Aromatic chemistry (incomplete)

Question 1

What is the molecular formula for benzene?

Answer 1

-C6H6

Question 2

What is the length of C-C bonds in benzene in relation to carbon- carbon double and single bonds?

Answer 2

-Shorter than single bonds.
-Longer than double bonds.

Question 3

Why cant benzene be a molecule with 3 double bonds?

Answer 3

-Benzene is a symmetrical molecule (all bonds
are the same length).
-Benzene has a hydrogenation value of -208KJ/mol for 3H2.

Question 4

What is the energy of hydrogenation for cyclohexa-1,3,5-triene (kekule structure)

Answer 4

-360KJ/mol

Question 5

What is the proof that benzene is not cyclo-1,3,5-triene?

Answer 5

-Energy of hydrogenation of cyclohexa-1,3,5-
triene is -360. Energy of hydrogenation of
benzene is -208 which has a 152KJ/mol
difference.

Question 6

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

Answer 6

-More energy is taken in when bonds are
broken, proving that benzene is a more
stable molecule.

Question 7

Why benzene more stable than cyclohexa-1,3,5-triene?

Answer 7

-Ring of delocalized electrons.

Question 8

What is the structure of benzene?

Answer 8

-Benzene is a planar molecule with a ring of
delocalized electrons both above and below
the plane of the ring.

Question 9

What mechanism does benzene undergo?

Answer 9

-Electrophilic substitution.

Question 10

What is an electrophile?

Answer 10

-Accepts lone pair.
-positive ion.

Question 11

What are the reagents for nitration of benzene?

Answer 11

-Concentrated nitric acid (HN03).
-Concentrated sulfuric acid (H2SO4).

Question 12

What is the electrophile for nitration of benzene and how is it formed?

Answer 12

-NO2
-HNO3 + 2H2SO4 —-> NO2+ + 2HSO4- + H3O+

Question 13

Describe the mechanism of nitration of benzene?

Answer 13

1) Draw an arrow from the benzene ring to
the positive nitrogen atom.
2) draw the benzene ring so that it’s positive
and broken around the carbon with the
NO2.
3) Draw an arrow from the hydrogen atom
(on same carbon atom) to the benzene
ring.

Question 14

What is monosubstitution and how is it done?

Answer 14

-When only one substitution takes place.
-Keep temperature below 50 degrees Celsius.

Question 15

Why don’t addition reactions occur in benzene?

Answer 15

-Because benzene is a very stable molecule.

Question 16

What is the electrophile used in Friedel crafts acylation of benzene and how is it formed?

Answer 16

-RCO+
-RCOCl + AlCl3 –> RCO+ + AlCl4-

Question 17

Describe the mechanism for Friedel crafts acylation of benzene?

Answer 17

1) Draw an arrow from the benzene ring to
the C+ ion.
2) Draw the benzene rin as positive and
broken around the Carbon atom.
3) Draw an arrow from the hydrogen
connected to the carbon to the benzene
ring.