Sciencemadness Discussion Board

Destroying N-methylpyridinium Chloride with Fenton's Reagent ?

nimgoldman - 25-1-2020 at 19:31

I plan to use pyridine and pyridine hydrochloride (Py.HCl) in O-demethylation, e.g.:

R-O-CH3 + nPy.HCl -> R-OH + (n-1)Py.HCl + Py.CH3Cl

The problem is how to dispose the Py.CH3Cl (N-methylpyridinium chloride).

It seems to be highly soluble in water and maybe Fenton's Reagent could be used to destroy it? It works on pyridine and benzene, but I have no idea how it would work on such quaternary salt... What would be the final product?

nimgoldman - 26-1-2020 at 08:25

My best guess so far was to neutralize the rxn. mixture with NaOH - turning the methylpyridinium halide to perhaps methylpyridine and salt. ... but this compound does not exist, only n-methylpiperidine.

I assume that could then be destroyed/disposed in the same manner as pyridine (incineration, permanganate oxidation).

Here is the Pyridine entry from [1]:

ackage Lots: Recycle or package and label for disposal by burning.10
Small Quantities: Wear eye protection, laboratory coat, and rubber gloves. Dissolve
the pyridine (1 mL) in 50 mL of 3 M sulfuric acid (prepared by slowly adding 8 mL of
concentrated sulfuric acid to 21 mL of water). Weigh 10 g of potassium permanganate
and stir small portions of the solid into the pyridine solution over a period of about 1
hour. Stir the mixture at room temperature for 48 hours, and then neutralize the solution
by adding solid sodium carbonate or a 10% solution of sodium hydroxide. Add solid
sodium bisulfite until the solution is colorless. Decant the clear liquid into the drain and
discard any brown solid with normal refuse.

The book does not mention pyridinium derivatives and salts specifically, except for Pyridinium Perchlorate:

Wear eye protection, laboratory coat, and nitrile rubber gloves. Work in the fume hood.
Carefully add solid to a large volume of water in a beaker diluting to a concentration of
less than 5%. Cautiously neutralize with 10% sodium hydroxide. Flush solution down the
drain with at least 50 times its volume of water.

[1] Armour, Margaret-Ann. Hazardous laboratory chemicals disposal guide. CRC press, 1996.

[Edited on 26-1-2020 by nimgoldman]

unionised - 26-1-2020 at 08:55

Quote: Originally posted by nimgoldman  
My best guess so far was

[Edited on 26-1-2020 by nimgoldman]

It may be better not to guess when you clearly don't know.
It's likely that a fenton reaction would eventually destroy the stuff down to nitrogen (or maybe nitrate) CO2, HCl and water.

I'm not sure the proposed reaction to demethylate an ether would produce the quaternary amine but... maybe.

What scale are you thinking of doing this?
If you are talking about a few grams then it's hardly worth worrying about the by-products.
Flushing it down the drain (as nimgoldman suggests) may be a reasonable option

unionised - 26-1-2020 at 08:58

The evidence suggests it's not hugely toxic.