Photoinduced ion-molecule reactions of the primary ions occurring in a number of thiols and alkyl sulfides have been investigated over the pressure range 1-20 mTorr using a Kr resonance lamp (10.03 and 10.6 eV) as the excitation source. Rate coefficients at 298 K have been determined for the reaction R2_"+SHn + R2_nSH" -* R,_"+SHn+1 + R2-"SHri (-H) (ki), n = 0,1. For the mercaptans values of kx were found to be 14.1,12.5,11.3, and 5.7 X 10"10 cm3 s"1 for R = CH3, C,H5, C3H7, and (CH3)3C. These values agree with the general trend established for the analogous reactions in amines. In the case of (CH3)2S and (C2H5)2S, no hydrogen transfer was observed. Photoionization of C2H5SH in CH3OH could indicate that mercaptans behave as hydrogen atom acceptors rather than as proton donors. However, for fert-butyl mercaptan, the proton transfer reaction (CH3)3C+ + (CH3)3CSH -»• (CH3)2CCH2 + (CH3)3CS+H2 (k2) was also observed.
Mit Hilfe eines Hochdruck‐Quadrupolmassenspektrometers (1‐20m Torr) mit einer Kr‐Resonanzlampe (10,03 und 10,6 eV) als Photoionisationsquelle werden die Geschwindigkeitskonstanten der Reaktionen A bestimmt.
Photoinduced ion-molecule reactions of the molecular ions of hydrazine and methylhydrazine have been studied in the pressure range from 1 to 12 mtorr with Kr and Xe resonance lamps as ionization sources (principal resonance lines at 10.03 and 8.44 eV, respectively). The rate constants for the loss of the parent molecular ions due to proton transfer were found to be 11.3 X 10"10 cm3 s"1 for hydrazine and 6.63 X 10~10 cm3 s'1 for methylhydrazine with the Kr ionization source. The respective values for the Xe radiation were 6.82 X 10"10 and 5.00 X 10"10 cm3 s'1. The observed rate constants follow the trend predicted by the ADO theory, however, for both compounds the values are considerably lower than the theoretically predicted collision rates. The effect of the excess ion energy on the rate constant is reversed from that normally expected: The observed rate constants increase whh increasing excess energy and it is suggested that this may be interpreted on the basis of the known photoelectron spectra.
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