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.