When one hydrogen atom is removed from an alkane, it is called ?

In organic chemistry, alkanes are the simplest hydrocarbons, consisting only of single bonds between carbon atoms and hydrogen atoms. Their general molecular formula is CₙH₂ₙ₊₂. When one hydrogen atom is removed from an alkane molecule, the resulting group is no longer a stable molecule on its own but becomes a radical fragment known as an alkyl group.

The general formula for an alkyl group is CₙH₂ₙ₊₁, derived from the parent alkane by removing one hydrogen atom. This removal creates a valence vacancy, meaning the alkyl group can attach to another atom or functional group to form more complex organic compounds. For example:

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  Methane (CH₄) → remove one hydrogen → Methyl group (–CH₃)

  
  


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  Ethane (C₂H₆) → remove one hydrogen → Ethyl group (–C₂H₅)

  
  


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  Propane (C₃H₈) → remove one hydrogen → Propyl group (–C₃H₇)

  
  

These alkyl groups act as substituents in larger organic molecules. They are commonly represented by the symbol R, such as in R–OH (alcohol), R–Cl (alkyl halide), or R–COOH (carboxylic acid).

The removal of one hydrogen atom does not make the compound unsaturated because there is no formation of a double or triple bond — the remaining carbon atoms remain saturated with single bonds. This differentiates alkyl groups from alkenes (which contain double bonds) and alkynes (which contain triple bonds).

Key Points:

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  Parent hydrocarbon: Alkane (CₙH₂ₙ₊₂)

  
  


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  Resulting group: Alkyl (CₙH₂ₙ₊₁)

  
  


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  Common examples: Methyl (–CH₃), Ethyl (–C₂H₅), Propyl (–C₃H₇)

  
  


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  Alkyl groups are substituents and never exist freely in nature.

  
  


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  Symbol used for alkyl group: R

  
  

✅ Correct Answer: B) Alkyl