Reactions medium

The catalyzed oxidation of p-xylene produces terephthalic acid (TPA). Cobalt acetate promoted with either NaBr or HBr is used as a catalyst in an acetic acid medium. Reaction conditions are approximately 200°C and 15 atmospheres. The yield is about 95% ... 

P 42] Typically, a flow rate of 150 pi min was used [71]. A 0.1 M furan solution containing 0.1 M NaCl04 and 5 mM NaBr was used as reaction medium. Reaction was carried out at room temperature. Interdigitated band electrodes with 100 pm wide gaps and 500 pm band widths were tested in a 800 pm deep Perspex micro reactor. 

Glucose hydrogenation to sorbitol was carried out on 40 wt% aqueous solution at 100°C, under 80 bar H2-pressure, in the presence of Ru/ACC catalysts prepared by cationic exchange and anionic impregnation. The hydrogenation of 10 wt% aqueous glucosone solution was conducted at 80°C under 80 bar H2-pressure on 2.5 wt%Pd/ACC catalyst in the presence of small amounts of NaHC03 added to increase the pH of reaction medium. Reaction kinetics was followed by HPLC and GC analysis of the reaction medium at different time intervals. 

Another pertinent observation is the fact that the reaction proceeded twice as fast in -butyraldehyde (polar) as in benzene (nonpolar), even though the catalyst concentration was reduced to only one-third the comparable level. A graphic illustration of this effect is given in Fig. 9. The rate of gas uptake is plotted as a function of time for a reaction conducted in benzene and again for a second reaction conducted in butyraldehyde. The rate of reaction in the polar solvent was initially fast and decreased with time. The rate in the nonpolar benzene was initially slow, became faster as the solvent became more polar with the presence of product aldehyde, and then subsequently diminished with time. When the data were replotted as the log of unreacted olefin vs. time, the polar medium reaction showed first-order dependence on olefin concentration, whereas the nonpolar solvent reaction showed no definite order, owing to the constantly changing polarity. 

Thermal Hazards of Chemical Reactions (Grewer 1994). Addresses the characterization of thermal hazards involved in reactions of liquid and solid substances and mixtures, particularly those having low to medium reaction energies. The publication aims to present methods for distinguishing hazardous from nonhazardous reactions. 

A combustion wave is established in an explosive medium by application of a local source of ignition. As heat and, possibly, chain carriers of various kinds flow from the source into the adjacent medium, reaction is initiated in the layer next to the source which in turn becomes a source for igniting the next layer, and so on. Let us consider a mass element of the unburned mixture being overrun by the combustion wave. The reaction rate is virtually zero at the initial temperature but increases with temperature at... 

For production of Co111 1 2 complexes, a cobalt salt is generally added after coupling and warmed to 60-90°C in a weakly alkaline medium. Reaction with chromium requires more severe reaction conditions, for example, refluxing for 20 h [67],... 

The mechanisms of ester hydrolysis are distinguished with abbreviations of the type medium.. .., . , , reaction order. The medium of acid-catalyzed hydroly-... 

Molecules interact with the surfaces of solids in almost every environment in the universe. In addition to purely intellectual interest, we customarily justify studying these interactions on technological grounds, heterogeneous catalysis and the fabrication of microchips being the most frequently listed applications. However the field is much more broadly relevant the adsorption and desorption of atoms and molecules on the surfaces of dust grains is very important to molecule formation in the interstellar medium, reactions on the surfaces of ice crystals is important in atmospheric chemistry and reactions at surfaces determine the behaviour of medical implants in our bodies. 

Bermejo-Barrera, P., Moreda-Pineiro, J., Moreda-Pineiro, A., Bermejo-Barrera, A. Selective medium reactions for the arsenic(III), arsenic(V), dimethylarsonic acid and mono-methylarsonic acid determination in waters by hydride generation online electrothermal atomic absorption spectrometry with in situ preconcentration on Zr-coated graphite tubes. Anal. Chim. Acta 374, 231-240 (1998)... 

Now let me come back to primary substitutions at the ferrocene nucleus. Together with Vil chevskaya, we phosphorylated ferrocene and its derivatives to triferrocenylphosphine oxides [263, 264). An unusual reaction, discovered in collaboration with Perevalova and Yur eva, was the direct cyanation of ferrocene with hydrocyanic acid in the presence of ferric chloride [265,272). Initially, cyanide attacks the iron atom of the ferricinium cation, then the cyanide group transfers to the ring while the iron is simultaneously reduced. The reaction was termed by us as the ricochet (from the metal to the nucleus) substitution it may be applied to many substituted ferrocenes and to the ruthenocenium cation [273), and it is now the simplest route to ferrocene carboxylic acids through their nitriles. Further, ferrocene was studied in acid-medium reactions with oxo compounds. With aldehydes [274), the reaction was complicated by the transformation of ferro-cenylalkyl carbinol formed Initially via the carbonium ion, followed by transformation to a radical which, in its turn, was coupled to 1,2-bis-(ferrocenylalkyl)ethane (27.5). The reaction with acetone led to 2,2-di-ferrocenylpropane (276). 

Table 3 European Society of Urogenital Radiology (ESUR) Guidelines on prevention of generalized contrast medium reactions in adults...

B. To reduce the risk of generalized contrast medium reactions... 

Burchardt P, Flenker H, Schoop HJ. Todlicher Kontrastmittelzwischenfall bei unbehandeltem Morbus Waldenstrom. [Fatal contrast medium reaction in untreated Waldenstrom s disease.] Dtsch Med Wochenschr 1981 106(38) 1223-5. 

The catalyst behavior was tested in liquid medium reaction for the esterification of acetic acid with isoamyl alcohol to obtain isoamyl acetate. This compound is an important product for flavor and fragance industries. The isoamyl acetate can be used as for instance flavor in mineral waters and syrups, perfume in diverse products, as shoe polish, and in the manufacture of materials like artificial silk and other textiles, among other uses. 

The MPA and TPA based catalysts supported on a new amine-functionalized SiMCM-41 carrier showed important activity in the esterification reaction of acetic acid with isoamyl alcohol. On the other hand, low TPA (MPA) solubility during the leaching was observed. Then, these catalysts are very attractive for their use in liquid medium reactions. 

In the presence of triethylamine, phenylacetyl chloride reacts with a racemic amine to yield a phenylacetyl derivative 4. Heptane or ethyl acetate can be used as the reaction medium. Reaction at room temperature for 2 hours gave the desired product 4 (Fig. 3). As the final product xemilofiban 1 does not contain the tri-methylsilyl group at the alkyne carbon, it was preferable to perform desilylation prior to the enzymatic deacylation. Desilylation of the phenylacetyl derivative 4 was achieved by treatment with 0.2 equivalents of sodium ethoxide in ethanol at room temperature. Desilylation to provide 5 was complete in 1 hour. 

HNL catalysis in aqueous medium. Reaction in aqueous solution is performed with an appropriate acidic component and alkali cyanide for in situ development of the required HCN. The following procedure is a typical example194. ... 

---