Sciencemadness Discussion Board - Experimental: Alternative to Al/Hg - the Al/Cu

Experimental: Alternative to Al/Hg - the Al/Cu

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pauldir - 16-8-2014 at 03:34

... first " HELLO COMMUNITY ! "

(my english is bad ..)

@ TheCopperMan

you say we must check the ph from the steam destillation. Where must i check the ph correctly ? In the reaction flask or in the flask with the amine freebase + water
(after the steam destillation, the freebase swim on the top of water when it cooled)

for my understanding, when i do a steam destillation (easy way) i fill my reaction flask with NaOH, that i get a ph ~12, then i start heating ~ 100°C for boiling.
The water takes the freebase with the steam to the outher flask (when i start, this flask is empty

), from time to time i add some more lye to the reaction flask
(ph must about 12 here). Where can i now see it is finished ? All freebase is gone ?

i hope you all can help one more nooby. thank you and have a nice day !

[Edited on 17-8-2014 by pauldir]

TheCopperMan - 16-8-2014 at 15:33

@crystal
No attempt with Ga-salts yet, only Ga metal and it works pretty good. See http://www.sciencemadness.org/talk/viewthread.php?tid=31127

@pauldir
Check PH of the distillate, it should be basic, indicating amine. Then simply add acid until neutral and evaporate the water.

As for knowing when all freebase has distilled over, you need to occasionally check the PH of the drops as they come over. Once the drops coming over are neutral or close to it, all amine has been distilled over.

pauldir - 17-8-2014 at 02:00

thank you @TheCopperMan
..... ahhh i hope i understand now. The NaOH alone comes not over because it is dissolvably in water. Right ?

lullu - 17-8-2014 at 02:27

The NaOH will not end up in the receiver.

solo - 17-8-2014 at 09:17

....the method with cooper sulfate and sodium chloride was tried as posted , after adding the dissolved copper sulfate and sodium chloride the reaction was violent and made an impressive volcano trowing out most of the aluminum....I had a catch plate and return all the material back in and continued with the process .......

i was not able to get much back since i saw most of the aluminum when i filtered......next time when i try it with mny beta nitrostyrene i will heat the solution then pour in in a bucket and then add the copper sulfate and sodium chloride and let it rise as much as it wants since the polypropolene will take quite a bit heat ....

once it calms down i will pour it back in my flask and continue with the reaction or use a RBF ten times head space and run the reaction with no fear of volcanoes ocurring and perhaps the reaction will run its course without andy interruption....solo

Templar - 17-8-2014 at 21:48

I tried this reaction as per the writeup from copperman. I made sure I followed it very closely. I let it reflux for 24hrs after the initial reaction had died down.

After basification and extraction with toluene, I received no yield.

I have to try it again, but I am viewing this synthesis with a heavy dose of skepticism. The internet appears to be full of writeups that promise a lot and give nothing... although it is yet to be seen if this is undoubtably the case...

The fact that no one else has succeeded with this reaction except copperman is worrying.

It will be very dissapointing if it doesnt work a second or a third time, and if no one else can confirm results :mad:

Please note, I'm not saying it doesnt work yet, I'm just saying that it isnt promising when it is run with pure reagents closely following the writeup, and doesnt give anything, and when even nitromethane hasnt been successfully reduced from other members reports.

The substrate in question was a dimethoxylated nitrostyrene.

pepsimax - 17-8-2014 at 22:43

The reaction definitely does work, with beta nitrostyrene at least but I can't get consistent results.

There are two main issues I think....

A, stirring. It's hard to keep the Al under. My best results are when, by luck, the egg bar managed to hold it all down. Overhead stirring is best. But, I made a galluminium alloy which sank when broken up, this worked perfectly with copper chloride.

B, temp. I feel there's a point where if the temperature drops below, the reaction dies and won't restart. Unfortunately it seems to be very close to the bp of ethanol. My highest yielding runs have been very violent and the solvent has boiled away. When I kept the temp stable below 72 in the initial reaction i got no product.

Maybe a higher bp solvent would help, n-PrOH? I can't seem to find any but it looks a good candidate to me, primary alcohol,protic bp 97'c

Templar - 18-8-2014 at 00:31

Quote: Originally posted by pepsimax

The reaction definitely does work, with beta nitrostyrene at least but I can't get consistent results.

There are two main issues I think....

A, stirring. It's hard to keep the Al under. My best results are when, by luck, the egg bar managed to hold it all down. Overhead stirring is best. But, I made a galluminium alloy which sank when broken up, this worked perfectly with copper chloride.

B, temp. I feel there's a point where if the temperature drops below, the reaction dies and won't restart. Unfortunately it seems to be very close to the bp of ethanol. My highest yielding runs have been very violent and the solvent has boiled away. When I kept the temp stable below 72 in the initial reaction i got no product.

Maybe a higher bp solvent would help, n-PrOH? I can't seem to find any but it looks a good candidate to me, primary alcohol,protic bp 97'c

I used a large stir bar and aluminium turnings. Kept reaction rate consistent and under control. Works well for Al/Hg.

What yields have you gotten so far?

pepsimax - 18-8-2014 at 00:49

Well, with al turnings I got 0. Try with large flat strips like coppwrman suggested.

Yields have been 0-75%, sorry that isn't much help! Following the orginal post I always get something, though the side products vary in identity and quantity greatly. Your substrate must be very pure or side reactions compete...

When you have large flat strips you can see the copper plating on to it, I see that as a good sign, never had a complete failure like that.

Have you got any gallium? Look in coppermans other thread and try what I posted with copper chloride, works every time and is very clean!

Ps- what solvent did you use? Ipa doesn't work, ethanol or methanol does. Replicate the original post and I think it will be unlikely you won't see product.

[Edited on 18-8-2014 by pepsimax]

pauldir - 18-8-2014 at 01:29

Quote: Originally posted by pepsimax

Have you got any gallium? Look in coppermans other thread and try what I posted with copper chloride, works every time and is very clean!

[Edited on 18-8-2014 by pepsimax]

in a smal test, this was the same here. First test only with al/ga, the reaction will not realy start, than i add some copper chloride and the reaction looks great for me. now i need some gallium for real testing

pepsimax - 18-8-2014 at 02:12

Excellent, glad to hear one of my suggestions helped! Let us know how it scales, I've run out of gallium too!

Templar - 18-8-2014 at 03:14

Hmm I will try the aluminium strips then. It seems very strange though that Al turns would not work.

pepsimax - 18-8-2014 at 03:31

Good luck. Make sure to let it run as hot as possible whilst keeping it in the flask. If you still don't have any luck, the gallium/al/copper method will work in that scale, but you'll probably have to tweak it for large amounts

TheCopperMan - 18-8-2014 at 03:56

Templar : Did you try a regular Al/Hg on the styrene?

If a regular Al/Hg doesnt work then odds are Al/Cu or Al/Ga wont work either.

pauldir - 18-8-2014 at 04:35

@TheCopperMan
is it possible that you post some pictures from the work, step by step suitable to your first postings ? (use a tool like Exif Tag Remover for erase metadata from pictures)

Templar - 18-8-2014 at 14:23

Yes the nitrostyrene was well purified, light orange xtals.

A more cimprehensive writeup would likely help

Crypto - 24-8-2014 at 13:40

I can confirm that it works. I haven't had luck when I tried to reduce nitromethane but I did reduce b-nitrostyrene. I would not say that I was successful, because the yield was really low. I have to say thou that I just wanted to do a little test and I didn't make much effort. After some optimization of the procedure, the Al/Cu couple can be really useful.

Anyway this is how it went:

I mixed GAA, IPA and water. 100, 35 and 35 ml of each respectively. To the mixture I added 10 grams of CuCl2.H2O and heated it until most of it dissolved. To that I added 12 grams of freshly prepared and still wet (after the water wash) crystals of b-nitrostyrene. I can't tell how much of them there was really. I estimate that something between 6 to 10 grams, closer to 6 I think. After it all went into solution I threw in 10 grams of thick (1mm) Al ribbon. The temperature rose until reflux and kept at that level for 10 or 15 minutes. After it started to drop I just left it and went to eat dinner

No stirring or reflux was applied. After maybe an hour I basified everything and extracted an astounding yield of about 800mg. Loads of unreacted crystals were on the bottom of the flask. 5 grams of aluminum did not react as well.

My thoughts on it are:

- IPA can be used
- stirring and keeping under a reflux would probably increase the yield and the consumption of Al
- the yield would still suck (it would probably be around 1600mg)
- elemental copper present in the post reaction mixture was clogging my separatory funnel which was really annoying
- GAA may not be the solvent of choice for this reaction. Polsaer used only GAA and water, and got lower yields than I did. I used mostly GAA and some IPA with water, and the results were a little bit better. Maybe running it in a mix of mostly alcohol, without acetic acid, would give even better results. CopperMan used 300ml EtOH, 120ml water, 45ml GAA and claims 70% yields.
- the amount of copper salt needed to activate a certain amount of Al has to be determined.
- the amount of Al/Cu needed to reduce a given amount of substrate needs to be determined as well. I personally do belive that yields around 70% percent can be achieved but the amount of Aluminum and Copper used in the original procedure seems too low. Copper has lower overpotential for hydrogen evolution than Mercury so a lot of it can probably just reduce water instead of the substrate. Also more of the Aluminum is turned into AlCl3 because more chloride salt is used to activate it.
- copper doesn't stick to Aluminum like Mercury does when it forms an amalgam. It falls off not long after it plates the surface of Al. That leads me to think that using thin aluminum with a well balanced amount of a copper salt (enough to plate it but to little to consume it by the formation of AlCl3) could give better results than using thick metal and big amounts of salts.

Lastly I want to say that I'm not a scientist but a hobbyist and most, if not all, of my assumptions can be incorrect. Thank you.

[Edited on 24-8-2014 by Crypto]

pepsimax - 24-8-2014 at 18:22

Glad to hear it. Bit scared of copper salts myself, apparently they're incompatible with NM. Know any more?

I just condensed some 3,4-dihydroxybenzaldehyde with nitromethane. Will I have dopamine once it's reduced? By Cu/Al of course ...

Crypto - 25-8-2014 at 01:09

Apperently Copperman tried it without GAA and got worse results. Maybe just a little is needed. Unfortunately no one can reproduce his results.

the gay doctor2 - 10-9-2014 at 22:39

Hello, I have been watching this thread with great interest.

In reply temple, I reduced 2,5-dimethoxynitrostyrene to 2C-H in good yield. The styrenewas also of terrible quality. 4g was reduced to around 3ml.

Cu sulphate and salt were added originally, then another few grams of Al and cu chloride added when it died down.

I think the copper salts may damage the product. Once the reaction was ready for reflux I carefully added zinc dust. This is very foamy and exothermic.This quenches the excess copper chloride, then you must steam distil out your freebase. Yeild was extremely high, I'm not sure how much exactly as my styrene was brown and impure.

I was expecting nothing, got 3ml which was brominated to some sublime 2C-B. The zinc trick also helps with phenyl-2-nitropropene, though yields are OK with that anyway.

P2NP - CuSO4 50-60%

P2NP - CuSO4, then extra Al
nd CuCl, Zn before reflux - 78%.

There's no way you're extracting the zinc mess efficiently without distillation so don't
waste your time.

Templar - 10-9-2014 at 23:17

Quote: Originally posted by the gay doctor2

Hello, I have been watching this thread with great interest.

In reply temple, I reduced 2,5-dimethoxynitrostyrene to 2C-H in good yield. The styrenewas also of terrible quality. 4g was reduced to around 3ml.

Cu sulphate and salt were added originally, then another few grams of Al and cu chloride added when it died down.

I think the copper salts may damage the product. Once the reaction was ready for reflux I carefully added zinc dust. This is very foamy and exothermic.This quenches the excess copper chloride, then you must steam distil out your freebase. Yeild was extremely high, I'm not sure how much exactly as my styrene was brown and impure.

I was expecting nothing, got 3ml which was brominated to some sublime 2C-B. The zinc trick also helps with phenyl-2-nitropropene, though yields are OK with that anyway.

P2NP - CuSO4 50-60%

P2NP - CuSO4, then extra Al
nd CuCl, Zn before reflux - 78%.

There's no way you're extracting the zinc mess efficiently without distillation so don't
waste your time.

Well done.

So you did the reaction with half the needed aluminium at the start with all the nitrostyrene in solution, then added another half with some more Cu and sodium salts once it had died down?

Then you added Zn once the reaction reflux was complete and then steam distilled by adding water to the post reaction mix, basifying then just boiling it in a distillation setup?

Would you be able to go over your exact procedure as best as possible? Amount of Aluminium at the start, type of aluminium etc? (foil, turnings?)

the gay doctor2 - 11-9-2014 at 00:33

Hello friend.

I added 5g Al, thick good quality cut into 30 mm2 squares. 4g styrene, 20ml GAA, 150ml MeOH and 30ml water were brought to 70c.

This stirred via large ptfe paddle at high speed in a 1 litre RBF.

After 15 minutes 2.5g CuSO4 and 5g NaCl, dissolved in enough hot water, was added to the reaction. Within seconds an extremely hard reflux began, stirring was kept high and heat turned off. The temperature was carefully monitored and as it began to drop, heat was reintroduced carefully to keep the hard reflux. This shouldtake under 15m to reach.

Now, 750mg CuCl was again dissolved in minimum hot water, 2g of the Al was added and the copper solution as quickly as possible once the Al is in. You may need to reduce the heat for a few mins but still maintain hard boiling.

Once that has died down let stir at 75 for 30 mins. Now add small spatulas of zinc powder until it has all reacted and stopped foaming and getting hotter. I'm not sure how much Iused sorry,just a slight excess of what was needed.

Now reflux for one hour or so. After this filter the unreacted metals, then set up for distillation. Boil off the alcohol,basify, then steam out your product.

There is probably an excess of Al, perhaps reduce the initial portion like you said.

[Edited on 11-9-2014 by the gay doctor2]

Crypto - 12-9-2014 at 22:17

I'm curious how would the system work with imines. I was planning to give it a try but I haven't got anything to reductively aminate right now.

organichem - 13-9-2014 at 09:32

In-situ reduction of ketone/nitroalkane didn't work for me - I only got aminoalkane
Perhaps with pre-formed imine the reaction works?

TheCopperMan - 25-10-2014 at 05:56

Quote: Originally posted by the gay doctor2

Hi

That is a very high yield. When you got the 78% yield after it was steamed out, did you afterwards vacuum distill the amine to confirm it's purity? Or just add acid and boil down?

Also maybe you could try it without CuSO4 / NaCl, instead just add small amnts of CuCl2, it should work similarily and produce a similarily hard reflux. You would save a lot of copper and salt which when scaling up can be pretty crazy to use so much copper per mole substrate.

Like the Zn idea also. Refluxing for long time seems to actually reduce the yields somewhat, and produces some reddish stuff, so this guess indicates that the copper indeed attacks the amine or substrate or whatever. Adding ZN would help with this.

[Edited on 25-10-2014 by TheCopperMan]

Al/Cu reduction not working as expected

alking - 14-4-2017 at 16:34

Previously I have used the common Al/Hg method successfully, it's a pretty straight forward process. I'd like to find a less toxic alternative however and that is when I discovered Al/Cu as brought to my attention by another poster here. My first couple attempts have failed however and I'm at a loss as to why. So far this has only been tried on beta-nitrostyrene as it's cheap, mentioned as successful in that thread, and I did not see reason to try anything else if I'm getting failure here.

The rxn runs as expected, following TheCopperMan's procedure to the T, until I go to distill off the alcohol post reaction. For some reason during this I get a lot of red coloration forming (previously nearly clear/white post reduction), deep blood red, and after the alcohol is removed this floats on top as it is not water soluble. I have to assume this is, or rather was, my product. There is some mention of this in the thread, but not much is said about it.

My initial thought is that this is probably a copper complex forming, and with Al/Hg I normally basify and separate the alcohol layer before distilling it out so I too thought that may have something to do with it (though I don't see why). So I tried again exactly as I would do with Al/Hg.

So post rxn I drop it to RT, basify, separate the alcohol layer, and then filter off any metals that may still be floating about. From here I dilute with dH20, and neutralize it so as to not steam distill any freebase product as I'm stripping the alcohol and to protect it from any possible side reactions from any excess base. Again however I get a deep red coloration over the course of the distillation, and at this point there should be no copper left to form any complexes (right?) so I can rule that out.

This just leaves me kind of at a loss as to what is going on though. My best guess at this point is maybe the imine is formed but for some reason will not go to the amine and instead something causes it to polymerize, but I really don't understand why that would happen. The nitrostyrene is certainly reduced as noted by the solution going from yellow -> clear. If it can form an imine then it should be able to form an amine through the same process though I would think. Before wasting anymore time and materials I thought it best to look for some kind of insights. There are a lot of people reporting failure in that thread, but quite a few do have success and someone even reported, iirc, a 75% yield of PEA when reducing beta-nitrostyrene. I do believe that same person had a 0% or close to it yield in other attempts with no explanation why or what changed, but I'm convinced this must be a viable alternative and that I am just doing something incorrectly.

I guess I should mention too that the one deviation from copperman's writeup is that I am using a magnetic stirrer and since copper is magnetic that may pose a problem, however it's clearly being reduced to something and all or most of the aluminium dissolves as expected so I can't see that being a factor.

Melgar - 16-4-2017 at 04:19

Copper isn't magnetic... at least not ferromagnetic.

If something is behaving like an imine but is much more stable, that's a good sign you're dealing with an oxime, which is perhaps the most common intermediate that reduction methods get stuck on when reducing nitroalkenes.

If you're in the US, I could send you galinstan via ground shipping, for $0.50 / g +$10 shipping, btw. It's a nice alternative to Hg for Al reductions, although I've only confirmed that it will reduce nitroalkanes to amines experimentally, nitroalkenes should work, but I'd need standards to test against to make sure I'm getting the desired amine in the products.

clearly_not_atara - 16-4-2017 at 19:11

If a complex did form it could certainly be soluble in alcohol or other organic solvents. I know little about Al/Cu but what I do know about dissolving aluminum reductions is that they usually have to be vigorous or the reduction won't be complete. The oxime is a common byproduct. I don't know what you have to do exactly but the aluminum should be dissolving rapidly.

I think it's basically a galvanic process, so why not just use some alligator clips and wire and a piece of copper to serve as a cathode? :p

Alice - 17-4-2017 at 04:02

First of all, that's a very puzzling observation, alking.

So it turns red suddenly or constantly due to removal of the alcohol? Can you reverse the effect by adding alcohol again, adding HCl or NaOH? What was the pH of the mixture you've evaporated? What was the pH after removal of alcohol? Are you able to dissolve red precipitate in any sort of organic solvent? You may try to recrystallize red precipitate in order to find evidence for not having a polymer because polymers are hard to crystallize. You may exclude the presence of copper in red precipitate by the Beilstein test (adding a halogen salt like magnesium chloride).

As others have mentioned, this may be partially reduced nitro styrene, a polymer thereof as well as an oligomer, like a cyclic timer. Find evidence for partial reduction by using the double amount of Al. An oxime or an imine as monomer wouldn't be deep red normally unless it is a copper complex or a tautomer. The tautomer of the oxime is the hydroxylamino stryrene and the tautomer of the imine is the amino styrene, thus fully conjugated. No idea if this would be deep red. Of course these styrenes may also polymerize. But I'm just guessing.

[Edited on 17-4-2017 by Alice]

alking - 22-4-2017 at 07:43

It could be an oxime, though I'm not sure how to confirm that, and I still cannot figure out what might be hindering it from proceeding. To give a little more details on the process it seems that after separating the alcohol, neutralizing it, diluting it with H2O, and then distilling it off, it seems that when it hit around 60C the color change started to occur. First it's a light pink and as the distillation goes on this turns into a dark blood red. After the alcohol is removed there will be some pink in solution, a lot of dark red floating on top, and some crystals that are at the bottom which are also pink. I suspect these crystals are just aluminum salts that have absorbed some of the polymer, but I am not sure, I did not test them. When neutralizing the solution prior to distillation it goes from clear colorless, maybe the slightest tint of yellow (barely any color at all though), to a foggy white as something precipitates out. I assumed this was some aluminum hydroxide or maybe aluminum chloride coming out of solution and so I did not bother to filter it off. This happens with the Hg too and never posed an issue.

Also the 2nd time I did this experiment I refluxed it longer in case it didn't go to completion, maybe 2x as long, and still no polymer formed, so there's something about either the removal of the reducing agent or the removal of the alcohol that encourages the polymerization to occur. However as noted in the first test when distilling the alcohol directly out it still occurs which makes me think it has more to do with removal of the alcohol, which kind of confuses me too, there's a good amount of H2O and alcohol so it's not as if the alcohol would do much to prevent a rxn with the H2O if that's what's occurring.

The 2nd time I refluxed it longer because there was still a good bit of aluminum left, but I had the same amount left as before, and I tend to always have a similar amount left using mercury too.

Quote: Originally posted by clearly_not_atara

If a complex did form it could certainly be soluble in alcohol or other organic solvents. I know little about Al/Cu but what I do know about dissolving aluminum reductions is that they usually have to be vigorous or the reduction won't be complete. The oxime is a common byproduct. I don't know what you have to do exactly but the aluminum should be dissolving rapidly.

I think it's basically a galvanic process, so why not just use some alligator clips and wire and a piece of copper to serve as a cathode? :p

I did not mention it, but the 2nd time I used an addition funnel to slowly add the styrene as well specifically to not create a vigorous reaction. I do not think this mattered though as both times the results were the same, and that's how I do the mercury reductions too, I don't even let them get to a reflux temperature and I have not had issues. In fact I even have better results as if I add it all at once I get some polymer formation with mercury, though not much, yet when I add it slow and keep it below 70C after the rxn is complete my solution is completely colorless (the polymer formation happens during the rxn in this case, not afterward). Why does the speed of the reaction matter? I can't see any reason it would, or would be halted. There's no side rxns you're trying to out compete and so long as you have active aluminum you should be reducing/generating hydrogen regardless of the rate. Am I missing something involved there?

Quote: Originally posted by Alice

First of all, that's a very puzzling observation, alking.

So it turns red suddenly or constantly due to removal of the alcohol? Can you reverse the effect by adding alcohol again, adding HCl or NaOH? What was the pH of the mixture you've evaporated? What was the pH after removal of alcohol? Are you able to dissolve red precipitate in any sort of organic solvent? You may try to recrystallize red precipitate in order to find evidence for not having a polymer because polymers are hard to crystallize. You may exclude the presence of copper in red precipitate by the Beilstein test (adding a halogen salt like magnesium chloride).

As others have mentioned, this may be partially reduced nitro styrene, a polymer thereof as well as an oligomer, like a cyclic timer. Find evidence for partial reduction by using the double amount of Al. An oxime or an imine as monomer wouldn't be deep red normally unless it is a copper complex or a tautomer. The tautomer of the oxime is the hydroxylamino stryrene and the tautomer of the imine is the amino styrene, thus fully conjugated. No idea if this would be deep red. Of course these styrenes may also polymerize. But I'm just guessing.

[Edited on 17-4-2017 by Alice]

It turns red constantly, it's a slow transition over maybe 30 minutes from the point it hits about 60C. It turns light pink and then by the time maybe half the alcohol is removed it seems to be completely polymerized, or at least there's no further color change noted. The PH I measured before distilling was 6.9, but I did not calibrate my meter so it could be off. If anything it would have been slightly acidic though and within .3 or less as I calibrated it later that day (or maybe the next?) and it measured a 7.0 calibration solution as 7.1. I did not test the PH afterward. The red stuff is readily soluble in organic solvents. Basifying it does not change the color, nor does acidifying it, and it does not form salts as acidifying it does not make it water soluble. I'm quite certain it's a polymer formation, I'm just not sure from what, why, and more so why it only happens at the point in which it does (as opposed to during the reduction itself), the last one is really what puzzles me. I assume an intermediate imine of course as they're prone to polymerizing and due to the lack of yellow color I have to assume the styrene was fully reduced. I always have excess aluminum left so it's not due to running out of reducing agent.

I have largely dismissed a complex due to the fact that ALL of the product seems to form this red color and there's not enough copper present to complex all of it, unless I'm misunderstanding how that works anyway. After filtering it and then washing my funnel with HCl to remove the aluminium I'm left with small bits of copper on the filter too, so if it is forming a complex it's not occuring with all of the copper. Of course this copper could be inactive too, it is kind of brown as opposed to shiny, not sure why as copper oxides are not brown.

I am correct in that a complex is similar to a salt, so you'd need an equimolar amount (or some fraction there of anyway) of metal:amine right? Since I am using ~300mg of copper and 3g of styrene most of my product should still be left uncomplexed if that is what's going on. Maybe the complex forms and prevents further activation of the aluminum, thus halting the reaction? That is a possibility I have not thought of.
[Edited on 22-4-2017 by alking]

[Edited on 22-4-2017 by alking]

[Edited on 22-4-2017 by alking]

clearly_not_atara - 22-4-2017 at 11:02

There are at least two side reactions. The first is the rearrangement of nitrosoalkene intermediate to oxime. The reduction proceeds:

Nitroalkene -> nitroalkane -> nitrosoalkane -> hydroxylamine -> amine

The other side reaction occurs when the nitroalkane reacts with the nitroalkene in a Michael addition. This occurs because nitroalkenes are Michael acceptors and nitroalkanes are Michael donors. This reaction is promoted by base and suppressed by acid.

The other other side reaction is the hydrolysis of oxime intermediate to ketone; this only occurs if the rxn mixture is far too acidic. It should never be a problem and you'll notice way too much H2 and heat if it does happen.

Reduction of the Michael rxn dimer produces a 1,3-diamine that may complex with copper or the corresponding 1,3-dioxime. This might be a good ligand for copper. Copper can bind to two bidentate ligants in one complex as is seen with e.g. Fehling's reagent.

However you don't care about any of the theoretical nonsense you want the rxn to work and I agree. I think the pH should be about 5 or so. This ought to suppress the Michael reaction.

Alice - 22-4-2017 at 16:30

Sometimes a solution looks almost colorless despite having some colored compounds in it which becomes only visible by evaporation. Therefor I've asked for reversibility. From your answers I suspect this is not the case here.
The Cu⁺ tetramine complex is soluble colorless and is oxidized by air giving Cu²⁺ tetramine. This way copper might be invisibly present in the solution.
For comparison, the copper glyoxime complex is red and maybe other oxime complexes are red too. Cu²⁺ usually has four ligands (e.g. the tetramine complex) plus two water molecules. A hypothetical complex may consist of a Cu²⁺ ion and four ligands or a polymer-like aggregate of the same ratio.

Quote:

I am correct in that a complex is similar to a salt, so you'd need an equimolar amount (or some fraction there of anyway) of metal:amine right? Since I am using ~300mg of copper and 3g of styrene most of my product should still be left uncomplexed if that is what's going on. Maybe the complex forms and prevents further activation of the aluminum, thus halting the reaction? That is a possibility I have not thought of.

3 g styrene is 20 mmol and 0.3 g copper is 4.7 mmol. About 4:1. But as some styrene is reduced fully, some partially, some styrene is lost due to polymerization or other side reactions, and some copper is reduced to metal and removed by filtration, we're dealing with an unknown ratio which might or might not suit this hypothesis. What's the weight of the red residue after removal of solvent?

All of this is just meant as a vague possibility until there is at least a qualitative test for copper.

lordofthechemicals - 26-4-2017 at 02:47

I have tried this method 2 times with p2np with no result. product smells like amine but isnt stable becomes dark red after 4 5 hours and isnt soluble anymore in petr ether. Copper isnt soluble in ether so i think complexes should be excluded. There is some kind of polymerization going on i suppose? i use sulfuric in ethanol 10% as sulfate isnt soluble in ethanol and if evrything is ok should fall off in white flakes. Maybe its really the pH that should around 5 during the reaction?

[Edited on 26-4-2017 by lordofthechemicals]

Alice - 26-4-2017 at 04:24

Quote:

Copper isnt soluble in ether

What do you mean by "copper"? I assume a copper salt? Or the metal?

A complex isn't really the same as just a salt. Just think about all those transition metal complexes and the various reactions run in organic solvents, called homogeneous catalysis. Petrol ether is a highly nonpolar solvent. Many organic compounds are insoluble in petrol ether.

clearly_not_atara - 26-4-2017 at 10:53

Quote:

Not exactly on topic but it's a trick of the trade that terminal nitrostyrenes can be reduced effectively with zinc powder and HCl (Leminger reduction), whereas internal nitroalkenes such as phenyl-2-nitropropene require more advanced approaches.

Perhaps when analyzing the results of this reduction it would benefit our investigation to note whether a terminal or internal nitroalkene is being reduced. It is possible that terminal nitroalkenes are reduced more easily by Al/Cu as well, which could account for inconsistent results with this method.

tsathoggua1 - 27-4-2017 at 17:04

I attempted to reduce propan-2-one last night using Al (as foil), HCOOH (54%) and CuCl2 (before finding out it doesn't work worth shit on small liear aliphatic ketones), not out of any great desire for the end product, just on a test tube scale, since I was sleepless and wanted something to do.

First a nugget of rolled up Al foil was added to the tube, followed by acetone, then the formic acid. There was no reaction of any kind until addition of CuCl2 (an initial 2 drops of saturated solution to get the rxn started, then a further 6 drops to a test tube filled with 50-50 acetone/HCOOH upon which vigorous hydrogen evolution began, along with deposition of a fine sludge of dark ruddy color, later produced via addition of CuCl2 to Al, and isolated, forming a fine black powder when heated in the hottest portion of a propane torch flame, the powder appears to be copper metal in finely divided form.

Rate of attack seems strongly dependent upon concentration of the CuCl2, for the initiation of the rxn succeeded (with substrate ketone and acid) with just two drops taken from a bowl of almost fully crystallized solution of the chloride, but began to bubble violently when the remaining drops were added.

Also, whilst the H2 evolution continued with CuCl2/Al/H2O alone for a considerable duration (I ended up going to bed eventually, and, having taken my antiseizure medication (chlormethiazole, fairly strong sedative) and as I was tired but sleepless, some 15mg nitrazepam, and opioid pain medication (I'd get no sleep at all otherwise, with my screwed up joints and nerve damage) did not again wake until almost 6:30 or so the next evening by which time any CuCl2 ought to have been reduced to copper (0), and there indeed was a sizeable quantity of copper, with respect to the amount of CuCl2 used, however evolution of H2 whilst slowed after many hours, carried on, and although almost so, it STILL has not ceased 100%, its still giving off a slow stream of hydrogen bubbles now. Another lot, upon deliberate addition of a tetrammoniumcopper (II) complex (the chloride, so as not to complicate things anymore than needs be with other anions) it instantly discharged the deep blue of the copper complex, prepared from aqueous NH3 and CuCl2 (aq) and seemed to cause significant foaming and turned much of the remaining Al to sludge of a fine consistency and grey color, like one would expect from an Al/Hg amalgam reduction post completion and workup and dramatically slowed the hydrogen evolution down. Its still going however.

I wonder if its acting (with just CuCl2 and HCOOH/Al or CuCl2/Al/H2O) as an electrolytic couple like zinc-copper, nickel-copper couples, since the reaction seemed to accelerate after some initial deposition of copper once all CuCl2 to be added had been so, and decomposed water/acid via catalytic or galvanic means), with an initial acceleration followed by a slowing as the CuCl2 appeared to be largely consumed, then subsequent pickup of rate of evolution of H2 after some Cu deposition.

Will try using the Al/Cu system to attempt reduction of an aliphatic nitroalkane (nitroethane, since the ethylamine could easily be detected, and trapped in alcohol solution, to be driven off by a little brief heating when ready to assay the results, aiming for a qualitative assay at first, since I have no current need for ethylamine, I've got plenty nitroethane, I'd try reduction of a beta-nitrostyrene, but unfortunately currently have no nitromethane, only nitroethane, annd given the formation of a coordinating lewis acid/presence of same to begin with I'd expect the reactivity of the nitro group to be increased and to obtain if anything useful, 1-phenyl-propan-2-one rather than amphetamine, or possibly in-situ formation of some N-ethylamphetamine via reduction of nitroethane to ethylamine and reductive amination of P2P in-situ with unreacted ethylamine.

I'm not hugely enthusiastic about trying this for P2P synthesis, since Fe/HCl/FeCl3 can already do this. And given the substrate being tested is a nitropropene rather than nitrostyrene, the Fe/HCl/FeCl3 system won't reduce nitropropenes to the amine, unlike beta-nitrostyrenes.

lordofthechemicals - 28-4-2017 at 01:24

can someone give detailed literature references about pH ,temperature and reagent concentrations needed for successful reduction of p2np to amine ?

woelen - 28-4-2017 at 02:09

@lordofthechemicals : What are you up to? If it smells like cookery, then it most likely is cookery. We do not allow spoonfeeding requests for the synthesis of drugs or drugs-precursors!

[Edited on 28-4-17 by woelen]

alking - 28-4-2017 at 10:21

Quote: Originally posted by lordofthechemicals

can someone give detailed literature references about pH ,temperature and reagent concentrations needed for successful reduction of p2np to amine ?

This does smell like cookery, but regardless there's plenty of references out there as is of known methods, if you knew what you were doing you could easily find them with a google search. This thread is about experimenting with a new method though so whether you're trying to make something illegal or not this post isn't particularly relevant to the topic at hand.

Corrosive Joeseph - 28-4-2017 at 14:50

Quote: Originally posted by lordofthechemicals

can someone give detailed literature references about pH ,temperature and reagent concentrations needed for successful reduction of p2np to amine ?

1 - Charge a round bottom flask with 100 grams of P2NP

2 - Read until your eyes catch fire

3 - Think about it all til your brain explodes

4 - Refux all that for a couple of months

Yields are about 50% with this method

/CJ

Thank me later, there is no fee for this......................

[EDIT] - Sorry, couldn't help myself..................

[Edited on 29-4-2017 by Corrosive Joeseph]

lordofthechemicals - 29-4-2017 at 02:13

am not at anything if wanted to make phenethylamine would choose al/hg,al/ga, lialh4 or others syntheses with higher yields not al/cu. I use p2np because of its internal double bond and aliphatic nitro group eg harder reduction than styrene reduction lets say. whats interesting to me is the mechanism of al/cu reduction and why use copper instead of other transition metal... , to compare this methods yield with others for p2np and also have lots of benzaldehyde and nitroethane at hand. if this method is useful for this it would be useful for a lot of other compounds. I really dont understand this moral policing and flaming done everywhere lets complain about alchohol which is more dangerous than nearly every other "ILLEGAL" compound.

Alice - 29-4-2017 at 03:56

Lordofthechemicals, your opinion about what should be legal and illegal doesn't matter if you're getting charged for the manufacture of a controlled/scheduled substance. It is not sufficient having just science in mind. Even if you're working at a university or in the industry there is (depending where you live) a well defined procedure to adhere before being allowed to work with controlled/scheduled substances. This usually involves communication with the relevant authorities before doing anything practical and a gapless and transparent record of what you were doing.
On the other hand, depending where you live, and because you stated your product may be amphetamine it may be even illegal to give you any advice enabling you to achieve that goal. Therefor the reactions you received have nothing to do with being square or not. It has something to do with people not being keen on becoming part of your vortex of self-destruction.

Corrosive Joeseph - 29-4-2017 at 15:24

@ alking - Any update on this....................? Are you still using magnetic stirring...............?

Copper isn't magnetic but it interacts with magnets in strange ways - check the video in the first link

http://terpconnect.umd.edu/~wbreslyn/chemistry/is-copper-mag...

https://www.quora.com/Is-copper-magnetic

"To be technically precise, pure copper is diamagnetic, meaning that it has no unpaired electrons and will interact with magnetic fields only very weakly."

The red coloration is puzzling.

I didn't post until now but from what I have I read of this thread before I really wouldn't have much faith.

Seems very hard to get consistent results. I would love to see it work.

beta-nitrostyrene SHOULD be even easier to reduce than P2NP from what I have read.............

/CJ

tsathoggua1 - 30-4-2017 at 12:51

Just a warning-with Al/Hg reduction, DON'T try doing 100g at a time, start with a tenth of that. That will take up a 1 liter flask nearly to the brim once the end dissolution of the surplus, unreacted Al foil (don't try using powder, foil crumpled into balls still generates a LOT of heat) is complete. Both the initial amalgamation is highly exothermic, so have yourself an ice bath handy, temperature should be between 60-70 'C, although allowances for a brief exotherm can be made with plain P2NP.

Up to 40 degrees 'C whilst amalgamation is being prepared for, then take the heat OFF, and get ready to shift from maintaining at 40 to rapid changeover to ice bath or it will take off like a rocket. Additional portions of GAA may help once it begins to peter out a bit, as will loading the Al in several portions. Three, four portions for a 10g reduction should do it, with the addition, with stirring of a little bit more mercuric salt (make sure its Hg (II), the chloride works just fine, IMO since a nitro group is being reduced mercuric nitrate may decrease the yield a little, tried with Hg (II) sulfate, this is not a great approach and despite addition in two portions, rxn needed another crack, using HgCl2 because the sulfate is not terribly stable, although corrosive sublimate can be prepared from it and this salt sublimed (carefully, you really, really do not want to breathe this in, ingest it, or get it on your skin, it could mean the end of you.

As for Hg quantities, have heard plenty things, from 1g/10g nitroalkene to a little off the tip of a knife. The latter works, 1g/10g seems excessive really. And can always add a little more in portions with each portion of Al, plus a little extra GAA.

Sometimes GAA alone will restart the reaction.

Apparently Fe/HCl or Zn/HCl works well enough on nitrostyrenes, with nitropropenes however it gives the corresponding P2P (although an in-situ reduction of nitromethane with the same technique can give the secondary amines, otherwise this reduction using P2NPs gives the primary amine. Ideal if its simple amphetamine being produced, 5HT2a agonists of the phenethylamine/amphetamine type seem to require a primary amine, with secondary amines losing much activity, such as ARIADNE, etc.and according to Shulgin, being of antidepressant type effects primarily. Although I've never personally tasted the 'classic ladies'.

I'd be interested on hearing of results if you have success, or failure, with Al/Cu to reduce nitropropenes, and whether they have primarily electron-withdrawing or donating ring substitutions, as well as P2NP itself. If your already going to do it, then I'd like to know the results.

Oh and for Al/Hg, do use a long condenser setup, 10g backed up an ice-salt-water-alcohol-ethylene glycol-cooled allihn condenser into the vigreaux mounted on top, although it didn't get to the liebig above that, got about 1/3 of the way up into the vigreaux briefly, and heavy refluxing before it calmed down a bit.

Any alternative to Hg is a good thing though if it works with nitropropenes.

[Edited on 30-4-2017 by tsathoggua1]

alking - 1-5-2017 at 10:24

I haven't had time to try any further yet, been busy with other things and haven't had time for any chemistry really, something always seems to come up. I ordered some gallium as an alternative but haven't had a chance to mess with that yet either. I would like to experiment more with this if only for the sake of learning though, even if I can't get it to work it would be interesting to at least determine what is happening and why.

Corrosive Joeseph - 1-5-2017 at 14:28

tsathoggua1 - "DON'T try doing 100g"

Apologies for my sarcastic reply.............. Couldn't help myself after reading that post
Anybody who has spent more than 5 minutes reading about this will be well aware of the resulting mercury volcano
Although in fairness, he actually didn't even mention Hg..............

On a contributary note - alking's polymer/dimer/whatever that is, is confusing.............. First thing I would think is eliminate the magnetic stirring from the re-ax and try again.

And if possible, reproduce CopperMan's and the Gay Doctors work
I'm still not sold on this one..............

Information on reaction of amines and copper(II) ions - http://www.chemguide.co.uk/organicprops/amines/base.html
I remember reading somewhere a 10%NaOH solution cleaves this but I have no reference right now.

I would also recommend attempting reduction with Zinc-Copper salt and/or Zinc-Nickel salt (obviously separately and not together) if someone really wants to fully explore this (the propene). Like atara says above, Zinc and HCl is well-known for the nitrostyrene.

/CJ

No more spam. I promise..............!!

[Edited on 1-5-2017 by Corrosive Joeseph]

[Edited on 1-5-2017 by Corrosive Joeseph]

[Edited on 1-5-2017 by Corrosive Joeseph]

[Edited on 2-5-2017 by Corrosive Joeseph]

tsathoggua1 - 2-5-2017 at 13:40

Well yes. Just figured it was highly likely. And in a case involving the potential for 100g worth of 1P2NP, and the corresponding quantity of Hg (II) soluble salts, better spoon feed some cook type, than have him and whats more, others around them, exposed to a blast of vaporised and sprayed mercuric salt. 10g in a 1l flask (of P2NP is enough to need a 300mm vigreaux on top of the allihn reflux condenser (also had a 300mm liebig mounted on top just in case, and the quantity of Al 21-22g (weighed for convenience on a digital scale accurate to 1g for the Al, there was excess leftover after the fact) and it did indeed get up into the vigreaux, not a huge distance, but nevertheless, the allihn was cooled by an ice/denatured alcohol/H2O/salt/ethylene glycol bath and it still ended up going a few inches into the vigreaux)

100g P2NP would lead to quite a mess, which cannot be afforded with the likes of HgCl2. That kind of sarcasm could have gotten somebody killed if they were dumb enough to follow the quantity reccomendation and ignore the rest.

tsathoggua1 - 2-5-2017 at 13:48

Oh and Zn/acid is reported to work for nitrostyrenes but not nitropropenes. However, lewis acids can coordinate to the nitro group and result, IIRC in a P2P. Will have to test something lying around, but tried a Fe/HCl/FeCl2 catalyzed rxn on 2,5-dimethoxy-4-methyl-beta-nitrostyrene once and the product was liquid, have yet to test for double bond reduction (on the aliphatic chain that is not C=O, bisulfite adduct to test for that, its been a lower priority than reacquisition of more of the aldehyde)

Can try a P2NP reduction using Cu (II)/Al some time, got plenty nitroethane and benzaldehyde, but currently there are other things that need doing. And Al/Hg is of course known to work. But some spare P2NP can be knocked out at some point, not in a great hurry though, but it'd be no real loss trying on some 20-30g

HollowMan - 4-7-2017 at 04:14

Did someone tried the Al/Cu reduction once again successfully with a nitropropene as starting material?

njl - 30-11-2020 at 10:34

Can anyone provide more references for the activation of aluminum with copper ions? This thread had gone on for a surprisingly long time without citing any directly relevant literature. I do not doubt the efficacy of this system but there are several questions that remain unanswered here. Personally I am puzzled by the very nature of this reaction.

Is the Cu2+ ion actually relevant, or is it another species produced in situ?
Is the CuCl2 actually catalytic? If so, why does more need to be added in some instances?
Do we know the role the Chloride ion plays here? Is it somehow activating the aluminum by getting through the passive oxide layer?
When a solution of CuCl2 is dripped onto aluminum metal, copper can be seen plating out. If the Cu2+ is reduced to metallic copper, doesn't that imply that this process isn't catalytic?
Is using CuCl2 in the first place actually equivalent to in situ formation from CuSO4 + NaCl?
Several people have mentioned experimenting with various counterions. Do other halides work?

This article (https://sci-hub.st/https://doi.org/10.1021/ic402674z) claims that their copper catalyst was made by reducing copper salts with NaBH4, and that the same procedure was used for preparing nickel and cobalt particles. However, the reaction of NaBH4 with Ni2+ does not generate nickel metal nanoparticles, rather it forms the well characterized nickel boride (same goes for cobalt). Copper boride is (according to my research) a rare species at best, so the paper is essentially comparing metal nanoparticles to borides as though they were the same.

One of the few linked papers mentions the catalytic activity of Cu nanoparticles. Could it be that the active reduction reaction is the consumption Cu nanoparticles (as they are oxidized to Cu2+), followed by Cu2+ being reduced back to nanoparticles with the addition of aluminum?

Corrosive Joeseph - 30-11-2020 at 13:36

Quote: Originally posted by njl

Can anyone provide more references for the activation of aluminum with copper ions?

/CJ

Attachment: Activation of Aluminum as an Effective Reducing Agent by Pitting Corrosion for Wet-chemical Synthesis.pdf (1.9MB)
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Corrosive Joeseph - 30-11-2020 at 20:21

/CJ

Attachment: Mechanism of the Reaction of aluminum metal with copper (II) chloride solution.pdf (184kB)
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Mush - 1-12-2020 at 16:42

Quote: Originally posted by njl

C
seen plating out. If the Cu2+ is reduced to metallic copper, doesn't that imply that this process isn't catalytic?

It is catalytic imo. U-Cu aka Urushibara copper

NEW HYDROGENATING CATALYSTS p203

The discovery of the Urushibara catalysts was due to the exploitation of a novel method for the reduction of estrone. Hence, we shall begin with some of the earlier methods which are now of historical interest. The reduction of estrone, established in this early period,3' involves the addition of precipitated nickel to an alkaline solution of estrone, to which aluminum chips are then added to liberate hydrogen. It has subsequently developed that precipitated copper, in place of the precipitated nickel, also gives estradiol-17/S in a good yield.27'
The modified method is the following: Zinc dust is added to 5 g of CuS04.5H20 dissolved in 100 ml of water, until the color of the copper(II) ion disappears. The pre-cipitated copper is washed with water and added to 50 mg of estrone dissolved in 65 ml of 10% potassium hydroxide solution. The solution is heated on a water bath with stirring, while 3 g of aluminum chips are added in small portions over a period of 10 hours. When the reaction is over, solid matter is filtered off, and the filtrate, made acid with hydrochloric acid, is extracted with ether. From the extract, 40 mg of estradiol-17/3 is obtained. Copper(II) chloride or copper(II) acetate may be used instead of copper(II) sulfate with almost the same result. A further modification consists in the use of zinc dust in place of aluminum chips. Zinc dust (4 g) is added in one portion to 50 mg of estrone dissolved in 65 ml of 10% potassium hydroxide solution. The solution is heated on a water bath with stirring and the precipitated copper, prepared from 5 g of copper(II) sulfate crystals and zinc dust, is added in small portions over a period of 10 hours. The yield of estradiol-17/? is the same as in the former method.

US4273679 Aluminum alloys having a high reducing capacity and preparation thereof

ABSTRACT
This invention relates to a process for the preparation of
aluminum alloys having a high reducing capacity for
use in reductions in organic chemistry. According to
this method a discontinuous heterodisperse superficial
alloy is formed by subjecting an aluminum alloy pre
pared by a metallurgical process to superficial activa
tion and/or treating aluminum with a salt of a metal
having a greater normal electrode potential than that of
aluminum; whereby the solution of said metal in a protic
solvent is reacted with granular aluminum and/or an
aluminum alloy. The catalyst prepared according to the
invention is especially suitable for the reduction of a
nitro or nitroso group into an amino group. The aluminun alloys having a high reducing capacity are also
within the scope of the invention.

EXAMPLE 7
27 g. of aluminum grains (Al content 99%) are heated
in 200 ml. of 0.1 N hydrochloric acid with 3g of copper
powder for half an hour at 50° C. to 70° C. After cooling the metal is filtered off and may be used for reduction.

EXAMPLE 11
27 g. of aluminum grains (Al content 99%) are activated in 200 ml. of a 40% aqueous acetic acid solution
at 60° C. to 80° C. with 5 g. of cupric sulfate.

EXAMPLE 3
123. g. of nitrobenzene are dissolved in a mixture of 65
300 ml. of water and 300 ml. of methanol, whereupon
200 g. of an aluminum treated according to Example 1
are added. To the mixture 800 ml, of concentrated
hydrochloric acid are added under reflux, with stirring
and cooling within 90 minutes. After cooling the metal
is filtered off, the methanol is distilled off in vacuo and
about 200 g. of sodium chloride are added. After stand
ing for some hours the aniline can be separated. After
fractionation 85g. of aniline are obtained. Yield: 91%.

EXAMPLE 4
21.7 g of freshly prepared crystalline 1-phenyl-2,3-
dimethyl-4-nitroso-pyrazolone-5 are suspended in 200
ml. of ice cold water. 20 g. of aluminum grains-activated according to Example 5-are added, at a temperature between 0° C. and -10 C. under stirring,whereupon 100 ml. of concentrated hydrochloric acid
are added dropwise. After 30 minutes the reaction mixture becomes colourless and the reduced product goes
into solution. The metal is filtered off. Thus 18.3 g of
1-phenyl-2,3-dimethyl-4-amino-pyrazolone-5 are obtained. Yield: 18.3.g., 90%.

Corrosive Joeseph - 16-12-2020 at 12:01

/CJ

Attachment: Reductive Ring Cleavage of Nonconjugated D2-Isoxazolines to b-Hydroxy Ketones with Aluminum and Copper(II) Chloride.pdf (103kB)
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