Activity 9: EAS Reactions

EAS reaction

substitution of H with an electrophile

• know mech

benzene ring is nucleophilic, so double bond attacks E-X in first step

benzene ring is very stable, so will only react with something very reative/unstable (putting a pos charge on an electronegative atom)

RDS of EAS

the first peak that leads to formation of the carbocation

• kinetically unfavorable

• thermodynamically unfavorable (+ slow bc destroying aromaticity)

second peak is H loss (returning aromatcitiy)

• kinetically and thermodynamically favorable

why does arenium ion form

force it to form by introducing benzene to something so unstable

• arenium ion not aromatic but still nojugated

• has 3 resonance structires as charge moves aroung the ring

5 EAS reactions

• Benzene + X2, FeX3 → Ph-X

  • X = Cl, Br

• Benzene + HNO3, H2SO4 → Ph-NO2

• Benzene + SO3, H2SO4 → Ph-SO3H

• Benzene + CH3Cl, AlCl3 → Ph-CH3

• Benzene + RCOCl, AlCl3 → Ph-COCl 

EDS vs EWGs

EDGs on ring

• activate ring, donate e- density inoto ring, ring becomes more negative, directs E+ ortho para

EWGs on ring

• deactivate ring, pull e- density out of ring, ring becomes more pos, adds E+ meta