i have a 'ethanol benzene' and i have to add H3O+ (elimination). what will my product be? will the H3O attack the OH on the chain or will it attack the ring?
To determine the product when adding H3O+ to ethanol benzene, we need to understand the reaction mechanism for the elimination of H3O+.
The reaction you are referring to is called an elimination reaction, specifically an acid-catalyzed dehydration. In this reaction, the H3O+ ion acts as a proton source, removing a proton (H+) from the ethanol benzene molecule, leading to the formation of a double bond.
Now, let's consider the two possibilities for the H3O+ attack: the OH bond on the chain or the ring.
1. Attack on the OH group in the chain:
If the H3O+ ion attacks the OH group on the alkyl chain, it would result in an elimination reaction where the OH group is eliminated as water (H2O). This process would create a carbocation intermediate on the chain with a positive charge on the carbon atom where the OH group was initially attached.
2. Attack on the ring:
If the H3O+ ion attacks the benzene ring, it can generate a resonance-stabilized carbocation intermediate. The positive charge can be delocalized around the benzene ring due to the resonance effect, making it more stable than a carbocation on the chain.
Now, let's analyze which carbocation intermediate is more stable. The carbocation intermediate formed by attack on the ring is more stable due to resonance delocalization. Consequently, the H3O+ ion tends to attack the benzene ring to create the more stable carbocation intermediate.
Therefore, in the acid-catalyzed dehydration of ethanol benzene, the H3O+ ion would mostly attack the benzene ring rather than the OH group on the chain. This would lead to the formation of a more stable carbocation intermediate, followed by the elimination of water (H2O) to give the final product.
Please note that this explanation is based on general principles and assumptions. In organic chemistry, reactions can be influenced by various factors such as temperature, concentration, and steric effects, which might affect the product distribution. It is always recommended to consult reliable sources and reference materials for specific reaction details.