[nancyVIII]

Hi All,

I am trying to prepare dimethyl sulfoxide (DMSO) from dimethyl sulfide (DMS) by oxidizing it with a 30 wt. % solution of hydrogen peroxide in water (H₂O₂); for this reaction, I am planning to use 1 mol equivalent of DMS and H₂O₂.  I don't want any H₂O₂ in the product, so I'd like to know what the best method is to neutralize any H₂O₂ that may remain in the solution?

Thanks in advance,

Nancy

[discodermolide]

Hi All,

I am trying to prepare dimethyl sulfoxide (DMSO) from dimethyl sulfide (DMS) by oxidizing it with a 30 wt. % solution of hydrogen peroxide in water (H₂O₂); for this reaction, I am planning to use 1 mol equivalent of DMS and H₂O₂.  I don't want any H₂O₂ in the product, so I'd like to know what the best method is to neutralize any H₂O₂ that may remain in the solution?

Thanks in advance,

Nancy

H2O2 decomposes to water and O2 when treated with base.

[Borek]

H2O2 decomposes to water and O2 when treated with base.

Catalytic decomposition will be much safer - much less risk of contamination of the solution with something you don't want there.

[discodermolide]

H2O2 decomposes to water and O2 when treated with base.

Catalytic decomposition will be much safer - much less risk of contamination of the solution with something you don't want there.

Catalytic decomposition will cause it to decompose uncontrollably. A regular dosing of base controls the reaction, stop the addition the reaction stops.

[Borek]

OP wants to decompose everything, so IMHO it shouldn't be a problem.

Besides, I don't see how NaOH can react with H₂O₂ the way you state it does, can you elaborate? I fail to see how NaOH can be consumed in such a reaction, so I don't see how the reaction can stop after you stop adding base.

[discodermolide]

OP wants to decompose everything, so IMHO it shouldn't be a problem.

Besides, I don't see how NaOH can react with H₂O₂ the way you state it does, can you elaborate? I fail to see how NaOH can be consumed in such a reaction, so I don't see how the reaction can stop after you stop adding base.

I did not mention NaOH.
Think of the Evans chemistry, removal of the oxazolidine chiral aux.
LiOH, THF, H2O2, 90% of the H2O2 vanishes as O2 any H2O. If you stop addition of LiOH the reaction stops. I have done this many times on a very large scale.

[orgopete]

@OP
I don't think there is a problem here.

Me₂S + H₂O₂  Me₂S=O + H₂O

Me₂S=O + H₂O₂  Me₂SO₂ + H₂O

How to avoid hydrogen peroxide in product? Stop the addition. Dimethyl sulfide is a pretty good reductant. I don't think you need to do anything else.

@discodermolide
I'm not seeing this. What is the mechanism here? You can make the anion of hydrogen peroxide without decomposition. If you want to do a conjugate addition to an enone, use hydrogen peroxide and (catalytic amount) base.

I can write a balanced equation for the formation of oxygen and water without base. Therefore, a catalyst only need to change the reaction path, not the stoichiometry. As described, this is a stoichiometric reaction, "If you stop the addition of LiOH the reaction stops." I do not understand what is being oxidized.

If you do a Payne oxidation, if the reaction is basic, then oxygen is released.

RCN + H₂O₂ (base)  RCONH₂ + O (bracketed)

2O  O₂

If not basic, the peroxy imidate can be intercepted to form an epoxide.

[discodermolide]

There is not a problem. I am just saying that the H2O2 decomposition is accelerated by base. see measurements attached.
If you stop the base addition the oxygen generation stops. (I don't have that data on this pc). And oxygen generation is dangerous, as we all know.

[nancyVIII]

I have available an aqueous solution of sodium hydroxide (NaOH), as well as an aqueous mixture of sodium bisulfite (NaHSO₃) and sodium metabisulfite (Na₂S₂O₅).  Therefore, I could use either one to neutralize any unreacted H₂O₂, before purifying the DMSO (by vacuum distillation).  Would one of these choices be preferable for this particular reaction?