A study on ethylene and acetylene photoligomerization and photopolymerization

It is shown that ethylene irradiated with UV light forms divinylacetylene, benzene and a liquid oligomeric aromatic-naphthenic hydrocarbon. A similar mixture of products is obtained by irradiating acetylene in cyclohexane, demonstrating that ethylene is initially photolyzed to acetylene and hydrogen during the early stages of irradiation. The possible implications of these results to the atmospheric chemistry of the giant planets of the solar system as well as to the atmospheric and surface chemistry of Saturn's giant moon Titan are outlined. Moreover, it is shown that ethylene photopolymerizes in water solution giving a solid photopolymer whose Fourier tansform IR spectrum and whose elemental analysis are in good agreement with the photopolymer obtained directly from acetylene in the same environment, demonstrating once again that ethylene is firstly photolyzed to acetylene and hydrogen. It is proposed that divinylacetylene in cyclohexane is spontaneously isomerized to benzene since it is shown that this isomerization reaction is thermodynamically favored in the reaction conditions adopted.