1 / 30

Carboxylic Acid Derivatives: Nucleophilic Acyl Substitution

Carboxylic Acid Derivatives: Nucleophilic Acyl Substitution. Chapter 19. Reading Assignment. DO: Sections 19.0 - 19.1, 19.4, 19.5, 19.7 - 19.15, 19.17 - 19.20, 19.22 - 19.24, 19.35 Problems READ WITHOUT LECTURE: Sections 19.16, 19.26 - 19.34 SKIP: Sections 19.2 - 19.3, 19.6, 19.21, 19.25.

doctor
Download Presentation

Carboxylic Acid Derivatives: Nucleophilic Acyl Substitution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Carboxylic Acid Derivatives:Nucleophilic Acyl Substitution Chapter 19 WWU-Chemistry

  2. Reading Assignment • DO: • Sections 19.0 - 19.1, 19.4, 19.5, 19.7 - 19.15, 19.17 - 19.20, 19.22 - 19.24, 19.35 • Problems • READ WITHOUT LECTURE: • Sections 19.16, 19.26 - 19.34 • SKIP: • Sections 19.2 - 19.3, 19.6, 19.21, 19.25 WWU-Chemistry

  3. Organic Nomenclature Assignment • Esters • Amides WWU-Chemistry

  4. Problem Assignment • In-Text: • 19-4 - 19-7, 19-9 - 19-27, 19-31 - 19-40 • End-of-Chapter: • 1 - 3 (parts) • 4 - 21 WWU-Chemistry

  5. The Acyl Group All carboxylic acid derivatives contain an acyl group. The substituent attached to the acyl group determines the class of carboxylic acid derivative. WWU-Chemistry

  6. The Esters Every ester consists of two components, the acyl part and the alkylpart. WWU-Chemistry

  7. Naming the Esters • Esters may be treated as if they were the product of the reaction of a carboxylic acid and an alcohol. • Thus their names derive from the names of the carboxylic acid and the alcohol. WWU-Chemistry

  8. Nomenclature of the Esters • IUPAC • Change carboxylic acid ending from “-oic acid” to “-oate” • Add name of alkyl group • Form: • Alkyl alkanoate • Common • Same as above: change “-ic acid” to “-ate” and add alkyl group name. WWU-Chemistry

  9. Ethyl pentanoate Ethyl valerate WWU-Chemistry

  10. Methyl 2-methylpropanoate Methyl a-methylpropionate Methyl isobutyrate WWU-Chemistry

  11. Isopropyl benzoate Isopropyl benzenecarboxylate WWU-Chemistry

  12. tert-Butyl phenylethanoate tert-Butyl phenylacetate WWU-Chemistry

  13. Methylcyclohexanecarboxylate WWU-Chemistry

  14. Nomeclature of the Amides • IUPAC • Change carboxylic acid ending from “-oic acid” to “-amide”. • Form: • Alkanamide • Common • Same as above: change “-ic acid” to “-amide”. WWU-Chemistry

  15. Butanamide Butyramide WWU-Chemistry

  16. 4-Methylbenzenecarboxamide 4-Methylbenzamide (acceptable IUPAC alternative name) WWU-Chemistry

  17. Cycloheptanecarboxamide WWU-Chemistry

  18. A well-known characteristic of the esters is that they are the substances responsible for the characteristic flavors and fragrances of fruits and flowers. On the next image, you will see a partial list of esters and their characteristic flavors and fragrances. WWU-Chemistry

  19. Esters as Flavoring Substances WWU-Chemistry

  20. Carboxylic Acid Derivatives WWU-Chemistry

  21. Functional Group Interconversions • The next image outlines interconversions that can be made among the carboxylic acid derivatives. • The purpose of the image is to illustrate that all of the carboxylic acid derivatives are inter-related and that all can, in principle, be converted into one another. • Note the central location of the acid chlorides. All conversions from carboxylic acids to derivatives are best conducted through the corresponding acid chloride. WWU-Chemistry

  22. Functional Group Interconversions H2O OH- R’OH H2O H2O SOCl2 R’OH OH- NH3 NR’2H NH3 NR’2H RCOOH H2O RCOOH NH3 NR’2H NH3 NR’2H WWU-Chemistry

  23. Nucleophilic Acyl Substitution • All of the interconversions among carboxylic acids and their derivatives take place following one general mechanism • This mechanism is nucleophilic acyl substitution. • For each case, the only significant differences lies in the nature of the leaving group and the nucleophile. WWU-Chemistry

  24. Nucleophilic Acyl Substitution WWU-Chemistry

  25. Energy Profile for Nucleophilic Acyl Substitution Intermediate Energy Reactants Products Reaction Coordinate WWU-Chemistry

  26. This intermediate can collapse either by loss of the Y group (leads to a forward reaction) of by the loss of the Nu group (leads to a reverse reaction). Either pathway can take place, as this is a reversible process. WWU-Chemistry

  27. Nucleophilic Substitution(Acid-catalyzed Mechanism) • When the nucleophile is relatively weak (e.g., water, alcohols), an acid-catalyzed mechanism is preferred. • The role of the acid is to protonate the acyl oxygen, thus increasing the positive charge character on the acyl carbon (through resonance). • This makes the acyl carbon a better site for nucleophilic attack. WWU-Chemistry

  28. Nucleophilic Acyl Substitution(Acid-Catalyzed) WWU-Chemistry

  29. This intermediate can collapse either by loss of the Y group (leads to a forward reaction) of by the loss of the Nu group (leads to a reverse reaction). Either pathway can take place, as this is a reversible process. WWU-Chemistry

  30. The nucleophile (Nu) can be any of the following: WWU-Chemistry

More Related