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DDTea
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[*] posted on 19-5-2004 at 20:40
TEPP Synthesis


Well, we don't mind screwing around with Hydrogen Cyanide or Chloropicrin, so why not go a step further into the world of Organophosphates, with the harsh pesticide Tetraethyl Pyrophosphate? Of course, I'm not seriously suggesting anyone synthesize this because of its extremely high toxicity...but I am interested in discussing novel routes to it, preferably without the starting ingredients being Phosphorus, PCl3, POCl3, PCl5, or any other tightly-regulated chemicals. This shouldn't be too hard, actually.

One way of preparing TEPP has been to oxidize the pesticide Diazinon... The problem with this is that Diazinon is no longer found in stores, and the few remaining solutions have too many other things in it to prevent its hydrolysis or oxidation. So we'll have to work from scratch.

Here is the method I am proposing, with the main starting ingredient being Potassium Pyrophosphate--which can be bought for cheap and without question:

P2O7(4-) + 4 Ag+ --> Ag4P2O7(s)

Ag4P2O7 + 4 C2H5I --> (C2H5)4P2O7 + 4 AgI(s)

A simple, two stage process. It uses the known reaction between Silver Phosphate (or other variations on Phosphoric Acid) and an Alkyl Iodide. The only thing I added was where to get the Silver Phosphate in this case. This same reaction can be used to prepare DFP from Silver Monofluorophosphate, for example.

The second reaction would no doubt have to be done in some solvent...the question then is, what would be best? I'm not very familiar with solvents; just water, and I can safely say that this will not work here. In fact, in the second reaction, the precursors should be very dry since TEPP hydrolyzes easily.

So, ideas? Maybe ideas for an alternate synthesis?

Again and as you know, TEPP is extremely dangerous--and I say this in all seriousness. Seemingly negligible amounts can be lethal, or cause serious injury, which may be delayed up to 12 hours! Its Oral LD50 is ca 1.1 mg/kg...this is to say nothing of lethal concentrations in air, or concentrations in air which might cause other unpleasant effects. So, don't make it in your garage, just talk about how you would :)

[Edited on 5-20-04 by Samosa]
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[*] posted on 20-5-2004 at 06:07


This is going to call for DMF, since you need to dissolve an ionic salt. DMSO maybe, but imagine spilling TEPP containing DMSO over you...:o

Can you say skin penetration?




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[*] posted on 20-5-2004 at 14:13


Yes, and this is part of the reason why synthesis of TEPP would be exceedingly dangerous. However, with the right protective clothing, you should be safe from DMSO spills. Even Neoprene Gloves, easily available at hardware stores, offer protection from DMSO.

Another concern I have... Silver Nitrate is very expensive, and so we wouldn't be able to just throw it away as waste. Instead, we should find a way to recycle the Silver Iodide produced in this reaction.

Also, instead of Ethyl Iodide, wouldn't Ethyl Chloride work just as well? It would easy to get from the reaction between Diethyl Ether and Hydrochloric Acid:

(C2H5)2O + HCl --> C2H5OH + C2H5Cl

I'm sure the same reaction could be done with HI to yield Ethyl Iodide, but Iodine is significantly more expensive than Chlorine. My goal is to keep costs down as much as possible with this--which is why I'm trying to avoid Phosphorus or its Chlorides or other exotic ingredients.

So, here is the procedure I'm thinking of...generally, without measurements yet. Silver Nitrate is added to a solution of Potassium Pyrophosphate (TKPP). The solution is then cooled down, the precipitate filtered and dried. This precipitate is then added to very dry (solvent of choice), and dry Ethyl Chloride is added slowly. The resulting TEPP is then distilled under reduced pressure (so as to avoid its decomposition...it is not the most stable of compounds).
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[*] posted on 20-5-2004 at 14:48


I can help you with the inorganic bit.
Melt the AgI with NaOH
AgI +NaOH ---> Ag +NaI +H2O +O2
(Definitely works with the chloride and I think it should be OK here. Feel free to balance the equation if you think it looks tidy that way).
Then wash off the NaI + excess NaOH and disolve the Ag in HNO3.
Unfortunately, I think there is enough water in hydrochloric acid to hydrolyse any ethyl chloride formed. You might be able to use HCl gas from salt + H2SO4.
If you are going to do that you might as well use HI which will work better at cleaving the ether.
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[*] posted on 20-5-2004 at 19:47


Is there any reason why Silver is used in these reactions to esterify Phosphates? I mean, couldn't any other metal that forms an insoluble salt be used? Lead, for example, which is very cheap, forms insoluble Chlorides and Iodides. So could Lead Pyrophosphate be reacted with Ethyl Iodide, as opposed to Silver Pyrophosphate?

I have seen no references to other metals being used, but I'm not sure if that's just because yields would be lowered or Silver is prettier than Lead or whatever. Also, most of what I've read has been about synthesis on a technical scale, so they don't mind using expensive reagents.

Also, Ethyl Chloride hydrolyzes rather slowly (at least, in groundwater its half-life is around 30 days at 25*C), so the major reaction should be to form Ethanol and Ethyl Chloride and the hydrolysis should not occur significantly. If it does, the starting materials are cheap enough that it wouldn't matter much anyway :). However, the NaCl/H2SO4 route would probably be better, so long as the H2SO4 is nice and fumy (so that it may also absorb any water that is formed).

Quick question--does Ag dissolve in HNO3?? Because Ag is less reactive than H. Wouldn't it require an H2SO4/HNO3 solution? I've heard references to something or other only being able to be dissolved in H2SO4/HNO3--I don't remember if it was Gold or Silver.
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[*] posted on 20-5-2004 at 19:54


Yes silver does dissolve in nitric acid with a bit of heating. When I have made silver nitrate I used 70% nitric, not sure whether or not it still dissolves at lower concentrations.

[Edited on 21-5-2004 by rogue chemist]
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[*] posted on 20-5-2004 at 20:53


Ag dissolves well in dilute HNO3, especially if it contains some NO2/added nitrite. It is very easy to recover once used for whatever and every lab should have some.

Ethyl chloride is definitely not made from ether, a catalytic amount of ZnCl2 is added to ethanol and HCl bubbled in, as ethyl chloride is distilled out. This method is excellent and fast.
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[*] posted on 21-5-2004 at 05:20


Ethyl Chloride is not usually made from Ether, it can be: ROR + HX --> ROH + RX . I imagine your way would work a lot better (but I like to avoid working with gases wherever possible), I just didn't know the normal route to make Ethyl Chloride off hand.
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[*] posted on 22-5-2004 at 00:00


first some words to silver-recycling:
you take the precipiates of silver-halogenides and wash them with water until no more Hal- is detected. Then you add HCl and Zn and let stand it overnight. Then you add more HCl to solve the Zn, decant the solution from the precipiated silver and wash it until no more Cl- is detected. The silver is solved in conc. HNO3, precipiated as AgCl and the whole procedure repeated one more time.
instead of using Zn/HCl you may reduce the Halogenides by heating with Na2CO3 and powdered charcoal (ratio: 1:0,1 per g AgCl) to1050°C.
As a third method you may reduce it with NaOH/HCHO: per g AgCl you solve 0,82g NaOH in 25ml water.. The HAlogenide is added with strong stirring to the lye. Then 0,6ml of a 37% HCHO-sln. is added dropwise and the solution is stirred until no more CO2 is evolved. Then it is heated to 60-70°C for 1h and the silver then is collected by filtration.
It may be possible to replace HCHO by glucose. I tried this but it wasn´t something I would recomend you;)

So, finally I am able to pay attention to the "real" topic of the thread;)!
Samosa, the reaction you described looks like some kind of electrophil substitution! And if I am right the best soplvents are (as mentioned by vulture) DMSO and DMF. slightly better may be perhaps MeCN. The important thing is: it has to be polar, best is aprotic polar.
Coming to the ethyl-halogenides: here for the reaction I suggest the ethyl-iodide would be the best choice! perhaps the bromide may be useful to but I would not use the chloride (also th chloride has a b.p. of only 12°C!)
Some words to the "financial" worries about the alkyl-iodides: As Ag you may recycle iodine. So all you have to pay is some "starting" amount of let´s say iodine. You prepare the desired alkyl halogenide and got your iodine nearly quantitative back as AgI or may be NaI. These iodides could easily oxidised to the free iodine and you may again start with making alkyl-iodides!
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[*] posted on 22-5-2004 at 06:21


My best guess at the commercial manufacturing method for ethyl chloride would be the chlorination of ethane or the addition of HCl to ethylene because the reacants are cheap.
On the lab scale HCl and alcohol +a lewis acid catalyst seems the easy way.
(And I still think my way of recovering the silver is the easiest);)
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[*] posted on 24-5-2004 at 10:31


Alright, I have some calculations down for production of TEPP on a nice, small scale:

4 AgNO3 + Na4P2O7 --> Ag4P2O7 + 4 Na+ + 4 NO3-

25.0 g AgNO3 are dissolved in 50 mL of water. Separately, 9.78 g Na4P2O7 are dissolved in 50 mL of water. The two solutions are then combined in a 100 mL beaker, and the solution is cooled and allowed to sit to maximize the amount of precipitate (theoretically, 10.36 g). The precipitate, Ag4P2O7, is dried in a crucible.

Ag4P2O7 + 4 C2H5I -(DMSO)-> (C2H5)4P2O7 + 4 AgI

In a boiling flask, the Silver Pyrophosphite is dissolved in DMSO. Via addition funnel, 22.9 g (11.8 mL) of Ethyl Iodide is added. Once all of the EtI is added, the flask is heated to 135*C and the TEPP should distill over, leaving DMSO and AgI (34.5 g, theoretically) in the boiling flask. The theoretical yield for TEPP is 7.46 g, or 6.30 mL (assuming a density of 1.185 g/mL).

------------------------------------------------------

Questions, again; is AgI soluble in DMSO? And if so, could it be separated simply by adding water?

Also, I am suggesting using DMSO because it is very easy to get. MeCN would be ideal, but it is a watched chemical since those loonies in Japan used it in their Sarin synthesis.

I didn't mention sizes on the boiling flask because I don't know how much DMSO should be used--I imagine that Ethyl Iodide is very soluble in Organic Solvents like DMSO, but I am not sure about Silver Pyrophosphite... I guess that would have to be determined through experimentation (?)

And naturally, it would be a good idea to do the heating in a vacuum-distillation type setup so as to avoid contact with the TEPP.

------------------------------------------------------

I much like the idea of recovering Silver and Iodine via heating with NaOH... the Sodium Iodide formed could be reused in the synthesis of Ethyl Iodide:

H+ + I- --> HI

HI + (C2H5)2O --> C2H5I + C2H5OH

I just find the ether route to be the easiest, since we don't want to use straight Phosphorus.

------------------------------------------------------

Since we will be dissolving Ag into HNO3 to get Silver Nitrate again, perhaps we could recycle the NaNO3 solution produced in the first reaction for this purpose?

[Edited on 5-24-04 by Samosa]
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[*] posted on 24-5-2004 at 14:57


Did I miss something or have we changed from pyrophosphAtes to pyrophosphItes?
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[*] posted on 24-5-2004 at 16:55


No, we're still talking about Pyrophosphates... P2O74- is the Pyrophosphate ion:

O=P(O2)-O-(O2)P=O
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[*] posted on 25-5-2004 at 10:46
buying C2H5Cl


:D:D:D
Why not to buy ethyl chloride in drugstore !?? It is easily available as coolant spray for sportsmen !
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[*] posted on 25-5-2004 at 17:21


Quote:
Originally posted by heksogen
:D:D:D
Why not to buy ethyl chloride in drugstore !?? It is easily available as coolant spray for sportsmen !
frankly, if you can still buy pure ethyl chloride ("Kelen";) for this purpose OTC , you're lucky one.
the local-cooling sprays I know consist normally of dimethyl ether, (iso)butane, alcohol etc... no halogenated lower alkanes, since these are classified as cancerogenes ..
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[*] posted on 27-5-2004 at 04:22


I think you could use straight sodium pyrophosphate, isomer formation as in when making nitroalkanes isn't a problem.
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