MarkownikowRegel

The Markownikoff rule, also known as the Markownikov rule, is a principle in organic chemistry that describes the direction of addition reactions to carbon-carbon double bonds. It was formulated by Vladimir Markovnikov in 1870. The rule states that in the addition of a protic acid (such as water or hydrogen halides) to an alkene, the more substituted carbon of the double bond will attract the hydrogen atom, and the less substituted carbon will attract the hydroxyl group or the halogen atom.

For example, in the addition of water to propene, the product is 2-propanol, not 1-propanol. This is because the more substituted carbon (the one with two hydrogen atoms) attracts the hydrogen, and the less substituted carbon (the one with one hydrogen atom) attracts the hydroxyl group.

The Markownikoff rule is a general guideline and not an absolute rule. There are exceptions, such as in the addition of hydrogen bromide to 2-methylpropene, where the product is 2-bromopropane, not 3-bromopropane. This is due to the stability of the carbocation intermediate formed in the reaction.

The Markownikoff rule is important in understanding the mechanisms of addition reactions and in predicting the products of such reactions. It is also useful in designing synthetic routes for organic compounds.