A ring that contains at least one heteroatom (an atom other than carbon) is called a heterocycle, and a substance based on a heterocyclic ring is a heterocyclic compound. Heterocyclic compounds containing N, O or S are by far the most common
Compounds were classified as being either aliphatic or aromatic in the latter part of the nineteenth century. To be classified as aliphatic meant then that the chemical behavior of a compound was “fatlike”. To be classified as aromatic meant then that the compound had a low hydrogen/carbon ratio and that it was “fragrant
More environment-friendly methods Natural insect attractants — instead pesticide Less reactive compounds organic refrigerants and aerosol propellant — instead Freon (that destroy the Earth’s ozone layer) Cars with more efficient combustion engines — reduce the massive amount of automobile
