Of perchloric acid

Thiele acetylation. Quinones, when treated with acetic anhydride in the presence of perchloric acid or of concentrated sulphuric acid, undergo simultaneous r uctive acetylation and substitution to yield triacetoxy derivatives, e.g., benzoquinone gives 1 2 4-triacetoxybenzene. 

The rates of nitration of mesitylene-a-sulphonate anion (iii) and iso-durene-a -sulphonate anion (iv) in mixtures of aqueous nitric and perchloric acid followed a zeroth-order rate law. Although the rate of exchange of oxygen could not be measured because of the presence of perchloric acid, these results again show that, under conditions most amenable to its existence and involvement, the nitric acidium ion is ineffective in nitration. 

Lithium Perchlorate. Lithium perchlorate [7791 -03-9], LiClO, is prepared from neutralization of perchloric acid using lithium hydroxide or... 

Chlorine Heptoxide. The anhydride of perchloric acid is chlorine heptoxide [10294 8-1/, also known as dichlorine heptoxide. It is... 

The perchloryl fluoride [7616-94-6] FCIO, the acyl fluoride of perchloric acid, is a stable compound. Normally a gas having a melting poiat of —147.7° C and a boiling poiat of —46.7°C, it can be prepared by electrolysis of a saturated solution of sodium perchlorate ia anhydrous hydrofluoric acid. Some of its uses are as an effective fluorinating agent, as an oxidant ia rocket fuels, and as a gaseous dielectric for transformers (69). 

Perchlorates. Historically, perchlorates have been produced by a three-step process (/) electrochemical production of sodium chlorate (2) electrochemical oxidation of sodium chlorate to sodium perchlorate and (4) metathesis of sodium perchlorate to other metal perchlorates. The advent of commercially produced pure perchloric acid directly from hypochlorous acid means that several metal perchlorates can be prepared by the reaction of perchloric acid and a corresponding metal oxide, hydroxide, or carbonate. 

Anhydrous perchloric acid is not sold commercially. Aqueous solutions of perchloric acid are sold at low concentrations for analytical standard appHcations and at concentrations up to 70%. The price for 70% perchloric acid varies and starts at 2.70/kg, depending on the quantity and level of impurities. 

Bismuth Triperchlorate Pentahydrate. Bismuth(III) perchlorate pentahydrate [66172-92-7], Bi(C10 2 5H20, is prepared by dissolving Bi202 in 70% HCIO4. Anhydrous bismuth triperchlorate [14059-45-1], Bi(C10 2> maybe prepared by heating bismuthyl perchlorate monohydrate [66172-93-8], BiOClO H2O, between 80 and 100°C. Attempts to dissolve bismuth metal in concentrated perchloric acid have resulted in explosions. Treatment of bismuth or with dilute solutions of perchloric acid yields hydrates of bismuthyl perchlorate. 

Perchloric acid is a weU-known acetylation catalyst, especially in the fibrous method of preparing cellulose triacetate. Unlike sulfuric acid, perchloric acid does not combine with cellulose (78), ie, it does not form esters, and therefore virtually complete acetylation (DS 3.0, 44.8% acetyl) occurs. However, the extremely corrosive nature of perchloric acid and explosive nature of its salts have precluded its use industrially as an acetylation catalyst. 

Physical Properties. Aqueous chloric acid is a clear, colorless solution stable when cold up to ca 40 wt % (1). Upon heating, chlorine [7782-50-5] CI2, and chlorine dioxide [10049-04-4] CIO2, may evolve. Concentration of chloric acid by evaporation may be carried to >40% under reduced pressure. Decomposition at concentrations in excess of 40% is accompanied by evolution of chlorine and oxygen [7782-44-7] and the formation of perchloric acid [7601-90-3], HOCl, in proportions approximating those shown in equation 1. 

Use of the /3-thiodithiocarbonates (25) and acid results in ring closure to the 1,3-dithiol-2-one (26). Methyl, ethyl and isopropyl groups have been utilized in (25) (76S489), and when R = f-butyl, ring closure occurred in the presence of perchloric acid with extreme ease (74JOC95). Other variations of this synthetic route to 1,3-dithiole derivatives are described in Chapter 4.32. 

A similar utilization of two heteroatoms is illustrated by the reaction of the ethylenedithiol (120) with formic acid in the presence of perchloric acid. 4,5-Diphenyl-l,3-dithiolylium perchlorate (121) was formed in 45% yield (69MI40300). Introduction of a 2-oxo or 2-thioxo substituent as in (123 X = 0, S) is illustrated by the reaction of the disodium salt (122) with phosgene and thiophosgene, respectively (76S489). 

Isoxazolium salts can be prepared by reaction with alkyl iodides or sulfates, although the low basicity of isoxazoles and their sensitivity to nucleophilic attack may necessitate special care. Isoxazolium salts containing bulky Af-substituents can be prepared by the reaction of isoxazoles with alcohols in the presence of perchloric acid. For example, the reaction of 3,5-dimethylisoxazole (53) with some alcohols in the presence of 70% perchloric acid gave isoxazolium salts, (54a) in 29%, (54b) in 57% and (54c) in 82% yield 79AHC(25)147, 68JOC2397). Attempts to quaternize 3,5-dimethyl-4-nitroisoxazole failed 71JCS(B)2365). 

Treatment of 2-isoxazolines with acid usually leads to ring rupture and formation of chalcone products 62HC(l7)l), although 5-methyl-3-phenyl-2-isoxazoline forms a quaternary salt with dimethyl sulfate in the presence of perchloric acid (Scheme 51) (73BSF1390). 

Danger warning Mists of perchloric acid can condense in the exhausts of fume cupboards and lead to uncontrolled explosions So dipping is to be preferred. 

In the 6-chloro-A " series diazomethane addition and pyrazoline cleavage require more strenuous conditions. " An unexpected result is observed with the 4-chloro-A system (15) which adds two equivalents of diazomethane to give the 4-chloro-la,2a 6, 7 -dimethylene compound (16) in 16% yield after cleavage of the labile crude bispyrazoline with a catalytic amount of perchloric acid. The assignment of the -configuration to the 6,7-methylene group is based on the shift of the 19-H NMR resonance to higher field. 

Atotalof 6.2gof 17 -acetoxyandrosta-4,6-dien-3-one-[2a,la-c]-A -pyrazoline is added portionwise to a solution consisting of 2.4 ml of perchloric acid (70%) in 240 ml acetone. The reaction mixture is then poured into ice water and extracted with methylene dichloride. The organic layer is washed to neutrality with water, dried over anhydrous sodium sulfate and taken to dryness. The residue is chromatographed on 300 g silica gel (deactivated with water 10% v/w) and eluted with methylene dichloride to yield 3.32 g (58%) of 17 -acetoxy-la,2cc-methyleneandrosta-4,6-dien-3-one mp 178-179° (from diisopropyl ether) [aj 188°(CHCl3) 281 mfi (e20,700). Further... 

Oxidation-reduction reactions involving perchlorates have been mentioned in several of the preceding sections and the reactivity of aqueous solutions is similar to that of aqueous solutions of perchloric acid. 

An interesting application of this reaction was the use of macro-molecular anhydrides, namely, styrene-maleic anhydride or vinyl acetate-maleic anhydride copolymers in the presence of perchloric acid as catalyst, these copolymers acylate mesityl oxide or d rpnone to macromolecular pyrylium salts which, with aryl substituents, are fluorescent.No crystalline products could be obtained from succinic anhydride because of the solubility and ease of decarboxylation. 

Krivun, Shian, and Dorofeenko condensed acetylacetone or dibenzoylmethane with various ketones (acetone, acetophenone, acetothienone, 1-acetylnaphthalene, or 5-acetylacetaphthene) and obtained pyrylium salts in 10-20% yield in the presence of perchloric acid. 

On the other hand, 1,1,1-trisubstituted alkanes behave similarly to aldehydes, yielding pyrjdium salts (128) with identical substituents in positions 2 and 6. Thus, Dorofeenko and co-workers condensed 2 moles of acetophenone with 1 mole of benzotrichloride in the presence of perchloric acid obtaining 2,4,6-triphenjdpjTylium perchlorate with 1 mole of ethyl orthoformate, they obtained 2,6-diphenyl-pyrylium perchlorate (57) from o-hydroxyacetophenone, ortho-formic ester and perchloric acid, 4-ethoxybenzopyrylium perchlorate was formed. 

Hydrogenolysis of cxo-2-phenyl-9-oxabicyclo[3.3, l]nonan-2-ol proceeds exclusively with retention over Raney nickel and with inversion over palladium. No reduction with palladium occurred at all until a drop of perchloric acid was added (36). 

Next, 25.3 g, 0.125 mol, of the above product are dissolved in 250 ml ethyl acetate and 0.125 mol perchloric acid as a 70% aqueous solution is slowly added thereto with continuous stirring. Then, an excess of pivaloyl chloride, 280 ml. Is added and the mixture slowly warmed to reflux temperature. The reaction mixture is refluxed for about 5 hours and allowed to cool to room temperature with continuous stirring. The product is precipitated as the perchlorate salt by the addition of perchloric acid, HCIO4, in 500 ml ether. The product is isolated and purified by dissolving in 75 ml acetone and precipitating it with 150 to 200 ml of water. 

This was reacted with chlorine to give the dichloropregnene compound, then with selenium dioxide to give the dichloropregnadiene compound. By hydrolysis with methanolic potassium hydroxide there was obtained the free 6a-fluoro-9a,11/3-dichloro-A -pregnadiene-16a,-17a,21-triol-3,20-dione. By treatment with acetone in the presence of perchloric acid, the 16,17-acetonide of 6a-fluoro-9a,11/3-dichloro-A -pregnadiene 16a,17a,21-triol-3,20-dione was formed. 

A mixture of 1.38 grams of the above compound and 15 cc of dioxane was treated with 1.9 cc of a 0.5 N aqueous solution of perchloric acid and 600 mg of N-bromoacetamide, adding the latter in the dark, in three portions, in the course of half an hour and under continuous stirring. It was then stirred for a further 1% hours in the dark, then the excess of reagent was decomposed by the addition of aqueous sodium bisulfite solution and ice water was added the product was extracted with methylene chloride, washed with water, dried over anhydrous sodium sulfate and the solvent was evaporated under reduced pressure, thus giving a yellow oil consisting of the 16,21-diacetate of 6a-fluoro-9a-bromo-16o-hydroxy-hydrocortisone which was used for the next step without further purification. 

The corrosion of tin by nitric acid and its inhibition by n-alkylamines has been reportedThe action of perchloric acid on tin has been studied " and sulphuric acid corrosion inhibition by aniline, pyridine and their derivatives as well as sulphones, sulphoxides and sulphides described. Attack of tin by oxalic, citric and tartaric acids was found to be under the anodic control of the Sn salts in solution in oxygen free conditions . In a study of tin contaminated by up to 1200 ppm Sb, it was demonstrated that the modified surface chemistry catalysed the hydrogen evolution reaction in deaerated citric acid solution. 

But in the presence of perchloric acid, which is a far stronger acid, acetic acid will accept a proton ... 

Iodide. A 0.01 M solution of potassium iodide, prepared from the dry salt with boiled-out water, is suitable for practice in this determination. The experimental details are similar to those given for bromide, except that the indicator electrode consists of a silver rod immersed in the solution. The titration cell may be charged with 10.00 mL of the iodide solution, 30 mL of water, and 10 mL of the stock solution of perchloric acid + potassium nitrate. In the neighbourhood of the equivalence point it is necessary to allow at least 30-60 seconds to elapse before steady potentials are established. 

The cobalt complex is usually formed in a hot acetate-acetic acid medium. After the formation of the cobalt colour, hydrochloric acid or nitric acid is added to decompose the complexes of most of the other heavy metals present. Iron, copper, cerium(IV), chromium(III and VI), nickel, vanadyl vanadium, and copper interfere when present in appreciable quantities. Excess of the reagent minimises the interference of iron(II) iron(III) can be removed by diethyl ether extraction from a hydrochloric acid solution. Most of the interferences can be eliminated by treatment with potassium bromate, followed by the addition of an alkali fluoride. Cobalt may also be isolated by dithizone extraction from a basic medium after copper has been removed (if necessary) from acidic solution. An alumina column may also be used to adsorb the cobalt nitroso-R-chelate anion in the presence of perchloric acid, the other elements are eluted with warm 1M nitric acid, and finally the cobalt complex with 1M sulphuric acid, and the absorbance measured at 500 nm. 

Properties of Perchloric Acid—Acetic Anhydride—Acetic Acid Mixtures. P 144... 

Perchjorate, FNH3+C104 , mp 104-05° with decompn prepd by addn of N-iso-Pi-N-fluoro-ure thane to a so In of perchloric acid in chlf (work must be done behind a good safety shield as compds are expl) (Ref 5)... 

Fig 2 Properties of perchloric acid-acetic anhydride-acetic acid mixtures (from Ref 32)... 

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