Question

Why does the delocalization of electrons make a molecule (say, benzene) more stable? And why does adding a methyl group to benzene make it more stable?

Answer 1

Delocalized electrons are important for several reasons. One, an expected chemical reaction may not occur because the electrons delocalize to a more stable configuration, resulting in a reaction that happens at a different location. An example attempting the Friedel–Crafts alkylation of benzene with 1-chloro-2-methylpropane; the carbocation rearranges to a tert-butyl group stabilized by hyperconjugation, a particular form of delocalization. Delocalization leads to lengthening of wavelength of electron therefore decreases the energy.

Answer 2

because it lowers the potential energy of the system. methyls donate electron density into benzene rings through induction... i'm guessing that maybe adding more density to the pi system strengthens it, though i'm not sure not this last part.

Answer 3

Got it, thanks guys.

Answer 4

no problem