Sulfonated Resins

Another type of soHd supetacid is based on perfluorinated resin sulfonic acid such as the acid form of Du Font s Nafion resin, a copolymer of a perfluorinated epoxide and vinylsulfonic acid or soHd, high molecular weight petfluotoalkanesulfonic acids such as petfluotodecanesulfonic acid, CF2(CF2)qS02H. Such sohd catalysts have been found efficient in many alkylations of aromatic hydrocarbons (225) and other Friedel-Crafts reactions (226). 

Nafion-H (144), a perfluorinated resin-sulfonic acid, is an efficient Bronsted-acid catalyst which has two advantages it requires only catalytic amounts since it forms reversible complexes, and it avoids the destruction and separation of the catalyst upon completion of the reaction [94], Thus in the presence of Nafion-H, 1,4-benzoquinone and isoprene give the Diels-Alder adduct in 80% yield at 25 °C, and 1,3-cyclohexadiene reacts with acrolein at 25 °C affording 88 % of cycloadduct after 40 h, while the uncatalyzed reactions give very low yields after boiling for 1 h or at 100 °C for 3.5 h respectively [95], Other examples are given in Table 4.24. In the acid-catalyzed reactions that use highly reactive dienes such as isoprene and 2,3-dimethylbutadiene, polymerization of alkenes usually occurs with Nafion-H, no polymerization was observed. 

Very recent relevant observations reveal that the TCS approach albeit certainly significant as conceptual and operational tool in the issue of metal nanoclusters size control, requires a substantial further perfection. Resin sulfonated Bayer K1221 is a co styrene-divinylbenzene commercially available gel-type resin, in beaded form. Its cross-linking degree is ca. 4% mol and therefore K1221 is expectedly quite similar to DOMA-VP and MTEMA-DMAA 4-4 for example. In fact ISEC analysis reveals a nanoporosity featured by 4.0 and 2.0 nm nanopores only. The expectation is that a Pd°/K1221 nanocomposite obtained with a classic procedure [5,9,10] will exhibit diameters strictly ranging from 2 to 4 nm. 

Polysulfonated humic acid resin-sulfonated chromiimi humate, [1716]... 

Furthermore, the same sol-gel matrices have been used in a system where acid and base catalysis occur in the same pot without quenching either catalyst [29]. In this case, the acids were either entrapped Nafion (perfluorinated resin sulfonic super acid, a3) or entrapped molybdic acid (M03-Si02, a2), while the bases were two ORMOSILs (organically modified silica sol-gel materials), one with H2N (CH2)2NH(CH2)3 groups (bi) and the other guanidine base residues (b2) (Scheme 5.12). 

Review. Olah et al. have reviewed use of this resin sulfonic acid as a solid catalyst in organic synthesis (181 references). 

Peresters as initiators, 25 277 Perfluoiinated resin sulfonic acid, see Nafion-H... 

Bio-Rad AG50W resins (sulfonated PSDVB), 50-100 mesh, were treated with NaOH and distilled water washes. The weighing state was obtained after 12 hours of drying in air at 75-80 C. Reagent grade chemicals were used throughout. 

Neutralized vinsol resin, sulfonated hydrocarbon, and fatty-acid (detergent)-based AEAs give satisfactory AVSs, but at low dosages, only synthetic detergent-based materials can produce an adequate and stable spacing factor. 

Substantial progress has been made to carry out alkylation in the gas phase over solid superacid catalysts. Nafion-H, a perfluorinated resin-sulfonic acid, for example, catalyzes the methylation of benzene and methylbenzenes with methyl alcohol under relatively mild conditions. The reaction shows low substrate selectivity.203... 

Polymeric resin sulfonic acids including sulfonic acid resins complexed with Lewis acids and perfluorinated polymer resin acids (Nafion-H and Nafion-silica nanocomposites). 

It should be mentioned that a solventless method of hydrolytic modification of starch has recently been developed. The method employs solid superacids, per-fluorinated resin-sulfonic acids, which successfully catalyze hydrolysis of starch (and other polysaccharides) and offer the possibility of continuous-process applications in plug-flow reactors.34... 

Alkyl mesylates undergo alkylation reaction with benzene rings in the presence of Sc(OTf)3. " Allylic acetates undergo alkylation with Mo(CO)g and allylic chlorides react in the presence of ZnCl2/Si02. " Montmorillonite clay (KIO) is an effective medium for alkylation reactions.Nafion-H, a super acidic perfluori-nated resin sulfonic acid, is a very good catalyst for gas phase alkylations with alkyl halides, alcohols,or alkenes. 

Not only do these acids present an economic advantage over conventional acid technology, but there are also frequent selectivity eidiancements and changes in reactivity associated with the use of these heterogeneous catalysts. A number of different types of solid acids have been involved in synthetically useful reactions. They range from the hydrogen forms of various ion exchange resins and the perflourinated resin sulfonic acid, Nafion-H, to the amorphous acidic oxides, silica and aluminum silicate,the crystalline zeolites > and the natural clays. -9... 

The sulfonic acid resins such as Dowex-50 and Amberlyst-15 have been used to promote the alkylation of the more active aromatic rings but attempts to increase their acidity generally resulted in the degradation of the solid. 2 The more strongly acidic perfluorinated resin sulfonic acid, Nafion-H,2>3 has, however, been used to promote the alkylation of benzene and other aromatic compounds. Nafion-H catalyzed the vapor phase reaction between toluene and methanol. When nm at 185°C a 12% yield of the isomeric xylenes was obtained with the ortho isomer the major product. 0 Methylation of phenol at 205°C over this catalyst gave, at 63% conversion. 37% anisole and 10% of a mixture of the ortho and para cresols in a 2 1 ratio. Reaction of anisole with methanol under these conditions resulted in a 14% selectivity to the methyl anisoles at 40% conversion, with the ortho and para isomers formed in nearly equal amounts. ... 

The LEC experiment can be performed on ion exchange resins. Sulfonated PS beads were used to absorb the transition metal cation ions. The beads of low crosslinking (4-8% divinylbenzene) gave narrow and more symmetric chromatographic peaks. A variety of cations, from + 1 to + A valency, were loaded onto the resin numerous compounds such as phenols, alcohols, sugars, nucleic... 

Olah, G. A., Arvanaghi, M., Krishnamurthy, V. V. Heterogeneous catalysis by solid superacids. 17. Polymeric perfluorinated resin sulfonic acid (Nafion-H) catalyzed Fries rearrangement of aryl esters. J. Org. Chem. 1983,48, 3359-3360. 

Ji, J., Lu, X. Facile synthesis of 2,5-disubstituted furans via palladium complex and perfluorinated resin sulfonic acid catalyzed isomerization-dehydration of alkynediols. J. Chem. Soc., Chem. Common. 1993, 764-765. 

When an SPE sorbent shows good performance with an analyte its fitness for other analytes, however close in structure, should be experimentally confirmed. A case in point is the forensic analysis of the adrenergic agonists Clenbuterol (70) and Compound A (71), both forbidden for use as animal feed additives. Four types of sorbents were tested—cyanopropyl resin, sulfonic acid SCX, mixed SCX + Qg and nonendcapped ( is only the latter type was found to quantitatively extract 71 although the performance of all four was satisfactory for 70. End analysis was by GC-MS-MS127. 

Resin sulfonic acids Asphaltene sulfonic acids... 

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