Lab 2

 It’s the aliphatic portion of the alkylbenzene.

 Terms you should know : Free Radicals Benzylic radical Benzylic hydrogen atom Benzylic cation

 An atom or group of atoms that has at least one unpaired electron,so:  Unstable  Highly reactive

 Is the general name applies to all radicals that have unpaired electron on the carbon atom attached directly to the benzene ring.

 Is the hydrogen atom of the carbon atom that directly attached to the benzene ring.

 Is the departure of a leaving group (LG) from a benzylic position.

Side- chain halogenationRing halogenation It take place when the reaction is carried out in the absence of Lewis acid Require condition that favor the formation of the radicals. The halogens dissociate to produce halogen atoms The halogen atoms initiate chain reaction by abstracting hydrogen's of the methyl group. The electrophiles are positive ion or they are Lewis acid complexes with positive charge Need catalyst e.g. Lewis acid These positive electrophiles attack the ∏ electron of the benzene ring. Stabilized by Arenium ions the aromatic substitution takes place.

Chlorination

Chain Initiation Step 1 Chain propagation Step 2

Step 3 Chain Termination Step 4

 The oxidation can be carried out by the action of hot alkaline potassium permanganate.

 Oxidation of the side- chain take place initially at the benzylic carbon; any alkylbenzenes with alkyl group longer than methyl are ultimately degraded to benzoic acids:

 Reaction:

Thank you