Acetylation perchloric acid

Enol acetylation Perchloric acid. Sodium hydride. Epimerization Tetraethylammonium acetate. 

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. 

Under these first-order conditions the rates of nitration of a number of compounds with acetyl nitrate in acetic anhydride have been determined. The data show that the rates of nitration of compounds bearing activating substituents reach a limit by analogy with the similar phenomenon shown in nitration in aqueous sulphuric and perchloric acids ( 2.5) and in solutions of nitric acid in sulpholan and nitro-methane ( 3.3), this limit has been taken to be the rate of encounter of the nitrating entity with the aromatic molecule. 

Nearly all commercial acetylations are realized using acid catalysts. Catalytic acetylation of alcohols can be carried out using mineral acids, eg, perchloric acid [7601-90-3], phosphoric acid [7664-38-2], sulfuric acid [7664-93-9], benzenesulfonic acid [98-11-3], or methanesulfonic acid [75-75-2], as the catalyst. Certain acid-reacting ion-exchange resins may also be used, but these tend to decompose in hot acetic acid. Mordenite [12445-20-4], a decationized Y-zeohte, is a useful acetylation catalyst (28) and aluminum chloride [7446-70-0], catalyzes / -butanol [71-36-3] acetylation (29). 

Most cellulose acetate is manufactured by a solution process, ie, the cellulose acetate dissolves as it is produced. The cellulose is acetylated with acetic anhydride acetic acid is the solvent and sulfuric acid the catalyst. The latter can be present at 10—15 wt % based on cellulose (high catalyst process) or at ca 7 wt % (low catalyst process). In the second most common process, the solvent process, methylene chloride replaces the acetic acid as solvent, and perchloric acid is frequentiy the catalyst. There is also a seldom used heterogeneous process that employs an organic solvent as the medium, and the cellulose acetate produced never dissolves. More detailed information on these processes can be found in Reference 28. 

In the fibrous acetylation process, part or all of the acetic acid solvent is replaced with an inert dilutent, such as toluene, benzene, or hexane, to maintain the fibrous stmcture of cellulose throughout the reaction. Perchloric acid is often the catalyst of choice because of its high activity and because it does not react with cellulose to form acid esters. Fibrous acetylation also occurs upon treatment with acetic anhydride vapors after impregnation with a suitable catalyst such as zinc chloride (67). 

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. 

A 20) oiefin Formation via Enol Acetates and Ozonolysis A stock solution of acetylating mixture is prepared by dissolving 0.2 ml of 70-72% perchloric acid in 5 ml of acetic anhydride. To a solution of 5 g of 3a,6a-diacetoxy-5jff-pregnan-20-one in 50 ml of carbon tetrachloride is added 5 ml of the above stock perchloric acid-acetic anhydride solution and the mixture is allowed to stand at room temperature for 1.25 hr. The mixture is... 

II, C,Praill and Whitear obtained a crystalline perchlorate from acetic anhydride and perchloric acid on standing it proved to possess structure 218 and to undergo isomerization to 219 under the influence of water. The same products can be obtained on acetylating dehydroaeetic acid. 

Discussion. Hydroxyl groups present in carbohydrates can be readily acetylated by acetic (ethanoic) anhydride in ethyl acetate containing some perchloric acid. This reaction can be used as a basis for determining the number of hydroxyl groups in the carbohydrate molecule by carrying out the reaction with excess acetic anhydride followed by titration of the excess using sodium hydroxide in methyl cellosolve. 

Expls may be classified both from the chemical point of view and according to their uses. From the chemical viewpoint we distinguish between chemical individual substances and mixts. The former are divided into (1) nitro compds, (2) nitric esters, (3) nitramines, (4) derivatives of chloric and perchloric acids, (5) azides, and (6) various compds capable of pro-during an expln, for example fulminates, acetyl-ides, nitrogen rich compds such as tetrazene, peroxides and ozonides, etc... 

Dining acetylation of the enolised ketone, the 70% perchloric acid must be added last to the reaction mixture to provide maximum dilution and cooling effect. 

A. K. Chakraborti and R. Gulhane, Perchloric acid adsorbed on silica gel as a new, highly efficient, and versatile catalyst for acetylation of phenols, thiols, alcohols, and amines, Chem. Commun., 15 (2003) 1896-1897. 

B. Mukhopadhyay, D. A. Russell, andR. A. Field, One-pot acetalation-acetylation of sugar derivatives employing perchloric acid immobilised on silica, Carbohydr. Res., 340 (2005) 1075-1080. 

Acetyl perchlorate should be a strong acid in acetic anhydride, but it decomposes too rapidly for accurate measurement.203... 

The course of acid-catalyzed acetylations with acetic anhydride may depend markedly on the concentration of the acid and the type of acid. Reaction of 7-(3-deoxy-3-nitro-/3-D-galactopyrano-syl)theophylline with acetic anhydride in the presence of one molar equivalent of perchloric acid gave the 2, 4, 6 -triacetate in 89% yield, but, in the presence of only a trace of the acid, 82% of the 4, 6 -diacetate was obtained.93 Treatment of the manno isomer of the nucleoside with acetic anhydride-boron trifluoride gave the 4, 6 -diacetate as a crystalline product (24%), whereas phosphoric acid as the catalyst yielded the 2, 4, 6 -triester (45%). 

Acetate A general name for processes for making cellulose acetate fibers. Cellulose is acetylated, dissolved in acetone, and spun into fibers by injecting through orifices into heated chambers. Cellulose mono-acetate is made by acetylating with a mixture of acetic acid, acetic anhydride, and sulfuric acid as the catalyst. Cellulose tri-acetate is made in a similar fashion, but using perchloric acid as the catalyst, and dry-spinning from a solution in ethanol/ methylene chloride. Cellulose tri-acetate fibers were first made commercially by Courtaulds in London in 1950. 

Trimethylpyrylium perchlorate has been prepared from 2,6-dimethylpyrone and methylmagnesium halides 6 from mesityl oxide and sulfoacetic acid 6 from mesityl oxide (or less satisfactorily from acetone) and a mixture of acetic anhydride and perchloric acid 7 from mesityl oxide, acetyl chloride, and aluminum chloride 8 and from <-butyl chloride, acetyl chloride,... 

Acetylium tetrailuoroborate, 4 144t N-Acetyl-p-aminophenol (acetaminophen), acetic anhydride used in production of, 1 158. See also Acetaminophen Acetyl perchlorate, 1 157 Acetylsalicylic acid (aspirin), 22 17-21 acetic anhydride used in production of, 1 158... 

R = Ac or PhCO, R = Me or Ph) two cations can arise, [232] and [233], both involving aromatic stabilization of the ring. In the ultraviolet spectrum of the acetyl derivative (with R = Me) there is a bathochromic shift of the maximum absorption in ethanol when perchloric acid is added, which suggests a preference for the more extensively conjugated cation [233] in the salt. The infrared spectrum of the perchlorate shows no bcind near 1700 cm , which... 

Cationic polymerizations can be initiated with protic acids (e.g., sulfuric, perchloric, trifluoroacetic acid), with Lewis acids (see Sect. 3.2.1.1), and with compounds that form suitable cations (e.g., iodine, acetyl perchlorate). Some monomers are also polymerized by high-energy radiation according to a cationic mechanism. 

Cyclodehydration of l-carboxymethyl-2-pyridone with acetic anhydride and perchloric acid gave the corresponding 1,3-oxazolonium perchlorate which with triethylamine gave the dimer (72) directly. Similar dimerization of other meso-ionic l,3-oxazol-5-ones (66) have been reported. The monomer (71) could not be isolated, but acetyl (67, R = Me) and benzoyl (67, R = Ph) derivatives were prepared from a... 

A very important category of mistaken identity concerns the polymerisations allegedly initiated by acetyl perchlorate. Unless such experiments are conducted in high vacuum systems with really good technique, the residual water to be found under almost all other conditions produces a mixture of acetic and perchloric acids. The HCIO4 will participate in the reaction together with any unhydrolysed acetyl perchlorate. The real trouble... 

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