Each statement gives a structure and a proposed name. Use the rule: lowest locants to all multiple bonds together, and if still tied, to the double bond. Which statement(s) is/are correct?

A $CH X_{3} - CH = CH - C \equiv C - CH X_{3}$ is hex-4-en-2-yne.
B $CH X_{2} = CH - CH X_{2} - CH X_{2} - C \equiv CH$ is hex-1-en-5-yne.
C $CH X_{2} = CH - C \equiv C - CH X_{2} - CH X_{3}$ is hex-3-en-1-yne.
D $CH X_{3} - C \equiv C - CH X_{2} - CH = CH X_{2}$ is hex-5-en-2-yne.

Answer: B

CH2=CH-CH2-CH2-C#CH gives {1,5} either way, so the tie goes to the double bond: hex-1-en-5-yne is correct. CH3-C#C-CH2-CH=CH2 numbered from the CH2= end has the set {1,4}, lower than {2,5}, so it is hex-1-en-4-yne. CH3-CH=CH-C#C-CH3 gives {2,4} both ways, so the double bond gets 2: hex-2-en-4-yne, not hex-4-en-2-yne. CH2=CH-C#C-CH2-CH3 is hex-1-en-3-yne, so only the first statement is correct.

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Each statement gives a structure and a proposed name. Use the rule: lowest locants to all multiple bonds together, and if still tied, to the double bond. Which statement(s) is/are correct?

Answer: B

More questions on Nomenclature of alkanes, alkenes, alkynes and cyclic compounds