Order these compounds in order of increasing carbon–carbon bond strength: HCCH, H₂CCH₂, H₃CCH₃.

Key Concepts

Carbon-Carbon Bond Types

Carbon-carbon bonds can be classified into three types: single (sigma), double (one sigma and one pi), and triple bonds (one sigma and two pi). The strength of these bonds increases with the number of shared electron pairs; thus, triple bonds are stronger than double bonds, which are stronger than single bonds.

Hybridization

Hybridization refers to the mixing of atomic orbitals to form new hybrid orbitals that can form bonds. In the context of carbon, sp hybridization (as in HCCH) leads to stronger bonds due to the linear arrangement and greater s-character, while sp² (as in H2CCH2) and sp³ (as in H3CCH3) have different bond strengths due to their respective geometries and electron distributions.

Steric Effects

Steric effects arise from the spatial arrangement of atoms in a molecule, influencing bond strength and stability. In larger alkyl groups, such as in H3CCH3, increased steric hindrance can weaken the carbon-carbon bond compared to less hindered structures like HCCH, where the linear arrangement allows for closer approach of the bonding orbitals.