Carboxylic Acids

Objectives

  • Determine the physical and chemical properties of carboxylic acids, their derivatives, amines, and amides.

  • Learn the proper naming conventions for carboxylic acids and esters.

  • Familiarize with the structures of carboxylic acids and esters.

  • Identify key chemical reactions involving carboxylic acids and esters.

Carboxylic Acids

A. Structure and Derivatives

  • Definition: An organic compound with a carboxyl functional group (-COOH).

  • Carboxyl Group Structure: A carbonyl group (C=O) with a hydroxyl group (—OH) attached to the carbonyl carbon.

  • Simplest carboxylic acids contain a hydrogen atom attached to the carbon.

  • Cyclic carboxylic acids aren’t real

  • Organic compound can be synthesized or converted in a Carboxylic Acid

B. IUPAC Nomenclature and Common Names

Monocarboxylic Acids

  • Have one carboxyl group.

  • Naming Steps:

    1. Locate the carbon of the carboxyl as the parent chain.

    2. Select the longest chain including the carboxyl carbon.

    3. Change the “-e” to “-oic” acid for the parent chain name.

    4. Assign #1 to the carboxyl carbon for numbering.

    5. Note other substituents and number their location according to standard naming rules.

Dicarboxylic Acids

  • Have two carboxyl groups located at each end of the carbon chain.

  • Named by appending “-dioic acid” to the alkane name.

Aromatic Carboxylic Acids

  • Simplest example: Benzoic Acid.

  • Derivatives of benzoic acid are named based on substitutions on the aromatic ring.

  • The carboxyl group is always 1

Common names of Carboxylic Acids

  • Common names is more prevalent for carboxylic acids

  • Earliest classes of organic compounds studied are abundant

  • Derived from Latin or Greek words

C. Polyfunctional Carboxylic Acids

  • Definition: Contain additional functional groups alongside one or more carboxyl groups.

  • Types:

    • Unsaturated Acids: Mono: Acrylic acid (Propenoic acid). Di: Maleic acid, and Fumaric acid (Butenedioic acid)

    • Hydroxy Acids: -OH functional group: Glycolic acid (2-Hydroxyethanoic acid) and Lactic acid (2-Hydroxypropanoic acid)

    • Keto Acids: e.g., Pyruvic acid (2-oxopropanoic acid).

D. Acidity of Carboxylic Acids

  • Carboxylic acids are classified as weak acids.

  • Reaction in water produces hydrogen ions, resulting in hydronium and carboxylate ions.

Carboxylate Ion

  • Negative ion produced when a carboxylic acid loses one or more acidic hydrogen atoms.

    • Monocarboxylic acids always carry -1 charge

    • Dicarboxylic acids possess -2 charge

Physical Properties and Reactions

A. Carboxylic Acids

  • Physical Properties:

    • Straight-chain carboxylic acids with 1-9 carbon atoms are liquids with strong odors.

    • Longer chains (>10 C atoms) are waxy solids without strong odors.

    • Strong polar groups lead to high melting and boiling points due to H-bonding.

B. Carboxylic Acid Salts

  • Formed by reaction of carboxylic acids with strong bases.

  • Naming:

    1. Name the positive ion first.

    2. Use a separate word for the carboxylate ion resultant from the negative carboxylic portion.

  • Example: Formic Acid + Sodium Hydroxide ➔ Sodium Formate + Water

C. Naming –COOH salts

  • Write the chemical equation for the given carboxylic acid salt

  • Carboxylic acid salts are ionic compounds with the carboxylate ion as the negative part.

  • Salts can be converted back to carboxylic acids using a strong acid.

  • React the salt with a strong acid to convert a –COOH salt back to a carboxylic acid

Uses of Carboxylic Acid Salts

  • Enhance medication solubility.

  • Benzoate salts effective against yeast and mold in foods.

  • Sorbates inhibit microbial growth in perishable products.

  • Propionates used to preserve baked goods.