Hexavalent
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Pyridine from Niacin
I would like to repeat Magpie's synthesis of Pyridine, but modify it to use a different catalyst other than the chromite specified or the silver salts
suggested as I do not have the required reagents. Any ideas? What else can be used for decarboxylation of an aromatic compound?
[Edited on 12-5-2012 by Hexavalent]
[Edited on 12-5-2012 by Hexavalent]
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Nicodem
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Quote: Originally posted by Hexavalent  | | I would like to repeat Magpie's synthesis of Pyridine, but modify it to use Niacin as the starting mateeial as opposed to Nicotinic acid
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Is this some kind of a joke? You want to use niacin where nicotinic acid was successfully used? They are the same, so what exactly is the problem?
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Hexavalent
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Sorry for any confusion with the original post, what I meant to ask is what I've edited it to read now.
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Nicodem
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Have you done a literature search at all? You present us no references, not even the link to Magpie's work.
Copper powder in coordinating media can be used in Cu catalyzed decarboxylations of arylcarboxylic and acrylic acids, most commonly Cu in quinoline
(as in the Org. Synth. example). Of course, in the particular case of nicotinic acid, the use of a coordinating solvent would be irrational, but you can
still try copper powder as the catalyst in a neat thermolysis. Cupper(I) oxide or other Cu(I) compounds might also work to some degree. But in
essence, you only have two possibilities, either to do the necessary literature work or to do the reaction development work. The first would require
some effort from your side, while the second would still require the exact same effort plus some experimental work and access to analytical equipment.
Needless to say, just buying or preparing copper chromite is way easier.
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Hexavalent
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Don't bite my head off if I'm wrong, but is heating the acid, perhaps under reflux, an idea; similar to how salicylic acid can be decarboxylated to
phenol in such a manner?
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Nicodem
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| Quote: Originally posted by Hexavalent | | Don't bite my head off if I'm wrong, but is heating the acid, perhaps under reflux, an idea; similar to how salicylic acid can be decarboxylated to
phenol in such a manner? |
Just heating salicylic acid neat is unlikely to give you phenol preparatively. What is the reference for that?
Salicylic acid can be dacarboxylated via the retro-Kolbe-Schmitt reaction, for which you need a base, Ca(OH)2 being the most appropriate as it
additionally functions also as a CO2 scavenger. Nicotinic acid can not undergo this type of decarboxylation as it is not an para/ortho hydroxybenzoic
acid.
I suggest you to search the forum. There was a long discussion on this topic already and I don't feel like repeating myself here.
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Polverone
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Why don't you follow the example from that paper excerpted by madscientist in Magpie's thread and prepare the copper salt of nicotinic acid, then pyridine by pyrolysis from the salt? It is not as efficient as a catalytic
preparation, but it is simpler. According to that paper the decomposition goes quite cleanly. You surely have or could easily make a soluble copper
salt to combine with your niacin. If it works as well in your hands as it does in the paper, you will have contributed a previously undocumented
amateur-friendly preparation of pyridine. If it proves more difficult than expected, you may either refine the process for the challenges you face or
be able to document why this reaction that is simple on paper is actually unsuitable for preparative scale work.
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Hexavalent
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Thanks Polverone, could an acid/base neutralization reaction between the carboxyl group on the nicotinic acid (dissolved into solution) and an
insoluble copper base, e.g. CuCO3 be used to prepare the salt?
Also, what method would be used for the destructive distillation? Just heating the dry solid under a distillation setup?
Thankyou for your help.
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Polverone
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I'd try something like combining solutions of sodium nicotinate and copper sulfate. You could try treating copper carbonate with nicotinic acid
solution too -- it's an easy enough experiment -- but I think the reaction may be slow due to low reactant solubility.
According to the paper, rapid decomposition occurs around 280 C so you should have no problems distilling the dry salt in ordinary borosilicate
glassware.
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