Vibrating_Lights (Hive Addict)
05-13-02 15:32
No 307930
      one pot alkene->ketone idea  Bookmark   

Swim was wondering if it would be possible to rearrange an epoxide to a ketone without first isolating the epoxide. this is how swim thought it might go.
Mix alkene and small ammount of EtOH begin stirring.
in another vessel the buffered oxone solution oxone solution is prepared.  The oxone solution is then added to the stirring alkene through a filter funnel. Swim thinks this will improve stirability.  Any ways.
When the rxn is completed the Ph would be checked and adjusted to 7 as needed. Now could swim calculate a 15%sulferic acid solution by the ammount of h2O used in the epoxidation and add 98% directly to the post rxn mix. begin heating rigged for distillation. collecting the etoh as the epoxide gets rearranged. Since there are only sulfate salts in the peracid solution any way then why bother to isolate the epoxide at all.
Can anyone think of why this would not work????
Would it be better to first distill off the alcohol then rig for reflux.  Swim has noticed that when alcohol is not present or in low concentration, ketone/epoxide can be detected escaping through the air condensor.  which leads swim to another question after said isomerization took place could the rxn first be neutralized with bicarb then the ketone steam distilled out. Can MdP2P be steam distilled? As a side note to that swim wanted to do the rearrangement in a semi-open top vessel would ketone/epoxide be lost with escaping steam.
VL_
 
 
 
 
    psychokitty
()
05-13-02 22:14
No 308070
      >Swim was wondering if it would be possible to ...  Bookmark   

>Swim was wondering if it would be possible to rearrange an epoxide to a ketone without first isolating the epoxide.

Very possible, I would think.

>this is how swim thought it might go.
Mix alkene and small ammount of EtOH begin stirring.
in another vessel the buffered oxone solution oxone solution is prepared. 

Waiting until the popping and fizzing is over is best to minimize the "volcano effect".

>The oxone solution is then added to the stirring alkene through a filter funnel. Swim thinks this will improve stirability.  Any ways.

To remove what? The precipitation of potassium bisulfate forms when the alcohol is added.  In your scheme what will be added is water and dissolved oxone.  This step seems pointless unless you have added the alcohol to a water/oxone mixture whereby the potassium bisulfate will have already precipitated (then it can possibly be filtered to advantage).

>When the rxn is completed the Ph would be checked and adjusted to 7 as needed.

For epoxidation, yes.

>Now could swim calculate a 15%sulferic acid solution by the ammount of h2O used in the epoxidation and add 98% directly to the post rxn mix. begin heating rigged for distillation. collecting the etoh as the epoxide gets rearranged.

A prudent approach is to make sure all of the oxone is spent.  If the solution was buffered from the get-go, this shouldn't be a problem. Acidifying the solution with sulfuric acid will neutralize the bicarbonate yielding a mixture of potassium and sodium bisulfate and sulfate salts in molar proportions that will have to be calculated.

Also, it is a myth that spent oxone/alcohol/various acid sulfate salts/epoxide or glycol mixtures will explode if distilled at atmospheric pressure.

>Since there are only sulfate salts in the peracid solution any way then why bother to isolate the epoxide at all.

My view exactly.

>Can anyone think of why this would not work????

I think it will.

>Would it be better to first distill off the alcohol then rig for reflux. 

Probably.  The alcohol would take forever to distill at atmospheric pressure.  Utilizing vac distillation will remove the alcohol faster to get the solution to a more "epoxide rearrangement-friendly" state in that there will be a greater proportion of acid solution to alcohol solvent. 

>Swim has noticed that when alcohol is not present or in low concentration, ketone/epoxide can be detected escaping through the air condensor.  which leads swim to another question after said isomerization took place could the rxn first be neutralized with bicarb then the ketone steam distilled out. Can MdP2P be steam distilled?

I have read that ketones can be steam distilled out of such aqueous acid solutions.  About MD-P2P, I have never seen an example given in the literature but I'm sure there is one somewhere.

>As a side note to that swim wanted to do the rearrangement in a semi-open top vessel would ketone/epoxide be lost with escaping steam.

Use of a reflux might be best.  Theorectically speaking, however, yes, quite possibly ketone could be escaping with the steam.  If no reflux is to be used, then stirring with a water bath or other suitable source of heat below the bp of the water/acid/alcohol mixture may be in order.
 
 
 
 
    zed
(Hive Bee)
05-14-02 00:03
No 308127
      Steam distillation  Bookmark   

The MethyleneDioxy ring might not withstand boiling in acid solution. I believe that the ketone might be steam distilled, from a neutral solution; though it could take a quite a while.

Straight P2P takes a while, and as I recall, MDP2P has a much higher BP..... At ~100C the percentage of vapor pressure it will exert, won't be overwhelming. Still, Heinzelman steam distils o-methoxy-P2P in his Methoxyphenamine synthesis.

Why not MDP2P? It might work, but expect to distill over an impressive amount of water, for each Oz. of MDP2P that comes over.
 
 
 
 
    Chromic
(Hive Addict)
05-14-02 00:13
No 308131
      Problems
(Rated as: Good Explanation)
 Bookmark   

The major problem is the ridiculous amount of sulfuric is needed to get the concentration to 15% H2SO4. Run the reaction as listed, or go to another peracid technique like the peracetic or performic. You'll like them better than the oxone method.

Yes, MDP2P can be steam distilled but you're far better off distilling it under vacuum. I've used steam distillation before, and you need a large volume of water to get the MDP2P to come across and the separation isn't all that great (I remember something like 25-100ml/1g or something like that). Do the Raoult's Law calculations with MDP2P:

Bp is 283
Use the nomograph to estimate the vapor pressure at 100C: 1 torr
So at 760 torr... Ph2o + Pmdp2p = Patm = 760 torr. So 759 mol of H2O will distill over for every 1 mol MDP2P.

That's 13677g of h2o 178g MDP2P... or 77mL of water (you should use 100ml to be safe) for every gram of MDP2P you make.

Steam distillation is likely not the way you want to do it. There's also immense cooling needs for distilling water, so it requires cold tap water to cool the distillate (can't use a recirculating pump to do it)
 
 
 
 
    Vibrating_Lights
(Hive Addict)
05-14-02 01:36
No 308167
      Epoxidation temps.  Bookmark   

What is the deal with the epoxidation temps.  the refs for all peracid type rxns say to keep it around 40.  Sometimes with MeOH as the solvent it seems to climb as high as 53. or so.  Lower yeilds came with the higher temps.  It seams that the slower the stirring the hotter the rxn gets.  Perhaps 1/10 solvent volume of dcm could be added and run the epoxidation with an ice water reflux condensor?   Also the dupont data page states that higher availably Oxygen% can be attained with incresed tempatures.  Could it be possible to make the oxone solution  more concentrate by adding the oxone to boiling MeOH/H2Othen add the bicarb followed by rapid cooling  and filter during the addition into stirring Alkene. really wondering about the excess heat/DCM thing.  Also if the stirring goes out of wack and the sediment settles to the bottom there seems to be a higher concentration heat at the bottom near the sediment.  Would this be the rxn occuring at the bottom as the alkene settles or might it have something to do with the sediment. HOw important is the heat in other peracid rxns.  It seems like all the procedures call for the mix to be kept under 40.c or so.  Any one have experiences with excess heat build up and, besides the unfortunate volcano, how it affected yeilds.  any ways DCM wouldn't hurt to have in there anyways would it?
-------------
Sorry so jumbled just scheming on some shit seems productive anyways.
VL_
 
 
 
 
    zed
(Hive Bee)
05-14-02 14:10
No 308350
      Oxidation.  Bookmark   

The decision not to isolate the epoxide is probably a good one. Generally speaking, such materials are excellent carcinogens.

Usually, reaction temps. are carefully controlled during oxidations, to keep the oxidant from completely shredding the substrate. I'm not familiar with oxone, but boiling MeOH plus oxone, might be a very expensive way to produce formaldehyde/formic acid.

 
 
 
 
    psychokitty
()
05-14-02 18:50
No 308408
      Notes from old e-mail . . .  Bookmark   

Here are some notes (e-mailed to me from someone who wishes to remain anonymous) that have been in my files for seven months or so:

"Distillation of the spent oxone reaction (acidic for glycol) at atmopheric pressure leaves in the distilling flask a dark red aqueous mixture with a considerable amount of reddish solid by-products floating about--artifacts, no doubt of an over-oxidation.  The receiving flask provides a mixture of methanol and a sweet pleasant smelling water-soluble (or miscible) transparant liquid, probably the product of a reaction between excess oxone and methanol.  The distillation takes forever.  At reduced pressure, the methanol is distilled with ease at no expense to the final glycol product (presumably).

"Repeated trials above 400 mmol of substrate using standard equivalents of reagent materials with both methanol and ethanol as solvents yield ROUTINELY and REPEATEDLY anywhere from 45-55% of desired glycol (perhaps scaled-up buffered epoxide reactions will provide greater yields).  Either isoalkene is not good (not likely) or the consistent temp of 38-39 C is too high.  Possibly, cooling might help in the initial phase until room temp is achieved through the melting of a surrounding ice bath (as per classic peroxidation methods).  DCM, IMHO, would only add to the problem of solubility.  Reduced alcohol solvent volumes below 50% have yielded starting isoalkene only and possibly a minor amount of glycol."

Hope this is helpful.
 
 
 
 
    Vibrating_Lights
(Hive Addict)
05-18-02 21:08
No 310430
      solubilities  Bookmark   

I don't think the solubilities matter worth a shit in these types of reactions. It is all about the stirring speed.  an oxone epoxidation is pretty much a standard peracid rxn.  the only difference is that the peracid has been made into a salt.  In a buffered performic with dcm the excess formic acid(which could act as a solvent)is neutralized to sodium formate by the buffer so what is incresing the solubility there?  Is there a way to isolate the monopersulfate from the triple salt formula?
 
 
 
 
    Chromic
(Hive Addict)
05-18-02 22:37
No 310455
      acidic oxone rxns  Bookmark   

I wanted to repeat in this thread that I've never gotten the acidic oxone rxn to work (in good yields). I don't think it has the oxidizing power that the buffered oxone method has (and the JOC reference agrees with my observations). The sodium bicarbonate does something to accelerate the breakdown of sodium persulfate that reacts with the alkene. Use the buffering!

Btw, if you are unsatisfied with the solvent volumes, SWITCH TECHNIQUES! Why is everyone so afraid of ordering some glacial acetic acid or formic acid and going to a hydroponics store or pool store to buy hydrogen peroxide? Really! It's that easy!

There are better methods. I don't run the oxone oxidation rxns any more, and that's for a good reason!
 
 
 
 
    Vibrating_Lights
(Hive Addict)
05-19-02 06:04
No 310592
      oxone project  Bookmark   

This shit is just one of swims projects.  The scalability of the oxone rxn seems to be a problem.  Swim has done a peracetic, Mdp2np->ketone and a wacker.  They all work and they all just entail watching a pot stirr but there is a challenge with this oxone shit. A problem to be solved.
VL_
 
 
 
 
    psychokitty
()
05-19-02 22:32
No 310912
      Solubility a major issue  Bookmark   

Solubility is an issue and more than likely DCM will not work even if stirring is efficient.  Reduced methanol or ethanol below 50% of the recommended amount yields practically no glycol at all.  If solubility were not an issue, then these reactions in question would have worked.  Besides, simply using the isoalkene in this reaction without the use of a solvent has yielded zip, regardles of stirring speed (heat seems to help a bit though) which implies, again, that solubility is a major issue.
 
 
 
 
    Vibrating_Lights
(Hive Addict)
05-20-02 13:26
No 311270
      Heat might be a contributing factor in the fact ...  Bookmark   

Heat might be a contributing factor in the fact that it would allow a higher available oxygen...but.  any time it gets hot it chews up the shit.  perhaps instead of using 2 moles of oxone per mole of alkene  a 1:1 ratio could be used employing 1/2 volume of H2O and a solvent that would keep the temp around 40 taking advantage of the higher available oxygen making the rxn more volumetricly efficent.  the oxone solution could be preheated and added to alkene/solvent as the Oxygen is consumed.

How would acetic acid fair as a solvent.  Does any one have solubility info for oxone in a 75% AA .  then the oxidising solution woould almost be a solent as well.  and any excess O might possibly begin to form a peracetic.  swim thinks that AA could hold alot more oxone than just water.

VL_
 
 
 
 
    psychokitty
()
05-20-02 18:37
No 311335
      Acetic acid might work  Bookmark   

According to the literature, acetic acid has been used to advantage as a general solvent in the oxone reaction.