The correct order of octane number of butane, pentane, hexane and cyclohexane is
[amp_mcq option1=”butane > pentane > cyclohexane > hexane” option2=”butane > pentane > hexane > cyclohexane” option3=”butane > cyclohexane > pentane > hexane” option4=”cyclohexane > butane > pentane > hexane” correct=”option3″]
This question was previously asked in
UPSC CDS-1 – 2024
Comparing the standard (n-) forms:
n-Butane (C4H10) has a higher octane number than n-pentane (C5H12) and n-hexane (C6H14).
n-Pentane has a higher octane number than n-hexane.
Cyclohexane (C6H12), a cyclic alkane, has a higher octane number than the corresponding straight-chain alkane, n-hexane, and typically higher than n-pentane.
The typical order of RON (Research Octane Number) is approximately: n-Butane (~92) > Cyclohexane (~83) > n-Pentane (~62) > n-Hexane (~25).
Thus, the correct order of decreasing octane number is butane > cyclohexane > pentane > hexane.