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Is the three member ring of cyclic ether oxidised by periodic acid? As this also has oxygen attached to adjacent carbon so I think that cyclic ether of three members should be oxidised by periodic acid.
I know the mechanism of oxidation of 1,2 diols by periodic acid but ain't able to relate to this question. Please help me out here.
Cyclic ethers usually do not get oxidized by periodic acid. However, epoxides would do only if they were acidified first or use acidified periodic acid in the reaction (Ref.1). In general, acidified periodic acid has been used as a qualitative test for the presence of epoxide moiety in organic compounds (Ref.1). The procedure is a modification of the qualitative test for glycols (Ref.2). Hence, epoxide must be converted to 1,2-diols first by acid and oxidation by periodic acid must be followed. The test is described as follows:
Exactly 2 drops of concentrated nitric acid is added to 2 ml. of a 0.5% solution of periodic acid, and 1 or 2 drops of the unknown is added. Water-insoluble unknowns should first be dissolved in 2 ml. of dioxane or acetic acid. The mixture is shaken and 1 or 2 drops of 5% silver nitrate is added at room temperature. A positive test is the appearance of a white precipitate of silver iodate which usually forms immediately, but may require up to 5 minutes for complete precipitation. In all cases a blank should be run for comparison. The test is negative for simple aldehydes, ketones, and alcohols.
References:
This quote is from Comprehensive Organic Name Reactions and Reagents by Zerong Wang.
The oxidation of adjacent diols with periodic acid or its salt in aqueous solution is generally known as the Malaprade reaction. Several solvents have been used to increase the solubility of organic substrates and the reaction proceeds faster under acidic conditions. This reaction has been further extended to the cleavage of α‐hydroxy carbonyl compounds, 1,2‐dicarbonyl compounds, α‐amino alcohols, α‐amino acids, and polyhydroxy alcohols. .
The mechanism of Malaprade reaction reaction is as follows:
As per the requirements of mechanism , the three membred ether should be converted to a adjacent diols (viscinal) diol for it to be oxidised by periodic acid.
The epoxide in acidic hydrolysis undergos ring opening to give 1,2 diol .This would undergo oxidation with periodic acid.
