Aromatics

Question 1

Aromatic compound

Answer 1

• any compound containing a benzene ring

Question 2

Benzene

Answer 2

• planar, cyclic structure, empirical formula = C6H6
• very stable due to overlapping p-orbitals forming a ring of de-localised electrons
• length of bonds is between c-c and c=c, as it is more stable than a normal single but not quite a double
• if benzene is the main functional group, naming uses suffix -benzene
• if there are other functional groups it uses prefix phenyl-

Question 3

Electrophillic substitution

Answer 3

• Benzene ring attracts electrophiles due to de-localised electrons
• when it bonds to one of the carbons, it causes an imbalance in the orbitals, so the Hydrogen that was also bonded to it donates it’s electrons to re-stabilise it, hence it is substituted by the electrophile

Question 4

Nitration

Answer 4

• Nitric acid (HNO3) + benzene + (H2SO4 catalyst) -> Nitrobenzene + H2O
• H+ in acid bonds to OH- in nitric acid, makes NO2+ which acts as an electrophile in electrophillic substitution
• If done at a temperature over 50 degrees, multiple nitrations will take place. This is good for producing explosives as they decompose violently.

Question 5

Friedel-Crafts Acylation

Answer 5

• acyl chloride + AlCl3 -> Acylate ion + AlCl4-
• Acylate ion acts as elctrophile, substitutes into benzene ring.
• the displaced H+ reacts with AlCl4- to make HCl and AlCl3, so AlCl3 is a catalyst overall