Benzene and Its Derivative

Benzene and Its Derivative

Benzene

• Molecular formula C₆H₆

• Based on MF, it should be an alkene or alkyne

• But its chemical properties shown that it is an alkane (favored substitution than addition reaction)

Benzene Structure

• Cyclic (aromatic/arenes/aryl compound) alkane with alternating double bond

• The bond can resonate.

• Prove: double bond length: 1.34 Å, single bond length: 1.54 Å, while benzene bond length: 1.39 Å

Multiple Select

Benzene.....

• have alternating double bonds

• have bond length 1.34 Å

• have empirical formula CH

Benzene Structure

• The actual structure of benzene can be explained by considering the bonding in the molecule. Each carbon atom in the hexagonal ring is sp² hybridised sharing:

• one pair of electrons with one of its neighbouring carbon atoms

• one pair of electrons with its other neighbouring carbon atom

• one pair of electrons with a hydrogen atom

Benzene Structure

These are σ (sigma) bonds; covalent bonds with the pair of electrons found mainly between the nuclei of the atoms bonded to each other. Each carbon atom forms three σ bonds. That leaves one electron spare on each of the six carbon atoms. Each carbon atom contributes this one electron to a π (pi) bond. However, the π bonds formed are not localised between pairs of carbon atoms as in an alkene C=C bond. Instead, the π bonds in benzene spread over all six carbon atoms in the hexagonal ring. The six electrons in the π bonds are said to be delocalised.

Benzene Structure

The π bonding in benzene is formed by the overlap of carbon p atomic orbitals, one from each of the six carbon atoms. To achieve maximum overlap, the benzene molecule must be planar. The lobes of the p orbitals

overlap to form a ring of delocalised electrons above and below the plane of the carbon atoms in the benzene molecule

Multiple Select

Benzene...

• has sp² carbon atoms

• electrons is delocalised around the ring

• electrons from π orbital are shared only among 2 carbon with double bond

Benzene Derivatives

• These are some benzene derivatives and its name

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Multiple Choice

What is the name of this benzene derivative compound?

• aniline

• phenol

• toluene

• nitrobenzene