[Seks]

Can someone tell me if this is wrong

c6h5-ch3 treated with br2 in prescence of light --> C6H5-C(Br)3 [all H's replaced]
c6h5-ch3 treated with nbs in prescence of light --> C6H5-CH2Br [only one H replaced]

 

[sjb]

I don't know for sure, but experience with NBS and other toluenes (admittedly these were electron poor arenes, and with conc H₂SO₄ as well) leads me to suggest that there's more than the possibility you may get ring substitution as well as or instead of alkyl substitution as the favoured reaction.