2.6 CARBOXYLIC ACID

F. CARBOXYLIC ACIDS

Functional group
• Carboxyl group ( -COOH )

General formula
• CnH2n+1COOH (n=0,1,2,….)

2.6 Analysing carboxylic acid
State the general formula of carboxylic acids | Identify the functional group of carboxylic acids

n Name Molecular Structural Formulae
Formulae

0 Methanoic acid HCOOH

1 Ethanoic acid CH3COOH

2.6 Analysing carboxylic acid
List the names and the molecular formulae of the first four carboxylic acids

n Name Molecular Structural Formulae
Formulae

2 Propanoic acid C2H5COOH

3 Butanoic acid C3H7COOH

2.6 Analysing carboxylic acid
List the names and the molecular formulae of the first four carboxylic acids

Synthesised/making of ethanoic acids

Oxidation of alcohol

C2H5OH+ 2[O] → CH3COOH + H2O

Ethanol Ethanoic acid

• Reflux ethanol with acidified potassium
dichromate(VI) solution or acidified potassium
manganate(VII) solution

2.6 Analysing carboxylic acid
Describe the preparation of ethanoic acid in the laboratory

2.6 Analysing carboxylic acid
Describe the preparation of ethanoic acid in the laboratory

2.6 Analysing carboxylic acid
Describe the preparation of ethanoic acid in the laboratory

2.6 Analysing carboxylic acid
Describe the preparation of ethanoic acid in the laboratory

Solubility Colour

• Simple molecules are • Colourless
very soluble in water liquid

• Due to water molecule Boiling point
being strongly
attracted to the – • High boiling
COOH group point

• Solubility ↓ when Physical Odour
number of carbon per properties of
molecule ↑ • Sharp/unplea
carboxylic sant smell
State acids

• Larger molecules
(C10 above) are
wax-like solids

2.6 Analysing carboxylic acid
State the physical properties of ethanoic acid

Chemical properties

Acid properties

• CH3COOH is a weak monoprotic acid
• Only one hydrogen atom can ionize in water to

produce H+ ion

CH3COOH ↔ CH3COO- + H+

Ethanoic acid Ethanoate ion

• Partially dissociate in water

• Turn moist blue litmus → red

• React slowly with metals, bases and carbonates

2.6 Analysing carboxylic acid
Describe the chemical properties of ethanoic acid

Reaction with metals

Carboxylic acid + metal → salt + H2

2CH3COOH + Zn → Zn(CH3COO)2 + H2
Ethanoic acid Zinc ethanoate

2.6 Analysing carboxylic acid
Describe the chemical properties of ethanoic acid

2.6 Analysing carboxylic acid
Describe the chemical properties of ethanoic acid

Reaction with bases

Carboxylic acid + bases → salt + H2O

CH3COOH + NaOH → CH3COONa + H2O

Ethanoic acid Sodium

ethanoate

2CH3COOH + CuO → Cu(CH3COO) 2 + H2O
Ethanoic acid Copper

ethanoate

2.6 Analysing carboxylic acid

Describe the chemical properties of ethanoic acid

2.6 Analysing carboxylic acid
Describe the chemical properties of ethanoic acid

Reaction with carbonates

Carboxylic acid + carbonates → salt + CO2 + H2O

2CH3COOH + CaCO3 → Ca(CH3COO)2 + CO2 + H2O

Ethanoic acid Calcium
ethanoate

2.6 Analysing carboxylic acid
Describe the chemical properties of ethanoic acid

2.6 Analysing carboxylic acid
Describe the chemical properties of ethanoic acid

Reaction with alcohols

Carboxylic acid + alcohol → ester + H2O

Catalyst: Concentrated H2SO4

CH3COOH + C4H9OH → CH3COOC4H9 + H2O

Ethanoic Butan-1-ol Buthyl ethanoate

acid

2.6 Analysing carboxylic acid
Describe the chemical properties of ethanoic acid



Uses of carboxylic acids

Ethanoic acid
• As a flavouring
• As a preservative
• Used with other chemicals to make drugs, dyes, paints,

insecticides and plastics
Methanoic acid
• Used to coagulate latex
Fatty acids (long-chain carboxylic acids)
• Used in making soaps
Benzoic acid
• Preservative in food

2.6 Analysing carboxylic acid
Explain with examples the uses of carboxylic acids in everyday life