- Electrophilic Reactivity is the tendency of aromatic or unsaturated compounds to undergo reactions with electron-seeking species (electrophiles).
- Reactivity toward EAS depends on electron density in the ring. More electron-rich rings react more easily.
Comparison of EAS Reactivity
| Compound |
Electron Density |
Reactivity toward EAS |
Preferred Position of Attack |
| Pyrrole |
Highest |
Most reactive |
Position-2 (α) |
| Furan |
Moderate |
Intermediate |
Position-2 (α) |
| Thiophene |
Lowest (still high vs. benzene) |
Least reactive among the three |
Position-2 (α) |
Why?
-
- Pyrrole’s nitrogen donates electron density strongly → makes ring highly nucleophilic
- Furan’s oxygen is more electronegative → reduces overall electron density
- Thiophene is more stable and aromatic, making it less eager to undergo substitution
- Thus, electrophilic reactivity decreases in the order:
-
- Pyrrole > Furan > Thiophene
- Note: All three are more reactive than benzene in EAS reactions.
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