Chapter 15: Alcohols, Diols and Thiols Ch 15 contents

Oxidative Cleavage of Diols

periodic acid cleavage of 1,2-diols

Reaction type: Oxidation-reduction

Summary
 

  • 1,2- or vicinal diols are cleaved by periodic acid, HIO4, into two carbonyl compounds.
  • The reaction is selective for 1,2-diols.
  • The reaction occurs via the formation of a cyclic periodate ester (see right).
  • This can be used as a functional group test for 1,2-diols.
  • The products are determined by the substituents on the diol.
Questions:
Can you recall a reaction that forms carbonyl groups via cleavage of an alkene ? ozonolysis (see Ch6)
How are 1,2-diols made from alkenes ? hydroxylation : OsO4 / tBuO2H or KMnO4 / NaOH
What are the oxidation states of the iodine in HIO4 and HIO3 ? iodine VII and V respectively
 
PERIODATE CLEAVAGE OF 1,2-DIOLS
The mechanism is not trivial, so attention here is focussed on the actual cleavage step. Prior to this, the alcohol reacts to form a cyclic periodate ester (shown). The periodate ester undergoes arearrangement of the electrons, cleaving the C-C bond, and forming two C=O.
periodate cleavage of 1,2-diols

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