In theory the C10H15N molecule is the same in products for both rxns. Does the polarity differ assuming all reacants go to product?



(sorry about the previous thread with incorrect question, stoned when I wrote it)

Takes hand out of pants

looks at hand and sees virulent sexually transmitted rash caught from chooks

[This message has been edited by kirby (edited 11-17-2003).]

Good question.

SWIM knows for sure, although rp/I2 method is supposed to be stereospecific, it is often not. Some of the isomer gets rotated into levo position.

With the birch reduction being so quick and effective, SWIM would think it would be more stereospecific, as the shit usually gets reduced very quickly and the reaction is quenched before much harm can be done.

If you are starting with optically pure ephedrine(you most likely are) you will end up with optically pure product, that is on;y one isomer. There is no racemization in either reduction, it just doesn't happen.

and leave them chooks alone

Yes it does tryp. Beleive it or not. Like when you expose levo isomers to solutions of KOH, they tend to become racemic (I said that to prove my point that it does happen). There could be and definitely is a number of things going on in a rxn like rp/I2 that could cause optical rotation. That was learned from an organic chemistry textbook, not speculation.

Oh yeah, and by racemic I don't mean it'll come out of a HI reduction 50/50 like from a ketone. I meant there is an amount (even if it is a trace amount) that does optically rotate.

I don't know any textbooks used the HI reduction of pseudoephedrine to illustrate any points. In fact I can't think of any point that could be illustrated by putting that in a textbook.

There is no plausible mechanism that would lead to isomerization. Bottom line it doesn't happen, and I'm not speculating either.

Dammit you knew what I meant. I didn't say the book said anything about HI or meth. But it talks about isomerization of chiral compounds, which is done very easily.

Example:

It is a patented process (I beleive it's in one of Hoffmanns/Stolls patents, I'll check references (which I have buried somewhere) and get back to you) that the l-LSD and d-LSD is separated in the column during purification.

Then it talks about dissolving the l-LSD into methanolic KOH solution and letting sit for some time. It cites that this causes isomerization and forms racemic LSD, which is ran through the column again to separate the d-LSD.

That is a perfect example of isomerization. Now I have no idea of the criteria required to isomerize methamphetamine, but the fact of the matter is isomerization does happen and can happen with any reduction method whether it happens during reaction or workup or whatever. It happens, period. Anybody who knows anything about chirality knows this. Go back to school.

You can isomerize some double bonds under some conditions (ie basic reflux) but this is always a positional isomerization and can never mess with tetrahedral chiral centers. The position reduced in an HI reflux is a carbon away from the chiral center so it isn't touched.