Answer to Question #189526 in Organic Chemistry for Sam

Question

Explain how hybridisation can be used to explain the structure of benzene.

How does pi bonding help to explain the structure of benzene?

How does delocalisation of electrons help to explain the structure of benzene and disprove the structure suggested by Kekule?

Answer 1

The hybridization of benzene is said to be sp2 type. Benzene consists of 6 carbon and 6 hydrogen atoms where the central atom usually is hybridized.

Of pi bonds in each carbon in benzene there will be one unhybridized orbital that will overlap with other carbon axially to form pi bonds. Each two carbons will overlap axially to form pi bond. There Will be six carbons in benzene so,6÷2=3. Hence, we can say there are 3pi bonds are there in benzene.

In benzene, all of the carbon-carbon bond lengths are equal. Therefore, the Kekule structure shown below is an incorrect representation of benzene.

It is incorrect because it suggests that there are two different types of carbon-carbon bonds in benzene, a carbon-carbon double bond and a carbon-carbon single bond. Typically, the bond length in a carbon-carbon double bond is around 135 pm, a carbon-carbon single bond is around 147 pm long, while the carbon-carbon bond length in benzene is roughly in between at 140 pm.