Acidic epoxidation systems solution

We investigated the side reactions of CECs with acetic acid and its aqueous solutions at 10-40 °C. The reaction mixtures served as models of the epoxidation systems. The course of the reactions was followed by the determination of epoxy and carboxyl groups in the reaction mixture. Equimolar ratios of the reagents were applied [18]. 

Thermoset systems including epoxide systems, polyesters, polyimides, and polyurethanes are cured more quicHy by microwave heating than by conventional thermal heating. This benefit of microwave heating was concluded from many studies reviewed by Zong et al. [19], with one typical example pertaining to the unimolecular imidization of a polyamic acid in N-methylpyrrohdone solution (see Scheme 1.5). 

In practice, promising results have been obtained for several systems. For example, fair to good yields of epoxides are obtained when a two-phase system consisting of alkene and ethyl chloroformate is stirred with a buffered basic solution of hydrogen peroxide. The active oxidant is presumed to be O-ethyl peroxycarbonic acid.85... 

Several efficient procedures for alkene epoxidation using Oxone were reported, such as Oxone/aqueous NaOH, Oxone/acetone, Oxone/water , Oxone/PTC/benzene/ aqueous buffer solution or Oxone/2-butanone system. Thus, sorbic acid can be regioselectively oxidized using Oxone/aqueous NaOH to 4,5-epoxy-2-hexenoic acid in 84% yield. Similarly, cyclooctene is oxidized to cyclooctene oxide in 81% yield, just by stirring it with Oxone in water . 1-Dodecene is epoxidized in good yield by Oxone/PTC in benzene aqueous buffer solution. It is otherwise difficult to epoxidize 1-dodecene by other oxidizing reagents. ... 

Regeneration of spent reagent is easy, and no loss in peroxide content is seen even over several recycles. Physical properties of the material are essentially unchanged. Labile epoxides, such as the industrially important a-pinene oxide can also be prepared in good yield under relatively mild conditions. This may be attributed to the heterogeneous nature of the system, which means that the solution phase is non-acidic. 

Already in the first reports on olefin oxidation with the MTO/H2O2 system [3], it was noted that the formation of diols from the desired epoxides, caused by the Br0nsted acidity of the system, is a major drawback of this system. The solution for this problem was found in the same report by the addition of a nitrogen base. This method has been explored extensively since and has become an important factor in the MTO-catalyzed olefin epoxidation. 

Liquefaction of untreated wood can also be achieved at a lower temperature of 150°C and at atmospheric pressure in the presence of a catalyst [12]. Phenolsulfonic acid, sulfuric acid, hydrochloric acid, and phosphoric acid were used as catalysts. In this acid catalyst method, phenols and polyhydric alcohols can also be used for the coexisting organic solvents. Phenol, cresol, bisphenol A and F, and so forth are successfully adoptable as the phenols. Polyethylene glycols, polyether polyols (epoxide additionally reacted polyether polyol, polyethylene terephthalate polyol) have been found to liquify wood resulting in polyol solutions [13]. Liquefaction of wood in the presence of -caprolactone, glycerin, and sulfuric acid has also been accomplished. It was confirmed in this case that liquefaction and polymerization, the latter of which produces polycaprolactone, take place in the reaction system at the same time [14]. Besides the wood material, it has become apparent that trunk and coconut parts of palm, barks, bagasse, coffee bean wastes, and used OA papers can also be liquified [15]. 

The MTO/H2O2 system furthermore catalyzes the oxidation of cyclic /9-dike-tones to carboxylic acids (eq. (11)) [15]. Conversions are usually above 85% the product selectivity is nearly quantitative. It has been assumed that enolic forms which exist in solution are initially epoxidized. After a rearrangement step the C-C bond is cleaved and an oxygen inserted. Then an a-diketone intermediate forms which is finally oxidized to the carboxylic acid [15]. 

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