6.1.1 aromatic compounds

Question 1

What evidence disproves Kekule’s model?

Answer 1

Benzene is less reactive than expected.
Enthalpy change of hydrogenation is less exothermic than expected.
All carbon-carbon bonds are the same bond length.

Question 2

What is the delocalise pi ring system?

Answer 2

Each of the carbons donate 1 electron from its p-orbital which overlap to form pi bonds, delocalise to form a ring above and below the plane.

Question 3

What is a substitution reaction?

Answer 3

An atom or group of atoms is exchanged for another atom or group of atoms in a chemical reaction.

Question 4

What is the equation for the nitration of benzene?

Answer 4

Benzene+HNO3–>Nitrobenzene+H2O
(With H2SO4+50 degrees Celsius)

Question 5

What are the steps to the nitration of benzene?

Answer 5

Step 1: HNO3+H2SO4->NO2+ + HSO4- + H2O
Step 2: (mechanism)
Step 3: H+ + HSO4- —> H2SO4

Question 6

What are some examples of halogen carriers?

Answer 6

FeCl3
AlCl3
Fe

Question 7

What are the steps to the halogenation of benzene?

Answer 7

Step 1: Br2+FeBr3–>FeBr4-+Br+
Step 2: (mechanism)
Step 3: H+ + FeBr4- —> FeBr3 + HBr

Question 8

What causes multiple substitutions on Friedel-Crafts alkylation?

Answer 8

The alkyl group slightly adds electrons to the delocalised electron rings- making it more nucleophilic => increasing electron density leading to further substitutions.

Question 9

What is the reaction equation of benzene with chloroethane?

Answer 9

Benzene+C2H5Cl—>ethylbenzene +HCl

Question 10

Why is there only one substitution during Friedel-Craft acylation?

Answer 10

Less electron dense (electron withdrawing)