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Foss_Jeane
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Oh for the love of God! Didn't anyone notice the title of the initial post?
"the journal of irreproducible results presents: KCN from KOH and formamide"
It's a joke. Formamide + base/acid + water= ammonium formate + formic acid + ammonia Back before the Haber Process, it was easier to make cyanides
than ammonia, and that's how they made ammonia: by passing steam over red hot NaCN or KCN, giving the corresponding formate as a by-product they could
sell for extra profit.
I have yet to see any process that produced cyanides that wasn't a hot process: Nitrates or nitrites or metallic amides + carbon,
and lots of heat (think arc heating here) or passing the nitrogen or ammonia over carbon brought to orange heat, or passing gaseous
precursors through an electric arc.
If it sounds too good to be true, then it probably is.
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Polverone
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Actually, I gave that title to the thread after I split it off from the larger cyanide thread.
PGP Key and corresponding e-mail address
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un0me2
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K3wl
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S.C. Wack
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Here is your ref for formamide and NaOH giving NaCN. I am shocked, shocked to find that it involves hot formamide vapor ("Die Zersetzungstemperatur
wird am besten möglichst hoch genommen.") and is a little vague.
DE108152
EDIT: This was the only ref in Beilstein anywhere close, same for google's books on cyanide manufacture.
[Edited on 8-2-2010 by S.C. Wack]
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bbartlog
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Neat patent. Basically says that if you want to go straight from ammonium formate to cyanide, you need to send the gas through a molten alkali
solution at minimum 360 deg C, whereas if you first go to the trouble of distilling formamide from the ammonium formate you can get by with
temperatures as low as 200C (but still *piping the gas into the alkali*, not just mixing and heating). The vagueness in my opinion comes in because
molten alkali at 200C sounds like a hydrate melt though this is not explicitly specified. Anyway, it does clear up some confusion.
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kmno4
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Thanks. I was looking for any scientific informations about it but is turns out an old german patent. Definitely not scientific material, probably
equally irreproducible like other "wonderful" cyanide patents.
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Nicodem
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My skill in reading German sucks and I don't really want to be a party breaker, but that patent does not really claim that NaCN is formed from the
reaction of formamide and sodium hydroxide directly. Actually this patent is not only vague, but it does not even go to a chemical interpretation of
the process (kind of understandable given its age).
In my understanding, the formamide is thermolysed at >360°C and the products (containing HCN among other stuff) absorbed directly at this
temperature over potassium or sodium hydroxides to give NaCN or KCN. The formamide feed into the process is formed from the thermolysis of ammonium
formate in an autoclave at 200-300°C, with or without an acid catalyst (Chlorzinkammoniak). In the presence of the catalyst a little HCN
forms already in the autoclave, especially at higher temperatures. The patent even tells us that if the formamide vapours are being carried over the
hydroxides at a temperature lower than the one needed for the thermolysis then the hydroxide reacts with formamide by the usual manner yielding only
hydrolysis products:
"Kaltes oder mäfsig warmes Alkali zersetzt Ammoniumformiat oder Formamid zu Alkaliformiat und Ammoniak; geschmolzenes Alkali dagegen spaltet
Wasser ab und bildet glatt Blausäure, mit der es sich sofort zu alkali verbindet. Die Zersetzungstemperatur wird am besten möglichst hoch genommen.
Arbeitet man mit reinem Formamiddampf, so genügt allerdings schon eine Temperatur von 200° zur Zersetzung; ist aber noch Ammoniumformiatdampf oder
Wasserdampf zugegen, somufs man über 360° erhitzen."
As far as I could understand, this is also the only passage that mentions that the alkali hydroxides decompose formamide into HCN. But if you read
carefully it says that molten alkali does that, indicating that it is the heat that causes the decomposition of formamide into HCN and
not the reaction with the alkali hydroxide. Hence it says that the cyanide forms only at high enough temperature, preferably over 360°C. If the
alkali hydroxide would somehow react with the formamide, then HCN could not be a product, because HCN reacts with hydroxides to give cyanides and
water (obviously the authors were aware of this and if they would have believed the KCN/NaCN formed from the reaction of HCONH2 with KOH/NaOH, they
would have not be mentioning HCN as intermediate).
So what this patent is describing is actually only the usual thermolytical elimination of water from formamide and the neutralization of the so formed
HCN over molten hydroxides. The only difference from the other related HCONH2 -> HCN processes is in that they do not use alumina or any other
dehydration catalyst for the formamide decomposition into HCN. Since the reaction HCONH2 <-> H2O + HCN is highly reversible at the required
temperatures (300-500°C), there might be a rational reason for performing it over molten hydroxides. Namely, the HCN is absorbed as it forms,
therefore forcing further conversion. At such high temperatures (>360°C) the vast majority of formamide is probably in the gas phase and only tiny
amounts may be absorbed in the melt, the very high temperature thus paradoxically preventing hydrolysis (while gaseous acids react very rapidly with
molten hydroxides, the hydrolysis requires absorption, because the reaction can not occur easily just via an interphase boundary reaction like is the
case with proton exchanges). However, given that HCONH2 is itself a very weak acid it can be chemisorbed in molten NaOH by forming the sodium amide
salt and this then slowly hydrolysed. But if the temperature is high enough for the rapid formation of HCN (it being many thousand times stronger acid
than HCONH2), this will be competing at the phase boundary preventing the hydroxide from taking up formamide. Another reason for keeping the
temperature as high as possible.
I think we should all wait our funny cyanide kewls to provide the reference for their illogical claim that alkali cyanides can be made by reacting
formamide with alkali hydroxides. This patent is surely not what they had in mind (considering the required reaction conditions and all). It should
not be so difficult telling us where they read about a reaction so kewl that goes against chemical theory and against experimental data confirming
that formamide reacts with KOH and NaOH in the usual manner.
…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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bbartlog
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'It should not be so difficult telling us where they read about a reaction so kewl...'
Surely you could have guessed :-) -
http://en.wikipedia.org/wiki/Potassium_cyanide
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ramual
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CH3NO + KOH -> KCN + 2H2O
CH3NO (CN- , H30+) + ( K+, OH- ) -> KCN + 2H20
This is what happen when formamide(acid) reacts with Potassium hydrooxide(Base) -> KCN (Salt) + water
after that a second reaction occurs due to heat produced by first reaction
KCN + H20 -> HCN + KOH
The problem is How to convert HCN (Gas) into liquid or solid
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bbartlog
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Ah, really? That first equation is a reasonable gloss of the discussion to date, though I believe the question at this point is just how hot the KOH
needs to be in order for gas-phase formamide to react as described. Maybe you'd like to show us where you found that second reaction, where heat
decomposes potassium cyanide into hydrogen cyanide and potassium hydroxide. Because last time I checked KCN (with or without H2O) doesn't decompose
under heating in anything less than an electric furnace (and even then I doubt it splits neatly into acid and base).
| Quote: | | The problem is How to convert HCN (Gas) into liquid or solid |
The problem is that you can't be bothered to learn chemistry or read the entire contents of the thread. It sounds like you've seen gas coming off of
some KOH and formamide mix and erroneously concluded that since the formamide *must* have been turned into KCN and water, the vapors couldn't be
anything except cyanide. Chemically this makes about as much sense as boiling salt water to produce lye and hydrochloric acid (which is to say no
sense at all).
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Panache
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Mood: Instead of being my deliverance, she had a resemblance to a Kat named Frankenstein
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A great source of acidic or caustic vapour is simply produced by boiling water
H2O ---> OH-(g) + H+(g),
the trick is of course how do you manage to isolate those suckers before they find each other again.
I believe if you achieve this you will move science forward quite dramatically and after your work on this is complete you should move onto producing
an antigravity beam or trying to locate where the holy trinity hangout.
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Paddywhacker
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Quote: Originally posted by Panache  | A great source of acidic or caustic vapour is simply produced by boiling water
H2O ---> OH-(g) + H+(g),
the trick is of course how do you manage to isolate those suckers before they find each other again.
I believe if you achieve this you will move science forward quite dramatically and after your work on this is complete you should move onto producing
an antigravity beam or trying to locate where the holy trinity hangout. |
Isn't OH- seventeen times heavier than H+ ? So I'd say blowing on it would separate them nicely.
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ramual
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I've tried the same reaction with sodium hydroxide. but the result is same.
CH3NO + NaOH --> Gas + Something
????
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DJF90
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The "gas and something" will be ammonia and sodium formate.
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ramual
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I think the we got a conclusion
Formamide + Pottassium Hydroxide -- > Pottasium Formate + Amonia
CH3NO + KOH --> CHOOK + NH3
Formamide + Sodium Hydroxide -- > Sodium Formate + Amonia
CH3NO + NaOH --> CHOONa + NH3
[Edited on 18-2-2010 by ramual]
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