Question

The IUPAC name of the compound $C{H}_{3}CH=CHC\equiv CH$ is :

• A. pent-4-yn-2-ene
• B. pent-3-en-1-yne
• C. pent-2-en-4-yne
• D. pent-1-yn-3-ene

Answer 1

The correct option is B pent-3-en-1-yne

The IUPAC name of the compound $C{H}_{3}CH=CHC\equiv CH$ is pent-3-en-1-yne.

$\stackrel{5}{C}{H}_3\stackrel{4}{C}H=\stackrel{3}{C}H\stackrel{2}{C}\equiv \stackrel{1}{C}H$

Pent-3-en-1-yne

If a molecule contains both carbon-carbon double or triple bonds,

The numbering is done from the end which is nearer to the $=$ bond followed by the $\equiv$ bond, and according to the lowest sum of locant rule.

The numbering or sum rule will follow the alphabetical order of the substituent.

However, if the sum of numbers turns out to be the same starting from either of the carbon chain, then the lowest number is given to the $C=C$ double bond.

Hence, the correct option is B.