Which one of the following compounds shows intense knocking ?
Correct answer: D. n-heptane
- A. n-pentane
- B. iso-heptane
- C. iso-octane
- D. n-heptane
Explanation
Straight-chain hydrocarbons knock more readily because their combustion is less smooth and they have lower octane numbers than highly branched hydrocarbons. n-Heptane is assigned an octane number of 0 and is therefore the best choice; iso-octane is the likely distractor because its name is associated with the high-octane reference fuel.
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About Alkanes
Alkanes are saturated hydrocarbons containing only carbon-carbon and carbon-hydrogen single bonds, with the general formula CnH2n+2 for open chains. Their structure, isomerism, IUPAC nomenclature, physical properties, combustion, free-radical halogenation and conformations are covered, including the difference between substitution in alkanes and addition in unsaturated hydrocarbons.
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