unszaturated

Unsaturated is an adjective used in chemistry and nutrition to describe substances that have fewer than the maximum possible number of hydrogen atoms attached to carbon atoms. In organic chemistry this occurs when a molecule contains one or more double bonds, triple bonds, or rings that reduce hydrogen count relative to a fully saturated acyclic hydrocarbon. Common unsaturated structures include alkenes (C=C), alkynes (C≡C), cycloalkenes, and aromatic rings, all of which contribute to the molecule’s degree of unsaturation. Note that the term is usually spelled unsaturated; if encountered as unszaturated, it is typically a misspelling.

The degree of unsaturation (DoU) measures how many rings and pi bonds are present. DoU can be calculated from a molecular formula using DoU = (2C + 2 + N − H − X)/2, where C is carbon, H is hydrogen, N is nitrogen, and X is halogens. Each double bond, triple bond, or ring adds one to the DoU. This concept helps in deducing possible structures from a formula and in understanding reactivity patterns.

In nutrition, unsaturated fats are fatty acids that contain one or more carbon–carbon double bonds. They are divided into monounsaturated fats (one double bond) and polyunsaturated fats (two or more). They are typically liquid at room temperature and are commonly sourced from plants and fish. Diets higher in unsaturated fats, especially when replacing saturated fats, are associated with cardiovascular benefits; cis/trans configurations and oxidation risk are relevant considerations. Essential fatty acids, such as certain omega-3 and omega-6 types, must be obtained from the diet.

Overall, unsaturation is a central concept across chemistry and biochemistry, indicating a departure from full hydrogen saturation due to multiple bonds or rings.