Yes, your are correct. In theory, a monosubstituted benzene ring has
three different types of hydrogens, due to the bilateral symmetry of the
monosubstituted ring. So, except for coincidental overlap, the three
types should have different chemical shifts. However, in practice they
often have such similar chemical shifts that their signals all fall on top
of each other resulting in a 5H multiplet. Precisely how similar or
different the chemical shift of each of the sets of hydrogens are depends
on the effects of the substituent on the benzene ring. Hence sometimes
there is some separation of the signals for the various hydrogens around a
substituted benzene ring. You will learn more about this in chapter 14.
CBF
On Thu, 5 Dec 1996 hilleskl@PLU.edu wrote:
>
> I am having trouble understanding why in monosubstituted benzene rings all
> of the H on the benzene ring are equivalent in H NmR? The problems in the
> book had the substituted group was a ch2 with an OH or ch3. Wouldn't the
> H's closer to the substituted group be different than those farther away?
>
> Kristina
>
>
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Craig B. Fryhle, Ph.D. Office 206-535-8314 FAX 206-536-5055
Associate Professor Email fryhle@u.washington.edu
Department of Chemistry URL http://rainier.chem.plu.edu/fryhle.html
Pacific Lutheran University
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