02-09-02 19:28
No 267601
Would adding brine to a post oxone rxn mix provide a quicker migration of the epoxide into the dcm/ So basicly is the epoxide less soluble in a solution with more dissolved salts. Swim has been having to use alot of solvent to extract a little oil.
VL_
sorry for the basic question but the brain is working slow.
(Hive Addict)
02-09-02 19:58
No 267609
The solution is already saturated with K2SO4...
(Hive Bee)
02-09-02 21:30
No 267629
Noj had mentioned filtering the solids out prior to the reaction. Are all of the active persulfate(KSO5) and base dissolved in the H20 whereas only the inactive salts(KSO4) are precipitated out by the methanol? Swim was thinking about trying it out, to stirr more affectivly and easier final extraction. will swim lose any of the available oxygen in solution.
VL_
(Hive Addict)
02-09-02 22:07
No 267631
SWIM just gravity filters and washes with methanol, then combines everything (solution goes cloudy as more K2SO4 crashes out, but this doesn't affect the separation) and goes ahead.
Have you tried not filtering the mixture and then extracting with DCM? Simply keep the solids with the DCM, then add a solution of 10% Na2CO3 of equal volume to the DCM extracts (which will contain the solids)... everything should dissolve, and the Na2CO3 helps clean up the epoxide before rearrangement.
Try it, I bet it will work like a charm for you V_L.
(Hive Bee)
02-09-02 22:24
No 267632
In previous dreams the mix is poured through a funnel with 3scotchbrite pads in it into a bucket with dcm in it. then it is poured back and forth in another bucket for several minutes. theere is a drain valve in the bottom of one the buckets to remove the dcm. Mainly was concerned with improved stirability with out oxidation potential losses.
When done how chromic suggests except with 5% naoh washes the remaining insolubals will form a tiny mass of bubbles at the interface which can be scooped out with a celite pad then rungout to reclaim valuble liquids. I guess either method is comparable when thought out properly. These celite pads used with oxone clean very quickly with hot water and can be reused. Is there an advantage to doing the washes with bicarb as opposed to NaOH.
VL_
(Stranger)
02-09-02 23:25
No 267652
Referring to:
Have you tried not filtering the mixture and then extracting with DCM? Simply keep the solids with the DCM, then add a solution of 10% Na2CO3 of equal volume to the DCM extracts (which will contain the solids)... everything should dissolve, and the Na2CO3 helps clean up the epoxide before rearrangement.
I thought, according to psychokitty's Post 253402 (psychokitty: "Re: mdp2p from oxone", Methods Discourse) that the solids would be dissolved by a muriatic solution (acidic), last time I checked Na2CO3 would basify. I guess my ? is will both of these methods dissolve the solids in the post rxn. mixture? I just find it difficult to see acid/base having the same kind of effect. Can someone read Post 253402 (psychokitty: "Re: mdp2p from oxone", Methods Discourse) and explain to me the differences in the effects? I'd really appreciate it as this is confusing. And wouldn't basifying effect the h2so4 rearrangement? These are probably stupid ?'s
Flip
(Hive Bee)
02-10-02 01:12
No 267675
washing with weak basic solutions does not really affect the ph of a substance too much. however dH2O washes should follow any basic wash. If some of the base was to carry over then sodium sulfate would be produced by the H2SO4 would be produced which is inert in this type of reaction. Dilute basic washes are to remove impurities different basic solutions will remove different impurities.
VL_
(Hive Addict)
02-10-02 09:43
No 267752
The point is, the solids are water soluble. If you wash with 10% Na2CO3, the solids will dissolve. Plus it's got a high enough pH to remove any phenols that could have been formed in making the epoxide... (oxone can cleave methoxy and methylenedioxy groups to hydroxy groups...)
5% or 10% NaOH would work just as well.
(Stranger)
02-10-02 16:19
No 267842
Thanks Chromic, VL_, you've cleared up most of my confusion, the solids dissolve regardless in dH2O and the Na2CO3 or NaOH solution works as a wash to remove impurities and helps isolate the epoxide. Thanks.
(Pioneer Researcher)
02-11-02 05:41
No 268043
Epoxides react forming the diol in the presence of aq. acids or aq. NaOH. Probably it's better to isolate the epoxide without adding NaOH.
(Stoni's sexual toy)
02-11-02 06:32
No 268057
Why don't you guys wash the filtered off solids with DCM instead of MeOH?
I'm not fat just horizontally disproportionate.
(Hive Addict)
02-11-02 08:10
No 268080
Smart idea. I'm no chemist...
(Newbee)
02-11-02 13:48
No 268169
I knew that if the rxn. took place under buffered conditions it would form the epoxide and unbuffered conditions would form the glycol but I did not know that changing the conditions of the post rxn. mixture would change the epoxide > diol as well. Learn new things every day I guess. Then again I could have probably inferred this from the h2so4 rearrangement. oh well, thanks.
(Hive Bee)
02-11-02 22:22
No 268427
IN reply to
Epoxides react forming the diol in the presence of aq. acids or aq. NaOH. Probably it's better to isolate the epoxide without adding NaOH.
------
The diol with react similarly when rearranging to the ketone. that shoudnt pose any problem.
(Newbee)
02-11-02 23:47
No 268448
But would having the glycol as opposed to the epoxide effect the timing of the reaction significantly? I know that the h2so4 will eventually break up the molecule if the rxn is let run too long.