215F07-notes-10-12-07

215F07-notes-10-12-07 - Chem 215 F07 Notes Dr. Masato...

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Chem 215 F07 Notes – Dr. Masato Koreeda - Page 1 of 4. Date: October 12, 2007 Chapter 15: Carboxylic Acids and Their Derivatives VIII. Acylation of ammonia and Amines: Synthesis of Amides Acylation of amines: a. With acid anhydrides (cont’d) • Selective reaction on an amino group over a hydroxyl group + OH NH 2 H 3 C O CH 3 O O OH H N CH 3 O O CH 3 O (acetic anhydride) 2 OH NH 3 Note stoichiometry between an amine and acid anhydride (explanation on this in section VIII b below). Also, even if excess acetic anhydride is used, only the amide product can be obtained selectively. Acetylation of a hydroxyl group with an acid anhydride is quite slow at room temperature. However, when the reaction is carried out in the presence of pyridine, both NH 2 and OH get acetylated. + OH NH 2 H 3 C O CH 3 O O O H N CH 3 O O CH 3 O (acetic anhydride) N (pyridine) CH 3 O 2 N H 2 b. With acid chlorides: highly reactive with amines: Treatment of a 1°- or 2°-amine with an acid halide results in the rapid formation of its amide derivative. However, because of the extreme acidity of the N + -H in the initially produced amide-like product, at least two mol. equivalents of an amine are required (see the mechanism shown below). + Cl
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215F07-notes-10-12-07 - Chem 215 F07 Notes Dr. Masato...

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