Organic Chemistry
33
The Carboxylic Acids
Leaving Certificate Chemistry
The First 4 Carboxylic Acids
Structural Formulae
Methanoic Acid: HCOOH
O
―
―
1 CarbonLong
group present
― C ― OH
O
H
C
OH
The First 4 Carboxylic Acids
Structural Formulae
Ethanoic Acid: CH3COOH
O
H
―
―
2 Carbons
Long
― C ― OH
group present
H
O
C
C
H
OH
The First 4 Carboxylic Acids
Structural Formulae
Propanoic Acid: C2H5COOH
O
H
―
―
3 Carbons
Long
― C ― OH
group present
H
H
O
C
C
C
H
H
OH
Food Preservative
(Inhibits the growth
of bacteria and
mold like E. Coli)
The First 4 Carboxylic Acids
Structural Formulae
Butanoic Acid: C3H7COOH
O
H
―
―
4 Carbons
Long
― C ― OH
group present
H
H
H
O
C
C
C
C
H
H
H
OH
O
OH
C
Benzoic Acid
Physical Properties of the carboxylic acids
1. Use electronegativity differences to predict what kinds of
bonds are present in an carboxylic acid such as ethanoic
acids
2. Can you predict whether a carboxylic acid or its corresponding
alkane /aldehyde / alcohol would have a higher boiling point?
3. Can you explain why the boiling points of the carboxylic acids
increase with the length of the chain?
4. Would the lower or higher members of the carboxylic acids be
more soluble in water? HINT – water is polar.
Formation of
a carboxylic
acid
Oxidation of a primary
alcohol
Oxidation of a primary alcohol
Methanol CH3OH
H
H
C
O
Acidified Sodium
Dichromate
OH
H
C
C
Methanal
HCHO
O
H
H
OH
Methanoic Acid
HCOOH
Excess
H
Oxidation of a primary alcohol
Ethanol C2H5OH
H
H
H
C
C
H
H
O
H
H
C
H
C
Acidified Sodium
Dichromate
OH
OH
Excess
Ethanoic Acid
CH3COOH
H
H
O
C
C
H
Ethanal
CH3CHO
H
Oxidation of a primary alcohol
H
H
H
OH
H
C
C
C
H
H
H
Propanoic
Propanol
Propanal
Acid
C2CH23H
OH
5COOH
57CHO
O
OH
Acidified Sodium
Dichromate
Excess
Oxidation of a primary alcohol
H
H
H
H
H
OH
C
C
C
C
H
H
H
H
O
OH
Butanoic
Butanol
Butanal Acid
On reaction with acidified
sodium dichromate
In Excess
Substitution
using UV Light
The Alkanes
Ethane C2H6
+ H2
- H2
The Chloroalkanes
Chloroethane C2H5Cl
The Alkenes
+ HCl , + Cl2
Ethene C2H4
+ H2O
- H2O Aluminium Oxide
Catalyst
The Polymers
Polythene & Polypropene
The Alcohols
Ethanol C2H5OH
The Alcohols
Ethanol C2H5OH
Acidified sodium
dichromate
Hydrogen,
Nickel catalyst
Oxidation
Reduction
The Aldehydes
Ethanal CH3CHO
Acidified sodium
Reduction
dichromate
Hydrogen,
Oxidation
Nickel catalyst
The Carboxylic
Acids
Ethanoic Acid
CH3COOH
Tests on ethanoic acid
Colourless Liquid
Pungent odour
Reaction of an
acid with a
carbonate
Tests on ethanoic acid
Reaction with sodium carbonate
2 CH3COOH
+
Ethanoic
Acid
Na2CO3
Sodium
Carbonate
2 CHEffervesence
H22O
COONa
+(fizzing)
3
3
Sodium
Water
of carbon dioxide
Ethanoate
observed
+
2007: Q2 (f) (9)
2009: Q8 (d) (9)
CO2
Carbon
Dioxide
Reaction of an
acid with
magnesium
Tests on ethanoic acid
Reaction with magnesium
2 CH3COOH
+
Ethanoic
Acid
(CH3COO)2Mg
Mg
Magnesium
metal
+
H2
Effervesence (fizzing)
Reaction of an
acid and an
alcohol
(formation of an
ester)
Esterification
H
H
O
C
C
O
H
Ethanoic Acid
CH3COOH
H
H
Ethyl Group
Ethyl Ethanoate
CH3COOC2H5
H
CH3COOH H
CH3COOC2H5
O
C
C2H5OH
H
C
H
H
H2SO4
Ethanol
O
CH
H
2
2 5OH
Mandatory experiment
• Preparation of Benzoic acud
Mandatory experiment
• Recrystallization of Benzoic acid