organic chemistry ii lab 144phs 2013 n.
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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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Lab 1

Electrophilic Substitution

electrophilic substitution
Electrophilic Substitution

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

electrophilic substitution1
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

electrophilic substitution2
Electrophilic substitution
  • Electrophilic aromatic substitution
  • Electrophilic aliphatic substitution
electrophilic aromatic reaction substitution
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.
mechanism of eas arenium ions
Mechanism of EAS: arenium ions

Arenium ions

(nonaromatic cyclohexadienylcation)

Step 1(key step)

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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

halogenation of benzene
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
sulfonation of benzene
Sulfonation of benzene

Benzene sulfonic acid

preparation of nitrobenzene
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
nitration of benzene
Nitration of Benzene

Step 1

Step 2

NO2+ (electrophile)

nitration of benzene1
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

friedel crafts acylation
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