Author Topic: Henry condensation yield.  (Read 8108 times)

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  • Guest
Henry condensation yield.
« on: October 06, 2004, 08:06:00 AM »
SWIW has just finished his first Henry condensation, used 50 g 2,5-DMBA, procedure almost exactly like Pihkal # 20. After dissolving in IPA, filtering, washing the filter cake with IPA, repeat till filtrate not dark, got aproximately 65 g of a nice, homogeneous carrot colored substance, nice color, needles seen but kind of amorphous look. Still a bit wet with IPA.

My problem, the yield is close or higher than 100 %. Obviously there are impurities and/or IPA mixed in. My question, can I input this as it is for reduction ?

According to Shulgin, what he got was of sufficient purity to input to the reduction step. I am just hoping the impurities are not going to affect the reduction yield. Of course, I am sure Shulgin got better product than I did, but am just hoping impurities might not adversely affect reduction step yield, at least not too much. I hope to have enough to distill the 2C-H ( and hopefully the 2C-B also ).

Also, what would be a typical yield for the Henry condensation would be ?

Worth re-xtalizing this from IPA ? Or use as it is OK ?

Just in case, 2,5-DMBA 98 % pure; nitro from RC fuel; ammonium acetate reagent grade.

I am still overloaded with work, but hope to find time to try to reduce this to 2C-H, maybe next week.


  • Guest
nitrostyrene yields
« Reply #1 on: October 06, 2004, 05:31:00 PM »
You need to dry the nitrostyrene to a crisp first, especially if you are going for a hydride-based reduction. Check

for an overview of typical yields using various catalysts.


  • Guest
Thanks Rhodium. No, I am not planning to use...
« Reply #2 on: October 06, 2004, 10:25:00 PM »
Thanks Rhodium. No, I am not planning to use LAH or something like that. Will tell you what happened later. Will try to dry it, still too clumpy and wet.


  • Guest
Revised yield.
« Reply #3 on: October 07, 2004, 08:40:00 PM »
After drying, now nitrostyrene looks dry, powdery, IPA smell almost totally gone, weight went down to 39.6 g. This corresponds to 62 % yield, a bit less I guess.


  • Guest
Follow up.
« Reply #4 on: October 14, 2004, 04:07:00 PM »
SWIW has reduced 19 g of the above nitrostyrene with zinc dust 5:1 by weight, with good results. Got 13.1 g of a white powdery substance, just slightly yellow, hopefully 2C-H.HCl. Will try to brominate later on. Still want to reduce the remaining nitrostyrene first.


  • Guest
Where did you substitute the LAH for?
« Reply #5 on: October 14, 2004, 09:16:00 PM »
Where did you substitute the LAH for?
And did you mean 5:1 Zn didn't you use Zn+MeOH.


  • Guest
Zn instead of LAH
« Reply #6 on: October 14, 2004, 10:02:00 PM »
With nitroethenes, Zn/HCl substitutes for LAH... :P

(it reduces both the C=C bond and the nitro group, but doesn't work with longer alkyl chains like nitropropenes)

(edit: Yes, what you did is the Leminger reduction... but Zn/NH4Cl can reduce oximes - a modification of the Zn/formic reduction posted by Lego (

Post 477266 (missing)

(Lego: "Reduction of oximes with zinc/ammonium formate", Novel Discourse)
I just got confused as there is currently a thread in the novel discourse dealing with Zn reductions, too... (

Post 535551 (missing)

(pablos: "Oxime", Novel Discourse)
), and besides, Zn/HCOOH also reduces nitro groups..  sorry.)



  • Guest
« Reply #7 on: October 15, 2004, 03:45:00 AM »
As far as I know, the reducing agent is Zn dust only. Look in the Rhodium site, there is one paper under 2C-B, the autor is Leminger. I used MeOH as the solvent with some HCl excess. Temperature control under 30 C only OK. Got this from The Hive, private communication.

Worst part is the work up, but OK if done correctly. I cloggeg my sep funnel with Zn(OH)2, then decided to extract with toluene + big plastic container + stirrer, worked fine.

So far looks OK, clean, I will know for sure if bromination works as expected.


  • Guest
or maybe..
« Reply #8 on: October 15, 2004, 07:29:00 AM »
BTW you could also reduce the nitrostyrene to the nitroethane with NaBH4 (that is, if you have some), and then to the phenethylamine with Zn/NH4COOH - 2 steps vs. one, but maybe with more ease (and maybe higher yields?).

Usually the results are better if two reductions are done with two different reactions; but in this case Leminger is almost perfect.



  • Guest
Worth it ?
« Reply #9 on: October 15, 2004, 04:20:00 PM »
I have asked someone here about doing it with two reductions or one, I was advised to do it with one reduction. BTW, my yield is already 65 % ( coarse crystallization, not distilled yet ) and to beat that you would need something like 90 % followed by 75 % or so.

For instance, if you have say 0.9 * 0.7 = 0.63 it is less than 0.65.

Also, like to hear you say Leminger it is almost perfect for this reduction. I think it is very clean, no tar, final product looks like it has been gassed out.

Also, modifications to paper procedure include maximum temperature 30 C and also to add all nitrostyrene after the MeOH and HCl, then add the Zn in small portions.

I will tell you whatever happened later.


  • Guest
Zn/HCl method.
« Reply #10 on: October 15, 2004, 11:14:00 PM »
Hey, can you please post your proceedure for the reduction of the nitrostryene, swim has had aweful results when attempting it.


  • Guest
« Reply #11 on: October 15, 2004, 11:42:00 PM »
Keep your temperature under control at all times. Ice bath is good idea.


  • Guest
Reduction with Zinc Dust / Al ( by Wolfx )
« Reply #12 on: October 16, 2004, 05:14:00 AM »
Dear Amine, and others, there it is. I have not contacted the person who gave me the hints on this, but I assume he would not object. If he agrees, I will of course include his name later on. One word of caution, this still not finished, but, I have this fellow word it works, I have seen the amine on top, fishy smell, got it after the A/B, etc, looks right.

Reduction with Zinc Dust / Al ( by Wolfx )

     - Setup:

     - Place  a 2 l  BF over a stirrer, with a fitting funnel on top and
       also  a  thermometer. Don't let the thermometer to  hit the spin-
       ning  bar.  Cool  the  BF  with ice. During the zinc addition and
       after, do not let temperature to exceed 30 C.

     Reagents :

     - 2,5-dimethoxynitrostyrene ( 20 g )
     - Zinc dust ( 100 g )
     - MeOH ( 200 ml )
     - HCl 31 % ( 300 ml )

     Procedure :
     - Add 200 ml  MeOH to the BF. Slowly add 300 ml 31 % HCl. Watch the
       temperature, let it cool down to under 30 C.

     - Add  all  of the 2,5-dimethoxynitrostyrene all at once. It should
       dissolve easily, everything then a nice uniform orange color.

     - Start  dropping  in the zinc dust in small ammounts. It will foam
       a  bit,  but soon stops, foaming decreases. Watch the temperature
       at  every  zinc  dust addition. Don't let it go over 30 C. Should
       take one hour or more.

     - After  addition  complete, drip inside BF a small ammount of MeOH
       to wash orange foamed in sides of BF. Glass will look clear now.

     - Stir  for  a total reaction time of 7 h, including zinc addition.
       At the end, the orange color is completely gone, there is a clear
       watery  liquid  with  some zinc at the bottom. Color yellow-gray,
       clear, transparent.

     - Filter  out  zinc.  Should now have some 700 ml of a clear yellow
       liquid, looks like white wine.

     - Workup :

     - Setup for distillation, distill out HCl and most of the MeOH.

     - Dissolve 200 g NaOH in 600 ml water. It will heat up, let it cool
       down to RT or close.

     - With  cooling,  stirring,  slowly  drip  in the filtrate in small
       increments.  Newly  formed  Zn(OH)2 will make solution thick milk
       white. Keep stirring.

     - After  all filtrate added in, add some 150 ml of toluene and stir
       for a few minutes. Place in fridge ( optional ) and wait one hour
       or  so.  Now, most of the Zn(OH)2 on bottom. Carefully decant the
       top water + toluene layer. Filter out any Zn(OH)2 carried over.

     - Separate  the toluene, it will be on top of the water layer. Wash
       the toluene if you feel like.

     - Now, gas it or back extract with dilute HCl and dry on low heat.

     - Should have now 2C-H.HCl.

     - Comments :

     - This  is  a  modification of the Leminger reduction, hints on the
       reduction  procedure  and  workup  given  to  me  as private com-

     - Previous post has been edited. Changed title, added reagent ammounts, also added distilling out HCl + MeOH before dripping in NaOH. Have not tried workup whithout distilling out the HCl + MeOH first, but it should work, I think there is NaOH enough. In the original Leminger paper it is not done.


  • Guest
are you sure?
« Reply #13 on: October 16, 2004, 08:04:00 AM »
BTW you could also reduce the nitrostyrene to the nitroethane with NaBH4 (that is, if you have some), and then to the phenethylamine with Zn/NH4COOH - 2 steps vs. one, but maybe with more ease (and maybe higher yields?).

Is this from personal experience or are you theorizing? In my experience, Zn/formate reductions of nitroalkanes work but it's tricky to get good yields on a consistent basis. Other methods have been found to perform better.


  • Guest
Al instead of Zn!!!
« Reply #14 on: October 16, 2004, 08:50:00 AM »
Why don't you wanna try Al instead of all pain in the butt, you're have with other Reductians???
Original procedure:

Everything works very well.
Good luck.


  • Guest
Post edited.
« Reply #15 on: October 16, 2004, 03:55:00 PM »
The original one has been edited, but no major changes.
Added removing HCl + MeOH before dripping in NaOH solution.

Answering to Tricky, never tried the Al reduction, but this is nice and easy to do, the worst part is the Zn(OH)2 but easy to deal with. I have been told you can get 75 % yield.


  • Guest
no personal experience, but others have...
« Reply #16 on: October 16, 2004, 07:15:00 PM »

There are threads about experiences with Zn/NH4COOH, one I remember is by SpicyBrown: it is about 4-fluoroamphetamine and has the words "full report" in its title (or at least something similar  :P ). If you search for SBs posts, you will find it very quickly...



  • Guest
I know some have had success
« Reply #17 on: October 18, 2004, 08:30:00 PM »
I'm aware of the thread you are talking about (I've read most of the posts here over the last four or five years), but others (including very experienced bees) have experienced inconsistent yields using the Zn/NH4COOH method.


  • Guest
good to know
« Reply #18 on: October 19, 2004, 02:55:00 PM »


  • Guest
tricky indeed
« Reply #19 on: October 19, 2004, 03:23:00 PM »
The nitro reduction using Zn/HCOOH or Zn/NH4COOH is indeed and unofortunateley very inconsistent.

Has anyone tried to freebase the lemminger post reaction with aq NH3? This might improve the ease of workup.