Question

The correct IUPAC name of the given structures will be

• A. I- Hexane-dione ,II- Hexa-1,3-dien-5-yne
• B. I- 5 -oxohexanoic acid ,II- Hexa-1,3-dien-5-yne
• C. I- 5-oxohexanoic acid ,II- Hexadiene-5-yne
• D. I- 3-oxohexanoic acid ,II- Hexadiene-5-yne

Answer 1

Answer: (B)

In the given compound, two functional groups namely ketone and carboxylic acid are present. The principal functional group is the carboxylic acid group, hence the parent chain will be suffixed with 'oic acid'. Numbering of the chain starts from carbon of - COOH functional group. The keto group in the chain at carbon 5 is indicated by 'oxo'.
The longest chain including the principal functional group has 6 carbon atoms; hence the parent hydrocarbon is hexane. The compound is, therefore, named as 5-oxohexanoic acid.

The two $C==C$ functional groups are present at carbon atoms $1$ and $3$ , while the $C\equiv C$ functional group is
present at carbon $5$. These groups are indicated by suffixes 'diene' and 'yne' respectively. The longest chain containing the functional group has $6$ carbon atoms. Hence, the parent hydrocarbon is hexane. Thus, the name of compound is hexa-$1,3$-dien-$5$ yne.