My last MBRP Post, The easiest way!!!!

[SHORTY]

ADDkid, would you also suggest boiling the iodine made from tincture in water to remove any hcl present?  Earlier you said you have never tried this and now a few hours later you have tried both ways?

I know that hcl didn't hinder my rp rxns because i have done several with rp that had not been exposed to hcl as well as several in which the rp had been boiled in it.  There was no difference in either yeild nor quality.

[ADDkid]

Swig will respond..

This is what swig has concluded:

1.  Hydrobromic could be used, and using HBr would happen so fast, or with little heat.  The reaction follows the Sn1 mechanism.  The risk of cation rearrangements is very possible. However, a benylic cation is the most stable cation in the reaction, and the product will and should precede smoothly.  Problem:  Will HBr be a strong enough to reduce to methamphetamine?  Maybe, some of it, and even more if Phosphorus is present.
2:  Theory suggest that HI on the Phosphorus will not hinder reaction, but practice suggest otherwise in my opinion.  However HCL will hinder the reaction, and since there is no way to tell exactly how much HCl you have, only a fool would start a reaction with acidic Phosphorus.  ADDkid

[Rhodium]

Problem:  Will HBr be a strong enough to reduce to methamphetamine?  Maybe, some of it, and even more if Phosphorus is present.

HBr isn't a reducing agent.

[geezmeister]

How do you know that [HCl] did not hinder you[r] reaction[?]  Your yields might have been better if the HCl was not present on the RP.  There is know way to know.

If a little HCl was a hindrance to the HI reduction, one should find that pseudo HCl did not react as well as freebase pseudo does. For a time I was of the opinion that since the freebase pseudo would become pseudo HI in an HI environment, and since HI would not be an impediment to the HI reduction, the absence of the HCl must explain why I obtained higher yields with freebase pseudo than I did with pseudo HCl. I kept that opinon for the better part of a year, until a new extraction technique resulted in really clean pseudo HCl from the pills used as the source. With the long wet red phosphorous reflux, and again with the phosphorous acid reflux I obtained yields using HCl as good as those I achieved with the freebase. This experience convinced me that it was the cleanliness of the pseudoephedrine that made the difference in yields, not whether the freebase or salt form was used. The molar yield was virtually the same with either the freebase or the salt form.

That suggests to me that HCl is not an impediment to the HI reduction. (Then again, this observation might mean nothing to this debate. I don't know, I am just providing fodder from my experience for the chemistry-educated to discuss.)

[Nicodem]

The following is slightly off topic and might have already been written before, but since meth cooking isn’t really my field of interests I leave these thoughts for others to chew on.
I don’t know much about the reduction of ephedrine with P and HI but in the school we were taught that the HI reduces some R-OH in R-H by the following reaction scheme:

R-OH + HI ---> R-I +H₂O
R-I + HI ---> R-H + I₂

While the phosphorus reacts with I₂:

2 P + 3 I₂ ---> 2 PI₃

and PI₃ also reacts with the R-OH (as well as with water: R=H):

3 R-OH + PI₃ ---> 3 R-I + H₃PO₃

H₃PO₃ can also react with I₂ in the presence of water:

H₃PO₃ + I₂ + H₂O---> H₃PO₄ + 2 HI

Therefore the function of phosphorous is to shift the equilibrium of the first two reactions by removing iodine and recycling it into hydroiodic acid. At least in theory phosphorus could be exchanged with other acid stable reducents capable of performing the following (formal) reaction:

I₂ + H₃O + 2 e^- ---> 2 HI + O^2-

Though there might be many other reactions to speed up with catalytic effects (?) like:

R-I + H₃PO₃ --->[ R-P⁺(OH)₃ + I^- ]--( + H2O )--> R-H + H₃PO₄ + HI

It is obvious that phosphorous (and hypophosphoric acid) is just ideal, but other less efficacious reducents might perform satisfactorily. For example, the following ones come to my mind: SO₂, H₂S, colloidal S₈, copper (Cu) powder, organic (III) phosphates like Ph₃P, phosphine (PH₃), orthophsphoric acid (H₃PO₃) and compounds decomposing into it in the presence of water (PCl₃, P₂O₃ etc.), SnCl₂ and some others. But note that many are very poisonous gasses (H₂S and PH₃) others just a little less (SO₂) not to mention that they have to be generated and bubbled into the reaction mixture.

[Organikum]

ADDkid:
In the old days when HI reductions were common in industry, what was more than a hundred years ago, hydrochloric acid was used as solvent in those reactions. The need for pressure vessels and the corrosive nature of HCl and HI in addition to the availability of other starting materials caused that these reactions where replaced by other ways.

Solvents useful in HI reductions are:
- conc. HCl
- conc. HI
- conc. acetic acid
- conc. phosphoric acid (85%+ concentration)

In the old days fuming HI was the medium of choice, followed by HCl. GAA and H3PO4 where not cheaply available then.

The reaction as preferred here on this board - the "long wet reflux" uses HI as solvent, produced in the reaction "in situ". For reasons I dont know H3PO4 - phosphoric acid is rarly used although in certain parts of the world its use as solvent is quite common and it works very well and it has advantages. It is to be preferred over acetic acid because it lacks the obnoxious smell has an higher bp and is available OTC and easily concentrated so need arises.

Nicodem, I dont understand the copper-powder named by you. I know it is possible to use copper to scavenge free iodine from discolored HI solutions though. Can you enlighten me?  


PI3 under mainly anhydrous conditions halogenates alcohols faster, at lower temperatures and more completely than HI does for HI halogenation is an equilibrium reaction, PI3 halogenation is not. In the HI halogenation the equilibrium is shifted by the followup HI reduction of the formed iodoephedrine. This says that rather high temperatures and time is needed. All the time HI concentration has to be kept high.

The "long wet reflux" is a good and practical answer. It might be improved by the addition of some phosphoric acid after my best of knowledge. As long the concentration of the H3PO4 is over 85% the amount of acid is not very critical.

Other answers would be, either the use of PI3 (produced beforehand or in situ) under anhydrous conditions followed by the addition of some aqueous HI, or the use of fuming HI in a pressure vessel. This is not so practical at least the fuming HI under pressure isnt.  

ORG