Author Topic: New method for P2P  (Read 388896 times)

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New method for P2P
« on: December 09, 2001, 03:01:00 PM »
The following reactions are part of this novel synthesis of P2P:

1) An acid catalysed Aldol condensation of Benzaldehyde and Methyl Ethyl Ketone to give Methyl Phenyl Butenone:

C6H5CHO + CH3CH2COCH3 + HCl(g) ---> C6H5CH=C(COCH3)CH3

2) The unsaturated ketone undergoes the Baeyer-Villiger oxidation with peroxy acids to give the enol ester of Phenyl propanone:


3) The enol ester is then saponified with 10% NaOH solution to give Phenyl Propanone in about 35% yield based on the unsaturated ketone.

The Aldol Condensation.

The directions for this are in Organic Reactions

200 gms of Benzaldehyde and 300 gms of Methyl Ethyl Ketone are mixed in a 1 litre beaker and cooled below 5°C. HCl gas is bubbled through until 40gms has been added. The mixture goes from a clear solution to a red colour and becomes turbid so that you can't see through it. The mixture is kept over night and becomes a brown colour. It is washed with water and then 10% NaOH solution, the organic layer seperated and distilled. At 240°C a yellow oil comes accross and the temperature gradually rises to 260°C.

The oil can be crystalized by cooling in the freezer overnight. This in itself does not induce crystalization but if you also put a spoon in the freezer and then dip it in and out of the cool mixture you get some seed crystals that induce crystalization. The mass turns from an orange oil to sulfur coloured crystals, mp 38°C, 180 gms (Methyl Phenyl Butenone)

The Baeyer-Villiger Oxidation

The reaction of the above unsaturated ketone with peracetic acid was first done by Boesken reported in Rec. Trav. Chim.  55, 786 (1936). There is some discussion of this also in

Patent US3980708

.  Also see Organic Reactions Vols 9 & 43 I  think.  By following the directions in

Patent US5670661

you will get about 35% ketone based on the weight of the unsaturated ketone used. In that patent it is suggested that by recycling a higher percentage can be achieved.

To a 1 litre flask is added 625 ml of Glacial acetic acid and 143 grms of Sodium Perborate. To this is added 100 grms of the methyl phenyl butenone with stirring and the mixture is heated to 50°C. The mixture will heat up so  care has to be taken ie cooling. However if the mix gets too cool it solidifies. Stirring and heating continued for about 6 hours. Cooled poured into 1 litre H2O and extracted with toluene or DCM. The solvent is distilled leaving a yellow oil that has a pleasant smell. This is added to 500 mls of 10% NaOH solution (50/50 H20:EtOH) and stirred for 1-2 hours extracted with toluene or DCM and distilled and the fraction boiling between 210-220°C collected Phenyl-2-Propanone (About 35 gms)

In the Organic Reactions review of the Baeyer-Villiger there is a reference to the oxidation of alpha Methyl Cinnamaldehyde using H2O2 catalysed by a nitrobenzene selenic acid or something like that to give the same enol ester as above but in 90% yield.


  • Guest
Re: New method for P2P
« Reply #1 on: December 09, 2001, 04:57:00 PM »
Here are some references for the first reaction
The product is this correct?

Preparation of 3-methyl-3-penten-2-one and its analogs.
Pishch. Prom-st. (Moscow)  (1990),   (10),  44-5.
Journal  written in Russian. 
MeCOEt condensed with RCHO (R = Me, Et, Pr, Me2CH, MeOC6H4, PhCH:CH, Ph) in the presence of H2SO4 at 60-65° to give 40-79% RCH:CMeCOMe.  Analogous reaction of R1CH2COR2 [R1R2 = (CH2)3, (CH2)10; R1 = H, R2 = Ph, CH2CHMe2; R1 = C5H11, R2 = Me] with MeCHO (from paraldehyde) gave 8.6-38% MeCH:CR1COR2. 

Aldol condensation of butanone with various aldehydes.    
Sasaki, Kazuhiro.    Kobayashi Perfum. Co.,  Ichikawa,  Japan.   
Nippon Kagaku Zasshi  (1968),  89(8),  797-804. 
Journal  written in Japanese.   
Condensation of MeCOEt (I) with various aldehydes was investigated to find the effect of conditions on the ratio of RCH:CHCOEt (II) and RCH:CMeAc (III).  Citral and I, in the presence of alkali hydroxide or NaOEt, gave products contg. >86.8% II, whereas MeOH-KOH yielded products contg. III as a main product.  Citronella (IV) and I gave similar results except that Me2C:CHCH2CH2CHMeCH2CH(OMe)CH2COEt was formed using MeOH-KOH and Me2C:CHCH2CH2CH(Me)CH2CH(OH)CHMeAc was obtained with EtONa.  The results indicate that aldol corresponding to II is more readily dehydrated than that corresponding to III.  Condensation of IV with Me2CO in the presence of MeOH-KOH gave a mixt. of Me2C:CHCH2CH2CHMeCH2CH:CHAc and Me2C:CHCH2CH2CHMeCH2CH(OMe)CH2Ac.  Similar reaction of I with Et2CO gave Me2C:-CHCH2CH2CHMeCH2CH:CMeCOEt, b0.55 101-7°.  Condensation of I with BzH, PhCH:CHCHO (V) and furfural (VI) showed that the ratio II-III is also dependent on the type of aldehyde.  III is favored when KOH-MeOH is used with BzH and V, compared with the results with aq. NaOH, but the difference is much greater with BzH.  BzH and VI always favor formation of II.  PhCH:CHCH:CHCOEt, m. 55-6°, was prepd. by a modified Wittig reaction; semicarbazone m. 200-1°; phenylhydrazone m. 89-90°.  4-(2-Furyl)-3-methyl-3-buten-2-one, b10 114-15°, and 5-(2-furyl)-4-penten-3-one, b13 122-4°, were also prepd. by this method.  Orientation of condensation was postulated to be regulated by the steric requirement.  s-Cis and s-trans conformations of some of the unsatd. ketones were detected by ir spectra. 

A study of the reaction of butanone with benzaldehyde and p-nitrobenzaldehyde.    
Jung, Duksang.    Cheju Univ.,  Cheju,  S. Korea.  
Nonmunjip - Cheju Taehak  (1982),  14  27-31.
Journal  written in Korean.   
In alk. medium, the reaction of p-O2NC6H4CHO and MeCOEt gave three hydroxy ketones, indicating that both Me and CH2 positions were attacked to a comparable extent.  Dehydration of the intermediate hydroxy ketones is a slow step.  In acid medium, however, the addn. step of the reaction was selective, giving only 1 isomer.  Similarly, in alk. medium, PhCH(OH)CH2COEt (I) and PhCH(OH)CHMeCOMe (II), hydroxy ketone intermediates from the reaction between BzH and MeCOEt, gave PhCH:CHCOEt (III).  Treating I and II with acid gave III and PhCH:CMeCOMe, resp., with no evidence of rearrangement. 

These journal articles detail its synth also.

Double Michael addition reactions of some new 1,5-diaryl-2-alkyl-1,4-pentadien-3-ones: Part II.
Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem.  (2001),  40B(8),  667-673.

RuCl3 catalyzes aldol condensations of aldehydes and ketones.   
Tetrahedron  (1998),  54(32),  9475-9480. 

Synthesis of isoquinoline-1,3-dicarboxylic acid.    
Chin. Chem. Lett.  (1999),  10(11),  907-910. 
(in english)

Here is the baseic addition

Kinetics of condensation of benzaldehyde and its derivatives with acetone and methyl ethyl ketone catalyzed by aluminum oxide.   
Collect. Czech. Chem. Commun.  (1980),  45(6),  1812-19.
Journal  written in English.
The pseudo-1st-order aldol condensation kinetics of RC6H4CHO (R = H, 4-Me, 3-MeO, 4-MeO, 3-Cl,4-Cl) with excess Me2CO over Al2O3 at 60-160° and the pos. r indicated that the addn. step, to give hydroxy ketone, is rate detg.  r Decreases with increasing temp.; the isokinetic temp. is 449.8K.  At 60-90° the retroaldol reaction of PhCH(OH)CH2Ac is minor and the dehydration to PhCH:CHAc is major; the proportion of dehydration-retroaldol reaction increases with increasing solvent polarity and decreases with increasing temp.  The condensation of PhCHO with MeCOEt at 90-160° gives mostly PhCH:CHCOEt in a reaction catalyzed by the basic sites on Al2O3; the minor product, PhCH:CMeAc, formation is catalyzed by the acidic Al2O3 sites. 

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  • Guest
Re: New method for P2P
« Reply #2 on: December 09, 2001, 05:16:00 PM »
This review would probably bee very helpful.

The Baeyer-Villiger oxidation of ketones and aldehydes.
Krow, Grant R.
Org. React. (N. Y.)  (1993),  43  251-798.  
A review with >1092 refs. 

Refs for the second one(partial of this article)

Sn-zeolite beta as a heterogeneous chemoselective catalyst for Baeyer–Villiger oxidations
Nature 412, 423 - 425 (2001)
The Baeyer–Villiger oxidation, first reported more than 100 years ago1, has evolved into a versatile reaction widely used2 to convert ketones—readily available building blocks in organic chemistry—into more complex and valuable esters and lactones. Catalytic versions of the Baeyer–Villiger oxidation are particularly attractive for practical applications, because catalytic transformations simplify processing conditions while minimizing reactant use as well as waste production. Further benefits are expected from replacing peracids, the traditionally used oxidant, by cheaper and less polluting hydrogen peroxide3. Dissolved platinum complexes4 and solid acids, such as zeolites5, 6 or sulphonated resins7, efficiently activate ketone oxidation by hydrogen peroxide. But these catalysts lack sufficient selectivity for the desired product if the starting material contains functional groups other than the ketone group; they perform especially poorly in the presence of carbon–carbon double bonds. Here we show that upon incorporation of 1.6 weight per cent tin into its framework, zeolite beta acts as an efficient and stable heterogeneous catalyst for the Baeyer–Villiger oxidation of saturated as well as unsaturated ketones by hydrogen peroxide, with the desired lactones forming more than 98% of the reaction products. We ascribe this high selectivity to direct activation of the ketone group, whereas other catalysts first activate hydrogen peroxide, which can then interact with the ketone group as well as other functional groups.

When trying to avoid the use of peracids for the Baeyer–Villiger reaction, the methodology developed up to now involved catalysts able to activate hydrogen peroxide, H2O2. Amongst homogeneous catalysts, complexes of molybdenum8 and rhenium9 have been shown to activate H2O2, but their turnover numbers (TONs) and selectivities are relatively low (TONs are below 20 for overall reaction times ranging from 12 to 24 hours). Pt complexes achieve TONs of about 50 within 5 hours, but are not chemoselective when other functional groups are present10. Concerning heterogeneous catalysts, supported Pt complexes11 and TS-112 have been used, but have shown only limited activity and selectivity, respectively. Acid zeolites such as H-beta and USY activate hydrogen peroxide for the Baeyer–Villiger oxidation, but show selectivities of less than 60–70% (ref. 5). MeReO3 (ref. 13), TS-13 and Pt complexes14 are excellent epoxidation catalysts in the presence of H2O2 and consequently, epoxidation is favoured over the Baeyer–Villiger oxidation when using unsaturated ketones as starting material.

1. Baeyer, A. & Villiger, V. Einwirkung des Caro'schen Reagens auf Ketone. Chem. Ber. 32, 3625-3633 (1899).
2. Renz, M. & Meunier, B. 100 years of Baeyer-Villiger oxidations. Eur. J. Org. Chem. 737-750 (1999).
3. Arends, I. W. C. E., Sheldon, R. A., Wallau, M. & Schuchardt, U. Oxidative transformations of organic compounds mediated by redox molecular sieves. Angew. Chem. Int. Edn Engl. 36, 1145-1163 (1997).
4. Strukul, G. Transition metal catalysis in the Baeyer-Villiger oxidation of ketones. Angew. Chem. Int. Edn Engl. 37, 1198-1209 (1998).
5. Fischer, J. & Hölderich, W. F. Baeyer-Villiger-oxidation of cyclopentanone with aqueous hydrogen peroxide by acid heterogeneous catalysis. Appl. Catal. A 180, 435-443 (1999).
6. Chang, C. D. & Hellring, S. D. Production of lactones and omega-hydroxycarboxylic acids. US Patent No. 4870192 (1996).
7. Hoelderich, W., Fischer, J., Schindler, G. -P. & Arntz, D. Preparation of lactones by Baeyer-Villiger oxidation of cyclic ketones. German Patent DE 19745442 (1999).
8. Jacobson, S. E., Tang, R. & Mares, F. Oxidation of cyclic ketones by hydrogen peroxide catalysed by group 6 metal peroxo complexes. J. Chem. Soc. Chem. Commun. 888-889 (1978).
9. Herrmann, W. A., Fischer, R. W. & Correia, J. D. G. Multiple bonds between main-group elements and transition metals. Part 133. Methyltrioxorhenium as a catalyst of the Baeyer-Villiger oxidation. J. Mol. Catal. 94, 213-223 (1994).
10. Gavagnin, R., Cataldo, M., Pinna, F. & Strukul, G. Diphosphine-palladium and -platinum complexes as catalysts for the Baeyer-Villiger oxidation of ketones: effect of the diphosphine, oxidation of acyclic ketones, and mechanistic studies. Organometallics 17, 661-667 (1998).
11. Palazzi, C., Pinna, F. & Strukul, G. Polymer-anchored platinum complexes as catalysts for the Baeyer-Villiger oxidation of ketones: preparation and catalytic properties. J. Mol. Catal. A 151, 245-252 (2000).
12. Bhaumik, A., Kumar, P. & Kumar, R. Baeyer-Villiger rearrangement catalysed by titanium silicate molecular sieve (TS-1)/H2O2 system. Catal. Lett. 40, 47-50 (1996). 
13. Herrmann, W. A. Essays on organometallic chemistry, VII. Laboratory curiosities of yesterday, catalysts of tomorrow: organometallic oxides. J. Organomet. Chem. 500, 149-150 (1995).
14. Frisone, M. D. T., Pinna, F. & Strukul, G. Baeyer-Villiger oxidation of cyclic ketones with hydrogen peroxide catalyzed by cationic complexes of platinum(II): selectivity properties and mechanistic studies. Organometallics 12, 148-156 (1993).

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  • Guest
Re: New method for P2P
« Reply #3 on: December 09, 2001, 05:33:00 PM »
Not sure if this one will work, but there are some other reactions in there that might bee of interest to bees.  Benzaldehydes to phenols.

Baeyer-Villiger oxidation of b-aryl substituted unsaturated carbonyl compounds with hydrogen peroxide and catalytic selenium dioxide.
Synth. Commun.  (1995),  25(14),  2121-33.

A simple and cheap oxidative procedure using 30% H2O2 and catalytic SeO2 allows to transform 2-aralkylidenecycloalkanones and hydroxy- or alkoxybenzaldehydes to give, in high yields, enol lactones and aryl formates, resp. 

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  • Guest
Re: New method for P2P
« Reply #4 on: December 09, 2001, 06:03:00 PM »
Yes a-Methylcinnamaldehyde should work in the Oxidation also.

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  • Guest
Re: New method for P2P
« Reply #5 on: December 10, 2001, 11:54:00 PM »
This synthesis might aid the people trying to do the condensation step:


  • Guest
Re: New method for P2P
« Reply #6 on: December 11, 2001, 03:36:00 AM »
With all due respect Rhodium, the reference that you have given would not help any one with the condensation that I have mentioned. ie between benzaldehyde and butanone (methyl ethyl ketone).
Your reference concerns the condensation of aromatic aldehydes and acetone under basic conditions,
The literature on aldol condensations involving these reactants established the following:
C6H5CHO + CH3COCH3 + NaOH         ------> C6H5CH=CHCOCH3 and
C6H5CHO + CH3CH2COCH3 + NaOH -----> C6H5CH=CHCOCH2CH3 but
C6H5CHO + CH3CH2COCH3 + HCl     -----> C6H5CH=C(COCH3)CH3.
The condensation to get methyl phenyl butenone  needs to be done under acidic conditions. There is a French reference somewhere that states that the condensation can be done by reluxing equal volume amounts of benzaldehyde and butanone with hydrochloric acid and there are also references using  H2SO4. I have tried both of these and did not get the result that I did using dry HCl gas.


  • Guest
Re: New method for P2P
« Reply #7 on: December 11, 2001, 04:30:00 AM »
Okay, I'll shut up when it comes to aldol chemistry again. That's not my field.


  • Guest
Re: New method for P2P
« Reply #8 on: December 12, 2001, 12:32:00 PM »

Interesting. What is the reference for the first condensation reaction?

The references from the article on the first condensation from Organic Reactions 16 (entirely on aldol condensations) are from Rec Trav Chem 84 17 & 979 (1968)


  • Guest
Acidic condensation of Benzaldehyde & MEK
« Reply #9 on: November 17, 2003, 02:29:00 AM »
Benzaldehyde + methyl ethyl ketone -> 2-acetyl-propenylbenzene

Acid Catalyzed (HCl or H2SO4):

C.R.Hebd.Seances Acad.Sci. 226, 1095 (1948)
C.R.Hebd.Seances Acad.Sci. 226; 1948; 500.
Indian J.Chem.Sect.B 40(8), 667-673 (2001)
Bull.Chem.Soc.Jpn.; 69; 9; 1996; 2633-2638.
Bull.Soc.Chim.Fr.; <4>47; 1930; 195,199,200;
Bull.Soc.Chim.Fr.; 1970; 1497-1502.
Bull.Acad.Sci.USSR Div.Chem.Sci.(Engl.Transl.); EN; 5; 1966; 867-871;
Izv.Akad.Nauk SSSR Ser.Khim.; RU; 5; 1966; 909-914.
Pol.J.Chem.; EN; 52; 1978; 2233-2241.
Pol.J.Chem.; EN; 53; 1979; 849-853.
Gazz.Chim.Ital.; 67; 1937; 440, 442.
Gazz.Chim.Ital.; 63; 1933; 199, 202.
Ann.Sci.Univ.Jassy,Sect.1; 16; 1931; 536,540,542.
Arch.Pharm.(Weinheim Ger.); GE; 309; 1976; 969-978.
J.Pharm.Sci.; 64; 1975; 241-248.
Can.J.Chem.; 49; 1971; 105-117.
Chem.Ber.; 35; 1902; 970.
Ann.Chim.(Paris); <12>4; 1949; 242;

J. Amer. Chem. Soc. 65, 1824 (1943)

Tetrahedron: Asymmetry 6(9), 2143-2144 (1995) "Enones were prepared from the reaction of the corresponding aryl aldehyde with 2-butanone in 1M H2SO4 of acetic acid solution."

Ruthenium(III)Chloride (90% yield):

Tetrahedron 54(32), 9475-9480 (1998)


Phenylacetone by Bayer-Villiger Oxidation of 2-acetyl-1-phenylprop-1-ene
Boeeseken & Jacobs
Recl. Trav. Chim. Pays-Bas 55, 786 (1936)

Peracetic acid treatment of 2-acetyl-propenylbenzene (3-methyl-4-phenyl-but-3-en-2-one) below 30°C resulted in the formation of phenylacetone enol acetate (2-acetoxy-1-phenylprop-1-ene), mp 131°C and bp 103°C/3mmHg. Heating the crude reaction mixture with aqueous HCl at 80°C gave phenylacetone.


  • Guest
JACS article
« Reply #10 on: November 17, 2003, 02:28:00 PM »
This is fantastic yield increase from 60-94% using 1 to 1 molar ratio. I will try it in a few days. The twodogs procedure uses 2.2 mole MEK to 1 mole PhCHO.

What was not stated in the synthesis part was the temp used when HCL gasing. There is a footnote to this article saying they followed this procedure.,,,,,,,,,,,(5) Muller and Harries, Ber., 36, 9BG (1902).,,,,,,,,,,,,if anyone could find this it would be very helpfull.

I think perhaps the reason my recent yield was so much better (79%) is that I went slower to keep the temp below 5deg and based on earlier results added HCL to compensate for the weight not gained from what was passed. This resulted in a more saturated solution. The amount given (.58 mole HCL) does result in a saturated solution but it is easy to have a lot gas off. I also left it in the ice bath overnight to warm up.

Now if we can only find a non-exotic catalyst for the oxidation this method begins to get very attractive.


  • Guest
More MEK/Benzaldehyde condensation refs
« Reply #11 on: February 10, 2004, 04:31:00 AM »
Ueber die Condensation von Aethylmethylketon mit Benzaldehyd
C. Harries, G. H. Müller

Chem. Ber. 35, 966-971 (1902)


A mixture of 100g methyl ethyl ketone and 140g benzaldehyde is cooled in an ice/salt bath, and saturated with dry hydrogen chloride gas. The reaction mixture turns red, and is allowed to stand for 1-2 days, after which time the oily product is shaken with dilute sodium hydroxide, washed with water and dissolved in diethyl ether. From the ether the product crystallizes in large needles, which smells of camphor. The yield is quantitative. The ketone can be recrystallized from petroleum ether (1g is soluble in 8-9 mL at 20°C) to give fine needles, mp 38°C/bp 127-130°C/12mmHg.
____ ___ __ _

The Condensation of Phenolic Aldehydes and Their Ethers with Methyl Ethyl Ketone
Kenji Iwamoto

Bull. Chem. Soc. Jap. 2, 51-57 (1927)


Condensation of benzaldehydes with MEK under basic conditions (yielding PhCH=CHCOCH2CH3) and acidic (yielding PhCH=C(CH3)COCH3). The reactions are performed with 4-methoxy-, 4-hydroxy-, 3-methoxy-4-hydroxy-, and 3,4-methylenedioxy-benzaldehyde.


  • Guest
Peracid oxidation of unsaturated ketones
« Reply #12 on: February 11, 2004, 01:03:00 PM »
Here are all Boeseken's articles on the topic of peracid oxidation of unsaturated ketones, including the one mentioned in

Post 471343

(Rhodium: "Acidic condensation of Benzaldehyde & MEK", Novel Discourse)

The articles mentioned in

Post 246863

(lugh: "Re: New method for P2P", Novel Discourse)
does not contain any experimental parts, only theoretical studies of benzalacetones.

Sur L'Iso-Phényl-Vinyl-Acetate, C6H5CH=CHOAc, Produit de L'oxydation de la Mono-Benzalacétone par les Peracides
J. Boeseken, A. Kremer

Rec. Trav. Chim. 50, 827-832 (1931)

____ ___ __ _

Le Produit de L'oxydation de la Benzalacétone par L'acide Peracétique
J. Boeseken, A. L. Soesman

Rec. Trav. Chim. 52, 874-880 (1933)

____ ___ __ _

L'oxydation par les Peracides de la Double Liaison à Côte d'un Groupe Carbonyle
J. Boeseken, J. Jacobs

Rec. Trav. Chim. 55, 786-790 (1936)

____ ___ __ _

L'oxydation des 1,3-Dicétones par L'acide Peracétique
J. Boeseken, J. Jacobs

Rec. Trav. Chim. 55, 804-814 (1936)



  • Guest
about this method..
« Reply #13 on: February 16, 2004, 04:15:00 PM »
First of all I want to say that twodogs procedure works just as described.  I also want to mention that somebee has tried both aldehyde:ketone aldol ratios mentioned. Literature 1:1, and twodogs 1:2.2.  The yields from both trials were roughly the same 220-230g from 200g aldehyde.  The only difference was the latter contained a larger MEK forerun upon distillation.  The 1:1 ratio experiment might have yeilded a bit more (20-30g) if the experimenter was willing to relocate the heavy "tar" layer into a smaller flask and finish off the distillation..but it just didnt seem worth the time.
Two questions arise and I thought maybe to just include them in this post instead of starting a new thread.
1. Will heating the twodogs baeyer-villiger product (P2P enol ester) with 33% HCl perform the same function as the saponification step to arrive at P2P??
2.  If not, can another alcohol such as IPA, or MeOH be substituted for the 95% EtOH (everclear) in the saponification step?  Ironically the ethanol is probably the most expensive chem needed in the whole procedure ($13 750mL).


  • Guest
one to one ratio
« Reply #14 on: February 16, 2004, 06:10:00 PM »
The only thing I can see that bio has been doing (not reading german)different is that Harries et al saturated at salt bath temp and let sit for one to 2 days. So this was done at minus 5 degrees whereas previous runs were plus 5 degrees 21.2g/mole HCl passed about 18 absorbed. It did hold about 3 grams per mole more HCl and has not been worked up yet. Now twodogs stated too much HCl promoted polymerization so we will see. The 1:1.05 trial at 5 deg sat 10 hours and crystallized  nicely without distilling. First crop weighed in at 75g and the other is in the freezer. 1st crop washed with 96% EtOH will not need recrys. Looks as clean as the fractionated stuff.

Damn, Chilly are you paying alcohol tax? 96% EtOH here is $1.20 in then discount stores a little more in the drug stores. Actually cheaper than the tech stuff from the chem house and you get a nice heavy HDPE bottle to play with. Seems like no one else is interested in this simple non suspicious procedure. I wonder why?

I think the french articles discuss the concentration of HCl to saponify but I can't read it and what I can decipher may bee wrong. I'll ask bio to pst the pertinent paragraphs and maybee some kind frenchbee can translate. It's actually very short did you see it? Look at the 1936 Jacobs one.


  • Guest
one to one ratio
« Reply #15 on: February 17, 2004, 11:50:00 PM »
OK, the procedure done per the Berliner article (as much as could be deciphered anyway), details above, sat 39 hrs at ambient (ca 20deg). Washed with NaOH separated all but the last few drops to let settle a while. When ready to do the water wash noticed the crystals had already set up in the funnel. Heating the funnel now to melt the stuff. This has never happened before, hopefully a portend of the greater yield.


  • Guest
HBr Gas ? ?
« Reply #16 on: February 22, 2004, 09:48:00 PM »
"There is a French reference somewhere that states that the condensation can be done by reluxing equal volume amounts of benzaldehyde and butanone with hydrochloric acid and there are also references using  H2SO4. I have tried both of these and did not get the result that I did using dry HCl gas."

  Perhaps anhydrous HBr gas could be used instead? Dry HBr is easier for me to make.


  • Guest
« Reply #17 on: March 28, 2004, 06:09:00 PM »
You would think that oxone(Potassium Peroxymonosulfate) might bee good here for the per-acid.

2 cents,
This is a reaction deserves another look,!



  • Guest
Toluene ---> P2P with oxone & MEK?
« Reply #18 on: April 01, 2004, 06:42:00 AM »

You would think that oxone(Potassium Peroxymonosulfate) might bee good here for the per-acid.

2 cents,
This is a reaction deserves another look,!

Toluene can be oxidized to benzaldehyde with persulphate:

Post 208719

(Osmium: "Re: The easiest synth of benzaldehyde from toluene", Chemistry Discourse)

Condense the prepared benzaldehyde with MEK and do the Baeyer-Villiger with K2S2O8 - H2SO4 (ref.: Billups, Kramer, Lastomirsky: J. Org. Chem. (1970) vol 35, p 3080)

Hydrolize et voilà.


  • Guest
I have only access to the first page of this...
« Reply #19 on: April 04, 2004, 03:13:00 PM »
I have only access to the first page of this article online  ::)

The abstract says:
'Solutions of K2S2O8 in 20 - 60 % H2SO4 are advantageous for the Baeyer - Villiger oxidation of ketones.  Yields are quantitative and the differences in migratory aptitudes are larger than those found with other peracids.'

I guess the enol ester just will rearrange in situ to the P2P in the acidic environment (1 pot).
Now, I have been informed that somebee wants to try out this reaction.  Unfortunately, I can't get the journal in my hands until next month.

It would really surprise me if there was nobee with online access to the full journal.  I 'm sure the involved bee will produce a nice write-up for the hive collective.


  • Guest
Baeyer-Villiger with potassium peroxodisulfate
« Reply #20 on: April 04, 2004, 05:43:00 PM »
Rearrangement of aliphatic primary, secondary, and tertiary alkyl hydroperoxides in strong acid
Norman C. Deno, Wilbur E. Billups, Kenneth E. Kramer, and Robert R. Lastomirsky
Journal of Organic Chemistry, 35, 3080-3082 (1970)

The interesting question being: if there is potential for the double bond to react (epoxide for example), is it going to be a problem?


  • Guest
Thanks for obtaining this article, Moo.
« Reply #21 on: April 04, 2004, 07:15:00 PM »
Thanks for obtaining this article, Moo.  I know a bee who is going to be very gratefull.

The interesting question being: if there is potential for the double bond to react (epoxide for example), is it going to be a problem?

This can be a problem indeed, as shown in:

   (page 5/18).  

Another (hypothetical) problem I forsee is that, when the enol ester cleaves & rearranges to the P2P, that the P2P might undergo the Baeyer - Villiger reaction too.  But since the reaction proceeds in minutes, I think kinetics is on our side.  Don't think the benzyl group would migrate very rapidly too.    <--- don't take this info in this paragraph for granted, the Baeyer - Villiger reaction is not my speciality.

For the future experimentator's notice, I think it could be worth to try out the premade persulfuric acid 'dry' Baeyer - Villiger reagent too, for which preparative details (& solvents) are given in the same article (page 10 / 18).


  • Guest
Redox time
« Reply #22 on: April 22, 2004, 07:31:00 AM »
The article says that solutions of K2S2O8 in 20 - 60 % H2SO4 are advantageous for the Baeyer-Villiger oxidation of ketones.

Caro's acid (H2SO5 ) is a powerfull oxidant.  The ketone of the 2-acetyl-propenylbenzene gets protonated in the acidic medium and the peracid reacts with the ketone, whereupon the propenylbenzene migrates and the acetyl group is shopped off in the acidic medium  --> P2P.

Further in the article, is said: It was thus of some interest to find that solutions of K2S2O8 in 50 % H2SO4 gave quantitative yields of the Baeyer-Villiger products of a variety of simple aliphatic ketones.  The reactions were complete at 25 °C, and we cannot understand why this extremely simple procedure has not been utilized !!!

Caro 's acid is generated in situ by adding the K2S2O8 to aqueous sulfuric acid in the folliwing redox reaction:

ox: SO42- + H20  -->  SO52- + 2 H+ + 2 e-
red.: S2O82- + 2 e-  --> 2 SO42-

Or in other words:
H2S2O8 + H2O + H2SO4  -->  H2SO5 + 2 H2SO4

I think it could bee just as simple as that: just adding the 2-acetyl-propenylbenzene to a K2SO8 / H2SO4 solution.

Now, I have been informed that somebee wants to try out this reaction.

I guess the bee who PMed me for retrieving this article forfaited ... arghh: loyality  ::)


  • Guest
« Reply #23 on: April 22, 2004, 08:25:00 PM »
Would 3,4 methylenedioxy benzaldehyde react the same way too? My girlfriend brought me a heliotrope flower from her garden the other day and it struck me how similar it smelled to benzaldehyde...


  • Guest
Piperonal + MEK
« Reply #24 on: April 23, 2004, 03:19:00 AM »
Yes, as you can see here:

Post 487686

(Rhodium: "More MEK/Benzaldehyde condensation refs", Novel Discourse)

The yields aren't stellar though.


  • Guest
I seem to remember a patent about caro's acid...
« Reply #25 on: April 23, 2004, 04:28:00 AM »
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.


  • Guest
« Reply #26 on: April 23, 2004, 04:35:00 AM »
Here it is:

Patent US4049786

Process of preparing peroxymonosulfate
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 to F. After about 15 to 45 minutes, the solution is cooled rapidly to about room temperature.


  • Guest


  • Guest
From document: Fast, high-temperature, acid...
« Reply #28 on: April 26, 2004, 06:57:00 AM »
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   ::) .


  • Guest
Baeyer-Villiger on unsaturated ketones
« Reply #29 on: April 28, 2004, 11:05:00 AM »
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:


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)

____ ___ __ _

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)

____ ___ __ _

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)


  • Guest
Nice articles
« Reply #30 on: April 29, 2004, 06:34:00 AM »
Even though the yields will be low, it is nice to see that the peroxysulfuric acid oxidation works on unsaturated ketones.  Persulfate seems to be a rather usefull compound.  Osmium demonstrated that in

Patent US4146582

it can also be used to convert toluene to benzaldehyde  {unable to localize post due to technical reasons }

This P2P synthesis would be super easy, and rather not suspicious.


  • Guest
non-OTC method
« Reply #31 on: May 03, 2004, 12:08:00 PM »


  • Guest
Some further related references
« Reply #32 on: May 04, 2004, 01:22:00 PM »
Oxydation des aldéhydes ?,?-non-saturés par l'acide peroxoacétique
C. R. Zanesco

Helv. Chim. Acta 49, 1002-1012 (1966)


Baeyer-Villiger oxidation of ?-methyl-cinnamaldehyde with peracetic acid. Discussion of the reaction mechanisms at work, and the product distibution under different reaction conditions. Their best yield of P2P enol formate is 52%, and this is easily hydrolyzed to P2P by mere water.
____ ___ __ _

Synthesis of Heterocyclic Compounds from ?-Unsaturated 1,3-Diketo-esters.
Part II. ?-Substituted Styrylpyrazole- and Styrylisoxazole-carboxylic Esters

L. Rateb & G. Soliman

J. Chem. Soc. 1426-1430 (1966)


Preparation of various ring-substituted ?-methyl-benzalacetones from benzaldehydes and excess 2-butanone (MEK) with dry HCl gas at -5°C. With references to previous preparations.


  • Guest
Baeyer-Villiger on unsaturated ketones
« Reply #33 on: May 04, 2004, 03:29:00 PM »
The following article describes oxidation of benzylideneacetone to phenylacetaldehyde enol acetate with peracatic acid in acetic acid buffered with potassium acetate in 60% yield, also other unsaturated ketones relatively close to phenylacetone enol acetate are oxidised and "isolated in yields of 65-80%", 2-benzylidenecyclopentanone among them. What do you think, could the need for 90% hydrogen peroxide be avoided by use of UHP (urea hydrogen peroxide complex) here?

Reaction of peroxyacetic acid with a-aralkylidenecyclanones.
Walton, Henry M.
Journal of Organic Chemistry, 22, 1161-5 (1957).  Journal language unavailable.
CAN 52:29915  ISSN 0022-3263
The reaction of peroxyacetic acid (I) with a-aralkylidenecyclopentanones and a-aralkylidenecyclohexanones in AcOH media of different acidity resulted in the intrusion of an O atom between the CO and the methylidene C atoms, with the formation of new 5-enoic-5-hydroxy acid d-lactones and 6-enoic-6-hydroxy
acid e-lactones.  In the presence of massive amts. of KOAc further oxidation of the enol lactones under conditions of their formation was effectively suppressed.  a-Furfurylidenecyclohexanone (II) reacted similarly.  p-Anisaldehyde (28.5 g.), 18.0 g. cyclopentanone (III), 200 ml. Et2O, and 200 ml. N NaOH
stirred 64 hrs. at room temp., the aq. layer sepd. and extd. with Et2O, the combined Et2O exts. washed, dried, and concd., and the residue distd. in vacuo gave 30 g. p-anisalcyclopentanone (IV), b25 175 Deg, m. 68-9 Deg (iso-PrOH).  A higher yield of IV was obtained when the same reactants in Et2O and N NaOH were shaken 15 hrs. at room temp.  Furfural (32 g.), 28 g. III, 150 ml. Et2O, and 0.1N NaOH stirred 45 min. and the product distd. in vacuo gave 55 g. furfurylidenecyclopentanone, b15 154 Deg, m. 59-60 Deg (isopropyl ether).  BzH (212 g.), 218 g. cyclohexanone (V), and 1 l. N NaOH refluxed 3 hrs. gave 273 g. benzalcyclohexanone (Va), b10 173-83 Deg, m. 54 Deg (ligroine).  When substituted benzaldehydes were condensed with V, heating under reflux was applied 5-6 hrs.  With less reactive aldehydes (o- and p-chlorobenzaldehyde), two fold molar quantities of V gave improved yields.  The o-Cl deriv. b0.15
128 Deg and the p-Cl deriv. m. 82 Deg.  Furfural (196 g.) added in 2 portions to 200 g. cyclohexanone
and 2 l. N NaOH, after addn. of the first part the temp. reached 34 Deg in 2 hrs.; when the temp. dropped to 30 Deg the remaining half of the ketone was added and stirring continued 21 hrs., and the product isolated as above gave 217 g. II, b0.2 103 Deg, m. 46-7 Deg.  The I reagent was added rapidly with
stirring to a slight excess of cyclanone dissolved or suspd. in a five- or six-fold amt. of the appropriate solvent system.  The reaction was strongly exothermic and the temp. maintained at 30 Deg by cooling; after 20-30 min. the reaction slowed down, quenched by the addn. of Et2O and H2O, when 1.0 atom of active O had been consumed, and the product was isolated from the Et2O soln.  When the Et2O solns. obtained from reaction mixts. contg. massive amts. of KOAc were evapd. the residue usually crystd., furnishing crude lactones RC6H4CH:C.(CH2)n.CH2.C(O).O (VI); in a few cases partial purification by distn. in vacuo was necessary to bring about crystn.  Characterization of VI involved sapon. of the lactones in a slight excess of aq.-alc. alkali and treatment of the sapon. mixt. with semicarbazide reagent.
I (12 ml., contg. 0.076 mole peracid) was added during 10 min. to 14.05 g. Va in AcOH satd. with KOAc; after 40 min., about 93% of the I and 53% of the H2O2 content of the reagent had been consumed and after 70 min. about 95% and 68%, resp.  Extn. with Et2O and sepn. gave 8.4 g. VI (R = H, n = 2) (VIa).
Somewhat less pure material was isolated from the mother liquors to give a total yield of 67% based on I, 62% based on Va.  The following VI were thus prepd. (R, n, m.p. or b.p./mm., solvent of recrystn., m.p. of semicarbazone, recrystn. solvent, and neutralization equiv. are given): H (VIa), 2, 79-80 Deg, isopropyl ether, 162-3.5 Deg, aq. alc., 264; o-Cl, 2, 113.5-14.5 Deg, iso-PrOH, -, -, -; p-Cl, 2, 111-12 Deg, iso-PrOH, -, -, -; p-MeO (VIb), 2, 72-3 Deg, iso-PrOH, 157 Deg, aq. alc., -; 3,4-OCH2O, 2, 96-7 Deg, isopropyl ether-iso-PrOH, -, -, -; H, 3, 70-1 Deg, isopropyl ether, 158-9 Deg, aq. alc., 271; p-Cl, 3, 103-4 Deg, iso-PrOH, 163-3.5 Deg, aq. dioxane, -; p-MeO, 3, 67 Deg, isopropyl ether, -, -, -; H, (from 3-methyl-6-benzalcyclohexanone), 63.5 Deg, isopropyl ether, -, -, -; o-Cl, 3, 88-9 Deg, iso-PrOH, 188-9 Deg (decompn.), aq. dioxane, -; 2-furyl, 3, 137 Deg/1.5, -, 150 Deg, aq. MeOH, 269.  The
corresponding epoxides (VIIa) and (VIIb) were obtained similarly to VIa and VIb; VIIa m. 80 Deg (isopropyl ether) and VIIb m. 64 Deg (iso-PrOH).  They were isolated from mixts. obtained by using AcOH contg. small amts. of alkali acetate as the solvent.  7-Phenyl-6-hydroxy-6-heptenoic acid e-lactone (2.02
g.) was oxidized 16 hrs. at room temp. with 2% KMnO4, 5 g. K2CO3 added, the stirring continued 2 hrs., several small amts. of (CO2H)2 added to discharge the purple color of the soln., the mixt. filtered,
the filtrate concd., and the residue dissolved in H2O, acidified to pH 5, BzOH removed, and the filtrate worked up to give adipic acid.  VIa (1.3 g.) in 12 ml. AcOH treated 1 hr. with I gave 0.73 g. VIIa.  VIIa (0.10 g.) saponified at room temp. in 0.2N KOH in 3 ml. 50% alc. gave the acid, m. 62 Deg (CCl4-ligroine), neutralization equiv. 221.

The first of the two following articles describe a method for Baeyer-Villiger oxidation of unsaturated ketones with both hydrogen peroxide and a solution of sodium hydroxide added simultaneously to the unsaturated ketone in ethanol at -10°C. The formed enol acetate is hydrolyzed in situ, the products for 2-cyclopentylidenecyclopentanone being both 5-cyclopentyl-5-oxovaleric acid (25% yield) and it's ethyl ester (60% yield). Alkaline NaOH is a standard method for epoxidation of unsaturated ketones, so the fact that the reaction has been got to turn out as a Baeyer-Villiger oxidation is quite interesting. Guillanton even shows that the reaction really is a Baeyer-Villiger oxidation and does not proceed through the epoxide. The second article describes use of this reaction for preparing ketocarboxylic acids, although more sodium hydroxide is used. Too bad they don't tell the yields of the ester and the acid but go on and hydrolyse the crude reaction products by refluxing them in ethanolic KOH for ten hours. The hydrolysis and the use of fivefold amount of NaOH in the reaction might account for the lower yields, which range from 24% to the 45% for 2-benzylidenecyclopentanone. In my opinion the method of Guillanton should work for 3-benzylidene-2-butanone too with which there is no need to hydrolyze the formed ester ethyl acetate at all. Other oxidations are also described in these articles, K2SO8 among them, haven't compared it to the one posted already in this thread though.

Here is the method of Guillanton freely translated from French, I'd appreciate if someone better at French would proofread it and tell if there are errors.

To a solution of 0.5 mole of 2-cyclopentylidenecyclopentanone in 300 ml of ethanol or methanol cooled to -10°C is added a solution of 122 ml of 15% H2O2 and 18 ml of 4M NaOH simultaneously from two addition funnels regulating the addition so that the temperature does not rise (takes approximately 20 minutes). After returning to room temperature the mixture is neutralized with 10% H2SO4. Most of the ethanol is distilled off, the mixture is extracted with ether, the organic phase is dried with Na2SO4 and the solvent distilled off, leaving the crude product behind.

Action of epoxidizing agents on 2-alkylidenecyclopentanones.
Le Guillanton, Georges.
Bulletin de la Societe Chimique de France, (8), 2871-5 (1969).  Journal written in French.
CAN 71:112467  ISSN 0037-8968
Cyclic ketones I are treated with H2O2 to give d-oxoalkanoic acids RR1CHCO(CH2)3CO2H, where R and R1 and H and alkyl and aryl groups or (RR1C =) cyclopentylidene.  5-Cyclopentyl-5-oxovaleric acid is also
prepd. from the I compd. and K2S2O8 and HOOAc.

Synthesis of d-lactones.  IV.  6-Alkyl or 6-aralkyl d-lactones from cyclopentanone.
Ijima, Akie; Takahashi, Kiyoshi.
Chemical & Pharmaceutical Bulletin, 21(1), 215-19 (1973).  Journal written in French.
CAN 78:124397  ISSN 0009-2363
Reaction of cyclopentanone with aldehydes or ketones RCOR1 gave cyclopentanones (I; R = H, Me, Et; R1
= Me, Et, Pr, CHMe2, Bu CH2CHMe2, n-pentyl, n-hexyl, n-heptyl, n-octyl, Ph).  Hydrogenation of I gave
II, Baeyer-Villiger oxidn. of which gave III.


  • Guest
Maybe I expressed myself too cryptic up there...
« Reply #34 on: May 04, 2004, 03:40:00 PM »
The references you posted are good, but they aren't fully applicable for the case we are currently discussing, as alkyl cycloalkene ketones does not suffer from the side-reaction where the double bond gets epoxidized:

Post 503547

(Rhodium: "Baeyer-Villiger on unsaturated ketones", Novel Discourse)


  • Guest
Good to know. I tried to find out about that a
« Reply #35 on: May 04, 2004, 03:53:00 PM »
Good to know. I tried to find out about that a few months ago, but then forgot about it.


  • Guest
Seleninic acid catalyzed Baeyer-Villiger Oxidation
« Reply #36 on: May 14, 2004, 11:08:00 AM »
Here is the article I mentioned in

Post 503547

(Rhodium: "Baeyer-Villiger on unsaturated ketones", Novel Discourse)

Reaction of ?,?-unsaturated aldehydes with hydrogen peroxide catalysed by benzeneseleninic acids and their precursors
Ludwik Syper

Tetrahedron 43(12), 2853-2871 (1987)



Oxidation of ?,?-unsaturated aldehydes with hydrogen peroxide catalysed by benzeneseleninic acids and their precursors has been investigated. Bis 2-nitrophenyl diselenide has proved to be the most effective catalyst. The major products resulting from the oxidation are vinyl formates (a) which on hydrolysis give saturated aldehydes or ketones (g) having the carbon chain shortened by one carbon atom, compared with the starting aldehydes. The minor products are formyloxyoxiranes (b), ?-hydroxy-carbonyl (e) and ?-formyloxycarbonyl (f) compounds with the carbon chain shortened by one carbon atom. Carbonyl compounds (d), formally derived from an oxidative fission of the carbon-carbon double bond, have been also isolated. Diformyloxy (4c) and formyloxyacetoxy phenylmethane (5c) have been isolated when cinnamaldehyde (4) or 1-phenyl-2-formyloxypropane (5a) were oxidized, respectively. Possible mechanisms of formation of these products are discussed. Similar products resulted when ?,?-unsaturated aldehydes were oxidized with organic peroxyacids.

Offline carl

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Re: New method for P2P
« Reply #37 on: May 09, 2020, 11:04:44 PM »
Apparently, orthoboric acid can substitute the HCl in the condensation step between MEK and benzaldehyde.
Don't ask me for a reference though, it was told me from a first-hands experience.
I would suggest that you guys share information like it was the last day on Earth.  This information slowdown is all because of all that dumb unwillingness to share.  That is where the DEA is winning.  There goal is you not talking to each other.  Let the information flow.  I  promise we will always be 2 steps ahead of DEA chemists if we just keep sharing information
Real bees just hear the buzzing and it doesn´t ever stop. Ever.