Author Topic: Gassing pyridine with HCl  (Read 3923 times)

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  • Guest
Gassing pyridine with HCl
« on: December 10, 2002, 08:12:00 PM »
When pyridine is gassed directly with anhydrous HCl, the tube that delivers the gas(ID=0.25 cm)quickly clogs with pyridine HCl.  The tube was switched for a larger ID tube (0.5cm)and it still clogs. Swim has experienced a similar senario with the gassing of honey in toluene but has gotten away with just increasing the ID of the delivery tube.

A steady stream of gas is delivered which one would think would be sufficient to maintain the air way. This is not the case with pyridine.

Are there any other tricks to gassing a substance that salts out so quickly?  If the pyridine was "diluted" in a solvent that doesn't dissolve the resultant salt, would it be possible to slow its formation upon contact with the gas?

Thank you
c :)

Don't drug the mind-let the mind use the drug-it won't mind.


  • Guest
You cannot gas pyridine without using a solvent.
« Reply #1 on: December 10, 2002, 09:38:00 PM »
You cannot gas pyridine without using a solvent. You aren't gassing MDMA freebase without a solvent, right?


  • Guest
« Reply #2 on: December 11, 2002, 10:44:00 AM »
suggested solvent?  toluene/xylene/DCM?  aurelius would probably use DCM for ease of removal.


  • Guest
Preparative methods
« Reply #3 on: December 11, 2002, 11:30:00 AM »
Preparative methods
"Precipitates as a 98% yield of 99.8% pure white crystals when hydrogen chloride gas is passed through a solution of pyridine in ether1,2"

[1] Prey, V. CB 1942, 75, 445
[2] Taylor, M.D. Grant, L.R. J. Chem. Educ. 1955, 32, 39

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  • Guest
Pyridine HCl without gassing.
« Reply #4 on: December 11, 2002, 05:35:00 PM »
Following a procedure from rhodiums page, 10ml of pyridine was added to 12.5ml of conc. HCl.  The mixture was heated to evaporate off the water and after reducing the volume of the mixture to about 15ml volume mark on the beaker, it was removed from the heat and cooled.  Prior removal of heat, the vapour coming from the mix was thick, white, noxious of pyridine, unlike the clear vapour produced by evaporated water.  Pyridine HCl crystallized as a waxy light brown solid. The solid was extremely hydroscopic in much the same way methylamine HCl is.  An attempt was made to clean the product with DCM rinses, however there was little improvement.  Further purification could be had through recrystallization.  The product (with a brown tinge) did not look as clean as that produced by the previous attempt at gassing without solvent which appeared as a pure white solid clogging the dipersion tube. 

Swim believes that HCl gassing is just as inconvenient as dealing with the noxious fumes produced by the above method for the production of pyr HCl. Furthermore, additional purification steps will be required to achieve the same purity of product as that produced by HCl gassing.

In conclusion, it seems that producing pyridine HCl by gassing pyridine in DCM will will be both easiest and will provide the most pure product.

Thanks to the bees's for the input!


Don't drug the mind-let the mind use the drug-it won't mind.