[taurean]

I did an ozonolysis reaction in dichloromethane followed by reductive workup (Me2S), the byproduct is formaldehye.  How can I separate formaldehyde from the desired product (aldehyde) without having to do column chromatography?

Thanks for any help.

Taurean

[nj_bartel]

I know nothing about this reaction, but formaldehyde is an aldehyde.. What product are you trying to get?

[movies]

Formaldehyde is pretty volatile (bp is –19 degrees C).  It will probably boil off when you concentrate the reaction mixture.  It's also miscible with water, so you could wash it out with an aqueous workup.

[taurean]

Formaldehyde is pretty volatile (bp is –19 degrees C).  It will probably boil off when you concentrate the reaction mixture.  It's also miscible with water, so you could wash it out with an aqueous workup.

Movies,

After ozonolysis and Me2S workup, I did aqueous workup.  I could remove some of the byproduct (less intense spot on TLC).  Then I put it on high vaccum for at least 7 hrs (TLC still shows a less intense byproduct spot).  Now, I started thinking that it may not be formaldehyde.  Can formaldehyde dimerize, trimerize or polymerize on aqueous workup?  Please let me know.

Thanks,
Taurean

[movies]

Yeah, after that I would say it is probably something other than formaldehyde.  Formaldehyde can trimerize (the trimer is sometimes called trioxane) and polymerize (paraformaldehyde).  A number of other things might happen under ozonolysis conditions, the most likely would be over oxidation of your substrate.

[taurean]

Yeah, after that I would say it is probably something other than formaldehyde.  Formaldehyde can trimerize (the trimer is sometimes called trioxane) and polymerize (paraformaldehyde).  A number of other things might happen under ozonolysis conditions, the most likely would be over oxidation of your substrate.

I see my product on TLC along with some other spot (I assumed it to be formaldehyde).  If it is something else, what do you think is the best way to separate it?  I cannot chromatograph or distill; my product aldehyde is unstable.  The product aldehyde is not a solid either.  I know its difficult to answer something like this, but just want to know if you think of something different which I am not able to think.

Thanks for your help

[sjb]

How clean do you need your product? What's the next step? Could you take on crude and perhaps separate after this?

Of course, this is partially dependent on what the byproduct is - any clues on NMR or similar?

[movies]

Is the aldehyde unstable with respect to SiO₂ chromatography?  You might try something like Florisil which tends to be less abrasive to compounds.

Usually distillation at reduced pressure is good for thermally sensitive compounds.  If the bp is low enough, you can just do a vacuum transfer with no heating.

There are some other some other tricks, notably the aldehyde adduct with sulfite.

[Custos]

What scale are you working on? HPLC on reverse phase might be an option.

[taurean]

Guys! Thanks for all the help.  I was able to solve the problem by dissolving the reaction mixture in water, followed by extraction after 8 hrs.