---

Rhodium
(Chief Bee)
06-10-02 03:13
No 319315
         Purification is a MUST!   Bookmark  Reply    

If you subject hydratropic aldehyde to an Al/Hg reductive amination with methylamine, you will get N-methyl-2-phenylpropylamine, which to my knowledge is not tested in humans and is possibly toxic.

You must certainly remove all the aldehyde from your P2P before continuing. Ask Osmium about what OTC oxidant you should use, he must know what would work best for that.

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. 

---

(Never mind, the link fixed itself, hell yeah)

---

The transformation of aldehydes to ketones occurs easily under some heating in the presence of mercuric salts and especially easily, one may say, immediately, under the action of concentrated sulfuric acid with cooling. In this process, mercuric salts and concentrated sulfuric acid form loose complexes with the reactants and the reaction products. The end-products of the reaction (ketones) form more stable complexes than aldehydes do. This accounts for the fact that only ketone can be found in these complexes, especially in the case of concentrated sulfuric acid.

---

So it seems to me that in the particular reaction under discussion, i.e., reaction of 2-phenylpropanal with conc. H2SO4 at low temp, there should be none of the original aldehyde present -- and therefore no reason to worry about how to separate it from the p2p.

Hope that covers everything I quoted from, if not let me know.  :)

p.s. sorry if the links point to a post instead of a thread, I can't get them to work the way I want them to :/

---

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

---

....as read from Post 409076 (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.

---

.......as read from Post 409033 (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.

---

......as read from ../rhodium /phenylacetone.html


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 did.....java

---

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

---

............as taken from Jan1983 "Large scale P2P" post # 331698, not longer in existance at the hive.
..........and again repeating what Roger2003 pointed out .Post 319331 (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 scale.........java

---

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.