The Appel reaction uses a carbon tetrahalomethane and triphenylphosphine to convert a primary or secondary alcohol to an alkyl halide. First triphenylphosphine forms a phosphonium ion by abstracting a halogen from carbon tetrahalomethane. The alcohol then attacks the phosphonium ion, generating an oxyphosphonium intermediate. An S_N2 displacement by the halide ion produces triphenylphosphine oxide and the alkyl halide. Inversion of configuration occurs if the carbon is asymmetric.

• Reagents: Triphenyl Phosphine, Tetrahalomethane
• Reactant: Primary or Secondary Alcohol
• Product: Alkyl Halide
• Type of Reaction: S_N2

Mechanism

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