1058-RG6-10 - Chem 1058 J. Walcott LEARNING STRATEGIES...

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Chem 1058 J. Walcott LEARNING STRATEGIES CENTER Spring 2010 Review Guide #6 Lectures: 3/1/10 – 3/5/10 Chapter 16 I. Carboxylic Acid Derivatives = Esters, Anhydrides, Acid Halides, Amide and Nitriles (continued) Carboxylic acid derivatives are compounds that can be hydrolyzed (a cleavage reaction with water) under acid or basic conditions to give carboxylic acids. Except for nitriles, carboxylic acid derivatives contain a carbonyl group. A. Carboxylic acid derivatives are weak bases that can be protonated by strong acids on the carbonyl oxygen for esters and amides or on the nitrile nitrogen. B. The most characteristic reaction of carboxylic acid derivatives is nucleophilic acyl substitution. This reaction typically involves addition of a nucleophile at the carbonyl carbon to form a tetrahedral intermediate, which then loses a leaving group to form the product. 1. Hydrolysis reactions to produce carboxylic acids. 2. Nucleophilic acyl substitution to convert to other carboxylic acid derivatives Their relative reactivities : acid chlorides > anhydrides >> ester > amides > nitriles C. Nucelophilic acyl substitution is followed by addition in: 1. LiAlH 4 reduction reactions with a work-up. 2. Grignard reactions of esters where the aldehyde or ketone intermediates react further. D. Nitriles react by addition much like aldehydes and ketones. The product can undergo a second addition (as in reduction to primary amines) or substitution (as in hydrolysis). II. Reactions of Carboxylic Acid Derivatives A. Acid Chlorides 1. Nucleophilic acyl substitution a. Reaction with ammonia and amines: Acid chlorides react rapidly and irreversibly with ammonia or amines to give amides. Because a proton is removed from the amide nitrogen, the starting amine can act as base. Consequently, either two equivalents of amine must be used, or an equivalent of base must be added to prepare the amide. b.
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1058-RG6-10 - Chem 1058 J. Walcott LEARNING STRATEGIES...

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