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CHAPTER 7 CARBOXYLIC ACIDS AND THEIR DERIVATIVES

7.1. Structure. . 7.2. Nomenclature. Carboxylic Acids: Read 20-2, pg 935Esters: Read

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CHAPTER 7 CARBOXYLIC ACIDS AND THEIR DERIVATIVES

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    1. CHAPTER 7 CARBOXYLIC ACIDS AND THEIR DERIVATIVES Objectives: Determine the names using structures and structures using names, and Describe and explain the properties Describe, explain and predict the preparation methods and the reactions of carboxylic acids and their derivatives.

    2. 7.1. Structure

    3. 7.2. Nomenclature Carboxylic Acids: Read 20-2, pg 935 Esters: Read # 21-2A, pg 979 Amides: Read # 21-2B, pg 980 Acid Halides: Read # 21-2D, pg 982 Acid anhydrides: Read # 21-2E, pg 983 Spectroscopy: read # 21-4, pg 988

    4. 7.3. Properties a. Physical Properties * Carboxylic Acids: Read # 20-3, pg 939 Derivatives: Read 21-3, pg 985 b. Spectroscopy * Carboxylic Acids: Read #20-7, pg 949 * Derivatives: Read #21-4, pg 988

    5. c. Acidity. General Reaction: RCO2H + :B -> acid base -> RCO2(-) + BH(+) carboxylate anion conjugate acid

    6. Acidity (Examples)

    7. Acidity Measurement Acids Ionize in water RCO2H + H2O --------> RCO2(-) + H3O(+) Measure of acid strength = Ka = [RCO2-][H3O+] / [RCO2H] = dissociation constant of an acid. Ka values are usually small and hard to measure Remedy = pKa = -logKa Examples : acid Ka pKa acetic 1.8E-5 4.7 (3) oxalic 6.23E-2 1.2 (1) Benzoic 6.5E-5 4.2 (2)

    8. Substituent Effects on Acidity Acidity of R-CO2H depends on the properties of substituent R. Reference: H-CO2H General Rules Electron donating substituents decrease the acidity Electron withdrawing substituents increase the acidity

    9. Substituent Effects on Acidity (Examples)

    10. Substituent Effects on Acidity (Exercises) Answer questions 20-3 a-c(*), pg 944

    11. 6.4. Preparation a. Carboxylic Acids *1. Oxidation of primary Alcohols Substrate: R-CH2-OH. Reaction site: C carrying the OH group. Reagent: Oxidizing reagent. Most used: * compounds of Mn(VII). Example: KMnO4 * compounds of Cr(VI). Active ingredient: H2CrO4. Forms: - Na2Cr2O7 in sulfuric acid (Jones Reagent) - Na2Cr2O7 in acetic acid Reaction: oxidation of the reaction site

    12. Oxidation of primary Alcohols (Examples)

    13. Oxidation of primary Alcohols (Exercises) Answer Questions 20-35e & g, pg 972

    14. *2. Carboxylation of Grignard Reagents Substrate: CO2. Reaction site: C. Reactive property: electrophilic. Reagents: * R(-)(+)MgX (Grignard reagent) R(-) is a nucleophile. Binds to C of CO2. Result: a carboxylate anion * Acid: source of H(+). Provides the H to O of the carboxylate. Reaction: Nucleophilic addition Product: carboxylic acid

    15. Carboxylation of Grignard Reagents (Illustration)

    16. Carboxylation of Grignard Reagents (Exercises) Answer Questions 20-35 i, pg 972 20-39 d, pg 973

    17. *3. Oxidation of Alkenes and Alkynes Substrate: Alkene / Alkyne. Rxn site: C=C or C?C bond Reagent: KMnO4, Oxidizing agent, source of O atoms Products: * Carboxylic acids for the side of the C=C bond carrying a H * Ketones for the side of the C=C bond without a H

    18. *3. Oxidation of Alkenes / Alkynes (Illustration)

    19. Oxidation of Alkenes / Alkynes (Exercises) Answer Questions 20-35 D & G, pg 972

    20. *4. Ozonolysis of alkynes Substrates: Alkynes. Rxn site: C-C triple bond. Reagents: * Ozone. Binds the Os to the C?C bond. * Water. Provides the necessary Hs to form the expected carboxylic Acids.

    21. Ozonolysis of Alkynes ( Illustration)

    22. *5. Oxidation of Side-chains of Aromatic Compounds Substrates: Alkylated aromatic compounds Reagents: Oxidizing agents. Most common: Mn(VII) as in KMnO4 and Cr(VI) as in H2CrO4. Reaction: oxidation of the C next to the aromatic ring to a CO2H group.

    23. Oxidation of Side-chains of Aromatic Compounds (Illustration)

    24. Preparation of Carboxylic acids (Exercises) Answer the following questions: 20-11 a-c, pg 955

    25. *6. Formation and Hydrolysis of Nitriles Substrates: alkyl halides. Reaction site: C that carries the halogen. Reactive property: electrophilic. Reagents: * compounds of cyanide (C?N(-)) ion: nucleophile. C?N(-) replaces the halogen on the electrophilic site. Result: fomration of a nitrile * Acidic or basic H2O. Brings O and OH to the C of the C?N group. Result: carboxilic acid.

    26. Formation and Hydrolysis of Nitriles (Illustration)

    27. Formation and Hydrolysis of Nitriles (Exercises) Answer Questions: 20-35 a & b, pg 972

    28. b. Preparation of Esters (R-CO-OR) *1. Fischer esterification Substrates: R-CO2Hs. Reaction site: C of C=O group. Reactive property: electrophile Reagents: R-OHs. Nucleophile: O. The O binds to the C of the C=O group and replaces the OH group. Reaction conditions: presence of an acid> The H(+) of the acid help: (1) in making the electrophile available; (2) removing the OH of the R-CO2H. Reaction: nucleophilic substitution of OH by OR on the CO2 group.

    29. Fischer Esterification (General Pathway)

    30. Fischer Esterification (Examples)

    31. Fischer Esterification (Exercises) Answer questions * 20-35 j, pg 972 * 21-48 c, pg 1033

    32. c. Preparation of Acid Halides (R-CO-X) Substrates: R-CO2H. Rxn site: C of C=O. Reactive property: electrophile Reagents: sources of halogens (X). Most common: SOCl2, COCl2 Reaction : Nucleophilic substitution of OH of R-CO2H by X.

    33. Preparation of Acid Halides (General Pathway)

    34. 7.5. Reactions a. Carboxylic Acids Types of reactions: * Reactions with bases. Result Carboxylic acid salts * Reactions with nucleophiles. Electrophile: C of C=O group * Reactions with electrophiles. Nucleophile: O of OH group. *1. Reactions with bases Read 20-5, pg 944

    35. *2. Reduction of Carboxylic acids to primary alcohols Substrate: R-CO-OH Site: C of C=O Reagents: * Source of H(-) (the nucleophile). Most common sources: BH3 (best), LiAlH4. BH3 reacts with C=O group of CO2H preferentially to C=O of Aldehydes / Ketones. H(-) binds to C of C=O group. Result: Aldehyde which react with one more H(-). Ultimate result: alkoxide * Acidic water solution: source of H(+). H(+)s binds to the alkoxide. Result: primary alcohol

    36. Reduction of Carboxylic acids to primary alcohols (General Pathway)

    37. Reduction of Carboxylic acids to primary alcohols (Examples)

    38. Reduction of Carboxylic acids to primary alcohols (Exercises) Answer questions 20-19 a and c, pg 965.

    39. *3. Conversion of Carboxylic Acids to tertiary alcohols Substrate: R-CO-OH Site: C of C=O Reagents: * Sources of C nucleophiles. Most common: Alkyl lithium (R(-)(+)Li) and Grignard reagents (R(-)(+)MgX). Nucleophiles bind to C of C=O group. Ultimate result: Tertiary alkoxides. * Acidic water. Source of H(+). H(+) binds to tertiary alkoxide. Products: Tertiary alcohols

    40. Conversion to tertiary alcohols (General Pathway)

    41. Conversion to tertiary alcohols (Example)

    42. Conversion of Carboxylic Acids to Ketones Substrate: R-CO-OH Site: C of C=O Reagents: Sources of C nucleophiles. Most common: Alkyl lithium (R(-)(+)Li) and Grignard reagents (R(-)(+)MgX). Nucleophiles bind to C of C=O group. Reaction Condition: Use no more that 2 equivalents of reagent. Products: ketones

    43. Conversion to Ketones (General Pathway)

    44. Conversion to Ketones (Example)

    45. b. Reactions of Carboxylic Acid Derivatives *1. Nucleophilic Substitutions Substrates: R-CO-X. X = halogen, OR, NR2, O-CO-R. Most reactive: acid halides. Reaction site: C of C=O. Reactive property: electrophile. Reagents: any nucleophile. Nucleophile replaces the X on the C=O group. Products: R-CO-Nu. The high reactivity of R-CO-X (as a halide)and the wide variety of nucleophiles lead to a wide variety of products

    46. Nucleophilic Substitutions of Acid Halides (General Pathway)

    47. Nucleophilic Substitutions of Acid Halides (Examples)

    48. Nucleophilic Substitutions of Other Carboxylic Acid Derivatives Other carboxylic acid derivatives react similarly but less readily compared to acid halides

    49. Nucleophilic Substitutions of Carboxylic Acid Derivatives (Exercises) Answer to Questions * 21-48 a & b, pg 1033 * 21-50 a, b, d, g, pg 1035

    50. *2. Nucleophilic Addition Reactions of Carboxylic Acid Derivatives Substrates: R-CO-X Reagents: sources of H(-) or C(-) nucleophiles Reactions: Addition of H(-) or C(-)to C of C=O group. Products: aldehydes/ketones or alcohols

    51. *2a. Reduction of carboxylic Acid Derivatives to primary alcohols Substrates: R-CO-X Reaction site: C of C=O Reagents: * Source of H(-) (the nucleophile). Most common sources: LiAlH4 (LAH) . The H(-) binds C of C=O group. Ultimate result: primary alkoxides. * Acidic water. Source of H(+) which binds to the alkoxides. Products: primary alcohols. Note: Mild reagents: used to form adehydes. Example: LiAlH(t-butoxide)3 (LTTBAH)

    52. Reduction to primary alcohols (General Pathway)

    53. Reduction to primary alcohols (Examples)

    54. Reduction to primary alcohols (Exercises) Answer question 21-50 e & f, pg 1034

    55. *2b. Conversion of Carboxylic Acid Derivatives to Tertiary Alcohols Substrates: R-CO-X. Reaction site: C of C=O group. Reactive property: electrophile. Reagents: * Sources of C nucleophiles (R(-)). Most common: Alkyl Lithium (R(-)(+)Li) and Grignard Reagents (R(-)(+)MgX). R(-) binds to C of C=O group. Ultimate result: Alkoxides. * Acidic water. Source of H(+). H(+) binds to the O(-) of the alkoxides. Products: tertiary alcohols. Note: using mild reagents can lead to formation of ketones. Examples: Dialkyl Li Cuprates (R2CuLi)

    56. Acid Derivatives to Tertiary Alcohols (General Pathway)

    57. Acid Derivatives to Tertiary Alcohols (Examples)

    58. Acid Derivatives to Tertiary Alcohols (Exercises) Answer Questions: * 21-54 d, pg 1034 * 21-55, pg 1035

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