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Organic chemistry II lab 144phs 2013

Organic chemistry II lab 144phs 2013. Lab 1. Electrophilic Substitution. Electrophilic Substitution. Chemical reactions in which an electrophile displaces a group in a compound, typically but not always hydrogen. Electrophilic substitution. E lectrophile?

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Organic chemistry II lab 144phs 2013

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  1. Organic chemistry II lab 144phs2013

  2. Lab 1 Electrophilic Substitution

  3. Electrophilic Substitution Chemical reactions in which an electrophile displaces a group in a compound, typically but not always hydrogen.

  4. Electrophilic substitution Electrophile? An electrophile is an atom, ion, molecule or even a compound that has an affinity for electrons, meaning that it is tending to become negatively charged. It act as electronacceptors during a chemical reaction to make a new covalent bond

  5. Electrophilic substitution • Electrophilic aromatic substitution • Electrophilic aliphatic substitution

  6. Electrophilic aromatic reaction substitution Is reaction in which an electrophile replace one of the hydrogen atoms of the ring. • Type of electrophilic aromatic reaction; • Nitration • Halogenation • Sulfonation • Acylation and alkylating Friedel-Crafts reactions.

  7. Electrophilic aromatic reaction substitution

  8. Mechanism of EAS: arenium ions Arenium ions (nonaromatic cyclohexadienylcation) Step 1(key step)

  9. Mechanism of EAS: arenium ions Step 2 The proton is removed by any of the bases, for example by the anion derived from the electrophile

  10. Halogenation of benzene • Benzene does not react with Br2 or Cl2 unless a Lewis acid is present in mixture • Lewis acid is an electron-pair acceptor • Lewis acid is used to make halogen a stronger electrophile. • Lewis acids are: • FeCl3 • FeBr3 • AlCl3

  11. Bromination of benzene

  12. Sulfonation of benzene Benzene sulfonic acid

  13. Nitration of Benzene “Preparation of nitrobenzene” nitrobenzene benzene

  14. Preparation of nitrobenzene • Nitration are usually carried out at comparatively low temperatures 50-55C • At high temperature may loss of material because of oxidizing action of nitric acid

  15. Nitration of Benzene Step 1 Step 2 NO2+ (electrophile)

  16. Nitration of Benzene Step 3 Arenium ions The nitronium ion is the actual electrophile in nitration ; it reacts with benzene to form a resonance-stabilized arenium ion Step 4 The arenium ion then loses a proton to a Lewis base and becomes nitrobenzene

  17. Friedel-Crafts Alkylation

  18. Friedel-Crafts Acylation • Friedel-Crafts Acylation reaction is mean introducing an acyl group into aromatic ring • Two common acyl groups are acetyl group and benzoyl group benzoyl group acetyl group

  19. Friedel-Crafts Acylation

  20. Thank you

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