Carboxylic acids
Introduced| English | Meaning |
|---|---|
| carboxylic acid/ˌkɑːbəkˈsɪlɪk ˈæsɪd/ | An organic compound containing the COOH functional group. |
| ethanoic acid/ˌeθəˈnəʊɪk ˈæsɪd/ | The two-carbon carboxylic acid CH3COOH, also called acetic acid. |
| weak acids/wiːk ˈæsɪdz/ | An acid that only partially ionises in aqueous solution. |
| esters/ˈestəz/ | An organic compound containing a carbonyl group bonded to an oxygen atom that is bonded to another carbon group. |
The sour family
- The sharp taste of vinegar comes from a carboxylic acid 羧酸.
- They are a homologous series with the –COOH functional group.
The functional group of carboxylic acids is:
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Carboxylic acids contain –COOH.
The carboxylic acid found in vinegar is:
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Ethanoic acid (CH₃COOH) is in vinegar.
The carboxylic acid functional group is written –______.
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It is the carboxyl group.
The carboxylic acid family
- Carboxylic acids contain the –COOH functional group.
- Example: ethanoic acid 乙酸 (CH₃COOH), the acid in vinegar.
Carboxylic acids share the –COOH (carboxyl) functional group, as in ethanoic acid
A weak acid's pH
Carboxylic acids are weak acids — they only partly ionise, so they sit just below pH 7. Slide the scale to see where they fall.
Carboxylic acids are described as weak acids because they:
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Weak means partly ionised, not dilute.
Match each carboxylic-acid fact.
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Carboxylic acids contain –COOH, are weak acids, and fizz with carbonates.
Weak acids 弱酸
- Carboxylic acids are weak acids: they only partly ionise in water.
- They still show typical acid reactions, just less vigorously than strong acids.
A carboxylic acid and an alcohol react to make an ester and water
A carboxylic acid reacts with an alcohol to form a sweet-smelling:
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Acid + alcohol → ester.
Reactions
- They react with metals (→ salt + hydrogen) and carbonates (→ salt + water + CO₂).
- They react with alcohols to form sweet-smelling esters 酯.
Carboxylic acids are weak acids. Unlike hydrochloric acid (strong, fully ionised), they only partly ionise — so they react more gently. "Weak" describes ionisation, not concentration.
You've got it
- carboxylic acids have the –COOH group (e.g. ethanoic acid in vinegar)
- they are weak acids (only partly ionise) but show typical acid reactions
- they react with metals, carbonates, and with alcohols to form esters
Write from a carbonate that fizzes
- Ethanoic acid is added to solid sodium carbonate.
- The acid has the group COOH.
What is observed, and which gas causes it?
Acids react with carbonates to release carbon dioxide.
What happens when ethanoic acid meets sodium carbonate?
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The carbonate test releases carbon dioxide.