Final answer:
Beta-hydroxy carbonyl compounds cannot be isolated when their formation is inhibited due to the lack of reactivity or stability, such as with tertiary alcohols or hindered substrates, and in the case of molecules that are inherently stable in their cyclic forms like cyclic hemiacetals.
Step-by-step explanation:
The beta-hydroxy carbonyl compound cannot be isolated in certain instances where its stability is compromised. For example, tertiary alcohols, due to the lack of a hydrogen atom on the carbon to which the hydroxyl group is attached, cannot be readily oxidized to form the desired beta-hydroxy carbonyl structure. Furthermore, certain substrates like hindered 8-anthracenylboronic acid and its benzannulated analogs may resist coupling under specific conditions, hence failing to yield an isolable product.
When dealing with carbohydrates or substrates that form stable cyclic hemiacetals, it is possible that the reaction favors the formation of a stable cyclic structure rather than the beta-hydroxy carbonyl product. Additionally, compounds that are not prone to hydrolysis will not react to produce beta-hydroxy carbonyl compounds. In the realm of biochemical systems, highly reactive compounds such as acid halides and acid anhydrides, which would otherwise yield carbonyl compounds, typically do not survive due to their high reactivity.
Thus, the ability to isolate a beta-hydroxy carbonyl compound is contingent upon the chemical environment, the stability of the compound, and the reactivity of the intermediates involved.