Note: This page contains sample records for the topic alkane conversion chemistry from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Environmental chemistry and toxicology of polychlorinated n-alkanes.  

PubMed

Polychlorinated-n-alkanes (PCAs) or chlorinated paraffins consist of C10 to C30 n-alkanes with chlorine content from 30% to 70% by mass. PCAs are used as high-temperature lubricants, plasticizers, flame retardants, and additives in adhesives, paints, rubber, and sealants. This review presents the existing data on the environmental chemistry and toxicology of PCAs and a preliminary exposure and risk assessment. There is limited information on the levels, fate, or biological effects of PCAs in the environment. This results both from the difficulty associated with quantifying PCAs, because of the complexity inherent to commercial formulations, and from the limited knowledge of their physicochemical properties and biodegradation rates. There are indications that PCAs are widespread environmental contaminants at ng/L levels in surface waters and ng/g (wet wt) levels in biota. However, environmental measurements of PCAs are very limited in the U.S. and Canada, and are only slightly more detailed in western Europe. Assuming that reported water concentrations are mainly caused by the short chain (C10-C13) compounds, aquatic organisms may be at risk from exposure to PCAs. Fugacity level II modeling for two representative PCAs, using the best available physicochemical property data and estimated degradation rates, suggested that C16C24Cl10 would achieve higher concentrations in biota, sediment, and soil than C12H20Cl6 because of slower degradation rates and lower water solubility. Environmental residence time of C16H24Cl10 is estimated to be 520 d compared to 210 d for C12H20Cl6. Future studies will require better analytical methods and reference materials certified for PCA content. Additional data are needed to evaluate exposure of biota to PCAs in the environment, particularly in light of their continued production and usage around the globe. PMID:9751033

Tomy, G T; Fisk, A T; Westmore, J B; Muir, D C

1998-01-01

2

Catalytic conversion of light alkanes: Proof of concept stage  

SciTech Connect

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 materials in order to enhance the catalytic properties of the suprabiotic systems generated in our laboratories. Increases in catalytic activity and process selectivity as well as extensions of structure-activity relationships are examined. The research phase is intended to provide the process development phases with catalysts having superior properties for light alkane oxidation. The second concurrent phase, is the proof-of-concept phase. In this phase process development of oxidations which have succeeded in the research phase are carried out in a pre-pilot PDU. At the conclusion of the cooperative agreement we were developing a process for the conversion of isobutane to (TBA), We have identified two routes for this transformation: a one-step route directly from isobutane to TBA, and a two-step route in which the isobutane is oxidized first to tert-butyl hydroperoxide and then transformed into TBA catalytically. This paper presents the results of these activities.

Lyons, J.E.

1995-06-01

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

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

6

Co-metabolic conversion of toluene in anaerobic n-alkane-degrading bacteria.  

PubMed

Diverse microorganisms have been described to degrade petroleum hydrocarbons anaerobically. Strains able to utilize n-alkanes do not grow with aromatic hydrocarbons, whereas strains able to utilize aromatic hydrocarbons do not grow with n-alkanes. To investigate this specificity in more detail, three anaerobic n-alkane degraders (two denitrifying, one sulfate-reducing) and eight anaerobic alkylbenzene degraders (five denitrifying, three sulfate-reducing) were incubated with mixtures of n-alkanes and toluene. Whereas the toluene degradationers formed only the characteristic toluene-derived benzylsuccinate and benzoate, but no n-alkane-derived metabolites, the n-alkane degraders formed toluene-derived benzylsuccinate, 4-phenylbutanoate, phenylacetate and benzoate besides the regular n-alkane-derived (1-methylalkyl)succinates and methyl-branched alkanoates. The co-metabolic conversion of toluene by anaerobic n-alkane degraders to the level of benzoate obviously follows the anaerobic n-alkane degradation pathway with C-skeleton rearrangement and decarboxylation rather than the ?-oxidation pathway of anaerobic toluene metabolism. Hence, petroleum-derived aromatic metabolites detectable in anoxic environments may not be exclusively formed by genuine alkylbenzene degraders. In addition, the hitherto largely unexplored fate of fumarate hydrogen during the activation reactions was examined with (2,3-(2) H(2) )fumarate as co-substrate. Deuterium was completely exchanged with hydrogen at the substituted carbon atom (C-2) of the succinate adducts of n-alkanes, whereas it is retained in toluene-derived benzylsuccinate, regardless of the type of enzyme catalysing the fumarate addition reaction. PMID:21880102

Rabus, Ralf; Jarling, René; Lahme, Sven; Kühner, Simon; Heider, Johann; Widdel, Friedrich; Wilkes, Heinz

2011-08-22

7

Biological conversion of cyclic alkanes and cyclic alcohols into dicarboxylic acids: biochemical and molecular basis  

Microsoft Academic Search

. Biological oxidation of cyclic alkanes and cyclic alcohols normally results in formation of the corresponding dicarboxylic acids, which are further metabolized in the cell. The biochemical pathways for oxidative conversion of cyclic compounds are similar in various phylogenetically diverse bacteria. Significant progress has been made in the past 2 years in the isolation and characterization of genes involved in

Q. Cheng; S. M. Thomas; P. Rouvière

2002-01-01

8

Understanding cage effects in the n-alkane conversion on zeolites  

Microsoft Academic Search

Molecular simulations are used to provide insight into published catalytic reactivity data for zeolites that exhibit a cage effect, the selective and preferential conversion of short-chain rather than long-chain n-alkanes. This paper demonstrates that understanding cage effects for ERI-, AFX-, and FER-type zeolites requires consideration of four components: (1) adsorption thermodynamics, (2) adsorption kinetics, (3) conversion at the exterior surface

Theo L. M. Maesen; Edith Beerdsen; Sofia Calero; David Dubbeldam; Berend Smit

2006-01-01

9

Chemistry of energy conversion and storage.  

PubMed

Energy is a big issue in our society, fueled by growing awareness of the finite resources of liquid fossil fuels and the noticeable changes in our climate resulting from its consumption. The general consensus is that there should be a well-considered roadmap towards a future energy scenario, with the replacement of fossil energy by renewable energies as the final goal. This "Chemistry of Energy Conversion and Storage" issue contains papers dealing with the chemistry behind renewable energies. PMID:22407997

Su, Dang Sheng

2012-03-08

10

Catalytic conversion of light alkanes: Quarterly report, January 1-March 31, 1992  

SciTech Connect

The first Quarterly Report of 1992 on the Catalytic Conversion of Light Alkanes reviews the work done between January 1. 1992 and March 31, 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. During the past quarter we have continued 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. We continue to investigate three molecular environments for the active catalytic species that we are trying to generate: electron-deficient porphryinic macrocycles (PHASE I), polyoxometallates (PHASE II), and regular oxidic lattices including zeolites and related structures as well as other molecular surface structures having metal oxo groups (PHASE III).

Biscardi, J.; Bowden, P.T.; Durante, V.A.; Ellis, P.E. Jr.; Gray, H.B.; Gorbey, R.G.; Hayes, R.C.; Hodge, J.; Hughes, M.; Langdale, W.A.; Lyons, J.E.; Marcus, B.; Messick, D.; Merrill, R.A.; Moore, F.A.; Myers, H.K. Jr.; Seitzer, W.H.; Shaikh, S.N.; Tsao, W.H.; Wagner, R.W.; Warren, R.W.; Wijesekera, T.P.

1997-05-01

11

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

12

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

13

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

14

A process for microbial hydrocarbon synthesis: Overproduction of fatty acids in Escherichia coli and catalytic conversion to alkanes.  

PubMed

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 beta-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 beta-oxidation), with a composition dominated by C(12) and C(14) 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 C(12) fatty acids extracted from culture to alkanes has been demonstrated yielding a concentration of 0.44 g L(-1) (culture volume) undecane. PMID:20073090

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

2010-06-01

15

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

16

Experimental investigation of the atmospheric chemistry of aromatic hydrocarbons and long-chain alkanes. Final report  

Microsoft Academic Search

The interaction of volatile organic compounds (VOCs) and oxides of nitrogen in the presence of sunlight leads to the formation of ozone and other manifestations of photochemical air pollution. There are, however, significant uncertainties in our knowledge of the products and mechanisms of the atmospheric reactions of alkanes and aromatic hydrocarbons, important constituents of ambient air in urban areas, with

R. Atkinson; J. Arey; E. C. Tuazon; S. M. Aschmann; I. Bridier

1994-01-01

17

Experimental investigation of the atmospheric chemistry of aromatic hydrocarbons and long-chain alkanes. Final report  

SciTech Connect

The interaction of volatile organic compounds (VOCs) and oxides of nitrogen in the presence of sunlight leads to the formation of ozone and other manifestations of photochemical air pollution. There are, however, significant uncertainties in our knowledge of the products and mechanisms of the atmospheric reactions of alkanes and aromatic hydrocarbons, important constituents of ambient air in urban areas, with the hydroxyl (OH) radical. A series of product studies of the OH radical-initiated reactions of selected alkanes, ketones and alcohols have been carried out to obtain further insights into alkoxy radical isomerization. Product studies of the OH radical reaction with 4-methyl-2-pentanone, 2,6-dimethyl-4-heptanone, 2,4-dimethyl-2-pentanol and 3,5-dimethyl-3-hexanol in the presence of NOx have provided unambiguous evidence for alkoxy radical isomerization and these studies have provided rate constant ratios for the isomerization reaction versus alkoxy radical decomposition and reaction with O2.

Atkinson, R.; Arey, J.; Tuazon, E.C.; Aschmann, S.M.; Bridier, I.

1994-08-01

18

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

19

Bringing an "old" biological buffer to coordination chemistry: new 1D and 3D coordination polymers with [Cu(4)(Hbes)(4)] cores for mild hydrocarboxylation of alkanes.  

PubMed

New water-soluble 1D and 3D Cu(II)/Na coordination polymers 1-3 bearing unprecedented [Cu(4)(Hbes)(4)] cores have been easily generated by aqueous-medium self-assembly and fully characterized, thus opening up the use of the common biological buffer H(3)bes, (HO(3)SCH(2)CH(2))N(CH(2)CH(2)OH)(2), in synthetic coordination chemistry. Apart from representing the first isolated and structurally characterized coordination compounds derived from H(3)bes, 1-3 show a remarkable promoting effect in the mild aqueous-medium hydrocarboxylation, by CO and H(2)O, of gaseous alkanes (C(3)H(8) and n-C(4)H(10)) to the corresponding carboxylic acids, which are obtained in up to 95% yields based on the alkane. PMID:20545321

Kirillov, Alexander M; Coelho, Jaime A S; Kirillova, Marina V; da Silva, M Fátima C Guedes; Nesterov, Dmytro S; Gruenwald, Katrin R; Haukka, Matti; Pombeiro, Armando J L

2010-07-19

20

Dehydrogenation of n-alkanes catalyzed by iridium ``pincer`` complexes: Regioselective formation of {alpha}-olefins  

SciTech Connect

The development of methods for the functionalization of alkanes is of cardinal importance in catalytic chemistry. A specific functionalization of particularly great potential value is the conversion of n-alkanes to the corresponding 1-alkenes ({alpha}-olefins) since these serve as precursors for a wide range of commodity-scale chemicals (>2 {times} 10{sup 9} kg/yr). Such a conversion is also an intriguing challenge as viewed from a fundamental perspective. n-Alkanes are the simplest organic molecules with the potential to undergo regioselective transformations; {alpha}-olefins are the thermodynamically least stable of the corresponding double-bond isomers and any mechanism for their formation must presumably involve activation of the strongest bond (primary C-{single_bond}H) in the molecule.

Liu, F.; Singh, B.; Goldman, A.S. [Rutgers-the State Univ., Piscataway, NJ (United States). Dept. of Chemistry; Pak, E.B.; Jensen, C.M. [Univ. of Hawaii, Honolulu, HI (United States). Dept. of Chemistry

1999-04-28

21

Photoinitiation chemistry affects light transmission and degree of conversion of curing experimental dental resin composites  

Microsoft Academic Search

IntroductionThe effect of photoinitiator and co-initiator chemistry on the setting reaction and degree of conversion of dental resin-based composites (RBCs) has rarely been determined explicitly. This work examines the effect of type and concentration of photoinitiator and co-initiator on the rate of change of light transmission throughout polymerisation and degree of conversion of model RBC formulations.

A. Ogunyinka; W. M. Palin; A. C. Shortall; P. M. Marquis

2007-01-01

22

Can topological indices be used to predict gas-phase rate coefficients of importance to tropospheric chemistry? Free radical abstraction reactions of alkanes  

NASA Astrophysics Data System (ADS)

As tropospheric chemical models become ever more complex, reliable rate coefficient data for gas-phase hydrogen abstraction reactions involving trace hydrocarbons becomes increasingly necessary. There are hundreds of non-methane hydrocarbons (NMHCs) of potential importance to tropospheric chemistry, many of which have not been subjected to experimental inquiry. This study—the first of its kind to investigate hydrocarbons ranging from C 2 to C 10 using topological indices—aims to provide a reliable and accessible method of estimating rate coefficients for these species. Rate coefficients of free radical abstraction reactions of NMHCs were correlated with the Randi? and Balaban topological indices for radical moieties OH, Cl and NO 3. These correlations were compared with those of an established frontier orbital approach based on calculated ionization potentials (IPs). The Randi? index was found to correlate better than IP for each of the radicals studied, and correlated particularly effectively for the Cl radical. The Balaban index did not correlate for branched alkanes except for NO 3. Where only unbranched alkanes were considered, the Balaban index proved most reliable, demonstrating a clear linear relationship. Topological indices present an accurate and diverse method for estimating free radical abstraction rate coefficients that does not require the computing power, specialist software packages, or complex mathematics inherent in ab initio calculations. A further advantage of using topological indices is that they are calculated in an unambiguous manner. More reliable tools for estimating rate coefficients have direct implications for improving models, and may also provide a direction for future laboratory work, either by highlighting particularly reactive species or identifying potentially spurious rate coefficient data.

McGillen, Max R.; Percival, Carl J.; Raventos-Duran, Teresa; Sanchez-Reyna, Gabriela; Shallcross, Dudley E.

23

Role of ozone in SOA formation from alkane photooxidation  

NASA Astrophysics Data System (ADS)

Long-chain alkanes, which can be categorized as intermediate volatile organic compounds (IVOCs), are an important source of secondary organic aerosol (SOA). Mechanisms for the gas-phase OH-initiated oxidation of long-chain alkanes have been well documented; particle-phase chemistry, however, has received less attention. The ?-hydroxycarbonyl, which is generated from the isomerization of alkoxy radicals, can undergo heterogeneous cyclization to form substituted dihydrofuran. Due to the presence of C=C bonds, the substituted dihydrofuran is predicted to be highly reactive with OH, and even more so with O3 and NO3, thus opening a reaction pathway that is not usually accessible to alkanes. This work focuses on the role of substituted dihydrofuran formation and its subsequent reaction with OH, and more importantly ozone, in SOA formation from the photooxidation of long-chain alkanes. Experiments were carried out in the Caltech Environmental Chamber using dodecane as a representative alkane to investigate the difference in aerosol composition generated from "OH-oxidation dominating" vs. "ozonolysis dominating" environments. A detailed mechanism incorporating the specific gas-phase photochemistry, together with the heterogeneous formation of substituted dihydrofuran and its subsequent gas-phase OH/O3 oxidation, is presented to evaluate the importance of this reaction channel in the dodecane SOA formation. We conclude that: (1) the formation of ?-hydroxycarbonyl and its subsequent heterogeneous conversion to substituted dihydrofuran is significant in the presence of NOx; (2) the ozonolysis of substituted dihydrofuran dominates over the OH-initiated oxidation under conditions prevalent in urban and rural air; and (3) a spectrum of highly-oxygenated products with carboxylic acid, ester, and ether functional groups are produced from the substituted dihydrofuran chemistry, thereby affecting the average oxidation state of the SOA.

Zhang, X.; Schwantes, R. H.; Coggon, M. M.; Loza, C. L.; Schilling, K. A.; Flagan, R. C.; Seinfeld, J. H.

2013-09-01

24

Superacid catalysis of light hydrocarbon conversion. Eleventh quarterly report, April 1, 1996--June 30, 1996  

SciTech Connect

The new catalyst Fe- and Mn-promoted sulfated zirconia is remarkably active for the low-temperature (even room temperature) isomerization of n-butane to give isobutane in the near absence of side products. Thus this catalyst offers excellent potential for practical application in this process. The catalyst is so active that it even converts smaller alkanes, including propane and ethane. The ethane conversion is orders of magnitude slower than the butane conversion, and the prospects for practical application with ethane are apparently negligible. However, the results for ethane conversion provide strong evidence that the alkane conversions proceed (at least under some conditions) by protonation of the alkane with the catalyst; thus the catalyst is comparable to superacids, and the chemistry is analogous to that occurring in superacid solutions. This insight will be useful in further improvement of the catalyst and the potential process for butane isomerization. The catalyst is active for alkane cracking at temperatures of typically 200-300{degrees}C, and evidence, summarized here, indicates that numerous reactions of alkanes begin as the catalyst protonates the alkane reactant. The kinetics data for this family of reactions fall on a linear compensation effect plot; such data for reactions that do not proceed via such a mechanism do not fall near the line representing the compensation effect. Thus the analysis of the kinetics data provides a good diagnostic tool for understanding the fundamental chemistry of the acid-catalyzed hydrocarbon conversions.

Gates, B.C. [California Univ., Davis, CA (United States). Dept. of Chemical Engineering and Materials Science

1996-12-31

25

EDITORIAL: Non-thermal plasma-assisted fuel conversion for green chemistry Non-thermal plasma-assisted fuel conversion for green chemistry  

NASA Astrophysics Data System (ADS)

This special issue is based on the symposium on Non-thermal Plasma Assisted Fuel Conversion for Green Chemistry, a part of the 240th ACS National Meeting & Exposition held in Boston, MA, USA, 22-26 August 2010. Historically, the Division of Fuel Chemistry of the American Chemical Society (ACS) has featured three plasma-related symposia since 2000, and has launched special issues in Catalysis Today on three occasions: 'Catalyst Preparation using Plasma Technologies', Fall Meeting, Washington DC, USA, 2000. Special issue in Catalysis Today 72 (3-4) with 12 peer-reviewed articles. 'Plasma Technology and Catalysis', Spring Meeting, New Orleans, LA, USA, 2003. Special issue in Catalysis Today 89 (1-2) with more than 30 peer-reviewed articles. 'Utilization of Greenhouse Gases II' (partly focused on plasma-related technologies), Spring Meeting, Anaheim, CA, USA, 2004. Special issue in Catalysis Today 98 (4) with 25 peer-reviewed articles. This time, selected presentations are published in this Journal of Physics D: Applied Physics special issue. An industrial material and energy conversion technology platform is established on thermochemical processes including various catalytic reactions. Existing industry-scale technology is already well established; nevertheless, further improvement in energy efficiency and material saving has been continuously demanded. Drastic reduction of CO2 emission is also drawing keen attention with increasing recognition of energy and environmental issues. Green chemistry is a rapidly growing research field, and frequently highlights renewable bioenergy, bioprocesses, solar photocatalysis of water splitting, and regeneration of CO2 into useful chemicals. We would also like to emphasize 'plasma catalysis' of hydrocarbon resources as an important part of the innovative next-generation green technologies. The peculiarity of non-thermal plasma is that it can generate reactive species almost independently of reaction temperature. Plasma-generated reactive species are used to initiate chemical reactions at unexpectedly lower temperatures than conventional thermochemical reactions, leading to non-equilibrium product distribution or creating unconventional reaction pathways. When non-thermal plasma is combined with catalysts, a synergistic effect is frequently observed. Such unique properties of non-thermal plasma are expected to contribute excellent control over process parameters that meet the need for energy saving, environment protection, and material preservation. This special issue consists of eleven peer-reviewed papers including two invited publications. Professors Alexander Fridman and Alexander Rabinovich from Drexel University, and Dr Gutsol from the Chevron Energy Technology Company present a critical review of various industry-oriented practical plasma fuel conversion processes. Professor Richard Mallinson from University of Oklahoma describes his recent project on E85 (85%-ethanol/15%-gasoline) upgrading using non-thermal plasma and catalyst hybrid reactor, and highlights the synergistic effect on fuel conversion processes. Other papers focus on plasma/catalyst hybrid reactions for methane dry (CO2) reforming, plasma synthesis of carbon suboxide polymer from CO, the gas-to-liquid (GTL) process using a non-thermal plasma-combined micro-chemical reactor, and molecular beam characterization of plasma-generated reactive species. Much research regarding plasma catalysis is ongoing worldwide, but there is plenty of room for further development of plasma fuel processing, which could eventually provide a viable and flexible solution in future energy and material use. Finally, we would like to thank all symposium participants for their active discussion. We appreciate the sponsorship of the Division of Fuel Chemistry of the American Chemical Society. We express special thanks to the program chair of the Fuel Chemistry Division, Professor Chang-jun Liu at Tianjin University, for his dedication to the success of the symposium. We particularly express our appreciation to the Editorial Board of Journal

Nozaki, Tomohiro; Gutsol, Alexander

2011-07-01

26

Alkane hydroxylases involved in microbial alkane degradation  

Microsoft Academic Search

This review focuses on the role and distribution in the environment of alkane hydroxylases and their (potential) applications\\u000a in bioremediation and biocatalysis. Alkane hydroxylases play an important role in the microbial degradation of oil, chlorinated\\u000a hydrocarbons, fuel additives, and many other compounds. Environmental studies demonstrate the abundance of alkane degraders\\u000a and have lead to the identification of many new species,

Jan B. van Beilen; Enrico G. Funhoff

2007-01-01

27

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.

28

Superacid catalyzed coal conversion chemistry. Final technical report, September 1, 1983-September 1, 1986  

SciTech Connect

This research project involved the study of a raw comparatively mild coal conversion process. The goal of the project was to study model systems to understand the basic chemistry involved and to provide a possible effective pretreatment of coal which significantly improves liquefaction-depolymerization under mild conditions. The conversion process operates at relatively low temperatues (170/sup 0/C) and pressures and uses an easily recyclable, stable superacid catalysts (HF-BF/sub 3/). It consequently offers an attractive alternative to currently available processes. From the present studies it appears that the modification of coal structure by electrophilic alkylation and subsequent reaction of alkylated coal with HF-BF/sub 3/-H/sub 2/ system under mild conditions considerably improves the extractability of coal in pyridine and cyclohexane. On the other hand, nitration of coal and its subsequent reaction with HF-BF/sub 3/H/sub 2/ decreases the pyridine and cyclohexane extractability. Study of model compounds under conditions identical with the superacidic HF/BF/sub 3//H/sub 2/ system provided significant information about the basic chemistry of the involved cleavage-hydrogenation reactions.

Olah, G.A.

1986-01-01

29

Identification and Characterization of the CYP52 Family of Candida tropicalis ATCC 20336, Important for the Conversion of Fatty Acids and Alkanes to ?,?-Dicarboxylic Acids  

PubMed Central

Candida tropicalis ATCC 20336 excretes ?,?-dicarboxylic acids as a by-product when cultured on n-alkanes or fatty acids as the carbon source. Previously, a ?-oxidation-blocked derivative of ATCC 20336 was constructed which showed a dramatic increase in the production of dicarboxylic acids. This paper describes the next steps in strain improvement, which were directed toward the isolation and characterization of genes encoding the ?-hydroxylase enzymes catalyzing the first step in the ?-oxidation pathway. Cytochrome P450 monooxygenase (CYP) and the accompanying NADPH cytochrome P450 reductase (NCP) constitute the hydroxylase complex responsible for the first and rate-limiting step of ?-oxidation of n-alkanes and fatty acids. 10 members of the alkane-inducible P450 gene family (CYP52) of C. tropicalis ATCC20336 as well as the accompanying NCP were cloned and sequenced. The 10 CYP genes represent four unique genes with their putative alleles and two unique genes for which no allelic variant was identified. Of the 10 genes, CYP52A13 and CYP52A14 showed the highest levels of mRNA induction, as determined by quantitative competitive reverse transcription-PCR during fermentation with pure oleic fatty acid (27-fold increase), pure octadecane (32-fold increase), and a mixed fatty acid feed, Emersol 267 (54-fold increase). The allelic pair CYP52A17 and CYP52A18 was also induced under all three conditions but to a lesser extent. Moderate induction of CYP52A12 was observed. These results identify the CYP52 and NCP genes as being involved in ?,?-dicarboxylic acid production by C. tropicalis and provide the foundation for biocatalyst improvement.

Craft, David L.; Madduri, Krishna M.; Eshoo, Mark; Wilson, C. Ron

2003-01-01

30

Gas-to-Particle Conversion in Surface Discharge Nonthermal Plasmas and Its Implications for Atmospheric Chemistry  

PubMed Central

This paper presents some experimental data on gas-to-particle conversion of benzene using nonthermal plasma (NTP) technology and discusses the possibility of its technical application in atmospheric chemistry. Aerosol measurement using a differential mobility analyzer (DMA) revealed that the parts of benzene molecules were converted into a nanometer-sized aerosol. Aerosol formation was found to be highly related with the missing part in carbon balance. Scanning electron microscopy analysis showed that the aerosols formed in synthetic humid air are the collection of nanoparticles. The carbonyl band (C=O) was found to be an important chemical constituent in the aerosol. The potential of the NTP as an accelerated test tool in studying secondary organic aerosol (SOA) formation from VOCs will be also addressed.

Kim, Hyun-Ha; Ogata, Atsushi

2011-01-01

31

Nanocrystal conversion chemistry: A unified and materials-general strategy for the template-based synthesis of nanocrystalline solids  

Microsoft Academic Search

The concept of nanocrystal conversion chemistry, which involves the use of pre-formed nanoparticles as templates for chemical transformation into derivative solids, has emerged as a powerful approach for designing the synthesis of complex nanocrystalline solids. The general strategy exploits established synthetic capabilities in simple nanocrystal systems and uses these nanocrystals as templates that help to define the composition, crystal structure,

Yolanda Vasquez; Amanda E. Henkes; J. Chris Bauer; Raymond E. Schaak

2008-01-01

32

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

33

Exploratory study of coal-conversion chemistry. Quarterly report No. 4, February 19-May 18, 1982  

SciTech Connect

SRI is conducting a program on the chemistry of the conversion of coal to liquid fuels: Task A deals with mechanisms of donor solvent liquefaction; Task B is a study of the conversion of coal and model compounds in the CO/H/sub 2/O system. In Task A, determination of the products, rates, and mechanisms of central bond scission of diphenyl ether and 1,2-dinaphthylmethane in tetralin, 9,10-dihydroanthracene, and 9,10-dihydrophenanthrene allows us to determine the predominant mechanism of hydrogen transfer to these substrates. Diphenyl ether decomposes in the above three solvents by a radical addition-elimination mechanism, with defined first-order rate constants of approx. 1 x 10/sup -7/, 2 x 10/sup -6/, and 2 x 10/sup -7/ s/sup -1/, respectively. The relative reactivity of the two substrates, the relative reactivity in the three solvents, and the positional preference for hydrogen transfer provide compelling evidence for the previously unreported single-step transfer of hydrogen from a radical to a closed-shell ..pi..-system. Efforts in Task B were concentrated on the conversion of anisole in D/sub 2/O and in tetralin at 400/sup 0/C. Experiments were conducted in two different reactor systems, small glass ampoules and 1/4-in. 316 stainless steel tubes. Benzene and phenol were the major products with the rates of product formation affected by the reaction medium and the reactor walls. The rate of benzene formation was found to be more rapid in D/sub 2/O than tetralin, and somewhat greater in glass ampoules than in stainless steel reactors for 20 min. We also studied the conversion of bibenzyl in D/sub 2/O and in tetralin in stainless steel tubes at 400/sup 0/C. In tetralin, toluene was the major product. In D/sub 2/O, the products were toluene, benzene, diphenylmethane, stilbene, and phenanthrene. A novel hydration scheme is suggested for the reactions of bibenzyl in water.

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

1982-06-01

34

The hydrodeoxygenation of bioderived furans into alkanes.  

PubMed

The conversion of biomass into fuels and chemical feedstocks is one part of a drive to reduce the world's dependence on crude oil. For transportation fuels in particular, wholesale replacement of a fuel is logistically problematic, not least because of the infrastructure that is already in place. Here, we describe the catalytic defunctionalization of a series of biomass-derived molecules to provide linear alkanes suitable for use as transportation fuels. These biomass-derived molecules contain a variety of functional groups, including olefins, furan rings and carbonyl groups. We describe the removal of these in either a stepwise process or a one-pot process using common reagents and catalysts under mild reaction conditions to provide n-alkanes in good yields and with high selectivities. Our general synthetic approach is applicable to a range of precursors with different carbon content (chain length). This allows the selective generation of linear alkanes with carbon chain lengths between eight and sixteen carbons. PMID:23609095

Sutton, Andrew D; Waldie, Fraser D; Wu, Ruilian; Schlaf, Marcel; Silks, Louis A Pete; Gordon, John C

2013-04-07

35

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

36

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

37

Nanocrystal conversion chemistry: A unified and materials-general strategy for the template-based synthesis of nanocrystalline solids  

NASA Astrophysics Data System (ADS)

The concept of nanocrystal conversion chemistry, which involves the use of pre-formed nanoparticles as templates for chemical transformation into derivative solids, has emerged as a powerful approach for designing the synthesis of complex nanocrystalline solids. The general strategy exploits established synthetic capabilities in simple nanocrystal systems and uses these nanocrystals as templates that help to define the composition, crystal structure, and morphology of product nanocrystals. This article highlights key examples of “conversion chemistry” approaches to the synthesis of nanocrystalline solids using a variety of techniques, including galvanic replacement, diffusion, oxidation, and ion exchange. The discussion is organized according to classes of solids, highlighting the diverse target systems that are accessible using similar chemical concepts: metals, oxides, chalcogenides, phosphides, alloys, intermetallic compounds, sulfides, and nitrides.

Vasquez, Yolanda; Henkes, Amanda E.; Chris Bauer, J.; Schaak, Raymond E.

2008-07-01

38

Nanocrystal conversion chemistry: A unified and materials-general strategy for the template-based synthesis of nanocrystalline solids  

SciTech Connect

The concept of nanocrystal conversion chemistry, which involves the use of pre-formed nanoparticles as templates for chemical transformation into derivative solids, has emerged as a powerful approach for designing the synthesis of complex nanocrystalline solids. The general strategy exploits established synthetic capabilities in simple nanocrystal systems and uses these nanocrystals as templates that help to define the composition, crystal structure, and morphology of product nanocrystals. This article highlights key examples of 'conversion chemistry' approaches to the synthesis of nanocrystalline solids using a variety of techniques, including galvanic replacement, diffusion, oxidation, and ion exchange. The discussion is organized according to classes of solids, highlighting the diverse target systems that are accessible using similar chemical concepts: metals, oxides, chalcogenides, phosphides, alloys, intermetallic compounds, sulfides, and nitrides. - Graphical abstract: Nanocrystal conversion chemistry uses pre-formed nanoparticles as templates for chemical transformation into derivative solids, helping to define the composition, crystal structure, and morphology of product nanocrystals that have more complex features than their precursor templates. This article highlights the application of this concept to diverse classes of solids, including metals, oxides, chalcogenides, phosphides, alloys, intermetallics, sulfides, and nitrides.

Vasquez, Yolanda; Henkes, Amanda E.; Chris Bauer, J. [Department of Chemistry, Texas A and M University, College Station, TX 77842 (United States); Schaak, Raymond E. [Department of Chemistry, Texas A and M University, College Station, TX 77842 (United States); Department of Chemistry, Pennsylvania State University, University Park, PA 16802 (United States)], E-mail: schaak@chem.psu.edu

2008-07-15

39

Nature and Origin of Asphaltenes in Processed Coals: The Chemistry and Mechanisms of Coal Conversion to Clean Fuel. Annual Report, March 1976--February 1977.  

National Technical Information Service (NTIS)

Studies have been undertaken to develop a fundamental understanding of the chemistry and structure of coal and coal products and the mechanisms involved in the conversion of coal to soluble products under typical solvent refining conditions. Illinois, Ken...

D. D. Whitehurst M. Farcasiu T. O. Mitchell J. J. Dickert

1977-01-01

40

Chemistry  

NSDL National Science Digital Library

Finds ChemEd DL resources related to the sections of the General Chemistry textbook, Chemistry, by Kenneth W. Whitten, Raymond E. Davis, M. Larry Peck, George G. Stanley published by Brooks/Cole, 2010.

41

Rubredoxins Involved in Alkane Oxidation  

Microsoft Academic Search

Rubredoxins (Rds) are essential electron transfer components of bacterial membrane-bound alkane hydrox- ylase 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)

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

2002-01-01

42

Exploratory study of coal conversion chemistry. Quarterly report No. 9, May 19, 1983-August 18, 1983  

SciTech Connect

Work has begun on computer modeling of hydrogenolysis systems, incorporating the hydrogen transfer reactions we have invoked to explain the liquefaction effectiveness of pyrene. Additional coal conversion experiments have also been performed in a not yet successful attempt to clearly define the conversion conditions under which the differences between pyrene and the other solvents are maximized. We are also conducting a series of experiments designed to relate conversion in pure model compound systems to conversion in real coal systems and to further characterize certain coals for their radical-initilating and hydrogen transfer properties as compared with pure donor solvent systems. These latter experiments involve spiking coal liquefaction mixtures with model compounds under conditions where conversion of the model compounds can readily be determined. Our efforts in Conversion in CO/H/sub 2/O Systems were concentrated on analysis of the conversion products of an Illinois No. 6 coal, PSOC-1098, in CO/D/sub 2/O were analyzed for their deuterium content; the results reveal substantial levels of deuterium incorporation, even in the absence of conversion. Hence, supercritical water exchanges rapidly and extensively with coal at 400/sup 0/C. The behavior of benzaldehyde in CO/H/sub 2/O and CO/D/sub 2/O was also examined. The reduction of benzaldehyde to benzyl alcohol follows the water-gas shift reaction and exhibits an inverse isotope effect. This behavior is similar to the conversion behavior of the Illinois No. 6 coal in CO/H/sub 2/O. Evidence is also presented that supports the view that formate, the intermediate in the water-gas shift reaction, is responsible for conversion of the Illinois No. 6 coal.

Ross, D.S.; McMillen, D.F.; Ogler, W.C.; Chang, S.J.; Hum. G.P.; Mansani, R.; Green, T.K.

1983-09-01

43

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,

44

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

45

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

46

Catalytic, mild, and selective oxyfunctionalization of linear alkanes: current challenges.  

PubMed

Selective catalysts for sustainable oxidation of alkanes are highly demanded because of the abundance of these molecules in the environment, the possibility to transform them into higher-value compounds, such as chemicals or synthetic fuels, and the fact that, kinetically speaking, this is a difficult reaction. Numerous chemical and biological catalysts have been developed in the lasts decades for this purpose, rendering the overview over this field of chemistry difficult. After giving a definition of the ideal catalyst for alkane oxyfunctionalization, this review aims to present the catalysts available today that are closest to ideal. PMID:22996726

Bordeaux, Mélanie; Galarneau, Anne; Drone, Jullien

2012-09-20

47

Exploratory study of coal-conversion chemistry. Quarterly report No. 6, August 19, 1982-November 18, 1982  

SciTech Connect

Initial experiments combining compound-class (HPLC) separation of coal liquefaction products and field ionization mass spectrometric (FIMS) analysis of the various fractions to obtain improved correlations between donor-solvent structure and coal-conversion effectiveness have been performed. These experiments have used a very low-fluidity bituminous coal (PSOC-1116, Sunnyside, Utah) and tetralin and 1,2,3,4-tetrahydroquinoline (THQ) as donor solvents. Apart from indicating ways in which the chromatography procedure needs to be adjusted to achieve better separation on the basis of functional groups (compound-class separation), FIMS analysis of the various fractions has allowed us to conclude that the observed THQ incorporation (a 100%) is comprised less than 2% physical or hydrogen bonded incorporation, less than 30% by self-polymerization reactions of THQ, and at least 70% by covalent incorporation of the entire THQ molecule into coal structures. This incorporation apparently takes place by way of electrophilic substitution on coal structures, notwithstanding THQ's obvious nucleophilic properties. The conversion of bibenzyl in D/sub 2/O/CO systems at 400/sup 0/C was also studied. The experiments were conducted in stainless steel tubes. The products of the conversion of neat bibenzyl were in accord with previously reported chemistry, with toluene and stilbene the major products. D/sub 2/O had no effect on the product distributions. The addition of CO in the system reduced the amount of stilbene observed, and under basic conditions, stilbene was observed only as a minor product. The disappearance of stilbene paralleled the water-gas shift reaction. It is suggested that molecular hydrogen reacts with thermally produced benzyl radicals to give toluene and/or that stilbene is hydrogenated to give bibenzyl. The implications of this reaction in the conversion of coals in the CO/D/sub 2/O system are briefly discussed.

Ross, D.S.; McMillen, D.F.; Fleming, R.H.; Hum, G.P.; Mansani, R.; Green, T.K.

1982-01-01

48

Exploratory study of coal-conversion chemistry. Final report, September 20, 1979-March 19, 1981  

SciTech Connect

Under Task A, the surprisingly rapid rates at which the strong carbon-carbon and carbon-oxygen central bonds in hydroxydiphenylmethanes and hydroxydiphenyl ethers are broken, under homogeneous conditions, in tetralin at 400/sup 0/C, have been quantitatively accounted for by a mechanism involving tautomerization to the weakly bonded keto forms followed by homolysis of the central bonds. These homogeneous decomposition mechanisms bear directly on the susceptibility of these linkages to homogeneously and heterogeneously catalyzed cleavage. Iron oxides, particularly Fe/sub 3/O/sub 4/, were found to be effective and selective catalysts for these same cleaveages. Relative catalyst effectiveness suggests that the mechanism of catalysis involves radical cation formation. Under Task B, the conversion of coal to benzene-soluble coal products in CO/H/sub 2/O systems displays a striking dependence on the pH of the starting aqueous phase. Thus below a starting pH of 12.6, the product benzene solubility is about 10% and steeply climbs to the 50% level under more basic conditions. This increase in conversion is paralleled by an increase in the reaction rate of the water-gas shift reaction. A series of runs was conducted using a catalytic amount (3000 to 6000 ppM) of water-soluble salts of several metals. Thus potassium or sodium salts of molybdate (Mo(VI)), dichromate (Cr(VI)), and permanganate (Mn(VII)) were found to be effective for the coal conversion. In addition, the catalytic activity of these salts also depends on the starting pH of the aqueous solution adjusted with dilute KOH or HC1 solutions. This indicates that despite the catalytic activity of metal-oxyanions, the changes in conversion are large over small pH changes; plots of conversion versus initial pH are S-shaped curves similar to common titration curves.

Ross, D.S.; McMillen, D.; Ogier, W.; Nguyen, Q.

1981-08-12

49

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

50

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

51

Nanorheology of Liquid Alkanes  

SciTech Connect

We report molecular dynamics simulations of liquid alkanes, squalane and tetracosane, confined between moving walls to which butane chains are tethered, effectively screening the details of the wall. As in an experiment, heat is removed by thermostatting the tethered molecules. Results obtained at high strain rates, typical of practical applications, suggest little or no difference between the bulk rheology and confined flow, and the occurrence of a high degree of slip at the wall-fluid interface at the conditions studied. At relatively low velocities and high densities, tetracosane shows the formation of fully-extended chains at certain wall spacings.

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

1997-09-01

52

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

53

Alkane Self Assembling  

NASA Astrophysics Data System (ADS)

Self-assembling of organic molecules has awaken scientific and technological interest. In this work we study the self-assembling process of long chain hydrocarbons, mainly n-dotriacontane (n-C32H66). We dip-coated C32 monolayers onto silicon wafers covered by their native silicon oxide layer (Si(100)/SiO2). Our results show that withdrawing speed affects the coverage and morphology of the C32 films. For slow withdrawing speeds, alkanes formed islands with a dragon-fly shape, while for fast withdrawing alkanes assembled in stripes with widths in the order of microns. When we quantified coverage and morphology versus withdrawing speed, we found an inflection, which we associate with a transition between two film deposition kinetics. These transitions have been previously described by de Gennes [1]. For slow withdrawing, film deposition follows the Langmuir-Blodget process and above a threshold speed, solution on the solid enters a Landau-Levich regime. This work opens the possibility for growing microstructures with nanometric thickness using a very simple method. These organic microstructures could be used as templates or as grids for optical diffraction. [0pt] [1] P.G. de Gennes, Colloid & Polymer Sci. 264, 463-465 (1986).

Corrales, Tomas; Homm, Pia; Ferrari, Piero; Retamal, Maria Jose; Del Campo, Valeria; Volkmann, Ulrich G.

2011-03-01

54

Exploratory study of coal conversion chemistry. Quarterly report No. 11, November 19, 1983-February 18, 1984  

SciTech Connect

Work performed under Task A is reported in two parts: Part 1 describes the promotion, by the addition of real coals, of the cleavage of strong bonds in model coal structures, as predicted by our previously proposed hydrogen-transfer/bond-cleavage mechanism; and Part 2 is an analysis that reconciles the reported slow isotopic exchange (C) between tetralin and naphthalene with accepted or proposed mechanisms of radical generation and hydrogen transfer in such systems. Efforts in Task B, Conversion in CO/H/sub 2/O Systems involved a study of the conversion characteristics of Eastern Province bituminous coals in CO/H/sub 2/O. All coals were subjected to identical reaction conditions of 400/sup 0/C/20 min in CO/H/sub 2/O at pH 13. The amount of CO that reacted was nearly identical in all runs, indicating that the extent of water-gas-shift reaction is independent of the coal used in the reaction. The amount of toluene-soluble material varied widely from 85% (dmmf) for an Ohio No. 9 coal to only 3% for a Pocahontas No. 3 coal.

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

1984-03-01

55

Alkane desaturation by concerted double hydrogen atom transfer to benzyne.  

PubMed

The removal of two vicinal hydrogen atoms from an alkane to produce an alkene is a challenge for synthetic chemists. In nature, desaturases and acetylenases are adept at achieving this essential oxidative functionalization reaction, for example during the biosynthesis of unsaturated fatty acids, eicosanoids, gibberellins and carotenoids. Alkane-to-alkene conversion almost always involves one or more chemical intermediates in a multistep reaction pathway; these may be either isolable species (such as alcohols or alkyl halides) or reactive intermediates (such as carbocations, alkyl radicals, or ?-alkyl-metal species). Here we report a desaturation reaction of simple, unactivated alkanes that is mechanistically unique. We show that benzynes are capable of the concerted removal of two vicinal hydrogen atoms from a hydrocarbon. The discovery of this exothermic, net redox process was enabled by the simple thermal generation of reactive benzyne intermediates through the hexadehydro-Diels-Alder cycloisomerization reaction of triyne substrates. We are not aware of any single-step, bimolecular reaction in which two hydrogen atoms are simultaneously transferred from a saturated alkane. Computational studies indicate a preferred geometry with eclipsed vicinal C-H bonds in the alkane donor. PMID:24067712

Niu, Dawen; Willoughby, Patrick H; Woods, Brian P; Baire, Beeraiah; Hoye, Thomas R

2013-09-26

56

Trends in Alkane Boiling Points  

NSDL National Science Digital Library

This activity is an investigation into the relationship between alkane length and boiling points. Students develop a mathematical model of this relationship and use it to make predictions and error analysis.

Woods, Paula

57

One-pot conversion of sugar and sugar polyols to n-alkanes without C-C Dissociation over the Ir-ReOx /SiO2 catalyst combined with H-ZSM-5.  

PubMed

High (?95 % C) yields of n-hexane and n-pentane were obtained by hydrogenolysis of aqueous sorbitol and xylitol, respectively, at 413-443 K by using the Ir-ReOx /SiO2 catalyst combined with H-ZSM-5 as a cocatalyst and n-dodecane as a cosolvent. The direct production of n-hexane from glucose or cellobiose can be achieved by using the same system. The catalyst can be reused simply by the removal of the n-dodecane phase, which contains the product alkane, and the addition of fresh n-dodecane and substrate. PMID:23463694

Chen, Kaiyou; Tamura, Masazumi; Yuan, Zhenle; Nakagawa, Yoshinao; Tomishige, Keiichi

2013-03-05

58

Carbon-hydrogen bond activation by electrophilic transition-metal compounds. Palladium(II)-mediated oxidation of arenes and alkanes including methane  

Microsoft Academic Search

The activation of carbon-hydrogen bonds by transition metals that leads to the selective functionalization of hydrocarbons, especially alkanes, is one of the most challenging problems in organometallic chemistry. Herein, the authors report on the palladium(II)-mediated oxidation of arenes and alkanes through a nonradical, electrophilic C-H activation pathway.

Efi Gretz; Thomas F. Oliver; Ayusman Sen

1987-01-01

59

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

PubMed

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. PMID:19367794

Pierce, Flint; Tsige, Mesfin; Perahia, Dvora; Grest, Gary S

2008-12-18

60

Hydrogen isotopic compositions of individual alkanes as a new approach to petroleum correlation: case studies from the Western Canada Sedimentary Basin  

Microsoft Academic Search

Isotopic compositions of carbon-bound hydrogen in individual n-alkanes and acyclic isoprenoid alkanes, from a number of crude oil samples, were measured using gas chromatography-thermal conversion-isotope ratio mass spectrometry. The precision of this technique is better than 3‰ for most alkanes, compared to the large range of ?D variation among the samples (up to 160‰). The oils were selected from major

Maowen Li; Yongsong Huang; Mark Obermajer; Chunqing Jiang; Lloyd R Snowdon; Martin G Fowler

2001-01-01

61

Superacid catalysis of light hydrocarbon conversion. Sixth quarterly report, January 1, 1995--March 31, 1995  

SciTech Connect

Iron- and Manganese-promoted sulfated zirconia is a catalyst for the conversion of propane, but the rate of conversion of propane is much less than the rate of conversion of butane. Whereas this catalyst appears to be a good candidate for practical, industrial conversion of butane, it appears to lack sufficient activity for practical conversion of propane. Perhaps more active catalysts will be useful for propane conversion. The propane conversion data reported here provide excellent insights into the chemistry of the catalytic conversions; they are consistent with the inference that the catalyst is a superacid and that the chemistry is analogous to. that determined in superacid solutions by G.A. Olah, who was awarded the most recent Nobel Prize in chemistry for his work. The catalyst was tested for conversion of propane at 1 bar, 200--300{degrees}C and propane partial pressures in the range of 0.01--0.05 bar. At 250{degrees}C, catalysis was demonstrated, as the number of propane molecules converted was at least 1 per sulfate group after 16 days of operation in a continues flow reactor. Propane was converted in high yield to butanes, but the conversions were low, for example being only a fraction of a percent at a space velocity of 9.1 {times} 10{sup {minus}7} mol(g of catalysis {center_dot} s) and 250{degrees}C. Coke formation was rapid. The observation of butanes, pentanes, and methane as products is consistent with Olah superacid chemistry, whereby propane is first protonated by a very strong acid to form a carbonium ion. The carbonium ion then decomposes into methane and an ethyl cation which undergoes oligocondensation reactions with propane to form higher molecular weight alkanes. The results are consistent with the identification of iron- and manganese-promoted sulfated zirconia as a superacid.

Gates, B.C. [California Univ., Davis, CA (United States). Dept. of Chemical Engineering and Materials Science

1995-08-01

62

Alkane oxidation by osmium tetroxide.  

PubMed

Aqueous alkaline OsO4 at 85 degrees C oxidizes saturated alkanes, including primary, secondary, and tertiary C-H bonds. Isobutane affords tert-butanol in quantitative yield based on consumed OsO4. Cyclohexane is oxidized to a mixture of adipate and succinate. Ethane and propane are oxidized to acetate, which itself is further oxidized under the reaction conditions. A few turnovers of isobutane oxidation have been accomplished using NaIO4 as the terminal oxidant. The alkane oxidation is an example of ligand accelerated catalysis, as hydroxide binding to OsO4 is required for reaction. A concerted mechanism involving [3+2] addition of a C-H bond to two oxo groups of OsO4(OH)- is suggested, analogous to the pathways for dihydroxylation of alkenes by OsO4(L) and for addition of H2 to OsO4(L). PMID:15740101

Bales, Brian C; Brown, Peter; Dehestani, Ahmad; Mayer, James M

2005-03-01

63

Millisecond Oxidation of Alkanes  

SciTech Connect

This project was undertaken in response to the Department of Energy's call to research and develop technologies 'that will reduce energy consumption, enhance economic competitiveness, and reduce environmental impacts of the domestic chemical industry.' The current technology at the time for producing 140 billion pounds per year of propylene from naphtha and Liquified Petroleum Gas (LPG) relied on energy- and capital-intensive steam crackers and Fluidized Catalytic Cracking (FCC) units. The propylene is isolated from the product stream in a costly separation step and subsequently converted to acrylic acid and other derivatives in separate production facilities. This project proposed a Short Contact Time Reactor (SCTR)-based catalytic oxydehydrogenation process that could convert propane to propylene and acrylic acid in a cost-effective and energy-efficient fashion. Full implementation of this technology could lead to sizeable energy, economic and environmental benefits for the U. S. chemical industry by providing up to 45 trillion BTUs/year, cost savings of $1.8 billion/year and a combined 35 million pounds/year reduction in environmental pollutants such as COx, NOx, and SOx. Midway through the project term, the program directive changed, which approval from the DOE and its review panel, from direct propane oxidation to acrylic acid at millisecond contact times to a two-step process for making acrylic acid from propane. The first step was the primary focus, namely the conversion of propane to propylene in high yields assisted by the presence of CO2. The product stream from step one was then to be fed directly into a commercially practiced propylene-to-acrylic acid tandem reactor system.

Scott Han

2011-09-30

64

Exploratory study of coal-conversion chemistry. Quarterly report No. 7, November 19, 1982-February 18, 1983  

SciTech Connect

Work has continued on deriving improved correlations between donor-solvent structure and coal conversion effectiveness. Addition of pyrene to tetralin has been found to increase the conversion of a low fluidity bituminous coal to THF solubles from 80 to 96%. By comparison, phenanthrene, 1-phenyl-napthlalene, and fluoranthrene increased the conversion by no more than 2 to 3 percentage points. These results support earlier suggestions that pyrene exhibits particular effectiveness as a hydrogen transfer agent. Various possible explanations for this increased effectiveness are considered in the light of previous and current work in this project on the cleavage of strong coal linkages in polycyclic aromatic and hydroaromatic solvents. Work was extended with the base-catalyzed CO/H/sub 2/O conversion system to include another Illinois No. 6 coal, PSOC-1098. The behavior of this coal is similar to another coal from the same mine, beneficiated PSOC-26, in that conversion is more effective in CO than in H/sub 2/. However, H/sub 2/ converts PSOC-1098 more effectively than it does PSOC-26, suggesting that the mineral matter catalyzes the reaction between the coal and H/sub 2/. The maximum conversions of the two coals in CO are virtually identical, although PSOC-1098 is much more reactive toward the H/sub 2/ produced by the water-gas-shift (WGS) reaction. This suggests that the active CO intermediate and Ha2 are competing for the same reactive site in the coal.

Ross, D.S.; McMillen, D.F.; Ogier, W.C.; Chang, S.J.; Hum, G.P.; Mansani, R.; Green, T.K.

1983-03-01

65

Crystal nucleation in normal alkane liquids  

Microsoft Academic Search

The homogeneous nucleation of crystals in normal alkane liquids has been studied using a droplet technique for a range of alkanes between C16H34 and C5H12. The critical undercooling for nucleation, ?TN, relative to the melting point TE, increases significantly with decreasing length of the alkane chain n: ?TN\\/TE increases from 0.05 for C16H34 to 0.20 for C5H12, with separate variations

D. R. Uhlmann; G. Kritchevsky; R. Straff; G. Scherer

1975-01-01

66

Characterization of a novel long-chain n-alkane-degrading strain, Dietzia sp. E1.  

PubMed

The newly isolated strain E1, identified as a Dietzia sp., proved to have an excellent ability to degrade n-C12 to n-C38 alkane components of crude oil. The preferred substrate was the very long-chain alkane n-eicosane at an optimal temperature of 37 degrees C and an optimal pH of 8 under aerobic conditions. The growth and substrate uptake kinetics were monitored during the n-alkane fermentation process, and Dietzia sp. E1 cells were found to possess three distinct levels of cell-surface hydrophobicity. Gas chromatographic/mass spectrometric analysis revealed that intracellular substrate mineralization occurred through the conversion of n-alkane to the corresponding n-alkanal. The monoterminal oxidation pathway was presumably initiated by AlkB and CYP153 terminal alkane hydroxylases, both of their partial coding sequences were successfully detected in the genome of strain E1, a novel member of the Dietzia genus. PMID:21319712

Bihari, Zoltán; Szabó, Zsolt; Szvetnik, Attila; Balázs, Margit; Bartos, Péter; Tolmacsov, Péter; Zombori, Zoltán; Kiss, István

67

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

68

A new strategy for alkane oxidation with O 2 using N ?hydroxyphthalimide (NHPI) as a radical catalyst  

Microsoft Academic Search

A practical catalytic method to convert alkanes into the corresponding oxygen-containing compounds with O2 under mild conditions using N-hydroxyphthalimide (NHPI) in the presence or absence of a transition metal was developed. Thus, cyclohexane was successfully converted into adipic acid in good conversion and selectivity by a combined catalytic system consisting of NHPI and Mn(acac)2. Lower alkane such as isobutane was

Yasutaka Ishii; Satoshi Sakaguchi

1999-01-01

69

Chemical Analog-to-Digital Signal Conversion Based on Robust Threshold Chemistry and Its Evaluation in the Context of Microfluidics-Based Quantitative Assays.  

PubMed

In this article, we describe a nonlinear threshold chemistry based on enzymatic inhibition and demonstrate how it can be coupled with microfluidics to convert a chemical concentration (analog input) into patterns of ON or OFF reaction outcomes (chemical digital readout). Quantification of small changes in concentration is needed in a number of assays, such as that for cystatin C, where a 1.5-fold increase in concentration may indicate the presence of acute kidney injury or progression of chronic kidney disease. We developed an analog-to-digital chemical signal conversion that gives visual readout and applied it to an assay for cystatin C as a model target. The threshold chemistry is based on enzymatic inhibition and gives sharper responses with tighter inhibition. The chemistry described here uses acetylcholinesterase (AChE) and produces an unambiguous color change when the input is above a predetermined threshold concentration. An input gives a pattern of ON/OFF responses when subjected to a monotonic sequence of threshold concentrations, revealing the input concentration at the point of transition from OFF to ON outcomes. We demonstrated that this threshold chemistry can detect a 1.30-fold increase in concentration at 22 °C and that it is robust to experimental fluctuations: it provided the same output despite changes in temperature (22-34 °C) and readout time (10-fold range). We applied this threshold chemistry to diagnostics by coupling it with a traditional sandwich immunoassay for serum cystatin C. Because one quantitative measurement comprises several assays, each with its own threshold concentration, we used a microfluidic SlipChip device to process 12 assays in parallel, detecting a 1.5-fold increase (from 0.64 (49 nM) to 0.96 mg/L (74 nM)) of cystatin C in serum. We also demonstrated applicability to analysis of patient serum samples and the ability to image results using a cell phone camera. This work indicates that combining developments in nonlinear chemistries with microfluidics may lead to development of user-friendly diagnostic assays with simple readouts. PMID:24060606

Huynh, Toan; Sun, Bing; Li, Liang; Nichols, Kevin P; Koyner, Jay L; Ismagilov, Rustem F

2013-09-24

70

Plant Cell Walls: Basics of Structure, Chemistry, Accessibility and the Influence on Conversion - Aqueous Pretreatment of Plant Biomass for Biological and Chemical Conversion to Fuels and Chemicals  

SciTech Connect

This book is focused on the pretreatment of biomass, a necessary step for efficient conversion of the plant cell wall materials to fuels and other products. Pretreatment is required because it is difficult to access, separate, and release the monomeric sugars comprising the biopolymers within the biomass that can be further upgraded to products through chemical processes such as aqueous phase reforming or biological routes such as fermentation of the sugars to ethanol This resistance to degradation or difficulty to release the monomers (mostly sugars) is commonly referred to as recalcitrance. There are many methods to overcome plant recalcitrance, but the underlying cause of the recalcitrance lies in the complex combination of chemical and structural features of the plant cell walls.

Davison, Brian H [ORNL; Davis, Dr. Mark F. [National Renewable Energy Laboratory (NREL); Parks, Jerry M [ORNL; Donohoe, Bryan [National Renewable Energy Laboratory (NREL)

2013-01-01

71

Exploratory study of coal-conversion chemistry. Quarterly report No. 8, February 19, 1983-May 18, 1983  

SciTech Connect

In Subtask A.3 the correlation between hydrogen-transfer promoted bond cleavage (solvent-mediated hydrogenolysis) in coal-model compounds and donor-solvent thermochemical parameters has been quantified and extended to the pyrene/dihydropyrene system. The results are in general, but not exact, agreement with the thermochemical analysis, which predicts sequential five-fold and three-fold increases in solvent-mediated hydrogenolysis on moving from 9,10-dihydroanthracene to 9,10-dihyrophenanthrene and 4,5-dihydropyrene. This analysis assumes that the solvent system provides the radical steady-state concentration. The possible additional effects of high initial concentrations of thermally generated coal radicals are discussed in light of the peculiarities of the pyrene system. Our efforts in Task B Conversion in CO/H/sub 2/O Systems were concentrated on Subtask B.2 this quarter. We initiated studies using D/sub 2/O/CO in place of H/sub 2/O/CO. Conversion of coal was enhanced in D/sub 2/O/CO under an equivalent CO conversion. We propose a rationale to account for this solvent isotope effect. Initial interpretation of the NMR work on the D/sub 2/O/CO products show that deuterium is preferentially incorporated into benzylic structural positions. These results are similar to other NMR studies using d/sub 12/-tetralin and D/sub 2/ as conversion medium. Appendixes A and B have been entered separately.

Ross, D.S.; McMillen, D.F.; Ogier, W.C.; Chang, S.J.; Hum, G.P.; Mansani, R.; Green, T.K.

1983-06-01

72

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

National Technical Information Service (NTIS)

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 o...

B. C. Gates

1996-01-01

73

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

74

Multiple alkane hydroxylase systems in a marine alkane degrader, Alcanivorax dieselolei B-5.  

PubMed

Alcanivorax dieselolei strain B-5 is a marine bacterium that can utilize a broad range of n-alkanes (C(5) -C(36) ) as sole carbon source. However, the mechanisms responsible for this trait remain to be established. Here we report on the characterization of four alkane hydroxylases from A. dieselolei, including two homologues of AlkB (AlkB1 and AlkB2), a CYP153 homologue (P450), as well as an AlmA-like (AlmA) alkane hydroxylase. Heterologous expression of alkB1, alkB2, p450 and almA in Pseudomonas putida GPo12 (pGEc47?B) or P. fluorescens KOB2?1 verified their functions in alkane oxidation. Quantitative real-time RT-PCR analysis showed that these genes could be induced by alkanes ranging from C(8) to C(36) . Notably, the expression of the p450 and almA genes was only upregulated in the presence of medium-chain (C(8) -C(16) ) or long-chain (C(22) -C(36) ) n-alkanes, respectively; while alkB1 and alkB2 responded to both medium- and long-chain n-alkanes (C(12) -C(26) ). Moreover, branched alkanes (pristane and phytane) significantly elevated alkB1 and almA expression levels. Our findings demonstrate that the multiple alkane hydroxylase systems ensure the utilization of substrates of a broad chain length range. PMID:21261799

Liu, Chenli; Wang, Wanpeng; Wu, Yehui; Zhou, Zhongwen; Lai, Qiliang; Shao, Zongze

2011-01-24

75

Exploratory study of coal-conversion chemistry. Quarterly report No. 5, May 19, 1982-August 18, 1982  

SciTech Connect

Initial runs of coal liquefaction products through the automatically switched, multicolumn, solvent-extraction/high-pressure liquid chromatography systems have been performed. This separation was followed by field ionization mass spectrometric analysis of the volatile portions of each of the separated fractions. The separation scheme is described, and results of one of the initial separations are summarized. The FIMS spectrum of one of the fractions (lower molecular weight nitrogen heterocycles) is presented and the types of information available from this less-than-ideal case (i.e., broad HPLC fraction) are discussed in the context of the objective of this subtask. We studied the thermolysis of bibenzyl in D/sub 2/O at 400/sup 0/C. The major products were toluene and stilbene. Minor products were benzene, ethylbenzene, styrene, diphenylmethane, and phenanthrene. The recovered bibenzyl and products contained significant quantities of deuterium. From the degree of deuterium incorporation, a statistical determination for a simple series of consecutive exchange reactions was derived. The reaction scheme involves an initial slow homolysis of the starting bibenzyl to yield benzyl radical, which, in turn, reacts with D/sub 2/O to form OD. OD then rapidly reacts with bibenzyl to yield bibenzyl radical, and the formed bibenzyl radical abstracts deuterium from the medium to form products. The chemistry suggested here demonstrates that water can act as an H-donor because it readily transfers hydrogen to organic free radicals. We further suggest that water can generate hydrogen atoms if CO is present.

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

1982-10-01

76

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

77

A New Extruded Alkane-Imide Wire.  

National Technical Information Service (NTIS)

A new sandwich construction insulation system consisting completely of polyimides was developed to meet the need for smaller and lighter weight wires. This required the synthesis of a new alkane-imide polymer. This polymer, in combination with other polyi...

V. L. Lanza R. M. Halperin

1969-01-01

78

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

2009-07-18

79

Exploratory study of coal conversion chemistry. Final report, May 18, 1981-May 17, 1984. [Solvent mediated hydrogenolysis  

SciTech Connect

Studies with model compounds demonstrated that very strong bonds can be broken under donor solvent liquefaction conditions. Therefore, the liquefaction of coals under these conditions does not have to be, as traditionally held, dependent on the thermal scission of inherently weak links in the coal structure. These studies also showed that the actual conversions of coal reported by a number of workers show a dependence on donor solvent C-H bond strength that is not in accord with the traditional mechanism, in which the donor solvent operates solely as a scavenger or ''capper'' of thermally generated coal radicals. We have shown that the coal liquefaction effectiveness of various solvents parallels much more closely the observed cleavage of these strong linkages in donor solvent. Therefore, we have suggested that this type of cleavage reaction, which we have labeled ''solvent mediated hydrogenolysis,'' is responsible for the bulk of coal structure fragmentation during donor solvent coal liquefaction. The class of linkages susceptible to the type of cleavage addressed here is very large and almost certainly dominant in coals, no matter what the exact details of their structures turn out to be. For this class of linkage, the results presented here show that cleavage results from the direct bimolecular transfer of hydrogen from hydroaromatic solvent radicals, ArH(dot), to the ipso position of the Ar-X linkage. This sequence is formally hydrogenolysis, but it takes place without the intervention of free hydrogen atoms and therefore without the conditions of high hydrogen pressure and high temperature and/or catalysts that are generally required to provide free H-atoms.

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

1984-12-01

80

Structural insights into diversity and n-alkane biodegradation mechanisms of alkane hydroxylases.  

PubMed

Environmental microbes utilize four degradation pathways for the oxidation of n-alkanes. Although the enzymes degrading n-alkanes in different microbes may vary, enzymes functioning in the first step in the aerobic degradation of alkanes all belong to the alkane hydroxylases. Alkane hydroxylases are a class of enzymes that insert oxygen atoms derived from molecular oxygen into different sites of the alkane terminus (or termini) depending on the type of enzymes. In this review, we summarize the different types of alkane hydroxylases, their degrading steps, and compare typical enzymes from various classes with regard to their three-dimensional structures, in order to provide insights into how the enzymes mediate their different roles in the degradation of n-alkanes and what determines their different substrate ranges. Through the above analyzes, the degrading mechanisms of enzymes can be elucidated and molecular biological methods can be utilized to expand their catalytic roles in the petrochemical industry or in bioremediation of oil-contaminated environments. PMID:23519435

Ji, Yurui; Mao, Guannan; Wang, Yingying; Bartlam, Mark

2013-03-21

81

Evolution of an alkane-inducible biosensor for increased responsiveness to short-chain alkanes.  

PubMed

Synthetic alkane-inducible biosensors have applications as detectors for environmental hydrocarbon contamination and as novel inducible expression systems with low-cost inducers. Here, we have assembled and evolved an alkane-responsive biosensor with a fluorescence output signal in Escherichia coli by utilizing regulatory machinery from Pseudomonas putida's alkane metabolism. Within our system, the transcriptional regulator, AlkSp, is activated by the presence of alkanes and binds to the P(alkB) promoter, stimulating transcription of a Green Fluorescent Protein reporter. Through two successive rounds of directed evolution via error prone PCR and fluorescence activated cell sorting, we isolated alkS mutants enabling up to a 5 fold increase in fluorescence output signal in response to short-chain alkanes such as hexane and pentane. Further characterization of selected mutants demonstrated altered responsiveness to a wide range of linear alkanes (pentane to dodecane). Sequence analysis highlighted the S470T mutation as a likely candidate responsible for increased effectiveness of the AlkS protein for short-chain alkanes. This work represents the first evolution of a synthetic biosensor system for alkanes. PMID:22326628

Reed, Ben; Blazeck, John; Alper, Hal

2012-02-02

82

Characterization of the hydrogen isotopic composition of individual n-alkanes in terrestrial source rocks  

Microsoft Academic Search

In order to characterize the H isotopic compositions of individual lipid compounds from different terrestrial depositional environments, the ?D values of C-bound H in individual n-alkanes from typical terrestrial source rocks of the Liaohe Basin and the Turpan Basin, China, were measured using gas chromatography–thermal conversion–isotope ratio mass spectrometry (GC–TC–IRMS). The analytical results indicate that the ?D values of individual

Yongqiang Xiong; Ansong Geng; Changchun Pan; Deyong Liu; Pingan Peng

2005-01-01

83

Enzymes and genes involved in aerobic alkane degradation.  

PubMed

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. PMID:23755043

Wang, Wanpeng; Shao, Zongze

2013-05-28

84

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

2013-09-29

85

Sophorolipids from Torulopsis bombicola as microbial surfactants in alkane fermentations  

Microsoft Academic Search

The possible role of sophorolipids from Torulopsis bombicola was investigated in alkane fermentation. Sophorolipids and related model compounds specifically stimulated the growth of strains of Torulopsis yeasts on insoluble alkanes and may act as a specific growth factor. There may be more than one way for a yeast to be stimulated to incorporate alkanes for growth.

Shigeo Inoue; Susumu Ito

1982-01-01

86

In situ detection of anaerobic alkane metabolites in subsurface environments.  

PubMed

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. PMID:23761789

Agrawal, Akhil; Gieg, Lisa M

2013-06-04

87

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

88

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

89

Alkanes and alkenes in marine benthic algae  

Microsoft Academic Search

Saturated and olefinic hydrocarbons were determined in additional species of benthic marine algae from the Cape Cod (Massachusetts, USA) area (see: Youngblood et al., 1971). The distribution of homologous and isomeric olefins was studied in plants of different age and in morphologically different parts of the same specimen. With two minor exceptions, only normal alkanes and alkenes are present. The

W. W. Youngblood; M. Blumer

1973-01-01

90

Analysis of pump oil and alkanes evaporation  

Microsoft Academic Search

There are many products, including hard drives, which require trace amounts, on the order of several mg, of lubricants for proper operation. The following study investigated the evaporation rates of pump oil and several alkanes, which have a wide range of applications, using a thermogravimetric machine. Both static and dynamic temperature tests were conducted. The rate of evaporation of the

Nathaniel A Waldstein

2008-01-01

91

Electrophilic Nitration of Alkanes with Nitronium Hexafluorophosphate  

NASA Astrophysics Data System (ADS)

Nitration of alkanes such as methane, ethane, propane, n-butane, isobutane, neopentane, and cyclohexane was carried out with nitronium hexafluorophosphate in methylene chloride or nitroethane solution. Nitration of methane, albeit in poor yield, required protolytic activation of the nitronium ion. The results indicate direct electrophilic insertion of NO2+ into C-H and C-C ? -bonds.

Olah, George A.; Ramaiah, Pichika; Surya Prakash, G. K.

1997-10-01

92

Accelerated Molecular Dynamics Simulation of Alkane Desorption  

NASA Astrophysics Data System (ADS)

Thermal desorption has been the focus of much surface science research. Studies of alkanes on graphite^1 and gold^2 have shown prefactors that are constant with alkane chain length but vary by over six orders of magnitude. Other studies on magnesium oxide^3 and gold^4 show a prefactor that increases with increasing chain length. We have developed an all-atom model to study alkane desorption from graphite. Transition state theory is used to obtain rate constants from the simulation. Accelerated MD is used to extend the desorption simulation to experimentally relevant temperatures. Our results show a prefactor that increases with increasing chain length. We predict that it will become constant as internal conformational changes occur significantly. We examine the effect of desorption environment through varying the alkane surface coverage. 1. K.R. Paserba and A.J. Gellman, J. Chem. Phys. 115, 6737 (2001). 2. S.M. Wetterer et al., J. Phys. Chem. 102, 9266 (1998). 3. S.L. Tait et al., J. Chem. Phys. 122, 164707 (2005). 4. K.A. Fichthorn and R.A. Miron, Phys. Rev. Lett. 89, 196103 (2002).

McLaughlin, Kelly; Fichthorn, Kristen

2006-03-01

93

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

94

The origin of alkanes found in human skin surface lipids.  

PubMed

Lipids extracted from human skin contain variable amounts of paraffin hydrocarbons. Although the composition of these alkanes strongly resembles petroleum waxes, it has been proposed that they are biosynthetic products of human skin. To investigate this question, skin surface lipids from 15 normal subjects were analyzed for the amount and composition of alkanes, using quantitative thin-layer chromatography and quartz capillary gas chromatography. The alkanes were found to constitute 0.5% to 1.7% of the skin lipids. Subjects differed greatly in the chain length distribution of their alkanes between 15 and 35 carbon atoms, and in the relative amounts of normal alkanes (like those in petroleum waxes) and branched chain alkanes (like those in petroleum lubricating oils). In 6 subjects, the alkane content of cerumen from each ear was examined to investigate whether alkanes arrive at the skin surface by a systemic route or by direct contact with environmental surfaces. No trace of alkanes was found in 11 of the 12 cerumen samples. Using a tandem accelerator mass spectrometer for carbon-14 dating, a combined sample of the skin surface alkanes was found to have a theoretical age of 30,950 years, similar to that of a sample of petrolatum. These analyses indicate that the alkanes found on the surface of human skin are mixtures of a variety of petroleum distillation fractions that are acquired by direct contamination from the environment. PMID:2584738

Bortz, J T; Wertz, P W; Downing, D T

1989-12-01

95

Cytochrome P450 Alkane Hydroxylases of the CYP153 Family Are Common in Alkane-Degrading Eubacteria Lacking Integral Membrane Alkane Hydroxylases  

Microsoft Academic Search

Several strains that grow on medium-chain-length alkanes and catalyze interesting hydroxylation and epoxidation reactions do not possess integral membrane nonheme iron alkane hydroxylases. Using PCR, we show that most of these strains possess enzymes related to CYP153A1 and CYP153A6, cytochrome P450 enzymes that were characterized as alkane hydroxylases. A vector for the polycistronic coexpression of individual CYP153 genes with a

Jan B. van Beilen; Enrico G. Funhoff; Alexander van Loon; Andrea Just; Leo Kaysser; Manuel Bouza; R. Holtackers; M. Rothlisberger; Z. Li; B. Witholt

2006-01-01

96

Basic Chemistry Review  

NSDL National Science Digital Library

This assignment reviews basic of chemistry for students who should have had 2 introductory semesters of basic chemistry prior to enrolling in the Fundamental of Water Quality course for which the assignment is used. Assignment reviews basic equation balancing and questions about valence and concentration conversion that students will confront regularly in any geochemistry course.

Meixner, Thomas

97

Alkane biosynthesis by decarbonylation of aldehydes catalyzed by a particulate preparation from Pisum sativum  

SciTech Connect

Mechanism of enzymatic conversion of a fatty acid to the corresponding alkane by the loss of the carboxyl carbon was investigated with particulate preparations from Pisum sativum. A heavy particulate preparation (sp. gr., 1.30 g/cm/sup 3/) isolated by two density-gradient centrifugation steps catalyzed conversion of octadecanal to heptadecane and CO. Experiments with (1-/sup 3/H, 1-/sup 14/C)octadecanal showed the stoichiometry of the reaction and retention of the aldehydic hydrogen in the alkane during this enzymatic decarbonylation. This decarbonylase showed an optimal pH of 7.0 and a K/sub m/ of 35 ..mu..M for the aldehyde. This enzyme was severly inhibited by metal ion chelators and showed no requirement for any cofactors. Microsomal preparations and the particulate fractions from the first density-gradient step catalyzed acyl-CoA reduction to the corresponding aldehyde. Electron microscopic examination showed the presence of fragments of cell wall/cuticle but no vesicles in the decarbonylase preparation. It is concluded that the aldehydes produced by the acyl-CoA reductase located in the endomembranes of the epidermal cells are converted to alkanes by the decarbonylase located in the cell wall/cuticle region. 20 references, 4 figures, 1 tables.

Cheesbourgh, T.M.; Kolattukudy, P.E.

1984-11-01

98

Alkane biosynthesis by decarbonylation of aldehydes catalyzed by a particulate preparation from Pisum sativum.  

PubMed Central

Mechanism of enzymatic conversion of a fatty acid to the corresponding alkane by the loss of the carboxyl carbon was investigated with particulate preparations from Pisum sativum. A heavy particulate preparation (sp. gr., 1.30 g/cm3) isolated by two density-gradient centrifugation steps catalyzed conversion of octadecanal to heptadecane and CO. Experiments with [1-3H,1-14C]octadecanal showed the stoichiometry of the reaction and retention of the aldehydic hydrogen in the alkane during this enzymatic decarbonylation. This decarbonylase showed an optimal pH of 7.0 and a Km of 35 microM for the aldehyde. This enzyme was severely inhibited by metal ion chelators and showed no requirement for any cofactors. Microsomal preparations and the particulate fractions from the first density-gradient step catalyzed acyl-CoA reduction to the corresponding aldehyde. Electron microscopic examination showed the presence of fragments of cell wall/cuticle but no vesicles in the decarbonylase preparation. It is concluded that the aldehydes produced by the acyl-CoA reductase located in the endomembranes of the epidermal cells are converted to alkanes by the decarbonylase located in the cell wall/cuticle region.

Cheesbrough, T M; Kolattukudy, P E

1984-01-01

99

Perspectives on some challenges and approaches for developing the next generation of selective, low temperature, oxidation catalysts for alkane hydroxylation based on the CH activation reaction  

Microsoft Academic Search

The development of selective, energy efficient direct alkane oxidation chemistry could lead to a new paradigm in materials and energy technologies in the 21st century that is environmentally and economically superior and allow the vast reserves of natural gas to be employed directly as feedstocks for fuels and chemicals. The use of homogeneous catalysts that activate and functionalize the CH

Roy A. Periana; Gaurav Bhalla; William J. Tenn; Kenneth J. H. Young; Xiang Yang Liu; Oleg Mironov; CJ Jones; Vadim R. Ziatdinov

2004-01-01

100

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

101

Electrophilic nitration of alkanes with nitronium hexafluorophosphate  

PubMed Central

Nitration of alkanes such as methane, ethane, propane, n-butane, isobutane, neopentane, and cyclohexane was carried out with nitronium hexafluorophosphate in methylene chloride or nitroethane solution. Nitration of methane, albeit in poor yield, required protolytic activation of the nitronium ion. The results indicate direct electrophilic insertion of NO2+ into C 000000000000 000000000000 000000000000 000000000000 111111111111 000000000000 000000000000 000000000000 000000000000 H and CC ?-bonds.

Olah, George A.; Ramaiah, Pichika; Prakash, G. K. Surya

1997-01-01

102

Oxidative dehydrogenation of alkanes to unsaturated hydrocarbons  

DOEpatents

Oxidative dehydrogenation of alkanes to unsaturated hydrocarbons is carried out over metal vanadate catalysts under oxidizing conditions. The vanadate catalysts are represented by the formulas M.sub.3 (VO.sub.4).sub.2 and MV.sub.2 O.sub.6, M representing Mg, Zn, Ca, Pb, or Cd. The reaction is carried out in the presence of oxygen, but the formation of oxygenate by-products is suppressed.

Kung, Harold H. (Wilmette, IL); Chaar, Mohamed A. (Homs, SY)

1988-01-01

103

Oxidative dehydrogenation of alkanes to unsaturated hydrocarbons  

DOEpatents

Oxidative dehydrogenation of alkanes to unsaturated hydrocarbons is carried out over metal vanadate catalysts under oxidizing conditions. The vanadate catalysts are represented by the formulas M[sub 3](VO[sub 4])[sub 2] and MV[sub 2]O[sub 6], M representing Mg, Zn, Ca, Pb, or Cd. The reaction is carried out in the presence of oxygen, but the formation of oxygenate by-products is suppressed.

Kung, H.H.; Chaar, M.A.

1988-10-11

104

Integrated process for preparing a carboxylic acid from an alkane  

Microsoft Academic Search

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,

Abraham Benderly; Nitin Chadda; Douglass Sevon

2011-01-01

105

Highly sensitive alkane odour sensors based on functionalised gold nanoparticles  

Microsoft Academic Search

We deposit dense, ordered, thin films of Au–dodecanethiol core\\/shell nanoparticles by the Langmuir–Schäfer (LS) printing method, and find that their resistance at ambient temperature responds selectively and sensitively to alkane odours. Response is a rapid resistance increase due to swelling, and is strongest for alkane odours where the alkane chain is similar in length to the dodecane shell. For decane

Hadi AlQahtani; Mark Sugden; Delia Puzzovio; Lee Hague; Nic Mullin; Tim Richardson; Martin Grell

106

Kinetics of alkane adsorption on a solid cracking catalyst  

Microsoft Academic Search

A microreactor technique is developed for a study of alkane chemisorption on solid cracking catalysts. Kinetics of adsorption–desorption processes can be observed at ca. 200°C; it manifests itself as extensive tailing of alkane peaks in gas chromatograms. A kinetic model of the adsorption process is developed. The model allows calculation of two kinetic parameters, those of alkane adsorption, ka[C*], and

Yury V Kissin

1998-01-01

107

The vapor-particle partitioning of n-alkanes  

Microsoft Academic Search

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 particles as microcrystalline solids and subcooled liquids, respectively. The fraction of n-alkanes on atmospheric particles having plant wax and petroleum origins is estimated

Doskey

1994-01-01

108

Chemistry of Tantalum Clusters in Solution And on SiO(2) 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.L.; Browning, N.D.; Gates, B.C.

2009-06-03

109

Effects of surfactants on bacteria and the bacterial degradation of alkanes in crude oil.  

National Technical Information Service (NTIS)

This thesis investigates the effects of surfactants on the bacterial degradation of alkanes in crude oil. Several alkane oxidising Gram positive and Gram negative were tested for their abilities to oxidise alkanes in crude oil emulsified with surfactants....

P. Bruheim

1998-01-01

110

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

SciTech Connect

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 engineered P450s, and (3) the changes in redox control resulting from protein engineering. To reach these goals, we have established new methods for determining the kinetics and stabilities of multicomponent P450s such as CYP153A6. Using these, we were able to determine that CYP153A6 is proficient for hydroxylation of alkanes as small as ethane, an activity that has never been observed previously in any natural P450. To elucidate the structures of the engineered P450s, we obtained x-ray diffraction data for two variants in the P450PMO (propane monooxygenase) lineage and a preliminary structure for the most evolved variant. This structure shows changes in the substrate binding regions of the enzyme and a reduction in active site volume that are consistent with the observed changes in substrate specificity from fatty acids in the native enzyme to small alkanes in P450PMO. We also constructed semi-rational designed libraries mutating only residues in the enzyme active site that in one round of mutagenesis and screening produced variants that achieved nearly half of the activity of the most evolved enzymes of the P450PMO lineage. Finally, we found that changes in redox properties of the laboratory-evolved P450 alkane hydroxylases did not reflect the improvement in their electron transfer efficiency. The heme redox potential remained constant throughout evolution, while activity increased and coupling efficiency improved from 10% to 90%. The lack of correlation between heme redox potential and enzyme activity and coupling efficiency led us to search for other enzyme properties that could be better predictors for activity towards small alkanes, specifically methane. We investigated the oxidation potential of the radical oxidants of various P450s directly using a chemical approach to generate the radical in situ. This resulted in the first report of direct methane to methanol conversion by a heme porphyrin catalyst using the soluble P450 from Mycobacterium sp, CYP153A6.

Arnold, Frances H.

2012-02-27

111

Resonant diffusion of normal alkanes in zeolites: effect of the zeolite structure and alkane molecule vibrations  

Microsoft Academic Search

Diffusion of normal alkanes in one-dimensional zeolites is theoretically studied on the basis of the stochastic equation formalism. The calculated diffusion coefficient accounts for the vibrations of the diffusing molecule and zeolite framework, molecule-zeolite interaction, and specific structure of the zeolite. It is shown that when the interaction potential is predominantly determined by the zeolite pore structure, the diffusion coefficient

Roumen Tsekov; Panagiotis G. Smirniotis

1998-01-01

112

An overview of dehydration, aldol-condensation and hydrogenation processes for production of liquid alkanes from biomass-derived carbohydrates  

Microsoft Academic Search

We present results for the conversion of carbohydrate feedstocks to liquid alkanes by the combination of dehydration, aldol-condensation\\/hydrogenation, and dehydration\\/hydrogenation processing. With respect to the first dehydration step, we demonstrate that HMF can be produced in good selectivity from abundantly available polysaccharides (such as inulin, sucrose) containing fructose monomer units using a biphasic batch reactor system. The reaction system can

Juben N. Chheda; James A. Dumesic

2007-01-01

113

Melting of Linear Alkanes between Swollen Elastomers and Solid Substrates.  

PubMed

We have measured the melting and freezing behavior of linear alkanes confined between cross-linked poly(dimethylsiloxane) (PDMS) elastomers and solid sapphire substrates. Small molecules are often used as lubricants to reduce friction or as plasticizers, but very little is directly known about the migration or changes in physical properties of these small molecules at interfaces, particularly the changes in transition temperatures upon confinement. Our previous studies highlighted striking differences between the crystal structure of confined and unconfined pentadecane crystals in contact with sapphire substrates. Here, we have used surface-sensitive infrared-visible sum-frequency-generation spectroscopy (SFG) to study the melting temperatures (Tm) of alkanes in nanometer thick interfacial regions between swollen PDMS elastomers in contact with sapphire substrate. We find that confined alkanes show depression in Tm compared to the melting temperature of unconfined bulk alkanes. The depression in Tm is a function of chain length, and these differences were smallest for shorter alkanes and largest for 19 unit long alkanes. In comparison, the DSC results for swollen PDMS elastomer show a broad distribution of melting points corresponding to different sizes of crystals formed within the network. The Tm for confined alkanes has been modeled using the combination of Flory-Rehner and Gibbs-Thomson models, and the depression in Tm is related to the thickness of the confined alkanes. These findings have important implications in understanding friction and adhesion of soft elastomeric materials and also the effects of confinement between two solid materials. PMID:24004088

Nanjundiah, Kumar; Dhinojwala, Ali

2013-09-17

114

Process for Converting Light Alkanes to Higher Hydrocarbons.  

National Technical Information Service (NTIS)

A process is disclosed for the production of aromatic-rich, gasoline boiling range hydrocarbons from the lower alkanes, particularly from methane. The process is carried out in two stages. In the first, alkane is treated with oxygen and hydrogen chloride ...

R. P. Noceti C. E. Taylor

1987-01-01

115

The use of semifluorinated alkanes in blood-substitutes.  

PubMed

Semifluorinated alkanes are useful for blood-substitutes in two different ways: as co-surfactant to stabilize emulsions with perfluorocarbons as oxygen-carrier and as oxygen-carrier instead of perfluorocarbons. Semifluorinated alkanes act as co-surfactants in low concentrations because they are enriched at the interface perfluorodecalin/water. Emulsions with semifluorinated alkanes dissolve about the same amount of oxygen as emulsions with perfluorocarbons. The stability of these emulsions depends on the nature of the alkyl and the perfluoroalkyl chain. Semifluorinated alkanes do not eliminate hydrogen fluoride under clean-up conditions of perfluorocarbons. According to toxicity tests against human carcinoma cells semifluorinated alkanes with alkyl chains are harmless in the examined range from C6 to C10. PMID:8117848

Meinert, H; Knoblich, A

1993-01-01

116

Sophorolipids from Torulopsis bombicola: possible relation to alkane uptake.  

PubMed Central

Torulopsis bombicola produces extracellular sophorolipids when it is grown on water-insoluble alkanes. Sophorolipids and related model compounds, which were not themselves used for growth, were found to stimulate markedly the growth of T. bombicola on alkanes. This stimulatory effect was restricted to growth on C10 to C20 alkanes, whereas no significantly influence was observed for growth on fatty alcohols, fatty acids, glucose, or glycerol. The nonionic methyl ester of the glycolipid supported the greatest cell yield. However, a number of synthetic nonionic surfactants were unable to replace the glycolipid. When organisms were grown on hexadecane, stimulation of growth by sophorolipids was observed almost exclusively with strains of Torulopsis yeasts. In contrast, the growth of other typical alkane-utilizing yeasts, such as candida and Pichia strains, was inhibited or not affected. It appears that sophorolipids are involved in alkane dissimilation by T. bombicola through an undetermined mechanism.

Ito, S; Inoue, S

1982-01-01

117

Sophorolipids from Torulopsis bombicola: possible relation to alkane uptake.  

PubMed

Torulopsis bombicola produces extracellular sophorolipids when it is grown on water-insoluble alkanes. Sophorolipids and related model compounds, which were not themselves used for growth, were found to stimulate markedly the growth of T. bombicola on alkanes. This stimulatory effect was restricted to growth on C10 to C20 alkanes, whereas no significantly influence was observed for growth on fatty alcohols, fatty acids, glucose, or glycerol. The nonionic methyl ester of the glycolipid supported the greatest cell yield. However, a number of synthetic nonionic surfactants were unable to replace the glycolipid. When organisms were grown on hexadecane, stimulation of growth by sophorolipids was observed almost exclusively with strains of Torulopsis yeasts. In contrast, the growth of other typical alkane-utilizing yeasts, such as candida and Pichia strains, was inhibited or not affected. It appears that sophorolipids are involved in alkane dissimilation by T. bombicola through an undetermined mechanism. PMID:7201782

Ito, S; Inoue, S

1982-06-01

118

Alkanes in benthic organisms from the Buccaneer oil field  

SciTech Connect

About 200 g per day of alkanes are present in brine discharged from each of two production platforms in the Buccaneer oil field in the NW Gulf of Mexico. These alkanes disperse rapidly in the water column, so that seawater concentrations of petroleum alkanes in this region are generally very low. They can be taken up to some extent by plankton, fish, and barnacles, but the petroleum alkane concentrations in these organisms are also relatively low. The largest pool of petroleum alkanes is in the surficial sediments, where concentrations of up to 25 ppM are observed, with concentration gradients extending more than 20 m from the production platforms. Organisms are examined which are exposed to these sediments and, for comparison, other specimens from control sites around structures from which there are no discharges.

Middleditch, B.S.; Basile, B.

1980-06-01

119

Generalized Flory theory for hard alkane fluids  

NASA Astrophysics Data System (ADS)

Generalized Flory-dimer (GF-D) theory is extended to hard n-alkane fluids modelled as fused hard spheres constrained according to the rotational isomeric state approximation. Theoretical predictions for the second to the fifth virial coefficients for each conformer from n-butane to n-octane are compared with numerical results. Predictions for the second viral coefficient are in excellent agreement with recent simulation results; however, GF-D theory systematically overpredicts the third virial coefficient and underpredicts the fourth and the fifth virial coefficients. GF-D predictions for the compressibility factor for n-alkanes from n-butane to n-octane are compared with molecular dynamic simulation results for a closely related model. Despite the over- and underprediction of the individual virial coefficients, excellent agreement is observed between theory and simulation for the compressibility factors of n-butane and n-pentane using no adjustable parameters. However, in the cases of n-hexane, n-heptane and n-octane, GF-D theory slightly underpredicts the pressure at high volume fractions. Theoretical considerations suggest that probably the predictions of GF-D theory will deteriorate with increasing chain length.

Mehta, Sameer D.; Honnell, Kevin G.

120

The Origin of Carbon-Bearing Volatiles in a Continental Hydrothermal System in the Great Basin: Water Chemistry and Isotope Characterizations  

NASA Astrophysics Data System (ADS)

Two processes are proposed for the observed isotope values of carbon-bearing compounds in SVHS: thermogenic production of alkane homologs and formation of CO_2 by AOM. The geological background and fluid chemistry are used to support this scenario.

Fu, Q.; Socki, R. A.; Niles, P. B.; Romanek, C.; Datta, S.; Darnell, M.

2012-03-01

121

Synthesis of optically pure 2-azido-1-arylethanols with isolated enzymes and conversion to triazole-containing beta-blocker analogues employing click chemistry.  

PubMed

Both antipodes of 2-azido-1-arylethanols were synthesized with excellent optical purity via enzymatic reduction of the corresponding alpha-azidoacetophenone derivatives catalyzed by a recombinant carbonyl reductase from Candida magnoliae ( CMCR) or an alcohol dehydrogenase from Saccharomyces cerevisiae ( Ymr226c). This provides an effective route to this class of important compounds in optically pure form. ( S)-2-Azido-1-( p-chlorophenyl)ethanols reacted with alkynes employing click chemistry to afford high yields of optically pure triazole-containing beta-adrenergic receptor blocker analogues with potential biological activity. PMID:18630881

Ankati, Haribabu; Yang, Yan; Zhu, Dunming; Biehl, Edward R; Hua, Ling

2008-07-16

122

Expanding the product profile of a microbial alkane biosynthetic pathway.  

PubMed

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. PMID:23656326

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

2012-09-26

123

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.; Chang, C.; Fogler, H.S. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering

1997-09-01

124

Correlation effects on the relative stabilities of alkanes.  

PubMed

The "alkane branching effect" denotes the fact that simple alkanes with more highly branched carbon skeletons, for example, isobutane and neopentane, are more stable than their normal isomers, for example, n-butane and n-pentane. Although n-alkanes have no branches, the "kinks" (or "protobranches") in their chains (defined as the composite of 1,3-alkyl-alkyl interactions-including methine, methylene, and methyl groups as alkyl entities-present in most linear, cyclic, and branched alkanes, but not methane or ethane) also are associated with lower energies. Branching and protobranching stabilization energies are evaluated by isodesmic comparisons of protobranched alkanes with ethane. Accurate ab initio characterization of branching and protobranching stability requires post-self-consistent field (SCF) treatments, which account for medium range (?1.5-3.0 Å) electron correlation. Localized molecular orbital second-order Møller-Plesset (LMO-MP2) partitioning of the correlation energies of simple alkanes into localized contributions indicates that correlation effects between electrons in 1,3-alkyl groups are largely responsible for the enhanced correlation energies and general stabilities of branched and protobranched alkanes. PMID:23909666

McKee, William C; Schleyer, Paul von Ragué

2013-08-22

125

Gene Structures and Regulation of the Alkane Hydroxylase Complex in Acinetobacter sp. Strain M-1  

PubMed Central

In the long-chain n-alkane degrader Acinetobacter sp. strain M-1, two alkane hydroxylase complexes are switched by controlling the expression of two n-alkane hydroxylase-encoding genes in response to the chain length of n-alkanes, while rubredoxin and rubredoxin ruductase are encoded by a single gene and expressed constitutively.

Tani, Akio; Ishige, Takeru; Sakai, Yasuyoshi; Kato, Nobuo

2001-01-01

126

High-order harmonic generation in alkanes  

SciTech Connect

We have investigated the process of high-order harmonic generation in light alkanes by using femtosecond laser pulses. We show the experimental results cannot be matched by a model that assumes a single active electron only in a hydrogenic s orbital. Clear evidences are shown of the important role played by the p-like character originating from the covalent C-H bond. By constructing a suitable mixture of s-type and p-type atomic wave functions, an excellent agreement between measurements in methane and simulations is found, thus confirming the validity of the developed method as a general tool for the analysis of high-order harmonic generation in complex molecules.

Altucci, C.; Velotta, R.; Heesel, E.; Springate, E.; Marangos, J. P.; Vozzi, C.; Benedetti, E.; Calegari, F.; Sansone, G.; Stagira, S.; Nisoli, M.; Tosa, V. [CNISM-Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Naples (Italy); Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); National Laboratory for Ultrafast and Ultraintense Optical Science, CNR, INFM, Department of Physics, Politecnico, Milan (Italy); NIRDINT, Donath Street 71-103, 400293 Cluj-Napoca (Romania)

2006-04-15

127

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

128

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

129

Degradation pathways of cyclic alkanes in Rhodococcus sp. NDKK48  

Microsoft Academic Search

The degradation pathways for cyclic alkanes ( c-alkanes) in Rhodococcus sp. NDKK48 were investigated. Strain NDKK48 used dodecylcyclohexane as a sole carbon and energy source, and five metabolites in the dodecylcyclohexane degradation pathway were detected by gas-chromatography\\/mass spectra. The metabolites were identified as cyclohexanecarboxylic acid, cyclohexylacetic acid, 1-cyclohexene-1-acetic acid, 4-dodecylcyclohexanol, and 4-dodecylcyclohexanone. The strain degrades dodecylcyclohexane via a ring oxidation

D. Koma; Y. Sakashita; K. Kubota; Y. Fujii; F. Hasumi; S. Y. Chung; M. Kubo

2004-01-01

130

Diffusion of 1-alkenes and cyclohexene in alkane solvents  

NASA Astrophysics Data System (ADS)

The translational diffusion constant, D, has been measured for each of the 1-alkenes 1-C 6H 12, 1-C 8H 16, 1-C 12H 24, and 1-C 14H 28 in each of the even n-alkanes n-C 6H 14- n-C 14H 30; the D values have also been measured for 1-C 10H 20 in each of the even n-alkanes n-C 8H 18- n-C 14H 30. Cyclohexene has been studied in each of the even n-alkanes n-C 8H 18- n-C 14H 30 and cyclohexane. Deviations from the Stokes-Einstein (SE) relation ( D = kBT/6 ??r) were found. For a given solute, the hydrodynamic radius r decreased as the viscosity ? increased. Analyses of literature data for n-alkane solutes in n-alkane solvents, including self-diffusion, also gave values of r that decreased as ? increased. These solvent-dependent r values are discussed in terms of the relative sizes of the solutes and solvents. The data also were analyzed using D/ T = A/ ?p ( p = 1 for the SE relation). The p values for the 1-alkenes and the n-alkane solutes with six or more carbon atoms were all <1 and were not a strong function of size; those for the 1-alkenes ranged from 0.637 ± 0.027 for 1-hexene to 0.725 ± 0.017 for 1-tetradecene. The p values for the analogous n-alkane solutes were roughly the same and indicated that the similar shapes and polarities of the two types of hydrocarbon play key roles in determining their diffusion. In the n-alkane solvents, the p value of the more globular cyclohexene is somewhat larger than those of both 1-hexene and n-hexane.

Kowert, Bruce A.; Turner, Robert M., II; Caldwell, Cassondra V. C.

2008-02-01

131

Intramolecular Excimer Formation. I. Diphenyl and Triphenyl Alkanes  

Microsoft Academic Search

Fluorescence spectra have been measured for a variety of diphenyl and triphenyl alkanes in cyclohexane and in p-dioxane. A class of compounds which are so structured that the phenyl groups along a main alkane chain are separated by exactly three carbon atoms, e.g., 1,3-diphenylpropane, 1,3,5-triphenylpentane, has been found to possess unique fluorescence characteristics. These are the appearance of a long-wavelength

Fumio Hirayama

1965-01-01

132

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

133

Modelling LLE and VLE of methanol + n-alkane series using GC-PC-SAFT with a group contribution k ij  

Microsoft Academic Search

The fluid phase diagrams (LLE and VLE) of methanol+n-alkane mixtures series (from C4 up to C16) were modelled using GC-PC-SAFT EOS (Tamouza et al., Fluid Phase Equilibria 222–223 (2004) 67–76) combined with a recent method for computing kij based on the London theory (NguyenHuynh et al., Industrial & Engineering Chemistry Research 47 (2008) 8847–8858). This latter method requires pure compound

M. Mourah; D. NguyenHuynh; J. P. Passarello; J. C. de Hemptinne; P. Tobaly

2010-01-01

134

DFT derived solvation models for organic compounds in alkane solvents  

NASA Astrophysics Data System (ADS)

From a density functional theory (DFT) analysis of solvation and the different components which comprise the free energy of solvation we propose quantitative structure property relationship (QSPR) models to predict free energy of solvation, ?GS0, of organic compounds in seven alkane solvents (n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, and n-hexadecane). The data contains 151 structurally different compounds containing diverse organic functions: unbranched and branched alkanes, cycloalkanes, aromatics, alcohols, aldehydes, ketones, esters, ethers, amines, nitriles, pyridines, fluorinated hydrocarbons, thiols, sulfides, carboxylic acids and nitro hydrocarbons; covering a ?GS0 range from about -50 to 0 kJ/mol. The models for the seven n-alkane solvents contain the same two molecular descriptors, one DFT descriptor (softness) and one geometric (molecular surface area). This fact suggests that the physical mechanisms behind the solvation of organic compounds in n-alkane solvents are of the same nature, as expected from the similar physical and chemical properties of alkanes. The models proposed have the merit of predicting free energy of solvation in alkane solvents with fewer descriptors than other QSPR models reported in the literature having similar statistics, allowing in this way a well-defined physical interpretation. The two descriptors have definite physical meaning corresponding to the different components which comprise free energy of solvation. Thus, the models proposed reach the desired compromise among simpleness, physical interpretation and computation time.

Delgado, Eduardo J.; Alderete, Joel B.; Jaña, Gonzalo A.

2006-06-01

135

The effect of liquid phase chemistry on growth of lead magnesium niobate-lead titanate single crystals by seeded polycrystal conversion  

NASA Astrophysics Data System (ADS)

The effect that liquid phase content and chemistry has on single crystal growth was investigated in this study. This was accomplished by determining the single crystal growth mechanism as well as studying the effect of hot pressing environment. Characterization techniques played a large role in deciphering the relevance of each effect. One such technique was used because x-ray absorption of oxygen is significant in thin specimens of Pb(Mg1/3Nb2/3 )O3-35 mol% PbTiO3 [PMN-35PT] due to the presence of Pb and Nb. Using only XEDS data, the zeta-factor method provides absorption corrected compositional information, which was helpful to fully characterize the liquid phase. It was shown that the compositional data were in very good agreement with the nominal values for PMN-35 PT, whereas the uncorrected data underestimated the oxygen content by 300%. This technique linked the swelling of samples to changes in the oxygen to lead ratio of the excess PbO due to hot-pressing in air. This observation corroborates the microstructural and x-ray diffraction data that was obtained. The influence of excess PbO on {001} single crystal growth was studied in the range of 0-10 vol% PbO. It was found that up to 1.5 vol% PbO, the amount of single crystal and grain growth increased with increasing PbO additions. At higher PbO contents, however, the growth becomes independent of liquid fraction for all annealing times. In addition since the matrix grains were faceted and the growth best fit parabolic kinetics, interface reaction control was deemed the most likely growth mechanism. It was also shown that the chemistry of the liquid phase was dynamic as characterized in an Analytical Electron Microscope. In fact, MgO was found to precipitate out of the system due the saturation of MgO in the liquid, which in turn altered the liquid/solid surface energy. By changing the energy of the system, the matrix grains become more faceted, i.e. the frequency of {100} surfaces increases. This reduces the driving force for growth of the single crystal, which appears to be responsible for reducing the growth rate during annealing.

Gorzkowski, Edward P., III

136

An analytical approximation for high-temperature autoignition times of higher alkanes  

SciTech Connect

It is shown that, above about 1000 K, ignition delay times for propane and all higher alkanes, as well as for a number of other fuels, can be calculated well by employing rate parameters of only three types of elementary steps, namely C{sub m}H{sub n} + HO{sub 2} {yields} C{sub m}H{sub n-1} + H{sub 2}O{sub 2}, H{sub 2}O{sub 2} + M{yields}2OH + M and 2HO{sub 2} {yields} H{sub 2}O{sub 2} + O{sub 2}, only the first of which is fuel specific, the other two clearly being common to all fuels. The prediction of this remarkably simple result relies on a steady-state approximation for HO{sub 2}, as well as steady states for more active radicals during induction. The resulting approximation to the chemistry exhibits a slow, finite-rate buildup of H{sub 2}O{sub 2} and removal of fuel during the induction period. The criterion employed for termination of the induction period is the complete depletion of the original fuel subject to the approximations introduced. Numerical comparisons of the ignition-time formula with the experiments show that the predictions work well not only for higher alkanes but also for propene and JP-10. The analytical approximation thus produces reasonable results for a wide range of fuels. (author)

Saxena, P.; Peters, N.; Williams, F.A. [Center for Energy Research, Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500, Gilman Drive, Department 0411, La Jolla, CA 92093 (United States)

2007-04-15

137

Activation of carbon-hydrogen bonds in alkanes and other organic molecules using organotransition metal complexes  

SciTech Connect

The potential for using alkanes-which are among the most chemically inert organic molecules-as feedstocks in chemical synthesis has stimulated a search for metal complexes capable of undergoing the C-H oxidative addition process shown in eq. (1), so that alkane chemistry more selective than that available using free radical reagents might be developed. Intramolecular C-H oxidative addition to metal centers has been known for some time, but despite M + R-H {yields} R-M-H (1) many efforts a direct observation of the corresponding intermolecular C-H oxidative addition process illustrated in eq. (1) was not uncovered until 1982. At that time our group and Graham's independently found that irradiation of complexes such as Cp*(L)lrH{sub 2}(1, Cp* = ({eta}{sup 5}-C{sub 5}Me{sub 5}). L = PMe{sub 3}) and Cp*lr(CO){sub 2} causes successful insertion of the Cp*lrL fragment into C-H bonds in alkanes, leading to stable alkyliridium hydride complexes Cp*(L)lr(R)(H)(2). This reaction is exceedingly general. So far no organic liquid in which Cp*(L)lrH{sub 2} has been irradiated has failed to react with the intermediate generated in the reaction. Much has been learned about the scope and mechanism of this reaction. Following the initial studies with iridium, alkane C-H oxidative addition has been observed at several other third-row transition metal centers (where M-H and M-R bonds are expected to be relatively strong), such as rhodium, rhenium, platinum, and osmium and even at one first-row metal (iron). The selectivity of the iridium and rhodium C-H oxidative addition reaction has been investigated by carrying out competition studies with various hydrocarbon substrates. Although the absolute magnitudes of the selectivities are different for lr and Rh, their trends are parallel, indicating that C-H oxidative additions proceed by similar mechanisms at these two metal centers, but that the Rh reactions are less exothermic than their lr counterparts. 14 refs., 1 fig.

Bergman, R.G.

1990-05-17

138

Brookhaven National Laboratory: Chemistry Department  

NSDL National Science Digital Library

At this website, the Brookhaven National Laboratory presents its chemistry research dealing primarily with imaging and neuroscience, charge transfer for energy conversion, chemistry with ionizing radiation, catalysis and surface science, nanoscience, combustion, and nuclear chemistry. Within each category, users can find instructive text and supportive images about the specific projects and the leading researchers. Visitors can learn about the Beamline U7A at the National Synchrotron Light Source, the Laser-Electron Accelerator Facility (LEAF), the Positron Emission Tomography (PET) Facility, and other exceptional research facilities. The website features histories of the chemistry department and of the Brookhaven National Laboratory.

139

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

140

40 CFR 721.10103 - Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear.  

Code of Federal Regulations, 2013 CFR

... false Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear. ...10103 Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear. ...identified as naphtha (fischer-tropsch), C4-11-alkane, branched and...

2013-07-01

141

40 CFR 721.10103 - Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear.  

Code of Federal Regulations, 2010 CFR

... false Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear. ...10103 Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear. ...identified as naphtha (fischer-tropsch), C4-11-alkane, branched and...

2009-07-01

142

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

143

Variation in n-Alkane Distributions of Modern Plants: Questioning Applications of n-Alkanes in Chemotaxonomy and Paleoecology  

NASA Astrophysics Data System (ADS)

Long chain n-alkanes (n-C21 to n-C37) are synthesized as part of the epicuticular leaf wax of terrestrial plants and are among the most recognizable and widely used plant biomarkers. n-Alkane distributions have been utilized in previous studies on modern plant chemotaxonomy, testing whether taxa can be identified based on characteristic n-alkane profiles. Dominant n-alkanes (e.g. n-C27 or n-C31) have also been ascribed to major plant groups (e.g. trees or grasses respectively) and have been used in paleoecology studies to reconstruct fluctuations in plant functional types. However, many of these studies have been based on relatively few modern plant data; with the wealth of modern n-alkane studies, a more comprehensive analysis of n-alkanes in modern plants is now possible and can inform the usefulness of n-alkane distributions as paleoecological indicators. The work presented here is a combination of measurements made using plant leaves collected from the Chicago Botanic Garden and a compilation of published literature data from six continents. We categorized plants by type: angiosperms, gymnosperms, woody plants, forbs, grasses, ferns and pteridophytes, and mosses. We then quantified n-alkane distribution parameters such as carbon preference index (CPI), average chain length (ACL), and dispersion (a measure of the spread of the profile over multiple chain lengths) and used these to compare plant groups. Among all plants, one of the emergent correlations is a decrease in dispersion with increasing CPI. Within and among plant groups, n-alkane distributions show a very large range of variation, and the results show little or no correspondence between broad plant groups and a single dominant n-alkane or a ratio of n-alkanes. These findings are true both when data from six continents are combined and when plants from a given region are compared (North America). We also compared the n-alkane distributions of woody angiosperms, woody gymnosperms, and grasses with one another in order to test whether n-C27 and n-C29 represent trees and shrubs while n-C31 represents grasses as previously proposed. The average group profiles are not distinguishable from one another due to their large standard deviations. Although n-C31 is the predominant chain length in many (but not all) grasses, other chain lengths such as n-C29 are also abundant. For grasses as a group one chain length does not dominate significantly over the other. In mosses, while the genus Sphagnum appears to be typified by n-C23 and n-C25 alkanes, the same cannot be said for other moss genera which were more dominated by n-C27 and n-C29. Differences in n-alkane distributions may relate more to environmental changes such as temperature and precipitation than to shifts in dominant plant types.

Bush, R. T.; McInerney, F. A.

2010-12-01

144

Conversion careers  

Microsoft Academic Search

The typical view of conversion used by social scientists and laypeople alike usually involves distinguishing only between gradual and abrupt conversions. This simplistic approach may be accompanied by an assumption that a conversion is a single passive event: most people have one conversion, and that one, whether fast or slow, happens to a person and lasts a lifetime. Such a

James T. Richardson

1980-01-01

145

Session: Energy Conversion  

SciTech Connect

This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of five presentations: ''Hydrothermal Energy Conversion Technology'' by David Robertson and Raymond J. LaSala; ''Materials for Geothermal Production'' by Lawrence E. Kukacka; ''Supersaturated Turbine Expansions for Binary Geothermal Power Plants'' by Carl J. Bliem; ''Geothermal Waster Treatment Biotechnology: Progress and Advantages to the Utilities'' by Eugen T. Premuzic; and ''Geothermal Brine Chemistry Modeling Program'' by John H. Weare.

Robertson, David; LaSala, Raymond J.; Kukacka, Lawrence E.; Bliem, Carl J.; Premuzic, Eugene T.; Weare, John H.

1992-01-01

146

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

PubMed

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.' PMID:23717304

Callaghan, Amy V

2013-05-14

147

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- and low-NOx conditions, in which alkyl peroxy radicals (RO2) react primarily with NO and HO2, respectively, for multiple initial alkane concentrations. Experiments were run until 95-100% of the initial alkane had reacted. Particle wall loss was evaluated as two limiting cases. SOA yield differed by 2 orders of magnitude 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. 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 concentrations 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.

2013-08-01

148

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

149

Reduction of nitrogen(I) oxide with carbon monoxide and C 3 –C 4 alkanes on Fe-containing zeolite catalysts  

Microsoft Academic Search

It is shown that in the presence of reducing agents — light alkanes (C3–C4) or carbon monoxide — the temperature for the elimination of nitrogen(I) oxide over iron-containing zeolite catalysts of various structural types (Y, M, pentasil) is reduced by 70–150 °C. In the presence of excess oxygen (SCR process conditions) a greater conversion of N2O(90–94%) is achieved at even

S. N. Orlik; T. M. Pidruchna

2005-01-01

150

Hydrocracking product distributions from n-alkanes and iso-alkanes  

SciTech Connect

Coonradt and Garwood have found that the rate of C-C bond splitting in n-hexadecane hydrocracking over platinum is at its maximum in the center of the molecule and decreases toward the ends. Other studies provide data on the hydrocarbon product decomposition under conditions such that the secondary alkane cracking reactions may be ignored. Qualitatively, all the data are in agreement with those obtained by Coonradt and Garwood. These results pose the question as to whether there are any quantitative laws of hydrocarbon decomposition which would hold true for different catalysts. In an earlier paper, the authors made an attempt to define such laws based on the composition of the products from n-decane hydrocracking on NiMo/Al/sub 2/O/sub 3/. The hydrocracking products were analyzed using a chromatograph employing a flame-ionization detector which supplied a signal proportional to the number of carbon atoms in the hydrocarbon molecule. It was found that the relative rates of the reactions, C/sub 10/ ..-->.. C/sub 1/ + C/sub 9/ and C/sub 10/ ..-->.. C/sub 2/ + C/sub 9/, depended upon the conditions of catalyst pretreatment. On the other hand, the relative peak areas for the C/sub 7/, C/sub 6/, and C/sub 5/ alkanes were constant in n-decane hydrocracking on Pt/Al/sub 2/O/sub 3/. Moreover, peaks of equal area were found for C/sub 6/, C/sub 7/, and C/sub 8/ components in the products from decomposition of C/sub 11/H/sub 24/, and for C/sub 6/, C/sub 7/, C/sub 8/, and C/sub 9/ components in the products from decomposition of C/sub 12/H/sub 26/. These results are discussed along with an equation which enables one to forecast the yields of various hydrocarbons in the decomposition of alkanes. 5 references.

Goldfarb, Yu.Ya.; Katsobashvili, Ya. R.; Rozenthal, A.L.

1986-10-01

151

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....

152

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

153

Effect of chlorinated alkanes on hepatic triglyceride secretion.  

PubMed

The effect of a series of monochloroalkanes (1-chloropropane through 1-chlorohexane) and a series of dichloroalkanes (1,2-dichloroethane through 1,5-dichloropentane) on hepatic triglyceride secretion in vivo and in vitro was investigated. It was demonstrated that a dose related decrease in hepatic triglyceride secretion is a common effect produced by both series of chlorinated alkanes. Using isolated hepatocytes a positive correlation between chlorinated alkane potency and increasing solvent lipid solubility was observed. However, this order of potency did not correlate with in vivo findings in which the less lipid soluble solvents were found to be the most potent. Possible reasons for the discrepancy between the two systems are proposed. It is suggested that the lipophilicity of the chlorinated alkanes may be important factor in solvent induced inhibition in triglyceride secretion. PMID:3823612

Selan, F M; Evans, M A

1987-02-01

154

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

1996-12-01

155

Green Chemistry  

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, green chemistry links (including conferences), and an online preview of the ACS-published book Real-World Cases in Green Chemistry are all found at the site. Five video clips on green chemistry from the standpoint of academia, industry, and small business are also featured (Windows Media Player). 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. Check back often for updates.

2002-01-01

156

Characterization of polychlorinated alkane mixtures—a Monte Carlo modeling approach  

Microsoft Academic Search

A Monte Carlo model was developed to characterize the molecular composition of polychlorinated alkane mixtures. The model\\u000a is based upon a simulation of the free-radical chlorination process by which polychlorinated alkane mixtures are produced\\u000a industrially from n-alkanes. In the model, the free-radical chlorination reaction was simulated by randomly selecting a position on a partially\\u000a converted alkane molecule for target by

Soren R. Jensen; Wayne A. Brown; Ester Heath; David G. Cooper

2007-01-01

157

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

158

Modeling of alkane emissions from a wood stain  

SciTech Connect

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 function of time after the application of the wood stain. It was found that the test house concentrations can be simulated by an integrated IAQ model which takes into consideration source, sink, and ventilation effects. The alkane emissions were controlled by an evaporation-like process.

Chang, J.C.S.; Guo, Z.

1993-01-01

159

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

160

Regioselective alkane hydroxylation with a mutant AlkB enzyme  

SciTech Connect

AlkB from Pseudomonas putida was engineered using in-vivo directed evolution to hydroxylate small chain alkanes. Mutant AlkB-BMO1 hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. Mutant AlkB-BMO2 similarly hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. These biocatalysts are highly active for small chain alkane substrates and their regioselectivity is retained in whole-cell biotransformations.

Koch, Daniel J.; Arnold, Frances H.

2012-11-13

161

Solvent effects on the thermal reaction of photochromic dihydroindolizines: Friction or polarizability effect within the alkanes  

Microsoft Academic Search

The thermal reaction to a photochromic dihydroindolizine was studied in six alkane solutions. The reaction rate in the branched iso-octane compared to that in n-alkanes shows a distinct effect of the molecular shape of the solvent. This effect could be rationalized both by solvent friction as well as by solvent polarizability effects. The rates in all the alkanes, however, form

K. Dernbecher; G. Gauglitz

1992-01-01

162

Overview of coal conversion  

SciTech Connect

The structure of coal and the processes of coal gasification and coal liquefaction are reviewed. While coal conversion technology is not likely to provide a significant amount of synthetic fuel within the next several years, there is a clear interest both in government and private sectors in the development of this technology to hedge against ever-diminishing petroleum supplies, especially from foreign sources. It is evident from this rather cursory survey that there is some old technology that is highly reliable; new technology is being developed but is not ready for commercialization at the present state of development. The area of coal conversion is ripe for exploration both on the applied and basic research levels. A great deal more must be understood about the reactions of coal, the reactions of coal products, and the physics and chemistry involved in the various stages of coal conversion processes in order to make this technology economically viable.

Clark, B.R.

1981-03-27

163

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

164

Conversion disorder  

MedlinePLUS

Conversion disorder is a mental health condition in which a person has blindness, paralysis, or other nervous ... Conversion disorder symptoms may occur because of a psychological conflict. Symptoms usually begin suddenly after a stressful ...

165

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents background information, laboratory procedures, classroom materials/activities, and chemistry experiments. Topics include sublimation, electronegativity, electrolysis, experimental aspects of strontianite, halide test, evaluation of present and future computer programs in chemistry, formula building, care of glass/saturated calomel…

School Science Review, 1983

1983-01-01

166

Chemistry Notes.  

ERIC Educational Resources Information Center

|Presents background information, laboratory procedures, classroom materials/activities, and chemistry experiments. Topics include sublimation, electronegativity, electrolysis, experimental aspects of strontianite, halide test, evaluation of present and future computer programs in chemistry, formula building, care of glass/saturated calomel…

School Science Review, 1983

1983-01-01

167

Forensic Chemistry  

Microsoft Academic Search

“Forensic chemistry” is a broad term that, if taken literally, would encompass most of the functions within a crime laboratory.\\u000a Techniques used in forensic chemistry are also used by the toxicology and trace analysis sections. However, forensic chemistry\\u000a generally refers to controlled substance or drug analysis.

Donnell Christian

168

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

169

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

170

Influence of the Distribution General Shape of n-Alkane Molar Concentrations on the Structural State of Multi-Alkane Mixtures  

Microsoft Academic Search

X-ray diffraction analyses were carried out on four commercial multi-alkane samples and their fifty-fifty weight mixtures which present molar concentration distributions of the “normal logarithmic” type: all these systems form a single solid phase which is isostructural to the ?? ordered intermediate solid solution of n-alkane binary molecular alloys: they are the n-alkanes with carbon atom numbers, n, close to

V. Chevallier; A. J. Briard; D. Petitjean; N. Hubert; M. Bouroukba; M. Dirand

2000-01-01

171

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...

172

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...

173

Sampling artifact estimates for alkanes, hopanes, and aliphatic carboxylic acids  

NASA Astrophysics Data System (ADS)

Sampling artifacts for molecular markers from organic speciation of particulate matter were investigated by analyzing forty-one samples collected in Philadelphia as a part of the Northeast Oxidant and Particulate Study (NEOPS). Samples were collected using a high volume sampler with two quartz fiber filters in series. n-Alkanes (C23-C31), hopanes (C27-C31), and n-alkanoic acids (C10-C22) were analyzed by gas chromatography-mass spectrometry (GCMS). The extent of artifact error was dependent on vapor pressure and species concentration. Particulate organic species are classified into the following three categories: (1) the amount collected on the backup filter was often a large fraction of the amount collected on the front filters ( n-alkanes C23 and C24, n-carboxylic acids C10-C14); (2) the amount collected on the backup filter was consistently a small fraction of the amount collected on the front filter ( n-alkanes C25-C28, hopanes C27-C30, n-carboxylic acids C15-C18, and dicarboxylic acids C3-C9); (3) the species was rarely observed on backup filters ( n-alkanes C29-C31, hopanes C31 and C32).

Sihabut, Tanasri; Ray, Joshua; Northcross, Amanda; McDow, Stephen R.

174

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

175

Decarboxylative Allylation using Sulfones as Surrogates of Alkanes  

PubMed Central

?-Sulfonyl functional groups are traceless activating groups that facilitate catalytic decarboxylative allylations in high yield, yet can be cleaved to allow the synthesis of simple allylated alkanes. Substrate studies suggest that decarboxylation to form an ?–sulfonyl anion is rate-limiting. Furthermore, the anion is formed regiospecifically under formally neutral conditions.

Weaver, Jimmie D.; Tunge, Jon A.

2009-01-01

176

Johari-Goldstein secondary relaxation in methylated alkanes  

NASA Astrophysics Data System (ADS)

Dielectric relaxation measurements of the methylated alkanes, 3-methylpentane, 3-methylheptane, 4-methylheptane, 2,3-dimethylpentane, and 2,4,6-trimethylheptane by S. Shahriari, A. Mandanici, L-M Wang, and R. Richert [J. Chem. Phys. 121, 8960 (2004)] have found a primary ? relaxation of these glass-forming liquids and a slow secondary ? relaxation that are in close proximity to each other on the frequency scale. These glass formers have one or more methyl groups individually attached to various carbons on the alkane chain. They cannot contribute to such a slow secondary relaxation. Hence the observed secondary relaxations is not intramolecular in origin and, similar to secondary relaxations found in rigid molecules by Johari and Goldstein, they are potentially important in the consideration of a mechanism for the glass transition. These secondary relaxations in the methylated alkanes are special and belong to the class of Johari-Goldstein in a generalized sense. The coupling model has predicted that its primitive relaxation time should be approximately the same as the relaxation time of the secondary relaxation if the latter is of the Johari-Goldstein kind. This prediction has been shown to hold in many other glass formers. The published data of the methylated alkanes provide an opportunity to test this prediction once more. The results of this work confirm the prediction.

Ngai, K. L.

2005-06-01

177

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

178

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

179

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

180

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.

181

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

182

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

183

Energy conversion and storage program  

NASA Astrophysics Data System (ADS)

The Energy Conversion and Storage Program applies chemical and chemical engineering 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 storage; (4) characterization of complex chemical processes; and (5) the application of novel materials for energy conversion and transmission. Projects focus on transport-process principles, chemical kinetics, thermodynamics, separation processes, organic and physical chemistry, and advanced methods of analysis. The following five areas are discussed: electrochemical energy storage and conversion; microstructured materials; biotechnology; fossil fuels; and high temperature superconducting processing. Papers have been processed separately for inclusion on the data base.

1990-12-01

184

Surface vibrational structure at alkane liquid/vapor interfaces  

NASA Astrophysics Data System (ADS)

Broadband vibrational sum frequency spectroscopy (VSFS) has been used to examine the surface structure of alkane liquid/vapor interfaces. The alkanes range in length from n-nonane (C9H20) to n-heptadecane (C17H36), and all liquids except heptadecane are studied at temperatures well above their bulk (and surface) freezing temperatures. Intensities of vibrational bands in the CH stretching region acquired under different polarization conditions show systematic, chain length dependent changes. Data provide clear evidence of methyl group segregation at the liquid/vapor interface, but two different models of alkane chain structure can predict chain length dependent changes in band intensities. Each model leads to a different interpretation of the extent to which different chain segments contribute to the anisotropic interfacial region. One model postulates that changes in vibrational band intensities arise solely from a reduced surface coverage of methyl groups as alkane chain length increases. The additional methylene groups at the surface must be randomly distributed and make no net contribution to the observed VSF spectra. The second model considers a simple statistical distribution of methyl and methylene groups populating a three dimensional, interfacial lattice. This statistical picture implies that the VSF signal arises from a region extending several functional groups into the bulk liquid, and that the growing fraction of methylene groups in longer chain alkanes bears responsibility for the observed spectral changes. The data and resulting interpretations provide clear benchmarks for emerging theories of molecular structure and organization at liquid surfaces, especially for liquids lacking strong polar ordering.

Esenturk, Okan; Walker, Robert A.

2006-11-01

185

Chemistry explained by topology: an alternative approach.  

PubMed

Molecular topology can be considered an application of graph theory in which the molecular structure is characterized through a set of graph-theoretical descriptors called topological indices. Molecular topology has found applications in many different fields, particularly in biology, chemistry, and pharmacology. The first topological index was introduced by H. Wiener in 1947 [1]. Although its very first application was the prediction of the boiling points of the alkanes, the Wiener index has demonstrated since then a predictive capability far beyond that. Along with the Wiener index, in this paper we focus on a few pioneering topological indices, just to illustrate the connection between physicochemical properties and molecular connectivity. PMID:21375503

Galvez, Jorge; Villar, Vincent M; Galvez-Llompart, Maria; Amigó, José M

2011-05-01

186

Solar energy conversion by water photodissociation  

Microsoft Academic Search

Some aspects of the photochemical conversion of solar energy by simple nonbiological systems are discussed. The basic concepts of direct and catalyzed photodissociation of water are outlined. Water dissociation in closed-cycle processes based on endothermic photochemical reactions offers a potential solution to the problem of solar energy conversion. It is shown that transition metal commplexes whose excited state chemistry is

V. Balzani; L. Moggi; M. F. Manfrin; F. Bolletta; M. Gleria

1975-01-01

187

Photoelectroconversion by Semiconductors: A Physical Chemistry Experiment  

Microsoft Academic Search

A physical chemistry experiment illustrating photochemistry, cyclic voltammetry, the properties of semiconductors, and surface chemistry is described. The experiment consists of constructing a liquid-junction photochemical cell, determining the cell parameters, then modifying the surface of the electrode to enhance the conversion efficiency of the cell. The students will learn some fundamental physical and chemical principles related to light and electricity

Qinbai Fan; Debra Munro; L. M. Ng

1995-01-01

188

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

189

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

190

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

191

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

192

Doing Chemistry  

NSDL National Science Digital Library

This website includes over 150 chemistry experiments in the following areas: Atomic Structure, Bonding, Chemical Reactions, Colligative Properties, Condensed States, Electrochemistry, Equilibrium Gases, Instrumentation, Limiting Reactant and more.

Brooks, David W.

2010-05-25

193

Process for converting light alkanes to higher hydrocarbons  

SciTech Connect

A process is disclosed for the production of aromatic-rich, gasoline boiling range hydrocarbons from the lower alkanes, particularly from methane. The process is carried out in two stages. In the first, alkane is treated with oxygen and hydrogen chloride over an oxyhydrochlorination catalyst such as copper chloride with minor proportions of potassium chloride and rare earth chloride. This produces an intermediate gaseous mixture containing water and contacted with a crystalline aluminosilicate catalyst in the hydrogen or metal promoted form to produce gasoline range hydrocarbons with a high proportion of aromatics and a small percentage of light hydrocarbons (C/sub 2/-C/sub 4/). The light hydrocarbons can be recycled for further processing over the oxyhydrochlorination catalyst. 3 figs.

Noceti, R.P.; Taylor, C.E.

1987-03-04

194

Binary diffusion coefficients of low-density mixtures of alkanes  

NASA Astrophysics Data System (ADS)

The aim of this study is to present a reliable procedure for the calculation of the temperature dependencies of binary diffusion coefficients DAB of low-density mixtures of small alkanes CmH2m+2 (m<6) by means of the (nAB-6) Lennard Jones temperature dependent potential (LJTDP) in the temperature range 200 - 1200 K and pressures p <=0.10MPa. The parameters of the potential of interaction of unlike particles - potential well depth epsilonAB(T) and equilibrium distance RmAB(T) are obtained from corresponding pure alkanes potential parameters using the Hohm-Zarkova-Damyanova (HZD) mixing rule. A good agreement between the calculated and experimental values is obtained for those systems for which direct measurements and recalculations from mixture viscosity data are available.

Zarkova, L.; Hohm, U.; Damyanova, M.

2008-05-01

195

Melting of thin films of alkanes on magnesium oxide  

NASA Astrophysics Data System (ADS)

Recent incoherent neutron scattering investigations of the dynamics of thin alkane films adsorbed on the Magnesium Oxide (100) surface are reported. There are marked differences in the behaviour of these films, as a function of temperature and coverage, compared to similar measurements on graphite. In particular, it has previously been shown that adsorbed multilayer films on graphite exhibit an interfacial solid monolayer that coexists with bulk-like liquid, well above the bulk melting point. In contrast, these studies show that the alkane films on MgO exhibit no such stabilization of the solid layer closest to the substrate as a function of the film thickness, even though the monolayer crystal structures are remarkably similar. These studies are supported by extensive thermodynamic data, a growing body of structural data from neutron diffraction and state of the art computer modelling

Arnold, T.; Barbour, A.; Chanaa, S.; Cook, R. E.; Fernandez-Canato, D.; Landry, P.; Seydel, T.; Yaron, P.; Larese, J. Z.

2009-02-01

196

Visualizing Conversation  

Microsoft Academic Search

Although the archive of text generated by a persistent conversation (i.e. newsgroup, mailing list, recorded chat, etc.) is searchable, it is not very expressive of the underly- ing social patterns. In this paper we will discuss the design of graphical interfaces that reveal the social structure of the conversation by visualizing patterns such as bursts of activity, the arrival of

Judith S. Donath; Karrie Karahalios; Fernanda B. Viégas

1999-01-01

197

Alkane derivative-bacteriorhodopsin interaction: proton transport and protein structure.  

PubMed

The effects of alkane derivatives, 1-alcohols (ROH), aliphatic amine hydrochlorides (RNH(2).HCl) and sodium aliphatic carboxylates (ROONa), on the proton pumping activity of bacteriorhodopsin (bR) in a purple membrane have been examined. Photocurrents in bR in the purple membrane adsorbed onto polyester thin film were recorded before and after exposure to these test substances. The peak photocurrent in bR was reversibly suppressed by each substance. From the dose-response curve, the concentrations required to reduce the peak capacitive current by 50% were determined for each homolog and then the standard free energies per CH(2) for the adsorption of the alkane derivatives to the site of action were estimated: -3.13 kJ mol(-1) for ROH, -3.05 kJ mol(-1) for RNH(3)(+), and -2.95 kJ mol(-1) for ROO(-). The proton pumping activity of bR was mainly suppressed by the hydrophobic interaction with the additive. The relative potencies of the functional groups of the alkane derivatives were almost comparable between 1-octanol (C(8)OH) and octylamine hydrochloride (C(8)NH(3)(+)) and about 10 times less effective for sodium octanoate (C(8)OO(-)) than for others. The addition of C(8)OH or C(8)OO(-) changed the absorption spectra of bR with a maximum at 560 nm to the spectra of the intermediate state with a maximum at 480 nm, while the C(8)NH(3)(+) decreased the intensity of the 560 nm band only with no blue-shift by the 480 nm band. We conclude that the action of the alkane derivatives is nonspecific and directed to all organized purple membrane structures and that the binding sites of the ROH and ROO(-) are different from that of RNH(3)(+). PMID:11438238

Shibata, A; Ikema, H; Ueno, S; Muneyuki, E; Higuti, T

2001-09-01

198

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

199

Propagation and extinction of premixed C-Cn-alkane flames  

Microsoft Academic Search

Laminar flame speeds and extinction strain rates of premixed C-Cn-alkane flames were determined at atmospheric pressure and elevated unburned mixture temperatures, over a wide range of equivalence ratios. Experiments were performed in the counterflow configuration and flow velocities were measured using Laser Doppler Velocimetry. The laminar flame speeds were obtained using a non-linear extrapolation technique utilizing numerical simulations of the

Chunsheng Ji; Enoch Dames; Yang L. Wang; Hai Wang; Fokion N. Egolfopoulos

2010-01-01

200

Evaporation rates of alkanes and alkanols from acoustically levitated drops  

Microsoft Academic Search

Evaporation constants of acoustically levitated drops from the homologue series of n-alkanes and 1-alkanols in ambient air have been evaluated by size and temperature measurements. The size of the pure liquid drops, within a diameter range of 0.1 to 2.5 mm, was monitored using a CCD camera, while temperature measurements were carried out by IR thermography. During drop evaporation, water

Rudolf Tuckermann; Sigurd Bauerecker; Bernd Neidhart

2002-01-01

201

Cold-tolerant alkane-degrading Rhodococcus species from Antarctica  

Microsoft Academic Search

Bioremediation is a possible mechanism for clean-up of hydrocarbon-contaminated soils in the Antarctic. Microbes indigenous\\u000a to the Antarctic are required that degrade the hydrocarbon contaminants found in the soil, and that are able to survive and\\u000a maintain activity under in situ conditions. Alkane- degrading bacteria previously isolated from oil-contaminated soil from around Scott Base, Antarctica,\\u000a grew on a number of

Asim K. Bej; David Saul; Jackie Aislabie

2000-01-01

202

Evolution of tricyclic alkanes in the Espirito Santo Basin, Brazil  

Microsoft Academic Search

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 Cââ to Cââ were present throughout the sequence as a mixture of stereoisomers whose relative abundance changed with depth. The epimerization rates were

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

1986-01-01

203

Evolution of tricyclic alkanes in the Espirito Santo Basin, Brazil  

Microsoft Academic Search

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

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

1986-01-01

204

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

205

Johari-Goldstein secondary relaxation in methylated alkanes  

Microsoft Academic Search

Dielectric relaxation measurements of the methylated alkanes, 3-methylpentane, 3-methylheptane, 4-methylheptane, 2,3-dimethylpentane, and 2,4,6-trimethylheptane by S. Shahriari, A. Mandanici, L-M Wang, and R. Richert [J. Chem. Phys. 121, 8960 (2004)] have found a primary alpha relaxation of these glass-forming liquids and a slow secondary beta relaxation that are in close proximity to each other on the frequency scale. These glass formers

K. L. Ngai

2005-01-01

206

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

207

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

208

Modeling the role of alkanes, polycyclic aromatic hydrocarbons, and their oligomers in secondary organic aerosol formation.  

PubMed

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 over the United States. Oxidation of alkanes is predicted to produce more aerosol than oxidation of PAHs driven by relatively higher alkane emissions. SOA from alkanes and PAHs, although small in magnitude, can be a substantial fraction of the SOA from anthropogenic hydrocarbons, particularly in winter, and could contribute more if emission inventories lack intermediate volatility alkanes (>C(13)) or if the vehicle fleet shifts toward diesel-powered vehicles. The SOA produced from oxidation of alkanes correlates well with ozone and odd oxygen in many locations, but the lower correlation of anthropogenic oligomers with odd oxygen indicates that models may need additional photochemically dependent pathways to low-volatility SOA. PMID:22568386

Pye, Havala O T; Pouliot, George A

2012-05-08

209

Probing the structure of liquids with 129Xe NMR spectroscopy: n-alkanes, cycloalkanes, and branched alkanes.  

PubMed

The liquid organization of linear, branched, and cyclic alkanes was studied using atomic (129)Xe as a NMR probe. (129)Xe chemical shifts have been experimentally determined for xenon dissolved in a total of 21 alkanes. In order to allow the comparison of the different solvents at similar thermodynamic conditions, the measurements were performed over a wide range of temperatures, from the melting point of the solvent up to 350 K. The results were rationalized in terms of the density, nature, and organization of the chemical groups within xenon's coordination sphere. Additionally, molecular dynamics simulations were performed using established atomistic force fields to interpret and clarify the conclusions suggested by the experimental results. The analysis is able to interpret previous results in the literature for ethane and propane at very different experimental conditions. PMID:23834349

Morgado, Pedro; Bonifácio, Rui; Martins, Luís F G; Filipe, Eduardo J M

2013-07-22

210

Comparison of n-alkanes or chromium oxide methods for estimation of herbage intake by sheep  

Microsoft Academic Search

Herbage intake (HI) was estimated with two procedures: (a) with the n-alkanes method (HIal), which combines the use of odd-chain n-alkanes, naturally occurring in plants, and dosed even-chain n-alkanes, as internal and external markers, respectively; (b) with the ratio between faecal excretion, estimated with chromium sesquioxide (Cr2O3), and the herbage indigestibility, estimated in vitro (HICr). The two techniques were compared

E. Piasentier; S. Bovolenta; F. Malossini; P. Susmel

1995-01-01

211

Alkanes, Terpanes, and Aromatic Hydrocarbons in Surficial Sediments of Halifax Harbor  

Microsoft Academic Search

Hydrocarbons were quantified in surficial sediments of Halifax Harbor. Alkanes ranging from nC-15 to nC-33 were detected in all samples at a mean concentration of 23.2 - 12.3 w g\\/g, dry. A lower mean concentration of 7.0 - 3.3 w g\\/g, dry, was observed for the smaller nC-15 to nC-22 alkanes, which represented between 15% and 60% of summed alkanes.

J. Hellou; S. Steller; J. Leonard; J. Albaiges

2002-01-01

212

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

213

Comparisons of Completeness of Combustion for Alcohol and Alkane Laminar Wall Fires  

Microsoft Academic Search

Steady, fully burning wall fires were studied using alkanes (n-pentane, n-hexane, and n-heptane) burning in air. Completeness of combustion was characterized and evaluated for the three alkanes studied and was compared with results previously obtained for alcohols (methanol, I-propanol, and I-butanol) burning in air. When the alkanes were burred, with CO and CO2 the principal carbon-containing products, less than 15%

S. F. MALARY; J. K. AWAD

1991-01-01

214

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

215

The occurrence of alkanes in fulvic acid, a soil humic fraction  

Microsoft Academic Search

Normal plus branched-cyclic alkanes were found to account for a maximal 0.16 per cent of the weight of a water-soluble soil fulvic acid. Only 3 per cent of the total alkanes could be extracted by hexane, benzene and ethyl acetate from untreated solid fulvic acid. Nheptane extracted approximately 12 per cent of the total alkanes from a solution of fulvic

Gunnar Ogner; Morris Schnitzer

1970-01-01

216

Catagenesis and composition of petroleum: origin of n-alkanes and isoalkanes in petroleum crudes  

SciTech Connect

Distribution of n-alkanes and isoalkanes in ca. 50 petroleum crudes have been examined by the gas chromatography. Molar distributions of n-alkanes with respect to their c atom numbers in the majority of crudes follow the exponential law, which signifies a random, chemical nature of n-alkane-generating processes occurring in the catagenesis stage of petroleum maturation. Similar distributions of n-alkanes were found in the products of mild thermolysis of heavy n-alkanes. Isoalkanes represent a major, 10-25%, petroleum component. The principal types of isoalkanes in crudes are monomethyl-branched, with the branches randomly positioned in the chains, and dimethyl-branched with one of the methyl groups predominantly in the second position in the chains. Thermolysis studies of individual n-alkanes, alkanoic acids, and esters in the presence of various minerals provided an explanation of the n-alkane and isoalkane distributions. Selected heavy n-alkanes are initially formed in decarboxylation reactions of heavy n-alkanoic acids and esters. Extensive thermocracking produces mixtures of lighter n-alkanes and ..cap alpha..-olefins. The olefins, in the presence of acidic clays, are converted in cationic reactions into mixtures of predominantly mono- and dimethyl-branched isoalkanes.

Kissin, Y.V.

1987-09-01

217

Conversation Analysis.  

ERIC Educational Resources Information Center

|Summarizes the current state of research in conversation analysis, referring primarily to six different perspectives that have developed from the philosophy, sociology, anthropology, and linguistics disciplines. These include pragmatics; speech act theory; interactional sociolinguistics; ethnomethodology; ethnography of communication; and…

Schiffrin, Deborah

1990-01-01

218

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

219

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

220

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

221

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

222

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

223

Green Chemistry  

NSDL National Science Digital Library

Learn about a study in which participants discovered contaminants in their homes, and how green chemistry may provide alternatives to such everyday toxins, in this video adapted from Contaminated Without Consent.

Foundation, Wgbh E.

2011-03-21

224

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

225

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

226

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

227

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

228

Organosilicon Chemistry.  

National Technical Information Service (NTIS)

Several new aspects of the chemistry of silylenes, divalent reactive silicon intermediates, have been explored. Insertion reactions of dimethylsilylene into O-H bonds of primary, secondary, and tertiary alcohols were studied. This provides an efficient ro...

W. P. Weber

1982-01-01

229

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

230

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

231

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.

232

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

233

Experimental Investigation of the Atmospheric Chemistry of Aromatic Hydrocarbons and Long-Chain Alkanes.  

National Technical Information Service (NTIS)

The interaction of volatile organic compounds (VOCs) and oxides of nitrogen in the presence of sunlight leads to the formation of ozone and other manifestations of photochemical air pollution. There are, however, significant uncertainties in our knowledge...

R. Atkinson J. Arey E. C. Tuazon S. M. Aschmann I. Bridier E. S. C. Kwok

1994-01-01

234

Nucleation in n-alkanes: A density-functional approach  

NASA Astrophysics Data System (ADS)

A density-functional theory for a polyatomic system is applied to gas-liquid nucleation in n-butane and n-heptane, employing an interaction site model and the rotational isomeric state approximation. Effects of chain length and flexibility on equilibrium properties and nucleation are discussed. It is shown that the n-alkane systems cannot be well approximated by a system with the spherically symmetric Lennard-Jones potential, giving a nucleation rate scaled by the classical rate smaller by six orders of magnitude.

Seok, Chaok; Oxtoby, David W.

1998-11-01

235

Preliminary assessment of halogenated alkanes as vapor-phase tracers  

SciTech Connect

New tracers are needed to evaluate the efficiency of injection strategies in vapor-dominated environments. One group of compounds that seems to meet the requirements for vapor-phase tracing are the halogenated alkanes (HCFCs). HCFCs are generally nontoxic, and extrapolation of tabulated thermodynamic data indicate that they will be thermally stable and nonreactive in a geothermal environment. The solubilities and stabilities of these compounds, which form several homologous series, vary according to the substituent ratios of fluorine, chlorine, and hydrogen. Laboratory and field tests that will further define the suitability of HCFCs as vapor-phase tracers are under way.

Adams, Michael C.; Moore, Joseph N.; Hirtz, Paul

1991-01-01

236

Metric Conversions  

NSDL National Science Digital Library

The North Carolina Community College System BioNetwork's interactive eLearning tools (IETs) are reusable chunks of training that can be deployed in a variety of courses or training programs. IETs are designed to enhance, not replace hands-on training. Learners are able to enter a hands-on lab experience better prepared and more confident. This particular IET delves into metric conversions with this "excellent tool for refreshing your knowledge of dimensional analysis, English-to-Metric, Metric-to-English, and Metric-to-Metric conversions."

2012-10-15

237

Phase equilibria of alkanol\\/alkane mixtures in new oil and gas process development  

Microsoft Academic Search

With the reduction of lead in gasolines, a growing number of processes in which alkanols and alkanes co-exist to produce oxygenated additives for gasolines are under development or have already reached the industrial production stage. In the processes selected the knowledge of the alkane\\/alkanol equilibria is essential for the separation techniques to be applied : azeotropic distillation of ethanol or

A. Pucci

1989-01-01

238

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

PubMed

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. PMID:23825470

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

2013-05-10

239

Degradation of long-chain alkanes by a polyethylene-degrading fungus, Penicillium simplicissimum YK  

Microsoft Academic Search

This study investigated the removal of long-chain alkanes, which are released as the result of shipping activities and fuel oil spills, with Penicillium simplicissimum YK, a fungus that degrades polyethylene. Two branched alkanes (pristane and squalane) and a phosphoric ester (Plysurf A210G) were used separately as a dispersant. Yeast extract and malt extract were added as a supplementary nutrient, respectively,

Keiko Yamada-Onodera; Hiroshi Mukumoto; Yuji Katsuyama; Yoshiki Tani

2002-01-01

240

Experimental Proof for Resonant Diffusion of Normal Alkanes in LTL and ZSM-12 Zeolites  

Microsoft Academic Search

The intra-crystalline diffusion of normal alkanes in LTL and ZSM-12 zeolite was experimentally studied via gravimetric measurements performed at different temperatures. A periodic dependence of the diffusion coefficient on the number of carbon atoms in alkane was detected, which is an experimental proof for resonant diffusion. The present observations were described on the base of the existing theory of the

Kyesang Yoo; Roumen Tsekov; P. G. Smirniotis

2003-01-01

241

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

242

40 CFR 721.9300 - Reaction products of substituted hydroxy-alkanes and polyalkylpolyisocyanatocarbomono- cycle.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Reaction products of substituted hydroxy-alkanes...Substances § 721.9300 Reaction products of substituted hydroxy-alkanes...substance identified generically as reaction products of substituted...c) within 90 days from the time the employer becomes...

2010-07-01

243

Inductive modeling of physico-chemical properties: Flash point of alkanes  

Microsoft Academic Search

The problem of predicting flash points (T*) of alkanes from their molecular formula is revisited. Starting from an examination of the dependence of T* on the length of the carbon chain for n-alkanes, a new model is proposed. Despite its extreme simplicity, it performs better than published alternatives based on advanced regression techniques. This illustrates the interest of an inductive

D. Mathieu

2010-01-01

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

2012-06-12

245

The genome sequence of Desulfatibacillum alkenivorans AK-01: a blueprint for anaerobic alkane oxidation.  

PubMed

Desulfatibacillum alkenivorans AK-01 serves as a model organism for anaerobic alkane biodegradation because of its distinctive biochemistry and metabolic versatility. The D. alkenivorans genome provides a blueprint for understanding the genetic systems involved in alkane metabolism including substrate activation, CoA ligation, carbon-skeleton rearrangement and decarboxylation. Genomic analysis suggested a route to regenerate the fumarate needed for alkane activation via methylmalonyl-CoA and predicted the capability for syntrophic alkane metabolism, which was experimentally verified. Pathways involved in the oxidation of alkanes, alcohols, organic acids and n-saturated fatty acids coupled to sulfate reduction and the ability to grow chemolithoautotrophically were predicted. A complement of genes for motility and oxygen detoxification suggests that D. alkenivorans may be physiologically adapted to a wide range of environmental conditions. The D. alkenivorans genome serves as a platform for further study of anaerobic, hydrocarbon-oxidizing microorganisms and their roles in bioremediation, energy recovery and global carbon cycling. PMID:21651686

Callaghan, A V; Morris, B E L; Pereira, I A C; McInerney, M J; Austin, R N; Groves, J T; Kukor, J J; Suflita, J M; Young, L Y; Zylstra, G J; Wawrik, B

2011-06-08

246

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

247

Fraction Conversion  

NSDL National Science Digital Library

This lesson is designed to develop students' abilities to convert between fractions and decimals. This lesson provides links to discussions and activities related to fraction conversion as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with the current one.

2010-01-01

248

40 CFR 721.10626 - 1,4-Butanediol, polymer with substituted alkane and substituted methylene biscarbomonocycle, 2...  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false 1,4-Butanediol, polymer with substituted alkane and substituted... § 721.10626 1,4-Butanediol, polymer with substituted alkane and substituted...identified generically as 1,4-butanediol, polymer with substituted alkane and...

2013-07-01

249

40 CFR 721.10103 - Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear.  

Code of Federal Regulations, 2010 CFR

...Fischer-Tropsch), C4-11-alkane, branched and linear. 721.10103 Section...Fischer-Tropsch), C4-11-alkane, branched and linear. (a) Chemical substance...fischer-tropsch), C4-11-alkane, branched and linear (PMN P-04-235;...

2010-07-01

250

Radiation induced oxidation of liquid alkanes as a polymer model  

NASA Astrophysics Data System (ADS)

Radiation induced oxidation of liquid n-hexadecane (n-C16H34) and squalane (C30H62) as a polymer model has been investigated by the measurements of the gas evolution and O2 uptake, and analyses of the oxidation products. Low O2 uptake, [G(-O2)~6.0] in liquid alkanes, indicates that the oxidation reaction does not exhibit chain kinetics, which is a big contrast to the process observed in solid, G(-O2)>> 10. H2 is the main gas product. More than 90% of the consumed O2 are converted into the oxidation products in liquid phase, mainly carboxylic acids, which is also a big contrast to the results of the radiolysis of liquid cyclohexane in the presence of O2 and thermal oxidation of hexadecane at elevated temperatures, where ketones and alcohols are major products at the initial stage. In the presence of aromatic additives, energy and charge transfer to the additives taking place despite the presence of O2 reduce the H2 evolution and the acid formation in parallel. Although hydroaromatic compounds act as an energy and charge scavenger, they are selectively oxidized through the donation of hydrogen in cyclic alkyl part attached to the phenyl ring, leading to large O2 uptake and corresponding ketone formation. From the comparison of the G-values of the O2 uptake, it was found that the oxidation reactions of liquid alkanes reflect well the oxidation of amorphous part in polymers.

Soebianto, Yanti S.; Katsumura, Yosuke; Ishigure, Kenkichi; Kubo, Junichi; Hamakawa, Satoshi; Kudoh, Hisaaki; Seguchi, Tadao

1996-10-01

251

Resonant positron annihilation in rings and substituted alkanes  

NASA Astrophysics Data System (ADS)

Energy-resolved positron-on-molecule annihilation rates have been measured for a variety of molecules by passing a cold positron beam through test gases [1,2]. In many cases, the annihilation rates exceed the free electron annihilation rate by orders of magnitude. In particular, when the positron energy equals a vibrational mode energy minus the binding energy, large vibrational Feshbach resonances (VFR) are observed. In alkane molecules, the height of the C-H stretch resonances grow exponentially and the binding energy grows linearly with the number of carbons [1]. In this paper, we report new results for benzene, d-benzene, and 1-chlorohexane. Specifically, we examine the relationship between binding, C-H peak height, and molecular size. All these molecules have deeper binding than alkanes with similar numbers of carbons or atoms. An empirical trend will be discussed such that molecules with the same number of atoms have similar C-H peak heights when the simple kinematic effects of the binding energy on VFR are normalized out. [1] L. D. Barnes, et al., Phys. Rev. A 67, 032706 (2003). [2] L. D. Barnes, et al., Phys. Rev. A 74, 012706 (2006).

Young, J. A.; Surko, C. M.

2007-06-01

252

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

2011-12-30

253

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

254

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.

1992-11-01

255

Chemistry Now  

NSDL National Science Digital Library

The National Science Foundation (NSF) recently teamed up with NBC and the National Science Teachers Association to celebrate the International Year of Chemistry. Their big joint project was to create Chemistry Now, a weekly online video series that uncovers and explains the science of common, physical objects. There are over two dozen short films here that cover topics like the chemistry of salt, grapheme, safety glass, and the common cheeseburger. All of the videos are lively and interesting, and they can be used in a wide range of classroom settings to provide visual and audio reinforcement of topics that might be addressed in course lectures and other activities. The videos are completely free and the site includes links to other organizations that have created similar videos.

2012-08-17

256

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

257

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

258

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)

259

Chemistry Notes  

ERIC Educational Resources Information Center

Short articles on the kinetics of the hydrogen peroxide-iodide ion reaction, simulation of fluidization catalysis, the use of Newman projection diagrams to represent steric relationships in organic chemistry, the use of synthetic substrates for proteolytic enzyme reactions, and two simple clock reactions"--hydrolysis of halogenoalkanes and…

School Science Review, 1972

1972-01-01

260

Chemistry Notes  

ERIC Educational Resources Information Center

|Short articles on the kinetics of the hydrogen peroxide-iodide ion reaction, simulation of fluidization catalysis, the use of Newman projection diagrams to represent steric relationships in organic chemistry, the use of synthetic substrates for proteolytic enzyme reactions, and two simple clock reactions"--hydrolysis of halogenoalkanes and…

School Science Review, 1972

1972-01-01

261

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

262

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

263

Green Chemistry  

NSDL National Science Digital Library

This audio segment from PRI's The World Science Podcast explores the science of Green Chemistry. Hear about companies that are developing greener chemicals, and learn why they are fast becoming an attractive alternative for the multi-billion dollar chemical industry.

Foundation, Wgbh E.

2010-02-12

264

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents procedures, experiments, demonstrations, teaching suggestions, and information on a variety of chemistry topics including, for example, inert gases, light-induced reactions, calculators, identification of substituted acetophenones, the elements, analysis of copper minerals, extraction of metallic strontium, equilibrium, halogens, and…

School Science Review, 1982

1982-01-01

265

Confectionary Chemistry.  

ERIC Educational Resources Information Center

|Presents activities and demonstrations that enable teachers to use various types of confections as tactile experiences to spark chemistry students' interest and generate enthusiasm for learning. Presents uses of candy in teaching about atomic structure, spontaneous nuclear decay, chemical formulas, fractoluminescence, the effect of a molecular…

Levine, Elise Hilf

1996-01-01

266

Chemistry Notes.  

ERIC Educational Resources Information Center

|Presents procedures, experiments, demonstrations, teaching suggestions, and information on a variety of chemistry topics including, for example, inert gases, light-induced reactions, calculators, identification of substituted acetophenones, the elements, analysis of copper minerals, extraction of metallic strontium, equilibrium, halogens, and…

School Science Review, 1982

1982-01-01

267

Chemistry's year  

NASA Astrophysics Data System (ADS)

The United Nations has proclaimed 2011 to be the International Year of Chemistry. Under this banner, chemists should seize the opportunity to highlight the rich history and successes of our subject to a much broader audience - and explain how it can help to solve the global challenges we face today and in the future.

2011-01-01

268

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

269

Chlorine Chemistry  

NSDL National Science Digital Library

From poolcenter.com comes the Chlorine Chemistry Web site. Ten questions related to chlorine are answered such as What's the History of Chlorine, How Does Chlorine Work to Sanitize, and What Effect Does pH Have on Chlorine. Each is briefly explained in simple and non-technical language.

2008-01-25

270

Chemistry Activities  

NSDL National Science Digital Library

This collection of resource features demonstrations, laboratory investigations, teaching tips, worksheets and other chemistry-related activities. Materials include investigations of mols, nuclear energy, the periodic table, weight and mass, elements, calculations, equations, pH, atomic weight, half-lives, and reactions.

271

Chain length dependence of the thermodynamic properties of linear and cyclic alkanes and polymers.  

PubMed

The specific heat capacity was measured with step-scan differential scanning calorimetry for linear alkanes from pentane (C(5)H(12)) to nonadecane (C(19)H(40)), for several cyclic alkanes, for linear and cyclic polyethylenes, and for a linear and a cyclic polystyrene. For the linear alkanes, the specific heat capacity in the equilibrium liquid state decreases as chain length increases; above a carbon number N of 10 (decane) the specific heat asymptotes to a constant value. For the cyclic alkanes, the heat capacity in the equilibrium liquid state is lower than that of the corresponding linear chains and increases with increasing chain length. At high enough molecular weights, the heat capacities of cyclic and linear molecules are expected to be equal, and this is found to be the case for the polyethylenes and polystyrenes studied. In addition, the thermal properties of the solid-liquid and the solid-solid transitions are examined for the linear and cyclic alkanes; solid-solid transitions are observed only in the odd-numbered alkanes. The thermal expansion coefficients and the specific volumes of the linear and cyclic alkanes are also calculated from literature data and compared with the trends in the specific heats. PMID:15836092

Huang, Dinghai; Simon, Sindee L; McKenna, Gregory B

2005-02-22

272

Isolation and characterization of a novel n-alkane-degrading strain, Acinetobacter haemolyticus AR-46.  

PubMed

Strain AR-46, isolated and identified as Acinetobacter haemolyticus, evolutionally distant from the known hydrocarbon-degrading Acinetobacter spp., proved to have excellent long-chain n-alkane-degrading ability. This is the first detailed report on an n-alkane-utilizing strain belonging to this species. The preferred substrate is n-hexadecane, with an optimal temperature of 37 degrees C under aerobic conditions. Five complete and two partial open reading frames were sequenced and correlated with the early steps of monoterminal oxidation-initiated n-alkane mineralization. The encoded protein sequences and the arrangement of these genes displayed high similarity to those found in Acinetobacter sp. M-1, but AR-46 seemed to have only one alkane hydroxylase gene, with a completely different induction profile. Unique behaviour was also observed in n-alkane bioavailability. Substrate uptake occurred through the hydrophobic surface of n-alkane droplet-adhered cells possessing long, thick fimbriae, which were presumed to play a major role in n-alkane solubilization. A majority of the cells was in detached form, with thick, but short fimbriae. These free cells were permanently hydrophilic, unlike the cells of other Acinetobacter strains. PMID:17542497

Bihari, Zoltán; Pettkó-Szandtner, Aladár; Csanádi, Gyula; Balázs, Margit; Bartos, Péter; Kesseru, Péter; Kiss, István; Mécs, Imre

273

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

274

Activated aluminum oxide selectively retaining long chain n-alkanes. Part I, description of the retention properties.  

PubMed

Aluminum oxide activated by heating to 350-400 degrees C retains n-alkanes with more than about 20 carbon atoms, whereas iso-alkanes largely pass the column non-retained. Retention of n-alkanes is strong with n-pentane or n-hexane as mobile phase, but weak or negligible with cyclohexane or iso-octane. It is strongly reduced with increasing column temperature. Even small amounts of polar components, such as modifiers or impurities in the mobile phase, cause the retention of n-alkanes to irreversibly collapse. Since n-alkanes are not more polar than iso-alkanes and long chain n-alkanes not more polar than those of shorter chains, retention by a mechanism based on steric properties is assumed. The sensitivity to deactivation by polar components indicates that polar components and n-alkanes are retained by the same sites. The capacity for retaining n-alkanes is low, with the effect that the retention of n-alkanes depends on the load with retained paraffins. These retention properties are useful for the pre-separation of hydrocarbons in the context of the analysis of mineral oil paraffins in foodstuffs and tissue, where plant n-alkanes, typically ranging from C(23) to C(33), may severely disturb the analysis (subject of Part II). PMID:19154816

Fiselier, Katell; Fiorini, Dennis; Grob, Koni

2008-12-09

275

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

276

Intermolecular Forces in Introductory Chemistry Studied by Gas Chromatography, Computer Models, and Viscometry  

Microsoft Academic Search

An experiment on intermolecular forces for first-term introductory college chemistry is presented. The experiment integrates traditional viscometry-based measurements with modern chromatographic analysis and use of computer-based molecular models. Students performing gas chromatographic (GC) analyses of mixtures of n-alkanes and samples that simulate crime scene evidence discover that liquid mixtures can be separated rapidly into their components based upon intermolecular forces.

Jonathan C. Wedvik; Charity McManaman; Janet S. Anderson; Mary K. Carroll

1998-01-01

277

Hydrocarbon measurements during tropospheric ozone depletion events: Evidence for halogen atom chemistry  

Microsoft Academic Search

During the Arctic Tropospheric Ozone Chemistry 1996 (ARCTOC 96) field campaign (March 29 to May 15, 1996), in situ measurements of C2-C8 hydrocarbons, selected C1-C2 halocarbons, and carbon monoxide were carried out at Ny Ålesund, Svalbard (78°55'N,11°56'E). Two major tropospheric ozone depletions were observed during this period. In each case, concurrent depletion of alkanes and ethyne but no significant changes

B. Ramacher; J. Rudolph; R. Koppmann

1999-01-01

278

Effect of n-alkanes on asphaltene structuring in petroleum oils.  

PubMed

The interactions between asphaltenes and short- to medium-chain n-alkanes were studied using titration microcalorimetry and inverse chromatography. The exothermic heat effects observed upon mixing of asphaltenes and n-alkanes were interpreted in terms of assembling of the two types of compounds into mixed structures. We show that the energy of the interactions between n-alkanes and the asphaltene hydrocarbon chains is close to the energy of the interactions between the asphaltene chains. We propose that the latter interactions are responsible for the formation of the asphaltene aggregates and are the driving force of the aggregate assembly into higher structures. PMID:15896019

Stachowiak, Christian; Viguié, Jean-Romain; Grolier, Jean-Pierre E; Rogalski, Marek

2005-05-24

279

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

280

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

1989-01-01

281

Absorption cross section at 3.39 ?m of alkanes, aromatics and substituted hydrocarbons  

NASA Astrophysics Data System (ADS)

The present study reports gas phase absorption cross sections at 3.39 ?m of 21 liquid hydrocarbons. Measurements were performed in the temperature range 303-413 K using an infrared He-Ne laser. In addition to n-alkanes, a number of cyclo-alkane, aromatic, and substituted hydrocarbons were investigated. The results demonstrate that (i) the absorption cross sections are temperature independent in the studied range, and that (ii) the aromatic and substituted hydrocarbons exhibit much smaller cross sections than n-alkanes for an identical number of C-H bonds. A tentative empirical correlation has been developed and shown to accurately predicts the cross section.

Mével, R.; Boettcher, P. A.; Shepherd, J. E.

2012-04-01

282

Hydrothermal conversion of carbohydrates and related compounds  

NASA Astrophysics Data System (ADS)

The research described in this thesis was aimed at the (partial) elucidation of the chemistry of the major decarboxylation pathways occurring in the hydrothermal conversion of carbohydrates. Knowledge of the chemical background of this hydrothermal decarboxylation might enable more effective processing of biomass with respect to minimizing the oxygen content of hydrothermolysis products.

Luijkx, Gerardus Christianus Antonius

283

Iron disulfide for solar energy conversion  

Microsoft Academic Search

Pyrite (Eg = 0.95 eV) is being developed as a solar energy material due to its environmental compatibility and its very high light absorption coefficient. A compilation of material, electronic and interfacial chemical properties is presented, which is considered relevant for quantum energy conversion. In spite of intricate problems existing within material chemistry, high quantum efficiencies for photocurrent generation (Eta

A ENNAOUI; S FIECHTER; C PETTENKOFER; N ALONSOVANTE; K BUKER; M BRONOLD; C HOPFNER; H TRIBUTSCH

1993-01-01

284

Interfacial systems for photochemical energy conversion  

NASA Astrophysics Data System (ADS)

Research supported by the DOE falls in the areas of: (1) multicomponent redox molecules; (2) polymer-modified electrodes and semiconductor photoelectrodes; (3) semiconductor surface chemistry; and (4) multielectron transfer biological catalysts for redox energy conversion processes. Highlights of research in these areas are given. Plans for the concluding year of the grant are also summarized.

Wrighton, Mark S.

285

Resin Chemistry  

Microsoft Academic Search

\\u000a During the ensuing years since the last phenolic resins book was published, many new and remarkable developments have occurred\\u000a in the realm of phenolic chemistry and are given in this chapter.\\u000a \\u000a \\u000a A critical examination of the first step or addition step (methylolation) in the preparation of resoles is described and how\\u000a it can be controlled and compared with the typical

Louis Pilato

2010-01-01

286

Methane conversion to higher hydrocarbons in microwave plasma  

Microsoft Academic Search

Methane conversion to higher hydrocarbons C2 and above was investigated in a microwave plasma reactor The chemistry that needs to be studied in order to understand the conversion process is very similar to the chemical processes that are thought to take place in the stratospheres of reducing planetary atmospheres That is plasma is formed by lightning the plasma is rapidly

T. Kovács; T. Turányi; R. Deam

2006-01-01

287

Liquid alkanes with targeted molecular weights from biomass-derived carbohydrates.  

PubMed

Liquid transportation fuels must burn cleanly and have high energy densities, criteria that are currently fulfilled by petroleum, a non-renewable resource, the combustion of which leads to increasing levels of atmospheric CO(2). An attractive approach for the production of transportation fuels from renewable biomass resources is to convert carbohydrates into alkanes with targeted molecular weights, such as C(8)-C(15) for jet-fuel applications. Targeted n-alkanes can be produced directly from fructose by an integrated process involving first the dehydration of this C(6) sugar to form 5-hydroxymethylfurfural, followed by controlled formation of C-C bonds with acetone to form C(9) and C(15) compounds, and completed by hydrogenation and hydrodeoxygenation reactions to form the corresponding n-alkanes. Analogous reactions are demonstrated starting with 5-methylfurfural or 2-furaldehyde, with the latter leading to C(8) and C(13) n-alkanes. PMID:18702136

West, Ryan M; Liu, Zhen Y; Peter, Maximilian; Dumesic, James A

2008-01-01

288

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

289

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 ...

290

40 CFR 721.2625 - Reaction product of alkane-diol and epichlorohydrin.  

Code of Federal Regulations, 2013 CFR

...Uses for Specific Chemical Substances § 721.2625 Reaction product of alkane-diol...epichlorohydrin. (a) Chemical substance and significant...reporting. (1) The chemical substance identified generically as reaction product of...

2013-07-01

291

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

DOEpatents

Transition metal complexes of meso-haloalkylporphyrins, 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.

Wijesekera, Tilak (Glen Mills, PA); Lyons, James E. (Wallingford, PA); Ellis, Jr., Paul E. (Downingtown, PA); Bhinde, Manoj V. (Boothwyn, PA)

1998-01-01

292

Production of Liquid Alkanes by Aqueous-Phase Processing of Biomass-Derived Carbohydrates  

NASA Astrophysics Data System (ADS)

Liquid alkanes with the number of carbon atoms ranging from C7 to C15 were selectively produced from biomass-derived carbohydrates by acid-catalyzed dehydration, which was followed by aldol condensation over solid base catalysts to form large organic compounds. These molecules were then converted into alkanes by dehydration/hydrogenation over bifunctional catalysts that contained acid and metal sites in a four-phase reactor, in which the aqueous organic reactant becomes more hydrophobic and a hexadecane alkane stream removes hydrophobic species from the catalyst before they go on further to form coke. These liquid alkanes are of the appropriate molecular weight to be used as transportation fuel components, and they contain 90% of the energy of the carbohydrate and H2 feeds.

Huber, George W.; Chheda, Juben N.; Barrett, Christopher J.; Dumesic, James A.

2005-06-01

293

Degradation of long-chain n-alkanes in soil microcosms by two actinobacteria.  

PubMed

The ability of two recently isolated actinobacteria, that degrade medium and long chain n-alkanes in laboratory water medium, was investigated in soil microcosms using different standard soils that were artificially contaminated with n-alkanes of different length (C(12)- C(20)- C(24)- C(30)). The two strains, identified as Nocardia sp. SoB and Gordonia sp. SoCp, revealed a similar high HC degradation efficiency with an average of 75% alkane degraded after 28 days incubation. A selectivity of bacteria towards n-alkanes of different length was detected as well as a consistent effect of soil texture and other soil physical chemical characteristics on degradation. It was demonstrated the specific aptitude of these selected strains towards specific environmental conditions. PMID:22320689

De Pasquale, Claudio; Palazzolo, Eristanna; Lo Piccolo, Luca; Quatrini, Paola

2012-01-01

294

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

295

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

296

[Conversion disorders].  

PubMed

Classification, diagnostic and therapeutic problems are central to the disease concept of conversion disorders, which are based on the presentation of psychosocial suffering by means of pseudoneurological symptoms without an organic cause. The nosological status in the current diagnostic and statistical manual of mental disorders (DSM-IV) and international classification of diseases (ICD-10) is disputed. Prevalence rates ranging from 0.3 % in the general population to 50 % in high risk clinical samples underline the relevance. Traumatic experiences play a major role in the pathogenesis. High rates of comorbid mental disorders, the danger to end in a chronic course, a high secondary illness gain and a somatic illness concept complicate psychotherapeutic approaches which are clearly indicated. Clinical experiences and open studies indicate that both psychodynamic as well as cognitive-behaviour therapies are effective. PMID:23440369

Fricke-Neef, C; Spitzer, C

2013-03-01

297

Energy conversion  

SciTech Connect

Energy conversion capable of receiving input energy in thermal or radiant form at a variable rate and releasing energy in thermal, radiant or electrical form independent of rate is accomplished by providing a buffer member of a material that has three criteria: a melting temperature above 1300/sup degree/ K, a thermal conductance greater than 0.1 in calories per square centimeter per centimeter per degree per second and a latent heat of fusion of the order of 1 kilocalorie per mole. The converter can absorb energy of multiple types, store it and then release it in a form compatible with the prospective use. Sunlight of daylight duration and varying intensity is converted to steady 24 hour a day electrical output.

Woodall, J.M.

1982-02-16

298

Recommended Vapor–Liquid Equilibrium Data. Part 2: Binary Alkanol–Alkane Systems  

Microsoft Academic Search

The recommended vapor–liquid equilibrium (VLE) data for 36 binary systems involving primary, secondary, and tertiary alcohols with n-alkanes and isoalkanes [with the exception of 1-alkanols–n-alkane systems, which were presented in Part 1 of this series—J. Phys. Chem. Ref. Data 31(3), 702 (2002)] have been obtained after critical evaluation of all data (744 data sets) reported in the open literature up

Marian Go´ral; Adam Skrzecz; Andrzej Bok

2003-01-01

299

Expression and characterization of two new alkane-inducible cytochrome P450s from Trichoderma harzianum  

Microsoft Academic Search

n-Dodecane and fatty acids were good inducers of cytochrome P450 (CYP) and the ?-hydroxylase of lauric acid, which is a marker\\u000a for ?-hydroxylation of n-alkanes, in Trichoderma harzianum. A cDNA, containing an ORF of 1520 bp, encoding a CYP52 of 520 amino acids, was isolated by RACE. Another n-alkane-inducible CYP was identified by LLC-MS\\/MS analysis of a microsomal protein band induced

R. Del Carratore; P. G. Gervasi; M. P. Contini; P. Beffy; B. E. Maserti; G. Giovannetti; A. Brondolo; V. Longo

2011-01-01

300

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

Microsoft Academic Search

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

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

2005-01-01

301

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

302

The quantitative significance of Syntrophaceae and syntrophic partnerships in methanogenic degradation of crude oil alkanes  

PubMed Central

Libraries of 16S rRNA genes cloned from methanogenic oil degrading microcosms amended with North Sea crude oil and inoculated with estuarine sediment indicated that bacteria from the genera Smithella (Deltaproteobacteria, Syntrophaceace) and Marinobacter sp. (Gammaproteobacteria) were enriched during degradation. Growth yields and doubling times (36 days for both Smithella and Marinobacter) were determined using qPCR and quantitative data on alkanes, which were the predominant hydrocarbons degraded. The growth yield of the Smithella sp. [0.020 g(cell-C)/g(alkane-C)], assuming it utilized all alkanes removed was consistent with yields of bacteria that degrade hydrocarbons and other organic compounds in methanogenic consortia. Over 450 days of incubation predominance and exponential growth of Smithella was coincident with alkane removal and exponential accumulation of methane. This growth is consistent with Smithella's occurrence in near surface anoxic hydrocarbon degrading systems and their complete oxidation of crude oil alkanes to acetate and/or hydrogen in syntrophic partnership with methanogens in such systems. The calculated growth yield of the Marinobacter sp., assuming it grew on alkanes, was [0.0005 g(cell-C)/g(alkane-C)] suggesting that it played a minor role in alkane degradation. The dominant methanogens were hydrogenotrophs (Methanocalculus spp. from the Methanomicrobiales). Enrichment of hydrogen-oxidizing methanogens relative to acetoclastic methanogens was consistent with syntrophic acetate oxidation measured in methanogenic crude oil degrading enrichment cultures. qPCR of the Methanomicrobiales indicated growth characteristics consistent with measured rates of methane production and growth in partnership with Smithella.

Gray, N D; Sherry, A; Grant, R J; Rowan, A K; Hubert, C R J; Callbeck, C M; Aitken, C M; Jones, D M; Adams, J J; Larter, S R; Head, I M

2011-01-01

303

Modeling SOA formation from OH reactions with C 8–C 17 n-alkanes  

Microsoft Academic Search

Recent laboratory studies show that ?-hydroxycarbonyls formed via OH-initiated reactions with alkanes cyclize and then dehydrate to form substituted dihydrofurans. These dihydrofurans are highly reactive, with estimated lifetimes in the atmosphere of 1.3h (OH), 24s (NO3), and 7min (O3). These studies also show that secondary organic aerosol (SOA) yields from alkanes increase with carbon number from 4% for C8 to

C. E. Jordan; P. J. Ziemann; R. J. Griffin; Y. B. Lim; R. Atkinson; J. Arey

2008-01-01

304

Degradation of long-chain n-alkanes in soil microcosms by two actinobacteria  

Microsoft Academic Search

The ability of two recently isolated actinobacteria, that degrade medium and long chain n-alkanes in laboratory water medium, was investigated in soil microcosms using different standard soils that were artificially contaminated with n-alkanes of different length (C12- C20- C24- C30). The two strains, identified as Nocardia sp. SoB and Gordonia sp. SoCp, revealed a similar high HC degradation efficiency with

Claudio De Pasquale; Eristanna Palazzolo; Luca Lo Piccolo; Paola Quatrini

2012-01-01

305

Synthesis of adamantane and diamantane hydrocarbons by high-temperature cracking of higher n -alkanes  

Microsoft Academic Search

Adamantanes and diamantanes, whose abiogenic synthesis from carbon and hydrogen is feasible, were synthesized via the high-temperature\\u000a cracking of individual n-alkanes in order to reveal the possible ways of the genesis of hydrocarbons with a diamond-like structure. As a result of\\u000a the high-temperature cracking of n-alkanes, all theoretically possible isomers of C10–C13 adamantanes and C14–C16 diamantanes are formed, as well

G. N. Gordadze; M. V. Giruts

2008-01-01

306

Competition between n -alkane-assimilating yeasts and bacteria during colonization of sandy soil microcosms  

Microsoft Academic Search

An n-alkane-assimilating strain of Candida tropicalis was selected in sandy soil inoculated with microorganisms from contaminated sites. Competition experiments with n-alkane utilizers from different strain collections confirmed that yeasts overgrow bacteria in sandy soil. Acidification of\\u000a the soil is one of the colonization factors useful for the yeasts. It can be counteracted by addition of bentonite, a clay\\u000a mineral with

C. Schmitz; I. Goebel; S. Wagner; A. Vomberg; U. Klinner

2000-01-01

307

Different response of ?D values of n-alkanes, isoprenoids, and kerogen during thermal maturation  

NASA Astrophysics Data System (ADS)

This study investigates the extent of post-depositional alteration of ?D values of n-alkyl lipids, isoprenoids, and kerogen isolated from a continuous 450 m core that covers the transition from thermally immature to early mature sediments in the lacustrine Kissenda Formation, Lower Cretaceous, Gabon Basin. Large variations in ?D values (up to 40‰ for nC 17 and up to 30‰ for nC 29 alkanes as well as up to 10‰ for kerogen) in closely spaced samples are evident throughout the core and remain preserved even at the bottom of the section. ?D values of individual n-alkanes show a slight overall D-enrichment with depth, and a general trend of increasing ?D values with increasing n-alkane chain length characterizes all samples, particularly in those below 600 m depth. Hydrogen isotopic compositions of kerogen samples overlap with those of n-alkanes throughout the section. ?D values of pristane and phytane are more negative than those of nC 17 alkane by as much as 120‰ at shallow depths but increase dramatically and approach ?D values of nC 17 alkane in the samples closest to the oil window. Integration of analytical and computational results indicates that: (1) n-alkanes and isoprenoids have the potential to preserve the original biological signal before the onset of oil generation; (2) isomeric and structural rearrangements taking place at the beginning stages of oil generation do not influence significantly the ?D values of n-alkanes and kerogen. However, these processes have a major effect on the isotopic composition of isoprenoids, causing isotopic D-enrichment up to 90‰.

Pedentchouk, Nikolai; Freeman, Katherine H.; Harris, Nicholas B.

2006-04-01

308

Gas chromatography electron ionization mass spectrometric analysis of trimethylsilyl derivatives of bis(2-hydroxyethylthio)alkanes and bis(2-hydroxyethylsulfonyl) alkanes.  

PubMed

This communication describes GC-MS analysis of bis(trimethylsilyl) (bis-TMS) derivatives of bis(2-hydroxyethylthio)alkanes (BHETAs) and bis(2-hydroxyethylsulfonyl) alkanes (BHESAs) which are important markers of sulfur mustard class of chemical warfare agents. The study was undertaken with a view to develop spectral database of these compounds for verification analysis of Chemical Weapons Convention (CWC). Based on the obtained mass spectra of bis-TMS derivatives of BHETAs and BHESAs, the fragmentation routes are proposed, which explain most of the characteristic ions. PMID:17057283

Kanaujia, Pankaj K; Tak, Vijay; Pardasani, Deepak; Gupta, A K; Jain, Rajiv; Dubey, D K

2006-01-01

309

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.

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

310

Solvation of nitrophenol isomers: consequences for solute electronic structure and alkane/water partitioning.  

PubMed

Solute partitioning across a variety of alkane/aqueous interfaces was examined as a function of solute and alkane solvent structure. Solutes include p-nitrophenol (PNP), 3,5-dimethyl-p-nitrophenol (3,5-DMPNP), and 2,6-dimethyl-p-nitrophenol (2,6-DMPNP), the latter two being isomers distinguished solely by the location of methyl substituents on the aromatic ring. The alkane solvents included cylohexane, methylcyclohexane, octane, and iso-octane (2,2,4-trimethylpentane). PNP partitioned preferentially into the water by factors as high as 160:1. The dimethyl isomers partitioned more equally between water and the different alkanes. 2,6-DMPNP showed a 3-fold greater affinity for the alkane phase than 3,5-DMPNP. Ab initio calculations were used to characterize the molecular and electronic structure of the three solutes and to quantify individual contributions to each solute's solvation energy in model aqueous and alkane phases. Differences between 2,6-DMPNP and 3,5-DMPNP partitioning are interpreted based on the ability of the methyl groups in 2,6-DMPNP to weaken hydrogen bonding between the phenol group and adjacent water molecules. This diminished solvation interaction reduces the barrier to solute migration into the nonpolar organic phase despite the fact that 2,6-DMPNP has a larger (calculated) permanent, ground-state dipole than 3,5-DMPNP. PMID:19143574

Steel, William H; Foresman, James B; Burden, Daniel K; Lau, Yuen Y; Walker, Robert A

2009-01-22

311

Functional analysis of long-chain n-alkane degradation by Dietzia spp.  

PubMed

The genetic background of long-chain n-alkane degradation was investigated in detail in strain E1, a member of the genetically unexplored Dietzia genus. A suicide vector carrying a 518-bp alkB fragment was site-specifically integrated into the E1 chromosome, and the full alkB, as well as its chromosomal environment was sequenced after plasmid rescue experiments. Four out of the nine putative genes were strongly induced by long-chain n-alkanes in wild-type E1. ORF4 encoded a natural fusion protein consisting of an integral membrane alkane hydroxylase and a rubredoxin domain. The significance of the alkB-rub gene in n-alkane degradation was investigated in phenotypic tests, and the disruption mutant strain exhibited severely impaired growth on n-C(20) alkane carbon source. The mutation was successfully complemented with the expression of intact AlkB-Rub protein, the full-length form of which was detected by simultaneous immunoblotting. The presented data furnish the first experimental evidence of the in vivo existence of an AlkB-Rub natural fusion protein, which plays a major role in long-chain n-alkane degradation. PMID:21204932

Bihari, Zoltán; Szvetnik, Attila; Szabó, Zsolt; Blastyák, András; Zombori, Zoltán; Balázs, Margit; Kiss, István

2011-01-17

312

Hyperbaric reservoir fluids: High-pressure phase behavior of asymmetric methane + n-alkane systems  

NASA Astrophysics Data System (ADS)

In this paper, experimental three-phase equilibrium (solid n-alkane + liquid + vapor) data for binary methane + n-alkane systems are presented. For the binary system methane + tetracosane, the three-phase curve was determined based on two phase equilibrium measurements in a composition range from x c24 = 0.0027 to x c24 = 1.0. The second critical endpoint of this system was found at p = (1114.7 ± 0.5) M Pa. T = (322.6 ± 0.25) K, and a mole fraction of tetracosane in the critical fluidphase of x c24 = 0.0415 ± 0.0015. The second critical endpoint occurs where solid tetracosane is in equilibrium with a critical fluid phase ( S c24 + L = V). For the binary systems of methane with the n-alkanes tetradecane, triacontane, tetracontane, and pentacontane, only the coordinates of the second critical endpoints were measured. The second critical endpoint temperature is found close to the atmospheric melting point temperature of the n-alkane. The pressures at the second critical endpoints do not exceed 200 MPa. Based on these experimental data and data from the literature, correlations for the pressure. temperature, and fluid phase composition at the second critical endpoint of binary methane + n-alkane systems with n-alkanes between octane and pentacontane were developed.

Flöten, E.; de Loos, Th. W.; de Swaan Arons, J.

1995-01-01

313

(Pesticide chemistry)  

SciTech Connect

This report summarizes a trip by L. W. Barnthouse of the Environmental Sciences Division (ESD), Oak Ridge National Laboratory (ORNL), to Hamburg, Federal Republic of Germany (FRG), where he participated in the 7th International Congress of Pesticide Chemistry. He chaired a workshop on experimental systems for determining effects of pesticides on nontarget organisms and gave an oral presentation at a symposium on pesticide risk assessment. Before returning to the United States, Dr. Barnthouse visited the Netherlands Institute for Sea Research in Texel, the Netherlands.

Barnthouse, L.W.

1990-09-04

314

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

315

Identification of Novel Genes Involved in Long-Chain n-Alkane Degradation by Acinetobacter sp. Strain DSM 17874  

Microsoft Academic Search

Acinetobacter sp. strain DSM 17874 is capable of utilizing n-alkanes with chain lengths ranging from that of decane (C10H22) to that of tetracontane (C40H82) as a sole carbon source. Two genes encoding AlkB-type alkane hydroxylase homologues, designated alkMa and alkMb, have been shown to be involved in the degradation of n-alkanes with chain lengths of from 10 to 20 C

Mimmi Throne-Holst; Alexander Wentzel; Trond E. Ellingsen; Hans-Kristian Kotlar; Sergey B. Zotchev

2007-01-01

316

The air–water exchange of C 15–C 31 n-alkanes in a precipitation-dominated seepage lake  

Microsoft Academic Search

The air–water exchange of semivolatile n-alkanes in Crystal Lake, a small precipitation-dominated seepage lake in northern Wisconsin, was investigated with modeling and mass balance approaches. The results suggest that atmospheric deposition contributes approximately 80% of the allochthonous input of n-alkanes to Crystal Lake. Atmospheric deposition accounts for about 50% of the total annual input of n-alkanes to Crystal Lake, and

Paul V Doskey

2000-01-01

317

Environmental chemistry. Seventh edition  

SciTech Connect

This book presents a basic understanding of environmental chemistry and its applications. In addition to providing updated materials in this field, the book emphasizes the major concepts essential to the practice of environmental chemistry. Topics of discussion include the following: toxicological chemistry; toxicological chemistry of chemical substances; chemical analysis of water and wastewater; chemical analysis of wastes and solids; air and gas analysis; chemical analysis of biological materials and xenobiotics; fundamentals of chemistry; and fundamentals of organic chemistry.

Manahan, S.E. [Univ. of Missouri, Columbia, MO (United States)

1999-11-01

318

Decatungstate as an efficient photocatalyst in organic chemistry.  

PubMed

In view of its unique photocatalytic properties, decatungstate (W(10)O(32)(4-)) is rapidly emerging as a promising tool in organic chemistry. This tutorial review surveys recent developments in the chemistry of decatungstate, including mostly synthetic, and to a lesser extent mechanistic aspects. We have chosen to present several representative examples that illustrate the diverse uses of decatungstate in organic synthesis. Thus, the decatungstate-mediated radical functionalization of several classes of organic compounds such as alkanes, alkenes, alcohols, aldehydes and sulfides, under both aerobic and anaerobic conditions, represents reactions of fundamental and practical interest in academia and industry. Several new discoveries concerning the heterogenization of decatungstate for the development of sustainable methods with broad applications in catalysis, such as the photooxidation or photodegradation of various organic substrates, are also presented. PMID:19690741

Tzirakis, Manolis D; Lykakis, Ioannis N; Orfanopoulos, Michael

2009-07-10

319

What is Chemistry?  

NSDL National Science Digital Library

Provided by Kiwi Web Chemistry & New Zealand, the "What is Chemistry?" Web site offers a wealth of chemistry information and links. Visitors can read the definition of and link to other sites on inorganic chemistry, organic chemistry, analytical chemistry, physical chemistry, stoichiometry, nuclear chemistry, alchemy, and biochemistry. Other pages of the site explore acids and bases, redox reductions, equations, moles, periodic tables, and more. This extensive and interesting site does a good job of clearly explaining some difficult concepts as well as providing educators and students a good source of other quality sites containing similar content.

Campbell, Allan

320

Proteomic insights into metabolic adaptations in Alcanivorax borkumensis induced by alkane utilization.  

PubMed

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 beta-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. PMID:16707669

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

2006-06-01

321

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

2012-08-09

322

Astronomical chemistry.  

PubMed

The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic. PMID:21128763

Klemperer, William

2011-01-01

323

Astronomical Chemistry  

NASA Astrophysics Data System (ADS)

The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic.

Klemperer, William

2011-05-01

324

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

325

Gene diversity of CYP153A and AlkB alkane hydroxylases in oil-degrading bacteria isolated from the Atlantic Ocean.  

PubMed

Alkane hydroxylases, including the integral-membrane non-haem iron monooxygenase (AlkB) and cytochrome P450 CYP153 family, are key enzymes in bacterial alkane oxidation. Although both genes have been detected in a number of bacteria and environments, knowledge about the diversity of these genes in marine alkane-degrading bacteria is still limited, especially in pelagic areas. In this report, 177 bacterial isolates, comprising 43 genera, were obtained from 18 oil-degrading consortia enriched from surface seawater samples collected from the Atlantic Ocean. Many isolates were confirmed to be the first oil-degraders in their affiliated genera including Brachybacterium, Idiomarina, Leifsonia, Martelella, Kordiimonas, Parvibaculum and Tistrella. Using degenerate PCR primers, alkB and CYP153A P450 genes were surveyed in these bacteria. In total, 82 P450 and 52 alkB gene fragments were obtained from 80 of the isolates. These isolates mainly belonged to Alcanivorax, Bacillus, Erythrobacter, Martelella, Parvibaculum and Salinisphaera, some of which were reported, for the first time, to encode alkane hydroxylases. Phylogenetic analysis showed that both genes were quite diverse and formed several clusters, most of which were generated from various Alcanivorax bacteria. Noticeably, some sequences, such as those from the Salinisphaera genus, were grouped into a distantly related novel cluster. Inspection of the linkage between gene and host revealed that alkB and P450 tend to coexist in Alcanivorax and Salinisphaera, while in all isolates of Parvibaculum, only P450 genes were found, but of multiple homologues. Multiple homologues of alkB mostly cooccurred in Alcanivorax isolates. Conversely, distantly related isolates contained similar or even identical sequences. In summary, various oil-degrading bacteria, which harboured diverse P450 and alkB genes, were found in the surface water of Atlantic Ocean. Our results help to show the diversity of P450 and alkB genes in prokaryotes, and to portray the geographic distribution of oil-degrading bacteria in marine environments. PMID:20148932

Wang, Liping; Wang, Wanpeng; Lai, Qiliang; Shao, Zongze

2010-02-11

326

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

327

Hydrogen isotope ratios of lipid biomarkers (n alkanes) as paleohydrologic proxies: aquatic vs. terrestrial archives  

NASA Astrophysics Data System (ADS)

Hydrogen isotope ratios (?D) of lake and soil waters reflect both the isotopic composition of precipitation and the subsequent hydrologic processes that modify those waters. ?D values of lake waters are affected by precipitation/evaporation ratio, circulation, lake type, and groundwater interactions. Soil water ?D values are modified from precipitation values by evaporation, transpiration by plants and selective transport of soil waters. Organic compounds synthesized by algae and vascular plants retain a ?D signature of source water. Therefore, compound-specific ?D measurements of individual biomarkers present a promising tool for reconstructing paleohydrologic and paleoclimatic factors that determine ?D values of environmental waters. Here, we use two sample sets to explore the use of ?D of individual n-alkanes from different depositional environments to compare the paleoproxy potential of n-alkanes from aquatic vs. terrestrial plants. ?D values of n-alkanes (C15-C25) from a ˜400 m core of Lower Cretaceous lacustrine shale from the Gabon Basin were determined. C15 and C17 n-alkanes (phytoplankton source) exhibit a nearly identical pattern of ?D values down-core. C23 and C25 n-alkanes (aquatic macrophyte source) also share similar values and trends but are isotopically enriched relative to C15/C17. These ?D records correspond closely with the carbonate ?18O record suggesting the ?D values of n-alkanes preserve a record of changes in lake-water isotopic composition. ?D n-alkane records also co-vary with %TOC and Hydrogen Index indicating that a negative water balance leads to increased OM preservation. ?D of high molecular-weight n-alkanes (C27-C33), indicative of vascular plant leaf-waxes, can potentially be used to reconstruct changes in aridity and/or seasonality of precipitation in grasslands. A modern calibration set is being developed on the ?D of n-alkanes from grasses collected throughout the Great Plains of North America. The calibration set includes C_3 and C_4 grasses from sites with a range of precipitation ?D values and hydrologic conditions. Ultimately, this proxy will be applied to examine the effect of changing paleoprecipitation patterns on the late Miocene spread of C_4 grasses.

Smith, F. A.; Pedentchouk, N.; Freeman, K. H.

2003-04-01

328

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

PubMed

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. PMID:21951420

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

2011-09-25

329

ClogP(alk): a method for predicting alkane/water partition coefficient.  

PubMed

Alkane/water partition coefficients (P(alk)) are less familiar to the molecular design community than their 1-octanol/water equivalents and access to both data and prediction tools is much more limited. A method for predicting alkane/water partition coefficient from molecular structure is introduced. The basis for the ClogP(alk) model is the strong (R² = 0.987) relationship between alkane/water partition coefficient and molecular surface area (MSA) that was observed for saturated hydrocarbons. The model treats a molecule as a perturbation of a saturated hydrocarbon molecule with the same MSA and uses increments defined for functional groups to quantify the extent to which logP(alk) is perturbed by the introduction each functional group. Interactions between functional groups, such as intramolecular hydrogen bonds are also parameterized within a perturbation framework. The functional groups and interactions between them are specified substructurally in a transparent and reproducible manner using SMARTS notation. The ClogP(alk) model was parameterized using data measured for structurally prototypical compounds that dominate the literature on alkane/water partition coefficients and then validated using an external test set of 100 alkane/water logP measurements, the majority of which were for drugs. PMID:23737238

Kenny, Peter W; Montanari, Carlos A; Prokopczyk, Igor M

2013-06-05

330

Biodegradation of chlorinated alkanes and their commercial mixtures by Pseudomonas sp. strain 273.  

PubMed

The biodegradation of chlorinated alkanes was studied under oxic conditions with the objective of identifying favorable and unfavorable intramolecular chlorination sequences with respect to the enzymes studied. Several dehalogenating bacterial strains were screened for their ability to degrade middle-chain polychlorinated alkanes as well as a commercial mixture. Of the organisms tested, the most promising was Pseudomonas sp. strain 273, which possesses an oxygenolytic dehalogenase. The effects of carbon chain length (C(6)-C(16)), halogen position, and overall chlorine content (14-61% w/w) were examined using both commercially available compounds and molecules synthesized in our laboratory. The effects of co-substrates, solvents, and inducing agents were also studied. The results with pure chlorinated alkanes showed that the relative positions of the chlorine atoms strongly influenced the total amount of dehalogenation achieved. The greatest dehalogenation yields were associated with terminally chlorinated alkanes. The alpha- and alpha,omega-chlorinated compounds yielded similar results. Vicinal chlorination had the most dramatic impact on degradation. When present on both ends or at the center of the molecule, no dehalogenation was detected. Although partial dehalogenation of 1,2-dichlorodecane was observed, it was likely due to a combination of beta-oxidation and an abiotic mechanism. Cereclor S52 was appreciably dehalogenated in shake flasks only when 1,10-dichlorodecane was present as a co-substrate and after increasing the oil surface area through mechanical emulsification, demonstrating the importance of abiotic factors in degrading commercial polychlorinated alkane mixtures. PMID:16491365

Heath, Ester; Brown, Wayne A; Jensen, Soren R; Bratty, Michael P

2004-11-30

331

Nestmate recognition cues in the honey bee: differential importance of cuticular alkanes and alkenes.  

PubMed

In social insects, recognition of nestmates from aliens is based on olfactory cues, and many studies have demonstrated that such cues are contained within the lipid layer covering the insect cuticle. These lipids are usually a complex mixture of tens of compounds in which aliphatic hydrocarbons are generally the major components. The experiments described here tested whether artificial changes in the cuticular profile through supplementation of naturally occurring alkanes and alkenes in honeybees affect the behaviour of nestmate guards. Compounds were applied to live foragers in microgram quantities and the bees returned to their hive entrance where the behaviour of the guard bees was observed. In this fashion we compared the effect of single alkenes with that of single alkanes; the effect of mixtures of alkenes versus that of mixtures of alkanes and the whole alkane fraction separated from the cuticular lipids versus the alkene fraction. With only one exception (the comparison between n-C(19) and (Z)9-C(19)), in all the experiments bees treated with alkenes were attacked more intensively than bees treated with alkanes. This leads us to conclude that modification of the natural chemical profile with the two different classes of compounds has a different effect on acceptance and suggests that this may correspond to a differential importance in the recognition signature. PMID:15917370

Dani, Francesca R; Jones, Graeme R; Corsi, Silvia; Beard, Richard; Pradella, Duccio; Turillazzi, Stefano

2005-05-25

332

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

333

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.

334

Wetting of methanol on the n-alkanes: Observation of short-range critical wetting  

NASA Astrophysics Data System (ADS)

We present results of the wetting properties of methanol at the liquid-vapor interface of different n-alkanes ranging from hexane to undecane. Measurement of the contact angle shows that, as the bulk critical point is approached, wetting transitions occur for long alkanes, whereas drying is found for short alkanes. Measurement of the wetting layer thickness, as well as precise contact angle measurements close to the wetting temperature Tw, reveal a change in the order of the transition. First order (discontinuous) wetting occurs for Tw far from the bulk critical point Tc. Critical (continuous) wetting is observed for Tw close to Tc. The observed critical wetting transition has all the features of the long-sought short-range critical wetting transition. We argue that it is possible to observe short-range critical wetting in this system, because the long-range van der Waals interactions are negligible for wetting transitions close to the bulk critical point.

Ross, David; Bonn, Daniel; Meunier, Jacques

2001-02-01

335

Monitoring alkane degradation by single BioBrick integration to an optimal cellular framework.  

PubMed

Synthetic biology enables rewiring and reconstruction of desirable biochemical routes using well-characterized BioBricks. One goal is to optimize these biological systems in terms of robustness, functionality, and simplicity. Thus, in addition to optimizing the molecular level of the metabolic network, choosing an optimal "chassis" can have a great significance in the constructed system. As an example, this study presents a simplified system for monitoring and studying long-chain n-alkane degradation in Acinetobacter baylyi ADP1 online, provided by a single BioBrick insertion, bacterial luciferase luxAB. The system exploits the natural alkane degradation machinery of ADP1 and a sensitive response of bacterial luciferase to a specific intermediate, providing important aspects to natural alkane degradation kinetics. The study suggests the monitoring system to be applicable in the field of environmental biotechnology and emphasizes the utility of ADP1 as a host in both model systems and applications. PMID:23651046

Santala, Suvi; Karp, Matti; Santala, Ville

2011-11-02

336

Potential parameters of methyl and methylene obtained from second virial coefficients of n-alkanes  

NASA Astrophysics Data System (ADS)

The second virial coefficients of a number of n-alkanes (from butane to hexadecane) have been evaluated by using the Rotational Isomeric State model. Methyl and methylene groups have been modelled as Lennard-Jones (12 - 6) interaction sites centered on the position of the carbon atoms. Equal size has been assigned to the methyl and methylene groups but differences in the well-depth of the potential were considered. We have chosen the values of the potential well-depths of methyl and methylene group to fit the second virial coefficient of several n-alkanes in a range of about 300 K. The agreement with experimental results is good. Then, it is shown that a simple site-site potential model is able to reproduce the second virial coefficient of several n-alkanes in a wide range of temperatures.

López Rodríguez, Antonio; Vega, Carlos; Freire, Juan J.; Lago, Santiago

337

Synthetic studies in nitrogen chemistry  

SciTech Connect

N,N-Bis(benzotriazolylmethyl)arylamines were obtained quantitatively from mixtures of benzotriazole, formaldehyde and the corresponding arylamine in refluxing toluene with azeotropic removal of water. Treatment of these adducts with Grignard reagents or sodium borohydride afforded symmetrically substituted N,N-dialkylarylamines in high yields. Unsymmetrically substituted N,N-dialkylarylamines could also be obtained by similar stepwise procedures. Sterically hindered N,N-bis(sec-butyl)arylamines were prepared by alkylations of the anions of the corresponding arylamines with 2-iodobutane. Chlorosulfonation of 2-nitroanisole gave 4-methoxy-3-nitrobenzene-sulfon-yl chloride, which was converted with N-butyl-(3-phenylpropyl)-amine into the corresponding benzenesulfonamide. Hydrolysis of the methoxy group and reduction of the nitro substituent of this benzene-sulfonamide, followed by diazotization and coupling with 2-naphthol, afforded N-butyl-N-(3-phenylpropyl)-4-hydroxy-3-(2-hydroxy-1-naphthyl)azobenzenesulfonamide. Medium-sized (7 and 8) benzosultams were synthesized by Friedel-Crafts cyclizations of w-phenylaklanesulfamoyl chlorides. New (benzotriazol-1-y)methyl derivatives of type Bt(1)CH[sub 2] X [Bt(1) = benzotriazol-1-yl] were prepared. [alpha]-(Benzotriazol-1-yl)acetophenone was converted to a number of interesting derivatives. Lithiation of 1-methylbenzotriazole followed by treatments with electrophiles gave various [alpha]-substituted 1-methylbenzotriazoles. Simple treatments of 2-alkylbenzotriazoles by LDA gave symmetrical [alpha],[beta]-bis-(benzotriazol-2-yl)alkanes sterospecifically as the [alpha],[alpha]-coupled products in high yields. A molecule [Bt(2)CH(CH[sub 3])CH(CH[sub 3])CH(CH[sub 3])CH(CH[sub 3])Bt(2)] [Bt(2) = benzotriazole-2-yl] with four asymmetric centers derived from four molecules of 2-ethylbenzotriazole was obtained as a single isomer. A new radical mechanism was first proposed to account for the chemistry of 2-alkylbenzotriazoles.

Wu, J.

1992-01-01

338

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

339

Solvent-free synthesis of C10 and C11 branched alkanes from furfural and methyl isobutyl ketone.  

PubMed

Our best results jet: C10 and C11 branched alkanes, with low freezing points, are synthesized through the aldol condensation of furfural and methyl isobutyl ketone from lignocellulose, which is then followed by hydrodeoxygenation. These jet-fuel-range alkanes are obtained in high overall yields (?90%) under solvent-free conditions. PMID:23757334

Yang, Jinfan; Li, Ning; Li, Guangyi; Wang, Wentao; Wang, Aiqin; Wang, Xiaodong; Cong, Yu; Zhang, Tao

2013-06-11

340

Infrared study of H\\/D isotope exchange reaction of alkanes and Brønsted acidic hydroxyl groups on FER zeolite  

Microsoft Academic Search

H\\/D isotope exchange between n-alkanes and the acidic OD groups in ferrierite was observed by infrared spectroscopy. The real activation energies were estimated\\u000a by adding the heats of adsorption to the apparent activation energies, resulting in almost the same value for all n-alkanes. The transition state for the reaction is discussed.

Byongjin Lee; Junko N. Kondo; Fumitaka Wakabayashi; Kazunari Domen

1999-01-01

341

n-Alkane assimilation and tert-butyl alcohol (TBA) oxidation capacity in Mycobacterium austroafricanum strains.  

PubMed

Mycobacterium austroafricanum IFP 2012, which grows on methyl tert-butyl ether (MTBE) and on tert-butyl alcohol (TBA), the main intermediate of MTBE degradation, also grows on a broad range of n-alkanes (C2 to C16). A single alkB gene copy, encoding a non-heme alkane monooxygenase, was partially amplified from the genome of this bacterium. Its expression was induced after growth on n-propane, n-hexane, n-hexadecane and on TBA but not after growth on LB. The capacity of other fast-growing mycobacteria to grow on n-alkanes (C1 to C16) and to degrade TBA after growth on n-alkanes was compared to that of M. austroafricanum IFP 2012. We studied M. austroafricanum IFP 2012 and IFP 2015 able to grow on MTBE, M. austroafricanum IFP 2173 able to grow on isooctane, Mycobacterium sp. IFP 2009 able to grow on ethyl tert-butyl ether (ETBE), M. vaccae JOB5 (M. austroaafricanum ATCC 29678) able to degrade MTBE and TBA and M. smegmatis mc2 155 with no known degradation capacity towards fuel oxygenates. The M. austroafricanum strains grew on a broad range of n-alkanes and three were able to degrade TBA after growth on propane, hexane and hexadecane. An alkB gene was partially amplified from the genome of all mycobacteria and a sequence comparison demonstrated a close relationship among the M. austroafricanum strains. This is the first report suggesting the involvement of an alkane hydroxylase in TBA oxidation, a key step during MTBE metabolism. PMID:17347817

Lopes Ferreira, Nicolas; Mathis, Hugues; Labbé, Diane; Monot, Frédéric; Greer, Charles W; Fayolle-Guichard, Françoise

2007-03-09

342

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

343

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

344

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

345

Ocean wave energy conversion  

NASA Astrophysics Data System (ADS)

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.

McCormick, M. E.

346

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

347

Production of a recombinant alkane hydroxylase (AlkB2) from Alcanivorax borkumensis  

Microsoft Academic Search

Alcanivorax borkumensis is an oil-degrading marine bacterium. Its genome contains genes coding for three cytochrome P450s and two integral membrane\\u000a alkane hydroxylases (AlkB1 & AlkB2), all assumed to perform hydroxylation of different linear or branched alkanes. Although,\\u000a the sequence of alkB2 has been determined, the molecular characterization and the substrate specificity of AlkB2 require more precise investigation.\\u000a In this study,

Mandana Miri; Bijan Bambai; Fatemeh Tabandeh; Majid Sadeghizadeh; Nasrin Kamali

2010-01-01

348

Regioselective alkane hydroxylation with a mutant CYP153A6 enzyme  

DOEpatents

Cytochrome P450 CYP153A6 from Myobacterium sp. strain HXN1500 was engineered using in-vivo directed evolution to hydroxylate small-chain alkanes regioselectively. Mutant CYP153A6-BMO1 selectively hydroxylates butane and pentane at the terminal carbon to form 1-butanol and 1-pentanol, respectively, at rates greater than wild-type CYP153A6 enzymes. This biocatalyst is highly active for small-chain alkane substrates and the regioselectivity is retained in whole-cell biotransformations.

Koch, Daniel J.; Arnold, Frances H.

2013-01-29

349

Liposome fluidization and melting point depression by compressed and liquid n-alkanes  

Microsoft Academic Search

Fluidization and melting point depression of aqueous dipalmitoylphosphatidylcholine (DPPC, Tm?315K) liposomes by compressed\\/supercritical n-alkanes (C2 and C3; 0.8–20.7MPa) was quantified and compared to fluidization by liquid n-alkanes (C5–C10) using fluorescence anisotropy. The adsorption of ethane and propane into DPPC bilayers resulted in significant depression of the melting temperature (up to ?Tm=?16.2K at 7.0MPa ethane and propane). Pressure-dependent fluidization by gaseous

Geoffrey D. Bothun; Barbara L. Knutson; Herbert J. Strobel; Sue E. Nokes

2006-01-01

350

Determination of the molecular area on a liquid surface from thermodynamic functions: Application to alkanes  

SciTech Connect

A method is proposed to calculate the molecular area on the surface of a liquid from thermodynamic parameters such as the molar internal energy, the surface free energy, and the surface entropy. When the method is applied to the series of normal alkanes, it allows calculation of the area of the molecules on these liquid surfaces and to deduce the orientation of these molecules. Moreover, the molecular areas of the first terms of the alkane series and of hydrogen are also obtained by extrapolation.

Carre, A.; Vial, J. (Corning Europe, Inc., Avon (France))

1993-10-15

351

Influence of alcohols and alkanes on the aggregation behavior of ionic surfactants in water  

SciTech Connect

The influence of alkanes and medium- and long-chain alcohols on the aggregation behavior of ionic surfactants is investigated by fluorescence quenching. The aggregation number of the surfactant is observed to increase dramatically upon addition of alkanes. The influence of added alcohols, however, depends on the chain length. Except butanol, which decreases the size of the aggregate, addition of higher alcohols (from heptanol to decanol) leads to an increase of the size of the micellar aggregate. Addition of alcohols (from butanol to decanol) leads to an expansion of the hydrophobic region of the aggregate and to a promotion of the diffusion process in the interface of the aggregate.

Reekmans, S.; Luo, Hongwen; Van der Auweraer, M.; De Schryver, F.C. (Universiteit Leuven, Heverlee (Belgium))

1990-03-01

352

Reactions of bis(chlorophenylarsino) alkanes with palladium(II) salts  

SciTech Connect

The yields, results of elemental analysis for arsenic content, and IR- and UV-spectral data of the cyclic arsine oxides synthesized are given. The IR-spectral data confirmed the structure of these cyclic arsine oxides. The UV spectra of the compounds were determined in ethanol and the structure of the complexes was studied by vibrational spectroscopy. In the reactions of bis(chlorophenylarsino) alkanes and cyclic arsine oxides with palladium(II) salts, complex compounds of a single type are formed because the complex formation of palladium(II) salts with bis(chlorophenylarsino) alkanes is accompanied by the catalytic hydrolysis of the latter in the coordination sphere of palladium.

Gamayurova, V.S.; Shabrukova, N.V.; Chernova, A.V.; Shagidullin, R.R.; Doroshkina, G.M.

1988-01-20

353

Heat capacity anomalies of associated liquid-alkane mixtures near the liquid-liquid critical point  

NASA Astrophysics Data System (ADS)

The isobaric heat capacity for a set of critical binary mixtures composed by an associated liquid and an alkane was measured near the liquid-liquid critical point. From a careful analysis of experimental data, nonuniversal quantities such as critical temperatures and critical amplitudes were obtained. To obtain microscopic parameters that may characterise the critical behaviour of the studied systems, the critical amplitude of the correlation length was determined via two-scale factor universality. Useful insights into the influence of the molecular structure of the alkanes as well as the self-associating capability of the polar liquid on the aforementioned nonuniversal quantities are obtained.

Souto-Caride, M.; Troncoso, J.; Losada-Pérez, P.; Peleteiro, J.; Carballo, E.; Romani, L.

2009-06-01

354

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

355

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

356

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

357

A new mechanism for regional atmospheric chemistry modeling  

NASA Astrophysics Data System (ADS)

A new gas-phase chemical mechanism for the modeling of regional atmospheric chemistry, the "Regional Atmospheric Chemistry Mechanism" (RACM) is presented. The mechanism is intended to be valid for remote to polluted conditions and from the Earth's surface through the upper troposphere. The RACM mechanism is based upon the earlier Regional Acid Deposition Model, version 2 (RADM2) mechanism [Stockwell et al., 1990] and the more detailed Euro-RADM mechanism [Stockwell and Kley, 1994]. The RACM mechanism includes rate constants and product yields from the most recent laboratory measurements, and it has been tested against environmental chamber data. A new condensed reaction mechanism is included for biogenic compounds: isoprene, ?-pinene, and d-limonene. The branching ratios for alkane decay were reevaluated, and in the revised mechanism the aldehyde to ketone ratios were significantly reduced. The relatively large amounts of nitrates resulting from the reactions of unbranched alkenes with NO3 are now included, and the production of HO from the ozonolysis of alkenes has a much greater yield. The aromatic chemistry has been revised through the use of new laboratory data. The yield of cresol production from aromatics was reduced, while the reactions of HO, NO3, and O3 with unsaturated dicarbonyl species and unsaturated peroxynitrate are now included in the RACM mechanism. The peroxyacetyl nitrate chemistry and the organic peroxy radical-peroxy radical reactions were revised, and organic peroxy radical +NO3 reactions were added.

Stockwell, William R.; Kirchner, Frank; Kuhn, Michael; Seefeld, Stephan

1997-11-01

358

CHEMISTRY IN EVAPORATING ICES-UNEXPLORED TERRITORY  

SciTech Connect

We suggest that three-body chemistry may occur in warm high-density gas evaporating in transient co-desorption events on interstellar ices. Using a highly idealized computational model we explore the chemical conversion from simple species of the ice to more complex species containing several heavy atoms, as a function of density and of adopted three-body rate coefficients. We predict that there is a wide range of densities and rate coefficients in which a significant chemical conversion may occur. We discuss the implications of this idea for the astrochemistry of hot cores.

Cecchi-Pestellini, Cesare [INAF-Osservatorio Astronomico di Cagliari, Strada n.54, Loc. Poggio dei Pini, 09012 Capoterra (Italy); Rawlings, Jonathan M. C.; Viti, Serena; Williams, David A., E-mail: ccp@ca.astro.i, E-mail: jcr@star.ucl.ac.u, E-mail: sv@star.ucl.ac.u, E-mail: daw@star.ucl.ac.u [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2010-12-20

359

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

360

Constitutional dynamic chemistry: bridge from supramolecular chemistry to adaptive chemistry.  

PubMed

Supramolecular chemistry aims at implementing highly complex chemical systems from molecular components held together by non-covalent intermolecular forces and effecting molecular recognition, catalysis and transport processes. A further step consists in the investigation of chemical systems undergoing self-organization, i.e. systems capable of spontaneously generating well-defined functional supramolecular architectures by self-assembly from their components, thus behaving as programmed chemical systems. Supramolecular chemistry is intrinsically a dynamic chemistry in view of the lability of the interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their constituents. The same holds for molecular chemistry when the molecular entity contains covalent bonds that may form and break reversibility, so as to allow a continuous change in constitution by reorganization and exchange of building blocks. These features define a Constitutional Dynamic Chemistry (CDC) on both the molecular and supramolecular levels.CDC introduces a paradigm shift with respect to constitutionally static chemistry. The latter relies on design for the generation of a target entity, whereas CDC takes advantage of dynamic diversity to allow variation and selection. The implementation of selection in chemistry introduces a fundamental change in outlook. Whereas self-organization by design strives to achieve full control over the output molecular or supramolecular entity by explicit programming, self-organization with selection operates on dynamic constitutional diversity in response to either internal or external factors to achieve adaptation.The merging of the features: -information and programmability, -dynamics and reversibility, -constitution and structural diversity, points to the emergence of adaptive and evolutive chemistry, towards a chemistry of complex matter. PMID:22169958

Lehn, Jean-Marie

2012-01-01

361

Using n-alkanes for identification of oils in domestic wastewaters.  

PubMed

The aim of this work was to investigate whether linear aliphatic hydrocarbons had a usable potential for the determination of waste oil in wastewater. For that, n-alkanes analyses of wastewater samples from five sampling points (P1-P5) of the sewage system of Konya-Turkey were carried out by gas chromatographic technique and the parameters of carbon predominance index (ICP), n-C17/n-C18 and unresolved complex mixture (UCM)/n-alkanes ratios were determined. It was found that sampling points P1, P2, and P3, which had ICP values 1.52 +/- 0.04, 1.43 +/- 0.05 and 1.12 +/- 0.05, respectively, were polluted with petroleum hydrocarbons and the aliphatic hydrocarbons detected in the sampling points of P4 and P5, which had ICP values of 0.96 +/- 0.05 and 0.95 +/- 0.03, respectively, were from natural origin. These results were also supported by the parameters of n-C17/n-C18 and UCM/n-alkanes ratios and by the correlation between the parameters of ICP, n-C17/n-C18, UCM/n-alkanes and COD, Pb, Cr for all sampling points. PMID:16335604

Tor, A; Aydin, M E; Cengeloglu, Y; Ozcan, S

2005-11-01

362

Aerosols in equatorial Atlantic air - n-alkanes as a function of particle size  

Microsoft Academic Search

The concentrations and distributions of n-alkanes in the western equatorial Atlantic, Gulf of Guinea region were determined by aerosol sampling and calculated in terms of particle size. Data were gathered in the period May-June 1977 by means of a five stage cascade impactor for large air volumes mounted on the bow of a boat. The collected gases were separated into

J.-C. Marty; Alain Saliot

1982-01-01

363

Anaerobic biodegradation of long-chain n-alkanes under sulfate-reducing conditions  

SciTech Connect

The ability of anaerobic microorganisms to degrade a wide variety of crude oil components was investigated using chronically hydrocarbon-contaminated marine sediments as the source of inoculum. When sulfate reduction was the predominant electron-accepting process, gas chromatographic analysis revealed almost complete n-alkane removal (C{sub 15}-C{sub 34}) from a weathered oil within 201 d of incubation. No alteration of the oil was detected in sterile control incubations or when nitrate served as an alternate electron acceptor. The amount of sulfate reduced in the oil-amended nonsterile incubations was more than enough to account for the complete mineralization of the n-alkane fraction of the oil; no loss of this anion was observed in sterile control incubations. The mineralization of the alkanes was confirmed using {sup 14}C-14,15-octacosane (C{sub 28}H{sub 58}), with 97% of the radioactivity recovered as {sup 14}CO{sub 2}. These findings extend the range of hydrocarbons known to be amenable to anaerobic biodegradation. Moreover, the rapid and extensive alteration in the n-alkanes can no longer be considered a defining characteristic of aerobic oil biodegradation processes alone.

Caldwell, M.E.; Suflita, J.M. [Univ. of Oklahoma, Norman, OK (United States). Dept. of Botany and Microbiology; Garrett, R.M.; Prince, R.C. [Exxon Research and Engineering Co., Annandale, NJ (United States)

1998-07-15

364

Structure?reactivity relationships in dehydrohalogenation reactions of polychlorinated and polybrominated alkanes  

Microsoft Academic Search

Current information is inadequate to predict the rates at which polyhalogenated alkanes undergo dehydrohalogenation reactions under environmental conditions, forming olefins that are frequently more toxic and more recalcitrant than the products of substitution reactions. To permit evaluation of the relative importance of different potential transformation products, qualitative relationships between structure and reactivity via substitution and dehydrohalogenation pathways are reviewed. In

A. L. Roberts; P. M. Jeffers; N. L. Wolfe; P. M. Gschwent

1993-01-01

365

Improved GC/MS method for quantitation of n-Alkanes in plant and fecal material  

Technology Transfer Automated Retrieval System (TEKTRAN)

A gas chromatography-mass spectrometry (GC/MS) method for the quantitation of n-alkanes (carbon backbones ranging from 21 to 36 carbon atoms) in forage and fecal samples has been developed. Automated solid-liquid extraction using elevated temperature and pressure minimized extraction time to 30 min...

366

Sources and Significance of Alkane and PAH Hydrocarbons in Canadian Arctic Rivers  

Microsoft Academic Search

Hydrocarbon measurements have been made on dissolved, suspended particulate and sediment samples collected in 1987, 1993 and 1994 from the Mackenzie River delta and shelf and in 1993 from 10 smaller Northwest Territories and Nunavut rivers that drain into the Canadian Archipelago or Hudson's Bay. Suspended particulate samples from all rivers have a resolved higher alkane pattern with a well-defined

M. B. Yunker; S. M. Backus; E. Graf Pannatier; D. S. Jeffries; R. W. Macdonald

2002-01-01

367

Investigation of heavy atom effect of halide alkanes in ?-cyclodextrin induced room temperature phosphorimetry  

Microsoft Academic Search

Twenty-one alkyl halides were examined in detail for their heavy atom effect in ?-cyclodextrin induced room temperature phosphorescence (?-CD-RTP) with five polycyclic aromatic as mode compounds. The following conclusions were drawn from the experimental results. (1) The heavy atom enhancement effect (HAEE) of halogens in halide alkane are increased in the trend of Br > Cl ? I. (2) Among

Yan-Sheng Wei; Wei-Jun Jin; Ruo-Hua Zhu; Guo-Wen Xing; Chang-Song Liua; Shu-Se Zhang; Bai-Ling Zhou

1996-01-01

368

Kinetic model of alkane oxidation at high pressure from methane to n-heptane  

Microsoft Academic Search

This work describes the kinetic model of alkane oxidation which is the result of creating a united kinetic mechanism for a whole homologous series of hydrocarbons, in this case from methane to n-heptane. The detail kinetic model consists of 549 species and 2518 reactions. The developed mechanism was validated against experimental data from a shock tube. The kinetic model agrees

Victor P. Zhukov

2009-01-01

369

Femtosecond study of geminate electron--hole recombination in neat alkanes  

SciTech Connect

The first measurement of the geminate electron--hole recombination times of two neat octane isomers has been studied using femtosecond techniques. The recombination times were found to be 2.2 +- 1.0 ps in n-octane and 470 +- 40 fs in iso-octane, thus showing that the rates are strongly dependent on the structure of the alkane solvents.

Bowman, R.M.; Lu, H.; Eisenthal, K.B.

1988-07-01

370

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

371

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

372

ALKANES, METHYLALKANES, ALKENES AND ALKADIENES OF ADULT FLEA BEETLES, APHTHONA SPECIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

The adult beetles, Aphthona lacertosa and Aphthona nigriscutis, used as biocontrol agents for leafy spurge, had a complex mixture of hydrocarbons on their cuticular surface consisting of alkanes, methylalkanes, alkenes and alkadienes as determined by gas chromatography-mass spectrometry. A trace ...

373

Volatile Alkanes and Increased Concentrations of Isoprene in Exhaled Air during Hemodialysis  

Microsoft Academic Search

In this study we examined breath volatile hydrocarbon concentrations in exhaled air of hemodialysis patients. We assessed both C2–C5 alkanes – among them ethane and pentane the production of which in man is essentially due to the action free radicals exert on polyunsaturated fatty acids – and isoprene, an unsaturated hydrocarbon the biosynthesis and biological effects of which are the

Enrico Capodicasa; Gianfranco Trovarelli; Gianna Evelina De Medio; Maria Antonietta Pelli; Giorgio Lippi; Claudio Verdura; Mario Timio

1999-01-01

374

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

375

Phase behavior of nonionic surfactant\\/oil\\/water systems containing light alkanes  

Microsoft Academic Search

The phase behavior of nonionic ethoxylate surfactant\\/light alkane\\/water systems is reported in detail. In compressible liquids such as propane, phase transitions which are normally induced by changing temperature or salinity can also be accomplished with pressure. A complete transition from a lower to middle to upper phase microemulsion with pressure is reported for the first time in propane. Widely accepted

Gregory J. McFann; Keith P. Johnston

1993-01-01

376

Petrodiesel-like straight chain alkane and fatty alcohol production by the microalga Chlorella sorokiniana.  

PubMed

This study was to investigate the composition and characteristics of long-straight chain alkane and fatty alcohols from the microalga Chlorella Sorokiniana 21, isolated from the coastal water of Pearl River Delta, China. Under the optimized aeration growth condition, this strain yielded up to 1.44 g L(-1) biomass and 24.90% extracts of dry weight. The major compounds of the extracts were identified to be alkanes (35.93%) and alcohols (53.73%). Of the extracts, long-straight chain alkanes accounted for 30.54% with heptadecane (21.13%) as a predominant component. Furthermore, a large amount of fatty alcohols (53.73%) were identified in the algal extracts with 29.09% of 3-(2-methoxyethyl)-1-nonanol. Thus, this algal species is a promising feedstock for the production of supplement for petrodiesel-like fuels and biochemicals used in the cosmetics and food industries. This study represents the first report of long-straight chain alkane and fatty alcohols from microalgae isolated from coastal water of the region. PMID:23567672

Yang, Xuewei; Dai, Xin; Guo, Hui; Geng, Shu; Wang, Gangyi

2013-02-28

377

Electron Microscopy in the Catalysis of Alkane Oxidation, Environmental Control, and Alternative Energy Sources  

Microsoft Academic Search

The key role of electron microscopy in understanding and creating advanced catalyst materials and processes in selective alkane oxidation, environmental control, and alternative energy sources is reviewed. In many technological processes, catalysts are increasingly nanoscale heterogeneous materials. With growing regulatory guidelines requiring efficient and environmentally compatible catalytic processes, it is crucial to have a fundamental understanding of the catalyst nanostructure

Pratibha L. Gai; Jose J. Calvino

2005-01-01

378

Heat capacity anomalies of associated liquid–alkane mixtures near the liquid–liquid critical point  

Microsoft Academic Search

The isobaric heat capacity for a set of critical binary mixtures composed by an associated liquid and an alkane was measured near the liquid–liquid critical point. From a careful analysis of experimental data, nonuniversal quantities such as critical temperatures and critical amplitudes were obtained. To obtain microscopic parameters that may characterise the critical behaviour of the studied systems, the critical

M. Souto-Caride; J. Troncoso; P. Losada-Pérez; J. Peleteiro; E. Carballo; L. Romani

2009-01-01

379

Estimation of flash points and molecular masses of alkanes from their IR spectra  

Microsoft Academic Search

The use of transformed infrared spectra as descriptors of a molecular structure makes it possible to predict flash points\\u000a and relative molecular masses of alkanes. The prediction does not require additional information on the structure of molecules.

V. V. Vazhev; M. K. Aldabergenov; N. V. Vazheva

2006-01-01

380

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

381

Special Report: Brain Chemistry.  

ERIC Educational Resources Information Center

Chemical actions in the brain result in cognitive, emotional, neuroendocrine, neuromuscular, and/or neurocirculatory effects. Developments in understanding brain chemistry are discussed, considering among others, neurotransmitter chemistry, neuropeptides, drugs and the brain, antidepressants, and actions of minor tranquilizers. (JN)

Krassner, Michael B.

1983-01-01

382

Chemistry of Americium.  

National Technical Information Service (NTIS)

Essential features of the descriptive chemistry of americium are reviewed. Chapter titles are: discovery, atomic and nuclear properties, collateral reading, production and uses, chemistry in aqueous solution, metal, alloys, and compounds, and, recovery, s...

W. W. Schulz

1976-01-01

383

Environmental chemistry: Volume A  

SciTech Connect

This is an extensive introduction to environmental chemistry for engineering and chemical professionals. The contents of Volume A include a brief review of basic chemistry prior to coverage of litho, atmo, hydro, pedo, and biospheres.

Yen, T.F.

1999-08-01

384

Theory of phase equilibria for model mixtures of n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock surfactants  

NASA Astrophysics Data System (ADS)

An extension of the SAFT-VR equation of state, the so-called hetero-SAFT approach [Y. Peng, H. Zhao, and C. McCabe, Molec. Phys. 104, 571 (2006)], is used to examine the phase equilibria exhibited by a number of model binary mixtures of n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock surfactants. Despite the increasing recent interest in semifluorinated alkanes (or perfluoroalkylalkane diblock molecules), the phase behaviour of mixtures involving these molecules with n-alkanes or perfluoroalkanes is practically unknown from the experimental point of view. In this work, we use simple molecular models for n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock molecules to predict, from a molecular perspective, the phase behaviour of selected model mixtures of perfluoroalkylalkanes with n-alkanes and perfluoroalkanes. In particular, we focus our interest on the understanding of the microscopic conditions that control the liquid-liquid separation and the stabilization of these mixtures. n-Alkanes and perfluoroalkanes are modelled as tangentially bonded monomer segments with molecular parameters taken from the literature. The perfluoroalkylalkane diblock molecules are modelled as heterosegmented diblock chains, with parameters for the alkyl and perfluoroalkyl segments developed in earlier work. This simple approach, which was proposed in previous work [P. Morgado, H. Zhao, F. J. Blas, C. McCabe, L. P. N. Rebelo, and E. J. M. Filipe, J. Phys. Chem. B, 111, 2856], is now extended to describe model n-alkane (or perfluoroalkane) + perfluroalkylalkane binary mixtures. We have obtained the phase behaviour of different mixtures and studied the effect of the molecular weight of n-alkanes and perfluoroalkanes on the type of phase behaviour observed in these mixtures. We have also analysed the effect of the number of alkyl and perfluoroalkyl chemical groups in the surfactant molecule on the phase behaviour. In addition to the usual vapour-liquid phase separation, liquid-liquid, positive azeotropes, and Bancroft points are found for different mixtures. This rich phase behaviour is a consequence of a delicate balance between the alkyl-alkyl, perfluoroalkyl-perfluoroalkyl, and alkyl-perfluoroalkyl interactions in different molecules. We used the SAFT-VR microscopic description of chain-like systems to analyse the conditions that n-alkane (or perfluoroalkane) + perfluoroalkyalkane mixtures should posses in order to exhibit complete liquid miscibility. Although the model proposed here is chosen to reproduce most of the quantitative features of the phase equilibria of some pure perfluoroalkylalkane diblock surfactants and their mixtures with n-alkanes, this is the first time the SAFT approach has been used to predict the phase behaviour of the mixtures considered here. The lack of experimental data for these systems does not allow us to test the accuracy of our theoretical predictions directly. However, since SAFT has proven to be an excellent approach for the prediction of the phase behaviour of complex mixtures, we expect that the theory will reproduce the most important qualitative trends exhibited by real mixtures.

Dos Ramos, María Carolina; Blas, Felipe J.

2007-05-01

385

Should alkane biomarker results be corrected for degradation effects when reconstructing vegetation changes?  

NASA Astrophysics Data System (ADS)

N-alkanes with 25 to 33 carbon atoms are important constituents of plant leaf waxes and thereby typically reveal a strong odd over even predominance (OEP). The homologues C27 and C29 are characteristically dominant in most trees and shrubs, whereas C31 and C33 are dominant in grasses and herbs. With the litter-fall the cuticular alkanes are also deposited in sediments and soils, where they are regarded to be relatively resistant to degradation and therefore may serve as plant-derived biomarkers. Hence, alkane ratios like C31/C27 have been used in Quaternary studies to reconstruct vegetation changes. But in fact a change of alkane patterns has been reported when comparing fresh litter and the soil organic matter developing from it. This can be either attributed to a selective removal of alkanes during degradation, to the input of root or microbial biomass or to thermal degradation. On the one hand, the alkane patterns are getting more balanced, i.e. dominances of C27 in trees and C31 in grasses, respectively, are reduced and the ratios C31/C27 are approximating the value 1. Hence, reconstructed vegetation changes neglecting this effect may be invalid. On the other hand, it has been shown for several litter types that the OEP values, being high in fresh plant material, are becoming lower during organic matter degradation. Aiming at reconstructing vegetation changes in loess-palaeosol sequences of the Vojvodina, Serbia, we did not only sample the Quaternary sequence, but additionally analysed modern litter and topsoils from natural forests and grasslands. We propose to use the OEP as proxy for degradation and plot the alkane ratios in percent against the OEP in order to obtain ‘degradation lines' for grassland- versus forest- derived organic matter (Zech et al., 2009, Eiszeitalter und Gegenwart - Quaternary Science Journal, submitted). Accordingly, for a given loess or palaeosol sample, an improved (corrected for the degradation effect) estimation of the percentage contribution of tree- versus grass-derived alkanes can be determined in two steps. Firstly, using the OEP of a sample, the respective alkane ratio end-members for grassland and forest are calculated by means of the functions describing the degradation lines. Secondly, using the end members obtained for a certain sample, the percent contribution of the two vegetation types is estimated by means of a two component mixing equation. Modelling results for the alkane ratios C31/C27, C31/C29, C33/C27 and (C31+C33)/(C27+C29) from the investigated loess-palaeosol sequence in Serbia are very similar. Although they question the traditional and palynologically derived paradigm of treeless full-glacial palaeoenvironments, they are in apparent agreement with charcoal and malacological findings from the Carpathian Basin.

Zech, M.; Buggle, B.; Glaser, B.

2009-04-01

386

Aquatic Chemistry, Third Edition  

NASA Astrophysics Data System (ADS)

Most water scientists and environmental engineers will recognize this classic environmental chemistry text as “Stumm and Morgan” rather than Aquatic Chemistry. Publication of the first edition in 1970 established a standard for books dealing with environmental chemistry in terms of depth and breadth of coverage. Scientists and engineers concerned with issues of water quality are well advised to have Aquatic Chemistry as part of their personal libraries, or at least in their office libraries.

Schroeder, Edward D.; Young, Thomas M.

387

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

388

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

389

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

390

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

391

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

392

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

393

Aquatic Chemistry, Third Edition  

Microsoft Academic Search

Most water scientists and environmental engineers will recognize this classic environmental chemistry text as ``Stumm and Morgan'' rather than Aquatic Chemistry. Publication of the first edition in 1970 established a standard for books dealing with environmental chemistry in terms of depth and breadth of coverage. Scientists and engineers concerned with issues of water quality are well advised to have Aquatic

Edward D. Schroeder; Thomas M. Young

1996-01-01

394

Analytical chemistry instrumentation  

Microsoft Academic Search

Separate abstracts were prepared for 48 papers in these conference proceedings. The topics covered include: analytical chemistry and the environment; environmental radiochemistry; automated instrumentation; advances in analytical mass spectrometry; Fourier transform spectroscopy; analytical chemistry of plutonium; nuclear analytical chemistry; chemometrics; and nuclear fuel technology. (LEW)

Laing

1986-01-01

395

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

396

Towards Conversational Artifacts  

Microsoft Academic Search

\\u000a Conversation is a natural and powerful means of communication for people to collaboratively create and share information.\\u000a People are skillful in expressing meaning by coordinating multiple modalities, interpreting utterances by integrating partial\\u000a cues, and aligning their behavior to pursuing joint projects in conversation. A big challenge is to build conversational artifacts\\u000a – such as intelligent virtual agents or conversational robots

Toyoaki Nishida

397

Transcriptional profiling of the marine oil-degrading bacterium Alcanivorax borkumensis during growth on n-alkanes.  

PubMed

The marine oil-degrading bacterium Alcanivorax borkumensis SK2 has attracted significant interest due to its hydrocarbonoclastic lifestyle, its alkane-centered metabolism, and for playing an important ecological role in cleaning up marine oil spills. In this study, we used microarray technology to characterize the transcriptional responses of A. borkumensis to n-hexadecane exposure as opposed to pyruvate, which led to the identification of a total of 220 differentially expressed genes, with 109 genes being upregulated and 111 genes being downregulated. Among the genes upregulated on alkanes are systems predicted to be involved in the terminal oxidation of alkanes, biofilm formation, signal transduction, and regulation. PMID:21470299

Sabirova, Julia S; Becker, Anke; Lünsdorf, Heinrich; Nicaud, Jean-Marc; Timmis, Kenneth N; Golyshin, Peter N

2011-04-20

398

Charisma and conversion  

Microsoft Academic Search

The author examines the dynamic process involved in charisma and conversion. Conversion is discussed following Murphy's study of Puritan conversion as identification, introjection, and displacement. Charisma is described as a special power attributed to person(s) by observers. The affect of charisma on the convert in terms of the importance of the leader as the embodiment of faith, i.e., a model,

Lewis R. Rambo

1982-01-01

399

Retrospective Conversion of Serials  

Microsoft Academic Search

This article describes implementing the MARC holdings format through machine conversion and through hands-on coding and data entry. It presents two actual and one potential means of retrospective conversion that have taken place or are being tested at University Libraries, Virginia Polytechnic Institute and State University. One conversion project from nonstandard holdings in an online catalog, converted thorough holdings information

Gail McMillan

1992-01-01

400

Direct Conversion of Energy.  

ERIC Educational Resources Information Center

|This publication is one of a series of information booklets for the general public published by the United States Atomic Energy Commission. Direct energy conversion involves energy transformation without moving parts. The concepts of direct and dynamic energy conversion plus the laws governing energy conversion are investigated. Among the topics…

Corliss, William R.

401

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 ...

402

Alcohol, Chemistry and You  

NSDL National Science Digital Library

Developed by Kennesaw State University, ChemCases.com is a series of curriculum units that link responsible decision making in product development with chemical principles taught in college General Chemistry. Alcohol, Chemistry and You, by Dr. Bill Boggan, is the latest offering by the Web site, which "looks at the chemistry of beverage alcohol (ethyl alcohol) through the eyes of a General Chemistry student." The fourteen chapter lessons cover everything from what ethyl alcohol is to alcohol addiction, relating it to various principles learned in a general chemistry course.

2001-01-01

403

Carboxylic acid reductase is a versatile enzyme for the conversion of fatty acids into fuels and chemical commodities.  

PubMed

Aliphatic hydrocarbons such as fatty alcohols and petroleum-derived alkanes have numerous applications in the chemical industry. In recent years, the renewable synthesis of aliphatic hydrocarbons has been made possible by engineering microbes to overaccumulate fatty acids. However, to generate end products with the desired physicochemical properties (e.g., fatty aldehydes, alkanes, and alcohols), further conversion of the fatty acid is necessary. A carboxylic acid reductase (CAR) from Mycobacterium marinum was found to convert a wide range of aliphatic fatty acids (C(6)-C(18)) into corresponding aldehydes. Together with the broad-substrate specificity of an aldehyde reductase or an aldehyde decarbonylase, the catalytic conversion of fatty acids to fatty alcohols (C(8)-C(16)) or fatty alkanes (C(7)-C(15)) was reconstituted in vitro. This concept was applied in vivo, in combination with a chain-length-specific thioesterase, to engineer Escherichia coli BL21(DE3) strains that were capable of synthesizing fatty alcohols and alkanes. A fatty alcohol titer exceeding 350 mg·L(-1) was obtained in minimal media supplemented with glucose. Moreover, by combining the CAR-dependent pathway with an exogenous fatty acid-generating lipase, natural oils (coconut oil, palm oil, and algal oil bodies) were enzymatically converted into fatty alcohols across a broad chain-length range (C(8)-C(18)). Together with complementing enzymes, the broad substrate specificity and kinetic characteristics of CAR opens the road for direct and tailored enzyme-catalyzed conversion of lipids into user-ready chemical commodities. PMID:23248280

Akhtar, M Kalim; Turner, Nicholas J; Jones, Patrik R

2012-12-17

404

Organic composition of PM 2.5 and size-segregated aerosols and their sources during the 2002 Bay Regional Atmospheric Chemistry Experiment (BRACE), Florida, USA  

Microsoft Academic Search

PM2.5 and size-segregated aerosols were collected in May 2002 as part of the Bay Regional Atmospheric Chemistry Experiment (BRACE), Florida, USA. Aerosol organic composition was used to estimate sources of a series of alkanes and polycyclic aromatic hydrocarbons (PAHs) using chemical indices, hierarchical cluster analysis (HCA) and a chemical mass balance receptor model (CMB). Aerosols were collected on quartz fiber

Raphaël T. Tremblay; Daniel D. Riemer; Rod G. Zika

2007-01-01

405

Assessing anthropogenic contamination in surface sediments of Niger Delta, Nigeria with fecal sterols and n-alkanes as indicators.  

PubMed

The occurrence of sterols and n-alkanes in surface sediments from rivers and canals in the Niger Delta, Nigeria, determined with a gas chromatography-mass spectrometry method, was used to assess the impacts of anthropogenic activities in the area. The concentrations of total sterols (??Sterol) and n-alkanes (???n-alkane) in the sediments ranged from 133 to 2040 ng/g and 474 to 79,200 ng/g, respectively. An evaluation of the source diagnostic indices indicated that petroleum related sources (petrogenic) were the main contributor of n-alkanes in the samples, with minor contribution from higher plants waxes (biogenic), while the sterols were mainly of biogenic origin. The ratio of ?-cholestanone/(?-cholestanone+?-cholestanone), a commonly used source diagnostic index, implicated no fecal contamination in most of the sediment samples under investigation. These results have established the occurrence of anthropogenic contamination in Niger Delta sediments with significant contributions from petrogenic sources. PMID:23137973

Sojinu, Samuel O; Sonibare, Oluwadayo O; Ekundayo, O; Zeng, Eddy Y

2012-11-06

406

Conversion of biomass to selected chemical products.  

PubMed

This critical review provides a survey illustrated by recent references of different strategies to achieve a sustainable conversion of biomass to bioproducts. Because of the huge number of chemical products that can be potentially manufactured, a selection of starting materials and targeted chemicals has been done. Also, thermochemical conversion processes such as biomass pyrolysis or gasification as well as the synthesis of biofuels were not considered. The synthesis of chemicals by conversion of platform molecules obtained by depolymerisation and fermentation of biopolymers is presently the most widely envisioned approach. Successful catalytic conversion of these building blocks into intermediates, specialties and fine chemicals will be examined. However, the platform molecule value chain is in competition with well-optimised, cost-effective synthesis routes from fossil resources to produce chemicals that have already a market. The literature covering alternative value chains whereby biopolymers are converted in one or few steps to functional materials will be analysed. This approach which does not require the use of isolated, pure chemicals is well adapted to produce high tonnage products, such as paper additives, paints, resins, foams, surfactants, lubricants, and plasticisers. Another objective of the review was to examine critically the green character of conversion processes because using renewables as raw materials does not exempt from abiding by green chemistry principles (368 references). PMID:21909591

Gallezot, Pierre

2011-09-12

407

Size distribution of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) in urban and rural atmospheres of Guangzhou, China  

Microsoft Academic Search

n-Alkanes and polycyclic aromatic hydrocarbons (PAHs) were identified in particle-sized aerosols of the urban and rural atmospheres of Guangzhou, China. Most of the organic compounds were mainly associated with fine particles with aerodynamic diameters less than 1.5?m in the urban and rural atmospheres. In the urban aerosol close to the road, about 57% of n-alkanes and 62% of PAHs were

Xinhui Bi; Guoying Sheng; Ping’an Peng; Yingjun Chen; Jiamo Fu

2005-01-01

408

Are alkane hydroxylase genes ( alkB ) relevant to assess petroleum bioremediation processes in chronically polluted coastal sediments?  

Microsoft Academic Search

The diversity of alkB-related alkane hydroxylase sequences and the relationship between alkB gene expression and the hydrocarbon contamination level have been investigated in the chronically polluted Etang-de-Berre\\u000a sediments. For this purpose, these sediments were maintained in microcosms and submitted to a controlled oil input miming\\u000a an oil spill. New degenerated PCR primers targeting alkB-related alkane hydroxylase sequences were designed to

Sandrine Paisse; Robert Duran; Frédéric Coulon; Marisol Goñi-Urriza

409

Isolation of an alkane-degrading Alcanivorax sp. strain 2B5 and cloning of the alkB gene  

Microsoft Academic Search

A Gram-negative coccus, strain 2B5, was isolated from the sea mud of the crude oil-polluted Donghai area in China and identified as Alcanivorax sp. based on its physiological characteristics and analysis of its 16S rRNA gene sequence. Strain 2B5 was able to degrade C13–C30n-alkanes and branched alkanes (pristane and phytane) from crude oil as the sole carbon source. The optimal

Yi-Chen Liu; Ling-Zhi Li; Ying Wu; Wei Tian; Li-Ping Zhang; Lian Xu; Qi-Rong Shen; Biao Shen

2010-01-01

410

Carbon isotopic composition of individual n-alkanes in asphaltene pyrolysates of biodegraded crude oils from the Liaohe Basin, China  

Microsoft Academic Search

Biodegraded oils are widely distributed in the Liaohe basin, China. In order to develop effective oil-source correlation tools specifically for the biodegraded oils, carbon isotopic compositions of individual n-alkanes from crude oils and their asphaltene pyrolysates have been determined using the gas chromatography–isotope ratio mass spectrometry technique. No significant fractionation in the stable carbon isotopic ratios of n-alkanes in the

Yongqiang Xiong; Ansong Geng

2000-01-01

411

Stable Isotope Labeled n-Alkanes to Assess Digesta Passage Kinetics through the Digestive Tract of Ruminants  

PubMed Central

We describe the use of carbon stable isotope (13C) labeled n-alkanes as a potential internal tracer to assess passage kinetics of ingested nutrients in ruminants. Plant cuticular n-alkanes originating from intrinsically 13C labeled ryegrass plants were pulse dosed intraruminally in four rumen-cannulated lactating dairy cows receiving four contrasting ryegrass silage treatments that differed in nitrogen fertilization level (45 or 90 kg nitrogen ha?1) and maturity (early or late). Passage kinetics through the gastrointestinal tract were derived from the ?13C (i.e. the ratio 13C:12C) in apparently undigested fecal material. Isotopic enrichment was observed in a wide range of long-chain n-alkanes (C27–C36) and passage kinetics were determined for the most abundant C29, C31 and C33 n-alkanes, for which a sufficiently high response signal was detected by combustion isotope ratio mass spectrometry. Basal diet treatment and carbon chain length of n-alkanes did not affect fractional passage rates from the rumen (K1) among individual n-alkanes (3.71–3.95%/h). Peak concentration time and transit time showed a quantitatively small, significant (p?0.002) increase with carbon chain length. K1 estimates were comparable to those of the 13C labeled digestible dry matter fraction (3.38%/h; r?=?0.61 to 0.71; p?0.012). A literature review has shown that n-alkanes are not fermented by microorganisms in the rumen and affirms no preferential depletion of 13C versus 12C. Our results suggest that 13C labeled n-alkanes can be used as nutrient passage tracers and support the reliability of the ?13C signature of digestible feed nutrients as a tool to measure nutrient-specific passage kinetics.

Warner, Daniel; Ferreira, Luis M. M.; Breuer, Michel J. H.; Dijkstra, Jan; Pellikaan, Wilbert F.

2013-01-01

412

The influence of intermolecular interactions in n-pentane-alkane-1-ol systems on their physicochemical properties  

Microsoft Academic Search

The Helmholtz energy of dipole-dipole interaction (SigmaDeltad F) and its long-range (Deltad F°) and short-range (Deltad F*) components were calculated for n-pentane-alkane-1-ol (from methanol to dodecane-1-ol) systems at 298.15 K using the Winkelmann statistical model theory of liquid dielectrics. It was shown that the longer the alkane-1-ol hydrocarbon radical, the greater the extent to which the properties of the systems

E. D. Totchasov; G. A. Al'Per

2008-01-01

413

Stable Isotope Labeled n-Alkanes to Assess Digesta Passage Kinetics through the Digestive Tract of Ruminants.  

PubMed

We describe the use of carbon stable isotope ((13)C) labeled n-alkanes as a potential internal tracer to assess passage kinetics of ingested nutrients in ruminants. Plant cuticular n-alkanes originating from intrinsically (13)C labeled ryegrass plants were pulse dosed intraruminally in four rumen-cannulated lactating dairy cows receiving four contrasting ryegrass silage treatments that differed in nitrogen fertilization level (45 or 90 kg nitrogen ha(-1)) and maturity (early or late). Passage kinetics through the gastrointestinal tract were derived from the ?(13)C (i.e. the ratio (13)C:(12)C) in apparently undigested fecal material. Isotopic enrichment was observed in a wide range of long-chain n-alkanes (C27-C36) and passage kinetics were determined for the most abundant C29, C31 and C33 n-alkanes, for which a sufficiently high response signal was detected by combustion isotope ratio mass spectrometry. Basal diet treatment and carbon chain length of n-alkanes did not affect fractional passage rates from the rumen (K 1) among individual n-alkanes (3.71-3.95%/h). Peak concentration time and transit time showed a quantitatively small, significant (p?0.002) increase with carbon chain length. K 1 estimates were comparable to those of the (13)C labeled digestible dry matter fraction (3.38%/h; r?=?0.61 to 0.71; p?0.012). A literature review has shown that n-alkanes are not fermented by microorganisms in the rumen and affirms no preferential depletion of (13)C versus (12)C. Our results suggest that (13)C labeled n-alkanes can be used as nutrient passage tracers and support the reliability of the ?(13)C signature of digestible feed nutrients as a tool to measure nutrient-specific passage kinetics. PMID:24124493

Warner, Daniel; Ferreira, Luis M M; Breuer, Michel J H; Dijkstra, Jan; Pellikaan, Wilbert F

2013-10-04

414

Configurational-Bias Monte Carlo (CB-MC) Calculations of n-Alkane Sorption in Zeolites Rho and Fer  

Microsoft Academic Search

A newly-developed Monte Carlo method is used to simulate the energetics, location and conformation of n-alkanes from butane to decane inside all-silica polymorphs of zeolites rho and ferrierite. Sorption in ferrierite yields far larger heats of adsorption than in rho. In rho, the alkanes adopt highly coiled conformations within the ?-cages of the structure, whereas in ferrierite they are confined

Simon P. Bates; Willy J. M. Van Well; Rutger A. Van Santen; Berend Smit

1997-01-01

415

Molecular simulations of adsorption isotherms of small alkanes in FER, TON, MTW and DON-type zeolites  

Microsoft Academic Search

Computer simulations are a useful tool in the study of the adsorption of alkanes in zeolites, provided the zeolite–alkane interactions are described in an adequate manner. MFI-type zeolites are among the most frequently studied types of zeolite. Consequently, zeolite specific force fields are often parameterized using experimental data obtained on MFI-type zeolites. In this paper we examine whether these force

Jean-Marie B Ndjaka; Gooitzen Zwanenburg; Berend Smit; Merijn Schenk

2004-01-01

416

Charge transfer complex formation between p-chloranil and 1, n-di(9-anthryl)alkanes  

Microsoft Academic Search

Dimer model compounds of polyvinylanthracenes (1,n-di(9-anthryl)alkanes, when n=1–5) were synthesized to model the effects of distance and orientation between anthracene groups in polymeric systems. Charge transfer (CT) complexes of anthracene, 9-methylanthracene and 1,n-di(9-anthryl)alkanes with p-chloranil (p-CHL) have been investigated spectrophotometrically in dichloromethane. The colored products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptor.

Mustafa Arslan; John Masnovi

2006-01-01

417

Compound-specific deltaD-delta13C analyses of n-alkanes extracted from terrestrial and aquatic plants.  

PubMed

Stable hydrogen and carbon isotopic compositions of individual n-alkanes were determined for various terrestrial plants (33 samples including 27 species) and aquatic plants (six species) in natural environments from Japan and Thailand. In C3 plants, n-alkanes extracted from angiosperms have a deltaD value of -152+/-26 per thousand (relative to Standard Mean Ocean Water [SMOW]) and delta13C value of -36.1+/-2.7 per thousand (relative to Peedde Belemnite [PDB]), and those from gymnosperms have a deltaD value of -149+/-16 per thousand and delta13C value of -31.6+/-1.7 per thousand. Angiosperms have n-alkanes depleted in 13C relative to gymnosperms. n-Alkanes from C4 plants have a deltaD value of -171+/-12 per thousand and delta13C value of -20.5+/-2.1 per thousand, being a little depleted in D and much enriched in 13C compared to C3 plants. n-Alkanes of CAM plants are a little depleted in D and vary widely in delta13C relative to those of C3 and C4 plants. In aquatic plants, n-alkanes from freshwater plants have a deltaD value of -187+/-16 per thousand and delta13C value of -25.3+/-1.9 per thousand, and those from seaweeds have a deltaD value of -155+/-34 per thousand and delta13C value of -22.8+/-1.0 per thousand. All n-alkanes from various plant classes are more depleted in D and 13C relative to environmental water and bulk tissue, respectively. In addition, the hydrogen and carbon isotopic fractionations during n-alkane synthesis are distinctive for these various plant classes. While C3 plants have smaller isotopic fractionations in both D and 13C, seaweed has larger isotopic fractionations. PMID:12737985

Chikaraishi, Yoshito; Naraoka, Hiroshi

2003-06-01

418

Two-Dimensional Stable Isotope Fractionation During Aerobic and Anaerobic Alkane Biodegradation and Implications for the Field  

Microsoft Academic Search

Quantitatively, n-alkanes comprise a major portion of most crude oils. In petroliferous formations, it may be possible to relate the loss of these compounds to the levels of biodegradation occurring in situ [1]. Moreover, it is important to develop indicators of alkane degradation that may be used to monitor bioremediation of hydrocarbon-impacted environments. Desulfoglaeba alkanexedens and Pseudomonas putida GPo1 were

Brandon El Morris; Joseph M. Suflita; Hans-Hermann Richnow

2010-01-01

419

Long chain n-alkanes and their carbon isotopes in lichen species from western Hubei Province: implication for geological records  

NASA Astrophysics Data System (ADS)

Five coticolous lichen samples were collected from western Hubei Province of China to analyze the long chain n-alkanes and their carbon isotope compositions. The n-alkanes range in carbon number from C17 to C33 with strong odd-over-even predominance between C21 and C33. Lichens are dominated by n-C29 in the samples of Dajiuhu, Shennongjia Mountain, but by both n-C23 and n-C29 at Qizimei Mountain. This difference may result from the different environmental conditions in these two sites. The ? 13C values of long chain n-alkanes in lichen samples show the signature of C3 plants. Based on compoundspecific carbon isotopic values and previous results, we state that alkane homologs >C23 mainly originate from the symbiotic fungi, while symbiotic algae only contribute trace amount of long chain alkanes. Of great interesting is the occurrence of long chain 3-methylalkanes in the Qizimei samples. These anteiso compounds range from C24 to C32, displaying obvious even-over-odd predominance. This study reveals that the association of long chain 3-methylalkanes with n-C23 alkane might be used as proxies to reconstruct the paleoecological implications of lichens in Earth history.

Huang, Xianyu; Xue, Jiantao; Guo, Shouyu

2012-03-01

420

Selective alkane C–H-bond functionalizations utilizing oxidativesingle-electron transfer and organocatalysis  

Microsoft Academic Search

Alkane C-H-bond functionalization methods not utilizing metal-catalysis\\u000a\\u0009are discussed based on experimental and computational data, beginning\\u000a\\u0009with molecule-induced homolysis (reactions of alkanes with dioxiranes).\\u000a\\u0009Electrophilic reactions are elaborated next with an emphasis on mechanistic\\u000a\\u0009details that reveal that many so-called electrophilic C-H or C-C-bond\\u000a\\u0009insertions can be rationalized by electron-transfer reactions (inner\\u000a\\u0009sphere, H-coupled, and outer sphere). Finally, radical functionalizations

Peter R. Schreiner; Andrey A. Fokin

2004-01-01

421

Aerosols in equatorial Atlantic air - n-alkanes as a function of particle size  

NASA Astrophysics Data System (ADS)

The concentrations and distributions of n-alkanes in the western equatorial Atlantic, Gulf of Guinea region were determined by aerosol sampling and calculated in terms of particle size. Data were gathered in the period May-June 1977 by means of a five stage cascade impactor for large air volumes mounted on the bow of a boat. The collected gases were separated into six particle size fractions, and n-alkanes were identified by means of gas chromatography. Concentrations were found to vary from 6-13 ng/cu m, which contributes to previous findings that the tropical Atlantic has higher aerosol carbon concentrations than the tropical north Pacific Ocean. The major part of the observed aerosol mass was determined to reside in particles less than 1 micron across. It is concluded that the particles are expelled from the sea in bubbles which burst in the air.

Marty, J.-C.; Saliot, A.

1982-07-01

422

Adsorption layer properties of alkyltrimethylammonium bromides at interfaces between water and different alkanes.  

PubMed

We measured the interfacial tensions of aqueous solutions against different oil phases using drop profile analysis tensiometry (PAT-1, Sinterface Technologies, Germany) for decyl- and dodecyltrimethylammonium bromide (C10TAB and C12TAB) in phosphate buffer (10mM, pH7). The following alkanes were used as oil phases: hexane, heptane, octane, nonane, decane, dodecane and tetradecane. The obtained equilibrium interfacial tension isotherms were fitted by the Frumkin Ionic Compressibility model (FIC). The surfactants adsorb at the water/oil interface in competition with the oil molecules. At high surfactant surface coverage this competitive adsorption is manifested in two ways. First, for short chain surfactants, the oil molecules are embedded into the adsorption layer. Second, for long chain surfactants, the short alkane chains of the oil molecules are squeezed out from the adsorption layer due to strong mutual interaction between surfactants' chains. PMID:24011787

Mucic, N; Kovalchuk, N M; Aksenenko, E V; Fainerman, V B; Miller, R

2013-08-26

423

Bond Orbital-Connection Matrix Method to Predict Refractive Indices of Alkanes  

NASA Astrophysics Data System (ADS)

Based on the comprehension of the specific structural features affecting the refractive indices of the compounds, two descriptors ?X1CC and ?X1CH extracted from the bond orbital-connection matrix (BOCM) method were employed to develop a QSPR model for predicting the refractive indices of alkanes, chloroalkanes and bromoalkanes. The obtained results confirmed the usefulness of the BOCM method. ?X1CC and ?X1CH reflect the ability of the electronic cloud of the alkanes to be polarized; such ability is correlated with the refractive indices of substances. Therefore, the physical meaning of the obtained model can be rationally interpreted from the physical point of view. The present descriptors obtained by the BOCM method have the merit of topological indices (i.e. facility and rapid calculation of the descriptors) and the advantage of quantum descriptors (i.e. explicitly physical meaning of the parameters), which lead to an expectation of wide use in QSAR studies.

Cao, Chen-zhong; Gao, Shuo

2007-04-01

424

Possible mechanism of alkene/alkane production in oil shale retorting  

SciTech Connect

The purpose of the work reported is to clarify the reaction mechanisms which determine the observed alkene/alkane ratios under various conditions. The C/sub 1/ to C/sub 3/ hydrocarbons and hydrogen were measured as a function of time for oil shale heated at a constant rate. The effect of an inert sweep gas on the time-dependent ethene/ethane and propene/propane ratios and the integral 1-alkene/n-alkane ratios in the oil were also determined. It is shown that the C/sub 2/H/sub 4/-C/sub 2/H/sub 6/-H/sub 2/ system is not in thermal equilibrium. Results are interpreted in terms of a nonequilibrium free radical mechanism proposed by Raley.

Burnham, A.K.; Ward, R.L.

1980-03-01

425

Competition between n-alkane-assimilating yeasts and bacteria during colonization of sandy soil microcosms.  

PubMed

An n-alkane-assimilating strain of Candida tropicalis was selected in sandy soil inoculated with microorganisms from contaminated sites. Competition experiments with n-alkane utilizers from different strain collections confirmed that yeasts overgrow bacteria in sandy soil. Acidification of the soil is one of the colonization factors useful for the yeasts. It can be counteracted by addition of bentonite, a clay mineral with high ion exchange capacity, but not, however, by kaolin. Strains of different yeast species showed different levels of competitiveness. Strains of Arxula adeninivorans, Candida maltosa, and Yarrowia lipolytica overgrew strains of C. tropicalis, C. shehatae or Pichia stipitis. Two strains of C. maltosa and Y. lipolytica coexisted during several serial transfers under microcosm conditions. PMID:10952016

Schmitz, C; Goebel, I; Wagner, S; Vomberg, A; Klinner, U

2000-07-01

426

General Chemistry Online!  

NSDL National Science Digital Library

General Chemistry Online, created by Frederick Senese, a professor at Frostburg State University, is a guide and resource for introductory chemistry students. This site provides five areas of information: The Chemistry Home Companion, Just Ask Antoine!, Chemistry Exam Survival Guide, Tutorials, and a Featured Article. The Companion is a study guide covering the basic concepts of an introductory general chemistry course. Topics include measurement, molecules and compounds, and the quantum theory. Just Ask Antoine! allows students to post their chemistry questions. An archived list provides questions and answers for the past year. The Exam Survival Guide provides tips on passing exams, checklists of objectives and skills, and two online practice exams. The Tutorial currently contains only problems and quizzes for the measurement topic. The featured article for February is about Anandamide, a "messenger molecule that plays a role in pain, depression, appetite, memory, and fertility."

Senese, Frederick A.

427

Explicit modeling of organic chemistry and secondary organic aerosol partitioning for Mexico City and its outflow plume  

SciTech Connect

The evolution of organic aerosols (OA) in Mexico City and its outflow is investigated with the nearly explicit gas phase photochemistry model GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere), wherein precursor hydrocarbons are oxidized to numerous intermediate species for which vapor pressures are computed and used to determine gas/particle partitioning in a chemical box model. Precursor emissions included observed C3-10 alkanes, alkenes, and light aromatics, as well as larger n-alkanes (up to C25) not directly observed but estimated by scaling to particulate emissions according to their volatility. Conditions were selected for comparison with observations made in March 2006 (MILAGRO). The model successfully reproduces the magnitude and diurnal shape for both primary (POA) and secondary (SOA) organic aerosols, with POA peaking in the early morning at 15-20 ug m-3, and SOA peaking at 10-15 ?g m-3 during mid-day. The majority (> 75%) of the model SOA stems from the large n-alkanes, with the remainder mostly from the light aromatics. Simulated OA elemental composition reproduces observed H/C and O/C ratios reasonably well, although modeled ratios develop more slowly than observations suggest. SOA chemical composition is initially dominated by *- hydroxy ketones and nitrates from the large alkanes, with contributions from peroxy acyl nitrates and, at later times when NOx is lower, organic hydroperoxides. The simulated plume-integrated OA mass continues to increase for several days downwind despite dilution-induced particle evaporation, since oxidation chemistry leading to SOA formation remains strong. In this model, the plume SOA burden several days downwind exceeds that leaving the city by a factor of >3. These results suggest significant regional radiative impacts of SOA.

Lee-Taylor, J.; Madronich, Sasha; Aumont, B.; Baker, A.; Camredon, M.; Hodzic, Alma; Tyndall, G. S.; Apel, Eric; Zaveri, Rahul A.

2011-12-21

428

Using n-alkanes to estimate diet composition of herbivores: a novel mathematical approach.  

PubMed

N-alkanes are long-chain saturated hydrocarbons occurring in plant cuticles that can be used as chemical markers for estimating the diet composition of herbivores. An important constraint of using n-alkanes to estimate diet composition with currently employed mathematical procedures is that the number of markers must be equal or larger than the number of diet components. This is a considerable limitation when dealing with free-ranging herbivores feeding on complex plant communities. We present a novel approach for the estimation of diet composition using n-alkanes which applies equally to cases where the number of markers is lower, equal or greater than the number of plant species in the diet. The model uses linear programming to estimate the minimum and maximum proportions of each plant in the diet, and avoids the need for grouping species in order to reduce the number of estimated dietary components. We illustrate the model with two data sets of n-alkane content of plants and faeces obtained from a sheep grazing experiment conducted in Australia and a red deer study in Portugal. Our results are consistent with previous studies on those data sets and provide additional information on the proportions of individual species in the diet. Results show that sheep included in the diet high proportions of white clover (from 0.25 to 0.37), and relatively high proportions of grasses (e.g. brome from 0.14 to 0.26) but tended to avoid Lotus spp. (always less than 0.04 of the diet). For red deer we found high proportions of legumes (e.g. Trifolium angustifolium and Vicia sativa reaching maximum proportions of 0.42 and 0.30 of the diet, respectively) with grasses being less important and Cistus ladanifer, a browse, also having relevance (from 0.21 to 0.42 of the diet). PMID:22444217

Barcia, P; Bugalho, M N; Campagnolo, M L; Cerdeira, J O

2007-02-01

429

Genome Sequence of Rhodococcus sp. Strain BCP1, a Biodegrader of Alkanes and Chlorinated Compounds  

PubMed Central

Rhodococcus sp. strain BCP1 cometabolizes chlorinated compounds and mineralizes a broad range of alkanes, as it is highly tolerant to them. The high-quality draft genome sequence of Rhodococcus sp. strain BCP1, consisting of 6,231,823 bp, with a G+C content of 70.4%, 5,902 protein-coding genes, and 58 RNA genes, is presented here.

Cappelletti, M.; Di Gennaro, P.; D'Ursi, P.; Orro, A.; Mezzelani, A.; Landini, M.; Fedi, S.; Frascari, D.; Presentato, A.; Milanesi, L.

2013-01-01

430

Computer simulations of the adsorption process of light alkanes in high-silica zeolites  

Microsoft Academic Search

The methods of molecular mechanics (MM), molecular dynamics (MD) and Monte-Carlo (MC) were used to compute adsorption energies and to determine the preferred adsorption sites of light alkanes (methane, ethane, propane, n-butane, i-propane and neopentane) in silicalite and ZSM-5. In order to compare their performance the same simulation conditions were used in all the calculations. The effect of using specific

Marco Antonio Chaer Nascimento

1999-01-01

431

Relative permittivities of binary mixtures of 1-butanol + n -alkane AT 298.15 k  

Microsoft Academic Search

A previous study on the physical properties of 1-alkanol + n-alkane has establised a correlation between dielectric permittivity at 1 GHz and excess molar volumes for all binary systems\\u000a that were studied. In order to determine whether this behaviour is similar at lower frequencies, relative permittivity was\\u000a measured at 100 kHz. The refractive index was measured to explore the effects

B. E. de Cominges; M. M. Pineiro; E. Mascato; L. Mosteiro; T. P. Iglesias; J. L. Legido

2003-01-01

432

Branched aliphatic alkanes with quaternary substituted carbon atoms in modern and ancient geologic samples  

Microsoft Academic Search

A pseudohomologous series of branched aliphatic alkanes with a quaternary substituted carbon atom (BAQCs, specifically 2,2-dimethylalkanes and 3,3- and 5,5-diethylalkanes) were identified in warm (65°C) deep-sea hydrothermal waters and Late Cretaceous black shales. 5,5-Diethylalkanes were also observed in modern and Holocene marine shelf sediments and in shales spanning the last 800 million years of the geological record. The carbon number

Fabien Kenig; Dirk-Jan H. Simons; David Crich; James P. Cowen; Gregory T. Ventura; Tatiana Rehbein-Khalily; Todd C. Brown; Ken B. Anderson

2003-01-01

433

Isolation and characterization of a novel facultatively alkaliphilic bacterium, Corynebacterium sp., grown on n -alkanes  

Microsoft Academic Search

A novel facultatively alkaliphilic bacterium that grows on a chemically defined medium containing n-alkanes as the sole carbon source was isolated from soil. The isolate was obligately aerobic, non-motile, gram-positive,\\u000a and formed metachromatic granules. It was not acidfast and did not form endospores. The cell wall contained meso-diaminopimelic acid, arabinose, and galactose; the glycan moiety of the cell wall contained

Koji Ikeda; Kenji Nakajima; Isao Yumoto

1994-01-01

434

Influence of 2-phenyl alkane and tetralin content on solubility and viscosity of linear alkylbenzene sulfonate  

Microsoft Academic Search

Cloud and clear points and viscosities of linear alkylbenzene sulfonates (LAS) have been determined as a function of 2-phenyl\\u000a alkane and\\/or tetralin content over a wide interval. While the 2-phenyl content significantly affects the solubility, tetralins\\u000a have a marked depressive effect on viscosity. The investigation has established that LAS solubility can be explained by assuming\\u000a eutectic types of isomer and

L. Cohen; R. Vergara; A. Moreno; J. L. Berna

1995-01-01

435

Comparison of bulk and n-alkane PETM carbon isotope trends from the Bighorn Basin, Wyoming  

Microsoft Academic Search

The Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt, short-term, and large-scale global warming fueled by a large release of isotopically light carbon, is recorded in terrestrial and marine carbonates and organic carbon as a prominent negative carbon isotope excursion (CIE). Here we present a composite stable carbon isotope record from n-alkanes and four bulk organic carbon records from individual

A. A. Baczynski; F. A. McInerney; M. J. Kraus; S. Wing

2010-01-01

436

Propagation and extinction of premixed C 5–C 12 n-alkane flames  

Microsoft Academic Search

Laminar flame speeds and extinction strain rates of premixed C5–C12n-alkane flames were determined at atmospheric pressure and elevated unburned mixture temperatures, over a wide range of equivalence ratios. Experiments were performed in the counterflow configuration and flow velocities were measured using Laser Doppler Velocimetry. The laminar flame speeds were obtained using a non-linear extrapolation technique utilizing numerical simulations of the

Chunsheng Ji; Enoch Dames; Yang L. Wang; Hai Wang; Fokion N. Egolfopoulos

2010-01-01

437

Ignition of non-premixed C 3–C 12 n-alkane flames  

Microsoft Academic Search

Ignition temperatures of non-premixed C3 and C5–C12n-alkane flames were determined in the counterflow configuration at atmospheric pressure, a free-stream fuel\\/N2 mixture temperature of 448K, a local strain rate of 140s?1, and fuel mole fractions ranging from 1% to 12% in the fuel stream. The strain rate was measured on the fuel side using Laser Doppler Velocimetry. Simulations of the experiments

Ning Liu; Chunsheng Ji; Fokion N. Egolfopoulos

438

Isomers of long-chain alkane derivatives and nervous impulse blockage  

Microsoft Academic Search

Summary The potency to block nervous impulse of members of normal aliphatic homologous series of primary and secondary isomers of functional derivatives of alkanes was tested in bundles of a few axons from sciatic nerves of the toadBufo marinus. For the primary substituted functional derivates of pentane, the relative potency series was 1>H˜Br>Cl>COOCH3>F>CH2OH>COCH3>OH˜NH2>COOH. For the homologous series of primary alkanols,

J. Requena; M. E. Velaz; J. R. Guerrero; J. D. Medina

1985-01-01

439

Phase equilibria in mixtures of triglycerides with low-molecular weight alkanes  

Microsoft Academic Search

Phase equilibria of ternary ethane? propane-sunflower oil mixtures were measured at 313, 333 and 353 K, and at pressures of up to 120 bar. The region of partial liquid miscibility, at high hydrocarbon concentration, was particularly explored. The Soave-Redlich-Kwong equation of state was used to fit experimental vapor-liquid and liquid-liquid equilibria of alkane-vegetable oil mixtures. The application of a quadratic

Juan C de la Fuente B; Tiziana Fornari; Esteban Brignole; Susana Bottini

1997-01-01

440

Isochoric thermal conductivity of solid n-alkanes: Hexane C6H14  

NASA Astrophysics Data System (ADS)

The isochoric thermal conductivity of solid n-hexane C6H14 is studied using three samples with different densities for temperatures ranging from 100 K to the onset of melting. In all cases, the isochoric thermal conductivity varies more weakly than ?~1/T. The present results are compared with the thermal conductivities of other representatives of the n-alkanes. The contributions of low-frequency phonons and ``diffuse modes'' to the thermal conductivity are calculated.

Konstantinov, V. A.; Revyakin, V. P.; Sagan, V. V.

2011-05-01

441

Isolation and Characterization of a Sulfate-Reducing Bacterium That Anaerobically Degrades Alkanes  

PubMed Central

An alkane-degrading, sulfate-reducing bacterial strain, AK-01, was isolated from an estuarine sediment with a history of chronic petroleum contamination. The bacterium is a short, nonmotile, non-spore-forming, gram-negative rod. It is mesophilic and grows optimally at pH 6.9 to 7.0 and at an NaCl concentration of 1%. Formate, fatty acids (C4 to C16) and hydrogen were readily utilized as electron donors. Sulfate, sulfite, and thiosulfate were used as electron acceptors, but sulfur, nitrite, and nitrate were not. Phenotypic characterization and phylogenetic analysis based on 16S rRNA gene sequence indicate that AK-01 is most closely related to the genera Desulfosarcina, Desulfonema, and Desulfococcus in the delta subdivision of the class Proteobacteria. It is phenotypically and phylogenetically different from strains Hxd3 and TD3, two previously reported isolates of alkane-degrading, sulfate-reducing bacteria. The alkanes tested to support growth of AK-01 had chain lengths of C13 to C18. 1-Alkenes (C15 and C16) and 1-alkanols (C15 and C16) also supported growth. The doubling time for growth on hexadecane was 3 days, about four times longer than that for growth on hexadecanoate. Mineralization of hexadecane was indicated by the recovery of 14CO2 from cultures grown on [1-14C]hexadecane. Degradation of hexadecane was dependent on sulfate reduction. The stoichiometric ratio (as moles of sulfate reduced per mole of hexadecane degraded) was 10.6, which is very close to the theoretical ratio of 12.25, assuming a complete oxidation to CO2. Anaerobic alkane degradation by sulfate reducers may be a more widespread phenomenon than was previously thought.

So, Chi Ming; Young, L. Y.

1999-01-01

442

Adsorption of linear and branched alkanes in ferrierite: A computational study  

Microsoft Academic Search

Molecular simulations using the Configurational-bias Monte Carlo technique were per- formed to calculate the adsorption behavior of linear and branched alkanes (carbon numbers ranging from 4 to 6), and their 50%-50% mixtures on Ferrierite. It was found that small molecules (up to C4 backbone) can occupy both channels of Ferrierite while larger molecules (from C6 backbone) can only reside in

T. J. H. Vlugt; B. Smit; R. Krishna

1999-01-01

443

Calorimetric Study of Adsorption of Alkanes in High-Silica Zeolites  

Microsoft Academic Search

Isosteric heats and adsorption isotherms were measured for combinations of three alkanes (methane, ethane, propane) on a series of six high-silica zeolites (TON, MTW, UTD-1, MFI, FER, FAU). Three of these zeolites (TON, MTW, UTD-1) have one-dimensional channels, two (MFI, FER) have two-dimensional intersecting channels, and FAU has spherical cavities. Since the adsorbate molecules are nonpolar and the zeolites possess

Scott Savitz; Flor Siperstein; Raymond J. Gorte; Alan L. Myers

1998-01-01

444

Generalized Peng–Robinson equation of state with pair potential parameters for liquid n-alkanes  

Microsoft Academic Search

Peng–Robinson EOS is generalized with pair potential parameters for the PVT relation of liquid n-alkanes C1 to C30, C32, and C36 with the saturated vapors for temperatures near the normal boiling point to the critical point. The EOS is reduced with the Lennard–Jones pair potential depth parameter ? and the characteristic length d, which is determined with the pair potential

Yutaka Tada; Akihiko Tamakoshi; Yoshihito Kato; Yuichiro Nagatsu

2007-01-01

445

Severe emulsification after combined use of a partially fluorinated alkane and silicone oil  

Microsoft Academic Search

Purpose: To present a case with accidental incomplete removal of a partially fluorinated alkane during a direct exchange with silicone oil and a subsequent severe emulsification of the silicone oil. Case report: During a macular rotation procedure an incomplete exchange of perfluorohexyl-hexane (F6H6) with silicone oil occurred. Initial postoperative findings showed phase separation and exact visualization of the fundus. After

Hans Hoerauf; Horst Laqua

2002-01-01

446

Tools for characterizing the whole-cell bio-oxidation of alkanes at microscale.  

PubMed

This article describes the first reported microwell whole-cell bioconversion using a water immiscible substrate that matches the specific activity and yield achieved in a 1.2 L stirred tank bioreactor. Maximum yields of 0.6 g/L(total) 1-dodecanol achieved in 24 h compare favorably to 0.28 g/L(total) 1-dodecanol after 48 h obtained in a stirred tank reactor. Using the microwell platform we present a rapid and systematic approach to identify the key bottlenecks in the bio-oxidation of long-chain alkanes using Escherichia coli expressing the alkane hydroxylase (alkB) complex. The results indicate that mass transfer rates limit productivity in the n-dodecane bio-oxidation system, rather than inherent enzyme activity. Furthermore, substrate solubility, oxygen availability and glucose concentration act cooperatively to affect the amount of by-product, dodecanoic acid. Optimizing these factors using response surface methodology enabled specific yields of 1-dodecanol to increase eightfold and overoxidation to dodecanoic acid to be reduced from 95% to 55%. This resulted in specific activities of 10.4 µmol/min/g(dcw) on n-dodecane; approximately 50% of the 21 µmol/min/g(dcw) obtained with n-octane. For the first time, this in vivo rate difference is within the range reported for the purified enzyme. Finally, the results obtained also provide strong evidence that the mechanism of E. coli interaction with alkanes is mainly via uptake of alkanes dissolved in the aqueous phase rather than by direct cell-droplet contact. PMID:22473845

Grant, Chris; Pinto, Ana Catarina da Silva Damas; Lui, Hai-Po; Woodley, John M; Baganz, Frank

2012-04-17

447

Prediction of the flash points of alkanes by group bond contribution method using artificial neural networks  

Microsoft Academic Search

A group bond contribution model using artificial neural networks, which had the high ability of nonlinear of prediction, was\\u000a established to predict the flash points of alkanes. This model contained not only the information of group property but also\\u000a connectivity in molecules. A set of 16 group bonds were used as input parameters of neural networks to study the correlation

Yong Pan; Juncheng Jiang; Zhirong Wang

2007-01-01

448

Fidelity of fossil n-alkanes from leaf to paleosol and applications to the Paleocene-Eocene Thermal Maximum  

NASA Astrophysics Data System (ADS)

Long chain n-alkanes (C21-C35) are well-known as biomarkers of terrestrial plants. They can be preserved across a wide range of terrestrial and marine environments, survive in the sedimentary record for millions of years, and can serve as proxies for ancient environments. Most n-alkane records are derived from sediments rather than directly from fossil leaves. However, little is known about the fidelity of the n-alkane record: how and where leaf preservation relates to n-alkane preservation and how patterns of n-alkane carbon isotope ratios (?13C) compare to living relatives. To examine these questions, we analyzed n-alkanes from fluvial sediments and individual leaf fossils collected in the Bighorn Basin, Wyoming, across the Paleocene-Eocene Thermal Maximum (PETM) carbon isotope excursion. We assessed the fidelity of the n-alkane signature from individual fossil leaves via three separate means. 1) Spatial variations were assessed by comparing n-alkane concentrations on a fossil leaf and in sediments both directly adjacent to the leaf and farther away. Absolute concentrations were greater within the compression fossil than in the directly adjacent sediment, which were in turn greater than in more distant sediment. 2) n-Alkane abundances and distributions were examined in fossil leaves having a range of preservational quality, from fossils with intact cuticle to carbonized fossils lacking cuticle and higher-order venation. The best preserved fossils preserved a higher concentration of n-alkanes and showed the most similar n-alkane distribution to living relatives. However, a strong odd over even predominance suggests a relatively unmodified plant source occurred in all samples regardless of preservation state. 3) n-Alkane ?13C values were measured for both fossil leaves and their living relatives. Both the saw-tooth pattern of ?13C values between odd and even chain lengths and the general decrease in ?13C values with increasing chain length are consistent with modern plant data. These results suggest that n-alkanes extracted directly from a fossil leaf provide a true signature of an individual leaf fossil rather than a mixture from the entire plant community. Therefore, comparisons between fossil morphotypes and between fossil and related modern taxa should be robust. Furthermore, by placing fossil leaf data within the context of the chemostratigraphy of Bighorn Basin sediments across the P-E boundary, fossil leaf n-alkanes can be used to bridge the gap between our understanding of modern plant lipids and bulk lipid data from sediments across the PETM. It has been hypothesized that changes in the both the molecular distribution and carbon isotope composition of n-alkanes across the PETM were due to changes in the local plant community, which included a large proportion of deciduous gymnosperms before and after-but not during-the PETM. Analysis of fossils such as Ginkgo and angiosperms provides the opportunity to compare and distinguish the molecular and isotopic signatures of gymnosperms and angiosperms. These comparisons shed light on the dynamics of climate and ecosystem changes as they are recorded in the signatures of lipid biomarkers.

Bush, R. T.; McInerney, F. A.; Baczynski, A. A.; Wing, S. L.

2011-12-01

449

Middle School Chemistry  

NSDL National Science Digital Library

Middle school science resource from ACS. It includes activity-based lesson plans for teaching basic chemistry concepts that cover all the main concepts in middle school chemistry. Each lesson also contains integrated animations and video that a teacher can use to help explain student observations on the molecular level. Online professional development will also be available to introduce and familiarize teachers with the demonstrations, activities, and chemistry content in the site.

450

Kurnakov and analytical chemistry  

Microsoft Academic Search

The paper appreciates the role of Academician N.S. Kurnakov in holding the All-Union Conference on Analytical Chemistry (1939)\\u000a and creating the Commission on Analytical Chemistry at the Academy of Sciences of the USSR. The scientific works of Kurnakov\\u000a relating to chemical analysis are indicated; brief review is given to studies on analytical chemistry that were carried out\\u000a in the collectives

Yu. A. Zolotov

2010-01-01

451

Simulated Effects of Odd-Alkane Impurities in a Hexane Monolayer on Graphite  

NASA Astrophysics Data System (ADS)

We present the results of molecular dynamics (MD) simulations of odd alkane impurities present within the hexane (even alkane) monolayer. We simulate a series of temperatures at 3%, 5%, 10%, and 15% impurities of propane (C3H8), pentane (C5H12), heptane (C7H16), nonane (C9H20), and undecane (C11H24) to study both the changes in the monolayer structure and the phase transitions when odd alkanes, whose low-temperature solid structure has been experimentally observed to be much different than that of hexane, occupy space within the hexane monolayer in the low-temperature herringbone (HB) phase. We find that the most significant changes in the melting transition are imposed by impurities whose chain lengths are much different than that of hexane, and the impurities whose chain lengths most closely resemble hexane still give a melting temperature that is within 10K of the pure hexane monolayer melting temperature at high impurity composition. However, due to ``lattice misfits,'' we find that the transition into the intermediate phase exhibits drastic changes as compared to the pure hexane monolayer with the exception of pentane impurities, whose optimal impurity chain length allows the monolayer to exhibit a commensurate phase that is similar to the hexane monolayer, even with a high impurity composition.

Pint, Cary L.

2005-05-01

452

Environmental hazards and health risk of common liquid perfluoro-n-alkanes, potent greenhouse gases.  

PubMed

This article aimed at introducing the main physical properties and commercial/industrial uses of common liquid perfluoro-n-alkanes (including perfluoropentane, perfluorohexane, perfluoroheptane, perfluorooctane, and perfluorononane) and the environment and health hazards posed by their toxic decomposition products (especially in hydrogen fluoride and perfluoroisobutylene) because these perfluorocompounds are potent greenhouse gases, which have been blanketed into the Kyoto Protocol, but was rarely described in the National Inventory Reports by Annex I Parties. The environmental properties (including octanol-water partition coefficient, water solubility and Henry's law constant) of liquid perfluoro-n-alkanes were evaluated, and further discussed were its atmospheric implications according to the predicted properties and possible proposal for the formation of trifluoroacetic acid (CF(3)COOH) in the atmosphere by the ionized photolysis. These predicted values revealed that liquid perfluoro-n-alkanes tend to be hydrophobic and partitioned into organic matter, and they have exceptionally low solubility in water and extremely high vaporization from the water bodies, suggesting that it will sink into the atmosphere if it is released into the environment. PMID:18845341

Tsai, Wen-Tien

2008-10-09

453

In vitro rat hepatic metabolism of n-alkanes: nonane, decane, and tetradecane.  

PubMed

Jet propellant 8 (JP-8) jet fuel is a complex mixture of aromatic and aliphatic hydrocarbons. The aim of this study was to determine in vitro metabolic rate constants for semivolatile n-alkanes, nonane (C9), decane (C10), and tetradecane (C14), by rat liver microsomal oxidation. The metabolism was assessed by measuring the disappearance of parent compound by gas chromatography. Various concentrations of n-alkanes were incubated with liver microsomes from adult male F-344 rats. Nonlinear kinetic constants for nonane and decane were V(max) (nmol/mg protein/min) = 7.26 +/- 0.20 and 2.80 +/- 0.35, respectively, and K(M) (micro M) = 294.83 +/- 68.67 and 398.70 +/- 42.70, respectively. Metabolic capacity as assessed by intrinsic clearance (V(max)/K(M)) was approximately four-fold higher for nonane (0.03 +/- 0.005) than for decane (0.007 +/- 0.001). There was no appreciable metabolism of tetradecane even with higher microsomal protein concentration and longer incubation time. These results show a negative correlation between metabolic clearance and chain length of n-alkanes. These metabolic rate constants will be used to update existing physiologically based pharmacokinetic (PBPK) models for nonane and decane as part of developing a PBPK model for JP-8. PMID:17661223

Anand, Sathanandam S; Campbell, Jerry L; Fisher, Jeffrey W

454

Ozone-driven photochemical formation of carboxylic acid groups from alkane groups  

NASA Astrophysics Data System (ADS)

Carboxylic acids are ubiquitous in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were highly associated with trajectories from an industrial region with high organic mass (OM), likely from fossil fuel combustion emissions. The concentration of carboxylic acid groups peaked during daytime, suggesting a photochemical secondary formation mechanism. This daytime increase in concentration was tightly correlated with O3 mixing ratio, indicating O3 was the likely driver in acid formation. Based on the diurnal cycles of carboxylic acid and alkane groups, the covariation of carboxylic acid groups with O3, and the composition of the Combustion factor resulted from the factor analyses, gas-phase alkane oxidation by OH radicals to form dihyfrofuran followed by further oxidation of dihydrofuran by O3 is the likely acid formation mechanism. Using the multi-day average of the daytime increase of carboxylic acid group concentrations and m/z 44-based Aged Combustion factor, we estimated the lower-bound contributions of secondary organic aerosol (SOA) formed in 12-h daytime of processing in a single day to be 30% of the carboxylic acid groups and 25-45% of the Combustion factor concentration. These unique ambient observations of photochemically-driven acid formation suggest that gas-phase alkanes might be important sources of SOA formation in this coastal region.

Liu, S.; Day, D. A.; Shields, J. E.; Russell, L. M.

2011-03-01

455

Science Update: Analytical Chemistry.  

ERIC Educational Resources Information Center

|Briefly discusses new instrumentation in the field of analytical chemistry. Advances in liquid chromatography, photoacoustic spectroscopy, the use of lasers, and mass spectrometry are also discussed. (CS)|

Worthy, Ward

1980-01-01

456

Environmental chemistry: Volume B  

SciTech Connect

This is an extensive introduction to environmental chemistry for engineering and chemical professionals. The contents of Volume B include equilibria processes, chemical processes, biochemical processes, and physicochemical processes.

Yen, T.F.

1999-08-01

457

Open access and medicinal chemistry  

PubMed Central

Chemistry Central is a new open access website for chemists publishing peer-reviewed research in chemistry from a range of open access journals. A new addition, Chemistry Central Journal, will cover all of chemistry and will be broken down into discipline-specific sections, and Im delighted that Medicinal Chemistry will be a key discipline in this new journal.

Swain, Chris

2007-01-01

458

Influence of the aluminum content of zeolite H-ZSM-5 on the conversion of methylcyclohexane into a high-quality synthetic steamcracker feedstock  

Microsoft Academic Search

Methylcyclohexane is converted into a high-quality synthetic steamcracker feedstock over zeolites H-ZSM-5 with different nAl\\/(nAl+nSi) ratios. With increasing aluminum content, increasing conversion but slightly decreasing selectivities to the desired n-alkanes (maximal 78%, without methane) are observed at 400°C. Mechanistic aspects of the reaction are discussed, and the importance of non-classical Haag-Dessau cracking is emphasized.

Andreas Raichle; Michael Ramin; Dirk Singer; Michael Hunger; Yvonne Traa; Jens Weitkamp

2001-01-01

459

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.

460

Omar Yaghi on Chemistry and Metal Organic Frameworks  

ScienceCinema

In this edited version of the hour long talk, Omar Yaghi, director of the Molecular Foundry, sat down in conversation with Jeff Miller, head of Public Affairs, on July 11th, 2012 to discuss his fascination with the hidden world of chemistry and his work on Metal Organic Frameworks.

461

Coal science: An introduction to chemistry, technology and utilization  

SciTech Connect

This book presents the chemistry and geology of coal. It describes aspects of the petrology and petrographic characterization of coal, the processes involved in coal conversion and utilization, and the testing and analysis of coal. It includes recent statistics regarding production and utilization, as well as recent developments in structure, reactivity and routine analysis.

Hessley, R.K.; Reasoner, J.W.; Riley, J.T.

1986-01-01

462

Soap from Nutmeg: An Integrated Introductory Organic Chemistry Laboratory Experiment  

Microsoft Academic Search

The extraction of trimyristin from nutmeg, its purification, and its conversion to a soap (sodium myristate) are described. Concepts such as the isolation of a natural product, recrystallization, identification of a solid, solubility, acidity and basicity, and organic reaction can be presented to students using integrated experiments in an introductory experimental chemistry laboratory. These experiments can easily be done in

Marcio C. S. de Mattos; David E. Nicodem

2002-01-01

463

Dietary accumulation of C{sub 12}- and C{sub 16}-chlorinated alkanes by juvenile rainbow trout (Oncorhynchus mykiss)  

SciTech Connect

Dietary exposures using juvenile rainbow trout (Oncorhynchus mykiss) were conducted with four {sup 14}C-polychlorinated alkanes in order to measure bioaccumulation parameters, metabolism, and tissue distributions. These chlorinated alkanes are found in industrial chlorinated paraffin (CP) products, although their method of synthesis is different than that of CPs. Trout were exposed for 40 d to nominal concentrations of 20 and 200 ng/g of each chlorinated alkane, as well as to 2,000 ng/g for C{sub 16}H{sub 21}Cl{sub 13}, followed by an elimination period of up to 173 d. Whole-body half-lives in the rainbow trout ranged from 37 {+-} 2 d for C{sub 16}H{sub 31}Cl{sub 3} to 87 {+-} 11 d for C{sub 12}H{sub 16}Cl{sub 10}, and assimilation efficiencies of C{sub 16}H{sub 21}Cl{sub 13} to 2.15 for C{sub 12}H{sub 16}Cl{sub 10}. Accumulation of C{sub 16}H{sub 21}Cl{sub 13} may be sterically hindered due to its large molecular size. Lower chlorinated alkanes, e.g., C{sub 16}H{sub 31}Cl{sub 3}, had shorter half-lives than highly chlorinated alkanes, probably due to increased metabolism. High-performance liquid chromatography {sup 14}C analysis of fish tissue extracts revealed that the chlorinated alkane mixtures were selectively biotransformed with certain unknown components persisting in tissues. Lower chlorinated alkanes had greater proportions of polar {sup 14}C, which implies greater metabolism of these compounds. Highly chlorinated, short-carbon-chain (C{sub 10-13}) alkanes and lower chlorinated, medium-carbon-chain (C{sub 14-18}) alkanes appear to have the greatest potential for biomagnification among CP components. No reduced growth rates or hepatic monooxygenase enzyme induction were seen in any of the chlorinated alkane exposures when compared with controls.

Fisk, A.T. [Univ. of Manitoba, Winnipeg, Manitoba (Canada). Dept. of Soil Science; Cymbalisty, C.D.; Muir, D.C.G. [Department of Fisheries and Oceans, Winnipeg, Manitoba (Canada). Freshwater Inst.; Bergman, A. [Stockholm Univ. (Sweden)

1996-10-01

464

Ammonia chemistry in a flameless jet  

SciTech Connect

In this paper, the nitrogen chemistry in an ammonia (NH{sub 3}) doped flameless jet is investigated using a kinetic reactor network model. The reactor network model is used to explain the main differences in ammonia chemistry for methane (CH{sub 4})-containing fuels and methane-free fuels. The chemical pathways of nitrogen oxides (NO{sub x}) formation and destruction are identified using rate-of-production analysis. The results show that in the case of natural gas, ammonia reacts relatively late at fuel lean condition leading to high NO{sub x} emissions. In the pre-ignition zone, the ammonia chemistry is blocked due to the absence of free radicals which are consumed by methane-methyl radical (CH{sub 3}) conversion. In the case of methane-free gas, the ammonia reacted very rapidly and complete decomposition was reached in the fuel rich region of the jet. In this case the necessary radicals for the ammonia conversion are generated from hydrogen (H{sub 2}) oxidation. (author)

Zie