A structural isomer is a chemical formula that can take on different shapes. Saturated hydrocarbons have single bonds and cannot bond further, while unsaturated hydrocarbons have double or triple bonds and can bond with other compounds. Carboxylic acids have the basic structure of R-COOH and are used in esterification reactions with alcohols. Esterification is the reaction between an alcohol and a carboxylic acid to form an ester. Combustion reactions break down hydrocarbons and oxygen to produce water and carbon dioxide. Polymers are formed through polymerization reactions that link monomers together into chains.