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Acid Derivatives

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Acid Derivatives

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    1. Acid Derivatives

    2. Acid Derivatives All of them undergo nucleophilic reactions: Nucleophilic addition followed by elimination. Mechanism:

    3. Acid Derivatives Reactivity depends on: 1. Structure of acid derivatives Inductive effect of G exert on the carbonyl carbon The more negative the inductive effect, the more reactive the compound. However, the effect is small since difference of electronegativity between Cl, N and O is small.

    4. Acid Derivatives b. Mesomeric effect of G exert on the carbonyl carbon From the orbital approach, resonance energy is higher in acid amide, ester and acid anhydride due to the better interaction of the 2p orbitals of N and O with 2p orbital of C.

    5. While in acid chloride, resonance energy is least as 3p-2p interaction is weaker. Also, if the overlapping is more effective, the carbonyl carbon will be less positive, i.e. less reactive. Acid Derivatives

    6. Acid Derivatives Reactivity depends on: 2. Leaving group ability of G Less basic the anion, the better it acts as a leaving group. Basic strength: NH2- > OR- > OH- > RCOO- > Cl- Leaving ability: Cl- > RCOO- > OH- > OR- > NH2-

    7. Acid Derivatives From the 2 factors above (Structure of acid derivatives and Leaving group ability of G), the reactivity of the acid derivatives towards nucleophile decrease in the order: Acid chloride > Acid anhydride > Ester > Acid amide

    8. Acid Derivatives – Acid Chloride 1. Preparation

    9. Acid Derivatives – Acid Chloride 2. Physical properties Lower members are colourless liquid. It has a pungent and irritating smell.

    10. Acid Derivatives – Acid Chloride 3. Chemical properties Nucleophilic reaction occurs easily because Carbonyl carbon is more positive since it attaches to 2 electronegative atoms (O & Cl). The lateral overlapping of Cl with carbonyl carbon is the least among the acid derivatives. Cl- is a weak base and thus a good leaving group.

    11. Acid Derivatives – Acid Chloride 3. Chemical properties

    12. Acid Derivatives – Acid Chloride 3. Chemical properties – Reduction a. With LiAlH4

    13. Acid Derivatives – Acid Chloride 3. Chemical properties – Reduction b. To aldehyde

    14. Acid Derivatives – Acid Anhydride

    15. Acid Derivatives – Acid Anhydride 1. Preparation a. Dehydration of acid (for simple anhydride only)

    16. Acid Derivatives – Acid Anhydride 1. Preparation b. From acid chloride

    17. Acid Derivatives – Acid Anhydride 2. Physical properties a. Lower members are colourless liquid. b. It is slightly soluble in water. c. It has a pungent odour.

    18. Acid Derivatives – Acid Anhydride 3. Chemical properties Also undergo nucleophilic addition followed by eliminated. Carboxylate anion is a good leaving group and reaction of anhydride parallel those of the acid chloride. However, the lateral overlap of O with carbonyl carbon is more effective, and that the large carboxylate group increase steric crowding in forming the intermediate, so the anhydride are generally less reactive than acid chloride.

    19. Acid Derivatives – Acid Anhydride 3. Chemical properties a. Hydrolysis

    20. Acid Derivatives – Acid Anhydride 3. Chemical properties b. Ammonolysis

    21. Acid Derivatives – Acid Anhydride 3. Chemical properties c. Alcoholysis

    22. Acid Derivatives – Ester

    23. Acid Derivatives – Ester 1. Preparation a. Esterification

    24. Acid Derivatives – Ester 1. Preparation b. Acylation of alcohol / phenol

    25. Acid Derivatives – Ester 1. Preparation c. From alkyl iodide

    26. Acid Derivatives – Ester 2. Physical properties a. It is oily liquid solid. b. It has a fragrant fruity smell. c. It is insoluble in water.

    27. Acid Derivatives – Ester 3. Chemical properties a. Hydrolysis

    28. Acid Derivatives – Ester 3. Chemical properties

    29. Acid Derivatives – Ester 3. Chemical properties b. Ammonolysis

    30. Acid Derivatives – Ester 3. Chemical properties c. Alcoholysis / trans-esterification

    31. Acid Derivatives – Ester 3. Chemical properties d. Reduction

    32. Acid Derivatives – Acid Amide

    33. Acid Derivatives – Acid Amide 1. Preparation a. Ammonolysis

    34. Acid Derivatives – Acid Amide 1. Preparation b. From acid

    35. Acid Derivatives – Acid Amide 1. Preparation c. From acid nitrile

    36. Acid Derivatives – Acid Amide 2. Physical properties a. All 1o and 2o acid amides except methanamide are colourless solides because of the strong intermolecular H-bond. They have high m.p. and b.p. But 3o amides have normal m.p. and b.p.. (Why?) b. Lower members are soluble in water due to the formation of extensive H-bond with water.

    37. Acid Derivatives – Acid Amide 3. Chemical properties a. Hydrolysis

    38. Acid Derivatives – Acid Amide 3. Chemical properties b. Dehydration

    39. Acid Derivatives – Acid Amide 3. Chemical properties c. Reduction

    40. Acid Derivatives – Acid Amide 3. Chemical properties d. Hofmann Degradation (Reduce one carbon atom)

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