Azane
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Potential Preparatory Route for Formonitrile and Ethanedial
Two compounds I'm interested in making are ethanedial and formonitrile (HCN). Ethanedial is used in the preparation of HNIW, and HCN can be used to
make various cyanide salts and coordination compounds (hexacyanometallates), of which some can act as reductants in pyrolant mixtures and (perhaps
more importantly) as precursors to higher nitriles.
My practical experience in chemistry is effectively nil, so I'm coming here to see if anybody with more experience can validate or deny what I'm
hypothesizing.
First, ammonium tartrate is formed either by the direct neutralization of ammonia and tartaric acid,
2H3N + H2C4H4O6 --> (NH4)2C4H4O6
or by the reaction between ammonium chloride and tartaric acid, in which the formed HCl gas is driven off by heat:
2NH4Cl + H2C4H4O6 --> (NH4)2C4H4O6 +
2HCl
(The only reason why I'm considering two different reactions is because I don't know which is the more effective of the two).
(Could the reaction between ammonium chloride and tartaric acid proceed with a mixture of both compounds being heated in the solid phase?)
I don't think there's any doubt about the existence of ammonium tartrate, so what follows is where I have the most uncertainty.
I know that nitriles can be formed by the dehydration of ammonium carboxylate salts,
NH4CO2R-->2H2O+RCN
so my idea is that ammonium tartrate can be dehydrated (with various amide intermediates) into a hypothetical 1,3-dihydroxybutanedinitrile. Because of
the adjacent hydroxyl and nitrile groups on this compound, it could be considered a cyanohydrin. This cyanohydrin could be decomposed (through contact
with water?) into HCN and ethanedial:
C4H4N2O2-->2HCN+C2H2O2
However, for the sake of safety, this compound may be, more suitably, reacted with an alkali hydride to form hydrogen and the corresponding cyanide,
instead of HCN.
C4H4N2O2+LiH-->2LiCN+C2H2O2+H2
My hope is that the ethanedial and cyanide ions won't react, so that the ethanedial can be distilled into a separate container.
Also, could ethanedial cyanohydrin be stable, or will it just spontaneously decompose? Could it even form without intermediates reacting with one
another or the water being removed from them?
I'm interested to hear about any glaring problems that there might be in any of this.
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Metacelsus
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A Google search for glyoxal cyanohydrin shows that it can be hydrolyzed to tartaric acid. I'm not sure about the reverse reaction. Dehydration of
ammonium carboxylates to nitriles requires high tempertatures, which might just cause decomposition.
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roXefeller
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Lithium cyanide - the best of both worlds  But seriously ethanedial would be
cool to synthesize.
[Edited on 10-10-2014 by roXefeller]
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PHILOU Zrealone
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Diammonium tartrate is unstable upon heating.
It loses ammonia upon standing at standard pressure and temperature and forms monoammonium tartrate.
Upond heating it will maybe form H2N-CO-CHOH-CHOH-CO-NH2 but also a cyclic monoamide HN(-CO-CHOH-)2 or a polymeric amide (-NH-CO-CHOH-CHOH-CO-)n.
The hydroxy moeties may also dehydrate!
H2N-CO-CHOH-CHOH-CO-NH2 --> H2N-CO-CH=C(OH)-CO-NH2 <-=> H2N-CO-CH2-CO-CO-NH2 (or cyclic pentaring or polymeric monoamide).
The conversion of amides to nitriles usually requires very strong dehydratants like P2O5.
By virtue of the extreme acid stenght difference between HCl and tartric acid (over 10 pKa units...HCl is 10 billionth time more acidic so despite the
difference of volatility the reaction will be extreemely slow and inefficient (ammonia will remain with HCl as volatile NH4Cl))
NH4Cl + tartric acid <=======/--> ammonium tartrate + HCl
In conclusion your idea is far from realistic and a great loss of money or valuable reactants!
But  there must be cheaper ways!
1°)Formonitrile (cyanhydric acid) is reachable via Bucher's process:
N2 + 4C + Na2CO3 --Iron turnings/800-1000°C--> 2 NaCN + 3 CO
Or via Castner's process:
NaN2-CN + C --800-1000°C--> 2 NaCN
2°)Ethandial can be done by:
* CH3-CH=O via SeO2 oxydation
* CH3-CH=O via HNO2 oxydation
* maybe by oxydation of tartric acid by HOCl via hypochlorous ester (caution explosive!)
HO2C-CHOH-CHOH-CO2H + 2 HOCl --> HO2C-CH(OCl)-CH(OCl)-CO2H --> HO2C-CO-CO-CO2H + 2 HCl
HO2C-CO-CO-CO2H --> O=CH-CH=O + 2 CO2 (spontaneous decarboxylation)
*maybe via Hunsdiecker reaction
AgO2C-CHOH-CHOH-CO2Ag + 2 Br2 -CCl4-> Br-CHOH-CHOH-Br + 2 AgBr + 2 CO2
eventually with blocage/protection of the hydroxy groups by cyclic cetalisation with CH3-CO-CH3 and strong acid.
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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Praxichys
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Quote: Originally posted by Azane  | Two compounds I'm interested in making are ethanedial and formonitrile (HCN).
My practical experience in chemistry is effectively nil |
Not really a good combo. Be careful.
I believe cyanides form when roasting group 1 metal cyanurates at around 600C. I have used this method to successfully produce calcium cyanamide,
since group 2 metals roast from cyanurate to cyanate and finally cyanamide. Group 1 metals, however, should finish out as cyanides.
Of course, KCN or NaCN would be the goal. Acidify for HCN.
Be aware that HCN is extremely toxic. "Acute (short-term) inhalation exposure to 100 milligrams per cubic meter (mg/m3) or more of hydrogen cyanide
will cause death in humans." - epa.gov
We're working on glyoxal in a separate thread.
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Azane
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| Quote: Originally posted by Cheddite Cheese | | A Google search for glyoxal cyanohydrin shows that it can be hydrolyzed to tartaric acid. I'm not sure about the reverse reaction. Dehydration of
ammonium carboxylates to nitriles requires high tempertatures, which might just cause decomposition. |
The non-thermal dehydration of ammonium carboxylates and amides can be achieved with thionyl chloride, phosphoryl trichloride, or phosphoric
anhydride.
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