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

Short Answer: Determine the total number of valence electrons in benzene: 30 valence electrons. Draw the initial Lewis structure with carbon atoms in a hexagonal ring, each carbon bonded to a hydrogen atom and neighboring carbon atoms. Determine the two possible resonance structures: Structure A with double bonds between C1-C2, C3-C4, and C5-C6; and Structure B with double bonds between C2-C3, C4-C5, and C6-C1. The actual benzene structure has an electron distribution that's an average of both resonance structures, with bond lengths and strengths between a single bond and a double bond.

Step-by-step solution

Determine the total number of valence electrons

First, we need to determine the total number of valence electrons in a benzene molecule. Each carbon atom contributes four valence electrons, and each hydrogen atom contributes one valence electron. For the benzene molecule: Total valence electrons = (6 carbon atoms * 4) + (6 hydrogen atoms * 1) = 24 + 6 = 30 valence electrons

Draw the initial Lewis structure

Next, we'll draw the initial Lewis structure for the benzene molecule. Each carbon atom is connected to one hydrogen atom and two neighboring carbon atoms. To draw the initial Lewis structure: - Place six carbon atoms in a hexagonal ring. - Add one hydrogen atom to the outside of each carbon atom. - Draw single covalent bonds between each carbon and hydrogen atom and single covalent bonds between each neighboring carbon atoms.

Determine resonance structures

In the initial Lewis structure, each carbon atom forms three covalent bonds and has one unpaired electron. These unpaired electrons can participate in the formation of double bonds. To identify resonance structures: - Position double bonds between alternating carbon atoms in the ring, which will create two possible structures. 1. Structure A: Double bonds between C1-C2, C3-C4, and C5-C6 2. Structure B: Double bonds between C2-C3, C4-C5, and C6-C1 - These two resonance structures indicate that the actual electron distribution in the benzene molecule is an average of structures A and B. - The real structure of benzene has bond lengths and strengths between a single bond and a double bond. Benzene is also more stable than either of these structures would indicate on their own. #Final_output#: Step-by-step solution: \[ \textbf{Step 1: Determine the total number of valence electrons}\] Total valence electrons = (6 carbon atoms * 4) + (6 hydrogen atoms * 1) = 24 + 6 = 30 valence electrons \[ \textbf{Step 2: Draw the initial Lewis structure}\] Initial Lewis structure: - Carbon atoms in a hexagonal ring - Hydrogen atom bonded to each carbon atom outside the ring - Single covalent bonds between carbon and hydrogen atoms and neighboring carbon atoms \[ \textbf{Step 3: Determine resonance structures}\] Two possible resonance structures: - Structure A: Double bonds between C1-C2, C3-C4, and C5-C6 - Structure B: Double bonds between C2-C3, C4-C5, and C6-C1 - Actual electron distribution in benzene is an average of structures A and B, with bond lengths and strengths between a single bond and a double bond.

Key concepts

Benzene

Benzene, represented as \( \text{C}_6\text{H}_6 \), is a fascinating molecule known for its unique structure and stability. This compound is crucial in chemistry due to its role as the simplest aromatic hydrocarbon forming the basis for a range of more complex chemicals. Each benzene molecule consists of six carbon atoms arranged in a hexagonal ring. To complete the structure, each carbon atom is bonded to a single hydrogen atom. This gives benzene its iconic circular appearance.
Benzene's structure is not just about its aesthetic appeal; it plays a role in its chemical properties as well. The symmetrical distribution of its atoms and the way electrons are shared across bonds contribute to its remarkable stability, commonly referred to as "aromatic stability." Understanding benzene's ring structure is the key to grasping both its formation through Lewis structures and its behavior in chemical reactions.

Resonance Structures

The concept of resonance structures is a cornerstone in understanding molecules like benzene. Resonance refers to the ability of a molecule to have multiple valid structures, or configurations, that contribute to the actual form of the molecule. In the case of benzene, it has two primary resonance structures, often depicted with alternating double bonds in a hexagonal ring. This means when drawing benzene's Lewis structures, you consider all possible positions for these bonds.

• Structure A depicts double bonds between C1-C2, C3-C4, and C5-C6.
• Structure B shows double bonds between C2-C3, C4-C5, and C6-C1.

Resonance structures explain why the bonds in benzene have equal lengths and energies, which are intermediate between a single and double bond. The molecule does not flip back and forth between these forms; instead, it exists as a hybrid of both. The concept of resonance provides a more accurate depiction of the benzene molecule's electron distribution and contributes significantly to its stability.

Valence Electrons

Valence electrons are crucial when constructing Lewis structures, as they dictate the formation of bonds between atoms in a molecule. For benzene, which has the chemical formula \( \text{C}_6\text{H}_6 \), understanding the number and arrangement of valence electrons is essential.
Each carbon atom provides four valence electrons, resulting in a total of 24 from the six carbon atoms. Additionally, each of the six hydrogen atoms contributes one valence electron, making another 6 valence electrons. Together, benzene has a sum of 30 valence electrons to account for.
Distributing these electrons involves forming bonds between the carbon atoms to create the hexagonal ring and attaching hydrogen atoms to each carbon. The surplus electrons help form benzene's characteristic alternating double bonds in its resonance structures. This clever use of valence electrons explains both the connectivity within benzene and its properties as an aromatic compound.