lisäysreaktiossa

Lisäysreaktiossa or addition reaction is a fundamental concept in organic chemistry. It describes a type of reaction where two or more molecules combine to form a larger molecule. This typically occurs when a multiple bond, such as a double or triple bond, is present in one of the reactant molecules. The pi bonds in the multiple bond are broken, and new sigma bonds are formed, leading to the saturation of the carbon atoms that were previously involved in the multiple bond.

Common examples of addition reactions include the addition of hydrogen (hydrogenation), halogens (halogenation), hydrogen halides (hydrohalogenation), and water (hydration) to alkenes and alkynes. These reactions are crucial for synthesizing a wide range of organic compounds. For instance, hydrogenation is used to convert liquid vegetable oils into solid fats.

The regiochemistry of addition reactions, particularly to unsymmetrical alkenes or alkynes, is often governed by Markovnikov's rule or anti-Markovnikov addition, depending on the reaction conditions and reagents used. Markovnikov's rule generally predicts that the hydrogen atom will add to the carbon atom of the double bond that already has more hydrogen atoms attached. Anti-Markovnikov addition, often achieved through radical mechanisms, results in the opposite regioselectivity. Stereochemistry also plays a role, with additions often occurring in a syn (both new groups on the same side of the original multiple bond) or anti (new groups on opposite sides) manner. These reactions are essential tools in organic synthesis and are widely studied and applied.