Anion-exchange resins aldol reaction

The feasibility of the alternative process using heterogeneous catalysis was investigated by screening several anion-exchange resin catalysts [16] and optimizing the reaction conditions for the aldolization of butyraldehyde and propionaldehyde with formaldehyde the phase distribution coefficients of the... 

Several weakly basic anion-exchange resin catalysts were screened in laboratory-scale and the results showed that a very good product distribution with respect to aldol can be obtained. Extensive kinetic studies demonstrated that weakly basic anion-exchange resin catalysts promoted both the aldolization and elimination processes, but the product distribution can be steered by selection of the solvent and the ratio of the reactants. A kinetic model based on the aldolization and elimination reaction mechanisms was developed and sin5>lified. The model predictions were in good agreement with the... 

Anion-exchange resins are excellent catalysts for base-catalyzed reactions such as Knoevenagel condensations and aldol condensations. 

Catalysts for aldol condensation may be either acidic or basic, but basic catalysts are much more common. The most common catalyst is Ba(OH)2. Besides Ba(OH)2, alkali and alkaline earth hydroxides or phosphates, and anion exchange resins are examples of solid base catalysts for the reactions. 

Butylation of phenylacetonitrile with aqueous NaOH, as shown in Scheme 25, proceeds faster by use of high DF (>0.5) anion exchange resins.The strongly alkaline conditions degrade the quaternary ammonium ions of the catalyst. Catalyst (64) (1% DVB) is active for alkylation of phenylacetonitrile and benzyl phenyl ketone, and for Williamson ether synthesis, and it is much more stable in base than AERs. AERs in OH form are catalysts for dichlorocyclopropane syntheses from alkenes, chloroform and solid sodium hydroxide, and for dehydration of amides to nitriles. AERs in the appropriate hydroxide, acetate, or cyanide form are catalysts for aldol condensations, Michael reactions, Knoevenagel condensations, cyanoethylations and cyanohydrin syntheses. " ... 

Numerous types of basic heterogeneous catalysts, such as alkahne earth metal oxide, anion exchange resins and alkali metal compounds supported on alumina or zeolite can catalyze various chemical reactions such as isomerization, aldol, Michael, and Knoevenagel condensation, oxidation and transesterification [1], Today considerable attention is devoted to the production of biodiesel (FAMEs) as an alternative for petroleum-derived diesel fuel. Biodiesel is synthesized by direct transesterification of vegetable oil or animal fat with a short-chain alcohol, viz. methanol, ethanol, and isopropanol in presence of an acid, base or enzymatic catalyst [2], Considering the advantages of solid base catalysts, for easy separation and recovery, reduced corrosion and environmental acceptance [1], many studies have been conducted on basic heterogeneous catalysts development for biodiesel production [3-13],... 

---