Anhydrid, acetic sulfuric

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. 

Various processes involve acetic acid or hydrocarbons as solvents for either acetylation or washing. Normal operation involves the recovery or recycle of acetic acid, any solvent, and the mother Hquor. Other methods of preparing aspirin, which are not of commercial significance, involve acetyl chloride and saHcyHc acid, saHcyHc acid and acetic anhydride with sulfuric acid as the catalyst, reaction of saHcyHc acid and ketene, and the reaction of sodium saHcylate with acetyl chloride or acetic anhydride. 

Cellulose acetate [9004-35-7], prepared by reaction of cellulose with acetic anhydride, acetic acid, and sulfuric acid, is spun into acetate rayon fibers by dissolving it in acetone and spinning the solution into a column of warm air that evaporates the acetone. Cellulose acetate is also shaped into a variety of plastic products, and its solutions are used as coating dopes. Cellulose acetate butyrate [9004-36-8], made from cellulose, acetic anhydride, and butyric anhydride in the presence of sulfuric acid, is a shock-resistant plastic. 

Ca.ta.lysts for Acetylation. Sulfuric acid is the preferred catalyst for esterifying cellulose and is the only known catalyst used commercially for this function. The role of sulfuric acid during acetylation has been discussed (77,78). In the presence of acetic anhydride, sulfuric acid rapidly and almost quantitatively forms the cellulose sulfate acid ester (77). Even in the absence of anhydride, the sulfuric acid is physically or mechanically retained (sorbed) on the cellulose. The degree of absorption is a measure of the reactivity or accessibiUty of different celluloses. 

Similar transformations are based upon 1,2-thiazine 2,2-dioxides (5-sultones), easily obtained by treating a,/3- or /3,y-unsaturated ketones with acetic anhydride and sulfuric acid. These compounds can be converted subsequently into furans, thiophenes or pyrroles (Scheme 115). 

Workers at Lilly prepared the oxazole-containing, dual PPAR ot/y agonist 23, through Robinson-Gabriel cyclodehydration of ketone 22 with acetic anhydride and sulfuric acid in refluxing ethyl acetate. ... 

Linearly annelated 2-methyl-4,9-dioxo-4,9-dihydrooxazolo[4,5-g]quinoline 14 was prepared in 31% yield by cyclization of 6-acetamido-7-chloro-5,8-dioxo-5,8-dihydroquinoline in acetic anhydride and sulfuric acid (59LA108). 

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. 

Esterification is not difficult if xylan is first carefully precipitated from solution and dried to a fluffy, non-horny powder, or if the xylan can be highly swollen so as to make the polysaccharide molecules easily accessible to the esterifying reagents. Solechnik101 finds that swollen undried xylan, when treated with acetic anhydride containing sulfuric... 

When the temperature is allowed to rise above 20°, the acetic-sulfuric anhydride mixture acquires a yellow to orange color from which discolored crystals are subsequently deposited. The addition, which must be slow at first, requires 1-1.5 hours depending on the efficiency of the cooling bath. 

Anhydride. A chemical compound derived from an acid by elimination of the atoms that make up water. Example SO3, sulfur trioxide, is the anhydride of sulfuric acid, H2SO4. Anhydrides are a class of organic compounds derived from the combination of two carboxylic acids (R-COOH) by. elimination of a molecule of water. For example, acetic acid (CH3COOH) minus water gives acetic anhydride. 

A hexahydro-l,3,5-triacyl-5-triazine was first prepared by Duden and Scharff from ammonium chloride, formalin, and benzoyl chloride or from hexamethylenetetramine and benzoyl chloride. A procedure similar to the one described also has been used for the preparation of hexahydro-1,3,5-triacetyl-, tri(/8-chloropropionyl)-, triacrylyl-, trimethacrylyl-, and tribenzoyl-5-triazine. Several of these compounds also have been prepared by Wegler and Ballauf from the corresponding nitriles and paraformaldehyde in the presence of acetic anhydride and sulfuric acid. 

Twenty-five years ago the domestic supply of acetic acid came from the distillation of wood. This, in the form of calcium acetate, was reacted with acetyl chloride to produce acetic anhydride to satisfy the wants of the infant cellulose acetate rayon industry. Shortly thereafter a better process came on the scene utilizing the reactants sodium acetate, sulfur dichloride, and chlorine. 

In studies on the anomerization of acetylated aldopyranoses in acetic anhydride-acetic acid-sulfuric acid at 25°, it was found34 that the peracetates of 6-deoxy-D-glucopyranose anomerize about ten times as fast as those of D-glucopyranose. 

Aromatization of a tetrahydroquinolizone (5) by means of acetic anhydride and sulfuric acid or acetic anhydride alone leads to the formation of a variety of mono- or di-substituted quinolizinium compounds. Glover and Jones 8 achieved the synthesis of a number of these derivatives starting from 2-cyanopyridine and condensing it with appropriate Grignard reagents followed by cyclization and aromatization as outlined in Eq. (2). An identical method was simultaneously worked out by Nesmeyanov and Rybinskaya9 for the specific synthesis of 2-substituted quinolizinium compounds. This... 

Rate of acetolysis, relative to that of maltose, k = 0.12 h in 5 5 2 acetic anhydride-acetic acid-sulfuric acid at 40°. 

Trinitro-l-acetamidonaphthalene, cryst, dec ca 275°. Was prepd by treating 2,4,5-trinitro-l-aminonaphthalene with acetic anhydride coned sulfuric acid... 

There are several methods reported in the literature for transforming vicinal diols into ct-diketones while avoiding the risk of C-C bond cleavage.26 Examples include the standard Swem conditions (dimethyl sulfoxide and oxalyl chloride followed by triethylamine), or the use of DMSO activated by acetic anhydride, pyridine-sulfur trioxide complex, or dicyclohexylcarbodiimide (Mq/J-att oxidation). Diones are also obtained by treatment with benzalacetone as a hydride acceptor in the presence of catalytic amounts of tris(triphenylphosphine)ruthenium dichlonde [(PPh RuCFl.27 Recent developments include the use of w-iodoxyben/.oic acid28 or the oxoammonium salt of 4-acctamidoletramethylpipcridine-1-oxyl and y -toluencNulfonic acid.29... 

According to both the NFPA Guide and Bretherick (Refs 5 13), sulfuric acid causes explosions and/or fires when in intimate contact with a large number (over 70) of materials including acetic anhydride, acet and nitric acid, acrolein, alcohols, alcohols and hydrogen peroxide, anun hydroxide, aniline, bromine and metals, carbides, chlorates, cyclopentadiene, ethylene glycol, various hydrocarbons, hydrochloric acid, iron, mercuric nitride, powdered metals, perchlorates, picrates, pyridine, Na carbonate, steel, sucrose, vinyl acetate, and w. Illustrative... 

Finally, Thiele acetoxylation of quinones, by treatment with acetic anhydride and sulfuric acid, is another excellent method of introducing functionality at an alkene carbon atom, for further synthetic elaboration (equation 50)196. This reaction was recently used as a key synthetic step in the total synthesis of metachromin-A, a useful sesquiterpene quinone moiety197. 

---