Reactions of Benzene and Substituted Benzenes

benzene

planar, cyclic, conjugated, resonance stabilized, all bonds are 1.4 A CC

substituted benzenes

can be single, or ortho, meta, para

phenol

benzene with an alcohol group

arenes

hydrocarbons based on benzene units

reactivity of benzene

resonance energy is 36 kcalmol, pretty stable

higher e- density inside ring, nucleophilic character

favours substitution over addition reactions

aromaticity

property of significant extra stability of certain types of pi systems

criteria - cyclic, planar, conjugated (atoms all sp2 or sp hybridized), huckel’s rule (4n+2 pi electrons)

radical halogenation of benzylic position

type: radical substitution

reactants: Br₂ or Cl₂, light or heat

benzyl radical stable due to resonance

oxidation of alkyl benzenes

type: oxidation

reactants: [O], in form of Cr₂O₇^2- or MnO₄^-/H₂SO₄/heat

oxidized to carboxylic acid, alkyl substituent can be methyl, 1^o or 2^o alkyl (3^o lacks a benzylic hydrogen)