Percarboxylate esters

In this section we discuss the thermochemistry of some species with the general formulas, RC(=0)00H, RC(=0)00R and RC(=0)00C(=0)R. These species have the generic names peracids (peroxycarboxyUc acids), peresters (percarboxylate esters) and acyl peroxides. The enthalpy of formation values are in Table 3. Three formal reactions that are discussed here are conceptually the same as in the earlier sections. Because now there is a carbonyl group present, we rewrite equations 5, 6 and 9 as equations 14, 15 and 16. 

Percarboxylate esters enthalpies of formation, 159, 160-2 formal enthalpy of hydrogenation, 160 homologous series, 160 thermochemistry, 158, 160-2 thermolysis, 161 see also Peresters... 

The reaction of peracids with ketones proceeds relatively slowly but allows for the conversion of ketones to esters in good yield. In particular, the conversion of cyclic ketones to lactones is synthetically useful because only a single product is to be expected. The reaction has been carried out with both percarboxylic acids and Caro s acid (formed by the combination of potassium persulfate with sulfuric acid). Examples of both procedures are given. 

Performic acid is an unstable, hazardous percarboxylic acid, and must always be generated in situ. Epoxidation with in situ performic and peracetic acid are well established commercial processes. They find application in the epoxidation of alkenes, particularly those of high molecular weight. Many such epoxides are produced on a large scale, and can be classified as vegetable oils, unsaturated esters, unsaturated acids, a-alkenes, natural polymers and synthetic polymers. The most important vegetable oil which is epoxidized commercially is soyabean oil. World production of epoxidized soyabean oil (ESBO) exceeds 150000 metric tons per annum. Epoxidized linseed oil is also important, but produced at a lower rate than ESBO. Both products are formed by usual in situ performic and peracetic acid techniques.23,24 Typical procedures are outlined in Table 3.1.25... 

A new way to prepare peroxy acids was discovered by Novo Nordisk, DK (9-11). They showed that some lipases catalyze the conversion of fatty acids with hydrogen peroxide (preferably 60%) to peroxy fatty acids Novozym 435, an immobilized lipase from Candida antarctica on polyacrylic Lewatit, is the most active and stable biocatalyst for this purpose (Scheme 1). Recently we found that Novozym 435 is also capable of catalyzing perhydrolysis (12), i.e., the reaction of carboxylic acid esters with hydrogen peroxide to percarboxylic acids (Scheme 2). 

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