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acid anhydrides

acid anhydrides - GENERAL INFORMATION Acid Anhydrides 1...

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Unformatted text preview: GENERAL INFORMATION Acid Anhydrides 1 Acid Anhydrides [(RCO)20] Introduction: Acid anhydrides have two acyl groups bonded to the same oxygen atom. They have the formula (RCO)20, where the R groups can be the same or different alkyl groups. When both acyl groups are identical, the acid anhydrides are symmetric. The most common acid anhydride is acetic anhydride which is produced industrial- ly to make aspirin, perhaps one of the most widely used over-the-counter medications. Chemical Properties: ' The carbonyl carbon is 51.)2 hybridized and thus has planar geometry. - Acid anhydrides are less reactive than acyl halides; however, they are more reactive than esters and amides. Nomenclature: Symmetric acid anhydrides: When two acyl groups are identical (R = R’), the acid anhydride is named by replacing acid by anhydride, for example, E? ‘u’ CH3COCCHJ Acetic anhydride Asymmetric acid anhydrides: When two acyl groups are not identical (R at R’), the acyl groups are named in alphabetical order followed by the suffix anhydride, for example, Benzoie propanuic anhydride Spectroscopv: IR: There are two absorption peaks due to two C=0 bonds vibrating in and out of phase. For example, in acetic anhydride, the first peak is at 1750 cm'1 and the second one is at 1820 cm‘l. C NMR: Characteristic peak at 8 = 200 ppm. Summary of Acid Anhydride Reactions Synthesis ofAcid Anhydrides 0 From Carboxylic Acids and Acyl Halides o o easier: + cuzcnziia Acetic acid Propanoyl chloride [carboxylic acid) (acyl halide) Reaction of Acid Anhydrides - Preparation of Carboxylic Acids and Esters if i .d. EV—M me cuacoctmzcn3 Methanoic propanoic anhydride (acid anhydride) ‘i’ ‘1" cu’ ° ridine || CchocCH; + 0H3CHZCH20H 3L6 Cl-IacOH + CHacflchCH-zCHzCHg Acetic anhydride Propanoi Acetic acid Prapyl propanoate (and anhydride) (alcohol) 0 Preparation of Amides o o n u H n n ,CHRCHa H ,cuacu: u _\ (3| CHsCOCCH: + 2 H—N —> CHIC N + CHECO U H—N —CH;CH3 \CchHa \cngcm | Auelic m mad: 7 ‘ CH’CH’ .d m .d D'E'my’amme NJV—Dielhylethnnalrfide Dielhylnmmonium ncelale [an 34 n a] “mm” urN.NADie|hylacelamjde (ammonium sail} Eamide) ' Preparation of Ketones ‘i ‘n’ i? ‘n’ cmcoccu. 1. '@—ocuch, & Cflac @DCHRCHg 1 cHycaH Aceth anhydride AneLhcfle 47Ethaxyacerophenone Acetic acid " ‘° {acid anhydride: :arene) (kelunel Ecurhuiyliv acid) Note: Acid Anhydrides 2A Acid Anhydrides ZB Acid Anhydrides 2C Acid Anhydrides 2D The mechanisms for acid anhydrides reactions are very similar to those of acyi halides {see Acyl Halides 2 through 4 for detailed mechanisms). ...
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acid anhydrides - GENERAL INFORMATION Acid Anhydrides 1...

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