Organic chemistry studies carbon-based compounds that may contain other elements like hydrogen, nitrogen, oxygen, phosphorus, silicon and sulfur. Carbon bonds can be single, double, or triple. Common organic compounds include hydrocarbons, alcohols, carboxylic acids, and polymers. Hydrocarbons consist of hydrogen and carbon and include alkanes, alkenes, and alkynes. Alcohols contain a hydroxyl group bound to carbon. Carboxylic acids contain a carboxyl group bound to carbon. Polymers are large molecules composed of repeating structural units called monomers connected by covalent bonds.