Author Topic: Buffered performic end yields  (Read 3836 times)

0 Members and 1 Guest are viewing this topic.

biffman

  • Guest
Buffered performic end yields
« on: June 30, 2004, 06:56:00 AM »
Obviously the buffered performic method is preferable to the regular performic for a variety of reasons but has anyone noticed a decreased yield of the final aminated product when using the buffered ketone preparation method as opposed to the  regular performic ketone prep?
  Swim has noticed a consistent decrease in product yield with the buffered.  Sometimes wildly so but the main thing is it is inconsistant with each ketone batch.
  I have noticed by a few posters that they have used up to double the amount of NaHCO3 than what is on Rhodium's site.
  What would be the result of using too much NaHCO3 in the final product?  Any thoughts or experience anyone?

Rhodium

  • Guest
How's your ketone distillation technique?
« Reply #1 on: June 30, 2004, 07:26:00 AM »
If you are noticing a difference, you haven't distilled the MDP2P properly (i.e. doing it slowly and only collecting product within a narrow bp interval).

The buffered performic reaction is likely to yield some isosafrole epoxide in addition to the usual isosafrole glycol formates. In the acid rearrangement the epoxide is hydrolyzed to the plain glycol which rearranges to MDP2P a bit more sluggishly than the glycol formate esters, so you may have to increase the reaction time with 50% or so. A lot of the high-boiling residue you get when distilling your MDP2P will consist of isosafrole glycol (and its esters) so by subjecting it to another acid reflux will probably milk some more MDP2P from it.


biffman

  • Guest
bp range for fraction collection of ketone
« Reply #2 on: June 30, 2004, 08:36:00 AM »
Good info Rhodium thanks. 
That has always been a question in my head about the wide temperature range that the ketone appears to come over at and where should one stop collecting.
  In retrospect it was noticed that for the first time after the acid reflux almost all the dark ether extractable layer was at the top rather than the bottom as it usually is.  This seems to fit in with your possible explanation.
  Perhaps it should have been refluxed over night rather than for just 2-3 hours.  Still this has not been required in previous buffered production methods.
  Any thoughts on the amount of HaHCO3 used initially?
  I am loath to go back to dreaming about the classical performic method and am uncertain about future essential oil sourcing to start dreaming R&D with the Wacker method.
   Your suggestions have helped.  Many thanks.

Rhodium

  • Guest
There is no need to overdo either...
« Reply #3 on: June 30, 2004, 10:41:00 AM »
Perhaps it should have been refluxed over night rather than for just 2-3 hours.  Still this has not been required in previous buffered production methods.

Overnight reflux is definitely overkill and is likely to harm the formed MDP2P, leading to lower yields. Do not exceed 4-5 hours at the most! The optimum time is likely to be between 3-4 hours.

Any thoughts on the amount of HaHCO3 used initially?

Using more bicarbonate than indicated will simply lead to the buffer solution having a higher pH. I don't know how much the pH will change, or if it ends up outside the optimal range or not. If it does, the result would be a slower oxidation - but if you allow the reaction to progress for a full 16 hours as per the directions this should not be a huge issue.


Panoramix

  • Guest
Rxn time
« Reply #4 on: July 03, 2004, 12:03:00 PM »
I remember an experience that yielded about 40-50 %, with 16 hours rxn time and 2 hours of reflux. Then rxn time was increased to 24 hours and 3 hours of reflux yielding repeated times the desired 70 %.

placebo

  • Guest
Too short hydrolysis seems to be the common...
« Reply #5 on: July 04, 2004, 07:08:00 AM »
Too short hydrolysis seems to be the common problem here. A longer hydrolysis will have a better effect on yeild then extending the time of the performic longer then 18 hours. 3 hours is good if you preheat the acid and then add the glycol. Run longer if scaling up and cutting back on acid.

SWIM recently hydrolysed 1kg of glycol with 3L of 15% Hcl in a 5L flask for 5 hours and got 78% yeild.

If you are really anal you can distill your MDP2P and then add whatever remains in the flask after MDP2P has distilled can be hydrolysed again.


Rhodium

  • Guest
High yield
« Reply #6 on: July 04, 2004, 11:05:00 AM »
SWIM recently hydrolysed 1kg of glycol with 3L of 15% Hcl in a 5L flask for 5 hours and got 78% yeild.

78% yield from isosafrole or from the glycol? Was it a crude mixture of glycol and hlycol esters or pure glycol?
Did you skip the methanol co-solvent during the hydrolysis, and if not - did you run the reaction at 70°C or at reflux?


endo1

  • Guest
solvent or just water
« Reply #7 on: July 04, 2004, 11:36:00 PM »

SWIM recently hydrolysed 1kg of glycol with 3L of 15% Hcl in a 5L flask for 5 hours and got 78% yeild.


Was methanol used?

abacus

  • Guest
yes but does it animate
« Reply #8 on: July 05, 2004, 01:28:00 AM »
As far as I am aware, we are still waiting for animation results from bees that used 15% HCL in the hydrolysis to get the MDP-2-P from the iso glycol instead of using H2SO4.

Maybe some one could step up and tell us if the resulting ketone works as usual, thereby giving bees confidence to replace the H2SO4 with HCL.

Abacus

placebo

  • Guest
Terribly sorry for the lack of details ...
« Reply #9 on: July 05, 2004, 02:19:00 AM »
Terribly sorry for the lack of details gentlemen.

SWIM was extremely happy with yeild considering the post performic mix mis not orange colour as supposed to be, not even brown, it was black. SWIM postulated that it was due to using 50% H2O2 (calculated to use a smaller amount) and not adding water to dilute it.
Rhodium;
Yeild was calculated by weight and is from iso->MDP2P. Glycol was not actually weighed, just assumed there was about 1kg from 1kg of iso. Methanol was not used, due to volume restrictions of the 5L flask. Acid was preheated to 80c (This allows time to play with heat settings until you know it will hold 80c for a given volume) and then the still luke warm (assumed) glycol added. it was then mag stirred on a heating mantle and held at 80c for the 5 hours.

abacus;
SWIM thought it was a forgone conclusion that the Hcl hydrolysis worked, so SWIM went with it.  As for amination, due to lack of experience (2nd time) it was split into several portions/reactions. Following Os's writeup on Rhod's page, first portion yeilded about 50%, second portion yeilded 95+%, third portion yet to aminate. :)  So "works as usual", SWIM wouldn't know, but it sure works! Yes, it was tested!


Rhodium

  • Guest
molar yields
« Reply #10 on: July 05, 2004, 06:57:00 AM »
Yeild was calculated by weight and is from iso->MDP2P.

If so, then that 78% yield is rather a 71% molar yield. Please always indicate if you haven't calculated molar yields, but rather use the less descriptive "weight yields".


ranxerox

  • Guest
All in a 5L flask?
« Reply #11 on: July 10, 2004, 04:35:00 PM »

SWIM recently hydrolysed 1kg of glycol with 3L of 15% Hcl in a 5L flask for 5 hours and got 78% yeild.




Did you start with 1L of iso? And did you run the performic in a 5L flask as well? I thought the most you could hope for in a 5L flask was 750ml of iso, as per baal and labtop.

If you have the time, how about a complete writeup placebo?


placebo

  • Guest
Yes, SWIM started with 1kg of iso, it was...
« Reply #12 on: July 11, 2004, 06:24:00 AM »
Yes, SWIM started with 1kg of iso, it was split into 2x 500gm for the performic and run in a 3L flask with overhead stirring and no condensor. After addition was completed in about 2 hours, it was then swapped to the 5L flask and magstirred for 18 hours (total). Once flasks were changed then the second lot of 500gm was started with the overhead stirrer. So in 20 hours 1kg iso was processed.

A writeup would be presumptious at this stage. SWIM has only done this a few times. The other factor is, this shit is easy and more then enough has been written already. All SWIM did was follow the tried and true write-ups of Labtop and then tinker a little for efficiency and scaling.


icexool

  • Guest
What about getting the exess performic acid...
« Reply #13 on: July 15, 2004, 03:13:00 PM »
What about getting the exess performic acid out.
It seems to be a tedious work and only works under vacuum distilation.


It is also very tedious to remove all the excess formic acid by vacuum distillation (it cannot be distilled at ordinary pressure, or there is a risk of decomposition).




endo1

  • Guest
--"What about getting the exess performic
« Reply #14 on: July 16, 2004, 01:38:00 PM »
--"What about getting the exess performic acid out.
--It seems to be a tedious work and only works under vacuum distilation."


In the buffered performic, most of the performic acid remains in the water and is sepperated off. Most of the dcm can be distilled at atm and then the resulting syrup can be used in the next step. If a clean product is needed for storage or otherwise then the residual formic acid can be neutralized with a sodium bicarbonate wash before distilling. Not tediuos at all.

icexool

  • Guest
What did you use as a buffer in your performic
« Reply #15 on: July 21, 2004, 08:50:00 AM »
What did you use as a buffer in your performic acid?
Na2CO3? or NaOH or does it matter which one you use.
Since it is the best I've heard for peracetic acid to use sodiumacetate...

endo1

  • Guest
NaOH as buffer?
« Reply #16 on: July 22, 2004, 02:34:00 PM »
NaOH is not an option for a buffer in the performic as far as I know. Although NaOH is an option for the post wash (perhaps you are confused?). Typically Sodium carbonate/bicarbonate are used for a buffer.

moo

  • Guest
Check out your theory...
« Reply #17 on: July 22, 2004, 02:44:00 PM »
Check out your theory... you can't use a strong base or a strong acid as a buffer.


hypo

  • Guest
of course you can
« Reply #18 on: July 22, 2004, 02:54:00 PM »
somewhat unrelated, but:

weak acid + 50% strong base = weak acid:weak base 1:1  :)

but in this case i guess you want the CO2 pissing off.


baalchemist

  • Guest
With a little more reading one will learn that
« Reply #19 on: August 15, 2004, 09:15:00 AM »
With a little more reading one will learn that flooding the formic acid out w/H2O is the proper way of removal, neutralizing with a base causes unfavorable changes to it. Besides, its headed right back into an acidic environment for the final hydrolysis step so its pointless as well. The hydro. product is the one to wash with 5% bicarb/H2O. That will keep the acidity/high heat from extensively polymerizing your would be ketone during distillation.