Thermal cracking tendency: Among common hydrocarbon families, which is generally the easiest to crack under comparable conditions?

Introduction / Context:
Cracking severity and selectivity depend on molecular structure. Process designers assess relative crackability to predict yields in thermal or catalytic operations.

Given Data / Assumptions:

• Comparison across four families: paraffins, naphthenes, olefins, aromatics.
• General behavior under cracking conditions (not a specialized catalyst exception).

Concept / Approach:
Straight-chain paraffins have relatively weak C–C bonds and fewer stabilizing resonance effects, making β-scission favorable. Aromatics are most resistant due to aromatic ring stability. Naphthenes and olefins are intermediate.

Step-by-Step Solution:

Verification / Alternative check:
FCC/thermal data show higher cracking rates for long-chain paraffins compared to cyclic/aromatic species.

Why Other Options Are Wrong:

• Aromatics: Most resistant to cracking.
• Naphthenes / Olefins: Intermediate; easier than aromatics but harder than paraffins on average.

Common Pitfalls:
Assuming double bonds make olefins easiest; allylic stabilization and competing pathways complicate the picture compared to straight paraffins.

Final Answer:
Paraffins