin/saturated alcohol)ultrasound/(trans-olefin/saturated alcohol)silent] ratio quantity less than 0.5 at the reaction mid-point for both the C4 and C5 olefin systems. This indicates that ultrasound reduces trans-olefin production compared to the silent control experiment. Furthermore, there is an added 30% reduction for the C5 versus C4 olefin compounds again at reaction mid-point. We attribute differences in the ratio quantity as a moment of inertia effect. In principle, the C4 versus C5 olefins has a {approx}52% increase in moment of inertia about C2=C3 double bond slowing isomerization. Since seed oils are C18 multiple cis olefins and have an moment of inertia even greater than our C5 olefin here, our study suggests that even a greater reduction in trans-olefin content may occur for partial hydrogenation of C18 seed oils.

Disselkamp, Robert S.; Denslow, Kayte M.; Hart, Todd R.; White, James F.; Peden, Charles HF.

2005-07-15

100

Study on Sources of Volatile Organic Compounds (CMB) in Pearl River Delta region, China  

NASA Astrophysics Data System (ADS)

The profiles of major Volatile organic compounds (VOCs) sources including vehicle exhaust, gasoline vapor, painting, asphalt, liquefied petroleum gas (LPG), biomass burning and petrochemical industry in Pearl River Delta were experimentally determined. Source samples were taken by using dilution chamber for mobile and stationary sources, laboratory simulation for biomass burning. The concentrations of 108 VOC species of sources were quantified by using canister with pre-concentration-GC/MS system, from which 52 PAMS hydrocarbons and one kind of chlorinated hydrocarbon were deployed to build the source profiles for source apportionment of VOCs. Based the measurement of source profiles, the possible tracers for various emission sources were identified, e.g 2-methylbutane and 1,3-butadiene were the tracers for motor vehicle exhaust, the characteristic compounds of architectural and furnishing coatings are aromatics such as toluene and m/p-xylene; the light hydrocarbons, namely n-butane, trans-2-butene and n-pentane, dominated the composition of gasoline vapor; and the nonane, decane and undecane are found to represent the asphalt emissions etc.. The CMB receptor model was applied to source apportionment of 58 hydrocarbons measured at seven sites during the PRD campaign, 2004. The 12 kinds of VOC sources include gasoline/diesel-powered vehicle exhaust, gasoline/diesel headspace vapor, vehicle evaporative emissions, liquid petroleum gas (LPG) leakage, painting vapors, asphalt emission from paved road, biomass burning, coal burning, chemical industry and petroleum refinery. Vehicle exhaust was the largest sources contributing over half of the ambient VOCs at the three urban sites (GuangZhou, FoShan and ZhongShan). LPG leakage played an important role with the percentage of 8- 16% in most sites in PRD. Contributions from solvents usage were highest at DongGuan, an industrial site. At XinKen, the solvents and coatings had the largest percentage of 31% probably due to the influence of its upwind area of DongGuan. The local biomass burning was also found to be a noticeable source at XK.

Liu, Y.; Shao, M.; Lu, S.; Chang, C.; Wang, C. J.; Wang, B.

2007-05-01

101

Structural and acidic characterization of niobia aerogels  

SciTech Connect

A niobia (Nb[sub 2]O[sub 5]) gel was prepared by the hydrolysis and condensation of niobrium pentaethoxide and subsequently dried by supercritical extraction with carbon dioxide to produce an aerogel. The structural and acidic properties of this aerogel heat-treated at different temperatures were characterized by surface area measurements, X-ray diffraction, Raman spectroscopy, n-butylamine titration, pyridine adsorption, and 1-butene isomerization. These results were then compared to those of a niobia xerogel, a precipitated niobia, and a commerical niobic acid. The synthetic route to produce the aerogel was found to stabilize a porous network consisting of NbO[sub 6] octahedra with Nb [double bond] O bonds which gave rise to strong Lewis acid sites. Steady-state activity and selectivity data of 1-butene isomerization suggested that all niobia samples possessed comparable Broensted acidity.

Maurer, S.M.; Ko, E.I. (Carnegie Mellon Univ., Pittsburgh, PA (United States))

1992-05-01

102

Effect of alcohol on the corrosion of al alloys in 1 N H 2 SO 4 solution Part I  

Microsoft Academic Search

The aim of this paper is to examine the effects of alcohol (1-buten-3-ol-l, 2-methyl-3-butyn-2-ol, 3-methyl-2-buten-1-ol,\\u000a 3-methyl-3-buten-1-ol, 3-methyl-1-pentyn-3-ol, 5-hexen-1-ol) on the corrosion of Al alloys. The inhibiting effect of alcohol\\u000a was investigated by electrochemical current-potential curves, atomic absorption spectrometry (AAS), metal microscopy,SEM and\\u000a EDS. The results showed that alcohol (1-buten-3-ol, 2-methyl-3-butyn-2-ol, 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol, 3-methyl-1-pentyn-3-ol,\\u000a 5-hexen-1-ol) had an inhibiting effect on the

A. Buyuksagis; A. A. Aksut

2008-01-01

103

Reactivities of tantalum oxide cluster cations with unsaturated hydrocarbons  

Microsoft Academic Search

The reactivities of tantalum oxide cluster cations with unsaturated hydrocarbons have been probed using a triple quadrupole mass spectrometer coupled with a laser vaporization source. The reaction pathways observed for the tantalum oxide clusters with 1,3-butadiene (C4H6), 1-butene (C4H8), and (D6)benzene (C6D6) include association, atomic and molecular oxygen loss, cracking, minor dehydration, and possible dehydrogenation with the reactivities of different

K. A Zemski; R. C Bell; A. W Castleman

1999-01-01

104

Structural and acidic characterization of niobia aerogels  

Microsoft Academic Search

A niobia (Nb[sub 2]O[sub 5]) gel was prepared by the hydrolysis and condensation of niobrium pentaethoxide and subsequently dried by supercritical extraction with carbon dioxide to produce an aerogel. The structural and acidic properties of this aerogel heat-treated at different temperatures were characterized by surface area measurements, X-ray diffraction, Raman spectroscopy, n-butylamine titration, pyridine adsorption, and 1-butene isomerization. These results

S. M. Maurer; E. I. Ko

1992-01-01

105

Interaction between the reaction medium and an ion-exchange resin catalyst in the etherification of isoamylenes  

Microsoft Academic Search

tert-Amyl methyl ether (2-methoxy-2-methylbutane, TAME) is synthesised in a liquid-phase reaction of methanol (MeOH) and isoamylenes (2-methyl-1-butene (2M1B), and 2-methyl-2-butene (2M2B)). The reaction rates of the formation of TAME were measured in a continuous stirred tank reactor (CSTR) at the temperature range between 323 and 353K. The molar ratio of methanol to isoamylenes and the concentration of the reagents were

Liisa K Rihko-Struckmann; Petri V Latostenmaa; A. Outi I Krause

2001-01-01

106

Direct measurements of formation rate constants of allylic radical from hot olefins formed by internal conversion. I  

Microsoft Academic Search

The photofragmentation of 2,3,3-trimethyl-1-butene (TMB), 2,3-dimethyl-2-pentene (DMP), and tetramethylethylene (TME) has been studied in the gas phase by ArF (193 nm) laser flash photolysis. For the first time, the formation rate constants to the common product of trimethylallyl (TMA) radical have been measured directly under collision free conditions. The C–C bond (the C–H bond for TME) at the position ?

Nobuaki Nakashima; Noriaki Ikeda; Nobuo Shimo; Keitaro Yoshihara

1987-01-01

107

The emission characteristics of hydrocarbon from Chinese cooking under smoke control  

Microsoft Academic Search

To understand the hydrocarbon emissions in China, the source profile and emission factors of hydrocarbon species from cooking sources were measured. The measured commercial restaurants represented Sichuan cuisine, Zhejiang cuisine, household-style cuisine and Korean-style barbecue, respectively. Forty-one hydrocarbon species were quantified, in which the abundant species were n-butane, iso-butane, 2-methlybutane, pentane, propene, 1-butene, toluene and benzene. The hydrocarbon mixing ratios

Yun Lin; Min Shao; Sihua Lu

2010-01-01

108

CFD-DEM Study of Temperature and Concentration Distribution in a Polyethylene Fluidized Bed Reactor  

Microsoft Academic Search

Comprehensive modeling of the gas-phase polyethylene reactor was developed by combining discrete element method (for predicting motion of particulates), Navier-Stokes equation (for predicting velocity fields of gas phase), mass conservation equation (for predicting concentration of reactants), and energy conservation equation (for predicting temperature). A comprehensive kinetic mechanism was used to evaluate the rate of ethylene and 1-butene copolymerization reactions. Simultaneous

Sedigheh Karimi; Zahra Mansourpour; Navid Mostoufi; Rahmat Sotudeh-Gharebagh

2011-01-01

109

Flame temperature, fuel structure, and fuel concentration effects on soot formation in inverse diffusion flames  

Microsoft Academic Search

Insights into soot formation processes are gained from chemical sampling and thermocouple probing of co-flowing inverse diffusion flames (IDFs), with the oxidizer in the center. In this paper the transition from near-to slightly sooting flames and the effects of flame temperature, fuel concentration, and fuel structure (using methane, ethene, propene and 1-butene) are investigated. The aromatic content of IDFS scales

G. W. Sidebotham; I. Glassman

1992-01-01

110

Elucidation of n-Butane Isomerization on Sulfated Zirconia Using Olefin Addition  

Microsoft Academic Search

Olefin formation appears to play a key role in n-butane isomerization on sulfated zirconia (SZ). In order to better understand the pathway of the reaction, 1-butene (1-C4=) was added during reaction at low and at high reaction temperatures. Olefin addition, even at the lowest 1-C4=\\/n-C4 ratio, decreased the activity of the catalyst at 250°C, did not eliminate the reaction induction

Sonia Hammache; James G. Goodwin Jr.

2002-01-01

111

Selective oxidation of C 3–C 4 olefins over Mo-containing catalysts with tetragonal tungsten bronze structure  

Microsoft Academic Search

Mo–V–Nb–P–O-based catalysts with a tetragonal tungsten bronze-type (TTB) structure have been prepared hydrothemally from a H3PMo12O40 Keggin-type heteropolyacid. These catalysts have been tested in the oxidation of C3–C4 olefins (propene, isobutene and 1-butene). Although the catalytic performance depends on the nature of the olefin fed the TTB-type catalysts prepared in the presence of elements of the V and VI groups

P. Botella; B. Solsona; J. M. López Nieto

2009-01-01

112

The Thermodynamic Conjugation Stabilization of 1,3-Butadiyne Is Zero  

ERIC Educational Resources Information Center

|Many textbooks point out that the thermodynamic stabilization enthalpy of 1 mol of 1,3-butadiene relative to 2 mol of 1-butene or to 1 mol of 1,4-pentadiene is slightly less than 4 kcal mol[superscript -1], owing to conjugation between the double bonds in the 1,3 configuration. It is reasonable to suppose that the analogous thermochemical…

Rogers, Donald W.; Zavitsas, Andreas A.; Matsunaga, Nikita

2010-01-01

113

Catalytic conversion of secondary butyl alcohol on Sn-Mo-O system in the presence of oxygen  

SciTech Connect

It has been established that the optimal catalyst composition for the conversion of secondary butyl alcohol to methyl ethyl ketone in the presence of oxygen is Sn:Mo = 9.1. A comparative investigation of the conversions of 1-butene, isopropyl alcohol, and secondary butyl alcohol on Sn-Mo-O catalysts with various compositions has demonstrated the feasibility of using secondary butyl alcohol in evaluating the acid-base properties of oxide systems.

Adzhamov, K.Yu.; Klaime, S.R.; Alkhazov, T.G.

1988-02-01

114

Clustering of metal atoms in organic media--5. Production of tailored selectivity in nickel catalysts: comparison with Raney nickel  

Microsoft Academic Search

Metallic nickel catalysts were prepared by cocondensing nickel vapor with various proportions of pentane, hexane, toluene, or tetrahydrofuran at -196°C, warming the slurry to room temperature, and removing the excess solvent under vacuum. The resulting catalysts were characterized by X-ray diffraction, magnetic measurements, hydrogen adsorption, Curie and sintering temperature determinations, and measurements of activity for the hydrogenation of 1-butene, 1-heptene,

K. J. Klabunde; S. C. Davis; H. Hattori; Y. Tanaka

1978-01-01

115

Vacuum ultraviolet photochemistry of tetrahydrothiophene and sulfolane  

Microsoft Academic Search

The vacuum uv photolysis of tetrahydrothiophene (THT) involves the breaking of the S to ..cap alpha..-C bond. Besides ethylene, CâHâ and 1,3-butadiene are also formed. Photolyses of THT, tetrahydrofuran, and pyrrolidine are similar. The vacuum uv photolysis of tetramethylene sulfone (sulfolane) was also studied; products are SOâ, cyclobutane, 1-butene, and ethylene. No cis-2-butene was observed. (DLC)

A. A. Scala; I. Colon

1979-01-01

116

Cyanocobalamin Enables Activated Sludge Bacteria to Dechlorinate Hexachloro-1,3-butadiene to Nonchlorinated Gases  

Microsoft Academic Search

The ability of activated sludge obtained from a local wastewater treatment plant to dechlorinate hexachloro-1,3-butadiene (HCBD) in the presence of either acetate or lactate and cyanocobalamin was investigated. Results from headspace analysis indicated complete dechlorination of HCBD by the accumulation of fully dechlorinated C4 gases (1-buten-3-yne, 1,3-butadiene, and 1,3-butadiyne). Dechlorination products were not observed in the control cultures without cyanocobalamin.

D. L. James; R. Cord-Ruwisch; D. Schleheck; M. J. Lee; M. Manefield

2008-01-01

117

Fermentative production of isobutene.  

PubMed

Isobutene (2-methylpropene) is one of those chemicals for which bio-based production might replace the petrochemical production in the future. Currently, more than 10 million metric tons of isobutene are produced on a yearly basis. Even though bio-based production might also be achieved through chemocatalytic or thermochemical methods, this review focuses on fermentative routes from sugars. Although biological isobutene formation is known since the 1970s, extensive metabolic engineering is required to achieve economically viable yields and productivities. Two recent metabolic engineering developments may enable anaerobic production close to the theoretical stoichiometry of 1isobutene + 2CO(2) + 2H(2)O per mol of glucose. One relies on the conversion of 3-hydroxyisovalerate to isobutene as a side activity of mevalonate diphosphate decarboxylase and the other on isobutanol dehydration as a side activity of engineered oleate hydratase. The latter resembles the fermentative production of isobutanol followed by isobutanol recovery and chemocatalytic dehydration. The advantage of a completely biological route is that not isobutanol, but instead gaseous isobutene is recovered from the fermenter together with CO(2). The low aqueous solubility of isobutene might also minimize product toxicity to the microorganisms. Although developments are at their infancy, the potential of a large scale fermentative isobutene production process is assessed. The production costs estimate is 0.9 Euro kg(-1), which is reasonably competitive. About 70% of the production costs will be due to the costs of lignocellulose hydrolysate, which seems to be a preferred feedstock. PMID:22234536

van Leeuwen, Bianca N M; van der Wulp, Albertus M; Duijnstee, Isabelle; van Maris, Antonius J A; Straathof, Adrie J J

2012-01-11

118

Rate coefficients for the gas-phase reaction of OH radicals with dimethyl sulfide: temperature and O2 partial pressure dependence.  

PubMed

Rate coefficients for the gas-phase reaction of hydroxyl (OH) radicals with dimethyl sulfide (CH(3)SCH(3), DMS) have been determined using a relative rate technique. The experiments were performed under different conditions of temperature (250-299 K) and O(2) partial pressure (approximately 0 Torr O(2)-380 Torr O(2)), at a total pressure of 760 Torr bath gas (N(2) + O(2)), in a 336 l reaction chamber, using long path in situ Fourier transform (FTIR) absorption spectroscopy to monitor the disappearance rates of DMS and the reference compounds (ethene, propene and 2-methylpropene). OH was produced by the photolysis of H(2)O(2). The following Arrhenius expressions adequately describe the rate coefficients as a function of temperature (units are cm(3) molecule(-1) s(-1)): k = (1.56 +/- 0.20) x 10(-12) exp[(369 +/- 27)/T], for approximately 0 Torr O(2); (1.31 +/- 0.08) x 10(-14) exp[(1910 +/- 69)/T], for 155 Torr O(2); (5.18 +/- 0.71) x 10(-14) exp[(1587 +/- 24)/T], for 380 Torr O(2). The results are compared with previous investigations. PMID:16482313

Albu, Mihaela; Barnes, Ian; Becker, Karl H; Patroescu-Klotz, Iulia; Mocanu, Raluca; Benter, Thorsten

2005-11-23

119

Equilibrium constants for methyl tert-butyl ether and ethyl tert-butyl ether liquid-phase syntheses using C[sub 4] olefinic cut  

SciTech Connect

Equilibrium constants for the liquid-phase syntheses of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) were determined experimentally in the temperature range 313--353 K and at 1.6 MPa, using as source of 2-methylpropene (isobutylene) a C[sub 4] olefinic cut proceeding from a steam cracking unit. To reach etherification equilibrium, the macroporous sulfonic acid resin K-2631 (Bayer) was used as the catalyst. The thermodynamic equilibrium constants and the enthalpy, free energy, and entropy changes of reactions were given as a temperature function. At 298 K, the standard molar reaction enthalpy [Delta][sub r]H[sub m][degree](298 K, 1.6 MPa) for MTBE and ETBE are [minus](37.3 [+-] 2) and [minus](34.8 [+-] 1.3) kJ/mol, respectively, and are compared with literature data. A comparison of the equilibrium constant values with those obtained using pure reactants with and without small initial amounts of water (<5 wt %) is also included. The UNIFAC estimates of activity coefficients were used to describe the liquid-phase nonideality. The standard molar enthalpies of formation [Delta][sub f]H[sub m][degree](l, 298.2 K) of MTBE and ETBE are [minus]313.5 and [minus]349.9 kJ/mol, respectively.

Izquierdo, J.F.; Cunill, F.; Vila, M.; Iborra, M.; Tejero, J. (Univ. of Barcelona (Spain). Chemical Engineering Dept.)

1994-11-01

120

Measurements of nonmethane hydrocarbons in Phoenix, Arizona  

SciTech Connect

Nonmethane hydrocarbons (NMHCs) are precursors to oxidant formation. They are oxidized by hydroxyl radical (OH), forming a complex mixture of peroxy radicals that oxidize NO to NO{sub 2} without consuming ozone (O{sub 3}) and thus allow O{sub 3} to increase in the atmospheric boundary layer. The reactivities of the NMHCs that compose biogenic and anthropogenic emissions vary greatly. For example, isoprene, which is emitted by deciduous vegetation, has an atmospheric lifetime with respect to oxidation by OH of about 20 min in polluted air ([OH] = 10{sup 7} radicals cm{sup {minus}3}). The atmospheric lifetimes of 2-methylpropene, 2-methylbutane, and the xylenes, which are found in vehicle emissions, are approximately 30 min, 7 hr, and 1.5 hr, respectively. The authors made measurements of the NMHCs at a surface site and aloft aboard the Battelle Gulfstream (G-1) aircraft, as part of an air quality study in the Phoenix area during May 1998. Diurnal variations in the NMHC distributions and their propene-equivalent concentrations are used to examine origins and reactivities of the air masses that were sampled at the surface site.

Doskey, P. V.; Kotamarthi, V. R.; Rudolph, J.

1999-10-12

121

Genotoxicity of alkene epoxides in human peripheral blood mononuclear cells and HL60 leukaemia cells evaluated with the comet assay.  

PubMed

Volatile organic compounds (VOCs) exert their carcinogenic activity through the production of epoxide metabolites. Because of their high reactivity some epoxides are also produced in the chemical industry for the synthesis of other compounds. Therefore, human exposure to VOCs epoxides does occur and may be an important human health concern. In this study, the in vitro genotoxic potential of epoxides originating from 1,3-butadiene (3,4-epoxy-1-butene: EB; 1,2:3,4-diepoxybutane: DEB), isoprene (3,4-epoxy-2-methyl-1-butene: IO), styrene (styrene-7,8-oxide: SO), propylene (propylene oxide: PO) and 1-butene (1,2-epoxy-butane: BO) in human peripheral blood mononuclear cells (PBMCs) and promyelocytic leukaemia cells (HL60) was measured with the comet assay (single-cell gel electrophoresis, SCGE). The effect of inclusion of foetal calf serum (FCS, 5%) in the cell-culture medium and different durations of exposure (2h, 24h) were also investigated. All epoxides tested produced DNA damage in a concentration range that did not reduce cell viability. HL60 cells were more resistant than PBMCs to the DNA damage induced by the different epoxides. With the exception of IO, the treatment for 24h resulted in an increase of DNA damage. FCS slightly protected PBMCs from the genotoxic effects induced by IO and BO, whilst no such effect was noted for the other compounds. Overall, the dose-dependent effects that were seen allowed us to define a genotoxicity scale for the different epoxides as follows: SO>EB>DEB>IO>PO>BO, which is in partial agreement with the International Agency for Research on Cancer (IARC) classification of the carcinogenic hazards. PMID:22285587

Fabiani, Roberto; Rosignoli, Patrizia; De Bartolomeo, Angelo; Fuccelli, Raffaela; Morozzi, Guido

2012-01-21

122

Ultra-fast laser pulses provide an ion source for highly selective mass spectroscopy  

NASA Astrophysics Data System (ADS)

The mass spectra of two isomers of butane, 1-butene and cis-2-butene, interacting with linearly polarized Ti:sapphire laser pulses, were compared. It was demonstrated that the difference between the two spectra are much more pronounced than the corresponding spectra prepared by 100 eV electron ionization ion source. In addition, the difference could be varied by changing the peak laser intensity. The observation suggests potential application of dissociative multiphoton ionization by ultrafast laser pulses as a source for high performance mass spectroscopy.

Mehdi Sharifi, S.; Talebpour, A.; Chin, S. L.

2008-06-01

123

Mo(CO) 3(NCMe)(PPh 3) 2: Synthesis, X-ray structure and evaluation of its catalytic activity for the homogeneous hydrogenation of olefins and their mixtures  

Microsoft Academic Search

The complex Mo(CO)3(NCMe)(PPh3)2, was synthesized by the reaction of Mo(NCMe)3(CO)3 with two equivalents of PPh3 and characterized by UV–Vis, IR, NMR and X-ray diffraction. This complex was used as a catalyst precursor for the hydrogenation of 1-hexene, styrene, cyclohexene and 2,3-dimethyl-1-butene and their mixtures under moderate conditions in homogeneous media. Under mild reaction conditions (T=373K, P=60atm), the substrates showed the

Pablo J. Baricelli; Luis G. Melean; Santiago Ricardes; Victor Guanipa; Mariandry Rodriguez; Carlos Romero; Alvaro J. Pardey; Sergio Moya; Merlin Rosales

2009-01-01

124

Adjacency of molybdenum redox sites and the oxidation of butene  

SciTech Connect

The authors have attempted to determine the structure sensitivity of C-H activation and oxygen insertion during the oxidation of 1-butene by measuring how the rates of the reactions depend on variations in the sizes of very small ensembles of redox centers in a catalyst. The authors have employed polyoxometalate cluster compounds in which 3 or 12 of the tungsten ions initially present in a Keggin framework were replaced with molybdenum ions. As in previous work with methanol oxidation, the catalyst derived from the parent Keggin anion, [PW[sub 12]O[sub 40

Racine, B.N.; Sorensen, C.M.; Weber, R.S. (Univ. of Delaware, Newark, DE (United States))

1993-08-01

125

Estrogenic Activity of Styrene Oligomers after Metabolic Activation by Rat Liver Microsomes  

Microsoft Academic Search

In this study we examined estrogenic activity of styrene oligomers after metabolic activation by rat liver microsomes. trans-1,2-Diphenylcyclobutane (TCB), cis-1,2-diphenylcyclobutane (CCB), 1,3- diphenylpropane, 2,4-diphenyl-1-butene, 2,4,6-triphenyl-1-hexene, and 1?-phenyl-4?-(1´- phenylethyl)tetralin were negative in the yeast estrogen screening assay and estrogen reporter assay using estrogen-responsive human breast cancer cell line MCF-7. However, TCB exhibited estro- genic activity after incubation with liver microsomes of

Shigeyuki Kitamura; Motoko Ohmegi; Seigo Sanoh; Kazumi Sugihara; Shinichi Yoshihara; Nariaki Fujimoto; Shigeru Ohta

2002-01-01

126

Synthesis of higher carbon ethers from olefins and alcohols  

Microsoft Academic Search

Higher carbon ether compounds (HME; hexyl methyl ether and OME; octyl methyl ether) are produced from olefins (C6 olefins: 23DM1B; 2,3-dimethyl-1-butene and 23DM2B; 2,3-dimethyl-2-butene and C8 olefins: 244TM1P; 2,4,4-trimethyl-1-pentene and 244TM2P; 2,4,4-trimethyl-2-pentene) and methanol in the presence of commercially available Amberlyst 15 ion exchange catalyst. Stainless steel batch reactors are used and the experiments are conducted from 333 to 373

Jeff Snelling; Christine W. Curtis

2003-01-01

127

Protonation Sites and Dissociation Mechanisms of t-Butylcarbamates in Tandem Mass Spectrometric Assays for Newborn Screening  

PubMed Central

Structures of tert-butylcarbamate ions in the gas phase and methanol solution were studied for simple secondary and tertiary carbamates as well as for carbamate-containing products and internal standards for lysosomal enzyme assays used in newborn screening of a ?-galactosidase A deficiency (GLA, Fabry disease), mucopolysaccharidosis I (Hurler disease), and mucopolysaccharidosis II (Hunter disease). Protonation of simple t-butylcarbamates can occur at the carbonyl group which is the preferred site in the gas phase. Protonation in methanol solution is more favorable if occurring at the carbamate nitrogen atom. Protonation of more complex t-butylcarbamates occurs at amide and carbamate carbonyl groups, and the ions are stabilized by intramolecular hydrogen bonding which is affected by solvation. Tertiary carbamates containing aminophenol amide groups were calculated to have substantially greater gas-phase basicities than secondary carbamates containing coumarin amide groups. The main diagnostically important ion dissociation by elimination of 2-methylpropene (isobutylene, i-C4H8) and carbon dioxide is shown by experiment and theory to proceed in two steps. Energy-resolved collision-induced dissociation of the Hurler’s disease enzymatic product ion, which is a coumarin-diamine linker-t-butylcarbamate conjugate (3a+), indicated separate energy thresholds for the loss of i-C4H8 and CO2. Computational investigation of the potential energy surface along two presumed reaction pathways indicated kinetic preference for the migration of a t-butyl hydrogen atom to the carbamate carbonyl resulting in the isobutylene loss. The consequent loss of CO2 required further proton migrations that had to overcome energy barriers.

Spacil, Zdenek; Hui, Renjie; Gelb, Michael H.; Turecek, Frantisek

2011-01-01

128

Ring-expansion reactions in the thermal decomposition of tert-butyl-1,3-cyclopentadiene.  

PubMed

The thermal decomposition of tert-butyl-1,3-cyclopentadiene has been investigated in single-pulse shock-tube studies at shock pressures of 182-260 kPa and temperatures of 996-1127 K. Isobutene (2-methylpropene), 1,3-cyclopentadiene, and toluene were observed as the major stable products in the thermolysis of dilute mixtures of the substrate in the presence of a free-radical scavenger. Hydrogen atoms were also inferred to be a primary product of the decomposition and could be quantitatively determined on the basis of products derived from the free-radical scavenger. Of particular interest is the formation of toluene, which involves the expansion of the ring from a five- to a six-membered system. The overall reaction mechanism is suggested to include isomerization of the starting material; a molecular elimination channel; and C-C bond fission reactions, with toluene formation occurring via radical intermediates formed in the latter pathway. These radical intermediates are analogous to those believed to be important in soot formation reactions occurring during combustion. Molecular and thermodynamic properties of key species were determined from G3MP2B3 quantum chemistry calculations and are reported. The temperature dependence of the product spectrum was fit with a detailed chemical kinetic model, and best-fit kinetic parameters were derived using a Nelder-Mead simplex minimization algorithm. Our mechanism and rate constants are consistent with and provide experimental support for the H-atom-assisted routes to the conversion of fulvene to benzene that have been proposed in the literature on the basis of theoretical investigations. PMID:17125296

McGivern, W Sean; Manion, Jeffrey A; Tsang, Wing

2006-11-30

129

A simplified chemistry module for atmospheric transport and dispersion models: Proof-of-concept using SCIPUFF  

NASA Astrophysics Data System (ADS)

An atmospheric chemistry module was developed to predict the fate of environmentally hazardous compounds discharged into the atmosphere. The computationally efficient model captures the diurnal variation within the environment and in the degradation rates of the released compounds, follows the formation of toxic degradation products, runs rapidly, and in principle can be integrated with any atmospheric transport and dispersion model. To accomplish this, a detailed atmospheric chemistry mechanism for a target toxic industrial compound (TIC) was reduced to a simple empirical effective degradation rate term (keff). Empirically derived decay functions for keff were developed as a function of important meteorological parameters such as solar flux, temperature, humidity, and cloud cover for various land uses and locations by statistically analyzing data generated from a detailed chemistry mechanism run over a wide range of (typical) atmospheric conditions. 1-Butene and two degradation products (propanal and nitrooxybutanone) were used as representative chemicals in the algorithm development for this proof-of-concept demonstration of the capability of the model. The quality of the developed model was evaluated via comparison with experimental chamber data and the results (decay rates) compared favorably for ethene, propene, and 1-butene (within a factor of two 75% or more of the time).

Burns, Douglas S.; Rottmann, Shawn D.; Plitz, Angela B. L.; Wiseman, Floyd L.; Moore, William; Chynwat, Veeradej

2012-09-01

130

The activation of hydrocarbon C-H bonds over transition metal oxide catalysts: A FTIR study of hydrocarbon catalytic combustion over MgCr{sub 2}O{sub 4}  

SciTech Connect

The interaction of light hydrocarbons (methane, ethane, propane, propene, n-butane, isobutane, 1-butene, benzene, and toluene) with the oxidized surface of the spinel MgCr{sub 2}O{sub 4} (an active hydrocarbon combustion catalyst) has been investigated by FTIR spectroscopy in the temperature range 300-773 K. This interaction results in the reduction of the catalyst and the production of oxygen-containing adsorbed species. These species have been identified by comparison with the spectra of oxygen-containing species (alcohols, aldehydes, ketones, carboxylic acids, carbon oxides) directly adsorbed on the surface. It has been concluded that every hydrocarbon reacts at its weakest C-H bond on Cr{sup n+}=O (n = 5 or 6) surface sites giving rise by hydrogen abstraction and C-O bond formation to alkoxy groups. These species are further oxidized to carbonyl compounds and/or carboxylate anions and, finally, carbon oxides. The earlier intermediates (alkoxides, carbonyl compounds) are detectable only with the most reactive hydrocarbons (propane, n-butane, isobutane, propene, 1-butene, toluene), while with the least reactive hydrocarbons (methane and benzene), because of their two high activation temperature, only the final intermediates are detectable (carbonates, carboxylates). Molecular-level mechanism for C-H cleavage and hydrocarbon catalytic combustion are proposed. 47 refs., 11 figs., 1 tab.

Finnocchio, E.; Busca, G.; Lorenzelli, V. [Universita P.le Kennedy, Geneva (Italy); Willey, R.J. [Northeastern Univ., Boston, MA (United States)

1995-01-01

131

Palladium-Mediated Hydrogenation of Unsaturated Hydrocarbons with Hydrogen Gas Released during Anaerobic Cellulose Degradation  

PubMed Central

Among five hydrogenation catalysts, palladium on charcoal was the most reactive one when suspended in anaerobic culture medium, and Lindlar catalyst (Pd on CaCO3) was the most reactive one when suspended in the gas phase of culture tubes. Palladium on charcoal in the culture medium (40 to 200 mg 10 ml?1) completely inhibited growth of Neocallimastix frontalis and partly inhibited Ruminococcus albus. Lindlar catalyst (40 to 200 mg per tube) suspended in a glass pouch above the culture medium did not affect the rate of cellulose degradation or the ratio of fermentation products by these organisms. Acetylene added to tubes containing Lindlar catalyst in pouches, and either of the two organisms in monoculture or coculture with Methanospirillum hungatei, was reduced to ethylene and then ethane, followed by hydrogen production. Similar results were obtained with 1-pentene. Neither acetylene nor 1-pentene affected cellulose degradation but both inhibited methanogenesis. In the presence of Lindlar catalyst and propylene or 1-butene, fermenter-methanogen cocultures continued to produce methane at the same rate as controls and no olefin reduction occurred. Upon addition of bromoethanesulfonic acid, methanogenesis stopped and olefin reduction took place followed by hydrogen evolution. In a gas mixture consisting of propylene, 1-butene, and 1-pentene, the olefins were reduced at rates which decreased with increasing molecular size. These results demonstrate the technical feasibility of combining in one reactor the volatile fatty acid production by anaerobic digestion with chemical catalyst-mediated reductions, using the valuable by-product hydrogen.

Mountfort, Douglas O.; Kaspar, Heinrich F.

1986-01-01

132

Trace gas emissions from laboratory biomass fires measured by open-path Fourier transform infrared spectroscopy: Fires in grass and surface fuels  

NASA Astrophysics Data System (ADS)

The trace gas emissions from six biomass fires, including three grass fires, were measured using a Fourier transform infrared (FTIR) spectrometer coupled to an open-path, multipass cell (OP-FTIR). The quantified emissions consisted of carbon dioxide, nitric oxide, water vapor, carbon monoxide, methane, ammonia, ethylene, acetylene, isobutene, methanol, acetic acid, formic acid, formaldehyde, and hydroxyacetaldehyde. By including grass fires in this study we have now measured smoke composition from fires in each major vegetation class. The emission ratios of the oxygenated compounds, formaldehyde, methanol, and acetic acid, were 1-2% of CO in the grass fires, similar to our other laboratory and field measurements but significantly higher than in some other studies. These oxygenated compounds are important, as they affect O3 and HOx chemistry in both biomass fire plumes and the free troposphere. The OP-FTIR data and the simultaneously collected canister data indicated that the dominant C4 emission was isobutene (C4H8) and not 1-butene. The rate constant for the reaction of isobutene with the OH radical is 60% larger than that of 1-butene. We estimate that 67±9% of the fuel nitrogen was volatilized with the major nitrogen emissions, ammonia, and nitric oxide, accounting for 22±8%.

Goode, Jon G.; Yokelson, Robert J.; Susott, Ronald A.; Ward, Darold E.

1999-09-01

133

Conformational effects on optical rotation. 2-Substituted butanes.  

PubMed

The specific rotations of 2-substituted butanes (X = F, Cl, CN, and HCC) were calculated at the B3LYP/aug-cc-pVDZ level as a function of the C-C-C-C torsion angle. The results for the four compounds are remarkably similar, despite large differences in the electronic transition energies. The temperature dependence of the specific rotations for 2-methylbutyronitrile and for 2-chlorobutane was studied to give experimental information about the effect of the torsion angle on the specific rotation. The results were in good accord with B3LYP/aug-cc-pVDZ calculations. The specific rotations derived from the study of 2-chlorobutane are similar to those previously obtained for 3-chloro-1-butene, indicating that the double bond does not have a large effect on the optical rotations, but it did lead to a large difference between calculated and observed specific rotations. PMID:16833676

Wiberg, Kenneth B; Wang, Yi-gui; Vaccaro, Patrick H; Cheeseman, James R; Luderer, Matthew R

2005-04-21

134

Synthesis of an un-supported, high-flow ZSM-22 zeolite membrane  

DOEpatents

Novel methods for synthesizing wholly un-supported, high-flow catalytic membranes consisting of 100% crystalline ZSM-22 crystals with no binder phase, having sufficient porosity to allow high Weight Hourly Space Velocities of feedstock to pass through without generating back pressure. The ZSM-22 membranes perform favorably to existing bulk ZSM-22 catalysts (e.g., via 1-butene conversion and selectivity). The method of membrane synthesis, based on Vapor Phase Transport, allows free-standing, binder-less membranes to be fabricated in varied geometries and sizes so that membranes can be tailor-made for particular geometries applications. The ZSM-22 precursor gel may be consolidated into a semi-cohesive body prior to vapor phase crystallization, for example, by uniaxial pressing. These crystalline membranes may be modified by ion exchange, pore ion exchange, framework exchange, synthesis modification techniques to incorporate other elements into the framework, such as K, H, Mg, Zn, V, Ga, and Pt.

Thoma, Steven G. (Albuquerque, NM); Nenoff, Tina M. (Albuquerque, NM)

2006-10-10

135

Highly efficient dimerization of ethylene by (imido)vanadium complexes containing (2-anilidomethyl)pyridine ligands: notable ligand effect toward activity and selectivity.  

PubMed

(Imido)vanadium(V) complexes containing the (2-anilidomethyl)pyridine ligand, V(NR)Cl(2)[2-ArNCH(2)(C(5)H(4)N)] (R = 1-adamantyl (Ad), cyclohexyl (Cy), phenyl), exhibit remarkably high catalytic activities (e.g. TOF = 2 730 000 h(-1) (758 s(-1)) by V(NAd)Cl(2)[2-(2,6-Me(2)C(6)H(3))NCH(2)(C(5)H(4)N)) for ethylene dimerization in the presence of MAO, affording 1-butene exclusively (selectivity 90.4 to >99%). The steric bulk of the imido ligand plays an important role in the selectivity (polymerization vs dimerization), and the electronic nature directly affects the catalytic activity (activity: R = Ad > Cy > Ph). PMID:20218571

Zhang, Shu; Nomura, Kotohiro

2010-04-01

136

Excited State Isomerization of a Stilbene Analog: E / Z Phenylvinylacetylene  

NASA Astrophysics Data System (ADS)

The excited state isomerization of the E and Z forms of phenylvinylacetylene (PVA, 1-phenyl-1-buten-3-yne) has been studied using ultraviolet population transfer spectroscopy (UVPT). UVPT is a pump-probe experiment, where single isomers are selectively excited and after a wait time, the induced change in population of reactant and product isomers is probed. In these experiments, after initial cooling, an isomer of PVA is selectively excited to vibrational levels in the S_{1} electronic state. If the energy supplied by the excitation is above the barrier to isomerization population can be transferred into a product well. Excited molecules are collisionally cooled via supersonic expansion and a new population distribution can be detected downstream via R2PI spectroscopy. From these experiments, product isomerization quantum yields have been determined for both E to Z and Z to E excited state pathways as a function of excess energy above the S_{1} origin.

Newby, Josh J.; Müller, Christian W.; Liu, Ching-Ping; Lee, Hsiupu D.; Zwier, Timothy S.

2009-06-01

137

Reaction mechanism studies of unsaturated molecules using photofragment translational spectroscopy  

SciTech Connect

A number of molecules have been studied using the technique of photofragment translational spectroscopy. In Chapter One a brief introduction to the experimental technique is given. In Chapter Two the infrared multiphoton dissociation (IRMPD) of acetic acid is discussed. Carbon dioxide and methane were observed for the first time as products from dissociation under collisionless conditions. Chapter Three relates an IRMPD experiment of hexafluoropropene. The predominant channel produces CFCF{sub 3} or C{sub 2}F{sub 4} and CF{sub 2}, with the heavier species undergoing further dissociation to two CF{sub 2} fragments. In Chapter Four the ultraviolet (UV) dissociation of hexafluoropropene is investigated. Chapter Five explores the IRMPD of octafluoro-1-butene and octafluoro-2-butene.

Longfellow, C.A. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States). Chemical Sciences Div.

1996-05-01

138

Histrionicotoxins: roentgen-ray analysis of the novel allenic and acetylenie spiroalkaloids isolated from a Colombian frog, Dendrobates histrionicus.  

PubMed

The structures and absolute configuration of two unique alkaloids isolated from the Colombian frog, Dendrobates histrionicus, have been elucidated by Roentgen-ray (x-ray) crystallography. Histrionicotoxin is (2pR, 6S, 7pS, 8aS)-7-(cis-1-buten-3-ynyl)-8-hydroxy-2-(cis-2-penten-4- ynyl)-1-azaspiro[5.5] undecane, while in dihydro-isohistrionicotoxin the acetylenic 2-pentenynyl side chain is replaced by an allenic 2-(3,4 pentadienyl) substituent. Dendrobates histrionicus exhibits remarkable interpopulational variations in amounts and composition of skin toxins, in behavior, and in phenotypic characters, aspects of which are illustrated in a color plate. The histrionico-toxins are the third class of alkaloids isolated from the defensive skin secretions of Neotropical (Dendrobatidae) frogs. PMID:5288773

Daly, J W; Karle, I; Myers, C W; Tokuyama, T; Waters, J A; Witkop, B

1971-08-01

139

A remarkable shape-catalytic effect of confinement on the rotational isomerization of small hydrocarbons  

NASA Astrophysics Data System (ADS)

As part of an effort to understand the effect of confinement by porous carbons on chemical reactions, we have carried out density functional theory calculations on the rotational isomerization of three four-membered hydrocarbons: n-butane, 1-butene, and 1,3-butadiene. Our results show that the interactions with the carbon walls cause a dramatic change on the potential energy surface for pore sizes comparable to the molecular dimensions. The porous material enhances or hinders reactions depending on how similar is the shape of the transition state to the shape of the confining material. The structure of the stable states and their equilibrium distributions are also drastically modified by confinement. Our results are consistent with a doubly exponential behavior of the reaction rates as a function of pore size, illustrating how the shape of a catalytic support can dramatically change the efficiency of a catalyst.

Santiso, Erik E.; Buongiorno Nardelli, Marco; Gubbins, Keith E.

2008-01-01

140

A remarkable shape-catalytic effect of confinement on the rotational isomerization of small hydrocarbons  

SciTech Connect

As part of an effort to understand the effect of confinement by porous carbons on chemical reactions, we have carried out density functional theory calculations on the rotational isomerization of three four-membered hydrocarbons: n-butane, 1-butene, and 1,3-butadiene. Our results show that the interactions with the carbon walls cause a dramatic change on the potential energy surface for pore sizes comparable to the molecular dimensions. The porous material enhances or hinders reactions depending on how similar is the shape of the transition state to the shape of the confining material. The structure of the stable states and their equilibrium distributions are also drastically modified by confinement. Our results are consistent with a doubly exponential behavior of the reaction rates as a function of pore size, illustrating how the shape of a catalytic support can dramatically change the efficiency of a catalyst. (51 refs.)

Santiso, Erik E [ORNL; Gubbins, Keith E [ORNL; Buongiorno Nardelli, Marco [ORNL

2008-01-01

141

A remarkable shape-catalytic effect of confinement on the rotational isomerization of small hydrocarbons.  

PubMed

As part of an effort to understand the effect of confinement by porous carbons on chemical reactions, we have carried out density functional theory calculations on the rotational isomerization of three four-membered hydrocarbons: n-butane, 1-butene, and 1,3-butadiene. Our results show that the interactions with the carbon walls cause a dramatic change on the potential energy surface for pore sizes comparable to the molecular dimensions. The porous material enhances or hinders reactions depending on how similar is the shape of the transition state to the shape of the confining material. The structure of the stable states and their equilibrium distributions are also drastically modified by confinement. Our results are consistent with a doubly exponential behavior of the reaction rates as a function of pore size, illustrating how the shape of a catalytic support can dramatically change the efficiency of a catalyst. PMID:18205515

Santiso, Erik E; Buongiorno Nardelli, Marco; Gubbins, Keith E

2008-01-21

142

Fischer-tropsch slurry phase process variations to understand wax formation: Quarterly report for period July 1, 1988 to September 30, 1988  

SciTech Connect

A precipitated iron catalyst without any alkali promoters was studied for 2000 hours on stream in a slurry reactor. Reaction conditions were 230 to 260/degree/C (mostly 260/degree/C), 0.77 to 1.92 MPa, H/sub 2//CO feed ratios of 0.5 to 2.0 and CO + H/sub 2/ conversions of 10% to 65%. A Schulz-Flory carbon number distribution with two chain growth probabilities was required to describe the product. Effects of operating variables on 1-butene/n-butane ratio, methane and oxygenate selectivities, and ..cap alpha../sub 1/ and ..cap alpha../sub 2/ are reported. Kinetic models for secondary reactions of 1-alkenes were developed. Addition of potassium t-butoxide to the reactor substantially shifted both distributions to heavier products. 19 refs., 17 figs., 4 tabs.

Donnelly, T.; Satterfield, C.N.

1988-01-01

143

Ethylene polymerisation and oligomerisation with arene-substituted phenoxy-imine complexes of titanium: investigation of multi-mechanism catalytic behaviour.  

PubMed

A range of unsubstituted (1,2) and 6-substituted (3-5) ortho-phenoxy-imine ligands have been prepared and converted to their silyl ether derivatives (6-10). Reaction of silyl ethers with TiCl(4)(thf)(2) in the case of the unsubstituted species yields bis-ligated complexes while the substituted species react cleanly to yield complexes of the form [Ti(O^NR)Cl(3)(thf)]. In most cases the complexes have been characterised by X-ray crystallography. Testing of the complexes for ethylene oligomerisation and polymerisation has been undertaken employing alkylaluminium co-catalysts (AlEt(3), MAO). In all cases the predominant product formed is polyethylene however careful analysis of the liquid phase reveals a complex process by which 1-butene is most likely formed via Cossee mechanism while 1-hexene results from a metallacyclic process. PMID:23396556

Suttil, James A; McGuinness, David S; Gardiner, Michael G; Evans, Stephen J

2013-03-28

144

Histrionicotoxins: Roentgen-Ray Analysis of the Novel Allenic and Acetylenic Spiroalkaloids Isolated from a Colombian Frog, Dendrobates histrionicus  

PubMed Central

The structures and absolute configuration of two unique alkaloids isolated from the Colombian frog, Dendrobates histrionicus, have been elucidated by Roentgen-ray (x-ray) crystallography. Histrionicotoxin is (2pR, 6S, 7pS, 8aS)-7-(cis-1-buten-3-ynyl)-8-hydroxy-2-(cis-2-penten-4- ynyl)-1-azaspiro[5.5] undecane, while in dihydro-isohistrionicotoxin the acetylenic 2-pentenynyl side chain is replaced by an allenic 2-(3,4 pentadienyl) substituent. Dendrobates histrionicus exhibits remarkable interpopulational variations in amounts and composition of skin toxins, in behavior, and in phenotypic characters, aspects of which are illustrated in a color plate. The histrionico-toxins are the third class of alkaloids isolated from the defensive skin secretions of Neotropical (Dendrobatidae) frogs. Images

Daly, John W.; Karle, Isabella; Myers, Charles W.; Tokuyama, Takashi; Waters, James A.; Witkop, Bernhard

1971-01-01

145

Fuel structure and pressure effects on the formation of soot particles in diffusion flames. Annual technical report, 15 January 1988-15 January 1989  

SciTech Connect

Studies emphasizing the effects of fuel molecular structure on soot formation processes in laminar-diffusion flames were investigated. Particular attention was given to the particle inception and surface growth processes for a series of fuels. Studies of butane, 1-butene, and 1,3 butadiene have revealed that fuel structure strongly affects the soot-particle-inception process. However, subsequent surface-growth processes are largely determined by the available surface area. Thus, the surface growth process is independent of the fuel molecular structure following the initial particle-inception stage. Studies of the particle-inception region indicate that increased soot formation is strongly correlated with visible-fluorescence measurements attributed to large polynuclear aromatic hydrocarbon species in the flame.

Santoro, R.J.

1989-02-15

146

Double addition of diethylamine to biacetylene  

SciTech Connect

Biacetylene reacts with an excess of diethylamine in dilute solutions of anhydrous acetonitrile, methanol, ethanol, and THF to form the diadduct 1,3-bis(diethyl-amino)-1,3-butadiene (lambda/sub max/ 325 nm). During concentration of the reaction mixture the latter undergoes hydration by the residual amounts of water in the 3-(diethylamino)-2-butenal. The spectral characteristics (UV, IR, PMR) of the intermediate reaction products are given. The kinetics of the stage of addition of the diethylamine and water to the monoadduct, 1-(diethylamino)-1-buten-3-yne, were studied. It was concluded that the addition of the nucleophile to the triple bond during its secondary amination and hydration is facilitated by the concerted transfer of a proton.

Trofimov, B.A.; Vavilova, A.N.

1986-03-01

147

Crosslinking and degradation of polypropylene by electron beam irradiation in the presence of trifunctional monomers  

NASA Astrophysics Data System (ADS)

Homo-polypropylene (HPP) and random terpolymer of propylene with 2% ethylene and 1% 1-butene by weight (RTPP) can be crosslinked with relatively high gel contents even at doses less than 20kGy, when using trimethylpropanetriacrylate (TMPTA) and triallylcyanuate (TAC) as crosslinking agents. At high doses, HPP with TMPTA degrades more compared to HPP with TAC or RTPP with TMPTA, resulting in a significant increase of the melt index. Heat of fusion of the irradiated polypropylenes (PPs) indicates that the crosslinking and degradation are likely to have little effect on the crystallinity of the PP. Larger amounts of TMPTA in HPP gave rise to more degradation than crosslinking, since excesses of monomer prohibit crosslinking through homo-polymerization.

Han, Do Hung; Shin, Seung-Ho; Petrov, Serguei

2004-02-01

148

Recent Progress in Electron Impact Experiments in Hefei  

NASA Astrophysics Data System (ADS)

Using a new-built high-resolution multichannel (e,2 e) spectrometer and a fast high-resolution electron energy loss spectrometer, the electron momentum spectra for some molecules and the electron energy loss spectra for noble atoms were measured at an impact energy of 2500 eV. Then the orbital assignments and the spin-orbit interactions for the outer valence molecular orbitals, as well as the dynamic behaviors for the valence excitation process of noble atoms, were investigated. In addition, the recent experiment on 1-butene shows that electron momentum spectroscopy is feasible to determine the Boltzmann-weighted abundances and thus to predict the relative stability for different conformers.

Zhu, Lin-Fan; Chen, Xiang-Jun; Shan, Xu; Xu, Ke-Zun

2009-05-01

149

Corona chemistry in Titan.  

PubMed

The atmosphere of Titan is constantly bombarded by galactic cosmic rays and Saturnian magnetospheric electrons causing the formation of free electrons and primary ions, which are then stabilized by ion cluster formation and charging of aerosols. These charged particles accumulate in drops in cloud regions of the troposphere. Their abundance can substantially increase by friction, fragmentation or collisions during convective activity. Charge separation occurs with help of convection and gravitational settling leading to development of electric fields within the cloud and between the cloud and the ground. Neutralization of these charged particles leads to corona discharges which are characterized by low current densities. We have therefore, experimentally studied the corona discharge of a simulated Titan's atmosphere (10% methane and 2% argon in nitrogen) at 500 Torr and 298 K by GC-FTIR-MS techniques. The main products have been identified as hydrocarbons (ethane, ethyne, ethene, propane, propene+propyne, cyclopropane, butane, 2-methylpropane, 2-methylpropene, n-butane, 2-butene, 2,2-dimethylpropane, 2-methylbutane, 2-methylbutene, n-pentane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2,2-dimethylhexane, 2,2-dimethylpentane, 2,2,3-trimethylbutane, 2,3-dimethylpentane and n-heptane), nitriles (hydrogen cyanide, cyanogen, ethanenitrile, propanenitrile, 2-methylpropanenitrile and butanenitrile) and a highly branched hydrocarbon deposit. We present the trends of hydrocarbons and nitriles formation as a function of discharge time in an ample interval and have derived their initial yields of formation. The results clearly demonstrate that a complex organic chemistry can be initiated by corona processes in the lower atmosphere. Although photochemistry and charged particle chemistry occurring in the stratosphere can account for many of the observed hydrocarbon species in Titan, the predicted abundance of ethene is too low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, the production of ethene by corona processes and its subsequent diffusion into the stratosphere appears to be an adequate source. Because little UV penetrates to the lower atmosphere to destroy the molecules formed there, the corona-produced species may be long-lived and contribute significantly to the composition of the lower atmosphere and surface. PMID:11541887

Navarro-Gonzalez, R; Ramirez, S I; Matrajt, G; Basiuk, V; Basiuk, E

1998-06-01

150

The vertical distributions of VOCs in the atmosphere of Beijing in autumn.  

PubMed

Volatile organic compounds (VOCs) in the air of Beijing City were measured at the heights of 8, 32, 140 and 280 m on the Beijing 325 m meteorological tower in autumn 2005. Concentrations of fifty-five compounds were determined by quantitative analytical methods. Our study utilized GC/MS analysis of 0.5 l air sample that were cryo-concentrated prior to analysis. The vertical distributions of VOCs were also investigated using 1-butene, isopentane, dichloromethane and toluene as representative compounds of several different categories. It is shown that 1-butene followed by 2-butene, isopentane followed by n-pentane, dichloromethane followed by chloroform and toluene followed by benzene are the most abundant compounds in the categories of alkene, alkane, halocarbon and aromatic hydrocarbon, respectively. The concentrations of TVOCs range from 51.2+/-39.7 ppb to 83.6+/-44.4 ppb on clear days, but from 62.9+/-19.0 ppb to 105.0+/-59.2 ppb on haze days. While alkenes and halocarbons contribute little to TVOCs, alkanes provide the largest percentage, ranging from about 46% to 63% at four different heights, which are followed by aromatic hydrocarbons ranging from about 15% to 27%. The vertical distributions of VOCs are complex. On clear days most distribution profiles show a decreasing trend with increasing height. On haze days, however, they exhibit first a decrease with increasing altitude from 8 m to 140 m and then a significant increase at 280 m. These results are understood by analyzing how the vertical distributions of VOCs are affected jointly by several factors such as meteorological parameters and transport property. In addition, principal components analysis (PCA) and cluster analysis show that VOCs have different origins at different heights. PMID:17976686

Ting, Mao; Yue-Si, Wang; Jie, Jiang; Fang-kun, Wu; Mingxing, Wang

2007-10-31

151

Estrogenic activity of styrene oligomers after metabolic activation by rat liver microsomes.  

PubMed Central

In this study we examined estrogenic activity of styrene oligomers after metabolic activation by rat liver microsomes. Trans-1,2-diphenylcyclobutane (TCB), cis-1,2-diphenylcyclobutane (CCB), 1,3-diphenylpropane, 2,4-diphenyl-1-butene, 2,4,6-triphenyl-1-hexene, and 1-alpha-phenyl-4ss-(1 -phenylethyl)tetralin were negative in the yeast estrogen screening assay and estrogen reporter assay using estrogen-responsive human breast cancer cell line MCF-7. However, TCB exhibited estrogenic activity after incubation with liver microsomes of phenobarbital-treated rats in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH). Minor activity was observed when liver microsomes of untreated or 3-methylcholanthrene-treated rats were used instead of those from phenobarbital-treated rats. CCB, 1,3-diphenylpropane, and 2,4-diphenyl-1-butene also exhibited estrogenic activity after metabolic activation by liver microsomes, but the activity was lower than that of TCB. 2,4,6-Triphenyl-1-hexene and 1-alpha-phenyl-4ss-(1 -phenylethyl)tetralin did not show estrogenic activity after such incubation. When TCB was incubated with liver microsomes of phenobarbital-treated rats in the presence of NADPH, three metabolites were detected by high-performance liquid chromatography (HPLC). One metabolite isolated by HPLC exhibited a significant estrogenic activity. The active metabolite was identified as trans-1-(4-hydroxyphenyl)-2-phenylcyclobutane by mass and nuclear magnetic resonance spectral analysis. These results suggest that the estrogenic activity of TCB was caused by the formation of the 4-hydroxylated metabolite.

Kitamura, Shigeyuki; Ohmegi, Motoko; Sanoh, Seigo; Sugihara, Kazumi; Yoshihara, Shin'ichi; Fujimoto, Nariaki; Ohta, Shigeru

2003-01-01

152

Selective hydrogenation and H-D exchange of unsaturated hydrocarbons on Pd(100)-p(1x1)-H(D)  

SciTech Connect

The adsorption and reactions of unsaturated hydrocarbons (ethylene, propene, 1-butene, acetylene, allene, 1,3-butadiene, 1,3,5-hexatriene, and 1,5-hexadiene) have been investigated on the Pd(100)-p(1x1)-H and Pd(100)-p(1x1)-D surfaces using temperature-programmed reaction spectroscopy (TPRS). It is found that 1-alkenes (ethylene, propene, and 1-butene) undergo efficient H-D exchange reactions below 300 K for all C-H bonds, whereas no hydrogenation products (alkanes) are observed. Conjugated polyenes (acetylene, allene, 1,3-butadiene, and 1,3,5,-hexatriene) undergo selective hydrogenation to corresponding alkenes below or around 300 K, whereas no exchange reaction is observed to occur for the parent molecules. Nonconjugated polyene (1,5-hexadiene) undergoes both exchange and hydrogenation reactions, with its reactivity in between 1-alkenes and conjugated polyenes. The exchange reaction is proposed to occur via reversible hydrogenation to a half-hydrogenated intermediate. The relative quantities and evolution temperatures of successively H-D exchanged products are reproduced by kinetic simulations of competition between desorption and reaction. The absence of alkene hydrogenation may be due to stronger metal-hydrogen bonds on Pd(100) than on other metals such as Pt and Rh. Strong bonding of the half-hydrogenated intermediate to the surface may be the reason for the irreversible hydrogenation of conjugated polyenes to alkenes. Both exchange and hydrogenation reactions occur at all coverages, but at low coverages the reaction products dehydrogenate to C(a) and H(a) without product evolution. 23 refs., 8 figs., 2 tab.

Guo, Xing-Cai; Madix, R.J. [Stanford Univ., CA (United States)

1995-09-01

153

Modeling hydrodesulfurization catalysis (HDS) by solid-state synthesis, homogeneous desulfurization and heterogeneous probe reactions  

NASA Astrophysics Data System (ADS)

Three approaches towards modeling the HDS catalyst are discussed: structural investigations and catalytic measurements of intercalation compounds of MoSsb2, reactivity studies of soluble bimetallic clusters, and HDS of probe molecules over heterogeneous catalysts. In order to test the viability of the pseudo-intercalation model for the structure of the HDS active site, intercalation compounds of MoSsb2 were synthesized. Different Co species and Co loadings were introduced into the MoSsb2 host by flocculation of aqueous suspensions of single-layer MoSsb2. The structures of the intercalation compounds were determined by EXAFS, electron diffraction, and powder X-ray diffraction. The MoSsb2 layers in these materials are distorted 1T-type structures consisting of linked trimolybdenum clusters. After using these materials as catalysts for the HDS of thiophene, the initial structures of the intercalates were found to be unstable: the sulfide phases 2H-MoSsb2 and Cosb9Ssb8 were the only phases detected by EXAFS. These results strongly suggest that the pseudo-intercalation model would not be thermodynamically nor kinetically stable under the conditions of HDS catalysis. The reactivity of the butterfly cluster Cpsb2MOsb2COsb2Ssb3(CO)sb4 (7b, Cp = etasp5-Csb5Hsb5) for the desulfurization of thiols was investigated as a homogeneous model for the HDS mechanism. Both cyclopropylmethyl thiol (CPMT) and 5-hexenethiol (HET) were stoichiometrically desulfurized at 110sp° C by cluster 7b to form the cubane cluster, CPsb2MOsb2Cosb2Ssb4(CO)sb2, and rearranged organic products expected of "radical clocks" (1-butene and methylcyclopentane, respectively). In neat HET, the reaction with cluster 7a resulted in a mixture of rearranged and unrearranged (1-hexene) desulfurization products which allowed the calculation of the rate of hydrogen abstraction (ksb{abs} = 3.7× 10sp6\\ Msp{-1}ssp{-1}). Thus the reagent thiol was identified as the hydrogen atom donor. The free radical mechanistic model was tested by reacting these same thiols over a conventionally prepared heterogeneous HDS catalyst. The initial product from the HDS of CPMT was 1-butene, while the HDS of HET formed a mixture of hexenes. In this case, the rearranged product (methylcyclopentane) was not formed. A free radical mechanism is proposed with the rate of hydrogen abstraction faster in the heterogeneous system than in the homogeneous one.

Dungey, Keenan Edward

154

Synthesis, characterization and catalytic applications of vanadia and silica-based materials  

NASA Astrophysics Data System (ADS)

Vanadia gels synthesized from a peroxovanadate precursor were used as catalysts for the selective oxidation of 1,3-butadiene. These vanadia gels were previously characterized using 51V and 17O MAS NMR spectroscopy [Fontenot et al., J. Phys. Chem. B 105, p10496 (2000) and J. Am. Chem. Soc. 124, p8435 (2002)]. These studies had shown the presence of an incommensurate shifted layer (+- 1.7 A° along a-axis and +- 0.5 A° along the b-axis) between two commensurate layers of the vanadia gel. This created a special site for water adsorption in which the oxygen of the water molecule was adsorbed trans to the vanadyl oxygen and the two hydrogen atoms co-ordinated with two vanadyl oxygens of the next layer. Selective oxidation studies of 1,3-butadiene were carried out with and without water addition to the feed stream to understand the role of oxygen sites and the water adsorption site in the vanadia gel structure for hydrocarbon oxidation. The reaction mechanism involved intermediates such as 3,4-epoxy-1-butetne, crotonaldehyde, 2,5-dihydrofuran, 2-butene-1,4-dial and furan. The effect of water addition on the pathway for 1,3-butadiene selective oxidation was also investigated over peroxovanadate-derived vanadia and VMoO catalysts by using 3,4-epoxy-1-butene, crotonaldehyde, 2,5-dihydrofuran and furan as feed. Addition of 0-12% water to a reactant feed of 1.4% butadiene in an air-He mixture significantly increased catalytic activity and selectivity for crotonaldehyde and furan. Competitive adsorption was believed to occur between the hydrocarbon products and water; formation of acid sites through dissociative adsorption of water was also believed to be important. Temperature programmed desorption (TPD) experiments revealed five distinct adsorption sites that could be associated with terminal V=O, corner sharing V-O-V, and edge sharing V-O oxygen. The adsorption of water trans to the vanadyl oxygen (V=O) formed an equilibrium structure resulting in the increased reactivity of the vanadyl oxygen species for 1,2-electrophilic addition across the C=C double bond in 1,3-butadiene to form 3,4-epoxy-1-butene. A proposed dissociative mechanism of adsorbed water on the catalyst surface resulted in acidic H+ species that participated in ring opening mechanisms and nucleophilic O-2 species that could easily exchange with the lattice oxygen sites, thus replenishing the catalytic activity.

Yeragi, Dinesh Chandrakant

155

VOCs Speciation From Steam Boiler Stacks of Industries Located in Naucalpan  

NASA Astrophysics Data System (ADS)

Results of VOCs speciation from industrial steam boiler stacks located in Naucalpan are presented and discussed. This municipality is located north of the Metropolitan Zone of the Valley of Mexico (MZVM). Speciation of VOCs is important to generate information about sources of pollution, to update emission inventories, to study the dynamics of pollutants in the atmosphere, and to estimate possible risks of population exposure. This information is valuable for decision making on air pollution control strategies. Samples from 35 steam boilers form industries burning Diesel, LPG, or CNG were taken using the US-EPA Method 18. Selected samples from the use of different fuels were analyzed using gas chromatography and flame ionization detection (GC-FID) according to US-EPA protocol TO-14. The VOCs analyzed included alkanes of 9 carbons or less, alkenes of 7 carbons or less and aromatics (families of benzene). The results show consistency on the VOCs detected on Diesel samples. The main compounds found were 1- Butene+iButylene, m/p-Xylene, Ethane, Propene, Propane, Acetylene, 2Me-1Butene, and Toluene. The average concentrations of these compounds were in the range of 130 to 385 ppbC. The results of LPG samples did not show a definite pattern of VOCs, although light components predominate and, in some samples, Toluene and Xylene. These last components were not expected for industries reporting the use of LPG, perhaps due to the use of a combination of fuels and mistakes in the reports of fuel used at the time of sampling. The analysis of CNG samples show predominance of light VOCs, in the range of 90 to 300 ppbC. As in the case of LPG, some aromatics showed high concentrations in some samples analyzed perhaps due to the use of different fuels in the boiler. The results of this study are the first results of VOCs speciation obtained form exhaust gases from stacks of Mexican industries. The data reported are valuable to analyze emission inventories of VOCs and to better understand the dynamics of pollutants in the MZVM.

Mejia, G. M.; Tejeda, D. D.; Bremauntz, M. P.; Valdez, A.; Montufar, P. C.; Martinez, M. A.; Sierra, M. J.; Gonzalez, C. A.

2007-05-01

156

CAChe Molecular Modeling: A Visualization Tool Early in the Undergraduate Chemistry Curriculum  

NASA Astrophysics Data System (ADS)

In Dickinson's chemistry curriculum, "Synthesis & Reactivity" replaces the traditional organic chemistry sequence and begins in the second semester of the freshman year. A key aspect of our sequence is the correlation of laboratory experiments with lecture topics and the extension of laboratory exercises beyond the usual 4-hour period. With this goal in mind, a number of "Synthesis & Reactivity" experiments have been developed that include an out-of-class computational chemistry exercise using CAChe (1), a versatile molecular modeling software package. Because the first semester of "Synthesis & Reactivity" has a large number of freshmen, emphasis is placed on developing an insight for where nucleophiles and electrophiles might attack a molecule. The Visualizer+ routine in CAChe generates striking graphical images of these sites and the reaction of NBS/H2O with 3-sulfolene (2) presents an excellent opportunity to introduce CAChe into an experiment. Before the laboratory, students are introduced to CAChe to determine how NBS might interact with a nucleophile such as an alkene. Students then return to the laboratory to perform the bromohydrin synthesis but are asked to consider what the regiochemistry would be were the alkene not symmetric. Specifically, students are instructed to visit the computer laboratory during the week and perform calculations on the bromonium ion formed from 2-methylpropene to determine where a nucleophilic H2O molecule might attack. The MOPAC routine in CAChe provides data that are converted to a graphical depiction of the frontier density of the intermediate, indicating potential reactive sites based on electron distribution of orbitals near the HOMO and LUMO. When these data are manipulated by Visualizer+, the obvious conclusion is that the nucleophilic water molecule should attack the more highly substituted carbon of the bromonium ion (Fig. 1) and generate one regioisomer. Figure 1. Relative nucleophilic susceptibilities ofr the boromonium ion derived from 2-methyl-propene. In the second semester of "Synthesis & Reactivity", a more rigorous approach is followed. The reactivity of an aldehyde carbonyl and an ester carbonyl is the subject of an experiment in which students work in groups, with each member treating an equimolar mixture of octanal and methyl caprylate with a different hydride reducing agent. Depending upon the strength of the reducing agent (for example, LiAlH4 vs. NaBH4), students obtain octanol or a mixture of octanol and unreacted methyl caprylate, which is analyzed by gas chromatography. The difference in the reactivity of the carbonyl groups is assayed using CAChe. But in this instance, we sought more precision in comparing carbonyl reactivities than the graphical depictions allowed. CAChe's Project Leader feature allows the atoms of each molecule to be examined individually and reactivity is indicated numerically. After the laboratory, students are assigned the task of looking at the "Nucleophilic Susceptibility" of the carbonyl carbon atoms of the substrates (Fig. 2). Figure 2. Nucleophilic susceptibilities This option examines the electron distribution of orbitals near the LUMO using augmented MM2 to first optimize the geometry and then MOPAC to determine the susceptibility of the atom to attack by a nucleophile. Students are also asked to develop a means to reduce an ester in the presence of an aldehyde and use the calculations that CAChe provides to support their proposed solution. Most students have opted to protect the aldehyde as an acetal, reduce the ester with LiAlH4, and then deprotect the aldehyde. The nucleophilic susceptibility of the acetal carbon clearly indicates that it is unlikely to undergo reduction by LiAlH4. Currently, we are working to expand the use of CAChe to other experiments in "Synthesis & Reactivity" and throughout the curriculum. Acknowledgment We thank the National Science Foundation's Division of Undergraduate Education for financial support through the Instrumenta

Crouch, R. David; Holden, Michael S.; Samet, Cindy

1996-10-01

157

Electron-scattering cross sections for 1-pentene, H2C=CH-(CH2)2CH3, molecules  

NASA Astrophysics Data System (ADS)

Cross sections, both experimental and theoretical, are reported for electron scattering from 1-pentene (C5H10) molecules. Absolute grand-total cross sections (TCSs) were measured at electron impact energies ranging from 1 to 300 eV, using a linear electron-transmission technique. The dominant behaviour of the experimental TCS energy function is a distinct asymmetric enhancement with the maximum located around 6.5 eV. Discernible are also three weak TCS structures: a small peak in the vicinity of 1.8 eV and two broad shoulders located between 10 and 30 eV. The additivity rule was employed to calculate the elastic cross section (ECS) from 20 to 3000 eV, while the binary-encounter-Bethe approach was used for the computation of the ionization cross section (ICS), from the threshold up to 3000 eV. Within 30 and 300 eV, the sum of computed cross sections (ECS+ICS) quite reasonably reproduces the experimental TCS values. Comparison is also made between the experimental TCS energy curve for 1-pentene (H2C=CH-(CH2)2CH3) and those measured for the ethylene (H2C=CH2) molecule and its substituted derivatives: propene (H2C=CH-CH3) and 1-butene (H2C=CH-CH2CH3).

Szmytkowski, Czes?aw; Mo?ejko, Pawe?; Zawadzki, Mateusz; Ptasi?ska-Denga, El?bieta

2013-03-01

158

Isolation and functional analysis of cytochrome P450 CYP153A genes from various environments.  

PubMed

The cytochrome P450 CYP153 family is thought to mediate the terminal hydroxylation reactions of n-alkanes. We isolated 16 new P450 CYP153A genes (central region) from various environments such as petroleum-contaminated soil and groundwater, as well as one from the n-alkane-degrading bacterium Alcanivorax borkumensis SK2 (designated P450balk). The sequences of the new P450 genes were extended by PCR to generate full-length chimeric P450 genes, using the N- and C-terminal domains of P450balk. A differential CO-reduced P450 spectral analysis indicated that 8 P450 genes among the 16 chimeric genes were expressed in Escherichia coli to generate a soluble and functional enzyme. The several functional chimeric P450s and P450balk were further fused to the reductase domain of the self-sufficient P450 monooxygenase (P450RhF) at the C-terminus. E. coli cells expressing these self-sufficient P450 chimeric genes converted n-alkanes, cyclohexane, 1-octene, n-butylbenzene, and 4-phenyl-1-butene into 1-alkanols, cyclohexanol, 1,2-epoxyoctane, 1-phenyl-4-butanol, and 2-phenethyl-oxirane, respectively. PMID:16377903

Kubota, Mitsutoshi; Nodate, Miho; Yasumoto-Hirose, Mina; Uchiyama, Taku; Kagami, Osamu; Shizuri, Yoshikazu; Misawa, Norihiko

2005-12-01

159

The adsorption of 1,3-butadiene on Pd/Ni multilayers: The interplay between spin polarization and chemisorption strength  

NASA Astrophysics Data System (ADS)

The adsorption of 1,3-butadiene (BD) on the Pd/Ni(1 1 1) multilayers has been studied using the VASP method in the framework of the density functional theory (DFT). The adsorption on two different configurations of the Pdn/Nim(1 1 1) systems were considered. The most stable adsorption sites are dependent on the substrate composition and on the inclusion or not of spin polarization. On Pd1Ni3(1 1 1) surface, di-?-cis and 1,2,3,4-tetra-? adsorption structures are the most stable for non-spin polarized (NSP) and spin polarized (SP) levels of calculation, respectively. Conversely, on Pd3Ni1(1 1 1) surface, the 1,2,3,4-tetra-? adsorption structure is the most stable for both NSP and SP levels, respectively. The magnetization of the Pd atoms strongly modifies the adsorption energy of BD and its most stable adsorption mode. On the other hand, as a consequence of BD adsorption, the Pd magnetization decreases. The smaller adsorption energies of BD and 1-butene on the Pd1Ni3(1 1 1) surface than on Pd(1 1 1) can be associated to the strained Pd overlayer deposited on Ni(1 1 1).

Gómez, Guillermina; Belelli, Patricia G.; Cabeza, Gabriela F.; Castellani, Norberto J.

2010-12-01

160

Identification of a tomato gene for the ethylene-forming enzyme by expression in yeast.  

PubMed Central

The ethylene-forming enzyme (EFE), which catalyzes the last step in the biosynthesis of the plant hormone ethylene, has never been purified and no molecular probes are available. Recently, a putative cDNA clone for tomato EFE (pTOM13) has been identified by inhibiting ethylene synthesis with an antisense gene expressed in transgenic plants. A direct test of its function has been made by expression of a pTOM13 gene in Saccharomyces cerevisiae. After cloning artefacts were discovered in the 5' region of the cDNA, a corrected cDNA (pRC13) was created by the fusion of the 5' end of a genomic clone to the 3' end of the cDNA and expressed in S. cerevisiae. Cultures of transformed yeast converted 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, whereas control cells did not. This EFE activity displays similar characteristics to EFE found in plant tissue: it converts the trans isomer of the ACC analogue 1-amino-2-ethylcyclopropane-1-carboxylic acid to 1-butene in preference to the cis isomer, and it is strongly inhibited by cobaltous ions and 1,10-phenanthroline. Furthermore, information gained from the activity of effectors on yeast EFE activity supports the hypothesis that EFE is one of a group of hydroxylase enzymes. Images

Hamilton, A J; Bouzayen, M; Grierson, D

1991-01-01

161

Catalytic conversion of cellulose to liquid hydrocarbon fuels by progressive removal of oxygen to facilitate separation processes and achieve high selectivities  

DOEpatents

Described is a method to make liquid chemicals, such as functional intermediates, solvents, and liquid fuels from biomass-derived cellulose. The method is cascading; the product stream from an upstream reaction can be used as the feedstock in the next downstream reaction. The method includes the steps of deconstructing cellulose to yield a product mixture comprising levulinic acid and formic acid, converting the levulinic acid to .gamma.-valerolactone, and converting the .gamma.-valerolactone to pentanoic acid. Alternatively, the .gamma.-valerolactone can be converted to a mixture of n-butenes. The pentanoic acid so formed can be further reacted to yield a host of valuable products. For example, the pentanoic acid can be decarboxylated yield 1-butene or ketonized to yield 5-nonanone. The 5-nonanone can be hydrodeoxygenated to yield nonane, or 5-nonanone can be reduced to yield 5-nonanol. The 5-nonanol can be dehydrated to yield nonene, which can be dimerized to yield a mixture of C.sub.9 and C.sub.18 olefins, which can be hydrogenated to yield a mixture of alkanes. Alternatively, the nonene may be isomerized to yield a mixture of branched olefins, which can be hydrogenated to yield a mixture of branched alkanes. The mixture of n-butenes formed from .gamma.-valerolactone can also be subjected to isomerization and oligomerization to yield olefins in the gasoline, jet and Diesel fuel ranges.

Dumesic, James A. (Verona, WI); Ruiz, Juan Carlos Serrano (Madison, WI); West, Ryan M. (Madison, WI)

2012-04-03

162

Explosive photodissociation of methane induced by ultrafast intense laser.  

PubMed

A new type of molecular fragmentation induced by femtosecond intense laser at the intensity of 2 x 10(14) W/cm2 is reported. For the parent molecule of methane, ethylene, n-butane, and 1-butene, fluorescence from H (n = 3-->2), CH (A 2Delta, B 2Sigma-, and C 2Sigma+-->X 2Pi), or C2 (d 3Pi g-->a 3Pi u) is observed in the spectrum. It shows that the fragmentation is a universal property of neutral molecule in the intense laser field. Unlike breaking only one or two chemical bonds in conventional UV photodissociation, the fragmentation caused by the intense laser undergoes vigorous changes, breaking most of the bonds in the molecule, like an explosion. The fragments are neutral species and cannot be produced through Coulomb explosion of multiply charged ion. The laser power dependence of CH (A-->X) emission of methane on a log-log scale has a slope of 10 +/- 1. The fragmentation is thus explained as multiple channel dissociation of the superexcited state of parent molecule, which is created by multiphoton excitation. PMID:17029473

Kong, Fanao; Luo, Qi; Xu, Huailiang; Sharifi, Mehdi; Song, Di; Chin, See Leang

2006-10-01

163

Pyrolytic product characteristics of biosludge from the wastewater treatment plant of a petrochemical industry.  

PubMed

Biosludge was produced from the wastewater treatment plant of a petrochemical industry. The element compositions of pyrolytic residues, CO, CO(2), NOx, SOx, total hydrocarbons and detailed volatile organic compounds of pyrolytic gas, and C, H, N, S content and compositions in biofuel were determined in this study. Generally, 75-80% water content in sludge cakes and about 65-70% weight of water vapor and volatile compounds were volatilized during the drying process. Propene, propane, 1-butene, n-butane, isobutene, toluene and benzene were the major volatile organic compounds (VOCs) of the pyrolytic gas, and the concentrations for most of the top 20 VOC species were greater than 5 ppm. C(5)-C(9) compounds contributed 60% by weight of biofuel; 4-hydroxy-4-methyl-2-pentanone was the highest species, accounting for 28-53% of biofuel at various pyrolytic temperatures. Based on the dried residues, there was 8.5-13% weight in pyrolytic residues, 62-82% weight in liquid products (water and crude oil) and 5.8-30% weight in the gas phase after pyrolytic processing at 500-800 degrees C. Finally, 1.5-2.5 wt% liquid fuel was produced after the distillation process. The pyrolytic residues could be reused, the pyrolytic liquid product could be used as a fuel after distillation, and the pyrolytic gas could be recycled in the pyrolytic process to achieve non-toxic discharge and reduce the cost of sludge disposal. PMID:19570608

Lin, Kuo-Hsiung; Hsu, Hui-Tsung; Ko, Ya-Wen; Shieh, Zhu-Xin; Chiang, Hung-Lung

2009-06-06

164

Synthesis of novel acid electrolytes for phosphoric acid fuel cells. Final report, May 1985-October 1988  

SciTech Connect

Construction of a 40-millimole-per-hour-scale aerosol direct-fluorination reactor was completed June 26, 1986. F-Methyl F-4-methoxybutanoate and F-4-methoxybutanoyl fluoride were synthesized by aerosol direct fluorination of methyl 4-methoxybutanoate. Basic hydrolysis of the perfluorinated derivatives produce sodium F-4-methoxybutanoate which was pyrolyzed to F-3-methoxy-1-propene. Purification and shipment of 33 grams of F-3-methoxy-1-propene followed. Syntheses by analogous methods allowed production and shipment of 5 grams of F-3-ethoxy-1-propene, 18 grams of F-3-(2-methoxy.ethoxy)-1-propene, and 37 grams of F-3,3-dimethyl-1-butene. Eighteen grams of F-2,2-dimethyl-1-chloropropane was produced directly and shipped. As suggested by other contractors, 5 grams of F-3-methoxy-1-iodopropane, and 5 grams of F-3-(2-methoxy.ethoxy)-1-iodopropane were produced by converting the respective precursor acid sodium salts produced for olefin synthesis to the silver salts and pyrolyzing them with iodine. Each of these compounds was prepared for the first time by the aerosol fluorination process during the course of the contract. These samples were provided to other GRI contractors for synthesis of perfluorinated sulfur(VI) and phosphorous(V) acids.

Adcock, J.L.

1988-11-01

165

[Aluminum coordination and active sites on aluminas, Y-zeolites and pillared layered silicates]. Progress report  

SciTech Connect

This report is organized in four sections. In the first the authors will outline structural features which are common to all fine grained alumina, as well as to non-framework alumina in zeolites. This section will be followed by a study of the surface vs. bulk coordination of aluminum. The third section will deal with measurement of the number of acid sites and the scaling of their strength. The fourth and last section will describe three model reactions: the isomerization of 1-butene and of 2 cis-butene; the isomerization and disproportionation of oxtho-xylene; and the transformation of trichloroethane into vinyl chloride followed by the polymerization of the vinyl chloride. The relationship between chemical activity and selectivity and what is known of the local structure of the active catalytic sites will be underlined. Other kinds of zeolites besides Y zeolite have been studied. Instead of the aluminum pillared silicates they found it more interesting to study the substitution of silicon by aluminum in a layered structure containing a permanent porosity (aluminated sepiolite).

Fripiat, J.J.

1994-02-01

166

High-temperature pulsed-field-gradient multidimensional NMR of polymers.  

PubMed

The application of pulsed-field-gradient (PFG) techniques has been particularly important in providing the ability to detect 2D and 3D NMR cross peaks from minor structural components in synthetic organic polymers. The lack of mobility in a large percentage of polymers leads to rapid T2 relaxation which prevents the use of pulse sequences, such as the HMBC experiment, that operate based on coherence transfer via small, long-range J couplings. High-temperature NMR increases molecular motion with corresponding line narrowing (e.g., polyethylenes are typically analyzed at 120 degrees C). However, until now, the requirement for high temperature has precluded the use of PFG methods. Here we present data from a new probe which is capable of performing high-temperature PFG coherence selection experiments at temperatures typical of those used in many polymer analyses. We illustrate the performance of this probe with PFG-HMBC spectra of a copolymer from ethylene/1-hexene/1-butene at 120 degrees C. PMID:10497054

Liu, W; Ray, D G; Rinaldi, P L; Zens, T

1999-10-01

167

High-Temperature Pulsed-Field-Gradient Multidimensional NMR of Polymers  

NASA Astrophysics Data System (ADS)

The application of pulsed-field-gradient (PFG) techniques has been particularly important in providing the ability to detect 2D and 3D NMR cross peaks from minor structural components in synthetic organic polymers. The lack of mobility in a large percentage of polymers leads to rapid T2 relaxation which prevents the use of pulse sequences, such as the HMBC experiment, that operate based on coherence transfer via small, long-range J couplings. High-temperature NMR increases molecular motion with corresponding line narrowing (e.g., polyethylenes are typically analyzed at 120 degC). However, until now, the requirement for high temperature has precluded the use of PFG methods. Here we present data from a new probe which is capable of performing high-temperature PFG coherence selection experiments at temperatures typical of those used in many polymer analyses. We illustrate the performance of this probe with PFG-HMBC spectra of a copolymer from ethylene/1-hexene/1-butene at 120 degC.

Liu, Weixia; Ray, Dale G.; Rinaldi, Peter L.; Zens, Toby

1999-10-01

168

Ethers from ethanol. 2: Reaction equilibria of simultaneous tert-amyl ethyl ether synthesis and isoamylene isomerization  

SciTech Connect

The recent requirements for blending oxygenates with gasoline for pollution abatement and octane improvement have opened up huge markets for ethers, synthesized by catalytically reacting an isoolefin with an alcohol. Consequently, alternatives to isobutylene-derived methyl tert-butyl ether (MTBE) obtained from methanol and ethyl tert-butyl ether (ETBE) obtained from ethanol are being explored. This paper provides a thermodynamic analysis of the liquid phase etherification of ethanol with 2-methyl-1-butene (2M1B) and 2-methyl-2-butene (2M2B), the two reactive isoamylene isomers. Both these isomers produce tert-amyl ethyl ether (TAEE) but also undergo isomerization. Theoretical and experimental results are provided here for the simultaneous TAEE synthesis and isoamylene isomerization. Expressions for the three thermodynamic equilibrium constants as a function of temperature are developed. Gibbs free energy and the enthalpy of formation of TAEE are also obtained. The equilibrium constants` correlations are utilized to compute the effect of the feed mole ratio of the isoamylenes and the inert solvent to ethanol as well as the reaction temperature on the equilibrium conversions and selectivities. Conditions that maximize etherification conversion and selectivity are explored.

Kitchaiya, P.; Datta, R. [Univ. of Iowa, Iowa City, IA (United States). Dept. of Chemical and Biochemical Engineering

1995-04-01

169

Promoter effect of Pd in hydrogenation of 1,3-butadiene over Co-Pd catalysts  

SciTech Connect

Addition of a second metal or metal oxide often improves the selectivity of a supported catalyst for the hydrogenation of 1,3-butadiene impurities in commercial n-butene streams. This research has explored the effect of adding Pd to cobalt supported on alumina. Catalysts containing 5 wt% Co and varying amounts (0.1 to 1.0 wt%) of Pd were prepared and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, chemisorption of CO and H{sub 2}, and temperature-programmed reduction after having been subjected to a variety of carefully controlled pretreatments. Activities and product selectivities were tested for hydrogenation of pure 1,3-butadiene and butadiene in a mixture with 1-butene at room temperature. The presence of Pd increased the reducibility of the Co, and separate aluminate, Co, and Pd-Co bimetallic surface phases were identified following various pretreatments. Increasing the Co/Pd ratio decreased the formation of n-butane at room temperature relative to the rate of butadiene conversion, although the improved selectivity was achieved at the expense of increased olefin isomerization and deactivation due to accumulation of carbonaceous residues on the surface. It was not possible to determine unequivocally whether the observed modifications were due to electronic effects or selective poisoning of the separate Co sites. 38 refs., 13 figs., 5 tabs.

Sarkany, A.; Zsoldos, Z.; Stefler, G. [Inst. of Isotopes of the Hungarian Academy of Sciences, Budapest (Hungary)] [and others

1995-11-01

170

Gas-phase reactions of doubly charged actinide cations with alkanes and alkenes--probing the chemical activity of 5f electrons from Th to Cm.  

PubMed

Small alkanes (methane, ethane, propane, n-butane) and alkenes (ethene, propene, 1-butene) were used to probe the gas-phase reactivity of doubly charged actinide cations, An(2+) (An = Th, Pa, U, Np, Pu, Am, Cm), by means of Fourier transform ion cyclotron resonance mass spectrometry. Different combinations of doubly and singly charged ions were observed as reaction products, comprising species formed via metal-ion induced eliminations of small molecules, simple adducts and ions resulting from electron, hydride or methide transfer channels. Th(2+), Pa(2+), U(2+) and Np(2+) preferentially yielded doubly charged products of hydrocarbon activation, while Pu(2+), Am(2+) and Cm(2+) reacted mainly through transfer channels. Cm(2+) was also capable of forming doubly charged products with some of the hydrocarbons whereas Pu(2+) and Am(2+) were not, these latter two ions conversely being the only for which adduct formation was observed. The product distributions and the reaction efficiencies are discussed in relation to the electronic configurations of the metal ions, the energetics of the reactions and similar studies previously performed with doubly charged lanthanide and transition metal cations. The conditions for hydrocarbon activation to occur as related to the accessibility of electronic configurations with one or two 5f and/or 6d unpaired electrons are examined and the possible chemical activity of the 5f electrons in these early actinide ions, particularly Pa(2+), is considered. PMID:21850292

Marçalo, Joaquim; Santos, Marta; Gibson, John K

2011-08-17

171

C-C bond coupling between the organometallic cations CH3Ag2+, CH3Cu2+ and CH3AgCu+ and allyliodide.  

PubMed

Electrospray ionisation on a mixture of AgNO(3) (in MeOH/H(2)O/acetic acid), (CH(3)CO(2))(2)Cu (in MeOH) and acetic acid (in MeOH) yields the metal carboxylate cations CH(3)CO(2)Ag(2)(+), CH(3)CO(2)AgCu(+) and CH(3)CO(2)Cu(2)(+). Collision induced dissociation of these carboxylate cations yields the organometallic cations CH(3)Ag(2)(+), CH(3)AgCu(+) and CH(3)Cu(2)(+). The ion-molecule reactions of these organometallic cations with allyliodide were studied in a quadrupole ion trap mass spectrometer. C-C bond coupling occurred to yield the ionic products Ag(2)I(+), AgCuI(+) and Cu(2)I(+). DFT calculations were carried out on these C-C bond coupling reactions. In all cases, the reactions are highly exothermic and involve initial coordination of the allyliodide to both metal atoms, with the iodine coordinating to one atom and the alkene moiety coordinating to the other. The overall mechanism of C-C bond coupling involves oxidative addition of the allyliodide followed by reductive elimination of 1-butene. PMID:19333507

Khairallah, George N; Waters, Tom; O'Hair, Richard A J

2009-02-20

172

The effect of rhenium, sulfur and alumina on the conversion of hydrocarbons over platinum single crystals: Surface science and catalytic studies  

SciTech Connect

Conversion reactions of hydrocarbons over Pt-Re model catalyst surfaces modified by sulfur and alumina have been studied. A plasma deposition source has been developed to deposit Pt, Re, and Al on metal substrates variable coverage in ultrahigh vacuum without excessive heating. Conversion of n-hexane was performed over the Re-covered Pt and Pt-covered Re surfaces. The presence of the second metal increased hydrogenolysis activity of both Pt-Re surfaces. Addition of sulfur on the model Catalyst surfaces suppressed hydrogenolysis activity and increased the cyclization rate of n-hexane to methylcyclopentane over Pt-Re surfaces. Sulfiding also increased the dehydrogenation rate of cyclohexane to benzene Over Pt-Re surfaces. It has been proposed that the PtRe bimetallic catalysts show unique properties when combined with sulfur, and electronic interactions exist between platinum, rhenium and sulfur. Decomposition of hydrocarbons on the sulfur-covered Pt-Re surfaces supported that argument. For the conversion of 1-butene over the planar Pt/AlO[sub x], the addition of Pt increased the selectivity of hydrogenation over isomerization.

Kim, C.

1992-04-01

173

The effect of rhenium, sulfur and alumina on the conversion of hydrocarbons over platinum single crystals: Surface science and catalytic studies  

SciTech Connect

Conversion reactions of hydrocarbons over Pt-Re model catalyst surfaces modified by sulfur and alumina have been studied. A plasma deposition source has been developed to deposit Pt, Re, and Al on metal substrates variable coverage in ultrahigh vacuum without excessive heating. Conversion of n-hexane was performed over the Re-covered Pt and Pt-covered Re surfaces. The presence of the second metal increased hydrogenolysis activity of both Pt-Re surfaces. Addition of sulfur on the model Catalyst surfaces suppressed hydrogenolysis activity and increased the cyclization rate of n-hexane to methylcyclopentane over Pt-Re surfaces. Sulfiding also increased the dehydrogenation rate of cyclohexane to benzene Over Pt-Re surfaces. It has been proposed that the PtRe bimetallic catalysts show unique properties when combined with sulfur, and electronic interactions exist between platinum, rhenium and sulfur. Decomposition of hydrocarbons on the sulfur-covered Pt-Re surfaces supported that argument. For the conversion of 1-butene over the planar Pt/AlO{sub x}, the addition of Pt increased the selectivity of hydrogenation over isomerization.

Kim, C.

1992-04-01

174

The influence of overlap interactions on chemical reactions in confinement  

NASA Astrophysics Data System (ADS)

Chemical reactions are often carried out in nano-structured materials due to their large surface area per unit mass. It is, however, difficult to understand fully the role of the nano-structure in many reactions due to the superposition of multiple effects. Such effects include: the reduced dimensionality of the system, the heterogeneity of the pore surfaces, the selective adsorption of reactants/products, catalytic effects, and transport limitations. Experimental studies often show many of these effects at the same time, making the results difficult to interpret. In this work we present results of density functional theory calculations illustrating the influence of overlap interactions (shape-catalytic effects) on chemical reactions. In particular, we show the effect of confinement in small pores on the rates of rotational isomerizations of n-butane, 1-butene and 1,3-butadiene. We find that the rates of these transitions change as the double exponential of the pore size in the molecular sieving limit. These results are a first step towards an integrated model for the design of catalytic materials.

Santiso, Erik E.; Gubbins, Keith E.; George, Aaron M.; Buongiorno Nardelli, Marco

2007-03-01

175

Hydrocarbon Source Signatures in Houston, Texas: Influence of the Petrochemical Industry  

SciTech Connect

Observations of C1-C10 hydrocarbon mixing ratios measured by in-situ instrumentation at the La Porte super site during the TexAQS 2000 field experiment are reported. The La Porte data were compared to a roadway vehicle exhaust signature obtained from canister samples collected in the Houston Washburn tunnel during the same summer to better understand the impact of petrochemical emissions of hydrocarbons at the site. It is shown that the abundance of ethene, propene, 1-butene, C2-C4 alkanes, hexane, cyclohexane, methylcyclohexane, isopropylbenzene, and styrene at La Porte were systematically impacted by petrochemical industry emissions. Coherent power law relationships between frequency distribution widths of hydrocarbon mixing ratios and their local lifetimes clearly identify two major source groups, roadway vehicle emissions and industrial emissions. Distributions of most aromatics and long chain alkanes were consistent with roadway vehicle emissions as the dominant source. Airmass reactivity was generally dominated by C1-C3 aldehydes. Propene and ethene sometimes dominated air mass reactivity with HO loss frequencies often greater than 10 s-1. Ozone mixing ratios near 200 ppbv were observed on two separate occasions and these air masses appear to have been impacted by industrial emissions of alkenes from the Houston Ship Channel. The La Porte data provide evidence of the importance of industrial emissions of ethene and propene on air masses reactivity and ozone formation in Houston.

Jobson, B Tom T.; Berkowitz, Carl M.; Kuster, W. C.; Goldan, P. D.; Williams, E. J.; Fesenfeld, F.; Apel, Eric; Karl, Thomas G.; Lonneman, William A.; Riemer, D.

2004-12-22

176

Hydrocarbon source signatures in Houston, Texas: Influence of the petrochemical industry  

NASA Astrophysics Data System (ADS)

Observations of C1-C10 hydrocarbon mixing ratios measured by in situ instrumentation at the La Porte super site during the TexAQS 2000 field experiment are reported. The La Porte data were compared to a roadway vehicle exhaust signature obtained from canister samples collected in the Houston Washburn tunnel during the same summer to better understand the impact of petrochemical emissions of hydrocarbons at the site. It is shown that the abundance of ethene, propene, 1-butene, C2-C4 alkanes, hexane, cyclohexane, methylcyclohexane, isopropylbenzene, and styrene at La Porte were systematically affected by petrochemical industry emissions. Coherent power law relationships between frequency distribution widths of hydrocarbon mixing ratios and their local lifetimes clearly identify two major source groups, roadway vehicle emissions and industrial emissions. Distributions of most aromatics and long chain alkanes were consistent with roadway vehicle emissions as the dominant source. Air mass reactivity was generally dominated by C1-C3 aldehydes. Propene and ethene sometimes dominated air mass reactivity with HO loss frequencies often greater than 10 s-1. Ozone mixing ratios near 200 ppbv were observed on two separate occasions, and these air masses appear to have been affected by industrial emissions of alkenes from the Houston Ship Channel. The La Porte data provide evidence of the importance of industrial emissions of ethene and propene on air mass reactivity and ozone formation in Houston.

Jobson, B. T.; Berkowitz, C. M.; Kuster, W. C.; Goldan, P. D.; Williams, E. J.; Fesenfeld, F. C.; Apel, E. C.; Karl, T.; Lonneman, W. A.; Riemer, D.

2004-12-01

177

Characterization of non-methane hydrocarbons emitted from open burning of wheat straw and corn stover in China  

NASA Astrophysics Data System (ADS)

Field measurements were conducted to determine the characteristics of non-methane hydrocarbons (NMHCs) emitted from open burning of wheat straw and maize stover, two major agricultural residues in China. The headfire ignition technique was used with sampling downwind from the agricultural fire. Fifty-two NMHC species were quantified using gas chromatography/mass spectrometry. A carbon mass balance method was used to determine NMHC emission factors. The emission factors of the total speciated NMHCs from wheat straw and maize stover are 1690 ± 580 mg kg-1 and 1590 ± 430 mg kg-1, respectively. Propane, n-pentane, 2,3-dimethylbutane, 2-methylpentane, propene, benzene and toluene are the main species, together accounting for 55.3%-68.0% of the total NMHCs. On the basis of measured emission factors and the published maximum incremental reactivity values for NMHCs, we estimated the ozone forming potential (OFP) of speciated NMHCs. The results indicate that propene, 1-butene, isoprene, toluene and m,p-xylene have high OFP values and account for about 50% of the total OFP. Alkenes played the most important role in potential ozone formation, followed by aromatics and alkanes.

Li, Xinghua; Wang, Shuxiao; Duan, Lei; Hao, Jiming

2009-10-01

178

Kinetics and mechanism of n-butene isomerization over activated lanthanum oxide  

SciTech Connect

The catalytic behavior of lanthanum sesquioxide for double-bond isomerization of the n-butenes has been studied in the temperature range 0 to 50/sup 0/C. Initial activity for individual conversions of all three n-butene reactants increases with increasing pretreatment temperature, due to removal of surface hydroxyls, attains a maximum following evacuation at approx. 650/sup 0/C, and then declines with further increase in pretreatment temperature, due to decreases in surface anion disorder. Initial reaction rates of each isomer at 0/sup 0/C are described by a Langmuirian rate equation of the form Rate = kbP/(1 + bP), which reduces to a zero-order expression in the case of 1-butene reactant. Double bond migration in the n-butenes occurs very rapidly over La/sub 2/O/sub 3/, but the rates of direct cis ..-->.. trans interconversion are, by comparison, negligibly slow through the temperature range investigated, due possibly to the absence of surface sites that permit the necessary reversible anti-..pi..-allyl ..-->.. sysm of isomerization was in ce, Ti, Be, Co, Cu, Mo, Ni, P,f the Pd crystals of about 30 A. Possible mechanisms are discussed for isotope exchange in CO molecules in these catalysts and for the promoting effect of Pd on the activity of CuO.

Rosynek, M.P.; Fox, J.S.; Jensen, J.L.

1981-09-01

179

Selectivity control during the photoassisted oxidation of 1-butanol on titanium dioxide  

SciTech Connect

The authors have measured the rate and selectivity of the photoassisted decomposition of 1-butanol on TiO/sub 2/ powder as a function of feed composition and reactor temperature. The rate expression is first order in 1-butanol, zero order in O/sub 2/, and negative order in 1-butanol. The photoassisted reaction produces 1-butanal and 1-butene with 89% and 11% selectivity, respectively. The selectivity ratio of the photoassisted reaction is not affected by any of the variations in feed composition or temperature. The dark reaction becomes significant above 473 K and produces larger butene/butanal ratios as well as larger amounts of combustion products. They propose a mechanism for the overall reaction mechanism that is consistent with the observed kinetic and spectroscopic results and develop the rate expression for this mechanism along with a simplified version that applies under the present reaction conditions. Possible mechanistic implications of the selectivity of the alkoxide decomposition elementary step are discussed.

Blake, N.R.; Griffin, G.L.

1988-10-06

180

Polar organic marker compounds in atmospheric aerosols during the LBA-SMOCC 2002 biomass burning experiment in Rondônia, Brazil: sources and source processes, time series, diel variations and size distributions  

NASA Astrophysics Data System (ADS)

Measurements of polar organic marker compounds were performed on aerosols that were collected at a pasture site in the Amazon basin (Rondônia, Brazil) using a High-Volume dichotomous sampler (HVDS) and a Micro-Orifice Uniform Deposit Impactor (MOUDI). The samplings were conducted within the framework of the LBA-SMOCC (Large-Scale Biosphere Atmosphere Experiment in Amazônia - Smoke Aerosols, Clouds, Rainfall, and Climate: Aerosols From Biomass Burning Perturb Global and Regional Climate) campaign, which took place from 9 September till 14 November 2002, spanning the late dry season (biomass burning), the transition period, and the onset of the wet season (clean conditions). In the present study a more detailed discussion is presented compared to previous reports on the behavior of selected polar marker compounds, including: (a) levoglucosan, a tracer for biomass burning, (b) malic acid, a tracer for the oxidation of semivolatile carboxylic acids, (c) tracers for secondary organic aerosol (SOA) from isoprene, i.e., the 2-methyltetrols (2-methylthreitol and 2-methylerythritol) and the C5-alkene triols [2-methyl-1,3,4-trihydroxy-1-butene (cis and trans) and 3-methyl-2,3,4-trihydroxy-1-butene], and (d) sugar alcohols (arabitol, mannitol, and erythritol), tracers for fungal spores. The results obtained for levoglucosan are covered first with the aim to address its contrasting behavior with that of malic acid, the isoprene SOA tracers, and the fungal spore tracers. The tracer data are discussed taking into account new insights that recently became available into their stability and/or aerosol formation processes. During all three periods, levoglucosan was the most dominant identified organic species in the PM2.5 size fraction of the HVDS samples. In the dry period levoglucosan reached concentrations of up to 7.5 ?g m-3 and exhibited diel variations with a nighttime prevalence. It was closely associated with the PM mass in the size-segregated samples and was mainly present in the fine mode, except during the wet period where it peaked in the coarse mode. Isoprene SOA tracers showed an average concentration of 250 ng m-3 during the dry period versus 157 ng m-3 during the transition period and 52 ng m-3 during the wet period. Malic acid and the 2-methyltetrols exhibited a different size distribution pattern: while the 2-methyltetrols were mainly associated with the fine mode during all periods, malic acid was prevalent in the fine mode only during the dry and transition periods, while it was dominant in the coarse mode during the wet period, consistent with different formation processes. The sum of arabitol, mannitol, and erythritol in the PM2.5 fraction of the HVDS samples during the dry, transition, and wet periods was, on average, 54 ng m-3, 34 ng m-3, and 27 ng m-3, respectively, and revealed minor day/night variation. The mass size distributions of arabitol and mannitol during all periods showed similar patterns and an association with the coarse mode, consistent with their primary origin. The results show that even under the heavy smoke conditions of the dry period a natural background with contributions from bioaerosols and isoprene SOA can be revealed. The enhancement in isoprene SOA in the dry season is mainly attributed to an increased acidity of the aerosols and a decreased wet deposition.

Claeys, M.; Kourtchev, I.; Pashynska, V.; Vas, G.; Vermeylen, R.; Wang, W.; Cafmeyer, J.; Chi, X.; Artaxo, P.; Andreae, M. O.; Maenhaut, W.

2010-04-01

181

Calculational and experimental investigations of the pressure effects on radical-radical cross combination reactions: C2H5+C2H3.  

PubMed

Pressure-dependent product yields have been experimentally determined for the cross-radical reaction C2H5 + C2H3. These results have been extended by calculations. It is shown that the chemically activated combination adduct, 1-C4H8*, is either stabilized by bimolecular collisions or subject to a variety of unimolecular reactions including cyclizations and decompositions. Therefore the "apparent" combination/disproportionation ratio exhibits a complex pressure dependence. The experimental studies were performed at 298 K and at selected pressures between about 4 Torr (0.5 kPa) and 760 Torr (101 kPa). Ethyl and vinyl radicals were simultaneously produced by 193 nm excimer laser photolysis of C2H5COC2H3 or photolysis of C2H3Br and C2H5COC2H5. Gas chromatograph/mass spectrometry/flame ionization detection (GC/MS/FID) were used to identify and quantify the final reaction products. The major combination reactions at pressures between 500 (66.5 kPa) and 760 Torr are (1c) C2H5+C2H3-->1-butene, (2c) C2H5 + C2H5-->n-butane, and (3c) C2H3+C2H3-->1,3-butadiene. The major products of the disproportionation reactions are ethane, ethylene, and acetylene. At moderate and lower pressures, secondary products, including propene, propane, isobutene, 2-butene (cis and trans), 1-pentene, 1,4-pentadiene, and 1,5-hexadiene are also observed. Two isomers of C4H6, cyclobutene and/or 1,2-butadiene, were also among the likely products. The pressure-dependent yield of the cross-combination product, 1-butene, was compared to the yield of n-butane, the combination product of reaction (2c), which was found to be independent of pressure over the range of this study. The [1-C4H8]/[C4H10] ratio was reduced from approximately 1.2 at 760 Torr (101 kPa) to approximately 0.5 at 100 Torr (13.3 kPa) and approximately 0.1 at pressures lower than about 5 Torr (approximately 0.7 kPa). Electronic structure and RRKM calculations were used to simulate both unimolecular and bimolecular processes. The relative importance of C-C and C-H bond ruptures, cyclization, decyclization, and complex decompositions are discussed in terms of energetics and structural properties. The pressure dependence of the product yields were computed and dominant reaction paths in this chemically activated system were determined. Both modeling and experiment suggest that the observed pressure dependence of [1-C4H8]/[C4H10] is due to decomposition of the chemically activated combination adduct 1-C4H8* in which the weaker allylic C-C bond is broken: H2C=CHCH2CH3-->C3H5+CH3. This reaction occurs even at moderate pressures of approximately 200 Torr (26 kPa) and becomes more significant at lower pressures. The additional products detected at lower pressures are formed from secondary radical-radical reactions involving allyl, methyl, ethyl, and vinyl radicals. The modeling studies have extended the predictions of product distributions to different temperatures (200-700 K) and a wider range of pressures (10(-3)-10(5) Torr). These calculations indicate that the high-pressure [1-C4H8]/[C4H10] yield ratio is 1.3+/-0.1. PMID:17585737

Fahr, Askar; Halpern, Joshua B; Tardy, Dwight C

2007-06-22

182

Energy barriers for the addition of H, *CH3, and *C2H5 to *CH2=CHX [X = H, CH3, OH] and for H-atom addition to RCH=O [R = H, CH3, *C2H5, n-C3H7]: implications for the gas-phase chemistry of enols.  

PubMed

Although enols have been identified in alcohol and other flames and in interstellar space and have been implicated in the formation of carboxylic acids in the urban troposphere in the past few years, the reactions that give rise to them are virtually unknown. To address this data deficit, particularly with regard to biobutanol combustion, we have carried out a number of ab initio calculations with the multilevel methods CBS-QB3 and CBS-APNO to determine the activation enthalpies for methyl addition to the CH(2) group of CH(2)=CHX where X = H, OH, and CH(3). These average at 26.3 +/- 1.0 kJ mol(-1) and are not influenced by the nature of X; addition to the CHX end is energetically costlier and does show the influence of group X = OH and CH(3). Replacing the attacking methyl radical by ethyl makes very little difference to addition at CH(2) and follows the same trend of a higher barrier for addition to the CH(OH) end. In the case of H-addition it is more problematic to draw general conclusions since the DFT-based methodology, CBS-QB3, struggles to locate transition states for some reactions. However, the increase in barrier heights in reaction at the CHX end in comparison to addition at the methylene end is evident. For hydrogen atom reaction with the carbonyl group in the compounds methanal, ethanal, propanal, and butanal we see that for addition at the O-center the barrier heights of ca. 38 kJ mol(-1) are not influenced by the nature of the alkyl group whereas addition at the C-center is different on going from H --> alkyl but seems to be invariant at 20 kJ mol(-1) once alkylated. Rate constants for H-atom elimination from 1-hydroxyethyl, 1-hydroxypropyl, and 1-hydroxybutyl radicals, valid over the range 800-2000 K, are reported. These demonstrate that enols are more prevalent than previously suspected and that 1-buten-1-ol should be almost as abundant as its isomeric aldehyde 1-butanal during the combustion of 1-butanol and that this will also be the case for other alcohols provided that the appropriate structural features are present. Since the toxicity of enols is not known experiments and further theoretical studies are clearly desirable before the large-scale usage of alcohol biofuels commences. An enthalpy of formation for butanal of Delta(f)H(298.15 K) = -204.4 +/- 1.4 kJ mol(-1) [Buckley, E.; Cox, J. D. Trans. Faraday Soc. 1967, 63 , 895 901] is recommended, the uncertainty surrounding that for the 2-hydroxypropyl radical has been markedly reduced, and new values for 1-buten-1-ol, 1-propen-1-ol, and 2-propen-2-ol of -171.8 +/- 1.6, -151.8 +/- 1.7, and -169.9 +/- 1.5 kJ mol(-1), respectively, are proposed. PMID:19518123

Simmie, John M; Curran, Henry J

2009-07-01

183

Understanding conjugation and hyperconjugation from electronic delocalization measures.  

PubMed

The concepts of conjugation and hyperconjugation play an important role to provide an explanation for several fundamental phenomena observed in organic chemistry. Because these effects cannot be directly measured experimentally, their assessment became a primary concern for chemists from the very beginning. In general, the stabilization produced by both phenomena has been studied by means of isodesmic reactions and energy based analysis such as the energy decomposition analysis. In recent years, electronic delocalization measures have been successfully applied to elucidate the nature of chemical bonding and the aromatic character of all kind of molecules. Because conjugation and hyperconjugation stabilizations are strongly linked to the concept of electron delocalization, this paper will give an account of both effects from the point of view of electronic delocalization measures calculated within the framework of the quantum theory of atoms in molecules. In particular, we focus our attention in the controversial case of the stabilization by conjugation in 1,3-butadiyne and 1,3-butadiene. Unexpectedly, theoretical calculations based on the scheme proposed by Kistiakowsky to quantify the extent of stabilization due to conjugation predicted that the conjugation of 1,3-butadiyne was zero. Subsequent energetic analyses contradicted this observation. These studies pointed out the presence of hyperconjugation stabilization in the hydrogenated product of 1,3-butadiyne and 1,3-butadiene that were used as reference systems in the Kistiakowsky's scheme. Consequently, the extra stabilization of 1-butyne due to hyperconjugation hides the stabilization by conjugation of 1,3-butadiyne. Our results based on electron delocalization measures confirm both the presence of conjugation in 1,3-butadiene and 1,3-butadiyne and hyperconjugation stabilization in their respective hydrogenated products, 1-butene and 1-butyne. PMID:21932863

Feixas, Ferran; Matito, Eduard; Poater, Jordi; Solà, Miquel

2011-09-21

184

An evaluation of the single turnover (STO) procedure as a method for the determination of the active site densities on dispersed metal catalysts  

SciTech Connect

The extent of 2-butene formation during the STO reactions over Pd and Rh indicates that the alkene isomerization is nonstoichiometric. With Pt the extent of isomerization is also influenced by flow rate and reactant pulse size but to a lesser extent. Thus, the STO reaction procedure cannot be used for the determination of isomerization site densities on any of these catalysts. This procedure has been used to determine the saturation site densities on the EuroPt-I Pt/SiO{sub 2} and some northwestern Pt/SiO{sub 2} catalysts. The STO reaction sequence has also been run over Pt, Pd, and Rh catalysts using each of the isomeric butenes as the reactant alkene. Over all three catalysts the same amounts of direct and two-step saturation were observed regardless of the starting alkene showing that these saturation sites are not sensitive to the geometry of the reactant olefin. With Rh a near equilibrium mixture of all three double bond isomers is formed from each of the three starting alkenes. With Pt the extent of isomerization is characteristically low regardless of the starting olefin, so the low isomerization observed during the STO reaction of 1-butene on Pt is not the result of the formation of a primary metalalkyl on a large number of isomerization sites. The STO determined reactive site densities have been correlated with transition electron microscopy (TEM) measured metal particle sizes and turnover frequency (TOF) data for a number of reactions. From these results the sites on which specific reactions take place have been determined as has the site TOF for each of the active sites involved.

Augustine, R.L.; Baum, D.R.; High, K.G.; Szivos, L.S.; O'Leary, S.T. (Seton Hall Univ., South Orange, NJ (USA))

1991-02-01

185

Reaction of tributyl phosphite with oxidized iron: surface and tribological chemistry.  

PubMed

The surface chemistry of a model lubricant additive, tributyl phosphite (TBPi), is investigated on Fe3O4 in ultrahigh vacuum. A portion of the TBPi desorbs molecularly following adsorption at approximately 200 K, the remainder decomposing either by C-O bond scission to form 1-butyl species or by P-O bond cleavage to form butoxy species. Adsorbed butyl species either undergo beta-hydride elimination to desorb 1-butene or decompose to deposit carbon and hydrogen on the surface. The resulting adsorbed hydrogen reacts with the oxide to desorb water or with the butoxy species to form 1-butanol. Butoxy species are stable up to approximately 600 K at which temperature they also undergo beta-hydride elimination to form butanal and the released hydrogen reacts with other butoxy species to form 1-butanol. Only a small amount of carbon is deposited onto the surface following adsorption at approximately 200 K, which then desorbs as CO above approximately 750 K. Adsorbing TBPi at 300 K results in the deposition of more carbon and an Auger depth profile reveals that the carbon is located predominantly on the surface, while the phosphorus is rather uniformly distributed throughout the oxide film. This result is in accord with previous near-edge X-ray absorption fine structure measurements, which show the formation of phosphates and polyphosphate glasses. The resulting tribological film appears to be composed of a relatively hard polyphosphate glass formed by rapid diffusion of POx species into the oxide, covered by a low shear strength graphitic layer. PMID:15323502

Gao, Feng; Furlong, Octavio; Kotvis, Peter V; Tysoe, Wilfred T

2004-08-31

186

Octahedral Group 4 Metal Complexes That Contain Amine, Amido, and Aminopyridinato Ligands: Synthesis, Structure, and Application in alpha-Olefin Oligo- and Polymerization.  

PubMed

The reaction of trimethylsilyl-substituted 2-aminopyridines with mixed chloro(dialkylamido)metal complexes (titanium and zirconium) leads via amine elimination to octahedral group 4 metal complexes that contain amine, amido, and aminopyridinato ligands. The X-ray crystal structure analyses of (4-Me-TMS-APy)(NMe(2))(HNMe(2))TiCl(2) (1) (crystallographic data: P2(1)/c (No. 14), monoclinic, a = 16.754(2) Å, b = 14.395(2) Å, c = 17.890(3) Å, beta = 110.28(1) degrees, Z = 8) and (6-Me-TMS-APy)(NEt(2))(HNEt(2))ZrCl(2) (2) (crystallographic data: P2(1)/n (No. 14) monoclinic, a = 10.125(1) Å, b = 16.331(1) Å, c = 15.276(2) Å, beta = 93.90(1), Z = 4) prove the compounds to be mononuclear with a cisoid arrangement of the two chloro ligands embedded in a reactive pocket determined by the steric demand of the three nitrogen containing ligands. Oligo- and polymerization studies with propene and 1-butene reveal the following results. First, 1 is a remarkably active precatalyst in contrast to the very low activity of 2. Second, MAO, a 1:1 mixture of i-Bu(3)Al/B(C(6)F(5))(3) (homogeneous polymerization) and ethylaluminum sesquichloride (if 1 is incorporated in a MgCl(2)-matrix) have shown to be the most active cocatalysts. Third, the polymers and oligomers are atactic. PMID:11666837

Fuhrmann, Hans; Brenner, Simon; Arndt, Perdita; Kempe, Rhett

1996-11-01

187

The oxidation of soot and carbon monoxide in hydrocarbon diffusion flames  

SciTech Connect

Quantitative hydroxyl radical concentrations and primary soot particle sizes have been determined in the soot oxidation regions of axisymmetric diffusion flames burning methane, methane/butane, and methane/1-butene in air at atmospheric pressure. The total carbon flow rate was held constant in these flames while the maximum amount of soot varied by a factor of seven along the centerline. Laser-induced fluorescence measurements of OH were placed on an absolute basis by calibration against earlier absorption results. The primary size measurements of the soot particles were made using thermophoretic sampling and transmission electron microscopy. OH concentrations are greatly reduced in the presence of soot particles. Whereas large super-equilibrium ratios are observed in the high-temperature reaction zones in the absence of soot, the OH concentrations approach equilibrium values when the soot loading is high. The diminished OH concentrations are found to arise from reactions with the soot particles and only to a minor degree from lower temperatures due to soot radiation losses. Analysis of the soot oxidation rates computed from the primary particle size profiles as a function of time along the flame centerlines shows that OH is the dominant oxidizer of soot, with O[sub 2] making only a small contribution. Higher collision efficiencies of OH reactions with soot particles are found for the flames containing larger soot concentrations at lower temperatures. A comparison of the soot and CO oxidation rates shows that although CO is inherently more reactive than soot, the soot successfully competes with CO for OH and hence suppresses CO oxidation for large soot concentrations.

Puri, R.; Santoro, R.J. (Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering); Smyth, K.C. (National Inst. of Standards and Technology, Gaithersburg, MD (United States). Building and Fire Research Lab.)

1994-05-01

188

Rate rules, branching ratios, and pressure dependence of the HO2 + olefin addition channels.  

PubMed

In this work, we present high-pressure rate rules and branching ratios for the addition of HO2 to olefins through the concerted addition channel to form an alkyl peroxy radical (HO2 + olefin ? RO2) and through the radical addition channel to form a ?-hydroperoxy alkyl radical (HO2 + olefin ? ?-QOOH). These rate rules were developed by calculating rate constants for a series of addition reactions involving olefins with varying degrees of branching. The individual rate expressions were determined from electronic structure calculations performed at the CBS-QB3 level of theory combined with TST calculations. The calculated rate constants were found to be in good agreement with those reported in the literature. Next, we calculated apparent pressure- and temperature-dependent rate constants for HO2 addition to the terminal site of 1-butene using an energy-grained master equation (ME) approach and QRRK calculations with a modified strong collision (MSC) approximation. The two methods gave similar results for both reaction classes. We found that, for the radical addition reaction, the high-pressure limit for the stabilization channel is not reached until unusually high pressures (>1000 atm). Instead, this reaction leads to the direct formation of an oxirane + OH. In general, the results for the major channels are in reasonable agreement with prior theoretical and experimental data. Finally, to explicitly examine the effect of pressure, we compared concentration-time profiles for the reactions of HO2 plus butene in air that were obtained using both high-pressure and pressure-dependent mechanisms at 10 and 100 atm. These simulations showed that, contrary to general expectations, the manifestation of pressure falloff effects in kinetic modeling studies might be more prevalent at increasing pressures. This behavior is attributed to the reaction of ?-QOOH with O2, the rate of which increases with increasing pressure of air. This bimolecular reaction competes with the unimolecular reactions of ?-QOOH under conditions where falloff effects are important for that channel. PMID:23829768

Villano, Stephanie M; Carstensen, Hans-Heinrich; Dean, Anthony M

2013-07-18

189

Catalytic coal conversion support: use of laser flash-pyrolysis for structural analysis. Progress report, April 1-June 30, 1980  

SciTech Connect

Acid lignin was pyrolyzed and the pyrolysis products analyzed on the HP model 5830 GC/MS to increase our understanding of the pyrolysis process. Lignin is a high molecular weight polyphenol whose detailed structure is not known, but is believed to be constructed from phenylpropane derivatives. Consequently, if condensed ring compounds like indene and naphthalene are observed in the pyrolysis products of lignin, ring closure may be taking place during pyrolysis. The lignin was pyrolyzed with the Nd laser and the CO/sub 2/ laser, yielding significantly different pyrograms. Pyrolysis with the Nd laser yielded more than 30 products of which the major components are diacetylene and methoxyphenol. Acetylene was not detected. Pyrolysis with the CO/sub 2/ laser yielded more than 96 compounds. Products occurring in greater than 10 ..lambda.. relative abundance included benzene, toluene, styrene, and napthalene. Although both lasers produced CS/sub 2/, the CO/sub 2/ laser produced several sulfur-containing organics not observed with the Nd laser: thiophene, methylthiophenes, dimethylthiophenes, and benzothiophenes. The Nd laser produced acetylenic compounds not observed with the CO/sub 2/ laser: 1 buten-3-yne, diacetylene, and phenylacetylene. Similar aromatic and phenolic compounds were observed with both lasers. The presence of indene, naphthalene, and benzothiophene in the lower-energy CO/sub 2/ laser pyrolysis indicates that some ring-closing reactions are taking place. The greater amounts of acetylenic compounds produced by the Nd laser are most likely a result of the higher energy deposition by this laser.

Rofer-DePoorter, C.K. (comp.)

1981-10-01

190

The carbon kinetic isotope effects of ozone-alkene reactions in the gas-phase and the impact of ozone reactions on the stable carbon isotope ratios of alkenes in the atmosphere  

NASA Astrophysics Data System (ADS)

The kinetic isotope effects (KIEs) for several ozone-alkene reactions in the gas phase were studied in a 30 L PTFE reaction chamber. The time dependence of the stable carbon isotope ratios and the concentrations were determined using a gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) system. The following average KIE values were obtained: 18.9 +/- 2.8 (ethene), 9.5 +/- 2.5 (propene), 8.7 +/- 1 (1-butene), 8.1 +/- 0.4 (E-2-butene), 7.9 +/- 0.4 (1,3-butadiene), 6.7 +/- 0.9 (1-pentene), 7.3 +/- 0.2 (Z-2-pentene), 6.7 +/- 0.7 (cyclopentene), 6.1 +/- 1 (isoprene), 5.0 +/- 0.7 (1-hexene), 5.6 +/- 0.5 (cyclohexene), and 4.3 +/- 0.7 (1-heptene). These data are the first of their kind to be reported in the literature. The ozone-alkene KIE values show a systematic inverse dependence from alkene carbon number. Based on the observed KIEs, the contribution of ozone-alkene reactions to the isotopic fractionation of alkenes in the atmosphere can be estimated. On average this contribution is generally small compared to the impact of reaction with OH radicals. However, when OH-concentrations are very low, e.g. during nighttime and at high latitudes in winter, the contribution of the ozone reaction dominates and under these conditions the ozone-alkene reaction will have a clearly visible impact on the stable carbon isotope ratio of atmospheric alkenes.

Iannone, R.; Anderson, R. S.; Rudolph, J.; Huang, L.; Ernst, D.

2003-07-01

191

Rich methane premixed laminar flames doped with light unsaturated hydrocarbons  

SciTech Connect

The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of C{sub 3}H{sub 4} was added, corresponding to a ratio C{sub 3}H{sub 4}/CH{sub 4} of 12% and an equivalence ratio of 1.55. The three flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz microprobe. Quantified species included carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, propane, 1,2-butadiene, 1,3-butadiene, 1-butene, isobutene, 1-butyne, vinylacetylene, and benzene. The temperature was measured using a PtRh (6%)-PtRh (30%) thermocouple settled inside the enclosure and ranged from 700 K close to the burner up to 1850 K. In order to model these new results, some improvements have been made to a mechanism previously developed in our laboratory for the reactions of C{sub 3}-C{sub 4} unsaturated hydrocarbons. The main reaction pathways of consumption of allene and propyne and of formation of C{sub 6} aromatic species have been derived from flow rate analyses. (author)

Gueniche, H.A.; Glaude, P.A.; Dayma, G.; Fournet, R.; Battin-Leclerc, F. [Departement de Chimie-Physique des Reactions, Nancy University, CNRS, ENSIC, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France)

2006-09-15

192

Germ cell mutagenicity of three metabolites of 1,3-butadiene in the rat: Induction of spermatid micronuclei by butadiene mono-, Di-, and diolepoxides in vivo  

SciTech Connect

Three metabolites of the industrial chemical 1,3-butadiene (BD), namely butadiene monoepoxide (BMO, 3,4-epoxy-1-butene), diepoxide (DEB, 1,2;3,4-diepoxybutane), and diolepoxide (DE, 3,4,-epoxybutane-1,2-dial) were studied for germ cell mutagenicity using the rat spermatid micronucleus (MN) test. All three epoxides increase slightly, but significantly, the frequency of spermatid MN. The most sensitive stage to the action of BMO and DEB was preleptotene (meiotic S phase) harvested at 18- daytime intervals after treatment. The dose-response for BMO followed a second order curve at this time interval, with maximum MN induction at the dose of 186 {mu}mol/kg and lower induction at higher doses. Late stages of the meiotic prophase (late pachytene-diplotene-diakinesis) also showed some sensitivity to the three epoxides. Stem cell spermatogonia were affected by DEB as observed by a slight induction of spermatid micronuclei 50 days after treatment. No clear cytotoxic effects were observed by measuring testicular weight or cell numbers of seminiferous epithelial state 1 18 days after the treatments. DEB at the dose 387 {mu}mol/kg caused a slight inhibition of spermatogonial DNA synthesis in stage 1 and a delay of meiotic DNA replication observed in stage XII 72 hr after treatment. Since BMO is able to induce spermatid MN in the rat, the present results, together with previous data, indicate that rat bone marrow MN results that are negative for both BD and BMO cannot directly predict mutagenicity in male germ cells. The results also emphasize that tissue, species-, and strain-specific differences in metabolism have to be taken into account when the genetic risks of human butadiene exposure are evaluated. The results support the conclusion that 1,3-butadiene is a germ cell mutagen-possibly also in humans. 42 refs., 2 figs., 6 tabs.

Laehdetie, J.; Sjoeblom, T. [Univ. of Turku (Finland); Peltonen, K. [Inst. of Occupational Health, Helsinki (Finland)

1997-10-01

193

Dissociation of a protonated secondary amine in the gas phase via an ion-neutral complex  

NASA Astrophysics Data System (ADS)

Collisionally activated dissociation of conjugate acid ions of neopentyl isopropylamine (1) gives loss of a neutral C5H10 molecule, MH+-C5H10, as the predominant decomposition peak (>D70% of the total fragment ion abundance). Quantitative evaluation of the relative peak intensities from protonated 1 and its deuterated analogues permits an assessment of the contribution of hydrogen transfer from the CH3 of the neopentyl group ([gamma]-position) relative to the CH2 ([alpha]-position), as well as the corresponding kinetic isotope effects. The ratio of [gamma]-transfer to [alpha]-transfer 6rom the neopentyl group is on the order of 5:1, implying that loss of 2-methyl-1-butene is preferred over loss of 2-methyl-2-butene, despite the fact that the latter C5H10 isomer is >6 kJ mol-1 more stable than the former. An alternative interpretation of the [gamma]-/[alpha]-transfer ratio would suppose that all 11 hydrogens in the neopentyl group randomize prior to dissociation. Measured differences between [alpha]- and [gamma]-isotope effects argue against hydrogen randomization: the kH/kD for proton transfer from CH2 versus CD2 has a value close to unity, while the deuterium isotope effect for transfer from CH3 versus CD3 exhibits kH/kD = 1.6. Experimental results support a mechanism in which bond fission forms a [tert-amyl cation isopropylamine] ion-neutral complex, which then decomposes via proton transfer from the charged to the neutral partner.

Julian, Ryan R.; Ly, Tony; Finaldi, Anne-Marie; Morton, Thomas Hellman

2007-09-01

194

Generation, characterization, and reactivity of the transition metal-o-benzne analog of pyrazine (Fe{sup +}-2,3-didehydropyrazine) in the gas phase: An experimental and theoretical study  

SciTech Connect

Fe{sup +}-2,3-didehydropyrazine (2) has been generated and its reactivity with simple olefins and alkynes studied by using Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. 2, which is prepared by dehalogenation of chloropyrazine by Fe{sup +}, undergoes a simple adduct formation (no ligand coupling) with ethene and ethene-d{sub 4}. Ethyne also yields adduct formation; however, ligand coupling has clearly occurred in this reaction. Interestingly, reactions with propene and isobutene yield the same products with similar product distributions. Again, ligand coupling is involved and a metal-centered mechanism featuring activation of the allylic carbon-hydrogen bonds is proposed. Propyne, allene, 1-butene, and cis-2-butene yield a variety of products with 2. However, 2 yields exclusive dehydrogenation with 1,3-butadiene to generate FeC{sub 8}H{sub 6}N{sub 2}{sup +}. CID results suggest that this FeC{sub 8}H{sub 6}N{sub 2}{sup +} ion consists of quinoxaline bound to Fe{sup +}. Ligand displacement reactions yield a bond dissociation energy of 47 {+-} 5 kcal/mol for D{degree}(Fe{sup +}-quinoxaline). FeC{sub 4}H{sub 2}N{sub 2}{sup +} ion (2) has also been investigated theoretically. Density functional calculations predicted that the ground state of 2,3-didehydropyrazine is the triplet state, with the singlet state being 9.9 kcal/mol higher than the triplet state. 2 has C{sub 2{nu}} symmetry with the metal center coplanar with the 2,3-didehydropyrazine ring. 2 has a sextet ground state with doublet and quartet states 4.9 and 6.8 kcal/mol higher, respectively. The bond dissociation energy D{degree}(Fe{sup +}-C{sub 4}H{sub 2}N{sub 2}) for the sextet ground state is computed to be 87 {+-} 10 kcal/mol.

Chen, H.; Jacobson, D.B.; Freiser, B.S. [Purdue Univ., West Lafayette, IN (United States). H.C. Brown Lab. of Chemistry

1999-04-26

195

Reaction equilibria in the synthesis of 2-methoxy-2-methylbutane and 2-ethoxy-2-methylbutane in the liquid phase  

SciTech Connect

Tertiary ethers are used as octane-enhancing components in gasoline. Equilibrium constants for the liquid-phase synthesis of 2-methoxy-2-methylbutane (TAME) and 2-ethoxy-20methylbutane (TAEE) were measured in the temperature range 323-363 K. The equilibria were studied using the alcohol/alkene mixture in various mole ratios and the respective ether as a reagent in a batch reactor. A commercial cation exchange resin (Amberlyst 16) was used as the catalyst. The system was strongly nonideal, and the UNIQUAC estimation method was used in the calculation of the liquid-phase activity coefficients. The experimental equilibrium constants are given as a function of temperature. At 333 K the equilibrium constants K[sub a] for the synthesis of TAME were 39.6 [+-] 2.5 from methanol and 2-methyl-1-butene (2M1B) and 4.1 [+-] 0.3 from 2-methyl-2-butene (2M2B). The equilibrium constants for the synthesis of TAEE were 17.4 [+-] 1.1 from ethanol and 2M1B and 1.7 [+-] 0.1 from 2M2B. The experimental [Delta][sub r]H values for the liquid-phase synthesis of TAME were [minus]33.6[+-]5.1 kJ/mol (2M1B) and [minus]26.8 [+-] 2.3 kJ/mol (2M2B), and those for the synthesis of TAEE were [minus]35.2 [+-] 5.8 kJ/mol (2M1B) and [minus]27.3 [+-] 6.7 kJ/mol (2M2B). The results were compared with the literature values.

Rihko, L.K.; Linnekoski, J.A.; Krause, A.O.I. (Helsinki Univ. of Technology, Espoo (Finland). Dept. of Chemical Engineering)

1994-10-01

196

The adsorption of 1,3-butadiene on Pd/Ni multilayers: The interplay between spin polarization and chemisorption strength  

SciTech Connect

The adsorption of 1,3-butadiene (BD) on the Pd/Ni(1 1 1) multilayers has been studied using the VASP method in the framework of the density functional theory (DFT). The adsorption on two different configurations of the Pd{sub n}/Ni{sub m}(1 1 1) systems were considered. The most stable adsorption sites are dependent on the substrate composition and on the inclusion or not of spin polarization. On Pd{sub 1}Ni{sub 3}(1 1 1) surface, di-{pi}-cis and 1,2,3,4-tetra-{sigma} adsorption structures are the most stable for non-spin polarized (NSP) and spin polarized (SP) levels of calculation, respectively. Conversely, on Pd{sub 3}Ni{sub 1}(1 1 1) surface, the 1,2,3,4-tetra-{sigma} adsorption structure is the most stable for both NSP and SP levels, respectively. The magnetization of the Pd atoms strongly modifies the adsorption energy of BD and its most stable adsorption mode. On the other hand, as a consequence of BD adsorption, the Pd magnetization decreases. The smaller adsorption energies of BD and 1-butene on the Pd{sub 1}Ni{sub 3}(1 1 1) surface than on Pd(1 1 1) can be associated to the strained Pd overlayer deposited on Ni(1 1 1). -- Graphical Abstract: The adsorption of 1,3-butadiene on Pd/Ni(1 1 1) multilayers was theoretically studied. The most stable adsorption site depends on the substrate composition and on the inclusion of spin polarization. Display Omitted

Gomez, Guillermina [Grupo de Materiales y Sistemas Cataliticos, Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, Bahia Blanca B8000CPB (Argentina); Belelli, Patricia G., E-mail: pbelelli@plapiqui.edu.a [CONICET (Argentina); Cabeza, Gabriela F.; Castellani, Norberto J. [CONICET (Argentina)

2010-12-15

197

ANALYSIS OF VAPORS FROM METHYLENE CHLORIDE EXTRACTS OF NUCLEAR GRADE HEPA FILTER FIBERGLASS SAMPLES  

SciTech Connect

While several organic compounds were detected in the vapor samples used in the reenactment of the preparation of mounts from the extracts of nuclear grade high-efficiency particulate air filter fiberglass samples, the most significant species present in the samples were methylene chloride, phenol, phenol-d6, and 2-fluorophenol. These species were all known to be present in the extracts, but were expected to have evaporated during the preparation of the mounts, as the mounts appeared to be dry before any vapor was collected. These species were present at the following percentages of their respective occupational exposure limits: methylene chloride, 2%; phenol, 0.4%; and phenol-d6, 0.6%. However, there is no established limit for 2-fluorophenol. Several other compounds were detected at low levels for which, as in the case of 2-fluorophenol, there are no established permissible exposure limits. These compounds include 2-chlorophenol; N-nitroso-1-propanamine; 2-fluoro-1,1{prime}-biphenyl; 1,2-dihydroacenaphthylene; 2,5-cyclohexadiene-1,4-dione,2,6-bis(1,1-dimethylethyl); trimethyl oxirane; n-propylpropanamine; 2-(Propylamino)ethanol; 4-methoxy-1-butene; 6-methyl-5-hepten-2-one; and 3,4-dimethylpyridine. Some of these were among those added as surrogates or spike standards as part ofthe Advanced Technologies and Laboratories International, Inc. preparation ofthe extract of the HEPA filter media and are indicated as such in the data tables in Section 2, Results; other compounds found were not previously known to be present. The main inorganic species detected (sulfate, sodium, and sulfur) are also consistent with species added in the preparation of the methylene chloride extract of the high-efficiency particulate air sample.

FRYE JM; ANASTOS HL; GUTIERREZ FC

2012-06-07

198

Synthesis, structure solution, characterization, and catalytic properties of TNU-10: a high-silica zeolite with the STI topology.  

PubMed

A high-silica zeolite (Si/Al = 7.1) with the STI framework topology, denoted TNU-10, has been synthesized in the presence of 1,4-bis(N-methylpyrrolidinium)butane and Na(+) cations as structure-directing agents, and its structure in the proton form has been refined against laboratory powder X-ray data in space group Fmmm (a = 13.533(1) A, b = 17.925(2) A, c = 17.651(2) A). The space group symmetry is supported by electron diffraction and energy minimization studies. The as-made and proton form of TNU-10 are extensively characterized by elemental and thermal analyses, scanning electron microscopy, N(2) adsorption, multinuclear solid-state NMR, IR, and temperature-programmed desorption of ammonia, and the location of the organic structure-directing agent in the channel system is determined by molecular modeling. The catalytic properties of H-TNU-10 and Co-TNU-10 are evaluated for the skeletal isomerization of 1-butene to isobutene and the selective reduction of NO with methane, respectively. When compared to H-ferrierite, a low selectivity to isobutene is observed for H-TNU-10. However, it is found that Co-TNU-10 exhibits a maximum NO conversion of 93% at 823 K under conditions of high concentrations of methane (16,000 ppm) and water vapor (10%) and in the presence of 2.6% O(2), which is considerable higher than even the value (74%) obtained from Co-ferrierite, known as the best catalyst for this reaction, under the identical conditions. PMID:15125674

Hong, Suk Bong; Lear, Emily G; Wright, Paul A; Zhou, Wuzong; Cox, Paul A; Shin, Chae-Ho; Park, Joo-Hyoung; Nam, In-Sik

2004-05-12

199

Effect of acid strength on the catalytic activity of NiO-TiO sub 2 modified with acids  

SciTech Connect

Nickel oxide-silica is known to be effective for the dimerization of ethylene at room temperature. The catalyst is also active for the isomerization of n-butane, the mechanism of which has been proved to be of a proton donor-acceptor type. It has been suggested that the active site for dimerization is formed by an interaction of a low valent nickel ion with an acid site. In the previous papers from this laboratory, it has been shown that the NiO-TiO{sub 2} and NiO-ZrO{sub 2} modified with sulfate ion is very active for ethylene dimerization. High catalytic activities in the reactions were attributed to the enhanced acidic properties of the modified catalysts, which originated from the inductive effect of S{double bond}O bonds of the complex formed by the interaction of oxides with sulfate ion. The dependency of the catlaytic activity on the acid strength was reported by numerous investigators. The acid strength of a solid is the ability of the surface to convert an adsorbed neutral base into its conjugate acid as described by Walling. The present paper is concerned with the preparation of NiO-TiO{sub 2} modified with various acids, H{sub 2}SO{sub 4}, H{sub 3}PO{sub 4}, H{sub 3}BO{sub 3}, and H{sub 2}SeO{sub 4}, and the dependence of catalytic activity on acid strength. For this purpose, 1-butene isomerization and ethylene dimerization, which is known to be catalyzed by acid catalysts, were chosen as test reactions.

Sohn, J.R.; Jang, H.J.; Park, M.Y. (Kyungpook National Univ., Taegu (Korea)); Pae, Y.I. (Ulsan Univ. (Korea))

1991-01-01

200

The chemistry of tributyl phosphate at elevated temperatures in the Plutonium Finishing Plant Process Vessels  

SciTech Connect

Potentially violent chemical reactions of the tributyl phosphate solvent used by the Plutonium Finishing Plant at the Hanford Site were investigated. There is a small probability that a significant quantity of this solvent could be accidental transferred to heated process vessels and react there with nitric acid or plutonium nitrate also present in the solvent extraction process. The results of laboratory studies of the reactions show that exothermic oxidation of tributyl phosphate by either nitric acid or actinide nitrates is slow at temperatures expected in the heated vessels. Less than four percent of the tributyl phosphate will be oxidized in these vented vessels at temperatures between 125{degrees}C and 250{degrees}C because the oxidant will be lost from the vessels by vaporization or decomposition before the tributyl phosphate can be extensively oxidized. The net amounts of heat generated by oxidation with concentrated nitric acid and with thorium nitrate (a stand-in for plutonium nitrate) were determined to be about -150 and -220 joules per gram of tributyl phosphate initially present, respectively. This is not enough heat to cause violent reactions in the vessels. Pyrolysis of the tributyl phosphate occurred in these mixtures at temperatures of 110{degrees}C to 270{degrees}C and produced mainly 1-butene gas, water, and pyrophosphoric acid. Butene gas generation is slow at expected process vessel temperatures, but the rate is faster at higher temperatures. At 252{degrees}C the rate of butene gas generated was 0.33 g butene/min/g of tributyl phosphate present. The measured heat absorbed by the pyrolysis reaction was 228 J/g of tributyl phosphate initially present (or 14.5 kcal/mole of tributyl phosphate). Release of flammable butene gas into process areas where it could ignite appears to be the most serious safety consideration for the Plutonium Finishing Plant.

Barney, G.S.; Cooper, T.D.

1994-06-01

201

Synthesis of Ti(IV) complexes of donor-functionalised phenoxy-imine tridentates and their evaluation in ethylene oligomerisation and polymerisation.  

PubMed

A number of analogues of the Mitsui Chemicals ethylene trimerisation system (IV) have been explored, in which one of the donor atoms have been modified. Thus, a series of mono-anionic tridentate phenoxy-imine (3-(t-butyl)-2-(OH)-C6H4C=N(C(CH3)2CH2OMe) 1, 3-(adamantyl)-2-(OH)-C6H4C=N(2'-(2''-(SMe)C6H4)-C6H4) 2, 3-(t-butyl)-2-(OSiMe3)-C6H4C=N(C(CH3)2CH2OMe) 3) or phenoxy-amine (3,5-di(t-butyl)-2-(OH)-C6H4CH2-N(2'-(2''-(OMe)C6H4)-C6H4) 4) ligands have been prepared and reacted with TiCl4 or TiCl4(thf)2 to give the mono-ligand complexes 5-7. The solid state structures of compounds 4-6 have been determined. Complexes 5-7 have been tested for their potential as ethylene oligomerisation/polymerisation systems in conjunction with MAO activator and benchmarked against the Mitsui phenoxy-imine trimerisation system IV. While the phenoxy-amine complex 6 shows a propensity for polymer formation, the phenoxy-imine complexes 5 and 7 show somewhat increased formation of short chain LAOs. Complex 5 is selective for 1-butene in the oligomeric fraction, while 7 displays liquid phase selectivity to 1-hexene. As such 7, which is a sulfur substituted analogue of the Mitsui system IV, displays similar characteristics to the parent catalyst. However, its utility is limited by the lower activity and predominant formation of polyethylene. PMID:23403608

Suttil, James A; Shaw, Miranda F; McGuinness, David S; Gardiner, Michael G; Evans, Stephen J

2013-02-12

202

Heteropolyanions as redox components in heterogeneous Wacker oxidation catalysts  

SciTech Connect

Heteropolyanions (HPAs) of the Keggin type have been successfully applied as redox components in heterogeneous Wacker catalysts. The catalysts consist of a silica support covered with a layer of HPA of the series H{sub 3=n}PV{sub n}Mo{sub 12{minus}n}O{sub 40} on which a submonolayer of palladium sulfate is deposited. The initial butanone yield in the oxidation of 1-butene at 343 K is approximately 0.10 g butanone per gram of catalyst per hour. The steady-state activity increases with increasing number (n) of vanadium atoms per Keggin unit and when the protons of the HPA are replaced by Cu{sup 2+} or by Ni{sup 2+}. Even higher activity is obtained with palladium salts of heteropolyacids. In these palladium salts, the palladium reaction centre and the redox component are combined in one complex. The butanone selectivity of the catalysts with n > 0 is high, viz. >95%, and increases with increasing values of n to more than 98%. The butanone selectivity also increases when the protons are exchanged for metal cations, such as Cu{sup 2+}, Ni{sup 2+}, Pd{sup 2+}, or Cs{sup +}. The stability of the Keggin units under reaction conditions is high. Under Wacker oxidation conditions the HPAs are partly reduced, but DRIFT and ESR spectroscopy and TPR analysis of used catalysts show that the Keggin structure remains intact. Reoxidation of the reduced HPAs is, however, slow under reaction conditions. 31 refs., 12 figs., 2 tabs.

Kreemers-Stobbe, A.W.; Deilis, R.B.; Makkee, M. [Delft Univ. of Technology (Netherlands)] [and others

1995-07-01

203

Cl atom initiated oxidation of 1-alkenes under atmospheric conditions  

NASA Astrophysics Data System (ADS)

In view of the importance of the oxidation pathways of alkenes in the troposphere, and the significance of Cl atom as an oxidant in marine boundary layer (MBL) and polluted industrial atmosphere, the reactions of four 1-alkenes (C6-C9) with Cl atoms are investigated. The rate coefficients at 298 K are measured to be (4.0 ± 0.5), (4.4 ± 0.7), (5.5 ± 0.9) and (5.9 ± 1.7) × 10-10 cm3 molecule-1 s-1 for 1-hexene, 1-heptene, 1-octene and 1-nonene, respectively. The quoted errors include the experimental 2?, along with the error in the reference rate coefficients. From the systematic increase in the rate coefficients with the number of carbon atoms, an approximate value for the average rate coefficient for hydrogen abstraction per CH2 group in alkenes is estimated to be (4.9 ± 0.3) × 10-11 cm3 molecule-1 s-1. Based on these rate coefficients, the contribution of Cl atom reactions towards the degradation of these molecules is found to be comparable to that of OH radical reactions, under MBL conditions. The products identified in gas phase indicate that Cl atom addition occurs mainly at the terminal carbon, leading to the formation of 1-chloro-2-ketones and 1-chloro-2-ols. The major gas phase products from the alkenyl radicals (formed by H atom abstraction) are different positional isomers of long chain enols and enones. A preference for dissociation leading to an allyl radical, resulting in aldehydes, lower by three carbon atoms, is indicated. The observed relative yields suggest that in general, the increased contribution of the reactions of Cl atoms towards degradation of 1-alkenes in NOx free air does not result in an increase in the generation of small aldehydes (carbon number < 4), including chloroethanal, as compared to that in the reaction of 1-butene.

Walavalkar, M.; Sharma, A.; Alwe, H. D.; Pushpa, K. K.; Dhanya, S.; Naik, P. D.; Bajaj, P. N.

2013-03-01

204

Final report on EURAMET.QM-S6/1195: Bilateral comparison of liquefied hydrocarbon mixtures in constant pressure (piston) cylinders  

NASA Astrophysics Data System (ADS)

Traceable liquid hydrocarbon mixtures are required in order to underpin measurements of the composition and other physical properties of LPG (liquefied petroleum gas) and LNG (liquefied natural gas), thus meeting the needs of an increasingly large European industrial market. The development of traceable liquid hydrocarbon standards by National Measurement Institutes (NMIs) was still at a relatively early stage at the time this comparison was proposed in 2011. NPL and VSL, who were the only NMIs active in this area, had developed methods for the preparation and analysis of such standards in constant pressure (piston) cylinders, but neither laboratory had Calibration and Measurement Capabilities (CMCs) for these mixtures. This report presents the results of EURAMET 1195, the first comparison of liquid hydrocarbon mixtures between NMIs, which assessed the preparation and analytical capabilities of NPL and VSL for these mixtures. The comparison operated between August 2011 and January 2012. Each laboratory prepared a liquid hydrocarbon standard with nominally the same composition and these standards were exchanged for analysis. The results of the comparison show a good agreement between the laboratories' results and the comparison reference values for the six components with amount fractions greater than 1.0 cmol/mol (propane, propene, iso-butene, n-butane, iso-butane and 1-butene). Measurement of the three components with lower amount fractions (1,3-butadiene, iso-pentane and n-pentane) proved more challenging. In all but one case, the differences from the comparison reference values for these three components were greater than the expanded measurement uncertainty. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Brown, Andrew S.; Downey, Michael L.; Milton, Martin J. T.; van der Veen, Adriaan M. H.; Zalewska, Ewelina T.; Li, Jianrong

2013-01-01

205

In situ nonmethane hydrocarbon measurements on SAGA 3  

SciTech Connect

During the third Soviet-American Gas and Aerosol (SAGA 3) expedition to the central Pacific in February to March 1990 the authors observed C{sub 1}-C{sub 5} nonmethane hydrocarbons (NMHCs) both in the atmosphere and in the ocean. Atmospheric NMHCs project strongly on two factors: those NMHCs with lifetimes over 1 week (ethane, ethyne, propane, cyclopropane) display north-south latitudinal gradients whose magnitudes are proportional to their photochemical loss rates, which is consistent with a northern hemispheric, continental source, while those NMHCs with lifetimes under 1 week (all alkenes and pentane) do not display latitudinal gradients but do vary in common in a more complicated manner, consistent with a heterogeneous, marine source. Data taken from a sea water equilibrator shows that alkene concentrations vary strongly with wind speed, supporting previous conclusions that sea-air evasion is a major loss term for mixed layer alkenes. A reasonable balance exists between sea-air fluxes and atmospheric column removal for some alkenes (ethene, propene, 1-butene, and 1-pentene), while the remainder are out of balance, with partial pressures insufficient to support atmospheric observations. The total NMHC sea-air flux is about 0.8 {mu}mole m{sup {minus}2} d{sup {minus}1}. Both air and water concentrations measurements fall near the low end of previously observed ranges. It is argued that some previous higher atmospheric observations may reflect systematic problems with canister sampling. During SAGA 3 the role of NMHCs in the remote atmospheric OH budget was secondary though important, accounting (in conjunction with NMHC oxidation products) for 10 to 20% of all OH removal during baseline periods and a substantially larger fraction during episodes of increased NMHC mixing ratios. 37 refs., 13 figs., 2 tabs.

Donahue, N.M.; Prinn, R.G. [Massachusetts Institute of Technology, Cambridge, MA (United States)

1993-09-20

206

In situ nonmethane hydrocarbon measurements on SAGA 3  

NASA Astrophysics Data System (ADS)

During the third Soviet-American Gas and Aerosol (SAGA 3) expedition to the central Pacific in February to March 1990 we observed C1-C5 nonmethane hydrocarbons (NMHCs) both in the atmosphere and in the ocean. Atmospheric NMHCs project strongly on two factors: those NMHCs with lifetimes over 1 week (ethane, ethyne, propane, cyclopropane) display north-south latitudinal gradients whose magnitudes are proportional to their photochemical loss rates, which is consistent with a northern hemispheric, continental source, while those NMHCs with lifetimes under 1 week (all alkenes and pentane) do not display latitudinal gradients but do vary in common in a more complicated manner, consistent with a heterogeneous, marine source. Data taken from a sea water equilibrator shows that alkene concentrations vary strongly with wind speed, supporting previous conclusions that sea-air evasion is a major loss term for mixed layer alkenes. A reasonable balance exists between sea-air fluxes and atmospheric column removal for some alkenes (ethene, propene, 1-butene, and 1-pentene), while the remainder are out of balance, with partial pressures insufficient to support atmospheric observations. The total NMHC sea-air flux is about 0.8 ?mole m-2d-1. Both our air and water concentrations fall near the low end of previously observed ranges. It is argued that some previous higher atmospheric observations may reflect systematic problems with canister sampling. During SAGA 3 the role of NMHCs in the remote atmospheric OH budget was secondary though important, accounting (in conjunction with NMHC oxidation products) for 10 to 20% of all OH removal during baseline periods and a substantially larger fraction during episodes of increased NMHC mixing ratios.

Donahue, Neil M.; Prinn, Ronald G.

1993-01-01

207

Bimolecular rate constant and product branching ratio measurements for the reaction of C2H with ethene and propene at 79 K.  

PubMed

The reactions of the ethynyl radical (C(2)H) with ethene (C(2)H(4)) and propene (C(3)H(6)) are studied under low temperature conditions (79 K) in a pulsed Laval nozzle apparatus. Ethynyl radicals are formed by 193 nm photolysis of acetylene (C(2)H(2)) and the reactions are studied in nitrogen as a carrier gas. Reaction products are sampled and subsequently photoionized by the tunable vacuum ultraviolet radiation of the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. The product ions are detected mass selectively and time-resolved by a quadrupole mass spectrometer. Bimolecular rate coefficients are determined under pseudo-first-order conditions, yielding values in good agreement with previous measurements. Photoionization spectra are measured by scanning the ALS photon energy while detecting the ionized reaction products. Analysis of the photoionization spectra yields-for the first time-low temperature isomer resolved product branching ratios. The reaction between C(2)H and ethene is found to proceed by H-loss and yields 100% vinylacetylene. The reaction between C(2)H and propene results in (85 ± 10)% C(4)H(4) (m/z = 52) via CH(3)-loss and (15 ± 10)% C(5)H(6) (m/z = 66) by H-loss. The C(4)H(4) channel is found to consist of 100% vinylacetylene. For the C(5)H(6) channel, analysis of the photoionization spectrum reveals that (62 ± 16)% is in the form of 4-penten-1-yne, (27 ± 8)% is in the form of cis- and trans-3-penten-1-yne and (11 ± 10)% is in the form of 2-methyl-1-buten-3-yne. PMID:22429068

Bouwman, Jordy; Goulay, Fabien; Leone, Stephen R; Wilson, Kevin R

2012-04-09

208

Characterizations of volatile organic compounds during high ozone episodes in Beijing, China.  

PubMed

Air samples were collected in Beijing from June through August 2008, and concentrations of volatile organic compounds (VOCs) in those samples are here discussed. This sampling was performed to increase understanding of the distributions of their compositions, illustrate the overall characteristics of different classes of VOCs, assess the ages of air masses, and apportion sources of VOCs using principal compound analysis/absolute principal component scores (PCA/APCS). During the sampling periods, the relative abundance of the four classes of VOCs as determined by the concentration-based method was different from that determined by the reactivity approach. Alkanes were found to be most abundant (44.3-50.1%) by the concentration-based method, but aromatic compounds were most abundant (38.2-44.5%) by the reactivity approach. Aromatics and alkenes contributed most (73-84%) to the ozone formation potential. Toluene was the most abundant compound (11.8-12.7%) during every sampling period. When the maximum incremental reactivity approach was used, propene, toluene, m,p-xylene, 1-butene, and 1,2,4-trimethylbenzene were the five most abundant compounds during two sampling periods. X/B, T/B, and E/B ratios in this study were lower than those found in other cities, possibly due to the aging of the air mass at this site. Four components were extracted from application of PCA to the data. It was found that the contribution of vehicle exhaust to total VOCs accounted for 53% of VOCs, while emissions due to the solvent use contributed 33% of the total VOCs. Industrial sources contributed 3% and biogenic sources contributed 11%. The results showed that vehicle exhausts (i.e., unburned vehicle emissions + vehicle internal engine combustion) were dominant in VOC emissions during the experimental period. The solvent use made the second most significant contribution to ambient VOCs. PMID:21552987

An, Jun-lin; Wang, Yue-si; Wu, Fang-kun; Zhu, Bin

2011-05-07

209

Alcohol dehydrogenase- and rat liver cytosol-dependent bioactivation of 1-chloro-2-hydroxy-3-butene to 1-chloro-3-buten-2-one, a bifunctional alkylating agent.  

PubMed

1,3-Butadiene (BD) is an air pollutant whose toxicity and carcinogenicity have been considered primarily mediated by its reactive metabolites, 3,4-epoxy-1-butene and 1,2,3,4-diepoxybutane, formed in liver and extrahepatic tissues by cytochromes P450s. A possible alternative metabolic pathway in bone marrow and immune cells is the conversion of BD to the chlorinated allylic alcohol 1-chloro-2-hydroxy-3-butene (CHB) by myeloperoxidase in the presence of hydrogen peroxide and chloride ion. In the present study, we investigated the in vitro bioactivation of CHB by alcohol dehydrogenases (ADH) under in vitro physiological conditions (pH 7.4, 37 °C). The results provide clear evidence for CHB being converted to 1-chloro-3-buten-2-one (CBO) by purified horse liver ADH and rat liver cytosol. CBO readily reacted with glutathione (GSH) under assay conditions to form three products: two CBO-mono-GSH conjugates [1-chloro-4-(S-glutathionyl)butan-2-one (3) and 1-(S-glutathionyl)-3-buten-2-one (4)] and one CBO-di-GSH conjugate [1,4-bis(S-glutathionyl)butan-2-one (5)]. CHB bioactivation and the ratios of the three GSH conjugates formed were dependent upon incubation time, GSH and CHB concentrations, and the presence of ADH or rat liver cytosol. The ADH enzymatic reaction followed Michaelis-Menten kinetics with a K(m) at 3.5 mM and a k(cat) at 0.033 s(-1). After CBO was incubated with freshly isolated mouse erythrocytes, globin dimers were detected using SDS-PAGE and silver staining, providing evidence that CBO can act as a protein cross-linking agent. Collectively, the results provide clear evidence for CHB bioactivation by ADH and rat liver cytosol to yield CBO. The bifunctional alkylating ability of CBO suggests that it may play a role in BD toxicity and/or carcinogenicity. PMID:23110628

Elfarra, Adnan A; Zhang, Xin-Yu

2012-11-07

210

[Role of surface-generated gas-phase radicals in heterogeneous catalysis] Final Technical Report, January 1, 1994 - December 31, 2001  

SciTech Connect

A major theme in this research has been the role of surface-generated gas-phase radicals in heterogeneous catalysis, with emphasis on methyl radicals formed from methane. The activation of methane is of particular interest because of its abundance as a hydrocarbon resource. Previous studies on methyl radicals showed that they are an intermediate in the oxidative coupling of methane to form ethane and subsequently ethylene. More recent research on methyl radicals has focused on their coupling with allyl radicals, derived from propylene, to produce 1-butene and the methylation of ethylene to form propylene. As an extension of the work on methyl radicals, it has been shown that their reaction with vanadium oxide yields surface methoxide ions which either decompose to formaldehyde or react with water to form methanol. The surface and gas phase chemistry of methyl radicals also provided a link to the removal of NOx. In an attempt to explore the validity of a mechanism put forth by Vannice and co-workers, it was shown under this DOE grant that over basic metal oxides methyl radicals indeed react with gas phase NO to form nitrosomethane which is believed to be an intermediate in the selective catalytic reduction (SCR). Over one of these basic oxide catalysts (BaO/MgO), the decomposition of N2O was studied to determine the role of peroxide ions as an intermediate. Hydroxyl radicals also may be formed on surfaces and enter the gas phase where they can promote chain branching reactions during hydrocarbon oxidation. The formation of these radicals during the reaction of water with molecular oxygen over basic oxide catalysts has been studied in detail. A kinetic model provided evidence that these surface generated radicals may play a role in catalytic combustion. Since the hydroxyl radicals may undergo secondary reactions with a surface, this aspect of their chemistry was also explored. In contrast to the low probability of methyl radicals reacting with metal oxide surfaces, hydroxyl radicals have a high probability of sticking and reacting. A gold surface was even more effective in the removal of hydroxyl radicals than the metal oxides that were considered. Presumably, hydrogen peroxide is an intermediate in the reaction. The formation of hydrogen peroxide directly from molecular hydrogen and oxygen is the most recent extension of this research. This reaction was thought to occur over supported palladium in an acidified aqueous slurry; however, it has been shown in this laboratory that the active palladium is actually in the form of a colloid. The reaction rate is believed to be limited by the transport of reagents through a film between the gas bubbles and the surface of the colloidal particles.

Lunsford, Jack H.

2002-03-20

211

Coupling reactions of trifluoroethyl iodide on GaAs(100)  

NASA Astrophysics Data System (ADS)

We report on the reactions of 2-iodo-1,1,1-trifluoroethane (CF3CH2I) on gallium-rich GaAs(100)-(4×1), studied using the techniques of temperature programmed desorption and x-ray photoelectron spectroscopy. The study is to provide evidence for the formation of a higher fluorinated alkene, 1,1,4,4,4-pentafluoro-1-butene (CF2=CHCH2CF3) and alkane, 1,1,1,4,4,4-hexafluorobutane (CF3CH2CH2CF3) from the coupling reactions of covalently bonded surface alkyl (CF3CH2•) moieties. CF3CH2I adsorbs nondissociatively at 150 K. Thermal dissociation of this weakly chemisorbed state occurs below room temperature to form adsorbed CF3CH2• and I• species. The surface CF3CH2• species undergoes ?-fluoride elimination to form gaseous CF2=CH2 and this represents the major pathway for the removal of CF3CH2• species from the surface. In competition with the ?-fluoride elimination process the adsorbed CF3CH2• species also undergoes, recombination with surface iodine atoms to form recombinative molecular CF3CH2I, olefin insertion reaction with CF2=CH2 to form gaseous CF2=CHCH2CF3, and last self-coupling reaction to form CF3CH2CH2CF3. The adsorbed surface iodine atoms, formed by the dissociation of the molecularly chemisorbed CF3CH2I, and fluorine atoms formed during the ?-fluoride elimination reaction, both form etch products (GaI, GaF, AsI, AsF, and As2) by their reactions with the surface layer Ga atoms, subsurface As atoms, and GaAs substrate. In this article we discuss the mechanisms by which these products form from the adsorbed CF3CH2• and I• species, and the role that the GaAs surface plays in the proposed reaction pathways. We compare the reactivity of the GaAs surface with transition metals in its ability to facilitate dehydrogenation and coupling reactions in adsorbed alkyl species. .

Singh, N. K.; Kemp, N. T.; Paris, N.; Balan, V.

2004-07-01

212

Ab initio/Rice-Ramsperger-Kassel-Marcus study of the singlet C4H4 potential energy surface and of the reactions of C2(X 1?g+) with C4H4(X 1A1g+) and C(1D) with C3H4 (allene and methylacetylene)  

NASA Astrophysics Data System (ADS)

Ab initio modified Gaussian-2 G2M(RCC,MP2) calculations have been performed for various isomers and transition states on the singlet C4H4 potential energy surface. The computed relative energies and molecular parameters have then been used to calculate energy-dependent rate constants for different isomerization and dissociation processes in the C4H4 system employing Rice-Ramsperger-Kassel-Marcus theory and to predict branching ratios of possible products of the C2(1?g+)+C2H4, C(1D)+H2CCCH2, and C(1D)+H3CCCH reactions under single-collision conditions. The results show that C2 adds to the double C=C bond of ethylene without a barrier to form carbenecyclopropane, which then isomerizes to butatriene by a formal C2 ``insertion'' into the C-C bond of the C2H4 fragment. Butatriene can rearrange to the other isomers of C4H4, including allenylcarbene, methylenecyclopropene, vinylacetylene, methylpropargylene, cyclobutadiene, tetrahedrane, methylcyclopropenylidene, and bicyclobutene. The major decomposition products of the chemically activated C4H4 molecule formed in the C2(1?g+)+C2H4 reaction are calculated to be acetylene+vinylidene (48.6% at Ecol=0) and 1-buten-3-yne-2-yl radical [i-C4H3(X 2A'),H2C=C=C=CH.]+H (41.3%). As the collision energy increases from 0 to 10 kcal/mol, the relative yield of i-C4H3+H grows to 52.6% and that of C2H2+CCH2 decreases to 35.5%. For the C(1D)+allene reaction, the most important products are also i-C4H3+H (55.2%) and C2H2+CCH2 (30.1%), but for C(1D)+methylacetylene, which accesses a different region of the C4H4 singlet potential energy surface, the calculated product branching ratios differ significantly: 65%-69% for i-C4H3+H, 18%-14% for C2H2+CCH2, and ~8% for diacetylene+H2.

Mebel, A. M.; Kisiov, V. V.; Kaiser, R. I.

2006-10-01

213

The Nonlocalized Molecular Orbital Model to Analyze Infrared and Vibrational Circular Dichroism Spectra: a Database Approach.  

NASA Astrophysics Data System (ADS)

The nonlocalized molecular orbital model (NMO) of Nafie and Freedman is implemented at the ab initio level to calculate IR and VCD intensities based on contributions of fixed partial charges (FPC), charge flow along bonds (CF) and atomic polarizations (PP). It is theoretically demonstrated that NMO is equivalent to the ab initio RHF formalism for IR intensities. Using local symmetry coordinates suitable for creating intensity parameters that are transferable among structurally related molecular fragments, NMO is applied to various molecules to test its validity, and its utility for a database approach for predicting IR and VCD intensities of larger systems. The IR intensities of propane are investigated in terms of FPC, CF and PP, which provides new conceptual insight into electronic effects of vibrations. The VCD spectra of (S)-1,1,1,2-tetradeuteropropane, (S)-1-deuteroethanol and (R)-2-methyloxetane are calculated with NMO, reproducing high level ab initio vibronic coupling and experimental intensities. Procedures are developed to create and retrieve transferable parameters for IR and VCD intensity databases. The concept is examined by compiling an intensity database from parameters of 10 small organic molecules and subsequently predicting the IR and VCD spectra of (R)-1-deutero-ethyl methyl ether and (R)-3-deutero-1-butene. The resulting absorption intensities correspond to those determined directly with NMO. The VCD spectrum of only the former is reproduced well. Discrepancies in the spectrum of the latter are mainly due to CF but also PP terms neglected in the database approach. The NMO-VCD model is tested on a series of terpenes. The measured IR and Raman spectra of alpha -pinene, beta-pinene, nopinone and verbenone are assigned based on non-uniformly scaled ab initio 6-31G^{*0.3} force fields in the range 0-1500 cm^{-1} . A total of 210 observed transitions are reproduced with an average error of 3.7 cm^{-1 }. The NMO-VCD intensities are shown to compare well to experimental features for well determined normal modes. Discrepancies observed in the range 1100-1350 cm ^{-1} are attributed to inaccuracies in the normal mode descriptions rather than shortcomings of the model. In general, the NMO model was shown to be a valid and useful method for predicting VCD intensities and expedient for database applications.

Maurer, Felix

214

Radical Yields from the Ozonolysis of Small (C2-C6) Alkenes  

NASA Astrophysics Data System (ADS)

Unsaturated VOCs, alkenes, are emitted to the atmosphere from a wide range of anthropogenic and natural sources. They are significant primary pollutants in the boundary layer, contributing to total VOC emissions in urban air, where they may account for up to 30% of the total OH sink, however a key fate for alkenes is reaction with ozone, which may form the dominant loss pathway depending on local conditions, and leads to the non-photolytic production of OH, HO2 and RO2 radicals. Radical formation via ozonolysis is of interest as it may substantially influence the radical budget in urban and rural environments. While there are a number of quantitative indirect OH yield measurements from ozonolysis in the literature, obtained for example through the use of radical tracers / scavenger species, very few direct observations have been reported. Moreover, reported yields for HO2 and RO2 production have been largely inferred through the observation of associated stable products using assumed mechanisms. Gas-phase alkene-ozone reactions also generate a range of degradation products, notably secondary organic aerosol precursors, which together with many other products remain largely unidentified for biogenic alkenes. We present a comprehensive analysis of detailed simulation chamber experiments in which the total radical production and degradation products of alkene ozonolysis reactions have been directly observed for ethene, propene, methylpropene, 1-butene, trans/cis-2-butene and 2,3-dimethyl-2-butene. The experiments were carried out in the European photoreactor EUPHORE (Valencia, Spain), with instrumentation including chemical-ionization-reaction time-of-flight mass-spectrometer (CIR-TOF-MS) and laser-induced fluorescence (LIF) to measure stable VOC and radical products respectively. Alkene/ozone reactions were investigated with and without the presence of a radical scavenger, in order to suppress side reactions and to obtain reaction rate coefficients, primary carbonyl and stabilized Criegee yields. Radical concentrations were measured directly, and interpreted through detailed chemical box modelling drawing upon the Master Chemical Mechanism (MCMv3.1) with mechanistic updates from the recent literature and our results. Reaction rate coefficients, radical yields and stable product yields are compared with those simulated, and the implications for atmospheric oxidant levels are presented.

Alam, Mohammed; Camredon, Marie; Carr, Timo; Wyche, Kevin; Hornsby, Karen; Monks, Paul; Rickard, Andrew; Bloss, William

2010-05-01

215

Development and application of FI catalysts for olefin polymerization: unique catalysis and distinctive polymer formation.  

PubMed

Catalysts contribute to the efficient production of chemicals and materials in almost all processes in the chemical industry. The polyolefin industry is one prominent example of the importance of catalysts. The discovery of Ziegler-Natta catalysts in the 1950s resulted in the production of high-density polyethylenes (PEs) and isotactic polypropylenes (iPPs). Since then, further catalyst development has led to the production of a new series of polyolefins, including linear low-density PEs, amorphous ethylene/1-butene copolymers, ethylene/propylene/diene elastomers, and syndiotactic PPs (sPPs). Polyolefins are now the most important and the most produced synthetic polymers. This Account describes a family of next-generation olefin polymerization catalysts (FI catalysts) that are currently being used in the commercial production of value-added olefin-based materials. An FI catalyst is a heteroatom-coordinated early transition metal complex that combines a pair of nonsymmetric phenoxy-imine [O(-), N] chelating ligands with a group 4 transition metal. The catalytically active species derived from FI catalysts is highly electrophilic and can assume up to five isomeric structures based on the coordination of the phenoxy-imine ligand. In addition, the accessibility of the ligands of the FI catalysts and their amenability to modification offers an opportunity for the design of diverse catalytic structures. FI catalysts exhibit many unique chemical characteristics: precise control over chain transfers (including highly controlled living ethylene and propylene polymerizations), extremely high selectivity for ethylene, high functional group tolerance, MAO- and borate-free polymerization catalysis, significant morphology polymer formation, controlled multimodal behavior, high incorporation ability for higher alpha-olefins and norbornene, and highly syndiospecific and isospecific polymerizations of both propylene and styrene. These reactions also occur with very high catalyst efficiency. The reaction products include a wide variety of unique olefin-based materials, many of which were previously unavailable via other means of polymerization. We have produced selective vinyl- and Al-terminated PEs, ultrahigh molecular weight linear PEs, regio- and stereoirregular high molecular weight poly(higher alpha-olefin)s, ethylene- and propylene-based telechelic polymers, a wide array of polyolefinic block copolymers from ethylene, propylene, and higher alpha-olefins, and ultrafine noncoherent PE particles. FI catalysts are important from the organometallic, catalytic, and polymer science points of view, and the chemical industry is now using them for the production of value-added olefin-based materials. We anticipate that future research on FI catalysts will produce additional olefin-based materials with unique architectures and material properties and will offer scientists the chance to further study olefin polymerization catalysis and related reaction mechanisms. PMID:19588950

Makio, Haruyuki; Fujita, Terunori

2009-10-20

216

Shock tube study on the thermal decomposition of n-butanol.  

PubMed

Dilute concentrations of normal-butanol has been decomposed in single pulse shock tube studies in the presence of large quantities of a chemical inhibitor that suppresses contributions from chain decomposition. Reaction temperatures and pressures are in the range of [1126-1231] K and [1.3-6.5] bar. Ethylene and 1-butene are the only products. The mechanism of the initial decomposition steps involves direct elimination of water and C-C bond cleavage. The fundamental high pressure unimolecular decomposition rate expressions are k(C(4)H(9)OH ? CH(3) + CH(2)CH(2)CH(2)OH) = 10(16.4±0.4) exp(42410 ± 800 [K]/T) s(-1); k(C(4)H(9)OH ? CH(3)CH(2) + CH(2)CH(2)OH) = 10(16.4±0.4) exp(-41150 ± 800 [K]/T) s(-1); k(C(4)H(9)OH ? CH(3)CH(2)CH(2) + CH(2)OH) = 10(16.4±0.4) exp(-41150 ± 800 [K]/T) s(-1); and k(C(4)H(9)OH ? CH(3)CH(2)CH?CH(2) + H(2)O) = 10(14.0±0.4) exp(-35089 ± 800 [K]/T) s(-1), where the rate expressions for C-C bond cleavage are based on assumptions regarding the relative rates of the three processes derived from earlier studies on the effect of an OH group on rate expressions. All reactions are in the high pressure limit and suggest that the step size down in the presence of argon is at least 1300 cm(-1). These rate expressions are consistent with the following H-C bond dissociation energies: BDE(H-CH(2)CH(2)CH(2)OH) = 417.2 ± 7 kJ/mol, BDE(H-CH(2)CH(2)OH) = 419.2 ± 7 kJ/mol, and BDE(H-CH(2)OH) = 401.7 ± 9 kJ/mol, with an estimated uncertainty of 6 kJ/mol. The kinetics and thermodynamic results are compared with estimates used in the building of combustion kinetics databases. PMID:22934735

Rosado-Reyes, Claudette M; Tsang, Wing

2012-09-26

217

Catalytic characterization of lithium aluminum oxides: Including a study of both the cation replacement chemistry and the structure of the [alpha]LiAlO[sub 2]/[open quotes]HAlO[sub 2][close quotes] system  

SciTech Connect

Cation replacement is a low temperature synthetic technique used to replace most of the lithium cations in [alpha]LiAlO[sub 2] with protons without significantly modifying the structure of the reactant. Lauric acid worked well as a proton source because it was capable of 90% replacement without significant dissolution of [alpha]LiAlO[sub 2]. High pressure CO[sub 2]/H[sub 2]O treatment of the cation replaced product resulted in the decomposition of the reactant to form boehmite and Li[sub 2]CO[sub 3]. The XRD characterization of a series of partially replaced samples from the [alpha]LiAlO[sub 2]/HAlO[sub 2] system was used to develop an understanding of the cation replacement mechanism. A two phase mechanism is proposed, which consists of particles with an outer shell of lithiated HAlO[sub 2] and an inner core of [alpha]LiAlO[sub 2] (for 0.0 < x < 0.90). A model for the structure of HAlO[sub 2] was developed to describe the location of the protons and the lithium cations. The 3,3-dimethyl-1-isomerization reaction did not detect any intrinsic acidity on HAlO[sub 2] and detected only small amounts on calcined HAlO[sub 2] at 350[degrees]C. Lithium free [gamma]-alumina was extremely active for 3,3-dimethyl-1-butene isomerization demonstrating that the small concentration of lithium in both HAlO[sub 2] and calcined HAlO[sub 2] is sufficient to neutralize strong acid sites. The conversion of isopropyl alcohol produces propylene on acid-base sites and acetone on basic sites. [alpha]LiAlO[sub 2], [gamma]LiAlO[sub 2], and calcined HAlO[sub 2], produced varying amounts of propylene and acetone. [alpha]LiAlO[sub 2] and calcined HAlO[sub 2] produced a C6 diene, which indicates the presence of basic sites stronger than those needed for acetone formation. [alpha]LiAlO[sub 2] was the only sample that produced 4-methyl-2-pentanone and 4-methyl-2-pentanol.

Tomczak, D.C.

1993-01-01

218

Capillary HPLC-Accurate Mass MS/MS Quantitation of N7-(2,3,4-Trihydroxybut-1-yl)-guanine Adducts of 1,3-Butadiene in Human Leukocyte DNA.  

PubMed

1,3-Butadiene (BD) is a high volume industrial chemical commonly used in polymer and rubber production. It is also present in cigarette smoke, automobile exhaust, and urban air, leading to widespread exposure of human populations. Upon entering the body, BD is metabolized to electrophilic epoxides, 3,4-epoxy-1-butene (EB), diepoxybutane (DEB), and 3,4-epoxy-1,2-diol (EBD), which can alkylate DNA nucleobases. The most abundant BD epoxide, EBD, modifies the N7-guanine positions in DNA to form N7-(2, 3, 4-trihydroxybut-1-yl) guanine (N7-THBG) adducts, which can be useful as biomarkers of BD exposure and metabolic activation to DNA-reactive epoxides. In the present work, a capillary HPLC-high resolution ESI(+)-MS/MS (HPLC-ESI(+)-HRMS/MS) methodology was developed for accurate, sensitive, and reproducible quantification of N7-THBG in cell culture and in human white blood cells. In our approach, DNA is subjected to neutral thermal hydrolysis to release N7-guanine adducts from the DNA backbone, followed by ultrafiltration, solid-phase extraction, and isotope dilution HPLC-ESI(+)-HRMS/MS analysis on an Orbitrap Velos mass spectrometer. Following method validation, N7-THBG was quantified in human fibrosarcoma (HT1080) cells treated with micromolar concentrations of DEB and in DNA isolated from blood of smokers, nonsmokers, individuals participating in a smoking cessation program, and occupationally exposed workers. N7-THBG concentrations increased linearly from 31.4 ± 4.84 to 966.55 ± 128.05 adducts per 10(9) nucleotides in HT1080 cells treated with 1-100 ?M DEB. N7-THBG amounts in leukocyte DNA of nonsmokers, smokers, and occupationally exposed workers were 7.08 ± 5.29, 8.20 ± 5.12, and 9.72 ± 3.80 adducts per 10(9) nucleotides, respectively, suggesting the presence of an endogenous or environmental source for this adduct. The availability of sensitive HPLC-ESI(+)-HRMS/MS methodology for BD-induced DNA adducts in humans will enable future population studies of interindividual and ethnic differences in BD bioactivation to DNA-reactive epoxides. PMID:23937706

Sangaraju, Dewakar; Villalta, Peter; Goggin, Melissa; Agunsoye, Maria O; Campbell, Colin; Tretyakova, Natalia

2013-09-12

219

Pathway and Surface Mechanism Studies of 1,3-butadiene Selective Oxidation Over Vanadium-Molybdenum-Oxygen Catalysts  

SciTech Connect

The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9-14 m{sup 2}/g, and compositions were within the solid solution regime, i.e. below 15.0 mol % MoO{sub 3}/(MoO{sub 3} + V{sub 2}O{sub 5}). Laser Raman Spectroscopy and XRD data indicated that solid solutions were formed, and pre- and post-reaction XPS data indicated that catalyst surfaces contained some V{sup +4} and were further reduced in 1,3-butadiene oxidation. A reaction pathway for 1,3-butadiene partial oxidation to maleic anhydride was shown to involve intermediates such as 3,4-epoxy-1-butene, crotonaldehyde, furan, and 2-butene-1,4-dial. The addition of water to the reaction stream substantially increased catalyst activity and improved selectivity to crotonaldehyde and furan at specific reaction temperatures. At higher water addition concentrations, furan selectivity increased from 12% to over 25%. The catalytic effects of water addition were related to competitive adsorption with various V{sub 2}O{sub 5}-based surface sites, including the vanadyl V=O, corner sharing V-O-V and edge sharing V-O oxygen. Higher levels of water addition were proposed to impose acidic character by dissociative adsorption. In addition, a novel combinatorial synthesis technique for VMoO was used to investigate the phase transitions of V{sub 2}O{sub 5}, solid solutions of Mo in V{sub 2}O{sub 5}, V{sub 9}Mo{sub 6}O{sub 40}, and other reduced VMoO compounds, characterized by laser Raman spectroscopy. The natural composition gradient imposed by the sputter deposition apparatus was used to create VMoO arrays containing 225 samples ranging from 7.0-42 mol% MoO{sub 3}/(V{sub 2}O{sub 5} + MoO{sub 3}), determined by EDS analysis.

William David Schroeder

2002-05-27

220

Reactions of ruthenium vinylidene and acetylide complexes containing trichloromethyl groups: preparation of a cyclobutenonyl complex by solid-state photolysis.  

PubMed

Solid-state route to a cyclobutenone: Ruthenium perchlorocyclobutenonyl complex 2 is obtained by solid-state photoisomerization of ruthenium trichloroacetyl acetylide complex 1. The four-membered ring is sufficiently robust that transfer of the intact ligand could be readily achieved in a reaction of 2 with an enyne. Cyclobutenedionyl complex 3 was obtained by hydrolysis of 2 in H(2)O/THF.New reactions were observed for the cationic gamma-hydroxyvinylidene complex [Ru(2)]==C==CHC(OH)(CCl(3))(2) (+) (2, [Ru(2)]=CpRu(PPh(3))(2)). A rare chloroform elimination was observed when 2 was treated with nBu(4)NOH to give neutral acetylide complex [Ru(2)]--C[triple chemical bond]CC(==O)CCl(3) (3). Solid-state photoinduced isomerization of 3 generated ruthenium perchlorocyclobutenonyl complex [Ru(2)]--C(4)Cl(3)O (4) in high yield. This transformation was analyzed by DFT calculations, and 4 was found to be 4.22 kcal mol(-1) more stable in terms of Gibbs free energy than 3. In the coupling reaction of 4 with 2-methyl-1-buten-3-yne the four-membered cyclic ligand is transferred to the enyne to give substituted eta(3)-butadienyl complex 5 containing a cyclobutenonyl group. This coupling product could be removed from the metal by HCl. Deprotonation of 2 gave gamma-hydroxyacetylide complex [Ru(2)]--C[triple chemical bond]CC(OH)(CCl(3))(2) (9). In the photolysis of 9 phosphine dissociation is followed by addition of HCl to give neutral vinylidene complex Cl[Ru(1)]==C==CHC(OH)(CCl(3))(2) (10, [Ru(1)]=Cp(PPh(3))Ru). Complex 4 catalyzed the coupling reaction of dimethyl acetylenedicarboxylate with styrene yielding the diene PhCH==CHC(CO(2)Me)==CHCO(2)Me. Solid-state structures of 3-6 and 10 were determined by single-crystal X-ray diffraction analysis. PMID:19199302

Wu, Chung-Yeh; Chou, Hsien-Hsin; Lin, Ying-Chih; Wang, Yu; Liu, Yi-Hung

2009-01-01

221

Electron-impact ionization of benzoic acid, nicotinic acid and their n-butyl esters  

NASA Astrophysics Data System (ADS)

Electron-impact ionization mass spectra, the decay of metastable ions, ionization and appearance energies and bond energies, as dissociation energies, are reported for the title compounds. An ionization energy of 9.47 eV was obtained for benzoic acid, 9.43 eV for benzoic acid n-butyl ester, 9.61 eV for nicotinic acid and 9.97 eV for nicotinic acid n-butyl ester. Molecular ions of both butyl esters show two common main fragmentation pathways: the first process is a McLafferty rearrangement, characterized by the transfer of one H-atom from the aliphatic ester chain, which leads to the ions of either the organic acid or 1-butene. From their appearance energies and known thermodynamic data, gas-phase formation enthalpies () of the parent n-butyl esters are calculated. Values of for benzoic acid n-butyl ester and for nicotinic acid n-butyl ester were obtained. The second process is characterized by the transfer of two H-atoms from the ester chain leading to a protonated form of the corresponding organic acids and C4H7 radicals. Good evidence is provided for the formation of methylallyl radicals. Appearance energies are used to calculate a proton affinity (PA) for benzoic acid. The obtained value of PA = (8.73 ± 0.3) eV, corresponding to a protonation of the carbonyl group, is in close corroboration with published data (PA = 8.51 eV). Activation energies for the intermediate H-transfers were found to be insignificant. This methodic gateway is applied to the system of nicotinic acid and its butyl ester. Adopting the formation of a methylallyl radical, the obtained proton affinity of nicotinic acid, PA = 8.58 eV, is very near to the published data of benzoic acid. An alternative fragmentation mechanism leading to a value of PA [approximate] 9.5 eV (typical for a protonation of the pyridine-nitrogen) is very unlikely. It is concluded that this transfer of two H-atoms from the ester chain is controlled by a charge switching between the carboxylic oxygen atoms which leads to a regiospecific protonation site, in this case to the protonated carbonyl group. This is conform with a B3LYP DFT calculation with a corresponding proton affinity of PA = 8.29 eV.

Opitz, Joachim

2007-08-01

222

I. Synthesis, characterization, and base catalysis of novel zeolite supported super-basic materials II. Oxidative dehydrogenation of ethane over reduced heteropolyanion catalysts  

NASA Astrophysics Data System (ADS)

This thesis is composed of two separate and unrelated projects. The first part of this thesis outlines an investigation into the synthesis and characterization of a novel zeolite supported super-base capable of carbon-carbon olefin addition to alkyl aromatics. A zeolite supported basic material capable of such reactions would benefit many fine chemical syntheses, as well as vastly improve the economics associated with production of the high performance thermoplastic polyester polyethylene naphthalate. The thermal decomposition of alkali---metal azides impregnated in zeolite X is investigated as a novel route to the synthesis of a zeolite supported super-base. Impregnation of the alkali---metal azide precursor is shown to result in azide species occluded within the pores of the zeolite support by using high speed, solid-state 23Na MAS and 2D MQMAS NMR, FTIR, and TGA characterization methods. Addition of alkali---metal azides to the zeolite results in redistribution of the extra-lattice cations in the zeolite framework. Thermal decomposition of impregnated azide species produces further cation redistribution, but no neutral metallic clusters are detected by high speed, solid-state 23Na MAS NMR following thermal activation of the materials. Instead, it is possible that inactive ionic clusters are formed. The thermally activated materials do not promote base catalysis for the isomerization of 1-butene, the ethylation of toluene and o-xylene, and the alkenylation of o-xylene with 1,3-butadiene to produce 5-ortho-tolyl-pent-2-ene (5-OTP). The lack of catalytic activity in the materials is attributed to failure of the materials to form neutral metallic clusters during thermal treatment, possibly due to preferential formation of NMR silent ionic clusters. The formation of neutral metallic clusters is found to be insensitive to synthesis technique and activation procedure. It is concluded that the impregnation of alkali---metal azides in zeolite X does not provide a reliable precursor for the formation of zeolite supported super-basic materials. The second part of this thesis describes the oxidative dehydrogenation of ethane over partially reduced heteropolyanions. Niobium and pyridine exchanged salts of phosphomolybdic (NbPMo12Pyr) and phosphovanadomolybdic (NbPMo11VPyr) acids are investigated as catalyst precursors to prepare materials for catalyzing the oxidative dehydrogenation of ethane to ethylene and acetic acid at atmospheric pressure. The effects of feed composition, steam flow, temperature, and precursor composition on catalytic activity and selectivity are presented for both ethane and ethylene oxidation. Production of ethylene and acetic acid from ethane using the catalytic materials exceeds that reported in the literature for Mo-V-Nb-Ox systems under atmospheric or elevated pressure. Production of acetic acid from ethylene is also greater than that observed for Mo-V-Nb-Ox systems. Addition of vanadium reduces catalytic activity and selectivity to both ethylene and acetic acid while niobium is essential for the formation of acetic acid from ethane. Other metals such as antimony, iron, and gallium do not provide the same beneficial effect as niobium. Molybdenum in close proximity to niobium is the active site for ethane activation while niobium is directly involved in the transformation of ethylene to acetic acid. A balance of niobium and protonated pyridine is required to produce an active catalyst. Water is found to aid in desorption of acetic acid, thereby limiting deep oxidation to carbon oxides. A reaction scheme is proposed for the production of acetic acid from ethane over the catalytic materials.

Galownia, Jonathan M.

223

Tautomerism and metal complexation of 2-acylmethyl-2-oxazolines: a combined synthetic, spectroscopic, crystallographic and theoretical treatment.  

PubMed

A synthetic, structural and theoretical investigation into the solid-state, solution and gas phase structure(s) of six 2-acylmethyl-4,4-dimethyl-2-oxazolines is reported. Four of these materials, viz.?-[(4,5-dihydro-4,4-dimethyl-2-oxazolyl)methylene]benzenemethanol (3a), ?-[(4,5-dihydro-4,4-dimethyl-2-oxazolyl)methylene]-(4-nitrobenzene)methanol (3b), 1-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)-3,3-dimethyl-1-buten-2-ol (3d) and (E)-1-phenyl-2-((3aR)-3,3a,8,8a-tetrahydro-2H-indeno[1,2-d]oxazol-2-ylidene)ethanone (3f) have been characterised in the solid-state by single crystal X-ray diffraction studies. These data represent the first solid-state structural studies of this class of compounds and details the first synthesis and full characterisation of chiral derivative 3f. All four of these materials are shown to exist in the solid phase in the enamine tautomeric form (e.g., 3a is best described as 2-[4,4-dimethyl-2-oxazolidinylidene]-1-phenylethanone) and it is suggested (NMR, IR) that this isomeric form is likely also retained in solution (e.g., CDCl3) as the more stable isomer. An investigation of the relative gas phase stabilities of the three possible (i.e., the (Z)-enol, keto and enamine) isomers of all five compounds by DFT at the B3LYP/6-311G(d) level of theory confirms the latter as the most stable form. The energy differences between the enamine and keto tautomers have been calculated to be the lowest for derivative 3d. These results are compared and contrasted with the previously reported NMR studies of such compounds which have identified the keto form as being a minor (albeit solution) tautomer. Equilibrium solution tautomer distributions for 3d are found to be solvent dependent. The protonated form of 3a, isolated as the HSO4(-) salt (i.e.4a), has been further characterised in the solid state by single crystal X-ray diffraction. These data represent the first example of a protonated oxazoline to be structurally elucidated and confirms that upon protonation, the keto (oxazoline) tautomer is the energetically favoured form in the solid-state. This observation is further supported by DFT studies for the gas phase protonated forms of such materials. Further DFT (B3LYP/6-311G(d)) calculations employing the SM8 or SMD solvation models were then applied to address the observed solution isomeric distribution for 3d; these results corroborate the gas phase theoretical treatment and also yield values that predict the higher solution stability of the enamine form as observed, although they fail to account for the existence of the keto form as a minor solution state tautomer. To access the availability of an enol-form, via hypothetical de-protonation to the enolate, compound 3a was treated with hydrated Cu(NO3)2 in EtOH solution. The resulting isolated green-coloured product (5), the first metal derivative of this entire class of ligands, is best described (IR, X-ray diffraction) as a coordinated enolate complex, i.e., Cu(3a-H)2. Complex 5 crystallizes in the P21/c space group with four molecules in the unit cell. The coordination geometry around the formal Cu(2+) metal centre is determined to be highly distorted square planar in nature (?4 = 0.442). TD-DFT is used to give a reasonable explanation for the intensity of the absorbance band observed in the visible region for solutions of 5. These latter experiments strongly suggest that the title class of compounds may have considerable potential as ligands in coordination chemistry and/or metal-mediated catalysis. PMID:23591452

Jones, Roderick C; Herasymchuk, Khrystyna; Mahdi, Tayseer; Petrov, Anna; Resanovi?, Sanja; Vaughan, Douglas G; Lough, Alan J; Quail, J Wilson; Koivisto, Bryan D; Wylie, R Stephen; Gossage, Robert A

2013-04-17