Water Reflux Research Articles

High temperature preparation of vanadium phosphate catalysts using water as solvent

Vanadium phosphate catalysts prepared in aqueous solution at elevated temperature (145 °C) using either H3PO3 or V2O4 as reactants are described and discussed. This methodology produces catalysts with a much higher surface area (ca. 20 m2g−1) compared with those prepared using aqueous routes using HCl as reducing agent (ca. 4 m2g−1). The materials were characterised using a combination of powder XRD, BET surface area measurement, laser Raman spectroscopy, TGA, electron microscopy and 31P spin echo mapping NMR spectroscopy. Refluxing the precursors in water prior to activation was crucial in obtaining high surface area materials, and 31P spin echo mapping NMR together with electron microscopy data indicate that the water reflux step influences the relative amounts of V4+ and V5+ phases present in the catalyst, as well as reducing the size of the crystallites. A correlation between the activity of the catalyst and the surface area is observed. However, a small group of catalysts display a higher activity than that expected from this correlation, and this increased activity is discussed in terms of the interaction of V4+ and V5+ phases.

Cross-coupling reactions with boronic acids in water catalysed by oxime-derived palladacycles

Palladacycles derived from phenone-oximes 1 are efficient precatalysts for the Suzuki–Miyaura coupling of arylboronic acids with aromatic and heteroaromatic bromides and chlorides under water reflux under aerobic conditions. Alternatively, the coupling can also be carried out at room temperature in methanol–water. Aryl bromides gave biaryls with TON up to 10 5 and TOF up to 7×10 4 h −1. Activated and deactivated aryl chlorides need the presence of TBAB for the couplings, showing slightly lower efficiency (TON up to 9000 and TOF up to 3850 h −1). C(sp 2)C(sp 3) bonds can also be formed by cross-coupling reactions of trimethylboroxine and butylboronic acid with aromatic bromides and chlorides under water reflux and of benzylic and allylic chlorides or acetates with arylboronic acids in acetone–water at room temperature.

Studies on the phloroglucinol–HCl reactive material produced by squash fruit elicited with pectinase: Isolation using hydrolytic enzymes and release of p -coumaryl aldehyde by water reflux

Studies on the phloroglucinol–HCl reactive material produced by squash fruit elicited with pectinase: Isolation using hydrolytic enzymes and release of p -coumaryl aldehyde by water reflux

Studies on the phloroglucinol–HCl reactive material produced by squash fruit elicited with pectinase: Isolation using hydrolytic enzymes and release of p -coumaryl aldehyde by water reflux

Pathological tissues from a variety of plants turn red when treated with the histochemical reagent phloroglucinol (PG)–HCl. This induced PG–HCl reacting material has been termed both wound gum and, more recently, induced lignin or lignin-like material. We are exploring alternative approaches to better identify this induced material. In this report, we describe methods for purifying the PG–HCl reactive material from solvent-washed tissue preparations and measuring the amount of p -coumaryl aldehyde released from the purified material by boiling in water. Acorn squash fruit wall tissue was sliced, sprayed with pectinase to elicit the formation of PG–HCl reactive material and incubated up to 72 h at 27°C. Sampled tissue was washed extensively with water and organic solvents. Insoluble residues were treated with cell wall degrading enzymes to remove cell wall materials, and dimethyl sulfoxide was used to dissolve starch. Yields of residual material increased from 7.5% in the time zero samples to 29.7% after 72 h. Refluxing the purified material in water released <6 μ g p -coumaryl aldehyde g −1 from preparations of tissue at time zero and 8100 μ g p -coumaryl aldehyde g −1 from samples incubated for 48 h. These results suggest that the function of the material is to sequester phytoalexins, but are not consistent with the material being lignin. Published by Elsevier Science Ltd.

Green chemistry approaches to the Knoevenagel condensation: comparison of ethanol, water and solvent free (dry grind) approaches

We report a comparative study of the Knoevenagel condensation with a variety of substituted benzaldehydes (17 examples) and cyanoamides (3 examples), using three different methodologies: (a) traditional ethanol reflux; (b) water reflux; and (c) solvent free conditions. Almost without exception these reactions proceeded faster, more cleanly and in higher yields when the reactions were conducted in a solvent-free fashion. Additionally, our solvent free approach allowed the use of nitrobenzaldehydes, which failed to yield the desired products under traditional and water based approaches.

Determinação do teor de tanino de quatro variedades de sorgo por intermédio de métodos quantitativos

Este experimento foi realizado para comparar o conteúdo de tanino de quatro variedades de sorgo usando seis métodos quantitativos de determinação de tanino. Foi usado delineamento inteiramente ao acaso em arranjo fatorial 4 x 6 (variedade x método) com quatro repetições, em que T1 - Folin Denis (Refluxo com reagente de Folin Denis), T2 - Folin Denis (Refluxo com água), T3 - Folin Denis (refluxo com água, filtragem após o relfuxo), T4 - Lowental, T5 - Vanilina ácido clorídrico de Burns e T6 - Vanilina ácido clorídrico modificado de Burns. Maiores teores de tanino foram observados, quando determinados pelos métodos de Burns e os menores teores, pelo método de Lowental. Os resultados mostraram grande variabilidade entre os métodos usados para determinar tanino. Pela praticidade em nível de laboratório, o método Folin Denis - CNPSA pode ser o método mais recomendado.

Evaluation of No-Clean Fluxes for High Reliability Applications

ABSTRACTA series of rosin mildly activated, halide free, low residue fluxes have been evaluated for use with hot bar reflow of Tape Carrier Packages (TCP) to printed circuit boards (PCB). Materials were studied with respect to their wettability, SIR performance, water reflux extractable ionics and residue levels. Ionic levels were measured by FTIR and Ion chromatography. A flux was selected which has demonstrated acceptable performance in 156C/85%RH 10V biased stress testing.

Zeta Potential of Alumina Membrane

Since, the zeta potential of membranes affect the filtration characteristics of the solid-liquid separation process for membrane bioreactors, the variability of zeta potential with operating conditions was investigated for alumina membranes, used for membrane bioreactor system. The surface hydroxyl group density of alumina mambranes was also investigated. The distilled water immersion test revealed that the isoelectric point of the membrane shifts from 5.5, initial value, to 6.0 in distilled water at 37°C after 1000h, and also, to 6.5 after distilled water reflux for 100h. The measurement of surface hydroxyl group density showed that refluxing for 100h is equivalent to immersion in water at 37°C for several years. This suggests that the variability in zeta potential under normal mambrane operating conditions, for 2-3 years, is negligible. It is also apparent that the variability in pore size distribution has negligible effects.

Effects of theophylline, choleragen and loperamide on rabbit ileal fluid and electrolyte transport in vitro.

1 The effects of theophylline and cholera toxin on water and anion movements across rabbit ileum in vitro and the reversal of these effects by the opiate action of loperamide have been investigated. Water movement across the mucosal and serosal surfaces of the tissue was measured continuously by a high resolution method. 2 Theophylline caused an increase in short circuit current and reversed the direction of net C1- movement, due mainly to a decrease in mucosal-serosal flux. It also caused a rapid, but transient, reversal in the direction of fluid movement across the mucosal surface. Fluid outflow across the serosal surface was decreased but not reversed. Cholera toxin caused a slow inhibition of water movement across both mucosal and serosal surfaces. 3 Theophylline increased the exit rate of 77Br across the mucosal surface and decreased the exit rate of 77Br across the serosal surface. Theophylline increased the exit rate of 3H-labelled mannitol across the mucosal surface. 4 Loperamide reversed the effects of theophylline and cholera toxin on water flow across the mucosal and serosal surfaces and on net transepithelial C1- flux; it also increased the rate of 77Br exit across the serosal surface of theophylline-treated tissue. These effects of loperamide could be reversed by naloxone. 5 The hydraulic conductivity, Lp of the serosal surface was measured directly by determining the osmotic flow generated by low concentrations of polyethylene glycol (mol. wt. 20,000 and 90,000). Theophylline reduced the Lp by 57%. Loperamide added to theophylline-treated tissues increased the Lp by 340%. This effect was reversed by naloxone. 6 These results indicate that modulation of intestinal smooth muscle tone affects transepithelial ion and water flows in vitro. The increase in tone induced by secretagogues increases ion and water reflux via wide shunt channels in the mucosa and thereby reduces net absorption. The increased net fluid and electrolyte absorption induced by loperamide results from the opiate-dependent inhibition of acetylcholine release from intrinsic ganglia which reduces smooth muscle tone and thereby enhances the fluid and electrolyte conductance of the submucosal layers.

Is there an osmotic regulatory mechanism in algae and higher plants?

Under water-stress conditions the amounts of various polyols and also of the imino acid proline are found to increase significantly in different algae and higher plants. These substances have been interpreted until now to act osmotically by increasing the concentration in the cell, thus causing water reflux and balancing osmotic pressure difference from outside the cell to inside. A new concept is described, which proposes that the regulatory function of these accumulating substances is conducted by two mechanisms quite different from osmotic regulation. It is assumed that these regulatory pathways are connected with the hydrophobic groups of biopolymers in the cell cytoplasm. (1) Polyols can replace water molecules by means of their water like OH-groups and thus participate in the hydrophobically enforced water structure. (2) Proline is postulated to associate via its hydrophobic phot with hydrophobic side chains, thereby converting them into hydrophilic groups by exposure the carboxylic and imino group versus water molecules. The advantage is due to the fact that water associated with hydrophilic groups is bound via hydrogen bonding forces, in contrary to hydrophobic groups. In addition, the number of water molecules adjoining hydrophilic groups is far less than those involved with hydrophobic residues. By means of these two alternative mechanisms complete hydration of the biopolymers is maintained, even with a reduced number of available water molecules.

A search for amino acids in Apollo 11 and 12 Lunar fines

Lunar fines from the Apollo 11 and 12 missions have been analyzed for amino acids and a wide range of other derivatizable organic compounds by a highly sensitive gas-liquid chromatographic method. A minimum of 3 to 5 p.p.b. of each amino acid would have been detected, but there were no indications of the presence of free amino acids in the samples. The N-trifluoroacetyl n-butyl ester/gas-liquid chromatographic method has been shown to give recoveries greater than 80% when samples containing 5 ng of each of seventeen amino acids were taken through the total derivatization and chromatography, thus showing that losses due to adsorptive and substrate-derivative interactions were minimal. The method was also shown capable of detecting other organic classes as higher alcohols, amines, fatty acids, and dicarboxylic acids. The unhydrolyzed water reflux extract (17 h) of the Apollo 11 fines showed that the concentration of each of the free common amino acids were less than 4 ng/g, however, on hydrolysis of the water extract with 6 N HCl, a large peak was eluted on the glycine—serine region of the chromatogram, and two other peaks at 153° (80 ng/g) and 178° (40 ng/g). The large peak could be contamination as a smaller peak was observed at the same retention temperature in the parallel blank; or these peaks could be due to organic precursors which are hydrolyzed as reported by Fox. The Apollo 12 unhydrolyzed water reflux extract (13 h) was also investigated, and none of the free common amino acids were detected above background ( ca.