My dreams have involved a source of HI that only has a density of 1.62. 10 Litres are used for every 10 pounds of ephed. The yields are a consistent 50%. I will not post my whole procedure, as it has been posted many times by many other bees, and after several wacker oxidations, reductive aminations, and the like, this procedure is childs play.
Now it is clear to me that this acid needs to be dehydrated. The search engine has brought up many possibilities including:
1. Dehydrate the acid with dry HCL gas. This procedure works excellent for dehydrating hydrobromic acid for the conversion of safrole to bromosafrole, although some chlorosafrole is produced as a by-product. Since I have a cylinder of dry HCL gas for doing my crystallizing, this would be the most convenient if indeed it worked
2. Distilling the HI until the steam reaches 126C. This would work fine, although some HI would be lost in the first bit of distillate. It is also the slowest way to go
3. Adding GAA or a mix of hypophosphoric acid and iodine. Sounds interesting, but i don't have any of these right now. I could round up some GAA easy enough, but is it worth it?
So another thing I am wondering is if the use of this weaker acid, somewhere around 50% I gather, would result in the relatively poor yield? Or would it simply result in a higher concentration of by product in the end product? (iodoephedrine, unconverted ephedrine, etc)