Use of EPR Spin-Trapping Techniques to Detect Radicals from Rat Lung Lavage Fluid Following Sulfur Mustard Vapor Exposure

DTIC Science & Technology

1993-05-13

lung injury. Anesthetized rats were intratracheally intubated and exposed to 0.35 mg HD vapor over 50 min, Immediately, 1 hr or 24 hr after exposure...lungs were lavaged with the spin trap, alpha-phenyl-t-butyl nitrone (PBN; 0.35 mg/ml). Recovered lavage fluid was assayed by EPR spectroscopy for...in EtOH (100 Ml), or EtOH alone (control), was placed in a water Jacketed (37° C) vapor generator and the rats .ere exposed for 50 min. by which time

Learning and memory effects of neonatal methamphetamine exposure in rats: Role of reactive oxygen species and age at assessment.

PubMed

Jablonski, Sarah A; Williams, Michael T; Vorhees, Charles V

2017-11-01

In utero methamphetamine (MA) exposure leads to a range of adverse effects, such as decreased attention, reduced working-memory capability, behavioral dysregulation, and spatial memory impairments in exposed children. In the current experiment, preweaning Sprague-Dawley rats-as a model of third trimester human exposure-were administered the spin trapping agent, N-tert-butyl-α-phenylnitrone (PBN), daily prior to MA. Rats were given 0 (SAL) or 40 mg/kg PBN prior to each MA dose (10 mg/kg, 4× per day) from postnatal day (P) 6-15. Littermates underwent Cincinnati water maze, Morris water maze, and radial water maze assessment beginning on P30 (males) or P60 (females). Males were also tested for conditioned contextual and cued freezing, while females were trained in passive avoidance. Findings show that, regardless of age/sex, neonatal MA induced deficits in all tests, except passive avoidance. PBN did not ameliorate these effects, but had a few minor effects. Taken together, MA induced learning deficits emerge early and persist, but the mechanism remains unknown. © 2017 Wiley Periodicals, Inc.

ESR evidence for radical production from the reaction of ozone with unsaturated lipids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Church, D.F.; McAdams, M.L..; Pryor, W.A.

1991-03-15

The authors report electron spin resonance (ESR) spin trapping evidence for radical production by the reaction of ozone with unsaturated compounds. Soy and egg phosphatidylcholine liposomes, fatty acid emulsions, and homogeneous aqueous solutions of 3-hexenoic acid were treated with ozone in the presence of the spin trap {alpha}-phenyl-N-tert-butyl nitrone (PBN). Under these conditions, they observe spin adducts resulting from the trapping of both organic carbon- and oxygen-centered radicals. When the lipid-soluble antioxidant alpha-tocopherol is included in the liposomal systems, the formation of spin adducts is completely inhibited. The authors suggest that radicals giving rise to these spin adducts arise formmore » the rapid decomposition of the 1,2,3-trioxolane intermediate that is initially formed when ozone reacts with the carbon-carbon double bonds of the substrates. These free radicals are not formed by the decomposition of the Criegee ozonide, since little of the ozonide is formed in the presence of water. Although hydrogen peroxide is the predominate peroxidic product of the ozone/alkene reaction, its decomposition is not responsible for the observed radical production since neither catalase nor iron chelators significantly affect the spin adduct yield. The radical yield is approximately 1%. Since a polyunsaturated fatty acid (PUFA) such as linoleic acid produces much higher concentrations of spin trappable radicals than does the monounsaturated fatty oleic acid, the results also suggest that sites in the lung containing higher levels of PUFA may be an important target for radical formation.« less

Oxidation of spin-traps by chlorine dioxide (ClO2) radical in aqueous solutions: first ESR evidence of formation of new nitroxide radicals.

PubMed

Ozawa, T; Miura, Y; Ueda, J

1996-01-01

The reactivities of the chlorine dioxide (ClO2), which is a stable free radical towards some water-soluble spin-traps were investigated in aqueous solutions by an electron spin resonance (ESR) spectroscopy. The ClO2 radical was generated from the redox reaction of Ti3+ with potassium chlorate (KClO3) in aqueous solutions. When one of the spin-traps, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), was included in the Ti3+-KClO3 reaction system, ESR spectrum due to the ClO2 radical completely disappeared and a new ESR spectrum [aN(1) = 0.72 mT, aH(2) = 0.41 mT], which is different from that of DMPO-ClO2 adduct, was observed. The ESR parameters of this new ESR signal was identical to those of 5,5-dimethylpyrrolidone-(2)-oxyl-(1) (DMPOX), suggesting the radical species giving the new ESR spectrum is assignable to DMPOX. The similar ESR spectrum consisting of a triplet [aN(1) = 0.69 mT] was observed when the derivative of DMPO, 3,3,5,5-tetramethyl-1-pyrroline N-oxide (M4PO) was included in the Ti3+-KClO3 reaction system. This radical species is attributed to the oxidation product of M4PO, 3,3,5,5-tetramethylpyrrolidone-(2)-oxyl-(1) (M4POX). When another nitrone spin-trap, alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (POBN) was used as a spin-trap, the ESR signal intensity due to the ClO2 radical decreased and a new ESR signal consisting of a triplet [aN(1) = 0.76 mT] was observed. The similar ESR spectrum was observed when N-t-butyl-alpha- nitrone (PBN) was used as a spin-trap. This ESR parameter [a(N)(1) = 0.85 mT] was identical to the oxidation product of PBN, PBNX. Thus, the new ESR signal observed from POBN may be assigned to the oxidation product of POBN, POBNX. These results suggest that the ClO2, radical does not form the stable spin adducts with nitrone spin-traps, but oxidizes these spin-traps to give the corresponding nitroxyl radicals. On the other hand, nitroso spin-traps, 5,5-dibromo-4-nitrosobenzenesulfonate (DBNBS), and 2-methyl-2-nitrosopropane (MNP) did not trap the ClO2 radical. This result indicates that an unpaired electron of the ClO2 radical is localized on oxygen atom, because nitroso spin-traps cannot form the stable spin adduct with oxygen-centered radical.

Synthesis, structure, theoretical and experimental in vitro antioxidant/pharmacological properties of α-aryl, N-alkyl nitrones, as potential agents for the treatment of cerebral ischemia.

PubMed

Samadi, Abdelouahid; Soriano, Elena; Revuelta, Julia; Valderas, Carolina; Chioua, Mourad; Garrido, Ignacio; Bartolomé, Begoña; Tomassolli, Isabelle; Ismaili, Lhassane; González-Lafuente, Laura; Villarroya, Mercedes; García, Antonio G; Oset-Gasque, María J; Marco-Contelles, José

2011-01-15

The synthesis, structure, theoretical and experimental in vitro antioxidant properties using the DPPH, ORAC, and benzoic acid, as well as preliminary in vitro pharmacological activities of (Z)-α-aryl and heteroaryl N-alkyl-nitrones 6-15, 18, 19, 21, and 23, is reported. In the in vitro antioxidant activity, for the DPPH radical test, only nitrones bearing free phenol groups gave the best RSA (%) values, nitrones 13 and 14 showing the highest values in this assay. In the ORAC analysis, the most potent radical scavenger was nitrone indole 21, followed by the N-benzyl benzene-type nitrones 10 and 15. Interestingly enough, the archetypal nitrone 7 (PBN) gave a low RSA value (1.4%) in the DPPH test, or was inactive in the ORAC assay. Concerning the ability to scavenge the hydroxyl radical, all the nitrones studied proved active in this experiment, showing high values in the 94-97% range, the most potent being nitrone 14. The theoretical calculations for the prediction of the antioxidant power, and the potential of ionization confirm that nitrones 9 and 10 are among the best compounds in electron transfer processes, a result that is also in good agreement with the experimental values in the DPPH assay. The calculated energy values for the reaction of ROS (hydroxyl, peroxyl) with the nitrones predict that the most favourable adduct-spin will take place between nitrones 9, 10, and 21, a fact that would be in agreement with their experimentally observed scavenger ability. The in vitro pharmacological analysis showed that the neuroprotective profile of the target molecules was in general low, with values ranging from 0% to 18.7%, in human neuroblastoma cells stressed with a mixture of rotenone/oligomycin-A, being nitrones 18, and 6-8 the most potent, as they show values in the range 24-18.4%. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

Region-selective effects of neuroinflammation and antioxidant treatment on peripheral benzodiazepine receptors and NMDA receptors in the rat brain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biegon, A.; Alvarado, M.; Budinger, T.F.

2001-12-10

Following induction of acute neuroinflammation by intracisternal injection of endotoxin (lipopolysaccharide) in rats, quantitative autoradiography was used to assess the regional level of microglial activation and glutamate (NMDA) receptor binding. The possible protective action of the antioxidant phenyl-tert-butyl nitrone in this model was tested by administering the drug in the drinking water for 6 days starting 24 hours after endotoxin injection. Animals were killed 7 days post-injection and consecutive cryostat brain sections labeled with [3H]PK11195 as a marker of activated microglia and [125I]iodoMK801 as a marker of the open-channel, activated state of NMDA receptors. Lipopolysaccharide increased [3H]PK11195 binding in themore » brain, with the largest increases (2-3 fold) in temporal and entorhinal cortex, hippocampus, and substantia innominata. A significant (>50 percent) decrease in [125I]iodoMK801 binding was found in the same brain regions. Phenyl-tert-butyl nitrone treatment resulted in a partial inhibition ({approx}25 percent decrease) of the lipopolysaccharide-induced increase in [3H]PK11195 binding but completely reversed the lipopolysaccharide-induced decrease in [125I]iodoMK80 binding in the entorhinal cortex, hippocampus, and substantia innominata. Loss of NMDA receptor function in cortical and hippocampal regions may contribute to the cognitive deficits observed in diseases with a neuroinflammatory component, such as meningitis or Alzheimer's disease.« less

Free radical trap phenyl-N-tert-butylnitrone protects against light damage but does not rescue P23H and S334ter rhodopsin transgenic rats from inherited retinal degeneration.

PubMed

Ranchon, Isabelle; LaVail, Matthew M; Kotake, Yashige; Anderson, Robert E

2003-07-09

Phenyl-N-tert-butylnitrone (PBN) protects rat retinas against light damage. Because the degenerative process involved in light damage and inherited retinal degeneration both lead to a common final cell death, apoptosis, we used transgenic rats with a P23H or S334ter rhodopsin mutation to test the effects of PBN on retinal degeneration and light damage and the susceptibility of the transgenic rats to light damage. In the first study, 3-week-old mutant and wild-type rats were given no drug, 0.25% PBN in drinking water, or 0.25% PBN in drinking water plus three daily intraperitoneal injections of PBN (100 mg/kg, i.p., every 8 hr). Electroretinograms were recorded at postnatal day 49, after which the rats were killed for morphometric analysis. There was no photoreceptor rescue by PBN in P23H or S334ter rats, as evidenced by equivalent loss of function and photoreceptor cells in the three treatment groups. In the second study, P23H, S334ter, and wild-type rats were exposed for 24 hr to 2700 lux light. The rats were untreated or treated with PBN (50 mg/kg per injection, every 6 hr, starting before exposure). ERGs were recorded before and 1 d after exposure. Animals were killed 6 d later for morphometric analysis. PBN protected wild-type and P23H but not S334ter retinas from light damage. S334ter retinas were relatively less susceptible to light damage than P23H and wild-type rats. The results suggest that the initiating event(s) that causes photoreceptor cell death in the mutated rats is different from that which occurs in light damage, although both ultimately undergo an apoptotic cell death.

A series of (E)-5-(arylideneamino)-1-tert-butyl-1H-pyrrole-3-carbonitriles and their reduction products to secondary amines: syntheses and X-ray structural studies.

PubMed

Macías, Mario A; Castillo, Juan Carlos; Portilla, Jaime

2018-01-01

An efficent access to a series of N-(pyrrol-2-yl)amines, namely (E)-1-tert-butyl-5-[(4-chlorobenzylidene)amino]-1H-pyrrole-3-carbonitrile, C 16 H 16 ClN 3 , (7a), (E)-1-tert-butyl-5-[(2,4-dichlorobenzylidene)amino]-1H-pyrrole-3-carbonitrile, C 16 H 15 Cl 2 N 3 , (7b), (E)-1-tert-butyl-5-[(pyridin-4-ylmethylene)amino]-1H-pyrrole-3-carbonitrile, C 15 H 16 N 4 , (7c), 1-tert-butyl-5-[(4-chlorobenzyl)amino]-1H-pyrrole-3-carbonitrile, C 16 H 18 ClN 3 , (8a), and 1-tert-butyl-5-[(2,4-dichlorobenzyl)amino]-1H-pyrrole-3-carbonitrile, C 16 H 17 Cl 2 N 3 , (8b), by a two-step synthesis sequence (solvent-free condensation and reduction) starting from 5-amino-1-tert-butyl-1H-pyrrole-3-carbonitrile is described. The syntheses proceed via isolated N-(pyrrol-2-yl)imines, which are also key synthetic intermediates of other valuable compounds. The crystal structures of the reduced compounds showed a reduction in the symmetry compared with the corresponding precursors, viz. Pbcm to P-1 from compound (7a) to (8a) and P2 1 /c to P-1 from compound (7b) to (8b), probably due to a severe change in the molecular conformations, resulting in the loss of planarity observed in the nonreduced compounds. In all of the crystals, the supramolecular assembly is controlled mainly by strong (N,C)-H...N hydrogen bonds. However, in the case of (7a)-(7c), C-H...Cl interactions are strong enough to help in the three-dimensional architecture, as observed in Hirshfeld surface maps.

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

NASA Astrophysics Data System (ADS)

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

2014-01-01

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

Evaluation of Extracellular Endosulfatase HSULF-2 in Breast Cancer Cell WNT Signaling and Its Inhibition by a Sulfate Ester Derivative of Synthetic Antioxidant

DTIC Science & Technology

2010-08-01

Breast Cancer, Balb/c nude mice, hydrogen peroxide, extracellular matrix, sulfatase, extracellular sulfatase, aryl sulfatase, PBN, nitrones , phenyl...previously made in studying the anti‐cancer activity of the PBN  nitrones  has helped us generate new novel and testable  ideas for future research in...cancer development appears to be still in question.    Anti‐cancer activity of the PBN‐ nitrones . PBN refers to α‐phenyl‐tert‐butylnitrone. Our

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

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

2004-01-01

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…

Synthesis and evaluation of new antimalarial analogues of quinoline alkaloids derived from Cinchona ledgeriana Moens ex Trimen.

PubMed

Park, Byeoung-Soo; Kim, Dae-Young; Rosenthal, Philip J; Huh, Sun-Chul; Lee, Belinda J; Park, Eun -u; Kim, Sung-Min; Kim, Jang-Eok; Kim, Mi-Hee; Huh, Tae-Lin; Choi, Young-Jae; Suh, Ki-Hyung; Choi, Won-Sik; Lee, Sung-Eun

2002-05-20

In the course of attempts to develop antimalarial drugs, we have designed and synthesized a series of quinoline alkaloide derivatives. Three of them, N-(4-methoxy-3,5-di-tert-butylbenzyl)cinchonidinium bromide (OSL-5), O-benzyl-N-(3,5-di-tert-butyl-4-methoxybenzyl)cinchonidinium bromide (OSL-7), and N-(3,5-di-tert-butyl-4-methoxybenzyl)quininium bromide (OSL-14) show potent activity against Plasmodium falciparum.

The role of reactive oxygen species in methamphetamine self-administration and dopamine release in the nucleus accumbens.

PubMed

Jang, Eun Young; Yang, Chae Ha; Hedges, David M; Kim, Soo Phil; Lee, Jun Yeon; Ekins, Tyler G; Garcia, Brandon T; Kim, Hee Young; Nelson, Ashley C; Kim, Nam Jun; Steffensen, Scott C

2017-09-01

Methamphetamine (METH) markedly increases dopamine (DA) release in the mesolimbic DA system, which plays an important role in mediating the reinforcing effects of METH. METH-induced DA release results in the formation of reactive oxygen species (ROS), leading to oxidative damage. We have recently reported that ROS are implicated in behavior changes and DA release in the nucleus accumbens (NAc) following cocaine administration. The aim of this study was to evaluate the involvement of ROS in METH-induced locomotor activity, self-administration and enhancement of DA release in the NAc. Systemic administration of a non-specific ROS scavenger, N-tert-butyl-α-phenylnitrone (PBN; 0, 50 and 75 mg/kg, IP) or a superoxide-selective scavenger, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL; 0, 50 and 100 mg/kg, IP), attenuated METH-induced locomotor activity without affecting generalized behavior in METH-naïve rats. PBN and TEMPOL significantly attenuated METH self-administration without affecting food intake. Increased oxidative stress was found in neurons, but not astrocytes, microglia or oligodendrocytes, in the NAc of METH self-administering rats. In addition, TEMPOL significantly decreased METH enhancement of DA release in the NAc. Taken together, these results suggest that enhancement of ROS in the NAc contributes to the reinforcing effect of METH. © 2016 Society for the Study of Addiction.

Isolation and Characterization of 4-tert-Butylphenol-Utilizing Sphingobium fuliginis Strains from Phragmites australis Rhizosphere Sediment▿ †

PubMed Central

Toyama, Tadashi; Momotani, Naonori; Ogata, Yuka; Miyamori, Yuji; Inoue, Daisuke; Sei, Kazunari; Mori, Kazuhiro; Kikuchi, Shintaro; Ike, Michihiko

2010-01-01

We isolated three Sphingobium fuliginis strains from Phragmites australis rhizosphere sediment that were capable of utilizing 4-tert-butylphenol as a sole carbon and energy source. These strains are the first 4-tert-butylphenol-utilizing bacteria. The strain designated TIK-1 completely degraded 1.0 mM 4-tert-butylphenol in basal salts medium within 12 h, with concomitant cell growth. We identified 4-tert-butylcatechol and 3,3-dimethyl-2-butanone as internal metabolites by gas chromatography-mass spectrometry. When 3-fluorocatechol was used as an inactivator of meta-cleavage enzymes, strain TIK-1 could not degrade 4-tert-butylcatechol and 3,3-dimethyl-2-butanone was not detected. We concluded that metabolism of 4-tert-butylphenol by strain TIK-1 is initiated by hydroxylation to 4-tert-butylcatechol, followed by a meta-cleavage pathway. Growth experiments with 20 other alkylphenols showed that 4-isopropylphenol, 4-sec-butylphenol, and 4-tert-pentylphenol, which have alkyl side chains of three to five carbon atoms with α-quaternary or α-tertiary carbons, supported cell growth but that 4-n-alkylphenols, 4-tert-octylphenol, technical nonylphenol, 2-alkylphenols, and 3-alkylphenols did not. The rate of growth on 4-tert-butylphenol was much higher than that of growth on the other alkylphenols. Degradation experiments with various alkylphenols showed that strain TIK-1 cells grown on 4-tert-butylphenol could degrade 4-alkylphenols with variously sized and branched side chains (ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and branched nonyl) via a meta-cleavage pathway but not 2- or 3-alkylphenols. Along with the degradation of these alkylphenols, we detected methyl alkyl ketones that retained the structure of the original alkyl side chains. Strain TIK-1 may be useful in the bioremediation of environments polluted by 4-tert-butylphenol and various other 4-alkylphenols. PMID:20802076

N-tert-butylmethanimine N-oxide is an efficient spin-trapping probe for EPR analysis of glutathione thiyl radical

PubMed Central

Scott, Melanie J.; Billiar, Timothy R.; Stoyanovsky, Detcho A.

2016-01-01

The electron spin resonance (EPR) spin-trapping technique allows detection of radical species with nanosecond half-lives. This technique is based on the high rates of addition of radicals to nitrones or nitroso compounds (spin traps; STs). The paramagnetic nitroxides (spin-adducts) formed as a result of reactions between STs and radical species are relatively stable compounds whose EPR spectra represent “structural fingerprints” of the parent radical species. Herein we report a novel protocol for the synthesis of N-tert-butylmethanimine N-oxide (EBN), which is the simplest nitrone containing an α-H and a tertiary α′-C atom. We present EPR spin-trapping proof that: (i) EBN is an efficient probe for the analysis of glutathione thiyl radical (GS•); (ii) β-cyclodextrins increase the kinetic stability of the spin-adduct EBN/•SG; and (iii) in aqueous solutions, EBN does not react with superoxide anion radical (O2−•) to form EBN/•OOH to any significant extent. The data presented complement previous studies within the context of synthetic accessibility to EBN and efficient spin-trapping analysis of GS•. PMID:27941944

21 CFR 176.200 - Defoaming agents used in coatings.

Code of Federal Regulations, 2014 CFR

2014-04-01

... are provided: List of substances Limitations n-Butyl alcohol tert-Butyl alcohol Butyl stearate Castor... Glyceryl monostearate Hexane Hexylene glycol (2-methyl-2,4-pentanediol) Isobutyl alcohol Isopropyl alcohol...

40 CFR 60.707 - Chemicals affected by subpart RRR.

Code of Federal Regulations, 2012 CFR

2012-07-01

...-7 Brometone 76-08-4 1,3-Butadiene 106-99-0 Butadiene and butene fractions n-Butane 106-97-8 1,4-Butanediol 110-63-4 Butanes, mixed 1-Butene 106-98-9 2-Butene 25167-67-3 Butenes, mixed n-Butyl acetate 123-86-4 Butyl acrylate 141-32-2 n-Butyl alcohol 71-36-3 sec-Butyl alcohol 78-92-2 tert-Butyl alcohol 75...

40 CFR 60.707 - Chemicals affected by subpart RRR.

Code of Federal Regulations, 2010 CFR

2010-07-01

...-7 Brometone 76-08-4 1,3-Butadiene 106-99-0 Butadiene and butene fractions n-Butane 106-97-8 1,4-Butanediol 110-63-4 Butanes, mixed 1-Butene 106-98-9 2-Butene 25167-67-3 Butenes, mixed n-Butyl acetate 123-86-4 Butyl acrylate 141-32-2 n-Butyl alcohol 71-36-3 sec-Butyl alcohol 78-92-2 tert-Butyl alcohol 75...

40 CFR 60.707 - Chemicals affected by subpart RRR.

Code of Federal Regulations, 2011 CFR

2011-07-01

...-7 Brometone 76-08-4 1,3-Butadiene 106-99-0 Butadiene and butene fractions n-Butane 106-97-8 1,4-Butanediol 110-63-4 Butanes, mixed 1-Butene 106-98-9 2-Butene 25167-67-3 Butenes, mixed n-Butyl acetate 123-86-4 Butyl acrylate 141-32-2 n-Butyl alcohol 71-36-3 sec-Butyl alcohol 78-92-2 tert-Butyl alcohol 75...

N-tert-Butyl-N'-(5,7-dimethyl-1,8-naphthyridin-2-yl)urea.

PubMed

Lüning, U; Kühl, C; Bolte, M

2001-08-01

The title compound, C(15)H(20)N(4)O, has been synthesized as an AADD recognition unit for quadruple hydrogen bonds. All non-H atoms of the molecule apart from two methyl groups of the tert-butyl group lie in a common plane. An intramolecular hydrogen bond is formed connecting two N atoms. In the solid state, the title compound crystallizes as a centrosymmetric dimer connected by N-H...O=C interactions with an N...O distance of 2.824 (2) A.

Di-tert-butyl-chlorido(N,N-dibenzyl-dithio-carbamato)tin(IV).

PubMed

Abdul Muthalib, Amirah Faizah; Baba, Ibrahim; Mohamed Tahir, Mohamed Ibrahim; Tiekink, Edward R T

2011-02-26

The Sn(IV) atom in the title diorganotin dithio-carbamate, [Sn(C(4)H(9))(2)(C(15)H(14)NS(2))Cl], is penta-coordinated by an asymmetrically coordinating dithio-carbamate ligand, a Cl atom and two C atoms of the Sn-bound tert-butyl groups. The resulting C(2)ClS(2) donor set defines a coordination geometry inter-mediate between square pyramidal and trigonal bipyramidal with a slight tendency towards the former.

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

PubMed

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

2007-06-01

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

40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., Calcium Salt Maleic Anhydride Methacrylic Acid *Methacrylic Acid Esters Methane Methyl Ethyl Ketone Methyl Methacrylate Methyl Tert-Butyl Ether Methylisobutyl Ketone *n-Alkanes n-Butyl Alcohol n-Butylacetate n... Acid Nylon Salt Oxalic Acid *Oxo Aldehydes—Alcohols Pentaerythritol Pentane *Pentenes *Petroleum...

40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., Calcium Salt Maleic Anhydride Methacrylic Acid *Methacrylic Acid Esters Methane Methyl Ethyl Ketone Methyl Methacrylate Methyl Tert-Butyl Ether Methylisobutyl Ketone *n-Alkanes n-Butyl Alcohol n-Butylacetate n... Acid Nylon Salt Oxalic Acid *Oxo Aldehydes—Alcohols Pentaerythritol Pentane *Pentenes *Petroleum...

40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., Calcium Salt Maleic Anhydride Methacrylic Acid *Methacrylic Acid Esters Methane Methyl Ethyl Ketone Methyl Methacrylate Methyl Tert-Butyl Ether Methylisobutyl Ketone *n-Alkanes n-Butyl Alcohol n-Butylacetate n... Acid Nylon Salt Oxalic Acid *Oxo Aldehydes—Alcohols Pentaerythritol Pentane *Pentenes *Petroleum...

40 CFR 414.70 - Applicability; description of the bulk organic chemicals subcategory.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., Calcium Salt Maleic Anhydride Methacrylic Acid *Methacrylic Acid Esters Methane Methyl Ethyl Ketone Methyl Methacrylate Methyl Tert-Butyl Ether Methylisobutyl Ketone *n-Alkanes n-Butyl Alcohol n-Butylacetate n... Acid Nylon Salt Oxalic Acid *Oxo Aldehydes—Alcohols Pentaerythritol Pentane *Pentenes *Petroleum...

Di-tert-butyl­chlorido(N,N-dibenzyl­dithio­carbamato)tin(IV)

PubMed Central

Abdul Muthalib, Amirah Faizah; Baba, Ibrahim; Mohamed Tahir, Mohamed Ibrahim; Tiekink, Edward R. T.

2011-01-01

The SnIV atom in the title diorganotin dithio­carbamate, [Sn(C4H9)2(C15H14NS2)Cl], is penta­coordinated by an asymmetrically coordinating dithio­carbamate ligand, a Cl atom and two C atoms of the Sn-bound tert-butyl groups. The resulting C2ClS2 donor set defines a coordination geometry inter­mediate between square pyramidal and trigonal bipyramidal with a slight tendency towards the former. PMID:21522304

tert-Butyl 6-amino-5-cyano-2-(2-meth­oxy­eth­yl)nicotinate

PubMed Central

Chen, Yi-Ning; Zhao, Xing-Dong; Deng, Jie; Li, Qin-Geng

2012-01-01

The title compound, C14H19N3O3, was synthesized by the reaction of 3-meth­oxy­propionitrile, tert-butyl bromo­acetate and eth­oxy­methyl­enemalononitrile. In the crystal, N—H⋯O hydrogen bonds link the mol­ecules into chains propagating along the b axis. PMID:22737103

Regioisomer-Free C 4h β-Tetrakis(tert-butyl)metallo-phthalocyanines: Regioselective Synthesis and Spectral Investigations.

PubMed

Iida, Norihito; Tanaka, Kenta; Tokunaga, Etsuko; Takahashi, Hiromi; Shibata, Norio

2015-04-01

Metal β-tetrakis(tert-butyl)phthalocyanines are the most commonly used phthalocyanines due to their high solubility, stability, and accessibility. They are commonly used as a mixture of four regioisomers, which arise due to the tert-butyl substituent on the β-position, and to the best of our knowledge, their regioselective synthesis has yet to be reported. Herein, the C 4h -selective synthesis of β-tetrakis(tert-butyl)metallophthalocyanines is disclosed. Using tetramerization of α-trialkylsilyl phthalonitriles with metal salts following acid-mediated desilylation, the desired metallophthalocyanines were obtained in good yields. Upon investigation of regioisomer-free zinc β-tetrakis(tert-butyl)phthalocyanine using spectroscopy, the C 4h single isomer described here was found to be distinct in the solid state to zinc β-tetrakis(tert-butyl)phthalocyanine obtained by a conventional method.

27 CFR 21.101 - tert-Butyl alcohol.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false tert-Butyl alcohol. 21.101....101 tert-Butyl alcohol. (a) Acidity (as acetic acid). 0.003 percent by weight maximum. (b) Color. Colorless. (c) Distillation range. When 100 ml of tertiary butyl alcohol are distilled, none should distill...

27 CFR 21.101 - tert-Butyl alcohol.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false tert-Butyl alcohol. 21.101....101 tert-Butyl alcohol. (a) Acidity (as acetic acid). 0.003 percent by weight maximum. (b) Color. Colorless. (c) Distillation range. When 100 ml of tertiary butyl alcohol are distilled, none should distill...

Demethylation of 5,n-di-tert-butyl-8,n-dimethoxy[2.n]metacyclophane-1-ynes with BBr3 to afford novel [n]benzofuranophanes

NASA Astrophysics Data System (ADS)

Akther, Thamina; Islam, Md Monarul; Matsumoto, Taisuke; Tanaka, Junji; Feng, Xing; Redshaw, Carl; Yamato, Takehiko

2016-10-01

Novel [n]benzofuranophanes (n = 8 & 10) 2a-b have been prepared by successive intramolecular cyclization from 5,19-di-tert-butyl-8,22-dimethoxy[n]metacyclophane-1-yne (syn-1a-b) by treatment with BBr3 in CH2Cl2 at room temperature for 8h. [2.n]Benzofuranophanes 2a-b were also obtained by treatment of 1,2-di-endo-bromo-5,19-di-tert-butyl-8,22-dimethoxy[n]metacyclophane (meso-3a-b) with BBr3 in CH2Cl2 by using the same reaction conditions. 1H NMR spectra of 2a-b reveals the formation of intramolecular hydrogen bonding between hydroxyl proton with the oxygen of the furan moiety and X-ray analysis shows that the lengths between H (OH) and O (furan) are 1.981 and 1.823 Å̊, respectively. The conformation of [8]benzofuranophane 2a in solution is rigid with restricted rotation around the diaryl linkage rather than [10]benzofuranophane 2b because of weak intramolecular hydrogen bonding and the short length of the cross-linking chain.

Simultaneous analysis of tert-butylhydroquinone, tert-butylquinone, butylated hydroxytoluene, 2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, α-tocopherol, γ-tocopherol, and δ-tocopherol in edible oils by normal-phase high performance liquid chromatography.

PubMed

Li, Jun; Bi, Yanlan; Sun, Shangde; Peng, Dan

2017-11-01

A normal-phase high performance liquid chromatography method for the simultaneous determination of tert-butylhydroquinone, tert-butylquinone, butylated hydroxytoluene, 2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, α-tocopherol, γ-tocopherol, and δ-tocopherol in edible oils was investigated. A silica column was used to separate the analytes with the gradient elution. An ultraviolet-visible detector was set at dual wavelengths mode (280 and 310nm). The column temperature was 30°C. The analytes were directly extracted with methanol. Results showed that the normal-phase high performance liquid chromatography method performed well with wide liner ranges (0.10∼500.00μg/mL, R 2 >0.9998), low limits of detection and quantitation (below 0.40 and 1.21μg/mL, respectively), and good recoveries (81.38∼102.34% in soybean oils and 83.03∼100.79% in lard, respectively). The reduction of tert-butylquinone caused by the reverse-phase high performance liquid chromatography during the injection was avoided with the current normal-phase method. The two isomers of butylated hydroxyanisole can also be separated with good resolution. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ground-State Distortion in N-Acyl-tert-butyl-carbamates (Boc) and N-Acyl-tosylamides (Ts): Twisted Amides of Relevance to Amide N-C Cross-Coupling.

PubMed

Szostak, Roman; Shi, Shicheng; Meng, Guangrong; Lalancette, Roger; Szostak, Michal

2016-09-02

Amide N-C(O) bonds are generally unreactive in cross-coupling reactions employing low-valent transition metals due to nN → π*C═O resonance. Herein we demonstrate that N-acyl-tert-butyl-carbamates (Boc) and N-acyl-tosylamides (Ts), two classes of acyclic amides that have recently enabled the development of elusive amide bond N-C cross-coupling reactions with organometallic reagents, are intrinsically twisted around the N-C(O) axis. The data have important implications for the design of new amide cross-coupling reactions with the N-C(O) amide bond cleavage as a key step.

(N-Benzyl-N-ethyl-dithio-carbamato)di-tert-butyl-chloridotin(IV).

PubMed

Abdul Muthalib, Amirah Faizah; Baba, Ibrahim; Mohamed Tahir, Mohamed Ibrahim; Tiekink, Edward R T

2011-02-26

The Sn(IV) atom in the title diorganotin dithio-carbamate, [Sn(C(4)H(9))(2)Cl(C(10)H(12)NS(2))], is penta-coordinated by an asymmetrically coordinating dithio-carbamate ligand, a Cl and two C atoms of the Sn-bound tert-butyl groups. The resulting C(2)ClS(2) donor set defines a coordination geometry inter-mediate between square pyramidal and trigonal bipyramidal with a slight tendency towards the former. In the crystal structure, C-H⋯π contacts link centrosymmetrically related mol-ecules into dimeric aggregates.

46 CFR 30.25-1 - Cargoes carried in vessels certificated under the rules of this subchapter.

Code of Federal Regulations, 2013 CFR

2013-10-01

...-Amyl methyl ether (Methyl tert-pentyl ether) C Amyl methyl ketone, see Methyl amyl ketone D Animal and... heptyl ketone [C] Butyl methyl ketone, see Methyl butyl ketone n-Butyl propionate C Butyl stearate III... alcohol (all isomers) C Diisobutylene B Diisobutyl ketone D Diisobutyl phthalate B Diisodecyl phthalate...

Synthetic phenolic antioxidants, including butylated hydroxytoluene (BHT), in resin-based dental sealants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei; Kannan, Pranav; Xue, Jingchuan

Resin-based dental sealants (also referred to as pit-and-fissure sealants) have been studied for their contribution to bisphenol A (BPA) exposure in children. Nevertheless, little attention has been paid to the occurrence of other potentially toxic chemicals in dental sealants. In this study, the occurrence of six synthetic phenolic antioxidants (SPAs), including 2,6-di-tert-butyl-4-hydroxytoluene (BHT), 2,6-di-tert-butyl-4-(hydroxyethyl)phenol (BHT-OH), 3,5-di-tert-butyl-4-hydroxy-benzaldehyde (BHT-CHO), 2,6-di-tert-butylcyclohexa-2,5-diene-1,4-dione (BHT-Q), 3,5-di-tert-butyl-4-hydroxybenzoic acid (BHT-COOH) and 2-tert-butyl-4-methoxyphenol (BHA), was examined in 63 dental sealant products purchased from the U.S. market. BHT was found in all dental sealants at median and maximum concentrations of 56.8 and 1020 µg/g, respectively. The metabolites of BHT andmore » BHA were detected in 39–67% of samples, at concentration ranges of« less

Emulsion Polymerization of Butyl Acrylate: Spin Trapping and EPR Study

NASA Technical Reports Server (NTRS)

Kim, S.; Westmoreland, D.

1994-01-01

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.

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

USGS Publications Warehouse

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

2004-01-01

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

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, ...

The tert-butyl cation on zeolite Y: A theoretical and experimental study

NASA Astrophysics Data System (ADS)

Rosenbach, Nilton, Jr.; dos Santos, Alex P. A.; Franco, Marcelo; Mota, Claudio J. A.

2010-01-01

The structure and energy of the tert-butyl cation on zeolite Y were calculated at ONIOM(MP2(FULL)/6-31G( d, p):MNDO) level. The results indicated that the tert-butyl cation is a minimum and lies between 40 and 51 kJ mol -1 above in energy to the tert-butoxide, depending on the level of calculation. Both species are stabilized through hydrogen bonding interactions with the framework oxygen atoms. Experimental data of nucleophilic substitution of tert-butylchloride and bromide over NaY impregnated with NaCl or NaBr give additional support for the formation of the tert-butyl cation as a discrete intermediate on zeolite Y, in agreement with the calculations.

Protein oxidation and aging. I. Difficulties in measuring reactive protein carbonyls in tissues using 2,4-dinitrophenylhydrazine.

PubMed

Cao, G; Cutler, R G

1995-06-20

A current hypothesis explaining the aging process implicates the accumulation of oxidized protein in animal tissues. This hypothesis is based on a series of reports showing an age-dependent increase in protein carbonyl content and an age-dependent loss of enzyme function. This hypothesis is also supported by the report of a novel effect of N-tert-butyl-alpha-phenylnitrone (PBN) in reversing these age-dependent changes. Here we specifically study the method that was used to measure reactive protein carbonyls in tissues. This method uses 2,4-dinitrophenylhydrazine (DNPH) and includes a washing procedure. Our results indicate that reactive protein carbonyls in normal crude tissue extracts cannot be reliably measured by this method, although it does reliably measure reactive carbonyls in purified proteins which have been oxidatively modified in vitro. The nucleic acids in tissues could be a major problem encountered in the assay. Using the streptomycin sulfate treatment combined with a dialysis step, we were successful in removing most nucleic acids from a crude tissue extract, but then the reactive carbonyl level in the crude tissue extract was too low to be reliably measured. This streptomycin sulfate treatment procedure, however, had no effect on the reactive carbonyl measurement of an oxidized protein sample. The unwashed free DNPH was another major problem in the assay because of its very strong absorption around 370 nm, where reactive carbonyls were quantitated. Nevertheless, on using the procedure described in the literature to measure total "reactive carbonyls" in rat liver and gerbil brain cortex, no change with age or PBN treatment was found. Then, we investigated a HPLC procedure which uses sodium dodecyl sulfate in the mobile phase but this was also found to be unsuitable for the reactive protein carbonyl assay in tissues.

(N-Benzyl-N-ethyl­dithio­carbamato)di-tert-butyl­chloridotin(IV)

PubMed Central

Abdul Muthalib, Amirah Faizah; Baba, Ibrahim; Mohamed Tahir, Mohamed Ibrahim; Tiekink, Edward R. T.

2011-01-01

The SnIV atom in the title diorganotin dithio­carbamate, [Sn(C4H9)2Cl(C10H12NS2)], is penta­coordinated by an asymmetrically coordinating dithio­carbamate ligand, a Cl and two C atoms of the Sn-bound tert-butyl groups. The resulting C2ClS2 donor set defines a coordination geometry inter­mediate between square pyramidal and trigonal bipyramidal with a slight tendency towards the former. In the crystal structure, C—H⋯π contacts link centrosymmetrically related mol­ecules into dimeric aggregates. PMID:21522295

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

USGS Publications Warehouse

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

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.

Method for producing redox shuttles

DOEpatents

Pupek, Krzysztof Z.; Dzwiniel, Trevor L.; Krumdick, Gregory K.

2015-03-03

A single step method for producing a redox shuttle having the formula 2,5-di-tert-butyl-1,4-phenylene tetraethyl bis(phosphate) is provided, the method comprising phosphorylating tert butyl hydroquinone with a phosphate-containing reagent. Also provided is method for producing 2,5-di-tert-butyl-1,4-phenylene tetraethyl bis(phosphate), the method comprising solubilizing tert-butyl hydroquinone and tetrabutylammonium bromide with methyltetrahydrofuran to create a mixture; heating the mixture while adding base to the mixture in an amount to turn the mixture orange; and adding diethyl chlorophosphate to the orange mixture in an amount to phosphorylate the hydroquinone.

Tempol, an intracellular antioxidant, inhibits tissue factor expression, attenuates dendritic cell function, and is partially protective in a murine model of cerebral malaria.

PubMed

Francischetti, Ivo M B; Gordon, Emile; Bizzarro, Bruna; Gera, Nidhi; Andrade, Bruno B; Oliveira, Fabiano; Ma, Dongying; Assumpção, Teresa C F; Ribeiro, José M C; Pena, Mirna; Qi, Chen-Feng; Diouf, Ababacar; Moretz, Samuel E; Long, Carole A; Ackerman, Hans C; Pierce, Susan K; Sá-Nunes, Anderson; Waisberg, Michael

2014-01-01

The role of intracellular radical oxygen species (ROS) in pathogenesis of cerebral malaria (CM) remains incompletely understood. We undertook testing Tempol--a superoxide dismutase (SOD) mimetic and pleiotropic intracellular antioxidant--in cells relevant to malaria pathogenesis in the context of coagulation and inflammation. Tempol was also tested in a murine model of CM induced by Plasmodium berghei Anka infection. Tempol was found to prevent transcription and functional expression of procoagulant tissue factor in endothelial cells (ECs) stimulated by lipopolysaccharide (LPS). This effect was accompanied by inhibition of IL-6, IL-8, and monocyte chemoattractant protein (MCP-1) production. Tempol also attenuated platelet aggregation and human promyelocytic leukemia HL60 cells oxidative burst. In dendritic cells, Tempol inhibited LPS-induced production of TNF-α, IL-6, and IL-12p70, downregulated expression of co-stimulatory molecules, and prevented antigen-dependent lymphocyte proliferation. Notably, Tempol (20 mg/kg) partially increased the survival of mice with CM. Mechanistically, treated mice had lowered plasma levels of MCP-1, suggesting that Tempol downmodulates EC function and vascular inflammation. Tempol also diminished blood brain barrier permeability associated with CM when started at day 4 post infection but not at day 1, suggesting that ROS production is tightly regulated. Other antioxidants-such as α-phenyl N-tertiary-butyl nitrone (PBN; a spin trap), MnTe-2-PyP and MnTBAP (Mn-phorphyrin), Mitoquinone (MitoQ) and Mitotempo (mitochondrial antioxidants), M30 (an iron chelator), and epigallocatechin gallate (EGCG; polyphenol from green tea) did not improve survival. By contrast, these compounds (except PBN) inhibited Plasmodium falciparum growth in culture with different IC50s. Knockout mice for SOD1 or phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (gp91(phox-/-)) or mice treated with inhibitors of SOD (diethyldithiocarbamate) or NADPH oxidase (diphenyleneiodonium) did not show protection or exacerbation for CM. Results with Tempol suggest that intracellular ROS contribute, in part, to CM pathogenesis. Therapeutic targeting of intracellular ROS in CM is discussed.

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

ERIC Educational Resources Information Center

Hairfield, E. M.; And Others

1985-01-01

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

Effect of substrate interaction on the degradation of methyl tert-butyl ether, benzene, toluene, ethylbenzene, and xylene by Rhodococcus sp.

PubMed

Lee, Eun-Hee; Cho, Kyung-Suk

2009-08-15

It was examined the substrate interactions of benzene (B), tolulene (T), ethylbenzene (E), xylene (X), and methyl tert-butyl ether (M) in binary, ternary, quaternary, and quinary mixtures by Rhodococcus sp. EH831 that could aerobically degrade all of five single components. The specific degradation rates (SDRs) of B, T, E, X, and M were 234, 913, 131, 184 and 139 micromol g-dry cell weight (DCW)(-1)h(-1), respectively. In binary, ternary, quaternary, and quinary mixtures of them, ethylbenzene was the strongest inhibitor for the other substrates, and methyl tert-butyl ether was the weakest inhibitor. Interestingly, no degradation of benzene and methyl tert-butyl ether was found in the coexistence of ethylbenzene. The degradation of benzene followed only after toluene became exhausted when both was present. Ethylbenzene was least inhibited by methyl tert-butyl ether and most inhibited by toluene.

Antinociceptive effects of fisetin against diabetic neuropathic pain in mice: Engagement of antioxidant mechanisms and spinal GABAA receptors.

PubMed

Zhao, Xin; Li, Xin-Lin; Liu, Xin; Wang, Chuang; Zhou, Dong-Sheng; Ma, Qing; Zhou, Wen-Hua; Hu, Zhen-Yu

2015-12-01

Peripheral painful neuropathy is one of the most common complications in diabetes and necessitates improved treatment. Fisetin, a naturally occurring flavonoid, has been reported to exert antidepressant-like effect in previous studies. As antidepressant drugs are employed clinically to treat neuropathic pain, this work aimed to investigate whether fisetin possess beneficial effect on diabetic neuropathic pain and explore the mechanism(s). We subjected mice to diabetes by a single intraperitoneal (i.p.) injection of streptozotocin (200mg/kg), and von Frey test or Hargreaves test was used to assess mechanical allodynia or thermal hyperalgesia, respectively. Chronic treatment of diabetic mice with fisetin not only ameliorated the established symptoms of thermal hyperalgesia and mechanical allodynia, but also arrested the development of neuropathic pain when given at low doses. Although chronic fisetin administration did not impact on the symptom of hyperglycemia in diabetic mice, it reduced exacerbated oxidative stress in tissues of spinal cord, dorsal root ganglion (DRG) and sciatic verve. Furthermore, the analgesic actions of fisetin were abolished by repetitive co-treatment with the reactive oxygen species (ROS) donor tert-butyl hydroperoxide (t-BOOH), but potentiated by the ROS scavenger phenyl-N-tert-butylnitrone (PBN). Finally, acute blockade of spinal GABAA receptors by bicuculline totally counteracted such fisetin analgesia. These findings indicate that chronic fisetin treatment can delay or correct neuropathic hyperalgesia and allodynia in mice with type 1 diabetes. Mechanistically, the present fisetin analgesia may be associated with its antioxidant activity, and spinal GABAA receptors are likely rendered as downstream targets. Copyright © 2015 Elsevier Ltd. All rights reserved.

IRIS Toxicological Review of Tert-Butyl Alcohol (Tert-Butanol) (Public Comment Draft)

EPA Science Inventory

EPA is developing an Integrated Risk Information System (IRIS) assessment of tert-butyl Alcohol (tert-butanol) and has released the public comment draft assessment for public comment and external peer review. When final, the assessment will appear on the IRIS databa...

IRIS Toxicological Review of Tert-Butyl Alcohol (Tert-Butanol) (Interagency Science Consultation Draft)

EPA Science Inventory

On April 29, 2016, the Toxicological Review of tert-Butyl Alcohol (tert-Butanol) (Public Comment Draft) was released for public comment. The draft Toxicological Review and charge were reviewed internally by EPA and by other federal agencies and the Executive Office ...

IRIS Toxicological Review of Tert-Butyl Alcohol (Tert-Butanol) (External Review Draft)

EPA Science Inventory

The IRIS Toxicological Review of tert-Butyl Alcohol (tert-Butanol) was released for external peer review in June 2017. EPA’s Science Advisory Board’s (SAB) Chemical Assessment Advisory Committee (CAAC) will conduct a peer review of the scientific basis supporting ...

Hydrolysis of tert-butyl formate: Kinetics, products, and implications for the environmental impact of methyl tert-butyl ether

USGS Publications Warehouse

Church, Clinton D.; Pankow, James F.; Tratnyek, Paul G.

1999-01-01

Asessing the environmental fate of methyl tert-butyl ether (MTBE) has become a subject of renewed interest because of the large quantities of this compound that are being used as an oxygenated additive in gasoline. Various studies on the fate of MTBE have shown that it can be degraded to tert-butyl formate (TBF), particularly in the atmosphere. Although it is generally recognized that TBF is subject to hydrolysis, the kinetics and products of this reaction under environmentally relevant conditions have not been described previously. In this study, we determined the kinetics of TBF hydrolysis as a function of pH and temperature. Over the pH range of 5 to 7, the neutral hydrolysis pathway predominates, with kN = (1.0 ± 0.2) × 10−6/s. Outside this range, strong pH effects were observed because of acidic and basic hydrolyses, from which we determined that kA = (2.7 ± 0.5) × 10−3/(M·s) and kB = 1.7 ± 0.3/(M·s). Buffered and unbuffered systems gave the same hydrolysis rates for a given pH, indicating that buffer catalysis was not significant under the conditions tested. The activation energies corresponding to kN, kA, and kBwere determined to be 78 ± 5, 59 ± 4, and 88 ±11 kJ/mol, respectively. In all experiments, tert-butyl alcohol was found at concentrations corresponding to stoichiometric formation from TBF. Based on our kinetics data, the expected half-life for hydrolysis of TBF at pH = 2 and 4°C (as per some standard preservation protocols for water sampling) is 6 h. At neutral pH and 22°C, the estimated half-life is 5 d, and at pH = 11 and 22°C, the value is only 8 min.

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.

PubMed

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

2013-03-01

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, (1)H 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 μ(B) per Cu(II)) and 6 (2.79 μ(B) per Cu(II)) 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. Copyright © 2012 Elsevier B.V. All rights reserved.

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

USGS Publications Warehouse

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

1997-01-01

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.

The Knock-Limited Performance of Fuel Blends Containing Spiropentane, Methylenecyclobutane, Di-Tert-Butyl Ether, Methyl Tert-Butyl Ether, and Triptane

NASA Technical Reports Server (NTRS)

Meyer, Carl L.

1946-01-01

Tests show that at inlet-air temperatures of 250 deg F and 100 deg F the knock-limited performance of the base fuel of blends, leaded with 4 ml TEL per gallon and containing 20 percent spiropentane, was reduced at fuel/air ratios below 0.085. The 20 percent methylenecyclobutane reduced the knock-limited power of the base fuel at fuel/air ratios below 0.112. Di-tert-butyl ether, methyl-tert-butyl ether, and triptane increased the knock-limited power of the base fuel at all fuel/air ratios and at both temperatures.

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

PubMed

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

2015-04-01

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

Congested ferrocenyl polyphosphanes bearing electron-donating or electron-withdrawing phosphanyl groups: assessment of metallocene conformation from NMR spin couplings and use in palladium-catalyzed chloroarenes activation.

PubMed

Mom, Sophal; Beaupérin, Matthieu; Roy, David; Royer, Sylviane; Amardeil, Régine; Cattey, Hélène; Doucet, Henri; Hierso, J-C

2011-11-21

The synthesis of novel substituted cyclopentadienyl salts that incorporate both a congested branched alkyl group (tert-butyl, (triphenyl)methyl, or tri(4-tert-butyl)phenylmethyl) and a phosphanyl group is reported. The introduction of either electron-withdrawing or electron-donating substituents (furyl, i-propyl, cyclohexyl, tert-butyl) on P atoms was generally achieved in high yield. The modular synthesis of ferrocenyl polyphosphanes from an assembly of these cyclopentadienyl salts was investigated, leading to the formation of new triphosphanes (denoted as 9-12) and diphosphanes (denoted as 14-16). The resulting phosphanes are not sensitive to air or moisture, even when electron-rich substituents are present. This set of polyphosphanes displays varied conformational features, which are discussed in the light of their multinuclear NMR characterization in solution and of the X-ray solid state structure of the representative triphosphane 1,2-bis(diphenylphosphanyl)-1'-(diisopropylphosphanyl)-3'-(triphenyl)methyl-4-tert-butyl ferrocene, 11. In particular, the existence of a range of significantly different nonbonded ("through-space", TS) spin-spin coupling constants between heteroannular P atoms, for the triphosphanes of this class, allowed their preferred conformation in solution to be appraised. The study evidences an unanticipated flexibility of the ferrocene platform, despite the presence of very congested tert-butyl and trityl groups. Herein, we show that, contrary to our first belief, the preferred conformation for the backbone of ferrocenyl polyphosphanes can not only depend on the hindrance of the groups decorating the cyclopentadienyl rings but is also a function of the substituents of the phosphanyl groups. The interest of these robust phosphanes as ligands was illustrated in palladium catalysis for the arylation of n-butyl furan with chloroarenes, using direct C-H activation of the heteroaromatic in the presence of low metal/ligand loadings (0.5-1.0 mol %). Thus, 4-chlorobenzonitrile, 4-chloronitrobenzene, 4-chloropropiophenone, and 4-(trifluoromethyl)chlorobenzene were efficiently coupled to n-butyl furan, using Pd(OAc)(2) associated to the new diphosphane ligands 1,1'-bis(diisopropylphosphanyl)-3,3'-di(triphenyl)methyl ferrocene (15) or 1,1'-bis(dicyclohexylphosphanyl)-3,3'-di(triphenyl)methylferrocene (16), which respectively hold the electron-rich -Pi-Pr(2) and -PCy(2) groups.

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

USGS Publications Warehouse

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

1956-01-01

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

Chemistry and Technology of the Production of Fiber Nitron (Khimiya i Tekhnologiya Proizvodstva Volokna Nitron),

DTIC Science & Technology

1987-07-17

of some salts, mainly thiocyanate sodium. With wet spinning are used water/aqueous precipitation baths or organic coagulants (glycerin, hexanetriol ...comparatively small. During utilization of glycerine, isopropyl, butyl, hexanetriol baths into composition of bath for increasing elasticity of fiber...the number of C-atoms in the chain of their molecules. Therefore the glycerine bath is more than "rigid", than hexanetriol , whose effect/action is

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

PubMed Central

Gau, Michael R.; Zdilla, Michael J.

2016-01-01

Organolithium reagents are powerful tools in the synthetic chemist's toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented. PMID:27911386

21 CFR 177.2470 - Polyoxymethylene copolymer.

Code of Federal Regulations, 2013 CFR

2013-04-01

... its production. The quantity of any optional adjuvant substance employed in the production of the.... Tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. (2) Lubricant: N,N...

21 CFR 177.2470 - Polyoxymethylene copolymer.

Code of Federal Regulations, 2011 CFR

2011-04-01

... its production. The quantity of any optional adjuvant substance employed in the production of the.... Tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. (2) Lubricant: N,N...

21 CFR 177.2470 - Polyoxymethylene copolymer.

Code of Federal Regulations, 2010 CFR

2010-04-01

... its production. The quantity of any optional adjuvant substance employed in the production of the.... Tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. (2) Lubricant: N,N...

21 CFR 177.2470 - Polyoxymethylene copolymer.

Code of Federal Regulations, 2012 CFR

2012-04-01

... its production. The quantity of any optional adjuvant substance employed in the production of the.... Tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. (2) Lubricant: N,N...

Synthesis and evaluation of L-cystathionine as a standard for amino acid analysis.

PubMed

Amino, Yusuke; Suzuki, Yumiko

2017-01-01

L-Cystathionine is a key nonprotein amino acid related to metabolic conditions. The quantitative determination of L-cystathionine in physiological fluids by amino acid analysis is important for clinical diagnosis; however, certified reference material for L-cystathionine with satisfactory purity, content, and quantity has been unavailable until recently. Consequently, a practical and simple method for the preparation of L-cystathionine was examined, which involves thioalkylation of N-tert-butoxycarbonyl-L-cysteine tert-butyl ester, derived from L-cystine, with (2S)-2-(tert-butoxycarbonyl)amino-4-iodobutanoic acid tert-butyl ester, derived from L-aspartic acid, to obtain L-cystathionine with protecting groups, followed by single-step deprotection under mild conditions. This method produces L-cystathionine in high purity (99.4%) and having sufficient percentage content according to amino acid analysis, which could be used as a standard for the amino acid analysis of physiological fluids.

Enhanced cometabolic degradation of methyl tert-butyl ether by a Pseudomonas sp. strain grown on n-pentane

NASA Astrophysics Data System (ADS)

Li, S. S.; Wang, S.; Yan, W.

2016-08-01

When methyl tert-butyl ether (MTBE) is added as oxygenates it increases the octane number and decreases the release of nitric oxide from the incomplete combustion of reformulated gasoline. The extensive use of MTBE allowed it to be detectable as a pollutant in both ground-level and underground water worldwide. The present study focuses on the isolation and characterization of MTB-degrading microorganisms by cometabolism based on the results of growth on different carbon sources. It also focuses on the kinetic analysis and the continuous degradation of MTBE. A bacterial strain WL1 that can grow on both n-alkanes (C5-C8) and aromatics was isolated and named Pseudomonas sp. WL1 according to the 16S rDNA sequencing analysis. Strain WL1 could cometabolically degrade MTBE in the presence of n-alkanes with a desirable degradation rate. Diverse n-alkanes with different lengths of carbon chains showed significant influence on the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA). When strain WL1 cometabolically degraded MTBE in the presence of n-pentane, higher MTBE-degrading rate and lower TBA-accumulation were observed (Vmax = 38.1 nmol/min/mgprotei, Ks = 6.8 mmol/L). In the continuous degrading experiment, the removal efficiency of MTBE by Pseudomonas sp. WL1 did not show any obvious decrease after five subsequent additions.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Tingshun, E-mail: tshjiang@mail.ujs.edu.cn; Cheng, Jinlian; Liu, Wangping

2014-10-15

Several zirconium (or aluminum) incorporated mesoporous MCM-48 solid acid catalysts (SO{sub 4}{sup 2−}/Zr-MCM-48 and SO{sub 4}{sup 2−}/Al-MCM-48) were prepared by the impregnation method and their physicochemical properties were characterized by means of XRD, FT-IR, TEM, NH{sub 3}-TPD and N{sub 2} physical adsorption. Also, the catalytic activities of these solid acid catalysts were evaluated by the alkylation of phenol with tert-butyl alcohol. The effect of weight hour space velocity (WHSV), reaction time and reaction temperature on catalytic properties was also studied. The results show that the SO{sub 4}{sup 2−}/Zr-MCM-48 and SO{sub 4}{sup 2−}/Al-MCM-48 still have good mesoporous structure and long rangemore » ordering. Compared with the Zr (or Al)–MCM-48 samples, SO{sub 4}{sup 2−}/Zr-MCM-48 and SO{sub 4}{sup 2−}/Al-MCM-48 solid acid catalysts have strong acidity and exhibit high activities in alkylation reaction of phenol with tert-butyl alcohol. The SO{sub 4}{sup 2−}/Zr-MCM-48-25 (molar ratio of Si/Zr=0.04) catalyst was found to be the most promising and gave the highest phenol conversion among all catalysts. A maximum phenol conversion of 91.6% with 4-tert-butyl phenol (4-TBP) selectivity of 81.8% was achieved when the molar ratio of tert-butyl alcohol:phenol is 2:1, reaction time is 2 h, the WHSV is 2 h{sup −1} and the reaction temperature is 140 °C. - Highlights: • Sulfuric acid functional mesoporous solid acid catalysts were prepared via impregnation method. • The alkylation of phenol with tert-butyl alcohol was carried out over these solid acid catalysts. • The catalytic activity of SO{sub 4}{sup 2−}/Zr-MCM-48-25 catalyst is much higher than that of the others. • A maximum phenol conversion of 91.6% was achieved under optimum reaction conditions for SO{sub 4}{sup 2−}/Zr-MCM-48-25.« less

Formation of Germa-ketenimine on the Ge(100) Surface by Adsorption of tert-Butyl Isocyanide.

PubMed

Shong, Bonggeun; Yoo, Jong Suk; Sandoval, Tania E; Bent, Stacey F

2017-06-28

Reactions of the (100) surfaces of Ge and Si with organic molecules have been generally understood within the concept of "dimers" formed by the 2 × 1 surface reconstruction. In this work, the adsorption of tert-butyl isocyanide on the Ge(100)-2 × 1 surface at large exposures is investigated under ultrahigh vacuum conditions. A combination of infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption experiments along with dispersion-corrected density functional theory calculations is used to determine the surface products. Upon adsorption of a dense monolayer of tert-butyl isocyanide, a product whose structure resembles a germa-ketenimine (N=C=Ge) with σ donation toward and π back-donation from the Ge(100) surface appears. Formation of this structure involves divalent-type surface Ge atoms that arise from cleavage of the Ge(100)-2 × 1 surface dimers. Our results reveal an unprecedented class of reactions of organic molecules at the Ge(100) surface.

Bis[μ-N-(tert-butyl­dimethyl­silyl)-N-(pyridin-2-ylmeth­yl)amido]­bis­[methyl­cobalt(II)

PubMed Central

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

2012-01-01

The green title complex, [Co2(CH3)2(C12H21N2Si)2], was obtained from bis­{[μ-N-tert-butyl­dimethyl­silyl-N-(pyridin-2-ylmeth­yl)amido]­chloridocobalt(II)} and methyl­lithium in diethyl ether at 195 K via a metathesis reaction. The dimeric cobalt(II) complex exhibits a crystallographic center of inversion in the middle of the Co2N2 ring (average Co—N = 2.050 Å). The CoII atom shows a distorted tetra­hedral coordination sphere. The exocyclic Co—N bond length to the pyridyl group shows a similar value of 2.045 (4) Å. The exocyclic methyl group has a rather long Co—C bond length of 2.019 (5) Å. PMID:22969464

Mutagenic and Cytotoxicity LQB 123 Profile: Safety and Tripanocidal Effect of a Phenyl-t-Butylnitrone Derivative

PubMed Central

Cupello, Mauricio Peixoto; Saraiva, Francis Monique; Ippolito, Pedro; Fernandes, Andréia da Silva; Costa, Debora de Sousa dos Santos; Paula, Jessica Isis Oliveira; Costa, Paulo Roberto Ribeiro; Dias, Ayres Guimarães

2017-01-01

The therapeutic options for Chagas disease are limited and its treatment presents a number of drawbacks including toxicity, drug resistance, and insufficient effectiveness against the chronic stage of the disease. Therefore, new therapeutical options are mandatory. In the present work, we evaluated the effect of a phenyl-tert-butylnitrone (PBN) derivate, LQB 123, against Trypanosoma cruzi forms. LQB 123 presented a trypanocidal effect against bloodstream trypomastigotes (IC50 = 259.4 ± 6.1 μM) and intracellular amastigotes infecting peritoneal macrophages (IC50 = 188.2 ± 47.5 μM), with no harmful effects upon the mammalian cells (CC50 values greater than 4 mM), resulting in a high selectivity index (CC50/IC50 > 20). Additionally, metacyclic trypomastigotes submitted to LQB 123 presented an IC50 of about 191.8 ± 10.5 μM and epimastigotes forms incubated with different concentrations of LQB 123 presented an inhibition of parasite growth with an IC50 of 255.1 ± 3.6 μM. Finally, we investigated the mutagenic potential of the nitrone by the Salmonella/microsome assay and observed no induction of mutagenicity even in concentrations as high as 33000 μM. Taken together, these results present a nonmutagenic compound, with trypanocidal activity against all relevant forms of T. cruzi, offering new insights into CD treatment suggesting additional in vivo tests. PMID:28316976

Mutagenic and Cytotoxicity LQB 123 Profile: Safety and Tripanocidal Effect of a Phenyl-t-Butylnitrone Derivative.

PubMed

Cupello, Mauricio Peixoto; Saraiva, Francis Monique; Ippolito, Pedro; Fernandes, Andréia da Silva; Menna-Barreto, Rubem Figueiredo Sadoko; Costa, Debora de Sousa Dos Santos; Paula, Jessica Isis Oliveira; Costa, Paulo Roberto Ribeiro; Nogueira, Natália Pereira; Felzenswalb, Israel; Dias, Ayres Guimarães; Paes, Marcia Cristina

2017-01-01

The therapeutic options for Chagas disease are limited and its treatment presents a number of drawbacks including toxicity, drug resistance, and insufficient effectiveness against the chronic stage of the disease. Therefore, new therapeutical options are mandatory. In the present work, we evaluated the effect of a phenyl- tert -butylnitrone (PBN) derivate, LQB 123, against Trypanosoma cruzi forms. LQB 123 presented a trypanocidal effect against bloodstream trypomastigotes (IC 50 = 259.4 ± 6.1  μ M) and intracellular amastigotes infecting peritoneal macrophages (IC 50 = 188.2 ± 47.5  μ M), with no harmful effects upon the mammalian cells (CC 50 values greater than 4 mM), resulting in a high selectivity index (CC 50 /IC 50 > 20). Additionally, metacyclic trypomastigotes submitted to LQB 123 presented an IC 50 of about 191.8 ± 10.5  μ M and epimastigotes forms incubated with different concentrations of LQB 123 presented an inhibition of parasite growth with an IC 50 of 255.1 ± 3.6  μ M. Finally, we investigated the mutagenic potential of the nitrone by the Salmonella /microsome assay and observed no induction of mutagenicity even in concentrations as high as 33000  μ M. Taken together, these results present a nonmutagenic compound, with trypanocidal activity against all relevant forms of T. cruzi , offering new insights into CD treatment suggesting additional in vivo tests.

Azobenzene versus 3,3',5,5'-tetra-tert-butyl-azobenzene (TBA) at Au(111): characterizing the role of spacer groups.

PubMed

McNellis, Erik R; Bronner, Christopher; Meyer, Jörg; Weinelt, Martin; Tegeder, Petra; Reuter, Karsten

2010-06-28

We present large-scale density-functional theory (DFT) calculations and temperature programmed desorption measurements to characterize the structural, energetic and vibrational properties of the functionalized molecular switch 3,3',5,5'-tetra-tert-butyl-azobenzene (TBA) adsorbed at Au(111). Particular emphasis is placed on exploring the accuracy of the semi-empirical dispersion correction approach to semi-local DFT (DFT-D) in accounting for the substantial van der Waals component in the surface bonding. In line with previous findings for benzene and pure azobenzene at coinage metal surfaces, DFT-D significantly overbinds the molecule, but seems to yield an accurate adsorption geometry as far as can be judged from the experimental data. Comparing the trans adsorption geometry of TBA and azobenzene at Au(111) reveals a remarkable insensitivity of the structural and vibrational properties of the -N[double bond, length as m-dash]N- moiety. This questions the established view of the role of the bulky tert-butyl-spacer groups for the switching of TBA in terms of a mere geometric decoupling of the photochemically active diazo-bridge from the gold substrate.

IRIS Toxicological Review of Tert-Butyl Alcohol (Tert-Butanol) ...

EPA Pesticide Factsheets

The IRIS Toxicological Review of tert-Butyl Alcohol (tert-Butanol) was released for external peer review in June 2017. EPA’s Science Advisory Board’s (SAB) Chemical Assessment Advisory Committee (CAAC) will conduct a peer review of the scientific basis supporting the tert-butanol assessment and release a final report of their review. Information regarding the peer review can be found on the SAB website. EPA is conducting an Integrated Risk Information System (IRIS) health assessment for tert-butanol. The outcome of this project is a Toxicological Review and IRIS Summary for tert-butanol that will be entered into the IRIS database.

Composition and method for encapsulating photovoltaic devices

DOEpatents

Pern, Fu-Jann

2000-01-01

A composition and method for encapsulating a photovoltaic device which minimizes discoloration of the encapsulant. The composition includes an ethylene-vinyl acetate encapsulant, a curing agent, an optional ultraviolet light stabilizer, and/or an optional antioxidant. The curing agent is preferably 1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane; the ultraviolet light stabilizer is bis-(N-octyloxy-tetramethyl) piperidinyl sebacate and the antioxidant is selected from the group consisting of tris (2,4-di-tert-butylphenyl) phosphite, tetrakis methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate) methane, octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate, and 2,2'-ethylidene bis(4,6-di-t-butylphenyl) fluorophosponite. The composition is applied to a solar cell then cured. The cured product contains a minimal concentration of curing-generated chromophores and resists UV-induced degradation.

Secoisolariciresinol diglycoside, a flaxseed lignan, exerts analgesic effects in a mouse model of type 1 diabetes: Engagement of antioxidant mechanism.

PubMed

Hu, Pei; Mei, Qi-Yong; Ma, Li; Cui, Wu-Geng; Zhou, Wen-Hua; Zhou, Dong-Sheng; Zhao, Qing; Xu, Dong-Ying; Zhao, Xin; Lu, Qin; Hu, Zhen-Yu

2015-11-15

Peripheral painful neuropathy is one of the most common complications in diabetes and necessitates improved treatment. Secoisolariciresinol diglycoside (SDG), a predominant lignan in flaxseed, has been shown in our previous studies to exert antidepressant-like effect. As antidepressant drugs are clinically used to treat chronic neuropathic pain, this work aimed to investigate the potential analgesic efficacy of SDG against diabetic neuropathic pain in a mouse model of type 1 diabetes. We subjected mice to diabetes by a single intraperitoneal (i.p.) injection of streptozotocin (STZ, 200 mg/kg), and Hargreaves test or von Frey test was used to assess thermal hyperalgesia or mechanical allodynia, respectively. Chronic instead of acute SDG treatment (3, 10 or 30 mg/kg, p.o., twice per day for three weeks) ameliorated thermal hyperalgesia and mechanical allodynia in diabetic mice, and these analgesic actions persisted about three days when SDG treatment was terminated. Although chronic treatment of SDG to diabetic mice did not impact on the symptom of hyperglycemia, it greatly attenuated excessive oxidative stress in sciatic nerve and spinal cord tissues, and partially counteracted the condition of weight decrease. Furthermore, the analgesic actions of SDG were abolished by co-treatment with the reactive oxygen species donor tert-butyl hydroperoxide (t-BOOH), but potentiated by the reactive oxygen species scavenger phenyl-N-tert-butylnitrone (PBN). These findings indicate that chronic SDG treatment can correct neuropathic hyperalgesia and allodynia in mice with type 1 diabetes. Mechanistically, the analgesic actions of SDG in diabetic mice may be associated with its antioxidant activity. Copyright © 2015. Published by Elsevier B.V.

Identification of tert-Butyl Cations in Zeolite H-ZSM-5: Evidence from NMR Spectroscopy and DFT Calculations.

PubMed

Dai, Weili; Wang, Chuanming; Yi, Xianfeng; Zheng, Anmin; Li, Landong; Wu, Guangjun; Guan, Naijia; Xie, Zaiku; Dyballa, Michael; Hunger, Michael

2015-07-20

Experimental evidence for the presence of tert-butyl cations, which are important intermediates in acid-catalyzed heterogeneous reactions, on solid acids has still not been provided to date. By combining density functional theory (DFT) calculations with (1)H/(13)C magic-angle-spinning NMR spectroscopy, the tert-butyl cation was successfully identified on zeolite H-ZSM-5 upon conversion of isobutene by capturing this intermediate with ammonia. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analytical results from ground-water sampling using a direct-push technique at the Dover National Test Site, Dover Air Force Base, Delaware, June-July 2001

USGS Publications Warehouse

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

2004-01-01

A joint study by the Dover National Test Site and the U.S. Geological Survey was conducted from June 27 through July 18, 2001 to determine the spatial distribution of the gasoline oxygenate additive methyl tert-butyl ether and selected water-quality constituents in the surficial aquifer underlying the Dover National Test Site at Dover Air Force Base, Delaware. The study was conducted to support a planned enhanced bio-remediation demonstration and to assist the Dover National Test Site in identifying possible locations for future methyl tert-butyl ether remediation demonstrations. This report presents the analytical results from ground-water samples collected during the direct-push ground-water sampling study. A direct-push drill rig was used to quickly collect 115 ground-water samples over a large area at varying depths. The ground-water samples and associated quality-control samples were analyzed for volatile organic compounds and methyl tert-butyl ether by the Dover National Test Site analytical laboratory. Volatile organic compounds were above the method reporting limits in 59 of the 115 ground-water samples. The concentrations ranged from below detection limits to maximum values of 12.4 micrograms per liter of cis-1,2-dichloroethene, 1.14 micrograms per liter of trichloroethene, 2.65 micrograms per liter of tetrachloroethene, 1,070 micrograms per liter of methyl tert-butyl ether, 4.36 micrograms per liter of benzene, and 1.8 micrograms per liter of toluene. Vinyl chloride, ethylbenzene, p,m-xylene, and o-xylene were not detected in any of the samples collected during this investigation. Methyl tert-butyl ether was detected in 47 of the 115 ground-water samples. The highest methyl tert-butyl ether concentrations were found in the surficial aquifer from -4.6 to 6.4 feet mean sea level, however, methyl tert-butyl ether was detected as deep as -9.5 feet mean sea level. Increased methane concentrations and decreased dissolved oxygen concentrations were found in samples that contained methyl tert-butyl ether.

Organophosphazenes. 15. Reactions of Hexafluorocyclotriphosphazene with Tert- and n-Butyl Lithium Reagents

DTIC Science & Technology

1981-12-04

H ECU’ITY CLASSIFICATION OF THIS PAGE (When frl,* IFnfered) REPORT DOCUMENTATION PAGE - RE INSTRUCTIONSBEFORE COMPLETING FORM 1. REPORT NUMBER 2...GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER 10 _ _ _ _V11 * 4. TITLE (and Subtitle) S. TYPE OF REPORT I PERIOD COVERED Organoohosphazenes. 15...Reactions of Hexafluro- Technical Report cvclotriphosDhazene with Tert- and n-Butvl Lithium Reagents . PERFORMING ORG. REPORT NUMSER 7. AUTHOR•,) S

Crystal structure of (2,2′-bi­pyridine-κ2 N,N′)bis­(3,5-di-tert-butyl-o-benzo­quinonato-κ2 O,O′)ruthenium(II)

PubMed Central

Ali, Akram; Potaskalov, Vadim A.

2017-01-01

In the title mononuclear complex, [Ru(C14H20O2)2(C10H8N2)], the RuII ion has a distorted octa­hedral coordination environment defined by two N atoms of the chelating 2,2′-bi­pyridine ligand and four O atoms from two 3,5-di-tert-butyl-o-benzo­quinone ligands. In the crystal, the complex mol­ecules are linked by inter­molecular C—H⋯O hydrogen bonds and π–π stacking inter­actions between the 2,2′-bi­pyridine ligands [centroid–centroid distance = 3.538 (3) Å], resulting in a layer structure extending parallel to the ab plane. PMID:28316832

Gabapentin-base synthesis and theoretical studies of biologically active compounds: N-cyclohexyl-3-oxo-2-(3-oxo-2-azaspiro[4.5] decan-2-yl)-3-arylpropanamides and N-(tert-butyl)-2-(3-oxo-2-azaspiro[4.5]decan-2-yl)-2-arylacetamide derivatives

NASA Astrophysics Data System (ADS)

Amirani Poor, Mahboobe; Darehkordi, Ali; Anary-Abbasinejad, Mohammad; Mohammadi, Marziyeh

2018-01-01

An intermolecular Ugi reaction of 2-(1-(aminomethyl)cyclohexyl)acetic acid (gabapentin) with glyoxal and cyclohexyl isocyanide or aromatic aldehyde and tertbutyl isocyanide under mild conditions in ethanol have been developed to produce two novel class of N-cyclohexyl-3-(aryl)-3-oxo-2-(3-oxo-2-azaspiro[4.5]decan-2-yl)propanamideins and N-(tert-butyl)-2-(3-oxo-2-azaspiro[4.5]decan-2-yl)-2-arylacetamide derivatives in good to excellent yields. This presents the first report for the intermolecular Ugi three component reaction of gabapentin, glyoxal, and an isocyanide. Also according to the theoretical studies the electron-donating groups increase the strength of intramolecular hydrogen bond and electron-withdrawing groups decrease the strength of intramolecular hydrogen bond.

[Identification of migrants from nitrile-butadiene rubber gloves].

PubMed

Mutsuga, Motoh; Kawamura, Yoko; Wakui, Chiseko; Maitani, Tamio

2003-04-01

Polyvinyl chloride gloves containing di(2-ethylhexyl) phthalate are restricted for food contact use. In their place, disposable gloves made from nitrile-butadiene rubber (NBR) are used in contact with foodstuffs. Some unknown substances were found to migrate into n-heptane from NBR gloves. By GC/MS, HR-MS and NMR, their chemical structures were confirmed to be 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (used as a plasticizer), 4,4'-butylidenedi(6-tert-butyl-m-cresol), a mixture of styrenated phenols consisting of 2-(alpha-methylbenzyl)phenol, 4-(alpha-methylbenzyl)phenol, 2,6-di(alpha-methylbenzyl)phenol, 2,4-di(alpha-methylbenzyl)phenol and 2,4,6-tri(alpha-methylbenzyl)phenol (used as antioxidants), and 2,4-di-tert-butylphenol, which seems to a degradation product of antioxidant. Migration levels of these compounds were 1.68 micrograms/cm2 of 2,4-di-tert-butylphenol, 2.80 micrograms/cm2 of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, 46.08 micrograms/cm2 of styrenated phenols and 4.22 micrograms/cm2 of 4,4'-butylidenedi(6-tert-butyl-m-cresol) into n-heptane, respectively. The content of total styrenated phenols was 6,900 micrograms/g in NBR gloves.

Ionic-liquid-mediated poly(dimethylsiloxane)- grafted carbon nanotube fiber prepared by the sol-gel technique for the head space solid-phase microextraction of methyl tert-butyl ether using GC.

PubMed

Vatani, Hossein; Yazdi, Ali Sarafraz

2014-01-01

A headspace solid-phase microextraction method was developed for the preconcentration and extraction of methyl tert-butyl ether. An ionic-liquid-mediated multiwalled carbon nanotube-poly(dimethylsiloxane) hybrid coating, which was prepared by covalent functionalization of multiwalled carbon nanotubes with hydroxyl-terminated poly(dimethylsiloxane) using the sol-gel technique, was used as solid-phase microextraction adsorbent. This innovative fiber exhibited a highly porous surface structure, high thermal stability (at least 320°C) and long lifespan (over 210 uses). Potential factors affecting the extraction efficiency were optimized. Under the optimum conditions, the method LOD (S/N = 3) was 0.007 ng/mL and the LOQ (S/N = 10) was 0.03 ng/mL. The calibration curve was linear in the range of 0.03-200 ng/mL. The RSDs for one fiber (repeatability, n = 5) at three different concentrations (0.05, 1, and 150 ng/mL) were 5.1, 4.2, and 4.6% and for the fibers obtained from different batches (reproducibility, n = 3) were 6.5, 5.9, and 6.3%, respectively. The developed method was successfully applied to the determination of methyl tert-butyl ether in different real water samples on three consecutive days. The relative recoveries for the spiked samples with 0.05, 1, and 150 ng/mL were between 94-104%. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

N-heterocycle carbene (NHC)-ligated cyclopalladated N,N-dimethylbenzylamine: a highly active, practical and versatile catalyst for the Heck-Mizoroki reaction.

PubMed

Peh, Guang-Rong; Kantchev, Eric Assen B; Zhang, Chi; Ying, Jackie Y

2009-05-21

The wide dissemination of catalytic protocols in academic and industrial laboratories is facilitated by the development of catalysts that are not only highly active but also user-friendly, stable to moisture, air and long term storage and easy to prepare on a large scale. Herein we describe a protocol for the Heck-Mizoroki reaction mediated by cyclopalladated N,N-dimethylbenzylamine (dmba) ligated with a N-heterocyclic carbene, 1,3-bis(mesityl)imidazol-2-ylidene (IMes), that fulfils these criteria. The precatalyst can be synthesized on approximately 100 g scale by a tri-component, sequential, one-pot reaction of N,N-dimethylbenzylamine, PdCl2 and IMes.HCl in refluxing acetonitrile in air in the presence of K2CO3. This single component catalyst is stable to air, moisture and long term storage and can be conveniently dispensed as a stock solution in NMP. It mediates the Heck-Mizoroki reaction of a range of aryl- and heteroaryl bromides in reagent grade NMP at the 0.1-2 mol% range without the need for rigorous anhydrous techniques or a glovebox, and is active even in air. The catalyst is capable of achieving very high levels of catalytic activity (TON of up to 5.22 x 10(5)) for the coupling of a deactivated arylbromide, p-bromoanisole, with tBu acrylate as a benchmark substrate pair. A wide range of aryl bromides, iodides and, for the first time with a NHC-Pd catalyst, a triflate was coupled with diverse acrylate derivatives (nitrile, tert-butyl ester and amides) and styrene derivatives. The use of excess (>2 equiv.) of the aryl bromide and tert-butyl acrylate leads to mixture of tert-butyl beta,beta-diarylacrylate and tert-butyl cinnamate derivatives depending on the substitution pattern of the aryl bromide. Electron rich m- and p-substituted arylbromides give the diarylated products exclusively, whereas electron-poor aryl bromides give predominantly mono-arylated products. For o-substituted aryl bromides, no doubly arylated products could be obtained under any conditions. Overall, the active catalyst (IMes-Pd) shows higher activity with electron-rich aryl halides, a marked difference compared with the more commonly used phosphane-Pd or non-ligated Pd catalysts.

Monitoring of BHT-quinone and BHT-CHO in the gas of capsules of Asclepias physocarpa.

PubMed

Ma, Bing-Ji; Peng, Hua; Liu, Ji-Kai

2006-01-01

Three volatile components, namely benzoic acid ethyl ester (1), 2,6-di-tert-butyl-p-benzoquinone (BHT-quinone) (2), and 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) (3), were detected from the gas in the capsules of Asclepias physocarpa by means of GC/MS analysis. BHT-quinone and BHT-CHO as organic pollutants are the degradation products of the antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT). Ground water, lake water and/or rain water are a source of BHT metabolites in the plant Asclepias physocarpa.

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

USGS Publications Warehouse

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

1999-01-01

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

Methyl tert-butyl ether (MTBE)

Integrated Risk Information System (IRIS)

Methyl tert - butyl ether ( MTBE ) ; CASRN 1634 - 04 - 4 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments f

GVS-111 prevents oxidative damage and apoptosis in normal and Down's syndrome human cortical neurons.

PubMed

Pelsman, Alejandra; Hoyo-Vadillo, Carlos; Gudasheva, Tatiana A; Seredenin, Sergei B; Ostrovskaya, Rita U; Busciglio, Jorge

2003-05-01

The neuroprotective activity of a novel N-acylprolyl-containing dipeptide analog of the nootropic 2-oxo-1-pyrrolidine acetamide (Piracetam) designated as GVS-111 (DVD-111/Noopept) was tested in two in vitro models of neuronal degeneration mediated by oxidative stress: normal human cortical neurons treated with H(2)O(2), and Down's syndrome (DS) cortical neurons. Incubation of normal cortical neurons with 50 microM H(2)O(2) for 1h resulted in morphological and structural changes consistent with neuronal apoptosis and in the degeneration of more than 60% of the neurons present in the culture. GVS-111 significantly increased neuronal survival after H(2)O(2)-treatment displaying a dose-dependent neuroprotective activity from 10nM to 100 microM, and an IC(50) value of 1.21+/-0.07 microM. GVS-111 inhibited the accumulation of intracellular free radicals and lipid peroxidation damage in neurons treated with H(2)O(2) or FeSO(4), suggesting an antioxidant mechanism of action. GVS-111 exhibited significantly higher neuroprotection compared to the standard cognition enhancer Piracetam, or to the antioxidants Vitamin E, propyl gallate and N-tert-butyl-2-sulpho-phenylnitrone (s-PBN). In DS cortical cultures, chronic treatment with GVS-111 significantly reduced the appearance of degenerative changes and enhanced neuronal survival. The results suggest that the neuroprotective effect of GVS-111 against oxidative damage and its potential nootropic activity may present a valuable therapeutic combination for the treatment of mental retardation and chronic neurodegenerative disorders.

Vapor intrusion risk of fuel ether oxygenates methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME) and ethyl tert-butyl ether (ETBE): A modeling study.

PubMed

Ma, Jie; Xiong, Desen; Li, Haiyan; Ding, Yi; Xia, Xiangcheng; Yang, Yongqi

2017-06-15

Vapor intrusion of synthetic fuel additives represents a critical yet still neglected problem at sites contaminated by petroleum fuel releases. This study used an advanced numerical model to investigate the vapor intrusion potential of fuel ether oxygenates methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME), and ethyl tert-butyl ether (ETBE). Simulated indoor air concentration of these compounds can exceed USEPA indoor air screening level for MTBE (110μg/m 3 ). Our results also reveal that MTBE has much higher chance to cause vapor intrusion problems than TAME and ETBE. This study supports the statements made by USEPA in the Petroleum Vapor Intrusion (PVI) Guidance that the vertical screening criteria for petroleum hydrocarbons may not provide sufficient protectiveness for fuel additives, and ether oxygenates in particular. In addition to adverse impacts on human health, ether oxygenate vapor intrusion may also cause aesthetic problems (i.e., odour and flavour). Overall, this study points out that ether oxygenates can cause vapor intrusion problems. We recommend that USEPA consider including the field measurement data of synthetic fuel additives in the existing PVI database and possibly revising the PVI Guidance as necessary. Copyright © 2017 Elsevier B.V. All rights reserved.

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

EPA Science Inventory

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

Adduction of DNA with MTBE and TBA in mice studied by accelerator mass spectrometry.

PubMed

Yuan, Y; Wang, H F; Sun, H F; Du, H F; Xu, L H; Liu, Y F; Ding, X F; Fu, D P; Liu, K X

2007-12-01

Methyl tert-butyl ether (MTBE) is a currently worldwide used octane enhancer substituting for lead alkyls and gasoline oxygenate. Our previous study using doubly (14)C-labeled MTBE [(CH(3))(3) (14)CO(14)CH(3)] has shown that MTBE binds DNA to form DNA adducts at low dose levels in mice. To elucidate the mechanism of the binding reaction, in this study, the DNA adducts with singly (14)C-labeled MTBE, which was synthesized from (14)C-methanol and tert-butyl alcohol (TBA), or (14)C-labeled TBA in mice have been measured by ultra sensitive accelerator mass spectrometry. The results show that the methyl group of MTBE and tert-butyl alcohol definitely form adducts with DNA in mouse liver, lung, and kidney. The methyl group of MTBE is the predominant binding part in liver, while the methyl group and the tert-butyl group give comparable contributions to the adduct formation in lung and kidney.

Two related lithium calixarene complexes, [p-tert-butylcalix[4]arene(OMe)(OH)2(OLi)](2).4MeCN and {p-tert-butylcalix[4]arene(OH)2(OLi)[OLi(NCMe)2]}(2).8MeCN, determined using synchrotron radiation.

PubMed

Lee, Darren S; Elsegood, Mark R J; Redshaw, Carl; Zhan, Shuzhong

2009-08-01

The crystal structures of acetonitrile solvates of two related lithium calixarene complexes have been determined by low-temperature single-crystal X-ray diffraction using synchrotron radiation. Bis(mu-5,11,17,23-tetra-tert-butyl-26,28-dihydroxy-25-methoxy-27-oxidocalix[4]arene)dilithium(I) acetonitrile tetrasolvate, [Li2(C45H57O4)2].4C2H3N or [p-tert-butylcalix[4]arene(OMe)(OH)2(OLi)](2).4MeCN, (I), crystallizes with the complex across a centre of symmetry and with four molecules of unbound acetonitrile of crystallization per complex. Tetraacetonitrilebis(mu-5,11,17,23-tetra-tert-butyl-26,28-dihydroxy-25,27-dioxidocalix[4]arene)tetralithium(I) acetonitrile octasolvate, [Li4(C44H54O4)2(C2H3N)4].8C2H3N or {p-tert-butylcalix[4]arene(OH)2(OLi)[OLi(NCMe)2]}(2).8MeCN, (II), also crystallizes with the complex lying across a centre of symmetry and contains eight molecules of unbound acetonitrile per complex plus four more directly bound to two of the lithium ions, two on each ion. The cores of both complexes are partially supported by O-H...O hydrogen bonds. The methoxy methyl groups in (I) prevent the binding of any more than two Li+ ions, while the corresponding two O-atom sites in (II) bind an extra Li(+) ion each, making four in total. The calixarene cone adopts an undistorted cone conformation in (I), but an elliptical one in (II).

Influence of thermocleavable functionality on organic field-effect transistor performance of small molecules

NASA Astrophysics Data System (ADS)

Mahale, Rajashree Y.; Dharmapurikar, Satej S.; Chini, Mrinmoy Kumar; Venugopalan, Vijay

2017-06-01

Diketopyrrolopyrrole based donor-acceptor-donor conjugated small molecules using ethylene dioxythiophene as a donor was synthesized. Electron deficient diketopyrrolopyrrole unit was substituted with thermocleavable (tert-butyl acetate) side chains. The thermal treatment of the molecules at 160 °C eliminated the tert-butyl ester group results in the formation of corresponding acid. Optical and theoretical studies revealed that the molecules adopted a change in molecular arrangement after thermolysis. The conjugated small molecules possessed p-channel charge transport characteristics in organic field effect transistors. The charge carrier mobility was increased after thermolysis of tert-butyl ester group to 5.07 × 10-5 cm2/V s.

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...

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...

Hydroalumination of a chlorotrialkynylsilane: spontaneous stepwise 1,3-dyotropic rearrangement via an intermediate silyl cation.

PubMed

Uhl, Werner; Bohnemann, Jörg; Layh, Marcus; Würthwein, Ernst-Ulrich

2014-07-07

A new functionalised alkynylsilane, Cl-Si(CC-CMe3 )3 (3), was obtained by a facile multistep synthesis. Treatment of 3 with equimolar quantities of the hydrides H-M(CMe3 )2 (M=Al, Ga) gave the mixed alkenyl-di(alkynyl)silanes, in which the chlorine atom adopts a bridging position between the aluminium and silicon atoms. Dual hydrogallation of 3 resulted in the formation of a di(alkenyl)-alkynylsilane containing two gallium atoms, one of which is coordinated to the chlorine atom, and the second is bonded to the α-carbon atom of the remaining alkynyl group. A tert-butylsilane was unexpectedly formed by a unique 1,3-dyotropic chlorine-tert-butyl exchange for the corresponding dialuminium compound. One aluminium atom is bonded to a tert-butyl group, a terminal chlorine atom and the α-carbon atom of the ethynyl moiety; the second is coordinatively unsaturated, with two terminal tert-butyl substituents. High-level quantum-chemical calculations favour a stepwise dyotropic rearrangement with an intermediate cationic silicon species over a simultaneous tert-butyl-chlorine migration via a five-coordinate silicon atom in the transition state. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature effect on tert-butyl alcohol (TBA) biodegradation kinetics in hyporheic zone soils.

PubMed

Greenwood, Mark H; Sims, Ronald C; McLean, Joan E; Doucette, William J

2007-09-19

Remediation of tert-butyl alcohol (TBA) in subsurface waters should be taken into consideration at reformulated gasoline contaminated sites since it is a biodegradation intermediate of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-butyl formate (TBF). The effect of temperature on TBA biodegradation has not been not been published in the literature. Biodegradation of [U 14C] TBA was determined using hyporheic zone soil microcosms. First order mineralization rate constants of TBA at 5 degrees C, 15 degrees C and 25 degrees C were 7.84 +/- 0.14 x 10-3, 9.07 +/- 0.09 x 10-3, and 15.3 +/- 0.3 x 10-3 days-1, respectively (or 2.86 +/- 0.05, 3.31 +/- 0.03, 5.60 +/- 0.14 years-1, respectively). Temperature had a statistically significant effect on the mineralization rates and was modelled using the Arrhenius equation with frequency factor (A) and activation energy (Ea) of 154 day-1 and 23,006 mol/J, respectively. Results of this study are the first to determine mineralization rates of TBA for different temperatures. The kinetic rates determined in this study can be used in groundwater fate and transport modelling of TBA at the Ronan, MT site and provide an estimate for TBA removal at other similar shallow aquifer sites and hyporheic zones as a function of seasonal change in temperature.

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...

TREATMENT OF METHYL TERT-BUTYL ETHER CONTAMINATED WATER USING PHOTOCATALYSIS

EPA Science Inventory

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

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...

Discovery, Synthesis, And Structure-Based Optimization of a Series of N-(tert-Butyl)-2-(N-arylamido)-2-(pyridin-3-yl) Acetamides (ML188) as Potent Noncovalent Small Molecule Inhibitors of the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) 3CL Protease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, Jon; Grum-Tokars, Valerie; Zhou, Ya

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). But, unlike the majority of reported coronavirus 3CLpro inhibitors that act via covalent modification of the enzyme, 16-(R) is a noncovalent SARS-CoV 3CLpro inhibitor with moderate MW and good enzyme and antiviral inhibitory activity. A multicomponent Ugi reaction was utilized to rapidly explore structure–activity relationships within S1', S1, and S2enzyme binding pockets. Moreover, the X-ray structure of SARS-CoV 3CLpromore » 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 noncovalent mechanism of action.« less

(E)-2′-[(3,5-Di-tert-butyl-2-hy­droxy­benzyl­idene)amino]-1,1′-binaphthalen-2-ol methanol monosolvate

PubMed Central

He, Dian; Li, Chong; Wang, Xiaohong

2011-01-01

The title compound, C35H35NO2·CH4O, was obtained by the reaction of rac-2-amino-2-hy­droxy-1,1-binaphthyl and 3,5-di-tert-butyl-2-hy­droxy­benzaldehyde in absolute methanol. In the Schiff base mol­ecule, the two naphthyl bicycles are twisted by 71.15 (5)°. One hy­droxy group is involved in intra­molecular O—H⋯N hydrogen bond, while the methanol solvent mol­ecule is linked to another hy­droxy group via an inter­molecular O—H⋯O hydrogen bond. PMID:22219946

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

PubMed

Yavari, Issa; Nasiri, Farough; Djahaniani, Horieh

2004-01-01

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 the 1H NMR spectra. The calculated free-energy of activation for interconversion of the rotational isomers in 1-naphthyl and 8-quinolinyl derivatives amounts to about 99+/-2 and 68.5+/-2 kJ mol(-1), respectively.

Abiotic Reductive Dechlorination of Tetrachloroethylene and Trichloroethylene in Anaerobic Environments

DTIC Science & Technology

2009-01-15

Measurement of Henry’s Law Constant for methyl tert-butyl ether Using Solid-phase Microextraction. Environmental Toxicology and Chemistry 2001, 20, 1625...and Environmental Microbiology 2005, 71, 3413-3419. Nirmalakhandan, N. N., R. E. Speece. QSAR Model for Predicting Henry’s Constant. Environmental

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

PubMed Central

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

2012-01-01

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

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...

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

EPA Science Inventory

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

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...

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

EPA Science Inventory

The use of methyl tert-butyl ether (MTBE) as a gasoline additive has resulted in increasing pollution of ground water. Most of the conventional treatment technologies are inefficient or costly when the initial concentration of MTBE is low (<200 ug/L). In order to find an eco-frie...

ANAEROBIC DEGRADATION OF MTBE TO TBA IN GROUND WATER AT GASOLINE SPILL SITES IN ORANGE COUNTY, CALIFORNIA

EPA Science Inventory

Although tert-Butyl Alcohol (TBA) has not been used as a fuel oxygenate in Orange County, California, the concentrations of TBA in ground water at gasoline spill sites are high compared to the concentrations of the conventional fuel oxygenate Methyl tert-Butyl Ether (MTBE). In t...

STABLE ISOTOPE ANALYSIS OF MTBE TO EVALUATE THE SOURCE OF TBA IN GROUND WATER

EPA Science Inventory

Although tert-butyl alcohol (TBA) has not been used as a fuel oxygenate in Orange County, California, the concentrations of TBA in ground water at gasoline spill sites are high compared those of the conventional fuel oxygenate methyl tert-butyl ether (MTBE). In the year 2002, th...

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

EPA Science Inventory

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

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...

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...

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...

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...

Synthesis and characterization of novel chiral ionic liquids and investigation of their enantiomeric recognition properties.

PubMed

Bwambok, David K; Marwani, Hadi M; Fernand, Vivian E; Fakayode, Sayo O; Lowry, Mark; Negulescu, Ioan; Strongin, Robert M; Warner, Isiah M

2008-02-01

We report the synthesis and characterization of amino acid ester based chiral ionic liquids, derived from L- and D-alanine tert butyl ester chloride. The synthesis was accomplished via an anion metathesis reaction between commercially available L- and D-alanine tert butyl ester chloride using a variety of counterions such as lithium bis (trifluoromethane) sulfonimide, silver nitrate, silver lactate, and silver tetrafluoroborate. Both enantiomeric forms were obtained as confirmed by bands of opposite sign in the circular dichroism spectra. The L- and D-alanine tert butyl ester bis (trifluoromethane) sulfonimide were obtained as liquids at room temperature and intriguingly exhibited the highest thermal stability (up to 263 degrees C). In addition, the ionic liquids demonstrated enantiomeric recognition ability as evidenced by splitting of racemic Mosher's sodium salt signal using a liquid state (19)F nuclear magnetic resonance (NMR) and fluorescence spectroscopy. The L- and D-alanine tert butyl ester chloride resulted in solid salts with nitrate, lactate, and tetrafluoroborate anions. This illustrates the previously observed tunability of ionic liquid synthesis, resulting in ionic liquids of varying properties as a function of varying the anion.

Temperature effect on tert-butyl alcohol (TBA) biodegradation kinetics in hyporheic zone soils

PubMed Central

Greenwood, Mark H; Sims, Ronald C; McLean, Joan E; Doucette, William J

2007-01-01

Background Remediation of tert-butyl alcohol (TBA) in subsurface waters should be taken into consideration at reformulated gasoline contaminated sites since it is a biodegradation intermediate of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-butyl formate (TBF). The effect of temperature on TBA biodegradation has not been not been published in the literature. Methods Biodegradation of [U 14C] TBA was determined using hyporheic zone soil microcosms. Results First order mineralization rate constants of TBA at 5°C, 15°C and 25°C were 7.84 ± 0.14 × 10-3, 9.07 ± 0.09 × 10-3, and 15.3 ± 0.3 × 10-3 days-1, respectively (or 2.86 ± 0.05, 3.31 ± 0.03, 5.60 ± 0.14 years-1, respectively). Temperature had a statistically significant effect on the mineralization rates and was modelled using the Arrhenius equation with frequency factor (A) and activation energy (Ea) of 154 day-1 and 23,006 mol/J, respectively. Conclusion Results of this study are the first to determine mineralization rates of TBA for different temperatures. The kinetic rates determined in this study can be used in groundwater fate and transport modelling of TBA at the Ronan, MT site and provide an estimate for TBA removal at other similar shallow aquifer sites and hyporheic zones as a function of seasonal change in temperature. PMID:17877835

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...

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

EPA Science Inventory

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

An efficient synthesis of the constrained peptidomimetic 2-oxo-3-(N-9-fluorenyloxycarbonylamino)-1-azabicyclo[4.3.0]nonane-9-carboxylic acid from pyroglutamic acid.

PubMed

Mandal, Pijus Kumar; Kaluarachchi, Kumar K; Ogrin, Douglas; Bott, Simon G; McMurray, John S

2005-11-25

[reaction: see text] Azabicyclo[X.Y.0]alkane amino acids are rigid dipeptide mimetics that are useful tools for structure-activity studies in peptide-based drug discovery. Herein, we report an efficient synthesis of three diastereomers of 9-tert-butoxycarbonyl-2-oxo-3-(N-tert-butoxycarbonylamino)-1-azabicyclo[4.3.0]nonane (3S,6S,9S, 3S,6R,9R, and 3S,6R,9S). Methyl N-Boc-pyroglutamate is cleaved with vinylmagnesium bromide to produce an acyclic gamma-vinyl ketone. Michael addition of N-diphenylmethyleneglycine tert-butyl ester produces the N-Boc-delta-oxo-alpha,omega-diaminoazelate intermediate, which, on hydrogenloysis, gives the fused ring system. Acidolytic deprotection followed by Fmoc-protection provided building blocks suitable for solid-phase synthesis.

Characterization of Free Radicals Formed from COX-Catalyzed DGLA Peroxidation

PubMed Central

Xiao, Ying; Gu, Yan; Purwaha, Preeti; Ni, Kunyi; Law, Benedict; Mallik, Sanku; Qian, Steven Y.

2011-01-01

Like arachidonic acid (AA), dihomo-γ-linolenic acid (DGLA) is a 20-carbon ω-6 polyunsaturated fatty acid and a substrate of cyclooxygenase (COX). Through free radical reactions, COX metabolizes DGLA and AA to form well-known bioactive metabolites, namely, the 1- and 2-series of prostaglandins (PGs1 and PGs2), respectively. Unlike PGs2, which are viewed as pro-inflammatory, PGs1 possess anti-inflammatory and anticancer activities. However, the mechanisms linking the PGs to their bioactivities are still unclear, and radicals generated in COX-DGLA have not been detected. In order to better understand PGs biology and determine whether different reactions occur in COX-DGLA than in COX-AA, we have used LC/ESR/MS with a spin trap, α-[4-pyridyl-1-oxide]-N-tert-butyl nitrone (POBN), to characterize the carbon-centered radicals formed from COX-DGLA in vitro, including cellular peroxidation. A total of five types of DGLA-derived radicals were characterized as POBN adducts: m/z 266, m/z 296 and m/z 550 (same as and/or similar to COX-AA), and m/z 324 and m/z 354 (exclusively from COX-DGLA). Our results suggested that C-15 oxygenation to form PGGs occurs in both COX-DGLA and COX-AA; however, C-8 oxygenation occurs exclusively in COX-DGLA. This new finding will be further investigated for its association with different bioactivities of PGs, with potential implications for inflammatory diseases. PMID:21310230

N-heterocyclic carbene-catalyzed tandem aza-benzoin/Michael reactions: on site reversal of the reactivity of N-Boc imines.

PubMed

Wu, Ke-Jia; Li, Gong-Qiang; Li, Yi; Dai, Li-Xin; You, Shu-Li

2011-01-07

A tandem NHC-catalyzed aza-benzoin/Michael reaction has been developed as a method to efficiently produce dihydroindenones and pyrrolidinone-containing tricycles. The novel reaction pattern involves tert-butyl aryl(tosyl)methylcarbamates reacting as both electrophile and nucleophile on the same carbon.

In vitro study comparing the ability of mono-octanoin and mono-octanoin plus methyl tert-butyl ether to dissolve biliary stones.

PubMed

Tritapepe, R; Cesana, B

1996-01-01

This in vitro study compared the gallstone dissolution rates of mono-octanoin, mono-octanoin plus 10% distilled water, and mono-octanoin plus methyl tert-butyl ether 2:1. Sixteen stones were treated with each solvent at a slow perfusion rate of 3-4 ml/h and a rapid perfusion rate of 2.5 ml/30 min with 20-sec instillation/aspiration cycles, both with and without bile. The stones were weighed before, and 3, 6, 12 and 24 hrs after the start of treatment: the solvent was changed every 30 min. After 24 hrs of instillation/aspiration without bile, the mono-octanoin/methyl tert-butyl ether mixture reduced the weight of the stones by 93%, mono-octanoin plus water by 63%, and mono-octanoin alone by 52%; with bile, the figures were, respectively, 86%, 42% and 40%. The mono-octanoin/methyl tert-butyl ether mixture thus took approximately half the time needed by the other two preparations to dissolve the stones to the same extent, a finding which may be relevant for the clinical dissolution of bile duct stones.

Reaction of 1H-1-oxo-2,4,6,8-tetrakis(tert-butyl)phenoxazine with certain group II-IV metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karsanov, I.V.; Ivakhnenko, E.P.; Khandkarova, V.S.

1987-07-10

It has already been shown that 2-amino-4,6-di(tert-butyl)phenol reacts with 3,5-di(tert-butyl)-o-benzoquinone to form 1H-1-oxo-2,4,6,8-tetrakis(tert-butyl)phenoxazine (I), which is readily reduced by alkali metals to the corresponding semiquinone anion-radical (II), and further to the diamagnetic dianion (IIA). They made use of this ability of (I) to undergo reduction to prepare anion-radical salts with different group II-IV metals in the form of their amalgams. In the EPR spectrum of the anion-radical complex (III) formed in the reduction of (I) by a thallium amalgam, the HFI constants of the unpaired electron with magnetic nuclei of the organic ligand are close to those of the K-saltmore » (II), and a substantial HFI is observed with the /sup 203,205/Tl nuclei. This unequivocally proves that the complex has a semiquinone structure, since an HFI on the /sup 203,205/Tl nuclei of such an order of magnitude is characteristic of o-benzoquinone salts with a thallium cation.« less

Thin PDMS Films Using Long Spin Times or Tert-Butyl Alcohol as a Solvent

PubMed Central

Koschwanez, John H.; Carlson, Robert H.; Meldrum, Deirdre R.

2009-01-01

Thin polydimethylsiloxane (PDMS) films are frequently used in “lab on a chip” devices as flexible membranes. The common solvent used to dilute the PDMS for thin films is hexane, but hexane can swell the underlying PDMS substrate. A better solvent would be one that dissolves uncured PDMS but doesn't swell the underlying substrate. Here, we present protocols and spin curves for two alternatives to hexane dilution: longer spin times and dilution in tert-butyl alcohol. The thickness of the PDMS membranes under different spin speeds, spin times, and PDMS concentrations was measured using an optical profilometer. The use of tert-butyl alcohol to spin thin PDMS films does not swell the underlying PDMS substrate, and we have used these films to construct multilayer PDMS devices. PMID:19238212

Soluble, High Molecular Weight Polysilsesquioxanes with Carboxylate Functionalities

DOE Office of Scientific and Technical Information (OSTI.GOV)

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.; WHEELER,DAVID R.

2000-07-14

Trialkoxysilyl-containing monomers of the type (RO){sub 3}Si(CH{sub 2}){sub 3}C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyl esters CH{sub 3}CHCH{sub 2}C(O)OtBu. Acid- or base-catalyzed polymerization of the monomers leads to very high molecular weight polymers with relatively narrow polydispersities. The polymerization results in complete condensation of the alkoxy groups while the tert-butyl ester functionality remains fully intact. Partial or full deprotection of the tert-butyl group can easily be achieved to yield the corresponding carboxylic acid polymers. The ester and carboxylic acid functionalities of these new materials allow for their potential use in a variety ofmore » applications such as scavenging of heavy metals.« less

IRIS Toxicological Review of Tert-Butyl Alcohol (Tert-Butanol) ...

EPA Pesticide Factsheets

On April 29, 2016, the Toxicological Review of tert-Butyl Alcohol (tert-Butanol) (Public Comment Draft) was released for public comment. The draft Toxicological Review and charge were reviewed internally by EPA and by other federal agencies and the Executive Office of the President during Step 3 (Interagency Science Consultation) before public release. As part of the IRIS process, all written interagency comments on IRIS assessments will be made publicly available. Accordingly, interagency comments with EPA's response and the interagency science consultation drafts of the IRIS Toxicological Review of tert-Butanol and charge to external peer reviewers are posted on this site. EPA is undertaking a new health assessment for t-butyl alcohol (tert-butanol) for the Integrated Risk Information System (IRIS). The outcome of this project will be a Toxicological Review and IRIS and IRIS Summary of TBA that will be entered on the IRIS database. IRIS is an EPA database containing Agency scientific positions on potential adverse human health effects that may result from chronic (or lifetime) exposure to chemicals in the environment. IRIS contains chemical-specific summaries of qualitative and quantitative health information to evaluate potential public health risks associated with environmental contaminants. The IRIS database is relied on for the development of risk assessments, site-specific environmental decisions, and rule making.

21 CFR 177.2470 - Polyoxymethylene copolymer.

Code of Federal Regulations, 2014 CFR

2014-04-01

... paragraph (a) of this section may contain optional adjuvant substances required in its production. The quantity of any optional adjuvant substance employed in the production of the copolymer does not exceed the... (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. (2) Lubricant: N,N′Distearoylethyl-enediamine...

Lung toxicity and tumor promotion by hydroxylated derivatives of 2,6-di-tert-butyl-4-methylphenol (BHT) and 2-tert-butyl-4-methyl-6-iso-propylphenol: correlation with quinone methide reactivity.

PubMed

Kupfer, Rene; Dwyer-Nield, Lori D; Malkinson, Alvin M; Thompson, John A

2002-08-01

Acute pulmonary toxicity and tumor promotion by the food additive 2,6-di-tert-butyl-4-methylphenol (BHT) in mice are well documented. These effects have been attributed to either of two quinone methides, 2,6-di-tert-butyl-4-methylenecyclohexa-2,5-dienone (BHT-QM) formed through direct oxidation of BHT by pulmonary cytochrome P450 or a quinone methide formed by hydroxylation of a tert-butyl group of BHT (to form BHTOH) followed by oxidation of this metabolite to BHTOH-QM. BHTOH-QM is a more reactive electrophile compared to BHT-QM due to intramolecular interactions of the side-chain hydroxyl with the carbonyl oxygen. To further examine this bioactivation pathway, an analogue of BHTOH was prepared, 2-tert-butyl-6-(1'-hydroxy-1'-methyl)ethyl-4-methylphenol (BPPOH), that is structurally very similar to BHTOH but forms a quinone methide (BPPOH-QM) capable of more efficient intramolecular hydrogen bonding and, therefore, higher electrophilicity than BHTOH-QM. BPPOH-QM was synthesized and its reactivity with water, methanol, and glutathione determined to be >10-fold higher than that of BHTOH-QM. The conversions of BPPOH and BHTOH to quinone methides in lung microsomes from male BALB/cByJ mice were quantitatively similar, but in vivo the former was pneumotoxic at one-half of the dose required for the latter and one-eighth of the dose required for BHT, as determined by increased lung weight:body weight ratios following a single i.p. injection. Similar differences were found in the doses of BHT, BHTOH, or BPPOH required for tumor promotion after a single initiating dose of 3-methylcholanthrene followed by three weekly injections of the phenol. The downregulaton of calpain II, previously shown to accompany lung tumor promotion by BHT and BHTOH, also occurred with BPPOH. The correlation between biologic activities of these phenols and the reactivities of their corresponding quinone methides provides additional support for the role of BHTOH-QM as the principal metabolite responsible for the effects of BHT on mouse lung.

5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetra­methoxy­calix[4]arene dichloro­methane hemisolvate

PubMed Central

Fischer, Conrad; Gruber, Tobias; Seichter, Wilhelm; Schindler, Diana; Weber, Edwin

2008-01-01

In the title compound, C48H64O4·0.5CH2Cl2, both crystallographically independent calixarene mol­ecules display a partial cone conformation. Their crystal packing is stabilized by C—H⋯π contacts involving the meth­oxy groups. The solvent mol­ecule is located inter­stitially between two calixarene units with C—H⋯Cl contacts to meth­oxy and tert-butyl groups. One tert-butyl residue of each calixarene mol­ecule is disordered over two positions (occupancies 0.60/0.40 and 0.63/0.37), resulting in bond distances that deviate from ideal values. The tetra­mer calixarene mol­ecules present models with approximate non-crystallographic Cs symmetry. PMID:21202066

Peripheral substitution of pheophorbides and bacteriopheophorbides to promote inclusion into inert carrier systems for PDT

NASA Astrophysics Data System (ADS)

Roehrs, Susanne; Ruebner-Heuermann, Anja; Hartwich, G.; Scheer, H.; Moser, Joerg G.

1996-01-01

Pheophorbide a ethyl ester, pyropheophorbide a ethyl ester, and bacteriopheophorbide ethyl ester were substituted in 31-position with tert.butyl phenoxy or tert.butyl benzoic acid ester groups resp. in order to enhance affinity to (beta) -cyclodextrin dimers which form inclusion complexes with these photosensitizing drugs. This is a first step to construct inert transport complexes in order to photosensitize specifically cancer cells.

Highly reactive free radicals in electronic cigarette aerosols.

PubMed

Goel, Reema; Durand, Erwann; Trushin, Neil; Prokopczyk, Bogdan; Foulds, Jonathan; Elias, Ryan J; Richie, John P

2015-09-21

Electronic cigarette (EC) usage has increased exponentially, but limited data are available on its potential harmful effects. We tested for the presence of reactive, short-lived free radicals in EC aerosols by electron paramagnetic resonance spectroscopy (EPR) using the spin-trap phenyl-N-tert-butylnitrone (PBN). Radicals were detected in aerosols from all ECs and eliquids tested (2.5 × 10(13) to 10.3 × 10(13) radicals per puff at 3.3 V) and from eliquid solvents propylene glycol and glycerol and from "dry puffing". These results demonstrate, for the first time, the production of highly oxidizing free radicals from ECs which may present a potential toxicological risk to EC users.

elPBN neurons regulate rVLM activity through elPBN-rVLM projections during activation of cardiac sympathetic afferent nerves

PubMed Central

Longhurst, John C.; Tjen-A-Looi, Stephanie C.; Fu, Liang-Wu

2016-01-01

The external lateral parabrachial nucleus (elPBN) within the pons and rostral ventrolateral medulla (rVLM) contributes to central processing of excitatory cardiovascular reflexes during stimulation of cardiac sympathetic afferent nerves (CSAN). However, the importance of elPBN cardiovascular neurons in regulation of rVLM activity during CSAN activation remains unclear. We hypothesized that CSAN stimulation excites the elPBN cardiovascular neurons and, in turn, increases rVLM activity through elPBN-rVLM projections. Compared with controls, in rats subjected to microinjection of retrograde tracer into the rVLM, the numbers of elPBN neurons double-labeled with c-Fos (an immediate early gene) and the tracer were increased after CSAN stimulation (P < 0.05). The majority of these elPBN neurons contain vesicular glutamate transporter 3. In cats, epicardial bradykinin and electrical stimulation of CSAN increased the activity of elPBN cardiovascular neurons, which was attenuated (n = 6, P < 0.05) after blockade of glutamate receptors with iontophoresis of kynurenic acid (Kyn, 25 mM). In separate cats, microinjection of Kyn (1.25 nmol/50 nl) into the elPBN reduced rVLM activity evoked by both bradykinin and electrical stimulation (n = 5, P < 0.05). Excitation of the elPBN with microinjection of dl-homocysteic acid (2 nmol/50 nl) significantly increased basal and CSAN-evoked rVLM activity. However, the enhanced rVLM activity induced by dl-homocysteic acid injected into the elPBN was reversed following iontophoresis of Kyn into the rVLM (n = 7, P < 0.05). These data suggest that cardiac sympathetic afferent stimulation activates cardiovascular neurons in the elPBN and rVLM sequentially through a monosynaptic (glutamatergic) excitatory elPBN-rVLM pathway. PMID:27225950

21 CFR 181.27 - Plasticizers.

Code of Federal Regulations, 2010 CFR

2010-04-01

...: Acetyl tributyl citrate. Acetyl triethyl citrate. p-tert-Butylphenyl salicylate. Butyl stearate. Butylphthalyl butyl glycolate. Dibutyl sebacate. Di-(2-ethylhexyl) phthalate (for foods of high water content...

21 CFR 181.27 - Plasticizers.

Code of Federal Regulations, 2011 CFR

2011-04-01

...: Acetyl tributyl citrate. Acetyl triethyl citrate. p-tert-Butylphenyl salicylate. Butyl stearate. Butylphthalyl butyl glycolate. Dibutyl sebacate. Di-(2-ethylhexyl) phthalate (for foods of high water content...

Crystal structure of (2-{[(8-aminona-phthalen-1-yl)imino]-meth-yl}-4,6-di-tert-butyl-phenolato-κ3N,N',O)bromido-nickel(II).

PubMed

O'Brien, Patrick; Zeller, Matthias; Lee, Wei-Tsung

2018-04-01

The title compound, [NiBr(C 25 H 29 N 2 O)], contains an Ni II atom with a slightly distorted square-planar coordination environment defined by one O and two N atoms from the 2-{[(8-aminona-phthalen-1-yl)imino]-meth-yl}-4,6-di- tert -butyl-phenolate ligand and a bromide anion. The Ni-O and Ni-N bond lengths are slightly longer than those observed in the phenyl backbone counterpart, which can be attributed to the larger steric hindrance of the naphthyl group in the structure of the title compound. The mol-ecule as a whole is substanti-ally distorted, with both the planar naphthalene-1,8-di-amine and imino-meth-yl-phenolate substitutents rotated against the NiN 2 OBr plane by 38.92 (7) and 37.22 (8)°, respectively, giving the mol-ecule a twisted appearance. N-H⋯Br hydrogen bonds and N-H⋯C(π) contacts connect the mol-ecules into dimers, and additional C-H⋯Br contacts, C-H⋯π inter-actions, and an offset stacking inter-action between naphthyl units inter-connect these dimers into a three-dimensional network.

Arsenate-induced maternal glucose intolerance and neural tube defects in a mouse model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hill, Denise S.; Wlodarczyk, Bogdan J.; Mitchell, Laura E.

Background: Epidemiological studies have linked environmental arsenic (As) exposure to increased type 2 diabetes risk. Periconceptional hyperglycemia is a significant risk factor for neural tube defects (NTDs), the second most common structural birth defect. A suspected teratogen, arsenic (As) induces NTDs in laboratory animals. Objectives: We investigated whether maternal glucose homeostasis disruption was responsible for arsenate-induced NTDs in a well-established dosing regimen used in studies of arsenic's teratogenicity in early neurodevelopment. Methods: We evaluated maternal intraperitoneal (IP) exposure to As 9.6 mg/kg (as sodium arsenate) in LM/Bc/Fnn mice for teratogenicity and disruption of maternal plasma glucose and insulin levels. Selectedmore » compounds (insulin pellet, sodium selenate (SS), N-acetyl cysteine (NAC), L-methionine (L-Met), N-tert-Butyl-{alpha}-phenylnitrone (PBN)) were investigated for their potential to mitigate arsenate's effects. Results: Arsenate caused significant glucose elevation during an IP glucose tolerance test (IPGTT). Insulin levels were not different between arsenate and control dams before (arsenate, 0.55 ng/dl; control, 0.48 ng/dl) or after glucose challenge (arsenate, 1.09 ng/dl; control, 0.81 ng/dl). HOMA-IR index was higher for arsenate (3.9) vs control (2.5) dams (p = 0.0260). Arsenate caused NTDs (100%, p < 0.0001). Insulin pellet and NAC were the most successful rescue agents, reducing NTD rates to 45% and 35%. Conclusions: IPGTT, insulin assay, and HOMA-IR results suggest a modest failure of glucose stimulated insulin secretion and insulin resistance characteristic of glucose intolerance. Insulin's success in preventing arsenate-induced NTDs provides evidence that these arsenate-induced NTDs are secondary to elevated maternal glucose. The NAC rescue, which did not restore maternal glucose or insulin levels, suggests oxidative disruption plays a role.« less

Catalase Expression Is Modulated by Vancomycin and Ciprofloxacin and Influences the Formation of Free Radicals in Staphylococcus aureus Cultures

PubMed Central

Wang, Ying; Hougaard, Anni B.; Paulander, Wilhelm; Skibsted, Leif H.

2015-01-01

Detection of free radicals in biological systems is challenging due to their short half-lives. We have applied electron spin resonance (ESR) spectroscopy combined with spin traps using the probes PBN (N-tert-butyl-α-phenylnitrone) and DMPO (5,5-dimethyl-1-pyrroline N-oxide) to assess free radical formation in the human pathogen Staphylococcus aureus treated with a bactericidal antibiotic, vancomycin or ciprofloxacin. While we were unable to detect ESR signals in bacterial cells, hydroxyl radicals were observed in the supernatant of bacterial cell cultures. Surprisingly, the strongest signal was detected in broth medium without bacterial cells present and it was mitigated by iron chelation or by addition of catalase, which catalyzes the decomposition of hydrogen peroxide to water and oxygen. This suggests that the signal originates from hydroxyl radicals formed by the Fenton reaction, in which iron is oxidized by hydrogen peroxide. Previously, hydroxyl radicals have been proposed to be generated within bacterial cells in response to bactericidal antibiotics. We found that when S. aureus was exposed to vancomycin or ciprofloxacin, hydroxyl radical formation in the broth was indeed increased compared to the level seen with untreated bacterial cells. However, S. aureus cells express catalase, and the antibiotic-mediated increase in hydroxyl radical formation was correlated with reduced katA expression and catalase activity in the presence of either antibiotic. Therefore, our results show that in S. aureus, bactericidal antibiotics modulate catalase expression, which in turn influences the formation of free radicals in the surrounding broth medium. If similar regulation is found in other bacterial species, it might explain why bactericidal antibiotics are perceived as inducing formation of free radicals. PMID:26150471

Catalase Expression Is Modulated by Vancomycin and Ciprofloxacin and Influences the Formation of Free Radicals in Staphylococcus aureus Cultures.

PubMed

Wang, Ying; Hougaard, Anni B; Paulander, Wilhelm; Skibsted, Leif H; Ingmer, Hanne; Andersen, Mogens L

2015-09-01

Detection of free radicals in biological systems is challenging due to their short half-lives. We have applied electron spin resonance (ESR) spectroscopy combined with spin traps using the probes PBN (N-tert-butyl-α-phenylnitrone) and DMPO (5,5-dimethyl-1-pyrroline N-oxide) to assess free radical formation in the human pathogen Staphylococcus aureus treated with a bactericidal antibiotic, vancomycin or ciprofloxacin. While we were unable to detect ESR signals in bacterial cells, hydroxyl radicals were observed in the supernatant of bacterial cell cultures. Surprisingly, the strongest signal was detected in broth medium without bacterial cells present and it was mitigated by iron chelation or by addition of catalase, which catalyzes the decomposition of hydrogen peroxide to water and oxygen. This suggests that the signal originates from hydroxyl radicals formed by the Fenton reaction, in which iron is oxidized by hydrogen peroxide. Previously, hydroxyl radicals have been proposed to be generated within bacterial cells in response to bactericidal antibiotics. We found that when S. aureus was exposed to vancomycin or ciprofloxacin, hydroxyl radical formation in the broth was indeed increased compared to the level seen with untreated bacterial cells. However, S. aureus cells express catalase, and the antibiotic-mediated increase in hydroxyl radical formation was correlated with reduced katA expression and catalase activity in the presence of either antibiotic. Therefore, our results show that in S. aureus, bactericidal antibiotics modulate catalase expression, which in turn influences the formation of free radicals in the surrounding broth medium. If similar regulation is found in other bacterial species, it might explain why bactericidal antibiotics are perceived as inducing formation of free radicals. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Excellent deep-blue emitting materials based on anthracene derivatives for non-doped organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Liu, Wei; Xu, Chen; Ji, Baoming; Zheng, Caijun; Zhang, Xiaohong

2016-08-01

Two deep-blue emitting materials 2-tert-butyl-9,10-bis(3,5-diphenylphenyl)anthracene (An-1) and 2-tert-butyl-9,10-bis(3,5-diphenylbiphenyl-4‧-yl)anthracene (An-2) were successfully synthesized by the Pd-catalyzed Suzuki coupling reaction. Both of these compounds have high thermal stabilities and show strong deep-blue emission as solid-state film as well as in n-hexane solution. Two non-doped electroluminescent devices employing An-1 and An-2 as emitting layers were fabricated by vacuum vapor deposition. These devices exhibited highly efficient and stable deep-blue emission with high color purity. The CIE coordinate and maximum EQE of An-1 based device are 4.2% and (0.16, 0.06), respectively. Device based on An-2 achieved a maximum EQE of 4.0% and a CIE coordinate of (0.16, 0.10).

Acetylcholinesterase and Acetylcholine Receptor

DTIC Science & Technology

1989-01-30

trimethyl analogue, neopentyl alcohol, (CH 3 ) 3 CCH20H, Ki(comi - 29 mM, Ki(nonc)’ = 74 mM, and to the ether isomer of the latter, =-butyl methyl ether, (CH...Trietrylene glycol di-tert-butylether is being prepared from the glycol via the di-p-toluenesulfonate, mp 80-81"C from methanol, lit. 80-810C (60). 2-N,N

Bromine catalyzed conversion of S-tert-butyl groups into versatile and, for self-assembly processes accessible, acetyl-protected thiols.

PubMed

Blaszczyk, Alfred; Elbing, Mark; Mayor, Marcel

2004-10-07

The facile and efficient conversion of a tert-butyl protecting group to an acetyl protecting group for thiols by catalytic amounts of bromine in acetyl chloride and the presence of acetic acid has been developed. The fairly mild reaction conditions are of particular interest for new protecting group strategies for sulfur functionalised target structures. Copyright 2004 The Royal Society of Chemistry

On the competition between weak O-H···F and C-H···F hydrogen bonds, in cooperation with C-H···O contacts, in the difluoromethane – tert-butyl alcohol cluster

PubMed Central

Spada, Lorenzo; Tasinato, Nicola; Bosi, Giulio; Vazart, Fanny; Barone, Vincenzo; Puzzarini, Cristina

2017-01-01

The 1:1 complex of tert-butyl alcohol with difluoromethane has been characterized by means of a joint experimental-computational investigation. Its rotational spectrum has been recorded by using a pulsed-jet Fourier-Transform microwave spectrometer. The experimental work has been guided and supported by accurate quantum-chemical calculations. In particular, the computed potential energy landscape pointed out the formation of three stable isomers. However, the very low interconversion barriers explain why only one isomer, showing one O-H···F and two C-H···O weak hydrogen bonds, has been experimentally characterized. The effect of the H → tert-butyl- group substitution has been analyzed from the comparison to the difluoromethane-water adduct. PMID:28919646

The First Seven-Coordinated Triiodo Complex of Rhenium(III)

NASA Astrophysics Data System (ADS)

Schoultz, X.; Gerber, T. I. A.; Betz, R.; Hosten, E. C.

2017-12-01

The reaction of cis-[ReO2I(P Ph 3)2] with tert-butyl isocyanide in benzene led to the isolation of the complex [ReI3(CN- t-Bu)3(P Ph 3)] ( 1). The complex is unusual since it contains bulky ligands with large cone angles, i.e. three iodides, three isocyanides with tert-butyl groups and a triphenylphosphine as ligands in a seven-coordinate geometry around the rhenium(III) metal ion.

Synthesis and solution self-assembly of side-chain cobaltocenium-containing block copolymers.

PubMed

Ren, Lixia; Hardy, Christopher G; Tang, Chuanbing

2010-07-07

The synthesis of side-chain cobaltocenium-containing block copolymers and their self-assembly in solution was studied. Highly pure monocarboxycobaltocenium was prepared and subsequently attached to side chains of poly(tert-butyl acrylate)-block-poly(2-hydroxyethyl acrylate), yielding poly(tert-butyl acrylate)-block-poly(2-acryloyloxyethyl cobaltoceniumcarboxylate). The cobaltocenium block copolymers exhibited vesicle morphology in the mixture of acetone and water, while micelles of nanotubes were formed in the mixture of acetone and chloroform.

Formal [4+2] cycloaddition of di-tert-butyl 2-ethoxycyclobutane-1,1-dicarboxylate with ketones or aldehydes and tandem lactonization.

PubMed

Okado, Ryohei; Nowaki, Aya; Matsuo, Jun-Ichi; Ishibashi, Hiroyuki

2012-01-01

A catalytic amount of tin(IV) chloride catalyzed formal [4+2] cycloaddition reaction of di-tert-butyl 2-ethoxycyclobutane-1,1-carboxylate with ketones or aldehydes to give diethyl 6-ethoxydihydro-2H-pyran-3,3(4H)-dicarboxylates, whereas two equivalents of trimethylsilyl triflate promoted tandem [4+2] cycloaddition and lactonization to afford 3-oxo-2,6-dioxabicyclo[2.2.2]octane-4-carboxylate esters.

Mitochondrial reactive oxygen species production and respiratory complex activity in rats with pressure overload-induced heart failure

PubMed Central

Schwarzer, Michael; Osterholt, Moritz; Lunkenbein, Anne; Schrepper, Andrea; Amorim, Paulo; Doenst, Torsten

2014-01-01

We investigated the impact of cardiac reactive oxygen species (ROS) during the development of pressure overload-induced heart failure. We used our previously described rat model where transverse aortic constriction (TAC) induces compensated hypertrophy after 2 weeks, heart failure with preserved ejection fraction at 6 and 10 weeks, and heart failure with systolic dysfunction after 20 weeks. We measured mitochondrial ROS production rates, ROS damage and assessed the therapeutic potential of in vivo antioxidant therapies. In compensated hypertrophy (2 weeks of TAC) ROS production rates were normal at both mitochondrial ROS production sites (complexes I and III). Complex I ROS production rates increased with the appearance of diastolic dysfunction (6 weeks of TAC) and remained high thereafter. Surprisingly, maximal ROS production at complex III peaked at 6 weeks of pressure overload. Mitochondrial respiratory capacity (state 3 respiration) was elevated 2 and 6 weeks after TAC, decreased after this point and was significantly impaired at 20 weeks, when contractile function was also impaired and ROS damage was found with increased hydroxynonenal. Treatment with the ROS scavenger α-phenyl-N-tert-butyl nitrone or the uncoupling agent dinitrophenol significantly reduced ROS production rates at 6 weeks. Despite the decline in ROS production capacity, no differences in contractile function between treated and untreated animals were observed. Increased ROS production occurs early in the development of heart failure with a peak at the onset of diastolic dysfunction. However, ROS production may not be related to the onset of contractile dysfunction. PMID:24951621

Effect of H2 and redox condition on biotic and abiotic MTBE transformation

USGS Publications Warehouse

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

2006-01-01

Laboratory studies conducted with surface water sediment from a methyl tert-butyl ether (MTBE)-contaminated site in South Carolina demonstrated that, under methanogenic conditions, [U-14C] MTBE was transformed to 14C tert-butyl alcohol (TBA) with no measurable production of 14CO2. Production of TBA was not attributed to the activity of methanogenic microorganisms, however, because comparable transformation of [U-14C] MTBE to 14C-TBA also was observed in heat-sterilized controls with dissolved H2 concentrations > 5 nM. The results suggest that the transformation of MTBE to TBA may be an abiotic process that is driven by biologically produced H2 under in situ conditions. In contrast, mineralization of [U-14C] MTBE to 14CO2 was completely inhibited by heat sterilization and only observed in treatments characterized by dissolved H2 concentrations < 2 nM. These results suggest that the pathway of MTBE transformation is influenced by in situ H2 concentrations and that in situ H2 concentrations may be an useful indicator of MTBE transformation pathways in ground water systems.

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

NASA Astrophysics Data System (ADS)

Sert, Yusuf; Singer, L. M.; Findlater, M.; Doğan, Hatice; Çırak, Ç.

2014-07-01

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.

Design and synthesis of novel stiripentol analogues as potential anticonvulsants.

PubMed

Aboul-Enein, Mohamed N; El-Azzouny, Aida A; Attia, Mohamed I; Maklad, Yousreya A; Amin, Kamilia M; Abdel-Rehim, Mohamed; El-Behairy, Mohammed F

2012-01-01

A series of stiripentol (STP) analogues namely, 2-[(1E)-1-(1,3-benzodioxol-5-yl)-4,4-dimethylpent-1-en-3-ylidene]-N-(aryl/H)hydrazinecarboxamides 7a-h, (±)-(5RS)-N-(aryl/H)-(1,3-benzodioxol-5-yl)-3-tert-butyl-4,5-dihydro-1H-pyrazole-1-carboxamides (±)-8a-h, and (±)-[(5RS)-(1,3-benzodioxol-5-yl)-3-tert-butyl-4,5-dihydro-1H-pyrazol-1-yl](aryl)methanones (±)-13a-f was synthesized by adopting appropriate synthetic routes and was pharmacologically evaluated in the preliminary anticonvulsant screens. The selected bioactive new chemical entities were subjected to ED(50) determination and neurotoxicity evaluation. The most active congeners are 7h in MES screen and (±)-13b in scPTZ screen which displayed ED(50) values of 87 and 110 mg/kg, respectively, as compared to that of STP (ED(50) = 277.7 and 115 mg/kg in MES and scPTZ, respectively). Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Photochemistry and photooxidation of tetraphenyl-p-dioxin

DOE Office of Scientific and Technical Information (OSTI.GOV)

George, M.V.; Kumar, C.V.; Scaiano, J.C.

1979-09-20

Laser flash photolysis studies of tetraphenyl-p-dioxin have led to the characterization of its triplet state. The T-T absorption spectra shows maxima at 350 and 545 nm; the triplet has a lifetime of 535 ns in methanol and can be quenched by di-tert-butyl nitroxide, paraquat dications, oxygen, and di-tert-butyl selenoketone. The interaction of the triplet with oxygen leads to the formation of singlet oxygen which in turn reacts with the title compound to yield benzil.

Prostaglandin H synthase-catalyzed oxidation of all-trans- and 13-cis-retinoic acid to carbon-centered and peroxyl radical intermediates.

PubMed

Freyaldenhoven, M A; Lloyd, R V; Samokyszyn, V M

1996-06-01

Due to the importance of all-trans-retinoic acid (RA) in the treatment of various dermatological conditions and the wide distribution of prostaglandin H synthase (PGHS) in tissues, we have further examined the mechanisms involved in the hydroperoxide-dependent cooxidation of RA and its isomer, 13-cis-retinoic acid ((13Z)-RA), by PGHS. Hydroperoxide-dependent, PGHS-catalyzed oxidation of RA and (13Z)-RA was shown to form free radical adducts, using electron spin resonance (ESR) spin trapping techniques and 5-phenyl-4-penten-1-yl hydroperoxide (PPHP) or 13-hydroperoxy-9-cis-11-trans-octadecadienoic acid (13-OOH-18:2) as hydroperoxide substrates. Utilization of the spin trap alpha-phenyl-N-tert-butylnitrone (PBN) resulted in the detection of (13Z)-RA-PBN and RA-PBN adducts whose spectra were characterized by hyperfine coupling constants of aH = 4.16/aN = 15.69 and aH = 3.01/aN =15.92, respectively. Identical experiments under anaerobic conditions were carried out using the spin trap 2-methyl-2-nitrosopropane (NtB) which yielded nitroxide adducts whose spectra were characterized by a triplet of doublets with values of aH = 3.49/aN = 15.84 for the (13Z)-RA adduct and aH = 3.49/aN = 15.88 for the RA adduct. These results are indicative of secondary carbon-centered radical formation. We also used (+)-benzo[a]pyrene 7(S),8(S)-dihydrodiol ((+)-BP-7,8-diol) as a peroxyl radical probe. The results demonstrated the formation of (+)-BP-7,8-diol-derived tetrols, with the trans-anti tetrol representing the major oxidation product in systems undergoing PPHP-dependent, PGHS-catalyzed oxidation of (13Z)-RA or RA. These results are consistent with the formation of peroxyl radicals in these systems. In all experiments, the (13Z)-RA isomer appeared to be a better substrate for the enzyme compared to the all-trans isomer. Collectively these results provide further evidence to support the previously proposed mechanism for retinoid oxidation by PGHS involving the intermediacy of C4 carbon-centered radicals which subsequently react with dioxygen, yielding retinoid-derived peroxyl radicals.

Anaerobic biodegradability of alkylphenols and fuel oxygenates in the presence of alternative electron acceptors.

PubMed

Puig-Grajales, L; Tan, N G; van der Zee, F; Razo-Flores, E; Field, J A

2000-11-01

Alkylphenols and fuel oxygenates are important environmental pollutants produced by the petrochemical industry. A batch biodegradability test was conducted with selected ortho-substituted alkylphenols (2-cresol, 2,6-dimethylphenol and 2-ethylphenol), fuel oxygenates (methyl tert-butyl ether, ethyl tert-butyl ether and tert-amylmethyl ether) and tert-butyl alcohol (TBA) as model compounds. The ortho-substituted alkylphenols were not biodegraded after 100 days of incubation under methanogenic, sulfate-, or nitrate-reducing conditions. However, biodegradation of 2-cresol and 2-ethylphenol (150 mg l(-1)) was observed in the presence of Mn (IV) as electron acceptor. The biodegradation of these two compounds took place in less than 15 days and more than 90% removal was observed for both compounds. Mineralization was indicated since no UV-absorbing metabolites accumulated after 23 days of incubation. These alkylphenols were also slowly chemically oxidized by Mn (IV). No biodegradation of fuel oxygenates or TBA (1 g l(-1)) was observed after 80 or more days of incubation under methanogenic, Fe (III)-, or Mn (IV)-reducing conditions, suggesting that these compounds are recalcitrant under anaerobic conditions. The fuel oxygenates caused no toxicity towards acetoclastic methanogens activity in anaerobic granular sludge.

Vibrational and reorientationl relaxation in liquid tert-butyl bromide and tert-butyl bromide- d9

NASA Astrophysics Data System (ADS)

Szostak, R.; Hawranek, J. P.

1992-12-01

The vibrational and reorientational correlation functions of the ν s(CBr) mode in liquid tert-butyl bromide (TBBr) and in its deuterated analogue (TBBr- d9) were determined from Raman bandshapes. The Kubo product δτ m obtained by fitting the Rothschild equation to experimental data amounts to 0.36-0.45 for the studied bands, which indicates a fairly fast modulation regime in these systems. The approximation of experimental rotational correlation functions with the help of the J-diffusion model yields values of 0.11-0.12ps for the angular momentum correlation time. The second-order rotational correlation times (1.7-2.0ps) agree well with the NMR results of D.W. Aksnes, K. Ramstad and O.P. Björlykke, Magn. Reson. Chem., 25 (1987) 1063. Selected bandshape parameters for δ(CCC) in both compounds, ϱ(CH 3) in TBBr and ν s(CC) in TBBR- d9 were also quoted.

Cyclic cooperative intramolecular hydrogen bond in p-tert-butylcalix[6]arene according to FTIR spectroscopy and DFT studies

NASA Astrophysics Data System (ADS)

Furer, V. L.; Potapova, L. I.; Kovalenko, V. I.

2017-06-01

This article describes a comparative research of IR spectra and H-bonds in the p-tert-butylcalix[6]arene (TB6) and calix[6]arene (C6). IR spectra were computed for compressed cone conformation by DFT method. The assignment of the bands in the IR spectra of the TB6 and C6 was made. The effect of the bulky tert-butyl substituents on the structure and H-bonding in TB6 was established. Our research has shown that in TB6 and C6 the cyclic H-bond is realized, which ensures the existence of a compressed cone conformation. Introduction of tert-butyl substituents in TB6 leads to hardening of H-bonds. Examination of IR spectra showed that when heated TB6 remains in a compressed cone conformation. In a molecule of TB6 and C6 oxygen atoms are in a ;boat; conformation.

Entropy driven chain effects on ligation chemistry† †Electronic supplementary information (ESI) available: Synthetic details, applied MHKS parameters, SEC chromatograms of all samples, (HT) NMR data, experimental debonding values, SANS measurements, computational data (energy contributions and geometries in the form of Gaussian archive entries). See DOI: 10.1039/c4sc02908a Click here for additional data file.

PubMed Central

Pahnke, Kai; Brandt, Josef; Gryn'ova, Ganna; Lindner, Peter; Schweins, Ralf; Schmidt, Friedrich Georg

2015-01-01

We report the investigation of fundamental entropic chain effects that enable the tuning of modular ligation chemistry – for example dynamic Diels–Alder (DA) reactions in materials applications – not only classically via the chemistry of the applied reaction sites, but also via the physical and steric properties of the molecules that are being joined. Having a substantial impact on the reaction equilibrium of the reversible ligation chemistry, these effects are important when transferring reactions from small molecule studies to larger or other entropically very dissimilar systems. The effects on the DA equilibrium and thus the temperature dependent degree of debonding (%debond) of different cyclopentadienyl (di-)functional poly(meth-)acrylate backbones (poly(methyl methacrylate), poly(iso-butyl methacrylate), poly(tert-butyl methacrylate), poly(iso-butyl acrylate), poly(n-butyl acrylate), poly(tert-butyl acrylate), poly(methyl acrylate) and poly(isobornyl acrylate)), linked via a difunctional cyanodithioester (CDTE) were examined via high temperature (HT) NMR spectroscopy as well as temperature dependent (TD) SEC measurements. A significant impact of not only chain mass and length with a difference in the degree of debonding of up to 30% for different lengths of macromonomers of the same polymer type but – remarkably – as well the chain stiffness with a difference in bonding degrees of nearly 20% for isomeric poly(butyl acrylates) is found. The results were predicted, reproduced and interpreted via quantum chemical calculations, leading to a better understanding of the underlying entropic principles. PMID:29560194

Synthesis and Crystal Structure of Dibromido{2-[(4-tert-butylmethylphenyl) iminomethyl]pyridine-κ2 N, N'}Zinc

NASA Astrophysics Data System (ADS)

Khalaj, M.; Ghazanfarpour-Darjani, M.; Seftejani, F. B.; Lalegani, A.

2017-12-01

The title compound [Zn( dip)Br2] was synthesized using the Schiff base bidentate ligand (E)-4- tert-butyl- N-(pyridine-2-ylmethylene)benzeneamine ( dip) and zinc(II) bromide salts. It has been characterized by elemental analysis, X-ray diffraction, and optical spectroscopy. The X-ray diffraction analysis demonstrates that in this structure, the zinc(II) ion is located on an inversion center and exhibits a ZnN2Br2 tetrahedral geometry. In this structure the dip ligand is coordinated with zinc(II) ion in a cyclic-bidentate fashion forming a five-membered metallocyclic ring. The compound crystallizes in the monoclinic sp. gr. P21/ m with a = 9.2700(13) Å, b = 7.6128(11) Å, c = 12.3880(17) Å, and β = 97.021(3)°.

Catalytic performance of strong acid catalyst: Methyl modified SBA-15 loaded perfluorinated sulfonic acid obtained by the waste perfluorinated sulfonic acid ion exchange membrane

NASA Astrophysics Data System (ADS)

Jiang, Tingshun; Huang, Qiuyan; Li, Yingying; Fang, Minglan; Zhao, Qian

2018-02-01

Mesoporous molecular sieve (SBA-15) was modified using the trimethylchlorosilane as functional agent and the silylation SBA-15 mesoporous material was prepared in this work. The alcohol solution of perfluorinated sulfonic acid dissolved from the waste perfluorinated sulfonic acid ion exchange membrane (PFSIEM) was loaded onto the resulting mesoporous material by the impregnation method and their physicochemical properties were characterized by FT-IR, N2-physisorption, XRD, TG-DSC and TEM. The catalytic activities of these synthesized solid acid catalysts were evaluated by alkylation of phenol with tert-butyl alcohol. The influence of reaction temperature, weight hour space velocity (WHSV) and reaction time on the phenol conversion and product selectivity were assessed by means of a series of experiments. The results showed that with the increase of the active component of the catalyst, these catalysts still remained good mesoporous structure, but the mesoporous ordering decreased to some extent. These catalysts exhibited good catalytic performance for the alkylation of phenol with tert-butanol. The maximum phenol conversion of 89.3% with 70.9% selectivity to 4-t-butyl phenol (4-TBP) was achieved at 120 °C and the WHSV is 4 h-1. The methyl group was loaded on the surface of the catalyst by trimethylchlorosilane. This is beneficial to retard the deactivation of the catalyst. In this work, the alkylation of phenol with tert-butyl alcohol were carried out using the methyl modified SBA-15 mesoporous materials loaded perfluorinated sulfonic acid as catalysts. The results show that the resulting catalyst exhibited high catalytic activity.

Measurement of myocardial free radical production during exercise using EPR spectroscopy.

PubMed

Traverse, Jay H; Nesmelov, Yuri E; Crampton, Melanie; Lindstrom, Paul; Thomas, David D; Bache, Robert J

2006-06-01

Exercise is associated with an increase in oxygen flux through the mitochondrial electron transport chain that has recently been demonstrated to increase the production of reactive oxygen species (ROS) in skeletal muscle. This study examined whether exercise also causes free radical production in the heart. We measured ROS production in seven chronically instrumented dogs during rest and treadmill exercise (6.4 km/h at 10 degrees grade; and heart rate, 204 +/- 3 beats/min) using electron paramagnetic resonance spectroscopy in conjunction with the spin trap alpha-phenyl-tert-butylnitrone (PBN) (0.14 mol/l) in blood collected from the aorta and coronary sinus (CS). To improve signal detection, the free radical adducts were deoxygenated over a nitrogen stream for 15 min and extracted with toluene. The hyperfine splitting constants of the radicals were alpha(N) = 13.7 G and alpha(H) = 1.0 G, consistent with an alkoxyl or carbon-centered radical. Resting aortic and CS PBN adduct concentrations were 6.7 and 6.3 x 10(8) arbitrary units (P = not significant). Both aortic and CS adduct concentrations increased during exercise, but there was no significant difference between the aortic and CS concentrations. Thus, in contrast to skeletal muscle, submaximal treadmill exercise did not result in detectable free radical production by the heart.

Use B-spline interpolation fitting baseline for low concentration 2, 6-di-tertbutyl p-cresol determination in jet fuels by differential pulse voltammetry

NASA Astrophysics Data System (ADS)

Wen, D. S.; Wen, H.; Shi, Y. G.; Su, B.; Li, Z. C.; Fan, G. Z.

2018-01-01

The B-spline interpolation fitting baseline in electrochemical analysis by differential pulse voltammetry was established for determining the lower concentration 2,6-di-tert-butyl p-cresol(BHT) in Jet Fuel that was less than 5.0 mg/L in the condition of the presence of the 6-tert-butyl-2,4-xylenol.The experimental results has shown that the relative errors are less than 2.22%, the sum of standard deviations less than 0.134mg/L, the correlation coefficient more than 0.9851. If the 2,6-ditert-butyl p-cresol concentration is higher than 5.0mg/L, linear fitting baseline method would be more applicable and simpler.

C5H9N isomers: pointers to possible branched chain interstellar molecules

NASA Astrophysics Data System (ADS)

Etim, Emmanuel E.; Gorai, Prasanta; Das, Ankan; Arunan, Elangannan

2017-04-01

The astronomical observation of isopropyl cyanide further stresses the link between the chemical composition of the interstellar medium (ISM) and molecular composition of the meteorites in which there is a dominance of branched chain amino acids as compared to the straight. However, observations of more branched chain molecules in ISM will firmly establish this link. In the light of this, we have considered C5H9N isomeric group in which the next higher member of the alkyl cyanide and other branched chain isomers belong. High-level quantum chemical calculations have been employed in estimating accurate energies of these isomers. From the results, the only isomer of the group that has been astronomically searched, n-butyl cyanide is not the most stable isomer and therefore, which might explain why its search could only yield upper limits of its column density without a successful detection. Rather, the two most stable isomers of the group are the branched chain isomers; tert-butylnitrile and isobutyl cyanide. Based on the rotational constants of these isomers, it is found that the expected intensity of tert-butylnitrile is the maximum among this isomeric group. Thus, this is proposed as the most probable candidate for astronomical observation. A simple LTE (local thermodynamic equilibrium) modelling has also been carried out to check the possibility of detecting tert-butyl cyanide in the millimetre-wave region. Contribution to the Topical Issue "Low-Energy Interactions related to Atmospheric and Extreme Conditions", edited by S. Ptasinska, M. Smialek-Telega, A. Milosavljevic and B. Sivaraman.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1985-12-20

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

Data Report for an Extensive Store Separation Test Program Conducted at Supersonic Speeds.

DTIC Science & Technology

1979-12-01

PBn)/IDPI3/PBnil (Note: T PHIT ) 203 ALPLn - Flow angle based on total angle of attack and rolln angle, deg ALPLn TAN-[Tan(aT) * cos(T)] + [TANG(n...PB)yaw - CCORR1 - ACORR2 • SIN( PHIT n )] + TANG(n)yaw CCORRI = CIDP24/PBni 2.5 and C = (0.5)2.5 • 318.5 M 5 • (DP2 4/PBn )/IDP24/PBn TANG(n)yaw = Angle

Spin-crossover in an iron(III)-bispidine-alkylperoxide system.

PubMed

Bautz, Jochen; Comba, Peter; Que, Lawrence

2006-09-04

The iron(II) complex of a tetradentate bispidine ligand with two tertiary amines and two pyridine groups (L = dimethyl [3,7-dimethyl-9,9'-dihydroxy-2,4-di-(2-pyridyl)-3,7-diazabicyclo nonan-1,5-dicaboxylate]) is oxidized with tert-butyl hydroperoxide to the corresponding end-on tert-butylperoxo complex [Fe(III)(L)(OOtBu)(X)]n+ (X = solvent, anion). UV-vis, resonance Raman, and EPR spectroscopy, as a function of the solvent, show that this is a spin-crossover compound. The experimentally observed Raman vibrations for both low-spin and high-spin isomers are in good agreement with those computed by DFT.

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

PubMed

Sert, Yusuf; Singer, L M; Findlater, M; Doğan, Hatice; Çırak, Ç

2014-07-15

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. Copyright © 2014 Elsevier B.V. All rights reserved.

Anaerobic degradation of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA).

PubMed

Finneran, K T; Lovley, D R

2001-05-01

The potential for anaerobic degradation of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) was investigated in laboratory incubations of sediments from a petroleum-contaminated aquifer and in aquatic sediments. The addition of humic substances (HS) stimulated the anaerobic degradation of MTBE in aquifer sediments in which Fe(III) was available as an electron acceptor. This is attributed to the fact that HS and other extracellular quinones can stimulate the activity of Fe(III)-reducing microorganisms by acting as an electron shuttle between Fe(III)-reducing microorganisms and insoluble Fe(III) oxides. MTBE was not degraded in aquifer sediments without Fe(III) and HS. [14C]-MTBE added to aquatic sediments adapted for anaerobic MTBE degradation was converted to 14CO2 in the presence or absence of HS or the HS analog, anthraquione-2,6-disulfonate. Unamended aquatic sediments produced 14CH4 as well as 14CO2 from [14C]-MTBE. The aquatic sediments also rapidly consumed TBA under anaerobic conditions and converted [14C]-TBA to 14CH4 and 14CO2. An adaptation period of ca. 250-300 days was required prior to the most rapid anaerobic MTBE degradation in both sediment types, whereas TBA was metabolized in the aquatic sediments without a lag. These results demonstrate that, under the appropriate conditions, MTBE and TBA can be degraded in the absence of oxygen. This suggests that it may be possible to design strategies for the anaerobic remediation of MTBE in petroleum-contaminated subsurface environments.

Mono-, di-, and tri- tert-butyl ethers of glycerol . A molecular spectroscopic study

NASA Astrophysics Data System (ADS)

Jamróz, Małgorzata E.; Jarosz, Małgorzata; Witowska-Jarosz, Janina; Bednarek, Elżbieta; Tęcza, Witold; Jamróz, Michał H.; Dobrowolski, Jan Cz.; Kijeński, Jacek

2007-07-01

MS, NMR, IR and Raman molecular spectroscopy techniques were applied to characterize 3- tert-butoxy-propane-1,2-diol, 1,3-di- tert-butoxy-propan-2-ol, and 1,2,3-tri- tert-butoxy-propane. These ethers are the main products of glycerol etherification reaction and are excellent oxygen additives for diesel fuel. Computational DFT/ B3LYP/6-31G ** studies were performed to support and rationalize both vibrational spectroscopy analysis and the isomer ratio.

Novel non-symmetrical bifunctionally-substituted phthalonitriles and corresponding d-metal phthalocyaninates

NASA Astrophysics Data System (ADS)

Vashurin, Artur; Maizlish, Vladimir; Tikhomirova, Tatiyana; Nemtseva, Marina; Znoyko, Serafima; Aleksandriiskii, Viktor

2018-05-01

The work reports synthesis of 4-(2-tert-butyl-4,5-dicyanophenylsulfonyl)benzene and its analogue containing carboxyl group in phenyl fragment by nucleophilic substitution of nitro-group of 4-tert-butyl-5-nitrophthalonitrile. Unique structure of the obtained compounds is explained by presence of bulky tert-butyl substituent in combination with carboxyl group, which being part of phthalocyanine molecule impart it higher solubility within different solvents (organic and water mediums) and act as anchoring groups. Based on obtained nitriles phthalocyanine complexes of copper, nickel, cobalt and magnesium are synthesized with good yields. Demetallization of initial magnesium phthalocyanine by hydrochloric acid was performed in order to obtain ligand of phthalocyanine. Synthetic and purification techniques are described in detail. Obtained substances are of specific structure making them to be applied in sensorics for smart materials production, as sensitizers or part of molecular magnets. The structure, NMR and IR spectra are modeled using special software. Resulting experimental and theoretical data are compared. The results show sufficient correlation that confirms correctness of chosen methods and its applicability for theoretical studying compounds related to investigated ones.

Α-aryl-N-alkyl nitrones, as potential agents for stroke treatment: synthesis, theoretical calculations, antioxidant, anti-inflammatory, neuroprotective, and brain-blood barrier permeability properties.

PubMed

Chioua, Mourad; Sucunza, David; Soriano, Elena; Hadjipavlou-Litina, Dimitra; Alcázar, Alberto; Ayuso, Irene; Oset-Gasque, María Jesús; González, María Pilar; Monjas, Leticia; Rodríguez-Franco, María Isabel; Marco-Contelles, José; Samadi, Abdelouahid

2012-01-12

We report the synthesis, theoretical calculations, the antioxidant, anti-inflammatory, and neuroprotective properties, and the ability to cross the blood-brain barrier (BBB) of (Z)-α-aryl and heteroaryl-N-alkyl nitrones as potential agents for stroke treatment. The majority of nitrones compete with DMSO for hydroxyl radicals, and most of them are potent lipoxygenase inhibitors. Cell viability-related (MTT assay) studies clearly showed that nitrones 1-3 and 10 give rise to significant neuroprotection. When compounds 1-11 were tested for necrotic cell death (LDH release test) nitrones 1-3, 6, 7, and 9 proved to be neuroprotective agents. In vitro evaluation of the BBB penetration of selected nitrones 1, 2, 10, and 11 using the PAMPA-BBB assay showed that all of them cross the BBB. Permeable quinoline nitrones 2 and 3 show potent combined antioxidant and neuroprotective properties and, therefore, can be considered as new lead compounds for further development in specific tests for potential stroke treatment.

Reactions of nitroxide radicals in aqueous solutions exposed to non-thermal plasma: limitations of spin trapping of the plasma induced species

NASA Astrophysics Data System (ADS)

Gorbanev, Yury; Stehling, Nicola; O'Connell, Deborah; Chechik, Victor

2016-10-01

Low temperature (‘cold’) atmospheric pressure plasmas have gained much attention in recent years due to their biomedical effects achieved through the interactions of plasma-induced species with the biological substrate. Monitoring of the radical species in an aqueous biological milieu is usually performed via electron paramagnetic resonance (EPR) spectroscopy using various nitrone spin traps, which form persistent radical adducts with the short-lived radicals. However, the stability of these nitroxide radical adducts in the plasma-specific environment is not well known. In this work, chemical transformations of nitroxide radicals in aqueous solutions using a model nitroxide 4-oxo-TEMPO were studied using EPR and LC-MS. The kinetics of the nitroxide decay when the solution was exposed to plasma were assessed, and the reactive pathways proposed. The use of different scavengers enabled identification of the types of reactive species which cause the decay, indicating the predominant nitroxide group reduction in oxygen-free plasmas. The 2H adduct of the PBN spin trap (PBN-D) was shown to decay similarly to the model molecule 4-oxo-TEMPO. The decay of the spin adducts in plasma-treated solutions must be considered to avoid rendering the spin trapping results unreliable. In particular, the selectivity of the decay indicated the limitations of the PTIO/PTI nitroxide system in the detection of nitric oxide.

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...

2-(4-Bromo­benz­yl)-5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra­methoxy­calix[4]arene

PubMed Central

Fischer, Conrad; Lin, Guisheng; Seichter, Wilhelm; Weber, Edwin

2009-01-01

In the title compound, C55H69BrO4, the calixarene mol­ecule displays a ‘partial cone’ conformation bearing the lateral substituent in a sterically favorable equatorial arrangement between two syn-orientated arene units. The crystal packing is stabilized by weak C—H⋯π contacts, involving one tert-butyl group, and π–stacking inter­actions of the lateral bromo­benzene units [centroid–centroid distance = 3.706 (1) Å]. PMID:21582956

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

PubMed

Levchuk, Irina; Bhatnagar, Amit; Sillanpää, Mika

2014-04-01

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. Copyright © 2014. Published by Elsevier B.V.

Synchrotron Photoionization Investigation of the Oxidation of Ethyl tert-Butyl Ether.

PubMed

Winfough, Matthew; Yao, Rong; Ng, Martin; Catani, Katherine; Meloni, Giovanni

2017-02-23

The oxidation of ethyl tert-butyl ether (ETBE), a widely used fuel oxygenated additive, is investigated using Cl atoms as initiators in the presence of oxygen. The reaction is carried out at 293, 550, and 700 K. Reaction products are probed by a multiplexed chemical kinetics photoionization mass spectrometer coupled with the synchrotron radiation produced at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory. Products are identified on the basis of mass-to-charge ratio, ionization energies, and shape of photoionization spectra. Reaction pathways are proposed together with detected primary products.

Di-tert-butyl-bis(N-isopropyl-N-methyl-dithio-carbamato-κS,S')tin(IV).

PubMed

Muthalib, Amirah Faizah; Baba, Ibrahim; Samsudin, Mohd Wahid; Ng, Seik Weng

2010-03-03

The dithio-carbamate anions in the title compound, [Sn(C(4)H(9))(2)(C(5)H(10)NS(2))(2)], chelate to the Sn(IV) atom, which is six-coordinated in a skew-trapezoidal-bipyramidal geometry. The mol-ecule lies across a twofold rotation axis. The crystal studied was a non-merohedral twin, the ratio of the twin components being 0.82 (1):0.18 (1).

AVOIDING HYDROLYSIS OF FUEL ETHER OXYGENATES DURING STATIC HEADSPACE ANALYSIS

EPA Science Inventory

A headspace autosampler, gas chromatograph and ion trap mass spectrometer (headspace GC/MS) were used for trace analysis of fuel oxygenates and related compounds and aromatics in water. A method has been developed for determination of methyl tert-butyl ether (MTBE), ethyl tert-b...

IRIS Toxicological Review of Tert-Butyl Alcohol (Tert-Butanol) (Preliminary Assessment Materials)

EPA Science Inventory

In August 2013, EPA released the draft literature searches and associated search strategies, evidence tables, and exposure response arrays for TBA to obtain input from stakeholders and the public prior to developing the draft IRIS assessment. Specifically, EPA was interested in c...

In vitro growth inhibition of mastitis causing bacteria by phenolics and metal chelators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chew, B.P.; Tjoelker, L.W.; Tanaka, T.S.

1985-11-01

Antimicrobial activities of three phenolic compounds and four metal chelators were tested at 0, 250, 500, and 1000 ppm in vitro against four major mastitis-causing bacteria, Streptococcus agalactiae, Staphylococcus aureus, Klebsiella pnuemoniae, and Escherichia coli. Overall, butylated hydroxyanisole and tert-butylhydroquinone showed the greatest antimicrobial activity. These phenolics were bactericidal at 250 to 500 ppm against all four bacteria tested. The butylated hydroxytoluene was bactericidal against the gram-positive bacteria but was ineffective against the coliforms. At 250 ppm, disodium ethylenediaminetetraacetic acid was bactericidal against the gram-positive bacteria but much less effective against the gram-negatives. However, diethylene-triaminepentaacetic acid was more growth inhibitorymore » than ethylenediaminetetraacetic acid against the gram-negative bacteria and especially against Escherichia coli. All other compounds were generally much less effective or ineffective against all four microorganisms. Therefore, butylated hydroxyanisole, butylated hydroxytoluene, tert-butylhydroquinone, ethylenediaminetetraacetic acid, and diethylenetriaminepentaacetic acid may have practical implications in the prevention or treatment of bovine mastitis.« less

Using DNA-Stable Isotope Probing to Identify MTBE- and TBA-Degrading Microorganisms in Contaminated Groundwater.

PubMed

Key, Katherine C; Sublette, Kerry L; Duncan, Kathleen; Mackay, Douglas M; Scow, Kate M; Ogles, Dora

2013-01-01

Although the anaerobic biodegradation of methyl tert -butyl ether (MTBE) and tert -butyl alcohol (TBA) has been documented in the laboratory and the field, knowledge of the microorganisms and mechanisms involved is still lacking. In this study, DNA-stable isotope probing (SIP) was used to identify microorganisms involved in anaerobic fuel oxygenate biodegradation in a sulfate-reducing MTBE and TBA plume. Microorganisms were collected in the field using Bio-Sep® beads amended with 13 C 5 -MTBE, 13 C 1 -MTBE (only methoxy carbon labeled), or 13 C 4 -TBA. 13 C-DNA and 12 C-DNA extracted from the Bio-Sep beads were cloned and 16S rRNA gene sequences were used to identify the indigenous microorganisms involved in degrading the methoxy group of MTBE and the tert -butyl group of MTBE and TBA. Results indicated that microorganisms were actively degrading 13 C-labeled MTBE and TBA in situ and the 13 C was incorporated into their DNA. Several sequences related to known MTBE- and TBA-degraders in the Burkholderiales and the Sphingomonadales orders were detected in all three 13 C clone libraries and were likely to be primary degraders at the site. Sequences related to sulfate-reducing bacteria and iron-reducers, such as Geobacter and Geothrix , were only detected in the clone libraries where MTBE and TBA were fully labeled with 13 C, suggesting that they were involved in processing carbon from the tert -butyl group. Sequences similar to the Pseudomonas genus predominated in the clone library where only the methoxy carbon of MTBE was labeled with 13 C. It is likely that members of this genus were secondary degraders cross-feeding on 13 C-labeled metabolites such as acetate.

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

PubMed

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

2005-10-01

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.

Using DNA-Stable Isotope Probing to Identify MTBE- and TBA-Degrading Microorganisms in Contaminated Groundwater

PubMed Central

Key, Katherine C.; Sublette, Kerry L.; Duncan, Kathleen; Mackay, Douglas M.; Scow, Kate M.; Ogles, Dora

2014-01-01

Although the anaerobic biodegradation of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) has been documented in the laboratory and the field, knowledge of the microorganisms and mechanisms involved is still lacking. In this study, DNA-stable isotope probing (SIP) was used to identify microorganisms involved in anaerobic fuel oxygenate biodegradation in a sulfate-reducing MTBE and TBA plume. Microorganisms were collected in the field using Bio-Sep® beads amended with 13C5-MTBE, 13C1-MTBE (only methoxy carbon labeled), or13C4-TBA. 13C-DNA and 12C-DNA extracted from the Bio-Sep beads were cloned and 16S rRNA gene sequences were used to identify the indigenous microorganisms involved in degrading the methoxy group of MTBE and the tert-butyl group of MTBE and TBA. Results indicated that microorganisms were actively degrading 13C-labeled MTBE and TBA in situ and the 13C was incorporated into their DNA. Several sequences related to known MTBE- and TBA-degraders in the Burkholderiales and the Sphingomonadales orders were detected in all three13C clone libraries and were likely to be primary degraders at the site. Sequences related to sulfate-reducing bacteria and iron-reducers, such as Geobacter and Geothrix, were only detected in the clone libraries where MTBE and TBA were fully labeled with 13C, suggesting that they were involved in processing carbon from the tert-butyl group. Sequences similar to the Pseudomonas genus predominated in the clone library where only the methoxy carbon of MTBE was labeled with 13C. It is likely that members of this genus were secondary degraders cross-feeding on 13C-labeled metabolites such as acetate. PMID:25525320

NIOSH Manual of Analytical Methods (third edition). Fourth supplement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1990-08-15

The NIOSH Manual of Analytical Methods, 3rd edition, was updated for the following chemicals: allyl-glycidyl-ether, 2-aminopyridine, aspartame, bromine, chlorine, n-butylamine, n-butyl-glycidyl-ether, carbon-dioxide, carbon-monoxide, chlorinated-camphene, chloroacetaldehyde, p-chlorophenol, crotonaldehyde, 1,1-dimethylhydrazine, dinitro-o-cresol, ethyl-acetate, ethyl-formate, ethylenimine, sodium-fluoride, hydrogen-fluoride, cryolite, sodium-hexafluoroaluminate, formic-acid, hexachlorobutadiene, hydrogen-cyanide, hydrogen-sulfide, isopropyl-acetate, isopropyl-ether, isopropyl-glycidyl-ether, lead, lead-oxide, maleic-anhydride, methyl-acetate, methyl-acrylate, methyl-tert-butyl ether, methyl-cellosolve-acetate, methylcyclohexanol, 4,4'-methylenedianiline, monomethylaniline, monomethylhydrazine, nitric-oxide, p-nitroaniline, phenyl-ether, phenyl-ether-biphenyl mixture, phenyl-glycidyl-ether, phenylhydrazine, phosphine, ronnel, sulfuryl-fluoride, talc, tributyl-phosphate, 1,1,2-trichloro-1,2,2-trifluoroethane, trimellitic-anhydride, triorthocresyl-phosphate, triphenyl-phosphate, and vinyl-acetate.

21 CFR 176.200 - Defoaming agents used in coatings.

Code of Federal Regulations, 2011 CFR

2011-04-01

... alcohol tert-Butyl alcohol Butyl stearate Castor oil, sulfated, ammonium, potassium, or sodium salt Cetyl... palmitate Mineral oil Mustardseed oil, sulfated, ammonium, potassium, or sodium salt Myristyl alcohol... hydrocarbons As defined in § 178.3650 of this chapter. Oleic acid, sulfated, ammonium, potassium, or sodium...

21 CFR 176.200 - Defoaming agents used in coatings.

Code of Federal Regulations, 2010 CFR

2010-04-01

... alcohol tert-Butyl alcohol Butyl stearate Castor oil, sulfated, ammonium, potassium, or sodium salt Cetyl... palmitate Mineral oil Mustardseed oil, sulfated, ammonium, potassium, or sodium salt Myristyl alcohol... hydrocarbons As defined in § 178.3650 of this chapter. Oleic acid, sulfated, ammonium, potassium, or sodium...

PASS-predicted design, synthesis and biological evaluation of cyclic nitrones as nootropics.

PubMed

Marwaha, Alka; Goel, R K; Mahajan, Mohinder P

2007-09-15

Out of 400 virtually designed imidazoline N-oxides, five cyclic nitrones were selected on the basis of PASS prediction as potent nootropics and were evaluated for their biological activities in albino mice. The selected N-alkyl and aryl-substituted nitrones were found to be excellent nootropics. A series of lead compounds acting as cognition enhancers have been provided, which can be further exploited in search of such New Chemical Entities (NCEs).

The reactivity of phosphagermaallene Tip(t-Bu)Ge=C=PMes* with doubly and triply bonded nitrogen compounds.

PubMed

Ghereg, Dumitru; Gornitzka, Heinz; Escudié, Jean; Ladeira, Sonia

2010-11-15

Phosphagermaallene Tip(t-Bu)Ge=C=PMes* (1; Mes* = 2,4,6-tri-tert-butylphenyl, Tip = 2,4,6-triisopropylphenyl) gives, with N-benzylidenemethylamine and pivalonitrile, [2+2] cycloadditions between the Ge=C double bond and the C=N and C≡N unsaturations, leading to the formation of the corresponding four-membered heterocycles 2 and 9. With N-tert-butyl-α-phenylnitrone and benzonitrile oxide, [2+3] cycloadditions occur to form the five-membered ring derivatives 6 and 7. By treatment of 1 with derivatives which possess weak acidic hydrogens in α of the C=N or C≡N multiple bond, two types of reactions were observed: an ene reaction with methyl(benzylideneamino)acetate and a 1,2 addition with acetonitrile to afford azadienyl(germyl)ether (4) and 3-germa-1-phosphapropene (8), respectively. In the case of benzonitrile, phosphagermaallene 1 behaves as a 1,3-dipole, to give, via a cyclic phosphagermacarbene intermediate, the tricyclic derivative 10.

Chiral recognition by formation of paramagnetic diastereomeric complexes

NASA Astrophysics Data System (ADS)

Scheffler, K.; Höfler, U.; Schuler, P.; Stegmann, H. B.

The chiral 4-(α-hydroxy-benzyl)-2,6-di-tert. butyl-phenoxyl has been examined in its racemic form in toluene and carbontetrachloride. On adding of chiral auxiliaries (R)-resp. (S)-N,N-dimethyl-1-phenylethylamine or (S)-phenylethyl-amine two different couplings of the β-proton are recorded by ENDOR spectroscopy. The experimental results are interpreted by a ternary equilibrium between radical, solvent and auxiliary. A model for the suggested association processes is given and equilibrium constants and corresponding enthalpies are calculated.

tert-Butyl N-hydr­oxy-N-[(1S*,2R*)-2-(1-naphth­yl)cyclo­pent-3-en-1-yl]carbamate

PubMed Central

Lough, Alan J.; Machin, Ben P.; Tam, William

2009-01-01

The relative stereochemistry of the title compound, C20H23NO3, was established by X-ray analysis. The asymmetric unit contains two independent mol­ecules. In the crystal structure, each type of mol­ecule forms a centrosymmetric dimer via pairs of inter­molecular O—H⋯O hydrogen bonds, resulting in an R 2 2(10) loop in each case. PMID:21582783

Di-tert-butyl­bis(N-isopropyl-N-methyl­dithio­carbamato-κ2 S,S′)tin(IV)

PubMed Central

Muthalib, Amirah Faizah; Baba, Ibrahim; Samsudin, Mohd Wahid; Ng, Seik Weng

2010-01-01

The dithio­carbamate anions in the title compound, [Sn(C4H9)2(C5H10NS2)2], chelate to the SnIV atom, which is six-coordinated in a skew-trapezoidal-bipyramidal geometry. The mol­ecule lies across a twofold rotation axis. The crystal studied was a non-merohedral twin, the ratio of the twin components being 0.82 (1):0.18 (1). PMID:21580471

Historical and Experimental Studies of Alkali and Trinitrotoluene Reaction

DTIC Science & Technology

1975-04-01

tripotassium V • nitronate salts of toluene. LIST OF FIGURES Page Figure 1. Infrared snectrum of red TNT contsaninated with 32 sodium carbonate Figure II...to get an addition compound of TNT and methyl alcohol which is the nitronic acid from which the alkali metal salts are derived. Hantzsch 4 originally...Nielson3 1 discusses the infrared spectra of nitronic acids, esters and silts, The C = N absorption for nitronic acids occurs near 1620 - 1680 cm𔃻

EFFECT OF BTEX ON THE DEGRADATION OF MTBE AND TBA BY MIXED BACTERIAL CONSORTIUM

EPA Science Inventory

Methyl tert-butyl ether (MTBE) contamination in groundwater often coexists with benzene, toluene, ethylbenzene, and xylene (BTEX) near the source of the plume. Tertiary butyl alcohol (TBA) is a prevalent intermediate of MTBE degradation. Therefore, there is a significant p...

A tandem conjugate addition/cyclization protocol for the asymmetric synthesis of 2-aryl-4-aminotetrahydroquinoline-3-carboxylic acid derivatives.

PubMed

Davies, Stephen G; Mujtaba, Nadeam; Roberts, Paul M; Smith, Andrew D; Thomson, James E

2009-05-07

Condensation of tert-butyl (E)-3-(2'-aminophenyl)propenoate with a range of aromatic and heteroaromatic aldehydes gives the corresponding imines as single diastereoisomers (>98% de). Addition of lithium (R)-N-benzyl-N-(alpha-methylbenzyl)amide initiates a tandem conjugate addition/cyclization reaction to generate 2-aryl-4-aminotetrahydroquinoline-3-carboxylic acid derivatives in >98% de, >98% ee and high isolated yield. Hydrogenolysis of an N(1)-Boc protected derivative allows selective cleavage of the N-benzyl-N-alpha-methylbenzyl protecting groups without compromise of the diastereo- or enantiopurity.

Synthesis, antimalarial activity, and preclinical pharmacology of a novel series of 4'-fluoro and 4'-chloro analogues of amodiaquine. Identification of a suitable "back-up" compound for N-tert-butyl isoquine.

PubMed

O'Neill, Paul M; Shone, Alison E; Stanford, Deborah; Nixon, Gemma; Asadollahy, Eghbaleh; Park, B Kevin; Maggs, James L; Roberts, Phil; Stocks, Paul A; Biagini, Giancarlo; Bray, Patrick G; Davies, Jill; Berry, Neil; Hall, Charlotte; Rimmer, Karen; Winstanley, Peter A; Hindley, Stephen; Bambal, Ramesh B; Davis, Charles B; Bates, Martin; Gresham, Stephanie L; Brigandi, Richard A; Gomez-de-Las-Heras, Federico M; Gargallo, Domingo V; Parapini, Silvia; Vivas, Livia; Lander, Hollie; Taramelli, Donatella; Ward, Stephen A

2009-04-09

On the basis of a mechanistic understanding of the toxicity of the 4-aminoquinoline amodiaquine (1b), three series of amodiaquine analogues have been prepared where the 4-aminophenol "metabolic alert" has been modified by replacement of the 4'-hydroxy group with a hydrogen, fluorine, or chlorine atom. Following antimalarial assessment and studies on mechanism of action, two candidates were selected for detailed ADME studies and in vitro and in vivo toxicological assessment. 4'-Fluoro-N-tert-butylamodiaquine (2k) was subsequently identified as a candidate for further development studies based on potent activity versus chloroquine-sensitive and resistant parasites, moderate to excellent oral bioavailability, low toxicity in in vitro studies, and an acceptable safety profile.

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

EPA Science Inventory

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

IRIS Toxicological Review of Tert-Butyl Alcohol (Tert-Butanol) ...

EPA Pesticide Factsheets

EPA is developing an Integrated Risk Information System (IRIS) assessment of tert-butyl Alcohol (tert-butanol) and has released the public comment draft assessment for public comment and external peer review. When final, the assessment will appear on the IRIS database. This draft report is being released for public viewing and comment prior to a public meeting, providing an opportunity for the IRIS Program to engage in early discussions with stakeholders and the public on data that may be used to identify adverse health effects and characterize exposure-response relationships. EPA welcomes all comments on the draft literature search, preliminary evidence tables, and preliminary exposure-response arrays, such as remarks on the following: • the clarity and transparency of the materials; • the approach for identifying pertinent studies; • the selection of studies for data extraction to preliminary evidence tables and exposure-response arrays; • any methodological considerations that could affect the interpretation of or confidence in study results; and • any additional studies published or nearing publication that may provide data for the evaluation of human health hazard or dose-response relationships.

Effects of hydroxylated benzaldehyde derivatives on radiation-induced reactions involving various organic radicals

NASA Astrophysics Data System (ADS)

Ksendzova, G. A.; Samovich, S. N.; Sorokin, V. L.; Shadyro, O. I.

2018-05-01

In the present paper, the effects of hydroxylated benzaldehyde derivatives and gossypol - the known natural occurring compound - on formation of decomposition products resulting from radiolysis of ethanol and hexane in deaerated and oxygenated solutions were studied. The obtained data enabled the authors to make conclusions about the effects produced by the structure of the compounds under study on their reactivity towards oxygen- and carbon-centered radicals. It has been found that 2,3-dihydroxybenzaldehyde, 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde and 4,6-di-tert-butyl-3-(1,3-dioxane-2-yl)-1,2-dihydroxybenzene are not inferior in efficiency to butylated hydroxytoluene - the industrial antioxidant - as regards suppression of the radiation-induced oxidation processes occurring in hexane. The derivatives of hydroxylated benzaldehydes were shown to have a significant influence on radiation-induced reactions involving α-hydroxyalkyl radicals.

Topographic organizations of taste-responsive neurons in the parabrachial nucleus of C57BL/6J mice: An electrophysiological mapping study.

PubMed

Tokita, K; Boughter, J D

2016-03-01

The activities of 178 taste-responsive neurons were recorded extracellularly from the parabrachial nucleus (PbN) in the anesthetized C57BL/6J mouse. Taste stimuli included those representative of five basic taste qualities, sweet, salty, sour, bitter and umami. Umami synergism was represented by all sucrose-best and sweet-sensitive sodium chloride-best neurons. Mediolaterally the PbN was divided into medial, brachium conjunctivum (BC) and lateral subdivisions while rostrocaudally the PbN was divided into rostral and caudal subdivisions for mapping and reconstruction of recording sites. Neurons in the medial and BC subdivisions had a significantly greater magnitude of response to sucrose and to the mixture of monopotassium glutamate and inosine monophosphate than those found in the lateral subdivision. In contrast, neurons in the lateral subdivision possessed a more robust response to quinine hydrochloride. Rostrocaudally no difference was found in the mean magnitude of response. Analysis on the distribution pattern of neuron types classified by their best stimulus revealed that the proportion of neuron types in the medial vs. lateral and BC vs. lateral subdivisions was significantly different, with a greater amount of sucrose-best neurons found medially and within the BC, and a greater amount of sodium chloride-, citric acid- and quinine hydrochloride-best neurons found laterally. There was no significant difference in the neuron-type distribution between rostral and caudal PbN. We also assessed breadth of tuning in these neurons by calculating entropy (H) and noise-to-signal (N/S) ratio. The mean N/S ratio of all neurons (0.43) was significantly lower than that of H value (0.64). Neurons in the caudal PbN had a significantly higher H value than in the rostral PbN. In contrast, mean N/S ratios were not different both mediolaterally and rostrocaudally. These results suggest that although there is overlap in taste quality representation in the mouse PbN, taste-responsive neurons still possessed a topographic organization. Published by Elsevier Ltd.

Difunctionalization of alkenes with iodine and tert-butyl hydroperoxide (TBHP) at room temperature for the synthesis of 1-(tert-butylperoxy)-2-iodoethanes.

PubMed

Wang, Hao; Chen, Cui; Liu, Weibing; Zhu, Zhibo

2017-01-01

We developed a direct vicinal difunctionalization of alkenes with iodine and TBHP at room temperature. This iodination and peroxidation in a one-pot synthesis produces 1-( tert -butylperoxy)-2-iodoethanes, which are inaccessible through conventional synthetic methods. This method generates multiple radical intermediates in situ and has excellent regioselectivity, a broad substrate scope and mild conditions. The iodine and peroxide groups of 1-( tert -butylperoxy)-2-iodoethanes have several potential applications and allow further chemical modifications, enabling the preparation of synthetically valuable molecules.

A radical pathway in catecholase activity with nickel(II) complexes of phenol based "end-off" compartmental ligands.

PubMed

Ghosh, Totan; Adhikary, Jaydeep; Chakraborty, Prateeti; Sukul, Pradip K; Jana, Mahendra Sekhar; Mondal, Tapan Kumar; Zangrando, Ennio; Das, Debasis

2014-01-14

Seven dinuclear and one dinuclear based dicyanamide bridged polymeric Ni(II) complexes of phenol based compartmental ligands (HL(1)-HL(4)) have been synthesized with the aim to investigate their catecholase-like activity and to evaluate the most probable mechanistic pathway involved in this process. The complexes have been characterized by routine physicochemical studies as well as by X-ray single crystal structure analyses namely [Ni2(L(2))(SCN)3(H2O)(CH3OH)] (), [Ni2(L(4))(SCN)3(CH3OH)2] (), [Ni2(L(2))(SCN)2(AcO)(H2O)] (), [Ni2(L(4))(SCN)(AcO)2] (), [Ni2(L(2))(N3)3(H2O)2] (), [Ni2(L(4))(N3)3(H2O)2] (), [Ni2(L(1))(AcO)2(N(CN)2)]n () and [Ni2(L(3))(AcO)2(N(CN)2)] (), [SCN = isothiocyanate, AcO = acetate, N3 = azide, and N(CN)2 = dicyanamide anion; L(1-4) = 2,6-bis(R2-iminomethyl)-4-R1-phenolato, where R1 = methyl and tert-butyl, R2 = N,N-dimethyl ethylene for L(1-2) and R1 = methyl and tert-butyl, R2 = 2-(N-ethyl) pyridine for L(3-4)]. A UV-vis spectrophotometric study using 3,5-di-tert butylcatechol (3,5-DTBC) reveals that all the complexes are highly active in catalyzing the aerobic oxidation of (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) in methanol medium with the formation of hydrogen peroxide. An EPR study confirms the generation of radicals during the catalysis. Cyclic voltammetric studies of the complexes in the presence and absence of 3,5-DTBC have been performed. Reduction of Ni(II) to Ni(I) and that of the imine bond of the ligand system have been detected at ∼-1.0 V and ∼-1.5 V, respectively. Coulometric separation of the species at -1.5 V followed by the EPR study at 77 K confirms the species as an organic radical and thus most probably reduced imine species. Spectroelectrochemical analysis at -1.5 V clearly indicates the oxidation of 3,5-DTBC and thus suggests that the radical pathway is supposed to be responsible for the catecholase-like activity exhibited by the nickel complexes. The ligand centred radical generation has further been verified by density functional theory calculation.

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...

Light-Induced C-H Arylation of (Hetero)arenes by In Situ Generated Diazo Anhydrides.

PubMed

Cantillo, David; Mateos, Carlos; Rincon, Juan A; de Frutos, Oscar; Kappe, C Oliver

2015-09-07

Diazo anhydrides (Ar-N=N-O-N=N-Ar) have been known since 1896 but have rarely been used in synthesis. This communication describes the development of a photochemical catalyst-free C-H arylation methodology for the preparation of bi(hetero)aryls by the one-pot reaction of anilines with tert-butyl nitrite and (hetero)arenes under neutral conditions. The key step in this procedure is the in situ formation and subsequent photochemical (>300 nm) homolytic cleavage of a transient diazo anhydride intermediate. The generated aryl radical then efficiently reacts with a (hetero)arene to form the desired bi(hetero)aryls producing only nitrogen, water, and tert-butanol as byproducts. The scope of the reaction for several substituted anilines and (hetero)arenes was investigated. A continuous-flow protocol increasing selectivity and safety has been developed enabling the experimentally straightforward preparation of a variety of substituted bi(hetero)aryls within 45 min of reaction time. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Methyl tert-butyl ether biodegradation by microbial consortia obtained from soil samples of gasoline-polluted sites in Mexico.

PubMed

Morales, Marcia; Velázquez, Elia; Jan, Janet; Revah, Sergio; González, Uriel; Razo-Flores, Elías

2004-02-01

Microbial consortia obtained from soil samples of gasoline-polluted sites were individually enriched with pentane, hexane, isooctane and toluene. Cometabolism with methyl tert-butyl ether, (MTBE), gave maximum degradation rates of 49, 12, 32 and 0 mg g(-1)protein h(-1), respectively. MTBE was fully degraded even when pentane was completely depleted with a cometabolic coefficient of 1 mgMTBE mg(-1)pentane. The analysis of 16S rDNA from isolated microorganisms in the pentane-adapted consortia showed that microorganisms could be assigned to Pseudomonas. This is the first work reporting the cometabolic mineralization of MTBE by consortium of this genus.

Rotational Investigation of the Adducts of Formic Acid with Alcohols, Ethers and Esters

NASA Astrophysics Data System (ADS)

Evangelisti, Luca; Spada, Lorenzo; Li, Weixing; Caminati, Walther

2016-06-01

Mixtures of formic acid with methyl alcohol, with isopropyl alcohol, with tert-butyl alcohol, with dimethylether and with isopropylformiate have been supersonically expanded as pulsed jets. The obtained cool plumes have been analyzed by Fourier transform microwave spectroscopy. It has been possible to assign the rotational spectra of the 1:1 adducts of formic acid with tert-butyl alcohol, with dimethyl ether and with isopropylformiate. The conformational shapes and geometries of these adducts, as well as the topologies of their itermolecular hydrogen bonds will be presented. An explanation is given of the failure of the assignments of the rotational spectra of the adducts of formic acid with methyl alcohol and isopropyl alcohol.

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

PubMed Central

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

2011-01-01

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

Inhibitory effect of naturally occurring flavonoids on the formation of advanced glycation endproducts.

PubMed

Wu, Chi-Hao; Yen, Gow-Chin

2005-04-20

The objective of this study was to investigate the inhibitory effect of naturally occurring flavonoids on individual stage of protein glycation in vitro using the model systems of delta-Gluconolactone assay (early stage), BSA-methylglyoxal assay (middle stage), BSA-glucose assay, and G.K. peptide-ribose assay (last stage). In the early stage of protein glycation, luteolin, qucertin, and rutin exhibited significant inhibitory activity on HbA1C formation (p < 0.01), which were more effective than that of aminoguanidine (AG, 10 mM), a well-known inhibitor for advanced glycation endproducts (AGEs). For the middle stage, luteolin and rutin developed more significant inhibitory effect on methylglyoxal-medicated protein modification, and the IC50's were 66.1 and 71.8 microM, respectively. In the last stage of glycation, luteolin was found to be potent inhibitors of both the AGEs formation and the subsequent cross-linking of proteins. In addition, phenyl-tert-butyl-nitron served as a spin-trapping agent, and electron spin resonance (ESR) was used to explore the possible mechanism of the inhibitory effect of flavonoids on glycation. The results indicated that protein glycation was accompanied by oxidative reactions, as the ESR spectra showed a clear-cut radical signal. Statistical analysis showed that inhibitory capability of flavonoids against protein glycation was remarkably related to the scavenging free radicals derived from glycoxidation process (r = 0.79, p < 0.01). Consequently, the inhibitory mechanism of flavonoids against glycation was, at least partly, due to their antioxidant properties.

Analogues of methotrexate and aminopterin with gamma-methylene and gamma-cyano substitution of the glutamate side chain: synthesis and in vitro biological activity.

PubMed

Rosowsky, A; Bader, H; Freisheim, J H

1991-01-01

Analogues of methotrexate (MTX) and aminopterin (AMT) modified at the gamma-position of the glutamate side chain were synthesized and evaluated as dihydrofolate reductase (DHFR) inhibitors and tumor cell growth inhibitors. Condesations of 4-amino-4-deoxy-N10-methylpteroic acid (mAPA) with dimethyl DL-4-methyleneglutamate in the presence of diethyl phosphorocyanidate (DEPC) followed by alkaline hydrolysis yielded N-(4-amino-4-deoxy-N10-methylpteroyl)-DL-4-methyleneglutamic acid (gamma-methyleneMTX). Condensation of 4-amino-4-deoxy-N10-formylpteroic acid (fAPA) with dimethyl-DL-4-methyleneglutamate by the mixed carboxylic-carbonic anhydride method yielded N-4-amino-4-deoxypteroyl)-DL-4-methyleneglutamic acid (gamma-methyleneAMT). Also prepared via DEPC coupling was a mixture of the four possible diastereomers of N-(4-amino-4-deoxy-N10-methylpteroyl)-4-cyanoglutamic acid (gamma-cyanoMTX). The requisite intermediate gamma-tert-butyl alpha-methyl 4-cyanoglutamate, as a DL-threo/DL-erythro mixture, was prepared from methyl N alpha-Boc-O-tosyl-L-serinate by reaction with sodium tert-butyl cyanoacetate followed by mild trifluoroacetic treatment to selectively remove the Boc group. The gamma-methylene derivatives of MTX and AMT are attractive because of their potential to act as Michael acceptors within the DHFR active site. gamma-CyanoMTX may be viewed as a congener of the nonpolyglutamated MTX analogue gamma-fluoroMTX. In vitro bioassay data for the gamma-methylene and gamma-cyano compounds support the idea that the active site of DHFR, already known for its ability to tolerate modification of the gamma-carboxyl group of MTX and AMT, can likewise accommodate substitution on the gamma-carbon itself.

Enantioselective syntheses of carbanucleosides from the Pauson-Khand adduct of trimethylsilylacetylene and norbornadiene.

PubMed

Vázquez-Romero, Ana; Rodríguez, Julia; Lledó, Agustí; Verdaguer, Xavier; Riera, Antoni

2008-10-16

A new enantioselective approach to carbanucleosides from Pauson-Khand (PK) adduct 1 is disclosed. The chiral cyclopentenone 1 is readily accessible in enantiomerically pure form via PK reaction of trimethylsilylacetylene and norbornadiene using N-benzyl-N-diphenylphosphino-tert-butyl-sulfinamide as a chiral P,S ligand. (-)-Carbavir and (-)-Abacavir were enantioselectively synthesized starting from (-)-1. The key steps of the sequence are a photochemical conjugate addition of a hydroxymethyl radical, a retro-Diels-Alder reaction, and a palladium catalyzed allylic substitution to introduce the nucleobase.

Directed Evolution of Carbonyl Reductase from Rhodosporidium toruloides and Its Application in Stereoselective Synthesis of tert-Butyl (3R,5S)-6-Chloro-3,5-dihydroxyhexanoate.

PubMed

Liu, Zhi-Qiang; Wu, Lin; Zhang, Xiao-Jian; Xue, Ya-Ping; Zheng, Yu-Guo

2017-05-10

tert-Butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate ((3R,5S)-CDHH) is a key intermediate of atorvastatin and rosuvastatin synthesis. Carbonyl reductase RtSCR9 from Rhodosporidium toruloides exhibited excellent activity toward tert-butyl (S)-6-chloro-5-hydroxy-3-oxohexanoate ((S)-CHOH). For the activity of RtSCR9 to be improved, random mutagenesis and site-saturation mutagenesis were performed. Three positive mutants were obtained (mut-Gln95Asp, mut-Ile144Lys, and mut-Phe156Gln). These mutants exhibited 1.94-, 3.03-, and 1.61-fold and 1.93-, 3.15-, and 1.97-fold improvement in the specific activity and k cat /K m , respectively. Asymmetric reduction of (S)-CHOH by mut-Ile144Lys coupled with glucose dehydrogenase was conducted. The yield and enantiomeric excess of (3R,5S)-CDHH reached 98 and 99%, respectively, after 8 h bioconversion in a single batch reaction with 1 M (S)-CHOH, and the space-time yield reached 542.83 mmol L -1 h -1 g -1 wet cell weight. This study presents a new carbonyl reductase for efficient synthesis of (3R,5S)-CDHH.

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

NASA Astrophysics Data System (ADS)

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

2014-06-01

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

Redox Active Transition Metal ions Make Melanin Susceptible to Chemical Degradation Induced by Organic Peroxide.

PubMed

Zadlo, Andrzej; Pilat, Anna; Sarna, Michal; Pawlak, Anna; Sarna, Tadeusz

2017-12-01

With aging, retinal pigment epithelium melanosomes, by fusion with the age pigment lipofuscin, form complex granules called melanolipofuscin. Lipofuscin granules may contain oxidized proteins and lipid hydroperoxides, which in melanolipofuscin could chemically modify melanin polymer, while transition metal ions present in melanin can accelerate such oxidative modifications. The aim of this research was to examine the effect of selected transition metal ions on melanin susceptibility to chemical modification induced by the water-soluble tert-butyl hydroperoxide used as an oxidizing agent. Synthetic melanin obtained by DOPA autooxidation and melanosomes isolated from bovine retinal pigment epithelium were analyzed. To monitor tert-butyl hydroperoxide-induced oxidative changes of DMa and BMs, electron paramagnetic resonance spectroscopy, UV-vis absorption spectroscopy, dynamic light scattering, atomic force microscopy and electron paramagnetic resonance oximetry were employed. These measurements revealed that both copper and iron ions accelerated chemical degradation induced by tert-butyl hydroperoxide, while zinc ions had no effect. Strong prooxidant action was detected only in the case of melanosomes and melanin degraded in the presence of iron. It can be postulated that similar chemical processes, if they occur in situ in melanolipofuscin granules of the human retinal pigment epithelium, would modify antioxidant properties of melanin and its reactivity.

Solidification and solidification cracking in nitrogen-strengthened austenitic stainless steels

NASA Astrophysics Data System (ADS)

Ritter, Ann M.; Savage, Warren F.

1986-04-01

The solidification behavior of three heats of nitrogen-strengthened austenitic stainless steel was examined and was correlated with solidification mode predictions and with hot cracking resistance. The heat of NITRONIC* 50 solidified by the austenitic-ferrite mode, and the NITRONIC 50W and NITRONIC 50W - Nb heats solidified by the ferritic-austenitic mode. This behavior was in good agreement with predictions based on Espy’s formulas for Cr and Ni equivalents. Both the NITRONIC 50W and NITRONIC 50W + Nb welds contained primary delta-ferrite, with the latter weld and the NITRONIC 50 weld also containing some eutectic ferrite. Solute profiles in austenite near the eutectic ferrite showed decreasing Fe and increasing Cr, Ni, Mn, and Mo relative to austenite in the dendrite cores. Numerous Nb-rich precipitates were found on the eutectic ferrite/austenite interfaces and within the eutectic ferrite. The precipitates were mainly Nb(C, N), with some Z-phase, a Nb-rich nitride, also detected. One instance of the transformation of eutectic ferrite to sigma-phase was observed to have occurred during cooling of the NITRONIC 50 weld. Hot cracking was seen in the NITRONIC 50 and NITRONIC 50W + Nb welds and resulted from the formation of a niobium carbonitride eutectic in the interdendritic regions. In the absence of Nb, the NITRONIC 50W heat formed no observable eutectic constituents and did not hot crack. The presence of hot cracks in the NITRONIC 50W + Nb weld indicates that solidification by the ferritic-austenitic mode did not counteract the effects of small Nb additions.

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.

PubMed

Pruden, Amy; Suidan, Makram

2004-08-01

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 initial concentration levels of MTBE or TBA: 6-7; 15-17; and 40-45 mg/l, both with and without BTEX present cumulatively at about half of the MTBE or TBA molar mass in the system. The BTEX mixture was observed not to affect either the rate or the degradation lag period of MTBE or TBA degradation, except that the TBA degradation rate actually increased when BTEX was present initially in the highest concentration studies. When serving as the sole substrate, the MTBE degradation rate ranged from 48 +/- 1.2 to 200 +/- 7.0 mg(MTBE)/g(dw) h, and the TBA degradation rate from 140 +/- 18 to 530 +/- 70 mg(TBA)/g(dw) h. When present with BTEX, MTBE and TBA rates ranged from 46 +/- 2.2 to 210 +/- 14 and 170 +/- 28 to 780 +/- 43 mg(TBA)/g(dw) h, respectively. In studies where varying concentrations of TBA were present with 5 mg/l MTBE, both compounds were degraded simultaneously with no obvious preference for either substrate. In the highest concentration study of TBA with 5 mg/l MTBE, BTEX was also observed to increase the ultimate rate of TBA degradation. In addition to exploring the affect of BTEX, this study also provides general insight into the metabolism of MTBE and TBA by pure culture UC1.

A siloxane-incorporated copolymer as an in situ cross-linkable binder for high performance silicon anodes in Li-ion batteries

NASA Astrophysics Data System (ADS)

Jeena, M. T.; Bok, Taesoo; Kim, Si Hoon; Park, Sooham; Kim, Ju-Young; Park, Soojin; Ryu, Ja-Hyoung

2016-04-01

The electrochemical performance of Li-ion batteries (LIBs) can be highly tuned by various factors including the morphology of the anode material, the nature of the electrolyte, the binding material, and the percentage of conducting materials. Binding materials have been of particular interest to researchers over the decades as a means to further improve the cycle durability and columbic efficiency of LIBs. Such approaches include the introduction of different polymeric binders such as poly(acrylic acid) (PAA), carboxymethyl cellulose (CMC), and alginic acid (Alg) into the Si anode of LIBs. To achieve a better efficiency of LIBs, herein, we introduce a novel copolymer, poly(tert-butyl acrylate-co-triethoxyvinylsilane) (TBA-TEVS), as an efficient binder with stable cycle retention and excellent specific capacity. The binder forms a highly interconnected three-dimensional network upon thermal treatment as a result of de-protection of the tert-butyl group and the consequent inter-intra condensation reaction, which minimizes pulverization of the Si nanoparticles. Moreover, the siloxane group is expected to promote the formation of stable solid-electrolyte-interface (SEI) layers. A series of random copolymers were synthesized by varying the molar ratio of tert-butyl acrylate and triethoxyvinylsilane. Twenty-one percent of TEVS in the TBS-TEVS copolymer gave rise to a superior performance as a binder for Si anodes, where the anodes showed a stable specific capacity of 2551 mA h g-1 over hundreds of cycles and an initial columbic efficiency (ICE) of 81.8%.The electrochemical performance of Li-ion batteries (LIBs) can be highly tuned by various factors including the morphology of the anode material, the nature of the electrolyte, the binding material, and the percentage of conducting materials. Binding materials have been of particular interest to researchers over the decades as a means to further improve the cycle durability and columbic efficiency of LIBs. Such approaches include the introduction of different polymeric binders such as poly(acrylic acid) (PAA), carboxymethyl cellulose (CMC), and alginic acid (Alg) into the Si anode of LIBs. To achieve a better efficiency of LIBs, herein, we introduce a novel copolymer, poly(tert-butyl acrylate-co-triethoxyvinylsilane) (TBA-TEVS), as an efficient binder with stable cycle retention and excellent specific capacity. The binder forms a highly interconnected three-dimensional network upon thermal treatment as a result of de-protection of the tert-butyl group and the consequent inter-intra condensation reaction, which minimizes pulverization of the Si nanoparticles. Moreover, the siloxane group is expected to promote the formation of stable solid-electrolyte-interface (SEI) layers. A series of random copolymers were synthesized by varying the molar ratio of tert-butyl acrylate and triethoxyvinylsilane. Twenty-one percent of TEVS in the TBS-TEVS copolymer gave rise to a superior performance as a binder for Si anodes, where the anodes showed a stable specific capacity of 2551 mA h g-1 over hundreds of cycles and an initial columbic efficiency (ICE) of 81.8%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01559j

Draft genome sequence of Methylibium sp. strain T29, a novel fuel oxygenate-degrading bacterial isolate from Hungary.

PubMed

Szabó, Zsolt; Gyula, Péter; Robotka, Hermina; Bató, Emese; Gálik, Bence; Pach, Péter; Pekker, Péter; Papp, Ildikó; Bihari, Zoltán

2015-01-01

Methylibium sp. strain T29 was isolated from a gasoline-contaminated aquifer and proved to have excellent capabilities in degrading some common fuel oxygenates like methyl tert-butyl ether, tert-amyl methyl ether and tert-butyl alcohol along with other organic compounds. Here, we report the draft genome sequence of M. sp. strain T29 together with the description of the genome properties and its annotation. The draft genome consists of 608 contigs with a total size of 4,449,424 bp and an average coverage of 150×. The genome exhibits an average G + C content of 68.7 %, and contains 4754 protein coding and 52 RNA genes, including 48 tRNA genes. 71 % of the protein coding genes could be assigned to COG (Clusters of Orthologous Groups) categories. A formerly unknown circular plasmid designated as pT29A was isolated and sequenced separately and found to be 86,856 bp long.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1987-04-23

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

Toxicokinetics of ethers used as fuel oxygenates.

PubMed

Dekant, W; Bernauer, U; Rosner, E; Amberg, A

2001-10-15

The toxicokinetics and biotransformation of methyl-tert.butyl ether (MTBE), ethyl-tert.butyl ether (ETBE) and tert.amyl-methyl ether (TAME) in rats and humans are summarized. These ethers are used as gasoline additives in large amounts, and thus, a considerable potential for human exposure exists. After inhalation exposure MTBE, ETBE and TAME are rapidly taken up by both rats and humans; after termination of exposure, clearance by exhalation and biotransformation to urinary metabolites is rapid in rats. In humans, clearance by exhalation is slower in comparison to rats. Biotransformation of MTBE and ETBE is both qualitatively and quantitatively similar in humans and rats after inhalation exposure under identical conditions. The extent of biotransformation of TAME is also quantitatively similar in rats and humans; the metabolic pathways, however, are different. The results suggest that reactive and potentially toxic metabolites are not formed during biotransformation of these ethers and that toxic effects of these compounds initiated by covalent binding to cellular macromolecules are unlikely.

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

USGS Publications Warehouse

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

2008-01-01

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

Exceptionally long-lived light-emitting electrochemical cells: multiple intra-cation π-stacking interactions in [Ir(C^N)2(N^N)][PF6] emitters† †Electronic supplementary information (ESI) available: Experimental details. Fig. S1–S10: additional structural and NMR spectroscopic figures; voltage vs. time plots for LEC devices and electroluminescence spectra. CCDC 1019226–1019229. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4sc03942d

PubMed Central

Bünzli, Andreas M.; Constable, Edwin C.; Prescimone, Alessandro; Zampese, Jennifer A.; Longo, Giulia; Gil-Escrig, Lidón; Pertegás, Antonio; Ortí, Enrique

2015-01-01

A series of cyclometalated iridium(iii) complexes [Ir(C^N)2(N^N)][PF6] (N^N = 2,2′-bipyridine (1), 6-phenyl-2,2′-bipyridine (2), 4,4′-di-tert-butyl-2,2′-bipyridine (3), 4,4′-di-tert-butyl-6-phenyl-2,2′-bipyridine (4); HC^N = 2-(3-phenyl)phenylpyridine (HPhppy) or 2-(3,5-diphenyl)phenylpyridine (HPh2ppy)) are reported. They have been synthesized using solvento precursors so as to avoid the use of chlorido-dimer intermediates, chloride ion contaminant being detrimental to the performance of [Ir(C^N)2(N^N)][PF6] emitters in light-electrochemical cell (LEC) devices. Single crystal structure determinations and variable temperature solution 1H NMR spectroscopic data confirm that the pendant phenyl domains engage in multiple face-to-face π-interactions within the coordination sphere of the iridium(iii) centre. The series of [Ir(Phppy)2(N^N)]+ and [Ir(Ph2ppy)2(N^N)]+ complexes investigated include those with and without intra-cation face-to-face π-stacking. All the complexes display excellent luminescent properties, in particular when employed in thin solid films. The most important observation is that all the LECs using the [Ir(Phppy)2(N^N)]+ and [Ir(Ph2ppy)2(N^N)]+ emitters (i.e. with and without intra-cation π-stacking interactions) exhibit very stable luminance outputs over time, even when driven at elevated current densities. The most stable LEC had an extrapolated lifetime of more than 2500 hours under accelerated testing conditions. PMID:29142683

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

USGS Publications Warehouse

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

1995-01-01

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

CHLORINATED SOLVENT PLUME CONTROL

EPA Science Inventory

This lecture will cover recent success in controlling and assessing the treatment of shallow ground water plumes of chlorinated solvents, other halogenated organic compounds, and methyl tert-butyl ether (MTBE).

NCEL (Naval Civil Engineering Laboratory) Quarterly Abstracts of Technical Documents, 1 April to 30 June 1987.

DTIC Science & Technology

1987-06-30

release; distribution unlimited. 87 8 3075 TABLE OF CONTENTS page TECHNICAL NOTES N-1764 Validation of Nitronic 33 in Reinforced and Prestressed...TECHNICAL WES K- 1764 Validation of Nitrovic 33 In Reeinforced and Prestressed Concrete, Apr 1987, James F. Jenkins (public release) Nitronic 33...prestressing strand are not acceptable. Before Nitronic 33 stainless steel prestressed concrete waterfront structures were constructed, it was necessary to

Comparative transcriptome analysis of Methylibium petroleiphilum PM1 exposed to the fuel oxygenates methyl tert-butyl ether and ethanol.

PubMed

Hristova, Krassimira R; Schmidt, Radomir; Chakicherla, Anu Y; Legler, Tina C; Wu, Janice; Chain, Patrick S; Scow, Kate M; Kane, Staci R

2007-11-01

High-density whole-genome cDNA microarrays were used to investigate substrate-dependent gene expression of Methylibium petroleiphilum PM1, one of the best-characterized aerobic methyl tert-butyl ether (MTBE)-degrading bacteria. Differential gene expression profiling was conducted with PM1 grown on MTBE and ethanol as sole carbon sources. Based on microarray high scores and protein similarity analysis, an MTBE regulon located on the megaplasmid was identified for further investigation. Putative functions for enzymes encoded in this regulon are described with relevance to the predicted MTBE degradation pathway. A new unique dioxygenase enzyme system that carries out the hydroxylation of tert-butyl alcohol to 2-methyl-2-hydroxy-1-propanol in M. petroleiphilum PM1 was discovered. Hypotheses regarding the acquisition and evolution of MTBE genes as well as the involvement of IS elements in these complex processes were formulated. The pathways for toluene, phenol, and alkane oxidation via toluene monooxygenase, phenol hydroxylase, and propane monooxygenase, respectively, were upregulated in MTBE-grown cells compared to ethanol-grown cells. Four out of nine putative cyclohexanone monooxygenases were also upregulated in MTBE-grown cells. The expression data allowed prediction of several hitherto-unknown enzymes of the upper MTBE degradation pathway in M. petroleiphilum PM1 and aided our understanding of the regulation of metabolic processes that may occur in response to pollutant mixtures and perturbations in the environment.

Microbial community composition during anaerobic mineralization of tert-butyl alcohol (TBA) in fuel-contaminated aquifer material.

PubMed

Wei, Na; Finneran, Kevin T

2011-04-01

Anaerobic mineralization of tert-butyl alcohol (TBA) and methyl tert-butyl ether (MTBE) were studied in sediment incubations prepared with fuel-contaminated aquifer material. Microbial community compositions in all incubations were characterized by amplified ribosomal DNA restriction analysis (ARDRA). The aquifer material mineralized 42.3±9.9% of [U-(14)C]-TBA to 14CO2 without electron acceptor amendment. Fe(III), sulfate, and Fe(III) plus anthraquinone-2,6-disulfonate addition also promoted U-[14C]-TBA mineralization at levels similar to those of the unamended controls. Nitrate actually inhibited TBA mineralization relative to unamended controls. In contrast to TBA, [U-(14)C]-MTBE was not significantly mineralized in 400 days regardless of electron acceptor amendment. Microbial community analysis indicated that the abundance of one dominant clone group correlated closely with anaerobic TBA mineralization. The clone was phylogenetically distinct from known aerobic TBA-degrading microorganisms, Fe(III)- or sulfate-reducing bacteria. It was most closely associated with organisms belonging to the alphaproteobacteria. Microbial communities were different in MTBE and TBA amended incubations. Shannon indices and Simpson indices (statistical community comparison tools) both demonstrated that microbial community diversity decreased in incubations actively mineralizing TBA, with distinct "dominant" clones developing. These data contribute to our understanding of anaerobic microbial transformation of fuel oxygenates in contaminated aquifer material and the organisms that may catalyze the reactions.

Spectroscopic investigation of H atom transfer in a gas-phase dissociation reaction: McLafferty rearrangement of model gas-phase peptide ions.

PubMed

Van Stipdonk, Michael J; Kerstetter, Dale R; Leavitt, Christopher M; Groenewold, Gary S; Steill, Jeffrey; Oomens, Jos

2008-06-14

Wavelength-selective infrared multiple-photon photodissociation (WS-IRMPD) was used to study isotopically-labeled ions generated by McLafferty rearrangement of nicotinyl-glycine-tert-butyl ester and betaine-glycine-tert-butyl ester. The tert-butyl esters were incubated in a mixture of D(2)O and CH(3)OD to induce solution-phase hydrogen-deuterium exchange and then converted to gas-phase ions using electrospray ionization. McLafferty rearrangement was used to generate the free-acid forms of the respective model peptides through transfer of an H atom and elimination of butene. The specific aim was to use vibrational spectra generated by WS-IRMPD to determine whether the H atom remains at the acid group, or migrates to one or more of the other exchangeable sites. Comparison of the IRMPD results in the region from 1200-1900 cm(-1) to theoretical spectra for different isotopically-labeled isomers clearly shows that the H atom is situated at the C-terminal acid group and migration to amide positions is negligible on the time scale of the experiment. The results of this study suggest that use of the McLafferty rearrangement for peptide esters could be an effective approach for generation of H-atom isotope tracers, in situ, for subsequent investigation of intramolecular proton migration during peptide fragmentation studies.

Biosynthesis of tert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate by carbonyl reductase from Rhodosporidium toruloides in mono and biphasic media.

PubMed

Liu, Zhi-Qiang; Wu, Lin; Zheng, Ling; Wang, Wen-Zhong; Zhang, Xiao-Jian; Jin, Li-Qun; Zheng, Yu-Guo

2018-02-01

tert-Butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate ((3R,5S)-CDHH) is the key intermediate for synthesis of atorvastatin and rosuvastatin. Carbonyl reductase exhibits excellent activity toward tert-butyl (S)-6-chloro-5-hydroxy-3-oxohexanoate ((S)-CHOH) to synthesize (3R,5S)-CDHH. In this study, a whole cell biosynthesis reaction system to produce (3R,5S)-CDHH was constructed in organic solvents. A solution of 10% (v/v) Tween-80 was introduced to the reaction system as a co-solvent, which greatly enhanced biotransformation process, giving 98.9% yield, >99% ee and 1.8-fold higher space time yield in 5 h bioconversion of 1 M (S)-CHOH, compared with 98.7% yield and >99% ee in 9 h bioconversion of a purely aqueous reaction system. Moreover, a water-octanol biphasic reaction system was built and 20% of octanol was added as reservoir of substrate resulting in 98% yield, >99% ee and 4.08 mmol L -1  h -1  g -1 (wet cell weight) space time yield. This study paved a way for the whole cell biosynthesis of (3R,5S)-CDHH in mono and biphasic media. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

PubMed

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

2013-10-01

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

[18F]Fluorophenylazocarboxylates: Design and Synthesis of Potential Radioligands for Dopamine D3 and μ-Opioid Receptor

PubMed Central

2017-01-01

18F-Labeled building blocks from the type of [18F]fluorophenylazocarboxylic-tert-butyl esters offer a rapid, mild, and reliable method for the 18F-fluoroarylation of biomolecules. Two series of azocarboxamides were synthesized as potential radioligands for dopamine D3 and the μ-opioid receptor, revealing compounds 3d and 3e with single-digit and sub-nanomolar affinity for the D3 receptor and compound 4c with only micromolar affinity for the μ-opioid receptor, but enhanced selectivity for the μ-subtype in comparison to the lead compound AH-7921. A “minimalist procedure” without the use of a cryptand and base for the preparation of 4-[18F]fluorophenylazocarboxylic-tert-butyl ester [18F]2a was established, together with the radiosynthesis of methyl-, methoxy-, and phenyl-substituted derivatives ([18F]2b–f). With the substituted [18F]fluorophenylazocarbylates in hand, two prototype azocarboxylates radioligands were synthesized by 18F-fluoroarylation, namely the methoxy azocarboxamide [18F]3d as the D3 receptor radioligand and [18F]4a as a prototype structure of the μ-opioid receptor radioligand. By introducing the new series of [18F]fluorophenylazocarboxylic-tert-butyl esters, the method of 18F-fluoroarylation was significantly expanded, thereby demonstrating the versatility of 18F-labeled phenylazocarboxylates for the design of potential radiotracers for positron emission tomography . PMID:29479577

Tandem Carbocupration/Oxygenation of Terminal Alkynes

PubMed Central

Zhang, Donghui; Ready, Joseph M.

2008-01-01

A direct and general synthesis of α-branched aldehydes and their enol derivatives is described. Carbocupration of terminal alkynes and subsequent oxygenation with lithium tert-butyl peroxide generates a metallo-enolate. Trapping with various electrophiles provides α-branched aldehydes or stereo-defined trisubstituted enol esters or silyl ethers. The tandem carbocupration/oxygenation tolerates alkyl and silyl ethers, esters and tertiary amines. The reaction is effective with organocopper complexes derived from primary, secondary and tertiary Grignard reagents and from n-butyllithium. PMID:16321021

N,N′-Di-tert-butyl-N′′-(2,6-difluoro­benzo­yl)phospho­ric triamide

PubMed Central

Pourayoubi, Mehrdad; Tarahhomi, Atekeh; Rheingold, Arnold L.; Golen, James A.

2010-01-01

In the title compound, C15H24F2N3O2P, the phosphoryl and carbonyl groups adopt anti positions relative to each other. The P atom is in a tetra­hedral coordination environment and the environment of each N atom is essentially planar. In the crystal, adjacent mol­ecules are linked via N—H⋯O=P and N—H⋯O=C hydrogen bonds into an extended chain parallel to the a axis. The crystal studied was a non-merohedral twin with a minor twin component of 36.4 (1)%. PMID:21589456

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaja-Milatovic, Snjezana; Gupta, Ramesh C.; Aschner, Michael

Prophylactic agents acutely administered in response to anticholinesterases intoxication can prevent toxic symptoms, including fasciculations, seizures, convulsions and death. However, anticholinesterases also have long-term unknown pathophysiological effects, making rational prophylaxis/treatment problematic. Increasing evidence suggests that in addition to excessive cholinergic stimulation, organophosphate compounds such as diisopropylphosphorofluoridate (DFP) induce activation of glutamatergic neurons, generation of reactive oxygen (ROS) and nitrogen species (RNS), leading to neurodegeneration. The present study investigated multiple affectors of DFP exposure critical to cerebral oxidative damage and whether antioxidants and NMDA receptor antagonist memantine provide neuroprotection by preventing DFP-induced biochemical and morphometric changes in rat brain. Rats treatedmore » acutely with DFP (1.25 mg/kg, s.c.) developed onset of toxicity signs within 7-15 min that progressed to maximal severity of seizures and fasciculations within 60 min. At this time point, DFP caused significant (p < 0.01) increases in biomarkers of ROS (F{sub 2}-isoprostanes, F{sub 2}-IsoPs; and F{sub 4}-neuroprostanes, F{sub 4}-NeuroPs), RNS (citrulline), and declines in high-energy phosphates (HEP) in rat cerebrum. At the same time, quantitative morphometric analysis of pyramidal neurons of the hippocampal CA1 region revealed significant (p < 0.01) reductions in dendritic lengths and spine density. When rats were pretreated with the antioxidants N-tert-butyl-{alpha}-phenylnitrone (PBN, 200 mg/kg, i.p.), or vitamin E (100 mg/kg, i.p./day for 3 days), or memantine (18 mg/kg, i.p.), significant attenuations in DFP-induced increases in F{sub 2}-IsoPs, F{sub 4}-NeuroPs, citrulline, and depletion of HEP were noted. Furthermore, attenuation in oxidative damage following antioxidants or memantine pretreatment was accompanied by rescue from dendritic degeneration of pyramidal neurons in the CA1 hippocampal area. These findings closely associated DFP-induced lipid peroxidation with dendritic degeneration of pyramidal neurons in the CA1 hippocampal area and point to possible interventions to limit oxidative injury and dendritic degeneration induced by anticholinesterase neurotoxicity.« less

PHARMACOLOGIC SUPPRESSION OF OXIDATIVE DAMAGE AND DENDRITIC DEGENERATION FOLLOWING KAINIC ACID-INDUCED EXCITOTOXICITY IN MOUSE CEREBRUM

PubMed Central

Zaja-Milatovic, Snjezana; Gupta, Ramesh C.; Aschner, Michael; Montine, Thomas J.; Milatovic, Dejan

2008-01-01

Intense seizure activity associated with status epilepticus and excitatory amino acid (EAA) imbalance initiates oxidative damage and neuronal injury in CA1 of the ventral hippocampus. We tested the hypothesis that dendritic degeneration of pyramidal neurons in the CA1 hippocampal area resulting from seizure-induced neurotoxicity is modulated by cerebral oxidative damage. Kainic acid (KA, 1 nmol/5 μl) was injected intracerebroventricularly to C57Bl/6 mice. F2-isoprostanes (F2-IsoPs) and F4-neuroprostanes (F4-NeuroPs) were used as surrogate measures of in vivo oxidative stress and biomarkers of lipid peroxidation. Nitric oxide synthase (NOS) activity was quantified by evaluating citrulline level and pyramidal neuron dendrites and spines were evaluated using rapid Golgi stains and a Neurolucida system. KA produced severe seizures in mice immediately after its administration and a significant (p<0.001) increase in F2-IsoPs, F4-NeuroPs and citrulline levels were seen 30 min following treatment. At the same time, hippocampal pyramidal neurons showed significant (p<0.001) reduction in dendritic length and spine density. In contrast, no significant change in neuronal dendrite and spine density or F2-IsoP, F4-NeuroPs and citrulline levels were found in mice pretreated with Vitamin E (α-tocopherol, 100 mg/kg, ip) for 3 days, or with N-tert-butyl-α-phenylnitrone (PBN, 200 mg/kg, ip) or ibuprofen (inhibitors of cyclooxygenase, COX, 14 μg/ml of drinking water) for 2 weeks prior to KA treatment. These findings indicate novel interactions among free radical-induced generation of F2-IsoPs and F4-NeuroPs, nitric oxide and dendritic degeneration, closely associate oxidative damage to neuronal membranes with degeneration of the dendritic system, and point to possible interventions to limit severe damage in acute neurological disorders. PMID:18556069

In vivo evidence for free radical involvement in the degeneration of rat brain 5-HT following administration of MDMA (‘ecstasy') and p-chloroamphetamine but not the degeneration following fenfluramine

PubMed Central

Colado, M I; O'Shea, E; Granados, R; Murray, T K; Green, A R

1997-01-01

Administration of 3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy') to several species results in a long lasting neurotoxic degeneration of 5-hydroxytryptaminergic neurones in several regions of the brain. We have now investigated whether this degeneration is likely to be the result of free radical-induced damage. Free radical formation can be assessed by measuring the formation of 2,3- and 2,5-dihydroxybenzoic acid (2,3-DHBA and 2,5-DHBA) from salicylic acid. An existing method involving implantation of a probe into the hippocampus and in vivo microdialysis was modified and validated. Administration of MDMA (15 mg kg−1, i.p.) to Dark Agouti (DA) rats increased the formation of 2,3-DHBA (but not 2,5-DHBA) for at least 6 h. Seven days after this dose of MDMA, the concentration of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) was reduced by over 50% in hippocampus, cortex and striatum, reflecting neurotoxic damage. There was no change in the concentration of dopamine or 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum. p-Chloroamphetamine (PCA), another compound which produces a neurotoxic loss of cerebral 5-HT content, when given at a dose of 5 mg kg−1 also significantly increased the formation of 2,3-DHBA (but not 2,5-DHBA) in the dialysate for over 4.5 h. post-injection starting 2 h after treatment. In contrast, fenfluramine administration (15 mg kg−1, i.p.) failed to increase the 2,3-DHBA or 2,5-DHBA concentration in the dialysate. A single fenfluramine injection nevertheless also markedly decreased the concentration of 5-HT and 5-HIAA in the hippocampus, cortex and striatum seven days later. When rats pretreated with fenfluramine (15 mg kg−1, i.p.) seven days earlier were given MDMA (15 mg kg−1, i.p.) no increase in 2,3-DHBA was seen in the dialysate from the hippocampal probe. This indicates that the increase in free radical formation following MDMA is occurring in 5-HT neurones which have been damaged by the prior fenfluramine injection. Administration of the free radical scavenging agent α-phenyl-N-tert-butyl nitrone (PBN; 120 mg kg−1, i.p.) 10 min before and 120 min after an MDMA (15 mg kg−1, i.p.) injection prevented the acute rise in the 2,3-DHBA concentration in the dialysate and attenuated by 30% the long term damage to hippocampal 5-HT neurones (as indicated by a smaller MDMA-induced decrease in both the concentration of 5-HT and 5-HIAA and also the binding of [3H]-paroxetine). These data indicate that a major mechanism by which MDMA and PCA induce damage to 5-hydroxytryptaminergic neurones in rat brain is by increasing the formation of free radicals. These probably result from the degradation of catechol and quinone metabolites of these substituted amphetamines. In contrast, fenfluramine induces damage by another mechanism not involving free radicals; a proposal supported by some of our earlier indirect studies. We suggest that these different modes of action render untenable the recent suggestion that MDMA will not be neurotoxic in humans because fenfluramine appears safe at clinical doses. PMID:9222545

The Ketene-Surrogate Coupling: Catalytic Conversion of Aryl Iodides to Aryl Ketenes via Ynol Ethers**

PubMed Central

Zhang, Wenhan; Ready, Joseph M.

2014-01-01

tert-Butoxyacetylene is shown to undergo Sonogashira coupling with aryl iodides to yield aryl-substituted tert-butyl ynol ethers. These intermediates participate in a [1,5]-hydride shift, which results in the extrusion of isobutylene and the generation of aryl ketenes. The ketenes are trapped in situ with multiple nucleophiles or undergoelectrocyclic ring closure to yield hydroxynaphthalenes and quinolines. PMID:24975840

Enantioselective Reduction of Ketones Catalyzed by Rare-Earth Metals Complexed with Phenoxy Modified Chiral Prolinols.

PubMed

Song, Peng; Lu, Chengrong; Fei, Zenghui; Zhao, Bei; Yao, Yingming

2018-06-01

Enantioselective reduction of ketones and α,β-unsaturated ketones by pinacolborane (HBpin) has been well-established by using chiral rare-earth metal catalysts with phenoxy modified prolinols. A number of highly optically active alcohols were obtained from reduction of simple ketones catalyzed by ytterbium complex 1 [L 4 Yb(L 4 H)] (H 2 L 4 = ( S)-2- tert-butyl-6-((2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)phenol). Moreover, α,β-unsaturated ketones were selectively reduced to a wide range of chiral allylic alcohols with excellent yields, high enantioselectivity, and complete chemoselectivity, catalyzed by a single component chiral ytterbium complex 2 [L 1 Yb(L 1 H)] (H 2 L 1 = ( S)-2,4-di- tert-butyl-6-((2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)phenol).

Some features of the oxidative conversion of Mo(CO)/sub 6/ in a medium of hydroperoxide or tert-butyl hydroperoxide and an aromatic hydrocarbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fomin, V.M.; Lunin, A.V.; Aleksandrov, Yu.A.

1988-03-10

Occurrence of the reaction under study was followed from the decrease in hydroperoxide or of Mo(CO)/sub 6/. The Mo(CO)/sub 6/ content of the reaction was found by determining either the concentration of this compound directly or by determining the concentration of the gaseous products from its transformations (CO + CO/sub 2/). Hydroperoxides (I) and (II) were determined iodometrically. Metal-containing products of the oxidation of Mo(CO)/sub 6/, molybdenum oxides and peroxides, were analyzed by IR and ESR spectroscopy, elemental analysis, and iodometry. Analysis of transformation products of the hydroperoxides (phenol, acetone, dimethylphenylcarbinol, acetophenone, tert-butyl alcohol, water, and oxygen) was performed usingmore » gas chromatography. Results are presented.« less

Application of a source apportionment model in consideration of volatile organic compounds in an urban stream

USGS Publications Warehouse

Asher, W.E.; Luo, W.; Campo, K.W.; Bender, D.A.; Robinson, K.W.; Zogorski, J.S.; Pankow, J.F.

2007-01-01

Position-dependent concentrations of trichloroethylene and methyl-tert-butyl ether are considered for a 2.81-km section of the Aberjona River in Massachusetts, USA. This river flows through Woburn and Winchester (Massachusetts, USA), an area that is highly urbanized, has a long history of industrial activities dating to the early 1800s, and has gained national attention because of contamination from chlorinated solvent compounds in Woburn wells G and H. The river study section is in Winchester and begins approximately five stream kilometers downstream from the Woburn wells superfund site. Approximately 300 toxic release sites are documented in the watershed upstream from the terminus of the study section. The inflow to the river study section is considered one source of contamination. Other sources are the atmosphere, a tributary flow, and groundwater flows entering the river; the latter are categorized according to stream zone (1, 2, 3, etc.). Loss processes considered include outflows to groundwater and water-to-atmosphere transfer of volatile compounds. For both trichloroethylene and methyl-rerf-butyl ether, degradation is neglected over the timescale of interest. Source apportionment fractions with assigned values ??inflow, ??1, ??2, ??3, etc. are tracked by a source apportionment model. The strengths of the groundwater and tributary sources serve as fitting parameters when minimizing a reduced least squares statistic between water concentrations measured during a synoptic study in July 2001 versus predictions from the model. The model fits provide strong evidence of substantial unknown groundwater sources of trichloroethylene and methyl-tert-butyl ether amounting to tens of grams per day of trichloroethylene and methyl-tert-butyl ether in the river along the study section. Modeling in a source apportionment manner can be useful to water quality managers allocating limited resources for remediation and source control. ?? 2007 SETAC.

Synthesis and Larvicidal Activity of Novel Thenoylhydrazide Derivatives

NASA Astrophysics Data System (ADS)

Song, Gao-Peng; Hu, De-Kun; Tian, Hao; Li, Ya-Sheng; Cao, Yun-Shen; Jin, Hong-Wei; Cui, Zi-Ning

2016-03-01

A pair of chemical isomeric structures of novel N-tert-butylphenyl thenoylhydrazide compounds I and II were designed and synthesized. Their structures were characterized by MS, IR, 1H NMR, elemental analysis and X-ray single crystal diffraction. The regioselectivity of the Meerwein arylation reaction and the electrophilic substitution reaction of N-tert-butyl hydrazine were studied by density functional theory (DFT) quantum chemical method. The larvicidal tests revealed that some compounds I had excellent larvicidal activity against Culex pipiens pallens. As the candidates of insect growth regulators (IGRs), the larval growth inhibition and regulation against Culex pipiens pallens were examined for some compounds, especially I1 and I7. Compounds I1 and I7 were further indicated as an ecdysteroid agonist by reporter gene assay on the Spodoptera frugiperda cell line (Sf9 cells). Finally, a molecular docking study of compound I7 was conducted, which was not only beneficial to understand the structure-activity relationship, but also useful for development of new IGRs for the control of mosquitos.

Electronic structure and reactivity of high-spin iron--alkyl- and--pterinperoxo complexes.

PubMed

Lehnert, Nicolai; Fujisawa, Kiyoshi; Solomon, Edward I

2003-01-27

The spectroscopic properties and electronic structure of the four-coordinate high-spin [FeIII(L3)(OOtBu)]+ complex (1; L3 = hydrotris(3-tert-butyl-5-isopropyl-1-pyrazolyl)borate; tBu = tert-butyl) are investigated and compared to the six-coordinated high-spin [Fe(6-Me3TPA)(OHx)(OOtBu)]x+ system (TPA = tris(2-pyridylmethyl)amine, x = 1 or 2) studied earlier [Lehnert, N.; Ho, R. Y. N.; Que, L., Jr.; Solomon, E. I. J. Am. Chem. Soc. 2001, 123, 12802-12816]. Complex 1 is characterized by Raman features at 889 and 830 cm-1 which are assigned to the O-O stretch (mixed with the symmetric C-C stretch) and a band at 625 cm-1 that corresponds to nu(Fe-O). The UV-vis spectrum shows a charge-transfer (CT) transition at 510 nm from the alkylperoxo pi v* (v = vertical to C-O-O plane) to a d orbital of Fe(III). A second CT is identified from MCD at 370 nm that is assigned to a transition from pi h* (h = horizontal to C-O-O plane) to an Fe(III) d orbital. For the TPA complex the pi v* CT is at 560 nm while the pi h* CT is to higher energy than 250 nm. These spectroscopic differences between four- and six-coordinate Fe(III)-OOR complexes are interpreted on the basis of their different ligand fields. In addition, the electronic structure of Fe-OOPtn complexes with the biologically relevant pterinperoxo ligand are investigated. Substitution of the tert-butyl group in 1 by pterin leads to the corresponding Fe(III)-OOPtn species (2), which shows a stronger electron donation from the peroxide to Fe(III) than 1. This is related to the lower ionization potential of pterin. Reduction of 2 by one electron leads to the Fe(II)-OOPtn complex (3), which is relevant as a model for potential intermediates in pterin-dependent hydroxylases. However, in the four-coordinate ligand field of 3, the additional electron is located in a nonbonding d orbital of iron. Hence, the pterinperoxo ligand is not activated for heterolytic cleavage of the O-O bond in this system. This is also evident from the calculated reaction energies that are endothermic by at least 20 kcal/mol.

Phenoxide and alkoxide complexes of Mg, Al and Zn, and their use for the ring-opening polymerization of ℇ-caprolactone with initiators of different natures.

PubMed

Minyaev, Mikhail E; Nifant'ev, Ilya E; Shlyakhtin, Andrey V; Ivchenko, Pavel V; Lyssenko, Konstantin A

2018-05-01

A new packing polymorph of bis(2,6-di-tert-butyl-4-methylphenolato-κO)bis(tetrahydrofuran-κO)magnesium, [Mg(C 15 H 23 O) 2 (C 4 H 8 O) 2 ] or Mg(BHT) 2 (THF) 2 , (BHT is the 2,6-di-tert-butyl-4-methylphenoxide anion and THF is tetrahydrofuran), (1), has the same space group (P2 1 ) as the previously reported modification [Nifant'ev et al. (2017d). Dalton Trans. 46, 12132-12146], but contains three crystallographically independent molecules instead of one. The structure of (1) exhibits rotational disorder of the tert-butyl groups and positional disorder of a THF ligand. The complex of bis(2,6-di-tert-butyl-4-methylphenolato-κO)bis(μ 2 -ethyl glycolato-κ 2 O,O':κO)dimethyldialuminium, [Al 2 (CH 3 ) 2 (C 4 H 7 O 3 ) 2 (C 15 H 23 O) 2 ] or [(BHT)AlMe(OCH 2 COOEt)] 2 , (2), is a dimer located on an inversion centre and has an Al 2 O 2 rhomboid core. The 2-ethoxy-2-oxoethanolate ligand (OCH 2 COOEt) displays a μ 2 -κ 2 O,O':κO semi-bridging coordination mode, forming a five-membered heteronuclear Al-O-C-C-O ring. The same ligand exhibits positional disorder of the terminal methyl group. The redetermined structure of the heptanuclear complex octakis(μ 3 -benzyloxo-κO:κO:κO)hexaethylheptazinc, [Zn 7 (C 2 H 5 ) 6 (C 7 H 7 O) 8 ] or [Zn 7 (OCH 2 Ph) 8 Et 6 ], (3), possesses a bicubic Zn 7 O 8 core located at an inversion centre and demonstrates positional disorder of one crystallographically independent phenyl group. Cambridge Structural Database surveys are given for complexes structurally analogous to (2) and (3). Complexes (2) and (3), as well as derivatives of (1), are of interest as catalysts for the ring-opening polymerization of ℇ-caprolactone, and polymerization results are reported.

Fission of Polyanionic Metal Clusters

NASA Astrophysics Data System (ADS)

König, S.; Jankowski, A.; Marx, G.; Schweikhard, L.; Wolfram, M.

2018-04-01

Size-selected dianionic lead clusters Pbn2 -, n =34 - 56 , are stored in a Penning trap and studied with respect to their decay products upon photoexcitation. Contrary to the decay of other dianionic metal clusters, these lead clusters show a variety of decay channels. The mass spectra of the fragments are compared to the corresponding spectra of the monoanionic precursors. This comparison leads to the conclusion that, in the cluster size region below about n =48 , the fission reaction Pbn2 -→Pbn-10 -+Pb10- is the major decay process. Its disappearance at larger cluster sizes may be an indication of a nonmetal to metal transition. Recently, the pair of Pb10- and Pbn-10 - were observed as pronounced fragments in electron-attachment studies [S. König et al., Int. J. Mass Spectrom. 421, 129 (2017), 10.1016/j.ijms.2017.06.009]. The present findings suggest that this combination is the fingerprint of the decay of doubly charged lead clusters. With this assumption, the dianion clusters have been traced down to Pb212 -, whereas the smallest size for the direct observation was as high as n =28 .

Dissolution DNP-NMR spectroscopy using galvinoxyl as a polarizing agent

NASA Astrophysics Data System (ADS)

Lumata, Lloyd L.; Merritt, Matthew E.; Malloy, Craig R.; Sherry, A. Dean; van Tol, Johan; Song, Likai; Kovacs, Zoltan

2013-02-01

The goal of this work was to test feasibility of using galvinoxyl (2,6-di-tert-butyl-α-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-p-tolyloxy) as a polarizing agent for dissolution dynamic nuclear polarization (DNP) NMR spectroscopy. We have found that galvinoxyl is reasonably soluble in ethyl acetate, chloroform, or acetone and the solutions formed good glasses when mixed together or with other solvents such as dimethyl sulfoxide. W-band electron spin resonance (ESR) measurements revealed that galvinoxyl has an ESR linewidth D intermediate between that of carbon-centered free radical trityl OX063 and the nitroxide-based 4-oxo-TEMPO, thus the DNP with galvinoxyl for nuclei with low gyromagnetic ratio γ such as 13C and 15N is expected to proceed predominantly via the thermal mixing process. The optimum radical concentration that would afford the highest 13C nuclear polarization (approximately 6% for [1-13C]ethyl acetate) at 3.35 T and 1.4 K was found to be around 40 mM. After dissolution, large liquid-state NMR enhancements were achieved for a number of 13C and 15N compounds with long spin-lattice relaxation time T1. In addition, the hydrophobic galvinoxyl free radical can be easily filtered out from the dissolution liquid when water is used as the solvent. These results indicate that galvinoxyl can be considered as an easily available free radical polarizing agent for routine dissolution DNP-NMR spectroscopy.

Protective effect of black garlic extracts on tert-Butyl hydroperoxide-induced injury in hepatocytes via a c-Jun N-terminal kinase-dependent mechanism

PubMed Central

Lee, Ko-Chao; Teng, Chih-Chuan; Shen, Chien-Heng; Huang, Wen-Shih; Lu, Chien-Chang; Kuo, Hsing-Chun; Tung, Shui-Yi

2018-01-01

Black garlic has been reported to show multiple bioactivities against the development of different diseases. In the present study, the hepatoprotective effect of black garlic on injured liver cells was investigated. Rat clone-9 hepatocytes were used for all experiments; tert-Butyl hydroperoxide (tBHP) was used to induce injury of rat clone-9 hepatocytes. The contents of malondialdehyde (MDA) and glutathione (GSH); anti-oxidative enzyme activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx); and mRNA expression levels of interleukin (IL)-6 and IL-8 in rat clone-9 hepatocytes were determined to evaluate the level of cell damage. Black garlic extracts were demonstrated to significantly attenuate tBHP-induced cell death of rat clone-9 hepatocytes (P<0.05). Pretreatment with black garlic extracts antagonized GSH depletion, tBHP-increased MDA accumulation and the mRNA expression level of IL-6/IL-8, and tBHP-decreased antioxidative enzyme activities (all P<0.05). Moreover, the present study revealed that c-Jun N-terminal kinase signaling regulated black garlic-inhibited tBHP effects in rat clone-9 hepatocytes. Our findings demonstrate that black garlic has the hepatoprotective potential to block tBHP-damaged effects on cell death, lipid peroxidation, oxidative stress, and inflammation in rat clone-9 hepatocytes. Thus, the present study indicates that black garlic may be an excellent natural candidate in the development of adjuvant therapy and healthy foods for liver protection. PMID:29456651

Bidentate urea derivatives of p-tert-butyldihomooxacalix[4]arene: neutral receptors for anion complexation.

PubMed

Marcos, Paula M; Teixeira, Filipa A; Segurado, Manuel A P; Ascenso, José R; Bernardino, Raul J; Michel, Sylvia; Hubscher-Bruder, Véronique

2014-01-17

Three new bidentate ureidodihomooxacalix[4]arene derivatives (phenyl 5a, n-propyl 5b, and tert-butyl 5c) were synthesized in four steps from the parent compound p-tert-butyldihomooxacalix[4]arene and obtained in the cone conformation, as shown by NMR studies. The binding ability of these neutral receptors toward spherical, linear, trigonal planar, and tetrahedrical anions was assessed by (1)H NMR and UV-vis titrations. The structures and complexation energies of some complexes were also studied by DFT methods. The data showed that the association constants are strongly dependent on the nature of the substituent (aryl/alkyl) at the urea moiety. In general, for all the receptors, the association constants decrease with decrease of anion basicity. Ph-urea 5a is the best anion receptor, showing the strongest complexation for F(-) (log K(assoc) = 3.10 in CDCl3) and also high binding affinity for the carboxylates AcO(-) and BzO(-). Similar results were obtained by UV-vis studies and were also corroborated by DFT calculations.

From Macromolecular to Small-Molecular Triggers: Facile Method toward Photoinduced LCST Phase Behavior of Thermoresponsive Polymers in Mixed Ionic Liquids Containing an Azobenzene Moiety.

PubMed

Wang, Caihong; Ma, Xiaofeng; Kitazawa, Yuzo; Kobayashi, Yumi; Zhang, Shiguo; Kokubo, Hisashi; Watanabe, Masayoshi

2016-12-01

Instead of the reported photoinduced lower critical solution temperature (LCST) phase transition behavior in ionic liquids (ILs) achieved by photofunctional polymers, this study reports the facile photoinduced LCST phase behavior of nonfunctionalized polymers (poly(benzyl methacrylate) (PBnMA) and poly(2-phenylethyl methacrylate) (PPhEtMA)) in mixed ILs (1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)amide; [C 1 mim][NTf 2 ] and a newly designed functionalized IL containing an azobenzene moiety (1-butyl-3-(4-phenylazobenzyl)imidazolium bis(trifluoromethanesulfonyl)amide; [Azo][NTf 2 ])) as a small-molecular photo trigger. Interestingly, the length of the alkyl spacer between the ester and aryl groups, which is the only structural difference between the two polymers, leads to two different photoresponsive LCST phase transition behaviors. On the basis of spectroscopic studies, the different phase transition behaviors of PBnMA and PPhEtMA may attribute to the different cooperative interactions between the polymers and [C 1 mim][NTf 2 ]. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

21 CFR 177.2480 - Polyoxymethylene homopolymer.

Code of Federal Regulations, 2014 CFR

2014-04-01

... in its production. The quantity of any optional adjuvant substance employed in the production of the...), weight ratio 6/1 Do. Tetrakis[methylene(3,5-di-tert-butyl-4-hydroxy-hydrocinnamate)] methane At a maximum...

40 CFR 180.536 - Triazamate; tolerances for residues.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Specific Tolerances... the combined residues of triazamate (RH-7988) ethyl(3-tert-butyl-1-dimethylcarbamoyl-1H-1,2,4-triazol...

40 CFR 180.536 - Triazamate; tolerances for residues.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) PESTICIDE PROGRAMS TOLERANCES AND EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Specific Tolerances... the combined residues of triazamate (RH-7988) ethyl(3-tert-butyl-1-dimethylcarbamoyl-1H-1,2,4-triazol...

Microwave-assisted synthesis and crystal structure of oxo(diperoxo)(4,4'-di-tert-butyl-2,2'-bipyridine)-molybdenum(VI).

PubMed

Amarante, Tatiana R; Almeida Paz, Filipe A; Gago, Sandra; Gonçalves, Isabel S; Pillinger, Martyn; Rodrigues, Alírio E; Abrantes, Marta

2009-09-16

The oxodiperoxo complex MoO(O2)(2)(tbbpy) (tbbpy = 4,4'-di-tert-butyl-2,2'- bipyridine) was isolated from the reaction of MoO2Cl(2)(tbbpy) in water under microwaveassisted heating at 120 masculineC for 4 h. The structure of the oxodiperoxo complex was determined by single crystal X-ray diffraction. The Mo(VI) centre is seven-coordinated with a geometry which strongly resembles a highly distorted bipyramid. Individual MoO(O2)(2)(tbbpy) complexes are interdigitated along the [010] direction to form a column. The crystal structure is formed by the close packing of the columnar-stacked complexes. Interactions between neighbouring columns are essentially of van der Waals type mediated by the need to effectively fill the available space.

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

PubMed Central

Vlad, Elena; Bozga, Grigore

2012-01-01

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

Improving the Safety of Lithium-Ion Battery via a Redox Shuttle Additive 2,5-Di- tert-butyl-1,4-bis(2-methoxyethoxy)benzene (DBBB).

PubMed

Leonet, Olatz; Colmenares, Luis C; Kvasha, Andriy; Oyarbide, Mikel; Mainar, Aroa R; Glossmann, Tobias; Blázquez, J Alberto; Zhang, Zhengcheng

2018-03-21

2,5-Di- tert-butyl-1,4-bis(2-methoxyethoxy)benzene (DBBB) is studied as a redox shuttle additive for overcharge protection for a 1.5 Ah graphite/C-LFP lithium-ion pouch cell for the first time. The electrochemical performance demonstrated that the protecting additive remains inert during the extended standard cycling for 4000 cycles. When a 100% overcharge is introduced in the charging protocol, the baseline cell fails rapidly during the first abusive event, whereas the cell containing DBBB additive withstands 700 overcharge cycles with 87% capacity retention and no gas evolution or cell swelling was observed. It is the first time the effectiveness of the DBBB as overcharge protection additive in a large pouch cell format is demonstrated.

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

PubMed

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

2008-04-01

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

Anaerobic degradation of a mixture of MtBE, EtBE, TBA, and benzene under different redox conditions.

PubMed

van der Waals, Marcelle J; Pijls, Charles; Sinke, Anja J C; Langenhoff, Alette A M; Smidt, Hauke; Gerritse, Jan

2018-04-01

The increasing use of biobased fuels and fuel additives can potentially change the typical fuel-related contamination in soil and groundwater. Anaerobic biotransformation of the biofuel additive ethyl tert-butyl ether (EtBE), as well as of methyl tert-butyl ether (MtBE), benzene, and tert-butyl alcohol (TBA, a possible oxygenate metabolite), was studied at an industrially contaminated site and in the laboratory. Analysis of groundwater samples indicated that in the field MtBE was degraded, yielding TBA as major product. In batch microcosms, MtBE was degraded under different conditions: unamended control, with medium without added electron acceptors, or with ferrihydrite or sulfate (with or without medium) as electron acceptor, respectively. Degradation of EtBE was not observed under any of these conditions tested. TBA was partially depleted in parallel with MtBE. Results of microcosm experiments with MtBE substrate analogues, i.e., syringate, vanillate, or ferulate, were in line with the hypothesis that the observed TBA degradation is a cometabolic process. Microcosms with ferulate, syringate, isopropanol, or diethyl ether showed EtBE depletion up to 86.5% of the initial concentration after 83 days. Benzene was degraded in the unamended controls, with medium without added electron acceptors and with ferrihydrite, sulfate, or chlorate as electron acceptor, respectively. In the presence of nitrate, benzene was only degraded after addition of an anaerobic benzene-degrading community. Nitrate and chlorate hindered MtBE, EtBE, and TBA degradation.

Sterilization of Bacillus pumilus spores using supercritical fluid carbon dioxide containing various modifier solutions.

PubMed

Shieh, Edison; Paszczynski, Andrzej; Wai, Chien M; Lang, Qingyong; Crawford, Ronald L

2009-03-01

Supercritical fluid carbon dioxide (SF-CO(2)) with small amounts of chemical modifier(s) provides a very effective sterilization technique that should be useful for destroying microorganism on heat-sensitive devices such as instruments flown on planetary-bound spacecraft. Under a moderate temperature (50 degrees C) and pressure (100 atm), spores of Bacillus pumilus strains ATCC 7061 and SAFR 032 can be effectively inactivated/eliminated from metal surfaces and small electronic devices in only 45 min using optimized modifier concentrations. Modifiers explored in this study included hydrogen peroxide (H(2)O(2)), tert-butyl hydroperoxide, formic acid, and Triton X-100. During sterilization procedure the modifiers were continuously added to SF-CO(2) in either methanol or water at controlled concentrations. The lowest effective concentrations were established for each modifier. Complete elimination of both types of B. pumilus endospores occurred with an optimal modifier addition of either or 10% methanol containing 12% H(2)O(2) or 12% tert-butyl hydroperoxide in SF-CO(2), or a mixture of 6% H(2)O(2) and 6% tert-butyl hydroperoxide. Using water as the carrier of SF-CO(2) modifier, the complete elimination of spores viability of both B. pumilus strains occurred with an addition of either 3.3% water containing 3% H(2)O(2), or 3.3% water containing 10% methanol and 0.5% formic acid, or 3.3% water containing 10% methanol, 1% formic acid and 2% H(2)O(2).

Effect of benzene and ethylbenzene on the transcription of methyl-tert-butyl ether degradation genes of Methylibium petroleiphilum PM1.

PubMed

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

2016-09-01

Methyl-tert-butyl ether (MTBE) and its degradation by-product, tert-butyl alcohol (TBA), are widespread contaminants detected frequently in groundwater in California. Since MTBE was used as a fuel oxygenate for almost two decades, leaking underground fuel storage tanks are an important source of contamination. Gasoline components such as BTEX (benzene, toluene, ethylbenzene and xylenes) are often present in mixtures with MTBE and TBA. Investigations of interactions between BTEX and MTBE degradation have not yielded consistent trends, and the molecular mechanisms of BTEX compounds' impact on MTBE degradation are not well understood. We investigated trends in transcription of biodegradation genes in the MTBE-degrading bacterium, Methylibium petroleiphilum PM1 upon exposure to MTBE, TBA, ethylbenzene and benzene as individual compounds or in mixtures. We designed real-time quantitative PCR assays to target functional genes of strain PM1 and provide evidence for induction of genes mdpA (MTBE monooxygenase), mdpJ (TBA hydroxylase) and bmoA (benzene monooxygenase) in response to MTBE, TBA and benzene, respectively. Delayed induction of mdpA and mdpJ transcription occurred with mixtures of benzene and MTBE or TBA, respectively. bmoA transcription was similar in the presence of MTBE or TBA with benzene as in their absence. Our results also indicate that ethylbenzene, previously proposed as an inhibitor of MTBE degradation in some bacteria, inhibits transcription of mdpA, mdpJ and bmoAgenes in strain PM1.

Effect of benzene and ethylbenzene on the transcription of methyl-tert-butyl ether degradation genes of Methylibium petroleiphilum PM1

PubMed Central

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

2016-01-01

Methyl-tert-butyl ether (MTBE) and its degradation by-product, tert-butyl alcohol (TBA), are widespread contaminants detected frequently in groundwater in California. Since MTBE was used as a fuel oxygenate for almost two decades, leaking underground fuel storage tanks are an important source of contamination. Gasoline components such as BTEX (benzene, toluene, ethylbenzene and xylenes) are often present in mixtures with MTBE and TBA. Investigations of interactions between BTEX and MTBE degradation have not yielded consistent trends, and the molecular mechanisms of BTEX compounds’ impact on MTBE degradation are not well understood. We investigated trends in transcription of biodegradation genes in the MTBE-degrading bacterium, Methylibium petroleiphilum PM1 upon exposure to MTBE, TBA, ethylbenzene and benzene as individual compounds or in mixtures. We designed real-time quantitative PCR assays to target functional genes of strain PM1 and provide evidence for induction of genes mdpA (MTBE monooxygenase), mdpJ (TBA hydroxylase) and bmoA (benzene monooxygenase) in response to MTBE, TBA and benzene, respectively. Delayed induction of mdpA and mdpJ transcription occurred with mixtures of benzene and MTBE or TBA, respectively. bmoA transcription was similar in the presence of MTBE or TBA with benzene as in their absence. Our results also indicate that ethylbenzene, previously proposed as an inhibitor of MTBE degradation in some bacteria, inhibits transcription of mdpA, mdpJ and bmoAgenes in strain PM1. PMID:27450417

Investigation of steric influences on hydrogen-bonding motifs in cyclic ureas by using X-ray, neutron, and computational methods.

PubMed

McCormick, Laura J; McDonnell-Worth, Ciaran; Platts, James A; Edwards, Alison J; Turner, David R

2013-11-01

A series of urea-derived heterocycles, 5N-substituted hexahydro-1,3,5-triazin-2-ones, has been prepared and their structures have been determined for the first time. This family of compounds only differ in their substituent at the 5-position (which is derived from the corresponding primary amine), that is, methyl (1), ethyl (2), isopropyl (3), tert-butyl (4), benzyl (5), N,N-(diethyl)ethylamine (6), and 2-hydroxyethyl (7). The common heterocyclic core of these molecules is a cyclic urea, which has the potential to form a hydrogen-bonding tape motif that consists of self-associative R₂²(8) dimers. The results from X-ray crystallography and, where possible, Laue neutron crystallography show that the hydrogen-bonding motifs that are observed and the planarity of the hydrogen bonds appear to depend on the steric hindrance at the α-carbon atom of the N substituent. With the less-hindered substituents, methyl and ethyl, the anticipated tape motif is observed. When additional methyl groups are added onto the α-carbon atom, as in the isopropyl and tert-butyl derivatives, a different 2D hydrogen-bonding motif is observed. Despite the bulkiness of the substituents, the benzyl and N,N-(diethyl)ethylamine derivatives have methylene units at the α-carbon atom and, therefore, display the tape motif. The introduction of a competing hydrogen-bond donor/acceptor in the 2-hydroxyethyl derivative disrupts the tape motif, with a hydroxy group interrupting the N-H···O=C interactions. The geometry around the hydrogen-bearing nitrogen atoms, whether planar or non-planar, has been confirmed for compounds 2 and 5 by using Laue neutron diffraction and rationalized by using computational methods, thus demonstrating that distortion of O-C-N-H torsion angles occurs to maintain almost-linear hydrogen-bonding interactions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantitative electron spin resonance (ESR) analysis of antioxidative properties using the acetaldehyde/xanthine oxidase system

NASA Astrophysics Data System (ADS)

Souchard, J.-P.; Nepveu, F.

1998-05-01

We present a method for the quantitative ESR analysis of the antioxidant properties of drugs using the acetaldhehyde/xanthine oxidase (AC/XOD) superoxide generating system and 5,5-dimethyl-l-pyrroline-N-oxide (DMPO) as spin trap. In stoichiometric conditions (AC/XOD, 60 mM/0.018 U), the resulting paramagnetic DMPO adduct disappeared with superoxide dismutase and remained when catalase or DMSO were used. That adduct was dependent only on superoxide and resulted from the trapping of a carboxyl radical by DMPO (aN = 15.2 G, aH = 18.9 G). Similar results were obtained using 4-pyridyl-l-oxide-N-t-butyl nitrone (POBN) as spin trap. The ESR signal of the DMPO-CO2- adduct was very stable and allowed quantitative analysis of the antioxidative activity of redox molecules from an IC{50} value representing the concentration causing 50% inhibition of its intensity. Among the tested compounds, manganese(II), complexes were the most effective, 25 times as active as ascorbic acid or (+)catechin and 500-fold more antioxidative than Trolox^R. Nous présentons une méthode d'analyse quantitative de l'activité antioxydante de composés d'intérêt pharmaceutique basée sur le système acétaldéhyde/xanthine oxydase (AC/XOD), l'utilisation de la RPE et du piégeage de spin avec le 5,5-diméthyl-l-pyrroline-N-oxyde (DMPO). Dans les conditions stoechiométriques {AC/XOD, 60 mM/0,018 U/ml}, l'adduit radicalaire résultant de ce système disparaît en présence de superoxyde dismutase et persiste en présence de catalase ou de DMSO. Cet adduit ne dépend que de la présence de l'anion superoxyde et provient du piégeage d'un radical carboxyle CO2- sur le DMPO (aN = 15.2 G, aH = 18.9 G). Des résultats similaires ont été obtenus avec le piégeur de spin 4-pyridyl-l-oxyde-N-t-butyl nitrone (POBN). Le signal RPE de l'adduit DMPO-CO2- est très stable et permet la quantification de l'activité antioxydante de pharmacophores redox par la détermination de la CI{50}, concentration qui diminue de 50 % son intensité. Parmi les composés testés, les complexes du manganèse sont les plus antioxydants, 25 fois plus actifs que la vitamine C ou la catéchine(+), 500 fois plus antioxydants que le Trolox^R.

A Novel Access to Arylated and Heteroarylated Beta-Carboline Based PDE5 Inhibitors

PubMed Central

Ahmed, Nermin S.; Gary, Bernard D.; Piazza, Gary A.; Tinsley, Heather N.; Laufer, Stefan; Abadi, Ashraf H.

2016-01-01

Starting from a previously reported lead compound GR30040X (a hydantoin tetrahydro-β-carboline derivative with a 4- pyridinyl ring at C- 5), a series of structurally related tetrahydro-β-carboline derivatives were prepared. The tet-rahydro-β-carboline skeleton was fused either to a hydantoin or to a piperazindione ring, the pendant aryl group attached to C-5 or C-6 was changed to a 3, 4-dimethoxyphenyl or a 3-pyridinyl ring; different N-substituents on the terminal ring were introduced, a straight chain ethyl group, a branched tert. butyl and P-chlorophenyl group rather than n-butyl group of the lead compound. All four possible diastereomers of target tetrahydro-β-carboline derivatives were prepared, separated by column chromatography and the significance of these stereochemical manipulations was studied. Synthesized compounds were evaluated for their inhibitory effect versus PDE5. Seven hits were obtained with appreciable inhibitory activity versus PDE5 with IC50s 0.14 - 4.99 μM. PMID:21054274

Comparison of stabilization by Vitamin E and 2,6-di-tert-butylphenols during polyethylene radio-thermal-oxidation

NASA Astrophysics Data System (ADS)

Richaud, Emmanuel

2014-10-01

This paper reports a compilation of data for PE+Vitamin E and 2,6-di-tert-butylphenols oxidation in radio-thermal ageing. Data unambiguously show that Vitamin E reacts with Prad and POOrad whereas 2,6-di-tert-butyl phenols only react with POOrad. Kinetic parameters of the stabilization reactions for both kinds of antioxidants were tentatively extracted from phenol depletion curves, and discussed regarding the structure of the stabilizer. They were also used for completing an existing kinetic model used for predicting the stabilization by antioxidants. This one permits to compare the efficiency of stabilizer with dose rate or sample thickness.

N,N-difluorotris(tert-butyl)silylamine-the first organosilyl difluoroamine. Synthesis and computational studies.

PubMed

Majumder, Utpal; Armantrout, John R; Williams, Richard Vaughan; Shreeve, Jean'ne M

2002-11-29

The synthesis and characterization of the first stable trialkyl(difluoroamino)silane, R3SiNF2, as well as of R3SiNHF and R3SiN(CH3)F in moderate yields are reported. The (difluoroamino)silane has promise as a new synthon for the introduction of the -NF2 group into a variety of electrophilic inorganic and organic substrates. Activation barriers and relative energies were calculated for the unimolecular decompositions of Me3SiCF3 and t-Bu3SiNF2 using density functional theory (B3LYP/6-31G). The calculated activation energies confirm the long-assumed kinetic stability of Me3SiCF3.

High temperature phase chemistries and solidification mode prediction in nitrogen-strengthened austenitic stainless steels

NASA Astrophysics Data System (ADS)

Ritter, Ann M.; Henry, Michael F.; Savage, Warren F.

1984-07-01

Nitronic 50 and Nitronic 50W, two nitrogen-strengthened stainless steels, were heat treated over a wide range of temperatures, and the compositions of the ferrite and austenite at each temperature were measured with analytical electron microscopy techniques. The compositional data were used to generate the (γ + δ phase field on a 58 pct Fe vertical section. Volume fractions of ferrite and austenite were calculated from phase chemistries and compared with volume fractions determined from optical micrographs. Weld solidification modes were predicted by reference to the Cr and Ni contents of each alloy, and the results were compared with predictions based on the ratios of calculated Cr and Ni equivalents for the alloys. Nitronic 50, which contained ferrite and austenite at the solidus temperature of 1370 °C, solidified through the eutectic triangle, and the weld microstructure was similar to that of austenitic-ferritic solidification. Nitronic 50W was totally ferritic at 1340 °C and solidified as primary delta ferrite. During heat treatments, Nitronic 50 and Nitronic 50W precipitated secondary phases, notably Z-phase (NbCrN), sigma phase, and stringered phases rich in Mn and Cr.

46 CFR Appendix I to Part 150 - Exceptions to the Chart

Code of Federal Regulations, 2011 CFR

2011-10-01

... alcohol (20) tert-Butyl alcohol, Methanol mixtures Decyl alcohol (20) iso-Decyl alcohol (20) Diacetone... listed below have been determined to be dangerously reactive, based on either data obtained in the...

46 CFR Appendix I to Part 150 - Exceptions to the Chart

Code of Federal Regulations, 2010 CFR

2010-10-01

... alcohol (20) tert-Butyl alcohol, Methanol mixtures Decyl alcohol (20) iso-Decyl alcohol (20) Diacetone... listed below have been determined to be dangerously reactive, based on either data obtained in the...

ESI-MSn and LC-ESI-MS studies to characterize forced degradation products of bosentan and a validated stability-indicating LC-UV method.

PubMed

Bansal, Gulshan; Singh, Ranjit; Saini, Balraj; Bansal, Yogita

2013-01-01

The present study reports the characterization of forced degradation products of bosentan and a validated stability-indicating HPLC method for the stability testing of bosentan tablets. The forced degradation was carried out under the conditions of hydrolysis, oxidation, dry heat and photolysis. The drug was found unstable in acid, alkali and oxidative media whereas stable to the hydrolysis in water, to dry heat and to photolysis. In total, six degradation products were formed in all conditions which were resolved in a single run on a C-18 column with gradient elution using ammonium acetate buffer (pH 4.5, 5.0mM), methanol and acetonitrile. Structures of all the degradation products were characterized through +ESI-MS(n) and LC-ESI-MS spectral data of bosentan as well as LC-ESI-MS spectral data of the products. The products II-VI were characterized as 6-amino-[2,2']bipyrimidinyl-4,5-diol, 6-amino-5-(2-methoxyphenoxy)-[2,2']-bipyrimidinyl-4-ol, 2-[6-amino-5-(2-methoxyphenoxy)-[2,2']-bipyrimidinyl-4-yloxy]-ethanol, 4-tert-butyl-N-[6-(1-methoxyethoxy)-5-(2-methoxyphenoxy)-[2,2']-bipyrimidinyl-4-yl]-benzenesulfonamide and 4-tert-butyl-N-[6-hydroxy-5-(2-methoxyphenoxy)-[2,2']bipyrimidinyl-4-yl]-benzenesulfonamide, respectively. The peak of the product I was found to be due to two secondary degradation products which co-eluted and were characterized as β-hydroxyethyl p-tert-butylphenylsulfonate (Ia) and 2-[2-(2-hydroxyethoxy)-phenoxy]-ethanol (Ib). These products were formed due to hydrolysis of sulfonamide and alkylaryl ether and the diaryl ether linkages as well as dehydration of the primary alcohol group. The most probable degradation mechanisms were proposed. The HPLC method was found to be stability-indicating, linear (2-100 μg ml(-1)), accurate, precise, sensitive, specific, rugged and robust for quantitation of the drug. The method was applied to the stability testing of the commercially available bosentan tablets successfully. Copyright © 2012 Elsevier B.V. All rights reserved.

Sequestering ability of butylated hydroxytoluene, propyl gallate, resveratrol, and vitamins C and E against ABTS, DPPH, and hydroxyl free radicals in chemical and biological systems.

PubMed

Soares, Daniele G; Andreazza, Ana C; Salvador, Mirian

2003-02-12

The antioxidant capacity of butylated hydroxytoluene (BHT; 2,6-di-tert-butyl-p-cresol), propyl gallate (3,4,5-trihydroxybenzoic acid n-propyl ester), resveratrol (trans-3,4',5-trihydroxystilbene), and vitamins C (l-ascorbic acid) and E [(+)-alpha-tocopherol] was studied in chemical and biological systems. The chemical assays evaluated the capacity of these antioxidants to sequester 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS.) and 1,1 diphenyl-2-picrylhydrazyl (DPPH.). A new colorimetric method to determine hydroxyl radical scavenging is also described. The biological tests use the eucaryotic cells of Saccharomyces cerevisiae treated with the antioxidants in the presence of the stressing agents apomorphine, hydrogen peroxide, and paraquat dichloride (methylviologen; 1,1'-dimethyl-4,4'-bipyridinium dichloride). The results in chemical systems showed that all of the antioxidants were able to significantly inhibit the oxidation of beta-carotene by hydroxyl free radicals. The assays in yeast showed that the antioxidant activity of the tested compounds depended on the stressing agent used and the mechanism of action of the antioxidant.

An X-ray crystallographic and density functional theory study of (3Z)-4-(5-ethylsulfonyl-2-hydroxyanilino)pent-3-en-2-one and (3Z)-4-(5-tert-butyl-2-hydroxyanilino)pent-3-en-2-one.

PubMed

Akerman, Kate J; Munro, Orde Q

2013-03-01

The Schiff base enaminones (3Z)-4-(5-ethylsulfonyl-2-hydroxyanilino)pent-3-en-2-one, C13H17NO4S, (I), and (3Z)-4-(5-tert-butyl-2-hydroxyanilino)pent-3-en-2-one, C15H21NO2, (II), were studied by X-ray crystallography and density functional theory (DFT). Although the keto tautomer of these compounds is dominant, the O=C-C=C-N bond lengths are consistent with some electron delocalization and partial enol character. Both (I) and (II) are nonplanar, with the amino-phenol group canted relative to the rest of the molecule; the twist about the N(enamine)-C(aryl) bond leads to dihedral angles of 40.5 (2) and -116.7 (1)° for (I) and (II), respectively. Compound (I) has a bifurcated intramolecular hydrogen bond between the N-H group and the flanking carbonyl and hydroxy O atoms, as well as an intermolecular hydrogen bond, leading to an infinite one-dimensional hydrogen-bonded chain. Compound (II) has one intramolecular hydrogen bond and one intermolecular C=O...H-O hydrogen bond, and consequently also forms a one-dimensional hydrogen-bonded chain. The DFT-calculated structures [in vacuo, B3LYP/6-311G(d,p) level] for the keto tautomers compare favourably with the X-ray crystal structures of (I) and (II), confirming the dominance of the keto tautomer. The simulations indicate that the keto tautomers are 20.55 and 18.86 kJ mol(-1) lower in energy than the enol tautomers for (I) and (II), respectively.

21 CFR 177.1632 - Poly (phenyl-enetereph-thala-mide) resins.

Code of Federal Regulations, 2010 CFR

2010-04-01

...). Poly(oxyethylene) sorbitol monolaurate tetraoleate (CAS Reg. No. 71243-28-2). Poly(oxyethylene) sorbitol hexaoleate (CAS Reg. No. 57171-56-9). 4,4′-Butylidenebis (6-tert-butyl-m-cresol) (CAS Reg. No. 85...

Triblock copolyampholytes from 5-(N,N-dimethyl amino)isoprene styrene, and methacrylic acid: Synthesis and solution properties

NASA Astrophysics Data System (ADS)

Bieringer, R.; Abetz, V.; Müller, A. H. E.

ABC triblock copolymers of the type poly[5-(N,N-dimethyl amino)isoprene]-block-polystyrene-block-poly(tert-butyl methacrylate) (AiST) were synthesized and hydrolyzed to yield poly[5-(N,N-dimethyl amino)isoprene]-block-polystyrene-block-poly(methacrylic acid) (AiSA) triblock copolyampholytes. Due to a complex solubility behavior the solution properties of these materials had to be investigated in THF/water solvent mixtures. Potentiometric titrations of AiSA triblock copolyampholytes showed two inflection points with the A block being deprotonated prior to the Ai hydrochloride block thus forming a polyzwitterion at the isoelectric point (iep). The aggregation behavior was studied by dynamic light scattering (DLS) and freeze-fracture/transmission electron microscopy (TEM). Large vesicular structures with almost pH-independent radii were observed.

Catalytic Activity of μ-Carbido-Dimeric Iron(IV) Octapropylporphyrazinate in the 3,5,7,2',4'-Pentahydroxyflavone Oxidation Reaction with tert-Butyl Hydroperoxide

NASA Astrophysics Data System (ADS)

Tyurin, D. V.; Zaitseva, S. V.; Kudrik, E. V.

2018-05-01

It is found for the first time that μ-carbido-dimeric iron(IV) octapropylporphyrazinate displays catalytic activity in the oxidation reaction of natural flavonol morin with tert-butyl hydroperoxide, with the catalyst being stable under conditions of the reaction. The kinetics of this reaction are studied. It is shown the reaction proceeds via tentative formation of a complex between the catalyst and the oxidant, followed by O‒O bond homolytic cleavage. The kinetics of the reaction is described in the coordinates of the Michaelis-Menten equation. A linear dependence of the apparent reaction rate constant on the concentration of the catalyst is observed, testifying to its participation in the limiting reaction step. The equilibrium constants and rates of interaction are found. A mechanism is proposed for the reaction on the basis of the experimental data.

Protective effect of ganodermanondiol isolated from the Lingzhi mushroom against tert-butyl hydroperoxide-induced hepatotoxicity through Nrf2-mediated antioxidant enzymes.

PubMed

Li, Bin; Lee, Dong-Sung; Kang, Yue; Yao, Nai-Qi; An, Ren-Bo; Kim, Youn-Chul

2013-03-01

Ganodermanondiol, a biologically active compound, was isolated from the Lingzhi mushroom (Ganoderma lucidum). The present study examined the protective effects of ganodermanondiol against tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity. Ganodermanondiol protected human liver-derived HepG2 cells through nuclear factor-E2-related factor 2 (Nrf2) pathway-dependent heme oxygenase-1 expressions. Moreover, ganodermanondiol increased cellular glutathione levels and the expression of the glutamine-cysteine ligase gene in a dose-dependent manner. Furthermore, ganodermanondiol exposure enhanced the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and its upstream kinase activators, LKB1 and Ca(2+)/calmodulin-dependent protein kinase-II (CaMKII). This study indicates that ganodermanondiol exhibits potent cytoprotective effects on t-BHP-induced hepatotoxicity in human liver-derived HepG2 cells, presumably through Nrf2-mediated antioxidant enzymes and AMPK. Copyright © 2012 Elsevier Ltd. All rights reserved.

Protein dynamics in organic media at varying water activity studied by molecular dynamics simulation.

PubMed

Wedberg, Rasmus; Abildskov, Jens; Peters, Günther H

2012-03-01

In nonaqueous enzymology, control of enzyme hydration is commonly approached by fixing the thermodynamic water activity of the medium. In this work, we present a strategy for evaluating the water activity in molecular dynamics simulations of proteins in water/organic solvent mixtures. The method relies on determining the water content of the bulk phase and uses a combination of Kirkwood-Buff theory and free energy calculations to determine corresponding activity coefficients. We apply the method in a molecular dynamics study of Candida antarctica lipase B in pure water and the organic solvents methanol, tert-butyl alcohol, methyl tert-butyl ether, and hexane, each mixture at five different water activities. It is shown that similar water activity yields similar enzyme hydration in the different solvents. However, both solvent and water activity are shown to have profound effects on enzyme structure and flexibility.

Synthesis, structural characterization and theoretical studies of a new Schiff base 4-(((3-(tert-Butyl)-(1-phenyl)pyrazol-5-yl) imino)methyl)phenol

NASA Astrophysics Data System (ADS)

Cuenú, Fernando; Londoño-Salazar, Jennifer; Torres, John Eduard; Abonia, Rodrigo; D'Vries, Richard F.

2018-01-01

4-(((3-(tert-Butyl)-(1-phenyl)pyrazol-5-yl)imino)methyl)phenol (4-OHFPz) was synthesized and characterized by FT-IR, MS, NMR, and single-crystal X-ray diffraction. Optimization of molecular geometry, vibrational frequencies, and chemical shifts were calculated by using the methods of density functional theory (DFT) with B3LYP and B3PW91 as functionals and Hartree-Fock with 6-311G++(d,p) as basis set using the GAUSSIAN 09 program package. With the VEDA 4 software, the vibrational frequencies were assigned in terms of the potential energy distribution (PED). The equilibrium geometries calculated by all methods were compared with X-ray diffraction results, indicating that the theoretical results matches well with the experimental ones. The data obtained from the vibrational analysis and the calculated NMR are consistent with the experimental spectra.

A comparative study of biodiesel production using methanol, ethanol, and tert-butyl methyl ether (MTBE) under supercritical conditions.

PubMed

Farobie, Obie; Matsumura, Yukihiko

2015-09-01

In this study, biodiesel production under supercritical conditions among methanol, ethanol, and tert-butyl methyl ether (MTBE) was compared in order to elucidate the differences in their reaction behavior. A continuous reactor was employed, and experiments were conducted at various reaction temperatures (270-400 °C) and reaction times (3-30 min) and at a fixed pressure of 20 MPa and an oil-to-reactant molar ratio of 1:40. The results showed that under the same reaction conditions, the supercritical methanol method provided the highest yield of biodiesel. At 350 °C and 20 MPa, canola oil was completely converted to biodiesel after 10, 30, and 30 min in the case of - supercritical methanol, ethanol, and MTBE, respectively. The reaction kinetics of biodiesel production was also compared for supercritical methanol, ethanol, and MTBE. Copyright © 2015 Elsevier Ltd. All rights reserved.

Protective effect of vanilloids against tert-butyl hydroperoxide-induced oxidative stress in vero cells culture.

PubMed

Rosa, Antonella; Atzeri, Angela; Deiana, Monica; Melis, M Paola; Incani, Alessandra; Corona, Giulia; Loru, Debora; Appendino, Giovanni; Dessì, M Assunta

2008-05-28

This study investigated the effect of synthetic capsiate, a simplified analogue of capsiate, and vanillyl alcohol on the oxidative stress induced by tert-butyl hydroperoxide (TBH) in a line of fibroblasts derived from monkey kidney (Vero cells). In response to the TBH-mediated oxidative stress, a reduction of the levels of total unsaturated fatty acids and cholesterol was observed, and a rise in the concentrations of conjugated dienes fatty acids hydroperoxides and 7-ketocholesterol. Pretreatment with both synthetic capsiate and vanillyl alcohol preserved Vero cells from oxidative damage and showed a remarkable protective effect on the reduction of the levels of total unsaturated fatty acids and cholesterol, inhibiting the increase of MDA, conjugated dienes fatty acids hydroperoxides, and 7-ketocholesterol. Both compounds were effective against peroxidation of cell membrane lipids induced by TBH, with synthetic capsiate essentially acting as a pro-drug of vanillyl alcohol, its hydrophilic hydrolytic derivative.

Preparation of Langmuir-Blodgett thin films of calix[6]arenes and p-tert butyl group effect on their gas sensing properties

NASA Astrophysics Data System (ADS)

Ozmen, Mustafa; Ozbek, Zikriye; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, Rifat

2015-12-01

Organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of p-tert-butyl calix[6]arene and calix[6]arene, and their certain characterization are reported in this work. LB films of these calixarenes have been characterized by contact angle measurement, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. Forming of stable monolayers was observed at the water surface using surface pressure-area isotherm graph. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Due to the adsorption of vapors into the LB film structures; they yield a response to all vapors as of large, fast, and reproducible.

The application of silicalite-1/fly ash cenosphere (S/FAC) zeolite composite for the adsorption of methyl tert-butyl ether (MTBE).

PubMed

Lu, Jia; Xu, Fang; Wang, Deju; Huang, Jue; Cai, Weimin

2009-06-15

Silicalite-1/fly ash cenosphere (S/FAC) zeolite composite has been applied for batch adsorption of methyl tert-butyl ether (MTBE) from water systems. Here the key experimental conditions, including the ratio of initial MTBE concentration to the amount weight of S/FAC, adsorption time and temperature, have been discussed in detail. The results show that approximately 93-95% MTBE could be adsorbed with initial concentration of MTBE solution 1000 microg l(-1). The column flow-through experiments also prove the high capacity of S/FAC composite for MTBE removal. The distinct advantages of S/FAC zeolite composite as adsorbent lie in (1) enhanced adsorption rate and capacity based on hierarchical micro and meso/macroporosity of S/FAC; (2) more easily operation and recycling process by assembly of nano-sized silicalite-1 zeolite on FAC support.

2-tert-Butyl-5-(2-pyridyl)-2H-tetrazole as a chelating ligand in the direct synthesis of novel Cu(II) and heterobimetallic Cu(II)/Mn(II) complexes.

PubMed

Mosalkova, Anastasiya P; Voitekhovich, Sergei V; Lyakhov, Alexander S; Ivashkevich, Ludmila S; Lach, Jochen; Kersting, Berthold; Gaponik, Pavel N; Ivashkevich, Oleg A

2013-02-28

For the first time, a representative of the 2,5-disubstituted tetrazoles, namely, 2-tert-butyl-5-(2-pyridyl)-2H-tetrazole (L), has been found to participate in oxidative dissolution of copper powder in homometalic systems Cu0–L–NH4X–DMSO (X = Cl, SCN, ClO4) and heterobimetallic ones Cu0–Mn(OAc)2–L–NH4OAc–Solv (Solv = DMSO, DMF), providing the formation of molecular homometallic complexes [CuL2Cl2] (1), [CuL2(SCN)2] (2), and [CuL2(H2O)](ClO4)2 (3), heterobimetallic complex [Cu2MnL2(OAc)6] (4) from DMF solution and its mixture with complex [Cu2MnL2(OAc)6]·2DMSO (5) from DMSO solution. Free ligand L and complexes 1–4 were characterized by elemental analysis, IR spectroscopy, thermal and X-ray single crystal analyses, whereas complex 5 was characterized by X-ray analysis only. Compounds 1–3 are mononuclear complexes, with chelating coordination mode of L via the tetrazole ring N4 and pyridine ring N7 atoms. Heterobimetallic complexes 4 and 5 possess trinuclear structures, with a linear Cu–Mn–Cu arrangement of the metal atoms, linked by the acetate anions; each copper(II) atom is decorated by a chelating unit of L via the tetrazole ring N1 and pyridine ring N7 atoms in complex 4, and via the N4, N7 atoms in complex 5. Temperature-dependent magnetic susceptibility measurements of complex 4 revealed a weak antiferromagnetic coupling between the paramagnetic copper(II) and manganese(II) ions (J = −2.5 cm(−1), g(Cu) = 2.25 and g(Mn) = 2.01), with magnetic exchange through the acetato bridges.

PREPARATIVE ISOLATION AND PURIFICATION OF CHEMICAL CONSTITUENTS OF BELAMCANDA BY MPLC, HSCCC AND PREP-HPLC

PubMed Central

Wang, Xiaohong; Liang, Yong; Peng, Cuilin; Xie, Huichun; Pan, Man; Zhang, Tianyou; Ito, Yoichiro

2010-01-01

Combined with medium-pressure liquid chromatography (MPLC) and preparative high-pressure liquid chromatography (Prep-HPLC), high-speed countercurrent chromatography (HSCCC) was successfully applied for separation and purification of isoflavonoids from the extract of belamcanda. HSCCC separation was performed on a two-phase solvent system composed of methyl tert-butyl ether -ethyl acetate - n-butyl alcohol – acetonitrile −0.1% aqueous trifluoroacetic acid at a volume radio of 1:2:1:1:5. Semi-purified peak fractions from HSCCC separation were further purified by Prep-HPLC. Nine well-separated fractions were analyzed by HPLC-UV absorption spectrometry to determine their purities and characterized with ESI-MSn. Except for peaksland VII (unknown) seven compounds were identified as apocynin (peak II), mangiferin (peak III), 7-O-methylmangiferin (peak IV), hispidulin (peak V), 3′-hydroxyltectoridin (peak VI), iristectorin B (peak VII), isoiridin (peak IX). PMID:21552369

Phase-dependent ultrafast third-order optical nonlinearities in metallophthalocyanine thin films

NASA Astrophysics Data System (ADS)

Kumar, Samir; Anil Kumar, K. V.; Dharmaprakash, S. M.; Das, Ritwick

2016-09-01

We present a comprehensive study on the impact of phase transformations of metallophthalocyanine thin films on their third-order nonlinear optical (NLO) properties. The metallophthalocyanine thin films are prepared by thermally evaporating the commercially available Copper(II)2,9,16,23-Tetra-tert-butyl-29H,31H-phthalocyanine (CuPc) and Zinc(II) 2,9,16,23-Tetra-tert-butyl-29H,31H-phthalocyanine (ZnPc) powder on glass substrate. Thermal annealing causes a phase transformation which has a distinct signature in powder X-ray diffraction and UV-Vis-NIR spectroscopy. The NLO characteristics which include nonlinear refractive index n2, as well as nonlinear absorption coefficient (βeff), were measured by using a single beam Z-scan technique. An ultrashort pulsed fiber laser emitting femtosecond pulses (Δτ ≈ 250 fs) at 1064 nm central wavelength is used as a source for the Z-scan experiment. The βeff values in as prepared thin films were ascertained to be smaller as compared to the annealed one due to the smaller value of saturation intensity (Is) which, in turn, is a consequence of ground-state bleaching in the thermally unstable amorphous state of the molecule. Interestingly, the nonlinear refractive indices bear opposite sign for CuPc and ZnPc. The variations in the third-order nonlinearity in CuPc and ZnPc are discussed in terms of molecular packing and geometries of metallophthalocyanine molecules.

[Determination of migration of 25 primary aromatic amines from food contact plastic materials by gas chromatography-mass spectrometry].

PubMed

Li, Ying; Li, Chengfa; Xiao, Daoqing; Liang, Feng; Chen, Zhinan; Schen, Xuhui; Sun, Xiaoying; Li, Yongtao

2013-01-01

A solid phase extraction (SPE) combination with gas chromatography-mass spectrometry (GC-MS) was developed for the determination of the migration of 25 primary aromatic amines (PAAs) from food contact plastic materials and articles. The samples were extracted by deionized water and 30 g/L acetic acid, and the pH value of the solution was adjusted to 8 - 10 with ammonia. The extracts were cleaned up and concentrated on an SPE column, then eluted by equal volume of methyl-tert-butyl ether and ethanol. The analysis of the target compounds was performed by GC-MS. The results indicated that the limits of detection were in the range of 0.4 -2.0 microg/kg for different PAAs. The recoveries and relative standard deviations (n = 7) of 10 microg/kg PAAs ranged from 51.6% -118.4% and 0.5% -9.8%, respectively, except the 2,4-diaminoanisole in the acid simulant. The effects of different experimental conditions such as the pH value and volume ratio of methyl-tert-butyl ether and ethanol were studied. The results showed that the method is accurate and stable, and could meet the requirement of the European Commission Regulation (EU) No 10/2011 for the determination of primary aromatic amines. It can be applied in the analysis of the primary aromatic amines in real food contact plastic material and article samples.

A study of spin isovector giant resonances with the208Pb(n, p)208Tl reaction

NASA Astrophysics Data System (ADS)

Moinester, M. A.; Trudel, A.; Raywood, K.; Yen, S.; Spicer, B. M.; Abegg, R.; Alford, W. P.; Auerbach, N.; Celler, A.; Frekers, D.; Häusser, O.; Helmer, R. L.; Henderson, R.; Hicks, K. H.; Jackson, K. P.; Jeppesen, R. G.; King, N. S. P.; Long, S.; Miller, C. A.; Vetterli, M.; Watson, J.; Yavin, A. I.

1989-10-01

The208Pb(n, p)208Tl reaction was studied at 198 and 458 MeV in a search for isovector spin giant resonances. Peaks at 5.1 MeV and 13.6 MeV excitation in208Tl are observed and discussed as candidates for the T> spin giant dipole resonance (SGDR), the spin isovector monopole resonance (SIVM), and the spin isovector quadrupole resonance (SIVQ).

Potential hepatoprotective effects of new Cuban natural products in rat hepatocytes culture.

PubMed

Rodeiro, I; Donato, M T; Martínez, I; Hernández, I; Garrido, G; González-Lavaut, J A; Menéndez, R; Laguna, A; Castell, J V; Gómez-Lechón, M J

2008-08-01

The protective effects of five Cuban natural products (Mangifera indica L. (MSBE), Erythroxylum minutifolium, Erythroxylum confusum, Thalassia testudinum and Dictyota pinnatifida extracts and mangiferin) on the oxidative damage induced by model toxicants in rat hepatocyte cultures were studied. Cells were pre-incubated with the natural products (5-200 microg/mL) for 24 h. Then hepatotoxins (tert-butyl hydroperoxide, ethanol, carbon tetrachloride and lipopolysaccharide) were individually added and post-incubated for another 24 h. After treatments, cell viability was determined using the MTT assay. Mangiferin and MSBE exhibited the highest cytoprotective potential (EC50 between 50 and 125 microg/mL), followed by T. testudinum and Erythroxylum extracts, whereas no significant protective effects was produced by Dictyota extract treatment. Antioxidant properties of the natural products against lipid peroxidation and GSH depletion induced by tert-butyl hydroperoxide were then investigated. The results show that at 36 h pre-treatment of cells with mangiferin or MSBE, concentrations of T. testudinum and Erythroxylum extracts ranging from 25 to 100 microg/mL significantly inhibited lipid peroxidation induced by tert-butyl hydroperoxide (100 and 250 microM) and increased the GSH levels reduced by the toxicant. D. pinnatifida inhibited lipid peroxidation, but did not preserve GSH levels. In conclusion, MSBE, E. minutifolium, E. confusum and T. testudinum extracts and mangiferin showed hepatoprotective activity against induced damage in all the experimental series, where mangiferin and the extracts of MSBE and T. testudinum were the best candidates to inhibit "in vitro" damage to rat hepatocytes. This hepatoprotective effect found could be associated with the antioxidant properties observed for the products.

Poly(Acrylic Acid-b-Styrene) Amphiphilic Multiblock Copolymers as Building Blocks for the Assembly of Discrete Nanoparticles

PubMed Central

Greene, Anna C.; Zhu, Jiahua; Pochan, Darrin J.; Jia, Xinqiao; Kiick, Kristi L.

2011-01-01

In order to expand the utility of current polymeric micellar systems, we have developed amphiphilic multiblock copolymers containing alternating blocks of poly(acrylic acid) and poly(styrene). Heterotelechelic poly(tert-butyl acrylate-b-styrene) diblock copolymers containing an α-alkyne and an ω-azide were synthesized by atom transfer radical polymerization (ATRP), allowing control over the molecular weight while maintaining narrow polydispersity indices. The multiblock copolymers were constructed by copper-catalyzed azide-alkyne cycloaddition of azide-alkyne end functional diblock copolymers which were then characterized by 1H NMR, FT-IR and SEC. The tert-butyl moieties of the poly(tert-butyl acrylate-b-styrene) multiblock copolymers were easily removed to form the poly(acrylic acid-b-styrene) multiblock copolymer ((PAA-PS)9), which contained up to 9 diblock repeats. The amphiphilic multiblock (PAA-PS)9 (Mn = 73.3 kg/mol) was self-assembled by dissolution into tetrahydrofuran and extensive dialysis against deionized water for 4 days. The critical micelle concentration (CMC) for (PAA-PS)9 was determined by fluorescence spectroscopy using pyrene as a fluorescent probe and was found to be very low at 2 × 10-4 mg/mL. The (PAA-PS)9 multiblock was also analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The hydrodynamic diameter of the particles was found to be 11 nm. Discrete spherical particles were observed by TEM with an average particle diameter of 14 nm. The poly(acrylic acid) periphery of the spherical particles should allow for future conjugation of biomolecules. PMID:21552373

Mechanisms of perinatal cerebral injury in fetus and newborn.

PubMed

Delivoria-Papadopoulos, M; Mishra, O P

2000-01-01

Cerebral hypoxia in the fetus and newborn results in neonatal morbidity and mortality as well as long-term sequelae such as mental retardation, seizure disorders, and cerebral palsy. In the developing brain, determinants of susceptibility to hypoxia should include the lipid composition of the brain cell membrane, the rate of lipid peroxidation, the presence of antioxidant defenses, and the development and modulation of excitatory amino acid neurotransmitter receptors such as the N-methyl-D-aspartate (NMDA) receptor, the intracellular Ca2+, and the intranuclear Ca(2+)-dependent mechanisms. In addition to the developmental status of these cellular components, the response of these potential mechanisms to hypoxia determines the fate of the hypoxic brain cell in the developing brain. Using electron spin resonance spectroscopy of alpha-phenyl-N-tert-butyl-nitrone spin adducts, studies from our laboratory demonstrated that tissue hypoxia results in increased free radical generation in the cortex of fetal guinea pigs and newborn piglets. Pretreatment with MgSO4 significantly decreased the hypoxia-induced increase in free radical generation in the term fetal brain. We also showed that brain tissue hypoxia modifies the NMDA receptor ion-channel recognition and modulatory sites. Furthermore, a higher increase in NMDA receptor agonist-dependent Ca2+ in synaptosomes was demonstrated. The increase in intracellular Ca2+ may activate several enzymatic pathways such as phospholipase A2 and metabolism of archidonic acid by cyclooxygenase and lipoxygenase, conversion of xanthine dehydrogenase to xanthine oxidase by proteases, and activation of nitric oxide synthase. Using inhibitors of each of these enzymes such as cyclooxygenase (indomethacin), lipoxygenase (nordihydroguaiaretic acid), xanthine oxidase (allopurinol), and nitric oxide synthase (N-nitro-L-arginine), studies have shown that these enzyme reactions result in oxygen free radical generation, membrane peroxidation, and cell membrane dysfunction in the hypoxic brain. Specifically, generation of nitric oxide free radicals during hypoxia may lead to nitration and nitrosylation of specific membrane proteins and receptors, resulting in dysfunction of receptors and enzymes. We conclude that hypoxia-induced modification of the NMDA receptor leading to increased intracellular Ca2+ results in free radical generation and cell injury. We suggest that during hypoxia the increased intracellular Ca2+ may lead to increased intranuclear Ca2+ concentration and alter nuclear events including transcription of specific apoptotic genes and activation of endonucleases, resulting in programmed cell death.

FENTON-DRIVEN CHEMICAL REGENERATION OF MTBE-SPENT GAC

EPA Science Inventory

Methyl tert-butyl ether (MTBE)-spent granular activated carbon (GAC) was chemically regenerated utilizing the Fenton mechanism. Two successive GAC regeneration cycles were performed involving iterative adsorption and oxidation processes: MTBE was adsorbed to the GAC, oxidized, r...

Photo-inducible cytotoxic and clastogenic activities of 3,6-di-substituted acridines obtained by acylation of proflavine.

PubMed

Benchabane, Yohann; Di Giorgio, Carole; Boyer, Gérard; Sabatier, Anne-Sophie; Allegro, Diane; Peyrot, Vincent; De Méo, Michel

2009-06-01

The cytotoxicity and photo-enhanced cytotoxicity of a series of 18 3,6-di-substituted acridines were evaluated on both tumour CHO cells and human normal keratinocytes, and compared to their corresponding clastogenicity as assessed by the micronucleus assay. Compounds 2f tert-butyl N-[(6-tert-butoxycarbonylamino)acridin-3-yl]carbamate and 2d N-[6-(pivalamino)acridin-3-yl]pivalamide displayed a specific cytotoxicity on CHO cells. These results suggested that the two derivatives could be considered as interesting candidates for anticancer chemotherapy and hypothesized that the presence of 1,1-dimethylethyl substituents was responsible for a strong nonclastogenic cytotoxicity. Compounds 2b and 2c, on the contrary, displayed a strong clastogenicity. They indicated that the presence of nonbranched aliphatic chains on positions 3 and 6 of the acridine rings tended to induce a significant clastogenic effect. Finally, they established that most of the acridine compounds could be photo-activated by UVA-visible rays and focussed on the significant role of light irradiation on their biological properties.

Reaction of singlet-excited 2,3-diazabicyclo[2.2.2]oct-2-ene and tert-butoxyl radicals with aryl-substituted benzofuranones.

PubMed

Lundgren, Cecilia Vannesjö; Koner, Apurba L; Tinkl, Michael; Pischel, Uwe; Nau, Werner M

2006-03-03

5,7-Di-tert-butyl-3-aryl-3H-benzofuran-2-ones are lactones with potential antioxidant activity, owing to their abstractable benzylic C-H hydrogens. The fluorescence quenching of the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO), an established probe for the hydrogen-donor propensity of chain-breaking antioxidants, was investigated for 16 aryl-substituted benzofuranone derivatives [m,m-(CF3)2, p-CN, m-CN, p-CF3, p-COOCH3, m-CF3, p-Cl, p-F, H, m-CH3, p-CH3, m,p-(CH3)2, p-OCH3, o-CH3, o-CF3, o,m-(CH3)2]. Analysis of the rate data in terms of a linear free energy relationship yielded a reaction constant of rho = +0.35. This implies that n,pi*-excited DBO acts as nucleophilic species. In contrast, hydrogen abstraction of tert-butoxyl radicals from the benzofuranones was accelerated by electron-donating substituents (rho = -0.23), in conformity with the electrophilic character of oxygen-centered alkoxyl radicals. Possible implications for the optimization of the hydrogen-donor propensity of antioxidants through structural variation are discussed.

Chemical stabilization of polymers: Implications for dermal exposure to additives.

PubMed

Bartsch, N; Girard, M; Schneider, L; Weijgert, V Van De; Wilde, A; Kappenstein, O; Vieth, B; Hutzler, C; Luch, A

2018-04-16

Technical benefits of additives in polymers stand in marked contrast to their associated health risks. Here, a multi-analyte method based on gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) was developed to quantify polymer additives in complex matrices such as low-density polyethylene (LDPE) and isolated human skin layers after dermal exposure ex vivo. That way both technical aspects and dermal exposure were investigated. The effects of polymer additivation on the material were studied using the example of LDPE. To this end, a tailor-made polymer was applied in aging studies that had been furnished with two different mixtures of phenol- and diarylamine-based antioxidants, plasticizers and processing aids. Upon accelerated thermo-oxidative aging of the material, the formation of LDPE degradation products was monitored with attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy. Compared to pure LDPE, a protective effect of added antioxidants could be observed on the integrity of the polymer. Further, thermo-oxidative degradation of the additives and its kinetics were investigated using LDPE or squalane as matrix. The half-lives of additives in both matrices revealed significant differences between the tested additives as well as between LDPE and squalane. For instance, 2-tert-butyl-6-[(3-tert-butyl-2-hydroxy-5-methylphenyl)methyl]-4-methylphenol (Antioxidant 2246) showed a half-life 12 times lower when incorporated in LDPE as compared to squalane. As a model for dermal exposure of consumers, human skin was brought into contact with the tailor-made LDPE containing additives ex vivo in static Franz diffusion cells. The skin was then analyzed for additives and decomposition products. This study proved 10 polymer additives of diverse pysicochemical properties and functionalities to migrate out of the polymer and eventually overcome the intact human skin barrier during contact. Moreover, their individual distribution within distinct skin layers was demonstrated. This is exemplified by the penetration of the procarcinogenic antioxidant N-phenylnaphthalen-2-amine (Neozon D) into the viable epidermis and the permeation through the skin of the neurotoxic plasticizer N-butylbenzenesulfonamide (NBBS). In addition, the analyses of additive degradation products in the isolated skin layers revealed the presence of 2-tert-butyl-4-methylphenol in all layers after contact to a polymer with substances of origin like Antioxidant 2246. Thus, attention needs to be paid to absorption of polymer additives together with their degradation products when it comes to dermal exposure assessment.

Evaluation of some antioxidants in radiation vulcanized ethylene-propylene diene (EPDM) rubber

NASA Astrophysics Data System (ADS)

Abdel-Aziz, M. M.; Basfar, A. A.

2001-12-01

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) have been used to study the oxidation of γ-ray vulcanized ethylene-propylene diene rubber (EPDM) stabilized with various types of antioxidants. The antioxidants used were pentaerythrityl tetrakis(3,5-di-tert-butyl(-4-hydroxyphenyl))propionate (Irganox 1010), Irganox 1035, Irganox 1520D, as primary antioxidants; Irganox B561 and Irganox B900, as synergistic blends; hindered amine light stabilizer (HALS), i.e. Tinuvin 622 LD; N-isopropyl- N-phenyl- p-phenylene diamine (IPPD) and trimethyl quinoline (TMQ) and their mixtures. The measurements were carried out under atmospheric conditions. The effects of antioxidant type and its selected concentration were determined and mechanism of reaction proposed.

Fenton-Driven Regeneration of MTBE-spent Granular Activated Carbon

EPA Science Inventory

Fenton-driven regeneration of Methyl tert-butyl ether (MTBE)-spent granular activated carbon (GAC) involves the combined, synergistic use of two treatment technologies: adsorption of organic chemicals onto activated carbon and Fenton-driven oxidation regeneration of the spent-GAC...

Enantiodifferentiation of whisky and cognac lactones using gas chromatography with different cyclodextrin chiral stationary phases.

PubMed

Schmarr, Hans-Georg; Mathes, Maximilian; Wall, Kristina; Metzner, Frank; Fraefel, Marius

2017-09-22

The chiral lactone 5-butyl-4-methyloxolan-2-one or 5-butyl-4-methyldihydro-2(3H)-furanone, often named whisky lactone, is found in oak wood, then contributing to the appreciated flavor of beverages stored in such wooden barrels. Its next higher homologue is named cognac lactone (5-pentyl-4-methyloxolan-2-one or 5-pentyl-4-methyldihydro-2(3H)-furanone), however is much less known, probably due to its minor concentration level. In order to study the direct enantioseparation of both lactones by gas chromatography on chiral stationary phases, individual enantiomers, particularly for cognac lactone were made available. This was achieved by baker's yeast reduction of synthesized ethyl 3-methyl-4-oxononanoate or, after hydrolysis, of the corresponding 4-ketoacid, that gave access to individual enantiomers of cognac lactone. Good enantioseparation was achieved for both whisky and cognac lactone with high values for the chiral resolution with 6-O-tert. butyl dimethylsilyl-2,3-dialkylated or 6-O-tert. butyl dimethylsilyl-2,3-diacylated cyclodextrin derivatives as chiral selectors. The influence of the nature and position of derivatization of the cyclodextrin moiety revealed a strong impact on the chiral recognition mechanism, as the investigated alkylated derivatives heptakis-(2,6-di-O-iso-pentyl-3-O-allyl)-β-cyclodextrin and octakis-(2,3-di-O-pentyl-6-O-methyl)-γ-cyclodextrin did not provide any or only minor chiral selectivity for the two lactones. Copyright © 2017 Elsevier B.V. All rights reserved.

ANAEROBIC BIODEGRADATION OF MTBE AT A GASOLINE SPILL SITE

EPA Science Inventory

To manage risk or to implement natural attenuation as a remedy, regulatory agencies must understand the processes that attenuate methyl-tert-butyl ether (MTBE) in ground water. Most case studies and laboratory studies in the literature indicate that natural biodegradation is not ...

OBSERVATIONS FROM CONTAMINANT PLUMES ON LONG ISLAND

EPA Science Inventory

The aquifers of Long Island serve as a sole source drinking water supply for the entire
local population of about three million people. Where the shallow Upper Glacial Aquifer has been contaminated with petroleum hydrocarbons and methyl tert-butyl ether (MTBE), intensive site ...

COST OF MTBE REMEDIATION

EPA Science Inventory

Widespread contamination of methyl tert-butyl ether (MTBE) in ground water has raised concerns about the increased cost of remediation of MTBE releases compared to BTEX-only sites. To evaluate these cost, cost information for 311 sites was furnished by U.S. EPA Office of Undergr...

COSTS TO REMEDIATE MTBE-CONTAMINATED SITES

EPA Science Inventory

The extensive contamination of methyl tert-butyl ether (MTBE) in ground water has introduced concerns about the increased cost of remediation of MTBE releases compared to sites with BTEX only contamination. In an attempt to evaluate these costs, cost information for 311 sites wa...

Reaction of carnosine with aged proteins: another protective process?

PubMed

Hipkiss, Alan R; Brownson, Carol; Bertani, Mariana F; Ruiz, Emilio; Ferro, Albert

2002-04-01

Cellular aging is often associated with an increase in protein carbonyl groups arising from oxidation- and glycation-related phenomena and suppressed proteasome activity. These "aged" polypeptides may either be degraded by 20S proteasomes or cross-link to form structures intractable to proteolysis and inhibitory to proteasome activity. Carnosine (beta-alanyl-l-histidine) is present at surprisingly high levels (up to 20 mM) in muscle and nervous tissues in many animals, especially long-lived species. Carnosine can delay senescence in cultured human fibroblasts and reverse the senescent phenotype, restoring a more juvenile appearance. As better antioxidants/free-radical scavengers than carnosine do not demonstrate these antisenescent effects, additional properties of carnosine must contribute to its antisenescent activity. Having shown that carnosine can react with protein carbonyls, thereby generating "carnosinylated" polypeptides using model systems, we propose that similar adducts are generated in senescent cells exposed to carnosine. Polypeptide-carnosine adducts have been recently detected in beef products that are relatively rich in carnosine, and carnosine's reaction with carbonyl functions generated during amino acid deamidation has also been described. Growth of cultured human fibroblasts with carnosine stimulated proteolysis of long-labeled proteins as the cells approached their "Hayflick limit," consistent with the idea that carnosine ameliorates the senescence-associated proteolytic decline. We also find that carnosine suppresses induction of heme-oxygenase-1 activity following exposure of human endothelial cells to a glycated protein. The antisenescent activity of the spin-trap agent alpha-phenyl-N-t-butylnitrone (PBN) towards cultured human fibroblasts resides in N-t-butyl-hydroxylamine, its hydrolysis product. As hydroxylamines are reactive towards aldehydes and ketones, the antisenescent activity of N-t-butyl-hydroxylamine and other hydroxylamines may be mediated, at least in part, by reactivity towards macromolecular carbonyls, analogous to that proposed for carnosine.

A Study of the Curing and Flammability Properties of Bisphenol A Epoxy Diacrylate Resin Utilizing a Novel Flame Retardant Monomer, bis[di-acryloyloxyethyl]-p-tert-butyl-phenyl Phosphate

PubMed Central

Rwei, Syang-Peng; Chen, Yu-Ming; Chiang, Whe-Yi; Ting, Yi-Tien

2017-01-01

A UV-curable, flame-retardant monomer, DAPP (bis[di-acryloyloxyethyl]-p-tert-butyl-phenyl-phosphate), was synthesized based on BPDCP (4-tert-butylphenyl-dichloro phosphate) and HEA (2-hydroxy ethyl acrylate). DAPP was blended with regular bisphenol A epoxy acrylate (BAEA) in various ratios to yield various phosphorus contents. The TGA-IR (thermogravimetric analyzer interface with an infrared spectrometer) results demonstrate that compounding 30 mol % DAPP with BAEA significantly reduced the amount of released CO gas. In contrast, the peak intensity of CO2 is independent of phosphorus content. The limiting oxygen index (LOI), reaching the saturated value of 26, and the heat release rate (HRR) measured using a cone-calorimeter, 156.43 KW/m2, confirm the saturation point when 30 mol % DAPP was compounded into BAEA. A study of the kinetics of pyrolysis reveals that Ea decreases as the phosphorus content increases. Both the TGA-IR and pyrolysis results reveal that the phosphorus compound DAPP is easily decomposed during the initial stage of burning to form an insulating layer, which inhibits further burning of the resin and the consequent release of other flammable gases. PMID:28772562

Neuroprotection for Nerve Agent-Induced Brain Damage

DTIC Science & Technology

2002-01-01

fosphenytoin), antioxidants and free radical scavengers (trilazad, ebselen, nitrones ), other ion channel inhibitors (clomethiazole, MBQX, GM1...dihydrolipoic acid, free radical traps such as nitrones and inhibitors of N- acetylaspartylglutamate (NAAG) peptidase to reduce the formation of glutamate...1999). When administered 40 min after onset of seizures and despite having no effect on the severity or duration of the seizure activity HU-211

In vitro electron paramagnetic resonance characterization of free radicals: relevance to exercise-induced lipid peroxidation and implications of ascorbate prophylaxis.

PubMed

Davison, Gareth W; Ashton, Tony; Davies, Bruce; Bailey, Damian M

2008-04-01

This study tested the hypothesis that exercise-induced oxidative stress is caused by free radical-mediated damage to polyunsaturated fatty acids (PUFA) which can be prevented following ascorbate prophylaxis. Hyperfine coupling constants (HCC) of alpha-phenyl-tert-butylnitrone (PBN)-adducts were measured via room temperature electron paramagnetic resonance (EPR) spectroscopy in the venous blood of 12 subjects at rest and following maximal exercise during a randomized double-blind placebo-controlled trial and compared to those observed following room-air incubation (2 h at 37 degrees C) of L-alpha-phosphatidycholine, linoleic acid, alpha-linolenic acid and arachidonic acid. All adducts exhibited similar HCC [a(N) 13.6 Gauss (G) and a beta(H) 1.8 G] with the exception of L-alpha-phosphatidycholine [a(N1)=13.4 G, a beta(H1)=1.6 G (37%) and a(N2)=14.9 G, a beta(H2)=0.3 G (63%)] consistent with the trapping of lipid-derived alkoxyl and oleate radicals, respectively. Ascorbate pre-treatment ablated radical formation in both systems. These findings identify circulating PUFA as a potential source of secondary radicals that are capable of initiating oxidative stress in the exercising human.

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)

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

1999-12-01

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 λ = 685 nm, to the intensity I1270 of the photosensitised phosphorescence of 1O2 with the maximum at λ = 1270 nm in deuterated benzene when excited with λ = 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 μM), 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 α =(Idf0/I12700)kr/(γf[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; γf 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.

Enzymatic production of monoacylglycerols containing polyunsaturated fatty acids through an efficient glycerolysis system.

PubMed

Yang, Tiankui; Rebsdorf, Morten; Engelrud, Ulrik; Xu, Xuebing

2005-03-09

The aim of the study was to develop an efficient glycerolysis system for the enzymatic production of monoacylglycerols (MAGs) containing polyunsaturated fatty acids. Glycerolysis has been widely applied in industry for the chemical production of food MAGs under high temperature. The enzymatic glycerolysis system at 40-70 degrees C is unfortunately a multiphase system, which leads to the lower reaction efficiency. A tert-butyl alcohol system was developed after careful evaluation and more than 20-fold of the reaction efficiency from this system was obtained compared to the solvent-free system. Novozym 435 was employed as a catalyst in the glycerolysis from the screening. In the batch reaction system with tert-butyl alcohol, temperature higher than 40 degrees C was favored. The glycerol/oil ratio was best in the study with 4.5 while the solvent weight ratio from 1 to 3 had little effect. In general, 60-70% yield can be obtained at 2 h in the stirred tank reactor. The continuous glycerolysis was conducted in a packed bed reactor. MAG yield up to 70% was reached at 30-40 min residence time. The continuous glycerolysis was more sensitive to the amount of tert-butyl alcohol, and in the weight ratio to oil more than 2 was favored. The continuous process was optimized with the assistance of response surface methodology. Optimal conditions for the packed bed reactor after all considerations were recommended as glycerol/oil 4:1 (mol/mol), temperature 40 degrees C, and residence time 45 min. The operation stability study showed that there was no slight reduction of reaction performance at more than 30 days, implying a high feasibility in practical applications.

Thermal Stability of Hi-Nicalon SiC Fiber in Nitrogen and Silicon Environments

NASA Technical Reports Server (NTRS)

Bhatt, R. T.; Garg, A.

1995-01-01

The room temperature tensile strength of uncoated and two types of pyrolytic boron nitride coated (PBN and Si-rich PBN) Hi-Nicalon SiC fibers was determined after 1 to 400 hr heat treatments to 1800 C under N2 pressures of 0.1, 2, and 4 MPa, and under 0.1 Mpa argon and vacuum environments. In addition, strength stability of both uncoated and coated fibers embedded in silicon powder and exposed to 0.1 MPa N2 for 24 hrs at temperatures to 1400 C was investigated. The uncoated and both types of BN coated fibers exposed to N2 for 1 hr showed noticeable strength degradation above 1400 C and 1600 C, respectively. The strength degradation appeared independent of nitrogen pressure, time of heat treatment, and surface coatings. TEM microstructural analysis suggests that flaws created due to SiC grain growth are responsible for the strength degradation. In contact with silicon powder, the uncoated and both types of PBN coated fibers degrade rapidly above 1350 C.

GLP-1 Receptor Stimulation of the Lateral Parabrachial Nucleus Reduces Food Intake: Neuroanatomical, Electrophysiological, and Behavioral Evidence

PubMed Central

Richard, Jennifer E.; Farkas, Imre; Anesten, Fredrik; Anderberg, Rozita H.; Dickson, Suzanne L.; Gribble, Fiona M.; Reimann, Frank; Jansson, John-Olov; Liposits, Zsolt

2014-01-01

The parabrachial nucleus (PBN) is a key nucleus for the regulation of feeding behavior. Inhibitory inputs from the hypothalamus to the PBN play a crucial role in the normal maintenance of feeding behavior, because their loss leads to starvation. Viscerosensory stimuli result in neuronal activation of the PBN. However, the origin and neurochemical identity of the excitatory neuronal input to the PBN remain largely unexplored. Here, we hypothesize that hindbrain glucagon-like peptide 1 (GLP-1) neurons provide excitatory inputs to the PBN, activation of which may lead to a reduction in feeding behavior. Our data, obtained from mice expressing the yellow fluorescent protein in GLP-1-producing neurons, revealed that hindbrain GLP-1-producing neurons project to the lateral PBN (lPBN). Stimulation of lPBN GLP-1 receptors (GLP-1Rs) reduced the intake of chow and palatable food and decreased body weight in rats. It also activated lPBN neurons, reflected by an increase in the number of c-Fos-positive cells in this region. Further support for an excitatory role of GLP-1 in the PBN is provided by electrophysiological studies showing a remarkable increase in firing of lPBN neurons after Exendin-4 application. We show that within the PBN, GLP-1R activation increased gene expression of 2 energy balance regulating peptides, calcitonin gene-related peptide (CGRP) and IL-6. Moreover, nearly 70% of the lPBN GLP-1 fibers innervated lPBN CGRP neurons. Direct intra-lPBN CGRP application resulted in anorexia. Collectively, our molecular, anatomical, electrophysiological, pharmacological, and behavioral data provide evidence for a functional role of the GLP-1R for feeding control in the PBN. PMID:25116706

Sensitive multiresidue method by HS-SPME/GC-MS for 10 volatile organic compounds in urine matrix: a new tool for biomonitoring studies on children.

PubMed

Antonucci, Arianna; Vitali, Matteo; Avino, Pasquale; Manigrasso, Maurizio; Protano, Carmela

2016-08-01

A HS-SPME method coupled with GC-MS analysis has been developed for simultaneously measuring the concentration of 10 volatile organic compounds (VOCs) (benzene, toluene, ethylbenzene, o-, m-, and p-xylene, methyl tert-butyl ether, ethyl tert-butyl ether, 2-methyl-2-butyl methyl ether, and diisopropyl ether) in urine matrix as a biomonitoring tool for populations at low levels of exposure to such VOCs. These compounds, potentially toxic for human health, are common contaminants of both outdoor and indoor air, as they are released by autovehicular traffic; some of them are also present in environmental tobacco smoke (ETS). Thus, the exposure to these pollutants cannot be neglected and should be assessed. The low limits of detection and quantification (LODs and LOQs <6.5 and 7.5 ng L(-1), respectively) and the high reproducibility (CVs <4 %) make the developed method suited for biomonitoring populations exposed at low levels such as children. Further, the method is cost-effective and low in time-consumption; therefore, it is useful for investigating large populations. It has been applied to children exposed to traffic pollution and/or ETS; the relevant results are reported, and the relevant implications are discussed.

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...

HYDROLYSIS OF MTBE TO TBA IN GROUND WATER SAMPLES WITH HYDROCHLORIC ACID

EPA Science Inventory

Conventional sampling and analytical protocols have poor sensitivity for fuel oxygenates that are alcohols, such as tert-butyl alcohol (TBA). Because alcohols are miscible or highly soluble in water, alcohols are not efficiently transferred to the gas chromatograph for analysis....

SUMMARY OF WORKSHOP ON BIODEGRADATION OF MTBE FEBRUARY 1-3, 2000

EPA Science Inventory

A workshop on biodegradation of methyl tert butyl ether (MTBE) contaminated soils and groundwater was held in Cincinnati, Ohio, February 1-2, 2000, and was sponsored by the USEPA's NRMRL and the American Petroleum Institute. Researchers in academia, industry, and government were ...

Analysis of Fluorotelomer Alcohols in Soils: Optimization of Extraction and Chromatography

EPA Science Inventory

This article describes the development of an analytical method for the determination of fluorotelomer alcohols (FTOHs) in soil. The sensitive and selective determination of the telomer alcohols was performed by extraction with mthyl tert-butyl ether (MTBE) and analysis of the ext...

Provisional Peer-Reviewed Toxicity Values for Tert Butyl Formate

EPA Science Inventory

Provisional Peer-Reviewed Toxicity Values (PPRTV) assessments are developed for use by the Agency’s Office of Land and Emergency Management (OLEM) to support informed decisions in the Superfund program and at hazardous waste sites when a values is not available in the Integrated ...

Optimization of headspace solid-phase microextraction by means of an experimental design for the determination of methyl tert.-butyl ether in water by gas chromatography-flame ionization detection.

PubMed

Dron, Julien; Garcia, Rosa; Millán, Esmeralda

2002-07-19

A procedure for determination of methyl tert.-butyl ether (MTBE) in water by headspace solid-phase microextraction (HS-SPME) has been developed. The analysis was carried out by gas chromatography with flame ionization detection. The extraction procedure, using a 65-microm poly(dimethylsiloxane)-divinylbenzene SPME fiber, was optimized following experimental design. A fractional factorial design for screening and a central composite design for optimizing the significant variables were applied. Extraction temperature and sodium chloride concentration were significant variables, and 20 degrees C and 300 g/l were, respectively chosen for the best extraction response. With these conditions, an extraction time of 5 min was sufficient to extract MTBE. The calibration linear range for MTBE was 5-500 microg/l and the detection limit 0.45 microg/l. The relative standard deviation, for seven replicates of 250 microg/l MTBE in water, was 6.3%.

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

NASA Astrophysics Data System (ADS)

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

2011-12-01

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 400-4000 cm -1 and 50-3500 cm -1, respectively. In addition, the IR spectra in CCl 4 at various concentrations of DTBHQ are also recorded. The computed vibrational wavenumbers were compared with the IR and Raman experimental data. Computational calculations at B3LYP level with two different basis sets 6-31G(d,p) and 6-311++G(d,p) are also employed in the study of the possible conformer of DTBHQ. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated using VEDA 4 program. The general agreement between the observed and calculated frequencies was established.

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

PubMed Central

Fester, Thomas

2013-01-01

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

Microbial biosafety of pilot-scale bioreactor treating MTBE and TBA-contaminated drinking water supply.

PubMed

Schmidt, Radomir; Klemme, David A; Scow, Kate; Hristova, Krassimira

2012-03-30

A pilot-scale sand-based fluidized bed bioreactor (FBBR) was utilized to treat both methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) from a contaminated aquifer. To evaluate the potential for re-use of the treated water, we tested for a panel of water quality indicator microorganisms and potential waterborne pathogens including total coliforms, Escherichia coli, Salmonella and Shigella spp., Campylobacter jejuni, Aeromonas hydrophila, Legionella pneumophila, Vibrio cholerae, Yersinia enterocolytica and Mycobacterium avium in both influent and treated waters from the bioreactor. Total bacteria decreased during FBBR treatment. E. coli, Salmonella and Shigella spp., C. jejuni, V. cholerae, Y. enterocolytica and M. avium were not detected in aquifer water or bioreactor treated water samples. For those pathogens detected, including total coliforms, L. pneumophila and A. hydrophila, numbers were usually lower in treated water than influent samples, suggesting removal during treatment. The detection of particular bacterial species reflected their presence or absence in the influent waters. Copyright © 2012 Elsevier B.V. All rights reserved.

Polymer brush covalently attached to OH-functionalized mica surface via surface-initiated ATRP: control of grafting density and polymer chain length.

PubMed

Lego, Béatrice; François, Marion; Skene, W G; Giasson, Suzanne

2009-05-05

The controlled grafting density of poly(tert-butyl acrylate) was studied on OH-activated mica substrates via surface-initiated atom-transfer radical polymerization (ATRP). By properly adjusting parameters such as the immobilization reaction time and the concentration of an ATRP initiator, a wide range of initiator surface coverages and hence polymer densities on mica were possible. The covalently immobilized initiator successfully promoted the polymerization of tert-butyl acrylate on mica surfaces. The resulting polymer layer thickness was measured by AFM using a step-height method. Linear relationships of the polymer thickness with respect to the molecular weight of the free polymer and with respect to the monomer conversion were observed, suggesting that ATRP is well controlled and relatively densely end-grafted layers were obtained. The polymer grafting density controlled by adjusting the initiator surface coverage was confirmed by the polymer layer swelling capacity and film thickness measurements.

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

PubMed Central

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

2014-01-01

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

Methyl tert-butyl ether (MTBE) in finished drinking water in Germany.

PubMed

Kolb, Axel; Püttmann, Wilhelm

2006-03-01

In the present study 83 finished drinking water samples from 50 cities in Germany were analyzed for methyl tert-butyl ether (MTBE) content with a detection limit of 10 ng/L. The detection frequency was 46% and the concentrations ranged between 17 and 712 ng/L. Highest concentrations were found in the community water systems (CWSs) of Leuna and Spergau in Saxony-Anhalt. These CWSs are supplied with water possibly affected by MTBE contaminated groundwater. MTBE was detected at concentrations lower than 100 ng/L in drinking water supplied by CWSs using bank filtered water from Rhine and Main Rivers. The results from Leuna and Spergau show that large groundwater contaminations in the vicinity of CWSs pose the highest risk for MTBE contamination in drinking water. CWSs using bank filtered water from Rhine and Main Rivers are susceptible to low MTBE contaminations in finished drinking water. All measured MTBE concentrations were below proposed limit values for drinking water.

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

PubMed

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

2005-07-01

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.

Selective liquid phase oxidation of benzyl alcohol to benzaldehyde by tert-butyl hydroperoxide over γ-Al2O3 supported copper and gold nanoparticles

NASA Astrophysics Data System (ADS)

Ndolomingo, Matumuene Joe; Meijboom, Reinout

2017-03-01

Benzyl alcohol oxidation to benzaldehyde was performed by tert-butyl hydroperoxide (TBHP) in the absence of any solvent using γ-Al2O3 supported copper and gold nanoparticles. Li2O and ionic liquids were used as additive and stabilizers for the synthesis of the catalysts. The physico-chemical properties of the catalysts were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction spectroscopy (XRD), N2 absorption/desorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and temperature programmed reduction (TPR), whereas, the oxidation reaction was followed by gas chromatography with a flame ionization detector (GC-FID). The as prepared catalysts exhibited good catalytic performance in terms of conversion and selectivity towards benzaldehyde. The performance of the Au-based catalysts is significantly higher than that of the Cu-based catalysts. For both Cu and Au catalysts, the conversion of benzyl alcohol increased as the reaction proceeds, while the selectivity for benzaldehyde decreased. Moreover, the catalysts can be easily recycled and reused with neither significant loss of activity nor selectivity. A kinetic study for the Cu and Au-catalyzed oxidation of benzyl alcohol to benzyldehyde is reported. The rate at which the oxidation of benzyl alcohol is occurring as a function of catalyst and oxidant amounts was investigated, with the apparent rate constant, kapp being proportional to the amount of nano catalyst and oxygen present in the system.

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

PubMed

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

2011-04-01

An independent Pathology Working Group (PWG) re-evaluated the kidney changes in National Toxicology Program (NTP) toxicology/carcinogenicity studies of tert-butyl alcohol (TBA) in F344/N rats to determine possible mode(s) of action underlying renal tubule tumors in male rats at 2-years. In the 13-week study, the PWG confirmed that the normal pattern of round hyaline droplets in proximal convoluted tubules was replaced by angular droplet accumulation, and identified precursors of granular casts in the outer medulla, changes typical of alpha(2u)-globulin (α(2u)-g) nephropathy. In the 2-year study, the PWG confirmed the NTP observation of increased renal tubule tumors in treated male groups. Linear papillary mineralization, another hallmark of the α(2u)-g pathway was present only in treated male rats. Chronic progressive nephropathy (CPN) was exacerbated in high-dose males and females, with a relationship between advanced grades of CPN and renal tumor occurrence. Hyperplasia of the papilla lining was a component of CPN in both sexes, but there was no pelvic urothelial hyperplasia. High-dose females showed no TBA-related nephrotoxicity. The PWG concluded that both α(2u)-g nephropathy and exacerbated CPN modes of action were operative in TBA renal tumorigenicity in male rats, neither of which has relevance for human cancer risk. Copyright © 2011 Elsevier Inc. All rights reserved.

Development and application of a rat PBPK model to elucidate kidney and liver effects induced by ETBE and tert-butanol.

PubMed

Salazar, Keith D; Brinkerhoff, Christopher J; Lee, Janice S; Chiu, Weihsueh A

2015-11-01

Subchronic and chronic studies in rats of the gasoline oxygenates ethyl tert-butyl ether (ETBE) and tert-butanol (TBA) report similar noncancer kidney and liver effects but differing results with respect to kidney and liver tumors. Because TBA is a major metabolite of ETBE, it is possible that TBA is the active toxic moiety in all these studies, with reported differences due simply to differences in the internal dose. To test this hypothesis, a physiologically-based pharmacokinetic (PBPK) model was developed for ETBE and TBA to calculate internal dosimetrics of TBA following either TBA or ETBE exposure. This model, based on earlier PBPK models of methyl tert-butyl ether (MTBE), was used to evaluate whether kidney and liver effects are consistent across routes of exposure, as well as between ETBE and TBA studies, on the basis of estimated internal dose. The results demonstrate that noncancer kidney effects, including kidney weight changes, urothelial hyperplasia, and chronic progressive nephropathy (CPN), yielded consistent dose-response relationships across routes of exposure and across ETBE and TBA studies using TBA blood concentration as the dose metric. Relative liver weights were also consistent across studies on the basis of TBA metabolism, which is proportional to TBA liver concentrations. However, kidney and liver tumors were not consistent using any dose metric. These results support the hypothesis that TBA mediates the noncancer kidney and liver effects following ETBE administration; however, additional factors besides internal dose are necessary to explain the induction of liver and kidney tumors. Published by Elsevier Inc.

Enhanced induction of microspore embryogenesis after n-butanol treatment in wheat (Triticum aestivum L.) anther culture.

PubMed

Soriano, M; Cistué, L; Castillo, A M

2008-05-01

The aim of this study was the improvement of embryo production in wheat anther culture. Three butanol alcohols, n-butanol, sec-butanol and tert-butanol, were evaluated for their effect on microspore embryogenesis in two spring cultivars of wheat, Pavon and Caramba. Application of n-butanol, at 0.1 and 0.2% (v/v) in the induction media for 5 h, highly improved embryo production in both cultivars. Sec- and tert-butanol performed similarly to control plates. Regeneration ability was unaffected by any butyl-alcohol treatment. As a consequence of the higher embryo production after n-butanol treatment, the number of green regenerated plants increased up to five times in cultivar Pavon and up to three times in cultivar Caramba. The percentage of green plants was improved or unaffected by the treatment. Doubled haploid plant production was between 2 and 4 times higher after n-butanol treatment than in control plates. Therefore, n-butanol was successfully applied in the production of wheat doubled haploids. This primary alcohol is known as an activator of phospholipase D and has been previously reported to disrupt cortical microtubules and detach them from the plasma membrane in plants. Its effects on androgenetic induction could confirm the importance of microtubule regulation in plant cell fate, specifically in microspore development. A possible implication of phospholipase D is discussed.

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

PubMed

Roslev, Peter; Lentz, Trine; Hesselsoe, Martin

2015-02-01

The inhibitory effects of the fuel additive methyl tert-butyl ether (MTBE) and potential degradation products tert-butanol (TBA) and formaldehyde was examined using mixed microbial biomass, and six strains of bioluminescent bacteria and yeast. The purpose was to assess microbial toxicity with quantitative bioluminescent and fluorescent endpoints, and to identify sensitive proxies suitable for monitoring MTBE contamination. Bioluminescent Aliivibrio fischeri DSM 7151 (formerly Vibrio fischeri) appeared highly sensitive to MTBE exposure, and was a superior test organisms compared to lux-tagged Escherichia coli DH5α, Pseudomonas fluorescens DF57-40E7 and Saccharomyces cerevisiae BLYR. EC10 and EC50 for acute MTBE toxicity in A. fischeri were 1.1 and 10.9 mg L(-1), respectively. Long term (24h) MTBE exposure resulted in EC10 values of 0.01 mg L(-1). TBA was significantly less toxic with EC10 and EC50 for acute and chronic toxicity >1000 mg L(-1). Inhibition of bioluminescence was generally a more sensitive endpoint for MTBE toxicity than measuring intracellular ATP levels and heterotrophic CO2 assimilation. A weak estrogenic response was detected for MTBE at concentrations ⩾ 3.7 g L(-1) using an estrogen inducible bioluminescent yeast strain (S. cerevisiae BLYES). Microbial hydrolytic enzyme activity in groundwater was affected by MTBE with EC10 values of 0.5-787 mg L(-1), and EC50 values of 59-3073 for alkaline phosphatase, arylsulfatase, beta-1,4-glucanase, N-acetyl-beta-d-glucosaminidase, and leucine-aminopeptidase. Microbial alkaline phosphatase and beta-1,4-glucanase activity were most sensitive to MTBE exposure with EC50 ⩽ 64.8 mg L(-1). The study suggests that bioassays with luminescent A. fischeri, and fluorescent assays targeting hydrolytic enzyme activity are good candidates for monitoring microbial MTBE toxicity in contaminated water. Copyright © 2014 Elsevier Ltd. All rights reserved.

Quantifying residues from postharvest fumigation of almonds and walnuts with propylene oxide

USDA-ARS?s Scientific Manuscript database

A novel analytical approach, involving solvent extraction with methyl tert-butyl ether (MTBE) followed by gas chromatography (GC), was developed to quantify residues that result from the postharvest fumigation of almonds and walnuts with propylene oxide (PPO). Verification and quantification of PPO,...

DECISION-MAKING, SCIENCE AND GASOLINE ADDITIVES

EPA Science Inventory

Methyl-tert butyl ether (MTBE) has been used as a gasoline additive to serve two major purposes. The first use was as an octane-enhancer to replace organic lead, beginning in 1979. The second use, which began about 1992, was as an oxygenated additive to meet requirements ...

USE OF MEMBRANE BIOREACTOR FOR BIODEGRADATION OF MTBE IN CONTAMINATED WATER1

EPA Science Inventory

An ultrafiltration membrane bioreactor was evaluated for biodegradation of methyl tert-butyl ether (MTBE) in contaminated water. The system was fed 5 mg/L MTBE in granular activated carbon (GAC) treated Cincinnati tap water containing ample buffer and nutrients. Within 120...

IRIS Toxicological Review and Summary Documents for Methyl Tert-Butyl Ether (MTBE)

EPA Science Inventory

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

REMEDIAL COSTS FOR MTBE IN SOIL AND GROUND WATER

EPA Science Inventory

Widespread contamination of methyl tert-butyl ether (MTBE) in ground water has raised concerns about the increased cost of remediation of MTBE releases compared to BTEX-only sites. To evaluate these costs, cost information for 311 sites was furnished by U.S. EPA Office of Underg...

Crystal structure of (2,4-di-tert-butyl-6-{[(6,6'-dimethyl-2'-oxido-1,1'-biphenyl-2-yl)imino]methyl}phenolato-κ(3) O,N,O')bis(propan-2-olato-κO)titanium(IV).

PubMed

Chen, Liang; Wang, Huiran; Deng, Xuebin

2014-09-01

In the mononuclear Ti(IV) title complex, [Ti(C29H33NO2)(C3H6O)2], the TiNO4 coordination polyhedron comprises an N-atom and two O-atom donors from the dianionic Schiff base ligand and two O-atom donors from monodentate isopropoxide anions. The stereochemistry is distorted trigonal-bipyramidal with the N-donor in an elongated axial site [Ti-N = 2.2540 (17) Å], the O-donors having normal Ti-O bond lengths [1.7937 (14) Å (axial)-1.8690 (14) Å]. In the crystal, C-H⋯π inter-actions link mol-ecules into centrosymmetric dimers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inbar, S.; Linschitz, H.; Cohen, S.G.

Nanosecond flash photolysis, steady irradiation, and deuterium substitution studies have been carried out on solutions of benzophenone with added reductants. Quantum yields (phi/sub ketyl/) for reduction in benzene of benzophenone triplet to ketyl radical, based on phi = 2 for benzhydrol (I), were approx. 1 for cyclohexane (II), tert-butylamine (III), 2-aminobutane (IV), cyclohexylamine (V), di-n-propylamine (VI), and triethylamine (VII), approx. 0.7 for 1,4-diazabicyclo(2.2.2)octane (VIII), and approx. 0 for tert-butyl alcohol (IX). Thus, quenching, without radical formation by H abstraction from N and/or ..cap alpha..-C, does not occur with common aliphatic amines but does with Dabco (VIII). The latter quenching ismore » markedly increased by small additions of acetonitrile; the flash spectrum from this compound indicates formation of a triplet amine CT complex or radical ion pair. Triplet-reductant interaction rate constants, k/sur ir/, are high for the amines (approx. 10/sup 8/-10/sup 9/ M/sup -1/ s/sup -1/) but also show significant deuterium kinetic isotope effects: 1.9 with III-N-d/sub 2/; 1.4 with IV-N-d/sub 2/; 1.2-1.3 with IV-..cap alpha..-C-d. It is proposed that k/sub ir/ measures H atom abstraction, favored in the transition state by an initial charge-transfer interaction. Overall steady irradiation quantum yields of reduction by amines, phi/sub Red/, are much lower than phi/sub ketyl/. This is attributed to disproportionationreactions of ketyl and alkylaminyl radicals for primary and secondary amines, and, possibly, aminoalkyl radicals for tertiary amines. In the case of tert-butylamine, the rate constant for disproportionation is obtained from the decay kinetics of ketyl radical and leads to phi/sub Red/ in agreement with that directly measured.« less

3,3-Dimethyl-1-[5-(1H-1,2,4-triazol-1-yl­meth­yl)-1,3,4-thia­diazol-2-ylsulfan­yl]butan-2-one

PubMed Central

Wei, Qing-Li; He, Fu-Jin; Li, Fang; Bi, Sai

2008-01-01

In the mol­ecule of the title compound, C11H15N5OS2, the thia­diazole and triazole rings are not coplanar, the dihedral angle formed by their mean planes being 59.9 (2)°. The exocyclic S atom, and the methyl­ene, carbonyl, tert-butyl and one methyl carbon form an approximately planar zigzag chain, which makes a dihedral angle of 74.6 (1)° with the thia­diazole ring. PMID:21201440

Superior Energetic Materials that Contain Carbocations and Anions. Energetic Materials Restricted in Composition to C, H, N, and O Atoms

DTIC Science & Technology

1993-10-30

AMXRO-IP-Library. Summary Thiourea condensed with 1,4-diformnyl-2,3,5,6-tetrahydroxypiperazine 14 in the presence of 3 hydrochloric acid to give 2,6...b:4’,5"-e]pyrazine 20 to 2- oxo-2,3-dihydro-1,3-dinitro-lH-imidazo[4,5-b]pyrazine 21 was brought about by hydrochloric acid . Treatment with lithium...reaction with tert-butyl amine, and converted to 4,8-dihydro-4,8-dinitro- 1H,5H-diimidazo[4,5-b:4’,5’-e]pyrazine-2,6-disulfonic acid 17 by nitric acid

LOCALIZED RECHARGE INFLUENCES ON MTBE TRANSPORT AND WELL PLACEMENT CONSIDERATIONS

EPA Science Inventory

Vertical characterization of a gasoline release site at East Patchogue, New York showed that methyl tert-butyl ether (MTBE) and aromatic plumes "dived" as they passed beneath a sand pit. That this behavior was caused by aquifer recharge was shown by two pieces of evidence. Fir...

MTBE OXIDATION BYPRODUCTS FROM THE TREATMENT OF SURFACE WATERS BY OZONATION AND UV-OZONATION

EPA Science Inventory

In recent years, there has been considerable concern over the release of methyl tert-butyl ether (MTBE), as gasoline additive, into the aquifers used as potable water sources. MTBE readily dissolves in water and has entered the environment via gasoline spills and leaking...

Particle Size Effects on Fenton Regeneration of MTBE-spent Activated Carbon

EPA Science Inventory

Fenton-driven regeneration of spent granular activated carbon (GAC) is a developing technology that may reduce water treatment costs. In this study, the effect of GAC particle size on Fenton-driven oxidation of methyl tert-butyl ether (MTBE)-spent GAC was evaluated. The GAC was...

AN EXPERIMENTAL STUDY OF PHYTOREMEDIATION OF METHYL-TERT-BUTYL-ETHER (MTBE) IN GROUNDWATER. (R825549C062)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

NOVEL EMBEDDED CERAMIC ELECTRODE SYSTEM TO ACTIVATE NANOSTRUCTURED TITANIUM DIOXIDE FOR DEGRADATION OF MTBE

EPA Science Inventory

A novel reactor combining a flame-deposited nanostructured titanium dioxide film and a set of embedded ceramic electrodes was designed, developed and tested for degradation of methyl tert-butyl ether (MTBE) in water. On applying a voltage to the ceramic electrodes, a surface coro...

Persulfate Oxidation of MTBE- and Chloroform-Spent Granular Activated Carbon

EPA Science Inventory

Activated persulfate (Na2S2O8) regeneration of methyl tert-butyl ether (MTBE) and chloroform-spent GAC was evaluated in this study. Thermal-activation of persulfate was effective and resulted in greater MTBE removal than either alkaline-activation or H2O2–persulfate binary mixtur...

Iron Amendment and Fenton Oxidation of MTBE-Spent Granular Activated Carbon

EPA Science Inventory

Fenton-driven regeneration of Methyl tert-butyl ether (MTBE)-spent granular activated carbon (GAC) involves Fe amendment to the GAC to catalyze H2O2 reactions and to enhance the rate of MTBE oxidation and GAC regeneration. Four forms of iron (ferric sulfate, ferric chloride, fer...

EXPERIMENTAL MEASUREMENT OF THE RATE OF METHYL TERT-BUTYL ETHER HYDROLYSIS IN SUB- AND SUPERCRITICAL WATER. (R826738)

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...

CHEMICAL DESTRUCTION OF MTBE USING FENTON'S REAGENT: EFFECT OF FERROUS IRON/HYDROGEN PEROXIDE RATIO

EPA Science Inventory

In previous laboratory experiments Fenton's Reagent (FR) was successfully used as the source of hydroxyl radicals (OH*) for chemical treatment of low concentrations of methyl tert-butyl ether (MTBE) in water. Although under certain conditions MTBE degradation levels as high as 99...

Composition and Behavior of Fuel Ethanol

EPA Science Inventory

Ethanol usage in the United States has increased due in part to the elimination of methyl tert-butyl ether from the fuel supply and to the mandates of Congress. Two samples, one each from a wet mill and a dry mill ethanol plant, were obtained before denaturing. Each of these ...

BTEX MTBE BIOREMEDIATION: BIONETS CONTAINING ISOLITE, PM1, SOLID OXYGEN SOURCE

EPA Science Inventory

Methyl tert-Butyl Ether (MTBE), a gasoline additive, is a persistent and foul tasting contaminate that is more mobile in ground water than BTEX . It, along with BTEX, is turning up at many American crossroads. This study's objective was to determine if biologically active in sit...

MTBE BIOREMEDIATION WITH BIONETS CONTAINING ISOLITE, PMI, SOS ON AIR

EPA Science Inventory

Methyl tert-Butyl Ether (MTBE), a gasoline additive, is a persistent and foul tasting contaminant that is more mobile in ground water than BTEX. It is turning up at many American crossroads. This study's objective was to determine if biologically active in situ Bionets could bior...

MTBE BIODEGRADATION IN A GRAVITY FLOW, HIGH-BIOMASS RETAINING BIOREACTOR

EPA Science Inventory

The aerobic biodegradation of methyl tert-butyl ether (MtBE), a widely used fuel oxygenate, was investigated using a pilot-scale biomass-retaining bioreactor called a Biomass Concentrator Reactor (BCR). The reactor was operated for a year at a flow rate of 2500 L/d on Ci...

CONTROLLED, SHORT-TERM DERMAL AND INHALATION EXPOSURE TO MTBE AND DIBROMOCHLOROMETHANE

EPA Science Inventory

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

Identifying the site of spin trapping in proteins by a combination of liquid chromatography, ELISA, and off-line tandem mass spectrometry.

PubMed

Lardinois, Olivier M; Detweiler, Charles D; Tomer, Kenneth B; Mason, Ronald P; Deterding, Leesa J

2008-03-01

An off-line mass spectrometry method that combines immuno-spin trapping and chromatographic procedures has been developed for selective detection of the nitrone spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) covalently attached to proteins, an attachment which occurs only subsequent to DMPO trapping of free radicals. In this technique, the protein-DMPO nitrone adducts are digested to peptides with proteolytic agents, peptides from the enzymatic digest are separated by HPLC, and enzyme-linked immunosorbent assays (ELISA) using polyclonal anti-DMPO nitrone antiserum are used to detect the eluted HPLC fractions that contain DMPO nitrone adducts. The fractions showing positive ELISA signals are then concentrated and characterized by tandem mass spectrometry (MS/MS). This method, which constitutes the first liquid chromatography-ELISA-mass spectrometry (LC-ELISA-MS)-based strategy for selective identification of DMPO-trapped protein residues in complex peptide mixtures, facilitates location and preparative fractionation of DMPO nitrone adducts for further structural characterization. The strategy is demonstrated for human hemoglobin, horse heart myoglobin, and sperm whale myoglobin, three globin proteins known to form DMPO-trappable protein radicals on treatment with H(2)O(2). The results demonstrate the power of the new experimental strategy to select DMPO-labeled peptides and identify sites of DMPO covalent attachments.

Novel types of tetra-, hexa-, octa-, and dodecanuclear silver clusters containing (2,7-Di-tert-butylfluoren-9-ylidene)methanedithiolate.

PubMed

Vicente, José; González-Herrero, Pablo; García-Sánchez, Yolanda; Jones, Peter G

2009-03-02

The reaction of AgClO(4) with piperidinium 2,7-di-tert-butyl-9H-fluorene-9-carbodithioate (pipH)[S(2)C(t-Bu-Hfy)] (1) (t-Bu-Hfy = 2,7-di-tert-butylfluoren-9-yl) afforded [Ag(n){S(2)C(t-Bu-Hfy)}(n)] (2), which reacted with phosphines to give [Ag{S(2)C(t-Bu-Hfy)}L(2)] [L = PPh(3) (3a); L(2) = bis(diphenylphosphino)ethane (dppe, 3b), 1,1'-bis(diphenylphosphino)ferrocene (dppf, 3c). By reacting complex 2 with AgClO(4) and piperidine in a 1:1:1 molar ratio, the dodecanuclear cluster [Ag(12){S(2)C(t-Bu-fy)}(6)] (4) (t-Bu-fy = 2,7-di-tert-butylfluoren-9-ylidene) was obtained. Compound 4 can also be directly prepared from the reaction of 1 with AgClO(4) and piperidine in a 1:2:1 molar ratio. The reactions of 1 with AgClO(4), phosphines, and piperidine afforded the compounds [Ag(6){S(2)C(t-Bu-fy)}(3)L(5)] [1:2:2:1 molar ratio; L = PPh(3) (5a), P(p-To)(3) (5b)], [Ag(4){S(2)C(t-Bu-fy)}(2)(dppf)(2)] (6) (1:2:1:1 molar ratio), [Ag(n){S(2)C(t-Bu-fy)}(n/2){P(i-Pr)(3)}(n)] (7) (1:2:2:1 molar ratio), or [Ag(8){S(2)C(t-Bu-fy)}(4){P(i-Pr)(3)}(4)] (8) (1:2:1:1 molar ratio). Complexes 5a,b, 6, 7, and 8 can be also obtained by reacting 4 with the corresponding phosphine in the appropriate molar ratio. The crystal structures of 4, 5b, and 8 have been determined by X-ray diffraction studies. The nuclearity of complex 6 was established from its (31)P{(1)H} NMR data, which reveal a very fast dynamic process leading to an average coupling of each of the P atoms of the dppf ligands with four Ag atoms.

Self-ignition of S.I. engine model fuels: A shock tube investigation at high pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fieweger, K.; Blumenthal, R.; Adomeit, G.

1997-06-01

The self-ignition of several spark-ignition (SI) engine fuels (iso-octane, methanol, methyl tert-butyl ether and three different mixtures of iso-octane and n-heptane), mixed with air, was investigated experimentally under relevant engine conditions by the shock tube technique. Typical modes of the self-ignition process were registered cinematographically. For temperatures relevant to piston engine combustion, the self-ignition process always starts as an inhomogeneous, deflagrative mild ignition. This instant is defined by the ignition delay time, {tau}{sub defl}. The deflagration process in most cases is followed by a secondary explosion (DDT). This transition defines a second ignition delay time, {tau}{sub DDT}, which is amore » suitable approximation for the chemical ignition delay time, if the change of the thermodynamic conditions of the unburned test gas due to deflagration is taken into account. For iso-octane at p = 40 bar, a NTC (negative temperature coefficient), behavior connected with a two step (cool flame) self-ignition at low temperatures was observed. This process was very pronounced for rich and less pronounced for stoichiometric mixtures. The results of the {tau}{sub DDT} delays of the stoichiometric mixtures were shortened by the primary deflagration process in the temperature range between 800 and 1,000 K. Various mixtures of iso-octane and n-heptane were investigated. The results show a strong influence of the n-heptane fraction in the mixture, both on the ignition delay time and on the mode of self-ignition. The self-ignition of methanol and MTBE (methyl tert-butyl ether) is characterized by a very pronounced initial deflagration. For temperatures below 900 K (methanol: 800 K), no secondary explosion occurs. Taking into account the pressure increase due to deflagration, the measured delays {tau}{sub DDT} of the secondary explosion are shortened by up to one order of magnitude.« less

Gold(I) Complexes of Ferrocenyl Polyphosphines: Aurophilic Gold Chloride Formation and Phosphine-Concerted Shuttling of a Dinuclear [ClAu···AuCl] Fragment.

PubMed

Rampazzi, Vincent; Roger, Julien; Amardeil, Régine; Penouilh, Marie-José; Richard, Philippe; Fleurat-Lessard, Paul; Hierso, Jean-Cyrille

2016-11-07

A smart steric control of the metallocene backbone in bis- and poly(phosphino)ferrocene ligands favors intramolecular aurophilic interactions between [AuCl] fragments in polynuclear gold(I) complexes. We synthesized and characterized by multinuclear NMR and X-ray diffraction analysis mono-, di-, and polynuclear gold complexes of constrained ferrocenyl diphosphines, which bear either bulky tert-butyl groups or more flexible siloxane substituents at the cyclopentadienyl rings. The complexes meso-1,1'-bis(diphenylphosphino)-3,3'-di-tert-butylferrocene (4-m), rac-1,1'-bis[bis(5-methyl-2-furyl)phosphino]-3,3'-di-tert-butylferrocene (5-r), and rac-1,1'-bis(diphenylphosphino)-3,3'-bis[(tri-iso-propylsilyl)oxy]ferrocene (6-r) were used to form dinuclear gold complexes. Coordination of tert-butylated ferrocenyl phosphines generated aurophilic interactions in the corresponding dinuclear gold complexes, contrary to gold(I) complexes reported with 1,1'-bis(diphenylphosphino)ferrocene. The structurally related tetraphosphine 1,1',2,2'-tetrakis(diphenylphosphino)-4,4'-di-tert-butylferrocene (11) also gave access to mononuclear, dinuclear, and the original trinuclear gold chloride aurophilic complexes in which 14e - to 16e - gold centers coexist. In such complexes, nonbonded ("through-space") 31 P- 31 P' nuclear spin couplings were evidenced by high-resolution NMR. In these interactions nuclear spin information is transferred between the lone-pair electron of an uncoordinated phosphorus P and a phosphorus P' that is involved in a σ covalent bond Au-P'. The dinuclear aurophilic complex displayed a concerted shuttling of its [ClAu···AuCl] fragment between the four phosphorus donors of the tetraphosphine ligand. Thus, an aurophilic Au···Au bond, which is assumed to be a weak energy interaction, can be conserved within a dynamic shuttling process at high temperature involving an intramolecular coordination-decoordination process of digold(I) at phosphorus atoms.

Exposure to MTBE, TAME and aromatic hydrocarbons during gasoline pump maintenance, repair and inspection.

PubMed

Vainiotalo, Sinikka; Kuusimäki, Leea; Pekari, Kaija

2006-09-01

The exposure of gasoline pump repairers and inspectors to gasoline was studied at service stations and repair shops in Finland in April-June 2004. The average air temperature ranged from 7 degrees C to 16 degrees C and wind speed from 2.5 to 7 m/s. The gasoline blends contained mixtures of methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME), the total content of oxygenates being 11-12%. The content of benzene was <1%. Breathing zone air was collected during the work task using passive monitors. The mean sampling period was 4.5 h. The mean TWA-8 h concentrations for MTBE, TAME, hexane, benzene, toluene, ethylbenzene and xylene were 4.5, 1.3, 0.55, 0.23, 2.2, 0.26 and 1.1 mg/m3, respectively. None of the individual benzene concentrations exceeded the binding limit value for benzene (3.25 mg/m3). The sum concentration of MTBE and TAME in urine was between 8.9 and 530 nmol/l in individual post-shift samples. The individual sum concentrations of the metabolites tert-butyl alcohol and tert-amyl alcohol collected the following morning after the exposure ranged from 81 to 916 nmol/l. All individual results were below corresponding biological action levels. Exposure to aromatic hydrocarbons was estimated from post-shift urine samples, with benzene showing the highest concentration (range 4.4 and 35 nmol/l in non-smokers). The exposure levels were similar to those measured in previous studies during unloading of tanker lorries and railway wagons. The results indicated a slightly higher exposure for inspectors, who calibrated fuel pump gauges at the service stations, than for pump repairers. No significant skin exposure occurred during the study.

(Cryptand-222)potassium(+) (hydrogensulfido)[5,10,15,20-tetra-kis(2-pival-amido-phen-yl)porphyrinato]ferrate(II).

PubMed

Dhifet, Mondher; Belkhiria, Mohamed Salah; Daran, Jean-Claude; Nasri, Habib

2009-07-22

As part of a systematic investigation for a number of Fe(II) porphyrin complexes used as biomimetic models for cytochrome P450, crystals of the title compound, [K(C(18)H(36)N(2)O(6))][Fe(II)(C(64)H(64)N(8)O(4))(HS)], were prepared. The compound exhibits a non-planar conformation with major ruffling and saddling distortions. The average equatorial iron-pyrrole N atom [Fe-N(p) = 2.102 (2) Å] bond length and the distance between the Fe(II) atom and the 24-atom core of the porphyrin ring (Fe-P(C)= 0.558 Å) are typical for high-spin iron(II) penta-coordinate porphyrinates. One of the tert-butyl groups in the structure is disordered over two sets with occupancies of 0.84 and 0.16.

FT-IR and computer modeling study of hydrogen bonding in N-alkyl acrylamide-toluene binary mixtures

NASA Astrophysics Data System (ADS)

Rumyantsev, Misha; Kazantsev, Oleg A.; Kamorina, Sofia I.; Kamorin, Denis M.; Sivokhin, Alexey P.

2016-10-01

Degree of hydrogen bonding driven self-association of N-(n-butyl)acrylamide, N-(n-octyl)acrylamide, N-(sec-octyl)acrylamide and N-(tert-octyl)acrylamide in toluene was investigated using IR spectroscopy and computer modeling methods. Consistent results were demonstrated in the treatment of the Amide-I (νC=O), Amide-II (δN-H and νC-N) and Amide-A (νN-H) absorption bands in IR spectra. Thus, the content of non-bonded (free) amide groups decreases from 83-98% to 8-20% and the content of linear polyassociates increases to 80-90% with an increase in monomer concentration from 0.5 wt% to 50 wt%. The content of cyclic dimers was equal to the value between 5 and 10% regardless of the initial monomer concentration. Dependences of the association degree and the content of the linear polyassociates on the concentration were found to be similar for all of the studied amides.

Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trial.

PubMed

Davison, G W; Ashton, T; George, L; Young, I S; McEneny, J; Davies, B; Jackson, S K; Peters, J R; Bailey, D M

2008-11-01

Patients with type 1 diabetes mellitus are more susceptible than healthy individuals to exercise-induced oxidative stress and vascular endothelial dysfunction, which has important implications for the progression of disease. Thus, in the present study, we designed a randomised double-blind, placebo-controlled trial to test the original hypothesis that oral prophylaxis with vitamin C attenuates rest and exercise-induced free radical-mediated lipid peroxidation in type 1 diabetes mellitus. All data were collected from hospitalised diabetic patients. The electron paramagnetic resonance spectroscopic detection of spin-trapped alpha-phenyl-tert-butylnitrone (PBN) adducts was combined with the use of supporting markers of lipid peroxidation and non-enzymatic antioxidants to assess exercise-induced oxidative stress in male patients with type 1 diabetes (HbA(1c) 7.9 +/- 1%, n = 12) and healthy controls (HbA(1c) 4.6 +/- 0.5%, n = 14). Following participant randomisation using numbers in a sealed envelope, venous blood samples were obtained at rest, after a maximal exercise challenge and before and 2 h after oral ingestion of 1 g ascorbate or placebo. Participants and lead investigators were blinded to the administration of either placebo or ascorbate treatments. Primary outcome was the difference in changes in free radicals following ascorbate ingestion. Six diabetic patients and seven healthy control participants were randomised to each of the placebo and ascorbate groups. Diabetic patients (n = 12) exhibited an elevated concentration of PBN adducts (p < 0.05 vs healthy, n = 14), which were confirmed as secondary, lipid-derived oxygen-centred alkoxyl (RO.) radicals (a(nitrogen) = 1.37 mT and abeta(hydrogen) = 0.18 mT). Lipid hydroperoxides were also selectively elevated and associated with a depression of retinol and lycopene (p < 0.05 vs healthy). Vitamin C supplementation increased plasma vitamin C concentration to a similar degree in both groups (p < 0.05 vs pre-supplementation) and attenuated the exercise-induced oxidative stress response (p < 0.05 vs healthy). There were no selective treatment differences between groups in the primary outcome variable. These findings are the first to suggest that oral vitamin C supplementation provides an effective prophylaxis against exercise-induced free radical-mediated lipid peroxidation in human diabetic blood. ISRCTN96164937.

Separation of chlorogenic acid and concentration of trace caffeic acid from natural products by pH-zone-refining countercurrent chromatography.

PubMed

Lu, Yuanyuan; Dong, Genlai; Gu, Yanxiang; Ito, Yoichiro; Wei, Yun

2013-07-01

Chlorogenic acid and caffeic acid were selected as test samples for separation by the pH-zone-refining countercurrent chromatography (CCC). The separation of these test samples was performed with a two-phase solvent system composed of methyl-tert-butyl-ether/acetonitrile/water at a volume ratio of 4:1:5 v/v/v where trifluoroacetic acid (TFA; 8 mM) was added to the organic stationary phase as a retainer and NH4 OH (10 mM) to the aqueous mobile phase as an eluter. Chlorogenic acid was successfully separated from Flaveria bidentis (L.) Kuntze (F. bidentis) and Lonicerae Flos by pH-zone-refining CCC, a slightly polar two-phase solvent system composed of methyl-tert-butyl-ether/acetonitrile/n-butanol/water at a volume ratio of 4:1:1:5 v/v/v/v was selected where TFA (3 mM) was added to the organic stationary phase as a retainer and NH4 OH (3 mM) to the aqueous mobile phase as an eluter. A 16.2 mg amount of chlorogenic acid with the purity of 92% from 1.4 g of F. bidentis, and 134 mg of chlorogenic acid at the purity of 99% from 1.3 g of crude extract of Lonicerae Flos have been obtained. These results suggest that pH-zone-refining CCC is suitable for the isolation of the chlorogenic acid from the crude extracts of F. bidentis and Lonicerae Flos. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

PubMed

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

2010-10-14

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

C60 Recognition from Extended Tetrathiafulvalene Bis-acetylide Platinum(II) Complexes.

PubMed

Bastien, Guillaume; Dron, Paul I; Vincent, Manon; Canevet, David; Allain, Magali; Goeb, Sébastien; Sallé, Marc

2016-11-18

The favorable spatial organization imposed by the square planar 4,4'-di(tert-butyl)-2,2'-bipyridine (dbbpy) platinum(II) complex associated with the electronic and shape complementarity of π-extended tetrathiafulvalene derivatives (exTTF) toward fullerenes is usefully exploited to construct molecular tweezers, which display good affinities for C 60 .

Effects of Temperature and Acidic Pre-Treatment on Fenton-Driven Oxidation of MTBE-Spent Granular Activated Carbon

EPA Science Inventory

Temperature-dependent mechanisms in the Fenton-driven chemical oxidation of methyl tert-butyl ether (MTBE)-spent granular activated carbon (GAC) was investigated. Prior to iron (Fe) amendment to the GAC, acid-treatment altered the surface chemistry of the GAC and lowered the pH ...

Effects on temperature and acidic pre-treatment on Fenton-driven oxidation of MTBE-spent granular activated carbon

EPA Science Inventory

Temperature-dependent mechanisms in the Fenton-driven chemical oxidation of methyl tert-butyl ether (MTBE)-spent granular activated carbon (GAC) was investigated. Prior to iron (Fe) amendment to the GAC, acid-treatment altered the surface chemistry of the GAC and lowered the p...

Serotonergic ergoline derivatives.

PubMed

Mantegani, S; Brambilla, E; Caccia, C; Damiani, G; Fornaretto, M G; McArthur, R A; Varasi, M

1998-05-05

Novel classes of 13- and 14-tertbutyl-ergoline derivatives were prepared, and characterised in vitro for their affinity for adrenergic, dopaminergic and serotonergic binding sites. This study particularly examines the importance of the presence and the position of the tert-butyl group in conferring either significant 5-HT1A or 5-HT2 affinity and selectivity respectively.

21 CFR 175.105 - Adhesives.

Code of Federal Regulations, 2013 CFR

2013-04-01

...) content averages 9 or 30 moles endo-cis-5-Norbornene-2,3-dicarboxylic anhydride α-cis-9-Octadecenyl-omega...) Potassium tripolyphosphate α, α′, α″-1,2,3-Propanetriyltris [omega-(2,3-epoxypropoxy) poly (oxypropylene... (3,5-di-tert-butyl-4-hydroxy-hydro-cinnamate)] methane a[p-(1,1,3,3-Tetramethylbutyl) phenyl]-omega...

21 CFR 175.105 - Adhesives.

Code of Federal Regulations, 2012 CFR

2012-04-01

...) content averages 9 or 30 moles endo-cis-5-Norbornene-2,3-dicarboxylic anhydride α-cis-9-Octadecenyl-omega...) Potassium tripolyphosphate α, α′, α″-1,2,3-Propanetriyltris [omega-(2,3-epoxypropoxy) poly (oxypropylene... (3,5-di-tert-butyl-4-hydroxy-hydro-cinnamate)] methane a[p-(1,1,3,3-Tetramethylbutyl) phenyl]-omega...

21 CFR 175.105 - Adhesives.

Code of Federal Regulations, 2014 CFR

2014-04-01

...) content averages 9 or 30 moles endo-cis-5-Norbornene-2,3-dicarboxylic anhydride α-cis-9-Octadecenyl-omega...) Potassium tripolyphosphate α, α′, α″-1,2,3-Propanetriyltris [omega-(2,3-epoxypropoxy) poly (oxypropylene... (3,5-di-tert-butyl-4-hydroxy-hydro-cinnamate)] methane a[p-(1,1,3,3-Tetramethylbutyl) phenyl]-omega...

THE TRANSPORT AND FATE OF ETHANOL AND BTEX IN GROUNDWATER CONTAMINATED BY GASOHOL. (R821114)

EPA Science Inventory

Ethanol is used a component in all gasoline in Brazil, and its use could increase significantly in the U.S. to meet the requirements of the Clean Air Act Amendments. Recent problems with ground water contamination by methyl tert-butyl ether (MTBE) have made policymakers more c...

27 CFR 21.101 - tert-Butyl alcohol.

Code of Federal Regulations, 2013 CFR

2013-04-01

... needle). Above 20 °C. (f) Identification test. Place five drops of a solution containing approximately 0... (dissolve 5 grams of red mercuric oxide in 20 ml of concentrated sulfuric acid; add this solution to 80 ml of distilled water, and filter when cool). Heat the mixture just to the boiling point and remove from...

27 CFR 21.101 - tert-Butyl alcohol.

Code of Federal Regulations, 2014 CFR

2014-04-01

... needle). Above 20 °C. (f) Identification test. Place five drops of a solution containing approximately 0... (dissolve 5 grams of red mercuric oxide in 20 ml of concentrated sulfuric acid; add this solution to 80 ml of distilled water, and filter when cool). Heat the mixture just to the boiling point and remove from...

27 CFR 21.101 - tert-Butyl alcohol.

Code of Federal Regulations, 2012 CFR

2012-04-01

... needle). Above 20 °C. (f) Identification test. Place five drops of a solution containing approximately 0... (dissolve 5 grams of red mercuric oxide in 20 ml of concentrated sulfuric acid; add this solution to 80 ml of distilled water, and filter when cool). Heat the mixture just to the boiling point and remove from...

Transformation products and reaction kinetics of fragrances in advanced wastewater treatment with ozone.

PubMed

Janzen, Niklas; Dopp, Elke; Hesse, Julia; Richards, Jessica; Türk, Jochen; Bester, Kai

2011-11-01

The reaction of the fragrance compounds 4,6,6,7,8,8-hexamethyl-1,3,4,7-tetrahydrocyclopenta[g]isochromene (HHCB), 1-(3,5,5,6,8,8-hexamethyl-6,7-dihydronaphthalen-2-yl)ethanone (AHTN), 1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene (musk xylene/MX), 1-(4-tert-butyl-2,6-dimethyl-3,5-dinitrophenyl)ethanone (musk ketone/MK), and 1-(2,3,8,8-tetramethyl-1,3,4,5,6,7-hexahydronaphthalen-2-yl)ethanone (OTNE) with ozone in tap water as well as waste water treatment plant (WWTP) effluents is described. Several transformation products are characterized by means of gas chromatography coupled to mass spectrometry. One transformation product (HHCB-Lactone) was confirmed by means of a true standard. Musk xylene and musk ketone do not react with ozone under the conditions used in this study. AHTN and HHCB reacted slowly to a multitude of transformation products, while OTNE reacted quickly to several stable transformation products. The reaction constants and half lives are used to predict removal efficiencies for full scale reactors. Copyright © 2011 Elsevier Ltd. All rights reserved.

Effect of redox conditions on MTBE biodegradation in surface water Sediments

USGS Publications Warehouse

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

2001-01-01

Microbial degradation of methyl tert-butyl ether (MTBE) was observed in surface water-sediment microcosms under anaerobic conditions. The efficiency and products of anaerobic MTBE biodegradation were dependent on the predominant terminal electron-accepting conditions. In the presence of substantial methanogenic activity, MTBE biodegradation was nominal and involved reduction of MTBE to the toxic product, tert-butyl alcohol (TBA). In the absence of significant methanogenic activity, accumulation of [14C]TBA generally decreased, and mineralization of [U-14C]MTBE to 14CO2 generally increased as the oxidative potential of the predominant terminal electron acceptor increased in the order of SO4, Fe(III), Mn(IV) < NO3 < O2. Microbial mineralization of MTBE to CO2 under Mn(IV)or SO4-reducing conditions has not been reported previously. The results of this study indicate that microorganisms inhabiting the sediments of streams and lakes can degrade MTBE effectively under a range of anaerobic terminal electron-accepting conditions. Thus, anaerobic bed sediment microbial processes may provide a significant environmental sink for MTBE in surface water systems throughout the United States.

Crystal structure of 1-iodo-3-{[4-(tert-butyl­sulfan­yl)phen­yl]ethyn­yl}azulene

PubMed Central

Förster, Sebastian; Seichter, Wilhelm; Weber, Edwin

2015-01-01

The title compound, C20H19IS, features a 1,3-disubstituted azulene involving an ethynylene elongated 4-(tert-butyl­sulfanyl)­phenyl sidearm and an iodine atom as the substituents. The azulene ring system is almost planar (r.m.s. deviation = 0.012 Å) and subtends a dihedral angle of 35.7 (1)° with the benzene ring. As a result of the inherent dipole character of the azulene core, a supra­molecular π–π dimer [separation between the centroids of the five- and seven-membered rings = 3.7632 (10) Å] with anti­parallel orientated mol­ecules can be observed in the crystal. The packing is consolidated by an unusual I⋯π(acetyl­ene) contact [I⋯Cg = 3.34 Å, C—I⋯Cg = 173.3°], and a very weak C—H⋯π inter­action is also found in the structure, with the azulene five-membered ring as the acceptor. PMID:26396788

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

NASA Astrophysics Data System (ADS)

Banerjee, Saikat; Bagchi, Biman

2013-10-01

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

Interactions of poly(tert-butyl acrylate)-poly(styrene) diblock copolymers with lipids at the air-water interface.

PubMed

Mudgil, Poonam; Dennis, Gary R; Millar, Thomas J

2006-08-29

Diblock copolymers with hydrophilic poly(tert-butyl acrylate) (PtBA) and hydrophobic poly(styrene) (PS) blocks were synthesized with a view to use them as a surfactant in tear film for increasing the ocular comfort in dry eye syndrome. Interactions of six PtBA-PS copolymers with four important lipids found in the tear film, namely cholesterol, cholesteryl palmitate, dipalmitoyl phosphatidylcholine, and phosphatidylinositol, were studied at the air-water interface using a Langmuir trough. Thermodynamics of mixing of the copolymers and the lipids in the mixed monolayers was determined by calculating excess free energy of mixing. The diblock copolymers showed repulsive interactions with cholesteol and cholesteryl palmitate, near neutral interactions with dipalmitoyl phosphatidylcholine, and attractive interactions with phosphatidylinositol. The lipids interacted with the PS component of the copolymer. The results indicate that a copolymer with a small hydrophilic group and a big hydrophobic group can be a likely candidate for forming stable interactions with the lipids present in the tear film and hence increase the ocular comfort.

Calculated volatilization rates of fuel oxygenate compounds and other gasoline-related compounds from rivers and streams

USGS Publications Warehouse

Pankow, J.F.; Rathbun, R.E.; Zogorski, J.S.

1996-01-01

Large amounts of the 'fuel-oxygenate' compound methyl-tert-butyl ether (MTBE) are currently being used in gasoline to reduce carbon monoxide and ozone in urban air and to boost fuel octane. Because MTBE can be transported to surface waters in various ways, established theory was used to calculate half-lives for MTBE volatilizing from flowing surface waters. Similar calculations were made for benzene as a representative of the 'BTEX' group of compounds (benzene, toluene, ethyl benzene, and the xylenes), and for tert-butyl alcohol (TBA). The calculations were made as a function of the mean flow velocity u (m/day), the mean flow depth h (m), the ambient temperature, and the wind speed. In deep, slow-moving flows, MTBE volatilizes at rates which are similar to those for the BTEX compounds. In shallow, fast-moving flows, MTBE volatilizes more slowly than benzene, though in such flows both MTBE and benzene volatilize quickly enough that these differences may often not have much practical significance. TBA was found to be essentially nonvolatile from water.

The lightest organic radical cation for charge storage in redox flow batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Jinhua; Pan, Baofei; Duan, Wentao

2016-08-25

Electrochemically reversible fluids of high energy density are promising materials for capturing the electrical energy generated from intermittent sources like solar and wind. To meet this technological challenge there is a need to understand the fundamental limits and interplay of electrochemical potential, stability and solubility in “lean” derivatives of redox-active molecules. Here we describe the process of molecular pruning, illustrated for 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene, a molecule known to produce a persistently stable, high-potential radical cation. By systematically shedding molecular fragments considered important for radical cation steric stabilization, we discovered a minimalistic structure that retains long-term stability in its oxidized form. Interestingly, wemore » find the tert-butyl groups are unnecessary; high stability of the radical cation and high solubility are both realized in derivatives having appropriately positioned arene methyl groups. These stability trends are rationalized by mechanistic considerations of the postulated decomposition pathways. We suggest that the molecular pruning approach will uncover lean redox active derivatives for electrochemical energy storage leading to materials with long-term stability and high intrinsic capacity.« less

Antioxidant capacity of BO-653, 2,3-dihydro-5-hydroxy-4,6-di-tert-butyl-2,2-dipentylbenzofuran, and uric acid as evaluated by ORAC method and inhibition of lipid peroxidation.

PubMed

Niki, Etsuo; Fukuhara, Akiko; Omata, Yo; Saito, Yoshiro; Yoshida, Yasukazu

2008-04-01

The role of radical-scavenging antioxidant against oxidative stress has received much attention. The antioxidant capacity has been assessed by various methods. Above all, oxygen radical absorbance capacity (ORAC) has been frequently employed [Prior et.al., J. Agric. Food Chem.2005, 53, 4290]. In the present study, the antioxidant capacity of 2,3-dihydro-5-hydroxy-4,6-di-tert-butyl-2,2-dipentylbenzofuran (BO-653) and uric acid was assessed by ORAC method using pyranine as a reference probe and compared with that against lipid peroxidation of human plasma. It was found that BO-653 was assessed to be much less potent than uric acid by ORAC method, whereas BO-653 exerted much higher antioxidant activity than uric acid against plasma lipid peroxidation. The reason for such discrepancy is discussed. The results suggest that ORAC method is suitable for the assessment of free radical scavenging capacity, but not for the assessment of antioxidant capacity against lipid peroxidation in plasma.

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

PubMed Central

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

2010-01-01

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

Intriguing Morphology Evolution from Noncrosslinked Poly(tert-butyl acrylate) Seeds with Polar Functional Groups in Soap-Free Emulsion Polymerization of Styrene.

PubMed

Wang, Lu; Pan, Mingwang; Song, Shaofeng; Zhu, Lei; Yuan, Jinfeng; Liu, Gang

2016-08-09

Herein, we demonstrate a facile approach to prepare anisotropic poly(tert-butyl acrylate)/polystyrene (PtBA/PS) composite particles with controllable morphologies by soap-free seeded emulsion polymerization (SSEP). In the first step, noncrosslinked PtBA seeds with self-stabilizing polar functional groups (e.g., ester groups and radicals) are synthesized by soap-free emulsion polymerization. During the subsequent SSEP of styrene (St), PS bulges are nucleated on the PtBA seeds due to the microphase separation confined in the latex particles. The morphology evolution of PtBA/PS composite particles is tailored by varying the monomer/seed feed ratio, polymerization time, and polymerization temperature. Many intriguing morphologies, including hamburger-like, litchi-like, mushroom-like, strawberry-like, bowl-like, and snowman-like, have been acquired for PtBA/PS composite particles. The polar groups on the PtBA seed surface greatly influence the formation and further merging of PS/St bulges during the polymerization. A possible formation mechanism is proposed on the basis of experimental results. These complex composite particles are promising for applications in superhydrophobic coatings.

Environmental behavior and fate of methyl tert-butyl ether (MTBE)

USGS Publications Warehouse

Squillace, Paul J.; Pankow, James F.; Korte, Nic E.; Zogorski, John S.

1996-01-01

When gasoline that has been oxygenated with methyl tert-butyl ether (MTBE) comes in contact with water, large amounts of MTBE can dissolve; at 25 degrees Celsius the water solubility of MTBE is about 5,000 milligrams per liter for a gasoline that is 10 percent MTBE by weight. In contrast, for a nonoxygenated gasoline, the total hydrocarbon solubility in water is typically about 120 milligrams per liter. MTBE sorbs only weakly to soil and aquifer materials; therefore, sorption will not significantly retard MTBE's transport by ground water. In addition, MTBE generally resists degradation in ground water. The half-life of MTBE in the atmosphere can be as short as 3 days in a regional airshed. MTBE in the air tends to partition into atmospheric water, including precipitation. However, washout of gas-phase MTBE by precipitation would not, by itself, greatly alter the gas-phase concentration of the compound in the air. The partitioning of MTBE to precipitation is nevertheless strong enough to allow for up to 3 micrograms per liter or more inputs of MTBE to surface and ground water.

Methyl tert-butyl ether (MTBE) detected in abnormally high concentrations in postmortem blood and urine from two persons found dead inside a car containing a gasoline spill.

PubMed

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

2013-09-01

Two deep frozen persons, a female and a male, were found dead in a car. There had been an explosive fire inside the car which had extinguished itself. On the floor inside the car were large pools of liquid which smelled of gasoline. The autopsy findings and routine toxicological analyses could not explain the cause of death. Carboxyhemoglobin levels in the blood samples were <10%. Analysis with a headspace gas chromatography revealed methyl tert-butyl ether (MTBE) concentrations of 185 mg/L (female victim) and 115 mg/L (male victim) in peripheral blood. The urine MTBE concentrations were 150 mg/L and 256 mg/L, respectively. MTBE is a synthetic chemical which is added to gasoline as a fuel oxygenate. Gasoline poisoning is likely to be the cause of the death in these two cases, and MTBE can be a suitable marker of gasoline exposure, when other volatile components have vaporized. © 2013 American Academy of Forensic Sciences.

N-[2-(2,2-Di-methyl-propanamido)-pyrimidin-4-yl]-2,2-di-methyl-propanamide n-hexane 0.25-solvate hemihydrate.

PubMed

Ośmiałowski, Borys; Valkonen, Arto; Chęcińska, Lilianna

2013-10-05

The asymmetric unit of the title compound, C14H22N4O2·0.25C6H14·0.5H2O, contains two independent mol-ecules of 2,4-bis-(pivaloyl-amino)-pyrimidine (M) with similar conformations, one water mol-ecule and one-half n-hexane solvent mol-ecule situated on an inversion center. In one independent M mol-ecule, one of the two tert-butyl groups is rotationally disordered between two orientations in a 3:2 ratio. The n-hexane solvent mol-ecule is disordered between two conformations in the same ratio. The water mol-ecule bridges two independent M mol-ecules via O-H⋯O, N-H⋯O and O-H⋯N hydrogen bonds into a 2M·H2O unit, and these units are further linked by N-H⋯N hydrogen bonds into chains running in the [010] direction. Weak C-H⋯O inter-actions are observed between the adjacent chains.

Charge and Spin States in Schiff Base Metal Complexes with a Disiloxane Unit Exhibiting a Strong Noninnocent Ligand Character: Synthesis, Structure, Spectroelectrochemistry, and Theoretical Calculations.

PubMed

Cazacu, Maria; Shova, Sergiu; Soroceanu, Alina; Machata, Peter; Bucinsky, Lukas; Breza, Martin; Rapta, Peter; Telser, Joshua; Krzystek, J; Arion, Vladimir B

2015-06-15

Mononuclear nickel(II), copper(II), and manganese(III) complexes with a noninnocent tetradentate Schiff base ligand containing a disiloxane unit were prepared in situ by reaction of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 1,3-bis(3-aminopropyl)tetramethyldisiloxane followed by addition of the appropriate metal(II) salt. The ligand H2L resulting from these reactions is a 2:1 condensation product of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 1,3-bis(3-aminopropyl)tetramethyldisiloxane. The resulting metal complexes, NiL·0.5CH2Cl2, CuL·1.5H2O, and MnL(OAc)·0.15H2O, were characterized by elemental analysis, spectroscopic methods (IR, UV-vis, X-band EPR, HFEPR, (1)H NMR), ESI mass spectrometry, and single crystal X-ray diffraction. Taking into account the well-known strong stabilizing effects of tert-butyl groups in positions 3 and 5 of the aromatic ring on phenoxyl radicals, we studied the one-electron and two-electron oxidation of the compounds using both experimental (chiefly spectroelectrochemistry) and computational (DFT) techniques. The calculated spin-density distribution and localized orbitals analysis revealed the oxidation locus and the effect of the electrochemical electron transfer on the molecular structure of the complexes, while time-dependent DFT calculations helped to explain the absorption spectra of the electrochemically generated species. Hyperfine coupling constants, g-tensors, and zero-field splitting parameters have been calculated at the DFT level of theory. Finally, the CASSCF approach has been employed to theoretically explore the zero-field splitting of the S = 2 MnL(OAc) complex for comparison purposes with the DFT and experimental HFEPR results. It is found that the D parameter sign strongly depends on the metal coordination geometry.

Highly efficient enzymatic synthesis of tert-butyl (S)-6-chloro-5-hydroxy-3-oxohexanoate with a mutant alcohol dehydrogenase of Lactobacillus kefir.

PubMed

He, Xiu-Juan; Chen, Shao-Yun; Wu, Jian-Ping; Yang, Li-Rong; Xu, Gang

2015-11-01

tert-Butyl (S)-6-chloro-5-hydroxy-3-oxohexanoate ((S)-CHOH) is a valuable chiral synthon, which is used for the synthesis of the cholesterol-lowering drugs atorvastatin and rosuvastatin. To date, only the alcohol dehydrogenases from Lactobacillus brevis (LbADH) and Lactobacillus kefir (LkADH) have demonstrated catalytic activity toward the asymmetric reduction of tert-butyl 6-chloro-3,5-dioxohexanoate (CDOH) to (S)-CHOH. Herein, a tetrad mutant of LkADH (LkTADH), A94T/F147L/L199H/A202L, was screened to be more efficient in this bioreduction process, exhibiting a 3.7- and 42-fold improvement in specific activity toward CDOH (1.27 U/mg) over LbADH (0.34 U/mg) and wild-type LkADH (0.03 U/mg), respectively. The molecular basis for the improved catalytic activity of LkTADH toward CDOH was investigated using homology modeling and docking analysis. Two major issues had a significant impact on the biocatalytic efficiency of this process, including (i) the poor aqueous stability of the substrate and (ii) partial substrate inhibition. A fed-batch strategy was successfully developed to address these issues and maintain a suitably low substrate concentration throughout the entire process. Several other parameters were also optimized, including the pH, temperature, NADP(+) concentration and cell loading. A final CDOH concentration of 427 mM (100 g/L) gave (S)-CHOH in 94 % yield and 99.5 % e.e. after a reaction time of 38 h with whole cells expressing LkTADH. The space-time yield and turnover number of NADP(+) in this process were 10.6 mmol/L/h and 16,060 mol/mol, respectively, which were the highest values ever reported. This new approach therefore represents a promising alternative for the efficient synthesis of (S)-CHOH.

Biodegradation of buprofezin by Rhodococcus sp. strain YL-1 isolated from rice field soil.

PubMed

Li, Chao; Zhang, Ji; Wu, Zhi-Guo; Cao, Li; Yan, Xin; Li, Shun-Peng

2012-03-14

A buprofezin-degrading bacterium, YL-1, was isolated from rice field soil. YL-1 was identified as Rhodococcus sp. on the basis of the comparative analysis of 16S rDNA sequences. The strain could use buprofezin as the sole source of carbon and nitrogen for growth and was able to degrade 92.4% of 50 mg L(-1) buprofezin within 48 h in liquid culture. During the degradation of buprofezin, four possible metabolites, 2-tert-butylimino-3-isopropyl-1,3,5-thiadiazinan-4-one, N-tert-butyl-thioformimidic acid formylaminomethyl ester, 2-isothiocyanato-2-methyl-propane, and 2-isothiocyanato-propane, were identified using gas chromatography-mass spectrometry (GC-MS) analysis. The catechol 2,3-dioxygenase activity was strongly induced during the degradation of buprofezin. A novel microbial biodegradation pathway for buprofezin was proposed on the basis of these metabolites. The inoculation of soils treated with buprofezin with strain YL-1 resulted in a higher degradation rate than that observed in noninoculated soils, indicating that strain YL-1 has the potential to be used in the bioremediation of buprofezin-contaminated environments.

High temperature concrete composites containing organosiloxane crosslinked copolymers

DOEpatents

Zeldin, A.; Carciello, N.; Kukacka, L.; Fontana, J.

High temperature polymer concrete composites comprising about 10 to 30% by weight of a liquid monomer mixture is described. It consists essentially of an organosiloxane polymer crosslinked with an olefinically unsaturated monomer selected from the group consisting of styrene, methyl methacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, n-phenylmalimide, divinyl benzene and mixtures thereof. About 70 to 90% by weight of an inert inorganic filler system containing silica sand and portland cement, Fe/sub 2/O/sub 3/, carbon black or mixtures thereof. Optionally a free radical initiator such as di-tert-butyl peroxide, azobisisobyutyronitrile, benzoyl peroxide, lauryl peroxide and other organic peroxides are used to initiate crosspolymerization of the monomer mixture in the presence of the inorganic filler.

Unusual properties of aqueous solutions of L-proline: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Civera, Monica; Sironi, Maurizio; Fornili, Sandro L.

2005-11-01

Aqueous solutions of the bioprotectant proline are simulated for solute molar fractions ranging from 2.0 × 10 -3 to 2.3 × 10 -1. Statistical analyses show that proline affects the water structure more strongly than glycine betaine and trimethylamine- N-oxide, two of the most effective bioprotectants widely diffuse in nature, and as strongly as tert-butyl alcohol, a protein denaturant which at high concentration self-aggregates. No evidence is found, however, that proline self-aggregates as it has been previously suggested to explain experimental findings on concentrated proline solutions. Nevertheless, the behavior of the diffusion coefficients of proline and water vs. solute concentration qualitatively agrees with such results.

Regioselective alcoholysis of silychristin acetates catalyzed by lipases.

PubMed

Vavříková, Eva; Gavezzotti, Paolo; Purchartová, Kateřina; Fuksová, Kateřina; Biedermann, David; Kuzma, Marek; Riva, Sergio; Křen, Vladimír

2015-05-26

A panel of lipases was screened for the selective acetylation and alcoholysis of silychristin and silychristin peracetate, respectively. Acetylation at primary alcoholic group (C-22) of silychristin was accomplished by lipase PS (Pseudomonas cepacia) immobilized on diatomite using vinyl acetate as an acetyl donor, whereas selective deacetylation of 22-O-acetyl silychristin was accomplished by Novozym 435 in methyl tert-butyl ether/ n-butanol. Both of these reactions occurred without diastereomeric discrimination of silychristin A and B. Both of these enzymes were found to be capable to regioselective deacetylation of hexaacetyl silychristin to afford penta-, tetra- and tri-acetyl derivatives, which could be obtained as pure synthons for further selective modifications of the parent molecule.

Regioselective Alcoholysis of Silychristin Acetates Catalyzed by Lipases ‡

PubMed Central

Vavříková, Eva; Gavezzotti, Paolo; Purchartová, Kateřina; Fuksová, Kateřina; Biedermann, David; Kuzma, Marek; Riva, Sergio; Křen, Vladimír

2015-01-01

A panel of lipases was screened for the selective acetylation and alcoholysis of silychristin and silychristin peracetate, respectively. Acetylation at primary alcoholic group (C-22) of silychristin was accomplished by lipase PS (Pseudomonas cepacia) immobilized on diatomite using vinyl acetate as an acetyl donor, whereas selective deacetylation of 22-O-acetyl silychristin was accomplished by Novozym 435 in methyl tert-butyl ether/n-butanol. Both of these reactions occurred without diastereomeric discrimination of silychristin A and B. Both of these enzymes were found to be capable to regioselective deacetylation of hexaacetyl silychristin to afford penta-, tetra- and tri-acetyl derivatives, which could be obtained as pure synthons for further selective modifications of the parent molecule. PMID:26016503

Structural, optical and vibrational properties of self-assembled Pbn+1(Ti1−xFex)nO3n+1−δ Ruddlesden-Popper superstructures

PubMed Central

Doig, K. I.; Peters, J. J. P.; Nawaz, S.; Walker, D.; Walker, M.; Lees, M. R.; Beanland, R.; Sanchez, A. M.; McConville, C. F.; Palkar, V. R.; Lloyd-Hughes, J.

2015-01-01

Bulk crystals and thin films of PbTi1−xFexO3−δ (PTFO) are multiferroic, exhibiting ferroelectricity and ferromagnetism at room temperature. Here we report that the Ruddlesden-Popper phase Pbn+1(Ti1−xFex)nO3n+1−δ forms spontaneously during pulsed laser deposition of PTFO on LaAlO3 substrates. High-resolution transmission electron microscopy, x-ray diffraction and x-ray photoemission spectroscopy were utilised to perform a structural and compositional analysis, demonstrating that and . The complex dielectric function of the films was determined from far-infrared to ultraviolet energies using a combination of terahertz time-domain spectroscopy, Fourier transform spectroscopy, and spectroscopic ellipsometry. The simultaneous Raman and infrared activity of phonon modes and the observation of second harmonic generation establishes a non-centrosymmetric point group for Pbn+1(Ti0.5Fe0.5)nO3n+1−δ, a prerequisite for (but not proof of) ferroelectricity. No evidence of macroscopic ferromagnetism was found in SQUID magnetometry. The ultrafast optical response exhibited coherent magnon oscillations compatible with local magnetic order, and additionally was used to study photocarrier cooling on picosecond timescales. An optical gap smaller than that of BiFeO3 and long photocarrier lifetimes may make this system interesting as a ferroelectric photovoltaic. PMID:25591924

/sup 13/C NMR spectra of cyclic nitrones. 1. 2-substituted 4-methyl- and 4-phenyl-1-hydroxy-5,5-dimethyl-3-imidazoline 3-oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grigor'ev, I.A.; Martin, V.V.; Shchukin, G.I.

1985-08-01

The introduction of an N-oxide oxygen atom into azomethines leads to an upfield shift of the signals for the carbon atom of the C=N group in the /sup 13/C NMR spectra by 30-33 ppm. This is consistent with the increase in the electron density on this atom. The signal of the nitrone carbon atom is observed in the region of 140-147 ppm, depending on the nature of the substituent at the C/sub (2)/ atom of the 3-imidazoline 3-oxide ring.

Theoretical and Kinetic Tools for Selecting Effective Antioxidants: Application to the Protection of Omega-3 Oils with Natural and Synthetic Phenols

PubMed Central

Guitard, Romain; Nardello-Rataj, Véronique; Aubry, Jean-Marie

2016-01-01

Radical-scavenging antioxidants play crucial roles in the protection of unsaturated oils against autoxidation and, especially, edible oils rich in omega-3 because of their high sensitivity to oxygen. Two complementary tools are employed to select, among a large set of natural and synthetic phenols, the most promising antioxidants. On the one hand, density functional theory (DFT) calculations provide bond dissociation enthalpies (BDEs) of 70 natural (i.e., tocopherols, hydroxybenzoic and cinnamic acids, flavonoids, stilbenes, lignans, and coumarins) and synthetic (i.e., 2,6-di-tert-butyl-4-methylphenol (BHT), 3-tert-butyl-4-hydroxyanisol (BHA), and tert-butylhydroquinone (TBHQ)) phenols. These BDEs are discussed on the basis of structure–activity relationships with regard to their potential antioxidant activities. On the other hand, the kinetic rate constants and number of hydrogen atoms released per phenol molecule are measured by monitoring the reaction of phenols with 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical. The comparison of the results obtained with these two complementary methods allows highlighting the most promising antioxidants. Finally, the antioxidant effectiveness of the best candidates is assessed by following the absorption of oxygen by methyl esters of linseed oil containing 0.5 mmol L−1 of antioxidant and warmed at 90 °C under oxygen atmosphere. Under these conditions, some natural phenols namely epigallocatechin gallate, myricetin, rosmarinic and carnosic acids were found to be more effective antioxidants than α-tocopherol. PMID:27483242

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

PubMed

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

2010-01-01

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

Theoretical and Kinetic Tools for Selecting Effective Antioxidants: Application to the Protection of Omega-3 Oils with Natural and Synthetic Phenols.

PubMed

Guitard, Romain; Nardello-Rataj, Véronique; Aubry, Jean-Marie

2016-07-29

Radical-scavenging antioxidants play crucial roles in the protection of unsaturated oils against autoxidation and, especially, edible oils rich in omega-3 because of their high sensitivity to oxygen. Two complementary tools are employed to select, among a large set of natural and synthetic phenols, the most promising antioxidants. On the one hand, density functional theory (DFT) calculations provide bond dissociation enthalpies (BDEs) of 70 natural (i.e., tocopherols, hydroxybenzoic and cinnamic acids, flavonoids, stilbenes, lignans, and coumarins) and synthetic (i.e., 2,6-di-tert-butyl-4-methylphenol (BHT), 3-tert-butyl-4-hydroxyanisol (BHA), and tert-butylhydroquinone (TBHQ)) phenols. These BDEs are discussed on the basis of structure-activity relationships with regard to their potential antioxidant activities. On the other hand, the kinetic rate constants and number of hydrogen atoms released per phenol molecule are measured by monitoring the reaction of phenols with 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) radical. The comparison of the results obtained with these two complementary methods allows highlighting the most promising antioxidants. Finally, the antioxidant effectiveness of the best candidates is assessed by following the absorption of oxygen by methyl esters of linseed oil containing 0.5 mmol L(-1) of antioxidant and warmed at 90 °C under oxygen atmosphere. Under these conditions, some natural phenols namely epigallocatechin gallate, myricetin, rosmarinic and carnosic acids were found to be more effective antioxidants than α-tocopherol.

Preparation of Large-Diameter GaAs Crystals.

DTIC Science & Technology

1981-09-18

ionized impurity content for 40 n-type semi-insulating GaAs. Figure 17 Analysis (in wt %) of impurities in B203 after crystal growth 41 from PBN and quartz...encapsulant to the generation of defect clusters in LEC InP. (15 ) Statistics relative to the incidence of twinning for growth with dry ( ppm wt OH...and wet (> 1000 ppm wt OH) B203 are given in Fig. 5 for growths from fused-SiO 2 and PBN crucibles. A crystal is defined as having twinned if it

Fenton-driven regeneration of MTBE-spent granular activated carbon - Effects of particle size and Iron Amendment Procedures

EPA Science Inventory

Fenton-driven regeneration of spent granular activated carbon (GAC) is a technology being developed to regenerate organic contaminant-spent GAC. Here, the effect of GAC particle size (>2 mm to <0.35 mm) on Fenton-driven oxidation of methyl tert-butyl ether (MTBE)-spent GAC was ev...

Fenton-like Degradation of MTBE: Effects of Iron Counter Anion and Radical Scavengers

EPA Science Inventory

Fenton-driven oxidation of Methyl tert-butyl ether (MTBE) (0.11-0.16 mM) in batch reactors containing ferric iron (5 mM), hydrogen peroxide (H2O2) (6 mM) (pH=3) was performed to investigate MTBE transformation mechanisms. Independent variables included the form of iron (Fe) (Fe2(...

4,5-Dibromo-2,7-di-tert-butyl-9,9-dimethyl-9H-thioxanthene

PubMed Central

Rubio, Omayra H.; Fuentes de Arriba, Angel L.; Sanz, Francisca; Muniz, Francisco M.; Morán, Joaquín R.

2012-01-01

In the title compound, C23H28Br2S, the thioxanthene unit is twisted, showing a dihedral angle of 29.3 (5)° between the benzene rings. When projected along [001], the packing shows two types of channels. The crystal studied was a racemic twin. PMID:22719586

(Cryptand-222)potassium(+) (hydrogensulfido)[5,10,15,20-tetra­kis(2-pival­amido­phen­yl)porphyrinato]ferrate(II)

PubMed Central

Dhifet, Mondher; Belkhiria, Mohamed Salah; Daran, Jean-Claude; Nasri, Habib

2009-01-01

As part of a systematic investigation for a number of FeII porphyrin complexes used as biomimetic models for cytochrome P450, crystals of the title compound, [K(C18H36N2O6)][FeII(C64H64N8O4)(HS)], were prepared. The compound exhibits a non-planar conformation with major ruffling and saddling distortions. The average equatorial iron–pyrrole N atom [Fe—Np = 2.102 (2) Å] bond length and the distance between the FeII atom and the 24-atom core of the porphyrin ring (Fe—PC= 0.558 Å) are typical for high-spin iron(II) penta­coordinate porphyrinates. One of the tert-butyl groups in the structure is disordered over two sets with occupancies of 0.84 and 0.16. PMID:21583412

End Functionalized Nonionic Water-Dispersible Conjugated Polymers.

PubMed

Zhan, Ruoyu; Liu, Bin

2017-09-01

2,7-Dibromofluorene monomers carrying two or four oligo(ethylene glycol) (OEG) side chains are synthesized. Heck coupling between the monomers and 1,4-divinylbenzene followed by end capping with [4-(4-bromophenoxy)butyl]carbamic acid tert-butyl ester leads to two nonionic water-dispersible poly(fluorene-alt-1,4-divinylenephenylene)s end-functionalized with amine groups after hydrolysis. In water, the polymer with a lower OEG density (P1) has poor water dispersibility with a quantum yield of 0.24, while the polymer with a higher OEG density (P2) possesses excellent water-dispersibility with a high quantum yield of 0.45. Both polymers show fluorescence enhancement and blue-shifted absorption and emission maxima in the presence of surfactant sodium dodecyl sulfate and dodecyltrimethylammonium bromide. The polymers are also resistant to ionic strength with minimal nonspecific interactions to bovine serum albumin. When biotin is incorporated into the end of the polymer backbones through N-hydroxysuccinimide/amine coupling reaction, the biotinylated polymers interact specifically with streptavidin on solid surface. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Health assessment of gasoline and fuel oxygenate vapors: micronucleus and sister chromatid exchange evaluations.

PubMed

Schreiner, Ceinwen A; Hoffman, Gary M; Gudi, Ramadevi; Clark, Charles R

2014-11-01

Micronucleus and sister chromatid exchange (SCE) tests were performed for vapor condensate of baseline gasoline (BGVC), or gasoline with oxygenates, methyl tert-butyl ether (G/MTBE), ethyl tert butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), t-butyl alcohol (TBA), or ethanol (G/EtOH). Sprague Dawley rats (the same 5/sex/group for both endpoints) were exposed to 0, 2000, 10,000, or 20,000mg/m(3) of each condensate, 6h/day, 5days/week over 4weeks. Positive controls (5/sex/test) were given cyclophosphamide IP, 24h prior to sacrifice at 5mg/kg (SCE test) and 40mg/kg (micronucleus test). Blood was collected from the abdominal aorta for the SCE test and femurs removed for the micronucleus test. Blood cell cultures were treated with 5μg/ml bromodeoxyuridine (BrdU) for SCE evaluation. No significant increases in micronucleated immature erythrocytes were observed for any test material. Statistically significant increases in SCE were observed in rats given BGVC alone or in female rats given G/MTBE. G/TAME induced increased SCE in both sexes at the highest dose only. Although DNA perturbation was observed for several samples, DNA damage was not expressed as increased micronuclei in bone marrow cells. Inclusion of oxygenates in gasoline did not increase the effects of gasoline alone or produce a cytogenetic hazard. Copyright © 2014 Elsevier Inc. All rights reserved.

Glucagon-like Peptide-1 receptor signaling in the lateral parabrachial nucleus contributes to the control of food intake and motivation to feed.

PubMed

Alhadeff, Amber L; Baird, John-Paul; Swick, Jennifer C; Hayes, Matthew R; Grill, Harvey J

2014-08-01

Central glucagon-like peptide-1 receptor (GLP-1R) activation reduces food intake and the motivation to work for food, but the neurons and circuits mediating these effects are not fully understood. Although lateral parabrachial nucleus (lPBN) neurons are implicated in the control of food intake and reward, the specific role of GLP-1R-expressing lPBN neurons is unexplored. Here, neuroanatomical tracing, immunohistochemical, and behavioral/pharmacological techniques are used to test the hypothesis that lPBN neurons contribute to the anorexic effect of central GLP-1R activation. Results indicate that GLP-1-producing neurons in the nucleus tractus solitarius project monosynaptically to the lPBN, providing a potential endogenous mechanism by which lPBN GLP-1R signaling may exert effects on food intake control. Pharmacological activation of GLP-1R in the lPBN reduced food intake, and conversely, antagonism of GLP-1R in the lPBN increased food intake. In addition, lPBN GLP-1R activation reduced the motivation to work for food under a progressive ratio schedule of reinforcement. Taken together, these data establish the lPBN as a novel site of action for GLP-1R-mediated control of food intake and reward.

Theoretical study of chain transfer to solvent reactions of alkyl acrylates.

PubMed

Moghadam, Nazanin; Srinivasan, Sriraj; Grady, Michael C; Rappe, Andrew M; Soroush, Masoud

2014-07-24

This computational and theoretical study deals with chain transfer to solvent (CTS) reactions of methyl acrylate (MA), ethyl acrylate (EA), and n-butyl acrylate (n-BA) self-initiated homopolymerization in solvents such as butanol (polar, protic), methyl ethyl ketone (MEK) (polar, aprotic), and p-xylene (nonpolar). The results indicate that abstraction of a hydrogen atom from the methylene group next to the oxygen atom in n-butanol, from the methylene group in MEK, and from a methyl group in p-xylene by a live polymer chain are the most likely mechanisms of CTS reactions in MA, EA, and n-BA. Energy barriers and molecular geometries of reactants, products, and transition states are predicted. The sensitivity of the predictions to three hybrid functionals (B3LYP, X3LYP, and M06-2X) and three different basis sets (6-31G(d,p), 6-311G(d), and 6-311G(d,p)) is investigated. Among n-butanol, sec-butanol, and tert-butanol, tert-butanol has the highest CTS energy barrier and the lowest rate constant. Although the application of the conductor-like screening model (COSMO) does not affect the predicted CTS kinetic parameter values, the application of the polarizable continuum model (PCM) results in higher CTS energy barriers. This increase in the predicted CTS energy barriers is larger for butanol and MEK than for p-xylene. The higher rate constants of chain transfer to n-butanol reactions compared to those of chain transfer to MEK and p-xylene reactions suggest the higher CTS reactivity of n-butanol.

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

PubMed Central

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

2007-01-01

The utilization of the fuel oxygenate methyl tert-butyl ether (MTBE) and related compounds by microorganisms was investigated in a mainly theoretical study based on the YATP concept. Experiments were conducted to derive realistic maintenance coefficients and Ks values needed to calculate substrate fluxes available for biomass production. Aerobic substrate conversion and biomass synthesis were calculated for different putative pathways. The results suggest that MTBE is an effective heterotrophic substrate that can sustain growth yields of up to 0.87 g g−1, which contradicts previous calculation results (N. Fortin et al., Environ. Microbiol. 3:407-416, 2001). Sufficient energy equivalents were generated in several of the potential assimilatory routes to incorporate carbon into biomass without the necessity to dissimilate additional substrate, efficient energy transduction provided. However, when a growth-related kinetic model was included, the limits of productive degradation became obvious. Depending on the maintenance coefficient ms and its associated biomass decay term b, growth-associated carbon conversion became strongly dependent on substrate fluxes. Due to slow degradation kinetics, the calculations predicted relatively high threshold concentrations, Smin, below which growth would not further be supported. Smin strongly depended on the maximum growth rate μmax, and b and was directly correlated with the half maximum rate-associated substrate concentration Ks, meaning that any effect impacting this parameter would also change Smin. The primary metabolic step, catalyzing the cleavage of the ether bond in MTBE, is likely to control the substrate flux in various strains. In addition, deficits in oxygen as an external factor and in reduction equivalents as a cellular variable in this reaction should further increase Ks and Smin for MTBE. PMID:17220260

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

PubMed Central

Hartle, R

1993-01-01

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

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

PubMed

Hartle, R

1993-12-01

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)

Oxidative and proteolysis-related parameters of skeletal muscle from hamsters with experimental pulmonary emphysema: a comparison between papain and elastase induction.

PubMed

Brunnquell, Cláudia R; Vieira, Nichelle A; Sábio, Laís R; Sczepanski, Felipe; Cecchini, Alessandra L; Cecchini, Rubens; Guarnier, Flávia A

2015-06-01

The objective of this study was to investigate whether emphysema induced by elastase or papain triggers the same effects on skeletal muscle, related to oxidative stress and proteolysis, in hamsters. For this purpose, we evaluated pulmonary lesions, body weight, muscle loss, oxidative stress (thiobarbituric acid-reactive substances, total and oxidized glutathiones, chemiluminescence stimulated by tert-butyl hydroperoxide and carbonyl proteins), chymotrypsin-like and calpain-like proteolytic activities and muscle fibre cross-sectional area in the gastrocnemius muscles of emphysemic hamsters. Two groups of animals received different intratracheal inductions of experimental emphysema: by 40 mg/ml papain (EP) or 5.2 IU/100 g animal (EE) elastase (n = 10 animals/group). The control group received intratracheal instillation of 300 μl sterile NaCl 0.9%. Compared with the control group, the EP group had reduced muscle weight (18.34%) and the EE group had increased muscle weight (8.37%). Additionally, tert-butyl hydroperoxide-initiated chemiluminescence, carbonylated proteins and chymotrypsin-like proteolytic activity were all elevated in the EP group compared to the CS group, while total glutathione was decreased compared to the EE group. The EE group showed more fibres with increased cross-sectional areas and increased calpain-like activity. Together, these data show that elastase and papain, when used to induce experimental models of emphysema, lead to different speeds and types of adaptation. These findings provide more information on choosing a suitable experimental model for studying skeletal muscle adaptations in emphysema. © 2015 The Authors. International Journal of Experimental Pathology © 2015 International Journal of Experimental Pathology.

Cancer-induced anorexia and malaise are mediated by CGRP neurons in the parabrachial nucleus.

PubMed

Campos, Carlos A; Bowen, Anna J; Han, Sung; Wisse, Brent E; Palmiter, Richard D; Schwartz, Michael W

2017-07-01

Anorexia is a common manifestation of chronic diseases, including cancer. Here we investigate the contribution to cancer anorexia made by calcitonin gene-related peptide (CGRP) neurons in the parabrachial nucleus (PBN) that transmit anorexic signals. We show that CGRP PBN neurons are activated in mice implanted with Lewis lung carcinoma cells. Inactivation of CGRP PBN neurons before tumor implantation prevents anorexia and loss of lean mass, and their inhibition after symptom onset reverses anorexia. CGRP PBN neurons are also activated in Apc min/+ mice, which develop intestinal cancer and lose weight despite the absence of reduced food intake. Inactivation of CGRP PBN neurons in Apc min/+ mice permits hyperphagia that counteracts weight loss, revealing a role for these neurons in a 'nonanorexic' cancer model. We also demonstrate that inactivation of CGRP PBN neurons prevents lethargy, anxiety and malaise associated with cancer. These findings establish CGRP PBN neurons as key mediators of cancer-induced appetite suppression and associated behavioral changes.

Four coordination polymers based on 5-tert-butyl isophthalic acid and rigid bis(imidazol-1yl)benzene linkers: Synthesis, luminescence detection of acetone and optical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arıcı, Mürsel, E-mail: marici@ogu.edu.tr; Zafer Yeşilel, Okan; Büyükgüngör, Orhan

Four coordination polymers including, [Co(µ-Htbip){sub 2}(µ-dib)]{sub n} (1), [Co(µ-tbip)(µ-dmib){sub 0.5}]{sub n} (2), [Zn{sub 2}(µ-tbip)(µ{sub 3}-tbip)(µ-dmib){sub 1.5}]{sub n} (3) and [Cd(µ{sub 3}-tbip)(µ-dib){sub 0.5} (H{sub 2}O)]{sub n} (4) (tbip: 5-tert-butylisophthalate, dib: 1,4-bis(imidazol-1yl)benzene, dmib: 1,4-bis(imidazol-1yl)-2,5-dimethylbenzene), were hydrothermally synthesized and characterized by elemental analysis, IR spectra, single crystal and powder X-ray diffraction and thermal analysis (TG/DTA). The structural diversity is observed depending on ligands and coordination number of metal centers in the synthesized complexes. The tbip ligand displayed five different coordination modes in its complexes. In 1 and 2, complex 1 is 3D framework with the dia topology while complex 2 has 2D structuremore » with the sql topology depending on coordination geometries of Co ions. Complex 3 is 3D framework with the fsh 4,6-conn topology and complex 4 has 2D 4-connected sql topology. Photoluminescent properties of complex 3 dispersed in various organic solvents were investigated and the results showed that 3 dispersed in methanol could be used as a fluorescent sensor for the detection of acetone. Moreover, thermal and optical properties of the complexes were also studied. - Graphical abstract: Four coordination polymers were hydrothermally synthesized and characterized by various techniques. The complexes showed the structural diversity depending on ligands and coordination number of metal centers. The tbip ligand displayed four different coordination modes in its complexes. In 1 and 2, complexes 1 and 2 are 3D and 2D structures with the dia and sql topologies depending on coordination geometries of Co ions, respectively. Complexes 3 and 4 are 3D and 2D structures with the fsh 4,6-conn and sql topology, respectively. Photoluminescent properties of complex 3 dispersed in various organic solvents were investigated and the results showed that 3 dispersed in methanol could be used as a fluorescent sensor for the detection of acetone. Moreover, thermal and optical properties of the complexes were also studied. - Highlights: • Four new 2D and 3D coordination polymers with 5-tert-butyl isophthalic acid and rigid bis(imidazol-1yl)benzene linkers. • The structural diversity depending on ligands and coordination number of metal centers. • Fluorescent sensor for the detection of acetone.« less

Synthesis of Polystyrene and Molecular Weight Determination by [superscript 1]H NMR End-Group Analysis

ERIC Educational Resources Information Center

Wackerly, Jay Wm.; Dunne, James F.

2017-01-01

A procedure for the solution polymerization of styrene using di-"tert"-butyl peroxide (DTBP) as the initiator is described. The use of DTBP allows for end-group analysis by [superscript 1]H NMR spectroscopy and calculation of the number-average molecular weight of the polymer. This experiment was designed as a laboratory introduction to…

40 CFR 799.5000 - Testing consent orders for substances and mixtures with Chemical Abstract Service Registry Numbers.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Environmental Releases Report November 18, 1994. 112-35-6 Triethylene glycol monomethyl ether Health effects... Health effects November 23, 1993. 994-05-8 Tertiary-amyl methyl ether Health effects March 21, 1995. 1634-04-4 Methyl tert-butyl ether Health effects March 31, 1988. 2461-18-9 Lauryl glycidyl ether 1 Health...

[Occupational exposure to methyl tert-butyl ether (MTBE) at an oil refinery].

PubMed

Perbellini, L; Pasini, F; Prigioni, P; Rosina, A

2003-01-01

Methyl tert-butyl ether (MTBE) is widely used as an additive to gasoline, to increase oxygen content and reduce tailpipe emission of carbon monoxide. Our research dealt with 37 refinery workers in order to measure their occupational exposure to MTBE during two different seasonal periods. They provided blood and urine samples before and after a work shift during which they wore an active charcoal sampler for solvents. All samples were analysed by a gas-chromatograph equipped with a mass spectrometer detector. The concentration in air of MTBE was very low (median: 25 micrograms/m3 in spring and 5 micrograms/m3 in autumn). The blood and urine concentrations of MTBE at the end of the work shift were higher than those found before the shift. The increment in biological samples confirmed a small intake of MTBE by refinery workers: the biological monitoring of occupational exposure to this solvent yielded reliable results. Blood and urinary concentrations of MTBE obtained from workers split in relation to their smoking habit did not give a statistic significance to say that cigarette smoke is not a confusion factor in monitoring exposure to MTBE.

Detection of non-absorbing charge dynamics via refractive index change in dye-sensitized solar cells.

PubMed

Kuwahara, Shota; Hata, Hiroaki; Taya, Soichiro; Maeda, Naotaka; Shen, Qing; Toyoda, Taro; Katayama, Kenji

2013-04-28

The carrier dynamics in dye-sensitized solar cells was investigated by using the transient grating, in addition to the transient absorption method and transient photocurrent method on the order of microseconds to seconds. The signals for the same sample were obtained under a short-circuit condition to compare the carrier dynamics via refractive index change with the transient photocurrent measurement. Optically silent carrier dynamics by transient absorption have been successfully observed via a refractive index change. The corresponding signal components were originated from the charge dynamics at the solid/liquid interface, especially on the liquid side; rearrangement or diffusion motion of charged redox species occurred when the injected electrons were trapped at the TiO2 surface and when the electron-electrolyte recombination occurred at the interface. The assignments were confirmed from the dependence on the viscosity of the solvent and the presence of 4-tert-butyl pyridine. As the viscosity of the solvent increased, the rearrangement and the motion of the charged redox species were delayed. Since the rearrangement dynamics was changed by the presence of 4-tert-butyl pyridine, it affected not only the TiO2 surface but also the redox species close to the interface.

Production of o-diphenols by immobilized mushroom tyrosinase.

PubMed

Marín-Zamora, María Elisa; Rojas-Melgarejo, Francisco; García-Cánovas, Francisco; García-Ruiz, Pedro Antonio

2009-01-15

The o-diphenols 4-tert-butyl-catechol, 4-methyl-catechol, 4-methoxy-catechol, 3,4-dihydroxyphenylpropionic acid and 3,4-dihydroxyphenylacetic acid were produced from the corresponding monophenols (4-tert-butyl-phenol, 4-methyl-phenol, 4-methoxy-phenol, p-hydroxyphenylpropionic acid and p-hydroxyphenylacetic acid) using immobilized mushroom tyrosinase from Agaricus bisporus. In all cases the yield was R(diphenol)> or =88-96%, which, according to the literature, is the highest yield so far, obtained using tyrosinase. The reaction was carried out in 0.5M borate buffer pH 9.0 which was used to minimize the diphenolase activity of tyrosinase by complexing the o-diphenols generated. Hydroxylamine and ascorbic acid were also present in the reaction medium, the former being used to reduce mettyrosinase to deoxytyrosinase, closing the catalytic cycle, and the latter to reduce the o-quinone produced to o-diphenol. Inactivation of the tyrosinase by ascorbic acid was also minimized due to the formation of an ascorbic acid-borate complex. Concentrations of the o-diphenolic compounds obtained at several reaction times were determined by gas chromatography-mass spectrometry (GC-MS) and UV-vis spectroscopy. The experimental results are discussed.

The fate of MtBE during Fenton-like treatments through laboratory scale column tests.

PubMed

Piscitelli, Daniela; Zingaretti, Daniela; Verginelli, Iason; Gavasci, Renato; Baciocchi, Renato

2015-12-01

In Situ Chemical Oxidation (ISCO) based on the Fenton's process is a proven technology for the treatment of groundwater contaminated by organic compounds. Nevertheless, the application of this treatment process to methyl tert-butyl ether (MtBE) is questioned, as there are concerns about its capacity to achieve complete mineralization. Many existing studies have focused on water contaminated by MtBE and are thus not representative of in situ treatments since they do not consider the presence of soil. In this work, the effectiveness of a Fenton-like process for MtBE treatment was proven in soil column tests performed at operating conditions (i.e., oxidant and contaminant concentration and flow rates) resembling those typically used for in situ applications. No MtBE by-products were detected in any of the tested conditions, thus suggesting that the tert-butyl group of MtBE was completely degraded. A mass balance based on the CO2 produced was used as evidence that most of the MtBE removed was actually mineralized. Finally, the obtained results show that preconditioning of soil with a chelating agent (EDTA) significantly enhanced MtBE oxidation. Copyright © 2015 Elsevier B.V. All rights reserved.

New fluorescent perylene bisimide indicators--a platform for broadband pH optodes.

PubMed

Aigner, Daniel; Borisov, Sergey M; Klimant, Ingo

2011-06-01

Asymmetric perylene bisimide (PBI) dyes are prepared and are shown to be suitable for the preparation of fluorescence chemosensors for pH. They carry one amino-functional substituent which introduces pH sensitivity via photoinduced electron transfer (PET) while the other one increases solubility. The luminescence quantum yields for the new indicators exceed 75% in the protonated form. The new indicators are non-covalently entrapped in polyurethane hydrogel D4 and poly(hydroxyalkylmethacrylates). Several PET functions including aliphatic and aromatic amino groups were successfully used to tune the dynamic range of the sensor. Because of their virtually identical spectral properties, various PBIs with selected PET functions can easily be integrated into a single sensor with enlarged dynamic range (over 4 pH units). PBIs with two different substitution patterns in the bay position are investigated and possess variable spectral properties. Compared with their tetrachloro analogues, tetra-tert-butyl-substituted PBIs yield more long-wave excitable sensors which feature excellent photostability. Cross-sensitivity to ionic strength was found to be negligible. The practical applicability of the sensors may be compromised by the long response times (especially in case of tetra-tert-butyl-substituted PBIs).

Determination of organic peroxides by liquid chromatography with on-line post-column ultraviolet irradiation and peroxyoxalate chemiluminescence detection.

PubMed

Wada, Mitsuhiro; Inoue, Keiyu; Thara, Ayuko; Kishikawa, Naoya; Nakashima, Kenichiro; Kuroda, Naotaka

2003-02-14

A HPLC method was developed for the simultaneous determination of organic peroxides and hydrogen peroxide with peroxyoxalate chemiluminescence (PO-CL) detection following on-line UV irradiation. Organic peroxides [i.e., benzoyl peroxide (BP), tert.-butyl hydroperoxide (BHP), tert.-butyl perbenzoate (BPB), cumene hydroperoxide (CHP)] were UV irradiated (254 nm, 15 W) to generate hydrogen peroxide, which was determined by PO-CL detection. The conditions for UV irradiation and PO-CL detection were optimized by a flow injection analysis (FIA) system. Generation of hydrogen peroxide from peroxides with on-line UV irradiation also was confirmed by the FIA system by incorporating an enzyme column reactor immobilized with catalase. The separation of four organic peroxides and hydrogen peroxide by HPLC was accomplished isocratically on an ODS column within 30 min. The detection limits (signal-to-noise ratio=3) were 1.1 microM for hydrogen peroxide, 6.8 microM for BP, 31.3 microM for BHP, 7.5 microM for BPB and 1.3 microM for CHP. The proposed method was applied to the determination of BP in wheat flour.

FT-IR and Raman vibrational analysis, B3LYP and M06-2X simulations of 4-bromomethyl-6-tert-butyl-2H-chromen-2-one

NASA Astrophysics Data System (ADS)

Sert, Yusuf; Puttaraju, K. B.; Keskinoğlu, Sema; Shivashankar, K.; Ucun, Fatih

2015-01-01

In this study, the experimental and theoretical vibrational frequencies of a newly synthesized bacteriostatic and anti-tumor molecule namely, 4-bromomethyl-6-tert-butyl-2H-chromen-2-one have been investigated. The experimental FT-IR (4000-400 cm-1) and Raman spectra (4000-100 cm-1) of the compound in solid phase have been recorded. The theoretical vibrational frequencies and optimized geometric parameters have been calculated using density functional theory (DFT/B3LYP: Becke, 3-parameter, Lee-Yang-Parr and DFT/M06-2X: highly parametrized, empirical exchange correlation function) with 6-311++G(d, p) basis set by Gaussian 03 software, for the first time. The assignments of the vibrational frequencies have been done by potential energy distribution (PED) analysis using VEDA 4 software. The theoretical optimized geometric parameters and vibrational frequencies have been found to be in good agreement with the corresponding experimental data and results in the literature. In addition, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy and the other related molecular energy values of the compound have been investigated using the same theoretical calculations.

Bacopa monnieri protects SH-SY5Y cells against tert-Butyl hydroperoxide-induced cell death via the ERK and PI3K pathways.

PubMed

Petcharat, Kanoktip; Singh, Meharvan; Ingkaninan, Kornkanok; Attarat, Jongrak; Yasothornsrikul, Sukkid

2015-01-01

Oxidative stress plays an important role in the pathological processes of various neurodegenerative diseases. Bacopa monnieri (BM) has a potent antioxidant property. Therefore, the purpose of this study was to evaluate the neuroprotective potential of BM against SH-SY5Y neuroblastoma cell death induced by the pro-oxidant insult, tert -Butyl hydroperoxide (TBHP), and to identify possible mechanisms related to its neuroprotective action. The neuroprotective effect of BM was evaluated by the degree of protection against TBHP-induced cell death in human SH-SY5Y cells that was measured by calcein-AM assay. ERK1/2 and Akt phosphorylation was evaluated by immunoblotting. We found that BM exhibited protection against TBHP-mediated cytotoxicity. The neuroprotective effect of BM was abolished in the presence of either ERK1/2 or PI3K inhibitors. In addition, western blotting with anti-phospho-ERK1/2 and anti-phospho-Akt antibodies showed that BM increased both ERK1/2 and Akt phosphorylation. These results suggest that BM by activation of ERK/MAPK and PI3K/Akt signaling pathways protects SH-SY5Y cells from TBHP-induced cell death.

Polypyrrole-Grafted Coconut Shell Biological Carbon as a Potential Adsorbent for Methyl Tert-Butyl Ether Removal: Characterization and Adsorption Capability

PubMed Central

Li, Shanshan; Qian, Keke; Wang, Shan; Liang, Kaiqiang; Yan, Wei

2017-01-01

Methyl tert-butyl ether (MTBE) has been used as a common gasoline additive worldwide since the late twentieth century, and it has become the most frequently detected groundwater pollutant in many countries. This study aimed to synthesize a novel microbial carrier to improve its adsorptive capacity for MTBE and biofilm formation, compared to the traditional granular activated carbon (GAC). A polypyrrole (PPy)-modified GAC composite (PPy/GAC) was synthesized, and characterized by Fourier transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) surface area analysis. The adsorption behaviors of MTBE were well described by the pseudo-second-order and Langmuir isotherm models. Furthermore, three biofilm reactors were established with PPy/GAC, PPy, and GAC as the carriers, respectively, and the degradation of MTBE under continuous flow was investigated. Compared to the biofilm reactors with PPy or GAC (which both broke after a period of operation), the PPy/GAC biofilm column produced stable effluents under variable treatment conditions with a long-term effluent MTBE concentration <20 μg/L. Pseudomonas aeruginosa and Acinetobacter pittii may be the predominant bacteria responsible for MTBE degradation in these biofilm reactors. PMID:28125030

Antichaperone activity and heme degradation effect of methyl tert-butyl ether (MTBE) on normal and diabetic hemoglobins.

PubMed

Najdegerami, Ismaeil Hossein; Maghami, Parvaneh; Sheikh-Hasani, Vahid; Hosseinzadeh, Ghader; Sheibani, Nader; Moosavi-Movahedi, Ali A

2017-05-01

Because of the extensive use of methyl tert-butyl ether (MTBE) as an additive to increase the octane quality of gasoline, the environmental pollution by this compound has increased in recent decades. Environmental release of MTBE may lead to its entry to the blood stream through inhalation or drinking of contaminated water, and its interactions with biological molecules such as proteins. The present study was proposed to comparatively investigate the interactions of MTBE with hemoglobin (Hb) from diabetic and nondiabetic individuals using various spectroscopic methods including UV-visible, fluorescence, chemiluminescence, and circular dichroism. These results demonstrated the effects of MTBE on heme degradation of Hb and the reaction of these degradation products with water generating reactive oxygen species. Interaction of Hb with MTBE enhanced its aggregation rate and decreased lag time, indicating the antichaperone activity of MTBE upon interaction with Hb. Furthermore, the diabetic Hb showed more severe effects of MTBE, including heme degradation, reactive oxygen species production, unfolding, and antichaperone behavior than the nondiabetic Hb. The results from molecular docking suggested that the special interaction site of MTBE in the vicinity of Hb heme group is responsible for heme degradation. Copyright © 2016 John Wiley & Sons, Ltd.

Direct nuclear magnetic resonance observation of odorant binding to mouse odorant receptor MOR244-3.

PubMed

Burger, Jessica L; Jeerage, Kavita M; Bruno, Thomas J

2016-06-01

Mammals are able to perceive and differentiate a great number of structurally diverse odorants through the odorant's interaction with odorant receptors (ORs), proteins found within the cell membrane of olfactory sensory neurons. The natural gas industry has used human olfactory sensitivity to sulfur compounds (thiols, sulfides, etc.) to increase the safety of fuel gas transport, storage, and use through the odorization of this product. In the United States, mixtures of sulfur compounds are used, but the major constituent of odorant packages is 2-methylpropane-2-thiol, also known as tert-butyl mercaptan. It has been fundamentally challenging to understand olfaction and odorization due to the low affinity of odorous ligands to the ORs and the difficulty in expressing a sufficient number of OR proteins. Here, we directly observed the binding of tert-butyl mercaptan and another odiferous compound, cis-cyclooctene, to mouse OR MOR244-3 on living cells by saturation transfer difference (STD) nuclear magnetic resonance (NMR) spectroscopy. This effort lays the groundwork for resolving molecular mechanisms responsible for ligand binding and resulting signaling, which in turn will lead to a clearer understanding of odorant recognition and competition. Published by Elsevier Inc.

High temperature concrete composites containing organosiloxane crosslinked copolymers

DOEpatents

Zeldin, Arkady; Carciello, Neal; Kukacka, Lawrence; Fontana, Jack

1980-01-01

This invention relates to high temperature polymer concrete composites comprising about 10-30% by weight of a liquid monomer mixture consisting essentially of an organosiloxane polymer crosslinked with an olefinically unsaturated monomer selected from the group consisting of styrene, methyl methacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, n-phenylmalimide, divinyl benzene and mixtures theroef; and about 70-90% by weight of an inert inorganic filler system containing silica sand and preferably a member selected from the group consisting of portland cement, Fe.sub.2 O.sub.3, carbon black and mixtures thereof; and optionally a free radical initiator such as di-tert-butyl peroxide, azobisisobutyronitrile, benzoyl peroxide, lauryl peroxide and other organic peroxides to initiate crosspolymerization of the monomer mixture in the presence of the inorganic filler.

Enantioselective Synthesis of Chiral α-Azido and α-Aryloxy Quaternary Stereogenic Centers via the Phase-Transfer-Catalyzed α-Alkylation of α-Bromomalonates, Followed by SN2 Substitution.

PubMed

Kim, Doyoung; Ha, Min Woo; Hong, Suckchang; Park, Cheonhyoung; Kim, Byungsoo; Yang, Jewon; Park, Hyeung-Geun

2017-05-05

A new efficient synthetic method for chiral α-azido-α-alkylmalonates and α-aryloxy-α-alkylmalonates was developed. The enantioselective α-alkylation of diphenylmethyl tert-butyl α-bromomalonate under phase-transfer catalytic conditions [(S,S)-3,4,5-trifluorophenyl-NAS bromide, 50% KOH, toluene, and -40 °C) provided the corresponding α-bromo-α-alkylmalonates in high chemical yields (≤98%) and high optical yields (≤99% ee). The resulting α-alkylated products were converted to α-azido-α-alkylmalonates (≤96%, ≤97% ee) and α-aryloxy-α-alkylmalonates (≤79%, ≤93% ee) by S N 2 substitution with sodium azide and aryloxides, respectively.

Identification and characterization of N-tert-butoxycarbonyl-MDMA: a new MDMA precursor.

PubMed

Collins, Michael; Donnelly, Christopher; Cameron, Shane; Tahtouh, Mark; Salouros, Helen

2017-03-01

In September 2015, 80 litres of a viscous, light-red liquid, described as hair product, was seized by the Australian Border Force (ABF). Initial testing by ABF indicated that the liquid was the 3,4-methylenedioxymethamphetamine (MDMA) precursor chemical safrole and custody of the material was transferred to the Australian Federal Police (AFP) who coordinated all subsequent investigations. Initial gas chromatography-mass spectrometry (GC-MS) analysis by the AFP indicated that the material was not safrole and samples of the liquid were transferred to the National Measurement Institute Australia (NMIA) for identification. Using a combination of nuclear magnetic resonance spectroscopy (NMR), GC-MS, infrared spectroscopy, and synthesis, the unknown substance was identified as N-tert.-butoxycarbonyl-MDMA (t-BOC-MDMA). The substance was also converted in high yield to MDMA (aqueous HCl, 80 °C, 30 min). The possibility that the t-BOC-MDMA may act as a pro-drug following ingestion was explored by exposure to simulated gastric juice (pH 1.5) and monitored by NMR (37 °C) at various intervals. The majority of t-BOC-MDMA was converted to MDMA after 305 min, which suggested that this derivatized form might serve as a pro-drug in vivo. An investigation into the chemistry of potential pro-drugs showed that t-BOC derivatives of methamphetamine, pseudoephedrine and 4-methylmethcahtinone (mephedrone) could also be prepared using di-tert.-butyl dicarbonate. The appearance of t-BOC-derivatives on the drug market requires further monitoring. © 2016 Commonwealth of Australia. Drug Testing and Analysis © 2016 John Wiley & Sons, Ltd. © 2016 Commonwealth of Australia. Drug Testing and Analysis © 2016 John Wiley & Sons, Ltd.

Development and application of a rat PBPK model to elucidate kidney and liver effects induced by ETBE and tert-butanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salazar, Keith D., E-mail: Salazar.keith@epa.gov; Brinkerhoff, Christopher J., E-mail: Brinkerhoff.Chris@epa.gov; Lee, Janice S., E-mail: Lee.JaniceS@epa.gov

Subchronic and chronic studies in rats of the gasoline oxygenates ethyl tert-butyl ether (ETBE) and tert-butanol (TBA) report similar noncancer kidney and liver effects but differing results with respect to kidney and liver tumors. Because TBA is a major metabolite of ETBE, it is possible that TBA is the active toxic moiety in all these studies, with reported differences due simply to differences in the internal dose. To test this hypothesis, a physiologically-based pharmacokinetic (PBPK) model was developed for ETBE and TBA to calculate internal dosimetrics of TBA following either TBA or ETBE exposure. This model, based on earlier PBPKmore » models of methyl tert-butyl ether (MTBE), was used to evaluate whether kidney and liver effects are consistent across routes of exposure, as well as between ETBE and TBA studies, on the basis of estimated internal dose. The results demonstrate that noncancer kidney effects, including kidney weight changes, urothelial hyperplasia, and chronic progressive nephropathy (CPN), yielded consistent dose–response relationships across routes of exposure and across ETBE and TBA studies using TBA blood concentration as the dose metric. Relative liver weights were also consistent across studies on the basis of TBA metabolism, which is proportional to TBA liver concentrations. However, kidney and liver tumors were not consistent using any dose metric. These results support the hypothesis that TBA mediates the noncancer kidney and liver effects following ETBE administration; however, additional factors besides internal dose are necessary to explain the induction of liver and kidney tumors. - Highlights: • We model two metabolically-related fuel oxygenates to address toxicity data gaps. • Kidney and liver effects are compared on an internal dose basis. • Noncancer kidney effects are consistent using TBA blood concentration. • Liver weight changes are consistent using TBA metabolic rate. • Kidney and liver tumors are not consistent using any internal dose metric.« less

Oxidative desulfurization-fluorination of thioethers. Application for the synthesis of fluorinated nitrogen containing building blocks.

PubMed

Hugenberg, Verena; Fröhlich, Roland; Haufe, Günter

2010-12-21

An oxidative desulfurization-fluorination protocol has been used to synthesize (2S)-2-(difluoromethyl)-N-tosylpyrrolidine (6a) and (2S)-2-(trifluoromethyl)-N-tosylpyrrolidine (7a) from the (2S)-prolinol-derived (2S)-2-(4-chlorophenylthiomethyl)-N-tosylpyrrolidine (9) or (2S)-2-(dithian-2-yl)-N-tosylpyrrolidine (5). Efforts to prepare 3,3-difluoroalanine similarly from an N-protected S-aryl-cysteine ester 17 gave only traces of the target compound 18. Instead, an unique N-(α,α-difluorobenzyl)-N-α',α'-dibromoglycine ester 19 was formed by an unprecedented sequence of reaction steps. A plausible mechanism is suggested involving a sulfur-assisted deoxygenation-difluorination of an imino oxygen and a haloform reaction like carbon-carbon bond fission as key-steps. Efforts to prepare (2S)-2-(fluoromethyl)-N-tosylpyrrolidine (12) from (2S)-N-tosylprolinol (3) by treatment with Fluolead™ (1-tert-butyl-4-trifluorosulfanyl-3,5-dimethylbenzene) gave only 5% of the target compound, but 95% of (3R)-3-fluoro-N-tosylpiperidine (11a) by ring enlargement.

Release of drinking water contaminants and odor impacts caused by green building cross-linked polyethylene (PEX) plumbing systems.

PubMed

Kelley, Keven M; Stenson, Alexandra C; Dey, Rajarashi; Whelton, Andrew J

2014-12-15

Green buildings are increasingly being plumbed with crosslinked polyethylene (PEX) potable water pipe. Tap water quality was investigated at a six month old plumbing system and chemical and odor quality impacts of six PEX pipe brands were examined. Eleven PEX related contaminants were found in the plumbing system; one regulated (toluene) and several unregulated: Antioxidant degradation products, resin solvents, initiator degradation products, or manufacturing aides. Water chemical and odor quality was monitored for new PEX-a, -b and -c pipes with (2 mg/L free chlorine) and without disinfectant over 30 days. Odor and total organic carbon (TOC) levels decreased for all pipes, but odor remained greater than the USA's Environmental Protection Agency's (USEPA) secondary maximum contaminant level. Odors were not attributed to known odorants ethyl-tert-butyl ether (ETBE) or methyl-tert-butyl ether (MTBE). Free chlorine caused odor levels for PEX-a1 pipe to increase from 26 to 75 threshold odor number (TON) on day 3 and affected the rate at which TOC changed for each brand over 30 days. As TOC decreased, the ultraviolet absorbance at 254 nm increased. Pipes consumed as much as 0.5 mg/L as Cl2 during each 3 day stagnation period. Sixteen organic chemicals were identified, including toluene, pyridine, methylene trichloroacetate and 2,4-di-tert-butylphenol. Some were also detected during the plumbing system field investigation. Six brands of PEX pipes sold in the USA and a PEX-a green building plumbing system impacted chemical and drinking water odor quality. Copyright © 2014 Elsevier Ltd. All rights reserved.

MTBE, TBA, and TAME attenuation in diverse hyporheic zones.

PubMed

Landmeyer, James E; Bradley, Paul M; Trego, Donald A; Hale, Kevin G; Haas, Joseph E

2010-01-01

Groundwater contamination by fuel-related compounds such as the fuel oxygenates methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), and tert-amyl methyl ether (TAME) presents a significant issue to managers and consumers of groundwater and surface water that receives groundwater discharge. Four sites were investigated on Long Island, New York, characterized by groundwater contaminated with gasoline and fuel oxygenates that ultimately discharge to fresh, brackish, or saline surface water. For each site, contaminated groundwater discharge zones were delineated using pore water geochemistry data from 15 feet (4.5 m) beneath the bottom of the surface water body in the hyporheic zone and seepage-meter tests were conducted to measure discharge rates. These data when combined indicate that MTBE, TBA, and TAME concentrations in groundwater discharge in a 5-foot (1.5-m) thick section of the hyporheic zone were attenuated between 34% and 95%, in contrast to immeasurable attenuation in the shallow aquifer during contaminant transport between 0.1 and 1.5 miles (0.1 to 2.4 km). The attenuation observed in the hyporheic zone occurred primarily by physical processes such as mixing of groundwater and surface water. Biodegradation also occurred as confirmed in laboratory microcosms by the mineralization of U- (14)C-MTBE and U-(14)C-TBA to (14)CO(2) and the novel biodegradation of U- (14)C-TAME to (14)CO(2) under oxic and anoxic conditions. The implication of fuel oxygenate attenuation observed in diverse hyporheic zones suggests an assessment of the hyporheic zone attenuation potential (HZAP) merits inclusion as part of site assessment strategies associated with monitored or engineered attenuation.

Synthesis of high-temperature viscosity stabilizer used in drilling fluid

NASA Astrophysics Data System (ADS)

Zhang, Yanna; Luo, Huaidong; Shi, Libao; Huang, Hongjun

2018-02-01

Abstract For a well performance drilling fluid, when it operates in deep wells under high temperature, the most important property required is the thermal stability. The drilling fluid properties under high temperature can be controlled by proper selection of viscosity stabilizer, which can capture oxygen to protect polymer agent in the drilling fluid. In this paper a viscosity stabilizer PB-854 is described, which was synthesized by 4-phenoxybutyl bromide, paraformaldehyde, and phloroglucinol using etherification method and condensation reaction. We studied the effect of catalyst dosage, temperature, time, and stirring rate on the synthetic yield. Under this condition: molar ratio of 2-tert-Butylphenol, paraformaldehyde and phloroglucinol of 2:1:2.5, reacting temperature of 100 °C, stirring rate of 100 r min-1, and mass content of catalyst of 15 %, char yield of 5-bromine-3-tert-butyl salicylaldehyde reached 86 %. Under this condition: molar ratio of 5-bromine-3-tert-butyl salicylaldehyde and phloroglucinol of 4, reacting temperature of 60 °C, reacting time of 30 min, volume content of sulphuric acid of 80 %, char yield of the target product viscosity stabilizer PB-854 is 86%. Finally, in this paper, infrared spectroscopy is adopted to analyse the structure of the synthetic product PB-854.The improvement in the stability of drilling fluid was further shown after adding the viscosity stabilizer in the common polymer drilling fluid under high temperature conditions of 120 °C ˜ 180 °C. The results show significant change in terms of fluid stability in the presence of this new stabilizer as it provides better stability.

Contact Angles and Surface Tension of Germanium-Silicon Melts

NASA Technical Reports Server (NTRS)

Croell, A.; Kaiser, N.; Cobb, S.; Szofran, F. R.; Volz, M.; Rose, M. Franklin (Technical Monitor)

2001-01-01

Precise knowledge of material parameters is more and more important for improving crystal growth processes. Two important parameters are the contact (wetting) angle and the surface tension, determining meniscus shapes and surface-tension driven flows in a variety of methods (Czochralski, EFG, floating-zone, detached Bridgman growth). The sessile drop technique allows the measurement of both parameters simultaneously and has been used to measure the contact angles and the surface tension of Ge(1-x)Si(x) (0 less than or equal to x less than or equal to 1.3) alloys on various substrate materials. Fused quartz, Sapphire, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AIN, Si3N4, and polycrystalline CVD diamond were used as substrate materials. In addition, the effect of different cleaning procedures and surface treatments on the wetting behavior were investigated. Measurements were performed both under dynamic vacuum and gas atmospheres (argon or forming gas), with temperatures up to 1100 C. In some experiments, the sample was processed for longer times, up to a week, to investigate any changes of the contact angle and/or surface tension due to slow reactions with the substrate. For pure Ge, stable contact angles were found for carbon-based substrates and for pBN, for Ge(1-x)Si(x) only for pBN. The highest wetting angles were found for pBN substrates with angles around 170deg. For the surface tension of Ge, the most reliable values resulted in gamma(T) = (591- 0.077 (T-T(sub m)) 10(exp -3)N/m. The temperature dependence of the surface tension showed similar values for Ge(1-x)Si(x), around -0.08 x 10(exp -3)N/m K, and a compositional dependence of 2.2 x 10(exp -3)N/m at%Si.

Bis(azido) compounds of Pd and Pt with bulky phosphine ligands (dppn=1,8-bis(diphenylphosphino)naphthalene, dppf=1,1‧-bis(diphenylphosphino)ferrocene, 1-dpn=1-diphenylphosphino-naphthalene): Preparation, structures, and reactivity toward isocyanides

NASA Astrophysics Data System (ADS)

Huh, Hyun Sue; Lee, Yeon Kyoung; Lee, Soon W.

2006-05-01

Pd-bis(azido) compounds [Pd(dppn)(N 3) 2] and [Pd(dppf)(N 3) 2], which contain bulky chelating bis(phosphine) ligands (dppn=1,8-bis(diphenylphosphino)naphthalene, dppf=1,1'-bis(diphenylphosphino)ferrocene), were prepared from the corresponding chlorides and NaN 3. We also prepared the Pt-bis(azido) compound [Pt(1-dpn)(SMe 2)(N 3) 2] containing a bulky monodentate phosphine (1-dpn=1-diphenylphosphino-naphthalene). All these compounds underwent [2+3] cycloaddition with isocyanides (R-NC, R=cyclohexyl, tert-butyl, 2,6-dimethylphenyl) to convert azido ligands to five-membered, C-coordinated tetrazolate rings. In addition, we observed the [Pd(dppn)Cl 2]-mediated C-C coupling of PhC tbnd6 CH to generate the η 2-PhC tbnd6 C-C tbnd6 CPh ligand. All compounds have been structurally characterized by X-ray diffraction.

Ambient Carbon Dioxide Capture Using Boron-Rich Porous Boron Nitride: A Theoretical Study.

PubMed

Li, Lanlan; Liu, Yan; Yang, Xiaojing; Yu, Xiaofei; Fang, Yi; Li, Qiaoling; Jin, Peng; Tang, Chengchun

2017-05-10

The development of highly efficient sorbent materials for CO 2 capture under ambient conditions is of great importance for reducing the impact of CO 2 on the environment and climate change. In this account, strong CO 2 adsorption on a boron antisite (B N ) in boron-rich porous boron nitrides (p-BN) was developed and studied. The results indicated that the material achieved larger adsorption energies of 2.09 eV (201.66 kJ/mol, PBE-D). The electronic structure calculations suggested that the introduction of B N in p-BN induced defect electronic states in the energy gap region, which strongly impacted the adsorption properties of the material. The bonding between the B N defect and the CO 2 molecule was clarified, and it was found that the electron donation first occurred from CO 2 to the B N double-acceptor state then, followed by electron back-donation from B N to CO 2 accompanied by the formation of a B N -C bond. The thermodynamic properties indicated that the adsorption of CO 2 on the B N defect to form anionic CO 2 δ- species was spontaneous at temperatures below 350 K. Both the large adsorption energies and the thermodynamic properties ensured that p-BN with a B N defect could effectively capture CO 2 under ambient conditions. Finally, to evaluate the energetic stability, the defect formation energies were estimated. The formation energy of the B N defects was found to strongly depend on the chemical environment, and the selection of different reactants (B or N sources) would achieve the goal of reducing the formation energy. These findings provided a useful guidance for the design and fabrication of a porous BN sorbent for CO 2 capture.

Oxidation of stainless steel 316 and Nitronic 50 in supercritical and ultrasupercritical water

NASA Astrophysics Data System (ADS)

Rodriguez, David; Chidambaram, Dev

2015-08-01

Corrosion of stainless steel 316 and Nitronic 50 exposed to supercritical and ultrasupercritical water was studied as a function of temperature and exposure time. Post-exposure surface analysis was performed using Raman and X-ray photoelectron spectroscopies to determine the chemistry of the oxides formed as a result of the exposure. When exposed to supercritical water, Nitronic 50 and stainless steel 316 were observed to have similar weight gains; however, stainless steel 316 was found to gain less weight than Nitronic 50 in exposure tests performed in ultrasupercritical water. Stainless steel 316 developed surface films primarily composed of iron oxides, while the surface of Nitronic 50 contained a mixture of iron, chromium and manganese oxides. Based on these analyses, the differences in weight gain and oxidation characteristics of the two materials are attributed to the higher concentration of Cr and Mn in Nitronic 50 compared to stainless steel 316.

Design of Ceramic Springs for Use in Semiconductor Crystal Growth in Microgravity

NASA Technical Reports Server (NTRS)

Kaforey, M. F.; Deeb, C. W.; Matthiesen, D. H.

1999-01-01

Segregation studies can be done in microgravity to reduce buoyancy driven convection and investigate diffusion-controlled growth during the growth of semiconductor crystals. During these experiments, it is necessary to prevent free surface formation in order to avoid surface tension driven convection (Marangoni convection). Semiconductor materials such as gallium arsenide and germanium shrink upon melting, so a spring is necessary to reduce the volume of the growth chamber and prevent the formation of a free surface when the sample melts. A spring used in this application must be able to withstand both the high temperature and the processing atmosphere. During the growth of gallium arsenide crystals during the GTE Labs/USAF/NASA GaAs GAS Program and during the CWRU GaAs programs aboard the First and Second United States microgravity Laboratories, springs made of pyrolytic boron nitride (PBN) leaves were used. The mechanical properties of these PBN springs have been investigated and springs having spring constants ranging from 0.25 N/mm to 25 N/mm were measured. With this improved understanding comes the ability to design springs for more general applications, and guidelines are given for optimizing the design of PBN springs for crystal growth applications.

Parabrachial and hypothalamic interaction in sodium appetite

PubMed Central

Dayawansa, S.; Peckins, S.; Ruch, S.

2011-01-01

Rats with bilateral lesions of the lateral hypothalamus (LH) fail to exhibit sodium appetite. Lesions of the parabrachial nuclei (PBN) also block salt appetite. The PBN projection to the LH is largely ipsilateral. If these deficits are functionally dependent, damaging the PBN on one side and the LH on the other should also block Na appetite. First, bilateral ibotenic acid lesions of the LH were needed because the electrolytic damage used previously destroyed both cells and axons. The ibotenic LH lesions produced substantial weight loss and eliminated Na appetite. Controls with ipsilateral PBN and LH lesions gained weight and displayed robust sodium appetite. The rats with asymmetric PBN-LH lesions also gained weight, but after sodium depletion consistently failed to increase intake of 0.5 M NaCl. These results dissociate loss of sodium appetite from the classic weight loss after LH damage and prove that Na appetite requires communication between neurons in the LH and the PBN. PMID:21270347

Occurrence of synthetic musks in human breast milk samples from 12 provinces in China.

PubMed

Yin, Jie; Wang, Hao; Li, Jingguang; Wu, Yongning; Shao, Bing

2016-07-01

The levels of 12 synthetic musks and one musk metabolite in 24 pooled human milk samples were examined in order to assess the health risks of these contaminants to breast-feeding infants of China. The 24 pooled samples comprised of 1237 individual human milk samples collected from 12 provinces of China according to WHO guidelines. Among the 13 target analytes, OTNE ([1,2,3,4,5,6,7,8-octahydro-2,3,8,8-tetramethylnaphthalen-2yl]ethan-1-one), HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[γ]-2-benzopyran), AHTN (7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene), musk ketone (4-tert-butyl-2,6-dimethyl-3,5-dinitroacetophenone, MK), Musk T (1,4-dioxacyclohepta decane-5,17-dione), HHCB-lactone (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl cyclopenta[γ]-2-benzopyran-1-one) and musk ambrette (1-(1,1-dimethylethyl)-2-methoxy-4-methyl-3,5-dinitrobenzene, MA), were found in the milk samples analysed with mean (median) concentrations of 3.96 (3.91), 18.03 (15.10), 10.30 (9.38), 4.68 (4.45), < 3.70 (< 3.70), 10.02 (9.20) and < 5.20 (< 5.20) ng g(-1) lipid weight, respectively, whereas ADBI (4-acetyl-1,1-dimethyl-6-tert-butylindan), AHDI (6-acetyl-1,1,2,3,3,5-hexamethylindan), ATII (5-acetyl-1,1,2,6-tetramethyl-3-isopropylindan), musk xylene (1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene, MX), musk tibetene (1-tert-butyl-3,4,5-trimethyl-2,6-dinitrobenzene, MT) and musk moskene (1,1,3,3,5-pentamethyl-4,6-dinotroindane, MM) were not detected. Significantly positive associations were observed in concentration levels between HHCB and AHTN (p < 0.001), HHCB and HHCB-lactone (p < 0.05), AHTN and HHCB-lactone (p < 0.001), and MK and OTNE (p < 0.05). No statistical difference was found in musk concentrations between rural and urban areas in China (p > 0.05). The mean (median) estimated daily intakes by infants were 20.5 (20.2), 93.4 (78.2), 53.4 (48.6), 24.2 (23.0) and 51.9 (47.6) ng kg(-1) body weight for OTNE, HHCB, AHTN, MK and HHCB-lactone, respectively. The musk exposure levels of infants in China via breast feeding were very low according to the current toxicological information.

Non-Invasive Nanodiagnostics of Cancer (NINOC)

DTIC Science & Technology

2010-04-01

tested. CONCLUSIONS Well-defined diblock copolymers of poly(ethylene glycol) and polymethacrylic acid (PEG-b-PMA) with aldehyde functionality were...treatment of cancer, tumor-specific targeting has been proposed using a variety of targeting moieties such as folic acid , transferrin, RGD-peptides...tert-butyl and PEG groups (Table 1). In order to obtain the final block copolymer 6, the hydrolysis of copolymer 5 was carried out in the acidic

Functional electrolyte for lithium-ion batteries

DOEpatents

Zhang, Lu; Zhang, Zhengcheng; Amine, Khalil

2015-04-14

Functional electrolyte solvents include compounds having at least one aromatic ring with 2, 3, 4 or 5 substituents, at least one of which is a substituted or unsubstituted methoxy group, at least one of which is a tert-butyl group and at least one of which is a substituted or unsubstituted polyether or poly(ethylene oxide) (PEO) group bonded through oxygen to the aromatic ring, are provided.

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...

Biomimetic Oxidation Studies. 11. Alkane Functionalization in Aqueous Solution Utilizing in Situ Formed [Fe(2)O(eta(1)-H(2)O)(eta(1)-OAc)(TPA)(2)](3+), as an MMO Model Precatalyst, Embedded in Surface-Derivatized Silica and Contained in Micelles.

PubMed

Neimann, Karine; Neumann, Ronny; Rabion, Alain; Buchanan, Robert M.; Fish, Richard H.

1999-07-26

The biomimetic, methane monooxygenase enzyme (MMO) precatalyst, [Fe(2)O(eta(1)-H(2)O)(eta(1)-OAc)(TPA)(2)](3+) (TPA = tris[(2-pyridyl)methyl]amine), 1, formed in situ at pH 4.2 from [Fe(2)O(&mgr;-OAc)(TPA)(2)](3+), 2, was embedded in an amorphous silicate surface modified by a combination of hydrophilic poly(ethylene oxide) and hydrophobic poly(propylene oxide). The resulting catalytic assembly was found to be a biomimetic model for the MMO active site within a hydrophobic macroenvironment, allowing alkane functionalization with tert-butyl hydroperoxide (TBHP)/O(2) in an aqueous reaction medium (pH 4.2). For example, cyclohexane was oxidized to a mixture of cyclohexanone, cyclohexanol, and cyclohexyl-tert-butyl peroxide, in a ratio of approximately 3:1:2. The balance between poly(ethylene oxide) and poly(propylene oxide), tethered on the silica surface, was crucial for maximizing the catalytic activity. The silica-based catalytic assembly showed reactivity somewhat higher in comparison to an aqueous micelle system utilizing the surfactant, cetyltrimethylammonium hydrogen sulfate at its critical micelle concentration, in which functionalization of cyclohexane with TBHP/O(2) in the presence of 1 was also studied at pH 4.2 and was found to provide similar products: cyclohexanol, cyclohexanone, and cyclohexyl-tert-butyl peroxide, in a ratio of approximately 2:3:1. Moreover, the mechanism for both the silica-based catalytic assembly and the aqueous micelle system was found to occur via the Haber-Weiss process, in which redox chemistry between 1 and TBHP provides both the t-BuO(*)() and t-BuOO(*)()( )()radicals. The t-BuO(*)()( )()radical initiates the C-H functionalization reaction to form the carbon radical, followed by O(2) trapping, to provide cyclohexyl hydroperoxide, which produces the cyclohexanol and cyclohexanone in the presence of 1, whereas the coupling product emanates from t-BuOO(*)() and cyclohexyl radicals. A discussion concerning both approaches for alkane functionalization in water will be presented.

Quantum-Mechanical Studies on Chemical Reactivity and Ballistic Chemistry. VII. Semiempirical Molecular Orbital Calculations and Experimental Studies on Relative Chemical Reactivities of Isomeric Tetrazole Derivatives, and their Relationship to the Explosive Properties of some Tetrazole Derivatives

DTIC Science & Technology

1981-10-01

factor of about 20) than the methyl protons of the isomeric 2-phenyl compound-^6. Furthermore, when N-(4-dimethylaminophenyl) nitrones are reacted...34Tetrazoles from N-(4-Dimethylaminophenyl) nitrones and Hydrogen Azide", J. Heteroayol. Chem., 14, 757 (1977). 17 Further examples of...r—» , M < =< e 40 X rH u 03 ■l-J ■P u 0 6 H o u u 1— cd +J 1= c S B ■H u a> ft X U-l D W HJ -J H) o 0 Kl O < ■H a TS

An unusual methylene aziridine refined in P2(1)/c and the nonstandard setting P2(1)/n.

PubMed

Feast, George C; Haestier, James; Page, Lee W; Robertson, Jeremy; Thompson, Amber L; Watkin, David J

2009-12-01

The unusual methylene aziridine 6-tert-butyl-3-oxa-2-thia-1-azabicyclo[5.1.0]oct-6-ene 2,2-dioxide, C(9)H(15)NO(3)S, was found to crystallize with two molecules in the asymmetric unit. The structure was solved in both the approximately orthogonal and the oblique settings of space group No. 14, viz. P2(1)/n and P2(1)/c, respectively. A comparison of these results clearly displayed an increase in the correlation between coordinates in the ac plane for the oblique cell. The increase in the corresponding covariances makes a significant contribution to the standard uncertainties of derived parameters, e.g. bond lengths. Since there is yet no CIF definition for the full variance-covariance matrix, there are clear advantages to reporting the structure in the nonstandard space-group setting.

[Optical and morphological investigation on the interaction of dual dopants in poly (N-vinylcarzole)].

PubMed

Zhang, Ting; Xu, Zheng; Teng, Feng; Qian, Lei; Wang, Yong-Sheng; Xu, Xu-Rong

2006-05-01

The effect of optical and electrical properties of poly(N-vinylcarzole) (PVK) doped with two dyes, i. e. 8-tris-hydroxyquinoline (Alq3) and 4-(dicyanomethylene)-2-tert-butyl-6 (1, 1, 7, 7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), on the energy transfer and charge trapping processes was investigated. The phase separation in blends film at different doping concentration was also studied. More homogeneous dispersion of dyes in PVK with increasing doping concentration was showed. The results indicate that there is a certain interaction of Alq3 and DCJTB in this dual-doped system. It is the incorporation of DCJTB that untangled the aggregation of Alq3 owing to the interaction of DCJTB and Alq3. But for higher doping concentration, DCJTB results in an isolated charge transport channel that decreases the electroluminescence (EL) operating voltage.

Coordination Chemistry of a Strongly-Donating Hydroxylamine with Early Actinides: An Investigation of Redox Properties and Electronic Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

McSkimming, Alex; Su, Jing; Cheisson, Thibault

Separations of f-block elements are a critical aspect of nuclear waste processing. Redox-based separations offer promise, but challenges remain in stabilizing and differentiating actinides in high oxidation states. The investigation of new ligand types that provide thermodynamic stabilization to high-valent actinides is essential for expanding their fundamental chemistry and to elaborate new separation techniques and storage methods. We report herein the preparation and characterization of Th and U complexes of the pyridyl-hydroxylamine ligand, N-tert-butyl-N-(pyridin-2-yl)hydroxylamine (pyNO–). Electrochemical studies performed on the homoleptic complexes [M(pyNO) 4] (M = Th, U) revealed significant stabilization of the U complex upon one-electron oxidation. The saltmore » [U(pyNO) 4] + was isolated by chemical oxidation of [U(pyNO) 4]; spectroscopic and computational data support assignment as a U V cation.« less

Coordination Chemistry of a Strongly-Donating Hydroxylamine with Early Actinides: An Investigation of Redox Properties and Electronic Structure

DOE PAGES

McSkimming, Alex; Su, Jing; Cheisson, Thibault; ...

2018-03-23

Separations of f-block elements are a critical aspect of nuclear waste processing. Redox-based separations offer promise, but challenges remain in stabilizing and differentiating actinides in high oxidation states. The investigation of new ligand types that provide thermodynamic stabilization to high-valent actinides is essential for expanding their fundamental chemistry and to elaborate new separation techniques and storage methods. We report herein the preparation and characterization of Th and U complexes of the pyridyl-hydroxylamine ligand, N-tert-butyl-N-(pyridin-2-yl)hydroxylamine (pyNO–). Electrochemical studies performed on the homoleptic complexes [M(pyNO) 4] (M = Th, U) revealed significant stabilization of the U complex upon one-electron oxidation. The saltmore » [U(pyNO) 4] + was isolated by chemical oxidation of [U(pyNO) 4]; spectroscopic and computational data support assignment as a U V cation.« less

Novel pyrrolinones as N-methyl-D-aspartate receptor antagonists.

PubMed

Poschenrieder, Hermann; Stachel, Hans-Dietrich; Höfner, Georg; Mayer, Peter

2005-04-01

A series of oximes, deriving from 2-arylidene-pyrroline-3,4-diones (7, 8, 22, 23) has been prepared. The presence of tautomers in their solutions has been established by spectroscopic means. The compounds reacted with diazomethane chiefly by N-methylation forming nitrones (10, 11). The analogously prepared 2-arylidene-4-nitropyrrolin-3-ones (12, 13, 24, 25), formally derived from nitrotetramic acids, yielded nitronic acid esters (14, 15, 26) upon reaction with diazomethane. The structures were elucidated by spectral evidence and-in the case of compounds 10 and 20b-by X-ray diffraction analysis. The binding affinity of some of the new compounds toward the N-methyl-d-aspartate (NMDA) (glycine site) receptor has been measured thus providing the basis for further structure-activity relationship studies. Oxime 8b showed the highest binding potency (Ki= 9.2 microM).

Unipolar Barrier Dual-Band Infrared Detectors

NASA Technical Reports Server (NTRS)

Ting, David Z. (Inventor); Soibel, Alexander (Inventor); Khoshakhlagh, Arezou (Inventor); Gunapala, Sarath (Inventor)

2017-01-01

Dual-band barrier infrared detectors having structures configured to reduce spectral crosstalk between spectral bands and/or enhance quantum efficiency, and methods of their manufacture are provided. In particular, dual-band device structures are provided for constructing high-performance barrier infrared detectors having reduced crosstalk and/or enhance quantum efficiency using novel multi-segmented absorber regions. The novel absorber regions may comprise both p-type and n-type absorber sections. Utilizing such multi-segmented absorbers it is possible to construct any suitable barrier infrared detector having reduced crosstalk, including npBPN, nBPN, pBPN, npBN, npBP, pBN and nBP structures. The pBPN and pBN detector structures have high quantum efficiency and suppresses dark current, but has a smaller etch depth than conventional detectors and does not require a thick bottom contact layer.

Hydrosilylation induced by N→Si intramolecular coordination: spontaneous transformation of organosilanes into 1-aza-silole-type molecules in the absence of a catalyst.

PubMed

Novák, Miroslav; Dostál, Libor; Alonso, Mercedes; De Proft, Frank; Růžička, Aleš; Lyčka, Antonín; Jambor, Roman

2014-02-24

Our attempts to synthesize the N→Si intramolecularly coordinated organosilanes Ph2 L(1) SiH (1 a), PhL(1) SiH2 (2 a), Ph2 L(2) SiH (3 a), and PhL(2) SiH2 (4 a) containing a CH=N imine group (in which L(1) is the C,N-chelating ligand {2-[CH=N(C6 H3 -2,6-iPr2)]C6 H4}(-) and L(2) is {2-[CH=N(tBu)]C6 H4}(-)) yielded 1-[2,6-bis(diisopropyl)phenyl]-2,2-diphenyl-1-aza-silole (1), 1-[2,6-bis(diisopropyl)phenyl]-2-phenyl-2-hydrido-1-aza-silole (2), 1-tert-butyl-2,2-diphenyl-1-aza-silole (3), and 1-tert-butyl-2-phenyl-2-hydrido-1-aza-silole (4), respectively. Isolated organosilicon amides 1-4 are an outcome of the spontaneous hydrosilylation of the CH=N imine moiety induced by N→Si intramolecular coordination. Compounds 1-4 were characterized by NMR spectroscopy and X-ray diffraction analysis. The geometries of organosilanes 1 a-4 a and their corresponding hydrosilylated products 1-4 were optimized and fully characterized at the B3LYP/6-31++G(d,p) level of theory. The molecular structure determination of 1-3 suggested the presence of a Si-N double bond. Natural bond orbital (NBO) analysis, however, shows a very strong donor-acceptor interaction between the lone pair of the nitrogen atom and the formal empty p orbital on the silicon and therefore, the calculations show that the Si-N bond is highly polarized pointing to a predominantly zwitterionic Si(+) N(-) bond in 1-4. Since compounds 1-4 are hydrosilylated products of 1 a-4 a, the free energies (ΔG298), enthalpies (ΔH298), and entropies (ΔH298) were computed for the hydrosilylation reaction of 1 a-4 a with both B3LYP and B3LYP-D methods. On the basis of the very negative ΔG298 values, the hydrosilylation reaction is highly exergonic and compounds 1 a-4 a are spontaneously transformed into 1-4 in the absence of a catalyst. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Isolation of an oxomanganese(V) porphyrin intermediate in the reaction of a manganese(III) porphyrin complex and H2O2 in aqueous solution.

PubMed

Nam, Wonwoo; Kim, Inwoo; Lim, Mi Hee; Choi, Hye Jin; Lee, Je Seung; Jang, Ho G

2002-05-03

The reaction of [Mn(TF(4)TMAP)](CF(3)SO(3))(5) (TF(4)TMAP=meso-tetrakis(2,3,5,6-tetrafluoro-N,N,N-trimethyl-4-aniliniumyl)porphinato dianion) with H(2)O(2) (2 equiv) at pH 10.5 and 0 degrees C yielded an oxomanganese(V) porphyrin complex 1 in aqueous solution, whereas an oxomanganese(IV) porphyrin complex 2 was generated in the reactions of tert-alkyl hydroperoxides such as tert-butyl hydroperoxide and 2-methyl-1-phenyl-2-propyl hydroperoxide. Complex 1 was capable of epoxidizing olefins and exchanging its oxygen with H(2) (18)O, whereas 2 did not epoxidize olefins. From the reactions of [Mn(TF(4)TMAP)](5+) with various oxidants in the pH range 3-11, the O-O bond cleavage of hydroperoxides was found to be sensitive to the hydroperoxide substituent and the pH of the reaction solution. Whereas the O-O bond of hydroperoxides containing an electron-donating tert-alkyl group is cleaved homolytically, an electron-withdrawing substituent such as an acyl group in m-chloroperoxybenzoic acid (m-CPBA) facilitates O-O bond heterolysis. The mechanism of the O-O bond cleavage of H(2)O(2) depends on the pH of the reaction solution: O-O bond homolysis prevails at low pH and O-O bond heterolysis becomes a predominant pathway at high pH. The effect of pH on (18)O incorporation from H(2) (18)O into oxygenated products was examined over a wide pH range, by carrying out the epoxidation of carbamazepine (CBZ) with [Mn(TF(4)TMAP)](5+) and KHSO(5) in buffered H(2) (18)O solutions. A high proportion of (18)O was incorporated into the CBZ-10,11-oxide product at all pH values but this proportion was not affected significantly by the pH of the reaction solution.

A new family of dispersed repeats from Brassica nigra: characterization and localization.

PubMed

Kapila, R; Negi, M S; This, P; Delseny, M; Srivastava, P S; Lakshmikumaran, M

1996-11-01

The 459-bp HindIII (pBN-4) and the 1732-bp Eco RI (pBNE8) fragments from the Brassica nigra genome were cloned and shown to be members of a dispersed repeat family. Of the three major diploid Brassica species, the repeat pBN-4 was found to be highly specific for the B. nigra genome. The family also hybridized to Sinapis arvensis showing that B. nigra had a closer relationship with the S. arvensis genome than with B. oleracea or B. campestris. The clone pBNE8 showed homology to a number of tRNA species indicating that this family of repeats may have originated from a tRNA sequence. The species-specific 459-bp repeat pBN-4 was localized on the B. nigra chromosomes using monosomic addition lines. In addition to the localization of pBN-4, the chromosomal distribution of two other species-specific repeats, pBN34 and pBNBH35 (reported earlier), was studied. The dispersed repeats pBN-4 and pBNBH35 were found to be present on all of the chromosomes, whereas the tandem repeat pBN34 was localized on two chromosomes.

Recent development and biomedical applications of probabilistic Boolean networks

PubMed Central

2013-01-01

Probabilistic Boolean network (PBN) modelling is a semi-quantitative approach widely used for the study of the topology and dynamic aspects of biological systems. The combined use of rule-based representation and probability makes PBN appealing for large-scale modelling of biological networks where degrees of uncertainty need to be considered. A considerable expansion of our knowledge in the field of theoretical research on PBN can be observed over the past few years, with a focus on network inference, network intervention and control. With respect to areas of applications, PBN is mainly used for the study of gene regulatory networks though with an increasing emergence in signal transduction, metabolic, and also physiological networks. At the same time, a number of computational tools, facilitating the modelling and analysis of PBNs, are continuously developed. A concise yet comprehensive review of the state-of-the-art on PBN modelling is offered in this article, including a comparative discussion on PBN versus similar models with respect to concepts and biomedical applications. Due to their many advantages, we consider PBN to stand as a suitable modelling framework for the description and analysis of complex biological systems, ranging from molecular to physiological levels. PMID:23815817

Effects of countercations on the structures and redox and spectroscopic properties of diruthenium catecholate complexes with ligand-unsupported Ru-Ru bonds.

PubMed

Chang, Ho-Chol; Mochizuki, Katsunori; Kitagawa, Susumu

2005-05-30

The molecular structures and physicochemical properties of diruthenium complexes with ligand-unsupported Ru-Ru bonds, generally formulated as [A2{Ru2(DTBCat)4}] (DTB = 3,5- or 3,6-di-tert-butyl; Cat(2-) = catecholate), were studied in detail by changing the countercations. First, the binding structures of the cations in a family of [{A(DME)n}2{Ru2(3,5-DTBCat)4}] (n = 2 for A+ = Li+ and Na+ and n = 1 for A+ = K+ and Rb+) were systematically examined to reveal the effects of the cations on the molecular structures and electrochemical properties. Second, the complex (n-Bu4N)2[Ru2(3,6-DTBCat)4] with a cation-free structure was synthesized using tetra-n-butylammonium cations. The complex clearly demonstrates first that the ligand-unsupported Ru-Ru bonds are essentially stabilized by the dianionic nature of the catecholate derivatives without any other bridging or supporting species. In contrast, the redox potentials and absorption spectra of the complexes can sensitively respond to the countercations depending upon the polarity of the solvents.

Exploring molecular complexity with ALMA (EMoCA): Simulations of branched carbon-chain chemistry in Sgr B2(N)

NASA Astrophysics Data System (ADS)

Garrod, R. T.; Belloche, A.; Müller, H. S. P.; Menten, K. M.

2017-05-01

Context. Using millimeter wavelength data from the Atacama Large Millimeter/submillimeter Array (ALMA), the EMoCA spectral line survey recently revealed the presence of both the straight-chain (normal) and branched (iso) forms of propyl cyanide (C3H7CN) toward the Galactic Center star-forming source Sgr B2(N2). This was the first interstellar detection of a branched aliphatic molecule. Aims: Through computational methods, we seek to explain the observed I:n ratio for propyl cyanide, and to predict the abundances of the four different forms of the homologous nitrile, butyl cyanide (C4H9CN). We also investigate whether other molecules will show a similar degree of branching, by modeling the chemistry of alkanes up to pentane (C5H12). Methods: We use the coupled three-phase chemical kinetics model, MAGICKAL, to simulate the chemistry of the hot-core source Sgr B2(N2), using an updated chemical network that includes grain-surface/ice-mantle formation routes for branched nitriles and alkanes. The network explicitly considers radical species with an unpaired electron on either the primary or secondary carbon in a chain. We also include mechanisms for the addition of the cyanide radical, CN, to hydrocarbons with multiple bonds between carbon atoms, using activation energy barriers from the literature. We use the EMoCA survey data to search for the straight-chain form of butyl cyanide toward Sgr B2(N2). Results: The observed I:n ratio for propyl cyanide is reproduced by the models, with intermediate to fast warm-up timescales providing the most accurate result. Butyl cyanide is predicted to show similar abundances to propyl cyanide, and to exhibit strong branching, with the sec form clearly dominant over all others. Normal and iso-butyl cyanide are expected to have similar abundances to each other, while the tert form is significantly less abundant. The addition of CN to acetylene and ethene is found to be important to the production of vinyl, ethyl, propyl, and butyl cyanide. The alkanes also show significant branching. We report a non-detection of n-C4H9CN toward Sgr B2(N2), with an abundance at least 1.7 times lower than that of n-C3H7CN. This value is within the range predicted by the chemical models. Conclusions: The models indicate that the degree of branching rises with increasing molecular size. The efficiency of CN addition to unsaturated hydrocarbons boosts the abundances of nitriles in the model, and enhances the ratio of straight-to-branched molecule production. Other types of molecule may be less abundant, but show an even greater degree of branching. The predicted abundance of, in particular, s-C4H9CN, which at its peak is comparable to that of propyl cyanide, makes it a good candidate for future detection toward Sgr B2(N2).

Some Phthalocyanine and Naphthalocyanine Derivatives as Corrosion Inhibitors for Aluminium in Acidic Medium: Experimental, Quantum Chemical Calculations, QSAR Studies and Synergistic Effect of Iodide Ions.

PubMed

Dibetsoe, Masego; Olasunkanmi, Lukman O; Fayemi, Omolola E; Yesudass, Sasikumar; Ramaganthan, Baskar; Bahadur, Indra; Adekunle, Abolanle S; Kabanda, Mwadham M; Ebenso, Eno E

2015-08-28

The effects of seven macrocyclic compounds comprising four phthalocyanines (Pcs) namely 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (Pc1), 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine (Pc2), 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (Pc3) and 29H,31H-phthalocyanine (Pc4), and three naphthalocyanines namely 5,9,14,18,23,27,32,36-octabutoxy-2,3-naphthalocyanine (nPc1), 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (nPc2) and 2,3-naphthalocyanine (nP3) were investigated on the corrosion of aluminium (Al) in 1 M HCl using a gravimetric method, potentiodynamic polarization technique, quantum chemical calculations and quantitative structure activity relationship (QSAR). Synergistic effects of KI on the corrosion inhibition properties of the compounds were also investigated. All the studied compounds showed appreciable inhibition efficiencies, which decrease with increasing temperature from 30 °C to 70 °C. At each concentration of the inhibitor, addition of 0.1% KI increased the inhibition efficiency compared to the absence of KI indicating the occurrence of synergistic interactions between the studied molecules and I(-) ions. From the potentiodynamic polarization studies, the studied Pcs and nPcs are mixed type corrosion inhibitors both without and with addition of KI. The adsorption of the studied molecules on Al surface obeys the Langmuir adsorption isotherm, while the thermodynamic and kinetic parameters revealed that the adsorption of the studied compounds on Al surface is spontaneous and involves competitive physisorption and chemisorption mechanisms. The experimental results revealed the aggregated interactions between the inhibitor molecules and the results further indicated that the peripheral groups on the compounds affect these interactions. The calculated quantum chemical parameters and the QSAR results revealed the possibility of strong interactions between the studied inhibitors and metal surface. QSAR analysis on the quantum chemical parameters obtained with B3LYP/6-31G (d,p) method show that a combination of two quantum chemical parameters to form a composite index provides the best correlation with the experimental data.

pH-responsive supramolecular self-assembly of well-defined zwitterionic ABC miktoarm star terpolymers.

PubMed

Liu, Hao; Li, Changhua; Liu, Hewen; Liu, Shiyong

2009-04-21

We report the first example of the synthesis and pH-responsive supramolecular self-assembly of double hydrophilic ABC miktoarm star terpolymers. Well-defined ABC miktoarm star terpolymers consisting of poly(ethylene glycol), poly(tert-butyl methacrylate), and poly(2-(diethylamino)ethyl methacrylate) arms [PEG(-b-PtBMA)-b-PDEA] were synthesized via the combination of consecutive click reactions and atom transfer radical polymerization (ATRP), starting from a trifunctional core molecule, 1-azido-3-chloro-2-propanol (ACP). The click reaction of monoalkynyl-terminated PEG with an excess of ACP afforded difunctional PEG bearing a chlorine and a secondary hydroxyl moiety at the chain end, PEG113(-Cl)-OH (1). After azidation with NaN3, PEG-based macroinitiator PEG113(-N3)-Br (3) was prepared by the esterification of PEG113(-N3)-OH (2) with 2-bromoisobutyryl bromide and then employed in the ATRP of tert-butyl methacrylate (tBMA). The obtained PEG(-N3)-b-PtBMA copolymers (4) possessed an azido moiety at the diblock junction point. The preparation of PEG(-b-PtBMA)-b-PDEA miktoarm star terpolymers was then achieved via the click reaction of 4 with an excess of monoalkynyl-terminated PDEA. The obtained miktoarm star terpolymers were successfully converted into PEG(-b-PMAA)-b-PDEA, where PMAA is poly(methacrylic acid). In aqueous solution, PEG(-b-PMAA)-b-PDEA zwitterionic ABC miktoarm star terpolymers can self-assemble into three types of micellar aggregates by simply adjusting solution pH at room temperature. Above pH 8, PDEA-core micelles stabilized by PEG/ionized PMAA hybrid coronas were formed due to the insolubility of PDEA block. In the range of pH 5-7, micelles possessing polyion complex cores formed as a result of charge compensation between partially ionized PMAA and partially protonated PDEA sequences. At pH<4, hydrogen bonding interactions between fully protonated PMAA and PEG led to the formation of another type of micellar aggregates possessing hydrogen-bonded complex cores stabilized by protonated PDEA coronas. The fully reversible pH-responsive formation of three types of aggregates were characterized by 1H NMR, dynamic and static laser light scattering (LLS), and transmission electron microscopy (TEM).

Oxytocin-receptor-expressing neurons in the parabrachial nucleus regulate fluid intake.

PubMed

Ryan, Philip J; Ross, Silvano I; Campos, Carlos A; Derkach, Victor A; Palmiter, Richard D

2017-12-01

Brain regions that regulate fluid satiation are not well characterized, yet are essential for understanding fluid homeostasis. We found that oxytocin-receptor-expressing neurons in the parabrachial nucleus of mice (Oxtr PBN neurons) are key regulators of fluid satiation. Chemogenetic activation of Oxtr PBN neurons robustly suppressed noncaloric fluid intake, but did not decrease food intake after fasting or salt intake following salt depletion; inactivation increased saline intake after dehydration and hypertonic saline injection. Under physiological conditions, Oxtr PBN neurons were activated by fluid satiation and hypertonic saline injection. Oxtr PBN neurons were directly innervated by oxytocin neurons in the paraventricular hypothalamus (Oxt PVH  neurons), which mildly attenuated fluid intake. Activation of neurons in the nucleus of the solitary tract substantially suppressed fluid intake and activated Oxtr PBN neurons. Our results suggest that Oxtr PBN neurons act as a key node in the fluid satiation neurocircuitry, which acts to decrease water and/or saline intake to prevent or attenuate hypervolemia and hypernatremia.

Synthesis, spectroscopic characterization, thermal studies, catalytic epoxidation and biological activity of chromium and molybdenum hexacarbonyl bound to a novel N 2O 2 Schiff base

NASA Astrophysics Data System (ADS)

Abdel Aziz, Ayman A.

2010-08-01

Complexes of M(CO) 6 (M = Cr and Mo) with novel Schiff base N,N'-bis(salicylidene)4,5-dichloro-1,2-phenylenediamine (H 2L) were prepared in benzene in two different conditions: (i) under reduced pressure resulting the dicarbonyl precursors [Cr(CO) 2(H 2L)] and [Mo(CO) 2(L)] and (ii) in air resulting the oxo complex [Cr(O)(L)] and the dioxo complex [Mo(O) 2(L)]. The complexes were characterized by elemental analysis, IR, 1H NMR, mass spectrometry, and magnetic measurement. Thermal behaviors of the complexes were also studied by using thermogravimetric analysis (TGA). The catalytic activity of the novel complexes in the epoxidation of cyclooctene, cyclohexene, 1-octene and 1-hexene with tert-butyl-hydroperoxide (TBHP) in methylene chloride was investigated. The antimicrobial activities of the ligand and their complexes have been screened against various strains of bacteria and fungi and the results have been compared with some known antibiotics.

Reaction between aminoalkyl radicals and akyl halides: Dehalogenation by electron transfer?

NASA Astrophysics Data System (ADS)

Lalevée, J.; Fouassier, J. P.; Blanchard, N.; Ingold, K. U.

2011-07-01

Aminoalkyl radicals, such as Et2NCrad HCH3, have low oxidation potentials and are therefore powerful reducing agents. We have found that Et2NCrad HCH3 reacts with CCl4 and CBr4 in di-tert-butyl peroxide with bimolecular rate constants (measured by LFP) close, or equal, to the diffusion-controlled limit. For the less reactive halide, CH2Br2, the reaction rate is increased substantially by the addition of acetonitrile as a co-solvent. It is tentatively concluded that these reactions occur by electron-transfer from the aminoalkyl to the organohalide with formation of the iminium ion, Et2N+dbnd CHCH3 (NMR detection), halide ion and a halomethyl radical, e.g., rad CCl3 and rad CHCl2 (ESR, spin-trapping detection).

NMR crystallography of 2-acylamino-6-[1 H]-pyridones: Solid-state NMR, GIPAW computational, and single crystal X-ray diffraction studies

NASA Astrophysics Data System (ADS)

Ośmiałowski, Borys; Kolehmainen, Erkki; Ikonen, Satu; Ahonen, Kari; Löfman, Miika

2011-12-01

2-Acylamino-6-[1 H]-pyridones [acyl = RCO, where R = methyl ( 1), ethyl ( 2), iso-propyl ( 3), tert-butyl ( 4), and 1-adamantyl ( 5)] have been synthesized and characterized by NMR spectroscopy. From three congeners, 2, 3 and 5, also single crystal X-ray structures have been solved. For these derivatives GIPAW calculations acts as a "bridge" between solid-state NMR data and calculated chemical shifts based on X-ray determined geometry. In crystals all three compounds exist as pyridone tautomers possessing similar six-membered ring structure stabilized by intramolecular C dbnd O⋯HN hydrogen bond. Theoretical GIPAW calculated and experimental 13C and 15N CPMAS NMR shifts are in excellent agreement with each other.

Purification of dirucotide, a synthetic 17-aminoacid peptide, by ion exchange centrifugal partition chromatography.

PubMed

Boudesocque, Leslie; Forni, Luciano; Martinez, Agathe; Nuzillard, Jean-Marc; Giraud, Matthieu; Renault, Jean-Hugues

2017-09-01

Dirucotide is a synthetic drug candidate for the treatment of multiple sclerosis. This 17-aminoacid peptide was successfully purified by ion exchange centrifugal partition chromatography. The optimized conditions involved the biphasic methyl tert-butyl ether/acetonitrile/n-butanol/water (2:1:2:5, v/v) solvent system in the descending mode, the di(2-ethylhexyl)phosphoric acid cation-exchanger with an exchanger (di(2-ethylhexyl)phosphoric acid)/dirucotide mole ratio of 100 and Ca 2+ ions in aqueous solution as displacer. Critical impurities were efficiently eliminated and dirucotide was recovered in high yield and purity (69% and 98%, respectively) and with a productivity of 2.29g per liter of stationary phase per hour. Copyright © 2017 Elsevier B.V. All rights reserved.

Modified extraction procedure for gas-liquid chromatography applied to the identification of anaerobic bacteria.

PubMed Central

Thomann, W R; Hill, G B

1986-01-01

Chloroform and ether commonly are used as solvents to extract metabolic organic acids for analysis by gas-liquid chromatography in the identification of anaerobic bacteria. Because these solvents are potentially hazardous to personnel, modified extraction procedures involving the use of a safer solvent, methyl tert-butyl ether were developed which remained both simple to perform and effective for organism identification. PMID:3700623

Cu and Boron Doped Carbon Nitride for Highly Selective Oxidation of Toluene to Benzaldehyde.

PubMed

Han, Hongling; Ding, Guodong; Wu, Tianbin; Yang, Dexin; Jiang, Tao; Han, Buxing

2015-07-13

A novel Cu and boron doped graphitic carbon nitride catalyst (Cu-CNB) was synthesized using cheap precursors and systematically characterized. The selective oxidation of toluene proceeded very smoothly over the catalyst at 70 °C using tert-butyl hydroperoxide (TBHP) as the oxidant to exclusively afford benzaldehyde. The catalyst can be used for at least five cycles without decrease in activity and selectivity.

Solar photochemical oxidations of benzylic and allylic alcohols using catalytic organo-oxidation with DDQ: application to lignin models.

PubMed

Walsh, Katie; Sneddon, Helen F; Moody, Christopher J

2014-10-03

Visible light has a dramatic effect on the oxidation of benzylic and allylic alcohols, including those deactivated by electron-withdrawing groups, and β-O-4 lignin models, using catalytic amounts of the organo-oxidant 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Sodium nitrite or tert-butyl nitrite is used as cocatalyst, and oxygen is employed as the terminal oxidant.

Solid State Photochemical Generation of Triplet Phenoxy-Phenoxy Radical Pairs

DTIC Science & Technology

1990-04-01

of diphenyl oxalate . Tert-butylated bis-aryloxalat s show good radical pair stability, with triplet ESR signals surviving days at room temperature in...between the geminate phenoxyl radicals. The comparable breadth of the spectra for diphenyl carbonate and the oxalates implies a similar interaction strength...ferromagnetic coupling that may be achieved in geminate pairs generated from a diphenyl oxalate vs. a diphenyl carbonate. In addition, we see similar

Entanglement Dynamics in Miscible Polyisoprene / Poly(p-tert-butyl styrene) Blends

NASA Astrophysics Data System (ADS)

Watanabe, Hiroshi

2011-03-01

Viscoelastic and dielectric behavior was examined for well entangled, miscible blends of high- M cis-polyisoprene (PI) and poly(p-tert-butyl styrene) (PtBS). The dielectric data of the blends, reflecting the global motion of the PI chains having the type-A dipoles, indicated that PI and PtBS were the fast and slow components therein. At high temperatures T , the blends exhibited two-step entanglement plateau. The high frequency (ω) plateau height was well described by a simple mixing rule of the entanglement length based on the number fraction of the Kuhn segments. At low T , the blend exhibited the Rouse-like power-law behavior of storage and loss moduli, G ' = G ~ω0.5 , in the range of ω where the high- ω plateau was supposed to emerge. This lack of the high- ω plateau was attributed to retardation of the Rouse equilibration of the PI chain over the entanglement length due to the hindrance from the slow PtBS chains: The PI and PtBS chains were equilibrated cooperatively, and the retardation due to PtBS shortened the plateau for PI to a width not resolved experimentally. A simple model for this cooperative equilibration formulated on the basis of the dielectric data described the viscoelastic data surprisingly well.

Characterization of metabolites of larotaxel in rat by liquid chromatography coupled with Q exactive high-resolution benchtop quadrupole orbitrap mass spectrometer.

PubMed

Liu, Zhenzhen; Hou, Pengyi; Liu, Lian; Qian, Feng

2018-03-01

1. Liquid-chromatography (LC) high-resolution (HR) mass spectrometry (MS) analysis can record HR full scans for drug metabolism studies. Larotaxel is a taxane analog that has the potential for the treatment of various types of cancer. 2. In this study, the metabolism of larotaxel was evaluated after an intravenous dose of 8 mg/kg via the caudal vein to healthy rats and its metabolites were characterized by high performance liquid chromatography coupled with a Q Exactive high-resolution benchtop quadrupole orbitrap mass spectrometer. Rat bio-samples were separated on a Capcell Pak C 18 column (2.1 i.d. × 100 mm; 2.7 μm) with mobile phase of acetonitrile and water. 3. As a result, a total of 34 metabolites were detected and identified by comparing the molecular masses, retention times and spectral patterns of the analytes with those of the parent drug. Three metabolites were confirmed by comparison with reference substances. 4. The prominent metabolites were mainly hydroxyl, dihydroxyl, trihydroxyl and 10-desacetyl analogs of larotaxel, some of which resulted from oxidation of the tert-butyl groups on the side chain and further oxidation and cyclization of the tert-butyl hydroxylated metabolites.

Photoinduced electron transfer in covalent ruthenium-anthraquinone dyads: relative importance of driving-force, solvent polarity, and donor-bridge energy gap.

PubMed

Hankache, Jihane; Wenger, Oliver S

2012-02-28

Four rigid rod-like molecules comprised of a Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) photosensitizer, a 9,10-anthraquinone electron acceptor, and a molecular bridge connecting the two redox partners were synthesized and investigated by optical spectroscopic and electrochemical means. An attempt was made to assess the relative importance of driving-force, solvent polarity, and bridge variation on the rates of photoinduced electron transfer in these molecules. Expectedly, introduction of tert-butyl substituents in the bipyridine ligands of the ruthenium complex and a change in solvent from dichloromethane to acetonitrile lead to a significant acceleration of charge transfer rates. In dichloromethane, photoinduced electron transfer is not competitive with the inherent excited-state deactivation processes of the photosensitizer. In acetonitrile, an increase in driving-force by 0.2 eV through attachment of tert-butyl substituents to the bpy ancillary ligands causes an increase in electron transfer rates by an order of magnitude. Replacement of a p-xylene bridge by a p-dimethoxybenzene spacer entails an acceleration of charge transfer rates by a factor of 3.5. In the dyads from this study, the relative order of importance of individual influences on electron transfer rates is therefore as follows: solvent polarity ≥ driving-force > donor-bridge energy gap.

Protective effects of hesperidin against oxidative stress of tert-butyl hydroperoxide in human hepatocytes.

PubMed

Chen, Mingcang; Gu, Honggang; Ye, Yiyi; Lin, Bing; Sun, Lijuan; Deng, Weiping; Zhang, Jingzhe; Liu, Jianwen

2010-10-01

Increasing evidence regarding free radical generating agents and the inflammatory process suggest that accumulation of reactive oxygen species (ROS) could involve hepatotoxicity. Hesperidin, a naturally occurring flavonoid presents in fruits and vegetables, has been reported to exert a wide range of pharmacological effects that include antioxidant, anti-inflammatory, antihypercholesterolemic, and anticarcinogenic actions. However, the cytoprotection and mechanism of hesperidin to neutralize oxidative stress in human hepatic L02 cells remain unclear. In this work, we assessed the capability of hesperidin to prevent tert-butyl hydroperoxide (t-BuOOH)-induced cell damage by augmenting cellular antioxidant defense. Hesperidin significantly protected hepatocytes against t-BuOOH-induced cell cytotoxicity, such as mitochondrial membrane potential (MMP) deplete and lactate dehydrogenase (LDH) release. Hesperidin also remarkably prevented indicators of oxidative stress, such as the ROS and lipid peroxidation level in a dose-dependent manner. Western blot showed that hesperidin facilitated ERK/MAPK phosphorylation which appeared to be responsible for nuclear translocation of Nrf2, thereby inducing cytoprotective heme oxygenase-1 (HO-1) expression. Based on the results described above, it suggested that hesperidin has potential as a therapeutic agent in the treatment of oxidative stress-related hepatocytes injury and liver dysfunctions. Copyright © 2010 Elsevier Ltd. All rights reserved.

Novel syn intramolecular pathway in base-catalyzed 1,2-elimination reactions of beta-acetoxy esters.

PubMed

Mohrig, Jerry R; Carlson, Hans K; Coughlin, Jane M; Hofmeister, Gretchen E; McMartin, Lea A; Rowley, Elizabeth G; Trimmer, Elizabeth E; Wild, Andrew J; Schultz, Steve C

2007-02-02

As part of a comprehensive investigation of electronic effects on the stereochemistry of base-catalyzed 1,2-elimination reactions, we observed a new syn intramolecular pathway in the elimination of acetic acid from beta-acetoxy esters and thioesters. 1H and 2H NMR investigation of reactions using stereospecifically labeled tert-butyl (2R*,3R*)-3-acetoxy-2,3-2H2-butanoate (1) and its (2R*,3S*) diastereomer (2) shows that 23 +/- 2% syn elimination occurs. The elimination reactions were catalyzed with KOH or (CH3)4NOH in ethanol/water under rigorously non-ion-pairing conditions. By contrast, the more sterically hindered beta-trimethylacetoxy ester produces only 6 +/- 1% syn elimination. These data strongly support an intramolecular (Ei) syn path for elimination of acetic acid, most likely through the oxyanion produced by nucleophilic attack at the carbonyl carbon of the beta-acetoxy group. The analogous thioesters, S-tert-butyl (2R*,3R*)-3-acetoxy-2,3-2H2-butanethioate (3) and its (2R*,3S*) diastereomer (4), showed 18 +/- 2% syn elimination, whereas the beta-trimethylacetoxy substrate gave 5 +/- 1% syn elimination. The more acidic thioester substrates do not produce an increased amount of syn stereoselectivity even though their elimination reactions are at the E1cb interface.

Structural, energetic, and UV-Vis spectral analysis of UVA filter 4-tert-butyl-4'-methoxydibenzoylmethane.

PubMed

Pinto da Silva, Luís; Ferreira, Paulo J O; Duarte, Darío J R; Miranda, Margarida S; Esteves da Silva, Joaquim C G

2014-02-27

The growing awareness of the harmful effects of ultraviolet (UV) solar radiation has increased the production and consumption of sunscreen products, which contain organic and inorganic molecules named UV filters that absorb, reflect, or scatter UV radiation, thus minimizing negative human health effects. 4-tert-Butyl-4'-methoxydibenzoylmethane (BMDBM) is one of the few organic UVA filters and the most commonly used. BMDBM exists in sunscreens in the enol form which absorbs strongly in the UVA range. However, under sunlight irradiation tautomerization occurs to the keto form, resulting in the loss of UV protection. In this study we have performed quantum chemical calculations to study the excited-state molecular structure and excitation spectra of the enol and keto tautomers of BMDBM. This knowledge is of the utmost importance as the starting point for studies aiming at the understanding of its activity when applied on human skin and also its fate once released into the aquatic environment. The efficiency of excitation transitions was rationalized based on the concept of molecular orbital superposition. The loss of UV protection was attributed to the enol → keto phototautomerism and subsequent photodegradation. Although this process is not energetically favorable in the singlet bright state, photodegradation is possible because of intersystem crossing to the first two triplet states.

IRIS Toxicological Review of tert-Butyl Alcohol (tert-Butanol) ...

EPA Pesticide Factsheets

In August 2013, EPA released the draft literature searches and associated search strategies, evidence tables, and exposure response arrays for TBA to obtain input from stakeholders and the public prior to developing the draft IRIS assessment. Specifically, EPA was interested in comments on the following: Draft literature search strategies The approach for identifying studies The screening process for selecting pertinent studies The resulting list of pertinent studies Preliminary evidence tables The process for selecting studies to include in evidence tables The quality of the studies in the evidence tables The literature search strategy, which describes the processes for identifying scientific literature, contains the studies that EPA considered and selected to include in the evidence tables. The preliminary evidence tables and exposure-response arrays present the key study data in a standardized format. The evidence tables summarize the available critical scientific literature. The exposure-response figures provide a graphical representation of the responses at different levels of exposure for each study in the evidence table. EPA is undertaking a new health assessment for t-butyl alcohol (TBA) for the Integrated Risk Information System (IRIS). The outcome of this project will be a Toxicological Review and IRIS and IRIS Summary of TBA that will be entered on the IRIS database. IRIS is an EPA da

Semi-industrial isolation of salicin and amygdalin from plant extracts using slow rotary counter-current chromatography.

PubMed

Du, Qizhen; Jerz, Gerold; Ha, Yangchun; Li, Lei; Xu, Yuanjin; Zhang, Qi; Zheng, Qunxiong; Winterhalter, Peterb; Ito, Yoichiro

2005-05-13

Salicin in the bark extract of Salix alba and amygdalin in the fruit extract of Semen armeniacae were each separated by slow rotary counter-current chromatography (SRCCC). The apparatus was equipped with a 40-L column made of 17 mm i.d. convoluted Teflon tubing. A 500g amount of crude extract containing salicin at 13.5% was separated yielding 63.5 g of salicin at 95.3% purity in 20h using methyl tert-butyl ether-l-butanol (1:3) saturated by methanol-water (1:5) as a stationary phase and methanol-water (1:5) saturated by methyl tert-butyl ether-1-butanol (1:3) as a mobile phase. A 400g amount of crude extract containing amygdalin at 55.3% was isolated to yield 221.2g of amygdalin at 94.1% purity in 19h using ethyl acetate-1-butanol (1:2) saturated by water as a stationary phase and water saturated by ethyl acetate-1-butanol (1:2) as a mobile phase. The flow rate of the mobile phase was 50 ml/min. The results show that industrial SRCCC separation of salicin and amygdalin is feasible using a larger column at a higher flow rate of the mobile phase.

Bacopa monnieri protects SH-SY5Y cells against tert-Butyl hydroperoxide-induced cell death via the ERK and PI3K pathways

PubMed Central

Petcharat, Kanoktip; Singh, Meharvan; Ingkaninan, Kornkanok; Attarat, Jongrak; Yasothornsrikul, Sukkid

2017-01-01

Objective Oxidative stress plays an important role in the pathological processes of various neurodegenerative diseases. Bacopa monnieri (BM) has a potent antioxidant property. Therefore, the purpose of this study was to evaluate the neuroprotective potential of BM against SH-SY5Y neuroblastoma cell death induced by the pro-oxidant insult, tert-Butyl hydroperoxide (TBHP), and to identify possible mechanisms related to its neuroprotective action. Methods The neuroprotective effect of BM was evaluated by the degree of protection against TBHP-induced cell death in human SH-SY5Y cells that was measured by calcein-AM assay. ERK1/2 and Akt phosphorylation was evaluated by immunoblotting. Results We found that BM exhibited protection against TBHP-mediated cytotoxicity. The neuroprotective effect of BM was abolished in the presence of either ERK1/2 or PI3K inhibitors. In addition, western blotting with anti-phospho-ERK1/2 and anti-phospho-Akt antibodies showed that BM increased both ERK1/2 and Akt phosphorylation. Conclusion These results suggest that BM by activation of ERK/MAPK and PI3K/Akt signaling pathways protects SH-SY5Y cells from TBHP-induced cell death. PMID:29152617

Degradation of MTBE and TBA by a new isolate from MTBE-contaminated soil.

PubMed

Zhang, Rui-Ling; Huang, Guo-Qiang; Lian, Jing-Yan; Li, Xin-Gang

2007-01-01

Methyl tert-butyl ether (MTBE), a gasoline additive, possesses serious problems to the environmental health. In the present study, a bacterial culture named A-3 which could effectively degrade MTBE was isolated from the MTBE contaminated soil. The isolate was identified as Chryseobacterium sp., a new species capable of degrading MTBE. In order to enhance its degradation ability, selected environment factors were investigated. The results showed that the optimal temperature was in the range of 25-30 degrees C, the pH was 7.0, the inoculum size was 2 x 10(8) CFU/ml and the optimal concentration of MTBE was from 50 to 100 mg/L. The maximum MTBE utilization rate (upsilon(max)) was 102 nmol MTBE/(mg cell protein x h). Furthermore, it was found that the isolate could also degrade tert-butyl alcohol (TBA). The degradation rates of TBA were much faster than those of MTBE. The additional TBA would lead to the decrease of the initial MTBE degradation rate and the inhibitory effect of TBA increased with the increase of TBA concentration. Similar protein profiles at least seven peptides were demonstrated after SDS-PAGE analysis of crude extracts obtained from the cells growing in MTBE and TBA culture.

Field Confirmation and Monitoring Tools for Aerobic Bioremediation of TBA and MTBE

NASA Astrophysics Data System (ADS)

North, K.; Rasa, E.; Mackay, D. M.; Scow, K. M.; Hristova, K. R.

2009-12-01

We have been investigating in situ biotreatment of an existing tert-butyl alcohol (TBA) plume at Vandenberg AFB by recirculation/oxygenation and evaluating monitoring tools for microbial community composition and activity inside and outside of the treatment zone. Results indicate that recirculation/oxygenation by two pairs of recirculation wells is effective at adding oxygen and decreasing methyl tert-butyl ether (MTBE) and TBA concentrations to detection limits along the flowpaths predicted. Compound-specific isotope analyses (CSIA) of groundwater and microbial community analyses (extraction and analysis of DNA) of groundwater and sediments are underway for sampling locations along flowpaths inside and outside of the treatment zone to seek confirmation of in situ biodegradation. We are also evaluating a novel approach to compare the performance of microbial “traps” in characterizing microbial communities: groundwater from the aerobic treatment zone is extracted, separated and directed to multiple chambers located in an air-conditioned ex situ experimental setup. The “traps” under evaluation are in separate chambers; influent and effluent are monitored. The traps being evaluated include Bio-Trap® housings containing Bio-Sep® beads baited with MTBE or TBA labeled with 13C and various unbaited materials. Insights from the various monitoring approaches will be discussed and compared.

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, and trimethylgermyl derivatives of 3,3-dimethylcyclopropene II. 3,3-Dimethyl-1,2-bis(trimethylsilyl)cyclopropene

NASA Astrophysics Data System (ADS)

Panchenko, Yu. N.; De Maré, G. R.; Abramenkov, A. V.; Baird, M. S.; Tverezovsky, V. V.; Nizovtsev, A. V.; Bolesov, I. G.

2003-07-01

The IR and Raman spectra of 3,3-dimethyl-1,2-bis(trimethylsilyl)cyclopropene (I) (synthesised using standard procedures) were measured in the liquid phase. Total geometry optimisation was performed at the HF/6-31G* level. The HF/6-31G*//HF/6-31G* quantum mechanical force field (QMFF) was calculated and used to determine the theoretical fundamental vibrational frequencies, their predicted IR intensities, Raman activities, and Raman depolarisation ratios. Using Pulay's scaling method and the theoretical molecular geometry, the QMFF of I was scaled by a set of scaling factors used previously for 3,3-dimethyl-1,2-bis(tert-butyl)cyclopropene (17 scale factors for a 105-dimensional problem). The scaled QMFF obtained was used to solve the vibrational problem. The quantum mechanical values of the Raman activities were converted to differential Raman cross sections. The figures for the experimental and theoretical Raman and IR spectra are presented. Assignments of the experimental vibrational spectra of I are given. They take into account the calculated potential energy distribution and the correlation between the estimations of the experimental IR and Raman intensities and Raman depolarisation ratios and the corresponding theoretical values (including Raman cross sections) calculated using the unscaled QMFF.

Role of 6-shogaol in tert -butyl hydroperoxide-induced apoptosis of HepG2 cells.

PubMed

Kim, Sang Chan; Lee, Jong Rok; Park, Sook Jahr

2014-01-01

The aim of this study was to investigate the protective effects of 6-shogaol on tert-butyl hydroperoxide (tBHP)-induced oxidative stress leading to apoptosis in human hepatoma cell line HepG2. The cells were exposed to tBHP (100 μmol/l) after pretreatment with 6-shogaol (2.5 and 5 μmol/l), and then cell viability was measured. 6-Shogaol fully prevented HepG2 cell death caused by tBHP. Treatment of tBHP resulted in apoptotic cell death as assessed by TUNEL assay and the expression of apoptosis regulator proteins, Bcl-2 family, caspases and cytochrome c. Cells treated with 6-shogaol showed rapid reduction of apoptosis by restoring these markers of apoptotic cells. In addition, 6-shogaol significantly recovered disruption of mitochondrial membrane potential as a start sign of hepatic apoptosis induced by oxidative stress. In line with this observation, antioxidative 6-shogaol inhibited generation of reactive oxygen species and depletion of reduced glutathione in tBHP-stimulated HepG2 cells. Taken together, these results for the first time showed antioxidative and antiapoptotic activities of 6-shogaol in tBHP-treated hepatoma HepG2 cells, suggesting that 6-shogaol could be beneficial in hepatic disorders caused by oxidative stress. © 2014 S. Karger AG, Basel.

[Degradation of Organic Sunscreens 2-hydroxy-4-methoxybenzophenone by UV/ H2O2 Process: Kinetics and Factors].

PubMed

Feng, Xin-xin; Du, Er-deng; Guo, Ying-qing; Li, Hua-jie; Liu, Xiang; Zhou, Fang

2015-06-01

Organic sunscreens continue to enter the environment through people's daily consumption, and become a kind of emerging contaminants. The photochemical degradation of benzophenone-3 (BP-3) in water by UV/H2O2 process was investigated. Several factors, including the initial BP-3 concentration, H2O2 concentration, UV light intensity, coexisting cations and anions, humic acid and tert-butyl alcohol, were also discussed. The results showed that BP-3 degradation rate constant decreased with increasing initial BP-3 concentration, while increased with increasing H2O2 dosage and UV intensity. Coexisting anions could reduce the degradation rate, while coexisting ferric ions could stimulate the production of OH through Fenton-like reaction, further significantly accelerated BP-3 degradation process. The BP-3 degradation would be inhibited by humic acid or tert-butyl alcohol. The electrical energy per order (E(Eo)) values were also calculated to evaluate the cost of BP-3 degradation by UV/H2O2 process. The addition of ferric ions significantly reduced the value of E(Eo). The investigation of processing parameter could provide a reference for the practical engineering applications of benzophenone compounds removal by UV/H2O2 process.

Laboratory evidence of MTBE biodegradation in Borden aquifer material

NASA Astrophysics Data System (ADS)

Schirmer, Mario; Butler, Barbara J.; Church, Clinton D.; Barker, James F.; Nadarajah, Nalina

2003-02-01

Mainly due to intrinsic biodegradation, monitored natural attenuation can be an effective and inexpensive remediation strategy at petroleum release sites. However, gasoline additives such as methyl tert-butyl ether (MTBE) can jeopardize this strategy because these compounds often degrade, if at all, at a slower rate than the collectively benzene, toluene, ethylbenzene and the xylene (BTEX) compounds. Investigation of whether a compound degrades under certain conditions, and at what rate, is therefore important to the assessment of the intrinsic remediation potential of aquifers. A natural gradient experiment with dissolved MTBE-containing gasoline in the shallow, aerobic sand aquifer at Canadian Forces Base (CFB) Borden (Ontario, Canada) from 1988 to 1996 suggested that biodegradation was the main cause of attenuation for MTBE within the aquifer. This laboratory study demonstrates biologically catalyzed MTBE degradation in Borden aquifer-like environments, and so supports the idea that attenuation due to biodegradation may have occurred in the natural gradient experiment. In an experiment with batch microcosms of aquifer material, three of the microcosms ultimately degraded MTBE to below detection, although this required more than 189 days (or >300 days in one case). Failure to detect the daughter product tert-butyl alcohol (TBA) in the field and the batch experiments could be because TBA was more readily degradable than MTBE under Borden conditions.

Identification of leachable impurities in an ophthalmic drug product originating from a polymer additive Irganox 1010 using mass spectroscopy.

PubMed

Singh, Gagandeep; Gollapalli, Ramarao; Blinder, Alejandro; Patel, Milan

2018-04-15

Pharmaceutical packaging employs a wide variety of polymers owing to their desirable features, but the compounds that could leach from the polymers into the drug products can pose serious health risks. Therefore, it is extremely important to identify such compounds so that they can be adequately quantified and evaluated for toxicological impact/safety assessments. Not only the polymer components and the additives should be considered as sources for leachable impurities, their reaction/degradation products should also be evaluated. Irganox 1010 is a common commercial antioxidant (polymer additive) used in the manufacturing of polyolefin materials for container closure systems. In our study, we identified two Irganox1010 related leachable impurities in an ophthalmic drug product using rapid and straightforward orthogonal mass spectroscopy (LC-MS and GC-MS) methods The identified impurities were 7,9-Di-tert-butyl-1 oxaspiro[4.5]deca-6,9-diene-2,8-dione and 3-[3,5-bis(tert-butyl)-1-hydroxy-4-oxocyclohexa-2,5-dienyl]propanoic acid which leached into the ophthalmic drug solution during storage. The analytical methods employed could potentially be used to identify the similar class of compounds as is or in drug products. Copyright © 2018 Elsevier B.V. All rights reserved.

Separation and determination of methyl tert-butyl ether and its degradation products by a laboratory-constructed micro-cryogenic chromatographic oven.

PubMed

Liu, Jiemin; Jiang, Guibin; Zhou, Qunfang; Liu, Jingfu; Wen, Meijuan

2003-10-01

A laboratory-made micro-cryogenic chromatographic oven was mainly improved in size, which was controlled at 6 x 6 x 2.5 cm. A thermoelectric system was used to cool the capillary column instead of the traditional liquid cryogen. A cold block connected to the cryogenic module was directly solidified at room temperature with thermally conductive adhesive so that the uniformity of transferring heat was greatly improved, and the size of the system was reduced. Moreover, this system was inexpensive and convenient for both operation and control. The newly developed device coupled with headspace solid-phase microextraction (SPME) was successfully applied to the determination of methyl tert-butyl ether (MTBE) and its degradation products. During the analysis procedure, a 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was used to extract MTBE and its degradation products. The extraction was controlled at 50 degrees C for 30 min and the NaCl content in the sample was maintained at 35%. The limits of detection (LODs) ranged from 0.006 microg mL(-1) (for MTBE) to 0.206 microg mL(-1) (for methyl acetate) and the relative standard deviations (RSD%) were below 4%. The spiked recoveries for the developed method were evaluated using various water samples as a matrix.