Tetraethylammonium Acetate Research Articles

Liquid Salt Hydrate Acid Gas Absorbents: An Unusual Desorption Of Carbon Dioxide And Hydrogen Sulfide Upon Solidification

Abstract It was recently reported that certain salt hydrate melts can function as pressure swing absorbents for acid gases. The utility of these salt hydrates derives from their large and reversible acid gas absorption capacities. Typical is the salt hydrate tetramethylammonium fluoride tetrahydrate which as a melt absorbs 0.30 mol CO2/mol salt at 50[ddot]C and 100 kPa CO2. It has now been discovered that the reactivity of some of these salt hydrate melts with CO2 and H2S exhibits an unusual and unexpected temperature dependence. When certain specific salt hydrate melts containing absorbed CO2 were cooled to temperatures which resulted in solidification, CO2 was spontaneously desorbed. For example, a sample of tetraethylammonium acetate tetrahydrate (TEAA) containing 0.15 mol CO2/mol salt at 50[ddot]C and 102 kPa desorbed 90% of its bound CO2 upon cooling to 26[ddot]C. Gas absorption and desorption are completely reversible, and the absorbent can be cycled by simply raising or lowering the temperature through the point of solidification. Similarly, a sample of TEAA containing 0.30 mol H2S/mol salt at 50[ddot]C desorbed H2S upon cooling to 10[ddot]C. A rationale for this unusual temperature-dependent desorption of acid gases from salt hydrates is presented. The modest decrease in temperature required for an abrupt release of gas from TEAA may supply a kind of “on/off” switch for gas absorption which may be of considerable value for the separation of acid gases, particularly H2S, from process streams.

Ca 2+ currents in cerebellar granule neurones: Role of internal MG 2+ in altering characteristics and antagonist effects

Using the whole-cell patch-clamp technique, Ca 2+ channel currents were measured in cultured rat cerebellar granule neurones in the presence of 10 mM Ba 2+. Two different solutions were used to fill patch pipettes, one containing mainly tetraethylammonium acetate (TEA-Ac solution), and the other mainly caesium and HEPES (Cs-HEPES solution). Under these two different intracellular conditions markedly different Ca 2+ channel currents were recorded. When TEA-Ac solution was used intracellularly, small, Cd 2+-sensitive inward currents (approx. −55 pA) that were inhibited by the dihydropyridine antagonist (−)-202-791 and the GABA B agonist (−)-baclofen were observed. These currents were insensitive to the Ca 2+ channel clocking toxins ω-conotoxin GVIA (ω-CgTX) and ω-agatoxin IVA and were enhanced by the dihydropyridine agonist (+)-202-791. In contrast, when the Cs-HEPES solution was used, currents were 2–3 times larger (approx. −130pA), inhibited by (−)-202-791, ω-CgTX and ω-agatoxin IVA but were unaffected by (−)-baclofen. Furthermore, both (+)-202-791 and Bay K8644 in the presence of Cs-HEPES solution produced only a transient enhancement that was followed by an inhibition. Analysis of steady-state inactivation revealed two components of current in both cases, with similar voltage dependencies. The factor(s) giving rise to these differences were investigated in terms of current amplitude and responses to (−)-baclofen and ω-CgTX and were found to be mainly due to the concentrations of Mg 2+ and ATP added to the patch pipette solutions. Furthermore, free internal Mg 2+ concentrations of greater than 0.2 mM selectively inhibited ω-CgTX-sensitive Ca 2+ channels. Preliminary evidence indicates that the same may be true of ω-Aga IVA-sensitive P-type current. These data suggest that the N-type Ca 2+ channels in these cells are preferentially inhibited by intracellular Mg 2+ and this may provide an explanation for discrepancies between the results of different groups investigating Ca 2+ channel currents in similar cell types.

In vitro effects of the nephrotoxins ochratoxin A and citrinin upon biochemical function of porcine kidney.

Ochratoxin A and citrinin are nephrotoxic mycotoxins found in a variety of foods and feeds. Before studying possible interactions between these two toxins, their individual biochemical effects were examined in vitro by using renal cortical explants derived from male swine of the Hormel-Hanford strain. The following measurements were performed: macromolecule biosynthesis (protein, RNA, and DNA), respiration (14CO2 from [14C]glucose), organic ion (tetraethyl ammonium acetate, i.e., TEA) transport, and membrane perturbation (protein leakage into medium). Levels of the toxins ranged from 0.001 to 1 mM. Ochratoxin A inhibited macromolecule biosynthesis at a lower concentration (0.001 mM) than did citrinin. Protein and DNA synthesis were particularly sensitive to ochratoxin A. Syntheses of protein and DNA were inhibited at ochratoxin A concentrations of 0.01 and 0.001 mM, respectively. RNA synthesis was less sensitive to the mycotoxin; it was inhibited only 60% at 1 mM, the highest concentration of ochratoxin A tested. Citrinin levels of 0.01 mM were required for inhibition of RNA, DNA, and protein synthesis. Inhibition by citrinin was approximately equal for all three classes of macromolecules. Citrinin was more effective than ochratoxin A in the inhibition of respiration and TEA transport; the minimum effective levels of citrinin were 1 and 0.01 mM, respectively. Serious membrane damage as evidenced by increased protein leakage was not caused by either toxin. Stimulation of respiration, perhaps reflective of uncoupling of oxidative phosphorylation, was produced by an ochratoxin A concentration of 1 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversed-phase high-performance liquid chromatography of amphoteric β-lactam antibiotics: effects of columns, ion-pairing reagents and mobile phase pH on their retention times

The separation of five amino beta-lactam antibiotics by reversed-phase high-performance liquid chromatography was studied as an insight into their retention behaviour. These five amphoteric compounds are cephradine, cephalexine, cefaclor, ampicillin and amoxicillin. Both octadecylsilane-bonded silica (C18) columns and phenyl-bonded silica (phenyl) columns were used, with mobile phase pH values between 2.5 and 7.4. In the absence of ion-pairing reagents the retention times for all the five compounds were the shortest at pH 4-6. The phenyl column was found to improve the separation between cephradine and ampicillin at pH values lower than 3, when these two compounds appeared as fused peaks on the C18 on C18 columns, with mobile phases both with and without ion-pairing reagents, were compared. The addition of 0.005 or 0.02 M tetraethylammonium acetate to the mobile phase did not result in significant ion-pair formation, except at pH values higher than 5.5. A strong ion-pairing effect was obtained at pH values higher than 6 with 0.005 or 0.02 M tetrabutylammonium phosphate, and the retention was decreased at pH values lower than 4. On the other hand, 0.005 M heptanesulphonic acid exhibited an ion-pair retention effect at pH values lower than 5. The molecular structures and pK(a) values were used to account for the retention behaviour of these antibiotics in the various mobile phases.

Solvent polarity scales. 1. Determination of ET and π* values for phosphonium and ammonium melts

AbstractThe solvent polarity of a series of organic salts in their molten state has been determined using the solvatochromic dyes: pyridinium N‐phenolate betaine, the basis of the ET scale, and N,N‐diethyl‐4‐nitroniline, one of the primary standards for the π* scale. Each of these dyes was dissolved in the following liquids: lithium acetate–sodium acetate–potassium acetate eutectic; ethylammonium chloride; dimethylammonium cloride; diethylammonium nitrate; ammonium trifluoracetate; tetraethylammonium acetate; tetrabutylphosphonium chloride; octyltributylphosphonium chloride; dodecyltributylphosphonium chloride; tetrabutylammonium bromide; tetrabutylphosphonium bromide; octyltributylphosphonium bromide; dodecyltributylphosphonium bromide; octyltributylphosphonium iodide; dodecyltributylphosphonium iodide; tetrahexylammonium benzoate; methyltrioctylphosphonium dimethylphosphate; and methyltrioctylammonium chloride. The ultraviolet and visible spectra were measured for each of these. In addition, data were collected as a function of temperature and in the presence of neutral and ionic additives. In general, these molten salts represent solvent polarities equivalent to moderately polar aprotic solvents such as acetone and acetonitrile. The salts with cations capable of being hydrogen bond donors gave considerably higher values, equivalent to or higher than water, the solvent with the highest value on the ET scale. These and the eutectic mixture are thought to involve specific dye–solvent interactions which cause these anomalously high values.

ETUDE DE LA REACTION DE DIHYDROXYLATION DE PHOSPHONATES α,β-, β,γ- ET γ,δ-ETHYLENIQUES A L'AIDE D'HYDROPEROXYDES CATALYSEE PAR LE TETROXYDE D'OSMIUM: SPECIFICITE D'ACTION DE L'HYDROPEROXYDE DE TERTIOBUTYLE

Abstract The catalytic cis dihydroxylation of alkenyl phosphonates using Osmium tetraoxide is reported. First, we confirm that the hydrogen peroxide-Osmium tetroxide system leads to the diol-ketol mixture. On the other hand, the use of the tert-butyl hydroperoxide-Osmium tetroxide system in presence of tetraethylammonium acetate overcomes the overoxidation reaction and good yields of threo dihydroxyalkyl phosphonates are obtained. The stereoselectivity of the reaction and the intramolecular cyclisation of these diols are briefly discussed.

Tetraethylammonium acetate tetrahydrate, (C2H5)4N+ CH3COO? � 4H2O, a layer structure with cations sandwiched between nets of puckered polygons formed by hydrogen-bonded anions and water molecules

Crystals of (C2H5)4N+ CH3COOO− · 4H2O crystallize in space groupP ī, witha=12.327(2),b=17.196(6),c=8.753(3) A, α=94.28(2), β=91.09(2), γ=120.30(2)°, andZ=4. The structure was solved by direct methods and refined toR F -0.060 for 4803 MoKα data. In the crystal structure, ordered (C2H5)4N+ cations are sandwiched between puckered layers of hydrogen-bonded water molecules and acetate anions. Each wateranion layer is constructed from an edge-sharing assembly of six independent, irregular, and non-planar polygons (two nonagons, two hexagons and two pentagons). All protons in the scheme of hydrogen bonding are uniquely located.

Crystal structures of tetraethylammonium fluoride–water (4/11) and tetraethylammonium acetate tetrahydrate

Crystal structures of tetraethylammonium fluoride–water (4/11) and tetraethylammonium acetate tetrahydrate

ChemInform Abstract: A STEREOSELECTIVE SYNTHETIC ROUTE TO (R)‐ZEARALANONE

Abstract(S)‐Zearalenon (I) wird in die Derivate (II) und (III) übergeführt und dann alkalisch zu (IVa) gespalten, das zu (IVb) methyliert und weiter in das Tosylat (IVc) übergeführt wird.

A stereoselective synthetic route to (R)-zearalanone.

A stereoselective synthetic route to (R)-zearalanone was studied to determine the effect of absolute configuration on uterotropic activity. Starting with the naturally occurring (S)-zearalenone the phenolic groups were converted into their respective benzyl ethers followed by ketalization of the carbon-6 carbonyl function using ethylene glycol to give 3 in high yield. The 14-membered lactone could then be opened without racemization of the carbon-10 position by treatment of 3 with sodium hydroxide in dimethyl sulfoxide to yield 4 which was converted to its methyl ester 5 with diazomethane. The reaction of hydroxy ester 5 with p-toluenesulfonyl chloride in pyridine yielded toluenesulfonic ester 6. The reaction of 6 with tetraethylammonium acetate in refluxing methyl ethyl ketone gave 7. The methyl ester in 7 was hydrolyzed to give 8 which was hydrolyzed in aqueous tetrahydrofuran to yield 9. Hydroxy acid 9 was cyclized with trifluoroacetic anhydride in benzene to yield 10 which was reduced and hydrogeneolyzed to give (R)-zearalanone. The mouse uterotropic assay revealed that (R)-zearalanone had no activity but a mixture of (R) and (S) gave approximately the same response as (S) suggesting that (R) has a synergistic effect on the uterotropic activity of (S).

Studies on cyclic polyols: Part IX. Directive effects in the reactions of polysubstituted cyclopentanes

Earlier conclusions that an electronegative substituent exerts a strong influence on the direction of opening of an unhindered, adjacent epoxide by a nucleophilic reagent have been substantiated; the nucleophile attacks stereoselectively at the end of the oxirane ring farthest from the vicinal, electronegative substituent (OH or Br). cis-1,2:3,4-Diepoxycyclopentane 7 has been prepared, and, unlike the substituted monoepoxides of cyclopentane, this compound shows no stereoselectivity for the attack of a nucleophile (Br − or H 2O). When the anhydro- O-isopropylidene cyclopentanetetrols are subjected to acid-catalyzed hydrolysis, the first products are anhydrotetrols, because of the greater lability of the O-isopropylidene residue. The corresponding O-isopropylidenetetrols are not detected in partial hydrolyzates, which contain tetrols, anhydrotetrols, and starting material. When a hindered halocyclopentane, 3,5-dibromo-1,2- O-isopropylidene-(1,2/3,5)-1,2-cyclopentane-diol ( 14), reacts with tetraethylammonium acetate, the expected nucleophilic displacement of halogen by acetate is not observed; instead a 1,2-elimination of hydrogen bromide occurs. Favored conformations of several derivatives of cyclopentane cyclitols are assigned, on the basis of the presence of strong, intramolecular, hydrogen bonds and the need to minimize nonbonded repulsion. Improved methods of synthesis, and several new derivatives of cyclopentane cyclitols, are described. The strong band near 840 cm −1 in the infrared spectra of epoxides is assigned to a CO stretching, rather than to a CH rocking mode.

Cytotoxic compounds. IX. The dimethanesulphonates of 3-phenylthiopropane-1,2-diol and of 2-phenylthiopropane-1,3-diol; their reactions with nucleophiles, and rearrangements through sulphonium ions.

The products formed in the reactions of each of the above dimethanesulphonates with various nucleophiles have been examined by nuclear magnetic resonance spectroscopy. Substitution without rearrangement is the main reaction with methanolic sodium phenyl sulphide, sodium benzyl sulphide, and sodium ethyl sulphide, whilst elimination is dominant with tetraethylammonium acetate in acetone and with methanolic sodium methoxide. During solvolysis in acetic acid, thermodynamic control is established, and both dimethanesulphonates give only 3-phenylthiopropane-1,2-diol diacetate, but with potassium acetate in acetic anhydride each forms a mixture of the 1,2- and the 1,3-diacetate. Solvolysis in methanol also gives a mixture, of the 1,2- and the 1,3- dimethyl ether. The compositions of these mixtures, formed under kinetic control, considered in conjunction with the probable sequence of reactions involved, indicate that the primary carbon atom in the intermediate unsymmetrical cyclic sulphonium ions is preferentially, but not exclusively, attacked.

Proximity Effects. V. Reaction of Cycloöctene Dibromide with Tetraethylammonium Acetate

Proximity Effects. V. Reaction of Cycloöctene Dibromide with Tetraethylammonium Acetate