I have seen preps, based on sulfites, but these yield a mix of POCl3 and SOCl2 (and NaCl). It will be difficult to separate these two liquids. I
imagine that preps based on SO2 yield POCl3 and SOCl2 as well.
I never did it myself, but if I recall correctly, distilling SOCl2 is quite difficult. SOCl2 is not that stable and it partially decomposes at its
boiling point. You have to be very careful not to overheat. If you mix with POCl3, then most likely you need to heat a little bit further than with
pure SOCl2 and then you may decompose too much. It might be necessary to use (partial) vacuum distillation, but this may decrease the separation of
the two even more. |