Chemistry Fundamental Principles of Organic Chemistry BUMHS 2022
PMDC Verified Question 47 of 83
What is the name of \( \text{CH}_3\text{--CH}_2\text{--CH}=\text{CH--CH}_2\text{--CH}=\text{CH--CH}_3 \)?
A
2,3-octadiene
B
2,4-octadiene
C
2,5-octadiene
D
2,5-octadyne
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: 2,5-octadiene
Concept:

When naming dienes, the longest chain containing both double bonds is chosen, and numbered from the end closest to a double bond.

Solution:

  • Chain length: 8 carbons long \( \rightarrow \) "octa".


  • Numbering right to left: Double bonds start at carbons 2 and 5 (sum = 7).


  • Numbering left to right: Double bonds start at carbons 3 and 6 (sum = 9).


  • We use the lowest numbers: 2,5.


  • Since there are two double bonds, we use the suffix "-diene".


  • The name is 2,5-octadiene (or octa-2,5-diene).


Why other options are incorrect:

Incorrect numbering schemes result in 2,3 or 2,4. Option D uses "dyne", implying triple bonds, but the formula clearly shows double bonds.

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