Compound containing two halogen atoms on two adjacent carbon atoms are called as ?

In organic chemistry, dihalides are compounds that contain two halogen atoms (Cl, Br, I, or F) attached to a hydrocarbon chain. Depending on the position of the halogen atoms, dihalides are classified into two main types:

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   Vicinal dihalides – when the two halogen atoms are attached to two adjacent carbon atoms.

   
   
   
   
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     Example: CH₂Cl–CH₂Cl (1,2-dichloroethane).

     
     
   
   
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     The word "vicinal" comes from the Latin vicinus meaning “neighboring.”

     
     
   
   
   
   


2. 
   

   Geminal dihalides – when the two halogen atoms are attached to the same carbon atom.

   
   
   
   
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     Example: CHCl₂–CH₃ (1,1-dichloroethane).

     
     
   
   
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     The word "geminal" comes from gemini meaning “twins.”

     
     
   
   
   
   

Why option 2 (Vicinal dihalides) is correct?

Because the definition in the question clearly states two halogen atoms on two adjacent carbons, which is the exact definition of a vicinal dihalide.

Why the other options are incorrect?

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  Option 1 (Glycols): These are compounds with two hydroxyl (–OH) groups on adjacent carbons, not halogens.

  
  


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  Option 3 (Geminal dihalides): Wrong, because geminal dihalides have both halogen atoms on the same carbon atom.

  
  


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  Option 4 (Diols): These contain two hydroxyl groups (–OH) but no halogens.

  
  

Key facts about vicinal dihalides:

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  They are commonly prepared by the halogenation of alkenes. For example, when ethene reacts with Br₂, vicinal dibromoethane is formed.

  
  


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  They are important intermediates in organic synthesis. For example, vicinal dihalides can undergo dehydrohalogenation to form alkynes.

  
  


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  Industrially, compounds like 1,2-dichloroethane are used in the manufacture of vinyl chloride (PVC production).