A peroxy acid (often spelled as one word, peroxyacid, and sometimes called peracid) is an acid which contains an acidic –OOH group. The two main classes are those derived from conventional mineral acids, especially sulfuric acid, and the peroxy derivatives of organic carboxylic acids. They are generally strong oxidizers.
General formulas of an organic peroxy acid (top) compared with a carboxylic acid (bottom).
Peroxymonosulfuric acid (Caro's acid) is probably the most important inorganic peracid, at least in terms of its production scale.[1] It is used for the bleaching of pulp and for the detoxification of cyanide in the mining industry. It is produced by treating sulfuric acid with hydrogen peroxide. Peroxymonophosphoric acid (H3PO5) is prepared similarly.[2]
Some peroxy acids are only hypothetical, but their anions are known. This is the case for peroxycarbonate[3] and perborate (see sodium perborate).[4]
Organic peracidsedit
Several organic peroxyacids are commercially useful.[5] They can be prepared in several ways. Most commonly, peracids are generated by treating the corresponding carboxylic acid with hydrogen peroxide:[6]
RCO2H + H2O2 ⇌ RCO3H + H2O
A related reaction involves treatment of the carboxylic anhydride:
(RCO)2O + H2O2 → RCO3H + RCO2H
This method is popular for converting cyclic anhydrides to the corresponding monoperoxyacids, for example monoperoxyphthalic acid. The third method involves treatment of acid chlorides:
The products, however, react with the initial aldehyde forming the carboxylic acid:
Ar-COOOH + Ar-CHO → 2 Ar-COOH
Properties and usesedit
In terms of acidity, peroxycarboxylic acids are about 1000 times weaker than the parent carboxylic acid, due to the absence of resonance stabilization of the anion. For similar reasons, their pKa values tend also to be relatively insensitive to substituents.
The most common use of organic peroxy acids is for the conversion of alkenes to epoxides, the Prilezhaev reaction. Another common reaction is conversion of cyclic ketones to the ring-expanded esters using peracids in a Baeyer-Villiger oxidation. They are also used for the oxidation of amines and thioethers to amine oxides and sulfoxides. The laboratory applications of the valued reagent mCPBA illustrate these reactions.
Reaction of peroxycarboxylic acids with acid chlorides affords diacyl peroxides:
RC(O)Cl + RC(O)O2H → (RC(O))2O2 + HCl
The oxidizing tendency of peroxides is related to the electronegativity of the substituents. Electrophilic peroxides are stronger oxygen-atom transfer agents. The oxygen-atom donor tendency correlates with the acidity of the O−H bond. Thus, the order of oxidizing power is CF3CO3H > CH3CO3H > H2O2.
peroxy, acid, peroxy, acid, often, spelled, word, peroxyacid, sometimes, called, peracid, acid, which, contains, acidic, group, main, classes, those, derived, from, conventional, mineral, acids, especially, sulfuric, acid, peroxy, derivatives, organic, carboxy. A peroxy acid often spelled as one word peroxyacid and sometimes called peracid is an acid which contains an acidic OOH group The two main classes are those derived from conventional mineral acids especially sulfuric acid and the peroxy derivatives of organic carboxylic acids They are generally strong oxidizers General formulas of an organic peroxy acid top compared with a carboxylic acid bottom Contents 1 Inorganic peroxy acids 2 Organic peracids 2 1 Properties and uses 3 See also 4 ReferencesInorganic peroxy acids editSee also Peroxymonosulfuric acid Peroxynitric acid and Peroxymonophosphoric acid Peroxymonosulfuric acid Caro s acid is probably the most important inorganic peracid at least in terms of its production scale 1 It is used for the bleaching of pulp and for the detoxification of cyanide in the mining industry It is produced by treating sulfuric acid with hydrogen peroxide Peroxymonophosphoric acid H3PO5 is prepared similarly 2 Some peroxy acids are only hypothetical but their anions are known This is the case for peroxycarbonate 3 and perborate see sodium perborate 4 Organic peracids editSeveral organic peroxyacids are commercially useful 5 They can be prepared in several ways Most commonly peracids are generated by treating the corresponding carboxylic acid with hydrogen peroxide 6 RCO2H H2O2 RCO3H H2OA related reaction involves treatment of the carboxylic anhydride RCO 2O H2O2 RCO3H RCO2HThis method is popular for converting cyclic anhydrides to the corresponding monoperoxyacids for example monoperoxyphthalic acid The third method involves treatment of acid chlorides RC O Cl H2O2 RCO3H HClmeta Chloroperoxybenzoic acid mCPBA is prepared in this way 7 A related method starts with the peroxyanhydride 8 Aromatic aldehydes can be autoxidized to give peroxycarboxylic acids Ar CHO O2 Ar COOOH Ar aryl group The products however react with the initial aldehyde forming the carboxylic acid Ar COOOH Ar CHO 2 Ar COOHProperties and uses edit In terms of acidity peroxycarboxylic acids are about 1000 times weaker than the parent carboxylic acid due to the absence of resonance stabilization of the anion For similar reasons their pKa values tend also to be relatively insensitive to substituents The most common use of organic peroxy acids is for the conversion of alkenes to epoxides the Prilezhaev reaction Another common reaction is conversion of cyclic ketones to the ring expanded esters using peracids in a Baeyer Villiger oxidation They are also used for the oxidation of amines and thioethers to amine oxides and sulfoxides The laboratory applications of the valued reagent mCPBA illustrate these reactions Reaction of peroxycarboxylic acids with acid chlorides affords diacyl peroxides RC O Cl RC O O2H RC O 2O2 HClThe oxidizing tendency of peroxides is related to the electronegativity of the substituents Electrophilic peroxides are stronger oxygen atom transfer agents The oxygen atom donor tendency correlates with the acidity of the O H bond Thus the order of oxidizing power is CF3CO3H gt CH3CO3H gt H2O2 See also editOrganic peroxide Peracetic acid Peroxyacyl nitratesReferences edit Harald Jakob et al Peroxy Compounds Inorganic Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a19 177 pub2 Creaser I I Edwards J O 1972 Topics in phosphorus chemistry 7 379 435 Chen Li Jiang Lin Chang Jian Zuo Juan Song Ling Chun Huang Chao Ming 2004 First Spectroscopic Observation of Peroxocarbonate Peroxodicarbonate in Molten Carbonate The Journal of Physical Chemistry B 108 23 7553 7556 doi 10 1021 jp035749l perborate 2 CHEBI 30175 www ebi ac uk Herbert Klenk Peter H Gotz Rainer Siegmeier Wilfried Mayr Peroxy Compounds Organic Ullmann s Encyclopedia of Industrial Chemistry Weinheim Wiley VCH doi 10 1002 14356007 a19 199 Silbert L S Siegel E Swern D 1964 Peroxybenzoic Acid Org Synth 44 81 doi 10 15227 orgsyn 044 0081 Richard N McDonald Richard N Steppel James E Dorsey 1970 m Chloroperbenzoic Acid Org Synth 50 15 doi 10 15227 orgsyn 050 0015 Geza Braun 1928 Perbenzoic Acid Org Synth 8 30 doi 10 15227 orgsyn 008 0030 Retrieved from https en wikipedia org w index php title Peroxy acid amp oldid 1183874931 Peroxycarboxylic acid, wikipedia, wiki, book, books, library,
