Question

Benzene \(\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)\) consists of a six- membered ring of carbon atoms with one hydrogen bonded to each carbon. Write Lewis structures for benzene, including resonance structures.

Short answer

The benzene (C6H6) Lewis structures, including the resonance structures, are as follows: Resonance Structure 1: H H H \ / x \ C---C--C \\ / \\ C--C x / \ H H Resonance Structure 2: H H H x / \ x C--C--C \\ / \\ C--C / \ H H

Step-by-step solution

Count the Total Valence Electrons

Begin by counting the total number of valence electrons available in the benzene molecule. Each carbon atom has 4 valence electrons and each hydrogen atom has 1 valence electron. Since benzene contains 6 carbon and 6 hydrogen atoms, it has a total of (6 Carbon atoms × 4 e⁻/carbon) + (6 Hydrogen atoms × 1 e⁻/hydrogen) = 24 + 6 = 30 valence electrons.

Place Single Bonds

Arrange the six carbon atoms in a hexagonal shape that forms a ring. Then, connect each carbon atom to an adjacent carbon atom via a single bond. Finally, attach one hydrogen atom to each carbon atom via a single bond. At this point, we have used up 18 valence electrons in the single bonds connecting the carbon and hydrogen atoms (12 electrons in C--C bonds and 6 electrons in C--H bonds).

Add Double Bonds

Now, we need to add double bonds between carbon atoms to spread the remaining valence electrons (30 - 18 = 12 electrons). We can place a double bond between three pairs of adjacent carbon atoms, each with one double bond. This will use up the remaining 12 electrons (6 electron pairs) and give each carbon atom a full octet of electrons (4 bonds × 2 e⁻/bond = 8 e⁻).

Draw Resonance Structures

Resonance structures show different ways to arrange the double bonds within the carbon ring. First, draw a Lewis structure with the double bonds between C1-C2, C3-C4, and C5-C6. This is Resonance Structure 1. Next, create a new Lewis structure that shows the double bonds between C2-C3, C4-C5, and C6-C1 (moving to alternate carbon pairs). This is Resonance Structure 2. Both structures show the same molecule (benzene), but with different arrangements of double bonds. These resonance structures show that the electrons in the double bonds are delocalized across the entire carbon ring. Note that in reality, the electron distribution is an average of both resonance structures, with bond lengths between a single and a double bond. After following these steps, we can conclude that the benzene (C6H6) Lewis structures, including the resonance structures, are as follows: Resonance Structure 1: H H H \ / x \ C---C--C \\ / \\ C--C x / \ H H Resonance Structure 2: H H H x / \ x C--C--C \\ / \\ C--C / \ H H