Saturation (chemistry)

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The term saturation in chemistry is used in several ways:

  1. Saturation is the point at which a solution of a substance can dissolve no more of that substance. This point of maximum concentration, the saturation point, depends on the temperature of the liquid as well as the chemical nature of the substances involved. If a change in conditions (e.g. cooling) means that the concentration is higher than the saturation point, the solution has become 'supersaturated'.
  2. In organic chemistry, a saturated chemical compound has no double bond or triple bond or ring. In saturated hydrocarbons, every carbon atom is attached to two hydrogen atoms, except those at the ends of the chain, which have three hydrogen atoms.
  3. In biochemistry, the term saturation refers to the fraction of total protein binding sites that are occupied at any given time. Applies to enzymes, and molecules like haemoglobin.
  4. In organometallic chemistry, an unsaturated complex has fewer than 18 valence electrons and thus is susceptible to oxidative addition or coordination of an additional ligand. Unsaturation is characteristic of many catalysts because it is usually a requirement for substrate activation.