Acetical - Aspirin

Ketene is used as an acetylating agent in the production of cellulose acetate, aspirin, acetic anhydride, and in various organic syntheses. 

Acetylation. Boil i g. of salicylic acid with 4 ml. of an acetic anhydride-acetic acid mixture (equal volumes) under reflux for 10 minutes. Pour into water. Filter off the aspirin (p. 111), wash with water and recrystallise from aqueous acetic acid (1 1) m.p. l36 ... 

Phenols, unlike amines, cannot be acetylated satisfactorily in aqueous solution acetylation proceeds readily with acetic anhydride in the presence of a little concentrated sulphuric acid as catalyst. Salicylic acid (o-hydroxy-benzoic acid) upon acetylation yields acetylsalicylic acid or aspirin ... 

Currently, almost all acetic acid produced commercially comes from acetaldehyde oxidation, methanol or methyl acetate carbonylation, or light hydrocarbon Hquid-phase oxidation. Comparatively small amounts are generated by butane Hquid-phase oxidation, direct ethanol oxidation, and synthesis gas. Large amounts of acetic acid are recycled industrially in the production of cellulose acetate, poly(vinyl alcohol), and aspirin and in a broad array of other... 

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). 

Manufacture. Aspirin [50-78-2] is manufactured by the acetylation of sahcyhc acid with acetic anhydride (eq. 9) (37,38). 

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. 

However, this method is appHed only when esterification cannot be effected by the usual acid—alcohol reaction because of the higher cost of the anhydrides. The production of cellulose acetate (see Fibers, cellulose esters), phenyl acetate (used in acetaminophen production), and aspirin (acetylsahcyhc acid) (see Salicylic acid) are examples of the large-scale use of acetic anhydride. The speed of acylation is greatiy increased by the use of catalysts (68) such as sulfuric acid, perchloric acid, trifluoroacetic acid, phosphoms pentoxide, 2inc chloride, ferric chloride, sodium acetate, and tertiary amines, eg, 4-dimethylaminopyridine. 

Aspirin (sahcyhc acid, acetic anhydride) B L None 90 1 >ih [7] 89... 

Acetic anhydride is mainly used to make acetic esters and acetyl salicylic acid (aspirin). 

Important chemicals derived from phenol are salicylic acid acetylsali-cyclic acid (aspirin) 2,4-dichlorophenoxy acetic acid (2,4-D), and 2,4,5-triphenoxy acetic acid (2,4,5-T), which are selective herbicides and pentachlorophenol, a wood preservative ... 

Conversion of Acid Anhydrides into Esters Acetic anhydride is often used to prepare acetate esters from alcohols. For example, aspirin (acetylsalicylic acid) is prepared commercially by the acetylation of o-hydroxybenzoic acid (salicylic acid) with acetic anhydride. 

Add 2.0 g of salicylic acid, 5.0 mL of acetic anhydride, and 5 drops of 85% H3P04 to a 50-mL Erlenmeyer flask. Heat in a water bath at 75°C for 15 minutes. Add cautiously 20 mL of water and transfer to an ice bath at 0°C. Scratch the inside of the flask with a stirring rod to initiate crystallization. Separate aspirin from the solid-liquid mixture by filtering through a Buchner funnel 10 cm in diameter. 

Aspirin, C9H804, is prepared by reacting salicylic acid QHQ with acetic anhydride, C4He03> in die reaction... 

A student is told to prepare 45.0 g of aspirin. She is also told to use a 55.0% excess of acetic anhydride and to expect to get an 85.0% yield in the reaction. How many grams of each reactant should she use ... 

You will see, by examining this structure, that aspirin is an ester of acetic acid. Aspirin is mankind s most widely used drug. Somewhat over 20 million pounds of aspirin are manufactured each year in the United States alone This amounts to something like ISO five-grain tablets for every person in the country ... 

NSAIDs are of diverse chemical structures salicylates (aspirin, sulphasalazine), indole acetic acids (indomethacin, etodolac), heteroaryl acetic acids (diclofenac), arylpropionic acids (ibuprofen, naproxen), anthranilic acids (mefenamic acid) and enolic acids (piroxicam, meloxicam). 

Salicylic acid reacts with acetic acid to produce acetylsalicylic acid the active ingredient in aspirin. It also reacts with methanol to form methyl salicylate, more commonly known as oil of wintergreen. 

Aspirin (shown here as acetylsalicylic acid, Ka = 3.2 X 10 4) is a product of the reaction of salicylic acid with acetic anhydride. Calculate the ratio of the concentrations... 

Aspirin (34) is an available protected form of (38) and aceto acetate is an activated form of ethyl acetate, instead of the more usual malonate. 

Acetylene dichtoride, see 1,2-Oichl Acetylene tetrabromide Acet salicylic acid (aspirin) Acrolein Acrylamide ... 

C04-0014. Aspirin is produced by treating salicylic acid with acetic anhydride ... 

Suppose a chemist started with 152 g of salicylic acid and 86.8 g of acetic anhydride and produced 133 g of aspirin. What is the yield of this reaction ... 

Aspirin is a white, crystalline powder. It is odorless but might have a faint odor of acetic acid. 

Essentially, all methods of synthesis are variations of the reaction of acetylchloride, acetic anhydride or ketene11 with salicylic acid using a variety of catalysts such as pyridine12 or sulfuric acid13 and reaction conditions (c.f. 14). The preparation of aspirin labeled with a i4c iaj-,eie(j acetyl group has also been reported.15 Efforts to improve the commercial processes continue to the present day. 

---