
- A(4E)-5-Bromo-hex-4-en-2-yne
- B(2E)-2-Bromo-hex-4-yn-2-ene
- C(2E)-2-Bromo-hex-2-en-4-yne
- D(4E)-5-Bromo-hex-2-en-4-yne
View written solutionFree
Correct answer: C
-
Identify the parent chain
The structure corresponds to a six-carbon chain containing both a double bond and a triple bond, so the parent hydrocarbon is hex-en-yne.
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Number the chain to give lowest locants to multiple bonds
For compounds containing both and , numbering is chosen so that the set of locants for multiple bonds is lowest.
Possible numbering gives:
- From one end: double bond at , triple bond at
- From the other end: double bond at , triple bond at
Since in a tie the double bond gets the lower number, we choose:
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Locate the substituent
With this numbering, the bromo substituent is on carbon .
So the name becomes:
-
Assign stereochemistry of the double bond
At the double bond, assign CIP priorities:
- On one carbon, has higher priority than / H-type substituent.
- On the other carbon, the carbon chain has higher priority than H.
The higher-priority groups are on opposite sides of the double bond, so configuration is E.
Hence the full name is:
-
Check options
- A: -5-Bromo-hex-4-en-2-yne ❌
- Multiple bonds not numbered correctly.
- B: -2-Bromo-hex-4-yn-2-ene ❌
- Although similar in meaning, IUPAC format prefers en before yne in the suffix pattern as hex-2-en-4-yne.
- C: -2-Bromo-hex-2-en-4-yne ✅
- D: -5-Bromo-hex-2-en-4-yne ❌
- Wrong substituent position and stereodescriptor numbering.
- A: -5-Bromo-hex-4-en-2-yne ❌
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Final answer
The correct option is:
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