[Mcore]

Hello I have a quick question as I am new to studying chemistry.

Appently there are nine isomers of Heptane http://en.wikipedia.org/wiki/Heptane and http://www.3rd1000.com/chem301/heptane.htm

    * Heptane
    * 2-Methylhexane
    * 3-Methylhexane
    * 2,2-Dimethylpentane
    * 2,3-Dimethylpentane
    * 2,4-Dimethylpentane
    * 3,3-Dimethylpentane
    * 3-Ethylpentane
    * 2,2,3-Trimethylbutane

As you can see there is only 3-Ethylpentane. My question is why cant there be 2-Ethylpentane?

 
      H  H H  H H
      |  |  |  |  |    
   H-C-C-C-C-C-H      2-Ethlypentane? C₇H₁₆
      |  |  |  |  |
      H  | H  H  H
         |
      H-C-H
         |
      H-C-H
         |
         H 

[kryptoniitti]

Look for the longest carbon chain in 2-Ethlypentane and you'll see why it's named something else (that already appears in the list).

[Mcore]

 
      H  H H  H H
      |  |  |  |  |    
   H-c-C-C-C-C-H     
      |  |  |  |  |
      H  | H  H  H
         |
      H-C-H
         |
      H-C-H
         |
         H 

Ah I see now... I capitalised the longest carbon chain, so its actually 3 methlyhexane? xD

[kryptoniitti]

You got it, good job