1 / 18

Electrophilic Aromatic Substitution (EAS)Reactions

Electrophilic Aromatic Substitution (EAS)Reactions. Overall reaction. General Mechanism for Electrophilic Aromatic Substitution. Summary of ERS Reactions. Halogenation of Benzene. General Equation:. Electrophile = X +. EX:. Nitration of Benzene. General Equation:.

pravat
Download Presentation

Electrophilic Aromatic Substitution (EAS)Reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Electrophilic Aromatic Substitution (EAS)Reactions Overall reaction

  2. General Mechanism for Electrophilic Aromatic Substitution

  3. Summary of ERS Reactions

  4. Halogenation of Benzene General Equation: Electrophile = X+

  5. EX:

  6. Nitration of Benzene General Equation: Electrophile = +NO2 (nitronium ion)

  7. Sulfonation of Benzene General Equation: Electrophile = +SO3H(protonatedsulfer trioxide)

  8. Friedel–Crafts Alkylation General Equation: Electrophile = R+(carbocation) EX:

  9. Friedel–Crafts Acylation Acyl group: General Equation: Electrophile is R–C≡O⊕ (acylium ion)

  10. Substituents effect on reactivity and orientation EDG (electron-donating group): (R, OH, OR, NR2,) Reactivity: Ring is electron rich; Ring reacts faster than benzene with E+ (Activation) Orientation: Ortho (o), Para (p) position

  11. Substituents effect on reactivity and orientation EWG (electron-withdrawing group): (CF3 , NO2, SO3H,CN, ) Reactivity: Ring is electron poor; Ring reacts slower than benzene with E+ (Deactivation) Orientation: Meta (m) position

  12. Substituents effect on reactivity and orientation Halogens (X): (F, Cl, Br, I) Reactivity: Ring reacts slower than benzene with E+ (Deactivation) Orientation: Ortho (o), Para (p) position

  13. Reactivity towards electrophilic aromatic substitution

  14. arenium ion stabilized Effect of Electron-Donating (releasing) and Electron-Withdrawing Groups If G is electron-donating group then reaction is faster than with benzene

  15. arenium ion destabilized If G is an electron-withdrawing then reaction is slower than with benzene

  16. EDG activate the ring by: (1) Mesomeric (+M) Effects: Activate the ring by resonance (2) ) Inductive (+I): Activate the inductive (through σ bond) Note: Mesomeric effect stronger than Inductive effect

  17. EWG deactivate the ring by: (1) Mesomeric (-M) Effects: Deactivate the ring by resonance effect (2) ) Inductive (-I): Deactivate the ring by negative inductive effect Note: Mesomeric effect stronger than Inductive effect

  18. Exercises Ex1: Write the formulas for benzyl chloride, toluene, and benzoic acid, ortho-xylene, 4-ethyl-2,6-difluorotoluene, Ex2: Draw the important resonance contributors for the benzenonium intermediate in the bromination of aniline Ex3: Devise a synthesis for each of the following, starting with benzene: a. m-bromobenzenesulfonic acid b. p-nitrotoluene Ex4: Which compound is more reactive toward electrophilic substitution • Ex5: using benzene or toluene as the only aromatic starting material, devise a synthesis of each compound. • 2-bromo-4-nitrotoluene • p-nitroethylbenzene

More Related