Heteroaromatic Chemistry

Question 1

What is the intermediate in electrophilic aromatic substitution

Answer 1

1. Wheland intermediate

2. Positive charge

Question 2

What is the intermediate in nucleophilic aromatic substitution

Answer 2

1. Meisenheimer intermediate

2. Negative charge

Question 3

Describe structure of benzene

Answer 3

1. 6 sp2 hybridised carbon atoms
2. P-orbitals overlap, allowing electrons to spread out- delocalised
3. This confers a high level of stability

Question 4

What are Huckels rules

Answer 4

1. Cyclic system
2. Planar system
3. Fully conjugated
4. System has 4n+2 pi-electrons

Question 5

What is structure of a polycyclic aromatic

Answer 5

1. 2 or more fused 6-membered rings

2. Still aromatic character but less aromatic than benzene

Question 6

What is name of polycyclic aromatic with 2 and 3 rings

Answer 6

1. 2= napthalene

2. 3= anthracene

Question 7

Can non-neutral species be aromatic

Answer 7

1. Yes aromatic character is not restricted to neutral species
2. Key is the empty orbital/ filled orbital is in conjugation