The electron affinity of cyclopropyl radical measured by the kinetic method

Abstract

The electron affinity of cyclopropyl radical ( cC 3H 5 .) has been derived using a single reference variant of the Cooks kinetic method. Thiocarboxylate anions (RCOS: RPhCH 2, CH 2CH, CH 2CHCH 2, CH 3C(O), and cC 3H 5) were synthesized in a helium flow reactor by the addition of OCS to alkyl anions or by reaction of SH − with acyl chlorides. Collision-induced dissociation of these ions in a triple quadrupole mass analyzer generated, inter alia, R − and OCS − fragments. Plots of the electron affinities of R against the natural logarithms of the yield ratios of R − to OCS − were linearly correlated. From these calibration lines, the electron affinity of cC 3H 5 . was determined to be 0.397 ± 0.069 eV. This value is slightly lower than, but in good agreement with, the electron affinity of cC 3H 5 . predicted by G2 theory. Deleterious effects due to structural dissimilarity in the fragment ions and to multiple fragmentation channels are minimal.