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Author: Subject: preparation of e-caprolactone
chemx01
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[*] posted on 6-5-2012 at 06:24
preparation of e-caprolactone


I want to prepare caprolactone which will be later used to make capsaicin. I found one german patent which was titled:
Method of Preparing epsilon-Caprolactone and Derivatives thereof Free of Explosive Peroxides

Because it's in german I translated the procedure using google translator and got something like this:
50g of cyclohexanone and 110 g of 30% aqueous hydrogen peroxide were added dropwise with stirring at 50-55 C to carry out the oxidation. After the addition, the solution was kept at this temperature for four hours.

After cooling the reaction mixture, it was extracted with ether and 5.5 g of unreacted cyclohexanone were recovered.
The water layer was then neutralized with hydrochloric acid and was added to a solution comprising 5 g of cuprous chloride, 20 g of sodium chloride and some quantities of 6N aqueous hydrochloric acid.

The mixture was allowed to stand for an hour and complete decomposition of the peroxides took place.

The resultant oily product was extracted with ether, washed with water and concentrated. After removing the solvent, 0.5 g of sodium hydroxide was added and the mixture was introduced into a distillation apparatus.

After heating for three hours at 2800 C on an oil bath, the product was distilled in' vaciuo at 20 mm Hg and at further reduced pressure. 41 g of e-caprolactone having a boiling point of 78-820 C/3mm Hg were safely obtained (yield 70.6%).

Fisrtly I'd like someone who does speak German to check the original procedure if there aren't any mishaps in the translation.

I have a few questions regarding this procedure:
50g of cyclohexanone and 110 g of 30% aqueous hydrogen peroxide were added dropwise with stirring at 50-55 C to carry out the oxidation.(They mean to add H2O2 to cyclohexnone at 50°C right? Or some other way?)

After cooling the reaction mixture, it was extracted with ether and 5.5 g of unreacted cyclohexanone were recovered. (I don't understand this step, won't the caprolacton and hydroperoxides extract with ether as well, I wouldn't be happy concentration something explosive and I wouldn't be happy with removing the caprolacton from my reaction mixture)

The water layer was then neutralized with hydrochloric acid and was added to a solution comprising 5 g of cuprous chloride, 20 g of sodium chloride and some quantities of 6N aqueous hydrochloric acid. (they didn't mentioned any amount, so I suppose they mean acidic concentrated solution)

Do you think that this is a sfe procedure, I don't want to be messing with anything explosive, but I think that the peroxides will be safely decomposed.

The patent is in the attachment.





Attachment: DE1618245A1.pdf (893kB)
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Nicodem
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[*] posted on 6-5-2012 at 06:43


Quote: Originally posted by chemx01  
Fisrtly I'd like someone who does speak German to check the original procedure if there aren't any mishaps in the translation.

Why do you bother with machine translations when you can just read the patent application in English language? The application was nationalized in Great Britain as well, as GB1177516, and coincidently the official language there is English.
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Do you think that this is a sfe procedure, I don't want to be messing with anything explosive, but I think that the peroxides will be safely decomposed.

No, it does not look safe at all and does not make much sense after a cursory look either. I admit I only read the Example 1 and might have missed something obvious in the discussion part, but that procedure looks pretty much unusual and unsafe. You seem to have acknowledged that yourself, so why don't you just follow any other of the numerous procedures for the Baeyer-Villiger oxidations of cyclohexanone as described in the literature? I'm sure there are plenty that are repeatedly verified, simple and make more sense chemistry-wise.




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chemx01
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[*] posted on 6-5-2012 at 07:28


Thank you for you reply.
I tried searching for the patent in english but all I got was this:
http://www.wikipatents.com/GB-Patent-1177516/method-of-prepa...
The translation seems to be incomplete and I didn't find the original patent in English.

I tried searching in Vogel and those types of books but I haven't found any procedure involving cyclohexanone. I don't have acess to journals etc..

I have tried this oxidation using m-CPBA but that is not very cheap and suitable for me. I send a U2U to Klute, he mentioned having some preps fro caprolactone, but meanwhile I found this one and as you wrote it doesn't look very safe, but the yields are pretty good and the reagents cheap.

I'm looking for a prep using either peracetic acid(generated insitu since I don't have a solution of it),caro's acid,persulfates etc..
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[*] posted on 6-5-2012 at 08:12


Quote: Originally posted by chemx01  
I tried searching for the patent in english but all I got was this:
http://www.wikipatents.com/GB-Patent-1177516/method-of-prepa...
The translation seems to be incomplete and I didn't find the original patent in English.

Patents can be downloaded from the internet sites of patent offices or international patent cooperations. I though you were aware of this given that you had access to the DE nationalized version of this Japanese patent. You can download the GB version from Espacenet (use the "Download" option in the "Original document" section). The "Bibliographic data" section gives references to the other equivalents nationalized in other countries, among other data.
Quote:
I tried searching in Vogel and those types of books but I haven't found any procedure involving cyclohexanone. I don't have acess to journals etc..

Not having access to journals is a lame excuse. You obviously have access to this forum, don't you? So use its full potentials. We even have a dedicated section for literature!
I suspect your real problem is the poor literature searching skills. Worry not, as we have a cure for this this problem in our forum guidelines. There is a lot of reading, learning and literature work ahead of you, but I'm sure you will succeed at the end. Feel free to ask for assistance if you encounter new insurmountable barriers.




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chemx01
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[*] posted on 6-5-2012 at 08:42


I feel embarrased, I found the patent on this very same website but somehow I couldn't download it.

However thank you the guidlines and I hope I'm going to get better at literature searches.
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[*] posted on 6-5-2012 at 09:32


The espacecnet patent site is a little tricky. It's well worth the trouble to find your way around it. It seems like you're learning several different aspects of this problem at the same time. Or that the reaction is a catalyst for learning literature searching, translating, patent searching and web site manipulation. Be patient with yourself and enjoy the process. And as the man said, ask for help. On an another subject, is this a fun way to make the stuff? Because if my goal were to get a supply of capsaicin I would be inclined to extract peppers.



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Lambda-Eyde
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[*] posted on 6-5-2012 at 10:21


Quote: Originally posted by chemrox  
On an another subject, is this a fun way to make the stuff? Because if my goal were to get a supply of capsaicin I would be inclined to extract peppers.

You've got to be kidding me? :P You don't think it's intriguing to synthesize a natural product from simple raw materials, instead of recrystallizing something you can get from an over night soxhlet run?

While I agree that extracting chemicals can be rewarding and cool, actually making it from petroleum derivatives must be a million times cooler!


Edit: chemx01: UnintentionalChaos has been working on synthetic capsaicin. Instead of making caprolactone, he hydrolyzed polycaprolactone plastic and converted the 6-hydroxy acid to the 6-bromo derivative, as seen here.

[Edited on 6-5-2012 by Lambda-Eyde]




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chemx01
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[*] posted on 6-5-2012 at 10:54


I agree with Lambda-Eyde there is nothing like completing multistep synthesis. I already tried extraction but more or less only for fun and I used the extract for food purposes, but I was always interested in making pure stuff.
I have pretty well equiped lab so making the neccesary precursors isn't a problem.

I'm aware of the polycaprolactone route, but in my country polycaprolacton is virtually unavailable and I looked everywhere. Belive me it was my first choice of making the acid, but unfortunately the polycaprolacton from USA would cost me same as the 6-bromohexanoic acid from Sigma.
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