# Determination of brominated aromatics by 13C and 1H NMR spectroscopy

How can I identify 4-bromoazobenzene, 4-bromoazoxybenzene, and 4,4’-dibromo-$\ce{N,N}$’-diphenylhydrazine products using $^1\ce{H}$ and $^{13}\ce{C}$ NMR?

I’m really confused by the general shape of NMR peaks of aromatic protons. I want to distinguish each product from the other products, knowing that the three products are synthesized starting by the reaction of 4-bromonitrobenzene with sodium borohydride.

• Do you want to distinguish between those substances in a single mixture or one by one? – pH13 - Yet another Philipp Aug 14 '15 at 0:20
• I doubt the peak shapes are going to help you, since these are all para-substituted aromatics. You could probably distinguish by chemical shift. Try to find authentic spectra of each. They should be available. – jerepierre Aug 14 '15 at 0:21
• one by one in itself – Nado Aug 14 '15 at 19:07

In the $\ce{^1H}$ spectra of 4-bromoazoxybenzene, the protons closest to the azoxy -N+-O- should be deshielded a bit (maybe ~7.8-7.9 ppm?) compared to the aza analogue. Certainly it's also going to be a fairly congested spectrum.
I'll leave the $\ce{^13C}$ NMR as an exercise (or to others to answer).