Question

For all the chemistry people out there. Explain why Benzene is more stable that 1,3,5-hexatriene?

Answer 1

Benzene is more stable because it is aromatic, whereas 1,3,5-hexatriene, as a straight-chain alkene, is aliphatic. Aromatic compounds in general are more stable than their aliphatic counterparts because pi electrons are part of a conjugated system, meaning they are "shared" amongst all double-bonded atoms. This decreases the charge density at each double-bond, making the compound more stable.

In aliphatic compounds, pi electrons are localized to their double bond, so the charge density is somewhat greater. This explains why benzene is relatively inert, while 1,3,5-hexatriene more readily undergoes reactions.

There are more specific rules that define what is aromatic, which I can go into detail about if you want (or you can just google it). Let me know if anything about that is unclear. Hope that helps!

Answer 2

can you explain using MO

Answer 3

MO?

Answer 4

The pi bonding MOs in benzene are evenly spread around the entire ring, while those in the (hypothetical) hexatriene molecule would be localized between three pairs of carbons. That is, an electron in the benzene pi bonding MOs can travel freely around the entire ring, while an electron in the hexatriene pi bonding MOs would be restricted to travel between two adjacent carbons. Since in general the energy of an electron is lowered whenever it is less confined -- think of how the energy levels of a particle in a box are raised as the box gets smaller -- that means these bonding electrons have lower energy. Hence, the molecule is more stable.