ACETIC ANHYDRIDEWith a formula of C4H6O3 and molecular weight of 102.09 g, acetic anhydride is also called acetic or acetyl oxide, ethanoic anhydride, acetyl ether and acetyl acetate. A transparent, colorless liquid with a strong vinegar-like odor, when water is added, it forms acetic acid. It is soluble in benzene, chloroform or ether and reacts with alcohols. Prepared commercially, acetaldehyde
. is oxidized with a metal acetate catalyst, and the acetylene vapor is reacted with acetic acid.The acyl groups on either side of the ether bond in acetic anhydride can react with water for carboxylic acids, with alcohols or phenols to create esters and with ammonia or amines to make amides. Acetic anhydride is heated with salicylic acid to produce aspirin, used to manufacture cellulose acetate for fiber textiles and is involved in the manufacture of dyes, pigments, pesticides and pharmaceuticals. Acetic anhydride can manufacture acetyl compounds; is used as a solvent for wool fat, glycerol, fatty and volatile oils, or resins; can detect rosin and can synthesize organic chemicals. It is often a dehydrating agent in nitrations, sulfonations and other water removal reactions.Physical state = clear liquid with strong, sour acetic odor; lacrimatorMelting point = -73 CBoiling point = 139.9 CSpecific gravity = 1.082 g/cm3Solubility in water = slowly soluble due to decompositionVapor density = 3.52Vapor pressure = 0.5 kPa at 20 CHeat of vaporization = 52.0 kJ/molHeat of combustion = -1805 kJ/molStability = flammable gasAutoignition = 316 CRefractive index = 1.3904Toxicity = Oral rat LD50: 1780 mg/kgAnhydrides are formed by the removal water. They are typically dehydrated acids, while dehydrated bases are termed oxides and mixed anhydrides are created from two acids. Anhydrides of inorganic acids are often oxides of nometallic elements. Acid anhydrides form acids when reacted with water, while base anhydrides form bases in the same manner. Organic anhydrides have a carbonyl group and are formed by the same water molecule removal process or derived from corresponding carboxylic acids. Carboxylic anhydrides are the combination of two carboxylic acid molecules which have been dehydrated.Anhydrides are even more reactive than their parent acids. They are often the intermediates in the synthesis of other organic chemicals, such as esters and amides in industrial applications. The reactivity of carboxylic acid derivatives follows the order of acyl halides ---> anhydrides ---> esters ---> acids ---> amides. Anhydrides react with alcohols to form esters amd ammonia and primary or secondary amines to form amides.Anhydrides must be kept in cool, dry locations, away from fire or water. Acetic anhydride is corrosive to steel, galvanized iron, copper and copper alloys. For more information, please see the below links.More reference links: http://www.chemicalbook.com/ProductMSDSDetailCB2852742_EN.htm http://www.osha.gov/SLTC/healthguidelines/aceticanhydride/recognition.html
