Author Topic: Methylamine by metal-assisted reduction of Nitromethane  (Read 407 times)

bjuice

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Methylamine by metal-assisted reduction of Nitromethane
« on: February 23, 2013, 08:39:06 PM »
After spending way too much time dealing with separating Methylamine and Ammonium Chloride, dealing with formaldehyde fumes, and recrystalizing, I've began looking for alternate routes to Methylamine.  In digging around yesterday I came across the metal-assisted reduction of nitroalkanes.  It's been discussed on this board and other places around the net, but I've yet to see a full runthrough from nitromethane to methylamine.  I'd like to start off by talking a bit about the procedure.  Maybe get some input on it.  Then, in the next couple weeks, I'll plan on trying it out.

Here are the references I'm running off of:

1) Chemical Abstracts 11, page 1650 Synthesis of Alkylamines -- Chemiker Zeitung 40, 810 (1916

Quote
EtNO2 and MeNO2, which are readily prepared by a process recently patented (ref. not given) served as the mother substances for the corresponding alkylamines (RNH2). The latter were formed by reducing RNO2 in HCl with Fe. When 2.13 g. EtNO2 in 8 g. H2O, 7 g. Fe filings and 0.8 g. HCl were heated together at 50-60 degrees for 6 hrs. in a flask from which air was excluded, 0.96 g. EtNH2 (about 75% of the theoretical amount) was obtained.

In a similar experiment, in which the reaction mixture was heated for only 3 hours, the yield was materially decreased. In these experiments only 1/36 of the amt. of acid required by the following equation was used: RNO2 + 3Fe + 7HCl = RNH2.HCl + 3FeCl2 + 2H2O. Furthermore, the mixtures became alkaline long before the reduction was complete, and Fe(OH)2 was pptd. and rapidly oxidized to Fe(OH)3 by the excess of EtNO2.

In another experiment, RNO2 which remained unchanged when treated with Fe and H2O alone was reduced when small amounts of RNH2.HCl were added to the mixture It is evident, therefore, that the above equation does not accurately represent the mechanism of the reduction. Apparently Fe reacts further with the RNH2.HCl formed earlier in the reduction, according to the equations 2RNH2, HCl + Fe = 2RNH2 + FeCl2 + 2H. 2RNH2 + FeCl2 + 2H2O = 2RNH2.HCl + Fe(OH)2, and H and Fe(OH)2 are the active reducing agents. Very nearly quantitative yields of MeNH2 and EtNH2 were obtained by using 1.5 mols. of HCl per mol. of RNO2 in the reduction, and heating the reaction mixture at 70 degrees for about 1 hr.

Ratios:
  • Nitroalkane: 1.30 mol
  • HCl: 1.00 mol
  • Iron: 5.71 mol
  • Water: 366 ml

2) Vogel 5th Ed, p. 892
Quote
Cognate procedure: Setup a flask with reflux condenser in which .25 mol of nitromethane, .38 mol of granulated tin metal and a stirrer magnet have been added. Carefully pour 115mL of 31.45% hydrochloric acid (muriatic acid) down the reflux condenser in 10-15mL increments, waiting for the reaction to settle down before pouring the next aliquot. If the reaction seems to get out of hand (excessive frothing, vapor escaping the reflux condenser, etc...) then quickly slide an ice bath in place until it slackens back down. Once all the HCl has been added, heat the mixture to reflux with an electric mantle for 1hr. At the end of this time, allow to cool, preferably in an ice bath, then add, carefully, a chilled solution of 75g sodium hydroxide in 125mL of water. If the flask contents start to bubble violently you will watch your yield go out the window, so add slowly! Since methylamine readily dissolves in water, you will need to distill the reaction contents carefully to first liberate the 40% constant boiling solution (bp: 53°C) and then the gas itself. The product is best captured by bubbling the distillation vapor into a beaker of hydrochloric acid (use a slight molar excess of HCl to insure no loss). Proceed as above by evaporating the bubbler solution to yield the crystals (take care when evaporating HCl solutions, as the excess acid will vaporize into the air, corroding ovens, lungs, etc...)

Ratios:
  • Nitroalkane: 1.00 mol
  • HCl: 4.68 mol
  • Tin: 1.52 mol
  • Water: 390 ml

Note: Vogel uses Tin.  I vaguely recall seeing somewhere that when tin is used, more acid is necessary.  That would explain the higher HCl ratio in this procedure.

3) Johnson and Degering
Quote
To 35g of 40-mesh iron filings are added 75 ml of water and 10 ml of concd. hydrochloric acid . After the evolution of hydrogen has stopped , one-sixth of a mole of nitroparaffin is added and , with rapid stirring , the mass is heated at 100 ºC for thirteen to fifteen hours.

2-Nitro-2-methylpropane and other nitroalkanes were reduced to the corresponding aliphatic amines in 82–94% yields . The yields were 93–97% “in the presence of ferric chloride

Ratios:
  • Nitroalkane: 1.37 mol
  • HCl: 1.00 mol
  • Iron: 5.14 mol
  • Water: 667 ml

4) Eluesis
Quote
The lower nitroalkanes (sometimes refered to as nitroparaffins) are easily reduced by a multitude of systems, but by far the easiest, and also the highest yielding, is the Iron/Hydrochloric acid system. The reaction is:

4 RNO2 + 9 Fe + 4 H2O =HCl=> 4 RNH2 + 3 Fe3O4

First, your Nitromethane *may* require purification, especially if it was for "fuel" use. In this case, it needs to be vacuum distilled at a vacuum of better than 100mm Hg. At that pressure, it will come off at ~47°C. Distillation at atmospheric pressure is possible, but I do not recommend it due to the highly flammable nature of the compound and because it's flash point is 42°C. It's your choice.

*CAUTION*
The lower nitroalkanes form shock and/or temperature sensitive EXPLOSIVE compounds with amines and hydroxides. BE CAREFUL, DAMNIT! You have been warned.

Assemble a 500mL RB flask with claisen adapter, thermometer down the center to read the liquid temperature, and reflux condenser with a cork and tube leading to a beaker of 1M Hydrochloric acid. Drop a stirrer magnet in, then add 105g of 40 Mesh Iron filings, 225mL of water and 1g of Ferric Chloride. Next, add 35mL of concentrated Hydrochloric Acid ("muriatic acid" is ok). When the bubbling ceases, add 31g of Nitromethane.

Heat the reaction mixture to 100°C and hold for 14 hours. A temperature regulator is necessary if using a heating mantle, else use a large boiling water bath (if you will be doing it overnight, so it doesn't run out).

At the end of this time, allow to cool then add enough 25% Sodium Hydroxide solution to to get the pH above 11. Heat on a water bath or with gentle electric heat to drive the Methylamine off as a gas into the same beaker of Hydrochloric acid used as a trap during the reaction.

Evaporate the beaker contents to dryness on a glass plate in the oven to collect the crystals of Methylamine HCl (hygroscopic!). The yield should be approximately 15g (95%).

Note: I don't think Eleusis actually tried this procedure.  Notice the emphasized "should" above.  Also, I think the reaction would be done in much less than 14 hours with the addition of FeCl3.

Ratios:
  • Nitroalkane: 1.19 mol
  • HCl: 1.00 mol
  • Iron: 4.41 mol
  • Water:  588 ml

5) Hudlicky, "Reductions in Organic Chemistry" p. 213
Quote
A 500 ml three-necked rbf fitted with a robust mechanical stirrer, a reflux condenser, and an inlet is charged with 50g (0.3mol) of m-dinitrobenzene, 14g of 80 mesh iron filings, 45 ml of water, and 7.5ml of a 33% solution of ferric chloride (or 50 ml of water and 3.7g of sodium chloride).  The flask is immersed in a preheated water bath, stirring is started at 35 rpm, and additional iron filings are added to the mixture in two 13g portions after 30 minutes and 1 hours.  After 2.5 hours of stirring and heating the reaction mixture is cooled and extracted with ether, giving an essentially quantitative yield of m-nitroaniline.

Ratios:
  • Nitroalkane: 1.00 mol
  • Iron: 1.77 mol
  • Water:  173 ml

Now one very interesting thing in the last reference is that they don't use any acid at all.  Apparently the catalyst is enough to keep the reaction going.  In fact, they say earlier in the book:
Quote
Iron was one of the first metals employed for the reduction of organic compounds over 130 years ago.  it is used in the form of filings.  best results are obtained with 80 mesh grain [165].  Although some reductions are carried out in dilute or concentrated acetic acid, the majority are performed in water in the presence of small amounts of HCl, acetic acid, or salts such as ferric chloride (as little as 1.5-3%) [165], ferrous sulfate [166] and others.  Under these conditions iron is converted to iron oxide, Fe3O4.  Methanol or ethanol are used to increase the solubility of the organic material in the aqueous medium [166].

4RNO2 + 9Fe + 4H2O --> 4 RNH2 + Fe3O4

By the way, the listed amounts of water take into account any other water present -- such as in conc. HCl or ferric chloride solution.

Imagine, 1 gallon of nitromethane, 16 kg Fe (assuming 4 molar excess) (or 7 kg going by Hudlicky's procedure), and a few grams FeCl3 you could get 4.7 kg Methylamine HCl! 

I know, that looks like a lot of iron, but filings can be found for pretty cheap.

I have all the supplies on the way.  Thoughts?
« Last Edit: February 25, 2013, 05:35:59 AM by bjuice »

fishinabottle

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #1 on: February 23, 2013, 09:14:01 PM »
Thanks for posting all the information in this way it is immense helpful in my eyes.

There is this old german article by Krause (thanks to lugh for retrieving it times, ago still on the HIVE) which covered the nitromethane/ethane reduction to the amine more or less finally.

The procedure is like this:

1 mol of nitromethane or nitroethane
4.4 mol iron (pulverized cast iron filings, just use powder or more time)
about 1,5 mol Hcl
280 ml water

70°C , 1 hour, yields about quantitative.

Not all acid is added from beginning but it is added in portions, one bigger portion at start and then always a smaller portion when the reaction starts to smell fishy, amine. Should be possible to measure it too, it says the reaction has to stay slightly acidic. Not all the 1,5 mol HCl must have been be added in the end, thats just for orientation, when it doesn't go alkaline anymore, no fishy smell then it is finishes and further addition of HCl might diminish yields.

It is not explicitly mentioned but it is better to run this not in a open pot but with air more or less excluded, a loosely stoppered flask is sufficient for this purpose.

It works.

I just had a quick glance now on all the posted references but it seems most follow this line regarding ratios, just the successive addition of HCl is omitted and lower temperatures are used.
Personally I recommend the Krause procedure but with addition of a small amount of FeCl3 (the hydrated kind as for electronic platines etching) for kicking the reaction in for sure as it sometimes likes to slack and to go off rather sudden whats a bit to exiting for people at my age  :)

/ORG
« Last Edit: February 23, 2013, 09:30:47 PM by fishinabottle »

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #2 on: February 23, 2013, 09:21:19 PM »
Actually reference #1 in my post is the Kraus reference!    Don't suppose you could link me to that hive post (if you're using an online archive)?  Otherwise, can you give me the forum section it's in, and the name of the post?

fishinabottle

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #3 on: February 23, 2013, 09:43:58 PM »
Uups, overlooked it as no Krause is named.....

Well it was me who posted it, but not in thread about nitromethane to methylamine reduction but the thread was about the reductions of P2NP's and my posting was a bit out of line there.

There was astonishing little discussion on the nitromethane reduction on the HIVE anyways, most used Al/Hg (for they had it already) and I remember only one other posting (I think it was by Abacus) who used Tin (quite successful AFAIK).

But honestly I have no link and don't know what section it was in, but searching for "Krause" should turn it up. (OmG how embarrassing, it was not one of my brightest moments actually, the reference is valid and a great find though).



bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #4 on: February 23, 2013, 10:08:34 PM »
My bad on that reference -- I should have included the author's name  :)  By the way, here's where I found it: http://127.0.0.1/talk/index.php/topic,520.msg6044.html#msg6044

And yeah I'm also astonished at how little discussion there is on this method.  Seems like a quick, easy, high-yielding way to methylamine.

Got your PM.  Good call on including solvent ratios.  That would be helpful.  Especially considering that we are working with acid here.  I'll go ahead and modify the post.

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #5 on: February 23, 2013, 10:23:58 PM »
I wonder if iron nails would be effective.  I could probably get those even cheaper and more easily than filings.  I'm sure they would react more slowly.  I just wonder how much more slowly..

fishinabottle

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #6 on: February 23, 2013, 10:48:26 PM »
I wonder if iron nails would be effective.  I could probably get those even cheaper and more easily than filings.  I'm sure they would react more slowly.  I just wonder how much more slowly..
Iron powder cannot really be an issue, hey I can get this from the place everybody buys and sells stuff for 5€/kg in unlimited amoounts by several vendors, maybe time you dust off your sandblasting equipment and look for some decent sandblasting agents to use with?

You talking nails as hammer and nails? Thats a big jump from filings being sub-millimeter residues of filing a chunk of iron I would say and regarding the surface areas of both I might suggest some months for how long the reaction might take if it takes off at all.

The mayor drawback is probably the need for an overhead stirrer, same as in the P2NP to P2P reduction. Nitroethane is sparely soluble in water (about 8% IIRC) and even less so in acidic conditions, so strong stirring is a must and the iron fouling attempts to stir magnetically.....
Or shaking. 70°C says no condensor is needed so shaking is an option.
Still to much effort for most, but if you go big it doesn't matter at all. Although the benefits of an overhead stirrer are widely underestimated many have the illusion that a vortex is the crown of creation regarding stirring and thats just not so really true.

/ORG

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #7 on: February 24, 2013, 01:04:49 AM »
Ahh man you're starting to convince me that I should get an overhead stirrer.  I'm sort of on a budget but maybe I can make something out of an electric screwdriver...

As for the iron -- yeah I'm talking about hammer & nails nails.  Yeah, I know, they are much much bigger than 40-80 mesh filings.  I may at least give it a shot though.

Any ideas where I might find iron filings locally?  There are plenty of online sources but I was hoping to find something cheaper and more convenient.  There's always the option of getting a big magnet and going to the local playgrounds to gather from the sand, but I think that may be a little suspicious.  ;)

antibody2

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #8 on: February 26, 2013, 05:57:15 AM »
The in situ reduction of MeNO2 with Al/Hg for reductive amination of ketones was all the rage in its day 10 years ago

http://www.erowid.org/archive/rhodium/chemistry/ritter-alhg.html

http://www.erowid.org/archive/rhodium/chemistry/alhg-meno2.html

It runs REALLY hot though, so have cooling at hand

Sedit

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #9 on: February 26, 2013, 06:54:21 AM »

Any ideas where I might find iron filings locally?

Seriously?

Get a file and go to town on damn near anything metal in sight....

Or get those hand warmer packs they are fine Iron that on exposure to air oxidizes and warms up.
There once were some bees and you took all there stuff!
You pissed off the wasp now enough is enough!!!

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #10 on: March 03, 2013, 04:19:16 AM »
Seriously?

Get a file and go to town on damn near anything metal in sight....

Or get those hand warmer packs they are fine Iron that on exposure to air oxidizes and warms up.

Yes, seriously.  Maybe I should have specified that I'm looking for bulk amounts.

fishinabottle

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #11 on: March 03, 2013, 10:09:48 AM »
Seriously?

Get a file and go to town on damn near anything metal in sight....

Or get those hand warmer packs they are fine Iron that on exposure to air oxidizes and warms up.

Yes, seriously.  Maybe I should have specified that I'm looking for bulk amounts.

You dont have places where metal is collected for reuse or recycling, commonly called "scrapyard"? Usually they know pretty exactly about the purity ans quality of filings or shavings or drillings they have around for it is paid by this standards.
And there is still as I told you before: sandblasting agent.

Otherwise, if 5$/kg good quality (much less when you buy it bulk btw) are to much for you then you might consider another adventure not organic chemistry.

Or are you just fucking around with us?
Well see.

/ORG
« Last Edit: March 03, 2013, 10:11:28 AM by fishinabottle »

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #12 on: March 03, 2013, 10:41:58 AM »
It's not even an issue at this point as I already purchased a bunch online. I was just wondering if I could find it locally. And I appreciate your input fish.

Anyway, I followed the procedure in my last reference. After the reaction I set up for simple distillation and bubbled the gas into HCl solution. Evaporated the water and I was left with a small quantity of powder which I dripped NaOH onto. It had the distinct fishy ammonia smell of methylamine.

The water really doesn't want to boil off due to the high amount of solute so I  still have a lot of water (and hopefully methylamine) in the reaction flask. I'm considering an extraction with DCM followed by a wash with HCl/water.

My only concern here is bringing over unreacted nitromethane when I wash. The other option would be to gas the DCM with HCl.

Also, how would nitromethane react with HCl? I know it forms hydroxylamine when heated with HCl but there won't be any heat here. Seems to me one of the oxygens would pick up a proton. But that's a somewhat uneducated guess.

Assyl Fartrate

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #13 on: March 03, 2013, 10:46:50 AM »
The iron is the reducer, the HCl is the proton source.
Someone Who Is Me

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #14 on: March 03, 2013, 10:53:32 AM »
Right, my question was in regards to the workup. Thoughts on the DCM extraction and acid wash Assyl?

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #15 on: March 03, 2013, 11:31:37 AM »
On second thought, I don't think I need to worry about nitromethane coming over in the acid wash. I've already boiled it off. So the DCM/aqueous acid workup should be just fine.

no_dream

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #16 on: March 03, 2013, 11:35:31 AM »
Did someone found out the patent for nitromethane/ethane that Krause references? I found no patents applied by Krause for the time before 1916.

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #17 on: March 03, 2013, 09:57:37 PM »
I'm having issues coming up with a decent workup. I think it's possible that the majority of the methylamine was driven off when I first set up for distillation. I have the impression that bubbling through HCl solution was not a very effective way of capturing all the methylamine.  There was a good deal of colorless gas coming off the top of the HCl solution.

I'm starting to think that extraction with DCM would be ineffective. I'm not positive but it seems to me that the methylamine would have a higher affinity for water.

I'm running the reaction again today and am going to try to think of a better way to isolate the methylamine. If anyone else has ideas please let me know!

Assyl Fartrate

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #18 on: March 04, 2013, 06:39:37 AM »
MeNH2*HCl is almost entirely insoluble in DCM. The problem you will have is not extracting MeNH2 from DCM with HCl washes, but rather, extracting MeNH2 into DCM from water. It's extremely soluble in water and you won't be able to pull much out, unless you dump in such an obscene amount of Na2SO4 that all of the water is complexed. (This does work, it's just inefficient and ugly, requiring huge amounts of DCM and Na2SO4.)

MeNH2*HCl will sublime, so boiling down a dilute solution of it could lead to considerable losses.
Someone Who Is Me

bjuice

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Re: Methylamine by metal-assisted reduction of Nitromethane
« Reply #19 on: March 04, 2013, 07:01:08 AM »
Thanks Assyl. I'm not using HCl in the reaction though. I'm following the procedure in reference 5 which uses only nitromethane, FeCl3, iron, and water. The resulting methylamine should be the freebase and I've confirmed this by testing the pH of the reaction solution.

Heating seems to drive the freebase off just fine, but when bubbled through water I'm not catching a whole lot.

There's also the possibility that the low yields are a result of not using HCl in the reaction. To be honest though I don't fully understand the reaction mechanism, or how FeCl3 + Nitro + water + iron results in methylamine. My formal education is a bit lacking..