As expected, the compound has a kp/ktr value that is relatively low compared to the thionolactones 1, 2 and 5 prepared by Roth. Nevertheless, the values (164-298) are still higher than the ones of DOT (13-31) and thus will impede its use in rROP. To highlight the influence of the various structural parameters, we then focused and calculated seven-membered ring thionolactones with only one phenyl stabilizing group ( and). The addition rate in the case of styrene of the propagating radical onto the C=S bond is lower when the aromatic ring in a position of the carbonyl is removed (kadd close to 10