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Jor
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thionyl chloride synthesis
I really want some SOCl2, for making anhydrous metal salts (like CrCl3) from hydrated metal salts.
I have contacted Sauron and he gave me some inspiring ideas.
I want to avoid the SO3/SCl2 method. SCl2 stinks. SO3 destroy skin on contact, rendering it only useful in maybe a black powder formula  .
PCl5/SO2 , I also don't like that method. Takes a lot of time, and doesn't have good yeilds (50%). Besides I cannot give a good seperation of the
POCl3 from the SOCl2, as I do not have a vigreux.
A very promising method Sauron gave me is reacting SO2 with phthaloyl chloride. This is very expensive, but I can make it from relatively cheap
benzotrichloride and phthalic anhydride. However, i would need to buy a whole liter, for wich i have no other uses, so I want to look at the other
possibilities first.
I can make PCl5, and I can buy chlorosulfonic acid.
So:
-I would like to ask if anyone has information if SOCl2 can be made from chlorosulfonic acid. Sauron said he remembered there was a reaction with
mercuric nitrate, but he was not sure. Anyways, this is a no-no. That is too toxic. But are there more methods?
-Sauron also said he vaguely remembered anhydrous sodium sulphite could be reacted with PCl5. Is this true? Does this also give POCl3 as byproduct,
or rather NaCl and P2O5? This would be great if it works, as i have anhydrous sodium sulphite, and it would not involve generation of massive volumes
of SO2, and the POCl3 contamination may be less than the SO2 method.
Also other ideas are welcome.
Thanks in advance
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Sauron
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I did not vaguely remember that sodium sulfite reacts with PCl5 to produce SOCl2. I said that I found this reaction in the Encyclopedia Britannica
1911 edition online in the Sulfur article. I sent the quotation to you verbatim.
And I just sent you the balanced equation that I believe applies, although that is not in the Brittanica,
Na2SO3 + 2 PCl5 -> SOCl2 + 2 POCl3 + 2NaCl
So kindly do not misrepresent what I told you.
It is true that I remember a reaction between mercuric nitrate and chlorosulfonic acid, but I have not found the source and do not recall details. I
do not remember whether this produces SOCl2 or SO2Cl2. Anyway you have better choices to make SOCl2. You can use the Kyrides method, phthaloyl
chloride and you can make the reagent yourself using benzotrichloride and phthalic anhydride.
Len1 demonstrated making benzotrichloride on this forum, starting with toluene.
[Edited on 1-2-2009 by Sauron]
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Jor
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Sorry.
I did not have PMs at hand when typing this message. I was not sure if you said that you remembered the sulphite method or actually read it in 1911
britannica. Should have read that PM again, Im sorry my fault.
That equation indeed looks right. I was thinking all the time the sulphite would react 1:1 with the PCl5, and didn't think beyond that!
I'm making a lot of stupid mistakes today, as you can see. 
If anyone has papers on the sulphite reaction you would do me a great favour. I hate it that i can't access many papers, because you will have to pay
a lot of money for a membership.
Therefore my best resources are the SMDB Library 
Chlorosulfonic would also be a prefreed reagent to start with. I can buy it relatively cheaply, 500mL for 25 euro. And I find this a very interestign
chemical, wich i can use for many microscale test-tube experiments as well.
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Sauron
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Just go to Google, search for 1911 encyclopedia, and the Britannica free edition comes right up
Search on that page for thionyl chloride and the Sulfurmonograph comes up. Find the section on halogen derivatives of sulfurous acid. It will start
with SOF2, then SOCl2, then SOBr2.
It's there for anyone to read.
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woelen
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Can you really buy chlorosulphonic acid (labstuff?)? I have strong doubts about that, and if you ask for that, that there will be some serious
questions.
I also have strong doubts that this chemical can be used for making SOCl2. Chlorosulphonic acid contains sulphur in oxidation state +6 and with
mercuric nitrate I do not see how this could be reduced to oxidation state +4. I can imagine though that chlorosulphonic acid can be converted to
SO2Cl2 in some way, but that is not interesting for you (SO2Cl2 is much less reactive than SO2(OH)Cl).
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Jor
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Well, Wilco, I have not asked Labstuff yet, but he gave me a lot of restricted chemicals as you have seen, and chlorosulfonic acid was not included.
Why would it be restricted, do you know of illicit uses in the Netherlands?
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Sauron
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Here is the entry I am talking aout from Britannica 1911:
"There are various haloid derivatives of sulphurous acid. Thionyl fluoride, SOF 21 has been obtained as a fuming, gas by decomposing arsenic fluoride
with thionyl chloride (Moissan and Lebeau, Corn pt. rend., 1900, 130, p. 1436). It is decomposed by water into hydrofluoric and sulphurous acids.
Thionyl chloride, SOCl2 may be obtained by the action of phosphorus pentachloride on sodium sulphite; by the action of sulphur
trioxide on sulphur dichloride at 75 -80° C. (Journ. Chem. Soc., 1903, p. 420); and by the action of chlorine monoxide on sulphur at low temperature.
It is a colourless, highly refracting liquid, boiling at 78°; it fumes on exposure to moist air. Water decomposes it into hydrochloric and sulphurous
acids. On treatment with potassium bromide it yields thionyl bromide, SOBr2, an orange-yellow liquid which boils at 68° C. (40 mm.) (Hartoz and Sims,
Chem. News, 1893, 67, p. 82). "
I could not find the J Chem Soc reference 1903 p 420 but it may be a typo as there are many in that site.
The references for this reaction probably can be turned up in Mellor's volume on sulfur or in Gmelin.
The reaction between PCl5 and SO2 which is very similar is in Brauer on page 382.
Solid-solid reactions with moisture sensitive reactants and equally moisture sensitive products are always fun in the Chinese curse sense of fun.
Distilling SOCl2 off POCl3 requires a good column and several fractionations, so is tedious. I still recommend the Kyrides method which gives a
produce devoid of phosphorus-compound contamination.
[Edited on 1-2-2009 by Sauron]
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Sauron
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Besides the "new" sulfite method, which is only a variation on SO2 and PCl5, and thus only available to those who can get or make PCl5, and the
Kyrides method discussed above and in various threads by me, the other methods are:
SCl2/S2Cl2 and SO3 either neat or in oleum
Trichloroarenes sich as hexachloro-m-xylene, or the simplest case benzotrichloride, reacting with SO2 and a catalyst, in several patents and articles
posted before by me;
The disproportionation reaction over GAC between PCl3 and SO2Cl2, giving POCl2 and SOCl2 (only practical is you have PCl3, so rots of ruck)
The low temperature reaction of chlorine monoxide with sulfur, another one unlikely to be performed in a home lab;
Did I forget anything?
Jor does not wish to work with oleum so that oxidation of sulfur chlorides is out (he also regards sulfur chlorides as stinky and toxic.)
I think Jor is well advised to carefully consider the Kyrides methos (phthaloyl chloride and SO2).
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garage chemist
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SO2 + PCl5 reacts smoothly to POCl3 and SOCl2. The real problem is separation of the products. Fractionating this mixture SUCKS, even if you have a
good column. There's something with those substances that lets them cling onto one another and resist efficient separation.
I had to do this myself as a practical assignment. The yields and purity were horrible.
Please consider making and using SO3, Jor.
All you need to do is make a tube furnace, and proceed as I have done. Here's your second reason to make a tube furnace!
NaHSO4, when hit with enough heat, releases SO3 in good yield.
SO3 is a highly reactive and exceptionally useful chemical.
Len1 has demonstrated making SOCl2 from SO3 and SCl2 in detail. Follow his work.
Jor, do you have a glassblower that can make things out of fused quartz for you? You should find one.
My synthetic abilities were vastly extended once I started making use of the services of the glassblower at the nearest big university. I can have
EVERYTHING IMAGINABLE made out of every glass sort as long as I have the money for it. This is invaluable for a chemist! My tube furnace experiments
would have been impossible without this glassblower.
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panziandi
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That is what I don't understand with Jor... You say you don't want to work with SO3 or Oleum and you don't want to work with S2Cl2 because they are
corrosive and toxic and smelly, yet you will work with SO2 (also toxic and smell and corrosive) and you want to make SOCl2 which is water reactive,
toxic, corrosive and releases HCl and SO2. Anything to make SOCl2 will be nasty to work with, as will separating, purifying and working with the
desired product.
HCMX is something I was looking at. I have plenty of xylene and I never use it for anything really! I sometimes melt alkali metals under it but that
is about it and I rarely use it as a solvent. I thought about chlorinating it and using it as a nicer chlorinating agent than the usual candidates.
Sauron: Does HCMX or Benzotrichloride react with anhydrous sodium sulphite perhaps?
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Sauron
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Jor apparently has no fume hood.
I just looked up Cl2O in Brauer and this is not so bad. Cl2 dried with H2SO4 as usual us passed into a large U-tube packed loosely with shallow HgO
and glass wool plug alternating, the U tube is placed in a water bath regulated to 18-20 C. The best yields are when the Cl2 is admixed with 2 to 3
volumes of dry air. The exit gas is dried over P2O5. I do not yet have the details of the reaction with sulfur in the cold, but I would use the Cl2O
directly. It is a yellow-brown gas and EXPLODES ON CONTACT WITH ORGANIC MATTER so don't let it near any. It is also possible to prepare Cl2O in CCl4,
but whether that solution is suitable for the rxn with S is an open question. See the pages from Brauer 299-300 attached.
Now I launch myself into Melloe Ch 57.
[Edited on 1-2-2009 by Sauron]
Attachment: Pages from brauer_ocr.pdf (76kB)
This file has been downloaded 1288 times
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Jor
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I do not wish to work with SO3. It is extraordinary hazardous ,if I was told right.
First my fume hood motor will be destroyed by it. Second when you work with it a constant stream of smoke will exit the roof. The neighbours will be
thinking, what is happening .
Thirdly and most importantly, I am too afraid to work with it to be honest.
Don't get me wrong, I think it is an extremely useful chemical!
If really want SO3, I think I will one day make a large investment in 1 liter 65% oleum (110 euro Merck). .
I simply do not want to invest the time/money/room in a tube furnace. Realise 90% of my experiments are test-tube scale, making inorganic complexes. I
only sometimes do synthesis on a large scale. Thionyl chloride is one of those chems I want to make. But then I rather go via Kyrid.
I simply do not have much experiments that require a tube furnace. But in the future, when I will advance to more complex inorganics, I will make one,
as you need one quite often (for example Brauer).
How do you guys handle SO3? Fumehood or outside ofcourse. But what kind of gloves? Because skin will be destroyed instantly, to black tar.
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Sauron
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Consider adding a scrubber system.
You and your neighbors will be happier.
Your blower's motor should be totally isolated from hood exhaust. If it is not you will have a lot of grief.
WOW. I thought I knew my way round SOCl2 but I really ought to have had recourse to Mellor Ch. 57 pp 556-565 sooner. Here they are by attachment.
What I went fishing for, the Cl2O rxn with S, is there with refs, and details, and in addition there are a number of startling preparations which will
be of great interest.
The reaction of Cl2O with sulfur is normally very violent, so it is expedient to carry it out in S2Cl2 (sulfur monochloride) as solvent at -12 C.
I will not spoil the surprises for you all. Read the extracted pages.
[Edited on 1-2-2009 by Sauron]
Attachment: Pages from Mellor_ACTITC_S_v10_ch57_1930.pdf (318kB)
This file has been downloaded 1607 times
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S.C. Wack
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Well as you look in Mellor, or anywhere else, you may find it difficult to pin down the sulfite reference on any particular one of Carius' papers. His
name always comes up, but always in connection with two or more refs to different things, or none at all. Or calcium sulfite is mentioned instead. It
is not mentioned in Gmelin's SOX2 volume at all. In any case the ref is quite old and quite possibly without much detail, and it's a matter of just
doing it or not.
Suspects are:
http://dx.doi.org/10.1002/jlac.18581060309
http://dx.doi.org/10.1002/jlac.18591110111
I posted a link to Wurtz's paper on Cl2O and S in the relevant thread almost 4 years ago now - would you believe that SOCl2 has come up before, and
more than once. The link still works.
[Edited on 31-1-2009 by S.C. Wack]
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Sauron
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Thanks, S.C. Jor may want to look into that muddle but I am more interested in some of the other stuff in there. Sadly I do not have Gmelin.
mellor is a pain about references because of the manner in which he presents them. They are unnumbered, in order of their appearance in the text, and
run together. So while they are not random, they are still needles and it is still a haystack. Oh joy!
[Edited on 1-2-2009 by Sauron]
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solo
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................had you used the search engine ...you might have not started another thread on a subject that's been discussed at excess......solo
https://sciencemadness.org/talk/viewthread.php?tid=1439&...
Note - here is one method mentioned there....
The catalytic oxidation of sulphur dichloride by oxygen
Alwyn G. Evans and G. W. Meadows
Trans. Faraday Soc. 1947, 43, 667 - 674,
[Edited on 1-2-2009 by solo]
Attachment: synthesis of thionyl chloride-The catalytic oxidation of sulphur dichloride by oxygen .djvu (170kB)
This file has been downloaded 1141 times
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Sauron
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I like this Cl2O reaction more and more. You need some S2Cl2 as solvent, which is reusable. You need some HgO catalyst, which is partially converted
to HgCl2, and that is useful. Otherwise the materials are simply Cl2 and dry air on one hand and sulfur on the other and you can and should make your
own S2Cl2 from same two elements anyway
Make and use the Cl2O in situ.
Cl2O has a great affinity for water and forms HClO, so can be regarded as hypochlorous acid anhydride. Its incompatibility with organic material is
therefore underscored. The Cl2 and air need to be dry.
Cl2O converts CS2 to SOCl2 and phosgene. That one will be unpopular on both sides of the equation.
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woelen
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Jor, the CS2/Cl2O route might be an option for you. CS2 can be obtained easily for us, HgO can also be purchased and the others are not a problem at
all. Lead the phosgene into toluene, giving you a useful by-product.
The only thing is that I expect that the CS2 must be really cold, and the Cl2O must be diluted with air, otherwise I think you will get fireworks
instead of SOCl2  . Having the CS2 very cold has the added advantage that less
vapor is drawn into the phosgene stream, allowing for purer phosgene.
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Sauron
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CS2 is expensive and a fire hazard, combining something that flammable with a gas that is known to be a wee bit touchy strikes me as less than ideal.
To put the final nail in the coffin, unlike the rxn with sulfur in S2Cl2 at -12, the rxn between Cl2O and CS2 produces a mol phosgene for every mol
SOCl2.
So I think thumbs down on this one.
I recognize that Jor has certain qualms about sulfur chlorides, but he is going to have to deal with some of his phobias or else give up on making
thionyl chloride, which as chemoleo says is not exactly eau de cologne itself.
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woelen
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Remarkably, CS2 is not that expensive for us and we can buy it in 1 liter quantities, more than we ever need. But of course, I agree on the
flamability of this liquid and that's why I made the remark about the fireworks.
Whatever route one chooses for making SOCl2, one always has to be prepared to deal with nasty chemicals, this is not something for the average home
chemist.
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Sauron
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That's for sure.
Jor told me he already has HgO.
He was going to make his own PCl5 from red P so he was not averse to generating and drying Cl2. A cylinder of air or a compressor is a piece of cake.
S2Cl2 is a great solvent for S. Anyone who has ever made it will tell you that.
I don't want to imprimatur this method till I read the original Wurtz papers. I am still struggling with Melloe.
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panziandi
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Well indeed I thought it's a bit silly to say you want to avoid certain nasty chemicals for smelly, toxic, corrosive reasons yet you are making a
vicious toxic, smelly, reactive, and corrosive chemical anyway!
The Cl2O method sounds promising Sauron so long as the glassware is all spotlessly clean! I think anyone performing the Cl2O + S reaction should
probably operate from behind a perspex shield or take a similar precaution incase of an explosion in the set up. Other than that it does sound quite
simple. The first bit of chlorine produced could be lead into a flask containing excess sulphur, forming in situ sulphur chloride which would dissolve
the rest of the sulphur, then switch the chlorine path so that it is lead through the catalyst bed and over into the mix.
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Jor
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Panziandi, as a answer to your first post in this topic:
-sulfur chlorides just stink very bad, much worse than SO2 or SOCl2. I don't want to stink up the neighbourhood. For this reason I also never generate
any H2S.
-SOCl2 is also corrosive, just like SO3. But you know SO3 is extremely corrosive, and SOCl2 is 'just' very corrosive. I have had a drop of SOCl2 on
me. It hurts but I'm fine. SO3 would have left me with a black hole.
It's just that I don't like to work with chemicals wich can really harm you, even if you work very carefully. SOCl2 is not like that. it is corrosive,
can make you cough, but won't cause permanent injury or kill you if you work with care. Oleum can.
SOCl2, HCl, SO2, etc are toxic and corrosive, but not too bad. Not very stinky, not dangerously corrosive, not extremely toxic.
I think the Cl2O method is definately interesting. S2Cl2, ok I will generate a bit for use as solvent, to overcome my phobia.
I have HgO. Produced HgCl2 can be converted back to HgO.
i see one problem. Cl2O. We know how reactive a 5% acidified hypochlorite solution is. Cl2O, the ahydride... Sounds extremely dangerous. If I attempt
this, I will clean all glassware with boiling HNO3 or chromic acid.
The catalytic oxidation solo mentions also is interesting, but you need a lot of glassware for it. I will look into that later.
After all, I think Kyrid method is the less dangerous, easiest one. No use of very toxic chemicals, no smells, and risk of explosion. This is my
preferred method. By product is benzoyl chloride.
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Formatik
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Whereas CS2 causes a lively explosion with Cl2O forming SO2, CO2, Cl2 and S2Cl2. CCl4 can also be used to milden the reaction between CS2 and Cl2O
(see Schützenberger, Ber. 2 [1869] 219) to form SOCl2, COCl2.
Gmelin gives the reactivity of Cl2O. Concerning reaction with sulfur in a solvent or not, it is not much different than what is found in Mellor since
they both draw on some of the same references. Generating Cl2O, you would need to know more hazards about it. E.g. Cl2O explodes occasionally just at
room temperature. Valuable preparation and saftey also covered in Gmelin. I could scan all of the pages of Cl2O, but I haven't been able to find a
decent pdf compiling program of sufficient quality.
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panziandi
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Sorry I just found it a little amuzing that's all! Not calling you a twit or anything, I know HOW smelly sulphur chlorides are a flask broke once
whilst I was making some before...really not nice!
I would highly suggest you submerge all glassware in sulphuric/peroxide or chromic acid, trouble with boiling nitric is I could imagine U tubes etc
being hard to clean with refluxing nitric, and you really want to ensure NO organics on ANY part. But then again the reaction does seem nice! And the
sulphur chloride solvent could easily be made in situ and you wouldn't be exposed to it.
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