Final answer:
Alkenes can cause deshielding of nearby hydrogen atoms, resulting in a higher chemical shift. Aromatic rings can cause shielding of nearby hydrogen atoms, resulting in a lower chemical shift.
Step-by-step explanation:
Alkenes and aromatic rings can affect the chemical shift of hydrogen (H) atoms in different ways. Alkenes contain carbon-carbon double bonds and can cause deshielding of nearby hydrogen atoms. This means that the hydrogen atoms attached to the carbon atoms involved in the double bond experience a higher chemical shift compared to hydrogen atoms in saturated hydrocarbons (alkanes). Aromatic rings, on the other hand, can have a different effect on hydrogen atoms. The presence of an aromatic ring can cause shielding of nearby hydrogen atoms. This means that the hydrogen atoms attached to the carbon atoms in the aromatic ring experience a lower chemical shift compared to hydrogen atoms in saturated hydrocarbons.