Aromatics

Question 1

What is benzenes structure and formula?

Answer 1

C6H6
It is a hexagon with a circle in the middle to represent the 6 delocalised electrons

Question 2

What is the bond length of benzene between C atoms?

Answer 2

Intermediate between C-C and C=C
C=C < C- -C < C-C
Alkenes are the shortest and Alkanes are the longest

Question 3

What is the thermodynamic evidence that benzene is more stable than cyclohexa-1,3,5-triene?

Answer 3

Hydrogenation of cyclohexene = -120
Cyclohexa-1,3,5-triene = -360
Benzene hydrogenation = - 208
Therefore a 152 difference making it more stable

Question 4

What are the key pieces of evidence that proves the structure of benzene?

Answer 4

Lack of reactivity with bromine water (it is not an alkene)
The Carbon-Carbon bond lengths are all equal and are somewhere between the length of C-C and C=C

Question 5

How do you name compounds containing a benzene ring?

Answer 5

• benzene, or phenyl-
  Can designate position on ring using numbers if there is more than one substituent

Question 6

What is the electrophilic substitution mechanism for benzene?

Answer 6

Arrow coming from the inner circle to the electrophile
Circle becomes a C + shape, H and electrophile together. Arrow coming from H into the + C
Leaves the electrophile on the benzene and a H + comes off

Question 7

What is the nitration equation

Answer 7

H2SO4 + HNO3 —> HSO4 - + H2O + NO2+

Question 8

Nitration conditions and reagents

Answer 8

50°C
Concentrated nitric acid and sulphuric acid

Question 9

How is the H2SO4 regenerated?

Answer 9

H + reacts with HSO4

Question 10

What is Acylation

Answer 10

Sub of an acyl group (-RCO+)
Aluminium chloride as a catalyst
RCO+ regenerates by reaction of an acyl chloride and AlCl3

Question 11

How is AlCl3 regenerated?

Answer 11

H+ + AlCl4 - —> AlCl3 + HCl