Which of the following pairs of compounds are constitutional isomers?

• A. $\text{Butane}$ and $2-\text{methylpropane}$
• B. $\text{Ethane}$ and $\text{ethene}$
• C. $\text{Cyclohexane}$ and $\text{benzene}$
• D. $\text{Methanol}$ and $\text{ethanol}$

Answer: (A)

Verified step by step guidance

1. Understand the concept of constitutional isomers: Constitutional isomers are compounds that have the same molecular formula but differ in the connectivity of their atoms.
2. Analyze the molecular formula of each pair of compounds: Start by determining the molecular formula for each compound in the pairs given.
3. Compare the molecular formulas: Check if the compounds in each pair have the same molecular formula. If they do, they might be constitutional isomers.
4. Examine the connectivity of atoms: For pairs with the same molecular formula, analyze the structure to see if the connectivity of atoms differs between the two compounds.
5. Identify the pair that fits the definition: Based on the analysis, identify which pair of compounds are constitutional isomers by having the same molecular formula but different connectivity.