Introduction

A hydrocarbon is any compound built from just two elements, carbon and hydrogen. Hydrocarbons are organised along two independent lines: whether the carbon skeleton is an open (acyclic) chain or a closed ring (cyclic), and whether every carbon-carbon bond is a single bond (saturated) or the molecule contains at least one carbon-carbon double or triple bond (unsaturated). Open-chain saturated hydrocarbons are the alkanes taken up in this section; open-chain unsaturated hydrocarbons are alkenes and alkynes. Cyclic hydrocarbons split the same way into saturated (alicyclic) and unsaturated forms, and a cyclic unsaturated hydrocarbon is further classed as either aromatic or non-aromatic.