INFRARED MULTIPHOTON DISSOCIATION OF 2 PERFLUOROBUTENES

Photofragment translational spectroscopy was used to examine the infra red multiphoton dissociation of octafluoro-1-butene and octafluoro-2-b utene. The predominant unimolecular reaction in octafluoro-1-butene at moderate laser fluences is cleavage of a carbon-carbon single bond to give the products CF3 and C3F5. The two other reactions that take pla ce are CF2 elimination and the formation of equal weight fragments wit h the chemical composition C2F4; both reactions take place via a dirad ical intermediate. Dissociation of octafluoro-1-butene to the resonanc e stabilized perfluoroallyl radical is suggested to account for the fa voring of simple bond rupture. These three reaction pathways were also observed in octafluoro-2-butene dissociation, however, the branching fraction is different than from octafluoro-1-butene. In octafluoro-2-b utene all three channels occur with roughly equal probability. The rea ctions involving CF2 loss and C2F4 formation in octafluoro-2-butene ar e thought to proceed through the same diradical intermediate as in oct afluoro-1-butene, necessitating a 1,2-fluorine migration. (C) 1997 Ame rican Institute of Physics.