With Nafion cation-exchange

For laboratory-scale reactions, this electrocatalytic AD generally is performed in a glass H-type cell in which the anode and cathode compartments are separated by a semipermeable Nafion cation-exchange membrane and platinum electrodes are used. A 5% aqueous solution of phosphoric acid is used in the cathode compartment, and the reaction in the anode compartment is stirred vigorously, Under a controlled anode potential of 0.4 V (vs. Ag/AgCl) and with (DHQD)2-PHAL as chiral ligand, a-methylstyrene was converted to 7 -2-pheny 1-1,2-propanediol in 15 h with the electrical consumption of 2.1 F/mol. The product was isolated in 100% yield with 92% ee [ 37],... 

In the zinc/bromine cell, the halogen is stored in the electrolyte as a polybromide (mainly Bra ) and hence a separator is essential Nafion cation exchange membrane has again been used. The electrolyte is aqueous zinc bromide with tetraalkyl-ammonium bromide to aid the bromine complex formation. 

The upper part of Fig. 2 shows the molecular structure of the perfluorinated Nafion cation exchange membranes with sulfonic acid as well as with carboxylic acid groups as fixed ions. These are covalently bonded at the end of side chains of the PTFE (polytetrafiuoroethylene) polymer backbone. The polymer has excellent chemical and thermal stability, similar to PTFE [9]. 

Platinum RDE with Nafion Film Exchanged with Cation Species... 

As mentioned, this review is focused primarily on a survey of the vast literature dealing with the structure and properties of Nafion in the sulfonic acid and cation exchanged sulfonate forms. The literature on the carboxylate version is sparse and currently of lesser interest, as its application seems to be limited to membranes in chlor-alkali cells, and since it is a... 

Frequently substantially more than catalytic amounts of a Lewis acid metal halide are required to effect Friedel-Crafts alkylation. This is due partly to complex formation between the metal halide and the reagents or products, especially if they contain oxygen or other donor atoms. Another reason is the formation of red oils. Red oils consist of protonated (alkylated) aromatics (i.e., arenium ions) containing metal halides in the counterions or complexed with olefin oligomers. This considerable drawback, however, can be eliminated when using solid acids such as clays,97 98 zeolites (H-ZSM-5),99,100 acidic cation-exchange resins, and perfluoro-alkanesulfonic acid resins (Nafion-H).101-104... 

Electron hopping is not the only mechanism by which a multilayer film containing an electroactive species can be electrochemically oxidized or reduced. Consider an electrode surface that has been coated with a film of the cation-exchange polymer Nafion (Table 13.2). Let us assume that the electroactive cation Fe3+ has been ion-exchanged into this Nafion film (e.g., Eq. 13.4). In principle, the Fe3+ in this film can be reduced via the following redox reaction ... 

Reagents. Choline oxidase and glucose oxidase and their respective substrates, choline chloride and glucose were purchased from Sigma Chemical Co. (St.Louis, USA). The cationic exchangers AQ 29D and 55D were kindly supplied by Eastman Chemical Inc. (Kingsport, USA) and were obtained as dispersed polymer solutions at concentration of 30 and 28% (w/v) in water, respectively. A blend of the AQ polymer solutions was prepared by mixing the AQ 29D with the AQ 55D in a ratio (1 1), and was further diluted with water to a final concentration % (w/v) indicated in the text. Nafion (equivalent mass 1100 g) 5% (w/v) in a mixture of lower aliphatic alcohols and 10% of water was obtained from Aldrich (St.Louis, USA) and diluted with methanol to yield a stock solution of 0.5% (w/v). 

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