Dehydration of alcohols, leading to the formation of alkenes, occurs with protic acids (e.g., concentrated H₂SO₄ or H₃PO₄) or catalysts like anhydrous zinc chloride or alumina. The relative ease of dehydration follows the order: Tertiary > Secondary > Primary.
Describe the conditions and catalysts involved in the dehydration of alcohols, and what is the order of ease for dehydration among primary, secondary, and tertiary alcohols?
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Dehydration of alcohols involves the removal of water to form olefins (alkenes). Common conditions include heat and an acid catalyst, such as sulfuric acid (H₂SO₄). The acid protonates the alcohol, making it a better leaving group, facilitating elimination of water. Tertiary alcohols dehydrate most easily due to increased stability of the resulting tertiary carbocation intermediate. Secondary alcohols follow, while primary alcohols undergo dehydration less readily due to the formation of less stable primary carbocations. This order reflects the carbocation stability and influences the ease with which alcohols undergo dehydration reactions.