Carboxylic acids
| English | Chinese | Pinyin |
|---|---|---|
| carboxylic acid | 羧酸 | suō suān |
| carboxyl | 羧基 | suō jī |
| weak acid | 弱酸 | ruò suān |
| hydrolysis | 水解 | shuǐ jiě |
| nitrile | 腈 | jīng |
| esterification | 酯化 | zhǐ huà |
The sour organic acids
- A carboxylic acid 羧酸 has the –COOH (carboxyl 羧基) group.
- It is a weak acid 弱酸.
- It shows all the typical acid reactions.
Carboxylic acid reaction map
Follow carboxylic acids through neutralisation, esterification and reduction.
The functional group of a carboxylic acid is:
Carboxylic acids contain the –COOH group and behave as weak acids.
Carboxylic acids are weak acids that react with carbonates to give carbon dioxide.
A test for the –COOH group.
Making carboxylic acids
- oxidation of a primary alcohol or an aldehyde (acidified $\text{K}_2\text{Cr}_2\text{O}_7$, with reflux for full oxidation).
- hydrolysis 水解 of a nitrile 腈 (then acidify).
- hydrolysis of an ester (then acidify).
Carboxylic acids react as acids with metals, alkalis and carbonates
A carboxylic acid is made by oxidising a primary alcohol or aldehyde, using:
Reflux ensures full oxidation all the way to the carboxylic acid (distillation would stop at the aldehyde).
Match each carboxylic-acid fact.
Each item links the term to its correct meaning.
Acid reactions
- with a reactive metal → salt + hydrogen.
- with an alkali (neutralisation) → salt + water.
- with a carbonate → salt + water + carbon dioxide (the fizz is a test for a carboxylic acid).
Two reactions change the group: esterification 酯化 with an alcohol → an ester; reduction by $\text{LiAlH}_4$ → a primary alcohol.
Vinegar is a dilute solution of ethanoic acid, a carboxylic acid.
A carboxylic acid added to a carbonate gives a salt, water and:
Like other acids, it releases CO₂ from a carbonate — the fizz is a useful test.
Testing for a carboxylic acid
- Carboxylic acids fizz with carbonates, releasing CO₂ — a reliable test for –COOH.
- They are weak acids, only partly ionised in water.
Acid and alkaline hydrolysis of an ester give different products
A carboxylic acid reacting with an alcohol (conc. H₂SO₄ catalyst) makes:
Esterification joins the acid and alcohol into an ester (losing water).
You've got it
- carboxylic acid = –COOH, a weak acid
- made by oxidising a primary alcohol/aldehyde (reflux), or hydrolysing a nitrile/ester
- acid reactions: metal (+ H₂), alkali (+ water), carbonate (+ water + CO₂ — the fizz test)
- esterification → ester; reduction → primary alcohol