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1

Toxicity of methyl- tert-butyl ether to freshwater organisms  

Microsoft Academic Search

Increased input of the fuel oxygenate methyl-tert-butyl ether (MTBE) into aquatic systems has led to concerns about its effect(s) on aquatic life. As part of a study conducted by University of California scientists for the State of California, the Aquatic Toxicology Laboratory, UC Davis, reviewed existing literature on toxicity of MTBE to freshwater organisms, and new information was generated on

I Werner; C. S Koger; L. A Deanovic; D. E Hinton

2001-01-01

2

Dissolution of cholesterol gallstones using methyl tert-butyl ether  

Microsoft Academic Search

Symptomatic cholelithiasis affects a large segment of the population. Several nonoperative therapeutic alternatives for treatment\\u000a of these gallstones have recently been developed. We present here the technical aspects and results of gallstone dissolution\\u000a in 75 patients with the use of methyl tert-butyl ether (MTBE) administered via a small percutaneously placed cholecystostomy\\u000a catheter. Successful stone dissolution was achieved in 69 patients.

Hugh J. Williams; Claire E. Bender; Andrew J. LeRoy

1990-01-01

3

Microbial degradation and fate in the environment of methyl tert -butyl ether and related fuel oxygenates  

Microsoft Academic Search

Oxygenates, mainly methyl tert-butyl ether (MTBE), are commonly added to gasoline to enhance octane index and improve combustion efficiency. Other oxygenates used as gasoline additives are ethers such as ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and alcohols such as tert-butyl alcohol (TBA). As a result of its wide use, MTBE has been detected, mainly in the USA, in

F. Fayolle; J.-P. Vandecasteele; F. Monot

2001-01-01

4

Microbial degradation of methyl tert-butyl ether and tert-butyl alcohol in the subsurface.  

PubMed

The fate of fuel oxygenates such as methyl tert-butyl ether (MTBE) in the subsurface is governed by their degradability under various redox conditions. The key intermediate in degradation of MTBE and ethyl tert-butyl ether (ETBE) is tert-butyl alcohol (TBA) which was often found as accumulating intermediate or dead-end product in lab studies using microcosms or isolated cell suspensions. This review discusses in detail the thermodynamics of the degradation processes utilizing various terminal electron acceptors, and the aerobic degradation pathways of MTBE and TBA. It summarizes the present knowledge on MTBE and TBA degradation gained from either microcosm or pure culture studies and emphasizes the potential of compound-specific isotope analysis (CSIA) for identification and quantification of degradation processes of slowly biodegradable pollutants such as MTBE and TBA. Microcosm studies demonstrated that MTBE and TBA may be biodegradable under oxic and nearly all anoxic conditions, although results of various studies are often contradictory, which suggests that site-specific conditions are important parameters. So far, TBA degradation has not been shown under methanogenic conditions and it is currently widely accepted that TBA is a recalcitrant dead-end product of MTBE under these conditions. Reliable in situ degradation rates for MTBE and TBA under various geochemical conditions are not yet available. Furthermore, degradation pathways under anoxic conditions have not yet been elucidated. All pure cultures capable of MTBE or TBA degradation isolated so far use oxygen as terminal electron acceptor. In general, compared with hydrocarbons present in gasoline, fuel oxygenates biodegrade much slower, if at all. The presence of MTBE and related compounds in groundwater therefore frequently limits the use of in situ biodegradation as remediation option at gasoline-contaminated sites. Though degradation of MTBE and TBA in field studies has been reported under oxic conditions, there is hardly any evidence of substantial degradation in the absence of oxygen. The increasing availability of field data from CSIA will foster our understanding and may even allow the quantification of degradation of these recalcitrant compounds. Such information will help to elucidate the crucial factors of site-specific biogeochemical conditions that govern the capability of intrinsic oxygenate degradation. PMID:15134874

Schmidt, Torsten C; Schirmer, Mario; Weiss, Holger; Haderlein, Stefan B

2004-06-01

5

Effect of water presence on methyl tert-butyl ether and ethyl tert-butyl ether liquid-phase syntheses  

SciTech Connect

Equilibrium constants for the liquid-phase synthesis of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) were determined experimentally in the temperature range 40-80 C, using an initial water percentage range in the alcohol of 1.4-5 wt%. The initial molar alcohol-isobutylene ratio varied from 0.8 to 1.44. Both systems behave nonideally, and the equilibrium constants found agree with those determined without initial water quoted in the literature. In experimental kinetic runs performed at 40 C, ETBE and MTBE production rates are strongly lowered by the initial water presence. This inhibitor effect disappears as water is converted into tert-butyl alcohol (TBA). The TBA equilibrium is reached faster than those of the ethers, and the residual water is rather small.

Cunill, F.; Vila, M.; Izquierdo, J.F.; Iborra, M.; Tejero, J. (Univ. of Barcelona (Spain))

1993-03-01

6

Anaerobic biodegradation of methyl tert-butyl ether and tert-butyl alcohol in petrochemical wastewater.  

PubMed

A laboratory-scale anaerobic sequencing batch reactor was used to evaluate treatment of a synthetic substrate mixture representing petrochemical wastewater containing methyl tert-butyl ether (MTBE), ethanol and acetic acid. Influent MTBE concentrations were 5, 10 and 50 mg/l (corresponding to MTBE loading rates of 0.2, 0.4 and 2 mg/l.d) with overall organic loading rates (OLRs) of 1.51, 3.23 and 3.25 g COD/1.d, respectively. These OLRs resulted in removal efficiencies for MTBE of 78%, 98% and 88%. Removal efficiencies for chemical oxygen demand were 85% and 90% with influent MTBE concentrations of 5 and 10mg/l, but were significantly reduced to 72% with influent MTBE concentrations of 50mg/l. During all reactor runs, effluent concentrations oftert-butyl alcohol (TBA) were below the detection limit. Batch degradation of the organic substrate mixture demonstrated initial inhibitory effects when exposed to MTBE concentrations of 50 mg/l and complete inhibition with MTBE concentrations above 2000 mg/l. It is interesting to note that in batch tests using MTBE as the sole organic substrate (initial MTBE concentrations of 50, 100 and 200 mg/l), the specific methanogenic activity decreased to below detection within the first 96 hours, but following a 72-hour lag phase the methane production increased again. Based on low volatile fatty acid (VFA) concentration, disappearance of TBA peaks and no findings of any other intermediate via gas chromatography/mass spectrometry, while the MTBE concentration is still high, it can be suggested that during the batch tests the breakdown of gas production and the following lag phase were the direct effect of higher MTBE concentrations (more than 50 mg/l) and not because of the TBA or VFA accumulations. PMID:23240186

Ghasemian, Mohammad; Amin, Mohammad Mehdi; Morgenroth, Eberhard; Jaafarzadeh, Neemat

2012-09-01

7

Exposure of gasoline road-tanker drivers to methyl tert -butyl ether and methyl tert -amyl ether  

Microsoft Academic Search

Organic oxygenates, namely, methyl tert-butyl ether (MTBE) and methyl tert-amyl ether (MTAE), are added to gasoline to reduce carbon monoxide in exhausts and to enhance the octane number. The aim\\u000a of this study was to investigate road-tanker drivers' exposure to oxygenate vapors during road-tanker loading and unloading\\u000a as well as to evaluate the measurements of these ethers and their metabolites

Lauri Saarinen; Matti Hakkola; Kaija Pekari; Kaija Lappalainen; Antero Aitio

1998-01-01

8

Dissolution of cholesterol gallstones using methyl tert-butyl ether.  

PubMed

Symptomatic cholelithiasis affects a large segment of the population. Several nonoperative therapeutic alternatives for treatment of these gallstones have recently been developed. We present here the technical aspects and results of gallstone dissolution in 75 patients with the use of methyl tert-butyl ether (MTBE) administered via a small percutaneously placed cholecystostomy catheter. Successful stone dissolution was achieved in 69 patients. The average time required for stone dissolution was 12.4 h over an average of 2.4 days, with the success and rate of dissolution being very dependent on technique. Six patients have developed recurrent gallstones. Future efforts will focus on decreasing the labor intensity of the procedure, dealing with the noncholesterol components of gallstones, and preventing gallstone recurrence. PMID:2121355

Williams, H J; Bender, C E; LeRoy, A J

9

Enzymes and genes involved in the aerobic biodegradation of methyl tert -butyl ether (MTBE)  

Microsoft Academic Search

Fuel oxygenates, mainly methyl tert-butyl ether (MTBE) but also ethyl tert-butyl ether (ETBE), are added to gasoline in replacement of lead tetraethyl to enhance its octane index. Their addition also improves the combustion efficiency and therefore decreases the emission of pollutants (CO and hydrocarbons). On the other hand, MTBE, being highly soluble in water and recalcitrant to biodegradation, is a

Nicolas Lopes Ferreira; Cédric Malandain; Françoise Fayolle-Guichard

2006-01-01

10

Biodegradation of the gasoline oxygenates methyl tert-butyl ether, ethyl tert-butyl ether, and tert-amyl methyl ether by propane-oxidizing bacteria.  

PubMed Central

Several propane-oxidizing bacteria were tested for their ability to degrade gasoline oxygenates, including methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). Both a laboratory strain and natural isolates were able to degrade each compound after growth on propane. When propane-grown strain ENV425 was incubated with 20 mg of uniformly labeled [14C]MTBE per liter, the strain converted > 60% of the added MTBE to 14CO2 in < 30 h. The initial oxidation of MTBE and ETBE resulted in the production of nearly stoichiometric amounts of tert-butyl alcohol (TBA), while the initial oxidation of TAME resulted in the production of tert-amyl alcohol. The methoxy methyl group of MTBE was oxidized to formaldehyde and ultimately to CO2. TBA was further oxidized to 2-methyl-2-hydroxy-1-propanol and then 2-hydroxy isobutyric acid; however, neither of these degradation products was an effective growth substrate for the propane oxidizers. Analysis of cell extracts of ENV425 and experiments with enzyme inhibitors implicated a soluble P-450 enzyme in the oxidation of both MTBE and TBA. MTBE was oxidized to TBA by camphor-grown Pseudomonas putida CAM, which produces the well-characterized P-450cam, but not by Rhodococcus rhodochrous 116, which produces two P-450 enzymes. Rates of MTBE degradation by propane-oxidizing strains ranged from 3.9 to 9.2 nmol/min/mg of cell protein at 28 degrees C, whereas TBA was oxidized at a rate of only 1.8 to 2.4 nmol/min/mg of cell protein at the same temperature.

Steffan, R J; McClay, K; Vainberg, S; Condee, C W; Zhang, D

1997-01-01

11

ATTENUATION OF METHYL TERT-BUTYL ETHER IN WATER USING SUNLIGHT AND A PHOTOCATALYST  

EPA Science Inventory

The use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in increasing pollution of ground water. Most of the conventional treatment technologies are inefficient or costly when the initial concentration of MTBE is low (...

12

Determination of low level methyl tert-butyl ether, ethyl tert-butyl ether and methyl tert-amyl ether in human urine by HS-SPME gas chromatography\\/mass spectrometry  

Microsoft Academic Search

Methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) are oxygenated compounds added to gasoline to enhance octane rating and to improve combustion. They may be found as pollutants of living and working environments. In this work a robotized method for the quantification of low level MTBE, ETBE and TAME in human urine was developed and

Licia Scibetta; Laura Campo; Rosa Mercadante; Vito Foà; Silvia Fustinoni

2007-01-01

13

Selection and identification of bacterial strains with methyl-tert-butyl ether, ethyl-tert-butyl ether, and tert-amyl methyl ether degrading capacities.  

PubMed

Nine bacterial strains isolated from two hydrocarbon-contaminated soils were selected because of their capacity for growth in culture media amended with 200 mg/L of one of the following gasoline oxygenates: Methyl-tert-butyl ether (MTBE), ethyl-tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). These strains were identified by amplification of their 16S rRNA gene, using fDl and rD1 primers, and were tested for their capacity to grow and biotransform these oxygenates in both mineral and cometabolic media. The isolates were classified as Bacillus simplex, Bacillus drentensis, Arthrobacter sp., Acinetobacter calcoaceticus, Acinetobacter sp., Gordonia amicalis (two strains), Nocardioides sp., and Rhodococcus ruber. Arthrobacter sp. (strain MG) and A. calcoaceticus (strain M10) consumed 100 (cometabolic medium) and 82 mg/L (mineral medium) of oxygenate TAME in 21 d, respectively, under aerobic conditions. Rhodococcus ruber (strain E10) was observed to use MTBE and ETBE as the sole carbon and energy source, whereas G. amicalis (strain T3) used TAME as the sole carbon and energy source for growth. All the bacterial strains transformed oxygenates better in the presence of an alternative carbon source (ethanol) with the exception of A. calcoaceticus (strain M10). The capacity of the selected strains to remove MTBE, ETBE, and TAME looks promising for application in bioremediation technologies. PMID:18522454

Purswani, Jessica; Pozo, Clementina; Rodríguez-Díaz, Marina; González-López, Jesús

2008-11-01

14

Oxidation of Methyl tertButyl Ether (MTBE) and Ethyl tertButyl Ether (ETBE) by Ozone and Combined Ozone\\/Hydrogen Peroxide  

Microsoft Academic Search

The aim of this work was to study the reaction of ozone and combined ozone\\/hydrogen peroxide on oxygenated additives such as methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) in dilute aqueous solution using controlled experimental conditions. Experiments conducted in a semi-continuous reactor with MTBE and ETBE in combination (initial concentration: 2 mmol\\/L of each) showed that ETBE was

N. Karpel Vel Leitner; A.-L. Papailhou; J.-P. Croué; J. Peyrot; M. Doré

1994-01-01

15

Equilibrium constants for methyl tert-butyl ether and ethyl tert-butyl ether liquid-phase syntheses using C[sub 4] olefinic cut  

Microsoft Academic Search

Equilibrium constants for the liquid-phase syntheses of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) were determined experimentally in the temperature range 313--353 K and at 1.6 MPa, using as source of 2-methylpropene (isobutylene) a C[sub 4] olefinic cut proceeding from a steam cracking unit. To reach etherification equilibrium, the macroporous sulfonic acid resin K-2631 (Bayer) was used as

J. F. Izquierdo; F. Cunill; M. Vila; M. Iborra; J. Tejero

1994-01-01

16

Method for determination of methyl tert-butyl ether and its degradation products in water  

USGS Publications Warehouse

An analytical method is described that can detect the major alkyl ether compounds that are used as gasoline oxygenates (methyl tert-butyl ether, MTBE; ethyl tert-butyl ether, ETBE; and tert-amyl methyl ether, TAME) and their most characteristic degradation products (tert-butyl alcohol, TBA; tert-butyl formate, TBF; and tert-amyl alcohol, TAA) in water at sub-ppb concentrations. The new method involves gas chromatography (GC) with direct aqueous injection (DAI) onto a polar column via a splitless injector, coupled with detection by mass spectrometry (MS). DAI-GC/MS gives excellent agreement with conventional purge-and-trap methods for MTBE over a wide range of environmentally relevant concentrations. The new method can also give simultaneous identification of polar compounds that might occur as degradation products of gasoline oxygenates, such as TBA, TBF, TAA, methyl acetate, and acetone. When the method was applied to effluent from a column microcosm prepared with core material from an urban site in New Jersey, conversion of MTBE to TBA was observed after a lag period of 35 days. However, to date, analyses of water samples from six field sites using the DAI-GC/MS method have not produced evidence for the expected products of in situ degradation of MTBE.An analytical method is described that can detect the major alkyl ether compounds that are used as gasoline oxygenates (methyl tert-butyl ether, MTBE; ethyl tert-butyl ether, ETBE; and tert-amyl methyl ether, TAME) and their most characteristic degradation products (tert-butyl alcohol, TBA; tert-butyl formate, TBF; and tert-amyl alcohol, TAA) in water at sub-ppb concentrations. The new method involves gas chromatography (GC) with direct aqueous injection (DAI) onto a polar column via a splitless injector, coupled with detection by mass spectrometry (MS). DAI-GC/MS gives excellent agreement with conventional purge-and-trap methods for MTBE over a wide range of environmentally relevant concentrations. The new method can also give simultaneous identification of polar compounds that might occur as degradation products of gasoline oxygenates, such as TBA, TBF, TAA, methyl acetate, and acetone. When the method was applied to effluent from a column microcosm prepared with core material from an urban site in New Jersey, conversion of MTBE to TBA was observed after a lag period of 35 days. However, to date, analyses of water samples from six field sites using the DAI-GC/MS method have not produced evidence for the expected products of in situ degradation of MTBE.

Church, C. D.; Isabelle, L. M.; Pankow, J. F.; Rose, D. L.; Tratnyek, P. G.

1997-01-01

17

Isotopic fractionation of methyl tert-butyl ether suggests different initial reaction mechanisms during aerobic biodegradation.  

PubMed

Carbon isotopic enrichment factors (epsilonC) measured during cometabolic biodegradation of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME) by Pseudonocardia tetrahydrofuranoxydans strain K1 were -2.3 +/- 0.2 per thousand, -1.7 +/- 0.2 per thousand, and -1.7 +/- 0.3 per thousand, respectively. The measured carbon apparent kinetic isotope effect was 1.01 for all compounds, consistent with the expected kinetic isotope effects for both oxidation of the methoxy (or ethoxy) group and enzymatic SN1 biodegradation mechanisms. Significantly, delta13C measurements of the tert-butyl alcohol and tert-amyl alcohol products indicated that the tert-butyl and tert-amyl groups do not participate in the reaction and confirmed that ether biodegradation by strain K1 involves oxidation of the methoxy (or ethoxy) group. Measured hydrogen isotopic enrichment factors (epsilonH) were -100 +/- 10 per thousand, -73 +/- 7 per thousand, and -72 +/- 20 per thousand for MTBE, ETBE, and TAME respectively. Previous results reported for aerobic biodegradation of MTBE by Methylibium petroleiphilum PM1 and Methylibium R8 showed smaller epsilonH values (-35 per thousand and -42 per thousand, respectively). Plots of Delta2H/Delta13C show different slopes for strain K1 compared with strains PM1 and R8, suggesting that different mechanisms are utilized by K1 and PM1/R8 during aerobic MTBE biodegradation. PMID:19475952

McKelvie, Jennifer R; Hyman, Michael R; Elsner, Martin; Smith, Christy; Aslett, Denise M; Lacrampe-Couloume, Georges; Lollar, Barbara Sherwood

2009-04-15

18

Isothermal vapor-liquid equilibria for mixtures of methyl tert-butyl ether, methyl acetate, and ethyl acetate  

Microsoft Academic Search

A static apparatus was applied to measure isothermal vapor-liquid equilibrium (VLE) data for binary and ternary mixtures composed of methyl tert-butyl ether (MTBE), methyl acetate, and ethyl acetate at temperatures from 353 K to 373 K. Maximum pressure azeotropes were exhibited in the MTBE + methyl acetate system. All the binary data passed thermodynamic consistency tests. Data reduction was made

Ming-Jer Lee; Chien-Chih Hsiao; Ho-mu Lin

1997-01-01

19

Biodegradation of methyl tert -butyl ether by cold-adapted mixed and pure bacterial cultures  

Microsoft Academic Search

An aerobic mixed bacterial culture (CL-EMC-1) capable of utilizing methyl tert-butyl ether (MTBE) as the sole source of carbon and energy with a growth temperature range of 3 to 30°C and optimum of 18\\u000a to 22°C was enriched from activated sludge. Transient accumulation of tert-butanol (TBA) occurred during utilization of MTBE at temperatures from 3°C to 14°C, but TBA did

G. M. Zaitsev; J. S. Uotila; M. M. Häggblom

2007-01-01

20

Sorption of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) to synthetic resins.  

PubMed

Methyl tert-butyl ether (MTBE) is a widely used gasoline oxygenate. Contamination of MTBE and its major degradation product tert-butyl alcohol (TBA) in groundwater and surface water has received great attention. However, sorption affinity and sorption mechanisms of MTBE and TBA to synthetic resins, which can be potentially used in removal of these contaminants from water, in passive sampling, or in enrichment of bacteria, have not been studied systemically. In this study, kinetic and equilibrium sorption experiments (single solute and binary mixtures) on four synthetic resins were conducted. The sorption affinity of the investigated sorbents for MTBE and TBA decreases in the order Ambersorb 563>Optipore L493>Amberlite XAD4>Amberlite XAD7, and all show higher sorption affinity for MTBE than for TBA. Binary experiments with o-xylene, a major compound of gasoline as co-contaminant, imply that all resins preferentially sorb o-xylene over MTBE or TBA, i.e., there is sorption competition. In the equilibrium aqueous concentration (Ceq) range (0.1-139.0 mg/L for MTBE, and 0.01-48.4 mg/L for TBA), experimental and modeling results as well as sorbent characteristics indicate that micropore filling and/or some other type of adsorption process (e.g., adsorption to specific sites of high sorption potential at low concentrations) rather than partitioning were the dominant sorption mechanisms. Optipore L493 has favourable sorption and desorption characteristics, and is a suitable sorbent, e.g., in bacteria enrichment or passive sampling for moderately polar compounds. However, for highly polar compounds such as TBA, Ambersorb 563 might be a better choice, especially in water treatment. PMID:16139865

Bi, Erping; Haderlein, Stefan B; Schmidt, Torsten C

2005-09-02

21

Biotransformation and kinetics of excretion of methyl-tert-butyl ether in rats and humans  

Microsoft Academic Search

Methyl-tert-butyl ether (MTBE) is widely used as an additive to gasoline to increase oxygen content and reduce tail pipe emission of pollutants. Therefore, widespread human exposure may occur. To contribute to the characterization of potential adverse effects of MTBE, its biotransformation was compared in humans and rats after inhalation exposure. Human volunteers (3 males and 3 fe- males) and rats

Alexander Amberg; Elisabeth Rosner; Wolfgang Dekant

1999-01-01

22

Toxicity of methyl tert-butyl ether to marine organisms: ambient water quality criteria calculation  

Microsoft Academic Search

In response to increasing concerns over the detection of methyl tert-butyl ether (MTBE) in groundwater and surface water and its potential effects in aquatic ecosystems, industry and the United States Environmental Protection Agency (USEPA) began to collaborate in 1997 to develop aquatic toxicity databases sufficient to derive ambient water quality criteria for MTBE consistent with USEPA requirements. Acute toxicity data

Gary A. Rausina; Diana C. L. Wong; W. Raymon Arnold; Eugene R. Mancini; Alexis E. Steen

2002-01-01

23

Determination of Methyl tertButyl Ether in Air Using a Diffusive Sampler  

Microsoft Academic Search

United States production of methyl tert-butyl ether (MTBE) has risen more than 25% in the past decade. It is used in oxygenated fuel formulations as a response to mandates of the Clean Air Act. Recently, a method for the determination of MTBE in gasoline vapors was published by the National Institute for Occupational Safety and Health (NIOSH), which involves collection

Martin Harper; Amy A. Fiore

1995-01-01

24

ATTENUATION OF METHYL TERT-BUTYL ETHER IN WATER USING SUNLIGHT AND A PHOTOCATALYST: JOURNAL ARTICLE  

EPA Science Inventory

NRMRL-CIN-1535 Sahle-Demessie*, E., Enriquez*, J., and Gupta, G. Attenuation of Methyl tert-Butyl Ether in Water using Sunlight and a Photocatalyst. Water Environment Research (Virginia: Water Environment Federation) 74 (2):122-130 (2002). EPA/600/J-02/236. 07/19/2001 The use o...

25

PHOTOCATALYTIC OXIDATION OF METHYL-TERT-BUTYL ETHER FOR DRINKING WATER TREATMENT  

EPA Science Inventory

The photo-oxidation of methyl tert-butyl ether (MTBE) in water was investigated to determine the feasibility of using photocatalysis for the treatment of MTBE-contaminated drinking water. The feasibility assessment was conducted using slurries of titanium dioxide in both a photo-...

26

Methyl tert-Butyl Ether (MTBE) in Ground Water, Air, and Precipitation at North Windham, Maine.  

National Technical Information Service (NTIS)

Thirty-one monitoring wells in the Windham aquifer in North Windham, Maine, were sampled for methyl tert-butyl ether (MTBE) from July 1998 to May 1999. MTBE was detected in 35 percent of the wells sampled in the Windham aquifier. MTBE was detected in 64 p...

M. G. Nielsen J. M. Peckenham

2000-01-01

27

STRUCTURES AND BINDING ENERGIES OF METHYL TERT-BUTYL ETHER-WATER COMPLEXES  

EPA Science Inventory

Methyl tert-butyl ether (MTBE) is a well-known environmental contaminant owing to its high solubility in water. Since the early 1990s, MTBE has been added to gasoline to improve air quality in some metropolitan areas of the United States. Improved air quality was, however, achiev...

28

Gallstone dissolution in vitro using methyl tert-butyl ether: radiologic selection criteria.  

PubMed

Methyl tert-butyl ether dissolves cholesterol gallbladder stones when infused through a percutaneous transhepatic catheter. All gallstones, however, contain noncholesterol components that are insoluble in lipid solvents and may be too large to be aspirated through a small catheter or flushed from the gallbladder. To identify which patients have gallstones that are most likely to completely dissolve, we evaluated the ability of methyl tert-butyl ether to dissolve gallstones in vitro based on their radiodensity and size. Radiodensity influenced completeness of dissolution (p less than 0.01), but size did not (p greater than 0.5). Twenty-six of 32 radiolucent stones (81%) dissolved completely, leaving residual debris less than 2 mm in diameter. Only 2 of 32 radiopaque stones (6%) dissolved completely. Insoluble radiolucent and radiopaque stones less than 0.5 cm in diameter were black pigment stones. Four radiolucent and 19 of 22 radiopaque stones (86%) greater than 0.5 cm in diameter underwent partial dissolution leaving residual debris 2 mm or larger. By infrared spectroscopy, calcium bilirubinate and calcium carbonate were identified as the principal components of this methyl tert-butyl ether-insoluble debris. Until methods for dissolving or fragmenting noncholesterol components of gallstones are available, only patients with radiolucent gallstones should be treated with methyl tert-butyl ether. PMID:2323520

Nelson, P E; Moyer, T P; Thistle, J L

1990-05-01

29

The screening of microorganisms capable of methyl tert-butyl ether (MTBE) biodegradation.  

PubMed

As a result of examinations carried out, 16 strains of microorganisms able to grow on mineral media with methyl tert-butyl ether as the sole source of carbon and energy were isolated. Bacteria prevailed among the isolated microorganisms. The growth of microorganisms under laboratory conditions was long and accompanied by low biomass increase. Under the conditions of the experiment, the isolated microorganisms did not show any quantitatively measurable biodegradability of methyl tert-butyl ether (MTBE) under aerobic conditions. This requires far-reaching caution with respect to trading in MTBE-modified petrols in order to protect the natural environment in Poland against contamination with that hard-to-biodegrade substance. PMID:24053017

Wieczorek, Andrzej; Przybulewska, Krystyna; Karpowicz, Katarzyna; Nowak, Maciej J

2013-01-01

30

Review of the environmental behavior and fate of methyl tert-butyl ether  

Microsoft Academic Search

A review of pertinent equations and current research indicates that when gasoline oxygenated with methyl tert-butyl ether (MTBE) comes into contact with water, large amounts of MTBe can dissolve. At 25 C, the water solubility of MTBE is about 5,000 mg\\/L for a gasoline that is 10% MTBE by weight, whereas for a nonoxygenated gasoline, the total hydrocarbon solubility in

Paul J. Squillace; J. S. Zogorski; J. F. Pankow; N. E. Korte

1997-01-01

31

Biodegradation of Methyl Tert -butyl Ether in a Bioreactor using Immobilized Methylibium petroleiphilum PM1 Cells  

Microsoft Academic Search

Methylibium petroleiphilum PM1, which is capable of degrading of methyl tert-butyl ether (MTBE), was immobilized in calcium alginate gel beads. Various applications were explored to increase the mechanical\\u000a strength of these gel beads. The introduction of 0.3 mol\\/L calcium chloride into the crosslinking solution, 0.002 mol\\/L calcium\\u000a chloride into the growth medium, and 0.2% polyethyleneimine (PEI) as chemical crosslinking agent increased the

Zhuo-Wei Cheng; Jian-Meng Chen; Dong-Zhi Chen; Li-Li Zhang

2011-01-01

32

Exposure to methyl tert-butyl ether and benzene among service station attendants and operators  

Microsoft Academic Search

Concerns for atmospheric pollution from auto exhaust have led to the blending of {open_quotes}oxygenates{close_quotes} with motor fuels. The most common oxygenate, methyl tert-butyl ether (MTBE) is currently required within several metropolitan areas (Denver and Phoenix) in the range of 12% of the motor fuel. Amendments to the Clean Air Act may expand this requirement to as many as 44 other

Hartle

1993-01-01

33

Effect of operating conditions on pervaporation of methanol\\/methyl tert-butyl ether mixtures  

Microsoft Academic Search

Methanol\\/methyl tert-butyl ether (MTBE) mixtures were separated by pervaporation (PV) using polyvinyl alcohol (PVA) membranes. Effects of operating conditions such as temperature, permeate pressure, feed flow rate and composition on the membrane performance were studied. Experimental results were obtained at different methanol concentrations (10–30wt.%) and temperatures (25–45°C) as well as vacuum pressures in the range of 15–35mbar. Separation factor of

Mehrnaz Peivasti; Ali Madandar; Toraj Mohammadi

2008-01-01

34

Application of butane isomerization and dehydrogenation processes for the production of methyl tert-butyl ether  

Microsoft Academic Search

Methyl tert-butyl ether (MTBE) is analyzed for economic efficiency in the stage of blending commercial automotive gasolines. Calculations were performed in applications to a hypothetical refinery with relatively mild crude oil processing, manufacturing unleaded AI-93 and A-76 gasoline in a 20:80 ratio. The composition of commercial automotive gasolines before and after the use of MTBE is shown and techno-economic indexes

N. R. Bursian; P. N. Borutskii; S. B. Kogan; M. L. Kolesov; G. A. Lastovkin; A. A. Yakovlev

1988-01-01

35

Lipid extraction by methyl-tert-butyl ether for high-throughput lipidomics  

Microsoft Academic Search

Accurate profiling of lipidomes relies upon the quantitative and unbiased recovery of lipid species from analyzed cells, fluids, or tissues and is usually achieved by two-phase extraction with chloroform. We demonstrated that methyl-tert-butyl ether (MTBE) extraction allows faster and cleaner lipid recovery and is well suited for automated shotgun profiling. Because of MTBE's low density, lipid-containing organic phase forms the

Vitali Matyash; Gerhard Liebisch; Teymuras V. Kurzchalia; Andrej Shevchenko; Dominik Schwudke

2008-01-01

36

Gallstone dissolution in methyl tert-butyl ether after mechanical fragmentation: in vitro study.  

PubMed

Twenty sets of three gallstones matched for weight and appearance were selected from 20 surgically resected human gallbladders to test the effect of intracorporeal mechanical fragmentation on gallstone dissolution with methyl tert-butyl ether in vitro. One stone from each set was fragmented by a mechanical lithotriptor and then treated with methyl tert-butyl ether, and one was used as control and was treated intact. The third stone was analyzed for its density pattern on CT and biochemically for its cholesterol and calcium content. On the basis of CT appearance, the stones were classified as noncalcified, partially calcified, or heavily calcified. Mechanical fragmentation reduced dissolution time by 25-69% (mean +/- SD, 44 +/- 16%) for the noncalcified stones and by 20-42% (mean +/- SD, 30 +/- 8%) for the partially calcified stones. No significant reduction was observed for the heavily calcified stones. The degree of reduction was inversely related to maximal stone density (r = -.72) and was independent of its pattern of calcification. This study shows that mechanical fragmentation is effective in accelerating gallstone chemolysis by methyl tert-butyl ether for noncalcified and partially calcified but not for heavily calcified stones. PMID:2112866

Lu, D S; Ho, C S; Allen, L C

1990-07-01

37

Manual and automatic gallstone dissolution with methyl tert -butyl ether  

Microsoft Academic Search

The aim of the study was to establish the efficiency of cholesterol gallstone dissolution with methyltert-butyl ether in a large group of patients and to compare the results of patients treated manually by a nurse or using an automatic pump. Gallbladder puncture was successful in 228 patients (99%). After 9 hr, 211 patients (91%) were stone-free; 144 (68%) of them

U. Leuschner; A. Hellstern; A. Ansell; M. Gatzen; S. Güldütuna; M. Leuschner

1994-01-01

38

[Cytotoxicity and genotoxicity of methyl tert-butyl ether and its metabolite to human leukemia cells].  

PubMed

DNA damage of human leukemia (HL-60) cells caused by methyl tert-butyl ether (MTBE), a new gasoline additive, and its metabolites tert-butyl alcohol (TBA), a-hydroxyisobutyric acid (HIBA) and formaldehyde was determined by single cell gel electrophoresis (SCGE), with release of lactate dehydrogenase as an indicator for evaluating its cytotoxicity. Results showed that MTBE, TBA and HUBA at levels of 1 to 30 mmol/L could cause DNA damage in a dose-dependent pattern. Formaldehyde at level of 5 mumol/L could cause DNA damage, but at a higher level could decrease DNA migration. It suggested that MTBE and its metabolites could have genotoxicity, however, with doses causing genotoxic effects, no cytotoxic effect by MTBE, TBA and HIBA was observed, but formaldehyde presented obvious cytotoxic effect. PMID:9863065

Tang, G; Wang, J; Zhuang, Z

1997-11-01

39

Biotransformation of methyl tert-butyl ether by human cytochrome P450 2A6.  

PubMed

Methyl tert-butyl ether (MTBE) is widely used as gasoline oxygenate and octane number enhancer for more complete combustion in order to reduce the air pollution caused by motor vehicle exhaust. The possible adverse effects of MTBE on human health are of major public concern. However, information on the metabolism of MTBE in human tissues is scarce. The present study demonstrates that human cytochrome P450 2A6 is able to metabolize MTBE to tert-butyl alcohol (TBA), a major circulating metabolite and marker for exposure to MTBE. As CYP2A6 is known to be constitutively expressed in human livers, we infer that it may play a significant role in metabolism of gasoline ethers in liver tissue. PMID:21915685

Shamsipur, Mojtaba; Miran Beigi, Ali Akbar; Teymouri, Mohammad; Poursaberi, Tahereh; Mostafavi, S Mojtaba; Soleimani, Parviz; Chitsazian, Fereshteh; Tash, Shahram Abolhassan

2011-09-14

40

ETBE (ethyl tert butyl ether) and TAME (tert amyl methyl ether) affect microbial community structure and function in soils.  

PubMed

Ethyl tert butyl ether (ETBE) and tert amyl methyl ether (TAME) are oxygenates used in gasoline in order to reduce emissions from vehicles. The present study investigated their impact on a soil microflora that never was exposed to any contamination before. Therefore, soil was artificially contaminated and incubated over 6 weeks. Substrate induced respiration (SIR) measurements and phospholipid fatty acid (PLFA) analysis indicated shifts in both, microbial function and structure during incubation. The results showed an activation of microbial respiration in the presence of ETBE and TAME, suggesting biodegradation by the microflora. Furthermore, PLFA concentrations decreased in the presence of ETBE and TAME and Gram-positive bacteria became more dominant in the microbial community. PMID:21288640

Bartling, Johanna; Esperschütz, Jürgen; Wilke, Berndt-Michael; Schloter, Michael

2011-01-20

41

Determination of methyl tert-butyl ether in gasoline by infrared spectrometry  

SciTech Connect

An infrared method for determination of the concentration of ethanol in gasoline has been extended to include the determination of methyl tert-butyl ether in gasoline. Quantitative methods using attenuated total reflectance and transmittance measurements have been developed. Both techniques appear to be readily adaptable to on-stream processes. The ZnSe used in the windows and crystal is impervious to attack by water and is fairly durable as long as uneven stress is not applied to the crystal. The use of either technique provides reliable results in short time. 1 figure.

Fry, S.E.; Fuller, M.P.; White, F.T.; Battiste, D.R.

1983-02-01

42

Kinetics and effectiveness of catalyst for synthesis of methyl tert-butyl ether in catalytic distillation  

SciTech Connect

The macrokinetics and intrinsic kinetics were measured for synthesis of methyl tert-butyl ether (MTBE) within the catalyst bed packed in a special way in an industrialized catalytic distillation column. The corresponding kinetic equations for forward and backward reactions were obtained. The variation of total effectiveness factor of the catalyst considering the diffusion in the catalyst pocket and within a granule of catalyst with reaction temperature and diameter of the pocket was calculated from the results measured. It was indicated that the effect of the catalyst packed in this way could not be revealed under the present operation condition.

Xu, X.; Zheng, Y.; Zheng, G. [Tianjin Univ. (China). Dept. of Chemical Engineering

1995-07-01

43

Application of butane isomerization and dehydrogenation processes for the production of methyl tert-butyl ether  

SciTech Connect

Methyl tert-butyl ether (MTBE) is analyzed for economic efficiency in the stage of blending commercial automotive gasolines. Calculations were performed in applications to a hypothetical refinery with relatively mild crude oil processing, manufacturing unleaded AI-93 and A-76 gasoline in a 20:80 ratio. The composition of commercial automotive gasolines before and after the use of MTBE is shown and techno-economic indexes of automotive gasoline production in different processing schemes are given. The use of MTBE in combination with low-octane isomerizate may increase outputs of gasoline by 3.2%.

Bursian, N.R.; Borutskii, P.N.; Kogan, S.B.; Kolesov, M.L.; Lastovkin, G.A.; Yakovlev, A.A.

1988-03-01

44

[Dissolution of gallbladder lithiasis with methyl tert-butyl ether (MTBE). Preliminary results in 9 cases].  

PubMed

Instillation of Methyl tert-butyl ether in the gallbladder permits the dissolution of cholesterol stones. Percutaneous transhepatic puncture of the gallbladder is the currently used approach; but shortcomings of this procedure could make the transpapillary cannulation of the cystic duct preferable. The reproducibility of this procedure, however, is not established. "In situ" dissolution is useful in cases of multiples stones which are not amenable to treatment with extra corporeal shock wave lithotripsy (ESWL). It can also be complementary to standard ESWL by promoting rapid disappearance of stones fragments. Preliminary results obtained in 9 patients suggest the necessity of rigorous selection criterias particularly regarding the chemical nature of the stones. PMID:2279442

Liguory, C; Lefebvre, J F; Bonnel, D; Cornud, F

1990-01-01

45

Enhancement of methyl tert-butyl ether degradation by the addition of readily metabolizable organic substrates.  

PubMed

Supplements with readily metabolizable organic substrates were investigated to increase the biomass and enhance degradation of methyl tert-butyl ether (MTBE) due to the low biomass yield of MTBE which has been one of the factors for low-rate MTBE degradation. The influence of various organic substrates on the rate of aerobic degradation of methyl tert-butyl ether (MTBE) by Methylibium petroleiphilum PM1 was investigated, and only yeast extract (YE), beef extract and tryptone exhibited stimulatory effect. With the concentration of each substrate being 100 mg/L, the average MTBE removal rate could increase to 1.29, 1.20 and 1.04 mg/(Lh), respectively, in comparison with 0.71 mg/(Lh) when carried out in medium without addition. The stimulatory effects of YE addition, as well as induction period required by MTBE degradation, varied dramatically with the storage conditions, pre-culture medium and concentrations of the inoculums. The extent of stimulatory effects of YE might be closely related to the proportion of induction period in the total time of MTBE-degradation. The removal efficiency increased from about 50% to 90.5% with the addition of YE in a packed-bed reactor loaded with calcium alginate immobilized cells. PMID:19231071

Chen, Dongzhi; Chen, Jianmeng; Zhong, Weihong

2009-02-23

46

Gall stone dissolution with methyl tert-butyl ether: how to avoid complications.  

PubMed

Fifty of 52 patients with cholesterol gall bladder stones were treated with methyl tert-butyl ether. In 48 of 50 (96%) patients the stones dissolved after an average interval of 9.5 hours. Mean stone size was 1.7 cm (0.5-3.3 cm), mean stone number was 14.6 (1-70). Twelve patients (24%) complained of nausea, a burning sensation, or vomiting. In one patient bile leakage occurred and another suffered haematobilia (4%). The puncture set was improved, and a special basket was developed to extract stones that had escaped into the cystic duct. To prevent bile leakage or haemorrhage from the incision channel, a tissue adhesive was injected into the channel or ceruletid was administered subcutaneously before removing the catheter to induce contraction of the gall bladder. Thus we were able to treat 44 patients without any complications. Nausea and vomiting could be reduced if the treatment time was kept short and the perfusion volume was as low as possible. Methyl tert-butyl ether treatment is a successful treatment of gall bladder stones with few complications. PMID:2387519

Hellstern, A; Leuschner, M; Frenk, H; Dillinger, H W; Caspary, W; Leuschner, U

1990-08-01

47

Methyl tert-butyl ether (MTBE) degradation by a microbial consortium.  

PubMed

The widespread use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in a large number of cases of groundwater contamination. Bioremediation is often proposed as the most promising alternative after treatment. However, MTBE biodegradation appears to be quite different from the biodegradation of usual gasoline contaminants such as benzene, toluene, ethyl benzene and xylene (BTEX). In the present paper, the characteristics of a consortium degrading MTBE in liquid cultures are presented and discussed. MTBE degradation rate was fast and followed zero order kinetics when added at 100 mg l(-1). The residual MTBE concentration in batch degradation experiments ranged from below the detection limit (1 microg l(-1)) to 50 microg l(-1). The specific activity of the consortium ranged from 7 to 52 mgMTBE g(dw)(-1) h(-1) (i.e. 19-141 mgCOD g(dw) (-1) h(-1)). Radioisotope experiments showed that 79% of the carbon-MTBE was converted to carbon-carbon dioxide. The consortium was also capable of degrading a variety of hydrocarbons, including tert-butyl alcohol (TBA), tert-amyl methyl ether (TAME) and gasoline constituents such as benzene, toluene, ethylbenzene and xylene (BTEX). The consortium was also characterized by a very slow growth rate (0.1 d(-1)), a low overall biomass yield (0.11 gdw g(-1)MTBE; i.e. 0.040 gdw gCOD(-1)), a high affinity for MTBE and a low affinity for oxygen, which may be a reason for the slow or absence of MTBE biodegradation in situ. Still, the results presented here show promising perspectives for engineering the in situ bioremediation of MTBE. PMID:11472505

Fortin, N Y; Morales, M; Nakagawa, Y; Focht, D D; Deshusses, M A

2001-06-01

48

Determination of low level methyl tert-butyl ether, ethyl tert-butyl ether and methyl tert-amyl ether in human urine by HS-SPME gas chromatography/mass spectrometry.  

PubMed

Methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) are oxygenated compounds added to gasoline to enhance octane rating and to improve combustion. They may be found as pollutants of living and working environments. In this work a robotized method for the quantification of low level MTBE, ETBE and TAME in human urine was developed and validated. The analytes were sampled in the headspace of urine by SPME in the presence of MTBE-d12 as internal standard. Different fibers were compared for their linearity and extraction efficiency: carboxen/polydimethylsiloxane, polydimethylsiloxane/divinylbenzene, and polydimethylsiloxane. The first, although highly efficient, was discarded due to deviation of linearity for competitive displacement, and the polydimethylsiloxane/divinylbenzene fiber was chosen instead. The analysis was performed by GC/MS operating in the electron impact mode. The method is very specific, with range of linearity 30-4600 ng L(-1), within- and between-run precision, as coefficient of variation, <22 and <16%, accuracy within 20% the theoretical level, and limit of detection of 6 ng L(-1) for all the analytes. The influence of the matrix on the quantification of these ethers was evaluated analysing the specimens of seven traffic policemen exposed to autovehicular emissions: using the calibration curve and the method of standard additions comparable levels of MTBE (68-528 ng L(-1)), ETBE (<6 ng L(-1)), and TAME (<6 ng L(-1)) were obtained. PMID:17386425

Scibetta, Licia; Campo, Laura; Mercadante, Rosa; Foà, Vito; Fustinoni, Silvia

2006-08-07

49

Single-walled carbon nanotubes as an effective adsorbent in solid-phase microextraction of low level methyl tert-butyl ether, ethyl tert-butyl ether and methyl tert-amyl ether from human urine.  

PubMed

Carbon nanotubes (CNTs) are a kind of new carbon-based nano-materials which have drawn great attention in many application fields. The potential single-walled carbon nanotubes (SWCNTs) as solid-phase microextraction (SPME) adsorbents for the preconcentration of environmental pollutants have been investigated in recent years. The goal of this work was to investigate the feasibility of SWCNTs used as adsorbents for solid-phase microextraction of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) in human urine. SWCNTs were attached onto a stainless steel wire through organic binder. Potential factors affecting the extraction efficiency were optimized, including extraction time, extraction temperature, desorption time, desorption temperature, and salinity. The developed method showed good performance according to the ICH performance criteria for bioanalytical methods. The calibration curves of the ethers were linear (r(2)>or=0.992) in the range from 10 to 5000 ng L(-1). The limits of detection at a signal-to-noise (S/N) ratio of 3 were 10 ng L(-1) for all the analytes. In addition, compared with the commercial carboxen/polydimethylsiloxane (CAR/PDMS) fiber, the SWCNT fiber showed better thermal stability (over 350 degrees C) and longer life span (over 150 times). The developed method was applied successfully to determine trace level of the ethers in urine of 10 healthy male volunteers. PMID:19395320

Rastkari, Noushin; Ahmadkhaniha, Reza; Yunesian, Masud

2009-04-07

50

Combination of extracorporeal shock-wave lithotripsy and dissolution of gallbladder stones with methyl tert-butyl ether: a randomized study.  

PubMed

We conducted a prospective randomized study in gallstone patients to determine whether a combination of extracorporeal shock-wave lithotripsy and subsequent dissolution with methyl tert-butyl ether increases the success rate of methyl tert-butyl ether dissolution and shortens treatment time compared with monotherapy with methyl tert-butyl ether. Fifty patients were randomized into two groups. Twenty-five patients underwent extracorporeal shock-wave lithotripsy before contact dissolution with methyl tert-butyl ether, and 25 patients were treated with methyl tert-butyl ether alone. All patients had at least three stones or stones larger than 30 mm that were radiolucent on x-ray and had densities of less than 140 Hounsfield Units (HU) on computed tomography. Overall, the combined approach neither shortened the treatment time significantly vs. monotherapy with methyl tert-butyl ether nor reduced the time of hospitalization. The success rate was slightly but not significantly increased compared with that of methyl tert-butyl ether therapy alone. The recurrence rate was similar in the two groups after a median follow-up of 1 yr. However, when subgroups of patients with at least one stone larger than 15 mm or with stones with densities of more than 60 HU were analyzed, the clearance rate after 5 mo was significantly higher (p < 0.005 and p < 0.025, respectively) in patients subjected to a combination of extracorporeal shock-wave lithotripsy and methyl tert-butyl ether dissolution. Extracorporeal shock-wave lithotripsy and methyl tert-butyl ether did not expose patients to more adverse effects than did treatment with methyl tert-butyl ether alone. PMID:8276350

Neubrand, M; Holl, J; Sackmann, M; Klüppelberg, U; Pauletzki, J; Paumgartner, G; Sauerbruch, T

1994-01-01

51

Characterization of the Initial Reactions during the Cometabolic Oxidation of Methyl tertButyl Ether by Propane-Grown Mycobacterium vaccae JOB5  

Microsoft Academic Search

The initial reactions in the cometabolic oxidation of the gasoline oxygenate, methyl tert-butyl ether (MTBE), by Mycobacterium vaccae JOB5 have been characterized. Two products, tert-butyl formate (TBF) and tert-butyl alcohol (TBA), rapidly accumulated extracellularly when propane-grown cells were incubated with MTBE. Lower rates of TBF and TBA production from MTBE were also observed with cells grown on 1- or 2-propanol,

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

2003-01-01

52

Method for determination of methyl tert-butyl ether in gasoline by gas chromatography.  

PubMed

A simple method for the determination of methyl tert-butyl ether (MTBE) in gasoline has been developed. The separation of MTBE from other analytes was controlled by the use of gas chromatography-mass spectrometry in the full scan mode using the characteristic primary, secondary and tertiary ions m/z 73, 57 and 43. The sample mass spectrum did not show any superimposition of other analytes. The separation from the common gasoline component 2-methylpentane was sufficient for reliable quantitation. An application of the developed conditions using gas chromatography with flame ionization detection was performed by the analysis of regular, euro super, super premium unleaded and 'Optimax' gasoline from petrol stations in the area of Frankfurt/Main, Germany. Regular unleaded gasoline shows an average MTBE content of 0.4% (w/w), whereas the MTBE content in euro super gasoline varies between 0.4 and 4.2% (w/w). The blending of MTBE to super premium has increased from 8.2% (w/w) in 1998 to 9.8% (w/w) on average in 1999. The recently introduced gasoline 'Optimax' shows an average MTBE content of 11.9% (w/w). The presented method might also be used for the analysis of other ethers, such as ethyl tert-butyl ether, which requires the use of another internal standard. PMID:11261733

Achten, C; Püttmann, W

2001-03-01

53

Biodegradation of Methyl tert-Butyl Ether by a Pure Bacterial Culture  

PubMed Central

Biodegradation of methyl tert-butyl ether (MTBE) by the hydrogen-oxidizing bacterium Hydrogenophaga flava ENV735 was evaluated. ENV735 grew slowly on MTBE or tert-butyl alcohol (TBA) as sole sources of carbon and energy, but growth on these substrates was greatly enhanced by the addition of a small amount of yeast extract. The addition of H2 did not enhance or diminish MTBE degradation by the strain, and MTBE was only poorly degraded or not degraded by type strains of Hydrogenophaga or hydrogen-oxidizing enrichment cultures, respectively. MTBE degradation activity was constitutively expressed in ENV735 and was not greatly affected by formaldehyde, carbon monoxide, allyl thiourea, or acetylene. MTBE degradation was inhibited by 1-amino benzotriazole and butadiene monoepoxide. TBA degradation was inducible by TBA and was inhibited by formaldehyde at concentrations of >0.24 mM and by acetylene but not by the other inhibitors tested. These results demonstrate that separate, independently regulated genes encode MTBE and TBA metabolism in ENV735.

Hatzinger, Paul B.; McClay, Kevin; Vainberg, Simon; Tugusheva, Marina; Condee, Charles W.; Steffan, Robert J.

2001-01-01

54

Enzymes and genes involved in the aerobic biodegradation of methyl tert-butyl ether (MTBE).  

PubMed

Fuel oxygenates, mainly methyl tert-butyl ether (MTBE) but also ethyl tert-butyl ether (ETBE), are added to gasoline in replacement of lead tetraethyl to enhance its octane index. Their addition also improves the combustion efficiency and therefore decreases the emission of pollutants (CO and hydrocarbons). On the other hand, MTBE, being highly soluble in water and recalcitrant to biodegradation, is a major pollutant of water in aquifers contaminated by MTBE-supplemented gasoline during accidental release. MTBE was shown to be degraded through cometabolic oxidation or to be used as a carbon and energy source by a few microorganisms. We have summarized the present state of knowledge about the microorganisms involved in MTBE degradation and the MTBE catabolic pathways. The role of the different enzymes is discussed as well as the rare and recent data concerning the genes encoding the enzymes involved in the MTBE pathway. The phylogeny of the microorganisms isolated for their capacity to grow on MTBE is also described. PMID:16804692

Lopes Ferreira, Nicolas; Malandain, Cédric; Fayolle-Guichard, Françoise

2006-06-28

55

INTERACTION OF METHYL-TERT BUTYL ETHER AND WATER STRESS ON SEED GERMINATION AND SEEDLING GROWTH IN SOIL MICROCOSMS  

EPA Science Inventory

Methyl tert-butyl ether (MTBE) is a widespread contaminant in surface and ground water in the United States. Frequently irrigation is used to water fields to germinate planted seeds and sustain plant growth. A likely possibility exists that water used may have some MTBE. Our s...

56

Treatment Of Groundwater Contaminated With PAHs, Gasoline Hydrocarbons, And Methyl Tert -Butyl Ether In A Laboratory Biomass-Retaining Bioreactor  

EPA Science Inventory

In this study, we investigated the treatability of co-mingled groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs), gasoline hydrocarbons, and methyl tert -butyl ether (MtBE) using an ex-situ aerobic biotreatment system. The PAHs of interest were nap...

57

EVALUATION OF METHYL TERT-BUTYL ETHER (MTBE) AS AN INTERFERENCE ON COMMERCIAL BREATH-ALCOHOL ANALYZERS  

EPA Science Inventory

Anecdotal reports suggest that high environmental or occupational exposures to the fuel oxygenate methyl tert-butyl ether (MTBE) may result in breath concentrations that are sufficiently elevated to cause a false positive on commercial breath-alcohol analyzers. We evaluated th...

58

Photocatalytic degradation of methyl- tert-butyl ether in TiO 2 slurries: A proposed reaction scheme  

Microsoft Academic Search

Among the various alternatives to enhance the octane rating of gasoline, methyl-tert-butyl ether (MTBE) has become increasingly the compound of choice. Due to its high solubility in water there are some environmental concerns related to the remediation of waters contaminated with gasoline containing MTBE. Although MTBE is difficult to treat economically with conventional techniques, it has been found to be

Reynaldo D. Barreto; Kimberly A. Gray; Krista Anders

1995-01-01

59

Attenuation of methyl tert-butyl ether in water using sunlight and a photocatalyst.  

PubMed

The use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in increasing pollution of groundwater. Most of the conventional treatment technologies are inefficient or costly when the initial concentration of MTBE is low (< 200 microg/L). To find an ecology friendly and inexpensive method for MTBE remediation, we used solar radiation with titanium dioxide (TiO2) as a photocatalyst. For synthetic samples, almost complete degradation (99+%) of MTBE was observed at the end of 5-hour test run with 0.05 g/L of slurry TiO2. Intermediate products detected were tertiary butyl formate, tertiary butyl alcohol, and trace amounts of acetone. Studies conducted using contaminated groundwater samples with TiO2 and sunlight showed that aromatic organic species benzene, toluene, ethylbenzene, and xylenes (BTEX) were degraded up to a factor of 10 times faster than MTBE. However, dissolved metals (Fe2+) and chloride ions in contaminated waters decreased the photo-activity of TiO2 for the degradation of MTBE. Reducing the pH of the groundwater samples increased the MTBE degradation rate threefold. Photocatalysis accelerates the solar degradation of MTBE and reduces its half-life by more than 3 orders of magnitude. The study indicated that solar degradation is a low-cost and effective alternative to attenuate MTBE in drinking water supplies. PMID:12043968

Sahle-Demessie, E; Enriquez, J; Gupta, G

60

High levels of monoaromatic compounds limit the use of solid-phase microextraction of methyl tert-butyl ether and tert-butyl alcohol.  

PubMed

Recently, two papers reported the use of solid-phase microextraction (SPME) with poly(dimethylsiloxane)(PDMS)/Carboxen fibers to determine trace levels of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (tBA) in water. Attempts were made to apply this technique to the analysis of water samples containing high levels of benzene, toluene, ethylbenzene, xylenes, and trimethylbenzenes (BTEXsTMBs) as would be expected at leaking underground storage tank sites. It was found that when the sample contained total aromatic compounds above 1 ppm, the response of the internal standards, deuterated MTBE and tBA, dropped by more than 65%. As this decrease in internal standard peak area was unacceptable, a static headspace method was used instead. This headspace method was used successfully to analyze groundwater from 670 monitoring wells at 74 service stations located in the northeast United States. In these monitoring wells, 30% of the samples contained total BTEXsTMBs above 1 ppm. If the SPME method was used to analyze these samples, dilution of more than 200 samples would be required to minimize the adverse matrix effect that high aromatic content had on the internal standard peak area. PMID:11506001

Black, L; Fine, D

2001-08-01

61

Determination of methyl tert-butyl ether and tert-butyl alcohol in human urine by high-temperature purge-and-trap gas chromatography-mass spectrometry.  

PubMed

Methyl tert-butyl ether (MTBE) is the oxygenated gasoline additive most widely used in the U.S. to reduce the CO emission from motor vehicles. We developed a method using a high-temperature purge-and-trap procedure coupled with capillary gas chromatography-mass selective detection to determine MTBE and its metabolite, tert-butyl alcohol (TBA), in human urine. Several spiked-urine tests were conducted at different purging temperatures (25, 55, and 90 degrees C). The results indicated that the purging temperature affects the recovery of TBA from urine more than the recovery of MTBE. The mean recoveries of MTBE and TBA in the urine samples by the high temperature (90 degrees C) purge-and-trap gas chromatography-mass spectrometry method at different spike levels were 96.5+/-4.7% and 98.4+/-5.7%, respectively. The method was used to evaluate the urinary levels in a single subject exposed through inhalation to 1 ppm MTBE for 10 min in a controlled-environment facility. Increases in MTBE and TBA urinary excretion rates were clearly evident following the exposure to MTBE. Approximately 0.9% of the amount of MTBE inhaled was excreted unchanged as urinary MTBE, and 2.4% was excreted as urinary TBA within 10 h after exposure. The method developed is a simple, effective, sensitive, and reproducible procedure for evaluating human exposure to MTBE. PMID:9491962

Lee, C W; Weisel, C P

62

Equilibrium constants for methyl tert-butyl ether and ethyl tert-butyl ether liquid-phase syntheses using C[sub 4] olefinic cut  

SciTech Connect

Equilibrium constants for the liquid-phase syntheses of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) were determined experimentally in the temperature range 313--353 K and at 1.6 MPa, using as source of 2-methylpropene (isobutylene) a C[sub 4] olefinic cut proceeding from a steam cracking unit. To reach etherification equilibrium, the macroporous sulfonic acid resin K-2631 (Bayer) was used as the catalyst. The thermodynamic equilibrium constants and the enthalpy, free energy, and entropy changes of reactions were given as a temperature function. At 298 K, the standard molar reaction enthalpy [Delta][sub r]H[sub m][degree](298 K, 1.6 MPa) for MTBE and ETBE are [minus](37.3 [+-] 2) and [minus](34.8 [+-] 1.3) kJ/mol, respectively, and are compared with literature data. A comparison of the equilibrium constant values with those obtained using pure reactants with and without small initial amounts of water (<5 wt %) is also included. The UNIFAC estimates of activity coefficients were used to describe the liquid-phase nonideality. The standard molar enthalpies of formation [Delta][sub f]H[sub m][degree](l, 298.2 K) of MTBE and ETBE are [minus]313.5 and [minus]349.9 kJ/mol, respectively.

Izquierdo, J.F.; Cunill, F.; Vila, M.; Iborra, M.; Tejero, J. (Univ. of Barcelona (Spain). Chemical Engineering Dept.)

1994-11-01

63

Direct dissolution of gallstones with methyl tert-butyl ether by endoscopic cannulation of the gallbladder.  

PubMed

Methyl tert-butyl ether (MTBE) rapidly and effectively dissolves cholesterol gallbladder stones. Due to the invasive nature of transhepatic catheterization, we studied the safety and efficacy of MTBE stone dissolution, delivered by endoscopic, retrograde cannulation of the gallbladder. Extracorporeal shock-wave lithotripsy (ESWL) was employed in patients with multiple stones, to increase contact surface area and facilitate dissolution. We successfully cannulated the gallbladder in 13/17 patients (76.5%) attempted, with no associated complications. After cannulation, MTBE lysis was then conducted on all patients, and 10/13 patients (77%) cannulated were either stone-free at completion, or had only residual gallbladder sludge. Predissolution ESWL successfully fragmented stones in 6/7 patients (86%) in which it was attempted. Both ESWL and MTBE were well tolerated by all patients. Endoscopic retrograde cannulation of the gallbladder and MTBE dissolution is a promising alternative for the treatment of gallbladder stones in patients who will not receive surgery. PMID:8338092

Edison, S A; Maier, M; Kohler, B; Schlauch, D; Buttmann, A; Gauer, E; Riemann, J F

1993-08-01

64

Experimental gallstone dissolution with methyl-tert-butyl ether (MTBE) and transcutaneous ultrasound energy.  

PubMed

The simultaneous application of ultrasound energy greatly accelerated the rate of cholesterol gallstone dissolution by methyl-tert-butyl ether (MTBE). In vitro experiments using this treatment showed that a 498-mg stone burden could be dissolved in 19.5 minutes, approximately 100% faster than what could be achieved with MTBE alone. Pigs (n = 13) with surgically implanted gallstones were treated with MTBE and transcutaneously applied ultrasound from a prototype system built for clinical studies. The average stone reduction of all pigs was 470.46 mg +/- 60.44 mg; 91.39% of an average implanted burden of 515.08 +/- 18.03 mg. Control group pigs (n = 9), receiving only an MTBE infusion, showed an average stone reduction of 51.77%. Enzymes indicative of hepatocellular injury showed no significant abnormalities after 6 weeks. Gallbladder ablation with a fibrous remnant (ie, no mucosa, no lumen, patent cystic duct) occurred in 10 (70%) of the pigs. PMID:2312251

Griffith, S L; Burney, B T; Fry, F J; Franklin, T D

1990-02-01

65

Methyl tert butyl ether dissolution therapy for common bile duct stones.  

PubMed

Methyl tert butyl ether (MTBE) is a potent cholesterol solvent. We have used MTBE in twelve patients with 19 large radiolucent common bile duct stones which could not be removed endoscopically. MTBE was instilled directly into the common bile duct via a nasobiliary or percutaneous catheter. Successful clearance of the duct was achieved in ten patients. The stones disappeared completely in three patients with MTBE alone; in the remaining seven, it was possible to extract the stones endoscopically after MTBE, even though there was no change in the cholangiographic appearance. MTBE may have a role in the management of large retained common bile duct calculi but, given the practical difficulties of administration, its use should only be considered when other methods have failed and a non-surgical approach is desired. PMID:2365983

Kaye, G L; Summerfield, J A; McIntyre, N; Dooley, J S

1990-05-01

66

Lipid extraction by methyl-tert-butyl ether for high-throughput lipidomics*s?  

PubMed Central

Accurate profiling of lipidomes relies upon the quantitative and unbiased recovery of lipid species from analyzed cells, fluids, or tissues and is usually achieved by two-phase extraction with chloroform. We demonstrated that methyl-tert-butyl ether (MTBE) extraction allows faster and cleaner lipid recovery and is well suited for automated shotgun profiling. Because of MTBE's low density, lipid-containing organic phase forms the upper layer during phase separation, which simplifies its collection and minimizes dripping losses. Nonextractable matrix forms a dense pellet at the bottom of the extraction tube and is easily removed by centrifugation. Rigorous testing demonstrated that the MTBE protocol delivers similar or better recoveries of species of most all major lipid classes compared with the “gold-standard” Folch or Bligh and Dyer recipes.

Matyash, Vitali; Liebisch, Gerhard; Kurzchalia, Teymuras V.; Shevchenko, Andrej; Schwudke, Dominik

2008-01-01

67

Removal of Methyl-tert-butyl Ether from Water by a Pulsed Arc Electrohydraulic Discharge System  

NASA Astrophysics Data System (ADS)

The removal of methyl-tert-butyl ether (MTBE) from water by a pulsed arc electrohydraulic discharge (PAED) system was investigated experimentally at the laboratory scale. The effects of arc electrode gap, detention time and initial solution pH on the efficacy of MTBE treatment by PAED were investigated. A 0.3 kJ/pulse spark-gap-type power supply was employed in combination with a 3.0 L flow-through reactor. Experimental results showed that: 1) oxidation reactions are induced by this PAED system; 2) removal efficiency increases with increasing cumulative input energy (kW\\cdoth/m3 or kJ/L); 3) removal efficiency decreases with increasing arc electrode gap; and 4) initial solution pH does not have a significant effect on the efficacy of MTBE removal by PAED when the water matrix is buffered prior to treatment.

Angeloni, Danielle M.; Dickson, Sarah E.; Emelko, Monica B.; Chang, Jen-Shih

2006-10-01

68

Gallstone dissolution with methyl tert-butyl ether in 120 patients--efficacy and safety.  

PubMed

Of 612 patients with cholesterol gallbladder stones, 120 were eligible for percutaneous transhepatic litholysis with methyl tert-butyl ether (MTBE). Puncture of the gallbladder was successful in 117/120 (97.5%). In 113/117 (96.6%) the stones dissolved. With solitary stones, treatment lasted for an average of 4 hr, with multiple stones 10 hr. Mean hospitalization was 3.6 days. In 3/117 (2.6%) patients a bile leakage developed; 33% reported mild complaints. After the end of treatment 34% had some residue in the gallbladder; two of these patients developed recurrent stones. MTBE is exhaled, is distributed in fatty tissue, and is excreted renally together with its metabolite tert-butanol. Methanol was found only in traces. Gallbladder histology of six patients showed chronic cholecystitis. Since these findings were independent of treatment time and the interval between treatment end and operation, they are most consistent with stone-related changes rather than caused by MTBE. PMID:1988263

Leuschner, U; Hellstern, A; Schmidt, K; Fischer, H; Güldütuna, S; Hübner, K; Leuschner, M

1991-02-01

69

Biodegradation of Methyl tert-Butyl Ether and Other Fuel Oxygenates by a New Strain, Mycobacterium austroafricanum IFP 2012  

PubMed Central

A strain that efficiently degraded methyl tert-butyl ether (MTBE) was obtained by initial selection on the recalcitrant compound tert-butyl alcohol (TBA). This strain, a gram-positive methylotrophic bacterium identified as Mycobacterium austroafricanum IFP 2012, was also able to degrade tert-amyl methyl ether and tert-amyl alcohol. Ethyl tert-butyl ether was weakly degraded. tert-Butyl formate and 2-hydroxy isobutyrate (HIBA), two intermediates in the MTBE catabolism pathway, were detected during growth on MTBE. A positive effect of Co2+ during growth of M. austroafricanum IFP 2012 on HIBA was demonstrated. The specific rate of MTBE degradation was 0.6 mmol/h/g (dry weight) of cells, and the biomass yield on MTBE was 0.44 g (dry weight) per g of MTBE. MTBE, TBA, and HIBA degradation activities were induced by MTBE and TBA, and TBA was a good inducer. Involvement of at least one monooxygenase during degradation of MTBE and TBA was shown by (i) the requirement for oxygen, (ii) the production of propylene epoxide from propylene by MTBE- or TBA- grown cells, and (iii) the inhibition of MTBE or TBA degradation and of propylene epoxide production by acetylene. No cytochrome P-450 was detected in MTBE- or TBA-grown cells. Similar protein profiles were obtained after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude extracts from MTBE- and TBA-grown cells. Among the polypeptides induced by these substrates, two polypeptides (66 and 27 kDa) exhibited strong similarities with known oxidoreductases.

Francois, Alan; Mathis, Hugues; Godefroy, Davy; Piveteau, Pascal; Fayolle, Francoise; Monot, Frederic

2002-01-01

70

Biodegradation of methyl tert-butyl ether and other fuel oxygenates by a new strain, Mycobacterium austroafricanum IFP 2012.  

PubMed

A strain that efficiently degraded methyl tert-butyl ether (MTBE) was obtained by initial selection on the recalcitrant compound tert-butyl alcohol (TBA). This strain, a gram-positive methylotrophic bacterium identified as Mycobacterium austroafricanum IFP 2012, was also able to degrade tert-amyl methyl ether and tert-amyl alcohol. Ethyl tert-butyl ether was weakly degraded. tert-Butyl formate and 2-hydroxy isobutyrate (HIBA), two intermediates in the MTBE catabolism pathway, were detected during growth on MTBE. A positive effect of Co2+ during growth of M. austroafricanum IFP 2012 on HIBA was demonstrated. The specific rate of MTBE degradation was 0.6 mmol/h/g (dry weight) of cells, and the biomass yield on MTBE was 0.44 g (dry weight) per g of MTBE. MTBE, TBA, and HIBA degradation activities were induced by MTBE and TBA, and TBA was a good inducer. Involvement of at least one monooxygenase during degradation of MTBE and TBA was shown by (i) the requirement for oxygen, (ii) the production of propylene epoxide from propylene by MTBE- or TBA- grown cells, and (iii) the inhibition of MTBE or TBA degradation and of propylene epoxide production by acetylene. No cytochrome P-450 was detected in MTBE- or TBA-grown cells. Similar protein profiles were obtained after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude extracts from MTBE- and TBA-grown cells. Among the polypeptides induced by these substrates, two polypeptides (66 and 27 kDa) exhibited strong similarities with known oxidoreductases. PMID:12039730

François, Alan; Mathis, Hugues; Godefroy, Davy; Piveteau, Pascal; Fayolle, Françoise; Monot, Frédéric

2002-06-01

71

Dissolution of gallbladder stones with methyl tert-butyl ether and stone recurrence: a European survey.  

PubMed

Since there are now several ways to treat symptomatic gallstone disease, one is able to select treatment on the basis of the patient's comfort, the practicability, effectiveness, and side effects of the technique, and the relative costs. In order to assess the present status of contact dissolution with methyl tert-butyl ether with regard to these aspects, the present enquiry reports the data of 21 European hospitals. Eight hundred three patients were selected for contact litholysis of cholesterol gallbladder stones using methyl tert-butyl ether. Percutaneous transhepatic puncture of the gallbladder was performed under x-ray or ultrasound guidance. Dissolution rate, side effects, and treatment times of 268 patients from one single center were compared to those of 535 patients from the other 20 centers. Two hundred sixty-four patients were followed for five years to assess stone recurrence. Physicians were asked how they assessed the expenditure of the method, the discomfort to the patients, and the staffing situation. Patients were asked to indicate their acceptance on an analog scale. Puncture was successful in 761 (94.8%) patients. Prophylactic administration of antibiotics was not necessary. Stones were dissolved in 724 (95.1%) patients. In 315 (43.5%) sludge remained in the gallbladder. The most severe complication was bile leakage, which led 12 (1.6%) patients to have elective cholecystectomy. Toxic injuries due to the ether were not reported. Method-related lethality amounted to 0%, 30-day-lethality to 0.4%. Stone recurrence rate was about 40% in solitary stones and about 70% in multiple stones over five years. Patients with multiple stones developed recurrent stones almost twice as often as those with solitary stones. The probability of stone recurrence in patients with sludge in the gallbladder after catheter removal was not statistically significantly different from those without sludge. Seventy to 90% of the centers found the puncture to be simple and not distressing for patients and the relation between expenditure and therapeutic success to be acceptable. The acceptance of contact litholysis by the patients was excellent. Contact litholysis when applied by an experienced team provides real advantages in the treatment of gallstone disease. The method is technically simple, well accepted by the patients, and can be easily applied in community hospitals. Contact litholysis may be of particular value in patients who are not suitable for anesthesia or surgery. PMID:9590398

Hellstern, A; Leuschner, U; Benjaminov, A; Ackermann, H; Heine, T; Festi, D; Orsini, M; Roda, E; Northfield, T C; Jazrawi, R; Kurtz, W; Schmeck-Lindenau, H J; Stumpf, J; Eidsvoll, B E; Aadland, E; Lux, G; Boehnke, E; Wurbs, D; Delhaye, M; Cremer, M; Sinn, I; Höring, E; v Gaisberg, U; Neubrand, M; Paul, F

1998-05-01

72

[Dissolution of gallstones with methyl-tert-butyl ether. An alternative to surgery in high risk patients].  

PubMed

We treated 27 symptomatic patients by dissolving cholesterol gallstones with methyl tert-butyl ether. Three patients were treated twice. Mean age was 70.2 years. Most patients had elevated risk for surgery. A 5 French polyethylene catheter was introduced percutaneously, transhepatic to the gallbladder. The placement of the catheter was successful in 26 of 30 procedures (87%). Cholecystography showed complete dissolution of stones in 22 of 26 patients treated (85%). Mean treatment time was 11.7 h. In four patients the treatment was stopped before dissolution was complete. Side effects were nausea, pain, fever and vasovagal reaction. 15 patients were followed up for a mean of 22.7 months after dissolution. Ten patients had no biliary symptoms, five patients suffered symptomatic relapse and three had asymptomatic recurrence of stones. We conclude that dissolution of gallstones by methyl tert-butyl ether is an adequate alternative to surgery in selected high risk patients. PMID:8209339

Eidsvoll, B E; Aadland, E; Stiris, M; Lunde, O C

1994-02-20

73

Dissolution of Gallbladder Stones with Methyl tertButyl Ether and Stone Recurrence (A European Survey)  

Microsoft Academic Search

Since there are now several ways to treatsymptomatic gallstone disease, one is able to selecttreatment on the basis of the patient's comfort, thepracticability, effectiveness, and side effects of the technique, and the relative costs. In order toassess the present status of contact dissolution withmethyl tert-butyl ether with regard to these aspects,the present enquiry reports the data of 21 European hospitals.

Alfred Hellstern; Ulrich Leuschner; Ala Benjaminov; Hanns Ackermann; Thomas Heine; Davide Festi; Monica Orsini; Enrico Roda; Tim C. Northfield; Riadh Jazrawi; Winfried Kurtz; Hans Joachim Schmeck-Lindenau; Jochen Stumpf; Britt E. Eidsvoll; Erling Aadland; Gerd Lux; Eckhart Boehnke; Ditmar Wurbs; Myriam Delhaye; Michel Cremer; Ingolf Sinn; Erich Horing; Ulrich V. Gaisberg; Michael Neubrand; Tilmann Sauerbruch; Vladimir Salamon; Werner Swobodnik; Hasko V. Sanden; Wolfgang Schmitt; Thomas Kaser; Hans Schomerus; Johannes Georg Wechsler; Paul Janowitz; Jorn Lohmann; Heiner Porst; Adolfo Francesco Attili; Eberhard Bartels; Wolfgang Arnold Wolf; Dieter Strohm; Fred Paul

1998-01-01

74

Kinetics of methyl tert-butyl ether degradation and by-product formation during UV\\/hydrogen peroxide water treatment  

Microsoft Academic Search

Methyl tert-butyl ether (MTBE) was removed from aqueous solution by exposure to a low-pressure mercury lamp in the presence of hydrogen peroxide in a recirculating batch reactor. Dark and UV-only tests were conducted to separate the effects of MTBE loss to system components and photolytic processes. Experiments were conducted at initial peroxide:MTBE molar ratios of 4:1, 7:1 and 15:1. Benzene

Paulette B. L. Chang; Thomas M. Young

2000-01-01

75

Effects of co-substrates and inhibitors on the anaerobic O-demethylation of methyl tert -butyl ether (MTBE)  

Microsoft Academic Search

Methyl tert-butyl ether (MTBE) contamination is widespread in aquifers near urban areas around the world. Since this synthetic fuel oxygenate\\u000a is resistant to most physical methods of treating fuel-contaminated water, biodegradation may be a useful means of remediation.\\u000a Currently, information on anaerobic MTBE degradation is scarce. Depletion has been observed in soil and sediment microcosms\\u000a from a variety of locations

Laura K. G. Youngster; Piyapawn Somsamak; Max M. Häggblom

2008-01-01

76

Biodegradation Kinetics and Effects of Operating Parameters on the Performance of a Methyl TertButyl Ether Degrading Biofilter  

Microsoft Academic Search

The goals of the study were to determine the effectiveness of a laboratory-scale biofilter on the removal of methyl tert-butyl ether (MTBE) and investigate the operating parameter effects on biofilter performance. The experimental results show that average MTBE removals of 53.6–93.2% were observed at loads of 2.5–20.1 gm?3 h?1 and an empty-bed residence time of three minutes, after continuous operation

Yi-Cheng Chiu; Chi-Wen Lin; Tsang-Chih Kao; Xiao-Yan Tang

2006-01-01

77

Alterations in Endocrine Responses in Male Sprague-Dawley Rats following Oral Administration of Methyl tertButyl Ether  

Microsoft Academic Search

Methyl tert-butyl ether (MTBE) is an oxygenated fuel additive used to decrease carbon monoxide emissions during combustion. MTBE is a nongenotoxic chemical that induces Leydig cell tumors (LCT) in male rats. The mechanism of MTBE-induced LCT is not known; however, LCT induced by other nongenotoxic chemicals have been associated with the disruption of the hypothalamus- pituitary-testicular (HPT) axis. The objective

Tracy M. Williams; Russell C. Cattley; Susan J. Borghoff

2000-01-01

78

Dissolution of multiple biliary duct stones using methyl tert-butyl ether (MTBE): Experience in two cases  

Microsoft Academic Search

Methyl tert-butyl-ether (MTBE) was sucessfully used for stone dissolution in 2 patients with multiple bile duct cholesterol\\u000a stones. The presence of a biliary-enteric anastomosis precluded the endoccopic approach. Because of leakage of MTBE into the\\u000a bowel, dissolution time ranged from 7.5 to 36 h. No significant complications other than mild nausea were encountered. No\\u000a recurrence of stone formation has been

Ricardo Tobio-Calo; Jose M. Llerena; Isabel Pinto-Pabon; Wilfrido R. Castafieda-Zufiiga

1992-01-01

79

Direct dissolution of gallstones with methyl tert-butyl ether (MTBE) via endoscopic transpapillary catheterization in the gallbladder (ETCG)  

Microsoft Academic Search

In a pilot study of direct dissolution therapy of gallstones with methyl tert-butyl ether (MTBE), endoscopic transpapillary\\u000a catheterization in the gallbladder (ETCG) was performed. Complete dissolution was seen in 8 out of 12 (66%) patients and partial\\u000a dissolution was seen in 2 (16%) patients. In one of the 8 complete dissolution patients, combined extracorporeal shock wave\\u000a lithotripsy (ESWL) and dissolution

Naohito Uchida; Toshiaki Nakatsu; Shuko Hirabayashi; Atsushi Minami; Hiroki Fukuma; Toru Ezaki; Syed Ahmed Morshed; Chiaki Fuke; Kiyoshi Ameno; Iwao Ijiri; Mikio Nishioka

1994-01-01

80

Dissolution of multiple biliary duct stones using methyl tert-butyl ether (MTBE): experience in two cases.  

PubMed

Methyl tert-butyl-ether (MTBE) was successfully used for stone dissolution in 2 patients with multiple bile duct cholesterol stones. The presence of a biliary-enteric anastomosis precluded the endoscopic approach. Because of leakage of MTBE into the bowel, dissolution time ranged from 7.5 to 36 h. No significant complications other than mild nausea were encountered. No recurrence of stone formation has been found at a follow-up varying from 9 to 12 months. PMID:1394363

Tobio-Calo, R; Llerena, J M; Pinto-Pabon, I; Castañeda-Zúñiga, W R

81

Comparative and combined toxicities of toluene and methyl tert-butyl ether to an Asian earthworm Perionyx excavatus  

Microsoft Academic Search

An earthworm assay was used to assess the toxicity of two main gasoline components. Ecotoxicities of toluene and methyl tert-butyl ether (MTBE) were compared for Asian earthworm Perionyx excavatus separately and in combination. Sum of toxic unit (TU) at 50% mortality for the mixture (LC50mix) was estimated from the dose (TU-based)–response relationships by the Trimmed Spearman–Karber method. Toluene was shown

Youn-Joo An; Woo-Mi Lee

2008-01-01

82

Occurrence of Methyl tert Butyl Ether and Other Fuel Oxygenates in Source Water and Drinking Water of the United States  

Microsoft Academic Search

The National Water-Quality Assessment Program of the United States (US) Geological Survey conducted\\u000a surveys of the occurrence of methyl tert-butyl ether (MTBE) and other\\u000a fuel oxygenates in ground water used as a source of drinking water and in drinking water in the United\\u000a States (USA) from 1993 to 2001. MTBE was detected in about 4% of samples of source water collected

Michael Moran

83

Carbon Isotope Fractionation during Anaerobic Degradation of Methyl tertButyl Ether under Sulfate-Reducing and Methanogenic Conditions  

Microsoft Academic Search

Methyl tert-butyl ether (MTBE), an octane enhancer and a fuel oxygenate in reformulated gasoline, has received increasing public attention after it was detected as a major contaminant of water resources. Although several techniques have been developed to remediate MTBE-contaminated sites, the fate of MTBE is mainly dependent upon natural degradation processes. Compound-specific stable isotope analysis has been proposed as a

Piyapawn Somsamak; Hans H. Richnow; Max M. Haggblom

2006-01-01

84

Dissolution of calcium bilirubinate and calcium carbonate debris remaining after methyl tert-butyl ether dissolution of cholesterol gallstones.  

PubMed

Methyl tert-butyl ether rapidly dissolves cholesterol gallstones, although insoluble debris may remain. Total gallstone dissolution could be achieved if safe solvents for these noncholesterol components can be developed. We evaluated the in vitro ability of ethylenediaminetetraacetic acid, citrate, dimethyl sulfoxide, and ionic or nonionic detergents to dissolve the predominantly calcium bilirubinate and calcium carbonate debris remaining after methyl tert-butyl ether gallstone dissolution. Ethylenediaminetetraacetic acid 1% or 2% at pH 9.5 was the most effective of the solvents studied for dissolving calcium and bile pigment. The addition of cholate (25-200 mM) or polysorbate (1%-10%) to ethylenediaminetetraacetic acid 1% at pH 9.5 enhanced pigment dissolution compared to ethylenediaminetetraacetic acid alone. Dissolution of pellets prepared from human gallstones and composed predominantly of either calcium bilirubinate or calcium carbonate was 80% and 85% at 4 h using ethylenediaminetetraacetic acid 1% plus polysorbate-20 1% at pH 9.5. We conclude that ethylenediaminetetraacetic acid, either alone or with a detergent, is an effective solvent for methyl tert-butyl ether-insoluble gallstone debris and deserves assessment in vivo. PMID:2323524

Nelson, P E; Moyer, T P; Thistle, J L

1990-05-01

85

Methyl tert butyl ether targets developing vasculature in zebrafish (Danio rerio) embryos.  

PubMed

Disruption of vascular endothelial growth factor (VEGF) signaling during early development results in abnormal angiogenesis and increased vascular lesions. Embryonic exposure to 0.625-10mM methyl tert butyl ether (MTBE), a highly water soluble gasoline additive, resulted in a dose dependent increase in pooled blood in the common cardinal vein (CCV), cranial hemorrhages and abnormal intersegmental vessels (ISVs). The EC50s for the lesions ranked in terms of likelihood to occur with MTBE exposure were: pooled blood in the CCV, 3.2 mM [95% CI: 2.2-4.7]>cranial hemorrhage, 11 mM [5.9-20.5]>abnormal ISV, 14.5 mM [6.5-32.4]. Organ systems other than the vascular system appear to develop normally, which suggests MTBE toxicity targets developing blood vessels. Equal molar concentrations (0.625-10mM) of the primary metabolites, tertiary butyl alcohol (TBA) and formaldehyde, did not result in vascular lesions, which suggested that the parent compound is responsible for the toxicity. Stage specific exposures were carried out to determine the developmental period most sensitive to MTBE vascular disruption. Embryos treated until 6-somites or treated after Prim-5 stages did not exhibit a significant increase in lesions, while embryos treated between 6-somites and Prim-5 had a significant increase in vascular lesions (p?0.05). During the critical window for MTBE-induced vascular toxicity, expression of vegfa, vegfc, and flk1/kdr were significantly decreased 50, 70 and 40%, respectively. This is the first study to characterize disruption in vascular development following embryonic exposure to MTBE. The unique specificity of MTBE to disrupt angiogenesis may be mediated by the down regulation of critical genes in the VEGF pathway. PMID:21684239

Bonventre, Josephine A; White, Lori A; Cooper, Keith R

2011-05-13

86

Reaction calorimetry study of the liquid-phase synthesis of tert-butyl methyl ether  

SciTech Connect

The liquid-phase addition of methanol to isobutene to give tert-butyl methyl ether (MTBE) on the ion-exchange resin Lewatit K2631 has been studied in a calorimetric reactor. Heat capacity of MTBE and enthalpy of the MTBE synthesis reaction in the temperature range 312--333 K have been determined. MTBE heat capacity in the liquid phase has been found to obey the equation c[sub P] (J/mol[center dot]K) = 472.34 [minus] 2.468(T/K) + 0.005071(T/K)[sup 2]. At 298 K the standard molar reaction enthalpy is [Delta]H[degree] = [minus]33.8 kJ/mol. A method to estimate apparent activation energies from heat flow rate in a given reaction has been developed and proved to be valid for the MTBE synthesis. Using this method, an apparent activation energy of 91.1--95.2 kJ/mol is calculated. A [minus]3.8 kJ/mol value has been found for the adsorption enthalpy of methanol on the ion-exchange resin Lewatit K2631 by a combination of reaction calorimetry and thermogravimetry. This allows the calculation of an activation energy on the gel phase of the resin of 91 kJ/mol.

Sola, L.; Pericas, M.A.; Cunill, F.; Iborra, M. (Univ. de Barcelona (Spain). Dept. d'Enginyeria Quimica)

1994-11-01

87

Biodegradation of methyl tert-butyl ether under various substrate conditions.  

PubMed

Five aerobic enrichments efficient at degrading methyl tert-butyl ether (MTBE) under different substrate conditions were developed in well-mixed reactors containing a polyethlene porous pot for biomass retention. The five substrate conditions were as follows: MTBE alone; MTBE and diethyl ether (DEE); MTBE and diisopropyl ether (DIPE); MTBE and ethanol (EtOH); and MTBE with benzene, toluene, ethylbenzene, and xylene (BTEX). All five cultures demonstrated greater than 99.9% removal of MTBE. Addition of alternative substrate was found to have no effect on the performance of the reactors. The bacterial communities of the reactors were monitored periodically by denaturing gradient gel electrophoresis (DGGE) to determine when homeostasis was achieved. Phylogenetic analysis of the excised DGGE bands was done in order to compare the bacterial community compositions of the reactors. All cultures were found to be mixed cultures, and each enrichment was shown to have a unique composition. A majority of the bands in all reactors represented a group of organisms belonging to the Cytophaga-Flexibacter-Bacterioides (C-F-B) Phylum of bacteria. This was also the only group found in all of the reactors. This study demonstrates that MTBE can be degraded effectively in bioreactors under several substrate conditions and gives insight into the microorganisms potentially involved in the process. PMID:11718336

Pruden, A; Suidan, M T; Venosa, A D; Wilson, G J

2001-11-01

88

Radiation chemistry of methyl tert-butyl ether in aqueous solution.  

PubMed

The chemical kinetics of the free-radical-induced degradation of the gasoline oxygenate methyl tert-butyl ether (MTBE) in water have been investigated. Rate constants for the reaction of MTBE with the hydroxyl radical, hydrated electron, and hydrogen atom were determined in aqueous solution at room temperature, using electron pulse radiolysis and absorption spectroscopy (*OH and e- aq) and EPR free induction decay attenuation (*H) measurements. The rate constant for hydroxyl radical reaction of (1.71 +/- 0.02) x 10(9) M(-1) s(-1) showed that the oxidative process was the dominant pathway, relative to MTBE reaction with hydrogen atoms, (3.49 +/- 0.06) x 10(6) M(-1) s(-1), or hydrated electrons, <8.0 x 10(6) M(-1) s(-1). The hydroxyl radical reaction gives a transient carbon-centered radical which subsequently reacts with dissolved oxygen to form peroxyl radicals, the rate constant for this reaction was (2.17 +/- 0.06) x 10(9) M(-1) s(-1). The second-order decay of the MTBE peroxyl radical was 2k = (6.0 +/- 0.3) x 10(8) M(-1) s(-1). These rate constants, along with preliminary MTBE degradation product distribution measurements, were incorporated into a kinetic model that compared the predicted MTBE removal from water against experimental measurements performed under large-scale electron beam treatment conditions. PMID:15298211

Mezyk, Stephen P; Jones, Jace; Cooper, William J; Tobien, Thomas; Nickelsen, Michael G; Adams, J Wesley; O'Shea, Kevin E; Bartels, David M; Wishart, James F; Tornatore, Paul M; Newman, Kimberley S; Gregoire, Kellie; Weidman, Daniel J

2004-07-15

89

Potential ecotoxicological implication of methyl tert-butyl ether (MTBE) spills in the environment.  

PubMed

Streptomyceticidal activity of Methyl tert-butyl ether (MTBE) elucidated for the first time. Adverse effect of MTBE, the gasoline additive, against 11 soil inhabitant Streptomyces spp. isolates was investigated. MTBE, an octane enhancer is added to gasoline to reduce atmospheric concentrations of carbon monoxide and ozone. It contaminates soil and groundwater by fuel leaks and spills. Streptomyces spp. are of the major contributors to the biological buffering of soils by exerting beneficial and antagonistic activity against wide range of bacteria and fungi. To evaluate anti-streptomycetidal activity of MTBE, it was tested against 11 soil isolates of Streptomyces isolates and also a plant-root bacterial pathogen, Erwinia carotovora and a plant-root fungal pathogen, Fusarium solani. MTBE did not reveal any growth inhibitory activity against E. carotovora and F. solani, but showed strong inhibitory effect against Streptomyces isolates. The Minimum Inhibitory Concentration (MIC) on Streptomyces isolates was 1/800 of the original MTBE. Fuel leaks and spills have the potential to suppress or eliminate the Streptomyces role in the soil causing alteration in the balance of soil micro flora. This change can promote the domination of microorganisms with adverse biological or ecotoxicological effects. PMID:15673212

Bonjar, G H Shahidi

2004-10-01

90

Biomarkers of exposure to aromatic hydrocarbons and methyl tert-butyl ether in petrol station workers.  

PubMed

This cross-sectional study was aimed at reconstructing the exposure to gasoline in 102 petrol station attendants by environmental and biological monitoring of benzene, toluene, ethylbenzene and xylene (BTEX) and biomonitoring of methyl tert-butyl ether (MTBE). Airborne BTEX were higher for manual refuelers than self-service assistants and were highly correlated with each other. Significant relationships were found between airborne BTX and the corresponding urinary solvents (U-BTX) and beween airborne B and urinary MTBE (U-MTBE). Smokers eliminated higher values of U-B, trans,trans-muconic (t,t-MA) and S-phenylmercapturic (S-PMA) acids but not U-MTBE. All these biomarkers were, however, significantly raised during the shift, independently from smoking. Linear regression confirmed that occupational exposure was a main predictor of U-MTBE, U-B and S-PMA values, both the latter confounded by smoking habits. The study supports the usefulness of biomonitoring even at low exposure levels. PMID:22458326

De Palma, Giuseppe; Poli, Diana; Manini, Paola; Andreoli, Roberta; Mozzoni, Paola; Apostoli, Pietro; Mutti, Antonio

2012-03-29

91

Theoretical study of adsorption of methyl tert-butyl ether on broken clay minerals surfaces  

NASA Astrophysics Data System (ADS)

The interactions between methyl tert-butyl ether (MTBE) and differently defected tetrahedral and octahedral fragments of clay minerals containing Si4+, Al3+, and Mg2+ central cations have been studied at the B3LYP and MP2 levels of theory in conjunction with the 6-31G(d) basis set. MTBE interacts with defect clay structures due to the formation of multiple C?H...O and O?H...O hydrogen bonds. Interactions of MTBE with systems containing different types of defected mineral fragments were found to vary. Systems containing the same type of defected mineral fragment with different central cation interact almost the same way with MTBE. The formation of hydrogen bonds leads to changes in the geometrical parameters and to the polarization of MTBE. The values of the interaction energies depend on the charge of the mineral fragment. They amount to 5 kcal/mol-35 kcal/mol. MTBE interacts more preferably with octahedral fragments than with tetrahedral fragments that contain an Al3+ central cation.

Michalkova, A.; Johnson, L. D.; Gorb, L.; Zhikol, O. A.; Shishkin, O. V.; Leszczynski, J.

92

Manual and automatic gallstone dissolution with methyl tert-butyl ether.  

PubMed

The aim of the study was to establish the efficiency of cholesterol gallstone dissolution with methyl tert-butyl ether in a large group of patients and to compare the results of patients treated manually by a nurse or using an automatic pump. Gallbladder puncture was successful in 228 patients (99%). After 9 hr, 211 patients (91%) were stone-free; 144 (68%) of them left the hospital on the fourth day. In radiolucent stones not isodense with bile on a CT scan, dissolution rate decreased by 10%, treatment time was prolonged by 40%. Forty-two of the 228 patients were selected for the hand-syringed group, 42 patients, who matched these patients in stone size and number, were treated with an automatic pump (Baxter). Stone burden in matched pairs was comparable. Stones dissolved in 96% of the patients in both groups. Sludge remained in the gallbladder in 52% after manual treatment and 60% after automatic therapy. Side effects were identical in both groups. None of the side effects were pump-related. Automatic therapy reduced the time needed by the nurse to treat each patient by 70%. PMID:8200264

Leuschner, U; Hellstern, A; Ansell, A; Gatzen, M; Güldütuna, S; Leuschner, M

1994-06-01

93

Extracorporeal shock wave lithotripsy and methyl tert-butyl ether for gallbladder stones.  

PubMed

Twenty-one patients with gallbladder stones of 1.1-2.6 cm in diameter were treated by extracorporeal shock wave lithotripsy (ESWL) combined with dissolution using methyl tert-butyl ether (MTBE). In 18 of 21 patients, ESWLs were followed by MTBE instillation through a catheter placed percutaneously via the liver and the gallbladder bed under ultrasonographic and fluoroscopic guidance. As a result, 15 of the 18 patients were cleared of their stones after 54 minutes to 3 hours of dissolution. In the other three cases initially treated by MTBE, ESWLs were added because of no dissolution or poor efficacy. Consequently, after additional 3-5 hours of instillation, complete dissolution in one and subtotal dissolution in two were achieved. Our preliminary results indicated that ESWL followed by MTBE dissolution in the management of cholesterol gallbladder stones was reasonable. On the one hand, ESWL can enhance dissolution by increasing the surface area of stone, and on the other hand MTBE can instantly clear the fragments created by ESWL, so that long-term bile acid intake and potential side effects caused by fragment migration might be avoided. PMID:1458964

Hu, H; Xue, Y S; Wang, X Z; Zhang, S D

1992-08-01

94

[Contact chemical litholysis of gallbladder stones with methyl tert-butyl ether. Personal experience].  

PubMed

The purpose of the work is to estimate the efficiency and follow-ups of the contact chemical litholysis (CCL) of gallstones with methyl-tert-butyl ether (MTBE). The CCL has been carried to 5 women with plural (10-15) radiolucent gallstones, who refused from cholecystectomy. The percutaneous transhepatic puncture of the gallbladder has been executed to them under X-ray and ultrasonic control. Laboratory (general blood analysis, urine analysis, biochemical parameters of blood and bile) and tool (ultrasonic control, cholecystography) researches were carried out before the procedure, during dissolution, 2, 6, 9 months after the CCL. High litholytic activity of MTBE has been revealed by dissolution of cholesterol stones of the gallbladder with use of the above-mentioned agent. Local irritation, allergenic actions and essential collateral reactions were not observed. After the CCL, contractility function of the gallbladder has increased (before the procedure - 23,8 +/- 0,4%, after it - 37,5 +/- 0,8%, p < 0,001). PMID:17939195

Sa?futdinov, R G; Ryzhkova, O V

2007-01-01

95

Sensitivity of green and blue-green algae to methyl tert-butyl ether.  

PubMed

The toxicity of methyl tert-butyl ether (MTBE) to Chlorella ellipsoidea and Aphanizomenon flos-aquae was tested and assessed for a 15-d incubation with concentrations of MTBE from high (2.00 x 10(4) mg/L) to low (2 mg/L). The results showed that the toxicity was low when the concentration of MTBE was in the range 1.00 x 10(4) - 2.00 x 10(4) mg/L (the greatest inhibition of growth-rate was 70%-71%, occurred during the day 1-5). Low concentrations (2-500 mg/L) stimulated algal growth up to the greatest effect of 85%-200% when the concentration of MTBE was 50-100 mg/L during day 3-5. The toxicity of MTBE (72-120 h EC50) was 6.65 x 10(3) - 9.58 x 10(3) mg/L for C. ellipsoidea and that is 1.14 x 10(4) - 2.00 x 10(4) mg/L for A. floc-aquae. We found that the toxicity and ecological risk of MTBE for the algal community structure were low and the toxicity was influenced by the duration time of the test. PMID:19634428

Chen, Jianmeng; Ma, Jianyi; Cao, Wei; Wang, Pinwei; Tong, Senmiao; Sun, Yizhao

2009-01-01

96

Determination of Henry's law constant for methyl tert-butyl ether (MTBE) at groundwater temperatures.  

PubMed

The dimensionless Henry's law constant was determined for methyl tert-butyl ether (MTBE) at six temperatures (3, 5, 10, 15, 20 and 25 degrees C) by using a thermostatted flask (430 ml) containing an aqueous MTBE solution. The ratio between the gas phase and the water phase in the flask was approximately 1.7:1. The aim of this study was to acquire data needed to model the behaviour of MTBE at groundwater conditions. The dimensionless Henry's law constant at 10 degrees C is approximately 0.01 but is 0.03 at 25 degrees C. This is important for modelling MTBE because the variation of vaporization cannot be disregarded at groundwater temperatures. In a second experiment the water solubility of MTBE was determined to be 62.1 g/l at 5 degrees C and 35.5 g/l at 20 degrees C). The high solubility at low temperatures could cause MTBE plumes from spills (fuel accidents etc.) to spread rapidly. PMID:14602101

Fischer, A; Müller, M; Klasmeier, J

2004-02-01

97

Bis[tris(3-tert-butyl-5-methyl-pyrazol-1-yl)hydridoborato]ytterbium(II) toluene solvate  

PubMed Central

In the title compound, [Yb(C24H40BN6)2]·C7H8, the Yb atom is coordinated by two tris(3-tert-butyl-5-methyl­pyrazol-1-yl)hydridoborate [TptBu,Me] ligands. One ligand binds in the ?3 mode, throuh three N atoms of the pyrazolyl rings, the other ligand coordinates through two N atoms of the pyrazolyl rings and the H atom attached to the central B via an agostic-type inter­action through the B—H group of the second TptBu,Me ligand, giving an overall distorted octa­hedral geometry. One of the tert-butyl groups is disordered over two sites, with occupancies of 0.65 and 0.35.

Saliu, Kuburat O.; Takats, Josef; Ferguson, Michael J.

2009-01-01

98

Exposure to methyl tert-butyl ether and benzene among service station attendants and operators.  

PubMed Central

Concerns for atmospheric pollution from auto exhaust have led to the blending of "oxygenates" with motor fuels. The most common oxygenate, methyl tert-butyl ether (MTBE) is currently required within several metropolitan areas (Denver and Phoenix) in the range of 12% of the motor fuel. Amendments to the Clean Air Act may expand this requirement to as many as 44 other areas of the United States in the near future. In consideration of the magnitude of potential uncontrolled exposures from its extensive use and a related concern involving the potential influence of MTBE blending on exposures to other constituents of gasoline (particularly benzene), an evaluation of exposures among service station attendants and operators was undertaken at the request, and in cooperation with, the American Petroleum Institute during the latter part of 1990. For application of the survey results to a broad audience, three categories or types of service stations were identified with regard to MTBE use and exposure potential: a) service stations that do not use MTBE or use it only as an octane enhancer, b) service stations with seasonal requirements to use 12-15% MTBE (the Denver, Colorado, and Phoenix, Arizona, metropolitan areas), and c) service stations equipped with stage II (active) vapor recovery systems (several coastal areas, most notably Southern California). At the two sampled service stations that use only minimal amounts of MTBE (less than 1%), only 1 of 32 personal breathing zone (PBZ) samples from attendants was above the analytical limit of detection, reported at 0.16 ppm. The geometric mean concentration of benzene among this same population (n = 32) was 0.04 ppm.(ABSTRACT TRUNCATED AT 250 WORDS)

Hartle, R

1993-01-01

99

LIDEM unit for the production of methyl tert-butyl ether from butanes  

SciTech Connect

One of the basic problems in the production of motor fuels is how to obtain high-octane unleaded gasolines that will meet today`s ecological requirements. The term {open_quotes}reformulated gasolines{close_quotes} has come into general use throughout the world to denote fuels with a certain chemical composition. These gasolines consist of preselected components; as shown by worldwide experience, they must include oxygen-containing compounds that are distinguished by high octane numbers and low reactivities. Standards in effect in the United States, Japan, and certain Western European countries require that automotive gasolines must contain at least 2-4% by weight of oxygen-containing compounds (calculated as oxygen). In the last 15 years, in order to meet these requirements, production has been set up in various countries for the manufacture of high-octane oxygen-containing components known as oxygenates. The most common of these is methyl tert-butyl ether (MTBE), obtained by etherification of isobutene by methanol. Process technology developed by this last organization was used as the basis for constructing a unit in the Nizhnekamskneftekhim Production Association and at the Mazheikyai Petroleum Refinery in Lithuania. MTBE production has been held back mainly by a shortage of isobutene, which is obtained mainly from butane-butene cuts produced in cat crackers. In order to alleviate this shortage, it has been proposed that MTBE should be obtained from saturated C{sub 4} hydrocarbons that are recovered in processing oilfield associated gas, and also in the refinery from primary distillation units, catalytic reformers, and hydrocrackers. A working design was developed in 1991-1992 by Lengiproneftekhim for a basically new combination unit designed for the processing of saturated C{sub 4} hydrocarbons, which has been termed the LIDEM unit (Leningrad - isomerization - dehydrogenation - MTBE).

Rudin, M.G.; Zadvornov, M.A.

1994-09-01

100

Thin-layer chromatography to monitor cholesterol gallstone dissolution by methyl tert-butyl ether.  

PubMed

We describe a simple and inexpensive method of monitoring methyl tert-butyl ether (MTBE) dissolution of cholesterol gallstones with thin-layer chromatography (TLC) in 10 patients. TLC is a routine semiquantitative laboratory method that can be used to measure the cholesterol concentration present in the MTBE and bile mixture aspirated through the cholecystostomy catheter during gallstone dissolution. TLC is practical in the clinical setting because it can be used to determine if gallstone dissolution is occurring and when MTBE lavage is no longer effective. TLC is performed in the laboratory with routine material and is completed in 15 min. Each TLC measurement costs about $1. The procedure provides objective and specific chemical information on effectiveness and progression of gallstone dissolution, apart from the radiologic and sonographic studies. In our study, TLC signaled effective dissolution in the initial phase of gallstone dissolution by detecting large amounts of cholesterol in the MTBE and bile mixture even before a visible change in size or shape of the stone became apparent by transcatheter cholecystography or by sonography (six of 10 patients). Conversely, lack of cholesterol on TLC after 1 hr or more of MTBE infusion indicates that the stones are pigmented or contain substantial calcium. This means that dissolution with MTBE will be ineffective and that solvent infusion should be terminated. In those cases in which dissolution is progressing well, when TLC shows decreasing amounts of cholesterol in the effluent, only residual fragments insoluble to MTBE remain or the stone is sequestered from MTBE; at this point, solvent infusion should be discontinued or the catheter must be repositioned. Monitoring the rate of cholesterol dissolution by TLC provides important complementary information to cholecystography and sonography during gallstone treatment with MTBE. PMID:2048533

D'Agostino, H B; vanSonnenberg, E; Schteingart, C D; Hofmann, A F; Casola, G; Mathieson, J R

1991-07-01

101

Exposure to methyl tert-butyl ether and benzene among service station attendants and operators.  

PubMed

Concerns for atmospheric pollution from auto exhaust have led to the blending of "oxygenates" with motor fuels. The most common oxygenate, methyl tert-butyl ether (MTBE) is currently required within several metropolitan areas (Denver and Phoenix) in the range of 12% of the motor fuel. Amendments to the Clean Air Act may expand this requirement to as many as 44 other areas of the United States in the near future. In consideration of the magnitude of potential uncontrolled exposures from its extensive use and a related concern involving the potential influence of MTBE blending on exposures to other constituents of gasoline (particularly benzene), an evaluation of exposures among service station attendants and operators was undertaken at the request, and in cooperation with, the American Petroleum Institute during the latter part of 1990. For application of the survey results to a broad audience, three categories or types of service stations were identified with regard to MTBE use and exposure potential: a) service stations that do not use MTBE or use it only as an octane enhancer, b) service stations with seasonal requirements to use 12-15% MTBE (the Denver, Colorado, and Phoenix, Arizona, metropolitan areas), and c) service stations equipped with stage II (active) vapor recovery systems (several coastal areas, most notably Southern California). At the two sampled service stations that use only minimal amounts of MTBE (less than 1%), only 1 of 32 personal breathing zone (PBZ) samples from attendants was above the analytical limit of detection, reported at 0.16 ppm. The geometric mean concentration of benzene among this same population (n = 32) was 0.04 ppm.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8020445

Hartle, R

1993-12-01

102

Adsorption of methyl tert-butyl ether (MTBE) from aqueous solution by porous polymeric adsorbents.  

PubMed

MTBE has emerged as an important water pollutant because of its high mobility, persistence, and toxicity. In this study, a postcrosslinked polymeric adsorbent was prepared by postcrosslinking of a commercial chloromethylated polymer, and a nonpolar porous polymer with comparable surface area and micropore volume to the postcrosslinked polymer was prepared by suspended polymerization. The postcrosslinked polymer, nonpolar porous polymer and chloromethylated polymer were characterized by N2 adsorption, FTIR and XPS analysis. Results showed that postcrosslinking reaction led to the generation of a microporous postcrosslinked polymer with BET surface area 782m2g(-1), average pore width 3.0nm and micropore volume 0.33cm3g(-1). FTIR and XPS analysis indicated the formation of surface oxygen-containing groups on the postcrosslinked polymer. The three polymers were used as adsorbents to remove aqueous methyl tert-butyl ether (MTBE). Adsorption of MTBE over the postcrosslinked polymeric adsorbent was found to follow the linear adsorption isotherm, whereas MTBE adsorption onto the nonpolar porous polymer and chloromethylated polymer followed Langmuir adsorption model. Comparison of adsorption capacities of the postcrosslinked polymer, chloromethylated polymer and nonpolar porous polymer revealed that the adsorption of MTBE from aqueous solution is dependent on both pore structure and surface chemistry of polymeric adsorbents, and the high adsorption efficiency of the postcrosslinked polymer towards MTBE is attributed to its high surface area, large micropore volume and moderate hydrophility. The process of MTBE adsorption onto the adsorbents can be well described by pseudo-second-order kinetics, and the rate of adsorption decreased at higher MTBE initial concentration. PMID:18433995

Ji, Biyan; Shao, Fei; Hu, Guanjiu; Zheng, Shourong; Zhang, Qingmei; Xu, Zhaoyi

2008-03-20

103

Toxicokinetics of methyl tert-butyl ether and its metabolites in humans after oral exposure.  

PubMed

Methyl tert-butyl ether (MTBE) is widely used as an additive to gasoline, to increase oxygen content and reduce tailpipe emission of pollutants. Widespread human exposure to MTBE may occur due to leakage of gasoline storage tanks and a high stability and mobility of MTBE in ground water. To compare disposition of MTBE after different routes of exposure, its biotransformation was studied in humans after oral administration in water. Human volunteers (3 males and 3 females, identical individuals, exposures were performed 4 weeks apart) were exposed to 5 and 15 mg 13C-MTBE dissolved in 100 ml of water. Urine samples from the volunteers were collected for 96 h after administration in 6-h intervals and blood samples were taken in intervals for 24 h. In urine, MTBE and the MTBE-metabolites tert-butanol (t-butanol), 2-methyl-1,2-propane diol, and 2-hydroxyisobutyrate were quantified, MTBE and t-butanol were determined in blood samples and in exhaled air in a limited study of 3 male volunteers given 15 mg MTBE in 100 ml of water. MTBE blood concentrations were 0.69 +/- 0.25 microM after 15 mg MTBE and 0.10 +/- 0.03 microM after 5 mg MTBE. MTBE was rapidly cleared from blood with terminal half-lives of 3.7 +/- 0.9 h (15 mg MTBE) and 8.1 +/- 3.0 h (5 mg MTBE). The blood concentrations of t-butanol were 1.82 +/- 0.63 microM after 15 mg MTBE and 0.45 +/- 0.13 microM after 5 mg MTBE. Approximately 30% of the MTBE dose was cleared by exhalation as unchanged MTBE and as t-butanol. MTBE exhalation was rapid and maximal MTBE concentrations (100 nmol/l) in exhaled air were achieved within 10-20 min. Clearance of MTBE by exhalation paralleled clearance of MTBE from blood. T-butanol was cleared from blood with half-lives of 8.5 +/- 2.4 h (15 mg MTBE) and 8.1 +/- 1.6 h (5 mg MTBE). In urine samples, 2-hydroxyisobutyrate was recovered as major excretory product, t-butanol and 2-methyl-1,2-propane diol were minor metabolites. Elimination half-lives for the different urinary metabolites of MTBE were between 7.7 and 17.8 h. Approximately 50% of the administered MTBE was recovered in urine of the volunteers after both exposures, another 30% was recovered in exhaled air as unchanged MTBE and t-butanol. The obtained data indicate that MTBE-biotransformation and excretion after oral exposure is similar to inhalation exposure and suggest the absence of a significant first-pass metabolism of MTBE in the liver after oral administration. PMID:11294975

Amberg, A; Rosner, E; Dekant, W

2001-05-01

104

Biotransformation and kinetics of excretion of methyl-tert-butyl ether in rats and humans.  

PubMed

Methyl-tert-butyl ether (MTBE) is widely used as an additive to gasoline to increase oxygen content and reduce tail pipe emission of pollutants. Therefore, widespread human exposure may occur. To contribute to the characterization of potential adverse effects of MTBE, its biotransformation was compared in humans and rats after inhalation exposure. Human volunteers (3 males and 3 females) and rats (5 each, males and females) were exposed to 4 (4.5 +/- 0.4) and 40 (38.7 +/- 3.2) ppm MTBE for 4 h in a dynamic exposure system. Urine samples from rats and humans were collected for 72 h in 6-h intervals, and blood samples were taken in regular intervals for 48 h. In urine, MTBE and the MTBE metabolites tertiary-butanol (t-butanol), 2-methyl-1,2-propane diol, and 2-hydroxyisobutyrate were quantified; MTBE and t-butanol were determined in blood samples. After the end of the exposure period, inhalation of 40 ppm MTBE resulted in blood concentrations of MTBE 5.9 +/- 1.8 microM in rats and 6.7 +/- 1.6 microM in humans. The MTBE blood concentrations after inhalation of 4 ppm MTBE were 2.3 +/- 1.0 in rats and 1.9 +/- 0.4 microM in humans. MTBE was rapidly cleared from blood with a half-life of 2.6 +/- 0.9 h in humans and 0.5 +/- 0.2 h in rats. The blood concentrations of t-butanol were 21.8 +/- 3.7 microM in humans and 36.7 +/- 10.8 microM in rats after 40 ppm MTBE, and 2.6 +/- 0.3 in humans and 2.9 +/- 0.5 in rats after 4 ppm MTBE. In humans, t-butanol was cleared from blood with a half-life of 5.3 +/- 2.1 h. In urine samples from controls and in samples collected from the volunteers and rats before the exposure, low concentrations of t-butanol, 2-methyl-1,2-propane diol and 2-hydroxyisobutyrate were present. In urine of both humans and rats exposed to MTBE, the concentrations of these compounds were significantly increased. 2-Hydroxyisobutyrate was recovered as a major excretory product in urine; t-butanol and 2-methyl-1,2-propane diol were minor metabolites. All metabolites of MTBE excreted with urine were rapidly eliminated in both species after the end of the MTBE exposure. Elimination half-lives for the different urinary metabolites of MTBE were between 7.8 and 17.0 h in humans and 2.9 to 5.0 h in rats. The obtained data indicate that MTBE biotransformation and excretion are similar in rats and humans, and MTBE and its metabolites are rapidly excreted in both species. Between 35 and 69% of the MTBE retained after the end of the exposure was recovered as metabolites in urine of both humans and rats. PMID:10496672

Amberg, A; Rosner, E; Dekant, W

1999-09-01

105

Methyl tert-Butyl Ether (MTBE) in Ground Water, Air, and Precipitation at North Windham, Maine  

USGS Publications Warehouse

Thirty-one monitoring wells in the Windham aquifer in North Windham, Maine, were sampled for methyl tert-butyl ether (MTBE) from July 1998 to May 1999. MTBE was detected in 35 percent of the wells sampled in the Windham aquifer. MTBE was detected in 64 percent of wells in the high-yielding part of the aquifer; these wells account for 82 percent of all wells with detectable MTBE. Land cover also was found to be associated with MTBE in the wells in the study area, with the urban and low-density residential areas having more MTBE than undeveloped areas. The median concentration in wells with detectable MTBE was 1.13 micrograms per liter. Air and precipitation samples were collected in North Windham along with ground-water samples. Air samples were collected every 10 days from December 1998 to July 1999 (20 samples). MTBE was present in all 20 air samples collected, at concentrations ranging from 0.03 ppbv (parts per billion by volume) to 1.0 ppbv. Before Maine opted out of the reformulated gasoline (RFG) program in the spring of 1999, median concentrations in air at the North Windham site were 0.25 ppbv. After Maine stopped using RFG, the median concentration in air dropped to 0.09 ppbv. No MTBE was detected in four samples of precipitation at North Windham. The lack of rainfall during the study period prevented the collection of an adequate number of samples, and technical difficulties negated the results of some of the analyses of the samples that were collected. Based on the equilibrium partitioning of MTBE from the air into rain, the hypothetical average concentration of MTBE in rainfall during months when recharge typically occurs (March-April and October-December) would be approximately 0.3 to 0.4 micrograms per liter during the time that RFG was being used in Maine. After the phaseout of RFG, the maximum average concentration of MTBE in rainfall during these months would be approximately 0.1 micrograms per liter. The distribution and concentrations of MTBE that were detected in ground water indicate that recharge from precipation containing MTBE is not a likely explanation for the occurrence of MTBE in the Windham aquifer.

Nielsen, Martha G.; Peckenham, John M.

2000-01-01

106

Atmospheric and potable water exposures to methyl tert-butyl ether (MTBE).  

PubMed

This paper presents information on the ways in which people can be exposed to methyl tert-butyl ether (MTBE) via air and water and on the distribution of doses that can result from those exposures. Data on concentrations of MTBE in air were complied for 15 different occupational, commuting, or residential exposure categories, and concentrations in potable water were complied from five states in the MTBE-using areas of the United States. Based on these concentrations and characteristics of the exposed populations, average daily and lifetime average doses were estimated. Both the concentration data and several of the population characteristics were estimated as distributions rather than as point values so that the numbers of people exposed at various levels could be estimated. Arithmetic mean occupational doses via air were in the range of 0.1 to 1.0 mg/kg-day, while doses from residential exposures, commuting, and refueling were in the range of 0.0004 to 0.006 mg/kg-day. Lifetime doses for workers were in the range 0.01 to 0.1 mg/kg-day. The cumulative dose distribution for the entire population of the MTBE-using regions of the United States was estimated by combining the distributions of doses and the numbers of people in each exposure category. In the MTBE-using areas, arithmetic mean doses via air were estimated to be 0.0053 and 0.00185 mg/kg-day for the chronic and lifetime cases, respectively. Approximately 98.5% of the population living in MTBE-using regions uses water with concentrations affected only by atmospheric deposition, if at all, and too low to be detected with current methods (< 2 micrograms/liter). The remaining population uses water with an estimated geometric mean concentration of 0.36 microgram/liter, an arithmetic mean concentration of 49 micrograms/l, and a 95th percentile concentration of 64 micrograms/liter. Doses via ingestion, inhalation, and dermal absorption were included. The estimated arithmetic mean dose for the population exposed via water was 1.4 x 10(-3) mg/kg-day. PMID:9237328

Brown, S L

1997-06-01

107

U.S. Geological Survey laboratory method for methyl tert-Butyl ether and other fuel oxygenates  

USGS Publications Warehouse

Methyl tert-butyl ether (MTBE) was found in shallow ground-water samples in a study of 8 urban and 20 agricultural areas throughout the United States in 1993 and 1994 (Squillace and others, 1995, p. 1). The compound is added to gasoline either seasonally or year round in many parts of the United States to increase the octane level and to reduce carbon monoxide and ozone levels in the air. The U.S. Geological Survey (USGS) National Water Quality Laboratory (NWQL), near Denver, uses state-of-the-art technology to analyze samples for MTBE as part of the USGS water-quality studies. In addition, the NWQL offers custom analyses to determine two other fuel oxygenates--ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME). The NWQL was not able to obtain a reference standard for tert-amyl ethyl ether (TAEE), another possible fuel oxygenate (Shelley and Fouhy, 1994, p. 63). The shallow ground-water samples were collected as part of the USGS National Water-Quality Assessment Program. These samples were collected from 211 urban wells or springs and 562 agricultural wells sampled by the USGS in 1993 and 1994. The wells were keyed to specific land-use areas to assess the effects of different uses on ground-water quality (Squillace and others, 1995, p. 2). Ground-water samples were preserved on site to pH less than or equal to 2 with a solution of 1:1 hydrochloric acid. All samples were analyzed at the NWQL within 2 weeks after collection. The purpose of this fact sheet is to explain briefly the analytical method implemented by the USGS for determining MTBE and other fuel oxygenates. The scope is necessarily limited to an overview of the analytical method (instrumentation, sample preparation, calibration and quantitation, identification, and preservation of samples) and method performance (reagent blanks, accuracy, and precision).

Raese, Jon W.; Rose, Donna L.; Sandstrom, Mark W.

1995-01-01

108

Toxicokinetics of Methyl tertButyl Ether and Its Metabolites in Humans after Oral Exposure  

Microsoft Academic Search

13 C-MTBE dissolved in 100 ml of water. Urine samples from the volunteers were collected for 96 h after administration in 6-h intervals and blood samples were taken in intervals for 24 h. In urine, MTBE and the MTBE-metab- olites tert-butanol (t-butanol), 2-methyl-1,2-propane diol, and 2-hy- droxyisobutyrate were quantified, MTBE and t-butanol were deter- mined in blood samples and in

Alexander Amberg; Elisabeth Rosner; Wolfgang Dekant

2001-01-01

109

Bis[?-N-(tert-butyl-dimethyl-silyl)-N-(pyridin-2-ylmeth-yl)amido]-bis-[methyl-cobalt(II)  

PubMed Central

The green title complex, [Co2(CH3)2(C12H21N2Si)2], was obtained from bis­{[?-N-tert-butyl­dimethyl­silyl-N-(pyridin-2-ylmeth­yl)amido]­chloridocobalt(II)} and methyl­lithium in diethyl ether at 195?K via a metathesis reaction. The dimeric cobalt(II) complex exhibits a crystallographic center of inversion in the middle of the Co2N2 ring (average Co—N = 2.050?Å). The CoII atom shows a distorted tetra­hedral coordination sphere. The exocyclic Co—N bond length to the pyridyl group shows a similar value of 2.045?(4)?Å. The exocyclic methyl group has a rather long Co—C bond length of 2.019?(5)?Å.

Malassa, Astrid; Agthe, Christine; Gorls, Helmar; Westerhausen, Matthias

2012-01-01

110

Microbial degradation and fate in the environment of methyl tert-butyl ether and related fuel oxygenates.  

PubMed

Oxygenates, mainly methyl tert-butyl ether (MTBE), are commonly added to gasoline to enhance octane index and improve combustion efficiency. Other oxygenates used as gasoline additives are ethers such as ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and alcohols such as tert-butyl alcohol (TBA). As a result of its wide use, MTBE has been detected, mainly in the USA, in groundwater and surface waters, and is a cause of concern because of its possible health effects and other undesirable consequences. MTBE is a water-soluble and mobile compound that generates long pollution plumes in aquifers impacted by gasoline releases from leaking tanks. Field observations concur in estimating that, because of recalcitrance to biodegradation, natural attenuation is slow (half-life of at least 2 years). However, quite significant advances have been made in recent years concerning the microbiology of the degradation of MTBE and other oxygenated gasoline additives. The recalcitrance of these compounds results from the presence in their structure of an ether bond and of a tertiary carbon structure. For the most part, only aerobic microbial degradation systems have been reported so far. Consortia capable of mineralizing MTBE have been selected. Multiple instances of the cometabolism of MTBE with pure strains or with microflorae, growing on n-alkanes, isoalkanes, cyclohexane or ethers (diethyl ether, ETBE), have been described. MTBE was converted into TBA in all cases and was sometimes further degraded, but it was not used as a carbon source by the pure strains. However, mineralization of MTBE and TBA by several pure bacterial strains using these compounds as sole carbon and energy source has recently been reported. The pathways of metabolism of MTBE involve the initial attack by a monooxygenase. In several cases, the enzyme was characterized as a cytochrome P-450. After oxygenation, the release of a C -unit as formaldehyde or formate leads to the production of TBA, which can be converted to 2-hydroxyisobutyric acid and further metabolized. Developments in microbiology make biological treatment of water contaminated with MTBE and other oxygenates an attractive possibility. Work concerning ex situ treatment in biofilters by consortia and by pure strains, and involving or not cometabolism, is under way. Furthermore, the development of in situ treatment processes is a promisinggoal. PMID:11549000

Fayolle, F; Vandecasteele, J P; Monot, F

2001-08-01

111

Biodegradation of methyl tert-butyl ether by cometabolism with hexane in biofilters inoculated with Pseudomonas aeruginosa.  

PubMed

Biodegradation of methyl tert-butyl ether (MTBE) vapors by cometabolism with gaseous hexane (n-hexane > 95%) was investigated using Pseudomonas aeruginosa utilizing short chain aliphatic hydrocarbon (C(5)-C(8)). Kinetic batch experiments showed that MTBE was degraded even when hexane was completely exhausted with a cometabolic coefficient of 1.06 ± 0.16 mg MTBE mg hexane(-1). Intermediate tert-butyl alcohol (TBA) accumulation was observed followed by its gradual consumption. A maximum MTBE elimination capacity (EC(MAX)) of 35 g m(-3) h(-1) and removal efficiency (RE) of 70% were attained in mineral medium amended biofilters having an empty bed residence time (EBRT) of 1 min. For these experimental conditions, a maximum hexane EC of approximately 60 g m(-3) h(-1) was obtained at a load of 75 g m(-3) h(-1). Experiments under transient conditions revealed a competitive substrate interaction between MTBE and hexane. Biomass densities between 5.8 and 12.6 g L(biofilter) (-1) were obtained. Nevertheless, production of biopolymers caused non-uniform distribution flow rates that reduced the performance. Residence time distribution profiles showed an intermediate dispersion flow rate with a dispersion coefficient of 0.8 cm(2) s(-1). PMID:22486671

Salazar, Margarita; Morales, Marcia; Revah, Sergio

2012-01-01

112

Aerobic biodegradation of methyl tert-butyl ether by aquifer bacteria from leaking underground storage tank sites.  

PubMed

The potential for aerobic methyl tert-butyl ether (MTBE) degradation was investigated with microcosms containing aquifer sediment and groundwater from four MTBE-contaminated sites characterized by oxygen-limited in situ conditions. MTBE depletion was observed for sediments from two sites (e.g., 4.5 mg/liter degraded in 15 days after a 4-day lag period), whereas no consumption of MTBE was observed for sediments from the other sites after 75 days. For sediments in which MTBE was consumed, 43 to 54% of added [U-(14)C]MTBE was mineralized to (14)CO(2). Molecular phylogenetic analyses of these sediments indicated the enrichment of species closely related to a known MTBE-degrading bacterium, strain PM1. At only one site, the presence of water-soluble gasoline components significantly inhibited MTBE degradation and led to a more pronounced accumulation of the metabolite tert-butyl alcohol. Overall, these results suggest that the effects of oxygen and water-soluble gasoline components on in situ MTBE degradation will vary from site to site and that phylogenetic analysis may be a promising predictor of MTBE biodegradation potential. PMID:11722940

Kane, S R; Beller, H R; Legler, T C; Koester, C J; Pinkart, H C; Halden, R U; Happel, A M

2001-12-01

113

Aerobic Biodegradation of Methyl tert-Butyl Ether by Aquifer Bacteria from Leaking Underground Storage Tank Sites  

PubMed Central

The potential for aerobic methyl tert-butyl ether (MTBE) degradation was investigated with microcosms containing aquifer sediment and groundwater from four MTBE-contaminated sites characterized by oxygen-limited in situ conditions. MTBE depletion was observed for sediments from two sites (e.g., 4.5 mg/liter degraded in 15 days after a 4-day lag period), whereas no consumption of MTBE was observed for sediments from the other sites after 75 days. For sediments in which MTBE was consumed, 43 to 54% of added [U-14C]MTBE was mineralized to 14CO2. Molecular phylogenetic analyses of these sediments indicated the enrichment of species closely related to a known MTBE-degrading bacterium, strain PM1. At only one site, the presence of water-soluble gasoline components significantly inhibited MTBE degradation and led to a more pronounced accumulation of the metabolite tert-butyl alcohol. Overall, these results suggest that the effects of oxygen and water-soluble gasoline components on in situ MTBE degradation will vary from site to site and that phylogenetic analysis may be a promising predictor of MTBE biodegradation potential.

Kane, S. R.; Beller, H. R.; Legler, T. C.; Koester, C. J.; Pinkart, H. C.; Halden, R. U.; Happel, A. M.

2001-01-01

114

Occurrence and Temporal Variability of Methyl tert-ButylEther (MTBE) and Other Volatile Organic Compounds in Select Sources of Drinking Water: Results of the Focused Survey.  

National Technical Information Service (NTIS)

The large-scale use of the gasoline oxygenate methyl tert-butyl ether (MTBE), and its high solubility, low soil absorption, and low biodegradability, has resulted in its detection in ground water and surface water in many places throughout the United Stat...

G. C. Delzer T. Ivahnenko

2003-01-01

115

Addition of dimethylsulphoxide to methyl-tert-butyl ether and ethyl propionate increases cholesterol dissolving capacity and cholesterol gall stone dissolution in vitro  

Microsoft Academic Search

There is a discrepancy between in vitro cholesterol dissolving efficacy of methyl-tert-butyl ether (MTBE) and ethyl propionate and cholesterol gall stone dissolution in vivo. This study investigated whether the presence of bile changes the cholesterol dissolving capacity of MTBE and ethyl propionate. The addition of dimethylsulphoxide to MTBE or ethyl propionate was also studied to discover if it improves the

J J Bergman; A K Groen; K Huibregtse; G N Tytgat

1994-01-01

116

The first non-acid catalytic synthesis of tert-butyl ether from tert-butyl alcohol using ionic liquid as dehydrator.  

PubMed

Methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and isopropyl tert-butyl ether (IPTBE) have been synthesized for the first time over a non-acid ionic liquid as catalyst and dehydrator with high conversion (> 90%) and selectivity (> 90%) under mild conditions. PMID:12772899

Shi, Feng; Xiong, Hai; Gu, Yanlong; Guo, Shu; Deng, Youquan

2003-05-01

117

3,3?-Di-tert-butyl-1,1?-[1,3-phenyl-enebis(methyl-ene)]diurea  

PubMed Central

The title compound, C18H30N4O2, contains two tert-butyl urea groups, each connected to a benzene ring though a methyl­ene group. One of the groups occupies a position almost normal to the aromatic plane with a C—N—C—C torsion angle of ?94.4?(4)°, while the other is considerably twisted from the ring with a C—N—C—C torsion angle of ?136.1?(4)°. In the crystal, pairs of mol­ecules are connected to each other, forming centrosymmetric dimers in which two NH groups of one mol­ecule act as hydrogen-bond donors to one carbonyl O atom of the other mol­ecule. The dimers are linked into sheets parallel to (100) by N—H?O hydrogen bonds involving the remaining N—H and C=O groups.

Saeed, Musabbir A.; Fronczek, Frank R.; Hossain, Md. Alamgir

2010-01-01

118

Aromatic hydrocarbon and methyl tert-butyl ether measurements in ambient air of Helsinki (Finland) using diffusive samplers.  

PubMed

The diffusive sampling method was evaluated for measuring benzene, toluene, ethylbenzene, xylenes, styrene, propylbenzene, ethyltoluenes, trimethylbenzenes and methyl tert-butyl ether (MTBE) in the urban air of Helsinki, Finland. Concentrations were measured in 2-week periods at four different sites during the year 2000. Tube type adsorbent tubes were pre-packed with Carbopack-B (60/80). Analysis was conducted using thermal desorption and gas chromatograph coupled to a mass spectrometer. In different seasons, during five diffusive sampling periods, parallel measurements were conducted using pumped and online sampling. The compared techniques agreed reasonably well for other compounds than trimethylbenzenes. Based on comparisons, diffusive uptake rates for ethyltoluenes, styrene, propylbenzene and MTBE were determined, and for trimethylbenzenes, uptake rates were revised. The concentrations of aromatic compounds in Helsinki metropolitan area were also compared to the concentrations of a rural, forested site in Central Finland. PMID:12449329

Hellén, Heidi; Hakola, Hannele; Laurila, Tuomas; Hiltunen, Veijo; Koskentalo, Tarja

2002-10-21

119

Arbuscular mycorrhizal fungi in a wetland constructed for benzene-, methyl tert-butyl ether- and ammonia-contaminated groundwater bioremediation.  

PubMed

Arbuscular mycorrhizal fungi (AMF), which are present in most natural environments, have demonstrated capacity to promote biodegradation of organic pollutants in the greenhouse. However, it is not certain whether AMF can spontaneously establish in phytoremediation systems constructed to decontaminate groundwater, because of the unusual conditions during the construction and operation of such systems. To assess this possibility, root samples from a wetland constructed for the phytoremediation of groundwater contaminated with benzene, methyl tert-butyl ether and ammonia were analysed. Substantial AMF colonization was observed in plant roots sampled close to the inlet of a basin filled with fine gravel and planted with Phragmites australis. In addition, analysis of a fragment of the nuclear large ribosomal subunit, amplified by nested PCR, revealed the presence of AMF molecular operational taxonomic units closely related to Funneliformis mosseae and Rhizophagus irregularis in the samples. These findings demonstrate the capacity of generalist AMF strains to establish spontaneously, rapidly and extensively in groundwater bioremediation technical installations. PMID:22846140

Fester, Thomas

2012-07-31

120

Dissolution of cholesterol gallbladder stones with methyl tert-butyl ether in patients with increased surgical risk.  

PubMed

The safety and efficacy of methyl tert-butyl ether (MTBE) dissolution of cholesterol gallbladder stones were evaluated in 25 patients with increased risk for surgery. Two patients were treated twice. The MTBE was infused and aspirated manually through a percutaneous transhepatic catheter to the gallbladder. The placement of the catheter failed in three patients (11%). In 19 of 24 patients (79%) there was complete dissolution of stones after a mean treatment time of 12.2 h (range, 4.3-19.5 h). In five patients treatment was discontinued before complete dissolution owing to technical problems or side effects. Side effects were nausea, pain, vasovagal reaction, and fever. Fifteen patients were followed up for a mean of 15.7 months after dissolution. Stone recurrence was found in eight patients, five of whom suffered symptomatic relapse. We conclude that dissolution therapy with MTBE is a safe and adequate alternative to surgery in selected high-risk patients. PMID:8210992

Eidsvoll, B E; Aadland, E; Stiris, M; Lunde, O C

1993-08-01

121

Direct dissolution of gallstones with methyl tert-butyl ether (MTBE) via endoscopic transpapillary catheterization in the gallbladder (ETCG).  

PubMed

In a pilot study of direct dissolution therapy of gallstones with methyl tert-butyl ether (MTBE), endoscopic transpapillary catheterization in the gallbladder (ETCG) was performed. Complete dissolution was seen in 8 out of 12 (66%) patients and partial dissolution was seen in 2 (16%) patients. In one of the 8 complete dissolution patients, combined extracorporeal shock wave lithotripsy (ESWL) and dissolution therapy was carried out successfully. These 8 patients were followed up for 12-20 months with regular ultrasonography. During this period, 1 patient underwent laparoscopic cholecystectomy due to stone recurrence. Thickening of the gallbladder wall was seen in 2 patients, but there were no other complications. Using Tsuchiya's classification based on ultrasound, complete dissolution was seen in type Ia stones. This pilot study suggests that the direct dissolution of gallstones with MTBE via ETCG might be a useful and safe non-invasive treatment in patients with cholesterol stones in preserved gallbladders. PMID:7951860

Uchida, N; Nakatsu, T; Hirabayashi, S; Minami, A; Fukuma, H; Ezaki, T; Morshed, S A; Fuke, C; Ameno, K; Ijiri, I

1994-08-01

122

Increased blood levels of methyl tert-butyl ether but not of ethyl propionate during instillation with contact gallstone dissolution agents in the pig.  

PubMed

We performed experiments in anesthetized piglets with two cholesterol gallstone solvents, methyl tert-butyl ether and ethyl propionate, to determine whether blood levels of either solvent would increase during gallbladder instillation of these solvents under conditions simulating gallstone dissolution. The solvent was oscillated rapidly in and out of the gallbladder with a computer-controlled syringe pump; intraluminal pressure was set below the leakage pressure, and oscillating volume was set below the leakage volume to decrease loss of solvent into the intestine. Blood levels were measured with gas chromatography. Six piglets received methyl tert-butyl ether, and six piglets received ethyl propionate. During 2 hr of instillation with methyl tert-butyl ether, blood levels increased steadily to concentrations averaging 0.3 ml/L blood at 2 hr; during a 6-hr period of instillation, blood levels rose to above 0.4 ml/L blood. Replacement of methyl tert-butyl ether with saline solution in the gallbladder caused blood levels to decline gradually; plasma levels decreased by half in 90 min. In contrast, when ethyl propionate was infused for 2 or 6 hr, blood levels remained below the detection limit, probably because of high first-pass hepatic extraction. We conclude that, under conditions simulating those likely present in patients undergoing contact dissolution of gallbladder stones, the two solvents differ: Ethyl propionate is removed so rapidly from blood that its levels remain undetectable, whereas methyl tert-butyl ether levels in blood (and, presumably, peripheral tissues) increase continuously.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8340066

Esch, O; Schteingart, C D; Pappert, D; Kirby, D; Streich, R; Hofmann, A F

1993-08-01

123

Distribution of methyl tert-butyl ether (MTBE) and selected water-quality constituents in the surficial aquifer at the Dover National Test Site, Dover Air Force Base, Delaware, 2001  

USGS Publications Warehouse

A joint study by the Dover National Test Site, Dover Air Force Base, Delaware, and the U.S. Geological Survey was conducted from June 27 through July 18, 2001, to determine the spatial distribution of the gasoline oxygenate additive methyl tert-butyl ether and selected water-quality constituents in the surficial aquifer underlying the Dover National Test Site. This report provides a summary assessment of the distribution of methyl tert-butyl ether and a preliminary screening of selected constituents that may affect natural attenuation and remediation demonstrations at the Dover National Test Site. The information gathered during this study is designed to assist potential remedial investigators who are considering conducting a methyl tert-butyl ether remedial demonstration at the test site. In addition, the study supported a planned enhanced bioremediation demonstration and assisted the Dover National Test Site in identifying possible locations for future methyl tert-butyl ether remediation demonstrations. A direct-push drill rig was used to collect a total of 147 ground-water samples (115 VOC samples and 32 quality-assurance samples) at varying depths. Volatile organic compounds were above the method reporting limits in 59 of the 115 ground-water samples. The concentrations ranged from below detection limits to maximum values of 12.4 micrograms per liter of cis-1,2-dichloro-ethene, 1.14 micrograms per liter of trichloro-ethene, 2.65 micrograms per liter of tetrachloro-ethene, 1,070 micrograms per liter of methyl tert-butyl ether, 4.36 micrograms per liter of benzene, and 1.8 micrograms per liter of toluene. Vinyl chloride, ethylbenzene, p,m-xylene, and o-xylene were not detected in any of the samples collected during this investigation. Methyl tert-butyl ether was detected in 47 of the 115 ground-water samples. The highest concentrations of methyl tert-butyl ether were detected in the surficial aquifer from ?4.6 to 6.4 feet mean sea level; however, methyl tert-butyl ether was detected as deep as ?9.5 feet mean sea level. Increased methane concentrations and decreased dissolved oxygen concentrations that were found in association with the ground-water samples that contained methyl tert-butyl ether are preliminary indicators that will assist in determining if natural attenuation of methyl tert-butyl ether is occurring in the surficial aquifer. A full assessment of natural attenuation of methyl tert-butyl ether at the site is beyond the scope of this study, but the data collected during the study will be useful in selecting appropriate remedial methyl tert-butyl ether demonstrations.

Stewart, Marie; Guertal, William R.; Barbaro, Jeffrey R.; McHale, Timothy J.

2004-01-01

124

Mineralization of methyl tert-butyl ether and other gasoline oxygenates by Pseudomonads using short n-alkanes as growth source.  

PubMed

Biodegradation of methyl tert-butyl ether (MTBE) by cometabolism has shown to produce recalcitrant metabolic intermediates that often accumulate. In this work, a consortium containing Pseudomonads was studied for its ability to fully degrade oxygenates by cometabolism. This consortium mineralized MTBE and TBA with C3-C7 n-alkanes. The highest degradation rates for MTBE (75 +/- 5 mg g(protein) (-1) h(-1)) and TBA (86.9 +/- 7.3 mg g(protein) (-1) h(-1)) were obtained with n-pentane and n-propane, respectively. When incubated with radiolabeled MTBE and n-pentane, it converted more than 96% of the added MTBE to (14)C-CO(2). Furthermore, the consortium degraded tert-amyl methyl ether, tert-butyl alcohol (TBA), tert-amyl alcohol, ethyl tert-butyl ether (ETBE) when n-pentane was used as growth source. Three Pseudomonads were isolated but only two showed independent MTBE degradation activity. The maximum degradation rates were 101 and 182 mg g(protein) (-1) h(-1) for Pseudomonas aeruginosa and Pseudomonas citronellolis, respectively. The highest specific affinity (a degrees (MTBE)) value of 4.39 l g(protein) (-1) h(-1) was obtained for Pseudomonas aeruginosa and complete mineralization was attained with a MTBE: n-pentane ratio (w/w) of 0.7. This is the first time that Pseudomonads have been reported to fully mineralize MTBE by cometabolic degradation. PMID:18814038

Morales, Marcia; Nava, Verónica; Velásquez, Elia; Razo-Flores, Elías; Revah, Sergio

2008-09-24

125

13C(2)-Labeled methyl tert-butyl ether: toxicokinetics and characterization of urinary metabolites in humans.  

PubMed

After exposure to methyl tert-butyl ether (MTBE), a gasoline additive, only one metabolite [tert-butyl alcohol (TBA), <1% of dose] has been identified in human urine [Nihlén, A., et al. (1998) Toxicol. Appl. Pharmacol. 148, 274-280]. In the study presented here, metabolites of MTBE were characterized by (1)H-decoupled (13)C NMR spectroscopy in urine obtained from four volunteers experimentally exposed to 50 ppm (13)C-labeled MTBE ([1,2-(13)C(2)]MTBE) vapor (facemask) for 2 h during a light physical work load (50 W). Chemical shifts for the two adjacent (13)C-labeled carbons in [1, 2-(13)C(2)]MTBE-derived metabolites were consistent with the shifts obtained for spiked standards of alpha-hydroxyisobutyric acid (HBA) and 2-methyl-1,2-propanediol (MPD). NMR signals were not detected for labeled MTBE, TBA, or possible MTBE-derived conjugates. Quantification of HBA and MPD was performed by NMR for two urine samples (collected 20 h after exposure). One subject had 11% HBA and 1% MPD, and the other individual had 3% HBA and 1% MPD in the urine, expressed as a percentage of MTBE uptake. This indicates that HBA and MPD occur at significantly higher levels in the urine (detected by NMR) than MTBE and TBA (detected by GC). To our knowledge, this is the first characterization of MTBE metabolites, other than TBA, in humans. Further urine, blood, and expired air were collected up to 22 h after exposure, and the toxicokinetics of MTBE, TBA, and acetone were determined by GC. Low relative uptake (39%), a low level of postexposure exhalation of MTBE (17%), and low recovery of TBA in the urine (<1%) were observed. The same subjects had previously been exposed to unlabeled MTBE in a whole-body exposure study [Nihlén, A., et al. (1998) Toxicol. Appl. Pharmacol. 148, 274-280], and the toxicokinetics of MTBE and TBA in this facemask exposure did not differ from the previous whole-body chamber exposure. PMID:10490504

Nihlén, A; Sumner, S C; Löf, A; Johanson, G

1999-09-01

126

Detection and Quantification of Methyl tertButyl Ether-Degrading Strain PM1 by Real-Time TaqMan PCR  

Microsoft Academic Search

The fuel oxygenate methyl tert-butyl ether (MTBE), a widely distributed groundwater contaminant, shows potential for treatment by in situ bioremediation. The bacterial strain PM1 rapidly mineralizes and grows on MTBE in laboratory cultures and can degrade the contaminant when inoculated into groundwater or soil microcosms. We applied the TaqMan quantitative PCR method to detect and quantify strain PM1 in labora-

KRASSIMIRA R. HRISTOVA; CHRISTIAN M. LUTENEGGER; KATE M. SCOW

2001-01-01

127

Liquid–liquid equilibrium data of water with neohexane, methylcyclohexane, tert-butyl methyl ether, n-heptane and vapor–liquid–liquid equilibrium with methane  

Microsoft Academic Search

Liquid–liquid equilibrium (LLE) data for non-aqueous liquid (neohexane [NH], tert-butyl methyl ether [TBME], methylcyclohexane [MCH], or n-heptane [nC7]) and water have been measured under atmospheric pressure at 275.5, 283.15, and 298.15K. It was found that TBME is the most water soluble followed by NH, MCH, and nC7. As the temperature increased, the solubility of the non-aqueous liquids (NALs) in water

R. Susilo; J. D. Lee; P. Englezos

2005-01-01

128

Mathematical simulation and X-ray diffraction investigation of the crystal structure of 1-phenyl-1- tert-butyl-3-methyl-1,3-dihydroisobenzofuran  

Microsoft Academic Search

An algorithm for using a priori generation of crystal structures by the discrete modeling method for the interpretation of data obtained from single-crystal X-ray diffraction experiments is considered. The crystal structure of 1-phenyl-1- tert-butyl-3-methyl-1,3-dihydroisobenzofuran is mathematically simulated using the discrete modeling of molecular packings and studied by X-ray diffraction. The simulation is performed for two isomers of the initial chemical

A. V. Maleev; I. K. Zhitkov; K. A. Potekhin

2008-01-01

129

Method detection limit determination and application of a convenient headspace analysis method for methyl tert-butyl ether in water.  

PubMed

Methyl tert-butyl ether (MTBE) is a common groundwater contaminant, introduced to the environment by leaking petroleum storage tanks, urban runoff, and motorized watercraft. In this study. a simplified (static) headspace analysis method was adapted for determination of MTBE in water samples and soil water extracts. The MDL of the headspace method was calculated to be 2.0 microg L(-1) by the EPA single-concentration design method(1) and 1.2 microg L(-1) by a calibration method developed by Hubaux and Vos (Hubaux, A.; Vos, G. Anal. Chem. 1970,42, 849-855). The MDL calculated with the Hubaux and Vos method was favored because it considers both a true positive and a false positive. The static headspace method was applied to analysis of a tap water sample and a monitoring well sample from a gasoline service station, a river sample, and aqueous extracts from soil excavated during removal of a leaking underground storage tank (LUST). The water samples examined in this study had MTTBE concentrations ranging from 6 to 19 microg L(-1). Aqueous extracts of a soil sample taken from the LUST site had 8 microg L(-1) MTBE. PMID:12463380

O'Neill, Dennis T; Rochette, Elizabeth A; Ramsey, Philip J

2002-11-15

130

Synthesis of octane enhancers during slurry-phase Fischer-Tropsch. [801Methyl tert-butyl ether  

SciTech Connect

The objective of this project is to investigate three possible routes to the formation of ethers, in particular methyl tert-butyl ether (MTBE), during slurry phase Fischer-Tropsch reaction. The three reaction schemes to be investigated are: (1) Addition of isobutylene during the formation of methanol and/or higher alcohols directly from CO and H{sub 2} during slurry-phase Fischer-Tropsch. (2) Addition of isobutylene to FT liquid products including alcohols in a slurry-phase reactor containing an MTBE or other acid catalyst. (3) Addition of methanol to slurry phase FT synthesis making iso-olefins. During the sixth quarter we completed the construction of the slurry bubble column reactor (SBCR), conducted initial shake-down experiments in a cold-flow mode, and finalized the selection process of the acid catalysts for conversion of syngas-produced alcohols and isobutylene to MTBE (scheme 2). Tasks 3, 4, and 5 are awaiting complete implementation of the SBCR system.

Marcelin, G.

1992-06-24

131

O3/H2O2 treatment of methyl-tert-butyl ether (MTBE) in contaminated waters.  

PubMed

The kinetics and efficiency of oxidation of methyl-tert-butyl ether (MTBE) in contaminated water employing O3/H2O2 advanced oxidation process is presented in this paper. Kinetic simulation is based on the model mechanism published in literature (Staehelin and Hoigne, Environ. Sci. Technol. 16 (1982) 676; Glaze and Kang, Ind. Eng. Chem. Res. 26 (1989) 1573) indicates that the oxidation of MTBE is primarily induced by the hydroxyl radical. The degradation of MTBE can be described by a pseudo-first-order kinetics in two phases. The first-phase covers MTBE concentrations greater than 10 mg L(-1) and the second-phase covers MTBE concentrations below 10 mg L(-1). The rate of oxidation of MTBE (at least in the first-phase) is limited by ozone mass transfer and increases with increasing ozone gas flow rate. The pseudo-first-order reaction rate constant varies from 2.0 x 10(-3) to 5.4 x 10(-3) s(-1) over the range of ozone gas flow rate employed in this investigation. An efficiency index is defined and its value for the oxidation of MTBE in different water is provided. The data provided show that remediation of MTBE-contaminated groundwater by O3/H2O2 process is more efficient and less costly than by the UV/H2O2 process. PMID:11561633

Safarzadeh-Amiri, A

2001-10-01

132

Methylibium petroleiphilum gen. nov., sp. nov., a novel methyl tert-butyl ether-degrading methylotroph of the Betaproteobacteria.  

PubMed

A Gram-negative, rod-shaped, motile, non-pigmented, facultative aerobe that grew optimally at pH 6.5 and 30 degrees C (strain PM1T) was isolated for its ability to completely degrade the gasoline additive methyl tert-butyl ether. Analysis of the 16S rRNA gene sequence indicated that this bacterium was a member of the class Betaproteobacteria in the Sphaerotilus-Leptothrix group. The 16S rRNA gene sequence identity to other genera in this group, Leptothrix, Aquabacterium, Roseateles, Sphaerotilus, Ideonella and Rubrivivax, ranged from 93 to 96 %. The chemotaxonomic data including Q-8 as the major quinone, C16 : 1omega7c and C16 : 0 as the major fatty acids and a DNA G+C content of 69 mol%, support the inclusion of strain PM1T in the class Betaproteobacteria. It differed from other members of the Sphaerotilus-Leptothrix group by being a facultative methylotroph that used methanol as a sole carbon source, and by also being able to grow heterotrophically in defined media containing ethanol, toluene, benzene, ethylbenzene and dihydroxybenzoates as sole carbon sources. On the basis of the morphological, physiological, biochemical and genetic information, a new genus and species, Methylibium petroleiphilum gen. nov., sp. nov., is proposed, with PM1T (=ATCC BAA-1232T=LMG 22953T) as the type strain. PMID:16627642

Nakatsu, Cindy H; Hristova, Krassimira; Hanada, Satoshi; Meng, Xian-Ying; Hanson, Jessica R; Scow, Kate M; Kamagata, Yoichi

2006-05-01

133

Methyl tert-butyl ether (MTBE) induced Ca(2+)-dependent cytotoxicity in isolated rabbit tracheal epithelial cells.  

PubMed

As a volatile synthetic organic chemical, methyl tert-butyl ether (MTBE) was the most common gasoline additive. The increasing use of MTBE raised concern over its health safety. Inhalation was the principle route of exposure for the general population. This study used a model of rabbit tracheal epithelial cells (RTEs) in primary culture to investigate the cytotoxic effects induced by MTBE and the potential mechanism. RTEs were incubated with medium alone (control), 0.5, 50, 5000ppm MTBE respectively. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo liumbromide) assay, staining with fluorescein diacetate, propidium iodide and lactate dehydrogenase leakage ratio were used to assess MTBE cytotoxicity on cells. We also observed a significant elevation in cytosolic Ca2+ by fluorescence probe Fluo-3AM at 3, 6 and 12h following exposure to MTBE. Loss of mitochondrial membrane potential (MMP) was detected following 12 and 24h treatment of NP and assessment by rhodamine 123 (Rh123) staining. Activity changes of the Ca(2+)-ATPase, Ca(2+)-Mg(2+)-ATPase following MTBE treatment displayed a similar trend, suggesting an initial elevation before 6h and subsequent dramatic decrease at 12h. Our results demonstrated that induction of cell injury, associated with mitochondrial dysfunction, and alterations in cytosolic Ca2+ in RTEs represent key mechanisms by which MTBE exerts its cytotoxic effects. PMID:18715547

Wang, Yajing; Chen, Chang; Wu, Tao; Xu, Jing; Han, Xiaodong

2008-07-31

134

Cytotoxicity and oxidative stress study in cultured rat Sertoli cells with methyl tert-butyl ether (MTBE) exposure.  

PubMed

Cultured Sertoli cells were tested for their cytotoxicity and oxidative stress induced by methyl tert-butyl ether (MTBE) which has been extensively used as a gasoline additive. In cytotoxic experiments, Sertoli cells were cultured with medium alone (control), 5, 500, or 50,000 microM MTBE. Lactate dehydrogcnase (LDH) leakage assay, staining with fluorescein diacetate (FDA) and propidium iodide (PI), and flow cytometric analyses were used. In oxidative stress experiments, Sertoli cells were cultured with medium alone (control), 0.5, 50, or 5000 microM MTBE. The production of reactive oxygen species (ROS), maleic dialdehyde (MDA) content and the level of superoxide dismutase (SOD) activity in cell supernatants were measured. Meanwhile, the expression level of 8-oxoguanine DNA glycosidase (OGG1) and extracellular form of superoxide dismutase (SOD(EX)) in Sertoli cells were determined by RT-PCR. We also compared the current findings with the previous findings in rat spermatogenic cells exposed to MTBE. The present data indicate that high dose MTBE may exert a direct toxic effect on Sertoli cells. Oxidative stress induced by MTBE is a possible mechanism of cytotoxicity. PMID:19150650

Li, Dongmei; Liu, Qin; Gong, Yi; Huang, Yufeng; Han, Xiaodong

2008-12-30

135

Anaerobic methyl tert-butyl ether-degrading microorganisms identified in wastewater treatment plant samples by stable isotope probing.  

PubMed

Anaerobic methyl tert-butyl ether (MTBE) degradation potential was investigated in samples from a range of sources. From these 22 experimental variations, only one source (from wastewater treatment plant samples) exhibited MTBE degradation. These microcosms were methanogenic and were subjected to DNA-based stable isotope probing (SIP) targeted to both bacteria and archaea to identify the putative MTBE degraders. For this purpose, DNA was extracted at two time points, subjected to ultracentrifugation, fractioning, and terminal restriction fragment length polymorphism (TRFLP). In addition, bacterial and archaeal 16S rRNA gene clone libraries were constructed. The SIP experiments indicated bacteria in the phyla Firmicutes (family Ruminococcaceae) and Alphaproteobacteria (genus Sphingopyxis) were the dominant MTBE degraders. Previous studies have suggested a role for Firmicutes in anaerobic MTBE degradation; however, the putative MTBE-degrading microorganism in the current study is a novel MTBE-degrading phylotype within this phylum. Two archaeal phylotypes (genera Methanosarcina and Methanocorpusculum) were also enriched in the heavy fractions, and these organisms may be responsible for minor amounts of MTBE degradation or for the uptake of metabolites released from the primary MTBE degraders. Currently, limited information exists on the microorganisms able to degrade MTBE under anaerobic conditions. This work represents the first application of DNA-based SIP to identify anaerobic MTBE-degrading microorganisms in laboratory microcosms and therefore provides a valuable set of data to definitively link identity with anaerobic MTBE degradation. PMID:22327600

Sun, Weimin; Sun, Xiaoxu; Cupples, Alison M

2012-02-10

136

Anaerobic Methyl tert-Butyl Ether-Degrading Microorganisms Identified in Wastewater Treatment Plant Samples by Stable Isotope Probing  

PubMed Central

Anaerobic methyl tert-butyl ether (MTBE) degradation potential was investigated in samples from a range of sources. From these 22 experimental variations, only one source (from wastewater treatment plant samples) exhibited MTBE degradation. These microcosms were methanogenic and were subjected to DNA-based stable isotope probing (SIP) targeted to both bacteria and archaea to identify the putative MTBE degraders. For this purpose, DNA was extracted at two time points, subjected to ultracentrifugation, fractioning, and terminal restriction fragment length polymorphism (TRFLP). In addition, bacterial and archaeal 16S rRNA gene clone libraries were constructed. The SIP experiments indicated bacteria in the phyla Firmicutes (family Ruminococcaceae) and Alphaproteobacteria (genus Sphingopyxis) were the dominant MTBE degraders. Previous studies have suggested a role for Firmicutes in anaerobic MTBE degradation; however, the putative MTBE-degrading microorganism in the current study is a novel MTBE-degrading phylotype within this phylum. Two archaeal phylotypes (genera Methanosarcina and Methanocorpusculum) were also enriched in the heavy fractions, and these organisms may be responsible for minor amounts of MTBE degradation or for the uptake of metabolites released from the primary MTBE degraders. Currently, limited information exists on the microorganisms able to degrade MTBE under anaerobic conditions. This work represents the first application of DNA-based SIP to identify anaerobic MTBE-degrading microorganisms in laboratory microcosms and therefore provides a valuable set of data to definitively link identity with anaerobic MTBE degradation.

Sun, Weimin; Sun, Xiaoxu

2012-01-01

137

Methyl tert-butyl ether (MTBE) in public and private wells in New Hampshire: Occurrence, factors, and possible implications  

USGS Publications Warehouse

Methyl tert-butyl ether (MTBE) concentrations ???0.2 ??g/L were found in samples of untreated water in 18% of public-supply wells (n = 284) and 9.1% of private domestic wells (n = 264) sampled in 2005 and 2006 in New Hampshire. In counties that used reformulated gasoline (RFG), MTBE occurred at or above 0.2 ??g/L in 30% of public- and 17% of private-supply wells. Additionally, 52% of public-supply wells collocated with fuel storage and 71% of mobile home park wells had MTBE. MTBE occurrence in public-supply wells was predicted by factors such as proximity to sources of fuel, land use, and population density, as well as low pH and distance from mapped lineaments. RFG use, land-use variables, and pH were important predictors of private-well MTBE occurrence. Variables representing sources of MTBE, such as the distance to known fuel sources, were not significant predictors of MTBE occurrence in private-supply wells. It is hypothesized that private wells may become contaminated from the collective effects of sources in high population areas and from undocumented incidental releases from onsite or proximal gasoline use. From 2003 to 2005, MTBE occurrence decreased in 63 public-supply wells and increased in 60 private-supply wells, but neither trend was statistically significant. ?? 2008 American Chemical Society.

Ayotte, J. D.; Argue, D. M.; Mcgarry, F. J.; Degnan, J. R.; Hayes, L.; Flanagan, S. M.; Helsel, D. R.

2008-01-01

138

Methyl tert-butyl ether occurrence and related factors in public and private wells in Southeast New Hampshire  

USGS Publications Warehouse

The occurrence of methyl tert-butyl ether (MTBE) in water from public wells in New Hampshire has increased steadily over the past several years. Using a laboratory reporting level of 0.2 ??g/L, 40% of samples from public wells and 21% from private wells in southeast New Hampshire have measurable concentrations of MTBE. The rate of occurrence of MTBE varied significantly for public wells by establishment type; for example, 63% of public wells serving residential properties have MTBE concentrations above 0.2 ??g/L, whereas lower rates were found for schools (21%). MTBE concentrations correlate strongly with urban factors, such as population density. Surprisingly, MTBE was correlated positively with well depth for public supply wells. Well depth is inversely related to yield in New Hampshire bedrock wells, which may mean that there is less opportunity for dilution of MTBE captured by deep wells. Another possibility is that the source(s) of water to low-yield wells may be dominated by leakage from potentially contaminated shallow groundwater through near-surface fractures or along the well casing. These wells may also have relatively large contributing areas (due to low recharge at the bedrock surface) and therefore have a greater chance of intersecting MTBE sources. This finding is significant because deep bedrock wells are often considered to be less vulnerable to contamination than shallow wells, and in southeast New Hampshire, wells are being drilled deeper in search of increased supply.

Ayotte, J. D.; Argue, D. M.; McGarry, F. J.

2005-01-01

139

Percutaneous transhepatic gallstone dissolution with methyl tert-butyl ether in complicated stone diagnosis and gallbladder anomalies.  

PubMed

In a total of 117 successfully punctured patients with gallbladder stones that were to be treated with methyl tert-butyl ether, 11 showed shell-like structured concrements on the CT scan. In 2 patients, pigment stones and very old concrements were suspected. In these 13 patients solitary stones dissolved in 2.9 hours, multiple stones in 10.8 hours, which corresponds to the treatment time of the total group. In 4 patients we diagnosed cholesterol stones, but dissolution was very slow, suggesting that the stones were covered with pigment. In 21 patients we found marked gallbladder anomalies, such as extreme septation, two-chamber gallbladders, gallbladder diverticula with a wedged stone, or gallbladders in which the fundus was positioned cranially. In these patients puncture time was prolonged by 25%. However, since in all patients the stones dissolved in the same time as in the total group (solitary stones; 3.1 hours: multiple stones: 10.4 hours) and since in 33% there was also sludge in the gallbladder, shape variants of the gallbladder obviously have no influence on the stone type. Whether they induce recurrent stones more often than normal gallbladders cannot be assessed at present. Shape variants of the gallbladder and layered stones on CT scan, however, do not represent a contraindication to MTBE therapy. PMID:2272293

Hellstern, A; Rübesam, D; Leuschner, M; Wendt, T; Fuchs, H; Leuschner, U

1990-11-01

140

In vitro cholesterol gallstone dissolution: comparison of methyl tert-butyl ether with three new ester solvents.  

PubMed

The in vitro effectiveness of three new cholesterol gallstone solvents that have a potential for clinical use--ethyl propionate, isopropyl acetate, and n-propyl acetate--was compared with that of the well-known cholesterol solvent methyl tert-butyl ether (MTBE). Ten sets of matched gallstones were initially weighed, imaged with radiography and computed tomography (CT), and analyzed for content. One stone from each set was incubated in one of the four solvents at 37 degrees C. Solvents were changed at 30-minute intervals. The study was stopped either when the stones were completely dissolved or at the end of 7 hours. Any residual fragments were weighed, reimaged, and reanalyzed for content. There were no statistical differences between dissolution times of the stones in MTBE compared with those in the three new solvents. Ethyl propionate and n-propyl acetate appear to be as efficacious as MTBE in dissolving cholesterol stones and could be attractive alternatives for gallstone chemolysis. PMID:2052721

Long, C A; Teplick, S K; Baker, M L; Brandon, J C

1991-07-01

141

Iodinated contrast medium as an aid to gallstone dissolution with methyl tert-butyl ether: in vitro study.  

PubMed

Methyl tert-butyl ether (MTBE) floats on bile, whereas gallstones sink. Therefore, stones and MTBE are separated by a layer of bile. This study investigates the effect of contrast medium on flotation of gallstones in bile and its role in stone and fragment dissolution with MTBE. Fresh human gallstones, both calcified and noncalcified, from different patients were tested in vitro for flotation in bile, with and without addition of contrast medium. All gallstones or fragments sank in bile before the introduction of contrast medium. Noncalcified stones floated when the contrast medium-bile volume ratio was 1:6 or more, while double this amount of contrast medium was required to float calcified stones. Fragments did dissolve somewhat in MTBE in the presence of bile alone, but when contrast medium was added, almost complete dissolution occurred. This is thought to be due to increased contact between the fragments and MTBE, both floating on the contrast medium-bile mixture. Contrast material may be a useful adjuvant in gallstone dissolution therapy with MTBE in vivo. PMID:2326473

Zhou, J; Lee, S H; Rawat, B; Fache, J S; Maciejewska, U; Burhenne, H J

1990-05-01

142

Effect of laser fragmentation of cholesterol and mixed gallstones on in vitro dissolution in methyl tert-butyl ether.  

PubMed

This study examined cholesterol and mixed gallstone dissolution in vitro by methyl-tert-butyl ether (MTBE) after gallstone fragmentation. Three morphologically identical gallstones were obtained from 42 patients. One stone from each patient was fragmented with laser energy at a wavelength of 504 nm delivered to the stone surface with a 320-microns quartz fiber. Intact and fragmented stones from the same patient were incubated without stirring in MTBE and dissolution was expressed as the percent of initial stone weight remaining after 2 hr. Stone composition did not correlate with the amount of laser energy required for stone fragmentation. Fragmented stones dissolved faster than intact stones in MTBE with 13.97% +/- 0.37% vs 31.0% +/- 0.51% respectively (mean +/- SEM) of initial stone weight remaining at 2 hr (P less than 0.0001). Initial stone weight and stone matrix content significantly predicted dissolution of intact (P = 0.0033 and P = 0.0483, respectively) and fragmented stones (P = 0.003 and P = 0.0001, respectively) in MTBE. These data suggest that the gallstone matrix may inhibit stone dissolution even after stone fragmentation. PMID:2302982

Smith, B F

1990-02-01

143

Assessing soil ecotoxicity of methyl tert-butyl ether using earthworm bioassay; closed soil microcosm test for volatile organic compounds.  

PubMed

An earthworm bioassay was conducted to assess ecotoxicity in methyl tert-butyl ether (MTBE)-amended soils. Ecotoxicity of MTBE to earthworms was evaluated by a paper contact method, natural field soil test, and an OECD artificial soil test. All tests were conducted in closed systems to prevent volatilization of MTBE out of test units. Test earthworm species were Perionyx excavatus and Eisenia andrei. Mortality and abnormal morphology of earthworms exposed to different concentrations of MTBE were examined. MTBE was toxic to both earthworm species and the severity of response increased with increasing MTBE concentrations. Perionyx excavatus was more sensitive to MTBE than Eisenia andrei in filter papers and two different types of soils. MTBE toxicity was more severe in OECD artificial soils than in field soils, possibly due to the burrowing behavior of earthworms into artificial soils. The present study demonstrated that ecotoxicity of volatile organic compounds such as MTBE can be assessed using an earthworm bioassay in closed soil microcosm with short-term exposure duration. PMID:15589644

An, Youn-Joo

2005-03-01

144

Methyl tert-butyl ether (MTBE) in public and private wells in New Hampshire: occurrence, factors, and possible implications.  

PubMed

Methyl tert-butyl ether (MTBE) concentrations > or = 0.2 /microg/L were found in samples of untreated water in 18% of public-supply wells (n = 284) and 9.1% of private domestic wells (n = 264) sampled in 2005 and 2006 in New Hampshire. In counties that used reformulated gasoline (RFG), MTBE occurred at or above 0.2 microg/L in 30% of public- and 17% of private-supply wells. Additionally, 52% of public-supply wells collocated with fuel storage and 71% of mobile home park wells had MTBE. MTBE occurrence in public-supply wells was predicted by factors such as proximity to sources of fuel, land use, and population density, as well as low pH and distance from mapped lineaments. RFG use, land-use variables, and pH were important predictors of private-well MTBE occurrence. Variables representing sources of MTBE, such as the distance to known fuel sources, were not significant predictors of MTBE occurrence in private-supply wells. It is hypothesized that private wells may become contaminated from the collective effects of sources in high population areas and from undocumented incidental releases from onsite or proximal gasoline use. From 2003 to 2005, MTBE occurrence decreased in 63 public-supply wells and increased in 60 private-supply wells, but neither trend was statistically significant. PMID:18323087

Ayotte, Joseph D; Argue, Denise M; McGarry, Frederick J; Degnan, James R; Hayes, Laura; Flanagan, Sarah M; Helsel, Dennis R

2008-02-01

145

Epidemiology, toxicokinetics, and health effects of methyl tert -butyl ether (MTBE)  

Microsoft Academic Search

This paper reviews the published information assessing the kinetics and potential for adverse health effects related to exposure\\u000a to the fuel oxygenate, methyltert-butyl ether (MTBE). Data were obtained from previously published reports, using human data where possible. If human data\\u000a were not available, animal studies were cited. The kinetic profile of MTBE in humans is similar for ingestion and inhalation.

Scott Phillips; Robert B. Palmer; Aaron Brody

2008-01-01

146

Gallstone recurrence after direct contact dissolution with methyl tert -butyl ether  

Microsoft Academic Search

To determine the rate and characteristics of gallstone recurrence after direct contact dissolution with methyltert-butyl ether, 60 consecutive patients were followed for up to 4.5 years (median 2.2 years) after complete disappearance of all stone residues and debris and cessation of adjuvant bile acid therapy. Initial gallstones had been multiple in all but four patients. Twenty-eight of the 60 patients

Juergen Pauletzki; Joseph Holl; Michael Sackmann; Michael Neubrand; Ulrich Klueppelberg; Tilman Sauerbruch; Gustav Paumgartner

1995-01-01

147

Gallstone dissolution with methyl tert -butyl ether in 120 patients—Efficacy and safety  

Microsoft Academic Search

Of 612 patients with cholesterol gallbladder stones, 120 were eligible for percutaneous transhepatic litholysis with methyltert-butyl ether (MTBE). Puncture of the gallbladder was successful in 117\\/120 (97.5%). In 113\\/117 (96.6%) the stones dissolved. With solitary stones, treatment lasted for an average of 4 hr, with multiple stones 10 hr. Mean hospitalization was 3.6 days. In 3\\/117 (2.6%) patients a bile

U. Leuschner; A. Hellstern; K. Schmidt; H. Fischer; S. Güldütuna; K. Hübner; M. Leuschner

1991-01-01

148

Oxidation of methyl tert-butyl ether by alkane hydroxylase in dicyclopropylketone-induced and n-octane-grown Pseudomonas putida GPo1.  

PubMed

The alkane hydroxylase enzyme system in Pseudomonas putida GPo1 has previously been reported to be unreactive toward the gasoline oxygenate methyl tert-butyl ether (MTBE). We have reexamined this finding by using cells of strain GPo1 grown in rich medium containing dicyclopropylketone (DCPK), a potent gratuitous inducer of alkane hydroxylase activity. Cells grown with DCPK oxidized MTBE and generated stoichiometric quantities of tert-butyl alcohol (TBA). Cells grown in the presence of DCPK also oxidized tert-amyl methyl ether but did not appear to oxidize either TBA, ethyl tert-butyl ether, or tert-amyl alcohol. Evidence linking MTBE oxidation to alkane hydroxylase activity was obtained through several approaches. First, no TBA production from MTBE was observed with cells of strain GPo1 grown on rich medium without DCPK. Second, no TBA production from MTBE was observed in DCPK-treated cells of P. putida GPo12, a strain that lacks the alkane-hydroxylase-encoding OCT plasmid. Third, all n-alkanes that support the growth of strain GPo1 inhibited MTBE oxidation by DCPK-treated cells. Fourth, two non-growth-supporting n-alkanes (propane and n-butane) inhibited MTBE oxidation in a saturable, concentration-dependent process. Fifth, 1,7-octadiyne, a putative mechanism-based inactivator of alkane hydroxylase, fully inhibited TBA production from MTBE. Sixth, MTBE-oxidizing activity was also observed in n-octane-grown cells. Kinetic studies with strain GPo1 grown on n-octane or rich medium with DCPK suggest that MTBE-oxidizing activity may have previously gone undetected in n-octane-grown cells because of the unusually high K(s) value (20 to 40 mM) for MTBE. PMID:15294784

Smith, Christy A; Hyman, Michael R

2004-08-01

149

Oxidation of Methyl tert-Butyl Ether by Alkane Hydroxylase in Dicyclopropylketone-Induced and n-Octane-Grown Pseudomonas putida GPo1  

PubMed Central

The alkane hydroxylase enzyme system in Pseudomonas putida GPo1 has previously been reported to be unreactive toward the gasoline oxygenate methyl tert-butyl ether (MTBE). We have reexamined this finding by using cells of strain GPo1 grown in rich medium containing dicyclopropylketone (DCPK), a potent gratuitous inducer of alkane hydroxylase activity. Cells grown with DCPK oxidized MTBE and generated stoichiometric quantities of tert-butyl alcohol (TBA). Cells grown in the presence of DCPK also oxidized tert-amyl methyl ether but did not appear to oxidize either TBA, ethyl tert-butyl ether, or tert-amyl alcohol. Evidence linking MTBE oxidation to alkane hydroxylase activity was obtained through several approaches. First, no TBA production from MTBE was observed with cells of strain GPo1 grown on rich medium without DCPK. Second, no TBA production from MTBE was observed in DCPK-treated cells of P. putida GPo12, a strain that lacks the alkane-hydroxylase-encoding OCT plasmid. Third, all n-alkanes that support the growth of strain GPo1 inhibited MTBE oxidation by DCPK-treated cells. Fourth, two non-growth-supporting n-alkanes (propane and n-butane) inhibited MTBE oxidation in a saturable, concentration-dependent process. Fifth, 1,7-octadiyne, a putative mechanism-based inactivator of alkane hydroxylase, fully inhibited TBA production from MTBE. Sixth, MTBE-oxidizing activity was also observed in n-octane-grown cells. Kinetic studies with strain GPo1 grown on n-octane or rich medium with DCPK suggest that MTBE-oxidizing activity may have previously gone undetected in n-octane-grown cells because of the unusually high Ks value (20 to 40 mM) for MTBE.

Smith, Christy A.; Hyman, Michael R.

2004-01-01

150

tert-Butyl 5-(4-methoxy-phen-yl)-1-methyl-2-oxopyrrolidin-3-yl carbonate  

PubMed Central

In the title compound, C17H23NO5, the pyrrolidinone ring is in an envelope conformation. The tert-butyl carbonate and 4-methoxy­phenyl groups are arranged on the same side of the pyrrolidinone ring. The meth­oxy group is coplanar with the attached benzene ring. The mol­ecules are linked into chains along the b axis via C—H?O hydrogen bonds.

Mohammat, M. Fazli; Shaameri, Zurina; Hamzah, A. Sazali; Fun, Hoong-Kun; Chantrapromma, Suchada

2008-01-01

151

A physiologically based pharmacokinetic model for methyl tert-butyl ether in humans: implementing sensitivity and variability analyses.  

PubMed

Methyl tert-butyl ether (MTBE) is added to gasoline to reduce carbon monoxide and ozone precursors from automobile emissions. The objectives of this study were to verify the ability of a physiologically based pharmacokinetic (PBPK) model to predict MTBE blood levels in humans and to investigate the effect of variability in the metabolism of MTBE and its influence on the predicted MTBE blood levels. The model structure for MTBE was flow-limited and had six essential compartments: lung, liver, rapidly perfused tissues, slowly perfused tissues, fat, and kidney. In this model, two pathways of metabolism are described to occur in the liver by Michaelis-Menten kinetics. Metabolic rate constants were measured in vitro using human liver microsomes and extrapolated to in vivo whole-body metabolism. Model predictions were compared with data on blood levels of MTBE taken from humans during and after a 1-h inhalation exposure to 1.7 ppm MTBE and after 4-h inhalation exposures to 4 or 40 ppm MTBE. The PBPK model accurately predicted MTBE pharmacokinetics at the high and low MTBE exposure concentrations for all time points. At the intermediate MTBE exposure concentration, however, the model underpredicted early time points while adequately predicting later time points. Results of the sensitivity analysis indicated that the influence of metabolic parameters on model output was dependent on MTBE exposure concentration. Subsequent variability analysis indicated that there was more variability in the actual measured MTBE blood levels than in the blood levels predicted by the PBPK model when using the range of metabolic parameters measured in vitro in human liver samples. By incorporating an understanding of the metabolic processes, this PBPK model can be used to predict blood levels of MTBE, which is important in determining target tissue dose estimates for risk assessment. PMID:11452131

Licata, A C; Dekant, W; Smith, C E; Borghoff, S J

2001-08-01

152

Whole-Genome Analysis of the Methyl tert-Butyl Ether-Degrading Beta-Proteobacterium Methylibium petroleiphilum PM1? †  

PubMed Central

Methylibium petroleiphilum PM1 is a methylotroph distinguished by its ability to completely metabolize the fuel oxygenate methyl tert-butyl ether (MTBE). Strain PM1 also degrades aromatic (benzene, toluene, and xylene) and straight-chain (C5 to C12) hydrocarbons present in petroleum products. Whole-genome analysis of PM1 revealed an ?4-Mb circular chromosome and an ?600-kb megaplasmid, containing 3,831 and 646 genes, respectively. Aromatic hydrocarbon and alkane degradation, metal resistance, and methylotrophy are encoded on the chromosome. The megaplasmid contains an unusual t-RNA island, numerous insertion sequences, and large repeated elements, including a 40-kb region also present on the chromosome and a 29-kb tandem repeat encoding phosphonate transport and cobalamin biosynthesis. The megaplasmid also codes for alkane degradation and was shown to play an essential role in MTBE degradation through plasmid-curing experiments. Discrepancies between the insertion sequence element distribution patterns, the distributions of best BLASTP hits among major phylogenetic groups, and the G+C contents of the chromosome (69.2%) and plasmid (66%), together with comparative genome hybridization experiments, suggest that the plasmid was recently acquired and apparently carries the genetic information responsible for PM1's ability to degrade MTBE. Comparative genomic hybridization analysis with two PM1-like MTBE-degrading environmental isolates (?99% identical 16S rRNA gene sequences) showed that the plasmid was highly conserved (ca. 99% identical), whereas the chromosomes were too diverse to conduct resequencing analysis. PM1's genome sequence provides a foundation for investigating MTBE biodegradation and exploring the genetic regulation of multiple biodegradation pathways in M. petroleiphilum and other MTBE-degrading beta-proteobacteria.

Kane, Staci R.; Chakicherla, Anu Y.; Chain, Patrick S. G.; Schmidt, Radomir; Shin, Maria W.; Legler, Tina C.; Scow, Kate M.; Larimer, Frank W.; Lucas, Susan M.; Richardson, Paul M.; Hristova, Krassimira R.

2007-01-01

153

Carbon Conversion Efficiency and Limits of Productive Bacterial Degradation of Methyl tert-Butyl Ether and Related Compounds?  

PubMed Central

The utilization of the fuel oxygenate methyl tert-butyl ether (MTBE) and related compounds by microorganisms was investigated in a mainly theoretical study based on the YATP concept. Experiments were conducted to derive realistic maintenance coefficients and Ks values needed to calculate substrate fluxes available for biomass production. Aerobic substrate conversion and biomass synthesis were calculated for different putative pathways. The results suggest that MTBE is an effective heterotrophic substrate that can sustain growth yields of up to 0.87 g g?1, which contradicts previous calculation results (N. Fortin et al., Environ. Microbiol. 3:407-416, 2001). Sufficient energy equivalents were generated in several of the potential assimilatory routes to incorporate carbon into biomass without the necessity to dissimilate additional substrate, efficient energy transduction provided. However, when a growth-related kinetic model was included, the limits of productive degradation became obvious. Depending on the maintenance coefficient ms and its associated biomass decay term b, growth-associated carbon conversion became strongly dependent on substrate fluxes. Due to slow degradation kinetics, the calculations predicted relatively high threshold concentrations, Smin, below which growth would not further be supported. Smin strongly depended on the maximum growth rate ?max, and b and was directly correlated with the half maximum rate-associated substrate concentration Ks, meaning that any effect impacting this parameter would also change Smin. The primary metabolic step, catalyzing the cleavage of the ether bond in MTBE, is likely to control the substrate flux in various strains. In addition, deficits in oxygen as an external factor and in reduction equivalents as a cellular variable in this reaction should further increase Ks and Smin for MTBE.

Muller, Roland H.; Rohwerder, Thore; Harms, Hauke

2007-01-01

154

Enhancing Transport of Hydrogenophagaflava ENV735 for Bioaugmentation of Aquifers Contaminated with Methyl tert-Butyl Ether  

PubMed Central

The gasoline oxygenate methyl tert-butyl ether (MTBE) has become a widespread contaminant in groundwater throughout the United States. Bioaugmentation of aquifers with MTBE-degrading cultures may be necessary to enhance degradation of the oxygenate in some locations. However, poor cell transport has sometimes limited bioaugmentation efforts in the past. The objective of this study was to evaluate the transport characteristics of Hydrogenophaga flava ENV735, a pure culture capable of growth on MTBE, and to improve movement of the strain through aquifer solids. The wild-type culture moved only a few centimeters in columns of aquifer sediment. An adhesion-deficient variant (H. flava ENV735:24) of the wild-type strain that moved more readily through sediments was obtained by sequential passage of cells through columns of sterile sediment. Hydrophobic and electrostatic interaction chromatography revealed that the wild-type strain is much more hydrophobic than the adhesion-deficient variant. Electrophoretic mobility assays and transmission electron microscopy showed that the wild-type bacterium contains two distinct subpopulations, whereas the adhesion-deficient strain has only a single, homogeneous population. Both the wild-type strain and adhesion-deficient variant degraded MTBE, and both were identified by 16S rRNA analysis as pure cultures of H. flava. The effectiveness of surfactants for enhancing transport of the wild-type strain was also evaluated. Many of the surfactants tested were toxic to ENV735; however, one nonionic surfactant, Tween 20, enhanced cell transport in sand columns. Improving microbial transport may lead to a more effective bioaugmentation strategy for MTBE-contaminated sites where indigenous oxygenate degraders are absent.

Streger, Sheryl H.; Vainberg, Simon; Dong, Hailiang; Hatzinger, Paul B.

2002-01-01

155

Whole-genorne analysis of the methyl tert-butyl ether-degrading beta-proteobacterium Methylibium petroleiphilum PM1  

SciTech Connect

Methylibium petroleiphilum PM1 is a methylotroph distinguished by its ability to completely metabolize the fuel oxygenate methyl tert-butyl ether (MTBE). Strain PM1 also degrades aromatic (benzene, toluene, and xylene) and straight-chain (C, to C,,) hydrocarbons present in petroleum products. Whole-genome analysis of PM1 revealed an similar to 4-Mb circular chromosome and an similar to 600-kb megaplasmid, containing 3,831 and 646 genes, respectively. Aromatic hydrocarbon and alkane degradation, metal resistance, and methylotrophy are encoded on the chromosome. The megaplasmid contains an unusual t-RNA island, numerous insertion sequences, and large repeated elements, including a 40-kb region also present on the chromosome and a 29-kb tandem repeat encoding phosphonate transport and cobalamin biosynthesis. The megaplasmid also codes for alkane degradation and was shown to play an essential role in MTBE degradation through plasmid-curing experiments. Discrepancies between the insertion sequence element distribution patterns, the distributions of best BLASTP hits among major phylogenetic groups, and the G+C contents of the chromosome (69.2%) and plasmid (66%), together with comparative genome hybridization experiments, suggest that the plasmid was recently acquired and apparently carries the genetic information responsible for PM1's ability to degrade MTBE. Comparative genomic hybridization analysis with two PM1-like MTBE-degrading environmental isolates (similar to 99% identical 16S rRNA gene sequences) showed that the plasmid was highly conserved (ca. 99% identical), whereas the chromosomes were too diverse to conduct resequencing analysis. PM1's genome sequence provides a foundation for investigating MTBE biodegradation and exploring the genetic regulation of multiple biodegradation pathways in M. petroleiphilum and other MTBE-degrading beta-proteobacteria.

Kane, Staci R. [Lawrence Livermore National Laboratory (LLNL); Chakicherla, Anu Y. [Lawrence Livermore National Laboratory (LLNL); Chain, Patrick S. G. [Lawrence Livermore National Laboratory (LLNL); Schmidt, Radomir [University of California, Davis; Shin, M [U.S. Department of Energy, Joint Genome Institute; Legler, Tina C. [Lawrence Livermore National Laboratory (LLNL); Scow, Kate M. [University of California, Davis; Larimer, Frank W [ORNL; Lucas, Susan [Joint Genome Institute, Walnut Creek, California; Richardson, P M [U.S. Department of Energy, Joint Genome Institute; Hristova, Krassimira R. [University of California, Davis

2007-03-01

156

Evaluation of methyl tert-butyl ether (MTBE) as an interference on commercial breath-alcohol analyzers.  

PubMed

Anecdotal reports suggest that high environmental or occupational exposures to the fuel oxygenate methyl tert-butyl ether (MTBE) may result in breath concentrations that are sufficiently elevated to cause a false positive on commercial breath-alcohol analyzers. We evaluated this possibility in vitro by establishing a response curve for simulated breath containing MTBE in ethanol. Two types of breath-alcohol analyzers were evaluated. One analyzer's principle of operation involves in situ wet chemistry (oxidation of ethanol in a potassium dichromate solution) and absorption of visible light. The second instrument uses a combination of infrared absorption and an electrochemical sensor. Both types of instruments are currently used, although the former method represents older technology while the latter method represents newer technology.The percent blood alcohol response curve was evaluated over a breath concentration range thought to be relevant to high-level environmental or occupational exposure (0-361 microg/l). Results indicate that MTBE positively biases the response of the older technology Breathalyzer when evaluated as a single constituent or in combination with ethanol. We conclude that a false positive is possible on this instrument if the MTBE exposure is very high, recent with respect to testing, and occurs in combination with ethanol consumption. The interference can be identified on the older technology instrument by a time dependent post-reading increase in the instrument response that does not occur for ethanol alone. In contrast, the newer technology instrument using infrared and electrochemical detectors did not respond to MTBE at lower levels (0-36 microg/l), and at higher levels (>72 microg/l) the instrument indicated an "interference" or "error". For this instrument, a false positive does not occur even at high MTBE levels in the presence of ethanol. PMID:11728735

Buckley, T J; Pleil, J D; Bowyer, J R; Davis, J M

2001-12-01

157

Characterization of the Initial Reactions during the Cometabolic Oxidation of Methyl tert-Butyl Ether by Propane-Grown Mycobacterium vaccae JOB5  

PubMed Central

The initial reactions in the cometabolic oxidation of the gasoline oxygenate, methyl tert-butyl ether (MTBE), by Mycobacterium vaccae JOB5 have been characterized. Two products, tert-butyl formate (TBF) and tert-butyl alcohol (TBA), rapidly accumulated extracellularly when propane-grown cells were incubated with MTBE. Lower rates of TBF and TBA production from MTBE were also observed with cells grown on 1- or 2-propanol, while neither product was generated from MTBE by cells grown on casein-yeast extract-dextrose broth. Kinetic studies with propane-grown cells demonstrated that TBF is the dominant (?80%) initial product of MTBE oxidation and that TBA accumulates from further biotic and abiotic hydrolysis of TBF. Our results suggest that the biotic hydrolysis of TBF is catalyzed by a heat-stable esterase with activity toward several other tert-butyl esters. Propane-grown cells also oxidized TBA, but no further oxidation products were detected. Like the oxidation of MTBE, TBA oxidation was fully inhibited by acetylene, an inactivator of short-chain alkane monooxygenase in M. vaccae JOB5. Oxidation of both MTBE and TBA was also inhibited by propane (Ki = 3.3 to 4.4 ?M). Values for Ks of 1.36 and 1.18 mM and for Vmax of 24.4 and 10.4 nmol min?1 mg of protein?1 were derived for MTBE and TBA, respectively. We conclude that the initial steps in the pathway of MTBE oxidation by M. vaccae JOB5 involve two reactions catalyzed by the same monooxygenase (MTBE and TBA oxidation) that are temporally separated by an esterase-catalyzed hydrolysis of TBF to TBA. These results that suggest the initial reactions in MTBE oxidation by M. vaccae JOB5 are the same as those that we have previously characterized in gaseous alkane-utilizing fungi.

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

2003-01-01

158

Di-?-methanolato-bis[(2-tert-butyl-6-methylphenolato-?O)methyl-titanium(IV)  

PubMed Central

The molecule of the title compound, [Ti2(CH3)2(CH3O)2(C11H15O)4] or {[Ti(Me)(?-OCH3)(OC6H3CMe3-2-Me-6)]2}, has a centrosymmetric, dimeric structure with a distorted square pyramidal array about each titanium atom. The methoxide ligands form an asymmetric bridge between the two TiIV atoms [Ti—O bond lengths of 1.9794?(12) and 2.0603?(12)?Å] with the two phenolato ligands occupying the remaining basal sites [Ti—O 1.8218?(11) and 1.8135?(11)?Å]. The Ti—O—C phenolato bond angles are similar at 161.24?(10) and 160.66?(11)°. The methyl ligand attached to the metal atom has a Ti—C bond length of 2.0878?(17)?Å.

Nielson, Alastair J.; Shen, Chaohong; Waters, Joyce M.

2013-01-01

159

Methyl tert-butyl ether in the endoscopic treatment of common bile duct radiolucent stones in elderly patients with nasobiliary tube.  

PubMed

Methyl tert-butyl ether is an effective dissolution agent for cholesterol stones. The aim of this work was to evaluate the effect of methyl tert-butyl ether on radiolucent common bile duct stones in patients in whom endoscopic extraction has failed. From September 1985 to September 1987, 1374 patients underwent endoscopic retrograde cholangiopancreatography in our Liver Unit. An endoscopic sphincterotomy was indicated in 195 patients with common bile duct (CBD) stones because of an age over 65 years and/or surgical contraindications. Endoscopic sphincterotomy was efficient in 187 patients, allowing complete stone removal in association with conventional endoscopic methods and mechanical lithotripsy in 170 patients. Twelve of the 17 patients with failure of conventional endoscopic treatments were either older than 75 years (11 patients; mean age, 86 +/- 4.5 years) or exhibited a surgical contraindication. Stones completely obstructed CBD in six patients and had a diameter exceeding 25 mm in the six other patients. These subjects were selected for stone dissolution by methyl tert-butyl either (MTBE) according to the following protocol. MTBE was directly infused into CBD through a nasobiliary catheter, twice daily for 4-13 days (mean, seven days). Bile duct opacification, repeated after MTBE treatment, revealed the complete disappearance of CBD stones in one patient, a decrease in stone size in five patients and no change in the six other patients. MTBE treatment was well tolerated except in three patients who complained from transient abdominal pains and nausea. At the second attempt of endoscopic treatment, CBD stones were found to be softened and easily broken up, allowing a complete clearance in six patients.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1728535

Diaz, D; Bories, P; Ampelas, M; Larrey, D; Michel, H

1992-01-01

160

4,4?-Di-tert-butyl-2,2?-[imidazolidine-1,3-diylbis(methyl-ene)]diphenol  

PubMed Central

In the title compound, C25H36N2O2, the two tert-butyl-substituted benzene rings are inclined at an angle of 53.5?(3)° to one another. The imidazolidine ring has an envelope conformation with with one of the C atoms of the ethylene fragment as the flap. The structure displays two intra­molecular O—H?N hydrogen bonds that generate S(6) ring motifs. The crystal studied was a non-merohedral twin with a fractional contribution of 0.281(6) for the minor domain.

Rivera, Augusto; Nerio, Luz Stella; Bolte, Michael

2013-01-01

161

Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C9H12 Propylbenzene (VMSD1211, LB4620_V)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C9H12 Propylbenzene (VMSD1211, LB4620_V)' providing data from direct low-pressure dilatometric measurement of molar excess volume at variable mole fraction and constant temperature.

Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

162

Mathematical simulation and X-ray diffraction investigation of the crystal structure of 1-phenyl-1- tert -butyl-3-methyl-1,3-dihydroisobenzofuran  

Microsoft Academic Search

An algorithm for using a priori generation of crystal structures by the discrete modeling method for the interpretation of\\u000a data obtained from single-crystal X-ray diffraction experiments is considered. The crystal structure of 1-phenyl-1-tert-butyl-3-methyl-1,3-dihydroisobenzofuran is mathematically simulated using the discrete modeling of molecular packings and\\u000a studied by X-ray diffraction. The simulation is performed for two isomers of the initial chemical compound

A. V. Maleev; I. K. Zhitkov; K. A. Potekhin

2008-01-01

163

Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C6H6 Benzene (VMSD1211, LB4092_V)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C6H6 Benzene (VMSD1211, LB4092_V)' providing data from direct low-pressure dilatometric measurement of molar excess volume at variable mole fraction and constant temperature.

Cibulka, I.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

164

Isolate PM1 populations are dominant and novel methyl tert-butyl ether-degrading bacterial in compost biofilter enrichments.  

PubMed

The gasoline additive MTBE, methyl tert-butyl ether, is a widespread and persistent groundwater contaminant. MTBE undergoes rapid mineralization as the sole carbon and energy source of bacterial strain PM1, isolated from an enrichment culture of compost biofilter material. In this report, we describe the results of microbial community DNA profiling to assess the relative dominance of isolate PM1 and other bacterial strains cultured from the compost enrichment. Three polymerase chain reaction (PCR)-based profiling approaches were evaluated: denaturing gradient gel electrophoresis (DGGE) analysis of 230 bp 16S rDNA fragments; thermal gradient gel electrophoresis (TGGE) analysis of 575 bp 16S rDNA fragments; and non-denaturing polyacrylamide gel electrophoresis of 300-1,500 bp fragments containing 16S/23S ribosomal intergenic transcribed spacer (ITS) regions. Whereas all three DNA profiling approaches indicated that PM1-like bands predominated in mixtures from MTBE-grown enrichments, ITS profiling provided the most abundant and specific sequence data to confirm strain PM1's presence in the enrichment. Moreover, ITS profiling did not produce non-specific PCR products that were observed with T/DGGE. A further advantage of ITS community profiling over other methods requiring restriction digestion (e.g. terminal restriction fragment length polymorphisms) was that it did not require an additional digestion step or the use of automated sequencing equipment. ITS bands, excised from similar locations in profiles of the enrichment and PM1 pure culture, were 99.9% identical across 750 16S rDNA positions and 100% identical across 691 spacer positions. BLAST comparisons of nearly full-length 16S rDNA sequences showed 96% similarity between isolate PM1 and representatives of at least four different genera in the Leptothrix subgroup of the beta-Proteobacteria (Aquabacterium, Leptothrix, Rubrivivax and Ideonella). Maximum likelihood and parsimony analyses of 1,249 nucleotide positions supported isolate PM1's position in a separate lineage within the Leptothrix subgroup. PMID:11321538

Bruns, M A; Hanson, J R; Mefford, J; Scow, K M

2001-03-01

165

Catalysis by heteropoly compounds. 32. Synthesis of methyl tert-butyl ether catalyzed by heteropolyacids supported on silica  

SciTech Connect

Gas phase synthesis of methyl tert-butyl ether (MTBE) from methanol and isobutylene has been studied by using silica-supported heteropolyacids. The activity of a Dawson-type tungstophosphoric acid, H{sub 6}P{sub 2}W{sub 18}O{sub 62}/SiO{sub 2}, was comparable to that of a sulfonated polymer resin, Amberlyst 15, and the selectivity was higher than that of Amberlyst 15. A Keggin-type heteropoly-acid, H{sub 3}PW{sub 12}O{sub 40}/SiO{sub 2}, was also efficient for this reaction, while unsupported H{sub 3}PW{sub 12}O{sub 40} was much less active than unsupported H{sub 6}P{sub 2}W{sub 18}O{sub 62}. Calorimetry of NH{sub 3} absorption revealed that the difference in acid strength between H{sub 6}P{sub 2}W{sub 18}O{sub 62} and H{sub 3}PW{sub 12}O{sub 40} was large, but the difference between the two became smaller when they were supported. This partly explains the similar activities of the two supported heteropolyacids. By supporting H{sub 6}P{sub 2}W{sub 18}O{sub 62} on SiO{sub 2}, the MTBE selectivity on the basis of methanol increased, but the selectivity on the basis of isobutylene decreased, which was reasonably explained by the decrease of the relative contribution of pseudoliquid phase reaction to the surface reaction by supporting. The pressure dependency on methanol for H{sub 6}P{sub 2}W{sub 18}O{sub 62}, but it much differed from those of ordinary solid acids like SO{sub 4}{sup 2-}/ZrO{sub 2} and H-ZSM-5, showing that MTBE synthesis proceeds in the pseudoliquid phase of H{sub 6}P{sub 2}W{sub 18}O{sub 62}/SiO{sub 2}. 42 refs., 8 figs., 1 tab.

Shikata, Sawami; Okuhara, Toshio; Misono, Makoto [Univ. of Tokyo (Japan); Nakata, Shin-ichi [Chiyoda Corp., Yokohama (Japan)

1997-03-01

166

Determination of Methyl tert-Butyl Ether and tert-Butyl Alcohol in Water by Solid-Phase Microextraction/Head Space Analysis in Comparison to EPA Method 5030/8260B  

SciTech Connect

Methyl tert-butyl ether (MTBE) is now one of the most common groundwater contaminants in the United States. Groundwater contaminated with MTBE is also likely to be contaminated with tert-butyl alcohol (TBA), because TBA is a component of commercial grade MTBE, TBA can also be used as a fuel oxygenate, and TBA is a biodegradation product of MTBE. In California, MTBE is subject to reporting at concentrations greater than 3 {micro}g/L. TBA is classified as a ''contaminant of current interest'' and has a drinking water action level of 12 {micro}g/L. In this paper, we describe the development and optimization of a simple, automated solid phase microextraction (SPME) method for the analysis of MTBE and TBA in water and demonstrate the applicability of this method for monitoring MTBE and TBA contamination in groundwater, drinking water, and surface water. In this method, the headspace (HS) of a water sample is extracted with a carboxen/polydimethylsiloxane SPME fiber, the MTBE and TBA are desorbed into a gas chromatograph (GC), and detected using mass spectrometry (MS). The method is optimized for the routine analysis of MTBE and TBA with a level of quantitation of 0.3 {micro}g/L and 4 {micro}g/L, respectively, in water. MTBE quantitation was linear for over two orders of concentration (0.3 {micro}g/L -80 {micro}g/L). TBA was found to be linear within the range of 4 {micro}g/L-7,900 {micro}g/L. The lower level of detection for MTBE is 0.03 {micro}g/L using this method. This SPME method using headspace extraction was found to be advantageous over SPME methods requiring immersion of the fiber into the water samples, because it prolonged the life of the fiber by up to 400 sample analyses. This is the first time headspace extraction SPME has been shown to be applicable to the measurement of both MTBE and TBA at concentrations below regulatory action levels. This method was compared with the certified EPA Method 5030/8260B (purge-and-trap/GC/MS) using split samples from laboratory bioreactors treating MTBE contaminated water and applied to environmental samples collected throughout the East Bay area of California. Results from the SPME-HS/GC/MS method were directly comparable to the EPA Method 5030/8260B. This method provides an simple, inexpensive, accurate, and sensitive alternative to EPA Method 5030/8260B for the analysis of MTBE and TBA in water samples.

Oh, Keun-Chan; Stringfellow, William T.

2003-10-02

167

Occurrence of methyl tert-butyl ether (MTBE) in riverbank fiftered water and drnking water produced by riverbank filtration. 2.  

PubMed

Bank filtration of river or lake water represents an efficient and natural purification process used for the drinking water production in many countries and at an amount of about 15-16% in Germany. From experiences over decades particularly at the river Rhine and Elbe, it is known that the occurrence of persistent pollutants in river water can represent a problem for the quality of drinking water produced by bank filtration. The common detection of the gasoline additive methyl tert-butyl ether (MTBE) in drinking water and the announced phase-out of the oxygenate in the U.S. show that MTBE can contaminate large water amounts due to its physicochemical properties. The MTBE situation in the U.S differs from Europe, and significantly lower concentrations in the German environment can be expected. Average MTBE concentrations of 200-250 ng/L in the Lower Main and Lower Rhine river in 2000/2001 were reported. At two sites at the Lower Rhine and Lower Main rivers MTBE concentrations in bank filtered water (n = 22), recovering well water, raw water, and drinking water produced by the water utility at the Lower Rhine site (n = 30) and tap water at Frankfurt/M City (n = 13) were analyzed from 1999 to 2001. Sample analysis is performed by a combination of headspace-solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC/MS) with a detection limit of 10 ng/L and a relative standard deviation of 11%. At the Lower Rhine site up to 80 m from the river an average MTBE concentration of 88 ng/L in riverbank filtered water, recovering well water, and raw water (n = 7) and of 43-110 ng/L in drinking water (n = 3) result. At the Lower Main site up to 400 m from the river MTBE concentrations from 52 to 250 ng/L (n = 7) were measured. Tap water samples at Frankfurt/M (mean of 35 ng/L, maximum of 71 ng/L) were in the same range as MTBE amounts in drinking water at the Lower Rhine site. Measured MTBE amounts eliminated by bank filtration at the Lower Rhine site are comparable to other contaminants. The results of this study show that concentrations measured in river water and drinking water are approximately 2-3 orders of magnitude lower than the U.S. drinking water standard of 20-40 microg/L, represent trace-level concentrations, and are not of major concern nowadays. However, the unfavorable combination of the occurrence of nonpoint MTBE emissions and the persistent behavior of the ether in water even at low concentrations should not be neglected in future discussion. The reported MTBE concentrations are relevant for precautionary aspects. MTBE concentrations in German river water show a tendency toward increasing concentrations since 1999, and in the future possible higher concentrations could represent a risk for the quality of drinking water that is being produced by water utility using bank filtered river water. PMID:12322735

Achten, Christine; Kolb, Axel; Püttmann, Wilhelm

2002-09-01

168

Methyl tert-butyl ether degradation in the unsaturated zone and the relation between MTBE in the atmosphere and shallow groundwater  

USGS Publications Warehouse

Atmospheric methyl tert-butyl ether (MTBE) concentrations in southern New Jersey generally exceeded concentrations in samples taken from the unsaturated zone. A simple unsaturated zone transport model indicates that MTBE degradation can explain the attenuation with half-lives from a few months to a couple of years. Tert-butyl alcohol (TBA), a possible degradation product of MTBE, was detected in unsaturated-zone samples at concentrations exceeding atmospheric levels at some sites, suggesting the possible conversion of MTBE to TBA. At sites where MTBE was detected in shallow groundwater, the concentration was typically higher than the overlying unsaturated-zone concentration. This observation is consistent with outgassing from the aquifer and combined with the unsaturated-zone attenuation suggests some of the MTBE detections in shallow groundwater are nonatmospheric in origin, coming from leaking tanks, road runoff, or other sources. The identification of sources of MTBE in groundwater and attenuation mechanisms through the hydrologic cycle is critical in developing an understanding of the long-term effect of MTBE releases.

Baehr, A. L.; Charles, E. G.; Baker, R. J.

2001-01-01

169

Methyl tert-butyl ether degradation in the unsaturated zone and the relation between MTBE in the atmosphere and shallow groundwater  

NASA Astrophysics Data System (ADS)

Atmospheric methyl tert-butyl ether (MTBE) concentrations in southern New Jersey generally exceeded concentrations in samples taken from the unsaturated zone. A simple unsaturated zone transport model indicates that MTBE degradation can explain the attenuation with half-lives from a few months to a couple of years. Tert-butyl alcohol (TBA), a possible degradation product of MTBE, was detected in unsaturated-zone samples at concentrations exceeding atmospheric levels at some sites, suggesting the possible conversion of MTBE to TBA. At sites where MTBE was detected in shallow groundwater, the concentration was typically higher than the overlying unsaturated-zone concentration. This observation is consistent with outgassing from the aquifer and combined with the unsaturated-zone attenuation suggests some of the MTBE detections in shallow groundwater are nonatmospheric in origin, coming from leaking tanks, road runoff, or other sources. The identification of sources of MTBE in groundwater and attenuation mechanisms through the hydrologic cycle is critical in developing an understanding of the long-term effect of MTBE releases.

Baehr, Arthur L.; Charles, Emmanuel G.; Baker, Ronald J.

2001-02-01

170

Distribution of Methyl 'Tert'-Butyl Ether (MTBE) and Selected Water-Quality Constituents in the Surficial Aquifer at the Dover National Test Site, Dover Air Force Base, Delaware, 2001.  

National Technical Information Service (NTIS)

A joint study by the Dover National Test Site, Dover Air Force Base, Delaware, and the U.S. Geological Survey was conducted from June 27 through July 18, 2001, to determine the spatial distribution of the gasoline oxygenate additive methyl tert-butyl ethe...

M. Stewart W. R. Guertal J. R. Barbaro T. J. McHale

2004-01-01

171

Methyl tert-Butyl Ether (MTBE) Detected in Abnormally High Concentrations in Postmortem Blood and Urine from Two Persons Found Dead Inside a Car Containing a Gasoline Spill.  

PubMed

Two deep frozen persons, a female and a male, were found dead in a car. There had been an explosive fire inside the car which had extinguished itself. On the floor inside the car were large pools of liquid which smelled of gasoline. The autopsy findings and routine toxicological analyses could not explain the cause of death. Carboxyhemoglobin levels in the blood samples were <10%. Analysis with a headspace gas chromatography revealed methyl tert-butyl ether (MTBE) concentrations of 185 mg/L (female victim) and 115 mg/L (male victim) in peripheral blood. The urine MTBE concentrations were 150 mg/L and 256 mg/L, respectively. MTBE is a synthetic chemical which is added to gasoline as a fuel oxygenate. Gasoline poisoning is likely to be the cause of the death in these two cases, and MTBE can be a suitable marker of gasoline exposure, when other volatile components have vaporized. PMID:23879346

Karinen, Ritva; Vindenes, Vigdis; Morild, Inge; Johnsen, Lene; Le Nygaard, Ilah; Christophersen, Asbjørg S

2013-07-23

172

Could activated charcoal be used to adsorb intraduodenal methyl tert-butyl ether spillage during its use in the dissolution of gallstones?  

PubMed

Methyl tert-butyl ether (MTBE) is becoming more frequently used in the non-surgical removal of cholesterol gallstones. However, during its introduction into the biliary tract, some spillage can occur and subsequent systemic absorption has been reported to lead to a variety of side effects. We have carried out in vitro experiments to assess the ability of activated charcoal to adsorb MTBE. A 10% aqueous suspension of activated charcoal was mixed with MTBE and its adsorption was estimated subsequently by gas chromatography. Adsorption varied from 38% at an activated charcoal: MTBE ratio of 1:1, to 96% at a ratio of 8:1. Only 3.2% of the adsorbed MTBE could be desorbed by resuspending the sedimented activated charcoal: MTBE complex in an equivalent volume of fresh distilled water. The results indicate that a single dose of activated charcoal (greater than 12 g) may be effective in minimizing systemic absorption of MTBE spilt during gallstone dissolution. PMID:2129821

Ilett, K F; Laurence, B H; Hackett, L P

173

4-[(tert-Butyl-dimethyl-sil-yl)-oxy]-6-meth-oxy-7-methyl-5-(oxiran-2-ylmeth-yl)-2-benzofuran-3(1H)-one  

PubMed Central

The title compound, C19H28O5Si, was obtained in the reaction of 1,3-dihydro-4-[(tert-butyl­dimethyl­sil­yl)­oxy]-6-meth­oxy-7-methyl-3-oxo-5-(prop-2-en­yl)isobenzofuran with meta-chloro­perbenzoic acid. This reaction is one of the stages of the total synthesis of mycophenolic acid, which we attempted to modify. The title compound forms crystals with only weak inter­molecular inter­actions. The strongest stacking inter­action is found between the benzene and furan rings of inversion-related mol­ecules with a distance of 3.8773?(13)?Å between the ring centroids.

Malachowska-Ugarte, Magdalena; Cholewinski, Grzegorz; Chojnacki, Jaroslaw; Dzierzbicka, Krystyna

2011-01-01

174

Acute effects of topical methyl tert-butyl ether or ethyl propionate on gallbladder histology in animals: a comparison of two solvents for contact dissolution of cholesterol gallstones.  

PubMed

Experiments were performed in anesthetized rabbits and piglets to assess gallbladder mucosal injury during irrigation with methyl tert-butyl ether, a C5 ether, or ethyl propionate, a C5 ester--two organic solvents used in the contact dissolution of cholesterol gallstones. In 44 New Zealand White rabbits, the gallbladder was exposed to individual solvents or saline solution through a transhepatic catheter for 2 hr. Gallbladders were then harvested and fixed immediately or after a recovery period of 1, 4 or 8 days. Tissue sections were examined under light microscopy, and severity of injury was graded with predefined criteria by two pathologists blinded to the animals' treatment regimens. Histological assessment showed severe mucosal injury such as necrosis of the cells at the villus tips immediately after 2 hr of exposure to either solvent. After 4 days, injury had decreased significantly; after 8 days, complete mucosal healing had taken place. A similar study was performed in 32 piglets. Solvent or saline solution was oscillated in and out of the gallbladders of these piglets with a computer-controlled syringe pump at a pressure less than the leakage pressure of the gallbladder. Histological assessment was performed on tissue samples obtained immediately after the procedure or 8 days later. Both solvents caused severe mucosal injury; however, after 8 days complete mucosal healing had occurred, so that gallbladders exposed to solvent were indistinguishable from gallbladders exposed to saline solution, which was used as control. We conclude that both methyl tert-butyl ether and ethyl propionate cause moderate to severe epithelial injury but that the gallbladder epithelium regenerates within a few days.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1398506

Esch, O; Spinosa, J C; Hamilton, R L; Crombie, D L; Schteingart, C D; Rondinone, J F; D'Agostino, H B; Lillienau, J; Hofmann, A F

1992-10-01

175

N-tert-Butyl-3-mesitylpropanamide.  

PubMed

In the title compound, C(16)H(25)NO, the N-tert-butyl-propanamide fragment is essentially planar, with the exception of two C atoms of the tert-butyl group (r.m.s. deviation = 0.005?Å), forming a dihedral angle of 84.09?(10)° with the plane of the mesityl fragment (r.m.s. deviation = 0.002?Å). The crystal packing is stabilized by an inter-molecular N-H?O hydrogen bond, which links the mol-ecules into chains with graph-set notation C(4) running parallel to the c axis. PMID:21754709

Maharramov, Abel M; Khalilov, Ali N; Gurbanov, Atash V; Brito, Iván

2011-05-07

176

N-tert-Butyl-3-mesitylpropanamide  

PubMed Central

In the title compound, C16H25NO, the N-tert-butyl­propanamide fragment is essentially planar, with the exception of two C atoms of the tert-butyl group (r.m.s. deviation = 0.005?Å), forming a dihedral angle of 84.09?(10)° with the plane of the mesityl fragment (r.m.s. deviation = 0.002?Å). The crystal packing is stabilized by an inter­molecular N—H?O hydrogen bond, which links the mol­ecules into chains with graph-set notation C(4) running parallel to the c axis.

Maharramov, Abel M.; Khalilov, Ali N.; Gurbanov, Atash V.; Brito, Ivan

2011-01-01

177

The rapid detection of methyl tert-butyl ether (MtBE) in water using a prototype gas sensor system.  

PubMed

The gasoline additive Methyl-tertiary-Butyl Ether (MtBE) is the second most common contaminant of groundwater in the USA and represents an important soil contaminant. This compound has been detected in the groundwater in at least 27 states as a result of leaking underground storage facilities (gasoline storage tanks and pipelines). Since the health effects of MtBE are unclear the potential threat to drinking water supplies is serious. Therefore, the ability to detect MtBE at low levels (ppb) and on-line at high-risk groundwater sites would be highly desirable. This paper reports the use of 'commercial' and metal oxide sensor arrays for the detection of MtBE in drinking and surface waters at low ppb level (microg.L(-1) range). The output responses from some of the sensors were found to correlate well with MtBE concentrations under laboratory conditions. PMID:16312958

de Lacy Costello, B P J; Sivanand, P S; Ratcliffe, N M; Reynolds, D M

2005-01-01

178

Evaluation of standard methods for the analysis of methyl tert-butyl ether and related oxygenates in gasoline-contaminated groundwater.  

PubMed

The U.S. Environmental Protection Agency (EPA) now requires monitoring of oxygenate compounds in groundwater at leaking underground storage tank (LUST) sites nationwide. Three purge-and-trap gas chromatography methods most commonly employed for this purpose were tested, and their performance as a function of total petroleum hydrocarbon (TPH) content of the sample matrix was determined. Tests included a formal method evaluation, a round-robin study, and a split-sample study (424 groundwater samples). Consistently good results were achieved with EPA Method 8240B/60B (mass spectrometry) and ASTM Method D4815 (flame ionization detection) when five oxygenates were monitored in reagent water and gasoline. However, one protocol routinely employed for analysis of LUST samples had serious limitations: EPA Method 8020A/21B (photoiozination detection) was unfit for monitoring of tert-butyl alcohol (TBA) and frequently yielded false-positive (12-50% of samples) and inaccurate results when ether oxygenates were monitored in aqueous samples containing high concentrations of TPH (> 1,000 microg/ L). Thus, care should be taken in the analysis of LUST databases populated with EPA Method 8020/21 data because results reported for methyl tert-butyl ether (MTBE) in samples containing high levels of TPH have a high likelihood of being inaccurate or false-positive. For all three methods, detection limits determined in reagent water were sufficiently low for monitoring MTBE at the stringent primary (13 microg/L) and secondary (5 microg/L) action levels set by the state of California. PMID:11348088

Halden, R U; Happel, A M; Schoen, S R

2001-04-01

179

Methyl tert -butyl ether in the endoscopic treatment of common bile duct radiolucent stones in elderly patients with nasobiliary tube  

Microsoft Academic Search

Methyltert-butyl ether is an effective dissolution agent for cholesterol stones. The aim of this work was to evaluate the effect of methyltert-butyl ether on radiolucent common bile duct stones in patients in whom endoscopic extraction has failed. From September 1985 to September 1987, 1374 patients underwent endoscopic retrograde cholangiopancreatography in our Liver Unit. An endoscopic sphincterotomy was indicated in 195

D. Diaz; P. Bories; M. Ampelas; D. Larrey; H. Michel

1992-01-01

180

Simultaneous determination of methyl tert-butyl ether, its degradation products and other gasoline additives in soil samples by closed-system purge-and-trap gas chromatography-mass spectrometry.  

PubMed

A new protocol for the simultaneous determination of methyl tert-butyl ether (MTBE); its main degradation products: tert-butyl alcohol (TBA) and tert-butyl formate (TBF); other gasoline additives, oxygenate dialkyl ethers: ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME) and diisopropyl ether (DIPE); aromatics: benzene, toluene, ethylbenzene and xylenes (BTEX) and other compounds causing odour events such as dicyclopentadiene (DCPD) and trichloroethylene (TCE) in soils has been developed. On the basis of US Environmental Protection Agency (EPA) method 5035A, a fully automated closed-system purge-and-trap coupled to gas chromatography/mass spectrometry (P&T-GC/MS) was optimised and permitted to detect microg/kg concentrations in solid matrices avoiding losses of volatile compounds during operation processes. Parameters optimised were the sampling procedure, sample preservation and storage, purging temperature, matrix effects and quantification mode. Using 5 g of sample, detection limits were between 0.02 and 1.63 microg/kg and acceptable method precision and accuracy was obtained provided quantification was performed using adequate internal standards. Soil samples should be analysed as soon as possible after collection, stored under -15 degrees C for not longer than 7 days if degradation products have to be analysed. The non-preservative alternative (empty vial) provided good recoveries of the most analytes when freezing the samples up to 7 day holding time, however, if biologically active soil are analysed the preservation with trisodium phosphate dodecahydrate (Na(3)PO(4).12H(2)O or TSP) is strongly recommended more than sodium bisulphate (NaHSO(4)). The method was finally applied to provide threshold and background levels of several gasoline additives in a point source and in sites not influenced by gasoline spills. The proposed method provides the directions for the future application on real samples in current monitoring programs at gasoline pollution risk sites where till now little monitoring data for MTBE in soils are available. PMID:16904119

Rosell, Mònica; Lacorte, Sílvia; Barceló, Damià

2006-08-09

181

Simultaneous determination of methyl tert.-butyl ether and its degradation products, other gasoline oxygenates and benzene, toluene, ethylbenzene and xylenes in Catalonian groundwater by purge-and-trap-gas chromatography-mass spectrometry.  

PubMed

In Catalonia (northeast Spain), a monitoring program was carried out to determine methyl tert.-butyl ether (MTBE), its main degradation products, tert.-butyl alcohol (TBA), tert.-butyl formate (TBF), and other gasoline additives, the oxygenate dialkyl ethers ethyl tert.-butyl ether, tert.-amyl methyl ether and diisopropyl ether and the aromatic compounds benzene, toluene, ethylbenzene and xylene (BTEX) in 21 groundwater wells that were located near different gasoline point sources (a gasoline spill and underground storage tank leakage). Purge-and-trap coupled to gas chromatography-mass spectrometry was optimised for the simultaneous determination of the above mentioned compounds and enabled to detect concentrations at ng/l or sub-microg/l concentrations. Special attention was given to the determination of polar MTBE degradation products, TBA and TBF, since not much data on method performance and environmental levels are given on these compounds in groundwater. All samples analysed contained MTBE at levels between 0.3 and 70 microg/l. Seven contaminated hot spots were identified with levels up to US Environmental Protection Agency drinking water advisory (20-40 microg/l) and a maximum concentration of 670 microg/l (doubling the Danish suggested toxicity level of 350 microg/l). Samples with high levels of MTBE contained 0.1-60 microg/l of TBA, indicating (but not proving) in situ degradation of parent compound. In all cases, BTEX was at low concentrations or not detected showing less solubility and persistence than MTBE. This fact confirms the suitability of MTBE as a tracer or indicator of long-term gasoline contamination than the historically used BTEX. PMID:12800934

Rosell, Mònica; Lacorte, Sílvia; Ginebreda, Antoni; Barceló, Damià

2003-05-01

182

Treatment of methyl tert-butyl ether vapors in biotrickling filters. 1. Reactor startup, steady-state performance, and culture characteristics  

SciTech Connect

An aerobic microbial consortium able to biodegrade methyl tert-butyl ether (MTBE) was enriched in two waste air biotrickling filters after continuous operation for 6 months. After this acclimation phase, the two laboratory-scale biotrickling filters were able to degrade up to 50 g of MTBE per cubic meter of reactor per hour, a value comparable to other gasoline constituents. Such high performance could be sustained for at least 4--6 weeks. After the acclimation phase, the MTBE degrading biotrickling filters were characterized by their almost full conversion of MTBE to carbon dioxide and the absence of any degradation byproducts in either the gas or the liquid phase. They also exhibited a very high specific degradation activity per amount of biomass, and a low rate of biomass accumulation. An observed biomass yield of 0.1 g g{sup {minus}1} and a specific growth rate of 0.025 day{sup {minus}1} were determined for the biotrickling filter process culture. Further data on MTBE mass transfer and on the dynamic behavior of the biotrickling filter are presented in part 2 of this paper. Overall, the results demonstrate that MTBE can be effectively biodegraded under carefully controlled environmental conditions.

Fortin, N.Y.; Deshusses, M.A. [Univ. of California, Riverside, CA (United States). Dept. of Chemical and Environmental Engineering

1999-09-01

183

Liquid-gas partitioning of the gasoline oxygenate methyl tert-butyl ether (MTBE) under laboratory conditions and its effect on growth of selected algae.  

PubMed

The partitioning of the widely used gasoline additive methyl tert-butyl ether (MTBE) between liquid growth media and gaseous phase was measured daily under laboratory conditions to determine how closely dissolved MTBE concentrations matched nominal concentrations. Total (gaseous and dissolved) MTBE averaged across 6 days for 29.6, 503.2, and 1005.7 mg L-1 MTBE treatments were 89.9, 90.3, and 73.0% of nominal, respectively, and mean dissolved MTBE in these same treatments were 74.6, 73.8, and 69.6% of total MTBE, respectively. This suggests that dissolved MTBE concentrations can vary substantially from nominal. The effect of MTBE on the growth of selected algae was also evaluated under laboratory conditions. Three unicellular algae, Selenastrum capricornutum (Chlorophyta), Navicula pelliculosa (Bacillariophyta), and Synechococcus leopoliensis (= Anacystic nidulans, Cyanophyta = Cyanobacteria), representative of three taxonomic groups, were used as test organisms. Toxicity tests were acute and increase in cell number was used as an indicator of growth. Algal species were exposed by injection of MTBE into sealed vessels containing defined liquid growth media. The growth of N. pelliculosa and S. leopoliensis was negatively affected at nominal 2400 mg L-1 MTBE, whereas the growth of S. capricornutum was negatively affected at nominal 4800 mg L-1 MTBE and positively affected at nominal 600 mg L-1 MTBE. The differential sensitivity of the growth of these representative species suggests that MTBE may alter algal community composition in the natural environment. PMID:9419267

Rousch, J M; Sommerfeld, M R

1998-01-01

184

Long-term exposure to environmentally relevant doses of methyl-tert-butyl ether causes significant reproductive dysfunction in the zebrafish (Danio rerio).  

PubMed

Methyl-tert-butyl ether (MTBE), an anthropogenic chemical used as a gasoline additive, is being detected at an increasing frequency in the environment. The acute lethal concentration that kills 50% of the fish test population and the chronic effects of exposure to MTBE were investigated in the zebrafish (Danio rerio). Chronic exposure over three weeks to effective MTBE conceritrations as low as 0.11 mg/L induced a significant increase in the vitellogenin concentration of male fish. The impact of a chronic, eight-week exposure at effective concentrations ranging from 0.44 to 220 mg/L had no significant effect on fecundity, fertilization, or hatch rate but highly significant impacts on sperm motility. Spermatozoa of all MTBE-exposure groups showed a significantly lower straight-line velocity and lower average path velocity compared to those of the nonexposed group. These results suggest that chronic exposure to MTBE negatively affects fish sperm motility at concentrations that are environmentally relevant and several orders of magnitude lower than concentrations inducing acute effects. PMID:16986794

Moreels, David; Van Cauwenberghe, Karen; Debaere, Bruno; Rurangwa, Eugène; Vromant, Nico; Bastiaens, Leen; Diels, Ludo; Springael, Dirk; Merckx, Roel; Ollevier, Frans

2006-09-01

185

Detection of the gasoline components methyl tert-butyl ether, benzene, toluene, and m-xylene using ion mobility spectrometers with a radioactive and UV ionization source.  

PubMed

For the first time, ion mobility spectrometers (IMS) with radioactive and UV ionization sources in combination with multicapillary columns (MCCs) have been used to determine methyl tert-butyl ether (MTBE), a gasoline additive, in water and nitrogen as well as the monoaromatic compounds benzene, toluene, and m-xylene (BTX). A membrane extraction unit was set up to extract the substances from water, which is simple, effective, and easy to automate for further applications. Thus, the detection of MTBE and BTX of gasoline vapors was accomplished after a preliminary silicone membrane extraction. Two-dimensional data analyses of IMS-chromatograms allow us to separate these substances clearly according to their different retention and drift times. Method detection limits for MTBE were 2 microg/L (UV) and 30 pg/L (63Ni) in nitrogen and 20 mg/L (UV) and 1 microg/L (63Ni) in water. Rather a good reproducibility was achieved with relative standard deviations of between 2.9 and 9%. The method presented in this article has been proven to be suitable for nearly real-time monitoring as the total analysis time is less than 90 s. As an example of application, the detection of MTBE and BTX in a mixture of volatile organic compounds of pure gasoline using the 2-D IMS-chromatogram is presented. PMID:12659213

Baumbach, Jörg Ingo; Sielemann, Stefanie; Xie, Zhiyong; Schmidt, Hartwig

2003-03-15

186

Mechanistic considerations for the degradation of methyl tert-butyl ether (MTBE) by sonolysis: effect of argon vs. oxygen saturated solutions.  

PubMed

The ultrasonic degradation mechanism of methyl tert-butyl ether (MTBE) in aqueous solution is complex because of the competition between hydroxyl radical attack, pyrolysis, and hydrolysis reactions. A detailed investigation of degradation pathways using sonolysis has been performed using reaction byproducts identification. The observed bi-product distributions are rationalized in terms of hydroxyl radical (()OH) mediated processes and pyrolysis. The role of oxygen mediated and pyrolytic pathways were assessed using O(2) and Ar saturated solutions. Chemical destruction by sonolysis is often rationalized using hydroxyl radical chemistry. Pyrolysis is unique to this advanced oxidation process, and is important in the case of MTBE because it transfers into the cavitating bubbles. While ?-hydrogen abstraction by ()OH and low temperature pyrolysis was important, it was also shown that ?-hydrogen abstraction leads, in some cases, to the same reaction byproducts, which emphasized the importance of ?-hydrogen abstraction. High temperature pyrolysis resulted in minor degradation reactions based on the formation of reaction by-products. PMID:22227553

Kim, Duk Kyung; O'Shea, Kevin E; Cooper, William J

2011-12-23

187

Addition of dimethylsulphoxide to methyl-tert-butyl ether and ethyl propionate increases cholesterol dissolving capacity and cholesterol gall stone dissolution in vitro.  

PubMed

There is a discrepancy between in vitro cholesterol dissolving efficacy of methyl-tert-butyl ether (MTBE) and ethyl propionate and cholesterol gall stone dissolution in vivo. This study investigated whether the presence of bile changes the cholesterol dissolving capacity of MTBE and ethyl propionate. The addition of dimethylsulphoxide to MTBE or ethyl propionate was also studied to discover if it improves the dissolving capacity for cholesterol gall stones. The presence of bile caused a 25% decrease in cholesterol dissolving capacity of both MTBE and ethyl propionate (p < 0.0001). This inhibitory effect of bile could be overcome by the addition of dimethyl-sulphoxide: dimethylsulphoxide caused an increase in cholesterol dissolving capacity of MTBE and ethyl propionate, the increase depending on the dimethyl-sulphoxide/bile ratio in the mixture. Mean dissolution time of weight, size, and patient matched cholesterol gall stones was 220 minutes in MTBE and 130 minutes in MTBE/dimethylsulphoxide (p < 0.0001). No stones dissolved completely in ethyl propionate or ethyl propionate/dimethyl-sulphoxide within 300 minutes. In conclusion, MTBE/dimethylsulphoxide is a more potent dissolving agent for cholesterol gall stones than MTBE, giving a 40% reduction in dissolution time. Addition of dimethylsulphoxide to ethyl propionate does not result in faster stone dissolution. MTBE and MTBE/dimethylsulphoxide are far superior to ethyl propionate as solvents for cholesterol gall stones. PMID:7828992

Bergman, J J; Groen, A K; Huibregtse, K; Tytgat, G N

1994-11-01

188

Naturally Occurring Bacteria Similar to the Methyl tert-Butyl Ether (MTBE)-Degrading Strain PM1 Are Present in MTBE-Contaminated Groundwater  

PubMed Central

Methyl tert-butyl ether (MTBE) is a widespread groundwater contaminant that does not respond well to conventional treatment technologies. Growing evidence indicates that microbial communities indigenous to groundwater can degrade MTBE under aerobic and anaerobic conditions. Although pure cultures of microorganisms able to degrade or cometabolize MTBE have been reported, to date the specific organisms responsible for MTBE degradation in various field studies have not be identified. We report that DNA sequences almost identical (99% homology) to those of strain PM1, originally isolated from a biofilter in southern California, are naturally occurring in an MTBE-polluted aquifer in Vandenberg Air Force Base (VAFB), Lompoc, California. Cell densities of native PM1 (measured by TaqMan quantitative PCR) in VAFB groundwater samples ranged from below the detection limit (in anaerobic sites) to 103 to 104 cells/ml (in oxygen-amended sites). In groundwater from anaerobic or aerobic sites incubated in microcosms spiked with 10 ?g of MTBE/liter, densities of native PM1 increased to approximately 105 cells/ml. Native PM1 densities also increased during incubation of VAFB sediments during MTBE degradation. In controlled field plots amended with oxygen, artificially increasing the MTBE concentration was followed by an increase in the in situ native PM1 cell density. This is the first reported relationship between in situ MTBE biodegradation and densities of MTBE-degrading bacteria by quantitative molecular methods.

Hristova, Krassimira; Gebreyesus, Binyam; Mackay, Douglas; Scow, Kate M.

2003-01-01

189

Detection and Quantification of Methyl tert-Butyl Ether-Degrading Strain PM1 by Real-Time TaqMan PCR  

PubMed Central

The fuel oxygenate methyl tert-butyl ether (MTBE), a widely distributed groundwater contaminant, shows potential for treatment by in situ bioremediation. The bacterial strain PM1 rapidly mineralizes and grows on MTBE in laboratory cultures and can degrade the contaminant when inoculated into groundwater or soil microcosms. We applied the TaqMan quantitative PCR method to detect and quantify strain PM1 in laboratory and field samples. Specific primers and probes were designed for the 16S ribosomal DNA region, and specificity of the primers was confirmed with DNA from 15 related bacterial strains. A linear relationship was measured between the threshold fluorescence (CT) value and the quantity of PM1 DNA or PM1 cell density. The detection limit for PM1 TaqMan assay was 2 PM1 cells/ml in pure culture or 180 PM1 cells/ml in a mixture of PM1 with Escherichia coli cells. We could measure PM1 densities in solution culture, groundwater, and sediment samples spiked with PM1 as well as in groundwater collected from an MTBE bioaugmentation field study. In a microcosm biodegradation study, increases in the population density of PM1 corresponded to the rate of removal of MTBE.

Hristova, Krassimira R.; Lutenegger, Christian M.; Scow, Kate M.

2001-01-01

190

A cocrystal of two Mo(VI) complexes bearing different diastereomers of the 2,4-di-tert-butyl-6-{[(1-oxido-1-phenylpropan-2-yl)(methyl)amino]methyl}phenolate ligand derived from (+)-ephedrine.  

PubMed

The title cocrystal contains two chiral conformational diastereomers, viz. (1S,2R,RN)- and (1S,2R,SN)-, of [2,4-di-tert-butyl-6-{[(1-oxido-1-phenylpropan-2-yl)(methyl)amino]methyl}phenolato](methanol)-cis-dioxidomolybdenum(VI), [Mo(C25H35NO2)O2(CH3OH)], representing the first example of a structurally characterized molybdenum complex with enantiomerically pure ephedrine derivative ligands. The Mo(VI) cations exhibit differently distorted octahedral coordination environments, with two oxide ligands positioned cis to each other. The remainder of the coordination comprises phenoxide, alkoxide and methanol O atoms, with an amine N atom completing the octahedron. The distinct complexes are linked by strong intermolecular O-H···O hydrogen bonds, resulting in one-dimensional molecular chains. Furthermore, the phenyl rings are involved in weak T-shaped/edge-to-face ?-? interactions with each other. PMID:23629903

Sillanpää, Reijo; Hänninen, Mikko M

2013-04-24

191

Effect of laser fragmentation of cholesterol and mixed gallstones on in vitro dissolution in methyl tert -butyl ether  

Microsoft Academic Search

This study examined cholesterol and mixed gallstone dissolution in vitroby methyltert-butyl ether (MTBE) after gallstone fragmentation. Three morphologically identical gallstones were obtained from 42 patients. One stone from each patient was fragmented with laser energy at a wavelength of 504 nm delivered to the stone surface with a 320-µm quartz fiber. Intact and fragmented stones from the same patient were

Bernard F. Smith

1990-01-01

192

Occurrence and temporal variability of methyl tert-butyl ether (MTBE) and other volatile organic compounds in select sources of drinking water : results of the focused survey  

USGS Publications Warehouse

The large-scale use of the gasoline oxygenate methyl tert-butyl ether (MTBE), and its high solubility, low soil adsorption, and low biodegradability, has resulted in its detection in ground water and surface water in many places throughout the United States. Studies by numerous researchers, as well as many State and local environmental agencies, have discovered high levels of MTBE in soils and ground water at leaking underground gasoline-storage-tank sites and frequent occurrence of low to intermediate levels of MTBE in reservoirs used for both public water supply and recreational boating.In response to these findings, the American Water Works Association Research Foundation sponsored an investigation of MTBE and other volatile organic compounds (VOCs) in the Nation?s sources of drinking water. The goal of the investigation was to provide additional information on the frequency of occurrence, concentration, and temporal variability of MTBE and other VOCs in source water used by community water systems (CWSs). The investigation was completed in two stages: (1) reviews of available literature and (2) the collection of new data. Two surveys were associated with the collection of new data. The first, termed the Random Survey, employed a statistically stratified design for sampling source water from 954 randomly selected CWSs. The second, which is the focus of this report, is termed the Focused Survey, which included samples collected from 134 CWS source waters, including ground water, reservoirs, lakes, rivers, and streams, that were suspected or known to contain MTBE. The general intent of the Focused Survey was to compare results with the Random Survey and provide an improved understanding of the occurrence, concentration, temporal variability, and anthropogenic factors associated with frequently detected VOCs. Each sample collected was analyzed for 66 VOCs, including MTBE and three other ether gasoline oxygenates (hereafter termed gasoline oxygenates). As part of the Focused Survey, 451 source-water samples and 744 field quality-control (QC) samples were collected from 78 ground-water, 39 reservoir and (or) lake, and 17 river and (or) stream source waters at fixed intervals for a period of 1 year.Using a common assessment level of 0.2 ?g/L (micrograms per liter) (2.0 ?g/L for methyl ethyl ketone), 37 of the 66 VOCs analyzed were detected in both surveys. However, VOCs, especially MTBE and other gasoline oxygenates, were detected more frequently in the Focused Survey than in the Random Survey. MTBE was detected in 55.5 percent of the CWSs sampled in the Focused Survey and in 8.7 percent of those sampled in the Random Survey. Little difference in occurrence, however, was observed for trihalomethanes (THMs), which were detected in 16.4 and 14.8 percent of Focused Survey and The large-scale use of the gasoline oxygenate methyl tert-butyl ether (MTBE), and its high solubility, low soil adsorption, and low biodegradability, has resulted in its detection in ground water and surface water in many places throughout the United States. Studies by numerous researchers, as well as many State and local environmental agencies, have discovered high levels of MTBE in soils and ground water at leaking underground gasoline-storage-tank sites and frequent occurrence of low to intermediate levels of MTBE in reservoirs used for both public water supply and recreational boating.In response to these findings, the American Water Works Association Research Foundation sponsored an investigation of MTBE and other volatile organic compounds (VOCs) in the Nation?s sources of drinking water. The goal of the investigation was to provide additional information on the frequency of occurrence, concentration, and temporal variability of MTBE and other VOCs in source water used by community water systems (CWSs). The investigation was completed in two stages: (1) reviews of available literature and (2) the collection of new data. Two surveys wer

Delzer, Gregory C.; Ivahnenko, Tamara

2003-01-01

193

Effect of Ethanol and Methyl-tert-Butyl Ether on Monoaromatic Hydrocarbon Biodegradation: Response Variability for Different Aquifer Materials Under Various Electron-Accepting Conditions  

SciTech Connect

Aquifer microcosms were used to determine how ethanol and methyl-tert-butyl ether (MtBE) affect monoaromatic hydrocarbon degradation under different electron-accepting conditions commonly found in contaminated sites experiencing natural attenuation. Response variability was investigated by using aquifer material from four sites with different exposure history. The lag phase prior to BTEX (benzene, toluene, ethylbenzene, and xylenes) and ethanol degradation was typically shorter in microcosms with previously contaminated aquifer material, although previous exposure did not always result in high degradation activity. Toluene was degraded in all aquifer materials and generally under a broader range of electron-accepting conditions compared to benzene, which was degraded only under aerobic conditions. MtBE was not degraded within 100 days under any condition, and it did not affect BTEX or ethanol degradation patterns. Ethanol was often degraded before BTEX compounds, and had a variable effect on BTEX degradation as a function of electron-accepting conditions and aquifer material source. An occasional enhancement of toluene degradation by ethanol occurred in denitrifying microcosms with unlimited nitrate; this may be attributable to the fortuitous growth of toluene-degrading bacteria during ethanol degradation. Nevertheless, experiments with flow-through aquifer columns showed that this beneficial effect could be eclipsed by an ethanol-driven depletion of electron acceptors, which significantly inhibited BTEX degradation and is probably the most important mechanism by which ethanol could hinder BTEX natural attenuation. A decrease in natural attenuation could increase the likelihood that BTEX compounds reach a receptor as well as the potential duration of exposure.

Ruiz-Aguilar, G L; Fernandez-Sanchez, J M; Kane, S R; Kim, D; Alvarez, P J

2003-10-06

194

Headspace-solid-phase microextraction using a dodecylsulfate-doped polypyrrole film coupled to ion mobility spectrometry for analysis methyl tert-butyl ether in water and gasoline.  

PubMed

A simple and sensitive method for the determination of methyl tert-butyl ether (MTBE) in water using headspace-solid-phase microextraction (HS-SPME) at sub-ng mL(-1) concentrations is described. The analysis was carried out using a cooled SPME fiber coated with a film of dodecylsulfate-doped polypyrrole coupled to ion mobility spectrometry equipped with corona discharge ionization. The headspace-solid-phase microextraction experimental procedures to extract MTBE in water samples were optimized with a dodecylsulfate-doped polypyrrole coated fiber at a 30 min extraction time, extraction temperature of 40 degrees C, sodium chloride concentration of 2.5 mol L(-1) and desorption temperature of 140 degrees C. Two linear calibration curves respectively in the ranges of 2-17 ng mL(-1) and 10-70 ng mL(-1) with detection limits of 0.7 ng mL(-1) and 4.9 ng mL(-1) were obtained. Relative standard deviations for three replicates in water samples were <10%. The capability of dodecylsulfate-doped polypyrrole to extract MTBE has been compared with the results obtained based on the literature data for commercial fiber. The results shows that dodecylsulfate-doped polypyrrole, as a solid-phase microextraction fiber coating, is suitable for successful extraction of MTBE having detection limits comparable to what obtained with commercial fibers. Finally, the proposed method was applied to the analysis of MTBE in three ground water samples and regular unleaded gasoline from petrol station in Tehran central district, Iran. PMID:19427121

Alizadeh, Naader; Jafari, Mostafa; Mohammadi, Abdorreza

2009-04-15

195

In vitro uptake of methyl tert-butyl ether in male rat kidney: use of a two-compartment model to describe protein interactions.  

PubMed

Methyl tert-butyl ether (MTBE) is a gasoline additive that causes renal tumors in male rats. In the process of measuring chemical specific parameters necessary to develop a quantitative dosimetry model of MTBE in rats, the uptake of MTBE was found to be 5.5 times greater in male than in female F-344 rat kidney homogenate. The objectives of this study were to characterize the factor(s) that influences the high uptake of MTBE into male rat kidney in vitro and to develop a system to evaluate the interaction of MTBE with the male rat-specific protein, alpha 2u-globulin (alpha 2u). The uptake of MTBE in male, but not female, rat kidney homogenate was found to be dependent on protein and chemical concentrations. When [14C]MTBE was incubated with male rat kidney homogenate, radioactivity coeluted with the total protein fraction on a gel filtration column. An interaction between [14C]MTBE and male rat kidney proteins was not found under conditions of dialysis or anion exchange chromatography. A two-compartment vial equilibration model was used to assess the interaction between MTBE and alpha 2u. Using this system, the dissociation constant for MTBE and alpha 2u was estimated to be 2.15 x 10(-4) M, which is in the range of other chemicals known to bind to alpha 2u and cause alpha 2u-mediated nephropathy. d-Limonene oxide was used to validate this two-compartment vial equilibration system. These findings illustrate a technique useful in estimating the dissociation constant for a volatile chemical and a protein, as well as explain the process that contributes to the uptake of MTBE into male rat kidney homogenate in vitro. A description of the weak interaction between MTBE and alpha 2u will be used to refine a physiologically based pharmacokinetic model to describe the target tissue (kidney) concentrations of MTBE. PMID:9266807

Poet, T S; Borghoff, S J

1997-08-01

196

Toxicity of methyl tert butyl ether to soil invertebrates (springtails: Folsomia candida, Proisotoma minuta, and Onychiurus folsomi) and lettuce (Lactuca sativa).  

PubMed

Experiments were conducted to assess the toxicity of methyl tert butyl ether (MTBE) to three species of Collembola (Proisotoma minuta, Folsomia candida, and Onychiurus folsomi) and lettuce (Lactuca sativa L.) using an artificial Organization for Economic Cooperation and Development (OECD) soil and field-collected sandy loam and silt loam soil samples. Soil invertebrate tests were carried out in airtight vials to prevent volatilization of MTBE out of the test units and to allow for direct head-space sampling and gas chromatography-mass spectrometry (GC-MS) analysis for residual MTBE. The use of the airtight vial protocol proved to be very successful, in that the measured MTBE concentrations at the beginning of the experiments were within 95% of nominal concentrations. The test methods used in this study could be used to test the toxicity of other volatile organic compounds to Collembola. The soil invertebrates tested had inhibitory concentration (ICx) and lethal concentration (LCx) values that ranged from 242 to 844 mg MTBE/kg dry soil. When the three test species of Collembola were tested under identical conditions in the artificial OECD soil, O. folsomi was the most sensitive collembolan, with a median inhibitory concentration (IC50; reproduction) of 296 mg MTBE/kg dry soil. The most sensitive endpoint for lettuce was an IC50 for root length of 81 mg MTBE/kg dry soil after 5 d of germination in OECD soil. Data on the loss of MTBE from the three test soils over time indicated that MTBE was retained in the silt loam soil longer than in either the sandy loam or the artificial OECD soil. PMID:20821452

Dodd, Matthew; Addison, Janet A

2010-02-01

197

Effect of chlorides and sulfates on the performance of a Fe3+/H2O2 Fenton-like system in the degradation of methyl tert-butyl ether and its byproducts.  

PubMed

The effect of chloride and sulfate ions on the oxidation of methyl tert-butyl ether (MTBE) and its degradation products in a Fenton-like system was studied. Although both chloride and sulfate ions inhibited the decomposition of H202, chlorides were found to be the more effective inhibitor of MTBE degradation. In the presence of sulfates, MTBE decomposition can be attributed to oxidation not only by hydroxyl radicals, but also likely by SO4*- species. In the presence of chloride ions, it is possible that the dichloride radical is formed, which is less reactive than OH*. In the system under investigation, t-butyl alcohol was found to be the major byproduct, followed by t-butyl formate and acetone. The degradation rates of all intermediates and their inhibition in the presence of inorganic ions are similar to those obtained for MTBE, although their distributions are related to the concentrations of inorganic salts added. PMID:17966699

Siedlecka, Ewa M; Stepnowski, Piotr

2007-10-01

198

Reaction between tert-butyl isocyanide, dialkyl acetylenedicarboxylates, and aromatic carboxylic acids: an efficient method for the synthesis of dialkyl ( E)-2-{[benzoyl( tert-butyl)amino]carbonyl}-2-butenedioate derivatives  

Microsoft Academic Search

Protonation of the reactive intermediates produced in the reaction between tert-butyl isocyanide and dialkyl acetylenedicarboxylates by aromatic carboxylic acids leads to vinylnitrilium cations, which undergo nucleophilic reaction with conjugate bases of the carboxylic acids to produce dialkyl (E)-2-[(benzoyloxy)(tert-butylimino)methyl]-2-butenedioates and this intermediate rearranges to the dialkyl (E)-2-{[benzoyl(tert-butyl)amino]carbonyl}-2-butenedioate derivatives.

Abdolali Alizadeh; Sadegh Rostamnia; Long-Guan Zhu

2006-01-01

199

Bis-(3-tert-butyl-pyridine-?N)bis-(4-tert-butyl-pyridine-?N)bis(thio-cyanato-?N)cadmium  

PubMed Central

The asymmetric unit of the title compound, [Cd(NCS)2(C9H13N)4], consists of one CdII cation located on a centre of inversion, one thio­cyanate anion, one 3-tert-butyl­pyridine ligand and one 4-tert-butyl­pyridine ligand in general positions. The tert-butyl group of the 4-tert-butyl­pyridine ligand is disordered over two sets of sites in a 0.25:0.75 ratio and was refined using a split model. The CdII cation is coordinated by six N atoms of four tert-butyl­pyridine ligands and two N-bonded thio­cyanate anions within a slightly distorted octa­hedral coordination environment.

Reinert, Thorben; Jess, Inke; Nather, Christian

2012-01-01

200

Methyl tert-butyl ether (MTBE) and other volatile organic compounds in lakes in Byram Township, Sussex County, New Jersey, summer 1998  

USGS Publications Warehouse

Water samples were collected from four lakes in Byram Township, Sussex County, N.J., in the summer of 1998 as part of an investigation of the occurrence of volatile organic compounds (VOCs) in domestic wells of lakeside communities. Cranberry Lake and Lake Lackawanna are surrounded by densely populated communities where the use of gasoline-powered watercraft is prevalent, and water is supplied by lakeside wells. Forest Lake is surrounded by a densely populated community where the use of gasoline-powered watercraft is prohibited. Stag Pond is privately owned, is situated in a sparsely populated area, and is not navigated by gasoline-powered watercraft. Samples were collected from Cranberry Lake in early summer and again in late summer 1998. Concentrations of the gasoline oxygenate methyl tert-butyl ether (MTBE) ranged from 1.6 to 15.0 mg/L (micrograms per liter) on June 24 and decreased with depth. The depth-related concentration gradient is attributed to density stratification caused by the temperature gradient that is present in the lake during the early summer. MTBE concentrations ranged from 7.4 to 29.0 mg/L on September 8 and were uniform with depth, as was water temperature, indicating that the lake was vertically mixed. On the basis of these concentration profiles, the mass of MTBE in Cranberry Lake was estimated to be 15 kilograms on June 24 and 27 kilograms on September 8. These mass estimates are equal to the amount of MTBE in 52 and 95 gallons, respectively, of gasoline that contains 10 percent MTBE by volume. Concentrations of another gasoline oxygenate, tert-amyl-methyl ether (TAME), ranged from 0.07 to 0.43 mg/L on June 24 and from 0.2 to 0.69 mg/L on September 8. The highest concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) were 0.18, 1.2, 0.18, and 0.97 mg/L, respectively, on June 24. All BTEX concentrations in Cranberry Lake on September 8 were less than 0.2 mg/L. Samples were collected from Lake Lackawanna on September 9. Concentrations of MTBE and TAME ranged from 3.7 to 14.0 mg/L and from 0.17 to 0.38 mg/L, respectively. Like those in Cranberry Lake the previous day, BTEX concentrations were less than 0.2 mg/L, and VOC concentrations and water temperatures were nearly uniform with depth. The mass of MTBE in Lake Lackawanna on September 9 was estimated to be 6 kilograms, which is equal to the amount of MTBE in 21 gallons of gasoline that contains10 percent MTBE by volume. All VOC concentrations were less than 0.2 mg/L in samples collected from Forest Lake on September 8, 1998, and from Stag Pond on the following day. Oxygenated gasoline is used in watercraft on lakes across northern New Jersey. Many of these lakes are surrounded by communities similar to those at Cranberry Lake and at Lake Lackawanna, which depend largely on wells for water supply. Therefore, a regional assessment of the occurrence of these compounds in lakes and ground water is needed to determine the effect of the use of oxygenated gasoline on water quality in lakeside environments throughout northern New Jersey.

Baehr, Arthur L.; Zapecza, Otto S.

1998-01-01

201

3,3?,5,5?-Tetra-tert-butyl-2?-hy-droxy-[1,1?-biphen-yl]-2-yl 4-methyl-benzene-sulfonate  

PubMed Central

In the title mol­ecule, C37H48O4S, the benzene rings in the biphenyl fragment are inclined to each other at 61.1?(1)°. The hy­droxy group is involved in a weak intra­molecular O—H?Osulfonate hydrogen bond. One tert-butyl group is disodered over two orientations in a 0.682?(17):0.318?(17) ratio. In the crystal, weak C—H?O hydrogen bonds link the mol­ecules into columns in direction [100].

Jian, Chunli; Zhang, Jinjin; Wang, Lei; Tang, Ning; Wu, Jincai

2013-01-01

202

trans-Chloridobis(4-methyl-pyridine-?N)(4,4?,4??-tri-tert-butyl-2,2?:6?,2??-terpyridine-?3 N,N?,N??)ruthenium(II) hexa-fluoridophosphate acetone monosolvate  

PubMed Central

The title compound, [RuCl(C6H7N)2(C27H35N3)]PF6·C3H6O, was obtained unintentionally as the product of the reaction of 1,1?-methyl­enebis(4-methyl­pyridinium) hexa­fluoriso­phos­phate and RuCl3(tpy*) (tpy* is 4,4?,4??-tri-tert-butyl-2,2?:6?,2??-terpyridine) in the presence of triethyl­amine and LiCl. The mol­ecular structure of the complex displays an octa­hedral geometry around the RuII ion and the unit cell contains an acetone solvent mol­ecule and one orientationally disordered PF6 ? anion (occupancy ratio 0.75:0.25) which is hydrogen bonded to two H atoms of the tpy* ligand of the nearest [RuCl(pic)2(tpy*)]+ cation (pic is 4-methyl­pyridine). One of the tert-butyl groups of the tpy* ligand is also disordered over two sets of sites in a 0.75:0.25 ratio.

Redford, Christopher; Gimbert-Surinach, Carolina; Bhadbhade, Mohan; Colbran, Stephen B.

2012-01-01

203

Reaction of alkylphenols with acetals. II. Reaction of 4methyl-2-tert-butylphenol with dimethoxymethane  

SciTech Connect

The authors explain how di(hydroxydialkylaryl) derivatives of methane play an important role in the inhibition of oxidation processes in polymers, oils, fuels, and other organic materials. They investigate the reaction of 4-methyl-2-tert-butylphenol with dimethoxymethane, and established that the reaction mass contained 2-methoxymethyl-4-6-tert-butylphenol. The formation and the transformations of 2-methoxymethyl-4-methyl-6-tert-butylphenol do not have a significant effect on the synthesis of di(2-hydroxy-5-methyl-3-tert-butylphenyl) methane from 4-methyl-2-tert-butyl-phenol and dimethoxymethane.

Starikova, O.F.; Gurvich, Y.A.; Kumok, S.T.; Styskin, E.L.

1985-12-20

204

Identification and elimination of polysiloxane curing agent interference encountered in the quantification of low-picogram per milliliter methyl tert-butyl ether in blood by solid-phase microextraction headspace analysis.  

PubMed

Widespread use of the gasoline additive methyl tert-butyl ether (MTBE) and the subsequent human exposure that follows have led to the need to quantify MTBE in a variety of complex biological matrixes. In this work, we demonstrate our latest MTBE quantification assay for whole blood and uncover previously unidentified contamination sources that prevented routine quantification in the low picogram per milliliter (parts per trillion, ppt) range despite a sensitive and selective analytical approach. The most significant and unexpected sources of contamination were found in reagents and laboratory materials most relevant to sample preparation and quantification. In particular, significant levels of MTBE were identified in sample vial septa that use poly(dimethylsiloxane) (PDMS)-based polymers synthesized with peroxide curing agents having tert-butyl side groups. We propose that MTBE is one of the byproducts of these curing agents, which cross-link PDMS via the methyl side groups. Residual MTBE levels of approximately 20 microg/septa are seen in septa whose formulations use these curing agents. Fortunately, these levels can be significantly reduced (i.e., <0.2 ng/septa) by additional processing. Performance achieved with this sample preparation approach is demonstrated using a mass spectrometry-based method to quantify blood MTBE levels in the low-ppt range. PMID:15859611

Chambers, David M; McElprang, David O; Mauldin, Joshua P; Hughes, Timothy M; Blount, Benjamin C

2005-05-01

205

1,3-Alternate conformer 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra-kis-(4-methyl-sulfanylbenz-yloxy)-2,8,14,20-tetra-thia-calix[4]arene  

PubMed Central

The title thia­calix[4]arene derivative, C72H80O4S8, adopts a 1,3-alternate conformation, where the four 4-methyl­sul­fan­yl­benzyl groups are located alternately at the two sides of a virtual plane defined by the four bridging S atoms. In the crystal, there are no significant inter­molecular inter­actions present. Some of the peripheral tert-butyl and methyl­sulfanyl groups are disordered over two positions. A region of disordered electron density, occupying voids of ca 700?Å3 for an electron count of 124, was treated using the SQUEEZE routine in PLATON [Spek (2009 ?). Acta Cryst. D65, 148–155].

Gao, Qingsong; Xie, Dexun; An, Delie

2013-01-01

206

National survey of Methyl tert-Butyl Ether and other Volatile Organic Compounds in drinking-water sources: Results of the random source-water survey  

USGS Publications Warehouse

Methyl tert-butyl ether (MTBE) was detected in source water used by 8.7 percent of randomly selected community water systems (CWSs) in the United States at concentrations that ranged from 0.2 to 20 micrograms per liter (?g/L). The Random Survey conducted by the U.S. Geological Survey, in cooperation with the Metropolitan Water District of Southern California and the Oregon Health & Science University, was designed to provide an assessment of the frequency of detection, concentration, and distribution of MTBE, three other ether gasoline oxygenates, and 62 other volatile organic compounds (VOCs) in ground- and surface-water sources used for drinking-water supplies. The Random Survey was the first of two components of a national assessment of the quality of source water supplying CWSs sponsored by the American Water Works Association Research Foundation. A total of 954 CWSs were selected for VOC sampling from the population of nearly 47,000 active, self-supplied CWSs in all 50 States, Native American Lands, and Puerto Rico based on a statistical design that stratified on CWS size (population served), type of source water (ground and surface water), and geographic distribution (State).At a reporting level of 0.2 ?g/L, VOCs were detected in 27 percent of source-water samples collected from May 3, 1999 through October 23, 2000. Chloroform (in 13 percent of samples) was the most frequently detected of 42 VOCs present in the source-water samples, followed by MTBE. VOC concentrations were generally less than 10 ?g/L?95 percent of the 530 detections?and 63 percent were less than 1.0 ?g/L. Concentrations of 1,1-dichloroethene, tetrachloroethene, trichloroethene, vinyl chloride, and total trihalomethanes (TTHMs), however, exceeded drinking-water regulations in eight samples.Detections of most VOCs were more frequent in surface-water sources than in ground-water sources, with gasoline compounds collectively and MTBE individually detected significantly more often in surface water. Use of personal and commercial motorized watercraft on surface-water bodies that are drinking-water sources is probably the reason for the elevated detections of gasoline contaminants relative to ground water. MTBE detections demonstrated a seasonal pattern with more frequent detections in surface water in summer months, which is consistent with seasonal watercraft use.The detection frequency of most VOCs was significantly related to urban land use and population density. Detections of any VOC, non-trihalo-methane compounds, gasoline compounds collectively, the specific gasoline compounds benzene, toluene, ethylbenzene, and xylenes (BTEX), MTBE, solvents, and refrigerants were significantly greater in areas with more than 60 percent urban land use and (or) population density greater than 1,000 people per square mile than in source waters from less urbanized or lower population-density areas. MTBE detections were five times more frequent in source waters from areas with high MTBE use than in source waters from low or no MTBE use, but, unlike other gasoline compounds, MTBE detections were not significantly related to the density of gasoline storage tanks near drinking-water sources.

Grady, Stephen J.

2002-01-01

207

Bis(?-2-tert-butyl-phenyl-imido-1:2?N:N)chlorido-2?Cl-(diethyl ether-1?O)(2?-penta-methyl-cyclo-penta-dien-yl)lithiumtantalum(V).  

PubMed

In the title compound, [LiTa(C(10)H(15))(C(10)H(13)N)(2)Cl(C(4)H(10)O)], the Ta(V) atom is coordinated by a ?(5)-penta-methyl-cyclo-penta-dienyl (Cp*) ligand, a chloride ion and two N-bonded 2-tert-butyl-phenyl-imide dianions. With respect to the two N atoms, the chloride ion and the centroid of the Cp* ring, the tantalum coordination geometry is approximately tetra-hedral. The lithium cation is bonded to both the 2-tert-butyl-phenyl-imide dianions and also a diethyl ether mol-ecule, in an approximate trigonal planar arrangement. The Ta?Li separation is 2.681?(15)?Å. In the crystal, a weak C-H?Cl inter-action links the mol-ecules. When compared to the 2,6-diisopropyl-phenyl-imide analogue ('the Wigley derivative') of the title compound, the two structures are conformationally matched with an overall r.m.s. difference of 0.461Å. PMID:21754594

Cole, Jacqueline M; Chan, Michael C W; Gibson, Vernon C; Howard, Judith A K

2011-05-07

208

Characterization of tertButyl Alcohol Binding to alpha2u-Globulin in F-344 Rats  

Microsoft Academic Search

tert-Butyl alcohol (TBA) is widely used in the manufacturing of certain perfumes, cosmetics, drugs, paint removers, methyl tert- butyl ether (MTBE), and industrial solvents. In both rodents and humans, TBA is a major metabolite of MTBE, an oxygenated fuel additive. Chronic TBA exposure causes protein droplet nephrop- athy, a2u-globulin (a2u) accumulation, renal cell proliferation, and with chronic exposure, renal tumors

T. M. Williams; S. J. Borghoff

2001-01-01

209

A method to quantitatively compare in vivo the effects of gallstone solvents on intestinal mucosal function: a controlled study comparing mono-octanoin with methyl tert-butyl ether in the rat.  

PubMed

During contact dissolution of gallstones, solvents may escape from the gallbladder and damage the intestinal mucosa. In order to compare the extent of this potential injury, we developed a method to objectively quantify the effects of two commonly used cholesterol solvents, methyl tert-butyl ether and mono-octanoin, on mucosal transport function in the rat intestine. Two intestinal segments in each of 184 anesthetized rats were cannulated. Three milliliters of either solvent were instilled in one segment and left for varying periods of time, while saline was instilled in the other as control. The segments were then washed and perfused for 45 min with an isotonic solution containing [3H]polyethylene glycol 4000 (a nonabsorbable reference marker) and either [14C]alpha-aminoisobutyric acid (a marker for active absorption) or [14C]mannitol (a marker for passive permeability). Methyl tert-butyl ether caused more inhibition of alpha-aminoisobutyric acid absorption (64%) than mono-octanoin (48%) and a greater reduction of dry weight per centimeter of the perfused segment (22%) compared with mono-octanoin (10%). Such effects appeared after only 1 min of solvent exposure and did not appreciably increase with longer exposures. Permeation of mannitol increased by 26% after 1 min of exposure to mono-octanoin and by 54% after a similar period of exposure to methyl tert-butyl ether. Longer exposures to both solvents did not seem to cause progressive increases in mannitol permeation. The results indicate that brief exposure of the rat jejunum to either of the two solvents causes a reduction in active transport ([14C]alpha-aminoisobutyric acid absorption), an increase in passive permeability (mannitol permeation), and a loss of mucosal constituents. We conclude that the intestinal mucosa is susceptible to solvent damage and may be used as a selectively sensitive model that can characterize the biological injury of gallstone solvents. The study also suggests that escape of the currently available solvents into the small intestine in patients undergoing contact dissolution of gallbladder stones may cause injury to the small intestine. PMID:7770471

Zakko, S; Oberstein, R; Tomicic, T; Hajjar, J J

1995-06-01

210

1d-1-O-tert-Butyl-diphenyl-silyl-2,3,6-O-tris-(meth-oxy-methyl-ene)-myo-inositol 4,5-bis-(dibenzyl-phosphate)  

PubMed Central

The title compound [systematic name: tetra­benzyl (1R,2R,3S,4R,5R,6S)-4-(tert-butyl­diphenyl­sil­yloxy)-3,5,6-tris­(meth­oxy­meth­oxy)cyclo­hexane-1,2-diyl bis­phosphate], C56H68O15P2Si, was isolated as an inter­mediate in the preparation of a phosphatidylinositol phosphate for biological studies. In the crystal, the mol­ecules are connected via one methyl­ene C—H?? and two weak phen­yl–ether C—H?O inter­actions. One benz­yloxy group is disordered over two overlapping positions with an occupancy ratio of 0.649?(7):0.351?(7).

Anderson, Regan J.; Gainsford, Graeme J.

2012-01-01

211

1d-1-O-tert-Butyl-diphenyl-silyl-2,3,6-O-tris-(meth-oxy-methyl-ene)-myo-inositol 4,5-bis-(dibenzyl-phosphate).  

PubMed

THE TITLE COMPOUND [SYSTEMATIC NAME: tetra-benzyl (1R,2R,3S,4R,5R,6S)-4-(tert-butyl-diphenyl-sil-yloxy)-3,5,6-tris-(meth-oxy-meth-oxy)cyclo-hexane-1,2-diyl bis-phosphate], C(56)H(68)O(15)P(2)Si, was isolated as an inter-mediate in the preparation of a phosphatidylinositol phosphate for biological studies. In the crystal, the mol-ecules are connected via one methyl-ene C-H?? and two weak phen-yl-ether C-H?O inter-actions. One benz-yloxy group is disordered over two overlapping positions with an occupancy ratio of 0.649?(7):0.351?(7). PMID:22412748

Anderson, Regan J; Gainsford, Graeme J

2012-02-29

212

Homogeneous catalysis of ethyl tert-butyl ether formation from tert-butyl alcohol in hot, compressed liquid ethanol  

SciTech Connect

Ethyl tert-butyl ether (ETBE) and isobutene are the only significant products of the sulfuric acid ({le} 0.001 M) catalyzed reactions of tert-butyl alcohol in water/ethanol mixtures at 3 MPa and 170 C. Equilibrium is established after a few minutes or less. A 10 parameter kinetic model which embodies a first order elimination reaction and a first order nucleophilic substitution reaction adequately describes the influences of reactant (ethanol, water, and tert-butyl alcohol) concentrations, acid concentration, and residence time on product yields. The fit of the model to the data improves when the influence of water on the solvent`s dielectric constant is included by the addition of two more parameters. One finding of the simulation effort is that protonated isobutene (the key ingredient in ETBE formation) forms only from tert-butyl alcohol (not isobutene) under the conditions employed in this work. Thus tert-butyl alcohol should be preferred over isobutene as a reactant for ETBE synthesis at elevated pressures and temperatures.

Habenicht, C.; Kam, L.C.; Wilschut, M.J.; Antal, M.J. Jr. [Univ. of Hawaii, Honolulu, HI (United States)

1995-11-01

213

Structure and electronic properties of ( N, N?-bis(4-methyl-6-tert-butyl-2-methyl-phenolato)- N, N?-bismethyl-1,2-diaminoethane Fe III (DBSQ). Spectroelectrochemical study of the red-ox properties. Relevance to intradiol catechol dioxygenases  

Microsoft Academic Search

The species LFeIIICl (1) was synthesized where L2? is the dianion N,N?-bis(4-methyl-6-tert-butyl-2-methyl-phenolato)-N,N?-bismethyl1,2-diaminoethane. It crystallizes in the triclinic space group P-1 with a = 14.704(6), b = 17.421(7), c = 17.328(8) A?, ? = 89.45(8), ? = 129.76(9), ? = 102.71(9)°, V = 3277(2) A?3and Z = 2. The molecule has approximately a square pyramidal structure. In the presence of DBCH2

Pierre Mialane; Elodie Anxolabéhère-Mallart; Geneviève Blondin; Alexander Nivorojkine; Jean Guilhem; Lyuba Tchertanova; Michèle Cesario; Natarajan Ravi; Emile Bominaar; Jean-Jacques Girerd; Eckart Münck

1997-01-01

214

1-Bromo-2,7-di-tert-butyl-pyrene.  

PubMed

In the title mol-ecule, C(24)H(25)Br, one of two tert-butyl groups is rotationally disordered between two orientations in a 0.59?(3):0.41?(3) ratio. The crystal packing exhibits no ?-? inter-actions; however, relatively short inter-molecular Br?Br contacts of 3.654?(1)?Å are observed. PMID:21580100

Xia, Guang-Ming; Liu, Zhi-Qiang; Lu, Ping; Sun, Guo-Xin; Chen, Hong-Yu

2009-12-19

215

Study of fuel oxygenates solubility in aqueous media as a function of temperature and tert-butyl alcohol concentration.  

PubMed

Methyl tert-butyl ether (MTBE) is the most widely used oxygenate in gasoline blending and has become one of the world's most widespread groundwater and surface water pollutants. Alternative oxygenates to MTBE, namely ethyl tert-butyl ether (ETBE), tert-amyl ether (TAME) and diisopropyl ether (DIPE) have been hardly studied yet. The solubility of these chemicals is a key thermodynamic information for the assessment of the fate and transport of these pollutants. This work reports experimental data of water solubility at the range from 278.15 to 313.15K and atmospheric pressure of ethers used in fuels (MTBE, ETBE, TAME and DIPE) due to the strong influence of temperature on its trend. From the experimental data, temperature dependent polynomials were fitted, thermodynamic parameters were calculated and theoretical models were used for prediction. Finally, the tert-butyl alcohol (TBA) influence in the solubility of MTBE and ETBE in aqueous media was studied. PMID:18299142

Gonzalez-Olmos, R; Iglesias, M

2008-03-04

216

Effect of Parameters on Oxychlorination of Tert-Butyl Ethers.  

PubMed

The effect of concentration, molar ratios of reagents, pH, and temperature on formation of chloro-organic products in reaction of tert-butyl ethers with chloride ions and hydrogen peroxide has been determined. A significant effect of Cl(-) ions and H(2)O(2) molar ratios on the rate of chloro-organic product formation has been observed. Studies on oxychlorination of tert-butylethyl ether (ETBE) at pH 7, 3.5, and 2.5 have been carried out. It was found that introduction of hydronium ions into the reaction system considerably hastened the process of chloro-organic product formation. Hydronium ions contribute to the formation of the reactive tert-butyl carbocation, which undergoes secondary reactions in the presence of reactive forms of chlorine and oxygen. Moreover, the effect of temperature on ETBE (tert-butylethyl ether) and MTBE (tert-butylmethyl ether) conversions was verified. The reactions of MTBE and ETBE oxychlorination were carried out at temperatures of 5 degrees C, 20 degrees C, and 35 degrees C. PMID:19696944

Gaca, Jerzy; Gackowska, Alicja; Belt, Natalia

2008-06-23

217

Effect of Parameters on Oxychlorination of Tert-Butyl Ethers  

PubMed Central

The effect of concentration, molar ratios of reagents, pH, and temperature on formation of chloro-organic products in reaction of tert-butyl ethers with chloride ions and hydrogen peroxide has been determined. A significant effect of Cl? ions and H2O2 molar ratios on the rate of chloro-organic product formation has been observed. Studies on oxychlorination of tert-butylethyl ether (ETBE) at pH 7, 3.5, and 2.5 have been carried out. It was found that introduction of hydronium ions into the reaction system considerably hastened the process of chloro-organic product formation. Hydronium ions contribute to the formation of the reactive tert-butyl carbocation, which undergoes secondary reactions in the presence of reactive forms of chlorine and oxygen. Moreover, the effect of temperature on ETBE (tert-butylethyl ether) and MTBE (tert-butylmethyl ether) conversions was verified. The reactions of MTBE and ETBE oxychlorination were carried out at temperatures of 5°C, 20°C, and 35°C.

Gaca, Jerzy; Gackowska, Alicja; Belt, Natalia

2008-01-01

218

Biodegradation of tert-butyl alcohol and related xenobiotics by a methylotrophic bacterial isolate.  

PubMed

A new aerobic bacterial strain, CIP 1-2052, isolated from an activated sludge sample, was able to use tert-butyl alcohol (TBA), a product of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) degradation, as its sole carbon and energy source. Cobalt ions stimulated TBA mineralization. The maximum growth and TBA degradation rates were 0.032 +/- 0.004 h(-1) and 35.8 +/- 8.5 mg TBA x g(-1) (cell dry mass) per h, respectively. The growth yield on TBA was 0.54 +/- 0.02 g x g(-1). Strain CIP 1-2052 exhibited a particular substrate specificity towards alcohols. It degraded tertiary alcohols, TBA and tert-amyl alcohol (TAA), but neither their primary and secondary alcohol homologues, nor ethanol. However, one-carbon compounds, namely methanol and formate, were degraded by strain CIP 1-2052, showing the methylotrophic nature of this isolate. The properties of this new strain suggest that it could be used for bioremediation of contaminated aquifers. PMID:11341321

Piveteau, P; Fayolle, F; Vandecasteele, J P; Monot, F

2001-04-01

219

{gamma}-aminobutyric acid{sub A} (GABA{sub A}) receptor regulates ERK1/2 phosphorylation in rat hippocampus in high doses of Methyl Tert-Butyl Ether (MTBE)-induced impairment of spatial memory  

SciTech Connect

Experimental and occupational exposure to Methyl Tert-Butyl Ether (MTBE) has been reported to induce neurotoxicological and neurobehavioral effects, such as headache, nausea, dizziness, and disorientation, etc. However, the molecular mechanisms involved in MTBE-induced neurotoxicity are still not well understood. In the present study, we investigated the effects of MTBE on spatial memory and the expression and function of GABA{sub A} receptor in the hippocampus. Our results demonstrated that intraventricular injection of MTBE impaired the performance of the rats in a Morris water maze task, and significantly increased the expression of GABA{sub A} receptor {alpha}1 subunit in the hippocampus. The phosphorylation of ERK1/2 decreased after the MTBE injection. Furthermore, the decreased ability of learning and the reduction of phosphorylated ERK1/2 level of the MTBE-treated rats was partly reversed by bicuculline injected 30 min before the training. These results suggested that MTBE exposure could result in impaired spatial memory. GABA{sub A} receptor may play an important role in the MTBE-induced impairment of learning and memory by regulating the phosphorylation of ERK in the hippocampus.

Zheng Gang; Zhang Wenbin [Department of Occupational and Environmental Health, School of Public Health and Military Preventive Medicine, Fourth Military Medical University, Xi'an 710032 (China); Zhang Yun [465 Hospital, Jilin Medical College, Jilin 132001 (China); Chen Yaoming; Liu Mingchao; Yao Ting; Yang Yanxia; Zhao Fang [Department of Occupational and Environmental Health, School of Public Health and Military Preventive Medicine, Fourth Military Medical University, Xi'an 710032 (China); Li Jingxia; Huang Chuanshu [Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, New York 10987 (United States); Luo Wenjing [Department of Occupational and Environmental Health, School of Public Health and Military Preventive Medicine, Fourth Military Medical University, Xi'an 710032 (China)], E-mail: luowenj@fmmu.edu.cn; Chen Jingyuan [Department of Occupational and Environmental Health, School of Public Health and Military Preventive Medicine, Fourth Military Medical University, Xi'an 710032 (China)], E-mail: jy_chen@fmmu.edu.cn

2009-04-15

220

Octanorcucurbitane triterpenoids protect against tert-butyl hydroperoxide-induced hepatotoxicity from the stems of Momordica charantia.  

PubMed

Four novel octanorcucurbitane triterpenes, octanorcucurbitacins A-D (1-4), together with one known octanorcucurbitane triterpene, kuguacin M (5), were isolated from the methyl alcohol extract of the stems of Momordica charantia. Their structures were elucidated on the basis of extensive spectroscopic analyses. Compound 3 inhibited tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity against HepG2 cells. PMID:20118584

Chang, Chi-I; Chen, Chiy-Rong; Liao, Yun-Wen; Shih, Wen-Ling; Cheng, Hsueh-Ling; Tzeng, Chih-Ying; Li, Jia-Wei; Kung, Ming-Ting

2010-02-01

221

Isolation and characterization of two aerobic bacterial strains that completely degrade ethyl tert-butyl ether (ETBE).  

PubMed

Two bacterial strains, E1 and E2, isolated from gasoline-polluted soil completely degraded ethyl tert-butyl ether (ETBE), as the sole source of carbon and energy, at specific rates of about 80 mg g(-1) and 58 mg g(-1) of cell protein day(-1), respectively. On the basis of morphological and phenotypic characteristics, strain E1 was tentatively identified as Comamonas testosteroni and strain E2 as belonging to Centre for Disease Control group A-5. The inhibitory effect of metyrapone on the degradative ability of both strains was the first evidence indicating the involvement of a soluble cytochrome P-450 in the cleavage of the ETBE ether bond. This observation was confirmed by spectrophotometric analysis of reduced cell extracts that gave, in the presence of carbon monoxide, a major absorbance peak at about 450 nm. Both strains were also able to degrade, as the sole source of carbon and energy, ETBE's major metabolic intermediates (tert-butyl alcohol and tert-butyl formate) and other gasoline oxygenates (methyl tert-butyl ether and tert-amyl methyl ether). The degradation rates varied considerably, with both strains exhibiting a preferential activity for ETBE's metabolic intermediates. PMID:11341318

Kharoune, M; Kharoune, L; Lebeault, J M; Pauss, A

2001-04-01

222

Rotational features of carbon-nitrogen bonds in axially chiral o- tert-butyl anilides and related molecules. Potential substrates for the ‘prochiral auxiliary’ approach to asymmetric synthesis  

Microsoft Academic Search

A new strategy for asymmetric induction termed the ‘prochiral auxiliary’ approach is introduced. Reactions of acylating agents with prochiral N-methyl-o-tert-butyl aniline provide anilides that are axially chiral by virtue of restricted rotation about the N?Ar bond. Rotamer populations about the amide bond (E\\/Z) were studied by 1H NMR. Several pairs of enantiomeric o-tert-butyl anilides were separated by chiral chromatography and

Dennis P. Curran; Gregory R. Hale; Steven J. Geib; Aaron Balog; Quezia B. Cass; Ana Luiza G. Degani; Marcelo Z. Hernandes; Luiz Carlos G. Freitas

1997-01-01

223

Structure and properties of bis{[2-(4- tert -butyl)phen]ethyl}phosphine sulfide  

Microsoft Academic Search

Previously unknown bis[2-(4-tert-butyl)phen]ethylphosphine sulfide is obtained with a high yield from 4-tert-butyl styrene, red phosphorus, and elemental sulfur. Using single crystal XRD, multinuclear NMR, IR, and UV spectroscopy,\\u000a it is found that the phosphorus atom is four-coordinated in the bis[2-(4-tert-butyl)phen]ethylphosphine sulfide molecule (regardless of the phase state of the compound: crystal, solution). By the example\\u000a of phosphorylation of bis[2-(4-tert-butyl)phen]ethylphosphine sulfide

N. K. Gusarova; S. F. Malysheva; N. A. Belogorlova; O. N. Kazheva; A. N. Chekhlov; G. G. Aleksandrov; O. A. D’yachenko; L. M. Sinegovskaya; B. A. Trofimov

2010-01-01

224

Combined treatment of symptomatic gallbladder stones by extracorporeal shock-wave lithotripsy (ESWL) and instillation of methyl, Tert -butyl ether (MTBE)  

Microsoft Academic Search

Twenty-four patients with symptomatic gallbladder stones (12 radiolucent and 12 calcified) were treated by a combined approach of extracorporeal shock-wave lithotripsy (ESWL) and subsequent instillation of methyltert-butyl ether (MTBE). The patients received a mean of 1500±185 shock-wave discharges. The mean instillation time of MTBE was 13±4.2 hr. Treatment was tolerated without major adverse effects. Within a time period of three

Joseph Holl; Tilman Sauerbruch; Michael Sackmann; Jürgen Pauletzki; Gustav Paumgartner

1991-01-01

225

40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Butyl acrylate, polymer with substituted methyl styrene, methyl...Substances § 721.6920 Butyl acrylate, polymer with substituted methyl styrene, methyl...substance identified as butyl acrylate, polymer with substituted methyl styrene,...

2013-07-01

226

Differentiation and classification of user-specified bacterial groups by in situ thermal hydrolysis and methylation of whole bacterial cells with tert-butyl bromide chemical ionization ion trap mass spectrometry  

Microsoft Academic Search

Fatty acid methyl esters (FAMEs) from 20 bacterial samples, formed through in situ thermal hydrolysis and methylation (THM) of lipids from whole bacterial cells using tetramethylammonium hydroxide, have been investigated by t-butyl bromide chemical ionization (CI) ion trap mass spectrometry (MS). The mass spectra, in the early portion of the total ion profile, contained as major peaks the protonated saturated

Ming Xu; Franco Basile; Kent J Voorhees

2000-01-01

227

Linking Low-Level Stable Isotope Fractionation to Expression of the Cytochrome P450 Monooxygenase-Encoding ethB Gene for Elucidation of Methyl tert-Butyl Ether Biodegradation in Aerated Treatment Pond Systems? †  

PubMed Central

Multidimensional compound-specific stable isotope analysis (CSIA) was applied in combination with RNA-based molecular tools to characterize methyl tertiary (tert-) butyl ether (MTBE) degradation mechanisms occurring in biofilms in an aerated treatment pond used for remediation of MTBE-contaminated groundwater. The main pathway for MTBE oxidation was elucidated by linking the low-level stable isotope fractionation (mean carbon isotopic enrichment factor [?C] of ?0.37‰ ± 0.05‰ and no significant hydrogen isotopic enrichment factor [?H]) observed in microcosm experiments to expression of the ethB gene encoding a cytochrome P450 monooxygenase able to catalyze the oxidation of MTBE in biofilm samples both from the microcosms and directly from the ponds. 16S rRNA-specific primers revealed the presence of a sequence 100% identical to that of Methylibium petroleiphilum PM1, a well-characterized MTBE degrader. However, neither expression of the mdpA genes encoding the alkane hydroxylase-like enzyme responsible for MTBE oxidation in this strain nor the related MTBE isotope fractionation pattern produced by PM1 could be detected, suggesting that this enzyme was not active in this system. Additionally, observed low inverse fractionation of carbon (?C of +0.11‰ ± 0.03‰) and low fractionation of hydrogen (?H of ?5‰ ± 1‰) in laboratory experiments simulating MTBE stripping from an open surface water body suggest that the application of CSIA in field investigations to detect biodegradation may lead to false-negative results when volatilization effects coincide with the activity of low-fractionating enzymes. As shown in this study, complementary examination of expression of specific catabolic genes can be used as additional direct evidence for microbial degradation activity and may overcome this problem.

Jechalke, Sven; Rosell, Monica; Martinez-Lavanchy, Paula M.; Perez-Leiva, Paola; Rohwerder, Thore; Vogt, Carsten; Richnow, Hans H.

2011-01-01

228

Di-tert-butyl N-{[1-(pyridin-4-yl)-1H-1,2,3-triazol-4-yl]methyl}iminodiacetate  

PubMed Central

In the title compound, C20H29N5O4, the pyridine ring makes a dihedral angle of 10.41?(16)° with the triazole ring, which exhibits an azo-like character. In the crystal, mol­ecules are linked by C—H?O and C—H?N hydrogen bonds, and C—H?? inter­actions involving a methyl group and the pyridine ring of a neighbouring mol­ecule, leading to the formation of a three-dimensional network.

Francois, Alison; Marty, Louise; Picard, Claude; Mallet-Ladeira, Sonia; Benoist, Eric

2012-01-01

229

Transition metal ion initiated chain reactions between tert-butyl hydroperoxide and rhodium hydrides. Rapid hydrogen atom abstraction from rhodium hydrides by methyl radicals  

SciTech Connect

In the absence of catalysts, there is no reaction between t-BuOOH and macrocyclic rhodium hydrides LRhH{sup 2+} (L{sup 1} = [14]aneN{sub 4}, L{sup 2} = Me{sub 6}-[14]aneN{sub 4}). The addition of Fe{sub aq}{sup 2+} to such solutions results in rapid and catalytic oxidation of rhodium hydrides (LRhH{sup 2+} + (CH{sub 3}){sub 3}COOH + H{sup +} {yields} LRh{sup 3+} + CH{sub 4} + (CH{sub 3}){sub 2}CO). This reaction occurs by a chain mechanism featuring methyl radicals and LRh{sup 2+} as reactive intermediates. The rates are independent of the absolute concentrations of iron but vary with the ratio of the two oxidation states. The rate constants k{sub obs} are directly proportional to [H{sup +}]. In 0.10 M aqueous HClO{sub 4} at 25 C, the values are 80.8 M{sup {minus}1} s{sup {minus}1} (L{sup 1}RhH{sup 2+}) and 7.0 M{sup {minus}1} s{sup {minus}1} (L{sup 2}RhH{sup 2+}). A macrocyclic cobalt(II) complex, L{sup 2}Co{sup 2+}, is also an effective chain initiator. This reaction is not catalytic in L{sup 2}Co{sup 2+}, which is slowly consumed in the initiation and termination steps. Methyl radicals react rapidly with L{sup 1}RhH{sup 2+} (k = 1.0 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}), L{sup 2}RhH{sup 2+} (1.4 {times} 10{sup 8}), and L{sup 1}Rh{sup 2+} (8.6 {times} 10{sup 8}).

Bakac, A. [Ames Lab., IA (United States)

1998-07-13

230

Aerobic degradation of ethyl-tert-butyl ether by a microbial consortium: selection and evaluation of biodegradation ability.  

PubMed

A microbial consortium that degrades ethyl-tert-butyl ether (ETBE) as the sole source of carbon and energy under aerobic conditions was selected from a gasoline-polluted soil. This consortium consists of a variety of microorganisms with a predominance of filamentous morphology. Degradation of ETBE was found to be solely related to bacterial activity. After prolonged cultivation followed by successive transfers, the consortium's degradation ability was improved and reached a specific degradation rate of 95 mg/g(protein)/h (about 146 mg/g(dry wt)/h). This exceeds the previously reported rates in the literature for ETBE-degrading microorganisms as pure or mixed cultures. Furthermore, a stoichiometric balance of chemical oxygen demand (COD) removal and oxygen uptake with ETBE removal provides indirect evidence of complete degradation. The consortium's activity was not inhibited by high ETBE concentrations (< or = 1,600 mg/L), and large inoculum sizes (> or = 120 mg(protein)/L) were desirable for a faster and complete degradation of ETBE. The enriched consortium was also able to completely degrade methyl-tert-butyl ether (MTBE), tert-amyl methyl ether (TAME), and tert-butyl alcohol (TBA). both alone and in mixture with ETBE, without any measurable release of major degradation intermediates. In each case, MTBE and TAME exhibited the most significant resistance to degradation while TBA was rapidly degraded. PMID:12371480

Kharoune, Mourad; Kharoune, Lynda; Lebault, Jean-Michael; Pauss, André

2002-10-01

231

Hydrogen atom reactivity toward aqueous tert-butyl alcohol.  

PubMed

Through a combination of pulse radiolysis, purification, and analysis techniques, the rate constant for the H + (CH(3))(3)COH ? H(2) + (•)CH(2)C(CH(3))(2)OH reaction in aqueous solution is definitively determined to be (1.0 ± 0.15) × 10(5) M(-1) s(-1), which is about half of the tabulated number and 10 times lower than the more recently suggested revision. Our value fits on the Polanyi-type, rate-enthalpy linear correlation ln(k/n) = (0.80 ± 0.05)?H + (3.2 ± 0.8) that is found for the analogous reactions of other aqueous aliphatic alcohols with n equivalent abstractable H atoms. The existence of such a correlation and its large slope are interpreted as an indication of the mechanistic similarity of the H atom abstraction from ?- and ?-carbon atoms in alcohols occurring through the late, product-like transition state. tert-Butyl alcohol is commonly contaminated by much more reactive secondary and primary alcohols (2-propanol, 2-butanol, ethanol, and methanol), whose content can be sufficient for nearly quantitative scavenging of the H atoms, skewing the H atom reactivity pattern, and explaining the disparity of the literature data on the H + (CH(3))(3)COH rate constant. The ubiquitous use of tert-butyl alcohol in pulse radiolysis for investigating H atom reactivity and the results of this work suggest that many other previously reported rate constants for the H atom, particularly the smaller ones, may be in jeopardy. PMID:22229877

Lymar, Sergei V; Schwarz, Harold A

2012-01-25

232

1Isopropyl3-tert-butyl-1,2-diaza-1,3-butadiene in [4 + 2]-cycloaddition reactions  

Microsoft Academic Search

1-Isopropyl-3-tert-butyl-1,2-diaza-1,3-butadiene (I), which is formed as a result of the reaction of a-chloropinacoline with isopropyl hydrazine, exists in the form of a mixture of cisoid and transold conformations and is extremely active in the diene synthesis with maleic anhydride, maleimide, dimethyl fumarate, and methyl vinyl ketone. The conformations of the derivatives obtained, which contain a ?2-tetrahydropyridazine ring, were established on

K. N. Zelenin; V. A. Nikitin; N. M. Anodina

1973-01-01

233

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

PubMed

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

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

2007-03-09

234

Acid zeolites as catalysts in organic reactions. tert-Butylation of anthracene, naphthalene and thianthrene  

Microsoft Academic Search

Liquid phase tert-butylation of anthracene, naphthalene and thianthrene to afford 2-tert-butyl plus 2,6- and 2,7-di tert-butyl derivatives were carried out at atmospheric pressure and moderate temperatures (below 100°C) in the presence of a series of large pore zeolites and mesoporous aluminosilicates including HY-100 (Si\\/Al 2.6), HY-D1 (Si\\/Al 2.75), HY-D2 (Si\\/Al 15), H?, HMor and MCM-41. The activity increases from MCM-41

Elvira Armengol; Avelino Corma; Hermenegildo García; Jaime Primo

1997-01-01

235

Synthesis of carbon-11-, fluorine-18-, and iodine-125-labeled GABAA-gated chloride ion channel blockers: substituted 5-tert-butyl-2-phenyl-1,3-dithianes and -dithiane oxides.  

PubMed

A series of substituted 5-tert-butyl-2-phenyl-1,3-dithianes and 5-tert-butyl-2-phenyl-1,1,3,3-tetraoxo-1,3-dithianes was synthesized as ligands for the GABAA receptor complex-associated neuronal chloride ion channels. The in vitro binding affinities of these compounds for the GABA-gated chloride ion channel were determined by their ability to compete with [3H]TBOB for binding to rat brain slices. Of the eight compounds tested, trans-5-tert-butyl-2-(4-cyanophenyl)-2-methyl-1,1,3,3-tetraoxo+ ++-1,3-dithiane, 9b, trans-5-tert-butyl-2-(4-fluorophenyl)-1,1,3,3-tetraoxo-1,3-dithian e, 10, and trans-5-tert-butyl-2-(4-iodophenyl)-2-methyl-1,1,3,3-tetraoxo-1,3- dithiane, 11, showed moderately high binding affinities (Ki = 41, 180, and 105 nM, respectively). Four radioligand candidates from this series, 5-tert-butyl-2-(4-cyanophenyl)-2-[11C]methyl-1,3-dithiane, [11C]6, 5-tert-butyl-2-(4-[18F]fluorophenyl)-1,3-dithiane, [18F]7, 5-tert-butyl-2-(4-[18F]-fluorophenyl)-1,1,3,3-tetraoxo-1,3- dithiane, [18F]10, and 5-tert-butyl-2-(4-[125I]iodophenyl)-2-methyl-1,1,3,3- tetraoxo-1,3-dithiane, [125I]11, have been successfully prepared for evaluation as in vivo imaging agents useful for positron emission tomography and single photon emission computed tomography. Preliminary in vivo studies indicate significant uptake into mouse brain for [18F]7, [18F]10, and [125I]11. PMID:7629805

Snyder, S E; Kume, A; Jung, Y W; Connor, S E; Sherman, P S; Albin, R L; Wieland, D M; Kilbourn, M R

1995-07-01

236

Influence of Temperature on Thermodynamic Properties of Methyl t-Butyl Ether (MTBE) + Gasoline Additives  

NASA Astrophysics Data System (ADS)

The densities and sound speeds of binary mixtures of methyl tert-butyl ether (MTBE) + (benzene, toluene, ethylbenzene, isooctane, tert-butyl alcohol) have been measured at temperatures from 288.15 to 323.15 K and at atmospheric pressure over the complete concentration range. The experimental excess volumes and deviations of isentropic compressibility were calculated. The deviation of isentropic compressibility data have been analyzed in terms of different theoretical models; adequate agreement between the experimental and predicted values is obtained. The data from this study improve the data situation related to gasoline additives and help to understand the MTBE volumetric and acoustic behavior for various chemical systems.

Gonzalez-Olmos, R.; Iglesias, M.; Goenaga, J. M.; Resa, J. M.

2007-08-01

237

Water Quality and Occurrence of Methyl Tert-Butyl Ether (MTBE) and Other Fuel-Related Compounds in Lakes and Ground Water at Lakeside Communities in Sussex and Morris Counties, New Jersey, 1998-1999  

USGS Publications Warehouse

Densely populated communities surround many of the larger lakes in northwestern New Jersey. These communities derive most of their water supply from wells. The lakes can be navigated by gasoline-powered watercraft, can be in various stages of eutrophication, may contain pathogens associated with bathing and waterfowl, and are periodically subjected to chemical applications to control aquatic plant growth. Another feature that contributes to water-quality concerns in lakeside communities is the widespread use of septic tanks. Concentrations of methyl tert-butyl ether (MTBE), a gasoline oxygenate, in samples from Cranberry Lake and Lake Lackawanna ranged from 20 to 30 ug/L (micrograms per liter) and 5 to 14 ug/L during the summers of 1998 and 1999, respectively. These levels were persistent throughout the depth of the lakes when mixing conditions were present. MTBE concentrations in samples from the top 20 feet of Lake Hopatcong during summer 1999 were about 10 ug/L and about 2 to 3 ug/L in samples below 20 feet. The source of the MTBE in the lakes was determined to be gasoline-powered watercraft. Other constituents of gasoline--tertiary amyl methyl ether (TAME) and benzene, toluene, ethylbenzene, and xylenes (BTEX)--were detected in the lakes but at much lower concentrations than MTBE. Ambient ground-water quality at Cranberry Lake and Lake Lackawanna appears to be affected by the use of gasoline-powered watercraft. MTBE was detected in water samples from 13 of the 14 wells sampled at Cranberry Lake in fall 1998 and summer 1999. The wells were selected to monitor ambient ground-water quality and had no history of contamination. In ground-water samples collected during fall 1998, MTBE concentrations ranged from 0.12 to 19.8 ug/L, and the median concentration was 0.43 ug/L. In samples from summer 1999, MTBE concentrations ranged from 0.14 to 13.2 ug/L, and the median concentration was 0.38 ug/L. MTBE was detected in samples from four of the five wells at Lake Lackawanna in summer 1999;concentrations ranged from 0.05 to 0.19 ug/L. Lake/ground water interaction is a feasible explanation for the nearly ubiquitous presence of MTBE in ground water. The movement of water from lakes to wells is feasible because many static water levels and essentially all pumped water levels in the wells were below lake levels. Furthermore, diatom fragments were present in samples from the wells. Ambient ground water at Cranberry Lake also may be affected by septic-tank effluent, as indicated by the relation among concentrations of nitrate, boron, and chloroform. This result indicates potential vulnerability of the water supply to contamination by other chemicals and pathogens. Radon in ambient ground water is a concern throughout northern New Jersey. In particular, the median radon concentrations in ground-water samples collected from 14 wells at Cranberry Lake in 1998 and 1999 were 1,282 and 1,046 pCi/L, respectively. The median radon concentration in five ground-water samples collected at Lake Lackawanna in 1999 was 340 pCi/L. Although these values exceed regulatory levels, they are not high relative to radon concentrations measured in northwestern New Jersey. Eight wells in a neighborhood of Cranberry Lake with known MTBE contamination were sampled by the U.S. Geological Survey in summer 1998. MTBE was detected at concentrations greater than or equal to 40 ug/L in five of the wells. Concentrations of TAME, another gasoline oxygenate, were highly correlated with concentrations of MTBE; MTBE concentrations were about 10 times the TAME concentrations. In all samples, however, the concentrations of the BTEX compounds were less than 0.05 ug/L, and the sample from the most highly contaminated well, where the MTBE concentration was 900 ug/L, had no detectable BTEX.

Baehr, Arthur L.; Reilly, Timothy J.

2001-01-01

238

A cataluminescence gas sensor based on nanosized V2O5 for tert-butyl mercaptan.  

PubMed

This work proposed a gas sensor for the determination of tert-butyl mercaptan, one of the highly toxic volatile sulfur compounds, which was based on cataluminescence emission during its catalytic oxidation on the surface of nanosized V(2)O(5). The cataluminescence characteristics and the optimum conditions, including the morphology of sensing material, the wavelength of cataluminescence emission, the oxygen flow rate and working temperature were investigated in detail. Under the optimized conditions, the calibration curve of the relative cataluminescence intensity versus the concentration of tert-butyl mercaptan vapor was made, with the linear range of 5.6-196 microg mL(-1) and the detection limit of 0.5 microg mL(-1) (S/N=3). The relative standard deviation (R.S.D.) (n=5) of relative cataluminescence intensity for 84 microg mL(-1) tert-butyl mercaptan was 3.6%. There is no or weak response to some common substances, such as formic acid, alcohol (methanol, ethanol, propanol, isopropanol, n-butanol, isoamyl alcohol), o-dichlorobenzene, acetonitrile, ethyl acetate, aldehyde (formaldehyde, acetaldehyde and propanal), 1,2-dichloroethane and ammonia. Furthermore, the proposed sensor was successfully used for determining tert-butyl mercaptan in four artificial samples, with a good recovery. The results demonstrated that the proposed gas sensor had a promising capability for the tert-butyl mercaptan in routine monitoring. PMID:20602962

Zhang, Huili; Zhang, Lichun; Hu, Jing; Cai, Pingyang; Lv, Yi

2010-05-24

239

(2,4-Di-tert-butyl-6-{(E)-[(E)-2-(2-methoxy-benzyl-ideneamino)cyclo-hexyl]imino-meth-yl}phenolato)dimethyl-aluminum(III)  

PubMed Central

The title compound, [Al(CH3)2(C29H39N2O2)], exhibits disorder of one of the tert-butyl groups on the Schiff base ligand, where each methyl group is located over two sites, with occupancy factors of 0.57?(1) and 0.43?(1). The geometry around the AlIII atom is distorted tetra­hedral, defined by two methyl groups, one N and one O atom from the Schiff base ligand.

Wu, Jin-Cai

2009-01-01

240

TOXICITY OF METHYL-TERT BYTYL ETHER (MTBE) TO PLANTS (AVENA SATIVA, ZEA MAYS, TRITICUM AESTIVUM, AND LACTUCA SATIVA)  

EPA Science Inventory

Effects of Methyl tert-butyl ether (MTBE) on the germination of seeds and growth of the plant were studied in some laboratory experiments. Test plants were wild oat (Avena sative), sweet corn (Zea mays), wheat (Triticum aestivum), and lettuce (Lactuca sativa). Seed germination,...

241

Convulsant properties of L-glutamic acid di-tert butyl ester.  

PubMed

Glutamic acid di-tert butyl ester (GTBE) was found to have a pronounced convulsant effect in mice and rats, producing recurrent clonic convulsions combined with postural and respiratory disturbances in a dosage of 0.5 mmol/kg (148 mg/kg). Tert-butyl ester derivatives of aspartic acid and alanine, and glutamic acid gamma-benzyl ester did not produce seizures. Various other glutamate esters, such as glutamic acid diethyl ester and glutamic acid dimethyl ester, have previously been found to have anticonvulsant effects, and also do not induce seizures. It is suggested that glutamic acid di-tert butyl ester may have specific pharmacological properties which differ from those of other known convulsant drugs. PMID:2863766

Freed, W J; Ghoz, E H; Crump, S

242

Occurrence and distribution of methyl tert-butyl ether and other volatile organic compounds in drinking water in the Northeast and Mid-Atlantic regions of the United States, 1993-98  

USGS Publications Warehouse

Data on volatile organic compounds (VOCs) in drinking water supplied by 2,110 randomly selected community water systems (CWSs) in 12 Northeast and Mid-Atlantic States indicate 64 VOC analytes were detected at least once during 1993-98. Selection of the 2,110 CWSs inventoried for this study targeted 20 percent of the 10,479 active CWSs in the region and represented a random subset of the total distribution by State, source of water, and size of system. The data include 21,635 analyses of drinking water collected for compliance monitoring under the Safe Drinking Water Act; the data mostly represent finished drinking water collected at the pointof- entry to, or at more distal locations within, each CWS?s distribution system following any watertreatment processes. VOC detections were more common in drinking water supplied by large systems (serving more than 3,300 people) that tap surface-water sources or both surface- and groundwater sources than in small systems supplied exclusively by ground-water sources. Trihalomethane (THM) compounds, which are potentially formed during the process of disinfecting drinking water with chlorine, were detected in 45 percent of the randomly selected CWSs. Chloroform was the most frequently detected THM, reported in 39 percent of the CWSs. The gasoline additive methyl tert-butyl ether (MTBE) was the most frequently detected VOC in drinking water after the THMs. MTBE was detected in 8.9 percent of the 1,194 randomly selected CWSs that analyzed samples for MTBE at any reporting level, and it was detected in 7.8 percent of the 1,074 CWSs that provided MTBE data at the 1.0-?g/L (microgram per liter) reporting level. As with other VOCs reported in drinking water, most MTBE concentrations were less than 5.0 ?g/L, and less than 1 percent of CWSs reported MTBE concentrations at or above the 20.0-?g/L lower limit recommended by the U.S. Environmental Protection Agency?s Drinking-Water Advisory. The frequency of MTBE detections in drinking water is significantly related to high- MTBE-use patterns. Detections are five times more likely in areas where MTBE is or has been used in gasoline at greater than 5 percent by volume as part of the oxygenated or reformulated (OXY/RFG) fuels program. Detection frequencies of the individual gasoline compounds (benzene, toluene, ethylbenzene, and xylenes (BTEX)) were mostly less than 3 percent of the randomly selected CWSs, but collectively, BTEX compounds were detected in 8.4 percent of CWSs. BTEX concentrations also were low and just three drinkingwater samples contained BTEX at concentrations exceeding 20 ?g/L. Co-occurrence of MTBE and BTEX was rare, and only 0.8 percent of CWSs reported simultaneous detections of MTBE and BTEX compounds. Low concentrations and cooccurrence of MTBE and BTEX indicate most gasoline contaminants in drinking water probably represent nonpoint sources. Solvents were frequently detected in drinking water in the 12-State area. One or more of 27 individual solvent VOCs were detected at any reporting level in 3,080 drinking-water samples from 304 randomly selected CWSs (14 percent) and in 206 CWSs (9.8 percent) at concentrations at or above 1.0 ?g/L. High co-occurrence among solvents probably reflects common sources and the presence of transformation by-products. Other VOCs were relatively rarely detected in drinking water in the 12-State area. Six percent (127) of the 2,110 randomly selected CWSs reported concentrations of 16 VOCs at or above drinking-water criteria. The 127 CWSs collectively serve 2.6 million people. The occurrence of VOCs in drinking water was significantly associated (p<0.0001) with high population- density urban areas. New Jersey, Massachusetts, and Rhode Island, States with substantial urbanization and high population density, had the highest frequency of VOC detections among the 12 States. More than two-thirds of the randomly selected CWSs in New Jersey reported detecting VOC concentrations in drinking water at or above 1

Grady, S. J.; Casey, G. D.

2001-01-01

243

The oxidation of 2,6-di-tert-butyl-4-methylphenol  

USGS Publications Warehouse

The products formed in the oxidation of 2,6-di-tert-butyl-4-methylphenol with oxygen and sodium hydroxide at about 100?? are 3,5-di-tert-butyl-4-hydroxybenzaldehyde, trimethylacetic acid, an acidic compound C14H22O3, and probably 2,6-di-tert-butylbenzoquinone (which was actually isolated in the similar oxidation of the above-named benzaldehyde), in addition to compounds previously reported. Some of the properties of C14H22O3 are given, and the oxidation of it to 2,3-di-tert-butylsuccinic anhydride is described, but assignment of structure is reserved pending the completion of more experimental work.

Yohe, G. R.; Dunbar, J. E.; Pedrotti, R. L.; Scheidt, F. M.; Lee, F. G. H.; Smith, E. C.

1956-01-01

244

2,6-Di-tert-butyl-4-(3-chloro-2-hy-droxy-prop-yl)phenol  

PubMed Central

In the title 2-propanol derivative, C17H27ClO2, the two tert-butyl groups both have one methyl C atom lying in the plane of the aromatic ring. In the crystal, the phenol group forms a hydrogen bond to the hy­droxy O atom belonging to the alkyl substituent of an adjacent mol­ecule, forming a chain along the ac diagonal. The Cl atom is disordered over two positions in a 0.73?(4):0.27?(4) ratio.

Asgarova, Ayten R.; Maharramov, Abel M.; Khalilov, Ali N.; Gurbanov, Atash V.; Ng, Seik Weng

2011-01-01

245

2,6-Di-tert-butyl-4-(3-chloro-2-hy-droxy-prop-yl)phenol.  

PubMed

In the title 2-propanol derivative, C(17)H(27)ClO(2), the two tert-butyl groups both have one methyl C atom lying in the plane of the aromatic ring. In the crystal, the phenol group forms a hydrogen bond to the hy-droxy O atom belonging to the alkyl substituent of an adjacent mol-ecule, forming a chain along the ac diagonal. The Cl atom is disordered over two positions in a 0.73?(4):0.27?(4) ratio. PMID:21754133

Asgarova, Ayten R; Maharramov, Abel M; Khalilov, Ali N; Gurbanov, Atash V; Ng, Seik Weng

2011-03-12

246

5-tert-Butyl-2-[5-(5-tert-butyl-1,3-benzoxazol-2-yl)-2-thien-yl]-1,3-benzoxazole  

PubMed Central

The title compound, C26H26N2O2S, was prepared by the reaction of thio­phene-2,5-dicarboxylic acid and 2-amino-4-tert-butyl­phenol. One of the tert-butyl groups is disordered over two conformations, with occupancies of 0.539?(1) and 0.461?(2). The two 1,3-benzoxazole rings are almost planar, with dihedral angles of 0.83?(18) and 1.64?(17)° between the five- and six-membered rings. The thio­phene ring makes dihedral angles of 21.54?(19) and 4.49?(18)° with the planes of the five-membered oxazole rings. The crystal packing is controlled by ?–? stacking inter­actions involving the thio­phene and benzene rings, with a centroid–centroid distance of 3.748?(2)?Å.

Li, Yu-Feng; Wang, Lin-Tong; Jian, Fang-Fang

2008-01-01

247

6-{5-Amino-3-tert-butyl-4-[(E)-(3-methyl-1,2,4-thiadiazol-5-yl)diazen-yl]-1H-pyrazol-1-yl}-1,3,5-triazine-2,4(1H,3H)-dione-1-methyl-pyrrolidin-2-one-water (1/1/1)  

PubMed Central

In the title compound, C13H16N10O2S·C5H9NO·H2O, the entire 1-methylpyrrolidin-2-one (NMP) mol­ecule is disordered over two sites with occupancies of 0.488?(5) and 0.512?(5). The six-membered triazine ring and the two five-membered pyrazole and thiadia­zole rings, together with the diazene (–N=N–) linkage are almost coplanar (r.m.s. deviation for the non-H atoms = 0.0256?Å) with methyl groups from the tert-butyl substituent on the pyrazole ring located above and below the plane. Three intra­molecular N—H?N hydrogen bonds contribute to the planarity of the system. The O atom of the NMP mol­ecule is hydrogen bonded to an O—H group of water. In turn, the water mol­ecule is hydrogen bonded to the mono-azo skeleton through inter­molecular N—H?O and O—H?N hydrogen bonds. At both ends of the long mol­ecular axis of the main mol­ecule there are inter­molecular N—H?N hydrogen bonds, arranged in a head-to-tail fashion, between the N—H group of the triazine ring of one mol­ecule and the N atom of the thia­diazole ring of a neighboring mol­ecule. These form a polymeric chain along [110] or [10]. The main mol­ecules are stacked alternately along the b axis, which effectively cancels their dipole moments. In addition, pairs of alternate molecules are dimerized via inter­molecular hydrogen bonds involving the solvent mol­ecules.

Shibata, Hiroki; Mizuguchi, Jin

2010-01-01

248

Biotransformation and Kinetics of Excretion of Ethyl tertButyl Ether in Rats and Humans  

Microsoft Academic Search

Ethyl tert-butyl ether (ETBE) may be used in the future as an additive to gasoline to increase oxygen content and reduce tailpipe emissions of pollutants. Therefore, widespread human exposure may occur. To contribute to the characterization of potential adverse effects of ETBE, its biotransformation was compared in humans and rats after inhalation exposure. Human volunteers (3 males and 3 females)

Alexander Amberg; Elisabeth Rosner; Wolfgang Dekant

2000-01-01

249

IRIS Toxicological Review and Summary Document for Tert-Butyl Alcohol (TBA) (External Peer Review Draft)  

EPA Science Inventory

Tert-butyl alcohol (TBA) is used as a solvent; as a denaturant for ethanol and several other alcohols; in the manufacture of flotation agents, fruit essences, and perfumes; as an octane booster in gasoline; as a dehydrating agent; and as a chemical intermediate in the manufacture...

250

The Alkyl tert-Butyl Ether Intermediate 2-Hydroxyisobutyrate Is Degraded via a Novel Cobalamin-Dependent Mutase Pathway†  

PubMed Central

Fuel oxygenates such as methyl and ethyl tert-butyl ether (MTBE and ETBE, respectively) are degraded only by a limited number of bacterial strains. The aerobic pathway is generally thought to run via tert-butyl alcohol (TBA) and 2-hydroxyisobutyrate (2-HIBA), whereas further steps are unclear. We have now demonstrated for the newly isolated ?-proteobacterial strains L108 and L10, as well as for the closely related strain CIP I-2052, that 2-HIBA was degraded by a cobalamin-dependent enzymatic step. In these strains, growth on substrates containing the tert-butyl moiety, such as MTBE, TBA, and 2-HIBA, was strictly dependent on cobalt, which could be replaced by cobalamin. Tandem mass spectrometry identified a 2-HIBA-induced protein with high similarity to a peptide whose gene sequence was found in the finished genome of the MTBE-degrading strain Methylibium petroleiphilum PM1. Alignment analysis identified it as the small subunit of isobutyryl-coenzyme A (CoA) mutase (ICM; EC 5.4.99.13), which is a cobalamin-containing carbon skeleton-rearranging enzyme, originally described only in Streptomyces spp. Sequencing of the genes of both ICM subunits from strain L108 revealed nearly 100% identity with the corresponding peptide sequences from M. petroleiphilum PM1, suggesting a horizontal gene transfer event to have occurred between these strains. Enzyme activity was demonstrated in crude extracts of induced cells of strains L108 and L10, transforming 2-HIBA into 3-hydroxybutyrate in the presence of CoA and ATP. The physiological and evolutionary aspects of this novel pathway involved in MTBE and ETBE metabolism are discussed.

Rohwerder, Thore; Breuer, Uta; Benndorf, Dirk; Lechner, Ute; Muller, Roland H.

2006-01-01

251

The alkyl tert-butyl ether intermediate 2-hydroxyisobutyrate is degraded via a novel cobalamin-dependent mutase pathway.  

PubMed

Fuel oxygenates such as methyl and ethyl tert-butyl ether (MTBE and ETBE, respectively) are degraded only by a limited number of bacterial strains. The aerobic pathway is generally thought to run via tert-butyl alcohol (TBA) and 2-hydroxyisobutyrate (2-HIBA), whereas further steps are unclear. We have now demonstrated for the newly isolated beta-proteobacterial strains L108 and L10, as well as for the closely related strain CIP I-2052, that 2-HIBA was degraded by a cobalamin-dependent enzymatic step. In these strains, growth on substrates containing the tert-butyl moiety, such as MTBE, TBA, and 2-HIBA, was strictly dependent on cobalt, which could be replaced by cobalamin. Tandem mass spectrometry identified a 2-HIBA-induced protein with high similarity to a peptide whose gene sequence was found in the finished genome of the MTBE-degrading strain Methylibium petroleiphilum PM1. Alignment analysis identified it as the small subunit of isobutyryl-coenzyme A (CoA) mutase (ICM; EC 5.4.99.13), which is a cobalamin-containing carbon skeleton-rearranging enzyme, originally described only in Streptomyces spp. Sequencing of the genes of both ICM subunits from strain L108 revealed nearly 100% identity with the corresponding peptide sequences from M. petroleiphilum PM1, suggesting a horizontal gene transfer event to have occurred between these strains. Enzyme activity was demonstrated in crude extracts of induced cells of strains L108 and L10, transforming 2-HIBA into 3-hydroxybutyrate in the presence of CoA and ATP. The physiological and evolutionary aspects of this novel pathway involved in MTBE and ETBE metabolism are discussed. PMID:16751524

Rohwerder, Thore; Breuer, Uta; Benndorf, Dirk; Lechner, Ute; Müller, Roland H

2006-06-01

252

Methyl Tertiary Butyl Ether (MTBE) Groundwater Contamination  

NSDL National Science Digital Library

Methyl tertiary-butyl ether (MTBE), a fuel additive, is highly mobile in groundwater, dissolving and traveling faster than the other petroleum constituents which tend to biodegrade and adsorb to soil particles. This unit will introduce the problem of pollutants as they move through the various soil layers and contaminate the groundwater and challenge the students to investigate the effects of MTBE spills in the environment by researching the available literature on fuel oxygenates and learning their mode of transport through the soil. Experimentally determined data, obtained in lab activities, will facilitate building models of the contamination process of the groundwater. Mathematics modeling will involve the use of spreadsheet analysis of real-world-data obtained online.

253

Neuroprotection by 2-h Postischemia Administration of Two Free Radical Scavengers, ?-phenyl- n-tert-butyl-nitrone (PBN) and N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN), in Rats Subjected to Focal Embolic Cerebral Ischemia  

Microsoft Academic Search

Oxygen free radical generation may have important secondary damaging effects after the onset of cerebral ischemia. Free radical scavengers have been used successfully in attenuating neuronal damage in the reperfusion period in transient forebrain ischemia. There are limited data on effectiveness in models of focal ischemia. Two free radical scavengers, ?-phenyl-n-tert-butyl-nitrone (PBN) and N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN), have been shown to reduce

Yi Yang; Qiu Li; Ashfaq Shuaib

2000-01-01

254

Intramolecular interactions of N-(3,5-di- tert-butyl-2-hydroxyphenyl)acetamide derivatives  

NASA Astrophysics Data System (ADS)

IR-Fourier spectroscopy methods are adopted to the study of intramolecular interactions occurring in CCl4 solutions of antivirally active derivatives of N-(3,5-di- tert-butyl-2-hydroxyphenyl)acetamide. Analysis of IR spectra has shown that intramolecular H-bonds O-H···O=C and N-H···O=C are formed in solutions of these compounds. The O-H···O=C and N-H···O=C bond strengths and the direction of the equilibrium shift between the two types of conformers depend on the type of carbonyl group substituent. An intramolecular O-H···O=C H-bond is characteristic of highly active derivatives of N-(3,5-di- tert-butyl-2-hydroxyphenyl)acetamide.

Belkov, M. V.; Harbachova, A. N.; Ksendzova, G. A.; Polozov, G. I.; Skornyakov, I. V.; Sorokin, V. L.; Tolstorozhev, G. B.; Shadyro, O. I.

2010-03-01

255

(tert-Butyl-imido)bis-(?5-cyclo-penta-dien-yl)pyridine-zirconium(IV)  

PubMed Central

The title compound, [Zr(C5H5)2(C4H9N)(C5H5N)], was obtained from the reaction of (C5H5)2Zr(py)(?2-Me3SiC2SiMe3) (py is pyridine) and tBuN=C=NtBu alongside the formation of (C5H5)2Zr(CNtBu)(?2-Me3SiC2SiMe3). The zirconium atom is coordinated in a distorted tetra­hedral geometry by two cyclo­penta­dienyl ligands, a pyridine ligand, and a tert-butyl­imido ligand via a Zr=N double bond. The tert-butyl group is disordered over two positions in a 0.634?(5):0.366?(5) ratio.

Kaleta, Katharina; Arndt, Perdita; Spannenberg, Anke; Rosenthal, Uwe

2010-01-01

256

(tert-Butyl-imido)bis-(?-cyclo-penta-dien-yl)pyridine-zirconium(IV).  

PubMed

The title compound, [Zr(C(5)H(5))(2)(C(4)H(9)N)(C(5)H(5)N)], was obtained from the reaction of (C(5)H(5))(2)Zr(py)(?(2)-Me(3)SiC(2)SiMe(3)) (py is pyridine) and (t)BuN=C=N(t)Bu alongside the formation of (C(5)H(5))(2)Zr(CN(t)Bu)(?(2)-Me(3)SiC(2)SiMe(3)). The zirconium atom is coordinated in a distorted tetra-hedral geometry by two cyclo-penta-dienyl ligands, a pyridine ligand, and a tert-butyl-imido ligand via a Zr=N double bond. The tert-butyl group is disordered over two positions in a 0.634?(5):0.366?(5) ratio. PMID:21588566

Kaleta, Katharina; Arndt, Perdita; Spannenberg, Anke; Rosenthal, Uwe

2010-08-28

257

The free radical chemistry of tert-butyl formate: rate constants for hydroxyl radical, hydrated electron and hydrogen atom reaction in aqueous solution  

NASA Astrophysics Data System (ADS)

Transients generated in situ by advanced oxidation technologies (AOTs) to destroy organic contaminants in ground and drinking water often give large concentrations of chemical by-products. These by-products may have adverse health effects, and can also interfere with the desired chemical removal by competing for the generated transients, thus lowering the overall efficiency of the remediation process. To allow for a quantitative evaluation of the influence of tert-butyl formate (TBF), a major by-product formed in the AOT destruction of methyl tert-butyl ether, rate constants for TBF reaction with the hydroxyl radical, the hydrated electron and the hydrogen atom in aqueous solution were measured in this study. Absolute values of (5.23+/-0.07)×108, (5.48+/-0.09)×108 and (3.58+/-0.07)×106M-1s-1, were determined at 22°C, respectively.

Hardison, D. Ransom; Cooper, William J.; Mezyk, Stephen P.; Bartels, David M.

2002-11-01

258

40 CFR 721.10326 - 2-Propenoic acid, 2-methyl-, methyl ester, polymer with butyl 2-propenoate, ethyl 2-propenoate...  

Code of Federal Regulations, 2013 CFR

...2-Propenoic acid, 2-methyl-, methyl ester, polymer with butyl 2-propenoate, ethyl 2-propenoate...2-Propenoic acid, 2-methyl-, methyl ester, polymer with butyl 2-propenoate, ethyl 2-propenoate...2-propenoic acid, 2-methyl-, methyl ester, polymer with butyl 2-propenoate, ethyl...

2013-07-01

259

Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water  

PubMed Central

Summary Water induces a change in the product of radical multifunctionalization reactions of aliphatic alkenes involving an sp3 C–H functionalization by an 1,5-hydrogen shift using tert-butyl nitrite and molecular oxygen. The reaction without water, reported previously, gives nitrated ?-lactols, whereas the reaction in the presence of water produces 4-hydroxy-5-nitropentyl nitrate or 4-hydroxy-3-nitropentyl nitrate derivatives.

Hirose, Daisuke

2013-01-01

260

Protective effect of Hibiscus anthocyanins against tert-butyl hydroperoxide-induced hepatic toxicity in rats  

Microsoft Academic Search

Hibiscus anthocyanins (HAs), a group of natural pigments occurring in the dried flowers of Hibiscus sabdariffa L., which is a local soft drink material and medical herb, were studied for antioxidant bioactivity. The preliminary study showed that HAs were able to quench the free radicals of 1,1-diphenyl-2-picrylhydrazyl. This antioxidant bioactivitiy was further evaluated using the model of tert-butyl hydroperoxide (t-BHP)-induced

Chau-Jong Wang; Jin-Ming Wang; Wea-Lung Lin; Chia-Yih Chu; Fen-Pi Chou; Tsui-Hwa Tseng

2000-01-01

261

Tris(2,4-di-tert-butyl-phen-yl) phosphate  

PubMed Central

The title compound, C42H63O4P, was isolated from the leaves of Vitex negundo. Two of the tert-butyl groups are disordered over two orientations with occupancy ratios of 0.57?(1):0.43?(1) and 0.67?(1):0.33?(1). Several intra­molecular C—H?O inter­actions are observed in the mol­ecular structure.

Vinuchakkaravarthy, T.; Sangeetha, C. K.; Velmurugan, D.

2010-01-01

262

Kinetics of the liquid-phase synthesis of ethyl tert-butyl ether (ETBE)  

Microsoft Academic Search

The liquid-phase addition of ethanol to isobutene to give ethyl tert-butyl ether (ETBE) on the ion exchange resin Lewatit K2631 has been studied. Rate data were obtained free of mass transfer influence in a continuous differential reactor operated at 1.6 MPa and 40--90 C, measuring steady-state conversions <10% for ethanol-isobutene and ethanol-isobutene-ETBE feeds. The reaction is highly temperature-sensitive. Isobutene has

Carles Fite; Montserrat Iborra; Javier Tejero; Jose F. Izquierdo; Fidel Cunill

1994-01-01

263

A mechanistic investigation of di- tert-butyl nitroxide using scanning electrochemical microscopy (SECM)  

Microsoft Academic Search

Cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM) have been used to evaluate the electron-transfer mechanism of di-tert-butyl nitroxide (DTBN) in acetonitrile. The oxidation of DTBN is coupled to a rapid, irreversible chemical follow-up step that is difficult to characterize quantitatively with CV due to distortion of the voltammograms by solution resistance and mixed radial–linear diffusion within the scan rate

Lila McKay; Robert J. LeSuer

2008-01-01

264

A new amphiphilic derivative, N-{[4-(lactobionamido)methyl]benzylidene}-1,1-dimethyl-2-(octylsulfanyl)ethylamine N-oxide, has a protective effect against copper-induced fulminant hepatitis in Long-Evans Cinnamon rats at an extremely low concentration compared with its original form alpha-phenyl-N-(tert-butyl) nitrone.  

PubMed

An amphiphilic alpha-phenyl-N-(tert-butyl) nitrone (PBN) derivative, N-{[4-(lactobionamido)methyl]benzylidene}-1,1-dimethyl-2-(octylsulfanyl)ethylamine N-oxide (LPBNSH), newly synthesized from its original form PBN in hopes of clinical use, was intraperitoneally administered to Long-Evans Cinnamon (LEC) rats every 2 days at the concentrations of 0.1, 0.5, 1.0, and 2.0 mg/kg. We found that LPBNSH protected against copper-induced hepatitis with jaundice in LEC rats at concentrations of 0.1 and 0.5 mg/kg, which were extremely low compared with that of PBN. It also effectively prevented the loss of body weight, reduced the death rate, and suppressed the increase in serum aspartate aminotransferase and alanine aminotransferase values arising from fulminant hepatitis with jaundice at the same concentrations. Similar results were observed when PBN was administered at the concentration of 150 mg/kg. Immunohistochemical analysis of 8-hydroxy-2'-deoxyguanosine and measurement of thiobarbituric acid-reactive substances in the liver showed that LPBNSH largely suppressed the formation of these oxidative products at same concentrations. No difference in the abnormal accumulation of copper in the liver between the LPBNSH administered and control groups was observed. From these results, it was concluded that LPBNSH exhibited liver-protective effects against fulminant hepatitis with jaundice at ca. 1/1000, 500 the molar concentration of PBN and, therefore, was clinically promising. PMID:17886845

Asanuma, Taketoshi; Yasui, Hironobu; Inanami, Osamu; Waki, Kenji; Takahashi, Momoko; Iizuka, Daisuke; Uemura, Taketo; Durand, Grégory; Polidori, Ange; Kon, Yasuhiro; Pucci, Bernard; Kuwabara, Mikinori

2007-09-01

265

Discovery and application of new bacterial strains for asymmetric synthesis of L-tert-butyl leucine in high enantioselectivity.  

PubMed

Discovery of new bacterial strains with fast identification in a miniaturized system was performed for the synthesis of optically active L-tert-butyl leucine. With tert-butyl leucine amide as nitrogen source, one bacterial strain with high conversion and high enantioselectivity was discovered among 120 isolated microorganisms from local soils and identified as Mycobacterium sp. JX009. Glucose and ammonium chloride were examined as the good carbon source and nitrogen source for the cells' growth separately. The cells grew better at 30 °C and at pH 7.5 with higher activity of 2,650 U/l in comparison with other conditions. Cells' stability was improved by immobilization on synthetic resin 0730 without pretreatment. Tert-butyl leucine amide (30 mM) was successfully hydrolyzed by immobilized cells and examined as the highest chemical concentration that cells could endure. After six reaction cycles, the immobilized cells retained 90% activity with production of L-tert-butyl leucine in 98% ee. The results firstly reported the application of new bacterial strain in the hydrolysis of tert-butyl leucine amide to produce optically active L-tert-butyl leucine in an efficient way with investigation in detail. PMID:21153891

Jin, Jian-Zhong; Chang, Dong-Liang; Zhang, Jie

2010-12-14

266

(2,4-Di-tert-butyl-6-{(E)-[(E)-2-(2-methoxy-benzyl-ideneamino)cyclo-hexyl]imino-meth-yl}phenolato)dimethyl-aluminum(III).  

PubMed

The title compound, [Al(CH(3))(2)(C(29)H(39)N(2)O(2))], exhibits disorder of one of the tert-butyl groups on the Schiff base ligand, where each methyl group is located over two sites, with occupancy factors of 0.57?(1) and 0.43?(1). The geometry around the Al(III) atom is distorted tetra-hedral, defined by two methyl groups, one N and one O atom from the Schiff base ligand. PMID:21581558

Wu, Jin-Cai

2008-12-17

267

27 CFR 21.118 - Methyl n-butyl ketone.  

Code of Federal Regulations, 2013 CFR

... FORMULAS FOR DENATURED ALCOHOL AND RUM Specifications for Denaturants § 21.118 Methyl n -butyl ketone. (a) Acidity (as acetic acid). 0.02 percent by weight, maximum. (b) Color. Colorless. (c) Odor. Characteristic...

2013-04-01

268

Cytoprotective and antioxidant activity of seabuckthorn (Hippophae rhamnoides L.) flavones against tert-butyl hydroperoxide-induced cytotoxicity in lymphocytes.  

PubMed

This study was designed to determine the cytoprotective activity of flavones of seabuckthorn (Hippophae rhamnoides L.) against tert-butyl hydroperoxide (tert-BOOH), used as an oxidant to induce oxidative damage, with lymphocytes as the model system. Addition of tert-BOOH (250 microM) to the cells resulted in enhanced cytotoxicity and free radical production. The intracellular calcium levels, caspase activity, and apoptosis were significantly increased following tert-BOOH treatment. Seabuckthorn flavones at the concentration of 100 microg/mL significantly inhibited tert-BOOH-induced cytotoxicity and free radical production and also restored the antioxidant status to that of control cells. Seabuckthorn flavones also significantly restricted tert-BOOH-induced apoptosis by decreasing intracellular calcium levels and caspase activity. The extract also decreased tert-BOOH-induced formation of DNA breaks by 30%. These observations suggest that the flavones of seabuckthorn have marked cytoprotective properties, which could be attributed to the antioxidant activity. PMID:19298209

Geetha, S; Ram, M Sai; Sharma, S K; Ilavazhagan, G; Banerjee, P K; Sawhney, R C

2009-02-01

269

1,1?-Bis[bis-(4-tert-butyl-phen-yl)meth-yl]ferrocene  

PubMed Central

The molecule of the title compound, [Fe(C26H31)2], is located on an inversion center. The two cyclopentadienyl rings exhibit a staggered conformation, which results from the bulky bis(4-tert-butylphenyl)methyl substituents situated on opposite sides of the molecule.

Bauer, Heiko; Sun, Yu; Sitzmann, Helmut

2012-01-01

270

Biotransformation and kinetics of excretion of ethyl tert-butyl ether in rats and humans.  

PubMed

Ethyl tert-butyl ether (ETBE) may be used in the future as an additive to gasoline to increase oxygen content and reduce tailpipe emissions of pollutants. Therefore, widespread human exposure may occur. To contribute to the characterization of potential adverse effects of ETBE, its biotransformation was compared in humans and rats after inhalation exposure. Human volunteers (3 males and 3 females) and rats (5 males and 5 females) were exposed to 4 (4.5+/-0.6) and 40 (40.6+/-3.0) ppm ETBE for 4 h in a dynamic exposure system. Urine samples from rats and humans were collected for 72 h at 6-h intervals, and blood samples were taken in regular intervals for 48 h. In urine, ETBE and the ETBE-metabolites tert-butanol (t-butanol), 2-methyl-1,2-propane diol, and 2-hydroxyisobutyrate were quantified; ETBE and t-butanol were determined in blood samples. After the end of the exposure period to inhalation of 40-ppm ETBE, blood concentrations of ETBE were found at 5.3+/-1.2 microM in rats and 12.1+/-4.0 microM in humans. The ETBE blood concentrations, after inhalation of 4-ppm ETBE, were 1.0+/-0.7 microM in rats and 1.3+/-0.7 microM in humans. ETBE was rapidly cleared from blood. After the end of the 40-ppm ETBE exposure period, the blood concentrations of t-butanol were 13.9+/-2.2 microM in humans and 21.7+/-4.9 microM in rats. After 4-ppm ETBE exposure, blood concentrations of t-butanol were 1.8+/-0.2 microM in humans and 5.7+/-0.8 microM in rats. t-Butanol was cleared from human blood with a half-life of 9.8+/-1.4 h in humans after 40-ppm ETBE exposure. In urine samples from controls and in samples collected from the volunteers and rats before the exposure, low concentrations of t-butanol, 2-methyl-1,2-propane diol, and 2-hydroxyisobutyrate were present. In the urine of both humans and rats exposed to ETBE, the concentrations of these compounds were significantly increased. 2-Hydroxy-isobutyrate was recovered in urine as the major excretory product formed from ETBE; t-butanol and 2-methyl-1,2-propane diol were minor metabolites. All metabolites of ETBE excreted with urine were rapidly eliminated in both species after the end of the ETBE exposure. Excretion half-lives for the different urinary metabolites of ETBE were between 10.2 and 28.3 h in humans and 2.6 and 4.7 h in rats. The obtained data indicate that ETBE biotransformation and excretion are similar for rats and humans, and that ETBE and its metabolites are rapidly excreted by both species. Between 41 and 53% of the ETBE retained after the end of the exposure was recovered as metabolites in the urine of both humans and rats. PMID:10696767

Amberg, A; Rosner, E; Dekant, W

2000-02-01

271

Mechanism and temperature-dependent kinetics of the dehydration of tert-butyl alcohol in hot compressed liquid water  

SciTech Connect

In the presence of acid or base, or under neutral conditions, isobutylene is the only observed product of the reactions of tert-butyl alcohol in compressed liquid water at 225, 250, and 320 C. On the basis of a kinetic analysis of limited results at 250 C, an earlier paper concluded that tert-butyl alcohol dissociates as an Arrhenius acid at 250 C and thereby catalyzes its own dehydration to isobutylene. Kinetic analyses of the data sets contained in this paper do not corroborate the alleged ability of tert-butyl alcohol to protonate water. Instead, the authors find that hydronium ions formed by the ordinary dissociation of water are the primary catalytic agents for the dehydration reaction. In agreement with the earlier work, all three data sets are consistent with a heterolytic reaction mechanism involving protonated alcohol, carbocation, di-tert-butyl ether, and protonated ether as intermediates. The kinetics still suggest that tert-butyl alcohol weakly dissociated as a Bronsted acid at these conditions. Values of K{sub w} determined by the kinetic model enjoy good agreement with electrochemical values available in the literature. Values of the other parameters (rate constants) which compose the kinetic model are evaluated with less precision, and a novel method is proposed to estimate the uncertainty associated with each parameter.

Xu, X.; Antal, M.J. Jr. [Univ. of Hawaii, Honolulu, HI (United States); Anderson, D.G.M. [Harvard Univ., Cambridge, MA (United States). Aiken Computation Lab.

1997-01-01

272

4-tert-Butyl-3?,4?-bis-(4-methyl-phen-yl)-3,4-dihydro-1H,4?H-spiro-[naphthalene-2,5?-[1,2]oxazol]-1-one  

PubMed Central

In the title compound, C30H31NO2, the cyclo­hexa­none ring in the naphthalene fused-ring system adopts a half-chair conformation, presumably due to conjugation of the benzene ring. The naphthalene ring system makes dihedral angles of 86.63?(7), 65.15?(8) and 63.18?(8)° with respect to the two methyl­benzene planes and the 1,2-oxazole ring system. Inter­molecular C—H?O and C—H?N hydrogen bonding and C—H?? inter­actions stabilize the crystal structure. The H atoms of the two methyl groups of the methyl­phenyl groups are disordered over two positions with equal occupancies.

Akhazzane, Mohamed; Zouihri, Hafid; Bennani, A.Kella; Kerbal, Abdelali; Al Houari, Ghali

2011-01-01

273

Phosphoamide – modified p- tert-butyl calix[4]arene and its sodium complexes  

Microsoft Academic Search

A new modified calix[4]arene, namely 5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26,28-bis[(tetramethyldiamidophosphinyl)oxy]calix[4]arene (L) has been prepared by reacting the parent calixarene with tetramethyldiamidophosphoric acid chloride, and its structure was solved by the X-ray diffraction method in the solid state and characterized in solution using 1H, 13C, 31P NMR and mass spectral (ES-MS and FAB-MS) data. The coordination ability of L towards Na+ showed the formation of

Vladimira Videva; Tania Tosheva; Anne-Sophie Chauvin; Stoycho Shenkov; Rosica Petrova; Rosario Scopelliti; Emil Tashev; Sabi Varbanov; Mariana Mitewa

2006-01-01

274

Vapor-liquid equilibria of binary mixtures with ethyl tert-butyl ether  

SciTech Connect

In this work P-T-x-y vapor-liquid equilibria were obtained for ethyl tert-butyl ether (ETBE) + toluene at temperatures of 273.15, 311.15, and 333.15 K and for 2-methylbutane (isopentane) + ETBE at temperatures of 293.15 and 303.15 K. These mixtures are found to be almost ideal, and the reported data are well described using a Peng-Robinson equation of state, modified by Stryjek and Vera with the van der Waals one-fluid mixing rule.

Steinhagen, V. (Technische Univ., Berlin (Germany). Inst. fuer Thermodynamik und Reaktionstechnik); Sandler, S.I. (Univ. of Delaware, Newark, DE (United States). Dept. of Chemical Engineering)

1994-07-01

275

In vitro and in vivo properties of 3-tert-butyl-7-(5-methylisoxazol-3-yl)-2-(1-methyl-1H-1,2,4-triazol-5-ylmethoxy)-pyrazolo[1,5-d]-[1,2,4]triazine (MRK-016), a GABAA receptor alpha5 subtype-selective inverse agonist.  

PubMed

3-tert-Butyl-7-(5-methylisoxazol-3-yl)-2-(1-methyl-1H-1,2,4-triazol-5-ylmethoxy)-pyrazolo[1,5-d][1,2,4]triazine (MRK-016) is a pyrazolotriazine with an affinity of between 0.8 and 1.5 nM for the benzodiazepine binding site of native rat brain and recombinant human alpha1-, alpha2-, alpha3-, and alpha5-containing GABA(A) receptors. It has inverse agonist efficacy selective for the alpha5 subtype, and this alpha5 inverse agonism is greater than that of the prototypic alpha5-selective compound 3-(5-methylisoxazol-3-yl)-6-[(1-methyl-1,2,3-triazol-4-hdyl)methyloxy]-1,2,4-triazolo[3,4-a]phthalazine (alpha5IA). Consistent with its greater alpha5 inverse agonism, MRK-016 increased long-term potentiation in mouse hippocampal slices to a greater extent than alpha5IA. MRK-016 gave good receptor occupancy after oral dosing in rats, with the dose required to produce 50% occupancy being 0.39 mg/kg and a corresponding rat plasma EC(50) value of 15 ng/ml that was similar to the rhesus monkey plasma EC(50) value of 21 ng/ml obtained using [(11)C]flumazenil positron emission tomography. In normal rats, MRK-016 enhanced cognitive performance in the delayed matching-to-position version of the Morris water maze but was not anxiogenic, and in mice it was not proconvulsant and did not produce kindling. MRK-016 had a short half-life in rat, dog, and rhesus monkey (0.3-0.5 h) but had a much lower rate of turnover in human compared with rat, dog, or rhesus monkey hepatocytes. Accordingly, in human, MRK-016 had a longer half-life than in preclinical species ( approximately 3.5 h). Although it was well tolerated in young males, with a maximal tolerated single dose of 5 mg corresponding to an estimated occupancy in the region of 75%, MRK-016 was poorly tolerated in elderly subjects, even at a dose of 0.5 mg, which, along with its variable human pharmacokinetics, precluded its further development. PMID:19704033

Atack, John R; Maubach, Karen A; Wafford, Keith A; O'Connor, Desmond; Rodrigues, A David; Evans, David C; Tattersall, F David; Chambers, Mark S; MacLeod, Angus M; Eng, Wai-Si; Ryan, Christine; Hostetler, Eric; Sanabria, Sandra M; Gibson, Raymond E; Krause, Stephen; Burns, H Donald; Hargreaves, Richard J; Agrawal, Nancy G B; McKernan, Ruth M; Murphy, M Gail; Gingrich, Kevin; Dawson, Gerard R; Musson, Donald G; Petty, Kevin J

2009-08-24

276

New MTBE design now commercial. [Methyl tertiary butyl ether  

Microsoft Academic Search

MTBE is considered by many to be the most promising octane booster to replace lead in gasoline during the 1980s. MTBE (methyl tetriary butyl ether) is made by combining methanol and isobutylene. The economic attractiveness for making this gasoline component is greatly improved by using a patented catalyst support system to give simultaneous reaction and distillation in a standard carbon

L. A. Smith; M. N. Huddleston

1982-01-01

277

Vapor-phase synthesis of ethyl tert -butyl ether on heteropoly acid-polymer composite film catalysts  

Microsoft Academic Search

H3PMo12O40-polysulfone and H3PMo12O40-polyphenylene oxide composite film catalysts were prepared by a membrane preparation technique. They showed the higher catalytic activities than H3PMo12O40 in the vapor-phase synthesis of ethyl tert-butyl ether.

Gyo Ik Park; Seong Soo Lim; In Kyu Song; Wha Young Lee

2002-01-01

278

Quercetin protects human hepatoma HepG2 against oxidative stress induced by tert-butyl hydroperoxide  

SciTech Connect

Flavonols such as quercetin, have been reported to exhibit a wide range of biological activities related to their antioxidant capacity. The objective of the present study was to investigate the protective effect of quercetin on cell viability and redox status of cultured HepG2 cells submitted to oxidative stress induced by tert-butyl hydroperoxide. Concentrations of reduced glutathione and malondialdehyde, generation of reactive oxygen species and activity and gene expression of antioxidant enzymes were used as markers of cellular oxidative status. Pretreatment of HepG2 with 10 {mu}M quercetin completely prevented lactate dehydrogenase leakage from the cells. Pretreatment for 2 or 20 h with all doses of quercetin (0.1-10 {mu}M) prevented the decrease of reduced glutathione and the increase of malondialdehyde evoked by tert-butyl hydroperoxide in HepG2 cells. Reactive oxygen species generation induced by tert-butyl hydroperoxide was significantly reduced when cells were pretreated for 2 or 20 h with 10 {mu}M and for 20 h with 5 {mu}M quercetin. Finally, some of the quercetin treatments prevented the significant increase of glutathione peroxidase, superoxide dismutase, glutathione reductase and catalase activities induced by tert-butyl hydroperoxide. Gene expression of antioxidant enzymes was also affected by the treatment with the polyphenol. The results of the biomarkers analyzed clearly show that treatment of HepG2 cells in culture with the natural dietary antioxidant quercetin strongly protects the cells against an oxidative insult.

Alia, Mario [Departamento de Metabolismo y Nutricion, Instituto del Frio (CSIC), C/Jose Antonio Novais, 10, Ciudad Universitaria, 28040 Madrid (Spain); Ramos, Sonia [Departamento de Metabolismo y Nutricion, Instituto del Frio (CSIC), C/Jose Antonio Novais, 10, Ciudad Universitaria, 28040 Madrid (Spain); Mateos, Raquel [Departamento de Metabolismo y Nutricion, Instituto del Frio (CSIC), C/Jose Antonio Novais, 10, Ciudad Universitaria, 28040 Madrid (Spain); Granado-Serrano, Ana Belen [Departamento de Metabolismo y Nutricion, Instituto del Frio (CSIC), C/Jose Antonio Novais, 10, Ciudad Universitaria, 28040 Madrid (Spain); Bravo, Laura [Departamento de Metabolismo y Nutricion, Instituto del Frio (CSIC), C/Jose Antonio Novais, 10, Ciudad Universitaria, 28040 Madrid (Spain); Goya, Luis [Departamento de Metabolismo y Nutricion, Instituto del Frio (CSIC), C/Jose Antonio Novais, 10, Ciudad Universitaria, 28040 Madrid (Spain)]. E-mail: luisgoya@if.csic.es

2006-04-15

279

Discriminative Stimulus Effects of L-838,417 (7-tert-Butyl-3-(2,5-difluoro-phenyl)-6-(2-methyl-2H-[1,2,4]triazol-3-ylmethoxy)-[1,2,4]triazolo[4,3-b]pyridazine): Role of GABAA Receptor Subtypes  

PubMed Central

Previous reports suggest that ?-aminobutyric acid type A (GABAA) receptors containing ?1 subunits may play a pivotal role in mediating the discriminative stimulus effects of benzodiazepines (BZs). L-838,417 (7-tert-Butyl-3-(2,5-difluoro-phenyl)-6-(2-methyl-2H-[1,2,4]triazol-3-ylmethoxy)-[1,2,4]triazolo[4,3-b]pyridazine) is a GABAA receptor modulator with intrinsic efficacy in vitro at ?2, ?3, and ?5 subunit-containing GABAA receptors, and little demonstrable intrinsic efficacy in vitro at ?1 subunit-containing GABAA receptors. The present study evaluated the discriminative stimulus effects of L-838,417 in order to determine the extent to which the ?2, ?3, and ?5 subunit-containing GABAA receptors contribute to the interoceptive effects of BZ-type drugs. Squirrel monkeys (Saimiri sciureus) were trained to discriminate L-838,417 (0.3 mg/kg, i.v.) from vehicle under a 5-response fixed-ratio schedule of food reinforcement. Under test conditions, L-838,417 administration resulted in dose-dependent increases in drug lever responding that were antagonized by the BZ-site antagonist, flumazenil. Administration of non-selective BZs, compounds with 10-fold greater affinity for ?1 subunit-containing GABAA receptors compared to ?2, ?3, and ?5 subunit-containing GABAA receptors, barbiturates and ethanol (which modulate the GABAA receptor via a non-BZ site), all resulted in a majority of responses on the L-838,417-paired lever (65–100% drug-lever responding). ?CCT, an antagonist that binds with 20-fold greater affinity for ?1 subunit-containing GABAA receptors relative to ?2, ?3, and ?5-containing GABAA receptors, had no significant effect on the discriminative stimulus effects of L-838,417 or the L-838,417-like effects of diazepam or zolpidem. These data suggest that efficacy at ?2, ?3, and/or ?5 subunit-containing GABAA receptors likely are sufficient for engendering BZ-like discriminative stimulus effects.

Licata, Stephanie C.; Platt, Donna M.; Ruedi-Bettschen, Daniela; Atack, John R.; Dawson, Gerard R.; Van Linn, Michael L.; Cook, James M.; Rowlett, James K.

2009-01-01

280

Photoelectric conversion and electrochromic properties of lutetium tetrakis(tert-butyl)bisphthalocyaninate  

SciTech Connect

Both photoelectric and electrochromic effects on lutetium tetrakis(tert-butyl)bisphthalocyaninate (Lu(TBPc){sub 2}) have been carried out in this study. Lu(TBPc){sub 2} is known for its electrochromic performance, but its photoelectric effect has not mentioned in the literature. The electrochromic properties of Lu(TBPc){sub 2} have been measured by cyclic voltammetry (CV) and UV-Vis spectrometer at the same time. It takes less than 1.5 s for the color to change from red to green under 0.9 V. Its cycle life is at least over 500 times. Furthermore, we also investigate its photoelectric conversion properties. Its photoelectric cell exhibits a positive photo-electricity conversion effect with a short-circuit photocurrent (46.4 {mu}A/cm{sup 2}) under illumination of white light (1.201 mW/cm{sup 2})

Hu, Andrew Teh; Hu Tenyi; Liu Lungchang

2003-12-10

281

Atmospheric chemistry of diethyl ether and ethyl tert-butyl ether  

SciTech Connect

The mechanisms for the Cl-initiated and OH-initiated atmospheric oxidation of diethyl ether and ethyl tert-butyl ether (ETBE) have been determined. For diethyl ether the products are ethyl formate and formaldehyde and its atmospheric oxidation can be represented by C{sub 2}H{sub 5}OC{sub 2}H{sub 5} + OH + 2NO {yields} C{sub 2}H{sub 5}OC(O)H + HCHO + 2NO{sub 2} + HO{sub 2}. The mechanism for the atmospheric oxidation of ETBE is more complex, with 80% of the reaction being accounted for in terms of tert-butyl formate and formaldehyde. The remaining 20% the authors ascribe to 2-ethoxy-2-methylpropanal. The atmospheric oxidation of ETBE can be represented by ETBE + OH + 1.8NO {yields} 0.8HCOOC(CH{sub 3}){sub 3} + 0.2C{sub 2}H{sub 5}OC(CH{sub 3}){sub 2}CHO + HO{sub 2} + 0.8HCHO + 1.8NO{sub 2}. THe subsequent atmospheric chemistry of 2-ethoxy-2-methylpropanal the authors estimate to be represented by C{sub 2}H{sub 5}OC(CH{sub 3}){sub 2}CHO + OH + 3NO {yields} CO{sub 2} + H{sub 2}CO + C{sub 2}H{sub 5}OC(O)CH{sub 3} + HO{sub 2} + 3NO{sub 2}. These results are discussed in terms of the reactivity of these compounds in urban atmospheres.

Wallington, T.J.; Japar, S.M. (Ford Motor Company, Dearborn, MI (USA))

1991-03-01

282

Absolute rate constants of alkoxyl radical reactions in aqueous solution. [Tert-butyl hydroperoxide  

SciTech Connect

The pulse radiolysis technique was used to generate the alkoxyl radical derived from tert-butyl hydroperoxide (/sup t/BuOOH) in aqueous solution. The reactions of this radical with 2,2'-azinobis(3-ethyl-6-benzothiazolinesulfonate) (ABTS) and promethazine were monitored by kinetic spectroscopy. The unimolecular decay rate constant of the tert-butoxyl radical (/sup t/BuO) was determined to be 1.4 x 10/sup 6/ s/sup -1/. On the basis of this value, the rate constants for /sup t/BuO attack on quercetin, crocin, crocetin, ascorbate, isoascorbate, trolox c, glutathione, thymidine, adenosine, guanosine, and unsaturated fatty acids were determined. In addition, the reaction of /sup t/BuO with the polyunsaturated fatty acids (PUFA) was observed by directly monitoring the formation of the fatty acid pentadienyl radicals. Interestingly, the attack of /sup t/BuO on PUFA was found to be faster by about one order of magnitude as compared to the same reaction in a nonpolar solvent.

Erben-Russ, M.; Michel, C.; Bors, W.; Saran, M.

1987-04-23

283

Viscosities and Densities of Some Multicharged Electrolytes in Water-Tert Butyl Alcohol  

NASA Astrophysics Data System (ADS)

Viscosity and density data for aluminium ammonium sulphate and potassium aluminium sulphate in tert-butyl alcohol-water (tert. BuOH-H2O) solutions [5, 10, 15 and 20 wt%] at different concentrations and temperatures are presented. The viscosity data have been analysed by means of Jones-Dole equation. The activation parameters of viscous flow were obtained by means of the application of transition state theory in order to estimate the mechanism of the viscous flow. The density data have been analysed by using the Masson’s equation. The limiting apparent molar volume ?v0, and the experimental slope Sv, have been interpreted in terms of solute-solvent and solute-solute interactions, respectively. The ?v0 values vary with temperature as a power series of temperature. Structure making/breaking capacities of the multicharged electrolytes have also been inferred from the sign of (\\partial2?v0/{\\partial}T2). Both the electrolytes behave as structure makers/promotors.

Parmar, M. L.; Khanna, Anita

1986-11-01

284

Photosensitized dissociation of di-tert-butyl peroxide. Energy transfer to a repulsive excited state  

SciTech Connect

Energy transfer from a variety of aromatic hydrocarbons and ketones to di-tert-butyl peroxide has been examined by using nanosecond laser flash photolysis techniques. Triplet energy transfer to the peroxide leads to its efficient cleavage into two tert-butoxy radicals. Representative rate constants for triplet quenching in benzene at 25/sup 0/C are 7.9 x 10/sup 6/, 3.4 x 10/sup 6/, and 7.0 x 10/sup 4/M/sup -1/s/sup -1/ for p-methoxypropiophenone, benzophenone, and benz(a)anthracene, respectively. The rate of transfer for p-methoxypropiophenone (E/sub T/ = 72.5 kcal/mol) is approximately temperature independent; for lower energy sensitizers ca. 0.17 kcal/mol activation energy is required for each kilocalorie per mole decrease in triplet energy. No evidence indicating exciplex intermediacy was found. A model for energy transfer to a repulsive state of the peroxide is proposed in which no activation energy is required if the sensitizer meets the energy requirements at the 0-0 equilibrium distance. For sensitizers of lower triplet energy, energy transfer to a repulsive state is proposed to occur from a thermally activated ground state having a greater than equilibrium oxygen-oxygen bond length. The same mechanism may apply in other systems where the acceptor lacks low-lying excited states. A few rate constants for the quenching of singlet sensitizers have also been determined by using fluorescence techniques.

Scaiano, J.C.; Wubbels, G.G.

1981-02-11

285

N-tert-Butyl-2-methyl-propanamide  

PubMed Central

The title compound, C8H17NO, crystallizes with two independent mol­ecules in the asymmetric unit. In the crystal, inter­molecular N—H?O hydrogen bonding is observed between neighboring mol­ecules, forming continuous mol­ecular chains along the c-axis direction.

Kluge, Kelly A.; Fridyland, Diana; MacBeth, Cora E.; Hardcastle, Kenneth I.

2011-01-01

286

Cultivation of Aquincola tertiaricarbonis L108 on the fuel oxygenate intermediate tert-butyl alcohol induces aerobic anoxygenic photosynthesis at extremely low feeding rates.  

PubMed

Aerobic anoxygenic photosynthesis (AAP) is found in an increasing number of proteobacterial strains thriving in ecosystems ranging from extremely oligotrophic to eutrophic. Here, we have investigated whether the fuel oxygenate-degrading betaproteobacterium Aquincola tertiaricarbonis L108 can use AAP to compensate kinetic limitations at low heterotrophic substrate fluxes. In a fermenter experiment with complete biomass retention and also during chemostat cultivation, strain L108 was challenged with extremely low substrate feeding rates of tert-butyl alcohol (TBA), an intermediate of methyl tert-butyl ether (MTBE). Interestingly, formation of photosynthetic pigments, identified as bacteriochlorophyll a and spirilloxanthin, was only induced in growing cells at TBA feeding rates less than or equal to maintenance requirements observed under energy excess conditions. Growth continued at rates between 0.001 and 0.002 h(-1) even when the TBA feed was decreased to values close to 30?% of this maintenance rate. Partial sequencing of genomic DNA of strain L108 revealed a bacteriochlorophyll synthesis gene cluster (bchFNBHL) and photosynthesis regulator genes (ppsR and ppaA) typically found in AAP and other photosynthetic proteobacteria. The usage of light as auxiliary energy source enabling evolution of efficient degradation pathways for kinetically limited heterotrophic substrates and for lowering the threshold substrate concentration Smin at which growth becomes zero is discussed. PMID:23873782

Rohwerder, Thore; Müller, Roland H; Weichler, M Teresa; Schuster, Judith; Hübschmann, Thomas; Müller, Susann; Harms, Hauke

2013-07-19

287

Effects of ?-phenyl-tert-butyl nitrone on neuronal survival and motor function following intrastriatal injections of quinolinate or 3-nitropropionate  

Microsoft Academic Search

We have investigated the neuroprotective effects of the the spin-trapping agent ?-phenyl-tert-butyl nitrone on striatal lesions produced by local injections of the excitotoxin quinolinate or the mitochondrial toxin 3-nitropropionate. We have assessed both the behavioural and morphological consequences of the lesion. Thus, we tested paw-reaching ability and amphetamine- and apomorphine-induced rotational behaviour in lesioned rats with or without ?-phenyl-tert-butyl nitrone

N Nakao; P Brundin

1996-01-01

288

Reactive distillation for synthesizing ethyl tert-butyl ether from low-grade alcohol catalyzed by potassium hydrogen sulfate  

SciTech Connect

Synthesis of ethyl tert-butyl ether (ETBE) from the reaction between ethanol (EtOH) and tert-butyl alcohol (TBA) in the presence of different acid catalysts (KHSO{sub 4}, NaHSO{sub 4}, H{sub 2}SO{sub 4}, and Amberlyst 15) was investigated at low alcohol grade (mixture of 80 mol % water). Potassium hydrogen sulfate (KHSO{sub 4}) showed the highest selectivity among the tested catalysts. Other catalysts caused the dehydration of TBA into water (H{sub 2}O) and isobutene (IB). In the top of the reactive distillation column with total reflux, the condensate was split into two layers. The upper layer contained ETBE with a more than 60 mole fraction.

Matouq, M.; Quitain, A.T.; Takahashi, Katsuroku; Goto, Shigeo [Nagoya Univ. (Japan). Dept. of Chemical Engineering

1996-03-01

289

Ab initio molecular orbital calculations on the tert-butyl radical, its isoelectronic neighboring radical ions, and their third-row congeners  

SciTech Connect

Qualitative UHF/STO-3G calculations are used to characterize the combined effect of methyl rotation and pyramidal inversion in the tert-butyl radical, the trimethylaminium radical, and the isoelectronic borane radical anion and their third-row counterparts containing silicon, phosphorus, and aluminum, respectively. Energy barriers and structures are quantified by employing a split-valent UHF/3-21G procedure. At this level of theory full geometry optimizations are performed and some properties are derived. For the 33-electron species the optimized out-of-plane angles are 15.7, 9.0, and 0 for BMe3 , CMe3, and NMe3 , respectively. In the radical anion the predicted barriers to both inversion and concerted methyl rotation make these motions thermally unfeasible (at room temperature). For tert-butyl such processes are strongly coupled across a barrier of about 7 kJ mol . The planar aminium radical is predicted to be very easily deformable. Inversion in the third-row species is thermally inaccessible (at room temperature) and (uncoupled but concerted) methyl rotation takes place over barriers of about 11 kJ mol in AlMe3 and PMe3 and of about 14 kJ mol in SiMe3. The three third-row species considered are thus pyramidal with out-of-plane angles of 19.5, 18.4, and 14.6, respectively. UHF/3-21G charge and spin density properties are listed and a harmonic vibrational analysis predicts the inversion frequency at about 270 cm for CMe3 and an out-of-plane mode at about 340 cm for NMe3 . 56 references, 10 figures, 8 tables.

Carmichael, I.

1985-10-24

290

Calculation of carbon-14, chlorine-37, and deuterium kinetic isotope effects in the solvolysis of tert-butyl chloride  

Microsoft Academic Search

In the solvolysis of tert-butyl chloride, satisfactory ..cap alpha..-carbon-14, ..beta..-deuterium, and chlorine kinetic isotope effects (KIE) may be calculated for a productlike transition state characterized by bond orders n\\/sub C Cl\\/ = 0.2, n\\/sub C C\\/ = 1.18, and n\\/sub C H\\/ = 0.94, employing a diagonal valence force field, provided that allowance is made for hydrogen-bonded solvation of the

Graham W. Burton; Leslie B. Sims; Joe C. Wilson; Arthur Fry

1977-01-01

291

ESR spin trapping investigation of radical formation from the reaction between hematin and tert-butyl hydroperoxide  

Microsoft Academic Search

Various mechanisms have been proposed for the reaction between heme proteins and organic hydroperoxides, including a peroxidase-type mechanism and homolytic cleavage. We used electron spin resonance (ESR) spectroscopy to investigate the formation of radicals in a hematin\\/tert-butyl hydroperoxide system. Spin trapping studies, using 5,5-dimethyl-1-pyrroline N-oxide (DMPO), showed the formation of peroxyl and alkoxyl radicals in this system. At higher hematin

Jolanda Van Der Zee; David P. Barr; Ronald P. Mason

1996-01-01

292

Effects of G6PD Overexpression in NIH3T3 Cells Treated with TertButyl Hydroperoxide or Paraquat  

Microsoft Academic Search

The major physiological role of glucose-6-phosphate dehydrogenase (G6PD) is to provide NADPH, which is required for reductive biosynthesis and for detoxification of free radicals and peroxides in mature red blood cells. To study the function of G6PD in non-erythroid cells, we examined the sensitivity of NIH3T3 cells transfected with a plasmid containing human G6PD cDNA to tert-butyl hydroperoxide (TBH) and

Wei-Ying Kuo; Tang K Tang

1998-01-01

293

Glutathione protection against hydrogen peroxide, tert-butyl hydroperoxide and diamide cytotoxicity in rat hepatoma-derived Fa32 cells  

Microsoft Academic Search

1 Several ozonides, peroxides and aldehydes are formed during ozone therapy, recently introduced in medicine. tert-Butyl hydroperoxide (t-BHP), H2O2 and diamide were investigated as model substrate in rat hepatoma-derived Fa32 cells.2 The cytotoxicity was measured by the neutral red uptake inhibition assay after 1 h or 24 h treatment. The relative toxicities were quantified by the determination of the NI50.

P. J. Dierickx; G. van Nuffel; I. Alvarez

1999-01-01

294

Formation of triacylglycerol core aldehydes during rapid oxidation of corn and sunflower oils with tert -butyl hydroperoxide\\/Fe 2+  

Microsoft Academic Search

The lipid ester core aldehydes formed during a rapid oxidation (7.8 M tert-butyl hydroperoxide, 90 min at 37°C) of the triacylglycerols of purified corn and sunflower oils were isolated as dinitrophenylhydrazones\\u000a by preparative thin-layer chromatography and identified by reversed-phase high-performance liquid chromatography with on-line\\u000a electrospray ionization mass spectrometry and by reference to standards. A total of 113 species of triacylglycerol

Olli Sjövall; Arnis Kuksis; Heikki Kallio

2002-01-01

295

The tert-butyl dimethyl silyl group as an enhancer of drug cytotoxicity against human tumor cells  

Microsoft Academic Search

In this study, we synthesized a series of enantiomerically pure (2R,3S)-disubstituted tetrahydropyranes with diverse functional groups using known methodologies. In addition to the tert-butyl dimethyl silyl group, other common protecting groups for hydroxyl groups such as allyl, acetate, and benzoate were used to obtain appropriate derivatives. Pure compounds were evaluated in vitro against HL60 human leukemia cells and MCF7 human

Osvaldo J. Donadel; Tomás Martín; Víctor S. Martín; Jesús Villar; José M. Padrón

2005-01-01

296

Neuroprotection of ?-phenyl- n- tert-butyl-nitrone on the neonatal white matter is associated with anti-inflammation  

Microsoft Academic Search

Our previous study has demonstrated that ?-phenyl-tert-butyl-nitrone (PBN) provided neuroprotection to the neonatal white matter following cerebral hypoxia-ischemia (HI). Free radical scavenging was involved in the neuroprotection of PBN. To investigate if other mechanisms contribute to the neuroprotection of PBN, postnatal day 4 SD rats were subjected to bilateral common carotid artery ligation, followed by 8% oxygen exposure for 20min.

Shuying Lin; Helen J. Cox; Philip G. Rhodes; Zhengwei Cai

2006-01-01

297

?-Phenyl- n- tert-butyl-nitrone attenuates hypoxic–ischemic white matter injury in the neonatal rat brain  

Microsoft Academic Search

White matter of the neonatal brain is highly sensitive to hypoxic–ischemic insult. The susceptibility of premature oligodendrocytes (OLs) to free radicals (FRs) produced during hypoxia–ischemia (HI) has been proposed as one of the mechanisms involved. To test this hypothesis, and to further investigate if the FR scavenger ?-phenyl-N-tert-butyl-nitrone (PBN) attenuates hypoxic–ischemic white matter damage (WMD), postnatal day 4 (P4) SD

Shuying Lin; Philip G Rhodes; Manping Lei; Feng Zhang; Zhengwei Cai

2004-01-01

298

Antioxidant treatment with phenyl-?- tert-butyl nitrone (PBN) improves the cognitive performance and survival of aging rats  

Microsoft Academic Search

Accumulating evidence has implicated free radical production and resultant oxidative damage as a major contributing factor in brain aging and cognitive decline. In the present study, aging 24-month-old rats were chronically treated with the synthetic spin-trapping antioxidant phenyl-?-tert-butyl nitrone (PBN) for up to 9.5 months. Chronic PBN treatment (1) improved the cognitive performance of aged rats in several tasks, (2)

Candice A. Sack; Debra J. Socci; Blane M. Crandall; Gary W. Arendash

1996-01-01

299

Hydrophobic hydration of tert-butyl alcohol studied by Brillouin light and inelastic ultraviolet scattering.  

PubMed

The longitudinal viscosity of diluted water-tert-butyl alcohol solutions in the 10 GHz frequency region has been measured by means of Brillouin light scattering and inelastic ultraviolet scattering. The main advantage of our hypersonic investigation compared to more traditional ultrasonic measurements is that in the gigahertz frequency range slow relaxation processes involving the alcohol dynamics are completely unrelaxed, so that the measured viscosity mainly originates from the hydrogen bond restructuring of water. In contrast with previous determinations, we estimate an activation energy which is independent from the alcohol mole fraction up to X = 0.1, and comparable to that of bulk water. A simple two-component model is used to describe the steep increase of viscosity with increasing alcohol mole fraction, and a retardation factor 1.7 ± 0.2 is found between the relaxation times of hydration and bulk water. These findings endorse a dynamic scenario where the slowing down of hydration water is mainly due to a reduction of configurational entropy and does not involve an arrested, icelike, dynamics. PMID:21303164

Lupi, L; Comez, L; Masciovecchio, C; Morresi, A; Paolantoni, M; Sassi, P; Scarponi, F; Fioretto, D

2011-02-01

300

Protective effect of Hibiscus anthocyanins against tert-butyl hydroperoxide-induced hepatic toxicity in rats.  

PubMed

Hibiscus anthocyanins (HAs), a group of natural pigments occurring in the dried flowers of Hibiscus sabdariffa L., which is a local soft drink material and medical herb, were studied for antioxidant bioactivity. The preliminary study showed that HAs were able to quench the free radicals of 1,1-diphenyl-2-picrylhydrazyl. This antioxidant bioactivitiy was further evaluated using the model of tert-butyl hydroperoxide (t-BHP)-induced cytotoxicity in rat primary hepatocytes and hepatotoxicity in rats. The results demonstrated that HAs, at the concentrations of 0.10 and 0.20 mg/ml, significantly decreased the leakage of lactate dehydrogenase and the formation of malondialdehyde induced by a 30-min treatment of t-BHP (1.5 mM). The in vivo investigation showed that the oral pretreatment of HAs (100 and 200 mg/kg) for 5 days before a single dose of t-BHP (0.2 mmol/kg, ip) significantly lowered the serum levels of hepatic enzyme markers (alanine and aspartate aminotransferase) and reduced oxidative liver damage. The histopathological evaluation of the liver revealed that Hibiscus pigments reduced the incidence of liver lesions including inflammatory, leucocyte infiltration, and necrosis induced by t-BHP in rats. Based on the results described above, we speculate that Hibiscus pigments may play a role in the prevention of oxidative damage in living systems. PMID:10762726

Wang, C J; Wang, J M; Lin, W L; Chu, C Y; Chou, F P; Tseng, T H

2000-05-01

301

Kinetics of the liquid-phase synthesis of ethyl tert-butyl ether (ETBE)  

SciTech Connect

The liquid-phase addition of ethanol to isobutene to give ethyl tert-butyl ether (ETBE) on the ion exchange resin Lewatit K2631 has been studied. Rate data were obtained free of mass transfer influence in a continuous differential reactor operated at 1.6 MPa and 40--90 C, measuring steady-state conversions <10% for ethanol-isobutene and ethanol-isobutene-ETBE feeds. The reaction is highly temperature-sensitive. Isobutene has an enhancing effect on the rate whereas ethanol has an inhibitor one. Besides, low ETBE concentrations enhance the reaction but as chemical equilibrium is approached the ether shows an inhibitor effect, as expected. As alcohol-olefin-ether mixtures behave nonideally, kinetic analysis has been performed by using the UNIFAC liquid-phase activities of isobutene, ethanol, and ETBE. The best kinetic model stems from an Eley-Rideal mechanism in which the ethanol, adsorbed on one center, reacts with the isobutene from solution to give the ether adsorbed on one center. Surface reaction is the rate-limiting step. Two additional centers take part in this step.

Fite, C.; Iborra, M.; Tejero, J.; Izquierdo, J.F.; Cunill, F. (Univ. of Barcelona (Spain). Chemical Engineering Dept.)

1994-03-01

302

Predicted and experimental crystal structures of ethyl-tert-butyl ether.  

PubMed

Possible crystal structures of ethyl-tert-butyl ether (ETBE) were predicted by global lattice-energy minimizations using the force-field approach. 33 structures were found within an energy range of 2 kJmol(-1) above the global minimum. Low-temperature crystallization experiments were carried out at 80-160 K. The crystal structure was determined from X-ray powder data. ETBE crystallizes in C2/m, Z = 4, with molecules on mirror planes. The ETBE molecule adopts a trans conformation with a (CH(3))(3)C-O-C-C torsion angle of 180°. The experimental structure corresponds with high accuracy to the predicted structure with energy rank 2, which has an energy of 0.54 kJmol(-1) above the global minimum and is the most dense low-energy structure. In some crystallization experiments a second polymorph was observed, but the quality of the powder data did not allow the determination of the crystal structure. Possibilities and limitations are discussed for solving crystal structures from powder diffraction data by real-space methods and lattice-energy minimizations. PMID:21422614

Hammer, Sonja M; Alig, Edith; Fink, Lothar; Schmidt, Martin U

2011-02-19

303

Isotope Effects and the Mechanism of Epoxidation of Cyclohexenone with tert-Butyl Hydroperoxide  

PubMed Central

The mechanism of the epoxidation of 2-cyclohexen-1-one with tert-butyl hydroperoxide mediated by DBU was studied by a combination of experimental kinetic isotope effects and theoretical calculations. A large 12C/13C (k12C/k13C) isotope effect of ?1.032 was observed at the C3 (?) position of cyclohexenone, while a much smaller 12C/13C isotope effect of 1.010 was observed at the C2 (?) position. Qualitatively, these results are indicative of nucleophilic addition to the enone being the rate-limiting step. Theoretical calculations support this interpretation. Transition structures for the addition step lead to predicted isotope effects that approximate the experimental values, while the predicted isotope effects for the ring-closure step are not consistent with experiment. The calculations correctly favor a rate-limiting addition step, but suggest that the barriers for the addition and ring-closure steps are crudely similar in energy. The stereochemistry of these epoxidations is predicted to be governed by a preference for an initial axial addition, and the role of this preference in experimental diastereoselectivity observations is discussed.

Christian, Chad F.; Takeya, Tetsuya; Szymanski, Michael J.; Singleton, Daniel A.

2008-01-01

304

Entanglement Dynamics in Miscible Polyisoprene / Poly(p-tert-butyl styrene) Blends  

NASA Astrophysics Data System (ADS)

Viscoelastic and dielectric behavior was examined for well entangled, miscible blends of high-M cis-polyisoprene (PI) and poly(p-tert-butyl styrene) (PtBS). The dielectric data of the blends, reflecting the global motion of the PI chains having the type-A dipoles, indicated that PI and PtBS were the fast and slow components therein. At high temperatures T, the blends exhibited two-step entanglement plateau. The high frequency (?) plateau height was well described by a simple mixing rule of the entanglement length based on the number fraction of the Kuhn segments. At low T, the blend exhibited the Rouse-like power-law behavior of storage and loss moduli, G' = G" ˜0.5?, in the range of ? where the high-? plateau was supposed to emerge. This lack of the high-? plateau was attributed to retardation of the Rouse equilibration of the PI chain over the entanglement length due to the hindrance from the slow PtBS chains: The PI and PtBS chains were equilibrated cooperatively, and the retardation due to PtBS shortened the plateau for PI to a width not resolved experimentally. A simple model for this cooperative equilibration formulated on the basis of the dielectric data described the viscoelastic data surprisingly well.

Watanabe, Hiroshi

2011-03-01

305

Kinetics of Methyl t-Butyl Ether Cometabolism at Low Concentrations by Pure Cultures of Butane-Degrading Bacteria  

PubMed Central

Butane-oxidizing Arthrobacter (ATCC 27778) bacteria were shown to degrade low concentrations of methyl t-butyl ether (MTBE; range, 100 to 800 ?g/liter) with an apparent half-saturation concentration (Ks) of 2.14 mg/liter and a maximum substrate utilization rate (kc) of 0.43 mg/mg of total suspended solids per day. Arthrobacter bacteria demonstrated MTBE degradation activity when grown on butane but not when grown on glucose, butanol, or tryptose phosphate broth. The presence of butane, tert-butyl alcohol, or acetylene had a negative impact on the MTBE degradation rate. Neither Methylosinus trichosporium OB3b nor Streptomyces griseus was able to cometabolize MTBE.

Liu, Catherine Y.; Speitel, Gerald E.; Georgiou, George

2001-01-01

306

[Study on the genotoxicity of methyl tertiary-butyl ether].  

PubMed

Methyl tertiary-butyl ether(MTBE), a new gasoline additive, is added to gasoline as an octane enhancer and used to reduce automotive emissions. Using Ames test, unscheduled DNA synthesis (UDS) assay and cell micronucleus test, the authors evaluated the genotoxicity of domestic produced MTBE. MTBE did not show any mutagenic potential in Ames assay(TA98, TA100 strains) with or without rat liver-derived metabolic activation system (S-9). Rat primary hepatocyte UDS assay showed that MTBE could damage DNA. In NIH3T3 cell micronucleus test, MTBE showed negative results. It could be concluded that MTBE has some genotoxicity at DNA level. PMID:11939044

Zhou, W; Ye, S

1998-09-30

307

Biodegradation of ethyl t -butyl ether (ETBE), methyl t -butyl ether (MTBE) and t -amyl methyl ether (TAME) by Gordonia terrae  

Microsoft Academic Search

Gordonia terrae strain IFP 2001 was selected from activated sludge for its capacity to grow on ethyl t-butyl ether (ETBE) as sole carbon and energy source. ETBE was stoichiometrically degraded to t-butyl alcohol (TBA) and the activity was inducible. A constitutive strain, G. terrae IFP 2007, derived from strain IFP 2001, was also selected. Methyl t-butyl ether (MTBE) and t-amyl

Guillermina Hernandez-Perez; Françoise Fayolle; Jean-Paul Vandecasteele

2001-01-01

308

Ring-expansion reactions in the thermal decomposition of tert-butyl-1,3-cyclopentadiene.  

PubMed

The thermal decomposition of tert-butyl-1,3-cyclopentadiene has been investigated in single-pulse shock-tube studies at shock pressures of 182-260 kPa and temperatures of 996-1127 K. Isobutene (2-methylpropene), 1,3-cyclopentadiene, and toluene were observed as the major stable products in the thermolysis of dilute mixtures of the substrate in the presence of a free-radical scavenger. Hydrogen atoms were also inferred to be a primary product of the decomposition and could be quantitatively determined on the basis of products derived from the free-radical scavenger. Of particular interest is the formation of toluene, which involves the expansion of the ring from a five- to a six-membered system. The overall reaction mechanism is suggested to include isomerization of the starting material; a molecular elimination channel; and C-C bond fission reactions, with toluene formation occurring via radical intermediates formed in the latter pathway. These radical intermediates are analogous to those believed to be important in soot formation reactions occurring during combustion. Molecular and thermodynamic properties of key species were determined from G3MP2B3 quantum chemistry calculations and are reported. The temperature dependence of the product spectrum was fit with a detailed chemical kinetic model, and best-fit kinetic parameters were derived using a Nelder-Mead simplex minimization algorithm. Our mechanism and rate constants are consistent with and provide experimental support for the H-atom-assisted routes to the conversion of fulvene to benzene that have been proposed in the literature on the basis of theoretical investigations. PMID:17125296

McGivern, W Sean; Manion, Jeffrey A; Tsang, Wing

2006-11-30

309

Di(tert-butyl) phosphate complexes of aluminum: Precursors to aluminum phosphate xerogels and thin films  

SciTech Connect

Aluminophosphates and related materials are useful in a number of applications, in particular as catalysts and catalyst supports. In addition, aluminophosphates have been shown to possess interesting ion exchange and adsorption properties. Reactions of HO(O)P(O{sup t}Bu){sub 2} with Al{sub 2}Me{sub 6} and [Al(O{sup i}Pr){sub 3}]{sub 4} gave the new molecular aluminum phosphate complexes [Me{sub 2}AlO{sub 2}P(O{sup t}Bu){sub 2}]{sub 2} (1) and [Al(O{sup i}Pr){sub 2}O{sub 2}P(O{sup t}Bu){sub 2}]{sub 4} (2), respectively. In the solid state, 1 exists as a centrosymmetric dimer consisting of two four-coordinate Al centers bridged by two phosphate groups. In the solid state 2 exists as a centrosymmetric tetramer in which the unique half of the tetramer consists of two aluminum atoms bridged by two di(tert-butyl)phosphate groups. The central part of the molecule contains a planar Al{sub 2}O{sub 2} four-membered ring containing two symmetry-related Al(1) atoms bridged by two {minus}O{sup i}Pr ligands. Solution-phase thermolyses of 1 and 2 in organic solvents led to the formation of transparent and opaque xerogels, respectively, after air-drying. The xerogel derived from 1 in 2-propanol had a surface area of 442 m{sup 2} g{sup {minus}1} after calcination to 600 C in air. Thin, transparent films of aluminum phosphate were prepared by chemical vapor deposition (CVD) using both 1 and 2 as molecular precursors.

Lugmair, C.G.; Tilley, T.D. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley National Lab., CA (United States). Chemical Sciences Div.; Rheingold, A.L. [Univ. of Delaware, Newark, DE (United States). Dept. of Chemistry and Biochemistry

1999-06-01

310

The Synthesis and Isolation of N-Tert-Butyl-2-Phenylsuccinamic Acid and N-Tert-Butyl-3-Phenylsuccinamic Acid: An Undergraduate Organic Chemistry Laboratory Experiment  

ERIC Educational Resources Information Center

|The facile, high yielding synthesis of phenylsuccinamic acids is described and one of these syntheses, the reaction of phenylsuccinic anhydride with tert-butylamine, is successfully modified and adapted for use in the second-semester organic chemistry laboratory at St. John's University. Succinamic acids are compounds that contain both the amide…

Cesare, Victor; Sadarangani, Ishwar; Rollins, Janet; Costello, Dennis

2004-01-01

311

The Synthesis and Isolation of N-Tert-Butyl-2-Phenylsuccinamic Acid and N-Tert-Butyl-3-Phenylsuccinamic Acid: An Undergraduate Organic Chemistry Laboratory Experiment  

ERIC Educational Resources Information Center

The facile, high yielding synthesis of phenylsuccinamic acids is described and one of these syntheses, the reaction of phenylsuccinic anhydride with tert-butylamine, is successfully modified and adapted for use in the second-semester organic chemistry laboratory at St. John's University. Succinamic acids are compounds that contain both the amide…

Cesare, Victor; Sadarangani, Ishwar; Rollins, Janet; Costello, Dennis

2004-01-01

312

Br(2Pj) atom formation dynamics in ultraviolet photodissociation of tert-butyl bromide and iso-butyl bromide  

NASA Astrophysics Data System (ADS)

The photodissociation dynamics of tert-C4H9Br and iso-C4H9Br has been studied at 234 and 265 nm using two-dimensional velocity map imaging technique. The translational energy and angular distributions have been analyzed for Br, Br*, and tert-C4H9 radical. The energy distribution of Br atom in the photodissociation of tert-C4H9Br is found to consist of two Gaussian components. The two components are correlated to two independent reaction paths on the excited potential energy surfaces: (1) the high-energy component from the prompt dissociation along the C-Br stretching mode and (2) the low-energy component from the repulsive mode along the C-Br stretching, coupled with some bending motions. For the energy distribution of Br* atom in the photodissociation of tert-C4H9Br, a third multiphoton dissociative ionization channel is observed at 265 nm in addition to the two energy components corresponding to channels (1) and (2). The energy distributions of Br and Br* atoms in the photodissociation of iso-C4H9Br can be fitted using only one Gaussian function indicating a single formation channel. Relative quantum yields for Br(2P3/2) at 234 and 265 nm in the photodissociation of tert-C4H9Br are measured to be 0.76 and 0.65, respectively. For iso-C4H9Br, the measured value is ?234 nm(Br)=0.81. The contribution of bending modes to Br and Br* is much more obvious in the photodissociation of tert-C4H9Br than in iso-C4H9Br.

Wang, Yanmei; Zhang, Song; Wei, Zhengrong; Zheng, Qiusha; Zhang, Bing

2006-11-01

313

Br(2Pj) atom formation dynamics in ultraviolet photodissociation of tert-butyl bromide and iso-butyl bromide.  

PubMed

The photodissociation dynamics of tert-C(4)H(9)Br and iso-C(4)H(9)Br has been studied at 234 and 265 nm using two-dimensional velocity map imaging technique. The translational energy and angular distributions have been analyzed for Br, Br(*), and tert-C(4)H(9) radical. The energy distribution of Br atom in the photodissociation of tert-C(4)H(9)Br is found to consist of two Gaussian components. The two components are correlated to two independent reaction paths on the excited potential energy surfaces: (1) the high-energy component from the prompt dissociation along the C-Br stretching mode and (2) the low-energy component from the repulsive mode along the C-Br stretching, coupled with some bending motions. For the energy distribution of Br(*) atom in the photodissociation of tert-C(4)H(9)Br, a third multiphoton dissociative ionization channel is observed at 265 nm in addition to the two energy components corresponding to channels (1) and (2). The energy distributions of Br and Br(*) atoms in the photodissociation of iso-C(4)H(9)Br can be fitted using only one Gaussian function indicating a single formation channel. Relative quantum yields for Br((2)P(32)) at 234 and 265 nm in the photodissociation of tert-C(4)H(9)Br are measured to be 0.76 and 0.65, respectively. For iso-C(4)H(9)Br, the measured value is Phi(234 nm)(Br)=0.81. The contribution of bending modes to Br and Br(*) is much more obvious in the photodissociation of tert-C(4)H(9)Br than in iso-C(4)H(9)Br. PMID:17115752

Wang, Yanmei; Zhang, Song; Wei, Zhengrong; Zheng, Qiusha; Zhang, Bing

2006-11-14

314

Method for one-step synthesis of methyl t-butyl ether  

SciTech Connect

In a method where t-butanol is reacted with methanol in a reaction zone in the presence of a catalyst to provide methyl-tert-butyl ether, the improvement of accomplishing the reaction in one-step which comprises using as a catalyst a Y-zeolite selected from the group consisting of: an ammonium-exchanged, thermally stable Y-zeolite having a Si:Al ratio of ca. 11:1; and a rare-earth exchanged zeolite having a Si:Al ratio of between 1.5:1 and 2:1; and continuously contacting said t-butanol and methanol in a molar amount of about 0.1 to 10 moles of methanol per mole of t-butanol with said catalyst at a temperature of about 80 C to about 180 C and a pressure of about atmospheric to about 1,000 psig to obtain the methyl-tertbutyl product, wherein at 1,802 C, the product comprises a two phase mix of an isobutylene-MTBE product-rich phase and a heavier aqueous methanol-rich phase.

Knifton, J.F.

1993-05-25

315

N-1-tert-butyl-substituted quinolones: in vitro anti-Mycobacterium avium activities and structure-activity relationship studies.  

PubMed Central

We determined the MICs of 63 quinolones against 14 selected reference and clinical strains of the Mycobacterium avium-Mycobacterium intracellulare complex. Sixty-one of the compounds were selected from the quinolone library at Parke-Davis, Ann Arbor, Mich., including N-1-tert-butyl-substituted agents. T 3761 and tosufloxacin were also tested. The activities of all 63 compounds were compared with those of ciprofloxacin and sparfloxacin. The results showed 45 of the quinolones to be active against the M. avium-M. intracellulare complex, with MICs at which 50% of the strains were inhibited (MIC50s) of less than 32 micrograms/ml. Twenty-four of these quinolones had activities equivalent to or greater than that of ciprofloxacin, and nine of them had activities equivalent to or greater than that of sparfloxacin. The most active compounds were the N-1-tert-butyl-substituted quinolones, PD 161315 and PD 161314, with MIC50s of 0.25 microgram/ml and MIC90s of 1 microgram/ml; comparable values for ciprofloxacin were 2 and 4 micrograms/ml, respectively, while for sparfloxacin they were 1 and 2 micrograms/ml, respectively. The next most active compounds, with MIC50s of 0.5 microgram/ml and MIC90s of 1 microgram/ml, were the N-1-cyclopropyl-substituted quinolones, PD 138926 and PD 158804. These values show that the tert-butyl substituent is at least as good as cyclopropyl in rendering high levels of antimycobacterial activity. However, none of the quinolones showed activity against ciprofloxacin-resistant laboratory-derived M. avium-M. intracellulare complex strains. A MULTICASE program-based structure-activity relationship analysis of the inhibitory activities of these 63 quinolones and 109 quinolones previously studied against the most resistant clinical strain of M. avium was also performed and led to the identification of two major biophores and two biophobes.

Klopman, G; Fercu, D; Renau, T E; Jacobs, M R

1996-01-01

316

The fate of di-(3,5-di-tert.-butyl-4-hydroxyphenyl)methane (Ionox 220) in the rat  

PubMed Central

1. A large proportion of a single oral dose of [14C]Ionox 220 to rats is eliminated in 24 days: 89·3–97·4% of the label is excreted in the faeces (much of this is eliminated in the first 4 days after dosage), 1% in the urine and less than 0·1% in the expired gases; 4·06% of 14C is present in the carcass and viscera after removal of the gut, and most of this is in the fatty tissues. 2. About 87% of 14C in the faeces is due to unchanged antioxidant, 5% to the quinone methide, 5% to the free acid and 3% to an unidentified polar constituent. Three-fifths of 14C in the urine is due to 3,5-di-tert.-butyl-4-hydroxybenzoic acid and the remainder to the ester glucuronide. In three individual animals, one-half of 14C in the bile is due to the free acid, one-quarter to the ester glucuronide and the remainder to unchanged antioxidant, whereas in another all of 14C in the bile is due to Ionox 220. About 97% of 14C in the body fat is due to unchanged antioxidant and the remainder to the free acid. 3. Up to 20% of a single oral dose of Ionox 220 is absorbed in rats: 13–14% is metabolized. 3,5-Di-tert.-butyl-4-hydroxybenzoic acid accounts for just over 5% of a dose of Ionox 220, 3,5-di-tert.-butyl-4-hydroxybenzoyl-?-d-glucopyranosiduronic acid for less than 0·4%, the quinone methide for just over 5% and an unidentified compound for less than 3%. 4. The physiological and biochemical implications of ingesting Ionox 220 are discussed.

Wright, A. S.; Crowne, R. S.; Hathway, D. E.

1966-01-01

317

Synthesis and transformations of bis(trialkylstannyl)acetylenes containing tert-butyl radicals  

SciTech Connect

When studying the transformations of tri-tert-butylstannyl trimethylstannyl acetylene (I) they found the activity of the Sn-C/sub sp/ bond varying (depending on the configuration of the alkyl radicals near the atom of tin) with the reagents, e.g., halogens, that rupture these bonds by an ion mechanism. Thus, iodination or bromination of compound (I) occurs mainly at the Me/sub 3/Sn-C/sub sp/ bond with the formation of tri-tert-butylstannyl halogenoacetyelens. When compound (I) was iodinated in ether at -40/sup 0/C, the ratio of the tri-tert-butylstannyl iodoacetylene to the tri-tert-butylstannyl iodide was found to be approximately 9:1. Bromination of compound (I) in pentane at -70/sup 0/C resulted in the formation of tri-tert-butylstannyl bromoacetylene and tri-tert-butylstannyl bromide in the ratio of 7:3.

Girbasova, N.V.; Bogoradovskii, E.T.; Zavgorodnii, V.S.

1986-03-10

318

[Antioxidative activity of thiophane [bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propyl)sulfide].  

PubMed

The antioxidant activity, mutagenicity, and genotoxicity of bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propyl)sulfide (thiophane) were studied using bacterial tests. The results of both an Ames test and SOS chromotest, as well as those studying the survival of E. coli cells deficient in enzymes responsible for the repair of DNA oxidative damage, testify to the fact that thiophane is not mutagenic and genotoxic, and it protects Salmonella typhimurium cells better than the well-known antioxidant trolox. PMID:19621058

Ovchinnikova, L P; Rotskaia, U N; Vasiunina, E A; Sinitsina, O I; Kandalintseva, N V; Prosenko, A E; Nevinski?, G A

319

Ion kinetic energy distributions and cross sections for the electron impact ionization of ethyl tert-butyl ether  

NASA Astrophysics Data System (ADS)

The kinetic energy distributions and the cross sections of the ions produced in the electron impact of ethyl tert-butyl ether (ETBE) have been studied by time of flight (TOF) mass spectrometry. The kinetic energy distributions have been deduced from the TOF peak shape analysis and a Montecarlo simulation method of the ion trajectories has been used to evaluate the collection efficiency of the spectrometer as a function of the ion initial kinetic energy. The measured ion yields have been corrected for the collection efficiency and the partial and total ionization cross sections of ETBE determined in the range 20-150 eV.

Di Palma, T. M.; Apicella, B.; Armenante, M.; Velotta, R.; Wang, X.; Spinelli, N.

2005-11-01

320

1,4-Bis[4-(tert-butyl-diphenyl-silyl)buta-1,3-diyn-yl]benzene  

PubMed Central

The title centrosymmetric mol­ecule, C46H42Si2, is composed of a central benzene ring with buta-1,3-diynyl chains at positions 1 and 4. These chains are terminated by tert-butyl­diphenyl­silyl groups, hence the molecule is dumbbell in shape. The mol­ecules are connected via C—H?? inter­actions in the structure, so forming an undulating two-dimensional network in the bc plane. There is also a weak ?–? inter­action involving centrosymmetrically related phenyl rings with a centroid–centroid distance of 3.8359?(11)?Å.

Thevenet, Damien; Neier, Reinhard; Stoeckli-Evans, Helen

2010-01-01

321

Red fluorescent emitting materials based on di-tert-butyl chromene derivatives for organic light-emitting diodes.  

PubMed

In this paper are described two di-tert-butyl chromene-containing red fluorescent materials (Red 1 and Red 2). To explore the electroluminescence properties of these materials, multilayered OLEDs using these materials as dopants in a Alq3 host were fabricated. In particular, a device using Red 2 as the dopant material showed maximum luminous efficiencies and power efficiencies of 1.14 cd/A and 0.58 Im/W, respectively. The CIEx,y coordinates of this device were (0.67, 0.32) at 7.0 V. PMID:23646772

Na, Eun Jae; Lee, Kum Hee; Han, Hoon; Kim, Young Kwan; Yoon, Seung Soo

2013-01-01

322

Biotransformation of [(12)C]- and [(13)C]-tert-amyl methyl ether and tert-amyl alcohol.  

PubMed

tert-Amyl methyl ether (TAME) is intended for use as a gasoline additive to increase oxygen content. Increased oxygen content in gasoline reduces tailpipe emissions of hydrocarbons and carbon monoxide from cars. Due to possible widespread use of TAME, the toxicity of TAME is under investigation. We studied the biotransformation of TAME in rats and one human volunteer after inhalation of (12)C- or (13)C-labeled TAME. In addition, the biotransformation of [(13)C]-tert-amyl alcohol was studied in rats after gavage. Urinary metabolites were identified by GC/MS and (13)C NMR. Rats (two males and two females) were individually exposed to 2000 ppm [(12)C]- or [(13)C]TAME for 6 h, and urine was collected for 48 h. Free and glucuronidated 2-methyl-2,3-butanediol and a glucuronide of tert-amyl alcohol were identified by (13)C NMR, GC/MS, and LC/MS/MS as major urinary metabolites on the basis of the relative intensities of the (13)C NMR signals. The presence of several minor metabolites was also indicated by (13)C NMR; they were identified as tert-amyl alcohol, 2-hydroxy-2-methylbutyric acid, and 3-hydroxy-3-methylbutyric acid. One human volunteer was exposed to an initial concentration of 27 000 ppm [(13)C]TAME by inhalation for 4 min from a 2 L gas sampling bag, and metabolites of TAME excreted in urine were analyzed by (13)C NMR. All TAME metabolites identified in rats were also present in the human urine samples. To study tert-amyl alcohol biotransformation, male rats (n = 3) were treated with 250 mg/kg [(13)C]-tert-amyl alcohol dissolved in corn oil by gavage, and urine was collected for 48 h. (13)C NMR of the urine samples showed the presence of metabolites identical to those in the urine of [(13)C]TAME-treated rats. Our results suggest that TAME is extensively metabolized by rats and humans to tert-amyl alcohol which may be further oxidized to diols and carboxylic acids. These reactions are likely mediated by cytochrome P450-dependent oxidations. PMID:10525272

Amberg, A; Bernauer, U; Scheutzow, D; Dekant, W

1999-10-01

323

Aggregation in dilute aqueous tert-butyl alcohol solutions: Insights from large-scale simulations  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations employing up to 64 000 particles are used to investigate aggregation and microheterogeneity in aqueous tert-butyl alcohol (TBA) solutions for TBA mole fractions Xt <= 0.1. Four different force fields are considered. It is shown that the results obtained can be strongly dependent on the particular force field employed, and can be significantly influenced by system size. Two of the force fields considered show TBA aggregation in the concentration range Xt ~ 0.03 - 0.06. For these models, systems of 64 000 particles are minimally sufficient to accommodate the TBA aggregates. The structures resulting from TBA aggregation do not have a well-defined size and shape, as one might find in micellar systems, but are better described as TBA-rich and water-rich regions. All pair correlation functions exhibit long-range oscillatory behavior with wavelengths that are much larger than molecular length scales. The oscillations are not strongly damped and the correlations can easily exceed the size of the simulation cell, even for the low TBA concentrations considered here. We note that these long-range correlations pose a serious problem if one wishes to obtain certain physical properties such as Kirkwood-Buff integrals from simulation results. In contrast, two other force fields that we consider show little sign of aggregation for Xt <~ 0.08. In our 64 000 particle simulations all four models considered show demixing-like behavior for Xt >~ 0.1, although such behavior is not evident in smaller systems of 2000 particles. The meaning of the demixing-like behavior is unclear. Since real TBA-water solutions do not demix, it might be an indication that all four models we consider poorly represent the real system. Alternatively, it might be an artifact of finite system size. Possibly, the apparent demixing indicates that for Xt >~ 0.1, the stable TBA aggregates are simply too large to fit into the simulation cell. Our results provide a view of the possible nature of microheterogeneity in dilute TBA-water solutions, and of the associated long correlation lengths. It is clear that system size can be a very important factor in simulations of these solutions, and must be taken into account in the evaluation and development of TBA-water force fields.

Gupta, Rini; Patey, G. N.

2012-07-01

324

Dynamic properties of a poly(tert-butyl acrylate)/gold nanocomposite system  

NASA Astrophysics Data System (ADS)

Polymer dispersions play an important role in modern technology. These systems serve roles ranging from discontinuous fiber composites to magnetic storage media. The diffusional behavior of nanometer scale gold particles embedded in a poly (tert-butyl acrylate) (PTBA) matrix, as well as the effect of the gold particles on the matrix polymer are investigated in this thesis. The primary focus of the work consisted of diffusion experiments in which a very thin discontinuous film of gold particles was sandwiched between two thin PTBA layers, and heated to allow the particle suspension to diffuse by Brownian motion. Diffusion depth profiles were obtained using Rutherford Backscattering Spectrometry (RBS). The diffusion profiles were analyzed using a form of the Einstein equation, which yielded an effective degree of polymerization of a PTBA chain of sufficient length to mimic the diffusive behavior of the gold particles as measured by RBS. The results of the diffusion experiments showed that the diffusion coefficient of the particles obeyed the same temperature dependence as the bulk homopolymer, and that the number of effective monomer segments was extremely large, the equivalent of thousands of polymer chains diffusing as one unit. A model was constructed which assumed that polymer chains were kinetically grafted to gold particles, and the gold particles bridged by the kinetically grafted polymer strands. Numerical calculations formed the basis of the model, and our predictions are in very good qualitative agreement with the experimental results. Whereas the diffusion experiments probe the effects of the polymer matrix on the mobility of the gold particles, additional experiments were carried out to investigate the effect of the particles on the polymer melt. Dewetting experiments examining the rim velocity of a growing hole in a thin film of polymer with and without gold particles present show at most an order of magnitude reduction in dewetting velocity when particles are present. The dewetting experiments show that the polymer is affected by the presence of the particles to a much lower extent than the mobility of the particles is affected by the polymer.

Cole, Douglas Hampton

325

Total pressure measurements of binary mixtures containing tert-amyl methyl ether and tert-amyl alcohol  

SciTech Connect

Vapor-liquid equilibrium data are needed for the reformulation of gasoline to meet Federal Clear Air Act standards. Oxygenates, such as ethers and alcohols, are known to reduce Co emissions from motor vehicles, and ethers are used as a substitute for aromatics in gasoline to improve the octane rating. The vapor pressure of pure tert-amyl methyl ether (TAME) was measured together with isothermal P-x data for mixtures of pentane + TAME and pentane + tert-amyl alcohol (TAOH) at temperatures between 70 and 110 C. Also, activity coefficients at infinite dilution for the binary mixtures of TAME + TAOH were obtained in the 90--120 C temperature range. The P-T-x data were correlated using the Peng-Robinson equation of state separately with the van der Waals and Wong-Sandler mixing rules.

Semar, S.; Sandler, S.I. [Univ. of Delaware, Newark, DE (United States); Antosik, M. [Polish Academy of Sciences, Warszawa (Poland). Inst. of Physical Chemistry

1995-05-01

326

A one-pot synthesis of a branched tertiary phosphine oxide from red phosphorus and 1-( tert-butyl)-4-vinylbenzene in KOH–DMSO: an unusually facile addition of P-centered nucleophiles to a weakly electrophilic double bond  

Microsoft Academic Search

Red phosphorus reacts with 1-(tert-butyl)-4-vinylbenzene in a superbase media (KOH–DMSO, 90–100°C, 3h) to give tris[4-(tert-butyl)phenethyl]phosphine oxide in 77% yield. Microwave activation of the reaction affords the phosphine oxide in 82% yield in 6min.

Boris A. Trofimov; Svetlana F. Malysheva; Nina K. Gusarova; Vladimir A. Kuimov; Nataliya A. Belogorlova; Boris G. Sukhov

2008-01-01

327

Structural effects on the C-S bond cleavage in aryl tert-butyl sulfoxide radical cations.  

PubMed

The oxidation of a series of aryl tert-butyl sulfoxides (4-X-C6H4SOC(CH3)3: 1, X = OCH3; 2, X = CH3; 3, X = H; 4, X = Br) photosensitized by 3-cyano-N-methylquinolinium perchlorate (3-CN-NMQ(+)) has been investigated by steady-state irradiation and nanosecond laser flash photolysis (LFP) under nitrogen in MeCN. Products deriving from the C-S bond cleavage in the radical cations 1(+•)-4(+•) have been observed in the steady-state photolysis experiments. By laser irradiation, the formation of 3-CN-NMQ(•) (?(max) = 390 nm) and 1(+•)-4(+•) (?(max) = 500-620 nm) was observed. A first-order decay of the sulfoxide radical cations, attributable to C-S bond cleavage, was observed with fragmentation rate constants (k(f)) that decrease by increasing the electron donating power of the arylsulfinyl substituent from 1.8 × 10(6) s(-1) (4(+•)) to 2.3 × 10(5) s(-1) (1(+•)). DFT calculations showed that a significant fraction of the charge is delocalized in the tert-butyl group of the radical cations, thus explaining the small substituent effect on the C-S bond cleavage rate constants. Via application of the Marcus equation to the kinetic data, a very large value for the reorganization energy (? = 62 kcal mol(-1)) has been calculated for the C-S bond scission reaction in 1(+•)-4(+•). PMID:23581281

Cavattoni, Tullio; Del Giacco, Tiziana; Lanzalunga, Osvaldo; Mazzonna, Marco; Mencarelli, Paolo

2013-04-25

328

Syntheses, structures, and photoisomerization of (E)- and (Z)-2-tert-butyl-9-(2,2,2-triphenylethylidene)fluorene.  

PubMed

"Sterically geared" 9-(2,2,2-triphenylethylidene)fluorene (1) is of potential interest as a photoactive moiety in molecular devices, and the 2-tert-butyl derivative (6) has been synthesized to investigate photoisomerization. E and Z stereoisomers of 6 were separated and identified by X-ray crystallography. The tert-butyl group does not introduce additional strain, and its close proximity to the trityl group in the Z isomer suggests an attractive van der Waals interaction. The UV spectra of (E)-6 and (Z)-6 are nearly identical, showing absorption bands that are similar to those of fluorene occurring at wavelengths longer than 240 nm. Photoisomerization of 6 was investigated at 266, 280 and 320 nm. Solutions initially containing only (E)-6 or (Z)-6 were irradiated with pulsed laser light, monitoring isomerization by 1H NMR spectroscopy. Negligible photodecomposition was observed when the solutions were agitated by N2 ebullition. Experimental data were fitted to theoretical curves to obtain photoisomerization quantum yields (phi(ZE) and phi(EZ)) ranging from 0.04 to 0.09. This first photoisomerization study of a dibenzofulvene reveals significant quantum yields, despite theoretical prediction of inefficient or negligible isomerization of the parent hydrocarbon, fulvene. Thermal isomerization of 6 at 270 degrees C (t(1/2) = 120 min) was also followed by 1H NMR spectroscopy, resulting in an estimated activation energy (deltaG(double dagger)) of 43 kcal/mol. PMID:16366613

Barr, James W; Bell, Thomas W; Catalano, Vincent J; Cline, Joseph I; Phillips, Daniel J; Procupez, Rolando

2005-12-29

329

Controlled Ethyl tertButyl Ether (ETBE) Exposure of Male Volunteers  

Microsoft Academic Search

Ethyltert-butyl ether (ETBE) might replace methyltert-butyl ether (MTBE), a widely used additive in unleaded gasoline. The aim of this study was to evaluate uptake and disposition of ETBE, and eight healthy male volunteers were exposed to ETBE vapor (0, 5, 25, and 50 ppm) during 2 h of light physical exercise. ETBE and the proposed metabolitestert-butyl alcohol (TBA) and acetone

Annsofi Nihlén; Agneta Löf; Gunnar Johanson

1998-01-01

330

Mono-, di-, and tri-tert-butyl ethers of glycerol. A molecular spectroscopic study.  

PubMed

MS, NMR, IR and Raman molecular spectroscopy techniques were applied to characterize 3-tert-butoxy-propane-1,2-diol, 1,3-di-tert-butoxy-propan-2-ol, and 1,2,3-tri-tert-butoxy-propane. These ethers are the main products of glycerol etherification reaction and are excellent oxygen additives for diesel fuel. Computational DFT/ B3LYP/6-31G** studies were performed to support and rationalize both vibrational spectroscopy analysis and the isomer ratio. PMID:17085068

Jamróz, Ma?gorzata E; Jarosz, Ma?gorzata; Witowska-Jarosz, Janina; Bednarek, Elzbieta; Tecza, Witold; Jamróz, Micha? H; Dobrowolski, Jan Cz; Kije?ski, Jacek

2006-09-29

331

The effect of tert-butyl hydroperoxide on hepatic transcriptome expression patterns in the striped sea bream (Lithognathus mormyrus; Teleostei).  

PubMed

The study was aimed at examining the effects of tert-butyl hydroperoxide (tBHP) on hepatic transcriptome expression patterns of the teleost fish Lithognathus mormyrus. tBHP is an organic hydro-peroxide, widely used as a model pro-oxidant. It generates the reactive oxygen species (ROS) tert-butoxyl and tert-butylperoxyl. Complementary DNAs of tBHP-treated vs control fish were applied onto a previously produced cDNA microarray of approximately 1500 unique sequences. The effects of the tBHP application were demonstrated by leukocyte infiltration into the liver and by differential expression of various genes, some already known to be involved in ROS-related responses. Indicator genes of putative ROS effects were: aldehyde dehydrogenase 3A2, Heme oxygenase and the hemopexin-like protein. Putative indicators of transendothelial leukocyte migration and function were: p22phox, Rac1 and CD63-like genes. Interestingly, 7-dehydrocholesterol reductase was significantly down-regulated in response to all treatments. Several non-annotated genes revealed uniform directions of differential expression in response to all treatments. PMID:20553222

Auslander, Meirav; Neumann, Peter M; Tom, Moshe

2010-09-01

332

DNA Methylation Analysis of the Promoter Region of the Human Telomerase Reverse Transcriptase (hTERT) Gene  

Microsoft Academic Search

The promoter of the hTERT gene encoding the catalytic subunit of telomerase was recently cloned and has a dense CG-rich CpG island, suggesting a role for methylation in regulation of hTERT expression. In this study, we have initiated the analysis of the regulation of hTERT expression by examining the methylation status of up to 72 CpG sites extending from 500

Theodora R. Devereux; Izumi Horikawa; Colleen H. Anna; Lois A. Annab; Cynthia A. Afshari; J. Carl Barrett

1999-01-01

333

Exposure to methyl tertiary-butyl ether from oxygenated gasoline in Stamford, Connecticut  

SciTech Connect

In 1993, state health officials in Connecticut invited the Centers for Disease Control and Prevention (CDC) to assist in an investigation of exposure to methyl tertiary-butyl ether in oxygenated gasoline in Stamford, Connecticut. Venous blood samples were collected from 14 commuters and from 30 other persons who worked in the vicinity of traffic or automobiles, and the samples were analyzed for methyl tertiary-butyl ether, tertiary-butyl alcohol, benzene, m-/p-xylene, o-xylene, and toluene. The highest levels of methyl tertiary-butyl ether in blood were measured among gasoline service station attendants (median = 15 {mu}g/l, range = 7.6-28.9 {mu}g/l). Blood levels of methyl tertiary-butyl ether were highly variable among persons who worked in car-repair shops (median = 1.73 {mu}g/l, range = 0.17-36.7 {mu}/l) and were generally lowest among commuters (median = 0.11 {mu}g/l, range = <0.05-2.60 {mu}g/l). Blood levels of methyl tertiary-butyl ether were correlated strongly with personal-breathing-zone samples of methyl tertiary-butyl ether and blood levels of other volatile organic compounds. This exposure information should prove useful to a future risk analysis of this high-volume chemical. 18 refs., 5 figs., 2 tabs.

White, M.C.; Johnson, C.A.; Ashley, D.L. [National Center for Environmental Health, Atlanta, GA (United States)] [and others

1995-05-01

334

Tetrabutylammonium tetra ( tert-butyl alcohol) coordinated fluoride-an efficient reagent for the synthesis of fluorine derivatives of phosphorus(V) compounds  

Microsoft Academic Search

Direct conversion of phosphorus(V) chlorides to the corresponding phosphorus(V) fluorides was achieved using a solid reagent, tetrabutylammonium tetra (tert-butyl alcohol) coordinated fluoride. The phosphorus(V) fluorides were directly synthesized and efficiently isolated in very good yields.

Hemendra K. Gupta; Deepak Pardasani; Avik Mazumder; Ajay Kumar Purohit; Devendra K. Dubey

2009-01-01

335

Hydroxyalkylation of alpha-C-H bonds of tetrahydrofuran with aldehydes in the presence of triethylborane and tert-butyl hydroperoxide.  

PubMed

The alpha-hydroxyalkylation of tetrahydrofuran with aldehydes via radical C-H abstraction was conducted using triethylborane in the presence of tert-butyl hydroperoxide. This study presents a rare instance of direct intermolecular radical addition of unactivated cyclic ether to aldehydes. PMID:12530897

Yoshimitsu, Takehiko; Arano, Yoshimasa; Nagaoka, Hiroto

2003-01-24

336

Delayed Treatment with ?-Phenyl- N- tert-butyl Nitrone (PBN) Attenuates Secondary Mitochondrial Dysfunction after Transient Focal Cerebral Ischemia in the Rat  

Microsoft Academic Search

The present experiments were undertaken to explore the mechanisms of secondary brain damage in focal ischemia of long duration (2 h), followed by recirculation. Recirculation has previously been found to cause partial recovery and secondary deterioration of cellular bioenergetic state, the subsequent damage being ameliorated by a free radical spin trap, ?-phenyl-N-tert-butyl nitrone (PBN), even when the drug was given

Satoshi Kuroda; Ken-ichiro Katsura; Lars Hillered; Timothy E. Bates; Bo K. Siesjö

1996-01-01

337

Conformations and Barriers to Methyl Group Internal Rotation in Two Asymmetric Ethers: Propyl Methyl Ether and Butyl Methyl Ether  

NASA Astrophysics Data System (ADS)

The conformational preferences of the O-C-C-C unit are important in many biological systems with the unit generally preferring a gauche configuration compared to an anti configuration. Butyl methyl ether and propyl methyl ether provide very simple systems for this phenomenom to manifest. Pure rotational spectra of the title molecules have been recorded using chirped pulse Fourier transform microwave spectroscopy (CP-FTMW). In the case of butyl methyl ether, only one conformer has been observed. This conformer has torsional angles of COCC = 180°, OCCC = 62° and CCCC = 180° (anti-gauche-anti) and rotational constants of A = 10259.4591(33) MHz, B = 1445.6470(13) MHz, and C = 1356.2944(14) MHz. The rotational spectrum was doubled and has been analyzed to produce an effective barrier to methyl group internal rotation of 780(35) cm-1. A prior rotational spectroscopic study on propyl methyl ether had focused only on the high energy anti-anti conformer. We have analyzed spectra from the lowest energy anti-gauche conformer and the spectroscopic constants will be presented. A summary of the differences in conformational energies and methyl group internal rotation barriers for the class of aliphatic asymmetric ethers will be presented. K. N. Houk, J. E. Eksterowicz, Y.-D. Wu, C. D. Fuglesang, D. B. Mitchell. J. Am. Chem. Soc. 115 (4170), 1993. Hiroshi Kato, Jun Nakagawa, Michiro Hayashi. J. Mol. Spectrosc. 80 (272), 1980.

Long, B. E.; Dechirico, F.; Cooke, S. A.

2012-06-01

338

Decomposition of di-tert-butyl peroxide on the surface of KCl/SiO/sub 2/  

SciTech Connect

A study was carried out on carbon deposition on the surface of 5% KCl/SiO/sub 2/ upon the decomposition of di-tert-butyl peroxide, (DTBP). The EPR spectra of the paramagnetic sites in the carbon deposit depend on the amount of peroxide decomposed. The EPR spectrum of the RO/sub 2/ radicals stabilized on KCl crystals was recorded. Carbonization of the surface as a result of the decomposition of DTBP is responsible for the chemical reactions, including the reactions of adsorbed RO/sub 2/ radicals, the formation of carbon deposits with strongly delocalized electrons in the conductance band, and the reaction of the radicals with localized paramagnetic sites, which should hinder the removal of the radicals from the surface into the gas phase.

Chaltykyan, M.T.; Lazarev, E.G.; Aliev, R.K.; Gazaryan, K.G.; Garibyan, T.A.; Nalbandyan, A.B.; Gencheva, L.; Kotsev, N.K.; Shopov, D.M.

1989-02-01

339

Vibrational spectroscopic investigations and computational study of 5-tert-Butyl-N-(4-trifluoromethylphenyl)pyrazine-2-carboxamide  

NASA Astrophysics Data System (ADS)

Pyrazine and its derivatives form an important class of compounds present in several natural flavors and complex organic molecules. Quantum chemical calculations of the equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman activities of 5-tert-Butyl-N-(4-trifluoromethylphenyl)pyrazine-2-carboxamide in the ground state were carried out by using density functional methods. Potential energy distribution of normal modes of vibrations was done using GAR2PED program. Nonlinear optical behavior of the examined molecule was investigated by the determination of first hyperpolarizability. The calculated HOMO and LUMO energies show the chemical activity of the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The calculated geometrical parameters are in agreement with that of similar derivatives. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis.

Joseph, Tomy; Varghese, Hema Tresa; Yohannan Panicker, C.; Viswanathan, K.; Dolezal, Martin; Manojkumar, T. K.; Alsenoy, Christian Van

2013-09-01

340

Ethyl tert-butyl ether (ETBE) synthesis on H-Mordenite: Gas-phase kinetics and DRIFTS studies  

SciTech Connect

The ethyl tert-butyl ether (ETBE) formation between 313 and 363 K over an H-mordenite catalyst was studied in a packed-bed flow catalytic reactor at atmospheric pressure. An activation energy of 82 kJ/mol and reaction orders in isobutene and ethanol of 0.8 and -0.8 were found. In situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) was used to study the state of the catalyst under reaction conditions. The IR studies, coupled with the reaction kinetics information, are consistent with the idea that the stability of the H-mordenite catalyst requires the protective action of ethanol to prevent the occurrence of isobutene oligomerization products. The high ethanol concentrations found in the zeolite pores under the temperature and pressure conditions employed is also responsible for reaction inhibition. 27 refs., 13 figs., 1 tab.

Larsen, G.; Lotero, E.; Marquez, M. [Univ. of Nebraska-Lincoln, NB (United States)] [and others

1995-12-01

341

Ethers from ethanol. 1: Equilibrium thermodynamic analysis of the liquid-phase ethyl tert-butyl ether reaction  

SciTech Connect

The equilibrium-limited liquid-phase synthesis of ethyl tert-butyl ether (ETBE) from the combination of ethanol and isobutylene over an ion-exchange resin catalyst, typically Amberlyst 15, is a reaction of considerable industrial importance now. An equilibrium constant relationship is developed here for the liquid-phase ETBE reaction by following three alternative thermodynamic pathways and critically evaluating the resulting expressions. The final theoretical expression is compared against experimental data obtained in this study from the decomposition of ETBE over Amberlyst 15, as well as that reported in the literature for ETBE synthesis. It can thus be used with reasonable confidence for the calculation of the equilibrium constant, despite a dearth of thermodynamic data yet available in the literature for ETBE. In addition, an expression is derived for the gas-phase equilibrium constant and compared to experimental data from the literature. The thermodynamic approach utilized here should also be useful for other liquid-phase reaction systems.

Jensen, K.L.; Datta, R. (Univ. of Iowa, Iowa City, IA (United States). Dept. of Chemical and Biochemical Engineering)

1995-01-01

342

Functional polyolefins: poly(ethylene)-graft-poly(tert-butyl acrylate) via atom transfer radical polymerization from a polybrominated alkane.  

PubMed

Poly(cis-cyclooctene) is synthesized via ring-opening metathesis polymerization in the presence of a chain-transfer agent and quantitatively hydrobrominated. Subsequent graft polymerization of tert-butyl acrylate (tBA) via Cu-catalyzed atom transfer radical polymerization (ATRP) from the non-activated secondary alkyl bromide moieties finally results in PE-g-PtBA copolymer brushes. By varying the reaction conditions, a series of well-defined graft copolymers with different graft densities and graft lengths are prepared. The maximum extent of grafting in terms of bromoalkyl groups involved is approximately 80 mol%. DSC measurements on the obtained graft copolymers reveal a decrease in T(m) with increasing grafting density. PMID:22095785

Xu, Guangjuan; Wang, Dongren; Buchmeiser, Michael R

2011-11-18

343

The spin trap reagent alpha-phenyl-N-tert-butyl nitrone prevents 'ecstasy'-induced neurodegeneration of 5-hydroxytryptamine neurones.  

PubMed

Administration of a single dose (10 mg/kg i.p.) of 3,4-methylenedioxy-methamphetamine (MDMA or 'ecstasy') produced a 40% loss of 5-hydroxytryptamine (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in cortex and hippocampus of Dark Agouti rats 7 days later. Binding of [3H]paroxetine to the presynaptic 5-HT nerve terminals in cortex was decreased by approximately 30%. Injection of the spin trap reagent alpha-phenyl-N-tert-butyl nitrone (PBN; 150 mg/kg i.p.) 10 min prior and 120 min post MDMA administration totally prevented the loss in [3H]paroxetine binding in the cortex and attenuated the loss of 5-HT and 5-HIAA in both brain regions. PBN alone had no effect on [3H]paroxetine binding or brain 5-HT content. These data suggest that MDMA produces neurodegeneration of 5-HT neurones because of reactive free radical formation. PMID:8566105

Colado, M I; Green, A R

1995-07-14

344

Cytotoxicity of Dihydroartemisinin Toward Molt-4 Cells Attenuated by N-Tert-butyl-alpha-phenylnitrone and Deferoxamine.  

PubMed

Derivatives of artemisinin, a compound extracted from the wormwood Artemisia annua L, have potent anticancer properties. The anticancer mechanisms of artemisinin derivatives have not been fully-elucidated. We hypothesize that the cytotoxicity of these compounds is due to the free radicals formed by interaction of their endoperoxide moiety with intracellular iron in cancer cells. The effects of N-tert-butyl-alpha-phenylnitrone (PBN), a spin-trap free radical scavenger, and deferoxamine (DX), an iron chelating agent, on the in vitro cytotoxicity of dihyroartemisinin (DHA) toward Molt-4 human T-lymphoblastoid leukemia cells were investigated in the present study. Dihydroartemisinin effectively killed Molt-4 cells in vitro. Its cytotoxicity was significantly attenuated by PBN and DX. Based on the data of our present and previous studies, we conclude that one anticancer mechanism of dihydroartemisinin is the formation of toxic-free radicals via an iron-mediated process. PMID:24123007

Chan, Ho Wing; Singh, Narendra P; Lai, Henry C

2013-10-01

345

Study of an aquifer contaminated by ethyl tert-butyl ether (ETBE): site characterization and on-site bioremediation.  

PubMed

Ethyl tert-butyl ether (ETBE) was detected at high concentration (300mgL(-1)) in the groundwater below a gas-station. No significant carbon neither hydrogen isotopic fractionation of ETBE was detected along the plume. ETBE and BTEX biodegradation capacities of the indigenous microflora Pz1-ETBE and of a culture (MC-IFP) composed of Rhodococcus wratislaviensis IFP 2016, Rhodococcus aetherivorans IFP 2017 and Aquincola tertiaricarbonis IFP 2003 showed that ETBE and BTEX degradation rates were in the same range (ETBE: 0.91 and 0.83 mg L(-1)h(-1) and BTEX: 0.64 and 0.82 mg L(-1)h(-1), respectively) but tert-butanol (TBA) accumulated transiently at a high level using Pz1-ETBE (74 mg L(-1)). An on-site pilot plant (2m(3)) filled with polluted groundwater and inoculated by MC-IFP, successfully degraded four successive additions of ETBE and gasoline. However, an insignificant ETBE isotopic fractionation was also accompanying this decrease which suggested the involvement of low fractionating-strains using EthB enzymes, but required of additional proofs. The ethB gene encoding a cytochrome P450 involved in ETBE biodegradation (present in R. aetherivorans IFP 2017) was monitored by quantitative real-time polymerase chain reaction (q-PCR) on DNA extracted from water sampled in the pilot plant which yield up to 5×10(6) copies of ethB gene per L(-1). PMID:22177017

Fayolle-Guichard, Françoise; Durand, Jonathan; Cheucle, Mathilde; Rosell, Mònica; Michelland, Rory Julien; Tracol, Jean-Philippe; Le Roux, Françoise; Grundman, Geneviève; Atteia, Olivier; Richnow, Hans H; Dumestre, Alain; Benoit, Yves

2011-11-28

346

The formation of byproducts in the reaction of synthesis of isopropyl tert-butyl ether from isopropyl alcohol and isobutene on an acidic macroporous copolymer  

Microsoft Academic Search

The effect of temperature and of the initial molar isopropanol-isobutene ratio, RAO, on byproducts formation in isopropyl tert-butyl ether (IPTBE) synthesis in the presence of the resin Bayer K-2631 were determined. The formation of diisopropyl ether, diisobutene (2,4,4-trimethyl-l-pentene, and 2,4,4-trimethyl-2-pentene isomers), and tert-butanol was studied in the temperature range 30–80°C, with RA0 ranging from 1.0 to 4.3. The formation of

J. Tejero; A. Calderón; F. Cunill; J. F. Izquierdo; M. Iborra

1997-01-01

347

Evaluation of granular activated carbon technology for the removal of methyl tertiary butyl ether (MTBE) from drinking water.  

PubMed

This study evaluated granular activated carbons (GACs) using rapid small-scale column tests (RSSCTs) on methyl tert-butyl ether (MTBE) levels from 20 to 2000 microg/L, with or without the presence of tert-butyl alcohol, benzene, toluene, p-xylene (BTX) in two groundwater (South Lake Tahoe Utility District [Lake Tahoe, CA] and Arcadia Well Field [Santa Monica, CA]) and a surface water source (Lake Perris, CA). Direct comparison between two GACs was made for RSSCTs conducted with surface water from Lake Perris. The impact of natural organic matter on GAC performance was investigated and found to correspond with total organic carbon concentration in the three source waters. Significant reduction in GAC performance for MTBE due to competitive adsorption from soluble fuel components (e.g., BTX) was observed. Little or no difference in GAC usage rate or bed life was detected as the empty-bed contact time is changed from 10 to 20 min for RSSCTs conducted in the two groundwater sources, whereas the RSSCTs conducted in the surface water source exhibited significant increase in GAC usage rate as the empty-bed contact time is decreased from 20 to 10 min. This finding suggests that the higher NOM content of the surface water over the groundwater sources caused a greater competitive-adsorption effect that made more sites on the GAC to be unavailable to MTBE, thus decreasing its rate of adsorption and GAC performance for MTBE. Finally, the impact of differential influent MTBE concentration on GAC performance was demonstrated. PMID:12502065

Shih, Tom C; Wangpaichitr, Medhi; Suffet, Mel

2003-01-01

348

Effect of caffeic acid on tert-butyl hydroperoxide-induced oxidative stress in U937  

Microsoft Academic Search

Nonvitamin phenolic compounds are ubiquitous in food plants and therefore potentially present in human plasma in a diet-dependent concentration. The aim of this study was to evaluate the ability of caffeic acid, a phenolic acid with antioxidant activity, to affect cellular response in U937 human monocytic cells to t-butyl hydroperoxide-induced oxidative stress. In our experimental conditions caffeic acid was incorporated

Mirella Nardini; Paola Pisu; Vincenzo Gentili; Fausta Natella; Maurizio Di; FeliceEnza Piccolella; Cristina Scaccini

1998-01-01

349

ESR characterization of a novel spin-trapping agent, 15N-labeled N-tert-butyl-alpha-phenylnitrone, as a nitric oxide donor.  

PubMed

We previously found that one of the pharmacological effects of N-tert-butyl-alpha-phenylnitrone (PBN) is the release of nitric oxide (NO) under oxidative conditions. However, to confirm this hypothesis in vivo, NO released from PBN must be distinguished from NO produced in biological systems, and therefore we undertook the synthesis of PBN using labeled 15N to identify its corresponding 15NO in vivo. The properties were examined with an ESR spectrometer. To synthesize 15N-PBN, the starting material, ammonium-15N chloride, was converted to 2-amino-15N-2-methylpropane, oxidized to 2-methyl-2-nitropropane-15N, and finally reacted with benzaldehyde to give 15N-PBN. The final product was purified by repeated sublimation. With ferrous sulfate-methyl glucamine dithiocarbamate complex, Fe (MGD)2, as a trapping agent to measure the NO levels of 15N-PBN or 14N-PBN in vitro, the peak intensity of 15NO[Fe(MGD)2] was over 50% stronger than that of 14NO[Fe(MGD)2], and that 15NO and 14NO had the corresponding two-and three line hyperfine structures due to their nuclear spin quantum numbers. Subsequently, the ESR spectrum of 15NO derived from 15N-PBN was significantly different than that of lipopolysaccharide (LPS)-induced NO, which was derived from biological cells, and therefore we have demonstrated the possibility to distinguish 15NO from PBN and 14NO generated from cells. These results suggested that 15N-PBN is a useful molecule, not only as a spin-trapping agent, but also as an NO donor to explore the pharmacological mechanisms of PBN in vivo. PMID:12450131

Saito, Kieko; Yoshioka, Hisashi

2002-10-01

350

Methyl tertiary-butyl ether: studies for potential human health hazards.  

PubMed

When methyl tertiary-butyl ether (MTBE) in gasoline was first introduced to reduce vehicle exhaust emissions and comply with the Clean Air Act, in the United States, a pattern of complaints emerged characterised by seven "key symptoms." Later, carefully controlled volunteer studies did not confirm the existence of the specific key symptoms, although one study of self-reported sensitive (SRS) people did suggest that a threshold at about 11-15% MTBE in gasoline may exist for SRSs in total symptom scores. Neurobehavioral and psychophysiological studies on volunteers, including SRSs, found no adverse responses associated with MTBE at likely exposure levels. MTBE is well and rapidly absorbed following oral and inhalation exposures. Cmax values for MTBE are achieved almost immediately after oral dosing and within 2 h of continuous inhalation. It is rapidly eliminated, either by exhalation as unchanged MTBE or by urinary excretion of its less volatile metabolites. Metabolism is more rapid humans than in rats, for both MTBE and tert-butyl alcohol (TBA), its more persistent primary metabolite. The other primary metabolite, formaldehyde, is detoxified at a rate very much greater than its formation from MTBE. MTBE has no specific effects on reproduction or development, or on genetic material. Neurological effects were observed only at very high concentrations. In carcinogenicity studies of MTBE, TBA, and methanol (included as an endogenous precursor of formaldehyde, without the presence of TBA), some increases in tumor incidence have been observed, but consistency of outcome was lacking and even some degree of replication was observed in only three cases, none of which had human relevance: alpha(2u)-globulin nephropathy-related renal tubule cell adenoma in male rats; Leydig-cell adenoma in male rats, but not in mice, which provide the better model of the human disease; and B-cell-derived lymphoma/leukemia of doubtful pathogenesis that arose mainly in lungs of orally dosed female rats. In addition, hepatocellular adenomas were significantly higher in female CD-1 mice and thyroid follicular-cell adenomas were increased in female B6C3F1 mice treated with TBA, but these results lack any independent confirmation, which would have been possible from a number of other studies. PMID:16809102

McGregor, Douglas

2006-04-01

351

Methyl t-Butyl Ether Mineralization in Surface-Water Sediment Microcosms under Denitrifying Conditions  

USGS Publications Warehouse

Mineralization of [U-14C] methyl t-butyl ether (MTBE) to 14CO2 without accumulation of t-butyl alcohol (TBA) was observed in surface-water sediment microcosms under denitrifying conditions. Methanogenic activity and limited transformation of MTBE to TBA were observed in the absence of denitrification. Results indicate that bed sediment microorganisms can effectively degrade MTBE to nontoxic products under denitrifying conditions.

Bradley, P. M.; Chapelle, F. H.; Landmeyer, J. E.

2001-01-01

352

p-tert-Butyl thiacalix[4]arenes functionalized at the lower rim by amide, hydroxyl and ester groups as anion receptors.  

PubMed

New p-tert-butyl thiacalix[4]arenes differently substituted at the lower rim with amide, hydroxyl and ester groups were synthesized. Binding properties of the compounds toward some tetrabutylammonium salts n-Bu(4)NX (X = F(-), Cl(-), Br(-), I(-), CH(3)CO(2)(-), H(2)PO(4)(-), NO(3)(-)) were studied by UV spectroscopy. It was found that the stoichiometry of the complexes, generally, is 1 : 1, and the association constants are in the range of 10(3)-10(5) M(-1). The p-tert-butyl thiacalix[4]arenes containing secondary amide groups trisubstituted at the lower rim bind the studied anions most effectively. Selective receptors for fluoride and dihydrogen phosphate salts of tetrabutylammonium were found. PMID:21423989

Stoikov, Ivan I; Yantemirova, Alena A; Nosov, Roman V; Rizvanov, Ildar Kh; Julmetov, Ajdar R; Klochkov, Vladimir V; Antipin, Igor S; Konovalov, Alexander I; Zharov, Ilya

2011-03-22

353

Synthesis of asymmetric peroxides: transition metal (Cu, Fe, Mn, Co) catalyzed peroxidation of beta-dicarbonyl compounds with tert-butyl hydroperoxide.  

PubMed

The transition metal (Cu, Fe, Mn, Co) catalyzed peroxidation of beta-dicarbonyl compounds at the alpha position by tert-butyl hydroperoxide was discovered. A selective, experimentally convenient, and gram-scale method was developed for the synthesis of alpha-peroxidated derivatives of beta-diketones, beta-keto esters, and diethyl malonate. Virtually stoichiometric (2-3/1) molar ratios of tert-butyl hydroperoxide and a dicarbonyl compound were used in the reactions with beta-diketones and beta-keto esters. The target compounds were synthesized in the highest yields from beta-keto esters (45-90%) and in somewhat lower yields from beta-diketones (46-75%) and malonates (37-67%). PMID:20586497

Terent'ev, Alexander O; Borisov, Dmitry A; Yaremenko, Ivan A; Chernyshev, Vladimir V; Nikishin, Gennady I

2010-08-01

354

(2-tert-Butyl-3-phenyl-2,3-di-hydro-isoxazole-4,5-di-yl)bis-(phenyl-methanone)  

PubMed Central

The phenyl and tert-butyl groups of the title compound, C27H25NO3, exhibit a trans configuration in agreement with the stereochemistry of the Z phenyl-N-tert-butyl­nitrone starting material. The attached carbonyl groups are not coplanar with the neighboring di­hydro­isoxazole ring and the phenyl rings they are bonded to, with torsion angles of 59.26?(8), 17.53?(11), 16.52?(12) and 52.86?(7)°. The dihedral angle between the di­hydro­isoxazole ring and the directly attached phenyl group is 86.86?(8)°. There are two nonclassical inter­molecular C—H?O hydrogen-bonding inter­actions that operate together with an inter­molecular C—H?? inter­action to form a supramolecular architecture in the crystal system.

Sandhya, R.; Sithambaresan, M.; Prathapan, S.; Kurup, M. R. Prathapachandra

2013-01-01

355

Understanding the redox shuttle stability of 3,5-di-tert-butyl-1,2-dimethoxybenzene for overcharge protection of lithium-ion batteries.  

SciTech Connect

3,5-di-tert-butyl-1,2-dimethoxybenzene (DBDB) has been synthesized as a new redox shuttle additive for overcharge protection of lithium-ion batteries. DBDB can easily dissolve in carbonate-based electrolytes, which facilitates its practical use in lithium-ion batteries; however, it has poor electrochemical stability compared to 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB). The structures of DBDB and DDB were investigated using X-ray crystallography and density functional calculations. The structures differ in the conformations of the alkoxy bonds probably due to the formation of an intramolecular hydrogen bond in the case of DBDB. We investigated reaction energies for decomposition pathways of neutral DBDB and DDB and their radical cations and found little difference in the reaction energies, although it is clear that kinetically, decomposition of DBDB is more favorable.

Zhang, Z.; Zhang, L.; Schlueter, J. A.; Redfern, P. C.; Curtiss, L.; Amine, K.

2010-01-01

356

3,9-Di-tert-butyl-2,4,8,10-tetra-oxaspiro-[5.5]undeca-ne  

PubMed Central

The title compound, C15H28O4, was prepared by the condensation of pivalaldehyde with penta­erythritol. In the crystal, the two halves of the mol­ecule are related by a crystallographic twofold rotation axis passing through the central spiro-C atom. The two non-planar six-membered heterocycles both adopt chair conformations with the two tert-butyl groups both located in the equatorial positions.

Li, Zhengyi; Chen, Liang; Tang, Qiuzheng; Sun, Xiaoqiang

2010-01-01

357

Study on the chromatographic behavior of water-soluble vitamins on p- tert-butyl-calix[8]arene-bonded silica gel stationary phase by HPLC  

Microsoft Academic Search

In this paper, the chromatographic behavior of some water-soluble vitamins was studied on a new p-tert-butyl-calix[8]arene-bonded silica gel stationary phase (CABS, 5?m particle size, the bonded amount 0.071mmolg?1) by using vitamin standards as probes for HPLC. The comparative study of the separation of these compounds was done by using CABS and ODS as stationary phases under the same chromatographic conditions.

Lai-Sheng Li; Shi-Lu Da; Yu-Qi Feng; Min Liu

2004-01-01

358

Free radical scavenging abilities of flavonoids as mechanism of protection against mutagenicity induced by tert-butyl hydroperoxide or cumene hydroperoxide in Salmonella typhimurium TA102  

Microsoft Academic Search

Mutagenicity induced by tert-butyl hydroperoxide (BHP) or cumene hydroperoxide (CHP) in Salmonella typhimurium TA102 was effectively reduced by flavonols with 3?,4?-hydroxyl groups such as fisetin, quercetin, rutin, isoquercitrin, hyperoxide, myricetin, myricitrin, robinetin, and to a lesser extent also by morin and kaempferol (ID50=0.25–1.05?mol per plate). With the exception of isorhamnetin, rhamnetin, morin, and kaempferol, closely similar results were obtained with

R. Edenharder; D. Grünhage

2003-01-01

359

Hydrogen atom spin trapping in. gamma. -irradiated fluorinated alcohols. Solvent effects on coupling constants and relative radical yields. [Trapping with phenyl tert-butyl nitrone  

Microsoft Academic Search

H atoms and radicals in ..gamma..-irradiated (CFâ)âCHOH and CFâCFâCFâCHâOH liquids have been spin trapped with phenyl tert-butyl nitrone. The H adduct yields are comparable to the radical adduct yields in contrast to the nonfluorinated alcohols in which the H adduct yield is only about 10⁻² of the radical adduct yield. The coupling constants in the partially fluorinated alcohols (A\\/sup N\\/

A. C. Ling; L. Kevan

1977-01-01

360

Cloning of a Genetically Unstable Cytochrome P-450 Gene Cluster Involved in Degradation of the Pollutant Ethyl tertButyl Ether by Rhodococcus ruber  

Microsoft Academic Search

Rhodococcus ruber (formerly Gordonia terrae) IFP 2001 is one of a few bacterial strains able to degrade ethyl tert-butyl ether (ETBE), which is a major pollutant from gasoline. This strain was found to undergo a spontaneous 14.3-kbp chromosomal deletion, which results in the loss of the ability to degrade ETBE. Sequence analysis of the region corresponding to the deletion revealed

SYLVIE CHAUVAUX; FABIEN CHEVALIER; CORINNE LE DANTEC; FRANCOISE FAYOLLE; ISABELLE MIRAS; FRANK KUNST; PIERRE BEGUIN

2001-01-01

361

Asymmetric Formal Carbonyl-Ene Reactions of Formaldehyde tert-Butyl Hydrazone with ?-Keto Esters: Dual Activation by Bis-urea Catalysts.  

PubMed

The dual activation of ?-keto esters and formaldehyde tert-butyl hydrazone by BINAM-derived bis-ureas is the key to achieve high reactivity and excellent enantioselectivities in nucleophilic addition (formal carbonyl-ene reaction) to functionalized tertiary carbinols. Ensuing high-yielding diazene-to-aldehyde tranformations and subsequent derivatizations provides a direct entry to a variety of densely functionalized products. PMID:22823936

Crespo-Peña, Ana; Monge, David; Martín-Zamora, Eloísa; Alvarez, Eleuterio; Fernández, Rosario; Lassaletta, José M

2012-07-26

362

The synthesis of a geminally perfluoro-tert-butylated ?-amino acid and its protected forms as potential pharmacokinetic modulator and reporter for peptide-based pharmaceuticals  

PubMed Central

To modulate and report the pharmacokinetics of peptide-based pharmaceuticals, a novel geminally perfluro-tert-butylated ?-amino acid (?Fa) and its Fmoc- and Boc- protected forms were designed and synthesized. ?Fa was incorporated into a model tripeptide via standard solid-phase chemistry. Both the amino acid (free and protected) and the tripeptide show a sharp singlet 19F NMR signal. Reversed-phase chromatography and 1-octanol/water partition measurements demonstrate that ?Fa is extremely hydrophobic.

Jiang, Zhong-Xing; Yu, Y. Bruce

2008-01-01

363

Free radical spin trap ?-phenyl-N- tert-butyl-nitron inhibits caspase-3 activation and reduces brain damage following a severe forebrain ischemic injury  

Microsoft Academic Search

It has been documented that ?-phenyl-N-tert-butyl-nitron (PBN) possesses a potent neuroprotective effect when administered after transient focal cerebral ischemia. However, contradicting results were reported regarding its effect in transient global ischemia. To further elucidate the mechanism of PBN action, we have studied the effect of PBN on animal survival, histopathological outcome, and activation of caspase-3 following 30 min of global

Ping An Li; Qing Ping He; Leah Nakamura; Katalin Csiszar

2001-01-01

364

Combination Therapy with MK-801 and ?-Phenyl- tert-butyl-nitrone Enhances Protection against Ischemic Neuronal Damage in Organotypic Hippocampal Slice Cultures  

Microsoft Academic Search

In vitrocombinations of MK-801, an NMDA receptor antagonist, and ?-phenyl-tert-butyl-nitrone (PBN), a free radical scavenger, have been tested for possible additive neuroprotective effects against anoxia\\/hypoglycemia (Ax\\/Hg)-induced neuronal damage. Rat organotypic hippocampal slice cultures were exposed to Ax\\/Hg for different lengths of time to vary the severity of the insult. Cell death (CD) was assessed using propidium iodide fluorescence and expressed

Alain Barth; Laurence Barth; David W. Newell

1996-01-01

365

A physiological model for tert-amyl methyl ether and tert-amyl alcohol: hypothesis testing of model structures.  

PubMed

The oxygenate tert-amyl methyl ether (TAME) is a gasoline fuel additive used to reduce carbon monoxide in automobile emissions. To evaluate the relative health risk of TAME as a gasoline additive, information is needed on its pharmacokinetics and toxicity. The objective of this study was to use a physiologically-based pharmacokinetic (PBPK) model to describe the disposition of TAME and its major metabolite, tert-amyl alcohol (TAA), in male Fischer-344 rats. The model compartments for TAME and TAA were flow-limited. The TAME physiological model had 6 compartments: lung, liver, rapidly perfused tissues, slowly perfused tissues, fat, and kidney. The TAA model had 3 compartments: lung, liver, and total-body water. The 2 models were linked through metabolism of TAME to TAA in the liver. Model simulations were compared with data on blood concentrations of TAME and TAA taken from male Fischer-344 rats during and after a 6-hour inhalation exposure to 2500, 500, or 100 ppm TAME. The PBPK model predicted TAME pharmacokinetics when 2 saturable pathways for TAME oxidation were included. The TAA model, which included pathways for oxidation and glucuronide conjugation of TAA, underpredicted the experimental data collected at later times postexposure. To account for biological processes occurring during this time, three hypotheses were developed: nonspecific binding of TAA, diffusion-limited transport of TAA, and enterohepatic circulation of TAA glucuronide. These hypotheses were tested using three different model structures. Visual inspection and statistical evaluation involving maximum likelihood techniques indicated that the model incorporating nonspecific binding of TAA provided the best fit to the data. A correct model structure, based upon experimental data, statistical analyses, and biological interpretation, will allow a more accurate extrapolation to humans and, consequently, a greater understanding of human risk from exposure to TAME. PMID:10367338

Collins, A S; Sumner, S C; Borghoff, S J; Medinsky, M A

1999-05-01

366

The role of calcium in the toxic effects of tert-butyl hydroperoxide on adult rat cardiac myocytes.  

PubMed

Oxidant stress has been implicated in reoxygenation damage following hypoxia and can lead to loss of membrane integrity and cell death. In this study the effects of oxidant stress, induced by tert-butyl hydroperoxide (tBHP), on cell conformation and intracellular free calcium ([Ca2+]i) of cardiac myocytes isolated from rat ventricles were examined. Incubation in the presence of 1 mM tBHP lead to a rise in [Ca2+]i, hypercontracture and loss of membrane integrity (as judged by trypan blue staining and loss of fluorescence of fura-2 loaded cells). Incubation in calcium-free medium or medium containing 2,3 butanedione-monoxime (BDM), which decreases myofibrillar calcium sensitivity, delayed but did not prevent the cell shape changes and loss of membrane integrity. In the presence of BDM, hypercontracture occurred at a higher [Ca2+]i than in control cells, indicating a possible role for [Ca2+]i in the generation of hypercontracture in this model. Treatment with calcium antagonists (10(-6) or 10(-7) M nisoldipine or 10(-6) M amlodipine) did not afford any protection against tBHP. ATP depletion did not accelerate loss of membrane integrity. Pretreatment of cells with the iron chelator, desferrioxamine mesylate greatly attenuated the effect of tBPH, delaying the rise in [Ca2+]i, cell shape changes and loss of membrane integrity. It appears, therefore, that tBHP-induced changes are mediated by the iron dependent generation of butyl alkoxyl radicals. The evidence suggests that tBHP-induced contracture is [Ca2+]i dependent rather than ATP dependent. Calcium modifies, but is not essential for the action of tBHP on isolated myocytes. During reoxygenation of hypoxic hearts calcium overload and free radical generation may act synergistically resulting in the characteristic changes associated with this condition, including loss of sarcolemmal integrity. PMID:1803021

Daly, M J; Young, R J; Britnell, S L; Nayler, W G

1991-11-01

367

Chlorido[2,3,5,6-tetra-kis-(tert-butyl-sulfanylmeth-yl)phenyl-?3 S 2,C 1,S 6]palladium(II) dichloro-methane monosolvate  

PubMed Central

The title compound, [Pd(C26H45S4)Cl]·CH2Cl2, crystallizes with a disordered dichloro­methane solvent mol­ecule [occupancy ratio = 0.67?(4):0.33?(4)]. Two of the tert-butyl groups are also disordered [occupancy ratios = 0.70?(5):0.30?(5) and 0.63?(4):0.37?(4)]. Although the pincer ligand offers the possibility for coordination of two different metal atoms, the present structure shows only the coordination of a single PdII atom in a typical S—C—S tridentate pincer manner. The PdII atom is in a slightly distorted square-planar environment with the two tert-butyl­sulfanyl groups arranged in a trans con­formation and with a chloride ligand trans to the ?-bonded aromatic C atom. The structure exhibits a durene-like ligand frame, forming a dihedral angle of 13.6?(4)° with the metal coordination (Pd/S/S/Cl/C) environment. It is noteworthy that the tert-butyl groups are found in a syn arrangement, this being different to that found previously by Loeb, Shimizu & Wisner [(1998). Organometallics, 17, 2324–2327].

Paz-Morales, Evelyn; Hernandez-Ortega, Simon; Morales-Morales, David

2013-01-01

368

[Factors influencing the content of residual tert-butyl alcohol in cyclodextrin complex prepared by lyophilization cosolvent system].  

PubMed

In order to minimize the residual tert-butyl alcohol (TBA) level in cyclodextrin complex prepared by freeze drying TBA/water cosolvent system, the formulation and lyophilization procedure that may influence the residual TBA was studied. Residual TBA in freeze dried cyclodextrin complex was determined by gas chromatography. The significant formulation and processing factors that influence residual TBA were identified by adjusting the initial TBA concentration in cosolvent, selecting cyclodextrin type (beta-cyclodextrin or hydroxypropyl beta-cyclodextrin), changing sample volume in flasket, altering freezing mode (fast freezing or slow freezing) and modifying the duration of secondary drying. The results show that the amorphous cyclodextrin material (hydroxypropyl beta-cyclodextrin), initial low TBA concentration in cosolvent and fast freezing would lead to high TBA residue in cyclodextrin complex, annealing was effective in reducing the residual TBA. The duration of secondary drying had no distinct effect on residual TBA. It is concluded that in order to reduce residual TBA in cyclodextrin complex prepared by lyophilization monophase solution, the initial TBA concentration in cosolvent should be higher than the crystal formation concentration, the appropriate cyclodextrin type and freeze drying processing should be choosen. PMID:17520833

Wang, Zhi-Xuan; Deng, Ying-Jie; Zhang, Xiao-Peng; Yang, Jing-Wen; Li, Bao-Qi

2007-03-01

369

Effect of lithium chloride on the living polymerization of tert-butyl methacrylate and polymer microstructure using monofunctional initiators  

SciTech Connect

The effect of LiCl on the anionic polymerization of tert-butyl methacrylate (tBuMA) initiated with monofunctional alkali metal-based carbanionic species was investigated at [minus]78 C in THF. The propagation rate of the polymerization process was determined by gas chromatography and by gravimetry. It was found that, in the presence of LiCl in a molar ratio of 5 with respect to the initiator, the rate constant, k[sub p], is 20 times lower than that in the absence of LiCl. The polymers and oligomers were analyzed by size exclusion chromatography (SEC) and [sup 13]C NMR spectroscopy. The polymers obtained in the absence of LiCl had broad molecular weight distributions and contained significant amounts of oligomers, while those obtained in the presence of LiCl were monodisperse, without any noticeable oligomers. [sup 13]C NMR showed that the isotactic content of the polymers increased significantly when the molar ratio of LiCl to the initiator was higher than 2. The effect of LiCl on the rate constant and on the microstructure of the polymers was attributed to complex formation between LiCl and the living polymer chains.

Varshney, S.K. (Rt Polymer Source Inc., Pointe-Claire, Quebec (Canada)); Gao, Z. (Imperial Oil Ltd., Sarnia, Ontario (Canada). Research Dept.); Zhong, Xing Fu; Eisenberg, A. (McGill Univ., Montreal, Quebec (Canada). Dept. of Chemistry)

1994-02-28

370

tert-Butyl hydroperoxide, an organic peroxide, causes temporary delay in hair growth in a neonatal rat model  

PubMed Central

Summary tert-Butyl hydroperoxide (tBHP), an organic peroxide, has been shown to cause irreversible damage to keratinocytes in vitro with prolonged administration at high concentrations, and reversible damage with short-term administration at low concentrations. To investigate the effects of tBHP on keratinocytes in vivo, we analysed hair growth in tBHP-treated neonatal rats. Sprague–Dawley and Long–Evans rat pups were injected subcutaneously with tBHP or vehicle once daily for 6 days, and hair growth was monitored. The tBHP-treated rats had a significant delay in hair growth. However, this delay reversed within days, and the hair coats, including hair pigmentation, of tBHP-treated and sham-treated rats were indistinguishable 2 weeks later. Histological analysis and BrdU labelling of S phase cells confirmed the delay in hair-follicle growth and its reversal in tBHP-treated rats. Our results indicated that the changes incurred in hair follicles by short-term use of high-dose oxidants in vivo are temporary and reversible.

Wikramanayake, T. C.; Simon, J.; Mauro, L. M.; Perez, C. I.; Roberts, B.; Elgart, G.; Alvarez-Connelly, E.; Schachner, L. A.; Jimenez, J. J.

2011-01-01

371

Thermodynamic and kinetic studies of the liquid phase synthesis of tert-butyl ethyl ether using a reaction calorimeter  

SciTech Connect

The liquid-phase addition of ethanol to isobutene to give tert-butyl ethyl ether (ETBE) on the ion-exchange resin Lewatit K2631 has been studied in a calorimetric reactor. The heat capacity of ETBE and the enthalpy change of the ETBE synthesis reaction in the temperature range 312--333 K have been determined. ETBE heat capacity in the liquid phase has been found to follow the equation C{sub p} = 486.73 {minus} 2.253 (T/K) + 0.00479 (T/K){sup 2}. At 298 K the standard molar reaction enthalpy is {Delta}H{degree} = {minus}32.0 kJ/mol. A determination of the apparent activation energy of 86.5--89.2 kJ/mol has been performed graphically from the plots of heat flow rate versus time. An Eley-Rideal mechanism, with two active sites involved in the rate determining step, has been proved to be correct. From this model an apparent activation energy of 80.6 kJ/mol is deduced. A {minus}3.0 kJ/mol value has been found for the adsorption enthalpy of ethanol. This allows the estimation of the actual gel-phase activation energy of 77.6 kJ/mol.

Sola, L.; Pericas, M.A.; Cunill, F.; Tejero, J. [Univ. de Barcelona (Spain)

1995-11-01

372

Protective Effects of Alkaloid Compounds from Nelumbinis Plumula on tert-Butyl Hydroperoxide-Induced Oxidative Stress.  

PubMed

This study was conducted to investigate the effect of Nelumbinis Plumula total alkaloid (NPA) and its main alkaloid components on oxidative stress induced by tert-butyl hydroperoxide (t-BHP) in the human hepatocellular HepG2 cell line. According to HPLC analysis, several major alkaloid compounds such as liensinine, isoliensinine and neferine were present in NPA. The cytotoxic effects in 0.55 mM t-BHP-induced HepG2 cells were significantly inhibited by NPA and the major compound in NPA, neferine, showed the strongest activities. The protective effect of neferine against oxidative stress induced by t-BHP may be associated with decreased ROS formation, TBARS generation, LDH release and increased GSH levels, suggesting their involvement of the cytoprotective on oxidative stress. The effects were comparable with quercetin, which was used as positive control. Overall, total alkaloid and alkaloid compounds from Nelumbinis Plumula displayed a significant cytoprotective effect against oxidative stress. Further study is needed to elucidate the relationship between the chemical structures of the components in NPA and their protective effect on oxidative stress. PMID:24064445

Xie, Yong; Zhang, Yi; Zhang, Long-Tao; Zeng, Shao-Xiao; Guo, Ze-Bin; Zheng, Bao-Dong

2013-08-26

373

Preparation and evaluation of alpha-phenyl-n-tert-butyl nitrone (PBN)-encapsulated chitosan and PEGylated chitosan nanoparticles.  

PubMed

Alpha-phenyl-n-tert-butyl nitrone (PBN) shows its major effect by scavenging free radicals formed in the ischemia and it has the ability to penetrate through the blood brain barrier easily. The in vivo stability of PBN is very low and when administered systemically, it has a mean plasma half life of about three hours. Therefore, formulations which are able to prolong the plasma residence time of PBN are of major interest, because oxygen radicals are usually continuously formed under pathological conditions. In this study, PBN, a nitrone compound having neuroprotective properties, was encapsulated in chitosan (CS) and chitosan-poly(ethylene glycol) (CS-PEG) nanoparticles for treatment of diseases such as stroke, in which sustained free radical production is reported. The nanoparticles were characterized through particle size determination, zeta potential, encapsulation efficiency, surface morphology determinations and in vitro release studies. The surface morphologies were evaluated by transmission electron microscopy (TEM) and nanoparticles having spherical shapes were characterized. The particle size distribution was between approximately 97 nm and approximately 322 nm; and the zeta potentials varied between approximately 9 mV and approximately 33 mV. Size of the nanoparticle formulations was important for the release of PBN from nanoparticles. The quantitative determination of PBN has been evaluated by a validated analytical HPLC method. The presented chitosan-based nanotechnology opens new perspectives for testing antioxidant activity in vivo. PMID:19694179

Pinarbasli, O; Aktas, Y; Dalkara, T; Andrieux, K; Alonso, M J; Fernandez-Megia, E; Novoa-Carballal, R; Riguera, R; Couvreur, P; Capan, Y

2009-07-01

374

PAHs Formation in the Depositions in a Methyl tert Butyl Ether\\/Ar, a Methyl tert Butyl Ether\\/O 2 \\/Ar and a Methyl tert Butyl Ether\\/H 2 \\/Ar RF Plasma Environment  

Microsoft Academic Search

Contents and distributions of polycyclic aromatic hydrocarbons (PAHs) in the depositions were investigated and discussed in a MTBE\\/Ar, a MTBE\\/O2\\/Ar and a MTBE\\/H2\\/Ar plasma systems. A radio-frequency (RF) plasma system was used to produce the depositions under the designed operational condition. The identification and quantification of PAHs was accomplished by using a GC with a mass selectivity detector (GC\\/MS). Results

L.-T. Hsieh; G.-C. Fang; H. H. Yang; Y.-F. Wang; M.-C. Tsao; W.-T. Liao

2002-01-01

375

Hydrogen Oxidation Catalysis by a Nickel Diphosphine Complex with Pendant tert-Butyl Amines  

SciTech Connect

A bis-diphosphine nickel complex with t-butyl functionalized pendant amines [Ni(PCy2Nt-Bu2)2]2+ has been synthesized. It is a highly active electrocatalyst for the oxidation of hydrogen in the presence of base. The turn-over rate of 50 s 1 under 1.0 atm H2 at a potential of –0.77 V vs the ferrocene couple is 5 times faster than the rate reported heretofore for any other molecular H2 oxidation catalyst. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy. Computational resources were provided by the Environmental Molecular Science Laboratory (EMSL) and the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.

Yang, Jenny Y.; Chen, Shentan; Dougherty, William G.; Kassel, W. S.; Bullock, R. Morris; DuBois, Daniel L.; Raugei, Simone; Rousseau, Roger J.; Dupuis, Michel; Rakowski DuBois, Mary

2010-11-09

376

One step synthesis of methyl t-butyl ether from t-butanol using haloacid-modified clay catalysts  

SciTech Connect

In a method wherein t-butanol is reacted with methanol in a one step in the presence of a catalyst to provide methyl tert-butyl ether, the improvement is described comprising using as a catalyst a montmorillonite clay modified with a haloacid from the group consisting of haloaliphatic carboxylic acids selected from the group consisting of trifluoroacetic acid, pentafluoropropionic acid and trichloroacetic acid, haloaromatic carboxylic acids selected from the group consisting of pentafluorobenzoic acid and pentafluorobenzeneacetic acid, haloaromaticsulfonic acids selected from the group consisting of fluorobenzenesulfonic acids and sulfonyl chloride derivatives thereof, and haloaliphaticsulfonic acids selected from the group consisting of trichlormethanesulfonic acid and a sulfonyl chloride derivative thereof, and continuously contacting said t-butanol and methanol in a molar amount of about 0.1 to 10 moles of methanol per mole of t-butanol with said catalyst at a temperature of about 20 C to about 250 C and a pressure of about atmospheric to about 1,000 psig to obtain methyl tertbutyl ether product.

Knifton, J.F.

1993-05-25

377

Intra-arterial tert-Butyl-Hydroperoxide Infusion Induces an Exacerbated Sensory Response in the Rat Hind Limb and is Associated with an Impaired Tissue Oxygen Uptake  

PubMed Central

The objective of this study was to investigate oxidative stress and oxygen extraction mechanisms in an animal model of continuous intra-arterial infusion of a free radical donor and in an in vitro model using isolated mitochondria. tert-Butyl-hydroperoxide (tert-BuOOH, 25 mM) was infused for 24 h in the left hind limb of rats to induce soft tissue damage (n?=?8). After 7 days, we assessed local sensory response, tissue oxygen consumption, oxygen radicals, and antioxidant levels. In vitro mitochondrial function was measured after stimulation of isolated mitochondria of skeletal muscle cells with increasing doses of tert-BuOOH. tert-BuOOH infusion resulted in an increased skin temperature (p?=?0.04), impaired function, and a significantly increased pain sensation (p?=?0.03). Venous oxygen saturation levels (p?=?0.01) and the antioxidant ceruloplasmin (p?=?0.04) were increased. tert-BuOOH inhibited mitochondrial function in vitro. Induction of free radical formation in the rat hind limb results in an exacerbated sensory response and is associated with impaired oxygen extraction, which likely results from mitochondrial dysfunction caused by free radicals.

van Goor, Harry; Bahrami, Soheyl; Kozlov, Andrey V.; Leixnering, Martin; Redl, Heinz; Goris, R. Jan A.

2010-01-01

378

Miniemulsion copolymerization of methyl methacrylate and butyl acrylate in the presence of vinyl siloxane rubber  

Microsoft Academic Search

Vinyl siloxane rubber was successfully used as the co-stabilizer in the miniemulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA) initiated by ammonium persulfate. Effects of the molecular weight, vinyl content, and the amount of vinyl siloxane rubber on the kinetics and the particle morphology of the latex prepared were investigated. The rate of copolymerization was found to decrease

Zhang-Qing Yu; Pei-Hong Ni; Jie-Ai Li; Xiu-Lin Zhu

2004-01-01

379

Biotic and Abiotic Transformations of Methyl tertiary Butyl Ether (MTBE) * (6 pp)  

Microsoft Academic Search

Background. Methyl tertiary butyl ether (MTBE) is a fuel additive which is used all over the world. In recent years it has often been found in groundwater, mainly in the USA, but also in Europe. Although MTBE seems to be a minor toxic, it affects the taste and odour of water at concentrations of < 30 µg\\/L. Although MTBE is

Axel Fischer; Claudia Oehm; Michael Selle; Peter Werner

2005-01-01

380

REFINED PBPK MODEL OF AGGREGATE EXPOSURE TO METHYL TERTIARY-BUTYL ETHER  

EPA Science Inventory

Aggregate (multiple pathway) exposures to methyl tertiary-butyl ether (MTBE) in air and water occur via dermal, inhalation, and oral routes. Previously, physiologically-based pharmacokinetic (PBPK) models have been used to quantify the kinetic behavior of MTBE and its primary met...

381

DERMAL, ORAL, AND INHALATION PHARMACOKINETICS OF METHYL TERTIARY BUTYL ETHER (MTBE) IN HUMAN VOLUNTEERS  

EPA Science Inventory

Methyl tertiary butyl ether (MTBE), a gasoline additive, used to increase octane and reduce carbon monoxide emissions and ozone precursors has contaminated drinking water leading to exposure by oral, inhalation, and dermal routes. To determine its dermal, oral, and inhalation ki...

382

DERMAL, ORAL AND INHALATION PHARMACOKINETICS OF METHYL TERTIARY-BUTYL ETHER (MTBE) IN HUMAN VOLUNTEERS  

EPA Science Inventory

Methyl tertiary butyl ether (MTBE), a gasoline additive used to increase octane and reduce carbon monoxide emissions and ozone precursors, has contaminated drinking water and can lead to exposure by oral, inhalation, and dermal routes. To determine its dermal, oral, and inhal...

383

Choledocholithiasis--in vivo stone dissolution using methyl tertiary butyl ether (MTBE)  

Microsoft Academic Search

We report a series of 10 elderly patients with large bile duct calculi refractory to standard endoscopic extraction techniques who were treated by gall stone dissolution using methyl tertiary butyl ether (MTBE) instilled through a nasobiliary catheter. In eight patients complete bile duct clearance was achieved after an average of eight hours MTBE instillation. In two patients gall stone size

W R Murray; G LaFerla; G M Fullarton

1988-01-01

384

Biodegradation of ethyl t-butyl ether (ETBE), methyl t-butyl ether (MTBE) and t-amyl methyl ether (TAME) by Gordonia terrae.  

PubMed

Gordonia terrae strain IFP 2001 was selected from activated sludge for its capacity to grow on ethyl t-butyl ether (ETBE) as sole carbon and energy source. ETBE was stoichiometrically degraded to t-butyl alcohol (TBA) and the activity was inducible. A constitutive strain, G. terrae IFP 2007, derived from strain IFP 2001, was also selected. Methyl t-butyl ether (MTBE) and t-amyl methyl ether (TAME) were not used as carbon and energy sources by the two strains, but cometabolic degradation of MTBE and TAME was demonstrated, to TBA and t-amyl alcohol (TAA) respectively, in the presence of a carbon source such as ethanol. No two-carbon compound was detected during growth on ETBE, but formate was produced during cometabolic degradation of MTBE or TAME. A monooxygenase was involved in the degradation of ethers, because no degradation of ETBE was observed under anaerobic conditions and the presence of a cytochrome P-450 was demonstrated in G. terrae IFP 2001 after induction by cultivation on ETBE. PMID:11234952

Hernandez-Perez, G; Fayolle, F; Vandecasteele, J P

2001-01-01

385

A COMPARISON OF LIQUID AND GAS-PHASE PHOTOOXIDATION TREATMENT OF METHYL TERTIARY BUTYL ETHER: SYNTHETIC AND FIELD SAMPLES  

EPA Science Inventory

The feasibility of photo-oxidation treatment of metyl tert-butyl either (MTBE) in water was investigated using two systems, 1) a slurry falling film photo-reactor, and 2) an integrated air-stripping with gas phase photooxidation system. MTBE-contaminated synthetic water and field...

386

Development of a bladder instillation of the indoloquinone anticancer agent EO-9 using tert-butyl alcohol as lyophilization vehicle.  

PubMed

The purpose of this research was to develop a stable bladder instillation of EO-9 for the treatment of superficial bladder cancer. First, stability and dissolution studies were performed. Subsequently, the freeze-drying process was optimized by determination of the freeze-drying characteristics of the selected cosolvent/water system and differential scanning calorimetry analysis of the formulation solution. Furthermore, the influence of the freeze-drying process on crystallinity and morphology of the freeze-dried product was determined with x-ray diffraction analysis and scanning electron microscopy, respectively. Subsequently, a reconstitution solution was developed. This study revealed that tert-butyl alcohol (TBA) can be used to both dramatically improve the solubility and stability of EO-9 and to shorten the freeze-drying cycle by increasing the sublimation rate. During freeze drying, 3 TBA crystals were found: TBA hydrate-ice crystals, crystals of TBA hydrate, and a third crystal, probably composed of TBA hydrate crystals containing approximately 90% to 95% TBA. Furthermore, it was shown that crystallization of TBA hydrate was inhibited in the presence of both sodium bicarbonate (NaHCO3) and mannitol. Addition of an annealing step resulted in a minor increase in the crystallinity of the freeze-dried product and formation of the delta-polymorph of mannitol. A stable bladder instillation was obtained after reconstitution of the freeze-dried product (containing 8 mg of EO-9, 20 mg of NaHCO3, and 50 mg of mannitol per vial) to 20 mL with a reconstitution solution composed of propylene glycol/water for injection (WfI)/NaHCO3/sodium edetate 60%/40%/2%/0.02% vol/vol/wt/wt, followed by dilution with WfI to a final volume of 40 mL. PMID:17915811

van der Schoot, Sabien C; Nuijen, Bastiaan; Flesch, Frits M; Gore, Ashok; Mirejovsky, Dorla; Lenaz, Luigi; Beijnen, Jos H

2007-08-03

387

Modulatory effect of methanolic extract of Vernonia amygdalina (MEVA) on tert-butyl hydroperoxide-induced erythrocyte haemolysis.  

PubMed

Reactive oxygen species (ROS) have been implicated in the aetiology of several pathological and degenerative diseases. The protective effect of natural products possessing antioxidant properties has played a crucial role in ameliorating these deleterious effects. This study investigated the chemoprotective properties of the methanolic extract of Vernonia amygdalina (MEVA) in an experimental model of tert-butyl hydroperoxide (t-BHP)-induced human erythrocyte lysis in vitro. Haemolysis was induced by incubating erythrocytes with t-BHP (2 and 3?mM) in vitro. Samples of erythrocyte suspensions were removed at different intervals over a 6-h period, and the degree of haemolysis was measured. The anti-haemolytic effect of MEVA at 25-150?µg?ml(-1) concentrations on the samples were assessed and compared with Triton X-100. Administration of t-BHP at 2- and 3-mM concentrations significantly (p??0.05) at all concentrations by the sixth hour. The reduced glutathione level was, however, increased with the administration of t-BHP, while a delayed addition of MEVA had no protective effect on the t-BHP-induced cell lysis. These findings therefore suggest that MEVA may have protective antioxidant properties, making it suitable for incorporation into food and drug products. Copyright © 2012 John Wiley & Sons, Ltd. PMID:23192940

Adesanoye, Omolola A; Molehin, Olorunfemi R; Delima, Adetutu A; Adefegha, Adeniyi S; Farombi, Ebenezer O

2012-11-29

388

Vapor-liquid equilibria of hydrocarbons and tert-amyl methyl ether  

SciTech Connect

The P-T-x-y data for tert-amyl methyl ether (TAME) separately with 2,2,4-trimethylpentane (TMP), methylcyclohexane (MCHX), and toluene were obtained at three temperatures, 293, 311, and 333 K. The vapor-liquid equilibria of a five-components mixture (TAME + TMP + 1-heptene + MCHX + toluene) at the same temperature were measured as well. The data reported have been successfully described using a Peng-Robinson equation of state with van der Waals one-fluid mixing rules.

Antosik, M. (Polish Academy of Sciences, Warszawa (Poland). Inst. of Physical Chemistry); Sandler, S.I. (Univ. of Delaware, Newark, DE (United States). Dept. of Chemical Engineering)

1994-07-01

389

Controlled Ethyltert-Butyl Ether (ETBE) Exposure of Male Volunteers*1II. Acute Effects  

Microsoft Academic Search

The aim of this study was to evaluate acute effects of ethyl tert-butyl ether (ETBE) in man after short-term exposure. ETBE may in the future replace methyl tert-butyl ether, a widely used oxygenate in unleaded gasoline. Eight healthy male volunteers were exposed to ETBE vapor for 2 h at four levels (0, 5, 25, and 50 ppm) during light physical

Annsofi Nihlén; Agneta Löf; Gunnar Johanson

1998-01-01

390

A scalable synthesis of the (S)-4-(tert-butyl)-2-(pyridin-2-yl)-4,5-dihydrooxazole ((S)-t-BuPyOx) ligand.  

PubMed

An efficient method for the synthesis of the (S)-4-(tert-butyl)-2-(pyridin-2-yl)-4,5-dihydrooxazole ((S)-t-BuPyOx) ligand has been developed. Inconsistent yields and tedious purification in known routes to (S)-t-BuPyOx suggested the need for an efficient, dependable, and scalable synthetic route. Furthermore, a route suitable for the synthesis of PyOx derivatives is desirable. Herein, we describe the development of a three-step route from inexpensive and commercially available picolinic acid. This short procedure is amenable to multi-gram scale synthesis and provides the target ligand in 64% overall yield. PMID:24062823

Shimizu, Hideki; Holder, Jeffrey C; Stoltz, Brian M

2013-08-12

391

A scalable synthesis of the (S)-4-(tert-butyl)-2-(pyridin-2-yl)-4,5-dihydrooxazole ((S)-t-BuPyOx) ligand  

PubMed Central

Summary An efficient method for the synthesis of the (S)-4-(tert-butyl)-2-(pyridin-2-yl)-4,5-dihydrooxazole ((S)-t-BuPyOx) ligand has been developed. Inconsistent yields and tedious purification in known routes to (S)-t-BuPyOx suggested the need for an efficient, dependable, and scalable synthetic route. Furthermore, a route suitable for the synthesis of PyOx derivatives is desirable. Herein, we describe the development of a three-step route from inexpensive and commercially available picolinic acid. This short procedure is amenable to multi-gram scale synthesis and provides the target ligand in 64% overall yield.

Shimizu, Hideki; Holder, Jeffrey C

2013-01-01

392

The thermodynamic properties of (?,??-dipyridyl) bis (4-methoxy-3,6-di- tert -butyl- o -benzosemiquinone)cobalt over the temperature range from T ? 0 to 320 K  

Microsoft Academic Search

The heat capacity of (?,??-dipyridyl)bis(4-methoxy-3,6-di-tert-butyl-o-benzosemiquinone)cobalt over the temperature range 7–320 K was studied by precision adiabatic vacuum calorimetry. A physical\\u000a transformation observed at 134–222 K accompanied the reversible transition of the semiquinone-catecholate complex of low-spin\\u000a cobalt into the bis-semiquinone adduct of high-spin cobalt. The enthalpy and entropy of this redox-isomeric transition were determined. The data\\u000a obtained were used to calculate

G. A. Abakumov; M. P. Bubnov; V. K. Cherkasov; N. A. Skorodumova; A. V. Arapova; N. N. Smirnova

2008-01-01

393

N?-tert-Butyl-N?-(3,5-dimethyl-benzo-yl)-2,2-dimethyl-4-oxochroman-6-carbo-hydrazide  

PubMed Central

In the crystal structure of the title compound, C25H30N2O4, the steric size of the tert-butyl group causes the 3,5-dimethyl­phenyl ring to adopt a transoid geometry with respect to the N—C(O) bond. The six-membered heterocyclic ring is disordered over two sites, with occupancies of 0.553?(4) and 0.447?(4). Intra­molecular C—H?O inter­actions are present. In the crystal, mol­ecules are linked by inter­molecular N—H?O and C—H?O hydrogen bonds.

Zhou, Zhongzhen; You, Wenwei; Tang, Zhongkun; Zhao, Peiliang

2009-01-01

394

(E)-2'-[(3,5-Di-tert-butyl-2-hy-droxy-benzyl-idene)amino]-1,1'-binaphthalen-2-ol methanol monosolvate.  

PubMed

The title compound, C(35)H(35)NO(2)·CH(4)O, was obtained by the reaction of rac-2-amino-2-hy-droxy-1,1-binaphthyl and 3,5-di-tert-butyl-2-hy-droxy-benzaldehyde in absolute methanol. In the Schiff base mol-ecule, the two naphthyl bicycles are twisted by 71.15?(5)°. One hy-droxy group is involved in intra-molecular O-H?N hydrogen bond, while the methanol solvent mol-ecule is linked to another hy-droxy group via an inter-molecular O-H?O hydrogen bond. PMID:22219946

He, Dian; Li, Chong; Wang, Xiaohong

2011-10-12

395

The standard enthalpy of formation and low-temperature heat capacity of 1,1',3,3'-tetra-( tert-butyl)ferrocene  

NASA Astrophysics Data System (ADS)

The heat capacity of crystalline 1,1',3,3'-tetra-( tert-butyl)ferrocene (TTBF) was measured in an adiabatic vacuum calorimeter over the temperature range 5-302 K. The thermodynamic functions of TTBF in the crystalline state were calculated from T?0 to 302 K. The enthalpy of combustion of TTBF was determined in an isothermal calorimeter with a stationary bomb. The standard thermodynamic functions of formation of the compound in the crystalline state at 298.15 K were calculated.

Kozlova, M. S.; Larina, V. N.; Karyakin, N. V.; Sheiman, M. S.

2008-12-01

396

Bis({tris[2-(3,5-di-tert-butyl-2-oxido-benzylideneamino)ethyl]amine}cerium(III)) diethyl ether solvate  

PubMed Central

The title compound, 2[Ce(C51H75N4O3)]·C4H10O, was obtained in high yield (92%) by reduction of (TRENDSAL)CeIVCl [TRENDSAL is N,N?,N??-tris­(3,5-di-tert-butyl­salicyl­ide­natoamino)­triethyl­amine] with potassium in THF. The bulky tripodal TRENDSAL ligand effectively encapsulates the central CeIII cation with a Ce—N(imine) distance of 2.860?(2)?Å and an average C—N(amine) distance of 2.619?Å within a distorted monocapped octahedral coordination.

Drose, Peter; Hrib, Cristian G.; Edelmann, Frank T.

2010-01-01

397

Mass-spectrometric monitoring of the thermally induced decomposition of trimethylgallium, tris( tert -butyl)gallium, and triethylantimony at low pressure conditions  

Microsoft Academic Search

The thermal decomposition of trimethylgallium (GaMe3), tris(tert-butyl)gallium (Ga\\u000a t\\u000a Bu3) and triethylantimony (SbEt3) was investigated in a tubular hot-wall reactor coupled with a molecular-beam sampling mass spectrometer, and decomposition\\u000a mechanisms were proposed. The obtained results confirm the predominance of the surface reactions and reveal that the radical\\u000a decomposition path of Ga\\u000a t\\u000a Bu3 and SbEt3, responsible for the formation of

Naoufal Bahlawane; Frank Reilmann; Linda-Christin Salameh; Katharina Kohse-Höinghaus

2008-01-01

398

Disposition, metabolism, and toxicity of methyl tertiary butyl ether, an oxygenate for reformulated gasoline  

Microsoft Academic Search

Studies of the toxicology of methyl tertiary butyl ether (MTBE) were reviewed as a possible information base for evaluating the health effects of evaporative emissions from reformulated gasoline (RFG). Perirenal fat\\/blood MTBE concentration ratios ranged from 9.7 to 11.6 after 15 wk of intermittent exposure. During an oxyfuels program in Fairbanks, AK, blood levels of occupationally exposed workers were 0.2-31.5

Duncan E. Hutcheon; W. ten Hove; J. Boyle; J. D. Arnold

1996-01-01

399

A New GC-MS Experiment for the Undergraduate Instrumental Analysis Laboratory in Environmental Chemistry: Methyl-t-butyl Ether and Benzene in Gasoline  

NASA Astrophysics Data System (ADS)

With the recent ACS approval of an option in environmental chemistry at the undergraduate level, there is a need for new experiments that illustrate fundamental principles of instrumental analysis in the context of environmental chemistry. We describe an experiment that utilizes combined gas chromatography-mass spectrometry (GC-MS) in the qualitative and quantitative analysis of methyl tert-butyl ether (MTBE) and benzene in gasoline. This is particularly appropriate, given the increased use of oxygenates in reformulated gasolines in the United States. In addition to illustrating the fundamentals of GC and MS, this experiment demonstrates (i) the use of internal standards to improve precision; (ii) the application of the method of standard additions; and (iii) the importance of techniques such as selected ion extraction/monitoring in the identification and measurement of specific highly volatile organic compounds in complex environmental mixtures.

Quach, Dinh T.; Ciszkowski, Nancy A.; Finlayson-Pitts, Barbara J.

1998-12-01

400

Protective Effects of Rooibos (Aspalathus linearis) and/or Red Palm Oil (Elaeis guineensis) Supplementation on tert-Butyl Hydroperoxide-Induced Oxidative Hepatotoxicity in Wistar Rats  

PubMed Central

The possible protective effects of an aqueous rooibos extract (Aspalathus linearis), red palm oil (RPO) (Elaeis guineensis), or their combination on tert-butyl-hydroperoxide-(t-BHP-)induced oxidative hepatotoxicity in Wistar rats were investigated. tert-butyl hydroperoxide caused a significant (P < 0.05) elevation in conjugated dienes (CD) and malondialdehyde (MDA) levels, significantly (P < 0.05) decreased reduced glutathione (GSH) and GSH?:?GSSG ratio, and induced varying changes in activities of catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase in the blood and liver. This apparent oxidative injury was associated with histopathological changes in liver architecture and elevated levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH). Supplementation with rooibos, RPO, or their combination significantly (P < 0.05) decreased CD and MDA levels in the liver and reduced serum level of ALT, AST, and LDH. Likewise, changes observed in the activities of antioxidant enzymes and impairment in redox status in the erythrocytes and liver were reversed. The observed protective effects when rooibos and RPO were supplemented concomitantly were neither additive nor synergistic. Our results suggested that rooibos and RPO, either supplemented alone or combined, are capable of alleviating t-BHP-induced oxidative hepatotoxicity, and the mechanism of this protection may involve inhibition of lipid peroxidation and modulation of antioxidants enzymes and glutathione status.

Ajuwon, Olawale R.; Katengua-Thamahane, Emma; Van Rooyen, Jacques; Oguntibeju, Oluwafemi O.; Marnewick, Jeanine L.

2013-01-01

401

Biotransformation and Kinetics of Excretion of tert-Amyl-methyl Ether in Humans and Rats after Inhalation Exposure  

Microsoft Academic Search

tert-Amyl methyl ether (TAME) may be widely used as an additive to gasoline in the future. The presence of this ether in gasoline reduces the tail pipe emission of pollutants. Therefore, widespread human exposure to TAME may occur. To contribute to the characterization of potential adverse effects of TAME, its biotransformation was compared in humans and rats after inhalation exposure.

Alexander Amberg; Elisabeth Rosner; Wolfgang Dekant

2000-01-01

402

Stopped-flow study of the kinetics of the reaction of Rh (PPh/sub 3/) /sub 2/COC1 with cumyl and tert-butyl hydroperoxides  

SciTech Connect

A spectroscopic study showed the formation of complexes of bis (triphenylphosphine) carbonylrhodium chloride with cumyl hydroperoxide (CHP) and tert-butyl hydroperoxide (TBHP) in toluene solution at 20/sup 0/C. The equilibrium constants were found for the formation of these complexes (57.5 and 160 liters/mole, respectively) at different CHP and TBHP concentrations relative to the change in intensity of the absorption bands. The stopped-flow method was used to determine the rate constants for the formation (k/sub 1/) and decomposition (k/sub 2/) of these complexes: k/sub 1/, CHP = 2.0, k/sub 1/, TBHP = 0.55 liters/mole.sec and k/sub 2/CHP = 0.035, k/sub 2/, tbhp = 0.003 sec /sup -//sub 1/. It was proposed that ternary complexes are formed upon the addition of an olefin (cyclohexane) to the bis(triphenylphosphine) carbonylrhodium chloride-CHP system.

Tyutchenkova, L.D.; Malievskii, A.D.; Vinogradova, V.G.

1986-11-01

403

(2E)-4-tert-Butyl-2-(4-meth-oxy-benzyl-idene)-3,4-dihydro-naphthalen-1(2H)-one  

PubMed Central

In the title compound C22H24O2, the exocyclic C=C double bond is in an E configuration and the tert-butyl group is in an axial position on the cyclo­hexa­none ring. The cyclo­hexa­none ring in the dihydro­naphthalene fused-ring system adopts a half-chair conformation in both independent two mol­ecules in the asymetric unit. The benzene ring system is oriented angles of 43.97?(12) and 39.24?(12)° with respect to the naphthyl ring system in the two independent mol­ecules. In the crystal, mol­ecules are linked via C—H?O hydrogen bonds and C—H?? inter­actions.

Akhazzane, Mohamed; Zouihri, Hafid; Daoudi, Maria; Kerbal, Abdelali; Al Houari, Ghali

2011-01-01

404

Preparation of unconventional dendrimers that contain rigid NH-triazine linkages and peripheral tert-butyl moieties for CO2 -selective adsorption.  

PubMed

Three unconventional dendrimers that contained rigid NH-triazine linkages and peripheral tert-butyl moieties were prepared by using a convergent approach and characterized by (1)H and (13)C?NMR spectroscopy, mass spectrometry, and elemental analysis. Based on a thermogravimetric analysis study, these dendrimers were observed to display thermal stability at about 300?°C. The NH-triazine moiety, which possessed protonated and proton-free nitrogen sites (like the imidazole unit), displayed the capture of polarizable CO2 molecules through hydrogen-bond and/or dipole-quadrupole interactions. In addition, the adsorption of various amounts of CO2 and N2 at different pressures suggests that the dendritic pores, which arise from the stacking of the middle co-planar and rim protuberant dendrimers, Gn -N?N-Gn (n=1-3), either swell or shrink at high pressure, thus indicating that these dendrimers may have a breathing ability. PMID:23794529

Lee, Cheng-Hua; Tsai, Meng-Rong; Chang, Yen-Tzu; Lai, Long-Li; Lu, Kuang-Lieh; Cheng, Kung-Lung

2013-06-21

405

Protective effect of ganodermanondiol isolated from the Lingzhi mushroom against tert-butyl hydroperoxide-induced hepatotoxicity through Nrf2-mediated antioxidant enzymes.  

PubMed

Ganodermanondiol, a biologically active compound, was isolated from the Lingzhi mushroom (Ganoderma lucidum). The present study examined the protective effects of ganodermanondiol against tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity. Ganodermanondiol protected human liver-derived HepG2 cells through nuclear factor-E2-related factor 2 (Nrf2) pathway-dependent heme oxygenase-1 expressions. Moreover, ganodermanondiol increased cellular glutathione levels and the expression of the glutamine-cysteine ligase gene in a dose-dependent manner. Furthermore, ganodermanondiol exposure enhanced the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and its upstream kinase activators, LKB1 and Ca(2+)/calmodulin-dependent protein kinase-II (CaMKII). This study indicates that ganodermanondiol exhibits potent cytoprotective effects on t-BHP-induced hepatotoxicity in human liver-derived HepG2 cells, presumably through Nrf2-mediated antioxidant enzymes and AMPK. PMID:23266269

Li, Bin; Lee, Dong-Sung; Kang, Yue; Yao, Nai-Qi; An, Ren-Bo; Kim, Youn-Chul

2012-12-21

406

Pattern of addition of hydroxyl radicals to the spin traps. cap alpha. -pyridyl 1-oxide N-tert-butyl nitrone. [9-MeV electrons  

SciTech Connect

Hydroxyl radicals react with ..cap alpha..-2-, ..cap alpha..-3, and ..cap alpha..-4-pyridyl 1-oxide N-tert-butyl nitrones (POBN) with rate constants of 3.2 x 10/sup 9/, 4.8 x 10/sup 9/, and 3.5 x 10/sup 9/ M/sup -1/ s/sup -1/, respectively, via addition to two distinct sites. Addition to the pyridine ring yields short-lived radicals of the hydrozyazacyclohexadienyl type, while addition to the nitrone function in the side chain yields long-lived nitroxide radicals. The distribution of OH addition at the two molecular sites was determined by using differences in reducing power upon reaction of the different types of radicals with IrCl/sub 6//sup 2 -/. The fraction of OH attack on the pyridine ring is approx. 0.6, relatively independent of the isomeric structure of the POBN.

Neta, P. (Univ. of Notre Dame, IN); Steenken, S.; Janzen, E.G.; Shetty, R.V.

1980-03-06

407

4-Bromo-methyl-6-tert-butyl-2H-chromen-2-one  

PubMed Central

In the crystal structure of the title compound, C14H15BrO2, weak C—H?O inter­actions link the mol­ecules into zigzag chains extending along the c-axis direction. These chains are further assembled into (100) layers via ?–? stacking inter­actions between inversion-related chromenone fragments [inter­planar distance = 3.376?(2)?Å].

Nagarajaiah, H.; Puttaraju, K. B.; Shivashankar, K.; Begum, Noor Shahina

2013-01-01

408

Frontside versus backside reactivity in electron transfer to oriented tert butyl bromide and methyl bromide  

NASA Astrophysics Data System (ADS)

Electron transfer collisions between beams of neutral K atoms and neutral alkyl bromide (R-Br) molecules (R=CH3,t-C4H9) are observed by detecting positive and negative ions in coincidence for energies >~4 eV, the minimum energy for overcoming the Coulomb attraction between ions. The molecules are state selected by a hexapole electric field and oriented prior to the electron transfer. The steric asymmetry for both molecules above ~6 eV shows that ``frontside,'' or Br end attack, is favored to form Br-, with t-C4H9Br being more asymmetric than CH3Br. The asymmetry maximizes near 5 eV and as the energy decreases, apparently changes sign to favor ``backside,'' or alkyl-end attack. Free electrons (and K+) are detected from t-C4H9Br and show a similar change in preferred orientation: at low energies alkyl end attack is favored, and at high energies Br end is favored. These observations suggest that the electron is transferred into different orbitals with different spatial distributions as the energy is varied. Steric factors are evaluated from the experimental data. The steric factor for t-C4H9Br is generally smaller than for CH3Br and above about 5 eV, both increase with energy in Arrhenius-type dependence. The apparent ``steric activation energy'' is ~2.2 eV for CH3Br and 3.9 eV for t-C4H9Br.

Brooks, Philip R.; Harris, Sean A.

2002-09-01

409

TRANSPORT OF METHYL TERT-BUTYL ETHER THROUGH ALFALFA PLANTS. (R825549C062)  

EPA Science Inventory

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

410

PLANT UPTAKE OF METHYL-TERT-BUTYL-ETHER (MTBE) FROM GROUNDWATER. (R825549C062)  

EPA Science Inventory

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

411

Davy McKee's route to MTBE (methyl tert. -butyl ether) takes shape  

SciTech Connect

Davy McKee is offering a route to MTBE based on proven technology, under which butane, at a well head or gas fractionation site, would be isomerized to isobutane, followed by dehydrogenation to isobutylene. Methanol for the final etherification step would also be produced from gas at the site. According to Davy McKee, MTBE is best made close to the source of natural gas or gas liquids and then shipped to distribution centers for ultimate blending into gasoline to raise the octane rating; MTBE will soon become a high-volume commodity product with demand far outweighing current production capabilities.

Not Available

1980-10-27

412

Gallstone dissolution by methyl-tert-butyl ether (MTBE) via percutaneous transhepatic cholecystostomy.  

PubMed

Dissolution of gallbladder stones with MTBE appears to be an effective and safe treatment for patients with symptomatic gallstones who are unfit for surgery. However, the procedure is tedious and the stone recurrence rate is as yet unknown. PMID:2092663

Choong, M K; Phillips, G W

1990-11-01

413

Chemolysis of Gallbladder Debris Left Over After Contact Litholysis with Methyl tertButyl Ether  

Microsoft Academic Search

Rapid and safe gallbladder clearance fromresidual, post-MTBE stone debris is believed to beabsolutely necessary to reduce stone recurrence aftercontact litholysis. Because the clearing effect ofprokinetic agents is considered an uncertainpostdissolution trial, we investigated by in vitroexperiments whether and to what extent debris fromvarious cholesterol and “mixed stones” couldbe removed by direct (topical) chemolysis. Debris from radiolucentcholesterol stones could be dissolved

Ulrich Wosiewitz; Frauke Sabinski; Ulrich Leuschner

1997-01-01

414

Chemolysis of gallbladder debris left over after contact litholysis with methyl tert-butyl ether.  

PubMed

Rapid and safe gallbladder clearance from residual, post-MTBE stone debris is believed to be absolutely necessary to reduce stone recurrence after contact litholysis. Because the clearing effect of prokinetic agents is considered an uncertain postdissolution trial, we investigated by in vitro experiments whether and to what extent debris from various cholesterol and "mixed stones" could be removed by direct (topical) chemolysis. Debris from radiolucent cholesterol stones could be dissolved very easily, using the aqueous solvent S-01, composed of EDTA-2Na (1-2%), lauryl sulfobetaine-12 (0.1 M), and 0.1 M sodium carbonate/boric acid buffer, pH 9,5. Its dissolution capacity (DC) was 8.06 +/- 2.3 mg debris/ml and its dissolution efficacy (DE) was 16.2 +/- 4.6 mg debris/ml/hr. Debris from mixed, slightly to moderately calcified stones needed another treatment with S-05, composed of sodium citrate (0.25 M), lauryl sulfobetaine-12 (0.01 M), and citric acid. The initial pH was 5.2. The DC of S-05 ranged from 1.61 +/- 1.1 (debris enriched with Ca-phosphate) to 3.94 +/- 1.3 mg/ml (debris enriched with Ca-carbonate). Stones which did not respond immediately to MTBE because of a thin rim of inorganic or/and organic Ca salts could be made ready for MTBE litholysis by pretreatment with S-01 or S-05 or with a combination of both solvents. Debris containing large portions of biliary mucus could be dissolved most effectively by successive application of S-01 and S-06 (2 M urea). PMID:9009131

Wosiewitz, U; Sabinski, F; Leuschner, U

1997-01-01

415

Oxidation of methyl- and ethyl- tertiary-butyl ethers in rat liver microsomes: role of the cytochrome P450 isoforms  

Microsoft Academic Search

Methyl t-butyl ether (MTBE) and ethyl t-butyl ether (ETBE) are commonly used in unleaded gasoline to increase the oxygen\\u000a content of fuel and to reduce carbon monoxide emissions from motor vehicles. This study was undertaken to investigate: (1)\\u000a the effect of administration to rats of ETBE and its metabolite, t-butanol, on the induction and\\/or inhibition of hepatic\\u000a P450 isoenzymes; (2)

Alessandra Turini; Giada Amato; Vincenzo Longo; Pier Giovanni Gervasi

1998-01-01

416

Ethyl tert-butyl ether (ETBE) biodegradation by a syntrophic association of Rhodococcus sp. IFP 2042 and Bradyrhizobium sp. IFP 2049 isolated from a polluted aquifer.  

PubMed

Ethyl tert-butyl ether (ETBE) enrichment was obtained by adding contaminated groundwater to a mineral medium containing ETBE as the sole carbon and energy source. ETBE was completely degraded to biomass and CO2 with a transient production of tert-butanol (TBA) and a final biomass yield of 0.37?±?0.08 mg biomass (dry weight).mg(-1) ETBE. Two bacterial strains, IFP 2042 and IFP 2049, were isolated from the enrichment, and their 16S rRNA genes (rrs) were similar to Rhodococcus sp. (99 % similarity to Rhodococcus erythropolis) and Bradyrhizobium sp. (99 % similarity to Bradyrhizobium japonicum), respectively. Rhodococcus sp. IFP 2042 degraded ETBE to TBA, and Bradyrhizobium sp. IFP 2049 degraded TBA to biomass and CO2. A mixed culture of IFP 2042 and IFP 2049 degraded ETBE to CO2 with a biomass yield similar to the original ETBE enrichment (0.31?±?0.02 mg?biomass.mg(-1) ETBE). Among the genes previously described to be involved in ETBE, MTBE, and TBA degradation, only alkB was detected in Rhodococcus sp. IFP 2042 by PCR, and none were detected in Bradyrhizobium sp. IFP 2049. PMID:23474617

Le Digabel, Yoann; Demanèche, Sandrine; Benoit, Yves; Vogel, Timothy M; Fayolle-Guichard, Françoise

2013-03-10

417

Participation of covalent modification of Keap1 in the activation of Nrf2 by tert-butylbenzoquinone, an electrophilic metabolite of butylated hydroxyanisole  

SciTech Connect

Butylated hydroxyanisole (BHA) is an antioxidant and class-2B carcinogen. It is biotransformed to tert-butylhydroquinone (TBHQ), which readily auto-oxidizes to the electrophilic metabolite tert-butylbenzoquinone (TBQ). BHA and TBHQ activate Nrf2, a transcription factor that is negatively regulated by Keap1 and plays a role in the initial response to chemicals causing oxidative or electrophilic stress, although, the exact mechanism of Nrf2 activation remains unclear. Here, we examined the role of TBQ in Nrf2 activation. Exposure of RAW264.7 cells to TBQ activated Nrf2 and up-regulated its downstream proteins; under these conditions, TBQ produced cellular reactive oxygen species (ROS). However, while pretreatment with catalase conjugated with polyethylene glycol (PEG-CAT) did not affect the TBQ-induced activation of Nrf2, the ROS generation caused by TBQ was entirely abolished by PEG-CAT, suggesting that ROS is not the dominant factor for TBQ-dependent Nrf2 activation. A click chemistry technique indicated that TBQ chemically modifies Keap1. Furthermore, ultrahigh performance liquid chromatography-tandem mass spectrometry analysis with purified Keap1 revealed that TBQ covalently binds to Keap1 through Cys23, Cys151, Cys226, and Cys368. These results suggest that TBQ derived from BHA activates Nrf2 through electrophilic modification of Keap1 rather than ROS formation. - Research Highlights: > tert-Butylbenzoquinone (TBQ) activates Nrf2 in RAW264.7 cells. > ROS is not essential factor for Nrf2 activation caused by TBQ. > TBQ covalently binds to Keap1 through reactive thiols, resulting in Nrf2 activation.

Abiko, Yumi; Miura, Takashi [Doctoral Programs in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan); Phuc, Bui Hoang [Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan); Shinkai, Yasuhiro [Doctoral Programs in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan); Kumagai, Yoshito, E-mail: yk-em-tu@md.tsukuba.ac.jp [Doctoral Programs in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan); Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan)

2011-08-15

418

Interaction of Keap1 Modified by 2-tert-Butyl-1,4-benzoquinone with GSH: Evidence for S-Transarylation.  

PubMed

2-tert-Butyl-1,4-benzoquinone (TBQ), an electrophilic metabolite of butylated hydroxyanisole (BHA), causes activation of Nrf2 together with S-arylation of its negative regulator Keap1 in RAW264.7 cells. In a previous study, we found that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) covalently modified with 1,2-naphthoquinone (1,2-NQ) undergoes S-transarylation by GSH, resulting in a decline of the GAPDH-1,2-NQ adduct and formation of a 1,2-NQ-SG adduct ( Miura , T. et al. ( 2011 ) Chem. Res. Toxicol. 24 , 1836 -1844 ). In the present study, we explored the possibility of GSH-dependent S-transarylation of the Keap1-TBQ adduct. Pretreatment with l-buthionine-(S,R)-sulfoximine and N-acetylcysteine prior to TBQ exposure of HepG2 cells suggested that the Keap1-TBQ adduct appears to undergo GSH-mediated S-transarylation because the resulting alterations in the intracellular GSH concentration affected Nrf2 activation caused by TBQ. In support of this hypothesis, a cell-free study demonstrated that incubation of the Keap1-TBQ adduct with GSH results in the removal of TBQ from Keap1 with the production of mono- and di-GSH adducts of TB(H)Q. These results suggest that GSH plays a role in reversible covalent modification of TBQ derived from BHA to Keap1 through the formation of a C-S bond. PMID:23718696

Abiko, Yumi; Kumagai, Yoshito

2013-06-12

419

Mechanistic studies on the degradation of gasoline oxygenates by advanced oxidation technologies and the reaction of 4-methyl-1,2,4-triazoline-3,5-dione with tetracyclopropylethylene  

Microsoft Academic Search

Gasoline oxygenates (MTBE, methyl tert-butyl ether; DIPE, di-isopropyl ether; ETBE, ethyl tert-butyl ether; TAME, tert-amyl ether) are added to gasoline to boost octane and enhance combustion. The combination of large scale use, high water solubility and only minor biodegradability has now resulted in a significant gasoline oxygenate contamination occurring in surface, ground, and drinking water systems. Combination of hydroxyl radical

Duk Kyung Kim

2003-01-01

420

Molecular dynamics simulations of binary structure H hydrogen and methyl-tert-butylether clathrate hydrates  

NASA Astrophysics Data System (ADS)

Binary structure H (sH) hydrogen and methyl-tert-butylether (MTBE) clathrate hydrates are studied with molecular dynamics simulations. Simulations on a 3×3×3 sH unit cell with up to 4.7 mass % hydrogen gas are run at pressures of 100 bars and 2 kbars at 100 and 273 K. For the small and medium cages of the sH unit cell, H2 guest molecule occupancies of 0, 1 (single occupancy), and 2 (double occupancy) are considered with the MTBE molecule occupying all of the large cages. An increase of the small and medium cage occupancies from 1 to 2 leads to a jump in the unit cell volume and configurational energy. Calculations are also set up with 1/3, 2/3, and 8/9 of the MTBE molecules in the large cages replaced by sets of three to six H2 molecules, and the effects on the configurational energy and volume of the simulation cell are determined. As MTBE molecules are replaced with sets of H2 guests in the large cages, the configurational energy of the unit cell increases. At the lower temperature, the energy and volume of the clathrate are not sensitive to the number of hydrogen guests in the large cages; however, at higher temperatures the repulsions among the H2 guest molecules in the large cages cause an increase in the system energy and volume.

Alavi, Saman; Ripmeester, J. A.; Klug, D. D.

2006-05-01