Which of the following has higher enol content?
The enol form of (A) and (B) is:
Both the enols have hydrogen bonding.
If the oxygen were to accept the pi electrns from carbon forming a carbocation like this (a resonance structure):
the compound becomes stabilized due to resonance as well. So isn't (B) the answer?
Answer
The two main factors affecting the stability of the enol forms of (A) and (B) are
- Hydrogen bonding
- Aromaticity
In the enol form of both compounds, hydrogen bonding is present:
But the resonance structure of enol form of (B) is aromatic. It contains $6$ $\pi$-electrons:
The enol form of (A) lacks this stability. Hence, the enol content of (B) is more than that of (A)
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