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BromicAcid
International Hazard
Posts: 3245
Registered: 13-7-2003
Location: Wisconsin
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Mood: Rock n' Roll
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The reactivity of DMSO is fairly thoughly explained in the text "Technical Bulletin Reaction Solvent Dimethyl Sulfoxide" from Gaylord
Chemical Corporation. According to it DMSO reacts with anhydrous HCl to give an ionic salt:
CH3SOCH3 + HCl ---> [CH3S(OH)CH3]<sup>+</sup>Cl<sup>-</sup>
Even if you could find a nice way to convert to thionyl chloride, it would readily react with the DMSO present:
CH3SOCH3 + SOCl2 ---> CH3SCH2Cl + SO2 + HCl
So really I see no easy way to it, you would have to break the S-C bonds and they are fairly stable, they will survive direct chlorination to give
CH3SOCCl3. Unless the DMSO is under basic conditions halogens catalyze the decomposition to SO2 and CH3SO2CH3 and other crap. So I don't really
see a feasible way to thionyl chloride through DMSO.
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IrC
International Hazard
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Is there a way using a catalyst to break the C-S bonds?
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Natures Natrium
Hazard to Others
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Registered: 22-12-2004
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Oxychlorides of sulfur
Crap, I just wrote like 2 pages of stuff on this topic and lost it by clicking on the "review long topic" link. 
Ok, let's try this again.
I have read somewhere that refluxing an equimolar amount of SO2Cl2 and SCl2 would result in conversion to SOCl2. It sounds nice, but I have my
doubts, since in the trans-faraday article posted earlier in this thread they found the equilibrium of that reaction to lean toward thionyl at 193C
(in the gas phase over activated carbon). I happen to have both sulfur dichloride and sulfuryl chloride on hand currently, so this would be mighty
convienent. Anyone have any thoughts on this? Refluxing in the presence of activated carbon I'm not sure would work. The reason it would not
work is related to my attempts at SO2Cl2.
Following the procedure outlined in Inorganic Lab. Preps., I have twiced now had success synthesizing sulfuryl chloride. The first time I took my
300mm West condenser and packed it full of my activated carbon*. Other than that it went exactly as described in the book, and I made about 30g
SO2Cl2. Cleaned the excess Cl2 out (which I use in even greater excess since SO2 is a reagent that is precious to me  ) by adding 3g Hg metal and shaking for a bit.
The second time I made it, I ran into a bit of a problem I did not notice in the first run but which might have been affecting my overall yield. I
found that passing the gasses too quickly through the carbon, the end of my condenser (inside the 24/40 glass joint) began to get hot. This was
interesting to note since the parts of the carbon which were inside the cooled part of the condenser were clearly "wet" with SO2Cl2, whereas
the end carbon became dry and stayed that way. When this happened the flow of SO2Cl2 stopped entirely. I therefor hypothesize (guess) that hot
activated carbon is better at splitting SO2Cl2 than combining it. (This is why I doubt the SO2Cl2 + SCl2 -> SOCl2 in the presence of carbon.) A
look at US patent 5,498,400 shows that the yield of SO2Cl2 over carbon catalyst is much higher if the reaction is run at lower temps. This patent
gives multiple detailed examples. I suppose it also probably says that the gas rates were too high, since the SO2 (limiting reagent) was being fully
reacted before reaching the end of the tube. I then tried something a little different. I took the 500mL RBF that had been collecting the SO2Cl2,
through some of the still damp activated carbon in (about an equal volume), and then proceeded to pump in chlorine gas until saturated, then SO2. I
did this back and forth a number of times, stirrring/shaking by hand quite a bit, and managed to roughly triple the volume of SO2Cl2 I had collected.
I ended up with a total of 59.6g SO2Cl2 after decantation from the activated carbon. So, once some is made, it is clear that a camphor like approach
to this synthesis is possible. Whether or not it is to be preferred is dependent on disposition and equipment available, I suppose. It seemed to me
to be a lot more effecient however, since very little Cl2 or SO2 managed to escape the SO2Cl2 liquid.
I also managed to make a bit of thionyl chloride with my bootleg catalyst tube, although the process was horribly ineffecient. In this expirement I
passed Cl2 and SO2 over my activated carbon catalyst*, except this time it was heated to fairly high temperatures (guesstimation: >300C). After an
hour or so I ended up with a measly 5mL of a reddish liquid. This stuff seems much nastier than SO2Cl2, SCl2, or S2Cl2. It's hard to describe
the difference but essentially SOCl2 just instantly burned the crap out of the inside of my nostrils on the smallest accidental whif. The other
compounds just tend to reek of SO2, Cl2, and HCl. (As a side note, I may take a long haitus from chlorides of sulfur soon, or any synth that requires
chlorine...I got a whif of Cl2 earlier today and it smelled sweet and didn't physically bother me much!  ) US Patent 5,759,508 also shows it is possible to obtain thionyl chloride this way, although curiously they
don't state yield.
I made only one attempt at thionyl chloride based on the trans-faraday doc, and it was a waste since the carbon still contained way too much water
even though it was heated on a hot plate under vacuum. Speaking of which...
* My Activated Carbon. I ended up getting this stuff truely anhydrous and activated by deciding to dump about 20mL of my SCl2 directly into the glass
container which held the carbon. It boiled a bit and let out quite the stink before finally subsiding. I just let the carbon soak it all up. I have
not had a chance to use it for sulfur dichloride to thionyl chloride yet, as was my original intention, although it has proven to be an excellent
catalyst for SO2 + Cl2. Of course, it actually doesn't seem like it takes that much to get these two together, or break them apart. 
Ok, main question: Will refluxing an equimolar mixture of SCl2 and SO2Cl2 lead to a decent yield of SOCl2?
Comments, opinions, and ideas are most welcome.
Sincerely,
Nature's Natrium
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
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