Henryk Wincel

Charge-transfer reactions of C3+60 : bracketing the third ionization energy of C60

The occurrence or absence of charge transfer from C go” to several neutral molecules is reported. The results, which were obtained using the selected-ion flow tube technique operating at 294 t 2 K and a helium buffer gas pressure of 0.35 f 0.01 Torr, are in good agreement with earlier Fourier-transform ion cyclotron resonance experiments. Rapid charge transfer, often in competition with other product channels, was noted for the reactions of C go” with several neutrals having IE 6 11.02 eV. Charge transfer to OCS (IE = I 1.1736 eV) was observed to be inefftcient, and no charge transfer was seen to &II, (IE = 11.40 eV) or to neutrals having higher ionization energy. Consideration of the effects of Coulombic repulsion upon the occurrence of charge transfer from a triply-charged ion indicates IE(Cg)= 15.6kO.S eV, in disagreement with a value IE(~)=l7.0+0.75 eV determined by charge stripping. A value for the fourth ionization energy of Cdo, 19.5 eV, is estimated by extrapolation ofthe first three ionization energies.

ACETONITRILE IN GAS-PHASE ION/MOLECULE CHEMISTRY

Bate coefficients and branching ratios have been determined for the reactions of Nz, CO+, and COT with CHsCN utilixing the selected-ion flow tube (SIFT) technique. The ion/molecule reactions following the electron-beam irradiation of the gas mixtures CH,CN-M (where M=Ar, H,, N,, CO, COz, and CH,) have been examined in a high-pressure mass spectrometer (HPMS). Pathways are presented for reactions of cations produced from acetonitrile with ao. C3H:, and C,H,+ with CH,CN.

Gas-phase reactions of the buckminsterfullerene cations C·+60, C2+60, and C·3+60 with aldehydes, ketones, carboxylic acids, and esters

Abstract The reactions of the fullerene ions C·+60, C2+60, and C·+60 with the carbonyl and carboxyl-containing molecules RCHO (R = H, CH3, CH2H5), CH3COR (R  CH3, C2H, C2H5, n-C3H7), C2H5CO C2H5, c-C5H8O, R COOH (R = H, CH3), and RCOOCH3 (R = H, CH3), have been studied using a Selected-Ion Flow Tube (SIFT) at 294 ± 2K and 0.35 ± 0.01 Torr of helium. A wide range in reactivity was observed. The monocation C·+60 was unreactive with all of the neutrals surveyed. The dication C2+60 was observed to add to most of the neutrals: the efficiency of adduct formation was seen to be strongly dependent upon the functional group, and was also observed to increase with increasing size of the alkyl substituents. The adducts of ketones, aldehydes and carboxylic acids were observed to undergo proton transfer to the reactant neutral, as a secondary process; in contrast, proton transfer did not occur from the adducts of esters. Structural factors can account for these differences in reactivity. Proton transfer from carbonyl-containing adducts is presumed to involve deprotonation from an α carbon atom, as indicated by the failure of the dicationic adducts of benzaldehyde to undergo deprotonation. Proton transfer from the carboxylic acid adducts involves loss of the carboyxl proton rather than α CH proton loss, since the ester adducts did not display proton transfer. The reaction chemistry of C·3+60 with these neutrals was dominated by charge transfer, although addition to some neutrals with an ionization energy, IE > 9.9eV was noted also. General features of the secondary chemistry of the triply-charged adducts were similar to the features of the dication adduct chemistry: similar structural factors appear to influence the dication and trication adduct chemistry, although a greater tendency towards charge separation reactions was apparent in the chemistry of the tricationic adducts. Notably, a methyl cation transfer channel was observed in the reactions of the tricationic ester adducts with the parent neutrals.

Novel chemical role for polycyclic aromatic hydrocarbons in the synthesis of interstellar molecules

Results are reported from laboratory simulations of the formation of Si-containing interstellar molecules by the interaction of Si atoms with PAH molecules (represented by naphthalene). Data obtained in the selected-ion flow tube of the Ion Chemistry Laboratory at York University are presented in a table and briefly characterized. The implications of the results for the interstellar roles of larger PAH molecules and for reactions catalyzed by graphitic grain surfaces are indicated. 13 refs.