Chemical Properties of Ethyne

1. Combustion – It burns in oxygen to produce water and carbon (iv) oxide.
2C₂H_2(g) + 5O_2(g) → 4CO_2(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.
3C₂H_2(g) →  C₆H₆(L)

4. Substitution reaction – Ethyne reacts with ammoniacal copper (1) chloride to form reddish-brown copper (1) alkynide.
C₂H_2(g) + 2CuCL_(aq) →  Cu₂C_2(s) + 2HCL_(aq)

Also, they react with ammoniacal silver trioxonitrate (v) to form whitish-yellow precipitate of silver alkynide or dicarbide.  C2H_2(g) + 2AgNO_3(aq) →  Ag₂C_2(s) + 2HNO_3(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.