Lisäämisreaktiotyyppi

Lisäämisreaktiotyyppi, known in English as addition reaction, is a fundamental concept in organic chemistry describing a type of chemical reaction where two or more molecules combine to form a larger molecule. This process typically involves the breaking of a pi bond in an unsaturated molecule, such as an alkene or alkyne, and the formation of new sigma bonds with the atoms from the other reactant. The overall number of independent molecules decreases as a result of the reaction.

Addition reactions are characterized by the saturation of a previously unsaturated molecule. For example, in the addition of hydrogen to ethene (an alkene), the double bond in ethene is broken, and a hydrogen atom is added to each carbon atom of the original double bond, forming ethane. This type of addition, where hydrogen is added, is specifically called hydrogenation. Other common types of addition reactions include halogenation (addition of halogens like chlorine or bromine), hydrohalogenation (addition of hydrogen halides like HCl or HBr), and hydration (addition of water).

The regioselectivity and stereoselectivity of addition reactions are important considerations. Regioselectivity refers to the preference of a reaction to occur at one specific position over another when multiple positions are available. Stereoselectivity describes the preference for the formation of one stereoisomer over another. These aspects are often governed by reaction mechanisms, such as electrophilic addition or nucleophilic addition, and by the electronic and steric properties of the reactants. Addition reactions are crucial for synthesizing a wide range of organic compounds and play a vital role in industrial chemical processes.