11-26-03 16:17
No 473357
OK,
So if theoretically one wanted to do a thermal rearrangement but didn't have th correct high boiling point solvent, and decided to uses an alternative (ultrasene). What temperature should one use to acheive maximum yeild?
I know in the patent (see below) that they use Decalin and it's bp is 195.8'C (cis) or 187.3 (trans) and heat it to 180'C. So what should I do if the bp of my ultrasene is much higher (around 175-325????). I have done the heating till around 180'C but am not sure if I should continue to much higher because techniquily that is not a reflux.. right?
the patenet is:
Patent PAtentUS3254124
"Vanity is defintely my favourite sin"
-Devil's advocate
(Hive Bee)
11-26-03 18:43
No 473389
First of all, I don't know anything about Decalin. But shouldn't the trans boiling point be higher than the cis boiling point? It makes sense to me that a trans isomer will be more stable than a cis, resulting in a higher boiling point.
Anyways, a reflux is when you have a reaction mixture that you heat in a flask with a condenser attached (coolant flowing through the condenser). Then you heat up the material to boiling, but you don't lose any reagents because the condenser condenses the vapors and returns the liquid to the flask (I'm sure you already knew that though). My point is that you aren't refluxing unless you are evaporating reaction mixture and then condensing the vapors back into the flask. If you're heating reagents, but they aren't boiling, all you're doing is heating, and I'm willing to bet you aren't getting any thermal rearrangement.
I just tried to access your patent link, but it wouldn't let me, so I can't read the details. I think they use Decalin because it's a good solvent to use for what they want to do. (i.e., it dissolves what they want to dissolve without interfering with the reaction itself). Maybe you should look for a solvent with the same properties as decalin (is it polar? aprotic? close boiling point? is the solvent donating something in the reaction?).
D.A.R.E. = Drugs Are Really Exciting
(Hive Bee)
11-26-03 19:59
No 473398
Wellyour right.. I know that refluxing is.. but the thing is that the ultrasene is only the solvent.. the actual material that I am rearranging is a ketamine precusor... and that has a bp.. of... I dunno.. like... under 180 sicne it did that in the patent.. I jsut am wondering to increase the yeilds.. should the solvenet also be near refluxing?
since bp is whatever I menitioned before... anywyas..thanks.. I dunno... what else to say...
but the bp are correct check this link...
../rhodium/pdf /chemical-data
anways maybe my patent location is wrong 1 sec...
Patent US3254124
now patent works...
"Vanity is defintely my favourite sin"
-Devil's advocate
(Newbee)
11-27-03 05:30
No 473464
If you have a solvent that has a higher boiling point i suggest you heat it to 180 Celcius at that temperature the rearangement will occur, aside from the fact that your solvent is boiling or not at that temperature.
The decalin (decahydronaphtalene) normally comes as a mixture of cis and trans and has a boiling point of 187 Deg Celcius
The only problem in the case of the hydroxilimide is the fact that you would have to evaporate the higher boiling solvent under a decent vacuum, as solvent-solvent extraction using dilute hcl is very prone to give you nasty solids in the funnel and spotting where the 2 layers separate is rather hard due to the near black solution.
Hippler