aromatic compounds

Question 1

What is the molecular formula of benzene

Answer 1

C6H6

Question 2

What are aromatic, aliphatic and alicyclic compounds

Answer 2

Aromatic- containing benzene
aliphatic- ogranaic compound with open chain structure, can be cyclic but not benzene
alicyclic- cyclical but not benzene

Question 3

What was kekule model for benzene

Answer 3

6 member ring of carbon with alternating single and double bonds, snake eating tail

Question 4

Why did chemists disapprove with the kekule model

Answer 4

The model contain explain the physical and chemical properties of benzene

Question 5

What are the factors that disprove the kekule model

Answer 5

1- benzene contains double bonds and therefore should decolourise bromine what but instead it doesn’t undergo any electrophillic addition reaction(therefore cannot have C=C) bonds
2- The bond length measure using X-ray diffraction showed that the bond length of each C bond was the same meaning that there were no double bonds
3- due to the double bonds the enthalpy of hydrogenation was expected to be *3 that of cyclohexene but it is actually much lower -208 so benzene is more stable

Question 6

Delocalised model of benzene

Answer 6

• Each carbon atom has an electron in a p-orbital at right angles to the plain of bonded H atoms causing adjacent P orbitals to overlap causing a ring with high electron density
  -Pi bond system spreads over all the carbon atoms, they are said to be delocalised

Question 7

What are the groups that are prefixes to benzene

Answer 7

short alkyl chains, halogens and nitro groups

Question 8

What happens when the carbon chain is longer than 7

Answer 8

the benzene is considered substituent and becomes the prefix eg phenyl ethanone

Question 9

What are the 3 expections to this

Answer 9

Benzoic acid, phenylamine, benzaldehyde

Question 10

What kind of reaction does benzene undergo

Answer 10

Electrophillic substitution, electrophile attracted to high electron density(strong electrophiles)

Question 11

How do substitution reactions work on benzene

Answer 11

Hydrogen atom on benzene is replaced by atom atom/ group

Question 12

conditions for nitration of benzene

Answer 12

catalysed by sulfuric acid and heated at 50 degrees

Question 13

catalyst for the Nitration of benzene

Answer 13

HNO3
creation:
HNO3 + H2SO4 -> HSO4 + H2NO3
H2NO3 -> NO3- + H2O
restoring catalyst
HSO4- + H+ -> H2S04

Question 14

Halogen carrier for alkylation of benzene

Answer 14

Creation
CH3Cl + AlCl3 -> CH3+ + AlCl4-

AlCl4- + H+ -> AlCl3 + HCLl

Question 15

Halogen carrier for acylation of benzene

Answer 15

Ch3COCl + AlCl3 -> Ch3CO+ + AlCl4-

Question 16

All the hydrogen carriers

Answer 16

AlCl3, AlBr3, FeCl3

Question 17

Why does benzene require halogen carriers

Answer 17

Too stable to react with non-polar or weak electrophiles to electrophiles produced from halogen carrier catalysts are much stronger