Which reaction are anti-Markovnikov vs Markovnikov?
The reaction that is anti-Markovnikov is when the addition of a hydrogen halide (HX) occurs, and the halogen (X) attaches to the carbon atom that already contains fewer hydrogen atoms. In simple terms, the halogen is added to the less substituted carbon.
On the other hand, the Markovnikov's rule states that in the addition of a hydrogen halide to an unsymmetrical alkene, the hydrogen atom attaches to the carbon atom that already contains more hydrogen atoms. In this case, the hydrogen is added to the more substituted carbon.
The reactions that are labeled as anti-Markovnikov or Markovnikov refer to the regioselectivity in the addition of a protic acid (such as HX) to an alkene.
Markovnikov addition refers to the addition of the protic acid HX, where the hydrogen (H) from the acid attaches to the carbon atom with the most hydrogen atoms in the alkene, resulting in a more stable carbocation intermediate. The halogen X then attaches to the other carbon atom. An example of a Markovnikov addition is the reaction of HBr with propene, where H attaches to the carbon that was initially double-bonded to the less substituted carbon:
CH3CH=CH2 + HBr → CH3CH2CH2Br
Anti-Markovnikov addition, on the other hand, refers to the addition of the protic acid HX, where the hydrogen (H) attaches to the carbon atom with the fewer hydrogens in the alkene, resulting in a less stable carbocation intermediate. The halogen X then attaches to the other carbon atom. One method of achieving anti-Markovnikov addition is through the use of radical initiators, such as peroxides. An example of an anti-Markovnikov addition is the reaction of HBr with propene in the presence of a peroxide, where H attaches to the carbon that was initially double-bonded to the more substituted carbon:
CH3CH=CH2 + HBr (peroxide) → CH3CH2CH2Br
In summary, the main difference between anti-Markovnikov and Markovnikov addition lies in the regioselectivity of the hydrogen attachment during the addition of a protic acid to an alkene.
The reaction you are referring to is the addition reaction of hydrogen halides (such as HCl, HBr, or HI) to alkenes.
In the Markovnikov addition of a hydrogen halide, the hydrogen atom adds to the carbon atom of the double bond that already has more hydrogen atoms. This results in the formation of a more stable carbocation intermediate. The halide ion then adds to the carbocation to form the final product.
On the other hand, in the anti-Markovnikov addition of a hydrogen halide, the hydrogen atom adds to the carbon atom of the double bond that initially has fewer hydrogen atoms. This leads to the formation of a less stable, highly reactive radical intermediate. The halide ion then combines with the radical to form the final product.
To determine whether a reaction is anti-Markovnikov or Markovnikov, you need to know the specific reactants and conditions. However, in general, the addition of hydrogen halides to alkenes is typically Markovnikov unless specific reagents or catalysts are used to favor the anti-Markovnikov pathway.