Heterocyclic Aromatic Compounds

Question 1

Define heterocyclic compounds

Answer 1

Aromatic compounds that have other elements present in the ring
Most common →nitrogen, oxygen, and sulfur

Question 2

What is pyridine?

Answer 2

An aromatic nitrogen analogue of benzene
It has six-membered heterocyclic ring with 6 pi electrons

Question 3

What is the difference between pyridine and benzene ?

Answer 3

Pyridine has a nitrogen instead of one of the carbons and no binding pair of electrons on nitrogen replaces the benzene’s bond to a hydrogen atom

Question 4

Answer 4

Pyridine

Question 5

What is pyrrole ?

Answer 5

An aromatic five-membered heterocyclic compound, with one nitrogen atom and two double bonds

Question 6

What is the difference between pyrrole in pyridine ?

Answer 6

In pyrrole the lone pair on nitrogen occupies the p orbital and these electron take part in the pi bonding system

Question 7

What is pyrimidine ?

Answer 7

A six-membered heterocyclic compound with two nitrogen atoms situated in a 1,3 arrangement

Question 8

What is the difference between pyrimidine and pyrrole?

Answer 8

In pyrimidine the lone pairs are not needed for the aromatic sextet and the lone pairs are basic

Question 9

Answer 9

Pyrrole

Question 10

Answer 10

Pyrimidine

Question 11

What is imidazole ?

Answer 11

An aromatic five-membered heterocyclic compound with two nitrogen atoms

Question 12

What is special about imidazole?

Answer 12

Question 13

Answer 13

Imidazole

Question 14

What is furan ?

Answer 14

An aromatic five-membered heterocyclic compound with oxygen instead of one carbon

Question 15

Answer 15

Furan

Question 16

What is thiophene ?

Answer 16

An aromatic five-membered heterocyclic compound with sulfur atom instead of one oxygen

Question 17

What is the difference between thiophene and furan ?

Answer 17

In thiophene the sulfur atom uses the unhybridized 3p orbital to overlap with the 2p orbitals on the carbon atoms

Question 18

Answer 18

Thiophene