Question

identify the correct lewis structure for c₄h₆. select the single best answer.

Explanation:

Step1: Check carbon - carbon bond count

Carbon has 4 valence electrons and hydrogen has 1 valence electron. In $C_4H_6$, the total number of valence electrons is $4\times4 + 1\times6=22$. Each carbon - carbon single bond ($C - C$) has 2 electrons, double bond ($C = C$) has 4 electrons and triple bond ($C\equiv C$) has 6 electrons. Also, each carbon should have a total of 4 bonds.

Step2: Analyze each structure

• For the first structure: $H - C - C\equiv C - C - H$, it has the correct number of atoms and the carbon atoms have 4 bonds each.
• For the second structure: $H - C\equiv C - C\equiv C - H$, the formula would be $C_4H_2$ as each triple - bonded carbon has only 1 hydrogen, so it is incorrect.
• For the third structure: $H - C - C = C = C - H$, the central double - bonded carbons have an incomplete octet and this is a highly unstable cumulated diene structure not corresponding to $C_4H_6$ in a stable form, so it is incorrect.
• For the fourth structure: $H - C - C - C\equiv C - H$, the number of hydrogens is not consistent with $C_4H_6$ as written, so it is incorrect.
• For the fifth structure: $H - C - C = C - C - H$, the number of hydrogens and the bonding pattern do not match the valence - electron requirements for $C_4H_6$ correctly.

Answer:

The first structure $H - C - C\equiv C - C - H$