 Delocalised electrons are what makes benzene so stable and allow it to resist addition reactions.  Electron rich benzene rings are prone to attack from electrophiles  One or more of the 6 hydrogen atoms is replaced by a reacting functional group.

 E + = electrophile.  The overall equation is:  What do you think happened? + E+E+ + H+H+ E

 Positive electrophile attacks the delocalised electron ring.  A temporary intermediate is formed where the delocalisation is partially lost and the ring will join to both the original hydrogen and the new electrophile.  The overall charge of the molecule is positive so make sure you add this to your diagram.

 Y- comes from the system (remember that ions dissociate in solution).  It will be attracted to the H on the benzene ring and cause H to donate its electrons back to the ring.

 The nitronium ion/nitryl cation is NO 2 +  Firstly need to generate the nitronium ion CONCENTRATED!!! H 2 SO 4 + HNO 3  H 2 NO HSO 4 - H 2 NO 3 +  NO H 2 O

 NO 2 group is reduced to NH 2 group.  In industry, iron is used  In lab, tin is used with conc HCl as reductant.  Phenylamine is widely used in dye industry.

Adding an acyl C=O group to a benzene ring….

 Benzene reacts with an acyl chloride  Ethanoyl chloride is the most commonly used acyl chloride  AlCl 3 catalyst  Forms a phenyl ketone and HCl. AlCl 3

RCOCl + AlCl 3  RCO + + AlCl 4 -

 Where E+ = CH 3 CO

 Do questions 1, 4 and 5 in your books