The complete lecture — the chemistry comes alive in the live panel as you read. Scroll down; the animation keeps pace, and you can make an ester yourself.
1 — The –COOH group & the carboxylate ion
- Carboxyl group — –COOH, a C=O and an –OH on the same carbon, e.g. CH₃COOH (acetic acid, vinegar).
two equivalent resonance forms of RCOO⁻R–C(=O)–O⁻ ⇌ R–C(–O⁻)=O
2 — Preparation
routes to RCOOHR–CH₂OH →[O]→ R–CHO →[O]→ R–COOH
R–C≡N + H₂O → R–COOH · R–MgX + CO₂ → R–COOH
3 — Acidity & substituent effects
- Acidity — RCOOH ⇌ RCOO⁻ + H⁺. The resonance-stabilised carboxylate drives ionisation.
| Group | Acidity |
|---|
| –Cl, –NO₂ (withdrawing) | increase |
| –CH₃ (donating) | decrease |
4 — Salt formation
acid–base reactionsRCOOH + NaOH → RCOONa + H₂O
2RCOOH + Na₂CO₃ → 2RCOONa + H₂O + CO₂↑
5 — Esterification (the key reaction)
conc. H₂SO₄ catalyst & dehydrating agentR–COOH + R′OH ⇌ R–COOR′ + H₂O
The –OH of the acid and the –H of the alcohol leave together as water. Conc. H₂SO₄ removes that water, shifting the equilibrium toward more ester. Esters smell fruity — banana, pineapple, pear. Move the slider to drive off water and watch the yield.
6 — Reduction & decarboxylation
two more reactionsR–COOH →[LiAlH₄]→ R–CH₂OH (1° alcohol)
R–COONa + NaOH →[CaO,Δ]→ R–H + Na₂CO₃
7 — Derivatives & relative reactivity
- Acid derivatives — replace –OH of RCOOH with –Cl (acyl chloride), –OCOR (anhydride), –OR′ (ester) or –NH₂ (amide).
most reactive → least reactiveacyl chloride > anhydride > ester > amide
8 — Esters & saponification
base hydrolysis of a fatfat (ester) + NaOH → soap (RCOONa) + glycerol
Acyl chlorides are the most reactive acylating agents; amides are the least reactive. Aspirin is an ester.
9 — Exam recap
- The –COOH group; –oic acid names; resonance-stabilised RCOO⁻.
- Preparation: oxidation, nitrile/ester hydrolysis, Grignard + CO₂.
- Acidity: –Cl/–NO₂ up, –CH₃ down; acid > phenol > alcohol.
- Salts (CO₂ fizz); esterification; reduction; decarboxylation.
- Derivatives & reactivity: acyl chloride > anhydride > ester > amide; saponification → soap.