Orientation of Electrophilic Additions Markovnikovs Rule

Look carefully at the reactions shown in the previous section. In each case, an unsymmetrically substituted alkene has given a single addition product, rather than the mixture that might have been expected. For example, 2-methylpropene might have reacted with HCI to give l-chloro-2-methyI-propane (isobutyl chloride) in addition to 2-chloro-2-methylpropane, but it didn t. We say that such reactions are regiospecific (ree-jee-oh-specific) when only one of two possible orientations of addition occurs. 

After looking at the results of many such reactions, the Russian chemist Vladimir Markovnikov proposed in 1869 what has become known as Markovnikov s rule  

In the addition of HX to an alkene, the H attaches to the carbon with fewer alkyl substituents and the X attaches to the carbon with more alkyl substituents. 

Viadimir Vassilyevich Markovnikov (1838-1904) I was born in Nijni-Novgorod, Russia, and received his Ph.D. working with A. M, Butlerov at the university in Kazan. He was a professor in Kazan (1870), Odessa (1871), and Moscow (1873-1898). In addition to his work on the orientation of addition reactions, he was the first to synthesize a four-membered ring. 

When both ends of the double bond have the same degree of substitution, a mixture of products results  

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