To prepare 2-hexanol via acid-catalyzed hydration, we need to start with an appropriate alkene as our precursor. A common choice is to use 1-hexene, which is the simplest alkene that will yield 2-hexanol through this reaction. The process involves the following steps:
Step 1: Formation of Carbocation
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Protonation of Alkene: The first step in the acid-catalyzed hydration reaction involves the addition of a proton (H⁺) from an acid (commonly sulfuric acid, H₂SO₄) to the double bond of 1-hexene. This generates a carbocation intermediate.
The reaction can be represented as: \[ \text{C}6\text{H}{12} + \text{H}^+ \rightarrow \text{Carbocation (C}6\text{H}{13}^+\text{)} \]
The carbocation formed is a secondary carbocation because it is located at the carbon that becomes the second carbon in the 2-hexanol.
Step 2: Nucleophilic Attack
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Nucleophilic Attack by Water: Water (H₂O) then acts as a nucleophile and attacks the carbocation, leading to the formation of an alcohol.
The reaction can be written as follows: \[ \text{C}6\text{H}{13}^+ + \text{H}_2\text{O} \rightarrow \text{C}6\text{H}{13}\text{OH} + \text{H}^+ \]
Here, we are forming 2-hexanol (C₆H₁₄O). The proton is regenerated in this step, making the acid catalyst available for further reactions.
Step 3: Deprotonation
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Deprotonation: The final step involves the deprotonation of the alcohol to yield the final 2-hexanol product.
This can be represented as: \[ \text{C}6\text{H}{13}\text{OH} \xrightarrow{\text{Base}} \text{C}6\text{H}{13}\text{O}^- + \text{H}^+ \]
Summary Reaction
Overall, the acid-catalyzed hydration of 1-hexene yields 2-hexanol as follows: \[ \text{C}6\text{H}{12} + \text{H}_2\text{O} \xrightarrow{\text{H}^+} \text{C}6\text{H}{14}\text{O} \]
Mechanism Summary
- Protonation of the alkene forms a carbocation intermediate.
- Water attacks the carbocation, forming an alcohol.
- Deprotonation of the alcohol gives the final product, 2-hexanol.
This mechanism follows Markovnikov's rule, where the more substituted carbocation is formed, leading to the formation of 2-hexanol.