General Introduction to Organic Chemistry

For much of the eighteenth century, chemists believed that compounds obtained from living organisms were governed by a mysterious 'vital force' and could never be prepared from non-living (inorganic) starting materials -- a doctrine called vitalism. This belief was overturned in 1828, when the German chemist Friedrich Wohler heated ammonium cyanate, $\text{NH}_4\text{OCN}$, an inorganic salt, and obtained urea, $\text{NH}_2\text{CONH}_2$, a compound long known only as an animal-excretory product. Wohler's synthesis showed that organic compounds obey exactly the same physical and chemical laws as inorganic compounds and can be built in the laboratory; the name 'organic chemistry' survives today purely as a historical label for the branch of chemistry devoted to carbon compounds, not as evidence of any special life-force.

Carbon is unmatched among the elements in the sheer number of compounds it can form -- several million are known, far outnumbering the compounds of all the other elements put together. Three properties of carbon explain this. First, catenation: carbon atoms bond to one another with unusual strength and readiness, building long straight chains, branched chains and rings of essentially any length. Second, tetravalency: every carbon atom forms four covalent bonds, which can point in different directions in space, allowing branching and complex three-dimensional skeletons rather than just simple straight chains. Third, carbon forms strong, stable single, double and triple bonds both with itself and with a wide range of other elements -- hydrogen, oxygen, nitrogen, the halogens, sulphur and phosphorus -- giving rise to the huge diversity of functional groups that organic chemistry studies.

This enormous diversity is why organic chemistry touches almost every part of daily life: fuels such as petrol and natural gas, plastics and synthetic fibres, medicines and pharmaceuticals, dyes, soaps and detergents, and the carbohydrates, proteins, fats and nucleic acids that make up living systems are all organic compounds. This chapter lays the basic groundwork -- how organic compounds are classified and named, and how chemists describe the movement of electrons within them -- that every later chapter on individual families of organic compounds builds upon.