Author Topic: Thionyl Chloride Prep  (Read 2748 times)

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FloridaAlchemist

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Thionyl Chloride Prep
« on: March 23, 2001, 05:59:00 PM »
Here is something interesting.
Excess sulfur dioxide in conc. hydrochloric acid produces
thionyl chloride.
SO2 + 2HCl = SOCl2 + H2O
Ref: JCS 117 pg 1103 (1920)

halfapint

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Re: Thionyl Chloride Prep
« Reply #1 on: August 25, 2001, 10:19:00 AM »
That is indeed interesting. Wonder, would this work in gas phase?

Also: how do you define an "excess" of a gaseous reagent in a liquid?

Likewise: I can see two ways of performing this prep. One, in gas phase, within a glass tube, the mixed gases passed through moistened silica kitty litter beads, the liquid products SOCl2 and H2O continuously drained by gravity into a glass receptacle. Not knowing whether heat would be required, the rxn would first be tried at room temperature, though I should expect heating to help.

The second way would be as implied here, by bubbling SO2 through muriatic (31%) acid, though I again would probably enlist the aid of an HCl generator to continuously refortify the acid, since "concentrated" acid is called for, and the reaction produces H2O as a diluent.

In both cases I should expect to generate sulfur dioxide in the cleanest way, by heating powdered sulfur in 2 equivalents (plus an excess) of concentrated sulfuric acid. Neither with this gas, nor with the HCl if it bee used, do I see any necessity of removing the accompanying moisture formed in the gas generation.

Any comments, peanut gallery? (What's that phrase from? "Peanut gallery" sounds like a baseball term.) Will either of these produce my thionyl chloride satisfactorally, so I can make acid chlorides? Thionyl chloride is recommended as the cleanest way to make acid chlorides, since the by-products (HCl and SO2), are gaseous. Incidentally, were I to make acid chloride this way in substantial quantity, I should certainly run an HCl generator simultaneously, or bubble the gas mix through HCl, to regenerate thionyl chloride! (I'm very frugal.)

turning science fact into <<science fiction>>

Antoncho

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Re: Thionyl Chloride Prep
« Reply #2 on: August 25, 2001, 11:20:00 AM »
this got me very interested also. i'm currently amusing myself w/various OTC posssibilities for Vilsmeier formylation (see the corresponding thread) and this seems to bee a very promising route!

what i'd like to suggest is that this rxn will certainly run very well in conc. H2SO4, and SOCl2 can then bee conveniently sep'd by just distilling it off.

however it will only work if SO2 or/and HCl are soluble in it - does anyone know how much SO2 a liter of conc. sulfuric can dissolve?

if someone tells me that, SWIM will try to do this as soon as possible and report the results.

all sncerely yours,

Antoncho

halfapint

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Re: Thionyl Chloride Prep
« Reply #3 on: August 25, 2001, 01:11:00 PM »
Got me a bit confused here. What's the conc. sulfuric for? To remove water? And the chlorine?? SO2 + Cl2 --> SO2Cl2, sulfuryl chloride. I don't expect you could make thionyl chloride, SOCl2, in such an oxidizing environment as sulfuric acid, though I might bee wrong. Oh, I see you're trying to keep from having water present, but I think we would have better luck collecting the products into sulfuric acid after they have already reacted in gas phase.

Yet on the other hand, concentrated HCl will also do a fairly good job of holding onto water, at the 79o boiling point of thionyl chloride. This would bee particularly true if the acid has been fortified by addition of a slight amount of HCl gas, as I suggested. Let's not introduce the complication of sulfuric acid, which reacts, by the way, with both component gases! I have made many messes in concentrated sulfuric acid, and there's not much you can do with that.

turning science fact into <<science fiction>>

Antoncho

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Re: Thionyl Chloride Prep
« Reply #4 on: August 27, 2001, 08:53:00 AM »
Oh my dear friend Half-a-Pint!

Here are some comments, in order of time:


I can see two ways of performing this prep. One, in gas phase, within a glass tube, the mixed gases passed through moistened silica kitty litter beads, the liquid products SOCl2 and H2O continuously drained by gravity into a glass receptacle.




SOCl2 is decomposed by H2O! That's precisely the reason that i suggested H2SO4 for; obviously, the rxn is an equilibrium, and if one is to expect a decent yield, he must remove that water somehow. It must bee removed. Period. Maybee, bubbling in HCl, as you suggest, will help.


Not knowing whether heat would be required, the rxn would first be tried at room temperature, though I should expect heating to help




My textbook says that SOCl2 boils at 78 C (ChemFinder says 76 C) and decomposes just above this temp., so heating above 79 C is definitely not needed.


The second way would be as implied here, by bubbling SO2 through muriatic (31%) acid, though I again would probably enlist the aid of an HCl generator to continuously refortify the acid, since "concentrated" acid is called for, and the reaction produces H2O as a diluent.




I agree thoroughly.


I don't expect you could make thionyl chloride, SOCl2, in such an oxidizing environment as sulfuric acid, though I might bee wrong




Sulfur has a 4+ charge in SOCl2, just like in SO2, and i senceriously doubt H2SO4 will ox. it to S(VI) (sulfuryl chloride) :)  :)  :)


. Let's not introduce the complication of sulfuric acid, which reacts, by the way, with both component gases!




Now this needs to bee found out explicitly! What are the rxns, i'm very interested too - if you know, please, put them down here.

Beecause as i was typing all this into my beloved machine, the answer finally conglomerated itself inside of my head and beecame present in front of my eyes in a cloud of fire (ever read W. Blake? - "...hi my name's W. Blake, ever read my poetry?" :) .)

The most proper way of performing this rxn, i think would bee to

a) mix SO2 w/HCL thoroughly.

b) bubble the gas mixtr (to succeed w/this, you'll need a good gas disperser unit - some glasswool perversion will probably do, just make the bubbles as fine as possible) through conc. H2SO4 heated to 79 deg C. The resultant SOCl2 will bee dist'd off and collected continuously.

If the fact that some SOCl2 is formed in muriatic acid is true, this hasn't a slightest chance at not working! Maybee even in good yields i might say.

Well, good luck to you w/this one! Considering that clandestine research procedures very often look promising but very seldom do succeed, indeeed!.. Good luck! - bee sure to write up what will have happened!

Antoncho


foxy2

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Re: Thionyl Chloride Prep
« Reply #5 on: August 29, 2001, 04:14:00 PM »
Florida
Why don't you give their procedure??
Please

SO2 Generator
Sodium Hydrogen Sulfite(NaHSO3) can be reacted with HCl to make SO2.





Do Your Part To Win The War

Antoncho

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Re: Thionyl Chloride Prep
« Reply #6 on: August 30, 2001, 11:56:00 AM »
Half-a-Pint and all interested!

There's a proc. of making COCl2 i posted in the Vilsmeier thread. In the same article it is also mentioned that SOCl2 can bee produced by passing oxygene through SCl2, no details were given, however, since you can't heat SCl2 evrthng here is probably pretty straightforward.

We at HyperLab will try to get its details.

SCl2 is quite easily prepared, i have a good procedure, if anyone's interested, i'll post it.

Antoncho