Thermolysis of the polyyne C8H2 in hexane and methanol: Experimental and theoretical study

The mean lifetimes of polyyne C8H2 in hexane were determined at 50, 60, 80, and 100 °C and in methanol at 60 °C. The reactions are second order at all temperatures: ln k2 = 20.5 ± 1.5–10303 ± 520T−1 and the corresponding activation energy is 85.7 ± 6.3 kJ mol−1 (7164 cm−1). Extrapolation suggests that solutions at 1 mM concentration are significantly unstable at room temperature. Quantum chemical calculations show that polyynes CmH2 + CnH2 (m + n = 16) could be products, but these were not detected. Alternatively, C16H2 isomers could form. IR spectra of the solid residues from hexane and methanol solutions were obtained.