Organic chemistry is the study of carbon-containing compounds, especially those found in living things. Carbon is uniquely suited to form many different compounds due to its ability to form multiple bonds, including single, double, and triple bonds. Hydrocarbons are organic compounds made of carbon and hydrogen, and can be classified based on their bonding as alkanes, alkenes, or alkynes. Substituted hydrocarbons have one or more hydrogen atoms replaced by other functional groups such as alcohols, carboxylic acids, or esters.