Problem Set 3 – Aromatic
Systems
- Which
of the following structures represent aromatic systems?
- Sondheimer
synthesized a series of conjugated cyclic polyalkenes which are known as [n]-annulenes where n indicates the size
of the ring.
a.
[18]-annulene, shown below, is
aromatic. Explain.
b.
[14]-annulene is not aromatic. It reacts with bromine at ambiant
temperature. Explain.
- Azulene
is readily attacked by electrophiles at C-1 and by nucleophiles at C-4.
a.
Azulene,
is aromatic. Justify.
b.
One resonance structure of the cation
formed by attack at carbon-1 is shown below.
Justify electrophilic attack at this carbon.
c.
One resonance structure of the anion
formed by attack at carbon-4 is shown below.
Justify nucleophilic attack at this carbon.
