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1

Beyond Vinyl: Electronic Structure of Unsaturated Propen-1-yl, Propen-2-yl, 1-Buten-2-yl, and trans-2-Buten-2-yl Hydrocarbon Radicals  

E-print Network

Beyond Vinyl: Electronic Structure of Unsaturated Propen-1-yl, Propen-2-yl, 1-Buten-2-yl, and trans-2-Buten-2-yl Hydrocarbon Radicals Lucas Koziol, Sergey V. Levchenko, and Anna I. Krylov* Department for several valence and Rydberg electronic states of vinyl, propen-1-yl, propen-2-yl, 1-buten-2-yl, and trans

Krylov, Anna I.

2

The torsional spectra of the isomeric butenes. An ab initio study of the far infrared and Raman spectra of trans-2-butene, cis-2-butene and 2-methylpropene (isobutene)  

NASA Astrophysics Data System (ADS)

Torsional energy levels of trans-2-butene, cis-2-butene and 2-methylpropene (isobutene) were calculated within the restricted Hartree-Fock approximation with Møller-Plesset perturbation theory {MP2 }/{RHF} using double and triple zeta split orbitals with d and f polarization functions. The observed infrared and Raman band positions were correlated with their calculated positions, and it was concluded that, apart from some minor adjustments, the literature assignments of the fundamental and first sequence transitions are essentially correct. Whereas the terms in the potential that control the saddle point and the barrier maximum were found to be moderately sensitive to variations in the basis set, those that describe the intramolecular methyl-methyl coupling were sensitive to basis set contraction and polarization functions. The heights of the barriers (saddle point)/(barrier maxima) for trans-, cis- and iso-butenes at the level {MP2 }/{6-311 G(df,p)} were found to be {700.61}/{1438.38}, {222.04}/{460.80} and {736.14}/{1708.40 cm -1}, respectively.

Senent, M. L.; Moule, D. C.; Smeyers, Y. G.

1995-12-01

3

Liquid phase separation of 1-butene from 2-butenes on all-silica zeolite RUB-41.  

PubMed

The all-silica zeolite RUB-41, containing 8- and 10-membered rings, is able to separate trans-2-butene and cis-2-butene from 1-butene and represents a possible improvement in isolating pure 1-butene from a butene mixture. PMID:18491021

Tijsebaert, Bart; Varszegi, Csaba; Gies, Hermann; Xiao, Feng-Shou; Bao, Xinhe; Tatsumi, Takashi; Müller, Ulrich; De Vos, Dirk

2008-06-01

4

Reactions of 1-Butene and cis-2-Butene on Platinum Surfaces:Structure Sensitivity of cis-2-Butene Isomerization  

SciTech Connect

The hydrogenation and isomerization of 1-butene and cis-2-butene molecules are studied on platinum foil and single crystal(111), (100), and the stepped (755) surfaces at 300-350 K. In the presence of hydrogen, 1-butene and cis-2-butene are hydrogenated to butane. In addition, 1-butene is isomerized to cis- and trans-2-butenes,while cis-2-butene is converted to trans-2-butene. With a hydrogen pressure between 7 and 500 Torr, and a butene pressure of 3.5-70 Torr,both butene hydrogenation and isomerization rates exhibit a near-first-order dependence on the hydrogen pressure and a zero-order dependence on the hydrocarbon pressures. For both 1-butene and cis-2-butene molecules, the hydrogenation rates are insensitive to surface structures. The isomerization rate, however, is doubled for cis-2-butene molecules on the stepped platinum surface(Pt(755)).

Yoon, Cheonho; Yang, Michael X.; Somorjai, Gabor A.

1997-12-01

5

Stopped-flow studies of the mechanisms of ozone-alkene reactions in the gas phase: trans-2-butene  

Microsoft Academic Search

The reaction of ozone with trans-2-butene has been studied in the gas phase at 294 K and 530 Pa (4 Torr) by using a stopped-flow reactor coupled to a photoionization mass spectrometer. The concentrations of reactants and products were determined as a function of reaction time. A mechanism is proposed to account for the observed products: CHâCHO, HâCO, COâ, CHâ,

Richard I. Martinez; John T. Herron

1988-01-01

6

Reaction pathways of cis- and trans-2-butene on Mo(110) and C/Mo(110):. selective activation of ? and ? C-H bonds  

NASA Astrophysics Data System (ADS)

The reaction pathways of cis- and trans-2-butene on clean Mo(110) and carbide-modified Mo(110) surfaces have been studied using a combination of temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). The vibrational data reveal that the decomposition pathways of cis- and trans-2-butene are different on clean Mo(110). In the case of cis-2-butene, the olefinic ?(C-H) bonds are cleaved at 80 K to produce surface hydrogen and 2-butyne. In contrast, the initial decomposition of trans-2-butene also involves ?(C-H) bond scission, such that at least one of the methyl groups of the molecule is converted to a CH 2 group at temperatures below 150 K. On carbide-modified Mo(110), the initial decomposition step for both cis- and trans-2-butene involves ?(C-H) bond cleavage to form 2-butyne. This difference in reactivity of Mo(110) and carbide-modified Mo(110) towards the 2-butenes provides experimental evidence that the formation of the carbide overlayer enhances the selective activation of ?(C-H) bonds.

Eng, Joseph; Chen, Jingguang G.

1998-09-01

7

COI Name COI Synonym CAS 1-Pentene 109-67-1  

E-print Network

,4-Bis(2-chloroethylthio)-n-butane 142868-93-7 1,5-Bis(2-chloroethylthio)-n-pentane 142868-94-8 1-Butene [Propane, 2,2-dimethyl-] 463-82-1 2-Butene 107-01-7 2-Butene-cis 590-18-1 2-Butene-trans [2-Butene, (E-98-2 2-Methyl-1-butene 563-46-2 2-Methylpropene [1-Propene, 2-methyl-] 115-11-7 2-Pentene, (E)- 646

Movileanu, Liviu

8

The Bond Dissociation Energies of 1-Butene  

NASA Technical Reports Server (NTRS)

The bond dissociation energies of 1-butene and several calibration systems are computed using the G2(MP2) approach. The agreement between the calibration systems and experiment is very good. The computed values for 1-butene are compared with calibration systems and the agreement between the computed results for 1-butene and the "rule of thumb" values from the smaller systems is remarkably good.

Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

1994-01-01

9

Dissociation Channels of the 1-Buten-2-yl Radical and Its Photolytic Precursor 2-Bromo-1-butene  

E-print Network

Dissociation Channels of the 1-Buten-2-yl Radical and Its Photolytic Precursor 2-Bromo-1-butene. Photodissociation of the halogenated precursor 2-bromo-1-butene at 193 nm under collisionless conditions produced 1-buten-2-yl radicals with a range of internal energies spanning the predicted barriers

Butler, Laurie J.

10

An investigation of the electronic structure of some 3-monosubstituted-2-methylpropenes through computational chemistry and photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

The photoelectron (PE) spectra of some 3-monosubstituted 2-methylpropenes H 2C dbnd C(CH 3)CH 2X [X = Cl, Br, I, OH, OMe, OEt, SH, SMe, SEt, N(Me) 2 and N(Et) 2] have been recorded. A preliminary analysis is presented indicating some trends in the ionization potentials associated with application of OVGF method and NBO analysis from MP2/6-31G(d,p) and cc-pVDZ level of theory indicating that the more effective hyperconjugation effect leads to the most stable conformers. The sensitivity of the outermost ionization energies of selected molecules with respect to the level of theory was analyzed. Application of the CASPT2 method with ANO basis set and geometries from MP2 calculations provided results in excellent agreement with the experimental data.

Schuquel, Ivânia T. A.; Ducati, Lucas C.; Custodio, Rogério; Rittner, Roberto; Klapstein, Dieter

2008-06-01

11

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

12

Extensional flow-induced crystallization of isotactic poly-1-butene using a filament stretching rheometer  

E-print Network

Extensional flow-induced crystallization of isotactic poly-1-butene using a filament stretching isotactic poly-1-butene samples. The degree of crystallinity of the stretched fibers is quantified using and durations on a series of isotactic poly-1-butene samples with a range of molecular weights. Early works

Rothstein, Jonathan

13

Catalytic cracking process utilizing an iso-olefin enhancer catalyst additive  

SciTech Connect

A fluid catalytic cracking process is described for upgrading C[sub 9] + aromatic containing feeds to produce gasoline, distillate, and C[sub 4] olefins, including 1-butene, cis-2-butene, trans-2-butene, in a fluid catalytic cracking unit which includes a riser, a stripping unit and a regenerator, wherein the process comprises: (a) cracking a C[sub 9] + containing feed, selected from the group consisting of gas oil, resid and admixtures thereof, in a riser in the presence of a first catalyst component, under fluid catalytic cracking conditions, wherein the first catalyst component comprises an amorphous cracking catalyst, a large pore crystalline cracking catalyst or admixtures thereof, to provide gasoline boiling range components, and an amount of C[sub 4] olefins in a first product mixture; wherein the fluid catalytic cracking conditions include a riser top temperature within the range of from 950-1,150 F, a catalyst to feed ratio from 3:1-10:1, and a catalyst contact time from 0.5-10 seconds; (b) contacting said first product mixture with a second catalyst component which comprises ZSM-23, under conditions effective to increase isomerization, with no significant oligomerization to heavier molecules, of at least one of C[sub 4] olefins to 2-methylpropene, with no significant oligomerization to heavier molecules, and recovering a second product mixture which contains amounts of 2-methylpropene greater than that in the first effluent, wherein the conditions of the vapor phase catalytic isomerization of the 1-butene, cis-2-butene, and trans-2-butene to the isobutylene include a temperature within the range of from 950-1,150 F, a catalyst to feed ratio of from 3:1-10:1, and a catalyst contact time from 0.5-10 seconds.

Haag, W.O.; Harandi, M.N.; Owen, H.

1993-08-10

14

Skeletal isomerization of 1-butene on MCM-22 zeolite catalyst  

SciTech Connect

The skeletal isomerization of 1-butene has been studied on two MCM-22 zeolite catalysts synthesized with different Si/Al ratios, i.e., 15 and 47, under a wide range of operating conditions. Product yields are a function of n-butene conversion, and a maximum of isobutene yield is found at ca. 50% conversion. Besides isobutene, propylene and pentanes, which are formed by dimerization-cracking reactions products. Isobutene also takes part, together with the n-butenes, in the formation of by-products thorough dimerization and/or codimerization processes, which would also lead to a lower isobutene selectivity. Moreover, the yield of isobutene increases with increasing reaction temperature and decreasing 1-butene partial pressure, while the contrary holds for the formation of by-products. On the basis of these results the mechanism of formation of isobutene and the different by-products on MCM-22 is discussed. Finally, the selectivity to isobutene is strongly improved by increasing the Si/Al ratio of the zeolite, which is explained by a decrease of the undesired consecutive reactions when decreasing the density of Broensted acid sites of the zeolite. 24 refs., 6 figs., 6 tabs.

Asensi, M.A.; Corma, A.; Martinez, A. [Universidad Politecnica de Valencia (Spain)] [Universidad Politecnica de Valencia (Spain)

1996-02-01

15

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

16

Radical product yields from the ozonolysis of short chain alkenes under atmospheric boundary layer conditions.  

PubMed

The gas-phase reaction of ozone with unsaturated volatile organic compounds (VOCs), alkenes, is an important source of the critical atmospheric oxidant OH, especially at night when other photolytic radical initiation routes cannot occur. Alkene ozonolysis is also known to directly form HO2 radicals, which may be readily converted to OH through reaction with NO, but whose formation is poorly understood. We report a study of the radical (OH, HO2, and RO2) production from a series of small alkenes (propene, 1-butene, cis-2-butene, trans-2-butene, 2-methylpropene, 2,3-dimethyl-2-butene (tetramethyl ethene, TME), and isoprene). Experiments were performed in the European Photoreactor (EUPHORE) atmospheric simulation chamber, with OH and HO2 levels directly measured by laser-induced fluorescence (LIF) and HO2 + ?RO2 levels measured by peroxy-radical chemical amplification (PERCA). OH yields were found to be in good agreement with the majority of previous studies performed under comparable conditions (atmospheric pressure, long time scales) using tracer and scavenger approaches. HO2 yields ranged from 4% (trans-2-butene) to 34% (2-methylpropene), lower than previous experimental determinations. Increasing humidity further reduced the HO2 yields obtained, by typically 50% for an RH increase from 0.5 to 30%, suggesting that HOx production from alkene ozonolysis may be lower than current models suggest under (humid) ambient atmospheric boundary layer conditions. The mechanistic origin of the OH and HO2 production observed is discussed in the context of previous experimental and theoretical studies. PMID:24171583

Alam, Mohammed S; Rickard, Andrew R; Camredon, Marie; Wyche, Kevin P; Carr, Timo; Hornsby, Karen E; Monks, Paul S; Bloss, William J

2013-11-27

17

Conformational effects on optical rotation. 3-substituted 1-butenes.  

PubMed

A calculation of the optical rotation of (R)-(-)-3-chloro-1-butene found a remarkably large dependence on the C=C-C-C torsional angle. At tau = 0 degrees, [alpha](D) = +244 degrees, whereas at tau = 180 degrees, [alpha](D) = -526 degrees. The effect of conformation on the optical rotation was confirmed by a study of the temperature dependence of the rotation. An analysis of the data gave the difference in free energy between the low- and high-energy conformers as 1315 cal/mol and gave the optical rotation of the low-energy conformer and the average of the rotations of the higher energy forms. Although a large effect was found, the observed rotations are a factor of 2.6 smaller than the calculated values, independent of both conformation and wavelength from 589 to 365 nm. The effect of replacing Cl with F, CN, and CCH was examined theoretically. The effects of substituents are remarkably small despite large changes in the calculated electronic transition energies. PMID:12580616

Wiberg, Kenneth B; Vaccaro, Patrick H; Cheeseman, James R

2003-02-19

18

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

Code of Federal Regulations, 2011 CFR

...characteristic infrared spectra. (ii) Viscosity. Poly-1-butene resins and the...ethylene copolymers have an intrinsic viscosity 1.0 to 3.2 as determined by ASTM method...Standard Test Method for Dilute Solution Viscosity of Ethylene Polymers,”...

2011-04-01

19

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

...characteristic infrared spectra. (ii) Viscosity. Poly-1-butene resins and the...ethylene copolymers have an intrinsic viscosity 1.0 to 3.2 as determined by ASTM method...Standard Test Method for Dilute Solution Viscosity of Ethylene Polymers,”...

2014-04-01

20

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

Code of Federal Regulations, 2013 CFR

...characteristic infrared spectra. (ii) Viscosity. Poly-1-butene resins and the...ethylene copolymers have an intrinsic viscosity 1.0 to 3.2 as determined by ASTM method...Standard Test Method for Dilute Solution Viscosity of Ethylene Polymers,”...

2013-04-01

21

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

Code of Federal Regulations, 2012 CFR

...characteristic infrared spectra. (ii) Viscosity. Poly-1-butene resins and the...ethylene copolymers have an intrinsic viscosity 1.0 to 3.2 as determined by ASTM method...Standard Test Method for Dilute Solution Viscosity of Ethylene Polymers,”...

2012-04-01

22

1-butene and 2-butenes production using the positional isomerization of butenes catalyzed by sulfonic acid cation exchangers  

Microsoft Academic Search

Pure 1-butene and 2-butenes can be efficiently obtained from butane-butene fractions by combining the positional isomerization\\u000a of n-butenes on sulfonic acid cation exchanger catalysts with sharp distillation. At 50–60°C, an equilibrium 2-butenes: 1-butene\\u000a ratio of ?25: 1 is attained. The 2-butenes, which are comparatively high-boiling compounds, can be sufficiently completely\\u000a separated from detrimental impurities (1,3-butadiene and isobutene), 1-butene, and isobutane

O. S. Pavlov; S. A. Karsakov; S. Yu. Pavlov

2010-01-01

23

Surface properties of zirconium oxide and its catalytic activity for isomerization of 1-butene  

Microsoft Academic Search

Surface properties of zirconium oxide and its catalytic activity for isomerization of 1-butene isomerization, and its cis\\/trans selectivity were tested on catalysts calcined at 300°⁻⁹°°sup 0\\/C and correlated to the acidity, measured by IR spectroscopy of adsorbed pyridine; basicity measured by adsorption of COâ or ESR spectroscopy of adsorbed diphenylamine and oxygen; oxidizing sites, measured by ESR spectroscopy of adsorbed

Y. Nakano; T. Iizuka; H. Hattori; K. Tanabe

1979-01-01

24

Morphology, structure and properties of a poly(1-butene)\\/montmorillonite nanocomposite  

Microsoft Academic Search

A specifically formulated nanocomposite based on isotactic poly(1-butene) (PB) and montmorillonite was studied, by wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and polarized light optical microscopy, investigating the polymorphism of the polymer, and examining the interaction between PB and the silicate. Montmorillonite was found to disrupt the ordered morphology of the polymer, determining

Valerio Causin; Carla Marega; Antonio Marigo; Giuseppe Ferrara; Gulnaz Idiyatullina; Fabiana Fantinel

2006-01-01

25

Skeletal isomerization of 1-butene on 10-member ring zeolite catalysts  

SciTech Connect

Effects of zeolite pore structure on skeletal isomerization of 1-butenes are investigated. Three 10-member ring zeolites, ferrierite, ZSM-23, and ZSM-5, are studied and compared. Results show that ferrierite, with intersecting 10-MR and 8-MR channels, has better isomerization activity than ZSM-23, with monodirectional 10-MR channels, ZSM-5 with two intersecting 10-MR channels is not a selective isomerization catalyst. 13 refs., 2 figs., 1 tab.

NONE

1995-02-01

26

Adsorption of butane, 2-methylpropane, and 1-butene on activated carbon  

SciTech Connect

Four adsorption isotherms at 278, 288, 293, and 303 K of butane, 2-methylpropane, and 1-butene are obtained on activated carbon. The results at pressures up to 0.8P/P[sub s] are measured on 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.; Jadot, R. (Faculte Polytechnique de Mons (Belgium). Service de Thermodynamique)

1994-10-01

27

The infrared spectra of spiropentane methylenecyclobutane and 2-methyl-1-butene  

NASA Technical Reports Server (NTRS)

The infrared spectra of spiropentane, methylenecyclobutane, and 2-methyl-1-butene were measured in the region from 3 to 14 microns with a rock salt prism spectrometer of medium dispersion. The pure samples were prepared at the NACA Cleveland Laboratory. The vapors of these three C5 hydrocarbons were investigated at room temperature and at pressures in the range from 80 to 300 millimeters of mercury absolute in a 10-centimeter cell. The spectra were compared with each other and with Ramon spectra for the same compounds.

Cleaves, Alden P; Sherrick, Mildred E

1946-01-01

28

Palladium-catalyzed cross-coupling reactions of 2-iodo-4-(phenylchalcogenyl)-1-butenes.  

PubMed

[reaction: see text] 2-Iodo-4-(phenylchalcogenyl)-1-butenes 2 or 3, which are derived from the ring-opening reaction of methylenecyclopropanes (MCPs) 1 by iodine, can be applied to some palladium-catalyzed cross-coupling reactions such as the Sonogashira, Heck, Kumada, Suzuki, and Negishi reactions under mild conditions to give the corresponding coupling products in good yields. These reactions proceeded smoothly at room temperature (20 degrees C) in most cases without any phosphine ligand and additive. The phenylchalcogenyl group plays an important role in the reactions and a plausible reaction mechanism has been proposed. PMID:16323852

Shi, Min; Liu, Le-Ping; Tang, Jie

2005-12-01

29

Equation of state of 1-butene shocked to 54 GPa (540 kbar)  

NASA Astrophysics Data System (ADS)

Hugoniot equation-of-state data for liquid 1-butene were measured in the shock pressure range 12-54 GPa (120-540 kbar) using a two-stage light-gas gun. The data are compared with previous data for polybutene, a stoichiometrically equivalent liquid with a smaller initial specific volume. The data for both butenes are in agreement with chemical equilibrium calculations which assume that shock-compressed hydrocarbons dissociate and form a two-phase mixture consisting of molecular hydrogen and carbon in a stiff, diamond-like phase.

Hamilton, D. C.; Mitchell, A. C.; Ree, F. H.; Nellis, W. J.

1988-06-01

30

International Journal of Mass Spectrometry 249250 (2006) 420425 Mass spectrum of the 1-butene-3-yne-2-yl radical (i-C4H3; X2  

E-print Network

International Journal of Mass Spectrometry 249­250 (2006) 420­425 Mass spectrum of the 1-butene-3 beams method has been applied to produce the 1-butene-3-yne-2-yl radical, i-C4H3(X2 A ) under single that the intensity of the 13 C isotopic peak of the 1-butene-3-yne-2-yl radical at m/z = 52 (13 C12 C3H3 + ) is about

Kaiser, Ralf I.

31

Estimates of conformational energies and structures in chlorosubstituted 1-butenes based on results from related chlorosubstituted alkenes and alkanes  

NASA Astrophysics Data System (ADS)

Results obtained earlier for chlorosubstituted alkenes and alkanes have been used to predict results in chlorosubstituted 1-butenes. The conformational possibilities for the 96 chlorosubstituted 1-butenes may be classified into six classes. The largest number of possible conformational minima in one isomer is nine. However, energetically unfavourable X…X interactions due to parallel Cl?X…X?C3 or C2?X…;X?C4 (X ? Cl) bonds is reducing this number in most molecules. Results from experimental work, ab initio molecular orbital calculations and molecular-mechanics calculations have been included in the estimates presented in this work. Estimated values for structural parameters for some molecules, and conformational energies of all chlorosubstituted 1-butenes, are given.

Stølevik, Reidar; Hagen, Kolbjørn

1998-04-01

32

Gas-phase oxidation of 1-butene using nanoscale TiO{sub 2} photocatalysts  

SciTech Connect

The effects of preparation methods, humidity, and calcination temperatures on the behavior on nanoscale TiO{sub 2} photocatalysts were investigated in this study. Application of these photocatalysts were investigated in this study. Application of these photocatalysts in the gas-phase decomposition of 1-butene demonstrated that the nanoscale catalysts, prepared y the acid-assisted sol-gel technique, showed higher photocatalytic reactivity than commercially available Degussa P-25 TiO{sub 2}, while lower photoactivity was obtained on TiO{sub 2} catalysts prepared without photoactivity was obtained available Degussa P-25 TiO{sub 2}, while lower photoactivity was obtained on TiO{sub 2} catalysts prepared without adding acid to titanium isopropoxide. Experimental results revealed that the oxidation rates of 1-butene decreased exponentially with increasing water concentrations in the flowing stream. However, a trace amount of water vapor was indispensable in maintaining the stability of the catalysts. Proper calcination temperature (300 C) could promote the resistance of catalysts against the poisoning effects of humidity. Higher calcination temperature (400 C) unfavorably lowered the photoactivity due to phase transformation occurring at such a temperature. Amorphous and futile-typed TiO{sub 2} showed less photocatalytic reactivity. XRD patterns and BET measurements indicated that moderate surface areas (from 100 to 160 m{sup 2}/g), appropriate crystallite sizes (5{approximately}6 nm), and crystallinity to anatase were beneficial to the photocavity of TiO{sub 2} catalysts. In situ FTIR studies indicated that catalyst surfaces contained large amounts of chemisorbed water and hydroxyl groups, which are considered to be active sites in photocatalytic reactions. The accumulation of carbonate species on active sites resulted in the deactivation of TiO{sub 2} catalysts under dry conditions. quantum size effects were thought to be responsible for the high photoactivity achieved on the nanoscale TiO{sub 2} catalysts prepared by sol-gel methods.

Cao, L.; Huang, A.; Spiess, F.J.; Suib, S.L.

1999-11-15

33

Photodissociation of 1-bromo-2-butene, 4-bromo-1-butene, and cyclopropylmethyl bromide at 234 nm studied using velocity  

E-print Network

Photodissociation of 1-bromo-2-butene, 4-bromo-1-butene, and cyclopropylmethyl bromide at 234 nm, and 3-buten-1-yl radicals. The experiments use 2+1 resonance enhanced multiphoton ionization REMPI of their recoil velocity imparted upon photodissociation of 1-bromo-2-butene, cyclopropylmethyl bromide, and 4

Butler, Laurie J.

34

Correlation between the magnetism of non-stoichiometric zinc ferrites and their catalytic activity for oxidative dehydrogenation of 1-butene  

Microsoft Academic Search

Non-stoichiometric zinc ferrites, which were used as catalysts for the oxidative dehydrogentation of 1-butene, were synthesized by using co-precipitation and hydrothermal methods. Their atom local order was analyzed with Mössbauer spectroscopy and the refinement of the crystalline structures; their macroscopic magnetization was measured by the vibrating sample method. Their magnetic and catalytic properties depended on the synthesis conditions; the analysis

J. A Toledo-Antonio; N Nava; M Mart??nez; X Bokhimi

2002-01-01

35

Enynylation of 2-iodo-4-(phenylchalcogenyl)-1-butenes via intramolecular chelation: approach to the synthesis of conjugated dienynes or trienynes.  

PubMed

[reaction: see text] 2-Iodo-4-(phenylchalcogenyl)-1-butenes 3 and 4, which are derived from methylenecyclopropanes 1, can be enynylated with alkynes catalyzed by Pd(OAc)(2) to give conjugated dienynes 5 and 6 in the absence of any phosphine ligand and copper salt, and trienyne 9a can be obtained by oxidation of compound 5a. A plausible reaction mechanism has been proposed. PMID:15987211

Shi, Min; Liu, Le-Ping; Tang, Jie

2005-07-01

36

New bis(aryloxy)-Ti(IV) complexes and their use for the selective dimerization of ethylene to 1-butene.  

PubMed

New titanium complexes of general formula [(ArO)(n)Ti(Oi-Pr)((4-n))] were synthesized and used as pre-catalysts for the selective dimerization of ethylene to 1-butene. The complexes were prepared in cyclohexane using [Ti(Oi-Pr)(4)] and one or two equivalents of the corresponding phenols (ArOH) at room temperature. In this work, both monodentate and chelating phenols were evaluated. For alkyl-substituted phenols, it was demonstrated that large steric hindrance at both ortho and ortho' positions selectively yielded the mono-substituted complexes [(ArO)Ti(Oi-Pr)(3)]. Substitution at only one of the ortho positions allowed both the mono- and the di-substituted Ti complexes to be isolated. When a heteroatom was introduced on the phenol backbone, di-substitution systematically occurred except with phenols presenting a hemilabile -CH(2)NR(2) group at the ortho position. Upon activation with 3 equiv. of AlEt(3) at 20 bar and 60 °C, all the complexes selectively dimerized ethylene to 1-butene (>86% of butenes among which 99% of 1-butene). An increase of the steric bulk at the ortho position of the ligand or the introduction of a functional group led to decreased activity compared to [Ti(Oi-Pr)(4)]. PMID:22814869

Grasset, Fabien; Cazaux, Jean-Benoît; Magna, Lionel; Braunstein, Pierre; Oliver-Bourbigou, Hélène

2012-09-14

37

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

38

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

39

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

40

Evaluated kinetics of terminal and non-terminal addition of hydrogen atoms to 1-alkenes: a shock tube study of h + 1-butene.  

PubMed

Single-pulse shock tube methods have been used to thermally generate hydrogen atoms and investigate the kinetics of their addition reactions with 1-butene at temperatures of 880 to 1120 K and pressures of 145 to 245 kPa. Rate parameters for the unimolecular decomposition of 1-butene are also reported. Addition of H atoms to the ? bond of 1-butene results in displacement of either methyl or ethyl depending on whether addition occurs at the terminal or nonterminal position. Postshock monitoring of the initial alkene products has been used to determine the relative and absolute reaction rates. Absolute rate constants have been derived relative to the reference reaction of displacement of methyl from 1,3,5-trimethylbenzene (135TMB). With k(H + 135TMB ? m-xylene + CH3) = 6.7 × 10(13) exp(-3255/T) cm(3) mol(-1) s(-1), we find the following: k(H + 1-butene ? propene + CH3) = k10 = 3.93 × 10(13) exp(-1152 K/T) cm(3) mol(-1) s(-1), [880-1120 K; 145-245 kPa]; k(H + 1-butene ? ethene + C2H5) = k11 = 3.44 × 10(13) exp(-1971 K/T) cm(3) mol(-1) s(-1), [971-1120 K; 145-245 kPa]; k10/k11 = 10((0.058±0.059)) exp [(818 ± 141) K/T), 971-1120 K. Uncertainties (2?) in the absolute rate constants are about a factor of 1.5, while the relative rate constants should be accurate to within ±15%. The displacement rate constants are shown to be very close to the high pressure limiting rate constants for addition of H, and the present measurements are the first direct determination of the branching ratio for 1-olefins at high temperatures. At 1000 K, addition to the terminal site is favored over the nonterminal position by a factor of 2.59 ± 0.39, where the uncertainty is 2? and includes possible systematic errors. Combining the present results with evaluated data from the literature pertaining to temperatures of <440 K leads us to recommend the following: k?(H + 1-butene ? 2-butyl) = 1.05 × 10(9)T(1.40) exp(-366/T) cm(3) mol(-1) s(-1), [220-2000 K]; k?(H + 1-butene ? 1-butyl) = 9.02 × 10(8)T(1.40) exp(-1162/T) cm(3) mol(-1) s(-1) [220-2000 K]. Analogous rate constants for other unbranched 1-olefins should be very similar. Despite this, a factor of three discrepancy in the branching ratio for terminal and nonterminal addition is noted when comparing the present values with recommendations from a recent model of the important H + propene reaction. This difference is suggested to be well outside of the possible experimental errors of the present study or the expected differences with 1-butene. There thus appear to be inconsistencies in the current model for propene. In particular the addition branching ratio from that model should not be used as a reference value in extrapolations to other systems via rate rules or automated mechanism generation techniques. PMID:25517498

Manion, Jeffrey A; Awan, Iftikhar A

2015-01-22

41

A comparison of the conversion of 1-amino-2-ethylcyclopropane-1-carboxylic acid stereoisomers to 1-butene by pea epicotyls and by a cell-free system  

Microsoft Academic Search

The characteristics of the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene by pea (Pisum sativum L.) epicotyls and by pea epicotyl enzyme are compared. Of the four stereoisomers of 1-amino-2-ethylcyclopropane-1-carboxylic acid (AEC), only (1R,2S)-AEC is preferentially converted to 1-butene in pea epicotyls. This conversion is inhibited by ACC, indicating that butene production from (1R,2S)-AEC and ethylene production from ACC are

Thomas A. McKeon; Shang Fa Yang

1984-01-01

42

Grafting of diethyl maleate and maleic anhydride onto styrene- b-(ethylene- co-1-butene)- b-styrene triblock copolymer (SEBS)  

Microsoft Academic Search

In this paper a study of the bulk functionalization of styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) with diethyl maleate (DEM) or maleic anhydride (MAH) and dicumyl peroxide (DCP) as initiator in a Brabender mixer is described. The determination of the functionalization degree (FD) by NMR analysis indicates that the FD values depend on the feed composition and in particular on the DEM\\/DCP

E. Passaglia; S. Ghetti; F. Picchioni; G. Ruggeri

2000-01-01

43

Heterogeneous photocatalytic oxidation of 1-butene on SnO{sub 2} and TiO{sub 2} films  

SciTech Connect

Three types of films were prepared by a dip-coating process for the photocatalyzed decomposition of 1-butene in a gas-solid reaction. Under UV illumination ({lambda} > 300 nm, 352 nm peak intensity), ultrasmall SnO{sub 2} with a diameter of 5 nm exhibited initial photoactivity as high as 3 times that of P-25 TiO{sub 2} (30 nm) in the absence of water vapor whereas SnO{sub 2}-l (22 nm) did not show photoactivity. Quantum size effects were mainly responsible for the high photoactivity achieved by SnO{sub 2}. Inactivity of SnO{sub 2}-l film was due to the absence of active hydroxyl groups on the catalyst surface and low surface areas. By investigation of the effects of humidity, water has two different functions: maintaining constant oxidation rates at low water levels by replenishing hydroxyl groups and decreasing the photoactivity at high water levels by competitive adsorption with butene on active sites. Compared with TiO{sub 2}, SnO{sub 2} cannot withstand high humidity since it is very sensitive to water concentration. Hydroxyl groups on catalyst surfaces are the active centers for the reaction. The occurrence of obvious deactivation on SnO{sub 2} films was due to the depletion of hydroxyl groups and the accumulation of carbonate species on particle surfaces, i.e., M-OCOOR species in place of M-OH. The kinetic data correlate with a Langmuir-Hinshelwood single-site model. XRD, UV-vis spectroscopy, and FTIR techniques were employed to characterize the particle size, band gaps, and surface properties of the catalysts.

Cao, L.; Spiess, F.J.; Huang, A.; Suib, S.L. [Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemistry] [Univ. of Connecticut, Storrs, CT (United States). Dept. of Chemistry; Obee, T.N.; Hay, S.O.; Freihaut, J.D. [United Technologies Research Center, East Hartford, CT (United States)] [United Technologies Research Center, East Hartford, CT (United States)

1999-04-15

44

Figure A1 Time-series of N1 fan speed (% of maximum) and exhaust gas temperature for experiments conducted (a) 4% load, (b) 7% (c) 30% and (d) 85% engine loads. Warm-up and  

E-print Network

.9 hexylbenzene 16.6 a ARO2 1,2,4,5- tetramethylbenzene 27.2 a propene 696.2 6.3 1-butene 194.6 2.2 1-pentene 91.2 1-heptene and 2,2,4 - trimethylpentane 61.5 a iso-butene 71.7 5.5 1,3-butadiene 230.3 a trans-2-butene 61.0 4.3 cis-2-butene 11.7 0.9 1,2-butadiene 6.4 a 3-methyl-1-butene 29.5 a 2-methyl-1-butene 30

Meskhidze, Nicholas

45

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

46

High selectivity production of propylene from 2-butene: non-degenerate pathways to convert symmetric olefins via olefin metathesis.  

PubMed

The first example of propylene production from 2-butene in promising yield is described by reacting trans-2-butene over tungsten hydrides precursor W-H/Al(2)O(3) at 150 °C and different pressures in a continuous flow reactor. The tungsten carbene-hydride active site operates as a "bi-functional catalyst" through the disfavoured 2-butene isomerisation on W-hydride and 2-butenes/1-butene cross-metathesis on W-carbene. PMID:22395285

Mazoyer, Etienne; Szeto, Kai C; Basset, Jean-Marie; Nicholas, Christopher P; Taoufik, Mostafa

2012-04-14

47

Absolute rate constants and temperature dependencies for the gas phase reactions of H atoms with propene and the butenes in the temperature range 298 to 445 K  

NASA Astrophysics Data System (ADS)

We have employed a flash photolysis resonance fluorescence technique to study the rates of reaction of H atoms with propene, 1-butene, cis- and trans-2-butene, and isobutene as a function of temperature. The Arrhenius parameters for the overall reactions in the temperature range 298-445 K have been measured, and it was observed that the variation in room temperature rate constants among these alkenes arises both from differences in the A factors and from variations in the activation energies.

Harris, G. W.; Pitts, J. N., Jr.

1982-10-01

48

Evaluation of Kinetic and Mechanistic Data for Modeling of Photochemical Smog  

Microsoft Academic Search

This review is a critical evaluation of the rate constants, mechanisms, and products of selected atmospheric reactions of hydrocarbons, nitrogen oxides, and sulfur oxides in air. The evaluation considers eight hydrocarbons (n-butane, 2,3-dimethylbutane, ethene, propene, 1-butene, trans-2-butene, toluene, and m-xylene) for which smog chamber irradiations have been carried out under carefully controlled conditions and which have been the subject of

Roger Atkinson; Alan C. Lloyd

1984-01-01

49

Inhibitors of the fungal cell wall. Synthesis of 4-aryl-4- N-arylamine-1-butenes and related compounds with inhibitory activities on ?(1–3) glucan and chitin synthases  

Microsoft Academic Search

As part of our project devoted to the search for antifungal agents, which act via a selective mode of action, we synthesized a series of new 4-aryl- or 4-alkyl-N-arylamine-1-butenes and transformed some of them into 2-substituted 4-methyl-tetrahydroquinolines and quinolines by using a novel three-step synthesis. Results obtained in agar dilution assays have shown that 4-aryl homoallylamines not possessing halogen in

Juan M Urbina; Juan C. G Cortés; Alirio Palma; Silvia N López; Susana A Zacchino; Ricardo D Enriz; Juan C Ribas; Vladimir V Kouznetzov

2000-01-01

50

Antiestrogen basicity--activity relationships: a comparison of the estrogen receptor binding and antiuterotrophic potencies of several analogues of (Z)-1,2-diphenyl-1-[4-[2-(dimethylamino)ethoxy]phenyl]-1-butene (tamoxifen, Nolvadex) having altered basicity.  

PubMed

A series of N-substituted (Z)-1,2-diphenyl-1-[4-(2-aminoethoxy)phenyl]-1-butenes, analogues of the antiestrogen tamoxifen (Nolvadex), in which the side-chain basicity is varied over a wide range, has been prepared to probe the importance of basicity in evoking estrogen antagonism. All of the compounds, except the pyrrole analogue 14, were found to possess significant antiestrogenic activity in the rat, as measured by their ability to inhibit estrogen-induced uterine growth. This implies that in the tamoxifen series the level of side-chain basicity, at least in the Lowry-Brønsted sense, is not a determining factor in the estrogen antagonist potencies of these compounds. PMID:7057423

Robertson, D W; Katzenellenbogen, J A; Hayes, J R; Katzenellenbogen, B S

1982-02-01

51

Comparative DFT study of the adsorption of 1,3-butadiene, 1-butene and 2- cis/trans-butenes on the Pt(1 1 1) and Pd(1 1 1) surfaces  

NASA Astrophysics Data System (ADS)

The interaction of 1,3-butadiene, 1-butene and 2- cis/trans-butenes on the Pt(1 1 1) and Pd(1 1 1) surfaces has been studied with density functional theory methods (DFT). The same most stable adsorption modes have been found on both metal surfaces with similar adsorption energies. For 1,3-butadiene the 1,2,3,4-tetra-? adsorption structure is shown to be the most stable one, in competition with a 1,4-metallacycle-type mode, which is only less stable by 10-12 kJ mol -1. On Pt(1 1 1) these total energy calculations were combined with simulations of the vibrational spectra. This confirms that the 1,2,3,4-tetra-? adsorption is the most probable adsorption structure, but cannot exclude the 1,4-metallacycle as a minority species. Although similar in type and energy, the adsorption on the Pd(1 1 1) surface shows a markedly different geometry, with a smaller molecular distortion upon adsorption. The most stable adsorption structure for the butene isomers is the di-?-mode. Similarly to the case of the 1,3-butadiene, the adsorption geometry is closer to the gas phase one on Pd than on Pt, hence explaining the different spectroscopic results, without the previously assumed requirement of a different binding mode. Moreover the present study has shown that the different selectivity observed on Pt(1 1 1) and Pd(1 1 1) for the hydrogenation reaction of butadiene cannot be satisfactory explained by the single comparison of the relative stabilities of 1,3-butadiene and 1-butene on these metals.

Valcárcel, Ana; Clotet, Anna; Ricart, Josep M.; Delbecq, Françoise; Sautet, Philippe

2004-01-01

52

Selective oxidation of n-butane and butenes over vanadium-containing catalysts  

SciTech Connect

The oxidative dehydrogenation (OXDH) of n-butane, 1-butene, and trans-2-butene on different vanadia catalysts has been compared. MgO, alumina, and Mg-Al mixed oxides with Mg/(Al + Mg) ratios of 0.25 and 0.75 were used as supports. The catalytic data indicate that the higher the acid character of catalysts the lower is both the selectivity to C{sub 4}-olefins from n-butane and the selectivity to butadiene from both 1-butene or trans-2-butene. Thus, OXDH reactions are mainly observed from n-butane and butenes on basic catalysts. The different catalytic performance of both types of catalysts is a consequence of the isomerization of olefins on acid sites, which appears to be a competitive reaction with the selective way, i.e., the oxydehydrogenation process by a redox mechanism. Infrared spectroscopy data of 1-butene adsorbed on supported vanadium oxide catalysts suggest the presence of different adsorbed species. O-containing species (carbonyl and alkoxide species) are observed on catalysts with acid sites while adsorbed butadiene species are observed on catalysts with basic sites. According to these results a reaction network for the oxydehydrogenation of n-butane is proposed with parallel and consecutive reactions.

Nieto, J.M.L.; Concepcion, P.; Dejoz, A.; Knoezinger, H.; Melo, F.; Vazquez, M.I.

2000-01-01

53

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

54

FT-IR studies on light olefin skeletal isomerization catalysis: II. The interaction of C4 olefins and alcohols with HZSM5 zeolite  

SciTech Connect

The catalytic activity of the zeolite HZSM5 in n-butene conversion was investigated under conditions similar to those of a commercial process for skeletal isomerization. The catalyst was found to be very active in n-butene conversion, but selectivity to isobutene was low due to a predominance of cracking, coking, and oligomerization side reactions. The interaction of 1-butene, cis-2-butene, trans-2-butene, isobutene, sec-butanol, and tert-butanol was also investigated by FT-IR spectroscopy in the temperature range 150-673 K. 47 refs., 9 figs., 2 tabs.

Trombetta, M.; Busca, G. [Universita de Genova (Italy)] [Universita de Genova (Italy); Rossini, S. [Snamprogetti, Milan (Italy)] [and others] [Snamprogetti, Milan (Italy); and others

1997-06-01

55

Electrochemical reduction of 1,4-dihalobutanes at carbon cathodes in dimethylformamide  

Microsoft Academic Search

Cyclic voltammetry and controlled-potential electrolysis have been employed to investigate the electrochemical behavior of 1,4-dibromo-, 1,4-diiodo-, 1-bromo-4-chloro- and 1-chloro-4-iodobutane at glassy carbon cathodes in dimethylformamide containing tetramethylammonium perchlorate. Depending on the identity of the 1,4-dihalobutane electrolyzed and the choice of potential, reduction of these compounds leads to a myriad of products including cyclobutane, n-butane, n-octane, 1-butene, cis-and trans-2-butene, 1,3-butadiene, ethylene,

Wayne A. Pritts; Dennis G. Peters

1995-01-01

56

Inhibitors of the fungal cell wall. Synthesis of 4-aryl-4-N-arylamine-1-butenes and related compounds with inhibitory activities on beta(1-3) glucan and chitin synthases.  

PubMed

As part of our project devoted to the search for antifungal agents, which act via a selective mode of action, we synthesized a series of new 4-aryl- or 4-alkyl-N-arylamine-1-butenes and transformed some of them into 2-substituted 4-methyl-tetrahydroquinolines and quinolines by using a novel three-step synthesis. Results obtained in agar dilution assays have shown that 4-aryl homoallylamines not possessing halogen in their structures, tetrahydroquinolines and quinolines, display a range of antifungal properties in particular against Epidermophyton floccosum and Microsporum canis. Regarding the mode of action, all active compounds showed in vitro inhibitory activities against beta(1-3) glucan-synthase and mainly against chitin-synthase. These enzymes catalyze the synthesis of beta(1-3) glucan and chitin, respectively, major polymers of the fungal cell wall. Since fungal but not mammalian cells are encased in a cell wall, its inhibition may represent a useful mode of action for these antifungal compounds. PMID:10819157

Urbina, J M; Cortés, J C; Palma, A; López, S N; Zacchino, S A; Enriz, R D; Ribas, J C; Kouznetzov, V V

2000-04-01

57

Sum Frequency Generation Vibrational Spectroscopy of 1,3-Butadiene Hydrogenation on 4 nm Pt@SiO2, Pd@SiO2, and Rh@SiO2 Core-Shell Catalysts.  

PubMed

1,3-Butadiene (1,3-BD) hydrogenation was performed on 4 nm Pt, Pd, and Rh nanoparticles (NPs) encapsulated in SiO2 shells at 20, 60, and 100 °C. The core-shells were grown around polyvinylpyrrolidone (PVP) coated NPs (Stöber encapsulation) prepared by colloidal synthesis. Sum frequency generation (SFG) vibrational spectroscopy was performed to correlate surface intermediates observed in situ with reaction selectivity. It is shown that calcination is effective in removing PVP, and the SFG signal can be generated from the metal surface. Using SFG, it is possible to compare the surface vibrational spectrum of Pt@SiO2 (1,3-BD is hydrogenated through multiple paths and produces butane, 1-butene, and cis/trans-2-butene) to Pd@SiO2 (1,3-BD favors one path and produces 1-butene and cis/trans-2-butene). In contrast to Pt@SiO2 and Pd@SiO2, SFG and kinetic experiments of Rh@SiO2 show a permanent accumulation of organic material. PMID:25272243

Krier, James M; Michalak, William D; Cai, Xiaojun; Carl, Lindsay; Komvopoulos, Kyriakos; Somorjai, Gabor A

2015-01-14

58

On the structure of C 4 hydrocarbon species resulting from the adsorption of linear butenes on a Pt(111) surface as studied by thermal desorption and electron energy loss spectroscopies  

NASA Astrophysics Data System (ADS)

A combination of thermal desorption spectroscopy (TDS) and vibrational electron energy loss spectroscopy (EELS) has been used to study the compositions and structures of the species formed at different temperatures following the adsorption of 1-butene and the cis- and trans-2-butenes at 170 K on Pt(111). At this temperature each of the chemisorbed butenes gives a different EEL spectrum, corresponding to ?2 di-? adsorbed species. At 300 K, the TDS evidence shows that the species from 1-butene has the empirical composition C 4H 7 and the EEL spectrum is consistent with the presence of an n-butylidyne structure. Cis- and trans-2-butenes give identical TDS spectra which define a composition of C 4H 6 at 300 K. Comparison with the spectrum from the adsorption of 2-butyne and the model cluster compound Os 3(CO) 10(CH 3CCCH 3) leads to the assignment of a ?3- ?2 CH 3C:CCH 3 structure to the adsorbed species involving the central C:C bond in two ?-bonds and one ?-bond to the metal surface. By 450 K virtually identical EEL spectra are obtained from all these linear butenes, and TDS implies a surface composition of C 4H 2.

Avery, Neil R.; Sheppard, Norman

59

On the structure of C 4 hydrocarbon species resulting from the adsorption of linear butenes on a Pt(111) surface as studied by thermal desorption and electron energy loss spectroscopies  

NASA Astrophysics Data System (ADS)

A combination of thermal desorption spectroscopy (TDS) and vibrational electron energy loss spectroscopy (EELS) has been used to study the compositions and structures of the species formed at different temperatures following the adsorption of 1-butene and the cis- and trans-2-butenes at 170 K on Pt(111). At this temperature each of the chemisorbed butenes gives a different EEL spectrum, corresponding to ? 2 di-? adsorbed species. At 300 K, the TDS evidence shows that the species from 1-butene has the empirical composition C 4H 7 and the EEL spectrum is consistent with the presence of an n-butylidyne structure. Cis- and trans-2-butenes give identical TDS spectra which define a composition of C 4H 6 at 300 K. Comparison with the spectrum from the adsorption of 2-butyne and the model cluster compound Os 3(CO) 10(CH 3CCCH 3) leads to the assignment of a ? 3-? 2 CH 3C:CCH 3 structure to the adsorbed species involving the central C:C bond in two ?-bonds and one ?-bond to the metal surface. By 450 K virtually identical EEL spectra are obtained from all these linear butenes, and TDS implies a surface composition of C 4H 2.

Avery, Neil R.; Sheppard, Norman

1986-04-01

60

Butenes and butadiene in urban air.  

PubMed

Samples of urban air hydrocarbons were taken on specifically made adsorbent cartridges and analysed by gas chromatography after thermal desorption. The four isomeric butenes and 1,3-butadiene were favourably resolved and separated from the abundant alkanes on an aluminium oxide PLOT column. The concentrations of butadiene, reflecting outdoor urban exposure, were in the range of 0.5-5 micrograms/m3. An approximate 1:4 ratio was observed between butadiene and propene which both originate predominantly from vehicle exhaust. The four butenes made up approximately 50% of the propene concentration in exhaust-polluted air, with methylpropene greater than 1-butene greater than trans-2-butene greater than cis-2-butene. Petrol vapour contributed less than exhaust but about five times more to the 2-butenes than to methylpropene and 1-butene. The highest exposure levels of butadiene and butenes were consistently observed in the vicinity of exhaust pipes and petrol-fuelled vehicles. PMID:1384124

Löfgren, L; Petersson, G

1992-05-01

61

Anhydrous ferric chloride as an alkylation catalyst: The condensation of 2-methylpropene and benzene, preparation and identification of several fractions.  

E-print Network

-but~&) ion &&i:, ' a b:nzcnc . -. o. 'e- cole !&hich may also be activated by the nrc;;ence of il( : c ci. . I o ' de2 FeC1 = . 'I FeClg i Cj')3; -, C. CH2+ ii+ (CH ). . 0 re", ) & Reaction with a second t-bu. ; 1 ion Cives 1, '&-d. '. - t...

Mommessin, Pierre Robert

2012-06-07

62

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

63

Comparison of the kinetics of O([sup 3]P) reactions with the four butenes over wide temperature ranges  

SciTech Connect

Rate coefficients for reactions of ground-state oxygen atoms with isobutene, trans-2-butene, and cis-2-butene have been measured using the high-temperature photochemistry (HTP) technique. The oxygen atoms were generated by flash photolysis of either O[sub 2] or CO[sub 2] and the relative atom concentrations were monitored by resonance fluorescence. We find, in cm[sup 3] molecule[sup [minus]1] s[sup [minus]1] units, for isobutene, k(284-1015 K) = 2.0 x 10[sup [minus]15](T/K)[sup 1.28] exp(543 K/T); trans-2-butene, k(292-1022 K) = 3.9 x 10[sup [minus]17](T/K)[sup 1.87] exp(743 K/T); and cis-2-butene, k(292-1086 K) = 2.4 x 10[sup [minus]17](T/K)[sup 1.94] exp(716 K/T). The 2[sigma] precision limits are around [+-]10%, and the corresponding 2[sigma] accuracy limits are estimated to be about [+-]25%. Conventional transition-state-theory calculations for the electrophilic O-addition to the double bond yield at high temperatures rate coefficients smaller than observed. A method is developed for estimating rate coefficients for H abstraction. When the results are added to those of the addition, good agreement with experiments is attained. The differences between the k(T) expressions for the present three reactions and the corresponding 1-butene reaction are discussed. Based on these observations, a method is presented for estimating rate coefficients for O-atom reactions with higher olefins over wide temperature ranges. 38 refs., 8 figs., 4 tabs.

Adusei, G.Y.; Fontijn, A. (Rensselaer Polytechnic Inst., Troy, NY (United States))

1994-04-07

64

Fourier transform infrared study of butene adsorption and reaction on a silica-supported nickel catalyst  

SciTech Connect

The adsorption of 1-butene, trans-2-butene, cis-2-butene, and 1,1-d/sub 2/-1-butene on a well-characterized silica-supported nickel catalyst was studied using Fourier transform infrared spectroscopy. The resultant hydrocarbon surface species were subjected to vacuum and hydrogen. Reaction products were monitored at temperatures from 28 to 100/sup 0/C. The initial adsorption of each of the n-butenes resulted in similar infrared spectra. The main spectral features are proposed to be associated with two surface species: a weakly adsorbed 2,3-dimetallabutane and a strongly adsorbed 1,1,2- and/or 1,1,3-trimetallabutane. The surface orientations of the initially adsorbed metallabutanes are discussed along with the effect of the surface selection rule on the observed infrared bands. Heating the catalyst under vacuum resulted in the desorption of the 2,3-species to form butane and the further dehydrogenation of other metallabutanes. The addition of hydrogen to the initially adsorbed surface species resulted in the evolution of butane and the partial hydrogenation of the strongly adsorbed metallabutanes. The resultant structures were relatively stable in hydrogen at temperatures to 120/sup 0/C. Evidence was also found for the presence of allylic species during the linear isomerization of the n-butenes. It is proposed that allylic species may be precursors to the formation of the metallabutanes as well as possible intermediates in the isomerization reaction.

Campione, T.J.; Ekerdt, J.G.

1986-11-01

65

[Os{sub 2}(CO){sub 8}({mu}{sub 2}-{eta}{sup 1},{eta}{sup 1}-propene)] and related complexes as vibrational models for alkenes chemisorbed on single-crystal metal surfaces  

SciTech Connect

The FTIR spectra of [Os{sub 2}(CO){sub 8}({mu}{sub 2}-{eta}{sup 1},{eta}{sup 1}-C{sub 2}H{sub 3}CH{sub 3})] and of its methyl-d{sub 3} and d{sub 6} isotopologues have been measured and assigned. Comparison of these vibrational data with previously published EELS and RAIRS studies of propene chemisorbed on Pt(111) and Ni(111) at low temperatures indicates that, on these surfaces, the propene species are chemisorbed via a ({mu}{sub 2}-P{eta}{sup 1},{eta}{sup 1}-C{sub 2}H{sub 3}CH{sub 3}) bonding mode. However, differences in the intensity patterns between the spectra of the adsorbed species compared with that of the model compound imply additional twisting or tilting with respect to the surface. Assignment of the FTIR spectra of the corresponding 1-butene and trans-2-butene complexes [Os{sub 2}(CO){sub 8}({mu}{sub 2}-{eta}{sup 1},{eta}{sup 1}-C{sub 2}H{sub 3}C{sub 2}H{sub 5})] and [Os{sub 2}(CO){sub 8}({mu}{sub 2}{eta}{sup 1},{eta}{sup 1}-CH{sub 3}C{sub 2}H{sub 2}CH{sub 3})] indicates similar bonding modes for chemisorbed 1-butene and trans-2-butene on Pt(111). Infrared data for the mononuclear propene complex [Os(CO){sub 4}({eta}{sup 2}-C{sub 2}H{sub 3}CH{sub 3})], on the other hand, are in good agreement with published EEL data for propene on Ru(0001) and Rh(111), indicating that at low temperatures on these surfaces, propene is chemisorbed as a methyl-substituted metallacyclopropane-like species. These bonding modes are analogous to those established for low-temperature ethene chemisorption on these surfaces.

Anson, C.E.; Sheppard, N.; Bender, B.R.; Norton, J.R.

1999-01-27

66

Laboratory spectroscopic analyses of electron irradiated alkanes and alkenes in solar system ices  

NASA Astrophysics Data System (ADS)

We report results from laboratory experiments of 10 keV electron irradiation of thin ice films of water and short-chain hydrocarbons at ˜10-8 Torr and temperatures ranging from 70-100 K. Hydrocarbon mixtures include water with C3H8, C3H6, C4H10 (butane and isobutane), and C4H8, (1-butene and cis/trans-2-butene). The double bonds of the alkenes in our initial mixtures were rapidly destroyed or converted to single carbon bonds, covalent bonds with hydrogen, bonds with -OH (hydroxyl), bonds with oxygen (C-O), or double bonds with oxygen (carbonyl). Spectra resulting from irradiation of alkane and alkene ices are largely indistinguishable; the initial differences in film composition are destroyed and the resulting mixture includes long-chain, branched aliphatics, aldehydes, ketones, esters, and alcohols. Methane was observed as a product during radiolysis but CO was largely absent. We find that while some of the carbon is oxidized and lost to CO2 formation, some carbon is sequestered into highly refractory, long-chain aliphatic compounds that remain as a thin residue even after the ice film has been raised to standard temperature and pressure. We conclude that the high availability of hydrogen in our experiments leads to the formation of the formyl radical which then serves as the precursor for formaldehyde and polymerization of longer hydrocarbon chains.

Hand, K. P.; Carlson, R. W.

2012-03-01

67

Carbon K-shell electron energy loss spectra of 1- and 2-butenes, trans-1,3-butadiene, and perfluoro-2-butene. Carbon--carbon bond lengths from continuum shape resonances  

SciTech Connect

Electron energy loss spectra of 1-butene, cis-2-butene, trans-2-butene, trans-1,3-butadiene, and perfluoro-2-butene in the region of carbon K-shell (C 1s) excitation and ionization have been recorded under dipole-dominated inelastic electron scattering conditions. The features observed below the C 1s I.P. in the spectra of the butenes and butadiene are assigned to promotions of C 1s electrons to unoccupied valence (..pi..*) and Rydberg orbitals while broad features observed above the edge are assigned to sigma(C--C) and sigma(C--C) shape resonances. These spectra, along with carbon K-shell spectra of other hydrocarbons, are used to demonstrate that there is a quantitative relationship between carbon--carbon bond lengths and the location of sigma shape resonances relative to the C 1s ionization threshold (I.P.). The C 1s spectrum of perfluoro-2-butene demonstrates dramatic potential barrier effects, namely suppression of Rydberg transitions and strong enhancement of sigma(C--C) and sigma(C--F) shape resonances in the region of the C 1s ionization threshold.

Hitchcock, A.P.; Beaulieu, S.; Steel, T.; Stoehr, J.; Sette, F.

1984-05-01

68

Carbon K-shell electron energy loss spectra of 1- and 2-butenes, trans-1,3-butadiene, and perfluoro-2-butene. Carbon-carbon bond lengths from continuum shape resonances  

NASA Astrophysics Data System (ADS)

Electron energy loss spectra of 1-butene, cis-2-butene, trans-2-butene, trans-1,3-butadiene, and perfluoro-2-butene in the region of carbon K-shell (C 1s) excitation and ionization have been recorded under dipole-dominated inelastic electron scattering conditions. The features observed below the C 1s I.P. in the spectra of the butenes and butadiene are assigned to promotions of C 1s electrons to unoccupied valence (?*) and Rydberg orbitals while broad features observed above the edge are assigned to ?(C-C) and ?(C-C) shape resonances. These spectra, along with carbon K-shell spectra of other hydrocarbons, are used to demonstrate that there is a quantitative relationship between carbon-carbon bond lengths and the location of ? shape resonances relative to the C 1s ionization threshold (I.P.). The C 1s spectrum of perfluoro-2-butene demonstrates dramatic potential barrier effects, namely suppression of Rydberg transitions and strong enhancement of ?(C-C) and ?(C-F) shape resonances in the region of the C 1s ionization threshold.

Hitchcock, A. P.; Beaulieu, S.; Steel, T.; Stöhr, J.; Sette, F.

1984-05-01

69

Semiconductor-olefin adducts. Photoluminescent properties of cadmium sulfide and cadmium selenide in the presence of butenes  

NASA Astrophysics Data System (ADS)

Direct evidence for adduct formation between butenes and etched, single-crystal n-CdS and n-CdSe(CdS(e)) surfaces has been obtained from photoluminescence (PL) measurements. Exposure of CdS(e) to butenes causes enhancement of the solids' band edge PL relative to a N2 ambient. For 30 percent mixtures of the olefins in N2, the magnitude of the enhancement follows the order, 1,3-butadiene is greater than cis-2-butene trans-2-butene is greater than isobutylene 1-butene, and correlates with the olefin basicities, based on photoionization potentials. Enhancements in PL intensity can be fit to a dead-layer model, allowing the determination of the reduction in depletion width in the semiconductor resulting from olefin exposure; depletion width reductions reach a few hundred Angstroms for adducts of 1,3-butadiene with CdS(e). The PL changes were used in conjunction with the Langmuir adsorption isotherm model to yield equilibrium constants for adduct formation of 1,3-butadiene with CdS(e) of 9 plus or minus 4/atm at 293 K. Surface interactions that may contribute to the observed PL changes are discussed.

Meyer, Gerald J.; Leung, Larry K.; Yu, Jim C.; Lisensky, George C.; Ellis, Arthur B.

1989-05-01

70

Gas-phase chemistry of the yttrium-imido cation YNH{sup +} with alkenes: {Beta}-hydrogen activation by a d{sup 0} system via a multicentered transition state  

SciTech Connect

The gas-phase chemistry of the yttrium-imido carbon cations with alkenes was studied by using Fourier transform mass spectrometry to explore the chemistry of transition metal ion complexes with low-valence metal centers. The YNH{sup +} species was synthesized by reacting Y{sup +}, generated by laser desorption, with ammonia. The dehydrogenation reaction is exothermic, yielding a lower limit for the imido bond energy of D{degree}(Y{sup +}-NH) > 101 kcal/mol. Due to the electron deficiency of the metal center upon binding to NH, the further reactivity of YNH{sup +} can only be explained by a reaction mechanism involving a multicentered transition state. YNH{sup +} reacts with ethene predominantly by dehydrogenation to produce YC{sub 2}H{sub 3}N{sup +}. Thus, instead of the metathesis reaction involving the cleavage of the 2-aza-1-metallacyclobutane intermediate, a {beta}-hydrogen transfers to the metal center and is then eliminated with a hydrogen from the remaining CH{sub 2} group to complete the reaction. All three linear butenes, 1-butene, cis-2-butene, and trans-2-butene, react very similarly with YNH{sup +}, yielding a variety of product ions with the predominant loss of NH{sub 3} resulting in the formation of YCH{sub 4}H{sub 6}{sup +}. Structural studies on this ion suggest that it is bent metallacyclopent-3-ene, not the butadiene isomer. 34 refs., 1 fig.

Ranatunga, D.R.A.; Hill, Y.D.; Freiser, B.S. [Purdue Univ., West Lafayette, IN (United States)] [Purdue Univ., West Lafayette, IN (United States)

1996-02-20

71

Semiconductor-olefin adducts. Photoluminescent properties of cadmium sulfide and cadmium selenide in the presence of butenes  

SciTech Connect

Direct evidence for adduct formation between butenes and etched, single-crystal n-CdS and n-CdSe (CdS(e)) surfaces has been obtained from photoluminescence (PL) measurements. Exposure of CdS(e) to butenes causes enhancement of the solids' band edge PL relative to a N{sub 2} ambient. For 30% mixtures of the olefins in N{sub 2}, the magnitude of the enhancement follows the order 1,3-butadiene > cis-2-butene {approximately} trans-2-butene > isobutylene {approximately} 1-butene and correlates with the olefin basicities, on the basis of photoionization potentials. Enhancements in PL intensity can be fit to a dead-layer model, allowing the determination of the reduction in depletion width in the semiconductor resulting from olefin exposure; depletion width reductions reach a few hundred angstroms for adducts of 1,3-butadiene with CdS(e). The PL changes were used in conjunction with the Langmuir adsorption isotherm model to yield equilibrium constants for adduct formation of 1,3-butadiene with CdS(e) of 9 {plus minus} 4 atm{sup {minus}1} at 293 K. Surface interactions that may contribute to the observed PL changes are discussed.

Meyer, G.J.; Leung, L.K.; Ellis, A.B. (Univ. of Wisconsin, Madison (USA)); Yu, J.C. (Central Missouri State Univ., Warrensburg (USA)); Lisensky, G.C. (Beloit College, WI (USA))

1989-07-05

72

Crossed Molecular Beam Studies of Phenyl Radical Reactions with Propene and 2-Butene Daniel R. Albert, Michael A. Todt and H. Floyd Davis*  

E-print Network

Crossed Molecular Beam Studies of Phenyl Radical Reactions with Propene and 2-Butene Daniel R intermediates. For comparison, we have also studied the reaction of phenyl radicals with trans-2-butene at a collision energy of 97 kJ/mol. In this case, the symmetry of trans-2-butene allows for only one addition

Davis, H. Floyd

73

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

Code of Federal Regulations, 2010 CFR

...and Repeated Use Food Contact Surfaces § 177.1570...articles intended for use in contact with food subject to...Materials, 100 Barr Harbor Dr., West Conshohocken...Administration (NARA). For information on the availability...use in articles that contact food, and for...

2010-04-01

74

Investigation of the reaction of trimethylstannyl anionoids with 4-bromo-3,3-dimethyl-1-butene  

E-print Network

and 68% SN 2. The intrcduction of branching on the substrate did not appear to alter the mechanism for alkyl chlorides. No intermediates were trapped with either neopentyl or isobutyl chloride. Isobutyl bromide showed 3% while the icdide showed 54...) resulted in the reaction of (+)-2 ? bromooctane with Me3 SnLi (75%) and Ne3$nK (63%) than with Me3$nNa (56%). This trend 12 is not the normal monotonic one, which is Li, Na, K. A source of the difference may be attributed to the degree of aggregation...

Sanchez, Robert Michael

1985-01-01

75

Effect of molecular structure distribution on melting and crystallization behavior of 1-butene\\/ethylene copolymers  

Microsoft Academic Search

Short chain branching (SCB) and methylene sequence length (MSL) distributions were measured by TREF and DSC coupled with successive nucleation\\/annealing (SNA) for a Ziegler–Natta and a metallocene ethylene–butene copolymer. TREF analysis indicated that the copolymer made with Ziegler–Natta catalyst exhibited a broad bimodal SCB distribution, while the polymer made with the metallocene catalysts had a narrow SCB distribution. SNA-DSC analysis

M Zhang; D. T Lynch; S. E Wanke

2001-01-01

76

Catalytic cracking of 1-butene to propene and ethene on MCM-22 zeolite  

Microsoft Academic Search

Catalytic cracking of butene to propene and ethene was investigated over HMCM-22 zeolite. The performance of HMCM-22 zeolite was markedly influenced by time-on-stream (TOS) and reaction conditions. A rapid deactivation during the first 1h reaction, followed by a quasi-plateau in activity, was observed in the process along with significant changes in product distributions, which can be attributed to the fast

Xiangxue Zhu; Shenglin Liu; Yueqin Song; Sujuan Xie; Longya Xu

2005-01-01

77

Isotope effects and the temperature dependences of the hyperfine coupling constants of muoniated sec-butyl radicals in condensed phases.  

PubMed

Reported here is the first ?SR study of the muon (A(?)) and proton (A(p)) ?-hyperfine coupling constants (Hfcc) of muoniated sec-butyl radicals, formed by muonium (Mu) addition to 1-butene and to cis- and trans-2-butene. The data are compared with in vacuo spin-unrestricted MP2 and hybrid DFT/B3YLP calculations reported in the previous paper (I), which played an important part in the interpretation of the data. The T-dependences of both the (reduced) muon, A(?)?(T), and proton, A(p)(T), Hfcc are surprisingly well explained by a simple model, in which the calculated Hfcc from paper I at energy minima of 0 and near ±120° are thermally averaged, assuming an energy dependence given by a basic 2-fold torsional potential. Fitted torsional barriers to A(?)?(T) from this model are similar (~3 kJ/mol) for all muoniated butyl radicals, suggesting that these are dominated by ZPE effects arising from the C?Mu bond, but for A(p)(T) exhibit wide variations depending on environment. For the cis- and trans-2-butyl radicals formed from 2-butene, A(?)?(T) exhibits clear discontinuities at bulk butene melting points, evidence for molecular interactions enhancing these muon Hfcc in the environment of the solid state, similar to that found in earlier reports for muoniated tert-butyl. In contrast, for Mu?sec-butyl formed from 1-butene, there is no such discontinuity. The muon hfcc for the trans-2-butyl radical are seemingly very well predicted by B3LYP calculations in the solid phase, but for sec-butyl from 1-butene, showing the absence of further interactions, much better agreement is found with the MP2 calculations across the whole temperature range. Examples of large proton Hfcc near 0 K are also reported, due to eclipsed C?H bonds, in like manner to C?Mu, which then also exhibit clear discontinuities in A(p)(T) at bulk melting points. The data suggest that the good agreement found between theory and experiment from the B3LYP calculations for eclipsed bonds in the solid phase may be fortuitous. For the staggered protons of the sec-butyl radicals formed, no discontinuities are seen at all in A(p)(T), also demonstrating no further effects of molecular interactions on these particular proton Hfcc. PMID:21395224

Fleming, Donald G; Bridges, Michael D; Arseneau, Donald J; Chen, Ya Kun; Wang, Yan Alexander

2011-04-01

78

Sources of C2-C4 alkenes, the most important ozone nonmethane hydrocarbon precursors in the Pearl River Delta region.  

PubMed

Surface ozone is becoming an increasing concern in China's megacities such as the urban centers located in the highly industrialized and densely populated Pearl River Delta (PRD) region, where previous studies suggested that ozone production is sensitive to VOC emissions with alkenes being important precursors. However, little was known about sources of alkenes. Here we present our monitoring of ambient volatile organic compounds at four representative urban, suburban and rural sites in the PRD region during November-December 2009, which experienced frequent ozone episodes. C2-C4 alkenes, whose total mixing ratios were 11-20% of non-methane hydrocarbons (NMHCs) quantified, accounted for 38-64% of ozone formation potentials (OFPs) and 30-50% of the total hydroxyl radical (OH) reactivity by NMHCs. Ethylene was the most abundant alkene, accounting for 8-15% in total mixing ratios of NMHCs and contributed 25-46% of OFPs. Correlations between C2-C4 alkenes and typical source tracers suggested that ethylene might be largely related to vehicle exhausts and industry activities, while propene and butenes were much more LPG-related. Positive Matrix Factorization (PMF) confirmed that vehicle exhaust and liquefied petroleum gas (LPG) were two major sources that altogether accounted for 52-62%, 58-77%, 73-83%, 68-79% and 73-84% for ethylene, propene, 1-butene, trans-2-butene and cis-2-butene, respectively. Vehicle exhausts alone contributed 32-49% ethylene and 35-41% propene. Industry activities contributed 13-23% ethylene and 7-20% propene. LPG instead contributed the most to butenes (38-65%) and substantially to propene (23-36%). Extensive tests confirmed high fractions of propene and butenes in LPG then used in Guangzhou and in LPG combustion plumes; therefore, limiting alkene contents in LPG would benefit regional ozone control. PMID:25260169

Zhang, Yanli; Wang, Xinming; Zhang, Zhou; Lü, Sujun; Huang, Zhonghui; Li, Longfeng

2015-01-01

79

The synthesis and application of novel Ni(II) N-alkyl dipyridylaldiminato complexes as selective ethylene oligomerisation catalysts.  

PubMed

A series of N-alkyl 2,2'-dipyridylamine ligands of general formula (2-C5H3NR)2NR', (a): R = H, R' = Me; (b): R = H, R' = benzyl; (c): R = H, R' = methylcyclohexyl; (d): R = H, R' = neopentyl; (e): R = Me, R' = Me) were prepared by a modified method involving base-mediated N-alkylation with the respective alkyl halide. Reaction of the ligands, a-e, with NiCl2(DME) allowed for the isolation of ?-Cl Ni(ii) complexes: [Ni(?-Cl){a}Cl]2 (1a); [Ni(?-Cl){b}Cl]2 (1b); [Ni(?-Cl){c}Cl]2 (1c); [Ni(?-Cl){d}Cl]2 (1d) and [Ni(?-Cl){e}Cl]2 (1e). The complexes were characterised by FT-IR spectroscopy, magnetic susceptibility measurements, mass spectrometry, elemental analyses and in the case of 1a, SCD analysis. In the case of complex 1e, an acid-mediated hydrolysis process was identified. The product of hydrolysis, the protonated ligand and a tetrachloronickelate salt (1e-A), was characterised by SCD analysis. Activation of 1a-1e with alkyl aluminium reagents generated highly active catalysts for the oligomerisation of ethylene, with activities of up to 864 kgoligomers molNi(-1) h(-1) and high selectivity toward the formation of butenes. In general, trans 2-butene was observed as the major isomer, with the exception of 1e. In the case of 1e, the selectivity for 1-butene was 98%, thereby demonstrating the significant effect that the introduction of a low degree of steric pressure in the coordination sphere of the catalyst has on selectivity. PMID:24848302

Swarts, Andrew J; Mapolie, Selwyn F

2014-07-14

80

Degradation of chlorinated butenes and butadienes in granular iron columns.  

PubMed

Manufacturing facilities for production of chlorobutyl rubber have the potential to release a mixture of at least 5 chlorinated butenes and butadienes including trans-1,4-dichlorobutene-2 (1,4-DCB-2), 3,4-dichlorobutene-1 (3,4-DCB-1), 2,3,4-trichlorobutene-1 (TCB), 2-chlorobutadiene-1,3 (chloroprene) and 2,3-dichlorobutadiene-1,3 (DCBD) into groundwater environment. To evaluate the potential of using granular iron in the remediation of the above contaminants, a series of column experiments were conducted. Degradation of all 5 compounds followed pseudo-first-order kinetics. The three chlorinated butenes degraded much faster (surface area normalized half-lives, t(1/2)', ranged from 1.6 to 5.2 min m2/mL) than the 2 chlorinated butadienes (t(1/2)' ranged from 102 to 197 min m2/mL). All contaminants fully dechlorinated by granular iron to 1,3-butadiene as a common reaction intermediate that then degraded to a mixture of relatively non-harmful end products consisting of 1-butene, cis-2-butene, trans-2-butene and n-butane. Based on the kinetic data, product distributions, and chlorine mass balances, reaction pathways for these compounds are proposed. For the chlorinated butenes, 3,4-DCB-1 and TCB, undergo reductive beta-elimination reactions resulting in 1,3-butadiene and chloroprene intermediates. Dechlorination of 1,4-DCB-2 to 1,3-butadiene occurs through a reductive elimination similar to reductive beta-elimination. For dechlorination of the two chlorinated butadienes, chloroprene and DCBD, dechlorination occurs through a hydrogenolysis pathway. The common non-chlorinated intermediate, 1,3-butadiene, undergoes catalytic hydrogenation resulting in a mixture of butane isomers and n-butane. The results suggest that granular iron is an effective material for treatment of groundwater contaminated with these compounds. PMID:19847707

Hughes, Rodney; Gui, Lai; Gillham, Robert W

2009-10-01

81

Group 6 metal oxide-carbon aerogels. Their synthesis, characterization and catalytic activity in the skeletal isomerization of 1-butene  

Microsoft Academic Search

Group 6 metal–organic aerogels were prepared by polymerization of a resorcinol–formaldehyde mixture which contained metallic salts of the elements of this group. The aerogels prepared were carbonized both at 773 and 1273K to obtain the corresponding metal oxide–carbon aerogels. All these materials were characterized by different techniques including gas adsorption, mercury porosimetry, XRD, XPS and decomposition of isopropanol to determine

Carlos Moreno-Castilla; Francisco José Maldonado-Hódar; José Rivera-Utrilla; Enrique Rodr??guez-Castellón

1999-01-01

82

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

83

Vinyl hydrogen acidities of two stereoisomers.  

PubMed

The gas-phase acidities of the vinyl hydrogens of cis- and trans-2-butene were measured by the silane kinetic method in a Fourier-transform ion cyclotron resonance spectrometer. The acidities of ethene and the secondary vinyl hydrogen of propene were measured by the same method. The method was calibrated using the known acidities of methane and benzene. The vinyl hydrogens of trans-2-butene are more acidic than the vinyl hydrogens of cis-2-butene by 4.5 kcal/mol; the acidities of ethene and the secondary vinyl hydrogen of propene are between those of the two butenes. The acidity of cis-2-butene is 409 +/- 2 kcal/mol, and the acidity of trans-2-butene is 405 +/- 2 kcal/mol. Density functional theory calculations are in good agreement with the experiments. The results are discussed in terms of steric interactions, polarizabilities, dipole-dipole interactions, and charge-dipole interactions. PMID:17256827

Walthall, David A; Brauman, John I

2007-02-22

84

Effects of biomass burning on summertime nonmethane hydrocarbon concentrations in the Canadian wetlands  

NASA Technical Reports Server (NTRS)

Approximately 900 whole air samples were collected and assayed for selected C2-C10 hydrocarbons and seven halocarbons during the 5-week Arctic Boundary Layer Expedition (ABLE) 3B conducted in eastern Canadian wetland areas. In more than half of the 46 vertical profiles flown, enhanced nonmethane hydrocarbon (NMHC) concentrations attributable to plumes from Canadian forest fires were observed. Urban plumes, also enhanced in many NMHCs, were separately identified by their high correlation with elevated levels of perchloroethene. Emission factors relative to ethane were determined for 21 hydrocarbons released from Canadian biomass burning. Using these data for ethane, ethyne, propane, n-butane, and carbon monoxide enhancements from the literature, global emissions of these four NMHCs were estimated. Because of its very short atmospheric lifetime and its below detection limit background mixing ratio, 1,3-butadiene is an excellent indicator of recent combustion. No statistically significant emissions of nitrous oxide, isoprene, or CFC 12 were observed in the biomass-burning plumes encountered during ABLE 3B. The presence of the short-lived biogenically emitted isoprene at altitudes as high as 3000 m implies that mixing within the planetary boundary layer (PBL) was rapid. Although background levels of the longer-lived NMHCs in this Canadian region increase during the fire season, isoprene still dominated local hydroxyl radical photochemistry within the PBL except in the immediate vicinity of active fires. The average biomass-burning emission ratios for hydrocarbons from an active fire sampled within minutes of combustion were, relative to ethane, ethene, 2.45; ethyne 0.57; propane, 0.25; propene, 0.73; propyne, 0.06; n-butane, 0.09; i-butane, 0.01; 1-butene, 0.14; cis-2-butene, 0.02; trans-2-butene, 0.03; i-butylene, 0.07; 1,3-butadiene, 0.12; n-pentane, 0.05; i-pentane, 0.03; 1-pentene, 0.06; n-hexane, 0.05; 1-hexene, 0.07; benzene, 0.37; toluene, 0.16.

Blake, D. R.; Smith, T. W., Jr.; Chen, T.-Y.; Whipple, W. J.; Rowland, F. S.

1994-01-01

85

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

86

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

87

S0040-4039(96)00554-0 Tetrahedron Letters, Vol.37,No. 19,pp.3391-3394,1996  

E-print Network

2-BUTENE OZONIDE IN THK OZONATION OF TRANS-2-BUTENE IN THE GAS PHASE Radek Fajgara, Josef VitekaCentreforLightInducedProcesses,TheHebrewUniversityofJerusalem, 91904Jerusalem,Israel Abstract: GC/MS detection of secondary 2-butene ozonide in the gas-phase ozonation-butenes. The ozonation in the presence of oxygen at low pressures studied by photoionization mass

Haas, Yehuda

88

Olefin oxidation by cytochrome P-450: evidence for group migration in catalytic intermediates formed with vinylidene chloride and trans-1-phenyl-1-butene.  

PubMed

Oxidation of the carcinogen vinylidene chloride (VDC) by rat liver cytochrome P-450 (P-450) in microsomal and purified enzyme systems produced both ClCH2CO2H and Cl2CHCHO with concomitant suicide inactivation of three of the eight P-450 isozymes examined. The proposed intermediary role of VDC oxide in ClCH2CO2H and Cl2CHCHO production was evaluated by using chemical and kinetic studies. Aqueous decomposition of authentic VDC oxide, prepared by m-chloroperoxybenzoic acid oxidation of VDC and characterized by nuclear magnetic resonance (NMR) and mass spectrometry, failed to produce Cl2CHCHO and yielded ClCH2CO2H only at pH less than 2. Moreover, kinetic studies of VDC oxide production in the iodosobenzene-supported oxidation of VDC by P-450 did not support its proposed role as an obligate intermediate in the formation of ClCH2CO2H and Cl2CHCHO. [2,2-2H2]VDC was synthesized and found to be oxidized to Cl2C2HCO2H by microsomes supplemented with aldehyde dehydrogenase and NAD+, indicating transfer of deuterium in the formation of the precursor Cl2C2HC2HO. To test the hypothesis that the heme Fe(III) of P-450 acts as a Lewis acid in catalyzing the rearrangement of a transient epoxide intermediate to Cl2CHCHO, the decomposition of VDC oxide in the presence of Fe(III) was studied. While FeBr3-saturated CHCl3 effected approximately 50% rearrangement of epoxide to Cl2CHCHO, neither an equivalent concentration of (meso-tetraphenylporphyrinato)iron(III) chloride in CHCl3 nor highly purified cytochrome P-450 in aqueous buffer produced Cl2CHCHO from VDC oxide. Parallel studies using trans-1-phenylbutene 1,2-oxide, a stable model epoxide, indicated that, although binding of epoxide to P-450 did occur, ferric P-450 did not catalyze epoxide degradation.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6652073

Liebler, D C; Guengerich, F P

1983-11-22

89

Transferable Potentials for Phase Equilibria. 4. United-Atom Description of Linear and Branched Alkenes and Alkylbenzenes  

SciTech Connect

The Transferable Potentials for Phase Equilibria-United Atom (TraPPE-UA) force field for hydrocarbons is extended to alkenes and alkylbenzenes by introducing the following pseudo-atoms: CH{sub 2}(sp{sup 2}), CH(sp{sup 2}), CH(aro), R-C(aro) for the link to aliphatic side chains, and C(aro) for the link of two benzene rings. In this united-atom force field, the nonbonded interactions of the hydrocarbon pseudo-atoms are solely governed by Lennard-Jones 12-6 potentials, and the Lennard-Jones well depth and size parameters for the new pseudo-atoms were determined by fitting to the single-component vapor-liquid phase equilibria of a few selected model compounds. Configurational-bias Monte Carlo simulations in the NVT version of the Gibbs ensemble were carried out to calculate the single-component vapor-liquid coexistence curves for ethene, propene, 1-butene, trans- and cis-2-butene. 2-methylpropene, 1,5-hexadiene, 1-octene, benzene, toluene, ethylbenzene, propylbenzene, isopropylbenzene, o-, m-, and p-xylene, and naphthalene. The phase diagrams for the binary mixtures of (supercritical) ethene/n-heptane and benzene/n-pentane were determined from simulations in the NpT Gibbs ensemble. Although the TraPPE-UA force field is rather simple and makes use of relatively few different pseudo-atoms, its performance, as judged by comparisons to other popular force fields and available experimental data, is very satisfactory.

WICK,COLLIN D.; MARTIN,MARCUS G.; SIEPMANN,J. ILJA

2000-07-12

90

a Theoretical Study of Unsaturated Olefin Hydrogenation and Isomerization on Pd(111)  

NASA Astrophysics Data System (ADS)

The addition of hydrogen to the carbon-carbon double bond of 2-butenes adsorbed on Pd(111) was studied within the density functional theory (DFT) and using a periodic slab model. For that purpose, the Horiuti-Polanyi mechanisms for both complete hydrogenation and isomerization were considered. The hydrogenation of cis and trans-2-butene to produce butane proceeds via the formation of eclipsed and staggered-2-butyl intermediates, respectively. In both cases, a relatively high energy barrier to produce the half-hydrogenated intermediate makes the first hydrogen addition the slowest step of the reaction. The competitive production of trans-2-butene from cis-2-butene requires the conversion from the eclipsed-2-butyl to the staggered-2-butyl isomer. As the corresponding energy barrier is relatively small and because the first of these isomers is less stable than the second, an easy conversion is predicted.

Belelli, Patricia G.; Castellani, Norberto J.

91

Production of hydrogen peroxide and organic peroxides in the gas phase reactions of ozone with natural alkenes  

SciTech Connect

The formation of H{sub 2}O{sub 2} and organic peroxides in the reaction of O{sub 3} with trans-2-butene and naturally occurring alkenes has been studied using a 31 m{sup 3} reaction chamber. H{sub 2}O{sub 2} and organic peroxides were found to be products of the O{sub 3} reaction with trans-2-butene, isoprene, {alpha} and {beta}-pinene, and limonene. Water is necessary for the formation of H{sub 2}O{sub 2} and most of the H{sub 2}O{sub 2} is formed via a route that does not involve HO{sub 2} radicals. These results indicate that the reaction of O{sub 3} with natural alkenes may be a significant source of atmospheric H{sub 2}O{sub 2}, particularly in forest and rural areas.

Simonaitis, R.; Olszyna, K.J.; Meagher, J.F.

1991-01-01

92

Influence of process variables on the continuous alkylation of isobutane with 2-butene on superacid sulfated zirconia catalysts  

Microsoft Academic Search

Two sulfated zirconia catalysts have been prepared by impregnation of zirconium hydroxide with HâSOâ 0.3 N and 1 N. Both samples showed superacid sites as shown by a desorption temperature peak in the NHâ TPD at ca. 813 K. The activity and selectivity of these catalysts have been studied for the alkylation of isobutane with trans-2 butene in a computer-controlled

A. Corma; A. Martinez; C. Martinez

1994-01-01

93

Kinetic analysis of isobutane\\/butene alkylation over ultrastable H-Y zeolite  

Microsoft Academic Search

The alkylation of isobutane with trans-2-butene over ultrastable Y-type zeolites has been studied. It is well-known that this reaction is accompanied by a rapid deactivation of the catalyst. The objective of this study is to elucidate the route to catalyst deactivation so that the means of mitigating this problem can be identified. Using the initial reaction rate data, evidence has

Michael F. Simpson; James Wei; Sankaran Sundaresan

1996-01-01

94

Mono(cyclopentadienyl)titanium(II) Complexes with Hydride, Alkyl, and Tetrahydroborate Ligands: Synthesis, Crystal Structures, and  

E-print Network

to 1-butene; subsequent coupling reactions of 1-butene with ethylene gives the ethylene trimers 2-ethyl-1-butene and 3-methyl-1-pentene. The product distribution most strongly supports a coupling for the dimerization of ethylene to 1-butene are titanium(II) centers. Introduction Heterogeneous Ziegler

Girolami, Gregory S.

95

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

Microsoft Academic Search

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

Hin-Koon Woo

2004-01-01

96

Ionization efficiencies of C 3H 6, C 4H 8, C 6H 12, C 2H 6O, and C 3H 8O isomers  

NASA Astrophysics Data System (ADS)

Ionization efficiencies of 14 organic compounds have been measured in the wavelength region from 105 to 134nm using an ionization chamber. The compounds examined are cyclopropane, propylene, l-butene, isobutene, cis-and trans-2-butenes, cyclohexane, 1-hexane, tetramethylethylene, ethyl alcohol, dimethyl ether, n-, and iso-propyl alcohol, and ethyl methyl ether. The ionization efficiencies of cyclopropane and cyclohexane monotonically increase with increasing photon energy, but those for the others show a peak or a shoulder in the wavelength region of the present work.

Koizumi, H.; Shinsaka, K.; Yoshimi, T.; Hironaka, K.; Arai, S.; Ukai, M.; Morita, M.; Nakazawa, H.; Kimura, A.; Hatano, Y.; Ito, Y.; Zhang, Y.; Yagishita, A.; Ito, K.; Tanaka, K.

97

Fluid inclusion volatile analysis by gas chromatography with photoionization micro-thermal conductivity detectors: Applications to magmatic MoS 2 and other H 2O-CO 2 and H 2O-CH 4 fluids  

NASA Astrophysics Data System (ADS)

Eighteen fluid inclusion volatile peaks have been detected and identified from 1-2 g samples (quartz) by gas chromatography using heated (~105°C) on-line crushing, helium carrier gas, a single porous polymer column (HayeSep R; 10' × 1/8?: 100/120#; Ni alloy tubing), two temperature programme conditions for separate sample aliquots, micro-thermal conductivity (TCD) and photoionization detectors (PID; 11.7 eV lamp), and off-line digital peak processing. In order of retention time these volatile peaks are: N 2, Ar, CO, CH 4, CO 2, C 2H 4, C 2H 6, C 2H 2, COS, C 3H 6, C 3H 8, C 3H 4 (propyne), H 2O (22.7 min at 80°C), SO 2, ± iso- C4H10 ± C4H8 (1-butene) ± CH3SH, C 4H 8 (iso-butylene), (?) C 4H 6 (1,3 butadiene) and ± n- C4H10 ± C4H8 (trans-2-butene) (80 and -70°C temperature programme conditions combined). H 2O is analysed directly. O 2 can be analysed cryogenically between N 2 and Ar, but has not been detected in natural samples to date in this study. H 2S, SO 2, NH 3, HCl, HCN, and H 2 ca nnot be analysed at present. Blanks determined by crushing heat-treated Brazilian quartz (800-900°C/4 h) are zero for 80°C temperature programme conditions, except for a large, unidentified peak at ~64 min, but contain H 2O, CO 2, and some low molecular weight hydrocarbons at -70°C temperature conditions due to cryogenic accumulation from the carrier gas and subsequent elution. TCD detection limits are ~30 ppm molar in inclusions; PID detection limits are ~ 1 ppm molar in inclusions and lower for unsaturated hydrocarbons (e.g., ~0.2 ppm for C 2H 4; ~ 1 ppb for C 2H 2; ~0.3 ppb for C 3H 6). Precisions (1?) are ~ ±1-2% and ~ ± 13% for H 2O in terms of total moles detected; the latter value is equivalent to ±0.6 mol% at the 95 mol% H 2O level. Major fluid inclusion volatile species have been successfully analysed on a ~50 mg fluid inclusion section chip (~7 mm × ~10 mm × ~100 ?m). Initial inclusion volatile analyses of fluids of interpreted magmatic origin from the Cretaceous Boss Mtn. monzogranite stock-related MoS 2 deposit, central British Columbia of ~97 mol% H 2O, ~3% CO 2, ~ 140-150 ppm N 2, and ~16-39 ppm CH 4 (~300-350°C) are reasonable in comparison with high temperature (~400-900°C) volcanic gas analyses from four, active calc-alkaline volcanoes; e.g., the H 2O contents of volcanic gases from the White Island (New Zealand), Mount St. Helens (Washington, USA), Merapi (Bali, Indonesia), and Momotombo (Nicaragua) volcanoes are 88-95%, >90% (often >95%), 88-95% and ~93%, respectively; CO 2 contents are ~3-10%, 1-10%, 3-8%, and ~3.5%. CO 2/N 2 ratios for the Boss Mtn. MoS 2 fluids of ~ 190-220 are in the range for known volcanic gas ratios (e.g., ~ 150- 240; White Island). The ?S content of the Boss Mtn. MoS 2 fluid prior to S loss by sulphide precipitation may have been ~2 mol% since CO 2/?S molar ratios of analysed high-temperature volcanic gases are ~ 1.5. This estimate is supported by ?S contents for White Island, Merapi and Momotombo volcanic gases of ~2%, ~0.5-2.5%, and ~2%. COS has been determined in H 2O-CO 2 fluid inclusions of interpreted magmatic origin from the Boss Mtn. MoS 2 deposit and the Tanco zoned granitic pegmatite, S.E. Manitoba at ~50-100 ppm molar levels, which are consistent with levels in volcanic gases. It appears that low, but significant, concentrations of C 2-C 4 alkanes (~ 1-20 ppm), C 2-C 4 alkenes (~ 1-480 ppb) and alkynes (e.g., C 3H 4) have been detected in magmatically derived fluids (Boss Mtn. MoS 2 deposit; Tanco granitic pegmatite). Significantly higher, low molecular weight hydrocarbon concentrations have been determined in a CH 4-rich (~ 2%), externally derived fluid of possible metamorphic or deep crustal origin trapped as inclusions in metasomatic wall-rock tourmaline adjacent to the Tanco pegmatite (e.g., 300/470 ppm C 2H 6; 50/90 ppm C 3H 8; 3-60 ppm C 2H 4/C 3H 6 n-C 4H 10).

Bray, C. J.; Spooner, E. T. C.

1992-01-01

98

Simultaneous analysis of butene isomer mixtures using process mass spectrometry.  

PubMed

The feasibility of simultaneous analysis of mixtures containing two to four butene isomers and up to six total components using process mass spectrometry is assessed. As for typical (nonisomeric) applications of process mass spectrometry, simultaneous analysis is based on the assumption that the electron ionization mass spectra of mixtures are linear combinations of the spectra of the individual constituents. Limits of detection for binary isomer mixtures are on the order of 0.1% to 10%, limited by the ability to distinguish small differences between similar spectra. As spectral and mixture complexity increase, both accuracy and precision decrease. Not surprisingly the similarity of the spectra of stereoisomers cis- and trans-2-butene is greater than that of the other (nonstereoisomeric) isomer pairs, and mixtures containing both cis- and trans-2-butene are the most difficult to quantitate. However, even for mixtures of all four butenes, accuracy (root-mean-square error = 2.43%), precision (average coefficient of variation = 6.72%), and linearity (correlation coefficient of a plot of measured versus actual concentration r2 = 0.985 +/- 0.002) are reasonably good. PMID:11118115

Bennett, K H; Cook, K D; Seebach, G L

2000-12-01

99

Photochemical sources of organic acids. 1. Reaction of ozone with isoprene, propene, and 2-butenes under dry and humid conditions using SPME.  

PubMed

Formation of C4 and smaller carboxylic acids from gas-phase ozonolysis of several alkenes under dry (relative humidity (RH) < 1%) and humid (RH = 65%) conditions have been investigated. We have developed a technique based on solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) to quantify the acids, as well as other products, and applied it to the reactions of ozone with propene, trans-2-butene, 2,3-dimethyl-2-butene, and isoprene. Acetic acid yields from propene and trans-2-butene ozonolysis in the presence of an OH scavenger were 2.7 +/- 0.6 and 2.9 +/- 0.6%, respectively, under dry conditions and 1.8 +/- 0.4 and 2.3 +/- 0.5% at 65% RH. Isoprene ozonolysis produced methacrylic and propenoic acids with yields of 5.5 +/- 1 and 3.0 +/- 1%, under dry conditions and 4.1 +/- 1 and 1.5 +/- 0.3% under wet conditions, respectively. That water inhibits acid formation indicates that the water reaction with stabilized Criegee intermediates is at most a minor source of acids. Acids that may form as coproducts of the OH radical elimination pathway, acetic acid from 2,3-dimethylbutene and isoprene, and propenoic acid from isoprene were also observed with significant yields (up to 10%), although the production of acetic acid was not a linear function of the alkene reacted. Carbonyl products are also reported. PMID:16839060

Orzechowska, Grazyna E; Paulson, Suzanne E

2005-06-23

100

The Effect of Supercritical Fluids on Solid Acid Catalyst Alkylation  

SciTech Connect

The alkylation of isobutane with trans-2-butene was explored over six solid acid catalysts in the liquid, near-critical liquid, and supercritical regions through the addition of an inert cosolvent to the reaction feed mixture. The addition of supercritical cosolvents did not result in sustained catalytic alkylation activity. A modest improvement in product yield was obtained with the addition of methane in the modified-liquid region; however, catalyst longevity and product selectivity were decreased compared to cosolvent-free liquid conditions. This paper describes the catalyst screening and selection process, an exploration of catalyst performance with varying concentrations of methane, and an examination of the effects of seven supercritical fluids on catalyst performance. The catalysts included two zeolites, two sulfated metal oxides, and two Nafion catalysts. Three hydrocarbons, two fluorocarbons, carbon dioxide, and sulfur hexafluoride were explored as inert cosolvents added to the reaction mixture.

Ginosar, Daniel Michael; Thompson, David Neil; Burch, Kyle Coates; Zalewski, D. J.

2002-05-01

101

Use of propane as a quench gas in argon-filled proportional counters and comparison with other quench gases  

NASA Technical Reports Server (NTRS)

An experimental investigation of propane and six other quench gases was carried out in argon-filled proportional counters. The objective of the study was to find the best gas mixture for optimizing the gas gain and the energy resolution as well as to understand the role of the ionization potential of quench gases in determining these parameters. It was found that the best gas gains and energy resolutions are obtained with propane, ethane, and isobutane in that order. The ionization potentials of these three lie below the argon metastable potentials and have the lowest value of resonance defect compared to the other quench gases. The better results obtained with these mixtures can be explained by an increased ionization yield resulting from the Penning effect. Propylene and trans-2-butene give inferior performance compared to the above three gases. Methane and carbon dioxide, the most commonly used quench gases in the argon-filled detectors, provide the worst results.

Agrawal, P. C.; Ramsey, B. D.

1988-01-01

102

Vibrational C-H overtone spectroscopy and bond distances of butenes dissolved in liquid Xe  

NASA Astrophysics Data System (ADS)

Vibrational overtone spectra of isobutene, cis-2-butene, and trans-2-butene dissolved in liquid xenon at 163 K, have been recorded between 5000 and 16500 cm -1. Spectral regions for the first four overtones were measured using a Fourier transform spectrophotometer. The fifth overtone (? ? = 6) spectra were recorded with a double beam (pump-probe) thermal lens technique. Band deconvolution allowed isolation of individual transitions. Local-mode parameters were calculated for C-H oscillators in solution and compared with gas phase local-mode parameters. Density functional theory calculations were done to obtain C-H bond lengths and vibrational frequencies for the three butene isomers. Frequency shifts (? ?) with respect to gas phase results are attributed to changes in harmonic frequency and anharmonicity of the particular C-H bond of the sample dissolved in the inert liquid solvent.

Lopez-Calvo, Alfredo; Diez-y-Riega, Helena; Manzanares, Carlos E.

2009-10-01

103

Intensities of CH-stretching overtones in 2-butenes  

NASA Astrophysics Data System (ADS)

The gas phase vibrational overtone spectra of trans-2-butene and cis-2-butene are recorded in the ??CH=1-6 regions by Fourier transform infrared and conventional near infrared-visible spectroscopy. Overtone spectra in the ??CH=5-9 regions are recorded by intracavity dye/titanium: sapphire laser photoacoustic spectroscopy. Absolute oscillator strengths are obtained from the conventional spectra. Oscillator strengths are calculated with a harmonically coupled anharmonic oscillator local mode model and ab initio dipole moment functions. The experimental and calculated oscillator strengths are compared. Spectral absorptions that are not due to transitions to pure local mode states or to local mode combination states, are observed in the spectra of both molecules, and are believed to be due to absorptions that involve methyl group torsion.

Turnbull, David M.; Kjaergaard, Henrik G.; Henry, Bryan R.

1995-06-01

104

Introduction In this era of heightened environmental awareness and the  

E-print Network

the most attention, since the product 3-aryl-1-butenes are potential intermediates for widely used 2, the reaction is complicated by isomerization of the initially formed 3-aryl-1- butene (1) to a mixture of the Z- and E-2-aryl-2-butenes (2) and oligomerization of the starting olefins [Eq. (1)]. The best H3C Ar Ar CH3

RajanBabu, T. V. "Babu"

105

Tetrahedron Letters,Vo1.24,No.42,pp 4551-4554,1983 0040-4039/83 $3.00 + .OO Printed in Great Britain 01983 Pergamon Press Ltd.  

E-print Network

Britain 01983 Pergamon Press Ltd. ADDITIONOF l-METHOXY-l-BUTEN-3-YNE TO LACTONES: SYNTHESIS OF SUBSTITUTED for the preparation of a variety of substituted spiroketals from lactones and l- methoxy-1-buten-3-yne has been describe here a method for the preparation of several systems similar to 1 from l- methoxy-1-buten-3-yne g4

106

Figure S1. The 17-monitor-average daily maximal 8-hour O3 in the Houston metropolitan area during July-October in both 2000 and 2006; the time periods of the two TexAQS are marked by  

E-print Network

_all n_butane_all 1_butene_all t_2_butene_all c_2_butene_all 1_3_butandiene_all cyclopentane_all cyclopentene_all isopentane_all n_pentane_all 1_pentene_all t_2_pentene_all c_2_pentene_all 3_methyl_1_butene_all 2_methyl_2_butene_all 2_methyl_1_butene_all isoprene_all n_hexane_all 2_methyl_pentane_all 3_methyl

Meskhidze, Nicholas

107

IieprinreC frorn (irgantitnetaiiics.198{i,5, 1,1;:1. the Ar-rrerii.aii(-'hgmicil Societv arrd reprirtterl irr';rerntiisir,;tof the cr;p1'righttiwner.  

E-print Network

include (Z)- and (E)-2-butenes,t.itrtadiene,n-butane, and cyclopentene. f)ecomposition is tlrst order in l tricyclopentylphosphine into the 1-butene and probably involves initial cyclometalation. This latter processmay

Prentiss, Mara

108

Hydrocarbon conversion process  

SciTech Connect

1. A combination process is described for producing high octane blending components for gasolines which consists of (a) contacting a mixture of methanol and an olefinic C/sub 4/ cut comprising isobutene, 1-butene, and 2-butenes under etherification conditions to produce methyltertiarybutyl ether and unreacted C/sub 4/ olefinic hydrocarbons, (b) contacting the unreacted C/sub 4/ olefinic hydrocarbons with a molecular sieve to selectively adsorb 2-butenes leaving a stream comprising 1-butene, (c) subjecting at least a portion of the 1-butene stream to skeletal isomerization to form isobutene, (d) subjecting the remainder of the 1-butene stream to double bond isomerization to form 2-butenes, and (e) passing the 2-butenes formed by isomerization and an isoparaffin to alkylation to form alkylate.

Hutson, T. Jr.; Hann, P.D.

1986-04-08

109

Tunable phosphinite, phosphite and phosphoramidite ligands for the asymmetric hydrovinylation reactions  

E-print Network

lead to isomerization of the primary products (3-arylbutenes) to Z- and E-2-aryl-2-butenes. In a prototypical synthesis of a 2-arylproionic acid, (S)-3-(4-bromophenyl)-1-butene (89% ee) has be transformed

RajanBabu, T. V. "Babu"

110

Z .Synthetic Metals 100 1999 195204 Microstructure and electrochemical properties of some synthetic carbons  

E-print Network

-based polymers: poly Z -1-methoxy-4- x w Z . x Z . w Z . x w Z .phenyl-1-buten-3-yne -750 poly MPB EY -750 , poly 1,4-diphenyl-1-buten-3-yne -750 poly DPBEY -750 , poly 5- 2-pyridyl -2,4-pen- x w Z . x Z . Z,2-selective poly- Z . wZ .AbbreÃ?iations: Poly MPBEY -750, poly Z -1-methoxy-4-phenyl-1- x Z . Z .buten-3-yne

Kwak, Juhyoun

111

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

Microsoft Academic Search

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,

J. B. Bloys; R. F. Morgan

1993-01-01

112

Conjugation of isoprene monoepoxides with glutathione, catalyzed by ?, ?, ? and ?-class glutathione S-transferases of rat and man  

Microsoft Academic Search

In the present study, the enzymatic conjugation of the isoprene monoepoxides 3,4 epoxy-3-methyl-1-butene (EPOX-I) and 3,4-epoxy-2-methyl-1-butene (EPOX-II) with glutathione was investigated, using purified glutathione S-transferases (GSTs) of the ?, ?, ? and ?-class of rat and man. HPLC analysis of incubations of EPOX-I and EPOX-II with [35S]glutathione (GSH) showed the formation of two radioactive fractions for each isoprene monoepoxide. The

Jan J. P Bogaards; Joke C Venekamp; Florence G. C Salmon; Peter J van Bladeren

1999-01-01

113

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

114

The use of conditional probability functions and potential source contribution functions to identify source regions and advection pathways of hydrocarbon emissions in Houston, Texas  

NASA Astrophysics Data System (ADS)

In this study, we demonstrate the utility of conditional probability functions (CPFs), potential source contribution functions (PSCFs), and hierarchical clustering analysis (HAC) to identify the source region and transport pathways of hydrocarbons measured at five photochemical assessment monitoring stations (PAMS) near the Houston Ship Channel from June to October 2003. In contrast to scatter plots, which only show the pair-wise correlation of species, commonality in CPF figures shows both correlation and information on the source region of the species in question. In this study, we use over 50 hourly volatile organic compound (VOC) concentrations and surface wind observations to show that VOCs with similar CPF patterns likely have common transport pathways. This was established with the multivariate technique, which uses the hierarchical clustering analysis to define clusters of VOCs having similar CPF patterns. This method revealed that alkenes, and in particular those with geometric isomers such as cis-/ trans-2-butene and cis-/ trans-2-pentene, have similar CPF patterns and hence, a common area of origin. The alkane isomers often show CPF patterns among themselves, and similarly, aromatic compounds often show similar patterns. We also show how calculated trajectory information can be used in the PSCF analysis to produce a graphic picture that identifies specific geographic areas associated with a given VOC (or other pollutant). The use of these techniques in the chemically and meteorologically complex environment of Houston, Texas, suggests its further utility in other areas with relatively simpler conditions.

Xie, Yulong; Berkowitz, Carl M.

115

The Use of Conditional Probability Functions and Potential Source Contribution Functions to Identify Source Regions and Advection Pathways of Hydrocarbon Emissions in Houston, Texas  

SciTech Connect

In this study, we demonstrate the utility of conditional probability functions (CPFs), potential source contribution functions (PSCFs), and hierarchical clustering analysis to identify the source region and transport pathways of hydrocarbons measured at five photochemical assessment monitoring stations (PAMS) near the Houston ship channel from June to October 2003. Over 50 volatile organic compound (VOC) concentrations were measured on the hourly collected samples. Routine surface observations of wind directions measured at each of the receptor sites were used extensively. We show that VOCs with similar CPF patterns likely have common transport pathways. This was established with the multivariate technique, which uses the hierarchical clustering analysis to allow clusters of groups of VOCs to form with similar CPF patterns. This method revealed that alkenes, and in particular those with geometric isomers such as cis-/trans-2-butene and cis-/trans-2-pentene, have similar CPF patterns. The alkane isomers often show CPF patterns among themselves, and similarly, aromatic compounds often show similar patterns among themselves too. We also show how trajectory information can be used in conjunction with the PSCF analysis to produce a graphic analysis suggesting specific source areas for a given VOC. The use of these techniques in the chemically and meteorologically complex environment of Houston, Texas, suggests its further utility in other areas with relatively simpler conditions.

Xie, YuLong; Berkowitz, Carl M.

2007-09-01

116

Theoretical elucidation of the origins of substituent and strain effects on the rates of Diels-Alder reactions of 1,2,4,5-tetrazines.  

PubMed

The Diels-Alder reactions of seven 1,2,4,5-tetrazines with unstrained and strained alkenes and alkynes were studied with quantum mechanical calculations (M06-2X density functional theory) and analyzed with the distortion/interaction model. The higher reactivities of alkenes compared to alkynes in the Diels-Alder reactions with tetrazines arise from the differences in both interaction and distortion energies. Alkenes have HOMO energies higher than those of alkynes and therefore stronger interaction energies in inverse-electron-demand Diels-Alder reactions with tetrazines. We have also found that the energies to distort alkenes into the Diels-Alder transition-state geometries are smaller than for alkynes in these reactions. The strained dienophiles, trans-cyclooctene and cyclooctyne, are much more reactive than unstrained trans-2-butene and 2-butyne, because they are predistorted toward the Diels-Alder transition structures. The reactivities of substituted tetrazines correlate with the electron-withdrawing abilities of the substituents. Electron-withdrawing groups lower the LUMO+1 of tetrazines, resulting in stronger interactions with the HOMO of dienophiles. Moreover, electron-withdrawing substituents destabilize the tetrazines, and this leads to smaller distortion energies in the Diels-Alder transition states. PMID:25041719

Liu, Fang; Liang, Yong; Houk, K N

2014-08-13

117

An extended baseline examination of indoor VOCs in a city of low ambient pollution: Perth, Western Australia  

NASA Astrophysics Data System (ADS)

This study of indoor air quality reports VOC concentrations in 386 suburban homes located in Perth Western Australia, a city of low ambient pollution and temperate climate. Details of indoor VOC concentrations, temperature, relative humidity, and information on house characteristics and occupant activities were collected during the sampling periods. The concentration of VOCs observed in typical homes was low and individual compounds rarely exceeded 5 ?g m-3. Median individual VOC concentrations ranged from 0.06 ?g m-3 for 1,1,1 trichloroethane and butyl ether to 26.6 ?g m-3 for cis/trans 2-butene. Recently renovated homes had higher concentrations of VOCs than non renovated homes, including ?VOCs (p = 0.026), ?BTEX (p = 0.03), ?xylene (p = 0.013), toluene (p = 0.05), cyclohexane (p = 0.039), and propyl benzene (p = 0.039). Statistical analyses showed house age and attached garages were not significant factors for any of the VOCs tested. The concentrations of indoor VOCs in Perth were lower than overseas observations and those reported in recent Australian studies, with inferences made to differences in the climate and the occupant behaviour. The results are a baseline profile of indoor VOCs over the period 2006-2011, in an Australian city of low population density and of generally low ambient pollution.

Maisey, S. J.; Saunders, S. M.; West, N.; Franklin, P. J.

2013-12-01

118

The deposition rate dependence of plasma polymerization on the radius of curvature of the substrate  

NASA Astrophysics Data System (ADS)

In the plasma polymerization deposition of CH/sub x/ onto microspherical Inertial Fusion targets we have found that the coating rate varies with substrate diameter. Spherical shells ranging in diameter from 100 to 1000 microns were coated with several microns of plasma polymerized trans-2-butene under identical conditions and their coating thicknesses measured interferometrically. We found that the coating rate variation with shell radius could be described by an equation having the form dr/dt = A/(R + r) + B where dr/dt is the coating rate, R the initial sphere radius, r the coating thickness, and A and B parameters related to the plasma conditions. We also found that there exists a functional relationship between the parameters A and B which is dependent on the RF power density. A model has been developed to show how this observed rate dependence relates to the buildup of an electrical charge on the nonconducting substrate surface. The electric field which arises is dependent on the radius of curvature of the substrate and in turn affects the contribution to the film growth by the ionized species impinging upon the surface. Neutral species arriving at the surface are not affected and thus lead to the B term in the empirical form of the rate dependence.

Lintz, H. K.; Murrell, S. R.; Crawley, R. L.; Daukas, J. C.

119

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

120

A sputtering derived atomic oxygen source for studying fast atom reactions  

NASA Technical Reports Server (NTRS)

A technique for the generation of fast atomic oxygen was developed. These atoms are created by ion beam sputtering from metal oxide surfaces. Mass resolved ion beams at energies up to 60 KeV are produced for this purpose using a 150 cm isotope separator. Studies have shown that particles sputtered with 40 KeV Ar(+) on Ta2O5 were dominantly neutral and exclusively atomic. The atomic oxygen also resided exclusively in its 3P ground state. The translational energy distribution for these atoms peaked at ca 7 eV (the metal-oxygen bond energy). Additional measurements on V2O5 yielded a bimodal distribution with the lower energy peak at ca 5 eV coinciding reasonably well with the metal-oxygen bond energy. The 7 eV source was used to investigate fast oxygen atom reactions with the 2-butene stereoisomers. Relative excitation functions for H-abstraction and pi-bond reaction were measured with trans-2-butene. The abstraction channel, although of minor relative importance at thermal energy, becomes comparable to the addition channel at 0.9 eV and dominates the high-energy regime. Structural effects on the specific channels were also found to be important at high energy.

Ferrieri, Richard A.; Yung, Y. Chu; Wolf, Alfred P.

1987-01-01

121

Moessbauer spectra of ferrite catalysts used in oxidative dehydrogenation  

NASA Technical Reports Server (NTRS)

Room temperature Mossbauer spectroscopy was used to examine bulk changes which occur in low surface area CoFe2O4 and CuFe2O4 catalysts as a result of contact with various mixtures of trans-2-butene and O2 during oxidative dehydrogenation reactions at about 420 C. So long as there was at least some O2 in the gas phase, the CoFe2O4 spectrum was essentially unchanged. However, the spectrum changed from a random spinel in the oxidized state to an inverse spinel as it was reduced by oxide ion removal. The steady state catalyst lies very near the fully oxidized state. More dramatic solid state changes occurred as the CuFe2O4 underwent reduction. Under severe reduction, the ferrite was transformed into Cu and Fe3O4, but it could be reversibly recovered by oxidation. An intense doublet located near zero velocity persisted in all spectra of CuFe2O4 regardless of the state of reduction.

Cares, W. R.; Hightower, J. W.

1971-01-01

122

Reactions of alkenes on lanthana  

SciTech Connect

Reactions of ethene, propene, butenes, 2-methylpropene, cyclopentene, 2,3-dimethylbut-1-ene, and 3,3-dimethylbut-1-ene have been studied with hydrogen, and sometimes deuterium, on lanthana catalysts. Many alkene/lanthana systems show evidence of self-poisoning which is more marked with straight-chain hydrocarbons than with branched hydrocarbons and at higher temperatures; the catalysts are also highly sensitive to impurities. The temperature required to attain a fixed rate of hydrogenation (10/sup 16/ molecules s/sup -1/ m/sup -2/) varied from 220 K for ethene to over 373 K for the 2,3-dimethylbutenes. Fast hydrogenation without accompanying deuterium exchange was observed with alkenes which cannot form allylic species. The ability to form such species led to rapid isomerization of the butenes below 273 K and of 2-3-dimethylbut-1-ene at 373 K, and to exchange rates with deuterium which were comparable to (propene) or faster than (2-methylpropene) addition reactions at 380 K. Deuterium NMR spectroscopy was used for analysis of the products from the reactions with deuterium. Although the hydrogenation of 3,3-dimethylbut-1-ene occurred readily at 245 K, no isomerization was detected even at 510 K.

Bird, R.; Kemball, C.; Leach, H.F.

1987-05-01

123

Hydrogenation of lower alkenes and conjugated diene catalyzed by Ga2O3  

NASA Astrophysics Data System (ADS)

Hydrogenation of lower alkenes such as ethylene, propylene, and 1-butene proceeded over gallium oxide (Ga2O3). The rate of the hydrogenation was faster in the order of ethylene ? propylene > 1-butene over Ga2O3. Ga2O3 also showed the activity for hydrogenation of 1,3-butadiene where 1,4-addition of hydrogen to 1,3-butadiene mainly took place to give 2-butenes as main products. The formation rate of hydrogenated products depended on the amounts of H2 and alkenes adsorbed on Ga2O3. This implies that the hydrogenation proceeds on the basis of the Langmuir-Hinshelwood mechanism.

Shishido, Tetsuya; Kuno, Hirotaka; Teramura, Kentaro; Tanaka, Tsunehiro

2012-06-01

124

Novel multimetallic hydroisomerization catalysts  

SciTech Connect

Recent work in this laboratory with supported multimetallic catalysts has resulted in the discovery of a class of catalysts with unique selectivity and activity for the hydroisomerization of 1-butene, as well as the hydrogenation of butadiene. Specifically, it was found that catalysts particles are composed of three metallic components, one from the third row of the periodic table, one from the first row of rare earths, and a platinum group metal, have higher activity and are far more selective for 1-butene isomerization than any single metal catalyst, including commercial catalysts widely used for selective hydrogenation. 19 refs., 3 figs., 2 tabs.

Not Available

1994-04-01

125

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

126

Role of rare earth cations in Y zeolite for hydrocarbon cracking.  

PubMed

Reaction kinetics data were collected for isobutane conversion over a series of ultra stable Y (USY) zeolite catalysts with and without rare earth cations and subjected to various extents of dealumination by steaming. We conducted these reaction studies at low temperatures (523-573 K) using isobutane feed streams containing known levels of isobutylene (100-400 ppm) so that the kinetics were controlled by bimolecular hydride transfer and oligomerization/beta-scission processes with little or no participation of monomolecular initiation reactions. These experimental conditions led to stable catalyst performance with the main products of isobutane conversion being propane, n-butane, and isopentane, with smaller amounts of propylene, trans-2-butene, and cis-2-butene. The rates of formation of these products per Brønsted acid site (as counted by pyridine adsorption) depended exponentially on Brønsted acid site density, regardless of whether the catalyst contained rare earth cations. Kinetic modeling showed an exponential dependence of hydride transfer and oligomerization/ beta-scission reaction rates on Brønsted acid site density which translated into composite activation energies for these reactions having a linear relationship with site density. Based on results in the literature from theoretical calculations, we suggest that increasing Brønsted acid site density in zeolite Y leads to larger zeolite elasticity, increased stabilization of cationic transition states, and lower composite activation barriers for hydride transfer and beta-scission steps. The role of rare earth cations, therefore, is to ensure the retention of high Brønsted acid site density under hydrothermal conditions, such as in fluid catalytic cracking (FCC) regenerators, where steam would dealuminate the Y zeolite framework and reduce this site density. It is for this reason that hydride transfer reaction rates are high in the presence of rare earth cations and lead to higher yields of less olefinic gasoline during FCC. PMID:16851208

Sanchez-Castillo, Marco A; Madon, Rostam J; Dumesic, James A

2005-02-17

127

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

128

Kinetics of the gas-phase reactions of NO/sub 3/ radicals with a series of dialkenes, cycloalkenes, and monoterpenes at 295 +/- 1 K  

SciTech Connect

Rate constants for the gas-phase reactions of the NO/sub 3/ radical, an important reactive constituent of nighttime ambient atmospheres, have been determined for the first time for a series of dialkenes, cycloalkenes, and monoterpenes by using a relative rate technique. By use of a rate constant for the reaction of NO/sub 3/ radicals with trans-2-butene of (2.11 +/- 0.24) x 10 /sup -13/ cm/sup 3/ molecule /sup -1/s/sup -1/, the rate constants obtained at 295 +/- 1 K were the following (in cm/sup 3/ molecule/sup -1/s/sup -1/ units): 1,3-butadiene, (5.34 +/- 0.62) x 10/sup -14/; isoprene, (3.23 +/- 0.38) x 10/sup -13/; cyclohexene, (2.87 +/- 0.34) x 10/sup -13/; 1,3-cyclohexadiene, (7.2 +/- 1.7) x 10/sup -12/; 1,4-cyclohexadiene, (2.89 +/- 0.35) x 10/sup -13/; 1,3-cycloheptadiene, (3.8 +/- 0.9) x 10/sup -12/; ..cap alpha..-pinene, (3.4 +/- 0.8) x 10/sup -12/; ..beta..-pinene, (1.4 +/- 0.3) x 10/sup -12/; ..delta../sup 3/-carene, (5.9 +/- 1.3) x 10/sup -12/; d-limonene, (7.7 +/- 1.7) x 10/sup -12/. These NO/sub 3/ radical rate constants for the naturally emitted hydrocarbons isoprene and the monoterpenes, in conjunction with measured ambient NO/sub 3/ radical concentrations, show that nighttime reaction with the NO/sub 3/ radical can be an important, if not dominant, loss process for these organics. Similarly, these reactions can also be an important loss process for NO/sub 3/ radicals, and hence for NO/sub x/, during nighttime hours. 43 references.

Atkinson, R.; Aschmann, S.M.; Winer, A.M.; Pitts, J.N. Jr.

1984-05-01

129

Sources of Volatile Organic Compounds (VOCs) in the UAE  

NASA Astrophysics Data System (ADS)

The gas chromatography-flame ionization detection/mass spectrometry system has been used to identify major volatile organic compounds (VOCs) sources in the UAE (latitude 24.45N; longitude 54.22E). VOCs are emitted from an extensive number of sources in urban environments including fuel production, distribution, and consumption. Transport sources contribute a substantial portion of the VOC burden to the urban atmosphere in developed regions. UAE is located at the edge of the Persian Gulf and is highly affected by emissions from petrochemical industries in neighbouring Saudi Arabia, Qatar, and Iran. VOCs emerging from these industries can be transported to the UAE with jet streams. The analysis of the collected air samples at three locations in Sharjah, UAE during the autumn and winter seasons indicates the presence of more than 100 VOC species. The concentrations of these species vary in magnitudes but the most prominent are: acetylene, ethane, propane, butane, pentane, benzene, and toluene. The possible tracers for various emission sources have also been identified such as 2-methylpentane, 1, 3-butadiene and 2, 2-dimethlybutane for vehicle exhaust, the light hydrocarbons, namely n-butane, trans-2-butene, and n-pentane for gasoline vapor, and n-nonane, n-decane, and n-undecane for diesel vapor and asphalt application processes. As various emission sources are characterized by overlapping VOC species, the ratio of possible VOC tracers are used to quantify the contribution of different sources. Our aim in this paper is to explore and discuss possible impacts of transported emissions on the local VOC emission inventory from various sources for the UAE. This work is partially supported by Office of Development and Alumni Affairs at the American University of Sharjah, U.A.E.

Abbasi, Naveed; Majeed, Tariq; Iqbal, Mazhar; Riemer, Daniel; Apel, Eric; Lootah, Nadia

130

HREELS study of triethylphosphine (TEP) and tertiarybutylphosphine (TBP) on a Si(001)-(2 × 1) surface  

NASA Astrophysics Data System (ADS)

Adsorption and decomposition of TEP and TBP on a clean Si(001)-(2 × 1) surface have been studied using high-resolution electron energy loss spectroscopy (HREELS). TEP is adsorbed molecularly at 300 K and decomposed into ethylene, which is evolved from the surface, through ?-hydride elimination, leading to formation of Si?H. TBP is partially dissociated at 100 K and decomposed into isobutylene (2-methylpropene) through the same mechanism as TEP. It is suggested that ethyl ( t-butyl) groups bonded to phosphorus in TEP are not transferred to silicon and ethylene (isobutylene) as a decomposition product is not re-adsorbed on the surface. This would be the reason why carbon deposition does not occur on the surface upon annealing the sample exposed to TEP and TBP.

Kaneda, G.; Sanada, N.; Fukuda, Y.

1997-04-01

131

Characterization of oxygenated derivatives of isoprene related to 2-methyltetrols in Amazonian aerosols using trimethylsilylation and gas chromatography/ion trap mass spectrometry.  

PubMed

In the present study, we have tentatively identified the structures of three oxygenated derivatives of isoprene in Amazonian rain forest aerosols as the C(5) alkene triols, 2-methyl-1,3,4-trihydroxy-1-butene (cis and trans) and 3-methyl-2,3,4-trihydroxy-1-butene. The formation of these oxygenated derivatives of isoprene can be explained by acid-catalyzed ring opening of epoxydiol derivatives of isoprene, namely, 1,2-epoxy-2-methyl-3,4-dihydroxybutane and 1,2-dihydroxy-2-methyl-3,4-epoxybutane. The structural proposals of the C(5) alkene triols were based on chemical derivatization reactions and detailed interpretation of electron and chemical ionization mass spectral data, including data obtained from first-order mass spectra, deuterium labeling of the trimethylsilyl methyl groups, and MS(2) ion trap experiments. The characterization of 2-methyl-1,3,4-trihydroxy-1-butene (cis and trans) and 3-methyl-2,3,4-trihydroxy-1-butene in forest aerosols is important from an atmospheric chemistry viewpoint in that these compounds hint at the formation of intermediate isomeric epoxydiol derivatives of isoprene and as such provide mechanistic insights into the formation of the previously reported 2-methyltetrols through photooxidation of isoprene. PMID:15856536

Wang, Wu; Kourtchev, Ivan; Graham, Bim; Cafmeyer, Jan; Maenhaut, Willy; Claeys, Magda

2005-01-01

132

Identification of novel aroma-active thiols in pan-roasted white sesame seeds.  

PubMed

Screening for aroma-active compounds in an aroma distillate obtained from freshly pan-roasted sesame seeds by aroma extract dilution analysis revealed 32 odorants in the FD factor range of 2-2048, 29 of which could be identified. The highest FD factors were found for the coffee-like smelling 2-furfurylthiol, the caramel-like smelling 4-hydroxy-2,5-dimethyl-3(2H)-furanone, the coffee-like smelling 2-thenylthiol (thiophen-2-yl-methylthiol), and the clove-like smelling 2-methoxy-4-vinylphenol. In addition, 9 odor-active thiols with sulfurous, meaty, and/or catty, black-currant-like odors were identified for the first time in roasted sesame seeds. Among them, 2-methyl-1-propene-1-thiol, (Z)-3-methyl-1-butene-1-thiol, (E)-3-methyl-1-butene-1-thiol, (Z)-2-methyl-1-butene-1-thiol, (E)-2-methyl-1-butene-1-thiol, and 4-mercapto-3-hexanone were previously unknown as food constituents. Their structures were confirmed by comparing their mass spectra and retention indices as well as their sensory properties with those of synthesized reference compounds. The relatively unstable 1-alkene-1-thiols represent a new class of food odorants and are suggested as the key contributors to the characteristic, but quickly vanishing, aroma of freshly ground roasted sesame seeds. PMID:20491509

Tamura, Hitoshi; Fujita, Akira; Steinhaus, Martin; Takahisa, Eisuke; Watanabe, Hiroyuki; Schieberle, Peter

2010-06-23

133

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...

134

40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.  

Code of Federal Regulations, 2010 CFR

...n-Butyric Acid n-Butyric Anhydride *n-Paraffins n-Propyl Acetate n-Propyl Alcohol...Sorbitol Stearic Acid, Calcium Salt (Wax) Tert-Butyl Alcohol 1-Butene... Carbon Tetrachloride *Chlorinated Paraffins, 35-64 PCT, Chlorine...

2010-07-01

135

Straightforward one-pot stereoselective synthesis of substituted tetrahydrofurans from 1,3-butadienes and aldehydes  

E-print Network

-butenes as 1a­c.4,5 Unfortunately, addition of 1a or 1b to var- ious electrophilic reagents in the presence of Lewis acids led to compounds bearing a 4-trimethylsilyl-1-butene moiety in which the second

Paris-Sud XI, Université de

136

Direct Kinetics Study of the Product-Forming Channels  

E-print Network

for the reaction of 1- and 2-butene-derived hydroxyalkylperoxy radicals with NO. The measured hydroxyalkylnitrate product channel branching ratios were determined to be 0.061, 0.068, and 0.070 for the 1-butene, 2-butene

Elrod, Matthew J.

137

Tetrahedron Letters,Vo1.24,No.48,pp 5303-5304,1983 oo4o-4039/83 $3.00 + .OO Printed in Great Britain 01983 Pergamon Press Ltd.  

E-print Network

Chapel Hill, N.C. 27514 Abstract preparation of 2-alkyl-2,3-dihydro-y-pyronesfrm 1-methoxy-1-buten-3-yne acetylide of 1-methoxy-l-buten-3-yne$, to laytones followed by acid hydrolysis provides high yields of dihydropmne spiroketal SF- terns. Others have utilized the additi;n of the enolate of 4-methoxy-3-buten-2

138

Mechanistic Investigation of Iridium-Catalyzed Hydrovinylation of Jonas Oxgaard, Gaurav Bhalla, Roy A. Periana, and William A. Goddard, III*,  

E-print Network

CH-CH3) complex with a coordinating olefin, which can transfer a hydrogen to the product, 2-butene, via-butene or butadiene are feasible products. The presence of 1-butene in the product mixture is attributed to isomerization of 2-butene; that is, it is not a kinetic product. 1. Introduction Carbon-carbon bond

Goddard III, William A.

139

A Practical, Two-Step Synthesis of 2-Substituted 1,3-Butadienes  

PubMed Central

A two-step procedure for preparing 2-alkyl-1,3-butadienes is described. Cuprate addition to commercially available 1,4-dibromo-2-butene yields 3-alkyl-4-bromo-1-butene, a product of SN2? substitution. Dehydrohalogenation gives 2-alkyl-1,3-butadienes. PMID:19260696

Sen, Sushmita; Singh, Swapnil; Sieburth, Scott McN.

2009-01-01

140

Relation between adsorption and catalysis in the case of NiO and Co 3O 4  

NASA Astrophysics Data System (ADS)

Reversed flow-inverse gas chromatography is a quick, precise and effective methodology to characterize physicochemical properties of adsorbents. This is extended to the experimental measurement of the adsorption energy distribution function as well as of the differential energy of adsorption due to lateral interactions of molecules adsorbed on two catalysts, namely Co 3O 4 and NiO. Thus, the nature and the strength of the adsorbate-adsorbent and adsorbate-adsorbate interactions are extracted in order to give detailed answers to the questions: (a) where are the molecules on the heterogeneous surface and (b) which is the nature of the surface chemical bonds? Thus, adsorption of 1-butene was found to take place immediately and irreversibly. It holds a deep relation between adsorption and catalysis of 1-butene over these catalysts. As a consequence, the adsorption of 1-butene in the presence of hydrogen leads to isobutane and/or n-butane, depending on the temperature. It can be seen from the adsorption/desorption kinetic constants that the adsorption of 1-butene on Co 3O 4 is one order higher than over NiO. This fact in connection with the bigger activation energy and the lower kinetic coefficients concerning hydrogenation reaction over NiO shows that Co 3O 4 is a better catalyst for this kind of catalysis.

Arvaniti, I.; Netos, V.; Siokos, V.; Metaxa, E.; Kalantzopoulou, F. Roubani

2010-06-01

141

HIRAC - A Highly Instrumented Reactor for Atmospheric Chemistry  

NASA Astrophysics Data System (ADS)

Environmental chambers are an important part of an integrated and multifaceted approach to understanding chemical processes in the atmosphere, by bridging the gap between laboratory measurements of individual elementary reactions and the complexity of the real atmosphere. The University of Leeds HIRAC chamber is a 2 m3 stainless steel vessel capable of operating at a variety of temperatures and pressures, enabling wide ranging kinetics experiments. Photolysis reactions are initiated by 8 rows of internal lights positioned to maximise the volume of the cell (> 85 % ) receiving a uniform ( ± 10 % ) light intensity. HIRAC's includes a suite of analytical devices comprising of: a long path FTIR system (operating from the UV to the far IR), GC-HID and GC-FID for HCHO and hydrocarbons detection respectively, commercial NOx/O3/H2O vapour and CO analysers, and laser-induced fluorescence at low pressure (FAGE) detection system for OH and HO2 measurement (detection limit of ~106 molecule cm- 3). HIRAC aims to validate mechanisms of hydrocarbon oxidation relevant for models such as the Master Chemical Mechanism (MCM), to measure the kinetics of reactions which cannot be studied by isolated techniques such as laser flash photolysis or discharge flow, and to provide a test bed for the development and calibration of field instrumentation. This poster intends to give an insight in to the characterisation of HIRAC and initial results. Relative rate measurements have been used to measure the kinetics of OH radical and Cl atom reactions with a variety of VOCs, using GC and FTIR detection. Relative rate measurements avoid the effects of secondary reactions and the need for direct measurement of highly reactive radicals. Measurements have been made with very high precision, generating high quality fall-off curves for the pressure dependent ethene and Cl atom reactions. The reaction between O3 and trans-2-butene has been studied by the detection of reagents and product acetaldehyde, as well as OH and HO2 concentrations, with excellent precision. A model based on the MCM was able to calculate the temporal profiles extremely well.

Hemavibool, K.; Malkin, T. L.; Glowacki, D. R.; Goddard, A.; Heard, D. E.; Seakins, P. W.; Pilling, M. J.

2008-12-01

142

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

143

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

144

Role of ZSM-5 and ultrastable Y zeolites for increasing gasoline octane number  

Microsoft Academic Search

Octane number of gasoline made in a fluid catalytic cracker can be catalytically enhanced by using an ultrastable HY zeolite instead of one containing rare earth cations or by adding small amounts of ZSM-5 to a Y zeolite catalyst. ZSM-5 addition catalyzes both normal and branched olefin cracking to give mainly propylene, butenes, 2-methyl 1-butene, and 2-methyl 2-butene. Increase in

R MADON

1991-01-01

145

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

146

The hydrocarbon emission rates of tea-leafed willow ( Salix phylicifolia), silver birch ( Betula pendula) and European aspen ( Populus tremula)  

Microsoft Academic Search

The monoterpene, isoprene, and light hydrocarbon emission rates of tea-leafed willow (Salix phylicifolia), aspen (Populus tremula), and silver birch (Betula pendula) were measured during the growing season 1996 in the boreal vegetation zone using a dynamic flow-through technique. All tree species had significant (2.8–10?gg (dry weight)-1h-1) monoterpene emission rates when leaves were young in May. In addition, willow emitted 1-butene,

Hannele Hakola; Janne Rinne; Tuomas Laurila

1998-01-01

147

Cell-free ethylene-forming systems lack stereochemical fidelity  

Microsoft Academic Search

In-vitro systems for the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene have been reported using pea supernatants, carnation petal microsomes, olive leaf protein and, most recently, pea mitochondria. It has also been shown, in intact tissues of apple, mung bean and pea, that the system responsible for conversion of ACC to ethylene can produce 1-butene from isomers of 1-amino-2-ethylcyclopropane-1-carboxylic acid

Michael A. Venis

1984-01-01

148

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

149

Kinetics of n-butylbenzene dehydrocyclization over chromia-alumina  

SciTech Connect

The kinetics of dehydrogenation, cyclization, and isomerization steps in n-butylbenzene dehydrocyclization over precoked chromia-alumina has been investigated at 683--783 K. Apparent kinetic parameters of a pseudohomogeneous model were calculated from the initial-rate and integral-rate data measured with n-butylbenzene and 4-phenyl-1-butene in an isothermal fixed-bed reactor. Dehydrocyclization was shown to proceed by dehydrogenation of n-butylbenzene to n-butenylbenzenes, by their cyclization, and by dehydrogenation of the cyclic products to methylindenes and naphthalene. Direct cyclization of n-butylbenzene was of little importance over the precoked catalyst. According to the initial-rate data, dehydrogenation to n-butenylbenzenes followed an apparent order of 0.5 and the kinetic parameters seemed to be applicable also at higher conversions. The primary dehydrogenation products were 1-phenyl-1-butenes, and a surface model based on hydrogen abstraction from the {alpha}-carbon has been discussed. The initial cyclization rates measured with 4-phenyl-1-butene were appreciably lower than those observed in integral-rate experiments. The discrepancy was tentatively explained by the higher reactivity of 1-phenyl-1-butenes, which are the main constituents of the n-butenylbenzene fraction at longer contact times. High conversion runs with n-butylbenzene also showed that methylindenes and -indans were partly dealkylated and probably polymerized. The apparent orders ranged from 1 to 1.5 for 1,6-cyclization and from 0.5 to 0.8 for 1,5-cyclization. Skeletal isomerization of n-butylbenzene to sec-butyl- and sec-butenylbenzenes was rapidly subsided during coking, and on the coked catalyst at 783 K the reaction followed an apparent order of {minus}0.5.

Laatikainen, M.; Vahteristo, K.; Saukkonen, S.; Lindstroem, M. [Lappeenranta Univ. of Technology (Finland). Dept. of Chemical Technology] [Lappeenranta Univ. of Technology (Finland). Dept. of Chemical Technology

1996-07-01

150

Acidity of nickel silicate and its bearing on the catalytic activity for ethylene dimerization and butene isomerization  

Microsoft Academic Search

Experimental results obtained with nickel silicate catalysts precipitated at pH 6-10 (Group 1) or containing 4-90% nickel oxide (Group 2) provided evidence that 1-butene was the primary product of ethylene dimerization; that 2-butene was a secondary isomerization product; that the selectivity for 2-butene isomerization ran parallel to the previously measured dimerization activity, i.e., had maxima at 100° and 600°C pretreatment

J. R. Sohn; A. Ozaki

1980-01-01

151

The effect of supported MoO(X) structures on the reaction pathways of propene formation in the metathesis of ethylene and 2-butene.  

PubMed

The kind of surface MoOX structures on Al2O3-SiO2 was found to determine propene selectivity in the metathesis of ethylene and 2-butene. Compared to isolated tetrahedral MoOX species, their polymerized octahedral counterparts show significantly lower activity for isomerisation of 2- to 1-butene thus hindering non-selective metathesis of these butenes. In addition, they reveal higher ability to engage ethylene in propene formation. PMID:24819240

Hahn, T; Kondratenko, E V; Linke, D

2014-08-21

152

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

PubMed

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)-beta-D-glucan and mainly chitin synthases, enzymes that catalyze the synthesis of the major fungal cell wall polymers. PMID:12628677

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

2003-04-01

153

Hetero-cope rearrangements of nitrosobutenes. DFT studies of thermal and acid-catalyzed reactions.  

PubMed

[Structure: see text] Density functional theory studies of the hetero-Cope reactions of 4-nitroso-1-butenes and nitrosobicyclo[2.2.2]hexenes are reported. The reactions proceed via concerted mechanisms. The electron-withdrawing methoxycarbonyl group alpha- to the nitroso group decreases the activation barrier. Lewis acids such as SbF5 and TiCl4 accelerate the reactions, as has been found experimentally by Zakarian and Lu. PMID:17165908

Jabbari, Arash; Houk, K N

2006-12-21

154

Efficient asymmetric synthesis of silanediol precursors from 1,5-dihydrosiloles.  

PubMed

Dihydrosiloles are easily prepared from 1,3-dienes and dichlorosilanes, even on kilogram scale. Asymmetric hydroboration of a 3-alkyl-1,5-dihydrosilole, prepared from a 2-alkyl-1,3-diene, followed by treatment with aqueous HF results in Peterson fragmentation, forming optically active 3-alkyl-4-fluorosilyl-1-butenes. The fluorosilanes are stable to moisture but very reactive toward nucleophiles. In addition, they can be converted to nucleophilic silyllithium reagents. PMID:17967032

Sen, Sushmita; Purushotham, Madhusudhan; Qi, Yingmei; Sieburth, Scott McN

2007-11-22

155

Kinetic measurements on elementary fossil fuel combustion reactions over wide temperature ranges  

SciTech Connect

The goals of this work are to provide accurate data on the temperature dependence of the kinetics of elementary combustion reactions (i) for use by combustion modelers, and (ii) to gain a better fundamental understanding of, and hence predictive ability for, the chemistry involved. In this reporting period our work on the O + Hcl reaction was published, experimental work on the O + benzene and O + 1-butene reactions was completed, and measurements on the O + isobutene reaction were initiated.

Fontijn, A.

1991-01-01

156

Density Fluctuations in Crystallizing Polymers: Fact or Fiction?  

Microsoft Academic Search

The fact that, in polymer crystallization, nucleation might be accompanied by large scale density fluctuations has been investigated for the flow-induced crystallization of isotactic poly-1-butene (PB-1). Small Angle Light Scattering (SALS) was applied to measure density and orientation fluctuations, whereas complementary results were obtained from optical microscopy. The observations seem to indicate that the detected density fluctuations result from the

Jimmy Baert; Peter van Puyvelde

2008-01-01

157

Synthesis and asymmetric reactivity of enantiomerically pure cyclopentadienylmetal complexes derived from the chiral pool  

SciTech Connect

Starting from pulegone, camphor, and tartrate, three chiral cyclopentadienes were prepared efficiently. Metalation with Co/sub 2/(CO)/sub 8/ and TiCl/sub 3/ resulted in new chiral and enantiomerically pure substituted cyclopentadienyldicarbonylcobalt and -titanocene complexes. The latter were used in the quantitative catalytic asymmetric hydrogenation of 2-phenyl-1-butene in up to 34% optical yield. The former allowed the first asymmetric (2 + 2 + 2) cycloadditions promoted by chiral cyclopentadienylcobalt complexes to be observed.

Halterman, R.L.; Vollhardt, K.P.C.

1988-04-01

158

FTIR studies of reactions between the nitrate radical and chlorinated butenes  

SciTech Connect

The products formed in the reactions between the nitrate radical and 2-chloro-1-butene, 3-chloro-1-butene, 1-chloro-2-butene, and 2-chloro-2-butene were studied by FTIR spectroscopy. The experiments were performed in synthetic air in a glass/Teflon reactor and using N{sub 2}O{sub 5} as the NO{sub 3} source. The principal products formed with chlorobutenes, where the chlorine atom was substituted at a carbon participating in the double bond, were acid chlorides, aldehydes, and NO{sub 2}. The products formed from chlorobutenes with the chlorine atom substituted at a carbon next to the double bond were aldehydes, chlorinated carbonyl nitrate compounds, and NO{sub 2}. The reaction rate constant for the initial reaction step for 2-chloro-1-butene was determined to be 1.73 ({plus minus} 0.31) {times} 10{sup {minus}14} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} at 299 K by using a fast-flow system.

Waengberg, I.; Ljungstroem, E. (Univ. of Goeteborg and Chalmers Univ. of Technology (Sweden)); Hjorth, J.; Ottobrini, G. (Commission of the European Communities Joint Research Center, Ispra (Italy))

1990-10-18

159

Radical Ions in Photochemistry. 44. The Photo-NOCAS Reaction with Acetonitrile as the Nucleophile.  

PubMed

Studies on the photoinduced electron transfer (PET) reactions of isobutylene (2-methylpropene, 1) in the absence of methanol have identified a new photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction. Under these conditions acetonitrile was found to act as the nucleophile and to combine with the alkene radical cation. The resulting distonic radical cation then adds to the radical anion of 1,4-dicyanobenzene (2(-*)). The final product (6) results from cyclization into the ortho postion of the phenyl group. This product formation is rationalized on the basis of the relatively high oxidation potential of the alkene (i.e., one-electron oxidation yields a reactive radical cation), the fact that addition of the nucleophile (acetonitrile) to the radical cation is relatively unhindered, and the relatively low acidity of the radical cation due to the low radical stability of the allylic radical formed upon deprotonation. High-level ab initio molecular orbital calculations were used to determine the structures and relative energies of the possible intermediate distonic and bridged radical cations. The scope and mechanism of this type of photo-NOCAS reaction are discussed. PMID:11671982

de Lijser, H. J. P.; Arnold, Donald R.

1997-11-28

160

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

2012-02-01

161

Chemical mutagenesis testing in Drosophila. X. Results of 70 coded chemicals tested for the National Toxicology Program.  

PubMed

Seventy chemicals were tested for the ability to induce sex-linked recessive lethal (SLRL) mutations in postmeiotic and meiotic germ cells of male Drosophila melanogaster. As in the previous studies in this series, adult feeding was chosen as the first route of administration. If the compound failed to induce mutations by this route, injection exposure was used. Two chemicals, n-butane and propylene, were gaseous and therefore tested only by inhalation. One chemical (dimethylcarbamoyl chloride) was tested only by injection. Those chemicals that were mutagenic in the SLRL assay were further tested for the ability to induce reciprocal translocations. Sixteen of the 70 chemicals tested were mutagenic in the SLRL assay: 3-chloro-2-methylpropene, 3-(chloromethyl)pyridine HCl, dimethylcarbamoyl chloride, HC blue 1,3-iodo-1,2-propanediol, malaoxon, N,N'-methylene-bis-acrylamide, 4,4'-methylenedianiline 2HCl, ziram, cis-dichlorodiaminoplatinum II, 1,2-dibromoethane, dibromomannitol, 1,2-epoxypropane, glycidol, myleran, and toluene diisocyanate. The last seven also induced reciprocal translocations. A comparison of the results from the SLRL assay with other assays for mutagens and carcinogens suggests that the SLRL assay is highly specific, but poorly sensitive, both for mutagens and potential carcinogens. PMID:8162896

Foureman, P; Mason, J M; Valencia, R; Zimmering, S

1994-01-01

162

OH, HO2, partially speciated RO2 and OH reactivity measurements over a range of NOx during day and night (Invited)  

NASA Astrophysics Data System (ADS)

Measurements will be reported for OH, HO2, partially speciated RO2 (distinguishing smaller alkane related RO2 from larger alkane/alkene/aromatic related RO2) and OH reactivity measurements taken during the ClearfLo campaigns in central London in the winter and summer of 2012. Comparison with calculations from a detailed box model utilising the Master Chemical Mechanism v3.2 tested our ability to reproduce radical levels, and enabled detailed radical budgets to be determined, highlighting for example the important role of the photolysis of nitrous acid and carbonyl species as radical sources. Speciation of RO2 enabled the break-down of ozone production from different classes of VOCs to be calculated directly, and clear differences in the contribution from different types of RO2 were seen during warmer and cooler periods. Comparison of the total calculated chemical O3 production with observations showed that most of the ozone production observed was generated locally. The missing OH reactivity was greatest during morning and evening rush hours, with good agreement at other times. Long-term seasonal measurements of OH and HO2 radicals in the tropical marine boundary layer at the Cape Verde Atmospheric Observatory were reported in a recent publication [1] and here comparisons will be reported with both box model calculations utilising the Master Chemical Mechanism and the three-dimensional global chemical transport model GEOS-Chem. Both approaches result in over-predictions of OH and HO2 suggesting an incomplete description of sinks. In the box model bromine/iodine chemistry increases OH by ~10%, whereas the global model incorporating bromine chemistry decreases OH by ~ 5%. In the global model the impact of O3 destruction from bromine chemistry (and hence reduction of OH) is greater than the increase in OH from changes in HOx partitioning, whereas in the box model O3 is constrained to measurements, and hence the impact of halogens on OH can only derive from HOx partitioning. Measurements of HO2 at night made during the RONOCO campaign onboard the BAe-146 research aircraft will be reported with HO2 significantly higher in summer than in winter and with the highest HO2 observed for altitudes < 1.0 km. A strong positive correlation between HO2 and NO3 was observed (average r=0.89, as high as r=0.97 on one flight) and attributed to the production of HO2 from reactions of NO3 with alkenes, particularly trans-2-butene and other isomers of butene. Nighttime production of HO2 was dominated by NO3 in summer and O3 in winter. If time permits, field and laboratory studies of heterogeneous processing of HO2 by clouds and aerosols will be discussed. [1] S. Vaughan et al., Atmos. Chem. Phys., 12, 2149-2172, 2012.

Heard, D. E.; Whalley, L. K.; Gallaway, S.; Stone, D. J.; Ingham, T.; Walker, H.; Evans, M. J.

2013-12-01

163

Diacetoxylation of 1,3-butadiene  

SciTech Connect

The homogeneous catalytic diacetoxylation of 1,3-butadiene was found to proceed in a medium of acetic acid, palladium complexes and acetate ions more efficiently than upon using the nitrate-iodate reoxidative system. The major reaction products are cis- and trans-1,4-diacetoxy-2-butenes formed in 15-17 mass % yield and 48-50% selectivity and 3,4-diacetoxy-1-butene formed in 10 mass % yield and selectivity of about 40%. Two alternative mechanisms were proposed and the reasons for the low reactivity of butadiene under homogeneous catalysis conditions were discussed.

Devekki, A.V.; Yakushkin, M.I.

1988-03-01

164

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

Microsoft Academic Search

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,

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

1971-01-01

165

Difference-NMR techniques for selection of components on the basis of relaxation times.  

PubMed

This work describes a numerical methodology to obtain more efficient relaxation filters to selectively retain or remove components based on relaxation times. The procedure uses linear combinations of spectra with various recycle or filter delays to obtain components that are both quantitative and pure. Modulation profiles are calculated assuming exponential relaxation behavior. The method is general and can be applied to a wide range of solution or solid-state NMR experiments including direct-polarization (DP), or filtered cross-polarization (CP) spectra. 13C NMR experiments on isotactic poly(1-butene) and dimethyl sulfone showed the utility of the technique for selectively suppressing peaks. PMID:12762984

Harris, Douglas J; de Azevedo, Eduardo R; Bonagamba, Tito J

2003-05-01

166

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. PMID:22012676

Spá?il, Zden?k; Hui, Renjie; Gelb, Michael H.; Ture?ek, František

2011-01-01

167

Determination of the adsorption model of alkenes and alcohols on sulfonic copolymer by inverse gas chromatography.  

PubMed

The determination of a number of adsorption sites on sulfonated styrene-divinylbenzene copolymer for alkenes (propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, isobutene, 2-methyl-1-butene, 2-methyl-2-butene, 2-methyl-1-pentene, 2-methyl-2-pentene and 2-methyl-2-hexene) and alcohols (methanol, ethanol and n-propanol, n-butanol, 2-butanol and tert-butanol) was performed by the saturation copolymer with vapors of adsorbate, by removing the excess of adsorbate from copolymer by blowing the inert gas through copolymer bed and by the desorption of adsorbed alcohol in the programmed increase of temperature. The adsorption measurements were performed on sulfonated ion-exchange resin (Amberlyst 15) with different concentrations of the acid group, which means with a varying number of adsorption sites. The following adsorption models for alkenes were suggested: the first in which one molecule of alkene is adsorbed by two sulfonic groups, for linear alcohols, the second in which one sulfonic group can adsorb one molecule of alcohol and for non-linear alcohols the third where one molecule of alcohol is adsorbed by two or more sulfonic groups. PMID:15116927

S?omkiewicz, P M

2004-04-23

168

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

169

Kinetics of the heterogeneously catalyzed formation of tert-amyl ethyl ether  

SciTech Connect

In this work, the kinetics and equilibrium of the heterogeneously catalyzed liquid-phase formation of tert-amyl ethyl ether (TAEE) were studied. The catalyst used was a commercial sulfonic acid ion-exchange resin (Amberlyst 16W). The experiments were carried out in a continuous stirred-tank reactor, measuring stationary reaction rates. The measured reaction rates were fitted to three kinetic models; homogeneous, Eley-Rideal type, and Langmuir-Hinshelwood type. Of these, the Langmuir-Hinshelwood type model described the experimental results best. This model is based on single-site adsorption of every component, with the surface reaction being the rate-limiting step. The activation energies for the formation of tert-amyl ethyl ether from 2-methyl-1-butene were 90 and from 2-methyl-2-butene 108 kJ/mol. For the isomerization of 2-methyl-1-butene to 2-methyl-2-butene, an activation energy of 82 kJ/mol was obtained.

Linnekoski, J.A.; Krause, A.O. [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Industrial Chemistry] [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Industrial Chemistry; Rihko, L.K. [Neste Oy, Porvoo (Finland). Technology Center] [Neste Oy, Porvoo (Finland). Technology Center

1997-02-01

170

Hydrogenation of 1,3-Butadiene on Platinum Surfaces of DifferentStructures  

SciTech Connect

1,3-butadiene hydrogenation is studied on platinum foil and Pt(111), Pt(100), Pt(755) single-crystal surfaces at 300-375 K. The results are compared with the data of alkene hydrogenation reactions. Similar to the hydrogenation kinetics of butenes, 1,3-butadiene hydrogenation exhibits near zeroth-order dependence on hydrocarbon and near first-order dependence on hydrogen pressure. With the same hydrocarbon (3.5-70 Torr) and hydrogen (14-140 Torr) pressure, the rate of 1,3-butadiene hydrogenation is one order of magnitude lower than for the rates for n-butenes. The hydrogenation products include 1-butene, trans- and cis-2-butene, and n-butane. The reaction selectivity is independent of reactant mixture and platinum surface structure, but changes slightly as a function of reaction temperature. The butene product distribution is determined by surface reaction kinetics. While 1-butene is thermodynamically less stable than trans- and cis-2-butene, it is the major butene product in 1,3-butadiene hydrogenation.

Yoon, Cheonho; Yang, M.X.; Somorjai, G.A.

1997-05-01

171

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. PMID:16347167

Mountfort, Douglas O.; Kaspar, Heinrich F.

1986-01-01

172

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

173

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

SciTech Connect

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 with the fuel's sooting tendency, and suggests that the formation of the aromatic ring is a controlling step in soot formation. In addition to the relatively well-established reactions involving C4 and C2 species, benzene may form directly from two C3 species for fuels that readily produce C3 species during pyrolysis and/or oxidative pyrolysis. The total concentration of growth species increases almost linearly with fuel concentration, but depends more weakly on flame temperature than would be expected if pure pyrolysis governed the intermediate hydrocarbon behavior.

Sidebotham, G.W.; Glassman, I. (Dept. of Mechanical and Aerospace Engineering, Princeton Univ., Princeton, NJ (US))

1992-09-01

174

Transition metal promoted reactions of boron hydrides. 13. Platinum catalyzed synthesis of 6,9-dialkyldecaboranes  

SciTech Connect

Both chloroplatinic acid and platinum bromide have been found to catalyze the reactions of decaborane(14) with terminal olefins, including ethylene, propylene, 1-butene, and 1-pentene, to give the corresponding 6,9-R[sub 2]B[sub 10]H[sub 12] derivatives in high yields. Chemical studies of 6,9-(n-C[sub 5]H[sub 11])[sub 2]B[sub 10]H[sub 12] (1) show that, in contrast to decaborane(14), 1 does not react to form dibase adducts with the Lewis bases Et[sub 3]N, Ph[sub 3]P, Et[sub 2]S, or MeCN. However, 1 undergoes many other reactions, including deprotonation to 6,9-(n-C[sub 5]H[sub 11])[sub 2]B[sub 10]H[sub 11][sup [minus

Mazighi, K.; Carroll, P.J.; Sneddon, L.G. (Univ. of Pennsylvania, Philadelphia (United States))

1993-05-12

175

Partial oxidation of {alpha}-olefins over iron antimony oxide - influence of carbon number  

SciTech Connect

Iron antimony oxide is a well known catalyst for the partial oxidation of propane and 1-butene. Kinetic studies of the partial oxidation of {alpha}-olefins (C{sub 2}-C{sub 9}) revealed that the activity showed a maximum at C{sub 4}. The main products of the partial oxidation of {alpha}-olefins (larger than C{sub 2}) are the conjugated alkenal (acrolein) and dienes. The selectivity to these desired products decreases with increasing chain length probably caused by both the decrease in number of allylic hydrogen atoms and the shielding of them. Ethene could only be oxidized at relatively high temperatures (over 450{degrees}C) and the only observed products were CO and CO{sub 2} indicating the need for the presence of allylic hydrogen for low temperature selective partial oxidation. Increasing the carbon number increases the yield of CO and CO{sub 2} due to shielding of the allylic hydrogen.

Steen, E. van; Schnobel, M.; O`Connor, C.T. [Univ. of Cape Town, Rondebosch (South Africa)

1996-10-01

176

Alkene oxidation on Pd(100): Why total not partial?  

SciTech Connect

Partial alkene oxidation has previously been observed on Ag(110) and Rh(111) under ultrahigh vacuum conditions. Atomic oxygen on Ag(110) reacts with alkenes through acid-base reactions or epoxidations, whereas on Rh(111) alkenes can be oxidized to ketones. On Pd(100), a neighbor to both Ag and Rh in the periodic table, we detected no partial oxidation products for coverages of adsorbed oxygen up to one oxygen atom per surface palladium atom for any of the alkenes studied, including ethylene, propene, 1-butene, and 1,3-butadiene; only total oxidation (combustion) products were observed. Strong bonding of the alkenes to Pd(100) appears to invalidate the application of gas phase acidity concepts known to apply on Ag(110), and efficient O-H bond formation on Pd(100) seems to prevent ketone formation as observed on Rh(111). Two different combustion pathways were identified, namely, direct (oxygen-activated) combustion and indirect (decomposition and oxidation) combustion.

Guo, X.C.; Madix, R.J. [Stanford Univ., Stanford, CA (United States)

1996-10-01

177

Selectivity control for the catalytic 1,3-butadiene hydrogenation on Pt(111) and Pd(111) surfaces: Radical versus closed-shell intermediates.  

PubMed

The hydrogenation of 1,3-butadiene to different C4H8 species on both Pd(111) and Pt(111) surfaces has been studied by means of periodic slabs and DFT. We report the adsorption structures for the various mono- and dihydrogenated butadiene intermediates adsorbed on both metal surfaces. Radical species are more clearly stabilized on Pt than on Pd. The different pathways leading to these radicals have been investigated and compared to those producing 1-butene and 2-butene species. On palladium, the formation of butenes seems to be clearly favored, in agreement with the high selectivity to butenes observed experimentally. In contrast, the formation of dihydrogenated radical species seems to be competitive with that of butenes on platinum, which could explain its poorer selectivity to butenes and the formation of butane as a primary product. PMID:16852780

Valcarcel, Ana; Clotet, Anna; Ricart, Josep M; Delbecq, Françoise; Sautet, Philippe

2005-07-28

178

Syntheses and reactions of vinyl and phenyl fragments on Ag(111)  

SciTech Connect

Low-energy electron activation of monolayer ethylene and benzene, adsorbed on Ag(111) at 100 K, leads selectively to vinyl and phenyl fragments. An electron impact ionization model, followed by rapid reneutralization and C-H bond cleavage, is proposed. Upon heating, neither fragment undergoes further C-H or C-C bond cleavage; rather, both undergo carbon-carbon coupling to form 1,3-butadiene and biphenyl. When coadsorbed with methyl or ethyl fragments, temperature-programmed desorption yields propene or 1-butene for vinyl, whereas it yields toluene or ethylbenzene for phenyl. Kinetic parameters describing the electron-stimulated fragment synthesis and the subsequent thermal reactions were determined in the presence and absence of atomic iodine. 14 refs., 14 figs.

Zhou, X.L.; Schwaner, A.L.; White, J.M. (Univ. of Texas, Austin (United States))

1993-05-19

179

Time-resolved gas chromatography applied to submonolayer adsorption. Modeling and experimental approach  

NASA Astrophysics Data System (ADS)

The reversed-flow inverse gas chromatographic method was used to study the local adsorption parameters of the action of five hydrocarbons on one hand, namely, ethane, ethene, ethyne, propene and 1-butene and of ozone, on the other, on two known and widely used oxides, CaO and SiO 2, respectively. Five physicochemical parameters concerning adsorption have been obtained for each of 20 heterogeneous systems studied, namely local adsorption energy, local adsorption isotherm, local monolayer capacity, probability density function for adsorption energies and energies from lateral interactions. Thus, the RF-IGC method is engaged to provide a new pathway for heterogeneous surface characterization, which is the basis of many scientific investigations and technological applications.

Metaxa, E.; Agelakopoulou, T.; Bassiotis, I.; Margariti, S.; Siokos, V.; Roubani-Kalantzopoulou, F.

2007-04-01

180

Determination of quadrupole moments of light hydrocarbon molecules from rotationally inelastic state to state scattering cross sections  

NASA Astrophysics Data System (ADS)

A new method for determining quadrupole moments from measurements of rotationally inelastic cross sections was recently introduced by Borkenhagen . This method is based on the observation that the magnitude of the cross section for the rotational transition ( j, m) = (2,0) ? (3,0) of CsF in forward scattering is found, in agreement with the Born approximation, to depend linearly on the quadrupole moment of the target molecule. In the present paper we report on the determination of quadrupole moments for the following hydrocarbons: C 2H 2, C 2H 4, C 3H 4 (methylacetylene), C 3H 6, C 3H 8, C 4H 6 (butadiene), C 4H 8 (1-butene) and C 4H 8 (isobutene), most of which have not been studied previously. The new results are compared with estimates based on a simple bond dipole moment model.

Meyer, Gerhard; Peter Toennies, J.

1980-10-01

181

Acidity of nickel silicate and its bearing on the catalytic activity for ethylene dimerization and butene isomerization  

SciTech Connect

Experimental results obtained with nickel silicate catalysts precipitated at pH 6-10 (Group 1) or containing 4-90% nickel oxide (Group 2) provided evidence that 1-butene was the primary product of ethylene dimerization; that 2-butene was a secondary isomerization product; that the selectivity for 2-butene isomerization ran parallel to the previously measured dimerization activity, i.e., had maxima at 100/sup 0/ and 600/sup 0/C pretreatment temperatures; that the montmorillonite sites which were activated at 100/sup 0/C consisted of protonic acid sites; that the protonic sites for dimerization and isomerization differed and that the number of isomerization sites was about one order of magnitude greater than that of dimerization sites; and that the antigorite sites activated at 600/sup 0/C were nonprotonic acid sites. The experiments included n-butylamine titration with dicinnamalacetone indicator, ammonia chemisorption, selective poisoning studies with water and sodium, deuterium tracer studies, and IR spectroscopy.

Sohn, J.R.; Ozaki, A.

1980-01-01

182

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

183

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 PMID:5288773

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

1971-01-01

184

Shock tube study of the fuel structure effects on the chemical kinetic mechanisms responsible for soot formation, part 2  

NASA Technical Reports Server (NTRS)

Soot formation in oxidation of allene, 1,3-butadiene, vinylacetylene and chlorobenzene and in pyrolysis of ethylene, vinylacetylene, 1-butene, chlorobenzene, acetylen-hydrogen, benzene-acetylene, benzene-butadiene and chlorobenzene-acetylene argon-diluted mixtures was studied behind reflected shock waves. The results are rationalized within the framework of the conceptual models. It is shown that vinylacetylene is much less sooty than allene, which indicates that conjugation by itself is not a sufficient factor for determining the sooting tendency of a molecule. Structural reactivity in the context of the chemical kinetics is the dominant factor in soot formation. Detailed chemical kinetic modeling of soot formation in pyrolysis of acetylene is reported. The main mass growth was found to proceed through a single dominant route composed of conventional radical reactions. The practically irreversible formation reactions of the fused polycyclic aromatics and the overshoot by hydrogen atom over its equilibrium concentration are the g-driving kinetic forces for soot formation.

Frenklach, M.; Clary, D. W.; Ramachandra, M. K.

1985-01-01

185

Solid acid catalysts from clays: preparation of mesoporous catalysts by chemical activation of metakaolin under acid conditions.  

PubMed

Natural kaolin was treated at 850 or 950 degrees C in air flow to give respectively the metakaolin samples MK8 and MK9. The obtained materials were successively treated at 90 degrees C with a 1 M solution of H(2)SO(4), for various time lengths. The acid treatment of MK8 was found to give a high surface area microporous material with good catalytic properties related to the high density of acid sites, while MK9 gave an ordered mesoporous material with a low density of acid sites. The materials were characterized by several techniques, X-ray powder diffraction, thermogravimetric analysis, N(2) physisorption, scanning electron microscopy, and temperature-programmed desorption of ammonia. The 1-butene isomerization was used as test reaction to evaluate the acidity of the samples. PMID:17451736

Lenarda, M; Storaro, L; Talon, A; Moretti, E; Riello, P

2007-07-15

186

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

SciTech Connect

Described is a method to make liquid chemicals. The method includes 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 conveted to a mixture of n-butenes. 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.

Dumesic, James A [Verona, WI; Ruiz, Juan Carlos Serrano [Madison, WI; West, Ryan M [Madison, WI

2014-01-07

187

Corona discharge of Titan's troposphere.  

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 charge particles leads to corona discharges which are characterized by low current densities. These electric discharges could induce a number of chemical reactions in the troposphere and hence it is of interest to explore such effects. 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-butene, 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 an uncharacterized film deposit. We present their trends of formation as a function of discharge time in an ample interval and have derived their initial yields of formation. These 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 to low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, its production by corona processes and 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:11541341

Navarro-Gonzalez, R; Ramirez, S I

1997-01-01

188

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

189

Characterization of Dispersed Heteropoly Acid on Mesoporous Zeolite Using Solid-State P-31 NMR Spin-Lattice Relaxation  

SciTech Connect

Dispersion and quantitative characterization of supported catalysts is a grand challenge in catalytic science. In this paper, heteropoly acid H3PW12O40 (HPA) is dispersed on mesoporous zeolite silicalite-1 derived from hydrothermal synthesis using carbon black nanoparticle templates, and the catalytic activity is studied for 1-butene isomerization. The HPAs supported on conventional zeolite and on mesoporous zeolite exhibit very different activities and thus provide good model systems to investigate the structure dependence of the catalytic properties. The HPA on mesoporous silicalite-1 shows enhanced catalytic activity for 1-butene isomerization, while HPA on conventional silicalite-1 exhibits low activity. To elucidate the structural difference, supported HPA catalysts are characterized using a variety of techniques, including 31P magic angle spinning nuclear magnetic resonance, and are shown to contain a range of species on both mesoporous and conventional zeolites. However, contrary to studies reported in the literature, conventional NMR techniques and chemical shifts alone do not provide sufficient information to distinguish the dispersed and aggregated surface species. The dispersed phase and the nondispersed phase can only be unambiguously and quantitatively characterized using spin-lattice relaxation NMR techniques. The HPA supported on mesoporous zeolite contains a fast relaxation component related to the dispersed catalyst, giving a much higher activity, while the HPA supported on conventional zeolite has essentially only the slow relaxation component with very low activity. The results obtained from this work demonstrate that the combination of spinning sideband fitting and spin-lattice relaxation techniques can provide detailed structural information on not only the Keggin structure for HPA but also the degree of dispersion on the support.

Zhu, Kake; Hu, Jian Z.; She, Xiaoyan; Liu, Jun; Nie, Zimin; Wang, Yong; Peden, Charles HF; Kwak, Ja Hun

2009-09-01

190

Mechanisms of C-C bond formation and cleavage on metal surfaces: Formation of butenes and hexenes from linear and branched pentenes over Ru/SiO sub 2 catalysts  

SciTech Connect

Over Ru/SiO{sub 2} catalyst, at temperatures above 100-150C and in the presence of hydrogen, linear and branched pentenes (1-pentene, cis- and trans-2-pentene, 2-methyl-2-butene, 3-methyl-1-butene, and 2-methyl-1-butene) undergo isomerization, hydrogenation, hydrogenolysis, and homologation. The main primary products of these last two reactions of C-C bond cleavage and formation are methane, butenes, and hexanes. At low temperature (100-150C), the formation of methane is reduced and the major products are C{sub 4} and C{sub 6} olefinic hydrocarbons, which are obtained in roughly comparable amounts. The distribution of the butenes isomers and of the hexenes isomers strongly depends on the structure of the starting pentene (linear or branched, terminal or internal). The results confirm that hydrogenolysis and homologation of a C{sub 5} olefinic hydrocarbon occur at comparable rates and involve: (1) cleavage of mainly a terminal C-C bond of the pentene isomer leading to C{sup 4} and C{sup 1} fragments, (2) reaction of this C{sup 1} fragment with the starting C{sup 5} to give C{sup 6} hydrocarbons, and (or) (3) hydrogenation of the C{sup 1} fragment to methane. Two mechanisms, based on concepts of organometallic chemistry, can account for the results (especially for the distribution of the C{sup 4} and C{sup 6} olefinic isomers): (1) a methylene insertion-deinsertion mechanism or (2) a mechanism that involves formation and decomposition of dimetallacyclic intermediates. Several experimental results seem to be in favor of the last proposed mechanism.

Rodriguez, E.; Leconte, M.; Basset, J. (Conventionne a l'Universite Claude-Bernard, Lyon (France))

1991-12-01

191

Energetics of the allyl group.  

PubMed

Aiming to improve our understanding of the stability of radicals containing the allylic moiety, carbon-hydrogen bond dissociation enthalpies (BDEs) in propene, isobutene, 1-butene, (E)-2-butene, 3-metylbut-1-ene, (E)-2-pentene, (E)-1,3-pentadiene, 1,4-pentadiene, cyclohexene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene have been determined by quantum chemistry calculations. The BDEs in cyclohexene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene have also been obtained by time-resolved photoacoustic calorimetry. The theoretical study involved a DFT method as well as ab initio complete basis-set approaches, including the composite CBS-Q and CBS-QB3 procedures, and basis-set extrapolated coupled-cluster calculations (CCSD(T)). By taking the C(sp3)-H BDE in propene as a reference, we have concluded that one methyl group bonded to C3 in propene (i.e., 1-butene) leads to a decrease of 12 kJ mol(-1) and that a second methyl group bonded to C3 (3-methylbut-1-ene) further decreases the BDE by 8 kJ mol(-1). When the methyl group is bonded to C2 in propene (isobutene), an increase of 7 kJ mol(-1) is observed. Finally, a methyl group bonded to C1 in propene (2-butene) has essentially no effect (-1 kJ mol(-1)). While this trend can be rationalized in terms of stabilization of the corresponding radical (through hyperconjugation and pi-delocalization), the BDE values observed for the dienes can only be understood by considering the thermodynamic stabilities of the parent compounds. PMID:17924695

Agapito, Filipe; Nunes, Paulo M; Cabral, Benedito J Costa; dos Santos, Rui M Borges; Simões, José A Martinho

2007-11-01

192

Observation of 2-methyltetrols and related photo-oxidation products of isoprene in boreal forest aerosols from Hyytiälä, Finland  

NASA Astrophysics Data System (ADS)

Oxidation products of isoprene including 2-methyltetrols (2-methylthreitol and 2-methylerythritol), 2-methylglyceric acid and triol derivatives of isoprene (2-methyl-1,3,4-trihydroxy-1-butene (cis and trans) and 3-methyl-2,3,4-trihydroxy-1-butene) have been detected in boreal forest PM1 aerosols collected at Hyytiälä, southern Finland, during a 2004 summer period, at significant atmospheric concentrations (in total 51 ng m-3 in summer versus 0.46 ng m-3 in fall). On the basis of these results, it can be concluded that photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol formation during summer in this conifer forest ecosystem. In addition to isoprene oxidation products, malic acid, which can be regarded as an intermediate in the oxidation of unsaturated fatty acids, was also detected at high concentrations during the summer period (46 ng m-3 in summer versus 5.2 ng m-3 in fall), while levoglucosan, originating from biomass burning, became relatively more important during the fall period (29 ng m-3 in fall versus 10 ng m-3 in summer). Pinic acid, a major photo-oxidation product of ?-pinene in laboratory experiments, could only be detected at trace levels in the summer samples, suggesting that further oxidation of pinic acid occurs and/or that different oxidation pathways are followed. We hypothesize that photo-oxidation of isoprene may participate in the early stages of new particle formation, a phenomenon which has been well documented in the boreal forest environment.

Kourtchev, I.; Ruuskanen, T.; Maenhaut, W.; Kulmala, M.; Claeys, M.

2005-10-01

193

Observation of 2-methyltetrols and related photo-oxidation products of isoprene in boreal forest aerosols from Hyytiälä, Finland  

NASA Astrophysics Data System (ADS)

Oxidation products of isoprene including 2-methyltetrols (2-methylthreitol and 2-methylerythritol), 2-methylglyceric acid and triol derivatives of isoprene (2-methyl-1,3,4-trihydroxy-1-butene (cis and trans) and 3-methyl-2,3,4-trihydroxy-1-butene) have been detected in boreal forest PM1 aerosols collected at Hyytiälä, southern Finland, during a 2004 summer period, at significant atmospheric concentrations (in total 51 ng m-3 in summer versus 0.46 ng m-3 in fall). On the basis of these results, it can be concluded that photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol formation during summer in this conifer forest ecosystem. In addition to isoprene oxidation products, malic acid, which can be regarded as an end-oxidation product of unsaturated fatty acids, was also detected at high concentrations during the summer period (46 ng m-3 in summer versus 5.2 ng m-3 in fall), while levoglucosan, originating from biomass burning, became relatively more important during the fall period (29 ng m-3 in fall versus 10 ng m-3 in summer). Pinic acid, a major photo-oxidation product of ?-pinene in laboratory experiments, could only be detected at trace levels in the summer PM1 aerosol samples from Hyytiälä, suggesting that further oxidation of pinic acid occurs and/or that different oxidation pathways are followed. We hypothesize that photo-oxidation of isoprene may participate in the early stages of new particle formation, a phenomenon which has been well documented in the boreal forest environment.

Kourtchev, I.; Ruuskanen, T.; Maenhaut, W.; Kulmala, M.; Claeys, M.

2005-05-01

194

Cesium/nanoporous carbon, composite materials: Synthesis, characterization, and base catalysis  

NASA Astrophysics Data System (ADS)

Materials produced from alkali metals and carbon have been of interest to researchers for many years. Graphite intercalation compounds of alkali metals have been extensively studied and shown to be active base catalysts in reactions such as side-chain alkylation, 1-butene isomerization, and amine synthesis. Unfortunately, these materials were found to be pyrophoric, had relatively low surface area, and exfoliated at reaction temperature. Nanoporous carbons (NPC) are chemically inert solids that contain nanopores, formed from curvature induced by five- and seven-member rings that interrupt the symmetric aromatic structure. Cesium, introduced into a NPC structure, adsorbs strongly in these nanopore spaces and the curvature effects within the NPC pores provide for much higher thermal stability. There is an intimate relationship between the cesium and the NPC support. The cesium seems to be only a carrier of electrons. Immediately after its contact with the carbon, these electrons are pushed into the carbon matrix. Within the local carbon domains, anions and radical anions form. Electron spin resonance spectroscopy and x-ray photoelectron spectroscopy indicate strong evidence of this interaction. Not only are these electron de-localized into the carbon walls, available for catalysis, they can react with the carbon, causing it to reorganize. It has been a known property of NPC to contain stabilized free radicals. The addition of cesium attacks these regions of high strain, relaxing them and causing the carbon to restructure at a local level. High-resolution, transmission electron microscopy confirms that, if the conditions are right, this "seed structure" can grow and propagate, forming larger structures such as nested onions and graphitic sheets. X-ray diffraction measurements confirm this reorganization on a global scale when the cesium loading is high. The existence of radical anions indicates that these materials have the capability of donating one or two electrons to a reaction, promoting either Lewis-base or free-radical chemistry. In fact, these materials are exceptionally active base catalysts; they provide a greater than 25 to 1 ratio of the less stable cis-2-butene over the trans isomer in the isomerization of 1-butene at 200 K and couple toluene to propylene near atmospheric pressure. Its radical properties give Cs/NPC a very high affinity for hydrogen, breaking the extremely energetic C-H bond in benzene and promoting its condensation to biphenyl, opening a new class of chemical reactions to heterogeneous catalysis. Extending this chemistry to the extreme high-energy methyl radical, Cs/NPC has lowered the (oxygen-free) methane activation temperature from the purely thermal value of >900°C, to below 500°C.

Stevens, Mark Gardner

2000-10-01

195

Theoretical and kinetic study of the reaction of ethyl methyl ketone with HO2 for T = 600-1600 K. Part II: addition reaction channels.  

PubMed

The temperature and pressure dependence of the addition reaction of ethyl methyl ketone (EMK) with HO2 radical has been calculated using the master equation method employing conventional transition state theory estimates for the microcanonical rate coefficients in the temperature range of 600-1600 K. Geometries, frequencies, and hindrance potentials were obtained at the B3LYP/6-311G(d,p) level of theory. A modified G3(MP2,CC) method has been used to calculate accurate electronic energies for all of the species involved in the reactions. The rigid-rotor harmonic oscillator approximation has been used for all of the vibrations except for the torsional degrees of freedom which are being treated as 1D hindered rotors. Asymmetric Eckart barriers were used to model tunneling effect in a one-dimensional reaction coordinate through saddle points. Our calculated results show that the four reaction channels forming 1-buten-2-ol + HO2 radical (R5), 2-buten-2-ol + HO2 radical (R10), acetic acid + ethylene + OH radical (R13), and 2-methyl-2-oxetanol + OH radical (R15) are the dominant channels. When the temperature is below 1000 K, the reaction R15 forming the cyclic ether, 2-methyl-2-oxetanol, is dominant while the reaction R13 forming acetic acid + ethylene + OH radical becomes increasingly dominant at temperatures above 1000 K. The other two channels forming 1-buten-2-ol, 2-buten-2-ol, and HO2 radical are not dominant but are still important product channels over the whole temperature range investigated here. No pressure dependence has been found for the reaction channels forming 2-methyl-2-oxetanol + OH radical and acetic acid + ethylene + OH radical. A slightly negative pressure dependence has been found for the reaction channels producing the two butenols. Rate constants for the four important reaction channels at 1 atm (in cm(3) mol(-1) s(-1)) are k(R5) = 2.67 × 10(15) × T(-1.32)exp(-16637/T), k(R10) = 1.62 × 10(8) × T(0.57)exp(-13142/T), k(R13) = 2.29 × 10(17) × T(-1.66)exp(-18169/T), and k(R15) = 6.17 × 10(-2) × T(3.35)exp(-10136/T). A comparison of the total rate constants for the addition of HO2? radical to EMK and that for H-atom abstraction by HO2? radical from EMK has also been carried out. We find that the abstraction reaction channels are dominant over the entire temperature range of 600-1600 K. PMID:23590522

Zhou, Chong-Wen; Mendes, Jorge; Curran, Henry J

2013-06-01

196

(Phenoxyimidazolyl-salicylaldimine)iron complexes: synthesis, properties and iron catalysed ethylene reactions.  

PubMed

The reaction of 2-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L1), 2,4-di-tert-butyl-6-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L2) or 4-tert-butyl-2-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L3) with iron(ii) precursors produced either iron(ii) or iron(iii) complexes, depending on the nature of the anions in the iron(ii) precursor and the ligand. When the anion is chloride and the ligand L1, the product is [(L1)2Fe][FeCl4] (1), but when the anion is triflate (OTf(-)) and the ligand is L2, the product is [(L2)2Fe][OTf]2 (2). With iron(ii) halides and tert-butyl groups on the phenoxy ligands L2 and L3, the iron(iii) complexes [(L2)FeX2] {where X = Cl (3), Br (4) and I = (5)} and [(L3)FeCl2] (6) were formed. Complexes 1-6 were characterised by a combination of elemental analyses, IR spectroscopy and mass spectrometry; and in selected cases (3 and 4) by single crystal X-ray crystallography. The crystal structures of 3 and 4 indicated that the iron(ii) precursors oxidised to iron(iii) in forming complexes 3-6; an observation that was corroborated by the magnetic properties and the (57)Fe Mössbauer spectra of 3 and 4. The iron(iii) complexes 3-6 were used as pre-catalysts for the oligomerisation and polymerisation of ethylene. Products of these ethylene reactions depended on the solvent used. In toluene ethylene oligomerised mainly to 1-butene and was followed by the 1-butene alkylating the solvent to form butyl-toluenes via a Friedel-Crafts alkylation reaction. In chlorobenzene, ethylene oligomerised mainly to a mixture of C4-C12 alkenes. Interestingly small amounts of butyl-chlorobenzenes and hexyl-chlorobenzenes were also formed via a Friedel-Crafts alkylation with butenes and hexenes from the oligomerisation of ethylene. PMID:25111396

Yankey, Margaret; Obuah, Collins; Guzei, Ilia A; Osei-Twum, Emmanuel; Hearne, Giovanni; Darkwa, James

2014-10-01

197

Experimental study of the hydrothermal reactivity of organic acids and acid anions: II. Acetic acid, acetate, and valeric acid  

NASA Astrophysics Data System (ADS)

Organic acids and acid anions occur in substantial concentrations in many aqueous geologic fluids and are thought to take part in a variety of geochemical processes ranging from the transport of metals in ore-forming fluids to the formation of natural gas to serving as a metabolic energy source for microbes in subsurface habitats. The widespread occurrence of organic acids and their potential role in diverse geologic processes has led to numerous experimental studies of their thermal stability, yet there remain substantial gaps in our knowledge of the factors that control the rates and reaction pathways for the decomposition of these compounds under geologic conditions. In order to address some of these uncertainties, a series of laboratory experiments were conducted to examine the behavior of organic acids and acid anions under hydrothermal conditions in the presence of minerals. Reported here are results of experiments where aqueous solutions of acetic acid, sodium acetate, or valeric acid ( n-pentanoic acid) were heated at 325°C, 350 bars in the presence of the mineral assemblages hematite + magnetite + pyrite, pyrite + pyrrhotite + magnetite, and hematite + magnetite. The results indicate that aqueous acetic acid and acetate decompose by a combination of two reaction pathways: decarboxylation and oxidation. Both reactions are promoted by minerals, with hematite catalyzing the oxidation reaction while magnetite catalyzes decarboxylation. The oxidation reaction is much faster, so that oxidation dominates the decomposition of acetic acid and acetate when hematite is present. In contrast to previous reports that acetate decomposed more slowly than acetic acid, we found that acetate decomposed at slightly faster rates than the acid in the presence of minerals. Although longer-chain monocarboxylic acids are generally thought to decompose by decarboxylation, valeric acid appeared to decompose primarily by "deformylation" to 1-butene plus formic acid. Subsequent decomposition of 1-butene and formic acid generated a variety of short-chain (?C 4) hydrocarbons and moncarboxylic acids as well as CO 2. Valeric acid decomposition proceeded more rapidly (by a factor of 2) in the presence of hematite-magnetite-pyrite than with the other mineral assemblages, with the greater reaction rate apparently attributable to the effects of fluid chemistry. Valeric acid was observed to decompose at a substantially faster rate than acetic acid under similar conditions. The results suggest that decomposition of aqueous monocarboxylic acids may make a significant contribution to the conversion of petroleum to light hydrocarbons in natural gas and thermal fluids.

McCollom, Thomas M.; Seewald, Jeffrey S.

2003-10-01

198

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

199

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

200

Semi-quantitative immunohistochemical analysis of male rat-specific alpha2u-globulin accumulation for chemical toxicity evaluation.  

PubMed

We purified male rat urinary alpha(2u)-globulin, prepared the antibody in rabbits, and improved an immunohistochemical detection method using this antibody for male rat-specific alpha(2u)-globulin accumulation appearing as hyaline droplets in the kidneys. Our prepared antibody reacted specifically with alpha(2u)-globulin in both immunohistochemical and Western blotting analyses, furthermore, and the graded immuno-reactivities on the slide were well associated with computational image analyzing results. Using this method, we retrospectively analyzed the renal sections from the toxicity studies of 12 nephrotoxic chemicals, which had already been conducted under the Japanese Existing Chemicals Survey Program. We demonstrated that the hyaline droplets induced by treatment with 10 chemicals (1,4-dibromobenzene, dicyclopentadiene, 3,4-dimethylaniline, 1,4-dicyanobenzene, tetrahydrothiophene-1,1-dioxide, 1,3-dicyanobenzene, acenaphthene, 3,4-dichloro-1-butene, 3a,4,7,7a-tetrahydro-1H-indene and 3,5,5-trimethylhexan-1-ol) were directly associated with alpha(2u)-globulin accumulation. This immunohistochemical method is convenient for applying, even retrospectively, paraffin sections from general toxicity studies and could be useful for qualifying male rat-specific hyaline droplets consisting of alpha(2u)-globulin and renal risk in humans. PMID:16538042

Hamamura, Masao; Hirose, Akihiko; Kamata, Eiichi; Katoku, Koshiro; Kuwasaki, Emiko; Oshikata, Takafumi; Nakahara, Yutaka; Ema, Makoto; Hasegawa, Ryuichi

2006-02-01

201

Ethylene polymerization on a SiH4-modified Phillips catalyst: detection of in situ produced ?-olefins by operando FT-IR spectroscopy.  

PubMed

Ethylene polymerization on a model Cr(II)/SiO(2) Phillips catalyst modified with gas phase SiH(4) leads to a waxy product containing a bimodal MW distribution of ?-olefins (M(w) < 3000 g mol(-1)) and a highly branched polyethylene, LLDPE (M(w) ? 10(5) g mol(-1), T(m) = 123 °C), contrary to the unmodified catalyst which gives a linear and more dense PE, HDPE (M(w) = 86,000 g mol(-1) (PDI = 7), T(m) = 134 °C). Pressure and temperature resolved FT-IR spectroscopy under operando conditions (T = 130-230 K) allows us to detect ?-olefins, and in particular 1-hexene and 1-butene (characteristic IR absorption bands at 3581-3574, 1638 and 1598 cm(-1)) as intermediate species before their incorporation in the polymer chains. The polymerization rate is estimated, using time resolved FT-IR spectroscopy, to be 7 times higher on the SiH(4)-modified Phillips catalyst with respect to the unmodified one. PMID:22231639

Barzan, Caterina; Groppo, Elena; Quadrelli, Elsje Alessandra; Monteil, Vincent; Bordiga, Silvia

2012-02-21

202

Conformational Analysis of 1-ALKENE Secondary Ozonides by Means of Matrix Isolation FTIR Spectroscopy  

NASA Astrophysics Data System (ADS)

An ability of ozone to break double C=C bond in olefins is known for more than five decades. Understanding of those reactions is very important in atmospheric chemistry. During different steps of the reaction the primary ozonide (POZ), carbonyl oxide (COX) and the secondary ozonide (SOZ) are formed. Fate of the reaction depends on many parameters such as type of radical, conformation of alkene, temperature of the reaction and environmental effects. Despite of numerous studies of the reaction by different spectroscopic techniques the precise mechanism of the reaction is still unknown. It is experimentally observed that the SOZ is more stable than POZ. Stability of the SOZ depends on the size and configuration of the radical. Unfortunately, it is not much known about the spatial structures of the SOZ'es. The aim of this study is to define the geometrical structures and stability of the different conformers of the 1-butene and 1-heptene secondary ozonides by combined analysis of the matrix isolation FTIR spectral data with the results of Density Functional Theory (DFT) calculations.

Sablinskas, Valdas; Strazdaite, Simona; Ceponkus, Justinas

2009-06-01

203

Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes  

NASA Astrophysics Data System (ADS)

The reactions of Cl atoms with a series of unsaturated aldehydes have been investigated for the first time using a relative method. In order to obtain additional information for a qualitative structure versus reactivity discussion, we have also determined, for the first time, the rate coefficients for the reactions of atomic chlorine with their respective saturated aldehydes. These relative measurements were performed at room temperature and atmospheric pressure of air and N2, by using ethane, propene and 1-butene as reference compounds. The weighted average relative rate constants obtained, kCl±2? (in units of cm3 molecule-1 s-1) were: trans-2-pentenal (1.31±0.19)×10-10; trans-2-hexenal (1.92±0.22)×10-10; trans-2-heptenal (2.40±0.29)×10-10; n-pentanal (2.56±0.27)×10-10; n-hexanal (2.88±0.37)×10-10; n-heptanal (3.00±0.34)×10-10. Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO3 radicals.

Rodríguez, D.; Rodríguez, A.; Notario, A.; Aranda, A.; Díaz-de-Mera, Y.; Marínez, E.

2005-07-01

204

Kinetic study of the gas-phase reaction of atomic chlorine with a series of aldehydes  

NASA Astrophysics Data System (ADS)

The reactions of Cl atoms with a series of unsaturated aldehydes have been investigated for the first time using a relative method. In order to obtain additional information for a qualitative structure versus reactivity discussion, we have also determined the rate coefficients for the reactions of atomic chlorine with their respective saturated aldehydes. These relative measurements were performed at room temperature and atmospheric pressure of air and N2, by using ethane, propene and 1-butene as reference compounds. The weighted average relative rate constants obtained, kCl±2? (in units of cm3 molecule-1 s-1) were: trans-2-pentenal (1.31±0.19)×10-10; trans-2-hexenal (1.92±0.22)×10-10; trans-2-heptenal (2.40±0.29)×10-10; n-pentanal (2.56±0.27)×10-10; n-hexanal (2.88±0.37)×10-10; n-heptanal (3.00±0.34)×10-10.

Finally, results and atmospheric implications are discussed and compared with the reactivity with OH and NO3 radicals.

Rodríguez, D.; Rodríguez, A.; Notario, A.; Aranda, A.; Díaz-de-Mera, Y.; Martínez, E.

2005-12-01

205

Measurement of proton transfer reaction rates in a microwave cavity discharge flowing afterglow  

NASA Astrophysics Data System (ADS)

The reaction rate coefficients between the hydronium ion and the molecules ethene (C2H4), propene (C 3H6), 1-butene (C4H8) and hydrogen sulfide (H2S) were measured at 296 K. The measured reaction rates were compared to collision rates calculated using average dipole orientation (ADO) theory. Reaction efficiency depends primarily upon the proton affinity of the molecules. All the measurements were obtained using the newly developed microwave cavity discharge flowing afterglow (MCD-FA) apparatus. This device uses an Asmussen-type microwave cavity discharge ion source that is spatially separated from the flow tube, eliminating many of the problems inherent with the original FA devices. In addition to measuring reaction rate coefficients, the MCD-FA was shown to be an effective tool for measuring trace compounds in atmospheric air. This method has many advantages over current detection techniques since compounds can be detected in almost real time, large mass ranges can be scanned quickly, and repeated calibration is not required. Preliminary measurements were made of car exhaust and exhaled alveolar air. Car exhaust showed the presence of numerous hydrocarbons, such as butene, benzene and toluene while the exhaled alveolar air showed the presence of various volatile organic compounds such as methanol and acetone.

Brooke, George M., IV

206

The skeletal isomerization of n-butene over ferrierite catalysts  

NASA Astrophysics Data System (ADS)

The catalytic properties of H-ferrierite zeolites, prepared by hydrothermal and dry-state synthesis, were compared in the skeletal isomerization of 1-butene. The activity was found to be strongly influenced by the presence of extra-framework Al (EFAl) species in the zeolite micropores and by the carbonaceous deposit formed during the reaction. The dynamics of mass transport in the zeolite crystallites were studied by the frequency-response (FR) method using acetylene, propane, n- and i-butane as probe molecules. The selectivity of n-butene conversion showed correlation with the dynamics of the n-butane sorption process. Either the diffusion or the sorption was the rate-controlling slowest step of n-butane mass transport, depending on the amount and the distribution of the EFAl species in the sample. In the catalyst sample, free of EFAl, the transport was found to be controlled by the rate of sorption. At an EFAl content of about 0.5-1.0 EFAl/unit cell the diffusion resistance of the micropores governed the n-butane transport rate.

Onyestyák, Gy; Valyon, J.; Pál-Borbély, G.; Rees, L. V. C.

2002-08-01

207

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

2011-11-01

208

Alkene and arene combustion on Pd(111)  

SciTech Connect

Palladium-catalyzed combustion reactions can play a significant role in the control of auto emissions in the three-way catalytic converter. Oxidation reactions of ethene, propene, 1-butene, 1,3-butadiene, benzene, and toluene were studied on oxygen-precovered Pd(111) (0.25 ML--1.2 ML) using temperature-programmed reaction spectroscopy (TPRS). Combustion is the sole reaction pathway; no partial oxidation products are formed. Comparison of these results with those from Pd(100) demonstrates that the structure of the metal surface does not significantly affect the mechanism of catalytic oxidation of most of the olefins or aromatic hydrocarbons studied, although, in general, combustion occurs at higher temperatures on Pd(111). Only for benzene combustion is there an appreciable structure sensitivity. For all the hydrocarbons studied the CO{sub 2} and CO yields are maximized for an oxygen precoverage of 0.34 oxygen atoms per surface palladium atom. Abrupt increases in carbon oxide production at specific oxygen coverages indicate that oxygen-induced surface reconstructions may play a role in the combustion activity.

Harris, T.D.; Madix, R.J. [Stanford Univ., CA (United States)] [Stanford Univ., CA (United States)

1998-09-10

209

Temperature-programmed desorption investigation of the adsorption and reaction of butene isomers on Pt(111) and ordered Pt-Sn surface alloys  

SciTech Connect

The influence of alloyed Sn on the chemistry of C{sub 4} butene isomers, including 1-butene, cis-2-butene, and isobutene, chemisorbed on Pt(111) was investigated by temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-energy electron diffraction (LEED). Pt-Sn alloy chemistry was probed by investigation of two ordered surface alloys formed when Sn atoms were incorporated within the topmost layer on a Pt(111) substrate. All three butenes undergo decomposition on Pt(111) during TPD which accounts for 50-60% of the chemisorbed monolayer. Alloying Sn into the surface causes a large reduction in the reactivity of the surface, and the fraction of the chemisorbed layer which decomposes is decreased to 3-7% on the (2 x 2) alloy, and no decomposition occurs on the ({radical}3 x {radical}3)R30{degree} alloy. The strong reduction of decomposition on these two surface alloys may be due to the elimination of adjacent pure Pt 3-fold hollow sites. No large changes occur in the coverage of chemisorbed monolayer of butenes in the presence of up to 33% of a monolayer of alloyed Sn, showing that the adsorption ensemble requirement for chemisorption of these alkenes on Pt(111) and the two Sn/Pt(111) alloys is at most a few Pt atoms. 39 refs., 15 figs., 1 tab.

Tsai, Y.L.; Koel, B.E. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States)

1997-04-10

210

The adsorption and reactions of hydrocarbons on Molybdenum single crystal surfaces; when clean and in the presence of co-adsorbed sulfur or carbon  

NASA Astrophysics Data System (ADS)

The chemisorption and reactions of thiophene, 1,3-butadiene, butenes, and n-butane on clean Mo(100), and with sulfur or carbon overlayers, have been investigated using thermal desorption spectroscopy (TDS). The predominant reaction at low additive coverage (0-0.2 monolayers of S or C), and at low ambient pressure (10 -10 Torr) for unsaturated hydrocarbons is decomposition. Butane is the least reactive of the hydrocarbons, and a large fraction (95%) desorbs molecularly at all additive coverages. As additive (S or C) coverage increases the amount of decomposition decreases, enabling other reaction pathways to become more probable. Hydrogenation, partial dehydrogenation, and isomerization reactions are detected. Molecular binding on the additive overlayers was also found to be very different. On sulfur overlayers the binding of the hydrocarbons was weak (physisorption), usually on the order of the heat of sublimation (9-10 kcal/mol). However, molecular binding on carbon overlayers was stronger: the heat of desorption was 17-23 kcal/mol for thiophene and butadiene, 12-15 kcal/mol for the butenes, and 11 kcal/mol for butane. In addition, isomerization of 1-butene to 2-butene, occurred on the carbon overlayer. It is suggested that the metal sites control the reactions observed (except for isomerization). This accounts for the similarity in surface reaction product distributions, and explains why the difference in molecular hydrocarbon binding between the sulfur covered and carbon covered surface plays a minor role in these reactions.

Kelly, D. G.; Salmeron, M.; Somorjai, G. A.

1986-10-01

211

Expanding the scope of metathesis: a survey of polyfunctional, single-site supported tungsten systems for hydrocarbon valorization.  

PubMed

Olefin metathesis is increasingly incorporated in polyfunctional industrial processes. The classical WO3/SiO2 olefin metathesis catalyst is combined to other catalysts in order to afford higher added-value chemicals. However, the combination of several reactions, not only in a single reactor, but also stemming from a single, multifunctional surface species is a desirable improvement regarding process issues. Well-defined surface organometallic tungsten species can be designed to implement targeted functionalities (carbene, hydride, alkyl, …). By tuning the metal's coordination sphere, it is possible to combine metathesis with several reactions, such as (de)hydrogenation, dimerization or isomerization. Novel, unconventional reactions for the production and upgrading of alkanes and alkenes have thus been uncovered. The reactivity of this library of supported catalysts is discussed based on the type of mediated transformations: monofunctional (alkene and alkyne metathesis), bifunctional (1-butene or 2-butenes to propylene), trifunctional (ethylene to propylene, alkane metathesis, …). Mechanistic considerations will be discussed to put these results in a wider perspective for future developments. PMID:23945666

Popoff, Nicolas; Mazoyer, Etienne; Pelletier, Jérémie; Gauvin, Régis M; Taoufik, Mostafa

2013-12-01

212

Explosive photodissociation of methane induced by ultrafast intense laser  

SciTech Connect

A new type of molecular fragmentation induced by femtosecond intense laser at the intensity of 2x10{sup 14} W/cm{sup 2} is reported. For the parent molecule of methane, ethylene, n-butane, and 1-butene, fluorescence from H (n=3{yields}2), CH (A {sup 2}{delta}, B {sup 2}{sigma}{sup -}, and C {sup 2}{sigma}{sup +}{yields}X {sup 2}{pi}), or C{sub 2} (d {sup 3}{pi}{sub g}{yields}a {sup 3}{pi}{sub 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{yields}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.

Kong Fanao; Luo Qi; Xu Huailiang; Sharifi, Mehdi; Song Di; Chin, See Leang [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Department of Physics, Engineering Physics and Optics, Laval University, Quebec G1K 7P4, Canada and Center for Optics, Photonics, and Laser, Laval University, Quebec G1K 7P4 (Canada); Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Department of Physics, Engineering Physics and Optics, Laval University, Quebec G1K 7P4 (Canada) and Center for Optics, Photonics, and Laser, Laval University, Quebec G1K 7P4 (Canada)

2006-10-07

213

Evaluation of the acid properties of porous zirconium-doped and undoped silica materials  

SciTech Connect

A series of porous silica and Zr-doped silica molecular sieves, belonging to the MCM-41 and MSU families, were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N{sub 2} adsorption at 77 K. Their acid properties have been evaluated by NH{sub 3}-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FT-IR spectroscopy and the catalytic tests of isopropanol decomposition and isomerization of 1-butene. The acidity of purely siliceous solids were, in all cases, very low, while the incorporation of Zr(IV) into the siliceous framework produced an enhancement of the acidity. The adsorption of basic probe molecules and the catalytic behaviour revealed that Zr-doped MSU-type silica was more acidic than the analogous Zr-MCM-41 solid, with a similar Zr content. This high acidity observed in the case of Zr-doped silica samples is due to the presence of surface zirconium atoms with a low coordination, mainly creating Lewis acid sites. - Graphical abstract: The adsorption of basic probe molecules and the catalytic behaviour have revealed that MSU-type materials are more acidic than the analogous MCM-41 solids, mainly after the incorporation of zirconium into the silica framework.

Fuentes-Perujo, D. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga (Spain); Santamaria-Gonzalez, J. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga (Spain); Merida-Robles, J. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga (Spain); Rodriguez-Castellon, E. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga (Spain); Jimenez-Lopez, A. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga (Spain); Maireles-Torres, P. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga (Spain)]. E-mail: maireles@uma.es; Moreno-Tost, R. [Instituto de Catalisis y Petroleoquimica, CSIC, c/ Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Mariscal, R. [Instituto de Catalisis y Petroleoquimica, CSIC, c/ Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain)

2006-07-15

214

Synthesis and antitumor activity of 10-alkyl-10-deazaminopterins. A convenient synthesis of 10-deazaminopterin.  

PubMed

Requirements for large-scale synthesis of the potent antitumor drug 10-deazaminopterin have led to development of a facile synthesis of this compound and its 10-alkyl analogues. The lithium diisopropyl amide generated dianions of appropriate p-alkylbenzoic acids were alkylated with 3-methoxyallyl chloride. The resulting 4-(p-carboxyphenyl)-1-methoxy-1-butenes were brominated at pH 7-8 to afford the 2-bromo-4-(p-carboxyphenyl)butyraldehydes. Condensation with 2,4,5,6-tetraminopyrimidine and subsequent in situ oxidation of the resulting dihydropteridines yielded crystalline 10-alkyl-10-deaza-4-amino-4-deoxypteroic acids. The pteroic acids were coupled with diethyl glutamate via the mixed anhydride method, followed by saponification at room temperature, to give the target 10-deazaminopterins. The 10-alkyl compounds were approximately equipotent to 10-deazaminopterin as growth inhibitors of folate-dependent bacteria. Their abilities to inhibit Lactobacillus casei and L1210 derived dihydrofolate reductases were also similar. Transport properties in vitro were suggestive of an improved therapeutic index for the 10-alkyl analogues. Against L1210 in mice, the percent increase in life span at the LD10 dosage was +151% (methotrexate), +178% (10-deazaminopterin), +235% (10-methyl analogue), and +211% (10-ethyl analogue). 10,10-Dimethyl-10-deazaminopterin was less effective at an equimolar dosage, but the ILS at the maximum dose tested (72 mg/kg) was +135%. It was far less toxic than the other analogues possibly because of enhanced clearance. PMID:7143361

DeGraw, J I; Brown, V H; Tagawa, H; Kisliuk, R L; Gaumont, Y; Sirotnak, F M

1982-10-01

215

CYP 17 and CYP 19 inhibitors. Evaluation of fluorine effects on the inhibiting activity of regioselectively fluorinated 1-(Naphthalen-2-ylmethyl)imidazoles.  

PubMed

Regioselectively fluorinated 1-(naphth-2-ylmethyl)imidazoles 1a-h have been synthesized starting from the corresponding (naphth-2-yl)methanols (2). 2a-d have been obtained by LiAlH4-promoted reduction of fluorinated 1-methyl-2-naphthaldehydes. The latter were easily prepared in fairly good overall yields by ceric ammonium nitrate (CAN)-promoted oxidative addition of the suitable 3-(fluoroaryl)-1-trimethylsilyloxy-1-butenes to ethyl vinyl ether in methanol followed by cyclization of the resulting acetals in strongly acidic medium in the presence of DDQ. 2e-h were prepared by LiAlH4-promoted reduction of the corresponding fluorinated methyl 2-naphthoates. The latter were more profitably obtained by reacting the suitable benzyl bromide with the sodium salt of dimethyl 2-(2,2-dimethoxyethyl)malonate in DMF followed by demethoxycarbonylation and acid catalysed cyclization of the resulting acetals. Compared with the nonfluorinated parent compounds 1i-1, fluorinated 1-(naphth-2-yl)methylimidazoles 1a-h turned out to be potent inhibitors of CYP17 and CYP19 enzymes. The most active inhibitor of CYP17 is 1c, whereas CYP19 is strongly inhibited by 1b, 1e, and 1g. Interestingly, 1g is a potent dual inhibitor also being very active towards CYP19. PMID:15449729

Hartmann, Rolf W; Palusczak, Anja; Lacan, Fabrice; Ricci, Giacomo; Ruzziconi, Renzo

2004-04-01

216

Study of the Effect of Comonomer Type on the Properties of Rapidly Crystallized and Annealed Random Ethylene Copolymers  

NASA Astrophysics Data System (ADS)

The properties of a series of random ethylene copolymers prepared with the metallocene catalytic system rac-Et[Ind]2 ZrCl2/MAO were studied for a large variety of comonomer types. These include the classical 1-alkene type with length up to 10 carbons and those of the cyclic type such as cyclopentadiene and dicyclopentadiene. Under rapid crystallization, the melting temperatures of the newly synthesized copolymers followed the relation of model random copolymers indicating a behavior that conforms to that predicted by Flory's phase equilibrium theory. The molar entropy of fusion is not significantly altered by the comonomer type including the dicyclopentadiene type. All types of comonomers studied showed, for a fixed comonomer content, the same change in properties during annealing, except the ethylene 1-butenes. These latter copolymers and the hydrogenated polybutadienes showed a faster rate of change in thermal properties. This is consistent with a higher molecular diffusion for the butene comonomer than for the rest of comonomers analyzed. The properties of the interlamellar region were also studied as a function of comonomer type and content following the variation of the amorphous halo extracted from the WAXS diffractograms. The observed systematic decrease in the peak scattering angle with increasing comonomer content indicates a variation of the intermolecular liquid structure.

Alamo, Rufina; Simanke, Adriane; Galland, Griselda; Mauler, Raquel

2001-03-01

217

Competitive hydrogenation of butadiene and butene on palladium and platinum catalysts  

SciTech Connect

In a recent study of the selective hydrogenation of butadiene to butenes, the reactivity of palladium (in the form of single crystals and of supported catalysts) was compared with that of platinum. The reactivity of single-crystal faces with (111) orientation is comparable to that of SiO{sub 2}-supported catalysts. The argument put forward to explain the comparatively lower activity of platinum was its lower hydrogen coverage under a given pressure, in the presence of the hydrocarbons, arising from a heat of adsorption smaller than that on palladium (respectively 67 and 85 kJ/mol). Concerning its poorer selectivity toward butenes, the reason invoked was a similar heat of adsorption for butadiene and butenes: the olefinic intermediate compound remains partly on the surface and the reaction proceeds to butane. A powerful kinetic method which is able to provide direct evidence for this different adsorption of dienes and butenes would be the competitive hydrogenation of these two molecules. However, to distinguish between the ethylenic hydrocarbon formed during the reaction and the molecules already present in the reactants, the experiments were performed according to the sequence: competitive hydrogenation of a butadiene-propene mixture followed by the hydrogenation of a 1-butene-propene mixture. This paper describes a study which confirms that the reason for the selectivity of palladium (after stabilization of the catalyst) can be attributed unambiguously to its capacity of adsorbing a diene more strongly than an alkene molecule.

Ouchaib, T.; Massardier, J. Renouprez, A. (Institut de Recherche sur la Catalyse, Villeurbanne (France))

1989-10-01

218

Synthesis of butene-ethylene and hexene-butene-ethylene copolymers from ethylene via tandem action of well-defined homogeneous catalysts  

SciTech Connect

Recent progress in the chemistry of well-defined organometallic catalysts has made a significant impact in the manufacture of polyolefins. An ever-growing menu of metal-ligand combinations exists to control the activity, copolymerization aptitude, and stereoselectivity of the catalytic site. The authors recently reported the use of tandem catalysis to produce branched chain polyethylene from a single feedstock of ethylene. Mixtures of (C{sub 5}H{sub 5}B-OEt){sub 2}ZrCl{sub 2} (1) and [({eta}{sup 5}-C{sub 5}Me{sub 4})SiMe{sub 2}({eta}{sup 1}-NCMe{sub 3})]TiCl{sub 2} (2) produce branched polyethylene from ethylene when activated with methylaluminoxane (MAO). In this process, 1/MAO produces linear 1-alkenes which insert into the growing polyethylene chain at the 2/MAO site. In this paper the authors report how such a tandem catalysis system can be created for the synthesis of poly(ethylene-co-1-butene) or polyethylene with ethyl and butyl branches.

Komon, Z.J.A.; Bu, X.; Bazan, G.C.

2000-03-01

219

Modifications of surface properties of a H{sub 2}-treated RuS{sub 2}/SiO{sub 2} catalyst: A parallel between low-temperature CO FTIR spectroscopy and model reactions  

SciTech Connect

A silica-supported ruthenium sulfide catalyst was progressively reduced by hydrogen at increasing temperatures (423--673 K). The resulting modification of the surface properties was characterized by low-temperature CO adsorption FTIR spectroscopy and by test reactions such as CH{sub 3}SH condensation and 1-butene hydrogenation. On the nonreduced catalyst, CO adsorption spectra showed the presence of bands, indicating various CO forms on Ru sites in a sulfur-rich environment. When sulfur was progressively removed from the ruthenium sulfide phase, the number of coordinatively unsaturated Ru sites increased with the simultaneous formation of metallic Ru microdomains. A comparison of measurements of adsorption and catalytic activity showed that a rich sulfur environment was needed for the condensation of CH{sub 3}SH to CH{sub 3}SCH{sub 3}, a reaction that required acidic sites, while butene hydrogenation required highly depleted Ru sites. These results show that, upon reduction, RuS{sub 2} became less acidic and increasingly more metallic.

Berhault, G.; Mauge, F.; Lavalley, J.C.; Lacroix, M.; Breysse, M.

2000-01-25

220

Gas-phase pyrolytic reaction of 4-aryl-3-buten-2-ols and allyl benzyl ethers: kinetic and mechanistic study.  

PubMed

Flash vacuum pyrolysis (FVP) of 4-aryl-3-buten-2-ols [ArCH=CH-CH(CH3)OH, where Ar is phenyl, p-MeO, p-Me, p-Cl, p-NO2] gave the corresponding buta-1,3-dien-1-ylbenzene (ArCH=CH-CH=CH2, where Ar is Ph, p-MeO, p-Me, p-Cl, p-NO2) and 7-X-1,2-dihydronaphthalene derivatives (where X is H, MeO); FVP of 1-aryl-3-benzyloxy1-1-butenes and benzyl cinnamyl ethers [ArCH=CHCH(X)OCH2Ph, where Ar is phenyl, p-MeO, p-Me, p-Cl, X is H, Me, Ph] gave the corresponding but-2-en-1-ylbenzene derivatives (ArCH2CH=CH-X, where X is H, Me, Ph) together with benzaldehyde. The proposed mechanism of these pyrolytic transformations was supported by kinetic and product analysis. PMID:20110900

Al-Etaibi, Alya M; Al-Awadi, Nouria A; Ibrahim, Maher R; Ibrahim, Yehia A

2010-01-01

221

New analytical method for the determination of styrene oligomers formed from polystyrene decomposition and its application at the coastlines of the North-West Pacific ocean.  

PubMed

The pollution caused by plastic debris is an environmental problem with increasing concern in the oceans. Among the plastic polymers, polystyrene (PS) is one of the most problematic plastics due to the direct public health risk associated with their dispersion, as well as the numerous adverse environmental impacts which arise both directly from the plastics and from their degradation products. Little is known about their potential distribution characteristics throughout the oceans. For the first time, we report here on the regional distribution of styrene monomer (SM), styrene dimers (SD; 2,4-diphenyl-1-butene, SD1; 1,3-diphenyl propane, SD2), and styrene trimer (2,4,6-triphenyl-1-hexene: ST1), as products of PS decomposition determined from samples of sand and seawater from the shorelines of the North-West Pacific ocean. In order to quantitatively determine SM, SD (=SD1+SD2), and ST1, a new analytical method was developed. The detection limit was 3.3 ?g L(-1), based on a signal-to-noise ratio of three, which was well-suited to quantify levels of SM, SD, and ST1 in samples. Surprisingly, the concentrations of SM, SD, and ST1 in sand samples from the shorelines were consistently greater than those in seawater samples from the same location. The results of this study suggest that SM, SD, and ST1 can be widely dispersed throughout the North-West Pacific oceans. PMID:24394362

Saido, Katsuhiko; Koizumi, Koshiro; Sato, Hideto; Ogawa, Naoto; Kwon, Bum Gun; Chung, Seon-Yong; Kusui, Takashi; Nishimura, Masahiko; Kodera, Yoichi

2014-03-01

222

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

223

Characteristics of volatile organic compounds from motorcycle exhaust emission during real-world driving  

NASA Astrophysics Data System (ADS)

The number of motorcycles has increased significantly in Asia, Africa, Latin American and Europe in recent years due to their reasonable price, high mobility and low fuel consumption. However, motorcycles can emit significant amounts of air pollutants; therefore, the emission characteristics of motorcycles are an important consideration for the implementation of control measures for motorcycles in urban areas. Results of this study indicate that most volatile organic compound (VOC) emission factors were in the range of several decades mg/km during on-road driving. Toluene, isopentane, 1,2,4-trimethylbenzene, m,p-xylene, and o-xylene were the most abundant VOCs in motorcycle exhaust, with emission factors of hundreds mg/km. Motorcycle exhaust was 15.4 mg/km for 15 carbonyl species. Acetaldehyde, acetone, formaldehyde and benzaldehyde were the major carbonyl species, and their emission factors ranged from 1.4 to 3.5 mg/km 1,2,4-trimethylbenzene, m,p-xylene, 1-butene, toluene, o-xylene, 1,2,3-trimethylbenzene, propene, 1,3,5-trimethylbenzene, isoprene, m-diethylbenzene, and m-ethyltoluene were the main ozone formation potential (OFP) species, and their OFP was 200 mg-O3/km or higher.

Tsai, Jiun-Horng; Huang, Pei-Hsiu; Chiang, Hung-Lung

2014-12-01

224

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

225

Effect of pretreatment with dehulling and microwaving on the flavor characteristics of cold-pressed rapeseed oil by GC-MS-PCA and electronic nose discrimination.  

PubMed

Raw and dehulled rapeseeds were treated with microwave energy (800 W) from 1 to 8 min with 1-min intervals at a frequency of 2450 MHz to investigate the influence of microwaving and dehulling pretreatment on the flavor characteristics of rapeseed oil extracted by pressing. Headspace solid phase microextraction was used to isolate the volatile compounds of rapeseed oil, which were then identified by gas chromatography-mass spectrometry analysis. The results indicated that microwave and dehulling pretreatment of rapeseed can significantly influence the kinds and content of volatile compounds. The key flavor compounds in rapeseed oil were oxidized volatiles, heterocyclic compounds, and degradation products of glucosinolates. A pungent compound, 4-isothiocyanato-1-butene, was reduced by 97% in rapeseed treated for 3 min with microwaves energy when compared to the rapeseed oil without any treatment. The pyrazine compounds in the oil appeared after 6 min of microwave pretreatment and give a pleasant roasting flavor when compared to crude oils. Principal component analysis was able to differentiate between oils obtained using 4 pretreatment processes based on volatile compounds and electronic nose. The results showed that dehulling pretreatment could improve the flavor, yet microwaving had a greater effect on the flavor of rapeseed oils. PMID:23865448

Zhou, Qi; Yang, Mei; Huang, Fenghong; Zheng, Chang; Deng, Qianchun

2013-07-01

226

Role of ZSM-5 and ultrastable Y zeolites for increasing gasoline octane number  

SciTech Connect

Octane number of gasoline made in a fluid catalytic cracker can be catalytically enhanced by using an ultrastable HY zeolite instead of one containing rare earth cations or by adding small amounts of ZSM-5 to a Y zeolite catalyst. ZSM-5 addition catalyzes both normal and branched olefin cracking to give mainly propylene, butenes, 2-methyl 1-butene, and 2-methyl 2-butene. Increase in octane number is mainly due to an increase in yields of C{sub 7}{sup +} paraffins and straight olefins. The decrease in paraffin yield is due to the removal of olefins which would otherwise undergo secondary hydrogen addition. The USY zeolite gives a lighter gasoline with higher yields of C{sub 5} and C{sub 6} branched olefins than the REY zoelite which gives higher yields of C{sub 7}{sup +} branched paraffins. However, the USY catalyst, unlike the ZSM-5 addition case, does not decrease the yields of C{sub 7}{sup +} olefins. Reaction pathways that affect gasoline composition are different for the two cases; yet, in both cases, increases in C{sub 5} hydrocarbons and decreases in C{sub 7}{sup +} paraffins contribute significantly to the increase in octane number.

Madon, R.J. (Engelhard Corp., Edison, NJ (USA))

1991-05-01

227

Gas-Phase Reactions of Doubly Charged Lanthanide Cations with Alkanes and Alkenes. Trends in Metal(2+) Reactivity  

SciTech Connect

The gas-phase reactivity of doubly-charged lanthanide cations, Ln2+ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), with alkanes (methane, ethane, propane, n-butane) and alkenes (ethene, propene, 1-butene) was studied by Fourier transform ion cyclotron resonance mass spectrometry. The reaction products consisted of different combinations of doubly-charged organometallic ions?adducts or species formed via metal-ion-induced hydrogen, dihydrogen, alkyl, or alkane eliminations from the hydrocarbons?and singly-charged ions that resulted from electron, hydride, or methide transfers from the hydrocarbons to the metal ions. The only lanthanide cations capable of activating the hydrocarbons to form doubly-charged organometallic ions were La2+, Ce2+, Gd2+, and Tb2+, which have ground-state or low-lying d1 electronic configurations. Lu2+, with an accessible d1 electronic configuration but a rather high electron affinity, reacted only through transfer channels. The remaining Ln2+ reacted via transfer channels or adduct formation. The different accessibilities of d1 electronic configurations and the range of electron affinities of the Ln2+ cations allowed for a detailed analysis of the trends for metal(2+) reactivity and the conditions for occurrence of bond activation, adduct formation, and electron, hydride, and methide transfers.

Gibson, John K.; Marcalo, Joaquim; Santos, Marta; Pires de Matos, Antonio; Haire, Richard G.

2008-12-08

228

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

229

Effects of straw return on C2-C5 non-methane hydrocarbon (NMHC) emissions from agricultural soils  

NASA Astrophysics Data System (ADS)

The effect of crop straw return on C2-C5 non-methane hydrocarbon (NMHC) emissions from agricultural soils is investigated using a laboratory-controlled incubation of agricultural soils amended with crop straw for a period of 56 days. The average emission fluxes of total C2-C5 NMHCs from amended agricultural soils are 304 and 173 ng kg-1 h-1 under non-flooded and flooded conditions, respectively. Alkenes are the principal emitted C2-C5 NMHCs from amended agricultural soils, where a predominance of ethene, propene and 1-butene together shared 65% and 59% of the total C2-C5 NMHCs under non-flooded and flooded conditions, respectively. The emissions rates of the above top three alkenes and the total C2-C5 alkenes from amended agricultural soils under non-flooded conditions are one to four times those under flooded conditions, and these average values are 14-89 and 5-34 times those in their corresponding control treatments, respectively. These results imply that straw return contributes substantially to the emissions of light alkenes from agricultural soils, particularly under non-flooded conditions. The high correlation between microorganisms and C2-C5 NMHC fluxes from amended agricultural soils suggest that microbes play an important role in C2-C5 NMHC emissions from straw-amended agricultural soils. A rough estimate indicates that crop straw return could contribute insignificantly to global C2-C5 hydrocarbon budgets.

Wang, Ran; Wu, Ting; Dai, Wanhong; Liu, Hui; Zhao, Juan; Wang, Xinming; Huang, Feiyu; Wang, Zhe; Shi, Chengfei

2015-01-01

230

[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

231

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

232

Calculational and Experimental Investigations of the Pressure Effects on Radical - Radical Cross Combinations Reactions: C2H5 + C2H3  

NASA Technical Reports Server (NTRS)

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 yields 1-butene, (2c) C2H5 + C2H5 yields n-butane, and (3c) C2H3 + C2H3 yields 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 approx.1.2 at 760 Torr (101 kPa) to approx.0.5 at 100 Torr (13.3 kPa) and approx.0.1 at pressures lower than about 5 Torr (approx.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 yields C3H5 + CH3. This reaction occurs even at moderate pressures of approx.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(exp -3) - 10(exp 5) Torr). These calculations indicate that the high-pressure [1-C4H8]/[C4H10] yield ratio is 1.3 +/- 0.1.

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

2007-01-01

233

Controlling hydrogenation activity and selectivity of bimetallic surfaces and catalysts  

NASA Astrophysics Data System (ADS)

Studies of bimetallic systems are of great interest in catalysis due to the novel properties that they often show in comparison with the parent metals. The goals of this dissertation are: (1) to expand the studies of self-hydrogenation and hydrogenation reactions on bimetallic surfaces under ultra high vacuum conditions (UHV) using different hydrocarbon as probe molecules; (2) to attempt to correlate the surface science findings with supported catalyst studies under more realistic conditions; and (3) to investigate the competitive hydrogenation of C=C versus C=O bonds on Pt(111) modified by different 3d transition metals. Hydrogenation studies using temperature programmed desorption (TPD) on Ni/Pt(111) bimetallic surfaces have demonstrated an enhancement in the low temperature hydrogenation activity relative to that of clean Pt(111). This novel hydrogenation pathway can be achieved under UHV conditions by controlling the structures of the bimetallic surfaces. A low temperature hydrogenation activity of 1-hexene and 1-butene has been observed on a Pt-Ni-Pt(111) subsurface structure, where Ni atoms are mainly present on the second layer of the Pt(111) single crystal. These results are in agreement with previous studies of self-hydrogenation and hydrogenation of cyclohexene. However, a much higher dehydrogenation activity is observed in the reaction of cyclohexene to produce benzene, demonstrating that the hydrocarbon structure has an effect on the reaction pathways. On the other hand, self-hydrogenation of 1-butene is not observed on the Pt-Ni-Pt(111) surface, indicating that the chain length (or molecular weight) has a significant effect on the selfhydrogenation activity. The gas phase reaction of cyclohexene on Ni/Pt supported on alumina catalysts has also shown a higher self-hydrogenation activity in comparison with the same reaction performed on supported monometallic catalysts. The effects of metal loading and impregnation sequence of the metal precursors are also discussed. Chemisorption, TPD, FTIR using a batch reactor for the self-hydrogenation of cyclohexene and CO adsorbed on the bimetallic surfaces were carried out to correlate surface science findings with experiments on supported bimetallic catalysts. To expand the studies on the effect of bimetallic structures on hydrogenation reactions, molecules with multiple functional groups such as alpha,beta-unsaturated aldehydes were also investigated. Studies of selective hydrogenation of a,ss-unsaturated aldehydes toward the desired unsaturated alcohols are of interest for the production of fine chemicals and pharmaceuticals. In these compounds, competitive hydrogenation of the C=C and C=O bonds occurs. TPD and HREELS experiments of acrolein (CH2=CH-CH=O) on Pt-based bimetallic surfaces are performed to investigate their effects on the hydrogenation activity of the C-O bond. The production of the desired unsaturated alcohol, allyl alcohol, has been observed for the first time on Pt-Ni-Pt(111) under UHV conditions. However, the propionaldehyde yield is five times higher than the allyl alcohol yield. Thus, a preferential isomerization reaction of allyl alcohol to propionaldehyde is very likely to occur on the Pt-Ni-Pt(111) surface as observed on the desorption studies of allyl alcohol on this surface. The hydrogenation of acrolein is also carried out under UHV conditions on other 3d-transition metal/Pt(111) surfaces such as Co/Pt(111), Fe/Pt(111), and Cu/Pt(111). So far, the highest activity and allyl alcohol yield are found on the Pt-Ni-Pt(111) surface with pre-adsorbed hydrogen.

Murillo, Luis E.

234

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

235

Synthesis of a novel antiestrogen radioligand (99mTc-TOR-DTPA).  

PubMed

This study was aimed at developing a hydrophilic radioligand as an antiestrogen drug derivative to be used for imaging breast tumors. Toremifene [TOR; 4-chloro-1,2-diphenyl-1-(4-(2-(N,N-di-methylamino)ethoxy)phenyl)-1-butene, as citrate salt] was selected as the starting material to be derived, since it has been used extensively as an antiestrogen drug for treatment and prevention of human breast cancer. An antiestrogen drug derivative, TOR attached to diethylenetriamine pentaacetic acid (DTPA), was synthesized by two experimental treatments, including a purification and a reaction step. We described the synthesis of this TOR derivative, (3Z)-4-{4-[2-(dimethylamino) ethoxy] phenyl}-3,4-diphenylbut-3-en-1-ylN,N-bis[2-(2,6-dioxomorpholin-4-yl)ethyl]glycinate (TOR-DTPA), in detail. Mass spectroscopy confirmed the expected structures. TOR-DTPA was labeled with technetium-99m ((99m)Tc), using stannous chloride (SnCl(2)) as the reducing agent. Biodistribution studies were performed on female Albino Wistar rats. Quality controls, radiochemical yield, and stability studies were done utilizing high-performance liquid chromatography, radioelectrophoresis, thin-layer chromatography, and thin-layer radiochromatography methods. The synthesized compound was found to be hydrophilic and anionic, with high stability for the duration of the testing period in vitro. The results indicated that the radiolabeled compound has estrogen-receptor specificity, especially for the breast tissue. It is highly possible that this compound could be used for imaging breast tumors as a novel technetium-labeled hydrophilic estrogen derivative radioligand. PMID:20025551

Yurt, Ayfer; Muftuler, Fazilet Zumrut B; Unak, Perihan; Yolcular, Seniha; Acar, Cigdem; Enginar, Huseyin

2009-12-01

236

Photochemical cycloaddition reactions of cyanoacetylene and dicyanoacetylene  

NASA Technical Reports Server (NTRS)

Photolysis of cyanoacetylene with 185- or 206-nm light yields 1,3,5-tricyanobenzene while 254-nm radiation yields a mixture of tetracyanocyclooctatetraenes, 1,2,4- and 1,3,5-tricyanobenzene. A polymer of cyanoacetylene is the major photoproduct. 1,3,5-Tricarbomethoxybenzene was the only photoproduct identified from the irradiation of methyl propiolate at 254 nm. Mono-, di-, and tricyanobenzenes are formed by irradiation of mixtures of acetylene and cyanoacetylene at 185, 206, and 254 nm along with trace amounts of cyclooctatetraenes. No photoadducts were detected on photolysis of mixtures of cyanoacetylene and CO or HCN. The tetracyanocyclooctatetraene structures were established by UV, MS, and NMR analyses. The 1H NMR of the product mixture exhibited a singlet at delta 7.028 consistent with either 1 or 2 and two singlets at delta 6.85 and 6.91 assigned to 3. Photolysis of mixtures of dicyanoacetylene and acetylene with either 185- or 206-nm light yielded 1,2-dicyanobenzene and (E,Z)-1-buten-3-yne-1,4-dicarbonitrile. These products were also obtained using 254-nm light along with a mixture of tetracyanocyclooctatetraenes. The same three singlets were observed in this product mixture as were observed in the tetracyanocyclooctatetraenes obtained from cyanoacetylene. From this observation it was concluded that the delta 7.02 signal is due to 2 and not 1. The photolysis of cyanoacetylene and dicyanoacetylene in the presence of ethylene with 185-nm light yields 1-cyanocylobutene and 1,2-dicyanocyclobutene, respectively. 2-Cyanobutadiene and 2,3-dicyanobutadiene are the photoproducts with 254-nm light. Reaction pathways are proposed to explain these findings.

Ferris, J. P.; Guillemin, J. C.

1990-01-01

237

Photochemical cycloaddition reactions of cyanoacetylene and dicyanoacetylene.  

PubMed

Photolysis of cyanoacetylene with 185- or 206-nm light yields 1,3,5-tricyanobenzene while 254-nm radiation yields a mixture of tetracyanocyclooctatetraenes, 1,2,4- and 1,3,5-tricyanobenzene. A polymer of cyanoacetylene is the major photoproduct. 1,3,5-Tricarbomethoxybenzene was the only photoproduct identified from the irradiation of methyl propiolate at 254 nm. Mono-, di-, and tricyanobenzenes are formed by irradiation of mixtures of acetylene and cyanoacetylene at 185, 206, and 254 nm along with trace amounts of cyclooctatetraenes. No photoadducts were detected on photolysis of mixtures of cyanoacetylene and CO or HCN. The tetracyanocyclooctatetraene structures were established by UV, MS, and NMR analyses. The 1H NMR of the product mixture exhibited a singlet at delta 7.028 consistent with either 1 or 2 and two singlets at delta 6.85 and 6.91 assigned to 3. Photolysis of mixtures of dicyanoacetylene and acetylene with either 185- or 206-nm light yielded 1,2-dicyanobenzene and (E,Z)-1-buten-3-yne-1,4-dicarbonitrile. These products were also obtained using 254-nm light along with a mixture of tetracyanocyclooctatetraenes. The same three singlets were observed in this product mixture as were observed in the tetracyanocyclooctatetraenes obtained from cyanoacetylene. From this observation it was concluded that the delta 7.02 signal is due to 2 and not 1. The photolysis of cyanoacetylene and dicyanoacetylene in the presence of ethylene with 185-nm light yields 1-cyanocylobutene and 1,2-dicyanocyclobutene, respectively. 2-Cyanobutadiene and 2,3-dicyanobutadiene are the photoproducts with 254-nm light. Reaction pathways are proposed to explain these findings. PMID:11543604

Ferris, J P; Guillemin, J C

1990-01-01

238

Use of ferric sulfate: acid media for the desulfurization of model compounds of coal. [Dibenzothiophene, diphenyl sulfide, di-n-butyl sulfide  

SciTech Connect

The objective of this work has been to investigate the ability of ferric sulfate-acid leach systems to oxidize the sulfur in model compounds of coal. Ferric iron-acid leach systems have been shown to be quite effective at removal of inorganic sulfur in coal. In this study, the oxidative effect of ferric iron in acid-leach systems was studied using dibenzothiophene, diphenyl sulfide, and di-n-butyl sulfide as models of organic sulfur groups in coal. Nitrogen and oxygen, as well as various transition metal catalysts and oxidants, were utilized in this investigation. Dibenzothiophene was found to be quite refractory to oxidation, except in the case where metavanadate was added, where it appears that 40% oxidation to sulfone could have occurred per hour at 150/sup 0/C and mild oxygen pressure. Diphenyl sulfide was selectively oxidized to sulfoxide and sulfone in an iron and oxygen system. Approximately 15% conversion to sulfone occurred per hour under these conditions. Some of the di-n-butyl sulfide was cracked to 1-butene and 1-butanethiol under similar conditions. Zinc chloride and ferric iron were used at 200/sup 0/C in an attempt to desulfonate dibenzothiophene sulfone, diphenyl sulfone, and di-n-butyl sulfone. Di-n-butyl sulfone was completely desulfurized on one hour and fragmented to oxidized parafins, while dibenzothiophene sulfone and diphenyl sulfone were unaffected. These results suggest that an iron-acid leach process could only selectively oxidize aryl sulfides under mild conditions, representing only 20% of the organic sulfur in coal (8% of the total sulfur). Removal through desulfonation once selective sulfur oxidation had occurred was only demonstrated for alkyl sulfones, with severe oxidation of the fragmented paraffins also occurring in one hour.

Clary, L.R.; Vermeulen, T.; Lynn, S.

1980-12-01

239

A cryosolution infrared and DFT study of the complexes formed between vinylacetylene and hydrogen chloride  

NASA Astrophysics Data System (ADS)

The formation of weak molecular complexes between vinylacetylene (1-buten-3-yne, CH 2?CH-C?CH) and HCl or DCl dissolved in liquid argon has been investigated using infrared spectroscopy. In all spectra, evidence was found for the formation of a 1:1 van der Waals complex. At higher concentrations of hydrogen chloride, weak absorption bands due to 1:2 species were also observed. Using spectra recorded at different temperatures between 102 and 125 K, the complexation enthalpies for the 1:1 and the 1:2 complex were determined to be -10.2(9) and -16.9(15) kJ mol -1. A density function theory study of the structures and the vibrational frequencies of the complexes is performed at the B3LYP/6-311++G(d,p) level. These calculations show that HCl can form a complex with either the triple or the double carbon-carbon bond, with the former giving stable endo and exo conformers. Comparison of the experimental frequencies with the calculated ones shows that all observed complex bands are due to the endo conformer of the triple bond complex, while those of the 1:2 complex are due to a chain-type complex in which the second HCl is attached to the first one. Using free energy perturbation Monte Carlo simulations to calculate the solvent influences, and statistical thermodynamics to account for zero-point vibrational and thermal contributions the complexation energies for the C 4H 4·HCl and C 4H 4·(HCl) 2 are estimated from the experimental complexation enthalpies to be -17.3(20) and -34.6(32) kJ mol -1. These numbers are compared with the theoretical values obtained at the B3LYP/6-311++G(d,p) level and with single-point energies calculated at the MP2/aug-cc-PVTZ level.

Herrebout, W. A.; van der Veken, B. J.

2002-12-01

240

Characteristics of volatile organic compounds (VOCs) emitted from a petroleum refinery in Beijing, China  

NASA Astrophysics Data System (ADS)

This study made a field VOCs (volatile organic compounds) measurement for a petroleum refinery in Beijing by determining 56 PAMS VOCs, which are demanded for photochemical assessment in US, and obtained the characteristics of VOCs emitted from the whole refinery and from its inner main devices. During the monitoring period, this refinery brought about an average increase of 61 ppbv in the ambient TVOCs (sum of the PAMS VOCs) at the refinery surrounding area, while the background of TVOCs there was only 10-30 ppbv. In chemical profile, the VOCs emitted from the whole refinery was characteristic by isobutane (8.7%), n-butane (7.9%), isopentane (6.3%), n-pentane (4.9%%), n-hexane (7.6%), C6 branched alkanes (6.0%), propene (12.7%), 1-butene (4.1%), benzene (7.8%), and toluene (5.9%). On the other hand, the measurement for the inner 5 devices, catalytic cracking units (CCU2 and CCU3), catalytic reforming unit (CRU), tank farm (TF), and wastewater treatment(WT), revealed the higher level of VOCs pollutions (about several hundred ppbv of TVOCs), and the individual differences in VOCs chemical profiles. Based on the measured speciated VOCs data at the surrounding downwind area, PMF receptor model was applied to identify the VOCs sources in the refinery. Then, coupling with the VOCs chemical profiles measured at the device areas, we concluded that CCU1/3 contributes to 25.9% of the TVOCs at the surrounding downwind area by volume, followed by CCU2 (24.7%), CRU (18.9%), TF (18.3%) and WT (12.0%), which was accordant with the research of US EPA (2008). Finally, ozone formation potentials of the 5 devices were also calculated by MIR technique, which showed that catalytic cracking units, accounting for about 55.6% to photochemical ozone formation, should be given the consideration of VOCs control firstly.

Wei, Wei; Cheng, Shuiyuan; Li, Guohao; Wang, Gang; Wang, Haiyan

2014-06-01

241

Enhancement of bacterial mutagenicity of bifunctional alkylating agents by expression of mammalian glutathione S-transferase.  

PubMed

Recently, we inserted the plasmid vector pKK233-2 containing rat GSH S-transferase (GST) 5-5 cDNA into Salmonella typhimurium TA1535 and found that these bacteria [GST 5-5(+)] expressed the protein and produced mutations when ethylene or methylene dihalides were added [Thier, R., Taylor, J. B., Pemble, S. E., Ketterer, B., Persmark, M., Humphreys, W. G., and Guengerich, F. P. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 8576-8580]. After exposure to the known GST 5-5 substrate 1,2-epoxy-3-(4'-nitrophenoxy)propane, the GST 5-5(+) strain showed fewer mutants than the bacteria transfected with the cDNA clone in a reverse orientation [GST 5-5(-)], suggesting a protective role of GST 5-5. However, mutations were considerably enhanced in the GST 5-5(+) strain [as compared to GST 5-5(-)] when 1,2,3,4-diepoxybutane (butadiene diepoxide) or 1,2-epoxy-4-bromobutane was added. The GST 5-5(+) and GST 5-5(-) bacterial stains showed similar responses to 1,2-epoxypropane, 3,4-epoxy-1-butene, and 1,4-dibromobutane. The results suggest that some bifunctional activated butanes are transformed to mutagenic products through GSH conjugation. We also found that the GST 5-5(+) strain showed enhanced mutagenicity with 1,4-dibromo-2,3-epoxybutane, 1,2-epoxy-3-bromopropane (epibromohydrin), and (+/-)-1,4-dibromo-2,3-dihydroxybutane.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7578934

Thier, R; Müller, M; Taylor, J B; Pemble, S E; Ketterer, B; Guengerich, F P

1995-01-01

242

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 Central

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 P450. 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 Km at 3.5 mM and a kcat 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

2012-01-01

243

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

2013-07-01

244

Inverse co-flow approach to sooting laminar diffusion flames  

SciTech Connect

Normal and inverse diffusion flames (NDFs and IDFs) were used to study flame pyrolysis and soot formation processes. In an IDF, the reactant flows are reversed from the NDF configuration, that is, the oxidizer flows through the central tube into a surrounding co-flowing fuel stream. Soot formation processes are more effectively separated from oxidation processes in the IDF, which also tend to soot less. Temperature-controlled smoke height tests were applied to allene, 1,3-butadiene, several cyclic hydrocarbons, and branched aliphatic fuels. As found in previous studies, pyrolysis chemistry governs soot formation. Thermocouples and microprobe sampling were then used to measure thermal and chemical fields of NDF and IDF pyrolysis zones. First, NDF pyrolysis zones were probed using fuels with high sooting tendency, namely allene, 1,3-butadiene and benzene. The results support the growing consensus that aromatic ring formation is a controlling step in soot formation. The particular aromatic formation mechanism depends on flame type, fuel structure and local temperature. Next, the transition from near to slightly-sooting IDFs was examined using methane, ethene, propene and 1-butene as fuels. Soot inception occurred for the olefins when: (1) the temperature exceeded approximately 1300K in a predominantly pyrolytic regions; and (2) the location was sufficiently close to the main oxidation zone (where radicals are generated). Methane required higher temperatures to induce inception because it does not readily form acetylene. While these conditions determine whether inception will occur, the aromatic content, which scaled with the fuel's sooting tendency, affects the ultimate soot loading once inception has occurred.

Sidebotham, G.W.

1988-01-01

245

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

246

Probing the basic character of alkali-modified zeolites by CO{sub 2} adsorption microcalorimetry, butene isomerization, and toluene alkylation with ethylene  

SciTech Connect

Two types of alkali-modified zeolites X and Y were studied, namely, zeolites containing occluded cesium oxides and zeolites containing occluded alkali metals (Na, Cs). Zeolites with occluded CsO{sub X}, obtained via impregnation and decomposition of cesium acetate, exhibited higher CO{sub 2} adsorption capacities and higher heats of adsorption than the corresponding ion-exchanged zeolites. However, the heats of adsorption were significantly lower on the zeolite-supported oxides ({approximately}85 kJ/mol) compared to bulk cesium oxide ({approximately}270 kJ/mol). The CO{sub 2} adsorption capacities of the zeolites containing occluded CsO{sub X} increased linearly with the amount of occluded cesium (1 CO{sub 2} per 4 occluded Cs atoms), and the catalytic activity for 1-butene isomerization was commensurate with the CO{sub 2} uptake on the materials. Stronger base sites were created in zeolites by decomposition of impregnated alkali azides (Na, Cs), due to the formation of alkali metal species. These materials were active catalysts for the side-chain alkylation of toluene with ethylene, whereas zeolites containing occluded CsO{sub X} were inactive for the reaction. Dioxygen adsorption followed by thermal treatment of zeolites containing occluded alkali metal resulted in the elimination of their activity for toluene alkylation whereas their activity for butene isomerization was retained. Alkali oxide- and alkali metal-containing microporous carbon materials exhibited significantly different adsorption properties and catalytic activities from their zeolite counterparts, possibly due to the different nature of the occluded species and/or steric constraints in the amorphous carbon.

Bordawekar, S.V.; Davis, R.J.

2000-01-01

247

Rich premixed laminar methane flames doped by light unsaturated hydrocarbons. II. 1,3-Butadiene  

SciTech Connect

In line with the study presented in Part I of this paper, the structure of a rich premixed laminar methane flame doped with 1,3-butadiene has been investigated. The flame contains 20.7% (molar) of methane, 31.4% of oxygen, and 3.3% of 1,3-butadiene, corresponding to an equivalence ratio of 1.8, and a C{sub 4}H{sub 6}/CH{sub 4} ratio of 16%. The flame has 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 temperature ranged from 600 K close to the burner up to 2150 K. Quantified species included the usual methane C{sub 0}-C{sub 2} combustion products and 1,3-butadiene, but also propyne, allene, propene, propane, 1,2-butadiene, butynes, vinylacetylene, diacetylene, 1,3-pentadiene, 2-methyl-1,3-butadiene (isoprene), 1-pentene, 3-methyl-1-butene, benzene, and toluene. 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 1,3-butadiene and of formation of C{sub 6} aromatic species have been derived from flow rate analyses. In this case, the C{sub 4} route to benzene formation plays an important role in comparison to the C{sub 3} pathway. (author)

Gueniche, H.A.; Glaude, P.A.; Fournet, R.; Battin-Leclerc, F. [Departement de Chimie-Physique des Reactions, UMR 7630 CNRS, INPL-ENSIC, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France)

2007-10-15

248

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

249

Triarylphosphine Ligands with Hemilabile Alkoxy Groups. Ligands for Nickel(II)-Catalyzed Olefin Dimerization Reactions. Hydrovinylation of Vi-nylarenes, 1,3-Dienes, and Cycloisomerization of 1,6-Dienes.  

PubMed

Substitution of one of the phenyl groups of triphenylphosphine with a 2-benzyloxy-, 2-benzyloxymethyl- or 2-benzyloxyethyl-phenyl moiety results in a set of simple ligands, which exhibit strikingly different behaviour in various nickel(II)-catalyzed olefin dimerization reactions. Complexes of ligands with 2-benzyloxyphenyl-, 2-benzyloxymethylphenyl-diphenylphosphine (L5 and L6 respectively) are most active for hydrovinylation (HV) of vinylarenes, with the former leading to extensive isomerization of the primary 3-aryl-1-butenes into the conjugated 2-aryl-2-butenes even at -55 °C. However, 2-benzyloxymethyl-substituted ligand L6 is slightly less active, leading up to quantitative yields of the primary products of HV at ambient temperature with no trace of isomerization, thus providing the best option for a practical synthesis of these compounds. In sharp contrast, hydrovinylation of a variety of 1,3-dienes is best catalyzed by nickel(II)-complexes of 2-benzyloxyphenyldiphenylphosphine, L5. The other two ligands, 2-benzyloxymethyl-(L6) and 2-benzyloxyethyl-diphenylphosphine (L7) are much less effective in the HV of 1,3-dienes. Nickel(II)-catalyzed cycloisomerization of 1,6-dienes into methylenecyclopentanes, a reaction mechanistically related to the other hydrovinylation reactions, is also uniquely effected by nickel(II)-complexes of L5, but not of L6 or L7. In an attempt to prepare authentic samples of the methylencyclohexane products, nickel(II)-complexes of N-heterocyclic carbene-ligands were examined. In sharp contrast to the phosphines, which give the methylenecyclopentanes, methylenecyclohexanes are the major products in the (N-heterocyclic carbene)nickel(II)-mediated reactions. PMID:25395919

Biswas, Souvagya; Zhang, Aibin; Raya, Balaram; RajanBabu, T V

2014-07-01

250

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

2012-04-01

251

Principles of centerband-only detection of exchange in solid-state nuclear magnetic resonance, and extension to four-time centerband-only detection of exchange  

NASA Astrophysics Data System (ADS)

Theoretical principles and experimental details of the centerband-only detection of exchange (CODEX) nuclear magnetic resonance (NMR) experiment for characterizing slow segmental dynamics in solids are described. The experiment, which is performed under magic-angle spinning, employs recoupling of the chemical-shift anisotropy before and after a long mixing time during which molecular reorientations may occur. By an analysis in terms of the difference tensor of the chemical shifts before and after the mixing time, the dependence on the reorientation angle is obtained analytically for uniaxial interactions, and a relation to two-dimensional exchange NMR patterns is established; the same theory can also be applied for analyzing stimulated-echo and pure-exchange NMR data. A favorable linear dependence is derived generally for small rotations, which makes the experiment suitable for detecting small-amplitude motions. Quantification is excellent because the peaks are narrow and intense, unlike the broad powder or sideband spectra that are characteristic of all previous NMR experiments for probing slow segmental rotations. We also introduce and demonstrate a four-time CODEX experiment that yields information previously obtained only in 3D (three-dimensional) and reduced 4D (four-dimensional) exchange NMR experiments, such as the number of orientational sites accessible to the mobile groups. Chemical-shift anisotropies required in the CODEX analysis of motional amplitudes can be estimated using a closely related chemical-shift recoupling experiment. The implementation of total suppression of sidebands before detection is also explained. The experiments are demonstrated on dimethylsulfone, isotactic polypropylene, and poly(methyl methacrylate), PMMA. In isotactic poly(1-butene), the signals of the amorphous and interfacial regions have been observed selectively by using pure-exchange CODEX near the glass transition. The four-time CODEX experiment confirms that in the ?-relaxation process of glassy PMMA, fewer than half of the sidegroups perform jumps between two orientations.

deAzevedo, Eduardo R.; Hu, W.-G.; Bonagamba, Tito J.; Schmidt-Rohr, Klaus

2000-05-01

252

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

253

Polar organic marker compounds in atmospheric aerosols: Determination, time series, size distributions and sources  

NASA Astrophysics Data System (ADS)

Terrestrial vegetation releases substantial amounts of reactive volatile organic compounds (VOCs; e.g., isoprene, monoterpenes) into the atmosphere. The VOCs can be rapidly photooxidized under conditions of high solar radiation, yielding products that can participate in new particle formation and growth processes above forests. This thesis focuses on the characterization, identification and quantification of oxidation products of biogenic VOC (BVOCs) as well as other species (tracer compounds) that provide information on aerosol sources and source processes. Atmospheric aerosols from various forested sites (i.e., Hyytiala, southern Finland; Rondonia, Brazil; K-Puszta, Hungary and Julich, Germany) were analyzed with Gas Chromotography/Mass Spectrometry (GC/MS) using analytical procedure that targets polar organic compounds. The study demonstrated that isoprene (i.e., 2-methyerythritol, 2-methylthreitol, 2-methylglyceric acid and C5-alkene triols (2-methyl-1,3,4-trihydroxy-l-butene (cis and trans) and 3 methyl-2,3,4-trihydroxy-1-butene)) and monoterpene (pinic acid, norpinic acid, 3-hydroxyglutaric acid and 3-methyl-1,2,3-butanetricarboxylic acid) oxidation products were present in substantial concentrations in atmospheric aerosols suggesting that oxidation of BVOC from the vegetation is an important process in all studied sites. On the other hand, presence of levoglucosan, biomass burning marker, especially in Amazonian rain forest site at Rondonia, Brazil, pointed that all sites were affected by anthropogenic activities, namely biomass burning. Other identified compounds included plyols, arabitol, mannitol and erythritol, which are marker compounds for fungal spores and monosacharides, glucose and fructose, markers for plant polens. Temporal variations as well as mass size distributions of the detected species confirmed the possible formation mechanisms of marker compounds.

Kourtchev, Ivan

254

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

255

Mechanisms of catalyst poisoning in palladium-catalyzed cyanation of haloarenes. remarkably facile C-N bond activation in the [(Ph3P)4Pd]/[Bu4N]+ CN- system.  

PubMed

Reaction paths leading to palladium catalyst deactivation during cyanation of haloarenes (eq 1) have been identified and studied. Each key step of the catalytic loop (Scheme 1) can be disrupted by excess cyanide, including ArX oxidative addition, X/CN exchange, and ArCN reductive elimination. The catalytic reaction is terminated via the facile formation of inactive [(CN)4Pd]2-, [(CN)3PdH]2-, and [(CN)3PdAr]2-. Moisture is particularly harmful to the catalysis because of facile CN- hydrolysis to HCN that is highly reactive toward Pd(0). Depending on conditions, the reaction of [(Ph3P)4Pd] with HCN in the presence of extra CN- can give rise to [(CN)4Pd]2- and/or the remarkably stable new hydride [(CN)3PdH]2- (NMR, X-ray). The X/CN exchange and reductive elimination steps are vulnerable to excess CN- because of facile phosphine displacement leading to stable [(CN)3PdAr]2- that can undergo ArCN reductive elimination only in the absence of extra CN-. When a quaternary ammonium cation such as [Bu4N]+ is used as a phase-transfer agent for the cyanation reaction, C-N bond cleavage in the cation can occur via two different processes. In the presence of trace water, CN- hydrolysis yields HCN that reacts with Pd(0) to give [(CN)3PdH]2-. This also releases highly active OH- that causes Hofmann elimination of [Bu4N]+ to give Bu3N, 1-butene, and water. This decomposition mode is therefore catalytic in H2O. Under anhydrous conditions, the formation of a new species, [(CN)3PdBu]2-, is observed, and experimental studies suggest that electron-rich mixed cyano phosphine Pd(0) species are responsible for this unusual reaction. A combination of experimental (kinetics, labeling) and computational studies demonstrate that in this case C-N activation occurs via an S(N)2-type displacement of amine and rule out alternative 3-center C-N oxidative addition or Hofmann elimination processes. PMID:18336024

Erhardt, Stefan; Grushin, Vladimir V; Kilpatrick, Alison H; Macgregor, Stuart A; Marshall, William J; Roe, D Christopher

2008-04-01

256

Photoreduction of Pt(IV) halo-hydroxo complexes: possible hypohalous acid elimination.  

PubMed

Concentrated hydrogen peroxide addition to trans-Pt(PEt3)2Cl(R) [1 (R = 9-phenanthryl), 2 (R = 4-trifluoromethylphenyl)] yields hydroxo-hydroperoxo complexes trans-Pt(PEt3)2(Cl)(OOH)(OH)(R) [5 (R = 9-phenanthryl), 4 (R = 4-trifluoromethylphenyl)], where the hydroperoxo ligand is trans to R. Complex 5 is unstable and reacts with solvent CH2Cl2 to give trans,cis-Pt(PEt3)2(Cl)2(OH)(9-phenanthryl) (3). Treatment of 4 with HCl yields analogous trans,cis-Pt(PEt3)2(Cl)2(OH)(4-trifluoromethylphenyl) (6) and HBr gives trans-Pt(PEt3)2(Br)(Cl)(OH)(4-trifluoromethylphenyl) (7), where the Br and 4-trifluoromethylphenyl ligands are trans. Photolysis of 3 or 6 at 313 or 380 nm causes reduction to trans-Pt(PEt3)2Cl(R) (1 or 2, respectively). Expected coproduct HOCl is not detected, but authentic solutions of HOCl are shown to decompose under the reaction conditions. Chlorobenzene and other unidentified products that oxidize PPh3 to OPPh3 are detected in photolyzed benzene solutions. Photolysis of 3 or 6 in the presence of 2,3-dimethyl-2-butene (TME) yields the chlorohydrin (2-chloro-2,3-dimethyl-3-butanol), 3-chloro-2,3-dimethyl-1-butene, and acetone, all expected products from HOCl trapping, but additional oxidation products are also observed. Photolysis of mixed chloro-bromo complex 7 with TME yields the bromohydrin (2-bromo-2,3-dimethyl-3-butanol) and 2, consistent with cis-elimination of HOBr. Computational results (TDDFT and DFT) and photochemistry of related complexes suggest a dissociative triplet excited state reaction pathway and that HOCl elimination may occur by an incipient hydroxo radical abstraction of an adjacent halogen atom, but a pathway involving hydroxo radical reaction with solvent or TME to generate a carbon-based radical followed by halogen abstraction from Pt cannot be eliminated. PMID:24484204

Wickramasinghe, Lasantha A; Sharp, Paul R

2014-02-01

257

Probing E/Z isomerization on the C10H8 potential energy surface with ultraviolet population transfer spectroscopy.  

PubMed

The excited-state dynamics of phenylvinylacetylene (1-phenyl-1-buten-3-yne, PVA) have been studied using laser-induced fluorescence spectroscopy, ultraviolet depletion spectroscopy, and the newly developed method of ultraviolet population transfer spectroscopy. Both isomers of PVA (E and Z) show a substantial loss in fluorescence intensity as a function of excitation energy. This loss in fluorescence was shown to be due to the turn-on of a nonradiative process by comparison of the laser-induced fluorescence spectrum to the ultraviolet depletion spectrum of each isomer, with a threshold 600 cm(-1) above the electronic origin in Z-PVA and 1000 cm(-1) above the electronic origin in E-PVA. Ab initio and density functional theory calculations have been used to show that the most likely source of the nonradiative process is from the interaction of the pi pi* state with a close lying pi sigma* state whose minimum energy structure is bent along the terminal CCH group. Ultraviolet population transfer spectroscopy has been used to probe the extent to which excited-state isomerization is facilitated by the interaction with the pi sigma* state. In ultraviolet population transfer spectroscopy, each isomer was selectively excited to vibronic levels in the S(1) state with energies above and below the threshold for fluorescence quenching. The ultraviolet-excited populations are then recooled to the zero point levels using a reaction tube designed to constrain the supersonic expansion and increase the collision cooling capacity of the expansion. The new isomeric distribution was detected in a downstream position using resonant-2-photon ionization spectroscopy. From these spectra, relative isomerization quantum yields were calculated as a function of excitation energy. While the fluorescence quantum yield drops by a factor of 50-100, the isomerization quantum yields remain essentially constant, implying that the nonradiative process does not directly involve isomerization. On this basis, we postulate that isomerization occurs on the ground-state potential energy surface after internal conversion. In these experiments, the isomerization to naphthalene was not observed, implying a competition between isomerization and cooling on the ground-state potential energy surface. PMID:20067293

Newby, Josh J; Müller, Christian W; Liu, Ching-Ping; Zwier, Timothy S

2010-02-10

258

Characterization of hydrocarbons, halocarbons and carbonyls in the atmosphere of Hong Kong.  

PubMed

Ambient air quality measurements of 156 species including 39 alkanes, 32 alkenes, 2 alkynes, 24 aromatic hydrocarbons, 43 halocarbons and 16 carbonyls, were carried out for 120 air samples collected at two sampling stations (CW and TW) in 2001 throughout Hong Kong. Spatial variations of volatile organic compounds (VOCs) in the atmosphere were investigated. Levels of most alkanes and alkenes at TW site were higher than that at the CW site, while the BTEX concentrations at the two sites were close. The BTEX ratios at CW and TW were 1.6:10.1:1.0:1.6 and 2.1:10.8:1.0:2.0, respectively. For major halogenated hydrocarbons, the mean concentrations of chloromethane, CFCs 12 and 22 did not show spatial variations at the two sites. However, site-specific differences were observed for trichloroethene and tetrachloroethene. Furthermore, there were no significant differences for carbonyls such as formaldehyde, acetaldehyde and acetone between the two sites. The levels of selected hydrocarbons in winter were 1-5 times that in summer. There were no common seasonal trends for carbonyls in Hong Kong. The ambient level of formaldehyde, the most abundant carbonyl, was higher in summer. However, levels of acetaldehyde, acetone and benzaldehyde in winter were 1.6-3.8 times that in summer. The levels of CFCs 11 and 12, and chloromethane in summer were higher than that in winter. Strong correlation of most hydrocarbons with propene and n-butane suggested that the primary contributors of hydrocarbons were vehicular emissions in Hong Kong. In addition, gasoline evaporation, use of solvents, leakage of liquefied petroleum gas (LPG), natural gas leakage and other industrial emissions, and even biogenic emissions affected the ambient levels of hydrocarbons. The sources of halocarbons were mainly materials used in industrial processes and as solvents. Correlation analysis suggested that photochemical reactions made significant contributions to the ambient levels of carbonyls in summer whereas in winter motor vehicle emissions would be the major sources of the carbonyls. The photochemical reactivity of selected VOCs was estimated in this study. The largest contributors to ozone formation were formaldehyde, toluene, propene, m,p-xylene, acetaldehyde, 1-butene/i-butene, isoprene and n-butane, suggesting that motor vehicles, gasoline evaporation, use of solvents, leakage of LPG, photochemical processes and biogenic emission are sources in the production of ozone. On the other hand, VOCs from vehicles and gasoline evaporation were predominant with respect to reactions with OH radical. PMID:15519381

Guo, H; Lee, S C; Louie, P K K; Ho, K F

2004-12-01

259

Aqueous geochemistry of low molecular weight hydrocarbons at elevated temperatures and pressures: constraints from mineral buffered laboratory experiments  

NASA Astrophysics Data System (ADS)

Organic matter, water, and minerals coexist at elevated temperatures and pressures in sedimentary basins and participate in a wide range of geochemical processes that includes the generation of oil and natural gas. A series of laboratory experiments were conducted at 300 to 350°C and 350 bars to examine chemical interactions involving low molecular weight aqueous hydrocarbons with water and Fe-bearing minerals under hydrothermal conditions. Mineral buffers composed of hematite-magnetite-pyrite, hematite-magnetite, and pyrite-pyrrhotite-magnetite were added to each experiment to fix the redox state of the fluid and the activity of reduced sulfur species. During each experiment the chemical system was externally modified by addition of ethene, ethane, propene, 1-butene, or n-heptane, and variations in the abundance of aqueous organic species were monitored as a function of time and temperature. Results of the experiments indicate that decomposition of aqueous n-alkanes proceeds through a series of oxidation and hydration reactions that sequentially produce alkenes, alcohols, ketones, and organic acids as reaction intermediaries. Organic acids subsequently undergo decarboxylation and/or oxidation reactions to form carbon dioxide and shorter chain saturated hydrocarbons. This alteration assemblage is compositionally distinct from that produced by thermal cracking under anhydrous conditions, indicating that the presence of water and minerals provide alternative reaction pathways for the decomposition of hydrocarbons. The rate of hydrocarbon oxidation decreases substantially under reducing conditions and in the absence of catalytically active aqueous sulfur species. These results represent compelling evidence that the stability of aqueous hydrocarbons at elevated temperatures in natural environments is not a simple function of time and temperature alone. Under the appropriate geochemical conditions, stepwise oxidation represents a mechanism for the decomposition of low molecular weight hydrocarbons and the production of methane-rich ("dry") natural gas. Evaluation of aqueous reaction products generated during the experiments within a thermodynamic framework indicates that alkane-alkene, alkene-ketone, and alkene-alcohol reactions attained metastable thermodynamic equilibrium states. This equilibrium included water and iron-bearing minerals, demonstrating the direct involvement of inorganic species as reactants during organic transformations. The high reactivity of water and iron-bearing minerals suggests that they represent abundant sources of hydrogen and oxygen available for the formation of hydrocarbons and oxygenated alteration products. Thus, variations in elemental kerogen composition may not accurately reflect the timing and extent of hydrocarbon, carbon dioxide, and organic acid generation in sedimentary basins. This study demonstrates that the stabilities of aqueous hydrocarbons are strongly influenced by inorganic sediment composition at elevated temperatures. Incorporation of such interactions into geochemical models will greatly improve prediction of the occurrence of hydrocarbons in natural environments over geologic time.

Seewald, Jeffrey S.

2001-05-01

260

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 Central

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 ?molar 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 109 nucleotides in HT1080 cells treated with 1 -100 ?M DEB. N7-THBG amounts in leukocyte DNA of non-smokers, smokers, and occupationally exposed workers were 7.08 ± 5.29, 8.20 ± 5.12, and 9.72 ± 3.80 adducts per 109 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 inter-individual 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

2013-01-01

261

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

2012-10-11

262

Plasma discharge in N2 + CH4 at low pressures: experimental results and applications to Titan.  

PubMed

We report the yields of gaseous hydrocarbons and nitriles produced in a continuous flow, low-dose, cold plasma discharge excited in a 10% CH4, 90% N2 atmosphere at 295 K and pressures p of 17 and 0.24 mbar, and use the results to compute expected abundances of minor constituents in Titan's atmosphere. These experiments are, by design, relevant to the atmospheric chemistry induced by cosmic rays in Titan's troposphere and (at the lower pressure) to chemistry initiated by Saturnian magnetospheric electrons and other charged particle sources which excite stratospheric aurorae. At p = 17 mbar, 59 gaseous species including 27 nitriles are detected in overall yield 4.0 (C + N) atoms incorporated into products per 100 eV (heV). At p = 0.24 mbar, 19 species are detected, including six nitriles and three other unidentified N-bearing compounds; the yield is 0.79 (C + N)/heV, a mild decrease with pressure. The types of molecules formed change more markedly, with high degrees of multiple bonding at 0.24 mbar prevailing over more H-saturated molecules at 17 mbar. The molecules and yields at 0.24 mbar bear a striking resemblance to the minor constituents found in Titan's atmosphere, all of which are abundant products in the laboratory experiment. Using the altitude-integrated flux of charged particle energy deposition at Titan, the laboratory yields at p = 0.24 mb, and a simple eddy mixing model, we compute absolute stratospheric column abundances and mole fractions. These are found to be in very good agreement with the Voyager IRIS observations. Except for the primarily photochemical products, C2H6 and C3H8, the match is much better than that obtained by photochemical-kinetic models, demonstrating that properly designed laboratory experiments are directly applicable to modeling radiation-chemical processes in planetary atmospheres. On the basis of this agreement we expect CH3-C triple bond N (ethanenitrile = acetonitrile) CH2=CH-CH=CH2 (1,3-butadiene), CH2=C=CH2 (1,2-propadiene = allene), and CH2=CH-C triple bond CH (1-buten-3-yne) to be present at mol fractions X > 10(-9), and CH2=CH-C triple bond N (propenenitrile), CH3-CH=CH2 (propene), and CH3-CH2-C triple bond N (propanenitrile) at X > 10(-10) in Titan's atmosphere. PMID:11538099

Thompson, W R; Henry, T J; Schwartz, J M; Khare, B N; Sagan, C

1991-01-01

263

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

264

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? 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? 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

2013-10-21

265

Multinuclear group 4 catalysis: olefin polymerization pathways modified by strong metal-metal cooperative effects.  

PubMed

Polyolefins are produced today catalytically on a vast scale, and the manufactured polymers find use in everything from artificial limbs and food/medical packaging to automotive and electrical components and lubricants. Although polyolefin monomers are typically cheap (e.g., ethylene, propylene, ?-olefins), the resulting polymer properties can be dramatically tuned by the particular polymerization catalyst employed, and reflect a rich interplay of macromolecular chemistry, materials science, and physics. For example, linear low-density polyethylene (LLDPE), produced by copolymerization of ethylene with linear ?-olefin comonomers such as 1-butene, 1-hexene, or 1-octene, has small but significant levels of short alkyl branches (C2, C4, C6) along the polyethylene backbone, and is an important technology material due to outstanding rheological and mechanical properties. In 2013, the total world polyolefin production was approximately 211 million metric tons, of which about 11% was LLDPE. Historically, polyolefins were produced using ill-defined but highly active heterogeneous catalysts composed of supported groups 4 or 6 species (usually halides) activated by aluminum alkyls. In 1963, Karl Ziegler and Giulio Natta received the Nobel Prize for these discoveries. Beginning in the late 1980s, a new generation of group 4 molecule-based homogeneous olefin polymerization catalysts emerged from discoveries by Walter Kaminsky, a team led by James Stevens at The Dow Chemical Company, this Laboratory at Northwestern University, and a host of talented groups in Germany, Italy, Japan, the United Kingdom, and the United States. These new "single-site" catalysts and their activating cocatalysts were far better defined and more rationally tunable in terms of structure, mechanism, thermodynamics, and catalyst activity and selectivity than ever before possible. An explosion of research advances led to new catalysts, cocatalysts, deeper mechanistic understanding of both the homogeneous and heterogeneous systems, macromolecules with dramatically altered properties, and large-scale industrial processes. It is noteworthy that many metalloenzymes employ multiple active centers operating in close synergistic proximity to achieve high activity and selectivity. Such enzymes were the inspiration for the research discussed in this Account, focused on the properties of multimetallic olefin polymerization catalysts. Here we discuss how modifications in organic ligand architecture, metal···metal proximity, and cocatalyst can dramatically modify polyolefin molecular weight, branch structure, and selectively for olefinic comonomer enchainment. We first discuss bimetallic catalysts with identical group 4 metal centers and then heterobimetallic systems with either group 4 or groups 4 + 6 catalytic centers. We compare and contrast the polymerization properties of the bimetallic catalysts with their monometallic analogues, highlighting marked cooperative enchainment effects and unusual polymeric products possible via the proximate catalytic centers. Such multinuclear olefin polymerization catalysts exhibit the following distinctive features: (1) unprecedented levels of polyolefin branching; (2) enhanced enchainment selectivity for linear and encumbered ?-olefin comonomers; (3) enhanced polyolefin tacticity and molecular weight; (4) unusual 1,2-insertion regiochemistry for styrenic monomers; (5) modified chain transfer kinetics, such as M-polymer ?-hydride transfer to the metal or incoming monomer; (6) LLDPE synthesis with a single binuclear catalyst and ethylene. PMID:25075755

McInnis, Jennifer P; Delferro, Massimiliano; Marks, Tobin J

2014-08-19

266

Nickel and iron complexes with N,P,N-type ligands: synthesis, structure and catalytic oligomerization of ethylene.  

PubMed

The N,P,N-type ligands bis(2-picolyl)phenylphosphine (), bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine (), bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine () and bis(2-picolyloxy)phenylphosphine () were used to synthesize the corresponding pentacoordinated Ni(ii) complexes [Ni{bis(2-picolyl)phenylphosphine}Cl(2)] (), [Ni{bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine}Cl(2)] (), [Ni{bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine}Cl(2)] () and [Ni{bis(2-picolyloxy)phenylphosphine}Cl(2)] (), respectively. The hexacoordinated iron complexes [Fe{bis(2-picolyl)phenylphosphine}(2)][Cl(3)FeOFeCl(3)] (), [Fe{bis(4,5-dihydro-2-oxazolylmethyl)phenylphosphine}(2)][Cl(3)FeOFeCl(3)] () and the tetracoordinated complex [Fe{bis(4,4-dimethyl-2-oxazolylmethyl)phenylphosphine}Cl(2)] (abbreviated [FeCl(2)(NPN(Me2)-N,N)]) were prepared by reaction of FeCl(2).4H(2)O with ligands , respectively. The crystal structures of the octahedral complexes and , determined by X-ray diffraction, showed that two tridentate ligands are facially coordinated to the metal centre with a cis-arrangement of the P atoms and the dianion (mu-oxo)bis[trichloroferrate(iii)] compensates the doubly positive charge of the complex. The cyclic voltammograms of and showed two reversible redox couples attributed to the reduction of the dianion (Fe(2)OCl(6))(2-) (-0.24 V for and -0.20 V for vs. SCE) and to the oxidation of the Fe(ii) ion of the complex (0.67 V for and 0.52 V for vs. SCE). The cyclic voltammogram of [FeCl(2)(NPN(Me2)-N,N)] showed a reversible redox couple at -0.17 V vs. SCE assigned to the oxidation of the Fe(ii) atom and an irreversible process at 0.65 V. The complexes , and [FeCl(2)(NPN(Me2)-N,N)] have been evaluated in the catalytic oligomerization of ethylene with AlEtCl(2) or MAO as cocatalyst. The nickel complex proved to be the most active precatalyst in the series, with a turnover frequency (TOF) of 61 800 mol(C(2)H(4)) mol(Ni)(-1) h(-1) with 10 equiv. of AlEtCl(2) and 12 200 mol(C(2)H(4)) mol(Ni)(-1) h(-1) with 200 equiv. of MAO. Precatalysts and were the most selective in butenes, up to 90% with 6 equiv. of AlEtCl(2) and 89% with 2 equiv. of AlEtCl(2), respectively, and up to 92% butenes with 400 equiv. of MAO and 91% butenes with 200 equiv. MAO, respectively. The best selectivities for 1-butene were provided by and AlEtCl(2) (up to 31% with 6 equiv.) and with MAO (up to 72% with 200 equiv.). The iron complexes were not significantly active with AlEtCl(2) or MAO as cocatalyst. PMID:18493630

Kermagoret, Anthony; Tomicki, Falk; Braunstein, Pierre

2008-06-14

267

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.

268

Insights into Functional-Group-Tolerant Polymerization Catalysis with Phosphine-Sulfonamide Palladium(II) Complexes.  

PubMed

Two series of cationic palladium(II) methyl complexes {[(2-MeOC6 H4 )2 PC6 H4 SO2 NHC6 H3 (2,6-R(1) ,R(2) )]PdMe}2 [A]2 ((X) 1(+) -A: R(1) =R(2) =H: (H) 1(+) -A; R(1) =R(2) =CH(CH3 )2 : (DIPP) 1(+) -A; R(1) =H, R(2) =CF3 : (CF3) 1(+) -A; A=BF4 or SbF6 ) and neutral palladium(II) methyl complexes {[(2-MeOC6 H4 )2 PC6 H4 SO2 NC6 H3 (2,6-R(1) ,R(2) )]PdMe(L)} ((X) 1-acetone: L=acetone; (X) 1-dmso: L=dimethyl sulfoxide; (X) 1-pyr: L=pyridine) chelated by a phosphine-sulfonamide were synthesized and fully characterized. Stoichiometric insertion of methyl acrylate (MA) into all complexes revealed that a 2,1 regiochemistry dominates in the first insertion of MA. Subsequently, for the cationic complexes (X) 1(+) -A, ?-H elimination from the 2,1-insertion product (X) 2(+) -AMA-2,1 is overwhelmingly favored over a second MA insertion to yield two major products (X) 4(+) -AMA-1,2 and (X) 5(+) -AMA . By contrast, for the weakly coordinated neutral complexes (X) 1-acetone and (X) 1-dmso, a second MA insertion of the 2,1-insertion product (X) 2MA-2,1 is faster than ?-H elimination and gives (X) 3MA as major products. For the strongly coordinated neutral complexes (X) 1-pyr, no second MA insertion and no ?-H elimination (except for (DIPP) 2-pyrMA-2,1 ) were observed for the 2,1-insertion product (X) 2-pyrMA-2,1 . The cationic complexes (X) 1(+) -A exhibited high catalytic activities for ethylene dimerization, affording butenes (C4 ) with a high selectivity of up to 97.7?% (1-butene: 99.3?%). Differences in activities and selectivities suggest that the phosphine-sulfonamide ligands remain coordinated to the metal center in a bidentate fashion in the catalytically active species. By comparison, the neutral complexes (X) 1-acetone, (X) 1-dmso, and (X) 1-pyr showed very low activity towards ethylene to give traces of oligomers. DFT analyses taking into account the two possible coordination modes (O or N) of the sulfonamide ligand for the cationic system (CF3) 1(+) suggested that the experimentally observed high activity in ethylene dimerization is the result of a facile first ethylene insertion into the O-coordinated PdMe isomer and a subsequent favored ?-H elimination from the N-coordinated isomer formed by isomerization of the insertion product. Steric hindrance by the N-aryl substituent in the neutral systems (CF3) 1 and (H) 1 appears to contribute significantly to a higher barrier of insertion, which accounts for the experimentally observed low activity towards ethylene oligomerization. PMID:25487160

Jian, Zhongbao; Falivene, Laura; Wucher, Philipp; Roesle, Philipp; Caporaso, Lucia; Cavallo, Luigi; Göttker-Schnetmann, Inigo; Mecking, Stefan

2015-01-26

269

In vitro genotoxicity testing of (1-chloroethenyl)oxirane, a metabolite of beta-chloroprene.  

PubMed

(1-Chloroethenyl)oxirane (CEO) is a metabolite of beta-chloroprene (2-chloro-1,3-butadiene, CD). The purpose of this study was to evaluate the in vitro mutagenic and clastogenic (chromosome breaking) potential of CEO. For comparative purposes, the study also included an evaluation of the racemic compounds, 3,4-epoxy-1-butene (EB) and 1,2:3,4-diepoxybutane (DEB). Mutagenicity was evaluated in a bacterial reverse mutation test (Ames), using the pre-incubation method in the presence and absence of an exogenous metabolism system (Aroclor)-induced rat liver S9). Four Salmonella typhimurium tester strains, TA97a, TA98, TA100 and TA1535 were used. The exposure concentrations in the sealed incubation vials ranged from 0 to 69 mM for CEO, 0 to 102 mM for EB, and 0 to 83 mM for DEB. All three compounds showed signs of toxicity, with DEB being substantially more toxic than either CEO or EB. Mutagenic activity was observed with all three chemicals in primarily the base pair substitution strains (S. typhimurium TA100 and TA1535), but some activity was also seen in the frameshift elimination strains (S. typhimurium TA97a and TA98). The observed mutagenic responses after exposure with CEO or EB were greater than the observed response for DEB, most likely because of the higher toxicity of DEB. Generally, the mutagenic responses were unchanged in the frameshift strains and base pair substitution strains in the presence of S9 metabolism. In vitro clastogenicity was evaluated using the cytochalasin-B blocked micronucleus test in cultured Chinese hamster V79 cells. The test was conducted without S9 metabolism because of the absence of substantial changes in the Ames test. Exposure concentrations ranged from 0 to 0.943 mM for CEO, 0 to 3.0 mM for EB, and 0 to 0.035 mM for DEB, with the upper exposure concentrations dictated by cytotoxicity. Cytotoxicity, measured as a reduction in the proportion of binucleated cells and altered cell morphology, was observed for CEO at concentrations > or =0.175 mM. Exposure to EB led to a reduced proportion of binucleated cells at concentrations > or =2.0 mM, and cell death was observed after DEB exposure at concentrations > or =0.025 mM. No clastogenicity was observed in the V79 cells when tested up to cytotoxic concentrations of CEO, whereas an elevated frequency of micronuclei was observed after exposure to either EB (> or =1.0 mM) or DEB (> or =0.0125 mM). These results suggest that CEO-induced mutagenicity, but not clastogenicity, may contribute to the observed beta-chloroprene-induced carcinogenicity in the rodent bioassay studies. PMID:11397425

Himmelstein, M W; Gladnick, N L; Donner, E M; Snyder, R D; Valentine, R

2001-06-01

270

Theoretical investigations of the thermochemistry, structures, and internal rotation of conjugated polyynes  

NASA Astrophysics Data System (ADS)

Chapter 1 discusses the thermochemistry of conjugated double and triple bonds. The conjugation stabilization energies of dienes and diynes are considerably larger than estimates based on heat of hydrogenation differences between 1,3-butadiyne and 1-butyne as well as between 1,3-butadiene and 1-butene. Such comparisons do not take into account the counterbalancing hyperconjugative stabilization of the partially hydrogenated products by their ethyl groups. When alkyl hyperconjugation is considered, the conjugation stabilization of diynes (? 9.3 kcal/mol) is found by two methods (involving isomerization of non-conjugated into conjugated isomers and heats of hydrogenation) to be larger than that of dienes (? 8.2 kcal/mol). In Chapter 2 the stabilization of substituted organic radicals, relative to methyl, are computed using bond separation energies and the block localized wavefunction method. These energies are typically evaluated from C-H bond dissociation energies (computed here by the CBS-RAD method). However, this method gives stabilization energies of an increasing number of mono-, di-, and tri-substituted vinyl and ethynyl substituents, which differ from the predictions of Perturbation Molecular Orbital (PMO) and Huckel Molecular Orbital (HMO) theory. The saturation (attenuation) effect for both series should be monotonic and small. Instead, the attenuation computed by the allylic series is larger than that predicted by HMO theory and the behavior of the propargylic series is erratic. These discrepancies arise from the use of bond dissociation energy data in the evaluations, which depend not only on the stabilization of the radicals, but also on the substantial substituent effects (e.g., hyperconjugation) on the energies of the reference hydrocarbons. New evaluation schemes are proposed that avoid such complications and thus estimate radical stabilization effects directly; the results agree with PMO and HMO theories. Substitution effects are analyzed using isodesmic equations with CBS-RAD data and also with the block localized wavefunction (BLW) method. The new estimates give essentially the same vinyl (22.3 kcal/mol) and ethynyl (21.9 kcal/mol) stabilization energies in the allyl and propargyl radicals, contrary to conventional evaluations. Likewise, the vinyl and ethynyl stabilizations in di-substituted and tri-substituted radicals are similar. These conclusions are corroborated with the block localized wavefunction (BLW) method, which is used to analyze resonance stabilization energies in the radical systems and hyperconjugative stabilization energies in the reference hydrocarbons. Chapter 3 presents the structures, heats of formation, and strain energies of diacetylene (buta-1,3-diynediyl) expanded molecules computed with ab initio and molecular mechanics calculations. Expanded cubane, prismane, tetrahedrane, and expanded monocyclics and bicyclics were optimized at the HF/6-31G(d) and B3LYP/6-31G(d) levels. The heats of formation of these systems were obtained from isodesmic equations at the HF/6-31G(d) level. Heats of formation were also calculated from Benson group equivalents. The strain energies of these expanded molecules were estimated by several independent methods. An adapted MM3* molecular mechanics force field, specifically parameterized to treat conjugated acetylene units, was employed for one measure of strain energy and as an additional method for structural analysis. Expanded dodecahedrane and icosahedrane were calculated by this method. Expanded molecules were considered structurally in the context of their potential material applications. Chapter 4 addresses the computation of the rotational barriers of substituted ethynlene and butatriene as well as their geometric and electronic structures. The barriers to internal rotation of methylated, ethynylated, and vinylated butatrienes and alkenes were calculated at the CASPT2/6-31G(d)//B3LYP/6-31G(d) level. Calculated butatriene rotational barriers are lower than analogous alkenes, but there is a larger variance in rotational barrier for alkenes than

Jarowski, Peter D.