Properties of some epoxides

[uemura]

Introduction

In the Hive there is currently going on some research on the preparation of 2-propanones synthesised from the propenylbenzenes via the epoxides. This small write-up gives some details on the physical properties of two epoxides, namely the anethol-epoxide and the asarone-epoxide. The preparation is based on an rxn proposed by Osmium, publish at Rhodiums site (see

https://www.thevespiary.org/rhodium/Rhodium/chemistry/safrolepoxide.html

. Uemura modified the precedure to allow re-use of the MeCN used in this synthesis. A more OTC method for the epoxide synthesis has been provided by Chromic.

Epoxide Synthesis (described for anethole) [N1]
0.13mol anethole (approx 20ml) are dissolved in 200ml of a MeCN/MeOH (1:1) mixture. 2g NaCO3 are added and the mixture is stirred under room temperature with slow stirring. [N2]
Within 10-15 minutes the molar amount of 30% H2O2 is added dropwise under stirring. [N3] Stirring is continued at room temp for 18-24Hrs. After the time has elapsed, the MeCN/MeOH solvent is destilled off on a waterbath. [N4] An oily water-epoxide suspension remains. The crude epoxide is extracted with ether or another non-polar solvent. The ether is washed with Brine and dried over NaSO4. [N5] After drying the ether is destilled off on a water bath and the last traces of the ether are removed in vaccuum leaving the crude epoxide in the flask.

Crude Anethole Epoxide: This is a clear yellow pleasant smelling oil. (Yield about 90%)
Crude Asarone Epoxide: This is a brown-gold clear oil with smell of asarone. Not too much pleasant. (Yield 80%) [N6] The following picture shows the crude asarone epxoide.


Purification of the epoxides
To purify the crude epoxides slow vaccuum destillation has been applied.

Anethole Epoxide Destillation:  The yellow crude epoxide was destilled at 13Torr and 15.4g (70%) of a water-clear, very pleasant smelling oil came over in the range between 118 to 126 DegC. Höring reports 132DegC at 11Torr.[N7] In the destillation flask a deeper yellow oil with a higher bp. remains. [N8]
Pictures of the purified anethole epoxide and the high-boiling residue.


Asarone Epoxide Destillation: The golden-brown oil (17g) are destilled under maximum vacuum (2-4 Torr). Within the range of 125-135Deg a clear light yellow oil destilles over. The yellow oil has the typical epoxide smell, very similar to the anthole one, but very different from the crude asarone epoxide. Yield 8.3g In the destillation flask a red thick oil remains (weight 4,3g) which after cooling solidifies but does not cristallize. [N9]
Pictures of the purified asarone epoxide and the high-boiling residue.


Discussion
As the 'law of difficulty conservation' predicted, the epoxidation of asarone is much more picky than the one of anethole. In case of anethole consistent results and clean products have been received. In case of asarone, the yield of the desired epoxide is low (8.3 gram out of 20ml asarone) and it seems to bee esential to purify already the crude epoxide before going ahead. [N10] A first thermal re-arrangment run on anethole epoxide went smoothly [N11], the similar attempt for the asarone epoxide should be worth a try as soon as sufficient clean epoxide is available.

Notes
[N1] Same procedure has been applied for asarone.
[N2] Not all of the NaCO3 will dissolve, but this has no effect on the performance of the rxn. It keeps the ph in the alkine area (p.h. about 8.5)
[N3] Do not use more than 1.1 molar amount of the H2O2. In one run Uemura 'overshoot' the H2O2 and some of the Acetonitrile has been oxidized to Acetamide, which cristallised during destillation and has been identified by its smell.
[N4] Uemura found the evap of the solvent mix must not be done under reduced pressure. The destilled aceotrop of the MeOH and the MeCN can be reused for further runs, which is more advantegous than Osmiums description. Uemura found the yield do not differ significantly. Remove the last traces of the solvent by applying vaccuum (may help to minimise the emulsion later on).
[N5] Emulsion forming may appear and the seperation becomes sometimes a bit a pain-in-the-neck. Be patient.
[N6] 'Low' yield of 80% was caused by problems separating the solvent mix.
[N7] (1) Höring, 'Über die Dibromide aromatischer Propenylverbindungen', Ber 38, 1905, pg. 3464
[N8] Yields of destilled epoxides have been between 70-75% percent in all three runs.
[N9] Like glas or molten plastic, may indicated some kind of polymerisation took place?
[N10] Uemura reported already earlier on the failure from asarone -> ketone in one step.
[N11] succesful to some extend, a write-up may follow later on.
Carpe Diem

[Rhodium]

Wonderful! This goes right onto my page.

[Osmium]

 

Very good results!

[uemura]

Thanks a lot, bees! Your are very quick, Uemura hadn't even the time to massage and clean up a bit the write-up. Some red modifications done. Rhod, please check for further typos or more faulty thingies.
Carpe Diem

[Chromic]

Excellent work! I can't wait to see your work on rearranging asarone epoxide!

[uemura]

Bees, fasten your seat belts....  Uemura couldn't wait and did the following:

In a thick-walled test tube 1ml of the destilled asarone epoxide was added and the test tube mounted above a hot-air-pistol. A thermometer 0-300DegC was placed inside the test tube and some anti-bumping stones added.
The hot-air-pistol was switched on and the temperature climbed quickly up to 260DegC. Tiny air bubbles were released from the anti-bumping stones. 270DegC, still nothing.

Then, when the temperature was up at 280DegC, the asarone epoxide started to boil. The colour turned to orange but the destillate which climbed up the test tube at 285-290DegC was water clear, no sign of any decomposition. The boiling was continued for two minutes, then the heating was switched off.

After cooling a orange clear oil remained. The smell was different from the expoxide, it had the typical ketone flavour. The content of the test tube was poured into a petri dish waiting for cristallisation over night (hopefully).

The rest of the oil in the tube was diluted with a bit of EtOH, then bisulfit was added. Heavy shaking. Oily precipitate only. Heavy shaking continued. Some white cristals appeared. Oily precipitate seems to solidify.  Anyway:

ASARONE EPOXIDE THERMAL REARRANGMENT IS POSSIBLE.
KETONE BOILS AT 285-290Degc AT ROOM TEMPERATUR
SMELL IS KETONE LIKE; BISULFITE TEST INDICATES POSITIVE RESULT.
EXTRAPOLATION OF LITERATURE BP TO ATMOSPHERIC PRESSURE FITS PERFECTLY SEE

Post 241739 (missing)

(uemura: "Asarone ketone bp data", Chemistry Discourse)
Have a good night

[sunlight]

Wow Uemura, I'm impressed with your research, good work.

[Chromic]

Thanx! You're sure to make a dream come true.  

[uemura]

Postscript: In the morning the oil was still a oil. But this is not surprising since the mp of the pure ketone is only 45DegC. Impurities prevent cristallisation. The test tube with the bisulfite however shows a resonable amount of white precipitate, minor oil drops on top of the deep yellow bisulfite solution. (Either non reacted expoxide and/or sideproducts).
Next step ould bee proper rearrangement followed by destillation. Perhaps Uemura builds a small-scale dest apparatus. Carpe Diem

[uemura]

Postscript2: In the oil on the petri dish first white critalls appear  

[Antibody2]

My goodness, are you ever meticulous Uemura. Nice Work!
"All those memories lost like rain..."

[Vibrating_Lights]

Beautiful.  Any one know what the typical yeilds are for a hydroxlamine condensation followed by an al/Hg with the asarone ketone or does Umera posses the first asarone ketone. Again swim says beautiful.  TEE HEE

[Chromic]

The more I read of peracetic acid in dcm (sodium acetate to buffer the H2SO4), the more inclined I am to believe that they can be used to produce asarone epoxide as well... it appears that only strong acids will cleave the epoxides, and not weaker acids like acetic acid. I'm ready to try this reaction soon, I hope it works because MeCN isn't as easy for me to find.

[Rhodium]

The peracetic should work, if you use more buffering carbonate than usual (1 eqv).

[Antibody2]

procced with caution guys on that one guys. here is why

Post 36661

(Antibody2: "pseudonitrosites via Toennies method", Novel Discourse), you will see that after ca 24 hours in glacialacetic acid i had a purple mess, back then no one bothered to point out that the pseudonitrosite of asarone was not purple, (aside from Rhods faq)but we had been dealing at that time also with red and black pseudonitrosite yeilds, so no-one knew for sure what to look for from different reactions.

in retrospect i now realize that the reason that batch failed hydrogenation is because it was no pseudonitrosite, just a pretty batch of decomposed asarone. decomposed by the acetic acid.

Mind you, that was in galcial acetic acid, no dcm, no water from the H202 either and no buffer. The peracetic might work, but i wouldn't be placing any bets just yet. Goiterjoe attempted it a while ago, as far as i know it was not a sucess, he never reported back on amination yeilds from the red syrup, the rxn yeilded.

for what they are worth, my two cents
"All those memories lost like rain..."

[uemura]

Bees, say a nice 'Thank you' to sunlight. He provided Uemura with the following reference:

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

This is close to the rxn Uemura is using but has a very big advantage: It only uses the MeCN in molar equivalents, not in a 1:1 mixture with the MeOH.

Based on Osmiums write-up is was obvious to Uemura that the MeCN forms with H2O2 the oxidant agent acting on the olefine. So a 1:1 mix with MeOH looked to him as an overkill but he wasn't sure. Since the MeCN is 1) expensive, 2) not easy to aquire he redestilled the azeotrope off for futher use.

The reference allows 'waste' of it since the MeCN is used in molar equivalents only and it simplyfies the workup a bit (more important, evap of solvents can be done at low temp). Further Uemura thinks that -at least for asarone- the evap of solvents at boiling temp (i.e. 60DegC) may not do that good. He will test this on the current batch in his lab.
Carpe Diem

[uemura]

Bees,

I think it was ab2    who said 'what do you want to do with the ketone?'

Uemura thinks that is exactly where the previous experiments boil down to! The only written reference Uemura has seen is the Leuckart conversion on Rhod's site provided by R. Carter?

To avoid to get much off-topic, Uemura opened a new thread.
Carpe Diem

[Rhodium]

Uemura: I edited your document somewhat and put it here:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/epoxide.html

- Is that okay?

[Ritter]

Uemura and gang:

I have a theory based on a ref I saw many moons ago on a similar CH3CN/base/H2O2 catalyzed epoxidation reaction.  The ref used 50-55% H2O2 in CH3CN/NaOH to epoxidize cyclohexene in very high yield.

It certainly seems like you are getting great yields with the anethole epoxide, however I feel that the poor yields obtained from asarone can be increased dramatically by using a more highly concentrated H2O2 solution.  I'm willing to bet that if you were to use a 50-60% concentrated peroxide solution, yields would skyrocket.  Now here's the good news:  Our standard 35% H2O2 solutions can easily be concentrated to over 50% and if you have the courage up to 65% by simple distillation.  A standard fractional vacuum distillation is capable of concentrating the peroxide to a level of about 65% before it starts azeotroping and getting concentrated to the point it could explode.  If you decide to do this, please use appropriate blast shields and the cleanest glassware you can possibly get your hands on to avoid the chance of trace contaminants catalyzing decomposition(explosive) of the highly concentrated peroxide.  For more info on concentrating peroxide mixtures, do a google search for hydrogen peroxide and model rocketry.  Concentrated peroxide is used as an excellent monopropellant by model rocket enthusiasts and there is a plethora of info on the web on how to make and work with super concentrated peroxide solutions.  As a matter of fact, I recall one web page where some guys simply boiled down 35% solution on a hotplate in an open beaker with magnetic stirring until evapareted to roughly half its initial volume.  The resulting solution was at least 60%, so this can be done without too much trouble it seems.

[Rhodium]

Does anyone have a detailed description for titrimetric determination of hydrogen peroxide concentration determination? Or is a density measurement enough for the purpose?