Solid acid addition

The larger cations of Group 1 (K, Rb, Cs) can be precipitated from aqueous solution as white solids by addition of the reagent sodium tetraphenylborate, NaB(C( H5)4. Sodium can be precipitated as the yellow sodium zinc uranium oxide ethanoate (sodium zinc uranyl acetate). NaZn(U02)3(CH3C00)y. 9H2O. by adding a clear solution of zinc uranyl acetate in dilute ethanoic acid to a solution of a sodium salt. 

The apparatus employed in the preceding experiment is used. To 600 g of 98% sulfuric acid at O " (ice-salt bath) is added about 3 ml of 88 % formic acid. When the rapidly stirred solution becomes foamy with evolution of carbon monoxide, 50 g of decahydro-2-naphthol and 100 g of 88% formic acid are added from two dropping funnels over 3 hours. During the addition, the temperature is kept below 5° the mixture continues to foam. Work-up as for the cis acid gives about 85% of solid acid, predominantly trans. After three recrystallizations from acetone, about 7 g of the pure acid is obtained, mp 135-136°. 

C) Preparation of Doxapram Hydrochloride [3,3-Diphenyl-1-Ethyl-4-(2-Morpholino-Ethylj-2-Pyrrolidinone Hydrochloride Monohydrate] A solution of 25 grams (0.076 mol) of 4-(2-chloroethyl)-3,3-diphenyl-1-ethyl-2-pyrrolidinone and 13.3 grams (0.153 mol) of morpholine in 500 ml of absolute ethanol was heated at 95°-120°C for 21 hours in a closed system and concentrated in vacuo. The residue was dissolved in 3(X) ml of two normal hydrochloric acid and extracted with 150 ml of ethyl acetate. A solid crystallized (13 g) during the extraction and was removed by filtration. MP 217°-219°C. The acid extracts were made basic with sodium hydroxide and extracted with ether, and the ether solution was concentrated in vacuo and the residue was suspended in six normal hydrochloric acid. Additional crystalline product formed and was recrystallized from two normal hydrochloric acid. Yield, 10 grams MP 217°-219°C. Total yield, 23 grams (70%). 

Examples of commercially applied solid base catalysts are much fewer than for solid acids. Nevertheless, much attention is currently focused on the development of novel solid base catalysts for classical organic reactions such as aldol condensations, Michael additions, and Knoevenagel condensations, to name but a few. 

Addition of a solid acid catalyst such as Montmorillonite K10 increased the yield significantly under the action of either thermal heating (64%) or MW irradiation (66%) [52 c]. Under the latter conditions the reaction time was reduced. Comparable results were obtained for the synthesis of aminocoumarins 39-42 (Tab. 7.3) [53]. 

The catalyst is reported to be a true solid acid without halogen ion addition. In the patent describing the process (239), a Pt/USY zeolite with an alumina binder is employed. It was claimed that the catalyst is rather insensitive to feed impurities and feedstock composition, so that feed pretreatment can be less stringent than in conventional liquid acid-catalyzed processes. The process is operated at temperatures of 323-363 K, so that the cooling requirements are less than those of lower temperature processes. The molar isobutane/alkene feed ratio is kept between 8 and 10. Alkene space velocities are not reported. Akzo claims that the alkylate quality is identical to or higher than that attained with the liquid acid-catalyzed processes. 

In addition to this, solid acid catalysts can also be used in the hydroisomerization cracking of heavy paraffins, or as co-catalysts in Fischer-Tropsch processes. In the first case, it could also be possible to transform inexpensive refinery cuts with a low octane number (heavy paraffins, n-Cg 20) to fuel-grade gasoline (C4-C7) using bifunctional metal/acid catalysts. In the last case, by combining zeolites with platinum-promoted tungstate modified zirconia, hybrid catalysts provide a promising way to obtain clean synthetic liquid fuels from coal or natural gas. 

The requirement of small structural differences within the series of reactants for obtaining a LFER has its parallel in series of catalysts. Meaningful values of result only when the catalysts operate principally in the same way, that is, when the reaction mechanism is basically the same. This is most likely to occur when the catalysts differ only by minor modifications in the method of preparation or when their composition is only slightly modified by the addition of promoters. With chemically different catalysts the similarity is achieved when the active centers have as their decisive component a common species, for example, protons on solid acidic catalysts. 

An important advantage of the inclusion complexes of the cyclodextrins over those of other host compounds, particularly in regard to their use as models of enzyme-substrate complexes, is their ability to be formed in aqueous solution. In the case of clathrates, gas hydrates, and the inclusion complexes of such hosts as urea and deoxycholic acid, the cavity in which the guest molecule is situated is formed by the crystal lattice of the host. Thus, these inclusion complexes disintegrate when the crystal is dissolved. The cavity of the cyclodextrins, however, is a property of the size and shape of the molecule and hence it persists in solution. In fact, there is evidence that suggests that the ability of the cyclodextrins to form inclusion complexes is dependent on the presence of water. Once an inclusion complex has formed in solution, it can be crystallized however, in the solid state, additional cavities appear in the lattice, as in the case of the hosts previously mentioned, which enable the inclusion of further guest molecules. ... 

A Typical Lithium Aluminum Hydride Reduction. JACS, 72, 2781 (1950). To a well stirred mixture of 53 g lithium aluminum hydride (LAH) and 2500 ml of dry ether is added 55 g of 4-hydroxy-3-methoxy-B-nitrostyrene (or equimolar ratio of nitropropene or analog) in 150 ml of dry ether over an hour and 20 min. Stir and reflux for about 9 hours, taking care to exclude all moisture. Cool and add 3000 ml of ice cold 1.5 N sulfuric acid dropwise with good stirring (the acid addition can be speeded up after about half of it has been added). The water layer is separated and its pH adjusted to 6 with solid lithium carbonate. This solution is heated to boiling and the aluminum hydroxide that precipitates is filtered off The hot filtrate is mixed with a solution of 70 g of picric acid in the minimum amount of hot ethanol that it takes to dissolve the picric. Let stand for 4 hours, filter and recrystallize from water. 

As another variation, the production of alkanes can be accomplished by modifying the support with a mineral acid (such as HCl) that is co-fed with the aqueous sorbitol reactant. In general, the selectivities to heavier alkanes increase as more acid sites are added to a non-acidic Pt/alumina catalyst by making physical mixtures of Pt/alumina and silica-alumina. The alkane selectivities are similar for an acidic Pt/silica-alumina catalyst and a physical mixture of Pt/alumina and silica-alumina components, both having the same ratio of Pt to acid sites, indicating that the acid and metal sites need not be mixed at the atomic level. The alkane distribution also shifts to heavier alkanes for the non-addic Pt/alumina catalyst when the pH of the aqueous sorbitol feed is lowered by addition of HCl. The advantages of using a solid acid are... 

The chlorine adduct to the tetrasubstituted exocyclic double bond in 108 is quantitatively obtained by gas-solid reaction [27]. Conversely, related trisub-stituted double bonds lose HX after the gas-solid halogen addition such as in the reactions of 110 and 112 that give 111 and 113,respectively [28] (Scheme 12). The completion of these solid-state eliminations (Sect. 11) is faster at 100 °C. The product 113 is an interesting substrate for the synthesis of orotic acids. Furthermore, the production of 116 from solid 114 and chlorine gas proceeds with 100% yield via the intermediate adduct 115 [58,60-61] (Scheme 12). 

Interestingly, Qi, Smith, and co-workers reported that addition of an organic solvent such as acetone, DMSO, methanol, ethanol, ethylacetate, or supercritical carbon dioxide to BMIM Cl allowed the reaction to proceed at room temperature. For instance, in the presence of Amberlyst 15 as solid acid catalyst, authors showed that addition of 5 wt% of acetone to BMIM CF yielded, at room temperature, HMF with 86% selectivity at 90% conversion. Further investigations revealed that addition of an organic solvent to BMIM CF allowed one to overcome important mass transfer at room temperature due to the high viscosity of BMIM CD [96]. 

Table 3 shows the results of the reaction between carbonyl compounds with Me3SiCN in the presence of solid acids. Fe-Mont, which is the most acidic Hq -0.2) among the solid catalysts tested, revealed the highest activity for the addition reaction of 2-octanone. Compared with Fe-Mont, much less acidic Ca -exchanged montmorilIonite (Ca-Mont, +0.8[Pg.374]

Fe -exchanged montmorillonite, as well as Al and Sn -exchanged montmorillonite, not only works as an efficient solid acid catalyst in the addition reactions of carbonyl compounds using silylated nucleophiles, but also enables an easy work-up procedure which merely requires filtration to separate the products from the catalyst. 

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