Hydrogen, atmosphere, aqueous phase

Akashi and coworkers prepared small platinum nanoparticles by ethanol reduction of PtCl in the presence of various vinyl polymers with amide side chains [49]. These authors studied the effects of molecular weight and molar ratio [monomeric unit]/[Pt] on the particle sizes and size distributions by electron microscopy, and in some cases by the dispersion stability of the Pt colloids. The hydrogenation in aqueous phase of allyl alcohol was used as a model reaction to examine the change in catalytic activity of polymer-stabilized Pt colloids upon addition of Na2S04 to the reaction solution. The catalytic tests were performed in water or in Na2S04 aqueous solution at 25 °C under atmospheric pressure of... 

Hydrolysis. Heating 1,2-dichloroethane with excess water at 60°C in a nitrogen atmosphere produces some hydrogen chloride. The rate of evolution is dependent on the temperature and volume of the aqueous phase. Hydrolysis at 160—175°C and 1.5 MPa (15 atm) in the presence of an acid... 

Of this material 1.0 g is dissolved in 150 ml of warm 95% ethyl alcohol. To the solution is added 1.0 g of 5% palladium on carbon catalyst, and the mixture is hydrogenated at room temperature and atmospheric pressure by bubbling hydrogen into it for 3 hours with stirring. The hydrogenation product is filtered. The solid phase, comprising the catalyst and the desired product, is suspended in ethyl acetate and water and adjusted to pH 2 with hydrochloric acid. The suspension is filtered to remove the catalyst. The aqueous phase is separated from the filtrate, and is evaporated under vacuum to recover the desired product, 7-(D-a-aminophenylacetamido)cephalosporanic acid. 

Bj Pivaloyloxymethyl D(—)-Ot-aminobenzylpenicillinate. hydrochloride To a solution of pivaloyloxymethyl D(—)-a-azidobenzylpenicillinate (prepared as described above) in ethyl acetate (75 ml) a 0.2 M phosphate buffer (pH 2.2) (75 ml) and 10% palladium on carbon catalyst (4 g) were added, and the mixture was shaken in a hydrogen atmosphere for 2 hours at room temperature. The catalyst was filtered off, washed with ethyl acetate (25 ml) and phosphate buffer (25 ml), and the phases of the filtrate were separated. The aqueous phase was washed with ether, neutralized (pH 6.5 to 7.0) with aqueoussodium bicarbonate, and extracted with ethyl acetate (2 X 75 ml). To the combined extracts, water (75 ml) was added, and the pH adjusted to 25 with 1 N hydrochloric acid. The aqueous layer was separated, the organic phase extracted with water (25 ml), and the combined extracts were washed with ether, and freeze-dried. The desired compound was obtained as a colorless, amorphous powder. 

The dimer of chloro(l,5-hexadiene)rhodium is an excellent catalyst for the room temperature hydrogenation of aromatic hydrocarbons at atmospheric pressure. The reaction is selective for the arene ring in the presence of ester, amide, ether and ketone functionalities (except acetophenone). The most useful phase transfer agents are tetrabutylammonium hydrogen sulfate and cetyltrimethylammonium bromide. The aqueous phase is a buffer of pH 7.6 (the constituents of the buffer are not critical). In all but one case the reaction is stereospecific giving cis products... 

Dissolved organic sulfur was determined in aqueous solutions after isolation by solid-phase extraction on macroporous resins and reversed-phase sorbents.156 The sulfur in the extracts was determined by pyrohydrogenolysis of the extract in a heated quartz tube (1100°C) in a hydrogen atmosphere followed by flame photometric detection. 

The following route is described in US Patent 4,145,552 At ambient temperature, over a period of thirty minutes, a solution of 33.8g (O.lmol) of (-)-vincadiformine in a mixture of 140 ml of anhydrous dimethylformamide and 140 ml of anhydrous toluene is added to a suspension of 2.64 g (0.11 mol) of sodium hydride in a mixture of 200 ml of anhydrous tetrahydrofuran, 20 ml of anhydrous hexamethylphosphotriamide (EMPT) and 18.7 ml (0.14 mol) of trimethyl phosphite. When the release of hydrogen has finished (about two hours later), the solution is cooled to -10°C and then stirred under an oxygen atmosphere until absorption ceases (duration 3 hours). Still at -10°C, 136 ml of glacial acetic acid are added, and the mixture is then left at ambient temperature for two hours. After the addition of 500 ml of 1 N sulfuric acid, the aqueous phase is isolated, reextracted with 150 ml of isopropyl ether, made alkaline with 350 ml of 11 N ammonia, then extracted 3 times with 300 ml aliquots of methylene chloride. After drying over calcium... 

Kok, G. L. Heikes B. G. Lazrus, A. L. Gas and aqueous phase measurements of hydrogen peroxide. Symposium on Acid Rain I. Sources and Atmospheric Processes, Division of Petroleum Chemistry, Inc. American Chemical Society, preprints, 1986, Vol. 31, No. 2, pp. 541-544. 

A mixture of l,2-dimethyl-3-acetyl-4-isopropyl-5-phenyl pyrrole (12.75 g, 0.05 mol) and diethyl isopropylidene succinate (10.7 g, 0.05 mol) in dry toluene (70 ml) was added to a stirred solution of sodium hydride (80% dispersion in oil, 3.8 g, 0.125 mol) suspended in dry toluene (10 ml) under nitrogen atmosphere. A few drops of absolute ethanol were added to initiate the exothermic reaction. The reaction mixture was stirred for about 40 h at ambient temperature until no hydrogen was formed, and finally the reaction mixture was poured into crashed ice-water (100 ml). The organic layer was separated and extracted with saturated sodium carbonate solution (2 x 50 ml). The combined aqueous layer was extracted with toluene (50 ml), and then the aqueous phase was acidified slowly with 5 M hydrochloric acid and washed with toluene (3 x 100 ml). The toluene solution was dried with MgSO 4 and the solvent was removed the half-ester was obtained as a gum. 

Although the gas phase provides major pathway for hydroxyl radical and hydrogen peroxide production in the atmosphere, there is overwhelming evidence [158-168] that aqueous phases in the troposphere also provides a significant medium for the photolytic production of these important oxidants. 

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