Liquid Reaction Medium Research Articles

Whiskers 5. Copolyesters of 4‐hydroxybenzoic acid and 2‐(4‐carboxyphenyl)‐5‐hydroxybenzoxazole

Abstract2‐(4‐Carboxyphenyl)‐5‐hydroxybenzoxazole was obtained by a multi‐step synthesis starting from commercial 2,5‐dimethoxyaniline. Its homopolyester as well as its copolyester with 4‐hydroxybenzoic acid were prepared by polycondensation of the acetyl derivatives in an inert, liquid reaction medium at temperatures of 320, 350 or 400°C. The resulting polyesters are highly crystalline (>90% crystallinity), infusible and isoluble materials. They were characterized by elemental analyses, IR spectroscopy, WAXS and DSC measurements, and electron microscopy. The WAXS powder patterns show that the benzoxazole monomer does not fit well into the crystal modification 1 of poly(4‐hydroxybenzoic acid). Whisker‐type single crystals were obtained only when the 4‐oxybenzoate units represent 90% of the copolyesters. Polycondensations of monomers having silylated carboxyl groups did not yield better results.

Effects of concentrations of substrates supplied to N2-fixing soybean bacteroids in flow chamber reactions

A liquid reaction medium containing dissolved air, oxyleghaemoglobin and low concentrations (0-2 mM) of glucose, succinate, malate or ethanol, was supplied to bacteroids prepared from soybean root nodules and confined in a stirred reaction chamber. Measurements of concentrations of O$_{2}$, CO$_{2}$ and NH$_{3}$ from N$_{2}$ fixation, at various flow rates through the chamber, were used to calculate rates of respiration and N$_{2}$ fixation. Glucose was utilized poorly under all conditions. Ethanol was required at 0.2-2.0 mM before stimulations of O$_{2}$ demand and N$_{2}$ fixation were observed. Demand for O$_{2}$ was enhanced by 0.05 mM to 0.5 mM succinate and malate at concentrations of O$_{2}$ from 10 nM to 50 nM. However, the concentrations of C4-dicarboxylate and dissolved O$_{2}$ determined whether N$_{2}$ fixation was stimulated or inhibited by these substrates. It is postulated that these effects were associated with the presence in the bacteroids of two malic enzymes and a pyruvate dehydrogenase complex, the resulting acetyl-CoA being channelled through the tricarboxylic acid (TCA) cycle (N$_{2}$ fixation stimulated) or to poly-$\beta $-hydroxybutyrate (PHB) accumulation (N$_{2}$ fixation inhibited). Contrary to earlier results, the O$_{2}$ consumption data suggested that there was a single terminal oxidase (K$_{\text{m}}$ 20-26 nM and V$_{\max}$ 20-29 nmol O$_{2}$ min$^{-1}$ (mg dry mass)$^{-1}$ operating in the range of O$_{2}$ concentration in which N$_{2}$ fixation occurred.

Supply of O2 regulates O2 demand during utilization of reserves of poly-beta-hydroxybutyrate in N2-fixing soybean bacteroids.

A liquid reaction medium containing dissolved air and oxyleghaemoglobin, but no energy-yielding substrate, was supplied to bacteroids confined in a stirred flow reaction chamber. The relative oxygenation of the leghaemoglobin in the chamber was determined automatically by spectrophotometry of the effluent solution, and the concentrations of free, dissolved O2 ([O2]) and rates of O2 consumption were calculated. Dissolved CO2 and NH3 from N2 fixation were determined in fractions of the effluent solution. Bacteroids utilized endogenous reserves of poly-beta-hydroxybutyrate (PHB), which were depleted by 9.2% during a typical 5 h-long experiment. Stepwise increases in flow rate (increasing supply of O2) initially produced a drop in O2 demand and resulted in a rise in [O2] and a decline in N2 fixation. Subsequently, O2 demand rose (presumably because of increased mobilization of substrate from PHB) and [O2] declined to a low level. N2 fixation was fully restored, or even enhanced, within 15-20 min of establishment of a new, steady [O2]. This pattern of regulation by O2 supply was completely eliminated by adding low concentrations (20-50 microM) of oxidizable substrate (succinate, malate, ethanol) to the reaction medium. During endogenous activity, rates of CO2 evolution were proportional to, but less than, rates of O2 consumption up to 5.4 nmol O2 min-1 mg-1, above which CO2 evolution exceeded O2 consumption. These and other features of endogenous activity are discussed in relation to sustaining N2 fixation by nodules in vivo.

Bacteroids from soybean root nodules: accumulation of poly- β -hydroxybutyrate during supply of malate and succinate in relation to N 2 fixation in flow-chamber reactions

A liquid reaction medium containing dissolved air and oxyleghaemoglobin was supplied to bacteroids confined in a stirred reaction chamber with no gas phase. The relative oxygenation of leghaemoglobin, dissolved CO 2 and NH 3 from N 2 fixation were monitored before, during (when N 2 fixation was diminished) and after the supply of [ 14 C]malate and succinate. The amounts and location of 14 C-labelled products were determined in bacteroids recovered from the chamber and 14 CO 2 was measured in the effluent. During the supply of [ 14 C]succinate, the bacteroids accumulated most 14 C from C 2 and C 3 whereas 14 CO 2 arose primarily from C 1 and C 4 . This suggested that production of pyruvate from malate via malic enzyme was a central feature. For up to 80 min after removal of [ 14 C]malate and succinate, CO 2 arose from stored carbon and N 2 fixation was enhanced; during this period 14 C continued to accumulate in poly-β-hydroxybutyrate, until this accounted for about 90% of bacteroid 14 C. Thereafter CO 2 was evolved with steady, low radioactivity and enhanced N 2 fixation continued. These results supported the proposal that poly-β-hydroxybutyrate, which is present in large amounts (50-70% of dry mass) in these bacteroids, is a mobilizable, energy-yielding reserve that provides endogenous substrates for support of N 2 fixation when exogenous substrates are not available.

Synthesis of U‐14C‐labelled 5‐hydroxymethyl‐2‐furaldehyde

AbstractUniformally 14C‐labelled 5‐hydroxymethyl‐2‐furaldehyde was synthesized by dehydration of D‐[U‐14C]fructose on an H+ ion exchange resin and a water isobutylmethyl ketone biphasic liquid reaction medium. The optimal reaction time was 45min, and after HPLC purification the radiochemical yield was 50%. The whole process took 2 hours.

New polymer syntheses 16. LC‐copolyesters of 3‐(4‐hydroxyphenyl) propionic acid and 4‐hydroxy benzoic acids

AbstractThe polycondensation of 3‐(4‐hydroxy phenyl)‐propionic acid, 4‐Hypp, by means of acetanhydride or acetylchloride was conducted either in the presence or in the absence of a liquid reaction medium. DSC measurements, polarizing microscope, and X‐ray diffraction studies indicate poly(4‐Hypp) possesses at about 215°C a reversible first order transition between two solid phases. Copolyesters containing various mole ratios of 4‐Hypp and 4‐hydroxy benzoic acid, 4‐Hybe, were prepared by bulk condensation with acetanhydride at 320°C. At 4‐Hypp/4‐Hybe ratios less than 1.0:1.5 the reaction product was heterogeneous, containing crystals of pure poly(4‐Hybe). Neither increasing the reaction time nor the variation of the transesterification catalyst resulted in an entirely homogeneous copolyester. However, for 4‐Hypp/4‐Hybe ratios greater than 1.0:1.5, 13C NMR spectra indicate perfectly random sequences. Also, terpolyesters containing 3‐chloro‐4‐hydroxy‐ or 3,5‐dichloro‐4‐hydroxy‐benzoic acid were heterogeneous with less than 30 mol % 4‐Hypp. DSC measurements revealed for all polyesters a glass transition in the range of 55–78°C. Temperature dependent X‐ray diffraction studies confirm that the solid phase is a s.c. LC‐glss. Correspondingly low heat distortion temperatures were found by thermomechanical analyses. The copolyesters display under the polarizing microscope LC‐phase up to temperatures of 450–480°C, where rapid thermal degradation prevents further investigations. In the case of the 4‐Hypp/4‐Hybe 1:1 copolyester, the LC‐phase extends over a temperature range of about 400°C. TGA measurements indicate beginning thermal degradation at temperatures between 350 and 380°C.

Thermal agglomeration kinetics of low nuclearity molybdenum clusters in liquid poly(dimethylsiloxane-co-methylphenylsiloxane): stability of metal clusters in arene containing liquid reaction media. Part 3

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermal agglomeration kinetics of low nuclearity molybdenum clusters in liquid poly(dimethylsiloxane-co-methylphenylsiloxane): stability of metal clusters in arene containing liquid reaction media. Part 3Mark P. Andrews and Geoffrey A. OzinCite this: J. Phys. Chem. 1986, 90, 15, 3353–3359Publication Date (Print):July 1, 1986Publication History Published online1 May 2002Published inissue 1 July 1986https://doi.org/10.1021/j100406a010RIGHTS & PERMISSIONSArticle Views31Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (773 KB) Get e-Alerts

Oxidative coupling of phenols catalyzed by copper chloride coordinated to aminated polystyrene: a possible model reaction for dioxygen reduction by laccase and tyrosinase

The influence of ZnCl 2 on the reaction rate of the oxidative coupling of 2,6-disubstituted phenols, catalyzed by Cu—polyamine complexes has been investigated. It is shown that the role of free CuCl 2, previously shown to be essential for catalytic activity, can be taken over by ZnCl 2. Furthermore, the influences of the dioxygen pressure on the reaction has been investigated. The reaction rate at high phenol concentrations appears to be dependent on the dioxygen concentration, the type of phenol and the degree of substitution of dimethylaminomethylated polystyrene. Therefore it can be concluded that the reaction is not controlled by diffusion of dioxygen into the liquid reaction medium. The results are discussed in terms of mechanisms published by other authors in which dimeric copper species act as catalytic centers. A mechanism for the reduction of dioxygen by the copper complexes is suggested and its relation to the Type-3 Cu of laccase and the Cu-pair of tyrosinase is discussed.

Liquid-phase oxidation of propane

A process for the oxidation of propane is disclosed. The process comprises contracting oxygen with a liquid reaction medium comprising propane and a liquid organic material that is a solvent for propane and which is non-reactive with oxygen under the conditions of the process. The process is carried out under superatmospheric pressure, at an elevated temperature, and for a period of time sufficient to produce oxygenated products, including one or more of acetone and isopropyl alcohol. 1.

Determination of Oxygen in Yttrium Fluoride by Vaccum Distillation Technique

A conventional vacuum fusion gas analysis unit is used for the determination of oxygen in yttrium fluoride. The yttrium fluoride ia distilled from the furnace, leaving the less volatile oxygen-containing compounds to be reduced by the carbon crucible. Recoveries of oxygen are quantitative when a liquid reaction medium is provided for the reduction. The effect of platinum as the bath medium on the rate of carbon monoxide evolution is discussed. (auth)