picramic acid from picric

good information found!

Question

Synthesis

The purification of picric-, picramic-acid... salt`s
conditional by high water-solublety is always not easy.
It don`t say, you get a bad product when not produced
by picramic acid.

Here a example for potassium-picramate.
Potassium-picramate are very long beautiful brown needles
which are somewhat sensitive to friction and shock
and which can be easy detonated by flame.
It`s a strong eplosive which have no real practical
significance.

I think it`s not nessesary to purificate the crude product
which have a good quality as well as don`t produced by picramic-acid.
The disadvantage is a bit lower yield, but the
expenditure is lower.

What about

Lets say

Is this the color of Picramic acid. This was made by the addition of a soln of FeCl2 and HCl in Picric acid soln (made from ASA)

Vitamin C should do the trick as a reducing agent

In terms of simplicity and economy the method using the " polysulfide " reagent
made from the dry mixing and exothermic
melt reaction of S and NaOH is definitely
practical , and worth experimentation .
The experiments with that method were
not numerous to an extent for finding what exact proportions and conditions were optimum . The experiments were
only sufficient for identifying a general
method which would give worthwhile yields , by a few trial and error comparisons intended to improve upon
some of the earlier published black book
methods which give poor results .

The reducing agent which is produced by the high temperature melt reaction between S and NaOH is likely a mixture which is mainly two different sodium sulfur compounds , sodium hydrosulfide NaHS , and sodium polysulfide Na2S4 ? or Na ? S_(x) .

It is evident that the high temperature rapid reaction of the melt and lowered exposure to the air gives a product which
has more reducing properties than the product obtained by diluted solutions and boiling .

A patent US4156656 has compared the different compositions of the mixture which results for the reactions of alkali and sulfur under differing conditions of temperature and exposure to air . From the charted results it is evident that high temperature and minimized exposure to air results in a product much higher in the hydrosulfide which is the probable reducing reagent responsible for the conversion of picrates to picramates .
The " polysulfide " is probably a secondary
participant which may contribute to the reduction , although it is likely the polysulfide reagent could be more accurately named " hydrosulfide / polysulfide " reagent , when analysis of
its actual composition may be done .

The reaction is interesting because of the unknown nature of the stoichiometry for both the formation of the reagent , the reduction of the picrate to picramate ,
and the byproducts of the reduction .

I still do not understand exactly the reactions involved . I'll be damned if I can explain it to myself much less to anyone else how it works , only that it does work

For purification of the sodium picramate ,
I have read that the crude material
is dissolved in boiling water and filtered ,
and then dripped while still hot into a warm well stirred dilute HCl , which should result in the precipitation of the
only slightly soluble pure picramic acid
which is filtered out after cooling . The isolated pure picramic acid can then be used to produce whatever pure picramate
is desired by neutralizing with the base
for the desired salt .

Attached in this post will be the patent .
In the two following posts will be attached related files which shed more light on the soluble sulfide reducing reagents and reactions .

[Edited on 28-4-2005 by Rosco Bodine]

Attachment: US4156656 Preparation of Hydrosulfides.pdf (150kB)
This file has been downloaded 2271 times

Preparation from "Fundamental processes in dyes..."

The attached file is one of the listed references in PATR 2700 for Picramic Acid from the “Dictionnaire des Matières Explosives” (1902) by Daniel.

[Edited on 5-6-2013 by Polverone]

Well it's good that somebody has been curious enough to try vitamin C I have more good ideas than time for experiments , and I love it when you fellows check it out
and prove old Rosco right ! Great minds think alike ,
I tell you that's it And for when I'm wrong ....
well that's just the anomalous brainfart .

I suspect your orange coloration was from either unreduced
sodium picrate , or from free picramic acid due to pH being
a bit on the low side .

I have an untested idea that it could work best if you go a bit past neutralization of the ascorbic acid first with a sodium salt like ordinary baking soda , to the point
where it doesn't effervesce CO2 on further addition
of base . The warm concentrated solution of
slightly basic sodium ascorbate is probably air sensitive
like other reductants would be , so you may want to
minimize any overt exposure to air over any long period of time , keep the stuff closed up if it isn't going to be used right away for the reduction . And it might be good to use a piece of saran wrap and a rubber band over
the top of the reduction beaker , punch a hole or cut a slit for admitting the tip of the dripping funnel , to keep fresh air off the vortex surface of the reduction mixture .
The reduction should be done very gradually , running in the ascorbate solution while it is warm , into the prewarmed sodium picrate solution , pretty warm depending on the induction temperature .....there will
be a temperature where you can probably control the exotherm by rate of addition ....so the reaction proceeds
fairly rapidly but in a controlled way . Let it keep stirring
past the end of the addition for the time it takes to start
cooling down significantly on it's own , and then let
it sit in the refrigerator or a bath of melting ice overnight .
Sodium picramate will be a very dark burgundy red
precipitated fine prismatic crystal , a very dark maroon
or oxblood color ....and it is an intense dye much more
dark colored and soluble than free picramic acid .
The crystals should be so fine it will almost look like
mud on the filter , but in strong light it will glitter profusely revealing the crystalline nature plainly .

[Edited on 9-5-2006 by Rosco Bodine]

If I have it right , it simply loses one hydrogen
when reduced . I take it that " monodehydro " ( ascorbate ]
means " minus one hydrogen " ,
probably the atom and not the molecule ....
I have to be at least half right

This is from Wikipedia

http://en.wikipedia.org/wiki/Ascorbic_acid

Uses
Ascorbic acid is easily oxidized and so is used as a reductant in photographic developer solutions (among others) and as a preservative.

Exposure to oxygen, metals, light and heat destroy ascorbic acid, so it must be stored in dark and cold and not in a metal containment.

The oxidized form of ascorbic acid is known as dehydroascorbic acid.

The L-enantiomer of ascorbic acid is also known as vitamin C (the name "ascorbic" comes from its property of preventing and curing scurvy). Primates (including humans) and a few other species in all divisions of the animal kingdom, notably the guinea pig, have lost the ability to synthesise vitamin C and must obtain it in their food.

Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives. These compounds are water soluble and thus cannot protect fats from oxidation: for this purpose, the fat-soluble esters of ascorbic acid with long-chain fatty acids (ascorbyl palmitate or ascorbyl stearate) can be used as food antioxidants.

The relevant European food additive E numbers are: E300 ascorbic acid, E301 sodium ascorbate, E302 calcium ascorbate, E303 potassium ascorbate, E304 fatty acid esters of ascorbic acid (i) ascorbyl palmitate (ii) ascorbyl stearate.

[edit]
Antioxidant mechanism
Ascorbate acts as an antioxidant by being itself available for energeticaly favourable oxidation. Oxidants (scientifically referred to as reactive oxygen species) such as the hydroxyl radical (formed from hydrogen peroxide), contain an unpaired electron and thus are highly reactive and damaging to humans and plants at the molecular level. This is due to their interaction with nucleic acid, proteins and lipids. Reactive oxygen species can 'abstract' a hydrogen from ascorbate, which becomes monodehydroascorbate and soon gains another electron to become dehydroascorbate. The reactive oxygen species are reduced to water while the oxidized forms of ascorbate are relatively stable and unreactive, and do not cause cellular damage.

Dehydroascorbic acid (DHA) is one of oxidized forms of ascorbic acid. It is actively imported into the endoplasmic reticulum of cells and generates the oxidative potential found there. Protein disulfide isomerases are known to reduce DHA back to ascorbic acid, oxidizing their disulfide bonds in the process. Therefore L-dehydroascorbic acid is a vitamin C compound much like L-ascorbic acid. As a result of different contents of crystal water (hydrated water) there are different forms of DHA: the waterfree bis-DHA and the mono-DHA*H2O. In literature often mono-DHA without hydrate water molecule is used. Oxidized forms of esterified ascorbic acids can be numbered at C(5) or C(6) atoms and the (free) chemical radical semi-dehydroascorbate or semidehydro ascorbic acid (SDA) to the group of dehydroascorbic acids.

[Edited on 10-5-2006 by Rosco Bodine]

Some solutions were mixed, about 50mls of Na picrate soln. at RT, along with some slightly-warm sodium ascorbate solution. The solutions were dumped togeather in a erlenmeyer flask, stoppered loosely, and set on a low set hot-plate. Upon return 15 mins later, it was happily boiling slowly and was a very dark color, appearing alomst black. This was placed in an ice bath overnight, and was placed in the freezer for a bit to cool to 0 before filtering. I obtained a small (.25g) amount of sodium picramate. It is dark-red, maroonish color, and quite fine-grained. The crystalline structure is not particularily dense. I have not calculated the soluabilities, but this seems to be an OK yeild given circumstances and mistakes. Either way, it burns. I have yet to do a reduction with actual measuring.

I will add this to HCl in order to create free picramic acid and NaCl. This will then be acidified furthur, and a NaNO2 solution will be added at OC. If a diazo-product resembling DDNP is obtained, I dub ascorbic acid proved and worthy as a reducing agent for TNP.

Interesting... I happen to have some MHN on hand, and I belive I will try a co-precipitation and then attempt to detonate it as a primary, and just play with it.

Once again, after I recrystallize my TNP, I will get some numbers and figures to work with for the reduction, and hopefully results. I feel empowered.

Hydrazine sounds constructive, though, my reagents will need serious purifying before I will get any decent yeilds from it.

Too bad I messed up the DDNP batch, eh, live and learn. I am still midly amused the vitamin C actually worked nicely. Good idea

Do you think it would be worth it to make a thread about DPNA? That stands for diazoperchlorate-3-nitroaniline, and apparently is quite fun. Or, perhaps 2,4-dinitrobenzenediazonium perchlorate> Basically, I am interested in aromatic diazo salt primaries. Does that make any sense?

I can just see the checkout at the drugstore ,

A thousand aspirin tablets , and a kilo of vitamin C ....

yepper , got one hell of a headache , and feel a bad
case of scurvy coming on

That'll do it .

About the new thread , no I think there is already some extensive stuff posted on it , search and find .

I never tried something easily initiated like MHN as
a base charge for the low density DDNP , where it
would probably be fine . I most often use picric acid
as a base charge , which requires a pretty intense pulse
to initiate . And even for HMTD which has a really
good literature report of performance in unreenforced caps , it can be difficult and take a fair amount , which
is the way it looked for me concerning DDNP of the
fluffy variety ....nothing to campare with say lead azide
for example . So given the difficulty of making DDNP
and the light sensitivity , it just didn't impress me nearly
as good as say lead azide or the azo-clathrates . I
did not extensively test the DDNP , because its performance never seemed to come close to literature
references , and one good example of the exaggerated claims extended to the 50/50 eutectic with picric acid
which was reported in a patent to be fuse sensitive ,
which after my test I was forced to laugh and ask
in what quantities ...ten grams or twenty ?
So I just never really was much impressed with the
stuff . But I am sure it has potential usefulness if
the correct conditions are met , I just lost patience
with experiments with DDNP and moved on to other materials , thinking it was too fickle for my liking ,
not really a good general initiator . Azo-clathrates
are so slick I became enamored of them very quickly ,
and lost interest in alternatives which may still have value , particularly if made under more optimized conditions . I'll stay out on a limb here and say the
crystalline form still makes a difference no matter what
the literature may report to the contrary , and I would bet money that tests bear that out .

Yes, I also ran into some trouble as my Na picramate was not totally dry, and was thus still basic and some of the first amounts of HCl were titrated against NaOH, not Na picrate

So, the yeilds are a bit off! I will venture to guess I recieved >5g.

Azo-clarthates do look quite interesting, and at one time, I was inspired to try them! I am caught between hydrazine and aromatic diazo perchlorate salts.

I`ve read a document, picramic acid was made by the reduction with iron. I guessing iron is corrosive, but didn't think this method will work better.

Dissolve 1g of picric acid in 100 ml of glacial acetic acid at room themperature and this is stirred until all is dissolved. 0,5 g of finely powdered iron is added over a period of 24 hours and the mixture is stirred papidly. The liquid is stirred until the mixture turns to slight dark red and all iron is dissolved. The liquid is than evaporated by distillation.
I belive the result is better obtained when the mixture is diluted with H2O and the crystals are precipitated by cooling to 0 gegree celsius.

Is the result picramic acid and will this method give a purer product ? Some hints would help.

[Edited on 21-6-2006 by Mason_Grand_ANNdrews]

[Edited on 21-6-2006 by Mason_Grand_ANNdrews]

That reaction mixture will be a slurry , like porridge
probably and will likely be required to be stirred
for the duration of the reduction .....and it will probably
need makeup water to be added periodically to maintain the volume .

The reacted iron will probably be the black oxide which
is quite insoluble and will be intimately mixed with the
picramic acid which is also nearly insoluble , perhaps
a signifcant portion of the product being present in combined form as ferrous picramate . To isolate the
desired product in pure form it will be necessary to
dilute and digest the spent reduction mixture with an acid in order to convert any oxidized or combined iron
to a highly soluble ferrous salt which will be easy to
filter away from the free picramic acid . Using pool grade hydrochloric acid of 31.45% concentration for
this purpose 65 ml would be the minimum amount of
theory , but using 75ml would probably be better ,
and even as much as 100 ml to 110 ml would liklely be fine for a diluted spent reduction mixture . This digestion
will probably require heating the mixture to or near the
boiling point and stirring for a few minutes to complete ,
and the mixture can be cooled and diluted further before filtering . The excess of HCl is a good idea since it
will accommodate the likely oxidation of some of the
ferrous chloride to the ferric chloride from exposure to air and heating and stirring , and will keep all the iron in solution as the ferric chloride is even more soluble than the ferrous chloride expected as the initial product of the digestion .

My german isn't good enough to pick out whether this
was described in the article ....but take my word for it
that if it wasn't it should be . And HCl may not even do the trick of solubilizing the oxidized iron .....nitric may
be required , or the addition of a nitrate salt to the HCl
may provide sufficient nascent " aqua regia " to do
the trick . Sometimes the oxidized iron particularly if
it is the black oxide can be surprisingly " inert " as if
all the " fight " was gone from that poor iron after
being so brutally oxidized , ravaged by hordes of
rampaging horny nitrobrutes .

I have done a few of these reductions of other nitro compounds using iron , and FeCl3 as a catalyst ,
and driving the reaction directly with an HCl drip
while heating at the bp and stirring violently to
keep the iron in suspension and the insoluble nitro
compound emulsified in the mixture .

It may be as simple as it seems from the article
just stirring the slurry of the iron and the picric acid
since for this reduction the nitrocompound is soluble ,
but the isolation of the picramic acid product is
what will be the the trick .

I was also thinking about how to obtain picramic acid.
Is that correct, the addition of finely
powdered sulfur to a warm mix of picric acid/NaOH solution would be sodium picramate ?
I guessing, serveral steps will needed. The NaOH/sulfur should neutralised and filtered complete from the slurry
to prepricate the sodium picramate.
You are right, the described method with the iron powder was somethimes crap. Very low yield.
What is the result, dissolved phenol in NaOH solution was nitrated with dilute HNO3, second step - 70% HNO3.
A article says it is 2,4-dinitrophenol. This will be not a sodium salt ?
Even though, that during the formation of variably results by ratio dinitrate/trinitrate, HNO3/concetration by acid, H2SO4/HNO3. Why not picramic acid by 4-chloro-2,6-dinitrophenol.



[Edited on 24-6-2006 by Mason_Grand_ANNdrews]

I have just done a search on the net for information about the result but but i didn`t found
somehwat. Nasty H2S will bubble off sulfur is added. I belive that will work when the slurry is serveral cleaned
and contents are removed.
Sulfur/soluble in CCl4
NaOH/neutralization by HCl
I hope that will work. Picric acid is added to NaOH solution at 60 degeree celsius until
addition is saturated. Finly powdered sulfur is stirred to the mixture until nothing will dissolve.
To this, some dilute HCl and any ml of CCl4 will stirred in the mix. I hope the result can be obtained when,
the liquid is careful vaporizised or the slurry is diluted with water in a ratio 1/3, filtered and the crystal are prepricated
by cooling to 0 degree celcius. I'm not sure, alternative ways to obtaining the results are adding a large access of CCl4 to the mix and this will prepricate the picrate, adding HCl to neutralizing the salt and the picramic acid will prepricate or the mix will than diluted with H2O and this is cooled to 0 gegree celsius.

4-chloro-2,6-dinitrophenol
5g of 4-chlorophenol is careful added to a mix of 60 ml 90-95% HNO3 / 120 ml 96-98% H2SO4 and the mix
is careful heated and stirred over a period of 4 hours to 100 degree celcius. The crystals of 4-chloro-2,6-dinitrophenol are prepricated by adding 1000 ml cold water to the mix.
Several washings thoroughly with water will clean the crystals. As a possible alternative to that, 4-chlorophenol will be refluxed for two hours yield a purer result and don`t have remains of a mononitrate of 4-chlorophenol.


[Edited on 27-6-2006 by Mason_Grand_ANNdrews]

Searching the net should have included searching this thread including the link posted near the end of the first page , concerning Mr. Anonymous " dry method " for making
the Sodium Polysulfide reagent . The experimental method
is pasted below .


As promised, there is some info I can share regarding the polysulfide route to picramic acid. I will preface by saying there are better, more efficient uses for picric acid, from what I have observed about the usefulness of DDNP, which is what I presume is the ultimate object.

A good quality of deep red crystalline sodium picramate in good yields is possible via the sodium polysulfide reduction of sodium picrate. Several times I have repeated the experiments and found that slight adjustments in reaction conditions can improve the results, so I have not yet determined what conditions are optimum.

Please feel free to tweak the general process, if you want to do the work. The polysulfide reduction is quite similar to the synthesis described in your library. The problem that I have seen in the online descriptions of the polysulfide reduction, is a lack of detail about the correct method of preparation for the sodium polysulfide reagent. A thorough, intimate mixing of the correct proportions of NaOH and sulfur, being first thoroughly mixed as DRY ingredients, which absorb moisture from the air very gradually, darken in color, and initiate a spontaneous highly exothermic reaction while being stirred is the required approach for producing a good polysulfide reagent. If atmospheric moisture is low, a trigger mister can be used to get things going. The idea is to get the reaction going from a stirred dry powder which becomes crumbly as it warms and darkens and then a drop or two of water is added, the mixture stirred very well and a few more drops of water added, whereupon the reaction then proceeds on its own to form the polysulfide very quickly as a dark red but transparent liquid which looks bright yellow in thin layers. The stoichiometry for reactions involving polysulfides is not fully known. The goal is to get a good reduction without a great precipitation of elemental sulfur as a contaminant. My own theory is that if the alkalinity is just right, the higher polysulfide which is decomposed in the reduction can be converted to a lower polysulfide and remain in solution, instead of precipitating free sulfur. The polysulfide may possibly even reform from its fragments after acting as an unstable intermediate compound in the reduction. I am uncertain that the actual mechanism for the reaction involving polysulfide is even known, beyond the knowing that it just works somehow.

The following is from my old lab notes, with commentary ideas included.

Experimental:

On a hotplate stirrer is placed an 800ml beaker and with stirring, 22.9 grams, (.1 mole) picric acid is dissolved in 400ml boiling water. Heating is stopped. To the stirred still hot solution is added a solution of 4.2grams NaOH (.105 moles) in 25ml water.

comment: easy solution was noted so less water may be useful in subsequent syntheses.

While the slightly alkaline sodium picrate solution is cooling, a sodium polysulfide reagent is prepared as follows:

NOTE: All of the following procedures should be done with good ventilation, toxic gas is produced.

Into a 100ml beaker is placed 13 grams NaOH fine prills and 10.1 grams powdered sulfur (flowers of sulfur USP) Using a glass stirring rod the granular materials were manually mixed dry as thoroughly as posssible, and as the stirring was continued the mixture began to take up moisture from the air and darken in color slightly, and the physical texture changed as the mixture became stiffer and more difficult to stir. The particles become adherent to each other and the mixture begins to warm.

A couple of drops of water are fed from an eyedropper onto the stirring rod and stirred into the mixture, then two drops more, and stirring is assertively done between dropwise additions to blend the very gradually increasing moisture into the reactants. The induction of a highly exothermic reaction occurs concurrently with the slight dampening of the mixture which may need to be stirred yet a little more if any "dry lumping" is observed. The pasty mixture gets really hot and darkens quite rapidly, with an evolution of intense "sulfur fumes" from the melting and reacting sulfur. Hold the beaker by the upper rim where it is cool and do not get burned by touching the walls of the beaker near the reaction mixture. The addition of water two or three drops only, in each addition may be continued portionwise, with stirring between these small additions, in order to maintain the heat by reaction and heat of dilution, until a dark red transparent solution results. The hot reaction mixture should become a thin and mobile enough liquid that further mixing and dilution can be done by manually swirling the beaker lightly.

Once the pasty mixture has cleared to a hot solution (melt would probably be more accurate description), then gradual additions of water in increasing amounts should be made by the eyedropperfull until the volume of the resulting solution is about 40ml volume. If a dark red melt clear of solids fails to form completely on its own heat of reaction, at this point DO NOT add a lot more water and "boil" or a partly crystallized failed to complete reaction mixture will probably result.

If 1 or 2 ml of added water is insufficient to "kick" the reaction by heat of dilution, then supplemental heat will be required to drive the reaction to completion, before further dilution to a volume of 40 ml. This dilution should be sufficient to prevent the reagent from crystallizing upon cooling. Keep the polysulfide reagent from contact with the air after it is prepared. Air may degrade and cause precipitation of elemental sulfur from the polysulfide reagent if it is left standing uncovered. The prepared reagent is put into a separatory funnel and supported over the still warm sodium picrate solution prepared earlier. A piece of plastic wrap is secured over the top of the beaker with a rubber band and the plastic wrap is puntured in the center to admit the tip of the separatory funnel. This is done to exclude air from circulating freely around the surface of the solution in the beaker during the addition of the polysulfide solution. A seal is not needed here, a loose covering is sufficient.

To the stirred sodium picrate solution at 44 degrees centigrade, was added the sodium polysulfide at a rate of one drop per second to one drop per two seconds, with stirring continued for one hour. The mixture was then covered to the complete exclusion of air, and allowed to stand in the cold overnight, chilled to 5 degrees centigrade, filtered and the crystals of sodium picramate and the filter paper and filter cake were further dried by placing on a stack of paper blotters. The crystals were dark red prismatic and very fine granulation, and were used without further purification for the diazotation reaction.

Nice work, if you want to know some chemical information what any explosives are souluble in water. This will advise some to the extraction and solublity in chemicals.
2-nitrophenol 21 g/l
2,4-dinitrophenol insoluble, around 100 mg/l
2,4,6-trinitrophenol around 10 g/l at room themperature, 11g/l at 20 gegree celsius
sodium picrate and picramate around 5g/l to 6g/l
Looks like that the way by NaOH are always exotherm and will require a precise calculation by weight to the NaOH solution. Well known are any content of NaOH in the result can pumping out moisture from the air and the result will melt away.

[Edited on 28-6-2006 by Mason_Grand_ANNdrews]



[Edited on 29-6-2006 by Mason_Grand_ANNdrews]

Not optimized , but close enough for " government work "
and a lot better than the old " black book " method .

I don't know where you get your solubility figures ,
but IIRC sodium picrate is * more soluble * than picric acid ,
and so are the lower nitrophenols .

Quote:

Looks like that the way by NaOH are always exotherm and will require a precise calculation by weight to the NaOH solution. Well known are any content of NaOH in the result can pumping out moisture from the and the result will melt away.

Sorry about the lost word in the post, some login trouble.
Any solubility in H2O will tell the safety data sheets but to exposives, precise infos will hard to get that what exactly solublityes are. I would guess what you read somewhere will not correct always.
Also i belive, picrates are better obtained by a carbonate and will be better to store. Some stuff will decompose to fast on the open air by water.
Whats going on topic ?

A highly relevant article

concerning the origins of the " dry method "

I found a journal abstract that would agree with FRITZ post earlier in this thread that glucose is a valuble (and cheap) reducing agent for "alkaline picrate" (sodium picrate) forming picramic acid directly as a major byproduct.

The following is that abstract from PubMed:

"Effect of glucose upon alkaline picrate: a Jaffe interference.Viraraghavan S, Blass KG.
Department of Chemistry, University of Regina, Saskatchewan, Canada.

The reactivity of glucose in aqueous alkaline picrate was investigated by spectrophotometry and polarography at 25 degrees C in 0.51 mol/l sodium hydroxide. Thin-layer chromatography and infrared spectroscopy studies have conclusively identified the presence of picramic acid in 5:1 and 10:1 glucose picrate test solutions incubated at 25 degrees C. The polarographic data of an alkaline picrate blank with a concentration of 0.284 mmol/l, show three well-defined nitro group reduction waves with approximate half-wave potentials of -0.62 V, -0.78 V, and -0.93 V and a fourth broad wave appearing near -1.31 V versus a saturated calomel electrode. The addition of glucose to alkaline picrate resulted in a decreased diffusion current for reduction waves 1-3, with little change in reduction wave 4. The reactivity of test solutions containing glucose:picrate in 1:1, 2:1, 5:1 and 10:1 molar ratios was investigated at varied time intervals between 10 and 180 minutes. The absorption spectra of a 10:1 glucose:picrate solution shifted from 356 nm to 375 nm and a broad tailing shoulder absorbance formed in the 450-600 nm region. An orange coloured minor product, separated by thin-layer chromatography, was observed to fluoresce. The maximum excitation and emission wavelengths were 318 nm and 545 nm, respectively. A major, red-coloured product was isolated and identified as picramic acid by infrared spectroscopy. For 10:1 glucose:picrate test solutions incubated at 25 degrees C, picramic acid formed within 10 minutes. Within the first minute, the colour was observed to change from yellow to orange and then to red.

PMID: 2329319 [PubMed - indexed for MEDLINE]"

Hope it helps with the pursuit of an easy way to picramic acid! I wonder what the yield of picramic acid would be compared to the other products of the reaction? I'm still trying to interperet the reactions described in this absract, I guess a few tests to see what we get couldn't hurt.

Sickman

a theory distilled from the references ......

further information on Na2S

Yeah copper is exactly what I have been thinking about too ,
something like a small copper pot with a lid , deep enough
to put a layer of kerosene over the melt .

The molar ratio seems like it should be 8 or 9 NaOH to 3 S1 ,
perhaps even 10 to 3 , and run the reaction with supplemental heating
for at least 30 minutes , having it between perhaps 175C to 300C at the end ,
followed by a dilution and cooling to perhaps 150C when the NaHCO3 in an amount needed is added gradually to convert excess hydroxide to normal carbonate , and precipitate Na2S . I am studying what I can find about the solubilities and cosolubilities possible in such a system to try to guess the optimum dilution/s and filtration temperatures and sequence which should give the desired
Na2S from the unconventional mixture . If this can be done
reasonably well , then it will avoid the alternative of having
to use manganous or ferrous or zinc sulfate as a precipitant
of their insoluble monosulfides , as a precursor for an H2S
generation scheme to treat an NaOH solution and obtain
the product that way .

Reacting NaOH and sulfur does produce some of the active
reducing sulfur compounds desired , Na2S and Na2S2 are
both Zinin reagents ....but of course to get the yields of
picramic acid increased , the monosulfide is the desired product .
The minor problem is that the reaction mixture
is inclined to form a lot of higher polysulfides which are quite stable like Na2S4
....unless the reaction towards the lower sulfide is forced with excess alkali , high temperature , and reaction time , with the reactants in high concentration .
Trying to get these atoms to jump through the hoops and
sit on their appointed stools awaiting further commands ,
does require cracking the whip for this reaction

A bit more complicated , but technically superior

Sorry for bringing up this old thread.

Recently I tried the reduction of picric to picramic acid using polysulfide. The polysulfide was produced by the earlier mentioned dry melt of NaOH and S, kept at 150 deg. C.for half an hour after the initial exotherm in an airtight container.

The melt was dissolved in about 8 times it's volume of water and added to a near saturated solution of sodium picrate, produced by neutralizing double recrystalized Picric Acid with PA grade NaOH. The mixture was allowed to stand at room temperature for about 48 hours. Red crystals of sodium picramate collected at the bottom of the beaker. The crystals were washed thouroughly using ice water and dried. I noticed a distinct sulfur smell though, so I dissolved the crystals again in the least amount of water after which 10% HCl was added slowly to precipitate the pure picramic acid.

Now, there were several things that were unexpected:

1 The pure picramic acid collected as a fine amorphous BROWN powder, while PATR mentions a distinct RED color. Is this simply because of it beeing amourphous? What is the colour of picramic acid from others experiences?

2 The sulfur smell still is quite noticably

In the article: "The Preferential Reduction of Nitro-groups, etc. Pavt III, J[1]. Chem. Soc., 1945, 663 - 665" They mention brown dyes, called " sulfur dyes", as the by product of the partial reduction of Picric to Picramic acid using the sodium carbonate/sulfide process. Does anyone know what these sulfur dyes could be and which condition favour there formation? Could this relate tot the persistent sulfur smell?

Thanks...

additional methods of possible interest

(1)Here is another variant on the method using H2S which I was proposing in the previous post.
See attached file.

The purification of the crude picramic acid for removal of
sulfur would be avoided entirely by a different reduction method. Ascorbic acid (sodium ascorbate)
works as a reducing agent, and reducing sugars in alkaline condition and ferrous sulfate or possible better ferrous ammonium sulfate may also work as reducing agents, leading to a more easily purified product.

(2)Here is yet another reported method which may be done using powdered zinc to reduce ammonium picrate in H2O solution made basic with excess ammonia. I speculate that perhaps if some ammonium nitrate is present that this may improve the reaction via formation of nascent ammonia, but this would have to be tested by experiment. At the end of the reduction using zinc, I would expect that the reaction mixture would have to be acidified and digested with dilute HCl or H2SO4 to decompose the zinc picramate and precipitate and isolate the free picramic acid, leaving the soluble zinc salt and other byproducts as filterable solution. The original French pharmaceutical journal article probably has more detail on this.



[Edited on 22-2-2009 by Rosco Bodine]

Attachment: picramic acid preparation via H2S.pdf (180kB)
This file has been downloaded 1560 times

amalgamated sheet zinc may possibly work

back on topic ....nitrites are a separate matter
and for that much other methods could be used for diazotization.... also another topic

I have been looking at the early references
concerning the preparation of picramic acid from which I may post more excerpts later. Excerpt from article attached



This author, Aime Girard, named the compound picramic acid,
which had earlier been called by Wohler "reduced carbazotic acid" and had been called by Berzelius "nitrohaematic acid".

It appears the reduction is most definitely a pH sensitive reaction as observed by many researchers. In an acidic reaction system free picric acid is reduced all the way to triaminophenol but in an alkaline reaction condition the reduction is incomplete and selective for only the one nitro group and a picramate is the product. Even nascent hydrogen such as from electrolysis or an amalgam should
be selective for the limited reduction desired, so long as the reaction condition is kept at a basic pH. Free ammonia
either added as NH4OH or liberated in situ via an ammonium salt and an alkali would seem to me to be an applicable strategy for this reduction, though I have not seen that specifically reported in the literature. It just seems to be a likely approach worth trying. A possible method here is using aluminum amalgam and perhaps some ammonium nitrate or sulfate used as a source for in situ ammonia reaction byproduct to keep the reaction mixture basic.

Ferrous sulfate , ferrous chloride, stannous chloride, cuprous chloride will effect the selective reduction ....again only in an alkaline reaction system , a reaction mixture kept to a basic pH. The stannous and cuprous salts only act when freshly precipitated by ammonia, so it would seem it is the nascent hydroxides which are the active reductant and this possibly also holds true for the ferrous compound.

Also according to Girard reportedly soluble picramate salts do not cause a precipitate with soluble iron salts so this may be a tool for purification, possibly accomplishing removal of the occluded free sulfur microscopic particles or soluble sulfide impurity which seem to be a persistant contaminant, via precipitation of the undesired sulfur values using ferrous sulfate solution to sequester the unwanted sulfur as a precipitated iron sulfide which may be filtered from the solution of soluble picramate.
The behavior with respect to salts of manganese is the same,
also cobalt and nickel.

Ferrous sulfate itself may be used as the reductant for the
soluble picrate originally, if the reduction is carried out under alkaline condition, 6 of the Ferrous Sulfates required for the
theoretical, in the same way as are 6 Sodium Ascorbates,
for the theoretical conversion of 1 mole of alkaline picrate to 1 mole of alkaline picramate. The basic salts would most often be the sodium or ammonium or some mixture of these, owing to the greater solubility making these convenient, but
other soluble salts may also work in a more diluted reaction system.

The residual sulfur contamination which is attendant to the polysulfide reduction could probably be minimized by very careful neutralization. There is likely an optimum pH to which the filtered and redissolved sodium picramate can be adjusted with HCl or H2SO4 which will decompose any residual sodium sulfide or polysulfide and the H2S driven away by boiling, and the free sulfur settled and or filtered
from the warm solution of sodium picramate, prior to further
addition of acid to precipitate the free picramic acid.

One reference to an industrial scale production reported that
the reduction was run at a pH kept *neutral* by a gradual
addition of acid and the reaction temperature regulated at 80C, and that the sodium picramate precipitated from this
Na2S reduction of an ammonium picramate slurry, precipitated as the monohydrate sodium picramate. If that report is accurate, then a buffered reaction may also be feasible but what is the target pH desired I am not quite sure, and I am skeptical it is actually neutral pH which was being the regulation point there in that one reference.
Anyway it is established it can't be acidic so there is possibly
a range there close to neutral which is workable, erring on the basic range is what the more numerous references would indicate. Also a cosolvent system using methanol
and H2O for the reduction can increase yields by 10% or so
from the mid 80% to the mid 90% range.

[Edited on 27-2-2009 by Rosco Bodine]

Attachment: Pages from The Chemical Gazette, Or, Journal of Practical Chemistry, in All Its Applications to Pharmacy, Arts, and Manu (179kB)
This file has been downloaded 1652 times

Here's an excerpt from the Egerer J. Biol. Chem. article linked five posts above, which describes H2S in reaction with an ammoniacal solution of ammonium picrate, forming in situ the ammonium sulfide which acts as the actual reductant. Note the free sulfur byproduct mentioned as a contaminant using this even more refined alkaline sulfide reduction method. So it would seem that given this problematic contamination with free sulfur, that alternate methods of reduction which do not produce this contaminant as a byproduct are more interesting. This brings the entire matter full circle back to the ferrous sulfate reduction, or possibly to alternative reduction schemes like powdered zinc or amalgamated zinc or aluminum, to be considered as advancements over the alkaline sulfide reduction methods. Again, here the ferrous sulfate may have a value in either case, for purification if not better for the entrie reduction.



Attached is a more extensive article by Girard

[Edited on 27-2-2009 by Rosco Bodine]

Attachment: Pages from The Chemist pg348.pdf (314kB)
This file has been downloaded 1390 times

In my experience, it is very difficult to get completely rid of the sulfur/polysulfides while recrystallizing picramic acid. United States Patent 6268536 describes toluene extraction of picric acid from nitration mixtures.

Any idea what the solubility of picramic acid is in toluene, or maybe DCM? Thinking OTC paintstrippers and one step purification...

else the same principle could more or less apply here as well. Couldn't find the answer in PATR, Urbanski or Google...

Thanks

[Edited on 17-8-2010 by nitro-genes]

Picramic acid is soluble in alcohol and probably in acetone.
Toluene might be a poor choice because sulfur is very soluble
in toluene. Sulfur and hot toluene is described here by garage chemist. I think later he became an ascended being
http://www.sciencemadness.org/talk/viewthread.php?tid=3902#p...

This is an area of experimentation which I intend to revisit, and explore uses of reducing agents other than polysulfides. I have read in many different isolated references that many different reducing agents are effective in producing picramic acid via the reduction of picric acid, but more correctly stated it is not the reduction of picric acid itself at all, but reduction of the one of picric acid nitro groups on the picric acid while the picric acid is associated as a picrate salt in an alkaline medium. Therefore high pH is the reaction condition which determines that the reduction will be limited to the one nitro group of a picrate, as opposed to the reduction of picric acid itself which would lead to triaminophenol as the product
of a reduction carried out at low pH upon picric acid itself. So any reducing agent which functions in an alkaline condition should produce picramic acid, or more correctly a picramate salt as the product of the inherently milder and limited reduction as occurs for reduction of a picrate salt at high pH.

The operative issue then is one of clarifying the semantics that is confusing, recognizing that what is being done is not reduction of picric acid to picramic acid as that mechanism does not occur. What may occur and what we seek is reduction of a picrate salt, typically sodium picrate, to produce sodium picramate.

Many reducing agents should work for production of the desired picramate so long as the required pH range for the reduction of picrate to picramate exists in the reaction mixture. Ferrous sulfate, dextrose, ascorbic acid, amalgamated zinc or aluminum, probably even iron filings could be used.

Carefully done synthesis of DDNP under very specific reaction conditions which improve the crystalline size and bulk density of the product would probably evidence better performance for the DDNP than is gotten generally for tests of DDNP which is of lesser purity and lower density. Quality control can have great bearing on the product test results, particularly for materials that are sensitive to small variables.
Where the margin of acceptable performance is small for a material which is only useful in a particular form and quality, the quality control has to be stringent, and I believe this probably applies to DDNP.


[Edited on 17-8-2010 by Rosco Bodine]

Ammonium sulphide

A valdDNP synthesis?

Sorry to say, but I have the feeling that nothing about the synthesis of DDNP is easy when OTC materials are used. I think finding an OTC way of producing pure sodium (hydro) sulfate is indeed the way to go!

Quote: Originally posted by prometheus1970

. . . my naive optimism.