Thermodynamics of the formation of polyynes and aromatic species from methane and acetylene

The Gibbs free energies of the formation of several polyynes (C₆H₂, C₁₀H₂ and C₁₆H₂) and aromatic species (C₆H₆, C₁₀H₈ and C₁₆H₁₀) from methane and acetylene at temperatures of 1000–2600 K and atmospheric pressure were obtained by quantum chemical calculations using the RI-MP2 method in the ORCA open source software. At lower temperatures, aromatic species form more readily than polyynes, while at temperatures >2200 K the trend reverses and polyyne formation becomes predominant.