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Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH 3 CO) 2 O. ... Often a base such as pyridine is added to function as catalyst.
A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O)) 2 O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. [2] Thus, (CH 3 CO) 2 O is called acetic ...
The worldwide production of acetic anhydride is a major application, and uses approximately 25% to 30% of the global production of acetic acid. The main process involves dehydration of acetic acid to give ketene at 700–750 °C. Ketene is thereafter reacted with acetic acid to obtain the anhydride: [50] CH 3 CO 2 H → CH 2 =C=O + H 2 O
Acetic anhydride. This reagent is common in the laboratory; its use cogenerates acetic acid. [7] [10] Acetyl chloride. This reagent is also common in the laboratory, but its use cogenerates hydrogen chloride, which can be undesirable. [8] Ketene. At one time acetic anhydride was prepared by the reaction of ketene with acetic acid: [11]
Modern variations on the Dakin–West reaction permit many enolizable carboxylic acids – not merely amino acids – to be converted to their corresponding methyl ketones. For example, β-aryl carboxylic acids can be efficiently converted to β-aryl ketones by treatment of an acetic anhydride solution of the acid with catalytic N-methylimidazole.
A major factor in determining the reactivity of acyl derivatives is leaving group ability, which is related to acidity. Weak bases are better leaving groups than strong bases; a species with a strong conjugate acid (e.g. hydrochloric acid) will be a better leaving group than a species with a weak conjugate acid (e.g. acetic acid).
The catalytic cycle of the Monsanto process for production of acetic acid. The catalytically active species is the anion cis-[Rh(CO) 2 I 2] −. [6] which undergoes oxidative addition with methyl iodide. The related Tennessee Eastman acetic anhydride process affords acetic anhydride by carbonylation of methyl acetate. [7] CH 3 CO 2 CH 3 + CO ...
The term "acetyl" was coined by the German chemist Justus von Liebig in 1839 CE to describe what he incorrectly believed to be the radical of acetic acid (the main component of vinegar, aside from water), which is now known as the vinyl group (coined in 1851 CE); "acetyl" is derived from the Latin acētum, meaning "vinegar."