Final answer:
Radical stability generally increases from primary to tertiary, but without specific information on Radicals A, B, C, and D, an exact ranking cannot be provided. The ranking would depend on the degree of substitution of the respective radicals on the carbon atom.
Step-by-step explanation:
To rank the stability of radicals, one generally considers the degree of substitution on the carbon bearing the radical. According to radical stability, it increases in this order: primary (RCH₂) < secondary (R₂CH) < tertiary (R₃C). However, the student has provided radicals labeled A, B, C, and D rather than specific chemical structures. Therefore, we cannot provide an exact ranking without knowing the structures associated with these labels.
If we assume that Radical A is a primary radical, Radical B is a secondary radical, and Radical C and Radical D are tertiary radicals with the same substituents, we would rank the radical stability as follows: Radical A (primary) < Radical B (secondary) < Radical C = Radical D (tertiary). But again, this is based on an assumption, and the actual ranking would depend on the specific structures presented as Radical A, B, C, and D.
The stability of radicals is an important factor in organic chemistry, especially when predicting the outcomes of free radical reactions or explaining the mechanism of such reactions. It's also used to explain the prevalence of certain products over others when multiple pathways are possible.