Which of the following isomers will have the highest octane
number?
CH₃
|
(a) CH₃ - CH - CH₂ - C - CH₃
| |
CH₃ CH₃
(b) CH₃ - CH - CH - CH₂ - CH₂ - CH₃
| |
CH₃ CH₃
(c) CH₃ - CH - (CH₂)₄ - CH₃
|
CH₃
(d) CH₃ – (CH₂)₆ – CH₃
Answers
Answer:
Which of the following isomers will have the highest octane
number?
CH₃
|
(a) CH₃ - CH - CH₂ - C - CH₃
| |
CH₃ CH₃
(b) CH₃ - CH - CH - CH₂ - CH₂ - CH₃✔✔
| |
CH₃ CH₃
(c) CH₃ - CH - (CH₂)₄ - CH₃
|
CH₃
(d) CH₃ – (CH₂)₆ – CH₃
The options for the question, in a readable way, are :
(a) CH₃ - CHCH₃ - CH₂ - C(CH₃)₂ - CH₃
(b) CH₃ - CHCH₃ - CHCH₃ - CH₂ - CH₂ - CH₃
(c) CH₃ - CHCH₃ - (CH₂)₄ - CH₃
(d) CH₃ - (CH₂)₆ - CH₃
Option (a) - CH₃ - CHCH₃ - CH₂ - C(CH₃)₂ - CH₃ has the highest octane number.
• Octane number is a measure of the ability of a fuel to resist knocking in an engine.
• Knocking occurs when there is an uneven burning of the fuel in an internal combustion engine. The end part of the fuel burns before the front part causing a disturbing sound in the engine, called knocking.
• To prevent knocking, fuels with high octane numbers should be used in engines.
• The greater the branching in an isomer and smaller the length of its carbon chain, the higher is its octane number.
• Among the given options, isomer (a) - 2,2,4-trimethylpentane has the highest branching and the smallest chain length of five carbon atoms. Therefore, it has the highest octane number of 100.