Which of the following molecules contains the shortest carbon-carbon single bond?

Step-by-step solution

The length of a carbon-carbon single bond depends on the hybridization of the bonded carbon atoms. A higher percentage of s-character in the hybrid orbitals leads to a shorter and stronger bond. Let us analyze the hybridization of the carbons forming the single bond in each molecule: Ethane ( CH₃-CH₃ ): sp^3-sp^3 single bond (25% and 25% s-character). Propene ( CH₃-CH=CH₂ ): sp^3-sp^2 single bond (25% and 33.3% s-character). Propyne ( CH₃-C CH ): sp^3-sp single bond (25% and 50% s-character). But-1-en-3-yne ( CH₂=C