# Assignment of the 13C NMR spectrum of 4'-bromoacetophenone

I was doing a 13C NMR prediction of 4'-bromoacetophenone on chemdraw but I can't figure out why positions 5 and 5' appear further downfield than positions 4 and 4'.

I know both Br and the carbonyl are deactivating groups, with Br being ortho/para directing and carbonyl is meta directing. However, the mesomeric effect of both groups should "shield" position 5 but this is not the case. I'd appreciate an explanation that'd help me understand that.

Maybe this isn't the answer you are looking for, but $$\ce{^13C}$$ NMR shifts are often not amenable towards analysis via electron-withdrawing / electron-donating effects—in my experience this is especially so for aromatic rings. Any such analysis is quite unreliable and can lead to wrong conclusions if you try to use it for assigning peaks.