JEE Advanced 2024 — Paper 2 — CHEM-II solution

JEE Advanced2024Paper 2CHEM-II

The compound(s) having peroxide linkage is(are)

A
$H_{2} S_{2} O_{7}$
B
$H_{2} S_{2} O_{8}$
C
$H_{2} S_{2} O_{5}$
D
$H_{2} S O_{5}$

Solution

A peroxide linkage is an $- O - O -$ bond between two oxygen atoms. Examine each structure:

$H_{2} S_{2} O_{7}$ (pyrosulfuric acid): two $- S O_{3} H$ units linked by a single bridging oxygen, $H O - S O_{2} - O - S O_{2} - O H$ . No $O - O$ bond.

$H_{2} S_{2} O_{8}$ (peroxydisulfuric acid, Marshall's acid): two $- S O_{3} H$ units bridged by a peroxide linkage, $H O - S O_{2} - O - O - S O_{2} - O H$ . Contains one $- O - O -$ bond.

$H_{2} S_{2} O_{5}$ (pyrosulfurous acid): structure $H O - S O_{2} - S O - O H$ with a direct $S - S$ bond rather than an $O - O$ bond.

$H_{2} S O_{5}$ (peroxomonosulfuric acid, Caro's acid): one of the oxygens of the $S$ centre is replaced by a peroxide group, $H O - S O_{2} - O - O - H$ . Contains one $- O - O -$ bond.

Therefore peroxide linkages are present in $H_{2} S_{2} O_{8}$ and $H_{2} S O_{5}$ , giving options (B) and (D).

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