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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 Mller-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; Mller, 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: CHCHO, HCO, CO, CH,

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

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

E-print Network

'O x O O? o o ~O O I O O M M M ( O ? O C'l O --O I I + 1 O O I' DI. '&CUSSIQN Comparison o& the by-products formed by the condensation o. 2-methylpropene . . 'th benzene in the presence of anhydro:s ferric chloride - it!! those... . mer. CONCLUSIONS 1. When benzene is alkylated with 2-methylpropene in the presence of ferric chloride the following hydrocarbons can be identified among the products of the reaction: t-butylbenzene, t-amylbenzene, t-hexylbenzene, l-isopropy1-3-t...

Mommessin, Pierre Robert

2012-06-07

10

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.

11

Solvent-ligated copper(II) complexes for the homopolymerization of 2-methylpropene.  

PubMed

Copper(II) complexes with weakly coordinating counter anions can be utilized as highly efficient catalysts for the synthesis of poly(2-methylpropene) ("polyisobutene") with a high content of terminal double bonds. These copper(II) compounds are significantly more active than the manganese(II) complexes described previously, can be applied in chlorine-free solvents such as toluene, are easily accessible, and can be handled at room temperature and in laboratory atmospheres for brief periods, but they are sensitive to excess water, thereby losing their catalytic activity. Replacing the acetonitrile ligands by benzonitrile ligands improves the solubility and catalytic activity in nonpolar and nonchlorinated solvents. However, the benzonitrile copper(II) compounds have lower thermal stability than their acetonitrile congeners. PMID:18637647

Li, Yang; Voon, Lih Ting; Yeong, Hui Yee; Hijazi, Ahmed K; Radhakrishnan, Narayanan; Khler, Klaus; Voit, Brigitte; Nuyken, Oskar; Khn, Fritz E

2008-01-01

12

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, Ivnia T. A.; Ducati, Lucas C.; Custodio, Rogrio; Rittner, Roberto; Klapstein, Dieter

2008-06-01

13

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

14

Conformational stability of 1-butene: an electron momentum spectroscopy investigation.  

PubMed

The valence-shell electron momentum distributions for 1-butene are measured by electron momentum spectroscopy (EMS) employing non-coplanar symmetric geometry. The experimental electron momentum distributions are compared with the density functional theory (DFT) calculations using different-sized basis sets. Although the two conformers of 1-butene in the gas phase, namely the skew and syn, have very close ionization potentials, the electron momentum distributions, especially in the low momentum region, can show prominent differences for some of the valence orbitals. By comparing the experimental electron momentum profiles with the theoretical ones, the skew conformer is found to be more stable than the syn and their relative abundances at room temperature are estimated to be (69 +/- 6)% and (31 +/- 6)%, respectively. It demonstrates that EMS has the latent potential to study the relative stability of conformers. PMID:18447375

Wu, Fang; Chen, Xiangjun; Shan, Xu; Tian, Shan Xi; Li, Zhongjun; Xu, Kezun

2008-05-01

15

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

16

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

17

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

18

Published: March 11, 2011 r 2011 American Chemical Society 2778 dx.doi.org/10.1021/jp109676b |J. Phys. Chem. A 2011, 115, 27782793  

E-print Network

) addition to 1-butene and to cis- and trans-2-butene. The data are compared with in vacuo spin- unrestricted radicals formed from 2-butene, A 0 (T) exhibits clear discontinuities at bulk butene melting points

Wang, Yan Alexander

19

Table SI-1. kOH, a, F, and SOA yield values for VOCs. Not all VOCs are listed. Yields are for Mo = 5 g/m3. "(E)" indicates that the values are estimated.  

E-print Network

.99 0 propene 26 2.0 0.99 0 1-butene 31 2.0 0.98 0 trans-2-butene 64 2.0 0.97 (E) 0 cis-2-butene 56 2) 3-methyl-1-butene 2-methyl-1-butene 2-methyl-2butene butyne ethyne propyne cyclooctene cumene (T) 1

Meskhidze, Nicholas

20

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 CO 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

21

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

22

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

23

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

24

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

25

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

26

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.

27

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 XX interactions due to parallel Cl?XX?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.

Stlevik, Reidar; Hagen, Kolbjrn

1998-04-01

28

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

29

Regio-and Stereochemistry of Alkene Expulsion from Ionized sec-Alkyl Phenyl Ethers John C. Traeger  

E-print Network

among trans-2-butene, cis-2-butene, and 1-butene in a ratio of approximately 6:5:4, exhibiting-half at 11.92 eV. Ion-neutral complexes from sBuOPh yield nearly equal proportions of 1-butene and 2-butenes

Morton, Thomas Hellman

30

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.

31

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

32

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-Benot; Magna, Lionel; Braunstein, Pierre; Oliver-Bourbigou, Hlne

2012-09-14

33

Temperature-dependent absorption cross-section measurements of 1-butene (1-C4H8) in VUV and IR  

NASA Astrophysics Data System (ADS)

Vacuum ultraviolet (VUV) and infrared (IR) absorption cross-section measurements of 1-butene (1-C4H8; CH2=CHCH2CH3; Butylene) are reported over the temperature range of 296-529 K. The VUV measurements are performed between 115 and 205 nm using synchrotron radiation as a tunable VUV light source. Fourier Transform Infrared (FTIR) spectroscopy is employed to measure absorption cross-section and band strengths in the IR region between 1.54 and 25 ?m (6500-400 cm-1). The measured room-temperature VUV and IR absorption cross-sections are compared with available literature data and are found to be in good agreement. The oscillator strength for the electronic transition (A1A??X1A?) around 150-205 nm is determined to be 0.320.01.The gas temperature has a strong effect on both VUV and IR spectra. Measurements made in the VUV region show that the peak value of the band cross-section decreases and the background continuum increases with increasing gas temperature. This behavior is due to a change in the rotational and vibrational population distribution of 1-butene molecule. Similar changes in rotational population are observed in the IR spectra. Moreover, variation of the IR spectra with temperature is used to measure the enthalpy difference between syn and skew conformations of 1-butene and is found to be 0.240.03 kcal/mol, which is in excellent agreement with values reported in the literature. The measurements reported in this work will provide the much-needed spectroscopic information for the development of high-temperature quantitative diagnostics in combustion applications and validation of atmospheric chemistry models of extra-solar planets.

Es-sebbar, Et-touhami; Benilan, Yves; Farooq, Aamir

2013-01-01

34

High-pressure vapor-liquid equilibria for ethylene + 4-methyl-1-pentane and 1-butene + 1-hexene  

SciTech Connect

Isothermal vapor-liquid equilibria (VLE) for the ethylene + 4-methyl-1-pentene and 1-butene + 1-hexene binary systems were measured by the static method at several temperatures for pressures in the range (0.3 to 8.5) MPa. Representations of VLE data by the Soave and Peng-Robinson cubic equations of state are compared in both modes: predictive and binary parameter adjustment. As the two binary systems behave almost ideally, there is no significant difference between their representation qualities through both equations of state.

Laugier, S. [Ecole Nationale Superieure de Chimie et Physique de Bordeaux, Talence (France)] [Ecole Nationale Superieure de Chimie et Physique de Bordeaux, Talence (France); Richon, D. [Ecole Nationale Superieure des Mines de Paris, Fontainebleau (France)] [Ecole Nationale Superieure des Mines de Paris, Fontainebleau (France)

1996-03-01

35

Pure silica ITQ-32 zeolite allows separation of linear olefins from paraffins.  

PubMed

ITQ-32 is able to separate propene from propane and represents a clear improvement with respect to previous zeolites in achieving the separation of trans-2-butene and 1-butene from the C(4) fraction using only one zeolite. PMID:17356766

Palomino, Miguel; Cantn, Angel; Corma, Avelino; Leiva, Sandra; Rey, Fernando; Valencia, Susana

2007-03-28

36

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

37

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

SciTech Connect

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

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

1990-05-01

38

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

39

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

40

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

41

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

42

Stereospecific conversion of 1-aminocyclopropanecarboxylic Acid to ethylene by plant tissues : conversion of stereoisomers of 1-amino-2-ethylcyclopropanecarboxylic Acid to 1-butene.  

PubMed

Inasmuch as the molecule of 1-aminocyclopropanecarboxylic acid (ACC) possesses reflective symmetry but lacks rotational symmetry, the two chemically alike methylene groups can be distinguished by a stereospecific enzyme. To determine whether ACC conversion to ethylene by plant tissues proceeds in a stereospecific fashion, the four stereoisomers of 1-amino-2-ethylcyclopropanecarboxylic acid (AEC) were administered to postclimacteric apple (Malus sylvestris Mill., var. Golden Delicious), excised preclimacteric cantaloupe (Cucumis melo L., var. reticulatis Naud cv. PMR-45), and etiolated mung bean (Vigna radiata L., Wilczek, var. Berken) hypocotyls. In each case (1R,2S)-AEC was the preferred substrate yielding 1-butene. In contrast, all AEC isomers were converted equally well to butene by chemical oxidation using NaOCl. Both ACC and AEC appear to be substrates for the same enzyme since both reactions are inhibited in parallel by N(2) or Co(2+), both reactions are induced in parallel by excision, and when both substrates are present simultaneously each will act as an inhibitor with respect to the other. The aforementioned observations indicate that ACC is stereospecifically converted to ethylene. For AEC to be the most active precursor of 1-butene, the ethyl substituent should be trans to the carboxyl group and the pro-(S) methylene group should be unsubstituted. This observation leads to the suggestion that the enzyme interacts with amino, carboxyl, and pro-(S) methylene groups, a configuration corresponding to a l-amino acid. This view is consistent with the observation that the l-forms of alanine and methionine inhibit the conversion of ACC to ethylene more than the corresponding d-amino acids in the mung bean hypocotyl system. PMID:16662444

Hoffman, N E; Yang, S F; Ichihara, A; Sakamura, S

1982-07-01

43

5570 J.Org. Chem. 1987,52, 5570-5574 597-49-9; phenol, 108-95-2; 2,6-di-tert-butylphenol,128-39-2;  

E-print Network

acetate, 122-79-2; y- butyrolactone, 96-48-0; phthalide, 87-41-2; isopropenyl acetate, 108-22-5; 1-butene oxide, 106-88-7; styrene oxide, 96-09-3; cy- clohexene oxide, 286-20-4; trans-2-butene oxide, 21490-63-1; 2- methyl-2-butene oxide, 5076-19-7; 1-methylcyclohexene oxide, 1713-33-3; 2,3-dimethyl-2-butene

Keinan, Ehud

44

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

45

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

46

Metalorganic Chemical Vapor Deposition of Copper Using (Hexafluoroacetylacetonate)Cu(I)(3,3-dimethyl-1-butene) with a Liquid Delivery System  

NASA Astrophysics Data System (ADS)

From variable temperature (VT) 1H-nuclear magnetic resonance (NMR) and a heating test, it was found that (hexafluoroacetylacetonate)Cu(I)(3,3-dimethyl-1-butene) [(hfac)Cu(I)(DMB)] was stable up to 65C. The effects of various process conditions such as substrate temperature, liquid precursor flow rate and hydrogen carrier gas flow rate on the deposition rate, texture, microhardness, surface roughness and uniformity were studied using a direct liquid injection 200 mm metalorganic chemical vapor deposition (MOCVD) reactor with hollow-cathode magnetron (HCM) sputter-deposited Cu substrate on silicon wafer. The MOCVD Cu process with (hfac)Cu(I)(DMB) showed good conformality, continuous film morphology and low resistivity at a substrate temperature of 190C, vaporizer temperature of 55C, total pressure of 2.5 Torr and precursor flow rate of 0.5 cm3/min. X-ray diffraction (XRD) analyses demonstrated a strong (111) texture of the copper film. The higher (111) peak intensity and the narrower width at half maximum were obtained when the source feed rate was low. Also the higher (111) peak intensity was observed at higher substrate temperature. At temperature below about 200C, the microhardness was increased with increasing substrate temperature. In the high temperature regime (>200C), the hardness was decreased.

Choi, Kyeong-Keun; Pyo, Sung G.; Lee, Dok Won; Rhee, Shi-Woo

2002-05-01

47

Conformationally disordered crystals and their influence on material properties: The cases of isotactic polypropylene, isotactic poly(1-butene), and poly(L-lactic acid)  

NASA Astrophysics Data System (ADS)

This article provides a comprehensive review of the physical properties of the conformationally disordered (condis) structures of isotactic polypropylene (iPP), isotactic poly(1-butene) (iPB-1) and poly(L-lactic acid) (PLLA), in comparison with the respective more stable crystalline forms. The aim of this review is to define the influence of the condis modifications on the thermal and mechanical properties of these materials. The condis structures of the three polymers are metastable and spontaneously transform into the more stable crystalline structures upon annealing above a critical temperature. The transition from the mesophase to the more stable crystalline structure becomes possible when the chains have sufficient mobility to allow rearrangements of chain conformations. A rigid amorphous fraction develops during solidification of iPP, iPB-1 and PLLA. Crystallization of iPB-1 and PLLA into the more stable forms leads to a larger coupling of the amorphous and crystalline chain segments, compared to the conformationally disordered arrangements, which results in a higher fraction of rigid amorphous chain segments. The difference in chain packing, together with the varied mobility of the coupled amorphous chain portions, affects both the initial resistance to the tensile strain and the large strain properties. All the three stable crystalline forms have a higher Young's modulus compared to the condis mesophases, and can sustain lower deformation under mechanical stimuli.

Cocca, Mariacristina; Androsch, Ren; Righetti, Maria Cristina; Malinconico, Mario; Di Lorenzo, Maria Laura

2014-12-01

48

Inhibitors of the fungal cell wall. Synthesis of 4-aryl-4- N-arylamine-1-butenes and related compounds with inhibitory activities on ?(13) 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 Corts; Alirio Palma; Silvia N Lpez; Susana A Zacchino; Ricardo D Enriz; Juan C Ribas; Vladimir V Kouznetzov

2000-01-01

49

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-Brnsted 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

50

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.

Valcrcel, Ana; Clotet, Anna; Ricart, Josep M.; Delbecq, Franoise; Sautet, Philippe

2004-01-01

51

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

52

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 30-450C. n-Butenes were monomolecularly adsorbed via ?-bonding on H-FER at 30C. 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

53

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

54

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; Corts, J C; Palma, A; Lpez, S N; Zacchino, S A; Enriz, R D; Ribas, J C; Kouznetzov, V V

2000-04-01

55

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

56

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

57

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

Lfgren, L; Petersson, G

1992-05-01

58

Processing-structure-property studies of: (I) submicron polymeric fibers produced by electrospinning and (II) films of linear low density polyethylenes as influenced by the short chain branch length in copolymers of ethylene/1-butene, ethylene/1-hexene and ethylene/1-octene synthesized by a single site metallocene catalyst  

NASA Astrophysics Data System (ADS)

The overall theme of the research discussed in this dissertation has been to explore processing-structure-property relationships for submicron polymeric fibers produced by electrospinning (Part I) and to ascertain whether or not the length of the short chain branch has any effect on the physical properties of films of linear low-density polyethylenes (LLDPEs) (Part II). The research efforts discussed in Part I of this dissertation relate to some fundamental as well as more applied investigations involving electrospinning. These include investigating the effects of solution rheology on fiber formation and developing novel methodologies to fabricate polymeric mats comprising of high specific surface submicron fibers of more than one polymer, high chemical resistant substrates produced by in situ photo crosslinking during electrospinning, superparamagnetic flexible substrates by electrospinning a solution of an elastomeric polymer containing ferrite nanoparticles of Mn-Zn-Ni and substrates for filtration applications. Bicomponent electrospinning of poly(vinyl chloride)-polyurethane and poly(vinylidiene fluoride)-polyurethane was successfully performed. In addition, filtration properties of single and bicomponent electrospun mats of polyacrylonitrile and polystyrene were investigated. Results indicated lower aerosol penetration or higher filtration efficiencies of the filters based on submicron electrospun fibers in comparison to the conventional filter materials. In addition, Part II of this dissertation explores whether or not the length of the short chain branch affects the physical properties of blown and compression molded films of LLDPEs that were synthesized by a single site metallocene catalyst. Here, three resins based on copolymers of ethylene/1-butene, ethylene/1-hexene, and ethylene/1-octene were utilized that were very similar in terms of their molecular weight and distribution, melt rheology, density, crystallinity and short chain branching content and its distribution. Interestingly, at higher deformation rates (ca. 1m/s), the breaking, tear and impact strengths of films based on ethylene/1-hexene and ethylene/1-octene were found to be superior than those based on ethylene/1-butene. (Abstract shortened by UMI.)

Gupta, Pankaj

59

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

60

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

61

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

62

Kinetic studies of olefin binding to sulfido sites in dinuclear molybdenum complexes  

SciTech Connect

The reactions of olefins with a series of molybdenum complexes of the formula (R-CpMo-({mu}-S)){sub 2}S{sub 2}CHX, where R = H, CH{sub 3}, CO{sub 2}Na, and X = H, CN, CMe{sub 3}, have been studied. Olefin reagents have included propene, 1-butene, cis- and trans-2-butene, and isomers of hexene. Olefin additions to the sulfido ligands in the dimers result in alkanedithiolate complexes. The rates of these reactions have been monitored by visible spectroscopy, and rate constants, k{sub on}, have been compared as dimer substituent and olefin structure have been varied. The rate constants for olefin dissociation from the alkanedithiolate complexes, k{sub off}, have also been determined by NMR spectroscopy. The studies have permitted us to probe the relative contributions of k{sub on} and k{sub off} to the equilibrium constants for reversible olefin binding as inductive and steric effects are varied. The potential for using these systems in olefin separation schemes is discussed. 20 refs., 3 figs., 6 tabs.

Koval, C.R.; Lopez, L.L.; Kaul, B.B.; Renshaw, S.; Green, K.; DuBois, M.R. [Univ. of Colorado, Boulder, CO (United States)

1995-07-01

63

Effects of Beijing Olympics control measures on reducing reactive hydrocarbon species.  

PubMed

Stringent air-quality control measures were implemented for the 2008 Beijing Olympic Games. This large-scale manmade experiment provided an opportunity to evaluate the effectiveness of measures to reduce the reactivity of hydrocarbons (HCs) from emission sources, which is important for ground-level ozone abatement. Photochemical initial concentrations (PICs), i.e., the levels of HCs from sources before undergoing chemical reactions, were calculated from ambient measurements. PICs obtained using the ratio method for HCs and the sequential reaction model for alkyl nitrates were in good agreement. Propene, 1-butene, iso-butene, trans-2-butene, cis-2-butene, trans-2-pentene, and m,p-xylene were identified as key reactive species in terms of their photochemical consumptions and correspondent ozone formation potentials (OFPs). During the Olympics and Paralympics, the PICs of these seven species were reduced by 27-66%, contributing 20% to the reduction in total PICs and 60% to the reduction in total OFP compared with June levels. Source apportionments from the chemical mass balance model indicated that gasoline vehicle exhaust was the predominant contributor to the key reactive species (45-78%). Reductions of gasoline vehicle exhaust during the Olympics and Paralympics explained 53-77% and 59-68% of the reductions in PICs of the key reactive HCs and total OFP, respectively. PMID:21128631

Min, Shao; Bin, Wang; Sihua, Lu; Bin, Yuan; Ming, Wang

2011-01-15

64

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

65

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

66

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

67

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

68

C2-C10 hydrocarbon emissions from a boreal wetland and forest floor  

NASA Astrophysics Data System (ADS)

Emissions of various C2-C10 hydrocarbons and halogenated hydrocarbons from a boreal wetland and Scots pine forest floor were measured by static chamber technique in south-western Finland. Isoprene was the main non-methane hydrocarbon emitted by the wetland but also small emissions of ethene, propane, propene, 1-butene, 2-methylpropene, butane, pentane and hexane were detected. The isoprene emission from the wetland was observed to follow the commonly used isoprene emission algorithm. The mean emission potential of isoprene was 224 ?g m-2 h-1 for the whole season. This is lower than the emission potentials published earlier and probably least partly due to the cold and cloudy weather during the measurements. No emissions of monoterpenes or halogenated hydrocarbons from the wetland were detected. Highest hydrocarbon emissions from the Scots pine forest floor were measured in spring and autumn. Main emitted compounds were monoterpenes. Isoprene emissions were negligible. Highest monoterpene emissions were measured in spring after the snow had melted. Emissions dropped in the summer and increased again in autumn. The total monoterpene emission rates varied from zero to 373 ?g m-2 h-1. Probable source for these emissions is decaying plant litter. Also small emissions of chloroform (100-800 ng m-2 h-1), ethene, propane, propene, 2-methylpropene, cis-2-butene, pentane, hexane and heptane were detected.

Helln, H.; Hakola, H.; Pystynen, K.-H.; Rinne, J.; Haapanala, S.

2005-11-01

69

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

...melt index of 0.1 to 20 as determined by ASTM method D1238-82, condition E, Standard Test Method for Flow Rates of Thermoplastics by Extrusion Plastometer, which is incorporated by reference. The availability of this incorporation by reference...

2014-04-01

70

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

E-print Network

as the SN2 mechanism. Kuivila has trapped anions using a variety of hydrogen donors. He used tert-butyl alcohol initially because it reacted with 6 carbanion intermediates faster than it did with (trimethylstannyl)- alkalies. However, the tin anion...' for the cyclic but not for the acycl ic case. Tertiary halides react with trimethyltinsodium mostly by elimin- ation. For example, the reaction with tert-butyl bromide yielded no 7 tin substitution product. The reaction with 1-adamantyl chloride was too slow...

Sanchez, Robert Michael

2012-06-07

71

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 ZieglerNatta and a metallocene ethylenebutene copolymer. TREF analysis indicated that the copolymer made with ZieglerNatta 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

72

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

73

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

74

J. Am. Chem. SOC.1982, 104, 5519-5521 5519 Table 11. Frequency and Fluence Dependence of per Pulse Yields and Stationary States  

E-print Network

/cmZ t'c c't steady state,c % cis 2-butene 975 1.4 0.5 4.5 30 trans-2-butene and trans-2-pentene display a threshold fluence of ca.4 J/cm2, below which the per pulse-' irradiation of 2-pentene. Irradiation of trans-2-butene with fluence >6 J/cm2 induces more fragmentation than

Chait, Brian T.

75

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

76

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

77

Phase equilibria of binary and ternary n-alkane solutions in supercritical ethylene, 1-butene, and ethylene + 1-butene: Transition from type A through LCST to U-LCST behavior predicted and confirmed experimentally  

Microsoft Academic Search

Binary phase equilibria of C[sub 20] +, C[sub 30] +, and C[sub 40] + ethylene are correlated with three equations of state, the Redlich-Kwong-Soave (Soave), the generalized van der Waals-Prigogine (vdW-P), and the statistical associating fluid theory (SAFT), with special emphasis on the mixture critical region. The SAFT correlation is found to be the most reliable. SAFT predictive powers are

Christopher J. Gregg; Fred P. Stein; Shenjer Chen; Maciej Radosz

1993-01-01

78

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

Microsoft Academic Search

Group 6 metalorganic aerogels were prepared by polymerization of a resorcinolformaldehyde 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 oxidecarbon 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 Jos Maldonado-Hdar; Jos Rivera-Utrilla; Enrique Rodr??guez-Castelln

1999-01-01

79

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

80

Shock tube studies on the decomposition of 2-butanol.  

PubMed

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

Rosado-Reyes, Claudette M; Tsang, Wing

2012-10-01

81

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

82

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

83

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

84

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

85

Vapor pressures of some C/sub 4/ hydrocarbons and their mixtures  

SciTech Connect

A significant amount of new vapor pressure data has been determined on systems containing 1.3-butadiene, n-butane, trans-2-butene, and cls-2-butene. Integration of the binary Gibbs-Duhem equation gave relative volatilities with a probable error of no more than + or - 0.010 unit.

Flebbe, J.L.; Barclay, D.A.; Manley, D.B.

1982-10-01

86

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

EPA Science Inventory

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

87

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

88

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.

89

Topological description of the bond-breaking and bond-forming processes of the alkene protonation reaction in zeolite chemistry: an AIM study  

Microsoft Academic Search

Density functional theory and atoms in molecules theory were used to study bond breakage and bond formation in the trans-2-butene\\u000a protonation reaction in an acidic zeolitic cluster. The progress of this reaction along the intrinsic reaction coordinate,\\u000a in terms of several topological properties of relevant bond critical points and atomic properties of the key atoms involved\\u000a in these concerted mechanisms,

Mara Fernanda Zalazar; Nlida Maria Peruchena

90

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

91

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 HSO 0.3 N and 1 N. Both samples showed superacid sites as shown by a desorption temperature peak in the NH 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

92

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.

93

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

SciTech Connect

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

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

2004-01-25

94

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.

95

Hydrogenation of dienes and the selectivity for partial hydrogenation on a molybdenum disulfide catalyst  

Microsoft Academic Search

The reaction of butadiene with hydrogen\\/deuterium on molybdenum disulfide (MoS) proceeded via the sec.-butyl intermediate and yielded only 1-butene-3,4-d and 1-butene-d. The hydrogenation of isoprene on MoS yielded 2-methyl-1-butene about four times as fast as it gave 3-methyl-1-butene, as previously found for other heterogeneous catalysts and in opposition to available results for homogeneous catalysts, which have a high selectivity for

Toshio Okuhara; Hiroyuki Itoh; Koshiro Miyahara; Kenichi Tanaka

1978-01-01

96

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

97

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

98

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

99

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

100

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

101

Tetrahedron Letters,Vol.26,No.8,Dp 997-1000,1985 0040-4039/85 $3.00 + .OO Printed in Great Britain 01985 Perqamon Press Ltd.  

E-print Network

. Addition of 6 to a solution of the Grignard reagent derived from 4-bromo-1-butene in the presence of [Bu the Grignard reagent of 4-bromo- P-methyl-1-butene in the initial conjugate addition. Irradiation of 5a (hexane

102

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

103

J. Am. Chem. SOC.1992, 114, 10767-10775 10767 First Examples of Homogeneous Hydrogenolysis of Thiophene  

E-print Network

excess thiophenein the presenceof the hydrogen acceptor 3,3-dimethyl-l-butene resultsin the formation complexes, all of which contain a C-S-cleaved 1-butene-I-thiolateligand. Two of the complexescontain an S in the formation of the corresponding cis and trans dihydrido 1-butene-I-thiolate complexes ReH2(SCH=CHEt)(PMe3

Jones, William D.

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

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

106

Pressure and Temperature Dependence of the Reaction of Vinyl Radical with Alkenes III: Measured Rates and Predicted Product Distributions for Vinyl + Butene  

E-print Network

This work reports experimental and theoretical first-order rate constants for the reaction of vinyl radical with C4H8 alkenes: 1-butene, 2-butene, and iso-butene. The experiments are performed over a temperature range of ...

Ismail, Huzeifa

107

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"

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

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

110

(e.g. SiO2) Strong and high Tg, Tm  

E-print Network

/s) Pentene Butene Propanol ( 10 K/s) ( 107 K/s) Toluene OTP Ethanol Propene Benzene CCl4 Methanol Ethane effect Low-energy excitation #12;#12;Propane Propene 1-Butene 1-Pentene 3-Methylpentane Tg / K 45.5 56-Gibbs Theory) Propene 1-Butene 1-Pentene 3MP Propane #12;CS2 60 K 70 K #12;Q Q #12;Sm (Q) = Sm u (Q) + Sm (Q

Katsumoto, Shingo

111

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 .Abbre?iations: Poly MPBEY -750, poly Z -1-methoxy-4-phenyl-1- x Z . Z .buten-3-yne

Kwak, Juhyoun

112

Characterization of catalytic lanthanum oxide for double bond isomerization of n-butenes  

E-print Network

Material and Prepared La(OH)3, 2 Temperature Dependence of Surface Area and Phase Composi- tion of Lanthanum Oxide Catalyst. 20 24 3 Initial 1-Butene Reaction Rates at O'C for Successive Experiments Involving No Catalyst Pretreatment between Runs..., 37 LIST OF FIGURES Figure Page Schematic Representation of the Apparatus. . 16 Dependence of initial 1-butene reaction rate on final calcination temperature of La203. Solid points, normal pretreatment; open points, normal pretreatment; open...

Fox, Janan Sherlene

2012-06-07

113

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

114

The production of C xH x-1 film using low pressure plasma CVD  

NASA Astrophysics Data System (ADS)

In a practice experiment on ICF targets, a CH coating has been developed for the investigation of radiation-induced implosion. An ultra-high vacuum system has been constructed to coat CH layers. The system consists of a work chamber with ultimate vacuum of 510 -6 Pa, a cleaning chamber with ultimate vacuum of 510 -4 Pa, an RF generator of continuous power up to 300 W, and a "bounce-plate" with 60 small pits, in which micro-spheres are located. Using hydrogen and trans-2-butene as reaction gases, CH is coated onto plate and sphere targets, with thickness 5-20 ?m and mean smoothness 50 nm. Different deposition conditions have been studied in detail with Fourier Transform infrared and X-ray photoelectron spectroscopy. The stable lifetime of the C xH x-1 film and the density of the surface dangling bonds under different H 2 flow rates and different in-situ treatment time with H + are described. An effective method of decreasing the surface dangling bond density is to use a long H + treatment time in-situ.

Weidong, Wu; Jiangshan, Luo; Yong, Huang; Dangzhong, Gao; Zhanwen, Zhang; Chunpei, Zhao

2002-03-01

115

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.

116

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

117

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

118

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

119

Tris(triisopropylsilyl)silane and the generation of bis(triisopropylsilyl)silylene  

SciTech Connect

Tris(triisopropylsilyl)silane (iPr{sub 3}Si){sub 3}SiH has been synthesized and studied by X-rah and neutron diffraction. It possesses an unusual structure in which the four silicon atoms are nearly coplanar, {angle}Si-Si-Si = 118.41(5){degree}. The Si-H distance is found to have a normal value of 1.506(2) {angstrom}. Thermal and room-temperature photochemical decomposition of (iPr{sub 3}-Si){sub 3}SiH leads to the elimination of iPr{sub 3}SiH and the generation of bis(triisopropylsilyl)silylene, [(iPr{sub 3}Si){sub 2}Si:]. Reactions of (iPr{sub 3}Si){sub 2}Si: include precedented insertions into H-Si bonds and addition to the {pi}-bonds of olefins, alkyenes, and dienes. Despite theoretical predictions of a triplet ground state for [(iPr{sub 3}Si){sub 2}Si:], stereospecific addition to cis- and trans-2-butene was observed.

Gaspar, P.P.; Beatty, A.M.; Chen, T. [Washington Univ., Saint Louis, MO (United States). Dept. of Chemistry] [and others] [Washington Univ., Saint Louis, MO (United States). Dept. of Chemistry; and others

1999-09-13

120

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

SciTech Connect

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

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

1992-12-09

121

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

122

Reactions of hydroxyl radicals with alkenes in low-temperature matrices  

NASA Astrophysics Data System (ADS)

The reactions of hydroxyl radicals with a number of stable alkenes have been studied in low-temperature matrices. The reactions were initiated by broad band UV-visible irradiation of matrices containing H 2O 2 and the alkene under investigation. The hydroxyalkyl radical products were identified principally by comparison of their spectra with the spectra of corresponding stable alcohols. Accordingly, IR spectra were recorded for the following series of alcohols isolated in argon matrices methanol, ethanol, ethanol- d6, propan-1-ol, propan-2-ol, butan-2-ol, 2-methylpropan-1-ol ( iso-butyl alcohol), 2-methylpropan-2-ol ( tert-butyl alcohol), 2-methylbutan-2-ol ( tert-amyl alcohol), 3-methylbutan-2-ol and 2,3-dimethylbutan-2-ol. The hydroxyalkyl radicals, which appear to be formed from the alkenes studied were as follows from ethene, 2-hydroxyethyl radical; from cis- or trans-but-2-ene, 1-methyl-2-hydroxypropyl radical; from propene, 1-methyl-2-hydroxyethyl and 2-hydroxypropyl radicals; from but-1-ene, 1-hydroxymethylpropyl and 2-hydroxybutyl radicals; from 2-methylpropene ( iso-butene), 1,1-dimethyl-2-hydroxyethyl and 2-methyl-2-hydroxypropyl radicals; the radical products from buta-1,3-diene and isoprene could not be identified. In the cases, where two radical products were possible, i.e. when propene, but-1-ene or 2-methylpropene were the substrates, it was found that the concentration of the secondary or tertiary radical always exceeded that of the primary radical. However, the relative concentration of these radicals appears to be determined by subsequent photolysis to give carbonyl compounds. There seems, therefore, to be little preference for the secondary and tertiary radicals over the primary radicals in the primary addition process. Comments on the mechanism of the transformation from radical to carbonyl compound based upon identification of intermediates within the matrix and isotopic substitution experiments are made. The characterisation of the 2-hydroxyethyl radical has been backed up by experiments utilising isotopic substitution with 13C and D ( 2H). The other radicals have been identified with varying degrees of certainty. Those radicals, which are observed at the highest concentration and which are, therefore, characterised more certainly are 2-hydroxyethyl ( 1), from ethene; 1-methyl-2-hydroxypropyl ( 2), from cis- and trans-but-2-ene; 1-methyl-2-hydroxyethyl ( 3), from propene; 1-hydroxymethylpropyl ( 5), from but-1-ene; and 1,1- dimethyl-2-hydroxyethyl ( 8), from 2-methylpropene.

Feltham, Emma J.; Almond, Matthew J.; Marston, George; Wiltshire, Karen S.; Goldberg, Nicola

2000-11-01

123

Figure S1. Relative contribution to total OH reactivity (a), of observed VOCs to calculated OH reactivity (b) and alkyl nitrate production (c,d) in the afternoon (12pm  

E-print Network

.223 5.61E-12(5) 0.0065 0.045 n-Heptane 0.073 0.28 7.15E-12(2) 0.0029 0.015 Cis-2-butene 0.020 0.037 5(1) 0 0.14 1-butene 0.040 0.025 3.17E-11(3) 0.00056 0.043 #12;3 1-pentene 0.023 0.05 3.18E-11(3) 0.00068 0.026 2-methyl-1-butene 0.022 0.03 6.10E-11(6) 0.00083 0.054 3-methyl-1-butene 0.0055 0.025 3.22E-11

Meskhidze, Nicholas

124

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

Microsoft Academic Search

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

David W. Robertson; John A. Katzenellenbogen

1982-01-01

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

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

Microsoft Academic Search

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 Hyytil, 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

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

2005-01-01

127

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

128

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 Langmui-Hinshelwood mechanism.

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

2012-06-01

129

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

NASA Astrophysics Data System (ADS)

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

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

130

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

131

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

132

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

133

Development and Characterization of Gas Chromatographic Columns for the Analysis of  

E-print Network

-DMPS and DMPS phases. On CPPS-DMPS phase, the retention time decreased as 1,3-butadiene > 1-butene > n temperature intervals, the retention times of C4 hydro- carbons predicted by the thermodynamic retention in- dex model were comparable to experimentally deter- mined values. Experimental and modeled retention

Vertes, Akos

134

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

135

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.

136

77 FR 3750 - Notice of Intent To Grant a Partially Exclusive License; Cobalt Technologies, Inc.  

Federal Register 2010, 2011, 2012, 2013

...filed on August 26, 2011.//patent application 12/511796: Diesel and Jet Fuels Based on the Oligomerization of 1-Butene, filed on July 29, 2009.// patent application 12/769757: Turbine and Diesel Fuels and Methods of Making the Same,...

2012-01-25

137

78 FR 4138 - Notice of Intent To Grant Co-Exclusive Licenses  

Federal Register 2010, 2011, 2012, 2013

...aliphatic-hydrocarbon solvents.//Patent Application Serial No. 12/ 511796: Diesel and jet fuels based on the oligomerization of 1-butene./ /Patent Application Serial No. 12/769757: Turbine and diesel fuels and methods of making the same.//Patent...

2013-01-18

138

Systematic preparation of selective heterogeneous catalysts  

SciTech Connect

The Single Turnover (STO) procedure, involving pulses of hydrogen and 1-butene, was developed for studying the types of active sites present on supported metal catalysts. The STO procedure was used to study direct saturated sites and other topics. Frontier molecular orbital studies were also made.

Augustine, R.L.

1991-11-07

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

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

141

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

142

Systematic preparation of selective heterogeneous catalysts. Final report, September 1, 1984--August 31, 1991  

SciTech Connect

The Single Turnover (STO) procedure, involving pulses of hydrogen and 1-butene, was developed for studying the types of active sites present on supported metal catalysts. The STO procedure was used to study direct saturated sites and other topics. Frontier molecular orbital studies were also made.

Augustine, R.L.

1991-11-07

143

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.

144

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...

145

Transfer hydrogenation of alkenes using Ni/Ru/Pt/Au heteroquatermetallic nanoparticle catalysts: sequential cooperation of multiple nano-metal species.  

PubMed

Quatermetallic alloy nanoparticles of Ni/Ru/Pt/Au were prepared and found to promote the catalytic transfer hydrogenation of non-activated alkenes bearing conjugating units (e.g., 4-phenyl-1-butene) with 2-propanol, where the composition metals, Ni, Ru, Pt, and Au, act cooperatively to provide significant catalytic ability. PMID:25177750

Ito, Yoshikazu; Ohta, Hidetoshi; Yamada, Yoichi M A; Enoki, Toshiaki; Uozumi, Yasuhiro

2014-10-18

146

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

SciTech Connect

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

Li, Juan.

1991-10-01

147

[Pollution characteristics and health risk assessment of atmospheric VOCs in the downtown area of Guangzhou, China].  

PubMed

The measurements of 31 kinds of VOCs in the ambient air of a site were carried out in the downtown of Guangzhou by online method from November 5, 2009 to November 9, 2009. The ambient level and composition characteristics, temporal variation characteristics, sources identification, and chemical reactivity of VOCs were studied, and the health risk of VOCs in the ambient air in the study area was assessed by using the international recognized health risk assessment method. Results showed that the mean and the range of the mass concentrations of 31 VOCs were 114.51 microg x m(-3) and 29.42-546.06 microg x m(-3), respectively. The mass concentrations of 31 VOCs, and those of alkanes, alkenes, and aromatics all showed a changing trend of higher in the morning and in the evening, and lower at noontime. Vehicular exhaust, gasoline and liquefied petroleum gas evaporates were the main sources of VOCs with the volatilization of paints and solvents being important emission sources. Toluene, trans-2-butene, m/p-xylene, i-butane, and 1,3,5-trimethylbenzene were the key reactive species among the 31 VOCs. Vehicular exhaust and gasoline evaporation were the main sources of VOCs leading to the formation of ozone. Health risk assessment showed that n-hexane, 1,3-butadiene, benzene, toluene, ethylbenzene, m/p-xylene and o-xylene had no appreciable risk of adverse non-cancer health effect on the exposed population, but 1, 3-butadiene and benzene had potential cancer risk. By comparing the corresponding data about health risk assessment of benzene compounds in some cities in China, it is concluded that benzene can impose relatively high cancer risk to the exposed populations in the ambient air of some cities in China. Therefore, strict countermeasures should be taken to further control the pollution of benzene in the ambient air of cities, and it is imperative to start the related studies and develop the atmospheric environmental health criteria and national ambient air quality standard for benzene in China. PMID:24640890

Li, Lei; Li, Hong; Wang, Xue-Zhong; Zhang, Xin-Min; Wen, Chong

2013-12-01

148

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

SciTech Connect

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

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

2005-07-15

149

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

SciTech Connect

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

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

2005-07-15

150

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

151

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

152

Theoretical kinetics studies of two model reactions in biodiesel and diesel combustion  

NASA Astrophysics Data System (ADS)

We use 1-methylallyl radical (CH3CH=CH-CH2 ? CH3CH-CH=CH2) as a model of allylic radicals generated during combustion of unsaturated diesel fuel molecules. The chemically activated isomerization of 1-methylallyl generated in the highly exothermic (35 kcal/mol) OH + trans-2-butene reaction was considered by using RRKM/Master Equation calculations from 0.01 to 100 atm and from 300 to 700 K. Density functional theory (DFT) with the M05-2X, M06-2X and B3LYP functionals are used for structures, energies, vibrational frequencies, anharmonic constants, and the torsional potentials of methyl rotations. The cis:trans ratio formed upon quenching the radicals were, as might be expected, dependent on the functional, but, were even more sensitive when an vibrations were treated as anharmonic. The fraction of cis- 1-methylallyl is significant, if not dominant at 300 -700 K and 0.01 -10 atm. Sensitivity studies were carried out to determine the dependence of the cis:trans ratio on the extent of chemical activation, treatment of the K-rotor as active or inactive, and the rate of collisional energy transfer. All these parameters significantly influence the cis:trans ratio. The 1,5 H-migration reaction of 3-hydroperoxy-1-propylperoxy radical (HOOCH2CH2CH2OO) is a important as a model of a critical propagation step in diesel autoignition from alkanes or molecules with long alkyl tails. Its product may be the meta-stable alpha,gamma-dihydroperoxypropyl radical or, if unstable, OH + 3-hydroperoxypropanal. To study the possibly different tunneling effects of the two possible products, the quantum mechanical rate constants, including tunneling, are directly determined using semi-classical transition state theory (SCTST) at 200 K to 1700 K. Small-curvature tunneling (SCT) is to compute tunneling corrections to classical rate constants. The two reactions do not have obvious tunneling differences at above 700 K. Below 700 K, SCTST tunneling corrections are significantly higher than SCT corrections, for reasons which are poorly understood. The anharmonic, tunneling, and variational corrections to the TST rate constant are combined together as a total correction for transition state theory rate constants, resulting in rate constants 10 times larger at 500-1700 K than that by standard transition state theory with harmonic treatment of vibrations. The pressure-dependent rate constant are calculated using RRKM/Master Equation methods.

Sha, Yuan

153

Borenium Ion Catalyzed Hydroboration of Alkenes with N-Heterocyclic Carbene Boranes  

PubMed Central

Treatment of alkenes such as 3-hexene, 3-octene, and 1-cyclohexyl-1-butene with the N-heterocyclic carbene-derived borane 2 and catalytic HNTf2 effects hydroboration at room temperature. With 3-hexene, surprisingly facile migration of the boron atom from C3 of the hexyl group to C2 was observed over a time scale of minutes to hours. Oxidative workup gave a mixture of alcohols containing 2-hexanol as the major product. A similar preference for the C(2) alcohol was observed after oxidative workup of the 3-octene, and 1-cyclohexyl-1-butene hydroborations. NHC-borenium cations (or functional equivalents) are postulated as the species that accomplish the hydroborations, and the C(2) selective migrations are attributed to the 4-center inter-conversion of borenium cations with cationic NHC-borane olefin ?-complexes. PMID:22713106

Prokofjevs, Aleksandrs; Boussonniere, Anne; Li, Linfeng; Bonin, Helene; Lacote, Emmanuel; Curran, Dennis P.; Vedejs, Edwin

2012-01-01

154

Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site  

Microsoft Academic Search

Observation of diurnal cycles in atmospheric concentrations of reactive alkenes are reported from measurements performed at a North Atlantic coastal site (Mace Head, Eire 5319?34?N; 954?14?W). Species seen to exhibit distinct cycles included isoprene, ethene, propene, 1-butene, iso-butene and a substituted C6 alkene. Five hundred and thirty air mass classified measurements were performed over a 4 week period at approximately

A. C. Lewis; J. B. McQuaid; N. Carslaw; M. J. Pilling

1999-01-01

155

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

156

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

157

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

158

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, Mara V; Kouznetsov, Vladimir V; Urbina G, Juan M; Lpez, Silvia N; Sortino, Maximiliano; Enriz, Ricardo D; Ribas, Juan C; Zacchino, Susana

2003-04-01

159

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

160

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

161

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

162

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

163

Deuterium Kinetic Isotope Effects in Butadiene Epoxidation over Unpromoted and Cs-Promoted Silver Catalysts  

Microsoft Academic Search

Selectively deuterium-labeled isotopomers of 1,3-butadiene (CD2CDCDCD2, CD2CHCHCD2, and CH2CDCDCH2) have been used as feed reactants to study kinetic isotope effects (KIEs) in the epoxidation of butadiene over both unpromoted and Cs-promoted catalysts. On unpromoted catalysts, the rate of formation of the epoxide product, 3,4-epoxy-1-butene (EpB), is increased relative to that for unlabeled butadiene for the butadiene isotopomers labeled on the

J. Will Medlin; John R Monnier; Mark A Barteau

2001-01-01

164

Name: ____________________________________ CHEMISTRY 3351, Fall 1993  

E-print Network

step in the reaction of Br2/H2O with 1-butene is the following: BrH H2O Br OH2 This step is an SN2 reactions. If a racemate is formed, consider this to be one product, show only one of the enantiomers: ____________________________________ -5- 4) (15 pts) a) Give structures for all of the possible products of the following reaction. Draw

Walba, David

165

Synthetic Strategies for the Lepadiformines and Cylindricine C via Tandem Schmidt Reactions  

E-print Network

. Examples of aza-spirocenter construction from Table 1 Figure 5. Core of prostaglandins Figure 6. Ring-closing metathesis catalysts Figure 7. Ellipsoid drawing of 140 3 5 6 9 77 91 192 xi List of Schemes Scheme 1. Tokuyama synthesis... coupling results Scheme 69. SuzukiMiyaura reaction with 4.28 Scheme 70. Formation of 4-benzyloxy-3-hydroxy-1-butene Scheme 71. SuzukiMiyaura reaction with functionalized alkene Scheme 72. Benzylidene protecting group idea Scheme 73. Benzylidene protecting...

Meyer, Angelica Michelle

2011-12-31

166

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

167

Effects of metal and acidic sites on the reaction by-products of butyl acetate oxidation over palladium-based catalysts.  

PubMed

Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation method. All the catalysts were characterized by means of N2 adsorption-desorption, X-ray fluorescence (XRF), H2 temperature programmed reduction (H2-TPR), and NH3 temperature programmed desorption (NH3-TPD). Their catalytic performance was investigated in the oxidation of butyl acetate experiments. The by-products of the reaction were collected in thermal desorption tubes and identified by gas chromatography/mass spectrometry. It was found that the increase of Pd content slightly changed the catalytic activity of butyl acetate oxidation according to the yield of CO2 achieved at 90%, but decreased the cracking by-products, whereas the enhancement of strong acidity over Pd-based catalysts enriched the by-product species. The butyl acetate oxidation process involves a series of reaction steps including protolysis, dehydrogenation, dehydration, cracking, and isomerization. Generally, butyl acetate was cracked to acetic acid and 2-methylpropene and the latter was an intermediate of the other by-products, and the oxidation routes of typical by-products were proposed. Trace amounts of 3-methylpentane, hexane, 2-methylpentane, pentane, and 2-methylbutane originated from isomerization and protolysis reactions. PMID:25079284

Yue, Lin; He, Chi; Hao, Zhengping; Wang, Shunbing; Wang, Hailin

2014-03-01

168

OH yields in the gas-phase reactions of ozone with alkenes  

SciTech Connect

Hydroxyl radical yields are reported for the gas-phase ozonolyses of a range of alkenes. 1,3,5-Trimethylbenzene was employed as an OH tracer, and the diminution in its concentration was used to calculate OH yields by both a simple analytical kinetic expression and a numerically integrated model. The following OH yields were obtained, relative to alkene consumed: ethene (0.14), propene (0.32), 2-methylpropene (0.60), 2,3-dimethyl-2-butene (0.89), isoprene (0.44), {beta}-pinene (0.24), and {alpha}-pinene (0.83). A structure activity relationship (SAR) is presented for the estimation of OH yields based on structural moieties and reaction branching ratios. Reaction stoichiometries ({Delta}[alkene]/{Delta}[ozone]) are also reported, along with primary carbonyl yields measured in the presence and absence of excess SO{sub 2}, both under OH-free conditions. Reaction stoichiometries are shown to be correlated with alkene OH yields, and the mechanistic implications of this observation are discussed. The fractional increase in primary carbonyl yield in the presence of excess SO{sub 2} is shown to be inversely related to the OH yield and is interpreted as a measure of the fraction of the vibrationally excited Criegee intermediate that is stabilized in air at a pressure of 1 atm.

Rickard, A.R.; Johnson, D.; McGill, C.D.; Marston, G.

1999-09-23

169

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

PubMed

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

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

2012-08-30

170

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

171

Probing the Melt Miscibility of a Commercial Polyethylene Blend by Small-Angle Light Scattering  

Microsoft Academic Search

Small-angle light scattering (SALS) was used to determine the binary interaction parameter ? in a molten blend of linear polyethylene (LPE, Mw=52kg\\/mol, PDI=2.9) and linear low-density polyethylenes (LLDPEs) based on homogeneous ethylene-1-butene copolymers (LLDPE-1, 18.7 mol% butane branches, Mw=58.1kg\\/mol, and LLDPE-2, 5.9 mol% butene branches, Mw=70kg\\/mol). Traditional cloud point measurements (cooling at 0.53C\\/min) and melt annealing\\/isothermal measurements under VV (parallel-polarized)

Yvonne A. Akpalu; Ping Peng

2008-01-01

172

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

173

Near-threshold absolute photoionization cross-sections of some reaction intermediates in combustion  

NASA Astrophysics Data System (ADS)

The use of photoionization mass spectrometry for the development of quantitative kinetic models for the complex combustion chemistry of both conventional hydrocarbon fuels and oxygenated biofuels requires near-threshold measurements of absolute photoionization cross-sections for numerous reaction intermediates. Near-threshold absolute cross-sections for molecular and dissociative photoionization for 20 stable reaction intermediates (methane, ethane, propane, n-butane, cyclopropane, methylcyclopentane, 1-butene, cis-2-butene, isobutene, 1-pentene, cyclohexene, 3,3-dimethyl-1-butene, 1,3-hexadiene, 1,3-cyclohexadiene, methyl acetate, ethyl acetate, tetrahydrofuran, propanal, 1-butyne, 2-butyne) are presented. Previously measured total photoionization cross-sections for 9 of these molecules are in good agreement with the present results. The measurements are performed with photoionization mass spectrometry (PIMS) using a monochromated VUV synchrotron light source with an energy resolution of 40 meV (fwhm) comparable to that used for flame-sampling molecular beam PIMS studies of flame chemistry and reaction kinetics.

Wang, Juan; Yang, Bin; Cool, Terrill A.; Hansen, Nils; Kasper, Tina

2008-02-01

174

Type II Isopentenyl Diphosphate Isomerase: Probing the Mechanism with Alkyne/Allene Diphosphate Substrate Analogues  

PubMed Central

Isopentenyl diphosphate isomerase (IDI) catalyzes the interconversion of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), the basic five-carbon building blocks of isoprenoid molecules. Two structurally unrelated classes of IDI are known. Type I IPP isomerase (IDI-1) utilizes a divalent metal in a protonation-deprotonation reaction. In contrast, the type II enzyme (IDI-2) requires reduced flavin, raising the possibility that the reaction catalyzed by IDI-2 involves the net addition/abstraction of a hydrogen atom. As part of our studies of the mechanism of isomerization for IDI-2, we synthesized allene and alkyne substrate analogues for the enzyme. These molecules are predicted to be substantially less reactive toward proton addition than IPP and DMAPP, but have similar reactivities toward hydrogen atom addition. This prediction was verified by calculations of gas phase heats of reaction for addition of a proton and of a hydrogen atom to 1-butyne (3) and 1,2-butadiene (4) to form the 1-buten-2-yl carbocation and radical, respectively, and related affinities for 2-methyl-1-butene (5) and 2-methyl-2-butene (6) using G3MP2B3 and CBS-QB3 protocols. Alkyne 1-OPP and allene 2-OPP were not substrates for Thermus thermophilus IDI-2 or Escherichia coli IDI-1, but instead were competitive inhibitors. The experimental and computational results are consistent with a protonation-deprotonation mechanism for the enzyme-catalyzed isomerization of IPP and DMAPP. PMID:20560533

Sharma, Nagendra K.; Pan, Jian-Jung; Poulter, C. Dale

2010-01-01

175

Kinetic model for the etherification of isoamylenes with methanol  

SciTech Connect

The kinetics of the formation of tert-amyl methyl ether (TAME; 2-methoxy-2-methylbutane) was investigated in a batch reactor, using a commercial ion-exchange resin (Amberlyst 16) as catalyst. The effect of the methanol/isoamylene ratio on the etherification rate was measured at temperatures between 333 and 353 K. The initial rates of isomerization of 2-methyl-1-butene to 2-methyl-2-butene and the etherification of 2-methyl-1-butene to TAME were measured in the absence of 2-methyl-2-butene in the feed. The initial rate of etherification was found to be 2.3--2.7 times that of isomerization. The experimental results were best described by kinetic equations, which were based on a mechanism where the alcohol and the ether adsorbed on the catalyst surface and the isoamylenes reacted from the bulk liquid phase. The kinetic equations were written in terms of activities, using the UNIQUAC method for activity coefficient calculation. The activation energy was determined to be 81.6 kJ/mol for the isomerization and 72.6 kJ/mol for the etherification of 2M1B to TAME and 94.1 kJ/mol for the etherification of 2M2B. The experimental results were in good agreement with the results simulated by the proposed model.

Rihko, L.K. [Neste Oy, Porvoo (Finland)] [Neste Oy, Porvoo (Finland); Kiviranta-Paeaekkoenen, P.K.; Krause, A.O.I. [Helsinki Univ. of Technology, Espoo (Finland). Dept. of Chemical Engineering] [Helsinki Univ. of Technology, Espoo (Finland). Dept. of Chemical Engineering

1997-03-01

176

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

177

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

178

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

179

Aluminum coordination and active sites on aluminas, Y zeolites and pillared layered silicates. Progress report, June 1, 1990--January 31, 1992  

SciTech Connect

Our work has been deployed in four directions, namely, (1) Study of the distribution of aluminum within three possible kinds of coordination shells: four-fold (IV), five-fold (V), and six-fold (VI), in aluminas and dealuminated zeolites by high-resolution solid state NMR or magic angle NMR. Besides the classical one pulse spectra, nutation spectra have been studied. (2) Study of the electron deficient sites by electron paramagnetic resonance (EPR) of probe molecules on aluminas and decationated zeolites. Electron deficient sites are considered as Lewis sites. (3) Study of the model isomerization reaction 1 butene {yields} 2 cis or trans butene on the aluminas characterized in 1 and 2. (4) Synthesis of a silicate lattice in which silicon has been partially replaced by aluminum. The chosen silicate is that of the zeolite (fibrous) sepiolite. It has been characterized as indicated in 1 and 2.

Fripiat, J.J.

1991-12-31

180

Aluminum coordination and active sites on aluminas, Y zeolites and pillared layered silicates  

SciTech Connect

Our work has been deployed in four directions, namely, (1) Study of the distribution of aluminum within three possible kinds of coordination shells: four-fold (IV), five-fold (V), and six-fold (VI), in aluminas and dealuminated zeolites by high-resolution solid state NMR or magic angle NMR. Besides the classical one pulse spectra, nutation spectra have been studied. (2) Study of the electron deficient sites by electron paramagnetic resonance (EPR) of probe molecules on aluminas and decationated zeolites. Electron deficient sites are considered as Lewis sites. (3) Study of the model isomerization reaction 1 butene {yields} 2 cis or trans butene on the aluminas characterized in 1 and 2. (4) Synthesis of a silicate lattice in which silicon has been partially replaced by aluminum. The chosen silicate is that of the zeolite (fibrous) sepiolite. It has been characterized as indicated in 1 and 2.

Fripiat, J.J.

1991-01-01

181

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

182

Aqueous biphasic olefin hydroformylation catalyzed by water-soluble rhodium complexes  

Microsoft Academic Search

Catalysis with water-soluble rhodium complexes, RhCl(CO)(TPPMS)2, [TPPMS=P(C6H5)2(C6H4SO3)] (1), RhCl(CO)(TPPDS)2, [TPPDS=P(C6H5)(C6H4SO3)2] (2) and RhCl(CO)(TPPTS)2, [TPPTS=P(C6H4SO3)3] (3) in hydroformylation of 1-hexene, 2-pentene, 2,3-dimethyl-1-butene, cyclohexene and several mixtures of these olefins have\\u000a been studied, under moderate reaction conditions (T: 50150C; pCO\\/pH2=1; total p: 1468bar; Substrate\\/Catalyst: 600\\/1) in biphasic toluene\\/water media. The catalytic system shows high activity\\u000a but low selectivity. The linear and branched

Trino Surez; Bernardo Fontal; Gustavo Len; Marisela Reyes; Fernando Bellandi; Ricardo R. Contreras; Pedro Cancines

2006-01-01

183

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

184

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

185

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, Franoise; Sautet, Philippe

2005-07-28

186

Catalytic oxidation of furan on a Mo-Ti-O catalyst. Infrared and thermodesorption study  

SciTech Connect

The adsorption and oxidation of furan, an intermediate in the conversion of 1-butene to maleic anhydride, were studied on a catalyst containing 15.6% molybdenum as trioxide on titanium dioxide that yielded 53% maleic anhydride at 63% conversion. The results showed at furan adsorbed in two distinct modes, of which one was observed only on oxidized surface and the other was always present but depended on the degree of reduction. The adsorbed furan was oxidized in the presence of oxygen at temperatures above 235/sup 0/C, but it desorbed only above 320/sup 0/C. The Mo=O species did not seem to be important in the oxidation of furan to maleic anhydride.

Rivasseau, J.; Canesson, P.; Blanchard, M.

1980-10-16

187

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

SciTech Connect

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

Santoro, R.J.

1989-02-15

188

Precision Polyolefin Structure: Modeling Polyethylene Containing Methyl and Ethyl Branches  

NASA Astrophysics Data System (ADS)

Sequenced copolymers of ethylene and diverse species have been created using acyclic diene metathesis (ADMET) polymerization, a step growth, condensation- type polymerization driven to high conversion by the removal of ethylene. ADMET permits control over branch content and branch length, which can be predetermined during the monomer synthesis, allowing sequence control in the resultant unsaturated polymer. Monomers are symmetrical ?,?dienes with a pendant functionality. Diverse functional groups are compatible with ADMET polymerization when Schrocks or first-generation Grubbs catalysts are used. Saturation with hydrogen after ADMET polymerization affords a polyethylene (PE) backbone bearing specific functionalities in precise places. Varying both the pendant functional group and the spacing between functionalities alters the physical and chemical properties of the polymer. Incorporation of alkyl chains into the PE backbone via ADMET leads to the study of perfect structures modeling the copolymerization of ethylene with ?-olefins such as 1-propene, 1-butene, 1-hexene, and 1-octene.

Rojas, Giovanni; Wagener, Kenneth B.

189

Structure and entanglements in short chain branched polyolefin melts  

NASA Astrophysics Data System (ADS)

Atomistic models of short chain branched (SCB) polyethylene melts containing up to 20-40 mol% of comonomer (1-butene, 1-hexene, 1-octene or 1-decene) have been equilibrated at 450 K using a connectivity altering Monte Carlo method, and analyzed for topological constraints using Z1 and CReTA codes. The calculated tube diameters, , of SCB melts are found to scale with the backbone weight fraction, ?, as ?-0.46, close to the scaling predicted by the binary contact model, ?-0.5 and in disagreement with the packing model prediction ?-1.27. Similar scaling relationships are observed experimentally for polymer solutions, and reproduced by the present methods.

Moorthi, K.; Kamio, K.; Ramos, J.; Theodorou, D. N.

2013-02-01

190

Inhibitory potency of 4-carbon alkanes and alkenes toward CYP2E1 activity.  

PubMed

CYP2E1 has been implicated in the bioactivation of many small molecules into reactive metabolites which form adducts with proteins and DNA, and thus a better understanding of the molecular determinants of its selectivity are critical for accurate toxicological predictions. In this study, we determined the potency of inhibition of human CYP2E1 for various 4-carbon alkanes, alkenes and alcohols. In addition, known CYP2E1 substrates and inhibitors including 4-methylpyrazole, aniline, and dimethylnitrosamine were included to determine their relative potencies. Of the 1,3-butadiene-derived metabolites studied, 3,4-epoxy-1-butene was the strongest inhibitor with an IC50 of 110 ?M compared to 1700 ?M and 6600 ?M for 1,2-butenediol and 1,2:3,4-diepoxybutane, respectively. Compared to known inhibitors, inhibitory potency of 3,4-epoxy-1-butene is between 4-methylpyrazole (IC50 = 1.8 ?M) and dimethylnitrosamine (IC50 = 230 ?M). All three butadiene metabolites inhibit CYP2E1 activity through a simple competitive mechanism. Among the 4-carbon compounds studied, the presence and location of polar groups seems to influence inhibitory potency. To further examine this notion, the investigation was extended to include structurally and chemically similar analogues, including propylene oxide and various butane alcohols. Those results demonstrated preferential recognition of CYP2E1 toward the type and location of polar and hydrophobic structural elements. Taken together, CYP2E1 metabolism may be modified in vivo by exposure to 4-carbon compounds, such as drugs, and nutritional constituents, a finding that highlights the complexity of exposure to mixtures. PMID:24561005

Hartman, Jessica H; Miller, Grover P; Boysen, Gunnar

2014-04-01

191

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

192

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

193

Species and soot concentration measurements in a methane/air nonpremixed flame doped with C4 hydrocarbons  

SciTech Connect

The fuel in a co-flowing methane/air nonpremixed flame was doped with 7400 ppm of 1,3-butadiene, 1-butene, isobutene, and n-butane. Temperature, mole fractions of 24 stable C1 to C12 hydrocarbons, and soot volume fraction were measured along the centerline of the five resulting flames. The additives significantly increased the concentrations of aromatic species and of soot. The specific changes could be reasonably explained by conversion of the additives to aromatic ring precursors, but not by effects of the additives on temperature and H atom concentrations. Isobutene and 1-butene generated the highest concentrations of C4 products. However, several pathways readily interconvert C3 and C4 species, such that increases in both C3 and C4 species were observed for almost every additive. Recombination of propargyl radicals (C{sub 3}H{sub 3}) appears to be responsible for most aromatic ring formation on the centerline of these flames. Reactions of acetylene with n-C{sub 4}H{sub 5} and/or n-C{sub 4}H{sub 3} may also contribute in the 1.3-butadiene-doped flame. Benzene appears to be in partial equilibrium with acetylene in the upper half of the flames. The kinetic processes that establish this equilibrium are most likely ring fragmentation reactions in one direction and acetylene addition to n-C{sub 4}H{sub 3} in the other. The probable source of the n-C{sub 4}H{sub 3} is acetylene addition to C{sub 2}H, with the strong temperature-dependence of C{sub 2}H concentrations responsible for limiting this process to the upper half of the flames. Production of one-ring aromatic species is an important rate-limiting step to soot formation in these flames.

Mcenally, C.S.; Pfefferle, L.D. [Yale Univ., New Haven, CT (United States)] [Yale Univ., New Haven, CT (United States)

1998-10-01

194

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

195

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

196

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

197

(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 Mssbauer 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

198

Characterization and acidic properties of Al-SBA-15 materials prepared by post-synthesis alumination of a low-cost ordered mesoporous silica  

SciTech Connect

A series of Al-containing SBA-15 type materials with different Si/Al ratio, were prepared by post-synthesis modification of a pure highly ordered mesoporous silica SBA-15 obtained by using sodium silicate as silica source, and amphiphilic block copolymer as structure-directing agent. A high level of aluminum incorporation was achieved, reaching an Si/Al ratio of up to 5.5, without any significant loss in the textural properties of SBA-15. These materials were fully characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), {sup 27}Al NMR spectroscopy, and N{sub 2} adsorption at 77 K. The acid properties of these materials have been evaluated by NH{sub 3}-TPD, adsorption of pyridine and deuterated acetonitrile coupled to FTIR spectroscopy. The effective acidity of these materials was evaluated using two catalytic reactions: 2-propanol dehydrogenation and 1-butene isomerization. The adsorption of basic probe molecules and the catalytic behavior revealed an evolution of the acid properties with the Al content. These studies have shown that the Al-SBA-15 materials contain Bronsted and Lewis acid sites with medium acidity which makes them appropriate to be used as acid catalysts in heterogeneous catalysis, catalytic supports, and adsorbents. - Graphical abstract: Al KLL spectra of Al-SBA-15 materials with different Si/Al ratios.

Gomez-Cazalilla, M. [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.M. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia (Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga (Spain); Gurbani, A. [Instituto de Catalisis y Petroleoquimica, CSIC, Cantoblanco, 28049 Madrid (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)], E-mail: ajimenezl@uma.es

2007-03-15

199

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

200

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

201

Speciated VOC emission inventory and spatial patterns of ozone formation potential in the Pearl River Delta, China.  

PubMed

The Pearl River Delta region (PRD) of China has long suffered from severe ground-level ozone pollution. Knowledge of the sources of volatile organic compounds (VOCs) is essential for ozone chemistry. In this work, a speciated VOC emission inventory was established on the basis of updated emissions and local VOC source profiles. The top 10 species, in terms of ozone formation potentials (OFPs), consisted of isoprene, mp-xylene, toluene, ethylene, propene, o-xylene, 1,2,4-trimethylbenzene, 2-methyl-2-butene, 1-butene, and alpha-pinene. These species contributed only 35.9% to VOCs emissions but accounted for 64.1% of the OFP in the region. The spatial patterns of the VOC source inventory agreed well with city-based source apportionment results, especially for vehicle emissions and industry plus VOC product-related emissions. Mapping of the OFPs and measured ozone concentrations indicated that the formation of higher ozone in the south and southeast of the PRD region differed from that in the Conghua area, a remote area in the north of the PRD. We recommend that the priorities for the control of VOC sources include motorcycles, gasoline vehicles, and solvent use because of their larger OFP contributions. PMID:20028055

Zheng, Junyu; Shao, Min; Che, Wenwei; Zhang, Lijun; Zhong, Liuju; Zhang, Yuanhang; Streets, David

2009-11-15

202

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

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

203

[Characteristics of VOCs and their photochemical reactivity in autumn in Nanjing northern suburb].  

PubMed

A continuous observation campaign was carried out with the GC5000 volatile organics online monitoring system and the EMS system for one month in November 2011 in the northern suburb of Nanjing, and 56 VOC components and reactive gases (NO(x), CO and O3) were measured. The results showed that the VOC hourly averaged volume fraction in Nanjing northern suburb was about 48.17 x 10(-9), and the minimum value of VOCs occurred at 16:00. The diurnal variation showed a bimodal characteristic, indicating the significant impact of motor vehicle emission. The VOC concentration and O3 concentration exhibited negative correlation in the daytime. The average OH consumption rate of VOCs was approximately 3.26 x 10(-12) cm3 x (molecule x s)(-1), and the largest incremental reactivity was about 3.26 mol x mol(-1); Alkenes contributed the largest-parts of the OH consumption rate (L(OH)) and the ozone formation potential (OFP), followed by aromatics. Although alkanes were the most abundant components of VOCs in the atmosphere, it is not the main contributor of L(OH) and OFP. The key active components in VOCs were ethylene, propylene, 1-butene, m,p-xylene and isoprene, etc. The dominant factor of ozone formation was VOCs in this observation. PMID:24191532

Li, Yong-Yu; Zhu, Bin; An, Jun-Lin; Gao, Jin-Hui; Xia, Li; Zhang, Xiang-Zhi; Qin, Wei; Tang, Li-Li

2013-08-01

204

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

SciTech Connect

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

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

1995-04-01

205

An operando FTIR spectroscopic and kinetic study of carbon monoxide pressure influence on rhodium-catalyzed olefin hydroformylation.  

PubMed

The influence of carbon monoxide concentration on the kinetics of the hydroformylation of 3,3-dimethyl-1-butene with a phosphite-modified rhodium catalyst has been studied for the pressure range p(CO)=0.20-3.83?MPa. Highly resolved time-dependent concentration profiles of the organometallic intermediates were derived from IR spectroscopic data collected in situ for the entire olefin-conversion range. The dynamics of the catalyst and organic components are described by enzyme-type kinetics with competitive and uncompetitive inhibition reactions involving carbon monoxide taken into account. Saturation of the alkyl-rhodium intermediates with carbon monoxide as a cosubstrate occurs between 1.5 and 2?MPa of carbon monoxide pressure, which brings about a convergence of aldehyde regioselectivity. Hydrogenolysis of the acyl intermediate is fast at 30?C and low pressure of p(CO)=0.2?MPa, but is of minus first order with respect to the solution concentration of carbon monoxide. Resting 18-electron hydrido and acyl complexes that correspond to early and late rate-determining states, respectively, coexist as long as the conversion of the substrate is not complete. PMID:25081298

Kubis, Christoph; Sawall, Mathias; Block, Axel; Neymeyr, Klaus; Ludwig, Ralf; Brner, Armin; Selent, Detlef

2014-09-01

206

Photochemistry of 1 and 2-(2-methylphenyl)-1,6-heptadiene. [4a-methyl-1,2,3,4,4a,9,10,10a-octahydrophenanthrene  

SciTech Connect

In an attempt to synthesize partially saturated phenanthrene derivatives by an intramolecular Diels-Alder reaction between a photochemically produced o-xylylene (diene) and a tethered dienophile, it was found that 1 and 2 underwent a photochemically allowed (2 + 2) cycloaddition. Irradiation of 1 gave 6-(2-methylphenyl)bicyclo(3.2.0)heptane in 86% yield. Upon irradiation of 2, a benzvalene rearrangement of 2 first took place, producing the meta isomer 2-(3-methylphenyl)-1,6-heptadiene, followed by a (2 + 2) photocycloaddition giving 1-(3-methylphenyl)bicyclo(3.2.0)heptane in 15% yield. Direct irradiation of 2-(3-methylphenyl)-1,6-heptadiene gave the same bicyclo derivative as 2 in 34% yield. Examination of the fluorescence spectra of 1 and 2 in comparison with 1-(2-methylphenyl)propene and 2-(2-methylphenyl)-1-butene, respectively, has shown that 1 may be biased toward (2 + 2) cycloaddition where 2 is not biased toward (2 + 2) photocycloization. Attempts to produce 4a-methyl-1,2,3,4,4a,9,10,10a-octahydrophenanthrene by an intramolecular Diels-Alder reaction of the o-xylylene produced by irradiation of 3 will also be described.

Barrows, R.D.; Hornback, J.M.

1982-01-01

207

[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

208

The adsorption of C4 unsaturated hydrocarbons on highly dehydrated silica. An IR-spectroscopic and thermodynamic study.  

PubMed

The adsorptive interaction of 1-butyne and 1-butene with a highly dehydrated pyrogenic silica system has been studied to understand the thermodynamic behavior of the adsorption process by the application of the Langmuir model and of the Van't Hoff equation. In situ FTIR spectroscopy allowed the characterization of the adsorption phenomenon in terms of involved surface sites, gas-volumetric determinations yielded quantitative information relative to the adsorption process, and microcalorimetric results allowed the comparison between calculated and experimental data. K(eq) and Delta(ads)G degrees were obtained from Langmuir's model application; Delta(ads)H data were obtained from the Van't Hoff equation and by the isosteric heats method and were compared with experimental values. The virtual constancy of Delta(ads)H with equilibrium pressure and surface coverage (Langmuir model) allowed us to obtain the Delta(ads)H degrees values and, consequently, the Delta(ads)S degrees values for the systems of interest. PMID:15835958

Magnacca, Giuliana; Morterra, Claudio

2005-04-26

209

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

210

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

211

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

212

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

213

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

214

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

215

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

216

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

217

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

218

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, Jrmie; Gauvin, Rgis M; Taoufik, Mostafa

2013-12-01

219

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

220

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

221

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

222

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

223

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

224

Organic chemistry in the oceans of Titan  

NASA Astrophysics Data System (ADS)

On Titan, most of the organics present in the atmosphere must condense in the lower stratosphere and be solid near the surface, except methane, ethane, propane, propene and 1-butene which must be liquid and could form oceans containing large fractions of dissolved N2. Chemical evolution on Titan must have followed a way very different from the terrestrial one, involving physical chemical processes in a cryogenic apolar solvent mainly composed of CH4-C2H6-N2, in place of organic chemistry in water. Systematic study of the volumic mass and solubility of organics in such a cryogenic mixture of various compositions, at 94K, is presented, using thermodynamic modelling. The results suggest that the oceans of Titan could be free of any "icebergs" of organic compounds. These oceans could be very rich in dissolved organics, with relatively high concentrations, in the range 1 - 10-6M. In addition, the concentration of several of the organic solutes should be constant, buffered by a bottom layer of the corresponding compound in the solid phase.

Raulin, F.

225

Slow Dynamics at the Glass Transition in Semicrystalline Polymers Studied by Pure-Exchange ^13C NMR  

NASA Astrophysics Data System (ADS)

The dynamics in the amorphous regions of semicrystalline polymers exert important influences on mechanical properties but have been difficult to characterize. New solid-state nuclear magnetic resonance (NMR) techniques, PUREX (pure-exchange) and CODEX (centerband-only detection of exchange), enable studies of the molecular motions near the glass transition (T_g) in the amorphous regions of semicrystalline polymers. This is achieved by selectively suppressing the dominant signals of the static segments in the crystallites. We have applied both techniques to analyze the geometry and time scale of the slow motions around Tg in isotactic poly(1-butene) (iPB1), in polypropylenes (iPP, sPP, aPP), and in fully amorphous polyisobutylene (PIB) for reference. The apparent activation energies for iPB1, sPP, and PIB were found to be 90, 125, and 115 kJ/mol, respectively. In iPB1, indications of slow motions in two distinct regions were observed.

Bonagamba, Tito J.; Deazevedo, Eduardo R.; Becker-Guedes, Fabio; Schmidt-Rohr, Klaus

2001-03-01

226

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

227

On the Radiolysis of Ethylene Ices by Energetic Electrons and Implications to the Extraterrestrial Hydrocarbon Chemistry  

NASA Astrophysics Data System (ADS)

The chemical processing of ethylene ices (C2H4) by energetic electrons was investigated at 11 K to simulate the energy transfer processes and synthesis of new molecules induced by secondary electrons generated in the track of galactic cosmic ray particles. A combination of Fourier transform infrared spectrometry (solid state) and quadrupole mass spectrometry (gas phase) resulted in the identification of six hydrocarbon molecules: methane (CH4), the C2 species acetylene (C2H2), ethane (C2H6), the ethyl radical (C2H5), andfor the very first time in ethylene irradiation experimentsthe C4 hydrocarbons 1-butene (C4H8) and n-butane (C4H10). By tracing the temporal evolution of the newly formed molecules spectroscopically online and in situ, we were also able to fit the kinetic profiles with a system of coupled differential equations, eventually providing mechanistic information, reaction pathways, and rate constants on the radiolysis of ethylene ices and the inherent formation of smaller (C1) and more complex (C2, C4) hydrocarbons involving carbon-hydrogen bond ruptures, atomic hydrogen addition processes, and radical-radical recombination pathways. We also discuss the implications of these results on the hydrocarbon chemistry on Titan's surface and on ice-coated, methane-bearing interstellar grains as present in cold molecular clouds such as TMC-1.

Zhou, Li; Maity, Surajit; Abplanalp, Matt; Turner, Andrew; Kaiser, Ralf I.

2014-07-01

228

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

229

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

NASA Astrophysics Data System (ADS)

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 ?g g (dry weight) -1 h -1) monoterpene emission rates when leaves were young in May. In addition, willow emitted 1-butene, ethene, and propene when it was blooming in May. In August, silver birch emitted monoterpenes (6-12 ?g g (dry weight) -1 h -1). Then the main species emitted were ocimenes and sabinene. Birch emitted only minor amounts of isoprene. Willow and aspen are high isoprene emitters (up to 76 ?g g (dry weight) -1 h -1 in August). Isoprene emissions began 2-3 weeks after onset of leafing. The phenological state was estimated using the effective temperature sum. Isoprene synthase began when the effective temperature sum exceeded 120-210 and 120-280 degree days for willow and aspen, respectively. In addition to phenology, isoprene emissions were dependent on temperature and photosynthetically active radiation while the terpene emissions were dependent on temperature only.

Hakola, Hannele; Rinne, Janne; Laurila, Tuomas

230

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

231

Rate coefficients at 298 K and 1 atm for the tropospheric degradation of a series of C6, C7 and C8 biogenic unsaturated alcohols initiated by Cl atoms  

NASA Astrophysics Data System (ADS)

Rate coefficients for the gas-phase reactions of Cl atoms with a series of unsaturated biogenic alcohols at 298 3 K and 1 atm have been measured by the relative technique in an environmental chamber with in situ FTIR detection of reactants. The rate coefficients obtained using 1-butene and isobutene as reference compounds were (in units of 10-10 cm3 molecule-1 s-1): k1((E)-2-hexen-1-ol) = (3.49 0.82), k2((E)-3-hexen-1-ol) = (3.42 0.79), k3 ((Z)-3-hexen-1-ol) = (2.94 0.72), k4((Z)-3-hepten-1-ol) = (3.80 0.86) and k5((Z)-3-octen-1-ol) = (4.13 0.68). This work constitutes the first kinetic study of the reactions cited above. The rate coefficients are compared with those for other unsaturated alcohols and a correlation between the reactivity of unsaturated alcohols toward Cl atoms and the energy of the HOMO of the unsaturated alcohols is presented. Based on the obtained results, the atmospheric lifetimes of the unsaturated alcohols have been estimated and possible atmospheric implications assessed.

Gibilisco, Rodrigo G.; Bejan, Iustinian; Barnes, Ian; Wiesen, Peter; Teruel, Mariano A.

2014-09-01

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

Polar organic marker compounds in atmospheric aerosols during the LBA-SMOCC 2002 biomass burning experiment in Rondnia, 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 (Rondnia, 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 Amaznia - 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

234

Amylenes Do Not Lead to Bacterial Mutagenicity in Contrast to Structurally Related Epoxides  

PubMed Central

Amylenes are unsaturated hydrocarbons (C5H10), such as 1-pentene, 2-pentene, 2-methyl-but-1-en (3-methyl-1-butene), 2-methyl-but-2-en (isopentene), and 3-methyl-but-1-en. We investigated bacterial mutagenicity of 1-pentene, 2-pentene, and 3-methyl-but-1-en in the Ames test. 2-Pentene was investigated as racemate and as pure diastereomers. We included the methyltransferase deficient Salmonella Typhimurium strain YG7108 and the application of a gas-tight preincubation to reduce the risk of false negative results. 1,2-Epoxypentane which may arise from 1-pentene was used as positive control. None of the investigated amylenes showed mutagenic effects, whereas 1,2-epoxypentane was mutagenic exceeding 100??g per plate. An exceptional high reverse mutation in the negative control plates in the experiments with 1,2-epoxypentane was obviously caused by evaporation into the incubator which was shown by placing the control plates in a separate apparatus. No differences were seen upon use of YG7108 and its parent strain TA1535. In conclusion, 1,2-epoxypentane is most probably not a substrate of the deleted bacterial methyltransferases. The comparison of the bacterial mutagenicity of the investigated amylenes and 1,2-epoxipentane suggests that epoxidation of amylenes in the S9-mix does not proceed effectively or is counterbalanced by detoxifying reactions. The assessment of mutagenic effects of short chained aliphatic epoxides can be underestimated due to the evaporation of these compounds. PMID:24511538

Westphal, Gotz A.; Tushaus, Carolin; Monse, Christian; Rosenkranz, Nina; Bruning, Thomas; Bunger, Jurgen

2014-01-01

235

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

SciTech Connect

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

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

1994-06-01

236

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

PubMed

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

Elfarra, Adnan A; Zhang, Xin-Yu

2012-11-19

237

Laser absorption diagnostic for measuring acetylene concentrations in shock tubes  

NASA Astrophysics Data System (ADS)

A fixed-wavelength direct absorption laser diagnostic for high-temperature measurements of acetylene concentration was developed. The diagnostic, based on a tunable continuous wave distributed feedback diode laser, was optimized primarily for studying chemical kinetics behind reflected shock waves. The center wavelength (3335.55 cm-1) of the tunable diagnostic was typically set at the peak of the 3300 cm-1 absorption band of acetylene at high temperatures. The absorption spectrum of acetylene diluted in argon was characterized using scanned-wavelength direct absorption measurements from 1070 to 1720 K and 0.8 to 4.0 atm. Line fitting of the measured absorption spectra was not possible due to the large number of transitions overlapped by pressure broadening that contribute to the spectrum. Instead, empirical fits for the peak absorption coefficient and its corresponding wavelength as a function of temperature and pressure were generated. Furthermore, in order to allow for characterization of interference absorption in kinetic studies, empirical fits for the acetylene absorption coefficient in the region around the primary absorption feature were developed. Absorption coefficient measurements of propyne and 1-butyne, which may be the primary interference candidates, reveal that their absorption coefficients are constant in the wavelength range of interest, and are much smaller than those of acetylene. Therefore, the acetylene concentration in the presence of these interfering species can be inferred using two-color techniques. The utility of the acetylene diagnostic was demonstrated by measuring acetylene mole fraction time-histories during the pyrolysis of propene and 1-butene.

Stranic, Ivo; Hanson, Ronald K.

2014-07-01

238

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

239

Rich methane premixed laminar flames doped by light unsaturated hydrocarbons. III. Cyclopentene  

SciTech Connect

In line with the studies presented in Parts I (methane flame seeded with allene and propyne) and II (methane flame seeded with 1,3-butadiene) of this paper, the structure of a laminar rich premixed methane flame doped with cyclopentene has been investigated. The gases of this flame contain 15.3% (molar) of methane, 26.7% of oxygen, and 2.4% cyclopentene, corresponding to an overall equivalence ratio of 1.79 and a C{sub 5}H{sub 8}/CH{sub 4} ratio of 15.7%. 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 measured temperature ranged from 627 K close to the burner up to 2027 K. Species quantified by gas chromatography included the usual methane C{sub 0}-C{sub 2} combustion products, but also propyne, allene, propene, propane, 1-butene, 1,3-butadiene, 1,2-butadiene, vinylacetylene, diacetylene, cyclopentadiene, 1,3-pentadiene, benzene, and toluene. A new mechanism for the oxidation of cyclopentene has been developed and added to the former model for the oxidation of small unsaturated hydrocarbons, benzene, and toluene described in Parts I and II. The whole mechanism involved 175 species in 1134 reactions. The main reaction pathways of consumption of cyclopentene and of formation of benzene and toluene are presented and discussed from flow rate analyses. (author)

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

2008-01-15

240

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

241

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

242

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

243

Diphosphines with expandable bite angles: highly active ethylene dimerisation catalysts based on upper rim, distally diphosphinated calix[4]arenes.  

PubMed

The binding properties of two large diphosphines, cone-5,17-dibromo-11,23-bis(diphenylphosphino)-25,26,27,28-tetrapropoxycalix[4]arene (1) and cone-5,17-bis(diphenylphosphino)-25,26,27,28-tetrapropoxycalix[4]arene (2) toward Ni(II) centres have been investigated. Whatever the starting complex, NiBr2 or [NiCp]BF4, quantitative formation of a chelate complex was observed, illustrating the preorganisation of the ligands. An X-ray structure determination was carried out for [NiCp1]BF4 which revealed that the nickel atom is positioned to one side of the calixarene axis, the PNiP plane being roughly parallel to the calixarene reference plane. The molecule has C(1) symmetry in the solid state, a feature which is also observed in solution at low temperature. As shown by variable-temperature 1H and 31P NMR studies, the complex undergoes two distinct motions: 1) a fan-like swinging of the coordination plane which displaces the metal from one side of the calixarene axis to the other, a motion during which the PNiP angle is likely to undergo a significant enlargement; 2) a rapid oscillation of each PPh2 unit about the corresponding Ni--P bond. In the latter dynamics the two endo-oriented PPh rings alternately occupy the calixarene entry. The two flexible ligands were assessed in ethylene oligomerisation. Activation with methylaluminoxane of the paramagnetic complexes [NiBr2.(1 or 2)] afforded highly active ethylene dimerisation catalysts, with turnover frequencies up to 10(6) (mol C2H4) (mol Ni)(-1) h(-1). The selective formation of 1-butene can be rationally controlled by using low catalyst concentrations. PMID:15472914

Lejeune, Manuel; Smeril, David; Jeunesse, Catherine; Matt, Dominique; Peruch, Frdric; Lutz, Pierre J; Ricard, Louis

2004-10-25

244

Infrared multiphoton decomposition of cis-2-pentene and 3-methyl-cis-2-pentene  

SciTech Connect

The infrared multiphoton (IRMP) decomposition of cis-2-pentene and 3-methyl-cis-2-pentene has been studied in order to compare the fragmentation pattern of the photoexcited molecules with that observed in the vacuum ultraviolet photolysis. The decompositions were studied at pressures from 0.2 to 5 Torr, using a pulsed CO/sub 2/ laser weakly focused to five fluences from about 5 to 20 J/cm/sup 2/ in the focal region. The IRMP decomposition of both molecules can be explained on the basis of a primary dissociation of a ..beta..C-C bond, followed by secondary fragmentation of the allylic moiety and the usual stabilizing processes and radical-radical reactions. The fragmentation patterns are generally similar to those observed in the vacuum UV photolysis, and the present results simply show the possibility that the ground state is involved in the vacuum UV photolysis; the behavior of the latter system itself lends support to this. Differences between the two systems can be explained by the higher initial energy of the molecules excited in the vacuum UVC. Some isomerization was also observed, mostly arising from radical-radical reactions. The formation of 1-pentene, however, indicates that the sigmatropic 1,3 hydrogen atom transfer can take place via the vibrationally excited ground state of cis-2-pentene. Conversely, 2-methyl-1-butene is not observed; its formation requires an internal methylene shift, and its occurrence in the vacuum UV photolysis suggests its direct formation from an electronically excited state.

Back, R.A.; Collin, G.J.

1986-10-23

245

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

246

Understanding conjugation and hyperconjugation from electronic delocalization measures.  

PubMed

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

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

2011-11-17

247

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

PubMed

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

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

2012-04-19

248

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

249

PANs measurements on board theNOAA P-3 during TexAQS-II  

NASA Astrophysics Data System (ADS)

Measurements of peroxycarboxylic nitric anhydrides (PANs, i.e. PAN, PPN, PiBN, APAN, MPAN, and MoPAN) were made using the NCAR PAN-CIGARette chemical ionization mass spectrometer on board the NOAA P-3 aircraft during the 2006 Texas Air Quality Study II (TexAQS-II). In this poster, we present the PANs measurements made during the flight on September 27th as a case study. Two separate plumes from Downtown Houston and the Houston Ship Channel were transported in parallel to the north on that day. The flight track crossed these plumes 8 times at increasing distances downwind, and according to the CO distribution, dilution with surrounding air masses was very slow. These conditions make this very nice case for a pollutant transport and chemistry study. The PAN/PPN ratio increased about 18% as the air mass moved away from the pollution source to the furthest leg which is about 130 km north of downtown Houston. As the photolysis rates for PAN and PPN are similar to each other and the thermal decomposition of PAN is faster than PPN, this ratio change is most likely owing to the difference in the chemistry of the source hydrocarbons for these two PAN species, and indicates a faster depletion of PPN precursors (mainly propanal and 1-butene) as the air masses get older. Also, the relative production of ozone and PANs for the Houston city plume and the ship channel plume are analyzed and compared for this flight, demonstrating the difference in the photochemical processes for urban pollution vs. petroleum industry emissions.

Zheng, W.; Flocke, F. M.; Ryerson, T. B.; Trainer, M. K.; Atlas, E. L.; Schauffler, S.; Donnelly, S.; Holloway, J. S.

2007-12-01

250

SmoXYB1C1Z of Mycobacterium sp. strain NBB4: a soluble methane monooxygenase (sMMO)-like enzyme, active on C2 to C4 alkanes and alkenes.  

PubMed

Monooxygenase (MO) enzymes initiate the aerobic oxidation of alkanes and alkenes in bacteria. A cluster of MO genes (smoXYB1C1Z) of thus-far-unknown function was found previously in the genomes of two Mycobacterium strains (NBB3 and NBB4) which grow on hydrocarbons. The predicted Smo enzymes have only moderate amino acid identity (30 to 60%) to their closest homologs, the soluble methane and butane MOs (sMMO and sBMO), and the smo gene cluster has a different organization from those of sMMO and sBMO. The smoXYB1C1Z genes of NBB4 were cloned into pMycoFos to make pSmo, which was transformed into Mycobacterium smegmatis mc(2)-155. Cells of mc(2)-155(pSmo) metabolized C2 to C4 alkanes, alkenes, and chlorinated hydrocarbons. The activities of mc(2)-155(pSmo) cells were 0.94, 0.57, 0.12, and 0.04 nmol/min/mg of protein with ethene, ethane, propane, and butane as substrates, respectively. The mc(2)-155(pSmo) cells made epoxides from ethene, propene, and 1-butene, confirming that Smo was an oxygenase. Epoxides were not produced from larger alkenes (1-octene and styrene). Vinyl chloride and 1,2-dichloroethane were biodegraded by cells expressing Smo, with production of inorganic chloride. This study shows that Smo is a functional oxygenase which is active against small hydrocarbons. M. smegmatis mc(2)-155(pSmo) provides a new model for studying sMMO-like monooxygenases. PMID:25015887

Martin, Kiri E; Ozsvar, Jazmin; Coleman, Nicholas V

2014-09-01

251

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

252

Experimental and modeling study of the thermal decomposition of methyl decanoate  

PubMed Central

The experimental study of the thermal decomposition of methyl decanoate was performed in a jet-stirred reactor at temperatures ranging from 773 to 1123 K, at residence times between 1 and 4 s, at a pressure of 800 Torr (106.6 kPa) and at high dilution in helium (fuel inlet mole fraction of 0.0218). Species leaving the reactor were analyzed by gas chromatography. Main reaction products were hydrogen, carbon oxides, small hydrocarbons from C1 to C3, large 1-olefins from 1-butene to 1-nonene, and unsaturated esters with one double bond at the end of the alkyl chain from methyl-2-propenoate to methyl-8-nonenoate. At the highest temperatures, the formation of polyunsaturated species was observed: 1,3-butadiene, 1,3-cyclopentadiene, benzene, toluene, indene, and naphthalene. These results were compared with previous ones about the pyrolysis of n-dodecane, an n-alkane of similar size. The reactivity of both molecules was found to be very close. The alkane produces more olefins while the ester yields unsaturated oxygenated compounds. A detailed kinetic model for the thermal decomposition of methyl decanoate has been generated using the version of software EXGAS which was updated to take into account the specific chemistry involved in the oxidation of methyl esters. This model contains 324 species and 3231 reactions. It provided a very good prediction of the experimental data obtained in jet-stirred reactor. The formation of the major products was analyzed. The kinetic analysis showed that the retro-ene reactions of intermediate unsaturated methyl esters are of importance in low reactivity systems. PMID:23710078

Herbinet, Olivier; Glaude, Pierre-Alexandre; Warth, Valerie; Battin-Leclerc, Frederique

2013-01-01

253

Chemical dynamics in time and energy space  

SciTech Connect

The development of a versatile picosecond ultraviolet/vacuum ultraviolet temporal spectrometer and its potential use for measuring internal energy redistribution in isolated molecules are described in detail. A detailed description of the double-pass Nd:YAG amplifier and the dye amplifiers is given with the pulse energies achieved in the visible, ultraviolet, and vacuum ultraviolet. The amplified visible pulses are shown to be of sub-picosecond duration and near transform limited. The instrument`s temporal response ({le}10 ps) is derived from an instrument limited measurement of the dissociation lifetime of methyl iodide at 266 nm. The methyl iodide experiment is used to discuss the various sources of noise and background signals that are intrinsic to this type of experiment. Non-time-resolved experiments measuring the branching ratio and kinetic energy distributions of products from the 193 nm photodissociation of cyclopentadiene and thiophene are presented. These studies were done using the molecular beam Photofragment Translational Spectroscopy (PTS) technique. The results from the cyclopentadiene experiment confirm that H atom elimination to yield the cyclopentadienyl radical is the dominant dissociation channel. A barrier of {ge}5 kcal/mol can be understood in terms of the delocalization of the radical electron of the cyclopentadienyl fragment. A concerted elimination yielding cyclopropene and acetylene was also observed and is proposed to occur via a bicyclo-[2.1.0]pent-2-ene intermediate. Two other channels, yielding acetylene plus the CH{sub 2}CHCH triplet carbene, and CH{sub 2} plus 1-buten-3-yne, are postulated to occur via ring opening. The implications of the experimental results for bulk thermal oxidation and pyrolysis models are discussed. The thiophene experiment shows six competing dissociation channels. The postulated intermediates for the various thiophene dissociation channels include bicyclo, ring opened, and possibly ring contracted forms.

Myers, J.D.

1993-04-01

254

Pressure Effects on Product Channels of the Allyl Radical Reactions; C3H5+C3H5 and C3H5+CH3  

NASA Astrophysics Data System (ADS)

Relatively large hydrocarbon molecules (C4, C6 and larger) have been detected in several planetary environments. The mechanism for the formation of such large molecular species and detailed mechanism for their potential destruction are not well understood and are of considerable current interest. Previously we have studied the kinetics and product channels of small unsaturated hydrocarbon radical (C2 and C3s) reactions relevant to planetary atmospheric modeling. Reactions of C2 radicals (such as vinyl, H2CCH and ethynyl C2H) and C3 radicals (such as propargyl, HCCCH2) can affect the abundances of a large number of stable observable C3, C4, C5, C6 and larger molecules, including linear, aromatic and even poly aromatic molecules. Pressure-dependent product yields have been determined experimentally for the self- and cross-radical reactions performed at 298 K and at pressures between ~4 Torr (0.5 kPa) and 760 Torr (101 kPa). Final reaction products were quantitatively determined using a gas chromatograph with mass spectrometry/flame ionization detection (GC/MS/FID). In some cases complementary computational studies extended the pressure and temperature range of the experiments and provided valuable information on the complex reaction mechanisms. Theses studies provide a systematic framework so that important energetic and structural parameters for radical-radical reactions can be assessed. Here we report recent results for the allyl radical reactions H2CCCH3+ H2CCCH3 and H2CCCH3+CH3. For the allyl radical self-reaction, at high pressures the "head -to-head", combination channel forming 1,5-hexadiene is dominant with a combination/disproportionation = 1,5-hexadiene/propyne ratio of about 24 at 500 Torr (67 kPa, T=298K). At low pressures the ratio is substantially reduced to about 1.2 (at 0.3 kPa) and other major products are observed including allene, propene, 1-butene and propyne.

Halpern, J. B.; N'Doumi, M.; Fahr, A.

2011-12-01

255

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

SciTech Connect

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

Tomczak, D.C.

1993-01-01

256

Coupling reactions of trifluoroethyl iodide on GaAs(100)  

NASA Astrophysics Data System (ADS)

We report on the reactions of 2-iodo-1,1,1-trifluoroethane (CF3CH2I) on gallium-rich GaAs(100)-(41), studied using the techniques of temperature programmed desorption and x-ray photoelectron spectroscopy. The study is to provide evidence for the formation of a higher fluorinated alkene, 1,1,4,4,4-pentafluoro-1-butene (CF2=CHCH2CF3) and alkane, 1,1,1,4,4,4-hexafluorobutane (CF3CH2CH2CF3) from the coupling reactions of covalently bonded surface alkyl (CF3CH2) moieties. CF3CH2I adsorbs nondissociatively at 150 K. Thermal dissociation of this weakly chemisorbed state occurs below room temperature to form adsorbed CF3CH2 and I species. The surface CF3CH2 species undergoes ?-fluoride elimination to form gaseous CF2=CH2 and this represents the major pathway for the removal of CF3CH2 species from the surface. In competition with the ?-fluoride elimination process the adsorbed CF3CH2 species also undergoes, recombination with surface iodine atoms to form recombinative molecular CF3CH2I, olefin insertion reaction with CF2=CH2 to form gaseous CF2=CHCH2CF3, and last self-coupling reaction to form CF3CH2CH2CF3. The adsorbed surface iodine atoms, formed by the dissociation of the molecularly chemisorbed CF3CH2I, and fluorine atoms formed during the ?-fluoride elimination reaction, both form etch products (GaI, GaF, AsI, AsF, and As2) by their reactions with the surface layer Ga atoms, subsurface As atoms, and GaAs substrate. In this article we discuss the mechanisms by which these products form from the adsorbed CF3CH2 and I species, and the role that the GaAs surface plays in the proposed reaction pathways. We compare the reactivity of the GaAs surface with transition metals in its ability to facilitate dehydrogenation and coupling reactions in adsorbed alkyl species. .

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

2004-07-01

257

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(16.40.4) exp(42410 800 [K]/T) s(-1); k(C(4)H(9)OH ? CH(3)CH(2) + CH(2)CH(2)OH) = 10(16.40.4) exp(-41150 800 [K]/T) s(-1); k(C(4)H(9)OH ? CH(3)CH(2)CH(2) + CH(2)OH) = 10(16.40.4) 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(14.00.4) 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

258

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

PubMed

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

Makio, Haruyuki; Fujita, Terunori

2009-10-20

259

The influence of temperature and aerosol acidity on biogenic secondary organic aerosol tracers: Observations at a rural site in the central Pearl River Delta region, South China  

NASA Astrophysics Data System (ADS)

At a rural site in the central Pearl River Delta (PRD) region in south China, fine particle (PM 2.5) samples were collected during fall-winter 2007 to measure biogenic secondary organic aerosol (SOA) tracers, including isoprene SOA tracers (3-methyl-2,3,4-trihydroxy-1-butene, 2-methylglyceric acid, 2-methylthreitol and 2-methylerythritol), ?-pinene SOA tracers ( cis-pinonic acid, pinic acid, 3-methyl-1,2,3-butanetricarboxylic acid, 3-hydroxyglutaric acid and 3-hydroxy-4,4-dimethylglutaric acid) and a sesquiterpene SOA tracer (?-caryophyllinic acid). The isoprene-, ?-pinene- and sesquiterpene-SOA tracers averaged 30.8 15.9, 6.61 4.39, and 0.54 0.56 ng m -3, respectively; and 2-methyltetrols (sum of 2-methylthreitol and 2-methylerythritol, 27.6 15.1 ng m -3) and cis-pinonic acid (3.60 3.76 ng m -3) were the dominant isoprene- and ?-pinene-SOA tracers, respectively. 2-Methyltetrols exhibited significantly positive correlations ( p < 0.05) with ambient temperature, probably resulting from the enhanced isoprene emission strength and tracer formation rate under higher temperature. The significantly positive correlation ( p < 0.05) between 2-methyltetrols and the estimated aerosol acidity with a slope of 59.4 13.4 ng m -3 per ?mol [H +] m -3 reflected the enhancement of isoprene SOA formation by aerosol acidity, and acid-catalyzed heterogeneous reaction was probably the major formation pathway for 2-methyltetrols in the PRD region. 2-Methylglyceric acid showed poor correlations with both temperature and aerosol acidity. The ?-pinene SOA tracers showed poor correlations with temperature, probably due to the counteraction between temperature effects on the precursor emission/tracer formation and gas/particle partitioning. Among the ?-pinene SOA tracers, only cis-pinonic acid and pinic acid exhibited significant correlations with aerosol acidity with slopes of -11.7 3.7 and -2.2 0.8 ng m -3 per ?mol [H +] m -3, respectively. The negative correlations observed for ?-pinene SOA tracers might result from their transfer from particle to gas phase with the increase of aerosol acidity. The ratio of cis-pinonic acid plus pinic acid to 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) ranged from 0.28 to 28.9 with a mean of 7.19, indicating the relatively fresh ?-pinene SOA tracers during our campaign.

Ding, Xiang; Wang, Xin-Ming; Zheng, Mei

2011-02-01

260

NanoLC/ESI+ HRMS3 quantitation of DNA adducts induced by 1,3-butadiene.  

PubMed

Human exposure to 1,3-butadiene (BD) present in automobile exhaust, cigarette smoke, and forest fires is of great concern because of its potent carcinogenicity. The adverse health effects of BD are mediated by its epoxide metabolites such as 3,4-epoxy-1-butene (EB), which covalently modify genomic DNA to form promutagenic nucleobase adducts. Because of their direct role in cancer, BD-DNA adducts can be used as mechanism-based biomarkers of BD exposure. In the present work, a mass spectrometry-based methodology was developed for accurate, sensitive, and precise quantification of EB-induced N-7-(1-hydroxy-3-buten-2-yl) guanine (EB-GII) DNA adducts in vivo. In our approach, EB-GII adducts are selectively released from DNA backbone by neutral thermal hydrolysis, followed by ultrafiltration, offline HPLC purification, and isotope dilution nanoLC/ESI(+)-HRMS(3) analysis on an Orbitrap Velos mass spectrometer. Following method validation, EB-GII lesions were quantified in human fibrosarcoma (HT1080) cells treated with micromolar concentrations of EB and in liver tissues of rats exposed to sub-ppm concentrations of BD (0.5-1.5ppm). EB-GII concentrations increased linearly from 1.15??0.23 to 10.11??0.45 adducts per 10(6) nucleotides in HT1080 cells treated with 0.5-10?M DEB. EB-GII concentrations in DNA of laboratory rats exposed to 0.5, 1.0, and 1.5ppm BD were 0.17??0.05, 0.33??0.08, and 0.50??0.04 adducts per 10(6) nucleotides, respectively. We also used the new method to determine the in vivo half-life of EB-GII adducts in rat liver DNA (2.20??0.12 d) and to detect EB-GII in human blood DNA. To our knowledge, this is the first application of nanoLC/ESI(+)-HRMS(3) Orbitrap methodology to quantitative analysis of DNA adducts in vivo. PMID:24867429

Sangaraju, Dewakar; Villalta, Peter W; Wickramaratne, Susith; Swenberg, James; Tretyakova, Natalia

2014-07-01

261

Quantitation of DNA Adducts Induced by 1,3-Butadiene  

NASA Astrophysics Data System (ADS)

Human exposure to 1,3-butadiene (BD) present in automobile exhaust, cigarette smoke, and forest fires is of great concern because of its potent carcinogenicity. The adverse health effects of BD are mediated by its epoxide metabolites such as 3,4-epoxy-1-butene (EB), which covalently modify genomic DNA to form promutagenic nucleobase adducts. Because of their direct role in cancer, BD-DNA adducts can be used as mechanism-based biomarkers of BD exposure. In the present work, a mass spectrometry-based methodology was developed for accurate, sensitive, and precise quantification of EB-induced N-7-(1-hydroxy-3-buten-2-yl) guanine (EB-GII) DNA adducts in vivo. In our approach, EB-GII adducts are selectively released from DNA backbone by neutral thermal hydrolysis, followed by ultrafiltration, offline HPLC purification, and isotope dilution nanoLC/ESI+-HRMS3 analysis on an Orbitrap Velos mass spectrometer. Following method validation, EB-GII lesions were quantified in human fibrosarcoma (HT1080) cells treated with micromolar concentrations of EB and in liver tissues of rats exposed to sub-ppm concentrations of BD (0.5-1.5 ppm). EB-GII concentrations increased linearly from 1.15 0.23 to 10.11 0.45 adducts per 106 nucleotides in HT1080 cells treated with 0.5-10 ?M DEB. EB-GII concentrations in DNA of laboratory rats exposed to 0.5, 1.0, and 1.5 ppm BD were 0.17 0.05, 0.33 0.08, and 0.50 0.04 adducts per 106 nucleotides, respectively. We also used the new method to determine the in vivo half-life of EB-GII adducts in rat liver DNA (2.20 0.12 d) and to detect EB-GII in human blood DNA. To our knowledge, this is the first application of nanoLC/ESI+-HRMS3 Orbitrap methodology to quantitative analysis of DNA adducts in vivo.

Sangaraju, Dewakar; Villalta, Peter W.; Wickramaratne, Susith; Swenberg, James; Tretyakova, Natalia

2014-07-01

262

A Unique Equation to Estimate Flash Points of Selected Pure Liquids Application to the Correction of Probably Erroneous Flash Point Values  

NASA Astrophysics Data System (ADS)

A simple empirical equation is presented for the estimation of closed-cup flash points for pure organic liquids. Data needed for the estimation of a flash point (FP) are the normal boiling point (Teb), the standard enthalpy of vaporization at 298.15 K [?vapH(298.15 K)] of the compound, and the number of carbon atoms (n) in the molecule. The bounds for this equation are: -100?FP(C)?+200; 250?Teb(K)?650; 20??vap H(298.15 K)/(kJ mol-1)?110; 1?n?21. Compared to other methods (empirical equations, structural group contribution methods, and neural network quantitative structure-property relationships), this simple equation is shown to predict accurately the flash points for a variety of compounds, whatever their chemical groups (monofunctional compounds and polyfunctional compounds) and whatever their structure (linear, branched, cyclic). The same equation is shown to be valid for hydrocarbons, organic nitrogen compounds, organic oxygen compounds, organic sulfur compounds, organic halogen compounds, and organic silicone compounds. It seems that the flash points of organic deuterium compounds, organic tin compounds, organic nickel compounds, organic phosphorus compounds, organic boron compounds, and organic germanium compounds can also be predicted accurately by this equation. A mean absolute deviation of about 3 C, a standard deviation of about 2 C, and a maximum absolute deviation of 10 C are obtained when predictions are compared to experimental data for more than 600 compounds. For all these compounds, the absolute deviation is equal or lower than the reproductibility expected at a 95% confidence level for closed-cup flash point measurement. This estimation technique has its limitations concerning the polyhalogenated compounds for which the equation should be used with caution. The mean absolute deviation and maximum absolute deviation observed and the fact that the equation provides unbiaised predictions lead to the conclusion that several flash points have been reported erroneously, whatever the reason, in one or several reference compilations. In the following lists, the currently accepted flash points for bold compounds err, or probably err, on the hazardous side by at least 10 C and for the nonbolded compounds, the currently accepted flash points err, or probably err, on the nonhazardous side by at least 10 C: bicyclohexyl, sec-butylamine, tert-butylamine, 2-cyclohexen-1-one, ethanethiol, 1,3-cyclohexadiene, 1,4-pentadiene, methyl formate, acetonitrile, cinnamaldehyde, 1-pentanol, diethylene glycol, diethyl fumarate, diethyl phthalate, trimethylamine, dimethylamine, 1,6-hexanediol, propylamine, methanethiol, ethylamine, bromoethane, 1-bromopropane, tert-butylbenzene, 1-chloro-2-methylpropane, diacetone alcohol, diethanolamine, 2-ethylbutanal, and formic acid. For some other compounds, no other data than the currently accepted flash points are available. Therefore, it cannot be assessed that these flash point data are erroneous but it can be stated that they are probably erroneous. At least, they need experimental re-examination. They are probably erroneous by at least 15 C: 1,3-cyclopentadiene, di-tert-butyl sulfide, dimethyl ether, dipropyl ether, 4-heptanone, bis(2-chloroethyl)ether, 1-decanol, 1-phenyl-1-butanone, furan, ethylcyclopentane, 1-heptanethiol, 2,5-hexanediol, 3-hexanone, hexanoic acid methyl ester, 4-methyl-1,3-pentadiene, propanoyl chloride, tetramethylsilane, thiacyclopentane, 1-chloro-2-methyl-1-propene, trans-1,3-pentadiene, 2,3-dimethylheptane, triethylenetetramine, methylal, N-ethylisopropylamine, 3-methyl-2-pentene, and 2,3-dimethyl-1-butene.

Catoire, Laurent; Naudet, Valrie

2004-12-01

263

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

264

Synthesis and reactivity of a potential carcinogenic metabolite of tamoxifen: 3,4-dihydroxytamoxifen-o-quinone.  

PubMed

Although tamoxifen is approved for the treatment of hormone-dependent breast cancer as well as for the prevention of breast cancer in high-risk women, several studies in animal models have shown that tamoxifen is heptocarcinogenic, and in humans, tamoxifen has been associated with an increased risk of endometrial cancer. One potential mechanism of tamoxifen carcinogenesis could involve metabolism of tamoxifen to 3,4-dihydroxytamoxifen followed by oxidation to a highly reactive o-quinone which has the potential to alkylate and/or oxidize cellular macromolecules in vivo. In the study presented here, we synthesized the 3,4-dihydroxytamoxifen, prepared its o-quinone chemically and enzymatically, and studied the reactivity of the o-quinone with GSH and deoxynucleosides. The E (trans) and Z (cis) isomers of 3,4-dihydroxytamoxifen were synthesized using a concise synthetic pathway (four steps). This approach is based on the McMurry reaction between the key 4-(2-chloroethoxy)-3,4-methylenedioxybenzophenone and propiophenone, followed by selective removal of the methylenedioxy ring of (E, Z)-1-[4-[2-(N,N-dimethylamino)ethoxy]phenyl]-1-(3, 4-methylenedioxyphenyl)-2-phenyl-1-butene with BCl(3). Oxidation of 3,4-dihydroxytamoxifen by activated silver oxide or tyrosinase gave 3,4-dihydroxytamoxifen-o-quinone as a mixture of E and Z isomers. The resulting o-quinone has a half-life of approximately 80 min under physiological conditions. Reaction of the o-quinone with GSH gave two di-GSH conjugates and three mono GSH conjugates. Incubation of 3,4-dihydroxytamoxifen with GSH in the presence of microsomal P450 gave the same GSH conjugates which were also detected in incubations with human breast cancer cells (MCF-7). Reaction of 3, 4-dihydroxytamoxifen-o-quinone with deoxynucleosides gave only thymidine and deoxyguanosine adducts; neither deoxyadenosine nor deoxycytosine adducts were detected. Preliminary studies conducted with human breast cancer cell lines showed that 3, 4-dihydroxytamoxifen exhibited cytotoxic potency similar to that of 4-hydroxytamoxifen and tamoxifen in an estrogen receptor negative (ER(-)) cell line (MDA-MB-231); however, in the ER(+) cell line (MCF-7), the catechol metabolite was about half as toxic as the other two compounds. Finally, in the presence of microsomes and GSH, 4-hydroxytamoxifen gave predominantly quinone methide GSH conjugates as reported in the previous paper in this issue [Fan, P. W., et al. (2000) Chem. Res. Toxicol. 13, XX-XX]. However, in the presence of tyrosinase and GSH, 4-hydroxytamoxifen was primarily converted to o-quinone GSH conjugates. These results suggest that the catechol metabolite of tamoxifen has the potential to cause cytotoxicity in vivo through formation of 3,4-dihydroxytamoxifen-o-quinone. PMID:10649967

Zhang, F; Fan, P W; Liu, X; Shen, L; van Breeman, R B; Bolton, J L

2000-01-01