In the IUPAC name 2-methylbutane, the number 2 indicates
- A. the number of methyl groups present
- B. the total number of carbon atoms
- C. the position on the main chain where the methyl group is attached
- D. the number of double bonds
Explanation
The parent chain is numbered from the end that gives substituents the lowest possible locants, so the methyl group here sits on the second carbon of a four carbon chain. If two methyl groups were present the prefix would be dimethyl with both positions listed. Systematic naming exists precisely so that one formula corresponds to exactly one name.