6.1.1 Aromatic compounds

Question 1

molecular formualar of benzene

Answer 1

C6H6

Question 2

what mechanism does benzene undergo

Answer 2

electrophillic substitution

Question 3

how many bond lengths would benzene have to fit with kekule

Answer 3

2 different bond lengths due to double and single bonds

Question 4

how many bond lengths does benzene actually have

Answer 4

one

Question 5

what explains the anomalous properties of benzene

Answer 5

a ring structure where the spare pairs of electrons are delocalised around all 6 carbon atoms
- delocalised electrons above and below the plane of atoms

Question 6

bonding in benzene

Answer 6

each C has 4 outer electrons
1 used to bond to H
2 used to bond to adjacent carbons
remaining 6 are delocalised in a cloud above and below the plane of the ring

Question 7

what do the delocalised electrons in benzene cause

Answer 7

rise to extra stability called delocalisation energy

Question 8

isomer of arene compound for benzene

Answer 8

if had 3 double bonds it should have 2 isomers but benzene only has one

Question 9

enthalpy of hydrogenation for kekule structure to prove its wrong

Answer 9

it should undergo similar reactions to cyclohexene and cyclodihexene howeveer it doesnt as the enthalpy is lower

Question 10

Halogenation of benzene

Answer 10

halogen carrier must be present - FeCl3,AlBr3,FeBr3

Question 11

nitration of benzene

Answer 11

concentrated nitric acid with concentrated sulphuric acid - warm

Question 12

alkylation of benzene

Answer 12

reacting benzene with haloalkane with presence of AlCl3

Question 13

acylation of benzene

Answer 13

presence of AlCl3

Question 14

Directing effect

Answer 14

presence of substituted groups on a benzene ring will have an effect on the substitution of further groups

Question 15

what increase the electron density

Answer 15

releasing electrons

Question 16

what decreases the electron density

Answer 16

withdrawing electrons

Question 17

electron donating groups

Answer 17

-OH phenol
-NH2 amine

Question 18

electron withdrawing groups

Answer 18

• NO2 nitro

Question 19

activating groups

Answer 19

side chains that increase electron density allow electrophiles to react faster than with benzene

Question 20

what directing numbers are electron donating groups

Answer 20

2,4

Question 21

oxygen as a donating group and how it happens

Answer 21

O is very electronegative
has effect of pushing electrons forcing areas of charge over the 2,4,6 position causing negative dipoles that attract electrophiles more effectively

Question 22

deactivating groups

Answer 22

side chains that decrease electron density slow electrophile reactions compared to benzene

Question 23

NO2 directing numbers

Answer 23

3,5