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1

Atmospheric chemistry of alkanes  

Microsoft Academic Search

The reactions of the alkanes under atmospheric conditions and in the presence of oxides of nitrogen are reviewed and evaluated. Particular emphasis is placed upon their subsequent reactions after the initial OH radical reaction under conditions where the alkyl peroxy radicals produced react predominantly with NO, rather than with HO2 and\\/or RO2 radicals. Methods are discussed for estimating the overall

William P. L. Carter; Roger Atkinson

1985-01-01

2

Alkane metathesis by tandem alkane-dehydrogenation-olefin-metathesis catalysis and related chemistry.  

PubMed

Methods for the conversion of both renewable and non-petroleum fossil carbon sources to transportation fuels that are both efficient and economically viable could greatly enhance global security and prosperity. Currently, the major route to convert natural gas and coal to liquids is Fischer-Tropsch catalysis, which is potentially applicable to any source of synthesis gas including biomass and nonconventional fossil carbon sources. The major desired products of Fischer-Tropsch catalysis are n-alkanes that contain 9-19 carbons; they comprise a clean-burning and high combustion quality diesel, jet, and marine fuel. However, Fischer-Tropsch catalysis also results in significant yields of the much less valuable C(3) to C(8)n-alkanes; these are also present in large quantities in oil and gas reserves (natural gas liquids) and can be produced from the direct reduction of carbohydrates. Therefore, methods that could disproportionate medium-weight (C(3)-C(8)) n-alkanes into heavy and light n-alkanes offer great potential value as global demand for fuel increases and petroleum reserves decrease. This Account describes systems that we have developed for alkane metathesis based on the tandem operation of catalysts for alkane dehydrogenation and olefin metathesis. As dehydrogenation catalysts, we used pincer-ligated iridium complexes, and we initially investigated Schrock-type Mo or W alkylidene complexes as olefin metathesis catalysts. The interoperability of the catalysts typically represents a major challenge in tandem catalysis. In our systems, the rate of alkane dehydrogenation generally limits the overall reaction rate, whereas the lifetime of the alkylidene complexes at the relatively high temperatures required to obtain practical dehydrogenation rates (ca. 125 -200 °C) limits the total turnover numbers. Accordingly, we have focused on the development and use of more active dehydrogenation catalysts and more stable olefin-metathesis catalysts. We have used thermally stable solid metal oxides as the olefin-metathesis catalysts. Both the pincer complexes and the alkylidene complexes have been supported on alumina via adsorption through basic para-substituents. This process does not significantly affect catalyst activity, and in some cases it increases both the catalyst lifetime and the compatibility of the co-catalysts. These molecular catalysts are the first systems that effect alkane metathesis with molecular-weight selectivity, particularly for the conversion of C(n)n-alkanes to C(2n-2)n-alkanes plus ethane. This molecular-weight selectivity offers a critical advantage over the few previously reported alkane metathesis systems. We have studied the factors that determine molecular-weight selectivity in depth, including the isomerization of the olefinic intermediates and the regioselectivity of the pincer-iridium catalyst for dehydrogenation at the terminal position of the n-alkane. Our continuing work centers on the development of co-catalysts with improved interoperability, particularly olefin-metathesis catalysts that are more robust at high temperature and dehydrogenation catalysts that are more active at low temperature. We are also designing dehydrogenation catalysts based on metals other than iridium. Our ongoing mechanistic studies are focused on the apparently complex combination of factors that determine molecular-weight selectivity. PMID:22584036

Haibach, Michael C; Kundu, Sabuj; Brookhart, Maurice; Goldman, Alan S

2012-06-19

3

OXIDATION OF ALKANES WITH AIR USING IRON AND MANGANESE CATALYSTS. AN OVERALL GREEN CHEMISTRY APPROACH INCLUDING THE USE OF ALTERNATIVE SOLVENT SYSTEMS GENERATED BY PARIS II  

EPA Science Inventory

The selective oxidation of alkanes is an industrially important process that is often plagued by low conversions and the formation of unwanted by-products. Research being conducted at the USEPA, implements a Green chemistry approach which is utilized to improve these difficult o...

4

Products of Chemistry: Alkanes: Abundant, Pervasive, Important, and Essential.  

ERIC Educational Resources Information Center

Discusses the history and commercialization of alkanes. Examines the nomenclature and uses of alkanes. Studies polymerization and several types of polyethylenes: low-density, high-density, low-molecular-weight, cross-linked, linear low-density, and ultrahigh-molecular-weight. Includes a glossary of hydrocarbon terms. (MVL)

Seymour, Raymond B.

1989-01-01

5

The chemistry of energy conversion and storage.  

PubMed

What's in store: The sustainable development of our society requires the conversion and storage of renewable energy, and these should be scaled up to serve the global primary energy consumption. This special issue on "The Chemistry of Energy Conversion and Storage", assembled by guest editor Dangsheng Su, contains papers dealing with these aspects, and highlights important developments in the chemistry of energy conversion and storage during the last two years. PMID:24832535

Su, Dang Sheng

2014-05-01

6

Silica-Supported Tantalum Clusters: Catalyst for Alkane Conversion  

SciTech Connect

Silica-supported tantalum clusters (on average, approximately tritantalum) were formed by the treatment, in either H{sub 2} or ethane, of adsorbed Ta(CH{sub 2}Ph){sub 5}; the supported catalyst is active for ethane conversion to methane and propane at 523 K, with the used catalyst containing clusters of the same average nuclearity as the precursor.

Nemana ,S.; Gates, B.

2006-01-01

7

Experimental solubility data of various n-alkane waxes: effects of alkane chain length, alkane odd versus even carbon number structures, and solvent chemistry on solubility  

Microsoft Academic Search

Solubility data were measured for eight different n-alkanes ranging from tetracosane to tetratetracontane (C24H50–C44H90). Included are: (1) solubility data in toluene for all the n-alkanes studied and (2) solubility data of n-hexatriacontane (C36H74) in several solvent and solvent mixture systems. Illustrated in the data are the effects on solubility of alkane chain length, alkane odd versus even carbon number structures,

David W. Jennings; Klaus Weispfennig

2005-01-01

8

Catalytic conversion of light alkanes phase II. Topical report, January 1990--January 1993  

SciTech Connect

The Topical Report on Phase II of the project entitled, Catalytic Conversion of Light Alkanes reviews work done between January 1, 1990 and September 30, 1992 on the Cooperative Agreement. The mission of this work is to devise a new catalyst which can be used in a simple economic process to convert the light alkanes in natural gas to oxygenate products which can either be used as clean-burning, high octane liquid fuels, as fuel components or as precursors to liquid hydrocarbon transportation fuel. This Topical Report documents our efforts to design, prepare, characterize and test novel catalysts for the mild selective reaction of light hydrocarbons with air or oxygen to produce alcohols directly. These catalysts are designed to form active metal oxo (MO) species and to be uniquely active for the homolytic cleavage of the carbon-hydrogen bonds in light alkanes producing intermediates which can form alcohols. Research on the Cooperative Agreement is divided into three Phases relating to three molecular environments for the active catalytic species that we are trying to generate. In this report we present our work on catalysts which have oxidation-active metals in polyoxoanions (PHASE II).

NONE

1998-12-31

9

Catalytic conversion of light alkanes -- research and proof-of-concept stages  

SciTech Connect

Objective is to find new catalysts for direct reaction of methane, ethane, propane, butanes with O{sub 2} to form alcohols, and to develop practical processes for direct oxidative conversion of natural gas and its C{sub 1}-C{sub 4} components to produce alcohol-rich liquid oxygenates for use as alternative transportation fuels/environmentally superior reformulated gasolines. The proposed mechanism for oxidation activity of cytochrome P-450 and methane monoxygenase suggested that a catalyst able to reductively bind oxygen, not between Fe(III) center and a proton, but between two Fe(III) centers, might give the desired dioxygenase activity for alkane hydroxylation. Selective oxidation of light alkanes could be done by oxidation-active metal (Fe) centers in electron-deficient prophyrin-like macrocycles, polyoxoanions, and zeolites. In the isobutane conversion to tert-butanol proof-of-concept, it was found that nitro groups on the periphery of Fe porphyrin complexes give the greatest increase in Fe(III)/(II) reduction potential. 8 figs, 6 tabs, 40 refs.

Lyons, J.E.; Hancock, A.W. II

1993-12-31

10

Atmospheric Chemistry of Selected Linear, Branched and Cyclic C10 Alkane Components of Mineral Spirits.  

National Technical Information Service (NTIS)

Ozone pollution in urban areas is the result of the reactions of volatile organic compounds, including alkanes, with oxides of nitrogen under the influence of sunlight. Alkanes are significant components of gasoline and diesel fuels and of vehicle exhaust...

R. Atkinson J. Arey S. M. Aschmann E. S. Kwok

2001-01-01

11

Catalytic conversion of light alkanes, Phase 3. Topical report, January 1990--December 1992  

SciTech Connect

The mission of this work is to devise a new catalyst which can be used in the first simple, economic process to convert the light alkanes in natural gas to an alcohol-rich oxygenated product which can either be used as an environmentally friendly, high-performance liquid fuel, or a precursor to a liquid hydrocarbon transportation fuel. The authors have entered the proof-of-concept stage for converting isobutane to tert butyl alcohol in a practical process and are preparing to enter proof-of-concept of a propane to isopropyl alcohol process in the near future. Methane and ethane are more refractory and thus more difficult to oxidize than the C{sub 3} and C{sub 4} hydrocarbons. Nonetheless, advances made in this area indicate that further research progress could achieve the goal of their direct conversion to alcohols. Progress in Phase 3 catalytic vapor phase methane and ethane oxidation over metals in regular oxidic lattices are the subject of this topical report.

NONE

1992-12-31

12

A Process for Microbial Hydrocarbon Synthesis: Overproduction of Fatty Acids in Escherichia coli and Catalytic Conversion to Alkanes  

PubMed Central

The development of renewable alternatives to diesel and jet fuels is highly desirable for the heavy transportation sector, and would offer benefits over the production and use of short-chain alcohols for personal transportation. Here, we report the development of a metabolically engineered strain of Escherichia coli that overproduces medium-chain length fatty acids via three basic modifications: elimination of ?-oxidation, overexpression of the four subunits of acetyl-CoA carboxylase, and expression of a plant acyl–acyl carrier protein (ACP) thioesterase from Umbellularia californica (BTE). The expression level of BTE was optimized by comparing fatty acid production from strains harboring BTE on plasmids with four different copy numbers. Expression of BTE from low copy number plasmids resulted in the highest fatty acid production. Up to a seven-fold increase in total fatty acid production was observed in engineered strains over a negative control strain (lacking ?-oxidation), with a composition dominated by C12 and C14 saturated and unsaturated fatty acids. Next, a strategy for producing undecane via a combination of biotechnology and heterogeneous catalysis is demonstrated. Fatty acids were extracted from a culture of an overproducing strain into an alkane phase and fed to a Pd/C plug flow reactor, where the extracted fatty acids were decarboxylated into saturated alkanes. The result is an enriched alkane stream that can be recycled for continuous extractions. Complete conversion of C12 fatty acids extracted from culture to alkanes has been demonstrated yielding a concentration of 0.44 g L?1 (culture volume) undecane.

Lennen, Rebecca M.; Braden, Drew J.; West, Ryan M.; Dumesic, James A.; Pfleger, Brian F.

2013-01-01

13

Gas-Phase Tropospheric Chemistry of Volatile Organic Compounds: 1. Alkanes and Alkenes  

Microsoft Academic Search

Literature data (through mid-1996) concerning the gas-phase reactions of alkanes and alkenes (including isoprene and monoterpenes) leading to their first generation products are reviewed and evaluated for tropospheric conditions. The recommendations of the most recent IUPAC evaluation [J. Phys. Chem. Ref. Data, 26, No. 3 (1997)] are used for the ?C3 organic compounds, unless more recent data necessitates reevaluation. The

Roger Atkinson

1997-01-01

14

An Acid-Base Chemistry Example: Conversion of Nicotine  

NASA Astrophysics Data System (ADS)

The current government interest in nicotine conversion by cigarette companies provides an example of acid-base chemistry that can be explained to students in the second semester of general chemistry. In particular, the conversion by ammonia of the +1 form of nicotine to the easier-to-assimilate free-base form illustrates the effect of pH on acid-base equilibrium. The part played by ammonia in tobacco smoke is analogous to what takes place when cocaine is "free-based".

Summerfield, John H.

1999-10-01

15

Exploratory study of coal-conversion chemistry  

NASA Astrophysics Data System (ADS)

The mechanism of cleavage of key bond types present in coals, and catalysis of conversion in CO-H2O systems are described. Catalytic carbon-carbon and carbon-oxygen bond cleavage in coal related diphenylmethane and diphenyl ether structures were measured. The homogeneous scission of carbon-oxygen bonds in diphenyl ether structure was also studied. The CO-H2O conversion level is obtained with aqueous solutions either at a starting pH above 12.6 or in neutral solutions with water soluble catalysts present. Catalysts, including the potassium or sodium salts of molybdate, chromate, manganate, and tungstate was studied and it is found that all are effective in the 3000 to 6000 ppM range. The nitrate was converted to ammonium ion and formate was detected in the product aqueous phase. It is found that catalytic quantities of sodium formate in CO/H2O at pH 7 are effective in the conversion.

1981-03-01

16

Recent progress in the manufacture of alkanesulfonates: Photosulfochlorination of single-chain length (C 12 ?C 16 ) n -alkanes using SO 2 Cl 2 at high conversion rates in pure phase and in the presence of solvent  

Microsoft Academic Search

Increasing concentration of sulfuryl chloride during the photosulfochlorination reaction under visible light shows that under\\u000a these conditions n-alkanes react at high conversion rates instead of the conversion rate of 15% reported in the literature. This photosulfochlorination\\u000a with sulfuryl chloride leads to better and more interesting results compared with those of photosulfochlorination by gas mixture.\\u000a Indeed, nearly total conversion of n-alkanes,

Naziha Assassi; Hakima Azira; Amel Tazerouti

2006-01-01

17

Catalytic conversion of light alkanes. Final report, January 1, 1990--October 31, 1994  

SciTech Connect

During the course of the first three years of the Cooperative Agreement (Phase I-III), we uncovered a family of metal perhaloporphyrin complexes which had unprecedented activity for the selective air-oxidation of fight alkanes to alcohols. The reactivity of fight hydrocarbon substrates with air or oxygen was in the order: isobutane>propane>ethane>methane, in accord with their homolytic bond dissociation energies. Isobutane was so reactive that the proof-of concept stage of a process for producing tert-butyl alcohol from isobutane was begun (Phase V). It was proposed that as more active catalytic systems were developed (Phases IV, VI), propane, then ethane and finally methane oxidations will move into this stage (Phases VII through IX). As of this writing, however, the program has been terminated during the later stages of Phases V and VI so that further work is not anticipated. We made excellent progress during 1994 in generating a class of less costly new materials which have the potential for high catalytic activity. New routes were developed for replacing costly perfluorophenyl groups in the meso-position of metalloporphyrin catalysts with far less expensive and lower molecular weight perfluoromethyl groups.

NONE

1998-12-31

18

Catalytic conversion of light alkanes -- research and proof-of-concept stages  

Microsoft Academic Search

Objective is to find new catalysts for direct reaction of methane, ethane, propane, butanes with Oâ to form alcohols, and to develop practical processes for direct oxidative conversion of natural gas and its Câ-Câ components to produce alcohol-rich liquid oxygenates for use as alternative transportation fuels\\/environmentally superior reformulated gasolines. The proposed mechanism for oxidation activity of cytochrome P-450 and methane

J. E. Lyons; A. W. II Hancock

1993-01-01

19

Catalytic conversion of light alkanes-proof-of-concept stage -- Phase 6. Final report, February 1--October 31, 1994  

SciTech Connect

During the course of the first three years of the Cooperative Agreement, the authors uncovered a family of metal perhaloporphyrin complexes which had unprecedented activity for the selective air-oxidation of light alkanes to alcohols. The reactivity of light hydrocarbon substrates with air or oxygen was in the order: isobutane > propane > ethane > methane, in accord with their homolytic bond dissociation energies. Isobutane was so reactive that the proof-of-concept stage of a process for producing tert-butyl alcohol from isobutane was begun (Phase 5). It was proposed that as more active catalytic systems were developed (Phases 4, 6), propane, then ethane and finally methane oxidations will move into this stage (Phases 7 through 9). As of this writing, however, the program has been terminated during the later stages of Phase 5 and 6 so that further work is not anticipated. 72 refs.

NONE

1994-12-31

20

Functionalization of paraffinic hydrocarbons by heterogeneous vapor-phase oxidation III. Conversion of the C sub 2 -C sub 7 alkane series  

SciTech Connect

A new promising area of research in the field of vapor-phase heterogeneous catalysis is the functionalization of paraffinic hydrocarbons. At present, the selective oxidation of {und n}-butane to maleic anhydride is the only process which is highly selective and operative on a commercial scale. The peculiar characteristics of selectivity, the basis for interest in this reaction, are principally related to the specific nature of the active phase, vanadyl pyrophosphate. This catalyst is the only active phase discovered which is truly selective: however, the activity/selectivity is strictly related to the method of preparation. The aim of this work is to investigate if it is possible to extend the utilization of a (VO){sub 2}P{sub 2}O{sub 7} catalyst highly active/selective in {und n}-butane. Propane conversion has been studied on V-P-O catalysts where low selectivities to methanol or acrylic acid were found and on Ce-Te-Mo-O oxides doped with CdX{sub 2} (X=F, C1) that give low yields of acrolein. The aims of this paper are to explore the mild oxidation of the other alkanes using the same active phase as for {und n}-butane and to obtain a better understanding of the transformation of {und n}-butane to maleic anhydride.

Centti, G.; Trifiro, F. (Department of Industrial Chemistry and Materials, Bologna (Italy))

1987-08-01

21

Atmospheric chemistry of potential emissions from fuel conversion facilities. A smog chamber study. Final report  

Microsoft Academic Search

The atmospheric chemistry of chemical species that may be emitted from fuel conversion facilities were studied in smog chambers. Of 17 compounds assessed for ozone-forming potential, 6 compounds were selected along with a control species, propylene, for testing in the presence of nitrogen oxides in four outdoor smog chambers. Selected compounds were furan, pyrole, thiophene, methanethiol, methyl sulfide, and methyl

J. E. II Sickles; L. A. Ripperton; W. C. Eaton; R. S. Wright

1978-01-01

22

ATMOSPHERIC CHEMISTRY OF POTENTIAL EMISSIONS FROM FUEL CONVERSION FACILITIES. A SMOG CHAMBER STUDY  

EPA Science Inventory

The atmospheric chemistry of chemical species that may be emitted from fuel conversion facilities were studied in smog chambers. Of 17 compounds assessed for ozone-forming potential, 6 compounds were selected along with a control species, propylene, for testing in the presence of...

23

Integration of Homogeneous and Heterogeneous Catalytic Processes for a Multi-step Conversion of Biomass: From Sucrose to Levulinic Acid, ?-Valerolactone, 1,4-Pentanediol, 2-Methyl-tetrahydrofuran, and Alkanes  

Microsoft Academic Search

The multi-step conversion of sucrose to various C5-oxygenates and alkanes was achieved by integrating various homogeneous and heterogeneous catalytic systems. We have confirmed\\u000a that the dehydration of sucrose to levulinic and formic acids is currently limited to about 30–40% in the presence of H2SO4, HCl, or Nafion NR50 in water. Performing the dehydration in the presence of a P(m-C6H4SO3Na)3 modified

Hasan Mehdi; Viktória Fábos; Róbert Tuba; Andrea Bodor; László T. Mika; István T. Horváth

2008-01-01

24

Organic Chemistry  

NSDL National Science Digital Library

R. H. Logan, an chemistry instructor at North Lake College, created this introduction to organic chemistry. The introduction covers a eight types of organic compounds, including Alkanes, Alkyl Halides, and Acyl Compounds (forthcoming); Conformational Analysis and Stereoisomerism; and Instrumental Analysis of Organic Compounds, as well an extensive lesson in general chemistry.

25

Chemistry of Secondary Organic Aerosol Formation from OH Radical-Initiated Reactions of Linear, Branched, and Cyclic Alkanes in the Presence of NOx  

Microsoft Academic Search

The effects of molecular structure on the products and mechanisms of SOA formation from OH radical-initiated reactions of linear, branched, and cyclic alkanes in the presence of NOx were investigated in a series of environmental chamber experiments. SOA mass spectra were obtained in real time and off line using a thermal desorption particle beam mass spectrometer and used to identify

Yong Bin Lim; Paul J. Ziemann

2009-01-01

26

Thermal, catalytic, regiospecific functionalization of alkanes  

PubMed

The formation of a single product from terminal functionalization of linear alkanes from a transition metal-catalyzed reaction is reported. The rhodium complex Cp*Rh(eta(4)-C(6)Me(6)) (Cp*, C(5)Me(5); Me, methyl) catalyzes the high-yield formation of linear alkylboranes from commercially available borane reagents under thermal conditions. These reactions now allow catalytic, regiospecific functionalization of alkanes under thermal conditions. The organoborane products are among the most versatile synthetic intermediates in chemistry and serve as convenient precursors to alcohols, amines, and other common classes of functionalized molecules. PMID:10720320

Chen; Schlecht; Semple; Hartwig

2000-03-17

27

Metathesis of alkanes and related reactions.  

PubMed

The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, ([triple bond]SiO)(2)TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of alumina-supported tungsten hydride, W(H)(3)/Al(2)O(3), which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis of olefins or the selective transformation of ethylene into propylene. Alkane metathesis represents a powerful tool for making progress in a variety of areas, perhaps most notably in the petroleum and petrochemical fields. Modern civilization is currently confronting a host of problems that relate to energy production and its effects on the environment, and judicious application of alkane metathesis to the processing of fuels such as crude oil and natural gas may well afford solutions to these difficulties. PMID:19856892

Basset, Jean-Marie; Copéret, Christophe; Soulivong, Daravong; Taoufik, Mostafa; Cazat, Jean Thivolle

2010-02-16

28

Quantum chemistry study on internal conversion of diphenyldibenzofulvene in solid phase.  

PubMed

We investigate the nonradiative decay process of diphenyldibenzofulvene (DPDBF) in solid phase by using the quantum chemistry methods. To carry out the nonradiative rate constant calculation, we construct a solid phase model based on the ONIOM method. The geometry of the DPDBF molecule is optimized for the ground state by DFT and the first excited state by TD-DFT, and the corresponding vibrational frequencies and normal coordinates are computed. Under displaced-distorted harmonic oscillator potential approximation, Huang-Rhys factors are obtained. Vibronic coupling constants are calculated as a function of the normal mode based on Domcke's scheme. We find that vibronic coupling constants of 12 modes with large reorganization energies are of similar order, and if this result is still valid for other modes, the internal conversion rate would be determined by high frequency modes because they have a significant nuclear factor that is related to Franck-Condon overlap intergrals. We also find that geometrical changes are suppressed due to the stacking effect, which yields small Huang-Rhys values in the solid phase. PMID:22047212

Li, Ming-Chung; Hayashi, Michitoshi; Lin, Sheng-Hsien

2011-12-22

29

Drugs in the Chemistry Laboratory: The Conversion of Acetaminophen into Phenacetin.  

ERIC Educational Resources Information Center

Describes an experiment in which acetaminophen is converted into phenacetin, that has been used at Shepherd College in an introductory chemistry course for nurses and in the organic chemistry laboratory. (BT)

Volker, Eugene J.; And Others

1979-01-01

30

Reactivity of the hydrocarbon C–C bonds as a function of the reaction conditions in the conversion of C 6 alkanes and methylcyclopentane over Rh catalysts  

Microsoft Academic Search

The conversion of 3-methylpentane (3MP), 2-methylpentane (2MP), n-hexane (nH), and methylcyclopentane (MCP) was investigated on 0.3 and 10% Rh\\/Al2O3 and 5% Rh\\/SiO2 as a function of hydrogen pressure and temperature. The catalysts were prepared by the incipient wetness method. Metal accessibility was 57, 18 and 36%, which corresponded to mean particle size of 1.5, 5 and 2.5nm, respectively. The hydrogenolytic

D Teschner; D Duprez; Z Paál

2002-01-01

31

Synthesis and coordination chemistry (with platinum(II) and molybdenum(0)) of new bis(bis(trifluoromethyl)phosphano)alkanes. Structure of a new bis(phosphano)methanide complex  

SciTech Connect

Two known and four new bis(phosphano)alkanes (CF/sub 3/)/sub 2/P(CH/sub 2/)/sub n/P(CF/sub 3/)/sub 2/, n = 1-3; ((CF/sub 3/)/sub 2/PCR(CH/sub 3/)P(CF/sub 3/)/sub 2/, R = H, CH/sub 3/; (CF/sub 3/)/sub 2/P(CF/sub 2/)/sub 2/P(CF/sub 3/)/sub 2/) have been prepared in good yield by an improved procedure. PtCl/sub 2/ and Mo(CO)/sub 4/ complexes of these highly ..pi..-acidic ligands have been prepared by standard routes. Thus, displacement of benzonitrile from (PtCl/sub 2/(PhCN)/sub 2/) affords (PtCl/sub 2/LL)(LL = (CF/sub 3/)/sub 2/P(CH/sub 2/)/sub n/P(CF/sub 3/)/sub 2/, n = 2,3; LL = (CF/sub 3/)PCR(CH/sub 3/)P(CF/sub 3/)/sub 2/, R = H, CH/sub 3/; LL = (CF/sub 3/)/sub 2/P(CF/sub 2/)/sub 2/P(P)(CF/sub 3/)/sub 2/). Similarly, piperidine is displaced from cis-(Mo(CO)/sub 4/(piperidine)/sub 2/) to give (Mo(CO)/sub 4/(LL)), (LL = (CF/sub 3/)/sub 2/P(CH/sub 2/)/sub n/P(CF/sub 3/)/sub 2/, n = 2,3; LL = (CF/sub 3/)/sub 2/P(CF/sub 2/)/sub 2/P(CF/sub 3/)/sub 2/). Self-dehydrochlorination of (PtCl/sub 2/((CF/sub 3/)/sub 2/PCH(CH/sub 3/)P(CF/sub 3/)/sub 2/)) in the solid state at 150/degrees/C gives the complex (Pt/sub 2/(..mu..-Cl)/sub 2/((CF/sub 3/)/sub 2/PC(CH/sub 3/)P(CF/sub 3/)/sub 2/)/sub 2/) (34), shown by single-crystal X-ray crystallography to contain two chelating bis(phosphano)methanide ligands. The crystal parameters of 84 are reported. 47 references, 4 figures, 8 tables.

Phillips, I.G.; Ball, R.G.; Cavell, R.G.

1988-11-02

32

Mesoscale effects in electrochemical conversion: coupling of chemistry to atomic- and nanoscale structure in iron-based electrodes.  

PubMed

The complex coupling of atomic, chemical, and electronic transformations across multiple length scales underlies the performance of electrochemical energy storage devices. Here, the coupling of chemistry with atomic- and nanoscale structure in iron conversion electrodes is resolved by combining pair distribution function (PDF) and small-angle X-ray scattering (SAXS) analysis for a series of Fe fluorides, oxyfluorides, and oxides. The data show that the anion chemistry of the initial electrode influences the abundance of atomic defects in the Fe atomic lattice. This, in turn, is linked to different atom mobilities and propensity for particle growth. Competitive nanoparticle growth in mixed anion systems contributes to a distinct nanostructure, without the interconnected metallic nanoparticles formed for single anion systems. PMID:24735418

Wiaderek, Kamila M; Borkiewicz, Olaf J; Pereira, Nathalie; Ilavsky, Jan; Amatucci, Glenn G; Chupas, Peter J; Chapman, Karena W

2014-04-30

33

Plant Cell Walls: Basics of Structure, Chemistry, Accessibility and the Influence on Conversion.  

National Technical Information Service (NTIS)

This book is focused on the pretreatment of plant biomass, a necessary step for efficient conversion of plant cell-wall materials to liquid transportation fuels and other products. Pretreatment is required because it is difficult to access, separate, and ...

B. H. Davison B. S. Donohoe J. Parks M. F. Davis

2013-01-01

34

More than a Conversation: Using Cogenerative Dialogues in the Professional Development of High School Chemistry Teachers  

ERIC Educational Resources Information Center

This paper focuses on content-based and pedagogical instructors' use of cogenerative dialogues to improve instructional practice and to evaluate program effectiveness in a professional development program for high school chemistry teachers. We share our research findings from using cogenerative dialogues as an evaluative tool for general…

Martin, Sonya N.; Scantlebury, Kathryn

2009-01-01

35

Recent Advances and Future Aspects in the Selective Isomerization of High n?Alkanes  

Microsoft Academic Search

This article provides an overview of the advances that have been marked during the last decades in the field of hydroconversion of high n?alkanes (C7 ) with particular stress on the promising ways to meet the requirements for improved quality of motor fuels and oils. Particular attention is given to a catalyst formulation for selective conversion of high n?alkanes to

Vagif M. Akhmedov

2007-01-01

36

Chemistry  

NSDL National Science Digital Library

Chemistry is the scientific study of matter and its interaction with other matter and with energy. It is the branch of natural science that deals with the composition of substances and their properties and reactions.

K-12 Outreach,

37

Interfacial chemistry of organic conversion film on AZ61 magnesium alloy surface  

NASA Astrophysics Data System (ADS)

The anodic electrochemical behavior of AZ61 magnesium alloy in sodium hydroxide medium in the absence and presence of p-nitro-benzene-azo-resorcinol (PNBAR) was studied using electrochemical techniques. In the presence of PNBAR, organic conversion film formed on the surface of magnesium alloy. The nature of chemical mechanisms, bonds, and structures at the interface of PNBAR/magnesium alloy was investigated by using energy dispersive spectrometer (EDS) analysis and Fourier transform infrared spectroscopy. An in situ electrochemical deposition was evidenced to produce a corrosion protective barrier by the formation of organic conversion film of magnesium-PNBAR complex and to enhance film adhesion by the covalent bonds of Mg sbnd O sbnd N linkage. The linear sweep voltammetry experiments and the score tests were used to investigate the adhesion and evaluate the potential of corrosion resistance of organic conversion film. The results indicated the corrosion resistance of magnesium alloy was improved, the organic conversion film showed excellent adhesion not only to the substrate but also to the outer paint coatings.

Yang, Xu; Pan, Fusheng; Zhang, Dingfei

2008-12-01

38

Towards a practical development of light-driven acceptorless alkane dehydrogenation.  

PubMed

The efficient catalytic dehydrogenation of alkanes to olefins is one of the most investigated reactions in organic synthesis. In the coming years, an increased supply of shorter-chain alkanes from natural and shale gas will offer new opportunities for inexpensive carbon feedstock through such dehydrogenation processes. Existing methods for alkane dehydrogenation using heterogeneous catalysts require harsh reaction conditions and have a lack of selectivity, whereas homogeneous catalysis methods result in significant waste generation. A strong need exists for atom-efficient alkane dehydrogenations on a useful scale. Herein, we have developed improved acceptorless catalytic systems under optimal light transmittance conditions using trans-[Rh(PMe3 )2 (CO)Cl] as the catalyst with different additives. Unprecedented catalyst turnover numbers are obtained for the dehydrogenation of cyclic and linear (from C4 ) alkanes and liquid organic hydrogen carriers. These reactions proceed with unique conversion, thereby providing a basis for practical alkane dehydrogenations. PMID:24829085

Chowdhury, Abhishek Dutta; Weding, Nico; Julis, Jennifer; Franke, Robert; Jackstell, Ralf; Beller, Matthias

2014-06-16

39

Superacid catalysis of light hydrocarbon conversion. Final report, August 26, 1993--August 26, 1996  

SciTech Connect

Motivated by the goal of finding improved catalysts for low- temperature conversion of light alkanes into fuel components or precursors of fuel components, the researchers have investigated sulfated zirconia and promoted sulfated zirconia for conversion of butane, propane, and ethane. Catalyst performance data for sulfated zirconia promoted with iron and manganese show that it is the most active noncorrosive, nonhalide catalyst known for n-butane isomerization, and it is an excellent candidate catalyst for new low- temperature n-butane isomerization processes to make isobutane, which can be converted by established technology into methyl t-butyl ether (MTBE). Various transition metals have been found to work as promoters of sulfated zirconia for n-butane isomerization. The combination of iron and manganese is the best known combination of promoters yet discovered. The iron- and manganese-promoted sulfated zirconia is also a catalyst for conversion of propane and of ethane. Ethane is converted into ethylene and butanes in the presence of the iron- and manganese-promoted sulfated zirconia; propane is also converted into butane, among other products. However, the activities of the catalyst for these reactions are orders of magnitude less than the activity for n-butane conversion, and there is no evidence that the catalyst would be of practical value for conversion of alkanes lighter than butane. The product distribution data for ethane and propane conversion provide new insights into the nature of the catalyst and its acidity. These data suggest the involvement of Olah superacid chemistry, whereby the catalyst protonates the alkane itself, giving carbonium ions (as transition states). The mechanism of protonation of the alkane may also pertain to the conversion of butane, but there is good evidence that the butane conversion also proceeds via alkene intermediates by conventional mechanisms of carbenium ion formation and rearrangement.

Gates, B.C.

1996-12-31

40

Exploratory study of coal conversion chemistry. Quarterly report No. 10, August 19-November 18, 1983  

SciTech Connect

Work has continued to focus this quarter on Subtask A.3, Derivation of an Improved Correlation Between Coal-Conversion Effectiveness and Donor-Solvent Structure. We are taking two new approaches to test the hypothesis that the critical class of reactions, which distinguishes between good donor and poor donor solvents, is bimolecular transfer of hydrogen atoms from solvent radicals to the ipso positions of substituted aromatics Ar-X, resulting in solvent-mediated hydrogenolysis. In the first approach, experiments in which real coal liquefaction mixtures were doped with specific model compounds showed that hydrogen-transfer reactions promoted by the coal do engender bond scission in the dinaphthylmethane to an extent that the half-life for cleavage at 400/sup 0/C in tetralin is decreased from 200 hours to about 4 hours. This result greatly strengthens our suggestion that the cleavage of phenyl-alkyl bonds, formerly considered to be very refractory under liquefaction conditions, may play an important role in coal liquefaction. In the second approach to testing our liquefaction mechanism hypothesis, we have constructed a simplified numerical model for liquefaction of some coal-like structures, incorporating some of the rate constants for bond cleavage measured in this work to determine whether the calculated relative bond cleavage rate with various hydroaromatic contents successfully mimics the relative model compound and coal conversion rates measured in the laboratory. Our efforts in Task B were concentrated on Subtask B.1 Development and Evaluation of CO/H/sub 2/O Catalyst Systems. The study of conversion behavior of an Illinois No. 6 coal was extended to different reaction times and lower pH's. The results reveal that the primary reaction parameter that controls coal conversion at 400/sup 0/C is the amount of CO that is allowed to enter the reaction pathway. 24 references, 8 tables.

Ross, D.S.; McMillen, D.F.; Chang, S.J.; Hum, G.P.; Green, T.K.; Malhotra, R.

1983-12-01

41

Catalytic oxidation of light alkanes in presence of a base  

Microsoft Academic Search

The presence of a base in the reaction mixture in a metal-ligand catalyzed partial oxidation of alkanes results in sustained catalyst activity, and in greater percent conversion as compared with oxidation in the absence of base, while maintaining satisfactory selectivity for the desired oxidation, for example the oxidation of isobutane to isobutanol. 1 fig.

M. V. Bhinde; T. W. Bierl

1998-01-01

42

Catalytic oxidation of light alkanes in presence of a base  

DOEpatents

The presence of a base in the reaction mixture in a metal-ligand catalyzed partial oxidation of alkanes results in sustained catalyst activity, and in greater percent conversion as compared with oxidation in the absence of base, while maintaining satisfactory selectivity for the desired oxidation, for example the oxidation of isobutane to isobutanol.

Bhinde, Manoj V. (Boothwyn, PA); Bierl, Thomas W. (West Chester, PA)

1998-01-01

43

Catalytic oxidation of light alkanes in presence of a base  

DOEpatents

The presence of a base in the reaction mixture in a metal-ligand catalyzed partial oxidation of alkanes results in sustained catalyst activity, and in greater percent conversion as compared with oxidation in the absence of base, while maintaining satisfactory selectivity for the desired oxidation, for example the oxidation of isobutane to isobutanol. 1 fig.

Bhinde, M.V.; Bierl, T.W.

1998-03-03

44

Sulfated zirconia and iron- and manganese-promoted sulfated zirconia: do they protonate alkanes?  

Microsoft Academic Search

Because of their high activities for alkane conversion, sulfated zirconia and iron- and manganese-promoted sulfated zirconia\\u000a have been the objects of much recent attention as a possible next generation of solid acid catalysts for alkane conversion.\\u000a These catalysts have been suggested to be superacidic on the basis of measurements with adsorbed Hammett indicator bases,\\u000a but published data determined with other

T.-K. Cheung; B. C. Gates

1998-01-01

45

High Temperature Chemical Kinetic Combustion Modeling of Lightly Methylated Alkanes  

SciTech Connect

Conventional petroleum jet and diesel fuels, as well as alternative Fischer-Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed high temperature chemical kinetic mechanism for n-octane and three lightly branched isomers octane (i.e., 2-methylheptane, 3-methylheptane, and 2,5-dimethylhexane). The model is validated against experimental data from a variety of fundamental combustion devices. This new model is used to show how the location and number of methyl branches affects fuel reactivity including laminar flame speed and species formation.

Sarathy, S M; Westbrook, C K; Pitz, W J; Mehl, M

2011-03-01

46

The Numbers of Chiral and Achiral Alkanes and Monosubstituted Alkanes.  

National Technical Information Service (NTIS)

Whereas the theory for the enumeration of optical isomers of alkyl radicals and the alkanes has long been understood, this is not the case for the corresponding achiral isomers. Functional equations on various generating functions were derived. Polya's ex...

R. W. Robinson F. Harary A. T. Balaban

1974-01-01

47

Laboratory evolution of a soluble, self-sufficient, highly active alkane hydroxylase  

Microsoft Academic Search

We have converted cytochrome P450 BM-3 from Bacillus megaterium (P450 BM-3), a medium-chain (C12–C18) fatty acid monooxygenase, into a highly efficient catalyst for the conversion of alkanes to alcohols. The evolved P450 BM-3 exhibits higher turnover rates than any reported biocatalyst for the selective oxidation of hydrocarbons of small to medium chain length (C3–C8). Unlike naturally occurring alkane hydroxylases, the

Anton Glieder; Edgardo T. Farinas; Frances H. Arnold

2002-01-01

48

Rubredoxins Involved in Alkane Oxidation  

PubMed Central

Rubredoxins (Rds) are essential electron transfer components of bacterial membrane-bound alkane hydroxylase systems. Several Rd genes associated with alkane hydroxylase or Rd reductase genes were cloned from gram-positive and gram-negative organisms able to grow on n-alkanes (Alk-Rds). Complementation tests in an Escherichia coli recombinant containing all Pseudomonas putida GPo1 genes necessary for growth on alkanes except Rd 2 (AlkG) and sequence comparisons showed that the Alk-Rds can be divided in AlkG1- and AlkG2-type Rds. All alkane-degrading strains contain AlkG2-type Rds, which are able to replace the GPo1 Rd 2 in n-octane hydroxylation. Most strains also contain AlkG1-type Rds, which do not complement the deletion mutant but are highly conserved among gram-positive and gram-negative bacteria. Common to most Rds are the two iron-binding CXXCG motifs. All Alk-Rds possess four negatively charged residues that are not conserved in other Rds. The AlkG1-type Rds can be distinguished from the AlkG2-type Rds by the insertion of an arginine downstream of the second CXXCG motif. In addition, the glycines in the two CXXCG motifs are usually replaced by other amino acids. Mutagenesis of residues conserved in either the AlkG1- or the AlkG2-type Rds, but not between both types, shows that AlkG1 is unable to transfer electrons to the alkane hydroxylase mainly due to the insertion of the arginine, whereas the exchange of the glycines in the two CXXCG motifs only has a limited effect.

van Beilen, Jan B.; Neuenschwander, Martin; Smits, Theo H. M.; Roth, Christian; Balada, Stefanie B.; Witholt, Bernard

2002-01-01

49

Liquid-liquid interfaces of semifluorinated alkane diblock copolymers with water, alkanes, and perfluorinated alkanes.  

SciTech Connect

The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated alkanes are studied by fully atomistic molecular dynamics simulations. A modified version of the OPLS-AA (Optimized Parameter for Liquid Simulation All-Atom) force field of Jorgensen et al. has been used to study the interfacial behavior of semifluorinated diblocks. Aqueous interfaces are found to be sharp, with correspondingly large values of the interfacial tension. Due to the reduced hydrophobicity of the protonated block compared to the fluorinated block, hydrogen enhancement is observed at the interface. Water dipoles in the interfacial region are found to be oriented nearly parallel to the liquid-liquid interface. A number of protonated alkanes and perfluorinated alkanes are found to be mutually miscible with the semifluorinated diblocks. For these liquids, interdiffusion follows the expected Fickian behavior, and concentration-dependent diffusivities are determined.

Perahia, Dvora, Dr. (Clemson University, Clemson, SC); Pierce, Flint (Clemson University, Clemson, SC); Tsige, Mesfin (Southern Illinois University, Carbondale, IL); Grest, Gary Stephen, Dr.

2008-08-01

50

Integrated process for preparing a carboxylic acid from an alkane  

DOEpatents

The present invention relates to an integrated process for producing unsaturated carboxylic acids from the corresponding C.sub.2-C.sub.4 alkane. The process begins with performance of thermally integrated dehydrogenation reactions which convert a C.sub.2-C.sub.4 alkane to its corresponding C.sub.2-C.sub.4 alkene, and which involve exothermically converting a portion of an alkane to its corresponding alkene by oxidative dehydrogenation in an exothermic reaction zone, in the presence of oxygen and a suitable catalyst, and then feeding the products of the exothermic reaction zone to an endothermic reaction zone wherein at least a portion of the remaining unconverted alkane is endothermically dehydrogenated to form an additional quantity of the same corresponding alkene, in the presence of carbon dioxide and an other suitable catalyst. The alkene products of the thermally integrated dehydrogenation reactions are then provided to a catalytic vapor phase partial oxidation process for conversion of the alkene to the corresponding unsaturated carboxylic acid or nitrile. Unreacted alkene and carbon dioxide are recovered from the oxidation product stream and recycled back to the thermally integrated dehydrogenation reactions.

Benderly, Abraham (Elkins Park, PA); Chadda, Nitin (Radnor, PA); Sevon, Douglass (Fairless Hills, PA)

2011-12-20

51

Fundamental studies in the conversion of coals to fuels of increased hydrogen content. Volume 2. The chemistry and mechanisms of coal conversion to clean fuel: Appendixes. Interim report  

Microsoft Academic Search

Research has been carried out to investigate thermal coal dissolution at short reaction times as a first step toward exploring the interrelationship of thermal and catalytic processes in coal liquefaction. Related studies have examined the mechanisms of coal liquefaction in high boiling solvents. Coal conversions were examined at a variety of conditions. Reaction products were characterized by numerous techniques to

F. J. Derbyshire; G. A. Odoerfer; L. R. Rudnick; P. Varghese; D. D. Whitehurst

1981-01-01

52

Monomethyl-Branching of Long n-Alkanes in the Range from Decane to Tetracosane on Pt\\/H-ZSM-22 Bifunctional Catalyst  

Microsoft Academic Search

Single long n-alkanes in the range n-C10–n-C24 were hydroisomerized at 233° C in a fixed-bed down-flow vapor phase reactor loaded with Pt\\/H-ZSM-22 catalyst. The conversion was varied by varying the contact time. Up to ca. 60% conversion, the n-alkane molecules undergo almost exclusively a single methyl branching. In this conversion range, the distribution of positional methyl-branched isomers remains constant. The

Marion C. Claude; Johan A. Martens

2000-01-01

53

A Conversion of Methyl Ketones into Acetylenes: A Project for a Problem-Oriented or Microscale Organic Chemistry Course.  

ERIC Educational Resources Information Center

Describes a process for producing terminal or internal alkynes from ketones. Recommends using the experiment to aid in understanding acid-base strength, enolate anion chemistry, reaction at carbon versus oxygen, use of polar aprotic solvents, and elimination and nucleophilic substitution reactions. (ML)

Silveira, Augustine, Jr.; Orlando, Steven C.

1988-01-01

54

Environmental green chemistry as defined by photocatalysis.  

PubMed

Photocatalysis is efficient in several fields. Firstly, in selective mild oxidation: oxidation of gas and liquid hydrocarbons (alkanes, alkenes, cyclo-alkanes, aromatics) into aldehydes and ketons. Primary and secondary alcohols are also oxidized into their corresponding aldehydes or ketones. The high selectivity was ascribed to a photoactive neutral, atomic oxygen species. Once platinized (only 0.5wt.% Pt) titania may catalyze reactions involving hydrogen (deuterium-alkane isotopic exchange and alcohol dehydrogenation). For fine chemicals, high initial selectivities enable titania to address most of the twelve principles of "green chemistry", such as the synthesis of 4-tert-butyl-benzaldehyde, an important intermediate in perfume industry by direct selective oxidation of 4-tert-butyl-toluene with air. A new field recently appeared: thio-photocatalysis. Oxygen was replaced by sulfur, using H(2)S as a convenient and reactive source. For instance, the conversion of propene in 1-propanthiol was successfully obtained. The reaction was performed using either CdS or TiO(2). The latter was much more active than CdS. In environmental photocatalysis, titania becomes a total oxidation catalyst once in presence of water because of the photogeneration of OH radicals by neutralization of OH(-) surface groups by positive holes. Many toxic inorganic ions are oxidized in their harmless upper oxidized state. The total degradation of organic pollutants (pesticides, herbicides, insecticides, fungicides, dyes, etc. ...) is the main field of water photocatalytic decontamination. The UVA solar spectrum can de advantageously used as demonstrated by many campaigns performed in the solar pilot plant at the "Plataforma Solar de Almeria" (Spain). PMID:17532130

Herrmann, J-M; Duchamp, C; Karkmaz, M; Hoai, Bui Thu; Lachheb, H; Puzenat, E; Guillard, C

2007-07-31

55

Reflectance spectroscopy of organic compounds: 1. Alkanes  

Microsoft Academic Search

Reflectance spectra of the organic compounds comprising the alkane series are presented from the ultraviolet to midinfrared, 0.35 to 15.5 mum. Alkanes are hydrocarbon molecules containing only single carbon-carbon bonds, and are found naturally on the Earth and in the atmospheres of the giant planets and Saturn's moon, Titan. This paper presents the spectral properties of the alkanes as the

Roger N. Clark; John M. Curchin; Todd M. Hoefen; Gregg A. Swayze

2009-01-01

56

Reflectance spectroscopy of organic compounds: 1. Alkanes  

Microsoft Academic Search

Reflectance spectra of the organic compounds comprising the alkane series are presented from the ultraviolet to midinfrared, 0.35 to 15.5 ?m. Alkanes are hydrocarbon molecules containing only single carbon-carbon bonds, and are found naturally on the Earth and in the atmospheres of the giant planets and Saturn's moon, Titan. This paper presents the spectral properties of the alkanes as the

Roger N. Clark; John M. Curchin; Todd M. Hoefen; Gregg A. Swayze

2009-01-01

57

Genetics of alkane oxidation by Pseudomonas oleovorans  

Microsoft Academic Search

Many Pseudomonads are able to use linear alkanes as sole carbon and energy source. The genetics and enzymology of alkane metabolism have been investigated in depth forPseudomonas oleovorans, which is able to oxidize C5-C12 n-alkanes by virtue of two gene regions, localized on the OCT-plasmid. The so-calledalk-genes have been cloned in pLAFR1, and were subsequent analyzed using minicell expression experiments,

Jan B. Beilen; Marcel G. Wubbolts; Bernard Witholt

1994-01-01

58

A novel description of S(IV) to S(VI) conversion - Implications to the plume chemistry of jet aircraft  

NASA Astrophysics Data System (ADS)

The conversion of SO_2 into SO_3 (H_2SO_4) in the jet regime of a B-747 airliner has been modelled by means of the BOAT code. The gas phase reaction scheme previously developed in our work group has been updated by novel rate constants obtained from ab initio quantum-chemical calculations on the reaction SO_2 + OH rightarrow HSO_3. As a striking feature these rate constants predict the efficiency of SO_2 to SO_3/H_2SO_4 conversion to be lower by a factor of about three. From these findings we conclude that the well-known conversion ratio of about 1-2% confirmed by numerous air-borne experiments can be reproduced only assuming sufficient amounts of both SO_3 and H_2SO_4 to be formed already inside the engine. In addition, we have performed sensitivity calculations in order to quantify the impact of uncertainties in EI(NO_x) as well as of organics on the sulphur conversion ratio.

Gleitsmann, G.; Somnitz, H.; Zellner, R.

2003-04-01

59

A novel description of S(IV) to S(VI) conversion - Implications to the plume chemistry of jet aircraft  

Microsoft Academic Search

The conversion of SO_2 into SO_3 (H_2SO_4) in the jet regime of a B-747 airliner has been modelled by means of the BOAT code. The gas phase reaction scheme previously developed in our work group has been updated by novel rate constants obtained from ab initio quantum-chemical calculations on the reaction SO_2 + OH rightarrow HSO_3. As a striking feature

G. Gleitsmann; H. Somnitz; R. Zellner

2003-01-01

60

Intra-Catalyst Reductant Chemistry and NOx Conversion of Diesel Lean NOx Traps at Various Stages of Sulfur Loading  

SciTech Connect

Due to increasingly stringent emissions regulations, Lean NOX Trap (LNT) catalysts are being researched as a potential solution for diesel engine emissions reduction. LNTs are practical for diesel NOX reduction due to their ability to reduce NOX from the O2 rich environment produced by diesel engines. LNTs function by storing NOX on the catalyst surface during efficient lean operation then, under rich conditions, releasing and reducing the trapped NOX. One method of producing this rich environment which regenerates a LNT involves manipulating the fuel injection parameters and throttling the air intake. This process is called in-cylinder regeneration. Experiments will be described here in which a 1.7 L common rail diesel engine has been used to regenerate LNTs at various stages of sulfur exposure, a known poison of the LNT. In-cylinder regeneration strategies were used to produce a range of reductant chemistries which enabled the study of the role of various reductants as NOX was converted across the LNT. This study gives insight into how to most efficiently regenerate the LNT. Sulfur poisoning of a fresh LNT was accelerated via the use of bottled SO2. Regeneration studies at various states of sulfation and after catalyst desulfation are discussed, highlighting intra-catalyst measurements of reductant chemistry and NOX conversion through the catalyst. Results showed that as sulfur loading increased, NOX conversion efficiency decreased and reductant utilization shifted downstream. Hydrogen from in-cylinder combustion was consumed over the first half of the LNT then produced from other available reductants over the last half for some strategies and conditions. Hydrogen production over the last portion of the catalyst was found to be affected by sulfur.

Parks, II, James E [ORNL; Swartz, Matthew M [ORNL; Huff, Shean P [ORNL; West, Brian H [ORNL

2006-01-01

61

Microsomal preparation from an animal tissue catalyzes release of carbon monoxide from a fatty aldehyde to generate an alkane.  

PubMed

Alkanes are widely distributed in nature and impaired alkane synthesis was implicated in certain neurological disorders. However, the mechanism of synthesis of alkanes in animals is unknown. Our search to find a convenient animal tissue to study alkane biosynthesis resulted in the finding that the uropygial gland (a modified sebaceous gland) of the eared grebe (Podiceps nigricollis) produces large amounts of alkanes. These alkanes, which constitute 35-41% of the total lipid produced, are mainly C21, C23, C25, and C27 n-alkanes. Cell free homogenates of this tissue synthesized alkanes from both fatty acid and aldehyde in the absence of O2. Differential centrifugation of the homogenates indicated that this activity was located in the microsomal fraction. With isolated microsomes conversion of fatty acid to alkane required CoA, ATP, and NADH whereas conversion of an aldehyde to alkane did not require the addition of cofactors. That the final step in alkane synthesis is a decarbonylation was shown by the stoichiometric production of heptadecane and CO from octadecanal. CO was identified by adsorption to RhCl [(C6H6)3P]3 and oxidation of the trapped CO to CO2 by watergas shift reaction. The enzyme preparation also catalyzed incorporation of 14C from 14CO into octadecanal showing the reversible nature of the decarbonylase. This decarbonylase had a sharp pH optimum at 7.0, a Kapp of 180 microM and a V1/2 of 90 rho mol/min/mg protein for octadecanal. The enzyme was inhibited by the metal chelators EDTA, O-phenanthroline, and 8-hydroxyquinoline, but not by KCN. It was stimulated nearly 3-fold by 5 microM 2-mercaptoethanol and inhibited by the presence of O2. During the conversion of [1-3H]octadecanal to heptadecane, 3H was lost to water and 3H from 3H2O was incorporated into the alkane generated from unlabeled octadecanal. The mechanism of the decarbonylation and the nature of the enzyme remain to be elucidated. PMID:3343228

Cheesbrough, T M; Kolattukudy, P E

1988-02-25

62

Transcriptome response to alkane biofuels in Saccharomyces cerevisiae: identification of efflux pumps involved in alkane tolerance  

PubMed Central

Background Hydrocarbon alkanes have been recently considered as important next-generation biofuels because microbial production of alkane biofuels was demonstrated. However, the toxicity of alkanes to microbial hosts can possibly be a bottleneck for high productivity of alkane biofuels. To tackle this toxicity issue, it is essential to understand molecular mechanisms of interactions between alkanes and microbial hosts, and to harness these mechanisms to develop microbial host strains with improved tolerance against alkanes. In this study, we aimed to improve the tolerance of Saccharomyces cerevisiae, a model eukaryotic host of industrial significance, to alkane biofuels by exploiting cellular mechanisms underlying alkane response. Results To this end, we first confirmed that nonane (C9), decane (C10), and undecane (C11) were significantly toxic and accumulated in S. cerevisiae. Transcriptome analyses suggested that C9 and C10 induced a range of cellular mechanisms such as efflux pumps, membrane modification, radical detoxification, and energy supply. Since efflux pumps could possibly aid in alkane secretion, thereby reducing the cytotoxicity, we formed the hypothesis that those induced efflux pumps could contribute to alkane export and tolerance. In support of this hypothesis, we demonstrated the roles of the efflux pumps Snq2p and Pdr5p in reducing intracellular levels of C10 and C11, as well as enhancing tolerance levels against C10 and C11. This result provided the evidence that Snq2p and Pdr5p were associated with alkane export and tolerance in S. cerevisiae. Conclusions Here, we investigated the cellular mechanisms of S. cerevisiae response to alkane biofuels at a systems level through transcriptome analyses. Based on these mechanisms, we identified efflux pumps involved in alkane export and tolerance in S. cerevisiae. We believe that the results here provide valuable insights into designing microbial engineering strategies to improve cellular tolerance for highly efficient alkane biofuel production.

2013-01-01

63

Origin of stability in branched alkanes.  

PubMed

The potential origins of stability in branched alkanes are investigated, paying close attention to two recent hypotheses: geminal steric repulsion and protobranching. All alkane isomers through C(6)H(14) along with heptane and octane were investigated at the MPW1B95/6-311++G(d,p) level. Their geminal steric repulsion, total steric repulsion, and orbital interactions were evaluated by using natural bond orbital analysis. All measures of steric repulsion fail to explain the stability of branched alkanes. The extra stability of branched alkanes and protobranching, in general, is tied to stabilizing geminal sigma-->sigma* delocalization, particularly of the type that involves adjacent C-C bonds and, thus, preferentially stabilizes branched alkanes. This picture is corroborated by valence bond calculations that attribute the effect to additional ionic structures (e.g., CH(3) (+) :CH(2) :CH(3) (-) and CH(3):(-) CH(2): CH(3) (+) for propane) that are not possible without protobranching. PMID:20432414

Kemnitz, Carl R; Mackey, Joel L; Loewen, Mark J; Hargrove, Julie L; Lewis, Joshua L; Hawkins, Whitney E; Nielsen, Adam F

2010-06-18

64

Exploratory study of coal conversion chemistry. Quarterly report No. 2, August 19, 1981-November 18, 1981. [Hydroxydipnenylmethanes, triphenylmethane, diphenylether  

SciTech Connect

This report describes work accomplished under two tasks: Task A, mechanisms of donor-solvent coal liquefaction, and Task B, CO/H/sub 2/O conversion systems. Under Task A, we describe additional evidence relating to the question of the mechanism of the iron oxide catalyzed cleavage of hydroxydiphenylmethanes. o-Hydroxydiphenylmethane is relatively more sensitive to catalysis by Fe/sub 3/O/sub 4/, a possible one electron oxidant, and triphenylmethane is relatively more sensitive to catalyzed cleavage by SiO/sub 2//Al/sub 2/O/sub 3/, a strong Bronsted acid catalyst. This provides further evidence that in the former case the reactions of radical cations are important in the cleavage mechanism. Tests with Cr/sub 2/O/sub 3/ show it to be ineffective under our reaction conditions as a catalyst for hydroxydiphenylmethane cleavage. We have also used the decomposition of diphenylether in tetralin, which we have previously shown to occur by a radical displacement reaction, as an indicator of steady state radical concentration in tetralin. The results of these experiments indicate that radical concentrations in tetralin are not significantly increased by spiking the tetralin with 1,2-dihydronaphthalene. This in turn suggests that rapid disproportionation of 1,2-dihydronaphthalene to tetralin and naphthalene takes place by way of a concerted reaction, in addition to a slower radical disproportionation process that may provide the steady state radical concentration supported by the equilibrium concentration of 1,2-dihydronaphthalene. Under Task B1, we have found a correlation between initial pH and CO pressure on the conversion of PSOC-26 coal to toluene soluble products. A pH dependence was also observed for PSOC-233 coal, similar to results with PSOC-26. Under Task B2, we have studied anisole as a model oxygen containing structure in coal.

Not Available

1982-01-29

65

Selective monooxidation of light alkanes using chloride and iodate.  

PubMed

We describe an efficient system for the direct partial oxidation of methane, ethane, and propane using iodate salts with catalytic amounts of chloride in protic solvents. In HTFA (TFA = trifluoroacetate), >20% methane conversion with >85% selectivity for MeTFA have been achieved. The addition of substoichiometric amounts of chloride is essential, and for methane the conversion increases from <1% in the absence of chloride to >20%. The reaction also proceeds in aqueous HTFA as well as acetic acid to afford methyl acetate. (13)C labeling experiments showed that less than 2% of methane is overoxidized to (13)CO2 at 15% conversion of (13)CH4. The system is selective for higher alkanes: 30% ethane conversion with 98% selectivity for EtTFA and 19% propane conversion that is selective for mixtures of the mono- and difunctionalized TFA esters. Studies of methane conversion using a series of iodine-based reagents [I2, ICl, ICl3, I(TFA)3, I2O4, I2O5, (IO2)2S2O7, (IO)2SO4] indicated that the chloride enhancement is not limited to iodate. PMID:24866148

Fortman, George C; Boaz, Nicholas C; Munz, Dominik; Konnick, Michael M; Periana, Roy A; Groves, John T; Gunnoe, T Brent

2014-06-11

66

The chemistry of elemental events of catalytic conversions of hydrocarbons under the effect of transition-metal compounds  

SciTech Connect

The composition of the products of decomposition of organic compounds of a number of transition metals at the time of their formation was investigated, and it was found that: a) decomposition of methyl derivatives of Mo and W primarily takes place based on the mechanism of ..cap alpha..-disproportionation with formation of carbene and carbyne fragments; b) decomposition of benzyl and neophyl derivatives of neodymium and yttrium in THF quantitatively takes place with formation of stable carbene (carbyne) complexes; c) decomposition of trimethylsilyl(germyl)methyl derivatives of W, Mo, Ta, Re, Nb, Rh, Pd, and Pt is accompanied by formation of complexes containing carbene fragments to two types: (CH/sub 3/)/sub 3/SiCH: and CH/sub 2/: (in the case of W, Mo, Ta, Nb, and Rh compounds, this pathway of decomposition is determining); d) in the reaction of benzylmagnesium chloride with Mo, W, Re, Rh, Pt, and Pd chlorides, significant quantities of toluene, the product of ..cap alpha..-disproportionation of benzyl groups, and some quantities of stilbene and tolan, the products of recombination of carbene and carbyne fragments, are formed. Results based on the data in the literature and the data obtained in the present study concerning the mechanism of decomposition of organic compounds of transition metals, hypotheses were advanced concerning the chemistry of the elemental events in catalytic reactions taking place through organometallic compounds (hydrogenation, dehydrogenation, skeletal isomerization, and deuterium exchange).

Dolgoplosk, B.A.; Oreshkin, I.A.; Tinyakova, E.I.; Yakovlev, V.A.

1982-11-20

67

Catalytic dehydroaromatization of n-alkanes by pincer-ligated iridium complexes  

NASA Astrophysics Data System (ADS)

Aromatic hydrocarbons are among the most important building blocks in the chemical industry. Benzene, toluene and xylenes are obtained from the high temperature thermolysis of alkanes. Higher alkylaromatics are generally derived from arene-olefin coupling, which gives branched products—that is, secondary alkyl arenes—with olefins higher than ethylene. The dehydrogenation of acyclic alkanes to give alkylaromatics can be achieved using heterogeneous catalysts at high temperatures, but with low yields and low selectivity. We present here the first catalytic conversion of n-alkanes to alkylaromatics using homogeneous or molecular catalysts—specifically ‘pincer’-ligated iridium complexes—and olefinic hydrogen acceptors. For example, the reaction of n-octane affords up to 86% yield of aromatic product, primarily o-xylene and secondarily ethylbenzene. In the case of n-decane and n-dodecane, the resulting alkylarenes are exclusively unbranched (that is, n-alkyl-substituted), with selectivity for the corresponding o-(n-alkyl)toluene.

Ahuja, Ritu; Punji, Benudhar; Findlater, Michael; Supplee, Carolyn; Schinski, William; Brookhart, Maurice; Goldman, Alan S.

2011-02-01

68

Importance of dynamical processes in the coordination chemistry and redox conversion of copper amyloid-beta complexes.  

PubMed

Interaction of Cu ions with the amyloid-beta (Abeta) peptide is linked to the development of Alzheimer's disease; hence, determining the coordination of Cu(I) and Cu(II) ions to Abeta and the pathway of the Cu(I)(Abeta)/Cu(II)(Abeta) redox conversion is of great interest. In the present report, we use the room temperature X-ray absorption near edge structure to show that the binding sites of the Cu(I) and Cu(II) complexes are similar to those previously determined from frozen-solution studies. More precisely, the Cu(I) is coordinated by the imidazole groups of two histidine residues in a linear fashion. However, an NMR study unravels the involvement of all three histidine residues in the Cu(I) binding due to dynamical exchange between several set of ligands. The presence of an equilibrium is also responsible for the complex redox process observed by cyclic voltammetry and evidenced by a concentration-dependent electrochemical response. PMID:19618220

Hureau, Christelle; Balland, Véronique; Coppel, Yannick; Solari, Pier Lorenzo; Fonda, Emiliano; Faller, Peter

2009-09-01

69

Supported organoiridium catalysts for alkane dehydrogenation  

DOEpatents

Solid supported organoiridium catalysts, a process for preparing such solid supported organoiridium catalysts, and the use of such solid supported organoiridium catalysts in dehydrogenation reactions of alkanes is provided. The catalysts can be easily recovered and recycled.

Baker, R. Thomas; Sattelberger, Alfred P.; Li, Hongbo

2013-09-03

70

Catalytic conversion of light alkanes: Proof of concept stage.  

National Technical Information Service (NTIS)

During the stage at which this work ended, our program consisted of two phases which were running concurrently, a research phase and a proof-of-concept phase. The function of the research phase is to design synthesize and perform laboratory tests on new m...

J. E. Lyons

1995-01-01

71

The organization of n-alkanes in lipid bilayers.  

PubMed

The interaction of n-alkanes (C6--C16) with phosphatidylcholine has been studied by the combined use of differential scanning calorimetry, X-ray diffraction and monolayer techniques. It has been found that the thermal properties and ultrastructure of lipid-alkane vesicles are strongly dependent on the length of the n-alkanes. Long alkanes, such as tetradecane and hexadecane, increase the transition temperature of dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine, while the X-ray data indicate that these long alkanes align parallel to the lipid acyl chains. In contrast, shorter alkanes, such as hexane and octane, decrease and broaden the thermal transition and electron density profiles show that these alkanes increase bilayer width by partitioning between the apposing monolayers of the bilayer. For lipids in the gel and liquid crystalline states, the short alkanes form an alkane region in the geometric center of the bilayer. PMID:6892885

McIntosh, T J; Simon, S A; MacDonald, R C

1980-04-24

72

Geochemical characteristics of abiogenic alkane gases  

NASA Astrophysics Data System (ADS)

Recently abiogenic alkanes have been found in various locations in the world and other celestial bodies. The chemical composition of abiogenic alkane gases varies widely. The content of methane is low and nearly no C2+ is found in the abiogenic alkane gases from fluid inclusions in volcanic rocks or hot springs in China. In the unsedimented submarine hydrothermal vent system C1/C2+ ratios are much greater than those for the thermogenic gases, mostly >800 and in some cases up to 8,000. In the Songliao Basin, China, C1/C2+ of some abiogenic gases are often less than 150. Abiogenic alkane gases which have been found in nature often have carbon isotopic reversal among C1-C4 alkanes (?13C1>?13C2>?13C3>?13C4), whereas both regular and reversed hydrogen isotope distribution pattern among C1-C4 alkanes have been reported. The ?13C of abiogenic methane is mainly greater than -30° though laboratory synthesized methane can have ?13C as low as -57°, and its ?D1 values vary widely and overlap with biogenic gases. High 3He/4He ratios often indicate the addition of mantle-derived helium and are related to abiogenic gases. However, some biogenic gases can also have high 3He/4He ratios up to 8. The CH4/3He end-member is often lower than 106 for abiogenic alkane gases while greater than 10^13 for biogenic gases, and the values between these two end-members often reflect the mixing of biogenic and abiogenic gases.

Ni, Y.; Dai, J.

2009-12-01

73

Use of molecular modeling to design alkane activation catalysts  

SciTech Connect

Efficient alkane-activation catalysts are needed for a number of applications including methane conversion to liquid fuels, clean-up of dilute waste streams, and for oxidation of higher molecular weight alkanes, olefins, and aromatics. For some of these applications, high selectivity and regioselectively of the catalyst is desired. Our work takes a biomimetic approach to the development of shape and size selective catalysts using computer-aided molecular design (CAMD) techniques. The biomimetic CAMD methodology consists of several elements, including: (1) investigation of biological catalysts, especially those like methane monooxygenase and cytochrome P/sub 450/ that activate C-H bonds, to determine the structural features to be designed into a synthetic catalyst, (2) molecular mechanics calculations to evaluate potential catalysts, (3) synthesis of the designed catalyst, (4) spectroscopic characterization of the synthetic catalysts, and (5) catalyst testing for activity and selectivity. The activity tests and structural information provide a basis for making further improvements in the catalyst design. This biomimetic CAMD methodology is being used to design shape and size selective catalysts based on the metalloporphyrins. Designed metalloporphyrins with bulky substituents attached so as to give a small methane-binding cavity at the active metal center have been synthesized and tested. The photochemical production of the co-reductant required in the reaction that mimics cytochrome P/sub 450/ and the synthesis of bis-deep-pocket porphyrins are also described. 51 refs., 8 figs.

Shelnutt, J.A.

1989-07-28

74

The effect of environmental factors on stable isotopic composition of n-alkanes in Mediterranean olive oils  

NASA Astrophysics Data System (ADS)

Traceability of the geographic origin of olive oils is an important issue from both commercial and health perspectives. This study evaluates the impact of environmental factors on stable C and H isotope compositions of n-alkanes in extra virgin olive oils from Croatia, France, Greece, Italy, Morocco, Portugal, Slovenia, and Spain. The data are used to investigate the applicability of stable isotope methodology for olive oil regional classification in the Mediterranean region. Analysis of stable C isotope composition of n-C29 alkane showed that extra virgin olive oils from Portugal and Spain have the most positive n-C29 alkane delta13C values. Conversely, olive oils from Slovenia, northern and central Italy are characterized by the most negative values. Overall, the n-C29 alkane delta13C values show a positive correlation with the mean air temperature during August-December and a negative correlation with the mean relative humidity during these months. Analysis of stable H isotope composition of n-C29 alkane revealed that the deltaD values are the most positive in olive oils from Greece and Morocco and the most negative in oils from northern Italy. The deltaD values of oils show significant correlation with all the analyses geographical parameters: the mean air temperature and relative humidity during August-December, the total amount of rainfall (the same months) and the annual deltaD values of precipitation. As predictor variables in the Categorical Data Analysis, the n-C29 alkane deltaD values show the most significant discriminative power, followed by the n-C29 alkane delta13C values. Overall, 93.4% of olive oil samples have been classified correctly into one of the production regions. Our findings suggest that an integrated analysis of C and H isotope compositions of n-alkanes extracted from extra virgin olive oil could become a useful tool for geographical provenancing of this highly popular food commodity.

Pedentchouk, Nikolai; Mihailova, Alina; Abbado, Dimitri

2014-05-01

75

Simple chemical processes based on low molecular-mass alkanes as chemical feedstocks  

Microsoft Academic Search

The present state of new developments in direct catalytic conversion of low-molecular-mass alkanes (C1–C3) to petrochemical feedstocks and petrochemicals is reviewed. Special attention is given to the following reactions: methane to methanol and formaldehyde by partial oxidation as well as to C2 hydrocarbons by oxidative coupling, ethane and propane to their olefins by oxidative dehydrogenation and to their oxygenates, i.e.,

M Baerns; O Buyevskaya

1998-01-01

76

Cool-flame Extinction During N-Alkane Droplet Combustion in Microgravity  

NASA Technical Reports Server (NTRS)

Recent droplet combustion experiments onboard the International Space Station (ISS) have revealed that large n-alkane droplets can continue to burn quasi-steadily following radiative extinction in a low-temperature regime, characterized by negative-temperaturecoefficient (NTC) chemistry. In this study we report experimental observations of n-heptane, n-octane, and n-decane droplets of varying initial sizes burning in oxygen/nitrogen/carbon dioxide and oxygen/helium/nitrogen environments at 1.0, 0.7, and 0.5 atmospheric pressures. The oxygen concentration in these tests varied in the range of 14% to 25% by volume. Large n-alkane droplets exhibited quasi-steady low-temperature burning and extinction following radiative extinction of the visible flame while smaller droplets burned to completion or disruptively extinguished. A vapor-cloud formed in most cases slightly prior to or following the "cool flame" extinction. Results for droplet burning rates in both the hot-flame and cool-flame regimes as well as droplet extinction diameters at the end of each stage are presented. Time histories of radiant emission from the droplet captured using broadband radiometers are also presented. Remarkably the "cool flame" extinction diameters for all the three n-alkanes follow a trend reminiscent of the ignition delay times observed in previous studies. The similarities and differences among the n-alkanes during "cool flame" combustion are discussed using simplified theoretical models of the phenomenon

Nayagam, Vedha; Dietrich, Daniel L.; Hicks, Michael C.; Williams, Forman A.

2014-01-01

77

Enzymes and genes involved in aerobic alkane degradation  

PubMed Central

Alkanes are major constituents of crude oil. They are also present at low concentrations in diverse non-contaminated because many living organisms produce them as chemo-attractants or as protecting agents against water loss. Alkane degradation is a widespread phenomenon in nature. The numerous microorganisms, both prokaryotic and eukaryotic, capable of utilizing alkanes as a carbon and energy source, have been isolated and characterized. This review summarizes the current knowledge of how bacteria metabolize alkanes aerobically, with a particular emphasis on the oxidation of long-chain alkanes, including factors that are responsible for chemotaxis to alkanes, transport across cell membrane of alkanes, the regulation of alkane degradation gene and initial oxidation.

Wang, Wanpeng; Shao, Zongze

2013-01-01

78

Microbial production of short-chain alkanes.  

PubMed

Increasing concerns about limited fossil fuels and global environmental problems have focused attention on the need to develop sustainable biofuels from renewable resources. Although microbial production of diesel has been reported, production of another much in demand transport fuel, petrol (gasoline), has not yet been demonstrated. Here we report the development of platform Escherichia coli strains that are capable of producing short-chain alkanes (SCAs; petrol), free fatty acids (FFAs), fatty esters and fatty alcohols through the fatty acyl (acyl carrier protein (ACP)) to fatty acid to fatty acyl-CoA pathway. First, the ?-oxidation pathway was blocked by deleting the fadE gene to prevent the degradation of fatty acyl-CoAs generated in vivo. To increase the formation of short-chain fatty acids suitable for subsequent conversion to SCAs in vivo, the activity of 3-oxoacyl-ACP synthase (FabH), which is inhibited by unsaturated fatty acyl-ACPs, was enhanced to promote the initiation of fatty acid biosynthesis by deleting the fadR gene; deletion of the fadR gene prevents upregulation of the fabA and fabB genes responsible for unsaturated fatty acids biosynthesis. A modified thioesterase was used to convert short-chain fatty acyl-ACPs to the corresponding FFAs, which were then converted to SCAs by the sequential reactions of E. coli fatty acyl-CoA synthetase, Clostridium acetobutylicum fatty acyl-CoA reductase and Arabidopsis thaliana fatty aldehyde decarbonylase. The final engineered strain produced up to 580.8?mg?l(-1) of SCAs consisting of nonane (327.8?mg?l(-1)), dodecane (136.5?mg?l(-1)), tridecane (64.8?mg?l(-1)), 2-methyl-dodecane (42.8?mg?l(-1)) and tetradecane (8.9?mg?l(-1)), together with small amounts of other hydrocarbons. Furthermore, this platform strain could produce short-chain FFAs using a fadD-deleted strain, and short-chain fatty esters by introducing the Acinetobacter sp. ADP1 wax ester synthase (atfA) and the E. coli mutant alcohol dehydrogenase (adhE(mut)). PMID:24077097

Choi, Yong Jun; Lee, Sang Yup

2013-10-24

79

Pervaporation separation of alkane\\/thiophene mixtures with PDMS membrane  

Microsoft Academic Search

Worldwide concerns over environment have stimulated increasing interest both in academic and industry for deep desulfurization of gasoline. Polydimethylsiloxane (PDMS) composite membrane was used to separate the binary and multicomponent alkane\\/thiophene mixtures by pervaporation. Effect of carbon number and concentration of alkane, and of feed temperature, on the separation efficiency of alkane\\/thiophene mixtures was investigated experimentally. Experimental results of binary

Rongbin Qi; Yujun Wang; Jiding Li; Changwei Zhao; Shenlin Zhu

2006-01-01

80

40 CFR 721.10163 - Chloro fluoro alkane (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Chloro fluoro alkane (generic). 721.10163 ...Chemical Substances § 721.10163 Chloro fluoro alkane (generic). (a) Chemical...substance identified generically as chloro fluoro alkane (PMN P-08-33) is...

2013-07-01

81

40 CFR 721.10163 - Chloro fluoro alkane (generic).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Chloro fluoro alkane (generic). 721.10163 ...Chemical Substances § 721.10163 Chloro fluoro alkane (generic). (a) Chemical...substance identified generically as chloro fluoro alkane (PMN P-08-33) is...

2010-07-01

82

In situ detection of anaerobic alkane metabolites in subsurface environments  

PubMed Central

Alkanes comprise a substantial fraction of crude oil and refined fuels. As such, they are prevalent within deep subsurface fossil fuel deposits and in shallow subsurface environments such as aquifers that are contaminated with hydrocarbons. These environments are typically anaerobic, and host diverse microbial communities that can potentially use alkanes as substrates. Anaerobic alkane biodegradation has been reported to occur under nitrate-reducing, sulfate-reducing, and methanogenic conditions. Elucidating the pathways of anaerobic alkane metabolism has been of interest in order to understand how microbes can be used to remediate contaminated sites. Alkane activation primarily occurs by addition to fumarate, yielding alkylsuccinates, unique anaerobic metabolites that can be used to indicate in situ anaerobic alkane metabolism. These metabolites have been detected in hydrocarbon-contaminated shallow aquifers, offering strong evidence for intrinsic anaerobic bioremediation. Recently, studies have also revealed that alkylsuccinates are present in oil and coal seam production waters, indicating that anaerobic microbial communities can utilize alkanes in these deeper subsurface environments. In many crude oil reservoirs, the in situ anaerobic metabolism of hydrocarbons such as alkanes may be contributing to modern-day detrimental effects such as oilfield souring, or may lead to more beneficial technologies such as enhanced energy recovery from mature oilfields. In this review, we briefly describe the key metabolic pathways for anaerobic alkane (including n-alkanes, isoalkanes, and cyclic alkanes) metabolism and highlight several field reports wherein alkylsuccinates have provided evidence for anaerobic in situ alkane metabolism in shallow and deep subsurface environments.

Agrawal, Akhil; Gieg, Lisa M.

2013-01-01

83

Identification and structural characterisation of novel trehalose dinocardiomycolates from n -alkane-grown Rhodococcus opacus 1CP  

Microsoft Academic Search

Rhodococcus opacus 1CP, a potent degrader of (chloro-) aromatic compounds was found to utilise C10–C16\\u000a n-alkanes as sole carbon sources. Highest conversion rates were observed with n-tetradecane and n-hexadecane, whereas the utilisation of n-dodecane and n-decane was considerably slower. Thin-layer chromatography of organic extracts of n-alkane-grown 1CP cultures indicated the growth-associated formation of a glycolipid which was characterised as a

Susanne Niescher; Victor Wray; Siegmund Lang; Stefan R. Kaschabek; Michael Schlömann

2006-01-01

84

Light hydrocarbon gas conversion using porphyrin catalysts  

SciTech Connect

The objective of this project is to develop novel catalysts for the direct conversion of natural gas to a liquid fuel. The current work investigates the use of biomimetic metalloporphyrins as catalysts for the partial oxidation of light alkanes to alcohols.

Showalter, M.C.; Shelnutt, J.A.

1995-07-01

85

Determination of absolute photoionization cross-sections of alkanes and cyclo-alkanes.  

PubMed

Absolute photoionization and dissociative photoionization cross-sections of eleven n-alkanes (n-pentane, n-hexane, n-heptane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane and n-hexadecane), three cyclo-alkanes (cyclopentane, methylcyclohexane and trans-decahydronaphthalene) and iso-octane were measured for photon energies from the ionization thresholds to 11.5 eV. The measurements were performed with the binary-liquid-mixture method utilizing the photoionization cross-sections of benzene as a calibration standard. The ionization energies of n-alkanes and cyclo-alkanes were also calculated at the B3P86/6-31 + +G(d,p) level and by the G3B3 method. PMID:20391606

Zhou, Zhongyue; Zhang, Lidong; Xie, Mingfeng; Wang, Zhandong; Chen, Dongna; Qi, Fei

2010-05-15

86

Comprehensive chemical kinetic modeling of the oxidation of C8 and larger n-alkanes and 2-methylalkanes  

SciTech Connect

Conventional petroleum jet and diesel fuels, as well as alternative Fischer-Tropsch (FT) fuels and hydrotreated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed and reduced chemical kinetic mechanism for singly methylated iso-alkanes (i.e., 2-methylalkanes) ranging from C{sub 8} to C{sub 20}. The mechanism also includes an updated version of our previously published C{sub 8} to C{sub 16} n-alkanes model. The complete detailed mechanism contains approximately 7,200 species 31,400 reactions. The proposed model is validated against new experimental data from a variety of fundamental combustion devices including premixed and nonpremixed flames, perfectly stirred reactors and shock tubes. This new model is used to show how the presence of a methyl branch affects important combustion properties such as laminar flame propagation, ignition, and species formation.

Sarathy, S M; Westbrook, C K; Pitz, W J; Mehl, M; Togbe, C; Dagaut, P; Wang, H; Oehlschlaeger, M; NIemann, U; Seshadri, K; Veloo, P S; Ji, C; Egolfopoulos, F; Lu, T

2011-03-16

87

Steric hindrance of photoswitching in self-assembled monolayers of azobenzene and alkane thiols.  

PubMed

Surface-bound azobenzenes exhibit reversible photoswitching via trans-cis photoisomerization and have been proposed for a variety of applications such as photowritable optical media, liquid crystal displays, molecular electronics, and smart wetting surfaces. We report a novel synthetic route using simple protection chemistry to form azobenzene-functionalized SAMs on gold and present a mechanistic study of the molecular order, orientation, and conformation in these self-assembled monolayers (SAMs). We use vibrational sum-frequency generation (VSFG) to characterize their vibrational modes, molecular orientation, and photoisomerization kinetics. Trans-cis conformational change of azobenzene leads to the change in the orientation of the nitrile marker group detected by VSFG. Mixed SAMs of azobenzene and alkane thiols are used to investigate the steric hindrance effects. While 100% azobenzene SAMs do not exhibit photoisomerization due to tight packing, we observe reversible switching (>10 cycles) in mixed SAMs with only 34% and 50% of alkane thiol spacers. PMID:23924041

Valley, David T; Onstott, Matthew; Malyk, Sergey; Benderskii, Alexander V

2013-09-17

88

Reflectance spectroscopy of organic compounds: 1. Alkanes  

USGS Publications Warehouse

Reflectance spectra of the organic compounds comprising the alkane series are presented from the ultraviolet to midinfrared, 0.35 to 15.5 /??m. Alkanes are hydrocarbon molecules containing only single carbon-carbon bonds, and are found naturally on the Earth and in the atmospheres of the giant planets and Saturn's moon, Titan. This paper presents the spectral properties of the alkanes as the first in a series of papers to build a spectral database of organic compounds for use in remote sensing studies. Applications range from mapping the environment on the Earth, to the search for organic molecules and life in the solar system and throughout the. universe. We show that the spectral reflectance properties of organic compounds are rich, with major diagnostic spectral features throughout the spectral range studied. Little to no spectral change was observed as a function of temperature and only small shifts and changes in the width of absorption bands were observed between liquids and solids, making remote detection of spectral properties throughout the solar system simpler. Some high molecular weight organic compounds contain single-bonded carbon chains and have spectra similar to alkanes even ' when they fall into other families. Small spectral differences are often present allowing discrimination among some compounds, further illustrating the need to catalog spectral properties for accurate remote sensing identification with spectroscopy.

Clark, R. N.; Curchin, J. M.; Hoefen, T. M.; Swayze, G. A.

2009-01-01

89

Nitrated metalloporphyrins as catalysts for alkane oxidation  

DOEpatents

Alkanes are oxidized by contact with oxygen-containing gas in the presence as catalyst of a metalloporphyrin in which hydrogen atoms in the porphyrin ring have been replaced with one or more nitro groups. Hydrogen atoms in the porphyrin ring may also be substituted with halogen atoms.

Ellis, Jr., Paul E. (Downingtown, PA); Lyons, James E. (Wallingford, PA)

1992-01-01

90

Nitrated metalloporphyrins as catalysts for alkane oxidation  

DOEpatents

Compositions of matter comprising nitro-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has nitro groups attached thereto in meso and/or .beta.-pyrrolic positions.

Ellis, Jr., Paul E. (Downingtown, PA); Lyons, James E. (Wallingford, PA)

1994-01-01

91

Nitrated metalloporphyrins as catalysts for alkane oxidation  

DOEpatents

Compositions of matter comprising nitro-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has nitro groups attached thereto in meso and/or [beta]-pyrrolic positions.

Ellis, P.E. Jr.; Lyons, J.E.

1994-01-18

92

Modeling of Alkane Oxidation Using Constituents and Species  

NASA Technical Reports Server (NTRS)

It is currently not possible to perform simulations of turbulent reactive flows due in particular to complex chemistry, which may contain thousands of reactions and hundreds of species. This complex chemistry results in additional differential equations, making the numerical solution of the equation set computationally prohibitive. Reducing the chemical kinetics mathematical description is one of several important goals in turbulent reactive flow modeling. A chemical kinetics reduction model is proposed for alkane oxidation in air that is based on a parallel methodology to that used in turbulence modeling in the context of the Large Eddy Simulation. The objective of kinetic modeling is to predict the heat release and temperature evolution. This kinetic mechanism is valid over a pressure range from atmospheric to 60 bar, temperatures from 600 K to 2,500 K, and equivalence ratios from 0.125 to 8. This range encompasses diesel, HCCI, and gas-turbine engines, including cold ignition. A computationally efficient kinetic reduction has been proposed for alkanes that has been illustrated for n-heptane using the LLNL heptane mechanism. This model is consistent with turbulence modeling in that scales were first categorized into either those modeled or those computed as progress variables. Species were identified as being either light or heavy. The heavy species were decomposed into defined 13 constituents, and their total molar density was shown to evolve in a quasi-steady manner. The light species behave either in a quasi-steady or unsteady manner. The modeled scales are the total constituent molar density, Nc, and the molar density of the quasi-steady light species. The progress variables are the total constituent molar density rate evolution and the molar densities of the unsteady light species. The unsteady equations for the light species contain contributions of the type gain/loss rates from the heavy species that are modeled consistent with the developed mathematical forms for the total constituent molar density rate evolution; indeed, examination of these gain/loss rates shows that they also have a good quasi-steady behavior with a functional form resembling that of the constituent rate. This finding highlights the fact that the fitting technique provides a methodology that can be repeatedly used to obtain an accurate representation of full or skeletal kinetic models. Assuming success with the modified reduced model, the advantage of the modeling approach is clear. Because this model is based on the Nc rate rather than on that of individual heavy species, even if the number of species increases with increased carbon number in the alkane group, providing that the quasi-steady rate aspect persists, then extension of this model to higher alkanes should be conceptually straightforward, although it remains to be seen if the functional fits would remain valid or would require reconstruction.

Bellan, Jasette; Harstad, Kenneth G.

2010-01-01

93

Overcoming lability of extremely long alkane carbon-carbon bonds through dispersion forces.  

PubMed

Steric effects in chemistry are a consequence of the space required to accommodate the atoms and groups within a molecule, and are often thought to be dominated by repulsive forces arising from overlapping electron densities (Pauli repulsion). An appreciation of attractive interactions such as van der Waals forces (which include London dispersion forces) is necessary to understand chemical bonding and reactivity fully. This is evident from, for example, the strongly debated origin of the higher stability of branched alkanes relative to linear alkanes and the possibility of constructing hydrocarbons with extraordinarily long C-C single bonds through steric crowding. Although empirical bond distance/bond strength relationships have been established for C-C bonds (longer C-C bonds have smaller bond dissociation energies), these have no present theoretical basis. Nevertheless, these empirical considerations are fundamental to structural and energetic evaluations in chemistry, as summarized by Pauling as early as 1960 and confirmed more recently. Here we report the preparation of hydrocarbons with extremely long C-C bonds (up to 1.704?Å), the longest such bonds observed so far in alkanes. The prepared compounds are unexpectedly stable--noticeable decomposition occurs only above 200?°C. We prepared the alkanes by coupling nanometre-sized, diamond-like, highly rigid structures known as diamondoids. The extraordinary stability of the coupling products is due to overall attractive dispersion interactions between the intramolecular H•••H contact surfaces, as is evident from density functional theory computations with and without inclusion of dispersion corrections. PMID:21921913

Schreiner, Peter R; Chernish, Lesya V; Gunchenko, Pavel A; Tikhonchuk, Evgeniya Yu; Hausmann, Heike; Serafin, Michael; Schlecht, Sabine; Dahl, Jeremy E P; Carlson, Robert M K; Fokin, Andrey A

2011-09-15

94

Direct catalytic conversion of methane to acetic acid in an aqueous medium  

Microsoft Academic Search

ALTHOUGH methane is the most-abundant of alkanes, hazards of handling and distribution prevent known methane reserves1,2 from being fully exploited. Moreover, it is the least reactive alkane, so whereas selective conversion to more useful chemical products would be of great value, it is difficult to achieve. A useful target molecule for methane conversion is acetic acid, but existing approaches to

Minren Lin; Ayusman Sen

1994-01-01

95

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...  

Code of Federal Regulations, 2010 CFR

...alcohol, halogenated alkane, substituted epoxide, and amino compound (generic). 721...alcohol, halogenated alkane, substituted epoxide, and amino compound (generic). ...alcohol, halogenated alkane, substituted epoxide, and amino compound (PMN...

2010-07-01

96

n Alkane oxidation by a Pseudomonas  

Microsoft Academic Search

Summary  \\u000a \\u000a \\u000a \\u000a 1. \\u000a \\u000a APseudomonas oxidizingn-alkanes adaptively was used in experiments on hexane and heptane degradation.\\u000a \\u000a \\u000a \\u000a \\u000a 2. \\u000a \\u000a The R.Q. of heptane respiration by resting heptane-adapted cells was found to be 0.62. No appreciable accumulation of products\\u000a except CO2 and H2O seems to occur.\\u000a \\u000a \\u000a \\u000a \\u000a 3. \\u000a \\u000a Alkane oxidation proceeds by oxidation of one terminal methyl group, leading to the corresponding alcohols, aldehydes and\\u000a fatty

G. J. E. Thijsse; A. C. van der Linden

1958-01-01

97

Alkane biosynthesis by decarbonylation of aldehyde catalyzed by a microsomal preparation from Botryococcus braunii.  

PubMed

The final step in the synthesis of n-hydrocarbons in an animal and a higher plant involves enzymatic decarbonylation of aldehydes to the corresponding alkanes by loss of the carbonyl carbon. Whether such a novel reaction is involved in hydrocarbon synthesis in the colonial microalga, Botryococcus braunii, which is known to produce unusually high levels (up to 32% of dry weight) of n-C27, C29, and C31 alka-dienes and -trienes, was investigated. Dithioerythritol severely inhibited the incorporation of [1-14C]acetate into these hydrocarbons with accumulation of the label in the aldehyde fraction in the B. braunii cells. Microsomal preparations of the alga synthesized alkane from fatty acid and aldehyde in the absence of O2. Conversion of fatty acid to alkane required CoA, ATP, and NADH, whereas conversion of aldehyde to alkane did not require the addition of cofactors. That the alkane synthesis involves a decarbonylation was shown by the production of CO and heptadecane from octadecanal. CO was identified by adsorption to RhCl[(C6H6)3P]3. The decarbonylase had a pH optimum at 7.0, an apparent Km of 65 microM, a Vmax of 1.36 nmol/min/mg and was inhibited by the metal chelators EDTA, O-phenanthroline and 8-hydroxyquinoline. It was stimulated nearly threefold by 2 mM ascorbate and inhibited by the presence of O2. A partial (28%) retention of the aldehydic hydrogen of [1-3H]octadecanal in the heptadecane was observed; the remaining 3H was lost to H2O. The microsomal preparation also catalyzed the oxidation of 14CO to 14CO2, with a pH optimum of 7.0. This accounts for the nonstoichiometry of CO to heptadecane observed. In vivo studies with 14CO showed that the label was incorporated into metabolic products. This metabolic conversion of CO, not found in the previously examined hydrocarbon synthesizing systems, may be necessary for organisms that produce large amounts of hydrocarbons such as the present alga. The mechanism of the decarbonylation and the nature of the decarbonylase remain to be elucidated. PMID:1898004

Dennis, M W; Kolattukudy, P E

1991-06-01

98

Atmospheric pressure chemical ionization of alkanes, alkenes, and cycloalkanes  

Microsoft Academic Search

Normal and cyclic alkanes and alkenes form stable gas-phase ions in air at atmospheric pressure from 40 to 200°C when moisture\\u000a is below 1 ppm. Ionization of alkanes in a 63Ni source favored charge transfer over proton transfer through pathways involving [M?1]+ and [M?3]+ ions. Ion mobility spectra for alkanes showed sharp and symmetrical profiles while spectra for alkenes suggested

Suzanne Ehart Bell; Robert G. Ewing; Gary A. Eicernan; Zeev Karpas

1994-01-01

99

Plutonium(IV) and thorium(IV) hydrous polymer chemistry. [Conversion of hydrolye-bridged polymer links to oxygen-bridged linkages  

Microsoft Academic Search

The recent attention given to Pu(IV) polymers has warranted a review of plutonium and thorium hydrolysis chemistry with respect to the various experimental approaches and insights gained therein. Differing terminologies used in the experimental procedures have often confused the understanding of the chemical processes which occur between the first hydrolysis reaction of the tetravalent actinide and its final dehydration to

G. L. Johnson; L. M. Toth

1978-01-01

100

Chemistry of Tantalum Clusters in Solution and on SiO2 Supports: Analogies and Contrasts  

SciTech Connect

Tantalum clusters have been synthesized from Ta(CH{sub 2}Ph){sub 5} on the surface of porous fumed SiO{sub 2}. When these clusters are small, incorporating, on average, several Ta atoms, their chemistry is similar to that of molecular tantalum clusters (and other early transition-metal) clusters. For example, The Ta-Ta bonds in these small supported clusters have been characterized by extended X-ray absorption fine structure (EXAFS), IR, and UV-vis spectroscopy, being similar to those in molecular analogues. The redox reactions of the supported clusters, characterized by X-ray absorption near-edge structure, are analogous to those of early transition-metal clusters in solution. In contrast to the largest of these clusters in solution and in the solid state, those supported on SiO{sub 2} are raftlike, facilitating the substantial metal-support-oxygen bonding that is evident in the EXAFS spectra. Samples consisting of tantalum clusters on SiO{sub 2} catalyze alkane disproportionation and the conversion of methane with n-butane to give other alkanes, but catalytic properties of analogous clusters in solution have barely been explored.

Nemana,S.; Okamoto, N.; Browning, N.; Gates, B.

2007-01-01

101

Stimulation of Lipase Production During Bacterial Growth on Alkanes  

PubMed Central

Acinetobacter lwoffi strain O16, a facultative psychrophile, can grow on crude oil, hexadecane, octadecane, and most alkanes when tested at 20 but not at 30°C. Growth occurred on a few alkanes at 30°C but after a longer lag than at 20°C. Cells grown on alkanes as sole carbon sources had high levels of cell-bound lipase. In contrast, previous work has shown that those grown on complex medium produced cell-free lipase and those grown on defined medium without alkanes produced little or no lipase. Low concentrations of the detergent Triton X-100 caused the liberation of most of the lipase activity of alkane-grown cells and increased total lipase activity. When ethanol and hexadecane were both present in a mineral medium, diauxic growth occurred; until the ethanol was completely used up, hexadecane was not utilized, and the lipase activity was very low. When growth on hexadecane began, lipase activity increased, reaching a level 50- to 100-fold higher than that of cells growing on ethanol. A similar pattern of lipase formation and hexadecane utilization was observed with Pseudomonas aeruginosa. Whenever A. lwoffi and other bacteria degraded alkanes they exhibited substantial lipase activity. Not all bacteria that produced lipase, however, could attack alkanes. Bacteria that could not produce lipase did not attack alkanes. The results suggest that a correlation may exist between lipase formation and alkane utilization.

Breuil, Colette; Shindler, D. B.; Sijher, J. S.; Kushner, D. J.

1978-01-01

102

40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Mixture of hydrofluoro alkanes and hydrofluoro...Specific Chemical Substances § 721.4464 Mixture of hydrofluoro alkanes and hydrofluoro...substances identified generically as a mixture of hydrofluoro alkanes and...

2013-07-01

103

40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.  

Code of Federal Regulations, 2010 CFR

...of hydrofluoro alkanes and hydrofluoro alkene. 721.4464 Section 721.4464 ...of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical substance and significant...of hydrofluoro alkanes and hydrofluoro alkene (PMNs...

2009-07-01

104

40 CFR 721.4464 - Mixture of hydrofluoro alkanes and hydrofluoro alkene.  

Code of Federal Regulations, 2010 CFR

...of hydrofluoro alkanes and hydrofluoro alkene. 721.4464 Section 721.4464 ...of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical substance and significant...of hydrofluoro alkanes and hydrofluoro alkene (PMNs...

2010-07-01

105

Partial oxidation of light alkanes in transition-metal ion containing zeolites. Final technical report for the period September 15, 1986-September 14, 1989.  

National Technical Information Service (NTIS)

The objective of this research project was to provide the scientific foundation for the conversion of C(sub 1)-C(sub 3) alkanes to oxygenates, particularly alcohols, and to higher hydrocarbons. The objectives of these studies are (1) to prepare selected t...

J. Lin J. P. Lange K. Klier R. G. Herman

1990-01-01

106

Infrared spectra and structure of perfluoro-n-alkanes isolated in n-alkane matrices prepared by vapor deposition  

SciTech Connect

In this paper, low-temperature vapor deposition is used to make amorphous films of perfluoro-n-alkanes diluted in n-alkane matrices. Annealing these films leads to narrow infrared bands due to reduced intermolecular interaction between the perfluoro-n-alkane chains. Many intense bands in the 1100-1300 cm{sup -1} range, varying with chain length, are observed and assigned based on a simple coupled oscillator model. Isolated perfluoro-n-alkane chains are helical and highly ordered. 27 refs., 10 figs., 2 tabs.

Cho, H.G.; Strauss, H.L.; Snyder, R.G. [Univ. of California, Berkeley, CA (United States)

1992-06-25

107

Conformation of liquid N-alkanes.  

PubMed Central

The conformations of liquid n-alkanes have been studied using neutron scattering techniques to better understand the conformational forces present in membrane lipid interiors. We have studied hydrocarbon chains having lengths comparable to those found for esterified membrane lipid fatty acids, and find that the steric constraints of packing in the liquid state do not change the conformational distributions of hydrocarbon chains from those imposed by the intrachain forces present in the gas phase. It follows that the central region of membranes containing lipids in the disordered state should contain hydrocarbon chain conformations determined primarily by intrachain forces.

Goodsaid-Zalduondo, F; Engelman, D M

1981-01-01

108

Aggregation of n-alkanes in organic solvents  

Microsoft Academic Search

Normal alkanes are abundant in crude oils and diesel fuels. We have modelled diesel fuels by dissolving a realistic mixture of n-alkanes in toluene or nitrobenzene. The microstructures of those solutions have been comprehensively studied using the abosolutely calibrated SANS, SAXS and the dynamic light scattering techniques. The data have been collected for various paraffin concentrations in the temperature range

A. P. Radlinski; L. Barré; D. Espinat

1996-01-01

109

Vapor-particle partitioning of n-alkanes.  

National Technical Information Service (NTIS)

A mixed-phase partitioning model has been proposed to predict the distribution of n-alkanes between the vapor and particle phases in the atmosphere. n-Alkanes having terrestrial plant wax and petroleum origins are assumed to be associated with atmospheric...

P. V. Doskey

1994-01-01

110

Content of alkanes in two noncarbonaceous chondrites - Pavel and Goumoshnik  

Microsoft Academic Search

The analysis procedures and results of a determination of the alkanes and sulfur contents of the Pavel (P) and Goumoshnik (G) chondrites are reported. Samples were obtained with benzene extraction, treated with HCl acid, and examined with gas chromotography. Alkane carbon comprised 3.524 mg of every 10 gr of P, slightly less than the concentrations in G. Further carbon was

Kh. P. Ivanov; R. Zh. Stoianova

1984-01-01

111

Hydrogen isotopic composition of individual n-alkanes as an intrinsic tracer for bioremediation and source identification of petroleum contamination.  

PubMed

The isotopic signatures of crude oil hydrocarbons are potentially powerful intrinsic tracers to their origins and the processes by which the oils are modified in the environment. Stable carbon isotopic data are of limited use for studying petroleum contaminants because of the relatively small amount of isotopic fractionation that occurs during natural processes. Hydrogen isotopes, in contrast, are commonly fractionated to a much greater extent and as a result display larger variations in delta values. We studied the effect of in vitro aerobic biodegradation on the hydrogen isotopic composition of individual n-alkanes from crude oil. The isotopic analysis was conducted using gas chromatography-thermal conversion-isotope ratio mass spectrometry. In general, biodegradation rates decreased with increasing hydrocarbon chain length, consistent with previous studies. More importantly the n-alkanes that were degraded at the fastest rates (n-C15 to n-C18) also showed the largest overall isotopic fractionation (approximately 12-25 per thousand deuterium enrichment), suggesting that the lower molecular weight n-alkanes can be used to monitor in-situ bioremediation of crude oil contamination. The hydrogen isotopic compositions of the longer chain alkanes (n-C19 to n-C27) were relatively stable during biodegradation (<5%o overall deuterium enrichment), indicating that these compounds are effective tracers for oil-source identification studies. PMID:11878389

Pond, Kristy L; Huang, Yongsong; Wang, Yi; Kulpa, Charles F

2002-02-15

112

Spectroscopy of the A~ state of NO-alkane complexes (alkane = methane, ethane, propane, and n-butane)  

NASA Astrophysics Data System (ADS)

We have recorded (1+1) resonance-enhanced multiphoton ionization spectra of complexes formed between NO and the alkanes: CH4, C2H6, C3H8, and n-C4H10. The spectra correspond to the A~ <-- X~ transition, which is a NO-localized 3s <-- 2p?* transition. In line with previous work, the spectrum for NO-CH4 has well-defined structure, but this is only partially resolved for the other complexes. The spectra recorded in the NO+-alkane mass channels all show a slowly rising onset, followed by a sharp offset, which is associated with dissociation of NO-alkane, from which binding energies in the X~ and A~ states are deduced. Beyond this sharp offset, there is a further rise in signal, which is attributed to fragmentation of higher complexes, NO-(alkane)n. Analysis of these features allows binding energies for (NO-alkane) ... alkane to be estimated, and these suggest that in the NO-(alkane)2 complexes, the second alkane molecule is bound to the first, rather than to NO. Calculated structures for the 1:1 complexes are reported, as well as binding energies.

Tamé-Reyes, Victor M.; Gardner, Adrian M.; Harris, Joe P.; McDaniel, Jodie; Wright, Timothy G.

2012-12-01

113

Expanding the Product Profile of a Microbial Alkane Biosynthetic Pathway  

PubMed Central

Microbially produced alkanes are a new class of biofuels that closely match the chemical composition of petroleum-based fuels. Alkanes can be generated from the fatty acid biosynthetic pathway by the reduction of acyl-ACPs followed by decarbonylation of the resulting aldehydes. A current limitation of this pathway is the restricted product profile, which consists of n-alkanes of 13, 15, and 17 carbons in length. To expand the product profile, we incorporated a new part, FabH2 from Bacillus subtilis, an enzyme known to have a broader specificity profile for fatty acid initiation than the native FabH of Escherichia coli. When provided with the appropriate substrate, the addition of FabH2 resulted in an altered alkane product profile in which significant levels of n-alkanes of 14 and 16 carbons in length are produced. The production of even chain length alkanes represents initial steps toward the expansion of this recently discovered microbial alkane production pathway to synthesize complex fuels. This work was conceived and performed as part of the 2011 University of Washington international Genetically Engineered Machines (iGEM) project.

Harger, Matthew; Zheng, Lei; Moon, Austin; Ager, Casey; An, Ju Hye; Choe, Chris; Lai, Yi-Ling; Mo, Benjamin; Zong, David; Smith, Matthew D.; Egbert, Robert G.; Mills, Jeremy H.; Baker, David; Pultz, Ingrid Swanson; Siegel, Justin B.

2013-01-01

114

Kinetic study of asphaltene dissolution in amphiphile/alkane solutions  

SciTech Connect

The kinetics of dissolution of pentane-insoluble solid asphaltene precipitates by amphiphile/alkane solutions were investigated using a differential reactor flow system. Two amphiphiles, dodecylbenzenesulfonic acid and nonylphenol, and five alkane solvents, ranging from hexane to hexadecane, were used. Results showed that the rate of asphaltene dissolution in amphiphile/alkane fluids could be approximated with a first-order kinetics with respect to the undissolved asphaltene mass in solution. The specific dissolution rate constant, k, varied with the concentration of amphiphiles, the type of alkane solvents, the temperature, and the fluid flow rate. The rate of asphaltene dissolution displayed a Langmuir-Hinshelwood kinetics with respect to the concentration of amphiphiles. Increasing the temperature of amphiphile/alkane fluids also enhanced the rate of asphaltene dissolution. The apparent activation energy for asphaltene dissolution was approximated to be 4--7 kcal/mol. The rate of asphaltene dissolution was also greater in amphiphile solutions containing lighter alkanes, such as hexane, with lower viscosities. These trends suggest that both surface reaction and mass transfer processes are important to the rate of asphaltene dissolution in amphiphile/alkane fluids.

Permsukarome, P. [Chulalongkorn Univ., Bangkok (Thailand). Petrochemical Coll.] [Chulalongkorn Univ., Bangkok (Thailand). Petrochemical Coll.; Chang, C.; Fogler, H.S. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering] [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering

1997-09-01

115

Exploratory study of coal-conversion chemistry. Quarterly report No. 3, November 19, 1981-February 18, 1982. [Dihydronaphthalene, 1,2'-dinaphthylmethane, methoxynaphthalene diphenyl ether  

SciTech Connect

Work in Task A has provided additional data on the rate and mechanisms of radical-induced cleavage of strong C-C and C-0 bonds in coal structures. This work has shown that even resonance-stabilized radicals, which form relatively weak C-C bonds, can displace other resonance-stabilized radicals from methylene-bridged coal structures. Kinetic studies reveal that either the self-disproportionation of 1,2-dihydronaphthalene is much faster than previously reported or that the 1,2-dihydronaphthalene-tetralin disproportionation is much less important as a radical initiation process than thermochemical estimates had suggested. 1,2'-Dinaphthylmethane undergoes radical-induced CH/sub 2/-Ar bond scission ten times faster than diphenyl ether. This factor is shown to be consistent with the thermochemistry of displacement by tetralyl radical. In Task B we studied CO/H/sub 2/O conversion of a second, high volatile bituminous coal, PSOC-233. We found that, as with PSOC-026, the initial pH did affect the conversion rate, increasing with higher pH. We also conducted experiments with several oxygen-containing model compounds in CO/D/sub 2/O at 400/sup 0/C for 20 min. We had shown earlier in preliminary control experiments that simple aromatics, such as toluene, did not incorporate deuterium under these conditions. This quarter we found that anisole (Ph-O-CH/sub 3/) was converted to several products, with benzene as the most prominent. About 60% of the anisole was recovered in several experiments with mass balances at about 85%. There was a net incorporation of deuterium in the product benzene. The corresponding conversion in tetralin under the same conditions was two orders of magnitude slower and yielded phenol as the major product. We conclude that in the aqueous medium a chain process can occur that yields phenyl radical, which can then receive protium from a starting anisole or deuterium from the mineral medium.

Ross, D.S.; McMillen, D.F.; Ogier, W.C.; Bunnell, R.; Hum, G.P.

1982-03-01

116

Thermodynamic Properties of Alkanes in Confined Geometries  

NASA Astrophysics Data System (ADS)

Reported are the results of two related investigations. The first is a theoretical study of the thermal response of a model differential scanning calorimeter (DSC) yielding insights into proper techniques for sample preparation, instrument calibration, and interpretation of phase transition data. This is followed by a calorimetric study of the melting and freezing behavior of cyclohexane ( rm C_6H_{12}), cyclooctane (rm C_8H_{16}), and n-octane (rm C_8H_{18 }), confined within the pore spaces of a series of porous silica glasses with mean pore radii r between 4.1 +/- 0.3 and 64 +/- 5 nm. The melting and freezing temperatures and latent heats of the pore alkanes were found to be increasingly depressed from the bulk values with decreasing pore size r. Unlike previous studies of phase transitions of confined organic substances, we have observed melting temperature depressions which are stronger than r^{ -1}. These temperature depressions can be expressed by the empirical cluster equation rm T_{m} = T_{o} - A/(r - r_{rm o}). The latent heats were found to vary approximately linearly with the inverse pore radius. The transition data from incompletely filled pores indicate that the alkanes are not layering the pore walls evenly, but are gathering as plugs at the pore necks. Studies using glasses in which the silica surface was modified using a standard derivatization technique suggest that the replacement ligands are not forming a complete monolayer. We have also observed cyclooctane supercools by 10-15 K below the expected freezing point, both in bulk and confined within the porous glass.

Sheehan, Joseph F., III

117

Involvement of an Alkane Hydroxylase System of Gordonia sp. Strain SoCg in Degradation of Solid n-Alkanes?  

PubMed Central

Enzymes involved in oxidation of long-chain n-alkanes are still not well known, especially those in Gram-positive bacteria. This work describes the alkane degradation system of the n-alkane degrader actinobacterium Gordonia sp. strain SoCg, which is able to grow on n-alkanes from dodecane (C12) to hexatriacontane (C36) as the sole C source. SoCg harbors in its chromosome a single alk locus carrying six open reading frames (ORFs), which shows 78 to 79% identity with the alkane hydroxylase (AH)-encoding systems of other alkane-degrading actinobacteria. Quantitative reverse transcription-PCR showed that the genes encoding AlkB (alkane 1-monooxygenase), RubA3 (rubredoxin), RubA4 (rubredoxin), and RubB (rubredoxin reductase) were induced by both n-hexadecane and n-triacontane, which were chosen as representative long-chain liquid and solid n-alkane molecules, respectively. Biotransformation of n-hexadecane into the corresponding 1-hexadecanol was detected by solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME/GC-MS) analysis. The Gordonia SoCg alkB was heterologously expressed in Escherichia coli BL21 and in Streptomyces coelicolor M145, and both hosts acquired the ability to transform n-hexadecane into 1-hexadecanol, but the corresponding long-chain alcohol was never detected on n-triacontane. However, the recombinant S. coelicolor M145-AH, expressing the Gordonia alkB gene, was able to grow on n-triacontane as the sole C source. A SoCg alkB disruption mutant that is completely unable to grow on n-triacontane was obtained, demonstrating the role of an AlkB-type AH system in degradation of solid n-alkanes.

Lo Piccolo, Luca; De Pasquale, Claudio; Fodale, Roberta; Puglia, Anna Maria; Quatrini, Paola

2011-01-01

118

Involvement of an alkane hydroxylase system of Gordonia sp. strain SoCg in degradation of solid n-alkanes.  

PubMed

Enzymes involved in oxidation of long-chain n-alkanes are still not well known, especially those in gram-positive bacteria. This work describes the alkane degradation system of the n-alkane degrader actinobacterium Gordonia sp. strain SoCg, which is able to grow on n-alkanes from dodecane (C(12)) to hexatriacontane (C(36)) as the sole C source. SoCg harbors in its chromosome a single alk locus carrying six open reading frames (ORFs), which shows 78 to 79% identity with the alkane hydroxylase (AH)-encoding systems of other alkane-degrading actinobacteria. Quantitative reverse transcription-PCR showed that the genes encoding AlkB (alkane 1-monooxygenase), RubA3 (rubredoxin), RubA4 (rubredoxin), and RubB (rubredoxin reductase) were induced by both n-hexadecane and n-triacontane, which were chosen as representative long-chain liquid and solid n-alkane molecules, respectively. Biotransformation of n-hexadecane into the corresponding 1-hexadecanol was detected by solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME/GC-MS) analysis. The Gordonia SoCg alkB was heterologously expressed in Escherichia coli BL21 and in Streptomyces coelicolor M145, and both hosts acquired the ability to transform n-hexadecane into 1-hexadecanol, but the corresponding long-chain alcohol was never detected on n-triacontane. However, the recombinant S. coelicolor M145-AH, expressing the Gordonia alkB gene, was able to grow on n-triacontane as the sole C source. A SoCg alkB disruption mutant that is completely unable to grow on n-triacontane was obtained, demonstrating the role of an AlkB-type AH system in degradation of solid n-alkanes. PMID:21183636

Lo Piccolo, Luca; De Pasquale, Claudio; Fodale, Roberta; Puglia, Anna Maria; Quatrini, Paola

2011-02-01

119

Reversible Interconversion between Alkanes, Alkenes, Alcohols and Ketones under Hydrothermal Conditions  

NASA Astrophysics Data System (ADS)

Many transformation reactions involving hydrocarbons that occur in deep sedimentary systems and determine petroleum compositions occur in the presence of H2O. Hydrothermal transformations of organic material are thought to provide carbon sources for microbes in deep ocean sediments. Hydrothermal conditions may also mimic the conditions where life developed on an early Earth. Nevertheless, much remains to be learned about the mechanisms of hydrothermal organic reactions, including ways in which various reactions are interrelated and how reactions compete with each other. It can be argued that metastable equilibrium states develop over geological timescales and at geochemically relevant temperatures, suggesting that reactions occur under thermodynamic rather than kinetic control. The extent to which reactions are reversible, and how product distributions are determined, are primary tests of the metastable equilibrium model. Seewald (2001, GCA 65, 1641-1664) showed that under hydrothermal conditions and in the presence of a redox buffer, simple alkanes and alkenes undergo oxidation, reduction, and hydration reactions. He proposed a reaction scheme where alkanes interconvert with alkenes, followed by stepwise hydration of alkenes to alcohols, oxidation to ketones, and finally conversion to carboxylic acids, which can undergo decarboxylation. Here we describe experiments that further develop the scope of these functional group interconversions, determine relative reaction kinetics, and provide insight into competing reactions. Hydrothermal experiments were performed at 300°C and 100 MPa in gold capsules for 12 to 144 hours. The reactant structures were based on cyclohexane with one and two methyl groups that served as regio- and stereochemical markers for the reactions. Starting with the alkanes, the observed products include the corresponding alkenes, alcohols, ketones and enones, in support of the Seewald reaction scheme. Our experiments add a branch to this scheme with the addition of methylbenzene products that are observed in a competing reaction, formed by dehydrogenation of the alkenes presumably via diene structures. The functional group interconversions were found to be completely reversible, with the exception of the methylbenzenes. Starting with these compounds gave no conversion to any other products. Significantly, we found that no carboxylic acids are formed, even though other products derived via carbon-carbon bond cleavage are observed. The experiments allow the stabilities and reactivities of the various functional groups to be inferred under these experimental conditions. The dienes are the least stable, followed by the alcohols, then the alkenes, the ketones, and finally the alkanes. The aromatic methylbenzenes are the least reactive and most stable under the experimental conditions. Therefore, using our reaction scheme and the relative reaction rate information, starting with any of the functional groups the direction(s) and most likely major products can be predicted.

Shipp, J.; Hartnett, H. E.; Gould, I. R.; Shock, E.; Williams, L. B.

2011-12-01

120

DITERMINAL OXIDATION OF LONG-CHAIN ALKANES BY BACTERIA1  

PubMed Central

Kester, A. S. (The University of Texas, Austin) and J. W. Foster. Diterminal oxidation of long-chain alkanes by bacteria. J. Bacteriol. 85:859–869. 1963.—A corynebacterial organism capable of growing in mineral salts with individual pure alkanes as carbon sources produces a series of acids from the C10-C14 alkanes. They have been isolated in pure form and identified as monoic, ?-hydroxy monoic, and dioic acids containing the same number of carbon atoms as the substrate alkane. Oxidation took place at both terminal methyl groups—“diterminal oxidation.” Appropriate labeling experiments indicate that omega oxidation of fatty acids occurs in this organism and that an oxygenation with O2 occurs. Images

Kester, A. S.; Foster, J. W.

1963-01-01

121

Diverse alkane hydroxylase genes in microorganisms and environments  

PubMed Central

AlkB and CYP153 are important alkane hydroxylases responsible for aerobic alkane degradation in bioremediation of oil-polluted environments and microbial enhanced oil recovery. Since their distribution in nature is not clear, we made the investigation among thus-far sequenced 3,979 microbial genomes and 137 metagenomes from terrestrial, freshwater, and marine environments. Hundreds of diverse alkB and CYP153 genes including many novel ones were found in bacterial genomes, whereas none were found in archaeal genomes. Moreover, these genes were detected with different distributional patterns in the terrestrial, freshwater, and marine metagenomes. Hints for horizontal gene transfer, gene duplication, and gene fusion were found, which together are likely responsible for diversifying the alkB and CYP153 genes adapt to the ubiquitous distribution of different alkanes in nature. In addition, different distributions of these genes between bacterial genomes and metagenomes suggested the potentially important roles of unknown or less common alkane degraders in nature.

Nie, Yong; Chi, Chang-Qiao; Fang, Hui; Liang, Jie-Liang; Lu, She-Lian; Lai, Guo-Li; Tang, Yue-Qin; Wu, Xiao-Lei

2014-01-01

122

Alkane-induced edema formation and cutaneous barrier dysfunction  

Microsoft Academic Search

Certain mineral oils and hydrocarbons require repeated topical application to cause irritation. A structure activity relationship of pure n-alkanes was undertaken in a mouse ear edema model to investigate the mechanism of cumulative irritancy. Alkanes were applied twice daily over a 4-day period. Dodecane was found to be non-irritating, while tridecane elicited a response only at 96 h. Tetradecane was

S. J. Moloney; J. J. Teal

1988-01-01

123

Seed oil alkanes from leguminosae species: Evencarbon number preference  

Microsoft Academic Search

The presence of unusual low Mr and even-carbon numbered n-alkanes in seed oils of Leguminosae suggests that the inner tissue conditions could lead to a change in some enzyme systems.GC and GC-MS have been used to study the distribution of n-alkanes in the seed oil from 60 samples of 43 Leguminosae species. The occurrence of high percentages of low Mr,

Alicia L. Lamarque; Renée H. Fortunato; Carlos A. Guzmán

1998-01-01

124

Oxidation of long-chain alkanes by Acetobacter rancens  

Microsoft Academic Search

The degradation of hexadecane and tetradecane by Acetobacter rancens CCM 1774 was investigated. It was found that this strain is able to grow to a limited extent on hexadecane as a carbon source. The occurrence of n-alkanoic acids and alcohols among the reaction products of growing as well as resting cells indicates a monoterminal degradation of long-chain alkanes. Both alkane-grown

Rolf Hommel; Hans-Peter Kleber

1984-01-01

125

Dielectric constant of liquid alkanes and hydrocarbon mixtures  

Microsoft Academic Search

The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature

A. D. Sen; V. G. Anicich; T. Arakelian

1992-01-01

126

Detailed chemical kinetic models for large n-alkanes and iso-alkanes found in conventional and FT diesel fuels  

Microsoft Academic Search

Detailed chemical kinetic models are needed to simulate the combustion of current and future transportation fuels. These models should represent the various chemical classes in these fuels. Conventional diesel fuels are composed of n-alkanes, iso-alkanes, cycloalkanes and aromatics (Farrell et al. 2007). For future fuels, there is a renewed interest in Fischer-Tropsch (F-T) processes which can be used to synthesize

C K Westbrook; W J Pitz; H J Curran; M Mehl

2008-01-01

127

Selective hydroxylation of alkanes by an extracellular fungal peroxygenase  

PubMed Central

Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H2O2 as a cosubstrate. Little is known about the physiological role or the catalytic mechanism of these enzymes. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H2O2-dependent hydroxylation of linear alkanes at the 2-position and 3-position with high efficiency, as well as the regioselective monooxygenation of branched and cyclic alkanes. Experiments with n-heptane and n-octane showed that the hydroxylation proceeded with complete stereoselectivity for the (R)-enantiomer of the corresponding 3-alcohol. Investigations with a number of model substrates provided information about the route of alkane hydroxylation: (a) the hydroxylation of cyclohexane mediated by H218O2 resulted in complete incorporation of 18O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D7 showed a large intramolecular deuterium isotope effect [(kH/kD)obs] of 16.0 ± 1.0 for 2-hexanol and 8.9 ± 0.9 for 3-hexanol; and (c) the hydroxylation of the radical clock norcarane led to an estimated radical lifetime of 9.4 ps and an oxygen rebound rate of 1.06 × 1011 s?1. These results point to a hydrogen abstraction and oxygen rebound mechanism for alkane hydroxylation. The peroxygenase appeared to lack activity on long-chain alkanes (> C16) and highly branched alkanes (e.g. tetramethylpentane), but otherwise exhibited a broad substrate range. It may accordingly have a role in the bioconversion of natural and anthropogenic alkane-containing structures (including alkyl chains of complex biomaterials) in soils, plant litter, and wood.

Peter, Sebastian; Kinne, Matthias; Wang, Xiaoshi; Ullrich, Rene; Kayser, Gernot; Groves, John T.; Hofrichter, Martin

2013-01-01

128

One-step hydrotreatment of vegetable oil to produce high quality diesel-range alkanes.  

PubMed

A one-step hydrotreatment of vegetable oil combining deoxygenation and isomerization to directly produce low cloud point, high quality diesel is devised. The Pt/zeolite bifunctional catalysts prepared by using SAPO-11 and ZSM-22 zeolites as supports are used in this process. Catalytic reactions are conducted in a fixed-bed reactor under a hydrogen atmosphere. Over the bifunctional catalyst, 100 % conversion of soybean oil is obtained at 357 °C, 4 MPa, and 1 h(-1), and 80 % organic liquid yield is achieved, which is close to the maximum theoretical liquid yield. In the organic products, the alkanes selectivity is 100 % with an i-alkanes selectivity above 63 %. NH(3)-temperature programmed desorption (TPD), pyridine IR spectroscopy, and other characterization techniques are used to study the effect of the support acidity on the reaction pathway. Over the Pt/zeolite bifunctional catalyst with less strong Lewis acid sites, the reaction proceeds via the decarboxylation plus decarbonylation pathway. This one-step method provides a new strategy to produce low cloud point, high quality diesel from biomass feedstock in a more economic and attractive way. PMID:22764086

Wang, Congxin; Tian, Zhijian; Wang, Lei; Xu, Renshun; Liu, Qianhe; Qu, Wei; Ma, Huaijun; Wang, Bingchun

2012-10-01

129

Detailed chemical kinetic models for large n-alkanes and iso-alkanes found in conventional and F-T diesel fuels  

SciTech Connect

Detailed chemical kinetic models are needed to simulate the combustion of current and future transportation fuels. These models should represent the various chemical classes in these fuels. Conventional diesel fuels are composed of n-alkanes, iso-alkanes, cycloalkanes and aromatics (Farrell et al. 2007). For future fuels, there is a renewed interest in Fischer-Tropsch (F-T) processes which can be used to synthesize diesel and other transportation fuels from biomass, coal and natural gas. F-T diesel fuels are expected to be similar to F-T jet fuels which are commonly comprised of iso-alkanes with some n-alkanes (Smith and Bruno, 2008). Thus, n-alkanes and iso-alkanes are common chemical classes in these conventional and future fuels. This paper reports on the development of chemical kinetic models of large n-alkanes and iso-alkanes to represent these chemical classes in conventional and future fuels. Two large iso-alkanes are 2,2,4,4,6,8,8-heptamethylnonane, which is a primary reference fuel for diesel, and isooctane, a primary reference fuel for gasoline. Other iso-alkanes are branched alkanes with a single methyl side chain, typical of most F-T fuels. The chemical kinetic models are then used to predict the effect of these fuel components on ignition characteristics under conditions found in internal combustion engines.

Westbrook, C K; Pitz, W J; Curran, H J; Mehl, M

2008-12-15

130

Enzymes involved in the anaerobic oxidation of n-alkanes: from methane to long-chain paraffins  

PubMed Central

Anaerobic microorganisms play key roles in the biogeochemical cycling of methane and non-methane alkanes. To date, there appear to be at least three proposed mechanisms of anaerobic methane oxidation (AOM). The first pathway is mediated by consortia of archaeal anaerobic methane oxidizers and sulfate-reducing bacteria (SRB) via “reverse methanogenesis” and is catalyzed by a homolog of methyl-coenzyme M reductase. The second pathway is also mediated by anaerobic methane oxidizers and SRB, wherein the archaeal members catalyze both methane oxidation and sulfate reduction and zero-valent sulfur is a key intermediate. The third AOM mechanism is a nitrite-dependent, “intra-aerobic” pathway described for the denitrifying bacterium, ‘Candidatus Methylomirabilis oxyfera.’ It is hypothesized that AOM proceeds via reduction of nitrite to nitric oxide, followed by the conversion of two nitric oxide molecules to dinitrogen and molecular oxygen. The latter can be used to functionalize the methane via a particulate methane monooxygenase. With respect to non-methane alkanes, there also appear to be novel mechanisms of activation. The most well-described pathway is the addition of non-methane alkanes across the double bond of fumarate to form alkyl-substituted succinates via the putative glycyl radical enzyme, alkylsuccinate synthase (also known as methylalkylsuccinate synthase). Other proposed mechanisms include anaerobic hydroxylation via ethylbenzene dehydrogenase-like enzymes and an “intra-aerobic” denitrification pathway similar to that described for ‘Methylomirabilis oxyfera.’

Callaghan, Amy V.

2013-01-01

131

Surface freezing in binary alkane-alcohol mixtures  

SciTech Connect

Surface freezing was detected and studied in mixtures of alcohol and alkane molecules, using surface tensiometry and surface-specific x-ray scattering methods. Considering that surface freezing in pure alkanes forms an ordered monolayer and in alcohols it forms an ordered bilayer, the length mismatch repulsion was minimized by varying the carbon number of the alkane component around 2n, where n is the carbon number of the alcohol molecule. A solutionlike behavior was found for all mixtures, where the ideal liquid mixture phase-separates upon freezing both in the bulk and the surface. The solid exhibits a herringbone crystalline phase below an alkane mole fraction {phi}{sub t}{approx_equal}0.8 and a rotator phase above it. The surface frozen film below {phi}{sub t} is an alkane monolayer exhibiting a next-nearest neighbor molecular tilt of a composition-dependent magnitude. Above {phi}{sub t}, no diffraction peaks were observed. This could be explained by the intrinsically shorter-range order of the rotator phase and a possible proliferation of defects.

Ofer, E.; Sloutskin, E.; Tamam, L.; Deutsch, M. [Department of Physics, Bar-Ilan University, Ramat-Gan 52900 (Israel); Ocko, B. M. [Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2006-08-15

132

Alkane inducible proteins in Geobacillus thermoleovorans B23  

PubMed Central

Background Initial step of ?-oxidation is catalyzed by acyl-CoA dehydrogenase in prokaryotes and mitochondria, while acyl-CoA oxidase primarily functions in the peroxisomes of eukaryotes. Oxidase reaction accompanies emission of toxic by-product reactive oxygen molecules including superoxide anion, and superoxide dismutase and catalase activities are essential to detoxify them in the peroxisomes. Although there is an argument about whether primitive life was born and evolved under high temperature conditions, thermophilic archaea apparently share living systems with both bacteria and eukaryotes. We hypothesized that alkane degradation pathways in thermophilic microorganisms could be premature and useful to understand their evolution. Results An extremely thermophilic and alkane degrading Geobacillus thermoleovorans B23 was previously isolated from a deep subsurface oil reservoir in Japan. In the present study, we identified novel membrane proteins (P16, P21) and superoxide dismutase (P24) whose production levels were significantly increased upon alkane degradation. Unlike other bacteria acyl-CoA oxidase and catalase activities were also increased in strain B23 by addition of alkane. Conclusion We first suggested that peroxisomal ?-oxidation system exists in bacteria. This eukaryotic-type alkane degradation pathway in thermophilic bacterial cells might be a vestige of primitive living cell systems that had evolved into eukaryotes.

2009-01-01

133

Conversion Contraption  

NSDL National Science Digital Library

It's show time for eighth grade physical science students after a week of designing, building, and refining Conversion Contraptions. The contraptions are fun combinations of moving parts that use many forms of energy and many conversions of energy. It's t

Chahrour, Janet

2000-09-01

134

Microsecond Catalytic Partial Oxidation of Alkanes  

Microsoft Academic Search

A single layer of woven platinum-10 percent rhodium gauze was used as a catalyst for the partial oxidation of ethane, propane, n-butane, and isobutane. This configuration produced oxygen conversions of equal to or greater than 90 percent and had high selectivity to olefins and oxygenated hydrocarbons at contact times as short as 10 microseconds at atmospheric pressure. This reactor operates

Duane A. Goetsch; Lanny D. Schmidt

1996-01-01

135

Microsecond catalytic partial oxidation of alkanes  

Microsoft Academic Search

A single layer of woven platinum-10 percent rhodium gauze was used as a catalyst for the partial oxidation of ethane, propane, n-butane, and isobutane. This configuration produced oxygen conversions of equal to or greater than 90 percent and had high selectivity to olefins and oxygenated hydrocarbons at contact times as short as 10 microseconds at atmospheric pressure. This reactor operates

D. A. Goetsch; L. D. Schmidt

1996-01-01

136

Structural and Kinetic Studies of Novel Cytochrome P450 Small-Alkane Hydroxylases.  

National Technical Information Service (NTIS)

The goals of this project are to investigate (1) the kinetics and stabilities of engineered cytochrome P450 (P450) small alkane hydroxylases and their evolutionary intermediates, (2) the structural basis for catalytic proficiency on small alkanes of these...

F. H. Arnold

2012-01-01

137

BIODEGRADATION AND GAS-EXCHANGE OF GASEOUS ALKANES IN MODEL ESTUARINE ECOSYSTEMS  

EPA Science Inventory

Gas exchange-biodegradation experiments conducted in model estuarine ecosystems indicate that the ease of degradation of gaseious normal alkanes increases with chain length. The behavior of gaseous perhalogenated alkanes can be explained by gas exchange alone with no degradation....

138

40 CFR 721.785 - Halogenated alkane aromatic compound (generic name).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Halogenated alkane aromatic compound (generic name). 721.785 Section 721.785 Protection of Environment... § 721.785 Halogenated alkane aromatic compound (generic name). (a) Chemical substance and significant new uses...

2013-07-01

139

Iron-phthalocyanine immobilized on activated carbon black: A selective catalyst for alkane oxidation  

SciTech Connect

Carbon black is tested as a support for iron-phthalocyanine within the frame of the oxidation of hydrocarbons with t-butyl-hydroperoxide as oxygen donor. The increased hydrophobicity of the carrier surface, with respect to zeolite Y, changes the adsorption behavior of the components in the reaction mixture towards the alkane. A major improvement in the oxidation conversion and efficiency of cyclohexane has been established. Furthermore, the kinetic isotope effect and the reactivity order of secondary and tertiary carbon atoms measured with adamantane provide evidence for an {open_quotes}oxygen rebound{close_quotes} reaction mechanism, a non-free-radical oxidation pathway where the metallo-complex is responsible for the hydrogen abstraction. 40 refs., 7 figs., 2 tabs.

Parton, R.F.; Neys, P.E.; Jacobs, P.A. [Katholieke Universiteit Leuven, Heverlee (Belgium)] [and others] [Katholieke Universiteit Leuven, Heverlee (Belgium); and others

1996-12-01

140

Low-temperature dielectric absorption of polypropylene containing light alkanes  

NASA Astrophysics Data System (ADS)

We have measured the enhancement of the 1.2 kHz dielectric loss of polypropylene films due to the presence of propane, butane, pentane, hexane, heptane, decane, heptadecane, four branched alkanes, three cycloalkanes and various more strongly dipolar additives and additives with more rigid molecules for comparison. Each alkane except heptadecane caused at least one loss peak between 4 and 105 K. Butane, pentane, hexane, heptane and 2-methylbutane each caused a peak near 80 K attributed to ethyl rotations. The peak temperature increased regularly with chain length (decane, 95 K), an effect we attribute to a progressive changing intermolecular environment. Each of the other alkanes exhibited a single loss peak (in the case of propane, near 25 K) which we attribute to molecular reorientations, as also a butane peak near 40 K.

Gilchrist, John le G.; Vij, Jagdish K.

1986-07-01

141

Online Conversion  

NSDL National Science Digital Library

Need to convert joules to kilocalories? A rood to a square mile? 100 weight to stones? How about your age in dog years? You can do all of these conversions and over 8,000 more at Online Conversion. Conversions are organized by type (temperature, length, cooking, etc.), and each conversion page includes numerous options. Quick links to other conversions are also provided on each page so users don't have to return to the main page. Simply put, a very handy and easy-to-use site that belongs in the reference section of any user's bookmarks.

142

Biodegradation of variable-chain-length alkanes at low temperatures by a psychrotrophic Rhodococcus sp  

Microsoft Academic Search

The psychrotroph Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5 C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane.

LYLE G. WHYTE; JALAL HAWARI; EDWARD ZHOU; LUC BOURBONNIERE; C. W. Greer; W. E. Inniss

1998-01-01

143

Assimilation of chlorinated alkanes by hydrocarbon-utilizing fungi  

SciTech Connect

The fatty acid compositions of two filamentous fungi (Cunninghamella elegans and Penicillium zonatum) and a yeast (Candida lipolytica) were determined after the organisms were grown on 1-chlorohexadecane or 1-chlorooctadecane. These organisms utilized the chlorinated alkanes as sole sources of carbon and energy. Analyses of the fatty acids present after growth on the chlorinated alkanes indicated that 60 to 70% of the total fatty acids in C. elegans were chlorinated. Approximately 50% of the fatty acids in C. lipolytica were also chlorinated. P. zonatum contained 20% 1-chlorohexadecanoic acid after growth on either substrate but did not incorporate C/sub 18/ chlorinated fatty acids.

Murphy, G.L.; Perry, J.J.

1984-12-01

144

Assimilation of chlorinated alkanes by hydrocarbon-utilizing fungi.  

PubMed Central

The fatty acid compositions of two filamentous fungi (Cunninghamella elegans and Penicillium zonatum) and a yeast (Candida lipolytica) were determined after the organisms were grown on 1-chlorohexadecane or 1-chlorooctadecane. These organisms utilized the chlorinated alkanes as sole sources of carbon and energy. Analyses of the fatty acids present after growth on the chlorinated alkanes indicated that 60 to 70% of the total fatty acids in C. elegans were chlorinated. Approximately 50% of the fatty acids in C. lipolytica were also chlorinated. P. zonatum contained 20% 1-chlorohexadecanoic acid after growth on either substrate but did not incorporate C18 chlorinated fatty acids.

Murphy, G L; Perry, J J

1984-01-01

145

A nonequilibrium molecular dynamics study of the rheology of alkanes  

SciTech Connect

We examine the rheological properties of four different alkanes: n-decane, n-hexadecane, n-tetracosane, and squalane. Simulations of Couette flow are performed for a range of shear rates with 100 molecules in each case using a replicated data version of our code. Number of interaction sites ranges from 1000 to 3000. We have performed extremely long simulations required to obtain acceptable statistics at low shear rates. The alkanes show a transition from non-Newtonian to Newtonian behavior as the shear rate decreases to low values. 1 tab, 1 fig, 17 refs.

Gupta, S.A.; Cui, S.T.; Cummings, P.T.; Cochran, H.D. [Tennessee Univ., Knoxville, TN (United States). Dept. of Chemical Engineering]|[Oak Ridge National Lab., TN (United States)

1996-05-01

146

Pressure dependence of the density of n-alkanes  

SciTech Connect

Accurate density data for n-alkanes are essential for the measurement of interfacial tension of liquid-liquid systems as a function of pressure. The variation of density with pressure for three n-alkanes, n-hexane, n-heptane, and n-decane, was measured at 21.2[degrees]C and pressures ranging from 0.1 to 35 MPa with a digital density meter. The Tait equation of the form ([rho] [minus] [rho][sub 0])/[rho] = C log[(B + P)/(B + P[sub 0])] was used to represent the experimental data. 20 refs., 2 figs., 4 tabs.

Susnar, S.S.; Budziak, C.J.; Neumann, A.W. (Univ. of Toronto, Ontario (Canada)); Hamza, H.A. (CANMET, Devon, Alberta (Canada))

1992-05-01

147

Chemistry Notes.  

ERIC Educational Resources Information Center

Describes experiments, demonstrations, activities and ideas relating to various fields of chemistry to be used in chemistry courses of secondary schools. Three experiments concerning differential thermal analysis are among these notes presented. (HM)

School Science Review, 1978

1978-01-01

148

Chemistry Notes  

ERIC Educational Resources Information Center

Described are eight chemistry experiments and demonstrations applicable to introductory chemistry courses. Activities include: measure of lattice enthalpy, Le Chatelier's principle, decarboxylation of soap, use of pocket calculators in pH measurement, and making nylon. (SL)

School Science Review, 1976

1976-01-01

149

Chemistry Notes  

ERIC Educational Resources Information Center

Thirteen ideas are presented that may be of use to chemistry teachers. Topics covered include vitamin C, industrial chemistry, electrical conductivity, electrolysis, alkali metals, vibration modes infra-red, dynamic equilibrium, and some new demonstrations in gaseous combinations. (PS)

School Science Review, 1972

1972-01-01

150

Comparative Study of the Effects of Several n-Alkanes on Phospholipid Hexagonal Phases  

Microsoft Academic Search

The effects of a series of normal alkanes (decane, dodecane, tetradecane, hexadecane, and octadecane) on the hexagonal HII structures containing dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC) were studied using x-ray diffraction and osmotic stress. The alkanes affect structural dimensions and the monolayer intrinsic curvature and bending modulus. The alkane effects are chain-length dependent and are attributed to their different distribution within

Z. Chen; R. P. Rand

1998-01-01

151

The Alkane Hydroxylase Gene of Burkholderia cepacia RR10 Is under Catabolite Repression Control  

PubMed Central

In many microorganisms the first step for alkane degradation is the terminal oxidation of the molecule by an alkane hydroxylase. We report the characterization of a gene coding for an alkane hydroxylase in a Burkholderia cepacia strain isolated from an oil-contaminated site. The protein encoded showed similarity to other known or predicted bacterial alkane hydroxylases, although it clustered on a separate branch together with the predicted alkane hydroxylase of a Mycobacterium tuberculosis strain. Introduction of the cloned B. cepacia gene into an alkane hydroxylase knockout mutant of Pseudomonas fluorescens CHAO restored its ability to grow on alkanes, which confirms that the gene analyzed encodes a functional alkane hydroxylase. The gene, which was named alkB, is not linked to other genes of the alkane oxidation pathway. Its promoter was identified, and its expression was analyzed under different growth conditions. Transcription was induced by alkanes of chain lengths containing 12 to at least 30 carbon atoms as well as by alkanols. Although the gene was efficiently expressed during exponential growth, transcription increased about fivefold when cells approached stationary phase, a characteristic not shared by the few alkane degraders whose regulation has been studied. Expression of the alkB gene was under carbon catabolite repression when cells were cultured in the presence of several organic acids and sugars or in a complex (rich) medium. The catabolic repression process showed several characteristics that are clearly different from what has been observed in other alkane degradation pathways.

Marin, Mercedes M.; Smits, Theo H. M.; van Beilen, Jan B.; Rojo, Fernando

2001-01-01

152

Combustion and microexplosion of collision-merged methanol\\/alkane droplets  

Microsoft Academic Search

The combustion characteristics of freely falling droplets, individually generated by the merging of colliding methanol and alkane droplets, were investigated and compared with those for pure methanol and alkanes. The merging of the nominally immiscible methanol and alkanes was manifested in an apparently adhesive, but unmixed, manner in all test conditions. An air bubble was found to be trapped at

C. H. Wang; S. Y. Fu; L. J. Kung; C. K. Law

2005-01-01

153

Forensic Chemistry  

Microsoft Academic Search

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is

Suzanne Bell

2009-01-01

154

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents background information, laboratory procedures, classroom materials/activities, and experiments for chemistry. Topics include superheavy elements, polarizing power and chemistry of alkali metals, particulate carbon from combustion, tips for the chemistry laboratory, interesting/colorful experiments, behavior of bismuth (III) iodine, and…

School Science Review, 1982

1982-01-01

155

Digital biology and chemistry.  

PubMed

This account examines developments in "digital" biology and chemistry within the context of microfluidics, from a personal perspective. Using microfluidics as a frame of reference, we identify two areas of research within digital biology and chemistry that are of special interest: (i) the study of systems that switch between discrete states in response to changes in chemical concentration of signals, and (ii) the study of single biological entities such as molecules or cells. In particular, microfluidics accelerates analysis of switching systems (i.e., those that exhibit a sharp change in output over a narrow range of input) by enabling monitoring of multiple reactions in parallel over a range of concentrations of signals. Conversely, such switching systems can be used to create new kinds of microfluidic detection systems that provide "analog-to-digital" signal conversion and logic. Microfluidic compartmentalization technologies for studying and isolating single entities can be used to reconstruct and understand cellular processes, study interactions between single biological entities, and examine the intrinsic heterogeneity of populations of molecules, cells, or organisms. Furthermore, compartmentalization of single cells or molecules in "digital" microfluidic experiments can induce switching in a range of reaction systems to enable sensitive detection of cells or biomolecules, such as with digital ELISA or digital PCR. This "digitizing" offers advantages in terms of robustness, assay design, and simplicity because quantitative information can be obtained with qualitative measurements. While digital formats have been shown to improve the robustness of existing chemistries, we anticipate that in the future they will enable new chemistries to be used for quantitative measurements, and that digital biology and chemistry will continue to provide further opportunities for measuring biomolecules, understanding natural systems more deeply, and advancing molecular and cellular analysis. Microfluidics will impact digital biology and chemistry and will also benefit from them if it becomes massively distributed. PMID:24889331

Witters, Daan; Sun, Bing; Begolo, Stefano; Rodriguez-Manzano, Jesus; Robles, Whitney; Ismagilov, Rustem F

2014-07-29

156

Forensic Chemistry  

NASA Astrophysics Data System (ADS)

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.

Bell, Suzanne

2009-07-01

157

Forensic chemistry.  

PubMed

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence. PMID:20636064

Bell, Suzanne

2009-01-01

158

CLUSTER CHEMISTRY  

SciTech Connect

Metal cluster chemistry is one of the most rapidly developing areas of inorganic and organometallic chemistry. Prior to 1960 only a few metal clusters were well characterized. However, shortly after the early development of boron cluster chemistry, the field of metal cluster chemistry began to grow at a very rapid rate and a structural and a qualitative theoretical understanding of clusters came quickly. Analyzed here is the chemistry and the general significance of clusters with particular emphasis on the cluster research within my group. The importance of coordinately unsaturated, very reactive metal clusters is the major subject of discussion.

Muetterties, Earl L.

1980-05-01

159

Computational Chemistry for Chemistry Educators  

NSDL National Science Digital Library

This is a 15-session course on the technologies, techniques, and tools of computational chemistry. By using the same computational tools as research computational chemists, educators will have the opportunity to study chemistry in a manner very different than traditional teaching and education in chemistry.

Institute, Shodor C.

160

Hydrocarbons. Independent Learning Project for Advanced Chemistry (ILPAC). Unit O1.  

ERIC Educational Resources Information Center

This unit on hydrocarbons is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit is divided into sections dealing with alkanes, alkenes, alkynes, arenes, and several aspects of the petroleum industry. Two experiments, exercises (with answers), and pre- and post-tests are included.…

Inner London Education Authority (England).

161

Crystallization and prevention of supercooling of microencapsulated n-alkanes.  

PubMed

Microencapsulated n-alkanes (n-octadecane, n-nonadecane, and n-eicosane) were synthesized by in situ polymerization using urea-melamine-formaldehyde polymer as shells. Microcapsules 5.0 and 10.0 wt% of 1-tetradecanol, paraffin, and 1-octadecanol were used as nucleating agents. The fabrication was characterized using Fourier transform infrared, light microscopy, and scanning electron microscopy. The crystallization and prevention of supercooling of the microcapsules are studied using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction. The crystal system of the microencapsulated n-alkane is the same as that of the bulk. The enthalpies of the microcapsules containing 70 wt% n-alkanes are approximately 160 J/g. The melting temperature of the n-alkanes in the microcapsule is the same as that in the bulk. There are multiple peaks on the DSC cooling curves that are attributed to liquid-rotator, rotator-crystal, and liquid-crystal transitions. The DSC cooling behavior of microencapsulated n-octadecane is affected by the average diameters. The measured maximum degree of supercooling of the microencapsulated n-octadecane is approximately 26.0 degrees C at a heating and cooling rate of 10.0 degrees C/min. The degree of supercooling of microencapsulated n-octadecane is decreased by adding 10.0 wt% of 1-octadecanol as a nucleating agent. PMID:15571685

Zhang, Xing-xiang; Fan, Yao-feng; Tao, Xiao-ming; Yick, Kit-lun

2005-01-15

162

Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation  

DOEpatents

New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso- and/or [beta]-pyrrolic positions.

Ellis, P.E. Jr.; Lyons, J.E.

1993-05-18

163

Thermal analysis of n-alkane phase change material mixtures  

Microsoft Academic Search

Tests were performed to characterize the thermal behavior of it number of n-alkanes to be used as phase change materials (PCMs) in district cooling applications. Hexadecane and tetradecane were mixed in different fractions, and their thermal behavior was experimentally evaluated. Test results for melting temperature and fusion energy for laboratory grade hexadecane and tetradecane showed good agreement with datain the

Y. I. Chio; E. Choi; H. G. Lorsch

1991-01-01

164

Alkane-induced edema formation and cutaneous barrier dysfunction.  

PubMed

Certain mineral oils and hydrocarbons require repeated topical application to cause irritation. A structure activity relationship of pure n-alkanes was undertaken in a mouse ear edema model to investigate the mechanism of cumulative irritancy. Alkanes were applied twice daily over a 4-day period. Dodecane was found to be non-irritating, while tridecane elicited a response only at 96 h. Tetradecane was the strongest irritant with significant increases (p less than 0.05) in ear thickness observed at 48 h. Hexadecane, octadecane, and eicosane exhibited progressively decreasing activity. Permeability of the ears to hydrocortisone was monitored in vitro during tridecane- and tetradecane-induced irritation. Significant increases in permeability were observed 24 h before edema formation. A positive correlation was found between the extent of edema formation and enhancement of permeability. Loss of barrier function would result in increased cutaneous availability of the alkanes. Increased permeability prior to edema formation indicates that induction of barrier dysfunction may be a factor in the mechanism of alkane-induced irritation. PMID:3190267

Moloney, S J; Teal, J J

1988-01-01

165

Transport properties of alkanes through ceramic thin zeolite MFI membranes  

Microsoft Academic Search

Polycrystalline randomly oriented defect free zeolite layers on porous ?-Al2O3 supports are prepared with a thickness of less than 5 ?m by in situ crystallisation of silicalite-1. The flux of alkanes is a function of the sorption and intracrystalline diffusion. In mixtures of strongly and weakly adsorbing gases and a high loadings of the strongly adsorbing molecule in the zeolite

Z. A. E. P. Vroon; K. Keizer; M. J. Gilde; H. Verweij; A. J. Burggraaf

1996-01-01

166

Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation  

DOEpatents

New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or .beta.-pyrrolic positions.

Ellis, Jr., Paul E. (Downingtown, PA); Lyons, James E. (Wallingford, PA)

1995-01-01

167

Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation  

DOEpatents

New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or .beta.-pyrrolic positions.

Ellis, Jr., Paul E. (Downingtown, PA); Lyons, James E. (Wallingford, PA)

1993-01-01

168

Cyano- and polycyanometalloporphyrins as catalysts for alkane oxidation  

DOEpatents

Alkanes are oxidized by contact with oxygen-containing gas in the presence as catalyst of a metalloporphyrin in which hydrogen atoms in the porphyrin ring have been substituted with one or more cyano groups. Hydrogen atoms in the porphyrin ring may also be substituted with halogen atoms.

Ellis, Jr., Paul E. (Downingtown, PA); Lyons, James E. (Wallingford, PA)

1992-01-01

169

Diverse alkane hydroxylase genes in microorganisms and environments.  

PubMed

AlkB and CYP153 are important alkane hydroxylases responsible for aerobic alkane degradation in bioremediation of oil-polluted environments and microbial enhanced oil recovery. Since their distribution in nature is not clear, we made the investigation among thus-far sequenced 3,979 microbial genomes and 137 metagenomes from terrestrial, freshwater, and marine environments. Hundreds of diverse alkB and CYP153 genes including many novel ones were found in bacterial genomes, whereas none were found in archaeal genomes. Moreover, these genes were detected with different distributional patterns in the terrestrial, freshwater, and marine metagenomes. Hints for horizontal gene transfer, gene duplication, and gene fusion were found, which together are likely responsible for diversifying the alkB and CYP153 genes adapt to the ubiquitous distribution of different alkanes in nature. In addition, different distributions of these genes between bacterial genomes and metagenomes suggested the potentially important roles of unknown or less common alkane degraders in nature. PMID:24829093

Nie, Yong; Chi, Chang-Qiao; Fang, Hui; Liang, Jie-Liang; Lu, She-Lian; Lai, Guo-Li; Tang, Yue-Qin; Wu, Xiao-Lei

2014-01-01

170

Roaming radical pathways for the decomposition of alkanes.  

SciTech Connect

CASPT2 calculations predict the existence of roaming radical pathways for the decomposition of propane, n-butane, isobutane and neopentane. The roaming radical paths lead to the formation of an alkane and an alkene instead of the expected radical products. The predicted barriers for the roaming radical paths lie {approx}1 kcal/mol below the corresponding radical asymptotes.

Harding, L. B.; Klippenstein, S. J. (Chemical Sciences and Engineering Division)

2010-01-01

171

Molecular modeling of the physical properties of the alkanes  

Microsoft Academic Search

Eight physical properties (boiling points, molar volumes, molar refractions, heats of vaporization, surface tensions, melting points, critical temperatures, and critical pressures) of 74 normal and branched alkanes were examined by molecular modeling techniques. Structural parameters employed include Wiener indices, connectivity indices, ad hoc descriptors, information indices, and molecular volumes and surface areas. Most of the properties were well modeled (r²

Diane E. Needham; I Chien. Wei; Paul G. Seybold

1988-01-01

172

Oxidation of Light Alkanes Using Photocatalytic Thin Films.  

National Technical Information Service (NTIS)

This investigation studied the photocatalytic oxidation of light alkanes using photocatalytic thin films. In the research presented, nearly complete oxidation of isobutane, n-butane and propane using ZrO2/TiO2 thin films in a single pass reactor was demon...

T. M. Twesme

2006-01-01

173

Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation  

DOEpatents

New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or [beta]-pyrrolic positions.

Ellis, P.E. Jr.; Lyons, J.E.

1995-01-17

174

Site-selective Alkane Dehydrogenation of Fatty Acids.  

National Technical Information Service (NTIS)

The long-term goal of this research plan was to develop a catalyst to affect site-selective alkane dehydrogenations on fatty acid substrates. The one-year seed funding allowed us to investigate a number of iridium complexes in stoichiometric reactions wit...

J. P. Stambuli S. M. Whittemore

2011-01-01

175

MODELING OF ALKANE EMISSIONS FROM A WOOD STAIN  

EPA Science Inventory

The article discusses full-scale residential house tests to evaluate the effects of organic emissions from a wood finishing product--wood stain--on indoor air quality (IAQ). The test house concentrations of three alkane species, nonane, decane, and undecane, were measured as a fu...

176

MODELING OF ALKANE EMISSIONS FROM A WOOD STAIN  

EPA Science Inventory

The article discusses full-scale residential house tests to evaluate the effects of organic emissions from a wood finishing product--wood stain--on indoor air quality (IAQ). he test house concentrations of three alkane species, nonane, decane, and undecane, were measured as a fun...

177

p-Toluenesulfonylmethyl Isocyanide: A Versatile Synthon in Organic Chemistry  

Microsoft Academic Search

TosMIC, a versatile synthon in organic chemistry, has been extensively used for the synthesis of a wide variety of small, medium and large ring heterocycles. It has immense implications in the synthesis of nitriles, aldehydes, ketones, alkanes, cyclophanes and large number of natural products. Several drug intermediates and pharmacologically active compounds have been synthesized from TosMIC. In addition, chiral TosMIC

Vishnu K. Tandon; Sanjay Rai

2003-01-01

178

Reconstitution of plant alkane biosynthesis in yeast demonstrates that Arabidopsis ECERIFERUM1 and ECERIFERUM3 are core components of a very-long-chain alkane synthesis complex.  

PubMed

In land plants, very-long-chain (VLC) alkanes are major components of cuticular waxes that cover aerial organs, mainly acting as a waterproof barrier to prevent nonstomatal water loss. Although thoroughly investigated, plant alkane synthesis remains largely undiscovered. The Arabidopsis thaliana ECERIFERUM1 (CER1) protein has been recognized as an essential element of wax alkane synthesis; nevertheless, its function remains elusive. In this study, a screen for CER1 physical interaction partners was performed. The screen revealed that CER1 interacts with the wax-associated protein ECERIFERUM3 (CER3) and endoplasmic reticulum-localized cytochrome b5 isoforms (CYTB5s). The functional relevance of these interactions was assayed through an iterative approach using yeast as a heterologous expression system. In a yeast strain manipulated to produce VLC acyl-CoAs, a strict CER1 and CER3 coexpression resulted in VLC alkane synthesis. The additional presence of CYTB5s was found to enhance CER1/CER3 alkane production. Site-directed mutagenesis showed that CER1 His clusters are essential for alkane synthesis, whereas those of CER3 are not, suggesting that CYTB5s are specific CER1 cofactors. Collectively, our study reports the identification of plant alkane synthesis enzymatic components and supports a new model for alkane production in which CER1 interacts with both CER3 and CYTB5 to catalyze the redox-dependent synthesis of VLC alkanes from VLC acyl-CoAs. PMID:22773744

Bernard, Amélie; Domergue, Frédéric; Pascal, Stéphanie; Jetter, Reinhard; Renne, Charlotte; Faure, Jean-Denis; Haslam, Richard P; Napier, Johnathan A; Lessire, René; Joubès, Jérôme

2012-07-01

179

Functional Analysis of Alkane Hydroxylases from Gram-Negative and Gram-Positive Bacteria  

PubMed Central

We have cloned homologs of the Pseudomonas putida GPo1 alkane hydroxylase from Pseudomonas aeruginosa PAO1, Pseudomonas fluorescens CHA0, Alcanivorax borkumensis AP1, Mycobacterium tuberculosis H37Rv, and Prauserella rugosa NRRL B-2295. Sequence comparisons show that the level of protein sequence identity between the homologs is as low as 35%, and that the Pseudomonas alkane hydroxylases are as distantly related to each other as to the remaining alkane hydroxylases. Based on the observation that rubredoxin, an electron transfer component of the GPo1 alkane hydroxylase system, can be replaced by rubredoxins from other alkane hydroxylase systems, we have developed three recombinant host strains for the functional analysis of the novel alkane hydroxylase genes. Two hosts, Escherichia coli GEc137 and P. putida GPo12, were equipped with pGEc47?B, which encodes all proteins necessary for growth on medium-chain-length alkanes (C6 to C12), except a functional alkane hydroxylase. The third host was an alkB knockout derivative of P. fluorescens CHA0, which is no longer able to grow on C12 to C16 alkanes. All alkane hydroxylase homologs, except the Acinetobacter sp. ADP1 AlkM, allowed at least one of the three hosts to grow on n-alkanes.

Smits, Theo H. M.; Balada, Stefanie B.; Witholt, Bernard; van Beilen, Jan B.

2002-01-01

180

Acid strength of solids probed by catalytic isobutane conversion  

Microsoft Academic Search

The literature is controversial on whether sulfated zirconia (SZ) is “just” as strong acid as H-zeolites, or a strong superacid. Spectroscopic studies of adsorbed probe molecules concluded that SZ is not a superacid, whereas acidity measurements based on Hammett indicators, alkane transformations and the 1\\/2% isobutane conversion test [B. Umansky, J. Engelhardt, W.K. Hall, J. Catal. 127 (1991) 128; D.

Dan Fraenkel; Nicholas R. Jentzsch; Christopher A. Starr; Pandurang V. Nikrad

2010-01-01

181

Energy conversion & storage program. 1994 annual report  

SciTech Connect

The Energy Conversion and Storage Program investigates state-of-the-art electrochemistry, chemistry, and materials science technologies for: (1) development of high-performance rechargeable batteries and fuel cells; (2) development of high-efficiency thermochemical processes for energy conversion; (3) characterization of complex chemical processes and chemical species; (4) study and application of novel materials for energy conversion and transmission. Research projects focus on transport process principles, chemical kinetics, thermodynamics, separation processes, organic and physical chemistry, novel materials, and advanced methods of analysis.

Cairns, E.J.

1995-04-01

182

Energy Conversion & Storage Program, 1993 annual report  

SciTech Connect

The Energy Conversion and Storage Program applies chemistry and materials science principles to solve problems in: production of new synthetic fuels; development of high-performance rechargeable batteries and fuel cells; development of high-efficiency thermochemical processes for energy conversion; characterization of complex chemical processes and chemical species; and the study and application of novel materials for energy conversion and transmission. Projects focus on transport-process principles, chemical kinetics, thermodynamics, chemical kinetics, thermodynamics, separation processes, organic and physical chemistry, novel materials, and advanced methods of analysis.

Cairns, E.J.

1994-06-01

183

Cooperative Research in C1 Chemistry  

Microsoft Academic Search

C1 chemistry refers to the conversion of simple carbon-containing materials that contain one carbon atom per molecule into valuable products. The feedstocks for C1 chemistry include natural gas, carbon dioxide, carbon monoxide, methanol and synthesis gas (a mixture of carbon monoxide and hydrogen). Synthesis gas, or syngas, is produced primarily by the reaction of natural gas, which is principally methane,

Gerald P. Huffman

2000-01-01

184

To Form a Favorable Idea of Chemistry  

ERIC Educational Resources Information Center

"To confess the truth, Mrs. B., I am not disposed to form a very favorable idea of chemistry, nor do I expect to derive much entertainment from it." That 200-year-old statement by Caroline to Mrs. Bryan, her teacher, appeared on the first page of Jane Marcet's pioneering secondary school textbook, "Conversations on Chemistry". It was published 17…

Heikkinen, Henry W.

2010-01-01

185

The Doctorate in Chemistry. Carnegie Essays on the Doctorate: Chemistry.  

ERIC Educational Resources Information Center

The Carnegie Foundation commissioned a collection of essays as part of the Carnegie Initiative on the Doctorate (CID). Essays and essayists represent six disciplines that are part of the CID: chemistry, education, English, history, mathematics, and neuroscience. Intended to engender conversation about the conceptual foundation of doctoral…

Breslow, Ronald

186

Glucose transport and its inhibition by short-chain n-alkanes in Cladosporium resinae.  

PubMed Central

Glucose transport in Cladosporium resinae was studies with the aid of the non-metabolizable glucose analogue 3-O-methyl-D-glucose (3-O-MG). 3-O-MG, transported as a free sugar without phosphorylation, was found to inhibit glucose uptake competitively. Conversely, glucose was a competitive inhibitor of 3-O-MG uptake. Moreover, both glucose and 3-O-MG were able to bring about rapid counterflow intracellular 3-O-MG. Thus, glucose and 3-O-MG share the same entry and exit systems. The transport of 3-O-MG is carrier mediated and energy dependent as shown by saturation kinetics, strong temperature dependence, accumulation of unaltered 3-O-MG against a concentration gradient, and inhibition of uptake by NaN3, NaCN, and 2,4-dinitrophenol. The glucose transport system appeared to be constitutive for glucose transport in cells grown on fructose, galactose, mannose, xylose, or glucose. There was no derepressible low-Km glucose transport system in C. resinae. n-Hexane and n-heptane were found to inhibit 3-O-MG uptake rapidly at temperatures above 20 C. Over 50% inhibition of the uptake rate occurred after only 10 min of incubation with n-hexane at 30 C. The percentage of inhibition in the presence of n-hexane, compared to controls in the absence of n-hexane, was found to increase with increasing temperature. Longer-chain n-alkanes (C8 to C18) had no significant effect on uptake. The efflux of intracellular 3-O-MG, which appeared to occur by facilitated diffusion, was not affected by any of the n-alkanes tested including n-hexane.

Teh, J S

1975-01-01

187

Chemistry Notes.  

ERIC Educational Resources Information Center

Outlines laboratory procedures, demonstrations, teaching suggestions, and content information related to chemistry. Topics include polarizing power; calorimetry and momentum; microcomputers in school chemistry; a constant-volume dispenser for liquids, floating magnets, and crystal lattices; preparation of chromium; and solvent polarity and…

School Science Review, 1981

1981-01-01

188

SUPRAMOLECULAR CHEMISTRY  

Microsoft Academic Search

the photoinitiated forma- tion of substituted tropy- lium salts from arylcyclo- heptatrienes bearing a leaving group such as the methoxy group. Two topics of supramolecular chemistry are studied in the Supramolecular Photo- chemistry group: host-guest complexes based on calixarenes and photoswitchable rotaxanes. - Newly designed calix(4)arenes, substituted with a different number of cycloheptatrienyl or tropylium functions at the upper rim

Hans-Werner Abraham

189

Adsorption Kinetics of Alkanes on Purified HiPco Nanotubes  

NASA Astrophysics Data System (ADS)

We present results for the adsorption kinetics of methane, ethane and butane on purified HiPco SWNTs. We studied the adsorption kinetics by monitoring the evolution of the gas pressure with time from the instant at which a dose of adsorbate is added to the sample, until the moment at which equilibrium is reached. The waiting times for comparable coverages increase with increasing alkane chain length. For methane and ethane, the equilibration time decreases with increasing fractional coverage. For the butane, on the other hand, the kinetic measurements display a reverse trend: the equilibration times increase with increasing fractional coverage. We speculate that this observed increase in the waiting time is due to a possible reorientation of adsorbed molecules in the film. The observed differences in adsorption kinetics suggest the possibility of using adsorption as a means to achieve the separation of gaseous alkane mixtures.

Rawat, Dinesh; Bulut, Murat; Migone, Aldo

2008-03-01

190

The vibrational spectrum of water in liquid alkanes.  

PubMed Central

The water wire hypothesis of hydrogen-ion transport in lipid bilayers has prompted a search for water aggregates in bulk hydrocarbons. The asymmetric stretching vibration of the water dissolved in n-decane and in a number of other alkanes and alkenes has been observed. The water band in the alkanes is very wide and fits to the results of a J-diffusion calculation for the water rotation. This implies that the water is freely rotating between collisions with the solvent and certainly not hydrogen bonded to anything. The existence of water aggregates is thus most unlikely. In contrast, water in an alkene is hydrogen bonded to the solvent molecules (although not to other water molecules) and shows an entirely different spectrum.

Conrad, M P; Strauss, H L

1985-01-01

191

Surface crystallization and thin film melting in normal alkanes  

SciTech Connect

Normal alkanes of carbon number n > 14 exhibit surface crystallization at their liquid-vapor interface. This has been investigated with x-ray reflectivity, grazing incidence scattering and surface tension measurements. The structure and thermodynamics of the surface layer is consistent with a monolayer of the bulk rotator phase occurring at the surface above the bulk melting temperature. On the other hand, thin films of alkanes on SiO{sub 2}, exhibit a reduction of the melting temperature. The surface crystalline phase is observed for carbon number n > 14. The vanishing of surface phase for small n may be due to a transition from surface freezing to surface melting behavior. These measurements can yield the relative surface energies of the various phases. 41 refs.

Wu, X.Z. [Northern Illinois Univ., DeKalb, IL (United States). Physics Dept.]|[Argonne National Lab., IL (United States). Materials Science Div.; Shao, H.H. [Ohio State Univ., Columbus, OH (United States). Dept. of Physics]|[Exxon Research and Engineering Co., Annandale, NJ (United States). Corporate Research Science Labs.; Ocko, B.M. [Brookhaven National Lab., Upton, NY (United States). Physics Dept.; Deutsch, M. [Bar Ilan Univ., Ramat Gan (Israel). Physics Dept.; Sinha, S.K.; Kim, M.W.; King, H.E. Jr.; Sirota, E.B. [Exxon Research and Engineering Co., Annandale, NJ (United States). Corporate Research Science Labs.

1994-12-31

192

Applications of microwaves in nuclear chemistry and engineering  

Microsoft Academic Search

Microwave chemistry has been developed quickly and has been applied to almost every field of the chemistry over the past decades. With the nuclear renaissance, microwaves have been applied in nuclear chemistry and engineering in recent years. This paper is a brief review about microwave sintering of UO2 pellets, (U, Th)O2 and MOX powders, conversion of high enriched uranyl (HEU)

Yunfeng Zhao; Jing Chen

2008-01-01

193

Solubilization in alkanes by alcohols as reverse hydrotropes or "lipotropes".  

PubMed

Hydrotropes in aqueous systems do not aggregate in micelles, inhibit presence of mesophases and allow significant and progressive solubilization of "insoluble" molecules in water. It was shown that n-alcohols in alkanes develop the same properties, including the power-law for maximum solubilization of "hydrophilic" molecules. The aim of this paper is to highlight properties of reverse hydrotropes or "lipotropes" by taking n-alcohol/alkane mixtures as model systems. So as to establish a clear parallel between lipotropes and hydrotropes the same methodology used to characterize hydrotropes was applied to these systems. The solubilization of solutes insoluble in alkane, i.e. water and a hydrophilic dye in dodecane, enabled by the addition of n-alcohols ( n = 2, 3, 4 and 7) was studied. In parallel, the nonmicellar aggregation state of butan-1-ol and heptan-1-ol in dodecane was investigated by small-angle X-ray scattering. By applying the Porod's treatment the specific area of the H-bond network formed by heptan-1-ol and the area occupied by hydroxyl group in this network were determined as a function of concentration. A correlation between the aggregation of alcohols in dodecane and the solubilization was made. The disrupting of concentrated mesophases by a lipotrope was illustrated by studying the effect of adding n-alcohols to water/oil/extractant ternary systems used in liquid/liquid extraction. Under some conditions the organic phase splits up into two phases: an extractant mesophase and nearly pure oil. The amount of n-alcohols required to make the extractant mesophase disappear was determined for water/alkane/malonamide extractant systems. The influence of the chain length of the n-alcohol on the efficiency as lipotrope was also experimentally studied. The trend obtained was similar to the one observed with the solubilization experiments. PMID:18774856

Bauduin, P; Testard, F; Zemb, Th

2008-10-01

194

Hydroxylation of alkanes using sodium hypochlorite catalyzed by iron porphyrins  

SciTech Connect

This communication presents data about the oxidation of alkanes to alcohols with hypochlorite in the presence of Fe(III) phenylporphyrin derivatives in the system water-benzene. We used as catalysts the following compounds: tetraphenylporphyrin iron chloride, tetramesitylporphyrin iron chloride, tetra(2-fluorophenyl)porphyrin from chloride, and tetra (2-ntrophenyl)porphyrin iron chloride. The reaction products were analyzed by gas-liquid chromatography. The efficiency of the reaction was determined by the structure of the porphyrin used.

Sorokin, A.B.; Khenkin, A.M.

1988-10-01

195

Alkane Biosynthesis Genes in Cyanobacteria and Their Transcriptional Organization  

PubMed Central

In cyanobacteria, alkanes are synthesized from a fatty acyl-ACP by two enzymes, acyl–acyl carrier protein reductase and aldehyde deformylating oxygenase. Despite the great interest in the exploitation for biofuel production, nothing is known about the transcriptional organization of their genes or the physiological function of alkane synthesis. The comparison of 115 microarray datasets indicates the relatively constitutive expression of aar and ado genes. The analysis of 181 available genomes showed that in 90% of the genomes both genes are present, likely indicating their physiological relevance. In 61% of them they cluster together with genes encoding acetyl-CoA carboxyl transferase and a short-chain dehydrogenase, strengthening the link to fatty acid metabolism and in 76% of the genomes they are located in tandem, suggesting constraints on the gene arrangement. However, contrary to the expectations for an operon, we found in Synechocystis sp. PCC 6803 specific promoters for the two genes, sll0208 (ado) and sll0209 (aar), which give rise to monocistronic transcripts. Moreover, the upstream located ado gene is driven by a proximal as well as a second, distal, promoter, from which a third transcript, the ~160?nt sRNA SyR9 is transcribed. Thus, the transcriptional organization of the alkane biosynthesis genes in Synechocystis sp. PCC 6803 is of substantial complexity. We verified all three promoters to function independently from each other and show a similar promoter arrangement also in the more distant Nodularia spumigena, Trichodesmium erythraeum, Anabaena sp. PCC 7120, Prochlorococcus MIT9313, and MED4. The presence of separate regulatory elements and the dominance of monocistronic mRNAs suggest the possible autonomous regulation of ado and aar. The complex transcriptional organization of the alkane synthesis gene cluster has possible metabolic implications and should be considered when manipulating the expression of these genes in cyanobacteria.

Klahn, Stephan; Baumgartner, Desiree; Pfreundt, Ulrike; Voigt, Karsten; Schon, Verena; Steglich, Claudia; Hess, Wolfgang R.

2014-01-01

196

Alkane functionalization at ([mu]Oxo)diiron(III) centers  

Microsoft Academic Search

The reactivity of ([mu]-oxo)diferric complexes with [sup t]BuOOH (TBHP) for the functionalization of alkanes in CH[sub 3]CN has been investigated as part of our efforts to model dinuclear sites in nonheme iron enzymes. [Fe[sub 2](TPA)[sub 2]O(OAc)](CIO[sub 4])[sub 3] (1) (TPA = tris(2-pyridylmethyl)amine, OAc = acetate) is an efficient catalyst for cyclohexane oxidation, affording cyclohexanol (A, 9 equiv), cyclohexanone (K, 11

Randolph A. Leising; Jinheung Kim; Miguel A. Perez; Lawrence Que

1993-01-01

197

Utilization of n-alkanes by Pullularia pullulans.  

PubMed

Pullularia pullulans was tested for its ability to utilize a series of n-alkanes for growth. It utilized hydrocarbons containing higher C-numbers (13, 14, 16, and 18) to a greater degree than those containing lower numbers; in addition, an induction phenomenon was noted. Gas-liquid and thin-layer chromatography of ether extracts of the growth media revealed that oleic and palmitic acids were formed from tridecane, tetradecane, hexadecane, and octadecane. PMID:5498620

Merdinger, E; Merdinger, R P

1970-10-01

198

Crystallization and prevention of supercooling of microencapsulated n-alkanes  

Microsoft Academic Search

Microencapsulated n-alkanes (n-octadecane, n-nonadecane, and n-eicosane) were synthesized by in situ polymerization using urea–melamine–formaldehyde polymer as shells. Microcapsules 5.0 and 10.0 wt% of 1-tetradecanol, paraffin, and 1-octadecanol were used as nucleating agents. The fabrication was characterized using Fourier transform infrared, light microscopy, and scanning electron microscopy. The crystallization and prevention of supercooling of the microcapsules are studied using differential scanning

Xing-xiang Zhang; Yao-feng Fan; Xiao-ming Tao; Kit-lun Yick

2005-01-01

199

Ultrastructure of Candida yeasts grown on n -alkanes  

Microsoft Academic Search

Catalase activities of the cells growing onn-alkanes of various strains ofCandida yeasts wer markedly higher than those of the cells growing on glucose, ethanol or acetate. In connection with this, electron-microscopical studies revealed abundant appearance of specific microbodies having homogeneous matrix surrounded by single unit membrane in the hydrocarbon-growing cells. Localization of catalase activity in the microbodies, in addition to

Masako Osumi; Naoto Miwa; Yutaka Teranishi; Atsuo Tanaka; Saburo Fukui

1974-01-01

200

Monolayer solids of short (perfluoro)alkanes on graphite  

NASA Astrophysics Data System (ADS)

Calculations are reported for the relative stability of monolayer solid latices on graphite for C2H6, C3H8, C2F6, and C3F8. Triangular, centered rectangular and two-sublattice herringbone lattices are treated. The calculations use all-atom (AA) models and are based on non-bonding interactions formulated for three dimensional dense phases of alkanes and perfluoroalkanes.

Bruch, L. W.

2009-03-01

201

Secondary organic aerosol yields of 12-carbon alkanes  

NASA Astrophysics Data System (ADS)

Secondary organic aerosol (SOA) yields were measured for cyclododecane, hexylcyclohexane, n-dodecane, and 2-methylundecane under high-NOx conditions, in which alkyl proxy radicals (RO2) react primarily with NO, and under low-NOx conditions, in which RO2 reacts primarily with HO2. Experiments were run until 95-100% of the initial alkane had reacted. Particle wall loss was evaluated as two limiting cases using a new approach that requires only suspended particle number-size distribution data and accounts for size-dependent particle wall losses and condensation. SOA yield differed by a factor of 2 between the two limiting cases, but the same trends among alkane precursors were observed for both limiting cases. Vapor-phase wall losses were addressed through a modeling study and increased SOA yield uncertainty by approximately 30%. SOA yields were highest from cyclododecane under both NOx conditions. SOA yields ranged from 3.3% (dodecane, low-NOx conditions) to 160% (cyclododecane, high-NOx conditions). Under high-NOx conditions, SOA yields increased from 2-methylundecane < dodecane ~ hexylcyclohexane < cyclododecane, consistent with previous studies. Under low-NOx conditions, SOA yields increased from 2-methylundecane ~ dodecane < hexylcyclohexane < cyclododecane. The presence of cyclization in the parent alkane structure increased SOA yields, whereas the presence of branch points decreased SOA yields due to increased vapor-phase fragmentation. Vapor-phase fragmentation was found to be more prevalent under high-NOx conditions than under low-NOx conditions. For different initial mixing ratios of the same alkane and same NOx conditions, SOA yield did not correlate with SOA mass throughout SOA growth, suggesting kinetically limited SOA growth for these systems.

Loza, C. L.; Craven, J. S.; Yee, L. D.; Coggon, M. M.; Schwantes, R. H.; Shiraiwa, M.; Zhang, X.; Schilling, K. A.; Ng, N. L.; Canagaratna, M. R.; Ziemann, P. J.; Flagan, R. C.; Seinfeld, J. H.

2014-02-01

202

Dihydrogen contacts in alkanes are subtle but not faint  

NASA Astrophysics Data System (ADS)

Alkane molecules are held together in the crystal state by purportedly weak homonuclear R-H···H-R dihydrogen interactions. In an apparent contradiction, the high melting points and vaporization enthalpies of polyhedranes in condensed phases require quite strong intermolecular interactions. Two questions arise: ‘How strong can a weak C-H···H-C bond be?’ and ‘How do the size and topology of the carbon skeleton affect these bonding interactions?’ A systematic computational study of intermolecular interactions in dimers of n-alkanes and polyhedranes, such as tetrahedrane, cubane, octahedrane or dodecahedrane, showed that attractive C-H···H-C interactions are stronger than usually thought. We identified factors that account for the strength of these interactions, including the tertiary nature of the carbon atoms and their low pyramidality. An alkane with a bowl shape was designed in the search for stronger dihydrogen intermolecular bonding, and a dissociation energy as high as 12 kJ mol-1 is predicted by our calculations.

Echeverría, Jorge; Aullón, Gabriel; Danovich, David; Shaik, Sason; Alvarez, Santiago

2011-04-01

203

Cold-tolerant alkane-degrading Rhodococcus species from Antarctica  

SciTech Connect

Bioremediation is a possible mechanism for clean-up of hydrocarbon-contaminated soils in the Antarctic. Microbes indigenous to the Antarctic are required that degrade the hydrocarbon contaminants found in the soil, and that are able to survive and maintain activity under in situ conditions. Alkane-degrading bacteria previously isolated from oil-contaminated soil from around Scott Base, Antarctica, grew on a number of n-alkanes from hexane (C6) through to eicosane (C20) and the branched alkane pristane. Mineralization of {sup 14}C-dodecane was demonstrated with four strains. Representative isolates were identified as Rhodococcus species using 16S rDNA sequence analysis. Rhodococcus spp. strains 5/14 and 7/1 grew at -2 C but numbers of viable cells declined when incubated t 37 C. Both strains appear to have the major cold-shock gene cspA. Partial nucleotide sequence analyses of the PCR-amplified cspA open reading frame from Rhodococcus spp. strains 5/14 and 7/1 were approximately 60% identical to cspA from Escherichia coli.

Bej, A.K.; Saul, D.; Aislabie, J.

2000-07-01

204

Dielectric constant of liquid alkanes and hydrocarbon mixtures  

NASA Technical Reports Server (NTRS)

The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

Sen, A. D.; Anicich, V. G.; Arakelian, T.

1992-01-01

205

Biochemical studies on the metabolic activation of halogenated alkanes.  

PubMed Central

This paper reviews recent investigations by Slater and colleagues into the metabolic activation of halogenated alkanes in general and carbon tetrachloride in particular. It is becoming increasingly accepted that free radical intermediates are involved in the toxicity of many such compounds through mechanisms including lipid peroxidation, covalent binding, and cofactor depletion. Here we describe the experimental approaches that are used to establish that halogenated alkanes are metabolized in animal tissues to reactive free radicals. Electron spin resonance spectroscopy is used to identify free-radical products, often using spin-trapping compounds. The generation of specific free radicals by radiolytic methods is useful in the determination of the precise reactivity of radical intermediates postulated to be injurious to the cell. The enzymic mechanism of the production of such free radicals and their subsequent reactions with biological molecules is studied with specific metabolic inhibitors and free-radical scavengers. These combined techniques provide considerable insight into the process of metabolic activation of halogenated compounds. It is readily apparent, for instance, that the local oxygen concentration at the site of activation is of crucial importance to the subsequent reactions; the formation of peroxy radical derivatives from the primary free-radical product is shown to be of great significance in relation to carbon tetrachloride and may be of general importance. However, while these studies have provided much information on the biochemical mechanisms of halogenated alkane toxicity, it is clear that many problems remain to be solved.

Cheeseman, K H; Albano, E F; Tomasi, A; Slater, T F

1985-01-01

206

Energy Conversion and Storage Program  

NASA Astrophysics Data System (ADS)

This report is the 1992 annual progress report for the Energy Conversion and Storage Program, a part of the Energy and Environment Division of the Lawrence Berkeley Laboratory. Work described falls into three broad areas: electrochemistry; chemical applications; and materials applications. The Energy Conversion and Storage Program applies principles of chemistry and materials science to solve problems in several areas: (1) production of new synthetic fuels, (2) development of high-performance rechargeable batteries and fuel cells, (3) development of advanced thermochemical processes for energy conversion, (4) characterization of complex chemical processes and chemical species, and (5) study and application of novel materials for energy conversion and transmission. Projects focus on transport-process principles, chemical kinetics, thermodynamics, separation processes, organic and physical chemistry, novel materials, and advanced methods of analysis. Electrochemistry research aims to develop advanced power systems for electric vehicle and stationary energy storage applications. Chemical applications research includes topics such as separations, catalysis, fuels, and chemical analyses. Included in this program area are projects to develop improved, energy-efficient methods for processing product and waste streams from synfuel plants, coal gasifiers, and biomass conversion processes. Materials applications research includes evaluation of the properties of advanced materials, as well as development of novel preparation techniques. For example, techniques such as sputtering, laser ablation, and poised laser deposition are being used to produce high-temperature superconducting films.

Cairns, E. J.

1993-06-01

207

Photochemical dimerization and functionalization of alkanes, ethers, primary alcohols and silanes  

DOEpatents

The space-time yield and/or the selectivity of the photochemical dimerization of alkanes, ethers, primary alcohols and tertiary silanes with Hg and U.V. light is enhanced by refluxing the substrate in the irradiated reaction zone at a temperature at which the dimer product condenses and remains condensed promptly upon its formation. Cross-dimerization of the alkanes, ethers and silanes with primary alcohols is disclosed, as is the functionalization to aldehydes of the alkanes with carbon monoxide.

Crabtree, R.H.; Brown, S.H.

1988-02-16

208

Photochemical dimerization and functionalization of alkanes, ethers, primary alcohols and silanes  

DOEpatents

The space-time yield and/or the selectivity of the photochemical dimerization of alkanes, ethers, primary alcohols and tertiary silanes with Hg and U.V. light is enhanced by refluxing the substrate in the irradiated reaction zone at a temperature at which the dimer product condenses and remains condensed promptly upon its formation. Cross-dimerization of the alkanes, ethers and silanes with primary alcohols is disclosed, as is the functionalization to aldehydes of the alkanes with carbon monoxide.

Crabtree, Robert H. (Bethany, CT); Brown, Stephen H. (East Haven, CT)

1988-01-01

209

Fundamental Flame Velocities of Pure Hydrocarbons I : Alkanes, Alkenes, Alkynes Benzene, and Cyclohexane  

NASA Technical Reports Server (NTRS)

The flame velocities of 37 pure hydrocarbons including normal and branched alkanes, alkenes, and alkynes; as well as benzene and cyclohexane, together with the experimental technique employed are presented. The normal alkanes have about the same flame velocity from ethane through heptane with methane being about 16 percent lower. Unsaturation increases the flame velocity in the order of alkanes, alkenes, and alkynes. Branching reduces the flame velocity.

Gerstein, Melvin; Levine, Oscar; Wong, Edgar L

1950-01-01

210

Tropospheric Multiphase Chemistry: Current Foci  

NASA Astrophysics Data System (ADS)

In this contribution important aspects of tropospheric multiphase chemistry shall be reviewed in the three fields of (1) laboratory investigations covering the matrix in question and chemical conversions occurring. In the second part, (2) recent field work and, finally, (3) recent model developments will be discussed. In the first part a discussion will be led on the actual occurrence of the aqueous reaction medium, especially under aerosol particle conditions. Some recent kinetic investigations on radical and non-radical reactions of interest for aqueous chemistry are discussed. In the second part a short report on the hill-cap cloud experiment HCCT-2010 is given. In the third part a report on current work on CAPRAM is given. A mechanism generator has been put to work, there is a new model version for marine chemistry and an activity-based mechanism version for aerosol particle chemistry. An outlook on future directions will conclude the contribution.

Herrmann, Hartmut; Tilgner, Andreas; van Pinxteren, Dominik; Schöne, Luisa; Weller, Christian; Schaefer, Thomas; Bräuer, Peter; Rusumdar, Jhony

2014-05-01

211

Circumstellar chemistry  

NASA Technical Reports Server (NTRS)

The study of the outer envelopes of cool evolved stars has become an active area of research. The physical properties of CS envelopes are presented. Observations of many wavelengths bands are relevant. A summary of observations and a discussion of theoretical considerations concerning the chemistry are summarized. Recent theoretical considerations show that the thermal equilibrium model is of limited use for understanding the chemistry of the outer CS envelopes. The theoretical modeling of the chemistry of CS envelopes provides a quantitive test of chemical concepts which have a broader interest than the envelopes themselves.

Glassgold, Alfred E.; Huggins, Patrick J.

1987-01-01

212

Catalytic conversion of light alkanes - phase V. Topical report, February 1993--October 1994  

SciTech Connect

We have made excellent progress toward a practical route from field butanes to MTBE, the oxygenate of choice for high-octane, clean-burning, environmentally acceptable reformulated gasoline. We have evaluated two proprietary process possibilities with a potential commercial partner and have conducted a joint catalyst evaluation program. The first of the two potential processes considered during the past quarter utilizes a two-step route from isobutane to tert-butyl alcohol, TBA. Not only is TBA an intermediate for MTBE production but is equally applicable for ETBE-an oxygenate which utilizes renewable ethanol in its` manufacture. In the two-step process, isobutane is oxidized in a non-catalytic reaction to a roughly equal mixture of TBA and tert-butyl hydroperoxide. TBHP, eq. 1. We have developed an inexpensive new catalyst system based on an electron-deficient macrocyclic metal complex that selectively converts TBHP to TBA, eq. 2, and meets or exceeds all of the process criteria that we have set.

NONE

1998-12-31

213

Biodegradation of short-chain n-alkanes in oil sands tailings under methanogenic conditions.  

PubMed

The biodegradation of a mixture of low molecular weight n-alkanes (C6, C7, C8, and C10) was assessed under methanogenic conditions using mature fine tailings (MFT) produced by the oil sands industry in Alberta, Canada. Microorganisms present in the MFT mineralized the added n-alkane mixture, producing 16.2 (+/- 0.3) or 20.5 (+/- 0.1) mmol of methane in the headspace of microcosms spiked with 0.2% or 0.5% w/v n-alkanes, respectively, during 29 weeks of incubation. The spiked n-alkanes biodegraded in the sequence C10 > C8 > C7 > C6. Degradation of 100% C10, 97% C8, 74% C7, and 44% C6 occurred in a mixture of n-alkanes in the MFT spiked at 0.2% after 25 weeks of incubation. The same pattern of biodegradation was also observed in the MFT spiked with 0.5% n-alkanes. Stoichiometric calculations confirmed the mineralization of the degraded n-alkanes to methane. This study showed that the short-chain n-alkanes, which comprise a significant portion of the unrecovered naphtha used in bitumen extraction and released into the settling basins, can be biodegraded into methane. These findings may influence decisions regarding extraction processes and long-term management of MFT, and they suggest that intrinsic, methanogenic metabolism of these n-alkanes may occur in other anoxic environments. PMID:16999125

Siddique, Tariq; Fedorak, Phillip M; Foght, Julia M

2006-09-01

214

Biodegradation of Variable-Chain-Length Alkanes at Low Temperatures by a Psychrotrophic Rhodococcus sp.  

PubMed Central

The psychrotroph Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5°C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane. Q15 utilized a broad range of aliphatics (C10 to C21 alkanes, branched alkanes, and a substituted cyclohexane) present in diesel fuel at 5°C. Mineralization of hexadecane at 5°C was significantly greater in both hydrocarbon-contaminated and pristine soil microcosms seeded with Q15 cells than in uninoculated control soil microcosms. The detection of hexadecane and dodecane metabolic intermediates (1-hexadecanol and 2-hexadecanol and 1-dodecanol and 2-dodecanone, respectively) by solid-phase microextraction–gas chromatography-mass spectrometry and the utilization of potential metabolic intermediates indicated that Q15 oxidizes alkanes by both the terminal oxidation pathway and the subterminal oxidation pathway. Genetic characterization by PCR and nucleotide sequence analysis indicated that Q15 possesses an aliphatic aldehyde dehydrogenase gene highly homologous to the Rhodococcus erythropolis thcA gene. Rhodococcus sp. strain Q15 possessed two large plasmids of approximately 90 and 115 kb (shown to mediate Cd resistance) which were not required for alkane mineralization, although the 90-kb plasmid enhanced mineralization of some alkanes and growth on diesel oil at both 5 and 25°C.

Whyte, Lyle G.; Hawari, Jalal; Zhou, Edward; Bourbonniere, Luc; Inniss, William E.; Greer, Charles W.

1998-01-01

215

Revised charge equilibration parameters for more accurate hydration free energies of alkanes  

NASA Astrophysics Data System (ADS)

We present a refined alkane charge equilibration (CHEQ) force field, improving our previously reported CHEQ alkane force field [1] to better reproduce experimental hydration free energies. Experimental hydration free energies of ethane, propane, butane, pentane, hexane, and heptane are reproduced to within 3.6% on average. We demonstrate that explicit polarization results in a shift in molecular dipole moment for water molecules associated with the alkane molecule. We also show that our new parameters do not have a significant effect on the alkane-water interactions as measured by the radial distribution function (RDF).

Davis, Joseph E.; Patel, Sandeep

2010-01-01

216

Identification and structural characterisation of novel trehalose dinocardiomycolates from n-alkane-grown Rhodococcus opacus 1CP.  

PubMed

Rhodococcus opacus 1CP, a potent degrader of (chloro-) aromatic compounds was found to utilise C10-C16 n-alkanes as sole carbon sources. Highest conversion rates were observed with n-tetradecane and n-hexadecane, whereas the utilisation of n-dodecane and n-decane was considerably slower. Thin-layer chromatography of organic extracts of n-alkane-grown 1CP cultures indicated the growth-associated formation of a glycolipid which was characterised as a trehalose dimycolate by 1H-NMR spectroscopy and mass spectrometry. Total chain lengths between 48 and 54 carbons classify the fatty acid residues as nocardiomycolic acids. The presence of two double bonds in each mycolic acid is another feature that distinguishes the corresponding trehalose dinocardiomycolates from trehalose dicorynomycolates reported for Rhodococcus erythropolis DSM43215 and Rhodococcus ruber IEGM231. R. opacus 1CP was not found, even under nitrogen limitation, to produce anionic trehalose tetraesters which have previously been reported for R. erythropolis DSM43215. PMID:16133336

Niescher, Susanne; Wray, Victor; Lang, Siegmund; Kaschabek, Stefan R; Schlömann, Michael

2006-05-01

217

Radioanalytical Chemistry  

NSDL National Science Digital Library

This website provides a course on the use of radionuclides in analytical chemistry. Types of radioactive decay are discussed as well as the techniques of scintillation counting, neutron activation analysis, and gamma spectroscopy.

Hardy, James K.

2010-07-01

218

Chemistry Notes.  

ERIC Educational Resources Information Center

Describes equipment, activities, and experiments useful in chemistry instruction, including among others, a rapid method to determine available chlorine in bleach, simple flame testing apparatus, and a simple apparatus demonstrating the technique of flash photolysis. (SK)

School Science Review, 1980

1980-01-01

219

Chemistry Notes  

ERIC Educational Resources Information Center

Several ideas are proposed for chemistry teachers to try in their classrooms. Subjects included are polymerization of acrylate, polymerization of styrene, conductivity, pollution, preparation of chlorine, redox equations, chemiluminescence, and molecular sieves. (PS)

School Science Review, 1973

1973-01-01

220

Catalytic Chemistry.  

ERIC Educational Resources Information Center

Describes an approach for making chemistry relevant to everyday life. Involves the study of kinetics using the decomposition of hydrogen peroxide by vegetable juices. Allows students to design and carry out experiments and then draw conclusions from their results. (JRH)

Borer, Londa; And Others

1996-01-01

221

Organoleptic Chemistry.  

ERIC Educational Resources Information Center

Discusses how the concept of organoleptic chemistry permeates every modern chemical experiment. Six approaches for developing organoleptic attitudes which are crucial to the experimental aspects are also presented. (HM)

Slabaugh, W. H.

1980-01-01

222

Precolumbian Chemistry.  

ERIC Educational Resources Information Center

Describes the content and development of a curriculum that provides an approach to descriptive chemistry and the history of technology through consideration of the pottery, metallurgy, pigments, dyes, agriculture, and medicine of pre-Columbian people. (DDR)

Robinson, Janet Bond

1995-01-01

223

Nuclear Chemistry.  

ERIC Educational Resources Information Center

Provides a brief review of the latest developments in nuclear chemistry. Nuclear research today is directed toward increased activity in radiopharmaceuticals and formation of new isotopes by high-energy, heavy-ion collisions. (Author/BB)

Chemical and Engineering News, 1979

1979-01-01

224

Urine chemistry  

MedlinePLUS

Chemistry - urine ... For this test, a clean-catch (midstream) urine sample is needed. For more information, see: Urine collection - clean catch . Some tests require that you collect all of your urine for 24 ...

225

Chemistry Notes.  

ERIC Educational Resources Information Center

Describes 13 activities, experiments and demonstrations, including the preparation of iron (III) chloride, simple alpha-helix model, investigating camping gas, redox reactions of some organic compounds, a liquid crystal thermometer, and the oxidation number concept in organic chemistry. (JN)

School Science Review, 1981

1981-01-01

226

Cloning and expression of three ladA-type alkane monooxygenase genes from an extremely thermophilic alkane-degrading bacterium Geobacillus thermoleovorans B23.  

PubMed

An extremely thermophilic bacterium, Geobacillus thermoleovorans B23, is capable of degrading a broad range of alkanes (with carbon chain lengths ranging between C11 and C32) at 70 °C. Whole-genome sequence analysis revealed that unlike most alkane-degrading bacteria, strain B23 does not possess an alkB-type alkane monooxygenase gene. Instead, it possesses a cluster of three ladA-type genes, ladA?B23, ladA?B23, and ladB B23, on its chromosome, whose protein products share significant amino acid sequence identities, 49.8, 34.4, and 22.7 %, respectively, with that of ladA alkane monooxygenase gene found on a plasmid of Geobacillus thermodetrificans NG 80-2. Each of the three genes, ladA?B23, ladA?B23, and ladB B23, was heterologously expressed individually in an alkB1 deletion mutant strain, Pseudomonas fluorescens KOB2?1. It was found that all three genes were functional in P. fluorescens KOB2?1, and partially restored alkane degradation activity. In this study, we suggest that G. thermoleovorans B23 utilizes multiple LadA-type alkane monooxygenases for the degradation of a broad range of alkanes. PMID:24682607

Boonmak, Chanita; Takahashi, Yasunori; Morikawa, Masaaki

2014-05-01

227

Stratospheric chemistry  

SciTech Connect

Advances in stratospheric chemistry made by investigators in the United States from 1987 to 1990 are reviewed. Subject areas under consideration include photochemistry of the polar stratosphere, photochemistry of the global stratosphere, and assessments of inadvertent modification of the stratosphere by anthropogenic activity. Particular attention is given to early observations and theories, gas phase chemistry, Antarctic observations, Arctic observations, odd-oxygen, odd-hydrogen, odd-nitrogen, halogens, aerosols, modeling of stratospheric ozone, and reactive nitrogen effects.

Brune, W.H. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

228

Chemistry Tutorials  

NSDL National Science Digital Library

The California State University Stanislaus developed these interactive chemistry Web tutorials to assist college students in mass spectrometry, proton NMR chemical shifts, and more. With the many animations and figures, visitors will find assistance with the subtraction and absorption of light and with infrared absorption frequencies for numerous compounds. The titration tutorials simulate laboratory experiments without the hazards of dealing with chemicals. Students will also find a very informative lesson describing how to use Excel to record and analyze their chemistry data.

229

Utilization of n-alkanes by a newly isolated strain of Acinetobacter venetianus: the role of two AlkB-type alkane hydroxylases.  

PubMed

A bacterial strain capable of utilizing n-alkanes with chain lengths ranging from decane (C10H22) to tetracontane (C40H82) as a sole carbon source was isolated using a system for screening microorganisms able to grow on paraffin (mixed long-chain n-alkanes). The isolate, identified according to its 16S rRNA sequence as Acinetobacter venetianus, was designated A. venetianus 6A2. Two DNA fragments encoding parts of AlkB-type alkane hydroxylase homologues, designated alkMa and alkMb, were polymerase chain reaction-amplified from the genome of A. venetianus 6A2. To study the roles of these two alkM paralogues in n-alkane utilization in A. venetianus 6A2, we constructed alkMa, alkMb, and alkMa/alkMb disruption mutants. Studies on the growth patterns of the disruption mutants using n-alkanes with different chain lengths as sole carbon source demonstrated central roles for the alkMa and alkMb genes in utilization of C10 to C18 n-alkanes. Comparative analysis of these patterns also suggested different substrate preferences for AlkMa and AlkMb in n-alkane utilization. Because both single and double mutants were able to grow on n-alkanes with chain lengths of C20 and longer, we concluded that yet another enzyme(s) for the utilization of these n-alkanes must exist in A. venetianus 6A2. PMID:16520925

Throne-Holst, Mimmi; Markussen, Sidsel; Winnberg, Asgeir; Ellingsen, Trond E; Kotlar, Hans-Kristian; Zotchev, Sergey B

2006-09-01

230

Assessment of the GECKO-A modeling tool using chamber observations for C12 alkanes  

NASA Astrophysics Data System (ADS)

Secondary Organic Aerosol (SOA) production and ageing is the result of atmospheric oxidation processes leading to the progressive formation of organic species with higher oxidation state and lower volatility. Explicit chemical mechanisms reflect our understanding of these multigenerational oxidation steps. Major uncertainties remain concerning the processes leading to SOA formation and the development, assessment and improvement of such explicit schemes is therefore a key issue. The development of explicit mechanism to describe the oxidation of long chain hydrocarbons is however a challenge. Indeed, explicit oxidation schemes involve a large number of reactions and secondary organic species, far exceeding the size of chemical schemes that can be written manually. The chemical mechanism generator GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) is a computer program designed to overcome this difficulty. GECKO-A generates gas phase oxidation schemes according to a prescribed protocol assigning reaction pathways and kinetics data on the basis of experimental data and structure-activity relationships. In this study, we examine the ability of the generated schemes to explain SOA formation observed in the Caltech Environmental Chambers from various C12 alkane isomers and under high NOx and low NOx conditions. First results show that the model overestimates both the SOA yields and the O/C ratios. Various sensitivity tests are performed to explore processes that might be responsible for these disagreements.

Aumont, B.; La, S.; Ouzebidour, F.; Valorso, R.; Mouchel-Vallon, C.; Camredon, M.; Lee-Taylor, J. M.; Hodzic, A.; Madronich, S.; Yee, L. D.; Loza, C. L.; Craven, J. S.; Zhang, X.; Seinfeld, J.

2013-12-01

231

Conversation Classes.  

ERIC Educational Resources Information Center

Describes an activity for use in the conversational English-as-a-foreign-language classroom. The activity involves having each student say one or two sentences that continues a story being made up as the activity goes along. Students were positive about the activity, because saying only one or two sentences helped them not to feel pressured or…

Xia, Jiang

1998-01-01

232

Conversational Telugu.  

ERIC Educational Resources Information Center

The purpose of this text is to develop elementary conversational skills in Telugu. The language materials consist of four types of language learning activities. The first, and most predominant, is the unit microwave cycle. These cycles divide the learning process into two basic phases, the first of which involves mimicry, memorization, and…

Beinstein, Judith; And Others

233

Transporter engineering for improved tolerance against alkane biofuels in Saccharomyces cerevisiae  

PubMed Central

Background Hydrocarbon alkanes, components of major fossil fuels, are considered as next-generation biofuels because their biological production has recently been shown to be possible. However, high-yield alkane production requires robust host cells that are tolerant against alkanes, which exhibit cytotoxicity. In this study, we aimed to improve alkane tolerance in Saccharomyces cerevisiae, a key industrial microbial host, by harnessing heterologous transporters that potentially pump out alkanes. Results To this end, we attempted to exploit ABC transporters in Yarrowia lipolytica based on the observation that it utilizes alkanes as a carbon source. We confirmed the increased transcription of ABC2 and ABC3 transporters upon exposure to a range of alkanes in Y. lipolytica. We then showed that the heterologous expression of ABC2 and ABC3 transporters significantly increased tolerance against decane and undecane in S. cerevisiae through maintaining lower intracellular alkane level. In particular, ABC2 transporter increased the tolerance limit of S. cerevisiae about 80-fold against decane. Furthermore, through site-directed mutagenesis for glutamate (E988 for ABC2, and E989 for ABC3) and histidine (H1020 for ABC2, and H1021 for ABC3), we provided the evidence that glutamate was essential for the activity of ABC2 and ABC3 transporters, with ATP most likely to be hydrolyzed by a catalytic carboxylate mechanism. Conclusions Here, we demonstrated that transporter engineering through expression of heterologous efflux pumps led to significantly improved tolerance against alkane biofuels in S. cerevisiae. We believe that our results laid the groundwork for developing robust alkane-producing yeast cells through transporter engineering, which will greatly aid in next-generation alkane biofuel production and recovery.

2013-01-01

234

Computational Chemistry for Chemistry Educators  

NSDL National Science Digital Library

In this paper we describe an ongoing project where the goal is to develop competence and confidence among chemistry faculty so they are able to utilize computational chemistry as an effective teaching tool. Advances in hardware and software have made research-grade tools readily available to the academic community. Training is required so that faculty can take full advantage of this technology, begin to transform the educational landscape, and attract more students to the study of science.

Sendlinger, Shawn C.; Metz, Clyde R.

235

The in Vitro Estrogenic Activities of Polyfluorinated Iodine Alkanes  

PubMed Central

Background: Polyfluorinated iodine alkanes (PFIs) are important intermediates in the synthesis of organic fluoride products. Recently, PFIs have been detected in fluoropolymers as residual raw materials, as well as in the ambient environment. Objectives: High production volumes and potential environmental releases of PFIs might become a concern, but the exposure risk and toxicity of these chemicals are still unclear. In this study, we investigated the potential estrogenic effects of PFIs. Methods: We studied the estrogenic effects of fluorinated iodine alkanes (FIAs), fluorinated telomer iodides (FTIs), and fluorinated diiodine alkanes (FDIAs) using the E-screen and MVLN assays and the evaluation of estrogen-responsive genes in MCF-7 cells. Results: FIAs have an iodine atom at one end of the perfluorinated carbon chain. 1-Iodoperfluorohexane (PFHxI) and 1-iodoperfluorooctane (PFOI) promoted the proliferation of MCF-7 cells, induced luciferase activity in MVLN cells, and up-regulated the expression of TFF1 and EGR3. In these assays, other FIAs gave negative responses. FDIAs have an iodine atom at each end of the perfluorinated carbon chain, and all the FDIAs showed estrogenic effects. The estrogenic potencies of FIAs and FDIAs correlate well with the carbon chain length of the chemicals. The optimum chain length for estrogenic effects is six carbons, and then eight and four carbons. All FTIs have a single iodine atom at the end of a partially fluorinated carbon chain. None of the FTIs showed estrogenic effects in the tests. Conclusions: The estrogenic effects of PFIs are dependent on the structural features of iodine substitution and chain length. This research will be helpful in further understanding the estrogenic effects of perfluorinated compounds.

Wang, Chang; Wang, Thanh; Liu, Wei; Ruan, Ting; Zhou, Qunfang; Liu, Jiyan; Zhang, Aiqian; Zhao, Bin

2011-01-01

236

Activation of vanadium phosphorus oxide catalysts for alkane oxidation: The influence of the oxidation state on catalyst selectivity  

SciTech Connect

The selective conversion of light alkanes to oxygenates is important to both the petrochemical and energy industries. Oxygenates are used in the preparation of a large number of chemicals, polymers, and plastics. The reaction of n-butane with reactor equilibrated'' (VO)[sub 2]P[sub 2]O[sub 7]-based catalysts activated with different oxygen treatments has been investigated using high speed transient response techniques. It is shown that by maintaining the catalyst in a highly oxidized state the rate of maleic anhydride formation increases, and the n-butane selectivity to maleic anhydride improves. The activation energy for the reaction of n-butane was obtained by a kinetic analysis of the transient responses as a function of the temperature. The value of the activation energy depends on the oxidation state of the catalyst.

Schuurman, Y.; Gleaves, J.T. (Washington Univ., St. Louis, MO (United States). Dept. of Chemical Engineering)

1994-12-01

237

Evolution of tricyclic alkanes in the Espirito Santo Basin, Brazil  

NASA Astrophysics Data System (ADS)

The distributions of tricyclic isoprenoid alkanes were characterized in the Neocomian sequence from the Espirito Santo Basin, Brazil, by high-resolution gas chromatography-mass spectrometry and co-injection with synthetic standards where available. A suite of homologous components ranging from C 20 to C 28 were present throughout the sequence as a mixture of stereoisomers whose relative abundance changed with depth. The epimerization rates were similar for the various tricyclic compounds irrespective of side-chain length, achieving equilibrium ratios before the main stage of oil generation. This new maturity parameter should be useful as a supplement to sterane/hopane measurements.

Aquino Neto, F. R.; Cardoso, J. N.; Rodrigues, R.; Trindade, L. A. F.

1986-09-01

238

Scaling Laws for Diffusion Coefficients in Mixtures of Alkanes  

NASA Astrophysics Data System (ADS)

Natural fluids, such as crude oils, are often mixtures of a broad range of different molecules, and in situ measurement of their composition is highly desirable. Furthermore, the relationship between their composition and their physical properties has always been a challenge for such mixtures. We have analyzed diffusion in alkane mixtures to find a power law for the self-diffusion coefficient in terms of molecular sizes. We demonstrate that this power law can be used to obtain the molecular size distribution of crude oils using noninvasive measurements of diffusion distributions.

Freed, Denise E.; Burcaw, Lauren; Song, Yi-Qiao

2005-02-01

239

Radiation Chemistry  

NASA Astrophysics Data System (ADS)

Ionizing radiation causes chemical changes in the molecules of the interacting medium. The initial molecules change to new molecules, resulting in changes of the physical, chemical, and eventually biological properties of the material. For instance, water decomposes to its elements H2 and O2. In polymers, degradation and crosslinking take place. In biopolymers, e.g., DNS strand breaks and other alterations occur. Such changes are to be avoided in some cases (radiation protection), however, in other cases they are used for technological purposes (radiation processing). This chapter introduces radiation chemistry by discussing the sources of ionizing radiation (radionuclide sources, machine sources), absorption of radiation energy, techniques used in radiation chemistry research, and methods of absorbed energy (absorbed dose) measurements. Radiation chemistry of different classes of inorganic (water and aqueous solutions, inorganic solids, ionic liquids (ILs)) and organic substances (hydrocarbons, halogenated compounds, polymers, and biomolecules) is discussed in concise form together with theoretical and experimental backgrounds. An essential part of the chapter is the introduction of radiation processing technologies in the fields of polymer chemistry, food processing, and sterilization. The application of radiation chemistry to nuclear technology and to protection of environment (flue gas treatment, wastewater treatment) is also discussed.

Wojnárovits, L.

240

Energy Conversions  

NSDL National Science Digital Library

Students evaluate various everyday energy conversion devices and draw block flow diagrams to show the forms and states of energy into and out of the device. They also identify the forms of energy that are useful and the desired output of the device as well as the forms that are not useful for the intended use of the item. This can be used to lead into the law of conservation of energy and efficiency. The student activity is preceded by a demonstration of a more complicated system to convert chemical energy to heat energy to mechanical energy. Drawing the block energy conversion diagram for this system models the activity that the students then do themselves for other simpler systems.

Office Of Educational Partnerships

241

IT Conversations  

NSDL National Science Digital Library

For those who might see the words "IT Conversations", and think: "Oh no. A website dedicated to conversations about IT", think again. This delightful website started life in June 2003, under the careful direction of Doug Kaye and it currently contains dozens of compelling interviews, discussions, and heated debates with a number of fascinating individuals. The first-time visitor might want to begin by looking through some of the series listed on the homepage. Some of the themes addressed by these sessions include social innovation, technology development, and global security. Each interview can also be rated, so visitors may want to listen to some of the highest rated programs first, depending on their faith in such ratings. Of course, users may also wish to use the search engine offered here, as they can use this application to quickly locate different programs of interest.

Kaye, Doug

242

Energy conversion and storage program  

NASA Astrophysics Data System (ADS)

The Energy Conversion and Storage Program applies chemistry and materials science principles to solve problems in: (1) production of new synthetic fuels; (2) development of high-performance rechargeable batteries and fuel cells; (3) development of advanced thermochemical processes for energy conversion; (4) characterization of complex chemical processes; and (5) application of novel materials for energy conversion and transmission. Projects focus on transport-process principles, chemical kinetics, thermodynamics, separation processes, organic and physical chemistry, novel materials, and advanced methods of analysis. Electrochemistry research aims to develop advanced power systems for electric vehicle and stationary energy storage applications. Topics include identification of new electrochemical couples for advanced rechargeable batteries, improvements in battery and fuel-cell materials, and the establishment of engineering principles applicable to electrochemical energy storage and conversion. Chemical Applications research includes topics such as separations, catalysis, fuels, and chemical analyses. Included in this program area are projects to develop improved, energy-efficient methods for processing waste streams from synfuel plants and coal gasifiers. Other research projects seek to identify and characterize the constituents of liquid fuel-system streams and to devise energy-efficient means for their separation. Materials Applications research includes the evaluation of the properties of advanced materials, as well as the development of novel preparation techniques. For example, the use of advanced techniques, such as sputtering and laser ablation, are being used to produce high-temperature superconducting films.

Cairns, E. J.

1992-03-01

243

Energy Conversion and Storage Program  

SciTech Connect

The Energy Conversion and Storage Program applies chemistry and materials science principles to solve problems in (1) production of new synthetic fuels, (2) development of high-performance rechargeable batteries and fuel cells, (3) development of advanced thermochemical processes for energy conversion, (4) characterization of complex chemical processes, and (5) application of novel materials for energy conversion and transmission. Projects focus on transport-process principles, chemical kinetics, thermodynamics, separation processes, organic and physical chemistry, novel materials, and advanced methods of analysis. Electrochemistry research aims to develop advanced power systems for electric vehicle and stationary energy storage applications. Topics include identification of new electrochemical couples for advanced rechargeable batteries, improvements in battery and fuel-cell materials, and the establishment of engineering principles applicable to electrochemical energy storage and conversion. Chemical Applications research includes topics such as separations, catalysis, fuels, and chemical analyses. Included in this program area are projects to develop improved, energy-efficient methods for processing waste streams from synfuel plants and coal gasifiers. Other research projects seek to identify and characterize the constituents of liquid fuel-system streams and to devise energy-efficient means for their separation. Materials Applications research includes the evaluation of the properties of advanced materials, as well as the development of novel preparation techniques. For example, the use of advanced techniques, such as sputtering and laser ablation, are being used to produce high-temperature superconducting films.

Cairns, E.J.

1992-03-01

244

Analyses of n-alkanes degrading community dynamics of a high-temperature methanogenic consortium enriched from production water of a petroleum reservoir by a combination of molecular techniques.  

PubMed

Despite the knowledge on anaerobic degradation of hydrocarbons and signature metabolites in the oil reservoirs, little is known about the functioning microbes and the related biochemical pathways involved, especially about the methanogenic communities. In the present study, a methanogenic consortium enriched from high-temperature oil reservoir production water and incubated at 55 °C with a mixture of long chain n-alkanes (C(15)-C(20)) as the sole carbon and energy sources was characterized. Biodegradation of n-alkanes was observed as methane production in the alkanes-amended methanogenic enrichment reached 141.47 ?mol above the controls after 749 days of incubation, corresponding to 17 % of the theoretical total. GC-MS analysis confirmed the presence of putative downstream metabolites probably from the anaerobic biodegradation of n-alkanes and indicating an incomplete conversion of the n-alkanes to methane. Enrichment cultures taken at different incubation times were subjected to microbial community analysis. Both 16S rRNA gene clone libraries and DGGE profiles showed that alkanes-degrading community was dynamic during incubation. The dominant bacterial species in the enrichment cultures were affiliated with Firmicutes members clustering with thermophilic syntrophic bacteria of the genera Moorella sp. and Gelria sp. Other represented within the bacterial community were members of the Leptospiraceae, Thermodesulfobiaceae, Thermotogaceae, Chloroflexi, Bacteroidetes and Candidate Division OP1. The archaeal community was predominantly represented by members of the phyla Crenarchaeota and Euryarchaeota. Corresponding sequences within the Euryarchaeota were associated with methanogens clustering with orders Methanomicrobiales, Methanosarcinales and Methanobacteriales. On the other hand, PCR amplification for detection of functional genes encoding the alkylsuccinate synthase ?-subunit (assA) was positive in the enrichment cultures. Moreover, the appearance of a new assA gene sequence identified in day 749 supported the establishment of a functioning microbial species in the enrichment. Our results indicate that n-alkanes are converted to methane slowly by a microbial community enriched from oilfield production water and fumarate addition is most likely the initial activation step of n-alkanes degradation under thermophilic methanogenic conditions. PMID:22688358

Zhou, Lei; Li, Kai-Ping; Mbadinga, Serge Maurice; Yang, Shi-Zhong; Gu, Ji-Dong; Mu, Bo-Zhong

2012-08-01

245

Expression of Alkane Hydroxylase from Acinetobacter sp. Strain ADP1 Is Induced by a Broad Range of n-Alkanes and Requires the Transcriptional Activator AlkR  

PubMed Central

In Acinetobacter sp. strain ADP1, alkane degradation depends on at least five essential genes. rubAB and xcpR are constitutively transcribed. Here we describe inducible transcription of alkM, which strictly depends on the presence of the transcriptional activator AlkR. alkR itself is expressed at a low level, while a chromosomally located alkM::lacZ fusion is inducible by middle-chain-length alkanes from heptane to undecane, which do not support growth of ADP1, and by long-chain-length alkanes from dodecane to octadecane, which are used as sources of carbon and energy. The putative AlkM substrate 1-dodecene is also an effective inducer. Products of alkane hydroxylase activity like 1-dodecanol prevent induction of alkM expression. alkM is expressed only in stationary phase, suggesting its dependence on at least one other regulatory mechanism.

Ratajczak, Andreas; Geissdorfer, Walter; Hillen, Wolfgang

1998-01-01

246

Alkane biodegradation by a microbial community from contaminated sediments in Patagonia, Argentina  

Microsoft Academic Search

Biodegradation of a mix of normal alkanes (decane, dodecane, tetradecane, hexadecane, octadecane and eicosane) was studied in batch cultures after inoculating with microbial communities from pristine and hydrocarbon contaminated sediments. Analysis showed that the community from polluted sediments reduced the concentrations of all alkanes to < 5 mg l?1 after a 240-h incubation period (< 5% initial concentration), while the

Nelda L. Olivera; José L. Esteves; Marta G. Commendatore

1997-01-01

247

On the Assignments of Rotatory Lattice Modes in n-Alkanes and Polyethylene.  

National Technical Information Service (NTIS)

Considerable discrepancy exists in the recent literature on the assignments of the rotatory lattice modes of the n-alkanes and polyethylene. New low-temperature Raman data are presented on orthorhombic n-alkanes and on n-C36D74 and n-C16D34. Analyses of t...

B. Fanconi

1975-01-01

248

Molecular tilting and its impact on frictional properties of n-alkane self-assembled monolayers.  

PubMed

Hydrophobic, methyl-terminated self-assembled monolayer (SAM) surfaces can be used to reduce friction. Among methyl-terminated SAMs, the frictional properties of alkanethiol SAMs and silane SAMs have been well-studied. In this research, we investigated friction of methyl-terminated n-hexatriacontane (C36) SAM and compared its friction properties with the alkanethiol and silane SAMs. Alkane SAM does not have an anchoring group. The alkane molecules stand on the surface by physical adsorption, which leads to a higher surface mobility of alkane molecules. We found that C36 SAM has a higher coefficient of friction than that of octadecyltrichlorosilane (OTS) silane. When an atomic force microscope (AFM) tip was swiped across the alkane SAM with a loading force, we found that the alkane SAM can withstand the tip loading pressure up to 0.48 GPa. Between 0.48 and 0.49Ga, the AFM tip partially penetrated the SAM. When the tip moved away, the deformed SAM healed and maintained the structural integrity. When the loading pressure was higher than 0.49 GPa, the alkane SAM was shaved into small pieces by the tip. In addition, we found that the molecular tilting of C36 molecules interacted with the tribological properties of the alkane SAM surface. On one hand, a higher loading force can push the rod-like alkane molecules to a higher tilting angle; on the other hand, a higher molecular tilting leads to a lower friction surface. PMID:21488616

Lu, Lingbo; Cai, Yuguang

2011-05-17

249

Surfactant-induced phases in water-supported alkane monolayers: I. Thermodynamics.  

PubMed

Alkanes longer than n = 6 carbons do not spread on the water surface, but condense in a macroscopic lens. However, adding trimethylammonium-based surfactants, CmTAB, in submillimolar concentrations causes the alkanes to spread and form a single Langmuir-Gibbs (LG) monolayer of mixed alkanes and surfactant tails, which coexists with the alkane lenses. Upon cooling, this LG film surface-freezes at a temperature Ts above the bulk freezing temperature Tb. The thermodynamics of surface freezing (SF) of these LG films is studied by surface tension measurements for a range of alkanes (n = 12-21) and surfactant alkyl lengths (m = 14, 16, 18), at several concentrations c. The surface freezing range Ts-Tb observed is up to 25 °C, an order of magnitude larger than the temperature range of SF monolayers on the surface of pure alkane melts. The measured (n,T) surface phase diagram is accounted for well by a model based on mixtures' theory, which includes an interchange energy term ?. ? is found to be negative, implying attraction between unlike species, rather than the repulsion found for SF of binary alkane mixtures. Thus, the surfactant/alkane mixing is a necessary condition for the occurrence of SF in these LG films. The X-ray derived structure of the films is presented in an accompanying paper. PMID:24918482

Yefet, Shai; Sloutskin, Eli; Tamam, Lilach; Sapir, Zvi; Cohen, Asaf; Deutsch, Moshe; Ocko, Benjamin M

2014-07-15

250

Identity and mechanisms of alkane-oxidizing metalloenzymes from deep-sea hydrothermal vents  

PubMed Central

Six aerobic alkanotrophs (organism that can metabolize alkanes as their sole carbon source) isolated from deep-sea hydrothermal vents were characterized using the radical clock substrate norcarane to determine the metalloenzyme and reaction mechanism used to oxidize alkanes. The organisms studied were Alcanivorax sp. strains EPR7 and MAR14, Marinobacter sp. strain EPR21, Nocardioides sp. strains EPR26w, EPR28w, and Parvibaculum hydrocarbonoclasticum strain EPR92. Each organism was able to grow on n-alkanes as the sole carbon source and therefore must express genes encoding an alkane-oxidizing enzyme. Results from the oxidation of the radical-clock diagnostic substrate norcarane demonstrated that five of the six organisms (EPR7, MAR14, EPR21, EPR26w, and EPR28w) used an alkane hydroxylase functionally similar to AlkB to catalyze the oxidation of medium-chain alkanes, while the sixth organism (EPR92) used an alkane-oxidizing cytochrome P450 (CYP)-like protein to catalyze the oxidation. DNA sequencing indicated that EPR7 and EPR21 possess genes encoding AlkB proteins, while sequencing results from EPR92 confirmed the presence of a gene encoding CYP-like alkane hydroxylase, consistent with the results from the norcarane experiments.

Bertrand, Erin M.; Keddis, Ramaydalis; Groves, John T.; Vetriani, Costantino; Austin, Rachel Narehood

2013-01-01

251

Metabolism of n-alkanes and n-alkenes by anaerobic bacteria: A summary  

Microsoft Academic Search

Current knowledge of the pathways for the degradation of n-alkanes and n-alkenes by anaerobic bacteria is summarized and new results questioning the existence of an alternative pathway for anaerobic alkane degradation are introduced. Remaining gaps in our knowledge are also mentioned, together with the possible use of some specific metabolites as biomarkers of anaerobic hydrocarbon degradation.

Vincent Grossi; Cristiana Cravo-Laureau; Rémy Guyoneaud; Anthony Ranchou-Peyruse; Agnès Hirschler-Réa

2008-01-01

252

Chemistry & Industry  

NSDL National Science Digital Library

Chemistry and Industry Magazine, a bimonthly product of the Society of Chemical Industry, provides selected full-text articles from the print magazine in the areas of news, commentary, features, latest results from chemical literature, and highlights from the latest European patents. In addition, there is a searchable and browsable archive of past issues, a daily news section, and searchable jobs and meetings databases. The Society of Chemical Industry is "an international association of about 6000 members aimed at furthering applied chemistry." One of the highlights of its web site is its publication section, where, under "electronic publications," readers can find updated daily news, jobs and meetings listings on chemistry, pharmaceuticals, biotechnology, and the environment.

1997-01-01

253

Kitchen Chemistry  

NSDL National Science Digital Library

There is a great deal of chemistry going on in every kitchen, even though most cooks may not be cognizant of the various interactions going on in the pot, wok, or oven. MIT's popular OpenCourseWare Initiative has recently made the contents of Dr. Patricia Christie's course on kitchen chemistry available on this site. Visitors to the site can download the syllabus, take in some assigned readings (and recipes), and look over the assignments. The assignments include investigations that involve emulsifiers, ice cream, peer teaching, and pancakes, among other things. The site also includes links to helpful readings, such as those on chocolate, the health benefits of capsicum, and the world of gluten. For people who wish to bring back the frayed connective tissue between chemistry and the culinary arts, this site is absolutely essential.

Christie, Patricia

2006-01-01

254

Geomicrobiological linkages between short-chain alkane consumption and sulfate reduction rates in seep sediments  

PubMed Central

Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2–C5) and longer alkanes. C2–C4 alkanes such as ethane, propane, and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico (GoM) were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1–C4) then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist). Changes in the ?13C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4 and 4.5‰, respectively). The concurrent depletion in the ?13C of dissolved inorganic carbon (DIC) implies a transfer of carbon from the alkane to the DIC pool (?3.5 and ?6.7‰ for C3 and C4 incubations, respectively). Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1–C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3–C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community composition and density.

Bose, Arpita; Rogers, Daniel R.; Adams, Melissa M.; Joye, Samantha B.; Girguis, Peter R.

2013-01-01

255

Second NASA Conference on Laser Energy Conversion  

NASA Technical Reports Server (NTRS)

The possible transmission of high power laser beams over long distances and their conversion to thrust, electricity, or other useful forms of energy is considered. Specific topics discussed include: laser induced chemistry; developments in photovoltaics, including modification of the Schottky barrier devices and generation of high voltage emf'sby laser radiation of piezoelectric ceramics; the thermo electronic laser energy converter and the laser plasmadynamics converters; harmonic conversion of infrared laser radiation in molecular gases; and photon engines.

Billman, K. W. (editor)

1976-01-01

256

Chemistry Experiments  

NASA Technical Reports Server (NTRS)

The purpose of the chemistry component of the model comparison is to assess to what extent differences in the formulation of chemical processes explain the variance between model results. Observed concentrations of chemical compounds are used to estimate to what degree the various models represent realistic situations. For readability, the materials for the chemistry experiment are reported in three separate sections. This section discussed the data used to evaluate the models in their simulation of the source gases and the Nitrogen compounds (NO(y)) and Chlorine compounds (Cl(y)) species.

Brasseur, Guy; Remsberg, Ellis; Purcell, Patrick; Bhatt, Praful; Sage, Karen H.; Brown, Donald E.; Scott, Courtney J.; Ko, Malcolm K. W.; Tie, Xue-Xi; Huang, Theresa

1999-01-01

257

Comparative study of the effects of several n-alkanes on phospholipid hexagonal phases.  

PubMed

The effects of a series of normal alkanes (decane, dodecane, tetradecane, hexadecane, and octadecane) on the hexagonal H(II) structures containing dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC) were studied using x-ray diffraction and osmotic stress. The alkanes affect structural dimensions and the monolayer intrinsic curvature and bending modulus. The alkane effects are chain-length dependent and are attributed to their different distribution within the H(II) structure. The data suggest that short-chain alkanes are more uniformly distributed within the H(II) hydrocarbon regions and change the curvature and bending modulus of the monolayer, whereas longer-chain alkanes appear confined more to the interstitial region and do not change the curvature and bending modulus. PMID:9533705

Chen, Z; Rand, R P

1998-02-01

258

Comparative study of the effects of several n-alkanes on phospholipid hexagonal phases.  

PubMed Central

The effects of a series of normal alkanes (decane, dodecane, tetradecane, hexadecane, and octadecane) on the hexagonal H(II) structures containing dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC) were studied using x-ray diffraction and osmotic stress. The alkanes affect structural dimensions and the monolayer intrinsic curvature and bending modulus. The alkane effects are chain-length dependent and are attributed to their different distribution within the H(II) structure. The data suggest that short-chain alkanes are more uniformly distributed within the H(II) hydrocarbon regions and change the curvature and bending modulus of the monolayer, whereas longer-chain alkanes appear confined more to the interstitial region and do not change the curvature and bending modulus.

Chen, Z; Rand, R P

1998-01-01

259

Surveys of research in the Chemistry Division, Argonne National Laboratory  

SciTech Connect

Research reports are presented on reactive intermediates in condensed phase (radiation chemistry, photochemistry), electron transfer and energy conversion, photosynthesis and solar energy conversion, metal cluster chemistry, chemical dynamics in gas phase, photoionization-photoelectrons, characterization and reactivity of coal and coal macerals, premium coal sample program, chemical separations, heavy elements coordination chemistry, heavy elements photophysics/photochemistry, f-electron interactions, radiation chemistry of high-level wastes (gas generation in waste tanks), ultrafast molecular electronic devices, and nuclear medicine. Separate abstracts have been prepared. Accelerator activites and computer system/network services are also reported.

Grazis, B.M. (ed.)

1992-01-01

260

Composition of n-alkanes in natural populations of Pinus nigra from Serbia - chemotaxonomic implications.  

PubMed

This is the first report on the composition and variability of the needle-wax n-alkanes in natural populations of Pinus nigra in Serbia. Samples of 195 trees from seven populations belonging to several infraspecific taxa (ssp. nigra, var. gocensis, ssp. pallasiana, and var. banatica) were analyzed. In general, the size of the n-alkanes ranged from C(16) to C(33) , with the exception of ssp. nigra, for which it ranged from C(18) to C(33) . The most abundant were C(23) -, C(25) -, C(27) -, and C(29) -alkanes. The needle waxes of Populations?I-III and V were characterized by a higher content of C(23) -, C(25) -, and C(27) -alkanes and a lower content of C(24) -, C(26) -, C(28) -, and C(30) -alkanes, compared to the other populations, and the trees of these populations could be assigned to ssp. nigra. The samples of Population?VI were characterized by higher amounts of C(22) -, C(24) -, C(30) -, and C(32) -alkanes and lower amounts of C(25) - and C(27) -alkanes, and the trees could be considered as ssp. pallasiana. The samples of Population?VII, consisting of trees belonging to var. banatica, were richer in C(29) -, C(31) -, and C(33) -alkanes. The wax compositions of Populations?IV and V, both composed of trees previously determined as P. nigra var. gocensis, showed a tendency of splitting. Indeed, the alkane composition of Population?IV was closer to that of ssp. pallasiana pines, while that of Population?V was more similar to that of ssp. nigra pines. From the results presented here, it is obvious that in the central part of the Balkan Peninsula, significant diversification and differentiation of the populations of black pine exists, and these populations could be defined as different intraspecific taxa. Our results also indicate the validity of n-alkanes as chemotaxonomic characters within this aggregate. PMID:23255446

Bojovi?, Srdjan; Sarac, Zorica; Nikoli?, Biljana; Teševi?, Vele; Todosijevi?, Marina; Velji?, Milan; Marin, Petar D

2012-12-01

261

Genes involved in alkane degradation in the Alcanivorax hongdengensis strain A-11-3.  

PubMed

Alcanivorax hongdengensis A-11-3 is a newly identified type strain isolated from the surface water of the Malacca and Singapore Straits that can degrade a wide range of alkanes. To understand the degradation mechanism of this strain, the genes encoding alkane hydroxylases were obtained by PCR screening and shotgun sequencing of a genomic fosmid library. Six genes involved in alkane degradation were found, including alkB1, alkB2, p450-1, p450-2, p450-3 and almA. Heterogeneous expression analysis confirmed their functions as alkane oxidases in Pseudomonas putida GPo12 (pGEc47?B) or Pseudomonas fluorescens KOB2?1. Q-PCR revealed that the transcription of alkB1 and alkB2 was enhanced in the presence of n-alkanes C(12) to C(24); three p450 genes were up-regulated by C(8)-C(16) n-alkanes at different levels, whereas enhanced expression of almA was observed when strain A-11-3 grew with long-chain alkanes (C(24) to C(36)). In the case of branched alkanes, pristane significantly enhanced the expression of alkB1, p450-3 and almA. The six genes enable strain A-11-3 to degrade short (C(8)) to long (C(36)) alkanes that are straight or branched. The ability of A. hongdengensis A-11-3 to thrive in oil-polluted marine environments may be due to this strain's multiple systems for alkane degradation and its range of substrates. PMID:22207216

Wang, Wanpeng; Shao, Zongze

2012-04-01

262

Nuclear Chemistry  

NSDL National Science Digital Library

This page, from the University of North Carolina - Chapel Hill Chemistry Fundamentals program and the Shodor Education Foundation, discusses five different types of radioactive decay: alpha, beta negative, gamma, positron emission, and electron capture. After examining the numerous equations, students can test their dating skills by solving three practice problems. Solutions are included.

2008-03-12

263

Chemistry Notes  

ERIC Educational Resources Information Center

Short articles on the alkylation of aniline, the preparation and properties of perbromate, using scrap copper in chemistry instruction, a safe method of burning hydrogen, and the use of an ion-charge model as an alternative to the mole concept in secondary school instruction. (AL)

School Science Review, 1972

1972-01-01

264

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents 12 chemistry notes for British secondary school teachers. Some of these notes are: (1) a simple device for testing pH-meters; (2) portable fume cupboard safety screen; and (3) Mass spectroscopy-analysis of a mass peak. (HM)

School Science Review, 1980

1980-01-01

265

Chemistry Notes.  

ERIC Educational Resources Information Center

Describes some laboratory apparatus, chemistry experiments and demonstrations, such as a Kofler block melting point apparatus, chromatographic investigation of the phosphoric acid, x-ray diffraction, the fountain experiment, endothermic sherbet, the measurement of viscosity, ionization energies and electronic configurations. (GA)

School Science Review, 1978

1978-01-01

266

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents chemistry experiments, laboratory procedures, demonstrations, and classroom materials/activities. These include: experiments on colloids, processing of uranium ore, action of heat on carbonates; color test for phenols and aromatic amines; solvent properties of non-electrolytes; stereoscopic applications/methods; a valency balance;…

School Science Review, 1983

1983-01-01

267

Chemistry Notes  

ERIC Educational Resources Information Center

Describes several chemistry projects, including solubility, formula for magnesium oxide, dissociation of dinitrogen tetroxide, use of 1-chloro-2, 4-dinitrobenzene, migration of ions, heats of neutralizations, use of pocket calculators, sonic cleaning, oxidation states of manganese, and cell potentials. Includes an extract from Chemical Age on…

School Science Review, 1976

1976-01-01

268

Countertop Chemistry  

NSDL National Science Digital Library

Chemistry activities and demonstrations that use common household items and kitchen chemicals. There are activities appropriate for students in elementary school, middle school, and high school. The activities were designed and tested by the Science House, the science and mathematics learning outreach program of North Carolina State University.

269

Common Chemistry  

NSDL National Science Digital Library

A web resource that contains Chemical Abstracts Service (CAS) Registry Numbers for approximately 7,800 chemicals of widespread general public interest. Common Chemistry is helpful to non-chemists who know either a name or CAS Registry Number® of a common chemical and want to pair both pieces of information.

Chemical Abstracts Service (CAS)

270

Bad Chemistry  

NSDL National Science Digital Library

This site from the Princeton Section of the American Chemical Society consists of articles about common chemical misconceptions along with examinations of the scientific explanation. The purpose of this page is to reveal common misconceptions in the field of Chemistry. The intended audience is secondary school students and their teachers. The page is at present just beginning, and additions are welcome.

Lehmann, Kevin; University, Princeton

271

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents chemistry experiments, laboratory procedures, demonstrations, teaching suggestions, and classroom materials/activities. These include: game for teaching ionic formulas; method for balancing equations; description of useful redox series; computer programs (with listings) for water electrolysis simulation and for determining chemical…

School Science Review, 1983

1983-01-01

272

Chemistry Gateways and Resources  

NSDL National Science Digital Library

The Chemistry Gateways and Resources collection is comprised of chemistry-related web portals, web sites, and individual digital resources pertaining to many areas of the discipline - general chemistry, organic and inorganic chemistry, physical chemistry, and others - and intended for a wide range of audiences: educators and learners, the general public, and chemistry research communities.

2008-03-14

273

Fundamentals of environmental chemistry  

Microsoft Academic Search

This book is designed to be understandable and interesting without being overly simplistic. Topics addressed include an overview of basic chemistry; matter and the basis of its physical nature and behavior; organic chemistry; biological chemistry; the chemistry of water, soil, and air; industrial chemistry; toxicological chemistry as it pertains to occupational health and human exposure to pollutants and toxicants; energy;

Manahan

1993-01-01

274

On the large ?-hyperconjugation in alkanes and alkenes.  

PubMed

The conventional view that the ?CC and ?CH bonds in alkanes and unsaturated hydrocarbons are so highly localized that their non-steric interactions are negligible is scrutinized by the block-localized wavefunction (BLW) method. Even molecules considered conventionally to be "strain free" and "unperturbed" have surprisingly large and quite significant total ?-BLW-delocalization energies (DEs) due to their geminal and vicinal hyperconjugative interactions. Thus, the computed BLW-DEs (in kcal mol(-1)) for the antiperiplanar conformations of the n-alkanes (C(N)H(2N+2), N = 1-10) range from 11.6 for ethane to 82.2 for?n-decane and are 50.9 for cyclohexane and 91.0 for adamantane. Although ?-electron delocalization in unsaturated hydrocarbons usually is ignored, the ?-BLW-DEs (in kcal mol(-1)) are substantial, as exemplified by D2h ethylene (9.0), triplet D2d ethylene (16.4), allene (19.3), butadiene (19.0), hexatriene (28.3), benzene (28.1), and cyclobutadiene (21.1). While each individual geminal and vicinal hyperconjugative interaction between hydrocarbon ?-bonding and ?-antibonding orbitals tends to be smaller than an individual ? conjugative interaction (e.g., 10.2 kcal mol(-1) in anti-1,3-butadiene, the presence of many ?-hyperconjugative interactions (e.g., a total of 12 in anti-1,3-butadiene, see text), result in substantial total ?-stabilization energies (e.g., 19.0 kcal mol(-1) for butadiene), which may surpass those from the ? interactions. Although large in magnitude, ?-electron delocalization energies often are obscured by cancellation when two hydrocarbons are compared. Rather than being strain-free, cyclohexane, adamantane, and diamantane suffer from their increasing number of intramolecular 1,4-C…C repulsions resulting in elongated C-C bond lengths and reduced ?-hyperconjugation, compared to the (skew-free) antiperiplanar n-alkane conformers. Instead of being inconsequential, ?-bond interactions are important and merit consideration. PMID:24912591

Wu, Judy I-Chia; Wang, Changwei; McKee, William Chadwick; Schleyer, Paul von Ragué; Wu, Wei; Mo, Yirong

2014-06-01

275

Copper-catalyzed intermolecular amidation and imidation of unactivated alkanes.  

PubMed

We report a set of rare copper-catalyzed reactions of alkanes with simple amides, sulfonamides, and imides (i.e., benzamides, tosylamides, carbamates, and phthalimide) to form the corresponding N-alkyl products. The reactions lead to functionalization at secondary C-H bonds over tertiary C-H bonds and even occur at primary C-H bonds. [(phen)Cu(phth)] (1-phth) and [(phen)Cu(phth)2] (1-phth2), which are potential intermediates in the reaction, have been isolated and fully characterized. The stoichiometric reactions of 1-phth and 1-phth2 with alkanes, alkyl radicals, and radical probes were investigated to elucidate the mechanism of the amidation. The catalytic and stoichiometric reactions require both copper and tBuOOtBu for the generation of N-alkyl product. Neither 1-phth nor 1-phth2 reacted with excess cyclohexane at 100 °C without tBuOOtBu. However, the reactions of 1-phth and 1-phth2 with tBuOOtBu afforded N-cyclohexylphthalimide (Cy-phth), N-methylphthalimide, and tert-butoxycyclohexane (Cy-OtBu) in approximate ratios of 70:20:30, respectively. Reactions with radical traps support the intermediacy of a tert-butoxy radical, which forms an alkyl radical intermediate. The intermediacy of an alkyl radical was evidenced by the catalytic reaction of cyclohexane with benzamide in the presence of CBr4, which formed exclusively bromocyclohexane. Furthermore, stoichiometric reactions of [(phen)Cu(phth)2] with tBuOOtBu and (Ph(Me)2CO)2 at 100 °C without cyclohexane afforded N-methylphthalimide (Me-phth) from ?-Me scission of the alkoxy radicals to form a methyl radical. Separate reactions of cyclohexane and d12-cyclohexane with benzamide showed that the turnover-limiting step in the catalytic reaction is the C-H cleavage of cyclohexane by a tert-butoxy radical. These mechanistic data imply that the tert-butoxy radical reacts with the C-H bonds of alkanes, and the subsequent alkyl radical combines with 1-phth2 to form the corresponding N-alkyl imide product. PMID:24405209

Tran, Ba L; Li, Bijie; Driess, Matthias; Hartwig, John F

2014-02-12

276

Identification of an Amino Acid Position That Determines the Substrate Range of Integral Membrane Alkane Hydroxylases  

PubMed Central

Selection experiments and protein engineering were used to identify an amino acid position in integral membrane alkane hydroxylases (AHs) that determines whether long-chain-length alkanes can be hydroxylated by these enzymes. First, substrate range mutants of the Pseudomonas putida GPo1 and Alcanivorax borkumensis AP1 medium-chain-length AHs were obtained by selection experiments with a specially constructed host. In all mutants able to oxidize alkanes longer than C13, W55 (in the case of P. putida AlkB) or W58 (in the case of A. borkumensis AlkB1) had changed to a much less bulky amino acid, usually serine or cysteine. The corresponding position in AHs from other bacteria that oxidize alkanes longer than C13 is occupied by a less bulky hydrophobic residue (A, V, L, or I). Site-directed mutagenesis of this position in the Mycobacterium tuberculosis H37Rv AH, which oxidizes C10 to C16 alkanes, to introduce more bulky amino acids changed the substrate range in the opposite direction; L69F and L69W mutants oxidized only C10 and C11 alkanes. Subsequent selection for growth on longer alkanes restored the leucine codon. A structure model of AHs based on these results is discussed.

van Beilen, Jan B.; Smits, Theo H. M.; Roos, Franz F.; Brunner, Tobias; Balada, Stefanie B.; Rothlisberger, Martina; Witholt, Bernard

2005-01-01

277

The effect of molecular symmetry in alkane complexes of 2,5-diphenylfuran and related species  

NASA Astrophysics Data System (ADS)

Fluorescence excitation spectra are reported for van der Waals complexes of 2,5-diphenylfuran (PPF), 2,5-diphenyloxazole (PPO) and 2,5-diphenyloxa-1,3,4-diazole (PPD), with a number of normal alkanes ranging from pentane to dodecane, measured under supersonic jet conditions. It is shown that referencing the spectral red shifts for alkane complexes against the corresponding pyrene S 0 ? S 2 data provides a useful means of detecting structural variations. The PPF complexes with alkanes from heptane to dodecane show an odd—even effect, where n-alkane guests of different symmetries give rise alternately to single and doubled resonances. Thus, even-alkane complexes have two indistinguishable isomers of C 1 symmetry, which contribute to a single spectrum. On the other hand, odd-alkane complexes also have a C s isomer, which has a slightly different electronic origin resonance, so that a double spectrum results, with spacing on the order of 10 cm -1. These conclusions are consistent with the general predictions of atom—atom pair-potential calculations. We also show that further splitting may be induced in the spectra by complexation of the asymmetrical molecule 2,5-diphenyloxazole (PPO). Complexes with the shorter alkanes pentane and hexane show increased complexity in the spectrum, which is attributed to greater flexibility in the complexation geometry.

Mangle, Elisa A.; Motyka, Andrea L.; Salvi, Pier; Topp, Michael R.

1987-03-01

278

Cometabolism of Methyl tertiary Butyl Ether and Gaseous n-Alkanes by Pseudomonas mendocina KR-1 Grown on C5 to C8 n-Alkanes  

PubMed Central

Pseudomonas mendocina KR-1 grew well on toluene, n-alkanes (C5 to C8), and 1° alcohols (C2 to C8) but not on other aromatics, gaseous n-alkanes (C1 to C4), isoalkanes (C4 to C6), 2° alcohols (C3 to C8), methyl tertiary butyl ether (MTBE), or tertiary butyl alcohol (TBA). Cells grown under carbon-limited conditions on n-alkanes in the presence of MTBE (42 ?mol) oxidized up to 94% of the added MTBE to TBA. Less than 3% of the added MTBE was oxidized to TBA when cells were grown on either 1° alcohols, toluene, or dextrose in the presence of MTBE. Concentrated n-pentane-grown cells oxidized MTBE to TBA without a lag phase and without generating tertiary butyl formate (TBF) as an intermediate. Neither TBF nor TBA was consumed by n-pentane-grown cells, while formaldehyde, the expected C1 product of MTBE dealkylation, was rapidly consumed. Similar Ks values for MTBE were observed for cells grown on C5 to C8 n-alkanes (12.95 ± 2.04 mM), suggesting that the same enzyme oxidizes MTBE in cells grown on each n-alkane. All growth-supporting n-alkanes (C5 to C8) inhibited MTBE oxidation by resting n-pentane-grown cells. Propane (Ki = 53 ?M) and n-butane (Ki = 16 ?M) also inhibited MTBE oxidation, and both gases were also consumed by cells during growth on n-pentane. Cultures grown on C5 to C8 n-alkanes also exhibited up to twofold-higher levels of growth in the presence of propane or n-butane, whereas no growth stimulation was observed with methane, ethane, MTBE, TBA, or formaldehyde. The results are discussed in terms of their impacts on our understanding of MTBE biodegradation and cometabolism.

Smith, Christy A.; O'Reilly, Kirk T.; Hyman, Michael R.

2003-01-01

279

Measuring long chain alkanes in diesel engine exhaust by thermal desorption PTR-MS  

NASA Astrophysics Data System (ADS)

A method using thermal desorption sampling and analysis by PTR-MS to measure long chain alkanes (C12-C18) and other larger organics associated with diesel engine exhaust emissions is described. Long chain alkanes undergo dissociative proton transfer reactions forming a series of fragment ions with formula CnH2n+1. The PTR-MS is insensitive to n-alkanes less than C8 but displays an increasing sensitivity for larger alkanes. Fragment ion distribution and sensitivity is a function of drift conditions. At 80 Td the most abundant ion fragments from C10 to C16 n-alkanes were m/z 57, 71 and 85. The mass spectrum of gasoline and diesel fuel at 80 Td displayed ion group patterns that can be related to known fuel constituents, such as alkanes, alkylbenzenes and cycloalkanes, and other compound groups that are inferred from molecular weight distributions such as dihydronapthalenes and naphthenic monoaromatics. It is shown that thermal desorption sampling of gasoline and diesel engine exhausts at 80 Td allows for discrimination against light alkanes and alkenes which are a major constituent of both exhausts, allowing for quantification of higher molecular weight alkanes from the abundance of CnH2n+1 fragment ions. Using this approach, the molar abundance of C12-C18 alkanes in diesel engine exhaust was found to be 75% that of the total C1-C4 alkylbenzene abundance. While the PTR-MS mass spectra of gasoline and diesel exhaust looked similar, the abundance of higher molecular weight compounds relative to that of C4-alkylbenzenes was much greater in diesel engine exhaust. The abundance patterns of compounds determined by thermal desorption sampling may allow for emission profiles to be developed to better quantify the relative contributions of diesel and gasoline exhaust emissions of larger organic compounds to urban air concentrations.

Erickson, M. H.; Gueneron, M.; Jobson, B. T.

2013-07-01

280

CYP153A6, a Soluble P450 Oxygenase Catalyzing Terminal-Alkane Hydroxylation  

PubMed Central

The first and key step in alkane metabolism is the terminal hydroxylation of alkanes to 1-alkanols, a reaction catalyzed by a family of integral-membrane diiron enzymes related to Pseudomonas putida GPo1 AlkB, by a diverse group of methane, propane, and butane monooxygenases and by some membrane-bound cytochrome P450s. Recently, a family of cytoplasmic P450 enzymes was identified in prokaryotes that allow their host to grow on aliphatic alkanes. One member of this family, CYP153A6 from Mycobacterium sp. HXN-1500, hydroxylates medium-chain-length alkanes (C6 to C11) to 1-alkanols with a maximal turnover number of 70 min?1 and has a regiospecificity of ?95% for the terminal carbon atom position. Spectroscopic binding studies showed that C6-to-C11 aliphatic alkanes bind in the active site with Kd values varying from ?20 nM to 3.7 ?M. Longer alkanes bind more strongly than shorter alkanes, while the introduction of sterically hindering groups reduces the affinity. This suggests that the substrate-binding pocket is shaped such that linear alkanes are preferred. Electron paramagnetic resonance spectroscopy in the presence of the substrate showed the formation of an enzyme-substrate complex, which confirmed the binding of substrates observed in optical titrations. To rationalize the experimental observations on a molecular scale, homology modeling of CYP153A6 and docking of substrates were used to provide the first insight into structural features required for terminal alkane hydroxylation.

Funhoff, Enrico G.; Bauer, Ulrich; Garcia-Rubio, Ines; Witholt, Bernard; van Beilen, Jan B.

2006-01-01

281

n-alkane profiles of engine lubricating oil and particulate matter by molecular sieve extraction.  

PubMed

As part of the Canadian Atmospheric Fine Particle Research Program to obtain reliable primary source emission profiles, a molecular sieve method was developed to reliably determine n-alkanes in lubricating oils, vehicle emissions, and mobile source dominated ambient particulate matter (PM). This work was also initiated to better calculate carbon preference index values (CPI: the ratio of the sums of odd over even n-alkanes), a parameter for estimating anthropogenic versus biogenic contributions in PM. n-Alkanes in lubricating oil and mobile source dominated PM are difficult to identify and quantify by gas chromatography due to the presence of similar components that cannot be fully resolved. This results in a hump, the unresolved complex mixture (UCM) that leads to incorrect n-alkane concentrations and CPI values. The sieve method yielded better chromatography, unambiguous identification of n-alkanes and allowed examination of differences between n-alkane profiles in light (LDV) and heavy duty vehicle (HDV) lubricating oils that would have been otherwise difficult. These profile differences made it possible to relate the LDV profile to that of the PM samples collected during a tunnel study in August 2001 near Vancouver (British Columbia, Canada). The n-alkane PM data revealed that longer sampling times result in a negative artifact, i.e., the desorption of the more volatile n-alkanes from the filters. Furthermore, the sieve procedure yielded n-alkane data that allowed calculation of accurate CPI values for lubricating oils and PM samples. Finally, this method may prove helpful in estimating the respective diesel and gasoline contributions to ambient PM. PMID:17547199

Caravaggio, Gianni A; Charland, Jean-Pierre; Macdonald, Penny; Graham, Lisa

2007-05-15

282

Biodegradation of variable-chain-length alkanes at low temperatures by a psychrotrophic Rhodococcus sp.  

SciTech Connect

The psychrotroph Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5 C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane. Q15 utilized a broad range of aliphatics (C{sub 10} to C{sub 21} alkanes, branched alkanes, and a substituted cyclohexane) present in diesel fuel at 5 C. Mineralization of hexadecane at 5 C was significantly greater in both hydrocarbon-contaminated and pristine soil microcosms seeded with Q15 cells than in uninoculated control soil microcosms. The detection of hexadecane and dodecane metabolic intermediates (1-hexadecanol and 2-hexadecanol and 1-do-decanol and 2-dodecanone, respectively) by solid-phase microextraction-gas chromatography-mass spectrometry and the utilization of potential metabolic intermediates indicated that Q15 oxidizes alkanes by both the terminal oxidation pathway and the subterminal oxidation pathway. Genetic characterization by PCR and nucleotide sequence analysis indicated that Q15 possesses an aliphatic aldehyde dehydrogenase gene highly homologous to the Rhodococcus erythropolis thcA gene. Rhodococcus sp. strain Q15 possessed two large plasmids of approximately 90 and 115 kb (shown to mediate Cd resistance) which were not required for alkane mineralization, although the 90-kb plasmid enhanced mineralization of some alkanes and growth on diesel oil at both 5 and 25 C.

Whyte, L.G.; Hawari, J.; Zhou, E.; Bourbonniere, L.; Greer, C.W. [NRC-Biotechnology Research Inst., Montreal, Quebec (Canada); Inniss, W.E. [Univ. of Waterloo, Ontario (Canada). Dept. of Biology

1998-07-01

283

Hydrogen isotope exchange between n-alkanes and water under hydrothermal conditions  

NASA Astrophysics Data System (ADS)

To investigate the extent of hydrogen isotope ( 2H and 1H) exchange between hydrocarbons and water under hydrothermal conditions, we performed experiments heating C 1-C 5n-alkanes in aqueous solutions of varying initial 2H/ 1H ratios in the presence of a pyrite-pyrrhotite-magnetite redox buffer at 323 °C and 35-36 MPa. Extensive and reversible incorporation of water-derived hydrogen into C 2-C 5n-alkanes was observed on timescales of months. In contrast, comparatively minor exchange was observed for CH 4. Isotopic exchange is facilitated by reversible equilibration of n-alkanes and their corresponding n-alkenes with H 2 derived from the disproportionation of water. Rates of ? 2H variation in C 3+n-alkanes decreased with time, a trend that is consistent with an asymptotic approach to steady state isotopic compositions regulated by alkane-water isotopic equilibrium. Substantially slower ? 2H variation was observed for ethane relative to C 3-C 5n-alkanes, suggesting that the greater stability of C 3+ alkenes and isomerization reactions may dramatically enhance rates of 2H/ 1H exchange in C 3+n-alkanes. Thus, in reducing aqueous environments, reversible reaction of alkanes and their corresponding alkenes facilitates rapid 2H/ 1H exchange between water and alkyl-bound hydrogen on relatively short geological timescales at elevated temperatures and pressures. The proximity of some thermogenic and purported abiogenic alkane ? 2H values to those predicted for equilibrium 2H/ 1H fractionation with ambient water suggests that this process may regulate the ? 2H signatures of some naturally occurring hydrocarbons.

Reeves, Eoghan P.; Seewald, Jeffrey S.; Sylva, Sean P.

2012-01-01

284

Computational chemistry  

NASA Technical Reports Server (NTRS)

With the advent of supercomputers, modern computational chemistry algorithms and codes, a powerful tool was created to help fill NASA's continuing need for information on the properties of matter in hostile or unusual environments. Computational resources provided under the National Aerodynamics Simulator (NAS) program were a cornerstone for recent advancements in this field. Properties of gases, materials, and their interactions can be determined from solutions of the governing equations. In the case of gases, for example, radiative transition probabilites per particle, bond-dissociation energies, and rates of simple chemical reactions can be determined computationally as reliably as from experiment. The data are proving to be quite valuable in providing inputs to real-gas flow simulation codes used to compute aerothermodynamic loads on NASA's aeroassist orbital transfer vehicles and a host of problems related to the National Aerospace Plane Program. Although more approximate, similar solutions can be obtained for ensembles of atoms simulating small particles of materials with and without the presence of gases. Computational chemistry has application in studying catalysis, properties of polymers, all of interest to various NASA missions, including those previously mentioned. In addition to discussing these applications of computational chemistry within NASA, the governing equations and the need for supercomputers for their solution is outlined.

Arnold, J. O.

1987-01-01

285

Peroxidation of secondary carbon in alkanes and cycloalkanes  

US Patent & Trademark Office Database

A secondary carbon atom in an alkane, including alkyl groups attached to aromatic rings, or cycloalkane is peroxidized by molecular oxygen to the corresponding hydroperoxide in the absence of a catalyst. The peroxidation is carried out in the presence of a tertiary hydroperoxide initiator which provides the free radicals needed to maintain the reaction. The amount of tertiary alcohol in the initiator is limited. The initial product of the peroxidation contains the secondary hydroperoxide as well as unreacted hydrocarbon, unreacted tertiary hydroperoxide and tertiary alcohol. The tertiary alcohol is removed as an azeotrope with part of the unreacted hydrocarbon which may be then separated from the alcohol and recycled. A second azeotropic distillation follows where the unreacted tertiary hydroperoxide is removed as an azeotrope with the rest of the unreacted hydrocarbon. This azeotrope is directly recycled to the peroxidation reaction.

1994-08-02

286

Aggregation of a semifluorinated n-alkane in perfluorooctane  

SciTech Connect

The phase behavior of solutions of two semifluorinated n-alkanes, heptadecafluorotetracosane (F(CF[sub 2])[sub 8](CH[sub 2])[sub 16]H) and pentacosafluorooctacosane (F(CF[sub 2])[sub 12](CH[sub 2])[sub 16]H), in perfluorooctane and isooctane is studied. Viscosity, dynamic light-scattering, and small-angle neutron-scattering data show the presence of small, nearly spherical aggregates in heptadecafluorotetracosane/perfluorooctane solutions in the liquid phase above the critical micelle concentration. The authors determined the size and average aggregation number of these aggregates as a function of the fluorohydrocarbon concentration. Small-angle neutron-scattering results show that the perfluorooctane solvent penetrates appreciably into the micellar core. 21 refs., 6 figs., 2 tabs.

Nostro, P.L.; Chen, S.H. (Massachusetts Inst. of Technology, Cambridge (United States))

1993-06-17

287

Thermal analysis of n-alkane phase change material mixtures  

SciTech Connect

Tests were performed to characterize the thermal behavior of it number of n-alkanes to be used as phase change materials (PCMs) in district cooling applications. Hexadecane and tetradecane were mixed in different fractions, and their thermal behavior was experimentally evaluated. Test results for melting temperature and fusion energy for laboratory grade hexadecane and tetradecane showed good agreement with datain the literature. However, values for commercial grade hexadecane were found to be considerably lower. In the range of temperatures of interest for district cooling, mixtures of tetradecane and hexadecane can be treated as homogeneous substances. However, their heats of fusion are slightly lower than those of the pure substances. Their melting temperatures are also lower by an amount that can be predicted.

Chio, Y.I.; Choi, E.; Lorsch, H.G.

1991-03-31

288

Pairwise-additive hydrophobic effect for alkanes in water  

PubMed Central

Pairwise additivity of the hydrophobic effect is indicated by reliable experimental Henry's constants for a large number of linear and branched low-molecular-weight alkanes in water. Pairwise additivity suggests that the hydrophobic effect is primarily a local phenomenon and that the hydrophobic interaction may be represented by a semiempirical force field. By representing the hydrophobic potential between two methane molecules as a linear function of the overlap volume of the hydration layers, we find that the contact value of the hydrophobic potential (?0.72 kcal/mol) is smaller than that from quantum mechanics simulations (?2.8 kcal/mol) but is close to that from classical molecular dynamics (?0.5??0.9 kcal/mol).

Wu, Jianzhong; Prausnitz, John M.

2008-01-01

289

Photochemical dimerization and functionalization of alkanes, ethers, primary and secondary alcohols, phosphine oxides and silanes  

DOEpatents

The space-time yield and/or the selectivity of the photochemical dimerization of alkanes, ethers, primary and secondary alcohols, phosphine oxides and primary, secondary and tertiary silanes with Hg and U.V. light is enhanced by refluxing the substrate in the irradiated reaction zone at a temperature at which the dimer product condenses and remains condensed promptly upon its formation. Cross-dimerization of the alkanes, ethers and silanes with primary alcohols is disclosed, as is the functionalization to aldehydes of the alkanes with carbon monoxide.

Crabtree, R.H.; Brown, S.H.

1989-10-17

290

Initial Reactions in Anaerobic Alkane Degradation by a Sulfate Reducer, Strain AK-01  

PubMed Central

An alkane-degrading, sulfate-reducing bacterial strain, AK-01, isolated from a petroleum-contaminated sediment was studied to elucidate its mechanism of alkane metabolism. Total cellular fatty acids of AK-01 were predominantly C even when it was grown on C-even alkanes and were predominantly C odd when grown on C-odd alkanes, suggesting that the bacterium anaerobically oxidizes alkanes to fatty acids. Among these fatty acids, some 2-, 4-, and 6-methylated fatty acids were specifically found only when AK-01 was grown on alkanes, and their chain lengths always correlated with those of the alkanes. When [1,2-13C2]hexadecane or perdeuterated pentadecane was used as the growth substrate, 13C-labeled 2-Me-16:0, 4-Me-18:0, and 6-Me-20:0 fatty acids or deuterated 2-Me-15:0, 4-Me-17:0, and 6-Me-19:0 fatty acids were recovered, respectively, confirming that these monomethylated fatty acids were alkane derived. Examination of the 13C-labeled 2-, 4-, and 6-methylated fatty acids by mass spectrometry showed that each of them contained two 13C atoms, located at the methyl group and the adjacent carbon, thus indicating that the methyl group was the original terminal carbon of the [1,2-13C2]hexadecane. For perdeuterated pentadecane, the presence of three deuterium atoms, on the methyl group and its adjacent carbon, in each of the deuterated 2-, 4-, and 6-methylated fatty acids further supported the hypothesis that the methyl group was the terminal carbon of the alkane. Thus, exogenous carbon appears to be initially added to an alkane subterminally at the C-2 position such that the original terminal carbon of the alkane becomes a methyl group on the subsequently formed fatty acid. The carbon addition reaction, however, does not appear to be a direct carboxylation of inorganic bicarbonate. A pathway for anaerobic metabolism of alkanes by strain AK-01 is proposed.

So, Chi Ming; Young, L. Y.

1999-01-01

291

Adsorption and dissociation kinetics of alkanes on CaO(100)  

NASA Astrophysics Data System (ADS)

The adsorption kinetics of ethane, butane, pentane, and hexane on CaO(100) have been studied by multi-mass thermal desorption (TDS) spectroscopy. The sample cleanliness was checked by Auger electron spectroscopy. A molecular and dissociative adsorption pathway was evident for the alkanes, except for ethane, which does not undergo bond activation. Two TDS peaks appeared when recording the parent mass, which are assigned to different adsorption sites/configurations of the molecularly adsorbed alkanes. Bond activation leads to desorption of hydrogen and several alkane fragments assigned to methane and ethylene formation. Only one TDS feature is seen in this case. Formation of carbon residuals was absent.

Chakradhar, A.; Liu, Y.; Schmidt, J.; Kadossov, E.; Burghaus, U.

2011-08-01

292

Characterization of cyclic and acyclic alkanes in Forties and Kuwait petroleum crudes  

SciTech Connect

Alkane hydrocarbon fractions from Forties (North Sea) and Kuwait petroleum crudes, separated by distillation, solvent extraction and silicagel column chromatography and sub-fractionated by molecular-sieve adsorption, have been examined by gas chromatography (GC), {sup 1}H and {sup 13}C NMR spectroscopy, GC-mass spectrometry (MS) and field desorption (FD)MS. GC indicates that Forties contains rather more acyclic isoprenoids and cyclic alkanes than Kuwait; FDMS of Kuwait shows molecular-weight ranges for mono-, di-, tri-, tetra-, and pentacyclic alkanes. {sup 13}C NMR spectra provide evidence of higher aromatic carbon, C{sub A}, in Forties than Kuwait and longer T{sub 1} relaxation times.

Jones, D.W. (Chemistry and Chemical Technology, Univ. of Bradford, Bradford BD7 1DP (GB)); Pakdel, H. (Dept. de Genie Chimique, Univ. Laval, Cite Univ., Quebec G1K 6P4 (CA)); Bartle, K.D. (School of Chemistry, Univ. of Leeds, Leeds LS2 9JT (GB))

1990-01-01

293

Mixed thin films of a cationic amphiphilic porphyrin and n-alkanes.  

PubMed

Langmuir and Langmuir-Blodgett (LB) films of a cationic amphiphilic porphyrin mixed with n-alkanes octadecane and hexatriacontane were prepared and characterized, to examine the influence of the alkanes on film structure and stability. While the structure present in these films was controlled primarily by the porphyrin, the addition of the alkanes resulted in significant changes to both the phase behavior of the Langmuir films and the molecular arrangement of the LB films. These changes, as well as the observed chain length effects, are explained in terms of the intermolecular interactions present in the films. PMID:15248709

O'Driscoll, Benjamin M D; Ruggles, Jeremy L; Gentle, Ian R

2004-07-20

294

Prototheca zopfii Kr?ger Strain UMK-13 Growth on Acetate or n-Alkanes  

PubMed Central

A new strain of Prototheca zopfii Krüger was grown on acetate or on pure n-alkanes. A maximum acetate-supported exponential growth of 12 divisions day?1 occurred at pH 5 and 30°C. At 25°C, growth on n-alkanes was almost as fast, but no growth occurred at 30°C. After 4 days at 25°C, 34 to 45% of the n-alkanes had been removed, whereas at 21°C and slower growth, utilization was twofold greater after 15 days. Rates of growth and utilization increased markedly after a point of sudden emulsification.

Koenig, David W.; Ward, H. B.

1983-01-01

295

New developments in the photocatalytic conversion of methane to methanol  

Microsoft Academic Search

Investigation of direct conversion of methane to transportation fuels has been an on-going effort at FETC for over 14 years. One of our current areas of research is the conversion of methane to methanol, under mild conditions, using light, water, and a semiconductor photocatalyst. Research in our laboratory is directed toward adapting the chemistry developed for photolysis of water to

C. E Taylor; R. P Noceti

2000-01-01

296

Abiotic Organic Chemistry in Hydrothermal Systems.  

NASA Astrophysics Data System (ADS)

Abiotic organic chemistry in hydrothermal systems is of interest to biologists, geochemists and oceanographers. This chemistry consists of thermal alteration of organic matter and minor prebiotic synthesis of organic compounds. Thermal alteration has been extensively documented to yield petroleum and heavy bitumen products from contemporary organic detritus. Carbon dioxide, carbon monoxide, ammonia and sulfur species have been used as precursors in prebiotic synthesis experiments to organic compounds. These inorganic species are common components of hot spring gases and marine hydrothermal systems. It is of interest to further test their reactivities in reductive aqueous thermolysis. We have synthesized organic compounds (lipids) in aqueous solutions of oxalic acid, and with carbon disulfide or ammonium bicarbonate at temperatures from 175-400° C. The synthetic lipids from oxalic acid solutions consisted of n-alkanols, n-alkanoic acids, n-alkyl formates, n-alkanones, n-alkenes and n-alkanes, typically to C30 with no carbon number preferences. The products from CS2 in acidic aqueous solutions yielded cyclic thioalkanes, alkyl polysulfides, and thioesters with other numerous minor compounds. The synthesis products from oxalic acid and ammonium bicarbonate solutions were homologous series of n-alkyl amides, n-alkyl amines, n-alkanes and n-alkanoic acids, also to C30 with no carbon number predominance. Condensation (dehydration) reactions also occur under elevated temperatures in aqueous medium as tested by model reactions to form amide, ester and nitrile bonds. It is concluded that the abiotic formation of aliphatic lipids, condensation products (amides, esters, nitriles, and CS2 derivatives (alkyl polysulfides, cyclic polysulfides) is possible under hydrothermal conditions and warrants further studies.

Simoneit, B. R.; Rushdi, A. I.

2004-12-01

297

Interstellar chemistry  

PubMed Central

In the past half century, radioastronomy has changed our perception and understanding of the universe. In this issue of PNAS, the molecular chemistry directly observed within the galaxy is discussed. For the most part, the description of the molecular transformations requires specific kinetic schemes rather than chemical thermodynamics. Ionization of the very abundant molecular hydrogen and atomic helium followed by their secondary reactions is discussed. The rich variety of organic species observed is a challenge for complete understanding. The role and nature of reactions involving grain surfaces as well as new spectroscopic observations of interstellar and circumstellar regions are topics presented in this special feature.

Klemperer, William

2006-01-01

298

Azulene Chemistry  

NSDL National Science Digital Library

The month's featured molecules come from the paper An Azulene-Based Discovery Experiment: Challenging Students To Watch for the "False Assumption" by Charles Garner illustrating some of the chemistry of a substituted azulene. Azulene is a structural isomer of naphthalene and differs from it in several important ways, the most obvious being azulene's intense blue color, which arises from the S0 → S2 transition. Another unusual feature of this molecule is that its fluorescence arises from the reverse of this transition rather than from S1 → S0.

299

Industrial Chemistry  

NSDL National Science Digital Library

This Web site addresses Professor Dr. J. Gmehling's research group activities in "the synthesis and design of chemical processes with an emphasis on thermal separation processes." Ranging from the development of thermodynamic models to the construction of software tools and data banks, their research at the University of Oldenburg, covers a broad range in the field of Industrial Chemistry. Students and educators can view informative figures and images such as the Isothermal Flow Calorimeter and the Gas-Liquid Chromatography. Users can download the free software, Dortmund Data Bank (DDB), which searches the literature for experimental information.

300

Alkane oxidation with porphyrins and metal complexes thereof having haloalkyl side chains  

Microsoft Academic Search

Transition metal complexes of meso-haloalkylporphyrins are disclosed, wherein the haloalkyl groups contain 2 to 8 carbon atoms have been found to be highly effective catalysts for oxidation of alkanes and for the decomposition of hydroperoxides. 7 figs.

T. Wijesekera; J. E. Lyons; P. E. Jr. Ellis; M. V. Bhinde

1998-01-01

301

STRUCTURE-REACTIVITY RELATIONSHIPS IN DEHYDROHALOGENATION REACTIONS OF POLYCHLORINATED AND POLYBROMINATED ALKANES  

EPA Science Inventory

Current information is inadequate to predict the rates at which polyhalogenated alkanes undergo dehydrohalogenation rations under environmental conditions, forming olefins that are frequently more toxic and more recalcitrant than the products of substitution reactions. o permit e...

302

Alkane oxidation with porphyrins and metal complexes thereof having haloalkyl side chains  

DOEpatents

Transition metal complexes of meso-haloalkylporphyrins are disclosed, wherein the haloalkyl groups contain 2 to 8 carbon atoms have been found to be highly effective catalysts for oxidation of alkanes and for the decomposition of hydroperoxides. 7 figs.

Wijesekera, T.; Lyons, J.E.; Ellis, P.E. Jr.; Bhinde, M.V.

1998-06-23

303

Charge Transfer Reactions in Alkane and Cycloalkane Systems. Estimated Ionization Potentials.  

National Technical Information Service (NTIS)

This paper reports the results of a quantitative investigation of charge transfer reactions in alkane mixtures, carried out in an ion cyclotron resonance mass spectrometer. The study was undertaken in order to elucidate the influence of such factors as re...

S. G. Lias P. Ausloos Z. Horvath

1976-01-01

304

Identification of novel bicyclic alkanes from steroid precursors in crude oils from Kelamayi Oilfield of China  

NASA Astrophysics Data System (ADS)

A novel series of bicyclic alkanes in the C 19-C 22 range has been discovered in a number of crude oils from a variety of sources. Evidence is provided from laboratory studies to demonstrate that there is a correlation between these bicyclic alkanes and steranes, suggesting in turn that both series of compounds are actually derived from sterol precursors. These bicyclic alkanes appear to be resistant to the effects of biodegradation which in turn enhances their concentration in biodegraded oils following removal of other less resistant compounds. The value of this stability is demonstrated in the correlation of an oil and seep from the Anadarko Basin. The seep is biodegraded such that all regular steranes are removed leaving only rearranged steranes compared with an oil where all steranes are intact. The bicyclic alkane distributions are similar for both samples demonstrating their potential for correlation purposes. The effect of maturation on these components was not evaluated in detail in this particular study.

Zhusheng, Jiang; Philp, R. P.; Lewis, C. A.

1988-02-01

305

Modeling the Role of Alkanes, Polycyclic Aromatic Hydrocarbons, and Their Oligomers in Secondary Organic Aerosol Formation  

EPA Science Inventory

A computationally efficient method to treat secondary organic aerosol (SOA) from various length and structure alkanes as well as SOA from polycyclic aromatic hydrocarbons (PAHs) is implemented in the Community Multiscale Air Quality (CMAQ) model to predict aerosol concentrations ...

306

Possible Mechanism of Alkene/Alkane Production in Oil Shale Retorting.  

National Technical Information Service (NTIS)

The objective was to clarify the reaction mechanisms that determine the observed alkene/alkane ratios under various conditions. When oil shale is pyrolyzed either isothermally or nonisothermally, the hydrocarbon and hydrogen concentrations are all time de...

A. K. Burnham R. L. Ward

1980-01-01

307

Evaluation of n-alkanes and their carbon isotope enrichments (?(13)C) as diet composition markers.  

PubMed

Plant cuticular n-alkanes have been successfully used as markers to estimate diet composition and intake of grazing herbivores. However, additional markers may be required under grazing conditions in botanically diverse vegetation. This study was conducted to describe the n-alkane profiles and the carbon isotope enrichment of n-alkanes of common plant species from the Mid Rift Valley rangelands of Ethiopia, and evaluate their potential use as nutritional markers. A total of 23 plant species were collected and analysed for long-chain n-alkanes ranging from heptacosane to hexatriacontane (C(27) to C(36)), as well as their carbon isotopic ratio ((13)C/(12)C). The analysis was conducted by gas chromatography/combustion isotope ratio mass spectrometry following saponification, extraction and purification. The isotopic composition of the n-alkanes is reported in the delta notation (?(13)C) relative to the Vienna Pee Dee Belemnite standard. The dominant n-alkanes in the species were C(31) (mean ± s.d., 283 ± 246 mg/kg dry matter) and C(33) (149 ± 98 mg/kg dry matter). The carbon isotopic enrichment of the n-alkanes ranged from -19.37‰ to -37.40‰. Principal component analysis was used to examine interspecies differences based on n-alkane profiles and the carbon isotopic enrichments of individual n-alkanes. Large variability among the pasture species was observed. The first three principal components explained most of the interspecies variances. Comparison of the principal component scores using orthogonal procrustes rotation indicated that about 0.84 of the interspecies variances explained by the two types of data sets were independent of each other, suggesting that the use of a combination of the two markers can improve diet composition estimations. It was concluded that, while the n-alkane profile of the pasture species remains a useful marker for use in the study region, the ?(13)C values of n-alkanes can provide additional information in discriminating diet components of grazing animals. PMID:22440702

Bezabih, M; Pellikaan, W F; Tolera, A; Hendriks, W H

2011-01-01

308

Biochemistry of Short-Chain Alkanes (Tissue-Specific Biosynthesis of n-Heptane in Pinus jeffreyi).  

PubMed Central

Short-chain (C7-C11) alkanes accumulate as the volatile component of oleoresin (pitch) in several pine species native to western North America. To establish the tissue most amenable for use in detailed studies of short-chain alkane biosynthesis, we examined the tissue specificity of alkane accumulation and biosynthesis in Pinus jeffreyi Grev. & Balf. Short-chain alkane accumulation was highly tissue specific in both 2-year-old saplings and mature trees; heart-wood xylem accumulated alkanes up to 7.1 mg g-1 dry weight, whereas needles and other young green tissue contained oleoresin with monoterpenoid, rather than paraffinic, volatiles. These tissue-specific differences in oleoresin composition appear to be a result of tissue-specific rates of alkane and monoterpene biosynthesis; incubation of xylem tissue with [14C]sucrose resulted in accumulation of radiolabel in alkanes but not monoterpenes, whereas incubation of foliar tissue with 14CO2 resulted in the accumulation of radiolabel in monoterpenes but not alkanes. Furthermore, incubation of xylem sections with [14C]acetate resulted in incorporation of radiolabel into alkanes at rates up to 1.7 nmol h-1 g-1 fresh weight, a rate that exceeds most biosynthetic rates reported with other plant systems for the incorporation of this basic precursor into natural products. This suggests that P. jeffreyi may provide a suitable model for elucidating the enzymology and molecular biology of short-chain alkane biosynthesis.

Savage, T. J.; Hamilton, B. S.; Croteau, R.

1996-01-01

309

Understanding the factors affecting the activation of alkane by Cp?Rh(CO)2 (Cp? = Cp or Cp*)  

PubMed Central

Fast time-resolved infrared spectroscopic measurements have allowed precise determination of the rates of activation of alkanes by Cp?Rh(CO) (Cp? = ?5-C5H5 or ?5-C5Me5). We have monitored the kinetics of C?H activation in solution at room temperature and determined how the change in rate of oxidative cleavage varies from methane to decane. The lifetime of CpRh(CO)(alkane) shows a nearly linear behavior with respect to the length of the alkane chain, whereas the related Cp*Rh(CO)(alkane) has clear oscillatory behavior upon changing the alkane. Coupled cluster and density functional theory calculations on these complexes, transition states, and intermediates provide the insight into the mechanism and barriers in order to develop a kinetic simulation of the experimental results. The observed behavior is a subtle interplay between the rates of activation and migration. Unexpectedly, the calculations predict that the most rapid process in these Cp?Rh(CO)(alkane) systems is the 1,3-migration along the alkane chain. The linear behavior in the observed lifetime of CpRh(CO)(alkane) results from a mechanism in which the next most rapid process is the activation of primary C?H bonds (?CH3 groups), while the third key step in this system is 1,2-migration with a slightly slower rate. The oscillatory behavior in the lifetime of Cp*Rh(CO)(alkane) with respect to the alkane’s chain length follows from subtle interplay between more rapid migrations and less rapid primary C?H activation, with respect to CpRh(CO)(alkane), especially when the CH3 group is near a gauche turn. This interplay results in the activation being controlled by the percentage of alkane conformers.

George, Michael W.; Hall, Michael B.; Jina, Omar S.; Portius, Peter; Sun, Xue-Zhong; Towrie, Michael; Wu, Hong; Yang, Xinzheng; Zaric, Snezana D.

2010-01-01

310

Combustion Characteristics of Liquid Normal Alkane Fuels in a Model Combustor of Supersonic Combustion Ramjet Engine  

Microsoft Academic Search

Effect of kinds of one-component n-alkane liquid fuels on combustion characteristics was investigated experimentally using a model combustor of scramjet engine. The inlet condition of a model combustor is 2.0 of Mach number, up to 2400K of total temperature, and 0.38MPa of total pressure. Five kinds of n-alkane are tested, of which carbon numbers are 7, 8, 10, 13, and

2010-01-01

311

Solubility of anthracene in binary alkane?+?ethanol solvent mixtures at 298.15?K  

Microsoft Academic Search

Experimental solubilities are reported for anthracene in six binary alkane?+?ethanol solvent mixtures at 298.15?K. The alkane solvents studied were hexane, heptane, octane, cyclohexane, methylcyclohexane and 2,2,4-trimethylpentane. Results of these measurements were used to test a mathematical representation based on the combined nearly ideal binary solvent (NIBS)\\/Redlich–Kister equation. For the six systems studied, the combined NIBS\\/Redlich–Kister equation was found to accurately

Laura M. Grubbs; Kathleen Holley; Sai S. Achi; Racheal Pointer; Derek Casares; Ramie Hall; Jose Ruiz; William E. Acree

2011-01-01

312

Measuring long chain alkanes in diesel engine exhaust by thermal desorption PTR-MS  

NASA Astrophysics Data System (ADS)

A method using thermal desorption sampling and analysis by proton transfer reaction mass spectrometry (PTR-MS) to measure long chain alkanes (C12-C18) and other larger organics associated with diesel engine exhaust emissions is described. Long chain alkanes undergo dissociative proton transfer reactions forming a series of fragment ions with formula CnH2n+1. The PTR-MS is insensitive to n-alkanes less than C8 but displays an increasing sensitivity for larger alkanes. Fragment ion distribution and sensitivity is a function of drift conditions. At 80 Td the most abundant ion fragments from C10 to C16 n-alkanes were m/z 57, 71 and 85. The mass spectrum of gasoline and diesel fuel at 80 Td displayed ion group patterns that can be related to known fuel constituents, such as alkanes, alkylbenzenes and cycloalkanes, and other compound groups that are inferred from molecular weight distributions such as dihydronapthalenes and naphthenic monoaromatics. It is shown that thermal desorption sampling of gasoline and diesel engine exhausts at 80 Td allows for discrimination against volatile organic compounds, allowing for quantification of long chain alkanes from the abundance of CnH2n+1 fragment ions. The total abundance of long chain alkanes in diesel engine exhaust was measured to be similar to the total abundance of C1-C4 alkylbenzene compounds. The abundance patterns of compounds determined by thermal desorption sampling may allow for emission profiles to be developed to better quantify the relative contributions of diesel and gasoline exhaust emissions on organic compounds concentrations in urban air.

Erickson, M. H.; Gueneron, M.; Jobson, B. T.

2014-01-01

313

[Distribution and source apportionment of n-alkanes in atmospheric particle in Taiyuan, China].  

PubMed

The n-alkanes in PM10 and typical emission sources samples collected during heating and non-heating periods in Taiyuan were determined with GC-MS. Meanwhile, the distribution characteristics and source identification of n-alkanes were investigated with diagnostic parameters and principal component analysis (PCA). Concentrations of n-alkanes ranged from 213.74 to 573.32 ng.m-3 and 22.69 to 150.82 ng.m-3 in the heating and non-heating seasons, respectively. The n-alkanes concentrations in suburban districts including JY, JCP, XD and SL were higher than those in urban sites in the heating quarter, and the relative concentration in JS was 7 times higher than that in SL in the other period. The correlation of the total n-alkanes in PM10 with that derived from fossil fuel was higher than the correlation with those from plant in the heating quarter, while the opposite result was detected in the other period, manifesting higher contribution of fossil fuel in the heating days. CPI and % WNA values showed that the contribution from plant wax in the non-heating period was higher than that in the heating period, and the alkanes production rate was elevated along with the increase in environmental pressures. Information on higher organic matter maturity was obtained during the heating period by Cmax and OEP and the existence of UCM bulge confirmed that vehicles were the significant contributor to n-alkanes concentration during the whole year. PCA analysis indicated the major component was the mixture of vehicle emission and higher plant, accounting for 51.28% of the total variances, followed by coal dust, accounting for 43. 14%. Cooperating control of emissions from coal combustions and vehicles would be the effective way to lower the concentrations of the corresponding n-alkanes. PMID:24364286

Hu, Dong-Mei; Peng, Lin; Bai, Hui-Ling; Mu, Ling; Han, Feng; Liu, Xiao-Feng; Ji, Hao-Dong; Zhang, Peng-Jiu

2013-10-01

314

A smog chamber for studies of the reactions of terpenes and alkanes with ozone and OH  

Microsoft Academic Search

The design and performance of a smog chamber for the study of photochemical reactions under simulated environmental conditions is described. The chamber is thermostated for aerosol experiments, and it comprises a gas chromatographic sample enrichment system suitable for monitoring hydrocarbons at the ppbv level. By irradiating NOx\\/alkane-mixtures rate constants for the reaction of OH radicals with n-alkanes are determined from

F. Nolting; W. Behnke; C. Zetzsch

1988-01-01

315

Evidence for perpendicular n-alkane orientation at the liquid/graphite interface  

NASA Astrophysics Data System (ADS)

An STM study of the adsorption of n-hexatriacontane on highly oriented pyrolytic graphite has revealed evidence for a new surface structure. The geometry of this structure indicates that it is composed of an overlayer of n-alkane chains which are rotated by 90° relative to the underlying n-alkane lamellae. A simple argument based on symmetry suggests that the carbon backbone plane of the underlying lamellar assembly is oriented perpendicular to the graphite basal plane.

Gilbert, E. P.; White, J. W.; Senden, T. J.

1994-09-01

316

Hydrogen isotope ratios of recent lacustrine sedimentary n-alkanes record modern climate variability  

Microsoft Academic Search

Hydrogen isotope ratios were measured on n-alkanes (n-C12 to n-C31) extracted from recent lake surface sediments along a N-S European transect to test if modern climate variability is recorded in these biomarkers. ?D values of the n-alkanes are compared to ?D values of meteoric water from the IAEA-GNIP database spanning a range from ?119‰ in northern Sweden to ?41‰ in

D. Sachse; J. Radke; G. Gleixner

2004-01-01

317

An n-alkane proxy for the sedimentary input of submerged\\/floating freshwater aquatic macrophytes  

Microsoft Academic Search

Lipid analysis of aquatic plants from lakes on Mt. Kenya, E. Africa, revealed that non-emergent (submerged and floating-leaved) species displayed enhanced abundances of mid-chain length, C23 and C25n-alkanes. In contrast, the emergent aquatic plants had n-alkane distributions similar to those of the terrestrial vegetation, typically dominated by the long-chain length homologues (>C29). A proxy ratio, Paq, has been formulated to

K. J Ficken; B Li; D. L Swain; G Eglinton

2000-01-01

318

Two Distinct Monooxygenases for Alkane Oxidation in Nocardioides sp. Strain CF8  

Microsoft Academic Search

Alkane monooxygenases in Nocardioides sp. strain CF8 were examined at the physiological and genetic levels. Strain CF8 can utilize alkanes ranging in chain length from C2 to C16. Butane degradation by butane-grown cells was strongly inhibited by allylthiourea, a copper-selective chelator, while hexane-, octane-, and decane-grown cells showed detectable butane degradation activity in the presence of allylthiourea. Growth on butane

NATSUKO HAMAMURA; CHRIS M. YEAGER; DANIEL J. ARP

2001-01-01

319

Genome sequence of the alkane-degrading bacterium Alcanivorax hongdengensis type strain A-11-3.  

PubMed

Alcanivorax hongdengensis A-11-3(T) was isolated from an oil-enriched consortium enriched from the surface seawater of Hong-Deng dock in the Straits of Malacca and Singapore. Strain A-11-3(T) can degrade n-alkane and produce a lipopeptide biosurfactant. Here we report the genome of A-11-3(T) and the genes associated with alkane degradation. PMID:23209226

Lai, Qiliang; Shao, Zongze

2012-12-01

320

Genome Sequence of the Alkane-Degrading Bacterium Alcanivorax hongdengensis Type Strain A-11-3  

PubMed Central

Alcanivorax hongdengensis A-11-3T was isolated from an oil-enriched consortium enriched from the surface seawater of Hong-Deng dock in the Straits of Malacca and Singapore. Strain A-11-3T can degrade n-alkane and produce a lipopeptide biosurfactant. Here we report the genome of A-11-3T and the genes associated with alkane degradation.

Lai, Qiliang

2012-01-01

321

Industrial Chemistry and School Chemistry: Making chemistry studies more relevant  

Microsoft Academic Search

In this paper, we present the development and implementation over the period of more than 15 years of learning materials focusing on industrial chemistry as the main theme. The work was conducted in the Department of Science Teaching at the Weizmann Institute of Science, Israel. The project's general goal was to teach chemistry concepts in the context of industrial chemistry

Avi Hofstein; Miri Kesner

2006-01-01

322

Abundance of macroalgal organic matter in biofilms: evidence from n-alkane biomarkers.  

PubMed

Biofilm development on titanium panels immersed in the surface waters of Dona Paula Bay was investigated using molecular biomarkers such as n-alkanes and other chemical and biological parameters. Biofilm biomass measured as organic carbon (OC), organic nitrogen (ON), chlorophyll a, diatoms and bacterial numbers on the titanium panels generally increased over the period of immersion. Total lipids and n-alkane concentration also showed similar trends. n-alkanes from C(12) to C(30) were detected in the biofilm samples, which showed a bimodal distribution. The first mode consisted of n-alkanes > C(23) with a strong even over odd predominance. In the second mode, the n-alkanes < C(23) were more abundant with odd carbon number maxima at C(15), C(17) and C(19) and a strong odd over even carbon number predominance (Carbon Preference Index > 2). The predominance of these odd-chain n-alkanes strongly indicates that the organic matter derived from macroalgal sources was the major contributor to the biofilm organic matter developed on the titanium panels over the 15 d period of study. The data suggest that molecular characterization is a useful tool in understanding the sources of biofilm organic matter. The observed abundance of macroalgal organic matter during the 15 d period of biofilm development may play an important role in subsequent fouling by micro- and macrofouling organisms. PMID:15545065

Garg, Anita; Bhosle, Narayan

2004-06-01

323

Combustion Characteristics of Liquid Normal Alkane Fuels in a Model Combustor of Supersonic Combustion Ramjet Engine  

NASA Astrophysics Data System (ADS)

Effect of kinds of one-component n-alkane liquid fuels on combustion characteristics was investigated experimentally using a model combustor of scramjet engine. The inlet condition of a model combustor is 2.0 of Mach number, up to 2400K of total temperature, and 0.38MPa of total pressure. Five kinds of n-alkane are tested, of which carbon numbers are 7, 8, 10, 13, and 16. They are more chemically active and less volatile with an increase of alkane carbon number. Fuels are injected to the combustor in the upstream of cavity with barbotage nitrogen gas and self-ignition performance was investigated. The result shows that self-ignition occurs with less equivalence ratio when alkane carbon number is smaller. This indicates that physical characteristic of fuel, namely volatile of fuel, is dominant for self-ignition behavior. Effect on flame-holding performance is also examined with adding pilot hydrogen and combustion is kept after cutting off pilot hydrogen with the least equivalence ratio where alkane carbon number is from 8 to 10. These points are discussed qualitatively from the conflict effect of chemical and physical properties on alkane carbon number.

??, ?; ??, ??; ??, ??; ??, ???; ??, ??; ??, ??; ??, ??

324

Alkanes in flower surface waxes of Momordica cochinchinensis influence attraction to Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae).  

PubMed

Extraction, thin-layer chromatography, and gas chromatography-mass spectrophotometry analyses revealed 15 alkanes representing 97.14% of the total alkanes in the surface waxes of Momordica cochinchinensis Spreng flowers. Nonacosane was the prevailing alkane followed by hexatriacontane, nonadecane, heptacosane, and hentriacontane, accounting for 39.08%, 24.24%, 13.52%, 6.32%, and 5.12%, respectively. The alkanes from flower surface waxes followed by a synthetic mixture of alkanes mimicking alkanes of flower surface waxes elicited attraction of the female insect, Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae) between 2 and 10-?g/mL concentrations in a Y-shaped glass tube olfactometer bioassay under laboratory conditions. Synthetic nonadecane from 178.28-891.37 ng, heptacosane from 118.14-590.72 ng, and nonacosane at 784.73 ng showed attraction of the insect. A synthetic mixture of 534.82 ng nonadecane, 354.43 ng heptacosane, and 2,354.18 ng nonacosane elicited highest attraction of A. foveicollis. PMID:23949856

Mukherjee, A; Sarkar, N; Barik, A

2013-08-01

325

Two Distinct Monooxygenases for Alkane Oxidation in Nocardioides sp. Strain CF8  

PubMed Central

Alkane monooxygenases in Nocardioides sp. strain CF8 were examined at the physiological and genetic levels. Strain CF8 can utilize alkanes ranging in chain length from C2 to C16. Butane degradation by butane-grown cells was strongly inhibited by allylthiourea, a copper-selective chelator, while hexane-, octane-, and decane-grown cells showed detectable butane degradation activity in the presence of allylthiourea. Growth on butane and hexane was strongly inhibited by 1-hexyne, while 1-hexyne did not affect growth on octane or decane. A specific 30-kDa acetylene-binding polypeptide was observed for butane-, hexane-, octane-, and decane-grown cells but was absent from cells grown with octane or decane in the presence of 1-hexyne. These results suggest the presence of two monooxygenases in strain CF8. Degenerate primers designed for PCR amplification of genes related to the binuclear-iron-containing alkane hydroxylase from Pseudomonas oleovorans were used to clone a related gene from strain CF8. Reverse transcription-PCR and Northern blot analysis showed that this gene encoding a binuclear-iron-containing alkane hydroxylase was expressed in cells grown on alkanes above C6. These results indicate the presence of two distinct monooxygenases for alkane oxidation in Nocardioides sp. strain CF8.

Hamamura, Natsuko; Yeager, Chris M.; Arp, Daniel J.

2001-01-01

326

Computational Chemistry List  

NSDL National Science Digital Library

The Computational Chemistry List (CCL) was established as an independent electronic forum for chemistry researchers and educators from around the world. The discussions cover all aspects of computational chemistry.

327

Alkane functionalization at ([mu]-Oxo)diiron(III) centers  

SciTech Connect

The reactivity of ([mu]-oxo)diferric complexes with [sup t]BuOOH (TBHP) for the functionalization of alkanes in CH[sub 3]CN has been investigated as part of our efforts to model dinuclear sites in nonheme iron enzymes. [Fe[sub 2](TPA)[sub 2]O(OAc)](CIO[sub 4])[sub 3] (1) (TPA = tris(2-pyridylmethyl)amine, OAc = acetate) is an efficient catalyst for cyclohexane oxidation, affording cyclohexanol (A, 9 equiv), cyclohexanone (K, 11 equiv), and (tert-butylperoxy)cyclohexane (P, 16 equiv) in 0.25 h at ambient temperature and pressure under an argon atmosphere. The catalyst is remarkably robust, as indicated by the [sup 1]H NMR and UV-vis spectra of the reaction mixture during the catalytic reaction and by its ability to maintain its turnover efficiency with subsequent additions of oxidant. The catalytic mechanism for TBHP utilization was explored by observing the effects of varying the tripodal ligands on the ([mu]-oxo)([mu]-carboxylato)diferric catalysts and varying the bridge on Fe[sub 2]O(TPA)[sub 2] catalysts. The (A + K)/P ratio increased as the ligands became more electron donating. Solvent also played an important role in determining the partitioning of products between A + K and P, with benzonitrile favoring hydroxylated products at the expense of P and pyridine having the opposite effect. 49 refs., 2 figs., 3 tabs.

Leising, R.A.; Kim, J.; Perez, M.A.; Que, L. Jr. (Univ. of Minnesota, Minneapolis, MN (United States))

1993-10-20

328

Dynamics of n-alkanes: Comparison to Rouse model  

NASA Astrophysics Data System (ADS)

The crossover to Rouse-type behavior for the self-diffusion constant D, the viscosity ?, and the equilibrium structural statistics of n-alkanes (6<=n<=66) is studied numerically. For small n the chains are non-Gaussian and the mean squared end-to-end distance is greater than 6, where is the mean squared radius of gyration. As n increases, /-->6(1+a/n), where a depends on the interaction model. At constant density, the Rouse model is used to extract the monomeric friction coefficient ? and the viscosity ? independently from the diffusion constant D and the longest relaxation time ?R. ?D extracted from D is nearly independent of chain length while ?? obtained from ?R is much larger than ?D for small n. The viscosity measured in a nonequilibrium molecular dynamics simulation is closely approximated by the value of ? determined from ?R while ? inferred from D is smaller for small n. For n>~60, the two estimates for both ? and ? agree as predicted from the Rouse model. D calculated from three interaction models is studied for increasing n and compared to experimental data.

Mondello, Maurizio; Grest, Gary S.; Webb, Edmund B.; Peczak, P.

1998-07-01

329

Molecular-isotopic stratigraphy of long-chain n-alkanes in Lake Baikal Holocene and glacial age sediments  

Microsoft Academic Search

The molecular distribution and the carbon-isotopic composition (?13C) of n-alkanes extracted from a Lake Baikal core spanning the last 20 kyr of sediment accumulation have been investigated. A terrestrial origin has been inferred for the odd carbon-numbered long-chain (>C27) n-alkanes, on the basis of the observed high CPI27-33 values (range: 8.7–10.8) typical of n-alkanes derived from leaf waxes of higher

David Brincat; Keita Yamada; Ryoshi Ishiwatari; Hitoshi Uemura; Hiroshi Naraoka

2000-01-01

330

Influence of physiology and climate on ?D of leaf wax n-alkanes from C 3 and C 4 grasses  

Microsoft Academic Search

We measured hydrogen isotope compositions (?D) of high-molecular-weight n-alkanes (C27–C33) from grasses grown in greenhouses and collected from the US Great Plains. In both cases, n-alkanes from C4 grasses are enriched in D by more than 20‰ relative to those from C3 grasses. The apparent enrichment factor (?C29-GW) between C29n-alkane and greenhouse water is ?165±12‰ for C3 grasses and ?140±15‰

Francesca A. Smith; Katherine H. Freeman

2006-01-01

331

Thermodynamic and structural analyses of the solid phases in multi-alkane mixtures similar to petroleum cuts at ambient temperature  

Microsoft Academic Search

Structural analyses were carried out by X-ray diffraction, at ambient temperature, on multi-alkane samples whose mole fraction distribution shows a shape of the ‘exponential decreasing’ type, as observed in petroleum cuts. Nine samples, whose normal-alkane number varies from 15 to 23, have been studied with mole fraction continuous distributions of normal-alkanes going from C22–C36 to C14–C36: each mixture differs from

Anne-Julie Briard; Mohammed Bouroukba; Dominique Petitjean; Nathalie Hubert; Jean-Charles Moïse; Michel Dirand

2005-01-01

332

Interaction between Thermotropic-Liquid Crystalline Polypeptides having Long Alkyl Side-Chains and n-Alkanes  

Microsoft Academic Search

The behavior of mixtures of derivatives of poly(?-benzyl L-glutamate) (PBLG) having long alkyl side-chains as pendant groups and n-alkanes was investigated by means of differential scanning calorimetry, wide-angle X-ray diffraction, electron-spin resonance, and observation under crossed polarizers. When the n-alkane was not too long compared with the length of the alkyl side-chains of the polypeptide, the n-alkane molecules intruded into

E. Iizuka; S. Inoue; K. Hanabusa; H. Shirai

1987-01-01

333

Kinetics of supercritical-phase thermal decomposition of Cââ-Cââ normal alkanes and their mixtures  

Microsoft Academic Search

Kinetics of thermal decomposition of Cââ-Cââ n-alkanes and their mixtures was studied under near-critical and supercritical conditions. Supercritical-phase thermal decomposition of n-alkanes can be represented well by an apparent first-order kinetics, even though the decomposition was not a true first-order process. A generalized expression was developed to predict the apparent first-order rate constants for the decomposition of Câ-Cââ n-alkanes at

J. Yu; S. Eser

1997-01-01

334

Anaerobic n-Alkane Metabolism by a Sulfate-Reducing Bacterium, Desulfatibacillum aliphaticivorans Strain CV2803T  

Microsoft Academic Search

The alkane-degrading, sulfate-reducing bacterium Desulfatibacillum aliphaticivorans strain CV2803T, recently isolated from marine sediments, was investigated for n-alkane metabolism. The total cellular fatty acids of this strain had predominantly odd numbers of carbon atoms (C odd) when the strain was grown on a C-odd alkane (pentadecane) and even numbers of carbon atoms (C even) when it was grown on a C-even

Cristiana Cravo-Laureau; Vincent Grossi; Danielle Raphel; Robert Matheron; Agnes Hirschler-Rea

2005-01-01

335

Occurrence of n-alkanes and polycyclic aromatic hydrocarbons in the core sediments of the Yellow Sea  

Microsoft Academic Search

Three core sediments (YSA10, YSB7 and YSC5) were collected from the Yellow Sea to determine the composition of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) by GC. Concentrations and distributions of n-alkanes (n-C14 to n-C33) vary from 0.7 to 15.8 ?g g?1 dry weight in these core sediments. The alkane indexes (CPI and U\\/R) confirm that vascular plant inputs predominate in

Ying Wu; Jing Zhang; Tie-zhu Mi; Bin Li

2001-01-01

336

Proteomic Insights into Metabolic Adaptations in Alcanivorax borkumensis Induced by Alkane Utilization  

PubMed Central

Alcanivorax borkumensis is a ubiquitous marine petroleum oil-degrading bacterium with an unusual physiology specialized for alkane metabolism. This “hydrocarbonoclastic” bacterium degrades an exceptionally broad range of alkane hydrocarbons but few other substrates. The proteomic analysis presented here reveals metabolic features of the hydrocarbonoclastic lifestyle. Specifically, hexadecane-grown and pyruvate-grown cells differed in the expression of 97 cytoplasmic and membrane-associated proteins whose genes appeared to be components of 46 putative operon structures. Membrane proteins up-regulated in alkane-grown cells included three enzyme systems able to convert alkanes via terminal oxidation to fatty acids, namely, enzymes encoded by the well-known alkB1 gene cluster and two new alkane hydroxylating systems, a P450 cytochrome monooxygenase and a putative flavin-binding monooxygenase, and enzymes mediating ?-oxidation of fatty acids. Cytoplasmic proteins up-regulated in hexadecane-grown cells reflect a central metabolism based on a fatty acid diet, namely, enzymes of the glyoxylate bypass and of the gluconeogenesis pathway, able to provide key metabolic intermediates, like phosphoenolpyruvate, from fatty acids. They also include enzymes for synthesis of riboflavin and of unsaturated fatty acids and cardiolipin, which presumably reflect membrane restructuring required for membranes to adapt to perturbations induced by the massive influx of alkane oxidation enzymes. Ancillary functions up-regulated included the lipoprotein releasing system (Lol), presumably associated with biosurfactant release, and polyhydroxyalkanoate synthesis enzymes associated with carbon storage under conditions of carbon surfeit. The existence of three different alkane-oxidizing systems is consistent with the broad range of oil hydrocarbons degraded by A. borkumensis and its ecological success in oil-contaminated marine habitats.

Sabirova, Julia S.; Ferrer, Manuel; Regenhardt, Daniela; Timmis, Kenneth N.; Golyshin, Peter N.

2006-01-01

337

Rat tissue and blood partition coefficients for n-alkanes (C8 to C12).  

PubMed

Rat tissue:air and blood:air partition coefficients (PCs) for octane, nonane, decane, undecane, and dodecane (n-C8 to n-C12 n-alkanes) were determined by vial equilibration. The blood:air PC values for n-C8 to n-C12 were 3.1, 5.8, 8.1, 20.4, and 24.6, respectively. The lipid solubility of n-alkanes increases with carbon length, suggesting that lipid solubility is an important determinant in describing n-alkane blood:air PC values. The muscle:blood, liver: blood, brain:blood, and fat:blood PC values were octane (1.0, 1.9, 1.4, and 247), nonane (0.8, 1.9, 3.8, and 274), decane (0.9, 2.0, 4.8, and 328), undecane (0.7, 1.5, 1.7, and 529), and dodecane (1.2, 1.9, 19.8, and 671), respectively. The tissue:blood PC values were greatest in fat and the least in muscle. The brain:air PC value for undecane was inconsistent with other n-alkane values. Using the measured partition coefficient values of these n-alkanes, linear regression was used to predict tissue (except brain) and blood:air partition coefficient values for larger n-alkanes, tridecane, tetradecane, pentadecane, hexadecane, and heptadecane (n-C13 to n-C17). Good agreement between measured and predicted tissue:air and blood:air partition coefficient values for n-C8 to n-Cl2 offer confidence in the partition coefficient predictions for longer chain n-alkanes. PMID:15981738

Smith, A Q; Campbell, J L; Keys, D A; Fisher, J W

2005-01-01

338

Secondary organic aerosol formation from intermediate-volatility organic compounds: cyclic, linear, and branched alkanes.  

PubMed

Intermediate volatility organic compounds (IVOCs) are an important class of secondary organic aerosol (SOA) precursors that have not been traditionally included in chemical transport models. A challenge is that the vast majority of IVOCs cannot be speciated using traditional gas chromatography-based techniques; instead they are classified as an unresolved complex mixture (UCM) that is presumably made up of a complex mixture of branched and cyclic alkanes. To better understand SOA formation from IVOCs, a series of smog chamber experiments was conducted with different alkanes, including cyclic, branched, and linear compounds. The experiments focused on freshly formed SOA from hydroxyl (OH) radical-initiated reactions under high-NO(x) conditions at typical atmospheric organic aerosol concentrations (C(OA)). SOA yields from cyclic alkanes were comparable to yields from linear alkanes three to four carbons larger in size. For alkanes with equivalent carbon numbers, branched alkanes had the lowest SOA mass yields, ranging between 0.05 and 0.08 at a C(OA) of 15 ?g m(-3). The SOA yield of branched alkanes also depends on the methyl branch position on the carbon backbone. High-resolution aerosol mass spectrometer data indicate that the SOA oxygen-to-carbon ratios were largely controlled by the carbon number of the precursor compound. Depending on the precursor size, the mass spectrum of SOA produced from IVOCs is similar to the semivolatile-oxygenated and hydrocarbon-like organic aerosol factors derived from ambient data. Using the new yield data, we estimated SOA formation potential from diesel exhaust and predict the contribution from UCM vapors to be nearly four times larger than the contribution from single-ring aromatics and comparable to that of polycyclic aromatic hydrocarbons after several hours of oxidation at typical atmospheric conditions. Therefore, SOA from IVOCs may be an important contributor to urban OA and should be included in SOA models; the yield data presented in this study are suitable for such use. PMID:22823284

Tkacik, Daniel S; Presto, Albert A; Donahue, Neil M; Robinson, Allen L

2012-08-21

339

Alkane hydroxylase gene (alkB) phylotype composition and diversity in northern Gulf of Mexico bacterioplankton  

PubMed Central

Natural and anthropogenic activities introduce alkanes into marine systems where they are degraded by alkane hydroxylases expressed by phylogenetically diverse bacteria. Partial sequences for alkB, one of the structural genes of alkane hydroxylase, have been used to assess the composition of alkane-degrading communities, and to determine their responses to hydrocarbon inputs. We present here the first spatially extensive analysis of alkB in bacterioplankton of the northern Gulf of Mexico (nGoM), a region that experiences numerous hydrocarbon inputs. We have analyzed 401 partial alkB gene sequences amplified from genomic extracts collected during March 2010 from 17 water column samples that included surface waters and bathypelagic depths. Previous analyses of 16S rRNA gene sequences for these and related samples have shown that nGoM bacterial community composition and structure stratify strongly with depth, with distinctly different communities above and below 100 m. Although we hypothesized that alkB gene sequences would exhibit a similar pattern, PCA analyses of operational protein units (OPU) indicated that community composition did not vary consistently with depth or other major physical-chemical variables. We observed 22 distinct OPUs, one of which was ubiquitous and accounted for 57% of all sequences. This OPU clustered with AlkB sequences from known hydrocarbon oxidizers (e.g., Alcanivorax and Marinobacter). Some OPUs could not be associated with known alkane degraders, however, and perhaps represent novel hydrocarbon-oxidizing populations or genes. These results indicate that the capacity for alkane hydrolysis occurs widely in the nGoM, but that alkane degrader diversity varies substantially among sites and responds differently than bulk communities to physical-chemical variables.

Smith, Conor B.; Tolar, Bradley B.; Hollibaugh, James T.; King, Gary M.

2013-01-01

340

Chemistry of the outer planets  

NASA Technical Reports Server (NTRS)

Various aspects were studied of past or present chemistry in the atmospheres of the outer planets and their satellites using lab simulations. Three areas were studied: (1) organic chemistry induced by kinetically hot hydrogen atoms in the region of Jupiter's atmosphere containing the ammonia cirrus clouds; (2) the conversion of NH3 into N2 by plasmas associated with entry of meteors and other objects into the atmosphere of early Titan; and (3) the synthesis of simple hydrocarbons and HCN by lightning in mixtures containing N2, CH4, and NH3 representing the atmospheres of Titan and the outer planets. The results showed that: (1) hot H2 atoms formed from the photodissociation of NH3 in Jupiter's atmosphere could account for some of the atmospheric chemistry in the ammonia cirrus cloud region; (2) the thermalization of hot H2 atoms in atmospheres predominated by molecular H is not as rapid as predicted by elastic collision theory; (3) the net quantum loss of NH3 in the presence of a 200 fold excess of H2 is 0.02, much higher than was expected from the amount of H2 present; (4) the conversion of NH3 into N2 in plasmas associated with infalling meteors is very efficient and rapid, and could account for most of the N2 present on Titan; (5) the yields of C2H2 and HCN from lightning induced chemistry in mixtures of CH4 and N2 is consistent with quenched thermodynamic models of the discharge core; and (6) photolysis induced by the UV light emitted by the gases in the hot plasmas may account for some, if not most, of the excess production of C2H6 and the more complex hydrocarbons.

Scattergood, Thomas W.

1992-01-01

341

Radiation Research: Chemistry and Physics.  

National Technical Information Service (NTIS)

Papers in this Proceedings are grouped under the following headings: (1) primary processes in radiation physics and chemistry; (2) radiation chemistry - general chemistry; (3) radiation chemistry - DNA and model systems; (4) radiation chemistry - other mo...

J. J. Broerse G. W. Barendsen H. B. Kal A. J. van der Kogel

1983-01-01

342

Trace Chemistry  

NASA Technical Reports Server (NTRS)

The goals of the trace chemistry group were to identify the processes relevant to aerosol and aerosol precursor formation occurring within aircraft gas turbine engines; that is, within the combustor, turbine, and nozzle. The topics of discussion focused on whether the chemistry of aerosol formation is homogeneous or heterogeneous; what species are important for aerosol and aerosol precursor formation; what modeling/theoretical activities to pursue; what experiments to carry out that both support modeling activities and elucidate fundamental processes; and the role of particulates in aerosol and aerosol precursor formation. The consensus of the group was that attention should be focused on SO2, SO3, and aerosols. Of immediate concern is the measurement of the concentration of the species SO3, SO2, H2SO4 OH, HO2, H2O2, O, NO, NO2, HONO, HNO3, CO, and CO2 and particulates in various engines, both those currently in use and those in development. The recommendation was that concentration measurements should be made at both the combustor exit and the engine exit. At each location the above species were classified into one of four categories of decreasing importance, Priority I through IV, as follows: Combustor exit: Priority I species - SO3:SO2 ratio, SO3, SO2, and particulates; Priority II species: OH and O; Priority III species - NO and NO2; and Priority IV species - CO and CO2. For the Engine exit: Priority I species - SO3:SO2 ratio, SO3, SO2,H2SO4, and particulates; Priority II species: OH,HO2, H2O2, and O; Priority III species - NO, NO2, HONO, and HNO3; and Priority IV species - CO and CO2. Table I summarizes the anticipated concentration range of each of these species. For particulate matter, the quantities of interest are the number density, size distribution, and composition. In order to provide data for validating multidimensional reacting flow models, it would be desirable to make 2-D, time-resolved measurements of the concentrations of the above species and, in addition, of the pressure, temperature, and velocity. A near term goal of the experimental program should be to confirm the nonlinear effects of sulfur speciation, and if present, to provide an explanation for them. It is also desirable to examine if the particulate matter retains any sulfur. The recommendation is to examine the effects on SOx production of variations in fuel-bound sulfur and aromatic content (which may affect the amount of particulates formed). These experiments should help us to understand if there is a coupling between particulate formation and SO, concentration. Similarly, any coupling with NOx can be examined either by introducing NOx into the combustion air or by using fuel-bound nitrogen. Also of immediate urgency is the need to establish and validate a detailed mechanism for sulfur oxidation/aerosol formation, whose chemistry is concluded to be homogeneous, because there is not enough surface area for heterogeneous effects. It is envisaged that this work will involve both experimental and theoretical programs. The experimental work will require, in addition to the measurements described above, fundamental studies in devices such as flow reactors and shock tubes. Complementing this effort should be modeling and theoretical activities. One impediment to the successful modeling of sulfur oxidation is the lack of reliable data for thermodynamic and transport properties for several species, such as aqueous nitric acid, sulfur oxides, and sulfuric acid. Quantum mechanical calculations are recommended as a convenient means of deriving values for these properties. Such calculations would also help establish rate constants for several important reactions for which experimental measurements are inherently fraught with uncertainty. Efforts to implement sufficiently detailed chemistry into computational fluid dynamic codes should be continued. Zero- and one-dimensional flow models are also useful vehicles for elucidating the minimal set of species and reactions that must be included in two- and three-dimensional modeling studies.

Radhakrishnan, Krishnan; Whitefield, Philip

1999-01-01

343

Document Conversion Methodology.  

ERIC Educational Resources Information Center

Discusses digital imaging technology and examines document database conversion considerations. Two types of document imaging systems are described: (1) a work in process system, and (2) a storage and retrieval system. Conversion methodology is outlined, and a document conversion scenario is presented as a practical guide to conversion. (LRW)

Bovee, Donna

1990-01-01

344

Ocean wave energy conversion  

Microsoft Academic Search

The book provides a review of ocean wave mechanics and an introduction to wave energy conversion. Physical and mathematical descriptions are given of the nine generic wave energy conversion techniques along with their uses and performance characteristics. A number of electro-mechanical energy conversion techniques are described. Attention is also given to the possible environmental effects associated with wave energy conversion.

M. E. McCormick

1981-01-01

345

Quadrature frequency conversion  

Microsoft Academic Search

A technique for frequency conversion of high-power lasers is described which uses two crystals for each conversion step rather than one. The two crystals are oriented so that the waves generated in them are orthogonally polarized. The conversion efficiency of these quadrature arrangements is much less sensitive to laser pulse nonuniformities than that in single-crystal methods. Consequently, very high conversion

David Eimerl

1987-01-01

346

Leaf wax n-alkane distributions in and across modern plants: Implications for paleoecology and chemotaxonomy  

NASA Astrophysics Data System (ADS)

Long chain (C21 to C37) n-alkanes are among the most long-lived and widely utilized terrestrial plant biomarkers. Dozens of studies have examined the range and variation of n-alkane chain-length abundances in modern plants from around the world, and n-alkane distributions have been used for a variety of purposes in paleoclimatology and paleoecology as well as chemotaxonomy. However, most of the paleoecological applications of n-alkane distributions have been based on a narrow set of modern data that cannot address intra- and inter-plant variability. Here, we present the results of a study using trees from near Chicago, IL, USA, as well as a meta-analysis of published data on modern plant n-alkane distributions. First, we test the conformity of n-alkane distributions in mature leaves across the canopy of 38 individual plants from 24 species as well as across a single growing season and find no significant differences for either canopy position or time of leaf collection. Second, we compile 2093 observations from 86 sources, including the new data here, to examine the generalities of n-alkane parameters such as carbon preference index (CPI), average chain length (ACL), and chain-length ratios for different plant groups. We show that angiosperms generally produce more n-alkanes than do gymnosperms, supporting previous observations, and furthermore that CPI values show such variation in modern plants that it is prudent to discard the use of CPI as a quantitative indicator of n-alkane degradation in sediments. We also test the hypotheses that certain n-alkane chain lengths predominate in and therefore can be representative of particular plant groups, namely, C23 and C25 in Sphagnum mosses, C27 and C29 in woody plants, and C31 in graminoids (grasses). We find that chain-length distributions are highly variable within plant groups, such that chemotaxonomic distinctions between grasses and woody plants are difficult to make based on n-alkane abundances. In contrast, Sphagnum mosses are marked by their predominance of C23 and C25, chain lengths which are largely absent in terrestrial vascular plants. The results here support the use of C23 as a robust proxy for Sphagnum mosses in paleoecological studies, but not the use of C27, C29, and C31 to separate graminoids and woody plants from one another, as both groups produce highly variable but significant amounts of all three chain lengths. In Africa, C33 and C35 chain lengths appear to distinguish graminoids from some woody plants, but this may be a reflection of the differences in rainforest and savanna environments. Indeed, variation in the abundances of long n-alkane chain lengths may be responding in part to local environmental conditions, and this calls for a more directed examination of the effects of temperature and aridity on plant n-alkane distributions in natural environments.

Bush, Rosemary T.; McInerney, Francesca A.

2013-09-01

347

Anaerobic transformation of alkanes to fatty acids by a sulfate-reducing bacterium, strain Hxd3.  

PubMed

Strain Hxd3, an alkane-degrading sulfate reducer previously isolated and described by Aeckersberg et al. (F. Aeckersberg, F. Bak, and F. Widdel, Arch. Microbiol. 156:5-14, 1991), was studied for its alkane degradation mechanism by using deuterium and (13)C-labeled compounds. Deuterated fatty acids with even numbers of C atoms (C-even) and (13)C-labeled fatty acids with odd numbers of C atoms (C-odd) were recovered from cultures of Hxd3 grown on perdeuterated pentadecane and [1,2-(13)C(2)]hexadecane, respectively, underscoring evidence that C-odd alkanes are transformed to C-even fatty acids and vice versa. When Hxd3 was grown on unlabeled hexadecane in the presence of [(13)C]bicarbonate, the resulting 15:0 fatty acid, which was one carbon shorter than the alkane, incorporated a (13)C label to form its carboxyl group. The same results were observed when tetradecane, pentadecane, and perdeuterated pentadecane were used as the substrates. These observations indicate that the initial attack of alkanes includes both carboxylation with inorganic bicarbonate and the removal of two carbon atoms from the alkane chain terminus, resulting in a fatty acid one carbon shorter than the original alkane. The removal of two terminal carbon atoms is further evidenced by the observation that the [1,2-(13)C(2)]hexadecane-derived fatty acids contained either two (13)C labels located exclusively at their acyl chain termini or none at all. Furthermore, when perdeuterated pentadecane was used as the substrate, the 14:0 and 16:0 fatty acids formed both carried the same numbers of deuterium labels, while the latter was not deuterated at its carboxyl end. These observations provide further evidence that the 14:0 fatty acid was initially formed from perdeuterated pentadecane, while the 16:0 fatty acid was produced after chain elongation of the former fatty acid with nondeuterated carbon atoms. We propose that strain Hxd3 anaerobically transforms an alkane to a fatty acid through a mechanism which includes subterminal carboxylation at the C-3 position of the alkane and elimination of the two adjacent terminal carbon atoms. PMID:12839758

So, Chi Ming; Phelps, Craig D; Young, L Y

2003-07-01

348

Anaerobic Transformation of Alkanes to Fatty Acids by a Sulfate-Reducing Bacterium, Strain Hxd3  

PubMed Central

Strain Hxd3, an alkane-degrading sulfate reducer previously isolated and described by Aeckersberg et al. (F. Aeckersberg, F. Bak, and F. Widdel, Arch. Microbiol. 156:5-14, 1991), was studied for its alkane degradation mechanism by using deuterium and 13C-labeled compounds. Deuterated fatty acids with even numbers of C atoms (C-even) and 13C-labeled fatty acids with odd numbers of C atoms (C-odd) were recovered from cultures of Hxd3 grown on perdeuterated pentadecane and [1,2-13C2]hexadecane, respectively, underscoring evidence that C-odd alkanes are transformed to C-even fatty acids and vice versa. When Hxd3 was grown on unlabeled hexadecane in the presence of [13C]bicarbonate, the resulting 15:0 fatty acid, which was one carbon shorter than the alkane, incorporated a 13C label to form its carboxyl group. The same results were observed when tetradecane, pentadecane, and perdeuterated pentadecane were used as the substrates. These observations indicate that the initial attack of alkanes includes both carboxylation with inorganic bicarbonate and the removal of two carbon atoms from the alkane chain terminus, resulting in a fatty acid one carbon shorter than the original alkane. The removal of two terminal carbon atoms is further evidenced by the observation that the [1,2-13C2]hexadecane-derived fatty acids contained either two 13C labels located exclusively at their acyl chain termini or none at all. Furthermore, when perdeuterated pentadecane was used as the substrate, the 14:0 and 16:0 fatty acids formed both carried the same numbers of deuterium labels, while the latter was not deuterated at its carboxyl end. These observations provide further evidence that the 14:0 fatty acid was initially formed from perdeuterated pentadecane, while the 16:0 fatty acid was produced after chain elongation of the former fatty acid with nondeuterated carbon atoms. We propose that strain Hxd3 anaerobically transforms an alkane to a fatty acid through a mechanism which includes subterminal carboxylation at the C-3 position of the alkane and elimination of the two adjacent terminal carbon atoms.

So, Chi Ming; Phelps, Craig D.; Young, L. Y.

2003-01-01

349

Numerical and experimental studies of ethanol flames and autoignition theory for higher alkanes  

NASA Astrophysics Data System (ADS)

In order to enhance the fuel efficiency of an engine and to control pollutant formation, an improved understanding of the combustion chemistry of the fuels at a fundamental level is paramount. This knowledge can be gained by developing detailed reaction mechanisms of the fuels for various combustion processes and by studying combustion analytically employing reduced-chemistry descriptions. There is a need for small detailed reaction mechanisms for alkane and alcohol fuels with reduced uncertainties in their combustion chemistry that are computationally cheaper in multidimensional CFD calculations. Detailed mechanisms are the starting points in identifying reduced-chemistry descriptions of combustion processes to study problems analytically. This research includes numerical, experimental and analytical studies. The first part of the dissertation consists of numerical and experimental studies of ethanol flames. Although ethanol has gained popularity as a possible low-pollution source of renewable energy, significant uncertainties remain in its combustion chemistry. To begin to address ethanol combustion, first a relatively small detailed reaction mechanism, commonly known as the San Diego Mech, is developed for the combustion of hydrogen, carbon monoxide, formaldehyde, methane, methanol, ethane, ethylene, and acetylene, in air or oxygen-inert mixtures. This mechanism is tested for autoignition, premixed-flame burning velocities, and structures and extinction of diffusion flames and of partially premixed flames of many of these fuels. The reduction in uncertainties in the combustion chemistry can best be achieved by consistently updating a reaction mechanism with reaction rate data for the elementary steps based on newer studies in literature and by testing it against as many experimental conditions as available. The results of such a testing for abovementioned fuels are reported here along with the modifications of reaction-rate parameters of the most important elementary steps and the addition and deletion of a few key steps relevant to these tests. A mechanism developed in such a hierarchical way starting with simpler fuels such as hydrogen and carbon monoxide to the fuels with one and two carbon atoms has reduced uncertainties in the combustion chemistry of a fuel. This reaction mechanism, consisting of 137 reactions among 30 species, provides a robust building block upon which an ethanol mechanism is developed. The San Diego Mech is extended for ethanol combustion by adding 55 new reactions and 6 new species. Specifically, 33 reactions are added that involve C 2H5OH or one of the three isomers produced by abstraction of an H atom from it, CH3CHOH, CH2CH2OH and CH3CH2O, and 22 reactions are added that involve acetaldehyde or one of the two isomers produced by abstraction of H from it, CH2CHO and CH3CO. Ethanol combustion is investigated on the basis of a new reaction mechanism, thus developed, consisting of 192 elementary steps among 36 species, augmented by 53 additional steps and 14 additional species to address the formation of the oxides of nitrogen and 43 steps and 7 species to address formation of compounds involving three carbon atoms. The mechanism is tested against shock-tube autoignition-delay data, laminar burning velocities, counterflow diffusion-flame extinction and measurements of structures of counterflow partially premixed and diffusion flames. Measurements on ethanol-air flames at a strain rate of 100 s-1, employing prevaporized ethanol with a mole fraction of 0.3 in a nitrogen carrier stream, were made for the pure diffusion flame and for a partially premixed flame with a fuel-side equivalence ratio of 2.3 and involved thermocouple measurements of temperature profiles and determination of concentration profiles of C2H5OH, CO, CO2, H2, H2O, O2, N2, CH4, C2H6 and C2H2+C 2H4 by gas chromatographic analysis of samples withdrawn through fine quartz probes. Computational investigations also were made of profiles of oxides of nitrogen and other potential pollutants in similar partially premixed flames of etha

Saxena, Priyank

350

Effects of 4-hydroxynonenal on isolated hepatocytes. Studies on chemiluminescence response, alkane production and glutathione status.  

PubMed Central

The effect of 4-hydroxy-2,3-trans-nonenal, a diffusible product of lipid peroxidation, on isolated hepatocytes was evaluated with two non-invasive techniques measuring low-level chemiluminescence and alkane evolution. Oxygen-induced low-level chemiluminescence and ethane and n-pentane formation by hepatocytes is enhanced over 7-fold in the presence of 4-hydroxynonenal (2 mM). Glutathione-depleted hepatocytes show a higher increase than controls in both low-level chemiluminescence and alkane formation upon supplementation with 4-hydroxynonenal. The effects on both parameters are diminished by vitamin E pretreatment of rats and are absent under anaerobiosis. At variance with chemiluminescence and alkane formation, 4-hydroxynonenal does not elicit a concomitant increase in malonaldehyde or diene-conjugate formation. Addition of 4-hydroxynonenal to a suspension of hepatocytes causes a rapid loss of cellular glutathione in the form of a glutathione conjugate with the alkenal as observed with high-pressure liquid-chromatographic analysis. The reaction between glutathione and 4-hydroxynonenal proceeds also spontaneously in vitro at 1:1 stoichiometry. The cellular effects of 4-hydroxynonenal evaluated by low-level chemiluminescence and alkane formation are independent of the formation of a glutathione conjugate and seem to rely on the remaining not-bound 4-hydroxynonenal. The sensitivity of 4-hydroxynonenal-enhanced chemiluminescence and alkane formation to free-radical quenchers suggests the participation of a free-radical propagation process.

Cadenas, E; Muller, A; Brigelius, R; Esterbauer, H; Sies, H

1983-01-01

351

Co-crystallization of Alkanes with Longer Methlyene Segments within a Statistically Random Copolymer  

NASA Astrophysics Data System (ADS)

Binary blends of alkanes (CnH2n+2, n=24, 32, 36) and statistically random ethylene-co-vinyl acetate (EVA) copolymers with different vinyl acetate (18, 28 and 40%) contents have been studied to understand the phenomenon of co-crystallization of longer chain fractions. Using thermal fractionation, the distribution of various crystallizable ethylene chain sequences was established in EVA copolymers. Co-crystallization in blends was observed by changes in spectroscopic features of various unit cells (triclinic, even n<26; monoclinic, even n>26 and orthorhombic, odd n) using vibrational spectroscopy. In order to distinguish these changes, deuterated alkanes were blended with EVA. Orthorhombic unit cells show a doublet in the C-H rocking region due to crystal field splitting; this splitting was removed upon co-crystallization. In Raman spectra, the Longitudinal Acoustic Modes (LAM) are used to validate co-crystallization. LAM did not change significantly when an alkane was co-crystallized with EVA in comparison to the neat alkane. The Raman C-H stretching region changed when a monodispersed alkane was blended. Thermal and X-ray analysis support these spectroscopic results upon co-crystallization.

Kalish, Jeffrey; Ramalingham, Suriyakala; Yang, Yuning; Hsu, Shaw Ling

2009-03-01

352

Enhanced biodegradation of alkane hydrocarbons and crude oil by mixed strains and bacterial community analysis.  

PubMed

In this study, two strains, Acinetobacter sp. XM-02 and Pseudomonas sp. XM-01, were isolated from soil samples polluted by crude oil at Bohai offshore. The former one could degrade alkane hydrocarbons (crude oil and diesel, 1:4 (v/v)) and crude oil efficiently; the latter one failed to grow on alkane hydrocarbons but could produce rhamnolipid (a biosurfactant) with glycerol as sole carbon source. Compared with pure culture, mixed culture of the two strains showed higher capability in degrading alkane hydrocarbons and crude oil of which degradation rate were increased from 89.35 and 74.32?±?4.09 to 97.41 and 87.29?±?2.41 %, respectively. In the mixed culture, Acinetobacter sp. XM-02 grew fast with sufficient carbon source and produced intermediates which were subsequently utilized for the growth of Pseudomonas sp. XM-01 and then, rhamnolipid was produced by Pseudomonas sp. XM-01. Till the end of the process, Acinetobacter sp. XM-02 was inhibited by the rapid growth of Pseudomonas sp. XM-01. In addition, alkane hydrocarbon degradation rate of the mixed culture increased by 8.06 to 97.41 % compared with 87.29 % of the pure culture. The surface tension of medium dropping from 73.2?×?10(-3) to 28.6?×?10(-3) N/m. Based on newly found cooperation between the degrader and the coworking strain, rational investigations and optimal strategies to alkane hydrocarbons biodegradation were utilized for enhancing crude oil biodegradation. PMID:24532465

Chen, Yu; Li, Chen; Zhou, Zhengxi; Wen, Jianping; You, Xueyi; Mao, Youzhi; Lu, Chunzhe; Huo, Guangxin; Jia, Xiaoqiang

2014-04-01

353

Selective transport and accumulation of alkanes by Rhodococcus erythropolis S+14He.  

PubMed

Selective transport and accumulation of n-alkanes by Rhodococcus erythropolis S+14He was studied by growing cells on n-hexadecane, n-octadecane or the branched alkane pristane, and on mixtures of hydrocarbons. Ultrastructural analysis by transmission electron microscopy (TEM) revealed hydrocarbon inclusion bodies present in cells grown on the three alkanes, but not in cells grown on soluble media or exposed to nonmetabolized 2,2,4,4,6,8,8-heptamethylnonane (HMN). n-Hexadecane had the highest rates of accumulation within the cells and higher overall consumption rates relative to the other alkanes. These rates decreased when the molar concentration of n-hexadecane was decreased in hydrocarbon mixtures, but at the same time the accumulation of n-hexadecane in intracellular inclusions became increasingly selective. Sodium azide significantly inhibited the accumulation of n-hexadecane, consistent with an active transport mechanism for accumulation. These results indicate that R. erythropolis S+14He is able to selectively discriminate and preferentially transport n-hexadecane from mixtures of structurally similar alkanes into intracellular inclusions by an energy-driven transport system. This selective membrane transport of hydrocarbon isomers has potential application for separations, bioprocessing, and the development of novel biosensors. PMID:12378606

Kim, In Seon; Foght, Julia M; Gray, Murray R

2002-12-20

354

Effects of fuel properties on the burning characteristics of collision-merged alkane/water droplets  

SciTech Connect

The combustion characteristics of freely falling droplets, individually generated by the merging of colliding alkane and water droplets, were experimentally investigated. The outcome of the collision droplets was first studied and then the subsequent burning processes such as the flame appearance, ignition and burning behaviors were recorded, through either visual observation or microphotography with the aid of stroboscopic lighting. If the merged droplets were exhibited in an insertive manner, while the water droplet inserted into the alkane droplet, these yield the burning behaviors prior to the end of flame were very much similar to that of pure alkane. The burning was ended with droplet extinction for lower-C alkane, and with either droplet ''flash vaporization'' or extinction for hexadecane. And if the merged droplets were in adhesive manner, for hexadecane with large water content, they either could not be ignited for the large merged droplets, or be ignited with a much prolonged ignition delay, followed by a soot-reducing flame and an ending of droplet extinction for the small merged droplets. ''Homogeneous'' explosion was not observed in any of the tests, and ''heterogeneous'' explosion, induced by trapped air bubbles, occasionally occurred for merged droplets with C-atom in alkane is higher than dodecane. And the sudden disappearance of droplet definitely decreased the burning time and thus enhanced the burning intensity. Besides, the fuel mass consumption rates were increased, even in the cases that having droplet extinction, because of the enlargement of the surface area due to the stuffing of water droplet. (author)

Wang, C.H.; Pan, K.L.; Huang, W.C.; Wen, H.C. [Department of Mechanical Engineering, National Taiwan University, Taipei 106 (China); Yang, J.Y. [Institute of Applied Mechanics, National Taiwan University, Taipei 106 (China); Law, C.K. [Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544 (United States)

2008-04-15

355

Quantum chemical challenges for the binding of simple alkanes to supramolecular hosts.  

PubMed

Binding of hydrocarbon guests to supramolecular hosts can lead to unusual geometric changes such as bending or coiling of guests upon encapsulation. Cucurbiturils (CBs) are classic cation binders that were recently used for the selective binding of small-membered hydrocarbons with a very high association constant (Ka ? 10(6) M(-1)). In this study, we have systematically investigated the binding of some alkanes to CB-[6] using a series of quantum chemical methods. The calculated binding free energies are very strong and are largely influenced by guest orientations inside the host and reorganization of host and guests. The computed (1)H NMR chemical shifts of the encapsulated alkanes agree with the experimental estimates thus confirming guest encapsulation. Further, we have shown that although binding of both cyclopentane and neopentane have very strong binding affinities (>20 kcal mol(-1)), the selectivity of cyclopentane to neopentane at CB-[6] is a kinetically driven process through the computation of approximate transition state structures of both alkanes to CB-[6]. The calculated binding affinities with dispersion corrected density functionals (DFs) are very close to the experimental estimates, whereas DFs that lack dispersion correction predict that alkane binding to CB-[6] is largely unfavorable. Finally, we have investigated the binding of some long chain alkanes to several supramolecular hosts using dispersion corrected semiempirical methods which cannot be routinely studied through density functional theory methods due to the larger size of the system. PMID:24073855

Sundararajan, Mahesh

2013-10-31

356

Differential Expression of the Components of the Two Alkane Hydroxylases from Pseudomonas aeruginosa  

PubMed Central

Oxidation of n-alkanes in bacteria is normally initiated by an enzyme system formed by a membrane-bound alkane hydroxylase and two soluble proteins, rubredoxin and rubredoxin reductase. Pseudomonas aeruginosa strains PAO1 and RR1 contain genes encoding two alkane hydroxylases (alkB1 and alkB2), two rubredoxins (alkG1 and alkG2), and a rubredoxin reductase (alkT). We have localized the promoters for these genes and analyzed their expression under different conditions. The alkB1 and alkB2 genes were preferentially expressed at different moments of the growth phase; expression of alkB2 was highest during the early exponential phase, while alkB1 was induced at the late exponential phase, when the growth rate decreased. Both genes were induced by C10 to C22/C24 alkanes but not by their oxidation derivatives. However, the alkG1, alkG2, and alkT genes were expressed at constant levels in both the absence and presence of alkanes.

Marin, Mercedes M.; Yuste, Luis; Rojo, Fernando

2003-01-01

357

Whole-cell bacterial bioreporter for actively searching and sensing of alkanes and oil spills  

PubMed Central

Summary Acinetobacter baylyi ADP1 was found to tolerate seawater and have a special ability of adhering to an oil–water interface of 10–80?µm emulsified mineral and crude oil droplets. These properties make ADP1 an ideal bacterial chassis for constructing bioreporters that are able to actively search and sense oil spill in water and soils. Acinetobacter baylyi bioreporter ADPWH_alk was developed and applied to the detection of alkanes and alkenes in water, seawater and soils. Bioreporter ADPWH_alk was able to detect a broad range of alkanes and alkenes with carbon chain length from C7 to C36. So far, ADPWH_alk is the only bioreporter that is able to detect alkane with carbon chain length greater than C18. This bioreporter responded to the alkanes in about 30?min and it was independent to the cell growth phase because of two point mutations in alkM promoter recognized by alkane regulatory protein ALKR. ADPWH_alk was applied to detect mineral oil, Brent, Chestnut and Sirri crude oils in water and seawater in the range 0.1–100?mg?l?1, showing that the bioreporter oil detection was semi?quantitative. This study demonstrates that ADPWH_alk is a rapid, sensitive and semi?quantitative bioreporter that can be useful for environmental monitoring and assessment of oil spills in seawater and soils.

Zhang, Dayi; He, Yi; Wang, Yun; Wang, Hui; Wu, Lin; Aries, Eric; Huang, Wei E.

2012-01-01

358

The fate of primary cations in radiolysis of alkanes as studied by ESR  

NASA Astrophysics Data System (ADS)

The structures and reactions of alkane cations (RH +) have been studied by ESR to elucidate the fate of primary cations in radiolysis of alkanes. Radical cations of prototype alkanes such as C 2H 6, C 3H 8, iso-C 4H 10 and neo-C 5H 12 etc. as well as their partially deuterated analogues were stabilized in irradiated frozen matrices such as SF 6, CFCl 2CF 2Cl and CFCl 3 having a higher ionization potential than that of these alkanes contained as dilute solutes. RH + in SF 6 and in CFCl 2CF 2Cl converts into alkyl radicals by deprotonation probably through bimolecular reactions, whereas RH + in CFCl 3 unimolecularily decomposes into olefinic cations by H 2 and/or CH 4 elimination reactions. It is further found that the electronic structures of propane and isobutane cations in halocarbon matrices are different from those in SF 6 and the difference is drastically reflected in the site preference of their deprotonation reactions. The results are discussed in relation to the mechanisms of pairwise formation of alkyl radicals in low temperature radiolysis of neat alkanes and its suppression by addition of electron scavengers.

Iwasaki, Machio; Toriyama, Kazumi; Nunome, Keichi

359

Oxygenates from light alkanes catalyzed by NO{sub x} in the gas phase  

SciTech Connect

The partial oxidations of light alkanes (methane, ethane, propane, and iso-butane) catalyzed by NO{sub x} in the gas phase have been studied at a pressure of less than 1 bar. For all the alkanes tested, the addition of NO to the mixture of alkanes and O{sub 2} enhanced the selectivities and the yields of oxygenates remarkably. It was suggested that NO{sub 2} generated from NO and O{sub 2} initiated the oxidation of alkanes and would specifically accelerate the C-C bond fission, enhancing the formation of C{sub 1}-oxygenates from ethane, propane, and iso-butane. No{sub 2} and NO would be used as a homogeneous catalyst at >600 C because nitroalkanes formed were decomposed completely, releasing the NO{sub x}. The comparison of the product distributions for the decomposition and oxidation of nitroalkanes and alkylnitrites strongly suggested that the oxygenates (HCHO, CH{sub 3}CHO, and CH{sub 3}COCH{sub 3}) were formed from the corresponding alkylnitrites which must be the reaction intermediates during the oxidation of alkanes with an O{sub 2} and NO mixture.

Otsuka, Kiyoshi; Takahashi, Ryo; Yamanaka, Ichiro [Tokyo Inst. of Tech., (Japan). Dept. of Chemical Engineering] [Tokyo Inst. of Tech., (Japan). Dept. of Chemical Engineering

1999-07-01

360

Variability of n-alkanes and nonacosan-10-ol in natural populations of Picea omorika.  

PubMed

This is the first report of population variability of the contents of n-alkanes and nonacosan-10-ol in the needle epicuticular waxes of Serbian spruce (Picea omorika). The hexane extracts of needle samples originated from three natural populations in Serbia (Vranjak, Zmajeva?ki potok, and Mileševka Canyon) were investigated by GC and GC/MS analyses. The amount of nonacosan-10-ol varied individually from 50.05 to 74.42% (65.74% in average), but the differences between the three investigated populations were not statistically confirmed. The results exhibited variability of the composition of n-alkanes in the epicuticular waxes with their size ranging from C(18) to C(35). The most abundant n-alkanes were C(29), C(31), and C(27) (35.22, 13.77, and 12.28% in average, resp.). The carbon preference index of all the n-alkanes (CPI(total)) of the P. omorika populations (average of populations I-III) ranged from 3.3 to 11.5 (mean of 5.9), while the average chain length (ACL) ranged from 26.6 to 29.2. The principal component and cluster analyses of the contents of nine n-alkanes showed the greatest difference for the population growing in the Mileševka Canyon. The obtained results were compared with previous literature data given for other Picea species, and this comparison was briefly discussed. PMID:23495163

Nikoli?, Biljana; Teševi?, Vele; Ðor?evi?, Iris; Todosijevi?, Marina; Jadranin, Milka; Bojovi?, Srdjan; Marin, Petar D

2013-03-01

361

Surfactant-Induced Phases in Water-Supported Alkane Monolayers: II. Structure.  

PubMed

The structure of the Langmuir-Gibbs films of normal alkanes Cn of length n = 12-21 formed at the surface of aqueous solutions of CmTAB surfactants, m = 14, 16, and 18, was studied by surface-specific synchrotron X-ray methods. At high temperatures, a laterally disordered monolayer of mixed alkane molecules and surface-adsorbed surfactant tails is found, having thicknesses well below those of the alkanes' and surfactant tails' extended length. The mixed monolayer undergoes a freezing transition at a temperature Ts(n,m), which forms, for n ? m + 1, a crystalline monolayer of mixed alkane molecules and surfactant tails. For n ? m + 2, a bilayer forms, consisting of an upper pure-alkane, crystalline monolayer and a lower liquidlike monolayer. The crystalline monolayer in both cases consists of hexagonally packed extended, surface-normal-aligned chains. The hexagonal lattice constant is found to decrease with increasing n. The films' structure is discussed in conjunction with their thermodynamic properties presented in an accompanying paper. PMID:24918630

Yefet, Shai; Sloutskin, Eli; Tamam, Lilach; Sapir, Zvi; Deutsch, Moshe; Ocko, Benjamin M

2014-07-15

362

Oxidative methane conversion in dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

A dielectric barrier discharge was used for the oxidative coupling of methane (OCM) with oxygen at the pressure of 1.2 bar. A dielectric barrier discharge (DBD) reactor was powered at the frequency of about 6 kHz. Molar ratio CH4/O2 in the inlet gas containing 50% or 25% of argon was 3, 6 and 12. The effects of temperature (110, 150 and 340 ?C), gas flow rate, molar ratio of methane to oxygen on the overall methane and oxygen conversion and methane conversion to methanol, ethanol, hydrocarbons, carbon oxides and water were studied. In the studied system the increase of the temperature decreases the conversion of methane to methanol. The increase of the molar ratio of methane to oxygen increased the methane conversion to hydrocarbons and strongly decreased the methane conversion to alcohols. The conversion of methane to hydrocarbons increased and the conversion of methane to methanol decreased with the decrease of the gas flow rate from 2 to 1 NL/h. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

Krawczyk, Krzysztof; M?otek, Micha?; Ulejczyk, Bogdan; Pryciak, Krzysztof; Schmidt-Sza?owski, Krzysztof

2013-02-01

363

Crossover SAFT equation of state: Application for normal alkanes  

SciTech Connect

In this paper the authors develop a crossover modification of the statistical associating fluid theory (SAFT) equation of state for macromolecular chain fluids which incorporates the scaling laws asymptotically close to the critical point and is transformed into the original classical SAFT equation of state far away from the critical point. A comparison is made with experimental data for pure methane, ethane, n-hexane, n-decane, and n-eicosane in the one- and two-phase regions. The authors also present comparisons with experimental single-phase data for n-triacontane and n-tetracontane. They show that, over a wide range of states, the crossover SAFT model yields a much better representation of the thermodynamic properties of pure fluids than the original SAFT equation of state. The crossover SAFT equation of state reproduces the saturated pressure data in the entire temperature range from the triple point to the critical temperature with an average absolute deviation (AAD) of about 2.9% in the region bounded by 0.05{rho}{sub c} {le} {rho} {le} 2.5{rho}{sub c} and T{sub c} {le} T {le} 2T{sub c}, and the liquid density data with an AAD of about 3% at the pressures up to P = 2,000 bar. For the n-alkanes C{sub m}H{sub 2m+2} with the molecular weight M{sub w} {gt} 142 (m {gt} 10), the crossover SAFT model contains no adjustable parameters and can be used for the pure prediction of the fluid thermodynamic surface.

Kiselev, S.B.; Ely, J.F.

1999-12-01

364

Study of thermal conversion of naphthenic oils on the basis of analysis of their middle fractions  

SciTech Connect

The composition of the middle fractions of the thermal decomposition products of naphthenic oils obtained at 300, 350, and 400{degrees}C was studied. It was shown that the character of conversions of petroleum hydrocarbons is governed by the intensity of thermal treatment and by the chemical nature of the starting oil. The removal of aliphatic chains from high-boiling components of the petroleum at a temperature below 350{degrees}C results in the new formation of linear and isoprene alkanes in their middle fractions similarly to the catagenic transformations of oils in deposits. The rise in temperature up to 400{degrees}C enhances the destruction processes related to extension of the reactions of the homolytic cleavage of C-C bonds in aliphatic chains. This results in practically complete destruction of isoprene alkanes and in predominance of low-molecular homologs among the linear alkanes. On the basis of the results obtained it can be supposed that the thermal treatment is an important factor in the conversion of naphthenic oils into paraffin oils. 10 refs., 2 figs., 3 tabs.

Kayukova, G.P.; Kurbskii, G.P.; Mutalapova, R.I. [A.E. Arbuzov Inst. of Organic and Physical Chemistry, Kazan (Russian Federation)] [and others

1994-05-10

365

ACS Green Chemistry Institute  

NSDL National Science Digital Library

This special feature page from the American Chemical Society (ACS) showcases the up-and-coming field of "green chemistry," that is, the development of chemical products and processes that eliminate or reduce the use and generation of hazardous substances. A list of principles behind green chemistry, a searchable bibliography of green chemistry references, and green chemistry links (including conferences). This page comes from ACS's Green Chemistry Project, a three-year educational project to develop and disseminate green chemistry educational materials for graduate and undergraduate chemistry students.

2005-12-13

366

Anaerobic oxidation of short-chain alkanes in hydrothermal sediments: potential influences on sulfur cycling and microbial diversity  

PubMed Central

Short-chain alkanes play a substantial role in carbon and sulfur cycling at hydrocarbon-rich environments globally, yet few studies have examined the metabolism of ethane (C2), propane (C3), and butane (C4) in anoxic sediments in contrast to methane (C1). In hydrothermal vent systems, short-chain alkanes are formed over relatively short geological time scales via thermogenic processes and often exist at high concentrations. The sediment-covered hydrothermal vent systems at Middle Valley (MV, Juan de Fuca Ridge) are an ideal site for investigating the anaerobic oxidation of C1–C4 alkanes, given the elevated temperatures and dissolved hydrocarbon species characteristic of these metalliferous sediments. We examined whether MV microbial communities oxidized C1–C4 alkanes under mesophilic to thermophilic sulfate-reducing conditions. Here we present data from discrete temperature (25, 55, and 75°C) anaerobic batch reactor incubations of MV sediments supplemented with individual alkanes. Co-registered alkane consumption and sulfate reduction (SR) measurements provide clear evidence for C1–C4 alkane oxidation linked to SR over time and across temperatures. In these anaerobic batch reactor sediments, 16S ribosomal RNA pyrosequencing revealed that Deltaproteobacteria, particularly a novel sulfate-reducing lineage, were the likely phylotypes mediating the oxidation of C2–C4 alkanes. Maximum C1–C4 alkane oxidation rates occurred at 55°C, which reflects the mid-core sediment temperature profile and corroborates previous studies of rate maxima for the anaerobic oxidation of methane (AOM). Of the alkanes investigated, C3 was oxidized at the highest rate over time, then C4, C2, and C1, respectively. The implications of these results are discussed with respect to the potential competition between the anaerobic oxidation of C2–C4alkanes with AOM for available oxidants and the influence on the fate of C1 derived from these hydrothermal systems.

Adams, Melissa M.; Hoarfrost, Adrienne L.; Bose, Arpita; Joye, Samantha B.; Girguis, Peter R.

2013-01-01

367

PEROXYNITRITE CHEMISTRY  

SciTech Connect

This century old area of research has been experiencing a renaissance during the last decade, with the annual number of publications on the subject increasing from only one in 1990 to nearly 200 in the late-1990s. This renewed interest is stimulated by the discovery of biological roles of nitric oxide, distinguished by the 1998 Nobel prize, and the recognition that the conversion of nitric oxide into peroxynitrite may play major roles in human diseases associated with oxidative stress and in cellular defense against invading pathogens. Peroxynitrite (ONOO{sup {minus}})is a structural isomer of nitrate (NO{sub 3}{sup {minus}}) that contains a peroxo bond. The physiological route to ONOO{sup {minus}} is provided by the combination of nitric oxide ({center_dot}NO) with superoxide ({center_dot}O{sub 2}{sup {minus}}), an extremely rapid reaction occurring upon every encounter of these radicals (the upper dot denotes radical species). Both {center_dot}NO and {center_dot}O{sub 2}{sup {minus}} are the oxygen metabolic products simultaneously generated in a number of cell types within a human body. Compared to its precursors, peroxynitrite is a much stronger oxidant capable of oxidizing proteins, nucleic acids, and lipids.

Lymar, S.V.

2000-11-29

368

Chemistry in Titan's Hydrocarbon Seas  

NASA Astrophysics Data System (ADS)

Multiple lines of evidence from the Cassini-Huygens mission demonstrate that Titan's large lakes and seas are composed of liquid ethane and methane. In addition to the aforementioned constituents, recent work on solubility indicates that propane, dissolved acetylene and nitriles will be significant components (Cordier, D. et al., ApJ v. 707, 128, 2009). Here we make a preliminary examination of the kinds of chemistry that might occur in such a multicomponent organic solution at temperatures of 90 K subject to various energy sources including modulations of solar heating on seasonal and longer timescales (Aharonson et al., Nature Geoscience v. 2 851, 2009), cosmic rays, and (more speculatively) regional cryovolcanism. It is known that carbon cations (C+) can form in methane, and thus these cations might be found in the liquid methane and ethane comprising the polar seas of Titan. As a result, the methane would become a weak protic solvent, which opens the possibility of methane and its sister alkanes participating in more vigorous organic reactions and erosional processes with the surrounding bedrock than previously thought. We apply these considerations to several problems: (a) We calculate rates of chemical erosion of geological features surrounding the large seas, assuming the surrounding country rock to be (i) water, (ii) water-ammonia, (iii) solid organics. (b) We recompute the solubility of minor polar constituents in the seas, which should be enhanced thanks to the protic behavior of the methane. (c) Non-aqueous biochemistries in hydrocarbon liquids such as those proposed by Benner et al. (Current Opinions in Chem. Bio. v. 8, 672-689) will be aided by the potential for enhanced polarity of the liquid. This work was supported by the NASA Astrobiology Institute, and the program "Incentivazione alla mobilita' di studiosi straineri e italiani residenti all'estero."

Lunine, Jonathan I.; Jacobs, Norman; Cordier, Daniel; Mousis, Olivier

2010-05-01

369

Reflections on Doctoral Education in Chemistry. Carnegie Essays on the Doctorate: Chemistry.  

ERIC Educational Resources Information Center

The Carnegie Foundation commissioned a collection of essays as part of the Carnegie Initiative on the Doctorate (CID). Essays and essayists represent six disciplines that are part of the CID: chemistry, education, English, history, mathematics, and neuroscience. Intended to engender conversation about the conceptual foundation of doctoral…

Kwiram, Alvin L.

370

Delights of Chemistry  

NSDL National Science Digital Library

Developed by the University of Leeds, the Delights of Chemistry promotes the art of chemistry demonstrations. Users can find illustrations and explanations of forty chemistry experiments. Many animations of demonstrations including the magnesium lamp, thermite reaction, and the volcano reaction are available. The website is full of pictures of chemistry equipment and scientists at work. Through this site, students and educators are able to explore fun chemistry experiments without having to worry about the many hazards associated with working with chemicals.

371

Positron annihilation in argon intercalated n-alkanes at high pressure  

NASA Astrophysics Data System (ADS)

Positron annihilation lifetime spectroscopy was used to observe the effects of argon intercalation in some solid long-chain alkanes at high pressure. The ortho-Ps lifetime rises with argon pressure, which means increase of free volumes in the alkane structure. The range of pressures in which the rotator phase exists increases, comparing to pure alkane. In n-heptadecane, n-nonadecane, and possibly n-heneicosane, a stepwise change of ortho-Ps lifetime and intensity at ?12 MPa is observed, suggesting the transition to a new kind of the rotator phase. The transition rate is low, final lifetime value is ?3.3 ns. Despite a large size of free volumes corresponding to such a lifetime, their compressibility is found negligible up to the pressure of 90 MPa. At low pressures the compressibility of free volumes in the rotator phase is negative.

Zgardzi?ska, B.; Wawryszczuk, J.; Goworek, T.

2006-01-01

372

The rate-limiting step for alkane dehydrogenation in zeolite H-ZSM-5.  

SciTech Connect

We have carried out a computational study of protolytic cracking, dehydrogenation, and H/D exchange of ethane, propane, and butane using a cluster model of H-ZSM-5. Our previous work has demonstrated that quantum-chemical techniques can give quantitatively accurate activation energies for alkane cracking in zeolites [1]. Experimental kinetic studies have shown that the apparent activation energies for cracking and H/D exchange decrease with n-alkane chain length, while for dehydrogenation the energies increase [2,3]. Our goal is to study the dependence of the activation energy on the alkane chain length in these reactions and to understand why the dehydrogenation reaction behaves so differently.

Zygmunt, S. A.; Bootz, B. L.; Miller, A. W.; Curtiss, L. A.; Iton, L. E.

2000-11-01

373

Preferred orientations and stability of medium length n-alkanes solidified in mesoporous silicon  

SciTech Connect

The n-alkanes C{sub 16}H{sub 34}, C{sub 17}H{sub 36}, C{sub 19}H{sub 40}, and C{sub 25}H{sub 52} have been imbibed and solidified in mesoporous, crystalline silicon with a mean pore diameter of 10 nm. The structures and phase sequences have been determined by x-ray diffractometry. Apart from a reduction and the hysteresis of the melting-freezing transition, we find a set of six discrete orientation states (''domains'') of the confined alkane crystals with respect to the lattice of the silicon host. The growth process responsible for the domain selection is interpreted as a nanoscale version of the Bridgman technique known from single-crystal growth. Oxidation of the pore walls leads to extrusion of the hydrocarbons upon crystallization, whereas the solidified n-alkanes investigated in nonoxidized, porous silicon are thermodynamically stable.

Henschel, A.; Hofmann, T.; Huber, P.; Knorr, K. [Technische Physik, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany)

2007-02-15

374

Distribution, activity and function of short-chain alkane degrading phylotypes in hydrothermal vent sediments  

NASA Astrophysics Data System (ADS)

Global geochemical analyses suggest that C2-C4 short chain alkanes are a common component of the utilizable carbon pool in deep-sea sediments worldwide and have been found in diverse ecosystems. From a thermodynamic standpoint, the anaerobic microbial oxidation of these aliphatic hydrocarbons is more energetically yielding than the anaerobic oxidation of methane (AOM). Therefore, the preferential degradation of these hydrocarbons may compete with AOM for the use of oxidants such as sulfate, or other potential oxidants. Such processes could influence the fate of methane in the deep-sea. Sulfate-reducing bacteria (SRB) from hydrocarbon seep sediments of the Gulf of Mexico and Guaymas Basin have previously been enriched that anaerobically oxidize short chain alkanes to generate CO2 with the preferential utilization of 12C-enriched alkanes (Kniemeyer et al. 2007). Different temperature regimens along with multiple substrates were tested and a pure culture (deemed BuS5) was isolated from mesophilic enrichments with propane or n-butane as the sole carbon source. Through comparative sequence analysis, strain BuS5 was determined to cluster with the metabolically diverse Desulfosarcina / Desulfococcus cluster, which also contains the SRB found in consortia with anaerobic, methane-oxidizing archaea in seep sediments. Enrichments from a terrestrial, low temperature sulfidic hydrocarbon seep also corroborated that propane degradation occurred with most bacterial phylotypes surveyed belonging to the Deltaproteobacteria, particularly Desulfobacteraceae (Savage et al. 2011). To date, no microbes capable of ethane oxidation or anaerobic C2-C4 alkane oxidation at thermophilic temperature have been isolated. The sediment-covered, hydrothermal vent systems found at Middle Valley (Juan de Fuca Ridge, eastern Pacific Ocean) are a prime environment for investigating mesophilic to thermophilic anaerobic oxidation of short-chain alkanes, given the elevated temperatures and dissolved hydrocarbon species characteristic of these metalliferous sediments. These systems are also characterized by sharp physicochemical gradients that have been shown to have a pronounced effect on microbial ecology and activity. Sediments were collected from a Middle Valley field with relatively high concentrations of short-chain alkanes and incubated in anaerobic batch reactors with each individual alkane (C1, C2, C3 and C4, respectively) at a range of temperatures (25, 55 and 75 °C) to mimic environmental physico-chemical conditions in a closed system. Stable carbon isotope ratios and radiotracer incubations provide clear evidence for C2-C4 alkane oxidation in the sediments over time. Upon identifying sediments with anaerobic alkane oxidation activity, microbial communities were screened via 16S rRNA pyrosequencing, and key phylotypes were then quantified using both molecular and microscopic methods. There were shifts in overall community composition and putative alkane-oxidizing phylotypes after the incubation period with the alkane substrates. These are the first evidence to date indicating that anaerobic C2-C4 alkane oxidation occurs across a broad range of temperatures in metalliferous sediments.

Adams, M. M.; Joye, S. B.; Hoarfrost, A.; Girguis, P. R.

2012-12-01

375

Identification of phenylcycloparaffin alkanes and other monoaromatics in Green River shale by gas chromatography-mass spectrometry (GC-MS)  

Microsoft Academic Search

Analysis of an aromatics fraction confirmed the presence of 1 diaromatic and 23 monoaromatic hydrocarbons, including 10 phenyl(cyclohexyl)alkanes, 5 alkylbenzenes, 2 benzomonocycloparaffins, 3 benzodicycloparaffins, 2 benzocycloparaffins, 1 benzotricycloparaffin, and 1 naphthalenemonocycloparaffin. Substituted phenyl(cyclohexyl)- or (cyclopentyl)alkanes make up more than 50 percent of the total monoaromatics identified in Green River shale.

E. J. Gallegos

1973-01-01

376

The partially degraded hydrophilic silane pattern and its application in studying the structures of long chain alkane films.  

PubMed

We developed a protocol to fabricate hydrophilic patterns over an octadecyltrichlorosilane (OTS) film surface with an atomic force microscope (AFM). Through a local probe oxidation under a 100% humidity environment, the OTS was converted into a hydrophilic, carboxylic acid-terminated surface (OTSpd). The OTSpd pattern grew with the voltage dwell time applied on the conducting AFM probe. Eighty nanometer to submillimeter sized OTSpd patterns could be fabricated with a single scanning probe. The OTSpd patterns were used to study the spreading of long chain alkanes. Hexatriacontane (C36H74) was dip-coated on an OTSpd pattern. Subsequently, an additional hydrophilic OTSpd region was fabricated surrounding the coated C36H74. The alkane spread over this newly created region when heated above its melting point. After cooling to room temperature, the shape and structures of the solidified alkane patterns were characterized. On the methyl-terminated, low-energy surface, the alkane molecules stood directly on the surface. In contrast, on the hydrophilic, high-energy surface, the alkane formed seaweed-shaped patterns after spreading. On the OTSpd surface, the alkane molecules initially adsorbed on the hydrophilic surface with their alkyl chains parallel to the surface. Additional alkane molecules stood vertically or tilted on top of the parallel layer, forming the seaweed-shaped layer. The seaweed patterns were previously thought to consist of only vertically standing alkane molecules. We found that three additional tilted phases existed in the seaweed-shaped structures. PMID:19432492

Cai, Yuguang

2009-05-19

377

Biosynthetic and environmental effects on the stable carbon isotopic compositions of anteiso- (3-methyl) and iso- (2-methyl) alkanes in tobacco leaves  

Microsoft Academic Search

Nicotiana tabacum is the only plant known to synthesise large quantities of anteiso- (3-methyl) alkanes and iso- (2-methyl) alkanes. We investigated the carbon isotope ratios of individual long-chain n-alkanes, anteiso- and iso-alkanes (in the C29–C33 carbon number range) extracted from tobacco grown in chambers under controlled conditions to confirm the pathway used by the tobacco plant to synthesise these particular

Kliti Grice; Hong Lu; Youping Zhou; Hilary Stuart-Williams; Graham D. Farquhar

2008-01-01

378

Pashto Conversation Manual and Pashto Conversation Tapescript.  

ERIC Educational Resources Information Center

This conversation manual and tapescript are part of a set of materials that have been developed to teach oral and written Afghan Pashto to English speakers. In addition to the conversation manual and tapescript, the set consists of a beginning textbook, an intermediate textbook, a reader, and a set of taped lessons that correlate with the…

Tegey, Habibullah; Robson, Barbara

379

Leaf-wax n-alkanes record the plant-water environment at leaf flush  

PubMed Central

Leaf-wax n-alkanes 2H/1H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes ?2H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm species, Populus angustifolia, growing on water with a constant ?2H value and monitored the ?2H values of leaf-wax n-alkanes and of stem, leaf, stream, and atmospheric waters throughout the entire growing season. Here we found the ?2H values of leaf-wax n-alkanes recorded only a 2-wk period during leaf flush and did not vary for the 19 weeks thereafter when leaves remained active. We found ?2H values of leaf-wax n-alkanes of P. angustifolia record conditions earlier in the season rather than fully integrating the entire growing season. Using these data, we modeled precipitation ?2H values during the time of wax synthesis. We observed that the isotope ratios of this precipitation generally were 2H-enriched compared with mean annual precipitation. This model provides a mechanistic basis of the often-observed 2H-enrichment from the expected fractionation values in studies of broadleaf angiosperm leaf-wax ?2H. In addition, these findings may have implications for the spatial and temporal uses of n-alkane ?2H values in paleoapplications; when both plant community and growth form are known, this study allows the isolation of the precipitation dynamics of individual periods of the growing season.

Tipple, Brett J.; Berke, Melissa A.; Doman, Christine E.; Khachaturyan, Susanna; Ehleringer, James R.

2013-01-01

380

Molecular simulation of diffusion of hydrogen, carbon monoxide, and water in heavy n-alkanes.  

PubMed

The self-diffusion and mutual diffusion coefficients of hydrogen (H(2)), carbon monoxide (CO), and water (H(2)O) in n-alkanes were studied by molecular dynamics simulation. n-Alkane molecules were modeled based on the TraPPE united atom force field. NPT molecular dynamics (MD) simulations were performed for n-C(12) to n-C(96) at different temperature and pressure values to validate the accuracy of the force field. In all cases, good agreement was obtained between literature experimental data and model predictions for the density and structure properties of the n-alkanes. Subsequently, the self-diffusion coefficient of the three light components in the various n-alkanes was calculated at different temperatures. Model predictions were in very good agreement with limited experimental data. Furthermore, the Maxwell-Stefan diffusion coefficients of H(2) and CO in two n-alkanes, namely n-C(12) and n-C(28), were calculated based on long MD NVT simulations for different solute concentrations in the n-alkanes. Finally, the Fick diffusion coefficient of the components was calculated as a product of the Maxwell-Stefan diffusion coefficient and a thermodynamic factor. The latter was estimated from the statistical associating fluid theory (SAFT). The Fick diffusion coefficient was found to be higher than the Maxwell-Stefan diffusion coefficient for H(2) and CO in n-C(28). The empirical Darken equation was used to estimate the Maxwell-Stefan diffusion coefficient, and calculations were found to be in good agreement with simulation results. PMID:21254768

Makrodimitri, Zoi A; Unruh, Dominik J M; Economou, Ioannis G

2011-02-17

381

Leaf-wax n-alkanes record the plant-water environment at leaf flush.  

PubMed

Leaf-wax n-alkanes (2)H/(1)H ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relationship between n-alkanes ?(2)H values and climate is appreciated, the quantitative details of the proxy remain elusive. To examine these details under natural environmental conditions, we studied a riparian broadleaf angiosperm species, Populus angustifolia, growing on water with a constant ?(2)H value and monitored the ?(2)H values of leaf-wax n-alkanes and of stem, leaf, stream, and atmospheric waters throughout the entire growing season. Here we found the ?(2)H values of leaf-wax n-alkanes recorded only a 2-wk period during leaf flush and did not vary for the 19 weeks thereafter when leaves remained active. We found ?(2)H values of leaf-wax n-alkanes of P. angustifolia record conditions earlier in the season rather than fully integrating the entire growing season. Using these data, we modeled precipitation ?(2)H values during the time of wax synthesis. We observed that the isotope ratios of this precipitation generally were (2)H-enriched compared with mean annual precipitation. This model provides a mechanistic basis of the often-observed (2)H-enrichment from the expected fractionation values in studies of broadleaf angiosperm leaf-wax ?(2)H. In addition, these findings may have implications for the spatial and temporal uses of n-alkane ?(2)H values in paleoapplications; when both plant community and growth form are known, this study allows the isolation of the precipitation dynamics of individual periods of the growing season. PMID:23359675

Tipple, Brett J; Berke, Melissa A; Doman, Christine E; Khachaturyan, Susanna; Ehleringer, James R

2013-02-12

382

Determining diet composition on complex swards using n-alkanes and long-chain fatty alcohols.  

PubMed

We conducted an experiment to quantify the accuracy of methods based on n-alkanes and long-chain fatty alcohols for determining the diet composition of animals grazing complex swards. We cut forage from two indigenous vegetation communities, a Molinia caerulea-dominated grassland and a Calluna vulgaris-dominated dwarf-shrub community, and offered it to mature ewes in different ratios in a zero-grazing experiment. Nine dietary categories were identified within the forage offered: Molinia caerulea, Festuca spp., Juncus effusus, Carex spp., Calluna vulgaris, Erica tetralix, Vaccinium myrtillus, and dead grass. Samples of each of these categories together with fecal samples from each individual animal were analyzed for n-alkane and long-chain fatty alcohol concentrations. We analyzed the data using optimization software to minimize the sum of squares differences in the proportional profiles of n-alkanes and fatty alcohols in the diet and feces. Different combinations of n-alkane and fatty alcohols were investigated to assess which gave the most accurate measures of diet composition from the fecal profile. The most accurate estimates were obtained using combinations of the n-alkanes C25, C29, C31, and C33 and the long-chain fatty alcohols 1-C24-ol, 1-C28-ol, and 1-C30-ol, and these gave values for Lin's concordance correlation coefficient between estimated and actual values of >0.98. Our results demonstrate that n-alkanes and long-chain fatty alcohols can be used to estimate several components within the diet of animals grazing complex swards. Diet composition information obtained using this methodology has wide-ranging applications in terms of the assessment of the impact of grazing animals on particular ecosystems or the quantification of nutrient supply to the animal from different selection choices. PMID:17069381

Fraser, M D; Theobald, V J; Moorby, J M

2006-10-01

383

Chemistry Rocks: Redox Chemistry as a Geologic Tool.  

ERIC Educational Resources Information Center

Applies chemistry to earth science, uses rocks in chemistry laboratories, and teaches about transition metal chemistry, oxidation states, and oxidation-reduction reactions from firsthand experiences. (YDS)

Burns, Mary Sue

2001-01-01

384

Nonheuristic Computer Determination of Molecular Structure Based Upon Carbon-13 Nuclear Magnetic Resonance Data. Branched Alkanes  

PubMed Central

A computer-based system for elucidation of molecular structure is described for the branched alkanes, based upon 13C nuclear magnetic resonance data. All possible structures of a given carbon content are exhaustively generated in a DENDRAL-like manner, and scored according to the fit of their predicted spectral characteristics to those of the “unknown” alkane. The technique may be generalized to any class of organic compounds for which 13C chemical-shift additivity parameters are reliable, and shows promise for stereochemical elucidation.

Burlingame, A. L.; Mcpherron, R. V.; Wilson, D. M.

1973-01-01

385

Mass effect on the Soret coefficient in n-alkane mixtures  

NASA Astrophysics Data System (ADS)

We have determined the Soret coefficient of different equimolar and non equimolar n-alkane mixtures from measurements of the molecular diffusion and thermal diffusion coefficients. It is shown that equimolar mixtures behave as isotopic-like mixtures in which only the mass effect contributes to the Soret effect. In non equimolar mixtures, a small linear dependence with the molar fraction is observed. Finally, we have obtained a new correlation, which allows the determination of the Soret coefficient of n-alkane mixtures using the data of viscosity, the thermal expansion coefficient of the pure components, and the density of the equimolar mixture.

Alonso de Mezquia, David; Mounir Bou-Ali, M.; Madariaga, J. Antonio; Santamaría, Carlos

2014-02-01

386

Toxics release inventory: List of toxic chemicals within the polychlorinated alkanes category and guidance for reporting  

SciTech Connect

Section 313 of the Emergency Planning and Community Right-to-Know Act of 1986 (EPCRA) requires certain facilities manufacturing, processing, or otherwise using listed toxic chemicals to report their environmental releases of such chemicals annually. On November 30, 1994 EPA added 286 chemicals and chemical categories. Six chemical categories (nicotine and salts, strychnine and salts, polycyclic aromatic compounds, water dissociable nitrate compounds, diisocyanates, and polychlorinated alkanes) are included in these additions. At the time of the addition, EPA indicated that the Agency would develop, as appropriate, interpretations and guidance that the Agency determines are necessary to facilitate accurate reporting for these categories. This document constitutes such guidance for the polychlorinated alkanes category.

NONE

1995-02-01

387

Mass effect on the Soret coefficient in n-alkane mixtures.  

PubMed

We have determined the Soret coefficient of different equimolar and non equimolar n-alkane mixtures from measurements of the molecular diffusion and thermal diffusion coefficients. It is shown that equimolar mixtures behave as isotopic-like mixtures in which only the mass effect contributes to the Soret effect. In non equimolar mixtures, a small linear dependence with the molar fraction is observed. Finally, we have obtained a new correlation, which allows the determination of the Soret coefficient of n-alkane mixtures using the data of viscosity, the thermal expansion coefficient of the pure components, and the density of the equimolar mixture. PMID:24588181

Alonso de Mezquia, David; Bou-Ali, M Mounir; Madariaga, J Antonio; Santamaría, Carlos

2014-02-28

388

Electronic structure of alkane chains. Complete one-dimensional band structures of the valence states  

NASA Astrophysics Data System (ADS)

Several ultrathin films of oriented alkane chains were studied by ultraviolet photoelectron spectroscopy using UV photons in the energy range of 20-200 eV. From the experimental data the full valence band structure has been determined for self-assembled films of long-chain n-alkanethiols, Langmuir-Blodgett films of Cd-arachidate and thin films of hexatriacontane. Significant deviations from band structures obtained by ab initio calculations of Karpfen are found at the boundary of the one-dimensional Brillouin zone. Furthermore it is demonstrated that a mapping of the one-dimensional band structure can be used for precisely determining tilt angles of alkane chains.

Zubrägel, Ch.; Schneider, F.; Neumann, M.; Hähner, G.; Wöll, Ch.; Grunze, M.

1994-03-01

389

Increase of translatable mRNA for major microsomal proteins in n-alkane-grown Candida maltosa  

SciTech Connect

In an n-alkane-assimilating Candida sp., transfer from glucose- to n-alkane-containing medium induced changes in the microsomal proteins, and several distinctive polypeptides were demonstrated in the solubilized microsomal fraction derived from n-alkane-grown cells. Long-term-labeling and pulse-labeling experiments in vivo demonstrated the synthesis of the specific microsomal polypeptides. The polypeptides were synthesized as in vitro translation products directed by polyadenylated RNA extracted from n-alkane-grown cells. Two major polypeptides were partially purified from the microsomal fraction from n-alkane-grown cells, and antiserum was prepared in a rabbit. Immunoprecipitation of these two polypeptides was accompanied by an increase in the amount of translatable mRNA. The molecular weights of the polypeptides derived from long-term-labeling, pulse-labeling and in vitro translation experiments appeared to be identical.

Sunairi, M.; Watabe, K.; Takagi, M.; Yano, K.

1984-12-01

390

Detailed chemical kinetic models for large n-alkanes and iso-alkanes found in conventional and F-T diesel fuels  

SciTech Connect

n-Hexadecane and 2,2,4,4,6,8,8-heptamethylnonane represent the primary reference fuels for diesel that are used to determine cetane number, a measure of the ignition property of diesel fuel. With the development of chemical kinetics models for both primary reference fuels, a new capability is now available to model diesel fuel ignition. Additionally, we have developed chemical kinetic models for a whole series of large n-alkanes and a large iso-alkane to represent these chemical classes in fuel surrogates for conventional and future fuels. These chemical kinetic models are used to predict the effect of the aforementioned fuel components on ignition characteristics under conditions found in internal combustion engines.

Westbrook, C K; Pitz, W J; Mehl, M; Curran, H J

2009-03-09

391

Ab initio simulations reveal that reaction dynamics strongly affect product selectivity for the cracking of alkanes over H-MFI.  

PubMed

Product selectivity of alkane cracking catalysis in the H-MFI zeolite is investigated using both static and dynamic first-principles quantum mechanics/molecular mechanics simulations. These simulations account for the electrostatic- and shape-selective interactions in the zeolite and provide enthalpic barriers that are closely comparable to experiment. Cracking transition states for n-pentane lead to a metastable intermediate (a local minimum with relatively small barriers to escape to deeper minima) where the proton is shared between two hydrocarbon fragments. The zeolite strongly stabilizes these carbocations compared to the gas phase, and the conversion of this intermediate to more stable species determines the product selectivity. Static reaction pathways on the potential energy surface starting from the metastable intermediate include a variety of possible conversions into more stable products. One-picosecond quasiclassical trajectory simulations performed at 773 K indicate that dynamic paths are substantially more diverse than the potential energy paths. Vibrational motion that is dynamically sampled after the cracking transition state causes spilling of the metastable intermediate into a variety of different products. A nearly 10-fold change in the branching ratio between C2/C3 cracking channels is found upon inclusion of post-transition-state dynamics, relative to static electronic structure calculations. Agreement with experiment is improved by the same factor. Because dynamical effects occur soon after passing through the rate-limiting transition state, it is the dynamics, and not only the potential energy barriers, that determine the catalytic selectivity. This study suggests that selectivity in zeolite catalysis is determined by high temperature pathways that differ significantly from 0 K potential surfaces. PMID:23072346

Zimmerman, Paul M; Tranca, Diana C; Gomes, Joseph; Lambrecht, Daniel S; Head-Gordon, Martin; Bell, Alexis T

2012-11-28

392

Molecular simulation and macroscopic modeling of the diffusion of hydrogen, carbon monoxide and water in heavy n-alkane mixtures.  

PubMed

The self-diffusion coefficient of hydrogen (H(2)), carbon monoxide (CO) and water (H(2)O) in n-alkanes was studied by molecular dynamics simulation. Diffusion in a few pure n-alkanes (namely n-C(8), n-C(20), n-C(64) and n-C(96)) was examined. In addition, binary n-C(12)-n-C(96) mixtures with various compositions as well as more realistic five- and six-n-alkane component mixtures were simulated. In all cases, the TraPPE united atom force field was used for the n-alkane molecules. The force field for the mixture of n-alkanes was initially validated against experimental density values and was shown to be accurate. Moreover, macroscopic correlations for predicting diffusion coefficient of H(2), CO and H(2)O in n-alkanes and mixtures of n-alkanes were developed. The functional form of the correlation was based on the rough hard sphere theory (RHS). The correlation was applied to simulation data and an absolute average deviation (AAD) of 5.8% for pure n-alkanes and 3.4% for n-alkane mixtures was obtained. Correlation parameters vary in a systematic way with carbon number and so they can be used to provide predictions in the absence of any experimental or molecular simulation data. Finally, in order to reduce the number of adjustable parameters, for the n-alkane mixtures the "pseudo-carbon number" approach was used. This approach resulted in relatively higher deviation from MD simulation data (AAD of 18.2%); however, it provides a convenient and fast method to predict diffusion coefficients. The correlations developed here are expected to be useful for engineering calculations related to the design of the Gas-to-Liquid process. PMID:22354458

Makrodimitri, Zoi A; Unruh, Dominik J M; Economou, Ioannis G

2012-03-28

393

Changes in iso- and n-alkane distribution during biodegradation of crude oil under nitrate and sulphate reducing conditions.  

PubMed

Crude oil consists of a large number of hydrocarbons with different susceptibility to microbial degradation. The influence of hydrocarbon structure and molecular weight on hydrocarbon biodegradation under anaerobic conditions is not fully explored. In this study oxygen, nitrate and sulphate served as terminal electron acceptors (TEAs) for the microbial degradation of a paraffin-rich crude oil in a freshly contaminated soil. During 185 days of incubation, alkanes from n-C11 to n-C39, three n- to iso-alkane ratios commonly used as weathering indicators and the unresolved complex mixture (UCM) were quantified and statistically analyzed. The use of different TEAs for hydrocarbon degradation resulted in dissimilar degradative patterns for n- and iso-alkanes. While n-alkane biodegradation followed well-established patterns under aerobic conditions, lower molecular weight alkanes were found to be more recalcitrant than mid- to high-molecular weight alkanes under nitrate-reducing conditions. Biodegradation with sulphate as the TEA was most pronounced for long-chain (n-C32 to n-C39) alkanes. The observation of increasing ratios of n-C17 to pristane and of n-C18 to phytane provides first evidence of the preferential degradation of branched over normal alkanes under sulphate reducing conditions. The formation of distinctly different n- and iso-alkane biodegradation fingerprints under different electron accepting conditions may be used to assess the occurrence of specific degradation processes at a contaminated site. The use of n- to iso-alkane ratios for this purpose may require adjustment if applied for anaerobic sites. PMID:22001845

Hasinger, Marion; Scherr, Kerstin E; Lundaa, Tserennyam; Bräuer, Leopold; Zach, Clemens; Loibner, Andreas Paul

2012-02-20

394

Chemistry at the Organic-Mineral Interface Relevant to Titan  

NASA Astrophysics Data System (ADS)

The observation of rivers and lakes on Titan has generated considerable interest with regard to prebiotic chemistry, since these fluvial features provide a liquid medium for reactions and a transportation mechanism for catalytic mineral deposits left behind by meteorite impacts similar to the one that caused the Sinlap crater. Although numerous laboratory measurements and theoretical models have been used to study atmospheric chemistry applicable to Titan's potential astrobiology, few experiments have been performed to understand gas-/liquid-surface reactions. We are exploring heterogeneous chemistry relevant to Titan using low energy electrons (5-50 eV) as an analog of the incident cosmic rays and secondary electrons they generate. Amorphous alkane/acetylene ices have been deposited on mineral and carbon substrates to simulate lake environments. In some cases, small amounts of amorphous water ice have been deposited at the organic-mineral boundary to model the interface of the hydrocarbon "soil” and the underlying water-ice "bedrock” of Titan. Preliminary results suggest that protonation occurs readily even at the low temperatures observed on Titan's surface ( 100 K). These experiments are some of the first aimed at understanding chemistry at the organic-mineral interface under conditions relevant to Titan, in particular at the edges of hydrocarbon lakes. This work has been performed as part of the NASA Astrobiology Institute "Titan as a Prebiotic System” at the Jet Propulsion Laboratory.

Abbott-Lyon, Heather; Dawley, M.; McLain, J.; Grieves, G.; Orlando, T.

2010-10-01

395

Energy conversion & storage program. 1995 annual report  

SciTech Connect

The 1995 annual report discusses laboratory activities in the Energy Conversion and Storage (EC&S) Program. The report is divided into three categories: electrochemistry, chemical applications, and material applications. Research performed in each category during 1995 is described. Specific research topics relate to the development of high-performance rechargeable batteries and fuel cells, the development of high-efficiency thermochemical processes for energy conversion, the characterization of new chemical processes and complex chemical species, and the study and application of novel materials related to energy conversion and transmission. Research projects focus on transport-process principles, chemical kinetics, thermodynamics, separation processes, organic and physical chemistry, novel materials and deposition technologies, and advanced methods of analysis.

Cairns, E.J.

1996-06-01

396

Research in Energy Conversion.  

National Technical Information Service (NTIS)

The results of investigations dealing with a broad spectrum of topics in energy conversion are presented. The individual studies are: Techniques for fabrication of large, thin silicon single crystals; Cathodes for thermionic energy conversion; Carnot-limi...

W. B. Nowak K. Weiss R. N. Wiener

1967-01-01

397

Diversity of alkane degrading bacteria associated with plants in a petroleum oil-contaminated environment and expression of alkane monooxygenase (alkB) genes  

NASA Astrophysics Data System (ADS)

Among twenty-six different plant species, Italian ryegrass (Lolium multiflorum var. Taurus), Birdsfoot trefoil (Lotus corniculatus var. Leo), and the combination of both plants performed well in a petroleum oil contaminated soil. Hydrocarbon degrading bacteria were isolated from the rhizosphere, root interior and shoot interior and subjected to the analysis of 16S rRNA, the 16S and 23S rRNA intergenic spacer region and alkane hydroxylase genes. Higher numbers of culturable, degrading bacteria were associated with Italian ryegrass, which were also characterized by a higher diversity, particularly in the plant interior. Only half of the isolated bacteria hosted known alkane hydroxylase genes (alkB and cytochrome P153-like). Our results indicated that alkB genes have spread through horizontal gene transfer, particularly in the Italian ryegrass rhizosphere, and suggested mobility of catabolic genes between Gram-negative and Gram-positive bacteria. We furthermore studied the colonization behaviour of selected hydrocarbon-degrading strains (comprising an endopyhte and a rhizosphere strain) as well as the expression of their alkane monooxygenase genes in association with Italian ryegrass. Results showed that the endophyte strain better colonized the plant, particularly the plant interior, and also showed higher expression of alkB genes suggesting a more efficient degradation of the pollutant. Furthermore, plants inoculated with the endophyte were better able to grow in the presence of diesel. The rhizosphere strain colonized primarily the rhizosphere and showed low alkB gene expression in the plant interior.

Andria, V.; Yousaf, S.; Reichenauer, T. G.; Smalla, K.; Sessitsch, A.

2009-04-01

398

Conversations in Child Care  

MedlinePLUS

Conversations in Child Care Health & Safety Notes One of the measures of excellence in child care is the quality of the conversations ... listened to and respected. To encourage conversation in child care: • Ask open-ended questions: Ask questions that require ...

399

Collaborative Physical Chemistry Projects Involving Computational Chemistry  

Microsoft Academic Search

The physical chemistry classes from three colleges have collaborated on two computational chemistry projects using Quantum CAChe 3.0 and Gaussian 94W running on Pentium II PCs. Online communication by email and the World Wide Web was an important part of the collaboration. In the first project, students used molecular modeling to predict benzene derivatives that might be possible hair dyes.

David M. Whisnant; Jerry J. Howe; Lisa S. Lever

2000-01-01

400

Stable hydrogen and carbon isotopic compositions of long-chain (C21-C33) n-alkanes and n-alkenes in insects  

NASA Astrophysics Data System (ADS)

We report the molecular and stable isotopic (?D and ?13C) compositions of long-chain n-alkanes in common insects including the cabbage butterfly, swallowtail, wasp, hornet, grasshopper, and ladybug. Insect n-alkanes are potential candidates of the contamination of soil and sedimentary n-alkanes that are believed to be derived from vascular plant waxes. Long-chain n-alkanes (range C21-33; maximum C23-C29) are found to be abundant in the insects (31-781 ?g/dry g), with a carbon preference index (CPI) of 5.1-31.5 and an average chain length (ACL) of 24.9-29.3. The isotopic compositions (mean ± 1?, n = 33) of the n-alkanes are -195 ± 16‰ for hydrogen and -30.6 ± 2.4‰ for carbon. The insect n-alkanes are depleted in D by approximately 30-40‰ compared with wax n-alkanes from C3 (-155 ± 25‰) and C4 vascular plants (-167 ± 13‰), whereas their ?13C values fall between those of C3 (-36.2 ± 2.4‰) and C4 plants (-20.3 ± 2.4‰). Thus, the contribution of insect-derived n-alkanes to soil and sediment could potentially shift ?D records of n-alkanes toward more negative values and potentially muddle the assumed original C3/C4 balance in the ?13C records of the soil and sedimentary n-alkanes. n-Alkenes are also found in three insects (swallowtail, wasp and hornet). They are more depleted in D relative to the same carbon numbered n-alkanes (?Dn-alkene - ?Dn-alkane = -17 ± 16‰), but the ?13C values are almost identical to those of the n-alkanes (?13Cn-alkene - ?13Cn-alkane = 0.1 ± 0.2‰). These results suggest that these n-alkenes are desaturated products of the same carbon numbered n-alkanes.

Chikaraishi, Yoshito; Kaneko, Masanori; Ohkouchi, Naohiko

2012-10-01

401

Organometallic Chemistry of Molybdenum.  

ERIC Educational Resources Information Center

Suggests ways to avoid some of the problems students have learning the principles of organometallic chemistry. Provides a description of an experiment used in a third-year college chemistry laboratory on molybdenum. (TW)

Lucas, C. Robert; Walsh, Kelly A.

1987-01-01

402

Chemistry for Potters.  

ERIC Educational Resources Information Center

Relates pottery making to chemistry by providing chemical information about clay, its origin, composition, properties, and changes that occur during firing; also describes glaze compositions, examples of redox chemistry, salt glazing, crystalline glazes, and problems in toxicity. (CS)

Denio, Allen A.

1980-01-01

403

Creative Chemistry [last profiled in the Scout Report on January 23, 2004  

NSDL National Science Digital Library

Persons with a penchant for benzene rings, organic chemistry, and other related matters will find the Creative Chemistry a welcome addition to their references. The site collects hundreds of worksheets, teaching notes, and interactive quizzes for educators to use as they see fit. The site is maintained by Nigel Saunders, who has a biochemistry doctorate from the University of York, and includes twenty different thematic areas, including Balancing Equations, Concentration Game, The Slide Puzzle, and Chemistry Calculator. One section that should not be missed is called Molecular Models; as the name suggests, it features molecular models that visitors can play with at their leisure. Some of the models include alkanes, octahedral molecules, and isomers of organic compounds. Finally, visitors can search the site for specific topics via a helpful search engine.

Saunders, N. (Nigel)

2008-12-29

404

The Heats of Combustion and Strain Energies of Bicyclo(N.M.O)Alkanes.  

National Technical Information Service (NTIS)

The heats of combustion, vapor pressures, and liquid heat capacities of a number of bicyclic alkanes have been determined. The derived liquid and gas heats of formation in kilocalories/mole at 25C were found for the following: cis-bicyclo(3.1.0)hexane; ci...

S. Chang D. McNally S. Shary-Tehrany M. J. Hickey R. H. Boyd

1969-01-01

405

Retention index calculation without n-alkanes—the virtual carbon number  

Microsoft Academic Search

For the fast gas chromatographic identification of separated components the retention index is still one of the most often used tools, although mass spectrometry is available in almost all analytical laboratories. For the calculation of the retention indices it is not necessary to use n-alkanes or any other homologous series. If the analyte contains some compounds, not necessarily belonging to

János Harangi

2003-01-01

406

On droplet combustion of biodiesel fuel mixed with diesel\\/alkanes in microgravity condition  

Microsoft Academic Search

The burning characteristics of a biodiesel droplet mixed with diesel or alkanes such as dodecane and hexadecane were experimentally studied in a reduced-gravity environment so as to create a spherically symmetrical flame without the influence of natural convection due to buoyancy. Small droplets on the order of 500?m in diameter were initially injected via a piezoelectric technique onto the cross

Kuo-Long Pan; Je-Wei Li; Chien-Pei Chen; Ching-Hua Wang

2009-01-01

407

On droplet combustion of biodiesel fuel mixed with diesel\\/alkanes in microgravity condition  

Microsoft Academic Search

The burning characteristics of a biodiesel droplet mixed with diesel or alkanes such as dodecane and hexadecane were experimentally studied in a reduced-gravity environment so as to create a spherically symmetrical flame without the influence of natural convection due to buoyancy. Small droplets on the order of 500 μm in diameter were initially injected via a piezoelectric technique onto the

Kuo-Long Pan; Je-Wei Li; Chien-Pei Chen; Ching-Hua Wang

2009-01-01

408

Equilibrium behavior of n-alkanes from the convex molecule perturbation theory  

Microsoft Academic Search

Perturbation theory of convex molecule fluids is applied to determine the orthobaric data along the coexistence curve of n-alkanes from ethane to hexadecane. Equilibrium pressures and densities in the liquid and vapor phases are evaluated at the reduced temperatures T{sup *} < 0.9 from the perturbation scheme for the Kihara molecules of the rodlike shape. Fair agreement of the calculated

Jan Pavlicek; Tomas Boublik

1992-01-01

409

Stable Isotopic Studies of n-Alkane Metabolism by a Sulfate-Reducing Bacterial Enrichment Culture  

PubMed Central

Gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy were used to study the metabolism of deuterated n-alkanes (C6 to C12) and 1-13C-labeled n-hexane by a highly enriched sulfate-reducing bacterial culture. All substrates were activated via fumarate addition to form the corresponding alkylsuccinic acid derivatives as transient metabolites. Formation of d14-hexylsuccinic acid in cell extracts from exogenously added, fully deuterated n-hexane confirmed that this reaction was the initial step in anaerobic alkane metabolism. Analysis of resting cell suspensions amended with 1-13C-labeled n-hexane confirmed that addition of the fumarate occurred at the C-2 carbon of the parent substrate. Subsequent metabolism of hexylsuccinic acid resulted in the formation of 4-methyloctanoic acid, and 3-hydroxy-4-methyloctanoic acid was tentatively identified. We also found that 13C nuclei from 1-13C-labeled n-hexane became incorporated into the succinyl portion of the initial metabolite in a manner that indicated that 13C-labeled fumarate was formed and recycled during alkane metabolism. Collectively, the findings obtained with a sulfate-reducing culture using isotopically labeled alkanes augment and support the previously proposed pathway (H. Wilkes, R. Rabus, T. Fischer, A. Armstroff, A. Behrends, and F. Widdel, Arch. Microbiol. 177:235-243, 2002) for metabolism of deuterated n-hexane by a denitrifying bacterium.

Davidova, Irene A.; Gieg, Lisa M.; Nanny, Mark; Kropp, Kevin G.; Suflita, Joseph M.

2005-01-01

410

Single Molecule and Shpolskii Spectroscopy of Terrylene in a Series of N-Alkanes  

Microsoft Academic Search

We present a study of terrylene in a series of n-alkane matrices with increasing chain length, namely dodecane, tetradecane and hexadecane. Shpolskii absorption spectra provide the macroscopic characterization of the samples, such as site multiplicity, inhomogeneous line widths and positions. Based on this characterization the distributions of single molecule homogeneous line widths were measured in the maxima and in the

Martin Vacha; Yi Liu; Hiroki Nakatsuka; Toshiro Tani

1996-01-01

411

Effects of Defects on the Longitudinal Acoustic Mode of n-Alkane Chains.  

National Technical Information Service (NTIS)

Normal mode calculations show that a single conformational defect in an othewise all-trans n-alkane molecule disrupts the longitudinal acoustic mode (LAM) associated with the all-trans molecule. Similar calculations for a chain in the conformation produce...

D. H. Reneker B. Fanconi

1975-01-01

412

Gibbs ensemble simulations of vapour-liquid phase equilibria of cyclic alkanes  

Microsoft Academic Search

A new set of united atom Lennard-Jones interaction parameters for cyclic alkanes relevant to petrochemical research is proposed from fitting of simulation results to liquid coexistence densities and standard liquid densities. This parameter set leads to a critical temperature for cyclohexane which is only 4% below the experimental value. The critical temperatures for cyclopentane and cyclooctane are underestimated by roughly

B. Neubauer; A. Boutin; B. Tavitian; A. H. Fuchs

1999-01-01

413

Combined use of partially fluorinated alkanes, perfluorocarbon liquids and silicone oil: an experimental study  

Microsoft Academic Search

Background: Partially fluorinated alkanes (FALKs) are a new class of substances which can be used in vitreoretinal surgery as an intraoperative tool and as a long-term tamponade. The aim of this in vitro study was (1) to investigate the solubility of FALKs in silicone oil during direct exchange, (2) to study their combined use and solubility in PFCLs, (3) to

Hans Hoerauf; Karin Kobuch; Joachim Dresp; Dirk-Henning Menz

2001-01-01

414

Development of microbodies in Candida tropicalis during incubation in a n -alkane medium  

Microsoft Academic Search

Development of microbodies in Candida tropicalis pK 233 was studied mainly by electron microscopical observation. The yeast cells, precultured on malt extract, scarcely contained microbodies and showed very low catalase activity. When the precultured cells were transferred to a n-alkane medium and incubated with shaking, the number of microbodies increased and concomitantly the activity of catalase was enhanced. That is,

Masako Osumi; Fusako Fukuzumi; Yutaka Teranishi; Atsuo Tanaka; Saburo Fukui

1975-01-01

415

Alkyl nitrate formation from the atmospheric photoxidation of alkanes; a revised estimation method  

Microsoft Academic Search

The available experimental data concerning the yields of alkyl nitrates in the reactions of alkyl peroxy radicals with NO have been used to derive a revised expression for the estimation of alkyl nitrate yields in the atmospheric photooxidation of alkanes as a function of temperature and pressure. This revised expression gives more reasonable predictions of alkyl nitrate yields under high

William P. L. Carter; Roger Atkinson

1989-01-01

416

A Microporous MetalOrganic Framework for Gas Chromatographic Separation of Alkanes  

Microsoft Academic Search

A zinc-based metal-organic framework (MOF) can be transformed reversibly from an open (a) to a dense (b) configuration. The microporous solid is the first example of a MOF that is highly selective in the gas-chromatographic separation of alkanes.

Banglin Chen; Chengdu Liang; Jun Yang; Damacio S. Contreras; Yvette L. Clancy; Emil B. Lobkovsky; Omar M. Yaghi; Sheng Dai

2006-01-01

417

The role of alkane coordination in CH bond cleavage at a Pt(II) center  

PubMed Central

The rates of CH bond activation for various alkanes by [(N–N)Pt(Me)(TFEd3)]+ (N N = ArNC(Me)C(Me)NAr; Ar = 3,5-di-tert-butylphenyl; TFE-d3 = CF3CD2OD) were studied. Both linear and cyclic alkanes give the corresponding alkene-hydride cation [(N–N)Pt(H)(alkene)]+ via (i) rate determining alkane coordination to form a CH ? complex, (ii) oxidative cleavage of the coordinated CH bond to give a platinum(IV) alkyl-methyl-hydride intermediate, (iii) reductive coupling to generate a methane ? complex, (iv) dissociation of methane, and (v) ?-H elimination to form the observed product. Second-order rate constants for cycloalkane activation (CnH2n), are proportional to the size of the ring (k ? n). For cyclohexane, the deuterium kinetic isotope effect (kH/kD) of 1.28 (5) is consistent with the proposed rate determining alkane coordination to form a CH ? complex. Statistical scrambling of the five hydrogens of the Pt-methyl and the coordinated methylene unit, via rapid, reversible steps ii and iii, and interchange of geminal CH bonds of the methane and cyclohexane CH ? adducts, is observed before loss of methane.

Chen, George S.; Labinger, Jay A.; Bercaw, John E.

2007-01-01

418

Highly Correlating Distance\\/Connectivity-Based Topological Indices. 1: QSPR Studies of Alkanes  

Microsoft Academic Search

Some new topological indices based on the distance matrix and Randic connectivity (as graph invariants) are proposed. The calculation of these indices is simple and they have good discriminating ability toward alkanes. Incorporating the number of carbon atoms to one of the calculated indices gives a highly correlating topological index (Sh index) which found to correlate with select ed physicochemical

Mojtaba Shamsipur; Bahram Hemmateenejad; Morteza Akhond

419

Interaction of Ammonia Monooxygenase from Nitrosomonas europaea with Alkanes, Alkenes, and Alkynes  

PubMed Central

Ammonia monooxygenase of Nitrosomonas europaea catalyzes the oxidation of alkanes (up to C8) to alcohols and alkenes (up to C5) to epoxides and alcohols in the presence of ammonium ions. Straight-chain, N-terminal alkynes (up to C10) all exhibited a time-dependent inhibition of ammonia oxidation without effects on hydrazine oxidation.

Hyman, Michael R.; Murton, Ian B.; Arp, Daniel J.

1988-01-01

420

Biosurfactant-mediated biodegradation of straight and methyl-branched alkanes by Pseudomonas aeruginosa ATCC 55925  

PubMed Central

Accidental oil spills and waste disposal are important sources for environmental pollution. We investigated the biodegradation of alkanes by Pseudomonas aeruginosa ATCC 55925 in relation to a rhamnolipid surfactant produced by the same bacterial strain. Results showed that the linear C11-C21 compounds in a heating oil sample degraded from 6% to 100%, whereas the iso-alkanes tended to be recalcitrant unless they were exposed to the biosurfactant; under such condition total biodegradation was achieved. Only the biodegradation of the commercial C12-C19 alkanes could be demonstrated, ranging from 23% to 100%, depending on the experimental conditions. Pristane (a C19 branched alkane) only biodegraded when present alone with the biosurfactant and when included in an artificial mixture even without the biosurfactant. In all cases the biosurfactant significantly enhanced biodegradation. The electron scanning microscopy showed that cells depicted several adaptations to growth on hydrocarbons, such as biopolymeric spheres with embedded cells distributed over different layers on the spherical surfaces and cells linked to each other by extracellular appendages. Electron transmission microscopy revealed transparent inclusions, which were associated with hydrocarbon based-culture cells. These patterns of hydrocarbon biodegradation and cell adaptations depended on the substrate bioavailability, type and length of hydrocarbon.

2011-01-01

421

Biosurfactant-mediated biodegradation of straight and methyl-branched alkanes by Pseudomonas aeruginosa ATCC 55925.  

PubMed

Accidental oil spills and waste disposal are important sources for environmental pollution. We investigated the biodegradation of alkanes by Pseudomonas aeruginosa ATCC 55925 in relation to a rhamnolipid surfactant produced by the same bacterial strain. Results showed that the linear C11-C21 compounds in a heating oil sample degraded from 6% to 100%, whereas the iso-alkanes tended to be recalcitrant unless they were exposed to the biosurfactant; under such condition total biodegradation was achieved. Only the biodegradation of the commercial C12-C19 alkanes could be demonstrated, ranging from 23% to 100%, depending on the experimental conditions. Pristane (a C19 branched alkane) only biodegraded when present alone with the biosurfactant and when included in an artificial mixture even without the biosurfactant. In all cases the biosurfactant significantly enhanced biodegradation. The electron scanning microscopy showed that cells depicted several adaptations to growth on hydrocarbons, such as biopolymeric spheres with embedded cells distributed over different layers on the spherical surfaces and cells linked to each other by extracellular appendages. Electron transmission microscopy revealed transparent inclusions, which were associated with hydrocarbon based-culture cells. These patterns of hydrocarbon biodegradation and cell adaptations depended on the substrate bioavailability, type and length of hydrocarbon. PMID:21906343

Rocha, Carlos A; Pedregosa, Ana M; Laborda, Fernando

2011-01-01

422

School Chemistry vs. Chemistry in Research: An Exploratory Experiment.  

ERIC Educational Resources Information Center

Reports on a study exploring why students are not studying chemistry. Three groups of graduating high school students and their chemistry teachers stayed at a research institute working on molecular modeling and wrote essays on school chemistry versus chemistry in research. Concludes that school chemistry does not convey today's chemistry in…

Habraken, Clarisse L.; Buijs, Wim; Borkent, Hens; Ligeon, Willy; Wender, Harry; Meijer, Marijn

2001-01-01

423

History of Chemistry.  

ERIC Educational Resources Information Center

Discusses the development of chemistry in the United States by considering: (1) chemistry as an evolving body of ideas/techniques, and as a set of conceptual resources affecting and affected by the development of other sciences; and (2) chemistry related to the history of American social and economic institutions and practices. (JN)

Servos, John W.

1985-01-01

424

Mechanisms in Photographic Chemistry  

ERIC Educational Resources Information Center

Reviews current research interests in photographic chemistry, involving two proposed models for spectral sensitization of crystal defects and impurities in the photolysis reactivity and the mechanisms of development and complexation. Establishment of photographic chemistry in a chemistry curriculum is recommended. (CC)

Sahyun, M. R. V.

1974-01-01

425

Teaching School Chemistry.  

ERIC Educational Resources Information Center

This eight-chapter book is intended for use by chemistry teachers, curriculum developers, teacher educators, and other key personnel working in the field of chemical education. The chapters are: (1) "The Changing Face of Chemistry" (J. A. Campbell); (2) "Curriculum Innovation in School Chemistry" (R. B. Ingel and A. M. Ranaweera); (3) "Some…

Waddington, D. J., Ed.

426

Chemistry as General Education  

ERIC Educational Resources Information Center

The efficacy of different science and chemistry courses for science-major and non-major students, and the question of chemistry's contribution to general education are evaluated. Chemistry and science curriculum are too profession- and consumer-oriented, and to overcome this problem, it is advised that all disciplines must incorporate the major…

Tro, Nivaldo J.

2004-01-01

427

Chemistry on Stamps.  

ERIC Educational Resources Information Center

Suggests how postage stamps can be incorporated into chemistry teaching. Categories considered include emergence of chemistry as a science, metric system, atoms (and molecules and ions), stoichiometry, energy relationships in chemical systems, chemical bonding, nuclear chemistry, biochemistry, geochemistry, matter (gases, liquids, and solids),…

Schreck, James O.

1986-01-01

428

Green Chemistry and Education.  

ERIC Educational Resources Information Center

Many students today are profoundly interested in the sustainability of their world. Introduces Green Chemistry and its principles with teaching materials. Green Chemistry is the use of chemistry for pollution prevention and the design of chemical products and processes that are environmentally benign. (ASK)

Hjeresen, Dennis L.; Schutt, David L.; Boese, Janet M.

2000-01-01

429

Fuel Chemistry Preprints  

SciTech Connect

Papers are presented under the following symposia titles: advances in fuel cell research; biorefineries - renewable fuels and chemicals; chemistry of fuels and emerging fuel technologies; fuel processing for hydrogen production; membranes for energy and fuel applications; new progress in C1 chemistry; research challenges for the hydrogen economy, hydrogen storage; SciMix fuel chemistry; and ultraclean transportation fuels.

NONE

2005-09-30

430

Light-emitting diodes for analytical chemistry.  

PubMed

Light-emitting diodes (LEDs) are playing increasingly important roles in analytical chemistry, from the final analysis stage to photoreactors for analyte conversion to actual fabrication of and incorporation in microdevices for analytical use. The extremely fast turn-on/off rates of LEDs have made possible simple approaches to fluorescence lifetime measurement. Although they are increasingly being used as detectors, their wavelength selectivity as detectors has rarely been exploited. From their first proposed use for absorbance measurement in 1970, LEDs have been used in analytical chemistry in too many ways to make a comprehensive review possible. Hence, we critically review here the more recent literature on their use in optical detection and measurement systems. Cloudy as our crystal ball may be, we express our views on the future applications of LEDs in analytical chemistry: The horizon will certainly become wider as LEDs in the deep UV with sufficient intensity become available. PMID:24818811

Macka, Mirek; Piasecki, Tomasz; Dasgupta, Purnendu K

2014-06-12

431

Pretreatment of lignocellulosic biomass using Fenton chemistry.  

PubMed

In an attempt to mimic white-rot fungi lignin degradation via in vivo Fenton chemistry, solution phase Fenton chemistry (10g biomass, 176mmol hydrogen peroxide and 1.25mmol Fe(2+) in 200mL of water) was applied to four different biomass feedstocks. An enzymatic saccharification of Fenton pretreated biomass showed an average 212% increase relative to untreated control across all four feedstocks (P<0.05, statistically significant). A microbial fermentation of the same Fenton pretreated biomass showed a threefold increase in gas production upon a sequential co-culture with Clostridium thermocellum and Clostridium beijerinckii. These results demonstrate the use of solution phase Fenton chemistry as a viable pretreatment method to make cellulose more bioavailable for microbial biofuel conversion. PMID:24759643

Kato, Dawn M; Elía, Noelia; Flythe, Michael; Lynn, Bert C

2014-06-01

432

Integrated two-liquid phase bioconversion and product-recovery processes for the oxidation of alkanes: process design and economic evaluation  

PubMed

Pseudomonas oleovorans and recombinant strains containing the alkane oxidation genes can produce alkane oxidation products in two-liquid phase bioreactor systems. In these bioprocesses the cells, which grow in the aqueous phase, oxidize apolar, non-water soluble substrates. The apolar products typically accumulate in the emulsified apolar phase. We have studied both the bioconversion systems and several downstream processing systems to separate and purify alkanols from these two-liquid phase media. Based on the information generated in these studies, we have now designed bioconversion and downstream processing systems for the production of 1-alkanols from n-alkanes on a 10 kiloton/yr scale, taking the conversion of n-octane to 1-octanol as a model system. Here, we describe overall designs of fed-batch and continuous-fermentation processes for the oxidation of octane to 1-octanol by Pseudomonas oleovorans, and we discuss the economics of these processes. In both systems the two-liquid phase system consists of an apolar phase with hexadecene as the apolar carrier solvent into which n-octane is dissolved, while the cells are present in the aqueous phase. In one system, multiple-batch fermentations are followed by continuous processing of the product from the separated apolar phase. The second system is based on alkane oxidation by continuously growing cultures, again followed by continuous processing of the product. Fewer fermentors were required and a higher space-time-yield was possible for production of 1-octanol in a continuous process. The overall performance of each of these two systems has been modeled with Aspen software. Investment and operating costs were estimated with input from equipment manufacturers and bulk-material suppliers. Based on this study, the production cost of 1-octanol is about 7 US$kg-1 when produced in the fed-batch process, and 8 US$kg-1 when produced continuously. The comparison of upstream and downstream capital costs and production costs showed significantly higher upstream costs for the fed-batch process and slightly higher upstream costs for continuous fermentation. The largest cost contribution was due to variable production costs, mainly resulting from media costs. The organisms used in these systems are P. putida alk+ recombinants which oxidize alkanes, but cannot oxidize the resulting alkanols further. Hence, such cells need a second carbon source, which in these systems is glucose. Although the continuous process is about 10% more expensive than the fed-batch process, improvements to reduce overall cost can be achieved more easily for continuous than for fed-batch fermentation by decreasing the dilution rate while maintaining near constant productivity. Improvements relevant to both processes can be achieved by increasing the biocatalyst performance, which results in improved overall efficiency, decreased capital investment, and hence, decreased production cost. Copyright 1999 John Wiley & Sons, Inc. PMID:10397885

Mathys; Schmid; Witholt

1999-08-20

433

Chemistry of the Conversion of Nitrate Nitrogen to Smoke Products  

Microsoft Academic Search

NITRATE nitrogen has been of interest to us because of its natural occurrence in burley tobaccos and of its use as a tobacco additive. Sodium nitrate added to tobacco is known to reduce particulate matter, nicotine, phenol, and benzo(a)-pyrene in cigarette smoke1. It is thought that nitrates form oxygen and nitric oxide during smoking and thereby intercept radicals that would

W. R. Johnson; R. W. Hale; S. C. Clough; P. H. Chen

1973-01-01

434

Cement-based stabilization/solidification of oil refinery sludge: Leaching behavior of alkanes and PAHs.  

PubMed

Stabilization/solidification is a process widely applied for the immobilization of inorganic constituents of hazardous wastes, especially for metals. Cement is usually one of the most common binders for that purpose. However, limited results have been presented on immobilization of hydrocarbons in cement-based stabilized/solidified petroleum solid waste. In this study, real oil refinery sludge samples were stabilized and solidified with various additions of I42.5 and II42.5 cement (Portland and blended cement, respectively) and subject to leaching. The target analytes were total petroleum hydrocarbons, alkanes and 16 polycyclic aromatic hydrocarbons of the EPA priority pollutant list. The experiments showed that the waste was confined in the cement matrix by macroencapsulation. The rapture of the cement structure led to the increase of leachability for most of the hydrocarbons. Leaching of n-alkanes from II42.5 cement-solidified samples was lower than that from I42.5 solidified samples. Leaching of alkanes in the range of n-C(10) to n-C(27) was lower than that of long chain alkanes (>n-C(27)), regardless the amount of cement addition. Generally, increasing the cement content in the solidified waste samples, increased individual alkane leachability. This indicated that cement addition resulted in destabilization of the waste. Addition of I42.5 cement favored immobilization of anthracene, benzo[a]anthracene, benzo[b]fluoroanthene, benzo[k]fluoroanthene, benzo[a]pyrene and dibenzo[a,h]anthracene. However, addition of II42.5 favored 5 out of 16, i.e., naphthalene, anthracene, benzo[b]fluoroanthene, benzo[k]fluoroanthene and dibenzo[a,h]anthracene. PMID:17466451

Karamalidis, Athanasios K; Voudrias, Evangelos A

2007-09-01

435

Patterns of phase behavior in ternary ethoxylated alcohol-n-alkane-water mixtures  

SciTech Connect

Certain ternary mixtures of ethoxylated alcohols, n-alkanes, and water at 25/sup 0/C separate at equilibrium into three liquid phases. The development of an amphiphile-rich middle phase is sensitive to alcohol molecular weight, alkane carbon number (ACN), and temperature. A middle phase arises when all three variables are adjusted such that the alcohol has no preference to partition into either an oleic or aqueous phase. A change in one of these variables yields a sequence of ternary phase diagrams in which the range of the three phases is from one critical tie line to a second. There are two distinct patterns, however, in which the critical tie lines arise. With a low molecular weight ethoxylated alcohol, both critical tie lines lie in the miscibility gap between water-rich and alkane-rich phases. With larger ethoxylated alcohols, however, one of the critical tie lines arises from the fusion of that miscibility gap with the critical point on a second one between water-rich and alcohol-rich phases. Both patterns are modeled well by modifying the Flory-Huggins equation of state to account for the tendency of amphiphile to concentrate between water-rich and alkane-rich domains, thereby attenuating or screening the enthalpic repulsion between water and alkane. The screening is expressed by a factor which is exponential in amphiphile concentration. The type of three-phase equilibria which arises from fusion of two miscibility gaps requires a pair of screening factors. Other available thermodynamic models appear incapable of approximating this second pattern of three-phase equilibria.

Kilpatrick, P.K.; Gorman, C.A.; Davis, H.T.; Scriven, L.E.; Miller, W.G.

1986-10-09

436

Detailed chemical kinetic models for large n-alkanes and iso-alkanes found in conventional and F-T diesel fuels. 6th U.S. National Combustion Meeting Ann Arbor, MI, United States, June 17, 2009 through June 20, 2009.  

National Technical Information Service (NTIS)

Detailed chemical kinetic models are needed to simulate the combustion of current and future transportation fuels. These models should represent the various chemical classes in these fuels. Conventional diesel fuels are composed of n-alkanes, iso-alkanes,...

C. K. Westbrook H. J. Curran M. Mehl W. J. Pitz

2008-01-01

437

Adaptation of the hydrocarbonoclastic bacterium Alcanivorax borkumensis SK2 to alkanes and toxic organic compounds: a physiological and transcriptomic approach.  

PubMed

The marine hydrocarbonoclastic bacterium Alcanivorax borkumensis is able to degrade mixtures of n-alkanes as they occur in marine oil spills. However, investigations of growth behavior and physiology of these bacteria when cultivated with n-alkanes of different chain lengths (C6 to C30) as the substrates are still lacking. Growth rates increased with increasing alkane chain length up to a maximum between C12 and C19, with no evident difference between even- and odd-numbered chain lengths, before decreasing with chain lengths greater than C19. Surface hydrophobicity of alkane-grown cells, assessed by determination of the water contact angles, showed a similar pattern, with maximum values associated with growth rates on alkanes with chain lengths between C11 and C19 and significantly lower values for cells grown on pyruvate. A. borkumensis was found to incorporate and modify the fatty acid intermediates generated by the corresponding n-alkane degradation pathway. Cells grown on distinct n-alkanes proved that A. borkumensis is able to not only incorporate but also modify fatty acid intermediates derived from the alkane degradation pathway. Comparing cells grown on pyruvate with those cultivated on hexadecane in terms of their tolerance toward two groups of toxic organic compounds, chlorophenols and alkanols, representing intensely studied organic compounds, revealed similar tolerances toward chlorophenols, whereas the toxicities of different n-alkanols were significantly reduced when hexadecane was used as a carbon source. As one adaptive mechanism of A. borkumensis to these toxic organic solvents, the activity of cis-trans isomerization of unsaturated fatty acids was proven. These findings could be verified by a detailed transcriptomic comparison between cultures grown on hexadecane and pyruvate and including solvent stress caused by the addition of 1-octanol as the most toxic intermediate of n-alkane degradation. PMID:23645199

Naether, Daniela J; Slawtschew, Slavtscho; Stasik, Sebastian; Engel, Maria; Olzog, Martin; Wick, Lukas Y; Timmis, Kenneth N; Heipieper, Hermann J

2013-07-01

438

Adaptation of the Hydrocarbonoclastic Bacterium Alcanivorax borkumensis SK2 to Alkanes and Toxic Organic Compounds: a Physiological and Transcriptomic Approach  

PubMed Central

The marine hydrocarbonoclastic bacterium Alcanivorax borkumensis is able to degrade mixtures of n-alkanes as they occur in marine oil spills. However, investigations of growth behavior and physiology of these bacteria when cultivated with n-alkanes of different chain lengths (C6 to C30) as the substrates are still lacking. Growth rates increased with increasing alkane chain length up to a maximum between C12 and C19, with no evident difference between even- and odd-numbered chain lengths, before decreasing with chain lengths greater than C19. Surface hydrophobicity of alkane-grown cells, assessed by determination of the water contact angles, showed a similar pattern, with maximum values associated with growth rates on alkanes with chain lengths between C11 and C19 and significantly lower values for cells grown on pyruvate. A. borkumensis was found to incorporate and modify the fatty acid intermediates generated by the corresponding n-alkane degradation pathway. Cells grown on distinct n-alkanes proved that A. borkumensis is able to not only incorporate but also modify fatty acid intermediates derived from the alkane degradation pathway. Comparing cells grown on pyruvate with those cultivated on hexadecane in terms of their tolerance toward two groups of toxic organic compounds, chlorophenols and alkanols, representing intensely studied organic compounds, revealed similar tolerances toward chlorophenols, whereas the toxicities of different n-alkanols were significantly reduced when hexadecane was used as a carbon source. As one adaptive mechanism of A. borkumensis to these toxic organic solvents, the activity of cis-trans isomerization of unsaturated fatty acids was proven. These findings could be verified by a detailed transcriptomic comparison between cultures grown on hexadecane and pyruvate and including solvent stress caused by the addition of 1-octanol as the most toxic intermediate of n-alkane degradation.

Naether, Daniela J.; Slawtschew, Slavtscho; Stasik, Sebastian; Engel, Maria; Olzog, Martin; Wick, Lukas Y.; Timmis, Kenneth N.

2013-01-01

439

Principles of Environmental Chemistry  

NASA Astrophysics Data System (ADS)

Roy M. Harrison, Editor RSC Publishing; ISBN 0854043713; x + 363 pp.; 2006; $69.95 Environmental chemistry is an interdisciplinary science that includes chemistry of the air, water, and soil. Although it may be confused with green chemistry, which deals with potential pollution reduction, environmental chemistry is the scientific study of the chemical and biochemical principles that occur in nature. Therefore, it is the study of the sources, reactions, transport, effects, and fates of chemical species in the air, water, and soil environments, and the effect of human activity on them. Environmental chemistry not only explores each of these environments, but also closely examines the interfaces and boundaries where the environments intersect.

Hathaway, Ruth A.

2007-07-01

440

Conversion of methane to higher hydrocarbons in ac nonequilibrium plasmas  

Microsoft Academic Search

The effects of plasma chemistry on the conversion of methane were studied using a dielectric barrier discharge reactor at ambient temperatures. A dielectric barrier discharge reactor generates a nonequilibrium plasma when a sufficiently high voltage is applied across the reactor`s electrodes. Methane molecules are activated at this temperature and coupled to form Câ hydrocarbons, higher hydrocarbons, and hydrogen. The study

K. Thanyachotpaiboon; S. Chavadej; T. A. Caldwell; L. L. Lobban; R. G. Mallinson

1998-01-01

441

Metric Conversion Factors  

NSDL National Science Digital Library

Brought to the Web by Washington State Department of Transportation, the Metric Conversion Factors site contains a wealth of helpful physical science and engineering information. As you might guess, all sorts of conversion factors are presented, such as for area, force, hard conversions for construction materials, length, mass, pavement, pipe, plate, power, pressure or stress, reinforcing steel, sheet metal, sieve, symbols, temperature, volume, and several others. Although it's not an online conversion calculator, all of the pages are set up for efficient printing so that students can have the information with them while doing homework.

442

Synthesis and chemistry of low-valent iron complexes incorporating chelating perfluoroalkyl phosphine ligands: Synthetic approaches to alkane complexes  

Microsoft Academic Search

Chapter I presents a short review of C-H bond activation along with the advantages for using perfluoroalkylphosphine ligands in highly electrophilic, unsaturated complexes. Chapter II details efforts in the synthesis, structure and reactivity of bis(bis(pentafluoroethyl)phosphino)ethane (dfepe) derivatives of iron(0) complexes. Reaction of (C[sub 2]F[sub 5][sub 2])[sub 2]PCH[sub 2]CH[sub 2]P(C[sub 2]F[sub 5])[sub 2] with (benzylideneacetone)Fe(CO)[sub 3] gives [(C[sub 2]F[sub 5])[sub 2]PCH[sub

1992-01-01

443

Mixtures of numerous different n-alkanes: 1. Structural studies by X-ray diffraction at room temperature—Correlation between the crystallographic long c parameter and the average composition of multi-alkane phases  

Microsoft Academic Search

Two quaternary equimolar alloys (C22\\/C26\\/C30\\/C34 and C24\\/C28\\/C32\\/C36) and three commercial products, which respectively consist of 23 and 33 consecutive n-alkanes with chain lengths between 20 and 52 carbon atoms, are studied by X-ray diffraction analyses. A single orthorhombic solid solution, identical to one of the two intermediate phases seen in binary n-alkane systems, is observed in two commercial products and

V. Chevallier; E. Provost; J. B. Bourdet; M. Bouroukba; D. Petitjean; M. Dirand

1999-01-01

444

Conversion of methane to higher hydrocarbons in ac nonequilibrium plasmas  

SciTech Connect

The effects of plasma chemistry on the conversion of methane were studied using a dielectric barrier discharge reactor at ambient temperatures. A dielectric barrier discharge reactor generates a nonequilibrium plasma when a sufficiently high voltage is applied across the reactor`s electrodes. Methane molecules are activated at this temperature and coupled to form C{sub 2} hydrocarbons, higher hydrocarbons, and hydrogen. The study on the effect of voltage, residence time and third bodies on methane conversion and product selectivity shows that methane conversion initially increases with increasing voltage and residence time above the breakdown voltage, and product selectivities are essentially independent of the voltage. Production of hydrogen during the reaction limits olefin production. Methane conversion also increases when helium and ethane are in the feed stream. Helium and ethane both appear to be more easily activated than methane and enhance methane activation and conversion.

Thanyachotpaiboon, K.; Chavadej [Chulalongkorn Univ., Bangkok (Thailand). Petroleum and Petrochemical Coll.] [Chulalongkorn Univ., Bangkok (Thailand). Petroleum and Petrochemical Coll.; Caldwell, T.A.; Lobban, L.L.; Mallinson, R.G. [Univ. of Oklahoma, Norman, OK (United States)] [Univ. of Oklahoma, Norman, OK (United States)

1998-10-01