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Acidity of Carboxylic Acids

Acidity of Carboxylic Acids. Carboxylic acids are weakly acidic One of their most important properties. 20.4 Acid-Base Properties of Carboxylic Acids. p K a Values of Some Carboxylic Acids. 20.4 Acid-Base Properties of Carboxylic Acids. Effects of Substitution on Acidity.

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Acidity of Carboxylic Acids

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  1. Acidity of Carboxylic Acids • Carboxylic acids are weakly acidic • One of their most important properties 20.4 Acid-Base Properties of Carboxylic Acids

  2. pKa Values of Some Carboxylic Acids 20.4 Acid-Base Properties of Carboxylic Acids

  3. Effects of Substitution on Acidity

  4. Conjugate bases of carboxylic acids are called carboxylate ions • More soluble than carboxylic acids • Naming carboxylic acid salts • Name the cation • Name the anion by removing the “-ic acid” and replacing it with “-ate”

  5. Basicity of Carboxylic Acids • The carbonyl oxygen is weakly basic • plays an important role in many reactions • Note: Carboxylate protonation is less favorable 20.4 Acid-Base Properties of Carboxylic Acids

  6. Problems • You have a mixture of naphthalene and benzoic acid that you wish to separate. How might you take advantage of the acidity of one component in the mixture to accomplish the separation? • Without looking at a table of pKa values, rank the substances in each of the following groups in order of increasing acidity: fluoroacetic acid, 3-fluoropropanoic acid, iodoacetic acid

  7. Synthesis of Carboxylic Acids • Oxidation of primary alcohols • Side-chain oxidation of alkylbenzenes

  8. Grignard or organolithium with carbon dioxide

  9. Problem • How would you prepare butanoic acid using two different methods?

  10. Carboxylic Acid Reactions • There are four main types of reactions: 1. Reactions at the carbonyl group 2. Reactions at the carboxylate oxygen 3. Loss of the carboxy group as CO2 (decarboxylation) 4. Reactions involving the a-carbon (Ch 22) 20.7 Introduction to Carboxylic Acids Reactions

  11. Acid-Catalyzed Esterification • Ester: • Carboxylic acid + alcohol + acid catalyst = Ester • Also referred to as the Fischer esterification • Equilibrium is favorable, but not large • The alcohol needs to be present in large excess (commonly as the solvent)

  12. Problem • Write out the complete mechanism for the following reaction

  13. Esterification via SN2 Rxn with Carboxylate Anion

  14. Esterification by Alkylation • The carboxylate oxygen acts as a nucleophile 20.8 Conversion of Carboxylic Acids into Esters

  15. Problems • What reactants can you use to form the following ester using an SN2 reaction? • Draw the mechanism for the esterification of benzoic acid via alkylation using diazomethane.

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