Concept:IUPAC nomenclature dictates that the principal functional group determines the numbering of the carbon chain.
Solution:- The longest continuous carbon chain containing the aldehyde group has 5 carbons, so the parent name is pentanal.
- The aldehyde carbon (\( -CHO \)) is always assigned position number 1.
- Numbering the chain from right to left: C1 (\( CHO \)), C2 (\( CH_2 \)), C3 (\( CH_2 \)), C4 (\( CH(Cl) \)), C5 (\( CH_3 \)).
- The chlorine substituent is located on carbon 4.
- Combining these, the systematic IUPAC name is 4-chloropentanal.
Why other options are incorrect:Options A and D use Greek lettering, which belongs to common naming conventions, not IUPAC. Option B incorrectly assigns the numbering by starting from the methyl end rather than the high-priority aldehyde end.
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