Author Topic: Benzoquinone Synths  (Read 324 times)

Terror

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Benzoquinone Synths
« on: June 11, 2011, 08:07:03 AM »
Hi All,

SWIM has made p-benzo in the past using the bond-doublebond method (h2o2 / hydroquinone / i2 bringing the solution to a boil with a fairly exothermic reaction following)

SWIM attempted the h2o2 / hydroquinone / i2 synth as per Rhodium which is the same but instead of bringing the solution to a boil the reactant contents are left to stir for 3 hours, SWIM figured this route would not be as violent / runaway.

Anyway, the results from the each method seem to vary alot.. The bond-DB method always yielded long gold shard like crystals upon cooling, the Rhodium method seems just look like alot of fine gold speckles (not crystal masses) in a blackish like solution (due to the i2). This method didn't get boiling at all but obviously a reaction has occurred, maybe not completely?

Has SWIM done something wrong here or does the Rhodium / cold method simply not yield the same???

SWIM had a look around and couldn't find any answers online, so throwing it out there.

Thanks Beees!
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Terror

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Re: Benzoquinone Synths
« Reply #1 on: June 11, 2011, 10:07:33 AM »
Yeah, swim has heard! looks like it could be a goer...

Updating swims situation; swim dumped the rhodium style attempt and went for a bond-db, but something went wrong there too.. the reaction took off and everything looked good but nothing precipitated out during the boiling phase and now there is just a red liquid..??
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beanhead

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Re: Benzoquinone Synths
« Reply #2 on: June 11, 2011, 02:00:23 PM »
I know it's off topic, but you can make it too from paracetamol: h**p://www.versuchschemie.de/ptopic,223814.html

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Methyl Man

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Re: Benzoquinone Synths
« Reply #3 on: June 11, 2011, 07:05:02 PM »
This swim thinks that one of the best looking ways by far is the one treating hydroquinone with sodium nitrite in DCM under oxygen atmosphere. Very simple and clean looking. Scale it up 8x and you're in bizness. I can't see a way to screw it up other than failing to keep the flask cold.

-----------------------------------------------------------------------------------------------
Catalytic Oxidation of Hydroquinones Using Sodium Nitrite/Hydrochloric Acid.

 General Procedure:

Hydroquinone 9 (24.4 g, 100 mmol) and sodium nitrite (345 mg, 5 mmol)
were suspended in dichloromethane (100 mL) in 250-mL flask
equipped with a side arm. The flask was purged with O2 and
stoppered with a rubber septum and an O2-filled balloon attached
to the side arm. The flask was cooled in an ice-acetone bath
(approximately -10 C), and 1 drop of concentrated hydrochloric
acid added. The reaction mixture was stirred for 3 h, at which
time a clear yellow solution was obtained. It was dried over MgSO4,
and filtered; the removal of solvent gave quinone 9Q in
quantitative yield (24 9).
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POSEIDON

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Re: Benzoquinone Synths
« Reply #4 on: June 12, 2011, 01:49:48 AM »
The chemists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasures amid smoke and vapour, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I were to change places with the Persian king.
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NeilPatrickHarris

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Re: Benzoquinone Synths
« Reply #5 on: June 12, 2011, 03:02:33 AM »
Hi All,

SWIM has made p-benzo in the past using the bond-doublebond method (h2o2 / hydroquinone / i2 bringing the solution to a boil with a fairly exothermic reaction following)

SWIM attempted the h2o2 / hydroquinone / i2 synth as per Rhodium which is the same but instead of bringing the solution to a boil the reactant contents are left to stir for 3 hours, SWIM figured this route would not be as violent / runaway.

Anyway, the results from the each method seem to vary alot.. The bond-DB method always yielded long gold shard like crystals upon cooling, the Rhodium method seems just look like alot of fine gold speckles (not crystal masses) in a blackish like solution (due to the i2). This method didn't get boiling at all but obviously a reaction has occurred, maybe not completely?

Has SWIM done something wrong here or does the Rhodium / cold method simply not yield the same???

SWIM had a look around and couldn't find any answers online, so throwing it out there.

Thanks Beees!

the cold method is not running to completion.  the black with gold specs is quinhydrone.  quinhydrone is a complex of hydroquinone and benzoquinone.  the boil/reflux at the end is to ensure the reaction runs to completion and all the unreacted hydroquinone in the quinhydrone is oxidized properly to p-benzoquinone.  you'll find plenty of posts in the old hive archives of bees saying they have the same problem with the rhodium write-up that you did.  the rhodium variation is based on a patent and i THINK the problem was that bees were following that patent word for word but scaled up much higher than the patent does.  since they scaled up they need to let it react much longer.  the bond_doublebond method is where you boil/reflux it at the end.  increasing the temperature so much like that vastly increases the reaction rate, so the reaction is going at a much faster pace and is being run to completion in those circumstances.

Methyl Man

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Re: Benzoquinone Synths
« Reply #6 on: June 12, 2011, 11:10:19 PM »
Quote
the rhodium variation is based on a patent and i THINK the problem was that bees were following that patent word for word but scaled up much higher than the patent does.  since they scaled up they need to let it react much longer.

Hi Neil, you raise an interesting question for the one I'm talking about too. Since it's a cold reaction instead of one with heat, do you think the same would be true of this one? Would it still run in 3 hours, you think, or would one need to lengthen reaction time if scaling it up 8X?
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NeilPatrickHarris

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Re: Benzoquinone Synths
« Reply #7 on: June 13, 2011, 01:10:14 AM »
Hi Neil, you raise an interesting question for the one I'm talking about too. Since it's a cold reaction instead of one with heat, do you think the same would be true of this one? Would it still run in 3 hours, you think, or would one need to lengthen reaction time if scaling it up 8X?

regarding the benzoquinone synthesis found on rhodium and the patent, making it from hydroquinone/h2o2/i2.... if you scale it up 8X then you'd definitely have to let it run MUCH longer.  i've run this reaction a couple dozen times and i always did the addition rate at about 1 drop per second, i was never in any big rush.  if you get too aggressive with the drip-rate then it can runaway just like the nitro al/hg and h2o2 decomposes at around the bp of IPA doesn't it?  i vaguely remember reading that, but i can say for sure that applying heat at the tail end of the reaction doesn't decompose the h2o2.  i believe this is because the h2o2 reacts faster in the oxidation to benzoquinone than it decomposes, at least at the bp of IPA i believe this is true.  so i always applied external heat to reflux/boil the IPA for 5-7 minutes afterward.  why run it cold, why not apply heat at the end?  i've never run it cold through and through, i always applied heat at the end and always had satisfactory results.

some notes about the reaction itself: as the H2O2 is added the solution will turn to a dark red and eventually quinhydrone will begin to precipitate out of the solution making the solution very thick with gold specks.  i believe quinhydrone must be less soluble in IPA than hydroquinone and benzoquinone are by themselves, so as quinhydrone is formed it precipitates.  as i said in an earlier post, quinhydrone is a complex between hydroquinone and p-benzoquinone.  so that means the oxidation is only partially complete at this stage.  as the reaction continues the gold specks will dissolve back into the solution and the solution will begin to thin out again.  since i always apply external heat i'm not sure if this is because the additional heat is increasing the solubility of quinhydrone in the IPA or if the heat is increasing the reaction rate to a rate that's so fast that the quinhydrone complex is being broken due to the hydroquinone portion of it being oxidized to the desired benzoquinone.  i believe it is the latter but since i always applied external heat i can't say for sure.  so anyway the quinhydrone dissolving back into the solution is a sure sign that the reaction is being run to completion.  i often had to shake the flask by hand during the quinhydrone phase because it would get so thick that the stirbar gets stuck.

trying to figure out the desired reaction time is so complex, so many variables to consider, you have to really know the reaction inside and out to be able to figure out the reaction time.  it's not as simple as just increasing the reaction time 8X longer to fit the 8X larger scale.  when in doubt, i think that's a good idea to do but the temp changing also effects solubility of reactants so it makes the actual reaction time tough to figure out.  i know this reaction from trial and error and i know the basic mechanics of the reaction on paper but i'm no expert by any means :)  just to ensure the reaction goes to completion i would really recommend applying external heat at the end.

NeilPatrickHarris

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Re: Benzoquinone Synths
« Reply #8 on: June 13, 2011, 01:25:49 AM »
for everyone's viewing pleasure i'll just share my personal notes about this reaction.  this is a full write-up i made and tried to break down as much as i could to clear up any and all confusion from this reaction.  as i said i'm no expert, so take it for what it's worth.  hopefully it will help some people.  i attached a picture that is a snapshot of a table including information about all the chemicals involved in this reaction.


Synthesis of Benzoquinone via Hydroquinone/H2O2/I2
                  

Chemicals:
•   Precursor:

•   55g Hydroquinone (0.5088 moles)
•   Catalyst:
•   30ml 2% Iodine Tincture (to compensate for 1g Iodine which is 0.0039 moles of I2)
•   Oxidizer:
•   58g/51ml 35% H2O2 (1.7053 moles)
•   Reaction Solvent
•   103.5g/131ml 99% Isopropyl Alcohol (1.7224 moles)
•   Recrystallization Solvent
•   64.56g/51ml 91% Isopropyl Alcohol (same amount of ml as h2o2 used above)
•   Washing Solvent
•   91% Isopropyl Alcohol (eyeball it)

Introduction:
C6H4(OH)2 + H2O2 i2> C6H4O2 + 2H2O


All credit here goes out to Bond_DoubleBond and who modified the drip-rate of the h2o2 to purposely elevate the exothermic reaction which is what the patent synthesis (found on Rhodium) advises against doing.  Here’s what makes Bond_DoubleBond’s procedure so great:
After a lot of searching/reading old hive archives, it seems a lot of bees had a problem with the original Rhodium write-up of benzoquinone via the route of hydroquinone/h2o2/i2 due to them yielding the intermediate quinhydrone as the final product.  The color of quinhydrone can from olive green, a dark green that’s so dark it looks almost black, and it can also be gold; however all of these colors have a metallic look to it.  Benzoquinone is bright canary yellow, not metallic looking at all.  Quinhydrone is a complex between hydroquinone and benzoquinone (ref: http://www.jtbaker.com/msds/englishhtml/q3250.htm) that forms when hydroquinone comes into contact with benzoquinone (ref: hive\hiveboard\chemistrydiscourse\000313044.html).  So quinhydrone is an intermediate product between hydroquinone and benzoquinone, it’s the signal that you’re halfway through the reaction.  Mountaingirl (via the hive) says that quinhydrone works in the benzo wacker as well but would have to scale up 2x due to quinhydrone only having half the amount of benzoquinone, but why have to do guesswork and why deal with 2x the amount of quinone tar?  I’d also have to argue that the solution in the p-benzoquinone wacker gets very thick as it is without doubling the amount of quinone.  Just shoot for nice pure yellow benzoquinone and guarantee yourself a successful benzoquinone wacker!  Bond_DoubleBond uses an aggressive drip-rate paired with external heating after addition of the h2o2 to keep the temp high enough so that when the quinhydrone crashes out upon formation it will re-dissolve back into the solution due to high heat of the water bath, allowing the rxn to progress further and continue oxidation, while solution boils for an additional 5 or so minutes after all the quinhydrone is formed.  Note:  Benzoquinone is highly irritating to the eyes and to inhale, goggles & respirator at all times, long-sleeve shirt is a good idea.  It must be handled with care also, if it touches your skin then it will turn it black/brown and stain it for several weeks until the skins wears off so use typical lab safety procedures except you may want to also double-glove as benzo can go through a nitrile or latex glove.

Another change that has been made to this procedure is the amount of oxidizing solvent.  This is because the original method used by the patent and perfected by Bond_DoubleBond were used when pure Iodine could be obtained.  The original ratios were 55g Hydroquinone (0.5088 moles), 1g Iodine (0.0039 moles), 58g/51ml 35% H2O2 (1.7053 moles), and 115g/145ml 91% Isopropyl Alcohol (1.9137 moles).  Now that pure Iodine is no longer accessible it can only be sourced in tinctures.  Most iodine tinctures are 30ml and consist of a volume of 2% iodine solvated in 51% water and 49% alcohol, therefore 2 changes must be made.  First is that the use of 91% IPA must be replaced with 99% IPA (iso-heet) to compensate for the water present in the iodine tincture.  The second change is the amount of alcohol (IPA) must be reduced from 115g/145ml 91% IPA to 103.5g/131ml 99% IPA due to some alcohol already being present in the tincture.

Preparation:
Prepare an ice water bath and keep it in the refrigerator or freezer (if kept in freezer then check on it periodically and break the thin layer of ice that develops on the top to keep it from freezing), you will need this ice bath later.  Now, in a 1L 3-neck flask (at the 55g hydroquinone scale only a 1L flask is needed but if you want to you can oversize it if you have a 2L flask handy, just in case of accidental excessive drip-rate and boiling but again a 1L flask will suffice just fine if you keep an eye on the drip-rate): add a large stirbar, 30ml 2% iodine tincture, 55g hydroquinone, and 103.5g 99% IPA to the flask.  Then place flask into a water bath of 30-35C (86-95F).  Allow it to stir for an hour or so until all the hydroquinone dissolves then turn off the heat, unless room temp is cold like winter time then just leave the water bath on throughout the whole procedure but keep it at ~30C until addition of h2o2 is complete then you will be instructed to turn the heat up higher.  Before proceeding to the next step, attach a reflux condenser fed with cold water otherwise the room will smell of benzoquinone and IPA.  Now attach a sep funnel to one of the necks and clamp down the flask in multiple places to keep weight on one side of the flask from tipping it over.

Details:  Always test (density check) your h2o2 before using it to make sure it has not decomposed, decomposed or lower concentration h2o2 will result in failure or the reaction will stop at the formation of quinhydrone due to only partial oxidation.   “The iodine acts as the direct oxidant, oxidizing hydroquinone to benzoquinone and being reduced to I- in the process.  The hydrogen peroxide then reoxidizes the I- to I2 and so the cycle continues..." per “hive\hiveboard\newbee\000475341.html”.  The initial reason in the patent as to why to keep it under 80C is because part of the peroxide is decomposed before reacting per “hive\hiveboard\chemistrydiscourse\000245368.html”

Addition of the H2O2:
Now fill the sep funnel with 58g 35% h2o2 and set a drip-rate of 1 drop per second (don’t forget to tighten your stopcock!) until all the h2o2 has been added, some temperature evolution will be noted as the flask gets hot and may begin sweating or a very mild reflux.  After all of the h2o2 has been added then you should see gold flakes stirring in the solution (the un-dissolved hydroquinone turns gold) and the solution gets thicker.  Stirring may become difficult, if stirring stops then swirl by hand.  Now place the flask in a water bath and heat the solution to 88C (192F).  Allow the solution to boil for 5-6 minutes.  After letting it boil for 5-6 minutes then remove it from the water bath and swirl by hand for 2 minutes.

Details:  There will be a strong exothermic reaction, how hot it gets depends entirely on your drip-rate, the faster you drip in the H2O2 the more exothermic the reaction gets.  You shouldn’t dump all the H2O2 in at once because H2O2 decomposes at high temperatures.  You can use a pretty aggressive drip-rate (more than 1 drop per second) just as long as you don’t over-do it and stream it all in at once then yields will plummet because the H2O2 will decompose faster than it will react even though the reaction’s rate increases at higher heat.  As the H2O2 is added the solution will turn to a dark red and eventually quinhydrone will begin to precipitate out of the solution making the solution very thick with gold specks.  At this point it is only partially oxidized because quinhydrone is a complex between hydroquinone and p-benzoquinone.  As the reaction continues the gold specks will dissolve back into the solution and the solution will begin to thin out again.  This is good because the quinhydrone precipitate is dissolving back into the solution and will continue oxidation to p-benzoquinone.  You may have to adjust the stirbar’s speed to accommodate the reaction as it gets thicker and thinner.

Initial Crystallization:
After swirling it by hand for 2 minutes then let it sit and cool off for a few minutes.  After it has cooled down somewhat then plunge it into an ice water bath that you prepared earlier (10C or colder) and clamp it down so that it stays in the ice water bath (no stirring).  Allow the reflux condenser to continue being fed by ice cold water and leave the flask clamped down in the ice water bath for 30 minutes even though yellow shards will be noticed within about 5 minutes or so.  After the 30 minutes have passed then move onto the next step.  If you absolutely must stop here then remove the reflux condenser and stopper the neck (or use cyran wrap + rubber band, then aluminum foil over top of that) and put it in the freezer overnight but that is not recommended.

Details:  If you put the flask in the freezer for a few hours or overnight then the solution will get much thicker and harder to deal with when decanting or vacuum filtering, it gets almost syrupy.  The benzoquinone crystals seemingly suck up the iodine making the benzoquinone darker and red.  This will basically ensure that your benzoquinone isn’t as pure as it would’ve been by not keeping it in the freezer so long but ultimately it will still work fine in the benzoquinone wacker.  So only put it in the freezer overnight if you absolutely have to.  Otherwise it is best to decant or vacuum filter right after it sitting in the ice bath for 30 minutes.

Initial Washes:
Take the reaction flask once it has cooled down and the benzoquinone has precipitated out (or remove it from the freezer if you chose to do that) and carefully decant off the post-reaction solution (take your time).  Now vacuum filter what is remaining in the reaction flask with a #101 filter until it is dry.  Now add some ice cold 91% IPA to the reaction flask and swirl it around to be sure to get all the benzoquinone out of the flask.  Use this same ice cold 91% IPA to also wash the filter cake with.  Vacuum filter the filter cake dry after each wash then add more ice cold 91% IPA.  Repeat this 3-5 times or until the IPA stops picking up color.

Recystallization:
Now put the filtered crude benzoquinone back into the 1L RBF, attach a reflux condenser fed with cold water to the reaction flask, add 64.56g/51ml 91% IPA to the flask, and toss in a stirbar.  Turn on stirring and heat up the IPA almost to a boil or basically just until all solids in the flask are dissolved, swirl by hand if needed if the stirbar stops.  Once everything is dissolved then allow the IPA to continue to boil for a only couple minutes then turn off the heat and remove it from the water bath.  Swirl the flask by hand then let it sit and cool off for a few minutes.  After it has cooled down somewhat then plunge it into an ice bath that is 10C or colder and clamp it down just like you did after the initial reaction.  Be sure to keep the ice bath cold by refilling with extra ice as needed, wait for 30+ minutes before proceeding.  Alternatively you can stopper all the necks and put it in the freezer for one hour instead of using an ice bath, if you must stop here then you can leave the flask in the freezer overnight.

Details:  The iodine stains the crystals a shade of orange or red.  On a side note, again, you can put it in the freezer overnight if necessary but I recommend only putting it in the freezer overnight if absolutely necessary.

Washing & Vacuum Filtering:
After the benzoquinone has precipitated again then take the flask out of the ice bath or freezer and vacuum filter the contents with a #101 filter, you may add some 91% IPA to the reaction flask and swirl it around to be sure to get all the benzo out of the flask.  Wash the filter cake with 91% IPA until it stops picking up color.  Now dump out the filter cake and filter paper(s) onto a couple layers of paper towels that have aluminum foil underneath it (to keep the iodine/ipa from staining what is underneath it).

Drying the Benzoquinone (Fan or Desiccant Chamber):
Fan:  Now that you have a pile of benzo and filter papers sitting on the paper towels/aluminum foil, spread out the benzo so that it is thin and not piled up so it can dry out more thoroughly.  Now put a fan blowing on it for 1-2 hours to dry them out (Note: if you prefer not to stink up the room and is quite irritating to the eyes/throat to be around then this can be done outside at night as benzo is sensitive to light or you may use a desiccant chamber).

Desiccant Chamber:  You may alternatively use a desiccant chamber which will really help contain smells.  Put your damp benzoquinone into a large shallow tupperware container sitting on top of newspaper/paper towels/etc within a larger one with CaCl2 (weight your benzo and use 50% of CaCl2, IE: if you have 50g benzo then use 25g CaCl2).  In a few hours you will have nice large bright yellow crystals that don’t huff and puff like the powder does.

Details:  The directions for the desiccant chamber above are from Chilly_Willy at The Hive.


Storing the Benzoquinone:
Benzoquinone does not store very well or very long, not like hydroquinone which can be stored for decades if done properly.  Benzoquinone tends to turn green/brown over time and it will stain whatever it touches brown.  However some have claimed to have stored benzoquinone upwards of a year and it is the same color still.  Here is the secret to properly storing benzoquinone:  airtight container, dry conditions (store with a desiccant), and it is light sensitive so one must block out all light.

Put long bright yellow crystals into baggie with a little bit of CaCl2 (make a little paper towel pouch for the CaCl and tape it shut).  Now use put this baggie into another baggie (double-bag it), vacuum sealed is nice.  Now put these 2 bags in a light-proof jar or wrap them thoroughly with aluminum foil and put it in the freezer.


pyramid

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Re: Benzoquinone Synths
« Reply #9 on: June 13, 2011, 02:28:34 AM »
I don't really agree with the whole drip rate thing. I've done this numerous times and have done the following:
Using same amounts found in the Rhodium method, in a 1L flask with stir bar and condenser with a moist cotton ball on top of condenser to trap any possible I2/BQ vapors.

Add Hydroquinone and I2 to the IPA, I do not bother to wait for dissolution. Then the H2O2 is added in a single portion at once. I never experienced an exotherm or anything, just add it and stir for a minute.
Then after a couple of mins a low blowtorch flame is used to evenly heat the flask until the temp is around 75C at which the temp will rise on its own. Then the flask is immediately immersed into an ice bath to control the exotherm, but removed quite fast it is just to keep it under semi-control.
Really it is only immersed for about 30 seconds and then removed while the mixture boils on it's own.
Then just stir until it reaches room temp, place back in ice bath and large crystals of p-benzoquinone fall out. They are freed and slushed around, flask rinsed with ~30ml IPA, vacuum filtered and washed well with about 50ml of cold dry IPA.
After drying in air just until dry (it will sublimate quite a bit if left longer) and with frequent mixing and such to air it out well they are used in the next reactions..or stored.
The product is bright yellow, long crystals and extremely irritating.
Yields are excellent, the actual reaction takes like 45 minutes.

I think any use of water baths for slow heating, dripping in oxidant etc is quite a waste of time because it can be done as above very quickly.

Do not worry about crazy exotherms, it will boil but only at BP of IPA and only for a few minutes. Foaming is not huge, but use the liter flask for safety and use a good condenser.
BQ is quite toxic and should NEVER be dried in a closed room, all attempts should be made to keep the vapors in the reaction.

Edit: I should add that hydrogen peroxide from pool store (27.5%) has also been used, compensating for the lower percentage. It works fine. Also with 30% of course...And you can use 0.5g I2.

I thought i should post this just because this is one of those things that really does not need to take long or be difficult. We have other reactions to run! I don't want to spend my time with making benzoquinone!! :P

Edit once again: wait..is this bond-doublebond method exactly like what I just said? I'm not familiar with it. If so i feel like an idiot!
« Last Edit: June 13, 2011, 02:43:53 AM by pyramid »

Methyl Man

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Re: Benzoquinone Synths
« Reply #10 on: June 13, 2011, 02:35:43 AM »
Thank you for all that Neil, killer stuff. But, er... I was referring to the thing I posted about, the hydroquinone with sodium nitrate and HCl in DCM... asking whether you thought it would also need an increase in reaction time. That's what I get for posting a digression.

Maybe it was too much of a side road from the main subject of the thread. Better perhaps if I ask you privately. I don't want to divert the thread off course.

Awesome notes, man.

Check this out though, I just looked at some benzoquinone yesterday that is fully ten years old (maybe 11). It had been sealed all that time in the Science Alliance paint can type can. And it was the right color and looked fine! SOD is gonna use it.

Thanks to you too pyramid for your good notes. You posted them while I was writing... so, what kind of yields do you get doing it that way? Interesting if you don't get the heavy loss of yield NPH describes by throwing in the H2O2 all at once.
« Last Edit: June 13, 2011, 03:14:46 AM by Methyl Man »
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Terror

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Re: Benzoquinone Synths
« Reply #11 on: June 13, 2011, 03:51:24 AM »
Thanks for the input all but swim is fairly sure there was an issue in the reaction matrix.

With the bond method which swim has used many times before NO gold precipitate was seen during the exothermic phase. swim also left the reaction (red/black/thick) mix stirring and heating for a further 45 after the exothermic phase and nothing appeared. Putting it down to poor h2o2 quality.


On with the show..

Does anyone know about the chloranil contamination in the acetaminophen / nitric route?? Is it likely the contamination to the p-benzoquinone would be high and render it unsuitable for the wacker oxidation? Does anyone know a someone with actual test experience?

Also, swim has seen another route using acetaminophen / hypochlorite with dh20 as a medium -  yielding p-benzoquinone & N-acetyl-p-benzoquinone (and a combined further 7% yield of chloro-4-acetamidophenol & dichloro-4-acetamidophenol) - anyone tried this???




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Terror

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Re: Benzoquinone Synths
« Reply #12 on: June 13, 2011, 03:53:33 AM »
REF FOR THE SECOND REACTION..

Transformation of Acetaminophen by
Chlorination Produces the Toxicants
1,4-Benzoquinone and
N-Acetyl-p-benzoquinone Imine
M A R Y B E D N E R * A N D
W I L L I A M A . M A C C R E H A N
Analytical Chemistry Division, National Institute of
Standards and Technology, Mailstop 8392,
Gaithersburg, Maryland 20899-8392
The reaction of the common pain reliever acetaminophen
(paracetamol, 4-acetamidophenol) with hypochlorite
was investigated over time under conditions that simulate
wastewater disinfection. Initially, the reaction was
studied in pure water at neutral pH (7.0), a range of
reaction times (2-90 min), and a molar excess of hypochlorite
(2-57 times) relative to the acetaminophen concentration.
The reaction was monitored using reversed-phase
liquid chromatography (LC) with ultraviolet absorbance,
electrochemical, and mass spectrometric detection. At
1 ímol/L (150 ppb) and 10 ímol/L (1.5 ppm) levels,
acetaminophen readily reacted to form at least 11
discernible products, all of which exhibited greater LC
retention than the parent. Two of the products were
unequivocally identified as the toxic compounds 1,4-
benzoquinone and N-acetyl-p-benzoquinone imine (NAPQI),
which is the toxicant associated with lethality in acetaminophen
overdoses. With a hypochlorite dose of 57 ímol/L
(4 ppm as Cl2), 88% of the acetaminophen (10 ímol/L
initial) was transformed in 1 h. The two quinoidal oxidation
products 1,4-benzoquinone and NAPQI accounted for
25% and 1.5% of the initial acetaminophen concentration,
respectively, at a 1 h reaction time. Other products that
were identified included two ring chlorination products, chloro-
4-acetamidophenol and dichloro-4-acetamidophenol,
which combined were approximately 7% of the initial
acetaminophen concentration at 1 h. The reaction was
also studied in wastewater, where similar reactivity was
noted. These results demonstrate that acetaminophen is likely
to be transformed significantly during wastewater
chlorination. The reactivity of the chlorine-transformation
products was also studied with sulfite to simulate
dechlorination, and 1,4-benzoquinone and NAPQI were
completely reduced.

........NAPQI, however, is known to
be fairly unstable and readily hydrolyzes to the toxicant 1,4-
benzoquinone (III) in aqueous solution
« Last Edit: June 13, 2011, 03:55:08 AM by Terror »
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Terror

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Re: Benzoquinone Synths
« Reply #13 on: June 13, 2011, 03:56:58 AM »
Hi All,

SWIM has made p-benzo in the past using the bond-doublebond method (h2o2 / hydroquinone / i2 bringing the solution to a boil with a fairly exothermic reaction following)

SWIM attempted the h2o2 / hydroquinone / i2 synth as per Rhodium which is the same but instead of bringing the solution to a boil the reactant contents are left to stir for 3 hours, SWIM figured this route would not be as violent / runaway.

Anyway, the results from the each method seem to vary alot.. The bond-DB method always yielded long gold shard like crystals upon cooling, the Rhodium method seems just look like alot of fine gold speckles (not crystal masses) in a blackish like solution (due to the i2). This method didn't get boiling at all but obviously a reaction has occurred, maybe not completely?

Has SWIM done something wrong here or does the Rhodium / cold method simply not yield the same???

SWIM had a look around and couldn't find any answers online, so throwing it out there.

Thanks Beees!

the cold method is not running to completion.  the black with gold specs is quinhydrone.  quinhydrone is a complex of hydroquinone and benzoquinone.  the boil/reflux at the end is to ensure the reaction runs to completion and all the unreacted hydroquinone in the quinhydrone is oxidized properly to p-benzoquinone.  you'll find plenty of posts in the old hive archives of bees saying they have the same problem with the rhodium write-up that you did.  the rhodium variation is based on a patent and i THINK the problem was that bees were following that patent word for word but scaled up much higher than the patent does.  since they scaled up they need to let it react much longer.  the bond_doublebond method is where you boil/reflux it at the end.  increasing the temperature so much like that vastly increases the reaction rate, so the reaction is going at a much faster pace and is being run to completion in those circumstances.

Cheers Neil - swim didn't scale up though, 55g hydroquinone reaction..
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pyramid

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Re: Benzoquinone Synths
« Reply #14 on: June 13, 2011, 04:12:56 AM »
Methyl Man:

The yield is between 80-90%, all the other methods in my opinion have too much fussing around to compensate for any higher yield they might give.
All the reactants for this are very cheap and available, the reaction is extremely quick and can simply be run several times if large amounts are needed.

Plus, each time you are guaranteed canary yellow crystals, clean product, cheaply and quickly produced.. It's a winner IMO
Oh and no recrystallization is needed, just a washing/quick trituration.

As for the other methods discussed here, I can't add anything as I haven't ever tried!

Well...once I did try from paracetamol just to see how it goes. Not something i want to do again really, oh the foam...and smell. Never ended up actually working up and obtaining pure product, I was over it after the main reaction  :D

Terror

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Re: Benzoquinone Synths
« Reply #15 on: June 13, 2011, 11:49:08 AM »
Methyl Man:

The yield is between 80-90%, all the other methods in my opinion have too much fussing around to compensate for any higher yield they might give.
All the reactants for this are very cheap and available, the reaction is extremely quick and can simply be run several times if large amounts are needed.

Plus, each time you are guaranteed canary yellow crystals, clean product, cheaply and quickly produced.. It's a winner IMO
Oh and no recrystallization is needed, just a washing/quick trituration.

As for the other methods discussed here, I can't add anything as I haven't ever tried!

Well...once I did try from paracetamol just to see how it goes. Not something i want to do again really, oh the foam...and smell. Never ended up actually working up and obtaining pure product, I was over it after the main reaction  :D

Pyramid - if it was 'guaranteed' I wouldn't have started the thread lol!!! While the reactants may be easy to source etc, in swims case hydroquinone might cost $10 but the shipping is another $70 and then the time delays slow everything down. At the end of the day a paracetamol starting point actually seems quite feasible!! That's simply the way of the game, one thing might be easy for you to get and Ni-on impossible for the next guy; it just comes down to where you are, the rules of the game, the amount of risk you want to take. Basically, the 'best' process isn't always the most high yielding or simplest.
Confidence and arrogance are easily confused, but only one breeds contempt.

pyramid

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Re: Benzoquinone Synths
« Reply #16 on: June 13, 2011, 04:32:09 PM »
No Terror, I guarantee if you actually try the method how i posted it it will be 100% successful. I've never had success with the peroxide/I2 method any other way than what i posted. Did you read to see how I explained it? There are no slow additions or anything, it is a rapid reaction and it has never failed.

Unless paracetamol is very cheap for you it will still be cheaper to sourc Hydroquinone, yields are pretty bad with the paracetamol method.
I'm not trying to convince you not to do it, but what I posted is no misinformation and works every time and has never failed.

Your first post indicated you tried a bond-doublebond method, apparently only boiling at the end of a slow addition. It won't work!
Do it as I said, and it will work!

You must use I2. I've tried with KI and tinctures, does not work. If you don't have I2 make it from the tinctures or KI, but you can use 0.5g and it still works with I2 just as well.

And sure, I know very well about differing availability of precursors. However, apparently you have access to Hydroquinone as you tried making BQ with it and failed.

NeilPatrickHarris

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Re: Benzoquinone Synths
« Reply #17 on: June 14, 2011, 06:59:11 PM »
ah, sorry MM i've never run the sodium nitrate/HCl reaction before so i can't comment :\

pyramid, your experience and mine are night and day opposites for some reason.  i'll note the following differences:

1) you add all the h2o2 in at once and don't get a runaway reaction.  i've set a drip-rate on my addition funnel once before and left the room, i came back 2 min's later to find all the h2o2 had been added - the stopcock wasn't tightened enough i don't think.  anyway, within a minute or two everything had gotten out of control.  it was boiling/refluxing like crazy and reminded me a little bit of a very very very pissed off al/hg but without all the foam.  i had to put it in an ice bath because it was going up the condenser and about to spew everywhere.  an online buddy of mine did the same exact thing with this reaction once before too and said the same thing happened to him except he didn't put it in the ice bath to kill the reaction fast enough.  it spewed all over the place and he was coughing/choking/eyes watering from the freshly-reacted hot/volatile benzoquinone flying everywhere.  we both followed bond_doublebond's method to a "T" (except accidentally adding the h2o2 all in at once, big mistake when i did it) which is basically just what my write-up above is.  perhaps since you don't dissolve the reactants they don't start reacting until your heat is applied (causing them to then dissolve) and at that point you have careful temperature control regarding heating/cooling?

2) i2 tinctures don't work for you?  all i've ever used was i2 tinctures.  you're not using povidone-iodine right?  i used 2% i2 tinctures from the local drug every single time i ran the reaction, no problemo.
« Last Edit: June 14, 2011, 07:12:06 PM by NeilPatrickHarris »

Terror

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Re: Benzoquinone Synths
« Reply #18 on: June 15, 2011, 03:00:54 AM »
The one thing that makes swim uneasy about your synth pryamid is as follows:

"Then after a couple of mins a low blowtorch flame is used to evenly heat the flask until the temp is around 75C at which the temp will rise on its own. Then the flask is immediately immersed into an ice bath to control the exotherm, but removed quite fast it is just to keep it under semi-control."

Im sorry but I personally wouldn't have an open flame anywhere near a bubbling solution of isopropyl alcohol, it's a little reckless for my liking!

What swim determined is that the h2o2 had degraded to a point where the reaction was not completing, I can gaurentee you, 100% that with this particular h2o2, you would be 100% unsuccessful.
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akcom

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Re: Benzoquinone Synths
« Reply #19 on: June 15, 2011, 03:10:04 AM »
Use a heat gun if you'd prefer.  Same effect