| Pages:
1
2
3 |
VitaminX
Harmless
Posts: 17
Registered: 27-11-2012
Member Is Offline
Mood: Moody
|
|
Have you tried Oxidation of Hydrochinone with HNO3 in an organic solvent like Chloroform/DCM?
E. Baroni and W. Kleinau described quantitative oxidation to benzoquinone 1936 ("Die Nitrierung yon Phenolen in Chloroform):
"Setzt man zu einer Lösung yon Hydrochinon in Chloroform
einige Tropfen Salpetersäure, so entsteht sofort eine starke Gelbfärbung,
die auch bei weiterem Zusatz yon Salpetersäure sich
nicht ändert. Es bildet sich in quantitativer Ausbeute Chinon.
Eine vorübergehende Bildung yon Chinhydron war nicht zu beobachten."
They say you basically just have to add concentrated HNO3 dropwise to your solution, it will turn yellow and you got 100% Benzoquinone. Unfortunately
no molar ratios or anything like this is given but with a little bit of experimenting you can figure it out.
Edit: Maybe DCM would be better suited as a solvent for this particular reaction since its bp is much lower than CHCl3 and you can probabaly distill
it off losing less product.
[Edited on 17-12-2012 by VitaminX]
|
|
|
lolcat
Harmless
Posts: 10
Registered: 24-11-2012
Member Is Offline
Mood: No Mood
|
|
A few weeks ago I tried the synthesis of p-benzoquinone by route of the patent earlier noted. The experiment went alright until the vacuum filtration,
at which that point I could only ever see a few of the yellow crystals. My first concern was that the vacuum was not strong enough and that not enough
liquid was being pulled through, and although the pump that I use to run water through my aspirator is just a small aquarium pump, I don't think that
was the issue. The labeled 35% hydrogen peroxide that I used, had originally when I bought it not been in the freezer, I had just left it out at room
temperature for probably a month(I was scared that the label was lying, and that if I put it in the freezer, it would freeze and bust the bottle.
Shortly after reading this form though, I then started to store it in the freezer, although I think it might be too late.
I have two questions; is the degradation of hydrogen peroxide an issue in my case? Would it have degraded that much after a month, such that I did not
have an enough oxidizer in my experiment and that could be why I could only see such a small amount of yellow para-benzoquinone crystals?
My second question, (and forgive me if my chemistry is horrible, I am only a first year student at university) but could not more of a less
concentrated hydrogen peroxide be used? Could one not use stoichiometry to see how many moles of H2O2 are in X amount of 35% H2O2 and then see how
much say 3% H2O2 would need to be used? Admittedly, a great deal more 3% H2O2 would have to be used, but 3% is very cheap and can be bought at the
drug store compared to 35%. I would appreciate if someone would care to explain the chemistry of whether or not that works. I am rather new here, and
just learning chemistry, so please don't be too harsh.
|
|
|
DJF90
International Hazard
Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline
Mood: No Mood
|
|
You allowed the product to crystallise for long enough?
Hydrogen peroxide should not decompose that quickly. I store mine at room temperature, which reaches the mid twenties on the rare hot summer day. Its
also quite old (several years), and it worked fine for the reaction. Don't use a more dilute solution of peroxide; 30 and 35% are both available and
cheap (at least here in the uk).
|
|
|
mad.chemist
Harmless
Posts: 3
Registered: 24-1-2013
Member Is Offline
Mood: No Mood
|
|
I am interested in trying this reaction but I have one concern. About 2 months ago I purchased food grade, i think 30%, hydrogen peroxide but I
stupidly ignored the label and didn't put it in the freezer. Then about a month ago I read the wikipedia article on hydrogen peroxide and read that it
decomposes at higher concentrations, so then I put it in the freezer. So my question is, will a significant amount of it have decomposed during that
month period? I have tried looking online, but I haven't found any articles that discuss the rate of decomposition of hydrogen peroxide. Any advice or
resources would be appreciated.
|
|
|
Lambda-Eyde
National Hazard
Posts: 857
Registered: 20-11-2008
Location: Norway
Member Is Offline
Mood: Cleaved
|
|
In a month..? Not much. I have some 35% hydrogen peroxide that's probably ten years old, it's still good and fizzy. I don't know *how* fizzy, I'll
titrate it when I get the opportunity.
This just in: 95,5 % of the world population lives outside the USA
You should really listen to ABBAPlease drop by our IRC channel: #sciencemadness @ irc.efnet.org
|
|
|
declined
Harmless
Posts: 17
Registered: 5-2-2013
Member Is Offline
Mood: No Mood
|
|
Are we able to scale this up with, say, a 22L flask? Or do you think there can potentially be hazardous runaway rxns, or uncontrollable exothermic
heating?
|
|
|
VitaminX
Harmless
Posts: 17
Registered: 27-11-2012
Member Is Offline
Mood: Moody
|
|
Quote: Originally posted by declined  | | Are we able to scale this up with, say, a 22L flask? Or do you think there can potentially be hazardous runaway rxns, or uncontrollable exothermic
heating? |
I did it a while ago with about 180 grams Hydroquinone in a 1L flask. Total volume was about 750 ml and when it heated up it nearly poured out of my
condenser. I would say that your total rxn volume should NOT exceed 40% of the volume capacity of your flask, then you should be fine because there is
plenty of breathing room. Reaction works really nice though
|
|
|
angry tapir
Harmless
Posts: 2
Registered: 14-11-2013
Member Is Offline
Mood: No Mood
|
|
I just love to read all the fascinating highlights of amateur chemistry that can be found here but usually I´m not really the person that actively
participates. Suddenly erverything changed: I found myself in need of some benzoquinone and today is the day I finally give something back 
My desperate need made me check some of the techniques discussed. I have some lab experience, so I was not really sure why I fucked up the last 3
times. Today I finally found out how it can be accomplished. But let's not get ahead of ourselves.
My first try was the synthesis found on Rhodium. I tried the method with the IPA and hydrogen peroxide. (mine had a concentration of about 30% so that
*might* have something to do with it) The reaction mixture took on a dark colour, and in the end I heated everything to about 50 degree for three
hours. The next day the solution was nearly colorless, leaving me behind clueless.
The next try: I added some 20ml of 50% H2SO4 and heated to 40 degree before slowly dripping in the peroxide. I heated to 55 degree and stirred for 3
hours. I ended up with qiunhydron. I said to myself "well, that's better than nothing" and filtered it. yield sucked, filtration as well.
I thought that it might be necessary to add some acid so I tried the whole thing with 50% hydrogen peroxide (made by destilling of water of peroxide
with a rotary evaporator at 30 mbar) and added about 5 grams of p-Toluenesulfonic acid and did the reaction (0.5 mole scale) in 200ml IPA. After
dripping in the peroxide I ramped up the temperature to about 74 degree. It started to boil and I had a hard time keeping it from becoming to
vigorous. I ended up with black goo and no benzoquinone.
Then I did the following:
I concentrated peroxide with a rotovap to ~50% (I washed the flask with EDTA beforehand and added about 82ml of ~30% peroxide solution to a 250ml
flask, and concentrated it until ~30-40 ml water had been collected. I used a graduated cylinder on a scale to determine the concentration and ended
up with 48ml solution that weighed 56,2g, so this is a good way to concentrate peroxide solution without losing much of it) In a 500ml RBF I added
0.63g Iodine, 66,4g Benzoquinone and 200ml IPA. I heated to exactly 62 degree and started to add the peroxide at a rate of 1 drop every 2 seconds.
Quinhydrone started to precipitate and stirring became nearly impossible. (if you have them use the stir bars that look like weights, for me they did
a good job) After a bit less than half of the peroxide had been added I heated to 65 degree and decided to add the peroxide solution a bit faster. Two
minutes later it looked like the soultion started to boil at the spot where the peroxide drippped in. I lowered to temperature to 60 degree and
dripped in the peroxide more slowly. After having added all the peroxide heated to 64 degree again and 30 minurtes after that the precipitated
quinhydrone had gone leaving behind a dark yellow/orange solution. I put that in the fridge and nice yellow crystals started to seperate. I put the
flask in the freezer over night filtered the product and washed with ice cold IPA. The yield was 61,6g.
|
|
|
DJF90
International Hazard
Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline
Mood: No Mood
|
|
You do not need to pre-concentrate your peroxide. I've done this prep several times before on various scales, each time using 30% peroxide, and each
time it worked as described.
I suspect the failures people are having is due to the execution of the reaction, and not the reaction itself.
|
|
|
angry tapir
Harmless
Posts: 2
Registered: 14-11-2013
Member Is Offline
Mood: No Mood
|
|
I tried it again with 30% peroxide and did in the exact same way as before and it worked. So you´re right, it doesn´t depend on the concentration of
the peroxide. So my mistakes were 1. adding acid (not necessary) and the wrong teperature management.
Again the yield was over 90%
[Edited on 16-11-2013 by angry tapir]
|
|
|
| Pages:
1
2
3 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
