Phosphine reduction of pfed w/o I2?

[Lestat]

Would it bee possible, as phosphine is a reasonable reducing agent, to reduce ephedrine/pfed directly with either the liquid, and pyrophoric P2H4, made by condensing the gas formed by the action of water on calcium phosphide, the gas condensed by ice/salt in a U-tube, then the remaining "normal" phosphine (PH3) burned led through water then burned off.

Could this, or maybe even on of the solid phosphines such as P2H or P12H6 bee used also?

I should add, that this would NOT be suitable for inexperienced cooks, indoors, of for that matter, anybody without access to a diving air tank and mask as phosphine is EXTREMELY toxic, having irritant effects on the lungs, and destroys the liver after a delay of a day or so,

I repeat, do NOT even THINK about this if you are not 120% equipped to the hilt with all nescessary safety gear, closed circuit air tanks etc. or you WILL end up a rotting carcass floating in the gene pool

[stratosphere]

i could not find any exact numbers but from what i gather the water/metal phosphide rxn only makes a small amount of P2H4 and mostly PH3. so burning off the PH3 would be a very ineffecient use of your rat fumagant.

i can find no evidince that PH3 will reduce alcohols, the fact that the msds qoutes PH3 as being soluable in alcohol seems to indicate that no reaction takes place.

if the following reaction of Ph3P
Ph3P+ HO-R1 + Cl-R2 --> H-R2 + Cl-R1 + Ph3P=0

also applies to PH3 or at least does something very analogous then youd still be in buisness.


vis-a-vis start with

ephedrine + PH3 +Cl-R --> chloroephedrine + H-R + PH30

then add another equivalent of PH3 and of a alcohol

chloroephedrine + PH3 + HO-R --> meth + Cl-R + PH30

off course this assumes that PH3 behaves like Ph3P and also assumes the amine group doesnt result in any side reactions.

[Nicodem]

Off course PH₃ and other "phosphines" react with I₂ to produce HI and furthermore they are even more efficient as you get 8 moles of HI per each mol of PH₃:

PH₃ + 8I + 4H₂O  =>  H₃PO₄ + 8HI

instead of 5HI per each mol of phosphorous:

P + 5I + 4H₂O  =>  H3PO4 + 5HI

But the problem is that introducing phosphine or whatever oligophosphine into a boiling reflux of ephedrine/I₂/H₂O would represent a suicide for most bees without a proper equipment and even with the proper equipment and protection it would stil be too dangerous.
Even if it would be used just for the preparation of conc. HI from I₂ and water at ambient temperature in the H₂S style it would bee unacceptably dangerous. Though, at least the resulting acid would be a mixture of conc. HI_(aq) and H3PO4 which would make it an even better reducing system than plain conc. HI_(aq).

Lestat if you really want to play with toxic gases than I would recomend SO₂. If you introduce it into an appropriate mixture of I₂ and water you will get a concentrated mixture of HI and H₂SO₄. The sulphuric acid does not oxidase HI if it is dilluted enough. Less than 25% should do. Such a mixture should reduce ephedrine at a reflux temperature especialy if a further amount of SO₂ is introduced during the reflux to prevent the reverse reaction and to recycle the I₂ produced from the ephedrine reduction. At least in theory since I know of no such experiment.

SO₂ + I₂ + H₂O  <=>  H₂SO₄ + 2HI

SO₂ is much less toxic than PH₃ or H₂S and it is prepared practicaly OTC from any sulphite and hydrochloric acid. It is still quite dangerous for the the clumsy bees.

[stratosphere]

ahh, but the original poster was looking for a iodine free route.

one could avoid the danger of phosphine but still take avantage of a similiar chemistry and their access to metal phosphides(rat gasser?) by generating the trialkyl phosphane via AlP + Cl-R, perhaps even generating anhyd AlCl3 as a byproduct.
and then take advantage of the
chloroephedrine + R3P + alcohol-->meth +R3P0 + alkylchloride reduction scheme.