MCQ Detailed View

The oxygen–oxygen bond, also called the peroxide linkage (–O–O–), is a special type of covalent bond that exists in some compounds where two oxygen atoms are directly bonded to each other. Among sulfur oxoacids, this bond is a distinguishing feature of peroxydisulfuric acid (H₂S₂O₈).

Peroxydisulfuric acid, also known as Marshall’s acid, contains two sulfur atoms, each in a +6 oxidation state, bonded through oxygen atoms. Its structure includes a –O–O– linkage, which makes it different from other common sulfur acids. The O–O bond is relatively weak compared to other covalent bonds and contributes to the strong oxidizing properties of the compound.

Let us briefly compare the other options to understand why they do not contain an O–O bond:

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  Thiosulfuric acid (H₂S₂O₃): This acid contains sulfur atoms bonded with oxygen and one sulfur-sulfur linkage, but it does not contain an O–O bond.

  
  


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  Tetrathionic acid (H₂S₄O₆): This compound contains a chain of sulfur atoms but no peroxide linkage. Its bonding involves S–S linkages.

  
  


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  Dithionic acid (H₂S₂O₆): This acid has sulfur atoms in a higher oxidation state with oxygen bonds, but there is no O–O bond present.

  
  

Only H₂S₂O₈ (peroxydisulfuric acid) has the characteristic O–O bond. Because of this, it is classified as a peroxy acid, a special group of compounds that contain a peroxide linkage. These compounds are generally strong oxidizers and are important in both inorganic and industrial chemistry.

The presence of the O–O bond in peroxydisulfuric acid also explains its instability and reactivity compared to other sulfur oxoacids.

Thus, the compound that contains an O–O bond is peroxydisulfuric acid, H₂S₂O₈.