The ^19F, ^79Br, and ^81Br nuclei are NMR active. The presence of these nuclei i

Question

The ^19F, ^79Br, and ^81Br nuclei are NMR active. The presence of these nuclei in a molecule can result in additional coupling in the 'H-NMR spectrum. The 79Br and 81Br nuclei each have a spin quantum number / = 3/2, but both have large quadruple moments which make their nuclei almost undetectable in a normal 'H-NMR experiment. In contrast, the 19F nucleus has a spin quantum number I =1/2 (same as 'H and 13C nuclei) and is 100% abundant. These properties make l9F-NMR data easy to obtain, and allow 19F-'H and 19F-13C coupling to be observed in 1H- and 13C-NMR spectra. This "extra" coupling can be a powerful diagnostic tool for structural determination of 19F containing molecules. Use the Jhf coupling constants shown below to predict the 'H-NMR coupling pattern of each possible substituted benzoic acid product obtained from the Grignard reaction. For reference, Jcf coupling constants can be found on the course website.

Explanation / Answer

The coupling pattern is as follows for protons in the given compound

Ha - dd ( doublet of doublet ) from ortho proton and from F

Hb- doublet from ortho proton Ha

Ha1- dd ( doublet of doublet)

Hb1 - doublet from ortho proton Ha1

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