Chapter 17: Problem 126

Benzene is a hydrocarbon that has the molecular formula \(\mathrm{C}_{6} \mathrm{H}_{6}\). The benzene molecule contains a six-carbon ring and three double bonds. Draw its structural formula.

Short Answer

Expert verified

The structural formula of benzene (\(\mathrm{C}_{6}\mathrm{H}_{6}\)) is a hexagonal ring with alternating single and double bonds between the carbon atoms, with a hydrogen atom bonded to each carbon atom. The structure of benzene is a resonance hybrid where the double bonds are equally distributed around the ring, often represented by a single ring with a circle inside.

Step by step solution

Draw a six-carbon ring

Draw a hexagon to represent the six-carbon ring structure of benzene. Each vertex of the hexagon represents a carbon atom.

Add Hydrogen atoms

Add a hydrogen atom to each of the carbon atoms in the ring. As carbon atoms form four bonds, and we haven't added the double bonds yet, each carbon atom will have one bond connected to a hydrogen atom.

Draw alternating single and double bonds

Next, connect the carbon atoms in the ring with alternating single and double bonds. This means that around the six-carbon ring, there will be three double bonds and three single bonds. Start with a double bond connecting the first and second carbon atoms, and then add single bonds connecting the second and third, fourth and fifth carbon atoms. Finally, add double bonds connecting the third and fourth, fifth and sixth carbon atoms in the hexagon.

Emphasize resonance structures

Since benzene is a resonance hybrid of its two Kekulé structures, we need to emphasize the resonance nature of the structure. To do this, draw an alternative structure with the positions of double bonds shifted one position clockwise around the ring (or counter-clockwise, depending on how you drew the initial double bonds). Show that these two structures are in resonance by using a double-headed arrow between the two structures.

Combine resonance structures to form a complete structural formula

Finally, combine the two resonance structures into a single hybrid structure representing benzene. Remove the double-headed arrow and replace the double bonds with dash-dot bonds to indicate that the double bonds are not confined to one location but rather dispersed equally throughout the ring. Now you have the complete structural formula for benzene, which highlights both its cyclic nature and the resonance phenomenon that stabilizes its structure.

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Benzene is a hydrocarbon that has the molecular formula \(\mathrm{C}_{6} \mathrm{H}_{6}\). The benzene molecule contains a six-carbon ring and three double bonds. Draw its structural formula.

Short Answer

Step by step solution

Draw a six-carbon ring

Add Hydrogen atoms

Draw alternating single and double bonds

Emphasize resonance structures

Combine resonance structures to form a complete structural formula

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