Acetylation commercialization

Minimally Acetylated, Commercial, Liquid Lecithin Specification... 

Kerr and Cleveland also presented evidence that the reason for the reported resistance of dextrins to derivatization is quite likely to be due to physical causes instead of to the chemical structure of the product. Although, initially, they were unable to obtain the theoretical acetyl content for acetylated commercial dextrins by conventional acetylation procedures, modification of the method to include a preliminary swelling of the dextrin permitted the triacetate to be obtained in all instances. They concluded, therefore, that the ether linkages postulated by Caesar and Rixggeberg are improbable. 

Commercial preparations of acetyl chloride are best freed from volatile phos. phorus compounds and dissolved hydrogen chloride by redistillation from 5-10 per cent, of the volume of pure dimethylaniline. 

Commercial dialkyl-anilines may be purified by refluxing with an excess of acetic anhydride any unchanged aniline and monoalkyl-aniline are converted into the difficultly-volatile acetyl derivatives ... 

Phenacetiii may also be prepared by acetylation of the commercially available p phenetidine ... 

TO a solution of 0.10 mol of phenyl acetyl one (commercially available, see also Ref. 1) in 100 ml of dry THF was added a solution of 0.21 mol of butyllithium in about 145 ml of hexane. During this addition the temperature was kept below -20°C. The obtained solution was cooled to -65°C and a solution of 0.12 mol of KO-tert.--CijHg (commercially available, see Chapter IV, Exp. 4, note 2) in 100 ml of THF was added, while keeping the temperature below -55°C. After an additional 15 min the cooling bath was removed, the temperature was allowed to rise to -10°C and was kept at that level for 1 h (note 1). The reddish suspension was subsequently cooled to -50°C and 0.32 mol of trimethylchlorosi1ane was added in 10 min. The cooling bath was then removed and the temperature was allowed to rise to 10°C. 

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). 

Acetic anhydtide [108-24-7] (CH2C0)20, is a mobile, colorless liquid that has an acrid odor and is a more pierciag lacrimator than acetic acid [64-19-7]. It is the largest commercially produced carboxyUc acid anhydride U.S. production capacity is over 900,000 t yearly. Its chief iadustrial appHcation is for acetylation reactions it is also used ia many other appHcations ia organic synthesis, and it has some utility as a solvent ia chemical analysis. 

Acetyl chlotide is manufactured commercially in Europe and the Fat East. Some acetyl chlotide is produced in the United States for captive appHcations such as acetylation of pharmaceuticals. 

Acetyl chloride frequently contains 1—2% by weight of acetic acid or hydrochloric acid. Phosphoms or sulfur-containing acids may also be present in the commercial material. A simple test for purity involves addition of a few drops of Crystal Violet solution in CHCl. Pure acetyl chloride will retain the color for as long as 10 min, but hydrochloric, sulfuric, or acetic acid will cause the solution to become first green, then yellow (34). 

Little is known of the market for acetyl chloride. The production and sales are beUeved to be small, but may have potential for very large scale-up. The total U.S. market may amount to only 500 t annually. Acetyl chloride must be shipped in polyethylene-lined dmms having capacities of only 220 L it must be labeled as a corrosive substance. Acetyl chloride generated captively from purchased raw materials probably has a unit value of no more than 0.92—0.95/kg. Shipping costs and other factors set the price at about 3/kg for the commercial trade. 

Specifications and Analytical Methods. The commercial material is specified as 97% minimum purity, determined by gas chromatography or acetylation. Moisture is specified at 0.05% maximum (Kad-Fischer titration). Formaldehyde content is determined by bisulfite titration. 

The predominant cellulose ester fiber is cellulose acetate, a partially acetylated cellulose, also called acetate or secondary acetate. It is widely used in textiles because of its attractive economics, bright color, styling versatiUty, and other favorable aesthetic properties. However, its largest commercial appHcation is as the fibrous material in cigarette filters, where its smoke removal properties and contribution to taste make it the standard for the cigarette industry. Cellulose triacetate fiber, also known as primary cellulose acetate, is an almost completely acetylated cellulose. Although it has fiber properties that are different, and in many ways better than cellulose acetate, it is of lower commercial significance primarily because of environmental considerations in fiber preparation. 

Cellulose triacetate is obtained by the esterification of cellulose (qv) with acetic anhydride (see Cellulose esters). Commercial triacetate is not quite the precise chemical entity depicted as (1) because acetylation does not quite reach the maximum 3.0 acetyl groups per glucose unit. Secondary cellulose acetate is obtained by hydrolysis of the triacetate to an average degree of substitution (DS) of 2.4 acetyl groups per glucose unit. There is no satisfactory commercial means to acetylate direcdy to the 2.4 acetyl level and obtain a secondary acetate that has the desired solubiUty needed for fiber preparation. 

Secondary Acetate Processes. There is no commercial process to directiy produce secondary cellulose acetate sufficientiy soluble in acetone to produce fiber. Hence, the cellulose is completely acetylated to the triacetate during the dissolution step and then hydrolyzed to the required acetyl value. 

First,/)-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) are acetylated to produce the low melting acetate esters which are molten at 200°C. In an inert gas, the two monomers are melted together at 200°C. The temperature is raised to 250—280°C and acetic acid is coUected for 0.5 to 3 h. The temperature is raised to 280—340°C and additional acetic acid is removed in vacuum for a period of 10 to 60 min. The opalescent polymer melt produced is extmded through a spinning jet, foUowed by melt drawdown. The use of the paraUel offset monomer, acetylated HNA, results in the formation of a series of random copolyesters of different compositions, many of which faU within the commercially acceptable melting range of... 

Acetoiicetyliition Reactions. The best known and commercially most important reaction of diketene is the aceto acetylation of nucleophiles to give derivatives of acetoacetic acid (Fig. 2) (1,5,6). A wide variety of substances with acidic hydrogens can be acetoacetylated. This includes alcohols, amines, phenols, thiols, carboxyHc acids, amides, ureas, thioureas, urethanes, and sulfonamides. Where more than one functional group is present, ring closure often follows aceto acetylation, giving access to a variety of heterocycHc compounds. These reactions often require catalysts in the form of tertiary amines, acids, and mercury salts. Acetoacetate esters and acetoacetamides are the most important industrial intermediates prepared from diketene. 

A shippable but somewhat less reactive form of diketene is its acetone adduct, 2,2,6-trimethyl-4JT-l,3-dioxin-4-one (15) (103,104). Thermolysis of this safer to handle compound provides acetylketene, a reactive intermediate that can be used for acetoacetylation and cycloaddition reactions. The diketene—acetone adduct as weH as / fZ-butylaceto acetate [1694-31 -1] (also used for aceto acetylations by the trans aceto acetylation reaction) (130), are offered commercially. 

Acetophenone. Acetophenone [98-86-2] (methyl phenyl ketone) is a colorless Hquid that forms laminar crystals at low temperature (mp 20°C). It has a characteristic sweet orange blossom odor, and is soluble in alcohols and ethers. It is found in nature in oil of casatoreum, obtained from beavers oil of labdanum, recovered from plants and in buds of balsam poplar. It can be prepared by the Friedel-Crafts reaction (qv) of acetyl chloride with benzene in the presence of aluminum chloride however, this route is of Htde commercial significance. 

Acetyl cyclohexanesulfonyl peroxide has been produced commercially by the sulfoxidation of cyclohexane, presence of acetic... 

The hydroxyl number can be deterrnined in a number of ways such as acetylation, phthalation, reaction with phenyl isocyanate, and ir and nmr methods. An imidazole-catalyzed phthalation has been used to measure the hydroxyl number for a number of commercial polyether polyols and compared (favorably) to ASTM D2849 (uncatalyzed phthalation) (99). The uncatalyzed method requires two hours at 98°C compared to 15 minutes at the same temperature. 

Esters of the phenohc hydroxyl are obtained easily by the Schotten-Baumaim reaction. The reaction ia many cases iavolves an acid chloride as the acylating agent. However, acylation is achieved more commonly by reaction with an acid anhydride. The single most important commercial reaction of this type is the acetylation of sahcyhc acid with acetic anhydride to produce acetylsahcyhc acid [50-78-2] (aspirin). 

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. 

Uses ndReactions. The Prins reaction of 3-carene with formaldehyde in acetic acid gives mainly 2-carene-4-methanol acetate, which when saponified produces the 2-carene-4-methanol, both of which are commercial products of modest usage (60). 3-Carene (28) also reacts with acetic anhydride with a catalyst (ZnCl2) to give 4-acetyl-2-carene (29) (61), which is also a commercial product. Although 3-carene does not polymerize to produce terpene resins, copolymerization with phenol has been successfully commercialized by DRT in France (62). 

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