What is the mechanism of trinitration of phenol ? Is it one by one substitution of nitro groups ? For which wouldnt the nitro groups stop the reaction as they are deactivating groups Or is it the simulataneous activation of ortho and para positions of phenol and the nitro groups add on together ? For this mechanism , deactivating nature wont be a concern . but the probability of such a collision would be less . And this can be reason of the low yield . Please clarify the correct concept of the above .