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chemistry igcse acapprinted 110 · PDF 110
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Reaction: Alcohols, such as ethanol, can be oxidized by microbial action (e.g., acetic acid bacteria)
in the presence of oxygen.
Example: C₂H₅OH + O₂ → CH₃COOH + H₂O
Use: Commonly used in vinegar production.
Carboxylic Acids
General Properties
- Contain the -COOH functional group.
- React with metals, carbonates, and bases.
Reaction Example
- Ethanoic acid + Magnesium → Magnesium ethanoate + Hydrogen
- 2CH₃COOH + Mg → (CH₃COO)₂Mg + H₂
Reactions of Carboxylic Acids with Carbonates
Carboxylic acids react with metal carbonates to form salt, water, and carbon dioxide. This reaction
is used to test for carboxylic acids.
Carboxylic Acid + Metal Carbonate → Salt + Water + Carbon Dioxide
Example Reaction with Ethanoic Acid:
Ethanoic Acid + Sodium Carbonate → Sodium Ethanoate + Water + Carbon Dioxide
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂↑
Observation: Effervescence (bubbling) occurs due to the release of CO₂ gas, which can be
confirmed by bubbling it through limewater, causing it to turn cloudy.
Esters
1. Definition and Structure
Esters are organic compounds formed by the reaction of a carboxylic acid and an alcohol. They
typically have pleasant, fruity smells and are used in perfumes and food flavorings.
Functional Group: -COO-.
General Structure: R-COO-R', where "R" represents an alkyl group from the acid and "R'"
represents an alkyl group from the alcohol.
2. Formation of Esters (Esterification Reaction)
Esterification Reaction: The process of forming an ester is known as esterification. In this reaction,
a carboxylic acid reacts with an alcohol in the presence of a catalyst (typically concentrated sulfuric
acid).