Question

why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitution with difficulties​

Answer 1

so benzene undergoes electrophilic substitution reactions easily and nucleophilic substitution with difficulties

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Answer 2

Benzene ring according to Kekules theory, has a π electron cloud exactly above and below the ring of the six carbon electron compound.
So, because the benzene ring as a compound has high(rich) electron density, so an electrophile would have more affinity towards benzene rather than nucleophile.
Also,benzene ring supports just electrophilic substitution and not addition because otherwise it would lose it's aromaticity and consequently it's extra stability factor.

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