Give two structural features of hydrocarbons with high octane numbers. - Leaving Cert Chemistry - Question i - 2014

Short Chains: Hydrocarbons with high octane numbers typically have shorter carbon chains, which contribute to higher combustion efficiency. This results in better engine performance and reduced knocking.

Branched Structures: Hydrocarbons that feature branching in their molecular structure also tend to have higher octane ratings. The presence of branches helps to break the symmetry of the molecule, reducing the likelihood of auto-ignition during the combustion process.