Author Topic: Properties of some epoxides  (Read 16589 times)

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uemura

  • Guest
Re: What to do with it?
« Reply #20 on: December 02, 2001, 01:15:00 AM »
Rhod

Uemura: I edited your document somewhat ...  Is that okay?



Sure! Uemura however beliefs the rxn can still be optimised futher. Running it at lower temp and evap solvents under reduced pressure seems to give less deeply colored crude epoxides. Also, the Ritter proposal taking higher conc. H2O2 may improve yields as well. The guideline should nevertheless be the one described so far.

Ritter!

thanks for this direction. Uemura tried improving yields by other means (see above) but woudn't have come to the idea of user higer conc. H2O2. Would it be possible instead of the risky destillation under normal pressure to do either:
1) frac vaccum dest to concentrate the h2o2?
2) freeze out the water?


Carpe Diem

Ritter

  • Guest
Re: What to do with it?
« Reply #21 on: December 02, 2001, 08:52:00 AM »
Uemura,

One more tip on improving epoxide yields:
If you check this link carefully

http://www.orgsyn.org/orgsyn/prep.asp?prep=cv7p0126



you will see it mentions POTASSIUM carbonate is a superior base to sodium carbonate.  Perhaps if you switch bases, yields will go even higher!

uemura

  • Guest
Re: What to do with it?
« Reply #22 on: December 02, 2001, 08:57:00 AM »
Thank you Ritter,
this is the references sunlight also pm-ed me. Do you think you can just use K2CO3 instead of KHCO3? Uemura never gets the fine details when you have to take the carbonate resp. the di-carbonate. Could you perhaps give Uemura a hint when either one is appropiate. Is it the ph range which is different?
Carpe Diem

sunlight

  • Guest
Re: What to do with it?
« Reply #23 on: December 02, 2001, 11:37:00 AM »
Here you are the short text of the original CA reference Osmium gave us:
CA 107: 39790k Isosafrol epoxide:
Isosafrol epoxide, useful as a intemediate for drugs and perfumes was prepd by epoxidizing isosafrol in mixt. of aq. H2O2 and MeCN or PhCN at 15-45 C and pH 8-10.5. Thus, isosafrol was stirred with a mixture of MeCN and aq. H2O2 in MeOH contg. Na2CO3 at 30 C and pH 10 for 20 h. to give 93.8 % of isosafrol epoxide.

As you see they used Na2CO3 instead of KHCO3.
I've made a test of direct epoxidation of safrol based in orgsyn procedure, but using Na2CO3 ph 9, and at 40 hours a TLC showed two spots, one of safrol and the other supposedly of the epoxide, but it's a small spot and it seems the conversion has been too low to make it interesting.
If we get a 80-90 % of epoxide from iso, and a thermal rearragement with 70-80 % yield it would be a preferable alternative to the performic, due the simplicity of rxn and work-up.
Nice dreams.

terbium

  • Guest
Re: What to do with it?
« Reply #24 on: December 02, 2001, 12:04:00 PM »
I want to know if the nitrile solvent is essential or if perhaps something more OTC like dimethylsulfoxide would work.

Edit:
Nevermind! Sorry, should have reread the whole thread before posting. I see that the nitrile is presumed to take part in the reaction and thus is essential.

lugh

  • Guest
Hydrogen Peroxide Concentrations/Density
« Reply #25 on: December 02, 2001, 05:54:00 PM »
%         d184
  01         1.0022
  02         1.0058
  04         1.0131
  06         1.0204
  08         1.0277
  10      1.0351
  12         1.0425
  14         1.0499
  16         1.0574
  18         1.0649
  20         1.0725
  22         1.0802
  24         1.0880
  26         1.0959
  28         1.1040
  30         1.1122
  35         1.1327
  40         1.1536
  45         1.1749
  50         1.1966
  55         1.2188
  60         1.2416
  70         1.2897
  80         1.3406
  90         1.3931
100        1.4465


Rhodium

  • Guest
Asarone glycol distillation
« Reply #26 on: December 07, 2001, 02:04:00 AM »
It seems like the distillation of asarone glycol (and possibly also the distillaion of the epoxide, if water is present) forms a crystalline by-product, which is a glycol dimer, and not solely 2,4,5-trimethoxyphenyl-2-propanone.

Asarone 1,2-glycol

Distillation of asarone 1,2-glycol (an oil) at 170-230°C/4 mmHg gives a red oil, which solidifies on standing. Through crushing the crystals under ether, a solid was left undissolved, which after recrystallization from alcohol melted at at 204-205°C, and had the molecular formula C24H32O8 [Could possibly be the 2,5-dimethyl-3,6-(2,4,5-trimethoxyphenyl)-1,4-dioxane cyclic ether]. Evaporation of the ether from which the dimer was separated gave an oil which partly crystallized, and after purification through its semicarbazone (mp 157-158°C), 2,4,5-trimethoxyphenyl-2-propanone (mp 47-48°C) was obtained. On heating asarone 1,2-glycol with acetic anhydride, the dimeric compound is formed in quantitative yield.

Asarone dibromide

To 5g beta-asarone in 20ml dry ether cooled to -20°C, there was added 4g Br2 in 6ml CS2 [Use another solvent, like ether or DCM]. Removal of the solvent gave 0.4 g of a crystalline dibromide (mp 82-83°C), while the main product remained as an oil. The same procedure on alpha-(trans)-asarone gave 7g of a solid dibromide (mp 82-83°C).

Reference: J. Chem. Soc. 1338 (1937)

uemura

  • Guest
Re: Asarone glycol distillation
« Reply #27 on: December 07, 2001, 04:05:00 AM »
Things getting clearer!

The 1st run of the epoxidation of asarone gave indeed this red oil which solidified upon standing and is likely to be this glycol dimer.  Two things to add:

1) Uemura got in his 2nd run which has been performed under ice/water cooling at 4DegC warming up to rt after 16hrs (+ evap of solvents under reduced pressure) no red oil, but obviously unreacted? asarone! Only minor yellow color of crude epoxide, almost water clear destilled epoxide.

2) The yield (40%) was however not better than with run 1!. Uemura now thinks the idea of Ritter using highly conc. h2o2 would help a lot. Water seems to limit the yield and high temperature favours the dimer formation!

Now, a question on the dibromide. When the ref says Removal of the solvent gave 0.4 g of a crystalline dibromide (mp 82-83°C), while the main product remained as an oil. does this mean the oil is NOT the dibromide or is it just not crystallising?
Carpe Diem

Rhodium

  • Guest
Re: Asarone glycol distillation
« Reply #28 on: December 07, 2001, 04:25:00 AM »
The article are talking about dibromides formed from cis- and trans-asarone, respectively. The bromides formed have different stereocofiguration, one is solid and one is an oil. Both are 2,4,5-trimethoxyphenyl-1,2-dibromopropane, "asarone dibromide".

uemura

  • Guest
Water Reduction
« Reply #29 on: December 07, 2001, 06:05:00 AM »
An idea poped up in Uemuras head: He doesn't like the idea of concentrating the 30% H2O2 solution by means of destillation. Now, say you have 250ml organic, waterfree MeCN/MeOH solvent and you add 12ml H2O2 which is 4g H2O2 and 8g water. This means you have 3% water in your organic mix. Would it be possible to get rid off or to reduce this percentage by adding either
a) a neutral drying agent (MgSO4, Na2SO4) or
b) silica gel?
Would a) or b) interfere with the epoxidation? Or would you need too much? .... Some ideas?
Carpe Diem

Rhodium

  • Guest
Re: Water Reduction
« Reply #30 on: December 07, 2001, 06:31:00 AM »
Metal ions and possibly silica gel (definitely the indicating variety) may catalyze the breakdown of H2O2. Do you have molecular sieves, they should work.

uemura

  • Guest
DC Results
« Reply #31 on: December 20, 2001, 02:41:00 PM »
Bees,

x-mas is close ..... and here we have something interesting:

To allow to contemplate on a TLC picture Uemura presents some plates with results on his olefine epoxidation. The interpretation make sense, it shows the following evidence:

1) Asarone epoxidation shows that only a certain amount of asarone is epoxidised, the rest seems not to be  affected - second run under cold conditions-solvent evap in vac, see

Post 245271

(uemura: "Re: Asarone glycol distillation", Novel Discourse)
! (plate III, IV).
2) Crude anethole-epoxide destillation gives the epoxide together with some none affected anethole + obviously some glycols as mentioned in the reference provided by Rhod (plate V).

Green: pure anethole, Red: destilled indian asarone.

Perhaps the Hive moderators take some pre-x-mas time to have a look on the provided picture and to comment. BTW: the colours are Uemuras interpretation, the spots have been identified as indicated.

'Thermal Residue'='What has been left after destillation of the CRUDE epoxide in vacuum' Thermal has nothing to do with the 'thermal' re-arragement od the epoxide!. Sorry if this could lead to confusion
Again, it's late, uemura confused his write-up with results on plate I and II showing the anethole-ketone

Carpe Diem

sunlight

  • Guest
Re: DC Results
« Reply #32 on: December 20, 2001, 02:49:00 PM »
Very nice uemura, congratulations, you are making the Hive more serious.

uemura

  • Guest
Re: DC Results
« Reply #33 on: December 20, 2001, 03:23:00 PM »
Thanks a lot for the 'late night' congratulation, Sunlight  :)
 
Uemura has nevertheless to apologize (he's now veryyy tired....) He mixed up some wording in the post with his lab-book write-up concerning plate I and II. The above post only shows:

1) original substance (asarone, anethole)
2) destilled epoxide (asarone, anethole)
3) left over of epoxide-destillation in flask (asarone, anethole)


This was his first TLC attempt and on plate I and II he put down a anethole-ketone drop (from thermal rearragements) NOT SHOWN above! The plates just arrived yesterday.

Thanks again to Osmium and Rhodium to encourage Uemura to apply TLC. It's indeed easy and very helpful and leads to the Hive's scientific future!!!!!

Unobtainium, did Fritz disappear - how more pics are needed !!!  :)

Osmium

  • Guest
Re: DC Results
« Reply #34 on: December 20, 2001, 03:36:00 PM »
How much of the substances to be tested did you apply onto the plates? How did you apply it? Capillary? Diluted or undiluted? How did you detect the spots? And what solvent system was used?

uemura

  • Guest
Re: DC Results
« Reply #35 on: December 20, 2001, 04:16:00 PM »
Osmium,

you prevent me from going to bed. O.K. here we go:
  
1) Plates (25x80mm) are COTS
  • . 0.2mm Silical gel on PE foils with UV indicator. Chromatography paper sucks! Forget it for this purpose!

    2) Drops have been set via small Pasteur-pipette resulting in (undiluted) starting material with diameter < 1mm [**]

    3) Development in a saturated(=lid down long enough) glas pot with a 50:50 mix of drugstore pet-ether and ethylacetate (home made -- but not kitchen-style like, i.e. waterfree and not too much EtOh or GAA)

    4) Spot detection was surprisingly easy. Against a plant lamp the spots could be easily detected after drying the plates. Uemura found that the spots are even easier to see when looking at the back of the plate againt the lamp. No iodine or real UV lamp seemed required.

    5) Since the results made sense and the eperiments just started, no further verification have been done so far.

    Please advise how to confirm the above approach (without a genuine UV light).
    • COTS=Commercial Of The Shelf
    [**] Uemura knows: smaller is better!!!

    Have a good night

Rhodium

  • Guest
Re: DC Results
« Reply #36 on: December 20, 2001, 05:02:00 PM »
Don't use concentrated solution, 5% or less is sufficient with an UV lamp (which can be bought cheaply for detecting fake paper money).

Osmium

  • Guest
Re: DC Results
« Reply #37 on: December 20, 2001, 06:38:00 PM »
> Drops have been set via small Pasteur-pipette resulting
> in (undiluted) starting material with diameter < 1mm

Oh my god! WAY WAY WAY too concentrated!
Last time I did TLC I applied ~6µL of a diluted solution (1:5) with an adjustable volume (2-20µL) Eppendorf pipette, which resulted i a starting point about 3mm in diameter. Yours was so small because of the high viscosity material.
Separation at such a high concentration is abyssmal.
Use melting point capillaries to apply your (diluted!)samples.

> Spot detection was surprisingly easy. Against a plant
> lamp the spots could be easily detected after drying the
> plates. Uemura found that the spots are even easier to
> see when looking at the back of the plate againt the
> lamp. No iodine or real UV lamp seemed required.

Uh oh. You shouldn't be able to see anything at all once they are dried.
Iodine detection isn't the best method around, but it is the easiest. I2 often doesn't detect all components.

> UV lamp (which can be bought cheaply for detecting fake
> paper money).

Commercial overpriced UV lamps for TLC have two wavelenghts which can be used independently from each other, or together. Different compounds might show up at one wavelenght but not readily at the other.

uemura

  • Guest
Re: DC Results
« Reply #38 on: December 20, 2001, 11:59:00 PM »

Oh my god! WAY WAY WAY too concentrated!




OOps, still to much substance????

Compared with the results uemura got from a test using chromatography paper, the silica plates worked like the Hubble telecope. Circles of pure substances moved up as a circle of almost same size and did not smear out. Mixed components did seperate clearly.


Uh oh. You shouldn't be able to see anything at all once they are dried.



Under a 'normal' lamp there was indeed almost nothing to see, but the 'plant lamp' uemura has around helped to see the developed spots.


Iodine detection isn't the best method around, but it is the easiest.



Uemura will re-do the above samples and apply your recommendations. For the time being he will try it with iodine and will have a look for a detecting fake paper money device. Thanks for your input so far!


Carpe Diem

Unob! Thanxs for the new title! More pics to come soon...

sunlight

  • Guest
Re: DC Results
« Reply #39 on: December 21, 2001, 06:05:00 AM »
The faked money detect uv light doesn't show too much, we use the bactericide ones. Keep care with your eyes, I had a problem with them one day testing and H2O2 alkene addition (didn't work for safrol) catalyzed by uv, very irritant.