A7LAM CSCA ACADEMYCSCA Academy / Chemistry / Substances and their reactions
CSCA Chemistry · Lesson 9 of 21Alcohols, acids and esters
Alcools, acides et esters · الكحولات والأحماض والإسترات
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Replace a hydrogen in a hydrocarbon with a functional group and you get a new family with new properties.
Key ideas
- Alcohols (−OH): ethanol C₂H₅OH burns, reacts with Na to give H₂, and is oxidised to ethanal.
- Carboxylic acids (−COOH): acetic acid CH₃COOH is a weak acid and releases CO₂ from carbonates.
- Esterification: acid + alcohol ⇌ ester + water, with concentrated H₂SO₄ as catalyst.
- Esters smell fruity and hydrolyse back to an acid and an alcohol.
Formulas to know
- CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O
- 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂↑
- 2C₂H₅OH + O₂ → 2CH₃CHO + 2H₂O (Cu, heat)
Worked example
Find the molar mass of ethyl acetate, CH₃COOC₂H₅ (C = 12, H = 1, O = 16).
- Count: C₄H₈O₂ → 4 C, 8 H, 2 O
- Add: 4×12 + 8×1 + 2×16
- Total: 48 + 8 + 32 = 88 g/mol
Answer: 88 g/mol
Practice questions
1. Which releases CO₂ from sodium carbonate?
Ethanol · Acetic acid ✓ · Ethyl acetate · Ethane
Only the acid.
2. The functional group of an alcohol is:
−COOH · −OH ✓ · −CHO · −COO−
Hydroxyl.
3. Role of concentrated H₂SO₄ in esterification?
Reactant only · Catalyst and water absorber ✓ · Oxidising agent only · Solvent
It speeds it up and removes water.