The electrophile, $${E^ \oplus }$$ attacks the benzene ring to generate the intermediate $$\sigma - $$complex. Of the following, which $$\sigma - $$complex is lowest energy?

$$\alpha$$-D-(+)-glucose and $$\beta$$-D-(+)-glucose are

Phenol, when it first reacts with concentrated sulphuric acid and then with concentrated nitric acid, gives

The organic chloro compound, which shows complete stereochemical inversion during a S_N2 reaction, is