Electrophilic Aromatic Substitution Test - 4

Because the non-polar solvent (i.e. CCl₄) induces a weaker dipole in Br-Br as compared to the polar solvent (i.e. water), a weaker electrophile (Br+) is produced that undergoes electrophilic aromatic substitution with the benzene ring. Consequently, we get mono-bromination with Br (in CCl₄) with compared with tri-bromination Br (in aq.).

This reaction is sulphonation of benzene ring in which SO₃ is the real attacking electrophile and oleum will increase the concentration of SO₃.

In halogenation of benzene ring halonium ion (Cl⁺) will attack at benzene ring.

Toluene will undergo Friedel–Crafts alkylation with methyl chloride and aluminum chloride as because as weak electron withdrawing functional group — will not make the ring less electron dense, hence more reactive in an aromatic electrophilic substitution as compared to electron withdrawing group (benzoic acid, nitrobenzene, aniline).

-OH is a ortho and para directing group so attack of electrophile (carbocation- CH₃) will attack there, as shown below:

The electrophile in the electrophilic substitution reaction of acetyl chloride (CH₃COCl) and AlCl₃ reacting with benzene is R-CO⁺.

This reaction is nitration of benzene and conc. HNO₃ and conc. H₂SO₄ is used to carry out this synthesis although HNO₂ + HNO₃ can also be used.

This is Gattermann Koch Reaction in which HCl + CO + AlCl₃ are used as reactant. H-CO⁺ is the real attacking electrophile.

Here no reaction will take place because CCl₄ + Cl₂ show addition reaction and benzene don’t give addition reaction.

Groups with unshared pairs of electrons, such as the amino group of aniline, are strongly activating and ortho/para-directing by resonance. Such activating groups donate those unshared electrons to the pi system, creating a negative charge on the ortho and para positions. These positions are thus the most reactive towards an electron-poor electrophile. The highest electron density is located on both ortho and para positions, although this increased reactivity might be offset by steric hindrance between substituent and electrophile.