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Flashcards in 3.10 Aromatic Deck (10):
1

The rule of cyclics

All benzene are cyclic compounds; but not all cyclic compounds are benzene

2

What is benzene?

C6H6
Flat hexagon of carbon atoms
Delocalised rings of electrons

3

What is the thermochemical evidence of Benzene structure?

Cyclohexene + H2 → ∆H -120
Expected + H2 → ∆H -360
Benzene + H2 → ∆H -208

so we learn that benzene is 152 kJ more stable than predicted due to delocalised field

4

What is delocalisation of Benzene?

overlapping of electron density

sandwiched between 2 rings

5

How does bond length affect stability?

c=c is most stable 0.134
(B) c-c is 0.140
c-c is 0.154, the weakest

6

What is electrophilic substitution?
AROMATIC

Using benzene delocalised ring to donate electrons

7

How to prepare the Nitration of Benzene species?

H2SO4 + HNO3 → H2NO3+ + HSO4-

H2NO3+ → NO2+ +H2O

We use NO2+


H2SO4 is a catalyst as it is replenished at the end by H+ from benzene

8

What is nitrobenzene used for?

TNT
Bombs
Dyes

9

What is Friedel Craft acylation?

Adding a carbonyl group to benzene, with AlCl3 as a catalyst

RCOCl + AlCl3 → RCO+ + AlCl4-

10

Why does electrophilic substitution occur on benzene?

The delocalised repels nucleophiles
If addition occurred the ring would have to break which requires a lot of energy