Organic chemistry is the study of the chemistry of carbon compounds. Why focus on carbon? Carbon has properties that give its chemistry unparalleled complexity. It forms four covalent bonds, which give it great flexibility in bonding. It makes fairly strong bonds with itself (a characteristic called catenation ), allowing for the formation of large molecules; it also forms fairly strong bonds with other elements, allowing for the possibility of a wide variety of substances. No other element demonstrates the versatility of carbon when it comes to making compounds. So an entire field of chemistry is devoted to the study of the compounds and reactivity of one element. Because of the potential for complexity, chemists have defined a rather rigorous system to describe the chemistry of carbon. We will introduce some of that system in this chapter. Should you continue your study of chemistry beyond this text, you will find a much larger world of organic chemistry than we can cover in a single chapter. 16.1: Prelude to Organic Chemistry Photosynthesis involves a whole series of reactions with many chemicals, enzymes, breaking and making chemical bonds, the transfer of electrons and H+ ions, and other chemical processes. The elucidation of the actual steps of photosynthesis—a process still unduplicated artificially—is a major achievement of modern chemistry. 16.2: Hydrocarbons The simplest organic compounds are hydrocarbons and are composed of carbon and hydrogen. Hydrocarbons can be aliphatic or aromatic; aliphatic hydrocarbons are divided into alkanes, alkenes, and alkynes. The combustion of hydrocarbons is a primary source of energy for our society. 16.3: Branched Hydrocarbons A unique name can be given to branched hydrocarbons. A unique structure can be drawn for the name of a hydrocarbon. 16.4: Alkyl Halides and Alcohols The presence of a halogen atom (F, Cl, Br, or I; X is also used to represent any halogen atom) is one of the simplest functional groups. Organic compounds that contain a halogen atom are called alkyl halides. 16.5: Other Oxygen-Containing Functional Groups Aldehydes, ketones, carboxylic acids, esters, and ethers have oxygen-containing functional groups. 16.6: Other Functional Groups There are some common, and important, functional groups that contain elements other than oxygen. In this section, we will consider three of them: amine, amide, and thiol functional groups. 16.7: Polymers Polymers are long molecules composed of chains of units called monomers. Several important biological polymers include proteins, starch, cellulose, and DNA. 16.E: Organic Chemistry (Exercises) These are exercises and select solutions to accompany Chapter 16 of the "Beginning Chemistry" Textmap formulated around the Ball et al. textbook. Thumbnail: DNA Double Helix (Public Domain; National Human Genome Research Institute via Wikipedia ).