Phosphorus trihalides, alcohol halide using

The reaction is performed most simply by the addition of the propargylic alcohol to a solution of the phosphorus halide. Rearrangement of the phosphorus ester proceeds at ambient temperature or with mild heating. When phosphorus trihalides are used, the product can be isolated as the phosphonic dichloride.168169 Aqueous workup provides the phosphonic acid.162 In most instances, however, a dialkyl phosphorochloridite with only a single halogen on phosphorus available for reaction with alcohol has been used.165 170 174... 

Mechanism of the Reaction with Phosphorus Trihalides The mechanism of the reaction of alcohols with phosphorus trihalides explains why rearrangements are uncommon and why phosphorus halides work poorly with tertiary alcohols. The mechanism is shown here using PBr3 as the reagent PC13 and PI3 (generated from phosphorus and iodine) react in a similar manner. 

Alcohols can also be converted to alkyl halides using thionyl chloride or phosphorus trihalides. 

Alkyl halides can be prepared from alcohols by use of phosphorus trihalides ... 

Phosphorus trihalides can in some cases be used to halogenate alcohols (12.282) and to convert nitro compounds into cyanides (12.283). Carboxylic acids are converted to acyl halides (12.284) and deoxygenations can sometimes be effected (12.285). The triiodide is a useful deoxygenating agent. 

We have just seen that an alcohol can be converted into an alkyl halide by treating it with a hydrogen halide. Better yields of the alkyl halide are obtained and carbocation rearrangements can be avoided if a phosphorus trihalide (PCI3 or PBr3) or thionyl chloride (SOCI2) is used instead. 

---