Overview
This lecture covers the structures and reactions of the first four carboxylic acids, focusing on their behavior in water, reactions with metal carbonates, and ester formation with alcohols.
Structures of Carboxylic Acids
- The first four carboxylic acids share the same functional group: –COOH (carboxyl group).
- Carboxylic acids are a homologous series, meaning they have the same functional group and similar chemical properties.
- Both displayed and structural formulas are used to represent carboxylic acids in exams.
Carboxylic Acids in Water
- Carboxylic acids are weak acids because they only partially ionize in water.
- Example: Ethanoic acid ionizes reversibly to form the ethanoate ion and H+.
- Weak acids like carboxylic acids have a higher pH than strong acids (e.g., hydrochloric acid).
Reactions with Metal Carbonates
- Carboxylic acids react with metal carbonates to produce a salt, carbon dioxide, and water.
- Example: Ethanoic acid + sodium carbonate → sodium ethanoate + carbon dioxide + water.
- All carboxylic acids react similarly with metal carbonates.
Reaction with Alcohols (Ester Formation)
- Carboxylic acids react with alcohols to form esters and water.
- Example: Ethanoic acid + ethanol → ethyl ethanoate (an ester) + water.
- This reaction requires sulfuric acid as a catalyst.
- Ester formation is a reversible reaction.
Key Terms & Definitions
- Carboxylic acid — organic compound containing the –COOH functional group.
- Homologous series — a group of compounds with the same functional group and similar properties.
- Weak acid — an acid that only partially ionizes in water.
- Ester — compound formed from the reaction of a carboxylic acid with an alcohol.
- Catalyst — a substance that increases the rate of a chemical reaction without being consumed.
Action Items / Next Steps
- Learn the displayed and structural formulas for the first four carboxylic acids.
- Practice identifying carboxylic acids from different formula representations.
- Review workbook questions on carboxylic acids as assigned.