Question

Which of the following is an alkene?

• A. C\(_2\)H\(_6\)
• B. C\(_2\)H\(_4\)
• C. C\(_3\)H\(_8\)
• D. C\(_4\)H\(_{10}\)

Hint:

Key Fact: Alkenes: \( C_nH_{2n} \); look for a double bond in the structure.

Answer 1

The Correct Option is B

To identify an alkene, knowledge of alkane, alkene, and alkyne characteristics is required:

• Alkanes: Saturated hydrocarbons characterized by single bonds exclusively, adhering to the general formula C_nH_2n+2.
• Alkenes: Unsaturated hydrocarbons featuring at least one carbon-carbon double bond, with the general formula C_nH_2n.
• Alkynes: Unsaturated hydrocarbons possessing at least one carbon-carbon triple bond, following the general formula C_nH_2n-2.

Considering the provided options:

• C₂H₆: This compound corresponds to the alkane formula (C₂H₂₍₂₎₊₂) = C₂H₆, identifying it as an alkane.
• C₂H₄: This compound fits the alkene formula (C₂H₂₍₂₎) = C₂H₄, thus classifying it as an alkene.
• C₃H₈: This compound aligns with the alkane formula (C₃H₂₍₃₎₊₂) = C₃H₈, making it an alkane.
• C₄H₁₀: This compound conforms to the alkane formula (C₄H₂₍₄₎₊₂) = C₄H₁₀, identifying it as an alkane.

Among the presented options, C₂H₄ is the sole compound that adheres to the alkene formula, indicating the presence of the requisite double bond for an unsaturated hydrocarbon.