Aromatic and Heteroaromatic Chemistry

Question 1

What is the imine functional group

Answer 1

nitrogen with a double bond to a carbon

Question 2

How do you form an imine from a primary amine

Answer 2

React with a ketone and an acid catalyst
Amine will be nucleophile using LP, ketone will be attacked using electrohillic carbonyl carbon

Question 3

What is an enamine

Answer 3

ene + amine = enamine
An amine next to a carbon double bond

Question 4

How do you form an enamine from a secondary amine

Answer 4

React with ketone and acid catalyst
The mechanism is similar for imine, apart from the amine attacks twice, the second time at the α-proton

Question 5

What is Tautomerism

Answer 5

a reaction that (only) involves the intramolecular transfer of a proton

Question 6

What does acidic Keto-enol Tautomerism involve

Answer 6

• The carbonyl oxygen uses it LP to gain a hydrogen
• Water then picks up α-proton and carbonyl double bond is broke
  enol = alkene + alcohol

Question 7

What does basic Keto-enol Tautomerism involve

Answer 7

• Attack at the α-proton position, which pushes electron back onto carbon forming double bond and the results in the breaking of the carbonyl double bond
• negative charge on oxygen is then used to attack the hydrogen on water

Question 8

What does an acidic imine-enamine tautomerism involve

Answer 8

• Nitrogen uses LP to attack hydrogen, resulting in positive charge
• Water attacks α-proton, which pushes electrons back onto carbon forming a double bond, and the nitrogen-carbon double bond breaks

Question 9

What does a basic imine-enamine tautomerism involve

Answer 9

• Hydroxyl ion attacks α-carbon, which pushes electrons back onto carbon forming a double C=C bond, which in turn breaks the imine double bond
• The negative charge now on nitrgoen is used to attack hydrogen on water

Question 10

What compound is this

Answer 10

Toluene

Question 11

What compound is this

Answer 11

aniline

Question 12

What compound is this

Answer 12

naphthalene

Question 13

What compound is this

Answer 13

Styrene

Question 14

Why are carboxylic acids acidic?

Answer 14

Due to delocalisation
Delocalisation stabilises charged intermediates: the more resonance structures you can draw of a cation/anion, the more stable it is

Question 15

How can enamines react with electrophiles?

Answer 15

• Lone pair on nitrogen will delocalise, forming a double bond with carbon
• This causes the C=C to break and the negative charge to be pushed onto carbon
• Imine then attacks electrophile from the electron dense carbon

Question 16

How can enones react with nucleophiles

Answer 16

• Delocalisation of the C=C bond, will break the carbonyl double bond, pushing electron density onto oxygen
• The positive carbon from the delocalisation can tthen be attacked by a nucleophile

Question 17

Why is benzene relatively unreactive

Answer 17

Because of the resonance of stabilisation
It requires a lot of energy to break the aromaticity
This is due to the bonding MOs being lower energy than individual AOs,

Question 18

What are the 4 rules of aromaticity?

Answer 18

1. Cyclic
2. sp2 hybridised + fully conjugated
3. planar
4. Huckel’s rule (4n+2) pi electrons