Which pair are structural isomers?

Which pair are structural isomers?

• A. Butane and Isobutane
• B. Methane and Ethane
• C. Ethane and Propane
• D. Methane and Propane

Answer: (A)

Structural isomerism means two or more compounds have the same molecular formula but different ways of connecting the atoms. Butane and isobutane both have the formula C4H10, yet their carbon chains are arranged differently: butane is a straight chain, while isobutane has a branched structure. Because the atoms are connected differently while the overall formula stays the same, they are structural isomers. The other pairs don’t fit because their formulas aren’t the same. Methane and ethane are CH4 and C2H6, so they can’t be isomers. Ethane and propane are C2H6 and C3H8, not the same formula. Methane and propane are CH4 and C3H8, also not the same.

Structural isomerism means two or more compounds have the same molecular formula but different ways of connecting the atoms. Butane and isobutane both have the formula C4H10, yet their carbon chains are arranged differently: butane is a straight chain, while isobutane has a branched structure. Because the atoms are connected differently while the overall formula stays the same, they are structural isomers.

The other pairs don’t fit because their formulas aren’t the same. Methane and ethane are CH4 and C2H6, so they can’t be isomers. Ethane and propane are C2H6 and C3H8, not the same formula. Methane and propane are CH4 and C3H8, also not the same.