Aluminate reduction with

In this paper, the selectivity of the ECH method for the reduction of nitro compounds to the corresponding amines on RCu electrodes will be compared with that of reduction by RCu alloy powder in alkaline aqueous ethanol. In the latter method (termed chemical catalytic hydrogenation (CCH)), chemisorbed hydrogen is generated in situ but by reduction of water by aluminium (by leaching of the alloy) (equation [12]). The reductions by in situ leaching must be carried out in a basic medium in order to ensure the conversion of insoluble Al(OH)3 into soluble aluminate (equation [12]). The selectivity and efficiency of the electrochemical reduction of 5-nitro-indoles, -benzofurane, and -benzothiophene at RCu electrodes in neutral and alkaline aqueous ethanol will also be compared with that of the classical reduction with zinc in acidic medium. 

Reduction of O2 Plasma Treated Polypropylene Film. The oxygen plasma treated foils were stirred under N2 at room temperature in 12 ml dry THF and 3 ml of 1 M diborane solution for 18 hours. The foils were removed and immersed in an alkaline H2O2 and THF for 2 hours. Then, the foils were washed with THF, water (thrice) and with methanol. The modified foils were dried and stored in a desiccator. The reduction with LiAlH4 was performed in ether for 2 hours. Vitride (SDMA-Sodium dihydrobis(2-methoxyethoxy)aluminate) was processed in toluene for 2 hours and then the reaction product was hydrolized with NaOH. 

A ketone added to the aged solution is reduced effectively, but a carboxylic acid or ester is not reduced. This weak hydride donor is thus useful for the selective reduction of a keto acid to the corresponding hydroxy acid. Both intermolecular 2md intramolecular competition experiments with tetrakis-(N-dihydropyridyl)-aluminate showed that diaryl ketones are more reactive to this reagent than either dialkyl or aralkyl ketones. This relationship is the opposite of that found by H. C. Brown for reduction with sodium borohydride in isopropyl alcohol, where the order of reactivity is acetone > acetophenone > benzophenone. 

The trihydridobistriphenylphosphineiridium IrH L [fl was prepared by reduction with both sodium tetrahydridoborate and lithium tetrahydrido-aluminate, of Irl L or Irl HL. It is a white powder, stable to air and moisture, almost insoluble in all solvents, diamagnetic, m.p. 145 (dec.). The number of hydridic hydrogen atoms, which can not be determined by analysis only, was proved by the reaction with triphenylphosphine, which gave place very rapidly in the cold to the two isomeric forms of the well known trihydride IrH L (1). and by the following quantitative reactions ... 

Reductions with sodium hydridotriethoxoaluminate s. 13, 254 with sodium hydridotris(dimethylaminoethoxo)aluminate cf. O. Kfiz and J. Madiacek, Coll. 37,2175 (1972)... 

The first attempts to isolate aluminium in its metallic form were performed in 1825 by Hans Christian Oersted, a Danish physicist and chemist, and fulfilled in 1827 by Friedrich Wohler, a German chemist, who isolated the pure metal from aluminium trichloride via reduction with potassium. The viable scaling-up of aluminium production was a rather long process that led, on the one hand, to the sodium aluminate process of Carl J. Bayer disclosed in 1887 producing pure aluminium oxide and, on the other hand, to the process of Charles M. Hall and Paul-Louis Toussaint Heroult" coinvented independentiy in 1886, in which aluminium oxide is dissolved in cryolite to yield via electrolysis pure metallic aluminium. 

In a more general sense, this reduction method provides a convenient pathway for converting an aromatic carboxyl group to a methyl group (see Table I).7 Previously, this transformation has been achieved by reduction of the acid to the alcohol with lithium aluminum hydride, conversion of the alcohol to the tosylate, and a second reduction either with lithium aluminum hydride [Aluminate(l —), tetrahydro, lithium,... 

The replacement of vanadia-based catalysts in the reduction of NOx with ammonia is of interest due to the toxicity of vanadium. Tentative investigations on the use of noble metals in the NO + NH3 reaction have been nicely reviewed by Bosch and Janssen [85], More recently, Seker et al. [86] did not completely succeed on Pt/Al203 with a significant formation of N20 according to the temperature and the water composition. Moreover, 25 ppm S02 has a detrimental effect on the selectivity with selectivity towards the oxidation of NH3 into NO enhanced above 300°C. Supported copper-based catalysts have shown to exhibit excellent activity for NOx abatement. Recently Suarez et al and Blanco et al. [87,88] reported high performances of Cu0/Ni0-Al203 monolithic catalysts with NO/NOz = 1 at low temperature. Different oxidic copper species have been previously identified in those catalytic systems with Cu2+, copper aluminate and CuO species [89], Subsequent additions of Ni2+ in octahedral sites of subsurface layers induce a redistribution of Cu2+ with a surface copper enrichment. Such redistribution... 

Hydride reductions of C = N groups are well known in organic chemistry. It was therefore obvious to try to use chiral auxiliaries in order to render the reducing agent enantioselective [88]. The chiral catalyst is prepared by addition of a chiral diol or amino alcohol, and the active species is formed by reaction of OH or NH groups of the chiral auxiliary with the metal hydride. A major drawback of most hydride reduction methods is the fact that stoichiometric or higher amounts of chiral material are needed and that the hydrolyzed borates and aluminates must be disposed of, which leads to increased costs for the reduction step. 

This behaviour results from initial formation of an intermediate with two potential leaving groups, an amide anion R2N and the aluminate anion (OAlHs). Aluminate is the better leaving group, and its loss produces an iminium cation that is also subject to further reduction. This gives us the amine product. 

The reaction of complex hydrides with carbonyl compounds can be exemplified by the reduction of an aldehyde with lithium aluminum hydride. The reduction is assumed to involve a hydride transfer from a nucleophile -tetrahydroaluminate ion onto the carbonyl carbon as a place of the lowest electron density. The alkoxide ion thus generated complexes the remaining aluminum hydride and forms an alkoxytrihydroaluminate ion. This intermediate reacts with a second molecule of the aldehyde and forms a dialkoxy-dihydroaluminate ion which reacts with the third molecule of the aldehyde and forms a trialkoxyhydroaluminate ion. Finally the fourth molecule of the aldehyde converts the aluminate to the ultimate stage of tetraalkoxyaluminate ion that on contact with water liberates four molecules of an alcohol, aluminum hydroxide and lithium hydroxide. Four molecules of water are needed to hydrolyze the tetraalkoxyaluminate. The individual intermediates really exist and can also be prepared by a reaction of lithium aluminum hydride... 

If the reduction has been carried out in ether, the ether layer is separated after the acidification with dilute hydrochloric or sulfuric acid. Sometimes, especially when not very pure lithium aluminum hydride has been used, a gray voluminous emulsion is formed between the organic and aqueous layers. Suction filtration of this emulsion over a fairly large Buchner funnel is often helpful. In other instances, especially in the reductions of amides and nitriles when amines are the products, decomposition with alkalis is in order. With certain amounts of sodium hydroxide of proper concentration a granular by-product - sodium aluminate - may be separated without problems [121],... 

The separator is often the weakest component in any electrochemical cell. There are also difficulties in employing ion-exchange diaphragms in aprotic media. Particularly with large industrial cells, it is advantageous to devise reaction conditions that allow the use of an undivided cell. One solution to these problems for an electrochemical reduction process employs a sacrificial anode of magnesium, alumin-... 

The replacement of Portland cement by fly ash class F (ASTM C 618) has been found to reduce the rate of slump loss in a prolonged mixed concrete, and the extent of the reduction is greater with increased cement replacement (Fig. 7.37). Fly ash also was found to be beneficial in reducing slump loss in concretes with conventional water-reducing and retarding admixtures [95], The effect of fly ash on reducing slump loss can be attributed to chemical and physical factors. It was found that the surface of fly ash particles may be partly covered with a vapor-deposited alkali sulfate that is readily soluble [103, 104], Thus the early hydration process of Portland cement is effected because sulfate ions have a retarding effect on the formation of the aluminates. Indeed, fly ash was found to be a more effective retarder than an... 

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