enima
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Ozonolysis
Hi I'm looking for a proceedure, or references for a proceedure to an ozonolysis reaction, mainly the reduction of the ozonide with Zn and Acetic
acid. All the papers I have found seem to be in german or some other foreign language.
My goal is to covert eugenol to vanillin via ozonolysis of isoeugenol. (the propylbenzene).
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garage chemist
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I have a detailed synthesis of vanillin from isoeugenol. It involves reduction of the ozonide with sodium pyrosulfite and dithionite (IIRC).
It's in german. I can translate it and post it here, if you want (it's not that long).
Note that you need a powerful ozoniser (forget about that aquarium crap) and a bottle of pure oxygen for this. You also need chloroform as a solvent
and dry ice for cooling (reaction is carried out at -20°C).
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enima
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yes, I would greatly appreciate it, I'm curious whether the chloroform could be substituted with another solvent like acetic acid or ethanol as
both are used in ozonolysis.
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garage chemist
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Okay, I finally grabbed my Organikum (15th edition) and looked up the preparation of vanillin from isoeugenol.
First, let me tell you that vanillin is very easy and completely nonsuspicious to get (ebay!) if you need it as a synthesis chemical. (I have a nice
demethylation procedure to make 3,4-dihydroxybenzene).
But making it is interesting and one learns the techniques of ozonisation.
0,1mol Isoeugenol are ozonised in 200ml of chloroform at -10 to -20°C. After removing the chloroform at room temperature in vacuum, the raw ozonide
is stirred with 40ml water, 40g ice and 8g sodium dithionite for 30min.
16g cristalline sodium sulfite and 10g sodium pyrosulfite are added. The mixture is heated to 70°C until everything has dissolved.
The aldehyde is now in its bisulfite adduct, which is insoluble in ether.
By extraction with ether, impurities are removed.
After acidifying with 2N H2SO4 (and thus destroying the adduct) it is taken up in ether, the vanillic acid removed by washing with NaHCO3 solution and
the ethereal solution dried with MgSO4. The ether is distilled away and the raw Vanillin is purified by either vacuum distillation or
recrystallisation. bp 170°C (at 15 mbar), mp 81°C (Ligroin).
Yield 60%.
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Kinetic
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Directly related references
The following references should complement garage_chemist's procedure. All the below references are for the oxidation of isoeugenol to vanillin.
The first don't mention how the ozonide is destroyed, or what solvent is used:
J. Soc. Chem. Ind. London, 41, 70 R (1922);
Helv. Chim. Acta, 8, 407 (1925);
Helv. Chim. Acta, 7, 71 (1924)
The following two reactions are carried out in GAA:
Ann.Chim.(Paris), <7> 13, 123 (1898);
Chem. Ber., 48, 232 (1915)
Hopefully the most useful will be Chem. Ber., 48, 40 (1915). The reaction is carried out in GAA and the ozonide destroyed by
'zinc and acid'. It's the easiest thing in the world to OCR an old German paper and cut and paste the text into an online translator.
You usually get a pretty good idea of what the paper is getting at.
Also see patents DE97620 and DE192565.
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