The Hive > Novel Discourse
New method for P2P
Osmium:
I seem to remember a patent about caro's acid production. It said something about pouring conc. H2SO4 into a solution of persulfate contained in a dewar flask. The resulting mixture was left alone for awhile resulting in 80% yield. When the same was done by mixing the solutions in regular glass, with stirring and external heating the yields were much inferior.
Osmium:
Here it is:
Patent US4049786
Process of preparing peroxymonosulfate
Abstract
High strength peroxymonosulfate is prepared by adding concentrated sulfuric acid to a solution of a soluble peroxydisulfate whereby the heat of solvation of the sulfuric acid hydrolyzes the peroxydisulfate to the peroxymonosulfate; the temperature is controlled to provide a range of about 140.degree. to 160.degree. F. After about 15 to 45 minutes, the solution is cooled rapidly to about room temperature.
abolt:
http://www.fmcchemicals.com/Content/CPG/Images/AOD_Brochure_Persulfate.pdf
Megatherium:
From document:
Fast, high-temperature, acid hydrolysis, followed by chemical quenching will yield solutions of peroxymonosulfate
This is: Osmium 's procedure.
Strong acid [H+] > 0,5 M
S2O82- + H20 --> HSO4- + HSO5-
Now, there is substantial risk that the enol ether (I 'm practically sure of it) will be hydrolyzed is such acidic conditions (say 20 % H2SO4). This, combined with an excess of oxidant HSO5- or with a faster hydrolysis than Baeyer-Villiger oxidation will result in Baeyer-Villiger degradation of the P2P.
This bee thinks it would be preferable to use the above mentioned 'dry' Baeyer-Villiger oxidant in acetic acid: transesterification will yield the same product, while hydrolysis can be the first step in further decomposition.
Or mabey after all, it would be preferable to just use peracetic acid like in the original articles ::) .
Rhodium:
I did some reading on the Baeyer-Villiger reaction performed on ?,?-unsaturated ketones and aldehydes (mainly in Org. React. 43, 251-798 (1993) and references found therein), and found out that the main problem with the reaction on compounds like R1CH=CR2COCH3 with straight-chain alkyl substituents is not that the product enol acetate undergoes further oxidation to the epoxy acetate - it is that the majority of the starting material undergoes epoxidation to the epoxy ketone (this doesn't happen if the R groups are tied together in an alicyclic ring though), and there is no way of stopping this side-reaction, only decreasing it by choosing the right oxidant. Unfortunately the best oxidants are really big molecules, such as peroleic acid (CH3(CH2)16CO3H) or hydrogen peroxide with benzeneselenic acids (Ar-Se-Se-Ar). The yields are more promising with the homologous ?,?-unsaturated aldehydes, R1CH=CR2CHO (in our case 2-methylcinnamaldehyde), but on the other hand that starting material is instead harder to synthesize.
Some references which extrapolate on this follows below. The article using benzeneselenic acids as catalyst can be found at DOI:10.1016/S0040-4020(01)86890-3 if you have online access to Tetrahedron.
About the Baeyer-Villiger oxidation of 2-Methylcinnamaldehyde with peracetic acid, achieving a higher yield than with the corresponding methyl ketone.
Recherches sur l'oxydation de l'éthyl-2-hexène-2-al et de quelques aldéhydes apparentés. III.
Oxydation de I'éthyl-2-hexène-2-al et de l'éthyl-2-hexanal par l'acide peracétique
C. Schaer
Helv. Chim. Acta 41, 619-625 (1958) (https://www.thevespiary.org/rhodium/Rhodium/pdf/peracid.unsatd.aldehydes.pdf)
____ ___ __ _
Reaction mechanism and product distribution in the Baeyer-Villiger oxidation of analogs of our ketone of interest - 3-Methyl-4-Phenyl-2-Butanone - where either of the CH3 groups has been substituted by a phenyl group.
The Peracid Oxidation of Ketones. III. The Reaction of ?,?-Unsaturated Ketones with Peroxybenzoic Acid
By Tai Yokoyama and Fujio Nohara
Bull.Chem. Soc. Japan, 38(9), 1498-1500 (1965) (https://www.thevespiary.org/rhodium/Rhodium/pdf/peracid.unsatd.ketones.pdf)
____ ___ __ _
Baeyer-Villiger oxidation of 3-Aryl-4-Phenyl-2-Butanone with Persulfate in acetic acid with catalytic sulfuric acid.
trans-1-Aryl-2-aroyloxyethylenes. Persulfate Oxidation of Chalcones and Chalchone Analogues
D.N. Dhar & R.C. Munjai, Synthesis 542-543 (1973)
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