Pd/C preparations and varying activity!

[java]

Barium, thank you again for your insight and safety tips.
Keeping in mind that glass is a poor heat conductor and not having the modern reactor from Parr with the internal cooling coils, but the old type rocker. With no other way to cool but to put a cooling jacket around the glass container, with very little cooling. Not to be discouraged though, it will be attempted in small quantities until a good ratio of concentration of nitromethane and catalyst is found  as to keep the reaction under control.

In another page I read foxy2  find using the raney nickle with a yield of 80% of methylamine at room temp in just a few minutes......

Post 353051

(foxy2: "Raney Nickel CTH Reduction of Nitro/Nitrile Groups", Methods Discourse)

this can be a good alternative.......java

[armageddon]

Well, sice you are considering reducing nitromethane to methylamine with Pd/C, this might interest you:

Post 490818

(armageddon: "Reductive amination", Chemistry Discourse)

Or, perhaps more informative,

http://www.tech.chem.ethz.ch/hungerb/research/reaction/hydrogenation.html

, they investigate the calorimetry of the different steps involved in nitro-to-amine reductions of nitrobenzene...

Obviously, calorimetry is VERY important in terms of controlling industrial-scale hydrogenations with Pd/C...
They even designed a reaction calorimeter for that particular purpose!

..better have that bucket of ice/salt-water on hand....

Parr hydrogenators aren't nice when they explode, especially if they contain something like nitromethane!

http://tlf.cx/dearpenis.swf

[roger2003]

32 pages Hydrogenation Overview from Degussa:

http://www.strem.com/code/degussakit.html

"Recommendations Guide"

[armageddon]

WOW! That's a pretty cool compilation you found roger2003, THX! And the best things are page 4 (hydrogenation of c=c double bonds) and p. 17 (hydrogenation of alipathic nitro groups)...

According to these reaction schemes, the amount of hydrogen being necessary to achieve complete reduction of P2NP to Phenyl-2-aminopropane would be 8 molar equivalents, right? three H₂ for the nitro group and one H₂ for the double bond? What if one used ammonium formate as a hydrogen donor, would 8 molar equivalents be sufficient for "complete" reduction of P2NP (as complete as possible under these conditions, maybe 60% of theory? dunno..) or is it better to use even more HCOONH₄, SWIMs condenser was severely clogged with white precipitate last time he did a reduction... obviously this was a product of ammonium formate decomposition (maybe ammonium carbonate?), so maybe SWIM should account for that next time and use even more of it...

And wouldn't silica gel help to improve yields, taking up the water formed in the nitro-to-amine hydrogenation (2 mol H₂O per mol of styrene)? (Hmm, 120g silica gel for one mol nitrostyrene? it can soak up 30% of its weight of water)

Correct me if my few brain cells worked improperly here..

Oh, and a last question: in their hydrogenation overview, degussa states that the favorable temp. range for nitro reductions is 50-150°C, but the optimum temp. for double bond reductions is 5-100°, so what temp. between 50-100°C would be best for nitropropene reductions? I would think 100°, but I'm just guessing here. Any suggestions?

Thanks!

[hest]

You need high presure to reduce the nitropropene to the amine (much more than 3-6bar). Iff that's not posible stick to the two step reation. From nitropropen to nitroprpan and then to the amine (using RaNi (cheap)) Pd/C (starting material must bee pure but yeald is high) CTH(the best) Zn/AcOH(most getto) ect.

[armageddon]

Thanks for your response, hest!! But are you sure about the pressure thing? I'm thinking of

Post 108528 (missing)

(dormouse: "reduction of P2NitroPropene with Pd-C  -dreamer", Novel Discourse) and

Post 11380 (missing)

(psyloxy: "on reductions with Pd/C...", Chemistry Discourse)
I thought the procedure worked as described by dreamer.... he obviously didn't use pressure/hydrogen, but used NH₄COOH as internal hydrogen source (the formate is decomposed by the Pd/C and releases hydrogen)..

SWIM did some small scale experiments with P2NP a time ago, trying to use ammAcetate/formate as hydrogen source (the latter with more success   ), and is sure that at least SOMETHING happened to his P2NP (he got the same yellow oil dreamer described after basifying and xtracting post-reaction mxtr., and distilling away the solvent, but unfortunately he had no sulfuric at hand, so he wasn't able to make the salt and the tests were abandoned) He used dreamers procedure, but used iPrOH as solvent and added just a small amount of AcOH. SWIM still wonders if the yellow oil was amph or something else, but it was slightly alkaline and some of it dissolved in HCl!? Hmm...
Any idea what happened with his P2NP? The yellow oil SURELY was no P2NP at all! So something must have happened to it... Anyone who knows what it could be?

Anyway, how could one reduce said nitropropene to the amine without using NaBH₄ (expensive, hard to get) and forming the nitropropane, then reducing the nitro group? Besides of making ketone with HCl/Fe or the like? I'm all ears!

Thanks!

[armageddon]

Since SWIM is a VERY curious person sometimes , after I told him some hive bee stated pressurized hydrogen would bee necessary, he decided to find out if a Pd/C reduction of phenyl-2-nitropropene to phenyl-2-aminopropane (amph.) would bee possible without pressure. He instead wanted to use ammonium formate as hydrogen donor, like described in

Post 108528 (missing)

(dormouse: "reduction of P2NitroPropene with Pd-C  -dreamer", Novel Discourse) with slight modifications: SWIM wanted to use isopropanol as solvent, let the reaction run under anhydrous conditions and he wanted to use 8 mol. equivalents of ammonium formate. So, he reXtalized some P2NP, and got beautiful yellow needles up to 2cm in length...  He then weighed out 1.45g Pd/C 10% (from fresh bottle), slurried it with some iPrOH and heated it to 50° in a 250ml RBF for 5 minutes (see first post of this thread, patent US3458576, thx roger2003). Meanwhile, 7.3g of his just dried P2NP cryst. were dissolved again (they were SO nice ) in 25ml boiling iPrOH. And SWIM also weighed out 4 x 5g NH4COOH. He then dumped the P2NP solution, some 50ml iPrOH, the first of the 4 NH4COOH portions and a stirbar into the RBF with the Pd/carbon-sludge and added ~2ml GAA and some silica gel to maintain nearly anhydrous consitions (roughly one teaspoon?), put his superb new reflux condenser in place (the funky type which works like liebig,reflux condenser and allihn in one, you know?) and heated under stirring until many very small bubbles were almost foaming out of solution - hmm, looks rather different from normal reflux, SWIM thought, and holding his ear to the opening of the condenser, it sounded like a freshly opened cola..
Five minutes later, SWIM held his breath, removed the condenser and added the 2nd portion NH4COOH (adding it through this condenser would've been impossible ). After he reattached the condenser, it immediately was almost clogged by ammonium carbonate, so he added a bit of 60% acetic acid down the condenser, which helped (60%? silica will take care of H₂O, SWIM thought...)
He then added the remaining 2 portions in 10 minutes intervals, and he cranked the hotplate up to ~150°C. After 40 minutes total refluxing time, he cooled everything, removed his now snow-white condenser (perhaps it is not really superb for this purpose, SWIM thought) and added some benzene (no toluene at hand! bad..). Then he did one of the slowest filtrations he ever did...
Vacuum would've been nice here...
...hours later, SWIM added some water and sodium carbonate to his solution, and a yellow benzene layer separated out. Unfortunately, SWIM had broken his 1000ml sepfunnel two days ago, so he had to use a pipette to transfer this yellow layer to a clean flask. The benzene was removed by distillation, leaving a yellow oil which was dissolved in 15% HCl. This acid solution (yellowish, some darker stuff floated on top) was "washed" with colemans , using a stoppered erlenmayer and pipette   , basified with sodium carbonate, it foamed over and some product was lost...SHIT! SWIM thought, but suddenly the smell of the mixture evaporating as drops on his hotplate remembered swim of something he knows well...
Well, there was still enough oil layer present after his accident, so SWIM separated it with his shitty "new sepfunnel", added colemans, separated, destilled the  coleman away and got 2.7ml of clear, yellow oil which was slightly soluble in water (ph ~8.5) and smelled exactly like some kick ass street dope a friend had given him "to check its purity" just a few hours ago (and it WAS pure!)...

SWIM hasn't slept since then.

Maybe because of the vapors he inhaled while he repeatedly checked the smell of his oil, being impressed about how identical to "real" amphetamine it was indeed...
(he smelled it AT LEAST a dozen times, just to be sure...) Not to forget the vapors during his accident..

SWIM told me he dissolved the oil in 99,9% acetone, added a few granules of silica, stoppered it and placed it in the freezer. Now he's waiting for his sulfuric acid to arrive, it's ordered...
But I know NO substance that would have made SWIM wanting to smell it again and again, besides amph. (weed doesn't count, as it is unfortunately no product of the described reaction, not even a side product )

Will tell you about SWIMs efforts in getting sulfate salt as soon as he will tell me.

Oh, I forgot: SWIM told me the reason why he first heated to 100°C, then slowly to 150° was he wanted to get first optimal conditions for double bond hydrogenation (50-100°), and then shift to conditions best suited for nitro reduction (100-150°, some more AcOH as additional solvent) Thanks again roger2003!

(am I off-topic? forgive me, but that's the only active Pd/C thread..)

[Sunlight]

If you add formic acid instead of acetic you'll get an extra portion of am. formate. Your supposed amphetamine is actually amphetamine isopropyl imine... It have reacted with your anhydrous acetone. You shoud acidify in aqueus medium to go back to amphetamine, then extract and make the same but with ether, toluene etc...

[armageddon]

Thanks for your response, sunlight! Well, SWIM told me he added the GAA/60%acetic because the very complete hydrogenation overview at

http://www2.sivento.de/sivento/uploads_all/text/DC3969_Booklet.qk.pdf

says:

Hydrogenation of Aliphatic Nitro Groups

     R-NO₂     H_{2  >}    R-NH₂

Precious metal:         Pt, Pd
Conditions
Temperature range [°C]  50-150
Pressure Range [bar]    3-50
Supports                activated carbon
Solvents                low polar solvents, acetic acid
Catalyst modifier       e.g. Fe, V

But SWIM thinks that adding some additional formic acid won't hurt, but will reduce the amount of NH₄COOH needed, thus also reducing the amount of white precipitate in his shiny, but difficult to clean    condenser. but he thinks he will use acetic, too next time. But why "amphetamine isopropyl imine"? The yellow oil sitting in SWIMs freezer was the product of a/b extraction, followed by removal of the nonpolar through distillation - there was very little chance that there was isopropyl alcohol left from reaction. Besides, I see no reason in acidifying/extracting a freebase acetone solution that was already acidified in aequous medium, then basified and extracted w/nonpolar which was removed..
And, sorry to question your statement, dear sunlight, but should SWIM really try to extract an acetone solution with a non-polar (no matter whether it is basified or acidified bee4)? I think the acetone would really fuck up the two phases, and make further separation impossible. You surely meant SWIM should remove the acetone by distillation, dissolve the remaining oil in dil. HCl, basify and THEN Xtract w/nonpolar, hm? But anyway, SWIM will try to get the sulfate like planned as soon as his sulfuric arrives, of course he will make up a solution of it in acetone and drip that into his yellow oil/acetone mix, if no precipitate appears, you're probably right about amph isopropyl imine formation. But in that case SWIM could add just H₂O, some more acid, distill away the acetone, basify, extract and try again with benzene as solvent, right?

Sunlight, just for better understanding, could you explain how said imine would be formed if that was the case? I'd appreciate it very much! (dreamer claimed having formed the sulfate in acetone and ether in this thread

Post 108528 (missing)

(dormouse: "reduction of P2NitroPropene with Pd-C  -dreamer", Novel Discourse) and SWIM as well as me thought the ether was just left over from extracting, and acetone did the trick - due to the solubility of sulfate being very small compared to fairly high solubility of the free base..)

corrections are always welcome!

THX armageddon

[armageddon]

Since this is the Pd/C thread...

Check out

http://www2.sivento.de/sivento/uploads_all/text/PMPCHe.pdf

for safe handling of precious metal catalysts!

...and

Patent US6096924

about the use of vanadium as hydroxylamine disproportionating catalyst (unfortunately they reduced only aromatic nitro compounds, but the mechanism behind it is interesting anyway, perhaps a new yield booster for nitro reductions? Note the disproportionation is a shortcut, it significantly reduces the amount of hydrogen needed for total reduction, as it avoids the azo route)




     

Hope this will help some bees in understanding Pd/C better...

[armageddon]

Well, Sunlight, of course you were right and SWIM was wrong... ..you deserve it well being called "pioneer researcher"! And adding water to the acetone-"solution" produced 2 layers on acidification! DOH, SWIM thought, same thing as with post-rxn-mxtr.; alcohol is soluble in both polar and nonpolar solvents, but the addition of water causes separation of NP and alcohol..
One more error to correct: Dreamer used ether/ethanol, not acetone for precipitating the sulfate, the (obviously not working) procedure SWIM tried to use without success is in the "urushibara style amphetamine" document on Rhod's page... Unfortunately, SWIM got < 1ml  when he acidified (having first added some H₂O) and basified/extracted/distilled again, and it still didn't form any precipitate (solvent: dry toluene this time). Well, SWIM thinks that some acetone has made it through the A/B process, again interfering with precipitation
At the moment, SWIM is making more P2NP to be able to try again what smelled really as if it was successful    ...

He's SURE the complete reduction in one step works, and more experiments will be made. Next time, adding formic acid is on the to-do list along with using less formate, using strictly lab grade solvents and reagents (NO colemans !)

If someone has ideas about what else could bee made better, tell me!!

THX a

[armageddon]

Since his last experiment wasn't very successfull, SWIM decided to try once again to reduce P2NP to amphetamine directly via Pd/C and ammonium formate as hydrogen donor. Not wanting to waste any more of his P2nP (it was his 3rd try with this route   ), SWIM tried to follow the instructions in

Post 108528 (missing)

(dormouse: "reduction of P2NitroPropene with Pd-C  -dreamer", Novel Discourse)respectively

https://www.thevespiary.org/rhodium/Rhodium/chemistry/nitropropene.cth.txt

(using exactly same ratios, solvents etc.), at least as closely as it would be possible (he had no chloroform at hand, but tried to substitute it with DCM, which should work, not enough GAA, so he dedicded to use iPrOH as co-solvent, and he slightly modified the workup). Here is what he did:

First, SWIM weighed out 4,4 grams of Pd/C (10% Pd, used one time and reactivated like described in

Patent US3214385

.
The Pd/C was put in a 500ml RBF, moistened with iPrOH, then 40 ml AcOH (last try was with some formic and mainly produced loads of CO₂ smoking from top of his condenser   ), another 100 ml iPrOH and 20 g "relatively pure" P2NP (nice yellow crystals, not the bright yellow  ultrapure type, but they would be still good enough, SWIM thought) were put in, together with ~3g silica gel.
SWIM then heated to reflux (ca. 100°C). As soon as reflux started, he introduced 3x 13g NH₄COOH every 9 minutes and one last extra 5g portion was introduced after 25 minutes. After 35 minutes, SWIM cooled everything, added ~100ml DCM and set up for gravity filtration. (AAARGH!! It took 3,5 hours!    SWIM WANTS VACUUM!)
Then he added water until the DCM separated out nicely (~500ml). The DCM was separated, distilled away and SWIM got 11,7ml of a yellow oil with a VERY distinctive smell   . "Hmm, dreamer got more than 4ml more, but still ok" SWIM thought and proceeded with preparing 200ml of dilute (15%) HCl and saturated NaOH solution. Next, he dissolved his oil in 15% HCl, washed 3x with DCM (lots of red something were removed), basified carefully to pH > 9 and extracted with toluene twice. He then combined the toluene xtracts and washed them with saturated NaCl soln. The toluene lost its dirty appearance and became clear, but still colored.
Because SWIM always wants to be accurate, he decided to carefully distill away the toluene for being able to determine the amount of freebase, but unfortunately he ended up with just 3,3ml of a clear, yellow oil, pH of aequous soln. was 5-6 and it dissolved it HCl... and had THE SMELL..

Since his last attempts in forming the sulfate had failed miserably (got nothing..), he tried to be very careful this time. He thought "Hm, for a 4M solution, I would need to dilute 4,93ml of my oil to 10ml with iPrOH, assuming it was pure amine freebase. Ok, some toluene may be still in it, so I will use 0,6ml and dilute to 1ml and assume it is 4M concentration. And the sulfate is (C₉H₁₁NH₂)₂*H₂SO₄, so I should be able to neutralize my 4M with an equal amount of 2M sulfuric/iPrOH, or at least not over-acidify everything". Said, done. SWIM diluted his oil in a test tube, added calculated amount of acid soln. - CLEAR YELLOW...    "Bad, too much acid perhaps" SWIM thought and poured everything back into his oil (3,3ml total, to remember). And guess what, white precipitate formed! "Hmm, freebase is definitely not pure, calculations were wrong or sulfuric soln. was somewhat "wrong" (prepared a few days ago by mixing 54,4ml 98% H)₂SO₄ with 45,6ml 99,9% iPrOH and drying with silica gel)" SWIM thought, and added a bit of abs. ether (for better precipitation, to reduce solubility of formed sulfate) and put it in the freezer for 10 minutes.Then SWIM filtered the crystals and washed with ether and then 99,9% acetone.

But he only got 150mg of white (very pure) sulfate!  

Perhaps I should have dried my solvents with some drying agent, SWIM thought disappointed as he was drying his crystals. Or perhaps I should'nt have distilled off the toulene, perhaps there was still water present, and the freebase was steam distilled, but then, crystal formation should've been easier (nearly anhydrous conditions)

Can anybody help SWIM in improving his shitty yields (1%!?   )
He would greatly appreciate it!

Thanks A

[armageddon]

Note to myself: Sulfuric acid dissolved in alcohol is incompatible with silica gel - if you let it stand several days the silica gel will partially dissolve into something very viscous and stinky - perhaps Si(SO₄)₂ or something similar. At least the sulfuric solution becomes unusable...

 *LOL*