Saturated

Summary: Containing only single bonds between carbon atoms. Alkanes are saturated hydrocarbons. Tags: igcse chemistry definition organic-chem Created: 2026-07-14 Last Updated: 2026-07-14

In organic chemistry, a saturated compound is one in which all carbon-carbon bonds are single covalent bonds, meaning each carbon atom is bonded to the maximum possible number of hydrogen atoms, leaving no capacity for additional atoms to be added. Saturated hydrocarbons, known as alkanes, follow the general formula CₙH₂ₙ₊₂ and include familiar compounds such as methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₁₀), all of which have tetrahedral geometry around each carbon atom. Because they lack carbon-carbon double or triple bonds, saturated compounds cannot undergo addition reactions; instead, they participate only in substitution reactions, such as the photochemical reaction of alkanes with halogens in the presence of ultraviolet light where a hydrogen atom is replaced by a halogen atom. A key practical distinction is that saturated compounds do not decolourise bromine water — the orange-brown colour persists, unlike with unsaturated compounds where the bromine adds across the double bond and the colour disappears — making this the standard IGCSE chemical test to distinguish alkanes from alkenes. The term “saturated” also applies in other contexts, such as a saturated solution which contains the maximum amount of dissolved solute at a given temperature, and saturated fats in biochemistry which contain no carbon-carbon double bonds in their fatty acid chains.

Key term — IGCSE Chemistry (0620/0971) glossary.