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Q74.

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Organic Chemistry
Found in: Page 58

Short Answer

Question: Benzene is the simplest member of a whole class of compounds called aromatic hydrocarbons.

a. How is each carbon atom hybridized?

b. What is the geometry around each carbon atom? What is the overall geometry of the benzene ring?

c. Follow the indicated curved arrow notation to draw a second resonance structure.

d. Benzene and other aromatic hydrocarbons are shown in Chapter 17 to be very stable. Offer an explanation.

Answer

a.

b. The geometry around each carbon atom is trigonal planar. The overall geometry of the benzene ring is planar.

c.

d. Benzene is stable due to the two resonance hybrid structures.

See the step by step solution

Step by Step Solution

Step-by-Step Solution Step 1: Determination of hybridization on carbon in the benzene ring

When the one s and two 2p orbitals are hybridized, they form -hybridized orbitals with trigonal planar geometry.

The -hybridized orbitals overlap with the adjacent -hybridized orbital. In this way, one single and one double bond is formed in the benzene ring.

Step 2: Stability of benzene and other aromatic hydrocarbons

The benzene and other aromatic hydrocarbons have alternate pi bonds and follow the huckle rule. Therefore, the pi electrons delocalize and form the resonance structures.

Therefore, due to the resonance hybrid, the benzene and aromatic hydrocarbons are stable.

Step 3: Information on benzene

a. The carbon atom has four valence electrons, and it takes its one 2s orbital and the two 2p orbitals for hybridization in the benzene ring.

The one -hybridized orbital of each carbon overlaps sidewise to form a pi orbital and overlaps one to one to form a sigma bond.

Representation of sigma and pi bond formation

b. The geometry around each carbon is trigonal due to hybridization at. The geometry of the benzene ring is planar due to hybridization of each carbon atom.

c. Resonance structure is formed by the movement of pi electrons, as shown in the image below:

Resonance structures of benzene

d. The benzene and other aromatic hydrocarbons have alternate pi electrons, which continuously move and release energy.

Therefore, a resonance hybrid (overall movement of pi electrons) is shown, indicating the respective compounds' stability.

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