Question

You attempt to perform a bromination of trans-cinnamic acid in the hopes of producing the product shown below. You decide to take a ¹H NMR spectrum of what you hope is the product. Signals with which of the following approximate chemical shifts would indicate that the product did not form?

Br O OH Br

		The listed regions would not be useful in determing reaction success.
		~ 12.0 ppm
		~ 5.5 ppm
		~7.0 ppm

Answer 1

The approximate chemical shift values in ppm are shown above. As indicated by the chemical shift values, the peak around ~5.5 ppm will be the key factor in determining the formation of the brominated product. If bromination did not occur then there will be no peak at around ~5.5 ppm.

Br -5.5 OH -12 он -5.5 Br 12 Bromination 7 Br2