GOD (Hive Addict)
07-22-02 01:29
No 335575
      Pyridoxine -> Pyridine  Bookmark   

Post 215902 (Rhodium: "Re: OTC Pyridine & Acetic Anhydride", Chemicals & Equipment) , Rhodium states a simple decarboxylation to make pyridine out of pyridoxine.  Swim couldnt find a writeup on Rhodiums site, or here.  Any suggestions for a non-chemist?
thank you.

i FEEL funny.
 
 
 
 
    SPISSHAK
(Hive Bee)
07-22-02 05:55
No 335630
      Yes there is a good route  Bookmark   

One of our Russian friends, diafrag, posted a decarboxylation scheme of nicotinic acid using nicotinic acid and Calcium oxide in a 1/1.2 ratio and heating to 320 degess for 1.5 hours.
What I don't understand is the exact mechanism, e.g the carboxylic acid of pyridine here reacts with CaO and common  sense would tell you that water is a by-product and the calcium salt of the carboxylic acid.
Now, how does an ester like this give off CO2 and donate hydrogen to the aromatic ring of the now pyridine when hydrogen was diplaced in the acid/base reaction?
here is the posts regarding that.Diafrag
(ChemLover)
05-27-02 06:12
No 314749
         demethylation   Delete bookmark  Reply    

Demethylation of 3-methoxy-4,5-dioxyphenylethylamine by heating with conc. HCl in a closed ampoule.
K. Hahn, Ber., 71, 2141 (1938) someone can try to find that.

and i've just scanned an article about purification of nicotinic acid by sublimation and decarboxylation it to pyridine by 1,5 hours of heating it at 320C with CaO 1:1.2 in an ampoule. 


Diafrag
(ChemLover)
05-27-02 13:13
No 314880
         decarboxylation   Bookmark  Reply    

the authors of this article had only 6 mg of nicotinic acid they've obtained from some bacteriums and they had to purify it and decarboxylate it to obtain pyridine and prove that it was nicotinic acid. so after sublimating they put their 6 mg of acid and CaO in a ratio 1:1.2 in an ampoule, soldered it and then made a neck in the middle of it. then they bent this ampoule on it's neck about 45. then they put the whole ampoule in a sand bath, gradually increased temp. of the bath to 320C and maintained it for 1.5 hours. then, working with forceps they took the empty bent side of the ampoule and waited for drops to appear in it. then heating was turned off but the aumpule was standing in a bath for 30 min more. then they broke the ampoule and got 86-90% of pyridine. so they decarboxylated acid and distilled the product in one ampoule.

soon i'll post this in russian at my webpage and you will be able to see pictures

http://www.chemlover.narod.ru/articles/article16.djv

So, can somebody possibly explain the mechanism here?

Another thing, I don't know how well babelfish works to translate foreign documents, but I saw an interesting thing at fry's electronics.
It was an infrared pen that you can scan forein documents, plug into the usb port of your computer, and use the downloaded dictionaries from thier website to translate it with.
The pen costs around $200.00
But if I had the money I'd buy it and offer translating services to all of you.

 
 
 
 
    sYnThOmAtIc
(Hive Bee)
07-22-02 05:55
No 335631
      Eheheh, I was reading the label on this powerade ...  Bookmark   

Eheheh, I was reading the label on this powerade I was drinking the other day and saw pyridoxine.hcl on the label and wondered if this was related to pyidine (cause of the name) so that it may be isolated for some microwave chem experimentation. ANd shit what do you know! Ok lets lee artificial sweetener form coke can lead to methamphetamine precursors and powerade energy juice a useful chemical in many synths. Hmm what fucked up food additives we have these days.
 
 
 
 
    SPISSHAK
(Hive Bee)
07-22-02 08:59
No 335690
      let's see  Bookmark   

If I can't answer this, I heard that the by-product is a dimer of pyridine, and just maybe it isn't an acid base reaction in the brownstead-lowry sense because no water is around to promote ionic disassociation?
 
 
 
 
    GED
(Hive Addict)
07-22-02 12:11
No 335737
      Vitamin Confusion  Bookmark   

Between this thread and thread number Post 215008 (Eeyoredonkey: "OTC Pyridine & Acetic Anhydride", Chemicals & Equipment) 4 different vitamins appear to have been mentioned, as though they were the same thing.

Just for the record------

niacin, nicotinic acid = Vitamin B3
pyridoxine (hcl)       = Vitamin B6
pantothenic acid       = Vitamin B5
cobalamin              = Vitamin B12

 Anyone who can find a valuable use for kilos of out of date bulk Pyridoxine hcl (B6), please make suggestions.smile

 MadMax Post 218782 (MaDMAx: "Re: OTC Pyridine & Acetic Anhydride", Chemicals & Equipment) "Pyridoxine doesn't have anything to be decarboxylated."
 
 
 
 
    SPISSHAK
(Hive Bee)
07-22-02 17:31
No 335799
      why your right that's why I just say nicotinic  Bookmark   

acid, anyone know a mechanism for this?
 
 
 
 
    GOD
(Hive Addict)
07-22-02 19:51
No 335826
      Spisshack, wait your turn- havent awnsered my ?yet  Bookmark   

tonguetongue


whoever awnsers, could you please bee specific, I origionally asked about pyridoxene hcl.

Rhodium...there appears to bee a difference in opinion between you and MaDMAx regarding this.

i FEEL funny.tongue
 
 
 
 
    blondie
(Hive Bee)
07-23-02 01:18
No 335942
      pyridoxine  Bookmark   

At least according to chemfinder there is no carboxylic group on pyridoxine. Foxy2 found a ref for decarboxylating nicotinic acid which is 3 Pyridine carboxylic acid. see Post 223562 (foxy2: "Re: pyridine from decarboxylation of niacin?", Chemistry Discourse)
 
 
 
 
    SPISSHAK
(Hive Bee)
07-25-02 15:42
No 336928
      do you think  Bookmark   

the other method will work with calcium oxide?
 
 
 
 
    SPISSHAK
(Hive Bee)
09-03-02 00:22
No 351965
      Anyone have chemweb account?  Bookmark   

Get the full article and post it as a reply to this beilstien abstract?
It should clear up a lot of questions about the transition states, and thermodynamics of a Calcium nicotinate salt decraboxylation.


A Study on Solid State Thermal Decomposition Characteristics of Some Metallo-organic Compounds. Part-I : Dehydration and Decarboxylation of Hydrated Calcium Salts of Pyridine Monocarboxylic Acids
AUTHORS Ghosh, S.; Ray, S. K.; Ray, P. K.; Bandyopadhyay, T. K.
SOURCE J.Indian Chem.Soc. 1982, 59: 9 1034-1037
DOCUMENT TYPE Journal
CODEN JICSAH
LANGUAGE EN
CNR 5860857
ABSTRACT Solid stete dehydration of hydrated calcium salts of picolinic acid, nicotinic acid and isonicitinic acid and subsequent decarboxylation of the corresponding anhydrous salts have been studied by simultaneous TG, DTA and DTG techniques.From the analysis of the TG,DTA and DTG traces for the dehydration of the hydrated salts, the thermal stability order of the hydrates have been found to be Ca(pic)2*H2O > Ca(isoNic)2*4H2O > Ca(Nic)2*3H2O.But the trend observed in the decarboxylation process is Ca(Nic)2 > Ca(isoNic)2 > Ca(pic)2.Thermal parameters like activation energy, enthalpy change and order of reaction for each process have been computed by standard methods.An attempt has been made to correlate the trend in the thermal stability of the anhydrous salts towards decarboxylation with their molecular structure.
COPYRIGHT Copyright 1988-2001, Beilstein Institut fr Literatur der Organischen Chemie licenced to Beilstein Chemiedaten und Software GmbH and Beilstein Informationssysteme GmbH. All rights reserved.
 
 
 

 


 
 
 
 
    SPISSHAK
(Hive Bee)
09-05-02 07:19
No 352903
      Puuullllesssee!  Bookmark   

Pretty please, with a cherry on top, and sugar all around?
 
 
 
 
    weedar
(Verbose Viking)
09-05-02 17:23
No 353019
      I'm working on it!  Bookmark   

I tried finding it earlier today,with no luck..All I found
is the abstract,just give me some time..wink

Edit:Anyone who feels like telling me how I can get
the whole journal instead of just the abstract,please tell
me?I have a chemweb account,isn't that enough?I can't even
find the entire articel..


Weedar

Me fail English?That's unpossible!
 
 
 
 
    Rhodium
(Chief Bee)
09-05-02 18:29
No 353032
      The Journal of the Indian Chemical Society is not ...  Bookmark   

The Journal of the Indian Chemical Society is not available online, so you will have to go to your nearest University Library to make a copy of that article.
 
 
 
 
    SPISSHAK
(Hive Bee)
09-05-02 21:41
No 353110
      Well thank you  Bookmark   

For your effort anyhow fellows.
 
 
 
 
    weedar
(Verbose Viking)
09-06-02 13:39
No 353434
      Tomorrow  Bookmark   

I might visit my local university library tomorrow(Saturday)
so if no-one else posts the article I'll try getting it..wink

Weedar

Me fail English?That's unpossible!
 
 
 
 
    weedar
(Verbose Viking)
09-14-02 22:09
No 356334
      J. Ind. Chem. Soc.:Decarboxylation of pyridine
(Rated as: excellent)
 Bookmark   

J. Ind. Chem. Soc.:Decarboxylation of pyridine

Sorry for taking so much time,I've been busy,but I really
don't have an excuse,here it is:





A Study on Solid State Thermal Decomposition Characteristics of Some Metallo-organic Compounds.
Part-I: Dehydration and Decarboxylation of Hydrated Calcium
Salts of Pyridine Monocarboxylic Acids



Solid state dehydration of hydrated calcium salts of picolinic acid, nicotinic acid and isonicotinic acid and

subsequent decarboxylation of the corresponding anhydrous salts have been studied by simultaneous TG, DTA
and DTG techniques. From the analysis of the TG, DTA and DTG traces for the dehydration of the hydrated salts, the thermal

stability order of the hydrates has been found to be Ca(pic)2 . H2O > Ca(isoNic)2 .

4H2O > Ca(Nic)2 . 3H2O. But the trend observed in the decarboxylation process is

Ca(Nic)2 > Ca(isoNic)2 > Ca(pic)2. Thermal parameters like activation energy,

enthalpy change and order of reaction for each process have been computed by standard methods. An attempt has been made to

correlate the trend in the thermal stability of the anhydrous salts towards decarboxylation with their molecular

structure.





The calcium salts were prepared by the reaction of a slight excess of CaCO3 (G.R., E. Merck) with the appropriate

acids in hot aqueous solutions followed by filtration and subsequent crystallisation.


Simultaneous DTA, TG and DTG determination of the salts were carried out with a Paulik-Paulik-Erdey type MOM Derivatograph

with dry air as the atmospheric gas. The particle size of the samples was in the 100-150 mesh range. The heating reate was

about 4.25 per minute and sample size of 180-210 mg was used to make the volume nearly the same in each case. The referenc

material was aluminium oxide previously heated to 1600. The sample holder and the reference holder were made of platinum. TG

curves were utilised for calculating the activation energies of the processes involved, whereas DTA curves were used to

evaluate the enthalpy changes accompanying the reactions. The inital, peak and final temperatures for the dehyration and the

decarboxylation processes were noted from the corresponding DTG curves. The hydrated calcium salts and their dehydrated

varieties were characterised by recording their ir spectra in halocarbon mull on a Beckman IR 20A model spectrophotometer.

All the hydrated and the anhydrous compounds were analaysed for calcium by titration with a standard EDTA solution. Carbon,

hydrogen and nitrogen were determined by microanalytical techniques.


Results and Discussions

Dehydration process: On gradual heating from room temperature, the hydrated salts were completely dehydrated within

the temperature range 39-240. From the TG, DTG and DTA traces of the dehydration stage it was found that all the

dehydrations occurred in one step. All these processes might be represented by the general equation:

Ca(C6H4NO2)2 . x H2O =

Ca(C6H4NO2)2 + x H2O ; when X = 1 ,

C6H4NO-2 = picolinate ion ; X = 3 , C6H4NO-2 = nicotinate

ion ; x = 4 , C6H4NO-2 = isonicotinate ion.
Initial, peak and final temperatures of the dehydration of each species, as obtained from the relevant DTG curves along with

the corresponding weight loss are given in Table 1. Enthalpy changes accompanying dehydration of each species were determined

by standard methods from the peak area of the corresponding DTA curves using CuSO4 . 5H2O as the

standard1. Activation energies for each dehydration process were computed from an analysis of the corresponding TG

curves using the method of Horowitz and Metzger2 and the

ln ln W-Wft vs plots are presented in Fig 2.
     --------
     W-Wft
Note:substitue '' for the greek letter theta,I didn't understand how to type here since it isn't an ANSI

character.


The order of reaction was determined by standard methods2,3 and was found to be unity. The results obtained are

presented in Table 1 and the corresponding curves presented in Fig. 1. IR spectra of the hydrated and the anhydrous varieties

were recorded and compared to ascertain the completion of the dehydration process.

Decarboxylation processes: All the anhydrous salts exhibit considerable thermal stability and undergo decarboxylation

within the temperature range 340-600. Initial, peak and final temperatures for the decarboxylation processes of the

anhydrous salts along with the corresponding weight losses are given in Table 2. The final product left in the crucible was

found to be CaCO3. This has been confirmed by comparing the X-ray diffraction pattern of the end product with that

of a pure CaCO3 sample. Applying the same methods used in the dehydration processes, activation energies of the

decarboxylation processes were evaluated from the

ln ln W-Wft vs plots, given in Fig 3.
     --------
     W-Wft

Enthalpy changes accompanying each decarboxylation process were measured from the DTA cruves and are presented in Table 2.

the order for the decarboxylation reaction was found to be unity in all the three cases. The corresponding curves are

presented in Fig. 1.




I'm supposed to put two tables here,but I'm having some trouble,will post them later..




Solid state thermal decomposition of the salts of aromatic or heterocyclic acids has received little attention from the

kinetic point of view. Most of the workers, who studied the thermal decomposition of the salts of organic acids (mostly

aliphatic acids) in the solid state, used the maximum point method4-6 and the Freeman-Carrol method7

for the determination of the kinetic parameters. In the present work we have utilised Horowitz and Metzger's method, an

analytical technique which utilises a single TG plot to determine the pertinent Arrhenius parameters and reaction order. The

values obtained by the application of this method have been verified  by the Coats and Redfern8 method wherever

possible. We have utilised the DIA curves for the evalution of enthlpy changes for the dehydration as well as decarboxylation

processes.

The single step dehydration of calcium nicotinate trihydrate and the calcium isonicotinate tetrahydrate indicated that all

the water molecules in the nicotinate trihydrate are similarly bound and such is also the case with the water molecules in

the calcium isonicotinate tetrahydrate. A single endotherm in each of the DTA curves definitely points to the accuracy of the

above conclusion. In the single step dehydration of all the three hydrates represented by the general equation in Table 1,

the activation energies and enthalpy changes of dehydration are in order picolinate > isonicotinate > nicotinate. This

difference in thermal stabilities of the hydrates may be attributed to the differences in the mode of binding of the water

molecules in the crystals of the three different pyridine monocarboxylates. It may thus be concluded that the water molecules

in calcium picolinate are more firmly bound than those in isonicotinate and nicotinate and the water molecules in the calcium

isonicotinate are held more stronlgy in comparison to those present in the calcium nicotinate.
In the decarboxylation of the anhydrous salts represented by equations given in Table 2, the activation energy follows the

order nicotinate > isonicotinate > picolinate. The enthalpy change in the decarboxylation process also follows the same

order.

It may be concluded from the data in Table 2 that the thermal stabilities of the carboxylates follow the order nicotinate >

isonicotinate > picolinate. This trend is quite logical as the negatively charged carboxylate ion has a + I

effect8 and hence releases electrons with a consequent increase of electron density on the ring carbon atom which,

if present in a benzene ring, would have stabilized the ring carbon-carboxyl carbon bond. But in the present case, as the

ring is a heterocyclic ring, the nitrogen atom being much more electronegative than carbon, would change the situation

significantly and we find that unlike benzene, electron density distribution in the pyridine ring9 is as follows:

0.95   /----\ 0.85
       /         \
0.82 \         / 1.58
        \____/

Due to the ortho-para orienting influence of the carboxylate ion the positions ortho and para to the
ring carbon containing the carboxylate ion will have greater electron density and in the case of calcium picolinate, where

the electronegative nitrogen atom is present in the position ortho to the ring carbon containing the carboxylate ion,

it conveniently draws away this excess electron cloud towars itself and consequently reduces the electron cloud accumulated

on the adjacent ring carbon atom considerably. It thus weakens the ring carbon-carboxylate carbon bond to a significant

extent making it comparatively thermolabile.


In the case of the 4-picolinate anion, the enhanced electron density in the position para with respect to the

carboxylate ion is accomodated on the nitrogen atom as a result of which the 4-carbon atom is relieved of some of its

electron cloud acquired from the carboxylate anion and results the weakening of the ring carbon-carboxyl carbon bond and

consequently induces thermolability. But overall destabilisation effect is greater in 2-picolinate than in 4-picolinate due

to the closeness of the ring nitrogen to the carboxylate substituet in the former and makes the 4-picolinate thermally more

stable than the 2-picolinate compound. In  the case of the 3-picolinate, the ortho-para orienting carboxyate ion would

again result in electron enrichment in the ortho and para  positions leaving the meta position

unaffected. Thus, the increased electron density on the ring carbon atom containing the carboxylate ion is not decreased in

this case. This leads to the stabilisation of the ring carbon-carboxyl bond when compared to the 2- and 4-picolinates and

makes the 3-picolinate thermally stabler than the other two. Thus, the thermal stability order nicotinate > isonicotinate >

picolinate, observed in this study, is quite in accordance with the theoretical principles.



References

1. K. Sano, Sci. Rep. tohuku, Imp. Univ., 1st Ser., 1936, 24, 719.

2. H. H. Horowitz and G. M. Metzger, Anal. Chem., 1963, 35, 1464.

3. A. W. Coates and J. P. Redfern, Nature, 1964, 201, 68

4. K. Akita and M. Kase, J. Polymer Sci., 1967, A1, 833.

5. J. H. Flynn and L. A. Wall, J. Res. Nat. Bur. Stand., 1966, 70A, 487

6. R. M. Fuoss, I. D. Salver and H. S. Wilson, J. Polymer Sci., 1964, A2, 3147

7. E. S. Freeman and B. Carrol, J. Phys. Chem. Ithaca, 1959, 62, 394

8. J. March, "Advanced Organic Chemistry: Reactions, Machanisms and Structure", McGraw-Hill, 1968, p. 21.

9. I. L. Finar, "Organic Chemistry", ELBS and Longmans, Green, 1964, Vol 1, p. 760.



Sorry,I'll have to post the 2 missing tables tomorrow,I won't bee posting the two Figures,doubt they are useful and
my photocopies aren't very good.BTW,SPISSHAK,you owe me $1.5
wink

Weedar

Me fail English?That's unpossible!
 
 
 
 
    weedar
(Verbose Viking)
09-15-02 23:39
No 356654
      Missing Tables  Bookmark   

Trying hard to make the rows align with the columns,I
give up,hope you all can understand it though,or tip me off
how I can post tables with the Board software(psst Lilienthal!)..

Table 1



Reaction | Initiation | Peak     |Completion| Loss in wt. % | EACT       | Delta-H     | Order of |
            | temp.C | temp.C | temp.C  | Calcd. Found | Kcal/mole | Kcal/mole | reaction |

         
Ca(C6H4NO2)2.3H2O -> Ca(C6H4NO2)2+3H2O   39   90   120   15.97   16   15.55  46.37   1
Calcium nicotinate hydrate
Ca(C6H4NO2)2.4H2O -> Ca(C6H4NO2)2+4H2O   82   130   215   20.22  20   22.96   62.07   1
Calcium isonicotinate tetrahydrate
Ca(C6H4NO2)2.H2O -> Ca(C6H4NO2)2+H2O    160   193   240   5.96  5.88   52.13   26.24   1
Calcium picolinate monohydrate


Table 2 have the exact same names of the columns in Table 1..

Table 2



Ca(C6H4NO2)2 -> CaCO3 + products   432   560   622   64.78  60.84   76.14   166.3   1
Calcium nicotinate
Ca(C6H4NO2)2 -> CaCO3 + products   385   486   620   64.78  64.83   50.85   44.46   1
Calcium isonicotinate
Ca(C6H4NO2)2 -> CaCO3 + products   380   442   540   64.78  65.38   14.86   20.37   1
Calcium picolinate

Me fail English?That's unpossible!