See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the parent chain and functional groups. The molecule is CH3-CH=C(OCH3)-CH3. It contains a carbon-carbon double bond (alkene) and a methoxy group (-OCH3). We need to find the longest carbon chain that includes the double bond. Step 2 - Count the carbons in the longest chain containing the double bond. Carbon 1: CH3- (one end) Carbon 2: -CH= (part of double bond) Carbon 3: =C(OCH3)- (part of double bond, bears the methoxy substituent) Carbon 4: -CH3 (other end) This gives a 4-carbon chain, so the parent alkene is butene. Step 3 - Number the chain to give the double bond the lowest locant. Numbering from the CH3 end where the double bond starts earlier: C1: CH3, C2: CH=, C3: =C(OCH3), C4: CH3 The double bond is between C2 and C3, so it is but-2-ene. Step 4 - Name the substituent and its position. The -OCH3 (methoxy) group is on C3... wait, let us re-examine numbering to give the double bond the lowest possible locant. If we number from the left: C1=CH3, C2=CH=, C3==C(OCH3), C4=CH3 → double bond at C2 → but-2-ene. If we number from the right: C1=CH3, C2=C(OCH3)=, C3=CH=, C4=CH3 → double bond at C2 → but-2-ene (same locant). When there is a tie, give the substituent the lower number: methoxy on C2 (right-to-left numbering) vs C3 (left-to-right). Choose numbering giving methoxy the lower locant: C2. Therefore the name is 2-Methoxybut-2-ene. Step 5 - Evaluate options. (a) 1-Methoxy-1-methylpropene: Incorrect chain length and locants; the parent should be butene (4C), not propene (3C). (b) 2-Methoxybut-2-ene: Correct - 4-carbon chain, double bond at position 2, methoxy at position 2. (c) dimethylpropeneether: Not an IUPAC name; incorrect. (d) none of these: Incorrect because option (b) is valid. Therefore, the correct answer is B.