Carboxylic acids

Page 2: Carboxylic Acids

Definition

  • A carboxylic acid contains a carboxyl group, which consists of a hydroxyl group (-OH) attached to a carbonyl group (C=O).

Learning Goal

  • Write the IUPAC and common names for carboxylic acids.

  • Draw their condensed structural and line-angle formulas.

Page 3: IUPAC Names for Carboxylic Acids

Naming Convention

  • In IUPAC names of carboxylic acids:

    • The suffix -e in the alkane name is replaced with -oic acid.

    • Examples:

      • Methane → Methanoic acid

      • Ethane → Ethanoic acid

Page 4: Numbering Substituents

Rules for Substituents

  • Substituents are numbered starting from the carboxyl group, which is considered carbon 1.

Page 5: Placement of Substituents

Naming in Aromatic Carboxylic Acids

  • For compounds like benzoic acid, the positions of substituents are denoted using the prefixes:

    • ortho (o-): 1,2- positions

    • meta (m-): 1,3- positions

    • para (p-): 1,4- positions

Page 6: Common Names for Carboxylic Acids

Usage of Common Names

  • Many carboxylic acids retain their common names that use prefixes:

    • form: for 1 carbon

    • acet: for 2 carbons

    • propion: for 3 carbons

    • butyr: for 4 carbons

  • Greek letters are assigned to carbons adjacent to the carboxyl carbon when using common names.

Page 7: Examples of Common Carboxylic Acids

Notable Examples

  • Methanoic acid (formic acid):

    • Found in red ant stings, irritates the skin.

  • Ethanoic acid (acetic acid):

    • Responsible for the sour taste of vinegar.

Page 8: Naming Carboxylic Acids

Problem Analysis

  • Task: Give the IUPAC and common name for a specific carboxylic acid.

  • Given: A three-carbon chain with a methyl group.

  • Need: Identify location of methyl group, change alkane name to end in -oic acid.

Page 9: Steps in Naming

Step 1

  • Identify the longest carbon chain and replace the -e in the alkane name with -oic acid.

  • For three carbons:

    • IUPAC name: Propanoic acid

    • Common name: Propionic acid

Page 10: Continuation of Naming

Step 2

  • Name and number any substituents, counting the carboxyl group as carbon 1.

  • Results:

    • IUPAC name: 2-methylpropanoic acid

    • Common name: 2-methylpropionic acid

Page 11: Learning Check 1

Task Description

  • Assign the IUPAC name for each of two given compounds:

    • A.

    • B.

Page 12: Solution 1

Assigning IUPAC Names

  • A: 3-methylbutanoic acid

  • B: 3-bromobenzoic acid

Page 13: Learning Check 2

Task Description

  • Draw the line-angle formula for:

    • 4-chlorohexanoic acid

Page 14: Solution 2

Line-Angle Formula

  • Line-angle formula drawn for:

    • 4-chlorohexanoic acid

Page 15: Preparation of Carboxylic Acids

Methods of Preparation

  • Carboxylic acids can be synthesized from:

    • Primary alcohols

    • Aldehydes

  • Produced through oxidation steps:

    • Primary alcohols to aldehydes, then to carboxylic acids.

    • Example: Ethanol in wine oxidized to acetaldehyde and then to acetic acid (vinegar).

Page 16: Chemistry Link to Health: Alpha Hydroxy Acids

Alpha Hydroxy Acids (AHAs)

  • Found in fruits, milk, and sugar cane.

  • Naturally occurring carboxylic acids with a hydroxyl group adjacent to the carboxyl group.

  • Used by dermatologists to remove acne scars and improve skin texture (20-70% concentrations).

Page 17: Various AHAs in Skincare

Common Alpha Hydroxy Acids

  • Glycolic acid (from sugar cane)

    • Condensed Structural Formula: H-O-C-H2-C=O

  • Lactic acid (from sour milk)

    • Condensed Structural Formula: C-H3-C(OH)-C=O

  • Tartaric acid (from grapes)

    • Structural features include hydroxyls and carbon bonds.

  • Malic acid (from apples)

    • Characterized by hydroxyl and carbonyl groups.

  • Citric acid (from citrus fruits)

    • Contains multiple carboxyl groups in its structure.