Mercury-photosensitized reactions of cis-2-butene–ethanol and cis-2-butene–propylamine mixtures

The Hg(3P1)-photosensitized luminescence of propylamine (PA) and ethanol (ET) and the Hg(3P1)-photosensitized isomerization of cis-2-butene (cis-2B) were investigated in PA–cis-2B and ET–cis-2B mixtures under conditions of steady illumination at room temperature. The decreases in intensities of the luminescence from the HgPA* and HgET* complexes by the addition of cis-2B were much steeper than those expected by the competitive quenching of Hg(3P1) by PA (ET) and cis-2B. On the other hand, the decreases of the rate of isomerization of cis-2B by the additions of PA and ET were smaller than those expected by the competitive quenching by PA (ET) and cis-2B. The results for PA–cis-2B mixtures can be explained well by taking into account the additional reaction Hg(3P0) + cis-2B → Hg(1S0) + B* (B* is the triplet state of 2-butene). To explain the results for ET–cis-2B mixtures, it is necessary to add the further reaction HgET* + cis-2B → Hg(1S0) + ET + B*. Although the formation of HgCl was predominant and no cis–trans isomerization was observed in the Hg(3P1)-photosensitized reaction of cis- and trans-1,2-dichloroethene (DCE), we could follow the isomerization of DCE in the photosensitized reaction of DCE–ET ([DCE]0: [ET]0 = 1:100) mixture. These findings can also be explained by the reaction, HgET* + DCE → Hg(1S0) + ET + DCE*. This type of reaction was proposed for the first time.