Classification of organic compounds

With so many different organic structures to keep track of, chemists needed a systematic way to relate a molecule's structure to its chemical behaviour -- and that need is exactly what motivates classifying organic compounds in the first place. The book sets out two broad, independent classification schemes, developed one at a time in the two sections that follow: classification by CARBON SKELETON (the pattern in which the molecule's carbon atoms are themselves connected to one another -- open chains versus rings, and so on) and classification by FUNCTIONAL GROUP (which particular reactive group of atoms the molecule carries, regardless of how its carbon skeleton happens to be arranged). Before developing either scheme in detail, it is worth noting that chemists also build and use physical or computer-graphic MODELS of organic molecules to visualise their true three-dimensional shape more directly than any flat 2-D formula can -- a framework (skeletal) model that shows only the pattern of bonds and ignores atomic size, a ball-and-stick model that shows both connectivi …