Chemical Properties of Ethyne

1. Combustion – It burns in oxygen to produce water and carbon (iv) oxide.
2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(L)

2. Additional reaction – It undergoes additional reaction partially to form alkenes and completely to form Alkanes.
C2H2 + H2  → C2H2
C2H4 + H2  →  C2H6

3. Polymerization – It polymerizes to form benzene.
3C2H2(g) →  C6H6(L)

4. Substitution reaction – Ethyne reacts with ammoniacal copper (1) chloride to form reddish-brown copper (1) alkynide.
C2H2(g) + 2CuCL(aq) →  Cu2C2(s) + 2HCL(aq)

Also, they react with ammoniacal silver trioxonitrate (v) to form whitish-yellow precipitate of silver alkynide or dicarbide.  C2H2(g) + 2AgNO3(aq) →  Ag2C2(s) + 2HNO3(aq)

NB – This is a test, which distinguishes ethyne from ethane since ethane can not undergo substitution reaction. Also, it is only terminal alkynes like ethyne that can undergo this reaction. Non – terminal alkynes can not undergo this reaction.

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