Electrophilic Addition to Alkenes Mechanism



Electrophilic Addition to Alkenes Mechanism
Electrophilic addition to alkenes takes the following general form:



nuc: = nucleophile
E+ = electrophile
Electrophilic addition to alkenes starts with the pi electrons attacking an electrophile, forming a carbocation on the most stable carbon. A nucleophile then attacks the carbocation to form the product. There are many different kinds of such addition, including:
  • Hydroxylation
  • Hydrogenation
  • Halogenation
  • Oxidative Cleavage
  • Hydration
  • Epoxidation
  • Cyclopropanation
  • Halohydrin Formation
Clearly, there are numerous kinds of products that can be formed as a result of this mechanism.
Orientation of Addition: Electrophilic Addition adds to give the Markovnikov Product, with the nucleophile added to the more highly substituted carbon. This is because the carbocation intermediate is significantly stabilized by alkyl substituents.
Example of electophilic addition to alkenes:
First, formation of the carbocation on the most highly substituted carbon
                       
Followed by attack of chloride on the carbocation to give the addition product

  
                 
                                        ⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪⧪

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