Benzaldehyde synthesis from benzyl alcohol. 1 kg Scale.

[WillD]

Reaction scheme:​

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Synthesis:
1. A mixture of the benzyl alcohol (1000 g) and conc. H2SO4 (930 g) in DMSO (3000 ml) was stirred 2 hours under reflux conditions.
2. The mixture was then cooled to r.t., and brine (4000 ml) was added.
3. The organic phase was extracted with CH2Cl2 (3000 ml), and the organic layer was dried (Na2SO4), filtered, and concentrated under reduced pressure.
4. Benzaldehyde was obtained in good purity, which does not require additional purification.​

 

[Jack]

Sci-Hub | Sulfuric Acid-Promoted Oxidation of Benzylic Alcohols to Aromatic Aldehydes in Dimethyl Sulfoxide: An Efficient Metal-Free Oxidation Approach | 10.1055/s-0037-1609149

 

[The Silent Chemist]

2. The mixture was then cooled to r.t., and brine (4000 ml) was added.

Are they washing it here and then separating the 2 layers in a sep funnel or putting the whole 4000ml worth of brine in at once and leaving it in there for the next step
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3. The organic phase was extracted with CH2Cl2 (3000 ml), and the organic layer was dried (Na2SO4), filtered, and concentrated under reduced pressure.

I assume in this step the reaction mixture is washed with three portions of 1000ml DCM and then those are pooled together and reduced under a vacuum after being dried with Na2SO4 and filtered

 

[G.Patton]

Hi, this way is correct. You are right in the second statement.

 

[The Silent Chemist]

Im guessing MgSO4 can be used as a substitute to Na2SO4

Thank you for your response ! And thank you to the BB team

 

[Fenster]

This is a lot of sulfuric acid. I think a better route is dilute nitric acid with NaNO2 catalyst.

 

[BrownRiceSyrup]

Im hesitant to do this, and believe me i really fucking want to, but im afraid of what ive heard about dmso. That at even its own boiling temperature without vacuum it can go through thermal decomposition and have some runaway reaction that ultimately can explode or some shit. Having acids or bases, oxidizers or reductants and in particular halides in the mix dramatically lowers the temperature needed for this "runaway thermal decomposition"..... Meanwhile we are adding mega H2SO4..... and then the article posted above, refferring to this exact reaction, just casually mentions refluxing dmso in stuff that have higher boiling points than the dmso itself..... Can someone please offer some insight? Or am i misunderstanding some potential warning about dmso

 

[OrgUnikum]

Nobody in his right mind works with DMSO except there is no other option. Whats wrong with OTC ammonium or sodium persulfate (for etching electronic circuit boards)? Plenty of other ways to get from BzOH or Toluene to Benzaldehyde, you can find all the tried and true methods at sciencemadness.org, for German speakers I can also recommend lambdasyn.org.

Everybody here seems to be convinced its his calling to re-invent the wheel, it all looks strangely square to me though....

 

[The Silent Chemist]

That’s what’s iv thought, iv seen a lot of synthesis on science madness over the years with cheaper and more available reagents that seem like viable options just get ignored over here ? Why ?