# Oxidation of diols using periodic acid

What are the orders of rates of oxidation with $$\ce{HIO4}$$ of the following diols? Explain with reasons.

(a) $$\ce{Me2C(OH)C(OH)Me2}$$
(b) $$\ce{Me2C(OH)CH(OH)Me}$$
(c) $$\ce{CH2(OH)CH2(OH)}$$
(d) $$\ce{MeCH(OH)CH(OH)Me}$$

I know that the reaction proceeds by forming a cyclic diester of periodic acid followed by cleavage of $$\ce{C-C}$$ bond and formation of $$\ce{C=O}$$ bond. But how do we compare the rates of the given compounds?

My first thought was to think $$\ce{C-C}$$ cleavage as formation of a pseudo carbocation which would be stabilised by +I effect of the alkyl groups and also the hyperconjugation, but I don't think it is right.

• Could it possibly be related to stearic hinderance for the ring to form? – Sidharth Giri Mar 19 at 9:21
• Could be but I am not sure – Aditya Garg Mar 19 at 10:22
• @SidharthGiri and Aditya One thing which you can be assured is that,whatever the differentiating factor is,it will certainly be before the formation of thr cyclic intermediate as after that,it is a pericyclic intramolecular rearrangement which is pretty easy to be done in all the cases with minimum requirement of any activation energy.. – YUSUF HASAN Mar 19 at 10:39
• Also.. Is the answer a>b>d>c? – YUSUF HASAN Mar 19 at 11:10
• I don't have the answers and that is also a big problem – Aditya Garg Mar 19 at 13:04