How are quaternary ammonium salts distinquished from other snivel-like compounds?
What are chemical/physical methods of their evaluation, characterization, purification and analysis?
Recently i've isolated some substance from a clothes conditioner, and i beleive it could be quat-ammonium salt. There were many gossips in our local
chemistry forums that this conditioner contains cationic SAC, which is quaternary ammonium salt, some people even had "friends of their friends", who
added this conditioner directly to the reactions that require PCT. But there were no practical reports concerning isolation, purification and
characterization of the proposed quaternary ammonium salt, except one on the local drug forum, that failed.
Naturally this conditioner is a white emulsion, with aromatic scent. The claimed content is: cathionic SAC, preservative, aromatizer, water.
The product that i have obtained is an oily, glue-like substance, soluble in water, in ethanol, seems to be hydroscopic. It was obtained as oily
product after ethatol solution evaporation(45C), it is not solidifying at 0C, does not precepitate from by-eye made ethanol solution at 0C, but
crystallic precepitate fills the solution at -15C. Thats all i know about it
It was obtained using the following procedure:
the conditioner, was boiled with Na2CO3 until(normally 3-5 minutes) the emulsion devided into insoluble resin-like polymer* and the solution became
transparent. The solution was then filtered, and the filtrate was evaporated(with some NaCl addition) until a well-moist residue was formed, to which
some ethanol(3-5 times more then the residue volume) was added and the solution was left for 8 hours, shaked sometimes. After that, the
upper-layer(purest, without solid and water) was devided and evaporated to give an oily substance (scent is very likely aminic), with some crystallic
impurities(sodium salt perhaps). The rest solution was whole taken into filtration, and this time the residue contained much more crystalls(that
indicates that water layer also was filtered). Then the product was once again recrystallized with ethanol to eliminate sodium salts, but still some
crystallic impurities are present. The yield is approximately 0.5-1g/200ml of conditioner. To indicate the oily substance is not sodium hydroxide,
the same procedure was done without conditioner, no oil obtained.
(* It seems to be polymer, because previously i made several experiments with it to conclude it is not quaternary ammonium salt, or at least not
monomeric one. Thus, it does not dissolve in water, and is soluble extremely well in hot ethanol, but if the solution is cooled below 30, whole
polymer is immediately precepitated forming a gel that coveres whole solution, that is the case for dilute ethanol solutions also. It is melting at
58, but seems to have a wide melting point, it tends to supercool etc)
Now i want to examine this oily residue, to know wether it contains quaternary ammonium salts or not. I dont even know, what could be the major anion
of this salt, chloride or hydroxide or smth else?( the purpose of NaCl addition was to convert it mostly to chloride, which is known to be soluble in
orgainc solvents).
What is the easiest way to say wether it is a quaternary ammonium or not?
[Edited on 6-1-2009 by Ebao-lu]
[Edited on 6-1-2009 by Ebao-lu]
[Edited on 6-1-2009 by Ebao-lu]kmno4 - 6-1-2009 at 14:46
Take 1 cm3 of H2O and 1 cm3 of DCM. Add to it very smal crystal of KMnO4 - water turns pink, DCM not. Add a little of your "oil" - if it contains
[R4N+] cation, then also DCM turns pink. I cannot see simpler way to check wether it is a quaternary ammonium or not.
[Edited on 7-1-2009 by kmno4]Ebao-lu - 6-1-2009 at 14:54
thanks a lot! i'll try it, but currently DCM is not avaliable. could it be replaced by other solvents ( especially, benzene, chloroform, petroleum
ether, dichloroethane)?kmno4 - 6-1-2009 at 15:12
I think that all these solvents should work, but I would try chlorinated ones
[Edited on 7-1-2009 by kmno4]Formula409 - 7-1-2009 at 18:32
Awesome, thank you both for that, this will help me when looking for fabric softeners which could serve as OTC PTCs.
Formula409.Nicodem - 8-1-2009 at 00:01
Quats in fabric softeners have alkyl chains too long to be useful as PTC catalysts for most reactions. Also, if you boiled it with Na2CO3 (why?)
chances are you decomposed much of it into high MW trialkylamines. The fabric softeners usually contain 10-15% long chain quats and about nothing else
besides water. These quats obviously do not crystalize since they contain >C12 alkyl chains, instead they are wax-like substances. There used to be
a thread where this was discussed.
Anyway, why don't you use one of the OTC quats that can actually be used as PTC catalysts (like didecyldimethylammonium chloride,
benzyltrimethylammonium bromide, etc.). Surely you don't have troubles finding consumer products containing aq. solutions of these?Klute - 8-1-2009 at 11:58
And benzylalkylammonium salts are easily prepared, once you have either a trialkylamine and benzyl halide, or benzylamine and a alkyl halide, could
make an interesting project.
I think solutions of these quats are indeed availble in swimming pool shops as desinfectants.sparkgap - 9-1-2009 at 06:49
For those who didn't get why heating long-chain quats with base is a bad idea, it's because Hoffmann elimination can occur, decomposing your quat into
an alkene and a trialkylamine.
sparky (~_~)Ebao-lu - 11-1-2009 at 04:48
The experiment with benzene/KMnO4 failed. But this time i just added benzene to the wet residue, resulting from evaporation of solution, and took the
upper layer with a syringe containing permanganate solution. I'll try once again with isolated oil, and some another solvent to make sure there is no
quats. Still, according to Nicodem's note that quats from fabric softeners are useless for most PTC reactions, it seems that they do not cross the
phase boundary like normal PTC's, anyway this experiment will show wether my quat is useless or not
Quote:
Quats in fabric softeners have alkyl chains too long to be useful as PTC catalysts for most reactions. Also, if you boiled it with Na2CO3 (why?)
chances are you decomposed much of it into high MW trialkylamines. The fabric softeners usually contain 10-15% long chain quats and about nothing else
besides water.
First i also supposed the white solution should not contain anything but quat/water, so i attempted to dry it, and when it became soap-like, i thought
it was quat salt and added cold acetone/alcohol in order to wash water off and dried the precepitate. The result was white soap-like powder, melting
at 58. It was easily soluble in hot ethanol(>40) and practically insoluble in below 30. Later i'll uploaded one video demonstrating its solubility
in ethenol. Also, it is insoluble in water even if boiled, it is just melting. That indicates this brand of fabric softener contains some other
compounds, not(only) quats. Probably it is a polymer cathionic SAC, that is useless for PTC, and maybe it is some indifferent polymer, and the quats
are still present there in the softener(in the content, it was written "cathionic SACs"), so i decided to remove the polymer and see, wether this
polymer was the only compound or not. Due to the fact, that polymer was insoluble in water, i tried to boil the softener, but emulsion did not break
even while prolongen boiling, so i tried to use several salts. Boiling with Na2CO3 was an accidently found decision for resin removal. It seems that
all double charged anions can break this emulsion, i've tried Na2SO4 as well. Other salts(NaCl, NaOH, ets) do not cause breaking.
As for basic elimination, i've done experiments with hot NaOH solution, and there was no scent of amines, besides, if i am not mistaken, Hoffman
elimination requires AgOH as a catalyst.
Nicodem, Klute, thanks for the information. They realy seem to be avaliable. I started with this softener, because there were many mathes that it
containes quats and can be used in PTC. Or maybe they began to manufacture it with new content.
[Edited on 11-1-2009 by Ebao-lu]
[Edited on 11-1-2009 by Ebao-lu]
[Edited on 11-1-2009 by Ebao-lu]Nicodem - 12-1-2009 at 01:27
Quote:
Originally posted by Ebao-lu
As for basic elimination, i've done experiments with hot NaOH solution, and there was no scent of amines, besides, if i am not mistaken, Hoffman
elimination requires AgOH as a catalyst.
AgOH or Ag2O is generally used because it directly transform the quat halides into quat hydroxides (silver halide being insoluble). It is not a
catalyst but a stoichiometric reagent. Otherwise quats start decomposing via Hofmann elimination already above 120°C in the presence of carbonate or
hydroxide bases (but this actually depends very much on the type of alkyl chains). At >150°C the decomposition is very rapid, thus PTC catalysts
are generally useless at temperatures approaching these.
I suggest you to check the compositions of antiseptics containing aq solutions of didecyldimethylammonium chloride or pool algaecides containing
benzyltrialkyl quats. Or else just buy tetrabutylammonium bromide - it is not so expensive at all.
