11-26-01 04:15
No 240562
The purpose of this post is to clarify a few things.
1.which is the best method of addition. Swim has seen where iso/dcm are added to the flask first then the PerAcid Is dripped into that. But the methods on rhodiums page all show dripping the iso into the peracid.
Swim thinks that it might be better to add the Peracid last. With the Preacetic swim thinks 8 batches should be made as per LabTops performic method so that there will be fresh peracid. Any Input?
2. What will the PH be of a freshly prepared Peracetic solution; after exact predetermined H2SO4 neutralization.
3. Chromic mentioned a fully buffered RXN. are there no adverse side Rxns with a very basic enviroment. It is swims theory that this could speed reaction times. What would the best method of fully buffering be.
Swim purposes
Create a 2 phase system DCM/Iso & saturated solution of NaHCO3with the exact molar ammount of BiCarb to react with the AcOh that will be produced when the Peracid reacts. Peracetic acid is prepared 8 times in two hr incriments exactly 24Hrs before the planned addition. before the additions began the 2 Phase solution is brought to reflux under stirring.as soon as intial reflux is attained the heat is switched off and the additions would take place at a rate that would keep the Dcm in the condensor. stirring would be continued until the solution has returned to room temp and the PH is near neutral. Any Clarification to this proscess or better ideas for Ph Control are welcome.
(Hive Addict)
11-26-01 04:52
No 240575
>1.which is the best method of addition.
I definitely will be looking into this method, best idea is to check Organic Synthesis on their peracetic reaction which creates trans-stilbene epoxide (sic?).
>2. What will the PH be of a freshly prepared Peracetic solution; after exact predetermined
Just work out the stoichiometry and add excess sodium bicarbonate.
>3. Chromic mentioned a fully buffered RXN. are there no adverse side Rxns with a very basic enviroment.
It won't be very basic. It will be a mixture of sodium acetate, sodium bicarbonate and water. pKa of baking soda is like 8.3 in aqueous solution.
>It is swims theory that this could speed reaction times.
Neutral peracids do break down faster than acidic ones.
>any Clarification to this proscess or better ideas for Ph Control are welcome.
Research it, experiment, research, experiment... don't give up until you're hitting your head against a brick wall.
(Chief Bee)
11-26-01 09:27
No 240650
Vibrating: The addition sequence depends on what type of peracid reaction you are doing. The "Standard" method is to make the peracid and drip the isosafrole into that, while the "Modified Buffered" method makes a slurry of a carbonate in a solution of the isosafrole in DCM. I believe the addition methods are godd the way they are, depending on if you are doing a buffered reaction or not.