3.3.10 Aromatic Chemistry

Question 1

Generation of nitronium ion

Answer 1

H2SO4 + HNO3 —> HSO4^- + NO2^+ + H2O

Question 2

Use of AlCl3 as catalyst

Answer 2

AlCl3 + RCOCl —> AlCl4^- + RCO^+

Question 3

Why is the benzene ring planar hexagon

Answer 3

Each C forms trigonal planar complex
120° bond angles
Forms flat hexagon complex

Question 4

Explain why the carbon-carbon bonds are equal length in benzene

Answer 4

Resonance
Delocalised electrons delocalised over all 6 carbon atoms

Question 5

Arene reactions

Answer 5

Don’t undergo addition reactions as would break delocalisation and lose stability
Undergo electrophilic sub as attracted to electron dense ring

Question 6

Draw mechanism for nitration of benzene

Answer 6

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Question 7

Draw mechanism for acylation of benzene

Answer 7

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Question 8

3 problems with Kekulé’s structure of Benzene

Answer 8

C-C and C=C bonds different lengths but all benzene molecules are same length
Molecule more stable than model suggests
Rarely undergoes addition reactions- usually substitution