st0ne
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TNP from phenol and nitrate-acid mixture
I have searched for something like this but I haven't found anything. I have tried to make TNF from phenol, SA and ammonium nitrate, but the
result was very disappointing. I dissolved 95g phenol in 300ml hot SA and let the mixture to cool(15 centigrade). Then I began to add slowly 240g
NH4NO3 keeping the temperature lower than 20 centigrade. After all the nitrate was added I left the mixture for 15-20 minutes and them poured it in
1.5l cold water. The water became yellow and there was foam of TNF ot the top, but nothing more. What's wrog?
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garage chemist
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TNP production has to be made HOT.
At 20°C, the reaction speed is next to zero.
It produces enough TNP to make a yellow color, but about 95% of the phenol remains unchanged.
Anyway, there is an awful lot of discussion about TNP here. Search! Under its more common name "picric acid" you will find extensive
information
And there are lots of good recipes for TNP.
You just wasted 95g of precious phenol because you didn't know how to make TNP.
Other people would be very happy to have a few grams of phenol!
[Edited on 13-11-2005 by garage chemist]
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st0ne
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I know its common name is "picric acid" and I have searched but there is no synthesis of TNP from phenol and ammonium nitrate. Most of the
post are about TNP from aspirin.
And I have tried hot TNP production 2 times. But it doesn't seem to work with ammonium nitrate+hot sulfuric acid+sulfophenol because there were
awful runaways and a lot of NO2.
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Marvin
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"At 20°C, the reaction speed is next to zero.
It produces enough TNP to make a yellow color, but about 95% of the phenol remains unchanged. "
Words fail me.
If you don't sulphonate the phenol first the speed of nitration will destroy most of it. Find one of the methods in Davis (Chemistry of powder
and explosives). The ebook is floating around. I would advise against using ammonium nitrate even if it means using sodium or potassium nitrate.
(Keeping sodium or potassium ion containing solutions highly acidic to prevent precipitation of picric acid salts).
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chemoleo
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TNP synthesis
I am also not aware of a thread where dedicated to making TNP from phenol - but do tell if you find one and I will merge it.
Anyway, Marvin is of course correct, the phenol has to be sulphonated first, partyly to avoid undesirable side products that would occur without
sulphonation):
Synthesis of picric acid from phenol
20 g of phenol (0.21 mol) are heated in a beaker with 45 ml conc H2SO4, and while heating a brownish solutions forms. This is now 2, 4 phenol
sulphate.
To this, one adds 100 ml of conc HNO3 (d = 1.41 g/ml, 1.5 mol) dropwise, which is added in a 500 ml RBF under the fume hood. The temperature increases
rapidly while NOx is produced. To complete the reaction, the oilbath with the RBF is heated to 100 deg C until NOx evolution stops, then the
temperature is raised to 112 deg C for a few minutes. Already during cooling precipitation of picric acid occurs, which is completed by pouring this
into a 6-fold excess of water/ice.
Yield is about 72% (35 g). The PA can be recrystallised to colourless crystals from water/ethanol or benzene. MP: 122 deg C.
Synthesis taken from Gattermann.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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Rosco Bodine
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There were some experiments done by me using ammonium nitrate both solid and as concentrated ~60% aqueous solution , gradually added to the sulfonated
product of methyl salicylate to effect its nitration to picric acid , but the yield and purity of the end product was never what it should be .
However , the
same nitration scheme may work fine for phenol or aspirin , but the experiments
have not been done so it is unknown what value that method of nitration may have with other precursors than methyl salicylate . Anyway , you could
try adapting some of those experiments for methyl salicylcate nitration using ammonium nitrate to the nitration of phenol , if you are really
interested in
phenol as a precursor for picric acid and
using ammonium nitrate for nitration of the sulphonated phenol . IMO any decent synthesis for picric acid should give 90% yields or better , no
matter what is the precursor used , since it is very important to produce a crude product that is already highly pure directly from the nitration , or
else the final purification of the product can become very tedious .
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st0ne
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The phenol was sulphonated. I sulphonated it in 300ml of SA and then let it cool. After that I began to add the nitrate.
As I read the synthesis taken from Gattermann I think that my first try(without cooling the mixture of sulfophenol and SA) may give some results. But
the runaway was so violent so I thought that the sulfophenol had oxidised. If somebody gives me some exemplary synthesis, I will test it. I want to
know what the mistake in my synthesis is and how I can make TNP from phenol, SA and AN. I am interested in making TNP from phenol, SA and 60% nitric
acid too.
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Marvin
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I'd say the sulphonation failed. Too weak acid? Didnt heat for long enough?
I also suspect using too little sulphuric during the nitration will make oxidation more likely.
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Rosco Bodine
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Runaways are most often the result of an accumulation of unreacted material in the nitration mixture due to too rapid of addition of the nitric acid
or nitrate and generally also at too low a temperature .
Only the first third of the nitration for phenol is done at a relatively mild temperature and the temperature is much higher for the dinitration and
trinitration stages , typically over 100 C . Not following the favorable temperature curve required while pacing the additions to match the reaction
rate , is what causes
the accumulation of unreated material .
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Rosco Bodine
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@st0ne
On page 3 of the thread titled " picric acid different instructions " there was an experiment I proposed may be worth trying for the
nitration of phenol using sodium nitrate and this is perhaps adaptable to using ammonium nitrate in
94.1% the amounts given for sodium nitrate , the substitution adjusted according to the difference in the mole weight of NH4NO3 compared to NaNO3 ,
~ 80/85 = .941
You said in your post above that you are looking for an example experiment , and this is an untested example , based only
on a study of related patents and literature . So this is only a place to start
development of a good lab scale method .
Adjustments to this proposed experiments
parameters will very likely be necessary in order to refine the process , after it is seen how the reaction proceeds .
Quoted post from the earlier thread :
Honestly I have never looked too closely at methods for picric acid using phenol as the precursor , nor have I ever made any picric acid from phenol ,
simply because it is the least convenient and most expensive precursor . OTC precursors like
aspirin , salicylic acid , and oil of wintergreen , have always seemed more promising as starting materials . And honestly again aspirin is the only
precursor I have ever used for making picric acid , since it is cheap and I get about 90% yield . From what I have read
about the published methods , I would likely just use an adaptation of the method I already use for aspirin . I haven't tried this adaptation to
see how it would perform or know what adjustments would be needed to refine the method . This is purely off the top of my head as a possible
experimental method as I am interpolating and guessing a bit on this adaptation for phenol . I hesitate to describe an untested experiment because of
the unknowns , but anyone having some experience " reading " reactions as they are observed could try this approach and
make their own adjustments as it goes to
pin down the details . So for the got carbolic acid on the shelf but got no aspirin folks , here goes nuttin'
If you just want something different from one of the reported methods known to work , this seems possible , but I am not
entirely certain , this is hypothetical at this point .
This proposed method is untested and
most definitely EXPERIMENTAL :
The reaction contemplated would be performed in a two liter beaker or wide mouth erlenmeyer or flat bottomed florence or a similar sized pyrex teapot
,
sitting upon a stirrer hotplate with a good thermostatic heat control , not a rate controller , and using a three inch or larger
stirbar . A thermometer , addition funnel and wash bottle will also be required .
50 grams of liquified phenol is added slowly with stirring to 200 ml 92% H2SO4 @85 C , regulating the rate of addition to
maintain reaction temperature of 95 C to the end of the addition . The temperature is raised to 115 C and maintained for an additional 30 minutes and
then the heating discontinued .
When the mixture has cooled to 55 C ,
the stirred mixture is cautiously and slowly diluted with 75 ml H2O streamed onto the walls of the vessel from a syringe or wash bottle .
To the stirred mixture is added in small portions dry sodium nitrate , at a rate sufficient to maintain temperature in the
range of 55 C to 70 C , or just less than the temperature at which red fumes appear , until a total of 60 grams sodium nitrate have been added . Then
an additional 200 ml 92% H2SO4 is added at
a rate which maintains the temperature at
65 C . When the addition is completed ,
the temperature is maintained with supplemental heating for fifteen minutes
at 65 C , and then raised to 85 C . In small portions an additional 120 grams of
dry sodium nitrate is added to the stirred mixture as rapidly as the rate of reaction allows without producing red fumes . The
temperature rise allowable should steadily
increase as the nitration proceeds , particularly after the midpoint of the addition . A smooth nitration temperature
may be observed in the range of 95-100 C. At a point towards the end of the addition of the nitrate the exotherm should begin to diminish , and
supplemental heating should be applied to maintain the reaction temperature with an endpoint temperature of 115-120 C ,
held for three or four minutes , before
supplemental heating is discontinued .
Stirring should be continued for the mixture as it cools . After the mixture
has cooled to perhaps 80 C , it is again
cautiously diluted with water streamed
onto the inside wall and allowed to sheet
slowly into the stirred mixture , ~300 ml
of water being used for the dilution .
The still warm mixture is dumped onto twice its volume of ice cubes . After standing for a time all of the ice will be melted and the cold mixture is
filtered to obtain the crude picric acid . The still damp crystals are redissolved in boiling water and recrystallized on slow cooling to room
temperature . The filtered solution is concentrated by boiling until
some dark colored precipitate appears , allowed to cool slightly and decanted from the impurity . Upon cooling slowly a second crop of crystals will
be obtained ,
about 10% of the total yield from the second crop of crystals . The total yeild
should exceed 90% of theory based on phenol , about 110 grams of dried crystals of pure picric acid .
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