why electrophiles do not react with benzyne ?

An electrophilic substitution reaction on benzene does not always result in monosubstitution. While electrophilic substituents usually withdraw electrons from the aromatic ring and thus deactivate it against further reaction, a sufficiently strong electrophile can perform a second or even a third substitution. This is especially the case with the use of catalysts.

benzene doesnt react by addition : It would destroy aromatic stabilisation

Aromatic compounds react by substitution reactions.

These preserve the stability of aromatic sextet ( i.e., overall it remains aromatic )

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regards

Ramesh