Author Topic: 1st experience w/ Hydratropic Aldehyde -> P2P  (Read 23638 times)

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  • Guest
« Reply #20 on: June 26, 2004, 05:33:00 PM »
Does anyone have any thoughts on 1) Whether my interpretation of the article quoted in the post above is correct, and 2) Whether, if so, there might be other close-boiling fractions present other than the aldehyde, and what they might be (I ask because of xspikehead's first two posts in this thread, where he seems unsure that what he got was pure P2P, even after distillation).

Appreciate your comments.


  • Guest
another attempt
« Reply #21 on: July 01, 2004, 07:13:00 PM »
OK.  SWIM used the proper amount of ice this time, and with the acid suitably diluted by the melted ice, the reaction product did turn from brown to white, as it should have.

There is a good amount of yellow-whitish lumpy stuff, which SWIM thinks is some sort of sulfur compound, as there were what looked like sulfur clumps stuck to the inside of the flask after the reaction.

After extract with toluene, water wash, bicarbonate wash, attempted distill.  (Did not attempt to remove unreacted aldehyde, as there shouldn't be any left, according to the journal I quoted above, and because it doesn't smell at all like the aldehyde, which has a distinctive odor.)  While distilling off the toluene, the mixture suddenly turned to a darker color... not as dark as the original brown, but sort of a reddish dark gold.  After distilling the toluene at atmospheric pressure, SWIM did a vacuum distillation on the dark liquid which remained.

The russian article says that "condensation products" form, causing the dark brown color, but that they break up when the acid is diluted, allowing the p2p to be isolated.  That did appear to happen.  But then it seemed they reformed.  I'm not sure why that would happen, since I had washed the toluene, so there shouldn't have been more sulfuric left to form more of these condensation products.

Any suggestions?


  • Guest
Oxidation needed.....
« Reply #22 on: July 01, 2004, 08:50:00 PM »
It was recommended to use to oxidation  here are some quotes.......


To separate 2-phenylpropanal from phenyl-2-propanone you first need to oxidize the 2-phenylpropanal to 2-phenylpropanoic acid (perhaps with basic potassium permanganate or dilute potassium dichromate), then you can wash it away with aqueous base read from

Post 409076 (missing)

(Rhodium: "Read up some more first, you are confusing a...", Stimulants)

 a mixture of 2-phenylpropanal and phenyl-2-propanone? In that case, mild oxidation of the aldehyde to the acid shouldn't disturb the ketone, and the formed acid can be extracted as the sodium salt with 10% aqueous sodium carbonate, while the P2P will stay in the organic layer. read from

Post 409033 (missing)

(Rhodium: "Separating 2-phenylpropanal and phenyl-2-propanone", Stimulants)

It is not possible to effectively separate 2-phenylpropanal (bp 222°C/760mmHg) from phenyl-2-propanone (bp 214°C/760mmHg) through simple distillation and certainly not via vacuum distillation as the boiling points are too close. Fractional distillation could theoretically be used to separate them, but the size of the column that would have to be used makes that option impractical. A good idea for separating a mixture of the two is to oxidize the mixture with a mild oxidant which won't affect the P2P, but which will oxidize the aldehyde to 2-phenylpropionic acid. The acid can then be separated from the ketone by dissolving the mixture in a non-polar solvent and washing the solution with dilute sodium hydroxide. The P2P stays in the organic layer, which is then dried over MgSO4, the solvent removed under vacuum and the residue vacuum distilled to give pure P2P. read from

so you see even though you can't smell it it's gumming up the end product you want, Jan 1983 claims even in his large scale production ,post not existing , that he got good results without oxidation to salt out the aldehyde as an acid, but then he's not around to answer as to what he


  • Guest
I know this. But all of these assume that...
« Reply #23 on: July 01, 2004, 09:28:00 PM »
I know this.  But all of these assume that there is still aldehyde left in the solution.  Did you read my response to your request for references, above?  The last article, the Russian one from the "requested by java" thread, clearly says that none of the original aldehyde remains when using the conc. sulfuric / low temp variation of this reaction.  It mentions the fact several times.

I actually suspect that SWIM's bicarbonate wash was not sufficient.  Testing the pH of a final water wash should tell whether any acid remains.  A sulfur odor is detected in the final distillation product, SWIM has noted, so I'm thinking that the sulfuric residue caused the stuff to re-polymerize, or re-form the condensation products, or whatever it is doing, during distillation.

Well, guess SWIM will have to try again, and be more careful this time.


  • Guest
Ber. 60, 1050 (1927)
« Reply #24 on: July 01, 2004, 10:06:00 PM »
In Ber 60, 1050 (1927) they add 6 g Aldehyd to 30 ml conc. H2SO4 at -16°C in 35 minutes. Than this mixture was standing for 15 minutes under cooling to -15°C and than poured on ice. (Yield 48%)

In another experiment they take 9 g Aldehyde to 40 ml conc. H2SO4 under the same conditions (Yield 62%)

So I think it is at first a question of the time for adding (35 minutes) and standing (15 minutes) with a minimum (better cooling) of H2SO4

If you work with 100 g Aldehyde you have to do this also in 35 + 15 minutes.


  • Guest
The cooling time factor.....
« Reply #25 on: July 02, 2004, 07:49:00 AM »
Roger2003  You are correct in pointing this out , interesting that sometimes the smallest part in a synthesis can show it's ugly face with some unwanted results!  I was sold on the comments of oxidation but completely overloooked the time factor .....

after addition of H2SO4, let it stand on stirring for 3 hrs. then take the cap off ,a large vessel used to react the acid with the aldehyde, and take the 25 liter vessel and pour everything into the 100 liter ice bucket.....fine , now wait until ice has melted, then add 10 liters of Toluol seal the large vessel and try to shake it with 2 perons or kick  it around or do anything to mix the layers. then siphon of or take an adequate separator and separate the tolly, , repeat again with 5 liters and then again with 9 liters, vacumm distill the tolly then the loved stuff now you have not high purity P2P I think but it's ok for Al/Hg/Nitro. My yield was 53,98% of the method with 4 liters Hydrotropic aldehyde taken from Jan1983 "Large scale P2P" post # 331698, not longer in existance at the hive.
..........and again repeating what Roger2003 pointed out .

Post 319331 (missing)

(Jan1983: "P2P from 2-Phenylpropanal > 2-PHENYLPROPANAL ...", Stimulants)

I would also like to point out that the old Ref to the Danilov article that Azole so kindly translated was first mentioned to my knowledge, by Jan 1983 as quoted from the same post above.

Does anyone have any thoughts on 1) Whether my interpretation of the article quoted in the post above is correct, and 2) Whether, if so, there might be other close-boiling fractions present other than the aldehyde, and what they might be (I ask because of xspikehead's first two posts in this thread, where he seems unsure that what he got was pure P2P, even after distillation).

"......from CheshireHouse post , I'm not trying your patience only giving  you my thoughts of some small thing you might have missed, as you asked, I included a part of Jan1983 post to further support roger2003 point , as to the waiting period, as it was done in a larger


  • Guest
re: cooling time factor
« Reply #26 on: July 14, 2004, 01:14:00 AM »
I guess that's possible.  Though I can tell you from SWIM's experience that 2 different reactions, one in which the HTA was added over a much longer period, & allowed to stir for longer as well, seemed to yield identical results, as far as SWIM could tell.

The Danilov article mentions the formation of condensation products, which break down when the acid is diluted.  SWIM definitely noted that upon pouring the reaction product over crushed ice the dark brown color disappeared, to be replaced by some sort of whitish stuff that wasn't soluble in water (nor in the dilute acid mixture).  The stuff looked sort of like you'd imagine little pieces of white bread might appear after they had been floating in a jug of water for so long that they'd broken down into little semi-fibrous drifting stuff (note the high-tech analytical descriptive analogy I so skillfully deployed there ;)  ).

When toluene is added, it dissolves the whitish stuff, which seems like it could definitely be problematic, as whatever it is (I assume some sort of by-product of the breakdown of the "condensation products", but I don't know what it is) is now mixed in with the P2P which is hoped to be there.  So I wonder if it might be filtered out before the toluene extraction.

But I also wonder whether it might be bonding to the P2P to some extent -- because otherwise I would think that the P2P would separate from the dilute sulfuric solution... but leaving a sample of the reaction product / dilute sulfuric solution overnight did not show any separation (note, however, that the whitish stuff was not removed before letting it stand).

I have a feeling that this stuff is floating around in there with the P2P, and then after the solvent is removed, and with further heating during distillation, some sort of complex is reforming.  It definitely seemed like there was a sudden reversion to the brownish color while trying to distill the P2P from what was left after removal of the toluene.

I note that Jan1983 (and it seems as if someone else said the same thing in another post, I'm not sure) just used the crude product left after removal of the toluene as if it were the pure product, in completing the synth to meth.  Maybe that's the way to go, as I suspect that the water/alcohol mixture used in the standard methylamine/P2P synth would inhibit the formation of the unwanted gunk (SWIM's attempted distillation of the reaction product after the HTA/H2SO4 synth left a rock-hard amberish substance glued to the bottom of the flask, which only seemed to dissolve completely in acetone.  Upon pouring out the acetone into the sink, SWIM observed that the acetone with the dissolved gunk in it, which was a dark reddish-brown color, immediately turned white upon mixing with some standing water in the bottom of the sink... my take on this is that these same "loose complexes" that were broken down when pouring the reaction product over ice & allowing it to melt, reformed once they were free of the water & able to come into contact with the P2P again (when taken up into the toluene).  Washing the toluene with water didn't help; but when in the acetone, which is miscible with water, water again broke the stuff up.  So maybe the same thing would happen in the water/alcohol mixture used in the meth synth, the water allowing the P2P to break away from whatever it's bonding to.)

Alternatively, I was thinking that the P2P might be extracted from the stuff before distillation, as a bisulfite adduct, as mentioned here:

Chemical separations were conducted by means of a bisulfite addition complex and Girard's reagent T. The aqueous sodium bisulfate extraction of the reaction mixtures removed most of the P2P present; however, higher ketones do not produce bisulfite adducts as easily because of the sensitivity of the additions to steric hindrance45. The water-soluble bisulfite-P2P addition product may be hydrolyzed with strong acid or base to regenerate P2P for examination. The nonbisulfite retained compounds were reacted with Girard's reagent T, a material known to react with ketones to also form water-soluble adducts, which allows separation of ketonic and nonketonic compounds. An organic extraction allowed clean isolation of all nonketonic compounds into an organic phase.

That Girard's reagent T stuff sounds promising, as well, heh... though it sounds like it's really not needed for P2P, and that a sodium bisulfate extraction would work... though, again, if the P2P is already tied up in some sort of complex, I'm not sure whether it would react to form the bisulfite adduct...

*sigh*.  SWIM plans next time to just take the viscous liquid left after removing the toluene & toss it in to the Al/Hg/Nitro synth.  Maybe this is all much ado about nothing.

p.s. Please forgive my (undoubtedly) awkward way of describing my questions / problems / ideas about this stuff.  I'm well aware that I don't know squat about chemistry compared to a lot of people here, and so am not sure when whatever ideas I'm trying to express might be either ridiculous errors in understanding, or painfully obvious restatements of already well-known concepts that everyone else, as a matter of course, takes as a 'given'.  But I do my best to work things out using what little I do know, and what I'm able to gather from the research & ruminations of other bees who appear to know what they're talking about a lot more often than I do.  So thanks for all the help, peoples, and please bear with me.