Double bonds and aromatic rings produce large __ on their __ and __ protons.
These deshielding effects result from the same type of __ that normally shields nuclei from the magnetic field.
In benzene and its derivatives, the aromatic ring of pi bonding electrons acts as a __, and the external magnetic field induces a __. At the center fo the ring the induced field acts to __. These induced field lines curve around, however, and on the edge of the ring the induced field adds to the external field. As a result, the aromatic protons are strongly __, resulting in a large chemical shift.
- deshielding effects
- aromatic protons
- circulation of electrons
- ring current
- oppose the external field