Question

Which of the following will be oxidized by $HI{O}_4$ ?

$1.$ $R-\underset{O}{\underset{||}{C}}-\underset{O}{\underset{||}{C}}-R$

$2.$ $R-\underset{O}{\underset{||}{C}}-\underset{OH}{\underset{|}{\mathrm{CH}}}-R$

$3.$ $R-\underset{OH}{\underset{|}{\mathrm{CH}}}-C{H}_2-\underset{OH}{\underset{|}{\mathrm{CH}}}-R$

$4.$ $R-\underset{OH}{\underset{|}{\mathrm{CH}}}-\underset{OH}{\underset{|}{\mathrm{CH}}}-R$

Select the correct answer using the codes below

• A. 1, 2 and 3
• B. 1, 3 and 4
• C. 1, 2 and 4
• D. 2, 3 and 4

Answer 1

Answer: (C)

The net result of oxidation is the cleavage of the bond between C's with the attached O's with addition of OH to 'C' of each $C-O$ .

In 1, 2-diols, the net effect is the oxidation is the cleavage of bond and attachment of an OH to each 'C' atom. The gem-diol so formed loses a molecule of $H_{2}O$ .

$1.$ $R-\underset{O}{\underset{||}{C}}-\underset{O}{\underset{||}{C}}-R\stackrel{HI{O}_4}{\to }R-\underset{O}{\underset{||}{C}}-OH+HO-\underset{O}{\underset{||}{C}}-R$

$2.$ $R-\underset{O}{\underset{||}{C}}-\underset{OH}{\underset{|}{\mathrm{CH}}}-R\stackrel{HI{O}_4}{\to }R-\underset{O}{\underset{||}{C}}-OH+O=CH-R$

$4.$ $R-\underset{OH}{\underset{|}{\mathrm{CH}}}-\underset{OH}{\underset{|}{\mathrm{CH}}}-R\stackrel{HI{O}_4}{\to }R-CH=O+O=HCR$