Peroxy carboxylic acids

Alkene Peroxy acid Epoxide Carboxylic acid... 

The acids are converted to peroxy esters for use as polymerization initiators. The metal salts are used as driers in paint formulations (see Carboxylic acids, TRIALKYLACETIC ACIDS). 

Functional groups that stabilize radicals would be expected to increase susceptibility to autoxidation. This is illustrated by two cases that have been relatively well studied. Aldehydes, in which abstraction of the aldehyde hydrogen is fecile, are easily autoxidized. The autoxidation initially forms a peroxycarboxylic acid, but usually the corresponding carboxylic acid is isolated because the peroxy acid oxidizes additional aldehyde in a... 

Peroxyacetic acid (CH3COOH) is a weaker acid than acetic acid its p/Ca is 8.2 versus 4.7 for acetic acid. Why are peroxy acids weaker than carboxylic acids y... 

The analytical method described is also used in following the consumption of peroxybenzoic acid or other peroxy acids during an oxidation reaction it has also been used in determining the conversion of other carboxylic acids to peroxy acids when solvent extraction has been used in the isolation. 

Oxidation, of acids to peroxy acids by hydrogen peroxide, 43, 96 of alkylarenes to aromatic carboxylic acids, 43, 80... 

Peroxides, test for, 41, 92 Peroxy acids from carboxylic acids and 70% hydrogen peroxide, 43, 96 Peroxybenzoic acid, 43,93 iodometric analysis of, 43, 94 Peroxystearic acid, 43,96 Phenacylamine hydrochloride, 41, 82... 

We will now explore each aspect of this two-step process. In the first step, a peroxyacid (RCO3H), sometimes called a per-acid, reacts with the alkene. Compare the structure of a carboxylic acid with the structure of a peroxy acid ... 

Peroxy acids resemble carboxylic acids in structure, possessing just one additional oxygen atom. Peroxy acids are not very acidic, but they are used as strong oxidizing agents. Common examples of peroxy acids are ... 

The epoxidation can be done either with peroxy acids or DMDO. In the former case, the rearrangement is catalyzed by the carboxylic acid that is formed, whereas with DMDO, the intermediate epoxides can sometimes be isolated. 

The peroxy acid transfers an oxygen atom to the alkene in a cyclic, single-step mechanism. The result is the syn addition of the oxygen to the alkene, with formation of an epoxide and a carboxylic acid. 

Shibasaki et al. have reported a new approach to a,/3-epoxy esters the epoxidation of cv. j-unsaturated carboxylic acid imidazolides with a La(OPr )3, BINOL, Ph3As=0, and TBHP system provides epoxy-peroxy-esters (41), which are generated in situ from the intermediary epoxy acid imidazolide and converted to the corresponding methyl ester (42) upon treatment with methanol (Scheme 27).134... 

Acidic products result from further oxidation of aldehydes (or ketones), again by a radical process. Oxidation of an aldehyde to a carboxylic acid in the presence of air involves a peroxy acid (compare peroxyacetic acid. Section 8.1.2). Finally, a reaction between the peroxy acid and a molecule of aldehyde yields two carboxylic acid molecules this is not a radical reaction, but is an example of a Baeyer-Villiger oxidation. Baeyer-Villiger... 

Reactions with carboxylic acids yield peroxy acids ... 

Carboxylic acids can be converted into the corresponding peroxy acids using peroxydisulfate in the presence of a phase transfer catalyst in good to excellent yields . When o-methylbenzoic acid was treated with sodium peroxydisulfate in the presence of Ag(I)/Cu(It), the corresponding lactone was obtained in 56% yield. Acyl radicals were also trapped by quinohnes or alkenes in the presence of peroxydisulfate to give the products in high yields. 

Since the first synthesis of the peroxyphosphoms ester 66 °, considerable efforts have been made to characterize the expanding chemistry of organophosphorus peroxy esters. Later, unsymmetrical phosphorus peroxides, such as peroxyphosphates 67 , peroxyphos-phonates 68 and peroxyphosphinates 69 , were reported. They can be prepared by the reactions of the chlorides and a tertiary carboxylic acid in the presence of base. 

Intermolecular hydrogen bonding, peroxy carboxylic acids, 160 Intermolecular isotope effect, intrazeolite photooxygenation, 872-3... 

Hundreds of different carboxylic acids have been produced via this method (1), The industrial process, dubbed the Amoco MC process, produces billions of pounds of terephthalic add, isophthalic add and trimellitic add annually. Industrial processes using just cobalt as the catalyst rather than Co/Mn/Br have also been developed (2-3). The characteristics of the reaction suggest that it is, at least partially, a free radical chain mechanism involving peroxy... 

The nomenclature for this homologous series is somewhat confused. The term PANs has been used historically to denote peroxyacyl nitrates, and this terminology continues to be used extensively in the literature, despite the lack of adherence to traditional IUPAC rules of nomenclature. Because the PANs can be considered to be mixed anhydrides of carboxylic acids and nitric acid, another suggestion (Roberts, 1990) has been peroxyacetic nitric anhydride for CH,C(0)00NO2 and peroxy carboxylic nitric anhydrides for the whole class of compounds. Although it does not follow the IUPAC rules, it would be consistent with the widespread use of the name PAN but also reflect the structure more accurately. Table 6.20 shows the structures and commonly used names of some PANs that have been observed in the atmosphere and/or in laboratory studies. 

Oxidation of Carboxylic Acids to Peroxy Acids Peroxy-de-hydroxy-substitiition... 

The oxidation of carboxylic acids with H202 and an acid catalyst is the best general method for the preparation of peroxy acids.450 The most common catalyst for aliphatic R is concentrated sulfuric acid. The reaction is an equilibrium and is driven to the right by removal of water or by the use of excess reagents. For aromatic R the best catalyst is methanesulfonic acid, which is also used as the solvent. 

Oxidative hydrolysis transforms the intermediate ozonide into ketone(s) and/or carboxylic acid(s) in good yields. H202 in water, in sodium hydroxide solution, or in formic acid is the best proven oxidant.582,584,592 Peroxy acids and silver oxide are also employed. Rearrangement and overoxidation may be undesirable side-reactions. A simple two-step ozonation in MeOH yields methyl esters without added oxidizing agent.627... 

Solid Peroxygen Compounds. Hydrogen peroxide reacts with many compounds, such as borates, carbonates, pyrophosphates, sulfates, silicates, and a variety of oiganic carboxylic acids, esters, and anhydrides to give peroxy compounds or peroxyhydrates. A number of these compounds are stable solids that hydrolyze readily to give hydrogen peroxide in solution. 

Alkyl radicals for such reactions are available from many sources such as acyl peroxides, alkyl hydroperoxides, particularly by the oxidative decarboxylation of carboxylic acids using peroxy-disulfate catalyzed by silver. Pyridine and various substituted pyridines have been alkylated in the 2-position in high yield by these methods. Quinoline similarly reacts in the 2-, isoquinoline in the 1-, and acridine in the 9-position. Pyrazine and quinoxaline also give high yields of 2-substituted alkyl derivatives <74AHC(16)123). 

---