Introduction

Among all the elements of the periodic table, carbon alone is able to form an almost unlimited variety of compounds -- everything from methane, with its single carbon atom, up to deoxyribonucleic acid (DNA), which strings together billions of carbon atoms. This unique bonding ability is what makes organic chemistry -- the chemistry of carbon compounds -- worth studying as its own branch of chemistry. Crude oil is itself a huge natural mixture of organic compounds called hydrocarbons (compounds built only from carbon and hydrogen), and the pharmaceutical industry depends entirely on organic compounds for the medicines it produces. Beyond their industrial importance, organic compounds matter to us directly because so many everyday biological functions -- from the food we eat to the DNA that carries our genetic information -- are carried out by organic molecules. This chapter builds the foundational toolkit needed to study organic chemistry systematically: how to represent organic molecules on paper (in two and three dimensions), how to classify them into sensible families, how to name them by a single, unambiguous, worldwide system (IUPAC nomenclature), how the phenomenon of isomerism lets different real compounds share one molecular formula, and finally the theoretical machinery -- bond cleavage, reagent types, and electronic effects -- used to describe and predict how organic reactions actually happen.