Comparison of Aromatic and Ethylenic Protons
Aromatic and ethylenic protons, despite both being attached to sp² hybridized carbon atoms, exhibit different chemical environments that influence their magnetic shielding.

Deshielding of Aromatic Protons
- Aromatic protons are part of a cyclic structure with delocalized π electrons.
- The presence of this electron cloud creates a strong magnetic field, which affects the resonance frequency of the protons.
- This π electron cloud induces an additional magnetic field that opposes the external magnetic field during NMR spectroscopy, leading to greater deshielding.
- As a result, aromatic protons resonate at lower fields (higher ppm values) compared to ethylenic protons.

Shielding of Ethylenic Protons
- Ethylenic protons are bonded to sp² carbon atoms but are part of a double bond without significant π electron delocalization.
- The magnetic environment around these protons is less complex, leading to a relatively higher magnetic shielding.
- Consequently, ethylenic protons resonate at higher fields (lower ppm values) in NMR spectra compared to aromatic protons.

Conclusion
- In summary, the key difference lies in the extent of electron delocalization and the resultant magnetic effects experienced by the protons.
- Aromatic protons are more deshielded due to the influence of the delocalized π system causing them to resonate at lower fields.
- Ethylenic protons, being less affected by such factors, remain more shielded and resonate at higher fields.
This understanding is vital for interpreting NMR spectra and differentiating between various types of protons in organic compounds.