Final answer:
True, allylic radicals are more stable than primary, secondary, tertiary, or vinyl radicals due to resonance stabilization from the neighboring double bond.
Step-by-step explanation:
The stability of allylic radicals is indeed higher than that of primary, secondary, tertiary, or vinyl radicals. This increased stability is due to resonance stabilization whereby the unpaired electron is delocalized over the π-system of the neighboring double bond, thereby stabilizing the allylic radical. In contrast, primary, secondary, and tertiary radicals lack this system of delocalization and are less stable as they cannot spread out the electron density. Vinyl radicals, which are radicals on the carbon of a double bond, are also less stable because the unpaired electron is not in resonance with a π-system and is instead located in an sp2 orbital, which has more s-character and thus holds electrons more tightly than an sp3 orbital as in allylic positions.Comparing the stability of radicals is essential in understanding their reactivity, particularly when predicting the outcomes in reactions such as halogenation or polymerization, where radical intermediates are involved. For example, in halogenation, the most stable radical intermediate will be the favored product, hence allylic radicals often lead to allylic halogenation products.