Question

Which are not cleaved by $HI{O_4}$ ?
$I$ : glycerol
$II$ : Glycol
$III$ : $1,3$ -propanediol
$IV$ : methoxy- $2$ -propanol
(A) $I,II,III,IV$
(B) $I,II$
(C) $II,III$
(D) $III,IV$

Answer 1

Iodine in combination with oxygen forms oxyacids with different molecular formulas. One of them is periodic acid with a molecular formula of $HI{O_4}$ . It cleaves $1,2$ diols or the compounds consisting of hydroxyl groups attached to the adjacent carbon atoms.

Complete answer:
Glycerol is a polyhydroxy compound consisting of three hydroxyl groups attached to the three adjacent carbon atoms. The molecular formula of glycerol is ${C_3}{H_8}{O_3}$ . The structure of glycerol is:
$C{H_2}\left( {OH} \right) - CH\left( {OH} \right) - C{H_2}\left( {OH} \right)$
As it consists of adjacent carbon with hydroxyl group it can be cleaved by periodic acid $\left( {HI{O_4}} \right)$
Glycine is also a poly hydroxy compound consisting of two hydroxyl groups attached to the adjacent carbon atoms. Thus, it can also be cleaved by periodic acid $\left( {HI{O_4}} \right)$ . The structure of glycol is:
$C{H_2}\left( {OH} \right) - C{H_2}\left( {OH} \right)$
$1,3$ -propanediol has the two hydroxyl groups attached to the carbon atoms present in one and three positions. Thus, it cannot be reduced by periodic acid $\left( {HI{O_4}} \right)$
The structure of methoxy- $2$ -propanol will be $C{H_3} - CH\left( {OH} \right) - C{H_2}\left( {OC{H_3}} \right)$ . it does not have two adjacent carbon atoms with hydroxyl groups. Thus, it is not cleaved by periodic acid $\left( {HI{O_4}} \right)$
Thus, $1,3$ -propanediol and methoxy- $2$ -propanol will not cleaved by $HI{O_4}$
Thus, $III$ and $IV$ are not cleaved by $HI{O_4}$
Option D is the correct one.

Note:
If the two hydroxyl groups are attached to the same carbon atoms. Then that compound can be known as a geminal diol. If the two hydroxyl groups are attached to the adjacent carbon atoms, then that compound is known as a vicinal diol. Periodic acid cleaves vicinal diols mainly.