See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the parent structure. The molecule contains a four-membered ring (cyclobutane) with one double bond inside the ring, making it a cyclobutene. Step 2: Locate substituents on the ring. The double bond in the ring is between C1 and C2 (cyclobut-1-ene). At C1 (one end of the double bond) there is a methyl group (-CH3). At C2 (the other end of the double bond) there is a -CH2-CHO (acetaldehyde methylene) group. Step 3: Identify the principal characteristic group. The -CHO group is an aldehyde, which has the highest seniority among the functional groups present. For IUPAC nomenclature, when the aldehyde carbon is not part of the ring, the chain -CH2-CHO is named as ethanal with the ring as a substituent. Step 4: Name the ring substituent. The cyclobutene ring bearing a methyl group at C2 (relative to the point of attachment) is named 2-methylcyclobut-1-en-1-yl when the attachment point is C1 of the double bond. Step 5: Combine the names. The full compound is named as a derivative of ethanal: the -CH2- is C2 of ethanal, and the ring is attached at C2. Thus the name is 2-(2-methylcyclobut-1-enyl)ethanal. Step 6: Verify. The parent chain is ethanal (2 carbons ending in CHO). The substituent on C2 of ethanal is the 2-methylcyclobut-1-en-1-yl group (cyclobutene ring with methyl at C2 of the ring, double bond between C1 and C2 of the ring, attached via C1). This matches the structure drawn. Therefore, the correct answer is 2-(2-methylcyclobut-1-enyl)ethanal.