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Priority
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Ethyl centralite synthesis
Hi all,
How do one go about and prepare ethyl centralite or 3-Diethyl-1,3-diphenylurea. Wikipedia entry is just a stub, google search yields -apart from how
to detect it- very little, this board hasn't worked out the details of the synthesis yet, the elitists at weapons and explosives forums banned me for
asking this question (althogh it was empty there as well, and I have spent hours looking for it).
Such an important compound; so hard to find info on how to make it!
[Edited on 6-8-2008 by Priority]
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Ritter
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Quote: | Originally posted by Priority
Hi all,
How do one go about and prepare ethyl centralite or 3-Diethyl-1,3-diphenylurea. Wikipedia entry is just a stub, google search yields -apart from how
to detect it- very little, this board hasn't worked out the details of the synthesis yet, the elitists at weapons and explosives forums banned me for
asking this question (althogh it was empty there as well, and I have spent hours looking for it).
Such an important compound; so hard to find info on how to make it!
[Edited on 6-8-2008 by Priority] |
Not if you use Google to find the correct nomenclature for your compound (sym-diethyldiphenylurea) & then search the USPTO. Here is one prep
patent but it involves phosgene chemistry. Since this stuff is commercially available, I would try to obtain it through commercial channels.
http://www.pat2pdf.org/patents/pat2403068.pdf
Ritter
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\"The production of too many useful things results in too many useless people.\"
Karl Marx
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Priority
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Thanks alot Ritter. I've heard about the phosgen pathway, are you aware of any alternatives out there?
Here is the essence of the patent:
page 3 of the patent 2403068
1475 parts by weight of ethylaniline mix (65% of di- and 35% monoethylaniline) heated to 160-170 deg C. Stop heating. Carbonyl chloride (=Phosgen!)
gas is added to the liquid at a rate of about 105 parts by weight per hour initialy. Reaction is exothermic and temp will rise to 190 - 210. Temp
should be maintained at thes range for the remainder of the reaction period through the controlling of the flow of phosgen. The flow of phosgen is
stopped after about 300 parts by weight = the amount equivalent of diethylaniline content.
Authors report that cylindrical nickel reactors (tanks) with heating coils or jacket and preferably externally insulated against heat loss, would do
the job.
[Edited on 6-8-2008 by Priority]
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Ritter
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Quote: | Originally posted by Priority
Thanks alot Ritter. I've heard about the phosgene pathway, are you aware of any alternatives out there? |
Sure, but only paper chemistry. For instance, it might be possible to react N-ethylaniline with diethyl carbonate to make it. But it sounds like a lot
of effort to get something that should be commercially available.
[Edited on 6-8-2008 by Ritter]
Ritter
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Priority
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As you are already aware, I'm not a organic chemist, Ritter. I also understand your point in obtaining this chemical through commercial channels, but
i cannot help wanting to know exactly how one could prepare ethyl centralite (paper chemistry and speculation doesn't matter) . Would you care to
elaborate on how much N-ethylaniline with how much diethyl carbonate, under which conditions you THINK MIGHT produce ethyl centralite?
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Ritter
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Quote: | Originally posted by Priority
As you are already aware, I'm not a organic chemist, Ritter. I also understand your point in obtaining this chemical through commercial channels, but
i cannot help wanting to know exactly how one could prepare ethyl centralite (paper chemistry and speculation doesn't matter) . Would you care to
elaborate on how much N-ethylaniline with how much diethyl carbonate, under which conditions you THINK MIGHT produce ethyl centralite?
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If you have no background in chemistry & are only looking for a recipe, I can't help you. Professionals make this stuff on an industrial scale
using phosgene, which is a war gas. To steer you into just mixing chemicals without understanding what you're doing & why is a responsibility I'd
rather not take on.
Ritter
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Priority
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Not having a background as a chemist doesn't mean I am a complete moron. Anyone knows that phosgen is a WMD. Even dubya. A Phd is not required. That
is the reason I asked if there are alternatives to this preparation, preferably laboratory sized and not industrial scale.
Anyway, thanks alot for your help Ritter. Very friendly of you. If anyone knows of a safe viable labsized prep, please let us all know.
[Edited on 6-8-2008 by Priority]
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Beleive him, even properly trained, experienced and well equipped chemist are reluctant at using phosgene. If trying to attempt its use, your are
surely going to put you and others at risk.
And if your not a chemist, why do you want to make this compound anyway?
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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It seems that 1,3-Diethyldiphenylurea/N, N-Diethylcarbanilide was developed in Germany, so one might want to try searching the German chemical
literature for the information you seek instead of expecting someone else to do it for you
Chemistry is our Covalent Bond
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Obviously @Priority wants to avoid the use of phosgene.
I am unclear about whether or not this is a paper exercise for Prioruty or whether or not he wants to actually prepare ethyl centralite, and if so, on
what scale?
There are safe alternatives to phosgene such as the solid reagent "triphosgene" which is readily prepared by the UV chlorination of dimethyl
carbonate. It is commercially available but expensive. Better to make your own. It reacts like phosgene but slower, and is non-volatile.
For alternative preparative routes to various centralite derivatives, none directly involving phosgenation, the attached paper is very helpful.
Its methods might be modified to prepare centralite itself.
SYNTHESIS OF CERTAIN ETHYL, PHENYL, AND NITROPHENYL DERIVATIVES OF UREA2
PHILIP E. WILCOX, W. A. SCHROEDER
J. Org. Chem.; 1950; 15(5); 944-949. DOI: 10.1021/jo01151a004
Other suggestions:
Stepwise alkylation of sym-diphenylurea with ethyl iodide, diethyl sulfate, or triethyl phosphite.
Example of the use of modified method of the JOC paper:
Prepare ethyl isocyanate by method in footnote 4 (diethyl sulfate, KOCN, potassium carbonate heated together cautiously.) I will obtain the Ber.
reference.
React ethyl isocyanate with N-ethylaniline to obtain i,3-diethyl-1-phenylurea.
Alkylate that product with your choice of ethylating reagent to obtain the ethyl centralite.
By now you probably can see why phosgenation of N-ethylaniline is the industrial method.
Ethyl centralite is a common chemical commodity used as a modifier for propellants and as a plasticizer, mostly for cellulose.
If you can buy its precursors you can buy ethyl centralite itself.
So is this an academic exercise or what?
[Edited on 7-8-2008 by Sauron]
Attachment: jo01151a004.pdf (122kB) This file has been downloaded 1108 times
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Ullnann's suggests transamination of urea or substituted ureas with amines or amine salts in the melt is a productive route.
I am digging out the references now.
1,3-Diphenylurea can be prepared from aniline and urea.
Diphenylurea and ethylamine (2 mols) under autogenous pressure or ethylamine hydrochloride (more conveniently) give ethyl centralite.
THE UREA DEARRANGEMENT. II
Tenney L. Davis and Kenneth C. Blanchard
JACS 45 pp 1816 - 1820 (1923)
DOI: 10.1021/ja01660a038
THE UREA DEARRANGEMENT
Tenney L. Davis and H. W. Underwood
JACS 44 pp 2595 - 2604 (1922)
DOI: 10.1021/ja01432a028
I have requested these. Note they are by the author of THE CHEMISTRY OF POWDER AND EXPLOSIVES and I have little doubt that ethyl centralite was on his
mind when carrying out these studies.
[Edited on 7-8-2008 by Sauron]
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I don't understand what the original poster wants. If he needs the end compound then why buying N-ethylaniline and all the other reagents needed and
wasting time with a lab scale reaction when the end compound itself is already available and cheap? The way the question is asked it does not look
likely he wants to practice a reaction either. What kind of an energetic compound is this thing a precursor for anyway?
Quote: | Originally posted by Sauron
Diphenylurea and ethylamine (2 mols) under autogenous pressure or ethylamine hydrochloride (more conveniently) give ethyl centralite.
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Are you sure? I think that would give you a mixture of starting materials, aniline, PhNHCONHEt and EtNHCONHEt.
You can obtain EtNPhCONPhEt by heating urea and N-ethylaniline without solvent until no more ammonia evolves. A single recrystallization should give a
pure product. Alternatively, for a lab scale reaction you can react N-ethylaniline with carbonyldiimidazole (CDI) in THF at room temperature. The
reaction is fast (accompanied by CO2 evolution) and the work up easy.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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CDI is a very good suggestion. It is not particularly cheap, and making it of course requires phosgene or a substitute, so back to square one.
So is transamination of ethylaniline a good idea, or its hydrochloride, with urea.
Am I sure about diphenylurea and ethylamine? Well, I was confident enough to post it, but I have not yet read Davis's patent, and not yet obtained
anything but first pages of his JACS articles on this. Ullmann's strongly implies it will work but of course say nothing about details where the devil
always abides.
I also am not surer what the thread author wants, but I don't really care as long as the topic is interesting.
Ethyl centralite is not an energetics precursor but rather a burning rate moderator for smokeless powders. Also a plasticizer for cellulose.
But every time I point out that something is cheap and available commercially I get yelled at by those who never like to buy anything, so prepare
yourself for their brickbats.
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Nicodem
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Quote: | Originally posted by Sauron
Ethyl centralite is not an energetics precursor but rather a burning rate moderator for smokeless powders. Also a plasticizer for cellulose.
But every time I point out that something is cheap and available commercially I get yelled at by those who never like to buy anything, so prepare
yourself for their brickbats. |
I just thought it strange that he wants to buy the precursors but not the product itself when it is obvious from his posts that he is not really
interested in the chemistry itself. Otherwise, I surely rather see people doing some experimental work from the scratches rather than buying stuff -
that is the only way to learn the basics, as you start as close to the beginnings of the chemical chain as possible.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Sauron
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I concurr that the motives of the thread author are opaque; perhaps he is idly curious or, is letting us do his (academic) homework for him. That is
always annoying but I found the problem mildly interesting in its own right and therefore worth some attention. Ritter dismissed all alternatives to
phosgenation as "paper chemistry" with which I cordially disagree.
His own suggestion of diethyl carbonate and N-ethylaniline ought to work, Ullmann's gives a sheath of mostly 19th century German refs to this sort of
reaction. As diethyl carbonate leads us back to phosgene I see little point in going down that road, although it is not a dead end.
Your suggestion of urea and N-ethylaniline is probably the best, followed by CDI couplins, or a safe phosgenation reagent like triphosgene.
The Davis patent (attached) is not helpful as it is limited to primary alkyl amines and urea, probably because prior art forced him to exclude aryl
amines, such as discussed in his JACS articles.
[Edited on 7-8-2008 by Sauron]
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Ain't this a kick in the head?
Davis (see attached) teaches that: secondary amines as their hydrochlorides react with urea in boiling water under reflux to give unsym-disubstituted
ureas only. Ethylaniline hydrochloride and urea give only 1-pheny-3-ethylurea. No tetrasubstituted ureas are formed.
No reaction took place when ethylaniline base and urea were heated as melt, the melt was in two immiscible phases.
@Nicodem, any literature on the reaction of ethylaniline and urea you described. I hope so because otherwise this route is doom and gloom.
[Edited on 7-8-2008 by Sauron]
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Here's the first Davis paper describing the melts, rather than the aqueous reflux reactions.
[Edited on 7-8-2008 by Sauron]
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Nicodem
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Quote: | Originally posted by Sauron
No reaction took place when ethylaniline base and urea were heated as melt, the melt was in two immiscible phases.
@Nicodem, any literature on the reaction of ethylaniline and urea you described. I hope so because otherwise this route is doom and gloom.
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I have no references for that or else I would provide them or at least mention that it was actually done. However, I do know from experience that if
you heat anilines (or amines) and urea at temperatures of 150-200°C until no more ammonia evolves you get the N,N'-diphenylureas. Though I have to
admit that I never tried with N-alkylanilines, but as far as I know it should not make much difference as the method is based on urea<=>cyanate
equilibrium and differences in volatility of the aniline and ammonia. I have not read the paper you mention, but perhaps the reaction mixture was
simply not heated enough (or the biphasic melt not stirred intensively enough).
Also, if one can prepare EtPhN-CO-NH2 (either using urea or cyanate) it should be possible to heat above 200°C which causes such ureas to decompose
to tetrasubstituted ones (EtPhN-CO-NPhEt) and cynuric acid (again no references).
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
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I posted Davis's two JACS papers so you could read them, so kindly do so before you question Davis's competence to conduct a simple experiment. This
is the T.L.Davis whose THE CHEMSITRY OF POWDER AND EXPLOSIVES is a standard reference and in the forum library. Not some nonentity, after all.
I obtained those papers expecting to confirm your statements, not refute them. But, there we are. In the absence of any lit. to the contrary and until
such literature is turned up (by you, by me, or whoever) then what choice do we have but to accept Davis's experimental findings? It would be
irrational to do otherwise.
Davis says that under the only conditions producing any reaction between N-ethylaniline or its hydrochloride and urea, i.e., aqueoux reflux, the only
product, and that in small yield, was 1-phenyl-3-ethylurea.
Similar results were obtained with homologous compounds.
Primary arylamines react readily and in high yield.
Diphenylamine does not react at all.
Do have the courtesy to read the articles I posted when you can find the time and at your convenience of course.
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Since the job I'm supposed to be doing is too boring, I did a little experiment to see if N-alkylanilines do not work in this reaction while the
anilines do (as claimed in the paper Sauron provided above). I heated the mixture of 2 mmol urea with 4 mmol N-methylaniline (I don't have any
N-ethylaniline) to reflux in a test tube with the thermometer. The reflux temperature (using a heat gun) slowly increased and the starting biphasic
system slowly became homogenous at somewhere around 170°C. I heated for some 15 minutes more and the end temperature of the reflux was about 210°C
where it remained more or less constant. A few crystals formed (probably cyanuric acid or some other stuff from urea decomposition). The reaction
mixture was diluted with 1M HCl to dissolve any unreacted starting materials and there remained only a little mass that solidified. This was extracted
into a ml of ethyl acetate to perform a TLC and IR.
The TLC using a mildly polar mobile phase (petroleum ether : ethyl acetate = 2 : 1) showed two spots, one on the starting line and the other a on the
two thirds of the hight of the N-methylaniline spot (which did not show up in the extract since removed with HCl). Developing the TLC again, but this
time in ethyl acetate only, demonstrated that the spot on the starting line actually consists of two compounds. So, this makes for three UV absorbing
products (containing the UV absorbing anilino moiety): two highly polar (containing the CONH2 group?) and one non polar.
The IR (thin film on NaCl window): 1761 (weak), 1713, 1660, 1585, 1495, 1397 cm-1. So obviously there are at least two or three compounds with a
carbonyl group there (or one or two containing nonequivalent carbonyls).
The IR spectra of 1-methyl-1-phenylurea and 1,3-dimethyl-1,3-diphenylurea should be checked to see if any peak corresponds. For 1-methyl-1-phenylurea
the IR is supposed to be in Chemical & Pharmaceutical Bulletin, 31 (1983) 423-428. For 1,3-dimethyl-1,3-diphenylurea the spectra is at
SDBS where the major peaks are 1662, 1585, 1498 cm-1 which are all present also in the sample within error (to see the spectra you need to search
for "N,N'-dimethyl-N,N'-diphenylurea" or "C15H16N2O" since it is not possible to use static link on their site).
So, for now it appears like some substituted ureas do form, but compared to the reaction with N-unsubstituted anilines the reaction is unusually slow
and it is questionable if it is useful for preparative use. I do not fell interested enough to run an 1H NMR on the reaction mixture. Besides, I have
to continue with the job I'm paid for so I let someone evaluate the results.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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Sauron
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Sorry to hear your current official project is boring, but I guess that is why they call it "work".
Sluggishness and small yield are consistent with Davis. He of course lacked instrumental methods in the early 1920s. But the bottom line remains same:
prepareatively useless.
So there remains your proposal using carbonyldiimidazole.
Or phosgenation using hexachlorodimethyl carbonate (triphosgene).
Both starting with N-ethylaniline.
Or, I think we agree, just buy this stuff, which will be cheaper and easier than preparing it.
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Priority
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Sauron and Nicodem, thanks a bunch for this info. Very very friendly of you. And no, you're not doing my homework. This has become more or less a
paper exercise. The reason for this post was, I wanted to know if the possibility exists to make high quality homemade triple based smokeless
gunpowder from scratch (SAFE and SECURE). The other parts, nitrocellulose and nitroglycerine and diphenylamine are comparatively easy (not safe
though) to make. Obviously, putting it all together is very very hard, especially the ethyl centralite part. No wonder everyone buys the stuff. I
guess this project is shelved.
[Edited on 7-8-2008 by Priority]
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Sauron
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Ah. You have large bore artillery at home? Picking up where Gerry Bull left off with the Supergun project? Because that is what triple base
propellants are all about, lowering bore temperature to extend gun tube life. They have no small arms or medium caliber applications that I know of.
About possible applications to rocketry I have no idea.
There's a lot of highly specialized chemical engineering and technology that goes into propellant formulation, manufacture, control of particle size,
surface area, stabilization, and a myriad of other factors. Nitrocellulose loves to auto-oxidize. I hardly need to expound on the joys of
nitroglycerin. The other component is of course nitroguanidine. Additives are many and varied. Do you have Federoff's series (PATR)?
Anyway I am having a hard time conceptualizing triple base propellant as a home chemistry project. Hats off to you for the maddest mad science idea of
the month, maybe the year. Possibly the decade.
@Nicodem, back to an idea I was kicking around upthread:
N,N'-diphenyl-N-ethylurea is readily made from ethyl isocyanate and N-ethylaniline.
Can't one alkylate this to ethyl centralite? Say, iodoethane?
The isocyanate is readily made from diethyl sulfate, potassium cyanate and sodium carbonate by heating with caution as per:
Über Isocyanate, L: Darstellung aliphatischer Isocyanate
Ber., 58 (p 1320-1323)
K. H. Slotta, L. Lorenz
DOI: 10.1002/cber.19250580722
If not I'd like to know why not?
[Edited on 8-8-2008 by Sauron]
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Nicodem
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Well, N,N'-diphenylurea can be ethylated (I saw at least one reference using diethyl sulfate), so I'm sure N-ethyl-N,N'-diphenylurea can be as well.
But if you choose alkylation then it is better to start from aniline rather than any isocyanate and prepare N,N'-diphenylurea via urea+aniline which
gives nearly quantitative yields (and there are several references besides Davis's paper for this one). Now it is too late for searching the
literature - will do so tomorrow.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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Sauron
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Yes, I suppose making sym-diphenylurea and then alkylating both sides would make sense. Lower alkyl isocyanates are pretty unpleasant critters. Well,
so is diethyl sulfate for that matter.
No need to look these up, I just wanted to know if it was feasible. I couldn't see why not. Just thought I'd ask.
Thanks.
Sic gorgeamus a los subjectatus nunc.
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