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1

Conversion of light alkanes into aromatic hydrocarbons  

SciTech Connect

The aromatization of propane at 530[degrees]C on three MFI gallosilicates (Si/Ga = 30, 50 and 180) and on a MFI aluminosilicates (Si/Al = 30) was investigated. After pretreatment at 530[degrees]C under dry air flow, 30 Al MFI was seven times more active than 30 Ga MFI. This can be related to the greater strength of the acid sites of the aluminosilicate sample, which was shown by a calorimetric study of ammonia adsorption and by ammonia thermodesorption. Large differences were found in the catalytic product distribution, namely a lower initial cracking/dehydrogenation ration on 30 Ga MFI, greater selectivity to aromatics, and lower selectivity to alkanes (C[sub 1], C[sub 2], C[sub 4]) at high conversion, which can be explained by a dehydrogenating effect of gallium. The product distribution depended also on the Si/Ga ratio of the gallosilicate, a better selectivity to aromatics being found with 30 Ga MFI. The selectivity differences are mainly due to differences in the acid site density. The treatment of gallosilicates at 700-800[degrees]C under dry air flow caused a significant increase in their activity and in their selectivity for propane aromatization. This could be related to the formation of a small amount of extraframework gallium species, well dispersed in the crystallites and highly active for dehydrogenation of propane and of naphthene intermediates. On these catalysts propane aromatization occurred mainly through a bifunctional scheme and the formation of unwanted C[sub 1]C[sub 2] products, though acid cracking was very limited. The effect of the pretreatment temperature on the acid and dehydrogenating activity of the 30 Ga MFI sample showed that framework gallium species were much less active for dehydrogenation than extraframework species and indeed are probably inactive. 26 refs., 9 figs., 1 tab.

Giannetto, G. (Universidad Central de Venezuela, Los Chaguaramos, Caracas (Venezuela)); Montes, A. (Instituto Universitario de Technologia, Caracas (Venezuela)); Gnep, N.S.; Florentino, A.; Cartraud, P.; Guisnet, M. (Universite de Poitiers, Poitiers (France))

1994-01-01

2

Environmental Chemistry and Toxicology of Polychlorinated n Alkanes  

Microsoft Academic Search

\\u000a Polychlorinated-n-alkanes (PCAs) or chlorinated paraffins consist of C10to C30n-alkanes with chlorine content from 30% to 70% by mass. PCAs are used as high-temperature lubricants, plasticizers, flame\\u000a retardants, and additives in adhesives, paints, rubber, and sealants. This review presents the existing data on the environmental\\u000a chemistry and toxicology of PCAs and a preliminary exposure and risk assessment. There is limited information

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

3

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

PubMed

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

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

2012-06-19

4

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

5

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

6

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...

7

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

8

The chemistry of energy conversion and storage.  

PubMed

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

Su, Dang Sheng

2014-05-01

9

Organic Chemistry Self Instructional Package 5: Alkanes Preparations and Reactions.  

ERIC Educational Resources Information Center

This booklet, one of a series of 17 developed at Prince George's Community College, Largo, Maryland, provides an individualized, self-paced undergraduate organic chemistry instruction module designed to augment any course in organic chemistry but particularly those taught using the text "Organic Chemistry" by Morrison and Boyd. The entire series…

Zdravkovich, V.

10

Organic Chemistry Self Instructional Package 4: Alkanes-Nomenclature.  

ERIC Educational Resources Information Center

This booklet, one of a series of 17 developed at Prince George's Community College, Largo, Maryland, provides an individualized, self-paced undergraduate organic chemistry instruction module designed to augment any course in organic chemistry but particularly those taught using the text "Organic Chemistry" by Morrison and Boyd. The entire series…

Zdravkovich, V.

11

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

2012-03-12

12

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

13

Catalytic conversion of light alkanes, Phase 1. Topical report, January 1990--January 1993  

SciTech Connect

The authors have found a family of new catalytic materials which, if successfully developed, will be effective in the conversion of light alkanes to alcohols or other oxygenates. Catalysts of this type have the potential to convert natural gas to clean-burning high octane liquid fuels directly without requiring the energy-intensive steam reforming step. In addition they also have the potential to upgrade light hydrocarbons found in natural gas to a variety of high value fuel and chemical products. In order for commercially useful processes to be developed, increases in catalytic life, reaction rate and selectivity are required. Recent progress in the experimental program geared to the further improvement of these catalysts is outlined.

NONE

1993-12-31

14

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

15

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

PubMed Central

The development of renewable alternatives to diesel and jet fuels is highly desirable for the heavy transportation sector, and would offer benefits over the production and use of short-chain alcohols for personal transportation. Here, we report the development of a metabolically engineered strain of Escherichia coli that overproduces medium-chain length fatty acids via three basic modifications: elimination of ?-oxidation, overexpression of the four subunits of acetyl-CoA carboxylase, and expression of a plant acyl–acyl carrier protein (ACP) thioesterase from Umbellularia californica (BTE). The expression level of BTE was optimized by comparing fatty acid production from strains harboring BTE on plasmids with four different copy numbers. Expression of BTE from low copy number plasmids resulted in the highest fatty acid production. Up to a seven-fold increase in total fatty acid production was observed in engineered strains over a negative control strain (lacking ?-oxidation), with a composition dominated by C12 and C14 saturated and unsaturated fatty acids. Next, a strategy for producing undecane via a combination of biotechnology and heterogeneous catalysis is demonstrated. Fatty acids were extracted from a culture of an overproducing strain into an alkane phase and fed to a Pd/C plug flow reactor, where the extracted fatty acids were decarboxylated into saturated alkanes. The result is an enriched alkane stream that can be recycled for continuous extractions. Complete conversion of C12 fatty acids extracted from culture to alkanes has been demonstrated yielding a concentration of 0.44 g L?1 (culture volume) undecane. PMID:20073090

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

2013-01-01

16

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

17

An Acid-Base Chemistry Example: Conversion of Nicotine  

NASA Astrophysics Data System (ADS)

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

Summerfield, John H.

1999-10-01

18

Nanoparticle conversion chemistry: Kirkendall effect, galvanic exchange, and anion exchange  

NASA Astrophysics Data System (ADS)

Conversion chemistry is a rapidly maturing field, where chemical conversion of template nanoparticles (NPs) into new compositions is often accompanied by morphological changes, such as void formation. The principles and examples of three major classes of conversion chemical reactions are reviewed: the Kirkendall effect for metal NPs, galvanic exchange, and anion exchange, each of which can result in void formation in NPs. These reactions can be used to obtain complex structures that may not be attainable by other methods. During each kind of conversion chemical reaction, NPs undergo distinct chemical and morphological changes, and insights into the mechanisms of these reactions will allow for improved fine control and prediction of the structures of intermediates and products. Conversion of metal NPs into oxides, phosphides, sulphides, and selenides often occurs through the Kirkendall effect, where outward diffusion of metal atoms from the core is faster than inward diffusion of reactive species, resulting in void formation. In galvanic exchange reactions, metal NPs react with noble metal salts, where a redox reaction favours reduction and deposition of the noble metal (alloying) and oxidation and dissolution of the template metal (dealloying). In anion exchange reactions, addition of certain kinds of anions to solutions containing metal compound NPs drives anion exchange, which often results in significant morphological changes due to the large size of anions compared to cations. Conversion chemistry thus allows for the formation of NPs with complex compositions and structures, for which numerous applications are anticipated arising from their novel catalytic, electronic, optical, magnetic, and electrochemical properties.

Anderson, Bryan D.; Tracy, Joseph B.

2014-10-01

19

Organic Chemistry Self Instructional Package 3: Alkanes-Homologous Series and Isomerism.  

ERIC Educational Resources Information Center

This booklet, one of a series of 17 developed at Prince George's Community College, Largo, Maryland, provides an individualized, self-paced undergraduate organic chemistry instruction module designed to augment any course in organic chemistry but particularly those taught using the text "Organic Chemistry" by Morrison and Boyd. The entire series…

Zdravkovich, V.

20

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

21

Reactivity of alkanes on zeolites: a computational study of propane conversion reactions.  

PubMed

In this work, quantum chemical methods were used to study propane conversion reactions on zeolites; these reactions included protolytic cracking, primary hydrogen exchange, secondary hydrogen exchange, and dehydrogenation reactions. The reactants, products, and transition-state structures were optimized at the B3LYP/6-31G level and the energies were calculated with CBS-QB3, a complete basis set composite energy method. The computed activation barriers were 62.1 and 62.6 kcal/mol for protolytic cracking through two different transition states, 30.4 kcal/mol for primary hydrogen exchange, 29.8 kcal/mol for secondary hydrogen exchange, and 76.7 kcal/mol for dehydrogenation reactions. The effects of basis set for the geometry optimization and zeolite acidity on the reaction barriers were also investigated. Adding extra polarization and diffuse functions for the geometry optimization did not affect the activation barriers obtained with the composite energy method. The largest difference in calculated activation barriers is within 1 kcal/mol. Reaction activation barriers do change as zeolite acidity changes, however. Linear relationships were found between activation barriers and zeolite deprotonation energies. Analytical expressions for each reaction were proposed so that accurate activation barriers can be obtained when using different zeolites as catalysts, as long as the deprotonation energies are first acquired. PMID:16863122

Zheng, Xiaobo; Blowers, Paul

2005-12-01

22

Chemistry of Furan Conversion into Aromatics and Olefins over HZSM-5: A Model Biomass Conversion Reaction  

SciTech Connect

The conversion of furan (a model of cellulosic biomass) over HZSM-5 was investigated in a thermogravimetric analysis–mass spectrometry system, in situ Fourier transform infrared analysis, and in a continuous-flow fixed-bed reactor. Furan adsorbed as oligomers at room temperature with a 1.73 of adsorbed furan/Al ratio. These oligomers were polycyclic aromatic compounds that were converted to CO, CO?, aromatics, and olefins at temperatures from 400 to 600 °C. Aromatics (e.g., benzene, toluene, and naphthalene), oligomer isomers (e.g., benzofuran, 2,2-methylenebisfuran, and benzodioxane), and heavy oxygenates (C??{sub +} oligomers) were identified as intermediates formed inside HZSM-5 at different reaction temperatures. During furan conversion, graphite-type coke formed on the catalyst surface, which caused the aromatics and olefins formation to deactivate within the first 30 min of time on-stream. We have measured the effects of space velocity and temperature for furan conversion to help us understand the chemistry of biomass conversion inside zeolite catalysts. The major products for furan conversion included CO, CO?, allene, C?–C? olefins, benzene, toluene, styrene, benzofuran, indene, and naphthalene. The aromatics (benzene and toluene) and olefins (ethylene and propylene) selectivity decreased with increasing space velocity. Unsaturated hydrocarbons such as allene, cyclopentadiene, and aromatics selectivity increased with increasing space velocity. The product distribution was selective to olefins and CO at high temperatures (650 °C) but was selective to aromatics (benzene and toluene) at intermediate temperatures (450–600 °C). At low temperatures (450 °C), benzofuran and coke contributed 60% of the carbon selectivity. Several different reactions were occurring for furan conversion over zeolites. Some important reactions that we have identified in this study include Diels–Alder condensation (e.g., two furans form benzofuran and water), decarbonylation (e.g., furan forms CO and allene), oligomerization (allene forms olefins and aromatics plus hydrogen), and alkylation (e.g., furan plus olefins). The product distribution was far from thermodynamic equilibrium.

Cheng, Yu-Ting [Univ. of Massachusetts, Amherst, MA (United States); Huber, George W. [Univ. of Massachusetts, Amherst, MA (United States)

2011-06-03

23

Catalytic conversion of light alkanes-proof-of-concept stage - Phase IV. Topical report, February 1, 1994--January 31, 1995  

SciTech Connect

This report details the research performed on Phase IV of the extended Cooperative Agreement. This Phase, entitled C{sub 1}-C{sub 4} Research, provides the research support which accompanies the C{sub 4} Proof-of-Concept Phase (Phase V) as the two major activities of the Cooperative Agreement during calendar 1993. It is the objective of this phase to understand the nature of the catalysts and catalytic activity of perhaloporphyrin complexes uncovered during Phases I-III in order that superior catalytic materials can be made and tested which meet commercial criteria for the oxidation of the C{sub 1}-C{sub 4} light alkane gases found in natural gas and other available hydrocarbon streams. During Phase IV, we have examined the physical and electronic structures of the very active perhaloporphyrin catalysts which we have developed, and have gained an understanding of the properties which make them active. This has led us to design and synthesize materials which are cheaper, more active, more robust and, in general superior for carrying out practical catalysis. Our early generation perhaloporphyrin catalysts, while exhibiting unprecedented catalytic activity, were far too expensive for use in converting natural gas or its C{sub 1}-C{sub 4} components.

NONE

1998-12-31

24

Selective heterogeneous alkane oxidation  

SciTech Connect

Oxydehydrogenation of alkanes could provide significant advantages over steam cracking or catalytic dehydrogenation processes. High-temperature oxidations allow only limited selectivities due to homogeneous gas phase oxidation reactions which compete with surface reactions to produce significant amounts of carbon monoxide and carbon dioxide. Union Carbide`s molybdenum-vanadium-niobium oxide (MoVNb) and vanadyl pyrophosphate catalysts were compared with other literature oxidation catalysts for the oxidation of alkanes to the corresponding olefins at temperatures below 450{degrees}C. In addition, MoVNb catalysts of different compositions with and without promoters were explored for their abilities to selectively oxydehydrogenate alkanes. Alkene selectivity and alkane conversion in ethane and propane oxidation were correlated with the presence and amounts of different catalyst species determined for varying compositions of MoVNb catalysts using XPS, Raman, and XRD. Roles of the various catalyst species are proposed as a result of these studies. V is the active component and more V{sup 5+} favors oxydehydrogenation. Nb disperses V and prevents crystallization. Mo and possibly other promoters adjust the V{sup 5+}/V{sup 4+} ratio.

Warren, B.K.; Salaita, G.N. [Union Carbide Corporation, South Charleston, WV (United States)

1996-10-01

25

Symposium on the Physical Chemistry of Solar Energy Conversion, Indianapolis American Chemical Society Meetings, Fall 2013  

SciTech Connect

The Symposium on the Physical Chemistry of Solar Energy Conversion at the Fall ACS Meeting in Indianapolis, IN (Sept. 8-12) featured the following sessions (approx. 6 speakers per session): (1) Quantum Dots and Nanorods for Solar Energy Conversion (2 half-day sessions); (2) Artificial Photosynthesis: Water Oxidation; (3) Artificial Photosynthesis: Solar Fuels (2 half-day sessions); (4) Organic Solar Cells; (5) Novel Concepts for Solar Energy Conversion (2 half-day sessions); (6) Emerging Techniques for Solar Energy Conversion; (7) Interfacial Electron Transfer

Lian, Tianquan [PI, Emory Univ.

2013-09-01

26

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

27

Role of ozone in SOA formation from alkane photooxidation  

NASA Astrophysics Data System (ADS)

Long-chain alkanes, which can be categorized as intermediate volatility organic compounds, 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 and dehydration 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, thereby 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 used to evaluate the importance of this reaction channel in 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.

2014-02-01

28

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

29

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

EPA Science Inventory

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

30

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

31

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

32

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. PMID:14532053

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

2003-01-01

33

C3-C5 alkanes in the atmosphere: concentration, seasonal cycle and contribution to the atmospheric budgets of acetone and acetaldehyde  

NASA Astrophysics Data System (ADS)

The atmospheric chemistry of C3-C5 alkanes has been incorporated in the atmospheric-chemistry general circulation model EMAC. Model output is compared with observations from the NOAA/ESRL GMD cooperative air sampling network. A new series of measurements is used to evaluate the model in representing C3-C5 alkanes (i.e. propane, isobutane, butane, isopentane and pentane). While the representation of propane is within the measurement standard deviation, some deviations are found for the other tracers. The model is able to reproduce the main features of the C3-C5 alkanes (e.g., seasonality). However, in the Northern Hemisphere during winter the mixing ratios of these alkanes are generally overestimated. Conversely, the model shows an underestimation in the Southern Hemisphere. Moreover, only for iso-pentane there is a net overestimation of the mixing ratios, while for the other alkanes, the results are at the higher end of the measurement range. The effects of the C3-C5 alkanes to atmospheric acetone and acetaldehyde are quantified. The total amount of acetone produced by propane, isobutane and isopentane oxidation is 11.6 Tg/yr, 4.2 Tg/yr and 5.8 Tg/yr, respectively. These chemical sources are largely controlled by the reaction with OH, while the reactions with NO3 and Cl contribute only to a little extent. Moreover, 3.1, 4.5, 1.9 and 6.7 Tg/yr of acetaldehyde are formed from the oxidation of propane, butane, pentane and isopentane, respectively. Also for acetaldehyde, the formation is controlled by the reaction of alkanes with OH. However, since isopentane is generally overestimated, its contribution to the production of these oxygenated compounds represents an upper limit.

Pozzer, A.; Pollmann, J.; Taraborrelli, D.; Jöckel, P.; Helmig, D.; Tans, P.; Hueber, J.; Lelieveld, J.

2009-01-01

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

2013-05-01

35

Cation-alkane interaction.  

PubMed

Ab initio computations, up to CCSD(T)/CBS on model systems, and MP2/cc-pVTZ and DFT calculations are performed on cation-alkane and cation-alkene complexes, cation = Li(+), Na(+), Be(2+), Mg(2+), Ca(2+), Cu(+) and Zn(2+); alkane = C(n)H2(n+2) (n = 1-10) and C6H12; and alkene = C2H4 and C6H6. Density functional theory-symmetry adapted perturbation theory (DFT-SAPT) calculations reveal that the cation-alkane interactions are predominantly constituted of induction component. The dramatic modulation of the strength of their interaction and the topological features obtained from atoms in molecules (AIM) analysis are consistent with the characteristics of a typical noncovalent interaction. In contrast to many of the conventional noncovalent interactions, cation-alkane interactions are substantially strong and are comparable in strength to the well studied cation-? interactions. PMID:25384257

Premkumar, J Richard; Sastry, G Narahari

2014-12-01

36

Alkane oxidation catalysts  

SciTech Connect

This invention involves HPA and POA catalyzed, selective oxidation of alkanes with oxygen in the liquid phase at relatively mild conditions (usually under 200/sup 0/C) to a product rich in alcohol and with little or no burn of alkane to carbon oxides. The HPAs and POAs are promoted with certain metals and/or with an azide and may possess certain other modifications from a conventional HPA or POA.

Lyons, J.E.; Ellis, P.E. Jr.; Myers, H.K. Jr.; Suld, G.; Langdale, W.A

1989-02-07

37

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

SciTech Connect

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

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

1988-11-02

38

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

39

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

40

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

Microsoft Academic Search

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

Vagif M. Akhmedov

2007-01-01

41

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.

42

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

SciTech Connect

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

Gates, B.C.

1996-12-31

43

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

PubMed

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

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

2014-06-16

44

Force meets chemistry: Analysis of mechanochemical conversion in focal adhesions using fluorescence recovery after photobleaching  

Microsoft Academic Search

Mechanotransduction—the process by which mechanical forces are converted into changes of intracellular biochemistry—is critical for normal cell and tissue function. Integrins facilitate mechanochemical conversion by transferring physical forces from the extracellular matrix, across the cell surface, and to cytoskeletal- associated proteins within focal adhesions. It is likely that force alters biochemistry at these sites by altering molecular binding affinities of

Tanmay P. Lele; Charles K. Thodeti; Donald E. Ingber

2006-01-01

45

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

46

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

47

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

2012-10-22

48

Ceramic nanoparticle assemblies with tailored shapes and tailored chemistries via biosculpting and shape-preserving inorganic conversion.  

PubMed

A novel biosynthetic paradigm is introduced for fabricating three-dimensional (3-D) ceramic nanoparticle assemblies with tailored shapes and tailored chemistries: biosculpting and shape-preserving inorganic conversion (BaSIC). Biosculpting refers to the use of biomolecules that direct the precipitation of ceramic nanoparticles to form a continuous 3-D structure with a tailored shape. We used a peptide derived from a diatom (a type of unicellular algae) to biosculpt silica nanoparticle based assemblies that, in turn, were converted into a new (nonsilica) composition via a shape-preserving gas/silica displacement reaction. Interwoven, microfilamentary silica structures were prepared by exposing a peptide, derived from the silaffin-1A protein of the diatom Cylindrotheca fusiformis, to a tetramethylorthosilicate solution under a linear shear flow condition. Subsequent exposure of the silica microfilaments to magnesium gas at 900 degrees C resulted in conversion into nanocrystalline magnesium oxide microfilaments with a retention of fine (submicrometer) features. Fluid(gas or liquid)/silica displacement reactions leading to a variety of other oxides have also been identified. This hybrid (biogenic/synthetic) approach opens the door to biosculpted ceramic microcomponents with multifarious tailored shapes and compositions for a wide range of environmental, aerospace, biomedical, chemical, telecommunications, automotive, manufacturing, and defense applications. PMID:15762162

Dickerson, M B; Naik, R R; Sarosi, P M; Agarwal, G; Stone, M O; Sandhage, K H

2005-01-01

49

High Temperature Chemical Kinetic Combustion Modeling of Lightly Methylated Alkanes  

SciTech Connect

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

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

2011-03-01

50

Surface chemistry and corrosion behavior of aluminum-copper systems: Air-formed films to complex conversion coatings  

NASA Astrophysics Data System (ADS)

Understanding the mechanism of corrosion inhibition by carcinogenic chromates is critical to the development of environmentally safe coatings containing benign chromate substitutes. An integrated approach to correlate the surface chemistry and corrosion behavior of a wide range of systems has been undertaken. Electrochemical behavior was studied by open circuit potential (OCP) measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Surface chemistry was studied using variable-angle X-ray photoelectron spectroscopy (VAXPS), X-ray absorption near edge spectroscopy (XANES), secondary ion mass spectroscopy (SIMS), infrared spectroscopy and synchrotron infrared micro spectroscopy (SIRMS) and Raman spectroscopy. Using SIRMS, the ASTM recommended acetone degreasing was shown to initiate pitting of AA2024-T3 via photochemical formation of acetic acid. Due to the known tendency for photoreduction of Cr6+(3d0) following soft X-ray dosage during XPS, a novel method has been developed to prevent this reduction. This method yields, for the first time, an accurate determination of the Cr6+ content of a CCC. The pretreatment of the alloy prior to conversion coating has been shown to have significant influence on the surface intermetallic distribution, composition and corrosion resistance of the initial oxide film and subsequent conversion coating. AlconoxRTM pretreatment was found to result in a highly protective surface film that inhibits the subsequent formation of CCC. The study also shows that coupling of the alloy to platinum during the bromate pretreatment increases the corrosion resistance of the subsequently formed CCC by over an order of magnitude due to reduction in surface copper content. Adsorption of chromate ion on the passive oxide film formed on the metal surface was observed to induce fixed negative charges that inhibit chloride ingress on planar surfaces. While deprotonation of the aluminum hydroxide film by chromate was found to lead to corrosion resistant aluminum oxide, deprotonation induced by chloride ion resulted in the formation of a lower corrosion resistant aluminum oxyhydroxide. CCCs are considered to have the unique ability to repassivate the surface following a mechanical damage of the corrosion protective coating. Direct evidence for repassivation of AA2024-T3 by chromates has been provided for the first time using SIRMS, OCP measurements, SIMS, Raman spectroscopy. For the first time, molybdate ions have been found to not only repassivate mechanical damage but at rates significantly faster than chromates and hence represent a potential candidate for benign coating formulation. (Abstract shortened by UMI.)

Chidambaram, Devicharan

51

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.

Paula Woods

52

Chemistry  

NSDL National Science Digital Library

These sites willhelp you gain greater understanding of Chemistry! Weather is also available Three areas to be on the test. STUDY HARD!!!! Equations Types of Equations Types of Equations text/htmlMichigan Teacher Network Matter Density of solids Density of solids text/htmlICSD ScienceZone Metals Kidneys and Metals Problem Set Kidneys and Metals Problem Set image/tiffCenter for Digital Curriculum Research POTENTIAL SURROGATE METALS FOR INCINERATOR TRIAL BURNS POTENTIAL SURROGATE METALS FOR INCINERATOR TRIAL BURNS text/html Let it snow Interactive Weather Maker Interactive Weather Maker urlexample ...

Riley

2006-04-22

53

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

54

Integrated process for preparing a carboxylic acid from an alkane  

DOEpatents

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

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

2011-12-20

55

Rubredoxins Involved in Alkane Oxidation  

PubMed Central

Rubredoxins (Rds) are essential electron transfer components of bacterial membrane-bound alkane hydroxylase systems. Several Rd genes associated with alkane hydroxylase or Rd reductase genes were cloned from gram-positive and gram-negative organisms able to grow on n-alkanes (Alk-Rds). Complementation tests in an Escherichia coli recombinant containing all Pseudomonas putida GPo1 genes necessary for growth on alkanes except Rd 2 (AlkG) and sequence comparisons showed that the Alk-Rds can be divided in AlkG1- and AlkG2-type Rds. All alkane-degrading strains contain AlkG2-type Rds, which are able to replace the GPo1 Rd 2 in n-octane hydroxylation. Most strains also contain AlkG1-type Rds, which do not complement the deletion mutant but are highly conserved among gram-positive and gram-negative bacteria. Common to most Rds are the two iron-binding CXXCG motifs. All Alk-Rds possess four negatively charged residues that are not conserved in other Rds. The AlkG1-type Rds can be distinguished from the AlkG2-type Rds by the insertion of an arginine downstream of the second CXXCG motif. In addition, the glycines in the two CXXCG motifs are usually replaced by other amino acids. Mutagenesis of residues conserved in either the AlkG1- or the AlkG2-type Rds, but not between both types, shows that AlkG1 is unable to transfer electrons to the alkane hydroxylase mainly due to the insertion of the arginine, whereas the exchange of the glycines in the two CXXCG motifs only has a limited effect. PMID:11872724

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

2002-01-01

56

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

SciTech Connect

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

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

2008-08-01

57

Secondary Organic Aerosol Composition from C12 Alkanes.  

PubMed

The effects of structure, NOx conditions, relative humidity, and aerosol acidity on the chemical composition of secondary organic aerosol (SOA) are reported for the photooxidation of three C12 alkanes: n-dodecane, cyclododecane, and hexylcyclohexane. Acidity was modified through seed particle composition: NaCl, (NH4)2SO4, and (NH4)2SO4 + H2SO4. Off-line analysis of SOA was carried out by solvent extraction and gas chromatography-mass spectrometry (GC/MS) and direct analysis in real-time mass spectrometry. We report here 750 individual masses of SOA products identified from these three alkane systems and 324 isomers resolved by GC/MS analysis. The chemical compositions for each alkane system provide compelling evidence of particle-phase chemistry, including reactions leading to oligomer formation. Major oligomeric species for alkane SOA are peroxyhemiacetals, hemiacetals, esters, and aldol condensation products. Furans, dihydrofurans, hydroxycarbonyls, and their corresponding imine analogues are important participants in these oligomer-producing reactions. Imines are formed in the particle phase from the reaction of the ammonium sulfate seed aerosol with carbonyl-bearing compounds present in all the SOA systems. Under high-NO conditions, organonitrate products can lead to an increase of aerosol volume concentration by up to a factor of 5 over that in low-NO conditions. Structure was found to play a key role in determining the degree of functionalization and fragmentation of the parent alkane, influencing the mean molecular weight of the SOA produced and the mean atomic O:C ratio. PMID:24814371

Schilling Fahnestock, Katherine A; Yee, Lindsay D; Loza, Christine L; Coggon, Matthew M; Schwantes, Rebecca; Zhang, Xuan; Dalleska, Nathan F; Seinfeld, John H

2014-05-22

58

Quantification of Hydrogen Peroxide during the Low Temperature Oxidation of Alkanes  

E-print Network

1 Quantification of Hydrogen Peroxide during the Low Temperature Oxidation of Alkanes Chiheb'Ascq, France Abstract: The first reliable quantification of hydrogen peroxide (H2O2) formed) and related knock phenomena (4). Among the species involved in this chemistry, hydrogen peroxide

Paris-Sud XI, Université de

59

CH Bond Activation at Pt(II): A Route to Selective Alkane Oxidation?  

Microsoft Academic Search

A hypothetical catalytic cycle for the selective oxidation of alkanes to alcohols by dioxygen may be based on the activation to C-H bonds at Pt(II) centers, coupled with additional known organoplatinum chemistry. Mechanistic studies on the C-H activation process offer guides for designing potential for catalytic species.

Alan F. Heyduk; H. Annita Zhong; Jay A. Labinger; John E. Bercaw

2004-01-01

60

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

61

Virial coefficients of model alkanes  

NASA Astrophysics Data System (ADS)

We report the results from Mayer-sampling Monte Carlo calculations of the virial coefficients of the united-atom TraPPE-UA model of normal alkanes. For alkane chain lengths from n =2 to 20 (where n is the number of carbon atoms), results are given for the virial coefficients B2, B3, and B4; results for B5 are given for chains up to length n =12; and results for B6 are given for chains of length n =2, 3, and 4. In all cases, values are given for temperatures ranging from 200 K to 2000 K in 20-50 K increments. The values are used to calculate the equation of state for butane and the pressure-density behavior is compared to experimental data at 350 and 550 K. Critical points are calculated for all systems and compared to simulation data previously taken for the same molecular model, and to experiment. The comparison with temperature is very good (within 1.5% for all chain lengths up to n =12), while the critical density is underestimated by about 5%-15% and the critical pressure is given within about 10%. The convergence behavior of the virial equation of state as applied across the n-alkane series is well characterized by corresponding states, meaning that the accuracy at a given density relative to the critical density does not deteriorate with increasing chain length.

Schultz, Andrew J.; Kofke, David A.

2010-09-01

62

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

63

Exploratory study of coal-conversion chemistry. Quarterly report, December 20, 1979-March 19, 1980. [Ortho and para-hydroxydiphenylmethanes  

SciTech Connect

This report describes work accomplished under two tasks: Task A, Mechanism of Cleavage of Key Bond Types Present in Coals and Task B, Catalysis of Conversion in CO-H/sub 2/O Systems. Under Task A, the mechanism of the anomalously rapid donor solvent conversion of ortho- and para-hydroxydiphenylmethanes to phenol and toluene has been shown to involve an ionically established enol-keto equilibrium followed by rate limiting homolytic scission of the weakly bonded keto form. Consistent with a rate-limiting second step, the overall conversion rate is not subject to catalysis of acids, bases, or radical initiators, substances which could increase the rate at which the tautomeric pre-equilibrium is achieved. The rate of conversion, however, is markedly enhanced by the addition of iron oxides, with the mixed oxide Fe/sub 3/O/sub 4/ being roughly ten times more active than Fe/sub 2/O/sub 3/. Addition of crushed fused silica was also found to significantly enhance the conversion rates. Under Task B, the conversion of coal to 50% benzene soluble coal products in CO/H/sub 2/O systems displays a striking dependence on the pH of the starting aqueous phase (measured at room temperature). 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. The operation of the water-gas shift reaction parallels the conversion, with CO/sub 2/ and H/sub 2/ formed as product gases and CO consumed in the basic systems where conversion is effective. Hydrogen used in place of CO is ineffective. In a test of the intermediacy of formate in the system the use of potassium formate with nitrogen as the charge gas was similarly ineffective. Formate thus cannot be an intermediate in the conversion. The use of Mo(VI) (as molybdate) was effective, and a pH dependence on its operation was also observed.

McMillen, Donald F.; Ogier, Walter C.; Ross, David S.; Nguyen, Quyen Cu

1980-06-18

64

Modeling SOA production from the oxidation of intermediate volatility alkanes  

NASA Astrophysics Data System (ADS)

Secondary Organic Aerosols (SOA) production and ageing is a multigenerational oxidation process involving the formation of successive organic compounds with higher oxidation degree and lower vapour pressure. This process was investigated using the explicit oxidation model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere). Results for the C8-C24 n-alkane series show the expected trends, i.e. (i) SOA yield grows with the carbon backbone of the parent hydrocarbon, (ii) SOA yields decreases with the decreasing pre-existing organic aerosol concentration, (iii) the number of generations required to describe SOA production increases when the pre-existing organic aerosol concentration decreases. Most SOA contributors were found to be not oxidized enough to be categorized as highly oxygenated organic aerosols (OOA) but reduced enough to be categorized as hydrocarbon like organic aerosols (HOA). Branched alkanes are more prone to fragment in the early stage of the oxidation than their corresponding linear analogues. Fragmentation is expected to alter both the yield and the mean oxidation state of the SOA. Here, GECKO-A is applied to generate highly detailed oxidation schemes for various series of branched and cyclised alkanes. Branching and cyclisation effects on SOA yields and oxidation states will be examined.

Aumont, B.; Mouchel-Vallon, C.; Camredon, M.; Lee-Taylor, J.; Madronich, S.

2012-12-01

65

Genetics of alkane oxidation by Pseudomonas oleovorans  

Microsoft Academic Search

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

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

1994-01-01

66

Iron–Phthalocyanine Immobilized on Activated Carbon Black: A Selective Catalyst for Alkane Oxidation  

Microsoft Academic Search

Carbon black is tested as a support for iron–phthalocyanine within the frame of the oxidation of hydrocarbons witht-butylhydroperoxide 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

Rudy F. Parton; Patricia E. Neys; Peter A. Jacobs; Rosario C. Sosa; Paul G. Rouxhet

1996-01-01

67

Oxidation Products of Semi-volatile Alkanes by Hydroxyl Radicals  

NASA Astrophysics Data System (ADS)

Alkanes are ubiquitous in the atmosphere and are important components that influence atmospheric chemistry. Semi-volatile alkanes are partitioned between the gas- and the particle-phases and can be readily oxidized in both phases. Previous studies have demonstrated that reaction rates and the products of OH oxidation are very different for organic compounds in the gas- and particle phases. In the present study, n-octadecane (C18H38), n-eicosane (C20H42), n-docosane (C22H46), n-tricosane (C24H50), and n-pentadecylcyclohexane (C21H42) were chosen as model compounds for semi-volatile alkanes to examine their OH-initiated oxidation reactions in a flow tube reactor. OH exposure was varied in the experiments, equivalent to oxidation of up to one week in the atmosphere. Oxidation products were collected on filters and analyzed using two-dimensional gas chromatography coupled to a high-resolution time-of-flight electron impact ionization and vacuum ultraviolet photoionization mass spectrometer. Most of the oxygenated higher molecular weight isomers were separated and quantified. Our results suggest that aerosol samples formed in the n-octadecane experiment were more oxidized than the other model compounds (i.e., functionalization products with three oxygen atoms per molecule compared to two oxygen atoms per molecule) at similar OH exposures and aerosol mass loadings. This is likely due to the concentration of n-octadecane in the gas phase where oxidation is more rapid. We find that the first-generation gas-phase oxidation products quickly partition to the particle phase after which higher-generation oxidation likely occurs in the particle phase. Interestingly, functionalized carbonyl isomers for the normal alkanes were only observed on the 4 carbon positions closest to the molecule end in all cases, which is in contrast to structure-reactivity relationship (SRR) predictions for gas-phase reactions. For n-octadecane, the concentrations of first-generation functionalization products decreased on carbon positions closer to the molecule end. This trend is reversed for the other three normal alkanes, which show similar results to a recent study on heterogeneous oxidation of non-volatile alkane aerosols. Oxidation of n-pentadecylcyclohexane produces carbonyl and alcohol products on both the hexane ring and the side chain. Ring-opening products were not observed, likely due to the low ring strain energy of the hexane ring. This work provides insights into the oxidation mechanisms of semi-volatile organics leading to secondary aerosol formation and aging.

Zhang, H.; Worton, D. R.; Nah, T.; Goldstein, A. H.; Wilson, K. R.

2013-12-01

68

Surface chemistry and corrosion behavior of aluminum-copper systems: Air-formed films to complex conversion coatings  

Microsoft Academic Search

Understanding the mechanism of corrosion inhibition by carcinogenic chromates is critical to the development of environmentally safe coatings containing benign chromate substitutes. An integrated approach to correlate the surface chemistry and corrosion behavior of a wide range of systems has been undertaken. Electrochemical behavior was studied by open circuit potential (OCP) measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Surface

Devicharan Chidambaram

2003-01-01

69

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

70

40 CFR 721.535 - Halogenated alkane (generic).  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Halogenated alkane (generic). 721.535 Section 721...Substances § 721.535 Halogenated alkane (generic). (a) Chemical substance...substance identified generically as halogenated alkane (PMN P-01-433) is subject to...

2010-07-01

71

40 CFR 721.10163 - Chloro fluoro alkane (generic).  

Code of Federal Regulations, 2010 CFR

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

2010-07-01

72

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

PubMed Central

In this paper, 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 the 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 pre-determined 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 (0.64 mg/L (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 the 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.

2013-01-01

73

Comparison of alcohol and alkane oxidative dehydrogenation reactions over supported vanadium oxide catalysts: in situ infrared, Raman and UV–vis spectroscopic studies of surface alkoxide intermediates and of their surface chemistry  

Microsoft Academic Search

The surface chemistry of adsorbed isopropoxy groups on supported vanadia–alumina and vanadia–silica catalysts was investigated with multiple in situ spectroscopic techniques. The in situ FT-IR, Raman and UV–vis spectroscopic measurements provided molecular level information about the surface intermediates and the surface vanadium oxide species as a function of different conditions. The spectroscopic insights were compared to the steady state fixed

Carlo Resini; Tania Montanari; Guido Busca; Jih-Mirn Jehng; Israel E. Wachs

2005-01-01

74

Exploratory study of coal-conversion chemistry. Quarterly report No. 9, March 20, 1980-June 19, 1980. [Hydroxydiphenylmethane, diphenylether, diphenymethane  

SciTech Connect

This report describes work accomplished under two tasks: Task A, Mechanism of Cleavage of Key Bond Types Present in Coals, and Task B, Catalysis of Conversion in CO-H/sub 2/O Systems. Under Task A, the very effective catalysis of carbon-carbon bond cleavage by iron oxides in hydroxydiphenylmethane structures has been further characterized. An electron-transfer mechanism offers the most likely explanation of the observations that (1) alumina and silica-alumina surfaces are less active catalysts than Fe/sub 3/O/sub 4/, (2) meta-hydroxydiphenylmethane is almost as subject to catalysis as para-hydroxydiphenylmethane, (3) diphenyl ether is less subject to Fe/sub 3/O/sub 4/ catalysis than diphenylmethane, and (4) ortho-methoxydiphenylmethane exhibits the same susceptibility to Fe/sub 3/O/sub 4/ catalysis as ortho-hydroxydiphenylmethane. Under Task B, this quarter we have completed the survey of possible metal catalysts present in the Hastelloy C autoclave. We have found that coal conversion in CO-H/sub 2/O systems is effective when metal oxides such as MoO/sub 4//sup =/, Cr/sub 2/O/sub 7//sup =/, and MnO/sub 4//sup -/ are used as catalysts, but there is less or no coal conversion with FeCl/sub 3/ or Ni(CH/sub 3/COO)/sub 2/. While studying the fate of the catalyst after the reaction, we have isolated formate in the water-soluble fraction. This important information could help us in studying the role of formate in coal conversion. During this quarter, we have also studied the influence of reaction time and fresh CO on coal conversion in the presence of a catalyst. A striking result of 67% of benzene-soluble materials was obtained with an equivalent of 6000 ppM of Cr as sodium dichromate.

Not Available

1980-11-19

75

Alkane-Based Urethane Potting Compounds  

NASA Technical Reports Server (NTRS)

New low viscosity urethanes easily mixed, molded, and outgassed. Alkane-based urethanes resist hydrolysis and oxidation and have excellent dielectric properties. Low-viscosity alkane-based urethane prepolymer prepared by one-step reaction of either isophorone diisocyanate or methyl-bis (4-cyclohexyl isocyanate) with hydrogenated, hydroxy-terminated polybutadiene (HTPBD).

Morris, D. E.

1986-01-01

76

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

PubMed Central

Background Hydrocarbon alkanes have been recently considered as important next-generation biofuels because microbial production of alkane biofuels was demonstrated. However, the toxicity of alkanes to microbial hosts can possibly be a bottleneck for high productivity of alkane biofuels. To tackle this toxicity issue, it is essential to understand molecular mechanisms of interactions between alkanes and microbial hosts, and to harness these mechanisms to develop microbial host strains with improved tolerance against alkanes. In this study, we aimed to improve the tolerance of Saccharomyces cerevisiae, a model eukaryotic host of industrial significance, to alkane biofuels by exploiting cellular mechanisms underlying alkane response. Results To this end, we first confirmed that nonane (C9), decane (C10), and undecane (C11) were significantly toxic and accumulated in S. cerevisiae. Transcriptome analyses suggested that C9 and C10 induced a range of cellular mechanisms such as efflux pumps, membrane modification, radical detoxification, and energy supply. Since efflux pumps could possibly aid in alkane secretion, thereby reducing the cytotoxicity, we formed the hypothesis that those induced efflux pumps could contribute to alkane export and tolerance. In support of this hypothesis, we demonstrated the roles of the efflux pumps Snq2p and Pdr5p in reducing intracellular levels of C10 and C11, as well as enhancing tolerance levels against C10 and C11. This result provided the evidence that Snq2p and Pdr5p were associated with alkane export and tolerance in S. cerevisiae. Conclusions Here, we investigated the cellular mechanisms of S. cerevisiae response to alkane biofuels at a systems level through transcriptome analyses. Based on these mechanisms, we identified efflux pumps involved in alkane export and tolerance in S. cerevisiae. We believe that the results here provide valuable insights into designing microbial engineering strategies to improve cellular tolerance for highly efficient alkane biofuel production. PMID:23826995

2013-01-01

77

Selective monooxidation of light alkanes using chloride and iodate.  

PubMed

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

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

2014-06-11

78

The anaerobic degradation of gaseous, nonmethane alkanes — From in situ processes to microorganisms  

PubMed Central

The short chain, gaseous alkanes ethane, propane, n- and iso-butane are released in significant amounts into the atmosphere, where they contribute to tropospheric chemistry and ozone formation. Biodegradation of gaseous alkanes by aerobic microorganisms, mostly bacteria and fungi isolated from terrestrial environments, has been known for several decades. The first indications for short chain alkane anaerobic degradation were provided by geochemical studies of deep-sea environments around hydrocarbon seeps, and included the uncoupling of the sulfate-reduction and anaerobic oxidation of methane rates, the consumption of gaseous alkanes in anoxic sediments, or the enrichment in 13C of gases in interstitial water vs. the source gas. Microorganisms able to degrade gaseous alkanes were recently obtained from deep-sea and terrestrial sediments around hydrocarbon seeps. Up to date, only sulfate-reducing pure or enriched cultures with ethane, propane and n-butane have been reported. The only pure culture presently available, strain BuS5, is affiliated to the Desulfosarcina–Desulfococcus cluster of the Deltaproteobacteria. Other phylotypes involved in gaseous alkane degradation have been identified based on stable-isotope labeling and whole-cell hybridization. Under anoxic conditions, propane and n-butane are activated similar to the higher alkanes, by homolytic cleavage of the C—H bond of a subterminal carbon atom, and addition of the ensuing radical to fumarate, yielding methylalkylsuccinates. An additional mechanism of activation at the terminal carbon atoms was demonstrated for propane, which could in principle be employed also for the activation of ethane.

Musat, Florin

2015-01-01

79

Gas-phase chemistry during the conversion of cyclohexane to carbon: Flow reactor studies at low and intermediate pressure  

SciTech Connect

The gas-phase branching during the conversion of cyclohexane to solid carbon has been measured in a high-temperature-flow reactor. The experiments show that cyclohexane decomposes into a broad distribution of hydrocarbons that further decompose into the more kinetically stable products hydrogen, methane, acetylene, ethylene, benzene, and PAH. At 1363 K, the evolution to these species occurs quickly. We also observe the buildup of significant amounts of aromatic molecules at later stages in the decomposition, with as much as 15% of the total carbon in PAH and 25% in benzene. At later stages, the gas-phase molecules react slowly, even though the system is not at equilibrium, because of their kinetic stability and the smaller radical pool. The decomposition does not appear to depend sensitively on pressure in the regime of 25 to 250 torr. Thus, to a first approximation, these results can be extrapolated to atmospheric pressure.

Osterheld, T.H.; Allendorf, M.D.; Larson, R.

1995-07-01

80

Observed and simulated global distribution and budget of atmospheric C2-C5 alkanes  

NASA Astrophysics Data System (ADS)

The primary sources and atmospheric chemistry of C2-C5 alkanes have been incorporated into the atmospheric chemistry general circulation model EMAC. Model output is compared with new observations from the NOAA/ESRL GMD cooperative air sampling network. Based on the global coverage of the data, two different anthropogenic emission datasets for C4-C5 alkanes, widely used in the modelling community, are evaluated. We show that the model reproduces the main atmospheric features of the C2-C5 alkanes (e.g., seasonality). While the simulated values of ethane and propane are within a 20% range of the measurements, larger deviations are found for the other tracers. Finally the effect of C3-C5 alkanes on the concentration of acetone and acetaldehyde are assessed. Their chemical sources are largely controlled by the reaction with OH, while the reactions with NO3 and Cl contribute only to a little extent. The total amount of acetone produced by propane, i-butane and i-pentane oxidation is 11.2 Tg/yr, 4.2 Tg/yr and 5.8 Tg/yr, respectively. Moreover, 3.1, 3.3, 1.4 and 4.8 Tg/yr of acetaldehyde are formed by the oxidation of propane, n-butane, n-pentane and i-pentane, respectively.

Pozzer, A.; Pollmann, J.; Taraborrelli, D.; Jöckel, P.; Helmig, D.; Tans, P.; Hueber, J.; Lelieveld, J.

2010-01-01

81

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

82

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

83

Pd/NbOPO? multifunctional catalyst for the direct production of liquid alkanes from aldol adducts of furans.  

PubMed

Great efforts have been made to convert renewable biomass into transportation fuels. Herein, we report the novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes. Excellent activity and stability were observed with almost no decrease in octane yield (>90% throughout) in a 256?h time-on-stream test. Experimental and theoretical studies showed that NbO(x) species play the key role in C-O bond cleavage. As a multifunctional catalyst, Pd/NbOPO4 plays three roles in the conversion of aldol adducts into alkanes: 1)?The noble metal (in this case Pd) is the active center for hydrogenation; 2)?NbO(x) species help to cleave the C-O bond, especially of the tetrahydrofuran ring; and 3)?a niobium-based solid acid catalyzes the dehydration, thus enabling the quantitative conversion of furan-derived adducts into alkanes under mild conditions. PMID:25045056

Xia, Qi-Neng; Cuan, Qian; Liu, Xiao-Hui; Gong, Xue-Qing; Lu, Guan-Zhong; Wang, Yan-Qin

2014-09-01

84

Hydrocarbon chemistry  

SciTech Connect

The objective of this book is to provide a conprehensive up-to-date treatment of the field encompassing both basic chemistry and practical application. Topics include the following: basic information about hydrocarbons, their definitions, uses as energy sources, synthesis and conversion; hydrocarbon production from petroleum and natural gas and synthesis C1 sources; and various aspects of transformations of hydrocarbons.

Olah, G.A.; Molnar, A.

1995-08-01

85

Theoretical Description of the STM Images of Alkanes and Substituted Alkanes Adsorbed on Graphite  

E-print Network

Theoretical Description of the STM Images of Alkanes and Substituted Alkanes Adsorbed on Graphite the scanning tunneling microscopy (STM) images of molecules adsorbed on graphite. The model is applicable to a variety of different molecules with reasonable computational effort and provides images

Goddard III, William A.

86

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

87

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

88

Regio-and Enantioselective Alkane Hydroxylation with Engineered Cytochromes P450 BM-3  

E-print Network

alkanes regio- and enantioselectively using atmospheric dioxygen as an oxidant. BM-3 variant 9-10A-A328V biocatalysts for the controlled oxidation of alkanes. Linear alkanes are difficult to hydroxylate: the alkane C alkane oxidation reactions. The similarity of methylene C-H bond strengths in a linear alkane

Arnold, Frances H.

89

Light hydrocarbon gas conversion using porphyrin catalysts  

SciTech Connect

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

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

1995-07-01

90

Microbial production of short-chain alkanes.  

PubMed

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

Choi, Yong Jun; Lee, Sang Yup

2013-10-24

91

40 CFR 721.536 - Halogenated phenyl alkane.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Halogenated phenyl alkane. 721.536 Section 721.536 Protection...Substances § 721.536 Halogenated phenyl alkane. (a) Chemical substance and significant...identified generically as halogenated phenyl alkane (PMN P-89-867) is subject...

2010-07-01

92

In situ detection of anaerobic alkane metabolites in subsurface environments  

PubMed Central

Alkanes comprise a substantial fraction of crude oil and refined fuels. As such, they are prevalent within deep subsurface fossil fuel deposits and in shallow subsurface environments such as aquifers that are contaminated with hydrocarbons. These environments are typically anaerobic, and host diverse microbial communities that can potentially use alkanes as substrates. Anaerobic alkane biodegradation has been reported to occur under nitrate-reducing, sulfate-reducing, and methanogenic conditions. Elucidating the pathways of anaerobic alkane metabolism has been of interest in order to understand how microbes can be used to remediate contaminated sites. Alkane activation primarily occurs by addition to fumarate, yielding alkylsuccinates, unique anaerobic metabolites that can be used to indicate in situ anaerobic alkane metabolism. These metabolites have been detected in hydrocarbon-contaminated shallow aquifers, offering strong evidence for intrinsic anaerobic bioremediation. Recently, studies have also revealed that alkylsuccinates are present in oil and coal seam production waters, indicating that anaerobic microbial communities can utilize alkanes in these deeper subsurface environments. In many crude oil reservoirs, the in situ anaerobic metabolism of hydrocarbons such as alkanes may be contributing to modern-day detrimental effects such as oilfield souring, or may lead to more beneficial technologies such as enhanced energy recovery from mature oilfields. In this review, we briefly describe the key metabolic pathways for anaerobic alkane (including n-alkanes, isoalkanes, and cyclic alkanes) metabolism and highlight several field reports wherein alkylsuccinates have provided evidence for anaerobic in situ alkane metabolism in shallow and deep subsurface environments. PMID:23761789

Agrawal, Akhil; Gieg, Lisa M.

2013-01-01

93

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

2013-01-01

94

New Perspectives for light alkanes isomerization. Robert Hubaut*  

E-print Network

(2005) 101" #12;2 Abstract Isomerization of n-alkane into the high-octane number branched alkanes, into the high octane number di-branched alkanes is an important challenge for petroleum refining industry of the octane number. The research octane number (RON) and the motor octane number (MON) for some n

Paris-Sud XI, Université de

95

Chemistry of secondary organic aerosol formation  

NASA Astrophysics Data System (ADS)

The photooxidation of volatile organic compounds (VOCs) in the atmosphere can lead to the formation of secondary organic aerosol (SOA), a major component of fine particulate matter. Improvements to air quality require insight into the many reactive intermediates that lead to SOA formation, of which only a small fraction have been measured at the molecular level. This thesis describes the chemistry of secondary organic aerosol (SOA) formation from several atmospherically relevant hydrocarbon precursors. Photooxidation experiments of methoxyphenol and phenolic compounds and C12 alkanes were conducted in the Caltech Environmental Chamber. These experiments include the first photooxidation studies of these precursors run under sufficiently low NOx levels, such that RO2 + HO2 chemistry dominates, an important chemical regime in the atmosphere. Using online Chemical Ionization Mass Spectrometery (CIMS), key gas-phase intermediates that lead to SOA formation in these systems were identified. With complementary particle-phase analyses, chemical mechanisms elucidating the SOA formation from these compounds are proposed. Three methoxyphenol species (phenol, guaiacol, and syringol) were studied to model potential photooxidation schemes of biomass burning intermediates. SOA yields (ratio of mass of SOA formed to mass of primary organic reacted) exceeding 25% are observed. Aerosol growth is rapid and linear with the organic conversion, consistent with the formation of essentially non-volatile products. Gas and aerosol-phase oxidation products from the guaiacol system show that the chemical mechanism consists of highly oxidized aromatic species in the particle phase. Syringol SOA yields are lower than that of phenol and guaiacol, likely due to unique chemistry dependent on methoxy group position. The photooxidation of several C12 alkanes of varying structure n-dodecane, 2-methylundecane, cyclododecane, and hexylcyclohexane) were run under extended OH exposure to investigate the effect of molecular structure on SOA yields and photochemical aging. Peroxyhemiacetal formation from the reactions of several multifunctional hydroperoxides and aldehyde intermediates was found to be central to organic growth in all systems, and SOA yields increased with cyclic character of the starting hydrocarbon. All of these studies provide direction for future experiments and modeling in order to lessen outstanding discrepancies between predicted and measured SOA.

Yee, Lindsay Diana

96

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

97

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

98

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

99

Nitrated metalloporphyrins as catalysts for alkane oxidation  

DOEpatents

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

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

1994-01-01

100

Nitrated metalloporphyrins as catalysts for alkane oxidation  

DOEpatents

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

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

1992-01-01

101

Reflectance spectroscopy of organic compounds: 1. Alkanes  

USGS Publications Warehouse

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

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

2009-01-01

102

Modeling of Alkane Oxidation Using Constituents and Species  

NASA Technical Reports Server (NTRS)

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

Bellan, Jasette; Harstad, Kenneth G.

2010-01-01

103

Observed and simulated global distribution and budget of atmospheric C2-C5 alkanes  

NASA Astrophysics Data System (ADS)

The primary sources and atmospheric chemistry of C2-C5 alkanes were incorporated into the atmospheric chemistry general circulation model EMAC. Model output is compared with new observations from the NOAA/ESRL GMD Cooperative Air Sampling Network. Based on the global coverage of the data, two different anthropogenic emission datasets for C4-C5 alkanes, widely used in the modelling community, are evaluated. We show that the model reproduces the main atmospheric features of the C2-C5 alkanes (e.g., seasonality). While the simulated values for ethane and propane are within a 20% range of the measurements, larger deviations are found for the other tracers. According to the analysis, an oceanic source of butanes and pentanes larger than the current estimates would be necessary to match the observations at some coastal stations. Finally the effect of C2-C5 alkanes on the concentration of acetone and acetaldehyde are assessed. Their chemical sources are largely controlled by the reaction with OH, while the reactions with NO3 and Cl contribute only to a little extent. The total amount of acetone produced by propane, i-butane and i-pentane oxidation is 11.2 Tg/yr, 4.3 Tg/yr, and 5.8 Tg/yr, respectively. Moreover, 18.1, 3.1, 3.4, 1.4 and 4.8 Tg/yr of acetaldehyde are formed by the oxidation of ethane, propane, n-butane, n-pentane and i-pentane, respectively.

Pozzer, A.; Pollmann, J.; Taraborrelli, D.; Jöckel, P.; Helmig, D.; Tans, P.; Hueber, J.; Lelieveld, J.

2010-05-01

104

147Chemistry Chemistry (Chem)  

E-print Network

147Chemistry Chemistry (Chem) Bayly Foundation PROFESSORS FRANCE, PLEVA ASSOCIATE PROFESSORS ALty A student may complete only one of the majors listed in the Department of Chemistry. The major in chemistry leading to a Bachelor of Arts degree requires completion of 44 credits as follows: 1. Chemistry 111, 112

Dresden, Gregory

105

Vapor Pressures and Vaporization Enthalpies of the n-Alkanes from C21 to C30 at T ) 298.15 K by Correlation Gas Chromatography  

E-print Network

by Correlation Gas Chromatography James S. Chickos* and William Hanshaw Department of Chemistry and Biochemistry of transfer from solution to the gas phase as measured by gas chromatography.3 A plot of the vaporization interest in using the larger n-alkanes as stan- dards for correlation gas chromatography measurements (c

Chickos, James S.

106

Vapor Pressures and Vaporization Enthalpies of the n-Alkanes from C31 to C38 at T ) 298.15 K by Correlation Gas Chromatography  

E-print Network

by Correlation Gas Chromatography James S. Chickos* and William Hanshaw Department of Chemistry and Biochemistry-alkanes studied previously. Since studies using correlation gas chromatography work best when the standards of correlation gas chromatography. This technique relies entirely on the use of standards in assessment

Chickos, James S.

107

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.

Thomas Meixner

108

n Alkane oxidation by a Pseudomonas  

Microsoft Academic Search

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

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

1958-01-01

109

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

110

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

111

A mass spectrometry study of alkanes in air plasma at atmospheric pressure  

Microsoft Academic Search

The positive APCI-mass spectra in air of linear (n-pentane, n-hexane, n-heptane, n-octane), branched [2,4-dimethylpentane, 2,2-dimethylpentane and 2,2,4-trimethylpentane (i-octane)], and cyclic (cyclohexane) alkanes were analyzed at different mixing ratios and temperatures. The effect of air humidity\\u000a was also investigated. Complex ion chemistry is observed as a result of the interplay of several different reagent ions, including\\u000a atmospheric ions O2+•, NO+, H3O+,

Ester Marotta; Cristina Paradisi

2009-01-01

112

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

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Mixture of hydrofluoro alkanes and hydrofluoro alkene. 721.4464... § 721.4464 Mixture of hydrofluoro alkanes and hydrofluoro alkene. (a) Chemical...generically as a mixture of hydrofluoro alkanes and hydrofluoro alkene (PMNs...

2010-07-01

113

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

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Halogenated alkane aromatic compound (generic name...Substances § 721.785 Halogenated alkane aromatic compound (generic name...identified generically as a halogenated alkane aromatic compound (PMN...

2010-07-01

114

40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...721.10148 Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...generically as acryloxy alkanoic alkane derivative with mixed metal oxides (PMN...

2013-07-01

115

40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...721.10148 Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...generically as acryloxy alkanoic alkane derivative with mixed metal oxides (PMN...

2012-07-01

116

40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...721.10148 Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...generically as acryloxy alkanoic alkane derivative with mixed metal oxides (PMN...

2011-07-01

117

40 CFR 721.10148 - Acryloxy alkanoic alkane derivative with mixed metal oxides (generic).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...721.10148 Acryloxy alkanoic alkane derivative with mixed metal oxides (generic...generically as acryloxy alkanoic alkane derivative with mixed metal oxides (PMN...

2010-07-01

118

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

119

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

SciTech Connect

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

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

2007-01-01

120

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

121

Department of Chemistry & Biochemistry UCLA Chemistry, Biochemistry & Chemistry Material Science  

E-print Network

Department of Chemistry & Biochemistry UCLA Chemistry, Biochemistry & Chemistry Material Science ...........................................................................................................................................4 Chemistry & Biochemistry Undergraduate Office..............................................................................................6 Majors in Chemistry & Biochemistry

Levine, Alex J.

122

Alkane Coordination Selectivity in Hydrocarbon Activation by [TpRh(CNneopentyl)]: The Role of Alkane Complexes  

E-print Network

of Alkane Complexes Andrew J. Vetter, Christine Flaschenriem, and William D. Jones* Contribution from; Revised Manuscript Received June 20, 2005; E-mail: jones@chem.rochester.edu Abstract: The competitive. K.; McMaster, A. D.; Graham, W. A. G. J. Am. Chem. Soc. 1983, 105, 7190. (e) Jones, W. D.; Feher, F

Jones, William D.

123

A Toolkit to Enable Hydrocarbon Conversion in Aqueous Environments  

PubMed Central

This work puts forward a toolkit that enables the conversion of alkanes by Escherichia coli and presents a proof of principle of its applicability. The toolkit consists of multiple standard interchangeable parts (BioBricks)9 addressing the conversion of alkanes, regulation of gene expression and survival in toxic hydrocarbon-rich environments. A three-step pathway for alkane degradation was implemented in E. coli to enable the conversion of medium- and long-chain alkanes to their respective alkanols, alkanals and ultimately alkanoic-acids. The latter were metabolized via the native ?-oxidation pathway. To facilitate the oxidation of medium-chain alkanes (C5-C13) and cycloalkanes (C5-C8), four genes (alkB2, rubA3, rubA4and rubB) of the alkane hydroxylase system from Gordonia sp. TF68,21 were transformed into E. coli. For the conversion of long-chain alkanes (C15-C36), theladA gene from Geobacillus thermodenitrificans was implemented. For the required further steps of the degradation process, ADH and ALDH (originating from G. thermodenitrificans) were introduced10,11. The activity was measured by resting cell assays. For each oxidative step, enzyme activity was observed. To optimize the process efficiency, the expression was only induced under low glucose conditions: a substrate-regulated promoter, pCaiF, was used. pCaiF is present in E. coli K12 and regulates the expression of the genes involved in the degradation of non-glucose carbon sources. The last part of the toolkit - targeting survival - was implemented using solvent tolerance genes, PhPFD? and ?, both from Pyrococcus horikoshii OT3. Organic solvents can induce cell stress and decreased survivability by negatively affecting protein folding. As chaperones, PhPFD? and ? improve the protein folding process e.g. under the presence of alkanes. The expression of these genes led to an improved hydrocarbon tolerance shown by an increased growth rate (up to 50%) in the presences of 10% n-hexane in the culture medium were observed. Summarizing, the results indicate that the toolkit enables E. coli to convert and tolerate hydrocarbons in aqueous environments. As such, it represents an initial step towards a sustainable solution for oil-remediation using a synthetic biology approach. PMID:23052445

Brinkman, Eva K.; Schipper, Kira; Bongaerts, Nadine; Voges, Mathias J.; Abate, Alessandro; Wahl, S. Aljoscha

2012-01-01

124

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

PubMed

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

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

2002-02-15

125

A Fundamentally Based Correlation Between Alkane Structure and Octane Number  

Microsoft Academic Search

At temperatures below about 850 K, the autoignition of alkane\\/air mixtures takes place by a degenerate chain mechanism. We postulate here that the differences in ease of autoignition between alkanes are due predominantly to the different rates at which the kinetic branching agent is formed. This process involves two successive internal hydrogen abstractions (isomerisations) in peroxy radicals and is very

C. MORLEY

1987-01-01

126

Mechanism of conversion of methanol over ZSM-5 catalyst  

SciTech Connect

The work of Olah (J. Amer. Chem. Soc. 97:6807 (1975)) on alkanes in superacids indicated the importance of two-electron, three-center bonded carbonium ion transition states. Using Olah's work as a basis, a mechanism for the methanol conversion is proposed which involves methyl ethyl ether as an intermediate. (DLC)

Kagi, D.

1981-05-01

127

Thermal conductivity of liquid n-alkanes  

NASA Astrophysics Data System (ADS)

The thermal conductivity of liquids has been shown in the past to be difficult to predict with a reasonable accuracy, due to the lack of accurate experimental data and reliable prediction schemes. However, data of a high accuracy, and covering wide density ranges, obtained recently in laboratories in Boulder, Lisbon, and London with the transient hot-wire technique, can be used to revise an existing correlation scheme and to develop a new universal predictive technique for the thermal conductivity of liquid normal alkanes. The proposed correlation scheme is constructed on a theoretically based treatment of the van der Waals model of a liquid, which permits the prediction of the density dependence and the thermal conductivity of liquid n-alkanes, methane to tridecane, for temperatures between 110 and 370 K and pressures up to 0.6 MPa, i.e., for 0.3? T/T c?0.7 and 2.4? P/P c?3.7, with an accuracy of ±1%, given a known value of the thermal conductivity of the fluid at the desired temperature. A generalization of the hard-core volumes obtained, as a function of the number of carbon atoms, showed that it was possible to predict the thermal conductivity of pentane to tetradecane±2%, without the necessity of available experimental measurements.

Calado, J. C. G.; Fareleira, J. M. N. A.; Mardolcar, U. V.; Nieto de Castro, C. A.

1988-05-01

128

Superacid catalyzed coal conversion chemistry. 1st and 2nd quarterly technical progress reports, September 1, 1983-March 30, 1984. [Model compound consisting of 2 benzene rings connected with various bridging units such as alkylidene, ether, sulfide, etc  

SciTech Connect

In our laboratories we have previously developed a mild coal conversion process. This involves the use of a superacid system consisting of HF and BF/sub 3/ in presence of hydrogen and/or a hydrogen donor solvent. In order to understand the chemistry involved in the process of depolymerization of coal by the HF:BF/sub 3/:H/sub 2/ system we are carrying out a systematic study of a number of coal model compounds. The model compounds selected for present study have two benzene rings connected with various bridging units such as alkylidene, ether, sulfide etc. From studies so far carried out it appears that high pyridine extractibilities achieved by treating coal at temperature below 100/sup 0/C results from the cleavage of bridges such as present in bibenzyl, diphenyl methane, dibenzyl ether, dibenzyl sulfide etc. On the other hand the increased cyclohexane extractibility and distillability observed at relatively higher temperatures and hydrogen pressures reflects the hydrogenation and cleavage of the aromatic backbone in coal structure similar to what is seen in the conversion of model compounds such as biphenyl, diphenyl ether, diphenyl sulfide, anthracene, etc.

Olah, G.A.

1984-01-01

129

Expanding the Product Profile of a Microbial Alkane Biosynthetic Pathway  

PubMed Central

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

2013-01-01

130

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

2013-09-01

131

Kinetic study of asphaltene dissolution in amphiphile/alkane solutions  

SciTech Connect

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

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

1997-09-01

132

Heterogeneity of Alkane Chain Length in Freshwater and Marine Cyanobacteria  

PubMed Central

The potential utilization of cyanobacteria for the biological production of alkanes represents an exceptional system for the next generation of biofuels. Here, we analyzed a diverse group of freshwater and marine cyanobacterial isolates from Indian culture collections for their ability to produce both alkanes and alkenes. Among the 50 cyanobacterial isolates screened, 32 isolates; 14 freshwater and 18 marine isolates; produced predominantly alkanes. The GC-MS/MS profiles revealed a higher percentage of pentadecane and heptadecane production for marine and freshwater strains, respectively. Oscillatoria species were found to be the highest producers of alkanes. Among the freshwater isolates, Oscillatoria CCC305 produced the maximum alkane level with 0.43??g/mg dry cell weight, while Oscillatoria formosa BDU30603 was the highest producer among the marine isolates with 0.13??g/mg dry cell weight. Culturing these strains under different media compositions showed that the alkane chain length was not influenced by the growth medium but was rather an inherent property of the strains. Analysis of the cellular fatty acid content indicated the presence of predominantly C16 chain length fatty acids in marine strains, while the proportion of C18 chain length fatty acids increased in the majority of freshwater strains. These results correlated with alkane chain length specificity of marine and freshwater isolates indicating that alkane chain lengths may be primarily determined by the fatty acid synthesis pathway. Moreover, the phylogenetic analysis showed clustering of pentadecane-producing marine strains that was distinct from heptadecane-producing freshwater strains strongly suggesting a close association between alkane chain length and the cyanobacteria habitat.

Shakeel, Tabinda; Fatma, Zia; Fatma, Tasneem; Yazdani, Syed Shams

2015-01-01

133

Alkane separation using nanoporous graphene membranes.  

PubMed

We studied the permeability of graphene sheets with designed nanopores using the classical molecular dynamics. To characterize the energy profile for transmission we calculated the potential of the mean force. A high selectivity for methane + butane mixture with the hydrogen-passivated pore diameter of 0.32 nm was found where the volume exclusion mechanism governs the separation process. In the case of a slightly larger pore diameter of 0.64 nm the same alkane mixture separates completely unexpectedly: a larger butane molecule permeates much faster than a small methane one. The blocking effect of the permeation path by a larger mixture component when it worked like a cork was also observed. This is a promising perspective for using graphene to design intelligent membranes which can maintain a constant composition of mixtures in the permeable area. PMID:25410377

Nieszporek, Krzysztof; Drach, Mateusz

2015-01-14

134

Structurized surface layers of normal alkanes  

NASA Astrophysics Data System (ADS)

The elevated viscosity of micron interlayers of certain normal alkanes compared to their viscosity in the "volume" is determined experimentally in shear flow using a rotational viscometer. The observed difference is considered to be caused by the manifestation, in such interlayers, of structural inhomogeneity due to the presence of structurized polymolecular surface layers on the substrates bounding them. The structural parameters of such layers, i.e., their equilibrium initial thickness and "hydrodynamic strength," are calculated in the model of a constant-viscosity layer. The measured effective viscosity of the interlayers diminishes with growth in the shear-flow velocity, which is attributed to the "cutting" of the structurized layer. Surfactant doping of the liquids leads to an increase in the effective viscosity of the interlayers, which is produced by the strengthening of the layer structure.

Altoiz, B. A.; Kiriyan, S. V.

2010-07-01

135

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

136

One Instructor's Approach to Computer Assisted Instruction in General Chemistry.  

ERIC Educational Resources Information Center

Discusses advantages of using computer-assisted instruction in a college general chemistry course. Advantages include using programs which generate random equations with double arrows (equilibrium systems) or generate alkane structural formula, asking for the correct IUPAC name of the structure. (Author/JN)

DeLorenzo, Ronald

1982-01-01

137

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

138

Conversational Dominance.  

ERIC Educational Resources Information Center

Details of conversational behavior can often not be interpreted until the social interaction, including the rights and obligations of the participants, their intent, the topic, etc., has been defined. This paper presents a model of conversation in which the conversational image a person presents in a given conversational situation is a function of…

Esau, Helmut; Poth, Annette

139

Secondary organic aerosol formation from acyclic, monocyclic, and polycyclic alkanes.  

PubMed

A large number of organic species emitted into the atmosphere contain cycloalkyl groups. While cyclic species are believed to be important secondary organic aerosol (SOA) precursors, the specific role of cyclic moieties (particularly for species with multiple or fused rings) remains uncertain. Here we examine the yields and composition of SOA formed from the reaction of OH with a series of C10 (cyclo)alkanes, with 0-3 rings, in order to better understand the role of multiple cyclic moieties on aerosol formation pathways. A chamber oxidation technique using high, sustained OH radical concentrations was used to simulate long reaction times in the atmosphere. This aging technique leads to higher yields than in previously reported chamber experiments. Yields were highest for cyclic and polycyclic precursors, though yield exhibited little dependence on number of rings. However, the oxygen-to-carbon ratio of the SOA was highest for the polycyclic precursors. These trends are consistent with aerosol formation requiring two generations of oxidation and 3-4 oxygen-containing functional groups in order to condense. Cyclic, unbranched structures are protected from fragmentation during the first oxidation step, with C-C bond scission instead leading to ring opening, efficient functionalization, and high SOA yields. Fragmentation may occur during subsequent oxidation steps, limiting yields by forming volatile products. Polycyclic structures can undergo multiple ring opening reactions, but do not have markedly higher yields, likely due to enhanced fragmentation in the second oxidation step. By contrast, C-C bond scission for the linear and branched structures leads to fragmentation prior to condensation, resulting in low SOA yields. The results highlight the key roles of multigenerational chemistry and susceptibility to fragmentation in the formation and evolution of SOA. PMID:25093758

Hunter, James F; Carrasquillo, Anthony J; Daumit, Kelly E; Kroll, Jesse H

2014-09-01

140

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

141

Process for converting light alkanes to higher hydrocarbons  

DOEpatents

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 reacted 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 chlorinated alkanes. The chlorinated alkanes are 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.

Noceti, Richard P. (Pittsburgh, PA); Taylor, Charles E. (Pittsburgh, PA)

1988-01-01

142

DITERMINAL OXIDATION OF LONG-CHAIN ALKANES BY BACTERIA1  

PubMed Central

Kester, A. S. (The University of Texas, Austin) and J. W. Foster. Diterminal oxidation of long-chain alkanes by bacteria. J. Bacteriol. 85:859–869. 1963.—A corynebacterial organism capable of growing in mineral salts with individual pure alkanes as carbon sources produces a series of acids from the C10-C14 alkanes. They have been isolated in pure form and identified as monoic, ?-hydroxy monoic, and dioic acids containing the same number of carbon atoms as the substrate alkane. Oxidation took place at both terminal methyl groups—“diterminal oxidation.” Appropriate labeling experiments indicate that omega oxidation of fatty acids occurs in this organism and that an oxygenation with O2 occurs. Images PMID:14044955

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

1963-01-01

143

The heterogeneous partial oxidation of light alkanes  

E-print Network

(cont.) With this approach, an upper bound on the yield for OCM was computed. Results showed that even with optimal surface chemistry, strict limits existed on the attainable yield. Surface energetics necessary for superior ...

Su, Yee San, 1977-

2004-01-01

144

Bacterial metabolism of long-chain n -alkanes  

Microsoft Academic Search

Degradation of alkanes is a widespread phenomenon in nature, and numerous microorganisms, both prokaryotic and eukaryotic,\\u000a capable of utilizing these substrates as a carbon and energy source have been isolated and characterized. In this review,\\u000a we summarize recent advances in the understanding of bacterial metabolism of long-chain n-alkanes. Bacterial strategies for accessing these highly hydrophobic substrates are presented, along with

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

2007-01-01

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

Hydrogen-hydrogen bonds in highly branched alkanes and in alkane complexes: A DFT, ab initio, QTAIM, and ELF study.  

PubMed

The hydrogen-hydrogen (H-H) bond or hydrogen-hydrogen bonding is formed by the interaction between a pair of identical or similar hydrogen atoms that are close to electrical neutrality and it yields a stabilizing contribution to the overall molecular energy. This work provides new, important information regarding hydrogen-hydrogen bonds. We report that stability of alkane complexes and boiling point of alkanes are directly related to H-H bond, which means that intermolecular interactions between alkane chains are directional H-H bond, not nondirectional induced dipole-induced dipole. Moreover, we show the existence of intramolecular H-H bonds in highly branched alkanes playing a secondary role in their increased stabilities in comparison with linear or less branched isomers. These results were accomplished by different approaches: density functional theory (DFT), ab initio, quantum theory of atoms in molecules (QTAIM), and electron localization function (ELF). PMID:24533436

Monteiro, Norberto K V; Firme, Caio L

2014-03-01

147

Thermodynamics of alkanol-alkane mixtures  

SciTech Connect

A new theoretical approach is presented for the description of the thermodynamic behavior of systems containing associated compounds. A continuous linear association model is implemented in the lattice-fluid theory of Sanchez and Lacombe as modified recently by the author. The apparent equilibrium association constant, widely used in the various theories of associated solutions, is density dependent in the present model. The model can be applied to both liquids and gases at any external conditions down to the critical point. A single set of association enthalpy, association entropy, and association volume is used for all 1-alkanols; these association properties are pure-component properties. The theory is used to calculate vapor pressures, orthobaric densities, and heats of vaporization of 1-alkanols. New lattice-fluid scaling constants for these compounds are presented which are now close to the corresponding constants of their homomorph hydrocarbons. The theory is, subsequently, extended to mixtures and used to calculate the basic thermodynamic quantities of mixing for a number of alkanol-alkane systems. In its present form the theory is an approximate one since it does not take into account, besides others, the cooperative character of association phenomena in dilute liquid solutions and gases, but because of its simplicity it may form the basis for more refined treatments.

Panayiotou, C.G.

1988-05-19

148

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

PubMed

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

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

2012-10-01

149

148 Chemistry/Chinese Chemistry 347 (3)--Advanced Organic Chemistry  

E-print Network

148 Chemistry/Chinese Chemistry 347 (3)--Advanced Organic Chemistry Prerequisite: Chemistry 242,syntheticmethodology,mod- ernsyntheticreactions,protectinggroups,naturalprod- uctssynthesis,andcombinatorialchemistry.France. Spring Chemistry 350 (3)--Advanced Inorganic Chemistry Prerequisites: Chemistry 250, 252, and 262. Anintro

Dresden, Gregory

150

Thermodynamics of adsorption of ionic surfactants at water/alkane interfaces.  

PubMed

On the basis of experimental data for the homologous series of alkyltrimethylammonium bromides (CnTAB) the equilibrium surface tension isotherms at three types of liquid-fluid interfaces are discussed: solution/air, solution/alkane vapor and solution/liquid alkane interfaces. It is shown that the adsorption characteristics can be described at all three interfaces by the same thermodynamic approach. In the presence of alkane molecules (in the liquid alkane phase or in the alkane vapor phase) the CnTAB adsorption layers can be best described by a co-adsorption of the alkane molecules. PMID:24909966

Fainerman, V B; Aksenenko, E V; Mucic, N; Javadi, A; Miller, R

2014-09-28

151

Selective hydroxylation of alkanes by an extracellular fungal peroxygenase.  

PubMed

Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H(2)O(2) 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 H(2)O(2)-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 H(2)(18)(2) resulted in complete incorporation of (18)O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D(7) showed a large intramolecular deuterium isotope effect [(k(H)/k(D))(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 × 10(11) 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 (> C(16)) 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. PMID:21812933

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

2011-10-01

152

A General, Enantioselective Synthesis of 1-Azabicyclo[m.n.0]alkane Ring Systems  

PubMed Central

In this Letter, we describe a novel approach for the general and enantioselective synthesis of a diverse array of small to large 1-azabicyclo[m.n.0]alkyl ring systems with an embedded olefin handle for further functionalization. The stereochemistry is established via a highly diastereoselective indium-mediated allylation of an Ellman sulfinimine in greater than 9:1 dr., which is readily separable by column chromatography to afford a single diastereomer. This methodology allows for the rapid preparation of 1-azabicyclo[m.n.0]alkane ring systems that are not readily accessible through any other chemistry in excellent overall yields and, for many systems, the only enantioselective preparation reported to date. PMID:23459400

Senter, Timothy J.; Schulte, Michael L.; Konkol, Leah C.; Wadzinski, Tyler E.; Lindsley, Craig W.

2013-01-01

153

Recent Advances in Catalytic Conversion of Ethanol to Chemicals  

SciTech Connect

With increased availability and decreased cost, ethanol is potentially a promising platform molecule for the production of a variety of value-added chemicals. In this review, we provide a detailed summary of recent advances in catalytic conversion of ethanol to a wide range of chemicals and fuels. We particularly focus on catalyst advances and fundamental understanding of reaction mechanisms involved in ethanol steam reforming (ESR) to produce hydrogen, ethanol conversion to hydrocarbons ranging from light olefins to longer chain alkenes/alkanes and aromatics, and ethanol conversion to other oxygenates including 1-butanol, acetaldehyde, acetone, diethyl ether, and ethyl acetate.

Sun, Junming; Wang, Yong

2014-04-30

154

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.

155

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

156

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

SciTech Connect

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

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

1996-12-01

157

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....

158

Molecular simulation study of homogeneous crystal nucleation in n-alkane melts  

E-print Network

This work used molecular dynamics (MD) and Monte Carlo (MC) method to study the homogeneous crystal nucleation in the melts of n-alkanes, the simplest class of chain molecules. Three n-alkanes with progressive chain length ...

Yi, Peng, Ph. D. Massachusetts Institute of Technology

2011-01-01

159

Integrated two-liquid phase bioconversion and product-recovery processes for the oxidation of alkanes: Process design and economic evaluation  

SciTech Connect

Pseudomonas oleovorans and recombinant strains containing the alkane oxidation genes can product alkane oxidation genes can produce alkane oxidation products in two-liquid phase bioreactor systems. In these bioprocesses the cells, which grow in the aqueous phase, oxidize apolar, non-water soluble substrates. The apolar products typically accumulate in the emulsified apolar phase. The authors have studied both the bioconversion systems and several downstream processing systems to separate and purify alkanols from these two-liquid phase media. Based on the information generated in these studies, the authors have now designed bioconversion and downstream processing systems for the production of 1-alkanols from n-alkanes on a 10 kiloton/yr scale, taking the conversion of n-octane to 1-octanol as a model system. Here, the authors describe overall designs of fed-batch and continuous-fermentation processes for the oxidation of octane to 1-octanol by Pseudomonas oleovoran, and the authors discuss the economics of these processes. The overall performance of each of these two systems has been modeled with Aspen software. Although the continuous process is about 10% more expensive than the fed-batch process, improvements to reduce overall cost can be achieved more easily for continuous than for fed-batch fermentation by decreasing the dilution rate while maintaining near constant productivity. Improvements relevant to both processes can be achieved by increasing the biocatalyst performance, which results in improved overall efficiency, decreased capital investment, and hence, decreased production cost.

Mathys, R.G.; Schmid, A.; Witholt, B.

1999-08-20

160

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

161

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

162

Regioselective alkane hydroxylation with a mutant AlkB enzyme  

DOEpatents

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

163

Temperature dependence of the structure of Langmuir films of normal-alkanes on liquid mercury  

E-print Network

Temperature dependence of the structure of Langmuir films of normal-alkanes on liquid mercury H phase behavior of Langmuir films of n-alkanes CH3(CH2)n 2CH3 , denote Cn on mercury was studied surface normal, alkanes on mercury are always oriented surface parallel and show no long-range in

Ocko, Ben

164

580 ,. CHIAt. sot.. CHEM. COMMVN., 1~8~ Shape-selective Alkane Hydroxylation  

E-print Network

in the oxidation of alkanes with iodosylbcnzenr in the presence of manganese porphyrins Substrate Catalyst Pr580 ,. CHIAt. sot.. CHEM. COMMVN., 1~8~ Shape-selective Alkane Hydroxylation Kenneth Suslick: Sruc been used to catalyse shape-selective alkane hydroxylation, increasing the production of primary

Suslick, Kenneth S.

165

Directed Evolution of a Cytochrome P450 Monooxygenase for Alkane Oxidation  

E-print Network

Directed Evolution of a Cytochrome P450 Monooxygenase for Alkane Oxidation Edgardo T. Farinas alcohols and amides. How- ever, it is not known to oxidize alkanes. Here we re- port that P450 BM-3 = slight affinity) accurately reflects the nature of these com- pounds: alkanes are notoriously inert

Arnold, Frances H.

166

Alkane oxidation by an iron complex-hydrogen peroxide system in acetonitrile. The model of methanemonooxygenase  

Microsoft Academic Search

The oxidation of methane and other light alkanes in the system iron complex — hydrogen peroxide has been studied. The efficiency of this system of alkane oxidation depends on water concentration. The catalytic methanol formation from methane with respect to the binuclear iron complex has been observed. The role of iron-oxocomplexes in oxidation of alkanes by methanemonooxygenase and model systems

A. M. Khenkin; V. S. Belova; A. E. Shilov

1990-01-01

167

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

168

Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions.  

PubMed

Intermolecular potential models for water and alkanes describe pure component properties fairly well, but fail to reproduce properties of water-alkane mixtures. Understanding interactions between water and non-polar molecules like alkanes is important not only for the hydrocarbon industry but has implications to biological processes as well. Although non-polar solutes in water have been widely studied, much less work has focused on water in non-polar solvents. In this study we calculate the solubility of water in different alkanes (methane to dodecane) at ambient conditions where the water content in alkanes is very low so that the non-polar water-alkane interactions determine solubility. Only the alkane-rich phase is simulated since the fugacity of water in the water rich phase is calculated from an accurate equation of state. Using the SPC/E model for water and TraPPE model for alkanes along with Lorentz-Berthelot mixing rules for the cross parameters produces a water solubility that is an order of magnitude lower than the experimental value. It is found that an effective water Lennard-Jones energy ?(W)/k = 220?K is required to match the experimental water solubility in TraPPE alkanes. This number is much higher than used in most simulation water models (SPC/E-?(W)/k = 78.2?K). It is surprising that the interaction energy obtained here is also higher than the water-alkane interaction energy predicted by studies on solubility of alkanes in water. The reason for this high water-alkane interaction energy is not completely understood. Some factors that might contribute to the large interaction energy, such as polarizability of alkanes, octupole moment of methane, and clustering of water at low concentrations in alkanes, are examined. It is found that, though important, these factors do not completely explain the anomalously strong attraction between alkanes and water observed experimentally. PMID:25134597

Ballal, Deepti; Venkataraman, Pradeep; Fouad, Wael A; Cox, Kenneth R; Chapman, Walter G

2014-08-14

169

Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions  

NASA Astrophysics Data System (ADS)

Intermolecular potential models for water and alkanes describe pure component properties fairly well, but fail to reproduce properties of water-alkane mixtures. Understanding interactions between water and non-polar molecules like alkanes is important not only for the hydrocarbon industry but has implications to biological processes as well. Although non-polar solutes in water have been widely studied, much less work has focused on water in non-polar solvents. In this study we calculate the solubility of water in different alkanes (methane to dodecane) at ambient conditions where the water content in alkanes is very low so that the non-polar water-alkane interactions determine solubility. Only the alkane-rich phase is simulated since the fugacity of water in the water rich phase is calculated from an accurate equation of state. Using the SPC/E model for water and TraPPE model for alkanes along with Lorentz-Berthelot mixing rules for the cross parameters produces a water solubility that is an order of magnitude lower than the experimental value. It is found that an effective water Lennard-Jones energy ?W/k = 220 K is required to match the experimental water solubility in TraPPE alkanes. This number is much higher than used in most simulation water models (SPC/E—?W/k = 78.2 K). It is surprising that the interaction energy obtained here is also higher than the water-alkane interaction energy predicted by studies on solubility of alkanes in water. The reason for this high water-alkane interaction energy is not completely understood. Some factors that might contribute to the large interaction energy, such as polarizability of alkanes, octupole moment of methane, and clustering of water at low concentrations in alkanes, are examined. It is found that, though important, these factors do not completely explain the anomalously strong attraction between alkanes and water observed experimentally.

Ballal, Deepti; Venkataraman, Pradeep; Fouad, Wael A.; Cox, Kenneth R.; Chapman, Walter G.

2014-08-01

170

Electronic spectroscopy of intermediates involved in the conversion of methane to methanol by FeO  

E-print Network

Electronic spectroscopy of intermediates involved in the conversion of methane to methanol by Fe.1063/1.1448489 I. INTRODUCTION The direct oxidation of methane to an easily transport- able liquid such as methanol process and as the simplest model for alkane oxidation.1,2 Although no direct, efficient methane­methanol

Metz, Ricardo B.

171

Crystallization and prevention of supercooling of microencapsulated n-alkanes.  

PubMed

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

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

2005-01-15

172

Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation  

DOEpatents

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

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

1995-01-01

173

Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation  

DOEpatents

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

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

1993-01-01

174

Cyano- and polycyanometalloporphyrins as catalysts for alkane oxidation  

DOEpatents

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

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

1992-01-01

175

Partial oxidation of light alkanes by periodate and chloride salts.  

PubMed

The efficient and selective partial oxidation of light alkanes using potassium periodate and potassium chloride is reported. Yields of methane functionalization in trifluoroacetic acid reach >40% with high selectivity for methyl trifluoroacetate. Periodate and chloride also functionalize ethane and propane in good yields (>20%). PMID:25708552

Kalman, Steven E; Munz, Dominik; Fortman, George C; Boaz, Nicholas C; Groves, John T; Gunnoe, T Brent

2015-03-10

176

Diverse alkane hydroxylase genes in microorganisms and environments  

PubMed Central

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

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

2014-01-01

177

Diverse alkane hydroxylase genes in microorganisms and environments.  

PubMed

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

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

2014-01-01

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.

1995-01-17

179

Transport properties of alkanes through ceramic thin zeolite MFI membranes  

Microsoft Academic Search

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

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

1996-01-01

180

Roaming radical pathways for the decomposition of alkanes.  

SciTech Connect

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

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

2010-01-01

181

Energy conversion & storage program. 1994 annual report  

SciTech Connect

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

Cairns, E.J.

1995-04-01

182

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

PubMed

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

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

2012-07-01

183

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

184

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

ERIC Educational Resources Information Center

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

Inner London Education Authority (England).

185

Reaction chemistry of cerium  

SciTech Connect

It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

NONE

1997-01-01

186

Chemistry Notes  

ERIC Educational Resources Information Center

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

School Science Review, 1976

1976-01-01

187

ENVIRONMENTAL CHEMISTRY  

EPA Science Inventory

Environmental chemistry is applied to estimating the exposure of ecosystems and humans to various chemical environmental stressors. Among the stressors of concern are mercury, pesticides, and arsenic. Advanced analytical chemistry techniques are used to measure these stressors ...

188

Chemistry Notes  

ERIC Educational Resources Information Center

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

School Science Review, 1972

1972-01-01

189

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

190

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

191

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

192

Generalized Fundamental Equation of State for the Normal Alkanes  

NASA Astrophysics Data System (ADS)

Based on the extended three-parameter corresponding-states principle and the most reliable experimental data of -alkanes, a generalized fundamental equation of state for technical calculations has been developed. This equation is in the form of the reduced Helmholtz free energy and takes the reduced density, reduced temperature, and acentric factor as variables. The proposed equation satisfies the critical conditions and Maxwell rule, shows correct behavior for the ideal curves and for the derivatives of the thermodynamic potentials, and allows the calculation of all thermodynamic properties including phase equilibrium of -alkanes from -pentane to -pentacontane over a temperature range from the triple point to 700 K with pressures up to 100 MPa. The new equation differs from the previous generalized equations of other authors by a wider range of variation of the acentric factor to 1.8, and by more accurately predicting thermal properties.

Alexandrov, Igor; Gerasimov, Anatoly; Grigor'ev, Boris

2013-10-01

193

Site isolation in vanadium phosphorus oxide alkane oxidation  

SciTech Connect

Single crystal X-ray diffraction studies of vanadyl pyrophosphate indicate that at least two polytypical structures exists for this active and selective alkane oxidation catalyst. The crystal structures of these materials differ with respect to the symmetry and direction of columns of vanadyl groups within the unit cell. Single crystals of vanadyl pyrophosphate have been generated at extreme temperatures not often experienced by microcrystalline catalysts. The crystallography of the system suggests that other crystalline modifications or disordered phases might also exist. Zeroth-order models of crystal surface termination of vanadyl pyrophosphate have been constructed which conceptually illustrate the ability of vanadyl pyrophosphate to accommodate varying amounts of surface phosphorus parallel to (1,0,0), (0,1,0) and (0,2,4). Pyrophosphate termination of surfaces parallel to (1,0,0) likely results in the isolation of clusters of reactive centers and limits overoxidation of the alkane substrate. 23 refs., 6 figs.

Thompson, M R [Pacific Northwest Lab., Richland, WA (USA); Ebner, J R [Monsanto Co., St. Louis, MO (USA)

1991-06-01

194

Introduction to Solar Photon Conversion  

SciTech Connect

This Thematic Issue on Solar Photon Conversion will provide a review by leading researchers on the present status and prognosis of the science and technology of direct solar photoconversion to electricity and fuels. The topics covered include advanced and novel concepts for low-cost photovoltaic (PV) energy based on chemistry (dye-sensitized photoelectrodes, organic and molecular PV, multiple exciton generation in quantum dots, singlet fission), solar water splitting, redox catalysis for water oxidation and reduction, the role of nanoscience and nanocrystals in solar photoconversion, photoelectrochemical energy conversion, and photoinduced electron transfer.

Nozik, Arthur J; Miller, John

2010-01-01

195

Pretreatment of lignocellulosic biomass using Fenton chemistry  

Technology Transfer Automated Retrieval System (TEKTRAN)

Pretreatment is a necessary step in “biomass to biofuel conversion” due to the recalcitrant nature of lignocellulosic biomass. White-rot fungi utilize peroxidases and hydrogen peroxide (in vivo Fenton chemistry) to degrade lignin. In an attempt to mimic this process, solution phase Fenton chemistry ...

196

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."

197

Monolayer solids of short (perfluoro)alkanes on graphite  

NASA Astrophysics Data System (ADS)

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

Bruch, L. W.

2009-03-01

198

At what chain length do unbranched alkanes prefer folded conformations?  

PubMed

Short unbranched alkanes are known to prefer linear conformations, whereas long unbranched alkanes are folded. It is not known with certainty at what chain length the linear conformation is no longer the global minimum. To clarify this point, we use ab initio and density functional methods to compute the relative energies of the linear and hairpin alkane conformers for increasing chain lengths. Extensive electronic structure calculations are performed to obtain optimized geometries, harmonic frequencies, and accurate single point energies for the selected alkane conformers from octane through octadecane. Benchmark CCSD(T)/cc-pVTZ single point calculations are performed for chains through tetradecane, whereas approximate methods are required for the longer chains up to octadecane. Using frozen natural orbitals to unambiguously truncate the virtual orbital space, we are able to compute composite CCSD FNO(T) single point energies for all the chain lengths. This approximate composite method has significant computational savings compared to full CCSD(T) while retaining ?0.15 kcal/mol accuracy compared to the benchmark results. More approximate dual-basis resolution-of-the-identity double-hybrid DFT calculations are also performed and shown to have reasonable 0.2-0.4 kcal/mol errors compared with our benchmark values. After including contributions from temperature dependent internal energy shifts, we find the preference for folded conformations to lie between hexadecane and octadecane, in excellent agreement with recent experiments [ Lüttschwager , N. O. ; Wassermann , T. N. ; Mata , R. A. ; Suhm , M. A. Angew. Chem. Int. Ed. 2013 , 52 , 463 ]. PMID:24524689

Byrd, Jason N; Bartlett, Rodney J; Montgomery, John A

2014-03-01

199

Syngas in millisecond reactors: higher alkanes and fast lightoff  

Microsoft Academic Search

Steady-state and transient catalytic partial oxidation of hydrocarbons (methane, butane, cyclohexane, n-hexane, isooctane, decane) has been carried out on rhodium-coated alumina monoliths in an effort to determine whether higher alkanes can be successfully converted to H2 and CO in short contact time reactors. This process is also necessary to determine the feasibility of on-board hydrogen generation for fuel cell and

L. D. Schmidt; E. J. Klein; C. A. Leclerc; J. J. Krummenacher; K. N. West

2003-01-01

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

Alkane Biosynthesis Genes in Cyanobacteria and Their Transcriptional Organization  

PubMed Central

In cyanobacteria, alkanes are synthesized from a fatty acyl-ACP by two enzymes, acyl–acyl carrier protein reductase and aldehyde deformylating oxygenase. Despite the great interest in the exploitation for biofuel production, nothing is known about the transcriptional organization of their genes or the physiological function of alkane synthesis. The comparison of 115 microarray datasets indicates the relatively constitutive expression of aar and ado genes. The analysis of 181 available genomes showed that in 90% of the genomes both genes are present, likely indicating their physiological relevance. In 61% of them they cluster together with genes encoding acetyl-CoA carboxyl transferase and a short-chain dehydrogenase, strengthening the link to fatty acid metabolism and in 76% of the genomes they are located in tandem, suggesting constraints on the gene arrangement. However, contrary to the expectations for an operon, we found in Synechocystis sp. PCC 6803 specific promoters for the two genes, sll0208 (ado) and sll0209 (aar), which give rise to monocistronic transcripts. Moreover, the upstream located ado gene is driven by a proximal as well as a second, distal, promoter, from which a third transcript, the ~160?nt sRNA SyR9 is transcribed. Thus, the transcriptional organization of the alkane biosynthesis genes in Synechocystis sp. PCC 6803 is of substantial complexity. We verified all three promoters to function independently from each other and show a similar promoter arrangement also in the more distant Nodularia spumigena, Trichodesmium erythraeum, Anabaena sp. PCC 7120, Prochlorococcus MIT9313, and MED4. The presence of separate regulatory elements and the dominance of monocistronic mRNAs suggest the possible autonomous regulation of ado and aar. The complex transcriptional organization of the alkane synthesis gene cluster has possible metabolic implications and should be considered when manipulating the expression of these genes in cyanobacteria. PMID:25022427

Klähn, Stephan; Baumgartner, Desirée; Pfreundt, Ulrike; Voigt, Karsten; Schön, Verena; Steglich, Claudia; Hess, Wolfgang R.

2014-01-01

202

Ignition in alkane oxidation on noble-metal catalysts  

Microsoft Academic Search

The ignition behavior in the oxidation of four simple alkanes (methane, ethane, propane and isobutane) with air on a platinum-foil catalyst, as well as that of ethane\\/air mixtures on four noble-metal foil catalysts (Pt, Pd, Rh, and Ir) was studied at atmospheric pressure over the entire range of fuel-to-air ratios. While, Pd showed the widest range of surface flammability, ignition

Götz Veser; Murtaza Ziauddin; Lanny D. Schmidt

1999-01-01

203

Sensing of volatile alkanes by metal-oxide semiconductors  

Microsoft Academic Search

Sensing of volatile alkanes via chemoresistive gas sensors has been addressed. Screen-printed films of Au- and Pd-added SnO2 and a solid solution of mixed Sn and Ti oxides have been selected for the purpose. We demonstrate that the films sensitively detect 200ppm of such gases, a value which is by far lower than their alarm limits. Information about the working

M. C. Carotta; V. Guidi; G. Martinelli; M. Nagliati; D. Puzzovio; D. Vecchi

2008-01-01

204

Cobalt porphyrin-catalyzed alkane oxidations using dioxygen as oxidant  

Microsoft Academic Search

In a mixture of trifluoroacetic acid and water, cobalt(II) porphyrin complexes catalyze the oxidation of alkanes by dioxygen. Carbon monoxide is required as a coreductant for the oxidations to proceed. While the turnover rates are slow, the system displays unusual selectivity in that primary C?H bonds are more reactive than the weaker secondary C?H bonds or C?H bonds ? to

Hui Tang; Chengyu Shen; Minren Lin; Ayusman Sen

2000-01-01

205

Computational Chemistry for Chemistry Educators  

NSDL National Science Digital Library

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

Shodor Computational Science Institute

206

CHEMISTRY 320 PHYSICAL CHEMISTRY I  

E-print Network

CHEMISTRY 320 PHYSICAL CHEMISTRY I Fall 2009 9:00 am - 10:30 am, MW CNSB 211 INSTRUCTOR INFORMATION of the physical principles of chemistry. Goals/ Objectives: CHEM 320 presents chemical principles from a fundamental physical point of view. Topics covered include: properties of gases, thermodynamics (heat, work

Findley, Gary L.

207

Dielectric constant of liquid alkanes and hydrocarbon mixtures  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

208

Cold-tolerant alkane-degrading Rhodococcus species from Antarctica  

SciTech Connect

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

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

2000-07-01

209

Revisiting the hexane-water interface via molecular dynamics simulations using nonadditive alkane-water potentials  

NASA Astrophysics Data System (ADS)

We present results addressing properties of a polarizable force field for hexane based on the fluctuating charge (FQ) formalism and developed in conjunction with the Chemistry at Harvard Molecular Mechanics (CHARMM) potential function. Properties of bulk neat hexane, its liquid-vapor interface, and its interface with a polarizable water model (TIP4P-FQ) are discussed. The FQ model is compared to a recently modified alkane model, C27r, also based on the CHARMM potential energy function. With respect to bulk properties, both models predict bulk density within 1%; the FQ model predicts the liquid vaporization enthalpy within 2%, while the C27r force field underestimates the property by roughly 20% (and in this sense reflects the quality of the C27r force field across the spectrum of linear and branched alkanes). The FQ hexane model realistically captures the dielectric properties of the bulk in terms of a dielectric constant of 1.94, in excellent agreement with experimental values in the range of 1.9-2.02. This behavior is also in conformity with a recent polarizable alkane model based on Drude oscillators. Furthermore, the bulk dielectric is essentially captured in the infinite frequency, or optical, dielectric contribution. The FQ model is in this respect a more realistic force field for modeling lipid bilayer interiors for which most current state-of-the-art force fields do not accurately capture the dielectric environment. The molecular polarizability of the FQ model is 11.79Å3, in good agreement with the range of experimental and ab initio values. In contrast to FQ models of polar solvents such as alcohols and water, there was no need to scale gas-phase polarizabilities in order to avoid polarization catastrophes in the pure bulk. In terms of the liquid-vapor and liquid-liquid interfaces, the FQ model displays a rich orientational structure of alkane and water in the respective interfacial systems, in general conforming with earlier simulation studies of such interfaces. The FQ force field shows a marked deviation in the interfacial dipole potentials computed from the charge densities averaged over simulation trajectories. At the liquid-vapor interface, the FQ model predicts a potential drop of -178.71mV in contrast to the C27r estimate of -433.80mV. For the hexane-water interface, the FQ force field predicts a dipole potential drop of -379.40mV in contrast to the C27r value of -105.42mV. Although the surface dipole potential predicted by the FQ model is roughly 3.5 times that predicted by the C27r potential, it is consistent with reported experimental potentials across solvated lipid bilayers in the range of 400-600mV.

Patel, Sandeep A.; Brooks, Charles L.

2006-05-01

210

Synthesis and characterization of a rhodium(I) ?-alkane complex in the solid state.  

PubMed

Transition metal-alkane complexes-termed ?-complexes because the alkane donates electron density to the metal from a ?-symmetry carbon-hydrogen (C-H) orbital-are key intermediates in catalytic C-H activation processes, yet these complexes remain tantalizingly elusive to characterization in the solid state by single-crystal x-ray diffraction techniques. Here, we report an approach to the synthesis and characterization of transition metal-alkane complexes in the solid state by a simple gas-solid reaction to produce an alkane ?-complex directly. This strategy enables the structural determination, by x-ray diffraction, of an alkane (norbornane) ?-bound to a d(8)-rhodium(I) metal center, in which the chelating alkane ligand is coordinated to the pseudosquare planar metal center through two ?-C-H bonds. PMID:22923436

Pike, Sebastian D; Thompson, Amber L; Algarra, Andrés G; Apperley, David C; Macgregor, Stuart A; Weller, Andrew S

2012-09-28

211

Conversion, Fragmentation,  

E-print Network

YFFReview Forestland Conversion, Fragmentation, and Parcelization A summary of a forum exploring;Executive Summary It is increasingly evident that fragmentation is one of the most critical issues facing fragmentation of forestlands, especially those close to expanding population centers. Private forestlands

212

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.

2011-05-24

213

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

214

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

NASA Technical Reports Server (NTRS)

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

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

1950-01-01

215

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

216

Connected Chemistry  

NSDL National Science Digital Library

Connected Chemistry, a novel learning environment for teaching chemistry, is appropriate for use in both high school and undergraduate chemistry classrooms. Connected Chemistry comprises several molecular simulations designed to enable instructors to teach chemistry using the perspective of emergent phenomena. That is, it allows students to see observed macro-level chemical phenomena, like many other scientific phenomena, as resultant from the interactions of many individual agents on a micro-level. This perspective is especially appropriate to the study of chemistry where the interactions between multitudes of molecules on the atomic level give rise to the macro-level concepts that students study in the classroom. Connected Chemistry comprises molecular simulations embedded in the NetLogo modeling software (1). The collection contains several predesigned simulations of closed chemical systems to teach specific chemistry concepts. Currently, Connected Chemistry contains models for teaching Brønsted Lowry acid base theory, enzyme kinetics, radical polymerization, buffer chemistry, kinetics, chemical equilibrium, and crystallization. Instructors and students can individually tailor the predesigned simulations or generate new simulations as they are needed in the context of a particular lesson, classroom, or department.

217

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

218

Compound-specific hydrogen isotope composition of n-alkanes in combustion residuals of fossil fuels  

NASA Astrophysics Data System (ADS)

The hydrogen isotope compositions (?D) of n-alkanes present in the combustion residuals of fossil fuels (coal, gasoline, and diesel) were measured using GC-IRMS to distinguish between coal soot and vehicle exhaust. The n-alkane ?D values of industrial and domestic coal soot ranged from -95.3‰ to -219.6‰ and -128.1‰ to -188.6‰, respectively, exhibiting similar tendencies. The ?D values of the C15-C18n-alkanes in both types of coal soot were nearly consistent, and the ?D values of the C19-C24n-alkanes exhibited a zigzag profile. The ?D values of C16-C22n-alkanes in gasoline exhaust exhibited a saw-tooth distribution, decreased with the carbon number, and were more positive than the ?D values of C16-C22n-alkanes in diesel exhaust, which increased with the carbon number. However, the ?D values of the C23-C29n-alkanes in gasoline and diesel vehicle exhaust were mostly consistent. The weighted average ?D values of the C16-C19n-alkanes in industrial and domestic coal soot were similar to the average ?D values in gasoline and diesel vehicle exhausts; however, the average ?D values of the C21-C29n-alkanes in vehicle exhausts were richer in D than those in coal soot.

Bai, Huiling; Peng, Lin; Li, Zhongping; Liu, Xiaofeng; Song, Chongfang; Mu, Ling

2014-11-01

219

Functional characterization of genes involved in alkane oxidation by Pseudomonas aeruginosa  

Microsoft Academic Search

Most clinical isolates identified as Pseudomonas aeruginosa grow on long-chain n-alkanes, while environmental P. aeruginosa isolates often grow on medium- as well as long-chain n-alkanes. Heterologous expression showed that the two alkane hydroxylase homologs of P. aeruginosa PAO1 (AlkB1 and AlkB2) oxidize C12-C16\\u000a n-alkanes, while two rubredoxin (RubA1 and RubA2) and a rubredoxin reductase (RubB) homologs can replace their P.

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

2003-01-01

220

Organophosphorus chemistry  

E-print Network

2087 Organophosphorus chemistry Paul R. Hanson Editorial Open Access Address: Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045-7582, USA Email: Paul R. Hanson - phanson@ku.edu. Keywords: organophosphorus... Beilstein J. Org. Chem. 2014, 10, 2087–2088. doi:10.3762/bjoc.10.217 Received: 28 July 2014 Accepted: 06 August 2014 Published: 04 September 2014 This article is part of the Thematic Series "Organophosphorus chemistry" Guest Editor: P. R. Hanson © 2014...

Hanson, Paul R.

2014-09-04

221

Identification and use of an alkane transporter plug-in for applications in biocatalysis and whole-cell biosensing of alkanes.  

PubMed

Effective application of whole-cell devices in synthetic biology and biocatalysis will always require consideration of the uptake of molecules of interest into the cell. Here we demonstrate that the AlkL protein from Pseudomonas putida GPo1 is an alkane import protein capable of industrially relevant rates of uptake of C7-C16 n-alkanes. Without alkL expression, native E.coli n-alkane uptake was the rate-limiting step in both the whole-cell bioconversion of C7-C16 n-alkanes and in the activation of a whole-cell alkane biosensor by C10 and C11 alkanes. By coexpression of alkL as a transporter plug-in, specific yields improved by up to 100-fold for bioxidation of >C12 alkanes to fatty alcohols and acids. The alkL protein was shown to be toxic to the host when overexpressed but when expressed from a vector capable of controlled induction, yields of alkane oxidation were improved a further 10-fold (8?g/L and 1.7?g/g of total oxidized products). Further testing of activity on n-octane with the controlled expression vector revealed the highest reported rates of 120??mol/min/g and 1?g/L/h total oxidized products. This is the first time AlkL has been shown to directly facilitate enhanced uptake of C10-C16 alkanes and represents the highest reported gain in product yields resulting from its use. PMID:25068650

Grant, Chris; Deszcz, Dawid; Wei, Yu-Chia; Martínez-Torres, Rubéns Julio; Morris, Phattaraporn; Folliard, Thomas; Sreenivasan, Rakesh; Ward, John; Dalby, Paul; Woodley, John M; Baganz, Frank

2014-01-01

222

Identification and use of an alkane transporter plug-in for applications in biocatalysis and whole-cell biosensing of alkanes  

NASA Astrophysics Data System (ADS)

Effective application of whole-cell devices in synthetic biology and biocatalysis will always require consideration of the uptake of molecules of interest into the cell. Here we demonstrate that the AlkL protein from Pseudomonas putida GPo1 is an alkane import protein capable of industrially relevant rates of uptake of C7-C16 n-alkanes. Without alkL expression, native E.coli n-alkane uptake was the rate-limiting step in both the whole-cell bioconversion of C7-C16 n-alkanes and in the activation of a whole-cell alkane biosensor by C10 and C11 alkanes. By coexpression of alkL as a transporter plug-in, specific yields improved by up to 100-fold for bioxidation of >C12 alkanes to fatty alcohols and acids. The alkL protein was shown to be toxic to the host when overexpressed but when expressed from a vector capable of controlled induction, yields of alkane oxidation were improved a further 10-fold (8 g/L and 1.7 g/g of total oxidized products). Further testing of activity on n-octane with the controlled expression vector revealed the highest reported rates of 120 ?mol/min/g and 1 g/L/h total oxidized products. This is the first time AlkL has been shown to directly facilitate enhanced uptake of C10-C16 alkanes and represents the highest reported gain in product yields resulting from its use.

Grant, Chris; Deszcz, Dawid; Wei, Yu-Chia; Martínez-Torres, Rubéns Julio; Morris, Phattaraporn; Folliard, Thomas; Sreenivasan, Rakesh; Ward, John; Dalby, Paul; Woodley, John M.; Baganz, Frank

2014-07-01

223

Technetium chemistry  

SciTech Connect

Technetium chemistry is a young and developing field. Despite the limited knowledge of its chemistry, technetium is the workhorse for nuclear medicine. Technetium is also a significant environmental concern because it is formed as a byproduct of nuclear weapons production and fission-power generators. Development of new technetium radio-pharmaceuticals and effective environmental control depends strongly upon knowledge of basic technetium chemistry. The authors performed research into the basic coordination and organometallic chemistry of technetium and used this knowledge to address nuclear medicine and environmental applications. This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

Burns, C.; Bryan, J.; Cotton, F.; Ott, K.; Kubas, G.; Haefner, S. [Los Alamos National Lab., NM (United States); Barrera, J. [Dartmouth Coll., Hanover, NH (United States); Hall, K. [Univ. of Washington, Seattle, WA (United States); Burrell, A. [Massey Univ., Palmerston North (New Zealand)

1996-04-01

224

Chemistry Notes  

ERIC Educational Resources Information Center

Twelve new chemistry expermiments are described. Broad areas covered include atomic structure, solubility, gaseous diffusion, endothermic reactions, alcohols, equilibrium, atomic volumes, and some improvised apparatus. (PS)

School Science Review, 1972

1972-01-01

225

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.

226

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,

227

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

228

Conversational sensing  

NASA Astrophysics Data System (ADS)

Recent developments in sensing technologies, mobile devices and context-aware user interfaces have made it pos- sible to represent information fusion and situational awareness for Intelligence, Surveillance and Reconnaissance (ISR) activities as a conversational process among actors at or near the tactical edges of a network. Motivated by use cases in the domain of Company Intelligence Support Team (CoIST) tasks, this paper presents an approach to information collection, fusion and sense-making based on the use of natural language (NL) and controlled nat- ural language (CNL) to support richer forms of human-machine interaction. The approach uses a conversational protocol to facilitate a ow of collaborative messages from NL to CNL and back again in support of interactions such as: turning eyewitness reports from human observers into actionable information (from both soldier and civilian sources); fusing information from humans and physical sensors (with associated quality metadata); and assisting human analysts to make the best use of available sensing assets in an area of interest (governed by man- agement and security policies). CNL is used as a common formal knowledge representation for both machine and human agents to support reasoning, semantic information fusion and generation of rationale for inferences, in ways that remain transparent to human users. Examples are provided of various alternative styles for user feedback, including NL, CNL and graphical feedback. A pilot experiment with human subjects shows that a prototype conversational agent is able to gather usable CNL information from untrained human subjects.

Preece, Alun; Gwilliams, Chris; Parizas, Christos; Pizzocaro, Diego; Bakdash, Jonathan Z.; Braines, Dave

2014-05-01

229

Two Novel Alkane Hydroxylase-Rubredoxin Fusion Genes Isolated from a Dietzia Bacterium and the Functions of Fused Rubredoxin Domains in Long-Chain n-Alkane Degradation?  

PubMed Central

Two alkane hydroxylase-rubredoxin fusion gene homologs (alkW1 and alkW2) were cloned from a Dietzia strain, designated DQ12-45-1b, which can grow on crude oil and n-alkanes ranging in length from 6 to 40 carbon atoms as sole carbon sources. Both AlkW1 and AlkW2 have an integral-membrane alkane monooxygenase (AlkB) conserved domain and a rubredoxin (Rd) conserved domain which are fused together. Phylogenetic analysis showed that these two AlkB-fused Rd domains formed a novel third cluster with all the Rds from the alkane hydroxylase-rubredoxin fusion gene clusters in Gram-positive bacteria and that this third cluster was distant from the known AlkG1- and AlkG2-type Rds. Expression of the alkW1 gene in DQ12-45-1b was induced when cells were grown on C8 to C32 n-alkanes as sole carbon sources, but expression of the alkW2 gene was not detected. Functional heterologous expression in an alkB deletion mutant of Pseudomonas fluorescens KOB2?1 suggested the alkW1 could restore the growth of KOB2?1 on C14 and C16 n-alkanes and induce faster growth on C18 to C32 n-alkanes than alkW1?Rd, the Rd domain deletion mutant gene of alkW1, which also caused faster growth than KOB2?1 itself. In addition, the artificial fusion of AlkB from the Gram-negative P. fluorescens CHA0 and the Rds from both Gram-negative P. fluorescens CHA0 and Gram-positive Dietzia sp. DQ12-45-1b significantly increased the degradation of C32 alkane compared to that seen with AlkB itself. In conclusion, the alkW1 gene cloned from Dietzia species encoded an alkane hydroxylase which increased growth on and degradation of n-alkanes up to C32 in length, with its fused rubredoxin domain being necessary to maintain the functions. In addition, the fusion of alkane hydroxylase and rubredoxin genes from both Gram-positive and -negative bacteria can increase the degradation of long-chain n-alkanes (such as C32) in the Gram-negative bacterium. PMID:21873474

Nie, Yong; Liang, Jieliang; Fang, Hui; Tang, Yue-Qin; Wu, Xiao-Lei

2011-01-01

230

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. PMID:23402697

2013-01-01

231

Azafluorenes. Synthesis and conversions  

NASA Astrophysics Data System (ADS)

Data on the chemistry of azafluorenes (indenopyridines) for the last two decades are summarised. Methods of synthesis of all isomeric (as regards the position of the nitrogen atom) azafluorenes are considered. The main reactions of azafluorenes are analysed, their reactivity is determined by the presence and mutual influence of two different conjugated fused rings (benzene and pyridine) and the mode of fusion of the indene and pyridine fragments. The principal conversions of substituents at different positions of the azafluorene system are considered. Evidence is presented on the natural occurrence of azafluorenes, the biological activity of their synthetic derivatives, and on the structure and physicochemical properties of azafluorenes and their derivatives. The bibliography includes 204 references.

Prostakov, Nikolai S.; Soldatenkov, Anatoly T.; Kolyadina, Nadezhda M.; Obynochnyi, Arnol'd. A.

1997-02-01

232

Second NASA Conference on Laser Energy Conversion  

NASA Technical Reports Server (NTRS)

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

Billman, K. W. (editor)

1976-01-01

233

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

234

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. PMID:21990342

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

2011-01-01

235

Selective isomerization of alkanes on supported tungsten oxide acids  

SciTech Connect

Acid catalysis is a critical requirement in octane enhancement processes such as isomerization and alkylation. Currently, these processes rely on liquid acids and on metal oxides which pose corrosion problems and environmental challenges. Tungsten oxide species form strong acid sites on ZrO{sub 2} supports. After calcination at 1000-1100 K and promotion with Pt, these solids catalyze C{sub 7+} alkane isomerization at 400-500 K with much higher selectivity than sulfated oxides or zeolitic acids at similar turnover rates. Alkane isomerization proceeds via bimolecular reactions involving hydrogen transfer from alkanes or H{sub 2}, which cause the desorption of isomeric carbocations before P-scission occurs. On Pt/SO{sub x}-ZrO{sub 2}, carbocation desorption is slow, leading to long surface residence times and extensive cracking. On Pt/WO{sub x}-ZrO{sub 2}, carbocation desorption is rapid and surface isomerization steps limit n-heptane isomerization turnover rates. Saturation coverage by WO{sub x} surface species inhibits ZrO{sub 2} sintering and its tetragonal to monoclinic structural transformation. High isomerization turnover rates appear to require the presence of WO{sub x} clusters on ZrO{sub 2} surfaces. X-ray absorption at the W-L{sub I} and W-L{sub III} edges suggests the predominant presence of distorted octahedral species, even after dehydration at 673 K, in all WO{sub x}-ZrO{sub 2} samples calcined at 1073 K. Tetrahedral species, which lead to a strong pre-edge feature in the W-L{sub I} absorption edge, are not detectable in these samples. UV-visible spectra suggest an increase in WO{sub x} domain size with increasing loading. These distorted octahedral WO{sub x} domains on ZrO{sub 2} differ markedly in structure, reduction rates, and alkane isomerization turnover rates and selectivities from tetrahedral WO{sub x} species on Al{sub 2}O{sub 3}.

Iglesia, E.; Barton, D.G. [Univ. of California, Berkeley, CA (United States); Miseo, S. [Exxon Research and Engineering Co., Annandale, NJ (United States)] [and others

1996-12-31

236

USING N-ALKANES TO ESTIMATE DIET COMPOSITION OF HERBIVORES: A NOVEL MATHEMATICAL APPROACH  

E-print Network

USING N-ALKANES TO ESTIMATE DIET COMPOSITION OF HERBIVORES: A NOVEL MATHEMATICAL APPROACH PAULO the diet compo- sition of herbivores. An important constraint of using N-alkanes to estimate diet or larger than the number of diet com- ponents. This is a considerable limitation when dealing with free

Lisboa, Universidade Técnica de

237

Using cuticular wax alkanes to estimate herbage intake in animals fed supplements  

E-print Network

Using cuticular wax alkanes to estimate herbage intake in animals fed supplements H Dove RW Mayes M Freer !CSIRO Division of Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia; 2Macaulay Land Use-170), provided the faecal recoveries of the two alkanes are similar. The method also can be applied to animals

Boyer, Edmond

238

CHEMICAL REACTIONS AND TRANSPORT OF ALKANES AND THEIR PRODUCTS IN THE TROPOSPHERE  

EPA Science Inventory

The product distributions have been calculated the more abundant alkanes contributing most of the carbon atoms in the alkane fraction of an ambient air hydrocarbon mixture reasonably representative of U.S. emissions, The effects of ambient temperatures on product yields has been ...

239

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

PubMed Central

Six aerobic alkanotrophs (organism that can metabolize alkanes as their sole carbon source) isolated from deep-sea hydrothermal vents were characterized using the radical clock substrate norcarane to determine the metalloenzyme and reaction mechanism used to oxidize alkanes. The organisms studied were Alcanivorax sp. strains EPR7 and MAR14, Marinobacter sp. strain EPR21, Nocardioides sp. strains EPR26w, EPR28w, and Parvibaculum hydrocarbonoclasticum strain EPR92. Each organism was able to grow on n-alkanes as the sole carbon source and therefore must express genes encoding an alkane-oxidizing enzyme. Results from the oxidation of the radical-clock diagnostic substrate norcarane demonstrated that five of the six organisms (EPR7, MAR14, EPR21, EPR26w, and EPR28w) used an alkane hydroxylase functionally similar to AlkB to catalyze the oxidation of medium-chain alkanes, while the sixth organism (EPR92) used an alkane-oxidizing cytochrome P450 (CYP)-like protein to catalyze the oxidation. DNA sequencing indicated that EPR7 and EPR21 possess genes encoding AlkB proteins, while sequencing results from EPR92 confirmed the presence of a gene encoding CYP-like alkane hydroxylase, consistent with the results from the norcarane experiments. PMID:23825470

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

2013-01-01

240

Leaf-wax n-alkanes record the plantwater environment at leaf ush  

E-print Network

observations of 2 H values of n-alkanes have produced con icting data on the nature of this relationship (11 ratios are widely used as a proxy in climate reconstruction. Although the broad nature of the relation- ship between n-alkanes 2 H values and climate is appreciated, the quantitative details of the proxy

Tipple, Brett

241

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

PubMed

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

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

2014-07-15

242

Theoretical Simulation of n-Alkane Cracking on Zeolites Joseph A. Swisher,,|  

E-print Network

Theoretical Simulation of n-Alkane Cracking on Zeolites Joseph A. Swisher,,| Niels Hansen,,| Theo of alkane cracking in zeolites MFI and FAU have been simulated theoretically from first principles molecules per unit mass of zeolite that are close enough to a Brønsted-acid site to be in the reactant state

Bell, Alexis

243

Unit Conversions  

NSDL National Science Digital Library

This resource is a digital tool for performing unit conversions. It provides the additional feature of displaying cancellation of terms, enabling users to gain a deeper understanding of the mathematical processes involved in converting units. Users can convert among 25 quantities, including units such as force, temperature, energy, and current. Also available are less commonly used units, such as illuminance and magnetic flux. In addition, the calculations respect the number of significant figures. It is part of Web-Based Computer Aided Instruction, a set of free resources for teachers and learners.

Taha Mzoughi

244

ORGANIC CHEMISTRY UCLA Organic Chemistry Faculty  

E-print Network

ORGANIC CHEMISTRY UCLA Organic Chemistry Faculty perform research in molecular machines, exotic CHEMISTRY FACULTY RESEARCH INTERESTS Anne M. Andrews, Professor-in-Residence: Understanding how areas of interest include cross- coupling reactions, green chemistry, heterocycle synthesis, and natural

Levine, Alex J.

245

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

PubMed

Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2-C5) and longer alkanes. C2-C4 alkanes such as ethane, propane, and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico (GoM) were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1-C4) then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist). Changes in the ?(13)C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4 and 4.5‰, respectively). The concurrent depletion in the ?(13)C of dissolved inorganic carbon (DIC) implies a transfer of carbon from the alkane to the DIC pool (-3.5 and -6.7‰ for C3 and C4 incubations, respectively). Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1-C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3-C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community composition and density. PMID:24376442

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

2013-01-01

246

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

PubMed Central

Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C2–C5) and longer alkanes. C2–C4 alkanes such as ethane, propane, and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico (GoM) were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C1–C4) then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist). Changes in the ?13C of all the alkanes in the reactors show enrichment over the course of the incubation, with the C3 and C4 incubations showing the greatest enrichment (4.4 and 4.5‰, respectively). The concurrent depletion in the ?13C of dissolved inorganic carbon (DIC) implies a transfer of carbon from the alkane to the DIC pool (?3.5 and ?6.7‰ for C3 and C4 incubations, respectively). Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C1–C4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C3–C4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community composition and density. PMID:24376442

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

2013-01-01

247

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

Code of Federal Regulations, 2010 CFR

...Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear. 721.10103...Naphtha (Fischer-Tropsch), C4-11-alkane, branched and linear. (a) Chemical...naphtha (fischer-tropsch), C4-11-alkane, branched and linear (PMN...

2010-07-01

248

40 CFR 721.10178 - Distillates (Fischer-Tropsch), hydroisomerized middle, C10-13-branched alkane fraction.  

Code of Federal Regulations, 2010 CFR

...hydroisomerized middle, C10-13-branched alkane fraction. 721.10178 Section 721...hydroisomerized middle, C10-13-branched alkane fraction. (a) Chemical substance...hydroisomerized middle, C10-13-branched alkane fraction (PMN P-04-319; CAS...

2010-07-01

249

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

Code of Federal Regulations, 2014 CFR

...2014-07-01 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...

2014-07-01

250

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

251

Draft Genome Sequence of Uncultivated Firmicutes (Peptococcaceae SCADC) Single Cells Sorted from Methanogenic Alkane-Degrading Cultures  

PubMed Central

The draft genome of an uncultivated bacterium affiliated with the Peptococcaceae was reconstructed by co-assembling Illumina MiSeq sequences from three single cells sorted by microfluidics from two methanogenic alkane-degrading cultures. Peptococcaceae SCADC (short-chain alkane-degrading culture) may be genetically capable of anaerobic alkane activation by fumarate addition in the absence of sulfate. PMID:25212628

Tan, BoonFei; Charchuk, Rhianna; Li, Carmen; Nesbø, Camilla; Abu Laban, Nidal

2014-01-01

252

Extent of Reduction of Vanadium Oxides during Catalytic Oxidation of Alkanes Measured by in-Situ UV-Visible Spectroscopy  

E-print Network

Extent of Reduction of Vanadium Oxides during Catalytic Oxidation of Alkanes Measured by in-Situ UV to oxidation reactions using lattice oxygens as reactive intermediates. Introduction Oxidative alkane-visible spectroscopy probes the electronic structure of oxide domains commonly used in alkane ODH catalysis.6

Bell, Alexis T.

253

J. Am. Chem. SOC.1986,108, 7281-7286 7281 Shape Selective Alkane Hydroxylation by Metalloporphyrin  

E-print Network

to be shape selective alkane hydroxylationcatalysts. With iodosobenzeneas oxidant, good regioselectivity used as catalysts in a variety of oxidation reactions,6 including olefin epoxidation and alkane: both of which are capable of oxidizing alkanes in solution: (XMnrVTPP(OIPh)),O(X = CI-, Br-) and (N

Suslick, Kenneth S.

254

Investigation of the Mechanism of Alkane Reductive Elimination and Skeletal Isomerization in TpRh(CNneopentyl)(R)H Complexes: The  

E-print Network

for the involvement of alkane -complexes in oxidative addition/reductive elimination reactions of Tp is the microscopic reverse of oxidative addition of an alkane C-H bond to a coordinatively unsaturated metal center. Consequently, if formation of an alkane -complex precedes oxidative addition of a C-H bond, then this same

Jones, William D.

255

Circumstellar chemistry  

NASA Technical Reports Server (NTRS)

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

Glassgold, Alfred E.; Huggins, Patrick J.

1987-01-01

256

Multiple sources of alkanes in Quaternary oceanic sediment of Antarctica  

USGS Publications Warehouse

Normal alkanes (n-C13n-C36), isoprenoid hydrocarbons (i-C15, i-C16, i-C18, i-C19, and i-C20) triterpanes (C27C32), and (C27C29) are present in low concentrations offshore Antarctica in near-surface, Quaternary sediment of the Wilkes Land continental margin and of the western Ross Sea. The distributions of these hydrocarbons are interpreted relative to possible sources and processes. The hydrocarbons appear to be mixtures of primary and recycled material from marine and terrigenous sources. The n-alkanes are most abundant and are characterized by two distinct populations, one of probable marine origin and the other likely from terrigenous, vascular plant sources. Because the continent of Antarctica today is devoid of higher plants, the plant-derived hydrocarbons in these offshore sediments probably came from wind-blown material and recycled Antarctic sediment that contains land-plant remains from an earlier period of time. Isoprenoid hydrocarbons are partially recycled and mainly of marine origin; the dominance of pristane over phytane suggests oxic paleoenvironmental conditions. Both modern and ancient triterpanes and steranes are present, and the distribution of these indicates a mixture of primary and recycled bacterial, algal, and possible higher-plant materials. Although the sampled sediments were deposited during the Quaternary, they apparently contain a significant component of hydrocarbons of pre-Quaternary age. ?? 1987.

Kvenvolden, K.A.; Rapp, J.B.; Golan-Bac, M.; Hostettler, F.D.

1987-01-01

257

for Undergraduate CHEMISTRY MAJORS  

E-print Network

, Geochemistry, Hazardous Waste Management, Inorganic Chemistry, Materials Science, Medicinal Chemistry, OilHANDBOOK for Undergraduate CHEMISTRY MAJORS DEPARTMENT OF CHEMISTRY Fall 2010 #12;#12;TABLE OF CONTENTS A Career in Chemistry - What It Means ___________________________________________ 4 What do

Stuart, Steven J.

258

Radioanalytical Chemistry  

NSDL National Science Digital Library

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

2011-05-20

259

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

260

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.

WGBH Educational Foundation

2011-03-21

261

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

262

Cooperative Chemistry  

NSDL National Science Digital Library

Concept mapping in the organic chemistry laboratory can supplant cookbook activities with higher cognitive exercises. The common thread of most organic lab experiments is the synthesis, isolation, purification, and characterization of a carbon compound. T

Allan A. Gahr

2003-02-01

263

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

264

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.

265

Kinetic coupling and hydrogen surface fugacities in heterogeneous catalysis: I. Alkane reactions on Te/NaX, H-ZSM5, and Ga/H-ZSM5  

SciTech Connect

Hydrogen removal occurs by recombinative desorption and by hydrogen transfer during dehydrogenation steps required for alkane and cycloalkane conversion on Te/NaX, H-ZSM5, and Ga/H-ZSM5 catalysts. Recombinative desorption limits the rate of n-heptane and methylcyclohexane aromatization on Te/NaX and prevents equilibrium between gas-phase H[sub 2] and H-adatoms formed in intermediate dehydrogenation steps. The resulting high surface hydrogen fugacities lead to low steady-state concentrations of required unsaturated intermediates. Te ions catalyze rate-limiting hydrogen desorption steps during alkane reactions on Te/NaX. On H-ZSM5, hydrogen removal limits the rate of propane conversion to aromatics. Hydrogen adatoms are removed predominantly by reactions with coadsorbed hydrocarbon fragments, leading to high cracking selectivity. Ga ions introduce a recombinative desorption function that partially relieves the resulting high hydrogen surface fugacities and allows dehydrogenation steps to occur without concurrent cracking. Thus, Ga ions increase aromatics selectivity by providing a porthole for the removal of hydrogen adatoms as dihydrogen. The authors propose that rate-limiting hydrogen desorption steps, and the high surface hydrogen fugacities that result, control the rate and selectivity of dehydrogenation and related reactions on many nonmetal surfaces.

Iglesia, E.; Baumgartner, J.E.; Price, G.L. (Exxon Research and Engineering Corp., Annandale, NJ (United States))

1992-04-01

266

A Discovery-Based Experiment Involving Rearrangement in the Conversion of Alcohols to Alkyl Halides: Permanent Magnet [to the thirteenth power]C NMR in the First-Semester Organic Chemistry Lab  

ERIC Educational Resources Information Center

The use of permanent magnet [to the thirteenth power]C NMR in large-section first-semester organic chemistry lab courses is limited by the availability of experiments that not only hinge on first-semester lecture topics, but which also produce at least 0.5 mL of neat liquid sample. This article reports a discovery-based experiment that meets both…

Kjonaas, Richard A.; Tucker, Ryand J. F.

2008-01-01

267

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

268

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

269

Study of the Thermal Diffusion Behavior of Alkane/Benzene Mixtures by Thermal Diffusion Forced Rayleigh Scattering Experiments and Lattice Model Calculations  

E-print Network

Study of the Thermal Diffusion Behavior of Alkane/Benzene Mixtures by Thermal Diffusion Forced mixtures of linear alkanes (heptane, nonane, undecane, tridecane, pentadecane, heptadecane) in benzene has and temperatures. The Soret coefficient ST of the alkane was found to be negative for these n-alkane/benzene

Luettmer-Strathmann, Jutta

270

In situ NMR spectroscopy in heterogeneous catalysis: Kinetic study of hydrocarbon conversion mechanisms  

Microsoft Academic Search

The potential of high-resolution solid-state NMR spectroscopy for kinetic and mechanistic studies of hydrocarbon conversion\\u000a on solid acid catalysis between 20 and 300?C is considered. The use of this technique is illustrated by the elucidation of\\u000a the mechanisms of hydrogen exchange and 13C label transfer in alkanes and olefins, n-butane isomerization on sulfated zirconia, and ethane aromatization on zinc-containing zeolite

A. G. Stepanov; V. N. Parmon; D. Freude

2007-01-01

271

MIR and NIR group spectra of n-alkanes and 1-chloroalkanes.  

PubMed

Numerous attempts were undertaken to resolve the absorption originating from different parts of alkanes. The separation of the contributions from the terminal and midchain methylene units was observed only in the spectra of solid alkanes at low temperatures. On the other hand, for liquid alkanes this effect was not reported as yet. In this study, ATR-IR, Raman and NIR spectra of eight n-alkanes and seven 1-chloroalkanes in the liquid phase were measured from 1000 to 12,000cm(-1). The spectra were analyzed by using two-dimensional (2D) correlation approach and chemometrics methods. It was shown that in 2D asynchronous contour plots, constructed from the spectra of n-alkanes and 1-chloroalkanes, the methylene band was resolved into two components. These two components were assigned to the terminal and midchain methylene groups. For the first time, the contributions from these two molecular fragments were resolved in the spectra of liquid n-alkanes and 1-chloroalkanes. MCR-ALS resolved these spectra into two components that were assigned to the ethyl and midchain methylene groups. These components represent the group spectra that can be used for assignment, spectral analysis and prediction of unknown spectra. The spectral prediction based on the group spectra provides very good results for n-alkanes, especially in the first and second overtone regions. PMID:25727292

Kwa?niewicz, Micha?; Czarnecki, Miros?aw A

2015-05-15

272

Copper-Catalyzed Intermolecular Amidation and Imidation of Unactivated Alkanes  

PubMed Central

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

2015-01-01

273

Computational Chemistry for Chemistry Educators  

NSDL National Science Digital Library

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

Shawn C. Sendlinger

274

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

275

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

PubMed

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

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

2007-05-15

276

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

SciTech Connect

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

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

1998-07-01

277

Radiation Chemistry  

NASA Astrophysics Data System (ADS)

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

Wojnárovits, L.

278

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

279

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

SciTech Connect

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

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

1990-01-01

280

Optical rotamers of substituted simple alkanes induced by macroscopic translation-rotational motions  

NASA Astrophysics Data System (ADS)

Four substituted simple alkanes - 1-bromo-2-chloroethane, 1-chloropropane, 1,1-dichloropropane, and 1,1,2-trichlorotrifluoroethane - can exist in gauche positive (G), gauche negative (G'), and trans (T) conformers. The G and G' conformers are optical rotamers, while the T conformer is achiral. Here, the first observation of the preferential population of the optical rotamers in these alkanes induced by the molecular flow through molecular drag pumps is reported. The molecular mechanism of the observed enantiomeric excess of the studied alkanes is rationalized in the general framework of the molecular chirality generated through oriented collisions involving flowing molecules in macroscopic translation-rotational motions induced by a rotating surface.

Lee, Hao-Nan; Chang, Li-Chiao; Su, Tzu-Min

2011-04-01

281

Chemistry & Industry  

NSDL National Science Digital Library

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

282

Kitchen Chemistry  

NSDL National Science Digital Library

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

Christie, Patricia

2006-01-01

283

STM investigation of the dependence of alkane and alkane (C 18H 38, C 19H 40) derivatives self-assembly on molecular chemical structure on HOPG surface  

NASA Astrophysics Data System (ADS)

Alkane molecules and their derivatives are composed of alkyl chain and functional groups that dominate the interactions of intermolecule and molecule/substrate and result in different self-assemblies on solid surface. In the present paper, the self-assemblies of alkanes and alkane (C 18H 38, C 19H 40) derivatives are studied on HOPG surface at room temperature in ambient conditions by scanning tunneling microscopy (STM) to understand the structure and stability of these self-assemblies and to reveal the dependence of their self-assemblies on their chemical structures. It is found that the alkane molecules with short alkyl chains such as tridecane (C 13H 28), tetradecane (C 14H 30) and pentadecane (C 15H 32) can form lamellar structures on HOPG and be steadily imaged by STM. On the other hand, linear or herringbone structures can be observed in the self-assemblies formed by a series of derivatives of C 18H 38 and C 19H 40. The results are discussed based on STM results to understand the structures and structural stability of alkane molecular self-assemblies.

Chen, Qing; Yan, Hui-Juan; Yan, Cun-Ji; Pan, Ge-Bo; Wan, Li-Jun; Wen, Guo-Yong; Zhang, De-Qing

2008-03-01

284

Characterization of the medium- and long-chain n-alkanes degrading Pseudomonas aeruginosa strain SJTD-1 and its alkane hydroxylase genes.  

PubMed

A gram-negative aliphatic hydrocarbon-degrading bacterium SJTD-1 isolated from oil-contaminated soil was identified as Pseudomonas aeruginosa by comparative analyses of the 16S rRNA sequence, phenotype, and physiological features. SJTD-1 could efficiently mineralize medium- and long-chain n-alkanes (C12-C30) as its sole carbon source within seven days, showing the most optimal growth on n-hexadecane, followed by n-octadecane, and n-eicosane. In 36 h, 500 mg/L of tetradecane, hexadecane, and octadecane were transformed completely; and 2 g/L n-hexadecane was degraded to undetectable levels within 72 h. Two putative alkane-degrading genes (gene 3623 and gene 4712) were characterized and our results indicated that their gene products were rate-limiting enzymes involved in the synergetic catabolism of C12-C16 alkanes. On the basis of bioinformatics and transcriptional analysis, two P450 monooxygenases, along with a putative AlmA-like oxygenase, were examined. Genetically defective mutants lacking the characteristic alkane hydroxylase failed to degrade n-octadecane, thereby suggesting a different catalytic mechanism for the microbial transformation of alkanes with chain lengths over C18. PMID:25165808

Liu, Huan; Xu, Jing; Liang, Rubing; Liu, Jianhua

2014-01-01

285

Chemistry Experiments  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

286

Polymer Chemistry  

NASA Technical Reports Server (NTRS)

This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

Williams, Martha; Roberson, Luke; Caraccio, Anne

2010-01-01

287

Tropospheric chemistry  

NASA Technical Reports Server (NTRS)

The chemistry of the background troposphere, the source region, and the transition regions are discussed. The troposphere is governed by heterogeneous chemistry far more so than the stratosphere. Heterogeneous processes of interest involve scavenging of trace gases by aerosols, cloud and precipitation elements leading to aqueous phase chemical reactions and to temporary and permanent removal of material from the gas phase. Dry deposition is a major removal process for ozone, as well as for other gases of importance in tropospheric photochemistry. These processes are also discussed.

Mohnen, V. A.; Chameides, W.; Demerjian, K. L.; Lenschow, D. H.; Logan, J. A.; Mcneal, R. J.; Penkett, S. A.; Platt, U.; Schurath, U.; Dias, P. D.

1985-01-01

288

n-alkane adduct formation with urea in disel fuel distillate dewaxing  

SciTech Connect

This article reports on a study of the influence of the alcohol concentration and urea content of the solution and the temperature and time of adduct formation on the composition and completeness of recovery of n-alkanes from diesel fuel cuts. The study was carried out with solutions of n-alkanes in a 193-326/sup 0/C diesel fuel cut from Baku crudes containing 19.8% aromatic hydrocarbons. Dewaxing was performed in a cylindrical metal reactor with a blade stirrer. The quantities of n-alkanes remaining in the dewaxed fuel was determined by an adduct formation method. The adduct obtained in the basic dewaxing experiment was decomposed, and the composition of the paraffins that were recovered was determined chromatographically. It is determined that for maximum recovery of n-alkanes from diesel fuels containing 20% by weight of adduct-forming hydrocarbons, a 40% urea solution should be used.

Ismailov, A.G.; Abdullaev, E.S.; Gadzshiev, A.S.; Novruzov, F.N.

1984-01-01

289

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

290

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

EPA Science Inventory

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

291

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 ...

292

Diffusion of an alkane molecule in siliceous zeolite beta Matthew Aronson  

E-print Network

and reaction rates. Thus, the focus of this simulation study is to investigate will examine the how parameters such as chain length and temperature affect beta, as a function of chain length and temperature. The alkane was modeled

Shell, M. Scott

293

Oxidative dehydrogenation of C2-C4 alkanes into alkenes: Conventional catalytic systems and microwave catalysis  

NASA Astrophysics Data System (ADS)

Catalytic systems for the nonoxidative or oxidative dehydrogenation of C2-C4 alkanes into the respective alkenes are considered. Scanty data concerning microwave activation of these processes and the potential and advantages of microwave versus conventional technologies are analyzed.

Kustov, L. M.; Kucherov, A. V.; Finashina, E. D.

2013-03-01

294

Draft Genome Sequence of the Versatile Alkane-Degrading Bacterium Aquabacterium sp. Strain NJ1  

PubMed Central

The draft genome sequence of a soil bacterium, Aquabacterium sp. strain NJ1, capable of utilizing both liquid and solid alkanes, was deciphered. This is the first report of an Aquabacterium genome sequence. PMID:25477416

Shiwa, Yuh; Yoshikawa, Hirofumi; Zylstra, Gerben J.

2014-01-01

295

Calculation of the anisotropy of molecular polarizability of liquid n-alkanes and n-alcohols  

NASA Astrophysics Data System (ADS)

Light scattering from liquid n-alkanes and n-alcohols in a strong electric field is measured by a photoelectric colorimeter at various wavelengths. The anisotropy of molecular polarizability of the substances is calculated by the Rayleigh formula.

Shuvaeva, O. V.

2007-05-01

296

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

297

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

Code of Federal Regulations, 2011 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...

2011-07-01

298

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

Code of Federal Regulations, 2012 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...

2012-07-01

299

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

300

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

Code of Federal Regulations, 2014 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...

2014-07-01

301

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

Code of Federal Regulations, 2010 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...

2010-07-01

302

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

DOEpatents

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

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

1998-06-23

303

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

304

Use of alkane monolayer templates to modify the structure of alkyl ether monolayers on highly ordered pyrolytic graphite.  

PubMed

Scanning tunneling microscopy (STM) has been used to investigate the structure of pure and mixed monolayers formed by adsorption of long-chain alkanes and/or ethers on highly ordered pyrolytic graphite. Application of a pure phenyloctane solution of simple alkanes, such as tritriacontane, CH3(CH2)31CH3, produced a monolayer within which the individual molecular axes were oriented perpendicular to the lamellar axes. In contrast, a pure solution of symmetrical long-chain ethers, such as di-n-hexadecyl ether, CH3(CH2)15O(CH2)15CH3, produced a monolayer within which the molecular axes were oriented at an angle of approximately 65 degrees relative to the lamellar axes. The compositions of the overlying solutions were then gradually changed either from pure alkanes to nearly pure ethers or from pure ethers to nearly pure alkanes. When ethers replaced alkanes in the monolayer, the ethers conformed to the orientation within the existing alkane layer, rather than adopting the characteristic orientation of pure ether monolayers. However, when alkanes were incorporated into monolayers that had been formed from pure ether solutions, the orientation of the molecules within the monolayer converted to that characteristic of pure alkanes. Alkane monolayers thus acted as templates for subsequent ether layers, but ether monolayers did not act as templates for alkane layers. PMID:18171091

Papadantonakis, Kimberly M; Brunschwig, Bruce S; Lewis, Nathan S

2008-02-01

305

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. PMID:12226177

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

1996-01-01

306

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

307

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

308

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

309

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

310

Analytical Chemistry  

NSDL National Science Digital Library

This site features lecture notes for first and second level courses in analytical chemistry. Topics include titrations, gravimetry, kinetics and electrochemistry (redox). Potentiometry, coulometry, voltammetry, spectroscopic and separation methods are presented as well, and are illustrated with QuickTime animations.

Hardy, James K.

311

Bad Chemistry  

NSDL National Science Digital Library

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

Kevin Lehmann

312

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

313

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.

WGBH Educational Foundation

2010-02-12

314

Chemistry Notes  

ERIC Educational Resources Information Center

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

School Science Review, 1972

1972-01-01

315

Chemistry Notes.  

ERIC Educational Resources Information Center

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

School Science Review, 1978

1978-01-01

316

Atmospheric Chemistry  

NSDL National Science Digital Library

This set of links provides access to resources on atmospheric chemistry, especially acid deposition, air pollution, and air quality. The sites include personal and government pages, universities and research groups, non-governmental organizations and meetings, and products and services. There are also links to related search topics.

317

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

318

Reinventing chemistry.  

PubMed

Chemistry is in a period of change, from an era focused on molecules and reactions, to one in which manipulations of systems of molecules and reactions will be essential parts of controlling larger systems. This Essay traces paths from the past to possible futures. PMID:25682927

Whitesides, George M

2015-03-01

319

Nuclear Chemistry  

NSDL National Science Digital Library

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

320

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

321

n-alkane adduct formation with urea in disel fuel distillate dewaxing  

Microsoft Academic Search

This article reports on a study of the influence of the alcohol concentration and urea content of the solution and the temperature and time of adduct formation on the composition and completeness of recovery of n-alkanes from diesel fuel cuts. The study was carried out with solutions of n-alkanes in a 193-326°C diesel fuel cut from Baku crudes containing 19.8%

A. G. Ismailov; E. S. Abdullaev; A. S. Gadzshiev; F. N. Novruzov

1984-01-01

322

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. PMID:21914097

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

323

Increased mortality of Acanthoscelides obtectus by alkane-grown Beauveria bassiana  

Microsoft Academic Search

The effect of alkane-growth induction of theentomopathogenic fungus Beauveria bassiana(Balsamo) Vuillemin (Deuteromycotina:Hyphomycetes), on the ability to kill the beanweevil Acanthoscelides obtectus Say(Coleoptera: Bruchidae), was tested. Adultinsects were sprayed with an 0.01% Tween 20aqueous suspension of 4 × 106 conidia\\/ml.The performance of fungi grown in complete agarmedium containing glucose as carbon source(FS0) was compared to that of alkane-grownfungi (FS1) with n-hexadecane

R. Crespo; M. P. JUÁREZ; G. M. Dal Bello; S. Padín; G. Calderón Fernández; N. Pedrini

2002-01-01

324

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

Microsoft Academic Search

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

D. Sachse; J. Radke; G. Gleixner

2004-01-01

325

The regularities in the interaction of alkanes with CO 2 on oxide catalysts  

Microsoft Academic Search

Catalytic oxidation of C1-C7 alkanes by CO2 as a non-traditional oxidant was studied on oxide catalysts. The supported manganese oxide catalysts are the most active, selective and stable. Methane is converted mainly into synthesis gas. Ethane and propane give products of oxidative dehydrogenation. In the case of C4-C7 alkanes at first direct dehydrogenation takes place and after that reverse water

O. V. Krylov; A. Kh. Mamedov; S. R. Mirzabekova

1995-01-01

326

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

Microsoft Academic Search

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

F. Nolting; W. Behnke; C. Zetzsch

1988-01-01

327

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

328

Studies on the catalytic oxidation of alkanes and alkenes by titanium silicates  

Microsoft Academic Search

Titanium containing, aluminum-free ZSM-5 (TS-1) and amorphous TiOâ-SiOâ coprecipitate are investigated as catalysts for the selective oxidation of alkanes and alkenes using a variety of oxidants at temperatures below 100°C. Comparisons between the activities of TS-1 and and TiOâ-SiOâ coprecipitate for alkane oxidation and alkene epoxidation using nonaqueous HâOâ indicate that the absence of water is crucial for the catalytic

C. B. Khouw; C. B. Dartt; J. A. Labinger

1994-01-01

329

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

Microsoft Academic Search

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

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

2001-01-01

330

Synthesis of Imidazol-2-yl Amino Acids by Using Cells from Alkane-Oxidizing Bacteria  

Microsoft Academic Search

Sixty-one strains of alkane-oxidizing bacteria were tested for their ability to oxidize N-(2-hexylamino-4- phenylimidazol-1-yl)-acetamide to imidazol-2-yl amino acids applicable for pharmaceutical purposes. After growth with n-alkane, 15 strains formed different imidazol-2-yl amino acids identified by chemical structure analysis (mass and nuclear magnetic resonance spectrometry). High yields of imidazol-2-yl amino acids were produced by the strains Gordonia rubropertincta SBUG 105, Gordonia

Annett Mikolasch; Elke Hammer; Frieder Schauer

2003-01-01

331

Alkane oxidation with hydrogen peroxide catalyzed homogeneously by vanadium-containing polyphosphomolybdates  

Microsoft Academic Search

Alkanes (cyclooctane, n-octane, adamantane, ethane) can be efficiently oxidized by hydrogen peroxide in acetonitrile using tetra-n-butylammonium salts of the vanadium-containing polyphosphomolybdates [PMo11VO40]4? and [PMo6V5O39]12? as catalysts. The oxidation of alkanes gives rise to the corresponding alkyl hydroperoxides as the main products, which slowly decompose in the course of the reaction to produce the corresponding ketones (aldehydes) and alcohols. The reaction

Georg Süss-Fink; Laura Gonzalez; Georgiy B. Shul’pin

2001-01-01

332

Dehydrogenation of light alkanes over oxidized diamond-supported catalysts in the presence of carbon dioxide  

Microsoft Academic Search

Oxidized diamond demonstrated excellent support for the dehydrogenation of light alkanes to alkenes in the presence of CO2. Oxidized diamond-supported Cr2O3 and V2O5 catalysts exhibited comparatively higher catalytic activities in the dehydrogenation of lower alkanes in the presence of CO2. In the dehydrogenation of propane, the oxidized diamond-supported Cr2O3 and V2O5 catalysts in the presence of CO2 afforded nearly twofold

Kiyoharu Nakagawa; Chiaki Kajita; Na-oki Ikenaga; Mikka Nishitani-Gamo; Toshihiro Ando; Toshimitsu Suzuki

2003-01-01

333

Biodegradation of variable-chain-length n-alkanes in Rhodococcus opacus R7 and the involvement of an alkane hydroxylase system in the metabolism  

PubMed Central

Rhodococcus opacus R7 is a Gram-positive bacterium isolated from a polycyclic aromatic hydrocarbon contaminated soil for its versatile metabolism; indeed the strain is able to grow on naphthalene, o-xylene, and several long- and medium-chain n-alkanes. In this work we determined the degradation of n-alkanes in Rhodococcus opacus R7 in presence of n-dodecane (C12), n-hexadecane (C16), n-eicosane (C20), n-tetracosane (C24) and the metabolic pathway in presence of C12. The consumption rate of C12 was 88%, of C16 was 69%, of C20 was 51% and of C24 it was 78%. The decrement of the degradation rate seems to be correlated to the length of the aliphatic chain of these hydrocarbons. On the basis of the metabolic intermediates determined by the R7 growth on C12, our data indicated that R. opacus R7 metabolizes medium-chain n-alkanes by the primary alcohol formation. This represents a difference in comparison with other Rhodococcus strains, in which a mixture of the two alcohols was observed. By GC-MSD analysis we also identified the monocarboxylic acid, confirming the terminal oxidation. Moreover, the alkB gene cluster from R. opacus R7 was isolated and its involvement in the n-alkane degradation system was investigated by the cloning of this genomic region into a shuttle-vector E. coli-Rhodococcus to evaluate the alkane hydroxylase activity. Our results showed an increased biodegradation of C12 in the recombinant strain R. erythropolis AP (pTipQT1-alkR7) in comparison with the wild type strain R. erythropolis AP. These data supported the involvement of the alkB gene cluster in the n-alkane degradation in the R7 strain. PMID:25401074

2014-01-01

334

Isomerization of the hydridoalkylrhodium complexes formed on oxidative addition of rhodium to alkane C-H bonds. Evidence for the intermediacy of eta/sup 2/-alkane complexes  

SciTech Connect

The products of insertion of the coordinatively unsaturated fragment Cp*RhL (Cp* = eta/sup 5/-C/sub 5/Me/sub 5/; L = PMe/sub 3/) into alkane C-H bonds are generated by irradiation of Cp*(L)RhH/sub 2/ or thermal decomposition of Cp*(L)Rh(neopentyl)(H), at temperatures below -30/sup 0/C in alkane solvents. The hydridoalkylrhodium products can be synthesized independently, also at low temperature, from the corresponding haloalkyl complexes by lithiation with t-BuLi followed by protonation. Alternatively, the highly nucleophilic complex Li(Cp*(L)RhH), prepared by deprotonation of Cp*(L)RhH/sub 2/, leads the alkylhydridorhodium complexes upon treatment with alkyl tosylates R-OTs. When Cp*RhL is generated in mixtures of linear alkanes, only the products of insertion into primary C-H bonds are observed, even at -100/sup 0/C. The relative rate constants for the formation of these products correlate directly with the number of secondary C-H bonds in the alkane. This suggests that insertion occurs initially into all the C-H bonds of the alkane, but that even at very low temperatures the secondary insertion products rearrange quickly, and intramolecularly, to the primary products. The authors suggests that this rearrangement occurs through the intermediacy of eta/sup 2/-C-H alkane complexes. Further studies provide support for this idea. The synthetic procedures summarized above can be used to prepare regiospecifically /sup 2/H and /sup 13/C labeled alkyl hydrides at low temperatures. Warming these complexes to temperatures above -80/sup 0/C in aromatic solvent reveals rearrangements which confirms that the alkylhydridorhodium complexes are capable of interconverting with one another intramolecularly at rates competitive with or in some cases faster than they undergo reductive elimination.

Periana, R.A.; Bergman, R.G.

1986-11-12

335

UCLA CHEMISTRY & BIOCHEMISTRY  

E-print Network

UCLA CHEMISTRY & BIOCHEMISTRY ORIENTATION HANDBOOK 2012-2013 #12;Table of Contents Introduction .............................................................................................................................................2 Chemistry & Biochemistry Undergraduate Office ................................................................................................................................................4 Biochemistry

Levine, Alex J.

336

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

337

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.

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

338

This journal is The Royal Society of Chemistry 2014 Chem. Commun., 2014, 50, 6267--6269 | 6267 Cite this: Chem. Commun., 2014,  

E-print Network

- lum methylidenes and methylidynes attached to a silicon oxide surface were proposed to formally accomplish alkane metathesis resulting in the conversion of methane to ethane and even ethylene.15 Whereas Some of these few examples may be accessed via oxidation of reactive NbIII precursors,12 trapped,17

Baik, Mu-Hyun

339

Abiotic Organic Chemistry in Hydrothermal Systems.  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

340

Chemistry of sumanene.  

PubMed

Sumanene (C21 H12 ) is a bowl-shaped ?-conjugated molecule with C3v symmetry, consisting of alternating benzene rings and cyclopentadiene rings around the central benzene ring. The structure corresponds to the smallest C3v -symmetric fragment for the structural motifs of fullerenes or end-caps of carbon nanotubes. The presence of three sp(3) -hybridized benzylic sites is one of the most characteristic structural features in sumanene, which allows the different chemistry from that of corannulene. Since our first synthesis in 2003, we have engaged in the study of sumanene. This article summarizes our continuous study, including the synthesis, structure, dynamics, derivatization, complexation with transition metals, charge carrier mobility, and conversion to nitrogen-doped graphitic carbon, of sumanene. PMID:25474759

Amaya, Toru; Hirao, Toshikazu

2015-02-01

341

Environmental Chemistry  

NSDL National Science Digital Library

In this activity with several mini experiments, learners explore the chemistry that helps scientists learn about the environment and how they can help save it. Learners will determine if pollutants that have entered the ground water can also enter plants. Then, learners examine fossils to see if any changes have occurred over time in a particular species of sea mollusks. Finally, learners act as chemists to recycle paper by making paper from toilet paper.

2012-07-24

342

Computational chemistry  

NASA Technical Reports Server (NTRS)

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

Arnold, J. O.

1987-01-01

343

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

Microsoft Academic Search

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

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

2000-01-01

344

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

Microsoft Academic Search

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

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

2001-01-01

345

Gene cloning and characterization of an aldehyde dehydrogenase from long-chain alkane-degrading Geobacillus thermoleovorans B23  

Microsoft Academic Search

Geobacillus thermoleovorans B23 is capable of degrading long-chain alkanes at 70°C. Bt-aldh, an aldehyde dehydrogenase gene in B23, was located in the upstream region of p21 whose expression level was dramatically increased when alkane degradation was started (Kato et al. 2009, BMC Microbiol 9:60). Like p21, transcription level of Bt-aldh was also increased upon alkane degradation. Bt-Aldh (497 aa, MW = 53,886) was

Tomohisa Kato; Asuka Miyanaga; Shigenori Kanaya; Masaaki Morikawa

2010-01-01

346

?D values of individual n-alkanes from terrestrial plants along a climatic gradient – Implications for the sedimentary biomarker record  

Microsoft Academic Search

The compound-specific hydrogen isotope composition (?D) of sedimentary n-alkanes is increasingly used as a palaeoclimate proxy. To explore the origin of the hydrogen isotope signal of n-alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n-alkane composition and ?D values of 31 plant biomass samples (Birch (Betula), Beech (Fagus), Oak (Quercus), Alder

Dirk Sachse; Jens Radke; Gerd Gleixner

2006-01-01

347

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

Microsoft Academic Search

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

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

2005-01-01

348

Chemistry 411/611 Inorganic Chemistry (2011)  

E-print Network

1 Chemistry 411/611 Inorganic Chemistry (2011) Instructor: Assistant Professor Mathew M. Maye Chemistry", 5th Edition, Freeman Press. Available at SU bookstore. The solution manual is optional. (Suggested for CHE611 Students pursuing Inorganic) Huheey, "Inorganic Chemistry: Principles of Structure

Mather, Patrick T.

2011-01-01

349

Chemistry 106X -Spring 2011 General Chemistry  

E-print Network

Chemistry 106X - Spring 2011 General Chemistry Instructor: Christopher Iceman Class: MWF 1 and can be purchased in the UAF bookstore or elsewhere: · Chemistry and Chemical Reactivity 7th Ed for Chemistry and Chemical Reactivity 7th Ed. (1 or 2 semester) · TurningPoint Technologies ResponseCard RF

Wagner, Diane

350

Chemistry 675 (CHE 675) Advanced Organic Chemistry  

E-print Network

Chemistry 675 (CHE 675) Advanced Organic Chemistry Fall Semester 2011 Professor James Hougland675 is a graduate-level organic chemistry course that can be continued in the Spring semester as CHE685. These two courses focus on physical organic chemistry, which deals with the structure

Mather, Patrick T.

351

Chemistry 106X -Fall 2010 General Chemistry  

E-print Network

Chemistry 106X - Fall 2010 General Chemistry Instructor: Christopher Iceman Class: MWF 9 bookstore or elsewhere: · Chemistry and Chemical Reactivity 7th Ed. by Kotz, Treichel, and Townsend-0-495-38703-9 Electronic Book - ISBN 978-0-495-68043-7 · OWL pin number for Chemistry and Chemical Reactivity 7th Ed. (1

Wagner, Diane

352

Chemistry 411/611 Inorganic Chemistry (2010)  

E-print Network

1 Chemistry 411/611 Inorganic Chemistry (2010) Instructor: Assistant Professor Mathew M. Maye: M-W 4:00-5:00, and by appointment Credits: 3 Text: (Required) Shriver & Atkins, "Inorganic Chemistry. (Suggested for CHE611 Students pursuing Inorganic) Huheey, "Inorganic Chemistry: Principles of Structure

Mather, Patrick T.

353

Critical behavior of static properties for nitrobenzene-alkane mixtures  

NASA Astrophysics Data System (ADS)

We present experimental data of the isobaric heat capacity per unit volume Cp,xV-1 for mixtures containing nitrobenzene and an alkane (CNH2N+2, with N ranging from 6 to 15) upon approaching their liquid-liquid critical points along a path of constant composition. Values for the critical amplitude A+ have been determined. They have been combined with the previously reported ones for the leading term of the coexistence-curve width to obtain, with the aid of well-known universal relations, the critical amplitudes of the correlation length and of the osmotic susceptibility. The trends of all these critical parameters, which exhibit anomalous behavior in the low N region, are discussed in terms of particular microscopic phenomena characterizing NB-CNH2N+2 mixtures. The work is completed with an analysis of the analog of the Yang-Yang anomaly in liquid-liquid criticality: the behavior of the partial molar heat capacities of the two liquid components is found to illustrate previously uncovered asymmetry effects.

Pérez-Sánchez, Germán; Losada-Pérez, Patricia; Cerdeiriña, Claudio A.; Thoen, Jan

2010-06-01

354

The University of North Carolina at Chapel Hill: Chemistry Fundamentals Program  

NSDL National Science Digital Library

The University of North Carolina at Chapel Hill Chemistry Fundamentals Program offers an interactive review of the fundamentals of chemistry for incoming college freshman chemistry students. The basic link offers materials about chemical nomenclature, atomic structure, stoichiometry, and acid base chemistry. After learning about these essentials, users can progress to more advanced topics such as gas laws, thermodynamics, kinetics, and redox chemistry. The explanations are linked with a useful chemistry glossary. The website offers many online calculators to deal with compressibility, unit conversion, and various other chemical problems. Students can also find a helpful review of mathematics used in chemistry.

355

Pathological hepatic accumulation of long-chain n-alkanes ("paraffin liver") in cows (Harbitz and Fölling, 1940). An overlooked discovery. Description of lesions and identification of alkanes.  

PubMed

About 50 years ago crystalline deposits of a substance representing approximately 7 per cent wet tissue weight and believed to be hentriacontane or a mixture of similar long-chain n-alkanes (30-34 carbon atoms) were detected in two discoloured and swollen cow livers. Stored purified extracts from these livers were recently reanalysed using gas chromatography and mass spectrometry. They were found to contain about equal amounts of nonacosane and hentriacontane with a small admixture of tritriacontane and other long carbon-chain alkanes. On the basis of histological findings, five additional cases of "paraffin liver" in cows have been recorded. In the discussion comparison is made with the only known case of a similar disorder in a human, visceral accumulation of the same three alkanes as in the cows, which was recently described in the literature. Concerning the origin of the deposits, importance is given to the fact that the long-chain alkanes with odd carbon numbers identified both in cattle and man predominate in the cuticular waxes of many dietary plants. The very large quantities of the abnormal substance in the cow livers indicate low toxicity, and evidently accumulation over long periods of time. PMID:8363823

Halse, K; Solheim, E; Nordstoga, K

1993-06-01

356

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

PubMed

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

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

2005-01-01

357

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

PubMed Central

Natural and anthropogenic activities introduce alkanes into marine systems where they are degraded by alkane hydroxylases expressed by phylogenetically diverse bacteria. Partial sequences for alkB, one of the structural genes of alkane hydroxylase, have been used to assess the composition of alkane-degrading communities, and to determine their responses to hydrocarbon inputs. We present here the first spatially extensive analysis of alkB in bacterioplankton of the northern Gulf of Mexico (nGoM), a region that experiences numerous hydrocarbon inputs. We have analyzed 401 partial alkB gene sequences amplified from genomic extracts collected during March 2010 from 17 water column samples that included surface waters and bathypelagic depths. Previous analyses of 16S rRNA gene sequences for these and related samples have shown that nGoM bacterial community composition and structure stratify strongly with depth, with distinctly different communities above and below 100 m. Although we hypothesized that alkB gene sequences would exhibit a similar pattern, PCA analyses of operational protein units (OPU) indicated that community composition did not vary consistently with depth or other major physical-chemical variables. We observed 22 distinct OPUs, one of which was ubiquitous and accounted for 57% of all sequences. This OPU clustered with AlkB sequences from known hydrocarbon oxidizers (e.g., Alcanivorax and Marinobacter). Some OPUs could not be associated with known alkane degraders, however, and perhaps represent novel hydrocarbon-oxidizing populations or genes. These results indicate that the capacity for alkane hydrolysis occurs widely in the nGoM, but that alkane degrader diversity varies substantially among sites and responds differently than bulk communities to physical-chemical variables. PMID:24376439

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

2013-01-01

358

Fatty aldehyde dehydrogenase multigene family involved in the assimilation of n-alkanes in Yarrowia lipolytica.  

PubMed

In the n-alkane assimilating yeast Yarrowia lipolytica, n-alkanes are oxidized to fatty acids via fatty alcohols and fatty aldehydes, after which they are utilized as carbon sources. Here, we show that four genes (HFD1-HFD4) encoding fatty aldehyde dehydrogenases (FALDHs) are involved in the metabolism of n-alkanes in Y. lipolytica. A mutant, in which all of four HFD genes are deleted (?hfd1-4 strain), could not grow on n-alkanes of 12-18 carbons; however, the expression of one of those HFD genes restored its growth on n-alkanes. Production of Hfd2Ap or Hfd2Bp, translation products of transcript variants generated from HFD2 by the absence or presence of splicing, also supported the growth of the ?hfd1-4 strain on n-alkanes. The FALDH activity in the extract of the wild-type strain was increased when cells were incubated in the presence of n-decane, whereas this elevation in FALDH activity by n-decane was not observed in ?hfd1-4 strain extract. Substantial FALDH activities were detected in the extracts of Escherichia coli cells expressing the HFD genes. Fluorescent microscopic observation suggests that Hfd3p and Hfd2Bp are localized predominantly in the peroxisome, whereas Hfd1p and Hfd2Ap are localized in both the endoplasmic reticulum and the peroxisome. These results suggest that the HFD multigene family is responsible for the oxidation of fatty aldehydes to fatty acids in the metabolism of n-alkanes, and raise the possibility that Hfd proteins have diversified by gene multiplication and RNA splicing to efficiently assimilate or detoxify fatty aldehydes in Y. lipolytica. PMID:25315778

Iwama, Ryo; Kobayashi, Satoshi; Ohta, Akinori; Horiuchi, Hiroyuki; Fukuda, Ryouichi

2014-11-28

359

School of Chemistry CHEM3100: Chemistry at a Molecular Level  

E-print Network

School of Chemistry CHEM3100: Chemistry at a Molecular Level Tutorial Groups 2013/14 Name Programme Tutor Ahmed, Zacher Medicinal Chemistry Arif, Saboor Chemistry Bagnall, Samuel Chemistry Barbara, David Chemistry Beaumont, Nicholas Chemistry Quinn, Michael J Chemistry Bennett, Matthew Chemistry Booth, Natalie

Rzepa, Henry S.

360

Characterization of a CYP153 alkane hydroxylase gene in a Gram-positive Dietzia sp. DQ12-45-1b and its "team role" with alkW1 in alkane degradation.  

PubMed

CYP153 and AlkB-like hydroxylases were recently discovered in Gram-positive alkane-degrading bacteria. However, it is unclear whether they cooperate with each other in alkane degradation as they do in Gram-negative bacteria. In this paper, we cloned the CYP153 gene from a representative Gram-positive alkane-degrading bacterium, Dietzia sp. DQ12-45-1b. The CYP153 gene transcription in Dietzia sp. DQ12-45-1b and heterologous expression in alkB gene knockout mutant strain Pseudomonas fluorescens KOB2?1 both confirmed the functions of CYP153 on C6-C10 n-alkanes degradation, but not on longer chain-length n-alkanes. In addition, substrate-binding analysis of the purified CYP153 protein revealed different substrate affinities to C6-C16 n-alkanes, confirming n-alkanes binding to CYP153 protein. Along with AlkW1, an AlkB-like alkane hydroxylase in Dietzia sp. DQ12-45-1b, a teamwork pattern was found in n-alkane degradation, i.e. CYP153 was responsible for hydroxylating n-alkanes shorter than C10 while AlkW1 was responsible for those longer than C14. Further sequence analysis suggested that the high horizontal gene transfer (HGT) potential of CYP153 genes may be universal in Gram-positive alkane-degrading actinomycetes that contain both alkB and CYP153 genes. PMID:23504079

Nie, Yong; Liang, Jie-Liang; Fang, Hui; Tang, Yue-Qin; Wu, Xiao-Lei

2014-01-01

361

Chemistry References  

NSDL National Science Digital Library

This site highlights chemistry resources that we consider essentiala fabulous periodic table, a database of chemical compounds, a set of demonstrations of chemical reactions that are just plain spectacular, and, dont forget, laboratory safety. Articles from the web sites Whats That Stuff? and Science News for Kids can be used as supplemental reading all through the year. This site explains the history and characteristics of over 20 substances, such as sunscreen, Cheese Whiz, baseballs, fluoride, new car smell, ink, lipstick, bug spray, and licorice. The individual articles are nontechnical for the most part and are presented in a fun way that readers will enjoy. Also, if a ...

Kim

2007-08-08

362

Industrial Chemistry  

NSDL National Science Digital Library

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

363

Interstellar chemistry  

PubMed Central

In the past half century, radioastronomy has changed our perception and understanding of the universe. In this issue of PNAS, the molecular chemistry directly observed within the galaxy is discussed. For the most part, the description of the molecular transformations requires specific kinetic schemes rather than chemical thermodynamics. Ionization of the very abundant molecular hydrogen and atomic helium followed by their secondary reactions is discussed. The rich variety of organic species observed is a challenge for complete understanding. The role and nature of reactions involving grain surfaces as well as new spectroscopic observations of interstellar and circumstellar regions are topics presented in this special feature. PMID:16894148

Klemperer, William

2006-01-01

364

Hypercarbon chemistry  

SciTech Connect

This text points out the emerging significance of higher-valent carbon compounds. It describes the compounds of carbon with coordination numbers greater than four and explores the delocalized bonds of ..pi.. aromatic molecules as a basis for rational description of orbitals; localized multicentered orbitals; the interactions of metallic ions with other atoms and molecules; the skeletal electron counts as a guide for synthesis; and the isolobal concept. Illustrated are the ways in which these subjects bring together structure and reactivity in the great diversity of novel carbon chemistry and its relationship to that of boron, lithium, hydrogen, the metals, and others.

Olah, G.A.; Prakash, G.K.S.; Wade, K.; Field, I.D.; Williams, R.E.

1987-01-01

365

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

NASA Astrophysics Data System (ADS)

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

Bush, Rosemary T.; McInerney, Francesca A.

2013-09-01

366

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

NASA Astrophysics Data System (ADS)

Hydrogen isotope ratios were measured on n-alkanes (n-C 12 to n-C 31) extracted from recent lake surface sediments along a N-S European transect to test if modern climate variability is recorded in these biomarkers. ?D values of the n-alkanes are compared to ?D values of meteoric water from the IAEA-GNIP database spanning a range from -119‰ in northern Sweden to -41‰ in southern Italy, to lake water ?D values, and to mean annual temperatures, varying between -2.0°C in the north and 13.7°C in the south. ?D values of the short-chained n-alkanes n-C 12 to n-C 20, excluding algal derived n-C 17 and n-C 19, are higher in the north and lower in the south. The isotopic fractionation ? for hydrogen between meteoric water and the short-chained n-alkanes is increasing from N to S by more than 100‰ and is significantly correlated to mean annual temperature for n-C 16 and n-C 18. This suggests that these n-alkanes may originate from a different source in the northern lakes, possibly due to petroleum contamination, or are synthesized using a different biochemical pathway. The n-C 17 and n-C 19 alkanes of algal origin, the n-C 21 and n-C 23 alkanes originating from water plants, and the long-chain n-alkanes n-C 25, n-C 27, n-C 29, and n-C 31 of terrestrial origin, clearly correlate with ?D values of meteoric water, lake water, and mean annual temperature, indicating that they excellently record the ?D value of meteoric water. The mean hydrogen isotope fractionation ? C17/w of -157‰ (SD = 13) between n-C 17 and meteoric water is fairly constant over the wide range of different climates and lake environments, suggesting only minor influence of environmental factors on this biochemical fractionation. This suggests that ?D values of n-C 17 are suitable to reconstruct the isotopic composition of source water. The mean fractionation between the long-chain n-alkanes and water is -128‰ (SD = 12). The mean difference of 31‰ between both ? values is likely due to evaporative enrichment of deuterium in the leaf water. If this is the only influence on the enrichment, the difference between the ?D values of terrestrial and aquatic compounds might be suitable to reconstruct terrestrial evapotranspiration of the lake environment.

Sachse, D.; Radke, J.; Gleixner, G.

2004-12-01

367

Biogeographic variation of foliar n-alkanes of Juniperus communis var. saxatilis Pallas from the Balkans.  

PubMed

The composition of the epicuticular n-alkanes isolated from the leaves of ten populations of Juniperus communis L. var. saxatilis Pallas from central (continental) and western (coastal) areas of the Balkan Peninsula was characterized by GC-FID and GC/MS analyses. In the leaf waxes, 14 n-alkane homologues with chain-lengths ranging from C22 to C35 were identified. All samples were dominated by n-tritriacontane (C33 ), but differences in two other dominant n-alkanes allowed separating the coastal from the continental populations. Several statistical methods (ANOVA, principal component, discriminant, and cluster analyses as well as the Mantel test) were deployed to analyze the diversity and variability of the epicuticular-leaf-n-alkane patterns of the ten natural populations of J. communis var. saxatilis and their relation to different geographic and bioclimatic parameters. Cluster analysis showed a high correlation of the leaf-n-alkane patterns with the geographical distribution of the investigated samples, differentiating the coastal from the continental populations of this taxon. Several bioclimatic parameters related to aridity were highly correlated with this differentiation. PMID:25491336

Raj?evi?, Nemanja; Jana?kovi?, Pedja; Dodoš, Tanja; Teševi?, Vele; Marin, Petar D

2014-12-01

368

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

PubMed

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

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

2014-04-01

369

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

370

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

PubMed Central

Short-chain alkanes play a substantial role in carbon and sulfur cycling at hydrocarbon-rich environments globally, yet few studies have examined the metabolism of ethane (C2), propane (C3), and butane (C4) in anoxic sediments in contrast to methane (C1). In hydrothermal vent systems, short-chain alkanes are formed over relatively short geological time scales via thermogenic processes and often exist at high concentrations. The sediment-covered hydrothermal vent systems at Middle Valley (MV, Juan de Fuca Ridge) are an ideal site for investigating the anaerobic oxidation of C1–C4 alkanes, given the elevated temperatures and dissolved hydrocarbon species characteristic of these metalliferous sediments. We examined whether MV microbial communities oxidized C1–C4 alkanes under mesophilic to thermophilic sulfate-reducing conditions. Here we present data from discrete temperature (25, 55, and 75°C) anaerobic batch reactor incubations of MV sediments supplemented with individual alkanes. Co-registered alkane consumption and sulfate reduction (SR) measurements provide clear evidence for C1–C4 alkane oxidation linked to SR over time and across temperatures. In these anaerobic batch reactor sediments, 16S ribosomal RNA pyrosequencing revealed that Deltaproteobacteria, particularly a novel sulfate-reducing lineage, were the likely phylotypes mediating the oxidation of C2–C4 alkanes. Maximum C1–C4 alkane oxidation rates occurred at 55°C, which reflects the mid-core sediment temperature profile and corroborates previous studies of rate maxima for the anaerobic oxidation of methane (AOM). Of the alkanes investigated, C3 was oxidized at the highest rate over time, then C4, C2, and C1, respectively. The implications of these results are discussed with respect to the potential competition between the anaerobic oxidation of C2–C4alkanes with AOM for available oxidants and the influence on the fate of C1 derived from these hydrothermal systems. PMID:23717305

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

2013-01-01

371

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

PubMed

Short-chain alkanes play a substantial role in carbon and sulfur cycling at hydrocarbon-rich environments globally, yet few studies have examined the metabolism of ethane (C2), propane (C3), and butane (C4) in anoxic sediments in contrast to methane (C1). In hydrothermal vent systems, short-chain alkanes are formed over relatively short geological time scales via thermogenic processes and often exist at high concentrations. The sediment-covered hydrothermal vent systems at Middle Valley (MV, Juan de Fuca Ridge) are an ideal site for investigating the anaerobic oxidation of C1-C4 alkanes, given the elevated temperatures and dissolved hydrocarbon species characteristic of these metalliferous sediments. We examined whether MV microbial communities oxidized C1-C4 alkanes under mesophilic to thermophilic sulfate-reducing conditions. Here we present data from discrete temperature (25, 55, and 75°C) anaerobic batch reactor incubations of MV sediments supplemented with individual alkanes. Co-registered alkane consumption and sulfate reduction (SR) measurements provide clear evidence for C1-C4 alkane oxidation linked to SR over time and across temperatures. In these anaerobic batch reactor sediments, 16S ribosomal RNA pyrosequencing revealed that Deltaproteobacteria, particularly a novel sulfate-reducing lineage, were the likely phylotypes mediating the oxidation of C2-C4 alkanes. Maximum C1-C4 alkane oxidation rates occurred at 55°C, which reflects the mid-core sediment temperature profile and corroborates previous studies of rate maxima for the anaerobic oxidation of methane (AOM). Of the alkanes investigated, C3 was oxidized at the highest rate over time, then C4, C2, and C1, respectively. The implications of these results are discussed with respect to the potential competition between the anaerobic oxidation of C2-C4alkanes with AOM for available oxidants and the influence on the fate of C1 derived from these hydrothermal systems. PMID:23717305

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

2013-01-01

372

Crossover SAFT equation of state: Application for normal alkanes  

SciTech Connect

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

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

1999-12-01

373

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

NASA Astrophysics Data System (ADS)

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

Saxena, Priyank

374

Stories in Conversation  

E-print Network

Because conversational stories can be used for different purposes, they enter conversations in different ways. Sometimes they have a preface, sometimes not; sometimes a story fits smoothly into the ongoing talk, but other ...

Hofer, Roberta Senner

1991-01-01

375

Infrared spectra and structure of alkane- and cycloalkanecarbonitriles and of their carbanions: An ab initio force field treatment  

NASA Astrophysics Data System (ADS)

The structure of alkane- and cycloalkanecarbonitriles (seven compounds) and of their carbanions has been studied by both infrared spectrometry and ab initio force field calculations. The carbanions (counter ions Li +, Na + and K +) have been found to exist mainly as ionic aggregates in hexamethylphosphoric triamide solutions. The calculations describe well the marked decrease, by 124-214 cm -1, in the nitrile band frequencies and also the strong increase, by 1-2 orders, in the nitrile band integrated intensities which accompany the conversion of the parent neutral molecules into carbanions. Cyclopropanecarbonitrile is remarkable as having the highest nitrile band intensity among all the neutral molecules and the lowest one among all the carbanions studied. This result has also been predicted by the calculations, and it can be explained by certain peculiarities in the structure of the particles. The conjugation of the carbanionic charge with the cyano group in the cyclopropanecarbonitrile carbanion is greatly hindered by the considerable deviation (estimated at 56°) of the cyano group from the ring plane. The carbanionic charges of the carbanions studied are delocalized over the cyano groups (0.30-0.41 e -), carbanionic centres (0.08-0.29 e -) and hydrocarbon moieties (0.34-0.63 e -).

Juchnovski, I. N.; Tsenov, J. A.; Binev, I. G.

1996-08-01

376

Network generation and analysis of complex biomass conversion systems  

Microsoft Academic Search

A modular computational tool for automated generation and rule-based post-processing of reaction systems in biomass conversion is presented. Cheminformatics and graph theory algorithms are used to generate chemical transformations pertaining to heterogeneous and homogeneous chemistries in the automated rule-based network generator. A domain-specific language provides a user-friendly English-like chemistry specification interface to the network generator. A rule-based pathway analysis module

Srinivas Rangarajan; Ted Kaminski; Eric Van Wyk; Aditya Bhan; Prodromos Daoutidis

2011-01-01

377

Computational Chemistry List  

NSDL National Science Digital Library

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

378

CHEMISTRY 450 Spring, 2009  

E-print Network

of Science Journals: D-G WEEK 4 (28 January): Green Chemistry Journals: H-N WEEK 5 (4 February): Green Chemistry Journals: O-Z WEEK 6 (11 February): Green Chemistry; Group Presentations (Life-cycle analysis

Stuart, Steven J.

379

n-Alkanes in surficial sediments of Visakhapatnam harbour, east coast of India  

NASA Astrophysics Data System (ADS)

Surface sediments collected from 19 stations along Visakhapatnam harbour were analysed for organic carbon (OC), ? 13Coc, total lipids (TL), total hydrocarbon (THC), n-alkane concentration and composition. OC, ? 13Coc, TL and THC ranged from 0.6% to 7.6%, -29.3 to -23.8‰, 300 to 14,948 \\upmu g g - 1 dw, and 0.2 to 2,277 \\upmu g g - 1 dw, respectively. Predominance of even carbon numbers n-alkanes C12-C21 with carbon preference index (CPI) of <1 suggests major microbial influence. Fair abundance of odd carbon number n-alkanes in the range of C15-C22 and C23-C33 indicates some input from phytoplankton and terrestrial sources, respectively. Petrogenic input was evident from the presence of hopanes and steranes. The data suggest that organic matter (OM) sources varied spatially and were mostly derived from mixed source.

Punyu, V. R.; Harji, R. R.; Bhosle, N. B.; Sawant, S. S.; Venkat, K.

2013-04-01

380

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

381

The low temperature phase transition in octane and its possible generalisation to other n-alkanes  

NASA Astrophysics Data System (ADS)

A neutron powder diffraction study of three n-alkanes, octane, nonane and pentadecane, down to 2 K is presented. The temperature dependence of the octane diffraction pattern reveals a solid state phase transition between 40 and 55 K, which involves a doubling of the unit cell in the b direction, the space group remaining P 1¯. Confirmation of the phase transition, which results in a doubling of the number of crystallographically inequivalent methyl groups, is sought in the published NMR, tunnelling data and neutron scattering, vibrational data. Density functional theory and force field techniques are used to simulate spectroscopic data based on the measured structures. While no unequivocal evidence is found in spectroscopic data, the published data does not rule out the existence of energetically inequivalent methyl groups. Indeed close inspection of the spectroscopic data for other n-alkanes suggests that the phase transition may be common to many alkanes.

Neumann, M. A.; Johnson, M. R.; Radaelli, P. G.

2001-05-01

382

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

SciTech Connect

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

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

2007-02-15

383

Energy conversion & storage program. 1995 annual report  

SciTech Connect

The 1995 annual report discusses laboratory activities in the Energy Conversion and Storage (EC&S) Program. The report is divided into three categories: electrochemistry, chemical applications, and material applications. Research performed in each category during 1995 is described. Specific research topics relate to the development of high-performance rechargeable batteries and fuel cells, the development of high-efficiency thermochemical processes for energy conversion, the characterization of new chemical processes and complex chemical species, and the study and application of novel materials related to energy conversion and transmission. Research projects focus on transport-process principles, chemical kinetics, thermodynamics, separation processes, organic and physical chemistry, novel materials and deposition technologies, and advanced methods of analysis.

Cairns, E.J.

1996-06-01

384

Self-assembled alkane monolayers on MoSe2 and MoS, S. Cincotti*) and J P Rabeb). .  

E-print Network

carbon-carbon bond lengths in alkanes and graphite.' On the other hand, based on ther- modynamic at the in- terface between highly oriented pyrolytic graphite (HOPG) and organic alkane solutions has elucidated the structure in considerable detail.5-9 It was shown that the I ,- - small difference in carbon-carbon

Peters, Achim

385

Genome sequence of Pseudomonas aeruginosa DQ8, an efficient degrader of n-alkanes and polycyclic aromatic hydrocarbons.  

PubMed

Pseudomonas aeruginosa DQ8, which was isolated from the crude oil polluted soil in the Daqing oilfield of China, can efficiently degrade diesel, crude oil, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs). Here, we present a 6.8-Mb assembly of its genome sequence. We have annotated 23 coding sequences (CDSs) responsible for catabolism of n-alkanes and PAHs. PMID:23105052

Gai, Zhonghui; Zhang, Zhengzhi; Wang, Xiaoyu; Tao, Fei; Tang, Hongzhi; Xu, Ping

2012-11-01

386

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

Microsoft Academic Search

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

E. J. Gallegos

1973-01-01

387

Source of Image Contrast in STM Images of Functionalized Alkanes on Graphite: A Systematic Functional Group Approach  

E-print Network

Source of Image Contrast in STM Images of Functionalized Alkanes on Graphite: A Systematic of functionalized alkanes and/or alkyl alcohols have been prepared and imaged by scanning tunneling microscopy (STM collection of STM images at room temperature with submolecular resolution, in most cases allowing

Goddard III, William A.

388

Draft Genome Sequences of Three Smithella spp. Obtained from a Methanogenic Alkane-Degrading Culture and Oil Field Produced Water  

PubMed Central

Two draft genomes affiliated with Smithella spp. were obtained from a methanogenic alkane-degrading enrichment culture by single-cell sorting and metagenome contig binning, and a third was obtained by single-cell sorting of oil field produced water. Two genomes contained putative assABC genes encoding alkylsuccinate synthase, indicating genetic potential for fumarate activation of alkanes. PMID:25342693

Tan, BoonFei; de Araújo e Silva, Renata; Rozycki, Trent; Nesbø, Camilla

2014-01-01

389

OH-Initiated Heterogeneous Oxidation of Cholestane: A Model System for Understanding the Photochemical Aging of Cyclic Alkane  

E-print Network

of cyclic alkanes in a photochemical flow tube reactor. Oxidation products are collected on filtersOH-Initiated Heterogeneous Oxidation of Cholestane: A Model System for Understanding the Photochemical Aging of Cyclic Alkane Aerosols Haofei Zhang,, Christopher R. Ruehl, Arthur W. H. Chan,, Theodora

Cohen, Ronald C.

390

Effects of surfactant mixtures, including Corexit 9527, on bacterial oxidation of acetate and alkanes in crude oil  

Microsoft Academic Search

Mixtures of nonionic and anionic surfactants, including Corexit 9527, were tested to determine their effects on bacterial oxidation of acetate and alkanes in crude oil by cells pregrown on these substrates. Corexit 9527 inhibited oxidation of the alkanes in crude oil by Acinetobacter calcoaceticus ATCC 31012, while Span 80, a Corexit 9527 constituent, markedly increased the oil oxidation rate. Another

PER BRUHEIM; HARALD BREDHOLT; KJELL EIMHJELLEN

1999-01-01

391

A non-conventional dissimilation pathway for long chain n-alkanes in Acinetobacter sp. M-1 that starts with a dioxygenase reaction  

Microsoft Academic Search

n-Alkane oxidation in a long chain n-alkane utilizer, Acinetobacter sp. M-1, was investigated. In Acinetobacter, n-alkanes have been postulated to be converted to the acid via a non-conventional oxidation pathway: n-alkane?n-alkyl hydroperoxide?aldehyde?acid (Finnerty, W.R.: Lipids of Acinetobacter. In Proceedings of the World Conference on Biotechnology for the Fats and Oils Industry, 184–188, 1988). However, there is little biochemical information on

Yasuyoshi Sakai; Jun Ho Maeng; Seigo Kubota; Akio Tani; Yoshiki Tani; Nobuo Kato

1996-01-01

392

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.

393

Stratospheric chemistry  

NASA Technical Reports Server (NTRS)

Recent improvements in the data base for the currently identified reactions describing the chemistry of the major families of trace gas species, HO(x), NO(x), ClO(x), and hydrocarbons are assessed. The important coupling reactions between the families are introduced progressively. Chemical aspects such as heterogeneous reactions and reactions of sodium species, the importance of which are not yet completely established, are discussed. Recent attempts to reconcile some of the more unexpected kinetic behavior which has emerged from the extensive experimental studies of key reactions with current reaction rate theory are also examined. The uncertainties in the current kinetic and photochemical data base is given. The prospects for improvement of data for known reactions of atmospheric importance as well as for the identification of gaps in the chemical description of the atmosphere.

Cox, R. A.; Demore, W. B.; Ferguson, E. E.; Lesclaux, R.; Ravishankara, A. R.; Sander, S. P.; Sze, N. D.; Zellner, R.

1985-01-01

394

Combustion chemistry  

SciTech Connect

This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

395

Isomerization of alkanes on sulfated zirconia: Promotion by Pt and by adamantyl hydride transfer species  

SciTech Connect

The work shows that hydride transfer species, such as adamantane, increase isomerization rates and inhibit C-C scission reactions. n-Heptane isomerization rates show positive hydrogen kinetic orders, suggesting that the reaction proceeds on Pt/ZrO[sub 2]-SO[sub 4] via chain transfer pathways, in which carbenium ions propagate, after a chain initiation step involvings loss of hydrogen from alkanes, by hydride transfer from neutral species to carbonations. These pathways contrast with those involved in the bifunctional (metal-acid) catalytic sequences usually required for alkane isomerization, in which metal sites catalyze alkane dehydrogenation and acid sites catalyze skeletal rearrangements of alkenes. Rate-limiting hydride transfer steps are consistent with the strong influence of molecular hydride transfer agents such as adamantane, which act as co-catalysts and increase isomerization rate and selectivity. The addition of small amounts of adamantane (0.1-0.8 wt%) to n-heptane increases isomerizations rates by a factor of 3 and inhibits undesirable cracking reactions. Adamantane increases hydride transfer and carbenium ion termination rates, thus reducing the surface residence time required for a catalytic turnover. As a result, desorption occurs before secondary cracking of isomerized carbenium ions. Less effective hydride transfer agents (n-alkanes, isoalkanes) also increase n-alkanes isomerization rate and selectivity, but require much higher concentrations than adamantane. Dihydrogen also acts as a hydride source in alkane isomerization catalysis, but it requires the additional presence of metals or reducible oxides, which catalyze H[sub 2] dissociation and the formation of hydridic and protonic forms of hydrogen. 40 refs., 10 figs., 4 tabs.

Iglesia, E.; Soled, S.L.; Kramer, G.M. (Exxon Research and Engineering Co., Annadale, NJ (United States))

1993-11-01

396

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

397

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. PMID:23359675

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

2013-01-01

398

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

PubMed

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

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

2011-02-17

399

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

PubMed

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

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

2012-11-28

400

Chemistry -Bachelor of Science (SCH) Chemistry: ACS Certified  

E-print Network

Chemistry Lab I AND 1 CH 4110 Pharmaceutical Chemistry I 3 CH 1153 University Chemistry I Recitation 1 CH 4120 Pharmaceutical Chemistry II 3 OR CH 4320 Inorganic Chemistry II 3 CH 1112 University ChemistryChemistry - Bachelor of Science (SCH) Chemistry: ACS Certified Total Credits Required: 128 Required

401

Classification of vegetable oils according to their botanical origin using n-alkane profiles established by GC-MS.  

PubMed

n-Alkane profiles established by gas chromatography-mass spectrometry (GC-MS) were used to classify vegetable oils according to their botanical origin. The n-alkanes present in corn, grapeseed, hazelnut, olive, peanut and sunflower oils were isolated by means of alkaline hydrolysis followed by silica gel column chromatography of the unsaponifiable fractions. The n-alkane fraction was constituted mainly of n-alkanes in the range C8-C35, although only those most abundant (15 n-alkanes, from 21 to 35 carbon No.) were used as original variables to construct linear discriminant analysis (LDA) models. Ratios of the peak areas selected by pairs were used as predictors. All the oils were correctly classified according to their botanical origin, with assignment probabilities higher than 95%, using an LDA model. PMID:25148956

Troya, F; Lerma-García, M J; Herrero-Martínez, J M; Simó-Alfonso, E F

2015-01-15

402

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

PubMed Central

A computer-based system for elucidation of molecular structure is described for the branched alkanes, based upon 13C nuclear magnetic resonance data. All possible structures of a given carbon content are exhaustively generated in a DENDRAL-like manner, and scored according to the fit of their predicted spectral characteristics to those of the “unknown” alkane. The technique may be generalized to any class of organic compounds for which 13C chemical-shift additivity parameters are reliable, and shows promise for stereochemical elucidation. PMID:4519635

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

1973-01-01

403

Mass effect on the Soret coefficient in n-alkane mixtures  

SciTech Connect

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

Alonso de Mezquia, David; Mounir Bou-Ali, M., E-mail: mbouali@mondragon.edu [Mechanical and Manufacturing Department, Engineering Faculty of Mondragon Unibertsitatea, Loramendi 4 Apdo. 23, 20500 Mondragon (Spain); Madariaga, J. Antonio; Santamaría, Carlos [Department of Applied Physics II, University of Basque Country (UPV/EHU), Apdo. 644, 48080 Bilbao (Spain)] [Department of Applied Physics II, University of Basque Country (UPV/EHU), Apdo. 644, 48080 Bilbao (Spain)

2014-02-28

404

Mass effect on the Soret coefficient in n-alkane mixtures  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

405

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

PubMed

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

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

2014-02-28

406

Consistency of plant specific n-alkane patterns in plaggen ecosystems  

NASA Astrophysics Data System (ADS)

Plaggen soils are an important soil type in north-western Europe that were formed by input of various vegetational sources during century-long plaggen (i.e. sod) application. This resulted in remarkably stable organic matter that appears to persists in spite of abandonment of large scale plaggen agriculture with the advent of artificial fertilizers in the early 20th century. Molecular characterization of the organic matter stored in plaggen soils, and in particular linkage to specific vegetation sources, could provide insight in yet poorly understood stabilization mechanisms and the fate of organic matter with ongoing land use change. Plant derived n-alkanes with chain-lenghts of 20-36 carbon atoms are usually well preserved in plaggen soils and could serve as important biomarkers for this purpose. Source appointment in plaggen soils is based on the use of concentration patterns of preserved n-alkanes with modern vegetation sources functioning as proxies. A crucial prerequisite is that patterns as observed in relevant present-day vegetation are representative and consistent. While this is generally assumed, to our knowledge it was never explicitly tested for plaggen soils. Therefore, we evaluated published n-alkane patterns of plant species and parts representative of past and current input to plaggen soils. We analyzed distribution patterns showing relative abundances in chain-length range C17-36 for various shrub, tree and grass species. Here we present and discuss the published n-alkane patterns in detail. We attempt to link variation in observed patterns to potential (systematic) sources such as geographical, temporal and methodological variations. Published distribution patterns derive from a variety of studies, characterized by differing laboratory techniques, environmental conditions etc. In spite of a surprisingly concise set of published n-alkane patterns, along with considerable scatter in the analyzed data, we did find meaningful clustering of n-alkanes allowing for clear distinction of input by shrubs, trees and grasses to plaggen soils. Indications of systematic variation were observed for ontogeny and according to spatial conditions among tree species, while effects by other variation sources were less pronounced. Our results emphasize the need for further extension and systematic clustering of available data on plant derived n-alkanes. Concurrently, they highlight that application of n-alkane biomarkers in paleo-environmental reconstructions of plaggen soils is challenging, but not prevented a-priori.

Kirkels, Frédérique; Jansen, Boris; Kalbitz, Karsten

2013-04-01

407

Direct dissociative chemisorption of alkanes on Pt(111): Influence of molecular complexity  

SciTech Connect

The direct dissociative chemisorption of ethane, propane, n-butane, isobutane, and neopentane on Pt(111) was investigated as a function of the initial translational energy, E{sub T}, polar angle of incidence, {theta}{sub i}, initial vibrational temperature, and surface temperature using supersonic molecular beam techniques. For each alkane, the initial probability for direct dissociative chemisorption scales with the initial normal energy of the alkanes, E{sub n}=E{sub T} cos{sup 2} {theta}{sub i}, and is independent of both the surface temperature and initial vibrational energy of the alkanes under the experimental conditions employed. Above initial normal energies of approximately 125 kJ/mol, at constant E{sub n}, the dissociation probability decreases with increasing chain length of the C{sub 2}-C{sub 4} linear alkanes; however, the dissociation probability of neopentane is greater than that of isobutane, and both isobutane and neopentane are more reactive than n-butane. By assuming that cleavage of primary C-H bonds is the dominant reaction pathway for all of the alkanes investigated here, the trends in reactivity are best explained by considering the differences in the steric factors for primary C-H bond cleavage for these alkanes. Secondary C-H bond cleavage does appear to contribute to the reactivity of propane and n-butane but only at the highest energies examined. Additionally, the reaction probabilities of each of these alkanes were estimated using a statistical model recently proposed by Ukrainstev and Harrison [J. Chem. Phys. 101, 1564 (1994)]. Assuming cleavage of only primary C-H bonds, the trends in reactivity for ethane, propane, n-butane, and isobutane were qualitatively reproduced by the statistical model; however, except for ethane, which was used to obtain the necessary parameters for the theory, there was poor quantitative agreement, and the predictions for neopentane were significantly lower than the measured values. The model also predicts that the dissociation probability is enhanced by increasing the energy in all vibrational modes, which is inconsistent with the experimental results. Thus, we believe that direct alkane dissociation would be better described using a dynamical rather than statistical approach. (c) 2000 American Institute of Physics.

Weaver, Jason F. [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States)] [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States); Krzyzowski, Michael A. [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States)] [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States); Madix, Robert J. [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States)] [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States)

2000-01-01

408

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

409

Monocarboxylic acids from oxidation of acyclic isoprenoid alkanes by Mycobacterium fortuitum  

NASA Technical Reports Server (NTRS)

Mycobacterium fortuitum utilizes certain stereoisomeric mixtures of individual multimethyl branched alkanes as sole carbon source, including 2,6(R), 10(S), 14(RS)-tetramethylhexadecane; 2,6(R), 10(S), 14(RS)-tetramethylheptadecane; 2,6(RS), 10(RS)-trimethyltetradecane, and 2,6(R), 10(S)-trimethylpentadecane. Products of oxidation isolated from the bacterial lipids were acids derived predominantly from oxidation of the isopropyl terminus of each alkane, except in the case of 2,6(RS), 10(RS)-trimethyltetradecane. With the latter, acids from oxidation at either terminus were detected in comparable proportions.

Cox, R. E.; Maxwell, J. R.; Myers, R. N.

1976-01-01

410

CHEMISTRY 3020-42232 PHYSICAL CHEMISTRY I  

E-print Network

CHEMISTRY 3020-42232 PHYSICAL CHEMISTRY I Fall 2011 8:00 am - 8:50 am, MWF CNSB 211 INSTRUCTOR interpretations of the physical principles of chemistry. Goals/ Objectives: CHEM 3020 presents chemical principles from a fundamental physical point of view. Topics covered include: properties of gases, thermodynamics

Findley, Gary L.

411

CHEMISTRY 3022-63067 PHYSICAL CHEMISTRY II  

E-print Network

CHEMISTRY 3022-63067 PHYSICAL CHEMISTRY II Spring 2014 8:00 am - 8:50 am, MWF CNSB 211 INSTRUCTOR interpretations of the physical principles of chemistry. Goals/ Objectives: CHEM 3022 presents chemical principles consequences. Topics covered include: properties of gases, thermodynamics (heat, work, internal energy

Findley, Gary L.

412

FACULTY POSITION IN INORGANIC CHEMISTRY Department of Chemistry  

E-print Network

FACULTY POSITION IN INORGANIC CHEMISTRY Department of Chemistry Syracuse University The Department of Chemistry at Syracuse University invites applications for a tenure track faculty position at the Assistant Professor level in inorganic chemistry with specialization in materials chemistry (broadly defined

Doyle, Robert

413

Changes in iso- and n-alkane distribution during biodegradation of crude oil under nitrate and sulphate reducing conditions.  

PubMed

Crude oil consists of a large number of hydrocarbons with different susceptibility to microbial degradation. The influence of hydrocarbon structure and molecular weight on hydrocarbon biodegradation under anaerobic conditions is not fully explored. In this study oxygen, nitrate and sulphate served as terminal electron acceptors (TEAs) for the microbial degradation of a paraffin-rich crude oil in a freshly contaminated soil. During 185 days of incubation, alkanes from n-C11 to n-C39, three n- to iso-alkane ratios commonly used as weathering indicators and the unresolved complex mixture (UCM) were quantified and statistically analyzed. The use of different TEAs for hydrocarbon degradation resulted in dissimilar degradative patterns for n- and iso-alkanes. While n-alkane biodegradation followed well-established patterns under aerobic conditions, lower molecular weight alkanes were found to be more recalcitrant than mid- to high-molecular weight alkanes under nitrate-reducing conditions. Biodegradation with sulphate as the TEA was most pronounced for long-chain (n-C32 to n-C39) alkanes. The observation of increasing ratios of n-C17 to pristane and of n-C18 to phytane provides first evidence of the preferential degradation of branched over normal alkanes under sulphate reducing conditions. The formation of distinctly different n- and iso-alkane biodegradation fingerprints under different electron accepting conditions may be used to assess the occurrence of specific degradation processes at a contaminated site. The use of n- to iso-alkane ratios for this purpose may require adjustment if applied for anaerobic sites. PMID:22001845

Hasinger, Marion; Scherr, Kerstin E; Lundaa, Tserennyam; Bräuer, Leopold; Zach, Clemens; Loibner, Andreas Paul

2012-02-20

414

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

PubMed

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

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

2012-03-28

415

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

416

A CP-MAS NMR study of n-alkanes included in urea: conformational dependences of the substituent effects for n-substituted alkanes  

NASA Astrophysics Data System (ADS)

Solid state CP-MAS NMR spectra have been obtained for the urea inclusion complexes of the substituted alkanes; tridecane, myristyl alcohol, dioctylamine, myristic acid, and stearonitrile. Changes in the substituent effects on the chemical shift values, on inclusion complex formation, from those of solution NMR spectra are discussed on the assumption that long-chain molecules in urea inclusion complexes have the all- trans conformation.

Okazaki, Masaharu; McDowell, Charles A.

1984-08-01

417

Enhanced Translocation and Growth of Rhodococcus erythropolis PR4 in the Alkane Phase of Aqueous-Alkane Two Phase Cultures Were Mediated by GroEL2 Overexpression  

PubMed Central

We previously reported that R. erythropolis PR4 translocated from the aqueous to the alkane phase, and then grew in two phase cultures to which long-chain alkanes had been added. This was considered to be beneficial for bioremediation. In the present study, we investigated the proteins involved in the translocation of R. erythropolis PR4. The results of our proteogenomic analysis suggested that GroEL2 was upregulated more in cells that translocated inside of the pristane (C19) phase than in those located at the aqueous-alkane interface attached to the n-dodecane (C12) surface. PR4 (pK4-EL2-1) and PR4 (pK4-?EL2-1) strains were constructed to confirm the effects of the upregulation of GroEL2 in translocated cells. The expression of GroEL2 in PR4 (pK4-EL2-1) was 15.5-fold higher than that in PR4 (pK4-?EL2-1) in two phase cultures containing C12. The growth and cell surface lipophilicity of PR4 were enhanced by the introduction of pK4-EL2-1. These results suggested that the plasmid overexpression of groEL2 in PR4 (pK4-EL2-1) led to changes in cell localization, enhanced growth, and increased cell surface lipophilicity. Thus, we concluded that the overexpression of GroEL2 may play an important role in increasing the organic solvent tolerance of R. erythropolis PR4 in aqueous-alkane two phase cultures.

Takihara, Hayato; Ogihara, Jun; Yoshida, Takao; Okuda, Shujiro; Nakajima, Mutsuyasu; Iwabuchi, Noriyuki; Sunairi, Michio

2014-01-01

418

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

PubMed Central

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 (C6–C18) 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 (C8–C16) or fatty alkanes (C7–C15) 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 (C8–C18). 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.

2013-01-01

419

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

2013-01-01

420

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

421

Reprint of "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

2013-06-01

422

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

423

Trace Chemistry  

NASA Technical Reports Server (NTRS)

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

Radhakrishnan, Krishnan; Whitefield, Philip

1999-01-01

424

Alkane utilization by Rhodococcus strain NTU-1 alone and in its natural association with Bacillus fusiformis L-1 and Ochrobactrum sp.  

PubMed

Linear (n-hexadecane) and branched (pristane) alkanes were degraded by a mixed culture isolated from an oil-contaminated field. The degradation was accompanied by formation of biofloccules. The culture was composed of Rhodococcus strain NTU-1, Bacillus fusiformis L-1, and Ochrobactrum sp. Rhodococcus strain NTU-1 carried out the degradation of the alkane via a hydroxylase. Bacillus fusiformis L-1 and Ochrobactrum sp. did not degrade the alkanes but aided the flocculation by forming more rigid bacterial aggregates that enhanced the trapping of alkanes. In batch cultures, transformation and removal of the linear and branched alkanes was achieved within 66 h with more than 95% efficiency. PMID:17022676

Sayavedra-Soto, Luis A; Chang, Wei-Nung; Lin, Tze-Khai; Ho, Chung-Lin; Liu, Hwai-Shen

2006-01-01

425

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.

426

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

427

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

428

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 ...

429

Determination of Alkane Content in Fresh Fecal Samples to Estimate Intake on Pasture  

Technology Transfer Automated Retrieval System (TEKTRAN)

External markers of wax alkanes C32 and C36 are effective tools for determining intake of grazing animals. The technique requires daily dosing of markers which is impractical under extensive grazing conditions, so controlled release capsules (CRC) have been used. However, consistency of payout from ...

430

METHYL-BRANCHED ALKANES OF THE ADULT FLEA BEETLES, APHTHONA LACERTOSA AND APHTHONA NIGRISCUTIS  

Technology Transfer Automated Retrieval System (TEKTRAN)

An analysis was conducted of the hydrocarbon fraction of the cuticular waxes from two introduced biocontrol agents of leafy spurge, Aphthona lacertosa and A. nigriscutis. The adult beetles had a complex mixture of hydrocarbons on their cuticular surface consisting of alkanes, methylalkanes, alkenes...

431

Alkane production by the marine cyanobacterium Synechococcus sp. NKBG15041c possessing the ?-olefin biosynthesis pathway.  

PubMed

The production of alkanes in a marine cyanobacterium possessing the ?-olefin biosynthesis pathway was achieved by introducing an exogenous alkane biosynthesis pathway. Cyanobacterial hydrocarbons are synthesized via two separate pathways: the acyl-acyl carrier protein (ACP) reductase/aldehyde-deformylating oxygenase (AAR/ADO) pathway for the alkane biosynthesis and the ?-olefin synthase (OLS) pathway for the ?-olefin biosynthesis. Coexistence of these pathways has not yet been reported. In this study, the marine cyanobacterium Synechococcus sp. NKBG15041c was shown to produce ?-olefins similar to those of Synechococcus sp. PCC7002 via the ?-olefin biosynthesis pathway. The production of heptadecane in Synechococcus sp. NKBG15041c was achieved by expressing the AAR/ADO pathway genes from Synechococcus elongatus PCC 7942. The production yields of heptadecane in Synechococcus sp. NKBG15041c varied with the expression level of the aar and ado genes. The maximal yield of heptadecane was 4.2?±?1.2 ?g/g of dried cell weight in the transformant carrying a homologous promoter. Our results also suggested that the effective activation of ADO may be more important for the enhancement of alkane production by cyanobacteria. PMID:25527377

Yoshino, Tomoko; Liang, Yue; Arai, Daichi; Maeda, Yoshiaki; Honda, Toru; Muto, Masaki; Kakunaka, Natsumi; Tanaka, Tsuyoshi

2015-02-01

432

Z .Fluid Phase Equilibria 150151 1998 151159 Thermal diffusion in alkane binary mixtures  

E-print Network

. Keywords: Alkane mixture; Molecular simulation; Non-equilibrium molecular dynamics; Soret effect; Thermal gradient parallel to the thermal gradient. This effect is known as the Soret effect or the thermal in liquid mixtures by Soret, thermal diffusion has been the subject of both experimental and theoretical

Dysthe, Dag Kristian

433

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] [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)] [Exxon Research and Engineering Co., Annandale, NJ (United States)

1998-07-15

434

Biosurfactant-mediated biodegradation of straight and methyl-branched alkanes by Pseudomonas aeruginosa ATCC 55925  

PubMed Central

Accidental oil spills and waste disposal are important sources for environmental pollution. We investigated the biodegradation of alkanes by Pseudomonas aeruginosa ATCC 55925 in relation to a rhamnolipid surfactant produced by the same bacterial strain. Results showed that the linear C11-C21 compounds in a heating oil sample degraded from 6% to 100%, whereas the iso-alkanes tended to be recalcitrant unless they were exposed to the biosurfactant; under such condition total biodegradation was achieved. Only the biodegradation of the commercial C12-C19 alkanes could be demonstrated, ranging from 23% to 100%, depending on the experimental conditions. Pristane (a C19 branched alkane) only biodegraded when present alone with the biosurfactant and when included in an artificial mixture even without the biosurfactant. In all cases the biosurfactant significantly enhanced biodegradation. The electron scanning microscopy showed that cells depicted several adaptations to growth on hydrocarbons, such as biopolymeric spheres with embedded cells distributed over different layers on the spherical surfaces and cells linked to each other by extracellular appendages. Electron transmission microscopy revealed transparent inclusions, which were associated with hydrocarbon based-culture cells. These patterns of hydrocarbon biodegradation and cell adaptations depended on the substrate bioavailability, type and length of hydrocarbon. PMID:21906343

2011-01-01

435

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...

436

DOI: 10.1002/cctc.201000383 Catalytic Co-Homologation of Alkanes and Dimethyl Ether  

E-print Network

- lective formation of triptane and isobutane by means of the homologation of DME or methanol (Scheme 140/SiO2).[8] The remarkable selectivity to isobutane and triptane reflects a preference alkanes and isobutane on H-BEA zeo- lites, and for the role of adamantane as a hydride transfer co

Iglesia, Enrique

437

Development of a Polarizable Intermolecular Potential Function (PIPF) for Liquid Amides and Alkanes  

E-print Network

Development of a Polarizable Intermolecular Potential Function (PIPF) for Liquid Amides and Alkanes Received June 17, 2007 Abstract: A polarizable intermolecular potential function (PIPF) employing the Thole. In connection with the internal bonding terms of the CHARMM22 force field, the present PIPF- CHARMM potential

Minnesota, University of

438

Solvent isotope effects on alkane formation by cyanobacterial aldehyde deformylating oxygenase and their mechanistic implications.  

PubMed

The reaction catalyzed by cyanobacterial aldehyde deformylating oxygenase is of interest both because of its potential application to the production of biofuels and because of the highly unusual nature of the deformylation reaction it catalyzes. Whereas the proton in the product alkane derives ultimately from the solvent, the identity of the proton donor in the active site remains unclear. To investigate the proton transfer step, solvent isotope effect (SIE) studies were undertaken. The rate of alkane formation was found to be maximal at pH 6.8 and to be the same in D2O or H2O within experimental error, implying that proton transfer is not a kinetically significant step. However, when the ratio of protium to deuterium in the product alkane was measured as a function of the mole fraction of D2O, a (D2O)SIEobs of 2.19 ± 0.02 was observed. The SIE was invariant with the mole fraction of D2O, indicating the involvement of a single protic site in the reaction. We interpret this SIE as most likely arising from a reactant state equilibrium isotope effect on a proton donor with an inverse fractionation factor, for which ? = 0.45. These observations are consistent with an iron-bound water molecule being the proton donor to the alkane in the reaction. PMID:25142631

Waugh, Matthew W; Marsh, E Neil G

2014-09-01

439

Fe-Catalyzed Oxidation Reactions of Olefins, Alkanes, and Alcohols: Involvement of Oxo- and Peroxo Complexes  

NASA Astrophysics Data System (ADS)

In this review, recent developments of iron-catalyzed oxidations of olefins (epoxidation), alkanes, arenes, and alcohols are summarized. Special focus is given on the ligand systems and the catalytic performance of the iron complexes. In addition, the mechanistic involvement of high-valent iron-oxo species is discussed.

Schröder, Kristin; Junge, Kathrin; Bitterlich, Bianca; Beller, Matthias

440

Simulation study on the adsorption properties of linear alkanes on closed nanotube bundles.  

PubMed

Adsorption onto carbon nanotube bundles may find use in various applications such as gas preconcentration and separation, and as a result, it is of great interest to study the adsorption properties of such bundles. The adsorption of linear alkanes, with their systematic variation through chain length, is particularly useful to explore the effects of molecular length on adsorption characteristics. We have conducted grand-canonical Monte Carlo simulations of light linear alkanes adsorbing onto closed nanotube bundles to explore these effects in a systematic manner. Our results demonstrate how adsorption into the grooves of the bundle is favored with alignment of the alkanes along the nanotube axis. We describe in detail the effects of competition for adsorption in the grooves and on the bundle as a whole, and highlight how selectivity can be tuned through careful choice of pressure and temperature. Finally, we describe how it is possible to derive a systematic relation between the length of the alkane and its loading on the bundle, and discuss its usefulness in applying ideal adsorbed solution theory (IAST) to predicting competitive mixed adsorption over a wide range of pressures. We also focus in turn on the ability of IAST to capture adsorption-saturation effects. PMID:22764885

Cannon, James J; Vlugt, Thijs J H; Dubbeldam, David; Maruyama, Shigeo; Shiomi, Junichiro

2012-08-16

441

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. PMID:17416678

Chen, George S.; Labinger, Jay A.; Bercaw, John E.

2007-01-01

442

Combined use of partially fluorinated alkanes, perfluorocarbon liquids and silicone oil: an experimental study  

Microsoft Academic Search

Background: Partially fluorinated alkanes (FALKs) are a new class of substances which can be used in vitreoretinal surgery as an intraoperative tool and as a long-term tamponade. The aim of this in vitro study was (1) to investigate the solubility of FALKs in silicone oil during direct exchange, (2) to study their combined use and solubility in PFCLs, (3) to

Hans Hoerauf; Karin Kobuch; Joachim Dresp; Dirk-Henning Menz

2001-01-01

443

Development of microbodies in Candida tropicalis during incubation in a n -alkane medium  

Microsoft Academic Search

Development of microbodies in Candida tropicalis pK 233 was studied mainly by electron microscopical observation. The yeast cells, precultured on malt extract, scarcely contained microbodies and showed very low catalase activity. When the precultured cells were transferred to a n-alkane medium and incubated with shaking, the number of microbodies increased and concomitantly the activity of catalase was enhanced. That is,

Masako Osumi; Fusako Fukuzumi; Yutaka Teranishi; Atsuo Tanaka; Saburo Fukui

1975-01-01

444

Experimental Confirmation of the LowTemperature Oxidation Scheme of Alkanes  

E-print Network

Experimental Confirmation of the LowTemperature Oxidation Scheme of Alkanes Frédérique Battin Xie, and Fei Qi* Keywords: hydroperoxides mass spectrometry molecular beams oxidation], as well as improved safety in oxidation processes [3], rely on a good understanding of the kinetic

Paris-Sud XI, Université de

445

Heteropolyacid-based catalysts for selective alkane oxidation: mechanism of formation of maleic anhydride from propane  

Microsoft Academic Search

Highly active and selective alkane oxidation catalysts, obtained by heating pyridinium- and niobium-exchanged phosphomolybdate and phosphovanadomolybdate salts under inert atmosphere, can under some conditions lead to maleic anhydride as a major product of propane oxidation. Mechanistic studies based on oxidation of postulated intermediates as well as selectively isotopically labeled propane implicate a route involving oxidative dehydrogenation to propylene followed by

Christopher J. Dillon; Joseph H. Holles; Mark E. Davis; Jay A. Labinger

2003-01-01

446

Kinetics of Oxidative Dehydrogenation of C2?C3 Alkanes on Oxide Catalysts  

Microsoft Academic Search

This review is a survey of the main facts and concepts appeared in the last years on kinetics of oxidative dehydrogenation (ODH) of ethane, propane, butane and isobutane. The accent is put on the mechanisms and the kinetic models used for the description of this reaction. The main catalysts for ODH of light alkanes and the specific features of each

R. Grabowski

2006-01-01

447

Selective alkane oxidation: hot and cold approaches to a hot problem  

Microsoft Academic Search

A large number of attempts at the selective oxidation of alkanes may be classified into three basic types: high-temperature heterogeneous catalysis, biological\\/biomimetic catalysis, and organometallic activation. In this essay I discuss mechanistic similarities and differences between the three approaches, and their implications for the best opportunities for achieving desired selective transformations.

Jay A. Labinger

2004-01-01

448

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

449

Delights of Chemistry  

NSDL National Science Digital Library

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

450

Composition of leaf n-alkanes in three Satureja montana L. subspecies from the Balkan peninsula: ecological and taxonomic aspects.  

PubMed

The composition of the epicuticular leaf n-alkanes of eight populations of three Satureja montana subspecies (S. montana L. subsp. pisidica (Wettst.) Šili?, S. montana L. subsp. montana, and S. montana L. subsp. variegata (Host) P.?W. Ball), from central and western areas of the Balkan Peninsula was characterized by GC-FID and GC/MS analyses. In the leaf waxes, 15 n-alkane homologs with chain-lengths ranging from C21 to C35 were identified. The main n-alkane in almost all samples was n-nonacosane (C29 ), but differences in the contents of three other dominant n-alkanes allowed separating the coastal from the continental populations. The diversity and variability of the epicuticular-leaf-n-alkane patterns and their relation to different geographic and bioclimatic parameters were analyzed by several statistical methods (principal component, discriminant, and cluster analyses as well as the Mantel test). All tests showed a high correlation between the leaf n-alkane pattern and the geographical distribution of the investigated populations, confirming the differentiation between S. montana subsp. pisidica and the other two subspecies. The S. montana subsp. variegata and S. montana subsp. montana populations are geographically closer and their differentiation according to the leaf-n-alkane patterns was not clear, even though there was some indication of discrimination between them. Moreover, most of the bioclimatic parameters related to temperature were highly correlated with the differentiation of the coastal and the continental populations. PMID:25641844

Dodoš, Tanja; Raj?evi?, Nemanja; Teševi?, Vele; Matevski, Vlado; Jana?kovi?, Pedja; Marin, Petar D

2015-01-01

451

Conversing with Computers  

NASA Technical Reports Server (NTRS)

I/NET, Inc., is making the dream of natural human-computer conversation a practical reality. Through a combination of advanced artificial intelligence research and practical software design, I/NET has taken the complexity out of developing advanced, natural language interfaces. Conversational capabilities like pronoun resolution, anaphora and ellipsis processing, and dialog management that were once available only in the laboratory can now be brought to any application with any speech recognition system using I/NET s conversational engine middleware.

2004-01-01

452

Why chemistry? Chemistry is fundamental: it is the enabling  

E-print Network

Chemistry Why chemistry? Chemistry is fundamental: it is the enabling science that underlies many technology. A chemistry degree gives you the understanding to contribute to our future in very topical areas) in Chemistry BSc (Hons) in Chemistry MChem (Hons) in Chemistry (with an industrial placement year) MChem (Hons

Sussex, University of

453

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.

454

Generalization to conversational speech.  

PubMed

Although changes in children's phonological systems due to treatment have been documented in single-word testing, changes in conversational speech are less well known. Single-word and conversation samples were analyzed for 10 phonologically disordered children, before and after treatment and 3 months later. Results suggest that for most of the children, there were system changes in both single words and in conversational speech. It appears that many phonologically disordered children are able to extend their correct production to conversation without direct treatment on spontaneous speech. PMID:2232748

Elbert, M; Dinnsen, D A; Swartzlander, P; Chin, S B

1990-11-01

455

Selective Conversion of Diallylanilines and Arylimines to Josemon Jacob and William D. Jones*  

E-print Network

Selective Conversion of Diallylanilines and Arylimines to Quinolines Josemon Jacob and William D. Jones* Department of Chemistry, University of Rochester, Rochester, New York 14627 jones: Oxford, UK, 1996; Vol. 5, p 245. (5) Jones, G. In Comprehensive Heterocyclic Chemistry II; Katritzky, A

Jones, William D.

456

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

457

Studies on the catalytic oxidation of alkanes and alkenes by titanium silicates  

SciTech Connect

Titanium containing, aluminum-free ZSM-5 (TS-1) and amorphous TiO{sub 2}-SiO{sub 2} coprecipitate are investigated as catalysts for the selective oxidation of alkanes and alkenes using a variety of oxidants at temperatures below 100{degrees}C. Comparisons between the activities of TS-1 and and TiO{sub 2}-SiO{sub 2} coprecipitate for alkane oxidation and alkene epoxidation using nonaqueous H{sub 2}O{sub 2} indicate that the absence of water is crucial for the catalytic activity of silica-supported titanium. Due to the hydrophobicity of TS-1, the concentration of water surrounding the titanium is maintained at a low value, and thus TS-1 can be used as an oxidation catalysts with aqueous H{sub 2}O{sub 2} as oxidant. Alkyl hydroperoxides are active as oxidants for alkene epoxidation on the TiO{sub 2}-SiO{sub 2} coprecipitate but not for alkane oxidation reactions on both TS-1 and the TiO{sub 2}-SiO{sub 2} coprecipitate. A plausible explanation for the above results is provided. The presence of stereoscrambling without any {open_quotes}radical clock{close_quotes} rearrangement during alkane oxidation on TS-1 indicates that the radicals formed may have a very short lifetime, or their movements are restricted such that no rearrangement can occur. A proposal for the mechanism of alkane oxidation on TS-1 is given and compared to a mechanism suggested for alkene epoxidation on TS-1 and the TiO{sub 2}-SiO{sub 2} coprecipitate. 47 refs., 10 figs., 9 tabs.

Khouw, C.B.; Dartt, C.B.; Labinger, J.A. [California Institute of Technology, Pasadena, CA (United States)] [and others] [California Institute of Technology, Pasadena, CA (United States); and others

1994-09-01

458

Adaptation of the hydrocarbonoclastic bacterium Alcanivorax borkumensis SK2 to alkanes and toxic organic compounds: a physiological and transcriptomic approach.  

PubMed

The marine hydrocarbonoclastic bacterium Alcanivorax borkumensis is able to degrade mixtures of n-alkanes as they occur in marine oil spills. However, investigations of growth behavior and physiology of these bacteria when cultivated with n-alkanes of different chain lengths (C6 to C30) as the substrates are still lacking. Growth rates increased with increasing alkane chain length up to a maximum between C12 and C19, with no evident difference between even- and odd-numbered chain lengths, before decreasing with chain lengths greater than C19. Surface hydrophobicity of alkane-grown cells, assessed by determination of the water contact angles, showed a similar pattern, with maximum values associated with growth rates on alkanes with chain lengths between C11 and C19 and significantly lower values for cells grown on pyruvate. A. borkumensis was found to incorporate and modify the fatty acid intermediates generated by the corresponding n-alkane degradation pathway. Cells grown on distinct n-alkanes proved that A. borkumensis is able to not only incorporate but also modify fatty acid intermediates derived from the alkane degradation pathway. Comparing cells grown on pyruvate with those cultivated on hexadecane in terms of their tolerance toward two groups of toxic organic compounds, chlorophenols and alkanols, representing intensely studied organic compounds, revealed similar tolerances toward chlorophenols, whereas the toxicities of different n-alkanols were significantly reduced when hexadecane was used as a carbon source. As one adaptive mechanism of A. borkumensis to these toxic organic solvents, the activity of cis-trans isomerization of unsaturated fatty acids was proven. These findings could be verified by a detailed transcriptomic comparison between cultures grown on hexadecane and pyruvate and including solvent stress caused by the addition of 1-octanol as the most toxic intermediate of n-alkane degradation. PMID:23645199

Naether, Daniela J; Slawtschew, Slavtscho; Stasik, Sebastian; Engel, Maria; Olzog, Martin; Wick, Lukas Y; Timmis, Kenneth N; Heipieper, Hermann J

2013-07-01

459

Adaptation of the Hydrocarbonoclastic Bacterium Alcanivorax borkumensis SK2 to Alkanes and Toxic Organic Compounds: a Physiological and Transcriptomic Approach  

PubMed Central

The marine hydrocarbonoclastic bacterium Alcanivorax borkumensis is able to degrade mixtures of n-alkanes as they occur in marine oil spills. However, investigations of growth behavior and physiology of these bacteria when cultivated with n-alkanes of different chain lengths (C6 to C30) as the substrates are still lacking. Growth rates increased with increasing alkane chain length up to a maximum between C12 and C19, with no evident difference between even- and odd-numbered chain lengths, before decreasing with chain lengths greater than C19. Surface hydrophobicity of alkane-grown cells, assessed by determination of the water contact angles, showed a similar pattern, with maximum values associated with growth rates on alkanes with chain lengths between C11 and C19 and significantly lower values for cells grown on pyruvate. A. borkumensis was found to incorporate and modify the fatty acid intermediates generated by the corresponding n-alkane degradation pathway. Cells grown on distinct n-alkanes proved that A. borkumensis is able to not only incorporate but also modify fatty acid intermediates derived from the alkane degradation pathway. Comparing cells grown on pyruvate with those cultivated on hexadecane in terms of their tolerance toward two groups of toxic organic compounds, chlorophenols and alkanols, representing intensely studied organic compounds, revealed similar tolerances toward chlorophenols, whereas the toxicities of different n-alkanols were significantly reduced when hexadecane was used as a carbon source. As one adaptive mechanism of A. borkumensis to these toxic organic solvents, the activity of cis-trans isomerization of unsaturated fatty acids was proven. These findings could be verified by a detailed transcriptomic comparison between cultures grown on hexadecane and pyruvate and including solvent stress caused by the addition of 1-octanol as the most toxic intermediate of n-alkane degradation. PMID:23645199

Naether, Daniela J.; Slawtschew, Slavtscho; Stasik, Sebastian; Engel, Maria; Olzog, Martin; Wick, Lukas Y.; Timmis, Kenneth N.

2013-01-01

460

Review of solar fuel-producing quantum conversion processes  

Microsoft Academic Search

The status and potential of fuel-producing solar photochemical processes are discussed. Research focused on splitting water to produce dihydrogen and is at a relatively early stage of development. Current emphasis is primarily directed toward understanding the basic chemistry underlying such quantum conversion processes. Theoretical analyses by various investigators predict a limiting thermodynamic efficiency of 31% for devices with a single

D. B. Peterson; J. R. Biddle; T. Fujita

1984-01-01

461

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