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Why does the phenyl ring portion of the proton NMR for tirphenylmethanol (synthe

ID: 508452 • Letter: W

Question

Why does the phenyl ring portion of the proton NMR for tirphenylmethanol (synthesized using bromobenzene and benzophenone via Grignard reactions) integrate to over 17 here rather than expected 15? Know from other data that bromobenzene, benzophenone, and biphenyl are not impurities. Could it be benzene? If so wouldn't the integration come out to 21, rather than 17-18? Or are NMR protons from impurities not 1:1 on displays?

Solvent Does not matter 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 f1 (ppm0

Explanation / Answer

Answer:

There is two possibilites 1) NMR solvent 2) your suspecting benzene

If NMR have taken in CDCl3, CDCl3 peak comes at 7.26 ppm, that peak is merge with your compound peaks so the intrregration come 17.59 instead of 15.

The other way around is Benzene that is depend on what kind of solvent used in reaction condition and work up process. if you used benzene in your entire sequence , you suspect benzene present in your HNMR and that ratio would be triphenylmethanol: benzene=1:0.5 then you can get 17.5 protons in your HNMR

As per my point of view that is not benzene peaks , may be CDCl3

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