Excess molar volumes of the (cyclohexane + pentane,or hexane,or heptane,or octane,or nonane) systems at the temperature 298.15 K

The densities of the (cyclohexane + pentane, or hexane, or heptane, or octane, or nonane) systems were measured at the temperature 298.15 K by means of a vibrating-tube densimeter. Their respective excess molar volumes were calculated and correlated using the fourth-order Redlich—Kister equation, with the maximum likelihood principle being applied in the determination of the adjustable parameters. The values of excess molar volumes were negative for the cyclohexane + pentane system, whereas they were positive for the other systems with the values increasing with the number of carbon atoms in the respective alkane molecules.     

CH bond activation in the presence or absence of oxygen or nitrous oxide

The reaction of C₂H₆with lattice oxygen, O^2- (in the absence of gaseous oxygen), or “adsorbedℍ oxygen (in the presence of gaseous oxygen) over NiMoO₄ catalysts has been performed and compared to C₃H₈ activation. The results obtained indicate that adsorbed oxygen exhibits a higher reactivity to C₂H₆, while lattice oxygen is more reactive relative to C₃H₈. Kinetic studies of these two reactions in presence of molecular oxygen have indeed shown that the ethane oxidative dehydrogenation (ODH) is dependent on the oxygen partial pressure, whilst on the contrary propane ODH is not. In order to confirm the presence of “adsorbed” oxygen for ethane activation, ODH tests have been performed with N₂O. On increasing temperature, the O^- adsorbed species enhances the mild oxidation of ethane. The activation energy of ethane consumption E_C2H6, relative to propane (E_C3H8 = 133 kJ/mol) is 145 kJ/mol. A possible mechanism is proposed for the oxidative dehydrogenation of ethane. This revised version was published online in August 2006 with corrections to the Cover Date.     

Infrared determination of calcium or lithium nitrate in acetone solution determination of calcium or lithium in the presence of strontium or barium

A method is proposed for the infrared determination of calcium or lithium in the presence of strontium or barium. A mixture of the nitrates is treated with acetone which dissolves only the calcium or lithium nitrate. The strontium or barium nitrate is filtered off. The nitrate is evaporated to about 2 ml with a stream of dry air and then diluted to 5 ml with acetone. The infrared spectrum is scanned from 860 to 800 cm(-1) and the nitrate peak at 824 cm(-1) for calcium and 827 cm(-1) for lithium is measured. The recommended range is 1-80 mg of calcium or lithium nitrate in the presence of up to about 200 mg of strontium or barium nitrate.     

Saturated resins or stress of the resin

Although the solid-phase mode is an excellent strategy for the preparation of both biomolecules and small molecules, the synthesis of polyproline-based dendrimers has provided evidence that the capacity of the bead is limited. This phenomenon, which can be interpreted as saturation or stress of the resin, can lead to a complete breakdown of the bead structure.     

Studies on hydrozirconation of 1-alkynyl sulfoxides or sulfones and the application for the synthesis of stereodefined vinyl sulfoxides or sulfones

The hydrozirconation reaction of 1-alkynyl sulfoxides or sulfones with Cp2Zr(H)Cl in THF at room temperature predominantly gave Z-beta-zirconated vinyl sulfoxides or sulfones with excellent regioselectivity. Compared with 1-alkynyl sulfoxides, the hydrozirconation reaction of 1-alkynyl sulfones exhibits great synthetic potential, leading to the efficient preparation of Z-beta-halovinyl sulfones, Z-beta-sulfonyl alpha,beta-unsaturated ketones, and Z-beta-alkynyl vinyl sulfones. Although the reaction mechanisms are still not clear, the neighboring group participation of the sulfinyl or sulfonyl group may be playing an important role in this unique hydrozirconation reaction.     

Cross-coupling of Grignard reagents with alkyl halides or tosylates by the use of nickel or palladium containing perovskite

Nickel and palladium-containing perovskites, LaFe_0.8Ni_0.2O₃ (LFNO) and LaFe_0.95Pd_0.05O₃ (LFPO), could be employed as effective catalyst sources for the cross-coupling of nonactivated alkyl halides and tosylates with Grignard reagents in the presence of conjugated dienes. The reaction proceeded efficiently at room temperature or below using only ca. 1 mol % of catalysts with respect to Ni or Pd and the perovskites were reused without considerable loss of activity.     

Photometric or fluorimetric titration of small amounts of acids or bases

Summary Smaller amounts of acids and bases can often be determined when instead of logarithmic methods linear ones are used. If not linearized pH-curves are employed, however, but one of the other species participating in the reaction is measured, more strict conditions have to be fulfilled. The applicability is illustrated for the case of the titration of some substituted phenols.

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Photometrische oder fluorimetrische Titration kleiner Mengen von Säuren oder Basen

Zusammenfassung Wesentlich kleinere Mengen Säuren und Basen können oft bestimmt werden, wenn anstelle logarithmischer Indikationsmethoden lineare Methoden angewendet werden. Falls nicht die linearisierten pH-Kurven verwendet werden, sondern die Indikation über eines der anderen an der Reaktion teilnehmenden Teilchen verläuft, gelten andere Bedingungen. Diese Bedingungen werden abgeleitet und anhand einiger Titrationen substituierter Phenole geprüft.

Presented as poster at Euroanalysis II, Budapest 1975.     

The regioselectivity of the ring opening of 1-activated or nonactivated 2-alkoxycarbonyl or 2-cyanoaziridines by carbanions of the dicarbonyl compounds

Ring opening of title compounds with alkyl malonates, acetylacetone, methyl acetylacetate, and malononitrile was studied. The regioselectivity of the opening depends on several factors. A phenyl group on C? 3 favours C? 3? N bond cleavage, whereas C? 2? N bond cleavage is predominant with C? 3-substituted or C? 2? H aziridines. Cyanoaziridines are predominantly cleaved at C? 3? N. The aziridine configuration at C? 2 and C? 3 is maintained during the cyclisation in pyrrolidones.     

On the retrograde condensation of one or two liquids

This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out.     

Characterization of non-enzymatic acylation of amino or thiol groups of bionucleophiles by the acyl-adenylate or acyl-CoA thioester of cholic acid

Acyl-adenylates and acyl-CoA thioesters of bile acids (BAs) are highly electrophilic acyl-linked metabolites which can undergo transacylation reactions with amino and thiol groups of nucleophilic groups on acceptor molecules such as amino acids, peptides, and proteins. Here, non-enzymatic acylation at pH 7.4 of glycine, taurine, glutathione (GSH), and N-acetylcysteine (NAC) by cholyl-adenylate (CA-AMP) was compared with that mediated by cholyl-CoA thioester (CA-CoA) using a 1:1 mixture of stable isotopically labeled CA-AMP and unlabeled CA-CoA. The transacylation products of these substrates were analyzed by liquid chromatography/electrospray ionization linear ion-trap mass spectrometry in negative-ion detection mode. CA-AMP was more reactive than CA-CoA with the amino group of glycine or taurine than with the thiol group of GSH or NAC. In contrast, CA-CoA was more reactive than CA-AMP with the thiol group of GSH or NAC and was far less reactive with the amino group of glycine or taurine. These differences in the reactivity of CA-AMP as compared with that of CA-CoA towards amino and thiol groups may be attributed to the electrophilicity of the carbonyl carbon of these acyl-linked cholic acid metabolites and the nucleophilicity of the amino and thiol group in the bionucleophiles that were studied.     

Kinetic study of the Ce(III)- or ferroin-catalyzed Belousov-Zhabotinsky reaction with ethyl- or butyl-malonic acid

In a stirred batch experiment, ferroin (Fe(phen)₃²⁺) behaves differently from Ce(III) as a catalyst for the Belousov-Zhabotinsky reaction with ethyl- or n-butyl-malonic acid (EtMA or BuMA) The effects of bromate ion, organic substrate, metal-ion catalyst, and sulfuric acid on the oscillating pattern were investigated. The kinetics of the reactions of methylmalonic acid (MeMA), bromomethyl-malonic acid (BrMeMA), EtMA, bromoethylmalonic acid (BrEtMA), BuMA, bromo(n-butyl)malonic acid (BrBuMA) with Ce(IV) or Fe(phen)₃³⁺ ion were studied. Under aerobic or anaerobic conditions, the order of reactivity toward Ce(IV) oxidation is MeMA > EtMA > BuMA > BrMeMA >> (BrEtMA, BrBuMA). Under aerobic conditions, the order of reactivity toward reacting with Fe(phen)₃³⁺ ion is MeMA > (BuMA, EtMA) >> (BrMeMA, BrEtMA, BrBuMA). The experimental results are rationalized. © 1996 John Wiley & Sons, Inc.     

Aggregation of the Adsorbed Proteins—in Solution or on the Surface？

The adsorption of bovine serum albumin(BSA) on porous polyethylene(PE) membrane was studied based on adsorption and desorption measurements as well as FTIR analysis. A different mechanism was roposed which showed that a critical concentration existed in the adsorptional process. Below this concentration, the adsorption seems to be conducted in a normal side-on way; above this concentration,the adsorption is in an aggregation way.     

Measurement of VLE (TPx or TPxy data) for hydrogen sulfide + (dimethylsulfide or ethylmethylsulfide or carbon disulfide) and methane solubilities in (dimethylsulfide or ethylmethylsulfide or methylmercaptan or ethylmercaptan)

VLE data (gas solubilities (TPx data) or complete TPxy data) were measured for the following systems:

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hydrogen sulfide (H₂S) + dimethylsulfide (DMS) at 278, 293, 313, and 333 K.