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1

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

2

Detailed chemical kinetic mechanisms of ethyl methyl, methyl tert-butyl and ethyl tert-butyl ethers: The importance of uni-molecular elimination reactions  

Microsoft Academic Search

A reaction mechanism of ethyl methyl ether (EME), methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) for pyrolysis and oxidation have been constructed using the same method applied to di-ethyl ether (DEE) in our recent work [1]. The mechanism, comprising of 1051 reactions involving 215 species, was tested against the experimental data obtained using shock tubes with good agreement.

K. Yasunaga; J. M. Simmie; H. J. Curran; T. Koike; O. Takahashi; Y. Kuraguchi; Y. Hidaka

2011-01-01

3

Integral analysis of methyl tert-butyl ether synthesis kinetics  

SciTech Connect

Kinetics of the liquid phase synthesis of methyl tert-butyl ether (MTBE) from methanol and isobutylene were studied experimentally in an isothermal integral packed-bed reactor over a commercial ion exchange resin catalyst, Amberlyst 15, under conditions corresponding to those encountered in industrial practice. The reaction equilibrium was also studied experimentally and an expression for the equilibrium constant is proposed. The intrinsic kinetics were determined under conditions free of diffusional influence. The resulting effective activation energy, 85.4 kJ/mol, is about the average of those reported in the literature. Next, intraparticle diffusional limitations were investigated for compositions close to the stoichiometric feed and the results indicate that, with Amberlyst 15 catalyst of average diameter 0.74 mm, the reaction is substantially limited by intraparticle diffusion resistance at temperatures above 333 K and at isobutylene conversions closer to the equilibrium.

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

1995-03-01

4

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. PMID:9361407

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

1997-01-01

5

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 (...

6

INFLUENCE OF METHYL TERT-BUTYL ETHER (MTBE) ON LAKE WATER ALGAE: JOURNAL ARTICLE  

EPA Science Inventory

NRMRL-ADA-01209 Kampbell*, D.H., An, Y, and Williams, VR. Influence of Methyl tert-Butyl Ether (MTBE) on Lake Water Algae. Bulletin of Environmental Contamination and Toxicology 57 (4):675-681 (2001). ...

7

Effect of Benzene, Toluene, Ethylbenzene, and p Xylene (BTEX) Mixture on Biodegradation of Methyl tert Butyl Ether (MTBE) and tert Butyl Alcohol (TBA) by Pure Culture UC1  

Microsoft Academic Search

The effect of a BTEX mixture on the biodegradation of methyl tert-butyl ether (MTBE) and its degradation intermediate, tert-butyl alcohol (TBA) was investigated in the pure bacterial culture UC1, which has been identified to be a strain of the known MTBE-degrader PM1 based on greater than 99% 16S rDNA similarity. Several degradation studies were carried out on UC1 at three

Amy Pruden; Makram Suidan

2004-01-01

8

Preparation of methyl (1R,2S,5S)- and (1S,2R,5R)-2-amino-5-tert-butyl-cyclopentane-1-carboxylates by parallel kinetic resolution of methyl (RS)-5-tert-butyl-cyclopentene-1-carboxylate.  

PubMed

Comparison of the kinetic and parallel kinetic resolutions of methyl (RS)-5-tert-butyl-cyclopentene-1-carboxylate allows for the efficient synthesis of both (1R,2S,5S)- and (1S,2R,5R)-enantiomers of methyl 2-amino-5-tert-butyl-cyclopentane-1-carboxylate. PMID:14587706

Davies, Stephen G; Díez, David; El Hammouni, Mohamed M; Garner, A Christopher; Garrido, Narciso M; Long, Marcus J C; Morrison, Rachel M; Smith, Andrew D; Sweet, Miles J; Withey, Jonathan M

2003-10-01

9

Accurate Computer Simulation of Phase Equilibrium for Complex Fluid Mixtures. Application to Binaries Involving Isobutene, Methanol, Methyl tert-Butyl Ether, and  

E-print Network

to Binaries Involving Isobutene, Methanol, Methyl tert-Butyl Ether, and n-Butane Martin Li´sal,*,, William R + methyl tert-butyl ether (MTBE) and the binaries formed by methanol with isobutene, MTBE, and n

Lisal, Martin

10

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...

11

BIODEGRADATION OF METHYL TERT-BUTYL ETHER AND BTEX AT VARYING HYDRAULIC RETENTION TIMES  

EPA Science Inventory

The feasibility of biologically degrading methyl tert-butyl ether (MTBE) contaminated groundwater is dependent on the ability to degrade MTBE and its byproducts in the presence of other gasoline contaminants. This study investigates a mixed culture degrading both MTBE and benzene...

12

TREATMENT OF METHYL TERT-BUTYL ETHER CONTAMINATED WATER USING PHOTOCATALYSIS  

EPA Science Inventory

The feasibility of photo-oxidation treatment of methyl tert-butyl ether (MTBE) in water was investigated in three ways, 1) using a slurry falling film photo-reactor, 2) a batch solar reactor system, and 3) a combination of air-stripping and gas phase photooxidation system. MTBE-c...

13

BIODEGRADATION OF METHYL TERT-BUTYL ETHER USING AN INNOVATIVE BIOMASS CONCENTRATOR REACTOR  

EPA Science Inventory

The aerobic biodegradation of methyl tert-butyl ether (MTBE) was investigated using a pilot-scale Biomass Concentrator Reactor (BCR). The reactor was operated for a year at a flow rate of 2500 L/d of Cincinnati dechlorinated tap water and an influent MTBE concentration o...

14

Treatment of Methyl tert-Butyl Ether Vapors in Biotrickling Filters. 2.  

E-print Network

Treatment of Methyl tert-Butyl Ether Vapors in Biotrickling Filters. 2. Analysis of the Rate MTBE treatment are discussed. Introduction The rapidly rising number of reports of groundwater con environment. ThephysicochemicalpropertiesofMTBEposeachallenge for cost effective treatment, and the choice

15

INHALATION EXPOSURE TO METHYL TERT-BUTYL ETHER (MTBE) AND DIBROMOCHLOROMETHANE (DBCM) USING CONTINUOUS BREATH ANALYSIS  

EPA Science Inventory

The oxygenate methyl tert -butyl ether (MTBE) has been added to gasoline to help meet national ambient air quality standards in those parts of the U.S. that are non-compliant for carbon monoxide. Although MTBE has provided important health benefits in terms of reduced haza...

16

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-...

17

INFLUENCE OF METHYL TERT-BUTYL ETHER (MTBE) ON LAKE WATER ALGAE  

EPA Science Inventory

Methyl tert-butyl ether (MTBE) has been used as an octane booster in gasoline in the United States since the 1970s. MTBE use increased greatly in the 1990s with the implementation of the Clean Air Act Amendments of 1990. The MTBE enhanced a more complete combustion of fuel hydroc...

18

Oxidation of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) by ozone and combined ozone/hydrogen peroxide  

SciTech Connect

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 better eliminated than MTBE with both ozone and combined O[sub 3]/H[sub 2]O[sub 2]. batch experiments led to the determination of the ratio of the kinetic constants for the reaction of OH[degree]-radical with MTBE and ETBE (k[sub OH[degree]/ETBE]/k[sub OH[degree]//MTBE] = 1.7). Tert-butyl formate and tert-butyl acetate were identified as the ozonation byproducts of MTBE an ETBE, respectively, while tert-butyl alcohol was found to be produced during the ozonation of both compounds. 10 refs., 10 figs., 1 tab.

Leitner, N.K.V.; Papailhou, A.L.; Croue, J.P.; Dore, M. (Univ. de Poitiers (France)); Peyrot, J. (British Petroleum, Harfleur (France))

1994-01-01

19

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

20

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

2012-04-01

21

Kinetics of heat-assisted persulfate oxidation of methyl tert-butyl ether (MTBE)  

Microsoft Academic Search

The kinetics of heat-assisted persulfate oxidation of methyl tert-butyl ether (MTBE) in aqueous solutions at various pH, temperature, oxidant concentration and ionic strength levels was studied. The MTBE degradation was found to follow a pseudo-first-order decay model. The pseudo-first-order rate constants of MTBE degradation by persulfate (31.5 mM) at pH 7.0 and ionic strength 0.11 M are ?0.13×10?4, 0.48×10?4, 2.4×10?4

Kun-Chang Huang; Richard A Couttenye; George E Hoag

2002-01-01

22

Overview of technologies for removal of methyl tert-butyl ether (MTBE) from water.  

PubMed

Wide use of methyl tert-butyl ether (MTBE) as fuel oxygenates leads to worldwide environment contamination with this compound basically due to fuel leaks from storage or pipelines. Presence of MTBE in drinking water is of high environmental and social concern. Existing methods for MTBE removal from water have a number of limitations which can be possibly overcome in the future with use of emerging technologies. This work aims to provide an updated overview of recent developments in technologies for MTBE removal from water. PMID:24486497

Levchuk, Irina; Bhatnagar, Amit; Sillanpää, Mika

2014-04-01

23

Decreased toxicity to terrestrial plants associated with a mixture of methyl tert-butyl ether and its metabolite tert-butyl alcohol.  

PubMed

The influence of the main fuel oxygenate methyl tert-butyl ether (MTBE) and its key metabolite, tert-butyl alcohol (TBA), on the growth of a plant seedling was studied separately and in combination. The test plants were mung bean (Phaseolus radiatus), cucumber (Cucumis sativus), wheat (Triticum aestivum), sorghum (Sorghum bicolor), kale (Brassica alboglabra), Chinese cabbage (Brassica campestris), and sweet corn (Zea mays). The growth of all the plants was adversely affected by TBA and MTBE. The 5-d median effective concentration (EC50) for the plants exposed to MTBE and TBA were in the range of 680 to 1,000 mg MTBE/kg soil (dry wt) and 1,200 to 3,500 mg TBA/kg soil (dry wt), respectively. The relative order of the sensitivity rankings is almost the same for MTBE and TBA. Methyl tert-butyl ether is more toxic than TBA to most of the test species. Based on the EC50 values, MTBE is approximately 1.5 to 3 times more potent than TBA. The sum of the toxic unit (TU) at 50% inhibition of the mixture (EC50mix) was calculated from the dose (TU-based)-response relationships using the trimmed Spearman-Karber method. The combined effect of MTBE + TBA on the plant growth was less than additive because the EC50mix values were greater than I TU. This phenomenon may be due to the competition of MTBE and TBA in terms of their intake by plants. The combined effects of MTBE and TBA should be taken into account to assess their risk in gasoline-contaminated sites. PMID:17702346

An, Youn-Joo; Lee, Woo-Mi

2007-08-01

24

CO-OCCURRENCE OF METHYL- TERT-BUTYL ETHER (MTBE) AND BTEX COMPOUNDS AT MARINAS IN A LARGE RESEVOIR  

EPA Science Inventory

Methyl tert-butyl ether (MTBE) is released into the environment as one of some gasoline components, not as a pure compound. BTEX compounds (benzene, tolune, ethylbenzene, and xylenes) are major volatile constituents found in gasoline and are water soluble and mobile. This study...

25

Anaerobic Biodegradation Of Methyl tert -Butyl Ether Under Iron-Reducing Conditions In Batch And Continuous-Flow Cultures  

EPA Science Inventory

The feasibility of biodegradation of the fuel oxygenate methyl tert -butyl ether (MTBE) under iron-reducing conditions was explored in batch and continuous-flow systems. A porous pot completely-mixed reactor was seeded with diverse cultures and operated under iron-reducing...

26

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...

27

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...

28

DERMAL EXPOSURE TO METHYL TERT-BUTYL ETHER (MTBE) AND DIBROMOCHLOROMETHANE (DBCM) WHILE BATHING WITH CONTAMINATED WATER  

EPA Science Inventory

The oxygenate methyl tert-butyl ether (MTBE) has been added to gasoline to help meet national ambient air quality standards in those parts of the U.S. that are non-compliant for carbon monoxide. Although MTBE has provided important health benefits in terms of reduced hazardous a...

29

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...

30

Combined toxicities of methyl tert-butyl ether and its metabolite tert-butyl alcohol on earthworms via different exposure routes.  

PubMed

Methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) are among the major soil contaminants that threaten the health of soil ecosystems. Many MTBE-contaminated sites accumulate TBA, because TBA is the intermediate of MTBE biodegradation. To access the risk of MTBE and TBA in soil, we investigated the combined toxicities of MTBE and TBA using two earthworm species, Perionyx excavatus and Eisenia andrei, as well as the toxic effects via different exposure routes. The combined toxicity showed weak antagonistic effects (LC50mix values were slightly greater than 1.0), and sensitivity toward same pollutants differed in the two earthworm species. Moreover, the toxicity of MTBE and TBA was also affected by the exposure route; both filter paper and artificial soil tests showed that dermal-only exposure to MTBE had an even greater toxic effect than combined dermal and oral exposure. Thus, we suggest that diverse environmental factors including organic materials, the physicochemical properties of the contact media, and the exposure routes of the organism, should be taken into consideration when assessing the effects of pollutants on organisms in diverse environmental systems. PMID:25706436

Lee, Woo-Mi; Yoon, Youngdae; An, Youn-Joo

2015-06-01

31

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

32

Methyl tert-butyl ether (MTBE) degradation by ferrous ion-activated persulfate oxidation: feasibility and kinetics studies.  

PubMed

The objective of this study was to evaluate the feasibility of using ferrous ion-activated persulfate oxidation to remediate groundwater contaminated with methyl tert-butyl ether (MTBE). In this study, batch experiments were conducted to evaluate the effects of various factors on the efficiency of MTBE degradation including persulfate concentrations, ferrous ion concentrations, and persulfate coupled with hydrogen peroxide. Results show that ferrous ion-activated persulfate oxidation was capable of degrading MTBE efficiently. Persulfate and ferrous ion concentrations correlated with MTBE degradation rates. However, excess addition of ferrous ion resulted in decreased MTBE degrading rates most likely because of competition for sulfate free radicals between ferrous ion and MTBE. Two main byproducts of MTBE degradation, tert-butyl formate and tert-butyl alcohol, were detected in the experiments; both were, however, subsequently degraded. Results of sulfate analysis show that proper addition of ferrous ion could prevent unnecessary persulfate decomposition. PMID:19691249

Chen, K F; Kao, C M; Wu, L C; Surampalli, R Y; Liang, S H

2009-07-01

33

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

34

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. PMID:12039730

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

2002-01-01

35

CONCENTRATIONS, SOURCES, AND FATE OF THE GASOLINE OXYGENATE METHYL TERT-BUTYL ETHER (MTBE) IN A MULTIPLE-USE LAKE. (R826282)  

EPA Science Inventory

Discovery of the fuel additive methyl tert -butyl ether (MTBE) in drinking water supplies is of concern to public health officials, water suppliers, and the public. Despite recent policy decisions, few published studies exist on the concentrations, sources, a...

36

Impact of activation methods on persulfate oxidation of methyl tert-butyl ether.  

PubMed

To provide guidance on the selection of proper persulfate processes for the remediation of MTBE contaminated groundwater, MTBE aqueous solutions were treated with three common field persulfate processes including heat activated persulfate, Fe(III)-EDTA activated persulfate and alkaline persulfate, respectively. The results were compared with MTBE oxidation by Fenton's reagent and persulfate alone at 25°C. The impact of the activating conditions on the fate of MTBE and its daughter products was investigated. Heat activation at 40°C offered the most rapid removal of MTBE and its daughter products, while Fe(III)-EDTA activation showed higher efficiency of MTBE removal but low removal efficiency of its daughter products. On the other hand, alkaline persulfate showed slower kinetics for the removal of MTBE and less accumulation of the daughter products. Furthermore, tert-butyl alcohol and acetone were observed as the main purgeable daughter products along with a small amount of tert-butyl formate in persulfate oxidation of MTBE, while tert-butyl formate, tert-butyl alcohol and acetone were the main products in Fenton oxidation. Mechanistic analysis suggests that degradation of MTBE by persulfate most likely happens via non-oxygen demand pathways, different from the dominant oxygen demand degradation pathways observed in Fenton oxidation. PMID:24246442

Deng, Dayi; Peng, Libin; Guan, Mengyun; Kang, Yuan

2014-01-15

37

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

38

Microbial toxicity of methyl tert-butyl ether (MTBE) determined with fluorescent and luminescent bioassays.  

PubMed

The inhibitory effects of the fuel additive methyl tert-butyl ether (MTBE) and potential degradation products tert-butanol (TBA) and formaldehyde was examined using mixed microbial biomass, and six strains of bioluminescent bacteria and yeast. The purpose was to assess microbial toxicity with quantitative bioluminescent and fluorescent endpoints, and to identify sensitive proxies suitable for monitoring MTBE contamination. Bioluminescent Aliivibrio fischeri DSM 7151 (formerly Vibrio fischeri) appeared highly sensitive to MTBE exposure, and was a superior test organisms compared to lux-tagged Escherichia coli DH5?, Pseudomonas fluorescens DF57-40E7 and Saccharomyces cerevisiae BLYR. EC10 and EC50 for acute MTBE toxicity in A. fischeri were 1.1 and 10.9 mg L(-1), respectively. Long term (24h) MTBE exposure resulted in EC10 values of 0.01 mg L(-1). TBA was significantly less toxic with EC10 and EC50 for acute and chronic toxicity >1000 mg L(-1). Inhibition of bioluminescence was generally a more sensitive endpoint for MTBE toxicity than measuring intracellular ATP levels and heterotrophic CO2 assimilation. A weak estrogenic response was detected for MTBE at concentrations ? 3.7 g L(-1) using an estrogen inducible bioluminescent yeast strain (S. cerevisiae BLYES). Microbial hydrolytic enzyme activity in groundwater was affected by MTBE with EC10 values of 0.5-787 mg L(-1), and EC50 values of 59-3073 for alkaline phosphatase, arylsulfatase, beta-1,4-glucanase, N-acetyl-beta-d-glucosaminidase, and leucine-aminopeptidase. Microbial alkaline phosphatase and beta-1,4-glucanase activity were most sensitive to MTBE exposure with EC50 ? 64.8 mg L(-1). The study suggests that bioassays with luminescent A. fischeri, and fluorescent assays targeting hydrolytic enzyme activity are good candidates for monitoring microbial MTBE toxicity in contaminated water. PMID:25128634

Roslev, Peter; Lentz, Trine; Hesselsoe, Martin

2015-02-01

39

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

PubMed Central

Disruption of vascular endothelial growth factor (VEGF) signaling during early development results in abnormal angiogenesis and increased vascular lesions. Embryonic exposure to 0.625 to 10 mM 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 to 10 mM) 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.

2015-01-01

40

Enhanced biodegradation of methyl tert-butyl-ether by a microbial consortium.  

PubMed

The widespread use of Methyl tert-butyl-ether (MTBE) as a gasoline additive has resulted in a higher detection rate of MTBE in groundwater systems. Therefore, the researchers show more concern about the bioremediation of MTBE-impacted aquifers. In this paper, a MTBE-direct-degrading bacterial consortium was enriched (named RS1) and further studied. In order to identify the microbial community of the consortium, 17 and 12 different single strains were isolated from nutrient medium and MSM media (with MTBE as the sole carbon source), respectively. 16S rDNA-based phylogenetic analysis revealed that these diverse bacteria belonged to 14 genera, in which Pseudomonas was dominant. Several strains which can grow with MTBE as the sole carbon and energy source were also identified, such as M1, related to MTBE-degrading Arthrobacter sp. ATCC27778. Furthermore, the appropriate addition of certain single strain in consortium RS1 (M1:RS1 = 1:2) facilitates MTBE degradation by increasing the quantity of efficient MTBE-degrading bacteria. This work will provide microbial source and theoretical fundament for further bioremediation of MTBE-contaminated aquifers, which has applied potential and environmental importance. PMID:24162446

Li, Shan-shan; Zhang, Di; Yan, Wei

2014-03-01

41

Methyl tert-butyl ether (MTBE) in snow samples in Germany  

NASA Astrophysics Data System (ADS)

In the present study, experimental results of methyl tert-butyl ether (MTBE) analysis in 43 snow samples from 13 various locations during two winter seasons are presented. MTBE could be detected in 65% of the samples. The concentrations ranged from 11 to 631 ng L -1. The comparison to formerly analysed rainwater samples indicates atmospheric transfer of MTBE from urban to rural areas preferentially in winter due to lower atmospheric degradation rates and suggests that MTBE is more effectively scavenged from the atmosphere by snow than by rain. This result is in contrast to calculated distribution coefficients KRain/Air (-6.8°) and KSnow/Air (-6.8°) using different values for the specific snow surface area. MTBE concentrations measured in the collected snow samples from rural areas did not differ from MTBE concentrations in snow samples collected in the urban area of Frankfurt/M. The explanatory factor for this finding is also the lower atmospheric degradation rate of MTBE in winter. Particular meteorological conditions at the monitoring site Schmücke most probably explain maximum concentrations of 631 and 438 ng L -1 measured at this site. Decreasing MTBE amounts in snow samples collected at the monitoring site Schauinsland in January 2003 might have been due to increasing ambient temperatures. Varying MTBE amounts in snow samples collected at the Taunus Observatorium (Kleiner Feldberg) in February 2002 and in January/February 2003 cannot be explained by ambient temperatures. In future studies concurrent air sampling and morphological characterisation of the sampled snow would be required to clarify and confirm the results of the present study.

Kolb, Axel; Püttmann, Wilhelm

42

Methyl tert-butyl ether biodegradation by indigenous aquifer microorganisms under natural and artificial oxic conditions  

USGS Publications Warehouse

Microbial communities indigenous to a shallow groundwater system near Beaufort, SC, degraded milligram per liter concentrations of methyl tert-butyl ether (MTBE) under natural and artificial oxic conditions. Significant MTBE biodegradation was observed where anoxic, MTBE-contaminated groundwater discharged to a concrete-lined ditch. In the anoxic groundwater adjacent to the ditch, concentrations of MTBE were > 1 mg/L. Where groundwater discharge occurs, dissolved oxygen (DO) concentrations beneath the ditch exceeded 1.0 mg/L to a depth of 1.5 m, and MTBE concentrations decreased to <1 ??g/L prior to discharge. MTBE mass flux calculations indicate that 96% of MTBE mass loss occurs in the relatively small oxic zone prior to discharge. Samples of a natural microbial biofilm present in the oxic zone beneath the ditch completely degraded [U-14C]MTBE to [14C]CO2 in laboratory liquid culture studies, with no accumulation of intermediate compounds. Upgradient of the ditch in the anoxic, MTBE and BTEX-contaminated aquifer, addition of a soluble oxygen release compound resulted in oxic conditions and rapid MTBE biodegradation by indigenous microorganisms. In an observation well located closest to the oxygen addition area, DO concentrations increased from 0.4 to 12 mg/L in <60 days and MTBE concentrations decreased from 20 to 3 mg/L. In the same time period at a downgradient observation well, DO increased from <0.2 to 2 mg/L and MTBE concentrations decreased from 30 to <5 mg/L. These results indicate that microorganisms indigenous to the groundwater system at this site can degrade milligram per liter concentrations of MTBE under natural and artificial oxic conditions.

Landmeyer, J.E.; Chapelle, F.H.; Herlong, H.H.; Bradley, P.M.

2001-01-01

43

Responses of the steroidogenic pathway from exposure to methyl-tert-butyl ether and tert-butanol.  

PubMed

Methyl tertiary-butyl ether (MTBE) is a solvent and fuel additive included in reformulated gasoline to increase combustion efficiency. While widespread use in motor fuels in the U.S. was discontinued after MTBE was detected in surface and ground waters due to concerns about environmental persistence and water quality, it is still manufactured in the U.S. for export. Questions concerning the etiology of rat Leydig cell and mouse liver tumors identified in extremely high dose cancer studies have led to an interest in evaluating potential hormonal imbalances and endocrine system involvement. To address the possibility that MTBE or its metabolite, tert-butanol (TBA), are interacting with components of the endocrine system that are involved in steroidogenesis a number of targeted experiments were performed focusing mostly on the primary gonadal steroids, estradiol and testosterone. The goal of the experiments was to gain a better understanding of potential interactions with the steroidogenic pathway, including effects specifically on aromatase, the P450 enzyme that converts testosterone to estradiol. In three GLP-compliant in vitro guideline studies, MTBE and TBA were classified as non-binders to the androgen receptor, were classified negative for effects on testosterone and estradiol in the steroidogenesis assay, and were classified as non-inhibitors of aromatase activity. In three 14-day in vivo experiments involving gavaging of male Sprague-Dawley rats with doses of MTBE ranging from 400 to 1,500 mg/kg bw/day, the lack of definitive and consistent supporting statistically significant findings in steroid hormone measurements and aromatase activity and mRNA measured in liver and testis microsomes further suggested that it is unlikely that MTBE is interacting with the endocrine system directly. Evidence of other underlying systemic effects were also seen, including reduced body weight gain, increased adrenal weights, and elevated corticosterone suggestive of a more general stress response. Taken together, the results from these studies suggest that MTBE and TBA do not directly impact the steroidogenic pathways involved in estrogen and androgen production. PMID:24560773

de Peyster, Ann; Mihaich, Ellen; Kim, Do Hyung; Elyea, William A; Nemec, Matthew J; Hirakawa, Brad P; Leggieri, Shannon E

2014-05-01

44

Laboratory Method for Analysis of Small Concentrations of Methyl tert-Butyl Ether and Other Ether Gasoline Oxygenates in Water  

USGS Publications Warehouse

This Fact Sheet presents data for analysis of nanogram-per-liter concentrations of methyl tert-butyl ether (MTBE) and three other ether gasoline oxygenates, including methyl tert-pentyl ether (TAME), diisopropyl ether (DIPE), and ethyl tert-butyl ether (ETBE), by purge- and-trap capillary-column gas chromatography. Long-term method detection levels (LT-MDLs) for MTBE, TAME, DIPE, and ETBE ranged from 15 to 83 nanograms per liter (0.015 to 0.083 microgram per liter). Nanogram-per-liter-concentration detections are reported if all of the identification criteria are met, whereas previous methods censored detections at a pre-determined method reporting level. The reporting level for this method is defined as two times the LT-MDL, does not censor detections at less than this concentration, and is referred to as the nondetection value (NDV). Bias and variability data from multiple analyses, analysts, and instruments over a 60-day period show the oxygenate recoveries ranging from 100 to 109 percent, with 6 to 8 percent relative standard deviation. MTBE, TAME, DIPE, and ETBE were not detected in the analysis of 225 laboratory reagent blanks from January to December 1997. A preservation study in ground water and surface water indicates that all the oxygenates are stable at pH 2 for up to 216 days, with recoveries ranging from 94 to 115 percent on day 216, and relative standard deviations ranging from 5 to 9 percent for the duration of the study.

Rose, Donna L.; Connor, Brooke F.; Abney, Sonja R.; Raese, Jon W.

1998-01-01

45

Vacuum ultraviolet photoionization and ab initio Investigations of methyl tert-butyl ether (MTBE) clusters and MTBE-water clusters  

NASA Astrophysics Data System (ADS)

The structures and energetics of neutral, ionized and protonated methyl tert-butyl ether (MTBE) clusters and (MTBE)m(H2O)n clusters are investigated by tunable vacuum-UV photoionization mass spectrometry and DFT calculations. While the mass spectra of bare MTBE clusters show unprotonated and protonated clusters ions, the mass spectra of mixed clusters show protonated ions that exhibit magic numbers that correspond to n = m - 2 combinations. Ab initio calculations show that in the larger clusters a multiple proton transfer leads to a protonated water core where all available hydrogen bonds interact with MTBE molecules. The resulting bond structure explains the cluster stability.

Di Palma, Tonia M.; Bende, Attila

2013-03-01

46

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

47

Pyrolysis of methyl tert-butyl ether (MTBE). 2. Theoretical study of decomposition pathways.  

PubMed

The thermal decomposition pathways of MTBE have been investigated using the G3B3 method. On the basis of the experimental observation and theoretical calculation, the pyrolysis channels are provided, especially for primary pyrolysis reactions. The primary decomposition pathways include formation of methanol and isobutene, CH4 elimination, H2 elimination and C-H, C-C, C-O bond cleavage reactions. Among them, the formation channel of methanol and isobutene is the lowest energy pathway, which is in accordance with experimental observation. Furthermore, the secondary pyrolysis pathways have been calculated as well, including decomposition of tert-butyl radical, isobutene, methanol and acetone. The radicals play an important role in the formation of pyrolysis products, for example, tert-butyl radical and allyl radical are major precursors for the formation of allene and propyne. Although some isomers (isobutene and 1-butene, allene and propyne, acetone and propanal) are identified in our experiment, these isomerization reaction pathways occur merely at the high temperature due to their high activation energies. The theoretical calculation can explain the experimental results reported in part 1 and shed further light on the thermal decomposition pathways. PMID:18823102

Zhang, Taichang; Zhang, Lidong; Wang, Jing; Yuan, Tao; Hong, Xin; Qi, Fei

2008-10-23

48

Enhanced bioremediation of methyl tert-butyl ether (MTBE) by microbial consortia obtained from contaminated aquifer material.  

PubMed

A microcosm study was carried out to evaluate the potential for biodegradation of methyl tert-butyl ether (MTBE) impacting groundwater at a former oil refinery site located in Naples (SW Italy). A screening of aerobic, anaerobic and co-metabolic aerobic conditions was carried out by triplicate batch reactors, using contaminated soil and groundwater from the study site. All microcosms were amended with ammonium and phosphate salts and, if aerobic, they were supplied with excess oxygen throughout the static incubation period of 6 months. Propane, pentane and n-hexane were selected as the primary substrates for co-metabolic treatments. After the initial lag phase (40-60d), quantitative MTBE decay was repeatedly observed in the aerobic set amended only with nitrogen and phosphorus and further fed with MTBE, thus suggesting that the indigenous soil bacteria have the ability to degrade MTBE. All other treatments, i.e., anaerobic and co-metabolic aerobic, resulted unsuccessful after incubation extending up to 190d. Bacterial consortia in the active microcosms were later enriched and further studied through second and third generation batch reactors with no soil, operated under continuous mixing for 5-7 months. MTBE degradation rate progressively increased with reactor operating time, following a zero order kinetics in the concentration range 1-10mgL(-1) and leading to a residual concentration of less than 10microgL(-1). The calculated maximum biodegradation rate was 20mg(MTBE)g(VSS)(-1)h(-1). An accumulation of nitrite ions also occurred after long operating times, thus inhibiting MTBE degradation. This effect was minimized by replacing ammonium with nitrate. Identified degradation intermediates were tert-butyl alcohol and tert-butyl formate. Fluorescent in situ hybridization was applied for a preliminary microbiological screening of the consortia, suggesting that the detected cocci (about 0.5 and 1.5microm diameter, respectively) and long bacilli with a narrow diameter might be as yet undescribed species. PMID:19178929

Volpe, Angela; Del Moro, Guido; Rossetti, Simona; Tandoi, Valter; Lopez, Antonio

2009-04-01

49

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

50

Microbial community analyses of three distinct, liquid cultures that degrade methyl tert-butyl ether using anaerobic metabolism.  

PubMed

Methyl tert-butyl ether (MTBE) is a prevalent groundwater contaminant. In this study, three distinct MTBE-degrading, anaerobic cultures were derived from MTBE-contaminated aquifer material: cultures NW1, NW2 and NW3. The electron acceptors used are anthraquinone-2,6-disulfonate (AQDS; NW1), sulfate (NW2) and fumarate (NW3), respectively. About 1-2 mM MTBE is consistently degraded within 20-30 days in each culture. The 16S rDNA-based amplified ribosomal DNA restriction analysis (ARDRA) was used to analyze the microbial community in each culture. Results indicate novel microorganisms (i.e. no closely related known genera or species) catalyze anaerobic MTBE biodegradation, and microbial diversity varied with different electron acceptors. Tert-butyl alcohol (TBA) accumulated to nearly stoichiometric levels, and these cultures will be critical to understanding the factors that influence TBA accumulation versus degradation. The cultures presented here are the first stable anaerobic MTBE-degrading cultures that have been characterized with respect to taxonomy. PMID:19340592

Wei, Na; Finneran, Kevin T

2009-09-01

51

Framework for correlating composition dependent equilibrium conversion in methyl tert-butyl ether formation by ion-exchange catalysts  

SciTech Connect

Catalyst performance for the reaction of methanol and isobutylene (IB) to form methyl tert-butyl ether can be assessed based on maximum conversion. The equilibrium conversion attainable for this reaction is of practical interest since separation of products from reactants downstream of the reactor can be simplified as the extent of conversion increases. A framework is presented by which different catalysts can be compared on an internally consistent basis for different temperatures, isobutylene concentrations, and/or methanol/isobutylene mole ratios. An equilibrium expression which accounts for the presence of nonreacting components is presented to correlate the effect of methanol/IB ratios and IB concentrations with observed conversions for different catalysts. Assumptions inherent in this method are discussed and data for several types of ion-exchange catalysts illustrate use of this framework.

Ladisch, M.; Westgate, P.; Hendrickson, R.; Brewer, M. [Purdue Univ., West Lafayette, IN (United States)

1995-08-01

52

Crystal structure of O-isopropyl [bis­(tri­methyl­sil­yl)amino](tert-butyl­amino)­phosphino­thio­ate  

PubMed Central

[Bis(tri­methyl­sil­yl)amino](tert-butyl­imino)­thio­phospho­rane reacts in benzene with isopropyl alcohol via 1,2-addition of an iPrO–H bond across the P=N bond, resulting in the title compound, C13H35N2OPSSi2. In the mol­ecule, the P atom possesses a distorted tetra­hedral environment involving two N atoms from (Me3Si)2N– and tBuNH– groups, one O atom from an iPrO group and one S atom, therefore the mol­ecule has a stereocenter on the P atom but crystal symmetry leads to a racemate. In the crystal, a pair of enanti­omers form a centrosymmetric dimer via a pair of N—H?S hydrogen bonds. PMID:25705495

Kovalenko, Oleksandr O.; Kinzhybalo, Vasyl; Brusylovets, Oleksii A.; Lis, Tadeusz

2015-01-01

53

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

54

Complementarity of purge-and-trap and head-space capillary gas chromatographic methods for determination of methyl- tert.-butyl ether in water  

Microsoft Academic Search

An improved method has been developed for the quantitative determination of traces of methyl-tert.-butyl ether (MTBE) over a large range of concentrations in water samples based on two complementary techniques: head-space capillary gas chromatography and purge-and-trap gas chromatography. The interesting aspect of this study lies in the complementary performances of these two methods, each in its specific range, for the

B. Nouri; B. Fouillet; G. Toussaint; R. Chambon; P. Chambon

1996-01-01

55

Treatment of Methyl tert-Butyl Ether Vapors in Biotrickling Filters. 1.  

E-print Network

. Introduction Methyltert-butyl ether (MTBE) was first introduced in United States in the late 1970s as an octane among all chemicals in 1993. At the same time, an increasing number of groundwater contaminations

56

Continuous on-line determination of methyl tert-butyl ether in water samples using ion mobility spectrometry.  

PubMed

A rapid analytical procedure for the on-line determination of methyl tert-butyl ether (MTBE) in water samples was developed. A new membrane extraction unit was used to extract the MTBE from water samples. The concentration of MTBE was determined using ion mobility spectrometry with 63Ni ionization and corona discharge ionization without chromatographic separation. Both ionization methods permit the sensitive determination of MTBE. A detection limit of 100 microg/L was established for the on-line procedure. Neither the inorganic compounds, humic substances nor gasoline were found to exert a significant influence on the peak intensity of the MTBE. The screening procedure can be used for concentrations of monoaromatic compounds (benzene, toluene, xylene) up to 600 microg/L. No sample preparation is required and the analysis results are available within 5 min. In order to determine concentrations between 10 microg/L and 100 microg/L, a discontinuous procedure was developed on the basis of the same experimental set-up. PMID:15881458

Borsdorf, H; Rämmler, A

2005-04-22

57

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

58

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

59

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

60

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. PMID:22327600

Sun, Weimin; Sun, Xiaoxu

2012-01-01

61

The Efficient Photocatalytic Degradation of Methyl Tert-butyl Ether Under Pd/ZnO and Visible Light Irradiation.  

PubMed

Methyl tert-butyl ether is a commonly used fuel oxygenate that is present in gasoline. It was introduced to eliminate the use of leaded gasoline and to improve the octane quality because it aids in the complete combustion of fuel by supplying oxygen during the combustion process. Over the past decade, the use of MTBE has increased tremendously worldwide. For obvious reasons relating to accidental spillage, MTBE started to appear as an environmental and human health threat because of its nonbiodegradable nature and carcinogenic potential, respectively. In this work, MTBE was degraded with the help of an advanced oxidation process through the use of zinc oxide as a photocatalyst in the presence of visible light. A mixture of 200 mg of zinc oxide in 350 mL of 50 ppm MTBE aqueous solution was irradiated with visible light for a given time. The complete degradation of MTBE was recorded, and approximately 99% photocatalytic degradation of 100 ppm MTBE solution was observed. Additionally, the photoactivity of 1% Pd-doped ZnO was tested under similar conditions to understand the effect of Pd doping on ZnO. Our results obtained under visible light irradiation are very promising, and they could be further explored for the degradation of several nondegradable environmental pollutants. PMID:25400159

Seddigi, Zaki S; Ahmed, Saleh A; Bumajdad, Ali; Danish, Ekram Y; Shawky, Ahmed M; Gondal, Mohammed A; Soylak, Mustafa

2015-03-01

62

Atmospheric and Potable Water Exposures to Methyl tertButyl Ether (MTBE)  

Microsoft Academic Search

This paper presents information on the ways in which people can be exposed to methyltert-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 compiled for 15 different occupational, commuting, or residential exposure categories, and concentrations in potable water were compiled from five

Stephen L. Brown

1997-01-01

63

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. PMID:17158667

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

64

Manipulation of the HIF-Vegf pathway rescues methyl tert-butyl ether (MTBE)-induced vascular lesions  

PubMed Central

Methyl tert-butyl ether (MTBE) has been shown to be specifically anti-angiogenic in piscine and mammalian model systems at concentrations that appear non-toxic in other organ systems. The mechanism by which MTBE targets developing vascular structures is unknown. A global transcriptome analysis of zebrafish embryos developmentally exposed to 0.00625–5 mM MTBE suggested hypoxia inducible factor (HIF)-regulated pathways were affected. HIF-driven angiogenesis via vascular endothelial growth factor (vegf) is essential to the developing vasculature of an embryo. Three rescue studies were designed to rescue MTBE-induced vascular lesions: pooled blood in the common cardinal vein (CCV), cranial hemorrhages (CH), and abnormal intersegmental vessels (ISV), and test the hypothesis that MTBE toxicity was HIF-Vegf dependent. First, zebrafish vegf-a over-expression via plasmid injection, resulted in significantly fewer CH and ISV lesions, 46 and 35% respectively, in embryos exposed to 10mM MTBE. Then HIF degradation was inhibited in two ways. Chemical rescue by N-oxaloylglycine significantly reduced CCV and CH lesions by 30 and 32% in 10mM exposed embryos, and ISV lesions were reduced 24% in 5mM exposed zebrafish. Finally, a morpholino designed to knockdown ubiquitin associated von Hippel-Lindau protein, significantly reduced CCV lesions by 35% in 10mM exposed embryos. In addition, expression of some angiogenesis related genes altered by MTBE exposure were rescued. These studies demonstrated that MTBE vascular toxicity is mediated by a down regulation of HIF-Vegf driven angiogenesis. The selective toxicity of MTBE toward developing vasculature makes it a potentially useful chemical in the designing of new drugs or in elucidating roles for specific angiogenic proteins in future studies of vascular development. PMID:24128854

Bonventre, Josephine A.; Kung, Tiffany S.; White, Lori A.; Cooper, Keith R.

2014-01-01

65

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

66

Gene mdpC plays a regulatory role in the methyl-tert-butyl ether degradation pathway of Methylibium petroleiphilum strain PM1.  

PubMed

Among the few bacteria known to utilize methyl tert-butyl ether (MTBE) as a sole carbon source, Methylibium petroleiphilum PM1 is a well-characterized organism with a sequenced genome; however, knowledge of the genetic regulation of its MTBE degradation pathway is limited. We investigated the role of a putative transcriptional activator gene, mdpC, in the induction of MTBE-degradation genes mdpA (encoding MTBE monooxygenase) and mdpJ (encoding tert-butyl alcohol hydroxylase) of strain PM1 in a gene-knockout mutant mdpC(-). We also utilized quantitative reverse transcriptase PCR assays targeting genes mdpA, mdpJ and mdpC to determine the effects of the mutation on transcription of these genes. Our results indicate that gene mdpC is involved in the induction of both mdpA and mdpJ in response to MTBE and tert-butyl alcohol (TBA) exposure in PM1. An additional independent mechanism may be involved in the induction of mdpJ in the presence of TBA. PMID:25724531

Joshi, Geetika; Schmidt, Radomir; Scow, Kate M; Denison, Michael S; Hristova, Krassimira R

2015-04-01

67

Di-?-methanolato-bis[(2-tert-butyl-6-methylphenolato-?O)methyl­titanium(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. PMID:24098182

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

2013-01-01

68

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)] [Univ. of Tokyo (Japan); Nakata, Shin-ichi [Chiyoda Corp., Yokohama (Japan)] [Chiyoda Corp., Yokohama (Japan)

1997-03-01

69

Manipulation of the HIF–Vegf pathway rescues methyl tert-butyl ether (MTBE)-induced vascular lesions  

SciTech Connect

Methyl tert-butyl ether (MTBE) has been shown to be specifically anti-angiogenic in piscine and mammalian model systems at concentrations that appear non-toxic in other organ systems. The mechanism by which MTBE targets developing vascular structures is unknown. A global transcriptome analysis of zebrafish embryos developmentally exposed to 0.00625–5 mM MTBE suggested that hypoxia inducible factor (HIF)-regulated pathways were affected. HIF-driven angiogenesis via vascular endothelial growth factor (vegf) is essential to the developing vasculature of an embryo. Three rescue studies were designed to rescue MTBE-induced vascular lesions: pooled blood in the common cardinal vein (CCV), cranial hemorrhages (CH), and abnormal intersegmental vessels (ISV), and test the hypothesis that MTBE toxicity was HIF–Vegf dependent. First, zebrafish vegf-a over-expression via plasmid injection, resulted in significantly fewer CH and ISV lesions, 46 and 35% respectively, in embryos exposed to 10 mM MTBE. Then HIF degradation was inhibited in two ways. Chemical rescue by N-oxaloylglycine significantly reduced CCV and CH lesions by 30 and 32% in 10 mM exposed embryos, and ISV lesions were reduced 24% in 5 mM exposed zebrafish. Finally, a morpholino designed to knock-down ubiquitin associated von Hippel–Lindau protein, significantly reduced CCV lesions by 35% in 10 mM exposed embryos. In addition, expression of some angiogenesis related genes altered by MTBE exposure were rescued. These studies demonstrated that MTBE vascular toxicity is mediated by a down regulation of HIF–Vegf driven angiogenesis. The selective toxicity of MTBE toward developing vasculature makes it a potentially useful chemical in the designing of new drugs or in elucidating roles for specific angiogenic proteins in future studies of vascular development. - Highlights: • Global gene expression of MTBE exposed zebrafish suggested altered HIF1 signaling. • Over expression of zebrafish vegf-a rescues MTBE-induced vascular lesions. • Inhibiting PHD or knocking down VHL rescues MTBE-induced vascular lesions. • HIF1-Vegf driven angiogenesis is a target for MTBE vascular toxicity.

Bonventre, Josephine A., E-mail: josephine.bonventre@oregonstate.edu [Rutgers, The State University of New Jersey, Joint Graduate Program in Toxicology, 170 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Rutgers, The State University of New Jersey, Department of Biochemistry and Microbiology, 76 Lipman Dr., New Brunswick, NJ 08901 (United States); Oregon State University, Department of Environmental and Molecular Toxicology, 1011 Agricultural and Life Sciences Bldg, Corvallis, OR 97331 (United States); Kung, Tiffany S., E-mail: tiffany.kung@rutgers.edu [Rutgers, The State University of New Jersey, Joint Graduate Program in Toxicology, 170 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Rutgers, The State University of New Jersey, Department of Biochemistry and Microbiology, 76 Lipman Dr., New Brunswick, NJ 08901 (United States); White, Lori A., E-mail: lawhite@aesop.rutgers.edu [Rutgers, The State University of New Jersey, Joint Graduate Program in Toxicology, 170 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Rutgers, The State University of New Jersey, Department of Biochemistry and Microbiology, 76 Lipman Dr., New Brunswick, NJ 08901 (United States); Cooper, Keith R., E-mail: cooper@aesop.rutgers.edu [Rutgers, The State University of New Jersey, Joint Graduate Program in Toxicology, 170 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Rutgers, The State University of New Jersey, Department of Biochemistry and Microbiology, 76 Lipman Dr., New Brunswick, NJ 08901 (United States)

2013-12-15

70

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

71

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

72

Expression of an alkane monooxygenase (alkB) gene and methyl tert-butyl ether co-metabolic oxidation in Pseudomonas citronellolis.  

PubMed

Pseudomonas citronellolis UAM-Ps1 co-metabolically transforms methyl tert-butyl ether (MTBE) to tert-butyl alcohol with n-pentane (2.6 mM), n-octane (1.5 mM) or dicyclopropylketone (DCPK) (4.4 mM), a gratuitous inducer of alkane hydroxylase (AlkB) activity. The reverse transcription quantitative real-time PCR was used to quantify the alkane monooxygenase (alkB) gene expression. The alkB gene was expressed in the presence of n-alkanes and DCPK and MTBE oxidation occurred only in cultures when alkB was transcribed. A correlation between the number of alkB transcripts and MTBE consumption was found (???? consumption in ?mol = 1.44e(-13) x DNA copies, R(2) = 0.99) when MTBE (0.84 mM) was added. Furthermore, alkB was cloned and expressed into Escherichia coli and the recombinant AlkB had a molecular weight of 42 kDa. This is the first report where the expression of alkB is related to the co-metabolic oxidation of MTBE. PMID:25432418

Bravo, Ana Luisa; Sigala, Juan Carlos; Le Borgne, Sylvie; Morales, Marcia

2014-11-29

73

The effect of loading palladium on zinc oxide on the photocatalytic degradation of methyl tert-butyl ether (MTBE) in water.  

PubMed

A series of heterogeneous catalysts was prepared by doping zinc oxide with different palladium loadings in the range of 0.5%-1.5%. The prepared catalysts were characterized by SEM, TEM and XRD. These catalysts were applied to study the degradation of Methyl tert-Butyl Ether (MTBE). An amount of 100 mg of each of these catalysts was added to an aqueous solution of 100 ppm of MTBE. The resulting mixtures were irradiated with UV light for a period of 5 h. A 99.7% removal of MTBE was achieved in the case of the zinc oxide photocatalyst particles doped with 1% Pd. The photoreaction was found to be a first-order one. PMID:24446694

Seddigi, Zaki S; Ahmed, Saleh A; Ansari, Shahid P; Yarkandi, Naeema H; Danish, Ekram; Alkibash, Abdullah Abu; Oteef, Mohammed D Y; Ahmed, Shakeel

2014-01-01

74

Stable carbon and hydrogen isotope analysis of methyl tert-butyl ether and tert-amyl methyl ether by purge and trap-gas chromatography-isotope ratio mass spectrometry: method evaluation and application.  

PubMed

In order to monitor the behaviour of contaminants in the aqueous environment effective enrichment techniques often have to be employed due to their low concentrations. In this work a robust and sensitive purge and trap-gas chromatography-isotope ratio mass spectrometry method for carbon and hydrogen isotope analysis of fuel oxygenates in water is presented. The method evaluation included the determination of method detection limits, accuracy and reproducibility of deltaD and delta(13)C values. Lowest concentrations at which reliable delta(13)C values could be determined were 5 microg L(-1) and 28 microg L(-1) for TAME and MTBE, respectively. Stable deltaD values for MTBE and TAME could be achieved for concentrations as low as 25 and 50 microg L(-1). Good long-term reproducibility of delta(13)C and deltaD values was obtained for all target compounds. But deltaD values varying more than 5 per thousand were observed using different thermal conversion tubes. Thus, a correction of deltaD values in the analysis of groundwater samples was necessary to guarantee comparability of the results. The applicability of this method was shown by the analysis of groundwater samples from a gasoline contaminated site. By two dimensional isotope analysis two locations within this site were identified at which anaerobic and aerobic degradation of methyl tert-butyl ether occurred. PMID:20082031

Kujawinski, Dorothea M; Stephan, Manuel; Jochmann, Maik A; Krajenke, Karen; Haas, Joe; Schmidt, Torsten C

2010-01-01

75

Methyl tert butyl ether (MTBE) is anti- angiogenic in both in vitro and in vivo mammalian model systems  

PubMed Central

Methyl-tertiary butyl ether (MTBE), a well known gasoline oxygenate, and FDA approved gallstone treatment, has been previously shown to specifically target teleost embryonic angiogenesis. The studies reported here were to determine if similar vascular disrupting effects occurred in higher vertebrate models. Rat brain endothelial cells were isolated and allowed to form microcapillary-like tubes on Matrigel. MTBE (0.34–34.0 mM) exposure resulted in a dose-dependent reduction of tube formation, with the LOAEL at 0.34 mM, while MTBE’s primary metabolite, tertiary butyl alcohol had no effect on tube formation. HUVECs, a primary cell line representing macrovascular cells, were able to form tubes on Matrigel in the presence of MTBE (1.25 – 80 mM), but the tubes were narrower than those formed in the absence of MTBE. In a mouse Matrigel plug implantation assay, 34.0 mM MTBE completely inhibited vessel invasion into plugs containing Endothelial Cell Growth Supplement (ECGS) compared to control plugs with ECGS alone. When timed-pregnant Fisher 344 rats were gavaged with MTBE (500–1500 mg/kg) from day 6 of organogenesis through 10 days post parturition, no organ toxicity or histological changes in pup vasculature were observed. Therefore, MTBE is anti-angiogenic at mM concentrations and therefore a potential use as an anti-angiogenic treatment for solid tumors with minimal toxicity. PMID:22407988

Kozlosky, John; Bonventre, Josephine; Cooper, Keith

2015-01-01

76

Light-emitting thin films of glassy forming organic compounds containing 2-tert-butyl-6-methyl-4H-pyran-4-ylidene  

NASA Astrophysics Data System (ADS)

Low molecular mass organic compounds which make thin films from volatile organic solutions would be great benefit in future organic light emitting systems. Two most important advantages could be mentioned. First - the repetition of synthesis of small molecules is better than for polymers. Second - wet casting methods could be used. In this work we are presenting optical, electroluminescence and amplified spontaneous emission properties of four original glassy forming compounds containing 2-tert-butyl-6-methyl-4H-pyran-4-ylidene fragment as backbone of the molecule. They has the same N,N-dialkylamino electron donating group with incorporated bulky trityloxy ethyl groups. The difference of these compounds is in electron acceptor group. One has 1H-indene-1,3(2H)-dione group, second has pyrimidine-2,4,6(1H,3H,5H)-trione group, third has malononitrile group and fourth has 2-ethyl-2-cyanoacetate. Absorption maximum of the compounds is between 420 and 500 nm and is red shifted from weaker acceptor group to stronger one. The electroluminescence efficiency for simple device ITO/PEDOT:PSS/Organic compound/BaF/Al is low. For the best one with malononitrile group it was 0.13 cd/A and 0.036 lm/W. It could be increased by optimising the sample geometry or adding addition layers for charge carrier transport and exciton blocking. But nevertheless the use of these compounds in organic light emitting devices in neat films is unlikely. Attached bulky trityloxy ethyl groups and tert-butyl group decrease interaction between the molecules thus allowing to obtain amplified spontaneous emission in neat thin films for all investigated compounds.

Vembris, Aivars; Pudzs, Kaspars; Muzikante, Inta

2012-06-01

77

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

78

Groundwater remediation by an in situ biobarrier: a bench scale feasibility test for methyl tert-butyl ether and other gasoline compounds.  

PubMed

Most gasoline contains high percentages of methyl tert-butyl ether (MTBE) as an additive. The physico-chemical properties of this substance (high water solubility, low sorption in soil) result in high mobility and dissolved concentrations in soil. In situ permeable biological barriers (biobarriers, BBs) can remediate MTBE polluted groundwater by allowing pure cultures or microbial consortia to degrade MTBE when aerobic conditions are present, either by direct metabolism or cometabolism. Lab-scale batch and column tests were carried out to assess a selected microbial consortium in biodegrading MTBE and other gasoline compounds (benzene B, toluene T, ethylbenzene E, xylenes X) and to measure the parameters affecting the efficacy of a BB treatment of polluted groundwater. During the aerobic phase of the batch tests, the simultaneous biodegradation of MTBE, tert-butyl alcohol (TBA), B, T, E and o-X was observed. The rapid biodegradation of BTEXs resulted in decreased oxygen availability, but MTBE degradation was nevertheless measured in the presence of BTEXs. Stationary concentrations of MTBE and TBA were measured when anoxic conditions occurred in the systems. Values for a first order kinetic removal process were obtained for MTBE (0.031+/-0.001 d(-1)), B (0.045+/-0.002 d(-1)) and T (0.080+/-0.004 d(-1)) in the inoculated column tests. The estimate of the BB design parameters suggested that inoculation could significantly modify (double) the longitudinal dispersivity value of the biomass support medium. No effect was observed in the retardation factors for MTBE, B and T. PMID:19200654

Saponaro, Sabrina; Negri, Marco; Sezenna, Elena; Bonomo, Luca; Sorlini, Claudia

2009-08-15

79

Treatment of groundwater contaminated with PAHs, gasoline hydrocarbons, and methyl tert-butyl ether in a laboratory biomass-retaining bioreactor.  

PubMed

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 naphthalene, methyl-naphthalene, acenaphthene, acenaphthylene, and carbazole. The gasoline hydrocarbons included benzene, toluene, ethyl benzene, and p-xylene (BTEX). Two porous pot reactors were operated for a period of 10 months under the same influent contaminant concentrations. The contaminated groundwater was introduced into the reactors at a flow rate of 4 and 9 l/day, resulting in a hydraulic retention time (HRT) of 32 and 15 h, respectively. In both reactors, high removal efficiencies were achieved for the PAHs (>99%), BTEX and MtBE (>99.7%). All the PAHs of interest and the four BTEX compounds were detected at concentrations less than 1 mug/l throughout the study duration. Effluent MtBE from both reactors was observed at higher levels; nevertheless, its concentration was lower than the 5 mug/l Drinking Water Advisory for MtBE implemented in California. PMID:16453172

Zein, Maher M; Pinto, Patricio X; Garcia-Blanco, Susana; Suidan, Makram T; Venosa, Albert D

2006-02-01

80

A novel reusable ionic liquid chemically bonded fused-silica fiber for headspace solid-phase microextraction\\/gas chromatography-flame ionization detection of methyl tert-butyl ether in a gasoline sample  

Microsoft Academic Search

A novel ionic liquid (IL) bonded fused-sil-ica fiber for headspace solid-phase microextraction (HS-SPME)\\/gas chromatography-flame ionization detection (GC-FID) of methyl tert-butyl ether (MTBE) in a gasoline sample was prepared and used. The new proposed chemically bonded fiber has better thermal stability and durability than its corresponding physically coated fiber. Another advantage is that no spacer was used for the purpose of

Ramin Amini; Ahmad Rouhollahi; Mina Adibi; Ali Mehdinia

2011-01-01

81

Simultaneous determination of 22 volatile organic compounds, methyl- tert-butyl ether, 1,4-dioxane, 2-methylisoborneol and geosmin in water by headspace solid phase microextraction-gas chromatography–mass spectrometry  

Microsoft Academic Search

A method for the simultaneous determination of 22 volatile organic compounds (VOCs), methyl-tert-butyl ether (MTBE), 1,4-dioxane, 2-methylisoborneol (2-MIB) and geosmin in water by headspace solid phase microextraction (SPME)-gas chromatography–mass spectrometry (GC–MS) is described. Three types of SPME fibers (carboxen (CAR)\\/polydimethylsiloxane (PDMS), divinylbenzene (DVB)\\/PDMS and 100-?m PDMS) were evaluated to achieve the method detection limits and linear range required in Japanese

Sadao Nakamura; Shigeki Daishima

2005-01-01

82

Synthesis, optical, and thermal properties of glassy trityl group containing luminescent derivatives of 2-tert-butyl-6-methyl-4H-pyran-4-one  

NASA Astrophysics Data System (ADS)

In this work we present simple preparation of original trityl group containing glassy luminescent 6-styryl substituted derivatives of 2-(2-tert-butyl-4H-pyran-4-ylidene)malononitrile (DWK-1TB), 2-(2-tert-butyl-4H-pyran-4-ylidene)-2- ethyl-2-cyanoacetate (KWK-1TB), 2-(2-tert-butyl-4H-pyran-4-ylidene)-1H-indene-1,3(2H)-dione (ZWK-1TB) and 5-(2-tert-butyl-4H-pyran-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-trione (JWK-1TB). Their optical properties have been investigated. The absorption maxima of synthesized glasses is in region from 425 nm to 515 nm and emission maxima is from 470 nm to 625 nm in solution of dichloromethane. But absorption maxima of their solid films is from 425 nm to 500 nm and emission maxima is in range from 570 nm to 710 nm. Incorporation of bulky trityloxy ethyl groups combining with existing tert-butyl groups results in thin solid films formation of synthesized glasses from volatile organic solvents (chloroform, dichloromethane) without them being doped in any polymer. This makes them perspective for potential applications in organic light-emitting diodes and organic lasers by simple luminescent layer composition with cheap wet-casting approaches. All glasses show good thermal stability with thermal decomposition temperatures from 264° to 318°C and glass transition values up to 158°C for DWK-1TB. These thermal properties of synthesized glasses could make them also useful for potential applications in other optical materials such as materials for nonlinear optics.

Zarins, Elmars; Siltane, Karina; Misina, Elina; Kokars, Valdis; Lazdovica, Kristine; Vembris, Aivars; Kampars, Valdis; Muzikante, Inta; Rutkis, Martins

2012-06-01

83

A new disposable ionic liquid based coating for headspace solid-phase microextraction of methyl tert-butyl ether in a gasoline sample followed by gas chromatography–flame ionization detection  

Microsoft Academic Search

A new ionic liquid (IL) based solid-phase microextraction (SPME) fiber was investigated and used for headspace (HS) extraction of methyl tert-butyl ether (MTBE) in a gasoline sample. Using the new IL coated HS-SPME fiber with the combination of gas chromatography–flame ionization detection (GC–FID); sub-to-low ?gL?1 concentrations of MTBE were detected. Four different ILs including 1-butyl-3-methylimidazolium tetraflouroborate ([C4C1IM] [BF4]), 1-octyl-3-methylimidazolium tetraflouroborate

Ramin Amini; Ahmad Rouhollahi; Mina Adibi; Ali Mehdinia

2011-01-01

84

Response surface analysis of photocatalytic degradation of methyl tert-butyl ether by core/shell Fe3O4/ZnO nanoparticles  

PubMed Central

The degradation of methyl tert-butyl ether (MTBE) was investigated in the aqueous solution of coated ZnO onto magnetite nanoparticale based on an advanced photocatalytic oxidation process. The photocatalysts were synthesized by coating of ZnO onto magnetite using precipitation method. The sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibration sample magnetometer (VSM). Besides, specific surface area was also determined by BET method. The four effective factors including pH of the reaction mixture, Fe3O4/ZnO magnetic nanoparticles concentration, initial MTBE concentration and molar ratio of [H2O2]/ [MTBE] were optimized using response surface modeling (RSM). Using the four-factor-three-level Box–Behnken design, 29 runs were designed considering the effective ranges of the influential factors. The optimized values for the operational parameters under the respective constraints were obtained at PH of 7.2, Fe3O4/ZnO concentration of 1.78 g/L, initial MTBE concentration of 89.14 mg/L and [H2O2]/ [MTBE] molar ratio of 2.33. Moreover, kinetics of MTBE degradation was determined under optimum condition. The study about core/shell magnetic nanoparticles (MNPs) recycling were also carried out and after about four times, the percentage of the photocatalytic degradation was about 70%. PMID:24393372

2014-01-01

85

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

86

Spectroscopic investigation, natural bond orbital analysis, HOMO-LUMO and thermodynamic functions of 2-tert-butyl-5-methyl anisole using DFT (B3LYP) calculations  

NASA Astrophysics Data System (ADS)

The optimized molecular structure and corresponding vibrational assignments of 2-tert-butyl-5-methyl anisole (TBMA) have been investigated using density functional theory (DFT)/B3LYP with 6-31G(d,p) and 6-311++G(d,p) basis sets investigation of the relative orientation of the methoxy group has shown two conformers (O-cis) and (O-trans) exist. The vibrational analysis of the stable conformer of the title compound is performed by means of infrared absorption and Raman spectroscopy in combination with theoretical simultaneously. The natural bond orbital (NBO) analysis is useful to understand the intra-molecular hyper conjugative interaction lone pair and ??(Csbnd C), ??(Csbnd H) bond orbital. HOMO and LUMO energies show that charge transfer occurs in the molecule, therefore; HOMO, LUMO and molecular electrostatic potential (MEP) were calculated and analyzed. 1H and 13C NMR spectra by using gauge including atomic orbital (GIAO) method of studied compound were compared with experimental data. The thermodynamic functions of TBMA were calculated by B3LYP/6-311+G(d,p) basis set.

Balachandran, V.; Santhi, G.; Karpagam, V.; Revathi, B.; Karabacak, M.

2015-02-01

87

Aerobic degradation of methyl tert-butyl ether in a closed symbiotic system containing a mixed culture of Chlorella ellipsoidea and Methylibium petroleiphilum PM1.  

PubMed

The contamination of groundwater by methyl tert-butyl ether (MTBE) is one of the most serious environmental problems around the world. MTBE degradation in a closed algal-bacterial symbiotic system, containing a mixed culture of Methylibium petroleiphilum PM1 and Chlorella ellipsoidea, was investigated. The algal-bacterial symbiotic system showed increased MTBE degradation. The MTBE-degradation rate in the mixed culture (8.808 ± 0.007 mg l(-1) d(-1)) was higher than that in the pure bacterial culture (5.664 ± 0.017 mg l(-1) d(-1)). The level of dissolved oxygen was also higher in the mixed culture than that in the pure bacterial culture. However, the improved efficiency of MTBE degradation was not in proportional to the biomass of the alga. The optimal ratio of initial cell population of bacteria to algae was 100:1. An immobilized culture of mixed bacteria and algae also showed higher MTBE degradation rate than the immobilized pure bacterial culture. A mixed culture with algae and PM1 immobilized separately in different gel beads showed higher degradation rate (8.496 ± 0.636 mg l(-1) d(-1)) than that obtained with algae and PM1 immobilized in the same gel beads (5.424 ± 0.010 mg l(-1) d(-1)). PMID:21112690

Zhong, Weihong; Li, Yixiao; Sun, Kedan; Jin, Jing; Li, Xuanzhen; Zhang, Fuming; Chen, Jianmeng

2011-01-30

88

Spectroscopic investigation, natural bond orbital analysis, HOMO-LUMO and thermodynamic functions of 2-tert-butyl-5-methyl anisole using DFT (B3LYP) calculations.  

PubMed

The optimized molecular structure and corresponding vibrational assignments of 2-tert-butyl-5-methyl anisole (TBMA) have been investigated using density functional theory (DFT)/B3LYP with 6-31G(d,p) and 6-311++G(d,p) basis sets investigation of the relative orientation of the methoxy group has shown two conformers (O-cis) and (O-trans) exist. The vibrational analysis of the stable conformer of the title compound is performed by means of infrared absorption and Raman spectroscopy in combination with theoretical simultaneously. The natural bond orbital (NBO) analysis is useful to understand the intra-molecular hyper conjugative interaction lone pair and ?(?)(C-C), ?(?)(C-H) bond orbital. HOMO and LUMO energies show that charge transfer occurs in the molecule, therefore; HOMO, LUMO and molecular electrostatic potential (MEP) were calculated and analyzed. (1)H and (13)C NMR spectra by using gauge including atomic orbital (GIAO) method of studied compound were compared with experimental data. The thermodynamic functions of TBMA were calculated by B3LYP/6-311+G(d,p) basis set. PMID:25448946

Balachandran, V; Santhi, G; Karpagam, V; Revathi, B; Karabacak, M

2015-02-01

89

The study of binding of methyl tert-butyl ether to human telomeric G-quadruplex and calf thymus DNA by gas chromatography, a thermodynamic discussion.  

PubMed

Methyl-tert-butyl ether (MTBE) is widely used as an antiknock additive for increasing octane number of gasoline. Recently, the in vivo studies demonstrated that MTBE has genotoxic potential and able to form adducts with DNA. In the work, the interactions of MTBE with calf thymus DNA (ct-DNA) and the Na(+) form of G-quadruplex DNA (wtTel22) were studied by using of head space-solid phase microextraction technique coupled to gas chromatography. The binding equilibrium constants were measured through the equilibriums of a four phase system. In addition, the MTBE Henry's law constants for two different buffers in the temperature range of 283-303K were measured. Thermodynamic studies revealed that the complexation of MTBE to both DNAs is enthalpy favored and entropy disfavored. The thermodynamic results revealed that MTBE may have interaction with ct-DNA via the minor groove of DNA. Also, MTBE may be complexed into the basket of G-quadruplex structure. In addition, the low difference in the binding constants of MTBE for both different DNA targets may confirm that MTBE is poorly selective for different conformations of DNA. PMID:25280162

Ghasemi, Sahar; Ahmadi, Farhad

2014-11-15

90

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

91

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

92

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

93

3,3?,5,5?-Tetra-tert-butyl-2?-hy­droxy-[1,1?-biphen­yl]-2-yl 4-methyl­benzene­sulfonate  

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]. PMID:23424471

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

2013-01-01

94

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

The title thia-calix[4]arene derivative, C72H80O4S8, adopts a 1,3-alternate conformation, where the four 4-methyl-sul-fan-yl-benzyl 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 inter-molecular inter-actions present. Some of the peripheral tert-butyl and methyl-sulfanyl groups are disordered over two positions. A region of disordered electron density, occupying voids of ca 700?Å(3) for an electron count of 124, was treated using the SQUEEZE routine in PLATON [Spek (2009 ?). Acta Cryst. D65, 148-155]. PMID:24046595

Gao, Qingsong; Xie, Dexun; An, Delie

2013-01-01

95

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

96

Methyl tert-butyl ether in ground and surface water of the United States: National-scale relations between MTBE occurrence in surface and ground water and MTBE use in gasoline  

USGS Publications Warehouse

The detection frequency of methyl tert-butyl ether (MTBE) in ground and surface water of the United States is positively related to the content of MTBE in gasoline in various metropolitan areas of the U.S. The frequency of detection of MTBE is generally higher in areas that use larger amounts of MTBE in gasoline. Sampling of surface and ground water by the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program between 1993 and 1998 revealed a frequent detection of low concentrations of MTBE. In this analysis, data from several national-scale gasoline surveys are examined and data from one survey that is most extensive in geographic and temporal coverage is used to relate the detection of MTBE in ground and surface water to the volumetric content of MTBE in gasoline.

Moran, M.J.; Clawges, R.M.; Zogorski, J.S.

2002-01-01

97

Aerobic mineralization of MTBE and tert-butyl alcohol by stream-bed sediment microorganisms  

USGS Publications Warehouse

Microorganisms indigenous to the stream-bed sediments at two gasoline- contaminated groundwater sites demonstrated significant mineralization of the fuel oxygenates, methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA). Up to 73% of [U-14C]-MTBE and 84% of [U-14C]-TBA were degraded to 14CO2 under mixed aerobic/anaerobic conditions. No significant mineralization was observed under strictly anaerobic conditions. The results indicate that, under the mixed aerobic/anaerobic conditions characteristic of stream-bed sediments, microbial processes may provide a significant environmental sink for MTBE and TBA delivered to surface water bodies by contaminated groundwater or by other sources.Microorganisms indigenous to the stream-bed sediments at two gasoline-contaminated groundwater sites demonstrated significant mineralization of the fuel oxygenates, methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA). Up to 73% of [U-14C]-MTBE and 84% of [U-14C]-TBA were degraded to 14CO2 under mixed aerobic/anaerobic conditions. No significant mineralization was observed under strictly anaerobic conditions. The results indicate that, under the mixed aerobic/anaerobic conditions characteristic of stream-bed sediments, microbial processes may provide a significant environmental sink for MTBE and TBA delivered to surface water bodies by contaminated groundwater or by other sources.

Bradley, P.M.; Landmeyer, J.E.; Chapelle, F.H.

1999-01-01

98

A new disposable ionic liquid based coating for headspace solid-phase microextraction of methyl tert-butyl ether in a gasoline sample followed by gas chromatography-flame ionization detection.  

PubMed

A new ionic liquid (IL) based solid-phase microextraction (SPME) fiber was investigated and used for headspace (HS) extraction of methyl tert-butyl ether (MTBE) in a gasoline sample. Using the new IL coated HS-SPME fiber with the combination of gas chromatography-flame ionization detection (GC-FID); sub-to-low ?g L(-1) concentrations of MTBE were detected. Four different ILs including 1-butyl-3-methylimidazolium tetraflouroborate ([C(4)C(1)IM] [BF(4)]), 1-octyl-3-methylimidazolium tetraflouroborate ([C(8)C(1)IM] [BF(4)]), 1-octyl-3-methylimidazolium hexaflourophosphate ([C(8)C(1)IM] [PF(6)]) and 1-ethyl-3-methylimidazolium ethylsulphate ([C(2)C(1)IM] [ETSO(4)]) were synthesized and examined for extraction, preconcentration and determination of MTBE. It was observed that [C(8)C(1)IM] [BF(4)] showed the highest extraction efficiency and possessed the best extractability for MTBE. The fiber coating takes up the compounds from the sample by absorption in the case of liquid coatings. The calibration graph was linear in a concentration range of 1-120 ?g L(-1) (R(2)>0.994) with the detection limit of 0.09 ?g L(-1) level. The new IL-coated fiber was applied successfully for the determination of MTBE in a gasoline sample with good recoveries between 90 and 95%. PMID:21315889

Amini, Ramin; Rouhollahi, Ahmad; Adibi, Mina; Mehdinia, Ali

2011-03-15

99

Reactivities of substituted ?-phenyl-N-tert-butyl nitrones.  

PubMed

In this work, a series of ?-phenyl-N-tert-butyl nitrones bearing one, two, or three substituents on the tert-butyl group was synthesized. Cyclic voltammetry (CV) was used to investigate their electrochemical properties and showed a more pronounced substituent effect for oxidation than for reduction. Rate constants of superoxide radical (O2(•-)) reactions with nitrones were determined using a UV-vis stopped-flow method, and phenyl radical (Ph(•)) trapping rate constants were measured by EPR spectroscopy. The effect of N-tert-butyl substitution on the charge density and electron density localization of the nitronyl carbon as well as on the free energies of nitrone reactivity with O2(•-) and HO2(•) were computationally rationalized at the PCM/B3LYP/6-31+G**//B3LYP/6-31G* level of theory. Theoretical and experimental data showed that the rates of the reaction correlate with the nitronyl carbon charge density, suggesting a nucleophilic nature of O2(•-) and Ph(•) addition to the nitronyl carbon atom. Finally, the substituent effect was investigated in cell cultures exposed to hydrogen peroxide and a correlation between the cell viability and the oxidation potential of the nitrones was observed. Through a combination of computational methodologies and experimental methods, new insights into the reactivity of free radicals with nitrone derivatives have been proposed. PMID:24968285

Rosselin, Marie; Choteau, Fanny; Zéamari, Kamal; Nash, Kevin M; Das, Amlan; Lauricella, Robert; Lojou, Elisabeth; Tuccio, Béatrice; Villamena, Frederick A; Durand, Grégory

2014-07-18

100

A novel reusable ionic liquid chemically bonded fused-silica fiber for headspace solid-phase microextraction/gas chromatography-flame ionization detection of methyl tert-butyl ether in a gasoline sample.  

PubMed

A novel ionic liquid (IL) bonded fused-sil-ica fiber for headspace solid-phase microextraction (HS-SPME)/gas chromatography-flame ionization detection (GC-FID) of methyl tert-butyl ether (MTBE) in a gasoline sample was prepared and used. The new proposed chemically bonded fiber has better thermal stability and durability than its corresponding physically coated fiber. Another advantage is that no spacer was used for the purpose of bonding the IL to the surface of the fused-silica. The latter advantage makes the preparation of these fibers easier with lower cost than those prepared using sol-gel method. The ionic liquid 1-methyl-3-(3-trimethoxysilyl propyl) imidazolium bis(trifluoromethylsulfonyl) imide was synthesized and cross linked to the surface of the fused-silica fiber. Then, the chemically IL-modified fibers were applied to the headspace extraction of MTBE. The chemically IL-modified fibers showed improved thermal stability at temperatures up to 220 °C relative to the physically IL-modified fibers (180 °C). The chemically bonded IL film on the surface of the fused-silica fiber was durable over 16 headspace extractions without any significant loss of the IL film. The calibration graph was linear in a concentration range of 2-240 ?g L?¹ (R²=0.996) with the detection limit of 0.1 ?g L?¹ level. The reproducibility (RSD %, n=6) of the new IL bonded fused-silica fiber (8.9%) was better than the physically coated fiber (12%) suggesting that the proposed chemically IL-modified fiber is more robust than the physically IL-modified fiber. The optimum extraction conditions were the followings: 40 °C extraction temperature, 12 min extraction time, 30s desorption time and sample agitation at 200 rpm. PMID:21130999

Amini, Ramin; Rouhollahi, Ahmad; Adibi, Mina; Mehdinia, Ali

2011-01-01

101

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

Code of Federal Regulations, 2014 CFR

...2014-07-01 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,...

2014-07-01

102

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

103

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

Code of Federal Regulations, 2010 CFR

...2010-07-01 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,...

2010-07-01

104

Isotope effects on the metabolism and pulmonary toxicity of butylated hydroxytoluene in mice by deuteration of the 4-methyl group  

Microsoft Academic Search

A comparative test in mice for pulmonary toxicity between butylated hydroxytoluene (2,6-di-tert.-butyl-4-methylphenol, BHT) and 2,6-di-tert.-butyl-4-(alpha, alpha, alpha-2H3)methylphenol (BHT-d3) showed a significantly lower toxic potency of the latter. The rate of in vitro BHT metabolism to 2,6-di-tert.-butyl-4-methylene-2,5-cyclohexadienone (BHT-QM) was slowed by deuterating BHT in the 4-methyl group. On the other hand, the rate of in vitro metabolism to 2,6-di-tert.-butyl-4-hydroxy-4-methyl-2,5-cyclohexadienone (BHT-OH) was

T. Mizutani; K. Yamamoto; K. Tajima

1983-01-01

105

Isotope effects on the metabolism and pulmonary toxicity of butylated hydroxytoluene in mice by deuteration of the 4-methyl group  

SciTech Connect

A comparative test in mice for pulmonary toxicity between butylated hydroxytoluene (2,6-di-tert.-butyl-4-methylphenol, BHT) and 2,6-di-tert.-butyl-4-(alpha, alpha, alpha-2H3)methylphenol (BHT-d3) showed a significantly lower toxic potency of the latter. The rate of in vitro BHT metabolism to 2,6-di-tert.-butyl-4-methylene-2,5-cyclohexadienone (BHT-QM) was slowed by deuterating BHT in the 4-methyl group. On the other hand, the rate of in vitro metabolism to 2,6-di-tert.-butyl-4-hydroxy-4-methyl-2,5-cyclohexadienone (BHT-OH) was increased with the deuteration. A similar isotope effect of the deuterium substitution on the in vivo metabolic rates of BHT was observed. These observations support the concept that the lung damage caused by BHT is mediated by BHT-QM. The pulmonary toxicity of 2-tert.-butyl-4-ethylphenol (4-EP) and their deuterated analogs was also compared. 2-tert.-Butyl-4-(1,1-2H2)ethylphenol (4-EP-d2) showed a significantly lower toxic potency than 4-EP, whereas 2-tert.-butyl-4-(2,2,2-2H3)ethylphenol (4-EP-d3) showed a toxic potency comparable to that of 4-EP. This result is consistent with the hypothesis that a quinone methide metabolite is responsible for the onset of lung damage produced by 4-EP as well as BHT.

Mizutani, T.; Yamamoto, K.; Tajima, K.

1983-06-30

106

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. PMID:21148686

Jechalke, Sven; Rosell, Mònica; Martínez-Lavanchy, Paula M.; Pérez-Leiva, Paola; Rohwerder, Thore; Vogt, Carsten; Richnow, Hans H.

2011-01-01

107

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

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. PMID:21148686

Jechalke, Sven; Rosell, Mònica; Martínez-Lavanchy, Paula M; Pérez-Leiva, Paola; Rohwerder, Thore; Vogt, Carsten; Richnow, Hans H

2011-02-01

108

Control Study of Ethyl tert-Butyl Ether Reactive Distillation Muhammad A. Al-Arfaj  

E-print Network

Control Study of Ethyl tert-Butyl Ether Reactive Distillation Muhammad A. Al-Arfaj Department structures for ethyl tert-butyl ether (ETBE) reactive distillation columns are studied. Two process The use of reactive distillation has grown in recent years because it results in less expensive and more

Al-Arfaj, Muhammad A.

109

An efficient and scalable Ritter reaction for the synthesis of tert-butyl amides.  

PubMed

A scalable procedure for the conversion of nitriles to N-tert-butyl amides via the Ritter reaction was optimized employing tert-butyl acetate and acetic acid. The reaction has a broad scope for aromatic, alkyl, and alpha,beta-unsaturated nitriles. PMID:19245267

Baum, Jean C; Milne, Jacqueline E; Murry, Jerry A; Thiel, Oliver R

2009-03-01

110

he increasing frequency of detection of the widely used gasoline additive methyl tert-  

E-print Network

emissions, as well as ozone lev- els in urban air. For carbon monoxide, MTBE was se- lected by some gasolineT he increasing frequency of detection of the widely used gasoline additive methyl tert- butyl, the September 15, 1999, Report of the Blue Ribbon Panel on Oxygenates in Gasoline (1) states that between 5

111

METHYL TERTIARY-BUTYL ETHER (MTBE): Gasoline  

NSDL National Science Digital Library

This site gives an explanation of Methyl tertiary butyl ether (MTBE), also known as an oxygenate, a chemical compound used as a gasoline additive to enhance the octane and subsequently burn the fuel more completely.

112

O-Phenyl (tert-butyl­amido)(p-tolyl­amido)­phosphinate  

PubMed Central

In the title mol­ecule, C17H23N2O2P, the P atom has a distorted tetra­hedral environment. The P—N bond to the tolyl­amido fragment is 1.642?(4)?Å while that to the butyl­amido fragment is 1.629?(3)?Å. The dihedral angle between the two benzene rings is 82.3?(2)°. In the crystal, adjacent mol­ecules are linked via weak N—H?(O)P and N—H?N hydrogen-bonding inter­actions into an extended chain parallel to the b axis. The three methyl groups of the tert-butyl­amido substituent are disordered over two sets of sites with equal occupancies. The crystal studied was found to be a non-merohedral twin with the minor twin component = 23.1?(1)%. PMID:22199892

Pourayoubi, Mehrdad; Rheingold, Arnold L.; Chen, Chao; Karimi Ahmadabad, Fatemeh; Tarahhomi, Atekeh

2011-01-01

113

Trapping free radicals formed in the reaction of ozone with simple olefins using 2,6-Di-tert-butyl-4-cresol (BHT). [3,3-dimethylbutene  

SciTech Connect

Free radicals are detected from the ozonation of a series of olefins using a BHT trapping technique. We have determined the structure of the adduct when 3,3-dimethylbutene (tert-butylethylene) is ozonated at -78/sup 0/C and then warmed in the presence of BHT. The adduct can be rationalized as arising from trapping tert-butylperoxyl radicals by BHT to give 2,6-di-tert-butyl-4-(tert-butylperoxy)-4-methyl-2,5-cyclohexadienone. 17 references, 4 figures, 4 tables.

Pryor, W.A.; Gu, J.; Church, D.F.

1985-01-25

114

Hydrogen Atom Reactivity toward Aqueous tert-Butyl Alcohol  

SciTech Connect

Through a combination of pulse radiolysis, purification, and analysis techniques, the rate constant for the H + (CH{sub 3}){sub 3}COH {yields} H{sub 2} + {sm_bullet}CH{sub 2}C(CH{sub 3}){sub 2}OH reaction in aqueous solution is definitively determined to be (1.0 {+-} 0.15) x 10{sup 5} M{sup -1} s{sup -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){Delta}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 {alpha}- and {beta}-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{sub 3}){sub 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.

Lymar S. V.; Schwarz, H.A.

2012-02-09

115

Occurrence and implications of methyl tert-butyl ether and gasoline hydrocarbons in ground water and source water in the United States and in drinking water in 12 Northeast and Mid-Atlantic States, 1993-2002  

USGS Publications Warehouse

The occurrence and implications of methyl tert-butyl ether (MTBE) and gasoline hydrocarbons were examined in three surveys of water quality conducted by the U.S. Geological Survey?one national-scale survey of ground water, one national-scale survey of source water from ground water, and one regional-scale survey of drinking water from ground water. The overall detection frequency of MTBE in all three surveys was similar to the detection frequencies of some other volatile organic compounds (VOCs) that have much longer production and use histories in the United States. The detection frequency of MTBE was higher in drinking water and lower in source water and ground water. However, when the data for ground water and source water were limited to the same geographic extent as drinking-water data, the detection frequencies of MTBE were comparable to the detection frequency of MTBE in drinking water. In all three surveys, the detection frequency of any gasoline hydrocarbon was less than the detection frequency of MTBE. No concentration of MTBE in source water exceeded the lower limit of U.S. Environmental Protection Agency's Drinking-Water Advisory of 20 ?g/L (micrograms per liter). One concentration of MTBE in ground water exceeded 20 ?g/L, and 0.9 percent of drinking-water samples exceeded 20 ?g/L. The overall detection frequency of MTBE relative to other widely used VOCs indicates that MTBE is an important concern with respect to ground-water management. The probability of detecting MTBE was strongly associated with population density, use of MTBE in gasoline, and recharge, and weakly associated with density of leaking underground storage tanks, soil permeability, and aquifer consolidation. Only concentrations of MTBE above 0.5 ?g/L were associated with dissolved oxygen. Ground water underlying areas with high population density, ground water underlying areas where MTBE is used as a gasoline oxygenate, and ground water underlying areas with high recharge has a greater probability of MTBE contamination. Ground water from public-supply wells and shallow ground water underlying urban land-use areas has a greater probability of MTBE contamination compared to ground water from domestic wells and ground water underlying rural land-use areas.

Moran, Michael J.; Zogorski, John S.; Squillace, Paul J.

2004-01-01

116

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

117

Equilibria and reactivities of n-BUTYL, sec-BUTYL, and tert-BUTYL alcohols in reactions with isobutylene in liquid phase  

SciTech Connect

Reactions of aliphatic alcohols with isobutylene are of practical interest for synthesis of alkyl tert-butyl ethers which are used as high-octane additives to motor fuel. The kinetics and equilibria of reactions of butyl alcohols with isobutylene were studied in the liquid phase in the presence of the sulfonic cation exchanger KU-23 at 323 K.

Myshentseva, Yu.B.; Verevkin, S.P.; Rozhnov, A.M. [Samara State Technical Univ. (Russian Federation)

1995-11-20

118

Preparation of tert-butyl esters via Pd-catalyzed tert-butoxycarbonylation of (hetero)aryl boronic acid derivatives.  

PubMed

A novel protocol to synthesize tert-butyl esters from boronic acids or boronic acid pinacol esters and di-t-butyl dicarbonate has been successfully achieved. The cross-coupling reactions can produce up to 94% yields by using palladium acetate and triphenylphosphine as catalyst system, dioxane as a solvent. Moreover, a wide range of substrates including benzenes, pyridines, and quinolines boronic acids or boronic acid pinacol esters can fit with this system as well. PMID:24655126

Li, Xinjian; Zou, Dapeng; Zhu, Helong; Wang, Yaping; Li, Jingya; Wu, Yangjie; Wu, Yusheng

2014-04-01

119

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

120

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,...

121

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

122

Biodegradation of methyl t -butyl ether by aerobic granules under a cosubstrate condition  

Microsoft Academic Search

Aerobic granules efficient at degrading methyl tert-butyl ether (MTBE) with ethanol as a cosubstrate were successfully developed in a well-mixed sequencing batch reactor (SBR).\\u000a Aerobic granules were first observed about 100 days after reactor startup. Treatment efficiency of MTBE in the reactor during\\u000a stable operation exceeded 99.9%, and effluent MTBE was in the range of 15–50 ?g\\/L. The specific MTBE degradation rate

L. L. Zhang; J. M. Chen; F. Fang

2008-01-01

123

Methyl Tertiary Butyl Ether (MTBE): Drinking Water  

NSDL National Science Digital Library

MTBE, a gasoline oxygenater additive, has been detected in ground water sources throughout different parts of the country. These ground water sources are often the source of drinking water, and the presence of methyl tertiary butyl ether in even minute quantities can make the water undrinkable. Research to date has not conclusively identified any quantitative level at which serious health risks may occur. This site provides information on behalf of the Environmental Protection Agency on the concerns and occurence of MTBE in drinking water.

124

Studies on the Conformational Landscape of Tert-Butyl Acetate Using Microwave Spectroscopy and Quantum Chemical Calculations  

NASA Astrophysics Data System (ADS)

The tert-Butyl acetate molecule was studied using a combination of quantum chemical calculations and molecular beam Fourier transform microwave spectroscopy in the 9 to 14 GHz range. Due to its rather rigid frame, the molecule possesses only two different conformers: one of Cs and one of C1 symmetry. According to ab initio calculations, the Cs conformer is 46 kJ/mol lower in energy and is the one observed in the supersonic jet. We report on the structure and dynamics of the most abundant conformer of tert-butyl acetate, with accurate rotational and centrifugal distortion constants. Additionally, the barrier to internal rotation of the acetyl methyl group was determined. Splittings due to the internal rotation of the methyl group of up to 1.3 GHz were observed in the spectrum. Using the programs XIAM and BELGI-Cs, we determine the barrier height to be about 113 cm-1 and compare the molecular parameters obtained from these two codes. Additionally, the experimental rotational constants were used to validate numerous quantum chemical calculations. This study is part of a larger project which aims at determining the lowest energy conformers of organic esters and ketones which are of interest for flavor or perfume synthetic applications Project partly supported by the PHC PROCOPE 25059YB.

Zhao, YueYue; Mouhib, Halima; Li, Guohua; Stahl, Wolfgang; Kleiner, Isabelle

2014-06-01

125

27 CFR 21.101 - tert-Butyl alcohol.  

Code of Federal Regulations, 2013 CFR

...first needle). Above 20 °C. (f) Identification test. Place five drops of a solution containing approximately 0.1 percent tertiary butyl alcohol in ethyl alcohol in a test tube. Add 2 ml of Denige's reagent (dissolve 5...

2013-04-01

126

Novel A?B-type tert-butyl-substituted tribenzodiazepinoporphyrazine: synthesis, spectral properties and DFT study.  

PubMed

Novel A3B-type 8(9),13(14),18(19)-tri-tert-butyl-2(5),4(7)-bis(4-tert-butylphenyl)tribenzo[g,l,q]-6H-1,4-diazepino[2,3-b]porphyrazine, which has high solubility in organic solvents, was obtained by template co-condensation of 2,3-dicyano-5,7-bis(4-tert-butylphenyl)-6H-1,4-diazepine and 4-tert-butylphthalonitrile. It was characterized by UV/Vis, (1)H, (13)C NMR spectroscopy, and MALDI-TOF/TOF mass spectrometry. We have demonstrated for the first time using fluorescence spectroscopy measurements and quantum-chemical calculations that the complicated UV/Vis spectrum of A3B-type tribenzodiazepinoporphyrazine is due to the formation of stable H-type aggregates. PMID:25576944

Tarakanov, Pavel A; Simakov, Anton O; Tolbin, Alexandr Yu; Balashova, Irina O; Shestov, Vladimir I; Tomilova, Larisa G

2015-03-15

127

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.

128

Kinetics of proton transfer from tetra(4-nitro-5- tert-butyl)phthalocyanine to nitrogen-containing bases in benzene  

NASA Astrophysics Data System (ADS)

The acid-basic interaction between tetra(4-nitro-5- tert-butyl)phthalocyanine and pyridine, 2-methylpyridine, morpholine, piperidine, n-butylamine, diethylamine, and triethylamine in benzene is studied. It is found that the intermolecular transfer of protons of NH groups from tetra(4-nitro-5- tert-butyl)phthalocyanine to morpholine and diethylamine is characterized by unusually low values of the reaction constant rates. The effect of the structure of tetra(4-nitro-5- tert-butyl)phthalocyanine and tetra(3-nitro-5- tert-butyl)phthalocyanine, and of the nature of the base on the kinetic parameters of acid-base interaction is demonstrated. A structure is proposed for complexes with the transfer of displaced phthalocyanines' protons. It is found that they undergo decomposition over time.

Petrov, O. A.; Kuzmina, E. L.; Maizlish, V. E.; Rodionov, A. V.

2014-01-01

129

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

130

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

Code of Federal Regulations, 2014 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...

2014-07-01

131

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

132

Synthesis of sulfonic acid derivatives by oxidative deprotection of thiols using tert-butyl hypochlorite.  

PubMed

Starting from alkyl halides or Michael acceptors, thioacetates were prepared in situ and further treated with t-BuOCl, affording the corresponding sulfonyl chlorides which were trapped with nucleophiles such as water, alcohol, or amines. The three steps can be achieved in a one-pot procedure. Oxidative deprotection also proved to be efficient with S-trityl and S-tert-butyl groups, making it a convenient route toward cysteic acid derivatives. PMID:23639081

Joyard, Yoann; Papamicaël, Cyril; Bohn, Pierre; Bischoff, Laurent

2013-05-01

133

Evidence for C-H hydrogen bonding in salts of tert-butyl cation.  

PubMed

Environmentally sensitive: A combination of C-H anion hydrogen bonding and hyperconjugative charge delocalization explains the sensitivity of the IR spectrum of the tert-butyl cation to its anion (see high-resolution X-ray structure with a CHB(11)Cl(11)(-) counterion). The ?CH vibration of the cation scales linearly with the basicity of carborane anions on the ?NH scale. The same also holds for the C(6)H(7)(+) benzenium ion. PMID:22887067

Stoyanov, Evgenii S; Stoyanova, Irina V; Tham, Fook S; Reed, Christopher A

2012-09-01

134

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

135

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)] [Univ. of Hawaii, Honolulu, HI (United States); Anderson, D.G.M. [Harvard Univ., Cambridge, MA (United States). Aiken Computation Lab.] [Harvard Univ., Cambridge, MA (United States). Aiken Computation Lab.

1997-01-01

136

Enantioselective oxidation of di-tert-butyl disulfide with a vanadium catalyst: progress toward mechanism elucidation.  

PubMed

The mechanism of the oxidation of di-tert-butyl disulfide (1) to the chiral thiosulfinate (2) by H(2)O(2) catalyzed by bis(acetylacetonato)oxovanadium and a chiral Schiff-base ligand (3) has been investigated. Techniques included (51)V NMR spectroscopy, solvent effects on reaction enantioselectivity, and the isolation and full characterization of a 2:1 ligand-to-vanadium catalyst precursor. A model for the dramatic solvent effect on the enantioselectivity of this reaction was developed, based on the identification of a competing nonselective oxidation pathway. From this model, strategies for limiting this competing pathway were developed. PMID:12515473

Blum, Suzanne A; Bergman, Robert G; Ellman, Jonathan A

2003-01-10

137

4-tert-Butyl-3?,4?-bis­(4-methyl­phen­yl)-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. PMID:21837226

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

2011-01-01

138

Crystal structure of catena-poly[[(3-tert-butyl­pyridine-?N)(4-tert-butyl­pyridine-?N)cadmium]-di-?-thio­cyanato-?2 N:S;?2 S:N  

PubMed Central

In the crystal structure of the title compound, [Cd(NCS)2(C9H13N)2]n, the CdII cations are coordinated in a slightly distorted octa­hedral geometry by one 3-tert-butyl­pyridine ligand, one 4-tert-butyl­pyridine ligand and two pairs of translationally-equivalent ?-1,3-bridging thio­cyanate ligands, all of which are in general positions. These ?-1,3-bridging thio­cyante anions bridge the CdII cations, forming chains that propagate parallel to the b axis. PMID:25553011

Werner, Julia; Reinert, Thorben; Jess, Inke; Näther, Christian

2014-01-01

139

Analysis of molecular species of peroxide adducts of triacylglycerols following treatment of corn oil with tert -butyl hydroperoxide  

Microsoft Academic Search

We recently demonstrated that exposure of synthetic mono-and diunsaturated triacylglycerols to tert-butylhy-droperoxide (TBHP) leads to formation of stable adducts of the oxidizing agent and the unsaturated esters (Sjvall,\\u000a O., Kuksis, A., and Kallio, H., Reversed Phase High-Performance Liquid Chromatographic Separation of tert-Butyl Hydroperoxide Oxidation Products of Unsaturated Triacylglycerols. J. Chromatogr. A 905, 119–132, 2001). In the present study we isolated

O. Sjövall; A. Kuksis; H. Kallio

2001-01-01

140

Low-temperature CVD of g-Mn3N22x from bis[di(tert-butyl)amido]manganese(II) and ammonia  

E-print Network

Low-temperature CVD of g-Mn3N22x from bis[di(tert-butyl)amido]manganese(II) and ammonia Teresa S; published 8 April 2013) Manganese nitride films are grown by low-pressure chemical vapor deposition from the novel precursor bis[di(tert-butyl)amido]manganese(II) and ammonia. Mixed-phase films containing

Girolami, Gregory S.

141

The Epoxidation of 2,5-Di-tert-butyl-1,4-benzoquinone: A Consecutive Reaction for the Physical Chemistry Laboratory.  

ERIC Educational Resources Information Center

Reports a consecutive first-order reaction for which the concentrations of reactant, intermediate, and products can be determined simulataneously. This reaction is the epoxidation of 2,5-di-tert-butyl-1,4-benzoquinone (I) by alkaline hydroperoxidation using tert-butyl hydroperoxide and benzyltrimethylammonium hydroxide (Triton B) catalyst.…

Hairfield, E. M.; And Others

1985-01-01

142

Controlling on-surface molecular diffusion behaviors by functionalizing the organic molecules with tert-butyl groups  

NASA Astrophysics Data System (ADS)

We have performed the systematic studies on three structurally similar aromatic molecules with different functional groups on a Cu(110) surface and investigated their on-surface molecular diffusion behaviors by the interplay of scanning tunneling microscopy imaging and density functional theory calculations. We have found that the tert-butyl groups could significantly affect the molecular adsorption geometries and moreover the mobility of the molecules on the surface. These findings could give further insights into the understanding of diffusion behaviors of organic molecules specifically with tert-butyl groups on surfaces.

Sun, Qiang; Zhang, Chi; Li, Zhiwen; Sheng, Kai; Kong, Huihui; Wang, Likun; Pan, Yunxiang; Tan, Qinggang; Hu, Aiguo; Xu, Wei

2013-07-01

143

tert-Butyl(tert-butoxy)zinc Hydroxides: Hybrid Models for Single-Source Precursors of ZnO Nanocrystals.  

PubMed

Alkylzinc alkoxides, [RZnOR']4 , have received much attention as efficient precursors of ZnO nanocrystals (NCs), and their "Zn4 O4 " heterocubane core has been regarded as a "preorganized ZnO". A comprehensive investigation of the synthesis and characterization of a new family of tert-butyl(tert-butoxy)zinc hydroxides, [(tBu)4 Zn4 (?3 -OtBu)x (?3 -OH)4-x ], as model single-source precursors of ZnO NCs is reported. The direct reaction between well-defined [tBuZnOH]6 (16 ) and [tBuZnOtBu]4 (24 ) in various molar ratios allows the isolation of new mixed cubane aggregates as crystalline solids in a high yield: [(tBu)4 Zn4 (?3 -OtBu)3 (?3 -OH)] (3), [(tBu)4 Zn4 (?3 -OtBu)2 (?3 -OH)2 ] (4), [(tBu)4 Zn4 (?3 -OtBu)(?3 -OH)3 ] (5). The resulting products were characterized in solution by (1) H?NMR and IR spectroscopy, and in the solid state by single-crystal X-ray diffraction. The thermal transformations of 2-5 were monitored by in situ variable-temperature powder X-ray diffraction and thermogravimetric measurements. The investigation showed that the Zn?OH groups appeared to be a desirable feature for the solid-state synthesis of ZnO NCs that significantly decreased the decomposition temperature of crystalline precursors 3-5. PMID:25689691

Soko?owski, Kamil; Justyniak, Iwona; Bury, Wojciech; Grzonka, Justyna; Kaszkur, Zbigniew; M?kolski, ?ukasz; Dutkiewicz, Micha?; Lewalska, Agnieszka; Krajewska, El?bieta; Kubicki, Dominik; Wójcik, Katarzyna; Kurzyd?owski, Krzysztof J; Lewi?ski, Janusz

2015-03-27

144

Ethyl tert-butyl ether (ETBE)-degrading microbial communities in enrichments from polluted environments.  

PubMed

The ethyl tert-butyl ether (ETBE) degradation capacity and phylogenetic composition of five aerobic enrichment cultures with ETBE as the sole carbon and energy source were studied. In all cases, ETBE was entirely degraded to biomass and CO2. Clone libraries of the 16S rRNA gene were prepared from each enrichment. The analyses of the DNA sequences obtained showed different taxonomic compositions with a majority of Proteobacteria in three cases. The two other enrichments have different microbiota with an abundance of Acidobacteria in one case, whereas the microbiota in the second was more diverse (majority of Actinobacteria, Chlorobi and Gemmatimonadetes). Actinobacteria were detected in all five enrichments. Several bacterial strains were isolated from the enrichments and five were capable of degrading ETBE and/or tert-butyl alcohol (TBA), a degradation intermediate. The five included three Rhodococcus sp. (IFP 2040, IFP 2041, IFP 2043), one Betaproteobacteria (IFP 2047) belonging to the Rubrivivax/Leptothrix/Ideonella branch, and one Pseudonocardia sp. (IFP 2050). Quantification of these five strains and two other strains, Rhodococcus sp. IFP 2042 and Bradyrhizobium sp. IFP2049, which had been previously isolated from one of the enrichments was carried out on the different enrichments based on quantitative PCR with specific 16S rRNA gene primers and the results were consistent with the hypothesized role of Actinobacteria and Betaproteobacteria in the degradation of ETBE and the possible role of Bradyrhizobium strains in the degradation of TBA. PMID:25108826

Le Digabel, Yoann; Demanèche, Sandrine; Benoit, Yves; Fayolle-Guichard, Françoise; Vogel, Timothy M

2014-08-30

145

Radical-scavenging activity of butylated hydroxytoluene (BHT) and its metabolites  

Microsoft Academic Search

To clarify the radical-scavenging activity of butylated hydroxytoluene (BHT), a food additive, stoichiometric factors (n) and inhibition rate constants (kinh) were determined for 2,6-di-tert-butyl-4-methylphenol (BHT) and its metabolites 2,6-di-tert-butyl-p-benzoquinone (BHT-Q), 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHA-CHO) and 3,5-di-tert-butyl-4-hydroperoxy-4-methyl-2,5-cyclohexadiene-1-one (BHT-OOH). Values of n and kinh were determined from differential scanning calorimetry (DSC) monitoring of the polymerization of methyl methacrylate (MMA) initiated by 2,2?-azobis(isobutyronitrile) (AIBN) or

Seiichiro Fujisawa; Yoshinori Kadoma; Ichiro Yokoe

2004-01-01

146

(2,2?-Bipyridine-?2 N,N?)[2-tert-butyl­anilinato(2?)]dichloridooxido­molybdenum(VI) dichloro­methane hemisolvate  

PubMed Central

The MoVI atom in the title structure, [Mo(C10H13N)Cl2O(C10H8N2)]·0.5CH2Cl2, has a distorted octa­hedral coord­ination sphere with cis-orientated oxide and imide ligands, trans-chloride ligands and the 2,2?-bipyridine (bipy) ligand N atoms lying trans to the oxide and imide ligands. An imide-ligand tert-butyl-methyl-group H atom makes a close approach with the oxide ligand (distance = 2.53?Å) and the imide-ligand N atom (distance = 2.41?Å). Another imide-ligand tert-butyl-methyl-group H atom makes a close approach to a chloride ligand (distance = 2.82?Å). One bipy-ligand ?-H atom makes a close approach to the oxide ligand (distance = 2.4?Å) and the other ?-H atom makes a close approach to the imide-ligand phenyl-ring ortho-H atom (distance = 2.52?Å). These close approaches suggest the presence of weak intra­molecular hydrogen bonds. The solvent molecule has been modelled under consideration of half-occupancy. PMID:21589323

Nielson, Alastair J.; Waters, Joyce M.

2010-01-01

147

Crystal structure of 2-tert-butyl-1,3-thia­zolo[4,5-b]pyridine  

PubMed Central

The title compound, C10H12N2S, does not contain any strong hydrogen-bond donors but two long C—H?N contacts are observed in the crystal structure, with the most linear inter­action linking mol­ecules along [010]. The ellipsoids of the tert-butyl group indicate large librational motion. PMID:25309261

El-Hiti, Gamal A.; Smith, Keith; Hegazy, Amany S.; Masmali, Ali M.; Kariuki, Benson M.

2014-01-01

148

Oxidation of atactic polypropylene in the presence of 2,6-di- tert-butyl-4-phenylphenol  

Microsoft Academic Search

2,6-Di-tert-butyl-4-phenylphenol, which is a weak antioxidant in polypropylene above 180 °C, is an antioxidant of moderate effectiveness at 140 and 160 °C. The complicated character of its consumption at these temperatures is observed and explained.

Yury A. Shlyapnikov; E. S. Torsueva

1995-01-01

149

Design and Control of Glycerol-tert-Butyl Alcohol Etherification Process  

PubMed Central

Design, economics, and plantwide control of a glycerol-tert-butyl alcohol (TBA) etherification plant are presented. The reaction takes place in liquid phase, in a plug flow reactor, using Amberlyst 15 as a catalyst. The products' separation is achieved by two distillation columns where high-purity ethers are obtained and a section involving extractive distillation with 1,4-butanediol as solvent, which separates TBA from the TBA/water azeotrope. Details of design performed in AspenPlus and an economic evaluation of the process are given. Three plantwide control structures are examined using a mass balance model of the plant. The preferred control structure fixes the fresh glycerol flow rate and the ratio glycerol + monoether?:?TBA at reactor-inlet. The stability and robustness in the operation are checked by rigorous dynamic simulation in AspenDynamics. PMID:23365512

Vlad, Elena; Bozga, Grigore

2012-01-01

150

Design and control of glycerol-tert-butyl alcohol etherification process.  

PubMed

Design, economics, and plantwide control of a glycerol-tert-butyl alcohol (TBA) etherification plant are presented. The reaction takes place in liquid phase, in a plug flow reactor, using Amberlyst 15 as a catalyst. The products' separation is achieved by two distillation columns where high-purity ethers are obtained and a section involving extractive distillation with 1,4-butanediol as solvent, which separates TBA from the TBA/water azeotrope. Details of design performed in AspenPlus and an economic evaluation of the process are given. Three plantwide control structures are examined using a mass balance model of the plant. The preferred control structure fixes the fresh glycerol flow rate and the ratio glycerol + monoether : TBA at reactor-inlet. The stability and robustness in the operation are checked by rigorous dynamic simulation in AspenDynamics. PMID:23365512

Vlad, Elena; Bildea, Costin Sorin; Bozga, Grigore

2012-01-01

151

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

152

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

153

Inhibition of radical reactions for an improved potassium tert-butoxide-promoted (11) C-methylation strategy for the synthesis of ?-(11) C-methyl amino acids.  

PubMed

?-(11) C-Methyl amino acids are useful tools for biological imaging studies. However, a robust procedure for the labeling of amino acids has not yet been established. In this study, the (11) C-methylation of Schiff-base-activated ?-amino acid derivatives has been optimized for the radiosynthesis of various ?-(11) C-methyl amino acids. The benzophenone imine analog of methyl 2-amino butyrate was (11) C-methylated with [(11) C]methyl iodide following its initial deprotonation with potassium tert-butoxide (KOtBu). The use of an alternative base such as tetrabutylammonium fluoride, triethylamine, and 1,8-diazabicyclo[5.4.0]undec-7-ene did not result in the (11) C-methylated product. Furthermore, the KOtBu-promoted (11) C-methylation of the Schiff-base-activated amino acid analog was enhanced by the addition of 1,2,4,5-tetramethoxybenzene or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and inhibited by the addition of 1,10-phenanthroline. These results suggest that inhibition of radical generation induced by KOtBu improves the ?-(11) C-methylation of the Schiff-base-activated amino acids. The addition of a mixture of KOtBu and TEMPO to a solution of Schiff-base-activated amino acid ester and [(11) C]methyl iodide provided optimal results, and the tert-butyl ester and benzophenone imine groups could be readily hydrolyzed to give the desired ?-(11) C-methyl amino acids with a high radiochemical conversion. This strategy could be readily applied to the synthesis of other ?-(11) C-methyl amino acids. PMID:25690316

Suzuki, Chie; Kato, Koichi; Tsuji, Atsushi B; Zhang, Ming-Rong; Arano, Yasushi; Saga, Tsuneo

2015-03-01

154

Aerobic biodegradation of tert-butyl alcohol (TBA) by psychro- and thermo-tolerant cultures derived from granular activated carbon (GAC).  

PubMed

Tert-butyl alcohol (TBA) is a metabolite of methyl tert-butyl ether and is itself possibly a fuel oxygenate. The goals of this study were to enrich and characterize TBA-degrading micro-organism(s) from a granular activated carbon (GAC) unit currently treating TBA. The results reported herein describe the first aerobic, TBA-degrading cultures derived from GAC. Strains KR1 and YZ1 were enriched from a GAC sample in a bicarbonate-buffered freshwater medium. TBA was degraded to 10% of the initial concentration (2-5 mM) within 5 days after initial inoculation and was continuously degraded within 1 day of each re-amendment. Resting cell suspensions mineralized 70 and 60% of the TBA within 24 h for KR1 and YZ1, respectively. Performance optimization with resting cells was conducted to investigate kinetics and the extent of TBA degradation as influenced by oxygen, pH and temperature. The most favorable temperature was 37 degrees C; however, TBA was degraded from 4 to 60 degrees C, indicating that the culture will sufficiently treat groundwater without heating. This is also the first report of psychrotolerant or thermotolerant TBA biodegradation. The pH range for TBA degradation ran from 5.0 to 9.0. Phylogenetic data using a partial 16S rRNA gene sequence (570 bases) suggest that the primary members of KR1 and YZ1 include uncharacterized organisms within the genera Hydrogenophaga, Caulobacter, and Pannonibacter. PMID:17541707

Reinauer, Kimberly M; Zhang, Yang; Yang, Xiaomin; Finneran, Kevin T

2008-04-01

155

tert-Butyl N-[2-(N-isobutyl-4-meth­oxy­benzene­sulfonamido)­eth­yl]carbamate  

PubMed Central

The title compound, C18H30N2O5S, was synthesized by the reaction of tert-butyl 2-(iso­butyl­amino)­ethyl­carbamate with p-meth­oxy­phenyl­sulfonyl chloride. In the mol­ecule, two intra­molecular C—H?O hydrogen bonds are observed. In the crystal, mol­ecules are linked by N—H?O hydrogen bonds involving the imino group N atom and the ester group O atom into chains running parallel to the b axis. The chains are further connected by C—H?O hydrogen bonds, forming layers parallel to the bc plane. PMID:24940254

Bai, Xiao-Guang; Wang, Ju-Xian

2014-01-01

156

Synthesis and nonlinear optical examination of 3(4),15(16)-Bis-(4-tert-butyl-phenoxy)-10,22-diaminohemiporphyrazinato chloroindium  

NASA Astrophysics Data System (ADS)

3(4),15(16)-Bis-(4-tert-butyl-phenoxy)-10,22-diaminohemiporphyrazinato chloroindium hemiporphyrazine was synthesized from 1,3,5-triaminobenzene and 4-tert-butyl-phenoxyisoindoline. The structure of the complex was confirmed using mass, nuclear magnetic resonance and infrared spectroscopies. The nonlinear parameters of the compound was also analyzed in dimethylformamide and found to be significantly greater than previously analyzed phthalocyanines.

Britton, Jonathan; Antunes, Edith; Nyokong, Tebello

2013-09-01

157

[Chemical analytical aspects of hygiene safety of the use of methyl tertiary-butyl ether in the production of gasoline].  

PubMed

There was developed, certified and recommended for the practical application the technique for control in the water used as a high-octane oxygenated gasoline additive methyl tert-butyl ether with the use of chromatography-mass spectrometry method with a sensitivity of (0.005 mg/dm3) below the level of existing foreign regulations. Technique is introduced into the Federal Information Fund to ensure the unity of measurements. The possibility of applying the proposed method of analysis for monitoring chemical contamination of water sources and the quality control and safety of drinking water has been shown. PMID:25306710

Malysheva, A G; Rastyannikov, E G; Kozlova, N Yu; Artyushina, I Yu

2014-01-01

158

Correlation of the rates of solvolysis of tert-butyl chlorothioformate and observations concerning the reaction mechanism  

PubMed Central

The “parent” tertiary alkyl chloroformate, tert-butyl chloroformate, is unstable, but the tert-butyl chlorothioformate (1) is of increased stability and a kinetic investigation of the solvolyses is presented. Analyses in terms of the simple and extended Grunwald-Winstein equations are carried out. The original one-term equation satisfactorily correlates the data with a sensitivity towards changes in solvent ionizing power of 0.73 ±0.03. When the two-term equation is applied, the sensitivity towards changes in solvent nucleophilicity of 0.13 ± 0.09 is associated with a high (0.17) probability that the term that it governs is not statistically significant. PMID:23538747

Kyong, Jin Burm; Lee, Yelin; D’Souza, Malcolm John; Kevill, Dennis Neil; Kevill, Dennis Neil

2012-01-01

159

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

160

Features of the spectral dependences of transmittance of organic semiconductors based on tert-butyl substituted lutetium phthalocyanine molecules  

SciTech Connect

Vibronic properties of organic semiconductors based on tert-butyl substituted phthalocyanine lutetium diphthalocyanine molecules are studied by IR and Raman spectroscopy. It is shown that substitution of several carbon atoms in initial phthalocyanine (Pc) ligands with {sup 13}C isotope atoms causes a spectral shift in the main absorption lines attributed to benzene, isoindol, and peripheral C-H groups. A comparison of spectral characteristics showed that the shift can vary from 3 to 1 cm{sup -1}.

Belogorokhov, I. A., E-mail: jugqwerty@mail.ru [State Research and Project Institute of Rare-Metal Industry GIREDMET (Russian Federation); Tikhonov, E. V. [Moscow State University (Russian Federation); Dronov, M. A. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation); Belogorokhova, L. I. [Moscow State University (Russian Federation); Ryabchikov, Yu. V. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Tomilova, L. G.; Khokhlov, D. R. [Moscow State University (Russian Federation)

2011-11-15

161

Paradoxical Increase in 3-Nitropropionic Acid Neurotoxicity by -Phenyl-tert-butyl-nitrone, a Spin-Trapping Agent  

Microsoft Academic Search

Background: 3-Nitropropionic acid (3-NP), a mitochondrial toxin, impairs cellular energy generation by inhibiting succinate dehydrogenase. The basis of its neurotoxi- city is oxidative stress in the wake of cellular energy failure. -Phenyl-tert- butyl-nitrone (PBN), a spin-trapping agent with free radical-scavenging capability, has shown protective effects in various models of experimental brain insults. The effect of PBN on the 3-NP neurotoxicity

Min-Yu Lan; Yung-Yee Chang; Shun-Sheng Chen; Hsiu-Shan Wu; Wei-Hsi Chen; Jia-Shou Liu

162

N-tert-Butyl-alpha-Phenylnitrone Improves Recovery of Brain Energy State in Rats Following Transient Focal Ischemia  

Microsoft Academic Search

Recent results have demonstrated that the spin trapping agent N-tert-butyl-alpha-phenylnitrone (PBN) reduces infarct size due to middle cerebral artery occlusion (MCAO), even when given after ischemia. The objective of the present study was to explore whether PBN influences recovery of energy metabolism. MCAO of 2-hr duration was induced in rats by an intraluminal filament technique. Brains were frozen in situ

Jaroslava Folbergrova; Qi Zhao; Ken-Ichiro Katsura; Bo K. Siesjo

1995-01-01

163

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

Microsoft Academic Search

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

Mario Alía; Sonia Ramos; Raquel Mateos; Ana Belén Granado-Serrano; Laura Bravo; Luis. Goya

2006-01-01

164

Annealing effects on electrical, optical and structural properties of semiconducting transparent tetra-tert-butyl 2,3 naphthalocyanine thinfilms  

Microsoft Academic Search

Although there are lot of early reports on inorganic semiconducting transparent thinfilms, very few experimental results have been reported regarding the organic semiconducting transparent thinfilms especially in the area of Naphthalocyanines. Here we report on the preparation and characterization of transparent and semiconducting 2,11,20,29 Tetra Tert-Butyl 2,3 Naphthalocyanine (TTBNc) thinfilms using Physical Vapor Deposition Technique. Post deposition air and vacuum

I. Dhanya; C. S. Menon

2011-01-01

165

Promoting activity of 3- tert-butyl-4-hydroxyanisole (BHA) in BALB\\/3T3 cell transformation  

Microsoft Academic Search

3-Tert-butyl-4-hydroxyanisole (BHA), a synthetic antioxidant, is an initiator in the transformation of BALB\\/3T3 mouse embryo cells, when cells are treated first with the chemical and then with a tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. In the present study, BHA was examined for its promoting activity in BALB\\/3T3 cell transformation. BHA in a range of 5–20 ?g\\/ml enhanced transformation induced by a subthreshold dose

Ayako Sakai; Naoki Miyata; Atsushi Takahashi

1997-01-01

166

Two DSC Glass Transitions in Miscible Blends of Polyisoprene / Poly(4-tert-butyl styrene)  

NASA Astrophysics Data System (ADS)

Conventional and temperature modulated differential scanning calorimetry experiments have been carried out on miscible blends of polyisoprene (PI) and poly(4-tert-butyl styrene) (P4tBS) over a broad composition range. This system is characterized by an extraordinarily large component Tg difference (˜215 K) between the two homopolymers. Two distinct calorimetric Tgs were observed in blends with an intermediate composition range (25%˜50% PI) by both conventional and temperature modulated DSC. Good agreement was found between the Tg values measured by the two methods. Fitting of the measured Tgs to the Lodge-McLeish model gives a ?self of 0.62˜0.64 for PI in this blend and 0.02˜0.05 for P4tBS. The extracted ?self for PIis comparable to reported values for PEO in blends with PMMA and is significantly larger than those reported for other PI blends with smaller component Tg differences. This observation suggests the presence of a confinement effect in PI/P4tBS blends, which results in enhanced fast component dynamics below the effective Tg of the slow component.

Zhao, Junshu; Sun, Ye; Yu, Lian; Ediger, Mark

2009-03-01

167

Phenyl 3,5-di-tert-butyl-2-hy­droxy­benzoate  

PubMed Central

The title mol­ecule, C21H26O3, has a six-membered planar carbon ring as the central core, substituted at position 1 with phen­oxy­carbonyl, at position 2 with hy­droxy and at positions 3 and 5 with tert-butyl groups. The structure shows two independent but very similar mol­ecules within the asymmetric unit. For both independent mol­ecules, the ester carboxyl­ate group is coplanar with the central core, as reflected by the small C—C—O—C torsion angles [179.95?(17) and 173.70?(17)°]. In contrast, the phenyl substituent is almost perpendicular to the carboxyl­ate –CO2 fragment, as reflected by C—O—C—C torsion angles, ranging from 74 to 80°. The coplanarity between the central aromatic ring and the ester carboxyl­ate –CO2– group allows the formation of an intra­molecular hydrogen bond, with O?O distances of 2.563?(2) and 2.604?(2)?Å. PMID:21589569

Carreño, Alexander; Preite, Marcelo; Manriquez, Juan Manuel; Vega, Andrés; Chavez, Ivonne

2010-01-01

168

tert-Butyl hydroperoxide oxygenation of organic sulfides catalyzed by diruthenium(II,III) tetracarboxylates.  

PubMed

Diruthenium(II,III) carboxylates Ru2(esp)2Cl (1a), [Ru2(esp)2(H2O)2]BF4 (1b), and Ru2(OAc)4Cl (2) efficiently catalyze the oxygenation of organic sulfides. As noted in a previous work, 1a is active in oxygenation of organic sulfides with tert-butyl hydroperoxide (TBHP) in CH3CN. Reported herein in detail is the oxygenation activity of 1a, 1b, and 2, with the latter being highly selective in oxo-transfer to organic sulfides using TBHP under ambient conditions. Solvent-free oxidation reactions were achieved through dissolving 1a or 1b directly into the substrate with 2 equiv of TBHP, yielding TOF up to 2056 h(-1) with 1b. Also examined are the rate dependence on both catalyst and oxidant concentration for reactions with catalysts 1a and 2. Ru2(OAc)4Cl may be kinetically saturated with TBHP; however, Ru2(esp)2Cl does not display saturation kinetics. By use of a series of para-substituted thioanisoles, linear free-energy relationships were established for both 1a and 2, where the reactivity constants (?) are negative and that of 1a is about half that of 2. Given these reactivity data, two plausible reaction pathways were suggested. Density functional theory (DFT) calculation for the model compound Ru2(OAc)4Cl·TBHP, with TBHP on the open axial site, revealed elongation of the O-O bond of TBHP upon coordination. PMID:24116746

Villalobos, Leslie; Barker Paredes, Julia E; Cao, Zhi; Ren, Tong

2013-11-01

169

Spectral studies of tert-butyl isothiocyanate-inactivated P450 2E1.  

PubMed

Inactivation of cytochrome P450 2E1 by tert-butyl isothiocyanate (tBITC) resulted in a loss in the spectrally detectable P450-reduced CO complex. The heme prosthetic group does not appear to become modified, since little loss of the heme was observed in the absolute spectra or the pyridine hemochrome spectra, or in the amount of heme recovered from HPLC analysis of the tBITC-inactivated samples. Prolonged incubations of the inactivated P450 2E1 with dithionite and CO resulted in a recovery of both the CO complex and the enzymatic activity. Inactivated samples that were first reduced with dithionite for 1 h prior to CO exposure recovered their CO spectrum to the same extent as samples not pretreated with dithionite, suggesting that the major defect was an inability of the inactivated sample to bind CO. Spectral binding studies with 4-methylpyrazole indicated that the inactivated P450 2E1 had an impaired ability to bind the substrate. Enzymatic activity could not be restored with iodosobenzene as the alternate oxidant. EPR analysis indicated that approximately 24% of the tBITC-inactivated P450 2E1 was EPR-silent. Of the remaining tBITC-inactivated P450 2E1, approximately 45% exhibited an unusual low-spin EPR signal that was attributed to the displacement of a water molecule at the sixth position of the heme by a tBITC modification to the apoprotein. ESI-LC-MS analysis of the inactivated P450 2E1 showed an increase in the mass of the apoprotein of 115 Da. In combination, the data suggest that tBITC inactivated P450 2E1 by binding to a critical active site amino acid residue(s). This modified amino acid(s) presumably acts as the sixth ligand to the heme, thereby interfering with oxygen binding and substrate binding. PMID:11401573

Kent, U M; Roberts-Kirchhoff, E S; Moon, N; Dunham, W R; Hollenberg, P F

2001-06-19

170

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

171

Emulsion Polymerization of Butyl Acrylate: Spin Trapping and EPR Study  

NASA Technical Reports Server (NTRS)

The propagating radical in the emulsion polymerization reaction of butyl acrylate was detected by Electron Paramagnetic Resonance spectroscopy using two spin trapping agents, 2-methyl-2nitrosopropane and alpha -N-tert-butylnitrone.

Kim, S.; Westmoreland, D.

1994-01-01

172

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

173

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. PMID:5965331

Wright, A. S.; Crowne, R. S.; Hathway, D. E.

1966-01-01

174

Scanning thermal lithography of tailored tert-butyl ester protected carboxylic acid functionalized (meth)acrylate polymer platforms.  

PubMed

In this paper, we report on the development of tailored polymer films for high-resolution atomic force microscopy based scanning thermal lithography (SThL). In particular, full control of surface chemical and topographical structuring was sought. Thin cross-linked films comprising poly(tert-butyl methacrylate) (MA(20)) or poly(tert-butyl acrylate) (A(20)) were prepared via UV initiated free radical polymerization. Thermogravimetric analysis (TGA) and FTIR spectroscopy showed that the heat-induced thermal decomposition of MA(20) by oxidative depolymerization is initially the primary reaction followed by tert-butyl ester thermolysis. By contrast, no significant depolymerization was observed for A(20). For A(20) and MA(20) (at higher temperatures and/or longer reaction times) the thermolysis of the tert-butyl ester liberates isobutylene and yields carboxylic acid groups, which react further intramolecularly to cyclic anhydrides. The values of the apparent activation energies (E(a)) for the thermolysis were calculated to be 125 ± 13 kJ mol(-1) and 116 ± 7 kJ mol(-1) for MA(20) and A(20), respectively. Both MA(20) and A(20) films showed improved thermomechanical stability during SThL compared to non cross-linked films. Carboxylic acid functionalized lines written by SThL in A(20) films had a typically ~10 times smaller width compared to those written in MA(20) films regardless of the tip radius of the heated probe and did not show any evidence for thermochemically or thermomechanically induced modification of film topography. These observations and the E(a) of 45 ± 3 kJ mol(-1) for groove formation in MA(20) estimated from the observed volume loss are attributed to oxidative thermal depolymerization during SThL of MA(20) films, which is considered to be the dominant reaction mechanism for MA(20). The smallest line width values obtained for MA(20) and A(20) films with SThL were 83 ± 7 nm and 21 ± 2 nm, whereas the depth of the lines was below 1 nm, respectively. PMID:21919505

Duvigneau, Joost; Schönherr, Holger; Vancso, G Julius

2011-10-01

175

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

176

Degradation in chlorinated water of the UV filter 4-tert-butyl-4'-methoxydibenzoylmethane present in commercial sunscreens.  

PubMed

4-tert-Butyl-4'-methoxydibenzoylmethane (BMDM) is a widely used ultraviolet A filter. In this work, we have studied the effect of chlorine and dissolved organic matter (DOM) concentrations on the stability of UV filter (BMDM) present in two commercial sunscreen cream formulations in water. An experimental design was used to assess the effect of the two experimental factors on the degradation of BMDM. Higher concentrations of chlorine lead to higher degradation percentages of BMDM and higher concentrations of DOM inhibit its degradation. Moreover, a mono and a dichloro derivate of BMDM were identified as by-products. PMID:25399819

Crista, Diana M A; Miranda, Margarida S; Esteves da Silva, Joaquim C G

2015-05-01

177

Synthesis, crystal structure and spectroscopic properties of a novel carbacylamidophosphate: N-(3-nitrobenzoyl)-N',N''-bis(tert-butyl)phosphoric triamide.  

PubMed

The new compound N-(3-nitrobenzoyl)-N',N''-bis(tert-butyl)phosphoric triamide was synthesized by reacting 3-nitrobenzoyl phosphoramidic dichloride and tert-butyl amine, and characterized by multinuclear ((1)H, (13)C and (31)P) NMR and FTIR spectroscopy techniques. Structural and conformational properties were analyzed using single-crystal X-ray diffraction, vibrational spectra and theoretical calculations. The crystal structure contains three symmetry-independent disordered molecules, connected via intermolecular N-H...O=P and N-H...O=C hydrogen bonds to form a centrosymmetric hexameric chain extended along the [2,1,1] direction. The disorder is mainly caused by rotation of the tert-butyl groups around the C-N bonds. PMID:19617686

Gholivand, Khodayar; Mostaanzadeh, Hossein; Koval, Tomas; Dusek, Michal; Erben, Mauricio F; Della Védova, Carlos O

2009-08-01

178

Aggregation in dilute aqueous tert-butyl alcohol solutions: insights from large-scale simulations.  

PubMed

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 X(t) ? 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 X(t) ? 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 X(t) ? 0.08. In our 64,000 particle simulations all four models considered show demixing-like behavior for X(t) ? 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 X(t) ? 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. PMID:22830713

Gupta, Rini; Patey, G N

2012-07-21

179

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  

Microsoft Academic Search

The objective of this study was to investigate oxidative stress and oxygen extraction mechanisms in an animal model of continuous\\u000a 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

Edward C. T. H. Tan; Harry van Goor; Soheyl Bahrami; Andrey V. Kozlov; Martin Leixnering; Heinz Redl; R. Jan A. Goris

2011-01-01

180

2,6-di- tert -butyl-4-methylene-2,5-cyclohexadienone (BHT quinone methide): an active metabolite of BHT causing haemorrhages in rats  

Microsoft Academic Search

Male Sprague-Dawley rats and male ICR mice, species respectively susceptible and resistant to the haemorrhagic effect of butylated hydroxytoluene (BHT), were administered BHT quinone methide (2,6-di-tert-butyl4-methylene-2,5-cyclohexadienone) orally; 24 or 48 h later the plasma concentrations of blood coagulation factors II (prothrombin), VII, IX and X were determined. BHT quinone methide caused a decrease in factors II, VII, IX and X

Osamu Takahashi

1988-01-01

181

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

2007-07-01

182

Sulfuric acid functional zirconium (or aluminum) incorporated mesoporous MCM-48 solid acid catalysts for alkylation of phenol with tert-butyl alcohol  

NASA Astrophysics Data System (ADS)

Several zirconium (or aluminum) incorporated mesoporous MCM-48 solid acid catalysts (SO42-/Zr-MCM-48 and SO42-/Al-MCM-48) were prepared by the impregnation method and their physicochemical properties were characterized by means of XRD, FT-IR, TEM, NH3-TPD and N2 physical adsorption. Also, the catalytic activities of these solid acid catalysts were evaluated by the alkylation of phenol with tert-butyl alcohol. The effect of weight hour space velocity (WHSV), reaction time and reaction temperature on catalytic properties was also studied. The results show that the SO42-/Zr-MCM-48 and SO42-/Al-MCM-48 still have good mesoporous structure and long range ordering. Compared with the Zr (or Al)-MCM-48 samples, SO42-/Zr-MCM-48 and SO42-/Al-MCM-48 solid acid catalysts have strong acidity and exhibit high activities in alkylation reaction of phenol with tert-butyl alcohol. The SO42-/Zr-MCM-48-25 (molar ratio of Si/Zr=0.04) catalyst was found to be the most promising and gave the highest phenol conversion among all catalysts. A maximum phenol conversion of 91.6% with 4-tert-butyl phenol (4-TBP) selectivity of 81.8% was achieved when the molar ratio of tert-butyl alcohol:phenol is 2:1, reaction time is 2 h, the WHSV is 2 h-1 and the reaction temperature is 140 °C.

Jiang, Tingshun; Cheng, Jinlian; Liu, Wangping; Fu, Lie; Zhou, Xuping; Zhao, Qian; Yin, Hengbo

2014-10-01

183

State Restrictions on Methyl Tertiary Butyl Ether (released in AEO2006)  

EIA Publications

By the end of 2005, 25 states had barred, or passed laws banning, any more than trace levels of methyl tertiary butyl ether (MTBE) in their gasoline supplies, and legislation to ban MTBE was pending in 4 others. Some state laws address only MTBE; others also address ethers such as ethyl tertiary butyl ether (ETBE) and tertiary amyl methyl ether (TAME). Annual Energy Outlook 2006 assumes that all state MTBE bans prohibit the use of all ethers for gasoline blending.

2006-01-01

184

Removal of methyl tertiary-butyl ether (MTBE) from water by polymer–zeolite composites  

Microsoft Academic Search

Methyl tertiary-butyl ether (MTBE), a semi volatile organic compound used as a gasoline additive, has been extensively detected in surface and groundwater and therefore became a major issue as an environmental pollutant. The removal of methyl tertiary-butyl ether (MTBE) from water by high-silica zeolite, high-silica zeolite composites, and by granular activated carbon (GAC) was investigated in suspension and by filtration.

Dikla Zadaka-Amir; Ahmed Nasser; Shlomo Nir; Yael G. Mishael

185

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

186

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

187

Oxidative DNA Damage and Apoptosis Induced by Metabolites of Butylated Hydroxytoluene  

Microsoft Academic Search

DNA damage by metabolites of a food additive, butylated hydroxytoluene (BHT), was investigated as a potential mechanism of carcinogenicity. The mechanism of DNA damage by 2,6-di-tert-butyl-p-benzoquinone (BHT-quinone), 2,6-di-tert-butyl-4-hydroperoxyl-4-methyl-2,5-cyclohexadienone (BHT-OOH), and 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) in the presence of metal ions was investigated by using 32P-labeled DNA fragments obtained from the c-Ha-ras-1 proto-oncogene and the p53 tumor suppressor gene. BHT-OOH caused DNA damage

Saeko Oikawa; Kohsuke Nishino; Shinji Oikawa; Sumiko Inoue; Tamio Mizutani; Shosuke Kawanishi

1998-01-01

188

Effect of Lewis bases on the catalytic activity of meso-tetraphenylporphyrinatolutetium(III) hydroxide in the oxidation of styrene by tert-butyl hydroperoxide  

SciTech Connect

The effect of various Lewis bases (heteroatomic and aliphatic amines, potassium tert-butoxide, hexamethylposphoric triamide) on the catalytic oxidation of styrene by tert-butyl hydroperoxide was studied in the presence of the lutetium porphyrin complex. The rate of the catalytic reaction increases within one order of magnitude depending on the nature and amount of the base added. Various factors affecting the catalytic effect are discussed. The exchange of extraligands in the coordination sphere of lutetium ion contained in the lanthanide porphyrin was observed for the first time; it was detected spectrophotomtrically by the change in the position of Soret band of the porphyrin ligand. 16 refs., 4 tabs.

Vedernikov, A.N.; Kochnev, D.O.; Solomonov, B.N.

1993-08-10

189

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

190

(2-tert-Butyl-3-phenyl-2,3-di­hydro­isoxazole-4,5-di­yl)bis­(phenyl­methanone)  

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. PMID:24109366

Sandhya, R.; Sithambaresan, M.; Prathapan, S.; Kurup, M. R. Prathapachandra

2013-01-01

191

Classical trajectories and RRKM modeling of collisional excitation and dissociation of benzylammonium and tert -butyl benzylammonium ions in a quadrupole-hexapole-quadrupole tandem mass spectrometer  

Microsoft Academic Search

Collision-induced dissociation of the benzylammonium and the 4-tert-butyl benzylammonium ions was studied experimentally in an electrospray ionization quadrupole-hexapole-quadrupole tandem\\u000a mass spectrometer. Ion fragmentation efficiencies were determined as functions of the kinetic energy of ions and the collider\\u000a gas (argon) pressure. A theoretical Monte Carlo model of ion collisional excitation, scattering, and decomposition was developed.\\u000a The model includes simulation of the

Vadim D. Knyazev; Stephen E. Stein

2010-01-01

192

Demonstration of free radical generation in stunned myocardium of intact dogs with the use of the spin trap alpha-phenyl N-tert-butyl nitrone  

Microsoft Academic Search

Recent studies suggest that oxygen free radicals may mediate postischemic myocardial dysfunction (stunning), but all the evidence for this hypothesis is indirect. Thus, we used electron paramagnetic resonance (EPR) spectroscopy and the spin trap, alpha-phenyl N-tert-butyl nitrone (PBN), to directly investigate whether free radicals are produced after a 15-min coronary artery occlusion and subsequent reperfusion in 30 open-chest dogs. After

R. Bolli; B. S. Patel; M. O. Jeroudi; E. K. Lai; P. B. McCay

1988-01-01

193

Living Carbocationic Polymerization of Isobutylene with Blocked Bifunctional Initiators in the Presence of Di-tert-butylpyridine as a Proton Trap  

Microsoft Academic Search

The polymerization of isobutylene (IB) has been studied using 5-tert-butyl-1,3-dicumyl-chloride, 5-tert-butyl-1,3-dicumyl-methyl ether, and 5-tert-butyl-1,3-dicumyl-acetate initiators in the absence and presence of 2,6-di-tert-butylpyridine (DTBP) as a proton trap. It is demonstrated that living polymerization can be achieved in the IB\\/initiator\\/TiCl4\\/methylchloride-n-hexane (40:60 v:v)\\/DTBP\\/-80°C system, and that polymers with close to a Poisson molecular weight distribution can be obtained in the presence of

Miklos Gyor; Hsien-Chang Wang; Rudolf Faust

1992-01-01

194

Chlorido[2,3,5,6-tetra­kis­(tert-butyl­sulfanylmeth­yl)phenyl-?3 S 2,C 1,S 6]palladium(II) dichloro­methane 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]. PMID:23476488

Paz-Morales, Evelyn; Hernández-Ortega, Simón; Morales-Morales, David

2013-01-01

195

Two-year drinking water carcinogenicity study of methyl tertiary-butyl ether (MTBE) in Wistar rats.  

PubMed

Methyl tertiary-butyl ether (MTBE) has been used as a gasoline additive to reduce tailpipe emissions and its use has been discontinued. There remains a concern that drinking water sources have been contaminated with MTBE. A two-year drinking water carcinogenicity study of MTBE was conducted in Wistar rats (males, 0, 0.5, 3, 7.5 mg ml(-1); and females, 0, 0.5, 3, and 15 mg ml(-1)). Body weights were unaffected and water consumption was reduced in MTBE-exposed males and females. Wet weights of male kidneys were increased at the end of two years of exposure to 7.5 mg ml(-1) MTBE. Chronic progressive nephropathy was observed in males and females, was more severe in males, and was exacerbated in the high MTBE exposure groups. Brain was the only tissue with a statistically significant finding of neoplasms. One astrocytoma (1/50) was found in a female rat (15 mg ml(-1)). The incidence of brain astrocytomas in male rats was 1/50, 1/50, 1/50 and 4/50 for the 0, 0.5, 3 and 7.5 mg ml(-1) exposure groups, respectively. This was a marginally significant statistical trend, but not statistically significant when pairwise comparisons were made or when multiple comparisons were taken into account. The incidence of astrocytoma fell within historical control ranges for Wistar rats, and the brain has not been identified as a target organ following chronic administration of MTBE, ethyl tert-butyl ether, or tertiary butyl alcohol (in drinking water) to mice and rats. We conclude that the astrocytomas observed in this study are not associated with exposure to MTBE. PMID:22161475

Dodd, Darol; Willson, Gabrielle; Parkinson, Horace; Bermudez, Edilberto

2013-07-01

196

Syntheses, properties, and reactions of transition metal complexes of di(tert-butyl)amide and 2,2,6,6-tetramethylpiperidide  

NASA Astrophysics Data System (ADS)

Nitrides of the transition metals of groups 7-11 possess desirable properties, such as higher hardness and saturation magnetization than the corresponding metals. These nitrides have realized and potential applications in tool coatings and magnetic recording media. In order to develop new chemical vapor deposition (CVD) precursors for these late transition metal nitrides, we have explored the synthesis, characterization, and CVD of late transition metal complexes of the sterically demanding ligands di(tert-butyl)amide and 2,2,6,6-tetramethylpiperidide. Treatment of MnBr2(thf)2, FeBr2(dme), CoBr2(dme), and NiBr2(dme) with two equivalents of LiN(t-Bu)2 in pentane, followed by sublimation in static vacuum, affords the two-coordinate compounds M[N(t-Bu)2]2 (M = Mn, Fe, Co, Ni) previously reported by our group. Previous work established that the Mn and Fe compounds have linear N-M-N angles, whereas the Co and Ni compounds are bent. In addition, the Fe and Co compounds have large orbital contributions to their magnetic moments, whereas the Mn and Ni compounds do not. In order to understand these properties, the electronic structures of the M[N(t-Bu)2]2 compounds have been described using the Angular Overlap Model (AOM). Two conclusions help rationalize the previously observed molecular properties of these and other two-coordinate compounds: (1) The potential energy surfaces for two-coordinate compounds are nearly flat, varying only a few kcal/mol even with 30° changes in the N-M-N angle, and (2) the ground state configurations for two-coordinate d2 and d3 (and therefore also d7 and d8) compounds experience strong inter-electron repulsion and extensive state mixing. Low-temperature CVD from the reaction between these two-coordinate M[N(t-Bu)2]2 compounds and ammonia affords manganese, iron, cobalt, and nickel nitride thin films. Deposition rates as high as 18 nm/min are observed for cobalt nitride, and deposition temperatures as low as 25 °C are observed for iron nitride. The XPS binding energies confirm that the nitrogen is present as nitride in all cases. The M:N ratio in the deposited films decreases from Mn (2.5) to Fe (4) to Co (4.6-6) to Ni (9). Carbon contamination in the films is minimal for the manganese, iron, and cobalt nitride films, but similar to the nitrogen content in the nickel nitride films. Comparing the growth onset temperatures with the decomposition temperatures of the compounds M(NH2)2 supports the intermediacy in the film growth of the latter species, which are the expected products of the transamination of M[N(t-Bu)2]2 compounds with NH3. Treatment of MnBr2(thf)2, FeBr2(dme), and CoBr2(dme) with two equivalents of lithium 2,2,6,6-tetramethylpiperidide, Li(tmp), in pentane, followed by sublimation in static vacuum, affords the new compounds M(tmp)2 (M = Mn, Fe, Co). The heteroleptic, dinuclear three-coordinate compounds Fe2(tmp)3(OEt) and [Li(dme)][CoBr(tmp)2] have also been isolated. Crystallographic studies of Fe(tmp)2 demonstrate that the tmp ligand, which is the cyclic analogue of di(tert-butyl)amide with a slightly compressed C-N-C angle, can also enforce two-coordination. The Fe-N bonds are similar to those in the linear compound Fe[N(t-Bu)2]2, although the N-Fe-N angle of 173° and ligand dihedral angle of 73° are smaller. Fe(tmp)2 might therefore be expected to have a less degenerate ground state. Treatment of TiCl4 with two equivalents of H(tmp) affords the new compound Ti2Cl6(tmp)2. In contrast, treatment of TiCl4 or TiCl4(thf)2 with three equivalents of Li(tmp) induces ring-opening dealkylation of one tmp ligand and formation of a 1,1,5-trimethyl-5-hexenylimido ligand. A similar reaction is known for the di(tert-butyl)amido ligand.We conclude that the synthesis of early transition metal tmp and di(tert-butyl)amide compounds is hampered by the high electropositivity of these metals, which activates the methyl protons towards gamma-deprotonation. (Abstract shortened by UMI.).

Davis, Luke M.

197

The Effect of tert-Butyl Hydroperoxide-Induced Oxidative Stress on Lean and Steatotic Rat Hepatocytes In Vitro  

PubMed Central

Oxidative stress and mitochondrial dysfunction play an important role in the pathogenesis of nonalcoholic fatty liver disease and toxic liver injury. The present study was designed to evaluate the effect of exogenous inducer of oxidative stress (tert-butyl hydroperoxide, tBHP) on nonfatty and steatotic hepatocytes isolated from the liver of rats fed by standard and high-fat diet, respectively. In control steatotic hepatocytes, we found higher generation of ROS, increased lipoperoxidation, an altered redox state of glutathione, and decreased ADP-stimulated respiration using NADH-linked substrates, as compared to intact lean hepatocytes. Fatty hepatocytes exposed to tBHP exert more severe damage, lower reduced glutathione to total glutathione ratio, and higher formation of ROS and production of malondialdehyde and are more susceptible to tBHP-induced decrease in mitochondrial membrane potential. Respiratory control ratio of complex I was significantly reduced by tBHP in both lean and steatotic hepatocytes, but reduction in NADH-dependent state 3 respiration was more severe in fatty cells. In summary, our results collectively indicate that steatotic rat hepatocytes occur under conditions of enhanced oxidative stress and are more sensitive to the exogenous source of oxidative injury. This confirms the hypothesis of steatosis being the first hit sensitizing hepatocytes to further damage. PMID:24847414

Ku?era, Otto; Endlicher, René; Roušar, Tomáš; Lotková, Halka; Garnol, Tomáš; Drahota, Zden?k

2014-01-01

198

Conformational stability, vibrational and NMR analysis, chemical potential and thermodynamical parameter of 3-tert-butyl-4-hydroxyanisole  

NASA Astrophysics Data System (ADS)

The FT-IR and FT-Raman spectra of 3-tert-butyl-4-hydroxyanisole (TBHA) molecule have been recorded in the region 4000-400 cm-1 and 3500-100 cm-1, respectively. Optimized geometrical structure, harmonic vibrational frequencies has been computed by B3LYP level using 6-31G (d, p) and 6-311 + G (d, p) basis sets. The observed FT-IR and FT-Raman vibrational frequencies are analyzed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis, the first-order hyperpolarizability of the investigated molecule were computed using DFT calculations. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and analyzed. The isotropic chemical shift computed by 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the TBHA calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations.

Balachandran, V.; Karpagam, V.; Revathi, B.; Kavimani, M.; Santhi, G.

2015-01-01

199

Conformational stability, vibrational and NMR analysis, chemical potential and thermodynamical parameter of 3-tert-butyl-4-hydroxyanisole.  

PubMed

The FT-IR and FT-Raman spectra of 3-tert-butyl-4-hydroxyanisole (TBHA) molecule have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. Optimized geometrical structure, harmonic vibrational frequencies has been computed by B3LYP level using 6-31G (d,p) and 6-311+G (d,p) basis sets. The observed FT-IR and FT-Raman vibrational frequencies are analyzed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis, the first-order hyperpolarizability of the investigated molecule were computed using DFT calculations. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and analyzed. The isotropic chemical shift computed by (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the TBHA calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations. PMID:25173520

Balachandran, V; Karpagam, V; Revathi, B; Kavimani, M; Santhi, G

2015-01-25

200

Hepatoprotective effect of flavonoid glycosides from Lespedeza cuneata against oxidative stress induced by tert-butyl hyperoxide.  

PubMed

The aerial parts of Lespedeza cuneata G. Don, perennial legume native to Eastern Asia, have been used therapeutically in traditional Asian medicine to protect the function of liver, kidneys and lungs. However, little is known about the pharmaceutical effect of extracts from this plant. In the present study, the aerial parts of L. cuneata were used to prepare an ethanol extract, which was then tested for hepatoprotective effects against injury by tert-butyl hyperoxide (t-BHP). At a dose of 20 ?g/mL, the ethanol extract significantly protected HepG2 cells against the cytotoxicity of t-BHP. Further fractionation of the extract with ethyl acetate allowed the isolation of five flavonoid compounds that were structurally identified by ¹H and ¹³C NMR spectroscopy as isovitexin, hirsutrin, trifolin, avicularin and quercetin. Hirsutrin, avicularin and quercetin (10 ?M) showed clear hepatoprotective activity against injury by t-BHP in HepG2 cells, whereas isovitexin and trifolin showed no protective effects. The observed hepatoprotective effect of the investigated compounds showed a high correlation with radical scavenging activity, which followed the structure-activity relationships of the flavonoid aglycones. PMID:21226126

Kim, Sang Min; Kang, Kyungsu; Jho, Eun Hye; Jung, Yu-Jin; Nho, Chu Won; Um, Byung-Hun; Pan, Cheol-Ho

2011-07-01

201

Molecular dynamics and partitioning of di-tert-butyl nitroxide in stratum corneum membranes: effect of terpenes.  

PubMed

In this work, we have used electron paramagnetic resonance (EPR) spectroscopy of the small spin label di-tert-butyl nitroxide (DTBN), which partitions the aqueous and hydrocarbon phases, to study the interaction of the terpenes alpha-terpineol, 1,8-cineole, L(-)-carvone and (+)-limonene with the uppermost skin layer, the stratum corneum, and the membrane models of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The EPR spectra indicated that the terpenes increase both the partition coefficient and the rotational correlation time of the spin labels in the stratum corneum membranes, whereas similar effects were observed in the DMPC and DPPC bilayers only at temperatures below the liquid-crystalline phase. The EPR parameter associated to probe polarity inside the membranes showed thermotropically induced changes, suggesting relocations of spin probe, which were dependent on the membrane phases. While the DMPC and DPPC bilayers showed abrupt changes in the partitioning and rotational correlation time parameters in the phase transitions, the SC membranes were characterized by slight changes in the total range of measured temperatures, presenting the greatest changes or membranes reorganizations in the temperature range of approximately 50 to approximately 74 degrees C. The results suggest that terpenes act as spacers, weakening the hydrogen-bonded network at the polar interface and thus fluidizing the stratum corneum lipids. PMID:20361269

Camargos, Heverton Silva; Silva, Adolfo Henrique Moraes; Anjos, Jorge Luiz Vieira; Alonso, Antonio

2010-05-01

202

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

203

``Living polymers'' in organic solvents : stress relaxation in bicopper tetracarboxylate/tert-butyl cyclohexane solutions  

NASA Astrophysics Data System (ADS)

Viscoelastic solutions of a bicopper tetracarboxylate complex in tert-butylcyclohexane have been studied by dynamic rheology in a wide range of concentrations (0.5-1.5 % volume fraction). The zero shear viscosity, the elastic modulus, the terminal stress relaxation time and the height of the high-frequency dip, in a Cole-Cole representation of the complex elastic modulus, follow scaling laws. The related exponents are discussed in the context of the physics of “living polymers” : a term used to describe worm-like species undergoing scission/recombination reactions competing mainly with the reptation motions of the chains. The current system, made up of molecular threads (17.5 Å diameter) of Cu2(O2C-CH(C2H5)C4H9)4 in the apolar solvent, is representative of a “living polymer” where, instead of mechanisms involving transient star polymeric crosslinks, a reversible scission mechanism prevails. The dynamics in the high-frequency range evolves from a regime where reptation is the dominant relaxation mechanism to a cross-over regime where “breathing” fluctuations and Rouse motions become important. Large modifications of the stress relaxation function occur for more concentrated systems. The binary system is the first example of a “living polymer” in an organic solvent and exhibits elastic moduli (G ? ca. 120 Pa à ? = 1 %) which are at least 20 times larger than those found for the aqueous “living polymer” systems. Les solutions viscoélastiques d'un tétracarboxylate binucléaire de cuivre dans le tert-butylcyclohexane sont étudiées par rhéologie en mode dynamique dans une gamme étendue de concentrations (0,5 %-15,5 %). La viscosité à gradient nul, le module élastique, le temps terminal de relaxation et la hauteur du puits à haute fréquence, dans une représentation Cole-Cole du module élastique complexe, suivent des lois d'échelles. Les exposants correspondants sont discutés dans le contexte de la physique des “polymères vivants" : un terme utilisé pour décrire des espèces vermiformes subissant des réactions de scission/recombinaison en compétition principalement avec les mouvements de reptation des chaînes. Le système constitué de fils moléculaires (17,5 Å de diamètre) de Cu2(O2C-CH(C2H5)C4H9)4 dans le solvant apolaire est typique de “polymères vivants” où le mécanisme de scission réversible prévaut plutôt que les mécanismes impliquant des nœuds transitoires branchés. La dynamique dans le domaine des hautes fréquences évolue d'un régime où la reptation est le mécanisme de relaxation dominant vers un régime intermédiaire où les modes de “respiration” et de Rouse deviennent importants. D'importantes modifications de la relaxation de contrainte se produisent pour les systèmes concentrés. Le système binaire est le premier exemple de “polymère vivant” en milieu organique et présente des modules élastiques (G ? ca. 120 Pa à ? = 1 %) qui sont au moins 20 fois plus grands que ceux des homologues aqueux.

Terech, P.; Maldivi, P.; Dammer, C.

1994-10-01

204

PHYSIOLOGICALLY BASED PHARMACOKINETIC MODEL FOR HUMAN EXPOSURES TO METHYL TERTIARY-BUTYL ETHER  

EPA Science Inventory

Humans can be exposed by inhalation, ingestion, or dermal absorption to methyl tertiary-butyl ether (MTBE), an oxygenated fuel additive, from contaminated water sources. The purpose of this research was to develop a physiologically based pharmacokinetic model describing in human...

205

Enhanced diisobutene production in the presence of methyl tertiary butyl ether  

DOEpatents

In the liquid phase reaction of isobutene in the presence of resin cation exchange resins with itself in a C[sub 4] hydrocarbon stream to form dimers, the formation of higher polymers, oligomers, and co-dimer by-products is suppressed by the presence of 0.0001 to 1 mole per mole of isobutene of methyl tertiary butyl ether. 1 fig.

Smith, L.A. Jr.

1983-03-01

206

Enhanced diisobutene production in the presence of methyl tertiary butyl ether  

DOEpatents

In the liquid phase reaction of isobutene in the presence of resin cation exchange resins with itself in a C.sub.4 hydrocarbon stream to form dimers, the formation of higher polymers, oligomers, and co-dimer by-products is suppressed by the presence of 0.0001 to 1 mole per mole of isobutene of methyl tertiary butyl ether.

Smith, Jr., Lawrence A. (Bellaire, TX)

1983-01-01

207

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...

208

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...

209

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...

210

Parallel kinetic resolution of tert-butyl (RS)-3-alkyl-cyclopentene-1-carboxylates for the asymmetric synthesis of 3-alkyl-cispentacin derivatives.  

PubMed

The double mutual kinetic resolution of tert-butyl (RS)-3-benzyl-cyclopentene-1-carboxylate with a 50 : 50 mixture of lithium (RS)-N-benzyl-N-alpha-methylbenzylamide and lithium (RS)-N-3,4-dimethoxybenzyl-N-alpha-methylbenzylamide gives, after protonation with 2,6-di-tert-butylphenol, a 50 : 50 mixture of the readily separable N-benzyl-(1SR,2RS,3RS,alphaRS)- and N-3,4-dimethoxybenzyl-(1SR,2RS,3RS,alphaRS)-beta-amino esters in >98% de in each case. This product distribution indicates that these amides react at very similar rates and with no mutual interference to furnish readily separable products, and are thus ideal for parallel kinetic resolution. The efficient parallel kinetic resolution (E > 65) of a range of tert-butyl (RS)-3-alkyl-cyclopentene-1-carboxylates with a pseudoenantiomeric mixture of homochiral lithium (S)-N-benzyl-N-alpha-methylbenzylamide and lithium (R)-N-3,4-dimethoxybenzyl-N-alpha-methylbenzylamide gives, after separation and N-deprotection, a range of carboxylate protected 3-alkyl-cispentacin derivatives in >98% de and >95% ee. PMID:15534713

Davies, Stephen G; Garner, A Christopher; Long, Marcus J C; Smith, Andrew D; Sweet, Miles J; Withey, Jonathan M

2004-11-21

211

Volumetric Properties of the Mixture tert-Butyl ethyl ether C6H14O + C14H30 Tetradecane (VMSD1111, LB4723_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 ethyl ether C6H14O + C14H30 Tetradecane (VMSD1111, LB4723_V)' providing data from direct low-pressure measurement of mass density at variable mole fraction and constant temperature, in the single-phase region(s).

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

212

Volumetric Properties of the Mixture tert-Butyl ethyl ether C6H14O + C14H30 Tetradecane (VMSD1212, LB4714_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 ethyl ether C6H14O + C14H30 Tetradecane (VMSD1212, LB4714_V)' providing data by calculation of molar excess volume from low-pressure density measurements at variable mole fraction and constant temperature.

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

213

A new and facile preparation of tert-butyl (3 R,5 S)-6-hydroxy-3,5- O-isopropylidene-3,5-dihydroxyhexanoate  

Microsoft Academic Search

A facile method for the preparation of tert-butyl (3R,5S)-6-hydroxy-3,5-O-isopropylidene-3,5-dihydroxyhexanoate is described by a chemoenzymatic approach. In this method, one hydroxyl stereocenter at C5 is obtained with a high ee value (up to 98.0%) via an enzymatic transesterification resolution of l-chloro-3-(4-methylbenzyloxy)-2-propanol. The other hydroxyl stereocenter at C3 was built with 98.0% de, by acid-hydrolysis of a 1,3-diol-acetonide syn\\/anti-10. It is noteworthy

Fenglai Sun; Gang Xu; Jianping Wu; Lirong Yang

2007-01-01

214

Enhancementof LiverMicrosomeEpoxideHydrataseActivityin Rodents byTreatmentwith 2(3)tertButyl4-hyd roxyanisole1  

Microsoft Academic Search

Administrationof the antioxidant2(3)-tert-butyl-4-hy droxyanisole (BHA)in the dietcauseda markedincrease in the specific activity of epoxide hydratase (EC 4.2.1.63) in hepaticmicrosomesof CD-i mice. The increasesin epoxide hydratase activities produced by BHA were far greater(11-fold)thanwerethoseproducedbythe admin istrationof well-knownenzymeinducerssuchas 3-meth ylcholanthrene, phenobarbital, and Arocbor 1254(2- to 3- fold). The near-maximalIncreasein epoxidehydratase activitywas observedafterfeedingof the BHAdiet for 3 days.WhenBHAwasadministered by gastricintubation, the bevelof increasewas only

Young-Nam Cha; Fred Martz; Ernest Bueding

215

Chemical Synthesis of beta-Homonojirimycin, of Its N-Butyl Derivative, and of "Methyl Homoazacellobioside"  

PubMed

beta-Homonojirimycin (2) was prepared by the highly stereoselective double reductive amination of a 2,6-heptodiulose derivative (6 or 13) using ammonium formate and NaBH(3)CN. The process was unsuccessful with primary amines. The synthesis of N-butyl-beta-homonojirimycin (19) was achieved by the N-butanoylation of a derivative of 2 followed by the reduction of the resulting tertiary amide. Compound 19 was found to be completely devoid of anti-HIV activity, in marked contrast with N-butyl-1-deoxynojirimycin. The coupling of the 1-O-p-toluenesulfonyl derivative of 2, compound 20, with methyl 2,3,6-tri-O-benzyl-alpha-D-glucopyranoside, followed by a deprotection step, provided pseudodisaccharide 23, the "homoaza" analog of methyl alpha-cellobioside and a potential inhibitor of beta-glucan-processing enzymes. PMID:11667597

Saavedra, Oscar M.; Martin, Olivier R.

1996-10-01

216

Novel tert-butyl-tris(3-hydrocarbylpyrazol-1-yl)borate ligands: synthesis, spectroscopic studies, and coordination chemistry.  

PubMed

The lithium (1) and thallium (2) salts of five new tert-butyl-tris(3-hydrocarbylpyrazol-1-yl)borate ligands [t-BuTp(R)]- (R = H, a; Me, b; i-Pr, c; t-Bu, d; Ph, e) have been synthesized and characterized. Because of steric congestion at B, the reaction between t-BuBH3Li x 0.5 Et2O and excess 2,5-dimethylpyrazole Hpz(Me2) afforded the bis-pz(Me2) derivative, Tl[t-BuBH(3,5-Me2pz)2] (3) after metathesis with TlNO3. The compounds were characterized by elemental analysis and NMR spectroscopy. The Li salts 1a and 1c exhibit fluxional behavior on the NMR time scale in solution at room temperature. The solid-state 7Li and 11B NMR spectra of 1c suggest that this salt exists as a mixture of axial and equatorial isomers. The partial hydrolysis of 1d afforded the dimeric Li complex {Li[t-BuB(pz(t-Bu))2(mu-OH)]}2 (4). The crystal structure of 4 shows two Li cations encapsulated by the heteroscorpionate [t-BuB(OH)(3-t-Bupz)2]- ligands. A salt elimination reaction between FeCl2(THF)1.5 and 2 equiv of Li[t-BuTp(R)] (R = H, Me) followed by an in situ one-electron oxidation produced good yields of the homoleptic, paramagnetic low-spin iron(III) complexes [Fe(t-BuTp)2]PF6 (5) and [Fe(t-BuTp(Me))2]PF6 (6) that were characterized by elemental analyses, magnetic susceptibility measurements in solution and the solid phase, 1H NMR, high-resolution mass spectrometry, Mössbauer spectroscopy, and single-crystal X-ray diffraction. The crystals are composed of discrete molecular units with the central Fe(III) ion in an almost perfectly octahedral coordination to six nitrogen atoms. Compound 5 has the shortest Fe-N bond lengths ever reported for [Fe(RTp(R)')2]+-type compounds. PMID:16813432

Graziani, Olivier; Hamon, Paul; Thépot, Jean-Yves; Toupet, Loïc; Szilágyi, Petra A; Molnár, Gábor; Bousseksou, Azzedine; Tilset, Mats; Hamon, Jean-René

2006-07-10

217

Free radical oxidation of brain proteins in accelerated senescence and its modulation by?N-tert-butyl-?-phenylnitrone  

PubMed Central

According to the free radical theory of aging, reactive oxygen species cause oxidative damage, proposed to be an underlying factor of the aging process. In the current study, we have used electron paramagnetic resonance spin labeling, measurements of protein carbonyl content, an index of protein oxidation, and determination of the activity of glutamine synthetase (an oxidatively sensitive enzyme) to report that cortical synaptosomal membranes from the senescence accelerated-prone (SAMP8) mouse showed structural characteristics of free radical oxidative stress relative to the senescence accelerated-resistant (SAMR1) mouse. The SAMP8 mouse exhibited a decrease in the relevant EPR parameter consistent with oxidative stress (P < 0.002), a decreased glutamine synthetase activity (P < 0.05), and an increased protein carbonyl content (P < 0.01) compared with these parameters in the SAMR1 mouse. Further, because free radical trapping compounds have been demonstrated to extend maximum life span and improve cognition in SAMP8 mice, we investigated the protective nature of the known free radical scavenger, N-tert-butyl-?-phenylnitrone (PBN), on the physical state of cortical synaptosomal membrane proteins. For 14 days, SAMR1 and SAMP8 mice were injected with 30 mg/kg PBN while the controls were injected with the corresponding volume of saline. Characteristic of less oxidized systems, cortical synaptosomal membranes from the PBN-injected SAMP8 mouse exhibited a return toward normal values of the relevant EPR parameter [the MI = +1 low-field weakly immobilized line/MI = +1 low-field strongly immobilized line (W/S) ratio of a protein-specific spin label] (P < 0.001) compared with that from saline-injected SAMP8 mice. In SAMR1 mice, in contrast to SAMP8, there was no significant change in the conformation of membrane proteins or protein carbonyl content of cortical synaptosomal membranes from the PBN-injected and saline-injected SAMR1 mice, showing that PBN itself did not induce conformational changes in cortical synaptosomal membrane proteins. The results are discussed with reference to the use of free radical scavengers as potential anti-aging agents. PMID:9012843

Butterfield, D.?Allan; Howard, Beverly?J.; Yatin, Servet; Allen, Kerry?L.; Carney, John?M.

1997-01-01

218

Bioassay of methyl tertiary-butyl ether (MTBE) toxicity on rainbow trout fish  

Microsoft Academic Search

Methyl tertiary-butyl ether (MTBE) has been widely used as a gasoline additive. Water resource contamination due to spillage and accidental leakage of gasoline during fuel transportation may cause an important threat to aquatic life. In this work, the bioassay of MTBE toxicity on rainbow trout was performed. MTBE solutions of 250, 500, 750, 1000, and 1250mgL?1 were prepared in five

K. Naddafi; R. Nabizadeh; A. Baiggi

2008-01-01

219

Pathway, inhibition and regulation of methyl tertiary butyl ether oxidation in a filamentous fungus, Graphium sp  

Microsoft Academic Search

The filamentous fungus Graphium sp. (ATCC 58400) co-metabolically oxidizes the gasoline oxygenate methyl tertiary butyl ether (MTBE) after growth on gaseous n-alkanes. In this study, the enzymology and regulation of MTBE oxidation by propane-grown mycelia of Graphium sp. were further investigated and defined. The trends observed during MTBE oxidation closely resembled those described for\\u000a propane-grown cells of the bacterium Mycobacterium

Kristin M. Skinner; Adriana Martinez-Prado; Michael R. Hyman; Kenneth J. Williamson; Lynda M. Ciuffetti

2008-01-01

220

Modified 4-(dicyanomethylene)-2- tert-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4 H-pyran-containing red fluorescent emitters for efficient organic light-emitting diodes  

Microsoft Academic Search

Efficient red fluorescent compounds Red 1 and Red 2 based on bulky bicyclo[2,2,2]octane groups in the pyran moiety and tert-butyl or isopropyl group in the julolidine moiety of the 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran (DCJTB) skeleton were synthesized and characterized. As red-emitting dopants in an Alq3 single-host emitting system, Red 1 and Red 2 exhibited improved color purity and enhanced luminous efficiency compared to

Kum Hee Lee; Min Hye Park; Chi Sik Kim; Young Kwan Kim; Seung Soo Yoon

2011-01-01

221

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. PMID:23690869

Ajuwon, Olawale R.; Katengua-Thamahane, Emma; Van Rooyen, Jacques; Oguntibeju, Oluwafemi O.; Marnewick, Jeanine L.

2013-01-01

222

An evaluation of the 3M Organic Vapor Monitor #3500 as a short term exposure limit sampling device for acetone, methyl ethyl ketone, and methyl iso butyl ketone  

E-print Network

AN EVALUATION OF THE 3M ORGANIC VAPOR MONITOR 43500 AS A SHOR'I TERM EXPOSURE LIMIT SAMPLING DEVICE FOR ACETONE, METHYL ETHYL KETONE, AND METHYL ISO BUTYL KETONE A Thesis by LLOYD B. ANDREW III Submitted to the Graduate College of Texas ASM..., METHYL ETHYL KETONE, AND METHYL ISO BUTYL KETONE A Thesis by Lloyd B. Andrew III Approved as to style and content by: (Chai iy' of Co ' i tee) (He of Departme t) e4mY ~. (Member) C~& n (Member) December 1982 ABSTRACT An Evaluation of the 3M...

Andrew, Lloyd B.

1982-01-01

223

Site-specific methylation of CpG nucleotides in the hTERT promoter region can control the expression of hTERT during malignant progression of colorectal carcinoma.  

PubMed

Expression of hTERT has been recognized an important factor in cellular aging and immortalization. Therefore, to analyze regulatory mechanism of hTERT expression, we investigated the CpG methylation pattern of the hTERT promoter as an epigenetic mechanism and its implication in transcriptional regulation of hTERT using tissues of colorectal carcinoma. As a result, we were able to observe an increased pattern of hTERT expression according to the malignant progression of colorectal carcinoma. Additionally, we could find that hTERT expression was induced when the P1 and P2 region of hTERT were sufficiently hypermethylated and, oppositely, the G1 region of hTERT was hypomethylated. Importantly, we could find three specific CpG sites (7th CpG of P2 and 11th and 2nd-10th CpGs of P1) closely related with the increasing of hTERT expression. These findings may provide important clues to deducing the expression mechanisms of hTERT. PMID:17673177

Choi, Jee-Hye; Park, Soo Hyun; Park, Jina; Park, Borae G; Cha, Seong-Jae; Kong, Kwang-Hoon; Lee, Kwang-Ho; Park, Ae Ja

2007-09-28

224

Reaction temperature profiles and radical concentration measurements on batch emulsion copolymerizations of methyl methacrylate and butyl acrylate  

Microsoft Academic Search

Electron spin resonance (ESR) spectroscopy has been employed to monitor the occluded radical concentration during the batch (unseeded) emulsion copolymerization of methyl methacrylate and butyl acrylate. Occluded radical concentrations, above the detection limit of the ESR spectrometer, are only observed at methyl methacrylate mole fractions >0.96. The occluded radicals reach a maximum concentration at high conversion (ca 95%) and thereafter

Graham R. Cutting; Brian J. Tabner

1995-01-01

225

Solubilities of Carbon Dioxide and Oxygen in the Ionic Liquids Methyl Trioctyl Ammonium Bis(trifluoromethylsulfonyl)imide, 1-Butyl-3-Methyl Imidazolium Bis(trifluoromethylsulfonyl)imide, and 1-Butyl-3-Methyl Imidazolium Methyl Sulfate.  

PubMed

Ionic liquids (ILs) are being considered as solvents for gas absorption processes as they have the potential, in general, for improved efficiency of gas separations, as well as lower capital and operating costs compared to current commercial processes. In this study the solvent properties of ILs are investigated for use in the absorption of carbon dioxide (CO2) and oxygen (O2). The absorption of these gases in ILs was measured in the temperature range 303.15-333.15 K and at pressures up to 1.5 MPa by gravimetric analysis. The ILs used were methyl trioctyl ammonium bis (trifluoromethylsulfonyl) imide ([MOA][Tf2N]), 1-butyl-3-methyl imidazolium bis (trifluoromethylsulfonyl) imide ([BMIM][Tf2N]), and 1-butyl-3-methyl imidazolium methyl sulfate ([BMIM][MeSO4]). The measurement technique employed in this study is fast and accurate, and requires small quantities of solvent. The results indicated that absorption of both gases increased with a decrease in operating temperature and an increase in pressure. [MOA][Tf2N] had the highest CO2 and O2 solubility. [BMIM][Tf2N] was determined to have the highest selectivity for CO2 absorption. [BMIM][MeSO4] achieved the lowest CO2 absorption with a moderate O2 absorption, revealing this IL to be the least desirable for CO2 and O2 absorption. Calculation of Henry's law constants for all systems confirmed the deductions made from absorption data analysis. Calculation of enthalpy and entropy of absorption for each system revealed CO2 absorption in [MOA][Tf2N] to be the least sensitive to temperature increases. The absorption data was modeled using the generic Redlich-Kwong cubic equation of state (RK-EOS) coupled with a group contribution method. PMID:25478726

Bahadur, Indra; Osman, Khalid; Coquelet, Christophe; Naidoo, Paramespri; Ramjugernath, Deresh

2015-01-29

226

Multi-frequency ESR study of the polycrystalline phenoxyl radical of alpha-(3,5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butylnitrone in the diamagnetic matrix.  

PubMed

Multifrequency (X-, Q-, and W-band) electron spin resonance (ESR) spectroscopy has been used to characterize the phenoxyl radical produced from alpha-(3,5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butylnitrone, which is a new spin-trapping reagent. The X-band measurement did not resolve the powder-pattern ESR spectrum. Because of its higher resolution with g value, the Q-band ESR study revealed that the g factor has an axial-like symmetry and that the observed hyperfine structure in the Z-direction is caused by the nitrogen nucleus at the para-position. Furthermore, the results of the W-band ESR experiment more clearly distinguished the perpendicular components from the parallel component, resolving the perpendicular components into x and y components. The X-band powder spectrum was similar to the X-band ESR spectrum of the radical in a frozen solution of toluene. The computer simulation spectra performed using the obtained parameters fitted the experimental spectra well. A comparison of the amplitude of g( perpendicular)(gx, gy) with that of gz showed that the unpaired electron is delocalized over the pi-conjugated framework. Considering the hyperfine coupling constant, it was concluded that about 16% of the unpaired electron distributed over the nitrogen nucleus at the para-position. This study thus showed the significant potential of a multifrequency ESR approach to a powder sample radical in terms of its high resolution with g value. PMID:16420025

Yamaji, Toshiki; Noda, Yohei; Yamauchi, Seigo; Yamauchi, Jun

2006-01-26

227

Amine exchange reactions of 3- tert -butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide with amino acids  

Microsoft Academic Search

3-tert-Butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide enters into the amine exchange reaction with glycine\\u000a and ?-alanine in aqueous solution. The final exchange products are [4-(methylsulfanyl)-5,6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] acetate and 3-[4-(methylsulfanyl)-5, 6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] propanoate, respectively, crystallizing together with t-butylamine hydroiodide from aqueous or aqueous alcoholic solutions as ion associates, which also can be detected in solution\\u000a in DMSO-d\\u000a 6. [4-(Methylsulfanyl)-5,6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] acetate can be extracted directly from the reaction

Sun Min’yan’; S. M. Ramsh; V. S. Fundamenskii; S. Yu. Solov’eva; V. I. Zakharov

2010-01-01

228

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

2013-03-01

229

Dichloridobis[(1S,1S?,2R,2R?)-(+)-1,1?-di-tert-butyl-2,2?-diphospho­lane-?2 P,P?]ruthenium(II)  

PubMed Central

In the title compound, [RuCl2(C16H32P2)2], the RuII ion is situated on a twofold rotation axis, so the asymmetric unit contains one half-mol­ecule. The slightly distorted octa­hedral environment of the Ru center is formed by four P atoms [Ru—P = 2.4417?(6) and 2.4544?(6)?Å] from two different (1S,1S?,2R,2R?)-TangPhos ligands [(1S,1S?,2R,2R?)-TangPhos = (1S,1S?,2R,2R?)-(+)-1,1?-di-tert-butyl-2,2?-diphospho­lane] and two Cl atoms [Ru—Cl = 2.4267?(5)?Å]. PMID:21202447

Wang, Chubei; Tao, Haiyan; Ji, Baoming

2008-01-01

230

Determination of optical conductivity and different optical energy losses for non-crystalline Vanadyl tetra tert-butyl 2,3 Naphthalocyanine thinfilms  

SciTech Connect

Amorphous Vanadyl Tetra Tert Butyl 2, 3 naphthalocyanine thin films (VTTBNc) have been deposited using Physical Vapor Deposition technique. By analyzing the X-ray diffraction, the structure of as deposited films is found to be non-crystalline. Different optical properties of these thin films have been investigated by means of optical absorption and reflection spectra. Various optical constants like band gap energy, E{sub g} the width of band tails of localized states into the gap, E{sub U} and steepness parameter, {beta} gets calculated and the variation of different optical parameters like refractive index, extinction coefficient, dielectric constants, optical conductivity and surface and volume energy losses with photon energy are estimated.

Dhanya, I.; Menon, C. S. [School of Pure and Applied Physics, Mahatma Gandhi University, Priyadarshini Hills, Kottayam, Kerala, 686 560 (India)

2011-10-20

231

Growth and characterization of 2,6-Di-tert-butyl-4-(dimethylaminomethyl)phenol single crystal by the vertical Bridgman method  

NASA Astrophysics Data System (ADS)

Single crystal of 2,6-Di-tert-butyl-4-(dimethylaminomethyl)phenol has been grown by the modified vertical Bridgman method. Single crystal X-ray diffraction studies of the crystal confirm that the material belongs to the monoclinic system and space group C2. Fourier Transform Infrared Spectroscopy (FTIR) analysis ascertains the functional group of grown crystal. Thermogravimetric and differential scanning calorimetric analyses are used to assess the thermal characteristics. The surface laser damage value was determined using Q-switched Nd:YAG laser at a wavelength of 1064 nm, which is a positive property for nonlinear optical applications. Vickers's indentation test is performed to analyze the mechanical behavior of the materials. An optical transmission study is used to compute optical band gap and cutoff wavelength. Fluorescence studies were performed to the grown crystal. The Kurtz and Perry powder technique is used to determine the second harmonic conversion efficiency of the sample.

Siva Bala Solanki, S.; Perumal, Rajesh Narayana; Basheer Ahamed, M.

2015-02-01

232

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...

233

Treatment of Methyl tert-Butyl Ether Contaminated Water Using a Dense  

E-print Network

is transformed into a more toxic material or a substance that is more difficult to remediate, the treatment been concentrated in groundwater through leaks in underground storage tanks and gasoline spills

Dandy, David

234

MTBE (methyl tert. -butyl ether) aids efficiency of refinery C/sub 4/'s  

SciTech Connect

Chemical Research and Licensing Co. and Neochem Corp. have jointly developed an energy-efficient technology, licensed by Chemical Research, for converting the 9-12.5% isobutylene contained in a refinery butane-butene catalytic cracker stream to MTBE on a cost competitive basis. The process uses conventional reaction temperature and pressure and an available commercially proven proprietary catalyst system. Total potential MTBE production would be expanded from 65,000 bbl/day at present, to about 300,000-350,000 bbl/day if isobutylenes contained in refinery butane-butene were used as feedstock. The costs of producing 1358 bbl/day of MTBE from a stream containing 12.5% isobutylene at a typical-pattern 130,000 bbl/day Mid-Continent refinery are estimated at $0.946/gal (exclusive of royalties) with $2.9 million investment costs, and revenues are estimated at $19.9 million/yr as a result of a 407 bbl/day increase in gasoline production made possible by the high octane number of MTBE, which permits a reduction in reforming severity, and increased efficiency of isobutylene and energy use compared with direct use of the entire C/sub 4/ stream in alkylation.

Smith, L.A. (Chem. Res. Licensing Co.); Parker, K.E.

1980-08-11

235

Environmental Microbiology (2001) 3(6), 407416 Methyl tert-butyl ether (MTBE) degradation by a  

E-print Network

. Deshusses1 * Departments of 1 Chemical and Environmental Engineering, and 2 Plant Pathology, University char- acterized by a very slow growth rate (0.1 d21 ), a low overall biomass yield (0.11 gdw g21 MTBE to reduce smog and comply with the strict federal clean air standards, American oil companies are mandated

236

IRIS TOXICOLOGICAL REVIEW AND SUMMARY DOCUMENTS FOR METHYL TERT-BUTYL ETHER (MTBE)  

EPA Science Inventory

MTBE is a volatile organic chemical used to oxygenate gasoline. Oxygenated gasoline improves the exhaust emissions from gasoline engines. Since 1992 it has been used to comply with the Federal Reformulated Gasoline (begun in 1995) and Wintertime Oxygenated Fuel (begun in 1992) p...

237

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, and trimethylstannyl derivatives of 3,3-dimethylcyclopropene VII. 3,3-Dimethyl-1-(trimethylstannyl) cyclopropene.  

PubMed

The quantum mechanical force fields (QMFF's) of 3,3-dimethyl-1-(tert-butyl)cyclopropene (I), 3,3-dimethyl-1-(trimethylsilyl)cyclopropene (II), 3,3-dimethyl-1-(trimethylgermyl)cyclopropene (III), and 3,3-dimethyl-1-(trimethylstannyl)cyclopropene (IV) were calculated at the HF/3-21G*//HF/3-21G* level. The set of scale factors for the correction of HF/3-21G*//HF/3-21G* QMFF of II was determined using its well-characterised vibrational spectrum. Transferral of the set of scale factors obtained for II to the QMFF's of I, III and IV and calculation of the fundamental frequencies resulted in good agreement between the calculated and previously assigned experimental frequencies of III. This again demonstrates the feasibility of transferral of a set of scale factors obtained for the correction of the QMFF of a molecule to others containing heteroatoms from the same column of the Mendeleyev Periodic Table. Thus the calculations performed permitted the accurate assignment of the fundamental vibrational frequencies in the experimental IR spectrum of IV. The vibrational frequencies of 3,3-dimethyl-1-(tert-butyl)cyclopropene (I) were also calculated from the HF/6-31G*//HF/6-31G* QMFF, scaled by the set of scale factors used previously for the HF/6-31G*//HF/6-31G* QMFF's of II and III. Regularities in the trends of some vibrational frequencies with increasing atomic number of the heteroatom are observed. PMID:16546441

Panchenko, Yu N; De Mare, G R; Abramenkov, A V; de Meijere, A

2006-10-01

238

Antioxidant synergism between butylated hydroxyanisole and butylated hydroxytoluene  

Microsoft Academic Search

Decay of the 2,6-di-tert-butyl-4-methylphenoxy radical [butylated hydroxytoluene (BHT)-radical] in the presence of butylated hydroxyanisole (BHA)\\u000a was investigated in 1,2-dimethoxyethane with or without triethylamine. BHT-radical was conveniently generated by dissociation\\u000a of its unstable dimer in solution. The products were BHT, 3,3?-di-tert-butyl-5,5?-dimethoxy-2,2?-dihydroxybiphenyl (BHA-dimer), 2,6-di-tert-butyl-p-quinone methide (QM), 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)ethane, and 3,3?,5,5?-tetra-tert-butyl-4,4?-stilbenequinone. The reaction without added triethylamine gave larger quantities of the last two products

Kanji Omura

1995-01-01

239

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 3×3×3sH unit cell with up to 4.7mass% hydrogen gas are run at pressures of 100bars and 2kbars at 100 and 273K. 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

240

Spectroscopic, electrochemical, and alkylation reactions: tert-butyl N-(2-mercaptoethyl)carbamate copper(II) and nickel(II) complexes as structural mimics for the active site of thiolate-alkylating enzymes.  

PubMed

Two new dithiolate copper(II) and nickel(II) complexes with the ligand tert-butyl N-(2-mercaptoethyl)-carbamate (Boc-SH) were prepared. Their structures were established to be [(Boc-S)2M], where M=Cu (1) and Ni (2) by using elemental analysis, thermal analysis, molar conductivity, FT-IR, Raman, UV/VIS, and ESR as well as EI-mass spectroscopic methods. The X-ray structure of the ligand Boc-SH was also determined. Spectral data showed that the carbamate ligand act as anioinic bidentate through one immine nitrogen and one thiolate sulfur donor atoms. The spectral techniques suggest that both complexes appear to have square planar geometries. The very low electrical conductance of the two complexes supports their neutral nature. The redox behaviors of the obtained complexes were also investigated by cyclic voltammetry. The monomeric nature of both complexes was assessed from their magnetic susceptibility values. The thermoanalytical data evidence that complex (2) is stable up to 165°C and undergo complete decomposition, resulting in NiO as a residual product. The TEM image of the obtained oxide residue showed its nanosize cluster, suggesting that complex (2) may be used as a precursor for the formation of nanooxide. The methylation reactions of the two dithiolate complexes (1) and (2) with methyl iodide appear to occur intramolecularly at the metal(II)-bound dithiolates, forming the metal(II)-bound dithioether complexes [M(Boc-SCH3)2]I2 with clean second-order constants of 7.95×10(-2) and 10.59×10(-2) M(-1) s(-1), respectively. PMID:24290356

Ibrahim, Mohamed M; Mersal, Gaber A M; El-Shafai, Nagi; Ramadan, Abdel-Motaleb M; Youssef, Mohamed M

2014-01-01

241

tert-Butyl 6-amino-3,4-dihydro-2H-1,4-benzoxazine-4-carboxyl­ate  

PubMed Central

The title mol­ecule, C13H18N2O3, contains a benzene ring fused to an oxazine ring and one tert-but­oxy­carbonyl group bound to the N atom of the oxazine ring. A weak intra­molecular C—H?O inter­action occurs. In the crystal, inter­molecular N—H?O and C—H?O hydrogen bonds stack the mol­ecules down the b axis. Weak C—H?N contacts connect the stacks, generating a three-dimensional network. PMID:21589552

Gu, Xiao-Bo; Jiang, Meng-Jun; Cai, Gang-Ming; Zhou, Yao-Yuan

2010-01-01

242

IN-SITU BIOREMEDIATION OF METHYL TERTIARY BUTYL ETHER (MTBE) - ADVANCED FUEL HYDROCARBON REMEDIATION NATIONAL TEST LOCATION.  

EPA Science Inventory

Equilon's Westhollow Technology Center teamed with Arizona State University to evaluate an in-situ process for bioremediation of methyl tertiary butyl ether (MTBE). MTBE is a gasoline additive that was introduced in fuels to reduce emission of a number of air pollutants including...

243

Treatment of methyl t-butyl ether contaminated water using a dense medium plasma reactor, a mechanistic and kinetic investigation  

E-print Network

1 Treatment of methyl t-butyl ether contaminated water using a dense medium plasma reactor-7369 Email: david.dandy@colostate.edu Abstract Plasma treatment of contaminated water appears reactor configurations and two pin array spin rates. The oxidation products from the treatment of MTBE

Dandy, David

244

DEVELOPMENT OF PHYSIOLOGICAL-BASED PHARMACOKINETIC MODEL FOR DERMAL ABSORPTION NAD PENETRATION OF METHYL TERTIARY BUTYL ETHER IN HUMANS  

EPA Science Inventory

Background: Methyl tertiary butyl ether (MTBE) is a volatile organic chemical that is added to gasoline as an octane booster and to reduce vehicular emissions of carbon monoxide. MTBE is introduced into the environment through fuel spills, leakage of storage tanks, and evaporat...

245

Isolation of a Bacterial Culture That Degrades Methyl t-Butyl Ether  

PubMed Central

We have isolated a mixed bacterial culture (BC-1) which is capable of degrading the gasoline oxygenate methyl t-butyl ether (MTBE). BC-1 was developed from seed microorganisms present in a chemical plant biotreater sludge. This enrichment culture has been maintained in continuous culture treating high concentrations of MTBE (120 to 200 mg/liter) as the sole carbon source in a simple feed containing NH4+, PO43-, Mg2+, and Ca2+ nutrients. The unit had a stable MTBE removal rate when maintained with a long cell retention time (ca. 80 to 90 days); however, when operated at a ?50-day cell waste rate, loss of MTBE-degrading activity was observed. The following three noteworthy experimental data show that MTBE is biodegraded extensively by BC-1: (i) the continuous (oxygen-sparged) culture was able to sustain a population of autotrophic ammonia-oxidizing bacteria which could nitrify influent NH4+ concentrations at high rates and obtain CO2 (sole carbon source for growth) from the metabolism of the alkyl ether, (ii) BC-1 metabolized radiolabeled either (14CH3O-MTBE) to 14CO2 (40%) and 14C-labeled cells (40%), and (iii) cell suspensions of the culture were capable of degrading (substrate depletion experiments) MTBE to t-butyl alcohol, a primary metabolite of MTBE. BC-1 is a mixed culture containing several bacterial species and is the first culture of its kind which can completely degrade an alkyl ether. PMID:16349335

Salanitro, J. P.; Diaz, L. A.; Williams, M. P.; Wisniewski, H. L.

1994-01-01

246

Bacterial Degradation of tert-Amyl Alcohol Proceeds via Hemiterpene 2-Methyl-3-Buten-2-ol by Employing the Tertiary Alcohol Desaturase Function of the Rieske Nonheme Mononuclear Iron Oxygenase MdpJ  

PubMed Central

Tertiary alcohols, such as tert-butyl alcohol (TBA) and tert-amyl alcohol (TAA) and higher homologues, are only slowly degraded microbially. The conversion of TBA seems to proceed via hydroxylation to 2-methylpropan-1,2-diol, which is further oxidized to 2-hydroxyisobutyric acid. By analogy, a branched pathway is expected for the degradation of TAA, as this molecule possesses several potential hydroxylation sites. In Aquincola tertiaricarbonis L108 and Methylibium petroleiphilum PM1, a likely candidate catalyst for hydroxylations is the putative tertiary alcohol monooxygenase MdpJ. However, by comparing metabolite accumulations in wild-type strains of L108 and PM1 and in two mdpJ knockout mutants of strain L108, we could clearly show that MdpJ is not hydroxylating TAA to diols but functions as a desaturase, resulting in the formation of the hemiterpene 2-methyl-3-buten-2-ol. The latter is further processed via the hemiterpenes prenol, prenal, and 3-methylcrotonic acid. Likewise, 3-methyl-3-pentanol is degraded via 3-methyl-1-penten-3-ol. Wild-type strain L108 and mdpJ knockout mutants formed isoamylene and isoprene from TAA and 2-methyl-3-buten-2-ol, respectively. It is likely that this dehydratase activity is catalyzed by a not-yet-characterized enzyme postulated for the isomerization of 2-methyl-3-buten-2-ol and prenol. The vitamin requirements of strain L108 growing on TAA and the occurrence of 3-methylcrotonic acid as a metabolite indicate that TAA and hemiterpene degradation are linked with the catabolic route of the amino acid leucine, including an involvement of the biotin-dependent 3-methylcrotonyl coenzyme A (3-methylcrotonyl-CoA) carboxylase LiuBD. Evolutionary aspects of favored desaturase versus hydroxylation pathways for TAA conversion and the possible role of MdpJ in the degradation of higher tertiary alcohols are discussed. PMID:22194447

Schuster, Judith; Schäfer, Franziska; Hübler, Nora; Brandt, Anne; Rosell, Mònica; Härtig, Claus; Harms, Hauke; Müller, Roland H.

2012-01-01

247

Induction of Heme Oxygenase1 (HO1) and NAD[P]H: Quinone Oxidoreductase 1 (NQO1) by a Phenolic Antioxidant, Butylated Hydroxyanisole (BHA) and Its Metabolite, tert -Butylhydroquinone (tBHQ) in Primary-Cultured Human and Rat Hepatocytes  

Microsoft Academic Search

Purpose  This study was aimed to investigate the effects of a phenolic antioxidant, butylated hydroxyanisole (BHA) and its metabolite, tert-butylhydroquinone (tBHQ) on the induction of HO-1, NQO1 and Nrf2 proteins and their regulatory mechanisms in primary-cultured hepatocytes.Methods  After exposure of BHA and tBHQ to primary-cultured rat and human hepatocytes and mouse neonatal fibroblasts (MFs), Western blot, semi-quantitative RT-PCR and microarray analysis were

Young-Sam Keum; Yong-Hae Han; Celine Liew; Jung-Hwan Kim; Changjiang Xu; Xiaoling Yuan; Michael P. Shakarjian; Saeho Chong; Ah-Ng Kong

2006-01-01

248

Non-specific inhibition of ischemia- and acidosis-induced intracellular calcium elevations and membrane currents by ?-phenyl-N-tert-butylnitrone, butylated hydroxytoluene and trolox.  

PubMed

Ischemia, and subsequent acidosis, induces neuronal death following brain injury. Oxidative stress is believed to be a key component of this neuronal degeneration. Acute chemical ischemia (azide in the absence of external glucose) and acidosis (external media buffered to pH 6.0) produce increases in intracellular calcium concentration ([Ca2+]i) and inward membrane currents in cultured rat cortical neurons. Two ?-tocopherol analogues, trolox and butylated hydroxytoluene (BHT), and the spin trapping molecule ?-Phenyl-N-tert-butylnitrone (PBN) were used to determine the role of free radicals in these responses. PBN and BHT inhibited the initial transient increases in [Ca2+]i, produced by ischemia, acidosis and acidic ischemia and increased steady state levels in response to acidosis and the acidic ischemia. BHT and PBN also potentiated the rate at which [Ca2+]i increased after the initial transients during acidic ischemia. Trolox inhibited peak and sustained increases in [Ca2+]i during ischemia. BHT inhibited ischemia induced initial inward currents and trolox inhibited initial inward currents activated by acidosis and acidic ischemia. Given the inconsistent results obtained using these antioxidants, it is unlikely their effects were due to elimination of free radicals. Instead, it appears these compounds have non-specific effects on the ion channels and exchangers responsible for these responses. PMID:24583849

Katnik, Christopher; Cuevas, Javier

2014-01-01

249

Protective Effects of Black Rice Extracts on Oxidative Stress Induced by tert-Butyl Hydroperoxide in HepG2 Cells  

PubMed Central

Black rice contains many biologically active compounds. The aim of this study was to investigate the protective effects of black rice extracts (whole grain extract, WGE and rice bran extract, RBE) on tert-butyl hydroperoxide (TBHP)-induced oxidative injury in HepG2 cells. Cellular reactive oxygen species (ROS), antioxidant enzyme activities, malondialdehyde (MDA) and glutathione (GSH) concentrations were evaluated as biomarkers of cellular oxidative status. Cells pretreated with 50 and 100 ?g/mL of WGE or RBE were more resistant to oxidative stress in a dose-dependent manner. The highest WGE and BRE concentrations enhanced GSH concentrations and modulated antioxidant enzyme activities (glutathione reductase, glutathione-S-transferase, catalase, and superoxide dismutase) compared to TBHP-treated cells. Cells treated with RBE showed higher protective effect compared to cells treated with WGE against oxidative insult. Black rice extracts attenuated oxidative insult by inhibiting cellular ROS and MDA increase and by modulating antioxidant enzyme activities in HepG2 cells. PMID:25580401

Lee, Seon-Mi; Choi, Youngmin; Sung, Jeehye; Kim, Younghwa; Jeong, Heon-Sang; Lee, Junsoo

2014-01-01

250

Antioxidant activity and protective effect of extract of Celosia cristata L. flower on tert-butyl hydroperoxide-induced oxidative hepatotoxicity.  

PubMed

This study was undertaken to evaluate the antioxidant potential and protective effects of Celosia cristata L. (Family: Amaranthaceae) flower (CCF) extracts on tert-butyl-hydroperoxide (t-BHP)-induced oxidative damage in the hepatocytes of Chang cells and rat livers. In vitro, CCF extracts exhibited protective effect through their radical scavenging ability to enhance cell viability, prevent reactive oxygen species (ROS) generation, and inhibit mitochondrial membrane depolarisation in t-BHP-induced hepatotoxicity in Chang cells. In vivo, oral feeding of CCF (100mg and 500mg/kg of body weight) to rats for five consecutive days before a single dose of t-BHP (2mmol/kg, i.p.) showed a significant (p<0.05) protective effect by lowering serum levels of glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT). The extract decreased the hepatic levels of lipid peroxidation (MDA) and serum level of triglyceride (TG) against t-BHP-induced oxidative stress. These results indicate that CCF extract prevented oxidative stress-induced liver injury by enhancing hepatocyte antioxidant abilities. PMID:25172750

Kim, Yon-Suk; Hwang, Jin-Woo; Sung, Si-Heung; Jeon, You-Jin; Jeong, Jae-Hyun; Jeon, Byong-Tae; Moon, Sang-Ho; Park, Pyo-Jam

2015-02-01

251

Conformational stability, molecular orbital studies (chemical hardness and potential), vibrational investigation and theoretical NBO analysis of 4-tert-butyl-3-methoxy-2,6-dinitrotoluene.  

PubMed

The FT-IR and FT-Raman spectra of 4-tert-butyl-3-methoxy-2,6-dinitrotoluene (musk ambrette) have been recorded in the regions 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The total energy calculations of musk ambrette were tried for the possible conformers. The molecular structure, geometry optimization, vibrational frequencies were obtained by the density functional theory (DFT) using B3LYP and LSDA method with 6-311G(d,p) basis set for the most stable conformer "C1". The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated and the scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The stability of the molecule arising from hyper conjugate interactions and the charge delocalization has been analyzed using bond orbital (NBO) analysis. The HOMO and LUMO energy gap reveals that the energy gap reflects the chemical activity of the molecule. The dipole moment (?), polarizability (?), anisotropy polarizability (??) and first hyperpolarizability (?tot) of the molecule have been reported. The thermodynamic functions (heat capacity, entropy and enthalpy) were obtained for the range of temperature 100-1000 K. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron density isosurface with molecular electrostatic potential (MEP). PMID:24508884

Saravanan, S; Balachandran, V; Vishwanathan, K

2014-04-24

252

Solvent injection-lyophilization of tert-butyl alcohol/water cosolvent systems for the preparation of drug-loaded solid lipid nanoparticles.  

PubMed

A simple procedure involving solvent injection-lyophilization (SIL) was used to prepare solid lipid nanoparticles (SLNs). A tert-butyl alcohol (t-BA) solution containing lipids was injected into a stirred aqueous solution containing lyoprotectants to form SLNs dispersed in a t-BA/water cosolvent system. The t-BA/water cosolvent SLN dispersion was subsequently lyophilized to obtain a dry product which, upon rehydration, formed an aqueous dispersion of spherical SLNs with a size under 200 nm. A lipophilic drug, cinnarizine, was dissolved in t-BA at a drug-to-lipid mass ratio of 1:20 and almost 100% of the drug was entrapped in the formed SLNs following the SIL process. Likewise, hydrophilic 5-fluorouracil, after being solubilized in t-BA through forming anhydrous reverse micelles, could be entrapped in SLNs with an encapsulation efficiency up to 15.6%. Differential scanning calorimetry and small angle X-ray scattering analysis proved that the lipids in the formed SLNs were in a stable beta-form, and there was no recrystallization expulsion of drugs during storage. In contrast to the conventional solvent injection method, the SIL procedure was not time-consuming and no relatively high-temperature evaporation was needed to remove organic solvents. Moreover, the efficiency of the lyophilization was markedly enhanced due to use of the t-BA/water cosolvent system. Thus, the SIL procedure was found to be an efficient method for preparing stable drug-loaded SLNs. PMID:20447810

Wang, Ting; Wang, Ning; Zhang, Yingying; Shen, Wancui; Gao, Xingmei; Li, Tiefu

2010-08-01

253

Fluctuating micro-heterogeneity in water–tert-butyl alcohol mixtures and lambda-type divergence of the mean cluster size with phase transition-like multiple anomalies  

SciTech Connect

Water–tert-butyl alcohol (TBA) binary mixture exhibits a large number of thermodynamic and dynamic anomalies. These anomalies are observed at surprisingly low TBA mole fraction, with x{sub TBA} ? 0.03–0.07. We demonstrate here that the origin of the anomalies lies in the local structural changes that occur due to self-aggregation of TBA molecules. We observe a percolation transition of the TBA molecules at x{sub TBA} ? 0.05. We note that “islands” of TBA clusters form even below this mole fraction, while a large spanning cluster emerges above that mole fraction. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Alongside, the structure of water is also perturbed, albeit weakly, by the aggregation of TBA molecules. There is a monotonic decrease in the tetrahedral order parameter of water, while the dipole moment correlation shows a weak nonlinearity. Interestingly, water molecules themselves exhibit a reverse percolation transition at higher TBA concentration, x{sub TBA} ? 0.45, where large spanning water clusters now break-up into small clusters. This is accompanied by significant divergence of the fluctuations in the size of largest water cluster. This second transition gives rise to another set of anomalies around. Both the percolation transitions can be regarded as manifestations of Janus effect at small molecular level.

Banerjee, Saikat; Furtado, Jonathan; Bagchi, Biman, E-mail: bbagchi@sscu.iisc.ernet.in [SSCU, Indian Institute of Science, Bangalore 560012 (India)] [SSCU, Indian Institute of Science, Bangalore 560012 (India)

2014-05-21

254

Low-temperature CVD of iron, cobalt, and nickel nitride thin films from bis[di(tert-butyl)amido]metal(II) precursors and ammonia  

SciTech Connect

Thin films of late transition metal nitrides (where the metal is iron, cobalt, or nickel) are grown by low-pressure metalorganic chemical vapor deposition from bis[di(tert-butyl)amido]metal(II) precursors and ammonia. These metal nitrides are known to have useful mechanical and magnetic properties, but there are few thin film growth techniques to produce them based on a single precursor family. The authors report the deposition of metal nitride thin films below 300?°C from three recently synthesized M[N(t-Bu){sub 2}]{sub 2} precursors, where M?=?Fe, Co, and Ni, with growth onset as low as room temperature. Metal-rich phases are obtained with constant nitrogen content from growth onset to 200?°C over a range of feedstock partial pressures. Carbon contamination in the films is minimal for iron and cobalt nitride, but similar to the nitrogen concentration for nickel nitride. X-ray photoelectron spectroscopy indicates that the incorporated nitrogen is present as metal nitride, even for films grown at the reaction onset temperature. Deposition rates of up to 18?nm/min are observed. The film morphologies, growth rates, and compositions are consistent with a gas-phase transamination reaction that produces precursor species with high sticking coefficients and low surface mobilities.

Cloud, Andrew N.; Abelson, John R., E-mail: abelson@illinois.edu [Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 201 Materials Science and Engineering Building, 1304 W. Green St., Urbana, Illinois 61801 (United States); Davis, Luke M.; Girolami, Gregory S., E-mail: girolami@scs.illinois.edu [School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave., Urbana, Illinois 61801 (United States)

2014-03-15

255

The Cytoprotective Effect of Sulfuretin against tert-Butyl Hydroperoxide-Induced Hepatotoxicity through Nrf2/ARE and JNK/ERK MAPK-Mediated Heme Oxygenase-1 Expression  

PubMed Central

Sulfuretin is one of the major flavonoid components in Rhus verniciflua Stokes (Anacardiaceae) isolates. In this study, we investigated the protective effects of sulfuretin against tert-butyl hydroperoxide (t-BHP)-induced oxidative injury. The results indicated that the addition of sulfuretin before t-BHP treatment significantly inhibited cytotoxicity and reactive oxygen species (ROS) production in human liver-derived HepG2 cells. Sulfuretin up-regulated the activity of the antioxidant enzyme heme oxygenase (HO)-1 via nuclear factor E2-related factor 2 (Nrf2) translocation into the nucleus and increased the promoter activity of the antioxidant response element (ARE). Moreover, sulfuretin exposure enhanced the phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase 1/2 (ERK1/2), which are members of the mitogen-activated protein kinase (MAPK) family. Furthermore, cell treatment with a JNK inhibitor (SP600125) and ERK inhibitor (PD98059) reduced sulfuretin-induced HO-1 expression and decreased its protective effects. Taken together, these results suggest that the protective effect of sulfuretin against t-BHP-induced oxidative damage in human liver-derived HepG2 cells is attributable to its ability to scavenge ROS and up-regulate the activity of HO-1 through the Nrf2/ARE and JNK/ERK signaling pathways. Therefore, sulfuretin could be advantageous as a bioactive source for the prevention of oxidative injury. PMID:24857917

Lee, Dong-Sung; Kim, Kyoung-Su; Ko, Wonmin; Li, Bin; Jeong, Gil-Saeng; Jang, Jun-Hyeog; Oh, Hyuncheol; Kim, Youn-Chul

2014-01-01

256

The cytoprotective effect of sulfuretin against tert-butyl hydroperoxide-induced hepatotoxicity through Nrf2/ARE and JNK/ERK MAPK-mediated heme oxygenase-1 expression.  

PubMed

Sulfuretin is one of the major flavonoid components in Rhus verniciflua Stokes (Anacardiaceae) isolates. In this study, we investigated the protective effects of sulfuretin against tert-butyl hydroperoxide (t-BHP)-induced oxidative injury. The results indicated that the addition of sulfuretin before t-BHP treatment significantly inhibited cytotoxicity and reactive oxygen species (ROS) production in human liver-derived HepG2 cells. Sulfuretin up-regulated the activity of the antioxidant enzyme heme oxygenase (HO)-1 via nuclear factor E2-related factor 2 (Nrf2) translocation into the nucleus and increased the promoter activity of the antioxidant response element (ARE). Moreover, sulfuretin exposure enhanced the phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase 1/2 (ERK1/2), which are members of the mitogen-activated protein kinase (MAPK) family. Furthermore, cell treatment with a JNK inhibitor (SP600125) and ERK inhibitor (PD98059) reduced sulfuretin-induced HO-1 expression and decreased its protective effects. Taken together, these results suggest that the protective effect of sulfuretin against t-BHP-induced oxidative damage in human liver-derived HepG2 cells is attributable to its ability to scavenge ROS and up-regulate the activity of HO-1 through the Nrf2/ARE and JNK/ERK signaling pathways. Therefore, sulfuretin could be advantageous as a bioactive source for the prevention of oxidative injury. PMID:24857917

Lee, Dong-Sung; Kim, Kyoung-Su; Ko, Wonmin; Li, Bin; Jeong, Gil-Saeng; Jang, Jun-Hyeog; Oh, Hyuncheol; Kim, Youn-Chul

2014-01-01

257

Hepatoprotective activity of the Phyllanthus species on tert-butyl hydroperoxide (t-BH)-induced cytotoxicity in HepG2 cells  

PubMed Central

Background: Phyllanthus (Euphorbiaceae) species have long been used in folk medicine to treat various pathological conditions including liver diseases. Some species of Phyllanthus were found to exhibit hepatoprotective activity against drugs or toxins and this property was majorly attributed to phyllanthin and hypophyllanthin. In this study, we examined the hepatoprotective activity of five different species of Phyllanthus, namely, Phyllanthus amarus, Phyllanthus fraternus, Phyllanthus maderaspatensis, Phyllanthus urinaria, and Phyllanthus Rotundifolius. The extracts were also evaluated for the presence of key phytoconstituents, phyllanthin and hypophyllanthin. Materials and Methods: The extracts were evaluated for hepatoprotective activity against tert-butyl hydroxide (t-BH)-induced cytotoxicity using human hepatocarcinoma cells (HepG2 cell line). Results: Only P. urinaria and P. maderaspatensis exhibited significant hepatoprotective activity as evident from increased cell viability. The HPLC profile revealed that except P. amarus, the other extracts did not contain phyllanthin and hypophyllanthin. Conclusion: P. urinaria and P. maderaspatensis demonstrated dose-dependent hepatoprotective activity and hence, can provide promising therapeutic interventions against chemical–induced liver damage. PMID:21969794

Sharma, Surendra Kumar; Arogya, Sheela Meruga; Bhaskarmurthy, Deepak Hiraganahalli; Agarwal, Amit; Velusami, Chandrasekaran Chinampudar

2011-01-01

258

The Synergistic Effects of Heat Shock Protein 70 and Ginsenoside Rg1 against Tert-Butyl Hydroperoxide Damage Model In Vitro  

PubMed Central

Neural stem cells (NSCs) transplanted is one of the hottest research to treat Alzheimer's disease (AD), but cholinergic neurons from stem cells were also susceptible to cell death which Heat shock protein 70 (HSP70) was affirmed to reverse. Related to cognitive impairment, cholinergic nervous cells should be investigated and ginsenoside Rg1 (G-Rg1) was considered to increase them. We chose tert-butyl hydroperoxide (t-BHP) damage model to study in vitro. Functional properties of our recombination plasmid pEGFP-C2-HSP70 were affirmed by SH-SY5Y cells. To opposite the transitory appearance of HSP70, NSCs used as the vectors of HSP70 gene overexpressed HSP70 for at least 7 days in vitro. After transfection for 3 days, G-Rg1 pretreatment for 4 hours, and coculture for 3 days, the expression of acetylcholinesterase (ChAT), synaptophysin, and the ratio of NeuN and GFAP were assessed by western blot; Morphological properties were detected by 3D reconstruction and immunofluorescence. ChAT was markedly improved in the groups contained G-Rg1. In coculture system, the ratio of neurons/astrocytes and the filaments of neurons were increased; apoptosis cells were decreased, compared to monotherapy (P < 0.05). In conclusion, we demonstrated that, as a safe cotreatment affirmed in vitro, overexpression of HSP70 in NSCs plus G-Rg1 promoted nervous cells regeneration from chronic oxidative damage. PMID:25685255

Lu, Dan; Xu, Anding; Zhao, Jiayi; Zhang, Chanjuan; Qi, Renbin; Wang, Huadong; Lu, Daxiang; Zhu, Lihong

2015-01-01

259

Evaluation of ethyl tert-butyl ether biodegradation in a contaminated aquifer by compound-specific isotope analysis and in situ microcosms.  

PubMed

Ethyl tert-butyl ether (ETBE) is an upcoming groundwater pollutant in Europe whose environmental fate has been less investigated, thus far. In the present study, we investigated the in situ biodegradation of ETBE in a fuel-contaminated aquifer using compound-specific stable isotope analysis (CSIA), and in situ microcosms in combination with total lipid fatty acid (TLFA)-stable isotope probing (SIP). In a first field investigation, CSIA revealed insignificant carbon isotope fractionation, but low hydrogen isotope fractionation of up to +14‰ along the prevailing anoxic ETBE plume suggesting biodegradation of ETBE. Ten months later, oxygen injection was conducted to enhance the biodegradation of petroleum hydrocarbons (PH) at the field site. Within the framework of this remediation measure, in situ microcosms loaded with [(13)C6]-ETBE (BACTRAP(®)s) were exposed for 119 days in selected groundwater wells to assess the biodegradation of ETBE by TLFA-SIP under the following conditions: (i) ETBE as main contaminant; (ii) ETBE as main contaminant subjected to oxygen injection; (iii) ETBE plus other PH; (iv) ETBE plus other PH subjected to oxygen injection. Under all conditions investigated, significant (13)C-incorporation into microbial total lipid fatty acids extracted from the in situ microcosms was found, providing clear evidence of ETBE biodegradation. PMID:25559863

Bombach, Petra; Nägele, Norbert; Rosell, Mònica; Richnow, Hans H; Fischer, Anko

2015-04-01

260

Bis[O,O?-bis­(4-tert-butyl­phen­yl) di­thio­phosphato-?2 S,S?]bis­(pyridine-?N)lead(II)  

PubMed Central

In the title compound, [Pb(C20H26O2PS2)2(C5H5N)2], the PbII ion is coordinated by two S,S?-bidentate anions and two pyridine mol­ecules. The PbN2S4 coordination geometry approximates to a penta­gonal bipyramid with one equatorial site vacant. The N atoms occupy the axial sites. One of the pyridine mol­ecules is disordered over two sets of sites in a 0.907?(7):0.093?(7) ratio and one of the tert-butyl groups is disordered over two sets of sites in a 0.534?(6):0.466?(6) ratio. An intra­molecular C—H?O inter­action occurs in one of the ligands. In the crystal, pairs of short Pb?S contacts [3.4018?(11)?Å] generate a centrosymmetric dimeric assembly with the distant S atom lying in the region of the vacant coordination site of the metal atom. No directional packing inter­actions occur. PMID:24427011

Zhang, Xiulan; Xie, Bin; He, Linxin; Lu, Lu; Chen, Neng

2013-01-01

261

Nitric oxide prevents myoglobin/tert-butyl hydroperoxide-induced inhibition of Ca2+ transport in skeletal and cardiac sarcoplasmic reticulum.  

PubMed

Interaction of hydrogen peroxide or organic hydroperoxides with hemoproteins is known to produce oxoferryl hemoprotein species that act as very potent oxidants. Since skeletal and cardiac muscle cells contain high concentrations of myoglobin this reaction may be an important mechanism of initiation or enhancement of oxidative stress, which may impair their Ca2+ transport systems. Using skeletal and cardiac sarcoplasmic reticulum (SR) vesicles, we demonstrated by EPR the formation of alkoxyl radicals and protein-centered peroxyl radicals in the presence of myoglobin (Mb) and tert-butyl hydroperoxide (t-BuOOH). The low temperature EPR signal of the radicals was characterized by major feature at g = 2.016 and a shoulder at g = 2.036. In the presence of SR vesicles, the magnitude of the protein-centered peroxyl radical signal decreased, suggesting that the radicals were involved in oxidative modification of SR membranes. This was accompanied by SR membrane oxidative damage, as evidenced by accumulation of 2-thiobarbituric acid-reactive substances (TBARS) and the inhibition of Ca2+ transport. We have shown that nitric oxide (NO), reacting with redox-active heme iron, can prevent peroxyl radical formation activated by Mb/t-BuOOH. Incubation of SR membranes with an NO donor, PAPA/NO (a non-thiol compound that releases NO) at 200-500 microM completely prevented the t-BuOOH-dependent production of peroxyl radicals and formation of TBARS, and thus protected against oxidative inhibition of Ca2+ transport. PMID:10415548

Menshikova, E V; Ritov, V B; Gorbunov, N V; Salama, G; Claycamp, H G; Kagan, V E

1999-06-30

262

Effects of consumption of rooibos (Aspalathus linearis) and a rooibos-derived commercial supplement on hepatic tissue injury by tert-butyl hydroperoxide in Wistar rats.  

PubMed

This study investigated the antioxidative effect of rooibos herbal tea and a rooibos-derived commercial supplement on tert-butyl hydroperoxide- (t-BHP-) induced oxidative stress in the liver. Forty male Wistar rats consumed fermented rooibos, unfermented rooibos, a rooibos-derived commercial supplement, or water for 10 weeks, while oxidative stress was induced during the last 2 weeks via intraperitoneal injection of 30 µmole of t-BHP per 100 g body weight. None of the beverages impaired the body weight gain of the respective animals. Rats consuming the rooibos-derived commercial supplement had the highest (P < 0.05) daily total polyphenol intake (169 mg/day) followed by rats consuming the unfermented rooibos (93.4 mg/day) and fermented rooibos (73.1 mg/day). Intake of both the derived supplement and unfermented rooibos restored the t-BHP-induced reduction and increased (P < 0.05) the antioxidant capacity status of the liver, while not impacting on lipid peroxidation. The rooibos herbal tea did not affect the hepatic antioxidant enzymes, except fermented rooibos that caused a decrease (P < 0.05) in superoxide dismutase activity. This study confirms rooibos herbal tea as good dietary antioxidant sources and, in conjunction with its many other components, offers a significantly enhanced antioxidant status of the liver in an induced oxidative stress situation. PMID:24738022

Canda, B D; Oguntibeju, O O; Marnewick, J L

2014-01-01

263

2,(3)tert-butyl-4-hydroxyanisole does not reduce SCE induction by benzo(a) pyrene in bone marrow cells of C57BL/6 mice  

SciTech Connect

Recently, a number of publications have suggested that bone marrow cytogenetics may be used to detect anticarcinogenic or antimutagenic activity. In this work, 0.75% 2(3)-tert-butyl-4-hydroxyanisole (BHA), fed in the diet for 2 weeks, was tested for its ability to reduce the frequency of benzo(a)pyrene (BP)-induced SCE in mouse bone marrow. C57BL/6 male mice were injected i.p. with BP at 0, 33, 67, and 100 mg/kg body weight. There are no significant differences between animals on the control and BHA diets. Excretion of BP in urine over a 72 hr time period was significantly increased in animals on the BHA diet, at both low and high doses. Water-soluble metabolites accounted for all of this increase. It appears that bone marrow is not a good model for the gastrointestinal tract, and that short-term assays for anticarcinogens or antimutagens are more likely to be predictive if they are done in the target organs.

Van Horn, R.; DeWire, F.A.; Barnes, W.S. (Clarion Univ. of Pennsylvania (USA))

1990-01-01

264

Fluctuating micro-heterogeneity in water-tert-butyl alcohol mixtures and lambda-type divergence of the mean cluster size with phase transition-like multiple anomalies  

NASA Astrophysics Data System (ADS)

Water-tert-butyl alcohol (TBA) binary mixture exhibits a large number of thermodynamic and dynamic anomalies. These anomalies are observed at surprisingly low TBA mole fraction, with xTBA ? 0.03-0.07. We demonstrate here that the origin of the anomalies lies in the local structural changes that occur due to self-aggregation of TBA molecules. We observe a percolation transition of the TBA molecules at xTBA ? 0.05. We note that "islands" of TBA clusters form even below this mole fraction, while a large spanning cluster emerges above that mole fraction. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Alongside, the structure of water is also perturbed, albeit weakly, by the aggregation of TBA molecules. There is a monotonic decrease in the tetrahedral order parameter of water, while the dipole moment correlation shows a weak nonlinearity. Interestingly, water molecules themselves exhibit a reverse percolation transition at higher TBA concentration, xTBA ? 0.45, where large spanning water clusters now break-up into small clusters. This is accompanied by significant divergence of the fluctuations in the size of largest water cluster. This second transition gives rise to another set of anomalies around. Both the percolation transitions can be regarded as manifestations of Janus effect at small molecular level.

Banerjee, Saikat; Furtado, Jonathan; Bagchi, Biman

2014-05-01

265

Stability of fluctuating and transient aggregates of amphiphilic solutes in aqueous binary mixtures: studies of dimethylsulfoxide, ethanol, and tert-butyl alcohol.  

PubMed

In aqueous binary mixtures, amphiphilic solutes such as dimethylsulfoxide (DMSO), ethanol, tert-butyl alcohol (TBA), etc., are known to form aggregates (or large clusters) at small to intermediate solute concentrations. These aggregates are transient in nature. Although the system remains homogeneous on macroscopic length and time scales, the microheterogeneous aggregation may profoundly affect the properties of the mixture in several distinct ways, particularly if the survival times of the aggregates are longer than density relaxation times of the binary liquid. Here we propose a theoretical scheme to quantify the lifetime and thus the stability of these microheterogeneous clusters, and apply the scheme to calculate the same for water-ethanol, water-DMSO, and water-TBA mixtures. We show that the lifetime of these clusters can range from less than a picosecond (ps) for ethanol clusters to few tens of ps for DMSO and TBA clusters. This helps explaining the absence of a strong composition dependent anomaly in water-ethanol mixtures but the presence of the same in water-DMSO and water-TBA mixtures. PMID:24182023

Banerjee, Saikat; Bagchi, Biman

2013-10-28

266

Fluctuating micro-heterogeneity in water - tert-butyl alcohol mixtures and lambda-type divergence of the mean cluster size with phase transition-like multiple anomalies  

E-print Network

Water - tert-butyl alcohol (TBA) binary mixture exhibits a large number of thermodynamic and dynamic anomalies. These anomalies are observed at surprisingly low TBA mole fraction, with $x_{\\text{TBA}} \\approx 0.03 - 0.07$. We demonstrate here that the origin of the anomalies lies in the local structural changes that occur due to self-aggregation of TBA molecules. We observe a percolation transition of the TBA molecules at $x_{\\text{TBA}} \\approx 0.05$. We note that "islands" of TBA clusters form even below this mole fraction, while a large spanning cluster emerges above that mole fraction. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Alongside, the structure of water is also perturbed, albeit weakly, by the aggregation of TBA molecules. There is a monotonic decrease in the tetrahedral order parameter of water, while the dipole moment correlation shows a weak non-linearity. Interestingly, water mol...

Banerjee, Saikat; Bagchi, Biman

2014-01-01

267

Fluctuating micro-heterogeneity in water-tert-butyl alcohol mixtures and lambda-type divergence of the mean cluster size with phase transition-like multiple anomalies.  

PubMed

Water-tert-butyl alcohol (TBA) binary mixture exhibits a large number of thermodynamic and dynamic anomalies. These anomalies are observed at surprisingly low TBA mole fraction, with x(TBA) ? 0.03-0.07. We demonstrate here that the origin of the anomalies lies in the local structural changes that occur due to self-aggregation of TBA molecules. We observe a percolation transition of the TBA molecules at x(TBA) ? 0.05. We note that "islands" of TBA clusters form even below this mole fraction, while a large spanning cluster emerges above that mole fraction. At this percolation threshold, we observe a lambda-type divergence in the fluctuation of the size of the largest TBA cluster, reminiscent of a critical point. Alongside, the structure of water is also perturbed, albeit weakly, by the aggregation of TBA molecules. There is a monotonic decrease in the tetrahedral order parameter of water, while the dipole moment correlation shows a weak nonlinearity. Interestingly, water molecules themselves exhibit a reverse percolation transition at higher TBA concentration, x(TBA) ? 0.45, where large spanning water clusters now break-up into small clusters. This is accompanied by significant divergence of the fluctuations in the size of largest water cluster. This second transition gives rise to another set of anomalies around. Both the percolation transitions can be regarded as manifestations of Janus effect at small molecular level. PMID:24852545

Banerjee, Saikat; Furtado, Jonathan; Bagchi, Biman

2014-05-21

268

Stability of fluctuating and transient aggregates of amphiphilic solutes in aqueous binary mixtures: Studies of dimethylsulfoxide, ethanol, and tert-butyl alcohol  

NASA Astrophysics Data System (ADS)

In aqueous binary mixtures, amphiphilic solutes such as dimethylsulfoxide (DMSO), ethanol, tert-butyl alcohol (TBA), etc., are known to form aggregates (or large clusters) at small to intermediate solute concentrations. These aggregates are transient in nature. Although the system remains homogeneous on macroscopic length and time scales, the microheterogeneous aggregation may profoundly affect the properties of the mixture in several distinct ways, particularly if the survival times of the aggregates are longer than density relaxation times of the binary liquid. Here we propose a theoretical scheme to quantify the lifetime and thus the stability of these microheterogeneous clusters, and apply the scheme to calculate the same for water-ethanol, water-DMSO, and water-TBA mixtures. We show that the lifetime of these clusters can range from less than a picosecond (ps) for ethanol clusters to few tens of ps for DMSO and TBA clusters. This helps explaining the absence of a strong composition dependent anomaly in water-ethanol mixtures but the presence of the same in water-DMSO and water-TBA mixtures.

Banerjee, Saikat; Bagchi, Biman

2013-10-01

269

Infrared vibrational spectra of tert-butyl halides in dehydrated sodium-X and low-aluminum hydrogen-Y faujasites; vibrational excitation exchange and other effects of guest-host interactions  

NASA Astrophysics Data System (ADS)

Experimental, analytical and modeling techniques employed in this study elucidate interactions between adsorbate molecules and the interior surfaces of the porous faujasites (FAU). The vibrational spectroscopy of guest and host offers opportunities to locate the guest site in the host that can otherwise be approached only with low-temperature x-ray and neutron diffraction studies. Fourier transform infrared (FTIR) studies at 295 K of sodium X-type FAU (Na-X, Si/Al = 1.34, NaxSi(192-x)AlxO384) and low-aluminum acidic Y-type FAU (LAHY, Si/Al = 40, HxSi (192-x)AlxO384) supercage-included tert -butyl halides (CH3)3C-X (X = Cl, Br, I) are presented in comparison with the adsorbate molecular gas-phase and unloaded host solid-state spectra. For both FAU formula x = 1921+Si/Al . In the Na-X studies, four observations of tert-butyl halide (TBH) vibrational band changes (nu5, nu6, nu 7, and {nu3, nu16, nu17}, three of them concomitant with Na-X mode changes, together with computational modeling studies, point to a particular preferred siting of TBH at host hexagonal prisms (D6R). The siting involves simultaneous interactions of the host with methyl group axial protons and the halide atom. All three methyl group axial protons interact preferentially with a single D6R oxygen atom (type O1) via C-H···O bonding. The TBH halide atom interacts with a site III' Na cation. In addition, an exchange of quanta of vibrational excitation between TBH C-X stretching/CH 3 rocking skeletal mode nu5 and the Na-X Si-O-Si antisymmetric stretching band is observed. Analysis of the coalesced band is consistent with an interaction model involving one guest and one host mode. In the isostructural LAHY material, where cation-guest interactions are effectively absent, the weaker interactions of TBH with LAHY framework oxygen atoms are manifest in additional propensity toward the exchange of vibrational excitation quanta between both guest and host modes, and between two guest modes. In contrast to the Na-X results, the LAHY results reveal that guest-host vibrational excitation exchange is taking place between a single guest mode and multiple modes within a particular host band. This type of exchange phenomenon is observed for three different LAHY infrared bands. For both faujasite materials, the IR frequency shifts, exchange phenomena, pseudo-hydrogen bonding effects, and computational modeling studies are related to the siting of the guest molecules in the host supercages, and to the guest-host interactions at the guest sites.

Fox, Jack David

270

Synthesis and properties of optically active nanostructured polymers bearing amino acid moieties by direct polycondensation of 4,4'-thiobis(2-tert-butyl-5-methylphenol) with chiral diacids.  

PubMed

Four derivatives of N-trimellitylimido-L-amino acid (4a-4d) were prepared by the reaction of trimellitic anhydride (1) with the L-amino acids (2a-2d) in acetic acid as diacid monomers and were used with the aim to obtain a new family of amino acid based poly(ester-imide)s (PEI)s. The polymerization was performed by direct polycondensation of chiral diacids (4a-4d) with 4,4'-thiobis(2-tert-butyl-5-methylphenol) (5) in the presence of tosyl chloride (TsCl), pyridine and N,N-dimethyl formamide (DMF). Step-growth polymerization was carried out by varying the time of heating and the molar ratio of TsCl/diacid and the optimum conditions were achieved. The synthesized polymers were characterized by means of specific rotation experiments, FT-IR, 1H-NMR, X-ray diffraction techniques and elemental analysis. The surface morphology of the obtained polymers was studied by field emission scanning electron microscopy. The result showed nanostructure morphology of the resulting polymers. The obtained PEIs were soluble in polar aprotic solvents such as DMF, N,N-dimethyl acetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and protic solvents such as sulfuric acid. Thermal stability and the weight-loss behavior of the PEIs were studied by thermal gravimetric analysis (TGA) techniques. TGA showed that the 10% weight loss temperature in a nitrogen atmosphere was more than 402°C, therefore they had useful levels of thermal stability associated with excellent solubility. PMID:21691754

Mallakpour, Shadpour; Soltanian, Samaneh

2012-06-01

271

Effects of tert-butyl hydroperoxide on Ca(2+) ATPase activity in isolated rat hepatocytes and its reversal by antioxidants.  

PubMed

Calcium ions play an importantrole in various physiological processes such as nerve impulse transmission, muscle contraction, hormone action, blood clotting. They ions act as an intracellular second messenger, relaying information within cells to regulate their activity. To understand the mechanism of hepatotoxicity of t-BHP, studies were carried out using freshly isolated rat hepatocytes. The effect of t-BHP on Ca(2+) accumulation and Ca(2+) uptake by rat hepatocytes was monitored using 45Ca(2+). It caused decrease in 15% accumulation of 45Ca(2+) in comparison to the control group. t-BHP also significantly decreased the Ca(2+) ATPase activity in isolated hepatocytes .This decrease in Ca(2+) ATPase activity by t-BHP was reversed 40% by naturally occurring antioxidant glutathione (GSH) and 20% by the synthetic antioxidant butylated hydroxy toluene (BHT). These results indicate that the hepatotoxic action of t-BHP involves oxidative stress as evident by the protection accorded by various antioxidants employed in the study as well as impairment of intracellular calcium homeostasis which can lead to liver cell injury. PMID:23734452

Singh, Sangram; Agarwal, Richa; Jamal, Farrukh; Mehrotra, Sudhir; Singh, Rakesh

2012-09-01

272

Gastroprotective Activity of Ethyl-4-[(3,5-di-tert-butyl-2-hydroxybenzylidene) Amino]benzoate against Ethanol-Induced Gastric Mucosal Ulcer in Rats  

PubMed Central

Background The study was carried out to determine the cytotoxic, antioxidant and gastro-protective effect of ethyl-4-[(3,5-di-tert-butyl-2-hydroxybenzylid ene)amino] benzoate (ETHAB) in rats. Methodology/Principal Findings The cytotoxic effect of ETHAB was assessed using a MTT cleavage assay on a WRL68 cell line, while its antioxidant activity was evaluated in vitro. In the anti-ulcer study, rats were divided into six groups. Group 1 and group 2 received 10% Tween 20 (vehicle). Group 3 received 20 mg/kg Omeprazole. Groups 4, 5 and 6 received ETHAB at doses of 5, 10, and 20 mg/kg, respectively. After an hour, group 1 received the vehicle. Groups 2–6 received absolute ethanol to induce gastric mucosal lesions. In the WRL68 cell line, an IC50 of more than 100 µg/mL was observed. ETHAB results showed antioxidant activity in the DPPH, FRAP, nitric oxide and metal chelating assays. There was no acute toxicity even at the highest dosage (1000 mg/kg). Microscopy showed that rats pretreated with ETHAB revealed protection of gastric mucosa as ascertained by significant increases in superoxide dismutase (SOD), pH level, mucus secretion, reduced gastric lesions, malondialdehyde (MDA) level and remarkable flattened gastric mucosa. Histologically, pretreatment with ETHAB resulted in comparatively better gastric protection, due to reduction of submucosal edema with leucocyte infiltration. PAS staining showed increased intensity in uptake of Alcian blue. In terms of immunohistochemistry, ETHAB showed down-expression of Bax proteins and over-expression of Hsp70 proteins. Conclusion/Significance The gastroprotective effect of ETHAB may be attributed to antioxidant activity, increased gastric wall mucus, pH level of gastric contents, SOD activity, decrease in MDA level, ulcer area, flattening of gastric mucosa, reduction of edema and leucocyte infiltration of the submucosal layer, increased PAS staining, up-regulation of Hsp70 protein and suppressed expression of Bax. Key words: ethyl 4-(3, 5-di-ter-butyl-2-hydroxybenzylamino) benzoate; toxicity; antioxidant; gastric-ulcer; anti-ulcer; histology; immunohistochemistry. PMID:24800807

Halabi, Mohammed Farouq; Shakir, Raied Mustafa; Bardi, Daleya Abdulaziz; Al-Wajeeh, Nahla Saeed; Ablat, Abdulwali; Hassandarvish, Pouya; Hajrezaie, Maryam; Norazit, Anwar; Abdulla, Mahmood Ameen

2014-01-01

273

Teratology evaluation of methyl tertiary butyl ether in rats and mice  

SciTech Connect

Mated CD Sprague-Dawley rats and CD-1 mice were exposed during the period of organogenesis to target concentrations of 0.250, 1000, and 2500 ppm methyl t-butyl ether (MTBE). None of the control or test-group animals died during the treatment or posttreatment periods. Females were sacrificed on d 20 (rats) or d 18 (mice). No adverse effects of treatment were reflected in maternal parameters of body weight, water consumption, or liver weight or in physical examination data for either species. Food consumption fell in the groups of treated rats during d 9-12; similar but nonsignificant effects were observed for mice during d 12-15. In rats, no treatment-related changes were recorded in the uterine implantation data, fetal size parameters, or fetal sex distribution data. Examination of fetuses for external abnormalities, skeletal malformations or ossification variations did not reveal any changes caused by MTBE exposure. A slight increase in fetal resorptions was observed in the groups of mice exposed to low and high concentrations; this increase was attributed to two females in each group that had an unusually high number of resorptions, rather than to the treatment itself. No significant effects were observed in any groups of treated mice on external and soft-tissue examination or evaluation of skeletal abnormalities or ossification variations. The incidence of fused sternebrae in the high-concentration group increased slightly, which might be attributed to fetotoxicity.

Conaway, C.C.; Schroeder, R.E.; Snyder, N.K.

1985-01-01

274

Adsorption of methyl tertiary butyl ether on granular zeolites: Batch and column studies.  

PubMed

Methyl tertiary butyl ether (MTBE) has been shown to be readily removed from water with powdered zeolites, but the passage of water through fixed-beds of very small powdered zeolites produces high friction losses not encountered in flow through larger sized granular materials. In this study, equilibrium and kinetic adsorption of MTBE onto granular zeolites, a coconut shell granular activated carbon (CS-1240), and a commercial carbon adsorbent (CCA) sample was evaluated. In addition, the effect of natural organic matter (NOM) on MTBE adsorption was evaluated. Batch adsorption experiments determined that ZSM-5 was the most effective granular zeolite for MTBE adsorption. Further equilibrium and kinetic experiments verified that granular ZSM-5 is superior to CS-1240 and CCA in removing MTBE from water. No competitive adsorption effects between NOM and MTBE were observed for adsorption to granular ZSM-5 or CS-1240, however there was competition between NOM and MTBE for adsorption onto the CCA granules. Fixed-bed adsorption experiments for longer run times were performed using granular ZSM-5. The bed depth service time model (BDST) was used to analyze the breakthrough data. PMID:20153106

Abu-Lail, Laila; Bergendahl, John A; Thompson, Robert W

2010-06-15

275

Observation on the biodegradation and bioremediation potential of methyl t-butyl ether  

SciTech Connect

There have been few reports documenting evidence for the biodegradation of the fuel oxygenate alkyl ether, methyl t-butyl ether (MTBE) in groundwater, soils, and biosludges. Partial (or complete) microbial breakdown of MTBE has been observed in an anaerobic subsoil, a river sediment under methanogenic conditions, a cyclohexane-degrading bacterial consortium and a pure culture of the methylotroph, Methylisnus trichosporium OB3b. An aerobic bacterial enrichment (BC-1) isolated from an industrial transient (non-accumulating) metabolic intermediate. The studies suggest that MTBE is cleaved by BC-1 to TBA which is then metabolized via isopropanol and acetone. There is little information on the occurrence of indigenous MTBE-degraders in groundwater, soils and activated sludges. Preliminary evidence has been obtained, however, from a marketing terminal groundwater site that naturally-occurring MTBE-degraders are present in some monitoring wells. Microcosm experiments with groundwater from this aquifer show that MTBE is aerobically degraded (no TBA formed) with a first-order decay rate (0.31/day) similar to BTEX. Also, MTBE did not inhibit the intrinsic biodegradation potential of BTEX in groundwater microcosms. In summary, the data presented indicate that MTBE biodegradation has been observed in some environmental media. Further work is needed to assess the feasibility of using indigenous or derived aerobic and anaerobic MTBE-degrading cultures for treating fuel ethers in groundwaters or wastewater with in-situ or ex-situ bioremediation technologies.

Salanitro, J.; Wisniewski, H.; McAllister, P. [Shell Development Co., Houston, TX (United States)

1995-12-31

276

Toxicity of methyl tertiary butyl ether to Daphnia magna and photobacterium phosphoreum  

SciTech Connect

Methyl tertiary butyl ether (MTBE) is a liquid organic compound added to gasoline to increase its oxygen content and to reduce the emission of carbon monoxide during combustion in many urban areas. In order to meet the 1990 Clean Air Act amendments, gasoline must contain 2.7% oxygen (by weight) or 15% (by volume) of MTBE in gasoline to meet the regulations for the control of carbon monoxide emissions. Health effects caused by inhalation of MTBE include headaches, dizziness, irritated eyes and nausea; MTBE is one of cancer--causing chemicals. Intracaval injection of MTBE (0.2 mg/kg) caused the highest mortality (100%) in rats. General anesthetic effect induced by MTBE was found at or above 1200 mg/kg body weight; Rosenkranz and Klopman (1991) predicted that MTBE is neither a genotoxicant nor a carcinogen. Nevertheless, the safety of using MTBE in oxygenated fuels is now being questioned from its potential as groundwater pollutant. This study measures the toxicity of MTBE to Daphnia magna and Photobacterium phosphoreum. 13 refs.

Gupta, G.; Lin, Y.J. [Univ. of Maryland Eastern Shore, Princess Anne, MD (United States)

1995-10-01

277

Simultaneous determination of organotin compounds in textiles by gas chromatography-flame photometry following liquid/liquid partitioning with tert-butyl ethyl ether after reflux-extraction.  

PubMed

A rapid and relatively clean method for determining six organotin compounds (OtC) in textile goods with a gas chromatograph equipped with a conventional flame photometric detector (GC-FPD) has been developed. After the reflux-extraction to use methanol containing 1% (v/v) of hydrochloric acid, five hydrophobic OtC (e.g. tributyltin: TBT) and slightly less hydrophobic dibutyltin (DBT) could be drawn out through partitioning between the methanolic buffer solution and tert-butyl ethyl ether instead of hazardous dichloromethane, of which usage is provided by the official-methods notified in Japan, and following the ethylation procedure to use sodium tetraethylborate, the OtC were determined with the GC-FPD. The recoveries of DBT, TBT, tetrabutyltin, triphenyltin, dioctyltin, and trioctyltin from textile products (cloth diaper, socks, and undershirt) were 60-77, 89-98, 86-94, 71-78, 85-109, and 70-79% respectively, and their coefficients of variation were 2.5-16.5%. Calibration curves for OtC were linear (0.01-0.20 ?g as Sn mL(-1)), and the correlation coefficients were 0.9922-1.0000. Their detection limits were estimated to be 2.7-9.7 n gas Sn g(-1). These data suggested that this method would be applicable to their simultaneous determination. Five retailed textile goods were analyzed by this proposed method, and 0.013-0.65 µg as Sn g(-1) of OtC (e.g. DBT) were determined in three. Moreover, a possibility that various OtC including non-targeted species in textile would be specifically detected by applying the studying speciation-technique of controlling signal intensity-flame fuel gas pressures of the GC-FPD was found. PMID:24054605

Hamasaki, Tetsuo

2013-10-15

278

(CH3)3COOH (tert-butyl hydroperoxide): OH reaction rate coefficients between 206 and 375 K and the OH photolysis quantum yield at 248 nm.  

PubMed

Rate coefficients, k, for the gas-phase reaction of the OH radical with (CH(3))(3)COOH (tert-butyl hydroperoxide) were measured as a function of temperature (206-375 K) and pressure (25-200 Torr (He, N(2))). Rate coefficients were measured under pseudo-first-order conditions using pulsed laser photolysis to produce OH and laser induced fluorescence (PLP-LIF) to measure the OH temporal profile. Two independent methods were used to determine the gas-phase infrared cross sections of (CH(3))(3)COOH, absolute pressure and chemical titration, that were used to determine the (CH(3))(3)COOH concentration in the LIF reactor. The temperature dependence of the rate coefficients is described, within the measurement precision, by the Arrhenius expression k(1)(T) = (7.0 ± 1.0) × 10(-13) exp[(485 ± 20)/T] cm(3) molecule(-1) s(-1) where k(1)(296 K) was measured to be (3.58 ± 0.54) × 10(-12) cm(3) molecule(-1) s(-1). The uncertainties are 2? (95% confidence level) and include estimated systematic errors. UV absorption cross sections of (CH(3))(3)COOH were determined at 185, 214, 228, and 254 nm and over the wavelength range 210-300 nm. The OH quantum yield following the 248 nm pulsed laser photolysis of (CH(3))(3)COOH was measured relative to the OH quantum yields of H(2)O(2) and HNO(3) using PLP-LIF and found to be near unity. PMID:20694250

Baasandorj, Munkhbayar; Papanastasiou, Dimitrios K; Talukdar, Ranajit K; Hasson, Alam S; Burkholder, James B

2010-10-14

279

Role of sarcoplasmic reticulum in the contractile function of vascular smooth muscle as studied by 2,5-di-(tert-butyl)-1,4-benzohydroquinone.  

PubMed

The effects of 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBuBHQ), a potent selective inhibitor of hepatocyte endoplasmic reticulum Ca(2+)-ATPase, were functionally examined in rat aorta in order to assess whether tBuBHQ also acts as a Ca2+ pump inhibitor of sarcoplasmic reticulum (SR) in vascular smooth muscle. tBuBHQ elicited a slowly developing and gradually decreasing contraction which was dependent on extracellular Ca2+. We utilize the phenylephrine (PE)-induced transient contractile response in Ca(2+)-free medium as an indirect index on the status of intracellular Ca2+ store. When preparations, depleted of their PE-sensitive Ca2+ store, were allowed to replete their stores in Ca(2+)-containing medium, a sustained contraction in tBuBHQ-treated preparations was observed, whereas in untreated control preparations, readministration of Ca2+ elicited no contraction, or occasionally a weak, transient contraction. In control tissues, subsequent application of PE in Ca(2+)-free medium after Ca2+ loading resulted in full restoration of the transient contraction to PE; but such a transient contraction was not observed in the presence of tBuBHQ. These results indicated that the sequestration of Ca2+ into the PE-sensitive pool was inhibited by tBuBHQ. We also assessed effects of tBuBHQ on phentolamine-induced relaxation in PE-precontracted tissues in Ca(2+)-containing medium. A slower rate of relaxation was observed in preparations treated with tBuBHQ. In conclusion, our findings are consistent with the hypothesis that tBuBHQ acts as a SR Ca2+ pump inhibitor, interfering with effective refilling of PE-sensitive intracellular Ca2+ stores. PMID:1339176

Shimamoto, H; Majarais, I L; Shimamoto, Y; Kwan, C Y; Daniel, E E

1992-01-01

280

?-Phenyl-n-tert-butyl-nitrone Attenuates Lipopolysaccharide-induced Brain Injury and Improves Neurological Reflexes and Early Sensorimotor Behavioral Performance in Juvenile Rats  

PubMed Central

Our previous study showed that treatment with ?-phenyl-n-tert-butyl-nitrone (PBN) after exposure to lipopolysaccharide (LPS) reduced LPS-induced white matter injury in the neonatal rat brain. The object of the current study was to further examine whether PBN has long-lasting protective effects and ameliorates LPS-induced neurological dysfunction. Intracerebral (i.c.) injection of LPS (1 mg/kg) was performed in postnatal day (P) 5 Sprague Dawley rat pups and PBN (100 mg/kg) or saline was administered intraperitoneally 5 min after LPS injection. The control rats were injected (i.c.) with sterile saline. Neurobehavioral tests were carried out from P3 to P21, and brain injury was examined after these tests. LPS exposure resulted in severe brain damage, including enlargement of ventricles bilaterally, loss of mature oligodendrocytes, impaired myelination as indicated by the decrease in myelin basic protein immunostaining, and alterations in dendritic processes in the cortical gray matter of the parietal cortex. Electron microscopic examination showed that LPS exposure caused impaired myelination as indicated by the disintegrated myelin sheaths in the juvenile rat brain. LPS administration also significantly affected neurobehavioral functions such as performance in righting reflex, wire hanging maneuver, cliff avoidance, negative geotaxis, vibrissa-elicited forelimb-placing test, beam walking, and gait test. Treatment with PBN, a free radical scavenger and antioxidant, provided protection against LPS-induced brain injury and associated neurological dysfunction in juvenile rats, suggesting that antioxidation might be an effective approach for therapeutic treatment of neonatal brain injury induced by infection/inflammation. PMID:18683243

Fan, Lir-Wan; Chen, Ruei-Feng; Mitchell, Helen J.; Lin, Rick C. S.; Simpson, Kimberly L.; Rhodes, Philip G.; Cai, Zhengwei

2010-01-01

281

Protective effects of Hibiscus tiliaceus L. methanolic extract to V79 cells against cytotoxicity and genotoxicity induced by hydrogen peroxide and tert-butyl-hydroperoxide.  

PubMed

Plants of the genus Hibiscus thrives produce a diversity of molecules with bioactive properties. In a previous study of Hibiscus tiliaceus L. methanolic extract (HME) using bacteria and yeast, as test media, it has been shown that HME strongly inhibited the mutagenic action of H(2)O(2) or tert-butyl-hydroperoxide (t-BHP). Here, our interest is to evaluate the genotoxicity and the antigenotoxic/antimutagenic properties of HME using oxidative challenge with H(2)O(2) and t-BHP in V79 cells. We determined cytotoxicity using clonal survival assay; evaluated DNA damage using the comet assay and the micronucleus test in binucleated cells besides of the lipid peroxidation degree and the reduced glutathione content. We examined the ability of HME in quenching hydroxyl radical by means of a HPLC-based method utilizing the hypoxanthine/xanthine oxidase assay. At concentrations ranging from 0.001 to 0.1mg/mL, HME was not cytotoxic, genotoxic or mutagenic. Treatment with non-cytotoxic concentrations of HME increased cell survival after H(2)O(2) and t-BHP exposure and prevented DNA damage. The pre-treatment with HME also was able to decrease the mutagenic effect of these genotoxins, evaluated using the micronucleus test. HME prevented the increase in lipid peroxidation and decrease in GSH content in response to the oxidative challenge. Therefore, the ability in preventing against H(2)O(2)- and t-BHP-induced GSH depletion and lipid peroxidation was probably a major contribution to the cytoprotective effects. Moreover, HME acts as a hydroxyl radical scavenger. In summary, HME did not have a harmful or inhibitory effect on the growth of V79 cells and presented antioxidant activity, consequently, both antigenotoxic and antimutagenic effects against oxidative DNA damage. PMID:17683899

Rosa, Renato Moreira; Moura, Dinara Jaqueline; Melecchi, Maria Inês S; dos Santos, Rafael Santos; Richter, Marc François; Camarão, Elina Bastos; Henriques, João Antonio Pêgas; de Paula Ramos, Ana Lígia Lia; Saffi, Jenifer

2007-12-01

282

Diafenthiuron: 1-tert-butyl-3-(2,6-diisopropyl-4-phen­oxy­phen­yl)thio­urea  

PubMed Central

The title compound, C23H32N2OS, is a thio­urea-based insecticide. The dihedral angle between the phenyl ring and the diisopropyl benzene ring plane is 73.18?(6)°, while that between the plane of the thio­urea group and the diisopropyl benzene ring is 86.00?(5)°. Disorder was modelled for the S atom and the two methyl C atoms of the isopropyl group over two sets of sites with an occupancy ratio of 0.742?(4):0.258?(4). In the crystal, N—H?S hydrogen bonds link adjacent mol­ecules, forming R 2 2(8) inversion dimers that pack into chains along the b-axis direction. PMID:25161588

Jeon, Youngeun; Kang, Gihaeng; Cho, Seonghwa; Kim, Tae Ho

2014-01-01

283

Time course of ultrastructural changes and immunoelectron microscopic localization of neurocalcin in motor endplates of the lumbrical muscles of rats given a single administration of 2,5-di(tert-butyl)-1,4-hydroquinone  

Microsoft Academic Search

A time-course study of ultrastructural changes and immunoelectron microscopic localization of neurocalcin was performed on\\u000a motor endplates of the lumbrical muscles of female Wistar rats given a single oral administration of 2,5-di(tert-butyl)-1,4-hydroquinone\\u000a (DTBHQ) at a dose of 120 mg\\/kg. Toxic signs such as salivation and muscle weakness of the hind legs appeared from 3 h after\\u000a DTBHQ administration. No remarkable

Takayoshi Imazawa; Kunitoshi Mitsumori; Satoshi Kitajima; Hiroshi Onodera; Toru Tamura; Michihito Takahashi; Masao Hirose

2000-01-01

284

Discovery of N-(2,4-di-tert-butyl-5-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide (VX-770, ivacaftor), a potent and orally bioavailable CFTR potentiator.  

PubMed

Quinolinone-3-carboxamide 1, a novel CFTR potentiator, was discovered using high-throughput screening in NIH-3T3 cells expressing the F508del-CFTR mutation. Extensive medicinal chemistry and iterative structure-activity relationship (SAR) studies to evaluate potency, selectivity, and pharmacokinetic properties resulted in the identification of N-(2,4-di-tert-butyl-5-hydroxyphenyl)-4-oxo-1,4-dihydroquinoline-3-carboxamide (VX-770, 48, ivacaftor), an investigational drug candidate approved by the FDA for the treatment of CF patients 6 years of age and older carrying the G551D mutation. PMID:25441013

Hadida, Sabine; Van Goor, Fredrick; Zhou, Jinglan; Arumugam, Vijayalaksmi; McCartney, Jason; Hazlewood, Anna; Decker, Caroline; Negulescu, Paul; Grootenhuis, Peter D J

2014-12-11

285

Risk characterization of methyl tertiary butyl ether (MTBE) in tap water.  

PubMed

Methyl tertiary butyl ether (MTBE) can enter surface water and groundwater through wet atmospheric deposition or as a result of fuel leaks and spills. About 30% of the U.S. population lives in areas where MTBE is in regular use. Ninety-five percent of this population is unlikely to be exposed to MTBE in tap water at concentrations exceeding 2 ppb, and most will be exposed to concentrations that are much lower and may be zero. About 5% of this population may be exposed to higher levels of MTBE in tap water, resulting from fuel tank leaks and spills into surface or groundwater used for potable water supplies. This paper describes the concentration ranges found and anticipated in surface and groundwater, and estimates the distribution of doses experienced by humans using water containing MTBE to drink, prepare food, and shower/bathe. The toxic properties (including potency) of MTBE when ingested, inhaled, and in contact with the skin are summarized. Using a range of human toxic potency values derived from animal studies, margins of exposure (MOE) associated with alternative chronic exposure scenarios are estimated to range from 1700 to 140,000. Maximum concentrations of MTBE in tap water anticipated not to cause adverse health effects are determined to range from 700 to 14,000 ppb. The results of this analysis demonstrate that no health risks are likely to be associated with chronic and subchronic human exposures to MTBE in tap water. Although some individuals may be exposed to very high concentrations of MTBE in tap water immediately following a localized spill, these exposures are likely to be brief in duration due to large-scale dilution and rapid volatilization of MTBE, the institution of emergency response and remediation measures to minimize human exposures, and the low taste and odor thresholds of MTBE which ensure that its presence in tap water is readily detected at concentrations well below the threshold for human injury. PMID:9463929

Stern, B R; Tardiff, R G

1997-12-01

286

Coordination effects on electron distributions for rhodium complexes of the redox-active bis(3,5-di-tert-butyl-2-phenolate)amide ligand.  

PubMed

New rhodium complexes of bis(3,5-di-tert-butyl-2-phenol)amine ([ONO(cat)]H(3)) were synthesized, and their electronic properties were investigated. These compounds were prepared by combining [ONO(q)]K and [(cod)Rh(?-Cl)](2) in the presence of an auxiliary donor ligand to yield complexes of the type [ONO]RhL(n) (n = 3, L = py (1); n = 2, L = PMe(3) (2a), L = PMe(2)Ph (2b), PMePh(2) (2c), PPh(3) (2d)). Single-crystal X-ray diffraction studies on [ONO]Rh(py)(3) (1) revealed a six-coordinate, octahedral rhodium complex. In the case of [ONO]Rh(PMe(3))(2) (2a), X-ray diffraction showed a five-coordinate, distorted square-pyramidal coordination environment around the rhodium center. While 1 is static on the NMR time scale, complexes 2a-d are fluxional, displaying both rapid isomerization of the square-pyramidal structure and exchange of coordinated and free phosphine ligands. UV-vis spectroscopy shows stark electronic differences between 1 and 2a-d. Whereas 1 displays a strong absorbance at 380 nm with a much weaker band at 585 nm in the absorption spectrum, complexes 2a-d display an intense (? > 10(4) M(-1) cm(-1)), low-energy absorption band in the region 580-640 nm; however, in the cases of 2a and 2b, the addition of excess phosphine resulted in changes to the UV-vis spectrum indicating the formation of six-coordinate adducts [ONO]Rh(PMe(3))(3) (3a) and [ONO]Rh(PMe(2)Ph)(3) (3b), respectively. The experimental and DFT computational data for the six-coordinate complexes 1, 3a, and 3b are consistent with their formulation as classical, d(6), pseudo-octahedral, coordination complexes. In the five-coordinate complexes 2a-2d, ?-bonding between the rhodium center and the [ONO] ligand leads to a high degree of covalency and metal-ligand electron distributions that are not accurately described by formal oxidation state assignments. PMID:22482509

Szigethy, Géza; Shaffer, David W; Heyduk, Alan F

2012-12-01

287

Uranium(VI) Compounds Containing 1Butyl1-methyl-piperazinium Iodide: Synthesis and Characterisation  

Microsoft Academic Search

The white crystalline mono-quaternized diamine salt, 1-butyl-1-methylpiperazinium iodide, obtained by reacting 1-methylpiperazine and butyl iodide, reacts with uranyl acetate, nitrate, perchlorate, sulphate, thiocyanate, chloride, bromide and iodide in 1:1, 1:2 and 1:6 molar ratios giving products of varying stoichiometries. The complexes have been characterised on the basis of analytical data and infrared spectra. Infrared spectral studies show that only one

B. S. Manhas; Sunita; A. K. Trikha

1990-01-01

288

(1-Butyl-4-methyl-pyridinium)[Cu(SCN)2]: a coordination polymer and ionic liquid.  

PubMed

The compound (C4C1py)[Cu(SCN)2], (C4C1py = 1-Butyl-4-methyl-pyridinium), which can be obtained from CuSCN and the ionic liquid (C4C1py)(SCN), turns out to be a new organic-inorganic hybrid material as it qualifies both, as a coordination polymer and an ionic liquid. It features linked [Cu(SCN)2](-) units, in which the thiocyanates bridge the copper ions in a ?1,3-fashion. The resulting one-dimensional chains run along the a?axis, separated by the C4C1py counterions. Powder X-ray diffraction not only confirms the single-crystal X-ray structure solution but proves the reformation of the coordination polymer from an isotropic melt. However, the materials shows a complex thermal behavior often encountered for ionic liquids such as a strong tendency to form a supercooled melt. At a relatively high cooling rate, glass formation is observed. When heating this melt in differential scanning calorimetry (DSC) and temperature-dependent polarizing optical microscopy (POM), investigations reveal the existence of a less thermodynamically stable crystalline polymorph. Raman measurements conducted at 10 and 100?°C point towards the formation of polyanionic chain fragments in the melt. Solid-state UV/Vis spectroscopy shows a broad absorption band around 18,870?cm(-1) (530?nm) and another strong one below 20,000?cm(-1) (<500?nm). The latter is attributed to the d(Cu(I))??*(SCN)-MLCT (metal-to-ligand charge transfer) transition within the coordination polymer yielding an energy gap of 2.4?eV. At room temperature and upon irradiation with UV light, the material shows a weak fluorescence band at 15,870?cm(-1) (630?nm) with a quantum efficiency of 0.90(2)?% and a lifetime of 131(2)?ns. Upon lowering the temperature, the luminescence intensity strongly increases. Simultaneously, the band around 450?nm in the excitation spectrum decreases. PMID:24644064

Spielberg, Eike T; Edengeiser, Eugen; Mallick, Bert; Havenith, Martina; Mudring, Anja-Verena

2014-04-25

289

Synthesis of 3-(1-Methyl-1H-imidazol-2-ylthio)propanoic Acid and (E)-3-(1-Methyl-1H-imidazol-2-ylthio)acrylic Acid  

PubMed Central

The syntheses of 3-(1-methyl-1H-imidazol-2-ylthio)acrylic acid and 3-(1-methyl-1H-imidazol-2-ylthio)propanoic acid, mitochondria-targeted prodrugs of the antioxidant methimazole, are described. The method of Fan et al. (Fan et al., Synthesis 2006, 2286) for the reaction of phenols with propiolic acid and propiolate esters was modified to synthesize (E)-3-(1-methyl-1H-imidazol-2-ylthio)acrylic acid. The intermediate tert-butyl (E)-3-(1-methyl-1H-imidazol-2-ylthio)acrylate was prepared by the reaction of tert-butyl propiolate with methimazole; the use of tert-butyl propiolate rather than methyl propiolate gave tert-butyl (E)-3-(1-methyl-1H-imidazol-2-ylthio)acrylate as the predominant isomer. Acid hydrolysis of the intermediate ester afforded the target compound. 3-(1-Methyl-1H-imidazol-2-ylthio)propanoic acid was synthesized from 3-bromopropanoic acid and methimazole under conditions that gave preferential substitution on sulfur and minimized substitution on nitrogen. PMID:24882887

Hattan, Christopher M.; Shojaie, Jalil; Lau, Serrine S.; Anders, M. W.

2014-01-01

290

Synthesis of 3-(1-Methyl-1H-imidazol-2-ylthio)propanoic Acid and (E)-3-(1-Methyl-1H-imidazol-2-ylthio)acrylic Acid.  

PubMed

The syntheses of 3-(1-methyl-1H-imidazol-2-ylthio)acrylic acid and 3-(1-methyl-1H-imidazol-2-ylthio)propanoic acid, mitochondria-targeted prodrugs of the antioxidant methimazole, are described. The method of Fan et al. (Fan et al., Synthesis 2006, 2286) for the reaction of phenols with propiolic acid and propiolate esters was modified to synthesize (E)-3-(1-methyl-1H-imidazol-2-ylthio)acrylic acid. The intermediate tert-butyl (E)-3-(1-methyl-1H-imidazol-2-ylthio)acrylate was prepared by the reaction of tert-butyl propiolate with methimazole; the use of tert-butyl propiolate rather than methyl propiolate gave tert-butyl (E)-3-(1-methyl-1H-imidazol-2-ylthio)acrylate as the predominant isomer. Acid hydrolysis of the intermediate ester afforded the target compound. 3-(1-Methyl-1H-imidazol-2-ylthio)propanoic acid was synthesized from 3-bromopropanoic acid and methimazole under conditions that gave preferential substitution on sulfur and minimized substitution on nitrogen. PMID:24882887

Hattan, Christopher M; Shojaie, Jalil; Lau, Serrine S; Anders, M W

2013-01-01

291

Experimental neuropathy produced by 2,5-hexanedione--a major metabolite of the neurotoxic industrial solvent methyl n-butyl ketone  

Microsoft Academic Search

Chronic exposure of rats to 2,5-hexanedione (CH3COCH2CH2COCH3), a major metabolite of the neurotoxic industrial solvent methyl n-buryl ketone (CH3COCH2CH2CH2CH3), has been shown to cause a clinical peripheral neuropathy with dying-back peripheral and central nervous system degeneration characterized by giant axonal swellings filled with neurofilaments. This pattern of disease is similar to that produced by methyl n-butyl ketone.

P S Spencer; H H Schaumburg

1975-01-01

292

AN EXPERIMENTAL STUDY OF PHYTOREMEDIATION OF METHYL-TERT-BUTYL-ETHER (MTBE) IN 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...

293

IDENTIFYING THE USAGE PATTERNS OF METHYL TERT-BUTYL ETHER (MTBE) AND OTHER OXYGENATES IN GASOLINE USING GASOLINE  

E-print Network

to reduce levels of ozone and carbon monoxide in areas where air quality standards have not been attained in areas that do not meet National Ambient Air Quality Standards (NAAQS) for carbon monoxide and ozone if regulations meant to improve the Nation's air quality have resulted in inadvertent, detrimental effects

294

Identifying the usage patterns of methyl tert-butyl ether (MTBE) and other oxygenates in gasoline using gasoline surveys  

USGS Publications Warehouse

Data on the volumes of oxygenates and other compounds in gasoline are available from several sources collectively referred as gasoline surveys. The gasoline surveys provide the most definitive knowledge of which oxygenate, if any, and what volumes of that oxygenate are being used in various areas of the country. This information is important in water-quality assessments for relating the detection of MTBE in water to patterns of usage of MTBE in gasoline. General information on three surveys that have been conducted by the National Institute for Petroleum and Energy Research, the Motor Vehicle Manufacturers Association, and the EPA was presented. The samples were tested for physical properties and constituents including octane number, specific gravity, and volumes of olefins, aromatics, benzene, alcohols, and various ether oxygenates. The data in each survey had its own utility based on the type of assessment that is undertaken. Quality Assessment (NAWQA) Program. Using NAWQA data, the percent occurrence of MTBE in ground water in metropolitan areas that use substantial amounts of MTBE (> 5% by vol) was ??? 21%, compared to ??? 2% in areas that do not use substantial amounts of MTBE (< 5% by vol). When several other factors are considered in a logistic regression model including MTBE usage in RFG or OXY gasoline areas (??? 3% by vol) as a factor, a 4-6 fold increase in the detection frequency of MTBE in ground water was found when compared to areas that do not use MTBE or use it only for octane enhancement (< 3% by vol).

Moran, M.J.; Clawges, R.M.; Zogorski, J.S.

2000-01-01

295

Spectroscopic (FT-IR, FT-Raman), first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of 5-tert-Butyl-6-chloro-N-[(4-(trifluoromethyl)phenyl]pyrazine-2-carboxamide  

NASA Astrophysics Data System (ADS)

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 5-tert-Butyl-6-chloro-N-[(4-(trifluoromethyl)phenyl]pyrazine-2-carboxamide have been investigated experimentally and theoretically using Gaussian09 software package. Potential energy distribution of normal modes of vibrations was done using GAR2PED program. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. From the NBO analysis it is evident that the increased electron density at the nitrogen, carbon atoms leads to the elongation of respective bond length and a lowering of the corresponding stretching wave number. The calculated geometrical parameters are in agreement with that of similar derivatives. The calculated first hyperpolarizability is high and the calculated data suggest an extended ?-electron delocalization over the pyrazine ring and carboxamide moiety which is responsible for the nonlinearity of the molecule.

Bhagyasree, J. B.; Varghese, Hema Tresa; Panicker, C. Yohannan; Van Alsenoy, Christian; Al-Saadi, Abdulaziz A.; Dolezal, Martin; Samuel, Jadu

2015-02-01

296

Solution and solid-state study of the structure of azo-coupling products from isomeric enaminones possessing tert-butyl group: An unprecedented observation of pure hydrazo form in azo coupled N-alkyl ?-enaminones  

NASA Astrophysics Data System (ADS)

The structure of the azo-coupling products from enaminones derived from 4,4-dimethyl-1-phenylpentane-1,3-dione has been studied by means of solution-state 1H, 13C and 15N NMR spectroscopy and X-ray diffractometry. The presence of bulky tert-butyl group hinders or even prevents from the formation of planar conjugated heterodiene system Hsbnd Nsbnd Cdbnd Csbnd Ndbnd N with an intramolecular hydrogen bond Nsbnd H⋯Ndbnd which is the prerequisite for fast tautomeric exchange imino-hydrazo - enamino-azo. The minor amount of azo compounds is formed by a proton exchange through a hydrogen bond Nsbnd H⋯N, which is either intramolecular (in solution) or intermolecular (solid state). The intermolecular exchange proceeds via the dimers of the azo coupling products. This is unprecedented result among the similar molecules hitherto studied.

Šim?nek, Petr; Pad?lková, Zde?ka; Machá?ek, Vladimír

2014-10-01

297

PRODUCTS OF THE GAS-PHASE REACTIONS OF THE OH RADICAL WITH N-BUTYL METHYL ETHER AND 2-ISOPROPOXYETHANOL: REACTIONS OF ROC(O)< RADICALS. (R825252)  

EPA Science Inventory

The products of the gas-phase reactions of the OH radical with n -butyl methyl ether and 2-isopropoxyethanol in the presence of NO have been investigated at 298 ? 2 K and 740 Torr total pressure of air by gas chromatography and in situ atmospheric pressure ionization...

298

Cobalt(II)-mediated synthesis of 2,6-bis[5,7-di-tert-butyl-1,3-benzoxazol-2-yl]-pyridine: Structural analysis and coordination behavior  

NASA Astrophysics Data System (ADS)

The oxidative cyclization of 2,6-bis[2,4-di-tert-butyl-6-(methylidenylamino)phenol]-pyridine (L1) in acetonitrile, through the cobalt(II) coordination compound of L1, has resulted in a convenient route for the preparation of 2,6-bis[5,7-di-tert-butyl-1,3-benzoxazol-2-yl]-pyridine (L3). The X-ray diffraction analysis of L3 shows a planar molecule, with the oxygen atoms from the benzoxazole rings oriented to the pyridine nitrogen atom (conformer L3a). Ab initio calculations indicate that from the three possible planar conformers of L3, the more stable is L3a. The solid state conformation of the free ligand L3 and the relative energy of the three calculated conformers indicated stabilizing N ? O interactions. Calculations of the protonated derivative of L3, compound 7, indicated that the most stable conformer has the benzoxazole nitrogen atoms pointing to the protonated pyridine NH (7c). The X-ray crystal analysis of ligand L3 coordinated to cobalt(II) nitrate, compound 4 is presented and conformer L3c is found in this compound. Two acid:base complexes [Zn(NO3)2(H2O)2][L3c]2, compound 5, and [NEt2H2Cl][L3c], compound 6, have also been investigated. Complex 5 crystallized and its X-ray diffraction analysis is reported, whereas compound 6 was studied in solution by NMR, mass spectrometry and ab initio calculations. Both complexes show that conformer L3c can form stable hydrogen bonding associations, with molecules having the motif YH2 (Y = N or O), that are of interest for building up supramolecular associations.

Garza-Ortíz, Ariadna; Martínez, Pablo A.; Duarte-Hernández, Angelica M.; Mijangos, Edgar; Flores-Álamo, Marcos; Pérez-Casas, Carol; Camacho-Camacho, Carlos; Contreras, Rosalinda; Flores-Parra, Angelina; Reedijk, Jan; Barba-Behrens, Norah

2013-01-01

299

5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetra­kis[2-(2-chloro­ethoxy)eth­oxy]-2,8,14,20-tetra­sulfonyl­calix[4]arene  

PubMed Central

Mol­ecules of the title compound, C56H76Cl4O16S4, have crystallographic C 2 symmetry and adopt a 1,3-alternate conformation where the four –OCH2CH2OCH2CH2Cl groups are located alternately above and below the virtual plane (R) defined by the four bridging S atoms. The dihedral angles between the plane (R) and the phenolic rings are 72.85?(7) and 74.57?(7)°. An unusual 24-membered macrocyclic ring is formed in the crystal structure with an array of eight intra­molecular C—H?O hydrogen bonds between the ether arm H atoms and the sulfonyl O atoms. In the supra­molecular structure, the mol­ecular components are linked into infinite zigzag one-dimensional chains by a combination of four inter­molecular C—H?O hydrogen bonds, forming R 2 2(13), R 2 2(16), R 2 2(21) and R 2 2(26) ring motifs. These chains are augmented into a wave-like two-dimensional network by weak C?O inter­actions. One tert-butyl group shows rotational disorder, and one CH2CH2Cl group is disordered over two orientations; the site-occupation factors are 0.756?(6) and 0.244?(6) for the two tert-butyl groups, and 0.808?(3) and 0.192?(3) for the two CH2CH2Cl units. PMID:21581981

Hu, Ling; Liu, Yang; Ma, Jiang-Ping; Guo, Dian-Shun

2009-01-01

300

Metal-Free Preparation of Cycloalkyl Aryl Sulfides via Di-tert-butyl Peroxide-Promoted Oxidative C(sp3)[BOND]H Bond Thiolation of Cycloalkanes  

PubMed Central

A concise thiolation of C(sp3)–H bond of cycloalkanes with diaryl disulfides in the presence of oxidant of di-tert-butylperoxide (DTBP) has been developed. This reaction without using any of metal catalyst, tolerates varieties of disulfides and cycloalkanes substrates, giving good to excellent chemical yields, which provides a useful approach to cycloalkyl aryl sulfides from unactivated cycloalkanes. PMID:25505857

Zhao, Jincan; Fang, Hong; Han, Jianlin; Pan, Yi; Li, Guigen

2014-01-01

301

[2-(sec-Butyl­imino­meth­yl)quinoline]­chlorido(?6-1-isopropyl-4-methyl­benzene)­ruthenium(II) hexa­fluorido­phosphate  

PubMed Central

In the title compound, [RuCl(C10H14)(C14H16N2)]PF6, the aromatic ring of the isopropyl­methyl­benzene fragment shows an ?6-arene coordination to the ruthenium atom. Its coordination sphere is completed by a chloride ligand and 2-(sec-butyl­imino­meth­yl)quinoline. The dihedral angle between the ?6-arene ring and the quinoline Schiff base is 45.64?(9)°. The sec-butyl substituent and the PF6 ? anion are disordered over two positions with ratios of 0.595?(11):0.405?(11) and 0.752?(8):0.248?(8), respectively. PMID:21588544

Gárate-Morales, José Luis; Hernández-Ortega, Simón; Fernández-G, Juan Manuel

2010-01-01

302

Preoperative Percutaneous Injection of Methyl Methacrylate and N-Butyl Cyanoacrylate in Vertebral Hemangiomas  

Microsoft Academic Search

PURPOSE: To investigate the usefulness of preoperative percutaneous injections in vertebral hemangiomas. METHODS: Four patients presented with complicated vertebral hemangioma (spi- nal cord compression in three cases, intermittent spinal claudiction in one case). A three-part treatment was performed: initially, arterial embolization in three cases; 1 day later, percutaneous injections of methyl methacrylate into the vertebral body to strengthen it and

Anne Cotten; Bernard Cortet; Jean-Paul Lejeune; Xavier Leclerc; Patrick Chastanet; Jacques Clarisse

303

Tissue-specific Induction Patterns of Cancer-protective Enzymes in Mice by tertButyl4-hydroxyanisole and Related Substituted Phenols1  

Microsoft Academic Search

Some of the anticarcinogenic effects of 2(3)-ferf-butyl-4-hy- droxyanisole (BHA) are attributable to the induction of detoxifying enzymes in the liver and peripheral tissues. This study was designed to determine if the tissue specificity of enzyme induc tion could be manipulated by structural modification of BHA. The induction of glutathione S-transferases and quinone reducíase (EC 1.6.99.2) by the component isomers of

Mary J. De Long; Hans J. Prochaska; Paul Talalay

304

Final Report On the Safety Assessment of Glycolic Acid, Ammonium, Calcium, Potassium, and Sodium Glycolates, Methyl, Ethyl, Propyl, and Butyl Glycolates, and Lactic Acid, Ammonium, Calcium, Potassium, Sodium, and Tea-Lactates, Methyl, Ethyl, Isopropyl, and Butyl Lactates, and Lauryl, Myristyl, and Cetyl Lactates  

Microsoft Academic Search

This report provides a review of the safety of Glycolic Acid, Ammonium, Calcium, Potassium, and Sodium Glycolates, Methyl, Ethyl, Propyl, and Butyl Glycolates, Lactic Acid, Ammonium, Calcium, Potassium, Sodium, and TEA-Lactates, and Lauryl, Myristyl, and Cetyl Lactates. These ingredients belong to a group known as alpha-hydroxy acids (AHAs). Products containing these ingredients may be for consumer use, salon use, or

F. A. Andersen

1998-01-01

305

Containment of groundwater pollution (methyl tertiary butyl ether and benzene) to protect a drinking-water production site in Belgium  

NASA Astrophysics Data System (ADS)

The subsurface migration of methyl tertiary butyl ether (MTBE) and benzene towards a drinking-water production site in Belgium was monitored for 9 years. A large gasoline spill at a nearby fuel station had caused a 500-m long and 50-m-wide pollution plume of MTBE (10-30 mg/L) and benzene (2-10 mg/L). In order to prevent any intrusion of pollutants into the drinking-water supply, a conceptual model was used to design a pump-and-treat system that intercepted the gasoline-contaminated groundwater emanating from the spill. The contaminated soil in the spill zone was excavated. A numerical mass transport model was developed to evaluate the ongoing plume containment. The model describes the subsurface MTBE migration and was regularly updated, based on groundwater monitoring data and the measured mass of MTBE extracted with the pump-and-treat system. With continued interception pumping, the MTBE plume can be remediated in 14 years. Without it, MTBE and benzene concentrations up to 600 ?g/L could have reached the drinking-water production site and the plume would persist for 9 years longer. Source zone treatment combined with plume interception pumping is a suitable risk-based remediation strategy for the containment of MTBE and benzene groundwater pollution.

Haest, Pieter Jan; Lookman, Richard; van Keer, Ilse; Patyn, Johan; Bronders, Jan; Joris, Marjan; Bellon, Jan; de Smedt, Florimond

2010-12-01

306

Seasonal and daily variations in concentrations of methyl-tertiary-butyl ether (MTBE) at Cranberry Lake, New Jersey  

USGS Publications Warehouse

Methyl-tertiary-butyl ether (MTBE), an additive used to oxygenate gasoline, has been detected in lakes in northwestern New Jersey. This occurrence has been attributed to the use of gasoline-powered watercraft. This paper documents and explains both seasonal and daily variations in MTBE concentrations at Cranberry Lake. During a recent boating season (late April to September 1999), concentrations of MTBE typically exceeded 20??g/L. MTBE concentrations varied daily from 12 to 24??g/L over a 2-week period that included the Labor Day holiday. Concentrations were highest on weekends when there is more boat traffic, which had an immediate effect on MTBE mass throughout the lake. MTBE concentrations decreased to about 2??g/L shortly after the end of the summer recreational season. The loss of MTBE can be accounted for by volatilization, with a half-life on the order of 10 days. The volatilization rate was modeled with the daily decrease in MTBE then the modeled rate was validated using the data from the seasonal decline. ?? 2003 Elsevier Science Ltd. All rights reserved.

Toran, L.; Lipka, C.; Baehr, A.; Reilly, T.; Baker, R.

2003-01-01

307

Speciated hydrocarbon and carbon monoxide emissions from an internal combustion engine operating on methyl tertiary butyl ether-containing fuels.  

PubMed

In the present work, engine and tailpipe (after a three-way catalytic converter) emissions from an internal combustion engine operating on two oxygenated blend fuels [containing 2 and 11% weight/weight (w/w) methyl tertiary butyl ether (MTBE)] and on a nonoxygenated base fuel were characterized. The engine (OPEL 1.6 L) was operated under various conditions, in the range of 0-20 HP. Total unburned hydrocarbons, carbon monoxide, methane, hexane, ethylene, acetaldehyde, acetone, 2-propanol, benzene, toluene, 1,3-butadiene, acetic acid, and MTBE were measured at each engine operating condition. As concerns the total HC emissions, the use of MTBE was beneficial from 1.90 to 3.81 HP, which were by far the most polluting conditions. Moreover, CO emissions in tailpipe exhaust were decreased in the whole operation range with increasing MTBE in the fuel. The greatest advantage of MTBE addition to gasoline was the decrease in ethylene, acetaldehyde, benzene, toluene, and acetic acid emissions in engine exhaust, especially when MTBE content in the fuel was increased to 11% w/w. In tailpipe exhaust, the catalyst operation diminished the observed differences. Ethylene, methane, and acetaldehyde were the main compounds present in exhaust gases. Ethylene was easily oxidized over the catalyst, while acetaldehyde and methane were quite resistant to oxidation. PMID:15658218

Poulopoulos, S G; Philippopoulos, C J

2001-07-01

308

Construction of wettability gradient surface on copper substrate by controlled hydrolysis of poly(methyl methacrylate-butyl acrylate) films  

NASA Astrophysics Data System (ADS)

We report a gradient wettability surface on copper slide prepared by a simple controlled ester group hydrolysis procedure of poly(methyl methacrylate-butyl acrylate) [P (MMA-BA)] films coated on the copper substrate. In the method, sodium hydroxide solutions are selected to prepare surface gradient wettability on P (MMA-BA) films. The P (MMA-BA) copolymers with different MMA contents are first synthesized by a conventional free atom radical solution polymerization method. The transfer of surface chemical composition from the ester group to acid salt is achieved by hydrolysis in NaOH solution. The effects of different concentrations of NaOH solution and reaction times on the physicochemical properties of the resulting surfaces are studied. The field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) results show that the varying concentration along the substrate length is only attributed to the hydrolysis reaction of ester groups. The hydrolysis causes insignificant change on the morphology of the original film on the copper substrate. In addition, it is found that the MMA copolymer content has a significant influence on the concentration of ester groups on the outermost surface and thus important for forming the slope gradients.

Zhang, Yong; Cheng, Jiang; Yang, Zhuo-ru

2014-10-01

309

Formation of Alkenes via Degradation of tert-Alkyl Ethers and Alcohols by Aquincola tertiaricarbonis L108 and Methylibium spp. ?†  

PubMed Central

Bacterial degradation pathways of fuel oxygenates such as methyl tert-butyl and tert-amyl methyl ether (MTBE and TAME, respectively) have already been studied in some detail. However, many of the involved enzymes are still unknown, and possible side reactions have not yet been considered. In Aquincola tertiaricarbonis L108, Methylibium petroleiphilum PM1, and Methylibium sp. strain R8, we have now detected volatile hydrocarbons as by-products of the degradation of the tert-alkyl ether metabolites tert-butyl and tert-amyl alcohol (TBA and TAA, respectively). The alkene isobutene was formed only during TBA catabolism, while the beta and gamma isomers of isoamylene were produced only during TAA conversion. Both tert-alkyl alcohol degradation and alkene production were strictly oxygen dependent. However, the relative contribution of the dehydration reaction to total alcohol conversion increased with decreasing oxygen concentrations. In resting-cell experiments where the headspace oxygen content was adjusted to less than 2%, more than 50% of the TAA was converted to isoamylene. Isobutene formation from TBA was about 20-fold lower, reaching up to 4% alcohol turnover at low oxygen concentrations. It is likely that the putative tert-alkyl alcohol monooxygenase MdpJ, belonging to the Rieske nonheme mononuclear iron enzymes and found in all three strains tested, or an associated enzymatic step catalyzed the unusual elimination reaction. This was also supported by the detection of mdpJK genes in MTBE-degrading and isobutene-emitting enrichment cultures obtained from two treatment ponds operating at Leuna, Germany. The possible use of alkene formation as an easy-to-measure indicator of aerobic fuel oxygenate biodegradation in contaminated aquifers is discussed. PMID:21742915

Schäfer, Franziska; Muzica, Liudmila; Schuster, Judith; Treuter, Naemi; Rosell, Mònica; Harms, Hauke; Müller, Roland H.; Rohwerder, Thore

2011-01-01

310

N-{2-[(4S)-4-tert-Butyl-4,5-dihydro-1,3-oxazol-2-yl]phen­yl}-5,6-diphenyl-1,2,4-triazin-3-amine  

PubMed Central

The title compound, C28H27N5O, was synthesized using palladium cross-coupling amination of 3-bromo-5,6-diphenyl-1,2,4-triazine with 2-[(4S)-4-tert-butyl-4,5-dihydro-1,3-oxazol-2-yl]aniline. The oxazoline ring is almost planar, with a maximum atomic deviation of 0.023?(5)?Å. The phenyl rings make dihedral angles of 29.0?(1) and 54.6?(1)° with the triazine ring while the benzene ring makes a dihedral angle of 0.6?(1)° with the oxazoline ring. The conformation of the mol­ecule is influenced by strong intra­molecular N—H?N and weak C—H?N hydrogen bonds. In the crystal, screw-axis related mol­ecules are linked into supra­molecular chains by inter­molecular C—H?O hydrogen bonds. ?–? stacking is observed between the oxazoline and triazine rings of adjacent mol­ecules, with a centroid–centroid distance of 3.749?(2)?Å. PMID:21522403

Karczmarzyk, Zbigniew; Woli?ska, Ewa; Fruzi?ski, Andrzej

2011-01-01

311

Renal histopathology in toxicity and carcinogenicity studies with tert-butyl alcohol administered in drinking water to F344 rats: a pathology working group review and re-evaluation.  

PubMed

An independent Pathology Working Group (PWG) re-evaluated the kidney changes in National Toxicology Program (NTP) toxicology/carcinogenicity studies of tert-butyl alcohol (TBA) in F344/N rats to determine possible mode(s) of action underlying renal tubule tumors in male rats at 2-years. In the 13-week study, the PWG confirmed that the normal pattern of round hyaline droplets in proximal convoluted tubules was replaced by angular droplet accumulation, and identified precursors of granular casts in the outer medulla, changes typical of alpha(2u)-globulin (?(2u)-g) nephropathy. In the 2-year study, the PWG confirmed the NTP observation of increased renal tubule tumors in treated male groups. Linear papillary mineralization, another hallmark of the ?(2u)-g pathway was present only in treated male rats. Chronic progressive nephropathy (CPN) was exacerbated in high-dose males and females, with a relationship between advanced grades of CPN and renal tumor occurrence. Hyperplasia of the papilla lining was a component of CPN in both sexes, but there was no pelvic urothelial hyperplasia. High-dose females showed no TBA-related nephrotoxicity. The PWG concluded that both ?(2u)-g nephropathy and exacerbated CPN modes of action were operative in TBA renal tumorigenicity in male rats, neither of which has relevance for human cancer risk. PMID:21296119

Hard, Gordon C; Bruner, Richard H; Cohen, Samuel M; Pletcher, John M; Regan, Karen S

2011-04-01

312

Simultaneous liquid-liquid extraction of dibenzyl disulfide, 2,6-di-tert-butyl-p-cresol, and 1,2,3-benzotriazole from power transformer oil prior to GC and HPLC determination.  

PubMed

2,6-Di-tert-butyl-p-cresol (DBPC), dibenzyl disulfide (DBDS), and 1,2,3-benzotriazole (BTA) are additives that may be found concomitantly in the oil matrix of power transformer. DBPC and DBDS act as antioxidants while, BTA is a corrosion inhibitor that protects copper conductors inside the transformer unit from corrosion. A powerful analytical method is, therefore, required to determine these additives at trace levels in the transformer oil. This work describes a unique single liquid-liquid extraction pretreatment step prior to the determination of the components by gas chromatography (GC) and high-performance liquid chromatography (HPLC) techniques. The optimum volume ratio used in the pretreatment step was determined as 5:2:5 for mineral oil/n-hexane/acetonitrile, respectively. Relatively, the method is simple and quick with a minimal use of solvents. Analytical results indicate that the method is relatively sensitive, accurate, and precise for each of the three components in fresh and used mineral oil. The calibration curves for the three components demonstrate a significant increase in sensitivities. Detection limits found were, 100 mg L(-1) (0.01% w/v), 0.80 mg L(-1) , and 2.04 mg L(-1) for DBPC, DBDS, and BTA, respectively. The Student's t values determined at 95% confidence level indicate that there is no significant difference between the experimental means obtained by this method and the standard method for each component. PMID:22311820

Jaber, Abdul Muttaleb Yousef; Mehanna, Nemr Ahmed; Abulkibash, Abdalla Mahmoud

2012-03-01

313

Crystal structure of bis­(?5-cyclo­penta­dien­yl)(1,4-di-tert-butyl­buta-1-en-3-yn-1-yl)zirconium(IV) ?2-hydroxido-bis­[tris(penta­fluoro­phen­yl)borate  

PubMed Central

Alkyl zirconocene cations have been of considerable inter­est as reactive species in many polymerization processes. In the crystal structure of the title compound, [Zr(C12H19)(C5H5)2](C36HB2F30O), the [Zr(C5H5)2((t-Bu)C=C(H)—C2(t-Bu))]+ cation displays a buta-1-en-3-yne ligand side-on coordinated to a typical bent zirconocene [centroid(cp)—Zr—centroid(cp) = 131.4?(3)°, Zr—C(buta-1-en-3-yne) = 2.255?(3), 2.597?(3) and 2.452?(2)?Å]. In the [HO(B(C6F5)3)2]? anion, intra­molecular O—H?F hydrogen bonds are observed. One tert-butyl group in the complex cation is disordered over two sets of sites with occupancies 0.701(4):0.299(4). PMID:25844214

Burlakov, Vladimir V.; Spannenberg, Anke; Arndt, Perdita; Rosenthal, Uwe

2015-01-01

314

Spectroscopic (FT-IR, FT-Raman), first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of 5-tert-Butyl-6-chloro-N-[(4-(trifluoromethyl)phenyl]pyrazine-2-carboxamide.  

PubMed

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 5-tert-Butyl-6-chloro-N-[(4-(trifluoromethyl)phenyl]pyrazine-2-carboxamide have been investigated experimentally and theoretically using Gaussian09 software package. Potential energy distribution of normal modes of vibrations was done using GAR2PED program. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. From the NBO analysis it is evident that the increased electron density at the nitrogen, carbon atoms leads to the elongation of respective bond length and a lowering of the corresponding stretching wave number. The calculated geometrical parameters are in agreement with that of similar derivatives. The calculated first hyperpolarizability is high and the calculated data suggest an extended ?-electron delocalization over the pyrazine ring and carboxamide moiety which is responsible for the nonlinearity of the molecule. PMID:25218229

Bhagyasree, J B; Varghese, Hema Tresa; Panicker, C Yohannan; Van Alsenoy, Christian; Al-Saadi, Abdulaziz A; Dolezal, Martin; Samuel, Jadu

2015-02-25

315

tert-Butyl N-[(3R,4R)-1-(2-cyano­acet­yl)-4-methyl­piperidin-3-yl]-N-methyl­carbamate  

PubMed Central

The piperidine ring of the title compound, C15H25N3O3, adopts a slightly distorted chair conformation with the cis substituents displaying an N—C—C—C torsion angle of 43.0?(3)°. The cyano group (plane defined by C—C—C N atoms) is bent slightly out of the plane of the amide group by 13.3?(2)°. The carbamate group is oriented at a dihedral angle of 60.3?(5)° relative to the amide group. PMID:23795101

Gehringer, Matthias; Forster, Michael; Schollmeyer, Dieter; Laufer, Stefan

2013-01-01

316

A Ferrocenyl Kaleidoscope: Slow Interconversion of Six Diastereo-atropisomers of 2,6-Di-tert-butyl-9,10-diferrocenyltriptycene.  

PubMed

The title triptycene, 6, has been isolated as the product of 9,10-cycloaddition of benzyne to 9,10-diferrocenyl-2,6-di-tert-butylanthracene, 5, whose X-ray crystal structure is reported. Each ferrocenyl unit in 6 has access to the same three non-equivalent molecular environments, and their rotations relative to the molecular paddlewheel give rise to six slowly interconverting atropisomers. Their dynamic behaviour in solution is a challenging NMR puzzle that can be successfully solved by taking advantage of the recently described very large diamagnetic anisotropy of the ferrocenyl moiety, together with the C2 symmetry of particular atropisomers. Application of one- and two-dimensional NMR techniques over a range of temperatures together, with a detailed analysis of the homo- and heteronuclear correlations in 6, resulted in unequivocal mapping of the 99 (1) H and 162 (13) C positions in the six interconverting systems. Variable-temperature 2D-EXSY measurements revealed that, while the stability of the atropisomers is almost identical, they are separated by energy barriers which the ferrocenyls must overcome in the course of their interconversions. The heights of two different rotational barriers have been identified and these experimental findings are in good agreement with DFT calculations. PMID:25678469

Nikitin, Kirill; Muldoon, Jimmy; Müller-Bunz, Helge; McGlinchey, Michael J

2015-03-16

317

Solid state 1H spin-lattice relaxation and isolated-molecule and cluster electronic structure calculations in organic molecular solids: The relationship between structure and methyl group and t-butyl group rotation  

NASA Astrophysics Data System (ADS)

We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state 1H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl group rotation in a central target molecule in the cluster with the activation energies determined from fitting the 1H NMR spin-lattice relaxation data. We formulate a dynamical model for the superposition of t-butyl group rotation and the rotation of the t-butyl group's constituent methyl groups. The four compounds are 2,7-di-t-butylpyrene, 1,4-di-t-butylbenzene, 2,6-di-t-butylnaphthalene, and 3-t-butylchrysene. We comment on the unusual ground state orientation of the t-butyl groups in the crystal of the pyrene and we comment on the unusually high rotational barrier of these t-butyl groups.

Wang, Xianlong; Mallory, Frank B.; Mallory, Clelia W.; Odhner, Hosanna R.; Beckmann, Peter A.

2014-05-01

318

Solid state ¹H spin-lattice relaxation and isolated-molecule and cluster electronic structure calculations in organic molecular solids: the relationship between structure and methyl group and t-butyl group rotation.  

PubMed

We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state (1)H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl group rotation in a central target molecule in the cluster with the activation energies determined from fitting the (1)H NMR spin-lattice relaxation data. We formulate a dynamical model for the superposition of t-butyl group rotation and the rotation of the t-butyl group's constituent methyl groups. The four compounds are 2,7-di-t-butylpyrene, 1,4-di-t-butylbenzene, 2,6-di-t-butylnaphthalene, and 3-t-butylchrysene. We comment on the unusual ground state orientation of the t-butyl groups in the crystal of the pyrene and we comment on the unusually high rotational barrier of these t-butyl groups. PMID:24852535

Wang, Xianlong; Mallory, Frank B; Mallory, Clelia W; Odhner, Hosanna R; Beckmann, Peter A

2014-05-21

319

Solid state {sup 1}H spin-lattice relaxation and isolated-molecule and cluster electronic structure calculations in organic molecular solids: The relationship between structure and methyl group and t-butyl group rotation  

SciTech Connect

We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state {sup 1}H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl group rotation in a central target molecule in the cluster with the activation energies determined from fitting the {sup 1}H NMR spin-lattice relaxation data. We formulate a dynamical model for the superposition of t-butyl group rotation and the rotation of the t-butyl group's constituent methyl groups. The four compounds are 2,7-di-t-butylpyrene, 1,4-di-t-butylbenzene, 2,6-di-t-butylnaphthalene, and 3-t-butylchrysene. We comment on the unusual ground state orientation of the t-butyl groups in the crystal of the pyrene and we comment on the unusually high rotational barrier of these t-butyl groups.

Wang, Xianlong, E-mail: WangXianlong@uestc.edu.cn, E-mail: pbeckman@brynmawr.edu [Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, 4 North Jianshe Rd., 2nd Section, Chengdu 610054 (China)] [Key Laboratory for NeuroInformation of Ministry of Education, School of Life Science and Technology, University of Electronic Science and Technology of China, 4 North Jianshe Rd., 2nd Section, Chengdu 610054 (China); Mallory, Frank B. [Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899 (United States)] [Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899 (United States); Mallory, Clelia W. [Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899 (United States) [Department of Chemistry, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899 (United States); Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323 (United States); Odhner, Hosanna R.; Beckmann, Peter A., E-mail: WangXianlong@uestc.edu.cn, E-mail: pbeckman@brynmawr.edu [Department of Physics, Bryn Mawr College, 101 North Merion Ave., Bryn Mawr, Pennsylvania 19010-2899 (United States)

2014-05-21

320

Ion/neutral complexes generated during unimolecular fragmentation: Intra-complex hydride abstraction by tert-butyl cations from electron-rich and electron-poor 1,3-diphenylpropanes  

NASA Astrophysics Data System (ADS)

The hydride transfer and proton transfer occurring between the constituents of ion/neutral complexes of tert-butyl cations and electron-rich and electron-poor 1,3-diphenylpropanes, [(CH3)3C+ C6H5CH2CH2CH2C6H4X] were investigated by use of CI/MIKE spectrometry of nine 1-(tert-butylphenyl)-3-arylpropanes and 16 site-specific deuterium-labeled isotopomers. The competition between H- abstraction by the (CH3)3C+ ion from the neutral arene and H+ transfer to it was found to be strongly affected by the electron-donating substituents, in particular by X = OCH3, on the one hand, and X = F and CF3, on the other, suggesting that the 1,3-diphenylpropane molecule within the I/N complex acts and reacts as a bidentate solvating partner to the carbocation. The effect of the substituents X on the regioselectivity of the intra-complex hydride abstraction from the two benzylic CH2 groups, k[gamma]-H/k[alpha]-H, and their influence on the kinetic isotope effect (kH/kD)[gamma], operating during the abstraction from the substituted benzylic moiety, were determined in a semi-quantitative approach by assuming (kH/kD)[alpha] = 1.60, the generally observed value for the unsubstituted benzylic moiety. The regioselectivity range was found to span almost three orders of magnitude, from k[gamma]-H/k[alpha]-H >= 11.2 for the complex [(CH3)3C+ C6H5C[alpha]H2CH2C[gamma]H2C6H4(p-OCH3)] to k[gamma]-H/k[alpha]-H <= 0.04 for the complex [(CH3)3C+ C6H5C[alpha]H2CH2C[gamma]H2C6H4(p-CF3)].

Matthias, Carsten; Cartoni, Antonella; Kuck, Dietmar

2006-09-01

321

Free radical-derived quinone methide mediates skin tumor promotion by butylated hydroxytoluene hydroperoxide: expanded role for electrophiles in multistage carcinogenesis.  

PubMed Central

Free radical derivatives of peroxides, hydroperoxides, and anthrones are thought to mediate tumor promotion by these compounds. Further, the promoting activity of phorbol esters is attributed, in part, to their ability to stimulate the cellular generation of oxygen radicals. A hydroperoxide metabolite of butylated hydroxytoluene, 2,6-di-tert-butyl-4-hydroperoxyl-4-methyl-2,5-cyclohexadienone (BHTOOH), has previously been shown to be a tumor promoter in mouse skin. BHTOOH is extensively metabolized by murine keratinocytes to several radical species. The primary radical generated from BHTOOH is a phenoxyl radical that can disproportionate to form butylated hydroxytoluene quinone methide, a reactive electrophile. Since electrophilic species have not been previously postulated to mediate tumor promotion, the present study was undertaken to examine the role of this electrophile in the promoting activity of BHTOOH. The biological activities of two chemical analogs of BHTOOH, 4-trideuteromethyl-BHTOOH and 4-tert-butyl-BHTOOH, were compared with that of the parent compound. 4-Trideuteromethyl-BHTOOH and 4-tert-butyl-BHTOOH have a reduced ability or inability, respectively, to form a quinone methide; however, like the parent compound, they both generate a phenoxyl radical when incubated with keratinocyte cytosol. The potency of BHTOOH, 4-trideuteromethyl-BHTOOH, and 4-tert-butyl-BHTOOH as inducers of ornithine decarboxylase, a marker of tumor promotion, was commensurate with their capacity for generating butylated hydroxytoluene quinone methide. These initial results were confirmed in a two-stage tumor promotion protocol in female SENCAR mice. Together, these data indicate that a quinone methide is mediating tumor promotion by BHTOOH, providing direct evidence that an electrophilic intermediate can elicit this stage of carcinogenesis. PMID:1846971

Guyton, K Z; Bhan, P; Kuppusamy, P; Zweier, J L; Trush, M A; Kensler, T W

1991-01-01

322

Quantum mechanical study and spectroscopic (FT-IR, FT-Raman, UV-Visible) study, potential energy surface scan, Fukui function analysis and HOMO-LUMO analysis of 3-tert-butyl-4-methoxyphenol by DFT methods.  

PubMed

This study represents an integral approach towards understanding the electronic and structural aspects of 3-tert-butyl-4-methoxyphenol (TBMP). Fourier-transform Infrared (FT-IR) and Fourier-transform Raman (FT-Raman) spectra of TBMP was recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The molecular structures, vibrational wavenumbers, infrared intensities and Raman activities were calculated using DFT (B3LYP and LSDA) methods using 6-311++G (d,p) basis set. The most stable conformer of TBMP was identified from the computational results. The assignments of vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (?0) and related properties (?, ?0 and ??) of TBMP have been discussed. The stability and charge delocalization of the molecule was studied by Natural Bond Orbital (NBO) analysis. UV-Visible spectrum and effects of solvents have been discussed and the electronic properties such as HOMO and LUMO energies were determined by time-dependent TD-DFT approach with B3LYP/6-311++G (d,p) level of theory. The molecule orbital contributions are studied by density of energy states (DOSs). The reactivity sites are identified by mapping the electron density into electrostatic potential surface (MEP). Mulliken analysis of atomic charges is also calculated. The thermodynamic properties at different temperatures were calculated, revealing the correlations between standard heat capacities, standard entropy and standard enthalpy changes with temperatures. Global hardness, global softness, global electrophilicity and ionization potential of the title compound are determined. PMID:24813291

Saravanan, S; Balachandran, V

2014-09-15

323

Quantum mechanical study and spectroscopic (FT-IR, FT-Raman, UV-Visible) study, potential energy surface scan, Fukui function analysis and HOMO-LUMO analysis of 3-tert-butyl-4-methoxyphenol by DFT methods  

NASA Astrophysics Data System (ADS)

This study represents an integral approach towards understanding the electronic and structural aspects of 3-tert-butyl-4-methoxyphenol (TBMP). Fourier-transform Infrared (FT-IR) and Fourier-transform Raman (FT-Raman) spectra of TBMP was recorded in the region 4000-400 cm-1 and 3500-100 cm-1, respectively. The molecular structures, vibrational wavenumbers, infrared intensities and Raman activities were calculated using DFT (B3LYP and LSDA) methods using 6-311++G (d,p) basis set. The most stable conformer of TBMP was identified from the computational results. The assignments of vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (?0) and related properties (?, ?0 and ??) of TBMP have been discussed. The stability and charge delocalization of the molecule was studied by Natural Bond Orbital (NBO) analysis. UV-Visible spectrum and effects of solvents have been discussed and the electronic properties such as HOMO and LUMO energies were determined by time-dependent TD-DFT approach with B3LYP/6-311++G (d,p) level of theory. The molecule orbital contributions are studied by density of energy states (DOSs). The reactivity sites are identified by mapping the electron density into electrostatic potential surface (MEP). Mulliken analysis of atomic charges is also calculated. The thermodynamic properties at different temperatures were calculated, revealing the correlations between standard heat capacities, standard entropy and standard enthalpy changes with temperatures. Global hardness, global softness, global electrophilicity and ionization potential of the title compound are determined.

Saravanan, S.; Balachandran, V.

2014-09-01

324

Processed Panax ginseng, Sun Ginseng, Decreases Oxidative Damage Induced by tert-butyl Hydroperoxide via Regulation of Antioxidant Enzyme and Anti-apoptotic Molecules in HepG2 Cells  

PubMed Central

Potential antioxidant effect of processed ginseng (sun ginseng, SG) on oxidative stress generated by tert-butyl hydroperoxide (t-BHP) was investigated in HepG2 cells. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and lactate dehydrogenase (LDH) leakage test demonstrated that SG dose-dependently prevents a loss of cell viability against t-BHP-induced oxidative stress. Also, SG treatment dose-dependently relieved the increment of activities of hepatic enzymes, such as aspartate aminotrasferase and alanine aminotransferase, and lipid peroxidation mediated by t-BHP treatment in HepG2 cells. SG increased the gene expression of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione peroxidase. However, high dose of SG treatment caused decrease in mRNA level of glutathione peroxidase as compared to low dosage of SG-treated cells. The gene expression of glutathione reductase was found to be slightly increased by SG treatment. In addition, SG extract attributed its hepaprotective effect by inducing the mRNA level of bcl-2 and bcl-xL but reducing that of bax. But, the gene expression of bad showed no significant change in SG-treated HepG2 cells. These findings suggest that SG has hepatoprotective effect by showing reduction of LDH release, activities of hepatic enzymes and lipid peroxidation and regulating the gene expression of antioxidant enzymes and apoptosis-related molecules against oxdative stress caused by t-BHP in HepG2 cells. PMID:23717125

Lee, Hyejin; Kim, Jinhee; Lee, Seo Young; Park, Jeong Hill; Hwang, Gwi Seo

2012-01-01

325

Heat of Mixing and Solution of Butyl methyl ether C5H12O + C6H10 Hex-2-yne (HMSD1111, LB4294_H)  

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 'Heat of Mixing and Solution of Butyl methyl ether C5H12O + C6H10 Hex-2-yne (HMSD1111, LB4294_H)' providing data from direct low-pressure calorimetric measurement of molar excess enthalpy at variable mole fraction and constant temperature.

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

326

(±)-1-{8?-(tert-Butyl­diphenyl­silyloxy­meth­yl)-1?,7?-dioxaspiro­[5.5]undecan-2?-yl}uridine  

PubMed Central

The crystal structure of the title compound, C30H38N2O5Si, has been investigated to establish the relative stereochemistry at the spiro ring junction and the two anomeric centres. Each of the O atoms in the tetra­hydro­pyran rings adopts an axial position on the neighbouring ring. This bis­-diaxial conformation is adopted, thus gaining maximum stablization from the anomeric effect. The silyl-protected hydroxy­methyl and uracil substituents adopt equatorial positions on their associated tetra­hydro­pyran rings, thereby minimizing unfavourable steric inter­actions. The dimeric (2?R*,6?R*,8?R*)- and (2?S*,6?S*,8?S*)-uridine units are connected to each other across crystallographic inversion centres via inter­molecular N—H?O hydrogen bonds. PMID:21202106

Choi, Ka Wai; Brimble, Margaret A.; Groutso, Tania

2008-01-01

327

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

SciTech Connect

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

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

1995-04-01

328

Synthesis, Spectroscopic, DNA Binding, and Antimicrobial Studies on bis (1-amidino-O-alkylurea) Cu(II) Tartrate Complexes Where Alkyl = Methyl, Ethyl, n-Propyl, n-, or IsoButyl  

Microsoft Academic Search

Five New Cu(II) complexes, [bis(1-amidino-O-alkylurea) Cu(II)tartrate], where alkyl= methyl (1), ethyl (2), n-propyl (3), n-butyl (4), or iso-butyl (5) have been synthesized and characterized. The electron paramagnetic resonance spectra of complexes 1 and 2 showed features of mononuclear species whereas complexes 3, 4, and 5 in frozen DMSO solution show the existence of mononuclear and binuclear species in these complexes.

R. K. Hemakumar Singh; N. Shantibala Devi; L. Reena Devi; R. M. Kadam

2012-01-01

329

Synthesis, Spectroscopic, DNA Binding and Antimicrobial Studies on bis (1-amidino-O-alkylurea) Cu(II) tartrate complexes where alkyl = methyl, ethyl, n-propyl, n- or iso-butyl  

Microsoft Academic Search

Five New Cu(II) complexes, [bis(1-amidino-O-alkylurea)Cu(II)tartrate], where alkyl = methyl (1), ethyl (2), n-propyl (3), n-butyl (4) or iso-butyl (5) have been synthesized and characterized. The EPR spectra of complexes 1 and 2 showed features of mononuclear species whereas complexes 3, 4 and 5 in frozen DMSO solution show the existence of mononuclear and binuclear species in these complexes. Complexes crystallize

R. K. Hemakumar Singh; N. Shantibala Devi; L. Reena Devi; R. M. Kadam

2012-01-01

330

Efficacy of disodium 4-[( tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059), a free radical trapping agent, in a rat model of hemorrhagic stroke  

Microsoft Academic Search

Because free radical mechanisms may contribute to brain injury in hemorrhagic stroke, the effect of the free radical trapping agent disodium 4-[(tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059) was investigated on outcome following intracerebral hemorrhage (ICH) in rat. ICH was induced in 20 adult rats by infusion of collagenase into the caudate-putamen. Thirty minutes later rats were treated with NXY-059 (50 mg\\/kg subcutaneous plus

James Peeling; Marc R Del Bigio; Dale Corbett; A. Richard Green; David M Jackson

2001-01-01

331

A practical synthesis of ( S) 3- tert-Butoxycarbonylamino-2-oxo-2,3,4,5-tetrahydro-1,5-benzodiazepine-1-acetic acid methyl ester as a conformationally restricted dipeptido-Mimetic for caspase-1 (ICE) inhibitors  

Microsoft Academic Search

A simple and versatile method for the synthesis of (S) 3-tert-butoxycarbonylamino-2-oxo-2,3,4,5-tetrahydro-1,5-benzodiazepine-1-acetic acid methyl ester (4), a dipeptide mimetic, has been developed. The regioselective functionalization of the N1 and N5 ring nitrogens and the C3 amino group is demonstrated in the synthesis of an interleukin-1? converting enzyme inhibitor 13.

David J. Lauffer; Michael D. Mullican

2002-01-01

332

CYP2C8- and CYP3A-mediated C-demethylation of (3-{[(4-tert-butylbenzyl)-(pyridine-3-sulfonyl)-amino]-methyl}-phenoxy)-acetic acid (CP-533,536), an EP2 receptor-selective prostaglandin E2 agonist: characterization of metabolites by high-resolution liquid chromatography-tandem mass spectrometry and liquid chromatography/mass spectrometry-nuclear magnetic resonance.  

PubMed

CP-533,536, (3-{[(4-tert-butyl-benzyl)-(pyridine-3-sulfonyl)-amino]-methyl}-phenoxy)-acetic acid (1), an EP2 receptor-selective prostaglandin E2 agonist, is being developed to aid in the healing of bone fractures. To support the development of this program, in vitro metabolism of 1 was investigated in human liver microsomes and major recombinant human cytochrome P450 (P450) isoforms. 1 was metabolized in vitro by at least three recombinant human P450s: CYP3A4, CYP3A5, and CYP2C8. The turnover of 1 was NADPH-dependent and was completely inhibited by ketoconazole and quercetin in the CYP3A4/5 and CYP2C8 incubations, respectively. The major metabolic pathways were caused by oxidation of the tert-butyl moiety to form the omega-hydroxy metabolite (M4), oxidation of the pyridine moiety, and/or N-dealkylation of the methylphenoxy acetic acid moiety. The alcohol metabolite M4 was further oxidized to the corresponding carboxylic acid M3. In addition to these pathways, three unusual metabolites (M22, M23, and M26) resulting from C-demethylation of the tert-butyl group were identified using high-resolution liquid chromatography/tandem mass spectrometry and liquid chromatography/mass spectrometry/NMR. The C-demethylated metabolites were not detected on incubation of carboxylic acid metabolite M3 with either human liver microsomes or CYP3A/2C8 isoforms, suggesting that these metabolites were not derived from decarboxylation of M3. A possible mechanism for C-demethylation may involve the oxidation of M4 to form an aldehyde metabolite (M24), followed by P450-mediated deformylation, to give an unstable carbon-centered radical and formic acid. The carbon-centered radical intermediate then undergoes either oxygen rebound to form an alcohol metabolite M23 or hydrogen abstraction leading to an olefin metabolite M26. PMID:18653741

Prakash, Chandra; Wang, Weiwei; O'Connell, Thomas; Johnson, Kim A

2008-10-01

333

Fate of 3-tert-Butyl-4-hydroxyanisole, 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8- hexamethylcyclopenta(g)-2-benzopyrane and chlorpyrifos in a Conventional Wastewater Treatement Plant  

NASA Astrophysics Data System (ADS)

Emerging contaminants (ECs) are a major concern in the environment, particularly those found in waters. Wastewater treatment plants (WWTPs) play a key role in reducing the concentrations in the environment because compounds may be transformed under either aerobic or anaerobic conditions or may sorb to wastewater sludges and therefore be removed from waters. If these ECs are not contained or treated then effluent discharged from the WWTP and to a receiving stream may contain hazardous levels of these contaminants. Reported here is a study of the fate of three emerging contaminants (ECs): 3-tert-Butyl-4-hydroxyanisole (BHA), 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta(g)-2-benzopyrane (HHCB) and chlorpyrifos. Experiments were conducted on a laboratory scale by emulating conditions of a conventional WWTP in San Antonio, TX. The goal of the research was to determine general characteristics for both sorption (to wastewater sludges) and degradation. The sorption experiments were performed by exposing the sludge to a variety of initial concentration of ECs for 24 hours. After exposure these three ECs were extracted and analyzed using gas chromatography followed by flame ionization detector (GC/FID). Sorption experiments indicated that HHCB and chlorpyrifos are more hydrophobic than BHA and, therefore, would be mostly contained in the sludges. The degradation rates for these ECs were also considered for both aerobic and anaerobic conditions using different bench-scale reactor setups for 21 days. The differences between the reactor setups included volume of reactor, amount of sludge, mode of supply of nutrients and acclimatization of sludge to the ECs. One sludge was first acclimated to EC concentrations and then used in the experiment. The acclimated reactor had reaction rate constants approximately double that of the non-acclimated sludge reactor setups and followed first order reaction kinetics. Aerobic degradation occurred more readily for all three compounds than anaerobic degradation. These experiments supported the hypothesis that the WWTPs do capture and transform most of these compounds and, therefore, limit their reach to the effluent. However it cannot be supported that the compounds in the sludge phase are degraded to very low concentrations. Because of the changing dynamics of the sludge phase with time, further work needs to be conducted on the influence of time on sorption coefficients and, subsequently the effect of these temporal changes on degradation of these compounds.

Thomas, S. M.; Bodour, A.; Inniss, E. C.; Murray, K. E.

2007-12-01

334

Oxalic acid supported Si-18F-radiofluorination: one-step radiosynthesis of N-succinimidyl 3-(di-tert-butyl[18F]fluorosilyl)benzoate ([18F]SiFB) for protein labeling.  

PubMed

N-Succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB), a novel synthon for one-step labeling of proteins, was synthesized via a simple (18)F-(19)F isotopic exchange. A new labeling technique that circumvents the cleavage of the highly reactive active ester moiety under regular basic (18)F-labeling conditions was established. In order to synthesize high radioactivity amounts of [(18)F]SiFB, it was crucial to partially neutralize the potassium oxalate/hydroxide that was used to elute (18)F(-) from the QMA cartridge with oxalic acid to prevent decomposition of the active ester moiety. Purification of [(18)F]SiFB was performed by simple solid-phase extraction, which avoided time-consuming HPLC and yielded high specific activities of at least 525 Ci/mmol and radiochemical yields of 40-56%. In addition to conventional azeotropic drying of (18)F(-) in the presence of [K(+)?2.2.2.]C(2)O(4), a strong anion-exchange (SAX) cartridge was used to prepare anhydrous (18)F(-) for nucleophilic radio-fluorination omitting the vacuum assisted drying of (18)F(-). Using a lyophilized mixture of [K(+)?2.2.2.]OH resolubilized in acetonitrile, the (18)F(-) was eluted from the SAX cartridge and used directly for the [(18)F]SiFB synthesis. [(18)F]SiFB was applied to the labeling of various proteins in likeness to the most commonly used labeling synthon in protein labeling, N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB). Rat serum albumin (RSA), apo-transferrin, a ?-cell-specific single chain antibody, and erythropoietin were successfully labeled with [(18)F]SiFB in good radiochemical yields between 19% and 36%. [(18)F]SiFB- and [(18)F]SFB-derivatized RSA were directly compared as blood pool imaging agents in healthy rats using small animal positron emission tomography. Both compounds demonstrated identical biodistributions in healthy rats, accurately visualizing the blood pool with PET. PMID:22148255

Kostikov, Alexey P; Chin, Joshua; Orchowski, Katy; Niedermoser, Sabrina; Kovacevic, Miriam M; Aliaga, Antonio; Jurkschat, Klaus; Wängler, Bjoern; Wängler, Carmen; Wester, Hans-Jürgen; Schirrmacher, Ralf

2012-01-18

335

Fourier transform electron paramagnetic resonance study of the photoreduction of anthraquinone with 4-methyl-2,6-di-tert-butylphenol in alcoholic solutions  

SciTech Connect

Using FT-EPR following laser excitation, the primary photochemical process in the photoreduction of anthraquinone with 4-methyl-2,6-di-tert-butylphenol was investigated. High-resolved spin-polarized EPR spectra taken with nanosecond time resolution gave unambiguous evidence for a two-step hydrogen abstraction reaction, consisting of a primary electron transfer followed by proton abstraction with a time delay, which allows for a noticeable escape probability of the initially generated anthrasemiquinone radical anion (AQ{sup {sm_bullet}minus}). The time dependence of the EPR intensities of the neutral 10-hydroxy-anthroxyl radical (AQH{sup {sm_bullet}}) as well as of AQ{sup {sm_bullet}} could be simulated for the full experimentally accessible time interval of 10 ns to 100 {mu}s. The kinetic model used invokes optical spin polarization, spin-lattice relaxation, radical generation, and AQH{sup {sm_bullet}}AQ interconversion. In addition, from an analysis of the highly-resolved FT-EPR spectra a complete set of AQH{sup {sm_bullet}} hyperfine splitting (hfs) constants could be measured in two different alcohols for the first time. 30 refs., 4 figs., 2 tabs.

Plueschau, M.; Kroll, G. [Universitaet Dortmund (Germany); Dinse, K.P. [TH Darmstadt (Germany)] [and others

1992-10-29

336

Comparison of the effect of reactive and non-reactive steric stabilisers on the mechanism of film formation in methyl methacrylate\\/butyl acrylate copolymers latexes. Part 1. Differential scanning calorimetry, dynamic mechanical analysis and atomic force microscopy  

Microsoft Academic Search

A comparison of the film forming ability of methyl methacrylate (MMA)\\/butyl acrylate (BA) latex copolymers stabilised by either a reactive or a non-reactive steric stabiliser are reported. The study indicates the effects of constraining the stabiliser and change of the length of the hydrophilic ethylene oxide chain on the coalescence process. Segregation and diffusion of the stabiliser from the interfacial

Lynda A. Cannon; Richard A. Pethrick

2002-01-01

337

Differential distribution and placental transport of 2- and 3-t-(methyl-14C)butyl-4-hydroxyanisole (BHA) in pregnant mice  

SciTech Connect

The placental transport and localization in fetal and maternal tissues of 14C-BHA isomers, 2-t-(methyl-14C)butyl-4-hydroxyanisole (2-BHA) and 3-t-(methyl-14C)butyl-4-hydroxyanisole (3-BHA), were studied in pregnant mice by whole-body autoradiography techniques. BHA isomers were given (iv 50 microCi/100 g as a tracer dose) to pregnant mice at Day 11 (organogenesis) and Day 18 (postorganogenesis) of gestation. Peak levels of radioactivity occurred in various tissues 1-4 hr after iv administration of both isomers. 3-BHA and its metabolites have a higher affinity to fatty tissues and livers of pregnant mice. The concentration of radiocarbon in maternal liver and brown fat following treatment with 14C-3-BHA was much higher than the radioactivity concentration in the corresponding tissues of mothers treated with 2-BHA. On the other hand, the fetal concentration of radioactivity was higher in animals treated with 2-BHA than in those treated with 3-BHA. The radioactivity derived from both isomers accumulated in the fetal gastrointestinal tract. In both groups the radioactivity accumulated in the maternal nasal cavity and mucosa and the gastrointestinal contents. At 24 hr after treatment, retention of radioactivity in maternal lungs, amniotic fluid, and fetal gastrointestinal tissues was observed. Results from this study indicate that there are differences in the magnitude and extent of placental transport of 3-BHA and 2-BHA. Differences also exist in maternal organ uptake and radioactivity distribution of both isomers. Findings from this study are consistent with pharmacological differences existing between the isomers.

Ahmed, A.E.; Ansari, G.A.; Dencker, L.; Ullberg, S. (Univ. of Texas Medical Branch, Galveston (USA))

1991-02-01

338

Simulation of methyl tert-butyl ether (MTBE) transport to ground water from immobile sources of gasoline in the vadose zone  

USGS Publications Warehouse

The mathematical model, R-UNSAT, developed to simulate the transport of benzene and MTBE in representative sand and clay hydrogeologic systems was evaluated. The effects on groundwater were simulated for small, chronic-, and single-volume releases of gasoline trapped in unsaturated soil. Hydrocarbon biodegradation was simulated by using a dual Monod-type kinetics model that includes oxygen and the reactive constituents. MTBE was assumed to be non-reactive. For MTBE, infiltration had the greatest effect on transport to groundwater. Infiltration also affected mass losses of MTBE to the atmosphere, particularly, in fine-grained soils. Depth to groundwater and soil type primarily affected travel times of MTBE to groundwater, but could affect mass-loading rates to groundwater if infiltration is insignificant. For benzene, transport to groundwater was significant only if the depth to the water table was < 1 m or biodegradation was assumed to be negligible. Mass fluxed to groundwater were generally smaller for benzene than for MTBE by more than two orders of magnitude. Thus, water that recharges an aquifer beneath a spill can be enriched in MTBE relative to benzene when compared to the composition of water in equilibrium with gasoline.

Lahvis, M.A.; Rehmann, L.C.

1999-01-01

339

RELATIONS BETWEEN THE DETECTION OF METHYL TERT-BUTYL ETHER (MTBE) IN SURFACE AND GROUND WATER AND ITS CONTENT IN GASOLINE  

E-print Network

AND ITS CONTENT IN GASOLINE By Michael J. Moran, Mike J. Halde, Rick M. Clawges and John S. Zogorski U in the United States as an octane enhancer and oxygenate in gasoline. Octane enhancement began in the late 1970's with the phase-out of tetraethyl lead from gasoline. The use of oxygenates was expanded

340

Relations between the detection of methyl tert-butyl ether (MTBE) in surface and ground water and its content in gasoline  

USGS Publications Warehouse

The relations between the content of MTBE in gasoline and the detection frequency of MTBE in ground and surface water were analyzed using the percent by volume of MTBE in gasoline provided by NIPER. For groundwater, 21 metropolitan areas had information on detection frequency and percent volume of MTBE in gasoline, while for surface water, only 9 metropolitan areas had this information. For groundwater, three cities, i.e., Columbia, SC, Harrisburg, PA, and Norfolk, VA, had values of MTBE in gasoline for only 2 sampling periods and had a MTBE in gasoline for only 2 sampling periods. The frequency of detection of MTBE in surface and ground water had a positive relation to content of MTBE in gasoline. The occurrence of the fuel additive MTBE in ground and surface water was related to its issue in gasoline. The frequency of detection of MTBE was higher in areas that use greater amounts of MTBE in gasoline. As the percent by volume of MTBE in gasoline increased, the frequency of detection of MTBE in ground and surface water increased.

Moran, M.J.; Halde, M.J.; Clawges, R.M.; Zogorski, J.S.

2000-01-01

341

Synthesis and X-ray structural characterization of a series of dimeric [Hg2(SePh)2X2(PR2R?)2] compounds (R = tert-butyl; R? = 4-N,N-dimethylaniline and X = Cl, Br, I, SCN, SePh)  

NASA Astrophysics Data System (ADS)

This article presents the syntheses and characterization of five new compounds with the general formula [Hg2(SePh)2X2(PR2R?)2] (R = tert-butyl; R? = 4-N,N-dimethylaniline), where X = Cl (1a), Br (1b), I (1c), SCN (2), SePh (3). The compounds crystallized as dimeric {HgSe} units, although most of these chalcogenolate compounds appeared to be polymeric adamantanoid or fused adamantanoid species. The ligand structures of these compounds limited the growth of the molecular structures and promoted the formation of the dimeric form alone. The mercury centers were connected to one another through one ?-Cl and one ?-SePh bridge in 1a, and through two ?-SePh bridges in 1b, 1c, 2, and 3. The compounds were characterized by single crystal X-ray diffractometry, TGA, elemental analysis, and infrared spectroscopy.

Stieler, Rafael; Faoro, Eliandro; Cechin, Camila Nunes; Floriano, Luana; Lang, Ernesto Schulz

2015-01-01

342

Discovery, synthesis, and structure-based optimization of a series of N-(tert-butyl)-2-(N-arylamido)-2-(pyridin-3-yl) acetamides (ML188) as potent non-covalent small molecule inhibitors of the severe acute respiratory syndrome coronavirus (SARS-CoV) 3CL protease  

PubMed Central

A high-throughput screen of the NIH molecular libraries sample collection and subsequent optimization of a lead dipeptide-like series of severe acute respiratory syndrome (SARS) main protease (3CLpro) inhibitors led to the identification of probe compound ML188 (16-(R), (R)-N-(4-(tert-butyl)phenyl)-N-(2-(tert-butylamino)-2-oxo-1-(pyridin-3-yl)ethyl)furan-2-carboxamide, Pubchem CID: 46897844). Unlike the majority of reported coronavirus 3CLpro inhibitors that act via covalent modification of the enzyme, 16-(R) is a non-covalent SARS-CoV 3CLpro inhibitor with moderate MW and good enzyme and antiviral inhibitory activity. A multi-component Ugi reaction was utilized to rapidly explore structure activity relationships within S1?, S1, and S2 enzyme binding pockets. The X-ray structure of SARS-CoV 3CLpro bound with 16-(R) was instrumental in guiding subsequent rounds of chemistry optimization. 16-(R) provides an excellent starting point for the further design and refinement of 3CLpro inhibitors that act by a non-covalent mechanism of action. PMID:23231439

Jacobs, Jon; Tokars, Valerie; Zhou, Ya; Turlington, Mark; Saldanha, S. Adrian; Chase, Peter; Eggler, Aimee; Dawson, Eric S.; Baez-Santos, Yahira M.; Tomar, Sakshi; Mielech, Anna M.; Baker, Susan C.; Lindsley, Craig W.; Hodder, Peter; Mesecar, Andrew; Stauffer, Shaun R.

2013-01-01

343

Ultrasonic velocities, densities, and excess molar volumes of binary mixtures of N, N-dimethyl formamide with methyl acrylate, or ethyl acrylate, or butyl acrylate, or 2-ethyl hexyl acrylate at T = 308.15 K  

Microsoft Academic Search

Ultrasonic velocities, u, densities, ?, of binary mixtures of N,N-dimethyl formamide (DMF) with methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), and 2-ethyl hexyl acrylate (EHA), including pure liquids, over the entire composition range have been measured at T=308.15K. Using the experimental results, the excess molar volume, VmE, partial molar volumes, V¯m,1, V¯m,2, and excess partial molar volumes, V¯m,1E,

M. Kondaiah; D. Sravana Kumar; K. Sreekanth; D. Krishna Rao

2011-01-01

344

Study on the Growth and Photosynthetic Characteristics of Wheat Seedlings Under [C4mim][OAc] (1-butyl-3-methyl-imidazolium acetate) with Cd (2+) Stress.  

PubMed

In this paper, the joint effect of 0.5 mmol·L(-1) Cd(2+) and various concentrations (50-400 mg·L(-1)) of the ionic liquid 1-butyl-3-methyl-imidazolium acetate ([C4min][OAc]) on the growth and photosynthetic performance of wheat seedlings in hydroponic culture was investigated. Seedlings grown in presence of Cd(2+) and [C4min][OAc] showed significant (p < 0.05) improvement in growth (shoot and root lengths and dry weights) and photosynthetic performance (photosynthetic rate, stomatal conductance, transpiration rate, and chlorophyll a but not chlorophyll b) compared to seedlings grown in the presence of Cd(2+) but without [C4min][OAc]. However, this only happened under the lower range of [C4min][OAc] concentrations (50-200 mg·L(-1)). In addition, significant reduction in the level of Cd(2+) was also observed in the leaf tissue of wheat seedlings grown in the presence of 0.5 mmol·L(-1) Cd(2+) and 100 mg·L(-1) [C4min][OAc]. Overall, Cd(2+) exerted a stronger inhibition than [C4min][OAc] on the growth and photosynthetic performance of wheat seedlings. However, when both Cd(2+) and [C4min][OAc] were present in the culture, the toxicity of Cd(2+) could be mitigated by lower concentrations of [C4mim][OAc]. This phenomenon could be due to [C4mim][OAc] forming metal complexes with Cd(2+), thus reducing the toxicity of Cd(2+). PMID:25778420

Chen, Zhonglin; Feng, Yingying; Wang, Yan; Li, Yue; Liu, Qiang; Xu, Sunan; Guan, Wei

2015-05-01

345

Cunninghamella as a microbiological model for metabolism of histamine H(3) receptor antagonist 1-[3-(4-tert-butylphenoxy)propyl]piperidine.  

PubMed

The aim of the study was to analyze the ability of the microorganism Cunninghamella to carry out the biotransformation of 1-[3-(4-tert-butylphenoxy)propyl]piperidine (DL76) and to compare the obtained results with in silico models. Biotransformation was carried out by three strains of filamentous fungus: Cunninghamella echinulata, Cunninghamella blakesleeana, and Cunninghamella elegans. Most probable direction of DL76 metabolic transition was the oxidation of the methyl group in the tert-butyl moiety leading to the formation of the metabolite with I° alcohol properties. This kind of reaction was conducted by all three strains tested. However, only in the case of C. blakesleeana that biotransformation product had a structure of carboxylic acid. CYP2C19 was identified by Metasite software to be the isoform of major importance in the oxidation process in the tert-butyl moiety of DL76. In silico data coincide with the results of experiments conducted in vitro. It was confirmed that Cunninghamella fungi are a very good model to study the metabolism of xenobiotics. The computational methods and microbial models of metabolism can be used as useful tools in early ADME-Tox assays in the process of developing new drug candidates. PMID:22983742

P?kala, El?bieta; Kubowicz, Paulina; ?a?ewska, Dorota

2012-11-01

346

Ethers from ethanol. 4: Kinetics of the liquid-phase synthesis of two tert-hexyl ethyl ethers  

SciTech Connect

Tertiary ethers produced from reactive C{sub 5} and C{sub 6} olefins and ethanol or methanol are being investigated as oxygenate gasoline additives in addition to isobutylene-derived methyl tert-butyl ether and ethyl tert-butyl ether. The kinetics of liquid-phase etherification and accompanying isomerization of four reactive C{sub 6} olefin isomers with ethanol catalyzed by the ion-exchange resin catalyst Amberlyst 15 were determined at temperatures from 313 to 353 K and a pressure of 0.69 MPa in a differential packed-bed reactor. Rate expressions in terms of species activities, with the activity coefficients determined by the UNIFAC method, were developed to correlate the experimental data over a wide range of compositions. The rate expressions are based on the Langmuir-Hinshelwood-Hougen-Watson formalism involving a dual-site surface etherification reaction and a single-site surface isomerization reaction as the rate-limiting steps, along with the assumption of ethanol as the most abundant surface species. The negligibility of olefins and ether adsorption terms, but the nonnegligibility of vacant sites, was confirmed by independent liquid-phase adsorption experiments. The developed rate expressions were finally tested in an integral reactor and found to be accurate.

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

1995-07-01

347

Differential effect of methyl-, butyl- and propylparaben and 17?-estradiol on selected cell cycle and apoptosis gene and protein expression in MCF-7 breast cancer cells and MCF-10A non-malignant cells.  

PubMed

Parabens are alkyl esters of p-hydroxybenzoic acid used widely as antimicrobial preservatives in consumer products, including pharmaceuticals, foods and cosmetics. We showed previously that methyl-, butyl- and propylparaben parabens, even at low doses, stimulate the proliferation of MCF-7 breast cancer cells and non-transformed MCF-10A breast epithelial cells. The present study was undertaken to determine whether this represents a direct effect on cell cycle and apoptotic gene expression. MCF-7 and MCF-10A cells were exposed to methyl, butyl- and propylparaben (20?nm) or 17?-estradiol (10?nm). Cell cycle and apoptotic gene expression were evaluated by real-time polymerase chain reaction and protein expression by Western blot. 17?-estradiol upregulated G1 /S phase genes and downregulated cell cycle progression inhibitors in both MCF-7 and MCF-10A. Upregulation of Bcl-xL and downregulation of caspase 9 was observed in MCF-7, while upregulation of Bcl-xL, BCL2L2 and caspase 9 was noted in MCF-10A. Cyclins in MCF-7 cells were not affected by any of the parabens. Methyl- and butylparaben had no effect on the expression of selected apoptotic genes in MCF-7. In MCF-10A, all parabens tested increased the expression of G1 /S phase genes, and downregulated cell cycle inhibitors. Methylparaben increased pro-survival gene. Butylparaben increased BCL2L1 gene, as did 17?-estradiol, while propylparaben upregulated both the extrinsic and intrinsic apoptotic pathways. There are differences in cell cycle and apoptosis gene expression between parabens and 17?-estradiol in MCF-7 cells. In MCF-10A cells, most of the genes activated by parabens were comparable to those activated by 17?-estradiol. PMID:24481588

Wróbel, Anna Maria; Gregoraszczuk, Ewa ?ucja

2014-09-01

348

Depigmentation with t ert Butyl Hydroquinone using Black Guinea Pigs  

Microsoft Academic Search

tert-Butyl hydroquinone (TBHQ) has important and functional uses in consumer and commercial applications, some of which involve human exposure primarily through dermal contact. To assist in the safety evaluation of TBHQ, this study was conducted to determine whether TBHQ would produce changes in skin pigmentation after repeated dermal application to black guinea pigs. Hydroquinone (HQ) and hydroquinone monomethyl ether (HQMME)

E Patrick; D. R Juberg; J O'Donoghue; H. I Maibach

1999-01-01

349

Pharmacological characterization of N-tert-butyl-N'-[2-(4'-methylphenylamino)-5-nitrobenzenesulfonyl]urea (BM-573), a novel thromboxane A2 receptor antagonist and thromboxane synthase inhibitor in a rat model of arterial thrombosis and its effects on bleeding time.  

PubMed

The present study was undertaken to characterize the antiplatelet and antithrombotic effects of BM-573 [N-tert-butyl-N'-[2-(4'-methylphenylamino)-5-nitrobenzenesulfonyl]urea], an original combined thromboxane receptor antagonist and thromboxane synthase inhibitor in rats, and to determine its effects on mice bleeding time. Intraperitoneal injection of a single dose of 5 mg/kg BM-573 to rats inhibited U-46619 (9,11-dideoxy-9,11-methanoepoxy-prostaglandin F(2))-induced washed platelet aggregation 30 min and 1, 2, and 4 h after drug administration with a maximum antiplatelet effect observed after 1 and 2 h. In a rat model of thrombosis induced by ferric chloride application on the abdominal aorta, BM-573 significantly reduced the thrombus weight by 92.53, 80.20, 64.75, and 18.21% at doses of 5, 2, 0.5, and 0.2 mg/kg, respectively. Time to occlusion of abdominal aorta in the BM-573-treated group (41.50 +/- 5.21 min) was significantly prolonged compared with the vehicle-treated rats (16.16 +/- 0.79 min). Like furegrelate, seratrodast, and acetylsalicylic acid, BM-573 did not affect the tail bleeding time induced by tail transection in mice compared with vehicle-treated mice. Moreover, BM-573, a close derivative of the loop diuretic torasemide, failed to induce a significant increase in diuresis in rat and did not produce a decrease in blood glucose concentration as observed with the sulfonylurea glibenclamide. In conclusion, we have demonstrated that the nitrobenzenic sulfonylurea BM-573, an original combined thromboxane receptor antagonist and thromboxane synthase inhibitor, is a potent antithrombotic agent that does not affect bleeding time. Moreover, BM-573 lost the diuretic property of torasemide and has no impact on glycemia. PMID:14742735

Dogné, Jean-Michel; Hanson, Julien; de Leval, Xavier; Kolh, Philippe; Tchana-Sato, Vincent; de Leval, Laurence; Rolin, Stéphanie; Ghuysen, Alexandre; Segers, Patrick; Lambermont, Bernard; Masereel, Bernard; Pirotte, Bernard

2004-05-01

350

Analysis of the antioxidant butylated hydroxytoluene (BHT) in water by means of solid phase extraction combined with GC\\/MS  

Microsoft Academic Search

The antioxidant 3,5-di-tert-butyl-4-hydroxy-toluene (BHT) is widely used as an additive to increase the tenability of food and plastics. BHT is degraded to 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) in mammals, as well as in the natural environment such as in water and soils. BHT-CHO has been studied extensively in terms of their potential toxicities. The present investigation was carried out to quantify BHT and

Elke Fries; Wilhelm Püttmann

2002-01-01

351

Studies of the degradation mechanism of organic light-emitting diodes based on tris(8-quinolinolate)aluminum Alq and 2-tert-butyl-9,10-di(2-naphthyl)anthracene TBADN  

NASA Astrophysics Data System (ADS)

Previously, radical cation of tris(8-quinolinolate)aluminum (Alq•+) has been associated with the instability of Alq films subjected to holes-only electrical current. Yet, the questions remain (i) whether Alq•+ is the primary source of the intrinsic degradation of bipolar organic light-emitting diodes (OLEDs) based on Alq, (ii) whether Alq•+ reactions result in deep charge traps in holes-only devices as found in bipolar counterparts, and (iii) whether radical cations can be a common source of degradation of OLEDs irrespective of materials. With regards to generality of hole-current-related degradation, it is interesting to examine the behavior of 9,10-diarylanthracenes (DAAs)—the practically important class of blue-fluorescing light-emitting-layer hosts. These questions prompted our comparative study of the effects of unipolar currents in Alq and 2-t-butyl-9,10-di(2-naphthyl)anthracene (TBADN), which was chosen as a representative material of the DAA class. First, we identified device structures allowing for rigorous and stable unipolar conduction. Interestingly, even in pristine holes-only devices, our voltammetric measurements indicated that Alq contains a substantial density of deep hole traps (far deeper than what can be explained by energetic disorder), which can be charged by passing holes-only current and seemingly discharged by exposure to white light. As for aged holes-only Alq devices, they exhibited symptoms qualitatively matching those of aged bipolar Alq devices, viz., photoluminescence (PL) loss, transition voltage (V0) rise, and drive voltage (Vd) rise. Notably, PL and V0 are linearly correlated in both holes-only and bipolar devices, which reinforces the supposed link between Alq•+ and the degradation in both types of devices. Yet, there are indications the Alq•+ instability may not be the only degradation pathway in bipolar devices. Even though our observations for holes-only Alq devices agree qualitatively with previously reported ones, we observe far slower degradation rates [Alq PL fades up to ˜500 times slower in holes-only devices, while Alq electroluminescence (EL) fades ˜50 times slower in bipolar control devices]. It is possible that impurities play a significant, perhaps crucial role in the degradation mechanism of both bipolar and holes-only devices, especially the relatively shorter-lived ones. In sharp contrast to Alq, all three observables (PL, V0, and Vd) indicate that holes-only current in TBADN (neat or doped with a perylene-based blue dopant) does not result in degradation in the time that is sufficient for the corresponding bipolar control devices to lose 60%-80% of EL and 20%-30% of PL. We find that the electrons-only current in Alq or TBADN does not result in degradation either. Thus, the degradation of Alq and DAA bipolar devices may be caused by fundamentally dissimilar mechanisms: while hole current may damage the former, it does not appear to affect the latter, suggesting that the initiation step is different.

Jarikov, Viktor V.; Kondakov, Denis Y.

2009-02-01

352

Final amended report on the safety assessment of Ammonium Thioglycolate, Butyl Thioglycolate, Calcium Thioglycolate, Ethanolamine Thioglycolate, Ethyl Thioglycolate, Glyceryl Thioglycolate, Isooctyl Thioglycolate, Isopropyl Thioglycolate, Magnesium Thioglycolate, Methyl Thioglycolate, Potassium Thioglycolate, Sodium Thioglycolate, and Thioglycolic Acid.  

PubMed

This safety assessment includes Ammonium and Glyceryl Thioglycolate and Thioglycolic Acid Butyl, Calcium, Ethanolamine, Ethyl, Isooctyl, Isopropyl, Magnesium, Methyl, Potassium, and Sodium Thioglycolate, as used in cosmetics. Thioglycolates penetrate skin and distribute to the kidneys, lungs, small intestine, and spleen; excretion is primarily in urine. Thioglycolates were slightly toxic in rat acute oral toxicity studies. Thioglycolates are minimal to severe ocular irritants. Thioglycolates can be skin irritants in animal and in vitro tests, and can be sensitizers. A no-observable-adverse-effect level for reproductive and developmental toxicity of 100 mg/kg per day was determined using rats. Thioglycolates were not mutagenic, and there was no evidence of carcinogenicity. Thioglycolates were skin irritants in some clinical tests. Clinically significant adverse reactions to these ingredients used in depilatories are not commonly seen, suggesting current products are formulated to be practically nonirritating under conditions of recommended use. Formulators should take steps necessary to assure that current practices are followed. PMID:19636068

Burnett, Christina L; Bergfeld, Wilma F; Belsito, Donald V; Klaassen, Curtis D; Marks, James G; Shank, Ronald C; Slaga, Thomas J; Snyder, Paul W; Andersen, F Alan

2009-01-01

353

DNA cleavage by metabolites of butylated hydroxytoluene.  

PubMed

The effect of butylated hydroxytoluene (BHT) and its metabolites on DNA cleavage in vitro was studied with supercoiled plasmid DNA, pUC18, by agarose gel electrophoresis. Among several BHT metabolites, 2,6-di-t-butyl-p-benzoquinone (BHT-quinone) caused cleavage of supercoiled DNA (form I) at a concentration as low as 1 x 10(-6) M. The relative amount of linear form (form III) was increased with increasing concentration of BHT-quinone. 2,6-Di-t-butyl-4-hydroperoxy-4-methyl-2,5-cyclohexadienone (BHT-peroxyquinol) and 3,5-di-t-butyl-4-hydroxybenzaldehyde (BHT-CHO) also cleaved DNA, but to a lesser extent than BHT-quinone. No DNA cleavage was detected by BHT, 2,6-di-t-butyl-4-hydroxymethyl phenol (BHT-OH), 3,5-di-t-butyl-4-hydroxybenzoic acid (BHT-COOH), 2,6-di-t-butyl-4-hydroxy-4-methyl-2,5-cyclohexadienone (BHT-quinol) or 2,6-di-t-butyl-4-methylene-2,5-cyclohexadienone (BHT-quinone methide). The DNA cleavage by BHT-quinone was inhibited by oxygen radical scavengers including superoxide dismutase (SOD), catalase, polyethylene glycol, t-butyl alcohol, dimethyl sulfoxide, sodium azide, sodium benzoate, bovine serum albumin and methionine, while it was enhanced by the addition of FeCl2. The production of superoxide radical in a solution of BHT-quinone was confirmed by cytochrome c reduction assay. Superoxide was not produced by BHT or other BHT metabolites except for BHT-quinone. These results suggest that BHT-quinone, one of the principal metabolites of BHT, cleaves DNA strands via its generation of oxygen radicals.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8285854

Nagai, F; Ushiyama, K; Kano, I

1993-01-01

354

Ethers from ethanol. 3: Equilibrium conversion and selectivity limitations in the liquid-phase synthesis of two tert-hexyl ethyl ethers  

SciTech Connect

Alternatives to the conventional isobutylene-derived ethers, namely methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), are being explored, e.g., those produced from a combination of the branched C{sub 5} and C{sub 6} olefins with methanol or biomass-based ethanol. The conversion and selectivity of these ethers are thermodynamically limited. This paper, thus, describes the determination and analysis of the equilibrium limitations in the liquid-phase synthesis of two of the three possible isomers of tert-hexyl ethyl ether (THEE) from reactive C{sub 6} olefins and ethanol in the temperature range 298--353 K. The coupled reaction network for either of these two ethers involves two simultaneous esterification and one isomerization reactions, all being reversible. The equilibrium constants for these reactions, experimentally determined from equilibrium composition and the corresponding activity coefficients estimated by the UNIFAC method, decrease in the following order of tertiary olefins: 2M1P > isobutylene < 2,3DM1B {approx} 2M1B > 2M2P > 2M2B > 2,3DM2B for etherification reactions with ethanol, and (2,3DM1B {r_reversible} 2,3DM2B) > (2M1B {r_reversible} 2M2B) > (2M1P {r_reversible} 2M2P) for the isomerization reactions. This is explained on the basis of the relative stability of these olefins. The developed correlations are used to study the influence of process variables on the equilibrium conversion and selectivity of THEE formation.

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

1995-07-01

355

76 FR 77709 - Butyl acrylate-methacrylic acid-styrene polymer; Tolerance Exemption  

Federal Register 2010, 2011, 2012, 2013, 2014

...FRL-9327-6] Butyl acrylate-methacrylic acid-styrene polymer; Tolerance Exemption...tolerance for residues of 2-Propenoic acid, 2-methyl-, polymer with butyl 2-propenoate...also known as butyl acrylate-methacrylic acid-styrene polymer when used as an...

2011-12-14

356

27 CFR 21.101 - tert-Butyl alcohol.  

Code of Federal Regulations, 2011 CFR

...of 60° Bé1. gasoline. (e) Freezing point (first needle). Above 20 °C...this solution to 80 ml of distilled water, and filter when cool). Heat the mixture just to the boiling point and remove from the flame. A...

2011-04-01

357

27 CFR 21.101 - tert-Butyl alcohol.  

Code of Federal Regulations, 2010 CFR

...above 85 °C. More than 95 percent should distill between 81 °?83 °C. (d) Dryness at 20 °C. Miscible without turbidity with 19 volumes of 60° Bé1. gasoline. (e) Freezing point (first needle). Above 20 °C. (f)...

2010-04-01

358

27 CFR 21.101 - tert-Butyl alcohol.  

Code of Federal Regulations, 2014 CFR

...above 85 °C. More than 95 percent should distill between 81 °?83 °C. (d) Dryness at 20 °C. Miscible without turbidity with 19 volumes of 60° Bé1. gasoline. (e) Freezing point (first needle). Above 20 °C. (f)...

2014-04-01

359

27 CFR 21.101 - tert-Butyl alcohol.  

Code of Federal Regulations, 2012 CFR

...above 85 °C. More than 95 percent should distill between 81 °?83 °C. (d) Dryness at 20 °C. Miscible without turbidity with 19 volumes of 60° Bé1. gasoline. (e) Freezing point (first needle). Above 20 °C. (f)...

2012-04-01

360

Butylated hydroxyanisole and lung tumor development in A/J mice  

SciTech Connect

A diet containing 0.75% butylated hydroxyanisole (BHA) did not enhance the development of lung tumors in A/J mice if fed for 8 weeks after administration of urethane, benzo(a)pyrene (B(a)P), or dimethylnitrosamine (DMN). Prefeeding animals with BHA partially protected animals against the tumorigenic effect of urethane and B(a)P. Partial protection was also seen in animals given B(a)P and then exposed to BHA in the diet. The two isomers of BHA 3-tert.-butyl-4-hydroxyanisole and 2-tert.-butyl-4-hydroxyanisole) were synthesized and injected ip. They failed to enhance lung tumor development. It is concluded that BHA is not a promoting agent as is butylated hydroxytoluene (BHT) for lung tumors in mice. One possible explanation is that BHA in the diet does not produce the extensive cell proliferation seen in the lungs of mice fed BHT. 19 references, 5 tables.

Witschi, H.R.; Doherty, D.G.

1984-01-01

361

4-tert-Butyl-4?-(4-meth­oxy­phen­yl)-3?-(4-methyl­phen­yl)-1,2,3,4-tetra­hydro­spiro­[naphthalene-2,5?(4?H)-1,2-oxazol]-1-one  

PubMed Central

In the title compound, C30H31NO3, the tolyl ring is almost coplanar with the isoxazole ring [dihedral angle = 12.51?(7)°], whereas the meth­oxy­phenyl ring is almost perpendicular to the isoxazole ring [dihedral angle = 89.77?(5)°]. In the crystal, mol­ecules are connected through C—H?O hydrogen bonds, forming chains running along the a axis. PMID:21589194

Akhazzane, Mohamed; Zouihri, Hafid; Daoudi, Maria; Kerbal, Abdelali; Al Houari, Ghali

2010-01-01

362

Volumetric Properties of the Mixture 1,1,2-Trichlorotrifluoroethane C2Cl3F3 + C5H12O tert-Butyl methyl ether (LB2724, VMSD1111)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Binary Liquid Systems of Nonelectrolytes' of Volume 23 `Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV `Physical Chemistry'. It corresponds to the data set LB2724 of the ELBT database.

Cibulka, I.; Hn?dkovský, L.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

363

Volumetric Properties of the Mixture 1,1,2-Trichlorotrifluoroethane C2Cl3F3 + C5H12O tert-Butyl methyl ether (LB2695, VMSD1212)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Binary Liquid Systems of Nonelectrolytes' of Volume 23 `Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV `Physical Chemistry'. It corresponds to the data set LB2695 of the ELBT database.

Cibulka, I.; Hn?dkovský, L.; Fontaine, J.-C.; Sosnkowska-Kehiaian, K.; Kehiaian, H. V.

364

Toxicology and biochemistry of butylated hydroxyanisole and butylated hydroxytoluene  

Microsoft Academic Search

Butylated hydroxyanisole and butylated hydroxytoluene are used extensively as food antioxidants. It is estimated that man\\u000a consumes ca. 0.1 mg\\/kg body wt daily of these antioxidants. At levels 500 times this level (50 mg\\/kg\\/day), both butylated\\u000a hydroxyanisole and butylated hydroxytoluene appear to be free of any obviously injurious effects. However, at larger doses\\u000a (500 mg\\/kg\\/day), both butylated hydroxyanisole and butylated

A. L. Branen

1975-01-01

365

Regulation of the human catalytic subunit of telomerase (hTERT)  

PubMed Central

Over the past decade, there has been much interest in the regulation of telomerase, the enzyme responsible for maintaining the integrity of chromosomal ends, and its crucial role in cellular immortalization, tumorigenesis, and the progression of cancer. Telomerase activity is characterized by the expression of the telomerase reverse transcriptase (TERT) gene, suggesting that TERT serves as the major limiting agent for telomerase activity. Recent discoveries have led to characterization of various interactants that aid in the regulation of human TERT (hTERT), including numerous transcription factors; further supporting the pivotal role that transcription plays in both the expression and repression of telomerase. Several studies have suggested that epigenetic modulation of the hTERT core promoter region may provide an additional level of regulation. Although these studies have provided essential information on the regulation of hTERT, there has been ambiguity of the role of methylation within the core promoter region and the subsequent binding of various activating and repressive agents. As a result, we found it necessary to consolidate and summarize these recent developments and elucidate these discrepancies. In this review, we focus on the co-regulation of hTERT via transcriptional regulation, the presence or absence of various activators and repressors, as well as the epigenetic pathways of DNA methylation and histone modifications. PMID:22381618

Daniel, Michael; Peek, Gregory W.; Tollefsbol, Trygve O.

2012-01-01

366

Synthesis of a chiral calixarene: 5,11,17,23-tetra ( tert -butyl)-25,27-bis[((+)-camphor-10-sulfonyl)-oxy]-calix[4]arene-26,28-diol: crystal and molecular structure of its (1?2) complex with toluene  

Microsoft Academic Search

The title compound was obtained by treatment ofp-tert-butylcalix[4]arene with (+) camphorsulfonyl chloride in triethylamine and toluene. A (1:2) complex with toluene has been found. Its structure has been determined by X-ray crystallography. Crystals are triclinic with space group P1,a=16.426(3),b=18.553(3),c=13.661(2) Å, a=94.78(2), ß=110.76(2), ?=72.83(2)°,V=3720(2) Å3,dc=1.127 g\\/cm3Z=2. Refinement based on 10495 observed reflections led to a finalR value of 0.100. The two

Laure Motta; Jean-Bernard Regnouf De Vains; Claude Bavoux; Monique Perrin

1995-01-01

367

Microsolvation and sp2-stereoinversion of monomeric ?-(2,6-di-tert-butylphenyl)vinyllithium as measured by NMR  

PubMed Central

Summary The ?-unsubstituted title compound dissolves in THF as a uniformly trisolvated monomer, whereas it forms exclusively disolvated monomers in tert-butyl methyl ether, Et2O, TMEDA, or toluene with TMEDA (1.4 equiv). This was established at low temperatures through the observation of separated NMR signals for free and lithium-coordinated ligands and/or through the patterns and magnitudes of 13C,6Li NMR coupling constants. An aggregated form was observed only with Et2O (2 equiv) in toluene as the solvent. The olefinic geminal interproton coupling constants of the H2C= part can be used as a secondary criterion to differentiate between these differently solvated ground-states (3, 2, or <2 coordinated ligands per Li). Due to a kinetic trisolvation privilege of THF, the cis/trans sp2-stereoinversion rates could be measured through analyses of 1H NMR line broadening and coalescence only in THF as the solvent: The pseudomonomolecular (because THF-catalyzed), ionic mechanism is initialized by a C–Li bond heterolysis with the transient immobilization of one additional THF ligand, followed by stereoinversion of the quasi-sp2-hybridized carbanionic center in cooperation with a “conducted tour” migration of Li+(THF)4 along the ?-aryl group within the solvent-separated ion pair. PMID:25383123

Knittl, Monika; Rossmann, Eva C

2014-01-01

368

Microsolvation and sp(2)-stereoinversion of monomeric ?-(2,6-di-tert-butylphenyl)vinyllithium as measured by NMR.  

PubMed

The ?-unsubstituted title compound dissolves in THF as a uniformly trisolvated monomer, whereas it forms exclusively disolvated monomers in tert-butyl methyl ether, Et2O, TMEDA, or toluene with TMEDA (1.4 equiv). This was established at low temperatures through the observation of separated NMR signals for free and lithium-coordinated ligands and/or through the patterns and magnitudes of (13)C,(6)Li NMR coupling constants. An aggregated form was observed only with Et2O (2 equiv) in toluene as the solvent. The olefinic geminal interproton coupling constants of the H2C= part can be used as a secondary criterion to differentiate between these differently solvated ground-states (3, 2, or <2 coordinated ligands per Li). Due to a kinetic trisolvation privilege of THF, the cis/trans sp(2)-stereoinversion rates could be measured through analyses of (1)H NMR line broadening and coalescence only in THF as the solvent: The pseudomonomolecular (because THF-catalyzed), ionic mechanism is initialized by a C-Li bond heterolysis with the transient immobilization of one additional THF ligand, followed by stereoinversion of the quasi-sp(2)-hybridized carbanionic center in cooperation with a "conducted tour" migration of Li(+)(THF)4 along the ?-aryl group within the solvent-separated ion pair. PMID:25383123

Knorr, Rudolf; Knittl, Monika; Rossmann, Eva C

2014-01-01

369

Autoxidation of methyl linoleate initiated by the ozonide of allylbenzene  

SciTech Connect

Allylbenzene ozonide (ABO), a model for polyunsaturated fatty acid (PUFA) ozonides, initiates the autoxidation of methyl linoleate (18:2 ME) at 37 degrees C under 760 torr of oxygen. This process is inhibited by d-alpha-tocopherol (alpha-T) and 2,6-di-tert-butyl-4-methylphenol (BHT). The autoxidation was followed by the appearance of conjugated diene (CD), as well as by oxygen-uptake. The rates of autoxidation are proportional to the square root of ABO concentration, implying that the usual free radical autoxidation rate law is obeyed. Activation parameters for the thermal decomposition of ABO were determined under N2 in the presence of radical scavengers and found to be Ea = 28.2 +/- 0.3 kcal mol-1 and log A = 13.6 +/- 0.2; kd (37 degrees C) is calculated to be (5.1 +/- 0.3) X 10(-7) sec-1. Autoxidation data are also reported for ozonides of 18:2 ME and methyl oleate (18:1 ME).

Ewing, J.C.; Cosgrove, J.P.; Giamalva, D.H.; Church, D.F.; Pryor, W.A. (Louisiana State Univ., Baton Rouge (USA))

1989-07-01

370

Analysis of Organic Molecules Extracted from Mars Analogues and Influence of Their Mineralogy Using N-Methyl-N-(tert-butyldimethylsilyl)Trifluoroacetamide Derivatization Coupled with Gas Chromatography Mass Spectrometry in Preparation for the Sample Analysis at Mars Derivatization Experiment on the Mars Science Laboratory Mission  

NASA Technical Reports Server (NTRS)

The search for complex organic molecules on Mars, including important biomolecules such as amino acids and carboxylic acids will require a chemical extraction and derivatization step to transform these organic compounds into species that are sufficiently volatile to be detected by gas chromatography mass spectrometry (GCMS). We have developed, a one-pot extraction and chemical derivatization protocol using N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) and dimethylformamide (DMF) for the Sample Analysis at Mars (SAM) experiment on the Mars Science Laboratory (MSL). The temperature and duration the derivatization reaction, pre-concentration of chemical derivatives, and gas chromatographic separation parameters have been optimized under SAM instrument design constraints. MTBSTFA/DMF extraction and derivatization at 300 C for several minutes of a variety of terrestrial Mars analogue materials facilitated the detection of amino acids and carboxylic acids in a surface soil sample collected from the Atacama Desert and a carbonate-rich stromatolite sample from Svalbard. However, the rapid reaction of MTBSTFA with water in several analogue materials that contained high abundances of hydrated minerals and the possible deactivation of derivatized compounds by iron oxides, as detected by XRD/XRF using the CheMin field unit Terra, proved to be highly problematic for the direct extraction of organics using MTBSTFA, The combination of pyrolysis and two different chemical derivatization methods employed by SAM should enable a wide range of organic compounds to be detected by GCMS if present on Mars,

Stalport, F.; Glavin, D. P.; Eigenbrode, J. L.; Bish, D.; Blake, D.; Coll, P.; Szopa, C.; Buch, A.; McAdam, A.; Dworkin, J. P.; Mahaffy, P. R.

2012-01-01

371

N-tert-Butoxycarbonylation of Structurally Diverse Amines and Sulfamides under Water-Mediated Catalyst-Free Conditions  

PubMed Central

A simple, efficient, and eco-friendly protocol for the N-Boc protection of the amine moiety in a variety of compounds with di-tert-butyl dicarbonate under water-acetone catalyst-free conditions is described. The corresponding monocarbamate is obtained in excellent yields on short reaction times. No competitive side reactions such as isocyanate urea and O-Boc were observed. This method represents a reasonable alternative to the previous reported protection procedures. PMID:24052842

Cheraiet, Zinelaabine; Ouarna, Souad; Hessainia, Sihem; Berredjem, Malika; Aouf, Nour-Eddine

2012-01-01

372

Heteropoly acid supported on titania as solid acid catalyst in alkylation of p-cresol with tert-butanol  

Microsoft Academic Search

Butylation of p-cresol with tert-butanol was investigated on titania modified with 12-tungstophosphoric acid (TPA\\/TiO2) catalyst under vapor phase conditions. Catalysts with different TPA loadings (10–25wt.%) and calcination temperatures (650–750°C) were prepared by suspending titanium hydroxide in methanol solution of TPA followed by drying and calcination. These catalysts were characterized by surface area, XRD, 31P MAS NMR, XPS, NH3-TPD, and FTIR

Suresh M. Kumbar; G. V. Shanbhag; F. Lefebvre; S. B. Halligudi

2006-01-01

373

Nucleophilic Participation in the Solvolyses of (Arylthio)methyl Chlorides and Derivatives: Application of Simple and Extended Forms of the Grunwald-Winstein Equations  

PubMed Central

The specific rates of solvolysis of chloromethyl phenyl sulfide [(phenylthio)methyl chloride] and its p-chloro-derivative have been determined at 0.0 °C in a wide range of hydroxylic solvents, including several containing a fluroalcohol. Treatment in terms of a two-term Grunwald-Winstein equation, incorporating terms based on solvent ionizing power (YCl) and solvent nucleophilicity (NT) suggest a mechanism similar to that for the solvolyses of tert-butyl chloride, involving in the rate-determining step a nucleophilic solvation of the incipient carbocation in an ionization process. A previous suggestion, that a third-term governed by the aromatic ring parameter (I) is required, is shown both for the new and for the previously studied related substrates to be an artifact, resulting from an appreciable degree of multicollinearity between I values and a linear combination of NT and YCl values. PMID:22711999

Kevill, Dennis N.; Park, Young Hoon; Park, Byoung-Chun; D’Souza, Malcolm J.

2012-01-01

374

Molecular Structure of Di-t-butyl-peroxide  

NSDL National Science Digital Library

Di-tert-Butyl Peroxide is used as a polymerization initiator, curing agent and cross-linking agent. It is a highly reactive compound, which can be flammable when exposed to open flames and sparks. Upon exposure to heat, it undergoes gaseous decomposition. Its vapors are denser than air, hence it travels along the ground. It should be kept away from combustible material like wood, clothing, oil, and paper. This material may form flammable dust-air mixtures. Potential for a dust explosion may exist. Exposure to humans is mainly through inhalation, dermal contact. It can cause irritation to eye and skin, inhalation can cause cough, shortness of breath and sore throat, and ingestion can cause vomiting and abdominal cramps.

2002-09-27

375

Comparative cytotoxicity between butylated hydroxytoluene and its methylcarbamate derivative, terbucarb, on isolated rat hepatocytes  

SciTech Connect

Butylated hydroxytoluene (3,5-di-tert-butyl-4-hydroxytoluene; BHT) is widely used as phenolic antioxidant in processed foods, cosmetics and petroleum products. It is well known that high doses of BHT cause acute hepatic damage accompanied by centrilobular necrosis in rats. The hepatic damage is associated with prolonged depletion of glutathione (GSH). Terbucarb (2,6-di-tert-butyl-para-tolyl-methylcarbamate), which has a methylcarbamate group substituted for the phenol group on BHT, was developed as an insecticide and is also presently used as a herbicide on turfgrass. Despite the metabolic and toxicological details known about BHT in vivo and in vitro, no extensive studies have been reported on the metabolism and toxicity of Terbucarb. The isolated hepatocyte system provides a very useful system for the study of the temporal sequences leading to cell damage caused by chemicals and drugs. Here, using freshly isolated rat hepatocytes, we report on the comparative toxic effects of BHT and its methylcarbamate derivative, Terbucarb. 17 refs., 2 figs., 2 tabs.

Nakagawa, Y.; Yaguchi, K.; Suzuki, T. (Tokyo Metropolitan Research Lab. of Public Health (Japan))

1994-08-01

376

Protective effect of butylated hydroxylanisole against hydrogen peroxide-induced apoptosis in primary cultured mouse hepatocytes  

PubMed Central

Butylated hydroxyanisole (BHA) is a synthetic phenolic compound consisting of a mixture of two isomeric organic compounds: 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole. We examined the effect of BHA against hydrogen peroxide (H2O2)-induced apoptosis in primary cultured mouse hepatocytes. Cell viability was significantly decreased by H2O2 in a dose-dependent manner. Additionally, H2O2 treatment increased Bax, decreased Bcl-2, and promoted PARP-1 cleavage in a dose-dependent manner. Pretreatment with BHA before exposure to H2O2 significantly attenuated the H2O2-induced decrease of cell viability. H2O2 exposure resulted in an increase of intracellular reactive oxygen species (ROS) generation that was significantly inhibited by pretreatment with BHA or N-acetyl-cysteine (NAC, an ROS scavenger). H2O2-induced decrease of cell viability was also attenuated by pretreatment with BHA and NAC. Furthermore, H2O2-induced increase of Bax, decrease of Bcl-2, and PARP-1 cleavage was also inhibited by BHA. Taken together, results of this investigation demonstrated that BHA protects primary cultured mouse hepatocytes against H2O2-induced apoptosis by inhibiting ROS generation. PMID:25798044

Hwang, Geun Hye; Jeon, Yu Jin; Han, Ho Jae; Park, Soo Hyun; Baek, Kyoung Min; Chang, Woochul; Kim, Joong Sun; Kim, Lark Kyun; Lee, You-Mie; Lee, Sangkyu; Bae, Jong-Sup; Jee, Jun-Goo

2015-01-01

377

Protective effect of butylated hydroxylanisole against hydrogen peroxide-induced apoptosis in primary cultured mouse hepatocytes.  

PubMed

Butylated hydroxyanisole (BHA) is a synthetic phenolic compound consisting of a mixture of two isomeric organic compounds: 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole. We examined the effect of BHA against hydrogen peroxide (H2O2)-induced apoptosis in primary cultured mouse hepatocytes. Cell viability was significantly decreased by H2O2 in a dose-dependent manner. Additionally, H2O2 treatment increased Bax, decreased Bcl-2, and promoted PARP-1 cleavage in a dose-dependent manner. Pretreatment with BHA before exposure to H2O2 significantly attenuated the H2O2-induced decrease of cell viability. H2O2 exposure resulted in an increase of intracellular reactive oxygen species (ROS) generation that was significantly inhibited by pretreatment with BHA or N-acetyl-cysteine (NAC, an ROS scavenger). H2O2-induced decrease of cell viability was also attenuated by pretreatment with BHA and NAC. Furthermore, H2O2-induced increase of Bax, decrease of Bcl-2, and PARP-1 cleavage was also inhibited by BHA. Taken together, results of this investigation demonstrated that BHA protects primary cultured mouse hepatocytes against H2O2-induced apoptosis by inhibiting ROS generation. PMID:25798044

Hwang, Geun Hye; Jeon, Yu Jin; Han, Ho Jae; Park, Soo Hyun; Baek, Kyoung Min; Chang, Woochul; Kim, Joong Sun; Kim, Lark Kyun; Lee, You-Mie; Lee, Sangkyu; Bae, Jong-Sup; Jee, Jun-Goo; Lee, Min Young

2015-03-01

378

Protective effect of butylated hydroxylanisole against hydrogen peroxide-induced apoptosis in primary cultured mouse hepatocytes.  

PubMed

Butylated hydroxyanisole (BHA) is a synthetic phenolic compound consisting of a mixture of two isomeric organic compounds: 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole. We examined the effect of BHA against hydrogen peroxide (H2O2)-induced apoptosis in primary cultured mouse hepatocytes. Cell viability was significantly decreased by H2O2 in a dose-dependent manner. Additionally, H2O2 treatment increased Bax, decreased Bcl-2, and promoted PARP-1 cleavage in a dose-dependent manner. Pretreatment with BHA before exposure to H2O2 significantly attenuated the H2O2-induced decrease of cell viability. H2O2 exposure resulted in an increase of intracellular reactive oxygen species (ROS) generation that was significantly inhibited by pretreatment with BHA or N-acetyl-cysteine (NAC, an ROS scavenger). H2O2-induced decrease of cell viability was also attenuated by pretreatment with BHA and NAC. Furthermore, H2O2-induced increase of Bax, decrease of Bcl-2, and PARP-1 cleavage was also inhibited by BHA. Taken together, results of this investigation demonstrated that BHA protects primary cultured mouse hepatocytes against H2O2-induced apoptosis by inhibiting ROS generation. PMID:25293491

Hwang, Geun Hye; Jeon, Yu Jin; Han, Ho Jae; Park, Soo Hyun; Baek, Kyoung Min; Chang, Woochul; Kim, Joong Sun; Kim, Lark Kyun; Lee, You-Mie; Lee, Sangkyu; Bae, Jong-Sup; Jee, Jun-Goo; Lee, Min Young

2014-12-01

379

Peroxone chemistry: Formation of H2O3 and ring-(HO2)(HO3) from O3 H2O2  

E-print Network

with volatile organic compounds, polycyclic aromatic hydrocarbons, petroleum hydrocarbons, chlorinated solvents, metals, munitions, diesel fuel, methyl tert-butyl ether (MTBE), BTEX (benzene, toluene, ethylbenzene

Goddard III, William A.

380

Inhibition of cell proliferation and induction of apoptosis by oleanane triterpenoid (CDDO-Me) in pancreatic cancer cells is associated with the suppression of hTERT gene expression and its telomerase activity  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer CDDO-Me inhibits hTERT gene expression. Black-Right-Pointing-Pointer CDDO-Me inhibits hTERT protein expression. Black-Right-Pointing-Pointer CDDO-Me inhibits hTERT telomerase activity. Black-Right-Pointing-Pointer CDDO-Me inhibits hTERT regulatory proteins. -- Abstract: Methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) is a multifunctional oleanane synthetic triterpenoid with potent anti-inflammatory and antitumorigenic properties. The mechanisms of the antisurvival and apoptosis-inducing activities of CDDO-Me and related derivatives of oleanolic acid have been defined; however, to date, no study has been carried out on the effect of CDDOs on human telomerase reverse transcriptase (hTERT) gene or telomerase activity. Here we report for the first time that inhibition of cell proliferation and induction of apoptosis by CDDO-Me in pancreatic cancer cell lines is associated with the inhibition of hTERT gene expression, hTERT telomerase activity and a number of proteins that regulate hTERT expression and activity. Furthermore, abrogation or overexpression of hTERT protein altered the susceptibility of tumor cells to CDDO-Me. These findings suggest that telomerase (hTERT) is a relevant target of CDDO-Me in pancreatic cancer cells.

Deeb, Dorrah; Gao, Xiaohua; Liu, Yongbo [Department of Surgery, Henry Ford Health System, Detroit, MI (United States)] [Department of Surgery, Henry Ford Health System, Detroit, MI (United States); Kim, Sahn-Ho [Department of Urology, Henry Ford Health System, Detroit, MI (United States)] [Department of Urology, Henry Ford Health System, Detroit, MI (United States); Pindolia, Kirit R. [Department of Medical Genetics, Henry Ford Health System, Detroit, MI (United States)] [Department of Medical Genetics, Henry Ford Health System, Detroit, MI (United States); Arbab, Ali S. [Department of Radiology, Henry Ford Health System, Detroit, MI (United States)] [Department of Radiology, Henry Ford Health System, Detroit, MI (United States); Gautam, Subhash C., E-mail: sgautam1@hfhs.org [Department of Surgery, Henry Ford Health System, Detroit, MI (United States)

2012-06-15

381

Hydrogenophaga carboriunda sp. nov., a tertiary butyl alcohol-oxidizing, psychrotolerant aerobe derived from granular-activated carbon (GAC).  

PubMed

A Gram-negative, rod-shaped bacterium was isolated from a mixed culture that degraded tert-butyl alcohol (TBA) in a granular-activated carbon (GAC) sample from a Biological-GAC reactor. Strain YZ2(T) was assigned to the Betaproteobacteria within the family Comamonadaceae based on 16S rRNA gene similarities. The nearest phylogenetic relative (95.0 % similarity) with a valid name was Hydrogenophaga taeniospiralis. The DNA G+C content was 66.4 mol%. DNA:DNA hybridization indicated that the level of relatedness to members of the genus Hydrogenophaga ranged from 1.1 to 10.8 %. The dominant cellular fatty acids were: 18:1 w7c (75 %), 16:0 (4.9 %), 17:0 (3.85 %), 18:0 (2.93 %), 11 methyl 18:1 w7c (2.69 %), Summed Feature 2 (2.27 %), and 18:0 3OH (1.35 %). The primary substrate used was TBA, which is a fuel oxygenate and groundwater contaminant. YZ2(T) was non-motile, without apparent flagella. It is a psychrotolerant, facultative aerobe that grew between pH 6.5 and 9.5, and 4 and 30 °C. The culture grew on and mineralized TBA at 4 °C, which is the first report of psychrotolerant TBA degradation. Hydrogen was used as an alternative electron donor. The culture also grew well in defined freshwater medium with ethanol, butanol, hydroxy isobutyric acid, acetate, pyruvate, citrate, lactate, isopropanol, and benzoic acid as electron donors. Nitrate was reduced with hydrogen as the sole electron donor. On the basis of morphological, physiological, and chemotaxonomic data, a new species, Hydrogenophaga carboriunda is proposed, with YZ2(T) as the type strain. PMID:24343174

Reinauer, Kimberly M; Popovic, Jovan; Weber, Christopher D; Millerick, Kayleigh A; Kwon, Man Jae; Wei, Na; Zhang, Yang; Finneran, Kevin T

2014-04-01

382

Mechanisms of cytotoxicity of 2- or 2,6-di- tert-butylphenols and 2-methoxyphenols in terms of inhibition rate constant and a theoretical parameter  

Microsoft Academic Search

To clarify the mechanism of phenol toxicity, the radical-scavenging activity of 2- or 2,6-di-tert-butyl- and 2-methoxy-substituted phenols was investigated by combining two distinct approaches: first, the induction period method for methacrylate polymerization initiated by benzoyl peroxide or 2,2?-azobisisobutyronitrile; and secondly, 1,1?-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging test. The homolytic bond dissociation enthalpy (BDE) and ionization potential (IPkoopman) were calculated by the DFT\\/B3LYP

Yoshinori Kadoma; Shigeru Ito; Toshiko Atsumi; Seiichiro Fujisawa

2009-01-01

383

Preparation and Characterization of p-tert-Butylcalix[4]arene Modified Sol-Gel Column for Open-Tubular Capillary Electrochromatography  

Microsoft Academic Search

Using the sol-gel method, p-tert-butyl-calix[4]arene sol-gel coating capillary (BCx4-SGCC) was prepared and characterized by infrared spectroscopy and electroosmotic flow. Their separation performance was investigated by using benzenediol positional isomers and axially chiral binaphthyl derivative 2-amino-2?-hydroxy-1,1?-binaphthyl (BHA) without symmetric carbon center as probes. The migration behaviors of these analytes on the BCx4-SGCC with the open tubular capillary electrochromatography separation mode were

Kai Hu; Yulu Tian; Hui Yang; Junqiang Zhang; Jing Xie; Baoxian Ye; Yangjie Wu; Shusheng Zhang

2009-01-01

384

Mechanisms of cytotoxicity of 2- or 2,6-di-tert-butylphenols and 2-methoxyphenols in terms of inhibition rate constant and a theoretical parameter.  

PubMed

To clarify the mechanism of phenol toxicity, the radical-scavenging activity of 2- or 2,6-di-tert-butyl- and 2-methoxy-substituted phenols was investigated by combining two distinct approaches: first, the induction period method for methacrylate polymerization initiated by benzoyl peroxide or 2,2'-azobisisobutyronitrile; and secondly, 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging test. The homolytic bond dissociation enthalpy (BDE) and ionization potential (IP(koopman)) were calculated by the DFT/B3LYP method. The cytotoxicity was investigated using tumor cells (human submandibular gland carcinoma cells, HSG; human promyelocytic leukemia cells, HL-60) and primary cells (human gingival fibroblasts, HGF; human periodontal ligament fibroblasts, HPLF; human pulp fibroblasts, HPF) derived from oral tissues. The cytotoxicity between tumor and primary cells was similar, except for eugenol dimer showing less toxicity for primary cells. The DPPH assay was not useful for tert-butylphenols due to their steric hindrance. For both HSG and HGF cells, a linear relationship was found between 50% cytotoxic concentration (CC(50)) and inhibition rate constant (k(inh)), but not BDE, IP, or logP. The acceptable quantitative structure-activity relationships (QSAR) obtained for cytotoxicity vs. k(inh) suggested that the cytotoxicity of phenols may be dependent on radical reactions. The cytotoxicity of vanillin and 3,5-di-tert-butyl-4-hydroxy-benzaldehyde with large k(inh) values, weak antioxidants was markedly less than that of 2,6-di-tert-butyl-4-methylphenol, 2,4,6-tri-tert-butylphenol and curcumin with small k(inh) values, potent antioxidants. PMID:19084262

Kadoma, Yoshinori; Ito, Shigeru; Atsumi, Toshiko; Fujisawa, Seiichiro

2009-02-01

385

Kinetic resolution and parallel kinetic resolution of methyl (+/-)-5-alkyl-cyclopentene-1-carboxylates for the asymmetric synthesis of 5-alkyl-cispentacin derivatives.  

PubMed

Conjugate addition of lithium dibenzylamide to methyl 5-isopropyl, 5-phenyl- and 5-tert-butyl-cyclopentene-1-carboxylates occurs with high levels of substrate control (>88% de), with preferential addition to the face of the cyclic alpha,beta-unsaturated acceptor anti- to the stereodirecting 5-alkyl substituent. Treatment of a range of methyl (+/-)-5-alkyl-cyclopentene-1-carboxylates with both lithium (+/-)-N-benzyl-N-alpha-methylbenzylamide and lithium (+/-)-N-3,4-dimethoxybenzyl-N-alpha-methylbenzylamide indicates significant enantiorecognition in their mutual kinetic resolutions, with preferential addition anti- to the 5-alkyl substituent, giving the 1,2-syn-1,5-anti-arrangement (E >16) after enolate protonation anti- to the amino functionality. The kinetic resolution of a range of methyl (+/-)-5-alkyl-cyclopentene-1-carboxylates with lithium (S)-N-benzyl-N-alpha-methylbenzylamide, and their efficient parallel kinetic resolution with a pseudoenantiomeric mixture of lithium (S)-N-benzyl-N-alpha-methylbenzylamide and lithium (R)-N-3,4-dimethoxybenzyl-N-alpha-methylbenzylamide are also demonstrated, giving a range of 5-alkyl-cispentacin derivatives in >98% de and high ee after N-deprotection. PMID:16032355

Davies, Stephen G; Garner, A Christopher; Long, Marcus J C; Morrison, Rachel M; Roberts, Paul M; Savory, Edward D; Smith, Andrew D; Sweet, Miles J; Withey, Jonathan M

2005-08-01

386

Crystal structure of chlorido­{5,10,15,20-tetra­kis­[2-(2,2-di­methyl­propanamido)­phen­yl]porphyrinato-?4 N}iron(III)  

PubMed Central

The title compound, [Fe(C64H64N8O4)Cl], is a five-coordinate square-pyramidal porphyrin complex with a chloride ion in the axial position, being coordinated from the protected side of the porphyrin; the FeIII atom is displaced by 0.474?(5)?Å from the 24-atom mean plane of the porphyrin core towards the chloride. The porphyrin moiety is a ‘picket-fence’ 5,10,15,20-tetra­kis­[2-(2,2-di­methyl­propanamido)­phen­yl]porph­yrinate (por) group. The Fe—Cl bond length is 2.221?(2)?Å and the Fe—N(por) bond lengths are in the range 2.043?(5)–2.063?(5)?Å. The supra­molecular architecture of the crystal is sustained by C—H?O inter­actions between the pyrrolic and phenyl H atoms of one mol­ecule and the carbonyl O atoms of the 2,2-di­methyl­propanamido groups of adjacent mol­ecules. The methyl groups of three of the four tert-butyl substituents exhibited rotational disorder over two positions. The investigated crystal was twinned by a twofold rotation about the (001) axis with a refined twin ratio of 0.4086?(16).

Awasabisah, Dennis; Powell, Douglas R.; Richter-Addo, George B.

2015-01-01

387

Enantiodifferentiation of 3-sec-butyl-2-methoxypyrazine in different species using multidimensional and comprehensive two-dimensional gas chromatographic approaches.  

PubMed

With respect to the current hypothesis that natural amino acids may serve as starting material for the biosynthesis of alkyl-methoxypyrazines, the enantiomeric distribution of the potent aroma compound 3-sec-butyl-2-methoxypyrazine (SBMP) was determined in various species using heart-cut multidimensional gas chromatography (H/C MDGC) or comprehensive two-dimensional gas chromatography (GC?×?GC). Complementary to an earlier described separation on octakis-(6-O-methyl-2,3-di-O-pentyl)-?-cyclodextrin used as chiral stationary phase, we found a reversal of the elution order of SBMP enantiomers on heptakis-(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-?-cyclodextrin, providing further confirmation options for that type of analysis. Optimization of the enantioseparation of SBMP in a single-oven H/C enantio-MDGC system involved the use of a dual-jet cryo modulator for trapping of analytes transferred from the achiral (1)D column to the chiral (2)D column before starting the (2)D enantioseparation with an independent temperature ramp. For the enantiodifferentiation by enantio-GC?×?GC, the modulation period had to be significantly shortened to avoid loss of chiral resolution gained in (1)D. H/C MDGC with mass spectrometric detection (MS) using selected ion monitoring (SIM) was sufficient for parts per billion level analysis, whereas H/C MDGC-MS/MS or GC?×?GC time-of-flight (TOF) MS were necessary for parts per trillion level analysis. In various vegetables, lady beetles and Vitis vinifera species analyzed, only (S)-SBMP was detected, supporting the hypothesis of natural amino acids serving as starting material for the biosynthesis of alkyl-methoxypyrazines. PMID:25146352

Legrum, Charlotte; Slabizki, Petra; Schmarr, Hans-Georg

2015-01-01

388

Sprayed Coating Renews Butyl Rubber  

NASA Technical Reports Server (NTRS)

Damaged butyl rubber products are renewed by spray technique originally developed for protective suits worn by NASA workers. A commercial two-part adhesive is mixed with Freon-113 (or equivalent) trichlorotrifluoroethane to obtain optimum viscosity for spraying. Mix is applied with an external-air-mix spray gun.

Martin, R. B.

1982-01-01

389

Preparation of ? -methyl- ? -butyrolactone: Mechanism of its formation and utilization in 2-methyl-1-tetralone synthesis  

Microsoft Academic Search

?-Methyl-?-butyrolactone (III) has been prepared directly from ?-butyrolactone (I) in 89 % yield by selective monomethylation conditions: K2CO3\\/DMC\\/210°C\\/7 h. The reaction mechanism was elucidated and described. An intermediate and two byproducts: methyl tetrahydro-3-methyl-2-oxofuran-3-carboxylate\\u000a (II), 3-(methoxycarbonyl)propyl methyl carbonate (IV) and 3-(methoxycarbonyl)butyl methyl carbonate (V) were identified. The high temperature disproportionation of K2CO3 in the presence of dimethyl carbonate to MeOK was

Vladislav Semak; Andrej Bohá?; Marta Sališová; Gabriela Addová; Peter Danko

2008-01-01

390

2-Amino-4-tert-butyl-5-(4-chloro­benz­yl)thia­zole  

PubMed Central

In the title compound, C14H17ClN2S, the dihedral angle between the planes of the thia­zole and chloro­phenyl rings is 88.86?(3)°. In the crystal, inversion dimers occur, linked by pairs of N—H?N hydrogen bonds. PMID:21581324

Wang, Yong-Tao; Xia, Lin; Hu, Ai-Xi; Cao, Gao; Xu, Juan-Juan

2008-01-01

391

Di-tert-butyl-chlorido(pyrrolidine-1-dithio-carboxyl-ato-?S,S')tin(IV).  

PubMed

The title compound, [Sn(C(4)H(9))(2)(C(5)H(8)NS(2))Cl], contains two mol-ecules in the asymmetric unit, with similar conformations. In both mol-ecules, the Sn atom adopts a distorted trigonal-bipyramidal geometry arising from two C atoms, one Cl atom and two S atoms from the bidentate dithio-carbamate ligand, with one Sn-S bond much longer than the other. One C atom of the pyrrolidine ring is disordered equally over two sites. PMID:21200655

Li, Fahui; Li, Yantuan; Harrison, William T A; Wang, Weijie; Feng, Yanping

2007-01-01

392

Crystal structure of tert-butyl-N-phenyl-carbonitrilium tetra-chlorido-aluminate.  

PubMed

In the title compound, (C11H14N)[AlCl4], the nitrilium (systematic name: 2,2-dimethyl-N-phenyl-propane-nitrilium) ion adopts a slightly distorted linear configuration [C-N C = 178.87?(16) and N C-C = 179.13?(17)°]. In the crystal, while there are no inter-molecular hydrogen bonds, pairs of nitrilium ions are linked through ?-? inter-actions [inter-centroid distance = 3.8091?(13)?Å]. PMID:25484737

van Dijk, Tom; Zant, Dirk W; Wolf, Robert; Lammertsma, Koop; Slootweg, J Chris

2014-11-01

393

N,N'-Di-tert-butyl-N''-(2-chloro-acet-yl)phospho-ric triamide.  

PubMed

The P atom in the title mol-ecule, C(10)H(23)ClN(3)O(2)P, has a distorted tetra-hedral coordination. In the C(O)NHP(O) unit, which has syn-oriented phosphoryl and N-H groups, the P-N bond of 1.703?(2)?Å is longer and the O-P-N angle of 103.86?(7)° is contracted compared with the respective values in the two P(O)NHC(CH(3))(3) units [P-N = 1.632?(2) and 1.624?(2)?Å; O-P-N = 116.80?(8) and 115.32?(8)°]. In the crystal, each mol-ecule is hydrogen bonded to two adjacent mol-ecules via N-H?O hydrogen bonds, forming a linear sequence of alternating R(2) (2)(8) and R(2) (2)(12)/R(2) (1)(6)-fused rings along [010]. The O atom of the carbonyl group acts as a double H-atom acceptor. PMID:22219891

Pourayoubi, Mehrdad; Elahi, Behrouz; Parvez, Masood

2011-11-01

394

N,N?-Di-tert-butyl-N??-(2-chloro­acet­yl)phospho­ric triamide  

PubMed Central

The P atom in the title mol­ecule, C10H23ClN3O2P, has a distorted tetra­hedral coordination. In the C(O)NHP(O) unit, which has syn-oriented phosphoryl and N—H groups, the P—N bond of 1.703?(2)?Å is longer and the O—P—N angle of 103.86?(7)° is contracted compared with the respective values in the two P(O)NHC(CH3)3 units [P—N = 1.632?(2) and 1.624?(2)?Å; O—P—N = 116.80?(8) and 115.32?(8)°]. In the crystal, each mol­ecule is hydrogen bonded to two adjacent mol­ecules via N—H?O hydrogen bonds, forming a linear sequence of alternating R 2 2(8) and R 2 2(12)/R 2 1(6)-fused rings along [010]. The O atom of the carbonyl group acts as a double H-atom acceptor. PMID:22219891

Pourayoubi, Mehrdad; Elahi, Behrouz; Parvez, Masood

2011-01-01

395

N-4-Methansulfonamidobenzyl-N0 -2-substituted-4-tert-butyl-benzyl  

E-print Network

. Their structure­activity relationship reveals that there is a space for another hydrophobic binding interaction neurons,1,2 has been regarded as a new target for the treatment of pain.3 The agonists initially induce-butylbenzyl group of 2 in hydrophobic binding with VR1. So we expected that the introduction of another potential

Suh, Young-Ger

396

Photoelectron spectroscopy, gas phase acidity, and thermochemistry of tert-butyl hydroperoxide: Mechanisms for the rearrangement  

E-print Network

(X~ 2 A ). © 1998 American Institute of Physics. S0021-9606 98 01925-4 I. INTRODUCTION Atmospheric­11 10 12 cm3 molecule 1 s 1 . In combustion processes, alkylperoxyl radicals are formed by the rapid- peratures, and the rearrangement product RO2H is of practi- cal interest since it is implicated in ``engine

Lineberger, W. Carl

397

(E,E)-2,5-Bis(4-tert-butyl­benzyl­idene)­cyclo­penta­none  

PubMed Central

The asymmetric unit of the title compound, C27H32O, contains two and a half mol­ecules. In the crystal structure, one of the mol­ecules lies on a crystallographic twofold rotation axis. The dihedral angles between the benzene rings are 12.17?(6), 16.29?(11) and 51.24?(8)° for the three molecules. The dihedral angles between the benzene rings of each molecule in the asymmetric unit are 12.17?(6) and 16.29?(11)° PMID:21201737

Wei, Jian; Liang, Guang; Gai, Yuhong; Lu, Jingmei

2008-01-01

398

1,1'-Bis(tert-butyl-dimethyl-sil-yl)ferrocene.  

PubMed

The asymmetric unit of the title compound, [Fe(C11H19Si)2], consists of one half of a ferrocene derivative. The Fe(II) atom lies on a twofold rotation axis, giving an eclipsed conformation for the cyclo-penta-dienyl ligands. No significant inter-molecular inter-actions are observed in the crystal structure. PMID:23476342

Abri, Abdolreza; Soltani, Behzad; Ziegler, Christopher J; Engle, James T; Kia, Reza

2013-01-01

399

1,1?-Bis(tert-butyl­dimethyl­sil­yl)ferrocene  

PubMed Central

The asymmetric unit of the title compound, [Fe(C11H19Si)2], consists of one half of a ferrocene derivative. The FeII atom lies on a twofold rotation axis, giving an eclipsed conformation for the cyclo­penta­dienyl ligands. No significant inter­molecular inter­actions are observed in the crystal structure. PMID:23476342

Abri, Abdolreza; Soltani, Behzad; Ziegler, Christopher J.; Engle, James T.; Kia, Reza

2013-01-01

400

5-[(tert-Butyl­diphenyl­sil­yloxy)meth­yl]pyridazin-3(2H)-one  

PubMed Central

In the title compound, C21H24N2O2Si, a new pyridazin-3(2H)-one derivative, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether are located on the same side of the pyridazinone ring and the C—C—O—Si torsion angle is ?140.69?(17)°. In the crystal, mol­ecules are linked by pairs of strong N—H?O hydrogen bonds into centrosymmetric dimers with graph-set notation R 2 2(8). Weak C—H?? inter­actions are also observed. PMID:24454251

Costas-Lago, María Carmen; Costas, Tamara; Vila, Noemí; Terán, Carmen

2013-01-01

401

Crystal structure of tert-butyl-N-phenyl­carbonitrilium tetra­chlorido­aluminate  

PubMed Central

In the title compound, (C11H14N)[AlCl4], the nitrilium (systematic name: 2,2-dimethyl-N-phenyl­propane­nitrilium) ion adopts a slightly distorted linear configuration [C—N C = 178.87?(16) and N C—C = 179.13?(17)°]. In the crystal, while there are no inter­molecular hydrogen bonds, pairs of nitrilium ions are linked through ?–? inter­actions [inter–centroid distance = 3.8091?(13)?Å]. PMID:25484737

van Dijk, Tom; Zant, Dirk W.; Wolf, Robert; Lammertsma, Koop; Slootweg, J. Chris

2014-01-01

402

tert-Butyl 4-(3,4-dichloro­anilino)piperidine-1-carboxyl­ate  

PubMed Central

In the title compound, C16H22Cl2N2O2, the substituted piperidine ring adopts a chair conformation with both substituents in equatorial positions. In the crystal, N—H?O and C—H?O hydrogen bonds connect mol­ecules into ribbons along the a-axis direction. PMID:23424488

Mehr-un-Nisa; Munawar, Munawar Ali; Hall, Gabriel B.; Roberts, Sue A.; Hruby, Victor J.

2013-01-01

403

Determination of fuel dialkyl ethers and BTEX in water using headspace solid-phase microextraction and gas chromatography–flame ionization detection  

Microsoft Academic Search

A simple procedure for the determination of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), ethyl butyl ether (EBE), tert-amyl methyl ether (TAME), benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using headspace (HS) solid-phase microextraction (HS-SPME) was developed. The analysis was carried out by gas chromatography (GC) equipped with flame ionization detector (FID) and 100% dimethylpolysiloxane fused capillary column.

Idoia Arambarri; Maitena Lasa; Rosa Garcia; Esmeralda Millán

2004-01-01

404

Isolation and characterization of a new Mycobacterium austroafricanum strain, IFP 2015, growing on MTBE  

Microsoft Academic Search

A new Mycobacterium austroafricanum strain, IFP 2015, growing on methyl tert-butyl ether (MTBE) as a sole carbon source was isolated from an MTBE-degrading microcosm inoculated with drain water of an MTBE-supplemented gasoline storage tank. M. austroafricanum IFP 2015 was able to grow on tert-butyl formate, tert-butyl alcohol (TBA) and ?-hydroxyisobutyrate. 2-Methyl-1,2-propanediol was identified as the TBA oxidation product in M.

Nicolas Lopes Ferreira; Helena Maciel; Hugues Mathis; Frédéric Monot; Françoise Fayolle-Guichard; Charles W. Greer

2006-01-01

405

MLH1 mediates PARP-dependent cell death in response to the methylating agent N-methyl-N-nitrosourea  

Microsoft Academic Search

Background:Methylating agents such as N-methyl-N-nitrosourea (MNU) can cause cell cycle arrest and death either via caspase-dependent apoptosis or via a poly(ADP-ribose) polymerase (PARP)-dependent form of apoptosis. We wished to investigate the possible role of MLH1 in signalling cell death through PARP.Methods:Fibroblasts are particularly dependent on a PARP-mediated cell death response to methylating agents. We used hTERT-immortalised normal human fibroblasts (WT)

J R McDaid; J Loughery; P Dunne; J C Boyer; C S Downes; R A Farber; C P Walsh

2009-01-01

406

Equilibrium thermodynamic analysis of liquid-phase ethyl tert-butylether (ETBE) synthesis  

SciTech Connect

Methyl tertiary butyl ether (MTBE) is now the second largest volume organic chemical, only behind ethylene, produced in the U.S. This is remarkable since its commercial production began barely two decades ago. Although MTBE is currently the industry standard, it has been proposed that ethanol and other renewable additives make up to 30% of the oxygenate market. As a result, ethyl tertiary butyl ether (ETBE, or 2-ethyoxy 2-methyl propane), derived from renewable ethanol and isobutylene, has emerged as a promising new oxygenate. ETBE also has a somewhat lower blending Reid vapor pressure as well as a higher octane number than MTBE. This paper describes the thermodynamic equilibrium constant for the production of ETBE.

Jensen, K.L.; Datta, R. [Univ. of Iowa, Iowa City, IA (United States)

1994-12-31

407

Reactions of methyl radicals with propene at temperatures between 750 and 1000 K.  

PubMed

The pyrolysis of propene, initiated by methyl radicals, has been studied in the temperature range 750-1000 K and at a pressure of 0.13 bar in a quasi-wall-free reactor using laser heating by fast vibrational-translational (V-T) energy transfer. This is a convenient method to study homogeneous high-temperature kinetics since the reactor walls remain cold. The radial temperature distribution in the reactor has been investigated by four different methods: a stationary heat balance, optical absorption, pressure rise, and the temperature dependence of the rate of an isomerization reaction. Methyl radicals were produced via the fast thermal dissociation of di-tert-butyl-peroxide and the products were analysed using GC-MS. The main products of the overall reaction of the model system propene and methyl (C3H6 + CH3) were isopentane (iso-C5H12) and but-1-ene (1-C4H8), whereas allene (C3H4), trans-but-2-ene (trans-2-C4H8) and cis-but-2-ene (cis-2-C4H8) were minor components, all showing a strong dependence on temperature. The product distribution and the temperature dependence were analysed by a kinetic model of 61 species and 166 reactions developed for the high-temperature oxidation of butane and the low-temperature oxidation of n-pentane and isopentane. It was necessary to include a few missing reactions and to adjust some rate constants to make the modeling agree with the experimental investigations. This extended mechanism has to be evaluated further in forthcoming experiments. PMID:11877994

Goos, E; Hippler, H; Hoyermann, K; Jürges, B

2001-01-01

408

EFFECT OF BTEX ON THE DEGRADATION OF MTBE AND TBA BY MIXED BACTERIAL CONSORTIUM  

EPA Science Inventory

Methyl tert -butyl ether (MTBE) contamination in groundwater often coexists with benzene, toluene, ethylbenzene, and xylene (BTEX) near the source of the plume. Tertiary butyl alcohol (TBA) is a prevalent intermediate of MTBE degradation. Therefore, there is a significant p...

409

Induction of oxidative DNA damage and early lesions in rat gastro-intestinal epithelium in relation to prostaglandin H synthase-mediated metabolism of butylated hydroxyanisole  

Microsoft Academic Search

The effect of metabolic activation of the food additive 3-tert-butyl-4-hydroxyanisole (BHA) by prostaglandin H synthase on the gastro-intestinal cell proliferation was determined by studies of the nature and the time dependency of early lesions in the forestomach, glandular stomach and colon\\/rectum of rats given BHA with and without co-administration of acetylsalicyclic acid (ASA; an inhibitor of prostaglandin H synthase), in

P. A. E. L. Schilderman; F. J. ten Vaarwerk; J. T. Lutgerink; A. Van Der Wurff; F. ten Hoor; J. C. S. Kleinjans

1995-01-01

410

Group 4 complexes of a tert-butylphosphine-bridged biphenolate ligand.  

PubMed

The coordination chemistry of group 4 complexes supported by the tridentate, dianionic biphenolate phosphine ligand that carries a phosphorus-bound tert-butyl group, 2,2'-tert-butylphosphino-bis(4,6-di-tert-butylphenolate) ([(t)Bu-OPO](2-)), is described. Metathetical reactions of {[(t)Bu-OPO]Li(2)(DME)}(2) with 2 or 1 equiv of TiCl(4)(THF)(2) selectively produce [(t)Bu-OPO]TiCl(2)(THF) (1a) and Ti[(t)Bu-OPO](2) (2a), respectively. Protonolysis of Ti(O(i)Pr)(4) with 2 or 1 equiv of H(2)[(t)Bu-OPO] cleanly generates 2a and [(t)Bu-OPO]Ti(O(i)Pr)(2) (3a), respectively. Complex 1a can alternatively be prepared from comproportionation of 2a with 1 equiv of TiCl(4)(THF)(2). Treatment of 1a with 2 equiv of NaO(t)Bu affords [(t)Bu-OPO]Ti(O(t)Bu)(2) (4a). In contrast, reactions of {[(t)Bu-OPO]Li(2)(DME)}(2) with ZrCl(4)(THF)(2) or HfCl(4)(THF)(2), regardless of stoichiometry of the starting materials employed, selectively give bis-ligated M[(t)Bu-OPO](2) [M = Zr (2b), Hf (2c)]. Comproportionation of 2b,c with MCl(4)(THF)(2) (M = Zr, Hf) leads to the formation of [(t)Bu-OPO]MCl(2)(THF) [M = Zr (1b), Hf (1c)], which, upon being treated with 2 equiv of NaO(t)Bu, generates [(t)Bu-OPO]M(O(t)Bu)(2)(THF) (4b,c). These synthetic results are markedly different from those obtained from analogous reactions employing a biphenolate phosphine ligand bearing a phosphorus-bound phenyl group ([Ph-OPO](2-)), highlighting a profound phosphorus substituent effect on complex conformation. The alkoxide complexes 3a and 4a-c are all active initiators for catalytic ring-opening polymerization of ?-caprolactone. To assess the potential phosphorus substituent effect on catalysis, [Ph-OPO]Ti(O(i)Pr)(2) (5a) was prepared, and its reactivity was examined. Interestingly, polymers prepared from 3a are characterized by low polydispersities with molecular weights that are linearly dependent on the monomer-to-initiator ratio, thus featuring a living system. The polydispersitiy indexes of polymers prepared from 5a, however, are relatively larger, indicative of the significance of the phosphorus-bound tert-butyl group in 3a in view of discouraging the undesirable transesterification. PMID:21428317

Liang, Lan-Chang; Hsu, Yu-Lin; Lin, Sheng-Ta

2011-04-18

411

TERT promotes cellular and organismal survival independently of telomerase activity  

Microsoft Academic Search

The expression level of the telomerase catalytic subunit (telomerase reverse transcriptase, TERT) positively correlates with cell survival after exposure to several lethal stresses. However, whether the protective role of TERT is independent of telomerase activity has not yet been clearly explored. Here, we genetically evaluated the protective roles of both TERT and telomerase activity against cell death induced by staurosporine

J Lee; Y H Sung; C Cheong; Y S Choi; H K Jeon; W Sun; W C Hahn; F Ishikawa; H-W Lee

2008-01-01

412

Customer exposure to MTBE, TAME, C6 alkyl methyl ethers, and benzene during gasoline refueling.  

PubMed Central

We studied customer exposure during refueling by collecting air samples from customers' breathing zone. The measurements were carried out during 4 days in summer 1996 at two Finnish self-service gasoline stations with "stage I" vapor recovery systems. The 95-RON (research octane number) gasoline contained approximately 2.7% methyl tert-butyl ether (MTBE), approximately 8.5% tert-amyl methyl ether (TAME), approximately 3.2% C6 alkyl methyl ethers (C6 AMEs), and 0.75% benzene. The individual exposure concentrations showed a wide log-normal distribution, with low exposures being the most frequent. In over 90% of the samples, the concentration of MTBE was higher (range <0.02-51 mg/m3) than that of TAME. The MTBE values were well below the short-term (15 min) threshold limits set for occupational exposure (250-360 mg/m3). At station A, the geometric mean concentrations in individual samples were 3.9 mg/m3 MTBE and 2. 2 mg/m3 TAME. The corresponding values at station B were 2.4 and 1.7 mg/m3, respectively. The average refueling (sampling) time was 63 sec at station A and 74 sec at station B. No statistically significant difference was observed in customer exposures between the two service stations. The overall geometric means (n = 167) for an adjusted 1-min refueling time were 3.3 mg/m3 MTBE and 1.9 mg/m3 TAME. Each day an integrated breathing zone sample was also collected, corresponding to an arithmetic mean of 20-21 refuelings. The overall arithmetic mean concentrations in the integrated samples (n = 8) were 0.90 mg/m3 for benzene and 0.56 mg/m3 for C6 AMEs calculated as a group. Mean MTBE concentrations in ambient air (a stationary point in the middle of the pump island) were 0.16 mg/m3 for station A and 0.07 mg/m3 for station B. The mean ambient concentrations of TAME, C6 AMEs, and benzene were 0.031 mg/m3, approximately 0.005 mg/m3, and approximately 0.01 mg/m3, respectively, at both stations. The mean wind speed was 1.4 m/sec and mean air temperature was 21 degreesC. Of the gasoline refueled during the study, 75% was 95 grade and 25% was 98/99 grade, with an oxygenate (MTBE) content of 12.2%. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:9924009

Vainiotalo, S; Peltonen, Y; Ruonakangas, A; Pfäffli, P

1999-01-01

413

Carbon-yl{3,3'-di-tert-butyl-5,5'-dimeth-oxy-2,2'-bis-[(4,4,5,5-tetra-methyl-1,3,2-dioxaphospho-lan-2-yl)-oxy]biphenyl-?(2) P,P'}hydrido(triphenyl-phosphane-?P)rhodium(I) diethyl ether tris-olvate.  

PubMed

In the title compound, [RhH(C74H68O8P2)(C18H15P)(CO)]·3C4H10O, the CHP3 coordination set at the Rh(I) ion is arranged in a distorted trigonal-bipyramidal geometry with the P atoms adopting equatorial coordination sites and the C atom of the carbonyl ligand as well as the H atom adopting the axial sites. The asymmetric unit contains two very similar mol-ecules of the rhodium complex, two half-occupied diethyl ether mol-ecules and further diethyl ether solvent mol-ecules which could not be modelled successfully. Therefore contributions of the latter were removed from the diffraction data using the SQUEEZE procedure in PLATON [Spek (2009 ?). Acta Cryst. D65, 148-155]. PMID:23476316

Selent, Detlef; Spannenberg, Anke; Börner, Armin

2013-01-01

414

HUMAN EXPOSURE OF METHYL TERTIARY BUTYL ETHER (MTBE)  

EPA Science Inventory

Data on ambient air quality and microenvironmental exposures (e.g., during refueling, inside cards, in personal garages) are too limited for a quantitative estimate of population exposures to MTBE. t best, they can be used to estimate broad ranges of potential exposures. ecause o...

415

Matrix isolation spectroscopy and molecular dynamics simulations for 2,7,12,17-tetra-tert-butylporphycene in argon and xenon  

SciTech Connect

Electronic absorption spectra of 2,7,12,17-tetra-tert-butylporphycene (TTPC) have been recorded in low-temperature argon and xenon matrices for various deposition conditions. In the region of the S{sub 0}-S{sub 1} electronic transition, the spectra of TTPC in argon reveal a rich site structure, characterized by a series of more than 30 absorption peaks. Studies of the temperature dependence of the electronic spectra in solid argon demonstrated remarkable spectral changes, resulting in the broadening of all bands with increasing temperature. These temperature-induced spectral changes are, to a large degree, reversible, so lowering of temperature is accompanied by the recovery of the original fine-line spectrum. The absorption spectra in xenon reveal broad bands, on which a rich pattern of lines becomes superimposed at low temperatures. Trapping site distribution and the structure of the microenvironment around the TTPC chromophore, embedded in argon and xenon hosts, have been analyzed using molecular dynamics (MD) simulations. The MD results show that the trapping of TTPC in rare-gas solids is influenced by favorable embedding of the bulky tert-butyl groups inside the matrix cage. The crucial role of the tert-butyl groups for the thermodynamics and kinetics of matrix deposition is demonstrated by comparing the results with those obtained for the parent, unsubstituted porphycene.

Kyrychenko, Alexander; Gawinkowski, Sylwester; Urbanska, Natalia; Pietraszkiewicz, Marek; Waluk, Jacek [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01-224 Warsaw (Poland)

2007-10-07

416

Asymmetric Preparation of prim-, sec-, and tert-Amines Employing Selected Biocatalysts  

PubMed Central

This account focuses on the application of ?-transaminases, lyases, and oxidases for the preparation of amines considering mainly work from our own lab. Examples are given to access ?-chiral primary amines from the corresponding ketones as well as terminal amines from primary alcohols via a two-step biocascade. 2,6-Disubstituted piperidines, as examples for secondary amines, are prepared by biocatalytical regioselective asymmetric monoamination of designated diketones followed by spontaneous ring closure and a subsequent diastereoselective reduction step. Optically pure tert-amines such as berbines and N-methyl benzylisoquinolines are obtained by kinetic resolution via an enantioselective aerobic oxidative C–C bond formation. PMID:23794796

2013-01-01

417

Hydrogen Bonded Rings, Chains and Lassos: The Case of T-butyl Alcohol Clusters  

SciTech Connect

Infrared OH stretching spectra of hydrogen bonded 2-methyl-propan-2-ol (t-butyl alcohol) clusters are investigated by ragout-jet FTIR spectroscopy. A spectral difference technique is used to discriminate approximately between neighbouring cluster sizes. Dimers, trimers and cyclic tetramers can be detected along with larger clusters, which exhibit a surprisingly structured vibrational fingerprint. Comparison is made to the spectra of related alcohols and to energetic and harmonic vibrational predictions from electronic structure calculations.

Zimmermann, D; Haber, Th; Schaal, H; Suhm, M A.

2001-03-10

418

Cancer. TERT promoter mutations and telomerase reactivation in urothelial cancer.  

PubMed

Reactivation of telomerase, the chromosome end-replicating enzyme, drives human cell immortality and cancer. Point mutations in the telomerase reverse transcriptase (TERT) gene promoter occur at high frequency in multiple cancers, including urothelial cancer (UC), but their effect on telomerase function has been unclear. In a study of 23 human UC cell lines, we show that these promoter mutations correlate with higher levels of TERT messenger RNA (mRNA), TERT protein, telomerase enzymatic activity, and telomere length. Although previous studies found no relation between TERT promoter mutations and UC patient outcome, we find that elevated TERT mRNA expression strongly correlates with reduced disease-specific survival in two independent UC patient cohorts (n = 35; n = 87). These results suggest that high telomerase activity may be a better marker of aggressive UC tumors than TERT promoter mutations alone. PMID:25722414

Borah, Sumit; Xi, Linghe; Zaug, Arthur J; Powell, Natasha M; Dancik, Garrett M; Cohen, Scott B; Costello, James C; Theodorescu, Dan; Cech, Thomas R

2015-02-27

419

The K-band microwave spectra of t-butyl halides  

E-print Network

to those obtained from microwave spectra (1). For methyl chloride, for example, from pure quadrupole spectra in solids |eqQ|= 68.4 megacycles (11), and from microwave spectra eqQ = - 75.3 megacycles (3) (8). By using -62.3 as the value of eqQ (the minus... sign 24 appearing reasonable in view of the similarity of structure of methyl chloride and t-butyl ohloride) the values for 27 1 in megacycles, were calculated. These values are shown in Table V. It can be seen in Table V that the transitions...

Crook, George Hardy

1954-01-01

420

Crystal structures of N-tert-butyl-3-(4-fluoro­phenyl)-5-oxo-4-[2-(tri­fluoro­meth­oxy)phen­yl]-2,5-di­hydro­furan-2-carboxamide and 4-(2H-1,3-benzodioxol-5-yl)-N-cyclo­hexyl-5-oxo-3-[4-(tri­fluoro­meth­yl)phen­yl]-2,5-di­hydro­furan-2-carboxamide  

PubMed Central

The title compounds, C22H19F4NO4, (I), and C25H22F3NO5, (II), each contain a central nearly planar di­hydro­furan­one ring. The r.m.s. deviation from planarity of these rings is 0.015?Å in (I) and 0.027?Å in (II). The mol­ecules are T-shaped, with the major conformational difference being the O—C—C—O torsion angle [?178.9?(1) in (I) and 37.7?(2)° in (II)]. In the crystal of (I), mol­ecules are linked by N—H?O hydrogen bonds, forming chains along [001] while in (II) mol­ecules are linked by N—H?O hydrogen bonds, forming chains along [010]. In (II), the tri­fluoro­methyl substituent is disordered over two sets of sites, with refined occupancies of 0.751?(3) and 0.249?(3).

Roberts, Sue A.; Martinez-Ariza, Guillermo; Hulme, Christopher

2015-01-01

421

DNA cleavage by metabolites of butylated hydroxytoluene  

Microsoft Academic Search

The effect of butylated hydroxytoluene (BHT) and its metabolites on DNA cleavage in vitro was studied with supercoiled plasmid DNA, pUC18, by agarose gel electrophoresis. Among several BHT metabolites, 2,6-di -t-butyl-p-benzoquinone (BHT-quinone) caused cleavage of supercoiled DNA (form I) at a concentration as low as 1 × 10?6 M. The relative amount of linear form (form III) was increased with

Fumiko Nagai; Keiko Ushiyama; Itsu Kano

1993-01-01

422

SuperQuat 5,5-dimethyl-4-iso-propyloxazolidin-2-one as a mimic of Evans 4-tert-butyloxazolidin-2-one.  

PubMed

The incorporation of a gem-dimethyl group at the 5-position of a chiral oxazolidinone biases the conformation of the adjacent C(4)-stereodirecting group such that the gem-dimethyl-4-iso-propyl combination mimics a C(4)-tert-butyl group, providing higher levels of stereocontrol than a simple 4-iso-propyloxazolidinone. The generality of this principle is demonstrated with applications in stereoselective enolate alkylations, kinetic resolutions, Diels-Alder cycloadditions and Pd-catalysed asymmetric acetalisation reactions. PMID:16855744

Bull, Steven D; Davies, Stephen G; Garner, A Christopher; Kruchinin, Dennis; Key, Min-Suk; Roberts, Paul M; Savory, Edward D; Smith, Andrew D; Thomson, James E

2006-08-01

423

P. berghei Telomerase Subunit TERT is Essential for Parasite Survival  

PubMed Central

Telomeres define the ends of chromosomes protecting eukaryotic cells from chromosome instability and eventual cell death. The complex regulation of telomeres involves various proteins including telomerase, which is a specialized ribonucleoprotein responsible for telomere maintenance. Telomeres of chromosomes of malaria parasites are kept at a constant length during blood stage proliferation. The 7-bp telomere repeat sequence is universal across different Plasmodium species (GGGTTT/CA), though the average telomere length varies. The catalytic subunit of telomerase, telomerase reverse transcriptase (TERT), is present in all sequenced Plasmodium species and is approximately three times larger than other eukaryotic TERTs. The Plasmodium RNA component of TERT has recently been identified in silico. A strategy to delete the gene encoding TERT via double cross-over (DXO) homologous recombination was undertaken to study the telomerase function in P. berghei. Expression of both TERT and the RNA component (TR) in P. berghei blood stages was analysed by Western blotting and Northern analysis. Average telomere length was measured in several Plasmodium species using Telomere Restriction Fragment (TRF) analysis. TERT and TR were detected in blood stages and an average telomere length of ?950 bp established. Deletion of the tert gene was performed using standard transfection methodologies and we show the presence of tert? mutants in the transfected parasite populations. Cloning of tert- mutants has been attempted multiple times without success. Thorough analysis of the transfected parasite populations and the parasite obtained from extensive parasite cloning from these populations provide evidence for a so called delayed death phenotype as observed in different organisms lacking TERT. The findings indicate that TERT is essential for P. berghei cell survival. The study extends our current knowledge on telomere biology in malaria parasites and validates further investigations to identify telomerase inhibitors to induce parasite cell death. PMID:25275500

Religa, Agnieszka A.; Ramesar, Jai; Janse, Chris J.; Scherf, Artur; Waters, Andrew P.

2014-01-01

424

Diastereoselective synthesis of ?-heteroaryl syn-?-methyl-?-amino acid derivatives via a double chiral auxiliary approach.  

PubMed

The addition of the SuperQuat enolate to five- and six-membered heterocyclic tert-butyl sulfinimines led to a high syn-selectivity of up to 99:1 in good to excellent yields. The reaction is tentatively proposed to proceed through an open-chain transition state with the presence of an ?-heteroatom on the sulfinimine leading to high diastereoselectivities. The adducts were derivatized to ?-amino esters and amides in a facile manner. PMID:23343056

Bian, Jianwei; Blakemore, David; Warmus, Joseph S; Sun, Jianmin; Corbett, Matthew; Rose, Colin R; Bechle, Bruce M

2013-02-01

425

Altered Histone Mark Deposition and DNA Methylation at Homeobox Genes in Human Oral Squamous Cell Carcinoma Cells  

PubMed Central

We recently reported a role of Polycomb repressive complex 2 (PRC2) and PRC2 trimethylation of histone 3 lysine 27 (H3K27me3) in the regulation of homeobox (HOX) (Marcinkiewicz and Gudas, 2013) gene transcript levels in human oral keratinocytes (OKF6-TERT1R) and tongue squamous cell carcinoma (SCC) cells. Here, we assessed both the levels of various histone modifications at a subset of homeobox genes and genome wide DNA methylation patterns in OKF6-TERT1R and SCC-9 cells by using ERRBS (enhanced reduced representation bisulfite sequencing). We detected the H3K9me3 mark at HOXB7, HOXC10, HOXC13 and HOXD8 at levels higher in OKF6-TERT1R than in SCC-9 cells; at IRX1 and SIX2 the H3K9me3 levels were conversely higher in SCC-9 than in OKF6-TERT1R. The H3K79me3 mark was detectable only at IRX1 in OKF6-TERT1R and at IRX4 in SCC-9 cells. The levels of H3K4me3 and H3K36me3 marks correlate with the transcript levels of the assessed homeobox genes in both OKF6-TERT1R and SCC-9. We detected generally lower CpG methylation levels on DNA in SCC-9 cells at annotated genomic regions which were differentially methylated between OKF6-TERT1R and SCC-9 cells; however, some genomic regions, including the HOX gene clusters, showed DNA methylation at higher levels in SCC-9 than OKF6-TERT1R. Thus, both altered histone modification patterns and changes in DNA methylation are associated with dysregulation of homeobox gene expression in human oral cavity SCC cells, and this dysregulation potentially plays a role in the neoplastic phenotype of oral keratinocytes. PMID:24519855

Marcinkiewicz, Katarzyna M.; Gudas, Lorraine J.

2014-01-01

426

Safety Assessment of Butylated Hydroxyanisole and Butylated Hydroxytoluene as Antioxidant Food Additives  

Microsoft Academic Search

Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are widely used antioxidant food additives. They have been extensively studied for potential toxicities. This review details experimental studies of genotoxicity and carcinogenicity which bear on cancer hazard assessment of exposure to humans. We conclude that BHA and BHT pose no cancer hazard and, to the contrary, may be anticarcinogenic at current levels

G. M Williams; M. J Iatropoulos; J Whysner

1999-01-01

427

Metsulfuron-methyl-based herbicidal ionic liquids.  

PubMed

Ten sulfonylurea-based herbicidal ionic liquids (HILs) were prepared by combining the metsulfuron-methyl anion with various cation types including quaternary ammonium ([bis(2-hydroxyethyl)methyloleylammonium](+), [2-hydroxyethyltrimethylammonium](+)), pyridinium ([1-dodecylpyridinium](+)), piperidinium ([1-methyl-1-propylpiperidinium](+)), imidazolium ([1-allyl-3-methylimidazolium](+), [1-butyl-3-methylimidazolium](+)), pyrrolidinium ([1-butyl-1-methylpyrrolidinium](+)), morpholinium ([4-decyl-4-methylmorpholinium](+)), and phosphonium ([trihexyltetradecylphosphonium](+) and [tetrabutylphosphonium](+)). Their herbicidal efficacy was studied in both greenhouse tests and field trials. Preliminary results for the greenhouse tests showed at least twice the activity for all HILs when compared to the activity of commercial Galmet 20 SG, with HILs with phosphonium cations being the most effective. The results of two-year field studies showed significantly less enhancement of activity than observed in the greenhouse; nonetheless, it was found that the herbicidal efficacy was higher than that of the commercial analog, and efficacy varied depending on the plant species. PMID:25734891

Pernak, Juliusz; Niemczak, Micha?; Shamshina, Julia L; Gurau, Gabriela; G?owacki, Grzegorz; Praczyk, Tadeusz; Marcinkowska, Katarzyna; Rogers, Robin D

2015-04-01

428

Methylation matters  

PubMed Central

DNA methylation is not just for basic scientists any more. There is a growing awareness in the medical field that having the correct pattern of genomic methylation is essential for healthy cells and organs. If methylation patterns are not properly established or maintained, disorders as diverse as mental retardation, immune deficiency, and sporadic or inherited cancers may follow. Through inappropriate silencing of growth regulating genes and simultaneous destabilisation of whole chromosomes, methylation defects help create a chaotic state from which cancer cells evolve. Methylation defects are present in cells before the onset of obvious malignancy and therefore cannot be explained simply as a consequence of a deregulated cancer cell. Researchers are now able to detect with exquisite sensitivity the cells harbouring methylation defects, sometimes months or years before the time when cancer is clinically detectable. Furthermore, aberrant methylation of specific genes has been directly linked with the tumour response to chemotherapy and patient survival. Advances in our ability to observe the methylation status of the entire cancer cell genome have led us to the unmistakable conclusion that methylation abnormalities are far more prevalent than expected. This methylomics approach permits the integration of an ever growing repertoire of methylation defects with the genetic alterations catalogued from tumours over the past two decades. Here we discuss the current knowledge of DNA methylation in normal cells and disease states, and how this relates directly to our current understanding of the mechanisms by which tumours arise.???Keywords: methylation; cancer PMID:11333864

Costello, J.; Plass, C.

2001-01-01

429

ANAEROBIC DEGRADATION OF MTBE TO TBA IN GROUND WATER AT GASOLINE SPILL SITES IN ORANGE COUNTY, CALIFORNIA  

EPA Science Inventory

Although tert-Butyl Alcohol (TBA) has not been used as a fuel oxygenate in Orange County, California, the concentrations of TBA in ground water at gasoline spill sites are high compared to the concentrations of the conventional fuel oxygenate Methyl tert-Butyl Ether (MTBE). In t...

430

Arco gets ETBE boost from excise tax break  

SciTech Connect

Arco Chemical of Newtown Square, PA, has been extended an excise tax exemption for using ethyl tert-butyl ether (ETBE) in gasoline blends. An exemption is already in force for ethanol. The tax break may still not make ETBE competitive with methanol-based methyl tert-butyl ether (MTBE).

Lucas, A.

1994-10-12

431

STABLE ISOTOPE ANALYSIS OF MTBE TO EVALUATE THE SOURCE OF TBA IN GROUND WATER  

EPA Science Inventory

Although tert-butyl alcohol (TBA) has not been used as a fuel oxygenate in Orange County, California, the concentrations of TBA in ground water at gasoline spill sites are high compared those of the conventional fuel oxygenate methyl tert-butyl ether (MTBE). In the year 2002, th...

432

Facile Synthesis of Thick Films of Poly(methyl methacrylate), Poly(styrene), and Poly(vinyl pyridine) from Au Surfaces  

PubMed Central

Atom transfer radical polymerization (ATRP) is commonly used to grow polymer brushes from Au surfaces, but the resulting film thicknesses are usually significantly less than with ATRP from SiO2 substrates. On Au, growth of poly(methyl methacrylate) (PMMA) blocks from poly(tert-butyl acrylate) brushes occurs more rapidly than growth of PMMA from initiator monolayers, suggesting that the disparity between growth rates from Au and SiO2 stems from the Au surface. Radical quenching by electron transfer from Au is probably not the termination mechanism because polymerization from thin, cross-linked initiators gives film thicknesses that are essentially the same as the thicknesses of films grown from SiO2 under the same polymerization conditions. However, this result is consistent with termination through desorption of thiols from non-cross-linked films, and reaction of these thiols with growing polymer chains. The enhanced stability of cross-linked initiators allows ATRP at temperatures up to ~100 °C and enables the growth of thick films of PMMA (350 nm), polystyrene (120 nm) and poly(vinyl pyridine) (200 nm) from Au surfaces in 1 hour. At temperatures >100 °C, the polymer brush layers delaminate as large area films. PMID:21728374

Saha, Sampa

2011-01-01

433

hTERT Extends the Life of Human Fibroblasts without Compromising Type I Interferon Signaling  

E-print Network

transcriptase (TERT) gene extends the life of certain cell types. The effect that TERT expression has on the innate antiviral response to RNA- and DNA-containing viruses has not been examined. In the current study, we introduced the human TERT (hTERT) gene...

Smith, Miles Christian; Goddard, Erica T.; Perusina Lafranca, Mirna; Davido, David J.

2013-03-05

434

The DNA methylation inhibitor induces telomere dysfunction and apoptosis of leukemia cells that is attenuated by telomerase over-expression.  

PubMed

DNA methyltransferase inhibitors (DNMTIs) such as 5-azacytidine (5-AZA) have been used for treatment of acute myeloid leukemia (AML) and other malignancies. Although inhibiting global/gene-specific DNA methylation is widely accepted as a key mechanism behind DNMTI anti-tumor activity, other mechanisms are likely involved in DNMTI's action. Because telomerase reverse transcriptase (TERT) plays key roles in cancer through telomere elongation and telomere lengthening-independent activities, and TERT has been shown to confer chemo- or radio-resistance to cancer cells, we determine whether DNMTIs affect telomere function and whether TERT/telomerase interferes with their anti-cancer efficacy. We showed that 5-AZA induced DNA damage and telomere dysfunction in AML cell lines by demonstrating the presence of 53-BP1 foci and the co-localization of 53-BP1 foci with telomere signals, respectively. Telomere dysfunction was coupled with diminished TERT expression, shorter telomere and apoptosis in 5-AZA-treated cells. However, 5-AZA treatment did not lead to changes in the methylation status of subtelomere regions. Down-regulation of TERT expression similarly occurred in primary leukemic cells derived from AML patients exposed to 5-AZA. TERT over-expression significantly attenuated 5-AZA-mediated DNA damage, telomere dysfunction and apoptosis of AML cells. Collectively, 5-AZA mediates the down-regulation of TERT expression, and induces telomere dysfunction, which consequently exerts an anti-tumor activity. PMID:25682873

Zhang, Xiaolu; Li, Bingnan; de Jonge, Nick; Björkholm, Magnus; Xu, Dawei

2015-03-10

435

An Improved Model for the hTERT Promoter Quadruplex  

PubMed Central

Mutations occur at four specific sites in the hTERT promoter in >75% of glioblastomas and melanomas, but the mechanism by which the mutations affect gene expression remains unexplained. We report biophysical computational studies that show that the hTERT promoter sequence forms a novel G-quadruplex structure consisting of three contiguous, stacked parallel quadruplexes. The reported hTERT mutations map to the central quadruplex within this structure, and lead to an alteration of its hydrodynamic properties and stability. PMID:25526084

Chaires, Jonathan B.; Trent, John O.; Gray, Robert D.; Dean, William L.; Buscaglia, Robert; Thomas, Shelia D.; Miller, Donald M.

2014-01-01

436

40 CFR 180.232 - Butylate; tolerances for residues.  

Code of Federal Regulations, 2013 CFR

...Tolerances § 180.232 Butylate; tolerances for residues. (a) General. Tolerances are established for residues of the herbicide butylate, including its metabolites and degradates, in or on the commodities in the table in this paragraph....

2013-07-01

437

21 CFR 172.270 - Sulfated butyl oleate.  

Code of Federal Regulations, 2013 CFR

...FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Coatings, Films and Related Substances § 172.270 Sulfated butyl oleate. Sulfate butyl oleate may be safely used in food,...

2013-04-01

438

21 CFR 172.270 - Sulfated butyl oleate.  

Code of Federal Regulations, 2014 CFR

...HEALTH AND HUMAN SERVICES (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Coatings, Films and Related Substances § 172.270 Sulfated butyl oleate. Sulfate butyl oleate may be safely used in food,...

2014-04-01

439

21 CFR 172.270 - Sulfated butyl oleate.  

Code of Federal Regulations, 2011 CFR

...FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Coatings, Films and Related Substances § 172.270 Sulfated butyl oleate. Sulfate butyl oleate may be safely used in food,...

2011-04-01