Oxidative cleavage of 1,2-diols to give aldehydes/ketones
Description: Treatment of vicinal diols (1,2-diols) with an oxidant such as NaIO4, HIO4, or Pb(OAc)4 cleaves C–C bonds and forms carbonyl compounds.
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Notes: For our purposes NaIO4, HIO4, or Pb(OAc)4 are essentially equivalent for this purpose.
Examples:
Notes: Note that whether or not the carbonyl compound product is an aldehyde or ketone depends on the substitution pattern of the alcohol. Secondary alcohols are become aldehydes, tertiary alcohols become ketones, and primary alcohols become formaldehyde.
Mechanism: Four boring steps precede the important C–C cleavage step (Step 5). Attack of oxygen on iodine (Step 1, arrows A and B) is followed by a proton transfer (Step 2, arrows C and D). This is followed by a second iodine-oxygen bond being formed (Step 3, arrows E and F). and a second proton transfer (Step 4, arrows Ga nd H). Finally iodine is reduced from I(VII) to I(V) with accompanying C–O π bond formation and C–C bond cleavage to give the two carbonyls along with iodine (V).
Notes: The mechanism involving NaIO4 and Pb(OAc)4 are very similar.
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{ 9 comments… read them below or add one }
My question is regarding Lead(IV) acetate. Does the initial compound have to have both a secondary and tertiary alcohol in order to have the reaction or can the reaction occur in the presence of just a tertiary or a secondary alcohol? In other words, could the reaction occur if the initial compound was a simple alkane with a secondary alcohol attached? Thank you! Your website and resources are fantastic and very helpful :D
Hi Crystal – you absolutely need two adjacent alcohols. It won’t work with a single isolated alcohol. Hope this helps – James
can we have 2 alcohols on same carbon…. ???
Yes, it’s called a “geminal diol”, or sometimes, a “hydrate”. It will not undergo oxidative cleavage however
I was struggled do my uni organic synthesis tutorial . this helped me a lot. thanks
I have was just wondering if compounds, other than lead (IV) acetate, could be used in this oxidative cleavage? Such as Tin (IV) acetate or other acetate salts like ferric acetate or cupric acetate?
Sodium periodate will do it, as will periodic acid. Ruthenium tetraoxide will do this too. Tin acetate is not an oxidant; copper acetate won’t do it; Iron acetate will not lead to this oxidation in the absence of other oxidants. One could maybe add hydrogen peroxide to the Fe(III), but then all hell would break loose.
when does it become a ketone and when does it become an aldehyde
Tertiary alcohols become ketones; secondary alcohols become aldehydes; primary alcohols break off and become formaldehyde (which likely will be oxidized to CO2 under the reaction conditions)