Chapter 21 November 5

Chapter 21 November 5 - 5 Formation of Acid Chlorides from...

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1 Relative Reactivity of Carboxylic Acid Derivatives Nucleophiles react more readily with unhindered carbonyl groups: More electrophilic carbonyl groups are more reactive to addition (to form tetrahedral intermediates) The intermediate with the best leaving group forms the substitution product faster
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2 Consequences of Differing Reactivity on Synthesis: A more reactive acid derivative can be readily converted into a less reactive one (often through a single step/reaction) Less reactive acid derivatives can sometimes be converted into more reactive ones, but the process is much more complex, time consuming and delicate
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3 General Reaction Overview of Acyl Substitution Reactions
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4 Nucleophilic Acyl Substitution Reactions of Carboxylic Acids ­OH is a poor leaving group making direct nucleophilic acyl substitution difficult Increase/augment reactivity with:
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Unformatted text preview: 5 Formation of Acid Chlorides from Carboxylic Acids General Reaction: Reaction Mechanism: 6 Formation of Acid Anhydrides from Carboxylic Acids Examples: Two moles of carboxylic acids are heated together to eliminate 1 mole of H 2 O This is a difficult procedure. Acetic anhydride is the only anhydride commonly produced Cyclic anhydrides are commonly produced when 5/6 membered rings can be formed from the dehydration of a diacid 7 Fischer Esterification Reaction Mechanism: Formation of Esters from Carboxylic Acids S N 2 reaction of a carboxylate anion with a 1 o alkyl halide Fischer Esterification: Nucleophilic acyl substitution of a carboxylic acid with an alcohol 8 Formation of Amides from Carboxylic Acids General Reaction: This is a very difficult transformation to accomplish. Why? Reaction with DCC:...
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This note was uploaded on 12/20/2011 for the course CHEM 234-54 taught by Professor Morrison during the Fall '09 term at UGA.

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Chapter 21 November 5 - 5 Formation of Acid Chlorides from...

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