https://www.thevespiary.org/rhodium/Rhodium/chemistry/benzaldehydes.kmno4.html

it states here that to oxidise styrene to benzaldehyde, 4.65g of KMnO4/alumina reagent is required to oxidise 1mmol! that seems entirely rediculous! if one wanted to oxidise 100mmol, which is only about 5 grams, one would require over a pound of KMnO4/alumina reagent plus enough DCM to dissolve everything! why is so much reagent required to reduce so little? this seems entirely impractical if one wanted straight benzaldehyde...

if my calculations are right, then that's 5mmol KMnO4 per
1mmol styrene. do you know the theoretical amount? even
if it's equimolar (which i doubt), that's still 90g of
catalyst for 100mmol. sounds impractical.  
maybe using less alumina works too?
(afaik KMnO4 oxidations suck anyway)

> if one wanted to oxidise 100mmol, which is only about 5 gram

no, that's about 10g (styrene or benzaldehyde)

> plus enough DCM to dissolve everything!

no, i don't think the alumina/KMnO4 will dissolve in DCM  

yeah it is about 10g, my bad. when i say "enough DCM to dissolve everything" i mean enough DCM to hold everything together in a slurry for stirring. i sorta figured that the reagent wouldn't dissolve in a NP, me stoopid again.  

i noticed in another writeup for oxidising styrene to benzaldehyde styrene was used basically as a toluene substitute, it too being reacted with mnO2 + H2SO4 to form the aldehyde. i was wondering, since toluene can bee chlorinated to benzal chloride then reacted with either ZnCl or CaCO3 + H2O to form benzaldehyde, could styrene also bee chlorinated in the same fashion then reacted similarly to form benzaldehyde, just like a toluene substitute? (since they form the same compound when reacted with mnO2 + H2SO4)

any ideas?

the alternative low yielding aqueous permanganate oxidation doesn't
look tasty either:

https://www.thevespiary.org/rhodium/Rhodium/chemistry/tma2np.html

seems like permanganate oxidations simply do suck.

> i was wondering, since toluene can bee chlorinated to benzal chloride
> then reacted with either ZnCl or CaCO3 + H2O to form benzaldehyde, could
> styrene also bee chlorinated in the same fashion then reacted similarly to
> form benzaldehyde, just like a toluene substitute? (since they form the same
> compound when reacted with mnO2 + H2SO4)

no. chlorine would add accross the double bond giving an unwanted compound.
(something like 1,2-dichloro-1-phenyl-ethane)

but tell: you can get styrene and not toluene!?