aromatics and that

Question 1

aliphatic

Answer 1

organic open chains

Question 2

alicyclic

Answer 2

cyclic structures with aliphatic properties

Question 3

aromatic

Answer 3

organic compounds with a benzene ring

Question 4

describe kekule model

Answer 4

planar ring of carbon atoms with alternating single and double bonds. Each carbon is bonded to one hydrogen

Question 5

describe delocalised model

Answer 5

p orbitals of all six c-c atoms overlap to create pi system- 2 ring shaped clouds of electrons above and below plane. all bonds are the same legnth . electrons are delocalised dont belong to specific caron atom. each carbon is bonded to one hydrogen

Question 6

evidence for delocalised model

Answer 6

enthalpy of hydrogenation is less exothermic than expected, benzene is more stable than kekule with a stronger resistanve to reaction
x-0raydifffraction shows all bonds to be the same length

Question 7

first step of bromination of benzene

Answer 7

form an electrophile you need a halogen carrier febr3
2Fe+3Br2=”Febr3
FeBr3 + Br2 = Br+ + FeBr4-

Question 8

cl halogen carrier

Answer 8

AlCl3

Question 9

why do halogen carrier help make good electrophiles

Answer 9

accepts lond pair of e from halogen stom on electropphile. lone pair is pulled away, the polarisation in the moeculeincreases froming carbocation

Question 10

Similarities and differences between the bonding in kekule and delcolised model

Answer 10

Both involve sideways overlap of adjacent p-orbitals. But kekule has alternating pi bonds vs delocalised electrons in pi system

Question 11

Evidence for kekules model

Answer 11

Bond length
Enthoy change of hydrogenation is less exothermic than expected to reaction
Benzene is less reactive than alkenes. Bromination of benzene requires a catalyst

Question 12

Relative resistance to bromination of benzene vs phenol csncyclohexene

Answer 12

Cyclohexene has the least resistance then Relative then benzene. In benzene electrons are delocalised into the ring. Cyclohexane electrons are localised between 2 carbon atoms. Benzene cannot polarise br2

Question 13

How does halogen carrier allow reaction to take place

Answer 13

Introduced permanent dipole on halogen

Question 14

Binding and structure of benzene

Answer 14

Over lap of p orbitals each orbital donates one electron to delocalised pi system. Electron density above and below plane. It’s a planar ring with equal c c bonds lengths and the bond angle 120