Name this molecule: C4H8.

Name this molecule: C4H8.

• A. Butane
• B. Butene
• C. Butanone
• D. Butanol

Answer: (B)

Understanding saturation in hydrocarbons helps you see why C4H8 points to an unsaturated four-carbon molecule. Saturated hydrocarbons (alkanes) follow the rule CnH2n+2, so for four carbons you’d expect C4H10. C4H8 has two hydrogens fewer, meaning the molecule is unsaturated—there’s a double bond or a ring. Among the given options, only a four-carbon hydrocarbon with a double bond fits C4H8 without adding other atoms like oxygen. That makes butene the correct name. The other options would require extra atoms (oxygen) or be fully saturated with more hydrogens, so they don’t match the formula.

Understanding saturation in hydrocarbons helps you see why C4H8 points to an unsaturated four-carbon molecule. Saturated hydrocarbons (alkanes) follow the rule CnH2n+2, so for four carbons you’d expect C4H10. C4H8 has two hydrogens fewer, meaning the molecule is unsaturated—there’s a double bond or a ring. Among the given options, only a four-carbon hydrocarbon with a double bond fits C4H8 without adding other atoms like oxygen. That makes butene the correct name. The other options would require extra atoms (oxygen) or be fully saturated with more hydrogens, so they don’t match the formula.