AntiMarkovnikovtyyppinen

AntiMarkovnikovtyyppinen describes a type of chemical reaction where a substituent adds to a double or triple bond in a manner opposite to Markovnikov's rule. Markovnikov's rule, a principle in organic chemistry, states that in the addition of a protic acid (like HBr) to an alkene or alkyne, the hydrogen atom attaches to the carbon atom with the greater number of hydrogen atoms, and the halide atom attaches to the carbon atom with fewer hydrogen atoms. This typically leads to the formation of a more substituted, and therefore more stable, carbocation intermediate.

In contrast, an AntiMarkovnikovtyyppinen addition results in the substituent adding to the carbon atom that has fewer hydrogen atoms, and the hydrogen atom adding to the carbon atom with more hydrogen atoms. This outcome is often achieved through radical addition mechanisms, such as the hydrobromination of alkenes in the presence of peroxides. The peroxide initiates a radical chain reaction where the bromine radical adds first to the less substituted carbon of the double bond, leading to a more stable carbon radical intermediate. This intermediate then abstracts a hydrogen atom from HBr, completing the AntiMarkovnikovtyyppinen addition. Other methods to achieve AntiMarkovnikovtyyppinen addition include hydroboration-oxidation of alkenes, where boron adds to the less substituted carbon, followed by oxidation to form an alcohol with the hydroxyl group on the less substituted carbon. This regioselectivity is crucial in organic synthesis for creating specific molecular structures.