benzene

Question 1

describe the bonding in a benzene molecule?

Answer 1

-its a cyclic planar molecule
- carbon has 4 valent electrons
each carbon is bonded to 2 other carbons and 1 hydrogen molecule
- final lone electron is in the P-orbital and sticks out above and below the ring
-due to the delocalised electron structure, C-C bonds in the molecule are all the same bond length (139pm)
- all lone pair of electrons in D-orbital combine to form a delocalised electron ring

Question 2

why is benzene molecule more stable than the kekule model (cyclohexa-1,3,5-triene)

Answer 2

• we measure the stability by comapring enthalpy of hydrogenation

Question 3

what is the enthalpy change of cyclohexene containing one double bond in comparison to containing 3 double bonds? predcited value

Answer 3

-1 double bond is 1120KJmol-1
-3 double bond is 3x -120= -360

Question 4

what is the enthalpy change of cyclohexene (experimental data)? (3double bonds)

Answer 4

–208KJmol-1

Question 5

why does benzene have a higher enthalpy change than cyclohexa-1,3,5-triene)?

Answer 5

more energy needed to break bonds in benzene than cyclohexa….

Question 6

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

Answer 6

delocalised elctrons structure

Question 9

What happens during FRIEDEL-CRAFTS ACYLATION?

Answer 9

Reacts with acrylic chloride with a halogen carrier

Question 10

Why is a acyl group added to the benzene?

Answer 10

-after adding acyl group benzene is weaker and easier to modify to make useful products

Question 11

Why is a halogen carrier used?

Answer 11

-halogen pair is used to act as a catalyst in which it provides the electrophile with a stronger positive charge