07-24-02 20:29
No 336609
Some people had discussed around here not using the methanol during the H2SO4 rearrangent of glycols/epoxide. Well with 4 repeated trials it has been found that even when the temp is controled perfectly at 80.c ketone is not formed in any aminatable ammount. So we conclude that meOh is nescesary for the rearrangement.
Vl_
(Synaptic Self-Mutilator)
07-24-02 21:00
No 336619
Did you use magnetic stirring? What do you mean by "aminatable amount"? What oil was recovered? How did you isolate it?
I'm surprised that there would be any error in the chem abstracts reference. They used no methanol and got good results. In any case, I've always used methanol and would recommend it to everyone else. It works, doesn't cost much, allows you the convenience of running the reaction at reflus and doesn't increase the volume much.
(Hive Addict)
07-24-02 21:49
No 336644
Epoxide was made via Buffered oxone extracted with dcm (93% return of epoxide)15% H2SO4 in Shulagins ratios epoxide:Acid no methanol x3attempts distillation not done cause hotplate doesn't get that hot for an atm and vac adapter shattered recently. Amination gave no product. attempts with SHulagins epoxide:acid ratios with MeOHgave a final yeild of salt to alkene of 30% with no distillation of any intermediates. First they thought it was a switch to using EtOh for the amination that was causing the failure but when switching back to meOh the problem presisted at which point MeOh was used again for the H2SO4 rearrangement giving the final salt of 30%.
The tempature of the rearrangement was monitered internaly so as the liquid was a uniform 80*c
VL_
(Hive Addict)
07-24-02 21:52
No 336646
SWIM has not used methanol in their rearrangements and has been very disappointed in the performic results (even small scale runs to test procedure). unfortunately, there is no more formic acid around to test.
i learned a thing or two from charlie dontcha know.
(Chief Bee)
07-24-02 22:15
No 336654
I don't believe methanol specifically is needed for the reaction to work, the reason it is used is to provide a medium where both the acid and the ketone is soluble. As we all know, the reaction can work in anhydrous conditions using an acid soluble in toluene (tosic acid) too.
............
Solubility Chart - "O" means miscible
............MDP2P....H2SO4....Tosic Acid....MeOH..
Water..................O...........O.........O.. ..
Methanol......O........O...........O.........O.. ..
Toluene.......O....................O.........O.. ..
(Title on BackOrder)
07-25-02 00:38
No 336705
I've gotten piss poor results from not using methanol in the acid hydrolysis to produce ketone from epoxide. I believe the methanol is necessary to give the epoxide a way to interface with the acid. It's been a long time since I ran a unbuffered peracetic synthesis, but if I recall correctly, the methanol amounts weren't as critical for the hydrolysis of the glycol. The glycol appeared to be slightly more miscible with acidic water than an epoxide is. Personally, I don't know why anyone wouldn't want to add the small amount of methanol called for in the acid hydrolysis. It's not like you don't keep methanol around.
All paths are the same: they lead nowhere
(Synaptic Self-Mutilator)
07-25-02 01:42
No 336717
Rhodium, tosic acid is extremely soluble in water. (~0.7kg / L)
(Hive Addict)
07-25-02 03:20
No 336751
With all this in mind I guess we can say that yes the MeOh is nescesary.
VL_
(Bee without a Title)
07-25-02 03:55
No 336765
yes the MeOh is nescesary no, it definately is not for glycol.
(Hive Addict)
07-25-02 04:04
No 336769
Does the glycol not become the epoxide after the H2SO4 dehydrtes it? with out those hydrogens you got -O and -O that just aint happy cause their shells arent filled???????/
Vl_
(Synaptic Self-Mutilator)
07-25-02 04:10
No 336771
The glycol is most definitely not turned into the epoxide by H2SO4. Read up on the pinacol rearrangement.
(Hive Addict)
07-25-02 09:20
No 336865
ok, assuming you want to use MeOH, how much is needed? is it just a relatively fixed amount or a percentage of the sulphuric acid?
also, what temp would you run the hydrolysis? if you run it over ~65°C, then you need to use refluxing aparatus or lose the MeOH to evaporation. if you run it under ~65°C then does it still work? it was nice to be able to use a large stainless pot for those large rearrangements.
i learned a thing or two from charlie dontcha know.
(Hive Bee)
07-25-02 10:43
No 336892
If methanol is used for solubility with 15% h2so4 to interact cant a bee just use a solvent such as denatured alcohol? Would denatured alcohol work for the arrangement thing?
Thanks!
hcildoduedn
(Hive Bee)
07-25-02 19:34
No 336975
Why not just use MeOh? It cheap and otc. Why bother with denatured? There can sometimes be other junk in otc denatured.
The above post is purely fictional. Any resemblance to "real-life" is purely coincidental.
(Chief Bee)
07-26-02 08:02
No 337273
Chromic: Thanks for correcting me, and I have changed the chart accordingly. It does not change the point I was trying to make though.
(Synaptic Self-Mutilator)
07-26-02 18:54
No 337413
>ok, assuming you want to use MeOH, how much is needed?
These are the magic ratios I use (from Shulgin, I think):
glycol from 100mmol reaction (ie after extracting with DCM from a 16.2g isosafrole run)
25ml MeOH
120g 15% H2SO4 (18g H2SO4, 102g water)
Bring to a reflux, then hold for just over two hours with stirring. Cool, extract with DCM (3x20ml) and wash three times with 60ml of 5% NaOH. You can use up to 40ml of DCM for each extraction, but I've found it's not really needed.
>also, what temp would you run the hydrolysis?
At reflux (ie keep it boiling). I think it's about 80C.
>you need to use refluxing aparatus or lose the MeOH to evaporation.
>if you run it under ~65°C then does it still work?
Yes & who knows... why do it that way?
>it was nice to be able to use a large stainless pot for those large rearrangements
Without methanol, for this reaction to have any chance, you would need a lot of stirring. How did you stir through stainless steel?
(Hive Addict)
07-26-02 20:25
No 337426
> How did you stir through stainless steel?
with a 3" stir bar and lots of patience. it took a bit to get a good stir going, but was possible.
> >if you run it under ~65°C then does it still work?
> Yes & who knows... why do it that way?
if you're using MeOH not using a reflux aparatus, then you need to keep the temp low. but i realize this isn't the way you would do things, but if you're using ghetto-ware (like corning-ware, but different), then you want to keep this in mind, and keep adding MeOH.
i learned a thing or two from charlie dontcha know.
(Bee without a Title)
07-26-02 20:27
No 337427
How did you stir through stainless steel?
overhead stirring
(Hive Addict)
07-26-02 20:53
No 337431
coulda used that, too. there are a couple kicking around here, but they need shafts and paddles and proper stands an clamps. just be sure to cut a small opening in the lid of the pot for the shaft. using the pot lid is like a reflux condenser, keeping a lot of vapour in.
i learned a thing or two from charlie dontcha know.
(Hive Bee)
07-27-02 22:51
No 337812
different stainless alloys have differing magnetic properties- UTFGoogle.
the wall thickness too will influence flux penetration. not to mention the size of magnet, the size of the stir bar.
in fact there is ss that is quite magnetic. not good for spinning bees.....
OTEECEE & meeeee!!!!