killswitch
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P4O10 in aromatic nitrations
Mixed-acid nitrations (TNP, polyols) have their advantages in terms of the ease with which their precursors can be obtained. But many classic
energetic compounds such as TNT require oleum, which is difficult to acquire.
Oleum can be made from bisulfate/acid, but as with all do-it-yourself products, purity is not guaranteed.
I have not found instructions for making TNT, TNB, HNS, etc., with P2O5 on 98% H2SO4.
From what I understand, the reaction takes place in a thin region at the interface between the mostly immiscible acidic and organic layers. Does the
presence of phosphoric acid interfere in these procedures?
If phosphoric acid has a higher pKa than sulfuric, it would be protonated, but unlike HNO3 it would not then be dehydrated to form a good nucleophile.
I assume it would instead dehydrate the acid layer much in the manner of sulfuric acid.
Are there 1 or 2 step syntheses for TNT using 98% sulfuric, 70% nitric, and P2O5/P4O10? (I can raise the nitric acid concentration with DCM if need
be, but a 70% procedure is preferable).
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plante1999
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If I get some toluene, I migth try to put 3 nitro group on it using 70% nitric acid and phosphorus pentoxide freshly made from red phosphorus.
I never asked for this.
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AndersHoveland
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I think phosphorous pentoxide would irreversibly condense with most substrates one is attempting to nitrate. I think you would have to use P2O5 to dry
the acids first, then do the nitration separately.
Example: reaction of CH3OH with P2O5 would probably make phosphoric acid monomethyl ester. Unlike sulfate, the phosphate group in this case is
probably not going to come off easily and be replaced with a nitrato group.
If you were wondering, P2O5 and P4O10 are basically the same compound but different forms. The gas phase is usually P4O10, and can be directly
condensed into a solid, with the definite molecular formula P4O10. This solid is analogous to "flowers of sulfur". In contrast, P2O5 implies that the
solid has definite chemical composition ratio, but is an intermolecular compound. The best analogy I can think of is comparing trioxane to
polyoxymethylene plastic (formaldehyde has several different chemical forms).
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DraconicAcid
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Quote: Originally posted by AndersHoveland  | I think phosphorous pentoxide would irreversibly condense with most substrates one is attempting to nitrate. I think you would have to use P2O5 to dry
the acids first, then do the nitration separately.
Example: reaction of CH3OH with P2O5 would probably make phosphoric acid monomethyl ester. Unlike sulfate, the phosphate group in this case is
probably not going to come off easily and be replaced with a nitrato group. |
I don't think nitrate esters are the main goal here, but the addition of nitro groups to aromatic rings.
| Quote: | | If you were wondering, P2O5 and P4O10 are basically the same compound but different forms. The gas phase is usually P4O10, and can be directly
condensed into a solid, with the definite molecular formula P4O10. This solid is analogous to "flowers of sulfur". In contrast, P2O5 implies that the
solid has definite chemical composition ratio, but is an intermolecular compound. The best analogy I can think of is comparing trioxane to
polyoxymethylene plastic (formaldehyde has several different chemical forms). |
Do you have a cite for that? I was under the impression that the only form was P4O10, but that the name "phosphorus pentoxide"
had been used for so long that it is still used out of habit (much like "ammonium hydroxide" for aqueous ammonia).
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Bot0nist
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TNT can be made on a bench scale in a two or three step nitration without oleum, IIRC. Quicksilver once had a conversation with me concerning it, but
I cant seem to find it. It goes to DNP rather easily, but to get that third site nitrated takes refluxing fuming nitric acid and conc sulfuric. Do not
try this based on my words, as I havnt done this, and am talking from a memory of a conversation I cant seem to find.
Sorry for being OT.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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AndersHoveland
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wikipedia has a picture of the intermolecular structure
| Quote: | Phosphorous pentoxide exists in at least four polymorphic forms as well as a glass. the common variety of laboratory and commerce... consists of large
cage molecules... with only weak van der Waals-type forces between cages. There are also two orthorhomic crystalline forms which contain highly
polymerised arrangements (P2O5)n. ... The vapor from these forms is stable up to at least 1400 C, and at high temperatures the existence of dimeric
species is possible.
The three forms... have interesting differences in properties which can be related to their crystal structures. The highly polymerized forms have
higher melting points than the [P4O10] form. All three forms can be vaporized to produce the same cage molecules which exist in the [P4O10] form, but
there are differences in the liquids produced by melting.
The [P4O10] form first melts at 420 C to produce the metastable liquid with a high vapor pressure and consisting of discrete P4O10 units. This liquid
then rapidly polymerizes to form a glass... [which melts] at 562 C to give viscous liquid... Both [polymerized] forms are considerably less
deliquescent than the [P4O10] form.
Phosphorus: Chemistry, Biochemistry and Technology, Sixth Edition,D. E. C. Corbridge
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P2O5 is just the empirical formula. The only reason it is not written with only phosphorous is because the 5 oxygens are not divisible by 2.
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killswitch
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| Quote: Originally posted by Bot0nist | TNT can be made on a bench scale in a two or three step nitration without oleum, IIRC. Quicksilver once had a conversation with me concerning it, but
I cant seem to find it. It goes to DNP rather easily, but to get that third site nitrated takes refluxing fuming nitric acid and conc sulfuric. Do not
try this based on my words, as I havnt done this, and am talking from a memory of a conversation I cant seem to find.
Sorry for being OT. |
Do you happen to have this somewhere?
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Bot0nist
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Skim through the TNT threads here at SciMad. I am sure it is there. you could try it on a test tube scale. It should be easy to descern if you get a
good ratio on TNT to DNT through physical properties. Be safe.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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killswitch
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I have achieved the nitration of dinitrotoluene in good yield via phosphorus pentoxide, 98.3% sulfuric acid, and sodium nitrate.
100 grams of P2O5 was added to 150mL of concentrated sulfuric acid with stirring. The P2O5 has an unfortunate tendency to form spherical bubbles that
refuse to dissolve. Extended periods of stirring are required to overcome this.
When the phosphorus pentoxide has dissolved, add 60 grams of dinitrotoluene and stir until it has dissolved. A slight darkening of the solution may be
noticed as the DNT is sulfonated at the remaining o/p position.
While maintaining the temperature between 100 and 110 celsius, add 105 grams of sodium nitrate over a period of approximately 1 hour.
Afterwards, allow the solution to stir at 100 celsius for two to four hours, then let it settle for 8-12 hours. Then separate from the acid and
perform the standard purification techniques.
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