The correct order of octane number of butane, pentane, hexane and cyclohexane is

  1. A. butane \gt pentane \gt hexane \gt cyclohexane
  2. B. butane \gt pentane \gt cyclohexane \gt hexane
  3. C. butane \gt cyclohexane \gt pentane \gt hexane
  4. D. cyclohexane \gt butane \gt pentane \gt hexane

Correct Answer: C. butane \gt cyclohexane \gt pentane \gt hexane

Explanation

Octane number decreases as the straight carbon chain lengthens. Cyclic alkanes generally have higher octane ratings than straight chains of similar mass. The correct decreasing order is butane \gt cyclohexane \gt pentane \gt hexane.

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