Author Topic: acid/base -> 2,5-Dimethoxynitrostyrene ?  (Read 900 times)

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Midi

  • Guest
acid/base -> 2,5-Dimethoxynitrostyrene ?
« on: October 16, 2003, 07:28:00 AM »
From Rhodium:

"A mixture of 2,5-dimethoxybenzaldehyde (1.97 g, 11.8 mmol) and nitromethane (0.72 g, 11.8 mmol) in methanol (200 mL) was stirred at room temperature until the solids dissolved. The solution was cooled to 0 deg C and a 10.5 M NaOH solution (2 mL) was added dropwise over 20 min. The alkaline solution was added slowly to a 4% HCl solution (200 mL) maintained at 60 deg C. The pale yellow amorphous solid that formed was filtered and washed with water (200 mL). The crude product was recrystallized from absolute ethanol to give yellow needles (2.11 g, 85%)"

When the alkaline solution is added to the 4% hcl solution, is the 4% solution at 60c before this happens? Is it necessary for this to take place or can the 4% solution be added at room temp, then the whole mix heated to 60c?

Also, why is such a large amount of solvent used in this rxn? If scaled up by ten you are using 2L of MeOH, when 1L appears to disolve the 2,5 dmb just fine. Is this excess necessary for the the rxn to take place?


Midi

  • Guest
also..
« Reply #1 on: October 16, 2003, 09:02:00 AM »
Say you accidnetly scaled up the 10.5 M base addition x100 when it only should have been scaled up by 10???  ::)  

Would a very acidic solution (x10?) be necessary to neutralize the excess base? The correct amount to be added was 20'mls and of course 200ml's was added instead. That extra 180ml's couda came in handy x9  ;D


Bandil

  • Guest
Please post a link to what you are inteding to
« Reply #2 on: October 16, 2003, 09:24:00 AM »
Please post a link to what you are inteding to try out. It's very hard to help you with only a few lines of description.

Sodium hydroxide as catalyst usually produces nitroalcohol, so i really can't get the pieces to fit together here.


Midi

  • Guest
link
« Reply #3 on: October 16, 2003, 10:29:00 AM »
At the very bottom of the page you will find what I have posted in italics above. Has this been touched upon recently? I have utfse and found nothing, basically looking for anything in regards to this amazingly easy **sounding** route to the styrene.

https://www.thevespiary.org/rhodium/Rhodium/chemistry/2cb-new.txt




Bandil

  • Guest
It seems that they are forming the ...
« Reply #4 on: October 16, 2003, 10:44:00 AM »
It seems that they are forming the nitroalcohol first and then dehydrating it with the acid following(as they are using a 10X molar excess).

I suppose it can be done this way, but if you are going to play around with other benzaldehydes, better get the hang of doing it with some amine catalyst, as they work for most compounds. You can also get even better yields than they get, if you use a proper catalyst and reaction variables. The 2,5-dimethoxybenzaldehyde is notoriously easy to work with, so not sure how this method would yield with other compounds. It might just be a fluke of luck, that it does so rather well on this substance!


Midi

  • Guest
The condensation of 2,5-dmb with nitromethane...
« Reply #5 on: October 16, 2003, 11:31:00 AM »
The condensation of 2,5-dmb with nitromethane is the second most appealing/convienent route to 2,5 dimethoxynitrostyrene, this appearing to be the first.

I guess it couldn't hurt to just heat up 2L of 31% hcl and add the alkaline phase and see what happens. It's supposed to be an addition of 2L 4% hcl, but 31% is the highest strength available. Stupid little mistakes suck  :(


Rhodium

  • Guest
Do NOT use 2 liters of 31% HCl!
« Reply #6 on: October 16, 2003, 04:47:00 PM »
Do NOT use 2 liters of 31% HCl! That's WAY too much!

You scaled up the above synthesis x10, but used 200 mL 10.5 M NaOH instead of 20 mL?

0.2 L * 10.5 mol/L = 2.1 moles (you added 2.1 moles NaOH instead of 0.21 moles, i.e. ~1.9 moles too much).

You were supposed to use 2000 mL 4% HCl (4% HCl = ~1.3 M), which is equal to 2.0 L * 1.3 mol/L = 2.6 moles HCl

To neutralize the excess NaOH (1.9 moles) plus adding the originally required amount (2.6 moles), you need to use 1.9 + 2.6 = 4.5 moles. How much 31% HCl does that correspond to? Look here:

31% HCl = 10.0 M (moles/L)
4.5 moles HCl 
------------- = 0.45 L
10.0 moles/L


Thus, you need 450 mL 31% HCl.

Either you dilute that to the originally suggested volume (2 L) by adding 1550 mL water, or you dilute it to the originally suggested concentration (4%) by adding 3 L water, so that you end up with ~3.5 L 4% HCl. The latter dilution was calculated like this:

0.45 L * 31%
------------ = ~3.5 L
     4%



Midi

  • Guest
Ahh!
« Reply #7 on: October 17, 2003, 12:41:00 AM »
(wipes forehead) Good thing somone waited before ruining what may be salvagable!  ;)  Thanks Rhodium, I understand clearly what is laid about above. I was thinking in terms of multiplying the acids amount by 10, when the mole amounts is what I should have been looking at. Thank you for explaining that.

Now, it's time to nuetralize some excess base and reduce some nitrostryene.  :)


Midi

  • Guest
Nice!
« Reply #8 on: October 17, 2003, 08:41:00 AM »


Here sit's 24g of slightly moist suspected product. Does this stuff look familiar to anyone? I have never laid eyes on nitrostyrene, so I am unsure if it's the goods.

(3) 1L washes were performed instead of (2) 1L washes, and even the 3rd wash had a bit of yellow discoloration to it. Should the crude product be washed until it's washes are clean? Can you recrystalize this in acetone?

Nice route overall. A 5L 2 neck rbf served as a good vessel, utilizing 95% of it at the very end. Thanks!!!  :)


Bandil

  • Guest
Yes, that looks very nice!
« Reply #9 on: October 17, 2003, 10:01:00 AM »
Yes, that looks very nice!


Rhodium

  • Guest
Nice to see that I saved your batch in time...
« Reply #10 on: October 17, 2003, 10:04:00 AM »
I have never laid eyes on nitrostyrene, so I am unsure if it's the goods.

That is 2,5-dimethoxynitrostyrene for sure...

The condensation of 2,5-dmb with nitromethane is the second most appealing/convienent route to 2,5 dimethoxynitrostyrene, this appearing to be the first.

What are you trying to say here? "This" is also a "condensation of 2,5-dmb with nitromethane"...

even the 3rd wash had a bit of yellow discoloration to it. Should the crude product be washed until it's washes are clean?

No, it will never become completely colorless. Just follow the instructions.

Can you recrystalize this in acetone?

No, acetone will dissolve it too easily and it won't crystallize again. Use boiling 99% isopropanol instead.

Midi

  • Guest
Thanks!!
« Reply #11 on: October 17, 2003, 10:52:00 AM »
"This" is also a "condensation of 2,5-dmb with nitromethane"...

Sorry, I meant the condensation of 2,5-dmb with ammonia acetate and nitromethane. Originally that was the game plan, then this beauty came to light and.. wow, quick/easy/otc and you save 40 degrees in heat!  :)


imp

  • Guest
Good job!
« Reply #12 on: October 17, 2003, 11:39:00 PM »
Midi, what was your final yield from 2,5-DMB?

As a sidenote, NaOH/MeOH also works quite well with 3,4,5-TMB. Even with very impure aldehyde it gave 63% of the theoretical.

Midi

  • Guest
welp..
« Reply #13 on: October 18, 2003, 04:02:00 AM »
19.6g of 2,5-dmb were used, and after 24+ hours of drying the styrene weighs 18.27g

Now, if you would have asked me last night how it was going to form 2cb, I would muttered LAH reduction, on a small 5g basis. I have never used the stuff before, and im afraid to open the taped up 25g bottle, as it is probaly being stored under an inert atmosphere.. I have no N2 or argon at this time, so I am a bit worried of opening the bottle allowing fresh air in there. I then read a story using tfse that someones friend was playing with his LAH, weighing it and what not, moving it from container to container, and it worked fine for him anyway.

So that was the plan. Then late last night I found out my pressence on earth is going to be necessary for a long long time. I am not dissapointed in this, but happy and excited, although my dreams of blowing myself up using LAH have been flushed down the toilet. Instead I have to grown up a little, and be safe, and ensure I will be around to help take care of "it"  ;)

So, no more Mr. Badguy. I have been retired from the drug game for a few weeks, and this is purely for my own supply, my own fascination with trying new substances. How bad can a 5g LAH reduction go? If it went Boom would it remove body parts?? Im sure it won't go boom, but im thinkin what precautions can be taken in the event it does..

2 fire extingiushers,
2L of THF has been dried 2x
Ice bath during addition,
Dry atmosphere (not outside)

Maybe a dehumidifier running for a while in the basement?

I know I may sound like a big pussy, afraid of 5g of LAH, it's just that I have to be so much more careful today, than I felt was necessary yesterday.

If only there was a way to turn nitromethane into nitroethane, I could through some boro in the mix keep the hear rate down.  ::)


sYnThOmAtIc

  • Guest
Clarification.
« Reply #14 on: May 15, 2004, 05:05:00 AM »
The alkaline solution was added slowly to a 4% HCl solution (200 mL) maintained at 60 deg C.

Maintained how? By tha addition of the two or by external heat? Also, the alkaline solution is added to the acid and not the other way around? Just want to be sure before someting gets screwed up.

Rhodium

  • Guest
External heat. Solution added to acid.
« Reply #15 on: May 15, 2004, 03:45:00 PM »
External heat (some heat is evolved upon mixing, but not enough to make it to 60°C). The solution added to the acid, as we want a rapid change in pH. See

Post 320904

(Rhodium: "2,5-Dimethoxynitrostyrene w/ NaOH catalyst", Methods Discourse)



Schwa

  • Guest
LAH
« Reply #16 on: May 28, 2004, 02:19:00 AM »
We can certainly understand your concerns when it comes to that LAH reduction, but there are ways to minimize the risks.  If 5.0 g reacted in a dish, it'd be no big deal.  If it reacted in the ether inside your flask, it would depend on how much ether you had, but even with say 100 mL, your gonna get messed up if you are standing over it.  One thing you can do is avoid water.  Seriously dry your glassware.  Use only anhydrous ether straight from an unopened bottle from a reputable house.  Store the ether in the freezer.  Test a small amount in a test tube first with a very little piece of very clean sodium.  Weigh out the LAH in a glass weighing dish.  Add a few mLs of freezer chilled ether with a small glass syringe or pipette to the LAH in the dish to make a slurry.  Use additional freezer chilled ether from a glass pipette to rinse the slurry into the reaction flask.  Sometimes you can get granular and it is easier to work with, but if you are working with the powder, be aware that it is dusty and you do not want to get a wiff of it or get it on you.  Add freezer chilled ether up to specified amount to the LAH in the reaction flask.  After the adding the ether slowly raise the heat for the gently refluxing suspension (it all doesn't dissolve)  Use a serious drying tube.  Do not use a water bath.  Be mindful of condensation on the outside of your glassware.  Introduce the other reactant slowly using a pressure compensated addition funnel; a soxhlet extractor is highly recommended.   

LAH can be stored loosely capped and wrapped with tape under vacuum over drierite.  However, 20 g left in a bottle was stored inside a zip lock bag, in a zip lock bag, in a zip lock bag for over a year and no generation of gas was noted.  We have nothing against the argon blanket, but you should be able to get by with out it.

Good work with the nitrostyrene.  Congrats on your long term commitment.