Electrophilic addition reactions Zaitsev rule

Practically everything we ve said in previous chapters has been stated without any proof. We said in Section 6.8, for instance, that Markovnikov s rule is followed in alkene electrophilic addition reactions and that treatment of 1-butene with HC1 yields 2-chJorobutane rather than 1-chlorobutane. Similarly, we said in Section 11.7 that Zaitsev s rule is followed in elimination reactions and that treatment of 2-chlorobutane with NaOH yields 2-butene rather than 1-butene. But how do we know that these statements are correct The answer to these and many thousands of similar questions is that the structures of the reaction products have been determined experimentally. 

Butene is the final product because, after 1-butene forms, a proton from the acidic solution adds to the double bond (adding to the sp carbon bonded to the most hydrogens in accordance with the rule that governs electrophilic addition reactions), thereby forming a carbocation (Section 6.4). Loss of a proton from the j8-carbon bonded to the fewest hydrogens (Zaitsev s rule) forms 2-butene (Section 10.2). 

Markovnikov s rule like Zaitsev s organizes experimental observations in a form suitable for predicting the major product of a reaction The reasons why it works will appear when we examine the mechanism of electrophilic addition m more detail... 

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See also in sourсe #XX -- [ , , ]

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