Select the correct IUPAC name for the following cycloalkane: a six-membered ring with a methyl group attached to carbon $1$ and an ethyl group attached to carbon $3$.

• A. $1$-methyl-$3$-ethylcyclohexane
• B. $1$-ethyl-$3$-methylcyclohexane
• C. $3$-ethyl-$1$-methylcyclohexane
• D. $1$,$3$-dimethylcyclohexane

Answer: (C)

Verified step by step guidance

1. Identify the parent structure, which is a cyclohexane ring in this case.
2. Number the cyclohexane ring carbons to give the substituents the lowest possible set of locants. Start numbering at one substituent and proceed around the ring to minimize the numbers assigned to the substituents.
3. List the substituents in alphabetical order regardless of their position numbers. Here, 'ethyl' comes before 'methyl' alphabetically.
4. Combine the substituent names with their corresponding carbon numbers, separated by hyphens, and use commas to separate multiple locants for the same substituent if needed.
5. Write the full IUPAC name as: substituent with the lower number first, followed by the other substituent, then the parent name 'cyclohexane'. Ensure the numbering reflects the lowest possible numbers for substituents and the substituents are listed alphabetically.