Y2 Aromatics (O)

Question 1

What was Kekule’s dream?

Answer 1

Snake eating its own tail

Question 2

Enthalpy of hydrogenation

Answer 2

The enthalpy change when one mole of an unsaturated compound is saturated by reacting it with hydrogen under standard conditions

Question 3

What did Kekule propose?

Answer 3

Cyclohexa-1,3,5-triene

Question 4

Evidence against Cyclohexa-1,3,5-triene (4 things)

Answer 4

Bromine water - benzene does not decolourise bromine water as it is more stable and less reactive than Cyclohexa-1,3,5-triene.

Bond lengths - (C-C) bond length in benzene is 0.14nm (inbetween single and double (C-C) bond lengths), signifying a 1.5 bond, not complete.

Isomers of 1,2-dichlorobenzene - only one isomer ( see photo )

Enthalpies of hydrogenation. Suggested cyclohexane-1,3,5-triene has delta H = -360KJmol^-1. Benzene has a delta H = -208KJmol^-1. Therefore a difference of 152. Benzene is more stable

Question 5

sigma bonds

Answer 5

single bonds that bond head on (add photo)

Question 6

pi bonds

Answer 6

double bonds produced. p orbitals meet side on and bond above and below the atoms

Question 7

Benzene Molecule

Answer 7

pi bonds happen above and below the planar surface in a circle. (photo 1)

Creates a delocalised sea of electrons. It is impossible to determine where the electrons are at any one time.
(photo 2)

Delocalised electrons circulate above and below the benzene ring which makes it more stable.

Question 8

Difference in hydrogenation between benzene and cyclohexa-1,3,5-triene.

Answer 8

Difference of 152KJmol^-1. As less energy is produced by benzene, it is more stable

Question 9

Enthalpy of hydrogenation of Benzene

Answer 9

delta H= -208KJmol^-1

Question 10

Enthalpy of hydrogenation of cyclohexene

Answer 10

delta H = -120KJmol^-1

Question 11

Enthalpy of hydrogenation of cyclohexa-1,3,5-triene

Answer 11

delta H = -360KJmol^-1

Question 12

Benzene ring (donut form)

Answer 12

Delocalised electrons above and below the ring

Question 13

Reduction of nitro aromatics

Answer 13

Question 14

Answer 14

Benzaldehyde

Question 15

Answer 15

Benzoic acid

Question 16

Answer 16

Phenol

Question 17

Answer 17

Phenylamine

Question 18

Answer 18

Phenylethanoate

Question 19

Answer 19

2-methyl-1,3,5-trinitrobenzene or trinitrotoluene, aka TNT

Question 20

Why are substitution reactions prioritised?

Answer 20

Question 21

Reduction of nitro aromatics

Answer 21

Question 22

Reduction of nitro aromatics conditions

Answer 22

Conc HCI and Sn (tin)

Question 23

Nitration of benzene conditions

Answer 23

Question 24

Nitration of benzene forming of catalyst

Answer 24

Question 25

Nitration of benzene mechanism

Answer 25

Question 26

Answer 26

Question 27

Friedel Crafts acylation in a nutshell

Answer 27

Add acrylic group onto benzene

Question 28

Friedel crafts acylation conditions and forming of electrophile

Answer 28

Question 29

Friedel crafts acylation mechanism and reforming of catalyst

Answer 29

Question 30

is benzene and saturated hydrocarbon

Answer 30

no, it is unsaturated