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Klute
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Why not prepare it fresh with P2O5? You woul dbe sure of how dry it is 
\"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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panziandi
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Haha... but if you have P2O5 you may as well just use that to dehydrate! But I suppsoe that is your point!
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Klute
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Of course, logical.
but P2O5 usually isn't very expensive or hard to find? Well it's not in eevry grocery store, but I guess it is a chemical that is quite used outside
of stricly lab purpose, so more accesable.
\"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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hector2000
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somebody can explain p2o5 method complete?
Chemistry=Chem+ is+ Try
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panziandi
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Well there is no one method but OrgSyn has this for Nicotinonitrile which could be adapted. It's one I had bookmarked... so not totally random! Many
books on elementary practical organic chemistry, especially older books like Vogel and also Mann and Saunders list Acetonitrile from P2O5 method.
In a dry 1-l. round-bottomed flask are placed 100 g. (0.82 mole) of powered nicotinamide and 100 g. (0.70 mole) of phosphorus pentoxide. The flask is
stoppered and shaken to mix the two powders. It is then connected by means of a 10-mm. i.d. tube to an 80-cm. air condenser arranged for distillation.
A 125-ml. Claisen flask immersed in an ice-salt bath is used as the receiver (Note 1). The pressure is reduced to 15–20 mm., and the mixture is
heated with a large free flame of a high-temperature burner (such as a Fisher or Meker type). The flame is moved about freely to melt the material as
rapidly as possible, and then the mixture is heated vigorously until nothing more comes over or until foam reaches the top of the flask (15–20
minutes). The apparatus is allowed to cool (Note 2), and the product is rinsed out of the tube and condenser with ether (Note 3). The ether solution
is added to the distillate, the ether is distilled on a steam bath, and the product is distilled at atmospheric pressure using an air condenser. The
yield of nicotinonitrile, boiling at 205–208° and melting at 50–51°, is 71–72 g. (83–84%).
Taken from http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0706
Basically the P2O5 is such a powerfull dehydrating agent it literally rips the elements of water from the amide group leaving the nitrile group.
PCl5, POCl3, SOCl2 etc can also afford the dehydration.
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Dave Angel
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Palladium(II) catalysed dehydration of primary amides to nitriles
Whilst there is another acetonitrile related thread going at the moment, a total synthesis post seems more relevant here than in a sourcing post. I
think I've found a potential application for my palladium wire discussed in this thread; again, I feel it's better contributed here than in that stray thread, though I have a feeling I'll be looking to buy additional Pd
for this...
The 'missing link', as one might put it, for the amateur chemist to produce acetonitrile from readily available chemicals appears to be the
dehydration step; acetamide synthesis from thermal dehydration of ammonium acetate being trivial as discussed, with ammonium acetate aquisition /
production being more-so.
I've found this paper:
Attachment: Maffioli et. al. (33kB)
This file has been downloaded 990 times
The main hurdle (besides expensive catalyst) is the old classic of requiring the target material to make the target material; I
believe the same applies to one of the many synthetic routes for acetic anhydride debated at length.
Assuming this is overcome, the synthesis is, for the most part, reported as being performed in a 1:1 mix of acetonitrile and water, requiring water in
order for the reaction to go; anhydrous conditions do not work. This synthesis is also reversible and to favours dehydration of the primary amide and
hydration of the acetonitrile solvent. Good yields are reported.
It's not clear where the equilibrium lies, but in any case addition of excess acetamide and removal of water and acetonitrile (a balance of
reflux:distillation to be struck) should push the reaction in favour of the latter.
A simpler batch process could be favoured given the very mild conditions; the excess acetamide stirred at r.t. for a significant period, followed by
fractional distillation of the azeotropic product, this last step pushing even more acetamide to conversion as the equilibrium shifts.
The solvent ratio could also be played with - say 2:1 water to acetonitrile, allowing both more starting material to be dissolved and any residue to
stay dissolved during the final distillation.
Being someone who likes OTC chemistry, the need for some acetonitrile to start with still bothers me, but I still think this could be a step in the
right direction for home acetonitrile synthesis.
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Dave Angel
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Microwave nitrile synthesis from aldehydes
Another protential route to acetonitrile for exploration in this paper:
Attachment: Dewan et. al. MW nitriles.pdf (37kB)
This file has been downloaded 824 times
In summary, aldehydes are reacted with hydroxylamine chloride in the presence of a sodium sulphate or sodium bicarbonate catalyst under microwave
irradiation to form nitriles.
Things are rarely simple - the following hurdles to overcome:
1) Formaldehyde would need to be the aldehyde used; will H-CHO behave the same as R-CHO?
2) Conditions are 'dry media' so formalin isn't going to cut it - without modifying reaction conditions anyway. Even then, you have water absorbing a
lot of the MW energy and fomaldehyde escaping due to the heat. Perhaps one could use trioxane, raising the question of 'will it react in the same way
as R-CHO?'
3) Hydroxylamine hydrochloride... No readily available sources spring to mind in my experience. Perhaps we could synthesise from nitrous acid and
bisulphite, followed by neutralisation with HCl?
4) Formation of the volatile acetonitrile if successful - a means of safely removing and condensing the product from the microwave environment would
have to be devised.
Other than those minor concerns(!), simple eh?
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franklyn
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Methylurea heated with Ammonium Sulfamate yields Acetonitrile.
http://www.sciencemadness.org/talk/files.php?pid=262451&...
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Dronami_inc
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Quote: Originally posted by panziandi  | Well there is no one method but OrgSyn has this for Nicotinonitrile which could be adapted. It's one I had bookmarked... so not totally random! Many
books on elementary practical organic chemistry, especially older books like Vogel and also Mann and Saunders list Acetonitrile from P2O5 method.
In a dry 1-l. round-bottomed flask are placed 100 g. (0.82 mole) of powered nicotinamide and 100 g. (0.70 mole) of phosphorus pentoxide. The flask is
stoppered and shaken to mix the two powders. It is then connected by means of a 10-mm. i.d. tube to an 80-cm. air condenser arranged for distillation.
A 125-ml. Claisen flask immersed in an ice-salt bath is used as the receiver (Note 1). The pressure is reduced to 15–20 mm., and the mixture is
heated with a large free flame of a high-temperature burner (such as a Fisher or Meker type). The flame is moved about freely to melt the material as
rapidly as possible, and then the mixture is heated vigorously until nothing more comes over or until foam reaches the top of the flask (15–20
minutes). The apparatus is allowed to cool (Note 2), and the product is rinsed out of the tube and condenser with ether (Note 3). The ether solution
is added to the distillate, the ether is distilled on a steam bath, and the product is distilled at atmospheric pressure using an air condenser. The
yield of nicotinonitrile, boiling at 205–208° and melting at 50–51°, is 71–72 g. (83–84%).
Taken from http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0706
Basically the P2O5 is such a powerfull dehydrating agent it literally rips the elements of water from the amide group leaving the nitrile group.
PCl5, POCl3, SOCl2 etc can also afford the dehydration. |
when it comes to acetamide, you do not need so much heat, right? Its mixture with P2O5 heat to melt (81,5°C) and then acetonitrile steam will go?
(because i afraid of decomposition of acetonitrile). And is it necessary to reduce the pressure?
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byko3y
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Jeee, I can't sleep, I'm thinking all the time about sulphamate + acetamide for cheap OTC acetonitrile preparation.
The paper "A study of the reactions of ammonium sulphamate with amides and ureas" tell about 10% yield, but I bet it could be much higher.
So the question that bothers me is: why they've got 10% yield? Is there any way to reach higher yields? Am I gonna die because of decomposition
products: "Acetonitrile produces hydrogen cyanide when heated to decomposition or when reacted with acids or oxidizing agents".
Is there any simple qualitative analysis to determine whether exiting gases had HCN?
inb4: NaCN + (NH4)2S2 → NаSCN + (NН4)2S;
3NaSCN + FeCl3 → Fe(SCN)3 + 3NaCl
and
HCN + NaOH ↔ Н2О + NaCN;
2NaCN+FeSO4 ↔ Fe(CN)2+Na2S04;
Fe(CN)2 + 4NaCN → Na4[Fe(CN)6];
3Na4[Fe(CN)6] + 4FeCl3 → Fe4 [Fe(CN)6]3 + 12NaCl.
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halogen
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Fellows, dears, and other such inhabitants. For example, on page 291 of Paul Sabatier's (a frenchman and Nobel Prize WINNER!) book Catalysis
in Organic Chemistry, you will find the following quote. Book is public domain, available from Google Books, or Sciencemadness' very one
library: you will benefit from reading it in full. All kinds of life advice, for any situation. From divorce to tapestries, and even catalytic
leavening for breads and cakes.
QUOTE:
The dehydration of amides to nitriles can be effected by appropriate catalysts.
The amide mixed with the catalyst is heated to 250-60° for 4 hours in a flask fitted with a reflux condenser.
Four parts by weight of catalyst are used to one of amide. (54)
[54. M. BOBHNBB and ANDREWS, J. Amer. Chem. Soc., 38, 2503 (1916). see http://pubs.acs.org/toc/jacsat/38/11 ]
Acetamide with the catalysts listed below gave the following yields of acetonitrue:
alumina 68 %
lamp black 68
pumice 65
powdered glass 65
sand 52
horse teeth 35
But better yields are obtained by carrying the amide in a current of air over the catalyst heated to 420°, the yields being: (55)
[55. BOBHNBB and WARD, J. Amer. Chem. Soc., 38, 2505 (1916). see http://pubs.acs.org/toc/jacsat/38/11 ]
With pumice 91.5
alumina 82
sand 86.5
graphite 75.5
812. The same process can be applied to nascent amides furnished by the vapors of the acid with ammonia in excess in the presence of alumina or thoria
at around 500°.
Alumina gives the best results. Starting with acetic acid an 85% yield of the nitrile is obtained. (56)
[56. VAN EPPB and REID, J. Amer. Chem. Soc., 38, 2128 (1916). see http://pubs.acs.org/toc/jacsat/38/10 ]
813. We may put along side of the catalytic dehydration of amides to nitriles, the action of ammonia gas on the chlorides of acids in the presence of
catalytic oxides.
The amide formed is immediately dehydrated to the nitrile.
The mixture of ammonia and the acid chloride is passed over alumina at 490-500° and water and hydrogen chloride are eliminated:
R.COCl -I- NH, - R.CN + H8O + HCl.
High yields of the nitriles are obtained in this way from propionyl, isobulyryl, isovalyryl and benzoyl chlorides.
As the ammonia gas is used in excess, ammonium chloride is formed and deposits in crystals in a receiver placed at the end of the reaction tube. (57)
[57. MAILHB, Bull. Soc. Chim. (4), 23, 380 (1918).]
814. The aldoximes which are isomeric with the amides can be
transformed into nitriles in the same way. The vapors of the aldoximes
are passed over alumina or thoria maintained at 350-60° and give
the nitriles. Isovalerald-oxime gave isovalero-nitrile and oenanthaldoxime
gave hexyl cyanide. The ketoximes, when submitted to the
action of these dehydration agents, undergo a complex reaction in
which nitriles with one less carbon are formed. (68)
[58. MAILHB and DB GODON, Bull. Soc. Chim. (4), 33, 18 (1918).]
[Note: this process, the rearrangement of oxime to amide is called https://en.wikipedia.org/wiki/Beckmann_rearrangement ]
Seeing as byko3y was so excited at the prospect of using P205 as a dehydrating agent, this news is likely to cause him a great disturbance. Perhaps he
will run naked screaming through the streets.
[Edited on 21-6-2015 by halogen]
[Edited on 21-6-2015 by halogen]
F. de Lalande and M. Prud'homme showed that a mixture of boric oxide and sodium chloride is decomposed in a stream of dry air or oxygen at a red heat
with the evolution of chlorine.
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CuReUS
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| Quote: Originally posted by byko3y | Jeee, I can't sleep, I'm thinking all the time about sulphamate + acetamide for cheap OTC acetonitrile preparation.
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I hope this helps you sleep
http://www.sciencemadness.org/talk/viewthread.php?tid=45844#...
btw,someone suggested using ketene as the dehydrating agent.It seems ketene can char a PVC pipe
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byko3y
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wow, wow, Wow, WOW, this
is HUGE. To realize that 90 years ago people actually knew a good way of making acetonitrile. I knew it's possible make acetonitrile by vapour phase
pyrolysis, including passing ammonia+acetic acid vapor over catalyst but the problem is to make the appropriate equipment.
I really love those old chemists books, because nowadays the chemistry books are overloaded with a lot of useless information, implying everything
except large industrial production is completely obsolete, while it is clearly not.
This knowledge is giving me peace I need so much when being in oppisition to globalism and just stupid local laws.
There's a nice research about mechanism of the reaction http://dx.doi.org/10.1039/tf9686400965 , it's likely going via ketene and acetic-imidoyl anhydride, but the conditions used in it (500°C) are not
suitable for an amateur chemist.
P2O5, TEMPO are all useless crap when you can just pyrolyse the stuff with 65% yield.
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clearly_not_atara
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halogen lacks the direct link to the paper, and has incorrectly quoted the names of the authors (R.S. Boehner and C.E. Andrews):
http://pubs.acs.org/doi/pdf/10.1021/ja02268a025
and as I agree it is quite significant for practical synthesis of acetonitrile (I was not aware of such a method) I think it is worth preserving, so
the paper is attached:
| Quote: | | Since the products of decomposition of amides, namely the cyanides and water, have a much lower boiling point than the amides, it was thought that the
[vapor-phase dehydration] method referred to above might be modified by heating the amides with the contact material in a flask whose outlet
[temperature] was high enough to permit the cyanides and water to distill off, but would cause the amides to condense in the flask and drip back upon
the hot contact material. The contact substances used were aluminium oxide, pumice stone, glass, sand and graphite. |
Acetonitrile distills out of the flask as it forms; it will not remain in the flask during reflux. I didn't quite get this the first time I read
halogen's post :p
Experimentation with various clays and other available mineral powders may prove interesting. Zinc oxide has been reported as effective. Modifying the
surface of the catalyst by washing it with phosphoric acid is reported to increase the activity.
All studies after 1916 seem to report only on vapor-phase dehydration of a stream of acetonitrile passing through a tube and usually the highest
yields are at higher temperatures probably because this decreases the competing hydrolysis with formed water. It would be interesting to use a simple
dehydrating agent such as CaCl2 or MgSO4 and see how this affects the yields.
[Edited on 19-4-2017 by clearly_not_atara]
Attachment: boehner1916.pdf (199kB)
This file has been downloaded 599 times
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Dr.Bob
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One of my coworkers recently tried to make a nitrile from a primary amide, using P2O5. The first run was a mess, no product, just a flask filled with
goo at the end. The next one, he added some decalin to help form the melt, that one gave a few ml of it, which was enough, but the goo left in the
flask was like concrete. So use an old flask, and understand that dehydrations with P2O5 are very messy and not always high yielding. There is a
lot of careful technique to them, which is often left out of those papers, and require some trial and error work.
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Magpie
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Vogel has a procedure for making acetonitrile from acetamide. I did this a few years back after I found a source for P2O5. My yield was 56%, Vogel
claims 10g(72%). My notes say "quite a bit of charred residue left in pot."
The single most important condition for a successful synthesis is good mixing - Nicodem
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clearly_not_atara
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The method halogen and I posted does not use any P2O5. P2O5 is more expensive and difficult to make than acetonitrile by any route I am aware of,
unless there is an easy way of making it I don't know about.
Even the 723K vapor-phase version is still much easier than making P2O5! Although I have a suggestion: if you do want to use P2O5, convert this first
to POCl3 with gaseous HCl, and use an amine base or pyridine to dehydrohalogenate the Vilsmeier adduct. This should be much cleaner than P2O5
dehydration directly.
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Elemental Phosphorus
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I don't think you can make phosphorus oxychloride with phosphorus pentoxide. See the first thread I ever started. This pyrolysis method to
acetonitrile is huge though, since it will allow for the creation of acetic (and other) anhydrides without ketene or chlorinating agents. (Chemplayer
made a video on it) Also, the 250-260c pyrolysis route is open to anyone with a good hot plate, making this one of most OTC routes to nitriles and
anhydrides.
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tsathoggua1
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God thats some odd stuff used for catalysis experiments...horse teeth?
Afraid my lab is fresh out...hope sigma doesn't charge too much for those...
And oenanthyl? presumably the radical corresponding to oenanthetoxin, from Oenanthe crocata, similar to cicutoxin from Cicuta virosa, the water
hemlocks? I'll bet THAT was a popular assignment, given how much nastier than the coniine of the land hemlock they are (quite potent GABAa inverse
agonists, one bite is enough to finish off critters a lot bigger than we are, cows sometimes end up digging up the roots when they are exposed by
water currents, with fatal consequences)
Nasty way to go too, if I had to work on something like those polyyne alcohols, I think carotatoxin (from carrots) would have been a better bet, In
the poison water hemlocks there can be a fair amount of such polyyne toxins too, exudes out into chambers within the roots IIRC)
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karlos³
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No, just oenanthoic acid, better known as heptanoic acid.
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clearly_not_atara
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You most certainly can. In fact Melgar noted this in your thread but you were only interested in PCl5:
https://www.sciencemadness.org/whisper/viewthread.php?tid=71...
and Sauron was proven wrong when he was insistent that this was impossible before:
https://www.sciencemadness.org/whisper/viewthread.php?tid=9&...
Sauron's conviction that waiting 5 days for a reaction (since, as mentioned, the majority of HCl uptake happens within 5 days) is impractical appears
to be an attempt at self-defense, because it is obviously not impractical to spend 5 months arguing about the reaction on sciencemadness, so in my
opinion it is not going to be much harder to spend 5 days performing it. Although you will need a large container that can hold HCl gas for a long
time.
In any case the reaction of P2O5 with HCl works regardless of what anyone's intuition says about it. Also it appears that balancing the equation:
a*P2O5 + b*HCl >> c*POCl3 + d*HPO3
has become an introductory chemistry exercise, because all that comes up when I google this are students looking for someone to do their homework. (If
you found this thread on Google and you want to know the answer then you lose lol)
[Edited on 1-5-2017 by clearly_not_atara]
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Elemental Phosphorus
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I was actually interested in any phosphorus halide in that thread, if I didn't make it clear enough, I apologize. The reaction cited by Melgar is
correct, and actually you can use NaCl aparrently, forming NaPO3 instead of HPO3. I decided against ordering P2O5 for that purpose though, and I just
contacted a supplier to order ferrophosphorus to produce halides instead. Still though, when using the route with HCl or NaCl, you tie up half your
phosphorus as HPO3 or NaPO3 which is undesirable. You were right though, and I was on quick reply and didn't take the time to go back and read the
thread until now.
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PirateDocBrown
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Exactly where are people finding P2O5? Convenient and economical sources are proving elusive for me.
U2U me, if you don't wanna say out loud.
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JJay
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I know that Firefox carries it; they make you send in a copy of your driver's license and you probably have to sign some document stating that you
aren't making bombs, but it's pretty cheap. I haven't bought anything from them, but that P2O5 would look great in my collection.
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PirateDocBrown
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Hmm, ok! I'll check it out.
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