Question

Identify the correct sequence of increasing number of $\pi$ -bonds in the structures of the following molecules:
(I) $H_2{S}_2{O}_6$ (II) $H_2{SO}_3$ (III) $H_2{S}_2{O}_5$

• A. I, II, III
• B. II, III, I
• C. II, I, III
• D. I, III, II

Answer 1

The correct option is D I, III, II

$H_2{S}_2{O}_6$ $HO-\stackrel{O}{\underset{\underset{O}{||}}{\stackrel{||}{S}}}-\stackrel{O}{\underset{\underset{O}{||}}{\stackrel{||}{S}}}$ $4\pi -bonds$

$H_{2}S{O}_3$ $HO-\stackrel{O}{\underset{\underset{OH}{||}}{\stackrel{||}{S}}}$ $1\pi -bonds$

$H_2{S}_2{O}_5$ $HO-\stackrel{O}{\underset{\underset{O}{||}}{\stackrel{||}{S}}}-\stackrel{O}{\stackrel{||}{S}}-OH$ $3\pi -bonds$

Hence, option $D$ is correct.