1. Leaving Certificate Chemistry
Organic Chemistry
33 The Carboxylic Acids
Leaving Certificate Chemistry

2. The First 4 Carboxylic Acids Structural Formulae
Methanoic Acid: HCOOH O
group present ― ―
1 Carbon-Long
― C
― OH O H C OH

3. The First 4 Carboxylic Acids Structural Formulae
Ethanoic Acid: CH3COOH O ― ―
2 Carbons
Long
― C
― OH
group present H O H C C OH H

4. The First 4 Carboxylic Acids Structural Formulae
Propanoic Acid: C2H5COOH O ― ―
3 Carbons
Long
― C
― OH
group present H H O H C C C OH
Food Preservative (Inhibits the growth of bacteria and mold like E. Coli) H H

5. The First 4 Carboxylic Acids Structural Formulae
Butanoic Acid: C3H7COOH O ― ―
4 Carbons
Long
― C
― OH
group present H H H O H C C C OH C H H H

6. O OH
Benzoic Acid C

7. Physical Properties of the carboxylic acids
Use electronegativity differences to predict what kinds of bonds are present in an carboxylic acid such as ethanoic acids
Can you predict whether a carboxylic acid or its corresponding alkane /aldehyde / alcohol would have a higher boiling point?
Can you explain why the boiling points of the carboxylic acids increase with the length of the chain?
Would the lower or higher members of the carboxylic acids be more soluble in water? HINT – water is polar.

8. Formation of a carboxylic acid
Oxidation of a primary alcohol

9. Oxidation of a primary alcohol
Methanol CH3OH O H H
Acidified Sodium Dichromate H C H H C OH
Methanal HCHO H H O H C OH
Excess
Methanoic Acid HCOOH

10. Oxidation of a primary alcohol
Ethanol C2H5OH H
Acidified Sodium Dichromate H H H C C OH H H H H O H O H C C H
Excess H C C OH
Ethanoic Acid CH3COOH
Ethanal CH3CHO H H

11. Oxidation of a primary alcohol
Acidified Sodium Dichromate H H H
Propanoic Acid C2H5COOH
Propanol C3H7OH
Propanal C2H5CHO
Excess

12. Oxidation of a primary alcohol
Butanol
Butanal
Butanoic Acid
On reaction with acidified sodium dichromate
In Excess

13. The Alkanes - H2 The Chloroalkanes + H2 The Alkenes + HCl , + Cl2
Substitution
using UV Light
Ethane C2H6
- H2
The Chloroalkanes
+ H2
Chloroethane C2H5Cl
The Alkenes
+ HCl , + Cl2
Ethene C2H4
+ H2O
The Alcohols
Ethanol C2H5OH
- H2O
Aluminium Oxide Catalyst
The Polymers
Polythene & Polypropene

14. The Alcohols The Aldehydes The Carboxylic Acids Ethanol C2H5OH
Acidified sodium dichromate
Hydrogen,
Nickel catalyst
Oxidation
Reduction
The Aldehydes
Ethanal CH3CHO
Acidified sodium dichromate
Reduction
Hydrogen,
Nickel catalyst
Oxidation
The Carboxylic Acids
Ethanoic Acid CH3COOH

15. Reactions of Ethanoic Acid
Mandatory Experiment
Reactions of Ethanoic Acid

16. Tests on ethanoic acid
Colourless Liquid
Pungent odour

17. Reaction of an acid with a carbonate

18. Tests on ethanoic acid 2 2 2 Reaction with sodium carbonate CH3COOH +
Na2CO3
2007: Q2 (f) (9)
Ethanoic Acid
Sodium Carbonate
2009: Q8 (d) (9) 2 2
CH3COONa +
H2O
H2O +
CO2
CH3COONa + +
Effervesence (fizzing) of carbon dioxide observed
Sodium Ethanoate
Water
Carbon Dioxide
Sodium Ethanoate
Water

19. Reaction of an acid with magnesium

20. Tests on ethanoic acid 2 Reaction with magnesium CH3COOH + Mg
Magnesium metal
(CH3COO)2Mg + H2
Effervesence (fizzing)

21. Reaction of an acid and an alcohol
(formation of an ester)

22. Esterification Ethyl Ethanoate CH3COOC2H5 CH3COOH CH3COOC2H5 H2O
Ethanoic Acid
CH3COOH H C C O H H
Ethyl Ethanoate
CH3COOC2H5
Ethyl Group H H H
CH3COOH
CH3COOC2H5 O C C H
Ethanol
C2H5OH
H2SO4
H2O
C2H5OH H H

23. Mandatory experiment
Preparation of Benzoic acud

24. Mandatory experiment
Recrystallization of Benzoic acid