Proteios
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transforming base chloride into Carbonate!
Hey Guys.....This sounds like a suitable simple problem..... I got half a gram of Guanidinium Chloride which i wanna convert to Guanidinium
carbonate....
Gdm =CN3H6
....H.....H...
H-N......N-H
...... | ../.....
........C+....
.........|.......
.........N.....
.......H..H...
Ok... thats the general flava..... but here the trick... its 15N Gdm.... and is worth more than me!
Some background....
Gdm2CO3...v soluble
Gdm2Cl .....v soluble
[Edited on 7-3-2004 by Proteios]
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Theoretic
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"half a gram of Guanidinium Chloride"
"and is worth more than me!"
LOL, charming! Er, penny for the guy (not a creation of my imagination this phrase, it was referring to Guy Fawkes being caught in the act,
nitroguanidine is made by dehydrating guanidine nitrate and is used as an explosive so this has more relevance than meets the eye, whatever, sorry
 )?Either it's an ultra-pure analytical-grade chemical, or you're in a
mental state of, so to say, ground zero, or you've made the chemical yourself .
15N? is that 15 normal? In that case you need to add a precise quantity of sodium carbonate according to this reaction:
2GuCl + Na2CO3 = 2NaCl + Gu2CO3
and evaporate it, with luck guanidinium carbonate will sublime and condense on the colder part of your test tube (I assume a similarity with ammonium
carbonate).
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Proteios
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14 N is the natural one and is pretty much all of it, 15N is stable but quite a rare isotope.
14 99.634% Stable
15 0.366% Stable
Nice idea with the sublimation.... unfortuantely Melting Point: > 300 deg C.... 
Even under high vacuum Im not sure i fancy the chances of subliming this without decomposition... nice idea though!
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Polverone
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Well it's a nice idea that might or might not work. Why not try it with inexpensive ordinary guanidinium chloride, and apply it to the
expensive compound if it works, or keep searching if it doesn't?
Edit: thanks, Marvin
[Edited on 3-9-2004 by Polverone]
PGP Key and corresponding e-mail address
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Marvin
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I think it will be rapidly obvious that you should seek alternative sources of information. Listening to advice here will only cost you time and/or
money.
Aside from getting it wrong on the sublimation theoretic, you wernt right about ammonium carbonate either. It forms a mixture of ammonium carbamate
and ammonium hydrogen carbonate.
Guanindine salts have a nasty habit of hydrolysing to carbon doxide and ammonia, particulally in basic conditions. I wouldnt like to be in your
shoes. Maybe you should have bought the carbonate in the first place?! What is the application. The only method I know would work for certain would
involve significant loss. Silver nitrate would get you Guanidine nitrate in quantitive yeild (>99%), which you could nitrate to the nitro compound
(approx 90%). Then theres a process in Davis to turn this into guandine carbonate that has a 90% yeild. Overall youd lose 19% of your expensive
guanidine chloride and that makes this a long way away from being useable. If there was a compound with a high solubility for carbonate and a low
solubility for chloride you might be able to do it directlly in 1 step and in very high yeild but nothing springs to mind.
In theory, a metathesis of soluable salts should work to high yeild, you need very detailed data for precipitation of guandine salts though. Time for
you hit the library I think. A cunning synth might involve adding alcohol or ether to mix to cause one of the salts to crash out.
As a last ditch attempt you could also look up some of the much older synthesis of guandine compounds. These tend to start by forming guandine
thiocyanate and use metathesis to make everything else. Thiocyanate is a psudohalogen, so one might be applicable.
As polverone suggested, always try it out with the cheap stuff first, though he meant 'chloride' rather than 'carbonate' 
Ok, thats my tuppence worth of shit and sugar, sift it as you see fit.
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Proteios
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Thnx 4 that Marvin 
The broad details is that we needed the GdmCl for an experiement..... thats been done now.... but it would be really useful to get it into the
carbonate, and do another expt. Ive looked at the two stage synthesis with considerable discomofort..... mainly from the perspective of scale.... you
might get 90 % when you are doing on large scale but I have 400 mg..... not even half a gram!
Think the conversion might be possible with ion exchange resins.... but if it is ....
its a very obscure use for them!
So why post here... well this is kind of a funny reaction Im trying to do here, its really not the sort of thing conventional chemical wisdom will
help you with.....unconventional chemistry flows like water on this site!!!
As for the experiment.... its neutron scattering. You put one isotope in the beam... record a structure factor, then another isotope... with the same
structure... but because of the isotope, different neutron scattering properties. This gives you the structure of the nucleus you substituted.
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Theoretic
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"Aside from getting it wrong on the sublimation theoretic, you wernt right about ammonium carbonate either. It forms a mixture of ammonium
carbamate and ammonium hydrogen carbonate."
So that's what you get when condensing ammonium carbonate sublimate? By logic the other two products shuld be ammonia and water:
2(NH4)2CO3 = NH4COONH2 + NH4HCO3 + NH3 +H2O.
I can't see how this dehydration could happen at low temperatures, and when the vapour cools down I assume hydrolysis would happen.
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Proteios
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I think the thing with ammonium carbonate is its kinda unstable.....there are several chemical present in some funny equilibrium.
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unionised
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I would look at the reaction of the chloride with moist silver oxide to get the base and with CO2 to give the carbonae. (and I wouldn't have the
confidence to do this with the expensive stuff until I had checked it with the "normal" stuff).
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Proteios
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I think Ive cracked it!
CsCl and Cs2CO3... v. soluble in EtOH, and presumably acetone
GdmCl.... soluble in EtOH (76g/100g)...Insol. acetone
Gdm2CO3 soluble in EtOH (0.55g/100g)..... very small solubility... insol acetone.
Synthesis....
GdmCl... dissolve EtOH, add Cs2CO3....ppt Gdm2CO3. This gets the bulk of the yield. Maybe add some acetone to help out.
I dont get into a lab till sometime next week..... Ill tell ya how it goes!
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