I-Molecule Reactions of Ethane at Low Electron Energy

The ion-molecule reaction chemistry of ethane has been examined by ICR spectroscopy at 13 eV and ·10−4 torr pressure. The interpretation of single- and double-resonance peak heights under these conditions is discussed quantitatively, and the double resonance spectra are used to assign relative rates to the observed reactions. The chemistry is strikingly different from that at higher electron energy. Substantial formation of C3H9+ and C4H11+ was observed, while no C2H7+ was obtained, and this result is taken to show low internal excitation of the C2H6+ reactant ion under these conditions. The observed formation of the C3H3+ ion is not in accord with the energetics of the reaction derived from electron impact studies, and the previously proposed cyclopropenyl structure is suggested for the C3H3+ ion formed in this system. The marked contrast between the positive ion-molecule reactions in ethane and diborane is discussed.