Peroxyacids

Organic peroxides can be classified according to peroxide stmcture. There are seven principal classes hydroperoxides dialkyl peroxides a-oxygen substitued alkyl hydroperoxides and dialkyl peroxides primary and secondary ozonides peroxyacids diacyl peroxides (acyl and organosulfonyl peroxides) and alkyl peroxyesters (peroxycarboxylates, peroxysulfonates, and peroxyphosphates). 

There are two broad classes of organic peroxyacids peroxycarboxyUc acids, R[C(0)00H], where R is an alkyl, aralkyl, cycloalkyl, aryl, or heterocycHc group and n = 1 or 2, and organoperoxysulfonic acids, RSO2—OOH. PeroxycarboxyUc acids are commonly named by adding the prefix peroxy to the parent acid as in peroxypropionic acid. The prefix per- is accepted only for the weU-estabHshed products, ie, performic, peracetic, and perbenzoic acids. 

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. 

Synthesis. Many different methods for the preparation of peroxyacids have been described (165). The most widely used method is the direct, acid-cataly2ed equihbtium reaction of 30—98 wt % hydrogen peroxide with catboxyhc acids (168) ... 

Alkyl peroxyesters are commonly named like their nonperoxidic counterparts, except for incorporation of the peroxy- prefix. Trivial names are also commonly used, eg, tert-huty peracetate. Alkyl peroxyesters derived from di- and polybasic peroxyacids use 00- or O- when required to locate groups, eg, 00-tert-huty 0-isopropyl monoperoxycarbonate and 00-tert-huty 0-hydrogen monoperoxymaleate. Descriptions of alkyl peroxyesters have been given in the chemical hterature (1,4—6,19,20,44,168,213). 

Chemical Properties. Alkyl peroxyesters are hydroly2ed more readily than the analogous nonperoxidic esters and yield the original acids and hydroperoxides from which they were prepared rather than alcohols and peroxyacids ... 

Also due to the high barrier of inversion, optically active oxaziridines are stable and were prepared repeatedly. To avoid additional centres of asymmetry in the molecule, symmetrical ketones were used as starting materials and converted to oxaziridines by optically active peroxyacids via their ketimines (69CC1086, 69JCS(C)2648). In optically active oxaziridines, made from benzophenone, cyclohexanone and adamantanone, the order of magnitude of the inversion barriers was determined by racemization experiments and was found to be identical with former results of NMR study. Inversion barriers of 128-132 kJ moF were found in the A-isopropyl compounds of the ketones mentioned inversion barriers of the A-t-butyl compounds lie markedly lower (104-110 kJ moF ). Thus, the A-t-butyloxaziridine derived from adamantanone loses half of its chirality within 2.3 days at 20 C (73JCS(P2)1575). 

Nitrogen chirality may also be produced by the action of an achiral peroxyacid on a Schiff base containing a chiral amine (75JOC3878). In this case the oxaziridine contains a configurationally known centre of chirality relative to this, absolute configurations of the centres of chirality at nitrogen and carbon, and thus the complete absolute configuration of the molecule, can be determined (see Section 5.08.2.2). 

With a peroxyacid, the reagent used in their preparation, oxaziridines further react to yield aliphatic nitroso compounds. An electrophilic attack to ring nitrogen is plausible, leading to an intermediate oxaziridine N-oxide (81), which immediately decomposes to a nitroso compound and an aldehyde (57JA6522). 

Acetylenic compounds Alkyl hydroperoxides, peroxyacids Aminachromiiim peroxocomplexes Ammonium perchlorates Arenediazoates... 

The well-known reaction of Ni(II) with dimethylglyoxime (H Dm) in alkaline medium under the influence of such oxidants as persulphate and iodine is widely used for the photometric determination of nickel. The red product (RP) of this reaction is used for this purpose. However, the nature of this red compound has not been defined yet. Using of peroxyacids makes it possible to obtain additional data concerning the conditions and mechanism of generation of RP as well as to improve the metrological pai ameters of the method. 

The findings prove that peroxyacid oxidizes the reaction product from 2 to 3 moles of PMSA ai e spent per 1 mole of RP. If the components ai e mixed unintermptedly, the output of RP does not depend on the order of mixing. Value of (1.2-1.3)xl0 mole -cm -1 is close to values, given for other oxidants. At the sui plus of H Dm compai ed to nickel (6 1)3 moles of PMSA ai e spent per 1 mole of RP, while at the sui plus of PMSA (10 1) 3 moles of H Dm ai e spent per 1 mole of RP. The data obtained do not let us affirm what exactly oxidize in the RP - Ni(II) or H Dm. It is proved, that under conditions of formation, RP is not oxidized by PMSA. 

The use of peroxyacids, including PMSA, makes it possible to improve photometric method of nickel determination - to increase selectivity, accuracy and reproducibility of measurements. Peroxyacids as oxidants ai e used for nickel determination in aluminium and copper alloys, natural waters, stomatological products. 

Peroxyacids Peroxydisulphuric acid Peroxynitric acid Peroxy ditungstic acid... 

Destruction of the aromatic ring is the mam reaction in the oxidation of tetrafluoro-o phenyleiiediamine with lead tetraacetate by products are tetrafluorobenzotnazole and tetrafluorochinoxalme denvatives [92] (equation 85) Polyfluonnated benzylideneanilines are oxidized by peroxyacids to different products dependmg on reaction contitions at room temperature the benzylidene carbon is oxidized with the formation of peroxy bonds [93 94] (equation 86), whereas in refluxing agent, the azomethme bond is cleaved [93] (equation 86) Pentafluorobenzylidencanilme is oxidized by peroxyacetic acid in dichlo-romethane at room temperature to perfluorobenzoic acid in a 77% yield [93]... 

Alkenes are oxidized to give epoxides on treatment with a peroxyacid (RCO H), such as mefn-chloroperoxybenzoic acid. An epoxide, also called an oxirane, is a cyclic ether with an oxygen atom in a three-membered ring. For example ... 

Peroxyacids transfer an oxygen atom to the alkene with syn stereochemistry—both C-0 bonds form on the same face of the double bond-through a one-step mechanism without intermediates. The oxygen atom farthest from the carbonyl group is the one transferred. 

Alkenes are reduced by addition of H2 in the presence of a catalyst such as platinum or palladium to yield alkanes, a process called catalytic hydrogenation. Alkenes are also oxidized by reaction with a peroxyacid to give epoxides, which can be converted into lTans-l,2-diols by acid-catalyzed epoxide hydrolysis. The corresponding cis-l,2-diols can be made directly from alkenes by hydroxylation with 0s04. Alkenes can also be cleaved to produce carbonyl compounds by reaction with ozone, followed by reduction with zinc metal. 

In the laboratory, as we saw in Section 7.8, epoxides are prepared by treatment of an alkene with a peroxyacid (RC03H), typically m-chloroperoxybenzoic acid. 

Another difference between sulfides and ethers is that sulfides are easily oxidized. Treatment of a sulfide with hydrogen peroxide, H202, at room temperature yields the corresponding sulfoxide (R2SO), and further oxidation of the sulfoxide with a peroxyacid yields a sulfone (R2S02)-... 

Treatment of the following alkene with a peroxyacid yields an epoxide different from that obtained by reaction with aqueous Br2 followed by base treatment. Propose structures for the two epoxides, and explain the result. 

Peroxyacid (Section 7.8) A compound with the -C03H functional group. Peroxyacids react with alkenes to give epoxides. 

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