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what is the iupac name of this compound? h₃c | c=c | | h h | ch₂ch₃ opt…

Question

what is the iupac name of this compound?

h₃c
|
c=c
| |
h h
|
ch₂ch₃

options:

  • cis-3-pentene
  • cis-2-pentene
  • ethylpropene
  • 1-methyl-2-ethylpentene
  • trans-3-pentene

Explanation:

Brief Explanations
  1. First, identify the parent chain: The compound has a double bond (alkene) and the longest carbon chain with the double bond is 5 carbons (pentene).
  2. Number the chain to give the double bond the lowest number: The double bond is between carbon 2 and 3? Wait, no—wait, the structure is \( \ce{H3C - CH=CH - CH2CH3} \)? Wait, no, the given structure is \( \ce{H3C - C(H)=C(H) - CH2CH3} \). So the carbon chain is 5 carbons (pentene). The double bond is between carbon 2 and 3? Wait, no, let's number the carbons: C1: \( \ce{H3C} \), C2: \( \ce{C(H)=} \), C3: \( \ce{C(H) - CH2CH3} \)? Wait, no, the correct numbering: the parent chain is pentene (5 carbons). The double bond is between C2 and C3? Wait, no, let's see the substituents. Wait, the structure is \( \ce{CH3 - CH=CH - CH2CH3} \) (since the two H are on the same side, so cis). Now, number the chain so that the double bond has the lowest possible number. The double bond is between C2 and C3? Wait, no: C1: \( \ce{CH3} \), C2: \( \ce{CH} \) (attached to H and double bond), C3: \( \ce{CH} \) (attached to H and \( \ce{CH2CH3} \)), C4: \( \ce{CH2} \), C5: \( \ce{CH3} \)? Wait, no, the longest chain is 5 carbons (pentene). The double bond is between C2 and C3? Wait, no, the correct numbering: the double bond is at position 2 (since from the left, C2 and C3: wait, no, let's count the carbons. The first carbon is \( \ce{CH3} \), second is \( \ce{C} \) (with H and double bond), third is \( \ce{C} \) (with H and \( \ce{CH2CH3} \)), fourth is \( \ce{CH2} \), fifth is \( \ce{CH3} \). Wait, no, the \( \ce{CH2CH3} \) is a substituent? No, no—the structure is \( \ce{CH3 - CH=CH - CH2CH3} \), so the parent chain is 5 carbons (pentene). The double bond is between C2 and C3? Wait, no, the carbon atoms: C1: \( \ce{CH3} \), C2: \( \ce{CH} \) (double bond to C3), C3: \( \ce{CH} \) (double bond to C2, and attached to \( \ce{CH2CH3} \))? No, that can't be. Wait, the correct structure is \( \ce{CH3 - CH=CH - CH2CH3} \), so the parent chain is pentene (5 carbons). The double bond is between C2 and C3? Wait, no, the numbering should give the double bond the lowest number. So from the left, C1: \( \ce{CH3} \), C2: \( \ce{CH} \) (double bond), C3: \( \ce{CH} \) (double bond), C4: \( \ce{CH2} \), C5: \( \ce{CH3} \). Wait, no, the \( \ce{CH2CH3} \) is part of the parent chain? Wait, no, the structure is \( \ce{H3C - C(H)=C(H) - CH2CH3} \), so the carbon chain is 5 carbons: C1 (CH3), C2 (C with H and double bond), C3 (C with H and CH2CH3? No, CH2CH3 is two carbons, so that would make the chain longer. Wait, no, the correct parent chain is 5 carbons: C1 (CH3), C2 (C), C3 (C), C4 (CH2), C5 (CH3). The double bond is between C2 and C3. Now, the two H atoms are on the same side of the double bond (cis isomer). So the name is cis - 2 - pentene? Wait, no, wait: the substituents on the double - bonded carbons: C2 has CH3 and H, C3 has CH2CH3 and H. Since the two H atoms are on the same side, it's cis. Now, numbering: the double bond is at position 2 (because if we number from the left, the double bond is between C2 and C3; if we number from the right, it would be between C3 and C2, same numbering). Wait, the options: cis - 2 - pentene is an option. Let's check the other options: cis - 3 - pentene would have the double bond at position 3, but numbering should give the lowest number to the double bond, so position 2 is better. Ethylpropene: propene has 3 carbons, adding an ethyl would make it 5 carbons, but the parent chain should be the longest with the double bond, so pentene is better. 1 - methyl - 2 - ethylpentene: inco…

Answer:

B. cis - 2 - pentene