Dehydration of Alcohols

To dehydrate an alcohol (make it lose a water molecule) it needs to be heated in the presence of a suitable catalyst. Usually acids like H₂SO₄ or H₃PO₄ are used. Secondary and tertiary alcohols are dehydrated by an E1 mechanism since they can form stable carbocations, but watch out for rearrangements. Primary alcohols undergo E2 reactions since primary carbocations are unstable. During the dehydration of a primary alcohol a competing S_N2 reaction will occur. If multiple alkenes can be formed, the most stable alkene will be the main product.

Δ, H₃PO₄

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