Strahlungschemie von Kohlenwasserstoffen. 19. Mitteilung. Die Deuteriumabspaltung in isotop‐isomeren Cyclohexanen

Abstract

The G-value for D, production has been measured for C,D,, and for gem-, cis-, and trans-C,H,,D,. The G-values for the unimolecular process arc 0.24, 0.023, 0.010 and 0.004, resp. I n C,D,, two bimolecular processes can be distinguished: one includes 'hot' D-atoms, e.g. a species that shows no isotope effect for the hydrogen abstraction yielding D, and HU, resp. ; its G-value is 1.22. The other proccss goes via thermal D-atoms, it has a G-value of 1.97 and gives an isotope effect for abstraction: kD/kH = 0.075 (10°C). In the partially deuteriated cyclohexanes, only the former process can be observed. Its G-value depends on the irradiation temperature and phase, is independent of the position of the D-atoms in the molecule and amounts to 0.035 (lO°C), 0.028 (-40°C solid), 0.040 (-40°C liquid with 25% hexane). The following conclusions can be drawn: the unimolecular detachment shows no intramolecular isotope effect in partially deuteriated molecules and comes only from the gem-, cis-and trans-positions. Most of the G-values for the D, and HD production by different reaction paths can be cross-checked by G-values from different mixtures. The agreement between these values is excellent.Einleitung. -Dyne et al. haben in einer Reihe von Arbeiten gezeigt, dass man mit