Chapter 6: Reactions of Alkenes : Addition Reactions
 Ch 6 contents

Alkenes

Structure:
 

pi bond molecular orbital
  • The alkene functional group consists of two sp2 hybridised C atoms bonded to each other via a s and a p bond.
  • The p bond is produced by the side-to-side overlap of the p-orbitals not utilised in the hybrids (see left).
  • The substituents are attached to the C=C unit via s bonds.
  • The 2 C of the C=C and the 4 atoms attached directly to the C=C are all in the same plane.

Reactivity:

  • A  p bond  is a region of high electron density (red) so alkenes are typically nucleophiles.
  • Alkenes react with electrophiles (e.g. H+, X+)
  • Alkenes typically undergo addition reactions in which the p bond  is converted to two new stronger s bonds.
  • Overall reaction :  Electrophilic addition
 electrostatic potential of ethene

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