Aromatics (P2+P3)

Question 1

Describe the shape of Benzene

Answer 1

Planar
hexagonal - bond angle = 120
bond lengths are equal

Question 1

Describe the bonding in Benzene

Answer 1

each carbon bonded to 3 other atoms by covalent bonds
spare electrons in P orbitals overlap to form Pi bond
delocalisation of electrons

Question 2

Describe the stability of Benzene

Answer 2

delta H hydrogenation for cyclohexatriene is -360
delta H hydrogenation for benzene is 152 less exothermic than expected
benzene is more stable (less reactive)

Question 3

Name the mechanism, reagents and conditions for the nitration of benzene

Answer 3

Electrophilic substitution
reagents and conditions; conc H2SO4 and HNO3

Question 4

Equation for the NO2+ electrophile being formed for the nitration of benzene?

Answer 4

H2SO4 + HNO3 –> HSO4- + H2O + NO2+

Question 5

Name the mechanism, reagents and conditions for the acylation of benzene

Answer 5

Electrophilic substitution
reagents and conditions; acyl chloride and AlCl3 catalyst

Question 6

Equation for the RCO+ electrophile being formed for the acylation of benzene?

Answer 6

RCOCl + AlCl3 –> RCO+ + AlCl4-

Question 7

Equation for the reformation of the catalyst for nitration of benzene

Answer 7

H+ + HSO4- –> H2SO4

Question 8

Equation for the reformation of the catalyst for the acylation of benzene

Answer 8

AlCl4- + H+ –> HCl + AlCl3