Hydrolytic Dehydrogenation

Control of Shell Thickness of Hollow Silica-Alumina Composite Spheres and their Activity for Hydrolytic Dehydrogenation of Ammonia Borane... 

Control of shell thickness of hollow silica-alumina composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane... 

Keywords Hollow silica-alumina composite spheres Shell thickness Hydrolytic dehydrogenation Ammonia borane... 

A number of catalysts or acids have been reported for the hydrolysis of NH3BH3 [7-12]. Among these catalysts or acids, solid acids such as zeolites (H-BEA and H-MOR) have been reported to be active for hydrolytic dehydrogenation of NH3BH3 [11, 12]. However, there are few reports on solid acids, and the relationship between their structure and activity has not been clearly shown. For a systematic... 

We have already fabricated hollow silica-alumina composite spheres prepared by sol-gel based method using aqueous ammonia solution as a promoter of sol-gel reaction [4], and have revealed the influence of their nanostructure of the hollow spheres on their catalytic activity for hydrolysis of NH3BH3 [4], In the present study, we fabricated hollow silica-alumina composite spheres using PS template method and investigated their activity for hydrolytic dehydrogenation of ammonia borane. In addition, we firstly fabricated the hollow spheres using L(+)-arginine as the promoter for hydrolysis of tetraethoxysilane (TEOS) [16],... 

The results indicate that hollow structure plays important role to show high activity for hydrolytic dehydrogenation of ammonia borane due to shorter diffusion distance that the reactants for hydrolysis of ammonia borane access to the active sites or larger amount of active site on the hollow spheres compared with the amount on the spherical particles. 

If this cleavage principle is applied to the molecule of aniline black it will be found that from it four molecules of quinone, three molecules of p-phenylenediamine, and one molecule each of aniline and ammonia arise. Since an excess of chromic acid is present, the p-phenylene-diamine is readily dehydrogenated to quinonediimine, which is hydrolytically decomposed into quinone and ammonia. The single molecule of aniline begins the cycle anew. 

In contrast to oxidative dechlorination, the hydrolytic dechlorination of chloramphenicol replaces a Cl-atom with a OH group to yield a (monochlo-ro)hydroxyacetamido intermediate. The latter, like the dichloro analogue, also eliminates HC1, but the product is an aldehyde that is far less reactive than the oxamoyl chloride intermediate. Chloramphenicol-aldehyde undergoes the usual biotransformation of aldehydes, namely reduction to the primary alcohol 11.41 and dehydrogenation to the oxamic acid derivative 11.40 (Fig. 11.7). 

Finally, the possible biogenesis of echitamine remains for discussion (88). This can readily be rationalized, using as an intermediate a base such as geissoschizine (LX), one of the hydrolytic fission products of the alkaloid geissospermine. Geissoschizine can clearly be obtained from tryptamine and dihydroxyphenylalanine or prephenic acid by a route which has many analogies in indole alkaloid chemistry. Dehydrogenation... 

A solution of sulfur in dimethylformamide can act as an oxidant of certain A -blocked piperazine-2,5-dione derivatives, resulting in net dehydrogenation (1068). For example, (cis trans)-l,4-diacetyl-3,6-dibenzylpiperazine-2,5-dione (101) reacted with sulfur in dimethylformamide and triethylamine to form, after hydrolytic removal of the acetyl groups, 3-benzyl-6-benzylidenepiperazine-2,5-dione (102) (1968). Oxidation of 1,3,4,6-tetramethylpiperazine-2,5-dione (103) with lead tetraacetate in benzene gave 3,6-diacetoxy-3-acetoxymethyl-l,4,6-trimethylpiperazine-... 

Hydrolytic and non-hydrolytic sol-gel routes are implemented to prepare various pure and silica-dispersed vanadium- or niobium-based oxide catalysts corresponding to the compositions Nb-V, Sb-V and Nb-V-M (M = Sb, Mo, Si). Starting reagents in the hydrolytic procedure are isopropanol solutions of the metal alkoxides. The non-hydrolytic route is based on reactions between metal and Si alkoxides and hexane suspensions of niobium(V) chloride. The catalysts are tested in propane oxidative dehydrogenation. NbVOs, SbV04 and Nb2Mo30n are the major crystalline phases detected in the fresh catalysts, but structural modifications are in some cases observed after the use in the catalytic tests. At 500 C, propane conversions of 30 % and selectivities to propene between 20 and 40 % are attained. When the space velocity is decreased, acrolein is in some cases found as by-product. 

In this work, pure or silica-dispersed Nb-V systems were prepared by either the hydrolytic or the non-hydrolytic procedures. Moreover, the hydrolytic sol-gel route was extended to the preparation of pure or silica-dispersed Sb-V and Nb-V-M (M = Sb, Mo) oxide systems. The catalytic performances of these mked-oxide systems in propane oxidative dehydrogenation were investigated. 

Dehydrogenative cyclization of 2-alkyl- or 2-arylsulfanylphenylureas 1 with bromine and sodium methoxide in anhydrous methanol leads to the lA4,2,4-benzothiadiazin-3(4//)-ones 2.122 These compounds are cyclic sulfimines which undergo hydrolysis even on recrystallization. When compounds 2 are heated in dioxane/water (1 1) the S1-N2 double bond is hydrolytically cleaved to afford the ureidophenyl sulfoxide 3. Since compounds 2 possess a free electron pair at the sulfur atom, they can be oxidized in good yields to the 1-oxides 4 by treatment with potassium permanganate. In contrast to compounds 2, oxides 4 are not hydrolyzed in boiling, dilute acids. 

Closely related to the vinylbenzo[b]thiophene reactions are the condensations of the bisbenzo[b]thienyls 108 and 110 with maleic anhydride in the presence of the dehydrogenating agent chloranil to form 419 and 420, respectively (55-78%), which are hydrolytically decarboxylated (37-62%) to the parent pentacycles 56 and 54 by means of soda lime at 400°C.146... 

Phase I reactions, which often create anchor points in the xenobiotic molecule for subsequent conjugation, comprise oxidations (electron removal, dehydrogenation and hydroxylation), reductions (electron donation, hydrogenation and removal of oxygen), and hydrolytic reactions. Many metabolic reactions take place in the endoplasmic reticulum of the liver cells. Other organs, particularly kidneys and lungs, also participate in drug metabolism. In addition, a variety of other tissues (brain, skin, intestinal mucosa) have the capacity to metabolize xenobiotics. 

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