Explain how alcohols react with phosphorus trihalides

Alcohols reaction with phosphorus trihalides”

(i) Alcohols react with liquid called phosphorus trichloride to make chloroalkanes. The reaction is given below:

3CH3CH2CH2OH+PCl3→3CH3CH2CH2Cl+H3PO3

(ii) Using phosphorus(III) bromide or iodide, the alcohol is usually heated under reflux with a mixture of red phosphorus and either bromine or iodine. First, the phosphorus reacts with the bromine or iodine to yield phosphorus(III) halide.

2P(s)+3Br2→2PBr3
Then these furtherreact with the alcohol to give the corresponding halogenoalkane, that can be later separated by distillation.

3CH3CH2CH2OH+PBr3→3CH3CH2CH2Br+H3PO3

CH3CH2CH2OH+PI3→3CH3CH2CH2I+H3PO3

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