ochem 2 Chapter 17 exam 3

Carboxylic Acid Derivatives

  • Characterized by the presence of a carbonyl group (C=O) and a leaving group.

  • Major Derivatives:

    1. Acyl (or acid) chloride: RCOCl

    2. Acid anhydride: (RCO)₂O

    3. Esters: RCOOR'

    4. Amides: RCONR'R"

    5. Nitriles: RCN

Carboxylic Nomenclature

  • Naming conventions for carboxylic acids include suffixes and descriptors:

    • Example: 4-Methylhexanoic acid

    • Example: (E)-3-Heptenoic acid or (E)-hept-3-enoic acid.

Carboxylate Salts

  • Formed from carboxylic acids and bases, typically sodium carbonate or NaOH.

  • Example: Benzoic Acid (water insoluble) vs. Sodium Benzoate (water soluble).

Inductive Effects From Alpha Carbon

  • Effect on acidity depends on substituents present on carbons associated with the carboxylic group:

    • Acidity series based on pKa values:

    • OH > OH > OH > OH

    • pKa = 0.70, 1.48, 2.86, 4.76 for various substituted versions.

Dicarboxylic Acids

  • Common structures and pKa values:

    • Oxalic acid: HO₂C—CO₂H, mp: 189 °C, pKa1: 1.2, pKa2: 4.2

    • Malonic acid: HO₂CCH₂CO₂H, mp: 136 °C, pKa1: 2.9, pKa2: 5.7

    • Succinic acid: HO₂C(CH₂)₂CO₂H, mp: 187 °C, pKa1: 4.2, pKa2: 5.6

    • Glutaric acid: HO₂C(CH₂)₃CO₂H, mp: 98 °C, pKa1: 4.3, pKa2: 5.4

    • Adipic acid: HO₂C(CH₂)₄CO₂H, mp: 153 °C, pKa1: 4.4, pKa2: 5.6

    • Maleic acid: cis-HO₂CCH=CH–CO₂H, mp: 131 °C, pKa1: 1.9, pKa2: 6.1

    • Fumaric acid: trans-HO₂C-CH=CH-CO₂H, mp: 287 °C, pKa1: 3.0, pKa2: 4.4
      …

Ester Nomenclature

  • Common esters include:

    • Ethyl acetate or ethyl ethanoate

    • tert-Butyl propanoate

    • Vinyl acetate or ethenyl ethanoate.

Sweet Smell of Esters

  • Ester compounds such as Isopentyl acetate (synthetic banana flavor) and Isopentyl pentanoate (synthetic apple flavor).

Carboxylic Acid Anhydrides

  • Examples of anhydrides:

    • Acetic anhydride (melting point -73 °C).

    • Succinic anhydride (mp 121 °C).

    • Phthalic anhydride (mp 131 °C).

    • Maleic anhydride (mp 53 °C).

Acyl Chlorides

  • Structures and properties:

    • Acetyl chloride (ethanoyl chloride), mp -112 °C; bp 51 °C.

    • Propanoyl chloride, mp -94 °C; bp 80 °C.

    • Benzoyl chloride, mp -1 °C; bp 197 °C.

Amides

  • Examples:

    • Acetamide (ethanamide), mp 82 °C; bp 221 °C.

    • N,N-Dimethylacetamide, mp -20 °C; bp 166 °C.

    • Benzamide, mp 130 °C; bp 290 °C.

Hydrogen Bonding in Amides

  • Orientation of hydrogen bonding between amide molecules and peptide chains, interaction critical to protein structure.

Nitriles

  • Nitriles include ethanenitrile (acetonitrile) and propenenitrile (acrylonitrile).

Carbonyl Group IR Absorbance

  • Approximate frequencies for functionalities (cm-1):

    • Acid chloride: 1840 - 1815.

    • Acid anhydride: 1820 - 1800.

    • Ester/lactone, carboxylic acid, aldehyde, ketone, amide/lactam…

Infrared Spectrum of Propanoic Acid

  • Characteristic peaks with relation to molecular vibrations: O-H stretches and other C-H and C-O bonds.

NMR Spectroscopy

  • 1H NMR of Methyl Propanoate shows specific chemical shifts.

  • 13C shifts commonly monitored for carbonyl/nitrile carbon detection.

Carboxylic Acids by Alkene Oxidation

  • Conditions include KMnO₄, HO⁻ and heat.

Carboxylic Acids by Alcohol/Aldehyde Oxidation

  • Reagents include Ag2O or Ag(NH₃)₂*HO⁻, followed by acidification.

Carboxylic Acids by Benzene Oxidation

  • Involves ozonolysis followed by hydrogen peroxide addition.

Saponification of Esters

  • Reaction with NaOH leading to the production of a sodium carboxylate and an alcohol.

Fischer Esterification Mechanism

  • Acid-catalyzed process involving alcohol and carboxylic acid to yield ester and water with mechanisms detailed.

Amides From Acid Chlorides

  • React with ammonia or amines.

Amides Hydrolysis

  • Hydrolysis mechanisms differ for acidic and basic environments, leading to overall consumption or generation of amine/nitrogen products.

General Summary of Reactions

  • Review dependencies and common outcomes for reactions involving carboxylic acids, esters, amides, and their derivatives in various settings.

  • Emphasize reagents, conditions, and reaction types.