I was reading about synthesis of alkyl halides from $\ce{PX3}$. I want to know the mechanism for this reaction. According to Solomons and Fryhle, no rearrangement takes place in case of $\ce{PBr3}$ , which leads me to think that the mechanism is SN2. But what about phosphorus bromides and iodides?

A Google search confirmed that the mechanism for reaction with phosphorus tribromide is indeed SN2, but I could not find anything on trichlorides and iodides. I need help for those.


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    $\begingroup$ Why do you think they may be different? $\endgroup$
    – Waylander
    Apr 24, 2018 at 11:59
  • $\begingroup$ HBr undergoes AMK addition to an alkene in the presence of peroxide whereas other hydrogen halides do not. I think that anything is possible in chemistry and I do not want to make a mistake if a tricky question based on this appears in my exam. $\endgroup$ Apr 24, 2018 at 12:21
  • $\begingroup$ The HBr is quite different from the phosphorus halides as there is no protonation step on the alcohol $\endgroup$
    – Waylander
    Apr 24, 2018 at 14:15
  • $\begingroup$ chemistry.stackexchange.com/questions/69063/… $\endgroup$
    – Mithoron
    Apr 24, 2018 at 15:25
  • $\begingroup$ Thanks for the links @Mithoron ! The reaction with $PCl_3$ looks like S_N^2 or S_N^i to me but I can't quite tell which. Which one is it? $\endgroup$ Apr 25, 2018 at 9:03