1. Leaving Certificate Chemistry
Organic Chemistry
12 – Ethyne
Leaving Certificate Chemistry

2. Carbon-Carbon triple bond
The Alkynes: CnH2n - 2
Ethyne: C2H2
Carbon-Carbon triple bond
2 Carbons Longest Chain H C C H
2 planar carbons

3. The Alkynes - Ethyne

4. Mandatory Experiment
Preparation of Ethyne

5. Acidified Copper Sulfate Solution CuSO4
Preparation of Ethyne
Calcium Dicarbide
CaC2
Water
H2O
Acidified Copper Sulfate Solution CuSO4
Water added to calcium dicarbide produces ethyne gas with impurities. These impurities are removed by passing them through acidified copper sulfate solution.

6. Preparation of Ethyne

7. Impurities Calcium dicarbide Calcium sulfide solid Hydrogen sulfide
gas
Phosphine
gas
Calcium phosphide
solid
Calcium dicarbide

8. Preparation of Ethyne
The first couple of test tubes collected are usually discarded as they contain displaced air from the reaction boiling tube.

9. Balanced Equation for the Synthesis of Ethyne
Preparation of Ethyne
Balanced Equation for the Synthesis of Ethyne
CaC2 +
H2O 2
C2H2 +
Ca(OH)2
Water
Ethyne
Calcium
Dicarbide
Calcium
Hydroxide

10. Preparation of Ethyne 10

11. Ethyne reaction with acidified potassium permanganate
When ethyne gas is bubbled through a solution of acidified potassium permanganate solution a colour change from pink to colourless is observed.
This proves that ethyne is an unsaturated compound.

12. Ethyne reaction with bromine water
When ethyne gas is bubbled through a solution of bromine water, colour change from yellow to colourless is observed.
This proves that ethyne is an unsaturated compound.

13. Ethyne Combustion Reaction
Preparation of Ethyne
Ethene is
Ethyne Combustion Reaction
Balanced Equation for the Combustion of Ethyne
C2H2 + 2½ O2 2
CO2 +
H2O
Turns blue cobalt chloride paper pink
Turns Limewater Milky

14. Oxy-acetylene Flame for cutting metals
Uses of ethyne
Oxy-acetylene Flame for cutting metals
Fuel for Carbide Lamps

15. So far in organic chemistry