Hi guys,
I thought it would be due to aromaticity breaking difficulty?
In the bromination reaction, why are the double bonds which are par t of the phenyl r ing not brominated?
A. We only added one equiv alent bromine.
B. T he phenyl r ing is aromatic and aromaticity is diffic ul t to break .
C. Because they are in a ring
D. Because they are too hindered
I think you are right. The aromatic ring has extra stability due to resonance.
Yes B. I presume that the attempted bromination was carried out under addition reaction conditons?
To determine why the double bonds in the phenyl ring are not brominated in the bromination reaction, we need to evaluate the given choices:
A. We only added one equivalent bromine: This choice suggests that the absence of bromination is due to a limitation in the amount of bromine added. However, the number of equivalents of bromine added is not directly relevant to the question.
B. The phenyl ring is aromatic and aromaticity is difficult to break: This choice suggests that the lack of bromination is due to the difficulty in breaking aromaticity. Aromatic compounds are known to possess exceptional stability due to delocalized pi electrons. This stability makes it challenging for bromination to occur on aromatic rings.
C. Because they are in a ring: This choice points out that the lack of bromination is a consequence of the phenyl ring being part of a cyclic structure. While it is true that cyclic structures can influence chemical reactivity, this choice does not directly address the specific reason for the lack of bromination.
D. Because they are too hindered: This choice suggests that the hindered nature of the double bonds prevents bromination. Hindered double bonds, such as those in the phenyl ring, can be less reactive towards electrophilic bromination reactions.
To answer this question, we can eliminate choices A and C as they do not address the specific reason for the lack of bromination. Now, we are left with choices B and D.
To differentiate between choices B and D, we need to consider the unique properties of aromatic compounds. Due to the stability associated with aromaticity, aromatic rings are generally less reactive towards electrophilic substitutions, such as bromination. Therefore, choice B, which explains the lack of bromination as a result of aromaticity difficulty, is the most accurate explanation.
Therefore, the correct answer is B. The phenyl ring is aromatic and aromaticity is difficult to break.