Aromaticity

Question 1

What is the benzene ring composed of?

Answer 1

6 carbons, 3 double bonds (alkene)

Question 2

What is unique about benzene / aromatics?

Answer 2

Pi electrons spread equally over all C atoms

Question 3

What is the hybridisation of benzene?

Answer 3

Sp2

Question 4

What is the purpose of hydrogenation?

Answer 4

Adding hydrogen bonds to remove double bonds, hence no longer aromatic

Question 5

What are the main characteristics of aromatic compounds?

Answer 5

• Must be cyclic
• Electrons must be conjugated around the ring
• Must be planar
• Must obey huckles rule, must have 4n + 2 pi electrons

Question 6

What are the 3 relative locations on a benzene ring in clockwise direction?

Answer 6

Ortho, meta and Para

Question 7

What is a heteroaromatic compound?

Answer 7

Contain an element other than carbon in the ring

Question 8

What are phenols?

Answer 8

Aromatic compounds containing a hydroxyl group (OH) bonded to the aromatic ring

Question 9

Why is the pKa of phenol lower than that of ethanol?

Answer 9

The lone pair of electrons on oxygen delocalises into the benzene ring (mesomeric effect) which reduces the electron density in the O-H bond. The O-H bonds is weaker and therefore breaks more easily in comparison to ethanol.
The lone pair can move to other and para position, attracting electrophiles without presence of catalyst

Question 10

What is an aniline?

Answer 10

Aromatic compound with amine group (hydrocarbon group with N attached)