Oxone question + Lab Safety Rules

[SuperStar]

SWIM has a question. The following was taken from Chromic's writeup on Rhodium's site.  This is following the H2SO4 rearrangement.


Let it cool. Load it into a sep funnel and pour off as much of the more dense ketone as possible (both PMP2P and MDP2P are more dense than water). Now extract with 3x20ml DCM.


SWIM is confused. "pour off as much of the more dense ketone".  Now extract with DCM. Extract what?  Extract what is left in the sep funnel or what you just poured off into a beaker that has been reloaded into the sep funnel.  SWIM is over analyzing this and need someone to reword this step.


Pardon my friend officer, He's a little slow.

[riobard]

Hi,

What he means is that you will have a 2 phase liquid in your flask. the top is the aqueous layer, the bottom is dirty ketone. The ketone is more dense, that's why. You'll tap it off(drain it) until you only have the top aqueous layer in your funnel. Then you extract that layer with the DCM(pour in an aliquot[20ml] of dcm, shake, wait for separation, drain off bottom small layer of dcm/ketone, repeat 3 times).

Hope this helps. Remember that organic chemistry is a loose art when it comes to wording. Know your densities to know which layer is on the top or bottom in extractions. KNow what happens to your extracted product when you add base or acid. In short, pay attention, and learn your chemistry if you wish for sucess.

Good luck

[SuperStar]

So let SWIM make sure this is correct. Tap/drain off the densed MD2P2 into a beaker. Left with water layer in sep funnel. Now use DCM to extract the last little bit of MD2P2 from the water layer and combine with the original part you drained from the bottom in the first step.
Pardon my friend officer, He's a little slow.

[Rhodium]

Superstar: exactly.

[Chromic]

Rhodium, I think that particular sentence has confused 3 different people reading that write up. Would you care to replace the phase "pour off" with the phrase "drain off"? Thanks, and sorry about the confusion! I thought I made an alright technical writer... guess not!

[pickler]

Swim must admit, he actually got a little confused on this part himself. But once you do the synth and see everything you understand it. Trying to picture it in your head seems to mess swim up all the time.
We'll soon find out if I'm a chemist or not!

[cheeseboy]

Just how much MDP-2-P is able to be mixed in with the aqueous layer after tapping most of it off? Cheese always wondered about this, as MDP-2-P is NOT miscible with water so why even do the dcm extractions?
May De Sorce Bee Wit Chu-Always

[Chromic]

Chromic has wondered too, but does the DCM extractions anyways... they're necessary for the washing at the end, for sure...

[SuperStar]

Chromic,

What do you mean the DCM extracts are necessary for the washing at the end?  SWIM understand 2 times for DCM. Once for after the Oxone run. Once after the H2SO4 treatment.  Someone, cheese or pickler, where suggesting that skipping both of these would be possible, just reduce yeilds? Do you agree?
Pardon my friend officer, He's a little slow.

[SuperStar]

Update Chromic,

SWIM needed to reread.  Can't do the NaOH washes after the rearrangement without the DCM.  Okay so no skip on that one but how bad do you think yields would hurt if skipping the first DCM extract?  Seems like would save SWIM significant time since entire dist setup must be setup, cleaned, and stored each time (about 2hr process).
Pardon my friend officer, He's a little slow.

[Chromic]

I've cut back on the amount of DCM a # of times in working up the rxn (no difference in yields), but I've never cut it out... sorry, no info.

[Rhodium]

Chromic: I have mofified your writeup according to your suggestion.

Superstar: After the ketone is tapped off, it cannot be properly washed with NaOH solution without being diluted with the combined DCM washes. Also, I believe you will lose at least 5% of your ketone if you are not extracting the aqueous layer as it easily forms an emulsion/suspension in the water. The NaOH washes are VERY good for purification of the ketone, as it removes any phenolic impurities/decomposition products and prevents those impurities to affect your product further down the road...

[pickler]

Swim skips the dcm extracts from both. If you filter the oxone before adding the iso to the mix, when it's done mixing, all the epoxide is at the bottom. There might be a tiny amount left, but time is money for swim. So Swim would rather lose a little $$$ and be able to do more runs. Just a personal choice. Why couldn't you skip the last dcm extract. Washings cause no problems for swim.
We'll soon find out if I'm a chemist or not!

[Chromic]

Why not do multiple batches of epoxide, then process the epoxide to ketone all at once so you only do that step once?

[pickler]

That's exactly with swim does Chromic. Swim does 4 to 5 64gram batches and then does the h2so4 reflux. Much easier.
We'll soon find out if I'm a chemist or not!

[sYnThOmAtIc]

I thought that the epoxide wasn't supposed to sit for long or it would rearrange to the glycol shich is not convertable or some shit. Or maybe I'm confusing it with the mdp2pol mehtod where to p2pol rearranges to the 1p and is useless. Input anybody?

[pickler]

The epoxide can sit, for how long, swim doesn't know. When you do the h2so4 rearrangment, the epoxide get rearranged to ketone and the glycol gets dehydrated to epoxide then to ketone. Both get rearranged to ketone. Weather you have epoxide or the glycol has to do with the ph of the oxone/meoh ph. If it's near 7, then you get epoxide. If it's more acidic, the you get the glycol. Both will yield ketone with the h2so4 rearrangement. If your doing the thermal rearrangement, you need the epoxide for ketone.
We'll soon find out if I'm a chemist or not!

[goiterjoe]

Would there be any advantage to using sodium percarbonate to buffer the oxone instead of bicarbonate?  Percarbonate releases the carbon dioxide at a MUCH slower rate than bicarbonate does, and it also might provide a means to recreate the persulfate, as sodium percarbonate has been used for creating other peracids.

[Vibrating_Lights]

How would one calculate the ammount of newly formed peracid ,by the percarbonate,  to be used in relation to alkene. do you have any links for creating peracids from percarbonate?
VL_

[goiterjoe]

most of the references I found for using percarbonates for forming epoxides used a different oxidizer as well, and the sources they listed as having success with just percarbonate were either Japanese or Brazilian journals that I couldn't find online or at school.  I would say to calculate the amount of sodium percarbonate needed to buffer the oxone, and not worry about the peroxide calculations.  this would add excess H2O2 to the reaction, but I don't think it would degrade the alkene.