215F07-notes-10-12-07(new)

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

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Chem 215 F07 Notes – Dr. Masato Koreeda - Page 1 of 6. 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 O HN(CH 3 ) 2 2 + N O H 2 N(CH 3 ) 2 CH 3 CH 3 Cl Mechanism: Cl O HN(CH 3 ) 2 Cl O N H 3 C CH 3 H O N H 3 C CH 3 H HN(CH 3 ) 2 + N O H 2 N(CH 3 ) 2 CH 3 CH 3 Cl Cl extremely acidic! Alternatively, with the use of an appropriate base (usually a tertiary amine), an amide can be prepared in high yield with only one mol. equivalent of a 1°- or 2°-amine. + Cl O HN(CH 3 ) 2 + N O HN(CH 2 CH 3 ) 3 CH 3 CH 3 Cl N(CH 2 CH 3 ) 3 N(CH 2 CH 3 ) 3 O Note: Even if a tertiary amine reacts with an acid halide, the resulting quaternary amine product undergoes reaction with a halide anion to recover the original acid halide. Cl
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Chem 215 F07 Notes – Dr. Masato Koreeda - Page 2 of 6. Date: October 12, 2007 Chapter 15: Carboxylic Acids and Their Derivatives VIII. Acylation of ammonia and Amines: Synthesis of Amides
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This note was uploaded on 04/01/2008 for the course CHEM 215 taught by Professor Koreeda during the Fall '07 term at University of Michigan.

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

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