# Why is heterocyclic chemistry such a vast field?

Add in a nitrogen heteroatom, and we add another layer onto the chemistry, i.e. we go from ${C}_{n} {H}_{2 n + 2}$ to ${C}_{n} {H}_{2 n + 1} N$, the same thing will occur with oxygen, sulfur, etc. There is a whole army of chemists who deal with heterocyclic chemistry.......pyrroles, furans, thiophenes, etc....... The heteroatom adds vast possibilities for structure and chemistry; the presence of lone pairs on the nitrogen or oxygen centre gives so-called $\pi - \text{excessive}$ molecules that ARE MORE reactive than benzene.