Association Reactions of Trimethylsilyl Ions

Article abstract of DOI:10.1002/oms.1210260605

Adduct ions, (1+), were produced by bimolecular association reactions of trimethylsilyl ions, (CH3)3Si(1+), with acetone, cyclohexanone, anisole, dimethyl ether, 2,5-dimethylfuran, 2-methylfuran and furan in ion cyclotron resonance experiments at 300 K and at pressures of ca. 10^-7 Torr (1 Torr = 133,3 Pa).The rate constants, k_a, for the association reactions varied from 100percent to 2 percent of the collision rate constants, k_c.The rate constants were independent of pressure, except for furan.Measurements were also made of bond dissociation energies for these adduct ions, D<(CH3)3Si(1+)-X>, from equilibrium measurements.The a ssociation efficiency, k_a/k_c, increased with increasing bond dissociation energy and with increasing numbers of degrees of freedom, in qualitative aggreement with theoretical predictions.Observations pertinent to the dependence of k_a on reactant temperature and relative kinetic energy are discussed.The possibility of determining ion-neutral complex binding energies from radiative association rate constants is considered.