What are the structures of 1-butene and ethanol, and how does the addition of an acid catalyst (H₂SO₄) promote an electrophilic addition mechanism?

To understand the reaction between 1-butene and ethanol in the presence of sulfuric acid (H₂SO₄), we first need to look at the structures of the two reactants.

Structures:

• 1-Butene: C₄H₈
  
  
• Ethanol: C₂H₆O
  
  

Mechanism and Electrophile/Nucleophile:

In the presence of sulfuric acid, the mechanism involves the following steps:

1. Protonation of 1-Butene: The double bond in 1-butene acts as a nucleophile and attacks the proton (H⁺) from sulfuric acid. This forms a carbocation intermediate. Here, 1-butene (the nucleophile) donates a pair of electrons to the proton.
2. Formation of Alkyl Hydrogen Sulfate: The carbocation can then react with the bisulfate ion (HSO₄^–) from sulfuric acid to form alkyl hydrogen sulfate.
3. Nucleophilic Attack by Ethanol: Ethanol acts as a nucleophile and attacks the carbocation, replacing the sulfate group, which leads to the formation of ethyl hydrogen sulfate.
4. Hydrolysis: Finally, the reaction can be hydrolyzed by adding water or by simply having the water present in the reaction medium. This step leads to the formation of ethanol and regenerates the sulfuric acid catalyst.

Summary:

During this electrophilic addition mechanism, the nucleophile is the double bond of 1-butene and the electrophile is the proton from sulfuric acid. This results in the formation of a product that is an ether, specifically ethyl hydrogen sulfate.

The overall balanced reaction can be summarized as follows:

1-butene + H₂SO₄ + H₂O → Ethanol + H₂SO₄