See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1 – Identify the principal characteristic group (PCG). The compound contains two carbonyl-based functional groups: an amide (–CONH2) and an aldehyde (–CHO). In IUPAC priority order, aldehyde outranks amide as the principal characteristic group, so the aldehyde would normally be the suffix. However, looking at the structure again: the chain is drawn with C1 bearing –CONH2 and a methyl branch, then a double bond, then the terminal –CHO. If we number so that the amide carbon is C1, the chain is: C1(CONH2)(CH3)–C2=C3–C4H2–CHO at C5 — but let me recount from the structure. Step 2 – Read the structure carefully. The structure shows: a central carbon bearing –CONH2 and –CH3, connected via a double bond (shown by the wedge/zig-zag) to a –CH2–CHO chain. This gives a six-carbon chain if the amide carbon is C1: C1(CONH2)(CH3)–C2... wait, the amide itself is the C1 carbon (the carbonyl carbon of the amide). So the longest chain including the amide carbonyl: C1(=O)(NH2)–C2(CH3)–C3=C4–C5–C6(=O)H. That is a six-carbon chain with an amide at C1 (suffix: -amide), methyl branch at C2, double bond at C3 (hex-3-en-), and an oxo (=O) group at C6 (6-oxo-). Step 3 – Build the IUPAC name. Parent chain = hexan-amide (6 carbons, amide as principal group at C1). Substituents: 2-methyl, double bond between C3–C4 (hex-3-en), aldehyde at C6 expressed as 6-oxo (since the chain terminus aldehyde when the amide is the principal group becomes an oxo substituent). Full name: 2-methyl-6-oxohex-3-enamide. Step 4 – Evaluate other options. (b) '6-keto-2-methyl hexanamide' uses 'keto' which is non-IUPAC/substitutive and misses the double bond. (c) '2-carbamoylhexanal' would make the aldehyde the principal group, missing the double bond and placing amide as a substituent 'carbamoyl'; also does not indicate the double bond. (d) '2-carbamoylhex-3-enal' makes the aldehyde the principal group and treats amide as carbamoyl substituent, but in IUPAC nomenclature when both amide and aldehyde are present and the amide carbon is in the main chain, the amide takes priority as suffix — also the methyl group is missing in this name. Therefore, the correct answer is A.