Epoxidation and hydroxylation of ethylenic compounds

D. Swern, Epoxidation and Hydroxylation of Ethylenic Compounds with Organic Peracids, Org. React. 1953, 7, 378 133. 

Note that, in some studies, poly(ethylene oxide) oligomers, micelle-forming surfactants derived from them, and their complexes were used to perform such reactions in aqueous and alcohol solutions as hydroformylation [31-33], Wacker oxidation [34,35], hydroxylation of aromatic compounds [36-38], carbon dioxide hydrogenation [39], and epoxidation [40]. It was shown that using poly(ethylene oxide)s substantially increases the reaction rate and, in some cases, allows us to separate a metal complex containing oligo(ethylene oxide) [31,40]. 

The chemical reactivity of the catalyst support may make important contributions to the catalytic chemistry of the material. We noted earlier that the catalyst support contains acidic and basic hydroxyls. The chemical nature of these hydroxyls will be described in detail in Chapter 5. Whereas the number of basic hydroxyls dominates in alumina, the few highly acidic hydroxyl groups also present on the alumina surface can also dramatically affect catalytic reactions. An example is the selective oxidation of ethylene catalyzed by silver supported by alumina. The epoxide, which is produced by the catalytic reaction of oxygen and ethylene over Ag, can be isomerized to acetaldehyde via the acidic protons present on the surface of the alumina support. The acetaldehyde can then be rapidly oxidized over Ag to COg and H2O. This total combustion reaction system is an example of bifunctional catalysis. This example provides an opportunity to describe the role of promoting compounds added in small amounts to a catalyst to enhance its selectivity or activity by altering the properties of the catalyst support. To suppress the total combustion reaction of ethylene, alkali metal ions such as Cs+ or K+ are typically added to the catalyst support. The alkali metal ions can exchange with the acidic support protons, thus suppressing the isomerization reaction of epoxide to acetaldehyde. This decreases the total combustion and improves the overall catalytic selectivity. 

These compounds are typically produced by reacting an acceptor molecule with an epoxide. The acceptor can be monomeric or polymeric in nature and possess free hydroxyl groups onto which the epoxide reacts. The epoxide is typically ethylene oxide (EO), propylene oxide (PO), butylene oxide, or a combination of oxides. 

Branched or star-block copolymers were made (187) by first polymerizing ethylene oxide onto a starter using cationic initiation. These compounds were then coupled with the diglycidyl ether of bisphenol A to increase molecular weight and to provide pendant hydroxyl group functionality in the central portions of the alkylene oxide/glycidyl epoxide copolymer. 

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