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Author: Subject: Pyridine synthesis/extraction
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smile.gif posted on 28-12-2007 at 16:52
Pyridine synthesis/extraction


Hi!

Does anyone here know a good synthesis of pyridine from extremly OTC-chemicals like B6, nicotine or similar things? In "ancient" times it was made by dry destillation of bones.
In my opinion (which isn't much influenced by very much knowledge of bones btw.) this dry destillation is a pyrolysis reaction of some proteins. Maybe there is another source for these kind of proteins...

I would be grateful for any help!
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[*] posted on 28-12-2007 at 17:58


Use the search engine before starting a thread

http://www.sciencemadness.org/talk/viewthread.php?tid=9650

http://www.sciencemadness.org/talk/viewthread.php?tid=286
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[*] posted on 28-12-2007 at 22:01


its partially responsible for the smell of coffee i hear.....
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[*] posted on 28-12-2007 at 22:47


Ew, now that you mention it, I kind of can detect that odour! Thanks for ruining coffee for me :-/



In all fairness to SpeechDiscussionTalk, we do not have a good thread on the synthesis of pyridine or the acquisition from common OTC chemicals.
Don't look to me for information though, I'm no organic chemist, but I know there are people here who know how to synthesize it or extract it (that should be easy).

I remember it being mentioned that pyridine is used as a denaturant in ethyl alcohol, but in what proportions, I do not know.

Pyridine is useful indeed, many wonderful complexes can be made from it (oxidizing agents, halogenating agents) and it also serves a catalytic function in many reactions.

So why not discuss it some? I think it would be easy to buy, but why not try making it for the sake of making it?




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[*] posted on 29-12-2007 at 00:04


Pyridine is produced industrially by the reaction of acetaldehyde, formaldehyde and ammonia at elevated temperature and pressure over a catalyst. The three isomeric picolines are formed simultaneously and the products fractionated.

There are other processes, but none of them OTC and all of them quite industrial.

[Edited on 29-12-2007 by Sauron]




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[*] posted on 29-12-2007 at 04:11


The decarboxylation of niacin seems to be a good method to make pyridine. Is the decarboxylation of a compound like niacin anything else than making the the Ca-salt and gentle heating until it slowly decomposes? Should i take some other things into account i forgot, or is it really that simple from niacin?
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[*] posted on 29-12-2007 at 04:36


I dont believe this gives a measurable yield. Decarboxilating in the 3-position is much harder than in the benzene ring due to electron deficiency there, is my understanding. Plus I have not seen such a reaction in any standard texts, rather the much more complicated condensation of acetaldehyde, formaldehyde and ammonia. Len

[Edited on 29-12-2007 by len1]
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[*] posted on 29-12-2007 at 04:42


Yields aren't great, you'll get some bipyridines/bipyridyls and other stuff, so you'll need to fractionate the product. The actual temperature needed can be rather high, see the benzene from benzoic acid threads, including the on in Prepublication.
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[*] posted on 29-12-2007 at 19:02


1.5 g nicotinic acid and 2.5 g CaCO3, when heated to decarboxylation with a bunsen burner give 0.3 ml pyridine :P



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[*] posted on 29-12-2007 at 19:17


Well now youve got me interested, I shall ahve to try this out!
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[*] posted on 29-12-2007 at 19:39


I'm more interested in having a shot at the high temperature route with the aldehydes and ammonia. Apologies in advance for being damn lazy, but what pressure does it run at? If it's a few atm. I can go for it, anymore though and out of my league it will be.



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[*] posted on 29-12-2007 at 20:12


Quote:
Originally posted by leu
1.5 g nicotinic acid and 2.5 g CaCO3, when heated to decarboxylation with a bunsen burner give 0.3 ml pyridine :P


Surely you mean decarboxylation with Ca(OH)2 to give CaCO3. I cant see how CaCO3 will give you anuthing until it gets 'decarboxylated' itself at 700-900C! But there wont be much organics left at that temperature... Im afraid ive got my doubts again ...
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[*] posted on 31-12-2007 at 12:38


Pyridine on eBay.
1L
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=120204...
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[*] posted on 31-12-2007 at 17:48


Quote:
Surely you mean decarboxylation with Ca(OH)2 to give CaCO3. I cant see how CaCO3 will give you anuthing until it gets 'decarboxylated' itself at 700-900C! But there wont be much organics left at that temperature... Im afraid ive got my doubts again ...



Decarboxylation is a well known chemical reaction, the site where that information came from isn't on the internet anymore so you can either accept it or reject it; it matters little in the grand scheme of things :P The person who originally posted it is a well known member who can verify that he did if he wants to, but such spoon feeding seems unlikely :D It's been discussed at another forum known to many of the members:

http://www.roguesci.org/theforum/showthread.php?t=3289&h...

http://www.roguesci.org/theforum/showthread.php?s=9684ba78f1...

There at least a dozen other little known methods such as:

Patent DE944251

Example 2

A solution of 200 parts 1,5-pentanedial in 800 parts 3% sulfuric acid is added, over the course of 2 h, to a boiling solution of 1100 parts crystallized Fe2(SO4)3 and 200 parts (NH4)2SO4 in 1500 parts water. Workup as in example 1 yields 82% pure pyridine.

workup as in example 1: rxn-mixture is made alkaline and the aromatic base is distilled off.


and

While hydrogenations of pyridine forming piperidine have been the topic of many posts; the corresponding dehydrogenation of piperidine forming pyridine seems to have escaped notice so far. This reaction can be carried out either by heating to 300° with concentrated sulphuric acid, or with nitrobenzene at 200°; or with silver acetate in acetic acid :) An old preparation of piperidine is by heating pentamethylenediamine hydrochloride (cadaverine); which is the result of putrefactive enzymes on lysine. Cadaverine is quite toxic in addition to being very obnoxious, but the hydrochloride salt isn't so toxic. An alternative synthesis can be found in Ber 56 625-30 (1926):

[Edited on 2-1-2008 by leu]

Attachment: pummerer.djvu (126kB)
This file has been downloaded 897 times





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[*] posted on 31-12-2007 at 20:39


The ZIP file appears to be broken, near the end of it in the central directory the "version made by" offset is bad, looks like the zip creator stuttered and had 0x1414 instead of 0x0014. What was used to create it?

As it is a DJVU file, zipping it saves little if any space. If the zip was needed to get the board software to take it, that's one thing and perhaps the board could be configured to accept .djvu files, otherwise it might be better not to zip single .djvu files.
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[*] posted on 31-12-2007 at 21:21


We are having similar hassles in References. arkansas posted a zip file to me, no good. And a zip file to Rosco_Bodine also no good.

kmno4 was eventually able to recover the pdfs from Rosco's zip but, only after a lot of effort.

As for my requested files I am awaiting arkansas to kindly repost them without compression. As they are already pdf's, the only point of zipping is to make one file out of two, but useless if it fucks them up, as something seems to be doing.




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[*] posted on 1-1-2008 at 10:23


Quote:
Originally posted by leu An alternative synthesis can be found in Ber 56 625-30 (1926)


------------------------------------------------------------------------------------------

Über eine verbesserte Methode zur Darstellung von Diaminen und Amino-alkoholen
N. Putochin:
Berichte der deutschen chemischen Gesellschaft (A and B Series Volume 59, Issue 4 (p 625-630), 1926

Attachment: Über eine verbesserte Methode zur Darstellung von Diaminen und Amino-alkoholen (p 625-630) .pdf (434kB)
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[*] posted on 1-1-2008 at 18:29


IZArc was used to zip the deja vu file, the forum software is corrupting zip files :( Pyridine is produced from the reaction of pyrrole and carbene; and Tschitschibabin published his laboratory studies of various syntheses of pyridines made by passing ammonia and aldehyde vapors over granular alumina between 200 to 350 º C in JCS Abstr 1906, i, 451; 1915, i, 638; 1923, i, 1121-3 :) He obtained pyridine itself from the vapors of acetaldehyde and acrolein with ammonia over alumina in these experiments :D



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[*] posted on 2-1-2008 at 08:41


I have yet to see a reaction where pyridine can not be substituted with another mild base (unless of course pyridine is used as reaction substrate). Besides any method of its preparation is uninteresting as long as it is so cheap and so easily available (you can find it in just about any organic lab).
But if it is just for the fun of preparing it, I guess nicotinic acid could be used. Though using CaCO3 (no need for Ca(OH)2 here, since nicotinic acid is an acid, as the name implies anyway, and CaCO3 is a base) seems a bit counterintuitive since it is well known that the thermolysis of calcium carboxylates gives mainly the products of decarboxylative ketonization and nearly no products of decarboxylation. For example, heating calcium acetate gives mainly acetone and not methane as one would expect from the analogy of the reaction: NaOCOCH3 + NaOH => Na2CO3 + CH4; or the analogous: NaOCOPh + NaOH => Na2CO3 + PhH. So, I would tend to believe the thermolysis of calcium nicotinate gives more bis(3-pyridyl) ketone than it would give pyridine. Though perhaps no ketonization occurs with carboxylic acids lacking any alpha hydrogens. Still, rather give it rather a try with the more classical thermolysis of sodium carboxylates in NaOH as it so well described for benzoic acid on this forum.




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[*] posted on 2-1-2008 at 13:19


Everything is an acid and everything is a base - its just a question of how strong.

Nicotinic acid is a weak acid, weaker than benzoic because the nitrogen withdraws electrons from the ring, and CaCO3 is a weak base, the weaker the base the lower te yield in what is already a very low yield process. Try CaCO3 with benzoic acid.

[Edited on 2-1-2008 by len1]
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[*] posted on 3-1-2008 at 03:43


I just remembered that decarboxylative ketonization proceeds also with acids lacking the alpha hydrogens (at least in the case of mixed calcium formate/benzoate which gives benzaldehyde). So I would skip idea of using calcium carbonate and try with NaOH according to the method used for benzoic acid.

Quote:
Originally posted by len1
Nicotinic acid is a weak acid, weaker than benzoic because the nitrogen withdraws electrons from the ring, and CaCO3 is a weak base, the weaker the base the lower te yield in what is already a very low yield process. Try CaCO3 with benzoic acid.


Nicotinic acid is indeed somewhat less acidic than benzoic acid (pKa 4.9 vs. 4.2). But that is not because electron withdrawal since electron withdrawing groups on benzoic acids increase their acidity (as long as there is no neighboring effect in o-substituted ones – like in salicylic acid, for example). For example, you can compare: p-NO2-benzoic acid (pKa 3.44), m-NO2-benzoic acid (pKa 3.45), o-NO2-benzoic acid (pKa 2.17), benzoic acid (pKa 4.20), p-MeO-benzoic acid (pKa 4.47).
Also, you confuse the proton transfer reactions in aqueous solution with what appears as an acid-base reaction among solids in melt (as is the case here). If one of the products is a gas (CO2 in our case) then the reaction will proceed almost regardless how strong the acid and base are since the reaction equilibrium will not be dependant on proton affinity, but on the removal of the volatile component (CO2). This is how glass is made from SiO2 and alkali carbonates even though silicates are more basic than carbonates - the reaction proceeds by the removal of CO2 and not as acid/base equilibrium. Another inorganic example is the reaction of boric acid (a very weak acid) with carbonates at high temperatures.




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[*] posted on 3-1-2008 at 18:33


1) In your previous post you stated CaCO3 is a good reagent to decarboxylate niacin because its a base, now you are stating its got nothing to do with it - it actually just CO2 formation that drives equilibrium.

2) Sorry - electron withdrawl from the ring does make the COOH group more acidic, however you are out of luck with niacin - COOH is in the meta position and nitrogen lone pair mops up the protons.

3) Acidity isnt just of relevance in aquesous solutions

4) Things are actually a lot more complicated. Both drive the reaction. If it was just gas formation then CaCO3 is not needed, but the decarboxylation will occur at way too high T to save the pyridine - thats why a base is added in the reaction, it lowers delH and the reaction proceeds at a lower temp The stronger the base - the better - (thats actually part of the the reason for your observation that Ca(OH)2 doesnt decarboxylate as well as NaOH).

5) Take a close look at what you are proposing:

niacin + CaCO3 -> Pyridine + CO2 + CaCO3

CaCO3 contributes nothing to the delH of the reaction - you are suggesting it as a catalyst. Good luck with the reaction.

[Edited on 4-1-2008 by len1]
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[*] posted on 4-1-2008 at 03:19


1.) Obviously, you misunderstood my post since I was saying just the opposite. I was commenting Leu's citation about nicotinic acid decarboxylation over CaCO3, expressing my opinion that the use of CaCO3 is a bad choice if pyridine is the target product since it is well known that the main path in calcium carboxylates thermolysis is not the decaboxylation but decarboxylative ketonization instead (see the attached review if you are unfamiliar with this reaction). Hence the main product would not be pyridine but bis(pyridin-3-yl) ketone (aka dipyridin-3-ylmethanone). In such ketonizations the base can indeed be used as catalyst since it is unaffected by the reaction (see the example using ThO2 in Vogel's). When such catalytic methods are not used, the carboxylates of Ca, Ba, Pb, Fe and other multivalent metals are preprepared from the corresponding carbonates or hydroxides and then subjected to the thermolysis yielding the corresponding ketones.
But if decarboxylation is the desired path, one better stick to the original conditions using NaOH in excess (like I already said). There is a mechanistic explanation on why excess hydroxide is required (you can also use thermodynamic arguments like you did, but I prefer mechanistics). And according to this reaction mechanism, the reaction can not proceed equally with CaCO3.

2.) Pyridine is not a substituted phenyl ring. Your comparison makes no sense. The electronic characteristics of pyridinyl group are different from the phenyl group. Hence the pKa of nicotinic acids are not the same as for benzoic acid, neither are they comparable from the substitution point of view (also, substituents on the meta position of benzoic acid do influence the acidity through inductive effect; see the examples in my previous post). I was not explaining the origin of their difference, but merely correcting your erroneous statement: "Nicotinic acid is a weak acid, weaker than benzoic because the nitrogen withdraws electrons from the ring". What I also found strange in your comparison with benzoic acid is in that you seem to claim that benzoic acid would form the carboxylate with CaCO3 while nicotinic acid wouldn't, even though the benzoic acid is only 5 times more acidic than nicotinic acid.

3.) Never said it is of relevance only in aq. solutions. Proton transfers occur in all kind of solvents, just the proton affinity changes with the solvent properties. I just said that you should not only count the acid/base equilibrium where there are present also other equilibriums that drive the reaction to competition.

4 and 5.) I was proposing:

A.) 2 {pyridin–3-yl}–COOH + CaCO<sub>3</sub> => Ca(OOC–{pyridin-3-yl})<sub>2</sub> + CO<sub>2</sub>

B.) Ca(OOC-{pyridin-3-yl})2 => CaCO3 + {pyridin-3-yl}–CO–{pyridin-3-yl}

… and side products among which there might be pyridine as indicated from Leu's post.

Obviously the reaction A proceeds without problems at the temperature where the nicotinic acid melts (238°C; though it is probably over by that T since the partial pressure of nicotinic acid is not zero at temperatures lower than that). The reaction B also requires temperatures higher than 200°C, generally 300-400°C.

Attachment: Ketonization of Carboxylic Acids by Decarboxylation_Mechanism and Scope.pdf (154kB)
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[*] posted on 4-1-2008 at 03:52


I think weve reached the point of diminishing returns - youve stated your position Ive stated mine. Fortunately this isnt abstract psychology, the reaction is simple enough to be tested, putting the misunderstandings aside, there are real differences between what you and I say.

PS I mentioned CaCO3 + benzoic acid in jest, sure I dont expect it to work. Plus the fact that niacin resists decarboxilation, is in the literature, precisely because its in the meta position.

PSS I dont expect substituted benzene and pyridine rings to be identical, where do I say that? But the principle of resonance structures applies equally to both!

Now if there is an actual testable disagreement it is this:

You expect

benzoic acid + Na2CO3 -> benzene + CO2 + Na2CO3

to yield well, just as

benzoic acid + 2NaOH -> benzene + CO2 + Na2CO3 + H2O

I expect much better results in the later, for the reasons I have outlined (but you havent understood).

we shall see..


[Edited on 4-1-2008 by len1]
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[*] posted on 4-1-2008 at 05:02


Quote:
Originally posted by len1
Now if there is an actual testable disagreement it is this:

You expect

benzoic acid + Na2CO3 -> benzene + CO2 + Na2CO3

to yield well, just as

benzoic acid + 2NaOH -> benzene + CO2 + Na2CO3 + H2O

I expect much better results in the later, for the reasons I have outlined (but you havent understood).

we shall see..

Read my previous post again. I said exactly the opposite, that:
benzoic acid + Na2CO3 -> benzene + CO2 + Na2CO3"
does not go because benzophenone is the main product! <-wrong, see bellow

Edit:
Sorry, this time it was me who misread your post. I thought the above was about "benzoic acid + CaCO3". I don't know why you brought out Na2CO3 when the issue was about CaCO3, but in the case of "benzoic acid + Na2CO3" the main products should be benzene, sodium phthalate and other byproducts, depending also on the temperature, closed/open system, O2 and H2O presence, etc.. Benzophenone forms only when the calcium salt is used where ketonization is the main pathway. In the themolysis of sodium benzoate less than 3% of conversion is accounted to the ketonization, while the themolysis of the potassium salt is even cleaner, yielding only benzene and potassium phthalate in 4.75 : 1 ratio. On the contrary, calcium benzoate yields benzene and benzophenone in a 2 : 1 ratio in a closed deareated system at 400-500°C (the formation of benzene is attributed to the presence of moisture in the starting material – obviously there is no explanation for its formation unless a proton donor is present). See: Energy & Fuels, 19 (2005) 365–373 and references therein for a better understanding.

[Edited on 4/1/2008 by Nicodem]




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