Peroxyacetic acid, epoxidation

A commonly used peroxy acid is peroxyacetic acid (CH3CO2OH) Peroxyacetic acid is normally used m acetic acid as the solvent but epoxidation reactions tolerate a variety of solvents and are often earned out m dichloromethane or chloroform... 

Relative Rates of Epoxidation of Some Representative Alkenes with Peroxyacetic Acid... 

Figure 7 7 shows why equal amounts of (R) and (5) 1 2 epoxypropane are formed m the epoxidation of propene There is no difference between the top face of the dou ble bond and the bottom face Peroxyacetic acid can transfer oxygen to either face with equal facility the rates of formation of the R and S enantiomers of the product are the same and the product is racemic... 

Epoxidation of alkenes is a stereospecific syn addition Which stereoisomer of 2 butene reacts with peroxyacetic acid to give meso 2 3 epoxybu tane Which one gives a racemic mixture of (2/ 3/ ) and (25 35) 2 3 epoxybutane ... 

Esters. The monoisobutyrate ester of 2,2,4-trimethyl-1,3-pentanediol is prepared from isobutyraldehyde ia a Tishchenko reaction (58,59). Diesters, such as trimethylpentane dipelargonate (2,2,4-trimethylpentane 1,3-dinonanoate), are prepared by the reaction of 2 mol of the monocarboxyhc acid with 1 mol of the glycol at 150—200°C (60,61). The lower aUphatic carboxyHc acid diesters of trimethylpentanediol undergo pyrolysis to the corresponding ester of 2,2,4-trimethyl-3-penten-l-ol (62). These unsaturated esters reportedly can be epoxidized by peroxyacetic acid (63). 

Three peroxyacids are produced commercially for the merchant market peroxyacetic acid as a 40 wt % solution in acetic acid, y -chloroperoxybenzoic acid, and magnesium monoperoxyphthalate hexahydrate. Other peroxyacids are produced for captive use, eg, peroxyformic acid generated in situ as an epoxidizing agent. 

Toxicity. The peroxy acid is highly toxic and may cause death or permanent injury after very short exposure to small quants (Ref 12) Uses. Peroxyacetic acid is the most important epoxidation reagent used today because of its economical availability and ease of use with a wide variety of reactants (Ref 10). It also finds wide usage as an organic oxidizing agent (Ref 11) Refs 1) Beil 2, 169, (78), [174] [379 ... 

Further studies were conducted to improve this scheme to the A-ring unit, particularly, with respect to cost and scale-up practicality. Replacement of expensive meta-chloroperoxybenzoic acid by 30-40% peroxyacetic acid in acetic acid (four equivalents at 0°C) gave a 94% yield of epoxides 3a,b in a 9 1 ratio. 

Another method of making epoxides is the electrophilic reaction of alkenes with a peroxy acid such as peroxyacetic acid (sometimes simply peracetic acid). Thus, cyclohexene may be converted into the epoxide in a single reaction. 

One of the more intriguing features of peracid epoxidation is that the strength of the 0—0 bond has little impact on the rate of oxygen atom transfer. For example, peroxyacetic acid and peroxytrilluoroacetic acid have nearly identical 0—0 BDE (G2MP2, AH° =... 

Direct anti hydroxylation of an alkene (without isolation of the epoxide intermediate) is possible by using an acidic aqueous solution of a peroxyacid. As soon as the epoxide is formed, it hydrolyzes to the glycol. Peroxyacetic acid (CH3CO3H) and peroxyformic acid (HCO3H) are often used for the anti hydroxylation of alkenes. 

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