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guy
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HCN by chloroform and ammonia in base
Carbylamine reaction is reaction of chloroform with an amine and alcoholic KOH to produce an isonitrile. If you can do this with ammonia instead, it
should be able to make hydrocyanic acid. Is this plausible?
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Polverone
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It is plausible and I have done it, confirmed by the prussian blue test. It is not a terribly efficient method, of course. I was unable to get it to
work with household aqueous ammonia (5%? 10%? something like that) but there was a vigorous reaction when I used 28% concentration. I seem to remember
that I was able to get it to work in water, without ethanol, if I added a bit of winter pool algaecide (mixed quaternary ammonium salts).
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not_important
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With the KOH there, I asume that you would get KCN rather than HCN. I fthat is the caserunning in alcoholic KOH would make isolation of the KCN easier
than from water, unless you really wanted to acidify it and distill the HCN from it.
When you say it is not terribly efficient, how do you mean this? Low conversion, with lose of chloroform as formate?
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Polverone
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I mean that you end up with a lot more chloride than cyanide (of course), and that the use of chloroform, strong aqueous ammonia, and alcoholic KOH
seems like a rather expensive way to make impure KCN.
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guy
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I was thinking about bubbling gaseous ammonia into the solution. Actually the cyanide salt is what I want not HCN. So if I use KOH I would get a
mixture of KCl and KCN, and the best way to separate this would be to add Pb2+ precipitate to Cl-. Then filter that off and leaves you with fairly
pure KCN. Unless lead cyanide is also insoluble...
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Dr. Beaker
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I used a very efficient way to make nitriles from aldehydes using iodine and aquaos amonia. look for Fang and nitrile in scifinder.
the mechanism involves oxidation of the imine and elimination of HI, so if u keep the right stoichiometry there shouldn't be oxidation of the exta
alpha H.
btw - the notorious NI3*NH3 forms, but it's not dangerous when wet, and the black ppt. of that sensetive exposive dissapears with the advance of the
reaction.
advantages:
1. cheap reagents (methanol or formaldehyde), I2, amonium hydroxide
2. very quick (mostly minutes) rxn. time and easy to follow (wait until the black ppt. dissolves)
3. easy to seperat the product - kill excess I2 with Na2S2O3 and add KOH in same amount of HCN, then evap. the solution (u can recycle excess of NH3)
and seperat NH4I and KCN by fraction crystelazation or by sublim. NH4I. (maybe even NH4+ and CN-react to give NH3 and HCN which u can remove and
condense.
u can then easily get back the I2 by oxidation with, say bleech+HCl (also good way to eliminate any traces of cyanides)
[Edited on 26-10-2006 by Dr. Beaker]
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not_important
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| Quote: | Originally posted by Polverone
I mean that you end up with a lot more chloride than cyanide (of course), and that the use of chloroform, strong aqueous ammonia, and alcoholic KOH
seems like a rather expensive way to make impure KCN. |
Very true, but easier for many than the high temperature routes. I find I find blowing air through steel pipe filled with charcoal and soda ash fun,
but some people might not have the room to do it.
Fang :
http://www.sciencemadness.org/talk/viewthread.php?tid=5864
Updates
http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/j...
http://www.chemistrymag.org/cji/2005/071004ne.htm
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guy
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| Quote: | Originally posted by Polverone
It is plausible and I have done it, confirmed by the prussian blue test. It is not a terribly efficient method, of course. I was unable to get it to
work with household aqueous ammonia (5%? 10%? something like that) but there was a vigorous reaction when I used 28% concentration. I seem to remember
that I was able to get it to work in water, without ethanol, if I added a bit of winter pool algaecide (mixed quaternary ammonium salts).
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Ok so does a vigorous reaction means lots of heat? Should I cool the reaction to increase yields?
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Polverone
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| Quote: | Originally posted by guy
Ok so does a vigorous reaction means lots of heat? Should I cool the reaction to increase yields? |
It did noticeably generate heat. I don't know how bad it would be on a large scale, nor do I know if yields are affected (apart from the obvious
problem of volatilizing reactants). I only tried this enough times to confirm that it works -- how to optimize it will be a project for you to have
fun with  .
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not_important
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Hmm... long stainless steel tube and packed with NaOH or KOH. Still pot with CHCl3 and alcohol. Feed ammonia gas into the still pot, heat the pot so
the chloroform-ethanol boils. Take the ternary azotrope of chloroform-ethanol-water off the top, fairly dry product accumulates in the still pot.
Any hydroxide carried done into the still pot should react there. Vent to a flame or outside, as some carbon monoxide will be formed. At the end wash
the remaining hydroxide with alcohol, run the pot contents through a filter to remove the alkali chloride, evaporate to recover the cyanide. Might
work.
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guy
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I have a question, for the reaction with the quaternary ammonium salts, will 10% ammonia solution work?
I didn't have too much luck when I bubbled ammonia gas in; I don't think it dissolved well enough. I used 10g NaOH in about 100mL ethanol with 5mL
chloroform. I bubbled in ammonia gas. Then I tried adding the solution to iron(II) and iron(III) sulfate but did not get any blue color.
Edit:
For the Carbylamine reaction, refluxing is nessecary!
http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6...
[Edited on 10/26/2006 by guy]
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Polverone
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I don't know if 10% is enough. How did you generate the ammonia? I thought that NH3 should be readily absorbed in ethanol, but if not you might add a
bit of water.
If you really don't care about purity initially, you might try mixing an ammonium salt with excess alkali hydroxide in alcohol and then add
chloroform.
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guy
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I used NaOH and (NH4)2SO4 to generate the gas. I think when water is present a phase transfer catalyst in necessary to give satisfactory yields. So
gots to get some of that pool algaecide.
28% ammonia is needed, so is that about 13M ammonia.
Theoretical procedure:
26 g NaOH is dissolved in 50mL water and reacted with 43g ammonium sulfate. This gives about 28% ammonia solution.
Then some quaternary ammonium salts are added as a phase transfer catalyst.
10 g of additonal NaOH and 5mL chloroform are added to the solution.
~~~~~~
also one experiment, I accidentally added CHCl3 to basic ethanol first and got a very violent exothermic reaction that produced some orange
liquid...weird
[Edited on 10/26/2006 by guy]
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Polverone
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No, PTC isn't needed if the alcohol concentration is high enough, so there's no distinct phases. I used it only when I tried an alcohol-free reaction.
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guy
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So I tried it again today. I didnt get it to work the Prussian blue test (I mixed the solution with FeSO4 and put a drop of H2O2 and acetic acid in).
But when I put CuSO4 and FeSO4 I got some brown precipitate.
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Polverone
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Did you make sure the solution was slightly acid before you added the H2O2? Depending on the size of your reaction, a single drop of acetic acid may
not be sufficient. I tried it again recently to refresh my memory. Some water is useful because it increases NaOH solubility, and if you don't add too
much, chloroform will still dissolve. It seems denatured alcohol (large percentage MeOH) works better than 95% ethanol, because two phases form in
ethanol/water when NaOH is added. I used NaOH in denatured alcohol with finely ground ammonium sulfate or nitrate as the ammonia source; nitrate works
better because of higher solubility. It was easy to get a boilover even with just a few grams of reactants in 20 mL or so of liquid, so you probably
do need reflux apparatus, slow addition of chloroform, temperature control, or some combination of the above. And, of course, you would probably want
to use ammonia gas or aqueous ammonia rather than just dumping a salt in if you hope to eventually produce somewhat pure cyanides.
I acidifed with citric acid, added a bit of iron oxalate, and was rewarded with the lovely prussian blue when H2O2 was introduced.
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guy
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Wow, it seems I just have bad luck. Ill follow you procedure exactly tommorow and hope to get some luck.
Do you remember how much of each reagent you used? Like how much NaOH? Your total volume was about 20mL, so how much water vs. denatured did you
use?
And btw, I appreciate you trying it out again to check it.
[Edited on 10/31/2006 by guy]
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Polverone
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I'd try 6 equivalents NaOH, 2 NH4NO3, and 1 CHCl3 (hydroxide and ammonia in excess to favor cyanide over formate and to help make sure that chloroform
doesn't react too slowly as hydroxide is used up). 15 mL denatured alcohol and 5 mL water dissolve 4.8 g NaOH, and then 3.2 g finely powdered NH4NO3
are added. It won't all dissolve. While the mixture is still warm, 2.4 g of chloroform are added and the mixture is swirled around.
After the reaction is over and the mixture has cooled to room temperature, try the prussian blue test.
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guy
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YEs! I finally did it. At first I was mixing only a little of the cyanide solution in so I didnt get any results (probably my big mistake from other
runs). So I was dissapointed, so I was like "what the heck" and dumped all my iron sulfate into the cyanide solution and put a whole bunch of vinegar
in. And then I put a few drops of H2O2 and got a beautiful prussian blue color!
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ScienceHideout
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Sorry to bring back an old topic- but the preparation of cyanides is really sparking my interest now, and I was thinking if there is any way to
produce them without high heat or encounter with HCN gas... I started thinking about this and trying some stoiciometry.
If I simply bubble NH3 gas though some alcoholic NaOH and CHCl3, couldn't I get the cyanide, chloide, and water?
NH3 + CHCl3 + 4 NaOH ---> NaCN + 3 NaCl + 4 H2O
I should get 4.901 g NaCN if I use 11.938 g of chloroform and 15.999 g NaOH. I need a tenth of a mole of NH3, so that means what- 2.24 L? That can be
prepared quite easily.
Anyways- I am just wondering a couple things:
Can I get a delta G value to see if this will work? Delta G's are telltale of if inorganic reactions will work, but because this is derived from the
carbylamine reaction, I was not sure if I could get a delta G.
If this reaction will work at all, do I need a catalyst?
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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ScienceSquirrel
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You have to remember that the reaction is not remotely stochiometric.
The first step in the reaction is deprotonation of the chloroform and the loss of chloride to form dichlorocarbene, this then reacts with ammonia to
form an addition product that loses hydrogen chloride to form the cyanide.
I would guess a twenty per cent yield would be good with the rest turning in to other possible products.
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S.C. Wack
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People go (went) about extracting amines via A/B (NaOH) and chloroform all the time.
http://books.google.com/books?id=uelSAAAAcAAJ&pg=PA114
http://books.google.com/books?id=A49KAAAAYAAJ&pg=RA1-PA3...
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ScienceHideout
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Ooh! Time to test my German skills! "Ueber eine neue Reihe von Homologen der Cyanwasserstoffsaeure"
No expert- but cyanwasserstoffsaeure is cyanide hydrogen acid- hydrocyanic acid HCN- YIKES! It also seems to discuss much about amines. In this post
we discuss a reaction where we replace an amine with ammonia.
"On the behavior of chloroform to other bodies, especially for ammonia, with higher temperature" seems more relevent, but it doesn't seem to talk much
about cyanide. Hmm....
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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DoctorZET
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I tryed 3 different series of reactions:
1)
4NH3(gas) + 3Cl2(gas) (excess) -( INTENSE BLUE LIGHT )-> NCl3(liquid) + 3NH4Cl(fine divided solid)
NCl3 (excess)(gas) + CH4(gas) -( AlCl3 cristals deposited in a glass tube, 80-100*C )-> NCH + 3HCl
___now you have HCN ...or, try the next method (is also a very well process)
2)
BLEACH (with little excess)(aq) + PROPANONE(acetone) (aq) -(some time)-> HCCl3 (insoluble layer under water) + CO2 + Others_compounds
HCCl3 (excess)(gas) + NH3 (gas) --(traces of H2O + AlCl3 cristals deposited in a glass tube, 90-150*C)--> HCN + 3HCl
___now you can have HCN in big amounts ... but if you have acces to some laboratory chemicals try next reaction:
3)
2 K Fe (CN)6 (potassium hexacyanoferrate) + 3 H2SO4 -(instant)-> K2SO4 + 2 FeSO4 + 12 HCN
___where 12 HCN means you can make a HUGE amount of hydrogen cyanide in no time ... but only if you have access to the hexacyanoferrate ion
[Edited on 13-4-2014 by DoctorZET]
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Pickardjr
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Dont know about you guys but the ferrocyanide and sulfuric works everytime, all you have to do is add KOH or NaOH to the distillate in stiochemetric
amount and you have an aqueous cyanide salt. done it a gazillion times. cake walk
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