whats chem behind ketamine thermal rearrangement?

[miss_biggie]

I have heard through grapevine that industrial size batches are performed with ethyl benzoate as solvent and the hcl salt of the hydroxylimine.  The examples on rhodiums site use decalin and a long chained alkane (zealot).

Apparenlty it does not work with kerosene.. 

Performing the rearrang. with the imide salt seems to improve yeilds and decrease black tar.

Does the solvent need to be able to donate anything to assist the rearrangement?  Are ethyl benzoate and decalin special in any way that would assist with the rearrangement?   Are they "lewis acids"?  (excuse my chem-ignorance)

What might that mean about other solvents that might work for the rearrangement?

[Vaaguh]

The solvents you mentioned are not special in a way that they facilitate the rearangement. They are simply used because of their high boiling points.

The rearangement of the hydrochloride salt seems to cause less polymerization compared to the freebase, another advantage is that it doesnt tend to stick to the
sides of the flask/vessel as much as the hydrochloride salt during the rearangement.

[miss_biggie]

Not true, distilled kerosene does not work.   It doesn't matter how long it's held at the right temperature.  And it does solvate the imine.  There seems to be no good reason why it doesn't work, that's why I posted.

[Rhodium]

But "kerosene" isn't a pure compound. You never know what inhibiting substances are present in it.

[Vaaguh]

Not true, distilled kerosene does not work.   It doesn't matter how long it's held at the right temperature.  And it does solvate the imine.

Altough i do agree with Rhodium, could you clarify how you observe that the rearangement did not work?

Also the compound does not need to bee solvated for it to thermally rearange, in fact the ethyl benzoate does not dissolve the methylketimine.

[miss_biggie]

I observe by intravenous injection.  Plus the solubility and melting point of the imine easily distingushs it from the amine. 

The kerosene, which is distilled for the 180-200+ fraction, does not appear to react with the imine.  In the end you have a lot of polymerized imine.

So I would guess that either it hinders the reaction or does not posses some property which would facilitate the reaction.  Either way there must be some reason besides just temperature to explain it.  Yes, I know, the kerosene is a variable, but please don't let that stop anybody from speculating on what helps the rxn go in a different solvent.   

Starting from the free imine results in a lot of tarry imine but it does disolve right from the start.  Starting from the imine hcl gives maybe 10-20% if you are lucky and it does not disolve, maybe a little at higher temperatures but I think it's most likely a homogenized solution of melted salt.  That's trying it over a range of temperatures, stirring, times and solvent volumes.  It simply does not work.

So what other otc oils could be tried?  I was thinking synthetic bitter almond oil.   There must be other commonly available non-petro oils out there that have a bp > 180'?

[miss_biggie]

Excuse my chemignorance but wouldn't haven't extra hydrogens around, like with a lewis acid, which decalin and ethyl benzoate are (I think), help the O= loosen up??

http://www.meta-synthesis.com/webbook/13_lab-matrix/LAB_matrix.html

[Vaaguh]

I dont think that would make a difference, kerosene has quite some hydrogens around with those 10-14 carbon molecules.

btw did you inject the brown post mixture ?  

[Rhodium]

I was thinking synthetic bitter almond oilDon't. It consists of benzaldehyde, and it is not suitable for this reaction. You could however oxidize it to benzoic acid and esterify it with ethanol, and there you have ethyl benzoate, which is.

[Vaaguh]

the practical workup can be found in this post(also found in vogel):

Post 487721

(Vaaguh: "steps 5 to 10", Methods Discourse)

[k0dog]

My intial theory is because both decalin, and ethyl benzoate have pi bond in their rings structures.  These electrons could be used as temporary relief for the thermal rearrangement.

Now the use of undecane, dis proves this theory altho does undecane posses anything werid about it?