[Babcock_Hall]

Thanks for all of the replies.  Sulfuryl chloride boils at 68-70 °C; therefore, reducing it to thionyl chloride is an attractive approach.  In reading through the paper in JCS Chem. Soc., it sounds as if triphenyl phosphite reacts with thionyl chloride and other sulfur chlorides, as well as sulfuryl chloride, just not as quickly.  The authors used 0.5 hours of reaction time.  It might be that long reaction times would create more problems.

[phth]

Thanks for all of the replies.  Sulfuryl chloride boils at 68-70 °C; therefore, reducing it to thionyl chloride is an attractive approach.  In reading through the paper in JCS Chem. Soc., it sounds as if triphenyl phosphite reacts with thionyl chloride and other sulfur chlorides, as well as sulfuryl chloride, just not as quickly.  The authors used 0.5 hours of reaction time.  It might be that long reaction times would create more problems.

It is easier for phosphorus to take an oxygen from sufuryl chloride than thionyl chloride because the average bond order of the oxygens is different.  It's a better bet not to go over.  Thionyl chloride is the thermodynamic product on the way to phosphonate.

[Babcock_Hall]

I redistilled some of the moderately yellow material after stirring with P(OPh)₃.  The second fraction was pale yellow, and the third fraction was almost clear.

[Babcock_Hall]

In the past couple of days I have tried to reproduce the first step of the synthesis from Inorganic Chemistry, the synthesis of sodium trichloromethylsulfinate.  After the synthesis, I removed solvent, added methanol and filtered away some precipitate, and removed the solvent with rotary evaporation.  I dried for about 5.5 hours at 80 °C under vacuum and for a couple of hours at room temperature under vacuum.  The mass was roughly 33% higher than theoretical.  The authors of the paper claimed a 60% yield at this point.  Therefore, I put the material back on high vacuum overnight at room temperature, and the mass is virtually unchanged.

The next step of the synthesis is to acidify with sulfuric acid and then to distill the product, which is the free sulfinic acid.  Should I proceed to the next step, should I make an additional attempt to dry the material, or should I try the methanol step over again?
ETA
If the impurity is a salt, it might be NaBr, NaHCO₃, or the sulfur-containing byproduct created by the attack of dithionite on bromotrichloromethane.

[Babcock_Hall]

Here is the reaction scheme from Zhang et al., Inorganic Chemistry 1991, 32, 492-494.  I am not sure how to proceed, given my greater than theoretical yield.

[zarhym]

Yuan Fa Zhang, Robert L. Kirchmeier, Jean'ne M. Shreeve
Inorg. Chem., 1992, 31 (3), pp 492–494
DOI: 10.1021/ic00029a028

are you talking about this paper?

[zarhym]

The procedure says 'the residue was treated with 50 mL of absolute methanol'.
I would guess removing water from the system is the key in this synthesis, otherwise it's very likely you end up have some water in the crystal structure. 

If this is the reason, you can try drying your crude solid from acetonitrile/water layer and also dry your methanol before you mix them together.
In organic synthesis, organic layers are often dried with MgSO4 or Na2SO4. Since you are synthesis a salt, you may have to find another drying agent.

[Babcock_Hall]

Yuan Fa Zhang, Robert L. Kirchmeier, Jean'ne M. Shreeve
Inorg. Chem., 1992, 31 (3), pp 492–494
DOI: 10.1021/ic00029a028

are you talking about this paper?

Yes.  With respect to the methanol, I used a high grade of commercial solvent.  I have decided to dry some myself if I repeat either the methanol step or the whole synthesis.  However, I think that another source of water is the acetonitrile layers that I combined.  There must have been at least some water in the acetonitrile.  However, the protocol that I am following does not call for drying the combined acetonitrile layers.

[BRSM]

Yes, phosphites probably are not that flammable, but still strong neurotoxins.  It could form a positive azeotrope, which can change the distillation, so I would agree with BRSM going with the literature examples.
3. Pi acidity changes how it interacts with the impurities.  It's the ability to interact with electron density of the impurities which has everything to do with the distillation.  I was not referring to cone angle, just that it is a common reference comparing phosphorus L type ligands electronic properties.  It has everything to do with phosphorus' ability to be effective.

Forgive my ignorance, but I still can't see the relevance of Pi acidity here. Pi acidity refers to the ability of a compound to accept electron density into empty Pi orbitals. This interaction is impossible with SOCl₂, S₂Cl₂, SCl₂ etc --- they simply don't have orbitals of the correct symmetry for this kind of interaction. Seriously, draw me an orbital diagram; if I'm wrong I'd like to know why. Have a look at a metal-phosphine two-way bond (https://en.wikipedia.org/wiki/Metal_phosphine_complex) and explain to me how chlorine is doing that.

All that's going on here is attack of the phosphite lone pair on an electrophile of the "Cl⁺" type: S₂Cl₂, SCl₂, whatever. One way movement of electrons. Simple, first year orgo. No electron density is moving from the electrophile to phosphorus. Thus pi acidity---the ability of the phosphine to accept electron density---does not seem relevant to me. The phosphite is just sucking up "Cl⁺" donating impurities in SOCl₂ as a sigma nucleophile. That's why the alternative of olefin-rich terpines like linseed oil is offered in The Purification of Laboratory Compounds. Really, any soft nucleophile will do. Pi acceptor ability isn't needed here.

Also, nobody's serious proposing the preparation of SOCl₂ from sulfuryl chloride (SO₂Cl₂), right? SOCl₂ is dirt cheap, and actually making it from any other substance is not going to be worth your time. Firstly, I wouldn't count on phosphites to reduce SO₂Cl₂ in the way you mean, as SO₂Cl₂ is chlorine rather than an oxygen donor. Look at its reactivity --- it's a chlorinating reagent! Can anyone find me a reaction where a nucleophile attacks SO₂Cl₂ on oxygen? And even if you could reduce SO₂Cl₂ to SOCl₂, in my opinion you'd be crazy to even bother.

[phth]

Yes, phosphites probably are not that flammable, but still strong neurotoxins.  It could form a positive azeotrope, which can change the distillation, so I would agree with BRSM going with the literature examples.
3. Pi acidity changes how it interacts with the impurities.  It's the ability to interact with electron density of the impurities which has everything to do with the distillation.  I was not referring to cone angle, just that it is a common reference comparing phosphorus L type ligands electronic properties.  It has everything to do with phosphorus' ability to be effective.

Forgive my ignorance, but I still can't see the relevance of Pi acidity here. Pi acidity refers to the ability of a compound to accept electron density into empty Pi orbitals. This interaction is impossible with SOCl₂, S₂Cl₂, SCl₂ etc --- they simply don't have orbitals of the correct symmetry for this kind of interaction. Seriously, draw me an orbital diagram; if I'm wrong I'd like to know why. Have a look at a metal-phosphine two-way bond (https://en.wikipedia.org/wiki/Metal_phosphine_complex) and explain to me how chlorine is doing that.

All that's going on here is attack of the phosphite lone pair on an electrophile of the "Cl⁺" type: S₂Cl₂, SCl₂, whatever. One way movement of electrons. Simple, first year orgo. No electron density is moving from the electrophile to phosphorus. Thus pi acidity---the ability of the phosphine to accept electron density---does not seem relevant to me. The phosphite is just sucking up "Cl⁺" donating impurities in SOCl₂ as a sigma nucleophile. That's why the alternative of olefin-rich terpines like linseed oil is offered in The Purification of Laboratory Compounds. Really, any soft nucleophile will do. Pi acceptor ability isn't needed here.

Also, nobody's serious proposing the preparation of SOCl₂ from sulfuryl chloride (SO₂Cl₂), right? SOCl₂ is dirt cheap, and actually making it from any other substance is not going to be worth your time. Firstly, I wouldn't count on phosphites to reduce SO₂Cl₂ in the way you mean, as SO₂Cl₂ is chlorine rather than an oxygen donor. Look at its reactivity --- it's a chlorinating reagent! Can anyone find me a reaction where a nucleophile attacks SO₂Cl₂ on oxygen? And even if you could reduce SO₂Cl₂ to SOCl₂, in my opinion you'd be crazy to even bother.

Yes, you sir are right, but I'm not so good with words sometimes; no one but Chem engineers would turn SO₂Cl₂ to thionyl chloride.  Phosphorus has empty pi orbitals like this. 


If chloride has pi electrons, which are not solely sp³, then it will constructively interfere with any empty orbital.  Even lone pairs will constructively interfere with other lone pairs aka the alpha effect eg HOOH.  Once the phosphite forms a complex with Cl+, it can form a trig bipyramid complex with a the rest of the complex.  It will better accept electrons here if it is more pi acidic, P(OPh)₃ also is more favorable for steric reasons.  Therefore, it will drive the reaction in the forward direction if there is less electron density...phosphorus has accessible d orbitals so it acts like a metal

[Babcock_Hall]

Also, nobody's serious proposing the preparation of SOCl₂ from sulfuryl chloride (SO₂Cl₂), right? SOCl₂ is dirt cheap, and actually making it from any other substance is not going to be worth your time. Firstly, I wouldn't count on phosphites to reduce SO₂Cl₂ in the way you mean, as SO₂Cl₂ is chlorine rather than an oxygen donor. Look at its reactivity --- it's a chlorinating reagent! Can anyone find me a reaction where a nucleophile attacks SO₂Cl₂ on oxygen? And even if you could reduce SO₂Cl₂ to SOCl₂, in my opinion you'd be crazy to even bother.

I think that sulfuryl chloride is a common impurity in thionyl chloride, and one that is difficult to remove by distillation because of their closeness in boiling points.  The purpose of reducing it to thionyl chloride is to produce thionyl chloride of greater purity.

With respect to the excess mass in the synthesis of sodium trichloromethanesulfinate (the first step in the synthesis), I have heard back from one of the authors of the paper, who was friendly but who was not able to offer any advice.

[Babcock_Hall]

Yesterday I added sulfuric acid and attempted to bring the solid into solution, but it remained a partial suspension.  I attempted a distillation at reduced pressure.  An unpleasant gas was given off, and I collected very little product.  All I obtained was a little bit of an orange liquid and a yellow semi-solid.

[phth]

₃Read a patent a while ago but I can't find the correct method.  SO₂+Cl₂.  The way the reaction is controlled is through a cylindrical chamber of hot catalyst; the extent of the reaction varies by Δx, so it's really easy to make sufuryl chloride or thionyl chloride.  Sufuryl chloride is the shorter distance of the two

I think it's work a scifinder search.  Pass it through activated carbon with metals to stabilize the stationary phase in a distillation column.  They tested the spiked carbon by oxidative stress of the catalyst using thermal gravimetry temperature step.  After a certain point the carbon, spiked with e.g. a 1000 ppm Fe..., would suppress the formation of the byproducts such as CCl₂4, CHCl₃, DCM.   

[Babcock_Hall]

I think my first attempt to make sodium trichloromethanesulfinate can be declared to be a bust, but I won't have time to try again for a little while.  That may be a good thing; perhaps like Sherlock Holmes, I need to sit on a pillow and smoke a bunch of bowls of tobacco until it comes to me.  I don't remember which story that was...

[Enthalpy]

Hey Babcock_Hall, are you still interested in this ClSOCCl₃ intermediate? It may be a candidate for the intermolecular photocoupling
http://www.chemicalforums.com/index.php?topic=81721.0
if heat doesn't suffice. Sketch appended.

Starting with SOCl₂ and CHCl₃:

• Both have a usable vapour pressure, 16kPa and 26kPa at +25°C, still 5kPa and 8kPa at 0°C
  https://en.wikipedia.org/wiki/Thionyl_chloride
  https://en.wikipedia.org/wiki/Chloroform
  and ClSOCCl₃ is expected to be less volatile hence exit the reaction zone, avoiding a further step.
• At 254nm from a low-pressure mercury lamp, SOCl₂ molecules have 6.3*10^-18cm² cross-section, but CHCl₃ only 2.0*10^-23cm² and HCl <<3.4*10^-23cm², CCl₄ (represents C₂Cl₆) 1*10^-21cm², N₂ nothing
  http://satellite.mpic.de/spectral_atlas
  At +25°C and half the SOCl₂ vapour pressure, the exponential attenuation distance is 0.4mm, and at 0°C 2.5mm.
• Under the small assumption that an absorbed photon breaks a Cl-SOCl, the °Cl radical abstracts an °H from CHCl₃ to create HCl and °CCl₃. Since H-CCl₃ is 8kJ weaker than at t-butyl it must proceed quickly even at 0°C.
  http://staff.ustc.edu.cn/~luo971/2010-91-CRC-BDEs-Tables.pdf
• Does °CCl₃ break the abundent Cl-SOCl? I have no data for the bond dissociation energy. The unwanted reaction seems to be energetically neutral, the activation energy is unknown. That's a big uncertainty. Cold must improve.
• °SOCl and °CCl₃ hopefully recombine as C₂Cl₆, S_xO_yCl_z and, with 50% yield at best, ClSO-CCl₃. Fortunately, the reactants are much cheaper than the sought intermediate.
• 28W light from 87W electricity make 5mol/day photons, and at 50% best possible yield, 519g/day ClSOCCl₃.
  http://www.light-sources.com/germicidal-uvc/products/low-pressure-mercury-lamps/high-output-quartz

How common is such a photochemical reactor in labs? Besides toxicity, the setup looks rather simple.
Marc Schaefer, aka Enthalpy