GUIDED ION-BEAM STUDIES OF THE REACTIONS OF AG+ WITH C2H6, C3H8, HC(CH3)(3), AND C-C3H6

Reactions of Ag+ with C2H6, C3H8, HC(CH3)(3), and C-C3H6 have been studied by using guided ion beam mass spectrometry. By using a meter-long flow tube ion source, we are able to create Ag+ ions that are in the a(1)S ground electronic state and obtain corresponding state-specific reaction cross sections as a function of kinetic energy. It is found that C-C bond cleavage is the predominant process in all of these systems. Dehydrogenation and formation of AgH+ + R products are not observed. The reaction mechanisms are believed to be similar to those for the analogous Cu+ reactions proposed in previous studies. The energy dependence of the endothermic reaction cross sections are modeled to obtain thermodynamic information. Unlike the results for most other metal ions studied previously, the thermochemistry derived for Ag+ from several systems is inconsistent, such that the accuracies of the bond energies derived are suspect. Possible explanations for these problems are discussed, and the most likely 0 K bond dissociation energies (in eV) are found to be D-0(Ag+-CH3) = 0.69 +/- 0.05, D-0(Ag+-C2H5) = 0.68 +/- 0.08, D-0(Ag-H) = 2.06 +/- 0.10, and D-0(Ag-CH3) = 1.39 +/- 0.07 eV, and lower limits of D-0(Ag+-CH2) greater than or equal to 1.11 +/- 0.04 and D-0(Ag+-C2H4) greater than or equal to 0.23 +/- 0.07 eV. All these values are most conservatively viewed as lower limits, a conclusion that appears to be verified by comparisons with other experimental and theoretical results from the literature.