Synthesis of Barium Sulfate

J. D. Hopwood and S. Mann, Synthesis of barium sulfate nanoparticles and nanofilaments in... 

The reaction is used for the chain extension of aldoses in the synthesis of new or unusual sugars In this case the starting material l arabinose is an abundant natural product and possesses the correct configurations at its three chirality centers for elaboration to the relatively rare l enantiomers of glucose and mannose After cyanohydrin formation the cyano groups are converted to aldehyde functions by hydrogenation m aqueous solution Under these conditions —C=N is reduced to —CH=NH and hydrolyzes rapidly to —CH=0 Use of a poisoned palladium on barium sulfate catalyst prevents further reduction to the alditols... 

Nitdles may be prepared by several methods (1). The first nitrile to be prepared was propionitdle, which was obtained in 1834 by distilling barium ethyl sulfate with potassium cyanide. This is a general preparation of nitriles from sulfonate salts and is referred to as the Pelou2e reaction (2). Although not commonly practiced today, dehydration of amides has been widely used to produce nitriles and was the first commercial synthesis of a nitrile. The reaction of alkyl hahdes with sodium cyanide to produce nitriles (eq. 1) also is a general reaction with wide appHcabiUty ... 

Nitrates. Iron(II) nitrate hexahydrate [14013-86-6], Fe(N03)2 6H20, is a green crystalline material prepared by dissolving iron in cold nitric acid that has a specific gravity of less than 1.034 g/cm. Use of denser, more concentrated acid leads to oxidation to iron(III). An alternative method of preparation is the reaction of iron(II) sulfate and barium or lead nitrate. The compound is very soluble in water. Crystallisation at temperatures below — 12°C affords an nonahydrate. Iron(II) nitrate is a useful reagent for the synthesis of other iron-containing compounds and is used as a catalyst for reduction reactions. 

A portion of this weight is due to water, since the material is only air dried for 15 minutes after preparation. If the synthesis is performed with completely dried barium salt, difficulty is encountered in this step since all Ba[Pt(CN)4]-4H20 is not consumed by 4.14 g of guanidine sulfate. 

One of the first reports of the synthesis of a luminescent material dates from 1603, when Casciavolus attempted to obtain gold by heating certain minerals, but instead obtained a rock that emitted reddish light in the dark. Here barium sulfide was formed by reduction of rock containing barium sulfate. 

Phenylethylamine has been made by a number of reactions, many of which are unsuitable for preparative purposes. Only the most important methods, from a preparative point of view, are given here. The present method is adapted from that of Adkins,1 which in turn was based upon those of Mignonac,2 von Braun and coworkers,3 and Mailhe.4 Benzyl cyanide has been converted to the amine by catalytic reduction with palladium on charcoal,5 with palladium on barium sulfate,6 and with Adams catalyst 7 by chemical reduction with sodium and alcohol,8 and with zinc dust and mineral acids.9 Hydrocinnamic acid has been converted to the azide and thence by the Curtius rearrangement to /3-phenyl-ethylamine 10 also the Hofmann degradation of hydrocinnamide has been used successfully.11 /3-Nitrostyrene,12 phenylthioaceta-mide,13 and the benzoyl derivative of mandelonitrile 14 all yield /3-phenylethylamine upon reduction. The amine has also been prepared by cleavage of N- (/3-phenylethyl) -phthalimide 15 with hydrazine by the Delepine synthesis from /3-phenylethyl iodide and hexamethylenetetramine 16 by the hydrolysis of the corre-... 

The Intermediate In this synthesis of disparlure, (Z)-2-tridecenol, Is obtained by hydrogenation of 2-trldecynol In the presence of a palladium catalyst poisoned with barium sulfate and quinoline. Oxidation of (Z)-2-tridecenol with tert-butyl hydroperoxlde/tItanium tetralsopropoxlde/D (-)-diethyl tartrate gives (2R, 3S)-epoxytrldecanol In enantiomeric excess reported to be as much as 98 percent after recrystalllzatlon. 

Another commercial aldehyde synthesis is the catalytic dehydrogenation of primary alcohols at high temperature in the presence of a copper or a copper-chromite catalyst. Although there are several other synthetic processes employed, these tend to be smaller scale reactions. For example, acyl halides can be reduced to the aldehyde (Rosemnund reaction) using a palladium-on-barium sulfate catalyst. Formylation of aryl compounds, similar to hydrofomiylation, using HCN and HQ (Gatterman reaction) or carbon monoxide and HQ (Gatterman-Koch reaction) can be used to produce aromatic aldehydes. 

Palladium on barium sulfate has been used in the hydrogenolysis of epoxides in natural product synthesis. The reaction in equation (25) illustrates its high level of functional group compatibility. 

The first recorded synthesis of silver(I) sulfamate was that by Berglund in 1876 he used the very slow reaction between silver(I) sulfate and barium(II) sulfamate. Later methods have employed the reaction between sulfamic acid and silver(I) oxide or silver(I) carbonate an electrolytic process has also been described. ... 

These suggestions were tested experimentally by Wasteneys and Borsook (68), who found that a peptic hydrolysate of protein gave, in the presence of concentrated pepsin solution and emulsion droplets of benzene or benzaldehyde, appreciable synthesis of a complex, less soluble material. Without the oil drops, reaction was very much slower, as the data in Fig. 24 show. Emulsions of fats, however, were noncatalytic, and xylol, talc, kieselguhr and barium sulfate were but weakly effective in increasing the rate. If the original protein is only slightly degraded, the yield in the synthesis is independent of the presence of the catalyst, but. 

In the first step of the synthesis (the Kiliani portion), the aldose is treated with sodium cyanide and HCl (Section 18.4). Addition of cyanide ion to the carbonyl group creates a new asymmetric carbon. Consequently, two cyanohydrins that differ only in configuration at C-2 are formed. The configurations of the other asymmetric carbons do not change, because no bond to any of the asymmetric carbons is broken during the course of the reaction (Section 5.12). Kiliani went on to hydrolyze the cyanohydrins to aldonic acids (Section 17.18), and Fischer had previously developed a method to convert aldonic acids to aldoses. This reaction sequence was used for many years, but the method currently employed to convert the cyanohydrins to aldoses was developed by Serianni and Barker in 1979 it is referred to as the modified Kiliani-Fischer synthesis. Serianni and Barker reduced the cyanohydrins to imines, using a partially deactivated palladium (on barium sulfate) catalyst so that the imines would not be further reduced to amines. The imines could then be hydrolyzed to aldoses (Section 18.6). 

The foregoing synthesis has been considerably simplified by the discovery that 2 6-distyrylpyridine rapidly adds two moles of bromine and the resulting compound on treatment with alcoholic potash gives rise to 2 6-diphenethinylpyridine (LXIV). Hydration of this diacetylenic compound with sulfuric acid yields 2 6-diphenacylpyridine (LXV) which can be hydrogenated in methanol over a platinic oxide-barium sulfate catalyst... 

From biguanide sulfate (synthesis 14) the free base can be obtained by treating a solution of the sulfate with barium hydroxide or sodium hydroxide/ or by refluxing biguanide sulfate with alcoholic sodium ethoxide. The procedure using sodium hydroxide is simple and cheap and produces a satisfactory product. 

The salt is made in essentially the same way as described for sodium azide synthesis according to Wislicenus [86], neutraHzing of hydrazoic acid with rubidium carbonate [75], or reacting of rubidium sulfate and barium azide [62,73,101,109]. 

The bromates are quite soluble, but the solubilities vary greatly from one element to another. Because the bromates have a very great temperature coefficient of solubility, they are exceedingly valuable in fractional crystallization processes. They may be prepared by dissolving the hydroxides in bromic acid or by double decomposition of the sulfates with barium bromate (synthesis 17). 

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