Summary CIE AS Chemistry Note Unit 19 - Carboxylic acids and derivatives

Alevel Chemistry Revision OC 19
Revision Material
Duration: 9th – 14th March

Topic 19 Carboxylic acids
This topic introduces the chemistry of the carboxylic acids and their derivatives



Learning outcomes
Candidates should be able to:
19.1 Carboxylic acids (a) describe the formation of carboxylic acids from alcohols, aldehydes and nitriles
(b) describe the reactions of carboxylic acids in the formation of:
(i) salts, by the use of reactive metals, alkalis or carbonates
(ii) alkyl esters
(iii) alcohols, by the use of LiAlH4




19.2 Esters (a) describe the acid and base hydrolysis of esters
(b) state the major commercial uses of esters, e.g. solvents, perfumes, flavourings

, 19.1 Carboxylic acids
(a) Introduction
1. Structure
Carboxylic acid ester Carboxylic acid ester
CnH2nO2 CnH2nO2 CH3CH2CH2COOH HCO2CH2CH2CH3
Butanoic acid
CH3CHCOOH
CH3
2-methylpropanoic acid
(–COOH ) alkyl




2. Physical properties
Carboxylic acid ester
- pungent smelling (vinegar) - sweet smelling
- soluble in water (C≤4) - insoluble in water
The b.p. of carboxylic acid is higher than the b.p. of an ester
Because there are hydrogen bonds formed between ‘–COOH’
group and this makes the intermolecular forces stronger


Summary to the solubility of organic compounds
C×3 –OH
–CHO
R
–COOH
Water-hating group water-loving group
(alkyl group) (forming hydrogen bonds with H2O molecules )
Van Der Waals’ Forces


(b) Carboxylic acid
1. Manufacture of carboxylic acid


Method I: Bio-method (fermentation)
CH3CH2OH → ([O], yeast) CH3COOH


Method II: oxidation of primary alcohol
R–CH2OH + 2[O] → R–COOH + H2O
- acidified K2Cr2O7(aq) reflux
- acidified KMnO4(aq) reflux


Method III: oxidation of aldehydes
RCHO + [O] → RCOOH
- acidified K2Cr2O7(aq) reflux orange solution turns green
- acidified KMnO4(aq) reflux purple solution turn colorless.
- Tollen’s reagent, warm silver mirror
- Fehling solution warm brick red ppt (Cu2O)