Aromatic Chemistry 2

Question 1

describe the pi-orbitals in benzene?

Answer 1

total no of molecular orbitals = total no of atomic orbitals

6 remaining p orbital, we need 6 pi orbitals

Question 2

synthesis of cyclooctatetraene?

Answer 2

4 (ethene) reacted with Ni(cn)2

modern synthesis carried out through reaction of acetylene

Question 3

properties of cyclooctatetraene?

Answer 3

• tub shape

- no overlap can take place between orbitals of adjacent double bonds

Question 4

cyclobutadiene

Answer 4

• too unstable = characterised directly

- at ambient temp -> dimerises to tricyclic system

Question 5

huckel divided annuelenes into 2 classes

what are they?

Answer 5

aromatic

anti aromatic

Question 6

aromatic

Answer 6

annuelenes 6, 10, 14, 18
(4n+2) pi electrons n = 1,2,3,4

stability inc with planarity

Question 7

anti aromatic

Answer 7

annuelenes 4, 8, 12, 16
4n pi electrons n = 1,2,3,4

very unstable/ have alternating single/double bonds

Question 8

why does azulene have large dipole moment?

Answer 8

there is separation of pos and neg charges