lisäysreaktioille

Lisäysreaktioille is a Finnish term that translates to "addition reactions" in English, commonly encountered in organic chemistry. These reactions involve the addition of one or more atoms or groups of atoms to a molecule that contains a double or triple bond. Typically, the pi bond in the unsaturated molecule breaks, and new sigma bonds are formed with the added species.

A characteristic feature of addition reactions is that the degree of unsaturation in the molecule decreases. For instance, an alkene, with one double bond, will transform into an alkane, which has only single bonds, upon undergoing an addition reaction. Similarly, an alkyne, with a triple bond, can undergo two successive addition reactions to become an alkene and then an alkane.

Common types of addition reactions include hydrogenation, halogenation, hydrohalogenation, and hydration. Hydrogenation involves the addition of hydrogen (H2) across the double or triple bond, usually catalyzed by metals like platinum, palladium, or nickel. Halogenation is the addition of halogens (e.g., Cl2, Br2) to the unsaturated compound. Hydrohalogenation is the addition of hydrogen halides (e.g., HCl, HBr), often following Markovnikov's rule, which predicts the regioselectivity of the addition. Hydration is the addition of water (H2O), typically under acidic conditions, to form an alcohol.

Addition reactions are fundamental in organic synthesis, allowing for the transformation of unsaturated compounds into a wide range of saturated derivatives with altered functional groups and properties. They are crucial in the production of various industrial chemicals, polymers, and pharmaceuticals.