C5H8O2

C5H8O2 is a molecular formula that refers to any of several organic compounds containing five carbon atoms, eight hydrogen atoms, and two oxygen atoms. The formula corresponds to a nominal molecular weight of about 100.1 g/mol.

With five carbons and two oxygens, the degree of unsaturation is two, meaning each isomer must accommodate two rings and/or pi bonds. This allows combinations such as a carbonyl within a carboxyl or ester group plus an additional double bond or a ring, leading to a variety of structures that share the same formula but differ in connectivity and functional groups.

Two well-known examples of C5H8O2 isomers are gamma-valerolactone (GVL), a five-membered lactone used as a solvent and potential biofuel additive; and the unsaturated carboxylic acids pent-2-enoic acid (2-pentenoic acid) and pent-3-enoic acid, which have a carboxyl group and a carbon–carbon double bond in the five-carbon chain.

Other possible isomers include additional esters and cyclic enones, illustrating the structural diversity possible for this formula. The properties of each isomer vary widely, so identification of a sample with this formula requires structural characterization such as spectroscopic analysis.