REACTIVE SCATTERING OF A SUPERSONIC FLUORINE-ATOM BEAM - F+C2H5I,C3H7I,(CH3)2CHI

Reactive scattering of F atoms with C2H5I, C3H7I and (CH3)2CHI molecules has been studied at an initial translational energy E 38kJmol-1 using a supersonic beam of F atoms seeded in He buffer gas. Centre-of-mass angular distributions of IF scattering show peaking in the forward and backward directions, which is consistent with reaction via persistent F—I—C2H5, F—I—C3H7 and F—I—CH(CH3)2 complexes with lifetimes greater than two rotational periods. The extended microcanonical theory indicates that the angular distribution of reactive scattering for F + C2H5I arises from a range of transition state configurations generated by internal rotation about the extended C—I bond. The reactive scattering for F + C3H7I arises from a wide range of transition-state configurations, with sharply peaked forward and backward scattering from extended configurations and mildly peaked scattering from more contracted configurations. However, the range of transition-state configurations is much more limited for F + (CH3)2CHI. This distinction confirms the persistence of significant C—I bonding, which restricts the rotation of the IF and C2H5, C3H7 or (CH3)2CH fragments in these product transition states. © 1990 Taylor and Francis Ltd.