draw the product of di-acetylation of biphenyl. Explain why acetylation does not occur twice on the same ring.
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To draw the product of di-acetylation of biphenyl, we need to understand the acetylation reaction and the structural features of biphenyl.
Acetylation is a chemical reaction that involves introducing an acetyl group (-COCH3) onto a molecule. In the case of biphenyl, it consists of two benzene rings attached to each other by a single bond.
To perform di-acetylation of biphenyl, we can use acetyl chloride (CH3COCl) or acetic anhydride ( (CH3CO)2O) as the acetylation reagent. The reaction is typically carried out in the presence of a Lewis acid catalyst such as aluminum chloride (AlCl3) or phosphoric acid (H3PO4).
Now, let's consider why acetylation does not occur twice on the same ring in biphenyl. The key factor is the reactivity of electron-rich aromatic rings and the steric hindrance caused by the first acetyl group attached to biphenyl.
In the first step of acetylation, the Lewis acid catalyst coordinates with the acetyl chloride or acetic anhydride, activating it for the reaction. This allows the acetyl group to undergo electrophilic aromatic substitution with one of the benzene rings in biphenyl. The reaction results in the substitution of a hydrogen atom by the acetyl group, forming an acetylated product.
However, the introduction of the first acetyl group creates steric hindrance on the benzene ring. This steric hindrance inhibits the access of the reagent, reducing the likelihood of a second acetylation occurring on the same ring.
Moreover, when the first acetyl group is attached, it adds electron-withdrawing character to the ring, making it less reactive towards further acetylation. As a result, the second acetyl group tends to preferentially undergo electrophilic aromatic substitution on the other benzene ring, which is sterically more accessible and less hindered.
To summarize, the di-acetylation of biphenyl produces a product where the two acetyl groups are attached to different benzene rings due to steric hindrance and differences in reactivity caused by the first acetylation.
To draw the product of diacetylation of biphenyl, we need to first understand the structure of biphenyl. Biphenyl consists of two benzene rings connected by a single bond.
The process of acetylation involves the addition of an acetyl group (-COCH3) to a compound. In the case of biphenyl, two acetyl groups are added to the molecule.
To draw the product, we start with biphenyl and add an acetyl group to each benzene ring. Each acetyl group replaces one hydrogen atom on the benzene ring. The resulting structure is 4-(acetyloxy)biphenyl.
Now, let's understand why acetylation does not occur twice on the same ring. Acetylation involves the addition of an electrophile (the acetyl group) to the aromatic compound. This reaction is typically catalyzed by Lewis acids, such as aluminum chloride (AlCl3).
When the first acetyl group is added to the ring, it changes the electronic distribution of the ring. The addition of the acetyl group makes the ring less electron-rich, which decreases its reactivity towards further acetylation. This reduction in reactivity prevents a second acetyl group from being added to the same ring.
In addition, the steric hindrance created by the first acetyl group also makes it difficult for a second acetyl group to come and add to the same ring. The bulkiness of the acetyl group makes it challenging for another acetyl group to approach and react with the same ring.
Therefore, due to the reduced electron density and increased steric hindrance on the first acetylated ring, acetylation does not occur twice on the same ring in biphenyl.