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2,2-dimethylbutane | |
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2,3-dimethylbutane |
These compounds are all isomers of one another. That is they have the same number of carbon (6) and hydrogen (14) atoms. They are only different in the exact way the atoms are bonded together. These are structural or constitutional isomers. These isomers can be distinguished by their names. The different locations of the methyl groups are indicated by the different numbers in the name.
The numbering of the parent chain is acheived by looking for the "first point of difference" in the molecule starting from either end of the parent chain. Thus the second isomer is 2-methylpentane not 4-methylpentane since the first point of difference is the methyl group attached on the second carbon when numbering from the right, and isomer 4 is 2,2-dimethylbutane not 3,3-dimethylbutane again since the first point of difference is the methyl groups attached on the second carbon when numbering from the right.
Again, notice commas between numbers, and hyphens between numbers and letters.
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