Sciencemadness Discussion Board

Zinc reduction for 2C-H from nitrostyrene

xwinorb - 30-11-2005 at 14:11

More than one user here asked me for this modified Leminger procedure, sorry for posting it so late. I though this was still available on The Hive archives, looks like that is not the case. It was given to me by Sunlight ( old Hive ).

Here it is :

Reduction with Zn / HCl :

- Setup : Use 2 l boiling flask, stirrer, funnel on top of BF,
use a pyrex bowl with ice for cooling.

- Reagents :
- nitrostyrene 20 g
- zinc dust 100 g
- methanol 200 ml
- HCl 31 % 300 ml
- NaOH 200 g
- H2O 600 g

- Main reaction :

- Add MeOH to 2 l boiling flask.
- Carefully add the HCl, wait till it cools down to RT.
- Add the nitrostyrene, all at once.
- Slowly add the zinc dust in small ammounts with a spoon.
It will foam. After each addition, insert the thermometer
and measure the temperature. Should take one hour or more.
Don't let the temperature to go over 30 C. After all zinc
dust added, drip in a bit MeOH to wash orange foam from the
walls of the boiling flask.
- Let stir for a total reaction time of 7 h. At the end, the
orange color should be totally gone, now inside the BF only
a clear, light yellow liquid with some solid zinc dust on
the bottom. Looks like white wine.

- Workup :

- Filter out zinc dust.
- Setup for distillation. Evaporate HCl and part of the MeOH.
Don't overdo it, seems to make product more dark yellow
- Prepare NaOH solution ( 200 g NaOH with 600 g H2O ).
- Set a big container with the NaOH 25 %, in ice, use magnetic
- Move output of reduction to big separatory funnel. With
cooling, slowly drip into NaOH solution. Should see white
flakes of Zn(OH)2 forming and soon dissolving. Also should
see amine ( 2C-H ) floating on top, fishy smell noticeable.
After drip, solution should be thick, opaque, milk white.
- Add some 300 ml toluene. Stir for a while. Place inside
fridge for about 1 h. After that, now should have a clear
transparent liquid on top, all the white Zn(OH)2 now on
bottom. The toluene / amine layer would be on top, the color
is light yellow.
- Decant top liquid, filter. Separate toluene.

- Titration :

- Add about half volume water to the toluene. Dropwise add
HCl till pH is aprox. 3.
- Separate water and dry in shallow pyrex dish on hotplate,
low heat. After dry, scrap, press and stir with spoon till
looks like uniform white powder. Should have now crude solid

- Distillation :

- Dissolve 2C-H.HCl in minimum ammount of water, make basic
with NaOH 25%, extract with DCM and distill with short path.
- After distillation, fast, dissolve 2C-H in minimum ammount
of toluene. Repeat titration procedure to xtalize

Comments : If you prefer just gas the toluene, don't have to titrate.

I also recomend dripping HCl 31 % in toluene to xtalize the 2C-B ( I mean 2C-B, NOT 2C-H here ). See "Aromatic bromination with NBS".

Tried this twice, good, easy, clean, yields were 65 % and 55 %.

Please follow the stated workup procedure or you will have trouble with the Zn(OH)2

[Edited on 30-11-2005 by xwinorb]

Fixed title. Chemoleo

[Edited on 3-3-2009 by chemoleo]

Sandmeyer - 30-11-2005 at 17:50


Distillation is overkill. It is enough to simply extract the crude product from toluene with HCl (aq), make this slightly basic with NaOH (aq), then extract with ether, evaporate, resulting freease is very pure. 7 h sounds like way to short an amount of time, 30-40 % yield was obtained after 8 h reaction time (not on 2C-H though), but this was the first attampt.

I'm glad you tied MeOH, unlike ethanol, it is avaiable pure over-the-counter. It is cool that reaction can be done at room temp without much impact on yield.

Of course, the method is very good, perfect for 2C freaks, luckily tweakers haven't found any use for nitromethane so it remains over the counter, muahahahaha...

Good work, btw.

[Edited on 1-12-2005 by Sandmeyer]

solo - 30-11-2005 at 18:07

Here is a related post on the attempt to use Zn/HCl with some of the comments by starlight to Bandil's attempt and results.......solo

xwinorb - 30-11-2005 at 19:33

I am not sure about the time it takes to reduce it, I run it for 7 h. Yields as I have posted. I have seeen posted when orange color is gone the reaction is done, but not sure about it. I am sure ethanol can be used, not sure which one is best.

I agree the output is clean, I still would recomend distilling it. Don't let the 2C-H freebase exposed to air for more than 30 min or so, otherwise OK, don't need special precautions if distilling it. Just xtalize it as the .HCl as soon as it is done. It takes sometime to form the carbonate, but it does so.

I remember seeing Bandil's post on the old Hive. Looks like he had trouble with the Zn(OH)2. I have tried to separate it but is is impossible to do anything. Just stir with toluene, let is settle down, then decant, filter, and then it is possible to extract some more if one wants to. There should be a thin white bottom layer, a large top clear layer, then above all the yellowish toluene layer.


joe_aldehyde - 14-12-2005 at 22:28

nice one!

[Edited on 15-12-2005 by joe_aldehyde]

a123x - 4-1-2006 at 00:46

Is this method only applicable for making 2C-H or will it work for reducing a variety of nitrostyrenes to phenethylamines?

enima - 5-1-2006 at 09:06

it will work for other nitrostyrenes. it however does not work on nitropropenes.

zooligan - 12-1-2006 at 09:32

Originally posted by xwinorb

I also recomend dripping HCl 31 % in toluene to xtalize the 2C-B ( I mean 2C-B, NOT 2C-H here ). See "Aromatic bromination with NBS".

[Edited on 30-11-2005 by xwinorb]

Anybody have "aromatic bromination with NBS"??


enima - 12-1-2006 at 09:51

J. Org. Chem. 1993,58, 3072-3075

solo - 12-1-2006 at 12:01

Biphasic Electrophilic Halogenation of Activated Aromatics and
Heteroaromatics with N-Halosuccinimides Catalyzed by Perchloric

Yuri Goldberg and Howard Alper'
J. Org. Chem. 1993,58, 3072-3075

Catalytic amounts of 70% perchloric acid (0.1-10, mostly 0.1-1, mol % , based on substrate) initiate the regioselective halogenation of activated aromatics [mesitylene, 1,3-dimethoxybenzene, 2,3- dimethylanisole, o-xylene] and heteroaromatics [thiophene, its 2-methyl, 2-halo (chloro, bromo,iodo), and 3-bromo derivatives] with N-halosuccinimide (NXS, X = C1 or Br) in two-phase solid liquid systems (NXS/hexane or NXS/CCW at room temperature to give ring-halogenated products in high yields. For example, thiophene is transformed to 2-halo or 2,5-dihalo derivatives (yield 82-98%) using 1 or 2 equiv of NXS, respectively. Unsymmetrical 2,5-dihalothiophenes are obtained in 7042% yield by reacting 2-halothiophenes with an appropriate NXS. The reaction of 3-bromothiophene with NBS affords 2,3-dibromothiophene in 93-99 % yield. 1,3-Dimethoxybenzene and 2,3-dimethylanisole are halogenated regiospecifically at the 4 position to give the corresponding products in 81-94% yield.

Attachment: jo00063a028.pdf (447kB)
This file has been downloaded 1439 times

a123x - 12-1-2006 at 15:10

I successfully made 4-methoxyphenethylamine(or at least I think I did). I reacted 1g of anisaldehyde with .9g nitromethane in methanol with .2g NaOH catalyst. This was followed with addition of 5ml diluted H2SO4(20% or so) to dehydrate the product of the Henry reaction to the nitrostyrene. A yield of only .4g of yellow nitrostyrene was obtained after vacuum filtration(improvised using a special cork and little pump meant for removing air from opened wine bottles so the wine will keep longer), rinsing with water, and drying. Does anyone have any information about producing nitrostyrenes with this method? It worked but the yield was low so I'd like to improve it.

As for the reduction. I ground up a couple pennies to get 1.9g of zinc powder. The nitrostyrene was dissolved in a mixture of 10ml methanol and 10ml 30% HCl. The solution became a clear yellow although there was a lot of nitrostyrene which didn't dissolve. The zinc was added over like 15minutes with the reaction cooled in an ice bath(probably could have added it much quicker for such a small reaction). This was allowed to sit for 5 hours with the reaction being swirled up periodically. After this point the solution was colorless and all the nitrostyrene dissolved. There was also no longer any gas being evolved. The zinc was filtered out and the solution pipetted into solution of 4g NaOH in 12ml of water. Lots of zinc hydroxide precipitated. I extracted twice with ethyl acetate(around 10ml each time). I added the ethyl acetate to some HCl(didn't really pay attention to how much). Stirred it up a couple of times and then seperated the acid layer and allowed it to dry to give abour .2g of 4-methoxyphenethylamine hydrochloride(around 50% yield).

xwinorb - 16-1-2006 at 19:20

There is a thread in this forum with the name of "Aromatic bromination with NBS".

enima - 8-3-2006 at 19:46

Does this method dehalogenate aromatic halogen groups?

a123x - 16-3-2006 at 21:32

I was trying to figure out an alternative work-up for this synthesis and this is what I thought of:

After filtering out the zinc, add the solution to an NaOH solution, then vacuum filter out the water. After this, rinse the Zn(OH)2 in the funnel with methanol, reapply vacuum to pull out the methanol, then wash again with some methanol in the funnel, filter more. Acidify the filtrate, evaporate the methanol, and then do a standard acid/base extraction.

Would this be an effective method for dealing with all the Zn(OH)2?

madchem - 25-3-2006 at 19:16

Sunlight was a wicked chemist and contributed Immensely to the Hive so props to him and props
to you xwinorb for sharing it with the rest of us. If you have anymore of his research you should post it.

knowledge is the strongest weapon
put the guns down and pick up a book and pen

Sunlight and workup

xwinorb - 6-4-2006 at 17:21

Sorry to say I just exchanged a couple of emails with Sunlight, all about 2C-B. I have posted all I got from him. I lost contact with him after The Hive closed down.

Workup :

The Zn(OH)2 makes filtration very difficult. I tried with Celite, it clogged. Sep funnel, also clogged.

I would suggest just stir strongly with toluene or any nonpolar lighter than water, separate, then gas or titrate, it is an easy A/B. The 2C-H freebase tends to go atop the water, the white trash to the bottom. I don't think there is much left there, and good yields seem to confirm that.


xwinorb - 6-4-2006 at 17:26

When I said "separate", I mean, let it stand for one hour, wait till Zn(OH)2 precipitates. Decant top clear layer. Filter any white Zn(OH)2 carried over ( a small ammount can be filtered OK ).

Now, separate top nonpolar from bottom aqueous layer. The 2C-H freebase is in the nonpolar ( top layer ) of course. Then gas it or titrate.

gonzo - 11-2-2009 at 16:02

Edit by Nicodem: Post removed due to SWIM-ing.

[Edited on 12/2/2009 by Nicodem]

Sedit - 11-2-2009 at 16:19

Hi swim. something tells me swimmers as your self drown quite often here at Science Madness. Quite possibly swim should be changed to I but Im relitively new posting here my self so just a little helpful advice. ;)

PS: Please dont think SWIM gives you anything to lean against if the law comes after you they care not if swim is used and wasting your time.


chemrox - 12-2-2009 at 01:51

I read a procedure where the carbonate was deliberately formed by gassing the freebase with CO2 before the operator made the mineral acid salt.. not sure why
"it will work for other nitrostyrenes. it however does not work on nitropropenes" any more information available on this? I couldn't find anything in Augustine about it.

[Edited on 12-2-2009 by chemrox]

Globey - 12-2-2009 at 07:29

for what it's worth, have never had problems reducing nitrostyrenes directly to the amine using only basic (aq) isopropanol and aluminum.
------------------------------------------------------------------------------------------------------------------------------------------------------ -------

"The taboo of“Trolling” is the modern online equivalent of McCarthyism. It is all too frequently invoked (regardless of merit), whenever someone of authority perceives a threat. Ironically, those who cry “trolling” the most (you know who they are…they often have fancy, esoteric quotes added to their posts, in an attempt to demonstrate to everyone just how sophisticated they think they are), usually abuse their power of moderation to troll the most. Having blanket license to troll (as moderator) makes one’s intellect dull, as instead of defending one’s wit with the mighty pen (or keyboard), a dictator can just execute all threats, and cleanse/falsify the record.

Time to stop crying “trolling, troll!” every time a nobody (in your book), has out witted you.

[Edited on 12-2-2009 by Globey]

Sedit - 12-2-2009 at 18:34

WTF... your trolling right now.

Globey - 12-2-2009 at 19:57

Sedit, I don't think either of us is.

Sedit - 12-2-2009 at 22:15

At least that makes one of us.

starman - 12-2-2009 at 23:32

Originally posted by chemrox

"it will work for other nitrostyrenes. it however does not work on nitropropenes" any more information available on this? I couldn't find anything in Augustine about it.

[Edited on 12-2-2009 by chemrox]

Have a look at the "reductions using zinc and acid" thread,especially Nicodem's posts.

DNA - 17-2-2009 at 05:34

I think it would be nice actually to steam distill the freebase directly out of the reaction mixture, this prevents you from dealing with large amounts of zinc salts and the whole reaction mixture crap.
After the steam distillation you will have your freebase very pure which also enhances the bromination.
And when it forms the carbonate then it does but actually it is not a problem if it does so, because before the bromination you will dissolve it in glacial acetic acid anyway so if you have the carbonate salt or the HCl salt or the freebase it is all the same in the end of the day ;)

smuv - 18-2-2009 at 21:22

precipitate the zinc salts w/ oxalic acid, remove the zinc oxalate, then deal with them amine...

2c-h distilling

gonzo - 2-3-2009 at 14:45

hi. is it possible to distill 2c-h with an aspirator vacuum ? what is the boiling point of 2c-h ? Is an 100mmHg vacuum enough to distill it ?

thanx in advance

DNA - 5-3-2009 at 00:19

No it is not enough vacuum to distill 2C-H.
I don't know the boiling point by heart but you can look it up in pihkal.
Then with a nomograph you can calculate the boiling point at 100mmHg but probably the 2C-H will decompose at the temperature you will need at 100mmHg.

gardenvariety - 31-3-2010 at 08:54

Has anyone attempted to bubble HCl into the alcohol rather than using 31% in water? I'm wondering if you could get substantially more nitrostyrene into a batch if the solvent wasn't half water.

Going to try this and compare in a few weeks but wondering if anyone else looked down that path.

xwinorb - 2-4-2010 at 14:18

I have never tried it. The yield is quite high already anyway.

My best 75 %, my worse 55 %.

The more significant factor I could relate to higher yields was the color ( I guess that means purity ) of the nitrostyrene.

When I used a more dull, brownish one, the yields were lower. When the nitrostyrene had a better, nice, bright orange color the yield was better.

It works.

Bronstein - 11-12-2012 at 14:04

I was thinking about using this procedure to reduce another nitrostyrene and I thought what smuv wrote about using oxalic acid seemed intreresting.

Quote: Originally posted by smuv  
precipitate the zinc salts w/ oxalic acid, remove the zinc oxalate, then deal with them amine...

But when I think more about it, to precipitate the 100g zinc used in this procedure you would need 192g oxalic acid (dihydrate). And oxalic acid dissolves at ~14g/100ml water (according to wiki), so if you dissolved it before you added it you would need more than 1.3L of water. And this reaction already has a quite large volume.

But perhaps you could add it dry directly to the reaction mixture?

Or perhaps it's not worth the extra trouble to use oxalic acid, I don't know...