Caros’ acid

Oxidants suitable for the partial oxidation of amines to nitroso compounds are peroxy acids Caro acid, which is prepared in situ from potassium persulfate and sulfuric acid [195, 199 potassium peroxysulfate (Oxone) [295] peroxyacetic acid [i53], and peroxybenzoic add [1186], 3-Nitro-o-toluidine [195] and 5-nitro-o-toluidine [199] in aqueous-alcoholic solutions, when treated with a mixture of potassium persulfate and concentrated sulfuric acid, give 3-nitro-2-nitrosotoluene and 5-nitro-2-nitrosotoluene in respective yields of 60 and 55-66%. Organic peroxy acids convert 2,6-dihaloanilines into 2,6-dihalonitrosobenzenes (equation 497) [753, 1186]. p-Phenylenediamine (1,4-diaminobenzene) is oxidized by Oxone (2KHS05 KHS04 K2S04) in an aqueous suspension at room temperature to p-dinitrosobenzene in a quantitative yield [205]. 

Further use of this oxidant to produce a number of poly nitro aromatics was reported by Nielsen and co-workers [71] in their remarkable paper. The authors also reviewed work on the other oxidants used to pass from HN to NO Caro acid, peracetic, permaleic, m-chloroperbenzoic and perbenzoic acids. They pointed out that the power of the oxidant is proportional to the acid strength of deoxy peracid. Peracetic and m-chloroperbenzoic acids are suitable for the oxidation of aliphatic primary amines, whereas peracetic, peroxytrifluoroacetic and peroxymaleic acids are best for the oxidation of ring substituted anilines. Potassium persulphate in sulphuric acid was also used successfully [71 ]. 

Caros acid, HO-O-SOsH, a strong oxidizing agent.Succinic acid... 

Caro s acid, H2SOS. See persulphuric acid, carotene, C4qHs6- M.p. 18 J-J82°C. Carotene... 

Powell, J. R. Tucker, S. A. Acree, Jr., et al. A Student-Designed Potentiometric Titration Quantitative Determination oflron(ll) by Caro s Acid Titration, ... 

Caro s acid, H2SO5 is used as a titrant for determining Fe +. Directions are given for exploring the method of end point detection, the titrant s shelf-life, the method s accuracy and precision, and the susceptibility of the method to interference from other species. 

Carob bean waste (Carob)gum [9000-40-2] Carob seed gum Caroflex MP Caro s acid... 

The electrolytic processes for commercial production of hydrogen peroxide are based on (/) the oxidation of sulfuric acid or sulfates to peroxydisulfuric acid [13445-49-3] (peroxydisulfates) with the formation of hydrogen and (2) the double hydrolysis of the peroxydisulfuric acid (peroxydisulfates) to Caro s acid and then hydrogen peroxide. To avoid electrolysis of water, smooth platinum electrodes are used because of the high oxygen overvoltage. The overall reaction is... 

Peroxosulfiiric Acids and Their Salts. Two kiads of peroxosulfiiric acid are known peroxomonosulfuric and peroxodisulfuric acids. Neither is available commercially ia the pure state. The name Caro s acid is commonly used as a synonym for peroxomonosulfuric acid, but is better reserved for the equiUbrium mixture with sulfuric acid. 

Peroxomonosulfuric acid oxidi2es cyanide to cyanate, chloride to chlorine, and sulfide to sulfate (60). It readily oxidi2es carboxyflc acids, alcohols, alkenes, ketones, aromatic aldehydes, phenols, and hydroquiaone (61). Peroxomonosulfuric acid hydroly2es rapidly at pH <2 to hydrogen peroxide and sulfuric acid. It is usually made and used ia the form of Caro s acid. 

Ca.ro s Acid. Caro s acid is named after Heinrich Caro (1834—1910), who first described its preparation and oxidi2ing properties ia 1898. Hereia Caro s acid is used to designate the equiUbrium mixtures that result from mixing hydrogen peroxide and sulfuric acid. These Hquids mix iastantly, generating a considerable amount of heat. The equiUbrium constant for this reaction is 0.1 (62). 

Caro s acid is finding increasing appHcation ia hydrometaHurgy, pulp bleaching, effluent treatment, and electronics. There are several appHcations of Caro s acid ia hydrometaHurgy. It is usually made on-site by either the isothermal or the adiabatic process. The latter method is preferred because its capital cost is less and the system is safer due to the fact that the product is used as soon as it is made. 

Caro s acid has been used ia AustraUa as an oxidant ia the acid-leaching of uranium ores. It acts by oxidising the iron present ia the solution from Fe " to Fe ". This Fe " then oxidizes the uranium. Alternative oxidants that have been used iaclude pyrolusite and chlorate ion. These are both undesirable because their effluents, containing Mn " or CF, contaminate watercourses. 

Another hydrometaHurgical use of Caro s acid is for destroying cyanide effluents from gold-leaching. It is more useful than catalyzed hydrogen peroxide for this duty because it also destroys thiocyanate ion. This appHcation has been demonstrated ia the laboratory (66) and at two gold mines (66,67). 

A proprietary form of Caro s acid is sold to the electronics iadustry under the trade name Nanostrip. Used for reclaiming defective siHcon wafers, it is manufactured by Cyantech (United States), Micro-Image Technology (UK), and RASA Industries (Japan). 

Caro s acid is effective ia delignifying wood pulp (qv) made by chlorine-free bleaching sequences. When conditions are carefully controlled, the mechanical properties of the final paper (qv) are not impaired. These processes were developed ia the 1980s and commercialized ia the 1990s (68). 

Caro s acid is highly corrosive and a powerfiil oxidant. Its acidic properties are similar to those of sulfuric acid of equivalent strength. A strong irritant, it is toxic and should always be handled accordingly. No specific toxicological data are available. 

Depending on the strength of the product, Caro s acid should be transported ia accordance with the relevant regulations pertaining to the most appropriate sulfuric acid solution or to those of Hquid oxidizers not otherwise specified (NOS). 

Because the peroxodisulfate salts are all made electrochemicaHy, the electrical energy cost is a significant part of thek manufacturing cost. The 1994 world capacity for peroxodisulfate salts was about 75,000 metric tons, valued at about 30 x 10 . The principal appHcations are in polymerization catalysis and the market broadly tracks the plastics business. The Caro s acid business is difficult to quantify because the product itself is not commercial but made on-site from purchased hydrogen peroxide. 

Potassium salts of the peroxides (27—29) are prepared from the reaction of Caro s acid [7722-86-3] H2SO, with acyl chlorides, chloroformates, or organosulfonyl chlorides in the presence of potassium hydroxide (44). 

Nitroso compounds are formed selectively via the oxidation of a primary aromatic amine with Caro s acid [7722-86-3] (H2SO ) or Oxone (Du Pont trademark) monopersulfate compound (2KHSO KHSO K SO aniline black [13007-86-8] is obtained if the oxidation is carried out with salts of persulfiiric acid (31). Oxidation of aromatic amines to nitro compounds can be carried out with peroxytrifluoroacetic acid (32). Hydrogen peroxide with acetonitrile converts aniline in a methanol solution to azoxybenzene [495-48-7] (33), perborate in glacial acetic acid yields azobenzene [103-33-3] (34). 

Sulfuric acid, H2SO4, the most important commercial sulfur compound (see Sulfuric acid and sulfur trioxide), and peroxymonosulfuric acid [7722-86-3] (Caro s acid), H2SO, are discussed elsewhere (see Peroxides and peroxide compounds, inorganic). The lower valent sulfur acids are not stable species at ordinary temperatures. Dithionous acid [15959-26-9] H2S2O4, sulfoxyHc acid [20196-46-7] H2SO2, and thiosulfuric acid [13686-28-7] H2S2O2 are unstable species. A discussion of efforts to isolate and characterize the unstable sulfur acids is given (330). 

Subsequendy, H. Caro and W. H. Perkin independendy developed the commercial manufacturing process of alizarin from anthraquinone (qv) through anthraquinone-2-sulfonic acid. Taking advantage of these inventions, many manufacturers came to produce various kinds of hydroxyanthraquinones, which were used as mordant dyes for dyeing cotton and wool. 

Use of Caro s acid does result in di-AT-oxidation of 2,3-dichloropyrazine and 2,3-dichloroquinoxaline, but it is of interest to note that other heterocycles such as pyridine... 

Keep away from organic matter as it is a STRONG OXIDANT. A detailed prepn of Caro s acid (hypersulfuric acid, HiSOs, [7722-86-3]) in crystalline form m -45° from H2O2 and chlorosulfonic acid was described by Feh6r in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Vol I p. 388 1963. 

Whiting, M. J. L. (1992). The Benefits of Process Intensification for Caro s Acid Production. Trans. IChemE 70 (March), 195-96. 

Carbomethoxymethylenetriphenylphos-phorane, 129 Carbon radicals, 240 Carbonyl-forming fragmentations, 239 2a-Carboxy-A-nor-5a-cholestane, 427 Caro s acid, 152 Chlorineazide, 25, 34, 35 Chloro c lene, 136, 138 A-chloroamine reactions, 257 5a-Chloro-6 -azidocholestan-3/3-ol, 25... 

Anhydrous peroxomonosulfuric acid (Caro s acid) can be prepared by reacting chlorosulfuric acid with anhydrous H2O2... 

Treatment of macrocycle 278 with an excess of Caro s acid resulted in oxidation of all the sulfur atoms to sulfones and the azo group to an azoxy group (Scheme 181) (99MI4). The oxidation product 279 was formed in 42% yield. Products with smaller oxygen contents were obtained using weaker oxidizing agents. 

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. 

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