Appel Reaction
Defination:
- Conversion of Alcohol to the corresponding halide in presence of
triphenyl-phosphine and carbon tetrahalide , viz. carbon tetrachloride, carbon tetra
bromide, carbon tetra iodide.
General Reaction:
-
Mechanism:
-
The reaction proceeds by activation of the triphenylphosphine by reaction
with the tetrahalomethane, followed by attack of the alcohol oxygen at
phosphorus to generate an oxyphosphonium intermediate. The oxygen is then
transformed into a leaving group, and an SN2 displacement by halide
takes place, proceeding with inversion of configuration if the carbon is
asymmetric. The driving force behind this reaction is the formation of the
strong PO double bond.
Significance: -
1. This
reaction can effectively used in synthesis.
2. The
reaction is somewhat similar to the Mitsunobu reaction.
Ex:
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