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1

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

Microsoft Academic Search

The fate of fuel oxygenates such as methyl tert-butyl ether (MTBE) in the subsurface is governed by their degradability under various redox conditions. The key intermediate in degradation of MTBE and ethyl tert-butyl ether (ETBE) is tert-butyl alcohol (TBA) which was often found as accumulating intermediate or dead-end product in lab studies using microcosms or isolated cell suspensions. This review

Torsten C. Schmidt; Mario Schirmer; Holger Weiß; Stefan B. Haderlein

2004-01-01

2

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

Microsoft Academic Search

Methyl tert-butyl ether (MTBE) is a widely used gasoline oxygenate. Contamination of MTBE and its major degradation product tert-butyl alcohol (TBA) in groundwater and surface water has received great attention. However, sorption affinity and sorption mechanisms of MTBE and TBA to synthetic resins, which can be potentially used in removal of these contaminants from water, in passive sampling, or in

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

2005-01-01

3

Methyl tert-butyl ether (MTBE) bioremediation studies  

Microsoft Academic Search

The massive production of methyl tert-butyl ether (MTBE), a primary con- stituent of reformulated gasoline, combined with its mobility, persistence and toxicity, makes it an important pollutant. It was considered recalcitrant until a few years ago, but recently MTBE biodegradation in aerobic conditions has been demonstrated with both mixed and pure cultures. Mixed cultures are generally the more effective for

E. ZANARDINI; C. PISONI; G. RANALLI; M. ZUCCHI; C. SORLINI

4

Cometabolism of methyl tert-butyl ether (MTBE) with alkanes  

Microsoft Academic Search

The release of methyl tert-butyl ether (MTBE) to the environment, mainly from damaged gasoline underground storage tanks or\\u000a distribution systems spills, has provoked extended groundwater pollution. Biological treatments are, in general, a good alternative\\u000a for bioremediation of polluted sites; however, MTBE elimination from environment has constituted a challenge because of its\\u000a chemical structure and physicochemical properties. The combination of a

Verónica Nava; Marcia Morales; Sergio Revah

2007-01-01

5

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

Microsoft Academic Search

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

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

2001-01-01

6

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

PubMed

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

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

2012-09-01

7

Excess enthalpies of ternary mixtures consisting of a normal alkane, methyl tert-butyl ether, and tert-amyl methyl ether  

SciTech Connect

The thermodynamic properties of hydrocarbon + ether mixtures are of interest in view of the use of ethers as oxygenating agents in gasoline technology. Excess molar enthalpies, measured at 298.15 K in a flow microcalorimeter, are reported for the two ternary systems heptane + methyl tert-butyl ether + tert-amyl methyl ether and decane + methyl tert-butyl ether + tert-amyl methyl ether. Smooth representations of the results and analyses in terms of the Flory theory are presented.

Tong, Z.; Benson, G.C.; Wang, L.L.; Lu, B.C.Y. [Univ. of Ottawa, Ontario (Canada). Dept. of Chemical Engineering] [Univ. of Ottawa, Ontario (Canada). Dept. of Chemical Engineering

1996-07-01

8

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

9

REDUCTIVE ACTIVATION OF DIOXYGEN FOR DEGRADATION OF METHYL TERT-BUTYL ETHER BY BIFUNCTION  

EPA Science Inventory

Bifunctional aluminum is prepared by sulfating aluminum metal with sulfuric acid. The use of bifunctional aluminum to degrade methyl tert-butyl ether (MTBE) in the presence of dioxygen has been examined using batch systems. Primary degradation products were tert-butyl alcohol, ...

10

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

Microsoft Academic Search

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

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

2007-01-01

11

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

12

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

USGS Publications Warehouse

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

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

1997-01-01

13

Reactions of unsaturated and macromolecular compounds communication 7. copolymerization of tert-butyl vinyl ether with methyl methacrylate  

Microsoft Academic Search

Summary 1.The copolymerization reaction of methyl methacrylate with tert-butyl vinyl ether was investigated, and some of their copolymers were prepared.2.It was established that the content of tert-butyl vinyl ether residues in the copolymer with methyl methacrylate increases with increase in the concentration of the vinyl ether in the original monomer mix.3.tert-Butyl vinyl ether does not polymerize in presence of benzoyl

M. F. Shostakovsky; A. M. Khomutov; V. I. Belyaev

1957-01-01

14

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

PubMed

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

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

2005-10-01

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

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

EPA Science Inventory

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

17

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...

18

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...

19

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...

20

Multiple steady states during reactive distillation of methyl tert-butyl ether  

Microsoft Academic Search

This paper presents results of computer simulations of the synthesis of methyl tert-butyl ether (MTBE) in a fixed-bed reactor and in a reactive distillation column. These calculations clearly showed the advantages of MTBE synthesis in a catalytic distillation tower. Furthermore, the computer simulations showed that multiple steady states may occur in the reactive distillation column during MTBE synthesis in a

S. A. Nijhuis; F. P. J. M. Kerkhof; A. N. S. Mak

1993-01-01

21

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

Microsoft Academic Search

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

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

1997-01-01

22

Biodegradation of methyl tert-butyl ether by a bacterial pure culture  

Microsoft Academic Search

A bacterial strain, PM1, which is able to utilize methyl tert-butyl ether (MTBE) as its sole carbon and energy source, was isolated from a mixed microbial consortium in a compost biofilter capable of degrading MTBE. Initial linear rates of MTBE degradation by 2 x 10⁶ cells ml⁻¹ were 0.07, 1.17, and 3.56 μg ml⁻¹ h⁻¹ for initial concentrations of 5,

JESSICA R. HANSON; CORINNE E. ACKERMAN; KATE M. SCOW

1999-01-01

23

Study of ion\\/molecule reactions of ion derived from tert-butyl methyl ether and trimethylsilyl methyl ether  

Microsoft Academic Search

The ion\\/molecule reactions of the ions (CH3)2C+–OCH3 (1a) and (CH3)2Si+–OCH3 (2a), which are the main fragment ions in the electron ionization mass spectrum of tert-butyl methyl ether (MTBE, 1) and trimethylsilyl methyl ether (MTSE, 2), respectively, and of the protonated MTBE (1H+) and protonated MTSE (2H+), generated by chemical ionization, with MTBE or MTSE, with acetone and with ammonia have

Michael Büchner; Hans Friedrich Grützmacher

2000-01-01

24

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

25

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

26

The sonolytic destruction of methyl tert-butyl ether present in contaminated groundwater.  

PubMed

Ultrasonic irradiation in the presence of ozone was used to efficiently eliminate methyl tert-butyl ether (MTBE) from groundwater. The sonolytic degradation of MTBE was investigated in three different reactor configurations and frequencies: vibrating-plate reactor (VPR, 358 kHz), near-field acoustical processor (NAP 20 and 16 kHz), and radial-tube resonator (RTR. 20 kHz). The sonochemical reactors can be ordered in terms of their efficiency with respect to the degradation of MTBE in the following way: VPR > RTR > NAP. The higher elimination rates of MTBE in groundwater by combined ultrasound-ozone systems are attributed to the effective conversion of ozone to the OH radical, even in the presence of high alkalinity. Carbonate radicals, which were formed from the oxidation of bicarbonate by hydroxyl radicals, are shown to react with MTBE via a hydrogen-atom abstraction pathway. Methyl-tert-butyl ether was also rapidly eliminated from the groundwater underlying a major intemational airport by direct chemical oxidation with a mixture of hydrogen peroxide and ozone. PMID:12540095

Hung, Hui-Ming; Kang, Joon-Wun; Hoffmann, Michael R

2002-01-01

27

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

PubMed

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

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

1990-08-01

28

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

29

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...

30

WATER QUALITY AT FIVE MARINAS IN LAKE TEXOMA AS RELATED TO METHYL TERT-BUTYL ETHER (MTBE)  

EPA Science Inventory

Occurrence of methyl tert-butyl ether (MTBE) in five marinas was monitored between June 1999 and November 2000 in Lake Texoma located on the border of Oklahoma and Texas. MTBE is a commonly used gasoline additive and a suspected carcinogen. Lake water was collected at locations i...

31

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...

32

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...

33

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

Microsoft Academic Search

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

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

1995-01-01

34

The mechanism of catalytic methylation of 2-phenylpyridine using di-tert-butyl peroxide.  

PubMed

The mechanism of palladium chloride-catalyzed direct methylation of arenes with peroxides is elucidated by using the energetics computed at the M06 density functional theory. The introduction of a methyl group by tert-butyl peroxides at the ortho-position of a prototypical 2-phenyl pyridine, a commonly used substrate in directed C-H functionalization reactions, is examined in detail by identifying the key intermediates and transition states involved in the reaction sequence. Different possibilities that differ in terms of the site of catalyst coordination with the substrate and the ensuing mechanism are presented. The important mechanistic events involved are (a) an oxidative or a homolytic cleavage of the peroxide O-O bond, (b) C-H bond activation, (c) C-C bond activation, and (d) reductive elimination involving methyl transfer to the aromatic ring. We have examined both radical and non-radical pathways. In the non-radical pathway, the lowest energy pathway involves C-H bond activation prior to the coordination of the peroxide to palladium, which is subsequently followed by the O-O bond cleavage of the peroxide and the C-C bond activation. Reductive elimination in the resulting intermediate leads to the vital C-C bond formation between methyl and aryl carbon atoms. In the non-radical pathway, the C-C bond activation is higher in energy and has been identified as the rate-limiting step of this reaction. In the radical pathway, however, the activation barrier for the C-C bond cleavage is lower than for the peroxide O-O bond cleavage. A combination of a radical pathway up to the formation of a palladium methyl intermediate and a subsequent non-radical pathway has been identified as the most favored pathway for the title reaction. The predicted mechanism is in good agreement with the experimental observations on PdCl2 catalyzed methylation of 2-phenyl pyridine using tert-butyl peroxide. PMID:24875675

Sharma, Akhilesh K; Roy, Dipankar; Sunoj, Raghavan B

2014-07-14

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

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

Microsoft Academic Search

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

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

2000-01-01

38

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

Microsoft Academic Search

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

Michael Moran

39

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

Microsoft Academic Search

Anecdotal reports suggest that high environmental or occupational exposures to the fuel oxygenate methyl tert-butyl ether (MTBE) may result in breath concentrations that are sufficiently elevated to cause a false positive on commercial breath-alcohol analyzers. We evaluated this possibility in vitro by establishing a response curve for simulated breath containing MTBE in ethanol. Two types of breath-alcohol analyzers were evaluated.

Timothy J. Buckley; Joachim D. Pleil; James R. Bowyer; J. Michael Davis

2001-01-01

40

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

PubMed

An aerobic mixed bacterial culture (CL-EMC-1) capable of utilizing methyl tert-butyl ether (MTBE) as the sole source of carbon and energy with a growth temperature range of 3 to 30 degrees C and optimum of 18 to 22 degrees C was enriched from activated sludge. Transient accumulation of tert-butanol (TBA) occurred during utilization of MTBE at temperatures from 3 degrees C to 14 degrees C, but TBA did not accumulate above 18 degrees C. The culture utilized MTBE at a concentration of up to 1.5 g l(-1) and TBA of up to 7 g l(-1). The culture grew on MTBE at a pH range of 5 to 9, with an optimum pH of 6.5 to 7.1. The specific growth rate of the CL-EMC-1 culture on 0.1 g l(-1) of MTBE at 22 degrees C and pH 7.1 was 0.012 h(-1), and the growth yield was 0.64 g (dry weight) g(-1). A new MTBE-utilizing bacterium, Variovorax paradoxus strain CL-8, isolated from the mixed culture utilized MTBE, TBA, 2-hydroxy isobutyrate, lactate, methacrylate, and acetate as sole sources of carbon and energy but not 2-propanol, acetone, methanol, formaldehyde, or formate. Two other isolates, Hyphomicrobium facilis strain CL-2 and Methylobacterium extorquens strain CL-4, isolated from the mixed culture were able to grow on C(1) compounds. The combined consortium could thus utilize all of the carbon of MTBE. PMID:17146651

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

2007-04-01

41

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

42

Effect of methyl tert-butyl ether in standard tests for mutagenicity and environmental toxicity.  

PubMed

Methyl tert-butyl ether (MTBE) is a synthetic compound that is used as a technological solution to problems created by air pollution from vehicle emissions. An important source of MTBE in the environment is leakage from underground storage tanks at gasoline stations or accidents during gasoline transport. The aim of this study was to evaluate the risk of MTBE leakage for the environment using the Microtox (Vibrio fischeri) toxicity test, Lactuca sativa seed germination test, and Ames bacterial mutagenicity test with Salmonella typhimurium his(-) strains TA98, TA100, YG1041, and YG1042, using both standard plate and preincubation protocols. The result of Microtox expressed as EC(50) was 33 mg (MTBE)/L. The effect of all tested MTBE concentration (0.05, 0.50, and 1.00% v/v) on Lactuca sativa roots elongation was negative and proved its toxicity. The highest tested concentration of MTBE that could be tested in Ames test was 3 mg (MTBE)/plate, because of cytotoxicity. No mutagenic response was observed at this or lower concentrations in any of the four strains used. PMID:17091504

Vosahlikova, Miluse; Cajthaml, Tomas; Demnerova, Katerina; Pazlarova, Jarmila

2006-12-01

43

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

PubMed

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

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

2012-06-01

44

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

PubMed Central

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

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

2009-01-01

45

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

PubMed

In the title compound, [Yb(C(24)H(40)BN(6))(2)]·C(7)H(8), the Yb atom is coordinated by two tris(3-tert-butyl-5-methyl-pyrazol-1-yl)hydridoborate [Tp(tBu,Me)] ligands. One ligand binds in the ?(3) mode, throuh three N atoms of the pyrazolyl rings, the other ligand coordinates through two N atoms of the pyrazolyl rings and the H atom attached to the central B via an agostic-type inter-action through the B-H group of the second Tp(tBu,Me) ligand, giving an overall distorted octa-hedral geometry. One of the tert-butyl groups is disordered over two sites, with occupancies of 0.65 and 0.35. PMID:21583010

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

2009-01-01

46

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

47

Electrocatalytic oxidation of methyl tert-butyl ether (MTBE) in aqueous solution at a nickel electrode.  

PubMed

This study utilized the electrocatalytic characteristics of nickel electrode to perform degradation of methyl tert-butyl ether (MTBE) in aqueous solution. Lab experiments were conducted in a spiltless bath type cell equipped with a nickel electrode as working electrode, a platinum wire as counter electrode, and an Ag/AgCl electrode as reference electrode. Effects of controlled potential, supporting electrolyte, and solution pH on the efficiency of MTBE removal were examined under the control of the constant-potential conditions. Experiment results showed that the optimum electrolytic condition was operated at 0.35 V in a 1M KOH electrolyte solution, and the initial 20 mgl(-1) MTBE was reduced by 73% within 180 min under the optimum control. As using 1M Na2SO4 and 1M KCl as electrolyte, the efficiency of MTBE removal dropped to 60% and 50% under the similar controls. Comparing with various pH controls, the strong basic condition is favorable for electrocatalytic oxidation of MTBE in the Ni-electrolytic system. The efficiency of MTBE removal showed a rising trend with increasing initial pH of the solution. The formation of a redox NiOOH/Ni(OH)2 layer on the anode surface, which was observed on the SEM image, can explain that nickel plays a mediator role on improving electrocatalytic oxidation of MTBE at 0.35 V in a strong basic condition. The by-products of MTBE degradation were identified as acetone and CO(2) by GC/MS, and the distributions of carbon atoms in acetone, CO2, and MTBE were found 22%, 51%, and 27% through the optimum control of electrochemical oxidation. PMID:17553546

Wu, Ting-Nien

2007-09-01

48

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

PubMed Central

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

Hartle, R

1993-01-01

49

Biodegradation of methyl tert-butyl ether by a bacterial pure culture  

SciTech Connect

A bacterial strain, PM1, which is able to utilize methyl tert-butyl ether (MTBE) as its sole carbon and energy source, was isolated from a mixed microbial consortium in a compost biofilter capable of degrading MTBE. Initial linear rates of MTBE degradation by 2 x 10{sup 6} cells ml{sup {minus}1} were 0.07, 1.17, and 3.56 {mu}g ml{sup {minus}1} h{sup {minus}1} for initial concentrations of 5, 50, and 500 {mu}g MTBE ml{sup {minus}1}, respectively. When incubated with 20 {mu}g of uniformly labeled [{sup 14}C]MTBE ml{sup {minus}1}, strain PM1 converted 46% to {sup 14}CO{sub 2} and 19% to {sup 14}C-labeled cells within 120 h. This yield is consistent with the measurement of protein accumulation at different MTBE concentrations from which was estimated a biomass yield of 0.18 of cells mg MTBE{sup {minus}1}. Strain PM1 was inoculated into sediment core material collected from a contaminated groundwater plume at Port Hueneme, California, in which there was no evidence of MTBE degradation. Strain PM1 readily degraded 20 {micro}g of MTBE ml{sup {minus}1} added to the core material. The rate of MTBE removal increased with additional inputs of 20 {micro}g of MTBE ml{sup {minus}1}. These results suggest that PM1 has potential for use in the remediation of MTBE-contaminated environments.

Hanson, J.R.; Ackerman, C.E.; Scow, K.M.

1999-11-01

50

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 1500mg/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

51

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

52

tert-Butyl cation affinities of maingroup-element hydrides: effect of methyl substituents at the protophilic center.  

PubMed

We have conducted an extensive computational exploration of how the gas-phase tert-butyl cation affinities (t-BCA) of archetypal anionic and neutral bases across the periodic system are affected by stepwise replacement of all hydrogen atoms at the protophilic center with methyl substituents. This study was conducted using zeroth-order regular approximation relativistic density functional theory (DFT) at the BP86/QZ4P//BP86/TZ2P level. The trends are interpreted in terms of the steric effects of methyl substituents at the protophilic center of the anionic (Me(m)XH(n-1-m)(-)) and neutral bases (Me(m)XH(n-m)). Besides insight, this work also provides an intrinsically consistent set of values of the 298 K tert-butyl cation affinities of all (partially) methyl-substituted or unsubstituted bases constituted by maingroup-element hydrides of groups 14-16 in anionic cases (Me(m)XH(n-1-m)(-)) and groups 15-17 in neutral ones (Me(m)XH(n-m)) along periods 2-6. The effect of long-range dispersion (van der Waals) interactions was estimated through dispersion-corrected density functional theory (DFT-D3) at the BP86-D3/QZ4P//BP86/TZ2P level. PMID:21718012

Ruiz, Juan M; Guerra, Célia Fonseca; Bickelhaupt, F Matthias

2011-07-28

53

Metabolism of Diethyl Ether and Cometabolism of Methyl tert-Butyl Ether by a Filamentous Fungus, a Graphium sp  

PubMed Central

In this study, evidence for two novel metabolic processes catalyzed by a filamentous fungus, Graphium sp. strain ATCC 58400, is presented. First, our results indicate that this Graphium sp. can utilize the widely used solvent diethyl ether (DEE) as the sole source of carbon and energy for growth. The kinetics of biomass accumulation and DEE consumption closely followed each other, and the molar growth yield on DEE was indistinguishable from that with n-butane. n-Butane-grown mycelia also immediately oxidized DEE without the extracellular accumulation of organic oxidation products. This suggests a common pathway for the oxidation of both compounds. Acetylene, ethylene, and other unsaturated gaseous hydrocarbons completely inhibited the growth of this Graphium sp. on DEE and DEE oxidation by n-butane-grown mycelia. Second, our results indicate that gaseous n-alkane-grown Graphium mycelia can cometabolically degrade the gasoline oxygenate methyl tert-butyl ether (MTBE). The degradation of MTBE was also completely inhibited by acetylene, ethylene, and other unsaturated hydrocarbons and was strongly influenced by n-butane. Two products of MTBE degradation, tert-butyl formate (TBF) and tert-butyl alcohol (TBA), were detected. The kinetics of product formation suggest that TBF production temporally precedes TBA accumulation and that TBF is hydrolyzed both biotically and abiotically to yield TBA. Extracellular accumulation of TBA accounted for only a maximum of 25% of the total MTBE consumed. Our results suggest that both DEE oxidation and MTBE oxidation are initiated by cytochrome P-450-catalyzed reactions which lead to scission of the ether bonds in these compounds. Our findings also suggest a potential role for gaseous n-alkane-oxidizing fungi in the remediation of MTBE contamination.

Hardison, L. K.; Curry, S. S.; Ciuffetti, L. M.; Hyman, M. R.

1997-01-01

54

Alkylation of phenol with MTBE and other tert-butyl ethers: cation exchange resins as catalysts  

Microsoft Academic Search

Alkylation of phenol was carried out using methyl tert-butyl ether, mono tert-butyl ether of mono ethylene glycol, tert-butanol and isobutylene in the presence of cation exchange resins, acid treated clay and para-toluene sulfonic acid as catalysts. The selectivity with respect to 2- and 4-tert-butyl phenol was studied.

K. Gokul Chandra; M. M. Sharma

1993-01-01

55

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

PubMed

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

Fester, Thomas

2013-01-01

56

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

PubMed Central

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

Fester, Thomas

2013-01-01

57

Detection of microphase separation in poly( tert-butyl acrylate- b-methyl methacrylate) synthesized via atom transfer radical polymerization by inverse gas chromatography  

Microsoft Academic Search

A trace amount of solvents such as n-octane, n-nonane, n-decane, ethyl acetate, n-propyl acetate, isoamyl acetate, toluene, ethyl benzene, n-propyl benzene, isopropyl benzene and chloro benzene was passed through the column of a gas chromatograph of which the stationary phase is poly(tert-butyl acrylate-b-methyl methacrylate), poly(tBA-b-MMA), block copolymer with low polydispersity, prepared via ATRP of tBA and MMA, respectively. The retention

Sevda Aydin; Tuba Erdogan; Dolunay Sakar; Gurkan Hizal; Ozlem Cankurtaran; Umit Tunca; Ferdane Karaman

2008-01-01

58

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

Microsoft Academic Search

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

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

2005-01-01

59

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

PubMed Central

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

Sun, Weimin; Sun, Xiaoxu

2012-01-01

60

Evaluating UV/H2O2 processes for methyl tert-butyl ether and tertiary butyl alcohol removal: effect of pretreatment options and light sources.  

PubMed

In this paper, we evaluate the efficiency of UV/H2O2 process to remove methyl tert-butyl ether (MtBE) and tertiary butyl alcohol (tBA) from a drinking water source. Kinetic models were used to evaluate the removal efficiency of the UV/H2O2 technologies with different pretreatment options and light sources. Two commercial UV light sources, i.e. low pressure, high intensity lamps and medium pressure, high intensity lamps, were evaluated. The following pretreatment alternatives were evaluated: (1) ion exchange softening with seawater regeneration (NaIX); (2) Pellet Softening; (3) weak acid ion exchange (WAIX); and (4) high pH lime softening followed by reverse osmosis (RO). The presence or absence of a dealkalization step prior to the UV/H2O2 Advanced Oxidation Process (AOP) was also evaluated for each pretreatment possibility. Pretreatment has a significant impact on the performance of UV/H2O2 process. The NaIX with dealkalization was shown to be the most cost effective. The electrical energy per order (EEO) values for MtBE and tBA using low pressure high output UV lamps (LPUV) and 10mg/LH2O2 are 0.77 and 3.0 kWh/kgal-order, or 0.20 and 0.79 kWh/m3-order, respectively. For medium pressure UV high output lamps (MPUV), EEO values for MtBE and tBA are 4.6 and 15 kWh/kgal-order, or 1.2 and 4.0 kWh/m3-order, for the same H2O2 dosage. PMID:18951605

Li, Ke; Hokanson, David R; Crittenden, John C; Trussell, Rhodes R; Minakata, Daisuke

2008-12-01

61

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

PubMed Central

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

Smith, Christy A.; Hyman, Michael R.

2004-01-01

62

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

Microsoft Academic Search

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

Scott Phillips; Robert B. Palmer; Aaron Brody

2008-01-01

63

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

PubMed Central

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

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

2008-01-01

64

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

PubMed Central

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

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

2002-01-01

65

The interactions of methyl tert-butyl ether on high silica zeolites: a combined experimental and computational study.  

PubMed

In this work, the interactions of methyl tert-butyl ether (MTBE) on different dealuminated high silica zeolites were studied by means of both experimental and computational approaches. Zeolites with different textural and surface features were selected as adsorbents and the effect of their physico-chemical properties (i.e. pore size architecture and type and amount of surface OH sites) on sorption capacity were studied. High silica mordenite (MOR) and Y zeolites (both with a SiO2/Al2O3 ratio of 200) and ZSM-5 solid (SiO2/Al2O3 ratio of 500) were selected as model sorbents. By combining FTIR and SS-NMR (both (1)H and (13)C CPMAS NMR) spectroscopy it was possible to follow accurately the MTBE adsorption process on highly defective MOR characterized by a high concentration of surface SiOH groups. The adsorption process is found to occur in different steps and to involve isolated silanol sites, weakly interacting silanols, and the siloxane network of the zeolite, respectively. H-bonding and van der Waals interactions occurring between the mordenite surface and MTBE molecules were modeled by DFT calculations using a large cluster of the MOR structure where two adjacent side-pockets were fused in a large micropore to simulate a dealumination process leading to silanol groups. This is the locus where MTBE molecules are more strongly bound and stabilized. FTIR spectroscopy and gravimetric measurements allowed determination of the interaction strength and sorption capacities of all three zeolites. In the case of both Y and MOR zeolites, medium-weak H-bonding with isolated silanols (both on internal and external zeolite surfaces) and van der Waals interactions are responsible for MTBE adsorption, whereas ZSM-5, in which a negligible amount of surface silanol species is present, displays a much lower amount of adsorbed MTBE retained mainly through van der Waals interactions with zeolite siloxane network. PMID:23860729

Sacchetto, V; Gatti, G; Paul, G; Braschi, I; Berlier, G; Cossi, M; Marchese, L; Bagatin, R; Bisio, C

2013-08-28

66

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

PubMed Central

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

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

2007-01-01

67

Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C7H8 Toluene (VMSD1211, LB4618_V)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C7H8 Toluene (VMSD1211, LB4618_V)' providing data from direct low-pressure dilatometric measurement of molar excess volume at variable mole fraction and constant temperature.

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

68

Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C7H8 Toluene (VMSD1111, LB3142_V)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C7H8 Toluene (VMSD1111, LB3142_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.

69

Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C7H8 Toluene (VMSD1212, LB3146_V)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume B 'Binary Liquid Systems of Nonelectrolytes II' of Volume 26 'Heats of Mixing, Vapor-Liquid Equilibrium, and Volumetric Properties of Mixtures and Solutions' of Landolt-Börnstein Group IV 'Physical Chemistry'. It contains the Chapter 'Volumetric Properties of the Mixture tert-Butyl methyl ether C5H12O + C7H8 Toluene (VMSD1212, LB3146_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.

70

Metabolically Stable tert-Butyl Replacement  

PubMed Central

Susceptibility to metabolism is a common issue with the tert-butyl group on compounds of medicinal interest. We demonstrate an approach of removing all the fully sp3 C–Hs from a tert-butyl group: replacing some C–Hs with C–Fs and increasing the s-character of the remaining C–Hs. This approach gave a trifluoromethylcyclopropyl group, which increased metabolic stability. Trifluoromethylcyclopropyl-containing analogues had consistently higher metabolic stability in vitro and in vivo compared to their tert-butyl-containing counterparts.

2013-01-01

71

Comparison of the self-exchange and interfacial charge-transfer rate constants for methyl- versus tert-butyl-substituted Os(III) polypyridyl complexes.  

PubMed

Differences in the self-exchange and interfacial electron-transfer rate constants have been evaluated for a relatively unhindered Os(III/II) redox system, osmium(III/II) tris(4,4'-di-methyl-2,2'-bipyridyl), [Os(Me2bpy)3]3+/2+, relative to those of a relatively hindered system, osmium(III/II) tris(4,4'-di-tert-butyl-2,2'-bipyridyl), [Os(t-Bu2bpy)3]3+/2+. In contrast to the predicted increase in rate constant by a factor of 2-3 due to the difference in reorganization energy of the two complexes, introduction of the tert-butyl functionality decreased the self-exchange rate constant, as measured by NMR line-broadening techniques, by a factor of approximately 50 as compared to that of the analogous methyl-substituted osmium complex. Steady-state current density versus potential measurements, in conjunction with differential capacitance versus potential measurements, were used to compare the interfacial electron-transfer rate constants at n-type ZnO electrodes of [Os(t-Bu2bpy)3]3+/2+ and [Os(Me2bpy)3]3+/2+. The interfacial electron-transfer rate constant for the reduction of [Os(t-Bu2bpy)3]3+ was 100 times smaller than that for [Os(Me2bpy)3]3+. The results indicate that the tert-butyl group can act as a spacer on an outer-sphere redox couple and significantly decrease the electronic coupling of the electron-transfer reaction in both self-exchange and interfacial electron-transfer processes. PMID:17166001

Hamann, Thomas W; Brunschwig, Bruce S; Lewis, Nathan S

2006-12-21

72

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

Microsoft Academic Search

A new aerobic bacterial strain, CIP I-2052, isolated from an activated sludge sample, was able to use tert-butyl alcohol (TBA), a product of methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) degradation, as its sole carbon and energy source. Cobalt ions stimulated TBA mineralization. The maximum growth and TBA degradation rates were 0.032ǂ.004 h-1 and 35.8NJ.5 mg TBA·g-1 (cell

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

2001-01-01

73

Enantioselective synthesis of tert-butyl tert-butanethiosulfinate catalyzed by cyclohexanone monooxygenase.  

PubMed

Cyclohexanone monooxygenase from Acinetobacter calcoaceticus catalyzes the asymmetric oxidation of tert-butyl disulfide to enantiomerically pure (R)-tert-butyl tert-butanethiosulfinate. Lower enantioselectivities and conversions were observed in the oxidation of i-propyl, n-butyl, p-tolyl tert-butyl disulfides and alkylthiophosphonates. PMID:11135413

Colonna, S; Gaggero, N; Carrea, G; Pasta, P; Alphand, V; Furstoss, R

2001-01-01

74

METHYL TERT-BUTYLETHER-WATER INTERACTION  

EPA Science Inventory

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

75

Thermodynamic properties and ideal-gas enthalpies of formation for butyl vinyl ether, 1,2-dimethoxyethane, methyl glycolate, bicyclo[2.2.1]hept-2-ene, 5-vinylbicyclo[2.2.1]hept-2-ene, trans-azobenzene, butyl acrylate, di-tert-butyl ether, and hexane-1,6-diol  

Microsoft Academic Search

Ideal-gas enthalpies of formation of butyl vinyl ether, 1,2-dimethoxyethane, methyl glycolate, bicyclo-[2.2.1]hept-2-ene, 5-vinylbicyclo[2.2.1]hept-2-ene, trans-azobenzene, butyl acrylate, di-tert-butyl ether, and hexane-1,6-diol are reported. Enthalpies of fusion were determined for bicyclo[2.2.1]hept-2-ene and trans-azobenzene. Two-phase (solid + vapor) or (liquid + vapor) heat capacities were determined from 300 K to the critical region or earlier decomposition temperature for each compound studied. Liquid-phase densities

W. V. Steele; R. D. Chirico; S. E. Knipmeyer; A. Nguyen; N. K. Smith

1996-01-01

76

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

2014-05-01

77

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

PubMed

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

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

1990-01-01

78

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

79

Thermodynamic properties and ideal-gas enthalpies of formation for butyl vinyl ether, 1,2-dimethoxyethane, methyl glycolate, bicyclo[2.2.1]hept-2-ene, 5-vinylbicyclo[2.2.1]hept-2-ene, trans-azobenzene, butyl acrylate, di-tert-butyl ether, and hexane-1,6-diol  

SciTech Connect

Ideal-gas enthalpies of formation of butyl vinyl ether, 1,2-dimethoxyethane, methyl glycolate, bicyclo-[2.2.1]hept-2-ene, 5-vinylbicyclo[2.2.1]hept-2-ene, trans-azobenzene, butyl acrylate, di-tert-butyl ether, and hexane-1,6-diol are reported. Enthalpies of fusion were determined for bicyclo[2.2.1]hept-2-ene and trans-azobenzene. Two-phase (solid + vapor) or (liquid + vapor) heat capacities were determined from 300 K to the critical region or earlier decomposition temperature for each compound studied. Liquid-phase densities along the saturation line were measured for bicyclo[2.2.1]hept-2-ene. For butyl vinyl ether and 1,2-dimethoxyethane, critical temperatures and critical densities were determined from the dsc results and corresponding critical pressures derived from the fitting procedures. Fitting procedures were used to derive critical temperatures, critical pressures, and critical densities for bicyclo[2.2.1]hept-2-ene, 5-vinylbicyclo[2.2.1]hept-2-ene, trans-azobenzene, butyl acrylate, and di-tert-butyl ether. Group-additivity parameters or ring-correction terms useful in the application of the Benson group-contribution correlations were derived.

Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Smith, N.K. [National Inst. for Petroleum and Energy Research, Bartlesville, OK (United States). IIT Research Inst.] [National Inst. for Petroleum and Energy Research, Bartlesville, OK (United States). IIT Research Inst.

1996-11-01

80

Two-Color Two-Photon Excited Fluorescence of 2-Methyl-5-tert-butyl-p-quaterphenyl (DMQ): Ab Initio Calculations and Experimental Determination of the Molecular Parameters.  

PubMed

The paper presents experimental and theoretical studies of two-photon excitation dynamics in 2-methyl-5-tert-butyl-p-quaterphenyl (DMQ) dissolved in cyclohexane/paraffin. Experimentally, a two-color two-photon (2C2P) excitation by two femtosecond laser pulses at 800 and 400 nm has been used in combination with the time-resolved detection of polarized molecular fluorescence. The fluorescence decay was found to be two-exponential, resulting in the molecular excited state lifetime of 753 ± 10 ps and the rotational correlation time of 724 ± 45 ps. Control over the excited and fluorescent photons polarization has been used for determination from experiment of seven independent molecular parameters. The experimental data were analyzed on the basis of the recent theoretical approach [ Shternin , P. S. , Gericke , K.-H. , and Vasyutinskii , O. S. Mol. Phys. 2010 , 108 , 813 - 825 ] supported by ab initio computations of the DMQ electronic structure and transition dipole moments. The results obtained imply that the two-photon absorption tensor S is mostly diagonal and that the Szz tensor component onto the molecular long axis gives the major contribution of 93%. However, it was also found that a number of different symmetry two-photon transitions related to the dipole moment components dxdz and dydz are excited in the conditions of our measurements. PMID:24964069

Herbrich, Sebastian; Gericke, Karl-Heinz; Smolin, Andrey G; Vasyutinskii, Oleg S

2014-07-17

81

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

PubMed

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

Safari, Mojtaba; Rostami, Mohammad Hossein; Alizadeh, Mehriana; Alizadehbirjandi, Atefeh; Nakhli, Seyyed Ali Akbar; Aminzadeh, Reza

2014-01-01

82

Tetra-chlorido-[N 2,N 2?-(di-methyl-silanedi-yl)bis-(N-tert-butyl-3-methyl-benzimid-amid-ato)-?2 N 2,N 2?]hafnium(IV)  

PubMed Central

The symmetric title mol­ecule, [Hf(C26H40N4Si)Cl4], lies about a twofold rotation axis. The HfIV and Si atoms lie on the rotation axis with all other atoms being in general positions. The HfIV atom is six-coordinated by two N atoms from the N 2,N 2?-(di­methyl­silanedi­yl)bis­(N-tert-butyl-3-methyl­benz­imid­amidate) ligand and four Cl? ions in a slightly distorted octa­hedral geometry. The two amidinate moieties are connected through the central Si atom with Si—N bond length of 1.762?(3)?Å, generating the characteristic N—C—N—Si—N—C—N skeleton of a silyl-linked ansa-bis­(amidine) species.

Wang, Tao; Zhao, Jian-Ping; Bai, Sheng-Di

2013-01-01

83

Application of NMR spectroscopy for assignment of the absolute configuration of 8-tert-butyl-2-hydroxy-7-methoxy-8-methyl-9-oxa-6-azaspiro[4.5]dec-6-en-10-one.  

PubMed

In order to assign the absolute configurations of 8-tert-butyl-2-hydroxy-7-methoxy-8-methyl-9-oxa-6-azaspiro[4.5]dec-6-en-10-one (2a,b), their esters (5a-d) with (R)- or (S)-2-methoxyphenylacetic acid (4a,b) have been synthesized. The absolute configurations of these compounds have been determined on the basis of NOESY correlations between the protons of the tert-butyl group and the cyclopentane fragment of the molecules. The crucial part of this analysis was assignment of the absolute configuration at C-5. Additionally, by calculation of the chemical shift anisotropy, ?(RS), for the relevant protons, it was also possible to confirm the absolute configurations at the C-2 centres of compounds 2a,b and 5a-d. PMID:23716294

Jakubowska, Anna; Sowa, Agnieszka; Zylewski, Marek; Kulig, Katarzyna

2013-07-01

84

Synthesis of [ 11C]methyl magnesium iodide and its application to the introduction of [ 11C]-N- tert-butyl groups and [ 11C]- sec-alcohols  

Microsoft Academic Search

The 11C labelled Grignard reagent methyl magnesium iodide was synthesized carrier and non-carrier added from [11C]methyl iodide and magnesium. This new 11C-synthon was applied in the synthesis of a [11C]-N-tert-butyl group by reaction with 2,2,3,4-tetramethyl-5-oxazolidine and in the synthesis of 11C-sec-alcohols by reaction with benzaldehyde and 3-phenylpropionaldehyde. The radiochemical yield was 18–29% (not corrected for decay) with a synthesis time

Philip H Elsinga; Erik Keller; Tjibbe J De Groot; Gerben M Visser; Willem Vaalburg

1995-01-01

85

Double- and triple-consecutive O-insertion into tert-butyl and triarylmethyl structures.  

PubMed

[reaction: see text] The concecutive Criegee rearrangement reactions were studied for tert-butyl trifluoroacetate, triarylcarbinols, and benzophenone ketales with trifluoroperacetic acid (TFPAA) in trifluoroacetic acid (TFA). The formation of methyl acetate and methyl trifluoroacetate indicates that the consecutive double-O-insertion process has taken place for tert-butyl trifluoroacetate. The intermediate dimethoxymethylcarbonium ion was detected below 5 degrees C. A consecutive triple-O-insertion process has been observed for triarylmethanols and benzophenone ketals. A new high yield method of corresponding diaryl carbonates synthesis was developed. PMID:15255685

Krasutsky, Pavel A; Kolomitsyn, Igor V; Krasutsky, Sergiy G; Kiprof, Paul

2004-07-22

86

OCCURRENCE OF METYL TERT-BUTYL ETHER (MTBE) AT FIVE MARINAS IN LAKE TEXOMA  

EPA Science Inventory

Occurrence of methyl tert-butyl ether (MTBE) in five marinas was monitored between June 1999 and November 2000 in Lake Texoma located on the border of Oklahoma and Texas. MTBE is a commonly used gasoline additive and a suspected carcinogen. Lake water was collected at loc...

87

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

Microsoft Academic Search

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 ¹⁴COâ under mixed aerobic\\/anaerobic conditions. No significant mineralization was observed under strictly anaerobic conditions. The results indicate that, under the mixed aerobic\\/anaerobic

Paul M. Bradley; James E. Landmeyer; Francis H. Chapelle

1999-01-01

88

4-tert-Butyl-pyridinium chloride-4,4?-(propane-2,2-di-yl)bis-(2,6-di-methyl-phenol)-toluene (2/2/1)  

PubMed Central

In the title solvated salt, C9H14N+·Cl?·C19H24O2·0.5C7H7, two mol­ecules of 4,4?-(propane-2,2-di­yl)bis­(2,6-di­methyl­phenol) are linked via O—H?Cl hydrogen bonds to two chloride ions, each of which is also engaged in N—H?Cl hydrogen bonding to a 4-tert-butyl­pyridinium cation, giving a cyclic hydrogen-bonded entity centred at 1/2, 1/2, 1/2. The toluene solvent mol­ecule resides in the lattice and resides on an inversion centre; the disorder of the methyl group requires it to have a site-occupancy factor of 0.5. No crystal packing channels are observed.

Nielson, Alastair J.; Waters, Joyce M.

2014-01-01

89

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

PubMed Central

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

Gao, Qingsong; Xie, Dexun; An, Delie

2013-01-01

90

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

Microsoft Academic Search

Received 12 January 2006\\/Accepted 24 March 2006 Fuel oxygenates such as methyl and ethyl tert-butyl ether (MTBE and ETBE, respectively) are degraded only by a limited number of bacterial strains. The aerobic pathway is generally thought to run via tert-butyl alcohol (TBA) and 2-hydroxyisobutyrate (2-HIBA), whereas further steps are unclear. We have now demonstrated for the newly isolated -proteobacterial strains

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

2006-01-01

91

Estimated daily intakes of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butyl hydroquinone (TBHQ) antioxidants in Korea  

Microsoft Academic Search

The study was conducted to establish the estimated daily intake (EDI) of antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butyl hydroquinone (TBHQ) in Korea. The EDIs were obtained from two sources. One of the estimations was based on the analytical determination of BHA, BHT and TBHQ in 12 food categories (ten food categories for TBHQ) and on

H.-J. Suh; M.-S. Chung; Y.-H. Cho; J.-W. Kim; D.-H. Kim; K.-W. Han; C.-J. Kim

2005-01-01

92

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

93

Synthesis of Poly-O-Tert-Butyl-L-Serine and Poly-L-Serine.  

National Technical Information Service (NTIS)

The synthesis of polymers containing O-tert-butyl-L-serine, O-tert-butyl-DL-serine, L-serine, and DL-serine is reported. The N-benzyloxycarbonyl-(L or DL)-serine benzyl ester was used to synthesize the corresponding N-benzyloxycarbonyl-O-tert-butyl-(L or ...

N. M. Tooney G. D. Fasman

1968-01-01

94

An unusual base-dependent ?-alkylation and ?-elimination of tert-butyl 2-phenyl-2-oxazoline-4-carboxylate: practical synthesis of (±)-?-alkylserines and tert-butyl benzamidoacrylate  

Microsoft Academic Search

Practical synthesis of (±)-?-alkylserines and tert-butyl benzamidoacrylate from tert-butyl 2-phenyl-2-oxazoline-4-carboxylate (6) were developed. The ?-alkylation and ?-elimination of 6 are dramatically dependent upon base conditions. The phase-transfer catalytic condition bearing solid KOH in toluene gives ?-alkylation (up to >99%), and t-BuOK in DMF gives ?-elimination (98%).

Hyeung-geun Park; Jihye Lee; Myoung Joo Kang; Yeon-Ju Lee; Byeong-Seon Jeong; Jeong-Hee Lee; Mi-Sook Yoo; Mi-Jeong Kim; Sea-hoon Choi; Sang-sup Jew

2004-01-01

95

Preparation, characterization and application of p-tert-butyl -calix[4]arene-SBA-15 mesoporous silica molecular sieves  

Microsoft Academic Search

p-tert-Butyl-calix[4]arene-SBA-15 mesoporous silica molecular sieves have been prepared and characterized by Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD) and nitrogen adsorption–desorption measurements. FT-IR spectra showed the presence of methylene (–CH2–), methyl (–CH3) and phenyl bands on the modified SBA-15. Powder XRD data indicated the structure of p-tert-butyl-calix[4]arene-SBA-15 remained the host SBA-15 structure. Brunauer–Emmett–Teller (BET) surface area analysis revealed

Huayu Huang; Chuande Zhao; Yongsheng Ji; Rong Nie; Pan Zhou; Haixia Zhang

2010-01-01

96

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

SciTech Connect

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

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

2009-04-15

97

Synthesis of tert-butyl hydroperoxide and tert-butyl peroxide and their optical investigation in relation to the problem of the structure of hydrogen peroxide  

Microsoft Academic Search

Summary 1.It is shown that test-butyl hydroperoxide and tert-butyl peroxide can be prepared from isobutene.2.It is shown that in previous investigations insufficient account has been taken of the part played by hydrogen bonding in hydrogen peroxide, of which tert-butyl hydroperoxide is a derivative (a fact that is amply confirmed by the presence in the Raman spectrum of the frequencies associated

A. P. Meshcheryakov; M. I. Batuev; A. D. Matveeva

1955-01-01

98

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

99

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

100

A plan for assessing the occurrence and distribution of methyl tert-butyl ether and other volatile organic compounds in drinking water and ambient ground water in the Northeast and Mid-Atlantic regions of the United States  

USGS Publications Warehouse

A plan to assess the occurrence and distribution of methyl tert-butyl ether (MTBE) and other volatile organic compounds (VOCs) in drinking water and ambient ground water in the Northeast and Mid-Atlantic regions of the United States was designed to meet two primary objectives. This study will provide the U.S. Environmental Protection Agency with information on potential human exposure to MTBE and other VOCs from drinking water. In addition, the study will further the goals of the U.S. Geological Survey's (USGS) National Water Quality Assessment Program (NAWQA) by providing additional information on the occurrence and distribution of VOCs in ambient ground water beneath a large, highly urbanized part of the Nation. The study will proceed in two phases-a drinking-water assessment (phase 1) and an ambient ground-water assessment (phase 2). The drinking-water assessment will involve compilation, review, and analysis of available water- quality and ancillary data for approximately 20 percent of the community water systems in 12 States in the Northeast and Mid-Atlantic regions. This effort will summarize the occurrence and distribution of MTBE and other VOCs in drinking water supplied by 2,110 community water systems. The ambient ground-water assessment will involve compilation, review, and analysis of data on MTBE and other VOCs from previous USGS studies in the 12-State area, including regional water-quality assessments conducted for the USGS's NAWQA, plus other available State or local datasets. These data will be related, to the extent allowed by the completeness and quality of the data, to land-use patterns, population density, and other anthropogenic and natural factors using statistical tests. The occurrence and distribution of MTBE and other VOCs in ambient ground water and, to the extent possible, drinking water in relation to such factors, will be evaluated.

Grady, Stephen J.; Casey, George D.

1999-01-01

101

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

102

13 C CP\\/MAS and 2 H NMR study of tert-butyl alcohol dehydration on H-ZSM-5 zeolite. Evidence for the formation of tert-butyl cation and tert-butyl silyl ether intermediates  

Microsoft Academic Search

The dehydration reaction of tert-butyl alcohol, selectively labelled with13C in CH3 or C-O groups (t-BuOH[2-13C2] andt-BuOH[1-13C]), as well as selectively deuterated in methyl groups (t-BuOH[2-2H9]), was studied on H-ZSM-5 zeolite simultaneously with13 C CP\\/MAS and2H solid state NMR. When adsorbed and dehydrated on zeolite at 296 K,t-BuOH[2-13C1] andt-BuOH[1-13C] give rise to identical13C CP\\/MAS NMR spectra of oligomeric aliphatic products. This

Alexander G. Stepanov; Kirill I. Zamaraev; John M. Thomas

1992-01-01

103

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.

2007-04-08

104

(E)-1-(4-Bromo-phen-yl)-2-(4-tert-butyl-phen-yl)-1-phenyl-ethene  

PubMed Central

In the structure of the title compound, C24H23Br, the configuration about the double bond is E. The dihedral angles between the tert-butyl-substituted benzene ring and the unsubstituted and Br-substituted rings are 57.1?(2) and 78.2?(2)°, respectively. The methyl groups are disordered over two positions; the site occupancy factors are ca 0.8 and 0.2.

Kim, Chul-Bae; Cho, Chul-Hee; Chai, Kyu Yun; Park, Kwangyong

2008-01-01

105

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

106

2-Oxo-2H-chromen-4-yl 4-tert-butyl-benzoate  

PubMed Central

In the title mol­ecule, C20H18O4, the three methyl groups of the tert-butyl substituent show rotational disorder. Each methyl group is split over three positions, with refined site-occupation factors of 0.711?(4), 0.146?(3) and 0.144?(4). The benzene ring of the benzoate group is oriented at a dihedral angle of 60.70?(7)° with respect to the planar chromene ring [maximum deviation = 0.046?(2)?Å]. The crystal structure features centrosymmetric R 2 2(8) dimers formed via C—H?O inter­actions, and these dimeric aggregates are connected by C—H?? inter­actions.

Abou, Akoun; Sessouma, Bintou; Djande, Abdoulaye; Saba, Adama; Kakou-Yao, Rita

2012-01-01

107

catena-Poly[[di-tert-butyl-tin(IV)]-?-oxalato  

PubMed Central

The title compound, [Sn(C4H9)2(C2O4)]n, an unexpected side product in the reaction of di-tert-butyl­tin(IV) oxide with nitric acid, represents the first diorganotin(IV) oxalate to be structurally characterized. The SnIV atom of the one-dimensional coordination polymer is located on a mirror plane and is coordinated by two chelating oxalate ions with two rather different Sn—O bond lengths of 2.150?(1) and 2.425?(1)?Å, and two t-butyl groups with Sn—C bond lengths of 2.186?(2) and 2.190?(2)?Å. The coordination polyhedron around the SnIV atom is a distorted tetra­gonal disphenoid. The centrosymmetric oxalate ion also has an asymmetric coordination geometry, as reflected by the two slightly different C—O bond lengths of 1.242?(2) and 1.269?(2)?Å. The chains of the polymer propagate along the b-axis direction. Only van der Waals inter­actions are observed between the chains.

Reichelt, Martin; Reuter, Hans

2014-01-01

108

Phase-Transfer Catalyzed Additions. IV. Addition of tertButyl Phenylacetate to Activated Double Bond  

Microsoft Academic Search

Tert-butyl phenylacetate is reacted with derivatives of cinnamic acid, chalkone and benzylideneaniline under phase-transfer catalysis conditions to give in good yields the corresponding addition products.

V. Dryanska

1985-01-01

109

(Z)-4-(2,5-Di-tert-butyl-anilino)pent-3-en-2-one.  

PubMed

In the crystal structure of the title ketoamine, C(19)H(29)NO, the bond lengths from the N atom through the alkene group to the ketone O atom show the presence of an extensively delocalized ?-system. The dihedral angle between the plane of the phenyl ring and that of the alkene component is 63.45?(7)° due to steric hindrance exerted by the tert-butyl groups. The mol-ecule has a Z-configured alkene function, which is facilitated by an intra-molecular N-H?O hydrogen bond between the amine and ketone groups. The mol-ecules are linked into extended chains, which run parallel to the [010] direction, by a very weak C-H?O inter-action between the methyl substituent of the alkene group and the ketone O atom of a neighbouring mol-ecule. PMID:21754790

Pastrán, Jesús; Ramírez, Andrea; Agrifoglio, Giuseppe; Linden, Anthony; Dorta, Romano

2011-06-01

110

(Z)-4-(2,5-Di-tert-butyl-anilino)pent-3-en-2-one  

PubMed Central

In the crystal structure of the title ketoamine, C19H29NO, the bond lengths from the N atom through the alkene group to the ketone O atom show the presence of an extensively delocalized ?-system. The dihedral angle between the plane of the phenyl ring and that of the alkene component is 63.45?(7)° due to steric hindrance exerted by the tert-butyl groups. The mol­ecule has a Z-configured alkene function, which is facilitated by an intra­molecular N—H?O hydrogen bond between the amine and ketone groups. The mol­ecules are linked into extended chains, which run parallel to the [010] direction, by a very weak C—H?O inter­action between the methyl substituent of the alkene group and the ketone O atom of a neighbouring mol­ecule.

Pastran, Jesus; Ramirez, Andrea; Agrifoglio, Giuseppe; Linden, Anthony; Dorta, Romano

2011-01-01

111

Voltammetric determination of butylated hydroxyanisole, butylated hydroxytoluene, propyl gallate and tert-butylhydroquinone by use of chemometric approaches  

Microsoft Academic Search

The voltammetric behavior of synthetic food antioxidants, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and tert-butylhydroquinone (TBHQ), at a glassy carbon electrode in solution of 0.1moll?1 perchloric acid containing 1% methanol has been investigated. The obtained linear sweep voltammograms (LSV) showed that all these four compounds have well-defined oxidation waves with peak potentials of 629, 818,

Yongnian Ni; Li Wang; Serge Kokot

2000-01-01

112

Synthesis of 3-Tert. Butyl-5, 8-Dimethyl-1, 10-Anthraquinones (Synthese des 3-Tert. Butyl-5, 8-Dimethyl-1, 10-Anthrachinons).  

National Technical Information Service (NTIS)

The goal of this study was to prepare a stable, i.e., isolatable derivative of 1,10-anthraquinone. The synthesis of 3-tert.butyl-1,10 anthraquinone was attempted. The preparation of the anthron occurred in three stages. Anthraquinone, however, could not b...

F. Setiabudi

1980-01-01

113

Formation of 8-hydroxydeoxyguanosine in calf thymus DNA treated with tert-butylhydroquinone, a major metabolite of butylated hydroxyanisole  

Microsoft Academic Search

Oxidative DNA damage caused by butylated hydroxyanisole (BHA), 2-tert-butyl(1,4)hydroquinone (TBHQ, a metabolite of BHA) and 2,5-di-tert-butyl(1,4)hydroquinone (DTBHQ), as well as 2,6-di-tert-butyl(1,4)benzoquinone (BHTQ, a metabolite of butylated hydroxytoluene), was evaluated by measuring the formation of 8-hydroxy-deoxyguanosine (80HdG) in calf thymus DNA. 80HdG formation was greatly increased by TBHQ in a concentration-dependent manner. This effect was strongly enhanced by CuCl2 and suppressed

Fumiko Nagai; Tomoko Okubo; Keiko Ushiyama; Kanako Satoh; Itsu Kano

1996-01-01

114

The Use of tertButyl Vinyl Ether in Stepwise Electrophilic Addition Reactions  

Microsoft Academic Search

tert-Butyl vinyl ether (1) reacts with p-TolSCl to give 2-tert-butoxy-2-chloroethyl p-tolyl sulfide (2). In the presence of SnCl4, 2 reacts with silyl enol ethers, allyltrimethylsilane, and vinyl ethers to form a C-C bond. In the case of vinyl ethers, the reaction proceeds through the formation of the 5-membered sulfonium salt intermediate which in turn can react with H2O, TMSCN, allyltrimethylsilane,

Leonid N. Koikov; Mingming Han; Dawn M. Wellman; Jim A. Kelly; Irina P. Smoliakova

2000-01-01

115

Unusual molecules - unusual reactions from tetra-tert-butyl-tetrahedrane to the dimer of carbon sulfide  

Microsoft Academic Search

Our perseverance in looking for a second way to pre- pare tetra-tert-butyltetrahedrane has finally been rewarded. By using a similar approach it is also possible to get tri- tert-butyl (trimethylsilyl) tricyclo (l. 1.0. Oz 3 butane - a se- cond, astonishingly stable tetrahedrane derivative. The attempts to synthesize the parent tetrahedrane required the extensive use of matrix isolation techniques. The

Gunther Maier

1991-01-01

116

Tert-Amyl Methyl Ether Catalytic Distillation Experiments and Simulations.  

National Technical Information Service (NTIS)

In this work the catalytic section of a reactive distillation column is studied. Experimental studies with a laboratory catalytic distillation column were carried out for the decomposition and production of tert-amyl methyl ether (TAME). The purpose of th...

K. Klemola A. Pyhaelahti

1996-01-01

117

Rate constants for the reaction of OH radicals with n-propyl, n-butyl, iso-butyl and tert-butyl vinyl ethers  

Microsoft Academic Search

Rate constants for the reaction of OH radicals with n-propyl vinyl ether (PVE, CH3CH2CH2OCHCH2), n-butyl vinyl ether (BVE, CH3CH2CH2CH2OCHCH2), iso-butyl vinyl ether (IBVE, (CH3)2CHCH2OCHCH2) and tert-butyl vinyl ether (TBVE, (CH3)3COCHCH2), have been measured in the temperature and pressure ranges 232–373K and 30–300Torr using the pulsed laser photolysis-laser-induced fluorescence method, and at 298K and 760Torr using the relative method. The obtained

G. Thiault; A. Mellouki

2006-01-01

118

Quantitative determination of butylated hydroxyanisole, butylated hydroxytoluene, and tert -butyl hydroquinone in oils, foods, and biological fluids by high-performance liquid chromatography with fluorometric detection  

Microsoft Academic Search

Concentrations of synthetic antioxidants butylated hydroxyanisole, butylated hydroxytoluene, and tert-butyl hydroquinone were quantified using a high-performance liquid chromatograph with spectrofluorometric detector. The antioxidants\\u000a were separated and eluted on a reversed-phase column by gradient of a mixture of H2O\\/acetonitrile\\/acetic acid (66.5: 28.5?5, by vol) and a mixture of acetonitrile\\/acetic acid (95?5, vol\\/vol). The eluants were\\u000a monitored at emission and excitation wavelengths

Vivienne V. Yankah; Hideki Ushio; Toshiaki Ohshima; Chiaki Koizumi

1998-01-01

119

1-[(E)-2-(5-tert-Butyl-2-hy-droxy-phen-yl)diazen-1-yl]naphthalen-2-ol  

PubMed Central

The non-H atoms of the title compound, C20H20N2O2, is located on a mirror plane except two methyl groups of the tert-butyl group. Intra­molecular N—H?O hydrogen bonds exist between the hy­droxy and diazenyl groups. In the crystal, mol­ecules are linked by weak C—H?O hydrogen bonds into supra­molecular chains running along the a-axis direction.

Bougueria, Hassiba; Mili, Assia; Benosmane, Ali; Bouchoul, Abd el kader; Bouaoud, Salaheddine

2014-01-01

120

1-[(E)-2-(5-tert-Butyl-2-hy-droxy-phen-yl)diazen-1-yl]naphthalen-2-ol.  

PubMed

The non-H atoms of the title compound, C20H20N2O2, is located on a mirror plane except two methyl groups of the tert-butyl group. Intra-molecular N-H?O hydrogen bonds exist between the hy-droxy and diazenyl groups. In the crystal, mol-ecules are linked by weak C-H?O hydrogen bonds into supra-molecular chains running along the a-axis direction. PMID:24764925

Bougueria, Hassiba; Mili, Assia; Benosmane, Ali; Bouchoul, Abd El Kader; Bouaoud, Salaheddine

2014-02-01

121

Synthesis and dynamic NMR study of ketenimines derived from tert -butyl isocyanide, alkyl 2-arylamino-2-oxo-acetates, and dialkyl acetylenedicarboxylates  

Microsoft Academic Search

The adduct produced in the reaction between tert-butyl isocyanide and dialkyl acetylenedicarboxylates was trapped by alkyl 2-arylamino-2-oxo-acetates. When the aryl group is 2-methyl-6-nitrophenyl or 2,6-di-isopropylphenyl, the product exists as two stable rotamers at room temperature as a result of restricted rotation around the Ar–N single bond. When the aryl group is 1-naphthyl or 8-quinolinyl, dynamic NMR effects are observed in

Issa Yavari; Farough Nasiri; Horieh Djahaniani

2004-01-01

122

Novel cytotoxic 3'-(tert-butyl) 3'-dephenyl analogs of paclitaxel and docetaxel.  

PubMed

3'-(tert-Butyl) 3'-dephenyl analogs of paclitaxel were synthesized from 10-deacetylbaccatin III and oxazolidinecarboxylic acid 7 followed by acylation of intermediate amines 10 and 11. Oxazolidinecarboxylic acid 7 was prepared in five steps and in good overall yield from L-tert-leucine. Twelve analogs were synthesized and evaluated for their in vitro ability to stimulate the formation of microtubules and for their cytotoxicity against B16 melanoma cells. Amide, carbamate, urea, and thiourea congeners were prepared. The most potent derivatives found in this study are the docetaxel analog 13, the N-[(tert-amyloxy)carbonyl] analog 17, and the 3'-phenylurea and 3'-tert-butylurea derivatives 20 and 23. Six of these analogs were shown to be ca. 90 times more soluble in water than paclitaxel and ca. 4-5 times more water-soluble than docetaxel. PMID:7562913

Ali, S M; Hoemann, M Z; Aubé, J; Mitscher, L A; Georg, G I; McCall, R; Jayasinghe, L R

1995-09-15

123

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.

124

Synthesis and Crystal Structure of 2- tertButyl5-(4- tert-butylbenzylthio)-4-chloropyridazin-3(2 H)-one  

Microsoft Academic Search

The title compound, 2-tert-butyl-5(4-tert-butylbenzylthio)-4-chloropyridazin-3(2H-one, was synthesized from 1-tert-butylhydrazine, (Z)-2,3-dichloro-3-formylacrylic acid and (4-tert-butylphenyl) methanethiol in several steps. It crystallized in an orthorhombic space group Pnma with Mr = 364.93 (C19H25CIN2OS), a = 1.0091(2) nm, b = 0.7076(2) nm, c = 2.8103(5) nm, V = 2.0066(6) nm3, Z = 4, Dc = 1.192 g\\/cm3, F(000) = 765, ? = 0.301 mm-1, final

Liang-zhong XU; Guan-ping YU; Zhong-jie XU; Gong-sheng ZHANG; Zhi-wei ZHAI

2006-01-01

125

Preparation of p?tert?Butyl?Calix[8]arene Bonded Silica Stationary Phase and Separation for Steroid Hormone Medicines  

Microsoft Academic Search

p?tert?Butyl?calix[8]arene bonded silica (CBS) gel stationary phase for high?performance liquid chromatography was first prepared by condensation reaction between chloropropyl bonded silica (CPS) and phenolic sodium salt of p?tert?butyl?calix[8]arene on solid phase surface. A new bonded stationary phase was characterized by elemental analysis, Fourier transform infrared (FTIR) analysis, and thermal analysis. The chromatographic behaviors on CBS for steroid hormone medicines were

Min Liu

2004-01-01

126

Synthesis of thienylhydrogermanes and their transformations in the presence of di( tert -butyl) peroxide  

Microsoft Academic Search

A method was developed for the synthesis of thienylhydrogermanes RnGeH4?n (where R=2-thienyl, n=1–3), involving the reduction of the corresponding ethoxygermanes by lithium aluminum hydride under the conditions of phase-transfer catalysis. The transformations of thienylhydrogermanes under the influence of di(tert-butyl) peroxide were studied. Features of the mass-spectrometric behavior of thienylethoxygermanes were analyzed.

E. Lukevics; O. A. Pudova; I. Mazheika; S. Grinberga

1997-01-01

127

Polyalkylation of primary polyols by 1,4-addition to tert-butyl acrylate and acrylonitrile  

Microsoft Academic Search

The very hydrophilic primary polyols pentaerythritol (PE), 1,1,1-tris(hydroxymethyl)ethane and tris(hydroxymethyl)aminomethane (TRIS), can be polyetherified in satisfactory yield by 1,4-addition to tert-butyl acrylate using phase-transfer catalysis. Polycyanoethylation of these polyols can also be accomplished with acrylonitrile. Preliminary results of chelation between some polyether-acids with samarium (III) are presented.

Agnès Dupraz; Philippe Guy; Claude Dupuy

1996-01-01

128

Coordination compounds based on 4,6-di- tert -butyl-2-nitrosophenol  

Microsoft Academic Search

New metal mono-, bis-, and tris(chelates) based on 4,6-di-tert-butyl-2-nitrosophenol were synthesized and their physicochemical properties were studied. Conclusions concerning the structures\\u000a of the complexes and the influence of the nature of the complexing metal on the electronic structure of the coordinated ligand\\u000a were drawn from X-ray diffraction, 1H NMR, magnetochemical, and electronic spectroscopy data.

S. N. Lyubchenko; A. M. Ionov; I. N. Shcherbakov; G. G. Aleksandrov; V. A. Kogan; A. Yu. Tsivadze

2006-01-01

129

Protective effects of baicalein on tert -butyl hydroperoxide-induced hepatic toxicity in rat hepatocytes  

Microsoft Academic Search

Summary Baicalein (BAL), a main flavonoid constituent of Scutellaria radix, was studied for its inhibitory effects on tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity and oxidative damage in primary cultures of rat hepatocytes. In a preliminary study, baicalein revealed effective antioxidant properties in a test of its capacity to quench the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). Further investigations showed that baicalein, at the concentrations of

Jin-Ming Hwang; Tsui-Hwa Tseng; Yu-Ying Tsai; Huei-Jane Lee; Feu-Pi Chou; Chau-Jong Wang; Chia-Yih Chu

2005-01-01

130

Copolymers from tert-butyl methacrylate and 2-propenyl isocyanate—polymers for photoresist application  

Microsoft Academic Search

Free radical copolymerisation of tert-butyl methacrylate (1) with 2-isopropenyl isocyanate (2) has been investigated. Reactivity ratios of r1=3.48±0.60 for 1 and r2=0.004±0.04 for 2 were obtained. As 2-propenyl isocyanate has almost no tendency to homopolymerise maximum isocyanate content is reached in an alternating copolymer. The reaction of the isocyanate functionality with morpholine was used to obtain compounds for determination of

Jens Ferbitz; Werner Mormann

2003-01-01

131

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

PubMed Central

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

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

2010-01-01

132

Highly isotactic poly(vinyl alcohol). III: Heterogeneous cationic polymerization of tert-butyl vinyl ether  

Microsoft Academic Search

We studied the polymerization of tert-butyl vinyl ether (tBVE) and benzyl vinyl ether with heterogeneous catalysts, that is, modified Ziegler type (Vandenberg type) catalysts and metal sulfate–sulfuric acid complexes.Vandenberg type catalysts gave high molecular weight and highly isotactic poly(tBVE)s with relatively narrow molecular weight distribution at high temperature, and then the resultant poly(tBVE)s were converted into the stereoregular poly(vinyl alcohol)s

Hiroyuki Ohgi; Toshiaki Sato

2002-01-01

133

Inhibitory effect of berberine on tert -butyl hydroperoxide-induced oxidative damage in rat liver  

Microsoft Academic Search

Berberine, a main protoberberine component of Coptidis Rhizoma, was studied for the mechanism of its inhibitory effects on the tert-butyl hydroperoxide (t-BHP)-induced cytotoxicity and lipid peroxidation in rat liver. In the preliminary study, berberine expressed an antioxidant property by its capacity for quenching the free radicals of 1,1-diphenyl-2-picrylhydrazyl (DPPH). Further investigations were conducted using t-BHP-induced cytotoxicity in rat primary hepatocytes

Jin-Ming Hwang; Chau-Jong Wang; Feu-Pi Chou; Tsui-Hwa Tseng; Yih-Shou Hsieh; Wea-Lung Lin; Chia-Yih Chu

2002-01-01

134

A cataluminescence gas sensor based on nanosized V 2O 5 for tert-butyl mercaptan  

Microsoft Academic Search

This work proposed a gas sensor for the determination of tert-butyl mercaptan, one of the highly toxic volatile sulfur compounds, which was based on cataluminescence emission during its catalytic oxidation on the surface of nanosized V2O5. The cataluminescence characteristics and the optimum conditions, including the morphology of sensing material, the wavelength of cataluminescence emission, the oxygen flow rate and working

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

2010-01-01

135

Chemoselective Nitration of Phenols with tert-Butyl Nitrite in Solution and on Solid Support  

PubMed Central

tert-Butyl nitrite was identified as a safe and chemoselective nitrating agent that provides preferentially mononitro derivatives of phenolic substrates in the presence of potentially competitive functional groups. On the basis of our control experiments, we propose that the reaction proceeds through the formation of O-nitrosyl intermediates prior to C-nitration via homolysis and oxidation. The reported nitration method is compatible with tyrosine-containing peptides on solid support in the synthesis of fluorogenic substrates for characterization of proteases.

Koley, Dipankar; Colon, Olvia C.; Savinov, Sergey N

2009-01-01

136

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

PubMed Central

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

Hirose, Daisuke

2013-01-01

137

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

138

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

Microsoft Academic Search

Two bacterial strains, E1 and E2, isolated from gasoline-polluted soil completely degraded ethyl tert-butyl ether (ETBE), as the sole source of carbon and energy, at specific rates of about 80 mg g-1 and 58 mg g-1 of cell protein day-1, respectively. On the basis of morphological and phenotypic characteristics, strain E1 was tentatively identified as Comamonas testosteroni and strain E2

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

2001-01-01

139

The discovery of N-((2H-tetrazol-5-yl)methyl)-4-((R)-1-((5r,8R)-8-(tert-butyl)-3-(3,5-dichlorophenyl)-2-oxo-1,4-diazaspiro[4.5]dec-3-en-1-yl)-4,4-dimethylpentyl)benzamide (SCH 900822): a potent and selective glucagon receptor antagonist.  

PubMed

A novel series of spiroimidazolone-based antagonists of the human glucagon receptor (hGCGR) has been developed. Our efforts have led to compound 1, N-((2H-tetrazol-5-yl)methyl)-4-((R)-1-((5r,8R)-8-(tert-butyl)-3-(3,5-dichlorophenyl)-2-oxo-1,4-diazaspiro[4.5]dec-3-en-1-yl)-4,4-dimethylpentyl)benzamide (SCH 900822), a potent hGCGR antagonist with exceptional selectivity over the human glucagon-like peptide-1 receptor. Oral administration of 1 lowered 24 h nonfasting glucose levels in imprinting control region mice on a high fat diet with diet-induced obesity following single oral doses of 3 and 10 mg/kg. Furthermore, compound 1, when dosed orally, was found to decrease fasting blood glucose at 30 mg/kg in a streptozotocin-treated, diet-induced obesity mouse pharmacodynamic assay and blunt exogenous glucagon-stimulated glucose excursion in prediabetic mice. PMID:24527772

DeMong, Duane; Dai, Xing; Hwa, Joyce; Miller, Michael; Lin, Sue-Ing; Kang, Ling; Stamford, Andrew; Greenlee, William; Yu, Wensheng; Wong, Michael; Lavey, Brian; Kozlowski, Joseph; Zhou, Guowei; Yang, De-Yi; Patel, Bhuneshwari; Soriano, Aileen; Zhai, Ying; Sondey, Christopher; Zhang, Hongtao; Lachowicz, Jean; Grotz, Diane; Cox, Kathleen; Morrison, Richard; Andreani, Teresa; Cao, Yang; Liang, Mark; Meng, Tao; McNamara, Paul; Wong, Jesse; Bradley, Prudence; Feng, Kung-I; Belani, Jitendra; Chen, Ping; Dai, Peng; Gauuan, Jolicia; Lin, Peishan; Zhao, He

2014-03-27

140

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

141

Oxidation of 2,6-di-tert-butyl-4-methylphenol. The structure of C14H22O3  

USGS Publications Warehouse

The acidic compound C14H22O3, previously reported without assignment of structure as an oxidation product of 2,6-di-tert-butyl-4-methylphenol, is now believed to be DL-trans-5,6-di-tert-butyl-2-hydroxy-1,4-diketo-2-cyclohexene (I). Chemical properties are described and infrared spectra are presented in support of this structure. This structure is of interest in relation to the problem of the existence of o-di-tert-alkylbenzene derivatives. The relatively easy racemization of optically active I suggests that its completely enolized form, 5,6-di-tert-butyl-1,2,4-trihydroxybenzene, is capable of transitory existence.

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

1959-01-01

142

Voltammetric determination of the phenolic antioxidants 3-tert-butyl-4-hydroxyanisole and tert-butylhydroquinone at a polypyrrole electrode modified with a nickel phthalocyanine complex  

Microsoft Academic Search

The voltammetric behaviour of the antioxidants 3-tert-butyl-4-hydroxyanisole (BHA) and tert-butylhydroquinone (TBHQ), at a polymer electrode modified with nickel phthalocyanine as electron mediator, is described, and an electroanalytical method for the determination of these antioxidants based on their electrochemical oxidation on the modified electrode is proposed. Cyclic voltammograms showed well-defined oxidation peaks slightly shifted towards less positive potentials with respect to

C de la Fuente; J. A Acuña; M. D Vázquez; M. L Tascón; P Sánchez Batanero

1999-01-01

143

Reaction Between 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione and tert Butyl Isocyanide in the Presence of Primary or Secondary Amines  

Microsoft Academic Search

Summary. 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione (the condensation product of Meldrum’s acid and acetone) reacts smoothly with tert-butyl isocyanide in the presence of primary or secondary amines to produce N- tert-butyl-2,2-dimethylbutyramide derivatives and\\/or 1- tert-butyl-4,4-dimethyl-2,5-dioxopyrrolidine-3-carboxamides in good yields.

Issa Yavari; Azizollah Habibi; Mohammad R. Hosseini-Tabatabaei; Hamid R. Bijanzadeh

2003-01-01

144

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

SciTech Connect

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

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

1994-07-01

145

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

PubMed Central

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

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

2011-01-01

146

(3S*,4S*,E)-tert-Butyl 3,4-dibromo-5-oxo-cyclo-oct-1-ene-carboxyl-ate  

PubMed Central

The title compound, C13H18Br2O3, was prepared by a bromination reaction of (1E,3Z)-methyl 5-oxocyclo­octa-1,3-diene­carboxyl­ate, which was obtained by an ep­oxy­dation reaction of tert-butyl cyclo­oct-1,3-diene­carboxyl­ate. The crystal structure confirms unequivocally the absolute configuration of both chiral centres to be S. In the crystal, C—H?O inter­actions link the mol­ecules into chains running along the c axis.

Blanco, Magda; Garrido, Narciso M.; Sanz, Francisca; Diez, David

2012-01-01

147

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.

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

2012-01-01

148

Rate constants for the reaction of OH radicals with n-propyl, n-butyl, iso-butyl and tert-butyl vinyl ethers  

NASA Astrophysics Data System (ADS)

Rate constants for the reaction of OH radicals with n-propyl vinyl ether (PVE, CH 3CH 2CH 2OCH dbnd CH 2), n-butyl vinyl ether (BVE, CH 3CH 2CH 2CH 2OCH dbnd CH 2), iso-butyl vinyl ether (IBVE, (CH 3) 2CHCH 2OCH dbnd CH 2) and tert-butyl vinyl ether (TBVE, (CH 3) 3COCH dbnd CH 2), have been measured in the temperature and pressure ranges 232-373 K and 30-300 Torr using the pulsed laser photolysis-laser-induced fluorescence method, and at 298 K and 760 Torr using the relative method. The obtained results are k1=(9.3±0.6)×10 -12 exp[(708±20)/ T], k2=(1.5±0.2)×10 -11 exp[(572±42)/ T], k3=(1.6±0.1)×10 -11 exp[(567±20)/ T], k4=(1.7±0.2)×10 -11 exp[(549±25)/ T] cm 3 molecule -1 s -1. The values at 298 K are k1=(1.0±0.1)×10 -10, k2=(1.0±0.1)×10 -10, k3=(1.1±0.1)×10 -10, k4=(1.1±0.1)×10 -10 cm 3 molecule -1 s -1. The deduced tropospheric lifetimes of these ethers for reaction with OH are of the order of 1 h and they are comparable to those for reaction with ozone.

Thiault, G.; Mellouki, A.

149

Facile synthesis of l-Dopa tert-butyl ester by catalytic enantioselective phase-transfer alkylation  

Microsoft Academic Search

Facile asymmetric synthesis of l-Dopa and related amino acid esters has been achieved by phase-transfer catalysis of the rationally designed C2-symmetric chiral quaternary ammonium salts 1. The ‘scale-up’ experiment performed with 5.00 g of tert-butyl glycinate-benzophenone Schiff base (2) represents the practical aspect of our approach.

Takashi Ooi; Minoru Kameda; Hidenori Tannai; Keiji Maruoka

2000-01-01

150

Corannulene and its penta-tert-butyl derivative co-crystallize 1:1 with pristine C60-fullerene.  

PubMed

The first X-ray structural determinations of pristine fullerene C(60), cocrystallized 1:1 with corannulene and with its pentaalkyl-substituted derivative, 1,3,5,7,9-penta-tert-butyl-corannulene, have now been achieved. PMID:22466755

Dawe, Louise N; AlHujran, Tayel A; Tran, Huu-Anh; Mercer, Jason I; Jackson, Edward A; Scott, Lawrence T; Georghiou, Paris E

2012-06-01

151

Radicals and Scavengers. V. Steric Hindrance and Cage Effects in the Decompositions of Several tert-Butyl Peresters.  

National Technical Information Service (NTIS)

Product isolation and scavenger methods have been used to study the cage effects in decompositions in cumene and chlorobenzene of several tert-butyl peresters, RCO3-t-Bu, including the peracetate (R = CH3), perpivalate (R = (CH3)3C),p-nitro-and p-methoxyp...

J. P. Lorand

1973-01-01

152

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

SciTech Connect

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

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

2006-04-15

153

New MTBE design now commercial. [Methyl tertiary butyl ether  

Microsoft Academic Search

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

L. A. Smith; M. N. Huddleston

1982-01-01

154

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

155

4-[(tert-Butyl-diphenyl-sil-yloxy)meth-yl]pyridazin-3(2H)-one  

PubMed Central

In the title compound, C21H24N2O2Si, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether group are placed toward opposite sides and the tert-butyl and pyridazinone moieties are anti-oriented across the Si—O bond [torsion angle = ?168.44?(19)°]. In the crystal, mol­ecules are assembled into inversion dimers through co-operative N—H?O hydrogen bonds between the NH groups and O atoms of the pyridazinone rings of neighbouring mol­ecules. The dimers are linked by ?–? inter­actions involving adjacent pyridazinone rings [centroid–centroid distance = 3.8095?(19)?Å], generating ladder-like chains along the b-axis direction. The chains are further linked into a two-dimensional network parallel to the ab plane through weak C—H?? inter­actions.

Costas-Lago, Maria Carmen; Costas, Tamara; Vila, Noemi; Besada, Pedro

2013-01-01

156

Hepatoprotective effects of irisolidone on tert-butyl hyperoxide-induced liver injury.  

PubMed

To clarify the hepatoprotective effects of kakkalide and its metabolite irisolidone by human fecal microflora, their effects on tert-butyl hydroperoxide (t-BHP)-injured HepG2 cells and mice were investigated. Irisolidone protected HepG2 cells against cytotoxicity induced by t-BHP. However, kakkalide did not protect cytotoxicity. When kakkalide 100 mg/kg was orally administered to mice injured by t-BHP, it significantly inhibited the increase in plasma alanine aminotransferase and aspartate aminotransferase activities by 84% and 85% of t-BHP-treated control group, respectively. The inhibitory effect of kakkalide is much more potent than that of silybin, a hepatoprotective agent. However, intraperitoneally administered kakkalide did not exhibit hepatoprotective activity. When irisolidone was intraperitoneally administered to mice, it exhibited potent hepatoprotective activity. Based on these findings, irisolidone can be hepatoprotective and kakkalide may be a prodrug transformed to irisolidone. PMID:15744084

Lee, Hae-Ung; Bae, Eun-Ah; Kim, Dong-Hyun

2005-03-01

157

Hepatoprotective effect of tectoridin and tectorigenin on tert-butyl hyperoxide-induced liver injury.  

PubMed

To clarify the hepatoprotective effects of tectoridin and tectorigenin from Puerariae Flos, their effects on tert-butyl hyperoxide (t-BHP)-injured HepG2 cells and mice were investigated. When tectorigenin at a dose of 50 mg/kg was intraperitoneally administered to mice injured by t-BHP, it significantly inhibited the increase the activities of plasma ALT and AST by 39% and 41%, respectively, in the t-BHP-treated group. The inhibitory effect of tectorigenin is much more potent than that of a commercially available dimethyl diphenyl bicarboxylate. Orally administered tectoridin showed hepatoprotective activity. However, when tectoridin was intraperitoneally administrated to mice, no hepatoprotective activity was observed. Tectorigenin also protected against the cytotoxicity of HepG2 cells induced by t-BHP. This protection may have originated from the inhibition of apoptosis. Tectorigenin may be hepatoprotective and tectoridin should be a prodrug that is transformed to tectorigenin. PMID:15821336

Lee, Hae-Ung; Bae, Eun-Ah; Kim, Dong-Hyun

2005-04-01

158

Vibrational Spectra and Density Functional Theory Calculations of Metallo-tetra-(tert-butyl)-tetra-azaporphyrines  

NASA Astrophysics Data System (ADS)

The infrared absorption and 514.5 nm excited Raman spectra were measured for the metallo-tetra-(tert-butyl)-tetraazaporphyrin (MT(tBu)TAP, M=Cu, Co, Ni, Zn). The ground-state structures and vibrational spectra of MT(tBu)TAPs have been calculated at the B3LYP level of theory. The observed Raman and IR bands have been assigned based on the calculation results and by comparing with the normal metalloporphyrins. The relationship between the Raman/IR frequencies and the structures of TAP ring was investigated. The results show that the frequencies of C?C?' stretch (Ag), asymmetric C?Nm stretch (Ag), and symmetric C?Nm stretch (Bg) modes increase linearly with the decrease of the core-sizes of TAP ring. Among the three modes, the later two are more sensitive to the core-size change.

Lu, Tong-tong; Gao, Hui-ling; He, Tian-jing; Liu, Fan-chen; Chen, Dong-ming

2010-10-01

159

Pressure effect on water dynamics in tert-butyl alcohol/water solutions  

NASA Astrophysics Data System (ADS)

We report here a quasi-elastic neutron scattering (QENS) investigation of the effect of pressure on the diffusivity properties of water in a dilute aqueous solution of hydrophobic molecules (tert-butyl alcohol, TBA). The experiment was performed at fixed TBA concentration (0.02 molar fraction) by varying pressure from 1 to 2000 bar at two different temperatures (268 and 278 K). The quasi-elastic line-shapes have been analysed in terms of a model based on the memory function formalism. Our data indicate that, on increasing pressure up to 2000 bar, the diffusion coefficient of water in the TBA/water mixture exhibits a relative increase larger than that of pure water under the same thermodynamic conditions. The extent of this effect increases with decreasing temperature. The observed behaviour is described in terms of pressure-induced distortions of the H-bonded random network of liquid water.

Calandrini, Vania; Deriu, Antonio; Onori, Giuseppe; Paciaroni, Alessandro; Telling, Mark T. F.

2006-09-01

160

MTBE for octane improvement. [Methyl tertiary-butyl ether  

Microsoft Academic Search

Methyl tertiary-butyl ether (MTBE), which shows promise as an octane improver, has been introduced commercially in the US after successful commercialization in Italy and Germany. Comparisons are made of the fuel properties, single-cylinder engine performance, and road octane readings between gasoline and MTBE-gasoline blends. The study concludes that the compatibility of MTBE with gasoline will improve the road performance of

B. Taniguchi; R. T. Johnson

1979-01-01

161

Toxic Polyneuropathy Produced by Methyl N-Butyl Ketone  

Microsoft Academic Search

A polyneuropathy affecting a large number of workers was recently observed at a plant producing plastic-coated and color-printed fabrics. Epidemiological data suggested strongly that methyl N-butyl ketone (MBK) was responsible for the outbreak. This hypothesis is now supported by the development of a peripheral neuropathy in chickens, rats, and cats exposed to MBK at atmospheric concentrations of 200 to 600

J. R. Mendell; K. Saida; M. F. Ganansia; D. B. Jackson; H. Weiss; R. W. Gardier; C. Chrisman; N. Allen; D. Couri; J. O'Neill; B. Marks; L. Hetland

1974-01-01

162

Computer experiments on aqueous solutions. VI. Potential energy function for tert-butyl alcohol dimer and molecular dynamics calculation of 3 mol % aqueous solution of tert-butyl alcohol  

Microsoft Academic Search

Molecular dynamics (MD) calculation has been carried out for a dilute aqueous solution of tert-butyl alcohol (TBA) at 298.15 K and with experimental density value by the use of constant temperature technique developed previously. The total number of molecule is 216, seven of which are TBA. The mole fraction of TBA is thus 0.032. For water–water and TBA–water interactions, the

Hideki Tanaka; Koichiro Nakanishi; Hidekazu Touhara

1984-01-01

163

tert-Butyl N-[2-(N-isobutyl-4-meth-oxy-benzene-sulfonamido)-eth-yl]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.

Bai, Xiao-Guang; Wang, Ju-Xian

2014-01-01

164

tert-Butyl N-[2-(N-isobutyl-4-meth-oxy-benzene-sulfonamido)-eth-yl]carbamate.  

PubMed

The title compound, C18H30N2O5S, was synthesized by the reaction of tert-butyl 2-(iso-butyl-amino)-ethyl-carbamate with p-meth-oxy-phenyl-sulfonyl chloride. In the mol-ecule, two intra-molecular C-H?O hydrogen bonds are observed. In the crystal, mol-ecules 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

2014-06-01

165

Indium(III) chloride-catalyzed oxidative cleavage of carbon–carbon multiple bonds by tert-butyl hydroperoxide in water—a safer alternative to ozonolysis  

Microsoft Academic Search

An efficient and general method for the oxidative cleavage of alkenes and alkynes using tert-butyl hydroperoxide and indium(III) chloride as catalyst in water to give the corresponding carboxylic acids or ketones has been achieved. The reaction conditions are compatible with sensitive moieties such as peptide bonds, tert-butyl carboxylic esters and N-Boc-protected tryptophan. The catalyst could be recycled.

Brindaban C. Ranu; Sukalyan Bhadra; Laksmikanta Adak

2008-01-01

166

Cytotoxicity of 2- tert-butyl hydroquinone glutathione conjugates after apical and basolateral exposure of rat renal proximal tubular cell monolayers  

Microsoft Academic Search

Confluent monolayers of renal proximal tubular (RPT) cells cultured on porous supports were used to investigate the cytotoxicity induced by glutathione conjugates of 2-tert-butyl-(1,4)-hydroquinone (SG-TBHQ) after apical and basolateral exposure. As judged from lactate dehydrogenase (LDH) leakage, cytotoxicity was observed after basolateral exposure of monolayers to 250 and 500 ?m 2-tert-butyl-5-(glutathion-S-yl)hydroquinone (5SG-TBHQ). In these experiments, LDH leakage was 22.3 ±

H. E. M. G. Haenen; E. Bleijlevens; H. Elzerman; J. H. M. Temmink; J. H. Koeman; P. J. Van Bladeren

1996-01-01

167

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

SciTech Connect

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

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

1996-03-01

168

Ethers from ethanol. 1: Equilibrium thermodynamic analysis of the liquid-phase ethyl tert-butyl ether reaction  

Microsoft Academic Search

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

Kyle L. Jensen; Ravindra Datta

1995-01-01

169

Highly enantioselective monoalkylation of p-chlorobenzaldehyde imine of glycine tert-butyl ester under mild phase-transfer conditions  

Microsoft Academic Search

The selective monoalkylation of glycine tert-butyl ester aldimine Schiff base 3 has been realized in high chemical yield with excellent enantioselectivity under mild liquid–liquid phase-transfer conditions by the use of binaphthyl-derived chiral quaternary ammonium bromides 7 and 8 as catalysts. This achievement demonstrates that 3 can be used as a cost-effective substrate for the preparation of optically active ?-alkyl-?-amino acid

Takashi Ooi; Yuichiro Arimura; Yukihiro Hiraiwa; Lin Ming Yuan; Taichi Kano; Toru Inoue; Jun Matsumoto; Keiji Maruoka

2006-01-01

170

Synthesis and characterization of cationic cyclopalladated complexes derived from p- tert-butyl-calix[4]arene bisphosphite with nitrogen donors  

Microsoft Academic Search

A series of new cationic cyclopalladated complexes 2–6 have been synthesized from neutral cyclopalladated complex 1 of p-tert-butyl-calix[4]arene bisphosphite with various nitrogen donor ligands (acetonitrile, pyridine, aniline, (R)-(+)-1-phenylethylamine and 4,4?-bipyridine) in presence of Ag(OSO2CF3) as a chloride scavenger. These cationic cyclopalladated complexes have been characterized by NMR spectroscopy. Single crystal X-ray diffraction studies performed on cationic cyclopalladated complexes 3 and

Pathik Maji

2011-01-01

171

Grafting of end-functionalized poly( tert-butyl acrylate) to poly(ethylene- co-acrylic acid) film  

Microsoft Academic Search

Poly(tert-butyl acrylate) (PtBA) was grafted to the surface of poly(ethylene-co-acrylic acid) (EAA) film and the pendant groups of the tethered PtBA were modified to create chemically tailored surface modifying layers. The carboxylic acid groups in the copolymer film served as the grafting sites for the covalent tethering of end-functionalized PtBA. The progression of these reactions was monitored using attenuated total

Keisha B. Walters; Douglas E. Hirt

2006-01-01

172

Poly( N- tert-butyl acrylamide- b- N-acryloylmorpholine) amphiphilic block copolymers via RAFT polymerization: Synthesis, purification and characterization  

Microsoft Academic Search

Amphiphilic block copolymers consisting of two poly(acrylamide) derivative blocks have been synthesized via the reversible addition fragmentation chain transfer (RAFT) polymerization process with a hydrophobic block, poly(N-tert-butyl acrylamide), poly(TBAm), and a non-ionic hydrophilic one, poly(N-acryloylmorpholine), poly(NAM). Both polymerization orders, poly(TBAm-b-NAM) and poly(NAM-b-TBAm), were compared in terms of conversion and control over molecular weights (MW). Purification of the block copolymers was

Bertrand de Lambert; Marie-Thérèse Charreyre; Carole Chaix; Christian Pichot

2007-01-01

173

A rapid method for analysis of tert-butyl hydroquinone (TBHQ) in ethyl esters of fish oil  

Microsoft Academic Search

A rapid, quantitative gas Chromatographic method is described for quantitating the phenolic antioxidant,tert- butyl hydroquinone (TBHQ), in fish oil ethyl esters. The procedure entails silyl derivatization of TBHQ in an acetonitrile\\u000a solution of ethyl esters followed by capillary gas chromatography (GC) analysis with an internal standard method of quantitation.\\u000a Average recoveries of spiked samples were 98% at the legal limit

Teresa P. Icenhour; Frances M. Van Dolah

1991-01-01

174

Reactive Imprint Lithography: Combined Topographical Patterning and Chemical Surface Functionalization of Polystyrene-block-poly(tert-butyl acrylate) Films  

Microsoft Academic Search

Here, reactive imprint lithography (RIL) is introduced as a new, one-step lithographic tool for the fabrication of large-area topographically patterned, chemically activated polymer platforms. Films of polystyrene-block-poly(tert-butyl acrylate) (PS-b-PtBA) are imprinted with PDMS master stamps at temperatures above the corresponding glass transition and chemical deprotection temperatures to yield structured films with exposed carboxylic acid and anhydride groups. Faithful pattern transfer

Joost Duvigneau; Stijn Cornelissen; Nuria Bardaj?´Valls; Holger Schönherr; G. Julius Vancso

2009-01-01

175

Atomic force microscopy based thermal lithography of poly(tert-butyl acrylate) block copolymer films for bioconjugation.  

PubMed

In this paper, we report on the local thermal activation of thin polymer films for area-selective surface chemical modification on micrometer and nanometer length scales. The thermally induced activation of tert-butyl ester moieties in polystyrene- block-poly(tert-butyl acrylate) (PS- b-PtBA) block copolymer films leads to the formation of pending carboxylic acid groups, which are among the versatile functionalities for subsequent bioconjugation. From Fourier transform infrared (FTIR) spectroscopic analyses, the apparent activation energy (Ea) for the tert-butyl ester deprotection in thin films was calculated to be 93 +/- 12 kJ/mol, which is in good agreement with values reported for the bulk. The availability of the deprotected carboxylic acid groups in subsequent wet chemical grafting reactions on neat thermolyzed films was confirmed by covalently immobilizing fluoresceinamine and amino end-functionalized poly(ethylene glycol) (PEG-NH2) using established 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) chemistry. Local thermal deprotection on micrometer and sub-micrometer length scales was achieved by scanning thermal microscopy using an atomic force microscope with heatable probe tips. Passivating PEG and fluoresceinamine layers were selectively covalently coupled to locally deprotected areas as small as 370 nm x 580 nm. PMID:18759464

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

2008-10-01

176

Generation of (nonafluoro-tert-butoxy)methyl ponytails for enhanced fluorous partition of aromatics and heterocycles.  

PubMed

The reaction of sodium perfluoro-tert-butoxide with benzylic carbon-bromide bond(s) leads to the formation of (nonafluoro-tert-butoxy)methyl ponytail(s), which can enhance the fluorous solubility and partition of aromatics and heterocycles. PMID:22245936

Zhao, Xi; Ng, Wing Yan; Lau, Kai-Chung; Collis, Alana E C; Horváth, István T

2012-03-21

177

hTERT promoter activity and CpG methylation in HPV-induced carcinogenesis  

PubMed Central

Background Activation of telomerase resulting from deregulated hTERT expression is a key event during high-risk human papillomavirus (hrHPV)-induced cervical carcinogenesis. In the present study we examined hTERT promoter activity and its relation to DNA methylation as one of the potential mechanisms underlying deregulated hTERT transcription in hrHPV-transformed cells. Methods Using luciferase reporter assays we analyzed hTERT promoter activity in primary keratinocytes, HPV16- and HPV18-immortalized keratinocyte cell lines and cervical cancer cell lines. In the same cells as well as cervical specimens we determined hTERT methylation by bisulfite sequencing analysis of the region spanning -442 to +566 (relative to the ATG) and quantitative methylation specific PCR (qMSP) analysis of two regions flanking the hTERT core promoter. Results We found that in most telomerase positive cells increased hTERT core promoter activity coincided with increased hTERT mRNA expression. On the other hand basal hTERT promoter activity was also detected in telomerase negative cells with no or strongly reduced hTERT mRNA expression levels. In both telomerase positive and negative cells regulatory sequences flanking both ends of the core promoter markedly repressed exogenous promoter activity. By extensive bisulfite sequencing a strong increase in CpG methylation was detected in hTERT positive cells compared to cells with no or strongly reduced hTERT expression. Subsequent qMSP analysis of a larger set of cervical tissue specimens revealed methylation of both regions analyzed in 100% of cervical carcinomas and 38% of the high-grade precursor lesions, compared to 9% of low grade precursor lesions and 5% of normal controls. Conclusions Methylation of transcriptionally repressive sequences in the hTERT promoter and proximal exonic sequences is correlated to deregulated hTERT transcription in HPV-immortalized cells and cervical cancer cells. The detection of DNA methylation at these repressive regions may provide an attractive biomarker for early detection of cervical cancer.

2010-01-01

178

Thermal radiation of di-tert-butyl peroxide pool fires-Experimental investigation and CFD simulation.  

PubMed

Instantaneous and time averaged flame temperatures T , surface emissive power SEP and time averaged irradiances E of di-tert-butyl peroxide (DTBP) pool fires with d=1.12 and 3.4m are investigated experimentally and by CFD simulation. Predicted centerline temperature profiles for d=1.12m are in good agreement with the experimental emission temperature profiles for x/d>0.9. For d=3.4m the CFD predicted maximum centerline temperature at x/d=1.4 is 1440 K whereas the emission temperature experimentally determined from thermograms at x/d approximately 1.3 is 1560 K. The predicted surface emissive power for d=1.12m is 115 kW/m(2) in comparison to the measured surface emissive power of 130 kW/m(2) whereas for d=3.4m these values are 180 and 250 kW/m(2). The predicted distance dependent irradiances agree well with the measured irradiances. PMID:19185989

Chun, Hyunjoo; Wehrstedt, Klaus-Dieter; Vela, Iris; Schönbucher, Axel

2009-08-15

179

Protection of rat hepatocytes from tert-butyl hydroperoxide-induced injury by catechol.  

PubMed

Metabolism of tert-butyl hydroperoxide (TBHP, 2.0 mM) by glutathione peroxidase within isolated rat hepatocytes caused a rapid oxidation of intracellular reduced glutathione and ultimately NADPH through glutathione reductase. TBHP also caused the formation of surface blebs in the hepatocyte plasma membrane followed by the leakage of cytosolic enzymes, such as lactate dehydrogenase, into the incubation medium. Catechol (0.1 mM) protected hepatocytes from the cytotoxic effects of TBHP but did not prevent the rapid oxidation of glutathione indicating normal metabolism of TBHP through glutathione reductase. In contrast, addition of catechol to the hepatocyte incubations prevented TBHP-induced depletion of intracellular NADPH and increased the total NADP+ + NADPH concentration without altering significantly the intracellular NADP+ content or the NADPH/NADP + NADPH ratio. Catechol did not alter TBHP stimulation of the pentose phosphate pathway. Hepatocytes incubated with sublethal concentrations of TBHP (1.0 mM) did not leak lactate dehydrogenase into the medium but did lose intracellular potassium. In these experiments, TBHP caused a sustained increase in phosphorylase alpha activity suggesting that TBHP metabolism may be associated with a sustained increase in cytosolic free Ca2+. In the presence of catechol, phosphorylase alpha activity was increased by 5 min but returned toward control by 20 min. These data suggest that catechol may be protecting hepatocytes from TBHP-induced injury by preventing a sustained rise in cytosolic free Ca2+ concentration. PMID:3726880

Rush, G F; Yodis, L A; Alberts, D

1986-07-01

180

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

SciTech Connect

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

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

1994-03-01

181

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

182

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

183

LC50 Determination of tert-Butyl Acetate using a Nose Only Inhalation Exposure in Rats  

PubMed Central

tert-Butyl acetate (TBAc) is an organic solvent, which is commonly used in architectural coatings and industrial solvents. It has recently been exempted from the definition of a volatile organic compound (VOC) by the Air Resources Board (ARB) . Since the use of TBAc as a substitute for other VOCs has increased, thus its potential risk in humans has also increased. However, its inhalation toxicity data in the literature are very limited. Hence, inhalation exposure to TBAc was carried out to investigate its toxic effects in this study. Adult male rats were exposed to TBAc for 4 h for 1 day by using a nose-only inhalation exposure chamber (low dose, 2370 mg/m3 (500 ppm) ; high dose, 9482 mg/m3 (2000 ppm) ) . Shamtreated control rats were exposed to clean air in the inhalation chamber for the same period. The animals were killed at 2, 7, and 15 days after exposure. At each time point, body weight measurement, bronchoalveolar lavage fluid (BALF) analysis, histopathological examination, and biochemical assay were performed. No treatment-related abnormal effects were observed in any group according to time course. Based on those findings, the median lethal concentration (LC50) of TBAc was over 9482 mg/m3 in this study. According to the MSDS, the 4 h LC50 for TBAc for rats is over 2230 mg/m3. We suggested that this value is changed and these findings may be applied in the risk assessment of TBAc which could be beneficial in a sub-acute study.

Yang, Young-Su; Lee, Jinsoo; Kwon, Soonjin; Seo, Heung-Sik; Choi, Seong-Jin; Yu, Hee-Jin; Song, Jeong-Ah; Lee, Kyuhong; Lee, Byoung-Seok; Heo, Jeong-Doo; Cho, Kyu-Hyuk

2010-01-01

184

Nitrogen nuclear quadrupole coupling constants and heavy atom substitution geometry of tert-butyl nitrite  

NASA Astrophysics Data System (ADS)

The microwave spectra of tert-butyl nitrite, including all of its heavy-atom singly substituted isotopomers, have been observed with a pulsed molecular beam microwave Fourier transform spectrometer. The analysis resulted in the following substitution structure parameters: r(O t?N) = 118.18(8) pm, r(N?O b) = 141.75(8) pm, r(O b?C ?) = 143.75(6) pm, r(C ??C i) = 152.34(3) pm, r(C ??C o) = 152.90(4) pm, ?(O tNO b) = 111.6(2)°, ?(NO bC ?) = 111.8(2)°, ?(O bC ?C i) = 103.0(1)° ?(O bC ?C o) = 110.1(1)°, and ?(NO bC ?C o) = 61.6(1)°. The molecule has an ab-plane of symmetry. All measurements on the isotopically labeled species have been made using the isotopomers in their natural abundances. From the nuclear quadrupole hyperfine structures of the normal isotopic species and the [ 13C i]-labeled species, the elements of the nitrogen coupling tensor and its orientation in the bond axis system of the molecule have been determined to be ?zz = -5.53(17) MHz, ?xx = +2.15(17) MHz, ?yy = +3.377(1) MHz, and ?( a, x) = 24.3(13)°. Thus, the z-axis of the coupling tensor is inclined to the bisector of the O tNO b-angle by about 16.5° toward the O t?N-bond.

Heineking, N.; Jäger, W.; Gerry, M. C. L.

1992-10-01

185

The Synthesis and Isolation of N-Tert-Butyl-2-Phenylsuccinamic Acid and N-Tert-Butyl-3-Phenylsuccinamic Acid: An Undergraduate Organic Chemistry Laboratory Experiment  

ERIC Educational Resources Information Center

The facile, high yielding synthesis of phenylsuccinamic acids is described and one of these syntheses, the reaction of phenylsuccinic anhydride with tert-butylamine, is successfully modified and adapted for use in the second-semester organic chemistry laboratory at St. John's University. Succinamic acids are compounds that contain both the amide…

Cesare, Victor; Sadarangani, Ishwar; Rollins, Janet; Costello, Dennis

2004-01-01

186

A comparison of linear optical properties and redox properties in chalcogenopyrylium dyes bearing ortho-substituted aryl substituents and tert-butyl substituents.  

PubMed

A series of thiapyrylium pentamethine dyes (4 and 12-15) bearing 2,2'-di-tert-butyl-6,6'-diphenyl, 2,2'-di-tert-butyl-6,6'-bis(2,6-dimethylphenyl), 2,2'-di-tert-butyl-6,6'-bis(2-methylphenyl), 2,2',6,6'-tetrakis(2,6-dimethylphenyl), and 2,2',6,6'-tetrakis(2-methylphenyl) substituents, respectively, were prepared and their linear optical properties and electrochemical redox properties were measured and compared to thiapyrylium pentamethine dyes 3 and 5. The tert-butyl and 2,6-dimethylphenyl substituents give nearly identical chromophores with respect to values of lambda(max), molar extinction coefficients (epsilon), bandwidths at half-height (nu(1/2)), and lack of absorption in the visible spectrum. The 2-methylphenyl substituent imparts linear optical properties that are intermediate between those of the tert-butyl and phenyl substituents. The 2,6-dimethylphenyl and 2-methylphenyl substituents impart greater oxidative stability based on anodic shifts in oxidation potential. PMID:12608794

Panda, Jagannath; Virkler, Peter R; Detty, Michael R

2003-03-01

187

Continuous synthesis of tert-butyl peroxypivalate using a single-channel microreactor equipped with orifices as emulsification units.  

PubMed

The two-step synthesis of tert-butyl peroxypivalate is performed in a single-channel microreactor. The first step, the deprotonation of tert-butyl hydroperoxide, is done in a simple mixer tube setup. The residence time section for the second reaction step is equipped with orifices for interfacial area renewal, needed for ensuring mass transfer between the two immiscible phases. The strong dependence of the reaction performance on the size of the interfacial area is demonstrated by using a setup with 4 orifices (distance of 52?cm), giving a HPLC yield of 71% at a residence time of 8?s and a reaction temperature of 23?°C. A further shortening of orifice distances helped to shorten the residence time down to 1.5?s and 0.5?s (using 9 orifices and 3 orifices with a distance of 5?cm). When using these setups, the produced heat could not be removed from the system sufficiently quickly (?T=38?K). The achieved yields (ca.?70% by HPLC) are close to the state of the art (cascaded batch processing) and provide an indication that the tert-butyl peroxypivalate synthesis can be performed at higher temperatures or at least, a more flexible process control can be allowed compared to high-volume batch reactors. Processing at higher reaction temperatures up to 70?°C shows a slight optimum at reaction temperatures between 40?°C to 50?°C, depending on the setup used. Knowing this novel process window as well as the optimum orifice geometry and distance will allow for tailored design of the microreactor. For the processing in the single-channel microreactor setup using 9 orifices (distance of 5?cm) and a reaction temperature of 40?°C a space-time-yield of 420,000?g? L(-1) ?h(-1) was reached which is higher than the space-time-yield for the industrial 3 cascaded batch reactor process (190?g? L(-1) ?h(-1)). PMID:21302363

Illg, Tobias; Hessel, Volker; Löb, Patrick; Schouten, Jaap C

2011-03-21

188

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

189

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

190

3,3?-Dibromo-5,5?-di-tert-butyl-2,2?-dimethoxy-biphen-yl  

PubMed Central

The title compound, C22H28Br2O2, crystallizes in a staggered arrangement to minimize the inter­actions of its ortho substituents, with a dihedral angle of 84.2?(3)° between the two aromatic rings. Short C—H?O hydrogen-bonding inter­actions between meth­oxy groups result in a one-dimensional polymeric chain of mol­ecules lying parallel to the b axis. One tert-butyl group is disordered equally over two positions.

Polson, Matthew I. J.; Steel, Peter J.

2008-01-01

191

Contact allergy to 2-hydroxy-5-tert-butyl benzylalcohol and 2,6-bis(hydroxymethyl)-4-tert-butylphenol, components of a phenolic resin used in marking pens.  

PubMed

2-hydroxy-5-tert-butyl benzylalcohol and 2,6-bis(hydroxymethyl)-4-tert-butylphenol were identified as contact allergens in a phenolic resin used as a tackifier in the ink of a marking pen, which, after being used directly on the skin, caused an acute contact dermatitis on the hand of a 13-year-old boy. The patient also reacted to 4-tert-butylphenol-formaldehyde resin (BPF resin) 1% pet. included in the European standard series. PMID:7821007

Hagdrup, H; Egsgaard, H; Carlsen, L; Andersen, K E

1994-09-01

192

Total pressure measurements of binary mixtures containing tert-amyl methyl ether and tert-amyl alcohol  

SciTech Connect

Vapor-liquid equilibrium data are needed for the reformulation of gasoline to meet Federal Clear Air Act standards. Oxygenates, such as ethers and alcohols, are known to reduce Co emissions from motor vehicles, and ethers are used as a substitute for aromatics in gasoline to improve the octane rating. The vapor pressure of pure tert-amyl methyl ether (TAME) was measured together with isothermal P-x data for mixtures of pentane + TAME and pentane + tert-amyl alcohol (TAOH) at temperatures between 70 and 110 C. Also, activity coefficients at infinite dilution for the binary mixtures of TAME + TAOH were obtained in the 90--120 C temperature range. The P-T-x data were correlated using the Peng-Robinson equation of state separately with the van der Waals and Wong-Sandler mixing rules.

Semar, S.; Sandler, S.I. [Univ. of Delaware, Newark, DE (United States); Antosik, M. [Polish Academy of Sciences, Warszawa (Poland). Inst. of Physical Chemistry

1995-05-01

193

Understanding the redox shuttle stability of 3,5-di- tert-butyl-1,2-dimethoxybenzene for overcharge protection of lithium-ion batteries  

Microsoft Academic Search

3,5-di-tert-butyl-1,2-dimethoxybenzene (DBDB) has been synthesized as a new redox shuttle additive for overcharge protection of lithium-ion batteries. DBDB can easily dissolve in carbonate-based electrolytes, which facilitates its practical use in lithium-ion batteries; however, it has poor electrochemical stability compared to 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB). The structures of DBDB and DDB were investigated using X-ray crystallography and density functional calculations. The structures differ

Zhengcheng Zhang; Lu Zhang; John A. Schlueter; Paul C. Redfern; Larry Curtiss; Khalil Amine

2010-01-01

194

Magnetic properties of a new N-TEMPO-tert-butyl substituted salicylaldimines and their biradical palladium(II) complexes  

NASA Astrophysics Data System (ADS)

A new TEMPO bearing tert-butylated salicylaldimines 1 and 2, as well as early reported 3, and their bis(N-TEMPO-tert-butylated salicylaldiminato)palladium(II) biradical complexes 4-6 have been synthesized and characterized by elemental analyses, IR, UV/vis, ESR and an SQUID magnetometer. The solid state g-factors (2.0116-2.0168) for 4-6 suggest the existence of the significant metal-orbital contribution to the SOMO of nitroxyl radicals. The ?mT vs. T plots for 1 and 2 indicate that the ?mT decreases as T is lowered from 300 to 20 K, suggesting the existence of weak antiferromagnetic interactions in these radicals. Variable-temperature dependence (10-300 K) magnetic susceptibility data for biradical complexes 4-6 revealed the existence of ferromagnetic and antiferromagnetic behavior around at 10-220 K range for 4. The 1/?m data for 1-6 follow the Curie-Weiss law with negative ? throughout the above temperature range.

Kasumov, Veli T.; Yerli, Yusuf; Topkaya, Ramazan

2013-01-01

195

The synthetic polyphenol tert-butyl-bisphenol inhibits myoglobin-induced dysfunction in cultured kidney epithelial cells.  

PubMed

Abstract Rhabdomyolysis caused by severe burn releases extracellular myoglobin (Mb) that accumulates in the kidney and urine (maximum [Mb] approximately 50 microM) (termed myoglobinuria). Extracellular Mb can be a pro-oxidant. This study cultured Madin-Darby-canine-kidney-Type-II (MDCK II) cells in the presence of Mb and tested whether supplementation with a synthetic tert-butyl-polyphenol (tert-butyl-bisphenol; t-BP) protects these renal cells from dysfunction. In the absence of t-BP, cells exposed to 0-100 microM Mb for 24 h showed a dose-dependent decrease in ATP and the total thiol (TSH) redox status without loss of viability. Gene expression of superoxide dismutases-1/2, haemoxygenase-1 and tumour necrosis factor increased and receptor-mediated endocytosis of transferrin and monolayer permeability decreased significantly. Supplementation with t-BP before Mb-insult maintained ATP and the TSH redox status, diminished antioxidant/pro-inflammatory gene responses, enhanced monolayer permissiveness and restored transferrin uptake. Overall, bolstering the total antioxidant capacity of the kidney may protect against oxidative stress induced by experimental myoglobinuria. PMID:20528578

Shanu, Anu; Parry, Sarah N; Wood, Sarah; Rodas, Elicia; Witting, Paul K

2010-08-01

196

Organosoluble and light-colored fluorinated polyimides from 4- tert-butyl-[1,2-bis(4-amino-2-trifluoromethylphenoxy)phenyl]benzene and aromatic dianhydrides  

Microsoft Academic Search

A novel fluorinated diamine monomer with the tert-buty group, 4-tert-butyl-[1,2-bis(4-amino-2-trifluoromethylphenoxy)phenyl]benzene (2), was prepared through the nucleophilic substitution reaction of 2-chloro-5-nitrobenzotrifluoride with 4-tert-butylcatechol in the presence of potassium carbonate to the yield intermediate dinitro (1), followed by catalytic reduction with hydrazine and Pd\\/C. Polyimides 5a–f were synthesized from diamine 2 and various aromatic dianhydrides 3a–f via thermal imidization with inherent viscosities

Chin-Ping Yang; Yu-Yang Su; Hsun-Ching Chiang

2006-01-01

197

Copper redox-dependent activation of 2- tert-butyl(1,4)hydroquinone: formation of reactive oxygen species and induction of oxidative DNA damage in isolated DNA and cultured rat hepatocytes  

Microsoft Academic Search

The biotransformation of butylated hydroxyanisole (BHA), a possible carcinogenic food antioxidant, includes o-demethylation to 2-tert-butyl(1,4)hydroquinone (TBHQ) which can subsequently be oxidized to 2-tert-butyl(1,4)paraquinone (TBQ). In this study, we have examined the capacity of Cu, a nuclei- and DNA-associated transition metal, to mediate the oxidation of TBHQ. In phosphate buffered saline (PBS), autooxidation of TBHQ to TBQ was not detectable, while

Yunbo Li; Andrew Seacat; Periannan Kuppusamy; Jay L Zweier; James D Yager; Michael A Trush

2002-01-01

198

Reactions at interfaces: oxygenation of n-butyl ligands anchored on silica surfaces with methyl(trifluoromethyl)dioxirane.  

PubMed

The oxygenation of n-butyl and n-butoxy chains bonded to silica with methyl(trifluoromethyl)dioxirane (1) revealed the ability of the silica matrix to release electron density toward the reacting C(2)-H ?-bond through the Si-C(1) and Si-O(1) ?-bonds connecting the alkyl chain to the surface (silicon ?-effect). The silica surface impedes neither the alkyl chain adopting the conformation required for the silicon ?-effect nor dioxirane 1 approaching the reactive C(2) methylene group. Reaction regioselectivity is insensitive to changes in the solvation of the reacting system, the location of organic ligands on the silica surface, and the H-bonding character of the silica surface. Reaction rates are faster for those organic ligands either within the silica pores or bonded to hydrophilic silica surfaces, which evidence the enhanced molecular dynamics of confined dioxirane 1 and the impact of surface phenomena on the reaction kinetics. The oxygenation of n-butyl and n-butoxy chains carrying trimethylsilyl, trimethoxysilyl, and tert-butyl groups with dioxirane 1 under homogeneous conditions confirms the electronic effects of the silyl substituents and the consequences of steric hindrance on the reaction rate and regioselectivity. Orthosilicic acid esters react preferentially at the methylene group adjacent to the oxygen atom in clear contrast with the reactivity of the carboxylic or sulfonic acid alkyl esters, which efficiently protect this position toward oxidation with 1. PMID:22066821

Mello, Rossella; Martínez-Ferrer, Jaime; Alcalde-Aragonés, Ana; Varea, Teresa; Acerete, Rafael; González-Núñez, María Elena; Asensio, Gregorio

2011-12-16

199

Isobaric vapor–liquid equilibrium for ternary mixtures of ethanol and methylcyclohexane with 3-methylpentane and tert-butyl alcohol at 101.3 kPa  

Microsoft Academic Search

Consistent vapor–liquid equilibrium (VLE) data for the ternary systems 3-methylpentane+ethanol+methylcyclohexane and ethanol+tert-butyl alcohol (TBA)+methylcyclohexane are reported at 101.3kPa. The VLE data have been correlated by Wilson, UNIQUAC and NRTL equations. The ternary systems do not present azeotrope and are well predicted from binary interaction parameters.

María del Carmen Sánchez-Russinyol; Antonio Aucejo; Sonia Loras

2007-01-01

200

Delayed Treatment with ?-Phenyl- N- tert-butyl Nitrone (PBN) Attenuates Secondary Mitochondrial Dysfunction after Transient Focal Cerebral Ischemia in the Rat  

Microsoft Academic Search

The present experiments were undertaken to explore the mechanisms of secondary brain damage in focal ischemia of long duration (2 h), followed by recirculation. Recirculation has previously been found to cause partial recovery and secondary deterioration of cellular bioenergetic state, the subsequent damage being ameliorated by a free radical spin trap, ?-phenyl-N-tert-butyl nitrone (PBN), even when the drug was given

Satoshi Kuroda; Ken-ichiro Katsura; Lars Hillered; Timothy E. Bates; Bo K. Siesjö

1996-01-01

201

Ferric chloride-catalyzed reaction of [60]fullerene with tert-butyl N-substituted carbamates: synthesis of oxazolidino[4,5:1,2][60]fullerenes.  

PubMed

The rare oxazolidinofullerenes have been prepared by the ferric chloride-catalyzed reaction of [60]fullerene with various tert-butyl N-substituted carbamates via t-Bu-O bond cleavage and heteroannulation under mild conditions. A possible mechanism for the formation of oxazolidinofullerenes is proposed. PMID:24328055

You, Xun; Wang, Guan-Wu

2014-01-01

202

Conformations and Barriers to Methyl Group Internal Rotation in Two Asymmetric Ethers: Propyl Methyl Ether and Butyl Methyl Ether  

NASA Astrophysics Data System (ADS)

The conformational preferences of the O-C-C-C unit are important in many biological systems with the unit generally preferring a gauche configuration compared to an anti configuration. Butyl methyl ether and propyl methyl ether provide very simple systems for this phenomenom to manifest. Pure rotational spectra of the title molecules have been recorded using chirped pulse Fourier transform microwave spectroscopy (CP-FTMW). In the case of butyl methyl ether, only one conformer has been observed. This conformer has torsional angles of COCC = 180°, OCCC = 62° and CCCC = 180° (anti-gauche-anti) and rotational constants of A = 10259.4591(33) MHz, B = 1445.6470(13) MHz, and C = 1356.2944(14) MHz. The rotational spectrum was doubled and has been analyzed to produce an effective barrier to methyl group internal rotation of 780(35) cm-1. A prior rotational spectroscopic study on propyl methyl ether had focused only on the high energy anti-anti conformer. We have analyzed spectra from the lowest energy anti-gauche conformer and the spectroscopic constants will be presented. A summary of the differences in conformational energies and methyl group internal rotation barriers for the class of aliphatic asymmetric ethers will be presented. K. N. Houk, J. E. Eksterowicz, Y.-D. Wu, C. D. Fuglesang, D. B. Mitchell. J. Am. Chem. Soc. 115 (4170), 1993. Hiroshi Kato, Jun Nakagawa, Michiro Hayashi. J. Mol. Spectrosc. 80 (272), 1980.

Long, B. E.; Dechirico, F.; Cooke, S. A.

2012-06-01

203

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.

Information Center

2006-02-01

204

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

205

Slow tert-butyl ester acidolysis and peptide 3(10)-helix to alpha-helix transition in HFIP solution.  

PubMed

We have already shown by CD and NMR techniques that the terminally protected homo-octapeptides Z (and Ac)-[L-(alphaMe)Val](8)-OtBu undergo a slow and irreversible 3(10)-helix to alpha-helix transition when dissolved in 1,1,1,3,3,3-hexafluoroisopropanol. In the present work, we find by HPLC and CD that under the aforementioned experimental conditions, a slow acidolysis of the tert-butyl ester functionality does take place affording the corresponding octapeptide free acids. The results of our combined chromatographic and spectroscopic experiments are confirmed by a comparison with the properties of independently synthesized and chemically characterized authentic compounds. PMID:17216636

Moretto, Alessandro; Crisma, Marco; Formaggio, Fernando; Kaptein, Bernard; Broxterman, Quirinus B; Keiderling, Timothy A; Toniolo, Claudio

2007-01-01

206

Strong carbon-surface dative bond formation by tert-butyl isocyanide on the Ge(100)-2 × 1 surface.  

PubMed

Carbon dative bond formation between an organic molecule and a semiconductor surface is reported here for the first time. Our studies show that the adsorption of tert-butyl isocyanide on the (100) surface of germanium, measured using Fourier transform infrared spectroscopy, temperature-programmed desorption, and density functional theory calculations, occurs via formation of a dative bond to the surface through the isocyanide carbon. The experimentally observed adsorption energy of 26.8 kcal/mol is the largest among any organic molecule dative bonded on the Ge(100)-2 × 1 surface studied to date. The dative-bonded adsorbate is characterized by a N?C stretching frequency significantly blue-shifted from that of the free molecule. Moreover, the adsorbate N?C vibrational frequency red-shifts back toward that of the free molecule upon increasing coverage. These spectroscopic effects are attributed to ?-donation of the isocyanide lone pair electrons to the surface. PMID:24725248

Shong, Bonggeun; Wong, Keith T; Bent, Stacey F

2014-04-23

207

Preparation of N-tBoc L-glutathione dimethyl and di-tert-butyl esters: versatile synthetic building blocks  

PubMed Central

The title L-glutathione derivatives, containing acid- and base-labile esters, respectively, were obtained in good overall yields. N-tBoc L-glutathione dimethyl ester was prepared via Fischer esterification of L-glutathione disulfide (GSSG) using HCl in dry methanol, protection of the amine with tBoc2O, and tributylphosphine cleavage of the disulfide in wet isopropanol. Alternatively, Fischer esterification and tBoc-protection of L-glutathione (GSH) also furnished N-tBoc glutathione dimethyl ester accompanied by a small amount of S-tBoc that was removed chromatographically. The di-tert--butyl ester was obtained by S-palmitoylation of GSH in TFA as solvent, N-tBoc-protection, esterification using tBuOH mediated by diisopropylcarbodiimide/copper(I) chloride, and saponification of the thioester. These L-glutathione derivatives are versatile synthetic building blocks for the preparation of S-glutathione adducts.

Falck, J. R.; Sangras, Bhavani; Capdevila, Jorge H.

2007-01-01

208

Poly[(?3-5-tert-butyl-benzene-1,3-di-carboxyl-ato)di-pyridine-cobalt(II)  

PubMed Central

In the title compound, [Co(C12H12O4)(C5H5N)2]n, the CoII cation is coordinated by four O atoms from three 5-tert-butyl­benzene-1,3-di­carboxyl­ate anions and two N atoms from pyridine mol­ecules in a distorted octa­hedral geometry. One carboxyl­ate group of the anionic ligand chelates a CoII cation while another carboxyl­ate group bridges two CoII cations, resulting in a polymeric layer parallel to (101). Weak C—H?O hydrogen bonds occur between adjacent polymeric layers. In the crystal, one of pyridine mol­ecules is equally disordered over two positions.

Noh, Kyungkyou; Kim, Jaheon

2013-01-01

209

Functional polyolefins: poly(ethylene)-graft-poly(tert-butyl acrylate) via atom transfer radical polymerization from a polybrominated alkane.  

PubMed

Poly(cis-cyclooctene) is synthesized via ring-opening metathesis polymerization in the presence of a chain-transfer agent and quantitatively hydrobrominated. Subsequent graft polymerization of tert-butyl acrylate (tBA) via Cu-catalyzed atom transfer radical polymerization (ATRP) from the non-activated secondary alkyl bromide moieties finally results in PE-g-PtBA copolymer brushes. By varying the reaction conditions, a series of well-defined graft copolymers with different graft densities and graft lengths are prepared. The maximum extent of grafting in terms of bromoalkyl groups involved is approximately 80 mol%. DSC measurements on the obtained graft copolymers reveal a decrease in T(m) with increasing grafting density. PMID:22095785

Xu, Guangjuan; Wang, Dongren; Buchmeiser, Michael R

2012-01-16

210

Regulation of the unbalanced redox state in a Schizosaccharomyces pombe tert-butyl hydroperoxide-resistant mutant.  

PubMed

The one-gene mutation in the tert-butyl hydroperoxide-resistant mutant hyd1-190 of the fission yeast Schizosaccharomyces pombe led to a 4-fold increase in resistance to t-BuOOH and decreased specific concentrations of superoxide and total thiols in comparison with the parental strain hyd+. It suggested an unbalanced redox state of the cells, which induced continuously increased specific activities of glutathione peroxidase, glutathione reductase and glutathione S-transferase and decreased activities of the antioxidant enzymes superoxide dismutases and glucose-6-phosphate dehydrogenase to regulate the redox balance of the mutation-induced permanent, low-level but tolerable internal stress. These results may contribute to the understanding of internal, oxidative stress-related human diseases. PMID:24873914

Gazdag, Z; Kálmán, Nikoletta; Blaskó, Agnes; Virág, Eszter; Belágyi, J; Pesti, M

2014-06-01

211

A low-temperature modification of hexa-tert-butyldisilane and a new polymorph of 1,1,2,2-tetra-tert-butyl-1,2-diphenyldisilane.  

PubMed

Crystals of hexa-tert-butyldisilane, C24H54Si2, undergo a reversible phase transition at 179?(2)?K. The space group changes from Ibca (high temperature) to Pbca (low temperature), but the lattice constants a, b and c do not change significantly during the phase transition. The crystallographic twofold axis of the molecule in the high-temperature phase is replaced by a noncrystallographic twofold axis in the low-temperature phase. The angle between the two axes is 2.36?(4)°. The centre of the molecule undergoes a translation of 0.123?(1)?Å during the phase transition, but the conformation angles of the molecule remain unchanged. Between the two tri-tert-butylsilyl subunits there are six short repulsive intramolecular C-H...H-C contacts, with H...H distances between 2.02 and 2.04?Å, resulting in a significant lengthening of the Si-Si and Si-C bonds. The Si-Si bond length is 2.6863?(5)?Å and the Si-C bond lengths are between 1.9860?(14) and 1.9933?(14)?Å. Torsion angles about the Si-Si and Si-C bonds deviate by approximately 15° from the values expected for staggered conformations due to intramolecular steric H...H repulsions. A new polymorph is reported for the crystal structure of 1,1,2,2-tetra-tert-butyl-1,2-diphenyldisilane, C28H46Si2. It has two independent molecules with rather similar conformations. The Si-Si bond lengths are 2.4869?(8) and 2.4944?(8)?Å. The C-Si-Si-C torsion angles deviate by between -3.4?(1) and -18.5?(1)° from the values expected for a staggered conformation. These deviations result from steric interactions. Four Si-C(t-Bu) bonds are almost staggered, while the other four Si-C(t-Bu) bonds are intermediate between a staggered and an eclipsed conformation. The latter Si-C(t-Bu) bonds are about 0.019?(2)?Å longer than the staggered Si-C(t-Bu) bonds. PMID:24992114

Scholz, Stefan; Lerner, Hans Wolfram; Bats, Jan W

2014-07-15

212

Ionization energy of tert-butyl-d{sub 9} alcohol and the appearance energy of protonated acetone: a nonequilibrium dissociation  

SciTech Connect

In the present photoionization study of tert-butyl alcohol, the parent ion of the deuterated isotopomer [(CD{sub 3}){sub 3}-COH] was observed and an ionization energy (IE) of 9.82{+-}0.02 eV was derived from a step-function threshold at 126.25 nm. The appearance energies (AE`s) of (CD{sub 3}){sub 2}COH{sup +} and (CH{sub 3}){sub 2}COH{sup +} were also determined. From these results, the IE of undeuterated tert-butyl alcohol (which was not observed) was estimated. The difference between the IE and the derived AE{sub 0} implies an upper limit for the barrier to dissociation of (CH{sub 3}){sub 3}COH{sup +}. A recent evaluation of the proton affinity of acetone was employed to derive a value for {Delta}{sub f}H{degree}{sub 0}[(CH{sub 3}){sub 2}COH{sup +}] and, thence, the enthalpy of reaction; and from this, an upper limit for the reverse barrier of the dissociation was obtained. RRKM calculations were performed by using the energies derived from the experimental (and estimated) values. For excitation energies >= 0.2 eV above threshold, RRKM calculations yield large rate coefficients for dissociation. Also, the kinetic energy release (KER) was calculated for various models of the dissociation complex. The calculated KER`s are consistent with experimental values when it is assumed that only 5 of the 38 vibrational modes of the transition state are active in the randomization of internal energy. 34 refs., 6 figs., 1 tab.

Tardy, D.C. [Univ. of Iowa, Iowa City, IA (United States)] [Univ. of Iowa, Iowa City, IA (United States); Kuo, S.C.; Zhang, Z.; Klemm, R.B. [Brookhaven National Lab., Upton, NY (United States)] [Brookhaven National Lab., Upton, NY (United States)

1996-05-16

213

Regioselective hydrolysis of ketenimines derived from NH-acids and acetylenic esters in the presence of tert -butyl isocyanide under neutral conditions  

Microsoft Academic Search

The regioselective hydrolysis of ketenimines derived from NH-acids, such as 2,2,2-trichloro-N-phenylacetamide or ethyl-2-anilino-2-oxoacetates and acetylenic esters in the presence of tert-butyl isocyanide in a THF\\/H2O system (1\\/1) without any catalysis leads to a diastereomeric mixture of dialkyl 2-[(tert-butylamino)carbonyl]-3-[(2,2,2-trichloroacetyl)anilino]succinates and dialkyl 2-[(tert-butylamino)carbonyl]-3-[2-ethoxy-2-oxoacetyl)anilino]-succinates in good yields. Dynamic NMR effects were observed in the\\u000a 13C NMR spectra of diethyl 2-[(tert-butylamino)carbonyl]-3-[(2,2,2-trichloroacetyl)anilino]succinate as a result

Farough Nasiri; Samiyeh Yosefdad

2008-01-01

214

Kinetic study of gas-phase reactions of OH and NO3 radicals and O3 with iso-butyl and tert-butyl vinyl ethers.  

PubMed

Using a relative rate technique, kinetic studies on the gas-phase reactions of OH radicals, ozone, and NO(3) radicals with iso-butyl vinyl ether (iBVE) and tert-butyl vinyl ether (tBVE) have been performed in a 405 L Duran glass chamber at (298 ± 3) K and atmospheric pressure (750 ± 10 Torr) in synthetic air using in situ FTIR spectroscopy to monitor the reactants. The following rate coefficients (in units of cm(3) molecule(-1) s(-1)) have been obtained: (1.08 ± 0.23) × 10(-10) and (1.25 ± 0.32) × 10(-10) for the reactions of OH with iBVE and tBVE, respectively; (2.85 ± 0.62) × 10(-16) and (5.30 ± 1.07) × 10(-16) for the ozonolysis of iBVE and tBVE, respectively; and (1.99 ± 0.56) × 10(-12) and (4.81 ± 1.01) × 10(-12) for the reactions of NO(3) with iBVE and tBVE, respectively. The rate coefficients for the NO(3) reactions are first-time determinations. The measured rate coefficients are compared with estimates using current structure activity relationship (SAR) methods and the effects of the alkoxy group on the gas-phase reactivity of the alkyl vinyl ethers toward the oxidants are compared and discussed. In addition, estimates of the tropospheric lifetimes of iBVE and tBVE with respect to their reactions with OH, ozone, and NO(3) for typical OH radical, ozone, and NO(3) radical concentrations are made, and their relevance for the environmental fate of compounds is considered. PMID:22897604

Zhou, Shouming; Barnes, Ian; Zhu, Tong; Benter, Thorsten

2012-09-01

215

Electrorheological Properties of Suspensions Prepared from Poly(Li-tert-butyl methacrylate) Ionomer  

Microsoft Academic Search

The synthesis, characterisation and partial hydrolysis of poly(tert-butylmethacrylate), (PTBMA), and the electrorheological (ER) properties of its suspensions were investigated. The polymer was syn- thesised by radical polymerisation and partially hydrolysed by para-toluenesulphonic acid monohydrate (PTSA.H2O), and then converted to a lithium salt (PTBMA-Li) by washing with a LiOH(aq) solution. From particle size measurements, the average particle size of PTBMA-Li was

Mustafa YAVUZ

216

Electrochemically and electrochromically stable polyimides bearing tert-butyl-blocked N, N, N?, N?-tetraphenyl-1,4-phenylenediamine units  

Microsoft Academic Search

A new class of electrochemically active polyimides with di-tert-butyl-substituted N,N,N?,N?-tetraphenyl-1,4-phenylenediamine units was prepared from N,N-bis(4-aminophenyl)-N?,N?-bis(4-tert-butylphenyl)-1,4-phenylenediamine and various aromatic tetracarboxylic dianhydrides via a conventional two-step procedure that included a ring-opening polyaddition to give poly(amic acid)s, followed by chemical or thermal cyclodehydration. Most of the polyimides are readily soluble in many organic solvents and can be solution-cast into tough and amorphous films.

Hui-Min Wang; Sheng-Huei Hsiao

2009-01-01

217

ESR characterization of a novel spin-trapping agent, 15N-labeled N-tert-butyl-alpha-phenylnitrone, as a nitric oxide donor.  

PubMed

We previously found that one of the pharmacological effects of N-tert-butyl-alpha-phenylnitrone (PBN) is the release of nitric oxide (NO) under oxidative conditions. However, to confirm this hypothesis in vivo, NO released from PBN must be distinguished from NO produced in biological systems, and therefore we undertook the synthesis of PBN using labeled 15N to identify its corresponding 15NO in vivo. The properties were examined with an ESR spectrometer. To synthesize 15N-PBN, the starting material, ammonium-15N chloride, was converted to 2-amino-15N-2-methylpropane, oxidized to 2-methyl-2-nitropropane-15N, and finally reacted with benzaldehyde to give 15N-PBN. The final product was purified by repeated sublimation. With ferrous sulfate-methyl glucamine dithiocarbamate complex, Fe (MGD)2, as a trapping agent to measure the NO levels of 15N-PBN or 14N-PBN in vitro, the peak intensity of 15NO[Fe(MGD)2] was over 50% stronger than that of 14NO[Fe(MGD)2], and that 15NO and 14NO had the corresponding two-and three line hyperfine structures due to their nuclear spin quantum numbers. Subsequently, the ESR spectrum of 15NO derived from 15N-PBN was significantly different than that of lipopolysaccharide (LPS)-induced NO, which was derived from biological cells, and therefore we have demonstrated the possibility to distinguish 15NO from PBN and 14NO generated from cells. These results suggested that 15N-PBN is a useful molecule, not only as a spin-trapping agent, but also as an NO donor to explore the pharmacological mechanisms of PBN in vivo. PMID:12450131

Saito, Kieko; Yoshioka, Hisashi

2002-10-01

218

(2-tert-Butyl-3-phenyl-2,3-di-hydro-isoxazole-4,5-di-yl)bis-(phenyl-methanone).  

PubMed

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-butyl-nitrone starting material. The attached carbonyl groups are not coplanar with the neighboring di-hydro-isoxazole 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 di-hydro-isoxazole ring and the directly attached phenyl group is 86.86?(8)°. There are two nonclassical inter-molecular C-H?O hydrogen-bonding inter-actions that operate together with an inter-molecular C-H?? inter-action to form a supramolecular architecture in the crystal system. PMID:24109366

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

2013-01-01

219

Understanding the redox shuttle stability of 3,5-di-tert-butyl-1,2-dimethoxybenzene for overcharge protection of lithium-ion batteries.  

SciTech Connect

3,5-di-tert-butyl-1,2-dimethoxybenzene (DBDB) has been synthesized as a new redox shuttle additive for overcharge protection of lithium-ion batteries. DBDB can easily dissolve in carbonate-based electrolytes, which facilitates its practical use in lithium-ion batteries; however, it has poor electrochemical stability compared to 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB). The structures of DBDB and DDB were investigated using X-ray crystallography and density functional calculations. The structures differ in the conformations of the alkoxy bonds probably due to the formation of an intramolecular hydrogen bond in the case of DBDB. We investigated reaction energies for decomposition pathways of neutral DBDB and DDB and their radical cations and found little difference in the reaction energies, although it is clear that kinetically, decomposition of DBDB is more favorable.

Zhang, Z.; Zhang, L.; Schlueter, J. A.; Redfern, P. C.; Curtiss, L.; Amine, K.

2010-01-01

220

HIGH LEVELS OF MONOAROMATIC COMPOUNDS LIMIT THE USE OF SOLID-PHASE MICROEXTRACTION OF METHYL TERTIARY BUTYL ETHER AND TERTIARY BUTYL ALCOHOL  

EPA Science Inventory

Recently, two papers reported the use of solid-phase microextraction (SPME) with polydimethylsiloxane(PDMS)/Carboxen fibers to determine trace levels of methyl tertiary butyl ether (MTBE) and tertiary butyl alcohol (tBA) in water. Attempts were made to apply this technique to th...

221

Free radical scavenging abilities of flavonoids as mechanism of protection against mutagenicity induced by tert-butyl hydroperoxide or cumene hydroperoxide in Salmonella typhimurium TA102  

Microsoft Academic Search

Mutagenicity induced by tert-butyl hydroperoxide (BHP) or cumene hydroperoxide (CHP) in Salmonella typhimurium TA102 was effectively reduced by flavonols with 3?,4?-hydroxyl groups such as fisetin, quercetin, rutin, isoquercitrin, hyperoxide, myricetin, myricitrin, robinetin, and to a lesser extent also by morin and kaempferol (ID50=0.25–1.05?mol per plate). With the exception of isorhamnetin, rhamnetin, morin, and kaempferol, closely similar results were obtained with

R. Edenharder; D. Grünhage

2003-01-01

222

Use of chiral B(III) complexes in the cycloaddition of C, N-diphenylnitrone to tert-butyl vinyl ether  

Microsoft Academic Search

The 1,3-dipolar cycloaddition of C,N-diphenylnitrone to tert-butyl vinyl ether in the presence of several chiral B(III) complexes which incorporate different bidentate ligands has been investigated. The use of these B(III) species reverses the endo\\/exo diastereoselectivity in relation to the uncatalysed reaction, giving trans cycloadducts as major products. Some of the catalysts gave very fast and high yielding reactions, but the

Pau Bayón; Pedro de March; Marta Figueredo; Jordi Medrano

2000-01-01

223

Use of chiral Ti(IV) complexes in the cycloaddition of C, N-diphenylnitrone to tert-butyl vinyl ether  

Microsoft Academic Search

The 1,3-dipolar cycloaddition of C,N-diphenylnitrone to tert-butyl vinyl ether in the presence of several chiral Ti(IV) species which incorporate different bidentate C2-symmetrical ligands has been investigated. Several complexes have shown very efficient catalytic activity. The endo\\/exo selectivity of the process can be dramatically reversed in relation to the uncatalysed reaction, but low enantioselectivities up to 41% ee are found.

Pau Bayón; Pedro de March; Mercè Espinosa; Marta Figueredo

2000-01-01

224

Modulatory influence of arecanut on antioxidant 2(3)- tert-butyl-4-hydroxy anisole-induced hepatic detoxification system and antioxidant defence mechanism in mice  

Microsoft Academic Search

This paper assesses the modificatory potential of arecanut (Areca catechu L.), a popular masticatory substance, on 2(3)-tert-butyl-4-hydroxy anisole (BHA)-induced changes in the hepatic detoxification system and antioxidant defence mechanisms in mice. The modulatory effects on biochemical parameters including glutathione S-transferase (GST), cytochrome b5, cytochrome P-450, acid soluble sulfhydryl (?SH) content and microsomal lipid peroxidation (MDA) levels were assessed. Mice were

Anjali Singh; A. R. Rao

1995-01-01

225

An analysis of 2,6-di-tert-butyl-p-cresol in insulating oils by high-performance liquid chromatography  

Microsoft Academic Search

The presence of antioxidant is the key factor in controlling the oxidation of an insulating oil. Any monitoring program set up to keep track of its concentration could result in substantial savings by prolonging the oil service life and slowing down the transformer aging process. This paper describes a method for measuring the amount of the antioxidant 2,6-di-tert-butyl-para-cresol (DBPC) in

C. Lamarre; A. Gendron

1995-01-01

226

Inverted Microcontact Printing on Polystyrene-block-Poly(tert-butyl acrylate) Films: A Versatile Approach to Fabricate Structured Biointerfaces Across the Length Scales  

Microsoft Academic Search

The combination of the recently introduced soft lithographic technique of inverted microcontact printing (i-?CP) and spin-coated films of polystyrene-block-poly(tert-butyl acrylate) (PS690-b-PtBA1210) as a reactive platform is shown to yield a versatile approach for the facile fabrication of topographically structured and chemically patterned biointerfaces with characteristic spacings and distances that cross many orders of magnitude. The shortcomings of conventional ?CP in

Anika Embrechts; Chuan Liang Feng; Christopher A. Mills; Michael Lee; Ilona Bredebusch; Ju?rgen Schnekenburger; Wolfram Domschke; G. Julius Vancso; Holger Schönherr

2008-01-01

227

Influence of transfer promoters on the deposition and wettability characteristics of copper tetra-tert-butyl phthalocyanine Langmuir–Blodgett films  

Microsoft Academic Search

This study investigated the influence of three transfer promoters on the deposition and wettability characteristics of copper tetra-tert-butyl phthalocyanine (CuTTBPc) Langmuir–Blodgett (L-B) films. With the addition of transfer promoters, such as stearyl alcohol, stearamide, and arachidic acid, two transitions corresponding to monolayer collapse were observed in the surface pressure-area isotherms of mixed CuTTBPc\\/transfer promoter monolayers at the air\\/water interface. Nevertheless,

I-Hsun Ku; Yuh-Lang Lee; Chien-Hsiang Chang; Yu-Min Yang; Jer-Ru Maa

2001-01-01

228

Interfacial Reactions in Confinement: Kinetics and Temperature Dependence of the Surface Hydrolysis of Polystyrene-block-poly(tert-butyl acrylate) Thin Films  

Microsoft Academic Search

The effect of confinement on the kinetics of the surface hydrolysis of polystyrene-block-poly(tert-butyl acrylate) (PSn-b-PtBAm) thin films on oxidized silicon substrates in 3 M aqueous hydrochloric acid was systematically investigated. As shown by X-ray photoelectron spectroscopy (XPS) and contact angle measurements, a skin layer of acid-sensitive PtBA is present on the surface of PSn-b-PtBAm films, consistent with the lower surface

Chuan Liang Feng; G. Julius Vancso; Holger Schönherr

2005-01-01

229

Mechanistic Basis for Inflammation and Tumor Promotion in Lungs of 2,6Di tert -butyl-4-methylphenol-Treated Mice:  Electrophilic Metabolites Alkylate and Inactivate Antioxidant Enzymes  

Microsoft Academic Search

An established model for mechanistic analysis of lung carcinogenesis involves administration of 3-methylcholanthrene to mice followed by several weekly injections of the tumor promoter 2,6-di-tert- butyl-4-methylphenol (BHT). BHT is metabolized to quinone methides (QMs) responsible for promoting tumor formation. QMs are strongly electrophilic and readily form adducts with proteins. The goal of the present study was to identify adducted proteins

Brent W. Meier; Jose D. Gomez; Oleg V. Kirichenko; John A. Thompson

2007-01-01

230

tert-Butyl hydroperoxide, an organic peroxide, causes temporary delay in hair growth in a neonatal rat model  

PubMed Central

Summary tert-Butyl hydroperoxide (tBHP), an organic peroxide, has been shown to cause irreversible damage to keratinocytes in vitro with prolonged administration at high concentrations, and reversible damage with short-term administration at low concentrations. To investigate the effects of tBHP on keratinocytes in vivo, we analysed hair growth in tBHP-treated neonatal rats. Sprague–Dawley and Long–Evans rat pups were injected subcutaneously with tBHP or vehicle once daily for 6 days, and hair growth was monitored. The tBHP-treated rats had a significant delay in hair growth. However, this delay reversed within days, and the hair coats, including hair pigmentation, of tBHP-treated and sham-treated rats were indistinguishable 2 weeks later. Histological analysis and BrdU labelling of S phase cells confirmed the delay in hair-follicle growth and its reversal in tBHP-treated rats. Our results indicated that the changes incurred in hair follicles by short-term use of high-dose oxidants in vivo are temporary and reversible.

Wikramanayake, T. C.; Simon, J.; Mauro, L. M.; Perez, C. I.; Roberts, B.; Elgart, G.; Alvarez-Connelly, E.; Schachner, L. A.; Jimenez, J. J.

2011-01-01

231

Excited state proton transfer in di-(2-hydroxy-3-formyl-5-tert butyl phenyl) methane and solvent effect  

NASA Astrophysics Data System (ADS)

The proton transfer reaction and the spectroscopic properties of di-(2-hydroxy-3-formyl-5-tert butyl phenyl) methane (HFPM) have been examined in different nonpolar and polar solvents at room temperature and 77 K, by means of absorption, emission and time resolved fluorescence spectroscopy. In the ground state, the primary closed form has been identified in all the nonpolar and polar solvents and the anion is detected only in presence of base in some of the polar solvents. After photoexcitation, the excited state intramolecular proton transfer (ESIPT) is indicated by a large Stokes shifted emission (˜10,600 cm -1) in all the nonpolar and polar solvents used, except in water and ethylene glycol (EG). The ESIPT band is likely to be originated from the enol tautomer of the HFPM. Two types of anion and H-bonded complex have been detected in the excited state. In water and EG, only anion and H-bonded complex have been detected in the excited state. At 77 K, HFPM shows phosphorescence in pure ethanol, and in n-hexane in presence of triethylamine. It has been suggested that the appearance of phosphorescence is due to the rotation of the formyl group. The measured nonradiative decay rates have always been found to dominate in the decay processes of the excited state of HFPM. Some semiempirical calculations have been undertaken to rationalize the experimental findings.

Mukhopadhyay, M.; Banerjee, D.; Mukherjee, S.

2006-05-01

232

The molecular structure and vibrational spectra of N-(3-tert-butyl-2-hydroxybenzylidene)-2,6-diphenyl-4-hydroxyaniline  

NASA Astrophysics Data System (ADS)

The molecular structure, vibrational frequencies and intensities of N-(3-tert-butyl-2-hydroxybenzylidene)-2,6-diphenyl-4-hydroxyaniline were calculated by the Density Functional Theory methods (BLYP, B3PW91 and B3LYP) using the 6-31G(d,p) basis set. The calculated geometric parameters were compared to the corresponding X-ray structure of the title compound. The comparison of the theoretical and experimental geometry of the title compound shows that the X-ray parameters fairly well reproduce the geometry of optimized by B3LYP method (r = 0.9825). The harmonic vibrations computed for this compound by the B3LYP/6-31G(d,p) method are in good agreement with the observed IR and Raman spectral data. The root mean square values error of the observed and calculated IR bands are found to be 9.80, 9.40 and 8.42 for B3LYP, B3PW91 and BLYP/6-31G(d,p) methods, respectively. Theoretical vibrational spectra of the title compound were interpreted by means of PEDs using the SQM 2.0 program. A general better performance of the investigated methods was calculated by PAVF 1.0 program.

Yabalak, Erdal; Günay, Funda; Kasumov, Veli T.; Arslan, Hakan

2013-06-01

233

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.

Kucera, Otto; Endlicher, Rene; Rousar, Tomas; Lotkova, Halka; Garnol, Tomas; Drahota, Zdenek

2014-01-01

234

The free radical scavenger alpha-phenyl-tert-butyl nitrone aggravates hippocampal apoptosis and learning deficits in experimental pneumococcal meningitis.  

PubMed

The effect of adjuvant therapy with the radical scavenger alpha-phenyl-tert-butyl nitrone (PBN; 100 mg/kg given intraperitoneally every 8 h for 5 days) on brain injury and learning function was evaluated in an infant rat model of pneumococcal meningitis. Meningitis led to cortical necrotic injury (median, 3.97% [range, 0%-38.9%] of the cortex), which was reduced to a median of 0% (range, 0%-30.9%) of the cortex (P<.001) by PBN. However, neuronal apoptosis in the hippocampal dentate gyrus was increased by PBN, compared with that by saline (median score, 1.15 [range, 0.04-1.73] vs. 0.31 [range, 0-0.92]; P<.001). Learning function 3 weeks after cured infection, as assessed by the Morris water maze, was decreased, compared with that in uninfected control animals (P<.001). Parallel to the increase in hippocampal apoptosis, PBN further impaired learning in infected animals, compared with that in saline-treated animals (P<.02). These results contrast with those of an earlier study, in which PBN reduced cortical and hippocampal neuronal injury in group B streptococcal meningitis. Thus, in pneumococcal meningitis, antioxidant therapy with PBN aggravates hippocampal injury and learning deficits. PMID:11110643

Loeffler, J M; Ringer, R; Hablützel, M; Täuber, M G; Leib, S L

2001-01-15

235

Gender-related response to a tert-butyl hydroperoxide-induced oxidation in human neonatal tissue.  

PubMed

Reports of gender-related differences in the activity of enzymes involved in the metabolism of intracellular antioxidants, led us to verify whether the prostaglandin response to tert-butyl hydroperoxide (TBH) differed according to the sex of infants. Segments of human umbilical veins were perfused in the presence or absence of TBH (0.25 mmol/l, and 1.0 mmol/l). Because TBH is quenched in the cell by glutathione peroxidase, total glutathione concentrations and production of glutathione-dependent prostaglandins (PGE2 and PGF2 alpha) as well as membrane-derived eicosanoids (PGI2 and thromboxane) were measured in the eluate. In veins from boys, TBH induced a sustained response for glutathione only, which was increased (p < 0.05). In female-derived tissue, the hydroperoxide induced a different response according to the dose of TBH. At 0.25 mmol/l, a drop (p < 0.005) in PGF2 alpha was associated with a rise (p < 0.001) in thromboxane. At 1.0 mmol/l, TBH had an opposite effect--there was a rise (p < 0.01) in PGE2 and PGI2. The prostaglandin concentration were not proportional to the oxidative stimulus, suggesting a critical level of TBH at which the oxidative state differs in tissues derived from boys or girls. PMID:8063193

Lavoie, J C; Chessex, P

1994-03-01

236

Assessment of the ability of seaweed extracts to protect against hydrogen peroxide and tert-butyl hydroperoxide induced cellular damage in Caco-2 cells.  

PubMed

The ability of brown seaweed extracts, Ascophyllum nodosum, Laminaria hyperborea, Pelvetia canaliculata, Fucus vesiculosus and Fucus serratus to protect against tert-butyl hydroperoxide (tert-BOOH) induced stress in Caco-2 cells was investigated. Oxidative stress was determined by measuring alteration in the enzymatic activity of catalase (CAT) and superoxide dismutases (SOD) and cellular levels of glutathione (GSH). L. hyperborea, P. canaliculata and F. serratus significantly protected against tert-BOOH induced SOD reduction but did not protect against the reduction in CAT activity or the increased cellular levels of GSH. The ability of F. serratus and F. vesiculosus to protect against H(2)O(2) and tert-BOOH induced DNA damage was also assessed. The DNA protective effects of the two seaweed extracts was compared to those of three metal chelators; deferoxamine mesylate (DFO), 1,10-phenanthroline (o-phen) and 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (BAPTA-AM). F. serratus and F. vesiculosus significantly protected (P<0.05) against H(2)O(2) (50 ?M) induced DNA damage but not tert-BOOH induced damage. PMID:23107739

O'Sullivan, A M; O'Callaghan, Y C; O'Grady, M N; Queguineur, B; Hanniffy, D; Troy, D J; Kerry, J P; O'Brien, N M

2012-09-15

237

Ligand dynamics of tert-butyl isocyanide oxido complexes of molybdenum(IV).  

PubMed

The six-coordinate molybdenum(IV) oxido isocyanide complex 1 [?,?-OC-6-2-3-[MoO(N(p)?N(i))2(CN(t)Bu)]; N(p)?N(i) = 4-tert-butylphenyl(pyrrolato-2-ylmethylene)amine] is obtained in diastereomerically pure form in the solid state, as revealed by single-crystal X-ray diffraction. In solution, this stereoisomer equilibrates with the ?,?-OC-6-2-4 diastereomer 2 at ambient temperature. The stereochemistry of both isomers has been elucidated by NMR, IR, and UV/vis spectroscopy in combination with density functional theory (DFT)/polarizable continuum model and time-dependent DFT calculations. The isomerization 1 ? 2 is suggested to proceed via a dissociative trigonal twist with dissociation of the imine nitrogen donor N(i) of one chelate ligand (hemilabile ligand) rather than dissociation of the monodentate isocyanide ligand. The isomerization barrier has been experimentally determined as 91 and 95 kJ mol(-1) in tetrahydrofuran and toluene, respectively. PMID:24392782

Leppin, Jana; Förster, Christoph; Heinze, Katja

2014-01-21

238

Purification and characterization of tert-butyl ester-hydrolyzing lipase from Burkholderia sp. YY62.  

PubMed

An intracellular novel lipase which can hydrolyze t-butyl octanoate (TBO) was purified to homogeneity from crude cell-free extracts of Burkholderia (formerly Pseudomonas) sp. YY62 with 9% overall yield. Seventy-four-fold purification was achieved by ammonium-sulfate precipitation, three consecutive open-column chromatographies (DEAE anion-exchange, Sepharose CL-6B gel-filtration, and the second DEAE anion-exchange columns), and two HPLCs (TSK G2000SWXL gel-filtration and phenyl 5PW hydrophobic interaction columns). Enzymes hydrolyzing p-nitrophenyl acetate were separated into two peaks (peak I and II) on the hydrophobic HPLC, and only peak II was found to have TBO-hydrolyzing activity. The peak preparation showed a single band of 40 kDa on SDS-PAGE and a molecular mass of 39 kDa on gel-filtration under non-denatured conditions, indicating the monomeric nature of the TBO-hydrolyzing lipase. The lipase showed maximum activity at pH 7.0 and 28 degrees C. The N-terminal 15 amino acid residues were determined as Met-Asp-Phe-Tyr-Asp-Ala-Asn-Glu-Thr-Arg-His-Pro-Glu-Gln-Arg, which showed no homology to known proteins, suggesting that the purified enzyme may belong to a novel class of hydrolase. PMID:9972257

Yeo, S H; Nihira, T; Yamada, Y

1998-12-01

239

Methyl tertiary--butyl ether, evaluation as a high octane blending component for unleaded gasoline  

Microsoft Academic Search

A study was conducted to evaluate methyl tertiary-butyl ether (MTBE) as a high octane number blending component for automotive gasoline. Road octane ratings with a 1976 model year (MY) Buick confirmed the octane increases indicated by Research and Motor octane number determinations. The blend of 15% MTBE with 86 RON gasoline had a road octane number equivalent to that of

R. T. Johnson; B. Y. Taniguchi

1978-01-01

240

Magnetic scanometric DNA microarray detection of methyl tertiary butyl ether degrading bacteria for environmental monitoring  

Microsoft Academic Search

A magnetoresistive biosensing platform based on a single magnetic tunnel junction (MTJ) scanning probe and DNA microarrays labeled with magnetic particles has been developed to provide an inexpensive, sensitive and reliable detection of DNA. The biosensing platform was demonstrated on a DNA microarray assay for quantifying bacteria capable of degrading methyl tertiary butyl ether (MTBE), where concentrations as low as

Mei-Lin Chan; Gerardo Jaramillo; Krassimira R. Hristova; David A. Horsley

2011-01-01

241

REFINED PBPK MODEL OF AGGREGATE EXPOSURE TO METHYL TERTIARY-BUTYL ETHER  

EPA Science Inventory

Aggregate (multiple pathway) exposures to methyl tertiary-butyl ether (MTBE) in air and water occur via dermal, inhalation, and oral routes. Previously, physiologically-based pharmacokinetic (PBPK) models have been used to quantify the kinetic behavior of MTBE and its primary met...

242

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...

243

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...

244

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...

245

Vapor-liquid equilibria of hydrocarbons and tert-amyl methyl ether  

SciTech Connect

The P-T-x-y data for tert-amyl methyl ether (TAME) separately with 2,2,4-trimethylpentane (TMP), methylcyclohexane (MCHX), and toluene were obtained at three temperatures, 293, 311, and 333 K. The vapor-liquid equilibria of a five-components mixture (TAME + TMP + 1-heptene + MCHX + toluene) at the same temperature were measured as well. The data reported have been successfully described using a Peng-Robinson equation of state with van der Waals one-fluid mixing rules.

Antosik, M. (Polish Academy of Sciences, Warszawa (Poland). Inst. of Physical Chemistry); Sandler, S.I. (Univ. of Delaware, Newark, DE (United States). Dept. of Chemical Engineering)

1994-07-01

246

Isolation of phlorotannins from Eisenia bicyclis and their hepatoprotective effect against oxidative stress induced by tert-butyl hyperoxide.  

PubMed

Eisenia bicyclis (Kjellman) Setchell is a common brown alga that inhabits the middle Pacific coast around Korea and Japan. In this study, the ethanol extract and its serial solvent fractions were prepared from fresh E. bicyclis, and their hepatoprotective effects were investigated against hepatotoxicity in tert-butyl hyperoxide(t-BHP)-injured HepG2 cells. When these samples were used at a dose of 10-40 ?g/mL?¹, they significantly protected the t-BHP-induced cell death in HepG2 cells. Among fractions, ethyl acetate fraction (EF) and n-butanol extract (BF) exhibited potent hepatoprotective activities (62.60% for EF and 64.86% for BF) in t-BHP-injured HepG2 cells at a concentration of 10 ?g/mL?¹. To find the potential factors for this activity, the samples were characterized on total phenolics, chlorophylls, carotenoids, and radical scavenging activity. Among them, EF showed the highest content of total phenolics and the strongest antioxidant activity both in on- and offline assays. Five phlorotannin compounds, oligomers of phloroglucinol, were isolated chromatographically from this fraction and structurally identified by (1)H-NMR and liquid chromatography-electrospray ionization-mass spectrometry analyses as eckol(1), 6,6'-bieckol(2), 8,8'-bieckol(3), dieckol(4), and phlorofucofuroeckol A(5). Compound 5 among five purified compounds showed the strongest protective activity (45.54%) at a concentration of 10 ?M. At the high dose (40 ?M), the protective activities of three compounds (compound 2, 4, and 5) were higher than that of quercetin treated with 10 ?M concentration. Therefore, we can speculate that they can be developed as potential candidates for natural hepatoprotective agents. PMID:21892616

Kim, Sang Min; Kang, Kyungsu; Jeon, Je-Seung; Jho, Eun Hye; Kim, Chul Young; Nho, Chu Won; Um, Byung-Hun

2011-11-01

247

Evaluation of the effects of alpha-phenyl-N-tert-butyl nitrone pretreatment on the neurobehavioral effects of methamphetamine.  

PubMed

A relationship between formation of reactive oxygen species (ROS) and energy depletion has been proposed to play an important role in mediating methamphetamine (METH)-induced neurotoxicity. To evaluate this relationship, we examined the effect of the spin-trap agent, alpha-phenyl-N-tert-butyl nitrone (PBN) on hyperthermia and self-injurious behavior (SIB) and striatal dopamine (DA) depletion produced by METH (4 injections of 4 mg/kg, 2 hr intervals, s.c.) in BALB/c mice. Repeated administration of METH induced hyperthermia, incidence of SIB and striatal DA depletion (84% after 3 days). Pretreatment with PBN (4 injections of 60 or 120 mg/kg, i.p.) reduced METH-induced hyperthermia, but did not significantly attenuate METH-induced SIB or the striatal DA depletion. On the other hand, pretreatment with high doses of PBN (4 injections of 180 or 240 mg/kg, i.p.) protected against METH-induced hyperthermia and SIB, and PBN (180 mg/kg) also completely protected against the acute striatal DA depletion 60 min after the last injection of the drug. However, the long-lasting striatal DA depletion was only attenuated by 52 or 56%, respectively. These results indicate that METH-induced hyperthermia contributes to, but is not solely responsible for METH-induced neurotoxicity, and supports a role for formation of ROS and other mechanisms in the generation of METH-induced striatal dopaminergic neurotoxicity. In addition, the difference in the efficacy of PBN to protect against the acute or long-lasting striatal DA depletion induced by METH may indicate that both ROS formation and other mechanisms are required for METH-induced neurotoxicity to develop. PMID:10983851

Kita, T; Matsunari, Y; Saraya, T; Shimada, K; O'Hara, K; Kubo, K; Wagner, G C; Nakashima, T

2000-08-18

248

Equilibrium constants for the liquid-phase synthesis of isopropyl tert-butyl ether from 2-propanol and isobutene  

SciTech Connect

Equilibrium constants for the liquid-phase addition of 2-propanol to isobutene to give isopropyl tert-butyl ether (IPTBE) were determined experimentally in the temperature range 303--353 K and at 1.6 MPa. To reach etherification equilibrium, the macroporous sulfonic resin Bayer K-2631 was used as the catalyst. The UNIFAC estimates of activity coefficients were used to describe the liquid-phase nonideality. The thermodynamic equilibrium constants and the enthalpy, free energy, and entropy changes of the reaction were given as a function of temperature. At 298.15 K, the standard molar reaction enthalpy {Delta}{sub r}H{degree}{sub m}(298.15 K) is {minus}(22.9 {+-} 1.3) kJ/mol, in agreement with literature data, and the standard molar reaction entropy {Delta}{sub r}S{degree}{sub m}(298.15 K) and free energy {Delta}{sub r}G{degree}{sub m}(298.15 K) are {minus}(60.3 {+-} 0.5) J/mol{times}K and {minus}(4.9 {+-} 1.4) kJ/mol, respectively. Finally, at 298.15 K the standard molar enthalpy of formation {Delta}{sub f}H{degree}{sub m}(l, 298.15 K) and the standard molar entropy of IPTBE S{degree}{sub m}(l, 298.15 K) were estimated to be {minus}(378.5 {+-} 2.7) kJ/mol and 337.6 {+-} 1.5 J/(mol{times}K), respectively.

Calderon, A.; Tejero, J.; Izquierdo, J.F.; Iborra, M.; Cunill, F. [Univ. of Barcelona (Spain) Chemical Engineering Dept.] [Univ. of Barcelona (Spain) Chemical Engineering Dept.

1997-03-01

249

FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular conformational analysis of 2,5-di-tert-butyl-hydroquinone  

Microsoft Academic Search

The purpose of finding conformer among six different possible conformers of 2,5-di-tert-butyl-hydroquinone (DTBHQ), its equilibrium geometry and harmonic wavenumbers were calculated by the B3LYP\\/6-31G(d,p) method. The infrared and Raman spectra of DTBHQ were recorded in the region 400–4000cm?1 and 50–3500cm?1, respectively. In addition, the IR spectra in CCl4 at various concentrations of DTBHQ are also recorded. The computed vibrational wavenumbers

N. Subramanian; N. Sundaraganesan; Ö. Dereli; E. Türkkan

2011-01-01

250

Carbonylmetal complexes (M?Cr, Mo, W) derived from Nbis(diisopropylamino)phosphinyl- N?-tert-butyl sulfur diimide. Novel five-membered metallacycles  

Microsoft Academic Search

N-bis(diisopropylamino)phosphinyl-N?-tert-butyl sulfur diimide (1) reacts with THF-stabilized complex fragments [M(CO)5] in THF solution to give the pentacarbonylmetal adducts 2a (M?Cr), 2b (M?Mo) and 2c (M?W) in which the metal is linked to phosphorus. These complexes are fluxional at room temperature with respect to fast E\\/Z?Z\\/E isomerization and adopt the Z\\/E configuration both at low temperature in solution and in the

Max Herberhold; Christian Köhler; Wolfgang Milius; Bernd Wrackmeyer

1995-01-01

251

Bis({tris[2-(3,5-di-tert-butyl-2-oxido-benzylideneamino)ethyl]amine}cerium(III)) diethyl ether solvate  

PubMed Central

The title compound, 2[Ce(C51H75N4O3)]·C4H10O, was obtained in high yield (92%) by reduction of (TRENDSAL)CeIVCl [TRENDSAL is N,N?,N??-tris­(3,5-di-tert-butyl­salicyl­ide­natoamino)­triethyl­amine] with potassium in THF. The bulky tripodal TRENDSAL ligand effectively encapsulates the central CeIII cation with a Ce—N(imine) distance of 2.860?(2)?Å and an average C—N(amine) distance of 2.619?Å within a distorted monocapped octahedral coordination.

Drose, Peter; Hrib, Cristian G.; Edelmann, Frank T.

2010-01-01

252

Synthesis of hyperbranched polycarbonate by novel polymerization of di-tert-butyl tricarbonate with 1,1,1-tris(4-hydroxyphenyl)ethane  

Microsoft Academic Search

Hyperbranched polycarbonates (HBPCs) with Mn=2.1–7.1 × 103 were synthesized by A2+B3 polymerization using di-tert-butyl tricarbonate as the A2 monomer and 1,1,1-tris(4-hydroxyphenyl)ethane as the B3 monomer. A2+B3 polymerization with different feed ratios was achieved, controlling the degree of branching (DB) and the ratio of terminal functional groups. The DB of the HBPCs is 0.5–0.7. The Boc-terminated PC was prepared by either

Makoto Miyasaka; Taichi Takazoe; Hiroto Kudo; Tadatomi Nishikubo

2010-01-01

253

A scalable synthesis of the (S)-4-(tert-butyl)-2-(pyridin-2-yl)-4,5-dihydrooxazole ((S)-t-BuPyOx) ligand  

PubMed Central

Summary An efficient method for the synthesis of the (S)-4-(tert-butyl)-2-(pyridin-2-yl)-4,5-dihydrooxazole ((S)-t-BuPyOx) ligand has been developed. Inconsistent yields and tedious purification in known routes to (S)-t-BuPyOx suggested the need for an efficient, dependable, and scalable synthetic route. Furthermore, a route suitable for the synthesis of PyOx derivatives is desirable. Herein, we describe the development of a three-step route from inexpensive and commercially available picolinic acid. This short procedure is amenable to multi-gram scale synthesis and provides the target ligand in 64% overall yield.

Shimizu, Hideki; Holder, Jeffrey C

2013-01-01

254

Liquid-phase synthesis of isopropyl tert-butyl ether by addition of 2-propanol to isobutene on the oversulfonated ion-exchange resin Amberlyst-35  

Microsoft Academic Search

The selectivity and kinetics of the liquid-phase addition of 2-propanol to isobutene to give isopropyl tert-butyl ether (IPTBE) was investigated in a batch reactor over the commercial oversulfonated ion-exchange Amberlyst-35 resin in the temperature range 60–90°C and 1.6MPa for 2-propanol\\/isobutene initial ratios ranging from 0.5 to 3.0. The effect of the initial 2-propanol\\/isobutene molar ratio and temperature on isobutene conversion

Marc Pera-Titus; Marta Bausach; Javier Tejero; Montserrat Iborra; Carles Fité; Fidel Cunill; J. Felipe Izquierdo

2007-01-01

255

Volumetric Properties of the Mixture tert-Butyl ethyl ether C6H14O + C7H8 Toluene (VMSD1212, LB3145_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 + C7H8 Toluene (VMSD1212, LB3145_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.

256

Volumetric Properties of the Mixture tert-Butyl ethyl ether C6H14O + C7H8 Toluene (VMSD1111, LB3141_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 + C7H8 Toluene (VMSD1111, LB3141_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.

257

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

258

Cometabolic biodegradation of methyl t -butyl ether by Pseudomonas aeruginosa grown on pentane  

Microsoft Academic Search

A bacterial strain identified as Pseudomonas aeruginosa was isolated from a soil consortium able to mineralize pentane. P. aeruginosa could metabolize methyl t-butyl ether (MTBE) in the presence of pentane as the sole carbon and energy source. The carbon balance for this strain, grown\\u000a on pentane, was established in order to determine the fate of pentane and the growth yield

P. M. Garnier; R. Auria; C. Augur; S. Revah

1999-01-01

259

Biodegradation of methyl t-butyl ether by pure bacterial cultures  

Microsoft Academic Search

Three pure bacterial cultures degrading methyl t-butyl ether (MTBE) were isolated from activated sludge and fruit of the Gingko tree. They have been classified as belonging\\u000a to the genuses Methylobacterium, Rhodococcus, and Arthrobacter. These cultures degraded 60?ppm MTBE in 1–2 weeks of incubation at 23–25?°C. The growth of the isolates on MTBE as sole carbon\\u000a source is very slow compared

K. Mo; C. O. Lora; A. E. Wanken; M. Javanmardian; X. Yang; C. F. Kulpa

1997-01-01

260

Biochemical effects of methyl tertiary -butyl ether in extended vapour exposure of rats  

Microsoft Academic Search

Male Wistar rats exposed to 50, 100 or 300 ppm methyl tertiary-butyl ether vapour for 2–15 weeks, 6 h daily, 5 days a week, showed a dose-dependent blood ether concentration after 2 weeks' exposure. Blood concentrations of teriary-butanol, were also dose dependent indicating metabolic breakdown of the ether in vivo. The blood ether concentrations decreased after 6 weeks of exposure

H. Savolainen; Pirkko Pffiffli; Eivor Elovaara

1985-01-01

261

Protective Effects of Rooibos (Aspalathus linearis) and/or Red Palm Oil (Elaeis guineensis) Supplementation on tert-Butyl Hydroperoxide-Induced Oxidative Hepatotoxicity in Wistar Rats  

PubMed Central

The possible protective effects of an aqueous rooibos extract (Aspalathus linearis), red palm oil (RPO) (Elaeis guineensis), or their combination on tert-butyl-hydroperoxide-(t-BHP-)induced oxidative hepatotoxicity in Wistar rats were investigated. tert-butyl hydroperoxide caused a significant (P < 0.05) elevation in conjugated dienes (CD) and malondialdehyde (MDA) levels, significantly (P < 0.05) decreased reduced glutathione (GSH) and GSH?:?GSSG ratio, and induced varying changes in activities of catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase in the blood and liver. This apparent oxidative injury was associated with histopathological changes in liver architecture and elevated levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH). Supplementation with rooibos, RPO, or their combination significantly (P < 0.05) decreased CD and MDA levels in the liver and reduced serum level of ALT, AST, and LDH. Likewise, changes observed in the activities of antioxidant enzymes and impairment in redox status in the erythrocytes and liver were reversed. The observed protective effects when rooibos and RPO were supplemented concomitantly were neither additive nor synergistic. Our results suggested that rooibos and RPO, either supplemented alone or combined, are capable of alleviating t-BHP-induced oxidative hepatotoxicity, and the mechanism of this protection may involve inhibition of lipid peroxidation and modulation of antioxidants enzymes and glutathione status.

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

2013-01-01

262

5,11,17,23,29-Penta-tert-butyl-31,32,33,34,35-penta-propoxycalix[5]arene dichloro-methane hemisolvate  

PubMed Central

The title compound, tert-butyl­propoxycalix[5]arene, C70H100O5·0.5CH2Cl2, crystallizes as a solvate with two mol­ecules of calix[5]arene in 1,2-alternate conformations and one mol­ecule of dichloro­methane in the asymmetric unit. One tert-butyl group in one of the mol­ecules and two in the other are disordered over two positions with occupancy factors fixed at 0.5917:0.4083, 0.5901:0.4099 and 0.8535:0.1465, respectively, in the final refinement. The C atoms of a prop­oxy group in each of the mol­ecules are also disordered over two positions with occupancies of 0.7372:0.2628 and 0.5027:0.4973. The mol­ecules form intra­molecular hydrogen bonds between prop­oxy O atoms and an adjacent CH2 group in a neighbouring prop­oxy chain. In the crystal, inter­molecular C—H?O and C—H?Cl inter­actions occur involving the dichloro­methane mol­ecule.

Pojarova, Michaela; Dusek, Michal; Budka, Jan; Cisarova, Ivana; Makrlik, Emanuel

2011-01-01

263

Dinuclear (d³-d³) diolate complexes of molybdenum and tungsten. 2. Derivatives of 2,2â²-methylenebis(6-tert-butyl-4-methylphenoxide). Direct observation of the conversion of bridged to chelate isomers (M = Mo) and reversible carbon-hydrogen bond oxidative addition (M = W)  

Microsoft Academic Search

Hydrocarbon solutions of Moâ(NMeâ)â and 2,2â²-methylenebis(6-tert-butyl-4-methylphenol)(â¥2 equiv), HO(2,2â²-methylenebis(6-tert-butyl-4-methylphenol)) CHâ(2,2â²-methylenebis(6-tert-butyl-4-methylphenol)) OH, yield Moâ(NMeâ)â(O(2,2â²-methylenebis(6-tert-butyl-4-methylphenol))CHâ(2,2â²-methylenebis(6-tert-butyl-4-methylphenol))O)â, I, which exists in bridged Ib and chelated Ic isomers. These are formed under kinetic control, and recrystallization allows the separation of Ib (orange cubes) from Ic (yellow cubes) both of which have been crystallographically characterized. In each there is an ethane-like OâNMo{triple_bond}MoOâN core with Mo-Mo = 2.2

M. H. Chisholm; Jui-Hsien Huang; J. C. Huffman; I. P. Parkin

1997-01-01

264

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

Code of Federal Regulations, 2010 CFR

...methyl methacrylate, and substituted silane. 721.6920 Section 721.6920 ...methyl methacrylate, and substituted silane. (a) Chemical substance and significant...methyl methacrylate, and substituted silane (PMN P-91-272) is subject to...

2010-07-01

265

C(sp{sup 2}){single_bond}C(sp{sup 3}) rotational barriers in simple amides: H{sub 2}N{single_bond}C({double_bond}O){single_bond}R (R = methyl, ethyl, i-propyl, tert-butyl)  

SciTech Connect

Potential energy surfaces for rotation about the C(sp{sup 2}){single_bond}C(sp{sup 3}) bond are reported for acetamide, propanamide, 2-methylpropanamide, and 2,2-dimethylpropanamide at different levels of ab initio electronic structure theory with correlation effects included. In all cases, fully optimized geometries of rotational minima are consistent with gas phase electron diffraction data and crystal structure data. The experimental barrier height for methyl rotation in acetamide is reproduced to within 0.1 kcal/mol. This study yields a set of improved criteria for the construction of rotational potentials for the C{sub a}{single_bond}C bond which are used to obtain improved MM3 torsional parameters. In addition, the authors find that the use of higher levels of theory leads to significantly different results than those obtained in prior Hartree-Fock studies on acetamide and 2-methylpropanamide.

Sandrone, G.; Dixon, D.A.; Hay, B.P. [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Science Lab.] [Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Science Lab.

1999-02-18

266

Solid phase microextraction procedure for the determination of alkylphenols in water by on-fiber derivatization with N-tert-butyl-dimethylsilyl-N-methyltrifluoroacetamide.  

PubMed

The solid phase microextraction (SPME) technique with on-fiber derivatization was evaluated for the analysis of alkylphenols (APs), including 4-tert-octylphenol (4-t-OP), technical nonylphenol isomers (t-NPs) and 4-nonylphenol (4-NP), in water. The 85 microm polyacrylate (PA) fiber was used and a two-step sample preparation procedure was established. In the first step, water sample of 2 mL was placed in a 4 mL PTFE-capped glass vial. Headspace extraction of APs in water was then performed under 65 degrees C for 30 min with 800 rpm magnetic stirring and the addition of 5% of sodium chloride. In the second step, the SPME fiber was placed in another 4 mL vial, which contained 100 microL of N-tert-butyl-dimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) with 1% tert-butyl-dimethylchlorosilane (TBDMCS). Headspace extraction of MTBSTFA and on-fiber derivatization with APs were performed at 45 degrees C for 10 min. Gas chromatography/mass spectrometry (GC/MS) was used for the analysis of derivatives formed on-fiber. The adsorption-time profiles were also examined. The precision, accuracy and method detection limits (MDLs) for the analysis of all the APs were evaluated with spiked water samples, including detergent water, chlorinated tap water, and lake water. The relative standard deviations were all less than 10% and the accuracies were 100+/-15%. With 2 mL of water sample, MDLs were in the range of 1.58-3.85 ng L(-1). Compared with other techniques, the study described here provided a simple, fast and reliable method for the analysis of APs in water. PMID:18706331

Pan, Yi-Ping; Tsai, Shih-Wei

2008-08-29

267

Synthesis of Isopropyl and Tertbutyl Pyridyl Ketones by Alkylation of Acetylpyridines with Methyl Iodide Using Phase Transfer Catalysis  

Microsoft Academic Search

Isomeric acetylpyridines undergo regiospecific alkylation with methyl iodide under solid\\/liquid phase transfer conditions (aromatic solvent\\/KOH\\/18-crown-6) to give the corresponding isopropyl and\\/or tert-butyl pyridyl ketones, depending on reaction conditions.

K. Rubina; Yu. Goldberg; M. Shymanska

1989-01-01

268

tert-Butyl peroxybenzoate (TBPB)-mediated 2-isocyanobiaryl insertion with 1,4-dioxane: efficient synthesis of 6-alkyl phenanthridines via C(sp(3))-H/C(sp(2))-H bond functionalization.  

PubMed

An efficient method for the construction of 6-alkyl phenanthridines by tert-butyl peroxybenzoate (TBPB)-mediated 2-isocyanobiaryl insertion with 1,4-dioxane was established. Two new C-C bonds were formed in this reaction via a sequential C(sp(3))-H/C(sp(2))-H bond functionalization under metal-free conditions. PMID:24699898

Cao, Jia-Jia; Zhu, Tong-Hao; Wang, Shun-Yi; Gu, Zheng-Yang; Wang, Xiang; Ji, Shun-Jun

2014-06-21

269

Di-tert-butyl 2,6,11-trioxo-2,3-dihydro-1H-anthra[1,2-d]imidazole-1,3-diacetate  

PubMed Central

The fused-ring system of the title compound, C27H28N2O7, which comprises one five- and three six-membered rings, is approximately planar (r.m.s. deviation = 0.133?Å), the system being buckled along the axis passing through the O atoms of the anthraquinone portion of the mol­ecule. Within the anthraquinone portion, the two benzene rings are aligned at 7.3?(2)°. In the crystal, one of the tert-butyl groups is disordered over two sets of sites in a 1:1 ratio. Weak inter­molecular C—H?O hydrogen bonding is present in the crystal structure.

Afrakssou, Zahra; Rodi, Yousef Kandri; Saffon, Natalie; Essassi, El Mokhtar; Ng, Seik Weng

2011-01-01

270

(2E)-4-tert-Butyl-2-(4-meth-oxy-benzyl-idene)-3,4-dihydro-naphthalen-1(2H)-one  

PubMed Central

In the title compound C22H24O2, the exocyclic C=C double bond is in an E configuration and the tert-butyl group is in an axial position on the cyclo­hexa­none ring. The cyclo­hexa­none ring in the dihydro­naphthalene fused-ring system adopts a half-chair conformation in both independent two mol­ecules in the asymetric unit. The benzene ring system is oriented angles of 43.97?(12) and 39.24?(12)° with respect to the naphthyl ring system in the two independent mol­ecules. In the crystal, mol­ecules are linked via C—H?O hydrogen bonds and C—H?? inter­actions.

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

2011-01-01

271

Direct observation of the intermolecular triplet-triplet energy transfer from UV-A absorber 4- tert -butyl-4?-methoxydibenzoylmethane to UV-B absorber octyl methoxycinnamate  

NASA Astrophysics Data System (ADS)

Triplet energy transfer (TET) is an important photostabilization process for organic UV absorbers, such as 4- tert-butyl-4'-methoxydibenzoylmethane (BM-DBM) and octyl methoxycinnamate (OMC). To characterize interactions between UV absorbers as TET the interactions between BM-DBM and OMC have been studied through measurements of EPR and time-resolved phosphorescence spectra. The EPR Bmin signals and the phosphorescence of OMC were observed through the selective excitation of BM-DBM at 365 nm in EtOH at 77 K. These results indicate that the intermolecular TET occurs from BM-DBM to OMC. This is the first report of the experimental evidence of the TET between the organic UV absorbers.

Kikuchi, Azusa; Yagi, Mikio

2011-09-01

272

Isobaric vapor-liquid equilibria in the system methyl propanoate + n-butyl alcohol  

SciTech Connect

Isobaric vapor-liquid equilibria were determined at 74.66, 101.32, and 127.99 kPa for binary mixtures containing methyl propanoate + n-butyl alcohol by using a dynamic still with vapor and liquid circulation. No azeotrope was detected. The data were found to be thermodynamically consistent according to the point to point test. Application of the group-contribution models ASOG, UNIFAC, and modified UNIFAC to the activity coefficients at the three pressures studied gives average errors of less than 10%, 11%, and 3%, respectively.

Susial, P.; Ortega, J. (Univ. de Las Palmas de Gran Canaria, Canary Islands (Spain). Lab. de Termodinamica y Fisicoquimica)

1993-10-01

273

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  

NASA Astrophysics Data System (ADS)

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.

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

2006-10-01

274

LASERS IN MEDICINE: Quantum efficiency of the laser-excited singlet-oxygen-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine  

NASA Astrophysics Data System (ADS)

An investigation was made of the ratios of the intensity Idf of the singlet-oxygen(1O2)-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine (ZnTBPc), with the maximum at ? = 685 nm, to the intensity I1270 of the photosensitised phosphorescence of 1O2 with the maximum at ? = 1270 nm in deuterated benzene when excited with ? = 337 nm nitrogen-laser pulses. Depending on the energy density of the laser radiation (0.25 — 0.7 mJ cm-2) and on the concentration of ZnTBPc (0.06 — 3.4 ?M), the ratio of the zero-time intensities of the delayed fluorescence of ZnTBPc and of the singlet-oxygen phosphorescence Idf0/I12700 varied from 0.01 to 0.2 in air-saturated solutions of ZnTBPc. The intensity Idf0 decreased fivefold as a result of saturation with oxygen of air-saturated solutions. The quantum efficiency of the delayed fluorescence was represented by the coefficient ? =(Idf0/I12700)kr/(?f[1O2]0[ZnTBPc]), where [1O2]0 is the zero-time concentration of 1O2 after a laser shot; kr is the rate constant of radiative deactivation of 1O2 in the investigated solvent; ?f is the quantum yield of the ZnTBPc fluorescence. It was established that in the case of air-saturated solutions of ZnTBPc this coefficient was approximately 200 times less than for metal-free tetra(4-tert-butyl)phthalocyanine and its absolute value was ~2 × 1011 M-2 s-1.

Bashtanov, M. E.; Drozdova, N. N.; Krasnovskii, A. A.

1999-12-01

275

Disposition and metabolism of a novel antineoplastic agent, 4-tert-butyl-[3-(2-chloroethyl)ureido]benzene, in mice.  

PubMed

1-Aryl-3-(2-chloroethyl)ureas are new agents that have shown promising cytotoxic and antineoplastic activities. In this work, we studied the disposition and metabolism of one of these molecules, 4-tert-butyl-[3-(2-chloroethyl)ureido]benzene (tBCEU). tBCEU was labeled with 14C and 13C in the urea function and in the chloroethyl moiety. After ip administration of the molecule labeled in the urea function, radioactivity was widely distributed in the whole organism, including the brain. HPLC analysis of plasma showed that tBCEU was extensively metabolized, with <20% being found in the plasma as unchanged tBCEU 1 hr after administration. One main metabolite was identified by NMR and MS analysis as N-[4-(2-hydroxy-1, 1-dimethylethyl)phenyl]urea, widely conjugated to glucuronic acid. The same metabolite was found in the urine. After administration of tBCEU labeled in the chloroethyl moiety, the same tissue affinities were observed, but the decrease of total radioactivity in blood and tissues was slower than that observed for the molecule labeled in the urea function. HPLC analysis of urine showed the presence of two main metabolites, identified by MS as thiodiacetic acid and its sulfoxide. From these results, we can deduce that the metabolic pathway of tBCEU involves N-dealkylation of the urea portion of the molecule and hydroxylation of the tert-butyl group. The strong cytochrome P450 reactivity of the carbon adjacent to the urea portion of tBCEU is probably related to particular sensitivity to oxidation at this position, based on the chemical structure of tBCEU. These results can explain the fact that the cytotoxic effect of tBCEU is not due to DNA alkylation, in contrast to that of its parent molecule, chloroethylnitrosourea. PMID:9456301

Maurizis, J C; Rapp, M; Azim, E M; Gaudreault, R C; Veyre, A; Madelmont, J C

1998-02-01

276

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...

277

tert-Butyl 2-hy-droxy-3-(4-methyl-benzene-sulfonamido)-butano-ate  

PubMed Central

In the crystal of the title compound, C15H23NO5S, mol­ecules are linked through N—H?O and O—H?O hydrogen-bond inter­actions, resulting in centrosymmetric dimers in which the N—H?O inter­actions generate R 2 2(12) rings and the O—H?O inter­actions generate R 2 2(14) rings. Weak inter­molecular C—H?O inter­actions are also observed.

Fadlalla, Mohamed I.; Friedrich, Holger B.; Maguire, Glenn E. M.; Omondi, Bernard

2011-01-01

278

Structural characterization of hydroxyl terminated polybutadiene bound 2, 2-thiobis (4-methyl-6-tert-butylphenol) and its thermo-oxidative aging resistance for natural rubber vulcanizates  

Microsoft Academic Search

A novel polymeric antioxidant, hydroxyl terminated polybutadiene bound 2, 2-thiobis (4-methyl-6-tert-butylphenol) (HTPB-IPDI-TPH), was prepared by binding 2, 2-thiobis (4-methyl-6-tert-butylphenol) (TPH) onto hydroxyl terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI). Fourier-transform infrared spectroscopy (FTIR), C nuclear magnetic resonance spectroscopy (C NMR) and gel permeation chromatography (GPC) were used to characterize the structure of HTPB-IPDI-TPH. The thermal stability of HTPB-IPDI-TPH was studied

YONGHONG WANG; XINGRONG ZENG; HONGQIANG LI; JIANHUA GUO

2012-01-01

279

Effect of p-tert-butyl group substitution on the quantum tunneling rate in quadruple proton rearrangement of calix[4]arene.  

PubMed

Glass-transition behaviors concerning the quadruple proton/deuteron rearrangements in the crystalline p-tert-butylcalix[4]arene-toluene (BC4A·T) host-guest compound were studied by adiabatic calorimetry. The glass-transition temperatures (Tg's) of the hydrated BC4A·T-h and deuterated BC4A·T-d were found to be around 90 and 181 K, respectively. The difference of 90 K is too big to be recognized as the ordinary isotope effect, which is about 5 K in classical thermal activation processes. The temperature interval over which the enthalpy relaxation effect was observed was beyond 50 K, being too wide, in BC4A·T-h, while it was 20-30 K in BC4A·T-d; the latter is the one ordinarily observed in the classical processes. The associated equilibration rate in BC4A·T-h was evaluated from the enthalpy relaxation curve observed at 62 K to evidence the non-Arrhenius nature of the temperature dependence. The relaxation effect was detected even at 20 K. These are quite the same behaviors as observed in calix[4]arene, and the quantum tunneling rate in the quadruple proton rearrangement was concluded to be only a little affected by the substitution of the tert-butyl group at the para-position of each phenol moiety. PMID:24144320

Ueda, Kouhei; Oguni, Masaharu

2013-11-14

280

Facile synthesis and physical and spectral characterization of 2,6-di-tert-butyl-4-nitrophenol (DBNP): A potentially powerful uncoupler of oxidative phosphorylation  

SciTech Connect

The compound 2,6-di-tert-butyl-4-nitrophenol (DBNP), a potentially powerful uncoupler of ATP-generating oxidative phosphorylation, has been physically and spectroscopically characterized using X-ray crystallography, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), GC-MS spectrometry, Fourier-transformed IR (FTIR) spectrophotometry, UV-Vis spectrophotometry, and FT [sup 1]H- and [sup 13]C-NMR spectroscopy. However, DBNP is not commercially available; therefore, it had to be synthesized in the laboratory prior to toxicity studies. The DBNP was prepared from 2,6-di-tert-butylphenol (DBP) precursor in hexane through an electrophilic aromatic substitution process using NO[sub 2]. A collective yield of 75% was obtained by using two empirically determined end points that prevented the coprecipitation of reaction by-products and resulted in the formation of DBNP in high purity. Excessive amounts of NO[sub 2] in reaction mixtures resulted in the decomposition of preformed DBNP. With a pK[sub a] value of 6.8 and a higher degree of lipophilicity, DBNP may prove to be a stronger uncoupler of oxidative phosphorylation than 2,4-dinitrophenol due to the expected enhancement of passive-diffusion kinetics across biological membranes at the physiological pH of 7.4. The present study is intended to provide analytical toxicologists, industrial hygiene monitors, and other professionals involved in chemical health and safety with a comprehensive source of basic information on the synthesis and analytical chemistry of DBNP.

Rivera-Nevares, J.A.; Wyman, J.F.; Minden, D.L. von; Lacy, N.; Macys, D.A. (Naval Medical Research Inst. Detachment, Wright-Patterson AFB, OH (United States)); Chabinyc, M.L.; Fratini, A.V. (Univ. of Dayton, OH (United States). Dept. of Chemistry)

1995-02-01

281

Participation of covalent modification of Keap1 in the activation of Nrf2 by tert-butylbenzoquinone, an electrophilic metabolite of butylated hydroxyanisole  

SciTech Connect

Butylated hydroxyanisole (BHA) is an antioxidant and class-2B carcinogen. It is biotransformed to tert-butylhydroquinone (TBHQ), which readily auto-oxidizes to the electrophilic metabolite tert-butylbenzoquinone (TBQ). BHA and TBHQ activate Nrf2, a transcription factor that is negatively regulated by Keap1 and plays a role in the initial response to chemicals causing oxidative or electrophilic stress, although, the exact mechanism of Nrf2 activation remains unclear. Here, we examined the role of TBQ in Nrf2 activation. Exposure of RAW264.7 cells to TBQ activated Nrf2 and up-regulated its downstream proteins; under these conditions, TBQ produced cellular reactive oxygen species (ROS). However, while pretreatment with catalase conjugated with polyethylene glycol (PEG-CAT) did not affect the TBQ-induced activation of Nrf2, the ROS generation caused by TBQ was entirely abolished by PEG-CAT, suggesting that ROS is not the dominant factor for TBQ-dependent Nrf2 activation. A click chemistry technique indicated that TBQ chemically modifies Keap1. Furthermore, ultrahigh performance liquid chromatography-tandem mass spectrometry analysis with purified Keap1 revealed that TBQ covalently binds to Keap1 through Cys23, Cys151, Cys226, and Cys368. These results suggest that TBQ derived from BHA activates Nrf2 through electrophilic modification of Keap1 rather than ROS formation. - Research Highlights: > tert-Butylbenzoquinone (TBQ) activates Nrf2 in RAW264.7 cells. > ROS is not essential factor for Nrf2 activation caused by TBQ. > TBQ covalently binds to Keap1 through reactive thiols, resulting in Nrf2 activation.

Abiko, Yumi; Miura, Takashi [Doctoral Programs in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan); Phuc, Bui Hoang [Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan); Shinkai, Yasuhiro [Doctoral Programs in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan); Kumagai, Yoshito, E-mail: yk-em-tu@md.tsukuba.ac.jp [Doctoral Programs in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan); Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575 (Japan)

2011-08-15

282

Isothermal vapor–liquid equilibria of the ternary system formed by ethanol, tert-amyl methyl ether and toluene  

Microsoft Academic Search

Vapor–liquid equilibrium (VLE) data are presented for the ternary system ethanol–tert-amyl methyl ether (TAME)–toluene at 333.15 K. The experimental results were measured by using a Boublik vapor–liquid recirculation still. The results are compared with values predicted from the PRSV equation of state with the modified Huron–Vidal first order (MHV1) and Wong–Sandler (WS) mixing rules. Good agreement is obtained.

Tatsuhiko Ohta; Masanari Ishio; Toshiro Yamada

1998-01-01

283

Interaction of Keap1 modified by 2-tert-butyl-1,4-benzoquinone with GSH: evidence for S-transarylation.  

PubMed

2-tert-Butyl-1,4-benzoquinone (TBQ), an electrophilic metabolite of butylated hydroxyanisole (BHA), causes activation of Nrf2 together with S-arylation of its negative regulator Keap1 in RAW264.7 cells. In a previous study, we found that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) covalently modified with 1,2-naphthoquinone (1,2-NQ) undergoes S-transarylation by GSH, resulting in a decline of the GAPDH-1,2-NQ adduct and formation of a 1,2-NQ-SG adduct ( Miura , T. et al. ( 2011 ) Chem. Res. Toxicol. 24 , 1836 -1844 ). In the present study, we explored the possibility of GSH-dependent S-transarylation of the Keap1-TBQ adduct. Pretreatment with l-buthionine-(S,R)-sulfoximine and N-acetylcysteine prior to TBQ exposure of HepG2 cells suggested that the Keap1-TBQ adduct appears to undergo GSH-mediated S-transarylation because the resulting alterations in the intracellular GSH concentration affected Nrf2 activation caused by TBQ. In support of this hypothesis, a cell-free study demonstrated that incubation of the Keap1-TBQ adduct with GSH results in the removal of TBQ from Keap1 with the production of mono- and di-GSH adducts of TB(H)Q. These results suggest that GSH plays a role in reversible covalent modification of TBQ derived from BHA to Keap1 through the formation of a C-S bond. PMID:23718696

Abiko, Yumi; Kumagai, Yoshito

2013-07-15

284

Tris(tetra-butyl-ammonium) hexa-kis-(tert-butane-thiol-ato-?S)hepta-?3-chlorido-?3-sulfido-hexa-molybdate dihydrate  

PubMed Central

The octa­hedral cluster core of the anion in the structure of the title compound, (C16H36N)3[Mo6(C4H9S)6(?3-Cl)7(?3-S)]·2H2O, has -3 site symmetry. Two ?3-Cl atoms fully occupy positions in the cluster core, while the remaining six positions are statistically occupied by Cl and S atoms in a 1:5 ratio. The fully occupied Cl-atom positions are located on sites with 3 symmetry, and the N atom of tetra­butyl­ammonium cation is located on a site with 2 symmetry. The structure contains also two disordered solvent water mol­ecules, one of which is located on a threefold rotation axis and the other in a general position, both with an occupancy of 0.25. The water mol­ecules are localized in cavities formed by the tetra­butyl­ammonium cations and the tert-butane­thiol­ate groups. The metal clusters are stacked in a cubic close packing arrangement along [001].

Petrov, Pavel A.; Naumov, Dmitry Yu.; Konchenko, Sergey N.

2012-01-01

285

Products of the OH radical-initiated reactions of 2-propyl nitrate, 3-methyl-2-butyl nitrate and 3-methyl-2-pentyl nitrate  

NASA Astrophysics Data System (ADS)

In the atmosphere, alkyl nitrates formed from the reactions of alkyl peroxy radicals with NO are chemically removed by photolysis and by reaction with OH radicals. Products of the gas-phase reactions of OH radicals with 2-propyl nitrate, 3-methyl-2-butyl nitrate and 3-methyl-2-pentyl nitrate at room temperature have been investigated. The products observed and quantified were: from 2-propyl nitrate, acetone (58 ± 18%); from 3-methyl-2-butyl nitrate, acetaldehyde (113 ± 39% from gas chromatographic analyses and 70 ± 25% from FT-IR analyses), acetone (55 ± 8%), and 3-methyl-2-butanone (17 ± 2%); and from 3-methyl-2-pentyl nitrate, acetaldehyde (120 ± 26% from gas chromatographic analyses and 80 ± 21% from FT-IR analyses), propanal (?1.1%), 2-butanone (33 ± 3%), 2-methylbutanal (?1.1%), and 3-methyl-2-pentanone (9 ± 1%), where the percentage molar yields are given in parentheses. Using these measured product yields together with predicted reaction schemes indicates that these products account for 58 ± 18%, 86 ± 15% and 63 ± 7% of the overall reaction pathways of the 2-propyl nitrate, 3-methyl-2-butyl nitrate and 3-methyl-2-pentyl nitrate reactions, respectively. The NO 2 present in the -ONO 2 group in these nitrates will be released in the reaction pathways leading to the observed products.

Aschmann, Sara M.; Tuazon, Ernesto C.; Arey, Janet; Atkinson, Roger

2011-03-01

286

Copolymerization of butyl vinyl ether and methyl methacrylate by combination of radical and radical promoted cationic mechanisms  

Microsoft Academic Search

Butyl vinyl ether (BVE) and methyl methacrylate (MMA) mixtures were polymerized by using free radical initiators in conjunction with a cationic initiator such as diphenyl iodonium salt. Polymerization mechanism involves free radical polymerization of MMA which is switched to cationic polymerization of BVE by addition of growing poly(MMA) radicals to BVE and subsequent oxidation of electron donating polymeric radicals to

Harald Braun; Yusuf Yagci; Oskar Nuyken

2002-01-01

287

5-methyl-3-butyl-octahydroindolizine, a novel type of pheromone attractive to Pharaoh's ants ( Monomorium pharaonis (L.)  

Microsoft Academic Search

Zusammenfassung Aus Arbeiterinnen der AmeiseMonomorium pharaonis (L.) wurde 5-Methyl-3-butyl-octahydroindolizin isoliert. Dieses Pheromon übt eine starke Lockstoffwirkung auf die Arbeiterinnen dieser Ameisenart aus. Die Struktur wurde durch Spektral-analyse und Synthese aufgeklärt. Unseres Wissens ist dies das erste Pheromon aus Insekten mit dem Indolizingerüst.

F. J. Ritter; I. E. M. Rotgans; E. Talman; P. E. J. Verwiel; F. Stein

1973-01-01

288

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...

289

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...

290

SENSITIZATION POTENTIALS OF METHYL, ETHYL, AND n-BUTYL METHACRYLATES AND MUTUAL CROSS-SENSITIVITY IN GUINEA PIGS  

Microsoft Academic Search

Guinea pigs could be strongly sensitized to methyl, ethyl, and n-butyl methacrylates in ethanol or olive oil by the topical route, or in saline by the intradermal route. For elicitation of skin reactions, topical challenge with the compounds in olive oil or intradermal challenge with saline as the solvent was necessary. Topical challenge with the methacrylates in ethanol failed to

Choong W. Chung; Albert L. Giles Jr.

1977-01-01

291

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.

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

1994-01-01

292

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.

Schuster, Judith; Schafer, Franziska; Hubler, Nora; Brandt, Anne; Rosell, Monica; Hartig, Claus; Harms, Hauke; Muller, Roland H.

2012-01-01

293

Quantum efficiency of the laser-excited singlet-oxygen-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine  

SciTech Connect

An investigation was made of the ratios of the intensity I{sub df} of the singlet-oxygen({sup 1}O{sub 2})-sensitised delayed fluorescence of the zinc complex of tetra(4-tert-butyl)phthalocyanine (ZnTBPc), with the maximum at {lambda} = 685 nm, to the intensity I{sub 1270} of the photosensitised phosphorescence of {sup 1}O{sub 2} with the maximum at {lambda} = 1270 nm in deuterated benzene when excited with {lambda} = 337 nm nitrogen-laser pulses. Depending on the energy density of the laser radiation (0.25 - 0.7 mJ cm{sup -2}) and on the concentration of ZnTBPc (0.06 - 3.4 {mu}M), the ratio of the zero-time intensities of the delayed fluorescence of ZnTBPc and of the singlet-oxygen phosphorescence I{sub df}{sup 0}/I{sub 1270}{sup 0} varied from 0.01 to 0.2 in air-saturated solutions of ZnTBPc. The intensity I{sub df}{sup 0} decreased fivefold as a result of saturation with oxygen of air-saturated solutions. The quantum efficiency of the delayed fluorescence was represented by the coefficient {alpha} =(I{sub df}{sup 0}/I{sub 1270}{sup 0})k{sub r}/({gamma}{sub f}[{sup 1}O{sub 2}]{sub 0}[ZnTBPc]), where [{sup 1}O{sub 2}]{sub 0} is the zero-time concentration of {sup 1}O{sub 2} after a laser shot; k{sub r} is the rate constant of radiative deactivation of {sup 1}O{sub 2} in the investigated solvent; {gamma}{sub f} is the quantum yield of the ZnTBPc fluorescence. It was established that in the case of air-saturated solutions of ZnTBPc this coefficient was approximately 200 times less than for metal-free tetra(4-tert-butyl)phthalocyanine and its absolute value was {approx}2 x 10{sup 11} M{sup -2} s{sup -1}. (lasers in medicine)

Bashtanov, M E; Drozdova, N N; Krasnovskii, A A [A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow (Russian Federation)

1999-12-31

294

Dinuclear and polynuclear transition metal complexes with macrocyclic ligands. 6. New dinuclear copper(ii) complexes with macrocyclic Schiff bases derived from 4- tert -butyl-2,6-diformylphenol  

Microsoft Academic Search

New dinuclear complexes containing CuII atoms in the cavity of a macrocyclic Schiff base were prepared by template condensation of 4-tert-butyl-2,6-diformylphenol with 1,3-diaminopropane in the presence of CuII trimethylacetate and chloride as well as by extra-ligand exchange. The mononuclear CuII complex with two 1,3-diaminopropane molecules can serve as an intermediate in this template synthesis. The reaction of CuII trimethylacetate with

V. V. Roznyatovsky; N. E. Borisova; M. D. Reshetova; Yu. A. Ustynyuk; G. G. Aleksandrov; I. L. Eremenko; I. I. Moiseev

2004-01-01

295

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

296

Photoactivatable 2-(4'-azidotetrafluorophenyl)-5-tert-butyl-1,3-dithiane-bis- sulfone and related compounds as candidate irreversible probes for the GABA-gated chloride channels.  

PubMed

Syntheses of 2-substituted photoactivatable derivatives of 5-tert-butyl-1,3-dithiane and their oxidized bis-sulfone derivatives are described with the aim of developing original photoaffinity probes for the GABA-gated chloride channel. Diazocyclohexadienone as well as fluorinated arylazido derivatives were chosen as photosensitive moieties. The dithiane molecules were synthesized by condensation of 2-tert-butylpropane-1,3-dithiol with the appropriate substituted benzaldehydes. The diazocyclohexadienonyl derivatives were synthesized either by diazotization of the corresponding dithiane arylamine precursors (compounds 1, 2, 17, and 18) or by diazotization of the bis-sulfone dithiane arylamine (compounds 19 and 20). The reversible binding properties of the photosensitive probes were established on bovine cortex P2 membranes by displacement of [3H]-tert-butylbicycloorthobenzoate. While the bromo-substituted diazocyclohexadienoyl dithiane derivatives (compounds 1 and 2) exhibited a Ki of about 2-4 microM 2-(4'-azidotetrafluorophenyl)-5-tert-butyl-1,3-dithiane-bis-sulfon e (compound 3) gave a Ki of 0.2 microM. On irradiation, probe 3 produced a 25% irreversible loss of TBOB binding sites in brain membranes. Moreover, this loss was fully protectable by TBOB, demonstrating the specificity of the photochemical inactivation by compound 3 for the convulsant site of the GABAA receptor. PMID:8289186

Kapfer, I; Hawkinson, J E; Casida, J E; Goeldner, M P

1994-01-01

297

Determination of endocrine disruptors in water after derivatization with N-methyl- N-( tert.-butyldimethyltrifluoroacetamide) using gas chromatography with mass spectrometric detection  

Microsoft Academic Search

The combined gas chromatographic determination of a number of hydroxyl-group containing endocrine disruptors, including 4-octylphenol, 4-nonylphenol, 2,4-dichlorophenol, pentachlorophenol, 4-tert.-butylbenzoic acid, bisphenol-A, 17?-estradiol and 17?-ethynylestradiol, was investigated. Derivatization, required for sensitive determination of these compounds, was carried out using N-methyl-N-(tert.-butyldimethyltrifluoroacetamide). A number of parameters affecting the derivatization reaction, like temperature, time, matrix, solvent, and amount of reagent were studied in detail.

Hans G. J Mol; Suryati Sunarto; Odile M Steijger

2000-01-01

298

7-(tert-Butyl-diphenyl-sil-yloxy)-2,2-dimethyl-1-benzofuran-3(2H)-one  

PubMed Central

The title compound, C26H28O3Si, is an allylic oxidation product of the tert-but­yl(2,2-dimethyl-2,3-dihydro­benzo­furan-7-yl­oxy)diphenyl­silane with N-bromo­succinimide and 2,2?-azobis-isobutyronitrile. The nine-atom bicyclic system is almost planar, with an r.m.s deviation of 0.0123?(2)?Å and a maximum deviation of 0.031?(2)?Å for the O atom. In the crystal, the mol­ecules pile up along the b axis but the strongest inter­molecular contacts are the ?–? stacking inter­actions between the benzene rings along the c axis [centroid–centroid distance = 3.655?(3)?Å].

Salas, Cristian O.; Tapia, Ricardo A.; Macias, Alejandro

2011-01-01

299

Complexation and Transport of Alkali and Alkaline Earth Metal Cations by p-tert-Butyldihomooxacalix[4]arene Tetraketone Derivatives  

Microsoft Academic Search

The binding properties of three p-tert-butyldihomooxacalix[4]arene tetraketone derivatives (tert-butyl 2b, adamantyl 2c and phenyl 2d) in the cone conformation and one derivative (methyl 2a) in a partial cone conformation, towards alkali and alkaline earth metal cations have been established by extraction studies of metal picrates from water into dichloromethane, stability constant measurements in methanol and acetonitrile, and by H NMR

Paula M. Marcos; Sandra Félix; Jose R. Ascenso; Manuel A. P. Segurado; Besma Mellah; Rym Abidi; Veronique Hubscher-Bruder; Françoise Arnaud-Neu

2006-01-01

300

N-tert-butyl hydroxylamine, a mitochondrial antioxidant, protects human retinal pigment epithelial cells from iron overload: relevance to macular degeneration  

PubMed Central

Age-related macular degeneration (AMD) is the leading cause of severe visual impairment in the elderly in developed countries. AMD patients have elevated levels of iron within the retinal pigment epithelia (RPE), which may lead to oxidative damage to mitochondria, disruption of retinal metabolism, and vision impairment or loss. As a possible model for iron-induced AMD, we investigated the effects of excess iron in cultured human fetal RPE cells on oxidant levels and mitochondrial cytochrome c oxidase (complex IV) function and tested for protection by N-tert-butyl hydroxylamine (Nt-BHA), a known mitochondrial antioxidant. RPE exposure to ferric ammonium citrate resulted in a time- and dose-dependent increase in intracellular iron, which increased oxidant production and decreased glutathione (GSH) levels and mitochondrial complex IV activity. NtBHA addition to iron-overloaded RPE cells led to a reduction of intracellular iron content, oxidative stress, and partial restoration of complex IV activity and GSH content. NtBHA might be useful in AMD due to its potential to reduce oxidative stress, mitochondrial damage, and age-related iron accumulation, which may damage normal RPE function and lead to loss of vision.

Voloboueva, Ludmila A.; Killilea, David W.; Atamna, Hani; Ames, Bruce N.

2008-01-01

301

Protective effect of 70% ethanolic extract of Lindera obtusiloba Blume on tert-butyl hydroperoxide-induced oxidative hepatotoxicity in rats.  

PubMed

Lindera obtusiloba Blume, a native plant of East Asia, has traditionally been used as a folk medicine for liver disease. We studied the in vitro antioxidant and in vivo hepatoprotective activities of a 70% ethanolic extract of L. obtusiloba (LOE) containing 62.9% quercitrin and 22.0% afzelin. LOE prevented tert-butyl hydroperoxide (t-BHP)-induced oxidative damage in HepG2 cells. Along with its high antioxidant potency in vitro, our animal study confirmed that pretreatment with LOE (500 or 2000 mg/kg) for 7 days prior to a single dose of t-BHP (i.p.: 0.5 mmol/kg) significantly lowered the serum levels of alanine and aspartate aminotransferases. In addition, glutathione levels were increased in the liver, and lipid peroxidation levels were decreased in a dose-dependent manner. The histopathological examinations of rat livers showed that LOE significantly reduced the incidence of liver lesions induced by t-BHP. Therefore, we concluded that LOE has merit as a potent candidate to protect the liver against oxidative damage. PMID:23211441

Hong, Chung-Oui; Rhee, Chae Hong; Won, Nam-Hee; Choi, Hee-Don; Lee, Kwang-Won

2013-03-01

302

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.

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

2011-01-01

303

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

304

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.

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

2014-01-01

305

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

306

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

307

Vibrational frequency analysis, FT-IR, DFT and M06-2X studies on tert-Butyl N-(thiophen-2yl)carbamate  

NASA Astrophysics Data System (ADS)

In this study, the experimental and theoretical vibrational frequencies of a newly synthesized tert-Butyl N-(thiophen-2yl)carbamate have been investigated. The experimental FT-IR (4000-400 cm-1) spectrum of the molecule in the solid phase have been recorded. The theoretical vibrational frequencies and optimized geometric parameters (bond lengths and bond angles) have been calculated by using density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee-Yang-Parr) and DFT/M06-2X (the highly parametrized, empirical exchange correlation function) quantum chemical methods with the 6-311++G(d,p) basis set by Gaussian 09W software, for the first time. The vibrational frequencies have been assigned using potential energy distribution (PED) analysis by using VEDA 4 software. The computational optimized geometric parameters and vibrational frequencies have been found to be in good agreement with the corresponding experimental data, and with related literature results. In addition, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies and the other related molecular energy values have been calculated and are depicted.

Sert, Yusuf; Singer, L. M.; Findlater, M.; Do?an, Hatice; Ç?rak, Ç.

2014-07-01

308

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

309

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

310

Synthesis and molecular structure of indium complexes based on 3,6-di-tert-butyl-o-benzoquinone. Looking for indium(I) o-semiquinolate.  

PubMed

The interaction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with indium in toluene leads to the tris-o-semiquinolate derivative (3,6-SQ)(3)In (3,6-SQ - radical-anion of 3,6-Q). According to single-crystal X-ray diffraction analysis, this complex has a trigonal prismatic structure. Magnetic measurements revealed that the exchange interactions between odd electrons of the paramagnetic ligands in (3,6-SQ)(3)In are antiferromagnetic in character. The treatment of (3,6-SQ)(3)In with 2,2'-dipyridyl (Dipy) causes the displacement of one o-quinone ligand and the formation of the (3,6-SQ)In(Dipy)(3,6-Cat) (3,6-Cat - dianion of 3,6-Q) derivative containing mixed charged o-quinoid ligands. The reaction of InI with (3,6-SQ)K in THF solution is accompanied by a redox process and the potassium-indium(iii) catecholate derivative was obtained as a result. The oxidation of InI with 3,6-Q in THF produces the dimeric In(iii) iodo-catecholate complex [(3,6-Cat)(2)In·2THF]InI(2). The same derivative can be synthesized by the interaction of indium metal with a mixture of I(2) and 3,6-Q. PMID:21116587

Piskunov, Alexandr V; Maleeva, Aryna V; Fukin, Georgii K; Baranov, Evgenii V; Bogomyakov, Artem S; Cherkasov, Vladimir K; Abakumov, Gleb A

2011-01-21

311

Vibrational frequency analysis, FT-IR, DFT and M06-2X studies on tert-Butyl N-(thiophen-2yl)carbamate.  

PubMed

In this study, the experimental and theoretical vibrational frequencies of a newly synthesized tert-Butyl N-(thiophen-2yl)carbamate have been investigated. The experimental FT-IR (4000-400cm(-1)) spectrum of the molecule in the solid phase have been recorded. The theoretical vibrational frequencies and optimized geometric parameters (bond lengths and bond angles) have been calculated by using density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee-Yang-Parr) and DFT/M06-2X (the highly parametrized, empirical exchange correlation function) quantum chemical methods with the 6-311++G(d,p) basis set by Gaussian 09W software, for the first time. The vibrational frequencies have been assigned using potential energy distribution (PED) analysis by using VEDA 4 software. The computational optimized geometric parameters and vibrational frequencies have been found to be in good agreement with the corresponding experimental data, and with related literature results. In addition, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies and the other related molecular energy values have been calculated and are depicted. PMID:24657467

Sert, Yusuf; Singer, L M; Findlater, M; Do?an, Hatice; C?rak, C

2014-07-15

312

Di-chlorido-(4,4?-di-tert-butyl-2,2?-bi-pyridine-?2 N,N?)palladium(II) dimethyl sulfoxide monosolvate monohydrate  

PubMed Central

The title compound, [PdCl2(C18H24N2)]·(CH3)2SO·H2O, the PdII ion is in a distorted square-planar geometry. The Pd—N bond distances are 2.022?(2) and 2.027?(2)?Å, the Pd—Cl bond distances are 2.2880?(7) and 2.2833?(7)?Å, and the ligand bite angle is 80.07?(9)°. The dimethyl sulfoxide and water mol­ecules form linear chains along [100] by O—H?O and O—H?S hydrogen bonds, generating eight- and 12-membered rings. C—H?Cl inter­actions link the chains, forming a three-dimensional arrangement. In addition, the 4,4-di-tert-butyl-2,2?-bi­pyridine ligand exhibits ?–? stacking inter­actions [centroid–centroid distances = 3.8741?(15) and 3.8353?(15)?Å]. The DMSO solvent is disordered and was refined with an occupancy ratio of 0.866?(3):0.134?(3).

Gutierrez-Marquez, Ricardo A.; Crisostomo-Lucas, Carmela; Reyes-Martinez, Reyna; Hernandez-Ortega, Simon; Morales-Morales, David

2014-01-01

313

Modulatory influence of arecanut on antioxidant 2(3)-tert-butyl-4-hydroxy anisole-induced hepatic detoxification system and antioxidant defence mechanism in mice.  

PubMed

This paper assesses the modificatory potential of arecanut (Areca catechu L.), a popular masticatory substance, on 2(3)-tert-butyl-4-hydroxy anisole (BHA)-induced changes in the hepatic detoxification system and antioxidant defence mechanisms in mice. The modulatory effects on biochemical parameters including glutathione S-transferase (GST), cytochrome b5, cytochrome P-450, acid soluble sulfhydryl (-SH) content and microsomal lipid peroxidation (MDA) levels were assessed. Mice were fed either a normal diet or diets containing 0.25%, 0.5% or 1% (w/w) arecanut for 45 days. During the last 10 days of treatment the feed was supplemented with 0.5% or 1% BHA. Inclusion of BHA in the diet significantly modulated the detoxification system enzymes, -SH content and malondialdehyde (MDA) levels in the liver of the mice. BHA-induced alterations in hepatic GST and -SH content were depressed while cytochrome b5, cytochrome P-450 and MDA levels were further elevated by the arecanut treatment. PMID:7750084

Singh, A; Rao, A R

1995-05-01

314

Adaptation to tert-butyl hydroperoxide at a plasma membrane level in the fission yeast Schizosaccharomyces pombe parental strain and its t-BuOOH-resistant mutant.  

PubMed

The one-gene mutant hyd1-190 of the fission yeast Schizosaccharomyces pombe displayed four-fold resistance to tert-butyl hydroperoxide (t-BuOOH) in comparison with its parental strain hyd(+). The cells of hyd1-190 exhibited a quantitative alteration in the sterol content and hence in the fatty acid composition of the plasma membrane, reflected in a two-fold amphotericin B sensitivity, increased rigidity of the plasma membrane, revealed by an elevated (?7.9?°C) phase-transition temperature, measured by means of electron paramagnetic resonance spectroscopy, and a significantly decreased uptake of glycerol. Treatment of the strains with a subinhibitory concentration (0.2?mM) of t-BuOOH induced adaptation via modification of the sterol and fatty acid compositions, resulting in increased (?3.95?°C) and decreased (?6.83?°C) phase-transition temperatures of the hyd(+) and hyd1-190 strains, respectively, in order to defend the cells against the consequences of t-BuOOH-induced external oxidative stress. However, in contrast with hyd(+), hyd1-190 lacks the ability to adapt to t-BuOOH at a cell level. PMID:23712692

Kálmán, Nikoletta; Gazdag, Zoltán; ?ertík, Milan; Belágyi, József; Selim, Samy A; Pócsi, István; Pesti, Miklós

2014-03-01

315

Spectroscopic and electrochemical characterization of di- tert-butylated sterically hindered Schiff bases and their phenoxyl radicals  

NASA Astrophysics Data System (ADS)

A series of sterically hindered N-arylsalicylaldimines (SAs) previously prepared from substituted salicylaldehydes (X-Sal, where X = H, Cl, Br, NO 2, OH, OCH 3) and 2,6-di- t-butyl-1-hydroxyaniline (L xH) and 2,5-di- t-butylaniline (L x'H) were characterized by 1H and 13C NMR, UV-Vis and electrochemical methods. The electronic spectra (ES) (X = OH, OCH 3) in alcoholic solvents (MeOH, EtOH, PrOH, iso-PrOH) unlike other solvents exhibit a new absorption band in the region 630-675 nm ( ?=19-242 M -1 cm -1), which are not characteristic for other SA known in literature. The ESR studies of primary phenoxyl radicals generated from L xH by their oxidation with PbO 2 reveal that some of them with the time are converted to more stable secondary Coppinger's radical. The cyclic voltammograms of L xH and L x'H except NO 2-substituted ones in CH 3CN are similar and along with two or three irreversible anodic waves at the potentials ranging from 0.0 to +1.9 V versus Ag/AgCl, also display one or two irreversible reduction waves at potentials -0.6 to +0.5 V. A series of a new SA prepared from 3,5-di- t-butylsalicylaldehyde and mono-substituted anilines (X = H, o-, p-F, Cl, Br, OCH 3, p- t-butyl, 5,6-benzo) were characterized by analytical, spectroscopic (IR, UV-Vis, 1H and 13C NMR), and electrochemical techniques. The ES spectra of o-, p-Cl, p-Br, o-CH 3 and 5,6-benzo-substituted SA did not exhibit expected absorptions at 400-500 nm in alcoholic solutions.

Kasumov, V. T.; Medjidov, A. A.; Yayli, N.; Zeren, Y.

2004-11-01

316

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

317

Perfluoro-tert-butyl-homoserine as a sensitive 19F NMR reporter for peptide-membrane interactions in solution.  

PubMed

Fluorine ((19)F) NMR is a valuable tool for studying dynamic biological processes. However, increasing the sensitivity of fluorinated reporter molecules is a key to reducing acquisition times and accessing transient biological interactions. Here, we evaluate the utility a novel amino acid, L-O-(perfluoro-t-butyl)-homoserine (pFtBSer), that can easily be synthesized and incorporated into peptides and provides greatly enhanced sensitivity over currently used (19)F biomolecular NMR probes. Incorporation of pFtBSer into the potent antimicrobial peptide MSI-78 results in a sharp (19)F NMR singlet that can be readily detected at concentrations of 5 µm and lower. We demonstrate that pFtBSer incorporation into MSI-78 provides a sensitive tool to study binding through (19)F NMR chemical shift and nuclear relaxation changes. These results establish future potential for pFtBSer to be incorporated into various proteins where NMR signal sensitivity is paramount, such as in-cell investigations. PMID:23509011

Buer, Benjamin C; Levin, Benjamin J; Marsh, E Neil G

2013-05-01

318

Methyl t-Butyl Ether (MTBE) Production: A Comparison of Montmorillonite-Derived Catalysts with an Ion-Exchange Resin  

Microsoft Academic Search

Montmorillonite-based catalysts were compared with an acidic ion-exchange resin of the type used industrially for the production of methyl t-butyl ether (MTBE) from methanol and isobutene or t-butanol. When 1,4-dioxan was used as solvent, Al3+-exchanged montmorillonites had about half the efficiency of the resin Arnberlyst 15 at 60~ they were, however, about twice as efficient at this temperature at Ti3+-montmorillonite

J. M. Adams; K. MARTIN; R. W. MCCABE; S. MURRAY

1986-01-01

319

Methyl ethyl ketone+water+secondary butyl alcohol: A potential system for the exploration of a quadruple critical point  

Microsoft Academic Search

We report preliminary experiments on the ternary-liquid mixture, methyl ethyl ketone (MEK)+water (W)+secondary butyl alcohol (sBA)-a promising system for the realization of the quadruple critical point (QCP). The unusual tunnel-shaped phase diagram shown by this system is characterized and visualized by us in the form of a prismatic phase diagram. Light-scattering experiments reveal that (MEK+W+sBA) shows near three-dimensional-Ising type of

P. K. Madhavan Unni

2006-01-01

320

Methyl ethyl ketone+water+secondary butyl alcohol: A potential system for the exploration of a quadruple critical point  

Microsoft Academic Search

We report preliminary experiments on the ternary-liquid mixture, methyl ethyl ketone (MEK)+water (W)+secondary butyl alcohol (sBA)—a promising system for the realization of the quadruple critical point (QCP). The unusual tunnel-shaped phase diagram shown by this system is characterized and visualized by us in the form of a prismatic phase diagram. Light-scattering experiments reveal that (MEK+W+sBA) shows near three-dimensional-Ising type of

P. K. Madhavan Unni

2006-01-01

321

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.

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

322

Nonclassical oxygen atom transfer as a synthetic strategy: preparation of an oxorhenium(V) complex of the bis(3,5-di-tert-butyl-2-phenoxo)amide ligand.  

PubMed

Oxo(triphenylphosphine)[bis(3,5-di-tert-butyl-2-phenoxo)amido]rhenium(V) [(ONO(Cat))ReO(PPh3)] is prepared by the reaction of iododioxobis(triphenylphosphine)rhenium(V) [ReO2(PPh3)2I] with lead bis(3,5-di-tert-butyl-1,2-quinone-1-(2-oxy-3,5-di-tert-butylphenyl)imine) [Pb(ONO(Q))2]. In this reaction, the ONO ligand undergoes a two-electron reduction, with concomitant oxidation of PPh3 to OPPh3 and transformation of the dioxorhenium(V) fragment into a monooxorhenium(V) fragment, constituting a net nonclassical oxygen atom transfer. (ONO(Cat))ReO(PPh3) adopts a square pyramidal geometry with an apical oxo group [d(ReO) = 1.6873(14) Å] and a highly folded ONO ligand [O-Re-O = 129.55(6)°]. The fully reduced, trianionic oxidation state of the ONO ligand is confirmed by spectroscopic and metrical data. PMID:23815641

Wright, Daniel D; Brown, Seth N

2013-07-15

323

Disposition, metabolism, and toxicity of methyl tertiary butyl ether, an oxygenate for reformulated gasoline  

SciTech Connect

Studies of the toxicology of methyl tertiary butyl ether (MTBE) were reviewed as a possible information base for evaluating the health effects of evaporative emissions from reformulated gasoline (RFG). Perirenal fat/blood MTBE concentration ratios ranged from 9.7 to 11.6 after 15 wk of intermittent exposure. During an oxyfuels program in Fairbanks, AK, blood levels of occupationally exposed workers were 0.2-31.5 {mu}g/L MTBE and 1.6 to 72.2 {mu}g/L TBA with a mean TBA:MTBE blood concentration ratio of 4.2. In patients who received MTBE by percutaneous, transhepatic puncture for the dissolution of cholesterol gallstones, concentrations of MTBE in fat tissue reached 60 and 300 {mu}g/g at a treatment time when mean blood MTBE was less than 20 {mu}g/ml. The results of laboratory and clinical studies indicate that metabolites of MTBE may contribute to the nephropathy, neoplasms, and other pathological changes associated with repeated exposure to MTBE in experimental animals. It is concluded that such studies can provide a well-defined database for quantitatitive safety comparisons and health risk-benefit analyses of MTBE and other oxygenates in RFG. 39 refs., 1 tab.

Hutcheon, D.E.; Hove, W. ten; Boyle, J. III [UMDNJ, New Jersey Medical Schook, Newark, NJ (United States)] [UMDNJ, New Jersey Medical Schook, Newark, NJ (United States); Arnold, J.D. [Arnold & Arnold, Inc., Kansas City, MO (United States)] [Arnold & Arnold, Inc., Kansas City, MO (United States)

1996-04-05

324

Adsorption of Methyl Tertiary Butyl Ether on Granular Zeolites: Batch and Column Studies  

PubMed Central

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.

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

2010-01-01

325

Magnetic Scanometric DNA Microarray Detection of Methyl Tertiary Butyl Ether Degrading Bacteria for Environmental Monitoring  

PubMed Central

A magnetoresistive biosensing platform based on a single magnetic tunnel junction (MTJ) scanning probe and DNA microarrays labeled with magnetic particles has been developed to provide an inexpensive, sensitive and reliable detection of DNA. The biosensing platform was demonstrated on a DNA microarray assay for quantifying bacteria capable of degrading methyl tertiary-butyl ether (MTBE), where concentrations as low as 10 pM were detectable. Synthetic probe bacterial DNA was immobilized on a microarray glass slide surface, hybridized with the 48 base pair long biotinylated target DNA and subsequently incubated with streptavidin-coated 2.8 ?m diameter magnetic particles. The biosensing platform then makes use of a micron-sized MTJ sensor that was raster scanned across a 3 mm by 5 mm glass slide area to capture the stray magnetic field from the tagged DNA and extract two dimensional magnetic field images of the microarray. The magnetic field output is then averaged over each 100 ?m diameter DNA array spot to extract the magnetic spot intensity, analogous to the fluorescence spot intensity used in conventional optical scanners. The magnetic scanning result is compared with results from a commercial laser scanner and particle coverage optical counting to demonstrate the dynamic range and linear sensitivity of the biosensing platform as a potentially inexpensive, sensitive and portable alternative for DNA microarray detection for field applications.

Chan, Mei-Lin; Jaramillo, Gerardo; Hristova, Krassimira R.; Horsley, David A.

2010-01-01

326

Disposition of 2,6-di-tert-butyl-4-nitrophenol (DBNP), a submarine atmosphere contaminant, in male Sprague-Dawley rats.  

PubMed

The phenol 2,6-di-tert-butyl-4-nitrophenol (DBNP) is a contaminant found onboard submarines and is formed by the nitration of an antioxidant present in turbine lubricating oil TEP 2190. DBNP has been found on submarine interior surfaces, on eating utensils and dishes, and on the skin of submariners. DBNP exposure is a potential health concern because it is an uncoupler of mitochondrial oxidative phosphorylation. Adult male rats were dosed once by oral gavage with 15 or 40 mg/kg DBNP mixed with 14C-DBNP in kanola oil and 0.8% v/v DMSO (n = 16/group). The distribution of 14C in major tissues was measured over time for up to 240 h post-dose. Unexpectedly, 6/16 (40%) of the rats gavaged with 40 mg/kg DBNP died within 24 h of dosing. Prostration, no auditory startle response, reduced locomotor activity, and muscular rigidity persisted in survivors for up to 8 days after dosing. For animals dosed with 15 mg/kg DBNP, radioactivity levels were significantly elevated in the following tissues 24h after dosing: fat>liver>kidneys>heart>lungs>brain>striated muscle>spleen. Radioactivity levels were elevated for fat, liver, kidney, heart, and lungs of animals euthanized 144 h post-dosing and in the liver of animals euthanized 240 h post-dosing. These findings suggest that DBNP may accumulate in the body as a result of continuous or repeat exposures of short interval to DBNP. PMID:15910791

Still, Kenneth R; Jung, Anne E; Ritchie, Glenn D; Jederberg, Warren W; Wilfong, Erin R; Briggs, G Bruce; Arfsten, Darryl P

2005-07-01

327

Beneficial effects of the synthetic antioxidant tert-butyl bisphenol on the hepatic microcirculation in a rat model of diabetes mellitus.  

PubMed

Diabetes mellitus is associated with oxidative injury to the vasculature. Here, the link between oxidative stress and ultrastructural changes in the hepatic microcirculation was investigated as well as the effects of a synthetic antioxidant, tert-butyl bisphenol (tBP). The study focused on the impact of experimental diabetes on liver sinusoidal endothelial cell (LSEC) fenestrations, which are pores in the liver endothelium that facilitate substrate transfer between blood and hepatocytes. Adult male rats were rendered diabetic using streptozotocin (60 mg/kg) and administered 1-2 IU insulin daily. After 8 weeks, animals received either 100 mg/kg tBP or vehicle alone, on 2 consecutive days. Livers were harvested 24 h later under isofluorane anaesthesia (5% v/v in O2(g) by inhalation) and fixed for scanning electron microscopy to evaluate fenestrations or for immuno-histochemical assessment of nitrotyrosine, a marker of nitrosative stress. Median fenestration diameter increased significantly following 8 weeks of diabetes (80 nm vs. 70 nm controls; P < 0.001). LSEC porosity increased by ~50% (P < 0.001). Treatment with tBP reversed these changes completely. Periportal nitrotyrosine staining was increased in diabetic livers, and this was abrogated by tBP, indicating that tBP reduced nitrosative stress in the liver. Early diabetes caused an increase in fenestration diameter and porosity. This was reversed by acute treatment with tBP, suggesting a link between nitrosative stress and regulation of liver endothelial fenestrations, and indicates that antioxidant therapy may protect the liver microvasculature against the effects of diabetes mellitus. PMID:22183926

McMahon, Aisling C; Parry, Sarah N; Benson, Victoria L; Witting, Paul K; Le Couteur, David G

2013-08-01

328

Synthesis, antiradical activity and in vitro cytotoxicity of novel organotin complexes based on 2,6-di-tert-butyl-4-mercaptophenol.  

PubMed

A series of organotin complexes with Sn-S bonds of formulae Me2Sn(SR)2 (1); Et2Sn(SR)2 (2); (n-Bu)2Sn(SR)2 (3); Ph2Sn(SR)2 (4); R2Sn(SR)2 (5); Me3SnSR (6); Ph3SnSR (7) (R = 3,5-di-tert-butyl-4-hydroxyphenyl) were synthesized and characterized by elemental analysis, (1)H, (13)C NMR, and IR. The crystal structures of compounds 1, 4, 5, and 7 were determined by X-ray diffraction analysis. The tetrahedral geometry around the Sn center in the monocrystals of 1, 4, 5, and 7 was confirmed by X-ray crystallography. The high radical scavenging activity of the complexes was confirmed spectrophotometrically in a DPPH-test. The binding affinity of 1-7 and the starting R2SnCl2 (8) towards tubulin through their interaction with SH groups of proteins was studied. It was found that the hindered organotin complexes could interact with the colchicine site of tubulin, which makes them promising antimitotic drugs. Compounds 1-8 were tested for their in vitro cytotoxicity against human breast (MCF-7) and human cervix (HeLa) adenocarcinoma cells. Complexes 1-8 were also tested against normal human fetal lung fibroblast cells (MRC-5). Complexes 2-4 and 8 exhibit significantly lower cytostatic activity against the normal MRC-5 cell line compared to the tumor cell lines MCF-7 and HeLa used. A high activity against both cell lines 250 nM (MCF-7) and 160 nM (HeLa) was determined for the triphenyltin complex 7 while the introduction of hindered phenol groups decreases the cytotoxicity of the complexes against normal cells. PMID:24658418

Shpakovsky, D B; Banti, C N; Mukhatova, E M; Gracheva, Yu A; Osipova, V P; Berberova, N T; Albov, D V; Antonenko, T A; Aslanov, L A; Milaeva, E R; Hadjikakou, S K

2014-05-14

329

Trimethylamine N-oxide (TMAO) and tert-butyl alcohol (TBA) at hydrophobic interfaces: insights from molecular dynamics simulations.  

PubMed

TMAO, a potent osmolyte, and TBA, a denaturant, have similar molecular architecture but somewhat different chemistry. We employ extensive molecular dynamics simulations to quantify their behavior at vapor-water and octane-water interfaces. We show that interfacial structure-density and orientation-and their dependence on solution concentration are markedly different for the two molecules. TMAO molecules are moderately surface active and adopt orientations with their N-O vector approximately parallel to the aqueous interface. That is, not all methyl groups of TMAO at the interface point away from the water phase. In contrast, TBA molecules act as molecular amphiphiles, are highly surface active, and, at low concentrations, adopt orientations with their methyl groups pointing away and the C-O vector pointing directly into water. The behavior of TMAO at aqueous interfaces is only weakly dependent on its solution concentration, whereas that of TBA depends strongly on concentration. We show that this concentration dependence arises from their different hydrogen bonding capabilities-TMAO can only accept hydrogen bonds from water, whereas TBA can accept (donate) hydrogen bonds from (to) water or other TBA molecules. The ability to self-associate, particularly visible in TBA molecules in the interfacial layer, allows them to sample a broad range of orientations at higher concentrations. In light of the role of TMAO and TBA in biomolecular stability, our results provide a reference with which to compare their behavior near biological interfaces. Also, given the ubiquity of aqueous interfaces in biology, chemistry, and technology, our results may be useful in the design of interfacially active small molecules with the aim to control their orientations and interactions. PMID:23687932

Fiore, Andrew; Venkateshwaran, Vasudevan; Garde, Shekhar

2013-06-25

330

Synthesis, spectroscopy, magnetic and redox behaviors of copper(II) complexes with tert-butylated salen type ligands bearing bis(4-aminophenyl)ethane and bis(4-aminophenyl)amide backbones  

NASA Astrophysics Data System (ADS)

New salen type ligands, N,N'-bis(X-3-tert-butylsalicylidene)-4,4'-ethylenedianiline [(X = H (1), 5-tert-butyl (2)] and N,N'-bis(X-3-tert-butylsalicylidene)-4,4'-amidedianiline [X = H (3), 5-tert (4)] and their copper(II) complexes 5-8, have been synthesized. Their spectroscopic (IR, 1H NMR, UV/vis, ESR) properties, as well as magnetic and redox-reactivity behavior are reported. IR spectra of 7 and 8 indicate the coordination of amide oxygen atoms of 3 and 4 ligands to Cu(II). The solid state ESR spectra of 5-8 exhibits less informative exchange narrowed isotropic or anisotropic signals with weak unresolved low field patterns. The magnetic moments of 5 (2.92 ?B per CuII) and 6 (2.79 ?B per CuII) are unusual for copper(II) complexes and considerably higher than those for complexes 7 and 8. Cryogenic measurements (300-10 K) show weak antiferromagnetic exchange interactions between the copper(II) centers in complexes 6 and 8. The results of electrochemical and chemical redox-reactivity studies are discussed.

Kasumov, Veli T.; Yerli, Yusuf; Kutluay, Aysegul; Aslanoglu, Mehmet

2013-03-01

331

Synthesis and magnetic properties of one-dimensional ferro- and ferrimagnetic chains made up of an alternating array of 1,3-bis( N- tert-butyl- N-oxyamino)benzene derivatives and Mn(II)(hfac) 2  

Microsoft Academic Search

Bis(hexafluoroacetylacetonato) manganese(II), Mn(hfac)2, reacts with the bisnitroxide radicals, 5-R-1,3-bis(N-tert-butyl-N-oxyamino)benzene (1R) (R=H, Cl and Br), yielding one-dimensional (1-D) polymeric complexes of formula [Mn(hfac)21R]n. X-ray analysis of the complexes has shown that they crystallize in the monoclinic space group P21\\/n. In this structure, the manganese(II) ions and 1R molecules make up one-dimensional chains with the bisnitroxide radical serving as a bidentate ligand

Katsuya Inoue; Fumiyasu Iwahori; Ashot S Markosyan; Hiizu Iwamura

2000-01-01

332

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

333

[Mechanisms of (2-methyl-n-butyl) shikonin induced apoptosis of gastric cancer SGC-7901 cells].  

PubMed

This study is to investigate the effect of (2-methyl-n-butyl) shikonin (MBS) on inducing apoptosis of human gastric cancer cell line SGC-7901 and the role of ERK1/2 signal pathway in the apoptosis. MTT assay was used to detect SGC-7901 cell proliferation. DNA condensation was measured by DAPI stain. Cell apoptosis was analyzed by flow cytometry. Mitochondrial membrane potential (MMP) was analyzed by JC-1 staining. The protein expressions of Bcl-2, Bax, Survivin, cleaved caspase-9, cleaved caspase-3, cleaved PARP, p-ERK1/2, ERK1/2, p-JNK, JNK, p-p38 and p38 were detected by Western blotting. The results showed that MBS reduced the cell viability of SGC-7901 cells in a dose- and time-dependent manner. The IC50 at 24 h and 48 h for SGC-7901 cells was 10.113 and 4.196 micromolL(-1), respectively. After being treated with MBS, the typical nuclear condensation was observed in SGC-7901 cells by DAPI stain. Apoptosis in SGC-7901 cells was induced by MBS in a dose dependent manner. The protein expression of Bcl-2 was down-regulated, while the protein expressions of cleaved caspase-9, cleaved caspase-3, cleaved PARP, p-ERK1/2 and p-JNK were up-regulated after MBS treatment. U0126, a specific MAP kinase (MEK1/2) inhibitor, blocked the ERK1/2 activation by MBS. MMP was decreased by MBS treatment. It can be concluded that MBS could inhibit SGC-7901 cell proliferation and induce apoptosis. Mitochondrial apoptosis pathway, ERK1/2 signal pathway and JNK signal pathway might be involved in this process. PMID:22919733

Wang, Hai-Bing; Ma, Xiao-Qiong

2012-06-01

334

Ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate for shotgun membrane proteomics.  

PubMed

The solubility and digestion efficiency are two crucial factors that might affect the identification of integral membrane proteins (IMPs). In this work, 1% (v/v) ionic liquid (IL), 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIM BF(4)), added in NH(4)HCO(3) buffer (pH 8.3), was applied as a sample preparation buffer for IMPs analysis. Compared to the commonly used sodium dodecyl sulfate and methanol methods, the number of identified IMPs from rat brain by microcolumn reversed phase liquid chromatography (?RPLC)-electrospray ionization tandem mass spectrometry (ESI-MS/MS) was improved by over three times, which might be due to the fact that BMIM BF(4) offered high solubilizing ability for IMPs and good compatibility for tryptic digestion. Furthermore, compared to Rapigest and urea methods, with BMIM BF(4) method, the number of identified IMPs from rat brain could be improved 25% and 80%, respectively, which might be contributed to the good solubilizing ability and high thermal stability of such IL. With the sample treated by BMIM BF(4) method, by 2D-nanoSCX-RPLC-ESI-MS/MS, 1,450 non-redundant proteins and 7,978 unique peptides were identified from rat brain, and 418 proteins contained at least one predicted transmembrane domain, with false discovery rates of less than 1% for peptide identification, and at least two identified unique peptides per protein. All these results demonstrate that the BMIM BF(4) method is of high potential for the large-scale identification of IMPs. PMID:21079928

Sun, Liangliang; Tao, Dingyin; Han, Bin; Ma, Junfeng; Zhu, Guijie; Liang, Zhen; Shan, Yichu; Zhang, Lihua; Zhang, Yukui

2011-04-01

335

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

336

The tert-butylchloride—lithium naphthalene radical anion and tert-butyllithium—naphthalene systems. Mechanism of metallation  

Microsoft Academic Search

A mechanism of lithiation of aromatics has been inferred from a comparative study of the systems tert-butyl chloride—lithium naphthalene radical anion and tert-butyllithium—naphthalene. Both systems give tert-butyldihydronaphthyllithiums, naphthyllithiums and tert-butylnaphthalenes. Although tert-butyllithium is a reaction product in the former system, it has been shown not to be involved in the formation of the products. In the system tert-butyllithium—naphthalene the distribution

Constantinos G. Screttas; Maria Micha-Screttas; Barry R. Steele

1997-01-01

337

Reinvestigation of a former concerted proton-electron transfer (CPET), the reduction of a hydrogen-bonded complex between a proton donor and the anion radical of 3,5-di-tert-butyl-1,2-benzoquinone.  

PubMed

In 2001, Lehmann and Evans (J. Phys. Chem. B, 2001, 105, 8877-8884) reported that the electrochemical reduction of a hydrogen-bonded complex between a proton donor and the anion radical of 3,5-di-tert-butyl-1,2-benzoquinone in acetonitrile proceeded by a concerted proton-electron transfer (CPET) reaction in which electron transfer from the electrode and proton transfer from proton donor to the quinone moiety occurred concertedly. Support for this conclusion was based upon ruling out both of the competing two-step processes, electron transfer followed by proton transfer (EP) and proton transfer followed by electron transfer (PE). In the course of studies of related compounds it was decided to reinvestigate the reduction of 3,5-di-tert-butyl-1,2-benzoquinone. It was discovered that the earlier conclusion that a CPET reaction was occurring was tenable only for the particular electrolyte that was used, tetrabutylammonium hexafluorophosphate and for lower concentrations of the quinone. Even the small change of carrying out the reduction of the quinone in the presence of water with tetramethylammonium hexafluorophosphate as electrolyte, produced voltammograms with clear signatures that the process was EP rather than CPET. Even more dramatic effects were seen with cesium, potassium or sodium ions in the electrolyte. A general reaction scheme to explain results with all electrolytes will be presented. PMID:22301672

Evans, Dennis H; René, Alice

2012-04-14

338

(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

339

MEASUREMENT OF EXHALED BREATH AND VENOUS BLOOD TO DEVELOP A PHYSIOLOGICALLY BASED PHARMACOKINETIC MODEL FOR HUMAN EXPOSURE TO METHYL TERTIARY-BUTYL ETHER AND THE PRODUCTION OF THE BIOMARKER TERTIARY-BUTYL ALCOHOL  

EPA Science Inventory

Methyl tertiary-butyl ether (MTBE) is a common fuel additive used to increase the availability of oxygen in gasoline to reduce winter-time carbon monoxide emissions from automobiles. Also, MTBE boosts gasoline "octane" rating and, as such, allows reduction of benzene...

340

Synthesis and Thermo-Oxidative Aging Resistance of Hydroxyl Terminated Polybutadiene Bound 2,2-Thiobis(4-methyl-6-tert-butylphenol)  

Microsoft Academic Search

A novel polymeric antioxidant HTPB-IPDI-TPH was synthesized by the reaction between 2,2-thiobis (4-methyl-6-tert-butylphenol) (TPH) and an adduct (HTPB-IPDI) from hydroxyl terminated polybutadiene (HTPB) and isophorone diisocyanate (IPDI). The effects of raw materials ratio and the reaction condition were investigated by measuring the content of the residual –NCO groups of the reactants during the reaction. The structure of HTPB-IPDI-TPH was characterized

Yonghong Wang; Xingrong Zeng; Hongqiang Li; Jianhua Guo

2012-01-01

341

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.

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

2014-01-01

342

Inhibition of p38 mitogen-activated protein kinase phosphorylation decrease tert-butyl hydroperoxide-induced apoptosis in human trabecular meshwork cells  

PubMed Central

Purpose Oxidative stress induced trabecular meshwork cells death is believed to be involved in the pathogenesis and progression of primary open-angle glaucoma (POAG). However, the intrinsic mechanism is yet to be clarified. This study is to investigate the role of p38 mitogen-activated protein kinase (p38MAPK) in tert-butyl hydroperoxide (tBHP)-induced apoptosis of human trabecular meshwork (iHTM) cells. Methods The human trabecular meshwork cells were treated with tBHP for 1 or 2 h with or without pretreatment of SB203580, an inhibitor of MAP kinase homologs. Cell viability was analyzed using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2h-tetrazolium bromide assay. Reactive oxygen species (ROS) levels were determined using dihydrodichlorofluorescein staining, and the chymotrypsin-like protease activities were measured using the Suc-LLVY-aminoluciferin substrate. Cell apoptosis was analyzed by Hoechst 33258 staining and annexin V-PI labeling. The protein level of phospho-p38 was measured using western blot analysis. Results The intracellular ROS increased more than 50 fold and more than 100 fold after tBHP exposure for 1 h and 2 h, respectively (p<0.05). However, there was no difference in ROS levels between SB203580(?) and SB203580(+) cells (p>0.05). In 1 h tBHP treatment group, the cell viability was significantly improved in SB203580(+) cells (81.08%±1.93%) compared to the SB203580(-) cells (69.35%±1.52%), the chymotrypsin-like proteasome inactivation decreased in SB203580(+) cells (60.94%±0.55%) compared to the SB203580(-) cells (70.59%±0.88%), and apoptosis was impoved in SB203580(+) cells (12.75%±1.91%) compared to the SB203580(-) (28.23%±3.23%) (p<0.05). In 2 h tBHP treatment group, cell viability improved in SB203580(+) cells (76.72%±2.11%) compared to SB203580(-) cells (57.88%±2.20%), chymotrypsin-like proteasome inactivation was improved in SB203580(+) cells (62.99%±0.41%) compared to SB203580(-) cells (74.93%±0.54%), and apoptosis was improved in SB203580(+) cells (20.40%±3.44%) compared to SB203580(-) cells (39.20%±5.91%) (p<0.05). Phosphorylation of p38MAPK was significantly increased after tBHP exposure in SB203580 (?) cells and decreased sharply in SB203580(+) cells than that of control group (p<0.05). While there was no difference on the original form of p38MAPK among SB203580(?) and SB203580(+) cells after tBHP exposure and control group (p>0.05). Conclusions Activation of p38MAPK plays an important role in tBHP-induced apoptosis of iHTM cells. Further study on the mechanisms of p38MAPK in human TM cell apoptosis may help to illuminate the pathogenesis of POAG.

Yang, Yuxia; Huang, Jingjing; Zhong, Yimin; Mao, Zhen; Xiao, Hui; Li, Mei; Zhuo, Yehong

2012-01-01

343

Subacute oral and dermal toxicity of tert-butyl hydroperoxide in Fischer F344/N rats and B6C3F1 mice.  

PubMed

Tert-butyl hydroperoxide (TBHP) is a catalyst frequently used in oxidation and sulfonation reactions in the plastics industry. Since the toxicological evaluation of TBHP remains unknown, the National Toxicology Program (NTP) designed studies to characterize and compare TBHP toxicity by the dermal and oral (gavage) routes in male and female Fischer 344 rats and B6C3F1 mice in 14-day exposures. Rats and mice were administered TBHP at 22, 44, 88, 176 or 352 mg/kg in 0.5% aqueous methylcellulose for the gavage studies. In the dermal studies, mice were administered the same doses as above, while rats were administered four doses (22, 44, 88, 176 mg/kg) in 50% aqueous acetone. Results from the gavage studies revealed treatment-related decreases in survival in male rats and body weights in both male and female rats in the 352 mg/kg group. Clinical signs included post-treatment lethargy, thinness, abnormal breathing, ruffled fur, and/or ataxia which occurred sporadically. The male mice showed a statistically significant decrease in body weight in the 44, 88, 176, and 352 mg/kg groups. The major target organs of toxicity were the forestomach in male and female rats and mice, and the esophagus in male and female rats and in male mice. In addition, there was an increase in the absolute and relative liver weight in female mice with hepatocellular hypertrophy in the top-dose group only. Results from spin trapping experiments revealed the presence of electron paramagnetic resonance signals from radical adducts in the blood and organic extracts of the liver and kidneys of rats treated by gavage with 176 mg/kg TBHP, suggesting the involvement of free- radical generation. The no observed adverse effect level (NOAEL) was considered to be 22 mg/kg in rats and male mice, and 44 mg/kg in female mice. In the dermal studies, there was no effect on survival, body weight, or organ weights in either rats or mice. TBHP administration at the site of application resulted in dermal irritation, hyperkeratosis, hyperplasia, and/or inflammation of the epidermis and inflammation of the dermis at 176 mg/kg and above in male and female rats. Dermal irritation at the site of application was noted in all the mice exposed to 352 mg/kg TBHP. Histopathological lesions in the epidermis and dermis were seen in the 88-352 mg/kg males and in the 176-352 mg/kg females. The NOAEL was found to be 88 mg/kg for male rats and female mice, and 44 mg/kg for female rats and male mice. In conclusion, these studies demonstrate that TBHP is metabolized to free radicals and is a contact irritant affecting skin by the dermal route of exposure, and forestomach and esophagus by oral administration. There was no evidence of systemic absorption by the dermal route of exposure based on lack of pathological findings (Supported by National Institute of Environmental Health Sciences Contract No. N01-ES-65406). PMID:22369679

Behl, Mamta; Kadiiska, Maria B; Hejtmancik, Milton R; Vasconcelos, Daphne; Chhabra, Rajendra S

2012-09-01

344

Differential effects of tert-butyl-benzohydroquinone, a putative SR Ca2+ pump inhibitor, on isometric relaxation during the staircase in the rabbit and rat ventricle.  

PubMed

1. The effects of 2,5 di-(tert-butyl)-1,4-benzohydroquinone (TBQ), a putative inhibitor of the sarcoplasmic reticulum Ca2+ pump, on mechanical relaxation and contraction-relaxation coupling have been studied at different frequencies (0.5-3 Hz) in isometrically contracting isolated right ventricular preparations of rabbit and rat at 37 degrees C. Two types of mechanical responses have been studied: the twitch tension and the force transient (rewarming spike, RSp) following a rapid cooling contracture (RCC, an index of sarcoplasmic reticulum Ca2+ content) on return to 37 degrees C. 2. The coupling between contraction and relaxation was assessed by two methods: (a) by evaluation of the variation of the slope relating the maximal rate of tension fall to twitch peak tension; (b) by modelling the twitch according to the following equation: TwT (t) = C x (t/A)B x exp(1-(t/AB) where TwT(t) is the time course of isometric tension, t is time, C and A are an inotropic and a chronotropic index respectively and B, a contraction-relaxation coupling index (Nwasokwa, 1993). 3. In the rabbit ventricle, 30 microM TBQ did not prevent the frequency-induced shortening of the twitch time to half-relaxation (t1/2) and of the time constant (tau) describing the final part of the RSp relaxation (tau decreased from 140 ms (0.5 Hz) to 133 ms (3 Hz) in control and from 253 ms (0.5 Hz) to 197 ms (3 Hz) after exposure to TBQ). By contrast, at a given frequency, the prolongation of relaxation induced by TBQ was proportional to its inotropic effect (unchanged slopes and B values) but TBQ did not prevent the acceleration of relaxation observed at high frequencies: B increased from 2.02 (0.5 Hz) to a peak value of 2.18 (1 Hz) in control and from 1.88 (0.5 Hz) to a maximum of 2.48 (2 Hz) after TBQ exposure. TBQ significantly attenuated the decay of RCCs elicited after increasingly longer periods of muscle quiescence as normally observed in control conditions. 4. In the rat ventricle, TBQ depressed relaxation more than expected on the basis of its negative inotropic effects (B decreased from 2.16 to 1.84 at 0.5 Hz and from 2.15 to 1.66 at 3 Hz). TBQ also slowed the rate of RSp relaxation (tau increased from 95 ms to 168 ms at 0.5 Hz, and from 109 ms to 149 ms at 3 Hz) and increased twitch t1/2. By contrast with the results obtained in the rabbit ventricle, B, tau and t1/2 were frequency-insensitive whether or not TBQ was present. 5. TBQ exerts negative inotropic effects consistent with inhibition of the SR Ca2+ pump. In the rabbit ventricle, the TBQ-induced potentiation of relaxation acceleration at high pacing frequencies suggests the involvement of counteracting Ca(2+)-mediated mechanisms probably via Ca(2+)-calmodulin-activated kinases. In the rat ventricle, TBQ did not have any differential effect on relaxation depending on the frequency, probably because the extent of the negative staircase was small in the present experimental conditions. PMID:8789378

Baudet, S; Khammari, A; Noireaud, J; Le Marec, H

1996-01-01

345

Dinuclear (d{sup 3}-d{sup 3}) diolate complexes of molybdenum and tungsten. 2. Derivatives of 2,2{prime}-methylenebis(6-tert-butyl-4-methylphenoxide). Direct observation of the conversion of bridged to chelate isomers (M = Mo) and reversible carbon-hydrogen bond oxidative addition (M = W)  

SciTech Connect

Hydrocarbon solutions of Mo{sub 2}(NMe{sub 2}){sub 6} and 2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol)({ge}2 equiv), HO(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol)) CH{sub 2}(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol)) OH, yield Mo{sub 2}(NMe{sub 2}){sub 2}(O(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol))CH{sub 2}(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol))O){sub 2}, I, which exists in bridged Ib and chelated Ic isomers. These are formed under kinetic control, and recrystallization allows the separation of Ib (orange cubes) from Ic (yellow cubes) both of which have been crystallographically characterized. In each there is an ethane-like O{sub 2}NMo{triple_bond}MoO{sub 2}N core with Mo-Mo = 2.2 {Angstrom} (average). In Ib the two O(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol))CH{sub 2}(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol))O ligands span the Mo{triple_bond}Mo bond yielding a molecule of C{sub 2} symmetry. In Ic the molecule has near-C{sub 2} symmetry in the solid state, but in solution there is either rapid rotation about the M{triple_bond}M bond or the anti-rotamer is preferred. In benzene-d{sub 6}, Ib and Ic do not interconvert at 110 {degrees}C over a period of days. However, the addition of pyridine or acetonitrile causes the isomerization of Ib to Ic, thereby establishing that Ic is the thermodynamic isomer. The rate of conversion of Ib to Ic has been shown to be dependent on the square of the concentration of added pyridine: k{sub obs} = k[py]{sup 2}. From the temperature dependence of k{sub obs}, we determine {Delta}H{sup {double_dagger}} = 19 ({+-}1) kcal/mol and {Delta}S{sup {double_dagger}} =-25 ({+-}3) eu for the pyridine-promoted isomerization of Ib to Ic. 25 refs., 10 figs., 9 tabs.

Chisholm, M.H.; Huang, Jui-Hsien; Huffman, J.C.; Parkin, I.P. [Indiana Univ., Bloomington, IN (United States)] [Indiana Univ., Bloomington, IN (United States)

1997-04-09

346

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

347

Preparation and characterization of Pd doped ceria-ZnO nanocomposite catalyst for methyl tert-butyl ether (MTBE) photodegradation.  

PubMed

A series of binary oxide catalysts (ceria-ZnO) were prepared and doped with different amounts of palladium in the range of 0.5%-1.5%. The prepared catalysts were characterized by SEM, TEM, XRD and XPS, as well as by N2 sorptiometry study. The XPS results confirmed the structure of the Pd CeO2-x-ZnO. The photocatalytic activity of these catalysts was evaluated for degradation of MTBE in water. These photocatalyst efficiently degrade a 100ppm aqueous solution of MTBE upon UV irradiation for 5h in the presence of 100mg of each of these photocatalysts. The removal of 99.6% of the MTBE was achieved with the ceria-ZnO catalyst doped with 1% Pd. In addition to the Pd loading, the N2 sorptiometry study introduced other factors that might affect the catalytic efficiency is the catalyst average pore sizes. The photoreaction was determined to be a first order reaction. PMID:24275473

Seddigi, Zaki S; Bumajdad, Ali; Ansari, Shahid P; Ahmed, Saleh A; Danish, Ekram Y; Yarkandi, Naeema H; Ahmed, Shakeel

2014-01-15

348

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

349

5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetra-kis[2-(2-chloro-ethoxy)eth-oxy]-2,8,14,20-tetra-sulfonyl-calix[4]arene.  

PubMed

Mol-ecules of the title compound, C(56)H(76)Cl(4)O(16)S(4), have crystallographic C(2) symmetry and adopt a 1,3-alternate conformation where the four -OCH(2)CH(2)OCH(2)CH(2)Cl 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 intra-molecular C-H?O hydrogen bonds between the ether arm H atoms and the sulfonyl O atoms. In the supra-molecular structure, the mol-ecular components are linked into infinite zigzag one-dimensional chains by a combination of four inter-molecular 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 inter-actions. One tert-butyl group shows rotational disorder, and one CH(2)CH(2)Cl 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 CH(2)CH(2)Cl units. PMID:21581981

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

2009-01-01

350

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...

351

Phenolic antioxidant 2,6-di-tert-butyl-p-cresol (vitamin E synthetic analogue) does not inhibit 1,1'-dimetyl-4,4'-bipyridium dichloride (paraquat)-induced structural chromosomal damage in cultured leukocytes of the dark-spotted-frog Pelophylax (Rana) nigromaculatus.  

PubMed

Pro-oxidative effect of phenolic antioxidant (vitamin E) in combination with the initiators on human low-density lipoprotein is known. Recently I reported that oxidative stress induced by vitamin E in combination with the herbicide paraquat enhances structural chromosomal damage in cultured anuran leukocytes. In the present study, the phenolic antioxidant vitamin E-synthetic-analogue 2,6-di-tert-butyl-p-cresol (BHT) in combination with paraquat was found to enhance structural chromosomal damage in cultured Pelophylax (Rana) nigromaculatus leukocytes more than paraquat only and paraquat plus nicotinamido adenine dinucleotido phosphate served as positive control, although BHT only had no effect on induction of structural chromosomal damage. Paraquat plus BHT-enhanced structural chromosomal damage was inhibited by combination of the superoxide dismutase mimic Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin and the hydrogen peroxide scavenger catalase. In test based on reduction of paraquat cation, BHT was found to reduce paraquat cation chemically to paraquat monocation radical. These results suggest that BHT functions in chemically donating electron to paraquat and thereby induces an acute accumulation of reactive oxygen species, resulting in increase in chromosomal damage. PMID:23121328

Hanada, Hideki

2012-10-01

352

IDENTIFICATION AND DETERMINATION OF TERT-ALKLYPHENOLS IN CARP FROM THE TRENTON CHANNEL OF THE DETROIT RIVER, MI  

EPA Science Inventory

Whole carp from the Detroit River were analyzed by gas chromatographic mass spectrometry. even tertiary alkyl phenols (tert-pentylphenols, tert-butyl-tert-pentylphenols, a di-tert-pentylphenol and a tri-tert-pentylphenol) and eight chlorinated derivatives of these compounds were ...

353

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

354

Performances of poly(vinylpyrrolidone-co-vinyl acetate)-cellulose acetate blend membranes in the pervaporation of ethanol–ethyl tert-butyl ether mixtures  

Microsoft Academic Search

High performance pervaporation membranes for the selective removal of ethanol from ethyl t-butyl ether (ETBE) were prepared by blending cellulose acetate with poly(vinylpyrrolidone-co-vinyl acetate) in different proportions and studied in sorption and pervaporation of ethanol–ETBE mixtures of compositions ranging from 5 to 25wt% ethanol. The membrane performances are improved when the copolymer content is higher due to strong flux enhancement.

Quang-Trong Nguyen; Robert Clément; Irwan Noezar; Pierre Lochon

1998-01-01

355

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

356

Structural Characterization of Hydroxyl-Terminated Polybutadiene-Bound 2, 2-Thiobis(4-methyl-6-tert-butylphenol) and Its Thermo-Oxidative Aging Resistance for Natural Rubber Vulcanizates  

Microsoft Academic Search

A novel polymeric antioxidant, hydroxyl-terminated polybutadiene-bound 2,2-thiobis(4-methyl-6-tert-butylphenol) (HTPB-IPDI-TPH), was prepared by binding 2, 2-thiobis(4-methyl-6-tert-butylphenol) (TPH) onto hydroxyl-terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI). Fourier-transform infrared spectroscopy (FTIR), C nuclear magnetic resonance spectroscopy (C NMR), and gel permeation chromatography (GPC) were used to characterize the structure of HTPB-IPDI-TPH. The thermal stability of HTPB-IPDI-TPH was studied by thermogravimetry analysis (TGA). The effect

Yonghong Wang; Xingrong Zeng; Hongqiang Li; Jianhua Guo

2012-01-01

357

Mechanistic basis for inflammation and tumor promotion in lungs of 2,6-di-tert-butyl-4-methylphenol-treated mice: electrophilic metabolites alkylate and inactivate antioxidant enzymes.  

PubMed

An established model for mechanistic analysis of lung carcinogenesis involves administration of 3-methylcholanthrene to mice followed by several weekly injections of the tumor promoter 2,6-di-tert-butyl-4-methylphenol (BHT). BHT is metabolized to quinone methides (QMs) responsible for promoting tumor formation. QMs are strongly electrophilic and readily form adducts with proteins. The goal of the present study was to identify adducted proteins in the lungs of mice injected with BHT and to assess the potential impact of these modifications on tumorigenesis. Cytosolic proteins from treated mouse lungs were separated by two-dimensional electrophoresis, adducts detected by immunoblotting, and proteins identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Eight adducts were detected in the lungs of most, or all, of six experimental groups of BALB mice. Of these adducts, several were structural proteins, but others, namely, peroxiredoxin 6 (Prx6), Cu,Zn-superoxide dismutase (SOD1), carbonyl reductase, and selenium-binding protein 1, have direct or indirect antioxidant functions. When the 9000g supernatant fraction of mouse lung was treated with BHT-QM (2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone), substantial lipid peroxidation and increases in hydrogen peroxide and superoxide formation were observed. Studies with human Prx6 and bovine SOD1 demonstrated inhibition of enzyme activity concomitant with adduct formation. LC-MS/MS analysis of digests of adducted Prx6 demonstrated adduction of both Cys 91 and Cys 47; the latter residue is essential for peroxidatic activity. Analysis of QM-treated bovine SOD1 by matrix-assisted laser desorption/ionization time-of-flight MS demonstrated the predominance of a monoadduct at His 78. This study provides evidence that indicates Prx6, SOD1, and possibly other antioxidant enzymes in mouse lung are inhibited by BHT-derived QMs leading to enhanced levels of reactive oxygen species and inflammation and providing a mechanistic basis for the effects of BHT on lung tumorigenesis. PMID:17305404

Meier, Brent W; Gomez, Jose D; Kirichenko, Oleg V; Thompson, John A

2007-02-01

358

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

359

Enantiomeric separation and discrimination of 2-hydroxy acids as O-trifluoroacetylated ( S)-(+)-3-methyl-2-butyl esters by achiral dual-capillary column gas chromatography  

Microsoft Academic Search

An efficient method is described for the simultaneous enantiomeric separation of 18 different racemic 2-hydroxy acids for the determination of their absolute configurations. It involves the conversion of each enantiomer into a diastereomeric O-trifluoroacetylated (S)-(+)-3-methyl-2-butyl ester for the direct separation by achiral dual-capillary column gas chromatography with subsequent identification and determination of its chirality by retention index (I) library matching.

Kyoung-Rae Kim; Jaeick Lee; Dongbum Ha; Jinah Jeon; Hyoung-Geun Park; Jung Han Kim

2000-01-01

360

Low-rate Dynamic Contact Angles on Poly(methyl methacrylate\\/n-butyl methacrylate) and the Determination of Solid Surface Tensions  

Microsoft Academic Search

Low-rate dynamic contact angles of 12 liquids on a poly(methyl methacrylate\\/n-butyl methacrylate) P(MMA\\/nBMA) copolymer are measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It is found that 6 liquids yield non-constant contact angles, and\\/or dissolve the polymer on contact. From the experimental contact angles of the remaining 6 liquids, it is found that the liquid- vapour surface tension times

D. Y. Kwok; C. N. C. Lam; A. Li; A. W. Neumann

1998-01-01

361

Molecular Recognition at Methyl Methacrylate\\/n-Butyl Acrylate (MMA\\/nBA) Moanomer Unit Boundaries of Phospholipids at pMMA\\/nBA Copolymer Surfaces  

Microsoft Academic Search

Lipid structural features and their interactions with proteins provide a useful vehicle for further advances in membrane proteins research. To mimic one of potential lipid-protein interactions we synthesized poly(methyl methacrylate\\/n-butyl acrylate) (p-MMA\\/nBA) colloidal particles that were stabilized by phospholipid (PLs). Upon the particle coalescence, PL stratification resulted in the formation of surface localized ionic clusters (SLICs). These entities are capable

Marek W. Urban; Yinghong Sheng; Jerzy Leszczynski

2008-01-01

362

Polystyrene nanoparticles based on poly(butyl methacrylate-g-methoxypoly(ethylene glycol)) and poly(methyl methacrylate-g-methoxypoly(ethylene glycol)) graft copolymers  

Microsoft Academic Search

The solubilization of styrene by poly(butyl methacrylate-g-methoxypoly(ethylene glycol)) and poly(methyl methacrylate-g-methoxypoly(ethylene glycol)) graft copolymers has been examined. From turbidity measurements the solubility limit of the monomer in the micelles was obtained and the distribution coefficients were evaluated. Dynamic light scattering revealed that below the solubility limit, solubilization leads to a slight increase in micelle size, while above the solubility limit,

Adrian Horgan; Brian Vincent

2003-01-01

363

Surface characterization of poly(methyl methacrylate-co- n-butyl acrylate-co-cyclopentylstyryl-polyhedral oligomeric silsesquioxane) by inverse gas chromatography  

Microsoft Academic Search

The surface properties of poly(methyl methacrylate-co-n-butyl acrylate-co-cyclopentylstyryl polyhedral oligomeric silsesquioxane) (poly(MMA-co-BA-co-styryl-POSS)) were studied by means of inverse gas chromatography (IGC) using 10 non-polar and polar solvents as the probes. Thermodynamic parameters of adsorption, e.g., specific retention volume, the dispersive component of the surface free energy, the specific interaction contribution to the free energy of adsorption and the acid\\/base constants were

Qi-Chao Zou; Shi-Ling Zhang; Qing-qiong Tang; Shi-Min Wang; Li-Min Wu

2006-01-01

364

Distribution of organic solutes in biphasic 1-n-butyl-3-methylimidazolium methyl sulfate-supercritical CO(2) system.  

PubMed

Interphase distribution of organic nonelectrolytes can be important in applications of biphasic solvent systems composed of a room-temperature ionic liquid and supercritical carbon dioxide (scCO(2)). Here, open tubular capillary-column supercritical fluid chromatography (SFC) with 1-n-butyl-3-methylimidazolium methyl sulfate ([bmim][MeSO(4)]) as the stationary liquid and scCO(2) as the carrier fluid was employed to measure retention factors of organic solutes within 313-353 K and 8.5-23.2 MPa. Solute selection included 18 compounds of diverse volatilities and chemical functionalities. The retention factors were converted to infinite-dilution solute partition coefficients in the biphasic [bmim][MeSO(4)]-scCO(2) system. At a constant temperature, an increase in scCO(2) density produced distinct shifts in relative retention (= separation factor), thus providing some pressure-tunable selectivity. At a particular temperature and density of CO(2), solute partition coefficients can be correlated in terms of linear solvation energy relationships. Analysis of the relative retention data by regular solution theory resulted in approximate values of the solubility parameter of CO(2)-expanded [bmim][MeSO(4)]. PMID:19537694

Planeta, Josef; Karásek, Pavel; Roth, Michal

2009-07-16

365

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.

Schafer, Franziska; Muzica, Liudmila; Schuster, Judith; Treuter, Naemi; Rosell, Monica; Harms, Hauke; Muller, Roland H.; Rohwerder, Thore

2011-01-01

366

Enantioselective Synthesis of (2R, 3S)- and (2S, 3R)-4,4,4-trifluoro-N-Fmoc-O-tert-butyl-threonine and their Racemization-free Incorporation into Oligopeptides via Solid-phase Synthesis  

PubMed Central

An efficient method for the enantioselective synthesis of (2R, 3S)- and (2S, 3R)-4,4,4-trifluoro-N-Fmoc-O-tert-butyl-threonine (tfT) on multi-gram scales was developed. Absolute configurations of the two stereoisomers were ascertained by X-ray crystallography. Racemization-free coupling conditions for the incorporation of tfT into oligopeptides were then explored. For solution-phase synthesis, tfT racemization was not an issue under conventional coupling conditions. For solid-phase synthesis, the following conditions were identified to achieve racemization-free synthesis: if tfT (3.0 eq.) was not the first amino acid to be linked to the resin (1.0 eq.), the condition is: 2.7 eq. DIC/3.0 eq. HOBt as the coupling reagent at 0 °C for 20 h; if tfT (3.0 eq.) was the first amino acid to be linked to the resin (1.0 eq.), then 1.0 eq. of CuCl2 needs to be added to the coupling reagent.

Xiao, Nu; Jiang, Zhong-Xing; Yu, Y. Bruce

2010-01-01

367

Automated radiosynthesis of N-succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB) for peptides and proteins radiolabeling for positron emission tomography.  

PubMed

Recently, silicon fluoride building blocks (SiFA) have emerged as valuable and promising tools to overcome challenges in the labeling of peptides and proteins for positron emission tomography (PET). Herein, we report a fully automated synthesis of N-succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB) by a commercially available Scintomics Hot Box 3 synthesis module, to be used as a prosthetic group for peptide and protein labeling. The drying of K2.2.2./K (18)F complex was performed according to the Munich method modified by our group (avoiding azeotropic drying) using oxalic acid to neutralize the base from the (18)F(-) containing QMA eluent. This K2.2.2./K (18)F complex was then used for SiFA (18)F-(19)F isotopic exchange followed by a fast purification by a solid-phase-extraction (SPE) to afford [(18)F]SiFB with an average preparative radiochemical yield (RCY) of 24±1% (non-decay corrected (NDC)) within a synthesis time of 30 min. The [(18)F]SiFB produced by automated synthesis was then used for the (18)F-labeling of rat serum albumin (RSA) as a proof of applicability. PMID:24631747

Koudih, R; Kostikov, A; Kovacevic, M; Jolly, D; Bernard-Gauthier, V; Chin, J; Jurkschat, K; Wängler, C; Wängler, B; Schirrmacher, R

2014-07-01

368

Phenolic antioxidants tert-butyl-bisphenol and vitamin E decrease oxidative stress and enhance vascular function in an animal model of rhabdomyolysis yet do not improve acute renal dysfunction.  

PubMed

Rhabdomyolysis (RM) caused by severe burn releases extracellular myoglobin (Mb) that accumulates in the kidney. Extracellular Mb is a pro-oxidant. This study tested whether supplementation with tert-butyl-bisphenol (BP) or vitamin E (Vit E, as ?-tocopherol) at 0.12% w/w in the diet inhibits acute renal failure (ARF) in an animal model of RM. After RM-induction in rats, creatinine clearance decreased (p < 0.01), proteinuria increased (p < 0.001) and renal-tubule damage was detected. Accompanying ARF, biomarkers of oxidative stress (lipid oxidation and hemeoxygenase-1 (HO-1) gene and protein activity) increased in the kidney (p < 0.05). Supplemented BP or Vit E decreased lipid oxidation (p < 0.05) and HO-1 gene/activity and restored aortic cyclic guanylyl monophosphate in control animals (p < 0.001), yet ARF was unaffected. Antioxidant supplementation inhibited oxidative stress, yet was unable to ameliorate ARF in this animal model indicating that oxidative stress in kidney and vascular cells may not be causally related to renal dysfunction elicited by RM. PMID:21726176

Kim, Hyun Bo; Shanu, Anu; Wood, Sarah; Parry, Sarah N; Collet, Michael; McMahon, Aisling; Witting, Paul K

2011-09-01

369

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.

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

2012-01-01

370

Preparation of Latexes with Poly(Methyl Methacrylate) Cores and Hydrophilic Polymer Shells Containing Amino Groups  

Microsoft Academic Search

Functional latexes with poly(methyl methacrylate) (PMMA) cores and amino?containing, water?soluble polymer shells were synthesized via direct graft copolymerization of methyl methacrylate from water?soluble polymers induced by a small amount of tert?butyl hydroperoxide (TBHP) at 80°C for 2 h. Amphiphilic graft copolymers and PMMA homopolymers were generated concurrently to form highly monodispersed latexes. The effects of water?soluble polymer containing different amino group,

Pei Li; Junmin Zhu; Panya Sunintaboon; Frank W. Harris

2003-01-01

371

[2-Butyl-4-(4-tert-butyl-benz-yl)-1,2,4-triazol-3-yl-idene]chlorido[(1,2,5,6-?)-cyclo-octa-1,5-diene]iridium(I)  

PubMed Central

In the title compound, [IrCl(C8H12)(C17H25N3)], the IrI ion has a distorted square-planar coordination geometry. The N-heterocyclic carbene ligand has an extended S-shaped conformation. The butyl group was refined using a two-part 1:1 disorder model. In the crystal, three unique weak C—H?Cl contacts are present. Two of these form a motif described as R 2 1(6) in graph-set notation, while a third forms an R 2 2(8) motif about a crystallographic inversion center. The result is a chain structure which extends parallel to the crystallographic a axis.

Nichol, Gary S.; Walton, David P.; Anna, Laura J.; Rajaseelan, Edward

2012-01-01

372

Phenyl-?-tert-butyl-nitrone and Benzonidazole Treatment Controlled the Mitochondrial Oxidative Stress and Evolution of Cardiomyopathy in Chronic Chagasic Rats  

PubMed Central

Objectives Determine the pathological importance of oxidative stress-induced injurious processes in chagasic heart dysfunction. Background Trypanosoma cruzi-induced inflammatory pathology and a feedback cycle of mitochondrial dysfunction and oxidative stress may contribute to Chagas disease. Methods Sprague Dawley rats were infected with T. cruzi, and treated with phenyl-?-tert-butylnitrone (PBN/antioxidant) and/or benzonidazole (BZ/anti-parasite). We monitored myocardial parasite burden, oxidative adducts, mitochondrial complex activities, respiration and ATP synthesis rates, and inflammatory and cardiac remodeling responses during disease development. Cardiac hemodynamics was determined for all rats. Results BZ (not PBN) decreased the parasite persistence and immune adverse events (proinflammatory cytokine expression, NADPH (?-Nicotinamide Adenine Dinucleotide Phosphate, reduced) oxidase and myeloperoxidase activities, and inflammatory infiltrate) in chronic hearts. PBN±BZ (not BZ alone) decreased the mtROS level, oxidative adducts (malonyldialdehyde, 4-hydroxynonenal, carbonyls), hypertrophic gene expression (ANP, BNP, ?sk-Actin), and collagen deposition, and preserved the respiratory chain efficiency and energy status in chronic hearts. Subsequently, left ventricular dysfunction was prevented in PBN±BZ-treated chagasic rats. Conclusions BZ treatment after acute stage decreased the parasite persistence and inflammatory pathology. Yet, oxidative adducts, mitochondrial dysfunction and remodeling responses persisted and contributed to declining cardiac function in chagasic rats. Combinatorial treatment (PBN+BZ) was beneficial in arresting the T. cruzi-induced inflammatory and oxidative pathology and chronic heart failure in chagasic rats.

Wen, Jian-Jun; Gupta, Shivali; Guan, Zhangjun; Dhiman, Monisha; Condon, David; Lui, Charles; Garg, Nisha Jain

2010-01-01

373

Chronic carcinogenicity study of gasoline vapor condensate (GVC) and GVC containing methyl tertiary-butyl ether in F344 rats.  

PubMed

Chronic inhalation studies were conducted to compare the toxicity and potential carcinogenicity of evaporative emissions from unleaded gasoline (GVC) and gasoline containing the oxygenate methyl tertiary-butyl ether (MTBE; GMVC). The test materials were manufactured to mimic vapors people would be exposed to during refueling at gas stations. Fifty F344 rats per gender per exposure level per test article were exposed 6 h/d, 5 d/wk for 104 wk in whole body chambers. Target total vapor concentrations were 0, 2, 10, or 20 g/m³ for the control, low-, mid-, and high-level exposures, respectively. Endpoints included survival, body weights, clinical observations, organs weights, and histopathology. GVC and GMVC exerted no marked effects on survival or clinical observations and few effects on organ weights. Terminal body weights were reduced in all mid- and high-level GVC groups and high-level GMVC groups. The major proliferative lesions attributable to gasoline exposure with or without MTBE were renal tubule adenomas and carcinomas in male rats. GMV exposure led to elevated testicular mesothelioma incidence and an increased trend for thyroid carcinomas in males. GVMC inhalation caused an increased trend for testicular tumors with exposure concentration. Mid- and high-level exposures of GVC and GMVC led to elevated incidences of nasal respiratory epithelial degeneration. Overall, in these chronic studies conducted under identical conditions, the health effects in F344 rats following 2 yr of GVC or GMVC exposure were comparable in the production of renal adenomas and carcinomas in male rats and similar in other endpoints. PMID:21432714

Benson, Janet M; Gigliotti, Andrew P; March, Thomas H; Barr, Edward B; Tibbetts, Brad M; Skipper, Betty J; Clark, Charles R; Twerdok, Lorraine

2011-01-01

374

Molecular and solid-state structure of methyl [2-(acridin-9-ylimino)-3-( tert-butylamino)-4-oxothiazolidin-5-ylidene]acetate  

Microsoft Academic Search

The molecular and solid-state structures of methyl [2-(acridin-9-ylimino)-3-(tert-butylamino)-4-oxothiazolidin-5-ylidene]acetate (4) were determined by X-ray diffraction, 1H NMR, 13C NMR, CI mass spectroscopy and B3LYP calculations using the basis sets 6-31G(d,p), 6-311+G(d,p) and 6-311++G(2d,2p). In particular, calculations of long-range heteronuclear coupling constants were found to be extraordinarily indicative for the E\\/Z configuration of a distal segment. Compound 4 (C23H22N4O3S, Mr=434.52) crystallized in

Jana Tomasciková; Ivan Danihel; Stanislav Böhm; Ján Imrich; Pavol Kristian; Ivan Potocnák; Jan ?ejka; Karel D. Klika

2008-01-01

375

Solid state (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.  

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

376

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

377

Henry’s law constants and infinite dilution activity coefficients of cis-2-butene, dimethylether, chloroethane, and 1,1-difluoroethane in methanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-methyl-2-butanol  

Microsoft Academic Search

Henry’s law constants and infinite dilution activity coefficients of cis-2-butene, dimethylether, chloroethane, and 1,1-difluoroethane in methanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-methyl-2-butanol in the temperature range of 250K to 330K were measured by a gas stripping method and partial molar excess enthalpies were calculated from the activity coefficients. A rigorous formula for evaluating

Yoshimori Miyano; Takahiro Kobashi; Hiroshi Shinjo; Shinya Kumada; Yusuke Watanabe; Wataru Niya; Yoko Tateishi

2006-01-01

378

Concentration fluctuations and collective properties in mixed liquid systems: Rayleigh-Brillouin spectra of tert-butyl alcohol/ 2,2'-dimethylbutane liquid mixture  

NASA Astrophysics Data System (ADS)

Rayleigh-Brillouin spectra have been measured in a range of temperatures and compositions of t-butyl alcohol/2,2'-dimethylbutane liquid mixture. The mixture mole fraction has been varied from pure alkane (xTBA=0) to pure alcohol (xTBA=1) at temperatures between 283 and 323 K. In the same composition and temperature ranges the authors also executed measurements of mass density, shear viscosity, and refractive index. From light scattering spectra the authors have extracted the hypersound velocities and adiabatic compressibilities and evaluated their excess values. Moreover, the authors attempted to evaluate the isothermal (40 °C) Landau-Placzek ratios at various mole fractions, but these values proved to be subject to significant errors due to great uncertainty in the central component intensity measurements. Thus, in discussing the results, this latter quantity was considered only from a qualitative point of view. These results highlight a nonideal behavior of the studied liquid mixture with a probable azeotropic composition around xTBA=0.7 due to formation of small clusters of hydrogen-bonded alcohol tetramers that are completely surrounded by solvent molecules and analogous or smaller clusters. These clusters, shaped as inverse micelles, offer their hydrophobic moiety towards the molecules that constitute the solvation shell, resulting in a low polarity solution structure that minimizes the solute-solvent interactions. Differences in thermal and compositional behavior of excess molar volumes and adiabatic compressibilities have been interpreted by attributing different weights to the solute-solvent interaction forces and to the hydrogen bond connectivity effects.

Cataliotti, Rosario Sergio; Palombo, Francesca; Paolantoni, Marco; Sassi, Poala; Raudino, Antonio

2007-01-01

379

Concentration fluctuations and collective properties in mixed liquid systems: Rayleigh-Brillouin spectra of tert-butyl alcohol/2,2'-dimethylbutane liquid mixture.  

PubMed

Rayleigh-Brillouin spectra have been measured in a range of temperatures and compositions of t-butyl alcohol/2,2(')-dimethylbutane liquid mixture. The mixture mole fraction has been varied from pure alkane (x(TBA)=0) to pure alcohol (x(TBA)=1) at temperatures between 283 and 323 K. In the same composition and temperature ranges the authors also executed measurements of mass density, shear viscosity, and refractive index. From light scattering spectra the authors have extracted the hypersound velocities and adiabatic compressibilities and evaluated their excess values. Moreover, the authors attempted to evaluate the isothermal (40 degrees C) Landau-Placzek ratios at various mole fractions, but these values proved to be subject to significant errors due to great uncertainty in the central component intensity measurements. Thus, in discussing the results, this latter quantity was considered only from a qualitative point of view. These results highlight a nonideal behavior of the studied liquid mixture with a probable azeotropic composition around x(TBA)=0.7 due to formation of small clusters of hydrogen-bonded alcohol tetramers that are completely surrounded by solvent molecules and analogous or smaller clusters. These clusters, shaped as inverse micelles, offer their hydrophobic moiety towards the molecules that constitute the solvation shell, resulting in a low polarity solution structure that minimizes the solute-solvent interactions. Differences in thermal and compositional behavior of excess molar volumes and adiabatic compressibilities have been interpreted by attributing different weights to the solute-solvent interaction forces and to the hydrogen bond connectivity effects. PMID:17286485

Cataliotti, Rosario Sergio; Palombo, Francesca; Paolantoni, Marco; Sassi, Poala; Raudino, Antonio

2007-01-28

380

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 4000-400cm(-1) and 3500-100cm(-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

381

Reversal of age-related increase in brain protein oxidation, decrease in enzyme activity, and loss in temporal and spatial memory by chronic administration of the spin-trapping compound N-tert-butyl-alpha-phenylnitrone  

SciTech Connect

Oxygen free radicals and oxidative events have been implicated as playing a role in bringing about the changes in cellular function that occur during aging. Brain readily undergoes oxidative damage, so it is important to determine if aging-induced changes in brain may be associated with oxidative events. Previously we demonstrated that brain damage caused by an ischemia/reperfusion insult involved oxidative events. In addition, pretreatment with the spin-trapping compound N-tert-butyl-alpha-phenylnitrone (PBN) diminished the increase in oxidized protein and the loss of glutamine synthetase (GS) activity that accompanied ischemia/reperfusion injury in brain. We report here that aged gerbils had a significantly higher level of oxidized protein as assessed by carbonyl residues and decreased GS and neutral protease activities as compared to young adult gerbils. We also found that chronic treatment with the spin-trapping compound PBN caused a decrease in the level of oxidized protein and an increase in both GS and neutral protease activity in aged Mongolian gerbil brain. In contrast to aged gerbils, PBN treatment of young adult gerbils had no significant effect on brain oxidized protein content or GS activity. Male gerbils, young adults (3 months of age) and retired breeders (15-18 months of age), were treated with PBN for 14 days with twice daily dosages of 32 mg/kg. If PBN administration was ceased after 2 weeks, the significantly decreased level of oxidized protein and increased GS and neutral protease activities in old gerbils changed in a monotonic fashion back to the levels observed in aged gerbils prior to PBN administration. We also report that old gerbils make more errors than young animals and that older gerbils treated with PBN made fewer errors in a radial arm maze test for temporal and spatial memory than the untreated aged controls.

Carney, J.M.; Starke-Reed, P.E.; Oliver, C.N.; Landum, R.W.; Cheng, M.S.; Wu, J.F.; Floyd, R.A. (Univ. of Kentucky, Lexington (USA))

1991-05-01

382

Theoretical studies on the structural and optical properties of a series of Os(II) diimine complexes [Os(N ?N)(CO) 2I 2] (N ?N = 2,2?-bipyridine(bpy), 4,4?-di- tert-butyl-2,2?-bipyridine(dbubpy), 4,4?-dichlorine-2,2?-bipyridine(dclbpy))  

Microsoft Academic Search

The ground- and excited-state structures for a series of Os(II) diimine complexes [Os(N?N)(CO)2I2] (N?N=2,2?-bipyridine (bpy) (1), 4,4?-di-tert-butyl-2,2?-bipyridine (dbubpy) (2), and 4,4?-dichlorine-2,2?-bipyridine (dclbpy) (3)) were optimized by the MP2 and CIS methods, respectively. The spectroscopic properties in dichloromethane solution were predicted at the time-dependent density functional theory (TD-DFT, B3LYP) level associated with the PCM solvent effect model. It was shown that

Yu-Hui Wu; Qing-Jiang Pan; Xin Zhou; Bao-Hui Xia; Tao Liu; Hong-Xing Zhang

2008-01-01

383

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

384

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

385

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

386

Acylated and unacylated ghrelin protect MC3T3-E1 cells against tert-butyl hydroperoxide-induced oxidative injury: pharmacological characterization of ghrelin receptor and possible epigenetic involvement.  

PubMed

Increasing evidence suggests a role for oxidative stress in age-related decrease in osteoblast number and function leading to the development of osteoporosis. This study was undertaken to investigate whether ghrelin, previously reported to stimulate osteoblast proliferation, counteracts tert-butyl hydroperoxide (t-BHP)-induced oxidative damage in MC3T3-E1 osteoblastic cells as well as to characterize the ghrelin receptor (GHS-R) involved in such activity. Pretreatment with ghrelin (10(-7)-10(-11 )M) significantly increased viability and reduced apoptosis of MC3T3-E1 cells cultured with t-BHP (250 ?M) for three hours at the low concentration of 10(-9 )M as shown by MTT assay and Hoechst-33258 staining. Furthermore, ghrelin prevented t-BHP-induced osteoblastic dysfunction and changes in the cytoskeleton organization evidenced by the staining of the actin fibers with Phalloidin-FITC by reducing reactive oxygen species generation. The GHS-R type 1a agonist, EP1572 (10(-7)-10(-11 )M), had no effect against t-BHP-induced cytotoxicity and pretreatment with the selective GHS-R1a antagonist, D-Lys(3)-GHRP-6 (10(-7 )M), failed to remove ghrelin (10(-9) M)-protective effects against oxidative injury, indicating that GHS-R1a is not involved in such ghrelin activity. Accordingly, unacylated ghrelin (DAG), not binding GHS-R1a, displays the same protective actions of ghrelin against t-BHP-induced cytotoxicity. Preliminary observations indicate that ghrelin increased the trimethylation of lys4 on histones H3, a known epigenetic mark activator, which may regulate the expression of some genes limiting oxidative damage. In conclusion, our data demonstrate that ghrelin and DAG promote survival of MC3T3-E1 cell exposed to t-BHP-induced oxidative damage. Such effect is independent of GHS-R1a and is likely mediated by a common ghrelin/DAG binding site. PMID:24705647

Dieci, Elisa; Casati, Lavinia; Pagani, Francesca; Celotti, Fabio; Sibilia, Valeria

2014-07-01

387

Calcium- and CaMKII-dependent chloride secretion induced by the microsomal Ca(2+)-ATPase inhibitor 2,5-di-(tert-butyl)-1,4-hydroquinone in cystic fibrosis pancreatic epithelial cells.  

PubMed Central

Microsomal Ca(2+)-ATPase inhibitors such as thapsigargin (THG), cyclopiazonic acid (CPA) and 2,5-di-(tert-butyl)-1,4-hydroquinone (DBHQ) have been shown to inhibit Ca2+ reuptake by the intracellular stores and increase cytosolic free Ca2+ ([Ca2+]i). DBHQ is a commercially available non-toxic synthetic compound chemically unrelated to THG and CPA. In this study, we tested the feasibility of utilizing DBHQ to improve Cl- secretion via the Ca(2+)-dependent pathway, in the cystic fibrosis (CF)-derived pancreatic epithelial cell line CFPAC-1. DBHQ stimulated 125I efflux and mobilized intracellular free Ca2+ in a dose-dependent manner. The maximal effects were seen at concentrations of 25-50 microM. DBHQ (25 microM) caused a short-term rise in [Ca2+]i in the absence of ambient Ca2+, and a sustained elevation of [Ca2+]i in cell monolayers bathed in the efflux solution (1.2 mM Ca2+), which was largely attenuated by Ni2+ (5 mM). Bath-application of DBHQ induced an outwardly-rectifying whole-cell Cl- current, which was abolished by pipette addition of BAPTA (5 mM) or CaMK [273-302] (20 microM), an inhibitory peptide of multifunctional Ca2+/calmodulin-dependent protein kinase (CaMKII). Pretreatment of monolayers of CFPAC-1 cells with DBHQ for 4-5 min significantly increased the Ca(2+)-independent or autonomous activity of CaMKII assayed in the cell homogenates. Thus, DBHQ appears to enhance Cl- channel activity via a Ca(2+)-dependent mechanism involving CaMKII. Pretreatment of CFPAC-1 cells with up to 50 microM DBHQ for 6 h did not cause any detectable change in cell viability and did not significantly affect the cell proliferation rate. These results suggest that appropriate selective microsomal Ca(2+)-ATPase inhibitors may be therapeutically useful in improving Cl- secretion in CF epithelial cells. Images

Chao, A C; Kouyama, K; Heist, E K; Dong, Y J; Gardner, P

1995-01-01

388

The Ground Spin States of Tris[ p-( N-oxyl- N- tert-butylamino)phenyl] amine, -Methyl, and -Borane. Prospects of Further Studies  

NASA Astrophysics Data System (ADS)

An exploratory study has been carried out on new poly(aminoxyl) radicals as potential bridging ligands for 2 p/3 d-hybrid-spin metal complexes having network structures. Temperature dependence of the magnetic susceptibility data on the title amine N in the range 2-300 K was analyzed to show that its ground state was a doublet with a quartet state lying 559 K (=1.11 kcal mol -1) above the doublet. B3LYP/6-31G *//B3LYP/6-31G computations on a simplified model molecule (N') confirmed the doublet ground state by 0.84 kcal mol -1. The methyl compound (C) is a triplet diradical with a singlet state lying 410 K above the triplet. The hexamethyl derivative (B') of the title borane B has a doublet ground state with an energy gap to a quartet state by 9.9 K. The electronic structures are described qualitatively by p-( N-oxyl- tert-butylamino)phenyl homologues of (·H 2C) 3X in which X=N,C·, and B atoms, and carries two, one, and no ?-electrons, respectively. N and B' showed two reversible redox waves. Mn II(hfac) 2 and C gave a black-violet crystalline complex in which the 3 d and 2 p spins ordered at 60 K.

Itoh, Tetsuji; Matsuda, Kenji; Iwamura, Hiizu; Hori, Kenzi

2001-07-01

389

Synthesis and Characterization of Poly[hexakis((methyl)(4-hydroxyphenoxy))cyclotriphosphazene  

SciTech Connect

The reaction of methylhydroquinone with hexachlorocyclotriphosphazene in the presence of a base, 4-picoline, in cyclohexane was investigated. Nuclear magnetic resonance spectroscopy, multiangle laser light scattering, and elemental analyses were performed on the product and two other related phosphazene materials produced by analogous synthetic routes: poly[hexakis(4-hydroxyphenoxy)cyclotriphosphazene] (1) and hexakis[(3-tert-butyl)(4-hydroxyphenoxy)]cyclotriphosphazene (2). Unlike the data for 2 where the tert-butyl moiety enforced regiospecific nucleophilic addition, the data for the methylhydroquinone-substituted cyclotriphosphazene product indicate that the less sterically bulky methyl group provides only limited protection for the adjacent hydroxyl group. The result is the formation of a low molecular weight oligomer, poly{hexakis[(methyl)(4-hydroxyphenoxy)]cyclotriphosphazene} (3), instead of a discrete cyclic trimer species. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3439-3446, 2001

Luther, Thomas Alan; Stewart, Frederick Forrest; Lash, Robert Paul; Wey, John Edwin; Harrup, Mason Kurt

2001-10-01

390

Structure-activity relationships of the p38alpha MAP kinase inhibitor 1-(5-tert-butyl-2-p-tolyl-2H-pyrazol-3-yl)-3-[4-(2-morpholin-4-yl-ethoxy)naph- thalen-1-yl]urea (BIRB 796).  

PubMed

We report on the structure-activity relationships (SAR) of 1-(5-tert-butyl-2-p-tolyl-2H-pyrazol-3-yl)-3-[4-(2-morpholin-4-yl-ethoxy)naphthalen-1-yl]urea (BIRB 796), an inhibitor of p38alpha MAP kinase which has advanced into human clinical trials for the treatment of autoimmune diseases. Thermal denaturation was used to establish molecular binding affinities for this class of p38alpha inhibitors. The tert-butyl group remains a critical binding element by occupying a lipophilic domain in the kinase which is exposed upon rearrangement of the activation loop. An aromatic ring attached to N-2 of the pyrazole nucleus provides important pi-CH(2) interactions with the kinase. The role of groups attached through an ethoxy group to the 4-position of the naphthalene and directed into the ATP-binding domain is elucidated. Pharmacophores with good hydrogen bonding potential, such as morpholine, pyridine, and imidazole, shift the melting temperature of p38alpha by 16-17 degrees C translating into K(d) values of 50-100 pM. Finally, we describe several compounds that potently inhibit TNF-alpha production when dosed orally in mice. PMID:14561087

Regan, John; Capolino, Alison; Cirillo, Pier F; Gilmore, Thomas; Graham, Anne G; Hickey, Eugene; Kroe, Rachel R; Madwed, Jeffrey; Moriak, Monica; Nelson, Richard; Pargellis, Christopher A; Swinamer, Alan; Torcellini, Carol; Tsang, Michele; Moss, Neil

2003-10-23

391

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

PubMed Central

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

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

2003-01-01

392

Theoretical study of the Michael addition of acetylacetone to methyl vinyl ketone catalyzed by the ionic liquid 1-butyl-3-methylimidazolium hydroxide  

NASA Astrophysics Data System (ADS)

By performing density functional theory calculations, we have investigated the Michael addition of acetylacetone to methyl vinyl ketone in the absence and presence of the ionic liquid 1-butyl-3-methylimidazolium hydroxide ([bmIm]OH). In the absence of ionic liquids, acetylacetone is firstly tautomerized to enol form and then takes place Michael addition to methyl vinyl ketone. As in the catalyzed Michael addition reaction, a bmIm+-OH- ion pair is introduced into the reaction system to model the effect of the ionic liquid environment on the reactivity. The calculated results show that the anion enhances nucleophilic ability of acetylacetone since the OH- anion captures a proton to form an acetylacetone anion-H2O complex, and the cation improves the electrophilic ability of methyl vinyl ketone by forming intermolecular hydrogen-bonds. Both the remarkable effects of the cation and anion on the reactivity of reactants promote this reaction, which take place more easily compared with uncatalyzed reaction. The calculated results show that the main product of the Michael addition is in its ketone form. Our study provides a detailed reaction mechanism of Michael addition catalyzed by basic ionic liquid [bmIm]OH and clearly reveal the catalytic role of ionic liquid in important chemical reaction.

Wei, Xiaofeng; Zhang, Dongju; Zhang, Changqiao; Liu, Chengbu

393

Thermally Switchable Thin Films of an ABC Triblock Copolymer of Poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate)  

SciTech Connect

The thermo-responsive behavior of polymer films consisting of novel linear triblock copolymers of poly(n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate) (PnBuMA-PMMA-P2FEMA) are reported using differential scanning calorimetry (DSC), atomic forcing microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contacting angle (CA) measurements. The surface morphology, wettability and chemical structure of thin films of these triblock copolymers on silicon wafers as a function of temperature have been investigated. It has been shown that the wettability of the films is thermally switchable. Detailed structural analysis shows that thermo-responsive surface composition changes are produced. The underlying mechanism of the thermoresponsive behavior is discussed.

Zhang, Shanju [Georgia Institute of Technology; Liu, Zhan [Georgia Institute of Technology; Bucknall, David G. [Georgia Institute of Technology; He, Lihong [ORNL; Hong, Kunlun [ORNL; Mays, Jimmy [ORNL; Allen, Mark [Georgia Institute of Technology

2011-01-01

394

Solidphase oxidation of 2,4Di tert -butylphenol and 3,6Di tert -butylpyrocatechol in the presence of alkali and alkaline earth metal halides under elastic deformation  

Microsoft Academic Search

Solid-phase oxidation of 2,4-di-tert-butylphenol to give 2,2?,4,4?-tert-butyl-6,6?-bisphenol and of 3,6-di-tert-butylpyrocatechol to afford 3,6-di-tert-butyl-l,2-benzoquinone was performed in the presence of alkali and alkaline earth metals halides under conditions of modified\\u000a extrusion. The formation of the corresponding metal 3,6-di-tert-butylsemiquinolates was registered by ESR method. The different behavior of chlorides, bromides, and iodides was observed\\u000a and rationalized basing on the dissimilar complexing ability

V. B. Vol’eva; A. I. Prokof’ev; I. S. Belostotskaya; A. Yu. Karmilov; N. L. Komissarova; T. I. Prokof’eva; V. V. Ershov

2000-01-01

395

2,4-Di-tert-butyl-6-({[2-(di-methyl-amino)-eth-yl](2-hy-droxy-benz-yl)amino}-meth-yl)phenol  

PubMed Central

The title compound, C26H40N2O2, has both its N atoms in trigonal-pyramidal geometries. The mol­ecular structure is stabilized by O—H?N and C—H?O hydrogen bonds. In the crystal, C—H?? inter­actions lead to the formation of a supramolecular helical chain along the b-axis direction.

Spaleniak, Grzegorz P.; Bisz, Elwira; Bialek, Marzena; Zarychta, Bartosz

2014-01-01

396

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

397

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

398

Bis{(R)-N-[(R)-2-benz-yloxy-1-(4-tert-butyl-phen-yl)eth-yl]-2-methyl-propane-2-sulfinamide} monohydrate  

PubMed Central

The asymmetric unit of the title compound, 2C23H33NO2S·H2O, contains one organic mol­ecule in a general position and one co-crystallized water mol­ecule on a crystallographic twofold axis. Each water mol­ecule serves as a hydrogen-bond donor to a pair of S=O acceptors on symmetry-related mol­ecules. Thus, each trio of mol­ecules forms one title formula unit. These groupings are further connected along [010] via weak non-classical C—H?O hydrogen bonds.

Humes, Charlotte L.; Banker, Tyler J.; Dorn, Stephanie C. M.; Shanahan, James P.; Brennessel, William W.; Weix, Daniel J.

2014-01-01

399

3-tert-Butyl 5-methyl (2R,4S,5R)-2-(4-methoxyphenyl)-4-(3-nitrophenyl)-1,3-oxazolidine-3,5-dicarboxylate  

PubMed Central

The title mol­ecule, C23H26N2O8, was synthesized in three steps starting from m-nitro­cinnamic acid. The central oxazolidine ring adopts an almost perfect envelope conformation with the O atom as the flap [puckering parameter ? = 0.3?(6)°]. The dihedral angle formed by the benzene rings is 61.81?(9)°. In the crystal, mol­ecules are connected into double chains parallel to [010] by C—H?O hydrogen bonds. The absolute configuration was assigned from the synthetic procedure.

Montiel-Smith, Sara; Bernes, Sylvain; Sandoval-Ramirez, Jesus; Meza-Reyes, Socorro; Dubois, Joelle

2012-01-01

400

SIMULATION OF A METHYL TERT-BUTYL ETHER (MTBE) PLUME WITH MODFLOW, MT3D AND THE HYDROCARBON SPILL SCREENING MODEL (HSSM)  

EPA Science Inventory

An MTBE plume in the Upper Glacial Aquifer of Long Island, NY was simulated by combining MODFLOW and MT3D with a semi-analytical model for a gasoline release. The first step was to develop and calibrate a 3-dimensional steady-state numerical ground water flow model of the aquife...

401

(6S)-2,4-Di-tert-butyl-6-[(4S,5R)-3-iso-propyl-4-methyl-5-phenyloxazolidin-2-yl]phenol  

PubMed Central

The title oxazolidine compound, C27H39NO2, was synthesized from N-isopropyl­norephedrine. The dihedral angle between the aromatic rings is 70.33?(5)°. The N atom of the heterocycle is oriented to allow intra­molecular O—H?N hydrogen bonding with the hydr­oxy substituent.

Campbell, Ian Sean; Edler, Kate L.; Parrott, Raleigh W.; Hitchcock, Shawn R.; Ferrence, Gregory M.

2010-01-01

402

(6R)-2-tert-Butyl-6-[(4R,5S)-3-isopropyl-4-methyl-5-phenyl-oxazolidin-2-yl]phenol  

PubMed Central

In the title compound, C23H31NO2, the lone pair on the nitro­gen atom is oriented to facilitate intra­molecular hydrogen bonding with the hydr­oxy group residing on the phenyl substituent. The five-membered ring adopts an envelope confornmation with the O atom at the flap. The absolute stereochemistry was verified by measurement of optical activity using a digital polarimeter.

Koyanagi, Takaoki; Edler, Kate L.; Parrott, Raleigh W.; Hitchcock, Shawn R.; Ferrence, Gregory M.

2010-01-01

403

2,4-Di-tert-butyl-6-({[2-(di-methyl-amino)-eth-yl](2-hy-droxy-benz-yl)amino}-meth-yl)phenol.  

PubMed

The title compound, C26H40N2O2, has both its N atoms in trigonal-pyramidal geometries. The mol-ecular structure is stabilized by O-H?N and C-H?O hydrogen bonds. In the crystal, C-H?? inter-actions lead to the formation of a supramolecular helical chain along the b-axis direction. PMID:24940258

Spaleniak, Grzegorz P; Bisz, Elwira; Bia?ek, Marzena; Zarychta, Bartosz

2014-06-01

404

Epoxide Polymerization and Copolymerization with Carbon Dioxide Using Diethylaluminum Chloride25,27-Dimethoxy-26,28-dihydroxy-p-tert-butyl-Calix[4]arene System as a New Homogeneous Catalyst  

Microsoft Academic Search

Previously unknown substituted chelate phenolatoaluminum chloride, (25,27-dimethoxy-p-tert-butylcalix[4]arene-26,28-diolato) aluminum chloride, was derived from the reaction of diethyl-aluminum chloride and 25,27-dimethoxy-26,28-dihydroxy-p-tert-butylcalix[4]arene at reactants 1:1 mole ratio. It was applied successfully for the polymerization of propylene oxide and cyclohexene oxide, and their copolymerization with carbon dioxide, leading to respective oligomers and co-oligomers. The catalyst structure and the structure of the obtained low-molecular-weight polymers

W. KURAN; T. LISTOS; M. ABRAMCZYK; A. DAWIDEK

1998-01-01

405

5Methyl4 H-1,3-dioxins, new chiral building blocks: transformation into ( R)- and ( S)-4-hydroxymethyl-4-methyl-1,3-dioxolanes via oxidation and rearrangement and determination of the absolute configuration  

Microsoft Academic Search

5-Methyl-4H-1,3-dioxins obtained by asymmetric double-bond isomerization have been transformed into 4-hydroxymethyl-4-methyl-1,3-dioxolanes by m-chloroperbenzoic acid oxidation, ring contraction and reduction. The stereochemical course of this transformation has been studied, while the relative configuration of the intermediate oxidation product and the absolute configuration of the resulting camphanyl ester of 2-tert-butyl-4-hydroxymethyl-4-methyl-1,3-dioxolane was established by X-ray crystallography. From these results, the absolute configuration of

Susanne Flock; Herbert Frauenrath; Carsten Wattenbach

2005-01-01

406

Characterization of Redox States of Ru(OH2)(Q)(tpy)2+ (Q = 3,5-di-tert-butyl-1,2-benzoquinone, tpy = 2,2#:6#,2#-terpyridine)and Related Species through Experimental and Theoretical Studies  

SciTech Connect

The redox states of Ru(OH{sub 2})(Q)(tpy){sup 2+} (Q = 3,5-di-tert-butyl-1,2-benzoquinone, tpy = 2,2':6',2''-terpyridine) are investigated through experimental and theoretical UV-vis spectra and Pourbaix diagrams. The electrochemical properties are reported for the species resulting from deprotonation and redox processes in aqueous solution. The formal oxidation states of the redox couples in the various intermediate complexes are systematically assigned using electronic structure theory. The controversy over the electronic assignment of ferromagnetic vs. antiferromagnetic coupling is investigated through comparison of ab initio methods and the broken-symmetry density functional theory (DFT) approach. The various pK{sub a} values and reduction potentials, including the consideration of proton-coupled electron-transfer (PCET) processes, are calculated, and the theoretical version of the Pourbaix diagram is constructed in order to elucidate and assign several previously ambiguous regions in the experimental diagram.

Muckerman, J.T.; Tsai, M.-K.; , Rochford, J.; Polyansky, D.E.; Wada, T.; Tanaka, K.; Fujita, E.

2009-04-27

407

Octyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(4-chlorophenyl)-1H-benzimidazole-5-carboxylate: complex sheets built from N-H...N, C-H...N and C-H...O hydrogen bonds.  

PubMed

In the title compound, C29H35ClN4O2, the bond lengths provide evidence for aromatic delocalization in the pyrazole ring but bond fixation in the fused imidazole ring, and the octyl chain is folded, rather than adopting an all-trans chain-extended conformation. A combination of N-H...N, C-H...N and C-H...O hydrogen bonds links the molecules into sheets, in which the hydrogen bonds occupy the central layer with the tert-butyl and octyl groups arranged on either side, such that the closest contacts between adjacent sheets involve only the octyl groups. Comparisons are made with the supramolecular assembly in some simpler analogues. PMID:24898969

Cortés, Edwar; Abonía, Rodrigo; Cobo, Justo; Glidewell, Christopher

2014-06-15

408

Cell death induced by the phenolic antioxidant tert-butylhydroquinone and its metabolite tert-butylquinone in human monocytic leukemia U937 cells  

Microsoft Academic Search

2-tert-Butyl-4-hydroquinone (TBHQ), a phenolic antioxidant used as a food additive, and its metabolite 2-tert-butyl-1,4-benzoquinone (TBQ) were both cytotoxic in human monocytic leukemia U937 cells, TBQ being the more strongly cytotoxic. Both compounds induced caspase activity towards DEVD-MCA as a substrate and the cleavage of poly(ADP-ribose) polymerase in cells. Enzyme activities of caspase-3,-7,-6 and -9 seemed to be induced, and procaspases-3

T Okubo; Y Yokoyama; K Kano; I Kano

2003-01-01

409

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.

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

410

Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (HPMBP) and diphenyl sulfoxide (DPSO), tri-n-butyl phosphate (TBP) or tri-n-octylphosphine oxide (TOPO)  

Microsoft Academic Search

Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and oxo donors with widely varying basicity, viz. diphenyl sulfoxide (DPSO), tri-n-butyl phosphate (TBP) and tri-n-octylphosphine-oxide (TOPO) has been studied at various fixed temperatures. Results indicate that the equilibrium constants in the organic phase for addition reactions (KS) with these donors follow their order of basicity (KH) viz. DPSO (0.033)TOPO (8.9) with

S. A. Pai; M. S. Subramanian

1985-01-01

411

New reactions of N-tert-butylimines; formation of N-heterocycles by methyl radical elimination on flash vacuum thermolysis of N-benzylidene- and N-(2-pyridylmethylidene)-tert-butylamines.  

PubMed

Thermal reactions of N-benzylidene- and N-(2-pyridylmethylidene)-tert-butylamines (5 and 13) under FVT conditions have been investigated. Unexpectedly, at 800?°C, compound 5 yields 1,2-dimethylindole and 3-methylisoquinoline. In the reaction of 13 at 800?°C, 3-methylimidazo[1,5-a]pyridine was obtained as the major product. Mechanisms of these reactions have been proposed on the basis of DFT calculations. Furthermore, UV-photoelectron spectroscopy combined with FVT has been applied for direct monitoring and characterization of the thermolysis products in situ. PMID:24108670

Vu, Thien Y; Chrostowska, Anna; Huynh, Thi Kieu Xuan; Khayar, Saïd; Dargelos, Alain; Justyna, Katarzyna; Pasternak, Beata; Le?niak, Stanis?aw; Wentrup, Curt

2013-10-25

412

Sensitive valence structures of [(pap)(2)Ru(Q)](n) (n = +2, +1, 0, -1, -2) with two different redox noninnocent ligands, Q = 3,5-Di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine and pap = 2-phenylazopyridine.  

PubMed

The complexes [(pap)(2)Ru(Q)]ClO(4), [1]ClO(4)-[4]ClO(4), with two different redox noninnocent ligands, Q = 3,5-di-tert-butyl-N-aryl-1,2-benzoquinonemonoimine (-aryl = m-(Cl)(2)C(6)H(3) (1(+)), C(6)H(5) (2(+)), m-(OCH(3))(2)C(6)H(3) (3(+)), and m-((t)Bu)(2)C(6)H(3) (4(+))) and pap = 2-phenylazopyridine, have been synthesized and characterized using various analytical techniques. The single-crystal X-ray structure of the representative [2]ClO(4).C(7)H(8) exhibits multiple intermolecular C-H...O hydrogen bondings and C-H...pi interactions. The C1-O1 = 1.287(4) (density functional theory, DFT, 1.311) and C6-N1 = 1.320(4) (DFT, 1.353) A and intraring bond distances associated with the sensitive quinine (Q) moiety along with the azo(pap) bond distances, N3-N4 = 1.278(4) (DFT, 1.297) and N6-N7 = 1.271(4) (DFT, 1.289) A, in 2(+) justify the [(pap)(2)Ru(II)(Q(*-))](+) valence configuration at the native state of 1(+)-4(+). Consequently, Mulliken spin densities on Q, pap, and Ru in 2(+) are calculated to be 0.8636, 0.1040, and 0.0187, respectively, and 1(+)-4(+) exhibit free radical sharp EPR spectra and one weak and broad transition around 1000 nm in CH(3)CN due to interligand transition involving a singly occupied molecular orbital (SOMO) of Q(*-) and the vacant pi* orbital of pap. Compounds 1(+)-4(+) undergo a quasi-reversible oxidation and three successive reductions. The valence structure of the electron paramagnetic resonance (EPR)-inactive oxidized state in 1(2+)-4(2+) has been established as [(pap)(2)Ru(II)(Q degrees )](2+) instead of the alternate formalism of antiferromagnetically coupled [(pap)(2)Ru(III)(Q(*-))](2+) on the basis of the DFT calculations on the optimized 2(+), which predict that the singly occupied molecular orbital is primarily composed of Q with 77% contribution. Accordingly, the optimized structure of 2(2+) predicts shorter C1-O1 (1.264) and C6-N1 (1.317 A) distances and longer Ru1-O1 (2.080) and Ru1-N1 (2.088 A) distances. Compounds 1(2+)-4(2+) exhibit the lowest energy transitions around 600 nm, corresponding to Ru(dpi)/Q(pi) --> pap(pi*). The presence of two sets of strongly pi-acceptor ligands, pap and Q, in 1(2+)-4(2+) stabilizes the Ru(II) state to a large extent such that the further oxidation of {Ru(II)-Q degrees } --> {Ru(III)-Q degrees } has not been detected within +2.0 V versus a saturated calomel electrode. The EPR-inactive reduced states 1-4 have been formulated as [(pap)(2)Ru(II)(Q(2-))] over the antiferromagnetically coupled alternate configuration, [(pap)(pap(*-))Ru(II)(Q(*-))]. The optimized structure of 2 predicts sensitive C1-O1 and C6-N1 bond distances of 1.337 and 1.390 A, respectively, close to the doubly reduced Q(2-) state, whereas the N horizontal lineN distances of pap, N3-N4 = 1.299 and N6-N7 = 1.306 A, remain close to the neutral state. In corroboration with the doubly reduced Q(2-) state, 1-4 exhibit a moderately strong interligand pi(Q(2-)) --> pi*(pap) transition in the near-IR region near 1300 nm. The subsequent two reductions are naturally centered around the azo functions of the pap ligands. PMID:19769396

Das, Dipanwita; Mondal, Tapan Kumar; Mobin, Shaikh M; Lahiri, Goutam Kumar

2009-10-19

413

Unexpected dilatation of the common bile duct after methyl tertiary butyl ether (MTBE) in rabbits. Possible implications to findings in man.  

PubMed Central

Methyl tertiary butyl ether (MTBE) rapidly dissolves cholesterol gall stones in vitro and in vivo. To further characterise tolerability and safety of this aliphatic ether, either MTBE (1 ml/kg body wt daily for two days) or an equal amount of saline was infused into the common bile duct (CBD) of eight cholecystectomised rabbits. Transient vomiting, dyspnoea and somnolence developed during MTBE instillation. Post-treatment values of serum transaminases and alkaline phosphatase were significantly higher in MTBE than in saline treated animals. Cholangiography one week after the last intraductal infusion showed a five-fold increase of CBD size in MTBE v control rabbits. At autopsy histological signs of chemical cholangitis and mild duodenitis were noted in MTBE treated animals. Prompted by these findings, we performed a cholangiography in two patients who had received intraductal MTBE (about 0.2 ml/kg body wt daily for one or two days) one year before: an abnormal dilatation of the CBD was present, which might represent a specific, hitherto undescribed permanent sequela of MTBE administration. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4

Tritapepe, R; Pozzi, C; Caspani, P; Di Padova, C

1989-01-01

414

Comparative analysis of skin sensitization potency of acrylates (methyl acrylate, ethyl acrylate, butyl acrylate, and ethylhexyl acrylate) using the local lymph node assay.  

PubMed

There are currently available no systematic experimental data on the skin sensitizing properties of acrylates that are of relevance in occupational settings. Limited information from previous guinea-pig tests or from the local lymph node assay (LLNA) is available; however, these data are incomplete and somewhat contradictory. For those reasons, we have examined in the LLNA 4 acrylates: butyl acrylate (BA), ethyl acrylate (EA), methyl acrylate (MA), and ethylhexyl acrylate (EHA). The LLNA data indicated that all 4 compounds have some potential to cause skin sensitization. In addition, the relative potencies of these acrylates were measured by derivation from LLNA dose-response analyses of EC3 values (the effective concentration of chemical required to induce a threefold increase in proliferation of draining lymph node cells compared with control values). On the basis of 1 scheme for the categorization of skin sensitization potency, BA, EA, and MA were each classified as weak sensitizers. Using the same scheme, EHA was considered a moderate sensitizer. However, it must be emphasized that the EC3 value for this chemical of 9.7% is on the borderline between moderate (<10%) and weak (>10%) categories. Thus, the judicious view is that all 4 chemicals possess relatively weak skin sensitizing potential. PMID:17868217

Dearman, Rebecca J; Betts, Catherine J; Farr, Craig; McLaughlin, James; Berdasco, Nancy; Wiench, Karin; Kimber, Ian

2007-10-01

415

Physiologically based pharmacokinetic rat model for methyl tertiary-butyl ether; comparison of selected dose metrics following various MTBE exposure scenarios used for toxicity and carcinogenicity evaluation.  

PubMed

There are a number of cancer and toxicity studies that have been carried out to assess hazard from methyl tertiary-butyl ether (MTBE) exposure via inhalation and oral administration. MTBE has been detected in surface as well as ground water supplies which emphasized the need to assess the risk from exposure via drinking water contamination. This model can now be used to evaluate route-to-route extrapolation issues concerning MTBE exposures but also as a means of comparing potential dose metrics that may provide insight to differences in biological responses observed in rats following different routes of MTBE exposure. Recently an updated rat physiologically based pharmacokinetic (PBPK) model was published that relied on a description of MTBE and its metabolite tertiary-butyl alcohol (TBA) binding to alpha 2u-globulin, a male rat-specific protein. This model was used to predict concentrations of MTBE and TBA in the kidney, a target tissue in the male rat. The objective of this study was to use this model to evaluate the dosimetry of MTBE and TBA in rats following different exposure scenarios, used to evaluate the toxicity and carcinogenicity of MTBE, and compare various dose metrics under these different conditions. Model simulations suggested that although inhalation and drinking water exposures show a similar pattern of MTBE and TBA exposure in the blood and kidney (i.e. concentration-time profiles), the total blood and kidney levels following exposure of MTBE to 7.5mg/ml MTBE in the drinking water for 90 days is in the same range as administration of an oral dose of 1000 mg/kg MTBE. Evaluation of the dose metrics also supports that a high oral bolus dose (i.e. 1000 mg/kg MTBE) results in a greater percentage of the dose exhaled as MTBE with a lower percent metabolized to TBA as compared to dose of MTBE that is delivered over a longer period of time as in the case of drinking water. PMID:20561556

Borghoff, Susan J; Parkinson, Horace; Leavens, Teresa L

2010-09-10

416

Synthesis and molecular structures of titanocene, zirconocene, and uranocene dichlorides containing 1,2-di- tert-butylcyclopentadienyl ligands  

Microsoft Academic Search

The 1,2-di-tert-butylcyclopentadienyl anion (1) has been used to prepare 1,1?,2,2?-tetra-tert-butyltitanocene dichloride (5), 1,1?,2,2?-tetra-tert-butylzirconocene dichloride (6), and 1,1?,2,2?-tetra-tert-butyluranocene dichloride (7). The bent metallocene structures of 5–7 have been confirmed by X-ray crystallography, and illustrate that the 1,2-di-tert-butylcyclopentadienyl ligands are arranged with all four tert-butyl groups in the open part of the wedge between the two canted cyclopentadienyl rings, but that steric

Russell P. Hughes; Jeffrey R. Lomprey; Arnold L. Rheingold; Brian S. Haggerty; Glenn P. A. Yap

1996-01-01

417

(?)-(4aR,5R,8S,8aR)-8-(tert-Butyl-dimethyl-sil-yloxy)-2,5,8a-trimethyl-4a,5,8,8a-tetra-hydro-naphthalene-1,4-dione  

PubMed Central

In the title compound, C19H30O3Si, both rings adopt a half-boat conformation. Overall, the mol­ecule approximates a U-shape as the cyclo-2-ene-1,4-dione and butyl­dimethyl­sil­yloxy substituents lie to the same side of the central cyclo­hexene ring; the methyl substituent lies to the other side of the mol­ecule. In the crystal, linear supra­molecular chains along the b axis are sustained by C—H?O inter­actions.

Delling, Felix N.; Zukerman-Schpector, Julio; Brocksom, Timothy J.; Brocksom, Ursula; Finelli, Fernanda G.; Tiekink, Edward R. T.

2013-01-01

418

Controlled human exposure to methyl tertiary butyl ether in gasoline: symptoms, psychophysiologic and neurobehavioral responses of self-reported sensitive persons.  

PubMed Central

The 1990 Clean Air Act mandated oxygenation of gasoline in regions where carbon monoxide standards were not met. To achieve this standard, methyl tertiary butyl ether (MTBE) was increased to 15% by volume during winter months in many locations. Subsequent to the increase of MTBE in gasoline, commuters reported increases in symptoms such as headache, nausea, and eye, nose, and throat irritation. The present study compared 12 individuals selected based on self-report of symptoms (self-reported sensitives; SRSs) associated with MTBE to 19 controls without self-reported sensitivities. In a double-blind, repeated measures, controlled exposure, subjects were exposed for 15 min to clean air, gasoline, gasoline with 11% MTBE, and gasoline with 15% MTBE. Symptoms, odor ratings, neurobehavioral performance on a task of driving simulation, and psychophysiologic responses (heart and respiration rate, end-tidal CO(2), finger pulse volume, electromyograph, finger temperature) were measured before, during, and immediately after exposure. Relative to controls, SRSs reported significantly more total symptoms when exposed to gasoline with 15% MTBE than when exposed to gasoline with 11% MTBE or to clean air. However, these differences in symptoms were not accompanied by significant differences in neurobehavioral performance or psychophysiologic responses. No significant differences in symptoms or neurobehavioral or psychophysiologic responses were observed when exposure to gasoline with 11% MTBE was compared to clean air or to gasoline. Thus, the present study, although showing increased total symptoms among SRSs when exposed to gasoline with 15% MTBE, did not support a dose-response relationship for MTBE exposure nor the symptom specificity associated with MTBE in epidemiologic studies. Images Figure 1 Figure 2

Fiedler, N; Kelly-McNeil, K; Mohr, S; Lehrer, P; Opiekun, R E; Lee, C; Wainman, T; Hamer, R; Weisel, C; Edelberg, R; Lioy, P J

2000-01-01

419

Molecular recognition at methyl methacrylate/n-butyl acrylate (MMA/nBA) monomer unit boundaries of phospholipids at p-MMA/nBA copolymer surfaces.  

PubMed

Lipid structural features and their interactions with proteins provide a useful vehicle for further advances in membrane proteins research. To mimic one of potential lipid-protein interactions we synthesized poly(methyl methacrylate/ n-butyl acrylate) (p-MMA/nBA) colloidal particles that were stabilized by phospholipid (PLs). Upon the particle coalescence, PL stratification resulted in the formation of surface localized ionic clusters (SLICs). These entities are capable of recognizing MMA/nBA monomer interfaces along the p-MMA/nBA copolymer backbone and form crystalline SLICs at the monomer interface. By utilizing attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy and selected area electron diffraction (SAD) combined with ab initio calculations, studies were conducted that identified the origin of SLICs as well as their structural features formed on the surface of p-MMA/nBA copolymer films stabilized by 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) PL. Specific entities responsible for SLIC formation are selective noncovalent bonds of anionic phosphate and cationic quaternary ammonium segments of DLPC that interact with two neighboring carbonyl groups of nBA and MMA monomers of the p-MMA/nBA polymer backbone. To the best of our knowledge this is the first example of molecular recognition facilitated by coalescence of copolymer colloidal particles and the ability of PLs to form SLICs at the boundaries of the neighboring MMA and nBA monomer units of the p-MMA/nBA chain. The dominating noncovalent bonds responsible for the molecular recognition is a combination of H-bonding and electrostatic interactions. PMID:18693704

Yu, Min; Urban, Marek W; Sheng, Yinghong; Leszczynski, Jerzy

2008-09-16

420

Electrophysiological actions of N-[1-[4-(4-fluorophenoxy)butyl]-4-piperidinyl]- N-methyl-2-benzothiazolamine (R56865) on CA1 neurons of the rat hippocampal slice during hypoxia  

Microsoft Academic Search

The electrophysiological effects of N-[1-[4-(4-fluorophenoxy)butyl]-4-piperidinyl]-N-methyl-2-benzothiazolamine (R56865), a drug which protects heart cells from ischemia-induced arrhythmias, was studied on intracellularly-recorded CA1 neurons of the rat hippocampal slice under normal or hypoxic conditions. On normoxic cells R56865 (1 ?M) reduced firing accommodation without changing passive membrane properties, spike characteristics or synaptic transmission. On hypoxic cells R56865 selectively reduced the amplitude of hypoxia-induced

M Barbieri; A Nistri

1999-01-01

421

New Poly(methyl methacrylate)\\/n-Butyl Acrylate\\/Pentafluorostyrene\\/Poly(ethylene glycol) (pMMA\\/nBA\\/PFS\\/PEG) Colloidal Dispersions: Synthesis, Film Formation, and Protein Adsorption  

Microsoft Academic Search

A new family of water-dispersible colloidal particles composed of poly(methyl methacrylate\\/n-butyl acrylate\\/pentafluorostyrene\\/poly(ethylene glycol) dimethacrylate) (p-MMA\\/nBA\\/PFS\\/PEG) copolymers which coalesce at room temperature was developed using free radical emulsion polymerization. These stable colloidal dispersions contain up to 30% w\\/w PEG and 35% w\\/w PFS and exhibit core-shell morphologies that consist of the p-MMA\\/nBA\\/PFS core and the PEG shell. Incorporation of PFS not

Marek W. Urban; William L. Jarrett

2009-01-01

422

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

423

The redox series [M(bpy)2(q)]n+, M = Ru or Os, Q = 3,5-di-tert-butyl-n-phenyl-1,2-benzoquinonemonoimine. Isolation and a complete X and W band EPR study of the semiquinone states (n = 1).  

PubMed

The complexes [M(bpy)(2)(Q)](PF(6)) (bpy = 2,2'-bipyridyl; M = Ru, Os; Q = 3,5-di-tert-butyl-N-phenyl-1,2-benzoquinonemonoimine) were isolated and studied by X and W band EPR in a dichloromethane solution at ambient temperatures and at 4 K. For M = Ru, the (14)N hyperfine splitting confirms the Ru(II)/semiquinone formulation, although at a > 1 mT, the (99,101)Ru satellite coupling is unusually high. W band EPR allowed us to determine the relatively small g anisotropy Delta g = g(1) - g(3) = 0.0665 for the ruthenium complex. The osmium analogue exhibits a much higher difference Delta g = 0.370, which is attributed not only to the larger spin-orbit coupling constant of Os versus that of Ru but also to a higher extent of metal contribution to the singly occupied molecular orbital. The difference Delta E between the oxidation and reduction potentials of the radical complexes is larger for the ruthenium compound (Delta E = 0.87 V) than for the osmium analogue (Delta E = 0.72), confirming the difference in metal/ligand interaction. The electrochemically generated states [M(bpy)(2)(Q)](n+), n = 0, 1, 2, and 3, were also characterized using UV-vis-near-infrared spectroelectrochemistry. PMID:15819573

Ye, Shengfa; Sarkar, Biprajit; Duboc, Carole; Fiedler, Jan; Kaim, Wolfgang

2005-04-18

424

The synthesis, characterization and spectral studies of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes with N,Nbis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl) methyl]amino}butyl) N?,N?-dihydroxyethanediimidamide  

Microsoft Academic Search

Co, Ni, Cu, Zn and Cd complexes of N,N-bis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl)methyl]amino}butyl)N?,N?-dihydroxyethanediimidamide (LH2) were synthesized and characterized by elemental analyses, IR, H- and C-NMR spectra, electronic spectra, magnetic susceptibility measurements, conductivity measurements and thermogravimetric analyses (TGA). The Co, Ni and Cu complexes of LH2 were synthesized with 1?:?2 metal ligand stoichiometry. Zn and Cd complexes with LH2 have a metal ligand ratio of

E. Canpolat; M. Kaya

2005-01-01

425

The preparation, characterization and X-ray structural analysis of tetrakis [1-methyl-3-(2-propyl)-2(3 H )-imidazolethione]zinc(II) tetrafluoroborate and tetrakis [1-methyl-3-(1-butyl)-2(3 H )- imidazolethione]zinc(II) tetrafluoroborate  

Microsoft Academic Search

Two compounds, [Zn(mipit)4][BF4]2 (1) and [Zn(mnbit)4][BF4]2 (2) have been synthesized and characterized via standard solid and solution state methods including single crystal X-ray crystallography (mipit: 1-methyl-3-(2-propyl)-2(3H)-imidazolethione and mnbit: 1-methyl-3-(1-butyl)-2(3H)-imidazolethione). Compound 1 crystallizes in monoclinic space group P21\\/n with a = 11.804(2) , b = 16.710(3) , c = 25.763(5) , ? = 90.14(3) and Z = 4, whereas compound 2 crystallizes in tetragonal

Daniel J. Williams; Javier J. Concepcion; Marina C. Koether; Kimberly A. Arrowood; Angela L. Carmack; Tiffany G. Hamilton; Stacy M. Luck; Madeleine Ndomo; C. Ryan Teel; Donald VanDerveer

2006-01-01

426

Co(II) and Cu(II) Schiff base complexes of bis( N -(4-diethylamino-2-methylphenyl)-3,5-di- tert -butylsalicylaldimine): Electrochemical and X-ray structural study  

Microsoft Academic Search

Copper(II) and cobalt(II) complexes of salicylaldimine obtained by the condensation of N,N-diethyl-2-methyl-1,4-phenylenediamine with 3,5-di-tert-butyl-2-hydroxybenzaldehyde have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements,\\u000a cyclic voltammetry, and FT-IR and UV–Vis spectroscopy. The molecular structure of the title copper(II) complex was determined\\u000a by the single crystal X-ray diffraction technique. The Cu(II) center is coordinated by four atoms of the donor

Mahmut Ulusoy; Hasan Karab?y?k; Rafet K?l?nçarslan; Muhittin Aygün; Bekir Çetinkaya; Santiago García-Granda

2008-01-01

427

Mass spectrometric evaluation of the tert.-butyldimethylsilyl derivatives of monohydroxyeicosatetraenoic acids and leukotrienes.  

PubMed

The tert.-butyldimethylsilyl (t-BDMS) derivatives of the hydroxyl and the carboxyl groups on the monohydroxyeicosatetraenoic acids (HETEs) 5-, 12- and 15-hydroxyeicosatetraenoic acid (5-HETE, 12-HETE and 15-HETE, respectively) as well as leukotriene B4 (LTB4), 20-carboxy-LTB4 (20-COOH-LTB4) and 20-hydroxy-LTB4 (20-OH-LTB4) have been prepared. The derivatization reagents N-methyl-N-tert.-butyldimethylsilyltrifluoroacetamide (MTBSTFA) and tert.-butyldimethylsilylimidazole (t-BDMSIM) were utilized and the derivatization yields evaluated by gas chromatographic analysis. While the derivatization of 12-HETE and 15-HETE was achieved with good yield using MTBSTFA, the 5-hydroxylated compounds could only be derivatized satisfactorily with t-BDMSIM. The t-BDMS ester derivatives of monohydroxy fatty acids and 20-COOH-LTB4 were found quite susceptible to hydrolysis upon attempted isolation. The mass spectrometric fragmentation patterns of the HETEs, LTB4, 20-COOH-LTB4 and 20-OH-LTB4 and their reduced analogues as the t-BDMS ester and ether derivatives were examined. The fragmentation of the unsaturated compounds was mainly influenced by the double bonds while, on the contrary, the saturated compounds showed intense high-mass ions derived from elimination of a tert.-butyl radical. Furthermore, it was observed that the t-BDMS ester moiety of the unsaturated compounds exerted certain influence upon the fragmentation pattern. With regard to earlier results obtained with the methyl ester t-BDMS ether derivative, it was demonstrated that the use of the t-BDMS ester derivative resulted in decreased intensities of high-mass ions with a few exceptions. Taking into account the mass spectrometric fragmentation and the poor hydrolytic stability of the t-BDMS ester derivatives of some of the studied compounds, the use of these derivatives was not found to constitute a major advantage over the use of the methyl ester derivative. However, a favourable fragmentation pattern with a very intense high-mass ion was obtained for 15-HETE and the levels of this compound were determined in human lung tissue samples. PMID:3443640

Steffenrud, S; Borgeat, P; Evans, M J; Bertrand, M J

1987-12-25

428

Preparation and Baeyer-Villiger Reaction of certain 2-carbalkoxycyclopropyl methyl ketones.  

PubMed

Treatment of mixed anhydrides derived from cis- and trans-2-carbobenzyloxycyclopropanecarboxylic acids and ethyl chloroformate with ethoxymagnesio di-tert-butyl malonate and subsequent treatment of the resulting adducts with p-toluenesulfonic acid afforded cis- and trans-benzyl-2-acetylcyclopropanecarboxylates in good to excellent yields, with retention of the original stereochemistry of the systems. These methyl ketones and an open chain congener, benzyl levulinate, were inert toward m-chloroperbenzoic acid. The cis-isomer and benzyl levulinate underwent normal Baeyer-Villiger reactions mediated by trifluoroperacetic acid, forming moderate yields of the acetate ester insertion products. PMID:1133733

Cannon, J G; Garst, J E

1975-06-01

429

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. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24481588

Wróbel, Anna Maria; Gregoraszczuk, Ewa ?ucja

2014-09-01

430

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

431

Tert-butylhydroquinone as a phenolic activator of nrf2 antagonizes arsenic-induced oxidative cytotoxicity but promotes arsenic methylation and detoxication in human hepatocyte cell line.  

PubMed

Oxidative stress plays crucial roles in exerting a variety of damages upon arsenic exposure. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a master transcriptional regulator protecting cells and tissues from oxidative injuries. The objective of this study was to test whether tert-butylhydroquinone (tBHQ), a well-known synthetic Nrf2 inducer, could protect human hepatocytes against arsenic-induced cytotoxicity and oxidative injuries. Our results showed that 5 and 25 ?mol/l tBHQ pretreatment suppressed the arsenic-induced hepatocellular cytotoxicity, reactive oxygen species generation, and hepatic lipid peroxidation, while relieved the arsenic-induced disturbances of intracellular glutathione balance. In addition, we also observed that tBHQ treatment promoted the arsenic biomethylation process and upregulated Nrf2-regulated downstream heme oxygenase-1 and NADPH: quinine oxidoreductase 1 mRNA expressions. Collectively, we suspected that Nrf2 signaling pathway may be involved in the protective effects of tBHQ against arsenic invasion in hepatocytes. These data suggest that phenolic Nrf2 inducers, such as tBHQ, represent novel therapeutic or dietary candidates for the population at high risk of arsenic poisoning. PMID:24970285

Duan, Xiaoxu; Liu, Dan; Xing, Xiaoyue; Li, Jinlong; Zhao, Shuo; Nie, Huifang; Zhang, Yang; Sun, Guifan; Li, Bing

2014-08-01

432

Recovery of anhydrous Na{sub 2}SO{sub 4} from SO{sub 2}-scrubbing liquor by extractive crystallization: Liquid-liquid equilibria for aqueous solutions of sodium carbonate, sulfate, and/or sulfite plus acetone, 2-propanol, or tert-butyl alcohol  

SciTech Connect

Sodium carbonate is a superior scrubbing agent for removing SO{sub 2} from combustion gases, but the resulting sodium sulfate (or sulfite) must be recovered for environmental reasons. Recovery by evaporative crystallization is energy-intensive; extractive crystallization provides an attractive alterative when technically feasible. Liquid/liquid equilibrium data were determined for two-phase mixtures containing aqueous solutions of sodium carbonate, sulfate, or sulfite and a polar organic solvent: acetone, 2-propanol, and 2-methylpropan-1-ol (i.e., tert-butyl alcohol). In the salt-saturated two-phase region, data were obtained between the lower consolute temperature and 60 C (50 C for acetone). data were also obtained at 35 C for liquid/liquid systems that were subsaturated with their respective salts and for liquid/liquid systems with overall molar ratios of sodium sulfite/sodium sulfate fixed at 25/75, 50/50, and 75/25. In the latter systems, it was found that the sulfite/sulfate ratios in the organic and aqueous phases were the same, i.e., there is no selectivity by these solvents for one salt relative to the other. The data show that any one of these solvents can be used to extract water from a concentrated solution of either sodium sulfite or sodium sulfate in a countercurrent extractor at 35 C, causing the anhydrous salt to crystallize. The wet solvent can be dried for recycle in a similar countercurrent operation at 35 C, using a saturated solution of Na{sub 2}CO{sub 3} as the drying agent. The number of moles of carbonate required for drying does not exceed the number of moles of sulfite-plus-sulfate precipitated. The process energy is about 0% of that required for single-stage evaporative crystallization of the same liquor.

Lynn, S.; Cos, R.; Prausnitz, J.M. [Univ. of California, Berkeley, CA (United States). Ept. of Chemical Engineering] [Univ. of California, Berkeley, CA (United States). Ept. of Chemical Engineering; [Lawrence Berkeley National Lab., CA (United States); Schiozer, A.L. [Unilever, Valhinds (Brazil)] [Unilever, Valhinds (Brazil); Jaecksch, W.L. [Merck, West Point, PA (United States)] [Merck, West Point, PA (United States)

1996-11-01

433

Molecular Engineering of Liquid Crystal Polymers by Living Polymerization. 16. Tailor-Made sC* Mesophase in Copolymers of 4-((S(-)-2-Methyl-1-Butyl)Oxycarbonyl)-4'-(omega-Oxyalkyl-1-Vinyl Ether)Biphenyl With Undecanyl and Octyl Alkyl Groups.  

National Technical Information Service (NTIS)

The synthesis and living cationic polymerization of 4-((S(-)-2-methyl-1-butyl)oxycarbonyl)-4'-(8-oxyoctyl-1-vinyl ether)biphenyl are described. Polymers with degree of polymerization lower than 40 and polydispersities were synthesized and characterized by...

M. Lee Q. Zheng V. Percec

1991-01-01

434

Contribution of oxygen radicals to DNA cleavage by quinone compounds derived from phenolic antioxidants, tert-butylhydroquinone and 2,5-di-tert-butylhydroquinone  

Microsoft Academic Search

The effects of synthetic phenolic antioxidants, tert-butylhydroquinone (TBHQ), 2,5-di-tert-butylhydroquinone (DTBHQ) and 3-tert-butyl-4-hydroxyanisole (BHA), on DNA cleavage were examined with supercoiled plasmid DNA, pUC18, in vitro. Extensive single and double strand breaks of DNA by TBHQ were observed and almost all the DNA was converted to the linear form at 10?2 M. The cleavage was stimulated by both CuCl2 and FeCl2,

Tomoko Okubo; Fumiko Nagai; Keiko Ushiyama; Itsu Kano

1997-01-01

435

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

436

Structure and spectral properties of a squarylium dye, 2,4-bis((1-n-butyl-2(1H)-quinolylidene)methyl)-1,3-cyclobutadienediylium-1,3-diolate  

SciTech Connect

Structural and spectral characterizations of the title compound, 2,4-bis((1-n-butyl-2(1H)-quinolylidene)methyl)-1,3-cyclobutadienediylium-1,3-diolate (BQMS), a prime candidate for a solar energy material, have been carried out. Crystals are monoclinic, P2/sub 1//n with a = 9.586 (2) A, b = 9.730 (2) A, c = 13.894 (3) A, ..beta.. = 99.77 (9)/sup 0/, and Z = 2. The structure has been solved by direct methods and refined by using 1078 reflections for which F > 2 sigma (F) with anisotropic temperature factors on the non-hydrogen atoms to R = 0.098 and R/sub w/ = 0.074. Quasi-metallic reflection is observed along both principal directions for the (101) and (001) faces. The transition moment is found to be polarized along the long axis of the molecule. 16 references, 5 figures, 1 table.

Bernstein, J.; Tristani-Kendra, M.; Eckhardt, C.J.

1986-03-13

437

3-(4-Bromo-phen-yl)-1-butyl-5-[1-(2-chloro-6-methyl-phen-yl)-1H-tetra-zol-5-yl]imidazolidine-2,4-dione  

PubMed Central

In the title mol­ecule, C21H20BrClN6O2, the chloro-substituted benzene ring forms a dihedral angle of 77.84?(7)° with the tetra­zole ring and the bromo-substituted ring forms a dihedral angle of 43.95?(6)° with the imidazole ring. The dihedral angle between the tetra­zole and imidazole rings is 67.42?(8)°. The terminal methyl group of the butyl substituent is disordered over two sets of sites, with refined occupancies 0.67?(3) and 0.33?(3). In the crystal, there is a short Br?N contact of 3.183?(2)?Å.

Hall, Gabriel B.; Medda, Federico; Roberts, Sue A.; Hulme, Christopher

2013-01-01

438

Improved synthesis of three methyl-branched pheromone components produced by the female lichen moth.  

PubMed

Female moths of Lyclene dharma dharma (Arctiidae, Lithosiinae) produce a novel sex pheromone composed of three methyl-branched ketones: 6-methyl-2-octadecanone (I), 14-methyl-2-octadecanone (II), and 6,14-dimethyl-2-octadecanone (III). Their structures were confirmed by syntheses accomplished by a different route for each component. In order to obtain a sufficient amount of the synthetic pheromone, we developed new routes via methyl-branched 1-alkenes: 6-methyl-1-octadecene (1), 14-methyl-1-octadecene (2), and 6,14-dimethyl-1-octadecene (3). Compound 1 was synthesized by coupling between a C(10)-chain bromide and a 3-methyl-branched C(8) unit (A) prepared from 3-methyl-1,5-pentanediol, 2, by coupling between a C(11)-chain bromide and a 3-methyl-branched C(7) unit (B) prepared from 2-hexanone, and 3, by connecting A and B, using propargyl alcohol as a C(3) linchpin. The use of 3-chloro-1-propanol and tert-butyl acetoacetate as the linchpin was also examined to connect the two synthetic blocks in the synthesis of 3. Components I-III were obtained by Wacker oxidation of the corresponding 1-alkenes 1-3 in good yields. PMID:20057134

Taguri, Tomonori; Yamakawa, Rei; Adachi, Yasushi; Mori, Kenji; Ando, Tetsu

2010-01-01

439

Theoretical study of gas-phase formation enthalpies and isomerism for 4(5)-nitro-1,2,3-triazole and its N-alkyl derivatives and experimental determination of formation enthalpy for 2-methyl-4-nitro-1,2,3-triazole  

Microsoft Academic Search

The formation enthalpies of tautomeric forms of 1,2,3-triazole, 4(5)-nitro-1,2,3-triazole and isomeric N-alkyl-4(5)-nitro-1,2,3-triazoles (alkyl=methyl, ethyl, isopropyl and tert-butyl) have been calculated with the density functional theory B3LYP method by means of designed isolobal, isodesmic and isomerisation reactions. The experimental ideal-gas formation enthalpy of 2-methyl-4-nitro-1,2,3-triazole has been determined based on the formation enthalpy in the crystalline state and the sublimation enthalpy. The

Vadim E. Matulis; Oleg A. Ivashkevich; Pavel N. Gaponik; Pavel D. Elkind; Gennady T. Sukhanov; Ala B. Bazyleva; Dzmitry H. Zaitsau

2008-01-01

440

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 Enginee